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Sample records for optical sensing technique

  1. Transformer insulation monitoring by optical sensing techniques

    NASA Astrophysics Data System (ADS)

    Uttamchandani, Deepak G.; Blue, Robert; Farish, O.

    1998-08-01

    High voltage transformers use paper to insulate the electrical windings present in the core which is then subsequently immersed in oil. In service, the temperature of the windings will increase to typically 80 degrees C. If the transformer is loaded to beyond its design ratings, the temperature can exceed 100 degrees C causing the cellulose chains in the paper to cleave at an accelerated rate, resulting in the degradation of mechanical strength and performance of the insulation. If unchecked, this can lead to catastrophic failure of the transformed and accompanying disruption to electricity supply and large economic losses to the operating utility. Furfuraldehyde (FFA) is a chemical by-product which is released into the oil by the thermal degradation of the paper winding. The concentration of FFA within the oil has been directly related to the condition of the paper insulation. We have developed absorbance and fluorescence optical techniques incorporating a novel FFA- sensitive material which we have invested at our laboratories. This material has been incorporated into a prototype portable optoelectronic instrument for the measurement of FFA at the site of the transformer. Results of experiments will be presented, and the implication of these results for condition monitoring of HV transformer will be discussed.

  2. Frequency-Shifted Interferometry — A Versatile Fiber-Optic Sensing Technique

    PubMed Central

    Ye, Fei; Zhang, Yiwei; Qi, Bing; Qian, Li

    2014-01-01

    Fiber-optic sensing is a field that is developing at a fast pace. Novel fiber-optic sensor designs and sensing principles constantly open doors for new opportunities. In this paper, we review a fiber-optic sensing technique developed in our research group called frequency-shifted interferometry (FSI). This technique uses a continuous-wave light source, an optical frequency shifter, and a slow detector. We discuss the operation principles of several FSI implementations and show their applications in fiber length and dispersion measurement, locating weak reflections along a fiber link, fiber-optic sensor multiplexing, and high-sensitivity cavity ring-down measurement. Detailed analysis of FSI system parameters is also presented. PMID:24955943

  3. Remote sensing of stress using electro-optics imaging technique

    NASA Astrophysics Data System (ADS)

    Chen, Tong; Yuen, Peter; Hong, Kan; Tsitiridis, Aristeidis; Kam, Firmin; Jackman, James; James, David; Richardson, Mark; Oxford, William; Piper, Jonathan; Thomas, Francis; Lightman, Stafford

    2009-09-01

    Emotional or physical stresses induce a surge of adrenaline in the blood stream under the command of the sympathetic nerve system, which, cannot be suppressed by training. The onset of this alleviated level of adrenaline triggers a number of physiological chain reactions in the body, such as dilation of pupil and an increased feed of blood to muscles etc. This paper reports for the first time how Electro-Optics (EO) technologies such as hyperspectral [1,2] and thermal imaging[3] methods can be used for the detection of stress remotely. Preliminary result using hyperspectral imaging technique has shown a positive identification of stress through an elevation of haemoglobin oxygenation saturation level in the facial region, and the effect is seen more prominently for the physical stressor than the emotional one. However, all results presented so far in this work have been interpreted together with the base line information as the reference point, and that really has limited the overall usefulness of the developing technology. The present result has highlighted this drawback and it prompts for the need of a quantitative assessment of the oxygenation saturation and to correlate it directly with the stress level as the top priority of the next stage of research.

  4. Advanced materials and techniques for fibre-optic sensing

    NASA Astrophysics Data System (ADS)

    Henderson, Philip J.

    2014-06-01

    Fibre-optic monitoring systems came of age in about 1999 upon the emergence of the world's first significant commercialising company - a spin-out from the UK's collaborative MAST project. By using embedded fibre-optic technology, the MAST project successfully measured transient strain within high-performance composite yacht masts. Since then, applications have extended from smart composites into civil engineering, energy, military, aerospace, medicine and other sectors. Fibre-optic sensors come in various forms, and may be subject to embedment, retrofitting, and remote interrogation. The unique challenges presented by each implementation require careful scrutiny before widespread adoption can take place. Accordingly, various aspects of design and reliability are discussed spanning a range of representative technologies that include resonant microsilicon structures, MEMS, Bragg gratings, advanced forms of spectroscopy, and modern trends in nanotechnology. Keywords: Fibre-optic sensors, fibre Bragg gratings, MEMS, MOEMS, nanotechnology, plasmon.

  5. Current achievements of nanoparticle applications in developing optical sensing and imaging techniques

    NASA Astrophysics Data System (ADS)

    Choi, Jong-ryul; Shin, Dong-Myeong; Song, Hyerin; Lee, Donghoon; Kim, Kyujung

    2016-11-01

    Metallic nanostructures have recently been demonstrated to improve the performance of optical sensing and imaging techniques due to their remarkable localization capability of electromagnetic fields. Particularly, the zero-dimensional nanostructure, commonly called a nanoparticle, is a promising component for optical measurement systems due to its attractive features, e.g., ease of fabrication, capability of surface modification and relatively high biocompatibility. This review summarizes the work to date on metallic nanoparticles for optical sensing and imaging applications, starting with the theoretical backgrounds of plasmonic effects in nanoparticles and moving through the applications in Raman spectroscopy and fluorescence biosensors. Various efforts for enhancing the sensitivity, selectivity and biocompatibility are summarized, and the future outlooks for this field are discussed. Convergent studies in optical sensing and imaging have been emerging field for the development of medical applications, including clinical diagnosis and therapeutic applications.

  6. Optical technique for photovoltaic spatial current response measurements using compressive sensing and random binary projections

    NASA Astrophysics Data System (ADS)

    Cashmore, Matt. T.; Koutsourakis, George; Gottschalg, Ralph; Hall, Simon. R. G.

    2016-04-01

    Compressive sensing has been widely used in image compression and signal recovery techniques in recent years; however, it has received limited attention in the field of optical measurement. This paper describes the use of compressive sensing for measurements of photovoltaic (PV) solar cells, using fully random sensing matrices, rather than mapping an orthogonal basis set directly. Existing compressive sensing systems optically image the surface of the object under test, this contrasts with the method described, where illumination patterns defined by precalculated sensing matrices, probe PV devices. We discuss the use of spatially modulated light fields to probe a PV sample to produce a photocurrent map of the optical response. This allows for faster measurements than would be possible using traditional translational laser beam induced current techniques. Results produced to a 90% correlation to raster scanned measurements, which can be achieved with under 25% of the conventionally required number of data points. In addition, both crack and spot type defects are detected at resolutions comparable to electroluminescence techniques, with 50% of the number of measurements required for a conventional scan.

  7. An optical fiber sensing technique for temperature distribution measurements in microwave heating

    NASA Astrophysics Data System (ADS)

    Wada, Daichi; Sugiyama, Jun-ichi; Zushi, Hiroaki; Murayama, Hideaki

    2015-08-01

    We introduce an optical fiber sensing technique that can measure the temperature distributions along a fiber during microwave heating. We used a long-length fiber Bragg grating (FBG) as an electromagnetic-immune sensor and interrogated temperature distributions along the FBG by an optical frequency domain reflectometry. Water in a glass tube with a length of 820 mm was heated in a microwave oven, and its temperature distribution along the glass tube was measured using the sensing system. The temperature distribution was obtained in 5 mm intervals. Infrared radiometry was also used to compare the temperature measurement results. Time and spatial variations of the temperature distribution profiles were monitored for several microwave input powers. The results clearly depict inhomogeneous temperature profiles. The applicability and effectiveness of the optical fiber distributed measurement technique in microwave heating are demonstrated.

  8. Classification of remotely sensed data using OCR-inspired neural network techniques. [Optical Character Recognition

    NASA Technical Reports Server (NTRS)

    Kiang, Richard K.

    1992-01-01

    Neural networks have been applied to classifications of remotely sensed data with some success. To improve the performance of this approach, an examination was made of how neural networks are applied to the optical character recognition (OCR) of handwritten digits and letters. A three-layer, feedforward network, along with techniques adopted from OCR, was used to classify Landsat-4 Thematic Mapper data. Good results were obtained. To overcome the difficulties that are characteristic of remote sensing applications and to attain significant improvements in classification accuracy, a special network architecture may be required.

  9. Classification of remotely sensed data using OCR-inspired neural network techniques. [Optical Character Recognition

    NASA Technical Reports Server (NTRS)

    Kiang, Richard K.

    1992-01-01

    Neural networks have been applied to classifications of remotely sensed data with some success. To improve the performance of this approach, an examination was made of how neural networks are applied to the optical character recognition (OCR) of handwritten digits and letters. A three-layer, feedforward network, along with techniques adopted from OCR, was used to classify Landsat-4 Thematic Mapper data. Good results were obtained. To overcome the difficulties that are characteristic of remote sensing applications and to attain significant improvements in classification accuracy, a special network architecture may be required.

  10. Distributed fiber optical HC leakage and pH sensing techniques for implementation into smart structures

    NASA Astrophysics Data System (ADS)

    Buerck, Jochen M.; Vogel, Bernhard H.; Roth, Siegmar; Ebrahimi, Sasan; Kraemer, Karl

    2004-07-01

    Interaction of target molecules with the evanescent wave of light guided in optical fibers is among the most promising sensing schemes for building up smart chemical sensor technologies. If the technique of optical time domain reflectometry (OTDR) is combined with silicone-clad quartz glass fibers distributed chemical sensing is possible. Hydrocarbon (HC) detection and location is done by automated identification of the position of the corresponding step drop (light loss) in the backscatter signal induced by local refractive index increase in the silicone cladding due to a penetrating HC compound. A commercially available mini-OTDR was adapted to sensing fibers of up to nearly 2-kilometer length and location of typical HC fuels could be demonstrated. The instrument is applicable for fuel leakage monitoring in large technical installations such as tanks or pipelines with spatial resolution down to 1 m. A similar technique using measurements in the Vis spectral range is being developed for health monitoring of large structures, e.g., for early detection of corrosion caused by water ingress and pH changes in reinforced concrete. Here, a pH indicator dye and a phase transfer reagent are immobilized in the originally hydrophobic fiber cladding, leading to a pH induced absorption increase and a step drop signal in the backscatter curve. The configuration of the distributed sensing cables, the instrumental setups, and examples for HC and pH sensing are presented.

  11. Optical sensing of peroxide using ceria nanoparticles via fluorescence quenching technique

    NASA Astrophysics Data System (ADS)

    Shehata, Nader; Samir, Effat; Gaballah, Soha; Salah, Mohammed

    2016-07-01

    This study introduces the application of ceria nanoparticles (NPs) as an optical sensor for peroxide using fluorescence quenching technique. Our synthesized ceria NPs have the ability to adsorb peroxides via its oxygen vacancies. Ceria NPs solution with added variable concentrations of hydrogen peroxides is exposed through near-UV excitation and the detected visible fluorescent emission is found to be at ˜520 nm. The fluorescent intensity peak is found to be reduced with increasing the peroxide concentrations due to static fluorescence quenching technique. The relative intensity change of the visible fluorescent emission has been reduced to more than 50% at added peroxide concentrations up to 10 wt. %. In order to increase ceria peroxides sensing sensitivity, lanthanide elements such as samarium (Sm) are used as ceria NPs dopant. This research work could be applied further in optical sensors of radicals in biomedical engineering and environmental monitoring.

  12. Fabricate Optical Microfiber by Using Flame Brushing Technique and Coated with Polymer Polyaniline for Sensing Application

    NASA Astrophysics Data System (ADS)

    Razak, N. A.; Hamida, B. A.; Irawati, N.; Habaebi, M. H.

    2017-06-01

    Adiabaticity is one of the essential criteria in producing good fabricated tapered fibers. Good tapered fibers can be use in sensor application such as humidity sensor, temperature sensor and refractive index sensor. In this paper, good tapering silica fiber is produced by using flame brushing technique and then, the microfiber is coated with polymer Polyaniline (PAni) to sense different type of alcohols with different concentrations. The outcome of this experiment gives excellent repeatability in the detection of alcohol sensing with a sensitivity of 0.1332 μW/% and a resolution of 3.764%. In conclusion, conducting polymer coated optical microfiber sensor for alcohol detection with low cost, effective and simple set-up was successfully achieved in this study.

  13. High performance optical encryption based on computational ghost imaging with QR code and compressive sensing technique

    NASA Astrophysics Data System (ADS)

    Zhao, Shengmei; Wang, Le; Liang, Wenqiang; Cheng, Weiwen; Gong, Longyan

    2015-10-01

    In this paper, we propose a high performance optical encryption (OE) scheme based on computational ghost imaging (GI) with QR code and compressive sensing (CS) technique, named QR-CGI-OE scheme. N random phase screens, generated by Alice, is a secret key and be shared with its authorized user, Bob. The information is first encoded by Alice with QR code, and the QR-coded image is then encrypted with the aid of computational ghost imaging optical system. Here, measurement results from the GI optical system's bucket detector are the encrypted information and be transmitted to Bob. With the key, Bob decrypts the encrypted information to obtain the QR-coded image with GI and CS techniques, and further recovers the information by QR decoding. The experimental and numerical simulated results show that the authorized users can recover completely the original image, whereas the eavesdroppers can not acquire any information about the image even the eavesdropping ratio (ER) is up to 60% at the given measurement times. For the proposed scheme, the number of bits sent from Alice to Bob are reduced considerably and the robustness is enhanced significantly. Meantime, the measurement times in GI system is reduced and the quality of the reconstructed QR-coded image is improved.

  14. An ameliorative technique for distributed Brillouin-based fiber optics sensing

    NASA Astrophysics Data System (ADS)

    Yang, Xing-hong; Li, Yong-qian; Yang, Zhi; Yoshino, Toshihiko

    2008-12-01

    This paper reports an ameliorative technique for distributed fiber optics sensing based on Brillouin optical time-domain reflectometry (BOTDR) and Brillouin optical-fiber time-domain analysis (BOTDA). Because the electro-optic modulator in BOTDR system has a finite extinction ratio, the pulsed laser always contains a CW component, which is hereafter called leakage. The frequency of the leakage is pv which is the same as that of the pulse, and the frequency of the Stokes wave is sv. The frequency of the acoustic wave bv at each point along the fiber matches the beat frequency of the leakage and the Stokes wave. As a result, when given an appropriate extinction ratio, the leakage will have a biggish effect on the Stokes wave, which is the same as the function between the continuous wave and the Stokes in BOTDA system. The Stokes component in spontaneous Brillouin scattering (SPBS) is amplified by the leakage along the distance when it backs to the laser end, which is the well known stimulated Brillouin scattering (SBS) phenomena. So long as the distance from the point where the SPBS engender to the laser end is long, the intensity of the SBS signal is relatively large owing to the longer amplified interval. In BOTDR system, when setting the extinction ratio at 20dB, using the SBS signal we can achieve a SNR which is approximately 5 dB greater than that of traditional system and the dynamic range performance 3 dB greater. Utilizing this new technique in BOTDR system it also has an ascendency compared with BOTDA system in respect that it access to only one end of the fiber with probe pulse light.

  15. Alignment signal extraction of the optically degenerate RSE interferometer using the wave front sensing technique

    NASA Astrophysics Data System (ADS)

    Sato, S.; Kawamura, S.

    2008-07-01

    The alignment sensing and control scheme of the resonant sideband extraction interferometer is still an unsettled issue for the next-generation gravitational wave antennas. The issue is that it is difficult to extract separate error signals for all 12 angular degrees of freedom, which is mainly arising from the complexity of the optical system and cavity 'degeneracy'. We have suggested a new sensing scheme giving reasonably separated signals which is fully compatible with the length sensing scheme. The key of this idea is to resolve the 'degeneracy' of the optical cavities. By choosing an appropriate Gouy phase for the degenerate cavities, alignment error signals with much less admixtures can be extracted.

  16. Subsea downhole optical sensing

    NASA Astrophysics Data System (ADS)

    McStay, D.; Shiach, G.; McAvoy, S.

    2009-07-01

    The potential for subsea downhole optical fibre sensing to optimize hydrocarbon production and hence contribute to enhanced oil recovery is described. The components of susbea downhole optical sensing systems are reviewed and the performance of a new subsea optical fibre feed-through for downhole optical fibre sensing reported.

  17. Estimating biophysical properties of eucalyptus plantations using optical remote sensing techniques

    NASA Astrophysics Data System (ADS)

    Soares, Joao V.; Xavier, Alexandre C.; de Almeida, Auro C.; da Costa Freitas, Corina

    1998-12-01

    The feasibility of the inversion of optical remote sensing products to measure critical biophysical properties of Eucalyptus Forests at regional scales is investigated here. The biophysical variables used were leaf area Index, LAI, Diameter at Breast Height, DBH, Height and Age of Eucalyptus stands pertaining to a combination of different genetic materials (E. urophylla x E. grandis hybrids) and propagating systems (seeds or cuttings) and management system (planting and coppicing). The field sampling was done daily during 3 months, from April to June 1997, and covered 130 stands of minimum sizes of 9 hectares, within an Eucalyptus farming area of about 800 km2, centered at 19 degrees South, 42 degrees West, Brazil. The stands ranged from 12 to 84 months old. The measurements of LAI were done using two pairs of LAI-2000 (LICOR) under conditions of diffuse light. The Normalized Difference Vegetation Index, NDVI, and the Soil Adjusted Vegetation Index, SAVI, were derived from a LANDSAT-TM image acquired on June 5, 1997. Furthermore, a mixture model technique was applied to derive three new parameters: fraction of green vegetation, FGV, fraction of shadow, FSH, and fraction of soil, FS. Regression analysis were done between biophysical variables and remote sensing products. Linear correlation with coefficients of determination, R2, as high as 0.8 were found between LAI versus FGV and LAI versus SAVI, on all genetic materials. In general, SAVI was shown to give better estimates of LAI than NDVI, which is explained by the openings in the canopy as the Eucalyptus grow older. The correlation with the other biophysical variables (Height and DBH) were also shown to be significant, although the R2 ranged from 0.4 to 0.6. The correlation between FGV and SAVI was higher than 90% such that they can be used to estimate Eucalyptus biophysical parameters with the same statistical significance.

  18. Demonstration of distributed fiber-optic temperature sensing with PM fiber using polarization crosstalk analysis technique

    NASA Astrophysics Data System (ADS)

    Su, Hongxin; Zhao, Ziwei; Feng, Ting; Ding, Dongliang; Li, Zhihong; Yao, X. Steve

    2016-11-01

    Polarization crosstalk is a phenomenon that the powers of two orthogonal polarization modes propagating in a polarization maintaining (PM) fiber couple into each other. Because there is certain mathematical relationship between the polarization crosstalk signals and external perturbations such as stress and temperature variations, stress and temperature sensing in PM fiber can be simultaneously achieved by measuring the strengths and locations of polarization crosstalk signals. In this paper, we report what we believe the first distributed temperature sensing demonstration using polarization crosstalk analysis in PM fibers. Firstly, by measuring the spacing changes between two crosstalk peaks at different fiber length locations, we obtained the temperature sensing coefficient (TSC) of approximately -0.73 μm/(°C•m), which means that the spacing between two crosstalk peaks induced at two locations changes by 0.73 μm when the temperature changes by 1 °C over a fiber length of 1 meter. Secondly, in order to bring different temperature values at different axial locations along a PM fiber to verify the distributed temperature sensing, four heating-strips are used to heat different fiber sections of the PM fiber under test, and the temperatures measured by the proposed fiber sensing method according to the obtained TSC are almost consistent with those of heating-strips measured by a thermoelectric thermometer. As a new type of distributed fiber temperature sensing technique, we believe that our method will find broad applications in the near future.

  19. Mechanism analysis on biofouling detection based on optical fiber sensing technique

    NASA Astrophysics Data System (ADS)

    Ma, Huiping; Yuan, Feng; Liu, Yongmeng; Jiang, Xiuzhen

    2010-08-01

    More attention is paid to on-line monitoring of biofouling in industrial water process systems. Based on optical fiber sensing technology, biofouling detection mechanism is put forward in the paper. With biofouling formation, optical characteristics and the relation between light intensity and refractive index studied, schematic diagram of optical fiber self-referencing detecting system and technological flowchart are presented. Immunity to electromagnetic interference and other influencing factors by which the precision is great improved is also remarkable characteristic. Absorption spectrum of fluid medium molecule is measured by infrared spectrum and impurity is analyzed by character fingerprints of different liquid. Other pollutant source can be identified by means of infrared spectrum and arithmetic research of artificial neural networks (ANN) technology. It can be used in other fields such as mining, environment protection, medical treatment and transportation of oil, gas and water.

  20. A streak camera based fiber optic pulsed polarimetry technique for magnetic sensing to sub-mm resolution.

    PubMed

    Smith, R J; Weber, T E

    2016-11-01

    The technique of fiber optic pulsed polarimetry, which provides a distributed (local) measurement of the magnetic field along an optical fiber, has been improved to the point where, for the first time, photocathode based optical detection of backscatter is possible with sub-mm spatial resolutions. This has been realized through the writing of an array of deterministic fiber Bragg gratings along the fiber, a so-called backscatter-tailored optical fiber, producing a 34 000-fold increase in backscatter levels over Rayleigh. With such high backscatter levels, high repetition rate lasers are now sufficiently bright to allow near continuous field sensing in both space and time with field resolutions as low as 0.005 T and as high as 170 T over a ∼mm interval given available fiber materials.

  1. Novel Technique and Technologies for Active Optical Remote Sensing of Greenhouse Gases

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta

    2017-01-01

    The societal benefits of understanding climate change through identification of global carbon dioxide sources and sinks led to the desired NASA's active sensing of carbon dioxide emissions over nights, days, and seasons (ASCENDS) space-based missions of global carbon dioxide measurements. For more than 15 years, NASA Langley Research Center (LaRC) have developed several carbon dioxide active remote sensors using the differential absorption lidar (DIAL) technique operating at the two-micron wavelength. Currently, an airborne two-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development. This IPDA lidar measures carbon dioxide as well as water vapor, the dominant interfering molecule on carbon dioxide remote sensing. Advancement of this triple-pulse IPDA lidar development is presented.

  2. Optical sensing of peroxide using ceria nanoparticles via fluorescence quenching technique

    NASA Astrophysics Data System (ADS)

    Shehata, N.; Samir, E.; Gaballah, S.

    2016-04-01

    This study introduces the application of small ceria nanoparticles (NPs) as optical sensor for peroxide using fluorescence quenching technique. Our synthesized ceria nanoparticles have the ability to adsorb peroxides via its oxygen vacancies. Ceria nanoparticles (NPs) solution with added variable concentrations of hydrogen peroxides is exposed through near UV excitation and the detected visible fluorescent emission is found to be at 520nm, with reduced peak intensity peaks with increasing the peroxide concentrations due to static fluorescence quenching technique. The relative intensity change of the visible fluorescent emission has been reduced to more than 50% at added peroxide concentrations up to 10 wt.%. This research work could be applied further in optical sensors of radicals in biomedical engineering and environmental monitoring.

  3. Sub-THz-range linearly chirped signals characterized using linear optical sampling technique to enable sub-millimeter resolution for optical sensing applications.

    PubMed

    Wang, Shuai; Fan, Xinyu; Wang, Bin; Yang, Guangyao; He, Zuyuan

    2017-05-01

    Pulse compression technique is a particularly competitive method that enables both high spatial resolution and dynamic range in coherent radar and distributed fiber sensing systems. Up to now, the frequency bandwidths of most pulse compression techniques are restricted to tens of GHz. In this paper, we propose an all-optic sub-THz-range linearly chirped optical source and a large-bandwidth detection system to characterize it. Taking advantage of the chromatic dispersion effect, ultrashort optical pulses are stretched to be ~10 ns linearly chirped pulses with sub-THz range, which yields a large time-bandwidth product of 4500, a high compression ratio of 4167 and a chirp rate of 45 GHz/ns. The generated waveform is characterized with high precision thanks to the large detection bandwidth of linear optical sampling technique. A spatial resolution of 120 μm and an extinction ratio of 20.4 dB is demonstrated by using this technique, which paves the way for ultra-high spatial resolution and long range sensing applications such as LIDAR and optical reflectometry.

  4. Vibration monitoring of a helicopter blade model using the optical fiber distributed strain sensing technique.

    PubMed

    Wada, Daichi; Igawa, Hirotaka; Kasai, Tokio

    2016-09-01

    We demonstrate a dynamic distributed monitoring technique using a long-length fiber Bragg grating (FBG) interrogated by optical frequency domain reflectometry (OFDR) that measures strain at a speed of 150 Hz, spatial resolution of 1 mm, and measurement range of 20 m. A 5 m FBG is bonded to a 5.5 m helicopter blade model, and vibration is applied by the step relaxation method. The time domain responses of the strain distributions are measured, and the blade deflections are calculated based on the strain distributions. Frequency response functions are obtained using the time domain responses of the calculated deflection induced by the preload release, and the modal parameters are retrieved. Experimental results demonstrated the dynamic monitoring performances and the applicability to the modal analysis of the OFDR-FBG technique.

  5. Coating-free reflection technique for fiber-optic sensors based on multimode interference: A temperature sensing study

    NASA Astrophysics Data System (ADS)

    Taue, Shuji; Takahashi, Tsuyoshi; Fukano, Hideki

    2016-08-01

    A novel reflection technique for use in fiber-optic sensors is investigated and applied to a multimode interference structure. The reflectivity at a fiber end face is increased with two operations. Firstly, the light intensity is increased toward the periphery of the end-face by adjusting the fiber length, which is determined theoretically. Secondly, the fiber end-face is deformed into an ellipsoid by heating it with a gas torch. The deformed shape is characterized from microscopic images. The reflected light intensity is increased by more than 10 dB as a result of controlling the fiber length and deforming its end-face. Temperature sensing was performed using the reflection-type multimode interference structure immersed in temperature-controlled silicone oil. The resulting sensitivity was 0.028 °C for a 29.60 mm sensing region, achieved without using any reflection coating.

  6. An air flow sensor for neonatal mechanical ventilation applications based on a novel fiber-optic sensing technique

    SciTech Connect

    Battista, L.; Sciuto, S. A.; Scorza, A.

    2013-03-15

    In this work, a simple and low-cost air flow sensor, based on a novel fiber-optic sensing technique has been developed for monitoring air flows rates supplied by a neonatal ventilator to support infants in intensive care units. The device is based on a fiber optic sensing technique allowing (a) the immunity to light intensity variations independent by measurand and (b) the reduction of typical shortcomings affecting all biomedical fields (electromagnetic interference and patient electrical safety). The sensing principle is based on the measurement of transversal displacement of an emitting fiber-optic cantilever due to action of air flow acting on it; the fiber tip displacement is measured by means of a photodiode linear array, placed in front of the entrance face of the emitting optical fiber in order to detect its light intensity profile. As the measurement system is based on a detection of the illumination pattern, and not on an intensity modulation technique, it results less sensitive to light intensity fluctuation independent by measurand than intensity-based sensors. The considered technique is here adopted in order to develop two different configurations for an air flow sensor suitable for the measurement of air flow rates typically occurring during mechanical ventilation of newborns: a mono-directional and a bi-directional transducer have been proposed. A mathematical model for the air flow sensor is here proposed and a static calibration of two different arrangements has been performed: a measurement range up to 3.00 Multiplication-Sign 10{sup -4} m{sup 3}/s (18.0 l/min) for the mono-directional sensor and a measurement range of {+-}3.00 Multiplication-Sign 10{sup -4} m{sup 3}/s ({+-}18.0 l/min) for the bi-directional sensor are experimentally evaluated, according to the air flow rates normally encountered during tidal breathing of infants with a mass lower than 10 kg. Experimental data of static calibration result in accordance with the proposed

  7. An air flow sensor for neonatal mechanical ventilation applications based on a novel fiber-optic sensing technique

    NASA Astrophysics Data System (ADS)

    Battista, L.; Sciuto, S. A.; Scorza, A.

    2013-03-01

    In this work, a simple and low-cost air flow sensor, based on a novel fiber-optic sensing technique has been developed for monitoring air flows rates supplied by a neonatal ventilator to support infants in intensive care units. The device is based on a fiber optic sensing technique allowing (a) the immunity to light intensity variations independent by measurand and (b) the reduction of typical shortcomings affecting all biomedical fields (electromagnetic interference and patient electrical safety). The sensing principle is based on the measurement of transversal displacement of an emitting fiber-optic cantilever due to action of air flow acting on it; the fiber tip displacement is measured by means of a photodiode linear array, placed in front of the entrance face of the emitting optical fiber in order to detect its light intensity profile. As the measurement system is based on a detection of the illumination pattern, and not on an intensity modulation technique, it results less sensitive to light intensity fluctuation independent by measurand than intensity-based sensors. The considered technique is here adopted in order to develop two different configurations for an air flow sensor suitable for the measurement of air flow rates typically occurring during mechanical ventilation of newborns: a mono-directional and a bi-directional transducer have been proposed. A mathematical model for the air flow sensor is here proposed and a static calibration of two different arrangements has been performed: a measurement range up to 3.00 × 10-4 m3/s (18.0 l/min) for the mono-directional sensor and a measurement range of ±3.00 × 10-4 m3/s (±18.0 l/min) for the bi-directional sensor are experimentally evaluated, according to the air flow rates normally encountered during tidal breathing of infants with a mass lower than 10 kg. Experimental data of static calibration result in accordance with the proposed theoretical model: for the mono-directional configuration, the

  8. An air flow sensor for neonatal mechanical ventilation applications based on a novel fiber-optic sensing technique.

    PubMed

    Battista, L; Sciuto, S A; Scorza, A

    2013-03-01

    In this work, a simple and low-cost air flow sensor, based on a novel fiber-optic sensing technique has been developed for monitoring air flows rates supplied by a neonatal ventilator to support infants in intensive care units. The device is based on a fiber optic sensing technique allowing (a) the immunity to light intensity variations independent by measurand and (b) the reduction of typical shortcomings affecting all biomedical fields (electromagnetic interference and patient electrical safety). The sensing principle is based on the measurement of transversal displacement of an emitting fiber-optic cantilever due to action of air flow acting on it; the fiber tip displacement is measured by means of a photodiode linear array, placed in front of the entrance face of the emitting optical fiber in order to detect its light intensity profile. As the measurement system is based on a detection of the illumination pattern, and not on an intensity modulation technique, it results less sensitive to light intensity fluctuation independent by measurand than intensity-based sensors. The considered technique is here adopted in order to develop two different configurations for an air flow sensor suitable for the measurement of air flow rates typically occurring during mechanical ventilation of newborns: a mono-directional and a bi-directional transducer have been proposed. A mathematical model for the air flow sensor is here proposed and a static calibration of two different arrangements has been performed: a measurement range up to 3.00 × 10(-4) m(3)∕s (18.0 l∕min) for the mono-directional sensor and a measurement range of ±3.00 × 10(-4) m(3)∕s (±18.0 l∕min) for the bi-directional sensor are experimentally evaluated, according to the air flow rates normally encountered during tidal breathing of infants with a mass lower than 10 kg. Experimental data of static calibration result in accordance with the proposed theoretical model: for the mono

  9. Yangon River Geomorphology Identification and its Enviromental Imapacts Analsysi by Optical and Radar Sensing Techniques

    NASA Astrophysics Data System (ADS)

    Lwin, A.; Khaing, M. M.

    2012-07-01

    The Yangon river, also known as the Rangoon river, is about 40 km long (25miles), and flows from southern Myanmar as an outlet of the Irrawaddy (Ayeyarwady) river into the Ayeyarwady delta. The Yangon river drains the Pegu Mountains; both the Yangon and the Pathein rivers enter the Ayeyarwady at the delta. Fluvial geomorphology is based primarily on rivers of manageable dimensions. The emphasis is on geomorphology, sedimentology of Yangon river and techniques for their identification and management. Present techniques such as remote sensing have made it easier to investigate and interpret in details analysis of river geomorphology. In this paper, attempt has been made the complicated issues of geomorphology, sedimentation patterns and management of river system and evolution studied. The analysis was carried out for the impact of land use/ land cover (LULC) changes on stream flow patterns. The hydrologic response to intense, flood producing rainfall events bears the signatures of the geomorphic structure of the channel network and of the characteristic slope lengths defining the drainage density of the basin. The interpretation of the hydrologic response as the travel time distribution of a water particle randomly injected in a distributed manner across the landscape inspired many geomorphic insights. In 2008, Cyclone Nargis was seriously damaged to mangrove area and its biodiversity system in and around of Yangon river terraces. A combination of digital image processing techniques was employed for enhancement and classification process. It is observed from the study that middle infra red band (0.77mm - 0.86mm) is highly suitable for mapping mangroves. Two major classes of mangroves, dense and open mangroves were delineated from the digital data.

  10. Spectrum sensing of trace C(2)H(2) detection in differential optical absorption spectroscopy technique.

    PubMed

    Chen, Xi; Dong, Xiaopeng

    2014-09-10

    An improved algorithm for trace C(2)H(2) detection is presented in this paper. The trace concentration is accurately calculated by focusing on the absorption spectrum from the frequency domain perspective. The advantage of the absorption spectroscopy frequency domain algorithm is its anti-interference capability. First, the influence of the background noise on the minimum detectable concentration is greatly reduced. Second, the time-consuming preprocess of spectra calibration in the differential optical absorption spectroscopy technique is skipped. Experimental results showed the detection limit of 50 ppm is achieved at a lightpath length of 0.2 m. This algorithm can be used in real-time spectrum analysis with high accuracy.

  11. Nanostructured Substrates for Optical Sensing

    PubMed Central

    Kemling, Jonathan W.; Qavi, Abraham J.; Bailey, Ryan C.

    2011-01-01

    Sensors that change color have the advantages of versatility, ease of use, high sensitivity, and low cost. The recent development of optically based chemical sensing platforms has increasingly employed substrates manufactured with advanced processing or fabrication techniques to provide precise control over shape and morphology of the sensor micro- and nano-structure. New sensors have resulted with improved capabilities for a number of sensing applications, including the detection of biomolecules and environmental monitoring. This perspective focuses on recent optical sensor devices that utilize nanostructured substrates. PMID:22174955

  12. Specificity of noninvasive blood glucose sensing using optical coherence tomography technique: a pilot study

    NASA Astrophysics Data System (ADS)

    Larin, Kirill V.; Motamedi, Massoud; Ashitkov, Taras V.; Esenaliev, Rinat O.

    2003-05-01

    Noninvasive monitoring of blood glucose concentration in diabetic patients would significantly reduce complications and mortality associated with this disease. In this paper, we experimentally and theoretically studied specificity of noninvasive blood glucose monitoring with the optical coherence tomography (OCT) technique. OCT images and signals were obtained from skin of Yucatan micropigs and New Zealand rabbits. Obtained results demonstrate that: (1) several body osmolytes may change the refractive index mismatch between the interstitial fluid (ISF) and scattering centres in tissue, however the effect of the glucose is approximately one to two orders of magnitude higher; (2) an increase of the ISF glucose concentration in the physiological range (3-30 mM) may decrease the scattering coefficient by 0.22% mM-1 due to cell volume change; (3) stability of the OCT signal slope is dependent on tissue heterogeneity and motion artefacts; and (4) moderate skin temperature fluctuations (+/-1 °C) do not decrease accuracy and specificity of the OCT-based glucose sensor, however substantial skin heating or cooling (several °C) significantly change the OCT signal slope. These results suggest that the OCT technique may provide blood glucose concentration monitoring with sufficient specificity under normal physiological conditions.

  13. Monitoring of Emissions From a Refinery Tank Farm Using a Combination of Optical Remote Sensing Techniques

    NASA Astrophysics Data System (ADS)

    Polidori, A.; Tisopulos, L.; Pikelnaya, O.; Mellqvist, J.; Samuelsson, J.; Marianne, E.; Robinson, R. A.; Innocenti, F.; Finlayson, A.; Hashmonay, R.

    2016-12-01

    Despite great advances in reducing air pollution, the South Coast Air Basin (SCAB) still faces challenges to attain federal health standards for air quality. Refineries are large sources of ozone precursors and, hence contribute to the air quality problems of the region. Additionally, petrochemical facilities are also sources of other hazardous air pollutants (HAP) that adversely affect human health, for example aromatic hydrocarbons. In order to assure safe operation, decrease air pollution and minimize population exposure to HAP the South Coast Air Quality Management District (SCAQMD) has a number of regulations for petrochemical facilities. However, significant uncertainties still exist in emission estimates and traditional monitoring techniques often do not allow for real-time emission monitoring. In the fall of 2015 the SCAQMD, Fluxsense Inc., the National Physical Laboratory (NPL), and Atmosfir Optics Ltd. conducted a measurement study to characterize and quantify gaseous emissions from the tank farm of one of the largest oil refineries in the SCAB. Fluxsense used a vehicle equipped with Solar Occultation Flux (SOF), Differential Optical Absorption Spectroscopy (DOAS), and Extractive Fourier Transform Infrared (FTIR) spectroscopy instruments. Concurrently, NPL operated their Differential Absorption Lidar (DIAL) system. Both research groups quantified emissions from the entire tank farm and identified fugitive emission sources within the farm. At the same time, Atmosfir operated an Open Path FTIR (OP-FTIR) spectrometer along the fenceline of the tank farm. During this presentation we will discuss the results of the emission measurements from the tank farm of the petrochemical facility. Emission rates resulting from measurements by different ORS methods will be compared and discussed in detail.

  14. Multichannel optical sensing device

    DOEpatents

    Selkowitz, S.E.

    1985-08-16

    A multichannel optical sensing device is disclosed, for measuring the outdoor sky luminance or illuminance or the luminance or illuminance distribution in a room, comprising a plurality of light receptors, an optical shutter matrix including a plurality of liquid crystal optical shutter elements operable by electrical control signals between light transmitting and light stopping conditions, fiber optical elements connected between the receptors and the shutter elements, a microprocessor based programmable control unit for selectively supplying control signals to the optical shutter elements in a programmable sequence, a photodetector including an optical integrating spherical chamber having an input port for receiving the light from the shutter matrix and at least one detector element in the spherical chamber for producing output signals corresponding to the light, and output units for utilizing the output signals including a storage unit having a control connection to the microprocessor based programmable control unit for storing the output signals under the sequence control of the programmable control unit.

  15. Multichannel optical sensing device

    DOEpatents

    Selkowitz, Stephen E.

    1990-01-01

    A multichannel optical sensing device is disclosed, for measuring the outr sky luminance or illuminance or the luminance or illuminance distribution in a room, comprising a plurality of light receptors, an optical shutter matrix including a plurality of liquid crystal optical shutter elements operable by electrical control signals between light transmitting and light stopping conditions, fiber optic elements connected between the receptors and the shutter elements, a microprocessor based programmable control unit for selectively supplying control signals to the optical shutter elements in a programmable sequence, a photodetector including an optical integrating spherical chamber having an input port for receiving the light from the shutter matrix and at least one detector element in the spherical chamber for producing output signals corresponding to the light, and output units for utilizing the output signals including a storage unit having a control connection to the microprocessor based programmable control unit for storing the output signals under the sequence control of the programmable control unit.

  16. Fiber Loop Ringdown — a Time-Domain Sensing Technique for Multi-Function Fiber Optic Sensor Platforms: Current Status and Design Perspectives

    PubMed Central

    Wang, Chuji

    2009-01-01

    Fiber loop ringdown (FLRD) utilizes an inexpensive telecommunications light source, a photodiode, and a section of single-mode fiber to form a uniform fiber optic sensor platform for sensing various quantities, such as pressure, temperature, strain, refractive index, chemical species, biological cells, and small volume of fluids. In FLRD, optical losses of a light pulse in a fiber loop induced by changes in a quantity are measured by the light decay time constants. FLRD measures time to detect a quantity; thus, FLRD is referred to as a time-domain sensing technique. FLRD sensors have near real-time response, multi-pass enhanced high-sensitivity, and relatively low cost (i.e., without using an optical spectral analyzer). During the last eight years since the introduction of the original form of fiber ringdown spectroscopy, there has been increasing interest in the FLRD technique in fiber optic sensor developments, and new application potential is being explored. This paper first discusses the challenging issues in development of multi-function, fiber optic sensors or sensor networks using current fiber optic sensor sensing schemes, and then gives a review on current fiber optic sensor development using FLRD technique. Finally, design perspectives on new generation, multi-function, fiber optic sensor platforms using FLRD technique are particularly presented. PMID:22408471

  17. Fiber loop ringdown - a time-domain sensing technique for multi-function fiber optic sensor platforms: current status and design perspectives.

    PubMed

    Wang, Chuji

    2009-01-01

    Fiber loop ringdown (FLRD) utilizes an inexpensive telecommunications light source, a photodiode, and a section of single-mode fiber to form a uniform fiber optic sensor platform for sensing various quantities, such as pressure, temperature, strain, refractive index, chemical species, biological cells, and small volume of fluids. In FLRD, optical losses of a light pulse in a fiber loop induced by changes in a quantity are measured by the light decay time constants. FLRD measures time to detect a quantity; thus, FLRD is referred to as a time-domain sensing technique. FLRD sensors have near real-time response, multi-pass enhanced high-sensitivity, and relatively low cost (i.e., without using an optical spectral analyzer). During the last eight years since the introduction of the original form of fiber ringdown spectroscopy, there has been increasing interest in the FLRD technique in fiber optic sensor developments, and new application potential is being explored. This paper first discusses the challenging issues in development of multi-function, fiber optic sensors or sensor networks using current fiber optic sensor sensing schemes, and then gives a review on current fiber optic sensor development using FLRD technique. Finally, design perspectives on new generation, multi-function, fiber optic sensor platforms using FLRD technique are particularly presented.

  18. Fiber-Optic Sensing Technology

    SciTech Connect

    Milnes, M.; Baylor, L.C.; Bave, S.

    1996-10-24

    This article offers a basic review of fiber-optic sensing technology, or more specifically, fiber-optic sensing technology as applied to the qualitative or quantitative identification of a chemical sample, and how it works,

  19. Optical techniques for sensing and measurement in hostile environments; Proceedings of the Meeting, Orlando, FL, May 21, 22, 1987

    NASA Astrophysics Data System (ADS)

    Gillespie, Calvin H.; Greenwell, Roger A.

    1987-01-01

    Papers are presented on referencing in fiber optic sensing systems, optical fiber chemical sensing networks, and the radiation response of new pure silica fibers. Also considered are a comparison of gamma, neutron, and proton irradiations of multimode fibers, a pinhole camera for hot environment viewing of electron beam materials processing, and the utilization of optical image data from the advanced test accelerator. Other topics include the application of an interferometer spectrometer aboard the Space Shuttle with a payload specialist in the control loop, hydrogen chloride measurements in launch-vehicle exhaust clouds, and a rocket-borne telescoped Fourier transform spectrometer operating at 10 K.

  20. Transmission optical coherence tomography sensing

    NASA Astrophysics Data System (ADS)

    Trull, A. K.; van der Horst, J.; Bijster, J. G.; Kalkman, J.

    2016-04-01

    We demonstrate that Fourier-domain transmission OCT is a versatile tool to measure optical material properties of turbid media. We develop an analytical expression for the transmission OCT signal. Based on this analysis we determine the group refractive index, group velocity dispersion, absorption coefficient, and scattering coefficient. The optical dispersion is accurately measured for glasses, liquids, and water/glucose mixtures. The optical attenuation is measured in the spatial domain and compared to Mie calculations combined with concentration dependent scattering effects. In the wave vector domain the spectral dependence of the optical attenuation is measured and compared to literature values. The developed technique can be used for optical sensing of attenuation and dispersion.

  1. Optical methods for quantitative and label-free sensing in living human tissues: principles, techniques, and applications.

    PubMed

    Wilson, Robert H; Vishwanath, Karthik; Mycek, Mary-Ann

    2016-01-01

    We present an overview of quantitative and label-free optical methods used to characterize living biological tissues, with an emphasis on emerging applications in clinical tissue diagnostics. Specifically, this review focuses on diffuse optical spectroscopy, imaging, and tomography, optical coherence-based techniques, and non-linear optical methods for molecular imaging. The potential for non- or minimally-invasive assessment, quantitative diagnostics, and continuous monitoring enabled by these tissue-optics technologies provides significant promise for continued clinical translation.

  2. Femtosecond laser fabricated multimode fiber sensors interrogated by optical-carrier-based microwave interferometry technique for distributed strain sensing

    NASA Astrophysics Data System (ADS)

    Hua, Liwei; Song, Yang; Huang, Jie; Cheng, Baokai; Zhu, Wenge; Xiao, Hai

    2016-03-01

    A multimode fiber (MMF) based cascaded intrinsic Fabry-Perot interferometers (IFPIs) system is presented and the distributed strain sensing has been experimentally demonstrated by using such system. The proposed 13 cascaded IFPIs have been formed by 14 cascaded reflectors that have been fabricated on a grade index MMF. Each reflector has been made by drawing a line on the center of the cross-section of the MMF through a femtosecond laser. The distance between any two adjacent reflectors is around 100 cm. The optical carrier based microwave interferometry (OCMI) technique has been used to interrogate the MMF based cascaded FPIs system by reading the optical interference information in the microwave domain. The location along with the shift of the interference fringe pattern for each FPI can be resolved though signal processing based on the microwave domain information. The multimode interference showed very little influence to the microwave domain signals. By using such system the strain of 10-4 for each FPI sensor and the spatial resolution of less than 5 cm for the system can be easily achieved.

  3. Discriminative sensing techniques

    NASA Astrophysics Data System (ADS)

    Lewis, Keith

    2008-10-01

    The typical human vision system is able to discriminate between a million or so different colours, yet is able to do this with a chromatic sensor array that is fundamentally based on three different receptors, sensitive to light in the blue, green and red portions of the visible spectrum. Some biological organisms have extended capabilities, providing vision in the ultra-violet, whilst others, such as some species of mantis shrimp reportedly have sixteen different types of photo-receptors. In general the biological imaging sensor takes a minimalist approach to sensing its environment, whereas current optical engineering approaches follow a 'brute' force solution where the challenge of hyperspectral imaging is addressed by various schemes for spatial and spectral dispersion of radiation across existing detector arrays. This results in a problem for others to solve in the processing and communication of the generated hypercube of data. This paper explores the parallels between some of those biological systems and the various design concepts being developed for discriminative imaging, drawing on activity supported by the UK Electro-Magnetic Remote Sensing Defence Technology Centre (EMRS DTC).

  4. Curcumin based optical sensing of fluoride in organo-aqueous media using irradiation technique

    NASA Astrophysics Data System (ADS)

    Venkataraj, Roopa; Radhakrishnan, P.; Kailasnath, M.

    2017-06-01

    The present work describes the degradation of natural dye Curcumin in organic-aqueous media upon irradiation by a multi-wavelength source of light like mercury lamp. The presence of anions in the solution leads to degradation of Curcumin and this degradation is especially enhanced in the case of fluoride ion. The degradation of Curcumin is investigated by studying the change in its absorption and fluorescence characteristics in organoaqueous solution upon irradiation. A broad detection range of fluoride ranging from 2.3×10-6-2.22×10-3 M points to the potential of the method of visible light irradiation enabling aqueous based sensing of fluoride using Curcumin.

  5. Sensing interrogation technique for fiber-optic interferometer type of sensors based on a single-passband RF filter.

    PubMed

    Chen, Hao; Zhang, Shiwei; Fu, Hongyan; Zhou, Bin; Chen, Nan

    2016-02-08

    In this paper, a sensing interrogation system for fiber-optic interferometer type of sensors by using a single-passband radio-frequency (RF) filter has been proposed and experimentally demonstrated. The fiber-optic interferometer based sensors can give continuous optical sampling, and along with dispersive medium a single-passband RF frequency response can be achieved. The sensing parameter variation on the fiber-optic interferometer type of sensors will affect their free spectrum range, and thus the peak frequency of the RF filter. By tracking the central frequency of the passband the sensing parameter can be demodulated. As a demonstration, in our experiment a fiber Mach-Zehnder interferometer (FMZI) based temperature sensor has been interrogated. By tracking the peak frequency of the passband the temperature variation can be monitored. In our experiment, the sensing responsivity of 10.5 MHz/°C, 20.0 MHz/°C and 41.2 MHz/°C, when the lengths of sensing fiber are 1 m, 2 m and 4 m have been achieved.

  6. Application of optical remote sensing techniques to quantify emissions from urban oil wells, storage tanks, and other small stationary sources

    NASA Astrophysics Data System (ADS)

    Pikelnaya, O.; Polidori, A.; Tisopulos, L.; Mellqvist, J.; Samuelsson, J.; Robinson, R. A.; Innocenti, F.; Perry, S.

    2016-12-01

    Oil fields in the Los Angeles Basin remain very productive even after more than a century-long history of exploration. There are currently over 5,000 active oil wells the South Coast Air Basin (SCAB), with a large portion placed in close proximity of residences, schools and other sensitive receptors. Gaseous emissions from oil wells and equipment related to oil extraction can have a significant impact on air quality. The South Coast Air Quality Management District (SCAQMD) and other state regulatory agencies have a number of rules aimed to reduce Volatile Organic Compound (VOC) emissions and to minimize potential impacts to nearby communities. However, little information is available on the effectiveness of current control measures and magnitude of emissions remain largely unknown. To fill this knowledge gap, in the fall of 2015 the SCAQMD, Fluxsense Inc., the National Physical Laboratory (NPL), and Kassay Field Services Inc. conducted a comprehensive five-week study to measure gaseous emissions from oil wells, oil pumps, intermediate storage tanks, and other small point sources. A combination of optical remote sensing (ORS) techniques was used to detect and quantify emissions VOCs, methane, nitrogen oxides (NOx) and other gaseous pollutants. Fluxsense used Solar Occultation Flux (SOF), Differential Optical Absorption Spectroscopy (DOAS), and Extractive Fourier Transform Infrared (FTIR) spectroscopy to survey a large number of oil extraction sites and other small emission sources within SCAB. Similarly, Kassay Field Services carried out open-path FTIR measurements to complement observations provided by Fluxsense. Concurrently, NPL operated their Differential Absorption Lidar (DIAL) system on a smaller sub-set of sources to validate the emission results provided by Fluxsense and Kassay. During this presentation we will discuss the results of this joined measurement effort and the potential impacts of the observed emissions on neighboring communities. Additionally

  7. Compressive Sensing with Optical Chaos

    PubMed Central

    Rontani, D.; Choi, D.; Chang, C.-Y.; Locquet, A.; Citrin, D. S.

    2016-01-01

    Compressive sensing (CS) is a technique to sample a sparse signal below the Nyquist-Shannon limit, yet still enabling its reconstruction. As such, CS permits an extremely parsimonious way to store and transmit large and important classes of signals and images that would be far more data intensive should they be sampled following the prescription of the Nyquist-Shannon theorem. CS has found applications as diverse as seismology and biomedical imaging. In this work, we use actual optical signals generated from temporal intensity chaos from external-cavity semiconductor lasers (ECSL) to construct the sensing matrix that is employed to compress a sparse signal. The chaotic time series produced having their relevant dynamics on the 100 ps timescale, our results open the way to ultrahigh-speed compression of sparse signals. PMID:27910863

  8. Compressive Sensing with Optical Chaos

    NASA Astrophysics Data System (ADS)

    Rontani, D.; Choi, D.; Chang, C.-Y.; Locquet, A.; Citrin, D. S.

    2016-12-01

    Compressive sensing (CS) is a technique to sample a sparse signal below the Nyquist-Shannon limit, yet still enabling its reconstruction. As such, CS permits an extremely parsimonious way to store and transmit large and important classes of signals and images that would be far more data intensive should they be sampled following the prescription of the Nyquist-Shannon theorem. CS has found applications as diverse as seismology and biomedical imaging. In this work, we use actual optical signals generated from temporal intensity chaos from external-cavity semiconductor lasers (ECSL) to construct the sensing matrix that is employed to compress a sparse signal. The chaotic time series produced having their relevant dynamics on the 100 ps timescale, our results open the way to ultrahigh-speed compression of sparse signals.

  9. Biophotonic endoscopy: a review of clinical research techniques for optical imaging and sensing of early gastrointestinal cancer

    PubMed Central

    Coda, Sergio; Siersema, Peter D.; Stamp, Gordon W. H.; Thillainayagam, Andrew V.

    2015-01-01

    Detection, characterization, and staging constitute the fundamental elements in the endoscopic diagnosis of gastrointestinal diseases, but histology still remains the diagnostic gold standard. New developments in endoscopic techniques may challenge histopathology in the near future. An ideal endoscopic technique should combine a wide-field, “red flag” screening technique with an optical contrast or microscopy method for characterization and staging, all simultaneously available during the procedure. In theory, biophotonic advances have the potential to unite these elements to allow in vivo “optical biopsy.” These techniques may ultimately offer the potential to increase the rates of detection of high risk lesions and the ability to target biopsies and resections, and so reduce the need for biopsy, costs, and uncertainty for patients. However, their utility and sensitivity in clinical practice must be evaluated against those of conventional histopathology. This review describes some of the most recent applications of biophotonics in endoscopic optical imaging and metrology, along with their fundamental principles and the clinical experience that has been acquired in their deployment as tools for the endoscopist. Particular emphasis has been placed on translational label-free optical techniques, such as fluorescence spectroscopy, fluorescence lifetime imaging microscopy (FLIM), two-photon and multi-photon microscopy, second harmonic generation (SHG) and third harmonic generation (THG) imaging, optical coherence tomography (OCT), diffuse reflectance, Raman spectroscopy, and molecular imaging. PMID:26528489

  10. Remote hydrogen sensing techniques

    NASA Technical Reports Server (NTRS)

    Perry, Cortes L.

    1992-01-01

    The objective of this project is to evaluate remote hydrogen sensing methodologies utilizing metal oxide semi-conductor field effect transistors (MOS-FET) and mass spectrometric (MS) technologies and combinations thereof.

  11. Optical fibre sensing during critical care

    NASA Astrophysics Data System (ADS)

    Hernandez, F. U.; Wang, T.; Korposh, S.; Correia, R.; Hayes-Gill, B. R.; Hromadka, J.; Mohd Hazlan, N. N.; Norris, A.; Evans, D.; Lee, S.-W.; Morgan, S. P.

    2017-04-01

    Optical fibre sensing is a platform technology for applications in biomedical and environmental monitoring. Fibre Bragg Gratings can be used to monitor parameters such as pressure and temperature. Alternatively, coating the fibres with functional layers, either at the tip of the fibre, on a U-shaped fibre, or a long period grating enables sensing of analytes in liquids and gases. This paper describes the application of optical fibre sensing techniques during mechanical ventilation via an endotracheal tube in critical care. Functional coatings on the fibres are used to monitor humidity of inspired air and can be used to monitor other analytes.

  12. Assessing Natural Disaster Impacts and Recovery Using Multifrequency, Fully-Polarimetric Synthetic Aperture Radar (SAR) and Optical Remote Sensing Techniques

    NASA Astrophysics Data System (ADS)

    Weissel, J. K.; Czuchlewski, K. R.; Kim, Y.

    2002-12-01

    Many natural disasters involving landslides, volcanic eruptions, fires, or floods entail terrain resurfacing, followed by subsequent recovery. Modern satellite and airborne remote sensing technologies, which combine broad spatial coverage and high spatial resolution with time-sequential site revisit capability, can provide important information on the extent and duration of major landscape disturbance. In humid climate settings, these hazards temporarily remove or replace a natural vegetation cover and in doing so, modify the physical properties of the land surface. In optical remote sensing, removal of vegetation alters surface albedo in the visible -- near infrared (V-NIR) waveband, particularly the high reflectance from vegetation in the NIR. For SAR remote sensing, removal of vegetation cover causes a change in dominant microwave scattering mechanism for the areas affected. SAR has operational advantages over optical sensors for rapid disaster assessment because of its day/night acquisition capability, the ability to ``see through'' smoke, clouds and dust, and the side-looking viewing geometry, which is an advantage whenever data collection directly above the site would prove dangerous. We show how multifrequency, fully-polarimetric airborne SAR data can be ``inverted'' for parameters that reflect scattering mechanism signatures diagnostic of different surface cover types. We apply a uniform approach to map landslides resulting from the 1999 Mw 7.6 Chi-Chi earthquake in Taiwan, volcanic flows from the major 1996 eruption of Manam volcano in Papua New Guinea, and the extent of damage from the summer 2002 Rodeo -- Chediski wildfire in Arizona. In addition, earlier work has shown that multifrequency SAR polarimetric backscatter is sensitive to total above-ground biomass. This attribute can be exploited to calculate vegetation loss during a disaster and for assessment of regrowth during the recovery phase.

  13. Recycling optical fibers for sensing

    NASA Astrophysics Data System (ADS)

    André, Paulo; Domingues, Fátima; Alberto, Nélia; Marques, Carlos; Antunes, Paulo

    2016-04-01

    Optical fiber sensors has become one of the most promising sensing technologies. Within all the optical fiber sensing technologies, the Fabry-Perot interferometer (FPI) micro-cavities are one of the most attractive, due to the size, linearity and higher sensitivity. In this work we present the recent results, achieved by our group, regarding the production of optical sensors, by recycling optical fibers destroyed through the catastrophic fuse effect. This enabled the production of FPI sensors, in a cost effective way, tailored for the monitoring of several physical parameters, such as relative humidity (RH), refractive index (RI) and hydrostatic pressure.

  14. New optical sensing technique of tissue viability and blood flow based on nanophotonic iterative multi-plane reflectance measurements

    PubMed Central

    Yariv, Inbar; Haddad, Menashe; Duadi, Hamootal; Motiei, Menachem; Fixler, Dror

    2016-01-01

    Physiological substances pose a challenge for researchers since their optical properties change constantly according to their physiological state. Examination of those substances noninvasively can be achieved by different optical methods with high sensitivity. Our research suggests the application of a novel noninvasive nanophotonics technique, ie, iterative multi-plane optical property extraction (IMOPE) based on reflectance measurements, for tissue viability examination and gold nanorods (GNRs) and blood flow detection. The IMOPE model combines an experimental setup designed for recording light intensity images with the multi-plane iterative Gerchberg-Saxton algorithm for reconstructing the reemitted light phase and calculating its standard deviation (STD). Changes in tissue composition affect its optical properties which results in changes in the light phase that can be measured by its STD. We have demonstrated this new concept of correlating the light phase STD and the optical properties of a substance, using transmission measurements only. This paper presents, for the first time, reflectance based IMOPE tissue viability examination, producing a decrease in the computed STD for older tissues, as well as investigating their organic material absorption capability. Finally, differentiation of the femoral vein from adjacent tissues using GNRs and the detection of their presence within blood circulation and tissues are also presented with high sensitivity (better than computed tomography) to low quantities of GNRs (<3 mg). PMID:27785024

  15. Fiber optic wide region temperature sensing system

    NASA Astrophysics Data System (ADS)

    Xu, Xunjian; Nonaka, Koji; Song, Hongbin

    2008-12-01

    A fiber optic wide region temperature sensing system based on optical pulse correlation measurement and SHG differential detection technique is proposed and demonstrated. In order to establish the reliability of this fiber optic temperature sensing system, a long-term wide region outside temperature monitoring experiment with a new designed 20ps time-bias optical pulse correlation unit for wide measurement rang was carried out. The temperature measured by means of a correlation sensor had the same variation as and higher sensitivity and quick measurement response than the digital thermometer. The resolution of the correlation sensor is approximately +/-0.01 oC . This fiber optic temperature sensor can measure even in very tough environment and low and high temperature range. Not only point temperature but also a field area average temperature can monitor by this system.

  16. Optical Fiber Sensing Using Quantum Dots

    PubMed Central

    Jorge, Pedro; Martins, Manuel António; Trindade, Tito; Santos, José Luís; Farahi, Faramarz

    2007-01-01

    Recent advances in the application of semiconductor nanocrystals, or quantum dots, as biochemical sensors are reviewed. Quantum dots have unique optical properties that make them promising alternatives to traditional dyes in many luminescence based bioanalytical techniques. An overview of the more relevant progresses in the application of quantum dots as biochemical probes is addressed. Special focus will be given to configurations where the sensing dots are incorporated in solid membranes and immobilized in optical fibers or planar waveguide platforms.

  17. Tapered optical fibres for sensing

    NASA Astrophysics Data System (ADS)

    Martan, Tomas; Kanka, Jiri; Kasik, Ivan; Matejec, Vlastimil

    2008-11-01

    Recently, optical fibre tapers have intensively been investigated for many applications e.g. in telecommunications, medicine and (bio-) chemical sensing. The paper deals with enhancement of evanescent-field sensitivity of the solid-core microstructured fibre with steering-wheel air-cladding. Enhancement of a performance of the microstructured fibre is based on reduction of fibre core diameter down to narrow filament by tapering thereby defined part of light power is guided by an evanescent wave traveling in axial cladding air holes. The original fibre structure with outer diameter of 125 µm was reduced 2×, 2.5×, 3.33×, and 4× for increasing relatively small intensity overlap of guided core mode at wavelength of 1.55 μm with axial air holes. The inner structures of tapered microstructured fibre with steering-wheel aircladding were numerically analyzed and mode intensity distributions were calculated using the FDTD technique. Analyzed fiber tapers were prepared by constructed fibre puller employing 'flame brush technique'.

  18. Emerging optical nanoscopy techniques

    PubMed Central

    Montgomery, Paul C; Leong-Hoi, Audrey

    2015-01-01

    To face the challenges of modern health care, new imaging techniques with subcellular resolution or detection over wide fields are required. Far field optical nanoscopy presents many new solutions, providing high resolution or detection at high speed. We present a new classification scheme to help appreciate the growing number of optical nanoscopy techniques. We underline an important distinction between superresolution techniques that provide improved resolving power and nanodetection techniques for characterizing unresolved nanostructures. Some of the emerging techniques within these two categories are highlighted with applications in biophysics and medicine. Recent techniques employing wider angle imaging by digital holography and scattering lens microscopy allow superresolution to be achieved for subcellular and even in vivo, imaging without labeling. Nanodetection techniques are divided into four subcategories using contrast, phase, deconvolution, and nanomarkers. Contrast enhancement is illustrated by means of a polarized light-based technique and with strobed phase-contrast microscopy to reveal nanostructures. Very high sensitivity phase measurement using interference microscopy is shown to provide nanometric surface roughness measurement or to reveal internal nanometric structures. Finally, the use of nanomarkers is illustrated with stochastic fluorescence microscopy for mapping intracellular structures. We also present some of the future perspectives of optical nanoscopy. PMID:26491270

  19. Fiber optic sensing system

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory (Inventor)

    1991-01-01

    A fiber optic interferometer utilizes a low coherence light emitting diode (LED) laser as a light source which is filtered and driven at two RF frequencies, high and low, that are specific to the initial length of the resonator chamber. A displacement of a reflecting mirror changes the length traveled by the nonreferencing signal. The low frequency light undergoes destructive interference which reduces the average intensity of the wave while the high frequency light undergoes constructive interference which increases the average intensity of the wave. The ratio of these two intensity measurements is proportional to the displacement incurred.

  20. Improving Crop Classification Techniques Using Optical Remote Sensing Imagery, High-Resolution Agriculture Resource Inventory Shapefiles and Decision Trees

    NASA Astrophysics Data System (ADS)

    Melnychuk, A. L.; Berg, A. A.; Sweeney, S.

    2010-12-01

    Recognition of anthropogenic effects of land use management practices on bodies of water is important for remediating and preventing eutrophication. In the case of Lake Simcoe, Ontario the main surrounding landuse is agriculture. To better manage the nutrient flow into the lake, knowledge of the management of the agricultural land is important. For this basin, a comprehensive agricultural resource inventory is required for assessment of policy and for input into water quality management and assessment tools. Supervised decision tree classification schemes, used in many previous applications, have yielded reliable classifications in agricultural land-use systems. However, when using these classification techniques the user is confronted with numerous data sources. In this study we use a large inventory of optical satellite image products (Landsat, AWiFS, SPOT and MODIS) and ancillary data sources (temporal MODIS-NDVI product signatures, digital elevation models and soil maps) at various spatial and temporal resolutions in a decision tree classification scheme. The sensitivity of the classification accuracy to various products is assessed to identify optimal data sources for classifying crop systems.

  1. A Geostatistical Data Fusion Technique for Merging Remote Sensing and Ground-Based Observations of Aerosol Optical Thickness

    NASA Technical Reports Server (NTRS)

    Chatterjee, Abhishek; Michalak, Anna M.; Kahn, Ralph A.; Paradise, Susan R.; Braverman, Amy J.; Miller, Charles E.

    2010-01-01

    Particles in the atmosphere reflect incoming sunlight, tending to cool the Earth below. Some particles, such as soot, also absorb sunlight, which tens to warm the ambient atmosphere. Aerosol optical depth (AOD) is a measure of the amount of particulate matter in the atmosphere, and is a key input to computer models that simulate and predict Earth's changing climate. The global AOD products from the Multi-angle Imaging SpectroRadiometer (MISR) and the MODerate resolution Imaging Spectroradiometer (MODIS), both of which fly on the NASA Earth Observing System's Terra satellite, provide complementary views of the particles in the atmosphere. Whereas MODIS offers global coverage about four times as frequent as MISR, the multi-angle data makes it possible to separate the surface and atmospheric contributions to the observed top-of-atmosphere radiances, and also to more effectively discriminate particle type. Surface-based AERONET sun photometers retrieve AOD with smaller uncertainties than the satellite instruments, but only at a few fixed locations. So there are clear reasons to combine these data sets in a way that takes advantage of their respective strengths. This paper represents an effort at combining MISR, MODIS and AERONET AOD products over the continental US, using a common spatial statistical technique called kriging. The technique uses the correlation between the satellite data and the "ground-truth" sun photometer observations to assign uncertainty to the satellite data on a region-by-region basis. The larger fraction of the sun photometer variance that is duplicated by the satellite data, the higher the confidence assigned to the satellite data in that region. In the Western and Central US, MISR AOD correlation with AERONET are significantly higher than those with MODIS, likely due to bright surfaces in these regions, which pose greater challenges for the single-view MODIS retrievals. In the east, MODIS correlations are higher, due to more frequent sampling

  2. Single-end simultaneous temperature and strain sensing techniques based on Brillouin optical time domain reflectometry in few-mode fibers.

    PubMed

    Weng, Yi; Ip, Ezra; Pan, Zhongqi; Wang, Ting

    2015-04-06

    Recently there is a growing interest in developing few-mode fiber (FMF) based distributed sensors, which can attain higher spatial resolution and sensitivity compared with the conventional single-mode approaches. However, current techniques require two lightwaves injected into both ends of FMF, resulting in their complicated setup and high cost, which causes a big issue for geotechnical and petroleum applications. In this paper, we present a single-end FMF-based distributed sensing system that allows simultaneous temperature and strain measurement by Brillouin optical time-domain reflectometry (BOTDR) and heterodyne detection. Theoretical analysis and experimental assessment of multi-parameter discriminative measurement techniques applied to distributed FMF sensors are presented. Experimental results confirm that FM-BOTDR has similar performance with two-end methods such as FM-BOTDA, but with simpler setup and lower cost. The temperature-induced expansion strain (TIES) in response to different modes is discussed as well. Furthermore, we optimized the FMF design by exploiting modal profile and doping concentration, which indicates up to fivefold enhancement in measurement accuracy. This novel distributed FM-sensing system endows with good sensitivity characteristics and can prevent catastrophic failure in many applications.

  3. Optical Microbottle Resonators for Sensing

    PubMed Central

    Bianucci, Pablo

    2016-01-01

    Whispering gallery mode (WGM) optical microresonators have been shown to be the basis for sensors able to detect minute changes in their environment. This has made them a well-established platform for highly sensitive physical, chemical, and biological sensors. Microbottle resonators (MBR) are a type of WGM optical microresonator. They share characteristics with other, more established, resonator geometries such as cylinders and spheres, while presenting their unique spectral signature and other distinguishing features. In this review, we discuss recent advances in the theory and fabrication of different kinds of MBRs, including hollow ones, and their application to optofluidic sensing. PMID:27827834

  4. Optical sensing: recognition elements and devices

    NASA Astrophysics Data System (ADS)

    Gauglitz, Guenter G.

    2012-09-01

    The requirements in chemical and biochemical sensing with respect to recognition elements, avoiding non-specific interactions, and high loading of the surface for detection of low concentrations as well as optimized detection systems are discussed. Among the many detection principles the optical techniques are classified. Methods using labeled compounds like Total Internal Reflection Fluorescence (TIRF) and direct optical methods like micro reflectometry or refractometry are discussed in comparison. Reflectometric Interference Spectroscopy (RIfS) is presented as a robust simple method for biosensing. As applications, trace analysis of endocrine disruptors in water, hormones in food, detection of viruses and bacteria in food and clinical diagnostics are discussed.

  5. Fiber-Optic Sensing for In-Space Inspection

    NASA Technical Reports Server (NTRS)

    Pena, Francisco; Richards, W. Lance; Piazza, Anthony; Parker, Allen R.; Hudson, Larry D.

    2014-01-01

    This presentation provides examples of fiber optic sensing technology development activities performed at NASA Armstrong. Examples of current and previous work that support in-space inspection techniques and methodologies are highlighted.

  6. Ocean Optical Remote Sensing Capability Statement.

    DTIC Science & Technology

    1984-03-01

    illustrated in relation toIother oceanographic parameters. > reevavy programs which have supported the Remote Sensing Branch’s developments in water ...optics are described. The Navy relevance of water optics to these programs is indicated.’ "I 1 ’ ( ;j "IJl: ,t n ! /H i.i OCEAN OPTICAL REMOTE SENSING...Development Activity (NORDA) Remote Sensing Branch (Code 321) has been conducting investigative programs in water optics since 1977. The major thrust of

  7. Fiber optic sensing systems using high frequency resonant sensing heads with intensity sensors

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Maitland, Duncan J., IV

    1988-01-01

    Optical fibers have an inherent capability of transmitting high bandwidth analog and digital signals. To apply this property of fiber optics to remote sensing, special sensing heads as well as signal processing electronics have to be developed. In systems employing intensity modulating sensors, there is also a need for a referencing technique to compensate for changes in the transmission of the connecting fibers and light source intensity. Fiber optic sensing systems incorporated in sensing heads of a special configuration are discussed. Different modes of operation as well as resonant conditions are explained. Theoretical and experimental analyses are also given.

  8. Fiber optic sensing systems using high frequency resonant sensing heads with intensity sensors

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Maitland, Duncan J., IV

    1989-01-01

    Optical fibers have an inherent capability of transmitting high bandwidth analog and digital signals. To apply this property of fiber optics to remote sensing, special sensing heads as well as signal processing electronics have to be developed. In systems employing intensity modulating sensors, there is also a need for a referencing technique to compensate for changes in the transmission of the connecting fibers and light source intensity. Fiber optic sensing systems incorporated in sensing heads of a special configuration are discussed. Different modes of operation as well as resonant conditions are explained. Theoretical and experimental analyses are also given.

  9. Fiber optic sensing systems using high frequency resonant sensing heads with intensity sensors

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Maitland, Duncan J., IV

    1989-01-01

    Optical fibers have an inherent capability of transmitting high bandwidth analog and digital signals. To apply this property of fiber optics to remote sensing, special sensing heads as well as signal processing electronics have to be developed. In systems employing intensity modulating sensors, there is also a need for a referencing technique to compensate for changes in the transmission of the connecting fibers and light source intensity. Fiber optic sensing systems incorporated in sensing heads of a special configuration are discussed. Different modes of operation as well as resonant conditions are explained. Theoretical and experimental analyses are also given.

  10. Optical display for radar sensing

    NASA Astrophysics Data System (ADS)

    Szu, Harold; Hsu, Charles; Willey, Jefferson; Landa, Joseph; Hsieh, Minder; Larsen, Louis V.; Krzywicki, Alan T.; Tran, Binh Q.; Hoekstra, Philip; Dillard, John T.; Krapels, Keith A.; Wardlaw, Michael; Chu, Kai-Dee

    2015-05-01

    Boltzmann headstone S = kB Log W turns out to be the Rosette stone for Greek physics translation optical display of the microwave sensing hieroglyphics. The LHS is the molecular entropy S measuring the degree of uniformity scattering off the sensing cross sections. The RHS is the inverse relationship (equation) predicting the Planck radiation spectral distribution parameterized by the Kelvin temperature T. Use is made of the conservation energy law of the heat capacity of Reservoir (RV) change T Δ S = -ΔE equals to the internal energy change of black box (bb) subsystem. Moreover, an irreversible thermodynamics Δ S > 0 for collision mixing toward totally larger uniformity of heat death, asserted by Boltzmann, that derived the so-called Maxwell-Boltzmann canonical probability. Given the zero boundary condition black box, Planck solved a discrete standing wave eigenstates (equation). Together with the canonical partition function (equation) an average ensemble average of all possible internal energy yielded the celebrated Planck radiation spectral (equation) where the density of states (equation). In summary, given the multispectral sensing data (equation), we applied Lagrange Constraint Neural Network (LCNN) to solve the Blind Sources Separation (BSS) for a set of equivalent bb target temperatures. From the measurements of specific value, slopes and shapes we can fit a set of Kelvin temperatures T's for each bb targets. As a result, we could apply the analytical continuation for each entropy sources along the temperature-unique Planck spectral curves always toward the RGB color temperature display for any sensing probing frequency.

  11. Remote tire pressure sensing technique

    NASA Technical Reports Server (NTRS)

    Robinson, Howard H. (Inventor); Mcginnis, Timothy A. (Inventor); Daugherty, Robert H. (Inventor)

    1993-01-01

    A remote tire pressure sensing technique is provided which uses vibration frequency to determine tire pressure. A vibration frequency measuring device is attached to the external surface of a tire which is then struck with an object, causing the tire to vibrate. The frequency measuring device measures the vibrations and converts the vibrations into corresponding electrical impulses. The electrical impulses are then fed into the frequency analyzing system which uses the electrical impulses to determine the relative peaks of the vibration frequencies as detected by the frequency measuring device. The measured vibration frequency peaks are then compared to predetermined data describing the location of vibration frequency peaks for a given pressure, thereby determining the air pressure of the tire.

  12. Optical Techniques in Optogenetics

    PubMed Central

    Mohanty, Samarendra K.; Lakshminarayananan, Vasudevan

    2015-01-01

    Optogenetics is an innovative technique for optical control of cells. This field has exploded over the past decade or so and has given rise to great advances in neuroscience. A variety of applications both from the basic and applied research have emerged, turning the early ideas into a powerful paradigm for cell biology, neuroscience and medical research. This review aims at highlighting the basic concepts that are essential for a comprehensive understanding of optogenetics and some important biological/biomedical applications. Further, emphasis is placed on advancement in optogenetics-associated light-based methods for controlling gene expression, spatially-controlled optogenetic stimulation and detection of cellular activities. PMID:26412943

  13. Optical techniques in optogenetics

    NASA Astrophysics Data System (ADS)

    Mohanty, Samarendra K.; Lakshminarayananan, Vasudevan

    2015-07-01

    Optogenetics is an innovative technique for optical control of cells. This field has exploded over the past decade or so and has given rise to great advances in neuroscience. A variety of applications both from the basic and applied research have emerged, turning the early ideas into a powerful paradigm for cell biology, neuroscience, and medical research. This review aims at highlighting the basic concepts that are essential for a comprehensive understanding of optogenetics and some important biological/biomedical applications. Further, emphasis is placed on advancement in optogenetics-associated light-based methods for controlling gene expression, spatially controlled optogenetic stimulation and detection of cellular activities.

  14. Hall Effect and Magneto Optical MFL Sensing

    NASA Astrophysics Data System (ADS)

    Jallouli, Wissem

    The need for a reliable sensing tool has stimulated countless researchers to develop techniques trying to extract maximum information. In the field of nondestructive testing (NDT), various sensors have been established to fulfill that function. Examples include the ultrasonic, eddy current, and magnetic flux leakage (MFL) based techniques. Because they are extremely reliable, MFL based techniques represent one of the best inspection technologies. These technologies have numerous applications in diverse domains, including petroleum pipeline and tank inspections, airplane inspections, and production quality control. In this work, we will present two technologies based on MFL technique. The first is the Hall Effect sensor. This device has been extensively developed during the last century, especially after the use of integrated circuit technology. Its reliable results even under extreme conditions made it an extremely useful tool. The second technology is Magneto Optical Imaging. This technique rose very recently, and scientists hold high expectations about its performance once proper techniques are developed. The study of these two sensing devices gives a better understanding of the MFL technique by allowing us to investigate the potential of each technology, experience each in studied conditions to derive its characteristics, and discuss its performance.

  15. Quantum limited particle sensing in optical tweezers

    SciTech Connect

    Tay, J.W.; Hsu, Magnus T. L.; Bowen, Warwick P.

    2009-12-15

    Particle sensing in optical tweezers systems provides information on the position, velocity, and force of the specimen particles. The conventional quadrant detection scheme is applied ubiquitously in optical tweezers experiments to quantify these parameters. In this paper, we show that quadrant detection is nonoptimal for particle sensing in optical tweezers and propose an alternative optimal particle sensing scheme based on spatial homodyne detection. A formalism for particle sensing in terms of transverse spatial modes is developed and numerical simulations of the efficacies of both quadrant and spatial homodyne detection are shown. We demonstrate that 1 order of magnitude improvement in particle sensing sensitivity can be achieved using spatial homodyne over quadrant detection.

  16. SO2 emissions from Popocatépetl volcano: emission rates and plume imaging using optical remote sensing techniques

    NASA Astrophysics Data System (ADS)

    Grutter, M.; Basaldud, R.; Rivera, C.; Harig, R.; Junkerman, W.; Caetano, E.; Delgado-Granados, H.

    2008-11-01

    Sulfur dioxide emissions from the Popocatépetl volcano in central Mexico were measured during the MILAGRO field campaign in March 2006. A stationary scanning DOAS (Differential Optical Absorption Spectrometer) was used to monitor the SO2 emissions from the volcano and the results were compared with traverses done with a COSPEC from the ground and a DOAS instrument on board an ultra-light aircraft. Daytime evolutions as well as day-to-day variation of the SO2 emissions are reported. A value of 2.45±1.39 Gg/day of SO2 is reported from all the daily averages obtained during the month of March 2006, with large variation in maximum and minimum daily averages of 5.97 and 0.56 Gg/day, respectively. The large short-term fluctuations in the SO2 emissions obtained could be confirmed through 2-D visualizations of the SO2 plume measured with a scanning imaging infrared spectrometer. This instrument, based on the passive detection of thermal radiation from the volcanic gas and analysis with FTIR spectrometry, is used for the first time for plume visualization of a specific volcanic gas. A 48-h forward trajectory analysis indicates that the volcanic plume was predominantly directed towards the Puebla/Tlaxcala region (63%), followed by the Mexico City and Cuernavaca/Cuautla regions with 19 and 18% occurrences, respectively. 25% of the modeled trajectories going towards the Puebla region reached altitudes lower than 4000 m a.s.l. but all trajectories remained over this altitude for the other two regions.

  17. SO2 emissions from Popocatépetl volcano: emission rates and plume imaging using optical remote sensing techniques

    NASA Astrophysics Data System (ADS)

    Grutter, M.; Basaldud, R.; Rivera, C.; Harig, R.; Junkerman, W.; Caetano, E.; Delgado-Granados, H.

    2008-04-01

    Sulfur dioxide emissions from Popocatépetl volcano in central Mexico were measured during the MILAGRO field campaign in March 2006. A stationary scanning DOAS (Differential Optical Absorption Spectrometer) was used to monitor the SO2 emissions from the volcano and the results were compared with traverses done with a COSPEC from the ground and a DOAS instrument on board an ultra-light aircraft. Daytime evolutions as well as day-to-day variation of the SO2 emissions are reported. A value of 2.45±1.39 Gg/day of SO2 is reported from all the daily averages obtained during the month of March 2006, with large variation in maximum and minimum daily averages of 5.97 and 0.56 Gg/day, respectively. The large short-term fluctuations in the SO2 emissions obtained could be confirmed through 2-D visualizations of the SO2 plume measured with a scanning imaging infrared spectrometer. This instrument, based on the passive detection of thermal radiation from the volcanic gas and analysis with FTIR spectrometry, is used for the first time for plume visualization of a specific volcanic gas. A 48-h forward trajectory analysis indicates that the volcanic plume was predominately directed towards the Puebla/Tlaxcala region (63%), followed by the Mexico City and Cuernavaca/Cuautla regions with 19 and 18% occurrences, respectively. 25% of the modeled trajectories going towards the Puebla region reached altitudes lower than 4000 m a.s.l. and all trajectories remained over this altitude for the other two regions.

  18. Adaptive holography for optical sensing applications

    NASA Astrophysics Data System (ADS)

    Residori, S.; Bortolozzo, U.; Peigné, A.; Molin, S.; Nouchi, P.; Dolfi, D.; Huignard, J. P.

    2016-03-01

    Adaptive holography is a promising method for high sensitivity phase modulation measurements in the presence of slow perturbations from the environment. The technique is based on the use of a nonlinear recombining medium, here an optically addressed spatial light modulator specifically realized to operate at 1.55 μm. Owing to the physical mechanisms involved, the interferometer adapts to slow phase variations within a range of 5-10 Hz, thus filtering out low frequency noise while transmitting higher frequency phase modulations. We present the basic principles of the adaptive interferometer and show that it can be used in association with a sensing fiber in order to detect phase modulations. Finally, a phase-OTDR architecture using the adaptive holographic interferometer is presented and shown to allows the detection of localized perturbations along the sensing fiber.

  19. Optical fiber gas sensing system based on FBG filtering

    NASA Astrophysics Data System (ADS)

    Wang, Shutao

    2008-10-01

    An optical fiber gas sensing system based on the law of Beer-Lambert is designed to determine the concentration of gas. This technique relies on the fact that the target gas has a unique, well-defined absorption characteristic within the infrared region of electromagnetic spectrum. The narrow-band filtering characteristic of optical fiber Bragg grating is used to produce the narrow spectrum light signal. An aspheric objective optical fiber collimator is used in the system as an optical fiber gas sensing detector to improve the sensitivity and stability. Experimental results show there is a high measuring sensitivity at 0.01%, and the measuring range goes beyond 5%.

  20. Combinatorial Chemistry for Optical Sensing Applications

    NASA Astrophysics Data System (ADS)

    Díaz-García, M. E.; Luis, G. Pina; Rivero-Espejel, I. A.

    The recent interest in combinatorial chemistry for the synthesis of selective recognition materials for optical sensing applications is presented. The preparation, screening, and applications of libraries of ligands and chemosensors against molecular species and metal ions are first considered. Included in this chapter are also the developments involving applications of combinatorial approaches to the discovery of sol-gel and acrylic-based imprinted materials for optical sensing of antibiotics and pesticides, as well as libraries of doped sol-gels for high-throughput optical sensing of oxygen. The potential of combinatorial chemistry applied to the discovery of new sensing materials is highlighted.

  1. Nanocomposite thin films for optical temperature sensing

    DOEpatents

    Ohodnicki, Jr., Paul R.; Brown, Thomas D.; Buric, Michael P.; Matranga, Christopher

    2017-02-14

    The disclosure relates to an optical method for temperature sensing utilizing a temperature sensing material. In an embodiment the gas stream, liquid, or solid has a temperature greater than about 500.degree. C. The temperature sensing material is comprised of metallic nanoparticles dispersed in a dielectric matrix. The metallic nanoparticles have an electronic conductivity greater than approximately 10.sup.-1 S/cm at the temperature of the temperature sensing material. The dielectric matrix has an electronic conductivity at least two orders of magnitude less than the dispersed metallic nanoparticles at the temperature of the temperature sensing material. In some embodiments, the chemical composition of a gas stream or liquid is simultaneously monitored by optical signal shifts through multiple or broadband wavelength interrogation approaches. In some embodiments, the dielectric matrix provides additional functionality due to a temperature dependent band-edge, an optimized chemical sensing response, or an optimized refractive index of the temperature sensing material for integration with optical waveguides.

  2. Laser and Optical Remote Sensing: Instrumentation and Techniques Topical Meeting Held in North Falmoth Massachusetts on September 28 - October 1, 1987. Volume 18. Technical Digest Series

    DTIC Science & Technology

    1987-10-01

    because of its wavelength agility the CO2 laser is a very attractive one for this kind of analysis. The aim of this paper is to present the results of...acOusto-optic madiator. SC the optical scanner, u and v the pupils. L2 tin Fourier transfom lens, and PD the photo-detecto. U) h) Figure 3. (a) Lowpass...Aircraft Company 75 Coromar Dr. Goleta. Ca. 93117 A low-cost, high-performance sensor design for low-earth-orbit ocean-color remote sensing Is

  3. Optical interconnection techniques for Hypercube

    NASA Technical Reports Server (NTRS)

    Johnston, A. R.; Bergman, L. A.; Wu, W. H.

    1988-01-01

    Direct free-space optical interconnection techniques are described for the Hypercube concurrent processor machine using a holographic optical element. Computational requirements and optical constraints on implementation are briefly summarized with regard to topology, power consumption, and available technologies. A hybrid lens/HOE approach is described that can support an eight-dimensional cube of 256 nodes.

  4. Development of sensing techniques for weaponry health monitoring

    NASA Astrophysics Data System (ADS)

    Edwards, Eugene; Ruffin, Paul B.; Walker, Ebonee A.; Brantley, Christina L.

    2013-04-01

    Due to the costliness of destructive evaluation methods for assessing the aging and shelf-life of missile and rocket components, the identification of nondestructive evaluation methods has become increasingly important to the Army. Verifying that there is a sufficient concentration of stabilizer is a dependable indicator that the missile's double-based solid propellant is viable. The research outlined in this paper summarizes the Army Aviation and Missile Research, Development, and Engineering Center's (AMRDEC's) comparative use of nanoporous membranes, carbon nanotubes, and optical spectroscopic configured sensing techniques for detecting degradation in rocket motor propellant. The first sensing technique utilizes a gas collecting chamber consisting of nanoporous structures that trap the smaller solid propellant particles for measurement by a gas analysis device. In collaboration with NASA-Ames, sensing methods are developed that utilize functionalized single-walled carbon nanotubes as the key sensing element. The optical spectroscopic sensing method is based on a unique light collecting optical fiber system designed to detect the concentration of the propellant stabilizer. Experimental setups, laboratory results, and overall effectiveness of each technique are presented in this paper. Expectations are for the three sensing mechanisms to provide nondestructive evaluation methods that will offer cost-savings and improved weaponry health monitoring.

  5. Fiber Optic-Based Refractive Index Sensing at INESC Porto

    PubMed Central

    Jorge, Pedro A. S.; Silva, Susana O.; Gouveia, Carlos; Tafulo, Paula; Coelho, Luis; Caldas, Paulo; Viegas, Diana; Rego, Gaspar; Baptista, José M.; Santos, José L.; Frazão, Orlando

    2012-01-01

    A review of refractive index measurement based on different types of optical fiber sensor configurations and techniques is presented. It addresses the main developments in the area, with particular focus on results obtained at INESC Porto, Portugal. The optical fiber sensing structures studied include those based on Bragg and long period gratings, on micro-interferometers, on plasmonic effects in fibers and on multimode interference in a large spectrum of standard and microstructured optical fibers. PMID:22969405

  6. Phase Contrast Wavefront Sensing for Adaptive Optics

    NASA Technical Reports Server (NTRS)

    Bloemhof, E. E.; Wallace, J. K.; Bloemhof, E. E.

    2004-01-01

    Most ground-based adaptive optics systems use one of a small number of wavefront sensor technologies, notably (for relatively high-order systems) the Shack-Hartmann sensor, which provides local measurements of the phase slope (first-derivative) at a number of regularly-spaced points across the telescope pupil. The curvature sensor, with response proportional to the second derivative of the phase, is also sometimes used, but has undesirable noise propagation properties during wavefront reconstruction as the number of actuators becomes large. It is interesting to consider the use for astronomical adaptive optics of the "phase contrast" technique, originally developed for microscopy by Zemike to allow convenient viewing of phase objects. In this technique, the wavefront sensor provides a direct measurement of the local value of phase in each sub-aperture of the pupil. This approach has some obvious disadvantages compared to Shack-Hartmann wavefront sensing, but has some less obvious but substantial advantages as well. Here we evaluate the relative merits in a practical ground-based adaptive optics system.

  7. Nanomaterial-assisted aptamers for optical sensing.

    PubMed

    Wang, Guoqing; Wang, Yunqing; Chen, Lingxin; Choo, Jaebum

    2010-04-15

    Aptamers are single-strand DNA or RNA selected in vitro that bind specifically with a broad range of targets from metal ions, organic molecules, to proteins, cells and microorganisms. As an emerging class of recognition elements, aptamers offer remarkable convenience in the design and modification of their structures, which has motivated them to generate a great variety of aptamer sensors (aptasensors) that exhibit high sensitivity as well as specificity. On the other hand, the development of nanoscience and nanotechnology has generated nanomaterials with novel properties compared with their counterparts in macroscale. By integrating their strengths of both fields, recently, versatile aptamers coupling with novel nanomaterials for designing nanomaterial-assisted aptasensors (NAAs) make the combinations universal strategies for sensitive optical sensing. NAAs have been considered as an excellent sensing platform and found wide applications in analytical community. In this review, we summarize recent advances in the development of various optical NAAs, employing various detection techniques including colorimetry, fluorometry, surface-enhanced Raman scattering (SERS), magnetic resonance imaging (MRI) and surface plasmon resonance (SPR).

  8. OPEN PATH OPTICAL SENSING OF PARTICULATE MATTER

    EPA Science Inventory

    The paper discusses the concepts behind recent developments in optical remote sensing (ORS) and the results from experiments. Airborne fugitive and fine particulate matter (PM) from various sources contribute to exceedances of state and federal PM and visibility standards. Recent...

  9. OPEN PATH OPTICAL SENSING OF PARTICULATE MATTER

    EPA Science Inventory

    The paper discusses the concepts behind recent developments in optical remote sensing (ORS) and the results from experiments. Airborne fugitive and fine particulate matter (PM) from various sources contribute to exceedances of state and federal PM and visibility standards. Recent...

  10. Adaptive Optical Filtering Techniques.

    DTIC Science & Technology

    1985-05-01

    A space inte- Perhaps the most significant application of numeri- grating implementation using a parellel output wide- cal optical processors is in O... University Press, Daiumote. 19631. 177 C-5% 41% -~~ ~~~~~ % *~ .~ . e5 e r %. % *FILMED 9-85 DTIC

  11. Techniques for Optical Interferanemography.

    DTIC Science & Technology

    1985-12-01

    6563 ° .g NOTICE When Government drawings, specifications, or other data are used for any purpose other than in connection with a definitely related...measure the integrated index variation along the line of sight. Consequently, they do not provide spatial resolution and are only adequate in systems that... are symmetric along the line of sight. If spatial resolution is required, a tomographic system can be used but the optical access required exceeds

  12. New Adaptive Optics Technique Demonstrated

    NASA Astrophysics Data System (ADS)

    2007-03-01

    Enrico Marchetti, the MAD Project Manager. "The system behaviour was very stable and the acquisition and closed loop operations were fast and smooth." ESO PR Photo 19d/07 ESO PR Photo 19d/07 AO Strehl Maps After routine checks on the closed loop stability and preliminary scans of the system parameters, the telescope was pointed to Omega Centauri, a very crowded area in the sky, and an optimal test case for extracting accurate measurements on AO correction performance with good spatial resolution on the FoV. Three 11 magnitude stars within a circle of ~1.5 arcmin diameter were selected as the baseline for wavefront sensing and the MCAO loop was closed successfully. Omega Centauri will be observed for several nights more, in order to test the AO correction in different seeing conditions. "This is a tremendous achievement that opens new perspectives in the era of extremely large telescopes," said Catherine Cesarsky, ESO's Director General. " "I am very proud of the ESO staff and wish to congratulate all involved for their prowess," she added. The MAD images perfectly show the validity of the concept. The image quality was almost uniform over the whole field of view and beautifully corrected for some of the atmospheric turbulence. More Information The Multi-Conjugate Adaptive Optics (MCAO) Demonstrator MAD was built by ESO in collaboration with the Astronomical Observatories of Arcetri and Padova (Italy) and the Faculdade de Ciencias da Universidade de Lisboa (Portugal), as a pathfinder for 2nd generation VLT instrumentation and the European Extremely Large Telescope project. The MCAO technique is based on probing the atmospheric turbulence on a large volume of atmosphere by means of several wavefront sensors (WFS), which point at different locations in the observed field of view, and by means of several deformable mirrors - optically conjugated at different altitudes on the atmosphere above the telescope - which correct for the atmospheric disturbance. The signals provided

  13. Optical digital techniques

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Optical interface losses between transmitter-to-fiber interface, connector-to-connector interface, and fiber-to-receiver interface were studied. System effects such as pulse dispersion, risetimes of the sources and detectors, type of fibers used, output power of the sources, and detector sensitivity were considered. Data bus systems such as TEE, Star, and Hybrid were analyzed. The matter of single fiber versus bundle technologies for future avionics systems was considered. The existing data bus system on Space Shuttle was examined and an optical analog was derived for a fiber bundle system, along with the associated power margin. System tests were performed on a feasibility model of a 9-port Star data bus system including BER, star losses, connector losses, etc. The same system was subjected to EMI between the range of 200 Hz to 10 GHz at 20V/m levels. A lightning test was also performed which simulated the conditions similar to those on Space Shuttle. The data bus system was found to be EMI and lightning hard. It is concluded that an optical data bus system is feasible for shuttle orbiter type vehicles.

  14. Statistical-mode sensor for fiber optic vibration sensing uses.

    PubMed

    Spillman, W B; Kline, B R; Maurice, L B; Fuhr, P L

    1989-08-01

    A method of sensing vibration using the detection of changes in the spatial distribution of energy in the output of a multimode optical fiber has been demonstrated. Two implementations of the sensor have been built and tested. The first implementation involved simple optical processing of the output fiber speckle pattern using spatial filtering. The second implementation involved projecting the pattern on a CCD array and digitally processing observed changes in the intensity distribution. A mathematical model has been developed which has shown good agreement with observed sensor behavior. The sensor technique has been used to detect induced structural vibration in laboratory test specimens. Simple field testing has also demonstrated the ability of the technique to detect personnel and vehicles passing over a buried and electrically undetectable sensing cable. The sensing technique is compatible with off-the-shelf components and fiber cable and even allows for simultaneous telecommunication and sensing using the same optical fiber cable. Near term application of this technology could provide significant benefits for vibration sensing, intrusion detection, and acoustic sensing.

  15. Hyperspectral Remote Sensing of the Coastal Ocean: Adaptive Sampling and Forecasting of In situ Optical Properties

    DTIC Science & Technology

    2002-09-30

    integrated observation system that is being coupled to a data assimilative hydrodynamic bio-optical ecosystem model. The system was used adaptively to develop hyperspectral remote sensing techniques in optically complex nearshore coastal waters.

  16. Image Formation in Bio-optical Sensing

    NASA Astrophysics Data System (ADS)

    Miller, Eric

    2012-02-01

    Over the past two decades a number of optical sensing methods have emerged with potential to provide complementary information to traditional medical imaging modalities in application areas ranging from basic science to disease diagnosis and treatment monitoring. Though still largely in the research and development stage, modalities including diffuse optical tomography (DOT), fluorescence molecular tomography (FMT), photo-acoustic tomography (PAT), and bio-luminescence tomography (BLT) have excited much interest due to their natural functional imaging capability, their relatively low cost, and the fact that none required the use of ionizing radiation. These advantages however are tempered by a number of challenges associated with the processing of these data. Specifically, these data types all rely in one way or another on the interaction of light with tissue. The diffusive nature of this interaction inherently limits the spatial resolution of these modalities. As a result the process of forming an image is a far more delicate task than is the case with more standard imaging modalities such as X-ray computed tomography (CT). Two basic methods have been explored to address the ill-posedness of these problems in order to improve the information content in the resulting images. The optical data may be augmented either through the use of spectral diversity or by attempting to integrate optical data types with information from other modalities such as CT or MRI. Alternatively, a mathematical technique known as regularization can be used to impose physically-based constraints on the reconstruction. In this talk, I shall provide an overview of the work in my group in optical image formation within the contexts of DOT for breast cancer imaging and FMT for small animal imaging. The focus of the talk will be on methods that integrate data augmentation and mathematical regularization. In the case of FMT, we shall discuss our work in combining the optical data with information

  17. Optical sensing and analyte manipulation in solid-state nanopores.

    PubMed

    Gilboa, Tal; Meller, Amit

    2015-07-21

    The field of nanopore sensing has been gaining increasing attention. Much progress has been made towards biotechnological applications that involve electrical measurements of temporal changes in the ionic current flowing through the pore. But in many cases the electrical signal is restricted by the non-ideal noise components, limited throughput, and insufficient temporal or spatial resolutions. To address these limitations, high-sensitivity optical detection techniques that complement the electrical measurements have been developed. The optical techniques involve high-bandwidth, multicolor and high-throughput measurements. Here we review the recent advancements and developments that have been taking place in the field of optical sensing in solid-state nanopores. We describe the main optical methods used in this field involving total internal reflection and confocal microscopy in addition to sophisticated background suppression strategies. We further present the phenomenon of light induced analyte manipulation at the pore and the contribution of the optical sensing approach to possible nanopore sensing applications such as optical based DNA sequencing using nanopores.

  18. Enabling technologies for fiber optic sensing

    NASA Astrophysics Data System (ADS)

    Ibrahim, Selwan K.; Farnan, Martin; Karabacak, Devrez M.; Singer, Johannes M.

    2016-04-01

    In order for fiber optic sensors to compete with electrical sensors, several critical parameters need to be addressed such as performance, cost, size, reliability, etc. Relying on technologies developed in different industrial sectors helps to achieve this goal in a more efficient and cost effective way. FAZ Technology has developed a tunable laser based optical interrogator based on technologies developed in the telecommunication sector and optical transducer/sensors based on components sourced from the automotive market. Combining Fiber Bragg Grating (FBG) sensing technology with the above, high speed, high precision, reliable quasi distributed optical sensing systems for temperature, pressure, acoustics, acceleration, etc. has been developed. Careful design needs to be considered to filter out any sources of measurement drifts/errors due to different effects e.g. polarization and birefringence, coating imperfections, sensor packaging etc. Also to achieve high speed and high performance optical sensing systems, combining and synchronizing multiple optical interrogators similar to what has been used with computer/processors to deliver super computing power is an attractive solution. This path can be achieved by using photonic integrated circuit (PIC) technology which opens the doors to scaling up and delivering powerful optical sensing systems in an efficient and cost effective way.

  19. Optical waveguides for chemical sensing

    NASA Astrophysics Data System (ADS)

    Burgess, Lloyd W.

    1992-07-01

    Possibilities of employing thin film optical waveguides for chemical analysis are reviewed. Particular attention is given to the use of integrated or planar optical elements in sensors which may be applied to continuous or in situ monitoring in biomedical, environmental, and chemical processes.

  20. Optical frequency comb interference profilometry using compressive sensing.

    PubMed

    Pham, Quang Duc; Hayasaki, Yoshio

    2013-08-12

    We describe a new optical system using an ultra-stable mode-locked frequency comb femtosecond laser and compressive sensing to measure an object's surface profile. The ultra-stable frequency comb laser was used to precisely measure an object with a large depth, over a wide dynamic range. The compressive sensing technique was able to obtain the spatial information of the object with two single-pixel fast photo-receivers, with no mechanical scanning and fewer measurements than the number of sampling points. An optical experiment was performed to verify the advantages of the proposed method.

  1. The optics of wavefront sensing.

    PubMed

    Thibos, Larry N

    2004-06-01

    This article reviews the fundamental principles by which wavefront aberrometers measure ocular aberrations. Three different ways of interpreting aberration measurements are described in terms of wavefront phase, slope, and curvature. Although curvature is the more familiar concept from geometrical optics, the wave optics concept of wavefront phase is more useful for understanding the nature of aberrated retinal images and for prescribing treatments to correct high-order aberrations.

  2. Modeling of silica nanowires for optical sensing.

    PubMed

    Lou, Jingyi; Tong, Limin; Ye, Zhizhen

    2005-03-21

    Based on evanescent-wave guiding properties of nanowire waveguides, we propose to use single-mode subwavelength-diameter silica nanowires for optical sensing. Phase shift of the guided mode caused by index change is obtained by solving Maxwell's equation, and is used as a criterion for sensitivity estimation. Nanowire sensor employing a wire-assembled Mach-Zehnder structure is modeled. The result shows that optical nanowires, especially those fabricated by taper drawing of optical fibers, are promising for developing miniaturized optical sensors with high sensitivity.

  3. Ammonia Optical Sensing by Microring Resonators.

    PubMed

    Passaro, Vittorio M N; Dell'Olio, Francesco; De Leonardis, Francesco

    2007-11-15

    A very compact (device area around 40 μm²) optical ammonia sensor based on amicroring resonator is presented in this work. Silicon-on-insulator technology is used insensor design and a dye doped polymer is adopted as sensing material. The sensor exhibitsa very good linearity and a minimum detectable refractive index shift of sensing materialas low as 8x10(-5), with a detection limit around 4 ‰.

  4. Ammonia Optical Sensing by Microring Resonators

    PubMed Central

    Passaro, Vittorio M. N.; Dell'Olio, Francesco; De Leonardis, Francesco

    2007-01-01

    A very compact (device area around 40 μm2) optical ammonia sensor based on a microring resonator is presented in this work. Silicon-on-insulator technology is used in sensor design and a dye doped polymer is adopted as sensing material. The sensor exhibits a very good linearity and a minimum detectable refractive index shift of sensing material as low as 8×10-5, with a detection limit around 4 ‰. PMID:28903258

  5. Environmental monitoring using optical techniques

    NASA Astrophysics Data System (ADS)

    Svanberg, Sune

    2003-11-01

    An overview of optical techniques for environmental monitoring is presented. Range-resolved measurements of atmospheric pollutants can be performed using the differential absorption lidar technique. Fluorescence lidar allows assessment of vegetation status and also the conditions of the facades of historical buildings. Diode lasers provide particularly realistic schemes for atmospheric gas analysis, where certain wavelength ranges, which are not easily directly assessed, can be reached by sum- and difference frequency generation. Finally, the gas correlation principle can be used for real-time imaging of hydrocarbons. Several types of such optical environmental monitoring are illustrated with examples from research at the Lund Institute of Technology, Sweden.

  6. Distributed fiber optical sensing of oxygen with optical time domain reflectometry.

    PubMed

    Eich, Susanne; Schmälzlin, Elmar; Löhmannsröben, Hans-Gerd

    2013-05-31

    In many biological and environmental applications spatially resolved sensing of molecular oxygen is desirable. A powerful tool for distributed measurements is optical time domain reflectometry (OTDR) which is often used in the field of telecommunications. We combine this technique with a novel optical oxygen sensor dye, triangular-[4] phenylene (TP), immobilized in a polymer matrix. The TP luminescence decay time is 86 ns. The short decay time of the sensor dye is suitable to achieve a spatial resolution of some meters. In this paper we present the development and characterization of a reflectometer in the UV range of the electromagnetic spectrum as well as optical oxygen sensing with different fiber arrangements.

  7. Distributed Fiber Optical Sensing of Oxygen with Optical Time Domain Reflectometry

    PubMed Central

    Eich, Susanne; Schmälzlin, Elmar; Löhmannsröben, Hans-Gerd

    2013-01-01

    In many biological and environmental applications spatially resolved sensing of molecular oxygen is desirable. A powerful tool for distributed measurements is optical time domain reflectometry (OTDR) which is often used in the field of telecommunications. We combine this technique with a novel optical oxygen sensor dye, triangular-[4] phenylene (TP), immobilized in a polymer matrix. The TP luminescence decay time is 86 ns. The short decay time of the sensor dye is suitable to achieve a spatial resolution of some meters. In this paper we present the development and characterization of a reflectometer in the UV range of the electromagnetic spectrum as well as optical oxygen sensing with different fiber arrangements. PMID:23727953

  8. Fiber Optic Wing Shape Sensing on NASA's Ikhana UAV

    NASA Technical Reports Server (NTRS)

    Richards, Lance; Parker, Allen R.; Ko, William L.; Piazza, Anthony

    2008-01-01

    This document discusses the development of fiber optic wing shape sensing on NASA's Ikhana vehicle. The Dryden Flight Research Center's Aerostructures Branch initiated fiber-optic instrumentation development efforts in the mid-1990s. Motivated by a failure to control wing dihedral resulting in a mishap with the Helios aircraft, new wing displacement techniques were developed. Research objectives for Ikhana included validating fiber optic sensor measurements and real-time wing shape sensing predictions; the validation of fiber optic mathematical models and design tools; assessing technical viability and, if applicable, developing methodology and approaches to incorporate wing shape measurements within the vehicle flight control system; and, developing and flight validating approaches to perform active wing shape control using conventional control surfaces and active material concepts.

  9. Optical Fibers Would Sense Local Strains

    NASA Technical Reports Server (NTRS)

    Egalon, Claudio O.; Rogowski, Robert S.

    1994-01-01

    Proposed fiber-optic transducers measure local strains. Includes lead-in and lead-out lengths producing no changes in phase shifts, plus short sensing length in which phase shift is sensitive to strain. Phase shifts in single-mode fibers vary with strains. In alternative version, multiple portions of optical fiber sensitive to strains characteristic of specific vibrational mode of object. Same principle also used with two-mode fiber.

  10. Optical traffic-sensing concept

    NASA Technical Reports Server (NTRS)

    Johnston, A. R.; Shimada, K.

    1978-01-01

    Scaled-up optical proximity detector is versatile traffic sensor that replaces or augments existing systems such as inductive loops. Photosensor which does not depend on ambient light has several features that protect it against spurious or ambiguous inputs. It could be implemented in several forms to cope with different roadway conditions.

  11. Microwave assisted reconstruction of optical interferograms for distributed fiber optic sensing.

    PubMed

    Huang, Jie; Hua, Lei; Lan, Xinwei; Wei, Tao; Xiao, Hai

    2013-07-29

    This paper reports a distributed fiber optic sensing technique through microwave assisted separation and reconstruction of optical interferograms in spectrum domain. The approach involves sending a microwave-modulated optical signal through cascaded fiber optic interferometers. The microwave signal was used to resolve the position and reflectivity of each sensor along the optical fiber. By sweeping the optical wavelength and detecting the modulation signal, the optical spectrum of each sensor can be reconstructed. Three cascaded fiber optic extrinsic Fabry-Perot interferometric sensors were used to prove the concept. Their microwave-reconstructed interferogram matched well with those recorded individually using an optical spectrum analyzer. The application in distributed strain measurement has also been demonstrated.

  12. Optical fiber sensing based on reflection laser spectroscopy.

    PubMed

    Gagliardi, Gianluca; Salza, Mario; Ferraro, Pietro; Chehura, Edmond; Tatam, Ralph P; Gangopadhyay, Tarun K; Ballard, Nicholas; Paz-Soldan, Daniel; Barnes, Jack A; Loock, Hans-Peter; Lam, Timothy T-Y; Chow, Jong H; De Natale, Paolo

    2010-01-01

    An overview on high-resolution and fast interrogation of optical-fiber sensors relying on laser reflection spectroscopy is given. Fiber Bragg-gratings (FBGs) and FBG resonators built in fibers of different types are used for strain, temperature and acceleration measurements using heterodyne-detection and optical frequency-locking techniques. Silica fiber-ring cavities are used for chemical sensing based on evanescent-wave spectroscopy. Various arrangements for signal recovery and noise reduction, as an extension of most typical spectroscopic techniques, are illustrated and results on detection performances are presented.

  13. Vision sensing techniques in aeronautics and astronautics

    NASA Technical Reports Server (NTRS)

    Hall, E. L.

    1988-01-01

    The close relationship between sensing and other tasks in orbital space, and the integral role of vision sensing in practical aerospace applications, are illustrated. Typical space mission-vision tasks encompass the docking of space vehicles, the detection of unexpected objects, the diagnosis of spacecraft damage, and the inspection of critical spacecraft components. Attention is presently given to image functions, the 'windowing' of a view, the number of cameras required for inspection tasks, the choice of incoherent or coherent (laser) illumination, three-dimensional-to-two-dimensional model-matching, edge- and region-segmentation techniques, and motion analysis for tracking.

  14. Remote sensing as a mineral prospecting technique

    NASA Technical Reports Server (NTRS)

    Meneses, P. R. (Principal Investigator)

    1984-01-01

    Remote sensing and its application as an alternative technique to mineral resource exploration are reviewed. Emphasis is given here to the analysis of the three basic attributes of remote sensing, i.e., spatial attributes related to regional structural mapping, spectral attributes related to rock discrimination and seasonal attributes related to geobotanic anomalies mapping, all of which are employed in mineral exploration. Special emphasis is given to new developments of the Thematic Mapper of the LANDSAT-5, principally with reference to the application of the bands 1.6 and 2.2 microns to map hydrothermally altered rocks and the band of red and blue shift to geobotanical anomalies mapping.

  15. Optical remote sensing small satellite project

    NASA Astrophysics Data System (ADS)

    Cao, Xibin; Zhang, Fan; Lin, Xiaohui; Sun, Zhaowei; Xu, Guodong

    2004-01-01

    Optical Remote Sensing Small Satellite is for high-tech flight demonstration's test and three dimensions mapping. Its system overview is presented in the paper, and it includes such items as mission objective and mission requirements, satellite system scheme, reliability, cost budget project schedule and management and operation.

  16. OPTICAL REMOTE SENSING FOR AIR QUALITY MONITORING

    EPA Science Inventory

    The paper outlines recent developments in using optical remote sensing (ORS) instruments for air quality monitoring both for gaseous pollutants and airborne particulate matter (PM). The U.S. Environmental Protection Agency (EPA) has been using open-path Fourier transform infrared...

  17. Optical Fibers Would Sense Local Temperatures

    NASA Technical Reports Server (NTRS)

    Egalon, Claudio O.; Rogowski, Robert S.

    1994-01-01

    Proposed fiber-optic transducers measure local temperatures. Includes lead-in and lead-out lengths producing no changes in phase shifts, plus short sensing length in which phase shift sensitive to temperature. Phase shifts in two-mode fibers vary with temperatures.

  18. OPTICAL REMOTE SENSING FOR AIR QUALITY MONITORING

    EPA Science Inventory

    The paper outlines recent developments in using optical remote sensing (ORS) instruments for air quality monitoring both for gaseous pollutants and airborne particulate matter (PM). The U.S. Environmental Protection Agency (EPA) has been using open-path Fourier transform infrared...

  19. On Optical Mark-Sense Scanning

    NASA Astrophysics Data System (ADS)

    Jones, Douglas W.

    Optical mark-sense scanning has lead to a resurgence in the use of paper ballots in the United States, despite a century of strong competition from paperless direct-recording voting systems. By the time mark-sense technology emerged, procedural measures had been developed to counter most of the vulnerabilities of paper ballots. Automatic counting of paper ballots poses technical and legal problems, but by counting the paper ballots automatically in the presence of the voter, mark-sense systems address some of the remaining problems with paper ballots. The best current technology uses precinct-count optical scanners to capture pixelized images of each ballot and then process the marks on that image. While this technology may be among the best voting technologies available today for the conduct of complex general elections, it faces one significant problem, access to voters with disabilities. There are promising solutions to this problem, but work remains to be done.

  20. Fiber Optic Sensing: Prototype Results

    NASA Astrophysics Data System (ADS)

    Ortiz Martin, Jesus; Gonzalez Torres, Jose

    2015-09-01

    Airbus DS Crisa has been developing an interrogator of Fiber Bragg Grating sensors [1], aimed at measuring, mainly, temperature and strain by means of fiber optic links. This activity, funded by Airbus DS Crisa, ESA and HBM Fibersensing, finalizes with the manufacturing of a prototype. The present paper describes in detail the main outcomes of the testing activities of this prototype. At the moment of writing the paper all the functional tests have been concluded. The environmental tests, thermal and mechanical, will be conducted with the FOS interrogator forming part of the RTU2015, described in [2].

  1. Optical remote sensing of atmospheric compounds

    NASA Astrophysics Data System (ADS)

    Vazquez, Gabriel J.

    1996-02-01

    Human activities are altering the earth system at the local, regional, and global scales. It is therefore of the utmost importance to track the workings of mother earth in order to detect any changes at their early stages so that appropriate actions are taken to understand, assess, control or prevent the adverse effects. A number of deleterious effects to the environment can, at least in part, be ascribed to air pollution, namely, the thinning of the ozone layer, the related increase in the occurrence of skin cancer, the warming of the earth system, photochemical smog, acid rain/fog, acidification of soils and waters, forest decline, etc. It is therefore necessary to monitor the most relevant processes of the earth's atmosphere, namely, the energy input, the dynamics and the chemistry. In this contribution I mainly focus on the latter, specifically, on the measurement/monitoring of atmospheric compounds. To understand atmospheric chemistry and air pollution it is necessary to have reliable and accurate values of the mixing ratios of the numerous atmospheric gases and of their diurnal/seasonal variations and long-term trends. In this contribution I present an overview of the most relevant optical remote sensing techniques that are rapidly becoming the methods of choice to probe the chemical composition and physical state of the atmosphere, especially when high selectivity, sensitivity and fast-time response are required.

  2. Remote optical stethoscope and optomyography sensing device

    NASA Astrophysics Data System (ADS)

    Golberg, Mark; Polani, Sagi; Ozana, Nisan; Beiderman, Yevgeny; Garcia, Javier; Ruiz-Rivas Onses, Joaquin; Sanz Sabater, Martin; Shatsky, Max; Zalevsky, Zeev

    2017-02-01

    In this paper we present the usage of photonic remote laser based device for sensing nano-vibrations for detection of muscle contraction and fatigue, eye movements and in-vivo estimation of glucose concentration. The same concept is also used to realize a remote optical stethoscope. The advantage of doing the measurements from a distance is in preventing passage of infections as in the case of optical stethoscope or in the capability to monitor e.g. sleep quality without disturbing the patient. The remote monitoring of glucose concentration in the blood stream and the capability to perform opto-myography for the Messer muscles (chewing) is very useful for nutrition and weight control. The optical configuration for sensing the nano-vibrations is based upon analyzing the statistics of the secondary speckle patterns reflected from various tissues along the body of the subjects. Experimental results present the preliminary capability of the proposed configuration for the above mentioned applications.

  3. Strain sensing using optical fibers

    NASA Technical Reports Server (NTRS)

    Houghton, Richard; Hiles, Steven

    1994-01-01

    The main source of attenuation which will be studied is the optical fiber's sensitivity to bending at radii that are much larger than the radius of the fiber. This type of environmental attenuation causes losses that are a function of the severity of the bend. The average attenuation caused by bending varies exponentially with the bend radius. There are many different fibers, sources, and testing equipment available. This thesis describes tests that were performed to evaluate the variables that effect bending related attenuation and will discuss the consistency of the results. Descriptions and comparisons will be made between single mode and multimode fibers as well as instrumentation comparisons between detection equipment. Detailed analysis of the effects of the whispering gallery mode will be performed along with theorized methods for characterization of these modes.

  4. Information hiding technique using optical correlators

    NASA Astrophysics Data System (ADS)

    Kim, Kyu-Tae; Kim, Jung-Jin; Kim, Eun-Soo

    2001-08-01

    During the past few years a variety of techniques have emerged to hide specific information within multimedia data for copyright protection, tamper-proofing and secret communication. The schemes for information hiding that have been proposed so far used either digital signal processing software or hardware. So they inevitably have a problem in some applications like automatic copyright control system, which need fast data-extracting scheme. In this paper, we show that the newly proposed optical correlator-based information hiding system has an advantage in that sense. In this scheme it is possible to simultaneously extract all the data hidden in one stego image and furthermore it is also possible to simultaneously extract all the data hidden in several stego images using optical correlators such as matched spatial filter and joint transform correlator.

  5. Nanopaper as an Optical Sensing Platform.

    PubMed

    Morales-Narváez, Eden; Golmohammadi, Hamed; Naghdi, Tina; Yousefi, Hossein; Kostiv, Uliana; Horák, Daniel; Pourreza, Nahid; Merkoçi, Arben

    2015-07-28

    Bacterial cellulose nanopaper (BC) is a multifunctional material known for numerous desirable properties: sustainability, biocompatibility, biodegradability, optical transparency, thermal properties, flexibility, high mechanical strength, hydrophilicity, high porosity, broad chemical-modification capabilities and high surface area. Herein, we report various nanopaper-based optical sensing platforms and describe how they can be tuned, using nanomaterials, to exhibit plasmonic or photoluminescent properties that can be exploited for sensing applications. We also describe several nanopaper configurations, including cuvettes, plates and spots that we printed or punched on BC. The platforms include a colorimetric-based sensor based on nanopaper containing embedded silver and gold nanoparticles; a photoluminescent-based sensor, comprising CdSe@ZnS quantum dots conjugated to nanopaper; and a potential up-conversion sensing platform constructed from nanopaper functionalized with NaYF4:Yb(3+)@Er(3+)&SiO2 nanoparticles. We have explored modulation of the plasmonic or photoluminescent properties of these platforms using various model biologically relevant analytes. Moreover, we prove that BC is and advantageous preconcentration platform that facilitates the analysis of small volumes of optically active materials (∼4 μL). We are confident that these platforms will pave the way to optical (bio)sensors or theranostic devices that are simple, transparent, flexible, disposable, lightweight, miniaturized and perhaps wearable.

  6. Optical sensing with antiresonant capillary fibers

    NASA Astrophysics Data System (ADS)

    Osório, Jonas H.; Marques, Thiago H. R.; Figueredo, Igor C.; Serrão, Valdir A.; Franco, Marcos A. R.; Cordeiro, Cristiano M. B.

    2017-04-01

    Herein, we present a study of the use of polymer capillary optical fibers in sensing measurements. In particular, we approach the application of these fibers for temperature sensing. To do this, an analytical model for describing the spectral characteristics of the light transmitted through the capillaries was employed. Thermal expansion and thermooptic effect influences on the transmitted spectrum were evaluated. Moreover, a 140 +/- 6 pm/°C temperature sensitivity was measured, which is in good resemblance to simulated data and is around 14 times higher than the sensitivity attained in conventional Bragg gratings sensors.

  7. Electro-optical Synergy Technique

    PubMed Central

    El-Domyati, Moetaz; El-Ammawi, Tarek S.; Medhat, Walid; Moawad, Osama; Mahoney, My G.

    2010-01-01

    Objectives: Electro-optical synergy technology is one of the most recently described methods for nonablative skin rejuvenation. The aim of this study is to evaluate the effects of electro-optical synergy on connective tissue composition by histological and immunohistochemical techniques coupled with computerized morphometric analysis. Design: A prospective clinical study. Participants: Six volunteers with Fitzpatrick skin types 3 to 4 and Glogau class I to II wrinkles were subjected to three months (6 sessions at 2-week intervals) of electro-optical synergy treatment. Measurements: Standard photographs and skin biopsies were obtained at baseline as well as three and six months after the start of treatment. The authors performed quantitative evaluation of total elastin, tropoelastin, collagen types I, III, and VII, and newly synthesized collagen. Results: Noticeable clinical and histological improvement was observed after electro-optical synergy treatment. A statistically significant increase in the means of collagen types I, III, and VII, as well as newly synthesized collagen, together with increased levels of tropoelastin, were detected, while the mean level of total elastin was significantly decreased at the end of treatment and three months post-treatment. Conclusion: Electro-optical synergy is an effective treatment for contouring facial skin laxity. This modality stimulates the repair processes and reverses the clinical, as well as the histopathological, signs of aging with the advantage of being a relatively risk-free procedure with minimal patient recovery time. PMID:21203352

  8. Introduction to the physics and techniques of remote sensing

    NASA Technical Reports Server (NTRS)

    Elachi, Charles

    1987-01-01

    This book presents a comprehensive overview of the basics behind remote-sensing physics, techniques, and technology. The physics of wave/matter interactions, techniques of remote sensing across the electromagnetic spectrum, and the concepts behind remote sensing techniques now established and future ones under development are discussed. Applications of remote sensing are described for a wide variety of earth and planetary atmosphere and surface sciences. Solid surface sensing across the electromagnetic spectrum, ocean surface sensing, basic principles of atmospheric sensing and radiative transfer, and atmospheric remote sensing in the microwave, millimeter, submillimeter, and infrared regions are examined.

  9. Introduction to the physics and techniques of remote sensing

    NASA Technical Reports Server (NTRS)

    Elachi, Charles

    1987-01-01

    This book presents a comprehensive overview of the basics behind remote-sensing physics, techniques, and technology. The physics of wave/matter interactions, techniques of remote sensing across the electromagnetic spectrum, and the concepts behind remote sensing techniques now established and future ones under development are discussed. Applications of remote sensing are described for a wide variety of earth and planetary atmosphere and surface sciences. Solid surface sensing across the electromagnetic spectrum, ocean surface sensing, basic principles of atmospheric sensing and radiative transfer, and atmospheric remote sensing in the microwave, millimeter, submillimeter, and infrared regions are examined.

  10. Static optical designs for Wavefront Curvature Sensing

    NASA Astrophysics Data System (ADS)

    Bharmal, Nazim A.

    2006-06-01

    A bulk optic is presented, the Parallel Output Beamsplitter, which allows simultaneous imaging of two planes either side of the focus using static imaging optics. The POB is used to create novel optical configurations for Wavefront Curvature Sensing and two designs are presented. The first is suited to small-amplitude aberration measurements in situations where compactness, a large field of view, and high optical throughput are desirable. A laboratory experiment using a POB to make such a wavefront sensor was undertaken, and results are presented. The second design is a conceptual idea which offers image-scale invariant imaging of two planes whose conjugation satisfies the requirements of a conventional Wavefront Curvature Sensor concept.

  11. High temperature, minimally invasive optical sensing modules

    DOEpatents

    Riza, Nabeel Agha; Perez, Frank

    2008-02-05

    A remote temperature sensing system includes a light source selectively producing light at two different wavelengths and a sensor device having an optical path length that varies as a function of temperature. The sensor receives light emitted by the light source and redirects the light along the optical path length. The system also includes a detector receiving redirected light from the sensor device and generating respective signals indicative of respective intensities of received redirected light corresponding to respective wavelengths of light emitted by the light source. The system also includes a processor processing the signals generated by the detector to calculate a temperature of the device.

  12. Raman sensing in optical microresonantors (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Cocking, Alexander; Janisch, Corey; Huang, Steven H.; Yang, Lan; Liu, Zhiwen

    2016-10-01

    Ultrahigh-quality whispering gallery mode optical microresonators have been studied for their use as highly sensitive sensors. In this talk, we discuss the use of microsphere microresonators in Raman spectroscopy for interrogating particles adhered to the surface of the resonator. An external cavity diode laser is tuned to a resonant high-Q mode and the circulating optical field experiences a large buildup, resulting in enhanced Raman scattering. Here we present studies of Raman scattering spectroscopy of single particles. Raman sensing with different Q's is discussed.

  13. Control of a Quadcopter Aerial Robot Using Optic Flow Sensing

    NASA Astrophysics Data System (ADS)

    Hurd, Michael Brandon

    This thesis focuses on the motion control of a custom-built quadcopter aerial robot using optic flow sensing. Optic flow sensing is a vision-based approach that can provide a robot the ability to fly in global positioning system (GPS) denied environments, such as indoor environments. In this work, optic flow sensors are used to stabilize the motion of quadcopter robot, where an optic flow algorithm is applied to provide odometry measurements to the quadcopter's central processing unit to monitor the flight heading. The optic-flow sensor and algorithm are capable of gathering and processing the images at 250 frames/sec, and the sensor package weighs 2.5 g and has a footprint of 6 cm2 in area. The odometry value from the optic flow sensor is then used a feedback information in a simple proportional-integral-derivative (PID) controller on the quadcopter. Experimental results are presented to demonstrate the effectiveness of using optic flow for controlling the motion of the quadcopter aerial robot. The technique presented herein can be applied to different types of aerial robotic systems or unmanned aerial vehicles (UAVs), as well as unmanned ground vehicles (UGV).

  14. Optical apparatus and method for sensing uranyl

    DOEpatents

    Baylor, L.C.; Buchanan, B.R.

    1994-01-01

    An optical sensing device for uranyl and other substances, a method for making an optical sensing device and a method for chemically binding uranyl and other indicators to glass, quartz, cellulose and similar substrates. The indicator, such as arsenazo III, is immobilized on the substrate using a chemical binding process. The immobilized arsenazo III causes uranyl from a fluid sample to bind irreversibly to the substrate at its active sites, thus causing absorption of a portion of light transmitted through the substrate. Determination of the amount of light absorbed, using conventional means, yields the concentration of uranyl present in the sample fluid. The binding of uranyl on the substrate can be reversed by subsequent exposure of the substrate to a solution of 2,6-pyridinedicarboxylic acid. The chemical binding process is suitable for similarly binding other indicators, such as bromocresol green.

  15. Computational intelligence techniques for tactile sensing systems.

    PubMed

    Gastaldo, Paolo; Pinna, Luigi; Seminara, Lucia; Valle, Maurizio; Zunino, Rodolfo

    2014-06-19

    Tactile sensing helps robots interact with humans and objects effectively in real environments. Piezoelectric polymer sensors provide the functional building blocks of the robotic electronic skin, mainly thanks to their flexibility and suitability for detecting dynamic contact events and for recognizing the touch modality. The paper focuses on the ability of tactile sensing systems to support the challenging recognition of certain qualities/modalities of touch. The research applies novel computational intelligence techniques and a tensor-based approach for the classification of touch modalities; its main results consist in providing a procedure to enhance system generalization ability and architecture for multi-class recognition applications. An experimental campaign involving 70 participants using three different modalities in touching the upper surface of the sensor array was conducted, and confirmed the validity of the approach.

  16. Computational Intelligence Techniques for Tactile Sensing Systems

    PubMed Central

    Gastaldo, Paolo; Pinna, Luigi; Seminara, Lucia; Valle, Maurizio; Zunino, Rodolfo

    2014-01-01

    Tactile sensing helps robots interact with humans and objects effectively in real environments. Piezoelectric polymer sensors provide the functional building blocks of the robotic electronic skin, mainly thanks to their flexibility and suitability for detecting dynamic contact events and for recognizing the touch modality. The paper focuses on the ability of tactile sensing systems to support the challenging recognition of certain qualities/modalities of touch. The research applies novel computational intelligence techniques and a tensor-based approach for the classification of touch modalities; its main results consist in providing a procedure to enhance system generalization ability and architecture for multi-class recognition applications. An experimental campaign involving 70 participants using three different modalities in touching the upper surface of the sensor array was conducted, and confirmed the validity of the approach. PMID:24949646

  17. Industrial applications of fiber optic sensing

    NASA Astrophysics Data System (ADS)

    Desforges, Francois X.; Blocksidge, Robert

    1996-08-01

    Thanks to the growth of the fiber optics telecommunication industry, fiber optic components have become less expensive, more reliable and well known by potential fiber optic sensor users. LEDs, optical fibers, couplers and connectors are now widely distributed and are the building blocks for the fiber optic sensor manufacturer. Additionally, the huge demand in consumer electronics of the past 10 years has provided the manufacturer with cheap and powerful programmable logic components which reduce the development time as well as the cost of the associated instrumentation. This market trend has allowed Photonetics to develop, manufacture and sell fiber optic sensors for the last 10 years. The company contribution in the fields of fiber optic gyros (4 licenses sold world wide), white light interferometry and fiber optic sensor networks is widely recognized. Moreover, its 1992 acquisition of some of the assets of Metricor Inc., greatly reinforced its position and allowed it to pursue new markets. Over the past four years, Photonetics has done an important marketing effort to better understand the need of its customers. The result of this research has fed R&D efforts towards a new generation instrument, the Metricor 2000, better adapted to the expectations of fiber optic sensors users, thanks to its unique features: (1) universality -- the system can accept more than 20 different sensors (T, P, RI, . . .). (2) scalability -- depending on the customer needs, the system can be used with 1 to 64 sensors. (3) performance -- because of its improved design, overall accuracies of 0.01% FS can be reached. (4) versatility -- its modular design enables a fast and easy custom design for specific applications. This paper presents briefly the Metricor 2000 and its family of FO probes. Then, it describes two fiber optic sensing (FOS) applications/markets where FOS have proven to be very useful.

  18. Optical Shadow Sensing for Drag-Free Spacecraft Control

    NASA Astrophysics Data System (ADS)

    Leidecker, Nick; Trittler, A.; Conklin, J.; Buchman, S.; Sun, K.; Byer, R.; Trittler, M.; Goebel, J.

    2009-01-01

    Solar wind and residual atmospheric drag can produce disturbances that are unacceptable for high precision scientific experiments. The drag free concept is to shield a proof mass from these disturbances, and sense the proof mass position to fly the spacecraft around the proof mass. LISA and a large array of astrophysical missions must fly drag-free to achieve their desired scientific goals. In the modular gravitational reference sensor (MGRS), the proof mass is kept a large distance away from housing to minimize the disturbances, and will be suitable for advanced drag-free missions. We have proposed and demonstrated differential optical shadow sensing scheme, to generate the primary signal for spacecraft drag-free control. In this scheme, a pair of detectors spaced at the diameter of a spherical proof mass is used measure the proof mass movement. By differencing their outputs, the laser intensity noise is cancelled, while the proof mass displacement signal is doubled. We have designed and constructed an optical shadow sensing test platform comprised of a step motor driven actuator for large movement and a piezo driven flexture structure for fine adjustment. We investigated signal formation and methods of signal to noise ratio enhancement. We reduced the noise effects of electronics, electromagnetic interference, air flow and temperature. Currently we have achieved a sensitivity of 2 nm/Hz1/2 at 2 Hz, limited by lab air currents. The dynamic range is 1 mm, limited by the detector diameter. We applied the differential optical sensing technique to mass center determination measurement and improved the mass center precision to 200 nm. Further, we are designing and constructing a new platform that will have spinning spherical proof mass and multiple optical shadow sensors, to demonstrate full 3-d optical shadow sensing.

  19. Distributed Fiber Optic Gas Sensing for Harsh Environment

    SciTech Connect

    Juntao Wu

    2008-03-14

    This report summarizes work to develop a novel distributed fiber-optic micro-sensor that is capable of detecting common fossil fuel gases in harsh environments. During the 32-month research and development (R&D) program, GE Global Research successfully synthesized sensing materials using two techniques: sol-gel based fiber surface coating and magnetron sputtering based fiber micro-sensor integration. Palladium nanocrystalline embedded silica matrix material (nc-Pd/Silica), nanocrystalline palladium oxides (nc-PdO{sub x}) and palladium alloy (nc-PdAuN{sub 1}), and nanocrystalline tungsten (nc-WO{sub x}) sensing materials were identified to have high sensitivity and selectivity to hydrogen; while the palladium doped and un-doped nanocrystalline tin oxide (nc-PdSnO{sub 2} and nc-SnO{sub 2}) materials were verified to have high sensitivity and selectivity to carbon monoxide. The fiber micro-sensor comprises an apodized long-period grating in a single-mode fiber, and the fiber grating cladding surface was functionalized by above sensing materials with a typical thickness ranging from a few tens of nanometers to a few hundred nanometers. GE found that the morphologies of such sensing nanomaterials are either nanoparticle film or nanoporous film with a typical size distribution from 5-10 nanometers. nc-PdO{sub x} and alloy sensing materials were found to be highly sensitive to hydrogen gas within the temperature range from ambient to 150 C, while nc-Pd/Silica and nc-WO{sub x} sensing materials were found to be suitable to be operated from 150 C to 500 C for hydrogen gas detection. The palladium doped and un-doped nc-SnO{sub 2} materials also demonstrated sensitivity to carbon monoxide gas at approximately 500 C. The prototyped fiber gas sensing system developed in this R&D program is based on wavelength-division-multiplexing technology in which each fiber sensor is identified according to its transmission spectra features within the guiding mode and cladding modes. The

  20. Birefringent porous silicon membranes for optical sensing.

    PubMed

    Alvarez, Jesús; Bettotti, Paolo; Suárez, Isaac; Kumar, Neeraj; Hill, Daniel; Chirvony, Vladimir; Pavesi, Lorenzo; Martínez-Pastor, Juan

    2011-12-19

    In this work anisotropic porous silicon is investigated as a material for optical sensing. Birefringence and sensitivity of the anisotropic porous silicon membranes are thoroughly studied in the framework of Bruggeman model which is extended to incorporate the influence of environment effects, such as silicon oxidation. The membranes were also characterized optically demonstrating sensitivity as high as 1245 nm/RIU at 1500 nm. This experimental value only agrees with the theory when it takes into consideration the effect of silicon oxidation. Furthermore we demonstrate that oxidized porous silicon membranes have optical parameters with long term stability. Finally, we developed a new model to determine the contribution of the main depolarization sources to the overall depolarization process, and how it influences the measured spectra and the resolution of birefringence measurements.

  1. Optical microspherical resonators for biomedical sensing.

    PubMed

    Soria, Silvia; Berneschi, Simone; Brenci, Massimo; Cosi, Franco; Conti, Gualtiero Nunzi; Pelli, Stefano; Righini, Giancarlo C

    2011-01-01

    Optical resonators play an ubiquitous role in modern optics. A particular class of optical resonators is constituted by spherical dielectric structures, where optical rays are total internal reflected. Due to minimal reflection losses and to potentially very low material absorption, these guided modes, known as whispering gallery modes, can confer the resonator an exceptionally high quality factor Q, leading to high energy density, narrow resonant-wavelength lines and a lengthy cavity ringdown. These attractive characteristics make these miniaturized optical resonators especially suited as laser cavities and resonant filters, but also as very sensitive sensors. First, a brief analysis is presented of the characteristics of microspherical resonators, of their fabrication methods, and of the light coupling techniques. Then, we attempt to overview some of the recent advances in the development of microspherical biosensors, underlining a number of important applications in the biomedical field.

  2. Optical Microspherical Resonators for Biomedical Sensing

    PubMed Central

    Soria, Silvia; Berneschi, Simone; Brenci, Massimo; Cosi, Franco; Conti, Gualtiero Nunzi; Pelli, Stefano; Righini, Giancarlo C.

    2011-01-01

    Optical resonators play an ubiquitous role in modern optics. A particular class of optical resonators is constituted by spherical dielectric structures, where optical rays are total internal reflected. Due to minimal reflection losses and to potentially very low material absorption, these guided modes, known as whispering gallery modes, can confer the resonator an exceptionally high quality factor Q, leading to high energy density, narrow resonant-wavelength lines and a lengthy cavity ringdown. These attractive characteristics make these miniaturized optical resonators especially suited as laser cavities and resonant filters, but also as very sensitive sensors. First, a brief analysis is presented of the characteristics of microspherical resonators, of their fabrication methods, and of the light coupling techniques. Then, we attempt to overview some of the recent advances in the development of microspherical biosensors, underlining a number of important applications in the biomedical field. PMID:22346603

  3. Ultrasensitive mass sensing with nonlinear optics in a doubly clamped suspended carbon nanotube resonator

    SciTech Connect

    Chen, Hua-Jun; Zhu, Ka-Di

    2013-12-07

    Nanomechanical resonator makes itself as an ideal system for ultrasensitive mass sensing due to its ultralow mass and high vibrational frequency. The mass sensing principle is due to the linear relationship of the frequency-shift and mass-variation. In this work, we will propose a nonlinear optical mass sensor based on a doubly clamped suspended carbon nanotube resonator in all-optical domain. The masses of external particles (such as nitric oxide molecules) landing onto the surface of carbon nanotube can be determined directly and accurately via using the nonlinear optical spectroscopy. This mass sensing proposed here may provide a nonlinear optical measurement technique in quantum measurements and environmental science.

  4. Topical Meeting on Laser and Optical Remote Sensing: Instrumentation and Techniques Technical Digest Held in North Falmoth, Massachusetts on September 28-October 1, 1987. Volume 18.

    DTIC Science & Technology

    1988-08-01

    power and volume are achievable by utilizing emerging technologies in light-weighted mirrors and tunable solid state lasers, pumped by semiconductor...Cretien form of a Cassegrain telescope. The secondary mirror is fused quartz with an aluminum reflecting surface and the primary mirror features a...which receive and separate the backscattered laser signals. The optical assembly is mounted on an optical bench and suspended under the primary mirror

  5. Conjugated amplifying polymers for optical sensing applications.

    PubMed

    Rochat, Sébastien; Swager, Timothy M

    2013-06-12

    Thanks to their unique optical and electrochemical properties, conjugated polymers have attracted considerable attention over the last two decades and resulted in numerous technological innovations. In particular, their implementation in sensing schemes and devices was widely investigated and produced a multitude of sensory systems and transduction mechanisms. Conjugated polymers possess numerous attractive features that make them particularly suitable for a broad variety of sensing tasks. They display sensory signal amplification (compared to their small-molecule counterparts) and their structures can easily be tailored to adjust solubility, absorption/emission wavelengths, energy offsets for excited state electron transfer, and/or for use in solution or in the solid state. This versatility has made conjugated polymers a fluorescence sensory platform of choice in the recent years. In this review, we highlight a variety of conjugated polymer-based sensory mechanisms together with selected examples from the recent literature.

  6. Instrumentation for remote sensing over fiber optics

    NASA Astrophysics Data System (ADS)

    Hirschfeld, T.; Haugen, G.; Milanovich, F. P.

    1983-09-01

    The sensing and analytical abilities of the laser-fluorescence spectrometer was extended beyond the physical confines of the laboratory by means of communications-grade optical fibers. These fiber probes are extremely rugged, compared with sensitive laboratory equipment, and also extremely inexpensive. Sensitive chemical analyses may be performed in hostile environments without risking damage to the laser and the spectrometer. Special-purpose optrodes that are sensitive to selected chemicals were produced. With multiplexing, a number of fibers whose terminals are at widely scattered locations, gathering information in one central instrument without the expense and delay involved in manual sample gathering are scanned. A remote analyzer for monitoring rare earth ion migration in a nuclear-waste repository, an environment too hostile for any previous remote sensing device is being developed. Optrodes sensitive to a wide variety of non-chemical stimuli are being developed.

  7. Optical fibre sensing: a solution for industry

    NASA Astrophysics Data System (ADS)

    Sun, T.; Fabian, M.; Chen, Y.; Vidakovic, M.; Javdani, S.; Grattan, K. T. V.; Carlton, J.; Gerada, C.; Brun, L.

    2017-04-01

    Optical fibres have been explored widely for their sensing capability to meet increasing industrial needs, building on their success in telecommunications. This paper provides a review of research activities at City University of London in response to industrial challenges through the development of a range of fibre Bragg grating (FBG)-based sensors for transportation structural monitoring. For marine propellers, arrays of FBGs mapped onto the surface of propeller blades allow for capturing vibrational modes, with reference to simulation data. The research funded by EU Cleansky programme enables the development of self-sensing electric motor drives to support `More Electric Aircraft' concept. The partnership with Faiveley Brecknell Willis in the UK enables the integration of FBG sensors into the railway current-collecting pantographs for real-time condition monitoring when they are operating under 25kV conditions.

  8. Study of 3D remote sensing system based on optical scanning holography

    NASA Astrophysics Data System (ADS)

    Zhao, Shihu; Yan, Lei

    2009-06-01

    High-precision and real-time remote sensing imaging system is an important part of remote sensing development. Holography is a method of wave front record and recovery which was presented by Dennis Gabor. As a new kind of holography techniques, Optical scanning holography (OSH) and remote sensing imaging are intended to be combined together and applied in acquisition and interference measurement of remote sensing. The key principles and applicability of OSH are studied and the mathematic relation between Fresnel Zone Plate number, numerical aperture and object distance was deduced, which are proved to be feasible for OSH to apply in large scale remote sensing. At last, a new three-dimensional reflected OSH remote sensing imaging system is designed with the combination of scanning technique to record hologram patterns of large scale remote sensing scenes. This scheme is helpful for expanding OSH technique to remote sensing in future.

  9. Multiplexed refractive index-based sensing using optical fiber microcavities

    NASA Astrophysics Data System (ADS)

    Warren-Smith, Stephen C.; André, Ricardo M.; Dellith, Jan; Bartelt, Hartmut

    2016-04-01

    Optical fibers are promising tools for performing biological and biomedical sensing due to their small cross section and potential for multiplexing. In particular, fabricating ultra-small sensing devices is of increasing interest for measuring biological material such as cells. A promising direction is the use of interferometric techniques combined with optical fiber post-processing. In this work we present recent progress in the development of Fabry-Perot micro-cavities written into optical fiber tapers using focused ion beam (FIB) milling. We first demonstrate that FIB milled optical fiber microcavities are sensitive enough to measure polyelectrolyte layer deposition. We then present new results on the fabrication and optical characterization of serially-multiplexed dual cavity micro-sensors. Two cavities were written serially along the fiber with two different cavity lengths, producing a total of four reflecting surfaces and thus six possible interferometric pairs/cavities. By using fast Fourier transform it is possible to obtain de-multiplexed measurements for each cavity. This will be particularly important for bioassays where positive and negative controls are required to be measured within close spatial proximity.

  10. Mobile quantum sensing with spins in optically trapped nanodiamonds

    NASA Astrophysics Data System (ADS)

    Awschalom, David D.

    2013-03-01

    The nitrogen-vacancy (NV) color center in diamond has emerged as a powerful, optically addressable, spin-based probe of electromagnetic fields and temperature. For nanoscale sensing applications, the NV center's atom-like nature enables the close-range interactions necessary for both high spatial resolution and the detection of fields generated by proximal nuclei, electrons, or molecules. Using a custom-designed optical tweezers apparatus, we demonstrate three-dimensional position control of nanodiamonds in solution with simultaneous optical measurement of electron spin resonance (ESR)[3]. Despite the motion and random orientation of NV centers suspended in the optical trap, we observe distinct peaks in the ESR spectra from the ground-state spin transitions. Accounting for the random dynamics of the trapped nanodiamonds, we model the ESR spectra observed in an applied magnetic field and estimate the dc magnetic sensitivity based on the ESR line shapes to be 50 μT/√{ Hz }. We utilize the optically trapped nanodiamonds to characterize the magnetic field generated by current-carrying wires and ferromagnetic structures in microfluidic circuits. These measurements provide a pathway to spin-based sensing in fluidic environments and biophysical systems that are inaccessible to existing scanning probe techniques, such as the interiors of living cells. This work is supported by AFOSR and DARPA.

  11. Role of molar concentration in structural, optical and gas sensing performance of anatase phase TiO2 nanofilms: automated nebulizer spray pyrolysis (ANSP) technique

    NASA Astrophysics Data System (ADS)

    Gopala Krishnan, V.; Elango, P.; Ganesan, V.

    2017-07-01

    TiO2 nanofilms were deposited on a glass substrate at 500 °C using automated nebulizer spray pyrolysis. The anatase polycrystalline structure with increased grain size and variations of surfactant planes ( T c) were influenced by molar concentration on XRD study. AFM study shows the average roughness values were increased with increase in molar concentration. A granular domain like microstructure with crack and void-free particle was examined by FESEM. The maximum transmittance 95.5% (529.6 nm) for x = 0.05 M/L, further increment of molar concentration showed the decremented transmittance with red shift absorption edge and the calculated band gap values ( E g = 3.53-3.20 eV) also noted. The gas sensing performances of films were studied with respect to various gas sensing parameters and the ammonia (NH3) gas showed better sensing response ( S max = 89%) at 150 °C for 300 ppm gas concentration against other gases (C2H6O, CH4O, C3H8O and C3H6O).

  12. Distributed fiber optic moisture intrusion sensing system

    DOEpatents

    Weiss, Jonathan D.

    2003-06-24

    Method and system for monitoring and identifying moisture intrusion in soil such as is contained in landfills housing radioactive and/or hazardous waste. The invention utilizes the principle that moist or wet soil has a higher thermal conductance than dry soil. The invention employs optical time delay reflectometry in connection with a distributed temperature sensing system together with heating means in order to identify discrete areas within a volume of soil wherein temperature is lower. According to the invention an optical element and, optionally, a heating element may be included in a cable or other similar structure and arranged in a serpentine fashion within a volume of soil to achieve efficient temperature detection across a large area or three dimensional volume of soil. Remediation, moisture countermeasures, or other responsive action may then be coordinated based on the assumption that cooler regions within a soil volume may signal moisture intrusion where those regions are located.

  13. Multivariate image processing technique for noninvasive glucose sensing

    NASA Astrophysics Data System (ADS)

    Webb, Anthony J.; Cameron, Brent D.

    2010-02-01

    A potential noninvasive glucose sensing technique was investigated for application towards in vivo glucose monitoring for individuals afflicted with diabetes mellitus. Three dimensional ray tracing simulations using a realistic iris pattern integrated into an advanced human eye model are reported for physiological glucose concentrations ranging between 0 to 500 mg/dL. The anterior chamber of the human eye contains a clear fluid known as the aqueous humor. The optical refractive index of the aqueous humor varies on the order of 1.5x10-4 for a change in glucose concentration of 100 mg/dL. The simulation data was analyzed with a developed multivariate chemometrics procedure that utilizes iris-based images to form a calibration model. Results from these simulations show considerable potential for use of the developed method in the prediction of glucose. For further demonstration, an in vitro eye model was developed to validate the computer based modeling technique. In these experiments, a realistic iris pattern was placed in an analog eye model in which the glucose concentration within the fluid representing the aqueous humor was varied. A series of high resolution digital images were acquired using an optical imaging system. These images were then used to form an in vitro calibration model utilizing the same multivariate chemometric technique demonstrated in the 3-D optical simulations. In general, the developed method exhibits considerable applicability towards its use as an in vivo platform for the noninvasive monitoring of physiological glucose concentration.

  14. Nanostructured detector technologies for optical sensing applications

    NASA Astrophysics Data System (ADS)

    Sood, Ashok K.; Welser, Roger E.; Puri, Yash R.; Dhar, Nibir K.; Polla, Dennis L.; Wijewarnasuriya, Priyalal; Dubey, Madan

    2014-05-01

    Optical sensing technology is critical for optical communication, defense and security applications. Advances in optoelectronics materials in the UV, Visible and Infrared, using nanostructures, and use of novel materials such as CNT and Graphene have opened doors for new approaches to apply device design methodology that are expected to offer enhanced performance and low cost optical sensors in a wide range of applications. This paper is intended to review recent advancements and present different device architectures and analysis. The chapter will briefly introduce the basics of UV and Infrared detection physics and various wave bands of interest and their characteristics [1, 2] We will cover the UV band (200-400 nm) and address some of the recent advances in nanostructures growth and characterization using ZnO/MgZnO based technologies and their applications. Recent advancements in design and development of CNT and Graphene based detection technologies have shown promise for optical sensor applications. We will present theoretical and experimental results on these device and their potential applications in various bands of interest.

  15. Electro-optical and Magneto-optical Sensing Apparatus and Method for Characterizing Free-space Electromagnetic Radiation

    DOEpatents

    Zhang, Xi-Cheng; Riordan, Jenifer Ann; Sun, Feng-Guo

    2000-08-29

    Apparatus and methods for characterizing free-space electromagnetic energy, and in particular, apparatus/method suitable for real-time two-dimensional far-infrared imaging applications are presented. The sensing technique is based on a non-linear coupling between a low-frequency electric (or magnetic) field and a laser beam in an electro-optic (or magnetic-optic) crystal. In addition to a practical counter-propagating sensing technique, a co-linear approach is described which provides longer radiated field-optical beam interaction length, thereby making imaging applications practical.

  16. Real-time sensing of optical alignment

    NASA Technical Reports Server (NTRS)

    Stier, Mark T.; Wissinger, Alan B.

    1988-01-01

    The Large Deployable Reflector and other future segmented optical systems may require autonomous, real-time alignment of their optical surfaces. Researchers have developed gratings located directly on a mirror surface to provide interferometric sensing of the location and figure of the mirror. The grating diffracts a small portion of the incident beam to a diffractive focus where the designed diagnostics can be performed. Mirrors with diffraction gratings were fabricated in two separate ways. The formation of a holographic grating over the entire surface of a mirror, thereby forming a Zone Plate Mirror (ZPM) is described. Researchers have also used computer-generated hologram (CGH) patches for alignment and figure sensing of mirrors. When appropriately illuminated, a grid of patches spread over a mirror segment will yield a grid of point images at a wavefront sensor, with the relative location of the points providing information on the figure and location of the mirror. A particular advantage of using the CGH approach is that the holographic patches can be computed, fabricated, and replicated on a mirror segment in a mass production 1-g clean room environment.

  17. Cognitive optical networks: architectures and techniques

    NASA Astrophysics Data System (ADS)

    Grebeshkov, Alexander Y.

    2017-04-01

    This article analyzes architectures and techniques of the optical networks with taking into account the cognitive methodology based on continuous cycle "Observe-Orient-Plan-Decide-Act-Learn" and the ability of the cognitive systems adjust itself through an adaptive process by responding to new changes in the environment. Cognitive optical network architecture includes cognitive control layer with knowledge base for control of software-configurable devices as reconfigurable optical add-drop multiplexers, flexible optical transceivers, software-defined receivers. Some techniques for cognitive optical networks as flexible-grid technology, broker-oriented technique, machine learning are examined. Software defined optical network and integration of wireless and optical networks with radio over fiber technique and fiber-wireless technique in the context of cognitive technologies are discussed.

  18. Application of Spectral Analysis Techniques in the Intercomparison of Aerosol Data: 1. an EOF Approach to the Spatial-Temporal Variability of Aerosol Optical Depth Using Multiple Remote Sensing Data Sets

    NASA Technical Reports Server (NTRS)

    Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.

    2013-01-01

    Many remote sensing techniques and passive sensors have been developed to measure global aerosol properties. While instantaneous comparisons between pixel-level data often reveal quantitative differences, here we use Empirical Orthogonal Function (EOF) analysis, also known as Principal Component Analysis, to demonstrate that satellite-derived aerosol optical depth (AOD) data sets exhibit essentially the same spatial and temporal variability and are thus suitable for large-scale studies. Analysis results show that the first four EOF modes of AOD account for the bulk of the variance and agree well across the four data sets used in this study (i.e., Aqua MODIS, Terra MODIS, MISR, and SeaWiFS). Only SeaWiFS data over land have slightly different EOF patterns. Globally, the first two EOF modes show annual cycles and are mainly related to Sahara dust in the northern hemisphere and biomass burning in the southern hemisphere, respectively. After removing the mean seasonal cycle from the data, major aerosol sources, including biomass burning in South America and dust in West Africa, are revealed in the dominant modes due to the different interannual variability of aerosol emissions. The enhancement of biomass burning associated with El Niño over Indonesia and central South America is also captured with the EOF technique.

  19. Optically powered active sensing system for Internet Of Things

    NASA Astrophysics Data System (ADS)

    Gao, Chen; Wang, Jin; Yin, Long; Yang, Jing; Jiang, Jian; Wan, Hongdan

    2014-10-01

    Internet Of Things (IOT) drives a significant increase in the extent and type of sensing technology and equipment. Sensors, instrumentation, control electronics, data logging and transmission units comprising such sensing systems will all require to be powered. Conventionally, electrical powering is supplied by batteries or/and electric power cables. The power supply by batteries usually has a limited lifetime, while the electric power cables are susceptible to electromagnetic interference. In fact, the electromagnetic interference is the key issue limiting the power supply in the strong electromagnetic radiation area and other extreme environments. The novel alternative method of power supply is power over fiber (PoF) technique. As fibers are used as power supply lines instead, the delivery of the power is inherently immune to electromagnetic radiation, and avoids cumbersome shielding of power lines. Such a safer power supply mode would be a promising candidate for applications in IOT. In this work, we built up optically powered active sensing system, supplying uninterrupted power for the remote active sensors and communication modules. Also, we proposed a novel maximum power point tracking technique for photovoltaic power convertors. In our system, the actual output efficiency greater than 40% within 1W laser power. After 1km fiber transmission and opto-electric power conversion, a stable electric power of 210mW was obtained, which is sufficient for operating an active sensing system.

  20. Design of multiplexed fiber optic chemical sensing system using clad-removable optical fibers

    NASA Astrophysics Data System (ADS)

    Yun, Chang-Yong; Dhital, Dipesh; Lee, Jung-Ryul; Park, Gyuhae; Kwon, Il-Bum

    2012-02-01

    To prevent possible threats to public safety and economic loss from chemical leakage accidents, novel chemical sensing techniques for regular monitoring and leakage detection have been developed for various fields. We propose a fiber optic liquid chemical sensor (FOCS) system using specialty optical fibers and an optical time domain reflectometer (OTDR), and is based on the leaky wave mode sensing principle. OTDR enables simple multiplexing where individual sensor nodes along the fiber length could be interrogated by a common OTDR. The sensor node in the optical fiber is prepared by removing the desired length of a protective layer using mechanical stripping and chemical etching techniques. A novel laser stripping technique with superior capability to fabricate quasi-distributed dense sensor nodes is devised as well. The FOCS system is further analyzed to characterize the sensor response behavior in relation to the sensor node length and possible environmental and chemical temperature effect. Under the condition satisfying the leaky wave mode principle and within the minimum acceptable refractive index (RI) range by the system, this FOCS system could monitor numerous liquid chemicals with variable refractive indices and has been tested with positive results. In addition, the system shows the possibility for multi-point detection and is further expanded into a hybrid technique capable of estimating the refractive index range of the detected chemical.

  1. Fiber optic sensing of cyanides in solutions

    SciTech Connect

    Park, S.S.; Mackenzie, J.D.; Li, C.Y.; Guerreiro, P.; Peyghambarian, N.

    1996-12-31

    A novel sol-gel technique was used to immobilize malachite green ions (MG{sup +}) in stable, optically transparent, porous silica gel films. A simple and sensitive method was developed for the detection of cyanides in solutions using spectrophotometry to measure changes caused by cyanide ions (CN{sup {minus}}) in the absorption spectra of the green-colored silica gel films. After reaction with cyanide ions, the absorption spectra of the films changed with a typical decrease in absorbance at 620 nm. On the basis of the absorption spectra of the films, a portable and easy to use fiber optic cyanide film sensor was fabricated. Decolorization undergone by the green-colored gel films, as they were exposed to cyanide ions, was detected through a fiber. Preliminary results indicate concentrations on the order of a few ppm are detected using the fiber optic sensor.

  2. Advanced Adaptive Optics Control Techniques

    DTIC Science & Technology

    1979-01-01

    Optimal estimation and control methods for high energy laser adaptive optics systems are described. Three system types are examined: Active...the adaptive optics approaches and potential system implementations are recommended.

  3. Computational optical sensing and imaging: introduction to feature issue.

    PubMed

    Gerwe, David R; Harvey, Andrew; Gehm, Michael E

    2013-04-01

    The 2012 Computational Optical Sensing and Imaging (COSI) conference of the Optical Society of America was one of six colocated meetings composing the Imaging and Applied Optics Congress held in Monterey, California, 24-28 June. COSI, together with the Imaging Systems and Applications, Optical Sensors, Applied Industrial Optics, and Optical Remote Sensing of the Environment conferences, brought together a diverse group of scientists and engineers sharing a common interest in measuring and processing of information carried by optical fields. This special feature includes several papers based on presentations given at the 2012 COSI conference as well as independent contributions, which together highlight several important trends.

  4. Fast Brillouin Optical Time Domain Analysis for dynamic sensing.

    PubMed

    Peled, Yair; Motil, Avi; Tur, Moshe

    2012-04-09

    A new technique for the fast implementation of Brillouin Optical Time Domain Analysis (BOTDA) is proposed and demonstrated, carrying the classical BOTDA method to the dynamic sensing domain. By using a digital signal generator which enables fast switching among 100 scanning frequencies, we demonstrate a truly distributed and dynamic measurement of a 100 m long fiber with a sampling rate of ~10 kHz, limited only by the fiber length and the frequency granularity. With 10 averages the standard deviation of the measured strain was ~5 µε.

  5. Optical sample-position sensing for electrostatic levitation

    NASA Technical Reports Server (NTRS)

    Sridharan, G.; Chung, S.; Elleman, D.; Whim, W. K.

    1989-01-01

    A comparative study is conducted for optical position-sensing techniques applicable to micro-G conditions sample-levitation systems. CCD sensors are compared with one- and two-dimensional position detectors used in electrostatic particle levitation. In principle, the CCD camera method can be improved from current resolution levels of 200 microns through the incorporation of a higher-pixel device and more complex digital signal processor interface. Nevertheless, the one-dimensional position detectors exhibited superior, better-than-one-micron resolution.

  6. Distributed flow sensing using optical hot -wire grid.

    PubMed

    Chen, Tong; Wang, Qingqing; Zhang, Botao; Chen, Rongzhang; Chen, Kevin P

    2012-04-09

    An optical hot-wire flow sensing grid is presented using a single piece of self-heated optical fiber to perform distributed flow measurement. The flow-induced temperature loss profiles along the fiber are interrogated by the in-fiber Rayleigh backscattering, and spatially resolved in millimeter resolution using optical frequency domain reflectometry (OFDR). The flow rate, position, and flow direction are retrieved simultaneously. Both electrical and optical on-fiber heating were demonstrated to suit different flow sensing applications.

  7. Tapered splice technique for capillary optical fiber

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoliang; Xiang, Huoxing

    2017-07-01

    We propose a simple but effective technique. It is concerned with a tapered splice technique for capillary optical fiber. In order to contrast, we investigate two kinds of capillary optical fiber. One of the capillary optical fiber has the annular core around the air hole and the other one has the embedded annular core around the inner cladding. We demonstrate the tapered splice technique works for both of the capillary optical fiber in experiment. It is the key to improve the coupling efficiency of the capillary optical fiber. We also build a theoretical model to predict the optical power of the capillary optical fiber and it is confirmed by the experimental results. The method provides an insight of the mode conversion characteristics of capillary optical fiber. It should be used as an easy way to realize the fiber-based in-line components and should be more importantly to explore new possibilities with this kind of fiber.

  8. Remote Sensing Techniques for Monitoring Aquatic Vegetation

    NASA Astrophysics Data System (ADS)

    Blanco, Alfonso

    Hydrilla is an important submerged aquatic vegetation because it has a large capacity to absorb pollutants and it is an indicator of the eutrophic status of a waterbody. Monitoring and restoration of submerged aquatic vegetation is key for the preservation and restoration of the Chesapeake Bay. Remote sensing techniques have been used for assessing wetlands and non-invasive aquatic species, but there is limited studies of hydrilla monitoring combined with space-borne, airborne and in-situ remote sensing measurements for detecting and mapping hydrilla infestation. The first objective of this research was to establish a database of hydrilla spectral signatures from an experimental tank and from a field setting using a handheld spectrometer. The spectral signatures collected will be used to identify the optimal spectral and spatial characteristics that are required to identify and classify the distribution of hydrilla canopies in water bodies. The second objective is to process and analyze two hyperspectral images from a space-borne (Hyperion) and airborne (AISA) sensors with ENVI for detecting and mapping the infestation of hydrilla vertillicata in a coastal estuary in Chesapeake Bay. The third objective was to validate the satellite and airborne hyperspectral images with the spectral signatures collected with the in-situ field measurements. In addition, the Hyperion and AISA imaging results were compared with ground surveys and aerial photos collected by the Maryland Department of Natural Resources and the Virginia Institute of Marine Sciences for verifying the extent and the location of the hydrilla canopies. The hyperspectral analysis of both sensors provided for a dual results, one is the identification and classification of hydrilla from hyperspectral imaging sensors and secondly the identification of algae blooms in very productive waters. A hydrilla spectral signature database was established and housed in GMU's EastFIRE Lab of Environmental Science and

  9. Optical frequency domain reflectometry: principles and applications in fiber optic sensing

    NASA Astrophysics Data System (ADS)

    Kreger, Stephen T.; Rahim, Nur Aida Abdul; Garg, Naman; Klute, Sandra M.; Metrey, Daniel R.; Beaty, Noah; Jeans, James W.; Gamber, Robert

    2016-05-01

    Optical Frequency Domain Reflectometry (OFDR) is the basis of an emerging high-definition distributed fiber optic sensing (HD-FOS) technique that provides an unprecedented combination of resolution and sensitivity. OFDR employs swept laser interferometry to produce strain or temperature vs. sensor length with fiber Bragg gratings (FBGs) or Rayleigh scatter as the source signal. We look at the influence of HD-FOS on design and test of new, lighter weight, stronger and more fuel efficient vehicles. Examples include defect detection, model verification and structural health monitoring of composites, and temperature distribution monitoring of battery packs and inverters in hybrid and electric powertrains.

  10. Optical temperature sensing on flexible polymer foils

    NASA Astrophysics Data System (ADS)

    Sherman, Stanislav; Xiao, Yanfen; Hofmann, Meike; Schmidt, Thomas; Gleissner, Uwe; Zappe, Hans

    2016-04-01

    In contrast to established semiconductor waveguide-based or glass fiber-based integrated optical sensors, polymerbased optical systems offer tunable material properties, such as refractive index or viscosity, and thus provide additional degrees of freedom for sensor design and fabrication. Of particular interest in sensing applications are fully-integrated optical waveguide-based temperature sensors. These typically rely on Bragg gratings which induce a periodic refractive index variation in the waveguide so that a resonant wavelength of the structure is reflected.1,2 With broad-band excitation, a dip in the spectral output of the waveguide is thus generated at a precisely-defined wavelength. This resonant wavelength depends on the refractive index of the waveguide and the grating period, yet both of these quantities are temperature dependent by means of the thermo-optic effect (change in refractive index with temperature) and thermal expansion (change of the grating period with temperature). We show the design and fabrication of polymer waveguide-integrated temperature sensors based on Bragggratings, fabricated by replication technology on flexible PMMA foil substrates. The 175 μm thick foil serves as lower cladding for a polymeric waveguide fabricated from a custom-made UV-crosslinkable co-monomer composition. The fabrication of the grating structure includes a second replication step into a separate PMMA-foil. The dimensions of the Bragg-gratings are determined by simulations to set the bias point into the near infrared wavelength range, which allows Si-based detectors to be used. We present design considerations and performance data for the developed structures. The resulting sensor's signal is linear to temperature changes and shows a sensitivity of -306 nm/K, allowing high resolution temperature measurements.

  11. Wavefront Sensing for WFIRST with a Linear Optical Model

    NASA Technical Reports Server (NTRS)

    Jurling, Alden S.; Content, David A.

    2012-01-01

    In this paper we develop methods to use a linear optical model to capture the field dependence of wavefront aberrations in a nonlinear optimization-based phase retrieval algorithm for image-based wavefront sensing. The linear optical model is generated from a ray trace model of the system and allows the system state to be described in terms of mechanical alignment parameters rather than wavefront coefficients. This approach allows joint optimization over images taken at different field points and does not require separate convergence of phase retrieval at individual field points. Because the algorithm exploits field diversity, multiple defocused images per field point are not required for robustness. Furthermore, because it is possible to simultaneously fit images of many stars over the field, it is not necessary to use a fixed defocus to achieve adequate signal-to-noise ratio despite having images with high dynamic range. This allows high performance wavefront sensing using in-focus science data. We applied this technique in a simulation model based on the Wide Field Infrared Survey Telescope (WFIRST) Intermediate Design Reference Mission (IDRM) imager using a linear optical model with 25 field points. We demonstrate sub-thousandth-wave wavefront sensing accuracy in the presence of noise and moderate undersampling for both monochromatic and polychromatic images using 25 high-SNR target stars. Using these high-quality wavefront sensing results, we are able to generate upsampled point-spread functions (PSFs) and use them to determine PSF ellipticity to high accuracy in order to reduce the systematic impact of aberrations on the accuracy of galactic ellipticity determination for weak-lensing science.

  12. Wavefront sensing for WFIRST with a linear optical model

    NASA Astrophysics Data System (ADS)

    Jurling, Alden S.; Content, David A.

    2012-09-01

    In this paper we develop methods to use a linear optical model to capture the field dependence of wavefront aberrations in a nonlinear optimization-based phase retrieval algorithm for image-based wavefront sensing. The linear optical model is generated from a ray trace model of the system and allows the system state to be described in terms of mechanical alignment parameters rather than wavefront coefficients. This approach allows joint optimization over images taken at different field points and does not require separate convergence of phase retrieval at individual field points. Because the algorithm exploits field diversity, multiple defocused images per field point are not required for robustness. Furthermore, because it is possible to simultaneously fit images of many stars over the field, it is not necessary to use a fixed defocus to achieve adequate signal-to-noise ratio despite having images with high dynamic range. This allows high performance wavefront sensing using in-focus science data. We applied this technique in a simulation model based on the Wide Field Infrared Survey Telescope (WFIRST) Intermediate Design Reference Mission (IDRM) imager using a linear optical model with 25 field points. We demonstrate sub-thousandth-wave wavefront sensing accuracy in the presence of noise and moderate undersampling for both monochromatic and polychromatic images using 25 high-SNR target stars. Using these high-quality wavefront sensing results, we are able to generate upsampled point-spread functions (PSFs) and use them to determine PSF ellipticity to high accuracy in order to reduce the systematic impact of aberrations on the accuracy of galactic ellipticity determination for weak-lensing science.

  13. Spectral sensing technique for water constituents

    NASA Astrophysics Data System (ADS)

    Zhou, Jing

    Spectral measurements of optical properties of water were conducted throughout the Chesapeake Bay area during the 2005 summer cruise campaign. This included reflectance, absorption, attenuation and backscattering spectra. The analysis of the data illustrates the diversity and complexity of constituents that shape spectral features of the coastal water. A novel technique is proposed to separate the chlorophyll fluorescence component from the reflectance spectra of algae contained water. This approach utilizes of polarization properties of elastically scattered light and the unpolarized nature of fluorescence and was successfully applied to measurements of various algae species first in lab and later in field measurements. The efficiency and limitation of this approach has been further examined under various conditions as well as through vector radiative transfer modeling. Finally Twomey Iterative Method (TIM) has been applied to the retrieval of hydrosol microphysical properties for the first time. Assuming a known refractive index, both single and multi-mode distributions were successfully retrieved from both simulation and experiments through the introduction of an initial distribution biased towards larger particles. In addition, the technique is extended to the retrieval of an unknown refractive index, which is also validated using both simulation and experimental results.

  14. Fiber Optic Distributed Temperature Sensing of Snow

    NASA Astrophysics Data System (ADS)

    Huwald, H.; Higgins, C. W.; Diebold, M.; Lehning, M.; Tyler, S. W.; Selker, J. S.; Parlange, M. B.

    2009-12-01

    Physical properties of seasonal and perennial snow covers can vary significantly on the order of a few meters with direct impact on snow dynamics, thermodynamics, temporal evolution, and ultimately on local snow water storage representing a challenge for measurement and modeling efforts. Detailed knowledge on small scale variability in snow internal temperature, density, and resulting subsurface heat fluxes is relatively limited, and pertinent snow cover internal data are also difficult to obtain. Uncertainty in the quantification of the components of the surface and snow internal energy budget is a consequence. From an experimental point of view, acquisition of distributed temperature data in the snow pack is non-trivial since accumulation, ablation, metamorphosis, etc., lead to continuous changes in the snow surface level. To provide better observational evidence of small scale variability and the associated snow physical processes we use fiber optic distributed temperature sensing (DTS), a rapidly emerging technology in environmental sensing, which provides high resolution temperature measurements in space (1 meter) and time (a few minutes) with a resolution better than 0.1C over distances of several kilometers. Innovative experimental designs such as 2D transects and high resolution vertical temperature profiles using fiber optic cables were deployed and tested at high altitude sites in the Swiss Alps. The results of the experiments yield both expertise in the application of the novel measurement systems and new insight in snow pack thermodynamics such as 2D conductive heat fluxes. Also, wind pumping processes were investigated with a complimentary experimental system of synchronized high frequency measurements of atmospheric turbulence and barometric pressure fluctuations in the snow.

  15. Bridge SHM system based on fiber optical sensing technology

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Fan, Dian; Fu, Jiang-hua; Huang, Xing; Jiang, De-sheng

    2015-09-01

    The latest progress of our lab in recent 10 years on the area of bridge structural health monitoring (SHM) based on optical fiber sensing technology is introduced. Firstly, in the part of sensing technology, optical fiber force test-ring, optical fiber vibration sensor, optical fiber smart cable, optical fiber prestressing loss monitoring method and optical fiber continuous curve mode inspection system are developed, which not only rich the sensor types, but also provides new monitoring means that are needed for the bridge health monitoring system. Secondly, in the optical fiber sensing network and computer system platform, the monitoring system architecture model is designed to effectively meet the integration scale and effect requirement of engineering application, especially the bridge expert system proposed integration of sensing information and informatization manual inspection to realize the mode of multi index intelligence and practical monitoring, diagnosis and evaluation. Finally, the Jingyue bridge monitoring system as the representative, the research on the technology of engineering applications are given.

  16. Optical Omega network: a compact implementation technique

    NASA Astrophysics Data System (ADS)

    Wong, K. W.; Cheng, L. M.

    1995-10-01

    We propose a technique for the compact implementation of an optical Omega network. This technique utilizes the concept that both the perfect-shuffle interconnection and the switching stages can be realized by the same procedures, i.e., duplicate, shift, superimpose, and mask. As a result, a single set of optics is sufficient to realize the whole Omega network in a time-multiplexed recursive manner. Optical setups were designed and a proof-of-principle experiment was performed.

  17. Time-sharing wave-front-sensing adaptive optics.

    PubMed

    Hou, Jing

    2004-02-01

    Based on the concept of common-path/common-mode adaptive optics, the time-sharing wave-front-sensing adaptive optics system contains only one Hartmann-Shack (H-S) wave-front sensor, which detects two aberrations in the beam path alternately. After data fusion of the two aberrations, the actuator voltage of the deformable mirror (DM) is obtained. How the disturbances of the slope data and the response matrix influence the DM's actuator voltage in the data fusion methods is discussed, and the effective upper limits are given. Feasible data fusion methods are tested, and experiments verify that the performance of the system is good. The time-sharing technique is limited in sampling rate and is suitable only for corrections of slowly changing phases, because the H-S wave-front sensor's sampling frequency must be adequate for the alternate detection of two aberrations.

  18. Liquid seal for temperature sensing with fiber-optic refractometers.

    PubMed

    Xu, Ben; Li, Jianqing; Li, Yi; Xie, Jianglei; Dong, Xinyong

    2014-08-13

    Liquid sealing is an effective method to convert a fiber-optic refractometer into a simple and highly sensitive temperature sensor. A refractometer based on the thin-core fiber modal interferometer is sealed in a capillary tube filled with Cargille oil. Due to the thermo-optic effect of the sealing liquid, the high refractive-index sensitivity refractometer is subsequently sensitive to the ambient temperature. It is found that the liquid-sealed sensor produces a highest sensitivity of -2.30 nm/°C, which is over 250 times higher than its intrinsic sensitivity before sealing and significantly higher than that of a grating-based fiber sensors. The sensing mechanisms, including the incidental temperature-induced strain effect, are analyzed in detail both theoretically and experimentally. The liquid sealing technique is easy and low cost, and makes the sensor robust and insensitive to the surrounding refractive index. It can be applied to other fiber-optic refractometers for temperature sensing.

  19. Fluorescence decay time measurement - a new optical sensing scheme

    NASA Astrophysics Data System (ADS)

    Draxler, Sonja; Lippitsch, Max E.

    1994-02-01

    Optical sensors often suffer from poor long-term stability. This drawback can be overcome by using fluorescence decay-time measurement as the sensing principle. In this way calibration- free chemical sensors can be developed. The sensing scheme has been used so far mainly in connection with dynamic quenching, for example in oxygen sensors. We have succeeded in extending it to ground-state indicator-analyte reactions, thus obtaining stable optical sensors for decay-time sensing of various analytes.

  20. Bibliography of Remote Sensing Techniques Used in Wetland Research.

    DTIC Science & Technology

    1993-01-01

    remote sensing technology for detecting changes in wetland environments. This report documents a bibliographic search conducted as part of that work unit on applications of remote sensing techniques in wetland research. Results were used to guide research efforts on the use of remote sensing technology for wetland change detection and assessment. The citations are presented in three appendixes, organized by wetland type, sensor type, and author.... Change detection, Wetland assessment, Remote sensing ,

  1. An integrated sensing technique for smart monitoring of water pipelines

    NASA Astrophysics Data System (ADS)

    Bernini, Romeo; Catapano, Ilaria; Soldovieri, Francesco; Crocco, Lorenzo

    2014-05-01

    Lowering the rate of water leakage from the network of underground pipes is one of the requirements that "smart" cities have to comply with. In fact, losses in the water supply infrastructure have a remarkable social, environmental and economic impact, which obviously conflicts with the expected efficiency and sustainability of a smart city. As a consequence, there is a huge interest in developing prevention policies based on state-of-art sensing techniques and possibly their integration, as well as in envisaging ad hoc technical solutions designed for the application at hand. As a contribution to this framework, in this communication we present an approach aimed to pursue a thorough non-invasive monitoring of water pipelines, with both high spatial and temporal resolution. This goal is necessary to guarantee that maintenance operations are performed timely, so to reduce the extent of the leakage and its possible side effects, and precisely, so to minimize the cost and the discomfort resulting from operating on the water supply network. The proposed approach integrates two sensing techniques that work at different spatial and temporal scales. The first one is meant to provide a continuous (in both space and time) monitoring of the pipeline and exploits a distributed optic fiber sensor based on the Brillouin scattering phenomenon. This technique provides the "low" spatial resolution information (at meter scale) needed to reveal the presence of a leak and call for interventions [1]. The second technique is based on the use of Ground Penetrating Radar (GPR) and is meant to provide detailed images of area where the damage has been detected. GPR systems equipped with suitable data processing strategies [2,3] are indeed capable of providing images of the shallow underground, where the pipes would be buried, characterized by a spatial resolution in the order of a few centimeters. This capability is crucial to address in the most proper way maintenance operations, by for

  2. Use of polyethylene glycol coatings for optical fibre humidity sensing

    NASA Astrophysics Data System (ADS)

    Acikgoz, Sabriye; Bilen, Bukem; Demir, Mustafa Muamer; Menceloglu, Yusuf Ziya; Skarlatos, Yani; Aktas, Gulen; Inci, Mehmet Naci

    2008-03-01

    Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystalline structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed.

  3. A Ubiquitous Optical Microsystem Platform with Application to Optical Metrology and Chemical Sensing

    NASA Astrophysics Data System (ADS)

    Gerling, John David

    This dissertation is concerned with the development of a novel, versatile optical sensor platform for optical metrology and chemical sensing. We demonstrate the feasibility of embedding optical components between bonded silicon wafers with receptor cavities and optical windows to create a self-contained sensor microsystem that can be used for in-situ measurement of hostile environments. Arrays of these sensors internal to a silicon wafer can enable optical sensing for in-situ, real-time mapping and process development for the semiconductor industry in the form of an instrumented substrate. Single-die versions of these optical sensor platforms can also enable point-of-care diagnostics, high throughput disease screening, bio-warfare agent detection, and environmental monitoring. Our first discussion will focus on a single-wavelength interferometry-based prototype sensor. Several applications are demonstrated using this single wavelength prototype: refractive index monitoring, SiO2 plasma etching, chemical mechanical polishing, photoresist cure and dissolution, copper etch end-point detection, and also nanopore wetting phenomena. Subsequent sections of this dissertation will describe efforts to improve the optical sensor platform to achieve multi-wavelength sensing function. We explore the use of an off-the-shelf commercial RGB sensor for colorimetric monitoring of copper and aluminum thin-film etchings. We then expand upon our prior work and concepts to realize a fully integrated, chip-sized microspectrometer with a photon engine based on a diffraction grating. The design, fabrication, and demonstration of a working prototype with dimensions < 1 mm thick using standard planar microfabrication techniques is described. Proof-of-concept demonstrations indicate the working principle of dispersion, although with a low spectral resolution of 120 nm. With working knowledge of the issues of the first prototype, we present an improved 5-channel microspectrometer with a

  4. Optical waveguides for evanescent field sensing

    NASA Astrophysics Data System (ADS)

    Rehouma, F.; Persegol, D.; Kevorkian, A.

    1994-09-01

    A novel method based on the control of the topography of the guide during its elaboration was presented. This new method aimed to contribute to the working principle of integrated-optics sensors. The proposed technique is easy to use and allows to bury different regions of ion-exchange waveguides selectively. The surface interaction length of the component and the losses of the structure can be controlled by the width and the tilt angle of the mask. Moreover, the method presented a combination of numerous advantages.

  5. Optical Communications Using Retromodulation Techniques.

    DTIC Science & Technology

    1980-09-01

    other types, require terminals at both ends of the communication link for the two-way transfer of information. Shown in Fig. I is a schematic depicting...Optical Modulator... 66 F Beam-Spreading Losses Incurred at the Air-Water Interface... 73 Index of Photographs... 83 iii • t INTRODUCTION The Navy currently...a conventional optical communications system. It is noted that the two active terminals comprising the system are basically identical. The key

  6. Downhole fiber optic sensing: the oilfield service provider's perspective: from the cradle to the grave

    NASA Astrophysics Data System (ADS)

    Skinner, Neal G.; Maida, John L.

    2014-06-01

    For almost three decades, interest has continued to increase with respect to the application of fiber-optic sensing techniques for the upstream oil and gas industry. This paper reviews optical sensing technologies that have been and are being adopted downhole, as well as their drivers. A brief description of the life of a well, from the cradle to the grave, and the roles fiber-optic sensing can play in optimizing production, safety, and protection of the environment are also presented. The performance expectations (accuracy, resolution, stability, and operational lifetime) that oil companies and oil service companies have for fiber-optic sensing systems is described. Additionally, the environmental conditions (high hydrostatic pressures, high temperatures, shock, vibration, crush, and chemical exposure) that these systems must tolerate to provide reliable and economically attractive oilfield monitoring solutions are described.

  7. Wind Predictability and Remote Sensing Techniques,

    DTIC Science & Technology

    The report presents the unclassified findings from the Investigation of Airborne Wind Sensing Systems conducted under AIRTASK A30303/323/70F17311002. Included is a summary of the current accuracy of wind speed and direction forecasts, a list of possible methods for remote sensing meteorological data, a list of areas of application of the given methods and a list of contacts made for information relevant to this evaluation. (Author)

  8. Absolute distance sensing by two laser optical interferometry.

    PubMed

    Thurner, Klaus; Braun, Pierre-François; Karrai, Khaled

    2013-11-01

    We have developed a method for absolute distance sensing by two laser optical interferometry. A particularity of this technique is that a target distance is determined in absolute and is no longer limited to within an ambiguity range affecting usually multiple wavelength interferometers. We implemented the technique in a low-finesse Fabry-Pérot miniature fiber based interferometer. We used two diode lasers, both operating in the 1550 nm wavelength range. The wavelength difference is chosen to create a 25 μm long periodic beating interferometric pattern allowing a nanometer precise position measurement but limited to within an ambiguity range of 25 μm. The ambiguity is then eliminated by scanning one of the wavelengths over a small range (3.4 nm). We measured absolute distances in the sub-meter range and this with just few nanometer repeatability.

  9. Intensity-based fibre-optic sensing system using contrast modulation of subcarrier interference pattern

    NASA Technical Reports Server (NTRS)

    Adamovsky, G.; Sherer, T. N.; Maitland, D. J.

    1989-01-01

    A novel technique to compensate for unwanted intensity losses in a fiber-optic sensing system is described. The technique involves a continuous sinusoidal modulation of the light source intensity at radio frequencies and an intensity sensor placed in an unbalanced interferometer. The system shows high sensitivity and stability.

  10. Intensity-based fibre-optic sensing system using contrast modulation of subcarrier interference pattern

    NASA Technical Reports Server (NTRS)

    Adamovsky, G.; Sherer, T. N.; Maitland, D. J.

    1989-01-01

    A novel technique to compensate for unwanted intensity losses in a fiber-optic sensing system is described. The technique involves a continuous sinusoidal modulation of the light source intensity at radio frequencies and an intensity sensor placed in an unbalanced interferometer. The system shows high sensitivity and stability.

  11. Vehicle-Mounted Optical Sensing: An Objective Means for Evaluating Turf Quality.

    PubMed

    Bell, G. E.; Martin, D. L.; Wiese, S. G.; Dobson, D. D.; Smith, M. W.; Stone, M. L.; Solie, J. B.

    2002-01-01

    Visual evaluation of turfgrass quality is a subjective process that requires experienced personnel. Optical sensing of plant reflectance provides objective, quantitative turf quality evaluation and requires no turf experience. This study was conducted to assess the accuracy of optical sensing for evaluating turf quality, to compare the rating consistency among human evaluators and optical sensing, and to develop a model that describes a relationship between optically sensed measurements and visual turf quality. Visual evaluations for turf color, texture, percent live cover (PLC), and optically sensed measurements were collected on the National Turfgrass Evaluation Program (NTEP) tall fescue (Festuca arundinacea Schreb) and creeping bentgrass (Agrostis palustris Huds.) trials at Stillwater, OK. Measurements were made monthly for 12 consecutive months from June 1999 through May 2000. Red (R) and near infrared (NIR) reflectance were collected with sensors and converted to normalized difference vegetative indices (NDVI). The NDVI were closely correlated with visual evaluations for turf color, moderately correlated with percent live cover (PLC), and independent of texture. Measurements of turf color and PLC were evaluated more consistently with optical sensors than by visual ratings. Normalized difference vegetation index (Y) could be reliably predicted by the following generalized model for turf color (X) and PLC (Z): Y = B(0) + B(1)log10X + B(2)Z(3). Optical sensing provided fast, reliable turf assessment and deserves consideration as a supplemental or replacement technique for evaluating turf quality.

  12. Stitching Techniques Advance Optics Manufacturing

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Because NASA depends on the fabrication and testing of large, high-quality aspheric (nonspherical) optics for applications like the James Webb Space Telescope, it sought an improved method for measuring large aspheres. Through Small Business Innovation Research (SBIR) awards from Goddard Space Flight Center, QED Technologies, of Rochester, New York, upgraded and enhanced its stitching technology for aspheres. QED developed the SSI-A, which earned the company an R&D 100 award, and also developed a breakthrough machine tool called the aspheric stitching interferometer. The equipment is applied to advanced optics in telescopes, microscopes, cameras, medical scopes, binoculars, and photolithography."

  13. Instrumentation for optical ocean remote sensing

    NASA Technical Reports Server (NTRS)

    Esaias, W. E.

    1991-01-01

    Instruments used in ocean color remote sensing algorithm development, validation, and data acquisition which have the potential for further commercial development and marketing are discussed. The Ocean Data Acquisition System (ODAS) is an aircraft-borne radiometer system suitable for light aircraft, which has applications for rapid measurement of chlorophyll pigment concentrations along the flight line. The instrument package includes a three channel radiometer system for upwelling radiance, an infrared temperature sensor, a three-channel downwelling irradiance sensor, and Loran-C navigation. Data are stored on a PC and processed to transects or interpolated 'images' on the ground. The instrument has been in operational use for two and one half years. The accuracy of pigment concentrations from the instrument is quite good, even in complex Chesapeake Bay waters. To help meet the requirement for validation of future satellite missions, a prototype air-deployable drifting buoy for measurement of near-surface upwelled radiance in multiple channnels is undergoing test deployment. The optical drifter burst samples radiance, stores and processes the data, and uses the Argos system as a data link. Studies are underway to explore the limits to useful lifetime with respect to power and fouling.

  14. Optical routing and sensing with nanowire assemblies.

    PubMed

    Sirbuly, Donald J; Law, Matt; Pauzauskie, Peter; Yan, Haoquan; Maslov, Alex V; Knutsen, Kelly; Ning, Cun-Zheng; Saykally, Richard J; Yang, Peidong

    2005-05-31

    The manipulation of photons in structures smaller than the wavelength of light is central to the development of nanoscale integrated photonic systems for computing, communications, and sensing. We assemble small groups of freestanding, chemically synthesized nanoribbons and nanowires into model structures that illustrate how light is exchanged between subwavelength cavities made of three different semiconductors. The coupling strength of the optical linkages formed when nanowires are brought into contact depends both on their volume of interaction and angle of intersection. With simple coupling schemes, lasing nanowires can launch coherent pulses of light through ribbon waveguides that are up to a millimeter in length. Also, interwire coupling losses are low enough to allow light to propagate across several right-angle bends in a grid of crossed ribbons. The fraction of the guided wave traveling outside the wire/ribbon cavities is used to link nanowires through space and to separate colors within multiribbon networks. In addition, we find that nanoribbons function efficiently as waveguides in liquid media and provide a unique means for probing molecules in solution or in proximity to the waveguide surface. Our results lay the spadework for photonic devices based on assemblies of active and passive nanowire elements and presage the use of nanowire waveguides in microfluidics and biology.

  15. Optical tweezers technique and its applications

    NASA Astrophysics Data System (ADS)

    Guo, HongLian; Li, ZhiYuan

    2013-12-01

    Since their advent in the 1980s, optical tweezers have attracted more and more attention due to their unique non-contact and non-invasion characteristics and their wide applications in physics, biology, chemistry, medical science and nanoscience. In this paper, we introduce the basic principle, the history and typical applications of optical tweezers and review our recent experimental works on the development and application of optical tweezers technique. We will discuss in detail several technological issues, including high precision displacement and force measurement in single-trap and dual-trap optical tweezers, multi-trap optical tweezers with each trap independently and freely controlled by means of space light modulator, and incorporation of cylindrical vector optical beams to build diversified optical tweezers beyond the conventional Gaussian-beam optical tweezers. We will address the application of these optical tweezers techniques to study biophysical problems such as mechanical deformation of cell membrane and binding energy between plant microtubule and microtubule associated proteins. Finally we present application of the optical tweezers technique for trapping, transporting, and patterning of metallic nanoparticles, which can be harnessed to manipulate surface plasmon resonance properties of these nanoparticles.

  16. Optics and photonics research in the Lasers, Optics and Remote Sensing Department at Sandia National Laboratories

    SciTech Connect

    Simmons-Potter, K.; Meister, D.C.

    1997-04-01

    Photonic system and device technologies have claimed a significant share of the current high-tech market. In particular, laser systems and optical devices impact a broad range of technological areas including telecommunications, optical computing, optical data storage, integrated photonics, remote environmental sensing and biomedical applications. Below we present an overview of photonics research being conducted within the Lasers, Optics and Remote Sensing department of the Physical and Chemical Sciences Center at Sandia National Laboratories. Recent results in the fields of photosensitive materials and devices, binary optics device applications, wavelength generation using optical parametric oscillators, and remote sensing are highlighted. 11 refs., 6 figs.

  17. Polarization mode beating techniques for high-sensitivity intracavity sensing

    NASA Astrophysics Data System (ADS)

    Rosales-Garcia, Andrea

    high finesse and resolution of the system. Experimental changes in the refractive index of air as a function of pressure are in good agreement with theoretical predictions. An alternative fiber laser configuration, which incorporates non-reciprocal elements, allows measuring the optical activity of enantiomeric mixtures using PMB techniques. The sensitivity attained through PMB techniques demonstrates a potential method for ultra-sensitive biochemical sensing and explosive detection.

  18. Live Cell Optical Sensing for High Throughput Applications

    NASA Astrophysics Data System (ADS)

    Fang, Ye

    Live cell optical sensing employs label-free optical biosensors to non-invasively measure stimulus-induced dynamic mass redistribution (DMR) in live cells within the sensing volume of the biosensor. The resultant DMR signal is an integrated cellular response, and reflects cell signaling mediated through the cellular target(s) with which the stimulus intervenes. This article describes the uses of live cell optical sensing for probing cell biology and ligand pharmacology, with an emphasis of resonant waveguide grating biosensor cellular assays for high throughput applications.

  19. Optical Sensing of Microbial Life on Surfaces

    PubMed Central

    Triggs, G. J.; Krauss, T. F.

    2015-01-01

    The label-free detection of microbial cells attached to a surface is an active field of research. The field is driven by the need to understand and control the growth of biofilms in a number of applications, including basic research in natural environments, industrial facilities, and clinical devices, to name a few. Despite significant progress in the ability to monitor the growth of biofilms and related living cells, the sensitivity and selectivity of such sensors are still a challenge. We believe that among the many different technologies available for monitoring biofilm growth, optical techniques are the most promising, as they afford direct imaging and offer high sensitivity and specificity. Furthermore, as each technique offers different insights into the biofilm growth mechanism, our analysis allows us to provide an overview of the biological processes at play. In addition, we use a set of key parameters to compare state-of-the-art techniques in the field, including a critical assessment of each method, to identify the most promising types of sensors. We highlight the challenges that need to be overcome to improve the characteristics of current biofilm sensor technologies and indicate where further developments are required. In addition, we provide guidelines for selecting a suitable sensor for detecting microbial cells on a surface. PMID:26637605

  20. All-optical signal processing technique for secure optical communication

    NASA Astrophysics Data System (ADS)

    Qian, Feng-chen; Su, Bing; Ye, Ya-lin; Zhang, Qian; Lin, Shao-feng; Duan, Tao; Duan, Jie

    2015-10-01

    Secure optical communication technologies are important means to solve the physical layer security for optical network. We present a scheme of secure optical communication system by all-optical signal processing technique. The scheme consists of three parts, as all-optical signal processing unit, optical key sequence generator, and synchronous control unit. In the paper, all-optical signal processing method is key technology using all-optical exclusive disjunction (XOR) gate based on optical cross-gain modulation effect, has advantages of wide dynamic range of input optical signal, simple structure and so on. All-optical XOR gate composed of two semiconductor optical amplifiers (SOA) is a symmetrical structure. By controlling injection current, input signal power, delay and filter bandwidth, the extinction ratio of XOR can be greater than 8dB. Finally, some performance parameters are calculated and the results are analyzed. The simulation and experimental results show that the proposed method can be achieved over 10Gbps optical signal encryption and decryption, which is simple, easy to implement, and error-free diffusion.

  1. Optical signature utilization of remote sensing of nearshore waters

    SciTech Connect

    Bagheri, S.; Dios, R.A.; Pan, Zhengxiang

    1997-08-01

    Existing satellite sensors lack the spectral capabilities to discriminate phytoplankton pigments in water bodies. New satellite sensors (EOS planned for 1998 and SeaWIFS forthcoming) with narrow bandwidths can provide detailed spectral resolution necessary to distinguish optical properties of nearshore waters provided calibrated seatruth data are available. This will facilitate utility of spaceborne water color sensors for discrimination of bloom forming phytoplankton species and support oceanographic/coastal zone remote sensing missions of NASA, Navy and other agencies. The objective of the research was to develop a library of absorption spectra for the most common phytoplankton found locally within the Hudson/Raritan Estuary. Both culture grown and field samples of phytoplankton were concentrated and analyzed using standard techniques. Chlorophyll-a and phaeopigment concentrations were determined based on spectrometric analysis, producing characteristic absorption spectra. To further refine and discriminate pigment compositions which affect remote color sensing recorded by sensors, spectral derivative and polynomial regression analysis were applied to the absorption spectra. Using these models, it was possible to identify optimum wavelengths characterizing pigment compositions of phytoplankton species in the estuary. Future work will integrate the spectral library into GenIsis--hyperspectral image processing to establish correlation with remotely sensed data.

  2. Remote chemical sensing by laser optical pumping

    SciTech Connect

    Stevens, C.G.; Magnotta, F.

    1996-08-01

    We are exploring a new approach to remote chemical identification that promises higher precision than can be achieved by conventional DIAL approaches. This technique also addresses and potentially solves the problem of detecting a target gas in the presence of an interfering gas or gases. This new approach utilizes an eye-safe infrared optical pumping pulse to deplete the population of a specific rotational level(s) and then sends probe pulses at the same or different wavelengths to interrogate the bleaching of the absorption. We have experimentally measured optical saturation fluence level at atmospheric pressure for HCl, and find this level to be {approximately}1 mJ/cm{sup 2}, significantly below eye-safe limits in agreement with calculations. Calculations have been performed on other molecules of interest with similar results. In the laboratory, using time-delay-replicated pulses at a single frequency we have made absorption measurements with precision levels routinely approaching 0.1% after averaging 200 laser pulses. These results as well as those of two other pulse experiments will be presented. 5 refs., 9 figs., 1 tab.

  3. Estimation of Insulator Contaminations by Means of Remote Sensing Technique

    NASA Astrophysics Data System (ADS)

    Han, Ge; Gong, Wei; Cui, Xiaohui; Zhang, Miao; Chen, Jun

    2016-06-01

    The accurate estimation of deposits adhering on insulators is critical to prevent pollution flashovers which cause huge costs worldwide. The traditional evaluation method of insulator contaminations (IC) is based sparse manual in-situ measurements, resulting in insufficient spatial representativeness and poor timeliness. Filling that gap, we proposed a novel evaluation framework of IC based on remote sensing and data mining. Varieties of products derived from satellite data, such as aerosol optical depth (AOD), digital elevation model (DEM), land use and land cover and normalized difference vegetation index were obtained to estimate the severity of IC along with the necessary field investigation inventory (pollution sources, ambient atmosphere and meteorological data). Rough set theory was utilized to minimize input sets under the prerequisite that the resultant set is equivalent to the full sets in terms of the decision ability to distinguish severity levels of IC. We found that AOD, the strength of pollution source and the precipitation are the top 3 decisive factors to estimate insulator contaminations. On that basis, different classification algorithm such as mahalanobis minimum distance, support vector machine (SVM) and maximum likelihood method were utilized to estimate severity levels of IC. 10-fold cross-validation was carried out to evaluate the performances of different methods. SVM yielded the best overall accuracy among three algorithms. An overall accuracy of more than 70% was witnessed, suggesting a promising application of remote sensing in power maintenance. To our knowledge, this is the first trial to introduce remote sensing and relevant data analysis technique into the estimation of electrical insulator contaminations.

  4. Electro-Optical Sensing Apparatus and Method for Characterizing Free-Space Electromagnetic Radiation

    DOEpatents

    Zhang, Xi-Cheng; Libelo, Louis Francis; Wu, Qi

    1999-09-14

    Apparatus and methods for characterizing free-space electromagnetic energy, and in particular, apparatus/method suitable for real-time two-dimensional far-infrared imaging applications are presented. The sensing technique is based on a non-linear coupling between a low-frequency electric field and a laser beam in an electro-optic crystal. In addition to a practical counter-propagating sensing technique, a co-linear approach is described which provides longer radiated field--optical beam interaction length, thereby making imaging applications practical.

  5. Pressure Sensing with Fiber Optics and Interferometry.

    DTIC Science & Technology

    1980-12-01

    fiber optic pressure sensor could be commercially useful. Besides the changes already mentioned, the diaphragms must be etched...4 Michelson Interferometer ............. 4 Diaphragm mechanics................6 Fiber Optics ...................8 ANIII. Fiber Optic Pressure...achieved by mounting the diaphragm on the end of a single mode optical fiber ; the coupling apparatus used permits interference to occur with the fiber

  6. INTERCOMPARISON OF OPTICAL REMOTE SENSING SYSTEMS FOR ROADSIDE MEASUREMENTS

    EPA Science Inventory

    The presentation describes results of an intercomparison of three optical remote sensing systems for measurements of nitric oxide emitted from passenger cars and light-duty trucks. The intercomparison included a standards comparison to establish comparability of standards, follo...

  7. INTERCOMPARISON OF OPTICAL REMOTE SENSING SYSTEMS FOR ROADSIDE MEASUREMENTS

    EPA Science Inventory

    The presentation describes results of an intercomparison of three optical remote sensing systems for measurements of nitric oxide emitted from passenger cars and light-duty trucks. The intercomparison included a standards comparison to establish comparability of standards, follo...

  8. Coherent Optical Adaptive Techniques (COAT)

    DTIC Science & Technology

    1973-02-01

    E o U rt UJ c t- 3 c o ■p t) c u •H +» ft o \\ o •d H & ■H to ■ o 10 ..,. J,.-. ..»^-^A^.^-. mfiiTflMaaj— ft ! -^^ lUMI IJI...13) 2 2 2 J,(Tidp) array r n=-oo e e ^ a Jl( XR ^o +yo j o vo E 5 n--ae 0 n\\/-N , TTD XB - i 0 sinc XR Xo ( ft ...was found that the acousto-optic Bragg cell functioning as a frequency modulator can meet the unlimited dynamic range and bandwidth requirements

  9. Recent advancement in optical fiber sensing for aerospace composite structures

    NASA Astrophysics Data System (ADS)

    Minakuchi, Shu; Takeda, Nobuo

    2013-12-01

    Optical fiber sensors have attracted considerable attention in health monitoring of aerospace composite structures. This paper briefly reviews our recent advancement mainly in Brillouin-based distributed sensing. Damage detection, life cycle monitoring and shape reconstruction systems applicable to large-scale composite structures are presented, and new technical concepts, "smart crack arrester" and "hierarchical sensing system", are described as well, highlighting the great potential of optical fiber sensors for the structural health monitoring (SHM) field.

  10. Laser And Nonlinear Optical Materials For Laser Remote Sensing

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.

    2005-01-01

    NASA remote sensing missions involving laser systems and their economic impact are outlined. Potential remote sensing missions include: green house gasses, tropospheric winds, ozone, water vapor, and ice cap thickness. Systems to perform these measurements use lanthanide series lasers and nonlinear devices including second harmonic generators and parametric oscillators. Demands these missions place on the laser and nonlinear optical materials are discussed from a materials point of view. Methods of designing new laser and nonlinear optical materials to meet these demands are presented.

  11. Techniques For Optical Measurement Of Registration

    NASA Astrophysics Data System (ADS)

    Zych, L. J.; Spadini, G.

    1985-07-01

    This paper discusses an optical technique capable of reliably measuring registration to few hundredths of a micron on virtually any layer. It has overcome the accuracy limitations and the proximity effect error present in other optical techniques. In spite of the recent popularity of highly accurate computerized electrical registration measurements optical registration measurements are still popular and necessary. This is because nonconductive layers, including resist, cannot be measured electrically. A quick optical technique with a high degree of accuracy has been developed and put to use. The measurement is made through a microscope, and a computer pattern recognition follows. It is free of the resolution limits inherent in such structures as optical verniers, which are bound to typically 0.1 microns by the grid size used to make the mask. This method employs a direct optical misalignment measurement between two matching structures and is capable of resolving 0.01 microns. It is also free of the proximity effects which make many verniers and pattern recognition schemes inaccurate. Proper microscope calibration, adjustments, and pattern recognition algorithms are key in making this technique work. The apertures must be accurately aligned and the focus properly adjusted to provide the right image. An HP 9000-226 computer has been custom interfaced to a Leitz microscope and a set of algorithms written. The result is a highly accurate, fast, and user friendly optical measurement system capable of measuring registration on all layers.

  12. A comparison of force sensing techniques for planetary manipulation

    NASA Technical Reports Server (NTRS)

    Helmick, Daniel; Okon, Avi; DiCicco, Matt

    2006-01-01

    Five techniques for sensing forces with a manipulator are compared analytically and experimentally. The techniques compared are: a six-axis wrist force/torque sensor, joint torque sensors, link strain gauges, motor current sensors, and flexibility modeling. The accuracy and repeatability fo each technique is quantified and compared.

  13. A comparison of force sensing techniques for planetary manipulation

    NASA Technical Reports Server (NTRS)

    Helmick, Daniel; Okon, Avi; DiCicco, Matt

    2006-01-01

    Five techniques for sensing forces with a manipulator are compared analytically and experimentally. The techniques compared are: a six-axis wrist force/torque sensor, joint torque sensors, link strain gauges, motor current sensors, and flexibility modeling. The accuracy and repeatability fo each technique is quantified and compared.

  14. Optical multiple object tracking techniques

    NASA Astrophysics Data System (ADS)

    Liu, Hua-Kuang; Chao, Tien-Hsin

    1989-02-01

    Two multichannel multiple-object tracking techniques are reviewed. In the diffraction grating technique, the input scene is picked up by a TV camera and imaged onto a liquid-crystal light valve (LCLV), and the output side of the light valve is illuminated with a suitably polarized and collimated coherent laser beam to yield a reflected beam with polarization modulated according to the intensity of the incoherent input. This reflected beam passes through a beam splitter cube and an analyzer, resulting in an intensity modulated coherent image. An array of spectrum islands containing the information of the input appears after crossing a contact screen/lens combination. In the multiple-focus hololens technique, the scene of moving objects is sent into the LCTVSLM through a camera; a collimated laser beam is incident upon the LCTV screen; a low-pass filter is inserted between the LCTVSLM and the hololens for the removal of the high order diffractions due to the grid structure of the LCTV. The feasibility of the LCTVSLM and multiple-focus hololens technique is demonstrated.

  15. Optical multiple object tracking techniques

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang; Chao, Tien-Hsin

    1989-01-01

    Two multichannel multiple-object tracking techniques are reviewed. In the diffraction grating technique, the input scene is picked up by a TV camera and imaged onto a liquid-crystal light valve (LCLV), and the output side of the light valve is illuminated with a suitably polarized and collimated coherent laser beam to yield a reflected beam with polarization modulated according to the intensity of the incoherent input. This reflected beam passes through a beam splitter cube and an analyzer, resulting in an intensity modulated coherent image. An array of spectrum islands containing the information of the input appears after crossing a contact screen/lens combination. In the multiple-focus hololens technique, the scene of moving objects is sent into the LCTVSLM through a camera; a collimated laser beam is incident upon the LCTV screen; a low-pass filter is inserted between the LCTVSLM and the hololens for the removal of the high order diffractions due to the grid structure of the LCTV. The feasibility of the LCTVSLM and multiple-focus hololens technique is demonstrated.

  16. Optical microcavity: sensing down to single molecules and atoms.

    PubMed

    Yoshie, Tomoyuki; Tang, Lingling; Su, Shu-Yu

    2011-01-01

    This review article discusses fundamentals of dielectric, low-loss, optical micro-resonator sensing, including figures of merit and a variety of microcavity designs, and future perspectives in microcavity-based optical sensing. Resonance frequency and quality (Q) factor are altered as a means of detecting a small system perturbation, resulting in realization of optical sensing of a small amount of sample materials, down to even single molecules. Sensitivity, Q factor, minimum detectable index change, noises (in sensor system components and microcavity system including environments), microcavity size, and mode volume are essential parameters to be considered for optical sensing applications. Whispering gallery mode, photonic crystal, and slot-type microcavities typically provide compact, high-quality optical resonance modes for optical sensing applications. Surface Bloch modes induced on photonic crystals are shown to be a promising candidate thanks to large field overlap with a sample and ultra-high-Q resonances. Quantum optics effects based on microcavity quantum electrodynamics (QED) would provide novel single-photo-level detection of even single atoms and molecules via detection of doublet vacuum Rabi splitting peaks in strong coupling.

  17. Optical Microcavity: Sensing down to Single Molecules and Atoms

    PubMed Central

    Yoshie, Tomoyuki; Tang, Lingling; Su, Shu-Yu

    2011-01-01

    This review article discusses fundamentals of dielectric, low-loss, optical micro-resonator sensing, including figures of merit and a variety of microcavity designs, and future perspectives in microcavity-based optical sensing. Resonance frequency and quality (Q) factor are altered as a means of detecting a small system perturbation, resulting in realization of optical sensing of a small amount of sample materials, down to even single molecules. Sensitivity, Q factor, minimum detectable index change, noises (in sensor system components and microcavity system including environments), microcavity size, and mode volume are essential parameters to be considered for optical sensing applications. Whispering gallery mode, photonic crystal, and slot-type microcavities typically provide compact, high-quality optical resonance modes for optical sensing applications. Surface Bloch modes induced on photonic crystals are shown to be a promising candidate thanks to large field overlap with a sample and ultra-high-Q resonances. Quantum optics effects based on microcavity quantum electrodynamics (QED) would provide novel single-photo-level detection of even single atoms and molecules via detection of doublet vacuum Rabi splitting peaks in strong coupling. PMID:22319393

  18. Evaluation of reforestation using remote sensing techniques

    NASA Technical Reports Server (NTRS)

    Parada, N. D. J. (Principal Investigator); Filho, P. H.; Shimabukuro, Y. E.; Dossantos, J. R.

    1982-01-01

    The utilization of remotely sensed orbital data for forestry inventory. The study area (approximately 491,100 ha) encompasses the municipalities of Ribeirao Preto, Altinopolis, Cravinhos, Serra Azul, Luis Antonio, Sao Simao, Sant Rita do Passa Quatro and Santa Rosa do Viterbo (Sao Paulo State). Materials used were LANDSAT data from channels 5 and 7 (scale 1:250,000) and CCT's. Visual interpretation of the imagery showed that for 1977 a total of 37,766.00 ha and for 1979 38,003.75 ha were reforested with Pinus and Eucalyptus within the area under study. The results obtained show that LANDSAT data can be used efficiently in forestry inventory studies.

  19. Optical source and apparatus for remote sensing

    NASA Technical Reports Server (NTRS)

    Coyle, Donald Barry (Inventor)

    2011-01-01

    An optical amplifier is configured to amplify an injected seed optical pulse. The optical amplifier may include two or more gain sections coupled to form a continuous solid waveguide along a primary optical path. Each gain section may include: (i) an optical isolator forming an input to that gain section; (ii) a doped optical fiber having a first end coupled to the optical isolator and having a second end; (iii) a plurality of pump laser diodes; (iv) a controller providing drive signals to each of the plurality, the controller being configured to provide at least pulsed drive signals; and (v) an optical coupler having a first input port coupled to the second end, and a second input port coupled to the plurality and an output port.

  20. RF modulated fiber optic sensing systems and their applications

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Eustace, John G.

    1992-01-01

    A fiber optic sensing system with an intensity sensor and a Radio Frequency (RF) modulated source was shown to have sensitivity and resolution much higher than a comparable system employing low modulating frequencies or DC mode of operation. Also the RF modulation with an appropriate configuration of the sensing system provides compensation for the unwanted intensity losses. The basic principles and applications of a fiber optic sensing system employing an RF modulated source are described. In addition the paper discusses various configurations of the system itself, its components, and modulation and detection schemes. Experimental data are also presented.

  1. RF modulated fiber optic sensing systems and their applications

    NASA Technical Reports Server (NTRS)

    Adamovsky, G.; Eustace, J. G.

    1993-01-01

    A fiber optic sensing system with an intensity sensor and a Radio Frequency (RF) modulated source was shown to have sensitivity and resolution much higher than a comparable system employing low modulating frequencies or DC mode of operation. Also the RF modulation with an appropriate configuration of the sensing system provides compensation for the unwanted intensity losses. The basic principles and applications of a fiber optic sensing system employing an RF modulated source are described. In addition the paper discusses various configurations of the system itself, its components, and modulation and detection schemes. Experimental data are also presented.

  2. Frequency-shifted interferometry for fiber-optic sensing

    NASA Astrophysics Data System (ADS)

    Ye, Fei

    This thesis studies frequency-shifted interferometry (FSI), a useful and versatile technique for fiber-optic sensing. I first present FSI theory by describing practical FSI configurations and discussing the parameters that affect system performance. Then, I demonstrate the capabilities of FSI in fiber-optic sensor multiplexing and high sensitivity chemical analysis. We implemented a cryogenic liquid level sensing system in which an array of 3 fiber Bragg grating (FBG) based sensors was interrogated by FSI. Despite sensors' spectral overlap, FSI is able to separate sensor signals according to their spatial locations and to measure their spectra, from which whether a sensor is in liquid or air can be unambiguously determined. I showed that a broadband source paired with a fast tunable filter can be used in FSI systems as the light source. An array of 9 spectrally overlapping FBGs was successfully measured by such a system, indicating the potential of system cost reduction as well as measurement speed improvement. I invented the the FSI-CRD technique, a highly sensitive FSI-based fiber cavity ring-down (CRD) method capable of deducing minuscule loss change in a fiber cavity from the intensity decay rate of continuous-wave light circulating in the cavity. As a proof-of-principle experiment, I successfully measured the fiber bend loss introduced in the fiber cavity with FSI-CRD, which was found to be 0.172 dB/m at a bend radius of 12.5 mm. We then applied FSI-CRD to evanescent-field sensing. We incorporated fiber tapers as the sensor head in the system and measured the concentration of 1-octyne solutions. A minimum detectable 1-octyne concentration of 0.29% was achieved with measurement sensitivity of 0.0094 dB/% 1-octyne. The same system also accurately detected the concentration change of sodium chloride (NaCl) and glucose solutions. Refractive index sensitivity of 1 dB/RIU with a measurement error of 1x10-4 dB was attined for NaCl solutions. Finally, I proposed a

  3. Techniques for Solution- Assisted Optical Contacting

    NASA Technical Reports Server (NTRS)

    DeVine, Glenn; Ware, Brent; Wuchenich, Danielle M.; Spero, Robert E.; Klipstein, William M.; McKenzie, Kirk

    2012-01-01

    A document discusses a solution-assisted contacting technique for optical contacting. An optic of surface flatness Lambda/20 was successfully contacted with one of moderate surface quality, or Lambda/4. Optics used were both ultra-low expansion (ULE) glass (Lambda/4 and Lambda/20) and fused silica (Lambda/20). A stainless steel template of the intended interferometer layout was designed and constructed with three contact points per optic. The contact points were all on a common side of the template. The entire contacting jig was tilted at about 30 . Thus, when the isopropanol was applied, each optic slid due to gravity, resting on the contact points. All of the contacting was performed in a relatively dusty laboratory. A number of successful contacts were achieved where up to two or three visible pieces of dust could be seen. These were clearly visible due to refraction patterns between the optic and bench. On a number of optics, the final step of dropping isopropyl between the surfaces was repeated until a successful contact was achieved. The new procedures realized in this work represent a simplification for optical contacting in the laboratory. They will both save time and money spent during the contacting process, and research and development phases. The techniques outlined are suitable for laboratory experiments, research, and initial development stages.

  4. MTF online compensation in space optical remote sensing camera

    NASA Astrophysics Data System (ADS)

    Qu, Youshan; Zhai, Bo; Han, Yameng; Zhou, Jiang

    2015-02-01

    An ordinary space optical remote sensing camera is an optical diffraction-limited system and a low-pass filter from the theory of Fourier Optics, and all the digital imaging sensors, whether the CCD or CMOS, are low-pass filters as well. Therefore, when the optical image with abundant high-frequency components passes through an optical imaging system, the profuse middle-frequency information is attenuated and the rich high-frequency information is lost, which will blur the remote sensing image. In order to overcome this shortcoming of the space optical remote sensing camera, an online compensating approach of the Modulation Transfer Function in the space cameras is designed. The designed method was realized by a hardware analog circuit placed before the A/D converter, which was composed of adjustable low-pass filters with a calculated value of quality factor Q. Through the adjustment of the quality factor Q of the filters, the MTF of the processed image is compensated. The experiment results display that the realized compensating circuit in a space optical camera is capable of improving the MTF of an optical remote sensing imaging system 30% higher than that of no compensation. This quantized principle can efficiently instruct the MTF compensating circuit design in practice.

  5. Wavefront Sensing Analysis of Grazing Incidence Optical Systems

    NASA Technical Reports Server (NTRS)

    Rohrbach, Scott; Saha, Timo

    2012-01-01

    Wavefront sensing is a process by which optical system errors are deduced from the aberrations in the image of an ideal source. The method has been used successfully in near-normal incidence, but not for grazing incidence systems. This innovation highlights the ability to examine out-of-focus images from grazing incidence telescopes (typically operating in the x-ray wavelengths, but integrated using optical wavelengths) and determine the lower-order deformations. This is important because as a metrology tool, this method would allow the integration of high angular resolution optics without the use of normal incidence interferometry, which requires direct access to the front surface of each mirror. Measuring the surface figure of mirror segments in a highly nested x-ray telescope mirror assembly is difficult due to the tight packing of elements and blockage of all but the innermost elements to normal incidence light. While this can be done on an individual basis in a metrology mount, once the element is installed and permanently bonded into the assembly, it is impossible to verify the figure of each element and ensure that the necessary imaging quality will be maintained. By examining on-axis images of an ideal point source, one can gauge the low-order figure errors of individual elements, even when integrated into an assembly. This technique is known as wavefront sensing (WFS). By shining collimated light down the optical axis of the telescope and looking at out-of-focus images, the blur due to low-order figure errors of individual elements can be seen, and the figure error necessary to produce that blur can be calculated. The method avoids the problem of requiring normal incidence access to the surface of each mirror segment. Mirror figure errors span a wide range of spatial frequencies, from the lowest-order bending to the highest order micro-roughness. While all of these can be measured in normal incidence, only the lowest-order contributors can be determined

  6. Correlated electron perovskite films for optical sensing applications

    NASA Astrophysics Data System (ADS)

    Schultz, Andrew M.; Brown, Thomas D.; Ohodnicki, Paul R.

    2015-10-01

    Advanced power generation technologies including solid oxide fuel cells require advancements in sensor technologies for efficient operation. Gas sensors for SOFC anode streams must be stable in high temperature and under reducing atmospheres. Optical sensing technologies offer the potential for good stability and sensing response under harsh conditions but are relatively new as compared to alternative sensing approaches and require significant developments in underlying device and enabling materials technology. In this paper, the near infrared optical sensing response of La0.8Sr0.2MnO3, a representative correlated perovskite material, is presented. Hydrogen sensing performance was measured in laboratory scale sensing experiments in the range of 1-4% hydrogen. The effect of oxygen on sensor recovery behavior was also examined. The films show a large, recoverable response to the introduction of hydrogen to the gas stream. The results presented here suggest this unique class of materials is a strong candidate for future sensor development efforts targeted at optical sensor applications but also requires additional fundamental research to understand the mechanistic origin of observed optical sensing responses.

  7. Layered classification techniques for remote sensing applications

    NASA Technical Reports Server (NTRS)

    Swain, P. H.; Wu, C. L.; Landgrebe, D. A.; Hauska, H.

    1975-01-01

    The single-stage method of pattern classification utilizes all available features in a single test which assigns the unknown to a category according to a specific decision strategy (such as the maximum likelihood strategy). The layered classifier classifies the unknown through a sequence of tests, each of which may be dependent on the outcome of previous tests. Although the layered classifier was originally investigated as a means of improving classification accuracy and efficiency, it was found that in the context of remote sensing data analysis, other advantages also accrue due to many of the special characteristics of both the data and the applications pursued. The layered classifier method and several of the diverse applications of this approach are discussed.

  8. Optical polarimetry for noninvasive glucose sensing enabled by Sagnac interferometry.

    PubMed

    Winkler, Amy M; Bonnema, Garret T; Barton, Jennifer K

    2011-06-10

    Optical polarimetry is used in pharmaceutical drug testing and quality control for saccharide-containing products (juice, honey). More recently, it has been proposed as a method for noninvasive glucose sensing for diabetic patients. Sagnac interferometry is commonly used in optical gyroscopes, measuring minute Doppler shifts resulting from mechanical rotation. In this work, we demonstrate that Sagnac interferometers are also sensitive to optical rotation, or the rotation of linearly polarized light, and are therefore useful in optical polarimetry. Results from simulation and experiment show that Sagnac interferometers are advantageous in optical polarimetry as they are insensitive to net linear birefringence and alignment of polarization components.

  9. Optical fiber termination and splicing techniques

    NASA Astrophysics Data System (ADS)

    George, M.; Miller, M. M.

    1984-06-01

    This report details various techniques that have been developed during the course of optical fiber experimentation and installations. During the development phases, attempts have been made to devise the quickest and least tedious methods in each area of optical fiber work. These procedures include the termination and splicing of various cable types. Also included are appendices containing information on tools, connectors, jumpers, and splicing equipment.

  10. Compact Optical Technique for Streak Camera Calibration

    SciTech Connect

    Curt Allen; Terence Davies; Frans Janson; Ronald Justin; Bruce Marshall; Oliver Sweningsen; Perry Bell; Roger Griffith; Karla Hagans; Richard Lerche

    2004-04-01

    The National Ignition Facility is under construction at the Lawrence Livermore National Laboratory for the U.S. Department of Energy Stockpile Stewardship Program. Optical streak cameras are an integral part of the experimental diagnostics instrumentation. To accurately reduce data from the streak cameras a temporal calibration is required. This article describes a technique for generating trains of precisely timed short-duration optical pulses that are suitable for temporal calibrations.

  11. Fiber optic sensor having dual simultaneous sensitivities employing mode ring technique

    NASA Astrophysics Data System (ADS)

    Dekate, Sachin Narahari

    Fiber optic interferometric sensors have an extremely high maximum sensitivity when compared to fiber optic intensity based sensors. Their disadvantage is the complex and expensive signal demodulation techniques that are employed due to their multi-valued output signal in addition to zero-sensitivity at some measurand values. Employing two interferometric sensors of different sensitivity allows an extended range of operation with relatively high sensitivity, however; the two sensors can never be placed at the same exact spatial location. This dissertation documents the dual-sensitivity fiber optic strain sensor which provides two simultaneous outputs of different sensitivity enabling the unambiguous use of interferometric sensors over an extended range. The dual-sensitivity fiber optic strain sensor has one sensing region and therefore the measurand is sensed at one location. The dual-sensitivity fiber optic strain sensor combines two fiber optic sensor architectures: Two-Mode fiber optic interferometric strain sensor (low sensitivity) and the Mach-Zehnder fiber optic interferometric strain sensor (high sensitivity). The dual-sensitivity fiber optic strain sensor also employs the end-etched fiber technique that enables the separation of modes. This technique allows the separated modes to be recombined in inter-mode (different mode order interference yielding low sensitivity output) and intra-mode (same mode order interference yielding high sensitivity output) interference configurations. One sensing region, dual simultaneous sensitivities and the use of end-etched fiber for sensing applications are some of the unique features of the dual-sensitivity fiber optic strain sensor.

  12. Towards ultra-long-distance distributed fiber optic sensing

    NASA Astrophysics Data System (ADS)

    Wang, Zinan; Jia, Xinhong; Wu, Huijuan; Peng, Fei; Fu, Yun; Rao, Yunjiang

    2017-04-01

    Distributed fiber-optic sensing (DFOS) has drawn great attention in both academic research and industrial applications due to its unique advantages. Recent progress at University of Electronic Science and Technology of China (UESTC) in DFOS, mainly on ultra-long-distance Brillouin optical time-domain analysis (BOTDA) and phase-sensitive optical timedomain reflectometry (Φ-OTDR), is discussed in this paper, including research progress and real-life applications.

  13. Optical carrier-based microwave interferometers for sensing application

    NASA Astrophysics Data System (ADS)

    Huang, Jie; Lan, Xinwei; Wang, Hanzheng; Yuan, Lei; Xiao, Hai

    2014-06-01

    Optical fiber interferometers (OFIs) have been extensively utilized for precise measurements of various physical/chemical quantities (e.g., temperature, strain, pressure, rotation, refractive index, etc.). However, the random change of polarization states along the optical fibers and the strong dependence on the materials and geometries of the optical waveguides are problematic for acquiring high quality interference signal. Meanwhile, difficulty in multiplexing has always been a bottleneck on the application scopes of OFIs. Here, we present a sensing concept of optical carrier based microwave interferometry (OCMI) by reading optical interferometric sensors in microwave domain. It combines the advantages from both optics and microwave. The low oscillation frequency of the microwave can hardly distinguish the optical differences from both modal and polarization dispersion making it insensitive to the optical waveguides/materials. The phase information of the microwave can be unambiguitly resolved so that it has potential in fully distributed sensing. The OCMI concept has been implemented in different types of interferometers (i.e., Michelson, Mach-Zehnder, Fabry-Perot) among different optical waveguides (i.e., singlemode, multimode, and sapphire fibers) with excellent signal-to-noise ratio (SNR) and low polarization dependence. A spatially continuous distributed strain sensing has been demonstrated.

  14. Bioactive ``self-sensing'' optical systems

    NASA Astrophysics Data System (ADS)

    Domachuk, Peter; Perry, Hannah; Amsden, Jason J.; Kaplan, David L.; Omenetto, Fiorenzo G.

    2009-12-01

    Free-standing silk films are useful materials to manufacture nanopatterned optical elements and to immobilize bio-dopants such as enzymes while maintaining their biological activity. These traits were combined by incorporating hemoglobin into free-standing silk diffraction gratings to fabricate chemically responsive optofluidic devices responsive to ambient gas conditions, constituting a simple oxygen sensor. This type of self-analyzing optical system is enabled by the unique ability to reproduce high-fidelity optical structures in silk while maintaining the activity of entrapped proteins such as hemoglobin. These bioactive optical devices offer a direct readout capability, adding utility into the bioresponsive material arena.

  15. Fully-distributed fiber-optic high temperature sensing based on stimulated Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Hu, Di; Wang, Dorothy Y.; Wang, Anbo

    2013-06-01

    We proposed a Brillouin optical fiber time domain analysis (BOTDA)-based fully-distributed temperature system as high as 1000°C and spatial resolution to 5 meters. This technique is prominent for high spatial resolution fully distributed high temperature and stress sensing over long distance.

  16. Fiber-Optic Sensing System: Overview, Development and Deployment in Flight at NASA

    NASA Technical Reports Server (NTRS)

    Chan, Hon Man; Parker, Allen R.; Piazza, Anthony; Richards, W. Lance

    2015-01-01

    An overview of the research and technological development of the fiber-optic sensing system (FOSS) at the National Aeronautics and Space Administration Armstrong Flight Research Center (NASA AFRC) is presented. Theory behind fiber Bragg grating (FBG) sensors, as well as interrogation technique based on optical frequency domain reflectometry (OFDR) is discussed. Assessment and validation of FOSS as an accurate measurement tool for structural health monitoring is realized in the laboratory environment as well as large-scale flight deployment.

  17. Fluorescence sensing techniques for vegetation assessment.

    PubMed

    Corp, Lawrence A; Middleton, Elizabeth M; McMurtrey, James E; Campbell, Petya K Entcheva; Butcher, L Maryn

    2006-02-10

    Active fluorescence (F) sensing systems have long been suggested as a means to identify species composition and determine physiological status of plants. Passive F systems for large-scale remote assessment of vegetation will undoubtedly rely on solar-induced F (SIF), and this information could potentially be obtained from the Fraunhofer line depth (FLD) principle. However, understanding the relationships between the information and knowledge gained from active and passive systems remains to be addressed. Here we present an approach in which actively induced F spectral data are used to simulate and project the magnitude of SIF that can be expected from near-ground observations within selected solar Fraunhofer line regions. Comparisons among vegetative species and nitrogen (N) supply treatments were made with three F approaches: the passive FLD principle applied to telluric oxygen (O2) bands from field-acquired canopy reflectance spectra, simulated SIF from actively induced laboratory emission spectra of leaves at a series of solar Fraunhofer lines ranging from 422 to 758 nm, and examination of two dual-F excitation algorithms developed from laboratory data. From these analyses we infer that SIF from whole-plant canopies can be simulated by use of laboratory data from active systems on individual leaves and that SIF has application for the large-scale assessment of vegetation.

  18. Offshore winds using remote sensing techniques

    NASA Astrophysics Data System (ADS)

    Peña, Alfredo; Bay Hasager, Charlotte; Gryning, Sven-Erik; Courtney, Michael; Antoniou, Ioannis; Mikkelsen, Torben; Sørensen, Paul

    2007-07-01

    Ground-based remote sensing instruments can observe winds at different levels in the atmosphere where the wind characteristics change with height: the range of heights where modern turbine rotors are operating. A six-month wind assessment campaign has been made with a LiDAR (Light Detection And Ranging) and a SoDAR (Sound Detection and Ranging) on the transformer/platform of the world's largest offshore wind farm located at the West coast of Denmark to evaluate their ability to observe offshore winds. The high homogeneity and low turbulence levels registered allow the comparison of LiDAR and SoDAR with measurements from cups on masts surrounding the wind farm showing good agreement for both the mean wind speed and the longitudinal component of turbulence. An extension of mean wind speed profiles from cup measurements on masts with LiDAR observations results in a good match for the free sectors at different wind speeds. The log-linear profile is fitted to the extended profiles (averaged over all stabilities and roughness lengths) and the deviations are small. Extended profiles of turbulence intensity are also shown for different wind speeds up to 161 m. Friction velocities and roughness lengths calculated from the fitted log-linear profile are compared with the Charnock model which seems to overestimate the sea roughness for the free sectors.

  19. The study of optical fiber communication technology for space optical remote sensing

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Yu, Sheng-quan; Zhang, Xiao-hong; Zhang, Rong-hui; Ma, Jian-hua

    2012-11-01

    The latest trends of Space Optical Remote Sensing are high-resolution, multispectral, and wide swath detecting. High-speed digital image data transmission will be more important for remote sensing. At present, the data output interface of Space Optical Remote Sensing, after performing the image data compression and formatting, transfers the image data to data storage unit of the Spacecraft through LVDS circuit cables. But this method is not recommended for high-speed digital image data transmission. This type of image data transmission, called source synchronization, has the low performance for high-speed digital signal. Besides, it is difficult for cable installing and system testing in limited space of vehicle. To resolve these issues as above, this paper describes a high-speed interconnection device for Space Optical Remote Sensing with Spacecraft. To meet its objectives, this device is comprised of Virtex-5 FPGA with embedded high-speed series and power-efficient transceiver, fiber-optic transceiver module, the unit of fiber-optic connection and single mode optical fiber. The special communication protocol is performed for image data transferring system. The unit of fiber-optic connection with high reliability and flexibility is provided for transferring high-speed serial data with optical fiber. It is evident that this method provides many advantages for Space Optical Remote Sensing: 1. Improving the speed of image data transferring of Space Optical Remote Sensing; 2. Enhancing the reliability and safety of image data transferring; 3. Space Optical Remote Sensing will be reduced significantly in size and in weight; 4. System installing and system testing for Space Optical Remote Sensing will become easier.

  20. Distributed Long-Gauge Optical Fiber Sensors Based Self-Sensing FRP Bar for Concrete Structure.

    PubMed

    Tang, Yongsheng; Wu, Zhishen

    2016-02-25

    Brillouin scattering-based distributed optical fiber (OF) sensing technique presents advantages for concrete structure monitoring. However, the existence of spatial resolution greatly decreases strain measurement accuracy especially around cracks. Meanwhile, the brittle feature of OF also hinders its further application. In this paper, the distributed OF sensor was firstly proposed as long-gauge sensor to improve strain measurement accuracy. Then, a new type of self-sensing fiber reinforced polymer (FRP) bar was developed by embedding the packaged long-gauge OF sensors into FRP bar, followed by experimental studies on strain sensing, temperature sensing and basic mechanical properties. The results confirmed the superior strain sensing properties, namely satisfied accuracy, repeatability and linearity, as well as excellent mechanical performance. At the same time, the temperature sensing property was not influenced by the long-gauge package, making temperature compensation easy. Furthermore, the bonding performance between self-sensing FRP bar and concrete was investigated to study its influence on the sensing. Lastly, the sensing performance was further verified with static experiments of concrete beam reinforced with the proposed self-sensing FRP bar. Therefore, the self-sensing FRP bar has potential applications for long-term structural health monitoring (SHM) as embedded sensors as well as reinforcing materials for concrete structures.

  1. Distributed Long-Gauge Optical Fiber Sensors Based Self-Sensing FRP Bar for Concrete Structure

    PubMed Central

    Tang, Yongsheng; Wu, Zhishen

    2016-01-01

    Brillouin scattering-based distributed optical fiber (OF) sensing technique presents advantages for concrete structure monitoring. However, the existence of spatial resolution greatly decreases strain measurement accuracy especially around cracks. Meanwhile, the brittle feature of OF also hinders its further application. In this paper, the distributed OF sensor was firstly proposed as long-gauge sensor to improve strain measurement accuracy. Then, a new type of self-sensing fiber reinforced polymer (FRP) bar was developed by embedding the packaged long-gauge OF sensors into FRP bar, followed by experimental studies on strain sensing, temperature sensing and basic mechanical properties. The results confirmed the superior strain sensing properties, namely satisfied accuracy, repeatability and linearity, as well as excellent mechanical performance. At the same time, the temperature sensing property was not influenced by the long-gauge package, making temperature compensation easy. Furthermore, the bonding performance between self-sensing FRP bar and concrete was investigated to study its influence on the sensing. Lastly, the sensing performance was further verified with static experiments of concrete beam reinforced with the proposed self-sensing FRP bar. Therefore, the self-sensing FRP bar has potential applications for long-term structural health monitoring (SHM) as embedded sensors as well as reinforcing materials for concrete structures. PMID:26927110

  2. Evaluation of a Temperature Remote Sensing Technique.

    DTIC Science & Technology

    1987-07-01

    concnional Raman for the technique is to monitor temperature in a super- spectroscopy , shich rCqttircs the ncastrement of rela- somio acrod,,namic test...where atomic col- spread of the absorption line. It is normalized such that lisions are infrequent, the Doppler effect determines the width of the...ex- Note: Only the intense modes were recorded cellent tool for high-resolution spectroscopy . at each temperature Coarse frequency tuning of the laser

  3. Optical time-domain reflectometer based multiplexed sensing scheme for environmental sensing

    NASA Astrophysics Data System (ADS)

    Carvalho, J. P.; Gouveia, C.; Santos, J. L.; Jorge, P. A. S.; Baptista, J. M.

    2012-04-01

    In our study, remote environmental sensing is presented using a standard optical time domain reflectometer (OTDR). The measurement of environmental parameters using optical sensors is an expanding area of research with growing importance. Fiber optic sensors are an interesting solution for that due to their high sensitivity, small size, and capability for on-site, real-time, remote, and distributed sensing capabilities. Our multiplexing sensing scheme approach uses transmissive filters (long period gratings - LPGs) interrogated by the OTDR return pulses. The loss induced at the resonance wavelengths varies with changes in the environment refractive index, temperature or other physical parameters. Experimental results show that the insertion of an erbium amplifier improves the measurement resolution in certain situations. Further analysis show that a remote multiplexed sensing scheme allows us to perform simple and low cost real time measurement of refractive index and temperature over long distances.

  4. Fire Source Localization Based on Distributed Temperature Sensing by a Dual-Line Optical Fiber System.

    PubMed

    Sun, Miao; Tang, Yuquan; Yang, Shuang; Li, Jun; Sigrist, Markus W; Dong, Fengzhong

    2016-06-06

    We propose a method for localizing a fire source using an optical fiber distributed temperature sensor system. A section of two parallel optical fibers employed as the sensing element is installed near the ceiling of a closed room in which the fire source is located. By measuring the temperature of hot air flows, the problem of three-dimensional fire source localization is transformed to two dimensions. The method of the source location is verified with experiments using burning alcohol as fire source, and it is demonstrated that the method represents a robust and reliable technique for localizing a fire source also for long sensing ranges.

  5. Fire Source Localization Based on Distributed Temperature Sensing by a Dual-Line Optical Fiber System

    PubMed Central

    Sun, Miao; Tang, Yuquan; Yang, Shuang; Li, Jun; Sigrist, Markus W.; Dong, Fengzhong

    2016-01-01

    We propose a method for localizing a fire source using an optical fiber distributed temperature sensor system. A section of two parallel optical fibers employed as the sensing element is installed near the ceiling of a closed room in which the fire source is located. By measuring the temperature of hot air flows, the problem of three-dimensional fire source localization is transformed to two dimensions. The method of the source location is verified with experiments using burning alcohol as fire source, and it is demonstrated that the method represents a robust and reliable technique for localizing a fire source also for long sensing ranges. PMID:27275822

  6. Non-iterative adaptive optical microscopy using wavefront sensing

    NASA Astrophysics Data System (ADS)

    Tao, X.; Azucena, O.; Kubby, J.

    2016-03-01

    This paper will review the development of wide-field and confocal microscopes with wavefront sensing and adaptive optics for correcting refractive aberrations and compensating scattering when imaging through thick tissues (Drosophila embryos and mouse brain tissue). To make wavefront measurements in biological specimens we have modified the laser guide-star techniques used in astronomy for measuring wavefront aberrations that occur as star light passes through Earth's turbulent atmosphere. Here sodium atoms in Earth's mesosphere, at an altitude of 95 km, are excited to fluoresce at resonance by a high-power sodium laser. The fluorescent light creates a guide-star reference beacon at the top of the atmosphere that can be used for measuring wavefront aberrations that occur as the light passes through the atmosphere. We have developed a related approach for making wavefront measurements in biological specimens using cellular structures labeled with fluorescent proteins as laser guide-stars. An example is a fluorescently labeled centrosome in a fruit fly embryo or neurons and dendrites in mouse brains. Using adaptive optical microscopy we show that the Strehl ratio, the ratio of the peak intensity of an aberrated point source relative to the diffraction limited image, can be improved by an order of magnitude when imaging deeply into live dynamic specimens, enabling near diffraction limited deep tissue imaging.

  7. Examination of charge transfer in Au/YSZ for high-temperature optical gas sensing

    SciTech Connect

    Baltrus, John P.; Ohodnicki, Paul R.

    2014-01-01

    Au-nanoparticle incorporated oxide thin film materials demonstrate significant promise as functionalsensor materials for high temperature optical gas sensing in severe environments relevant for fossil andnuclear based power generation. The Au/yttria-stabilized zirconia (YSZ) system has been extensivelystudied in the literature and serves as a model system for fundamental investigations that seek to betterunderstand the mechanistic origin of the plasmonic gas sensing response. In this work, X-ray photoelec-tron spectroscopy techniques are applied to Au/YSZ films in an attempt to provide further experimentalevidence for a proposed sensing mechanism involving a change in free carrier density of Au nanoparticles due to charge transfer.

  8. Spatially-resolved spectroscopic technique for measuring optical properties of food

    USDA-ARS?s Scientific Manuscript database

    Quantification of optical properties is important to understand light interaction with biological materials, and to develop effective optical sensing techniques for property characterization and quality measurement of food products. This chapter reviews spatially-resolved method, with the focus on f...

  9. Optical Sensing and Trapping Based on Localized Surface Plasmons

    NASA Astrophysics Data System (ADS)

    Kang, Zhiwen

    This project involves the study of novel plasmonic nanodevices that provide unique functionality in optical sensing, surface-enhanced Raman scattering (SERS), and optical trapping. The first design is based on a coupling system involving double-layered metal nano-strips arrays. This system has the advantages of simple geometry and direct integration with microfluidic chips. The intense optical localization due to field coupling within the system can enhance detection sensitivity of target molecules, especially by virtue of the optical trapping of plasmonic nanoparticles. The optical resonant condition is obtained theoretically through analyzing the SPs modes. Numerical modeling based on two-dimensional (2D) finite-difference time-domain (FDTD) is consistent with the theoretical analysis and demonstrates the feasibility of using this system for optical sensing and trapping. In the second design, a gold nano-ring structure is demonstrated to be an effective approach for plasmonic nano-optical tweezers (PNOTs) for trapping metallic nanoparticles. In our demonstration example, we have optimized a device for SERS operation at the wavelength of 785 nm. Three-dimensional (3D) FDTD techniques have been employed to calculate the optical response, and the optical force distribution have been derived using the Maxwell stress tensor (MST) method. Simulation results indicate that the nano-ring produces a maximum trapping potential well of ~32 kBT on a 20 nm gold nanoparticle. The existence of multiple potential well results in a very large active trapping volume of ~106 nm3 for the target particles. Furthermore, the trapped gold nanoparticles further lead to the formation of nano-gaps that offer a near-field enhancement of ~160 times, resulting in an achievable EF of 108 for SERS. In the third design, we propose a concept of all-optical nano-manipulation. We show that target molecules, after being trapped, can be transferred between the trapping sites within a linear array of

  10. Monitoring marine pollution by airborne remote sensing techniques

    SciTech Connect

    Yuanfu, S.; Quanan, Z.

    1982-06-01

    In order to monitor marine pollution by airborne remote sensing techniques, some comprehensive test of airborne remote sensing, involving monitoring marine oil pollution, were performed at several bay areas of China. This paper presents some typical results of monitoring marine oil pollution. The features associated with the EM spectrum (visible, thermal infrared, and microwave) response of marine oil spills is briefly analyzed. It has been verified that the airborne oil surveillance systems manifested their advantages for monitoring the oil pollution of bay environments.

  11. Combining calcium imaging with other optical techniques.

    PubMed

    Canepari, Marco; Zecevic, Dejan; Vogt, Kaspar E; Ogden, David; De Waard, Michel

    2013-12-01

    Ca(2+) imaging is a commonly used approach for measuring Ca(2+) signals at high spatial resolution. The method is often combined with electrode recordings to correlate electrical and chemical signals or to investigate Ca(2+) signals following an electrical stimulation. To obtain information on electrical activity at the same spatial resolution, Ca(2+) imaging must be combined with membrane potential imaging. Similarly, stimulation of subcellular compartments requires photostimulation. Thus, combining Ca(2+) imaging with an additional optical technique facilitates the study of a number of physiological questions. The aim of this article is to introduce some basic principles regarding the combination of Ca(2+) imaging with other optical techniques. We discuss the design of the optics, the design of experimental protocols, the optical characteristics of Ca(2+) indicators used in combination with an optical probe, and the affinity of the Ca(2+) indicator in relation to the type of measurement. This information will enable the reader to devise an optimal strategy for combined optical experiments.

  12. Research on spectral resource optimization and self-healing technology of hybrid optical fiber sensing network

    NASA Astrophysics Data System (ADS)

    Chen, Cheng; Sang, Mei; Ge, Chunfeng; Chen, Guanghui; Liu, Tiegen

    2015-08-01

    We propose an optical-fiber-sensing-network (OFSN) to allow hybrid fiber sensors working in the same network and it achieves self-healing function. The discrete and distributed optical fiber sensors can be connected in sub-layers of the network. WDM-OTDM technique is introduced to convert multi-wavelengths of light source into a specific arranged wavelength in each sub-layer. Thus every sub-layer can share the system spectrum resources, and sensing signals of each sub-layer are transmitted together in the backbone network. To achieve self-healing function, double-ring structure is adopted in the backbone network. Node microprocessor program is designed to make switching to the protect fiber when working fiber is broken. The experimental backbone setup of the network demonstrates the practical reliability and intelligence of the optical sensing network.

  13. Nonlinear optical techniques for surface studies. [Monolayers

    SciTech Connect

    Shen, Y.R.

    1981-09-01

    Recent effort in developing nonlinear optical techniques for surface studies is reviewed. Emphasis is on monolayer detection of adsorbed molecules on surfaces. It is shown that surface coherent antiStokes Raman scattering (CARS) with picosecond pulses has the sensitivity of detecting submonolayer of molecules. On the other hand, second harmonic or sum-frequency generation is also sensitive enough to detect molecular monolayers. Surface-enhanced nonlinear optical effects on some rough metal surfaces have been observed. This facilitates the detection of molecular monolayers on such surfaces, and makes the study of molecular adsorption at a liquid-metal interface feasible. Advantages and disadvantages of the nonlinear optical techniques for surface studies are discussed.

  14. Dental diagnostics using optical coherence techniques

    SciTech Connect

    Nathel, H.; Colston, B.; Armitage, G.

    1994-11-15

    Optical radiation can be used for diagnostic purposes in oral medicine. However, due to the turbid, amorphous, and inhomogeneous nature of dental tissue conventional techniques used to transilluminate materials are not well suited to dental tissues. Optical coherence techniques either in the time- of frequency-domain offer the capabilities of discriminating scattered from unscattered light, thus allowing for imaging through turbid tissue. Currently, using optical time-domain reflectometry we are able to discriminate specular from diffuse reflections occurring at tissue boundaries. We have determined the specular reflectivity of enamel and dentin to be approximately 6.6 x 10{sup -5} and 1.3 x 10{sup -6}, respectively. Implications to periodontal imaging will be discussed.

  15. Optical/Infrared Signatures for Space-Based Remote Sensing

    DTIC Science & Technology

    2007-11-01

    have turned our attention more general techniques to enhance spatial resolution. Called generally superresolution techniques (for example...Mendlovic, Optical Superresolution , Springer-Verlag, New York, 2004. 56 57 PUBLICATIONS - 2000-2007

  16. Optical fiber sensing of human skin emanations

    NASA Astrophysics Data System (ADS)

    Lee, S.-W.; Wang, T.; Selyanchyn, R.; Korposh, S.; James, S. W.

    2015-07-01

    An evanescent-wave optical fibre sensor modified with tetrakis(4-sulfophenyl)porphine (TSPP) and poly(allylamine hydrochloride) (PAH) bilayers using an layer-by-layer (LbL) approach was tested to measure the gas emitted from human skin. Optical intensity changes at different wavelengths in the transmission spectrum of the porphyrin-based film were induced by the human skin gas and measured as sensor response. Influence of relative humidity, which can be a major interference to sensor response, was significantly different when compared to the influence of skin emanations. Responses of the current optical sensor system could be considered as composite sensor array, where different optical wavelengths act as channels that have selective response to specific volatile compounds. Data obtained from the sensor system was analyzed through principal component analysis (PCA). This approach enabled to distinguish skin odors of different people and their altered physiological conditions after alcohol consumption.

  17. Optical Interferometers for Sensing Electromagnetic Fields

    DTIC Science & Technology

    1991-03-29

    with 1000A of Ti at 1025 C for 8 hours. The crystal surface is subsequently etched in HF:HNO, at 80 to 90 C for 3 minutes 29 Figure 8. +Z oriented... semiconductors , dielectrics, such as potassium titanyl phosphate (KTP) and ferroelectrics, such as lithium niobate and lithium tantalate. Optical... surface of the substrate material. The waveguide is bounded only in one direction by the thickness of the waveguide layer. The optical beam is

  18. Liquid crystal optical fibers for sensing applications

    NASA Astrophysics Data System (ADS)

    Choudhury, P. K.

    2013-09-01

    Propagation characteristics of optical fibers are greatly dependent on materials, which the guides are comprised of. Varieties of materials have been developed and investigated for their usage in fabricating optical fibers for specific applications. Within the context, a liquid crystal medium is both inhomogeneous and optically anisotropic, and fibers made of such mediums are greatly useful. Also, liquid crystals exhibit strong electro-optic behavior, which allows alternation in their optical properties under the influence of external electric fields. These features make liquid crystal fibers greatly important for optical applications. The present communication is aimed at providing a glimpse of the efficacy of liquid crystals and/or fibers made of liquid crystals, followed by the analytical investigation of wave propagation through such guides. The sustainment of modes is explored in these fibers under varying fiber dimensions, and the novelty is discussed. The case of tapered liquid crystal fibers is also briefly discussed highlighting the usefulness. Control on the dispersion characteristics of such fibers may be imposed by making the guide even more complex; the possibility of devising such options is also touched upon.

  19. Optical sensing in a directional hearing aid microphone

    NASA Astrophysics Data System (ADS)

    Zhou, Shuang

    This thesis describes the simulation and analysis of the use of optical sensing for a MEMS directional microphone. Diffraction gratings integrated with micro-electromechanical-systems (MEMS) offer an optical sensing scheme with high detection sensitivity, low noise level and compact device structure. An optical sensing method is applied in a hearing aid microphone to detect the movement of the diaphragm due to sound. Diffraction grating fingers are fabricated on both sides of the diaphragm with a gold mirror on top. Two photo detectors are placed on the substrate symmetrically to detect the positive and negative first order diffraction of 850 nm VCSEL light. A finite element analysis model is built in COMSOL to study the light distribution and energy loss. The signal output, predicted using an analytical model is shown to agree well with those obtained using the finite element model.

  20. Optical Measurement Technique for Space Column Characterization

    NASA Technical Reports Server (NTRS)

    Barrows, Danny A.; Watson, Judith J.; Burner, Alpheus W.; Phelps, James E.

    2004-01-01

    A simple optical technique for the structural characterization of lightweight space columns is presented. The technique is useful for determining the coefficient of thermal expansion during cool down as well as the induced strain during tension and compression testing. The technique is based upon object-to-image plane scaling and does not require any photogrammetric calibrations or computations. Examples of the measurement of the coefficient of thermal expansion are presented for several lightweight space columns. Examples of strain measured during tension and compression testing are presented along with comparisons to results obtained with Linear Variable Differential Transformer (LVDT) position transducers.

  1. Macrobend optical sensing for pose measurement in soft robot arms

    NASA Astrophysics Data System (ADS)

    Sareh, Sina; Noh, Yohan; Li, Min; Ranzani, Tommaso; Liu, Hongbin; Althoefer, Kaspar

    2015-12-01

    This paper introduces a pose-sensing system for soft robot arms integrating a set of macrobend stretch sensors. The macrobend sensory design in this study consists of optical fibres and is based on the notion that bending an optical fibre modulates the intensity of the light transmitted through the fibre. This sensing method is capable of measuring bending, elongation and compression in soft continuum robots and is also applicable to wearable sensing technologies, e.g. pose sensing in the wrist joint of a human hand. In our arrangement, applied to a cylindrical soft robot arm, the optical fibres for macrobend sensing originate from the base, extend to the tip of the arm, and then loop back to the base. The connectors that link the fibres to the necessary opto-electronics are all placed at the base of the arm, resulting in a simplified overall design. The ability of this custom macrobend stretch sensor to flexibly adapt its configuration allows preserving the inherent softness and compliance of the robot which it is installed on. The macrobend sensing system is immune to electrical noise and magnetic fields, is safe (because no electricity is needed at the sensing site), and is suitable for modular implementation in multi-link soft continuum robotic arms. The measurable light outputs of the proposed stretch sensor vary due to bend-induced light attenuation (macrobend loss), which is a function of the fibre bend radius as well as the number of repeated turns. The experimental study conducted as part of this research revealed that the chosen bend radius has a far greater impact on the measured light intensity values than the number of turns (if greater than five). Taking into account that the bend radius is the only significantly influencing design parameter, the macrobend stretch sensors were developed to create a practical solution to the pose sensing in soft continuum robot arms. Henceforward, the proposed sensing design was benchmarked against an electromagnetic

  2. Millimeter-wave/THz FMCW radar techniques for sensing applications

    NASA Astrophysics Data System (ADS)

    Mirando, D. Amal; Higgins, Michael D.; Wang, Fenggui; Petkie, Douglas T.

    2016-10-01

    Millimeter-wave and terahertz continuous-wave radar systems have been used to measure physiological signatures for biometric applications and for a variety of non-destructive evaluation applications, such as the detection of defects in materials. Sensing strategies for the simplest homodyne systems, such as a Michelson Interferometer, can be enhanced by using Frequency Modulated Continuous Wave (FMCW) techniques. This allows multiple objects or surfaces to be range resolved while monitoring the phase of the signal in a particular range bin. We will discuss the latest developments in several studies aimed at demonstrating how FMCW techniques can enhance mmW/THz sensing applications.

  3. Extruded single ring hollow core optical fibers for Raman sensing

    NASA Astrophysics Data System (ADS)

    Tsiminis, G.; Rowland, K. J.; Ebendorff-Heidepriem, H.; Spooner, N. A.; Monro, T. M.

    2014-05-01

    In this work we report the fabrication of the first extruded hollow core optical fiber with a single ring of cladding holes. A lead-silicate glass billet is used to produce a preform through glass extrusion to create a larger-scale version of the final structure that is subsequently drawn to an optical fiber. The simple single suspended ring structure allows antiresonance reflection guiding. The resulting fibers were used to perform Raman sensing of liquid samples filling the length of the fiber, demonstrating its potential for fiber sensing applications.

  4. Development of a lidar technique for profiling optical turbulence

    NASA Astrophysics Data System (ADS)

    Gimmestad, Gary; Roberts, David; Stewart, John; Wood, Jack

    2012-10-01

    Many techniques have been proposed for active optical remote sensing of the strength of atmospheric refractive turbulence. The early techniques, based on degradation of laser beams by turbulence, were susceptible to artifacts. In 1999, we began investigating a new idea, based on differential image motion (DIM), which is inherently immune to artifacts. The new lidar technique can be seen as a combination of two astronomical instruments: a laser guide star transmitter/receiver and a DIM monitor. The technique was successfully demonstrated on a horizontal path, with a hard-target analog of a lidar, and then a true lidar was developed. Several investigations were carried out first, including an analysis to predict the system's performance; new hard-target field measurements in the vertical direction; development of a robust inversion technique; and wave optics simulations. A brassboard lidar was then constructed and operated in the field, along with instruments to acquire truth data. The tests revealed many problems and pitfalls that were all solvable with engineering changes, and the results served to verify the new lidar technique for profiling turbulence. The results also enabled accurate performance predictions for future versions of the lidar. A transportable turbulence lidar system is currently being developed to support field tests of high-energy lasers.

  5. Progress in distributed fiber optic temperature sensing

    NASA Astrophysics Data System (ADS)

    Hartog, Arthur H.

    2002-02-01

    The paper reviews the adoption of distributed temperature sensing (DTS) technology based on Raman backscatter. With one company alone having installed more than 400 units, the DTS is becoming accepted practice in several applications, notably in energy cable monitoring, specialised fire detection and oil production monitoring. The paper will provide case studies in these applications. In each case the benefit (whether economic or safety) will be addressed, together with key application engineering issues. The latter range from the selection and installation of the fibre sensor, the specific performance requirements of the opto-electronic equipment and the issues of data management. The paper will also address advanced applications of distributed sensing, notably the problem of monitoring very long ranges, which apply in subsea DC energy cables or in subsea oil wells linked to platforms through very long (e.g. 30km flowlines). These applications are creating the need for a new generation of DTS systems able to achieve measurements at up to 40km with very high temperature resolution, without sacrificing spatial resolution. This challenge is likely to drive the development of new concepts in the field of distributed sensing.

  6. Nanocomposite thin films for optical gas sensing

    DOEpatents

    Ohodnicki, Paul R; Brown, Thomas D

    2014-06-03

    The disclosure relates to a plasmon resonance-based method for gas sensing in a gas stream utilizing a gas sensing material. In an embodiment the gas stream has a temperature greater than about 500.degree. C. The gas sensing material is comprised of gold nanoparticles having an average nanoparticle diameter of less than about 100 nanometers dispersed in an inert matrix having a bandgap greater than or equal to 5 eV, and an oxygen ion conductivity less than approximately 10.sup.-7 S/cm at a temperature of 700.degree. C. Exemplary inert matrix materials include SiO.sub.2, Al.sub.2O.sub.3, and Si.sub.3N.sub.4 as well as modifications to modify the effective refractive indices through combinations and/or doping of such materials. Changes in the chemical composition of the gas stream are detected by changes in the plasmon resonance peak. The method disclosed offers significant advantage over active and reducible matrix materials typically utilized, such as yttria-stabilized zirconia (YSZ) or TiO.sub.2.

  7. Dynamic response of tapered optical multimode fiber coated with carbon nanotubes for ethanol sensing application.

    PubMed

    Shabaneh, Arafat; Girei, Saad; Arasu, Punitha; Mahdi, Mohd; Rashid, Suraya; Paiman, Suriati; Yaacob, Mohd

    2015-05-04

    Ethanol is a highly combustible chemical universally designed for biomedical applications. In this paper, optical sensing performance of tapered multimode fiber tip coated with carbon nanotube (CNT) thin film towards aqueous ethanol with different concentrations is investigated. The tapered optical multimode fiber tip is coated with CNT using drop-casting technique and is annealed at 70 °C to enhance the binding of the nanomaterial to the silica fiber tip. The optical fiber tip and the CNT sensing layer are micro-characterized using FESEM and Raman spectroscopy techniques. When the developed sensor was exposed to different concentrations of ethanol (5% to 80%), the sensor reflectance reduced proportionally. The developed sensors showed high sensitivity, repeatability and fast responses (<55 s) towards ethanol.

  8. Dynamic Response of Tapered Optical Multimode Fiber Coated with Carbon Nanotubes for Ethanol Sensing Application

    PubMed Central

    Shabaneh, Arafat; Girei, Saad; Arasu, Punitha; Mahdi, Mohd; Rashid, Suraya; Paiman, Suriati; Yaacob, Mohd

    2015-01-01

    Ethanol is a highly combustible chemical universally designed for biomedical applications. In this paper, optical sensing performance of tapered multimode fiber tip coated with carbon nanotube (CNT) thin film towards aqueous ethanol with different concentrations is investigated. The tapered optical multimode fiber tip is coated with CNT using drop-casting technique and is annealed at 70 °C to enhance the binding of the nanomaterial to the silica fiber tip. The optical fiber tip and the CNT sensing layer are micro-characterized using FESEM and Raman spectroscopy techniques. When the developed sensor was exposed to different concentrations of ethanol (5% to 80%), the sensor reflectance reduced proportionally. The developed sensors showed high sensitivity, repeatability and fast responses (<55 s) towards ethanol. PMID:25946634

  9. Optical multichannel sensing of skin blood pulsations

    NASA Astrophysics Data System (ADS)

    Spigulis, Janis; Erts, Renars; Kukulis, Indulis; Ozols, Maris; Prieditis, Karlis

    2004-09-01

    Time resolved detection and analysis of the skin back-scattered optical signals (reflection photoplethysmography or PPG) provide information on skin blood volume pulsations and can serve for cardiovascular assessment. The multi-channel PPG concept has been developed and clinically verified in this study. Portable two- and four-channel PPG monitoring devices have been designed for real-time data acquisition and processing. The multi-channel devices were successfully applied for cardiovascular fitness tests and for early detection of arterial occlusions in extremities. The optically measured heartbeat pulse wave propagation made possible to estimate relative arterial resistances for numerous patients and healthy volunteers.

  10. Optical remote sensing of oil in the marine environment

    NASA Astrophysics Data System (ADS)

    Byfield, Valborg

    1998-11-01

    Remote sensing has played an increasing role in the routine monitoring of oil pollution and in support of the operational response to major oil pollution incidents. This study develops the technique of optical measurement for the detection of oil in the Marine Environment. A theoretical model is proposed, which relates upwelling radiance from surface oil to the optical properties of the oil in question, to the thickness of the oil layer, and to a number of ancillary environmental parameters. It is used to interpret the results of laboratory experiments in artificial and natural light, and ultimately as a tool in the analysis of airborne optical data of surface oil in the field, including the Sea Empress oil spill. Laboratory experiments showed that the thickness of surface oil may be determined using spectral ratios, and the results compared well with the predictions made by the theoretical model. Using the peak to near-infrared ratio, relative thickness estimates can be made from remote sensing data, without extensive data processing. Absolute thickness measurements are more complex, and require the knowledge of a number of environmental parameters. Both the laboratory and airborne data show that classification of oils into broad groups is possible using spectral analysis. However, the number of environmental parameters that must be considered makes this a complex task for field data. The model predicts that sheen detection will be most reliable in regions of the spectrum where the sub-surface signal is low, such as the violet to deep blue and the near-infrared. This is confirmed by the laboratory experiments in natural light, and by the airborne data from the field experiments. When water-leaving radiance is high in the near-infrared, sheen detection may be more difficult, although it should still be possible in the violet to deep blue. The theoretical model and the field data suggest that dispersed oil may be detected if concentrations are sufficiently high. The

  11. Optical Technologies for UV Remote Sensing Instruments

    NASA Technical Reports Server (NTRS)

    Keski-Kuha, R. A. M.; Osantowski, J. F.; Leviton, D. B.; Saha, T. T.; Content, D. A.; Boucarut, R. A.; Gum, J. S.; Wright, G. A.; Fleetwood, C. M.; Madison, T. J.

    1993-01-01

    Over the last decade significant advances in technology have made possible development of instruments with substantially improved efficiency in the UV spectral region. In the area of optical coatings and materials, the importance of recent developments in chemical vapor deposited (CVD) silicon carbide (SiC) mirrors, SiC films, and multilayer coatings in the context of ultraviolet instrumentation design are discussed. For example, the development of chemically vapor deposited (CVD) silicon carbide (SiC) mirrors, with high ultraviolet (UV) reflectance and low scatter surfaces, provides the opportunity to extend higher spectral/spatial resolution capability into the 50-nm region. Optical coatings for normal incidence diffraction gratings are particularly important for the evolution of efficient extreme ultraviolet (EUV) spectrographs. SiC films are important for optimizing the spectrograph performance in the 90 nm spectral region. The performance evaluation of the flight optical components for the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument, a spectroscopic instrument to fly aboard the Solar and Heliospheric Observatory (SOHO) mission, designed to study dynamic processes, temperatures, and densities in the plasma of the upper atmosphere of the Sun in the wavelength range from 50 nm to 160 nm, is discussed. The optical components were evaluated for imaging and scatter in the UV. The performance evaluation of SOHO/CDS (Coronal Diagnostic Spectrometer) flight gratings tested for spectral resolution and scatter in the DGEF is reviewed and preliminary results on resolution and scatter testing of Space Telescope Imaging Spectrograph (STIS) technology development diffraction gratings are presented.

  12. Fiber-Optics -- A Sensing Device.

    DTIC Science & Technology

    1986-08-01

    perturbations in sound, displacement, temperature, pressure, magnetic fields, electric fields, rotation rate, strain, liquid level, and flow. The light...ReflectionllquId crystal ) hi Temperature Phololumutescence (phospher, semiconductor) intensy Spectrum Block body radiation M Polarization Birefringence...29]. The tranduction element consists of a thermochromic solution of a Cobalt salt that varies its optical absorption spectrum with temperature. A

  13. Remote sensing techniques for support of coastal zone resource management.

    NASA Technical Reports Server (NTRS)

    Piland, R. O.

    1973-01-01

    Description of remote sensing studies carried out for the purpose of developing and/or demonstrating techniques which can be employed for land use inventory, marsh vegetation classification, and water characteristics surveys. Attention is given to results obtained with (1) photo interpretation techniques and procedures for the development of land use information from high-altitude aircraft and satellite imagery, (2) computer based pattern recognition techniques utilizing multispectral scanner data for marsh vegetation classification, and (3) infrared and microwave techniques for the monitoring and surveying of coastal water temperature and salinity characteristics.

  14. Application of sensing techniques to cellular force measurement.

    PubMed

    Li, Bin; Wang, James H-C

    2010-01-01

    Cell traction forces (CTFs) are the forces produced by cells and exerted on extracellular matrix or an underlying substrate. CTFs function to maintain cell shape, enable cell migration, and generate and detect mechanical signals. As such, they play a vital role in many fundamental biological processes, including angiogenesis, inflammation, and wound healing. Therefore, a close examination of CTFs can enable better understanding of the cellular and molecular mechanisms of such processes. To this end, various force-sensing techniques for CTF measurement have been developed over the years. This article will provide a concise review of these sensing techniques and comment on the needs for improved force-sensing technologies for cell mechanics and biology research.

  15. Fully distributed fiber-optic sensing based on acoustically induced long-period grating

    NASA Astrophysics Data System (ADS)

    Wang, Dorothy Y.; Wang, Yunmiao; Han, Ming; Gong, Jianmin; Wang, Anbo

    2011-05-01

    This paper gives a review of a proposed fully-distributed fiber-optic sensing technique based on a traveling long-period grating (LPG) in a single-mode optical fiber. The LPG is generated by pulsed acoustic waves that propagate along the fiber. Based on this platform, first we demonstrated the fully-distributed temperature measurement in a 2.5m fiber. Then by coating the fiber with functional coatings, we demonstrated fully-distributed biological and chemical sensing. In the biological sensing experiment, immunoglobulin G (IgG) was immobilized onto the fiber surface, and we showed that only specific antigen-antibody binding can introduce a measurable shift in the transmission optical spectrum of the traveling LPG when it passes through the pretreated fiber segment. In the hydrogen sensing experiment, the fiber was coated with a platinum (Pt) catalyst layer, which is heated by the thermal energy released from Pt-assisted combustion of H2 and O2, and the resulted temperature change gives rise to a measurable LPG wavelength shift when the traveling LPG passes through. Hydrogen concentration from 1% to 3.8% was detected in the experiment. This technique may also permit measurement of other quantities by changing the functional coating on the fiber; therefore it is expected to be capable of other fully-distributed sensing applications.

  16. Hyperspectral remote sensing techniques for early detection of plant diseases

    NASA Astrophysics Data System (ADS)

    Krezhova, Dora; Maneva, Svetla; Zdravev, Tomas

    Hyperspectral remote sensing is an emerging, multidisciplinary field with diverse applications in Earth observation. Nowadays spectral remote sensing techniques allow presymptomatic monitoring of changes in the physiological state of plants with high spectral resolution. Hyperspectral leaf reflectance and chlorophyll fluorescence proved to be highly suitable for identification of growth anomalies of cultural plants that result from the environmental changes and different stress factors. Hyperspectral technologies can find place in many scientific areas, as well as for monitoring of plants status and functioning to help in making timely management decisions. This research aimed to detect a presence of viral infection in young pepper plants (Capsicum annuum L.) caused by Cucumber Mosaic Virus (CMV) by using hyperspectral reflectance and fluorescence data and to assess the effect of some growth regulators on the development of the disease. In Bulgaria CMV is one of the widest spread pathogens, causing the biggest economical losses in crop vegetable production. Leaf spectral reflectance and fluorescence data were collected by a portable fibre-optics spectrometer in the spectral ranges 450÷850 nm and 600-900 nm. Greenhouse experiment with pepper plants of two cultivars, Sivria (sensitive to CMV) and Ostrion (resistant to CMV) were used. The plants were divided into six groups. The first group consisted of healthy (control) plants. At growth stage 4-6 expanded leaf, the second group was inoculated with CMV. The other four groups were treated with growth regulators: Spermine, MEIA (beta-monomethyl ester of itaconic acid), ВТН (benzo(1,2,3)thiadiazole-7-carbothioic acid-S-methyl ester) and Phytoxin. On the next day, the pepper plants of these four groups were inoculated with CMV. The viral concentrations in the plants were determined by the serological method DAS-ELISA. Statistical, first derivative and cluster analysis were applied and several vegetation indices were

  17. Remote sensing techniques aid in preattack planning for fire management

    Treesearch

    Lucy Anne Salazar

    1982-01-01

    Remote sensing techniques were investigated as an alternative for documenting selected prettack fire planning information. Locations of fuel models, road systems, and water sources were recorded by Landsat satellite imagery and aerial photography for a portion of the Six Rivers National Forest in northwestern California. The two fuel model groups used were from the...

  18. Natural resource inventory for urban planning utilizing remote sensing techniques

    NASA Technical Reports Server (NTRS)

    Foster, K. E.; Mackey, P. F.; Bonham, C. D.

    1972-01-01

    Remote sensing techniques were applied to the lower Pantano Wash area to acquire data for planning an ecological balance between the expanding Tucson metropolitan area and its environment. The types and distribution of vegetation are discussed along with the hydrologic aspects of the Wash.

  19. Adaptive Remote-Sensing Techniques Implementing Swarms of Mobile Agents

    SciTech Connect

    Asher, R.B.; Cameron, S.M.; Loubriel, G.M.; Robinett, R.D.; Stantz, K.M.; Trahan, M.W.; Wagner, J.S.

    1998-11-25

    In many situations, stand-off remote-sensing and hazard-interdiction techniques over realistic operational areas are often impractical "and difficult to characterize. An alternative approach is to implement an adap- tively deployable array of sensitive agent-specific devices. Our group has been studying the collective be- havior of an autonomous, multi-agent system applied to chedbio detection and related emerging threat applications, The current physics-based models we are using coordinate a sensor array for mukivanate sig- nal optimization and coverage as re,alized by a swarm of robots or mobile vehicles. These intelligent control systems integrate'glob"ally operating decision-making systems and locally cooperative learning neural net- works to enhance re+-timp operational responses to dynarnical environments examples of which include obstacle avoidance, res~onding to prevailing wind patterns, and overcoming other natural obscurants or in- terferences. Collectively',tkensor nefirons with simple properties, interacting according to basic community rules, can accomplish complex interconnecting functions such as generalization, error correction, pattern recognition, sensor fusion, and localization. Neural nets provide a greater degree of robusmess and fault tolerance than conventional systems in that minor variations or imperfections do not impair performance. The robotic platforms would be equipped with sensor devices that perform opticaI detection of biologicais in combination with multivariate chemical analysis tools based on genetic and neural network algorithms, laser-diode LIDAR analysis, ultra-wideband short-pulsed transmitting and receiving antennas, thermal im- a:ing sensors, and optical Communication technology providing robust data throughput pathways. Mission scenarios under consideration include ground penetrating radar (GPR) for detection of underground struc- tures, airborne systems, and plume migration and mitigation. We will describe our research in

  20. RF switching network: a novel technique for IR sensing

    NASA Astrophysics Data System (ADS)

    Mechtel, Deborah M.; Jenkins, R. Brian; Joyce, Peter J.; Nelson, Charles L.

    2016-05-01

    Rapid sensing of near infrared (IR) energy on a composite structure would provide information that could mitigate damage to composite structures. This paper describes a novel technique that implements photoconductive sensors in a radio frequency (RF) switching network designed to locate in real time the position and intensity of IR radiation incident on a composite structure. In the implementation described here, photoconductive sensors act as rapid response switches in a two layer RF network embedded in an FR-4 laminate. To detect radiation, phosphorous doped silicon photoconductive sensors are inserted in GHz range RF transmission lines. Photoconductive sensors use semiconductor materials that are optically sensitive at material dependent wavelengths. Incident radiation at the appropriate wavelength produces hole-electron pairs, so that the semiconductor becomes a conductor. By permitting signal propagation only when a sensor is illuminated, the RF signals are selectively routed from the lower layer transmission lines to the upper layer lines, thereby pinpointing the location and strength of incident radiation on a structure. Simulations based on a high frequency 3D planar electromagnetics model are presented and compared to experimental results. Experimental results are described for GHz range RF signal control for 300 mW and 180 mW incident energy from 975 nm and 1060 nm wavelength lasers respectively, where upon illumination, RF transmission line signal output power doubled when compared to non-illuminated results. Experimental results are reported for 100 W incident energy from a 1060 nm laser. Test results illustrate that real-time signal processing would permit a structure or vehicle to be controlled in response to incident radiation

  1. Simple technique for integrating compact silicon devices within optical fibers.

    PubMed

    Micco, A; Ricciardi, A; Quero, G; Crescitelli, A; Bock, W J; Cusano, A

    2014-02-15

    In this work, we present a simple fabrication process enabling the integration of a subwavelength amorphous silicon layer inside optical fibers by means of the arc discharge technique. To assess our method, we have fabricated a compact in-line Fabry-Perot interferometer consisting of a thin (<1  μm) a-Si:H layer completely embedded within a standard single-mode optical fiber. The device exhibits low loss (1.3 dB) and high interference fringe visibility (~80%) both in reflection and transmission, due to the high refractive index contrast between silica and a-Si:H. A high linear temperature sensitivity up to 106  pm/°C is demonstrated in the range 120°C-400°C. The proposed interferometer is attractive for point monitoring applications as well as for ultrahigh-temperature sensing in harsh environments.

  2. Tamper indicating and sensing optical-based smart structures

    SciTech Connect

    Sliva, P.; Anheier, N.C.; Gordon, N.R.; Simmons, K.L.; Stahl, K.A.; Undem, H.A.

    1995-05-01

    This paper has presented an overview of the type of optical-based structures that can be designed and constructed. These smart structures are capable of responding to their environment. The examples given represent a modest sampling of the complexity that can be achieved in both design and practice. Tamper-indicating containers and smart, sensing windows demonstrate just a few of the applications. We have shown that optical-based smart structures can be made multifunctional with the sensing built in. The next generation smart structure will combine the sensing functionality of these optical-based smart structures with other sensors such as piezoelectrics and electro-rheological fluids to not only be able to respond to the environment, but to adapt to it as well. An example of functionality in this regime would be a piezosensor that senses pressure changes (e.g., shock waves), which then causes an electro-rheological fluid to change viscosity. A fiber sensor located in or near the electro-rheological fluid senses the stiffness change and sends a signal through a feedback loop back to the piezosensor for additional adjustments to the electro-rheological fluid.

  3. Surface Wear Measurement Using Optical Correlation Technique

    NASA Astrophysics Data System (ADS)

    Acinger, Kresimir

    1983-12-01

    The coherent optical correlation technique was applied for measuring the surface wear of a tappet (part of car engine), worn by friction with the camshaft. It was found that maximum correlation intensity decays exponentially with the number of wear cycles (i.e. camshaft revolutions). Tappets of the same make have an identical rate of correlation decay. Tappets of different makes have different rates of correlation decay which are in agreement with observed long term wear.

  4. Coherent optical data processing and remotely sensed imagery

    NASA Technical Reports Server (NTRS)

    Macdougall, E. B.

    1969-01-01

    It is shown that an automatic imaging system consisting of a combination of optical and digital computer elements is feasible and has considerable advantages over direct image scanning systems. With such a system, it is possible to process very large quantities of remotely sensed image spectra.

  5. RADIAL COMPUTED TOMOGRAPHY OF AIR CONTAMINANTS USING OPTICAL REMOTE SENSING

    EPA Science Inventory

    The paper describes the application of an optical remote-sensing (ORS) system to map air contaminants and locate fugitive emissions. Many ORD systems may utilize radial non-overlapping beam geometry and a computed tomography (CT) algorithm to map the concentrations in a plane. In...

  6. RADIAL COMPUTED TOMOGRAPHY OF AIR CONTAMINANTS USING OPTICAL REMOTE SENSING

    EPA Science Inventory

    The paper describes the application of an optical remote-sensing (ORS) system to map air contaminants and locate fugitive emissions. Many ORD systems may utilize radial non-overlapping beam geometry and a computed tomography (CT) algorithm to map the concentrations in a plane. In...

  7. Imaging techniques with refractive beam shaping optics

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim

    2012-10-01

    Applying of the refractive beam shapers in real research optical setups as well as in industrial installations requires very often manipulation of a final laser spot size. In many cases this task can be easily solved by using various imaging optical layouts presuming creating an image of a beam shaper output aperture. Due to the unique features of the refractive beam shapers of field mapping type, like flat wave front and low divergence of the collimated resulting beam with flattop or another intensity profile, there is a freedom in building of various imaging systems with using ordinary optical components, including off-the-shelf ones. There will be considered optical layouts providing high, up to 1/200×, de-magnifying factors, combining of refractive beam shapers like πShaper with scanning systems, building of relay imaging systems with extended depth of field. These optical layouts are widely used in such laser technologies like drilling holes in PCB, welding, various micromachining techniques with galvo-mirror scanning, interferometry and holography, various SLM-based applications. Examples of real implementations and experimental results will be presented as well.

  8. Photoinduced electron transfer based ion sensing within an optical fiber.

    PubMed

    Englich, Florian V; Foo, Tze Cheung; Richardson, Andrew C; Ebendorff-Heidepriem, Heike; Sumby, Christopher J; Monro, Tanya M

    2011-01-01

    We combine suspended-core microstructured optical fibers with the photoinduced electron transfer (PET) effect to demonstrate a new type of fluorescent optical fiber-dip sensing platform for small volume ion detection. A sensor design based on a simple model PET-fluoroionophore system and small core microstructured optical fiber capable of detecting sodium ions is demonstrated. The performance of the dip sensor operating in a high sodium concentration regime (925 ppm Na(+)) and for lower sodium concentration environments (18.4 ppm Na(+)) is explored and future approaches to improving the sensor's signal stability, sensitivity and selectivity are discussed.

  9. Spider silk: a novel optical fibre for biochemical sensing

    NASA Astrophysics Data System (ADS)

    Hey Tow, Kenny; Chow, Desmond M.; Vollrath, Fritz; Dicaire, Isabelle; Gheysens, Tom; Thévenaz, Luc

    2015-09-01

    Whilst being thoroughly used in the textile industry and biomedical sector, silk has not yet been exploited for fibre optics-based sensing although silk fibres directly obtained from spiders can guide light and have shown early promises to being sensitive to some solvents. In this communication, a pioneering optical fibre sensor based on spider silk is reported, demonstrating for the first time the use of spider silk as an optical fibre sensor to detect polar solvents such as water, ammonia and acetic acid.

  10. Plastic optical fiber fuse and its impact on sensing applications

    NASA Astrophysics Data System (ADS)

    Mizuno, Yosuke; Lee, Heeyoung; Hayashi, Neisei; Nakamura, Kentaro; Todoroki, Shin-ichi

    2017-04-01

    We review the unique properties of a so-called optical fiber fuse phenomenon in plastic optical fibers (POFs), including its slow propagation velocity (1-2 orders of magnitude slower than that in silica fibers) and threshold power density (1/180 of the value for silica fibers). We also show that an oscillatory continuous curve instead of periodic voids is formed after the passage of the fuse, and that the bright spot is not a plasma but an optical discharge, the temperature of which is 3600 K. We then discuss its impact on distributed Brillouin sensing based on POFs.

  11. Multiparameter fiber optic sensing system for monitoring enhanced geothermal systems

    SciTech Connect

    Challener, William A

    2014-12-04

    The goal of this project was to design, fabricate and test an optical fiber cable which supports multiple sensing modalities for measurements in the harsh environment of enhanced geothermal systems. To accomplish this task, optical fiber was tested at both high temperatures and strains for mechanical integrity, and in the presence of hydrogen for resistance to darkening. Both single mode (SM) and multimode (MM) commercially available optical fiber were identified and selected for the cable based on the results of these tests. The cable was designed and fabricated using a tube-within-tube construction containing two MM fibers and one SM fiber, and without supporting gel that is not suitable for high temperature environments. Commercial fiber optic sensing instruments using Raman DTS (distributed temperature sensing), Brillouin DTSS (distributed temperature and strain sensing), and Raleigh COTDR (coherent optical time domain reflectometry) were selected for field testing. A microelectromechanical systems (MEMS) pressure sensor was designed, fabricated, packaged, and calibrated for high pressure measurements at high temperatures and spliced to the cable. A fiber Bragg grating (FBG) temperature sensor was also spliced to the cable. A geothermal well was selected and its temperature and pressure were logged. The cable was then deployed in the well in two separate field tests and measurements were made on these different sensing modalities. Raman DTS measurements were found to be accurate to ±5°C, even with some residual hydrogen darkening. Brillouin DTSS measurements were in good agreement with the Raman results. The Rayleigh COTDR instrument was able to detect some acoustic signatures, but was generally disappointing. The FBG sensor was used to determine the effects of hydrogen darkening, but drift over time made it unreliable as a temperature or pressure sensor. The MEMS sensor was found to be highly stable and accurate to better than its 0.1% calibration.

  12. Interferometric nanoporous anodic alumina photonic coatings for optical sensing.

    PubMed

    Chen, Yuting; Santos, Abel; Wang, Ye; Kumeria, Tushar; Wang, Changhai; Li, Junsheng; Losic, Dusan

    2015-05-07

    Herein, we present a systematic study on the development, optical optimization and sensing applicability of colored photonic coatings based on nanoporous anodic alumina films grown on aluminum substrates. These optical nanostructures, so-called distributed Bragg reflectors (NAA-DBRs), are fabricated by galvanostatic pulse anodization process, in which the current density is altered in a periodic manner in order to engineer the effective medium of the resulting photonic coatings. As-prepared NAA-DBR photonic coatings present brilliant interference colors on the surface of aluminum, which can be tuned at will within the UV-visible spectrum by means of the anodization profile. A broad library of NAA-DBR colors is produced by means of different anodization profiles. Then, the effective medium of these NAA-DBR photonic coatings is systematically assessed in terms of optical sensitivity, low limit of detection and linearity by reflectometric interference spectroscopy (RIfS) in order to optimize their nanoporous structure toward optical sensors with enhanced sensing performance. Finally, we demonstrate the applicability of these photonic nanostructures as optical platforms by selectively detecting gold(iii) ions in aqueous solutions. The obtained results reveal that optimized NAA-DBR photonic coatings can achieve an outstanding sensing performance for gold(iii) ions, with a sensitivity of 22.16 nm μM(-1), a low limit of detection of 0.156 μM (i.e. 30.7 ppb) and excellent linearity within the working range (0.9983).

  13. Detection of southern corn leaf blight by remote sensing techniques.

    NASA Technical Reports Server (NTRS)

    Bauer, M. E.; Swain, P. H.; Mroczynski, R. P.; Anuta, P. E.; Macdonald, R. B.

    1971-01-01

    Multispectral photographic and scanner data were collected over western Indiana in August and September 1970, to determine the detectability of southern corn leaf blight by remote sensing. Measurements were made at altitudes of 3000 to 7000 ft. Color, color IR, and multiband black and white photography were collected at altitudes from 3000 to 60,000 ft. Six levels of infection based on the amount of leaf damage were identified in the fields. Three levels of infection were detected with color IR photography by standard photo-interpretive techniques. Up to five levels of infection were distinguished by applying automatic pattern recognition techniques to the multispectral scanner data. The results illustrate the potential of remote sensing techniques in the detection of crop diseases.

  14. Shift happens: optical sensing with Dyakonov-Tamm waves

    NASA Astrophysics Data System (ADS)

    Lakhtakia, Akhlesh; Faryad, Muhammad

    2014-08-01

    An optical modality to sense a fluid by exploiting Dyakonov-Tamm (DT) waves was devised. In the modality, the fluid is present on both sides of the guiding interface. Theory showed that the angular location of reflectance dip in a practically implementable configuration will shift if the refractive index of the fluid changes. Furthermore, the detection sensitivity will decrease as the refractive index of the fluid increases over a wide range, and should be comparable to that for sensing modalities that exploit surface-plasmon-polariton (SPP) waves. Higher sensitivities are available with DT waves than with SPP waves, and the DT-wave-based sensor should be simpler to fabricate than the SPP-wave-based sensor. Multiple DT waves are excitable at the same frequency, leading to multiple channels for more reliable sensing as well as for sensing multiple analytes simultaneously.

  15. Theory of optical sensing with Dyakonov-Tamm waves

    NASA Astrophysics Data System (ADS)

    Lakhtakia, Akhlesh; Faryad, Muhammad

    2014-01-01

    An optical modality to sense a fluid by exploiting Dyakonov-Tamm (DT) waves was devised. In the modality, the fluid is present on both sides of the guiding interface. Theoretical analysis indicated that the angular location of the reflectance dip in a practically implementable configuration will shift if the refractive index of the fluid changes. Furthermore, the detection sensitivity will decrease as the refractive index of the fluid increases over a wide range, and should be comparable to that for sensing modalities that exploit surface-plasmon-polariton (SPP) waves. Higher sensitivities are available with DT waves than with SPP waves, and the DT-wave-based sensor should be simpler to fabricate than the SPP-wave-based sensor. Multiple DT waves are excitable at the same frequency, leading to multiple channels for more reliable sensing as well as for sensing multiple analytes simultaneously.

  16. Optical remote sensing for forest area estimation

    Treesearch

    Randolph H. Wynne; Richard G. Oderwald; Gregory A. Reams; John A. Scrivani

    2000-01-01

    The air photo dot-count method is now widely and successfully used for estimating operational forest area in the USDA Forest Inventory and Analysis (FIA) program. Possible alternatives that would provide for more frequent updates, spectral change detection, and maps of forest area include the AVHRR calibration center technique and various Landsat TM classification...

  17. Novel technique for distributed fibre sensing based on coherent Rayleigh scattering measurements of birefringence

    NASA Astrophysics Data System (ADS)

    Lu, Xin; Soto, Marcelo A.; Thévenaz, Luc

    2016-05-01

    A novel distributed fibre sensing technique is described and experimentally validated, based on birefringence measurements using coherent Rayleigh scattering. It natively provides distributed measurements of temperature and strain with more than an order of magnitude higher sensitivity than Brillouin sensing, and requiring access to a single fibre-end. Unlike the traditional Rayleigh-based coherent optical time-domain reflectometry, this new method provides absolute measurements of the measurand and may lead to a robust discrimination between temperature and strain in combination with another technique. Since birefringence is purposely induced in the fibre by design, large degrees of freedom are offered to optimize and scale the sensitivity to a given quantity. The technique has been validated in 2 radically different types of birefringent fibres - elliptical-core and Panda polarization-maintaining fibres - with a good repeatability.

  18. Grazing Incidence Wavefront Sensing and Verification of X-Ray Optics Performance

    NASA Technical Reports Server (NTRS)

    Saha, Timo T.; Rohrbach, Scott; Zhang, William W.

    2011-01-01

    Evaluation of interferometrically measured mirror metrology data and characterization of a telescope wavefront can be powerful tools in understanding of image characteristics of an x-ray optical system. In the development of soft x-ray telescope for the International X-Ray Observatory (IXO), we have developed new approaches to support the telescope development process. Interferometrically measuring the optical components over all relevant spatial frequencies can be used to evaluate and predict the performance of an x-ray telescope. Typically, the mirrors are measured using a mount that minimizes the mount and gravity induced errors. In the assembly and mounting process the shape of the mirror segments can dramatically change. We have developed wavefront sensing techniques suitable for the x-ray optical components to aid us in the characterization and evaluation of these changes. Hartmann sensing of a telescope and its components is a simple method that can be used to evaluate low order mirror surface errors and alignment errors. Phase retrieval techniques can also be used to assess and estimate the low order axial errors of the primary and secondary mirror segments. In this paper we describe the mathematical foundation of our Hartmann and phase retrieval sensing techniques. We show how these techniques can be used in the evaluation and performance prediction process of x-ray telescopes.

  19. Polishing techniques for MEGARA pupil elements optics

    NASA Astrophysics Data System (ADS)

    Izazaga, R.; Carrasco, E.; Aguirre, D.; Salas, A.; Gil de Paz, A.; Gallego, J.; Iglesias, J.; Arroyo, J. M.; Hernández, M.; López, N.; López, V.; Quechol, J. T.; Salazar, M. F.; Carballo, C.; Cruz, E.; Arriaga, J.; De la Luz, J. A.; Huepa, A.; Jaimes, G. L.; Reyes, J.

    2016-07-01

    MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is the new integral-field and multi-object optical spectrograph for the 10.4m Gran Telescopio Canarias.. It will offer RFWHM 6,000, 12,000 and 18,700 for the low- , mid- and high-resolution, respectively in the wavelength range 3650-9700Å. .The dispersive elements are volume phase holographic (VPH) gratings, sandwiched between two flat Fused Silica windows of high optical precision in large apertures. The design, based in VPHs in combination with Ohara PBM2Y prisms allows to keep the collimator and camera angle fixed. Seventy three optical elements are being built in Mexico at INAOE and CIO. For the low resolution modes, the VPHs windows specifications in irregularity is 1 fringe in 210mm x 170mm and 0.5 fringe in 190mm x 160mm. for a window thickness of 25 mm. For the medium and high resolution modes the irregularity specification is 2 fringes in 220mm x 180mm and 1 fringe in 205mm x 160mm, for a window thickness of 20mm. In this work we present a description of the polishing techniques developed at INAOE optical workshop to fabricate the 36 Fused Silica windows and 24 PBM2Y prisms that allows us to achieve such demanding specifications. We include the processes of mounting, cutting, blocking, polishing and testing.

  20. Terrain-aided localization using electro-optical sensing (TALEOS)

    NASA Astrophysics Data System (ADS)

    Collins, Peter R. C.; Stephens, Arthur S.; Greenway, Phil; Deaves, Rob H.; Priestley, M. D. J.; Bullen, Mark

    1997-06-01

    The next generation of weapons systems will benefit from an array of new technologies which, when integrated, will provide the capability of accurately selecting the correct target. For example, target image features can be extracted from high resolution satellite data and this information can be fused with feature positions obtained from a weapon's imaging sensor. This will allow automatic target recognition to be performed. Terrain aided localization using electro-optical sensing (TALEOS) is a robust method of enhancing the performance of an imaging system through the exploitation of other sources of information. The primary image processing technique used in TALEOS is model-matching. The objective of model-matching is to discover the 3D position and orientation of an object (the model) with respect to the sensor reference frame by performing a match with corresponding features. In TALEOS, the model is derived from remotely sensed data and contains information about potentially observable features which might be extracted from the image. Embedded in this extended model is information about specific targets, including their known or estimated position, and features which characterize them. The Sowerby Research Center terrain model facility was used to gather realistic imagery. The terrain model is a 300:1 scale model of a 25 square kilometer area of real terrain. An overhead gantry system carries a video camera over the model enabling a wide variety of flight scenarios to be simulated experimentally. By a combination of special paint schemes and video inversion, pictures of the terrain model can provide a realistic simulation of infrared imagery. An image database was simulated using an overhead view of the model as if seen from a 'satellite' or reconnaissance aircraft. This imagery was utilized to evaluate the performance of the TALEOS technique for comparison with theoretical results. TALEOS integrates the data from the image processing subsystem with data from

  1. Chemical and Biological Sensing with a Fiber Optic Surface Plasmon Resonance Device

    NASA Astrophysics Data System (ADS)

    Shevchenko, Yanina

    Fiber biosensors have emerged as an alternative to other optical sensor platforms which utilize bulkier optical elements. Sensors manufactured using optical fiber offer considerable advantages over traditional platforms, such as simple manufacturing process, small size and possibility for in situ and remote measurements. The possibility to manufacture a compact sensor with very few optical elements and package it into a portable hand-held device makes it particularly useful in many biomedical applications. Such applications generate a growing demand for an improved understanding of how fiber sensors function as well as for sensor optimization techniques so later these devices can suit the needs of the applications they are developed for. Research presented in this thesis is focused on a development of a plasmonic fiber biosensor and its application towards biochemical sensing. The fiber sensor used in this study integrates plasmonics with tilted Bragg grating technology, creating a versatile sensing solution. Plasmonics alone is an established phenomenon that is widely employed in many sensing applications. The Bragg grating is also a well-researched optical component that has been extensively applied in telecommunication. By combining both plasmonics and Bragg gratings, it is possible to design a compact and very sensitive chemical sensor. The presented work focuses on the characterization and optimization of the fiber sensor so later it could be applied in biochemical sensing. It also explores several applications including real-time monitoring of polymer adsorption, detection of thrombin and cellular sensing. All applications are focused on studying processes that are very different in their nature and thus the various strengths of the developed sensing platform were leveraged to suit the requirements of these applications.

  2. Highly Sensitive and Wide-Dynamic-Range Multichannel Optical-Fiber pH Sensor Based on PWM Technique.

    PubMed

    Khan, Md Rajibur Rahaman; Kang, Shin-Won

    2016-11-09

    In this study, we propose a highly sensitive multichannel pH sensor that is based on an optical-fiber pulse width modulation (PWM) technique. According to the optical-fiber PWM method, the received sensing signal's pulse width changes when the optical-fiber pH sensing-element of the array comes into contact with pH buffer solutions. The proposed optical-fiber PWM pH-sensing system offers a linear sensing response over a wide range of pH values from 2 to 12, with a high pH-sensing ability. The sensitivity of the proposed pH sensor is 0.46 µs/pH, and the correlation coefficient R² is approximately 0.997. Additional advantages of the proposed optical-fiber PWM pH sensor include a short/fast response-time of about 8 s, good reproducibility properties with a relative standard deviation (RSD) of about 0.019, easy fabrication, low cost, small size, reusability of the optical-fiber sensing-element, and the capability of remote sensing. Finally, the performance of the proposed PWM pH sensor was compared with that of potentiometric, optical-fiber modal interferometer, and optical-fiber Fabry-Perot interferometer pH sensors with respect to dynamic range width, linearity as well as response and recovery times. We observed that the proposed sensing systems have better sensing abilities than the above-mentioned pH sensors.

  3. Distributed Humidity Sensing in PMMA Optical Fibers at 500 nm and 650 nm Wavelengths.

    PubMed

    Liehr, Sascha; Breithaupt, Mathias; Krebber, Katerina

    2017-03-31

    Distributed measurement of humidity is a sought-after capability for various fields of application, especially in the civil engineering and structural health monitoring sectors. This article presents a method for distributed humidity sensing along polymethyl methacrylate (PMMA) polymer optical fibers (POFs) by analyzing wavelength-dependent Rayleigh backscattering and attenuation characteristics at 500 nm and 650 nm wavelengths. Spatially resolved humidity sensing is obtained from backscatter traces of a dual-wavelength optical time domain reflectometer (OTDR). Backscatter dependence, attenuation dependence as well as the fiber length change are characterized as functions of relative humidity. Cross-sensitivity effects are discussed and quantified. The evaluation of the humidity-dependent backscatter effects at the two wavelength measurements allows for distributed and unambiguous measurement of relative humidity. The technique can be readily employed with low-cost standard polymer optical fibers and commercial OTDR devices.

  4. Chip-scale hybrid optical sensing systems using digital signal processing.

    PubMed

    Cho, Sang-Yeon; Borah, Deva K

    2009-01-05

    We propose a novel hybrid optical sensing system for standalone, chip-scale sensing applications. The hybrid optical sensing system detects any spectral shift of the microresonator sensor output by estimating the effective refractive index using maximum likelihood estimation. The performance evaluation of the proposed hybrid sensing system in the Gaussian-noise dominant environment shows excellent estimation accuracy. This innovative approach allows fully functional integrated hybrid sensing systems, offering great potential in various chip-scale sensing applications.

  5. Pattern Recognition in Optical Remote Sensing Data Processing

    NASA Astrophysics Data System (ADS)

    Kozoderov, Vladimir; Kondranin, Timofei; Dmitriev, Egor; Kamentsev, Vladimir

    Computational procedures of the land surface biophysical parameters retrieval imply that modeling techniques are available of the outgoing radiation description together with monitoring techniques of remote sensing data processing using registered radiances between the related optical sensors and the land surface objects called “patterns”. Pattern recognition techniques are a valuable approach to the processing of remote sensing data for images of the land surface - atmosphere system. Many simplified codes of the direct and inverse problems of atmospheric optics are considered applicable for the imagery processing of low and middle spatial resolution. Unless the authors are not interested in the accuracy of the final information products, they utilize these standard procedures. The emerging necessity of processing data of high spectral and spatial resolution given by imaging spectrometers puts forward the newly defined pattern recognition techniques. The proposed tools of using different types of classifiers combined with the parameter retrieval procedures for the forested environment are maintained to have much wider applications as compared with the image features and object shapes extraction, which relates to photometry and geometry in pixel-level reflectance representation of the forested land cover. The pixel fraction and reflectance of “end-members” (sunlit forest canopy, sunlit background and shaded background for a particular view and solar illumination angle) are only a part in the listed techniques. It is assumed that each pixel views collections of the individual forest trees and the pixel-level reflectance can thus be computed as a linear mixture of sunlit tree tops, sunlit background (or understory) and shadows. Instead of these photometry and geometry constraints, the improved models are developed of the functional description of outgoing spectral radiation, in which such parameters of the forest canopy like the vegetation biomass density for

  6. Development of carbon fiber-based piezoresistive linear sensing technique

    NASA Astrophysics Data System (ADS)

    Yang, Caiqian; Wu, Zhishen; Huang, Huang

    2009-03-01

    In this paper, the development of carbon fiber-based piezoresistive linear sensing technique and its application in civil engineering structures is studied and summarized. The sensing mechanism is based on the electrical conductivity and piezoresistivity of different types of carbon fibers. Firstly, the influences of values of signal currents and temperature on the sensing properties are studied to decide the suitable sensing current. Then, the linear temperature and strain sensing feasibility of different types of carbon fibers is addressed and discussed. Finally, the application of this kind of sensors is studied in monitoring the health of reinforced concrete (RC) and prestressed concrete (PC) structures. A good linearity of fractional change in electrical resistance (ER) (ΔR/R0)-strain and &DeltaR/R0-temperature is demonstrated. The &DeltaR/R0-strain and &DeltaR/R0-temperature curves of CFRP/HCFRP sensors can be well fitted with a line with a correlation coefficient larger than 0.978. All these reveal that carbon fibers reinforced polymer (CFRP) can be used as both piezoresistive linear strain and temperature sensors.

  7. Electrophoretic deposition as a new approach to produce optical sensing films adaptable to microdevices

    NASA Astrophysics Data System (ADS)

    Marín-Suárez, Marta; Medina-Rodríguez, Santiago; Ergeneman, Olgaç; Pané, Salvador; Fernández-Sánchez, Jorge F.; Nelson, Bradley J.; Fernández-Gutiérrez, Alberto

    2013-12-01

    We report the fabrication of optical oxygen sensor films using electrophoretic deposition (EPD) of poly(styrene-co-maleic anhydride) nanoparticles containing the oxygen-sensitive dye platinum(ii) meso-tetra(pentafluorophenyl)porphine. Compared to other deposition methods, the EPD is simple and allows easy control over deposition, which is crucial for the implementation of optical sensing films in microdevices. By optimizing the synthesis of the functional nanoparticles, anodic EPD can be performed. The amount of deposited particles can be tuned by varying either the electrical potential or the deposition time. The sensing phases were characterized using a phase-modulation technique showing a Stern-Volmer constant (kSV1) between 45 and 52 bar-1 for gas and of 20.72 bar-1 in the aqueous phase without leaching of the particles from the surface. The small thickness of the layers lead to short response times (<0.4 s). This is the first time that polymeric optical sensing films have been obtained by EPD from dispersions of oxygen sensing nanoparticles.We report the fabrication of optical oxygen sensor films using electrophoretic deposition (EPD) of poly(styrene-co-maleic anhydride) nanoparticles containing the oxygen-sensitive dye platinum(ii) meso-tetra(pentafluorophenyl)porphine. Compared to other deposition methods, the EPD is simple and allows easy control over deposition, which is crucial for the implementation of optical sensing films in microdevices. By optimizing the synthesis of the functional nanoparticles, anodic EPD can be performed. The amount of deposited particles can be tuned by varying either the electrical potential or the deposition time. The sensing phases were characterized using a phase-modulation technique showing a Stern-Volmer constant (kSV1) between 45 and 52 bar-1 for gas and of 20.72 bar-1 in the aqueous phase without leaching of the particles from the surface. The small thickness of the layers lead to short response times (<0.4 s). This is

  8. Molecular biology techniques and applications for ocean sensing

    NASA Astrophysics Data System (ADS)

    Zehr, J. P.; Hewson, I.; Moisander, P.

    2009-05-01

    The study of marine microorganisms using molecular biological techniques is now widespread in the ocean sciences. These techniques target nucleic acids which record the evolutionary history of microbes, and encode for processes which are active in the ocean today. Molecular techniques can form the basis of remote instrumentation sensing technologies for marine microbial diversity and ecological function. Here we review some of the most commonly used molecular biological techniques. These techniques include the polymerase chain reaction (PCR) and reverse-transcriptase PCR, quantitative PCR, whole assemblage "fingerprinting" approaches (based on nucleic acid sequence or length heterogeneity), oligonucleotide microarrays, and high-throughput shotgun sequencing of whole genomes and gene transcripts, which can be used to answer biological, ecological, evolutionary and biogeochemical questions in the ocean sciences. Moreover, molecular biological approaches may be deployed on ocean sensor platforms and hold promise for tracking of organisms or processes of interest in near-real time.

  9. Optical techniques for measurement of high temperatures

    SciTech Connect

    Veligdan, J.T.

    1991-10-25

    The availability of instrumentation to measure the high outlet gas temperature of a particle bed reactor is a topic of some concern. There are a number of possible techniques with advantages and disadvantages. In order to provide some baseline choice of instrumentation, a review has been conducted of these various technologies. This report summarizes the results of this review for a group of technologies loosely defined as optical techniques (excluding optical pyrometry). The review has concentrated on a number of questions for each technology investigated. These are: (1) Description of the technology, (2) Anticipated sensitivity and accuracy, (3) Requirements for implementation, (4) Necessary development time and costs, (5) Advantages and disadvantages of the technology. Each of these areas was considered for a technology and a large number of technologies were considered in a review of the literature. Based upon this review it was found that a large number of methods exist to measure temperatures in excess of 2000 K. None of the methods found were ideal. Four methods, however, appeared to warrant further consideration: opto-mechanical expansion thermometry, surface Raman spectroscopy, gas-phase Raman spectroscopy and coherent anti-Stokes Raman spectroscopy (CARS). These techniques will be discussed further in this document.

  10. Optical remote sensing of aircraft emissions with the K300

    SciTech Connect

    Bittner, H.; Klein, V.; Eisenmann, T.; Engler, F.; Resch, M.; Mosebach, H.; Erhard, M.; Rippel, H. )

    1993-01-01

    The K300 Double Pendulum Interferometer is a compact high resolution Fourier Transform spectrometer designed for outdoor optical remote sensing in the infrared spectral region. Apart from the known atmospheric pollution monitoring by long-path measurements and smoke stack remote sensing at power plants, the remote diagnostic of hot aircraft engine emissions is a very interesting application of the infrared spectroscopy. First results of such measurements performed with the Kayser-Threde Double Pendulum Interferometer K300 at the DLR airport, Oberpfaffenhofen on January 15, 1992 are presented and discussed.

  11. Pressure sensing with optical fiber-tip air bubbles

    NASA Astrophysics Data System (ADS)

    Yu, Wenbing; Fu, Cailing; Wang, D. N.; Wang, Ying

    2013-09-01

    Optical fiber-tip air bubbles are demonstrated for pressure sensing with ultrahigh sensitivity. The air bubble locates in the end facet of a single mode fiber (SMF) that spliced with a silica tube, which is naturally formed and acts as a compressible Fabry-Pérot interferometer (FPI) cavity when immersing the silica tube into liquid. The proposed device exhibits pressure sensitivity of <1000 nm/kPa. This kind of compressible FPI cavity may find potential applications in highly sensitive pressure and/or acoustic sensing.

  12. High-speed optical 3D sensing and its applications

    NASA Astrophysics Data System (ADS)

    Watanabe, Yoshihiro

    2016-12-01

    This paper reviews high-speed optical 3D sensing technologies for obtaining the 3D shape of a target using a camera. The focusing speed is from 100 to 1000 fps, exceeding normal camera frame rates, which are typically 30 fps. In particular, contactless, active, and real-time systems are introduced. Also, three example applications of this type of sensing technology are introduced, including surface reconstruction from time-sequential depth images, high-speed 3D user interaction, and high-speed digital archiving.

  13. Optical remote sensing of aircraft emissions with the K300

    NASA Astrophysics Data System (ADS)

    Bittner, H.; Klein, V.; Eisenmann, T.; Engler, F.; Resch, M.; Mosebach, H.; Erhard, M.; Rippel, H.

    1993-01-01

    The K300 Double Pendulum Interferometer is a compact high resolution Fourier Transform spectrometer designed for outdoor optical remote sensing in the infrared spectral region. Apart from the known atmospheric pollution monitoring by long-path measurements and smoke stack remote sensing at power plants, the remote diagnostic of hot aircraft engine emissions is a very interesting application of the infrared spectroscopy. First results of such measurements performed with the Kayser-Threde Double Pendulum Interferometer K300 at the DLR airport, Oberpfaffenhofen on January 15, 1992 are presented and discussed.

  14. Diffuse optical tomography based on time-resolved compressive sensing

    NASA Astrophysics Data System (ADS)

    Farina, A.; Betcke, M.; Di Sieno, L.; Bassi, A.; Ducros, N.; Pifferi, A.; Valentini, G.; Arridge, S.; D'Andrea, C.

    2017-02-01

    Diffuse Optical Tomography (DOT) can be described as a highly multidimensional problem generating a huge data set with long acquisition/computational times. Biological tissue behaves as a low pass filter in the spatial frequency domain, hence compressive sensing approaches, based on both patterned illumination and detection, are useful to reduce the data set while preserving the information content. In this work, a multiple-view time-domain compressed sensing DOT system is presented and experimentally validated on non-planar tissue-mimicking phantoms containing absorbing inclusions.

  15. An optical fiber sensor for remote pH sensing and imaging.

    PubMed

    Wang, Jian; Wang, Lili

    2012-03-01

    A fiber-optical probe for pH sensing and real-time imaging is successfully fabricated by connecting a polymer imaging fiber and a gradient index (GRIN) lens rod which was modified with a sensing film. By employing an improved metallographic microscope, an optical system is designed to cooperate with the probe. This novel technique has high-quality imaging capabilities for observing remote samples while measuring pH. The linear range of the probe is pH 1.2-3.5. This technique overcomes the difficulty that high-quality images cannot be obtained when directly using conventional imaging bundles for pH sensing and imaging. As preliminary applications, the corrosion behavior of an iron screw and the reaction process of rust were investigated in buffer solutions of pH 2.0 and 2.9, respectively. The experiment demonstrated that the pH values of the analytes' surface were higher than that of buffer solutions due to the chemical reaction. It provides great potential for applications in optical multifunctional detection, especially in chemical sensing and biosensing.

  16. Optical multichannel analyzer techniques for high resolution optical spectroscopy

    SciTech Connect

    Chao, J.L.

    1980-06-01

    The development of optical multichannel analyzer techniques for UV/VIS spectroscopy is presented. The research focuses on the development of spectroscopic techniques for measuring high resolution spectral lineshape functions from the exciton phosphorescence in H/sub 2/-1,2,4,5-tetrachlorobenzene. It is found that the temperature dependent frequency shifts and widths confirm a theoretical model based on an exchange theory. The exchange of low energy phonon modes which couple with excited state exciton transitions is shown to display the proper temperature dependent behavior. In addition to the techniques for using the optical multichannel analyzer (OMA) to perform low light level target integration, the use of the OMA for capturing spectral information in transient pulsed laser applications is discussed. An OMP data acquisition system developed for real-time signal processng is described. Both hardware and software interfacing considerations for control and data acquisition by a microcomputer are described. The OMA detector is described in terms of the principles behind its photoelectron detection capabilities and its design is compared with other optoelectronic devices.

  17. Computational ghost imaging: advanced compressive sensing (CS) technique

    NASA Astrophysics Data System (ADS)

    Katkovnik, Vladimir; Astola, Jaakko

    2012-10-01

    A novel efficient variational technique for speckle imaging is discussed. It is developed with the main motivation to filter noise, to wipe out the typical diffraction artifacts and to achieve crisp imaging. A sparse modeling is used for the wave field at the object plane in order to overcome the loss of information due to the ill-posedness of forward propagation image formation operators. This flexible and data adaptive modeling relies on the recent progress in sparse imaging and compressive sensing (CS). Being in line with the general formalism of CS, we develop an original approach to wave field reconstruction.7 In this paper we demonstrate this technique in its application for computational amplitude ghost imaging (GI), where a spatial light modulator (SLM) is used in order to generate a speckle wave field sensing a transmitted mask object.

  18. Adaptive remote sensing techniques implementing swarms of mobile agents

    NASA Astrophysics Data System (ADS)

    Cameron, Stewart M.; Loubriel, Guillermo M.; Robinett, Rush D., III; Stantz, Keith M.; Trahan, Michael W.; Wagner, John S.

    1999-07-01

    Measurement and signal intelligence of the battlespace has created new requirements in information management, communication and interoperability as they effect surveillance and situational awareness. In many situations, stand-off remote-sensing and hazard-interdiction techniques over realistic operational areas are often impractical and difficult to characterize. An alternative approach is to implement adaptive remote-sensing techniques with swarms of mobile agents employing collective behavior for optimization of mapping signatures and positional orientation (registration). We have expanded intelligent control theory using physics-based collective behavior models and genetic algorithms to produce a uniquely powerful implementation of distributed ground-based measurement incorporating both local collective behavior, and niter-operative global optimization for sensor fusion and mission oversight. By using a layered hierarchical control architecture to orchestrate adaptive reconfiguration of semi-autonomous robotic agents, we can improve overall robustness and functionality in dynamic tactical environments without information bottlenecking.

  19. Optical fiber meta-tips: perspectives in sensing applications

    NASA Astrophysics Data System (ADS)

    Principe, Maria; Consales, Marco; Micco, Alberto; Crescitelli, Alessio; Castaldi, Giuseppe; Esposito, Emanuela; La Ferrara, Vera; Cutolo, Antonello; Galdi, Vincenzo; Cusano, Andrea

    2017-04-01

    In this work we review the concept of optical fiber meta-tips, recently introduced by the authors. Optical fiber meta-tips come from the integration of plasmonic optical metasurfaces and the fiber optics technology. In particular, this integration is a major breakthrough in the recently emerged "Lab-On-Fiber" technology, where nanostructured platforms with special capabilities of light manipulation are integrated onto the tip of an optical fiber. Optical fiber meta-tips can, on one side, boost the real world applicability of optical metasurfaces, and, on the other side, bring about more advanced capabilities of on-fiber control and manipulation of light wavefront and polarization. With a view towards possible practical applications to label-free chemical and biological sensing, we inspect the potentialities of optical fiber meta-tips to work as sensors of local refractive index variations, and aim at studying the effect that the phase gradient impressed by the metasurface has on the surface sensitivity of proposed devices.

  20. Nanoimprinting on optical fiber end faces for chemical sensing

    NASA Astrophysics Data System (ADS)

    Kostovski, G.; White, D. J.; Mitchell, A.; Austin, M. W.; Stoddart, P. R.

    2008-04-01

    Optical fiber surface-enhanced Raman scattering (SERS) sensors offer a potential solution to monitoring low chemical concentrations in-situ or in remote sensing scenarios. We demonstrate the use of nanoimprint lithography to fabricate SERS-compatible nanoarrays on the end faces of standard silica optical fibers. The antireflective nanostructure found on cicada wings was used as a convenient template for the nanoarray, as high sensitivity SERS substrates have previously been demonstrated on these surfaces. Coating the high fidelity replicas with silver creates a dense array of regular nanoscale plasmonic resonators. A monolayer of thiophenol was used as a low concentration analyte, from which strong Raman spectra were collected using both direct endface illumination and through-fiber interrogation. This unique combination of nanoscale replication with optical fibers demonstrates a high-resolution, low-cost approach to fabricating high-performance optical fiber chemical sensors.

  1. LSPR based fiber optic sensor for fluoride impurity sensing in potable water

    NASA Astrophysics Data System (ADS)

    Tambe, Abhay; Kumbhaj, S.; Lalla, N. P.; Sen, P.

    2016-10-01

    We have designed localised surface plasmon resonance (LSPR) based fiber optic sensor. Silver nanoparticles are deposited on a few centimetre length of bare core at the middle part of plastic clad silica fiber by means of a simple and low cost laser induced nanoparticle deposition technique. The nanoparticle deposition was confirmed by TEM analysis. The nanoparticle coated fiber is used to design the sensor and the response of sensor was studied to sense fluoride impurity in water.

  2. Remote sensing techniques in cultural resource management archaeology

    NASA Astrophysics Data System (ADS)

    Johnson, Jay K.; Haley, Bryan S.

    2003-04-01

    Cultural resource management archaeology in the United States concerns compliance with legislation set in place to protect archaeological resources from the impact of modern activities. Traditionally, surface collection, shovel testing, test excavation, and mechanical stripping are used in these projects. These methods are expensive, time consuming, and may poorly represent the features within archaeological sites. The use of remote sensing techniques in cultural resource management archaeology may provide an answer to these problems. Near-surface geophysical techniques, including magnetometry, resistivity, electromagnetics, and ground penetrating radar, have proven to be particularly successful at efficiently locating archaeological features. Research has also indicated airborne and satellite remote sensing may hold some promise in the future for large-scale archaeological survey, although this is difficult in many areas of the world where ground cover reflect archaeological features in an indirect manner. A cost simulation of a hypothetical data recovery project on a large complex site in Mississippi is presented to illustrate the potential advantages of remote sensing in a cultural resource management setting. The results indicate these techniques can save a substantial amount of time and money for these projects.

  3. Optical Properties of Volcanic Ash: Improving Remote Sensing Observations

    NASA Astrophysics Data System (ADS)

    Whelley, P.; Colarco, P. R.; Aquila, V.; Krotkov, N. A.; Bleacher, J. E.; Garry, W. B.; Young, K. E.; Lima, A. R.; Martins, J. V.; Carn, S. A.

    2015-12-01

    Many times each year explosive volcanic eruptions loft ash into the atmosphere. Global travel and trade rely on aircraft vulnerable to encounters with airborne ash. Volcanic ash advisory centers (VAACs) rely on dispersion forecasts and satellite data to issue timely warnings. To improve ash forecasts model developers and satellite data providers need realistic information about volcanic ash microphysical and optical properties. In anticipation of future large eruptions we can study smaller events to improve our remote sensing and modeling skills so when the next Pinatubo 1991 or larger eruption occurs, ash can confidently be tracked in a quantitative way. At distances >100km from their sources, drifting ash plumes, often above meteorological clouds, are not easily detected from conventional remote sensing platforms, save deriving their quantitative characteristics, such as mass density. Quantitative interpretation of these observations depends on a priori knowledge of the spectral optical properties of the ash in UV (>0.3μm) and TIR wavelengths (>10μm). Incorrect assumptions about the optical properties result in large errors in inferred column mass loading and size distribution, which misguide operational ash forecasts. Similarly, simulating ash properties in global climate models also requires some knowledge of optical properties to improve aerosol speciation. Recent research has identified a wide range in volcanic ash optical properties among samples collected from the ground after different eruptions. The database of samples investigated remains relatively small, and measurements of optical properties at the relevant particle sizes and spectral channels are far from complete. Generalizing optical properties remains elusive, as does establishing relationships between ash composition and optical properties, which are essential for satellite retrievals. We are building a library of volcanic ash optical and microphysical properties. In this presentation we show

  4. Optical intersatellite link (OISL) for remote sensing satellites

    NASA Astrophysics Data System (ADS)

    Laxmiprasad, A. S.; Ranjith, R.; Raghubabu, P.; Kamalakar, J. A.

    2006-12-01

    Present day remote sensing satellites orbiting in low earth orbit (LEO) have increasingly sophisticated and high resolution onboard sensors. Their frequency and area of observation is also increasing. This generates large volume of data which needs to be communicated. However their visibility to ground station is limited. Free space optical communication between remote sensing satellite in LEO and communication satellite in geostationary earth orbit (GEO) can be favorable approach. Subsequently GEO satellite relays the data to ground station. To demonstrate this, a concept model operating at data rates greater than 1 Gbps is under development at LEOS. The system consisting of laser transmitter with 20cm diameter telescope and receiver with 30cm telescope is planned. It uses commercially available optical and optoelectronic components. This concept model will demonstrate and verify link margins available as against expected. Subsequent to this, it is planned to concentrate on design and other issues involved in acquisition, tracking and pointing (ATP) due to highly narrow laser beam.

  5. Space optical navigation techniques: an overview

    NASA Astrophysics Data System (ADS)

    Rebordão, J. M.

    2013-11-01

    Optical or vision-based navigation is an enabling technology for satellite autonomous navigation associated to different navigation approaches such as cruising, fly-by, terrain relative navigation, landing, rendezvous and docking between spacecrafts, rigidity of multi-satellite constellations. Since 2001, in many different ESA projects, the author and his team (at INETI and currently at FCUL) have been associated to most of the developments of the optical components of autonomous navigation, in cooperation with space primes or GNC subsystems suppliers. A unique experience related to seemingly simple photonic concepts associated to computational vision, photonic noises, camera tradeoffs and system concepts has emerged, and deserves a synthesis especially because some of these concepts are being implemented in the ESA Proba 3 mission and ESA is currently updating the technology in view of forthcoming planetary missions to Jupiter, Jupiter moons and asteroids. It is important to note that the US have already flown several missions relying on autonomous navigation and that NASA experience is at least one decade old. System approaches, sources of difficulty, some tradeoffs in both (and between) hardware and software, critical interface issues between the imaging and GNC (Guidance, Navigation and Control) subsystems, image processing techniques, utilization of apriori or to be estimated information, uncertainties, simulation of the imaging chain and non-cooperative environments will be addressed synthetically for both passive (optical) and active (lidar) systems.

  6. All-fiber bidirectional optical parametric oscillator for precision sensing.

    PubMed

    Gowda, R; Nguyen, N; Diels, J-C; Norwood, R A; Peyghambarian, N; Kieu, K

    2015-05-01

    We present the design and operation of an all-fiber, synchronously pumped, bidirectional optical parametric oscillator (OPO) for precision sensing applications. The fiber-based OPO (FOPO) generates two frequency combs with identical repetition rates but different carrier offset frequencies. A narrow beatnote was observed with full-width at half-maximum (FWHM) linewidth of <10  Hz when the two frequency combs were overlapped on a photodetector. The all-fiber design removes the need for free-space alignment and adjustment. In addition, an external delay line to overlap the two pulse trains in time on the detector is not needed since our unique design provides automatic delay compensation. We expect the novel FOPO to find important applications in precision measurements including rotation sensing with ultra-large sensing area and sensitivity.

  7. Modeling the optical coupling across the anterior chamber of the eye towards polarimetric glucose sensing

    NASA Astrophysics Data System (ADS)

    Pirnstill, Casey W.; Coté, Gerard L.

    2014-02-01

    Millions of people worldwide are affected by diabetes. While glucose sensing technology has come a long way over the past several decades, the current commercially available techniques are still invasive, often leading to poor patient compliance. To minimize invasiveness, focus has been placed on optical techniques to ascertain blood glucose concentrations. Optical polarimetry has shown promise and progress as a viable technique for glucose sensing. Recent developments in polarimetric glucose sensing have been focused on overcoming time varying corneal birefringence due to motion artifacts. Beyond corneal birefringence, the next hurdle toward making this approach viable is the ability to couple polarized light across the eye's anterior chamber. The eye is ideally suited to couple light to the retina. The index mismatch between the air and cornea is partially responsible for the beam bending toward the retina and, while good for vision, it complicates our ability to couple light across the anterior chamber without using an index matching device when performing polarimetric glucose monitoring. In this report, we have designed and modeled a non-index matched coupling scheme constructed with commercially available optics. The optical ray tracing model was performed using CODE V to verify the feasibility of a reflective based non-index matched coupling scheme with respect to index of refraction and anatomical restraints. The ray tracing model was developed for a dual-wavelength system and the effect of refraction and reflection at each optical interface within the setup was evaluated. The modeling results indicate a reflective based optical coupling design could be added to existing polarimetric glucose systems thus removing the need for placing an index matched eye-coupling mechanism over the eye prior to data collection.

  8. Adaptive interferometry for high sensitivity optical fiber sensing

    NASA Astrophysics Data System (ADS)

    Peigné, A.; Bortolozzo, U.; Residori, S.; Molin, S.; Dolfi, D.; Huignard, J.-P.

    2015-09-01

    We report on the use of an adaptive holographic interferometer, based on a liquid crystal light valve, to achieve phase shift measurements in an optical fiber. Owing to the physical mechanisms involved, the interferometer adapts itself to slow phase variations. As a consequence, it is possible to use a multimode fiber for sensing, which improves the sensitivity. Moreover, a distributed architecture relying on phase-OTDR principle is presented and a localization experiment is performed.

  9. Electronic implementation of optical burst switching techniques

    NASA Astrophysics Data System (ADS)

    Albanese, Ilijc; Darcie, Thomas E.; Ganti, Sudhakar

    2013-10-01

    Extensive research effort is ongoing in energy-efficient Internet-based communications. Optical Flow Switching (OFS) and Optical Burst Switching (OBS) offer potentially efficient alternatives to IP-router-based networks for large data transactions, but significant challenges remain. OFS requires each user to install expensive core network technology, limiting application to highly specialized nodes. OBS can achieve higher scalability but burst assembly/disassembly procedures reduce power efficiency. Finally both OFS and OBS use all-optical switching technologies for which energy efficiency and flexibility remain subject to debate. Our study aims at combining the advantages of both OBS and OFS while avoiding their shortcomings. We consider using a two-way resource reservation protocol for periodic concatenations of large (e.g. 1 Mb) packets or Media Frames (MFs). These chains of MFs (MFCs) are semi-transparent with a periodicity referred to as the "transparency degree". Each MFC is assembled and stored at an end-user machine during the resource reservation procedure and is then switched and buffered electronically along its path. The periodic configuration of each MFC enables interleaving of several chains using buffering only to align the MFs in each MFC in time, largely reducing the buffer requirements with respect to OBS. This periodicity also enables a simple scheduling algorithm to schedule large transactions with minimal control plane processing, achieving link utilization approaching 99.9%. In summary, results indicate that implementing optical burst switching techniques in the electronic domain is a compelling path forward to high-throughput power-efficient networking.

  10. A novel self-sensing technique for tapping-mode atomic force microscopy

    SciTech Connect

    Ruppert, Michael G.; Moheimani, S. O. Reza

    2013-12-15

    This work proposes a novel self-sensing tapping-mode atomic force microscopy operation utilizing charge measurement. A microcantilever coated with a single piezoelectric layer is simultaneously used for actuation and deflection sensing. The cantilever can be batch fabricated with existing micro electro mechanical system processes. The setup enables the omission of the optical beam deflection technique which is commonly used to measure the cantilever oscillation amplitude. Due to the high amount of capacitive feedthrough in the measured charge signal, a feedforward control technique is employed to increase the dynamic range from less than 1 dB to approximately 35 dB. Experiments show that the conditioned charge signal achieves excellent signal-to-noise ratio and can therefore be used as a feedback signal for atomic force microscopy imaging.

  11. Application of optical remote sensing in the Wenchuan earthquake assessment

    NASA Astrophysics Data System (ADS)

    Zhang, Bing; Lei, Liping; Zhang, Li; Liu, Liangyun; Zhu, Boqin; Zuo, Zhengli

    2009-06-01

    A mega-earthquake of magnitude 8 of Richter scale occurred in Wenchuan County, Sichuan Province, China on May 12, 2008. The earthquake inflicted heavy loss of human lives and properties. The Wenchuan earthquake induced geological disasters, house collapse, and road blockage. In this paper, we demonstrate an application of optical remote sensing images acquired from airborne and satellite platforms in assessing the earthquake damages. The high-resolution airborne images were acquired by the Chinese Academy of Sciences (CAS). The pre- and post-earthquake satellite images of QuickBird, IKONOS, Landsat TM, ALOS, and SPOT were collected by the Center for Earth Observation & Digital Earth (CEODE), CAS, and some of the satellite data were provided by the United States, Japan, and the European Space Agency. The pre- and post-earthquake remote sensing images integrated with DEM and GIS data were adopted to monitor and analyze various earthquake disasters, such as road blockage, house collapse, landslides, avalanches, rock debris flows, and barrier lakes. The results showed that airborne optical images provide a convenient tool for quick and timely monitoring and assessing of the distribution and dynamic changes of the disasters over the earthquake-struck regions. In addition, our study showed that the optical remote sensing data integrated with GIS data can be used to assess disaster conditions such as damaged farmlands, soil erosion, etc, which in turn provides useful information for the postdisaster reconstruction.

  12. Stochastic holey optical fibers for gas sensing applications

    NASA Astrophysics Data System (ADS)

    Pickrell, Gary; Scott, Brian; Ma, Cheng; Cooper, Kristie; Wang, Anbo

    2007-09-01

    Monitoring of gaseous species is important in a variety of applications including industrial process gas monitoring, mine safety, and homeland security. Fiber optic sensors have been used in a variety of forms to monitor various types of gaseous species. Optical fiber sensors utilizing both random hole and photonic crystal fibers have been investigated. One limitation to these types of fiber sensors is the fact that the holes run parallel to the optic axis of the fiber, requiring gases to diffuse over long distances. Diffusion of gases over long distances through tube sizes which are on the order of microns is a relatively slow process. This can significantly impact the response time of the sensors which are made from these types of fibers. This paper presents results on the development of optical fibers for gas sensing applications which have holes extending in the radial direction as opposed to the longitudinal direction (as in the case of photonic crystal fibers). The holes are made by a process which utilizes phase separation of the glass matrix at relatively low temperatures. The secondary phase is removed by subsequent leaching processes, leaving a three dimensionally porous structure. The porosity is arranged in a stochastic fashion within the fiber. Results of the fiber sensor development and testing will be presented. The microstructural analysis of the fibers by scanning electron microscopy as well as the optical characterization of the fibers will be presented. Fabrication procedures for the optical fibers and the optical fiber sensors will also be described.

  13. Interferometric nanoporous anodic alumina photonic coatings for optical sensing

    NASA Astrophysics Data System (ADS)

    Chen, Yuting; Santos, Abel; Wang, Ye; Kumeria, Tushar; Wang, Changhai; Li, Junsheng; Losic, Dusan

    2015-04-01

    Herein, we present a systematic study on the development, optical optimization and sensing applicability of colored photonic coatings based on nanoporous anodic alumina films grown on aluminum substrates. These optical nanostructures, so-called distributed Bragg reflectors (NAA-DBRs), are fabricated by galvanostatic pulse anodization process, in which the current density is altered in a periodic manner in order to engineer the effective medium of the resulting photonic coatings. As-prepared NAA-DBR photonic coatings present brilliant interference colors on the surface of aluminum, which can be tuned at will within the UV-visible spectrum by means of the anodization profile. A broad library of NAA-DBR colors is produced by means of different anodization profiles. Then, the effective medium of these NAA-DBR photonic coatings is systematically assessed in terms of optical sensitivity, low limit of detection and linearity by reflectometric interference spectroscopy (RIfS) in order to optimize their nanoporous structure toward optical sensors with enhanced sensing performance. Finally, we demonstrate the applicability of these photonic nanostructures as optical platforms by selectively detecting gold(iii) ions in aqueous solutions. The obtained results reveal that optimized NAA-DBR photonic coatings can achieve an outstanding sensing performance for gold(iii) ions, with a sensitivity of 22.16 nm μM-1, a low limit of detection of 0.156 μM (i.e. 30.7 ppb) and excellent linearity within the working range (0.9983).Herein, we present a systematic study on the development, optical optimization and sensing applicability of colored photonic coatings based on nanoporous anodic alumina films grown on aluminum substrates. These optical nanostructures, so-called distributed Bragg reflectors (NAA-DBRs), are fabricated by galvanostatic pulse anodization process, in which the current density is altered in a periodic manner in order to engineer the effective medium of the resulting

  14. A tactile sensing element based on a hetero-core optical fiber for force measurement and texture detection

    NASA Astrophysics Data System (ADS)

    Yamazaki, Hiroshi; Koyama, Yuya; Watanabe, Kazuhiro

    2014-05-01

    Tactile sensing technology can measure a given property of an object through physical contact between a sensing element and the object. Various tactile sensing techniques have been developed for several applications such as intelligent robots, tactile interface, medical support and nursing care support. A desirable tactile sensing element for supporting human daily life can be embedded in the soft material with high sensitivity and accuracy in order to prevent from damaging to human or object physically. This report describes a new tactile sensing element. Hetero-core optical fibers have high sensitivity of macro-bending at local sensor portion and temperature independency, including advantages of optical fiber itself; thin size, light weight, flexible transmission line, and immunity to electro-magnetic interference. The proposed tactile sensing element could detect textures of touched objects through the optical loss caused by the force applied to the sensing element. The characteristics of the sensing element have been evaluated, in which the sensing element has the monotonic and non-linear sensitivity against the normal force ranged from 0 to 5 N with lower accuracy than 0.25 dB. Additionally, texture detection have been successfully demonstrated in which small surface figures of 0.1 mm in height were detected with spatial resolution of 0.4 mm.

  15. Long-distance fiber optic sensing solutions for pipeline leakage, intrusion, and ground movement detection

    NASA Astrophysics Data System (ADS)

    Nikles, Marc

    2009-05-01

    An increasing number of pipelines are constructed in remote regions affected by harsh environmental conditions where pipeline routes often cross mountain areas which are characterized by unstable grounds and where soil texture changes between winter and summer increase the probability of hazards. Third party intentional interference or accidental intrusions are a major cause of pipeline failures leading to large leaks or even explosions. Due to the long distances to be monitored and the linear nature of pipelines, distributed fiber optic sensing techniques offer significant advantages and the capability to detect and localize pipeline disturbance with great precision. Furthermore pipeline owner/operators lay fiber optic cable parallel to transmission pipelines for telecommunication purposes and at minimum additional cost monitoring capabilities can be added to the communication system. The Brillouin-based Omnisens DITEST monitoring system has been used in several long distance pipeline projects. The technique is capable of measuring strain and temperature over 100's kilometers with meter spatial resolution. Dedicated fiber optic cables have been developed for continuous strain and temperature monitoring and their deployment along the pipeline has enabled permanent and continuous pipeline ground movement, intrusion and leak detection. This paper presents a description of the fiber optic Brillouin-based DITEST sensing technique, its measurement performance and limits, while addressing future perspectives for pipeline monitoring. The description is supported by case studies and illustrated by field data.

  16. Extrinsic fiber optic displacement sensors and displacement sensing systems

    DOEpatents

    Murphy, Kent A.; Gunther, Michael F.; Vengsarkar, Ashish M.; Claus, Richard O.

    1994-01-01

    An extrinsic Fizeau fiber optic sensor comprises a single-mode fiber, used as an input/output fiber, and a multimode fiber, used purely as a reflector, to form an air gap within a silica tube that acts as a Fizeau cavity. The Fresnel reflection from the glass/air interface at the front of the air gap (reference reflection) and the reflection from the air/glass interface at the far end of the air gap (sensing reflection) interfere in the input/output fiber. The two fibers are allowed to move in the silica tube, and changes in the air gap length cause changes in the phase difference between the reference reflection and the sensing reflection. This phase difference is observed as changes in intensity of the light monitored at the output arm of a fused biconical tapered coupler. The extrinsic Fizeau fiber optic sensor behaves identically whether it is surface mounted or embedded, which is unique to the extrinsic sensor in contrast to intrinsic Fabry-Perot sensors. The sensor may be modified to provide a quadrature phase shift extrinsic Fizeau fiber optic sensor for the detection of both the amplitude and the relative polarity of dynamically varying strain. The quadrature light signals may be generated by either mechanical or optical means. A plurality of the extrinsic sensors may connected in cascade and multiplexed to allow monitoring by a single analyzer.

  17. Extrinsic fiber optic displacement sensors and displacement sensing systems

    DOEpatents

    Murphy, K.A.; Gunther, M.F.; Vengsarkar, A.M.; Claus, R.O.

    1994-04-05

    An extrinsic Fizeau fiber optic sensor comprises a single-mode fiber, used as an input/output fiber, and a multimode fiber, used purely as a reflector, to form an air gap within a silica tube that acts as a Fizeau cavity. The Fresnel reflection from the glass/air interface at the front of the air gap (reference reflection) and the reflection from the air/glass interface at the far end of the air gap (sensing reflection) interfere in the input/output fiber. The two fibers are allowed to move in the silica tube, and changes in the air gap length cause changes in the phase difference between the reference reflection and the sensing reflection. This phase difference is observed as changes in intensity of the light monitored at the output arm of a fused biconical tapered coupler. The extrinsic Fizeau fiber optic sensor behaves identically whether it is surface mounted or embedded, which is unique to the extrinsic sensor in contrast to intrinsic Fabry-Perot sensors. The sensor may be modified to provide a quadrature phase shift extrinsic Fizeau fiber optic sensor for the detection of both the amplitude and the relative polarity of dynamically varying strain. The quadrature light signals may be generated by either mechanical or optical means. A plurality of the extrinsic sensors may connected in cascade and multiplexed to allow monitoring by a single analyzer. 14 figures.

  18. Feasibility of optical sensing for robotics in highly radioactive environments

    SciTech Connect

    Coenen, S.; Decreton, M. )

    1993-08-01

    The application of robotics for repair, refurbishing or dismantling of nuclear installations implies eventually severe radiation resistance requirements on embarked components and subsystems. This is particularly critical when optical sensing is considered. Optoelectronic components and optical fibers are indeed quite sensitive to radiation, and without special design are rapidly out-of-operation in such an environment. This paper reports the results of a series of [gamma] irradiation experiments on such devices, and identify their behavior under radiation. Test results show that carefully selected optical fibers can keep their radiation induced attenuation lower than 0.3 dB/m even up to a total dose of 10 MGy. Temperature annealing can even lower this attenuation down to 0.1 dB/m. On the other hand, commercially available light emitting diodes and photodiodes present attenuations figures up to 15 dB, even after a gamma irradiation as low as 250 kGy. However, properly chosen bias procedures are shown to greatly enhance this figure. The paper concludes by showing the feasibility of optical sensing for proximity measurement and data transmission for nuclear robots used under severe radiation conditions.

  19. Bromocresol green/mesoporous silica adsorbent for ammonia gas sensing via an optical sensing instrument.

    PubMed

    Chang, Yu-Chang; Bai, Hsunling; Li, Shou-Nan; Kuo, Chun-Nan

    2011-01-01

    A meso-structured Al-MCM-41 material was impregnated with bromocresol green (BG) dye and then incorporated into a UV-Vis DRA spectroscopic instrument for the online detection of ammonia gas. The absorption response of the Al-MCM-41/BG ammonia sensing material was very sensitive at the optical absorption wavelength of 630 nm. A high linear correlation was achieved for ppmv and sub-ppmv levels of ammonia gas. The response time for the quantitative detection of ammonia gas concentrations ranging from 0.25 to 2.0 ppmv was only a few minutes. The lower detection limit achieved was 0.185 ppmv. The color change process was fully reversible during tens of cycling tests. These features together make this mesoporous Al-MCM-41 material very promising for optical sensing applications.

  20. Bromocresol Green/Mesoporous Silica Adsorbent for Ammonia Gas Sensing via an Optical Sensing Instrument

    PubMed Central

    Chang, Yu-Chang; Bai, Hsunling; Li, Shou-Nan; Kuo, Chun-Nan

    2011-01-01

    A meso-structured Al-MCM-41 material was impregnated with bromocresol green (BG) dye and then incorporated into a UV-Vis DRA spectroscopic instrument for the online detection of ammonia gas. The absorption response of the Al-MCM-41/BG ammonia sensing material was very sensitive at the optical absorption wavelength of 630 nm. A high linear correlation was achieved for ppmv and sub-ppmv levels of ammonia gas. The response time for the quantitative detection of ammonia gas concentrations ranging from 0.25 to 2.0 ppmv was only a few minutes. The lower detection limit achieved was 0.185 ppmv. The color change process was fully reversible during tens of cycling tests. These features together make this mesoporous Al-MCM-41 material very promising for optical sensing applications. PMID:22163836

  1. Research on the demodulation techniques of long-period fiber gratings strain sensing with low cost

    NASA Astrophysics Data System (ADS)

    Wang, Qingwei; Liu, Yueming; Tian, Weijian; Feng, Guilan

    2012-10-01

    The working principle of LPFG(Long-Period Fiber Grating) is based on coupling effect between propagating core-mode and co-propagating cladding-modes. The effective refractive index of cladding-modes could be obviously influenced by the environmental changes resulting in LPFG more sensitive than FBG (Fiber Bragg Grating) in sensing areas, such as temperature, strain, concentration, bending and etc. LPFG should have more potential in the field of sensors compared with FBG. One of the challenges in using LPFG for environmental sensing is how to interrogate the signal from the LPFG transmission spectrum, due to the large spectral range of the resonant dip. Nowadays the application of LPFG is normally limited in signal interrogation of FBG as optical edge filter. The signal interrogation of LPFG itself needs further research. Presently research on signal interrogation of fiber grating focuses on wavelength interrogation. The aim of wavelength interrogation is to get the wavelength shift caused by environmental change. To solve these problems, a kind of strain sensing interrogation technique for LPFG with low-cost based on tunable FBGs has been developed. Comparing with the method using Fabry-Perot cavity, tunable FBGs can lower the cost with the guarantee of sensing precision. The cost is further lowered without using expensive optical instruments such as optical switch. The problem of temperature cross-sensitivity was solved by using reference gratings. An experiment was performed to demonstrate the interrogation system. And in the experiment, the sensing signal of LPFG applied 0-1300μɛ was successfully interrogated. The results of the interrogation system and OSA are similar.

  2. A satellite remote sensing technique for geological structure horizon mapping

    SciTech Connect

    Fraser, A.; Huggins, P.; Rees, J.

    1996-08-01

    A Satellite Remote Sensing Technique is demonstrated for generating near surface geological structure data. This technique enables the screening of large areas and targeting of seismic acquisition during hydrocarbon exploration. This is of particular advantage in terrains where surveying is logistically difficult. Landsat Thematic Mapper (TM) data and a high resolution Digital Elevation Model (DEM), are used to identify and map outcropping horizons. These are used to reconstruct the near surface structure. The technique is applied in Central Yemen which is characterised by a {open_quote}layer-cake{close_quote} geological and low dipping terrain. The results are validated using 2D seismic data. The near surface map images faults and structure not apparent in the raw data. Comparison with the structure map generated from a 2D seismic data indicates very good structural and fault correlation. The near surface map successfully highlights areas of potential closure at reservoir depths.

  3. Robust high-dynamic-range optical roll sensing.

    PubMed

    Gillmer, Steven R; Yu, Xiangzhi; Wang, Chen; Ellis, Jonathan D

    2015-06-01

    We present a robust optical-roll sensor with a high-dynamic range and high-throughput capabilities. The working principle relies on tracking the amplitude of an optical square wave-encoded light source. After encoding a square wave onto a polarization reference, quadrature demodulation of the polarized light allows us to cancel common-mode noise. Benefits of this sensor include its simplicity, low cost, high-throughput, insensitivity to source amplitude fluctuations, and no inherent drift. In this Letter, we present the working principle and experimentally validate a 43° usable working range with 0.002° resolution. This sensor has the highest reported dynamic range for optical roll sensing.

  4. Recognition as a challenging label-free optical sensing system

    NASA Astrophysics Data System (ADS)

    Gauglitz, Günter

    2013-05-01

    Optical biosensors are increasingly used in application areas of environmental analysis, healthcare and food safety. The quality of the biosensor's results depends on the interaction layer, the detection principles, and evaluation strategies, not only on the biopolymer layer but also especially on recognition elements. Using label-free optical sensing, non-specific interaction between sample and transducer has to be reduced, and the selectivity of recognition elements has to be improved. For this reason, strategies to avoid non-specific interaction even in blood and milk are discussed, a variety of upcoming recognition is given. Based on the classification of direct optical detection methods, some examples for the above mentioned applications are reviewed. Trends as well as advantages of parallel multisport detection for kinetic evaluation are also part of the lecture.

  5. Multiple irradiation sensing of the optical effective attenuation coefficient for spectral correction in handheld OA imaging.

    PubMed

    Held, K Gerrit; Jaeger, Michael; Rička, Jaro; Frenz, Martin; Akarçay, H Günhan

    2016-06-01

    Spectral optoacoustic (OA) imaging enables spatially-resolved measurement of blood oxygenation levels, based on the distinct optical absorption spectra of oxygenated and de-oxygenated blood. Wavelength-dependent optical attenuation in the bulk tissue, however, distorts the acquired OA spectrum and thus makes quantitative oxygenation measurements challenging. We demonstrate a correction for this spectral distortion without requiring a priori knowledge of the tissue optical properties, using the concept of multiple irradiation sensing: recording the OA signal amplitude of an absorbing structure (e.g. blood vessel), which serves as an intrinsic fluence detector, as function of irradiation position. This permits the reconstruction of the bulk effective optical attenuation coefficient μeff,λ . If performed at various irradiation wavelengths, a correction for the wavelength-dependent fluence attenuation is achieved, revealing accurate spectral information on the absorbing structures. Phantom studies were performed to show the potential of this technique for handheld clinical combined OA and ultrasound imaging.

  6. Compressive sensing optical coherence tomography using randomly accessible lasers

    NASA Astrophysics Data System (ADS)

    Harfouche, Mark; Satyan, Naresh; Vasilyev, Arseny; Yariv, Amnon

    2014-05-01

    We propose and demonstrate a novel a compressive sensing swept source optical coherence tomography (SSOCT) system that enables high speed images to be taken while maintaining the high resolution offered from a large bandwidth sweep. Conventional SSOCT systems sweep the optical frequency of a laser ω(t) to determine the depth of the reflectors at a given lateral location. A scatterer located at delay τ appears as a sinusoid cos (ω(t)τ ) at the photodetector. The finite optical chirp rate and the speed of analog to digital and digital to analog converters limit the acquisition rate of an axial scan. The proposed acquisition modality enables much faster image acquisition rates by interrogating the beat signal at randomly selected optical frequencies while preserving resolution and depth of field. The system utilizes a randomly accessible laser, a modulated grating Y-branch laser, to sample the interference pattern from a scene at randomly selected optical frequencies over an optical bandwidth of 5 THz , corresponding to a resolution of 30 μm in air. The depth profile is then reconstructed using an l1 minimization algorithm with a LASSO constraint. Signal-dependent noise sources, shot noise and phase noise, are analyzed and taken into consideration during the recovery. Redundant dictionaries are used to improve the reconstruction of the depth profile. A compression by a factor of 10 for sparse targets up to a depth of 15 mm in noisy environments is shown.

  7. Sensing Plasmon-Resonant Nanorods in Tissue with Optical Coherence Tomography

    NASA Astrophysics Data System (ADS)

    Oldenburg, Amy

    2009-11-01

    Gold nanoparticles (GNPs) are of high interest for biomedical imaging and photothermal therapy due to their plasmon-resonant nature. However, their utility is limited by transport and targeting to the disease of interest after administration in the living body. Optical coherence tomography can image the distribution of GNPs on the micro- to meso-scale, leading toward a better understanding of these limiting factors. Plasmon-resonant nanorods provide strong optical absorption at near-infrared wavelengths, and are studied using an optical coherence tomography system based on a broadband laser centered at 800nm. The ability to sense GNPs against a biological tissue background is treated as a sensing problem with parameters including the nanorod volume and aspect ratio, optical detection metrics including extinction, a new backscattering albedo metric based on the ratio of backscattering to extinction, and spectroscopic analysis. A key element of this analysis is determining the native tissue optical response, optical signal noise, and spatial heterogeneity before addition of the GNPs. Experiments are performed in skin-like tissue phantoms where a sensitivity of 30ppm is found. Experiments in excised human mammary tumors reveal additional challenges for imaging in real tissues, and the results of various processing techniques are compared.

  8. A review on reflective remote sensing and data assimilation techniques for enhanced agroecosystem modeling

    NASA Astrophysics Data System (ADS)

    Dorigo, W. A.; Zurita-Milla, R.; de Wit, A. J. W.; Brazile, J.; Singh, R.; Schaepman, M. E.

    2007-05-01

    During the last 50 years, the management of agroecosystems has been undergoing major changes to meet the growing demand for food, timber, fibre and fuel. As a result of this intensified use, the ecological status of many agroecosystems has been severely deteriorated. Modeling the behavior of agroecosystems is, therefore, of great help since it allows the definition of management strategies that maximize (crop) production while minimizing the environmental impacts. Remote sensing can support such modeling by offering information on the spatial and temporal variation of important canopy state variables which would be very difficult to obtain otherwise. In this paper, we present an overview of different methods that can be used to derive biophysical and biochemical canopy state variables from optical remote sensing data in the VNIR-SWIR regions. The overview is based on an extensive literature review where both statistical-empirical and physically based methods are discussed. Subsequently, the prevailing techniques of assimilating remote sensing data into agroecosystem models are outlined. The increasing complexity of data assimilation methods and of models describing agroecosystem functioning has significantly increased computational demands. For this reason, we include a short section on the potential of parallel processing to deal with the complex and computationally intensive algorithms described in the preceding sections. The studied literature reveals that many valuable techniques have been developed both for the retrieval of canopy state variables from reflective remote sensing data as for assimilating the retrieved variables in agroecosystem models. However, for agroecosystem modeling and remote sensing data assimilation to be commonly employed on a global operational basis, emphasis will have to be put on bridging the mismatch between data availability and accuracy on one hand, and model and user requirements on the other. This could be achieved by

  9. Chalcogenide Glass Fibers for Infrared Sensing and Space Optics

    NASA Astrophysics Data System (ADS)

    Bureau, Bruno; Maurugeon, Sébastien; Charpentier, Frederic; Adam, Jean-Luc; Boussard-Plédel, Catherine; Zhang, Xiang-Hua

    This review deals with chalcogenide glasses and fibers. Chemical compositions and physical properties are given for specific glasses well suited for fiber drawing. Fabrication techniques of glass perform are described. Single-index and step-index single-mode fibers are characterized in terms of optical losses in the infrared. Examples of applications of chalcogenide fibers are given, as well as optical sensors in the fields of environment, microbiology and health, and as mode-filters for infrared interferometry in space.

  10. LIFES: Laser Induced Fluorescence and Environmental Sensing. [remote sensing technique for marine environment

    NASA Technical Reports Server (NTRS)

    Houston, W. R.; Stephenson, D. G.; Measures, R. M.

    1975-01-01

    A laboratory investigation has been conducted to evaluate the detection and identification capabilities of laser induced fluorescence as a remote sensing technique for the marine environment. The relative merits of fluorescence parameters including emission and excitation profiles, intensity and lifetime measurements are discussed in relation to the identification of specific targets of the marine environment including crude oils, refined petroleum products, fish oils and algae. Temporal profiles displaying the variation of lifetime with emission wavelength have proven to add a new dimension of specificity and simplicity to the technique.

  11. LIFES: Laser Induced Fluorescence and Environmental Sensing. [remote sensing technique for marine environment

    NASA Technical Reports Server (NTRS)

    Houston, W. R.; Stephenson, D. G.; Measures, R. M.

    1975-01-01

    A laboratory investigation has been conducted to evaluate the detection and identification capabilities of laser induced fluorescence as a remote sensing technique for the marine environment. The relative merits of fluorescence parameters including emission and excitation profiles, intensity and lifetime measurements are discussed in relation to the identification of specific targets of the marine environment including crude oils, refined petroleum products, fish oils and algae. Temporal profiles displaying the variation of lifetime with emission wavelength have proven to add a new dimension of specificity and simplicity to the technique.

  12. Optics, illumination, and image sensing for machine vision VI; Proceedings of the Meeting, Boston, MA, Nov. 14, 15, 1991

    NASA Astrophysics Data System (ADS)

    Svetkoff, Donald J.

    Recent advances in research on imaging technologies and practical application of numerous techniques are reported. Consideration is given to illumination and sensing methods and systems, image and instrument models, optical processing and data manipulation, and 3D imaging techniques and systems. Particular attention is given to light source design for machine vision, multisource and color lighting for detection of small protuberances, VLSI sensor/processor circuitry for autonomous robots, calibration of an active stereoscopic imaging system, image processor development with synthetic images, optical morphological processing of disordered structures, a high-speed coherent optical correlator based on two MOSLMs, 3D line-scan intensity ratio sensing, pulsed time-of-flight laser range-finding techniques for industrial applications, and a comparison of continuous-wave and pulsed time-of-flight laser range-finding techniques.

  13. Optical code division multiplexed fiber Bragg grating sensing networks

    NASA Astrophysics Data System (ADS)

    Triana, Cristian; Varón, Margarita; Pastor, Daniel

    2015-09-01

    We present the application of Optical Code Division Multiplexing (OCDM) techniques in order to enhance the spectral operation and detection capability of fiber Bragg grating (FBG) sensors networks even under overlapping conditions. In this paper, Optical Orthogonal Codes (OOC) are used to design FBG sensors composed of more than one reflection band. Simulation of the interaction between the encoded Gaussian-shaped sensors is presented. Signal decoding is performed in the electrical domain without requiring additional optical components by means of the autocorrelation product between the reflected spectrum and each sensor-codeword. Results illustrate the accuracy and distinction capability of the method.

  14. Cleanliness and damage measurements of optics in atmospheric sensing high energy lasers

    SciTech Connect

    Harvey, G.A.; Chyba, T.H.; Cimolino, M.C.

    1996-12-31

    Langley Research Center has several atmospheric remote sensing programs which utilize, high energy pulsed lasers. These lasers typically have many damaged optics after several million shots. Damage is defined herein as color changes and/or optical flaws seen in microscopic inspection, and does not necessarily relate to measured performance degradation of the optic. Inspections and measurements of some of these optics indicate that energy thresholds for several million shots damage is about an order of magnitude lower than that for single shot damage. Damage initiation is often at micron size areas at the coating interface, which grows and sometimes develops as erosion of the top of the coating. There is a wide range in polish and coating quality of new optics, even on different faces of the same optic. Military Standard 1246C can be used to provide overall particulate, and molecular film, or nonvolatile residue (NTVR) cleanliness scales. Microscopic inspections and photography at I0x to 500x with brightfield (perpendicular) and darkfield (oblique) illumination are useful in assigning cleanliness levels of new and in-service optics. Microextraction (effecting concentration of molecular films to small areas) provides for enhanced optical detection and surface film chemical analysis by electron-microscope energy-dispersive-spectroscopy (EDS). Similar measurement techniques can be used to characterize and document optical damage initiation and optical damage growth. Surface contamination interferes with and complicates measurements of polish and coating quality, and of optical damage. This work indicates ultrasonic cleaning, and packaging of optics in Teflon sleeves or cups is advantageous over conventional cleaning and packaging for characterization of new optics.

  15. Cleanliness and damage measurements of optics in atmospheric-sensing high-energy lasers

    NASA Astrophysics Data System (ADS)

    Harvey, Gale A.; Chyba, Thomas H.; Cimolino, Marc C.

    1996-05-01

    Langley Research Center has several atmospheric remote sensing programs which utilize high energy pulsed lasers. These lasers typically have many damaged optics after several million shots. Damage is defined herein as color changes and/or optical flaws seen in microscopic inspection, and does not necessarily relate to measured performance degradation of the optic. Inspections and measurements of some of these optics indicate that energy thresholds for several million shots damage is about an order of magnitude lower than that for single shot damage. Damage initiation is often at micron size areas at the coating interface, which grows and sometimes develops as erosion of the top of the coating. There is a wide range in polish and coating quality of new optics, even on different faces of the same optic. Military Standard 1246C can be used to provide overall particulate, and molecular film, or nonvolatile residue cleanliness scales. Microscopic inspections and photography at 10X to 500X with brightfield (perpendicular) and darkfield (oblique) illumination are useful in assigning cleanliness levels of new and in-service optics. Microextraction (effecting concentration of molecular films to small areas) provides for enhanced optical detection and surface film chemical analysis by electron-microscope energy-dispersive-spectroscopy. Similar measurement techniques can be used to characterize and document optical damage initiation and optical damage growth. Surface contamination interferes with and complicated measurements of polish and coating quality, and of optical damage. Our work indicates ultrasonic cleaning, and packaging of optics in Teflon sleeves or cups is advantageous over conventional cleaning and packaging for characterization of new optics.

  16. TE/TM-based integrated optical sensing platforms

    NASA Astrophysics Data System (ADS)

    Koster, Tonnis Meindert

    An analysis, the design, the fabrication and the characterisation of two integrated optical bimodal evanscent field sensing platforms (read-out systems) are described: one for absorptive sensing of chemical concentrations and one for refractometric sensing. The first platform uses two modes to compensate for the influences of background absorption in the case of using thin transduction layers. The second platform is a differential refractometer, i.e. the two interrogation modes show a different sensitivity to the measurand and the output signals are a function of the difference in the sensitivity. For these sensing platforms, several integrated optical functionalities have been developed, amongst others a (wavelength tunable) passive polarisation converter and mode selective waveguide- detector coupling structures. The converter assures that a well known power ratio of the two interrogation modes is obtained. After interrogation the two modes are coupled, using coupling structures, to different detectors in order to separately obtain the information carried by the modes. The design of the platforms and individual optical functionalities has been done taking technological tolerances into account, resulting in the highest possible reproducibility for the given technology. The devices have been fabricated in SiON technology. The polarisation converter, an asymmetrical grating structure, proved to be highly efficient, with a 98% conversion for a length of 12 millimeters, and showed functional losses of 3 dB/cm. It has been theoretically and experimentally shown that using thermo-optical actuation, the position of the conversion peak can be tuned over a broad wavelength range. Experimentally, a 12 nm wavelength shift for a temperature change of 100 degrees Celcius has been shown. The amount of light coupled into monolithically integrated photodiodes by the coupling structures agrees very well with theory. Characterisation of the differential sensor showed a resolution

  17. A novel data adaptive detection scheme for distributed fiber optic acoustic sensing

    NASA Astrophysics Data System (ADS)

    Ölçer, Íbrahim; Öncü, Ahmet

    2016-05-01

    We introduce a new approach for distributed fiber optic sensing based on adaptive processing of phase sensitive optical time domain reflectometry (Φ-OTDR) signals. Instead of conventional methods which utilizes frame averaging of detected signal traces, our adaptive algorithm senses a set of noise parameters to enhance the signal-to-noise ratio (SNR) for improved detection performance. This data set is called the secondary data set from which a weight vector for the detection of a signal is computed. The signal presence is sought in the primary data set. This adaptive technique can be used for vibration detection of health monitoring of various civil structures as well as any other dynamic monitoring requirements such as pipeline and perimeter security applications.

  18. Melamine sensing based on evanescent field enhanced optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Luo, Ji; Yao, Jun; Wang, Wei-min; Zhuang, Xu-ye; Ma, Wen-ying; Lin, Qiao

    2013-08-01

    Melamine is an insalubrious chemical, and has been frequently added into milk products illegally, to make the products more protein-rich. However, it can cause some various diseases, such as kidney stones and bladder cancer. In this paper, a novel optical fiber sensor with high sensitivity based on absorption of the evanescent field for melamine detection is successfully proposed and developed. Different concentrations of melamine changing from 0 to 10mg/mL have been detected using the micro/nano-sensing fiber decorated with silver nanoparticles cluster layer. As the concentration increases, the sensing fiber's output intensity gradually deceases and the absorption of the analyte becomes large. The concentration changing of 1mg/ml can cause the absorbance varying 0.664 and the limit of the melamine detectable concentration is 1ug/mL. Besides, the coupling properties between silver nanoparticles have also been analyzed by the FDTD method. Overall, this evanescent field enhanced optical fiber sensor has potential to be used in oligo-analyte detection and will promote the development of biomolecular and chemical sensing applications.

  19. Optical sensing nanostructures for porous silicon rugate filters

    PubMed Central

    2012-01-01

    Porous silicon rugate filters [PSRFs] and combination PSRFs [C-PSRFs] are emerging as interesting sensing materials due to their specific nanostructures and superior optical properties. In this work, we present a systematic study of the PSRF fabrication and its nanostructure/optical characterization. Various PSRF chips were produced with resonance peaks that are adjustable from visible region to near-infrared region by simply increasing the periods of sine currents in a programmed electrochemical etching method. A regression analysis revealed a perfect linear correlation between the resonant peak wavelength and the period of etching current. By coupling the sine currents with several different periods, C-PSRFs were produced with defined multiple resonance peaks located at desired positions. A scanning electron microscope and a microfiber spectrophotometer were employed to analyze their physical structure and feature spectra, respectively. The sensing properties of C-PSRFs were investigated in an ethanol vapor, where the red shifts of the C-PSRF peaks had a good linear relationship with a certain concentration of ethanol vapor. As the concentration increased, the slope of the regression line also increased. The C-PSRF sensors indicated the high sensitivity, quick response, perfect durability, reproducibility, and versatility in other organic gas sensing. PMID:22252301

  20. Dynamic Force Sensing Using an Optically Trapped Probing System

    PubMed Central

    Huang, Yanan; Cheng, Peng; Menq, Chia-Hsiang

    2013-01-01

    This paper presents the design of an adaptive observer that is implemented to enable real-time dynamic force sensing and parameter estimation in an optically trapped probing system. According to the principle of separation of estimation and control, the design of this observer is independent of that of the feedback controller when operating within the linear range of the optical trap. Dynamic force sensing, probe steering/clamping, and Brownian motion control can, therefore, be developed separately and activated simultaneously. The adaptive observer utilizes the measured motion of the trapped probe and input control effort to recursively estimate the probe–sample interaction force in real time, along with the estimation of the probing system’s trapping bandwidth. This capability is very important to achieving accurate dynamic force sensing in a time-varying process, wherein the trapping dynamics is nonstationary due to local variations of the surrounding medium. The adaptive estimator utilizes the Kalman filter algorithm to compute the time-varying gain in real time and minimize the estimation error for force probing. A series of experiments are conducted to validate the design of and assess the performance of the adaptive observer. PMID:24382944

  1. Higher order Fano graphene metamaterials for nanoscale optical sensing.

    PubMed

    Guo, Xiangdong; Hu, Hai; Zhu, Xing; Yang, Xiaoxia; Dai, Qing

    2017-10-12

    Plasmonic Fano metamaterials provide a unique platform for optical sensing applications due to their sharp spectral response and the ability to confine light to nanoscale regions that make them a strong prospect for refractive-index sensing. Higher order Fano resonance modes in noble metal plasmonic structures can further improve the sensitivity, but their applications are heavily limited by crosstalk between different modes due to the large damping rates and broadband spectral responses of the metal plasmon modes. Here, we create pure higher order Fano modes by designing asymmetric metamaterials comprised of a split-ring resonator and disk with a low-loss graphene plasmon. These higher order modes are highly sensitive to the nanoscale analyte (8 nm thick) both in refractive-index and in infrared vibrational fingerprint sensing, as demonstrated by the numerical calculation. The frequency sensitivity and figure-of-merit of the hexacontatetrapolar mode can reach 289 cm(-1) per RIU and 29, respectively, and it can probe the weak infrared vibrational modes of the analyte with more than 400 times enhancement. The enhanced sensitivity and tunability of higher order Fano graphene metamaterials promise a high-performance nanoscale optical sensor.

  2. Nanoporous anodic alumina platforms: engineered surface chemistry and structure for optical sensing applications.

    PubMed

    Kumeria, Tushar; Santos, Abel; Losic, Dusan

    2014-07-07

    Electrochemical anodization of pure aluminum enables the growth of highly ordered nanoporous anodic alumina (NAA) structures. This has made NAA one of the most popular nanomaterials with applications including molecular separation, catalysis, photonics, optoelectronics, sensing, drug delivery, and template synthesis. Over the past decades, the ability to engineer the structure and surface chemistry of NAA and its optical properties has led to the establishment of distinctive photonic structures that can be explored for developing low-cost, portable, rapid-response and highly sensitive sensing devices in combination with surface plasmon resonance (SPR) and reflective interference spectroscopy (RIfS) techniques. This review article highlights the recent advances on fabrication, surface modification and structural engineering of NAA and its application and performance as a platform for SPR- and RIfS-based sensing and biosensing devices.

  3. Simultaneous strain and temperature sensing using a slightly tapered optical fiber with an inner cavity.

    PubMed

    Chen, H F; Wang, D N; Wang, Y

    2015-03-21

    An ultracompact optical fiber mode interferometer capable of performing simultaneous strain and temperature sensing is demonstrated. The device is fabricated by using femtosecond laser micromachining together with fusion splicing techniques and followed by a tapering process. The transmission spectrum of the device exhibits a number of resonance wavelength dips, corresponding to different orders of cladding mode, which allow simultaneous strain and temperature sensing by monitoring the variation of selected two wavelength dips. The sensitivity achieved is -16.12 pm με(-1) and 85.95 pm °C(-1) for strain and temperature, respectively. The device has a spatially precise sensing capability owing to the small size of the inner air-cavity.

  4. Nanoporous Anodic Alumina Platforms: Engineered Surface Chemistry and Structure for Optical Sensing Applications

    PubMed Central

    Kumeria, Tushar; Santos, Abel; Losic, Dusan

    2014-01-01

    Electrochemical anodization of pure aluminum enables the growth of highly ordered nanoporous anodic alumina (NAA) structures. This has made NAA one of the most popular nanomaterials with applications including molecular separation, catalysis, photonics, optoelectronics, sensing, drug delivery, and template synthesis. Over the past decades, the ability to engineer the structure and surface chemistry of NAA and its optical properties has led to the establishment of distinctive photonic structures that can be explored for developing low-cost, portable, rapid-response and highly sensitive sensing devices in combination with surface plasmon resonance (SPR) and reflective interference spectroscopy (RIfS) techniques. This review article highlights the recent advances on fabrication, surface modification and structural engineering of NAA and its application and performance as a platform for SPR- and RIfS-based sensing and biosensing devices. PMID:25004150

  5. Optical MEMS-based bimorph for thermal sensing

    NASA Astrophysics Data System (ADS)

    Rinaldi, Gino; Packirisamy, Muthukumaran; Stiharu, Ion G.

    2004-12-01

    Micro-electro-mechanical-systems (MEMS) offer many advantages for sensing a variety of physical parameters such as accceleration, pressure and temperature. Their small size allows them to operate in close proximity where conventional sensors cannot be introduced especially for thermal measurements. Temperature measurement and control is of fundamental importance to the optimal operating conditions of materials and machinery such as gas turbine engines, space exploration, etc. The temperature characterization will allow proper diagnosis of operating conditions and hence the optimization of controls and environment in order to augment performance and useful lifetime. MEMS based thermal measurements will be very useful as they are sensitive to small fluctuations in the operating conditions. Here, this paper proposes a novel MEMS based bimorph optical device as a thermal sensor. The paper includes the theoretical and experimental analysis on the thermal behavior of optical MEMS devices under different geometrical and parametric conditions. The paper also presents the static and dynamic behavior of optical MEMS based devices under different thermal environments. The results obtained verify the validity of the proposed designs for thermal sensing.

  6. Spectroelectrochemistry: The Combination of Optical and Electrochemical Techniques.

    ERIC Educational Resources Information Center

    Heineman, William R.

    1983-01-01

    Two different techniques, electrochemistry and spectroscopy, can be combined for studying the redox chemistry of inorganic, organic, and biological molecules. Several commonly used spectroelectrochemical methods and their applications are described. Includes discussions of optically transparent electrodes, optical absorption/fluorescence…

  7. Spectroelectrochemistry: The Combination of Optical and Electrochemical Techniques.

    ERIC Educational Resources Information Center

    Heineman, William R.

    1983-01-01

    Two different techniques, electrochemistry and spectroscopy, can be combined for studying the redox chemistry of inorganic, organic, and biological molecules. Several commonly used spectroelectrochemical methods and their applications are described. Includes discussions of optically transparent electrodes, optical absorption/fluorescence…

  8. Fiber optic device for sensing the presence of a gas

    DOEpatents

    Benson, David K.; Bechinger, Clemens S.; Tracy, C. Edwin

    1998-01-01

    A fiber-optic device for sensing the presence of a gas in an environment is provided. The device comprises a light source for directing a light beam to a layer system having a first surface and a second surface opposite the first surface. The first surface is exposable to the light beam and the second surface is exposable to the environment. A first light portion encounters and reflects from the first surface at an angle of incidence free from optical wave guide resonance phenomenon and the second light portion encounters and reflects from the first surface at an angle of incidence enabling an optical wave guide resonance phenomenon. The layer system is selected to reversibly react with the gas to be detected. The reaction between the gas and the material changes the material's optical properties and the wavelength at which the optical wave guide resonance occurs. Furthermore, a mechanism for measuring the intensity of the reflected first light portion relative to the reflected second light portion is provided with the ratio of the first and second light portions indicating the concentration of the gas presence in the environment.

  9. Fiber optic device for sensing the presence of a gas

    DOEpatents

    Benson, D.K.; Bechinger, C.S.; Tracy, C.E.

    1998-01-13

    A fiber-optic device for sensing the presence of a gas in an environment is provided. The device comprises a light source for directing a light beam to a layer system having a first surface and a second surface opposite the first surface. The first surface is exposable to the light beam and the second surface is exposable to the environment. A first light portion encounters and reflects from the first surface at an angle of incidence free from optical wave guide resonance phenomenon and the second light portion encounters and reflects from the first surface at an angle of incidence enabling an optical wave guide resonance phenomenon. The layer system is selected to reversibly react with the gas to be detected. The reaction between the gas and the material changes the material`s optical properties and the wavelength at which the optical wave guide resonance occurs. Furthermore, a mechanism for measuring the intensity of the reflected first light portion relative to the reflected second light portion is provided with the ratio of the first and second light portions indicating the concentration of the gas presence in the environment. 5 figs.

  10. Comparative study of infrared wavefront sensing solutions for adaptive optics

    NASA Astrophysics Data System (ADS)

    Plantet, C.; Fusco, T.; Guerineau, N.; Derelle, S.; Robert, C.

    2016-07-01

    The development of new low-noise infrared detectors, such as RAPID (CEA LETI/Sofradir) or SAPHIRA (Selex), has given the possibility to consider infrared wavefront sensing at low ux. We propose here a comparative study of near infrared (J and H bands) wavefront sensing concepts for mid and high orders estimation on a 8m- class telescope, relying on three existing wavefront sensors: the Shack-Hartmann sensor, the pyramid sensor and the quadri-wave lateral shearing interferometer. We consider several conceptual designs using the RAPID camera, making a trade-off between background flux, optical thickness and compatibility with a compact cryostat integration. We then study their sensitivity to noise in order to compare them in different practical scenarios. The pyramid provides the best performance, with a gain up to 0.5 magnitude, and has an advantageous setup.

  11. Design and Development of Nanostructured Surfaces for Enhanced Optical Sensing

    NASA Astrophysics Data System (ADS)

    Santiago Cordoba, Miguel A.

    At smaller size regimes, materials' physicochemical properties change with respect to bulk analogs. In the case of metal nanoparticles like gold or silver, specific wavelengths of light can induce a coherent oscillation of their conduction electrons, generating an optical field confined to the nanoparticle surface. This phenomenon is termed surface plasmon, and has been used as an enhancing mechanism in optical sensing, allowing the detection of foreign materials at small concentrations. The goal of this dissertation is to develop nanostructured materials relying on surface plasmons that can be combined with different optical sensing platforms in order to enhance current detection limits. Initially, we focus on the development of surfactant free, stimuli responsive nanoparticle thin films, which undergo an active release when exposed to a stimulus such as a change in pH. These nanoparticle thin films provide faster analyte particle transport and direct electronic coupling with the analyte molecule, all without attenuating the evanescent wave from the optical transducer to the particle. These stimuli responsive nanostructured substrates are tested within a surface enhanced Raman platform for the detection of biomolecular probes at sub-nanomolar concentrations and microL sample sizes. Furthermore, the developed nanosubstrates can be patterned, providing a versatile nanoparticle thin film for multiplexing analysis, offering a substantial advantage over conventional surface based nanoparticle detection methods. Our results encouraged further optimization of light-matter interactions in optical detection platforms. It is for that reason that this dissertation evolves towards confined optical systems. Particularly, whispering gallery microcavities confine electromagnetic waves - at high volumes - at the boundary of a dielectric resonator. In this dissertation, we examined the sensitivity of whispering gallery modes combining optical microcavities with plasmonic

  12. Optical microcavity sensing: from reactive to dissipative interactions (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Zhi, Yanyan; Shen, Bo-Qiang; Yu, Xiao-Chong; Wang, Li; Kim, Donghyun; Gong, Qihuang; Xiao, Yun-Feng

    2017-02-01

    Ultrasensitive optical detection of nanoparticles is highly desirable for applications in early-stage diagnosis of human diseases, environmental monitoring and homeland security, but remains extremely difficult due to ultralow polarizabilities of small-sized, low-index particles. Optical whispering-gallery-mode (WGM) microcavities, with high Q factors up to 108, provide a promising platforms for label-free detection of nano-scaled objects, due to significantly enhanced light-matter interaction. The mechanisms of the conventional WGM sensors, based on the reactive (or dispersive) interaction, measure the mode shift induced by the environmental variations of refractive index, which may fail to detect low-index nanoparticles. In this work, we propose a different dissipative sensing scheme, reacting as linewidth change of WGMs, to detect single nanoparticle using a silica toroidal microcavity fabricated on a silicon substrate. In experiment, detection of single gold nanorods in aqueous environment is realized by monitoring simultaneously the linewidth change and shift of cavity mode. Besides a good consistent with the theoretical predictions, the experimental result shows that the dissipative sensing achieves a better signal-to-noise-ratio compared to the dispersive mechanism. Remarkably, by setting the probe wavelength on and off the surface plasmon resonance of the gold nanoparticles, the great potential of the dissipative sensing method to detect single lossy nanoparticles is demonstrated. This dissipative sensing method holds great potential in detecting lossy nanoparticles, and may become a promising lab-on-a-chip platform for detecting small-sized, low-index particles with ultralow polarizabilities.

  13. Magnetic sensing techniques for humanitarian ordnance detection and discrimination

    NASA Astrophysics Data System (ADS)

    Keranen, Joe; Billings, Steve; Schultz, Gregory; Miller, Jonathan

    2011-06-01

    Detection and discrimination of unexploded ordnance (UXO) in areas of prior conflict is of high importance to the international community and the United States government. For humanitarian applications, sensors and processing methods need to be robust, reliable, and easy to train and implement using indigenous UXO removal personnel. This paper focuses on magnetometer sensing techniques, processing, and operation for UXO detection and discrimination applications. Specifically, we discuss the collection, processing, and discrimination of data collected using the PACMAG man-portable system consisting of arrays of sensitive total-field magnetometers, global positioning (GPS) combined with digital odometers, and a data acquisition system. We outline preliminary standard operating procedures for optimal collection of UXO-induced magnetic fields and associated position data using either a GPS, or odometer when surveying in GPS-denied areas. Processing techniques such as gridding and filtering, target picking, and discrimination lead to estimates of target size and location. Emphasis is placed on simplifying the production of magnetometer hardware and software for use by minimally-trained personnel with no advanced knowledge of magnetic sensing and geophysics.

  14. Compressed Sensing Techniques Applied to Ultrasonic Imaging of Cargo Containers.

    PubMed

    López, Yuri Álvarez; Lorenzo, José Ángel Martínez

    2017-01-15

    One of the key issues in the fight against the smuggling of goods has been the development of scanners for cargo inspection. X-ray-based radiographic system scanners are the most developed sensing modality. However, they are costly and use bulky sources that emit hazardous, ionizing radiation. Aiming to improve the probability of threat detection, an ultrasonic-based technique, capable of detecting the footprint of metallic containers or compartments concealed within the metallic structure of the inspected cargo, has been proposed. The system consists of an array of acoustic transceivers that is attached to the metallic structure-under-inspection, creating a guided acoustic Lamb wave. Reflections due to discontinuities are detected in the images, provided by an imaging algorithm. Taking into consideration that the majority of those images are sparse, this contribution analyzes the application of Compressed Sensing (CS) techniques in order to reduce the amount of measurements needed, thus achieving faster scanning, without compromising the detection capabilities of the system. A parametric study of the image quality, as a function of the samples needed in spatial and frequency domains, is presented, as well as the dependence on the sampling pattern. For this purpose, realistic cargo inspection scenarios have been simulated.

  15. Water quality assessment in Kelantan delta using remote sensing technique

    NASA Astrophysics Data System (ADS)

    Syahreza, S.; MatJafri, M. Z.; Lim, H. S.; Mustapha, M. R.

    2012-09-01

    This paper presents the utilities of remote sensing technique for water quality assessment in Kelantan Delta, Malaysia. Remote sensing is one of the effective methods for water quality monitoring through image analysis of study area. Spectral reflectance signatures of Kelantan Delta were measured from 20 stations using ASD Handheld spectroradiometer from regions with different turbidity level. Water samples collected from these stations were taken to the laboratory for measure turbidity in Nephelometric Turbidity Unit (NTU). The objective of this study is to examine the potential of ALOS on Japanese Earth Observing Satellite (JEOS) for assessing water quality in Kelantan Delta. There is a large correlation between NTU and the in-situ reflectance at 500 - 620 nm (maximum spectra band between 300 and 1100 nm) is shown by multiple linier regression model, resulting from increasing of turbidity levels, was developed and applied to ALOS band 2 and band 3 (0.42-069 nm). A simple atmospheric correction, based on darkest pixel technique was performed in this study. The ALOS data provides accurate estimates of the mean water quality (R2 = 0.95 and RMSE = 2.26 NTU). The result acquired is reliable to estimate of water quality values for the Kelantan Delta and its implication for future operation.

  16. Recent progress in bio-sensing techniques with encapsulated enzymes.

    PubMed

    Park, Byung-Wook; Yoon, Do-Young; Kim, Dong-Shik

    2010-09-15

    Biosensors with encapsulated enzymes have advantages of high substrate selectivity and sustained enzyme activity. Enzymes are encapsulated in various materials, such as liposome, polymer, and sol-gel or hydro-gel, depending on sensing conditions. By stabilizing the enzymes via encapsulation with new methods and materials the enzyme activity may be maintained for a longer time, and even the selectivity can possibly be enhanced. In general increased mass transfer limitation seems to be the major challenge to investigate more. Novel materials, encapsulation techniques, and sensing mechanisms have been studied intensively for encapsulated enzyme biosensors. In this review, we focus on the recent progress in encapsulated enzyme biosensors published in peer-reviewed journals over the last 10 years. The articles are categorized and reviewed in four groups based on encapsulation techniques incorporating with liposome, polymer, sol-gel or hydro-gel, and peptide. Research articles that are considered critical and noticeable are selected and compared according to these categorizations. Based on these article analyses, we suggested future direction in the encapsulated enzyme biosensor research.

  17. Compressed Sensing Techniques Applied to Ultrasonic Imaging of Cargo Containers

    PubMed Central

    Álvarez López, Yuri; Martínez Lorenzo, José Ángel

    2017-01-01

    One of the key issues in the fight against the smuggling of goods has been the development of scanners for cargo inspection. X-ray-based radiographic system scanners are the most developed sensing modality. However, they are costly and use bulky sources that emit hazardous, ionizing radiation. Aiming to improve the probability of threat detection, an ultrasonic-based technique, capable of detecting the footprint of metallic containers or compartments concealed within the metallic structure of the inspected cargo, has been proposed. The system consists of an array of acoustic transceivers that is attached to the metallic structure-under-inspection, creating a guided acoustic Lamb wave. Reflections due to discontinuities are detected in the images, provided by an imaging algorithm. Taking into consideration that the majority of those images are sparse, this contribution analyzes the application of Compressed Sensing (CS) techniques in order to reduce the amount of measurements needed, thus achieving faster scanning, without compromising the detection capabilities of the system. A parametric study of the image quality, as a function of the samples needed in spatial and frequency domains, is presented, as well as the dependence on the sampling pattern. For this purpose, realistic cargo inspection scenarios have been simulated. PMID:28098841

  18. Optimization of the polarization remote-sensing techniques of the ocean

    NASA Astrophysics Data System (ADS)

    Krotkov, Nickolay A.; Kondranin, Timofei V.; Vasilkov, Alexander P.

    1992-12-01

    A numerical code has been developed to calculate Stokes parameters of the visible solar radiation, scattered in the atmosphere-ocean system. Mathematical modeling is used to examine spectral and angular (azimuth and zenith angle) variations of degree of polarization at sea level and at different heights in the atmosphere above the sea surface. On the basis of a developed computer code the efficiency of the polarization measurements for different optical passive remote sensing techniques of the ocean has been investigated. For the passive spectral measurements of the water bio-productivity (chlorophyll-a, dissolved organic matter, concentration of suspended particles) the polarizer can improve signal-to-background ratio. The magnitude of this effect and optimum direction of the polarizer depend upon height, viewing direction, and solar zenith angle. Within the framework of polarization remote sensing technique the influence of the observation height and viewing direction on the results of water turbidity measurements is investigated. Optimal viewing directions in such polarization passive remote sensing technique are discussed.

  19. An inexpensive active optical remote sensing instrument for assessing aerosol distributions.

    PubMed

    Barnes, John E; Sharma, Nimmi C P

    2012-02-01

    Air quality studies on a broad variety of topics from health impacts to source/sink analyses, require information on the distributions of atmospheric aerosols over both altitude and time. An inexpensive, simple to implement, ground-based optical remote sensing technique has been developed to assess aerosol distributions. The technique, called CLidar (Charge Coupled Device Camera Light Detection and Ranging), provides aerosol altitude profiles over time. In the CLidar technique a relatively low-power laser transmits light vertically into the atmosphere. The transmitted laser light scatters off of air molecules, clouds, and aerosols. The entire beam from ground to zenith is imaged using a CCD camera and wide-angle (100 degree) optics which are a few hundred meters from the laser. The CLidar technique is optimized for low altitude (boundary layer and lower troposphere) measurements where most aerosols are found and where many other profiling techniques face difficulties. Currently the technique is limited to nighttime measurements. Using the CLidar technique aerosols may be mapped over both altitude and time. The instrumentation required is portable and can easily be moved to locations of interest (e.g. downwind from factories or power plants, near highways). This paper describes the CLidar technique, implementation and data analysis and offers specifics for users wishing to apply the technique for aerosol profiles.

  20. Modern fibre-optic coherent lidars for remote sensing

    NASA Astrophysics Data System (ADS)

    Hill, Chris

    2015-10-01

    This paper surveys some growth areas in optical sensing that exploit near-IR coherent laser sources and fibreoptic hardware from the telecoms industry. Advances in component availability and performance are promising benefits in several military and commercial applications. Previous work has emphasised Doppler wind speed measurements and wind / turbulence profiling for air safety, with recent sharp increases in numbers of lidar units sold and installed, and with wider recognition that different lidar / radar wavebands can and should complement each other. These advances are also enabling fields such as microDoppler measurement of sub-wavelength vibrations and acoustic waves, including non-lineof- sight acoustic sensing in challenging environments. To shed light on these different applications we review some fundamentals of coherent detection, measurement probe volume, and parameter estimation - starting with familiar similarities and differences between "radar" and "laser radar". The consequences of changing the operating wavelength by three or four orders of magnitude - from millimetric or centimetric radar to a typical fibre-optic lidar working near 1.5 μm - need regular review, partly because of continuing advances in telecoms technology and computing. Modern fibre-optic lidars tend to be less complicated, more reliable, and cheaper than their predecessors; and they more closely obey the textbook principles of easily adjusted and aligned Gaussian beams. The behaviours of noises and signals, and the appropriate processing strategies, are as expected different for the different wavelengths and applications. For example, the effective probe volumes are easily varied (e.g. by translating a fibre facet) through six or eight orders of magnitude; as the average number of contributing scatterers varies, from <<1 through ~1 to >>1, we should review any assumptions about "many" scatterers and Gaussian statistics. Finally, some much older but still relevant scientific

  1. Strain-independent temperature measurement by use of a fluorescence intensity ratio technique in optical fiber.

    PubMed

    Wade, S A; Collins, S F; Grattan, K T; Baxter, G W

    2000-06-20

    The strain sensitivity of the fluorescence intensity ratio temperature-sensing technique has been measured to be (2 +/- 3) x 10(-4)%/muepsilon in Yb3+-doped fiber, implying a temperature-to-strain cross sensitivity of (2 +/- 3) x 10(-4) degrees C/muepsilon. The near-zero strain sensitivity means that this optical-fiber sensor technique is well suited for temperature measurement in strain-affected environments.

  2. Optical fiber sensing of corroded materials with evanescent wave absorption measurements

    NASA Astrophysics Data System (ADS)

    Namkung, Juock; Schwartz, Andy

    2012-06-01

    This research effort is to demonstrate a remote sensing method using optical fibers with a Fourier Transform Infrared (FTIR) interferometer as an evanescent wave spectroscopic technique. In addition to the usual advantages of optical fiber sensors, such as small size and weight, optical fibers can be embedded in aircraft structures in locations where humidity and corrosion can accumulate but cannot be directly observed. A fiber-optic-FTIR experimental setup, including several samples of field corroded materials, has been assembled to spectrally detect Aluminum Hydroxide [Al(OH)3] which is one of the major components of aluminum corrosion. Absorption spectra of Al(OH)3 have been collected using an Attenuated Total Reflection (ATR) crystal as a reference spectral signature. The absorption spectra of samples from a simulated corrosion process and from the field corroded structures have been collected and compared with the reference Al(OH)3 spectra. Chalcogenide optical fibers are used for remote sensing purposes to detect corrosion. Two distinctive absorption peaks, attributable to aluminum hydroxide, are noticed from the simulated corrosion and from the field corroded structures.

  3. Recent progress in multidimensional optical sensing and imaging systems (MOSIS)

    NASA Astrophysics Data System (ADS)

    Shen, Xin; Javidi, Bahram

    2017-05-01

    We present recent progress of the previously reported Multidimensional Optical Sensing and Imaging Systems (MOSIS) 2.0 for target recognition, material inspection and integrated visualization. The degrees of freedom of MOSIS 2.0 include three-dimensional (3D) imaging, polarimetric imaging and multispectral imaging. Each of these features provides unique information about a scene. 3D computationally reconstructed images mitigate the occlusion in front of the object, which can be used for 3D object recognition. The degree of polarization (DoP) of the light reflected from object surface is measured by 3D polarimetric imaging. Multispectral imaging is able to segment targets with specific spectral properties.

  4. Fiber-Optic Photoelastic Device Senses Pressure Of Hot Gas

    NASA Technical Reports Server (NTRS)

    Redner, Alex S.; Wesson, L. N.

    1995-01-01

    Fiber-optic/photoelastic device measures gas pressures up to 600 psi at operating temperatures as high as 1,100 degrees C. Pressure on fused-silica sensing element gives rise to birefringence via photoelastic effect. Polarization of light changed by birefringence; change in polarization measured and used to infer pressure causing it. Device prototype of gas-pressure sensor for aircraft engine. Mounted in engine at or near desired measurement point, where it responds to both time-varying and steady components of pressure.

  5. Condition monitoring of a subsea pump using fibre optic sensing

    NASA Astrophysics Data System (ADS)

    Jones, Kevin; Staveley, Chris; Vialla, Jean-Francois

    2014-05-01

    With the growth in deep-water oil and gas production, condition monitoring of high-value subsea assets to give early warning of developing problems is vital. Offshore operators can then transport and deploy spare parts before a failure occurs thus minimizing equipment down- time. Results are presented from a suite of tests in which multiple elements of a subsea twin-screw pump were monitored using a single fibre optic sensing system that simultaneously measured dynamic strain on the main rotor bearings, pressure and temperature of the lube oil, distributed temperature through the motor stator windings and vibration of the motor housing.

  6. Inverse Problems in Optical Remote Sensing of Coastal Waters

    DTIC Science & Technology

    2008-01-01

    Optics-2006”, St. Petersburg, Russia, 2006, p. 304-308 [published]. 4. L. Dolin, A. Luchinin, V. Titov , D. Turlaev. Using sea surface images for...pages) [refereed, published]. 8. L.S. Dolin, A.G. Luchinin, V.I. Titov , D.G. Turlaev. Correcting images of underwater objects distorted by sea surface...E.M. Zuikova, V.Yu. Karaev, E. Meshkov, and V.I. Titov . Investigation of possibility of sea roughness remote sensing from the sun glitter aria

  7. New scanning technique for the optical vortex microscope.

    PubMed

    Augustyniak, Ireneusz; Popiołek-Masajada, Agnieszka; Masajada, Jan; Drobczyński, Sławomir

    2012-04-01

    In the optical vortex microscopy the focused Gaussian beam with optical vortex scans a sample. An optical vortex can be introduced into a laser beam with the use of a special optical element--a vortex lens. When moving the vortex lens, the optical vortex changes its position inside the spot formed by a focused laser beam. This effect can be used as a new precise scanning technique. In this paper, we study the optical vortex behavior at the sample plane. We also estimate if the new scanning technique results in observable effects that could be used for a phase object detection.

  8. High spatial resolution distributed sensing in optical fibers by Brillouin gain-profile tracing.

    PubMed

    Sperber, Tom; Eyal, Avishay; Tur, Moshe; Thévenaz, Luc

    2010-04-12

    A novel BOTDA technique for distributed sensing of the Brillouin frequency in optical fibers with cm-order spatial resolution is proposed. The technique is based upon a simple modulation scheme, requiring only a single long pump pulse for acoustic excitation, and no subsequent interrogating pulse. Instead, the desired spatial mapping of the Brillouin response is extracted by taking the derivative of the probe signal. As a result, the spatial resolution is limited by the fall-time of the pump modulation, and the phenomena of secondary "echo" signals, typically appearing in BOTDA sensing methods based upon pre-excitation, is mitigated. Experimental demonstration of the detection of a Brillouin frequency variation significantly smaller than the natural Brillouin linewidth, with a 2cm spatial resolution, is presented.

  9. Remote sensing of atmospheric winds using speckleturbulence interaction, a CO(2) laser, and optical heterodyne detection.

    PubMed

    Holmes, J F; Amzajerdian, F; Gudimetla, R V; Hunt, J M

    1988-06-15

    Speckle-turbulence interaction can be utilized to measure the vector wind in a plane perpendicular to the line of sight from a laser transmitter to a target. A continuous wave source of around 1 W and operating at 10.6 microm, in conjunction with an optical heterodyne receiver, has been used to measure atmospheric winds along horizontal paths. A theoretical basis, the experimental apparatus, processing techniques, and experimental results are presented. The technique has been demonstrated for remote sensing of atmospheric winds along horizontal paths but also has potential for global remote sensing of atmospheric winds and for onboard wind shear detection systems for aircraft. The results show that rms accuracies of the order of 0.5 m/s are possible with averaging times as short as 2 s.

  10. A Remote Sensing Technique For Combustion Gas Temperature Measurement In Black Liquor Recovery Boilers

    NASA Astrophysics Data System (ADS)

    Charagundla, S. R.; Semerjian, H. G.

    1986-10-01

    A remote sensing technique, based on the principles of emission spectroscopy, is being developed for temperature measurements in black liquor recovery boilers. Several tests have been carried out, both in the laboratory and at a number of recovery boilers, to characterize the emission spectra in the wavelength range of 300 nm to 800 nm. These tests have pointed out the potential for temperature measurements using the line intensity ratio technique based on a pair of emission lines at 404.4 nm and 766.5 nm observed in the recovery boiler combustion zone; these emission lines are due to potassium, a common constituent found in all the black liquors. Accordingly, a fiber optics based four-color system has been developed. This in-situ, nonintrusive temperature measurement technique, together with some of the more recent results, is described in this paper.

  11. Measurement of optical fiber sensing parameter using FBG with WDM

    NASA Astrophysics Data System (ADS)

    Yan, Huanhuan; Wang, Li; Peng, Zhaozhuang; Hu, Shuyang

    2016-11-01

    In this experiment, the optical parameters of optical fiber sensing measurements with the wavelength division multiplexer (WDM) and Fiber Bragg grating have obtained in temperature-controlled cabinet. The wavelength division multiplexer device not only make different wavelength illuminant input at the same time be possible, but also can achieve multi-channel output based on the feature of WDM. We design and put forward a new method which can realize various parameters measured at the same time, such as temperature and the refractive index or stress measurement. In addition, it can measure the same parameters with different wavelengths of laser at the same time. The contrast analysis results of different wavelengths of illuminant on the same parameter sensitivity and reliability of the measurement will use to provide reference to design the same illuminant with different parameter measurements.

  12. Optical microfiber mode interferometer for temperature-independent refractometric sensing.

    PubMed

    Salceda-Delgado, G; Monzon-Hernandez, D; Martinez-Rios, A; Cardenas-Sevilla, G A; Villatoro, J

    2012-06-01

    We report on a functional optical microfiber mode interferometer and its applications for absolute, temperature-insensitive refractive index sensing. A standard optical fiber was tapered down to 10 μm. The central part of the taper, i.e., the microfiber, is connected to the untapered regions with two identical abrupt transitions. The transmission spectrum of our device exhibited a sinusoidal pattern due to the beating between modes. In our interferometer the period of the pattern-an absolute parameter-depends strongly on the surrounding refractive index but it is insensitive to temperature changes. The period, hence the external index, can be accurately measured by taking the fast Fourier transform (FFT) of the detected interference pattern. The measuring refractive index range of the device here proposed goes from 1.33 to 1.428 and the maximum resolution is on the order of 3.7×10(-6).

  13. Optical and optomechanical resonators and their applications in communication and sensing

    NASA Astrophysics Data System (ADS)

    Liu, Fenfei

    combination of resonant optical sensing with optomechanical sensing in a single device. This so-called "dual-mode" sensing can be a powerful technique for measuring the properties (mass, density and refractive index) of micro/nano-particles and molecules. To boost the optical sensitivity of the dual-mode sensor, we also demonstrate a dynamic sensing method where the resonant photonic sensitivity is improved by over 50 times through thermally induced line narrowing.

  14. New Optical Sensing Materials for Application in Marine Research

    NASA Astrophysics Data System (ADS)

    Borisov, S.; Klimant, I.

    2012-04-01

    Optical chemosensors are versatile analytical tools which find application in numerous fields of science and technology. They proved to be a promising alternative to electrochemical methods and are applied increasingly often in marine research. However, not all state-of-the- art optical chemosensors are suitable for these demanding applications since they do not fully fulfil the requirements of high luminescence brightness, high chemical- and photochemical stability or their spectral properties are not adequate. Therefore, development of new advanced sensing materials is still of utmost importance. Here we present a set of novel optical sensing materials recently developed in the Institute of Analytical Chemistry and Food Chemistry which are optimized for marine applications. Particularly, we present new NIR indicators and sensors for oxygen and pH which feature high brightness and low level of autofluorescence. The oxygen sensors rely on highly photostable metal complexes of benzoporphyrins and azabenzoporphyrins and enable several important applications such as simultaneous monitoring of oxygen and chlorophyll or ultra-fast oxygen monitoring (Eddy correlation). We also developed ulta-sensitive oxygen optodes which enable monitoring in nM range and are primary designed for investigation of oxygen minimum zones. The dynamic range of our new NIR pH indicators based on aza-BODIPY dyes is optimized for the marine environment. A highly sensitive NIR luminescent phosphor (chromium(III) doped yttrium aluminium borate) can be used for non-invasive temperature measurements. Notably, the oxygen, pH sensors and temperature sensors are fully compatible with the commercially available fiber-optic readers (Firesting from PyroScience). An optical CO2 sensor for marine applications employs novel diketopyrrolopyrrol indicators and enables ratiometric imaging using a CCD camera. Oxygen, pH and temperature sensors suitable for lifetime and ratiometric imaging of analytes

  15. A practical CO2 flux remote sensing technique

    NASA Astrophysics Data System (ADS)

    Queisser, Manuel; Burton, Mike

    2017-04-01

    An accurate quantification of CO2 flux from both natural and anthropogenic sources is of great interest in various areas of the Earth, environmental and atmospheric sciences. As emitted excess CO2 quickly dilutes into the 400 ppm ambient CO2 concentration and degassing often occurs diffusively, measuring CO2 fluxes is challenging. Therefore, fluxes are usually derived from grids of in-situ measurements, which are labour intensive measurements. Other than a safe measurement distance, remote sensing offers quick, spatially integrated and thus a more thorough measurement of gas fluxes. Active remote sensing combines these merits with operation independent of sunlight or clear sky conditions. Due to their weight and size, active remote sensing platforms for CO2, such as LIDAR, cannot easily be applied in the field or transported overseas. Moreover, their complexity requires a rather lengthy setup procedure to be undertaken by skilled personal. To meet the need for a rugged, practical CO2 remote sensing technique to scan volcanic plumes, we have developed the CO2 LIDAR. It measures 1-D column densities of CO2 with sufficient sensitivity to reveal the contribution of magmatic CO2. The CO2 LIDAR has been mounted inside a small aircraft and used to measure atmospheric column CO2 concentrations between the aircraft and the ground. It was further employed on the ground, measuring CO2 emissions from mud volcanism. During the measurement campaign the CO2 LIDAR demonstrated reliability, portability, quick set-up time (10 to 15 min) and platform independence. This new technique opens the possibility of rapid, comprehensive surveys of point source, open-vent CO2 emissions, as well as emissions from more diffuse sources such as lakes and fumarole fields. Currently, within the proof-of-concept ERC project CarbSens, a further reduction in size, weight and operational complexity is underway with the goal to commercialize the platform. Areas of potential applications include fugitive

  16. Genetic optical design for a compressive sensing task

    NASA Astrophysics Data System (ADS)

    Horisaki, Ryoichi; Niihara, Takahiro; Tanida, Jun

    2016-10-01

    We present a sophisticated optical design method for reducing the number of photodetectors for a specific sensing task. The chosen design parameter is the point spread function, and the selected task is object recognition. The point spread function is optimized iteratively with a genetic algorithm for object recognition based on a neural network. In the experimental demonstration, binary classification of face and non-face datasets was performed with a single measurement using two photodetectors. A spatial light modulator operating in the amplitude modulation mode was provided in the imaging optics and was used to modulate the point spread function. In each generation of the genetic algorithm, the classification accuracy with a pattern displayed on the spatial light modulator was fed-back to the next generation to find better patterns. The proposed method increased the accuracy by about 30 % compared with a conventional imaging system in which the point spread function was the delta function. This approach is practically useful for compressing the cost, size, and observation time of optical sensors in specific applications, and robust for imperfections in optical elements.

  17. A Photostable Silicon Rhodamine Platform for Optical Voltage Sensing

    PubMed Central

    Huang, Yi-Lin; Walker, Alison S.; Miller, Evan W.

    2015-01-01

    This paper describes the design and synthesis of a photostable, far-red to near-infrared (NIR) platform for optical voltage sensing. We developed a new, sulfonated silicon rhodamine fluorophore and integrated it with a phenylenevinylene molecular wire to create a Berkeley Red Sensor of Transmembrane potential, or BeRST 1 (“burst”). BeRST 1 is the first member of a class of farred to NIR voltage sensitive dyes that make use of a photoinduced electron transfer (PeT) trigger for optical interrogation of membrane voltage. We show that BeRST 1 displays bright, membrane-localized fluorescence in living cells, high photostability, and excellent voltage sensitivity in neurons. Depolarization of the plasma membrane results in rapid fluorescence increases (24% ΔF/F per 100 mV). BeRST 1 can be used in conjunction with fluorescent stains for organelles, Ca2+ indicators, and voltage-sensitive fluorescent proteins. In addition, the red-shifted spectral profile of BeRST 1, relative to commonly employed optogenetic actuators like ChannelRhodopsin2 (ChR2), which require blue light, enables optical electrophysiology in neurons. The high speed, sensitivity, photostability and long-wavelength fluorescence profiles of BeRST 1 make it a useful platform for the non-invasive, optical dissection of neuronal activity. PMID:26237573

  18. [Research on symmetrical optical waveguide based surface plasmon resonance sensing with spectral interrogation].

    PubMed

    Zhang, Yi-long; Liu, Le; Guo, Jun; Zhang, Peng-fei; Guo, Ji-hua; Ma, Hui; He, Yong-hong

    2015-02-01

    Surface plasmon resonance (SPR) sensors with spectral interrogation can adopt fiber to transmit light signals, thus leaving the sensing part separated, which is very convenient for miniaturization, remote-sensing and on-site analysis. Symmetrical optical waveguide (SOW) SPR has the same refractive index of the-two buffer media layers adjacent to the metal film, resulting in longer propagation distance, deeper penetration depth and better performance compared to conventional SPR In the present paper, we developed a symmetrical optical, waveguide (SOW) SPR sensor with wavelength interrogation. In the system, MgF2-Au-MgF2 film was used as SOW module for glucose sensing, and a fiber based light source and detection was used in the spectral interrogation. In the experiment, a refractive index resolution of 2.8 x 10(-7) RIU in fluid protocol was acquired. This technique provides advantages of high resolution and could have potential use in compact design, on-site analysis and remote sensing.

  19. A hybrid fiber-optic sensing system for down-hole pressure and distributed temperature measurements

    NASA Astrophysics Data System (ADS)

    Chen, Ke; Zhou, Xinlei; Yang, Bokai; Peng, Wei; Yu, Qingxu

    2015-10-01

    A hybrid fiber-optic sensing technique, combining the extrinsic Fabry-Perot interferometer (EFPI) based pressure sensor with the incoherent optical frequency domain reflectometry (IOFDR) based distributed temperature sensor (DTS), is presented for down-hole measurements. By using a laser diode as the common light source, a highly integrated hybrid EFPI/DTS sensing system has been developed with a single fiber. With the injection current of the laser diode below lasing threshold, the broadband spontaneous emission light is used for EFPI based pressure sensing; while with the injection current above the threshold, the stimulated emission light is used for Raman based distributed temperature sensing. There is no overlap between the spectral range of the reflected light from the EFPI sensor and the spectral range of the Raman scattered light. Pressure and distributed temperature can thus be measured by using wavelength-division multiplexing (WDM) technology. Experimental results show that both the pressure and the distributed temperature are measured with little interference. Furthermore, the pressure measurement can be compensated by the measured temperature values.

  20. Surface diffusion studies by optical diffraction techniques

    SciTech Connect

    Xiao, X.D.

    1992-11-01

    The newly developed optical techniques have been combined with either second harmonic (SH) diffraction or linear diffraction off a monolayer adsorbate grating for surface diffusion measurement. Anisotropy of surface diffusion of CO on Ni(l10) was used as a demonstration for the second harmonic dim reaction method. The linear diffraction method, which possesses a much higher sensitivity than the SH diffraction method, was employed to study the effect of adsorbate-adsorbate interaction on CO diffusion on Ni(l10) surface. Results showed that only the short range direct CO-CO orbital overlapping interaction influences CO diffusion but not the long range dipole-dipole and CO-NI-CO interactions. Effects of impurities and defects on surface diffusion were further explored by using linear diffraction method on CO/Ni(110) system. It was found that a few percent S impurity can alter the CO diffusion barrier height to a much higher value through changing the Ni(110) surface. The point defects of Ni(l10) surface seem to speed up CO diffusion significantly. A mechanism with long jumps over multiple lattice distance initiated by CO filled vacancy is proposed to explain the observed defect effect.

  1. Optical techniques for determining dynamic material properties

    SciTech Connect

    Paisley, D.L.; Stahl, D.B.

    1996-12-31

    Miniature plates are laser-launched with a 10-Joule Nd:YAG for one-dimensional (1-D) impacts on to target materials much like gas gun experiments and explosive plane wave plate launch. By making the experiments small, flyer plates (3 mm diameter x 50 micron thick) and targets (10 mm diameter x 200 micron thick), 1-D impact experiments can be performed in a standard laser-optical laboratory with minimum confinement and collateral damage. The laser-launched plates do not require the traditional sabot on gas guns nor the explosives needed for explosive planewave lenses, and as a result are much more amenable to a wide variety of materials and applications. Because of the small size very high pressure gradients can be generated with relative ease. The high pressure gradients result in very high strains and strain rates that are not easily generated by other experimental methods. The small size and short shock duration (1 - 20 ns) are ideal for dynamically measuring bond strengths of micron-thick coatings. Experimental techniques, equipment, and dynamic material results are reported.

  2. Surface diffusion studies by optical diffraction techniques

    SciTech Connect

    Xiao, Xu -Dong

    1992-11-01

    The newly developed optical techniques have been combined with either second harmonic (SH) diffraction or linear diffraction off a monolayer adsorbate grating for surface diffusion measurement. Anisotropy of surface diffusion of CO on Ni(l10) was used as a demonstration for the second harmonic dim reaction method. The linear diffraction method, which possesses a much higher sensitivity than the SH diffraction method, was employed to study the effect of adsorbate-adsorbate interaction on CO diffusion on Ni(l10) surface. Results showed that only the short range direct CO-CO orbital overlapping interaction influences CO diffusion but not the long range dipole-dipole and CO-NI-CO interactions. Effects of impurities and defects on surface diffusion were further explored by using linear diffraction method on CO/Ni(110) system. It was found that a few percent S impurity can alter the CO diffusion barrier height to a much higher value through changing the Ni(110) surface. The point defects of Ni(l10) surface seem to speed up CO diffusion significantly. A mechanism with long jumps over multiple lattice distance initiated by CO filled vacancy is proposed to explain the observed defect effect.

  3. Real-time optimal sensing strategies for active control of optical systems

    NASA Astrophysics Data System (ADS)

    Moon, Suk-Min; Fowler, Leslie P.; Clark, Robert L.; Anderson, Eric H.

    2007-04-01

    The pointing and imaging performance of precision optical systems is degraded by disturbances on the system that create optical jitter. These disturbances can be caused by structural motion of optical components due to vibration sources that (1) originate within the optical system, (2) originate external to the system and are transmitted through the structural path in the environment, and (3) are air-induced vibrations from acoustic noise. Beam control systems can suppress optical jitter, and active control techniques can be used to extend performance by incorporating information from accelerometers, microphones, and other auxiliary sensors. In some applications, offline fixed gain controllers can be used to minimize jitter. However there are many applications in which a real-time adaptive control approach would yield improved optical performance. Often we would like the capability to adapt in real-time to a system which is time-varying or whose disturbances are non-stationary and hard to predict. In the presence of these harsh, ever-changing environments we would like to use every available tool to optimize performance. Improvements in control algorithms are important, but another potentially useful tool is a real-time adaptive control method employing optimal sensing strategies. In this approach, real-time updating of reference sensors is provided to minimize optical jitter. The technique selects an optimal subset of sensors to use as references from an array of possible sensor locations. The optimal, weighted reference sensor set is well correlated with the disturbance and when used with an adaptive control algorithm, results in improved line-of-sight jitter performance with less computational burden compared to a controller which uses multiple reference sensors. The proposed technique is applied to an experimental test bed in which multiple proof-mass actuators generate structural vibrations on a flexible plate. These vibrations are transmitted to an optical

  4. Quantitative and qualitative sensing techniques for biogenic volatile organic compounds and their oxidation products.

    PubMed

    Kim, Saewung; Guenther, Alex; Apel, Eric

    2013-07-01

    The physiological production mechanisms of some of the organics in plants, commonly known as biogenic volatile organic compounds (BVOCs), have been known for more than a century. Some BVOCs are emitted to the atmosphere and play a significant role in tropospheric photochemistry especially in ozone and secondary organic aerosol (SOA) productions as a result of interplays between BVOCs and atmospheric radicals such as hydroxyl radical (OH), ozone (O3) and NOX (NO + NO2). These findings have been drawn from comprehensive analysis of numerous field and laboratory studies that have characterized the ambient distribution of BVOCs and their oxidation products, and reaction kinetics between BVOCs and atmospheric oxidants. These investigations are limited by the capacity for identifying and quantifying these compounds. This review highlights the major analytical techniques that have been used to observe BVOCs and their oxidation products such as gas chromatography, mass spectrometry with hard and soft ionization methods, and optical techniques from laser induced fluorescence (LIF) to remote sensing. In addition, we discuss how new analytical techniques can advance our understanding of BVOC photochemical processes. The principles, advantages, and drawbacks of the analytical techniques are discussed along with specific examples of how the techniques were applied in field and laboratory measurements. Since a number of thorough review papers for each specific analytical technique are available, readers are referred to these publications rather than providing thorough descriptions of each technique. Therefore, the aim of this review is for readers to grasp the advantages and disadvantages of various sensing techniques for BVOCs and their oxidation products and to provide guidance for choosing the optimal technique for a specific research task.

  5. Channel estimation for OFDM system in atmospheric optical communication based on compressive sensing

    NASA Astrophysics Data System (ADS)

    Zhao, Qingsong; Hao, Shiqi; Geng, Hongjian; Sun, Han

    2015-10-01

    Orthogonal frequency division multiplexing (OFDM) technique applied to the atmospheric optical communication can improve data transmission rate, restrain pulse interference, and reduce effect of multipath caused by atmospheric scattering. Channel estimation, as one of the important modules in OFDM, has been investigated thoroughly and widely with great progress. In atmospheric optical communication system, channel estimation methods based on pilot are common approaches, such as traditional least-squares (LS) algorithm and minimum mean square error (MMSE) algorithm. However, sensitivity of the noise effects and high complexity of computation are shortcomings of LS algorithm and MMSE algorithm, respectively. Here, a new method based on compressive sensing is proposed to estimate the channel state information of atmospheric optical communication OFDM system, especially when the condition is closely associated with turbulence. Firstly, time-varying channel model is established under the condition of turbulence. Then, in consideration of multipath effect, sparse channel model is available for compressive sensing. And, the pilot signal is reconstructed with orthogonal matching tracking (OMP) algorithm, which is used for reconstruction. By contrast, the work of channel estimation is completed by LS algorithm as well. After that, simulations are conducted respectively in two different indexes -signal error rate (SER) and mean square error (MSE). Finally, result shows that compared with LS algorithm, the application of compressive sensing can improve the performance of SER and MSE. Theoretical analysis and simulation results show that the proposed method is reasonable and efficient.

  6. Investigation of remote sensing scale up for hot cell waste tank applications. CPAC optical moisture monitoring

    SciTech Connect

    Jones, P.L.

    1994-09-01

    This report discusses work done to investigate the feasibility of using non-contact optical absorption to remotely sense the surface moisture content of salt cake materials. Optical measurements were made in a dimensionally scaled setup to investigate this technique for in-situ waste tank applications. Moisture measurements were obtained from BY-104 simulant samples with 0 wt%, 10 wt%, and 20 wt% moisture content using the back-scattered light from a pulsed infrared optical parametric converter (OPC) laser source operating from 1.51 to 2.12 micron. An InGaAs detector, with 0.038 steradian solid angle (hemisphere = 6.28 steradians) collection angle was used to detect the back-scattered light. This work indicated that there was sufficient back-scatter from the BY-104 material to provide an indication of the surface moisture content.

  7. Optical power transfer and communication methods for wireless implantable sensing platforms

    NASA Astrophysics Data System (ADS)

    Mujeeb-U-Rahman, Muhammad; Adalian, Dvin; Chang, Chieh-Feng; Scherer, Axel

    2015-09-01

    Ultrasmall scale implants have recently attracted focus as valuable tools for monitoring both acute and chronic diseases. Semiconductor optical technologies are the key to miniaturizing these devices to the long-sought sub-mm scale, which will enable long-term use of these devices for medical applications. This can also enable the use of multiple implantable devices concurrently to form a true body area network of sensors. We demonstrate optical power transfer techniques and methods to effectively harness this power for implantable devices. Furthermore, we also present methods for optical data transfer from such implants. Simultaneous use of these technologies can result in miniaturized sensing platforms that can allow for large-scale use of such systems in real world applications.

  8. Optical power transfer and communication methods for wireless implantable sensing platforms.

    PubMed

    Mujeeb-U-Rahman, Muhammad; Adalian, Dvin; Chang, Chieh-Feng; Scherer, Axel

    2015-09-01

    Ultrasmall scale implants have recently attracted focus as valuable tools for monitoring both acute and chronic diseases. Semiconductor optical technologies are the key to miniaturizing these devices to the long-sought sub-mm scale, which will enable long-term use of these devices for medical applications. This can also enable the use of multiple implantable devices concurrently to form a true body area network of sensors. We demonstrate optical power transfer techniques and methods to effectively harness this power for implantable devices. Furthermore, we also present methods for optical data transfer from such implants. Simultaneous use of these technologies can result in miniaturized sensing platforms that can allow for large-scale use of such systems in real world applications.

  9. Tunnel-Site Selection by Remote Sensing Techniques

    DTIC Science & Technology

    A study of the role of remote sensing for geologic reconnaissance for tunnel-site selection was commenced. For this study, remote sensing was defined...conventional remote sensing . Future research directions are suggested, and the extension of remote sensing to include airborne passive microwave

  10. Integration of geological remote-sensing techniques in subsurface analysis

    USGS Publications Warehouse

    Taranik, James V.; Trautwein, Charles M.

    1976-01-01

    Geological remote sensing is defined as the study of the Earth utilizing electromagnetic radiation which is either reflected or emitted from its surface in wavelengths ranging from 0.3 micrometre to 3 metres. The natural surface of the Earth is composed of a diversified combination of surface cover types, and geologists must understand the characteristics of surface cover types to successfully evaluate remotely-sensed data. In some areas landscape surface cover changes throughout the year, and analysis of imagery acquired at different times of year can yield additional geological information. Integration of different scales of analysis allows landscape features to be effectively interpreted. Interpretation of the static elements displayed on imagery is referred to as an image interpretation. Image interpretation is dependent upon: (1) the geologist's understanding of the fundamental aspects of image formation, and (2.) his ability to detect, delineate, and classify image radiometric data; recognize radiometric patterns; and identify landscape surface characteristics as expressed on imagery. A geologic interpretation integrates surface characteristics of the landscape with subsurface geologic relationships. Development of a geologic interpretation from imagery is dependent upon: (1) the geologist's ability to interpret geomorphic processes from their static surface expression as landscape characteristics on imagery, (2) his ability to conceptualize the dynamic processes responsible for the evolution 6f interpreted geologic relationships (his ability to develop geologic models). The integration of geologic remote-sensing techniques in subsurface analysis is illustrated by development of an exploration model for ground water in the Tucson area of Arizona, and by the development of an exploration model for mineralization in southwest Idaho.

  11. Characterization of Flexible Copolymer Optical Fibers for Force Sensing Applications

    PubMed Central

    Krehel, Marek; Rossi, René M.; Bona, Gian-Luca; Scherer, Lukas J.

    2013-01-01

    In this paper, different polymer optical fibres for applications in force sensing systems in textile fabrics are reported. The proposed method is based on the deflection of the light in fibre waveguides. Applying a force on the fibre changes the geometry and affects the wave guiding properties and hence induces light loss in the optical fibre. Fibres out of three different elastic and transparent copolymer materials were successfully produced and tested. Moreover, the influence of the diameter on the sensing properties was studied. The detectable force ranges from 0.05 N to 40 N (applied on 3 cm of fibre length), which can be regulated with the material and the diameter of the fibre. The detected signal loss varied from 0.6% to 78.3%. The fibres have attenuation parameters between 0.16–0.25 dB/cm at 652 nm. We show that the cross-sensitivies to temperature, strain and bends are low. Moreover, the high yield strength (0.0039–0.0054 GPa) and flexibility make these fibres very attractive candidates for integration into textiles to form wearable sensors, medical textiles or even computing systems. PMID:24021967

  12. Characterization of flexible copolymer optical fibers for force sensing applications.

    PubMed

    Krehel, Marek; Rossi, René M; Bona, Gian-Luca; Scherer, Lukas J

    2013-09-09

    In this paper, different polymer optical fibres for applications in force sensing systems in textile fabrics are reported. The proposed method is based on the deflection of the light in fibre waveguides. Applying a force on the fibre changes the geometry and affects the wave guiding properties and hence induces light loss in the optical fibre. Fibres out of three different elastic and transparent copolymer materials were successfully produced and tested. Moreover, the influence of the diameter on the sensing properties was studied. The detectable force ranges from 0.05 N to 40 N (applied on 3 cm of fibre length), which can be regulated with the material and the diameter of the fibre. The detected signal loss varied from 0.6% to 78.3%. The fibres have attenuation parameters between 0.16-0.25 dB/cm at 652 nm. We show that the cross-sensitivies to temperature, strain and bends are low. Moreover, the high yield strength (0.0039-0.0054 GPa) and flexibility make these fibres very attractive candidates for integration into textiles to form wearable sensors, medical textiles or even computing systems.

  13. Hybrid micro-/nanogels for optical sensing and intracellular imaging

    PubMed Central

    Wu, Weitai; Zhou, Shuiqin

    2010-01-01

    Hybrid micro-/nanogels are playing an increasing important part in a diverse range of applications, due to their tunable dimensions, large surface area, stable interior network structure, and a very short response time. We review recent advances and challenges in the developments of hybrid micro-/nanogels toward applications for optical sensing of pH, temperature, glucose, ions, and other species as well as for intracellular imaging. Due to their unique advantages, hybrid micro-/nanogels as optical probes are attracting substantial interests for continuous monitoring of chemical parameters in complex samples such as blood and bioreactor fluids, in chemical research and industry, and in food quality control. In particular, their intracellular probing ability enables the monitoring of the biochemistry and biophysics of live cells over time and space, thus contributing to the explanation of intricate biological processes and the development of novel diagnoses. Unlike most other probes, hybrid micro-/nanogels could also combine other multiple functions into a single probe. The rational design of hybrid micro-/nanogels will not only improve the probing applications as desirable, but also implement their applications in new arenas. With ongoing rapid advances in bionanotechnology, the well-designed hybrid micro-/nanogel probes will be able to provide simultaneous sensing, imaging diagnosis, and therapy toward clinical applications. PMID:22110866

  14. Fiber optic humidity sensing with few layers molybdenum disulfide

    NASA Astrophysics Data System (ADS)

    Li, Dongquan; Lu, Huihui; Yu, Jianhui; Guan, Heyuan; Luo, Yunhan; Zhang, Jun; Wu, Zhuoqi; Chen, Zhe

    2016-04-01

    Because of high surface-to-volume ratio, few layers MoS2 material as a kind of 2D materials has been attracted more attention nowadays to be used for photonics devices. We investigated the performance of few-layer MoS2 when it is covered on a side polished fiber (SPF) to sense relative humidity (RH) of environments. The SPF was made by wheel side polishing method. The few layers MoS2 was deposited on the side polished surface to be a sensing material. As the environmental humidity changes, the output optical power of the all fiber sensor will change due to the interaction between evanescent field of fiber and MoS2 material. The change of output power of fiber sensor can reach 16.67dB in the relative humidity range of 40-85%. Experiments using the fiber sensor on human breathing have been made and the respondence has achieved. The experiments showed that the fiber sensor can be used in medical instruments. Key words: fiber sensor, side-polished fiber, humidity sensing, 2D material, MoS2.

  15. Optical sensing of the fatigue damage state of CFRP under realistic aeronautical load sequences.

    PubMed

    Zuluaga-Ramírez, Pablo; Arconada, Álvaro; Frövel, Malte; Belenguer, Tomás; Salazar, Félix

    2015-03-09

    We present an optical sensing methodology to estimate the fatigue damage state of structures made of carbon fiber reinforced polymer (CFRP), by measuring variations on the surface roughness. Variable amplitude loads (VAL), which represent realistic loads during aeronautical missions of fighter aircraft (FALSTAFF) have been applied to coupons until failure. Stiffness degradation and surface roughness variations have been measured during the life of the coupons obtaining a Pearson correlation of 0.75 between both variables. The data were compared with a previous study for Constant Amplitude Load (CAL) obtaining similar results. Conclusions suggest that the surface roughness measured in strategic zones is a useful technique for structural health monitoring of CFRP structures, and that it is independent of the type of load applied. Surface roughness can be measured in the field by optical techniques such as speckle, confocal perfilometers and interferometry, among others.

  16. Optical Sensing of the Fatigue Damage State of CFRP under Realistic Aeronautical Load Sequences

    PubMed Central

    Zuluaga-Ramírez, Pablo; Arconada, Álvaro; Frövel, Malte; Belenguer, Tomás; Salazar, Félix

    2015-01-01

    We present an optical sensing methodology to estimate the fatigue damage state of structures made of carbon fiber reinforced polymer (CFRP), by measuring variations on the surface roughness. Variable amplitude loads (VAL), which represent realistic loads during aeronautical missions of fighter aircraft (FALSTAFF) have been applied to coupons until failure. Stiffness degradation and surface roughness variations have been measured during the life of the coupons obtaining a Pearson correlation of 0.75 between both variables. The data were compared with a previous study for Constant Amplitude Load (CAL) obtaining similar results. Conclusions suggest that the surface roughness measured in strategic zones is a useful technique for structural health monitoring of CFRP structures, and that it is independent of the type of load applied. Surface roughness can be measured in the field by optical techniques such as speckle, confocal perfilometers and interferometry, among others. PMID:25760056

  17. Optical sensing elements for nitrogen dioxide (NO.sub.2) gas detection, a sol-gel method for making the sensing elements and fiber optic sensors incorporating nitrogen dioxide gas optical sensing elements

    DOEpatents

    Mechery, Shelly John; Singh, Jagdish P.

    2007-07-03

    A sensing element, a method of making a sensing element, and a fiber optic sensor incorporating the sensing element are described. The sensor can be used for the quantitative detection of NO.sub.2 in a mixture of gases. The sensing element can be made by incorporating a diazotizing reagent which reacts with nitrous ions to produce a diazo compound and a coupling reagent which couples with the diazo compound to produce an azo dye into a sol and allowing the sol to form an optically transparent gel. The sensing element changes color in the presence of NO.sub.2 gas. The temporal response of the absorption spectrum at various NO.sub.2 concentrations has also been recorded and analyzed. Sensors having different design configurations are described. The sensing element can detect NO.sub.2 gas at levels of parts per billion.

  18. Full-scale monitoring system for structural prestress loss based on distributed brillouin sensing technique

    NASA Astrophysics Data System (ADS)

    Chunguang, Lan; Liguang, Zhou; Zhiyu, Huo

    2017-08-01

    Prestress loss is critical to impact the safety of prestressed structures. Unfortunately, up to date, there are no qualified techniques to handle this issue due to the fact that it is too hard for sensors to survive the harsh construction environments and the time-dependent service life of the large-span prestressed structures. This paper proposes a novel technique to monitor prestress loss in prestressed beams using Brillouin optical fiber sensors. A novel smart steel strand based on the sensing technique of full-scale Brillouin optical fiber sensors was introduced. Two kinds of prestressed structure were used to verify the concept of monitoring prestress loss using smart steel strands. The prestress loss data have been taken by Brillouin optical fiber sensors. And the monitoring results agree well with those from the conventional sensors. The monitoring data can reveal both the full-scale distribution and the time history of prestress loss during the construction stage and also in-service phrase.

  19. Remote sensing techniques applied to seismic vulnerability assessment

    NASA Astrophysics Data System (ADS)

    Juan Arranz, Jose; Torres, Yolanda; Hahgi, Azade; Gaspar-Escribano, Jorge

    2016-04-01

    Advances in remote sensing and photogrammetry techniques have increased the degree of accuracy and resolution in the record of the earth's surface. This has expanded the range of possible applications of these data. In this research, we have used these data to document the construction characteristics of the urban environment of Lorca, Spain. An exposure database has been created with the gathered information to be used in seismic vulnerability assessment. To this end, we have used data from photogrammetric flights at different periods, using both orthorectified images in the visible and infrared spectrum. Furthermore, the analysis is completed using LiDAR data. From the combination of these data, it has been possible to delineate the building footprints and characterize the constructions with attributes such as the approximate date of construction, area, type of roof and even building materials. To carry out the calculation, we have developed different algorithms to compare images from different times, segment images, classify LiDAR data, and use the infrared data in order to remove vegetation or to compute roof surfaces with height value, tilt and spectral fingerprint. In addition, the accuracy of our results has been validated with ground truth data. Keywords: LiDAR, remote sensing, seismic vulnerability, Lorca

  20. Fibre optic system for biochemical and microbiological sensing

    NASA Astrophysics Data System (ADS)

    Penwill, L. A.; Slater, J. H.; Hayes, N. W.; Tremlett, C. J.

    2007-07-01

    This poster will discuss state-of-the-art fibre optic sensors based on evanescent wave technology emphasising chemophotonic sensors for biochemical reactions and microbe detection. Devices based on antibody specificity and unique DNA sequences will be described. The development of simple sensor devices with disposable single use sensor probes will be illustrated with a view to providing cost effective field based or point of care analysis of major themes such as hospital acquired infections or bioterrorism events. This presentation will discuss the nature and detection thresholds required, the optical detection techniques investigated, results of sensor trials and the potential for wider commercial application.

  1. Exceptional points enhance sensing in an optical microcavity

    NASA Astrophysics Data System (ADS)

    Chen, Weijian; Kaya Özdemir, Şahin; Zhao, Guangming; Wiersig, Jan; Yang, Lan

    2017-08-01

    Sensors play an important part in many aspects of daily life such as infrared sensors in home security systems, particle sensors for environmental monitoring and motion sensors in mobile phones. High-quality optical microcavities are prime candidates for sensing applications because of their ability to enhance light-matter interactions in a very confined volume. Examples of such devices include mechanical transducers, magnetometers, single-particle absorption spectrometers, and microcavity sensors for sizing single particles and detecting nanometre-scale objects such as single nanoparticles and atomic ions. Traditionally, a very small perturbation near an optical microcavity introduces either a change in the linewidth or a frequency shift or splitting of a resonance that is proportional to the strength of the perturbation. Here we demonstrate an alternative sensing scheme, by which the sensitivity of microcavities can be enhanced when operated at non-Hermitian spectral degeneracies known as exceptional points. In our experiments, we use two nanoscale scatterers to tune a whispering-gallery-mode micro-toroid cavity, in which light propagates along a concave surface by continuous total internal reflection, in a precise and controlled manner to exceptional points. A target nanoscale object that subsequently enters the evanescent field of the cavity perturbs the system from its exceptional point, leading to frequency splitting. Owing to the complex-square-root topology near an exceptional point, this frequency splitting scales as the square root of the perturbation strength and is therefore larger (for sufficiently small perturbations) than the splitting observed in traditional non-exceptional-point sensing schemes. Our demonstration of exceptional-point-enhanced sensitivity paves the way for sensors with unprecedented sensitivity.

  2. Passive optical remote sensing of Congo River bathymetry using Landsat

    NASA Astrophysics Data System (ADS)

    Ache Rocha Lopes, V.; Trigg, M. A.; O'Loughlin, F.; Laraque, A.

    2014-12-01

    While there have been notable advances in deriving river characteristics such as width, using satellite remote sensing datasets, deriving river bathymetry remains a significant challenge. Bathymetry is fundamental to hydrodynamic modelling of river systems and being able to estimate this parameter remotely would be of great benefit, especially when attempting to model hard to access areas where the collection of field data is difficult. One such region is the Congo Basin, where due to past political instability and large scale there are few studies that characterise river bathymetry. In this study we test whether it is possible to use passive optical remote sensing to estimate the depth of the Congo River using Landsat 8 imagery in the region around Malebo Pool, located just upstream of the Kinshasa gauging station. Methods of estimating bathymetry using remotely sensed datasets have been used extensively for coastal regions and now more recently have been demonstrated as feasible for optically shallow rivers. Previous river bathymetry studies have focused on shallow rivers and have generally used aerial imagery with a finer spatial resolution than Landsat. While the Congo River has relatively low suspended sediment concentration values the application of passive bathymetry estimation to a river of this scale has not been attempted before. Three different analysis methods are tested in this study: 1) a single band algorithm; 2) a log ratio method; and 3) a linear transform method. All three methods require depth data for calibration and in this study area bathymetry measurements are available for three cross-sections resulting in approximately 300 in-situ measurements of depth, which are used in the calibration and validation. The performance of each method is assessed, allowing the feasibility of passive depth measurement in the Congo River to be determined. Considering the scarcity of in-situ bathymetry measurements on the Congo River, even an approximate

  3. Radial velocity data analysis with compressed sensing techniques

    NASA Astrophysics Data System (ADS)

    Hara, Nathan C.; Boué, G.; Laskar, J.; Correia, A. C. M.

    2017-01-01

    We present a novel approach for analysing radial velocity data that combines two features: all the planets are searched at once and the algorithm is fast. This is achieved by utilizing compressed sensing techniques, which are modified to be compatible with the Gaussian process framework. The resulting tool can be used like a Lomb-Scargle periodogram and has the same aspect but with much fewer peaks due to aliasing. The method is applied to five systems with published radial velocity data sets: HD 69830, HD 10180, 55 Cnc, GJ 876 and a simulated very active star. The results are fully compatible with previous analysis, though obtained more straightforwardly. We further show that 55 Cnc e and f could have been respectively detected and suspected in early measurements from the Lick Observatory and Hobby-Eberly Telescope available in 2004, and that frequencies due to dynamical interactions in GJ 876 can be seen.

  4. Advanced Doppler radar physiological sensing technique for drone detection

    NASA Astrophysics Data System (ADS)

    Yoon, Ji Hwan; Xu, Hao; Garcia Carrillo, Luis R.

    2017-05-01

    A 24 GHz medium-range human detecting sensor, using the Doppler Radar Physiological Sensing (DRPS) technique, which can also detect unmanned aerial vehicles (UAVs or drones), is currently under development for potential rescue and anti-drone applications. DRPS systems are specifically designed to remotely monitor small movements of non-metallic human tissues such as cardiopulmonary activity and respiration. Once optimized, the unique capabilities of DRPS could be used to detect UAVs. Initial measurements have shown that DRPS technology is able to detect moving and stationary humans, as well as largely non-metallic multi-rotor drone helicopters. Further data processing will incorporate pattern recognition to detect multiple signatures (motor vibration and hovering patterns) of UAVs.

  5. Shape Sensing Techniques for Continuum Robots in Minimally Invasive Surgery: A Survey.

    PubMed

    Shi, Chaoyang; Luo, Xiongbiao; Qi, Peng; Li, Tianliang; Song, Shuang; Najdovski, Zoran; Fukuda, Toshio; Ren, Hongliang

    2017-08-01

    Continuum robots provide inherent structural compliance with high dexterity to access the surgical target sites along tortuous anatomical paths under constrained environments and enable to perform complex and delicate operations through small incisions in minimally invasive surgery. These advantages enable their broad applications with minimal trauma and make challenging clinical procedures possible with miniaturized instrumentation and high curvilinear access capabilities. However, their inherent deformable designs make it difficult to realize 3-D intraoperative real-time shape sensing to accurately model their shape. Solutions to this limitation can lead themselves to further develop closely associated techniques of closed-loop control, path planning, human-robot interaction, and surgical manipulation safety concerns in minimally invasive surgery. Although extensive model-based research that relies on kinematics and mechanics has been performed, accurate shape sensing of continuum robots remains challenging, particularly in cases of unknown and dynamic payloads. This survey investigates the recent advances in alternative emerging techniques for 3-D shape sensing in this field and focuses on the following categories: fiber-optic-sensor-based, electromagnetic-tracking-based, and intraoperative imaging modality-based shape-reconstruction methods. The limitations of existing technologies and prospects of new technologies are also discussed.

  6. Applications of optical sensing for laser cutting and drilling.

    PubMed

    Fox, Mahlen D T; French, Paul; Peters, Chris; Hand, Duncan P; Jones, Julian D C

    2002-08-20

    Any reliable automated production system must include process control and monitoring techniques. Two laser processing techniques potentially lending themselves to automation are percussion drilling and cutting. For drilling we investigate the performance of a modification of a nonintrusive optical focus control system we previously developed for laser welding, which exploits the chromatic aberrations of the processing optics to determine focal error. We further developed this focus control system for closed-loop control of laser cutting. We show that an extension of the technique can detect deterioration in cut quality, and we describe practical trials carried out on different materials using both oxygen and nitrogen assist gas. We base our techniques on monitoring the light generated by the process, captured nonintrusively by the effector optics and processed remotely from the workpiece. We describe the relationship between the temporal and the chromatic modulation of the detected light and process quality and show how the information can be used as the basis of a process control system.

  7. Applications of optical sensing for laser cutting and drilling

    NASA Astrophysics Data System (ADS)

    Fox, Mahlen D. T.; French, Paul; Peters, Chris; Hand, Duncan P.; Jones, Julian D. C.

    2002-08-01

    Any reliable automated production system must include process control and monitoring techniques. Two laser processing techniques potentially lending themselves to automation are percussion drilling and cutting. For drilling we investigate the performance of a modification of a nonintrusive optical focus control system we previously developed for laser welding, which exploits the chromatic aberrations of the processing optics to determine focal error. We further developed this focus control system for closed-loop control of laser cutting. We show that an extension of the technique can detect deterioration in cut quality, and we describe practical trials carried out on different materials using both oxygen and nitrogen assist gas. We base our techniques on monitoring the light generated by the process, captured nonintrusively by the effector optics and processed remotely from the workpiece. We describe the relationship between the temporal and the chromatic modulation of the detected light and process quality and show how the information can be used as the basis of a process control system.

  8. Closed-loop adaptive optics using a spatial light modulator for sensing and compensating of optical aberrations in ophthalmic applications

    NASA Astrophysics Data System (ADS)

    Akondi, Vyas; Jewel, Md. Atikur Rahman; Vohnsen, Brian

    2014-09-01

    Sensing and compensating of optical aberrations in closed-loop mode using a single spatial light modulator (SLM) for ophthalmic applications is demonstrated. Notwithstanding the disadvantages of the SLM, in certain cases, this multitasking capability of the device makes it advantageous over existing deformable mirrors (DMs), which are expensive and in general used for aberration compensation alone. A closed-loop adaptive optics (AO) system based on a single SLM was built. Beam resizing optics were used to utilize the large active area of the device and hence make it feasible to generate 137 active subapertures for wavefront sensing. While correcting Zernike aberrations up to fourth order introduced with the help of a DM (for testing purposes), diffraction-limited resolution was achieved. It is shown that matched filter and intensity-weighted centroiding techniques stand out among others. Closed-loop wavefront correction of aberrations in backscattered light from the eyes of three healthy human subjects was demonstrated after satisfactory results were obtained using an artificial eye, which was simulated with a short focal length lens and a sheet of white paper as diffuser. It is shown that the closed-loop AO system based on a single SLM is capable of diffraction-limited correction for ophthalmic applications.

  9. Diode laser interrogated single-mode fiber optics with a hetero-core structure for a wearable glove sensing application

    NASA Astrophysics Data System (ADS)

    Nishiyama, M.; Sasaki, H.; Kubota, Y.; Watanabe, K.

    2008-10-01

    We have developed hetero-core fiber techniques interrogated with a semiconductor diode laser based on single-mode transmission for wearable glove sensing applications. The hetero-core fiber sensor is suitable for the wearable sensing glove because of the advantages of the capable optical intensity-based measurement with the excellent stability of the usage of the single-mode transmission fiber and independence of temperature fluctuation. In order that the hetero-core sensor was unaffected to the random wrinkles at the position of joints in a glove garment, the hetero-core sensor elements were located in the back of hand. As a result, the hetero-core flexion sensor could detect the joint angle of fingers regardless of differences of their size of hands, and the hetero-core sensing technique enables the sensing glove to equip the minimum number of sensors. The optical loss performances of the hetero-core sensors have indicated monotonic characteristics with the flexion angle of joints. The optical loss change is 1.35 dB for the flexion angle of approximately 97.2 degrees with accuracy of detectable flexion angle of 0.84 degree. Real-time hand motion capturing was successfully demonstrated by means of the proposed wearable sensing glove with hetero-core fiber techniques without restricting human natural behaviors.

  10. Exposed-core chalcogenide microstructured optical fibers for chemical sensing

    NASA Astrophysics Data System (ADS)

    Troles, Johann; Toupin, Perrine; Brilland, Laurent; Boussard-Plédel, Catherine; Bureau, Bruno; Cui, Shuo; Mechin, David; Adam, Jean-Luc

    2013-05-01

    Chemical bonds of most of the molecules vibrate at a frequency corresponding to the near or mid infrared field. It is thus of a great interest to develop sensitive and portable devices for the detection of specific chemicals and biomolecules for various applications in health, the environment, national security and so on. Optical fibers define practical sensing tools. Chalcogenide glasses are known for their transparency in the infrared optical range and their ability to be drawn as fibers. They are consequently good candidates to be used in biological/chemical sensing. For that matter, in the past decade, chalcogenide glass fibers have been successfully implemented in evanescent wave spectroscopy experiments, for the detection of bio-chemical species in various fields of applications including microbiology and medicine, water pollution and CO2 detection. Different types of fiber can be used: single index fibers or microstructured fibers. Besides, in recent years a new configuration of microstructured fibers has been developed: microstructured exposed-core fibers. This design consists of an optical fiber with a suspended micron-scale core that is partially exposed to the external environment. This configuration has been chosen to elaborate, using the molding method, a chalcogenide fiber for chemical species detection. The sensitivity of this fiber to detect molecules such as propan-2-ol and acetone has been compared with those of single index fibers. Although evanescent wave absorption is inversely proportional to the fiber diameter, the result shows that an exposed-core fiber is much more sensitive than a single index fiber having a twice smaller external diameter.

  11. Estimating Crop Growth Stage by Combining Meteorological and Remote Sensing Based Techniques

    NASA Astrophysics Data System (ADS)

    Champagne, C.; Alavi-Shoushtari, N.; Davidson, A. M.; Chipanshi, A.; Zhang, Y.; Shang, J.

    2016-12-01

    Estimations of seeding, harvest and phenological growth stage of crops are important sources of information for monitoring crop progress and crop yield forecasting. Growth stage has been traditionally estimated at the regional level through surveys, which rely on field staff to collect the information. Automated techniques to estimate growth stage have included agrometeorological approaches that use temperature and day length information to estimate accumulated heat and photoperiod, with thresholds used to determine when these stages are most likely. These approaches however, are crop and hybrid dependent, and can give widely varying results depending on the method used, particularly if the seeding date is unknown. Methods to estimate growth stage from remote sensing have progressed greatly in the past decade, with time series information from the Normalized Difference Vegetation Index (NDVI) the most common approach. Time series NDVI provide information on growth stage through a variety of techniques, including fitting functions to a series of measured NDVI values or smoothing these values and using thresholds to detect changes in slope that are indicative of rapidly increasing or decreasing `greeness' in the vegetation cover. The key limitations of these techniques for agriculture are frequent cloud cover in optical data that lead to errors in estimating local features in the time series function, and the incongruity between changes in greenness and traditional agricultural growth stages. There is great potential to combine both meteorological approaches and remote sensing to overcome the limitations of each technique. This research will examine the accuracy of both meteorological and remote sensing approaches over several agricultural sites in Canada, and look at the potential to integrate these techniques to provide improved estimates of crop growth stage for common field crops.

  12. Optical addressing technique for a CMOS RAM

    NASA Technical Reports Server (NTRS)

    Wu, W. H.; Bergman, L. A.; Allen, R. A.; Johnston, A. R.

    1988-01-01

    Progress on optically addressing a CMOS RAM for a feasibility demonstration of free space optical interconnection is reported in this paper. The optical RAM chip has been fabricated and functional testing is in progress. Initial results seem promising. New design and SPICE simulation of optical gate cell (OGC) circuits have been carried out to correct the slow fall time of the 'weak pull down' OGC, which has been characterized experimentally. Methods of reducing the response times of the photodiodes and the associated circuits are discussed. Even with the current photodiode, it appears that an OGC can be designed with a performance that is compatible with a CMOS circuit such as the RAM.

  13. Optical beam forming techniques for phased array antennas

    NASA Technical Reports Server (NTRS)

    Wu, Te-Kao; Chandler, Charles W.

    1993-01-01

    Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are 1) the fiber replacement of conventional RF phased array distribution and control components, 2) spatial beam forming, and 3) optical beam splitting techniques. Two novel optical beam forming approaches, i.e., the spatial beam forming with a 'smart pixel' spatial light modulator (SLM) and the optical beam splitting approaches are conceived with integrated quasi-optical components. Also presented are the transmit and receive array architectures with the new SLM.

  14. Locating illicit connections in storm water sewers using fiber-optic distributed temperature sensing.

    PubMed

    Hoes, O A C; Schilperoort, R P S; Luxemburg, W M J; Clemens, F H L R; van de Giesen, N C

    2009-12-01

    A newly developed technique using distributed temperature sensing (DTS) has been developed to find illicit household sewage connections to storm water systems in the Netherlands. DTS allows for the accurate measurement of temperature along a fiber-optic cable, with high spatial (2m) and temporal (30s) resolution. We inserted a fiber-optic cable of 1300m in two storm water drains. At certain locations, significant temperature differences with an intermittent character were measured, indicating inflow of water that was not storm water. In all cases, we found that foul water from households or companies entered the storm water system through an illicit sewage connection. The method of using temperature differences for illicit connection detection in storm water networks is discussed. The technique of using fiber-optic cables for distributed temperature sensing is explained in detail. The DTS method is a reliable, inexpensive and practically feasible method to detect illicit connections to storm water systems, which does not require access to private property.

  15. Quantitative molecular sensing in biological tissues: an approach to non-invasive optical characterization

    NASA Astrophysics Data System (ADS)

    Chandra, Malavika; Vishwanath, Karthik; Fichter, Greg D.; Liao, Elly; Hollister, Scott J.; Mycek, Mary-Ann

    2006-06-01

    A method to non-invasively and quantitatively characterize thick biological tissues by combining both experimental and computational approaches in tissue optical spectroscopy was developed and validated on fifteen porcine articular cartilage (AC) tissue samples. To the best of our knowledge, this study is the first to couple non-invasive reflectance and fluorescence spectroscopic measurements on freshly harvested tissues with Monte Carlo computational modeling of time-resolved propagation of both excitation light and multi-fluorophore emission. For reflectance, quantitative agreement between simulation and experiment was achieved to better than 11%. Fluorescence data and simulations were used to extract the ratio of the absorption coefficients of constituent fluorophores for each measured AC tissue sample. This ratio could be used to monitor relative changes in concentration of the constituent fluorophores over time. The samples studied possessed the complexity and variability not found in artificial tissue-simulating phantoms and serve as a model for future optical molecular sensing studies on tissue engineered constructs intended for use in human therapeutics. An optical technique that could non-invasively and quantitatively assess soft tissue composition or physiologic status would represent a significant advance in tissue engineering. Moreover, the general approach described here for optical characterization should be broadly applicable to quantitative, non-invasive molecular sensing applications in complex, three-dimensional biological tissues.

  16. Ground-based optical-remote-sensing results from 1981 ASCOT field experiment

    SciTech Connect

    Porch, W M

    1982-05-01

    Ground based optical remote sensing techniques provided the following major results from the 1981 ASCOT field experiment: spatial averaging cross-path optical anemometry provide down- and up-valley winds for two confluent valleys which merged near the tracer release site; comparison and analyses of these data show evidence for interaction of two valley systems during nighttime drainage wind conditions with each other as well as with mesoscale sea-breeze influences; the timing of transition periods of drainage initiation and cessation gave important clues to the nature of the drainage process; spatially averaged lapse-rates were determined at selected times during two drainage wind experiment nights; these data compared well with tethersonde temperature profile data and will in the future provide data useful for Richardson Number estimation; and qualitative data of plume behavior was observed using searchlight aided nighttime photographic techniques. It is hoped that the effects of multiple valley flow convergence will be studied using more optical anemometers to isolate the separate effects of (1) beam height above the valley, (2) the length of the optical path, (3) the horizontal distance of the measurement from the convergence region, (4) the fetch and slope of the valley and (5) the relative impact of external mesoscale wind flow patterns. Closer interaction between tethersonde, acoustic sounder, and optical anemometer is recommended to not only help the studies of valley wind convergence but also improve lapse-rate determination in complex terrain under drainage wind conditions.

  17. Cloud cover estimation optical package: New facility, algorithms and techniques

    NASA Astrophysics Data System (ADS)

    Krinitskiy, Mikhail

    2017-02-01

    Short- and long-wave radiation is an important component of surface heat budget over sea and land. For estimating them accurate observations of the cloud cover are needed. While massively observed visually, for building accurate parameterizations cloud cover needs also to be quantified using precise instrumental measurements. Major disadvantages of the most of existing cloud-cameras are associated with their complicated design and inaccuracy of post-processing algorithms which typically result in the uncertainties of 20% to 30% in the camera-based estimates of cloud cover. The accuracy of these types of algorithm in terms of true scoring compared to human-observed values is typically less than 10%. We developed new generation package for cloud cover estimating, which provides much more accurate results and also allows for measuring additional characteristics. New algorithm, namely SAIL GrIx, based on routine approach, also developed for this package. It uses the synthetic controlling index ("grayness rate index") which allows to suppress the background sunburn effect. This makes it possible to increase the reliability of the detection of the optically thin clouds. The accuracy of this algorithm in terms of true scoring became 30%. One more approach, namely SAIL GrIx ML, we have used to increase the cloud cover estimating accuracy is the algorithm that uses machine learning technique along with some other signal processing techniques. Sun disk condition appears to be a strong feature in this kind of models. Artificial Neural Networks type of model demonstrates the best quality. This model accuracy in terms of true scoring increases up to 95,5%. Application of a new algorithm lets us to modify the design of the optical sensing package and to avoid the use of the solar trackers. This made the design of the cloud camera much more compact. New cloud-camera has already been tested in several missions across Atlantic and Indian oceans on board of IORAS research vessels.

  18. Active Ground Optical Remote Sensing for Improved Monitoring of Seedling Stress in Nurseries

    USDA-ARS?s Scientific Manuscript database

    Active ground optical remote sensing (AGORS) devices mounted on overhead irrigation booms could help to improve seedling quality by autonomously monitoring seedling stress. In contrast to traditionally used passive optical sensors, AGORS devices operate independently of ambient light conditions and ...

  19. Optical link upgrade by DDMS technique with compensating fiber in optical cable closure

    NASA Astrophysics Data System (ADS)

    Burdin, Vladimir A.; Dashkov, Michael V.; Bourdine, Anton V.; Volkov, Kirill A.

    2010-01-01

    A well-known dense dispersion management soliton (DDMS) technique is applied to increase bandwidth of metropolitan area network fiber optic links. This technique requires an installation of optical cables with dispersion compensating fibers (DCFs), which leads to high costs for upgrading of installed fiber optic links. To become the DDMS more applicable, we propose to place DCFs in optical fiber closures. Here results of numerical simulations of optical pulse propagation and following bit-error-ratio estimation in fiber optic link with DCFs in optical closures are represented.

  20. High power compatible internally sensed optical phased array.

    PubMed

    Roberts, Lyle E; Ward, Robert L; Francis, Samuel P; Sibley, Paul G; Fleddermann, Roland; Sutton, Andrew J; Smith, Craig; McClelland, David E; Shaddock, Daniel A

    2016-06-13

    The technical embodiment of the Huygens-Fresnel principle, an optical phased array (OPA) is an arrangement of optical emitters with relative phases controlled to create a desired beam profile after propagation. One important application of an OPA is coherent beam combining (CBC), which can be used to create beams of higher power than is possible with a single laser source, especially for narrow linewidth sources. Here we present an all-fiber architecture that stabilizes the relative output phase by inferring the relative path length differences between lasers using the small fraction of light that is back-reflected into the fiber at the OPA's glass-air interface, without the need for any external sampling optics. This architecture is compatible with high power continuous wave laser sources (e.g., fiber amplifiers) up to 100 W per channel. The high-power compatible internally sensed OPA was implemented experimentally using commercial 15 W fiber amplifiers, demonstrating an output RMS phase stability of λ/194, and the ability to steer the beam at up to 10 kHz.

  1. Advances in fibre-optic sensing in medicine and biology

    NASA Astrophysics Data System (ADS)

    Rolfe, Peter; Scopesi, Fabio; Serra, Giovanni

    2007-06-01

    This paper presents a review of medical and biological applications of optical fibres, which span a wide range from light-pipes and pressure or displacement sensors through to complex chemical sensors. Coherent fibre bundles are needed for endoscopic imaging whilst single fibres may be used in both near infrared tomography and optical coherence tomography. Delivery of light to tissues, for example to activate targeted chemo-therapeutic agents (PDT), is also achieved conveniently with fibres. Chemical sensing can simply be achieved by transporting light to and from a measurement site with a plain fibre light guide for spectrophotometric or fluorimetry analysis. A further family of fibre-optic chemical sensors has either surface attached molecular recognition sites or a reaction chamber for achieving specific molecular detection. These chemical sensors may be based on the principles of surface plasmon resonance, interferometry, spectrophotometry or fluorimetry. Biological recognition with enzymes or antigen-antibody binding are used to achieve high specificity. The range of potential target molecules has increased rapidly over recent years from simple gases and ions through to large molecules such as DNA.

  2. HETERODYNE DETECTION IN OPTICAL COMMUNICATION TECHNIQUES

    DTIC Science & Technology

    difference frequency in the presence of incoherent noise. The use of heterodyne detection in optical communication , demultiplexing of channels, demodulation...of FM and AM, Doppler and displacement measurements, and stabilization of LASERs is discussed. The elements of an optical communication link are discussed: LASERs, modulators, transmission path, and detectors.

  3. Antifouling leaching technique for optical lenses

    USGS Publications Warehouse

    Strahle, William J.; Perez, C. L.; Martini, Marinna A.

    1994-01-01

    The effectiveness of optical lenses deployed in water less than 100 m deep is significantly reduced by biofouling caused by the settlement of macrofauna, such as barnacles, hydroids, and tunicates. However, machineable porous plastic rings can be used to dispense antifoulant into the water in front of the lens to retard macrofaunal growth without obstructing the light path. Unlike coatings which can degrade the optical performance, antifouling rings do not interfere with the instrument optics. The authors have designed plastic, reusable cup-like antifouling rings to slip over the optical lenses of a transmissometer. These rings have been used for several deployments on shallow moorings in Massachusetts Bay, MA and have increased the time before fouling degrades optical characteristics

  4. Thermal characterization of submicron polyacrylonitrile fibers based on optical heating and electrical thermal sensing

    SciTech Connect

    Hou Jinbo; Wang Xinwei; Zhang Lijun

    2006-10-09

    In this work, the thermal diffusivity of single submicron ({approx}800 nm) polyacrylonitrile (PAN) fibers is characterized using the recently developed optical heating and electrical thermal sensing technique. In the experiment, a thin Au film (approximately in the nanometer range) is coated on the surface of nonconductive PAN fibers. A periodically modulated laser beam is used to irradiate suspended individual fibers to achieve noncontact periodical heating. The periodical temperature response of the sample is monitored by measuring the electrical resistance variation of the thin Au coating. The experimental results for three different synthesized PAN fibers with varying Au coating thickness are presented and discussed.

  5. Extending the sensing range of Brillouin optical time-domain analysis up to 325 km combining four optical repeaters

    NASA Astrophysics Data System (ADS)

    Gyger, F.; Rochat, E.; Chin, S.; Niklès, M.; Thévenaz, L.

    2014-05-01

    A novel scheme is proposed to extend the sensing range of Brillouin optical time-domain analyzers (BOTDA). Specially-designed erbium doped fiber amplifier (EDFA) repeaters are located every 65km fiber along the sensing cable to achieve a total sensing length of 325km, corresponding to a 650km loop. At the end of the sensing fibre, we experimentally demonstrated a measurement repeatability of 2°C (2σ) using a three meters spatial resolution.

  6. Recyclable optical microcavities for label-free sensing

    NASA Astrophysics Data System (ADS)

    Hunt, Heather K.; Armani, Andrea M.

    2011-10-01

    High-sensitivity, label-free biosensors, such as optical microcavities, have shown tremendous potential in medical diagnostics, environmental monitoring, and food safety evaluation, particularly when paired with a biochemical recognition element that grants high specificity towards a target of interest. Their primary limitation is that these systems are single-use, unless the recognition element can be regenerated. Therefore, the ability to selectively functionalize the optical microcavity for a specific target molecule and then recycle the system, without degrading device performance, is extremely important. Here, we present a bioconjugation strategy that not only imparts specificity to optical microcavities, but also allows for biosensor recycling. In this approach, we selectively functionalize the surface of silica microtoroids with a biotin recognition element. We then use a non-destructive O2 plasma treatment to remove the surface chemistry, refresh the recognition element, and recycle the device. The surface chemistry and optical performance of the functionalized and recycled devices are characterized by microcavity analysis, and typical spectroscopic techniques, respectively. The resulting devices can be recycled several times without performance degradation, and show high density surface coverage of biologically active recognition elements. This work represents one of the first examples of a recyclable, bioconjugation strategy for optical microtoroid resonators.

  7. Remote sensing image denoising by using discrete multiwavelet transform techniques

    NASA Astrophysics Data System (ADS)

    Wang, Haihui; Wang, Jun; Zhang, Jian

    2006-01-01

    We present a new method by using GHM discrete multiwavelet transform in image denoising on this paper. The developments in wavelet theory have given rise to the wavelet thresholding method, for extracting a signal from noisy data. The method of signal denoising via wavelet thresholding was popularized. Multiwavelets have recently been introduced and they offer simultaneous orthogonality, symmetry and short support. This property makes multiwavelets more suitable for various image processing applications, especially denoising. It is based on thresholding of multiwavelet coefficients arising from the standard scalar orthogonal wavelet transform. It takes into account the covariance structure of the transform. Denoising of images via thresholding of the multiwavelet coefficients result from preprocessing and the discrete multiwavelet transform can be carried out by treating the output in this paper. The form of the threshold is carefully formulated and is the key to the excellent results obtained in the extensive numerical simulations of image denoising. We apply the multiwavelet-based to remote sensing image denoising. Multiwavelet transform technique is rather a new method, and it has a big advantage over the other techniques that it less distorts spectral characteristics of the image denoising. The experimental results show that multiwavelet based image denoising schemes outperform wavelet based method both subjectively and objectively.

  8. A Laboratory Experiment for Demonstrating Post-Coronagraph Wave Front Sensing and Control for Extreme Adaptive Optics

    NASA Technical Reports Server (NTRS)

    Wallace, J. Kent; Bartos, Randall; Rao, Shanti; Samuele, Rocco; Schmidtlin, Edouard

    2006-01-01

    Direct detection of exo-planets from the ground will become a reality with the advent of a new class of extreme-adaptive optics instruments that will come on-line within the next few years. In particular, the Gemini Observatory will be developing the Gemini Planet Imager (GPI) that will be used to make direct observations of young exo-planets. One major technical challenge in reaching the requisite high contrast at small angles is the sensing and control of residual wave front errors after the starlight suppression system. This paper will discuss the nature of this problem, and our approach to the sensing and control task. We will describe a laboratory experiment whose purpose is to provide a means of validating our sensing techniques and control algorithms. The experimental demonstration of sensing and control will be described. Finally, we will comment on the applicability of this technique to other similar high-contrast instruments.

  9. River flow forecasting in mountainous areas using remote sensing techniques

    NASA Astrophysics Data System (ADS)

    Ikweiri, Fathi Saleh

    The objective of this research is to develop a simple semi-distributed, physically based hydrologic model (SDPB_HM) for mountainous watershed areas. Most of the required watershed parameters in this developed model were acquired using remotely sensed imagery and digital terrain data. A modified technique to involve the use of the land cover properties in the Morton (1983) evapotranspiration model was proposed in this research. This new modified technique was proposed to overcome one of the major disadvantages of the Morton's evapotranspiration model for not having any allowances for the properties of different land cover types (Kite, 1997). The suitability of estimation the evapotranspiration using this modified technique was judged in this research by comparing its results with other average daily evapotranspiration data for an adjacent basin; Cross River Basin in the Rocky Mountain in British Columbia, Canada during year 1987. A new modified procedure for estimating maximum storage capacity in a basin that could estimate the retained rain or snowmelt water within the watershed area related to sink pixels on DTED was presented in this research. A simplified procedure for performing the geometric correction to satellite images based on the Oguro et al. (2001) technique that is used to register these images by utilizing a simulated shaded DTED overlaid with simulated streamlines network image was proposed in this work. A complete three-stage computer classifier (EBPANN) was built in this research that was aimed at minimizing the negative affect of overlapping spectral signatures. This developed computer classifier model was written in C computer program language and utilized in its procedures the error back-propagation neural network this proposed classifier technique was applied to classify a large part from Kananaskis Country area in the Rocky Mountains, Alberta, Canada. An enhanced method was employed in this work for dividing the watershed areas. This new

  10. Remote optical sensing on the nanometer scale with a bowtie aperture nano-antenna on a fiber tip of scanning near-field optical microscopy

    SciTech Connect

    Atie, Elie M.; Xie, Zhihua; El Eter, Ali; Salut, Roland; Baida, Fadi I.; Grosjean, Thierry; Nedeljkovic, Dusan; Tannous, Tony

    2015-04-13

    Plasmonic nano-antennas have proven the outstanding ability of sensing chemical and physical processes down to the nanometer scale. Sensing is usually achieved within the highly confined optical fields generated resonantly by the nano-antennas, i.e., in contact to the nanostructures. In this paper, we demonstrate the sensing capability of nano-antennas to their larger scale environment, well beyond their plasmonic confinement volume, leading to the concept of “remote” (non contact) sensing on the nanometer scale. On the basis of a bowtie-aperture nano-antenna (BNA) integrated at the apex of a SNOM (Scanning Near-field Optical Microscopy) fiber tip, we introduce an ultra-compact, moveable, and background-free optical nanosensor for the remote sensing of a silicon surface (up to distance of 300 nm). Sensitivity of the BNA to its large scale environment is high enough to expect the monitoring and control of the spacing between the nano-antenna and a silicon surface with sub-nanometer accuracy. This work paves the way towards an alternative class of nanopositioning techniques, based on the monitoring of diffraction-free plasmon resonance, that are alternative to nanomechanical and diffraction-limited optical interference-based devices.

  11. Optical techniques for industrial inspection; Proceedings of the Meeting, Quebec, Canada, June 4-6, 1986

    SciTech Connect

    Cielo, P.G.

    1986-01-01

    Papers on optical inspection in industry; hot-slab surface inspection by the laser scanning method; surface inspection based on stochastic modeling; a semiconductor processing technique based on Faraday rotation measurements using a CO/sub 2/ laser; an intelligent vision controller for circuits card lead inspection; and noncontacting optical measurement and inspection systems are presented. Topics discussed include optical sensing techniques for three-dimensional machine vision; the performance analysis of a three-dimensional sensor based on time-of-flight measurements; triangulation with large dynamical range; and recognition for three-dimensional surface shape using multiple distance features. Consideration is given to Raman spectroscopy applied to polymer analysis; an optical approach to the measurement of the lignin content of kraft pulps and of delignification in kraft pulping; diagnostics from imaging inside gas turbine combustors; and environmental-noise analysis in active-vision systems for adaptive welding.

  12. Close-Range Sensing Techniques in Alpine Terrain

    NASA Astrophysics Data System (ADS)

    Rutzinger, M.; Höfle, B.; Lindenbergh, R.; Oude Elberink, S.; Pirotti, F.; Sailer, R.; Scaioni, M.; Stötter, J.; Wujanz, D.

    2016-06-01

    Early career researchers such as PhD students are a main driving force of scientific research and are for a large part responsible for research innovation. They work on specialized topics within focused research groups that have a limited number of members, but might also have limited capacity in terms of lab equipment. This poses a serious challenge for educating such students as it is difficult to group a sufficient number of them to enable efficient knowledge transfer. To overcome this problem, the Innsbruck Summer School of Alpine Research 2015 on close-range sensing techniques in Alpine terrain was organized in Obergurgl, Austria, by an international team from several universities and research centres. Of the applicants a group of 40 early career researchers were selected with interest in about ten types of specialized surveying tools, i.e. laser scanners, a remotely piloted aircraft system, a thermal camera, a backpack mobile mapping system and different grade photogrammetric equipment. During the one-week summer school, students were grouped according to their personal preference to work with one such type of equipment under guidance of an expert lecturer. All students were required to capture and process field data on a mountain-related theme like landslides or rock glaciers. The work on the assignments lasted the whole week but was interspersed with lectures on selected topics by invited experts. The final task of the summer school participants was to present and defend their results to their peers, lecturers and other colleagues in a symposium-like setting. Here we present the framework and content of this summer school which brought together scientists from close-range sensing and environmental and geosciences.

  13. Highly Sensitive and Wide-Dynamic-Range Multichannel Optical-Fiber pH Sensor Based on PWM Technique

    PubMed Central

    Khan, Md. Rajibur Rahaman; Kang, Shin-Won

    2016-01-01

    In this study, we propose a highly sensitive multichannel pH sensor that is based on an optical-fiber pulse width modulation (PWM) technique. According to the optical-fiber PWM method, the received sensing signal’s pulse width changes when the optical-fiber pH sensing-element of the array comes into contact with pH buffer solutions. The proposed optical-fiber PWM pH-sensing system offers a linear sensing response over a wide range of pH values from 2 to 12, with a high pH-sensing ability. The sensitivity of the proposed pH sensor is 0.46 µs/pH, and the correlation coefficient R2 is approximately 0.997. Additional advantages of the proposed optical-fiber PWM pH sensor include a short/fast response-time of about 8 s, good reproducibility properties with a relative standard deviation (RSD) of about 0.019, easy fabrication, low cost, small size, reusability of the optical-fiber sensing-element, and the capability of remote sensing. Finally, the performance of the proposed PWM pH sensor was compared with that of potentiometric, optical-fiber modal interferometer, and optical-fiber Fabry–Perot interferometer pH sensors with respect to dynamic range width, linearity as well as response and recovery times. We observed that the proposed sensing systems have better sensing abilities than the above-mentioned pH sensors. PMID:27834865

  14. On-Chip High-Finesse Fabry-Perot Microcavities for Optical Sensing and Quantum Information

    PubMed Central

    Bitarafan, Mohammad H.; DeCorby, Ray G.

    2017-01-01

    For applications in sensing and cavity-based quantum computing and metrology, open-access Fabry-Perot cavities—with an air or vacuum gap between a pair of high reflectance mirrors—offer important advantages compared to other types of microcavities. For example, they are inherently tunable using MEMS-based actuation strategies, and they enable atomic emitters or target analytes to be located at high field regions of the optical mode. Integration of curved-mirror Fabry-Perot cavities on chips containing electronic, optoelectronic, and optomechanical elements is a topic of emerging importance. Micro-fabrication techniques can be used to create mirrors with small radius-of-curvature, which is a prerequisite for cavities to support stable, small-volume modes. We review recent progress towards chip-based implementation of such cavities, and highlight their potential to address applications in sensing and cavity quantum electrodynamics. PMID:28758967

  15. Ring-toric lens for focus-error sensing in optical data storage.

    PubMed

    Descour, M R; Simon, D I; Yeh, W H

    1999-03-10

    We discuss the design and performance of diffractive ring-toric lenses for focus-error sensing in optical data storage. A ring-toric lens images a point source of light to a ring-shaped image. Focus-error sensing is accomplished by means of monitoring the change in ring radius: The ring expands in response to a diverging wave front, and the ring contracts in response to a converging wave front. We describe the use of a segmented phi detector to generate a focus-error signal (FES). We found that the FES slope, a measure of sensitivity to disk defocus, is higher for the ring-toric lenses described in this paper than for other techniques such as the astigmatic and the obscuration methods. We measured an FES slope of 0.7 per micrometer of disk defocus (microm(-1)). The corresponding theoretical FES slope is 0.96 microm(-1).

  16. Force and optical position sensors: limitations of sensors and sensing systems in robotic applications

    SciTech Connect

    Isik, C.; Chenette, E.R.

    1982-01-01

    Sensory feedback as an element of intelligent control, and force sensing and visual sensing within a hierarchical sensor-controller system are discussed. A six-component force sensor designed and developed in CIMAR laboratories is the main issue of this paper. Its single beam mechanical structure is described and signal processing and conditioning circuitry is explained. Basic limitations of force measurement using strain gages are studied and related design criteria suggested. The second part of the paper deals with different optical distance measurement techniques, and concentrates on the conceptual designs of two innovative methods which utilize triangulation, laser interferometry, and pulse width modulated light beams. Some basic limitation analysis and a tentative work plan are also included in this part of the paper.

  17. Application of optical distributed sensing and computation to control of large space structures

    NASA Technical Reports Server (NTRS)

    Balakrishnan, A. V.

    1992-01-01

    A real time holographic sensing technique is introduced and its advantages are investigated from the filtering and control point of view. A feature of holographic sensing is its capability to make distributed measurements of the position and velocity of moving objects, such as a vibrating flexible space structure. This work is based upon the distributed parameter models of linear time invariant systems, particularly including the linear oscillator equations describing the vibration of large flexible space structures. The general conclusion is that application of optical distributed sensors bring gains in the situation where Kalman filtering is necessary for state estimation. In this case, both steady state and transient filtering error covariance become smaller. This in turn results in smaller cost in the LQG problem.

  18. On-Chip High-Finesse Fabry-Perot Microcavities for Optical Sensing and Quantum Information.

    PubMed

    Bitarafan, Mohammad H; DeCorby, Ray G

    2017-07-31

    For applications in sensing and cavity-based quantum computing and metrology, open-access Fabry-Perot cavities-with an air or vacuum gap between a pair of high reflectance mirrors-offer important advantages compared to other types of microcavities. For example, they are inherently tunable using MEMS-based actuation strategies, and they enable atomic emitters or target analytes to be located at high field regions of the optical mode. Integration of curved-mirror Fabry-Perot cavities on chips containing electronic, optoelectronic, and optomechanical elements is a topic of emerging importance. Micro-fabrication techniques can be used to create mirrors with small radius-of-curvature, which is a prerequisite for cavities to support stable, small-volume modes. We review recent progress towards chip-based implementation of such cavities, and highlight their potential to address applications in sensing and cavity quantum electrodynamics.

  19. Exposed core microstructured optical fiber Bragg gratings: refractive index sensing.

    PubMed

    Warren-Smith, Stephen C; Monro, Tanya M

    2014-01-27

    Bragg gratings have been written in exposed-core microstructured optical fibers for the first time using a femtosecond laser. Second and third order gratings have been written and both show strong reflectivity at 1550 nm, with bandwidths as narrow as 60 pm. Due to the penetration of the guided field outside the fiber the Bragg reflections are sensitive to the external refractive index. As different modes have different sensitivities to refractive index but the same temperature sensitivity the sensor can provide temperature-compensated refractive index measurements. Since these Bragg gratings have been formed by physical ablation, these devices can also be used for high temperature sensing, demonstrated here up to 800°C. The fibers have been spliced to single mode fiber for improved handling and integration with commercial interrogation units.

  20. Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles

    SciTech Connect

    Manigandan, R.; Suresh, R.; Giribabu, K.; Narayanan, V.; Vijayalakshmi, L.; Stephen, A.

    2014-01-28

    Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.

  1. Refractive index sensing using ultrasonically crushed polymer optical fibers

    NASA Astrophysics Data System (ADS)

    Shimada, Shumpei; Lee, Heeyoung; Shizuka, Makoto; Tanaka, Hiroki; Hayashi, Neisei; Matsumoto, Yukihiro; Tanaka, Yosuke; Nakamura, Hitoshi; Mizuno, Yosuke; Nakamura, Kentaro

    2017-01-01

    We demonstrate power-based refractive index (RI) sensing using an ultrasonically crushed polymer optical fiber (POF). This structure can be easily and cost-effectively fabricated within a short time (i.e., ˜1 s) without the need to employ external heat sources or chemicals. The only requirement is to simply press a horn connected to an ultrasonic transducer against part of the POF. The RI dependence of the transmitted power shows linear trends in RI ranges of ˜1.32 to ˜1.36 [coefficient: -62 dB/RIU (RI unit)] and ˜1.40 to ˜1.44 (coefficient: -257 dB/RIU). The temperature dependence of the transmitted power is also investigated.

  2. Perfluorinated plastic optical fiber tapers for evanescent wave sensing.

    PubMed

    Gravina, Roberto; Testa, Genni; Bernini, Romeo

    2009-01-01

    In this work we describe the fabrication and the characterization of perfluorinated plastic-cladded optical fiber tapers. The heat-and-pull procedure has been used to fabricate symmetric tapers. Devices with different taper ratio have been produced and the repeatability of the process has been verified. The very low refractive indexes of the core-cladding perfluorinated polymers (n = 1.35-1.34) permit a strong enhancement of the evanescent wave power fraction in aqueous environments (n = 1.33), making them very attractive for evanescent wave sensing. The tapers have been characterized carrying out evanescent field absorbance measurements with different concentrations of methylene blue in water and fluorescence collection measurements in an aqueous solution containing Cy5 dye. A good sensitivity, tightly related to the low refractive index of the core-cladding materials and the geometrical profile, has been shown.

  3. Perfluorinated Plastic Optical Fiber Tapers for Evanescent Wave Sensing

    PubMed Central

    Gravina, Roberto; Testa, Genni; Bernini, Romeo

    2009-01-01

    In this work we describe the fabrication and the characterization of perfluorinated plastic-cladded optical fiber tapers. The heat-and-pull procedure has been used to fabricate symmetric tapers. Devices with different taper ratio have been produced and the repeatability of the process has been verified. The very low refractive indexes of the core-cladding perfluorinated polymers (n = 1.35−1.34) permit a strong enhancement of the evanescent wave power fraction in aqueous environments (n = 1.33), making them very attractive for evanescent wave sensing. The tapers have been characterized carrying out evanescent field absorbance measurements with different concentrations of methylene blue in water and fluorescence collection measurements in an aqueous solution containing Cy5 dye. A good sensitivity, tightly related to the low refractive index of the core-cladding materials and the geometrical profile, has been shown. PMID:22303182

  4. Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Manigandan, R.; Suresh, R.; Giribabu, K.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2014-01-01

    Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.

  5. Fiber optic distributed temperature sensing for fire source localization

    NASA Astrophysics Data System (ADS)

    Sun, Miao; Tang, Yuquan; Yang, Shuang; Sigrist, Markus W.; Li, Jun; Dong, Fengzhong

    2017-08-01

    A method for localizing a fire source based on a distributed temperature sensor system is proposed. Two sections of optical fibers were placed orthogonally to each other as the sensing elements. A tray of alcohol was lit to act as a fire outbreak in a cabinet with an uneven ceiling to simulate a real scene of fire. Experiments were carried out to demonstrate the feasibility of the method. Rather large fluctuations and systematic errors with respect to predicting the exact room coordinates of the fire source caused by the uneven ceiling were observed. Two mathematical methods (smoothing recorded temperature curves and finding temperature peak positions) to improve the prediction accuracy are presented, and the experimental results indicate that the fluctuation ranges and systematic errors are significantly reduced. The proposed scheme is simple and appears reliable enough to locate a fire source in large spaces.

  6. Non-linear optical crystal vibration sensing device

    DOEpatents

    Kalibjian, R.

    1994-08-09

    A non-linear optical crystal vibration sensing device including a photorefractive crystal and a laser is disclosed. The laser produces a coherent light beam which is split by a beam splitter into a first laser beam and a second laser beam. After passing through the crystal the first laser beam is counter-propagated back upon itself by a retro-mirror, creating a third laser beam. The laser beams are modulated, due to the mixing effect within the crystal by vibration of the crystal. In the third laser beam, modulation is stable and such modulation is converted by a photodetector into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal. 3 figs.

  7. Non-linear optical crystal vibration sensing device

    DOEpatents

    Kalibjian, Ralph

    1994-01-11

    A non-linear optical crystal vibration sensing device (10) including a photorefractive crystal (26) and a laser (12). The laser (12 ) produces a coherent light beam (14) which is split by a beam splitter (18) into a first laser beam (20) and a second laser beam (22). After passing through the crystal (26) the first laser beam (20) is counter-propagated back upon itself by a retro-mirror (32), creating a third laser beam (30). The laser beams (20, 22, 30) are modulated, due to the mixing effect within the crystal (26) by vibration of the crystal (30). In the third laser beam (30), modulation is stable and such modulation is converted by a photodetector (34) into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal (26).

  8. Optical fiber sensor technique for strain measurement

    DOEpatents

    Butler, Michael A.; Ginley, David S.

    1989-01-01

    Laser light from a common source is split and conveyed through two similar optical fibers and emitted at their respective ends to form an interference pattern, one of the optical fibers having a portion thereof subjected to a strain. Changes in the strain cause changes in the optical path length of the strain fiber, and generate corresponding changes in the interference pattern. The interference pattern is received and transduced into signals representative of fringe shifts corresponding to changes in the strain experienced by the strained one of the optical fibers. These signals are then processed to evaluate strain as a function of time, typical examples of the application of the apparatus including electrodeposition of a metallic film on a conductive surface provided on the outside of the optical fiber being strained, so that strains generated in the optical fiber during the course of the electrodeposition are measurable as a function of time. In one aspect of the invention, signals relating to the fringe shift are stored for subsequent processing and analysis, whereas in another aspect of the invention the signals are processed for real-time display of the strain changes under study.

  9. Biomimetric sentinel reef structures for optical sensing and communications

    NASA Astrophysics Data System (ADS)

    Fries, David; Hutcheson, Tim; Josef, Noam; Millie, David; Tate, Connor

    2017-05-01

    Traditional artificial reef structures are designed with uniform cellular architectures and topologies and do not mimic natural reef forms. Strings and ropes are a proven, common fisheries and mariculture construction element throughout the world and using them as artificial reef scaffolding can enable a diversity of ocean sensing, communications systems including the goal of sentinel reefs. The architecture and packaging of electronics is key to enabling such structures and systems. The distributed sensor reef concept leads toward a demonstrable science-engineering-informed framework for 3D smart habitat designs critical to stock fish development and coastal monitoring and protection. These `nature-inspired' reef infrastructures, can enable novel instrumented `reef observatories' capable of collecting real-time ecosystem data. Embedding lighting and electronic elements into artificial reef systems are the first systems conceptualized. This approach of bringing spatial light to the underwater world for optical sensing, communication and even a new breed of underwater robotic vehicle is an interdisciplinary research activity which integrates principles of electronic packaging, and ocean technology with art/design.

  10. Relating remotely sensed optical variability to marine benthic biodiversity.

    PubMed

    Herkül, Kristjan; Kotta, Jonne; Kutser, Tiit; Vahtmäe, Ele

    2013-01-01

    Biodiversity is important in maintaining ecosystem viability, and the availability of adequate biodiversity data is a prerequisite for the sustainable management of natural resources. As such, there is a clear need to map biodiversity at high spatial resolutions across large areas. Airborne and spaceborne optical remote sensing is a potential tool to provide such biodiversity data. The spectral variation hypothesis (SVH) predicts a positive correlation between spectral variability (SV) of a remotely sensed image and biodiversity. The SVH has only been tested on a few terrestrial plant communities. Our study is the first attempt to apply the SVH in the marine environment using hyperspectral imagery recorded by Compact Airborne Spectrographic Imager (CASI). All coverage-based diversity measures of benthic macrophytes and invertebrates showed low but statistically significant positive correlations with SV whereas the relationship between biomass-based diversity measures and SV were weak or lacking. The observed relationships did not vary with spatial scale. SV had the highest independent effect among predictor variables in the statistical models of coverage-derived total benthic species richness and Shannon index. Thus, the relevance of SVH in marine benthic habitats was proved and this forms a prerequisite for the future use of SV in benthic biodiversity assessments.

  11. Remote sensing techniques for vegetation moisture and fire risk estimation

    NASA Astrophysics Data System (ADS)

    Dasgupta, Swarvanu

    This dissertation is aimed at evaluating and improving remote sensing techniques for vegetation moisture and fire risk estimation. Empirical retrievals of vegetation moisture using liquid water absorption based spectral indices such as the NDWI (Normalized Difference Water Index) and NDII (Normalized Difference Infrared Index) may have uncertainties, since these indices cannot fully normalize the reflectance variability due to other biophysical, biochemical, soil and illumination viewing geometry factors. Coupled leaf-canopy reflectance models, National Fire Danger Rating System data and the FARSITE fire behavior model were used to estimate the effect of Live Fuel Moisture Content (LFMC) retrieval uncertainties on fire spread rate predictions. The uncertainty estimation was focused on the Okefenokee National Wildlife Refuge where errors in LFMC retrievals using NDWI and NDII were shown to result in considerable fire spread rate prediction errors at lower LFMC levels. Soil reflectance contamination driven by soil moisture variability was identified as a problem causing errors in Vegetation Water Content (VWC) retrievals over low vegetation conditions. Analysis of canopy reflectance simulations from coupled soil-leaf-canopy reflectance models revealed that VWC isolines were curved and did not converge at the origin of the 1.64mum--0.86mum space. These were identified as causes for the soil moisture contamination of the spectral index NDII. As an improvement strategy an origin transformed NDII, called the SANDII (Soil Adjusted NDII) was designed to minimize soil contamination. Further separate regression models between VWC and the SANDII for different soil moisture classes were proposed to account for the curved nature of VWC isolines. The new technique which requires categorical soil moisture information was shown to reduce VWC estimation errors by about 20% over grassland conditions. The approach was supported using data collected over pastures during the Soil

  12. Sensor Performance Requirements for the Retrieval of Atmospheric Aerosols by Airborne Optical Remote Sensing

    PubMed Central

    Seidel, Felix; Schläpfer, Daniel; Nieke, Jens; Itten, Klaus I.

    2008-01-01

    This study explores performance requirements for the retrieval of the atmospheric aerosol optical depth (AOD) by airborne optical remote sensing instruments. Independent of any retrieval techniques, the calculated AOD retrieval requirements are compared with the expected performance parameters of the upcoming hyperspectral sensor APEX at the reference wavelength of 550nm. The AOD accuracy requirements are defined to be capable of resolving transmittance differences of 0.01 to 0.04 according to the demands of atmospheric corrections for remote sensing applications. For the purposes of this analysis, the signal at the sensor level is simulated by radiation transfer equations. The resulting radiances are translated into the AOD retrieval sensitivity (Δτλaer) and compared to the available measuring sensitivity of the sensor (NEΔLλsensor). This is done for multiple signal-to-noise ratios (SNR) and surface reflectance values. It is shown that an SNR of 100 is adequate for AOD retrieval at 550nm under typical remote sensing conditions and a surface reflectance of 10% or less. Such dark surfaces require the lowest SNR values and therefore offer the best sensitivity for measuring AOD. Brighter surfaces with up to 30% reflectance require an SNR of around 300. It is shown that AOD retrieval for targets above 50% surface reflectance is more problematic with the current sensor performance as it may require an SNR larger than 1000. In general, feasibility is proven for the analyzed cases under simulated conditions. PMID:27879801

  13. Sensor Performance Requirements for the Retrieval of Atmospheric Aerosols by Airborne Optical Remote Sensing.

    PubMed

    Seidel, Felix; Schläpfer, Daniel; Nieke, Jens; Itten, Klaus I

    2008-03-18

    This study explores performance requirements for the retrieval of the atmospheric aerosol optical depth (AOD) by airborne optical remote sensing instruments. Independent of any retrieval techniques, the calculated AOD retrieval requirements are compared with the expected performance parameters of the upcoming hyperspectral sensor APEX at the reference wavelength of 550nm. The AOD accuracy requirements are defined to be capable of resolving transmittance differences of 0.01 to 0.04 according to the demands of atmospheric corrections for remote sensing applications. For the purposes of this analysis, the signal at the sensor level is simulated by radiation transfer equations. The resulting radiances are translated into the AOD retrieval sensitivity (Δτλ(aer) ) and compared to the available measuring sensitivity of the sensor (NE ΔLλ(sensor)). This is done for multiple signal-to-noise ratios (SNR) and surface reflectance values. It is shown that an SNR of 100 is adequate for AOD retrieval at 550nm under typical remote sensing conditions and a surface reflectance of 10% or less. Such dark surfaces require the lowest SNR values and therefore offer the best sensitivity for measuring AOD. Brighter surfaces with up to 30% reflectance require an SNR of around 300. It is shown that AOD retrieval for targets above 50% surface reflectance is more problematic with the current sensor performance as it may require an SNR larger than 1000. In general, feasibility is proven for the analyzed cases under simulated conditions.

  14. Fiber-optic based gas sensing in the UV region

    NASA Astrophysics Data System (ADS)

    Eckhardt, H. S.; Graubner, K.; Klein, K.-F.; Sun, T.; Grattan, K. T. V.

    2006-02-01

    The precise analysis of potential hazardous components within gases and the detection of trace gases in exhaled breath for early and non invasive diagnosis of illnesses have a great influence on the well-being of human beings. Besides the existing analysis techniques, which mostly require sample preparation, costly consumables, huge space and skilled personal carrying out the measurement, a measurement system based on optical absorption in the UV wavelength region might offer alternatives to existing techniques. Within this work a feasibility study based on measurements of different test gases at lowest concentrations and requirements for trace gases in exhaled breath in respect to detection limits, signal-to-noise ratio and system drifts were analyzed. A spectral database including over 1000 UV vapor-phase spectra allows the identification of unknown compounds within a mixture, as well as expanding the use of the measurement technique into new areas of application, for example automobile application.

  15. Analyzing Fourier Transforms for NASA DFRC's Fiber Optic Strain Sensing System

    NASA Technical Reports Server (NTRS)

    Fiechtner, Kaitlyn Leann

    2010-01-01

    This document provides a basic overview of the fiber optic technology used for sensing stress, strain, and temperature. Also, the document summarizes the research concerning speed and accuracy of the possible mathematical algorithms that can be used for NASA DFRC's Fiber Optic Strain Sensing (FOSS) system.

  16. Reflection based Extraordinary Optical Transmission Fiber Optic Probe for Refractive Index Sensing.

    PubMed

    Lan, Xinwei; Cheng, Baokai; Yang, Qingbo; Huang, Jie; Wang, Hanzheng; Ma, Yinfa; Shi, Honglan; Xiao, Hai

    2014-03-31

    Fiber optic probes for chemical sensing based on the extraordinary optical transmission (EOT) phenomenon are designed and fabricated by perforating subwavelength hole arrays on the gold film coated optical fiber endface. The device exhibits a red shift in response to the surrounding refractive index increases with high sensitivity, enabling a reflection-based refractive index sensor with a compact and simple configuration. By choosing the period of hole arrays, the sensor can be designed to operate in the near infrared telecommunication wavelength range, where the abundant source and detectors are available for easy instrumentation. The new sensor probe is demonstrated for refractive index measurement using refractive index matching fluids. The sensitivity reaches 573 nm/RIU in the 1.333~1.430 refractive index range.

  17. Variable separation in curvature sensing: fast method for solving the irradiance transport equation in the context of optical telescopes.

    PubMed

    Salas, L

    1996-04-01

    A method to evaluate wave-front aberrations in optical telescopes that is based on the method of curvature sensing but that solves the irradiance transport equation by variable separation is presented. This technique is simpler for processing than are previously released techniques and can perform more efficiently, as is required by active and adaptive optics. Testing for consistency of the method by evaluation of several sets of out-of-focus images obtained with the 2-m telescope at the Universidad Nacional Autónoma de México was carried out, and a stability of 10% for the derived values of Zernike coefficients was found.

  18. Free space optical sensor network for fixed infrastructure sensing

    NASA Astrophysics Data System (ADS)

    Agrawal, Navik; Milner, Stuart D.; Davis, Christopher C.

    2009-08-01

    Free space optical (FSO) links for indoor sensor networks can provide data rates that can range from bits/s to hundreds of Mb/s. In addition, they offer physical security, and in contrast with omnidirectional RF networks, they avoid interference with other electronic systems. These features are advantageous for communication over short distances in fixed infrastructure sensor networks. In this paper the system architecture for a fixed infrastructure FSO sensor network is presented. The system includes a network of small, low power (mW), sensor systems, or "motes," that transmit data optically to a central "cluster head," which controls the network traffic of all the motes and can aggregate the sensor information. The cluster head is designed with multiple vertical cavity surface emitting lasers oriented in different directions and controlled to diverge at 12º in order to provide signal coverage over a wide field of view. Both the cluster head and motes form a local area network. Our system design focuses on low-power wireless motes that can maintain successful communication over distances up to a few meters without having to use stringent optical alignment techniques, and our network design focuses on controlling mote sleep cycles for energy efficiency. This paper presents the design as well as the experimental link and optical communications performance of a prototype FSO-based sensor network.

  19. Group and phase delay sensing for cophasing large optical arrays

    NASA Astrophysics Data System (ADS)

    Mourard, D.; Dali Ali, W.; Meilland, A.; Tarmoul, N.; Patru, F.; Clausse, J. M.; Girard, P.; Hénault, F.; Marcotto, A.; Mauclert, N.

    2014-12-01

    The next generation of optical interferometers will provide high-resolution imaging of celestial objects by using either the aperture synthesis technique or the direct imaging principle. To determine the technical requirements, we have developed an interferometric test bench, called SIRIUS. To preserve the quality of the image, fast corrections of the optical path differences within a fraction of a wavelength have to be applied: this is the cophasing of the array, whereas making it coherent aims at stabilizing the optical path differences within a fraction of the coherence length. In the SIRIUS test bench, coherence and cophasing are achieved by fibred delay lines. Air delay lines are also used for the raw delay equalization. We present an original implementation of a piston sensor, called chromatic phase diversity, which is adaptable to any interferometer, whatever the configuration of the entrance pupil and the number of sub-pupils and whatever the interferometric combiner. Our method is based on the dispersed fringes principle and uses a derived version of the dispersed speckles method. The numerical simulation shows the performance of the method in terms of cophasing, accuracy and limiting magnitude. Experimental tests have been carried out both with optical turbulence and without. They show good results in both cases, despite some instrument-related limitations that can be eliminated. We show that our method is able to handle an amplitude of correction of ±11(λ/2) with an accuracy of ˜λ/30 over many minutes.

  20. Application of fiber optic sensing technology in anchor monitoring

    NASA Astrophysics Data System (ADS)

    Liang, Lei; Jiang, Desheng; Sun, Dongya

    2000-05-01

    Prestressed steel anchors are widely adopted in the stabilization of rock slope engineering. To ensure the safety of the stabilization system, reliable monitoring techniques should be used to evaluate the operating state of the anchorage system. Fiber optical sensors can achieve the distribution detection of strain along the whole length of the optical fiber. Therefore it will be very suitable to embed optical fiber in motar, esp. concrete to perform strain measurement as well as crack detection. This paper reports the development of a simple intensity modulated fiber optic sensor for detecting internal cracks of concrete structures. This sensor is embedded in a 1-meter-long concrete beam and its reliability and feasibility tests were conducted by loading this beam to failure. Experiments for the embedded sensor show that incipience and propagation of concrete cracks can be well displayed by light intensity meter and the sensor can endure large deformation before it cracks and the maximum concrete crack width endured by the sensor can reach 5 mm.

  1. Noninvasive glucose sensing in scattering media using OCT, PAS, and TOF techniques

    NASA Astrophysics Data System (ADS)

    Alarousu, Erkki; Hast, Jukka T.; Kinnunen, Matti T.; Kirillin, Mikhail Y.; Myllyla, Risto A.; Plucinski, Jerzy; Popov, Alexey P.; Priezzhev, Alexander V.; Prykari, Tuukka; Saarela, Juha; Zhao, Zuomin

    2004-08-01

    In this paper, optical measurement techniques, which enable non-invasive measurement, are superimposed to glucose sensing in scattering media. Used measurement techniques are Optical Coherence Tomography (OCT), Photoacoustic spectroscopy (PAS) and laser pulse Time-of-Flight (TOF) measurement using a streak camera. In parallel with measurements, a Monte-Carlo (MC) simulation models have been developed. Experimental in vitro measurements were performed using Intralipid fat emulsion as a tissue simulating phantom for OCT and TOF measurements. In PAS measurements, a pork meat was used as a subject but also preliminary in vivo measurements were done. OCT measurement results show that the slope of the OCT signal's envelope changes as a function of glucose content in the scattering media. TOF measurements show that the laser pulse full width of half maximum (FWHM) changes a little as function of glucose content. An agreement with MC-simulations and measurements with Intralipid was also found. Measurement results of PAS technique show that changes in glucose content in the pork meat tissue can be measured. In vivo measurements with a human volunteer show that other factors such as physiological change, blood circulation and body temperature drift may interfere the PA response of glucose.

  2. Magnetic Sensing with Ferrofluid and Fiber Optic Connectors

    PubMed Central

    Homa, Daniel; Pickrell, Gary

    2014-01-01

    A simple, cost effective and sensitive fiber optic magnetic sensor fabricated with ferrofluid and commercially available fiber optic components is described in this paper. The system uses a ferrofluid infiltrated extrinsic Fabry-Perot interferometer (EFPI) interrogated with an infrared wavelength spectrometer to measure magnetic flux density. The entire sensing system was developed with commercially available components so it can be easily and economically reproduced in large quantities. The device was tested with two different ferrofluid types over a range of magnetic flux densities to verify performance. The sensors readily detected magnetic flux densities in the range of 0.5 mT to 12.0 mT with measurement sensitivities in the range of 0.3 to 2.3 nm/mT depending on ferrofluid type. Assuming a conservative wavelength resolution of 0.1 nm for state of the art EFPI detection abilities, the estimated achievable measurement resolution is on the order 0.04 mT. The inherent small size and basic structure complimented with the fabrication ease make it well-suited for a wide array of research, industrial, educational and military applications. PMID:24573312

  3. Corrosion monitoring along infrastructures using distributed fiber optic sensing

    NASA Astrophysics Data System (ADS)

    Alhandawi, Khalil B.; Vahdati, Nader; Shiryayev, Oleg; Lawand, Lydia

    2016-04-01

    Pipeline Inspection Gauges (PIGs) are used for internal corrosion inspection of oil pipelines every 3-5 years. However, between inspection intervals, rapid corrosion may occur, potentially resulting in major accidents. The motivation behind this research project was to develop a safe distributed corrosion sensor placed inside oil pipelines continuously monitoring corrosion. The intrinsically safe nature of light provided motivation for researching fiber optic sensors as a solution. The sensing fiber's cladding features polymer plastic that is chemically sensitive to hydrocarbons within crude oil mixtures. A layer of metal, used in the oil pipeline's construction, is deposited on the polymer cladding, which upon corrosion, exposes the cladding to surrounding hydrocarbons. The hydrocarbon's interaction with the cladding locally increases the cladding's refractive index in the radial direction. Light intensity of a traveling pulse is reduced due to local reduction in the modal capacity which is interrogated by Optical Time Domain Reflectometery. Backscattered light is captured in real-time while using time delay to resolve location, allowing real-time spatial monitoring of environmental internal corrosion within pipelines spanning large distances. Step index theoretical solutions were used to calculate the power loss due changes in the intensity profile. The power loss is translated into an attenuation coefficient characterizing the expected OTDR trace which was verified against similar experimental results from the literature. A laboratory scale experiment is being developed to assess the validity of the model and the practicality of the solution.

  4. Integration of carbon fluxes and optical remote sensing

    NASA Astrophysics Data System (ADS)

    Castro-Contreras, S.; Nestola, E.; Flanagan, L. B.; Gamon, J. A.

    2013-12-01

    The integration of optical and flux measurements can improve our understanding of flux controls and dynamics. For our study, reflectance and flux measurements at a dry mixed-grass prairie grassland and crop ecosystem were collected. A LUE model was used to estimate productivity and then compared to eddy-covariance derived NEE and GPP. Both narrow band and low cost two-band radiometers were explored as alternative ways to estimate terms of the LUE model. The high temporal resolution in an automated broadband sensors system resulted in estimated carbon fluxes that accurately tracked the seasonal carbon flux dynamics, including the precise tracking of the phenologic cycle through green-up, maturity, and senescence. Furthermore, automated sensors offered a continuous time series that provide a novel approach for partitioning net carbon fluxes into its productivity and respiration components, as well as allowed gap filling missing eddy covariance data. Association between harvested biomass and NDVI derived from ground spectrometry provide a method for assessing variation in standing green biomass. By integrating remote sensing and flux measurement approaches, we can achieve a more comprehensive understanding of the dynamics involving the biospheric carbon budget. Having the optical and flux measurements a comparable location and time scale as the eddy covariance allows for up-scaling flux measurements, and could permit direct comparisons to aircraft and satellite measurements.

  5. Miniature fibre optic probe for minimally invasive photoacoustic sensing

    NASA Astrophysics Data System (ADS)

    Mathews, Sunish J.; Zhang, Edward Z.; Desjardins, Adrien E.; Beard, Paul C.

    2016-03-01

    A miniature (175 μm) all-optical photoacoustic probe has been developed for minimally invasive sensing and imaging applications. The probe comprises a single optical fibre which delivers the excitation light and a broadband 50 MHz Fabry-Pérot (F-P) ultrasound sensor at the distal end for detecting the photoacoustic waves. A graded index lens proximal to the F-P sensor is used to reduce beam walk-off and thus increase sensitivity as well as confine the excitation beam in order to increase lateral spatial resolution. The probe was evaluated in non-scattering media and found to provide lateral and axial resolutions of < 100 μm and < 150 μm respectively for distances up to 1 cm from the tip of the probe. The ability of the probe to detect a blood vessel mimicking phantom at distances up to 7 mm from the tip was demonstrated in order to illustrate its potential suitability for needle guidance applications.

  6. Optical properties and sensing applications of stellated and bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Smith, Alison F.

    This dissertation focuses on developing guidelines to aid in the design of new bimetallic platforms for sensing applications. Stellated metal nanostructures are a class of plasmonic colloids in which large electric field enhancements can occur at sharp features, making them excellent candidates for surface enhanced Raman spectroscopy (SERS) and surface enhanced infrared spectroscopy (SE-IRS) platforms. Shape-dependent rules for convex polyhedra such as cubes or octahedra exist, which describe far-field scattering and near-field enhancements. However, such rules are lacking for their concave (stellated) counterparts. This dissertation presents the optical response of stellated Au nanocrystals with Oh, D4h, D3h, C2v, and T d symmetry, which were modeled to systematically investigate the role of symmetry, branching, and particle orientation with respect to excitation source using finite difference time domain (FDTD) calculations. Expanding on stellated nanostructures, bimetallic compositions introduce an interplay between overall architecture and composition to provide tunable optical properties and the potential of new functionality. However, decoupling the complex compositional and structural contributions to the localized surface plasmon resonance (LSPR) remains a challenge, especially when the monometallic counterparts are not synthetically accessible for comparison and the theoretical tools for capturing gradient compositions are lacking. This dissertation explores a stellated Au-Pd nanocrystal model system with Oh symmetry to decouple structural and complex compositional effects on LSPR. (Abstract shortened by ProQuest.).

  7. Ultrasensitive plasmonic sensing in air using optical fibre spectral combs

    PubMed Central

    Caucheteur, Christophe; Guo, Tuan; Liu, Fu; Guan, Bai-Ou; Albert, Jacques

    2016-01-01

    Surface plasmon polaritons (SPP) can be excited on metal-coated optical fibres, enabling the accurate monitoring of refractive index changes. Configurations reported so far mainly operate in liquids but not in air because of a mismatch between permittivities of guided light modes and the surrounding medium. Here we demonstrate a plasmonic optical fibre platform that overcomes this limitation. The underpinning of our work is a grating architecture—a gold-coated highly tilted Bragg grating—that excites a spectral comb of narrowband-cladding modes with effective indices near 1.0 and below. Using conventional spectral interrogation, we measure shifts of the SPP-matched resonances in response to static atmospheric pressure changes. A dynamic experiment conducted using a laser lined-up with an SPP-matched resonance demonstrates the ability to detect an acoustic wave with a resolution of 10−8 refractive index unit (RIU). We believe that this configuration opens research directions for highly sensitive plasmonic sensing in gas. PMID:27834366

  8. Magnetic sensing with ferrofluid and fiber optic connectors.

    PubMed

    Homa, Daniel; Pickrell, Gary

    2014-02-25

    A simple, cost effective and sensitive fiber optic magnetic sensor fabricated with ferrofluid and commercially available fiber optic components is described in this paper. The system uses a ferrofluid infiltrated extrinsic Fabry-Perot interferometer (EFPI) interrogated with an infrared wavelength spectrometer to measure magnetic flux density. The entire sensing system was developed with commercially available components so it can be easily and economically reproduced in large quantities. The device was tested with two different ferrofluid types over a range of magnetic flux densities to verify performance. The sensors readily detected magnetic flux densities in the range of 0.5 mT to 12.0 mT with measurement sensitivities in the range of 0.3 to 2.3 nm/mT depending on ferrofluid type. Assuming a conservative wavelength resolution of 0.1 nm for state of the art EFPI detection abilities, the estimated achievable measurement resolution is on the order 0.04 mT. The inherent small size and basic structure complimented with the fabrication ease make it well-suited for a wide array of research, industrial, educational and military applications.

  9. Ultrasensitive plasmonic sensing in air using optical fibre spectral combs

    NASA Astrophysics Data System (ADS)

    Caucheteur, Christophe; Guo, Tuan; Liu, Fu; Guan, Bai-Ou; Albert, Jacques

    2016-11-01

    Surface plasmon polaritons (SPP) can be excited on metal-coated optical fibres, enabling the accurate monitoring of refractive index changes. Configurations reported so far mainly operate in liquids but not in air because of a mismatch between permittivities of guided light modes and the surrounding medium. Here we demonstrate a plasmonic optical fibre platform that overcomes this limitation. The underpinning of our work is a grating architecture--a gold-coated highly tilted Bragg grating--that excites a spectral comb of narrowband-cladding modes with effective indices near 1.0 and below. Using conventional spectral interrogation, we measure shifts of the SPP-matched resonances in response to static atmospheric pressure changes. A dynamic experiment conducted using a laser lined-up with an SPP-matched resonance demonstrates the ability to detect an acoustic wave with a resolution of 10-8 refractive index unit (RIU). We believe that this configuration opens research directions for highly sensitive plasmonic sensing in gas.

  10. Online technique for detecting state of onboard fiber optic gyroscope

    SciTech Connect

    Miao, Zhiyong; He, Kunpeng Pang, Shuwan; Xu, Dingjie; Tian, Chunmiao

    2015-02-15

    Although angle random walk (ARW) of fiber optic gyroscope (FOG) has been well modeled and identified before being integrated into the high-accuracy attitude control system of satellite, aging and unexpected failures can affect the performance of FOG after launch, resulting in the variation of ARW coefficient. Therefore, the ARW coefficient can be regarded as an indicator of “state of health” for FOG diagnosis in some sense. The Allan variance method can be used to estimate ARW coefficient of FOG, however, it requires a large amount of data to be stored. Moreover, the procedure of drawing slope lines for estimation is painful. To overcome the barriers, a weighted state-space model that directly models the ARW to obtain a nonlinear state-space model was established for FOG. Then, a neural extended-Kalman filter algorithm was implemented to estimate and track the variation of ARW in real time. The results of experiment show that the proposed approach is valid to detect the state of FOG. Moreover, the proposed technique effectively avoids the storage of data.

  11. Optical techniques for the studies on shock propagation in solids

    NASA Astrophysics Data System (ADS)

    Singh, Manjit; Singh, M. P.; Sethi, V. S.; Bola, M. S.

    1997-07-01

    Optical methods of recording the shock propagation in solids are described. A small air pocket or a tiny explosive pallet senses the shock arrival and produces a light flash which is transmitted through fibre cables to a Rotating Mirror Streak Camera and Logic Analyzer through an opto-electronic interface unit. The system has been used to measure the velocity and symmetry of the shock waves in various metals and non-metals. For the measurement of velocity, the fibre cables with a small air gap at the tip ends, are positioned at different depths inside the solid sample, in the direction of wave propagation. The fibre cables were positioned along the circle at a fixed depth for the measurement of shock wave symmetry. One more method of recording x-t profile of shock propagation is a single experimental trial is described. The air spaced prespex pallets are placed in a cylindrical hole drilled along the axis of wave propagation. The light pulses produced from each air gaps are multiplexed on a single fibre to the recording equipments. Since the measurements are made along the central axis of the sample, the rarefaction waves originating from the sample periphery do not interfere up to a considerable length. By using this technique the experimental data on shock attenuation and convergence in different materials are presented.

  12. Online technique for detecting state of onboard fiber optic gyroscope.

    PubMed

    Miao, Zhiyong; Xu, Dingjie; He, Kunpeng; Pang, Shuwan; Tian, Chunmiao

    2015-02-01

    Although angle random walk (ARW) of fiber optic gyroscope (FOG) has been well modeled and identified before being integrated into the high-accuracy attitude control system of satellite, aging and unexpected failures can affect the performance of FOG after launch, resulting in the variation of ARW coefficient. Therefore, the ARW coefficient can be regarded as an indicator of "state of health" for FOG diagnosis in some sense. The Allan variance method can be used to estimate ARW coefficient of FOG, however, it requires a large amount of data to be stored. Moreover, the procedure of drawing slope lines for estimation is painful. To overcome the barriers, a weighted state-space model that directly models the ARW to obtain a nonlinear state-space model was established for FOG. Then, a neural extended-Kalman filter algorithm was implemented to estimate and track the variation of ARW in real time. The results of experiment show that the proposed approach is valid to detect the state of FOG. Moreover, the proposed technique effectively avoids the storage of data.

  13. Optical Techniques for Space Environment Management

    NASA Astrophysics Data System (ADS)

    Greene, B.; Bennett, J.; Smith, C.

    2016-09-01

    The Space Environment Research Centre (SERC) is a fully-funded multi-national research collaboration for the management and mitigation of space debris using optical technologies. SERC is tasked with developing mitigation strategies for the many debris objects not amenable to space-based interventions. SERC research leverages very accurate information from a new optical space tracking network to develop viable near-term strategies to manage debris using only ground-based infrastructure. SERC has sufficient resources to conduct full-scale on-orbit testing of candidate approaches. We report on SERC progress in astrodynamics, precision catalogs, conjunction processing, adaptive optics and high power lasers as well as the architecture of the research effort.

  14. A Study of Synchronization Techniques for Optical Communication Systems

    NASA Technical Reports Server (NTRS)

    Gagliardi, R. M.

    1975-01-01

    The study of synchronization techniques and related topics in the design of high data rate, deep space, optical communication systems was reported. Data cover: (1) effects of timing errors in narrow pulsed digital optical systems, (2) accuracy of microwave timing systems operating in low powered optical systems, (3) development of improved tracking systems for the optical channel and determination of their tracking performance, (4) development of usable photodetector mathematical models for application to analysis and performance design in communication receivers, and (5) study application of multi-level block encoding to optical transmission of digital data.

  15. Basalt nuclear-waste repository remote sensing using electromagnetic techniques

    SciTech Connect

    Daily, W.D.; Buettner, H.M.

    1984-01-01

    The electromagnetic permittivity and attenuation rate of basalt, from the Near Surface Test Facility of the Basalt Waste Isolation Project at Hanford, Washington, have been measured in the laboratory as a function of water content at frequencies from 25 MHz to 1000 MHz. Both the permittivity and the attenuation rate are strongly related to water content of basalt in this frequency range. Completely dehydrated, the rock has a frequency-independent relative permittivity of about 8 and attenuation rates (inverse skin depths) of 0.04 m/sup -1/ and 3.2 m/sup -1/ at 25 MHz and 1000 MHz, respectively. When completely saturated by tap water to 6% by volume, the relative permittivity ranges from 16.5 to 10.0 and the attenuation ranges from 0.3 m/sup -1/ to 5.5 m/sup -1/ between 25 MHz and 1000 MHz. The data indicate that high-frequency electromagnetic remote sensing techniques, such as those used in radar, cross-borehole tomography, and borehole logging, may be useful in characterizing proposed basalt repositories and monitoring established waste repositories. Electromagnetic methods are particularly suited to delineating water content of the rock and, when completely saturated, crack and pore porosity of the rock mass within a repository. 7 references, 3 figures.

  16. Water Vapor Remote Sensing Techniques: Radiometry and Solar Spectrometry

    NASA Astrophysics Data System (ADS)

    Somieski, A.; Buerki, B.; Cocard, M.; Geiger, A.; Kahle, H.-G.

    The high variability of atmospheric water vapor content plays an important role in space geodesy, climatology and meteorology. Water vapor has a strong influence on transatmospheric satellite signals, the Earth's climate and thus the weather forecasting. Several remote sensing techniques have been developed for the determination of inte- grated precipitable water vapor (IPWV). The Geodesy and Geodynamics Lab (GGL) utilizes the methods of Water Vapor Radiometry and Solar Spectrometry to quantify the amount of tropospheric water vapor and its temporal variations. The Water Vapor Radiometer (WVR) measures the radiation intensity of the atmosphere in a frequency band ranging from 20 to 32 GHz. The Solar Atmospheric MOnitoring Spectrome- ter (SAMOS) of GGL is designed for high-resolution measurements of water vapor absorption lines using solar radiation. In the framework of the ESCOMPTE (ExpÊrience sur Site pour COntraindre les Mod- Éles de Pollution atmosphÊrique et de Transport d'Emissions) field campaign these instruments have been operated near Marseille in 2001. They have aquired a long time series of integrated precipitable water vapor content (IPWV). The accuracy of IPWV measured by WVR and SAMOS is 1 kg/m2. Furthermore meteorological data from radiosondes were used to calculate the IPWV in order to provide comparisons with the results of WVR and SAMOS. The methods of Water Vapor Radiometry and So- lar Spectrometry will be discussed and first preliminary results retrieved from WVR, SAMOS and radiosondes during the ESCOMPTE field campaign will be presented.

  17. Impact of dither-based Electro-Optic Modulator bias control on distributed Brillouin sensing system

    NASA Astrophysics Data System (ADS)

    Sun, Qiao; Tu, Xiaobo; Sun, Shilin; Hu, Xiaoyang; Meng, Zhou

    2015-10-01

    In most distributed Brillouin sensing systems, it is crucial to keep the long-term stability of the electro-optic modulator (EOM) operating point. The dither-tone based bias control methods are widely adopted in this kind of systems for its robustness and reliability, but the low frequency dither tone (a few kilohertz) added into the dc bias port of the EOM may have a detrimental impact on the sensing performance of the Brillouin sensing system. Experimental results show that the dither frequency should not be set around quarter of the pulse repetition rate or its multiples, and the employed dither amplitude should be in the range of 0.003Vπ to 0.015Vπ (Vπ is the RF half-wave voltage of the EOM), in order to overcome the limitation of dither tone based bias control techniques in BOTDA systems. These results will provide guidelines to improve the performance of the Brillouin sensing systems using dither-based EOM bias control method.

  18. Optical properties of shallow tropical cumuli derived from ARM ground-based remote sensing

    NASA Astrophysics Data System (ADS)

    McFarlane, S. A.; Grabowski, W. W.

    2007-03-01

    This paper presents results from ground-based remote sensing of optical properties of shallow convective clouds over the Nauru ARM site using the technique developed by McFarlane et al. (2002). Herein, the results of a pilot study are presented with analysis of about six months of cloud data. The effective radius r e shows large spatial variability, with the frequency of occurrence relatively narrow near the cloud base, and gradually widening aloft. Available column data for LWC and r e allow derivation of the pdf of the optical thickness τ. The pdf shows that clouds with τ in the range 5 to 10 are most frequent, but there is a long tail with clouds up to τ = 100. These results are discussed in the context of traditional observations of cloud microstructure using an instrumented aircraft.

  19. Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing.

    PubMed

    Klantsataya, Elizaveta; François, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M

    2015-09-29

    Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33-1.37) suitable for biosensing applications.

  20. Optical temperature sensing properties of Yb3+/Er3+ codoped LaF3 upconversion phosphor

    NASA Astrophysics Data System (ADS)

    Cheng, Xuerui; Ma, Xiaochun; Zhang, Huanjun; Ren, Yufen; Zhu, Kunkun

    2017-09-01

    The structural and optical properties of Er3+/Yb3+ codoped LaF3 phosphors are investigated using X-ray diffraction (XRD) and upconversion luminescence spectra. The result shows that the hexagonal phase of LaF3 keep stability at temperature lower than 800 °C in air condition and will be oxidized to be LaOF at higher temperature. Its upconversion emission intensity varies with the doping concentrations of Yb3+ ions and reaches a maximum at around 7 mol% Yb3+. The power-dependent luminescence reveals the possible emission mechanisms and the corresponding upconversion processes. Furthermore, the optical temperature sensing properties of LaF3: Er3+/Yb3+ are studied based on the fluorescence intensity ratio (FIR) technique for two thermally coupled levels (2H11/2 and 4S3/2) of Er3+. The maximum sensitivity is found to be about 0.00157 K-1 at 386 K, revealing this phosphor to be a promising prototype for applications in optical temperature sensing.