Polarization maintaining fiber magnetic sensor based on the digital phase generated carrier technology

NASA Astrophysics Data System (ADS)

Zhang, Xueliang; Meng, Zhou; Hu, Zhengliang; Yang, Huayong; Song, Zhangqi; Hu, Yongming

2008-12-01

A polarization maintaining fiber (PMF) magnetic field sensor based on a digital phase generated carrier (PGC) technology is presented. A magnetic sensor constructed with two magnetostrictive strips attached on the sensing fiber is joined in the sensing arm of a fiber Michelson interferometer. The fiber optic interferometric system is made of all PMF, which inhibits the polarization-induced signal fading. The light source is a fiber laser which can be modulated directly. The PGC metnod is used to demodulate magnetic field signal avoiding phase induced interferometric signal fading, and ensure the sensing partto be all fiber structure. A fiber optic magnetic field sensor with appreciate size for the fiber optic hydrophone towed array is obtained, which can be used to sense the enviromental magnetic field along the sensing direction.This sensor is a good choice for the directional angle measurement through sensing the Earth magnetic field in the array shape measurement of a fiber optic hydrophone towed array.

Fiber-optic push-pull sensor systems

NASA Technical Reports Server (NTRS)

Gardner, David L.; Brown, David A.; Garrett, Steven L.

1991-01-01

Fiber-optic push-pull sensors are those which exploit the intrinsically differential nature of an interferometer with concommitant benefits in common-mode rejection of undesired effects. Several fiber-optic accelerometer and hydrophone designs are described. Additionally, the recent development at the Naval Postgraduate School of a passive low-cost interferometric signal demodulator permits the development of economical fiber-optic sensor systems.

Measurement of morphing wing deflection by a cross-coherence fiber optic interferometric technique

NASA Astrophysics Data System (ADS)

Tomić, Miloš C.; Djinović, Zoran V.; Scheerer, Michael; Petricevic, Slobodan J.

2018-01-01

A fiber-optic interferometric technique aimed at measuring the deflection of aircrafts’ morphing wings is presented. The wing deflection induces a strain in the sensing fiber optic coils that are firmly fixed onto the wing. A change of the phase angle of the light propagating through the fiber is measured by an ‘all-in-fiber’ Michelson interferometer based on a 3 × 3 fiber-optic coupler. Two light sources of different coherence lengths and wavelengths are simultaneously used to ensure a wide measurement range and high accuracy. A new technique for determination of the zero deflection point using the cross-correlation of the two interferograms is proposed. The experiments performed on a specimen made of a carbon-fiber-reinforced plastic honeycomb structure demonstrated a relative uncertainty <1% and a precision of about 0.06° in the measuring range ±5° of the morphing wing deflection.

A modified cross-correlation method for white-light optical fiber extrinsic Fabry-Perot interferometric hydrogen sensors

NASA Astrophysics Data System (ADS)

Yang, Zhen; Zhang, Min; Liao, Yanbiao; Lai, Shurong; Tian, Qian; Li, Qisheng; Zhang, Yi; Zhuang, Zhi

2009-11-01

An extrinsic Fabry-Perot interferometric (EFPI) optical fiber hydrogen sensor based on palladium silver (Pd-Ag) film is designed for hydrogen leakage detection. A modified cross correlation signal processing method for an optical fiber EFPI hydrogen sensor is presented. As the applying of a special correlating factor which advises the effect on the fringe visibility of the gap length and wavelength, the cross correlation method has a high accuracy which is insensitive to light source power drift or changes in attenuation in the fiber, and the segment search method is employed to reduce computation and demodulating speed is fast. The Fabry-Perot gap length resolution of better than 0.2nm is achieved in a certain concentration of hydrogen.

Analysis of the tunable asymmetric fiber F-P cavity for fiber strain sensor edge-filter demodulation

NASA Astrophysics Data System (ADS)

Chen, Haotao; Liang, Youcheng

2014-12-01

An asymmetric fiber (Fabry-Pérot, F-P) interferometric cavity with the good linearity and wide dynamic range was successfully designed based on the optical thin film characteristic matrix theory; by adjusting the material of two different thin metallic layers, the asymmetric fiber F-P interferometric cavity was fabricated by depositing the multi-layer thin films on the optical fiber's end face. The asymmetric F-P cavity has the extensive potential application. In this paper, the demodulation method for the wavelength shift of the fiber Bragg grating (FBG) sensor based on the F-P cavity is demonstrated, and a theoretical formula is obtained. And the experimental results coincide well with the computational results obtained from the theoretical model.

Interferometric Fiber Optic Sensors

PubMed Central

Lee, Byeong Ha; Kim, Young Ho; Park, Kwan Seob; Eom, Joo Beom; Kim, Myoung Jin; Rho, Byung Sup; Choi, Hae Young

2012-01-01

Fiber optic interferometers to sense various physical parameters including temperature, strain, pressure, and refractive index have been widely investigated. They can be categorized into four types: Fabry-Perot, Mach-Zehnder, Michelson, and Sagnac. In this paper, each type of interferometric sensor is reviewed in terms of operating principles, fabrication methods, and application fields. Some specific examples of recently reported interferometeric sensor technologies are presented in detail to show their large potential in practical applications. Some of the simple to fabricate but exceedingly effective Fabry-Perot interferometers, implemented in both extrinsic and intrinsic structures, are discussed. Also, a wide variety of Mach-Zehnder and Michelson interferometric sensors based on photonic crystal fibers are introduced along with their remarkable sensing performances. Finally, the simultaneous multi-parameter sensing capability of a pair of long period fiber grating (LPG) is presented in two types of structures; one is the Mach-Zehnder interferometer formed in a double cladding fiber and the other is the highly sensitive Sagnac interferometer cascaded with an LPG pair. PMID:22736961

In-Line Fiber Optic Interferometric Sensors in Single-Mode Fibers

PubMed Central

Zhu, Tao; Wu, Di; Liu, Min; Duan, De-Wen

2012-01-01

In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented. PMID:23112608

Fiber optic and laser sensors IV; Proceedings of the Meeting, Cambridge, MA, Sept. 22-24, 1986

NASA Technical Reports Server (NTRS)

De Paula, Ramon P. (Editor); Udd, Eric (Editor)

1987-01-01

The conference presents papers on industrial uses of fiber optic sensors, point and distributed polarimetric optical fiber sensors, fiber optic electric field sensor technology, micromachined resonant structures, single-mode fibers for sensing applications, and measurement techniques for magnetic field gradient detection. Consideration is also given to electric field meter and temperature measurement techniques for the power industry, the calibration of high-temperature fiber-optic microbend pressure transducers, and interferometric sensors for dc measurands. Other topics include the recognition of colors and collision avoidance in robotics using optical fiber sensors, the loss compensation of intensity-modulating fiber-optic sensors, and an embedded optical fiber strain tensor for composite structure applications.

Four-Mode Squeezing For Optical Communications

NASA Technical Reports Server (NTRS)

Schumaker, Bonny L.

1989-01-01

Experiments demonstrated potential of four-mode squeezing for increasing immunity to noise in fiber-optical communication systems and interferometric devices. Four-mode squeezing reduces quantum noise more than ordinary squeezing and provides partial immunity to non-quantum-mechanical phase noise arising in such media as optical fibers.

Optical fiber extrinsic Fabry-Perot interferometric (EFPI)-based biosensors

NASA Astrophysics Data System (ADS)

Elster, Jennifer L.; Jones, Mark E.; Evans, Mishell K.; Lenahan, Shannon M.; Boyce, Christopher A.; Velander, William H.; VanTassell, Roger

2000-05-01

A novel system incorporating optical fiber extrinsic Fabry- Perot interferometric (EFPI)-based sensors for rapid detection of biological targets is presented. With the appropriate configuration, the EFPI senor is able to measure key environmental parameters by monitoring the interferometric fringes resulting from an optical path differences of reflected signals. The optical fiber EFPI sensor has been demonstrated for strain, pressure, and temperature measurements and can be readily modified for refractive index measurements by allowing solutions to flow into an open cavity. The sensor allows for highly sensitive, real-time, refractive index measurements and by applying affinity coatings containing ligands within this cavity, specific binding of target molecules can be accomplished. As target molecules bind to the coating, there is an increased density within the film, causing a measurable refractive index change that correlates to the concentration of detected target molecules. This sensor platform offers enhanced sensing capabilities for clinical diagnostics, pharmaceutical screening, environmental monitoring, food pathogen detection, biological warfare agent detection, and industrial bioprocessing. Promising applications also exist for process monitoring within the food/beverage, petroleum, and chemical industry.

Modeling and Validation of Performance Limitations for the Optimal Design of Interferometric and Intensity-Modulated Fiber Optic Displacement Sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moro, Erik A.

Optical fiber sensors offer advantages over traditional electromechanical sensors, making them particularly well-suited for certain measurement applications. Generally speaking, optical fiber sensors respond to a desired measurand through modulation of an optical signal's intensity, phase, or wavelength. Practically, non-contacting fiber optic displacement sensors are limited to intensity-modulated and interferometric (or phase-modulated) methodologies. Intensity-modulated fiber optic displacement sensors relate target displacement to a power measurement. The simplest intensity-modulated sensor architectures are not robust to environmental and hardware fluctuations, since such variability may cause changes in the measured power level that falsely indicate target displacement. Differential intensity-modulated sensors have been implemented, offeringmore » robustness to such intensity fluctuations, and the speed of these sensors is limited only by the combined speed of the photodetection hardware and the data acquisition system (kHz-MHz). The primary disadvantages of intensity-modulated sensing are the relatively low accuracy (?m-mm for low-power sensors) and the lack of robustness, which consequently must be designed, often with great difficulty, into the sensor's architecture. White light interferometric displacement sensors, on the other hand, offer increased accuracy and robustness. Unlike their monochromatic-interferometer counterparts, white light interferometric sensors offer absolute, unambiguous displacement measurements over large displacement ranges (cm for low-power, 5 mW, sources), necessitating no initial calibration, and requiring no environmental or feedback control. The primary disadvantage of white light interferometric displacement sensors is that their utility in dynamic testing scenarios is limited, both by hardware bandwidth and by their inherent high-sensitivity to Doppler-effects. The decision of whether to use either an intensity-modulated interferometric sensor depends on an appropriate performance function (e.g., desired displacement range, accuracy, robustness, etc.). In this dissertation, the performance limitations of a bundled differential intensity-modulated displacement sensor are analyzed, where the bundling configuration has been designed to optimize performance. The performance limitations of a white light Fabry-Perot displacement sensor are also analyzed. Both these sensors are non-contacting, but they have access to different regions of the performance-space. Further, both these sensors have different degrees of sensitivity to experimental uncertainty. Made in conjunction with careful analysis, the decision of which sensor to deploy need not be an uninformed one.« less

Radiation hardening commercial off-the-shelf erbium doped fibers by optimal photo-annealing source

NASA Astrophysics Data System (ADS)

Peng, Tz-Shiuan; Liu, Ren-Young; Lin, Yen-Chih; Mao, Ming-Hua; Wang, Lon A.

2017-09-01

Erbium doped fibers (EDFs) based devices are widely employed in space for optical communication [1], remote sensing [2], and navigation applications, e.g. interferometric fiber optic gyroscope (IFOG). However, the EDF suffers severely radiation induced attenuation (RIA) in radiation environments, e.g. space applications and nuclear reactors [3].

An accelerated gamma irradiation test of low dose rate for a single mode fiber

NASA Astrophysics Data System (ADS)

Chiou, Chung-An; Peng, Tz-Shiuan; Liu, Ren-Young

2017-09-01

Conventional single mode fiber (SMF), due to its electromagnetic interference immunity, light weight, physical flexibility and broad bandwidth for data transmission, has been well employed in space, such as optical communication [1], structural health monitoring of spacecraft [2], and attitude determining applications, e.g. interferometric fiber optic gyroscope (IFOG).

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.

Fabrication and Characterization of Tilted Fiber Optic Bragg Grating Filters over Various Wavelengths

NASA Technical Reports Server (NTRS)

Grant, Joseph; Jackson, Kurt V.; Wang, Y.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

2002-01-01

Fiber Optic Bragg Grating taps are fabricated and characterized at various wavelengths using a modified Talbot interferometric technique. Gratings are fabricated by tilting the photosensitive fiber to angles up to 45 degrees w.r.t. the writing angle. Diffraction characteristics of the tilted grating is monitored in first and second orders.

An interferometric fiber optic hydrophone with large upper limit of dynamic range

NASA Astrophysics Data System (ADS)

Zhang, Lei; Kan, Baoxi; Zheng, Baichao; Wang, Xuefeng; Zhang, Haiyan; Hao, Liangbin; Wang, Hailiang; Hou, Zhenxing; Yu, Wenpeng

2017-10-01

Interferometric fiber optic hydrophone based on heterodyne detection is used to measure the missile dropping point in the sea. The signal caused by the missile dropping in the water will be too large to be detected, so it is necessary to boost the upper limit of dynamic range (ULODR) of fiber optic hydrophone. In this article we analysis the factors which influence the ULODR of fiber optic hydrophone based on heterodyne detection, the ULODR is decided by the sampling frequency fsam and the heterodyne frequency Δf. The sampling frequency and the heterodyne frequency should be satisfied with the Nyquist sampling theorem which fsam will be two times larger than Δf, in this condition the ULODR is depended on the heterodyne frequency. In order to enlarge the ULODR, the Nyquist sampling theorem was broken, and we proposed a fiber optic hydrophone which the heterodyne frequency is larger than the sampling frequency. Both the simulation and experiment were done in this paper, the consequences are similar: When the sampling frequency is 100kHz, the ULODR of large heterodyne frequency fiber optic hydrophone is 2.6 times larger than that of the small heterodyne frequency fiber optic hydrophone. As the heterodyne frequency is larger than the sampling frequency, the ULODR is depended on the sampling frequency. If the sampling frequency was set at 2MHz, the ULODR of fiber optic hydrophone based on heterodyne detection will be boosted to 1000rad at 1kHz, and this large heterodyne fiber optic hydrophone can be applied to locate the drop position of the missile in the sea.

Development of an in-fiber white-light interferometric distance sensor for absolute measurement of arbitrary small distances.

PubMed

Majumdar, Ayan; Huang, Haiying

2008-05-20

The fabrication, implementation, and evaluation of an in-fiber white-light interferometric distance sensor that is capable of measuring the absolute value of an arbitrary small distance are presented. Taking advantage of the mode-coupling effect of a long-period fiber grating, an additional cavity distance is added to the optical path difference of the distance sensor; therefore, it can generate a sufficient number of fringes for distance demodulation even if the free-space cavity distance is very small. It is experimentally verified that the distance sensor is capable of measuring small distances that are beyond the capability of a Fabry-Perot interferometric distance sensor.

NASA's first in-space optical gyroscope: A technology experiment on the X ray Timing Explorer spacecraft

NASA Technical Reports Server (NTRS)

Unger, Glenn; Kaufman, David M.; Krainak, Michael; Sanders, Glenn; Taylor, Bill; Schulze, Norman R.

1993-01-01

A technology experiment on the X-ray Timing Explorer spacecraft to determine the feasibility of Interferometric Fiber Optic Gyroscopes for space flight navigation is described. The experiment consists of placing a medium grade fiber optic gyroscope in parallel with the spacecraft's inertial reference unit. The performance of the fiber optic gyroscope will be monitored and compared to the primary mechanical gyroscope's performance throughout the two-year mission life.

Passive demodulation of miniature fiber-optic-based interferometric sensors using a time-multiplexing technique.

PubMed

Santos, J L; Jackson, D A

1991-08-01

A passive demodulation technique suitable for interferometric interrogation of short optical cavities is described. It is based on time multiplexing of two low-finesse Fabry-Perot interferometers subject to the same measurand and with a differential optical phase of pi/2 (modulo 2pi). Independently of the cavity length, two optical outputs in quadrature are generated, which permits signal reading free of fading. The concept is demonstrated for the measurement of vibration using a simple processing scheme.

Great prospects for fiber optics sensors

NASA Technical Reports Server (NTRS)

Hansen, T. E.

1983-01-01

Fiber optic sensors provide noise immunity and galvanic insulation at the measurement point. Interest in such sensors is increasing for these reasons. In the United States sales are expected to increase from 12 million dollars in 1981 to 180 million in 1991. Interferometric sensors based on single modus fibers deliver extremely high sensitivity, while sensors based on multi-modus fibers are more easily manufactured. The fiber optic sensors which are available today are based on point measurements. Development of fiber optic sensors in Norway is being carried out at the Central institute and has resulted in the development of medical manometers which are now undergoing clinical testing.

Recovering Signals from Optical Fiber Interferometric Sensors

DTIC Science & Technology

1991-06-01

GROUP SUB* GROUp Demodulation-, optical fiber, fi ber optic, sensors, passive -homodyne demodulation, symmetric demodul -ation, asymmetric demodulation...interferomeler without feedback control or modulation ofl th laser itself and without requiring the use of electronics withi -n the interferometer. One of...the 3x3 coupler permits Passive Homodyne Demodulation -of the phase-modulated signals provided by the interferometcr without feedback control or

Concentric core optical fiber with multiple-mode signal transmission

DOEpatents

Muhs, J.D.

1997-05-06

A concentric core optical fiber provides for the simultaneous but independent transmission of signals over a single optical fiber. The concentric optical fiber is constructed of a single-mode or multimode inner optical fiber defined by a core and a cladding of a lower index of refraction than the core and an outer optical fiber defined by additional cladding concentrically disposed around the cladding and of an index of refraction lower than the first mentioned cladding whereby the latter functions as the core of the outer optical fiber. By employing such an optical fiber construction with a single-mode inner core or optical fiber, highly sensitive interferometric and stable less sensitive amplitude based sensors can be placed along the same length of a concentric core optical fiber. Also, by employing the concentric core optical fiber secure telecommunications can be achieved via the inner optical fiber since an intrusion of the concentric optical fiber will first cause a variation in the light being transmitted through the outer optical fiber and this variation of light being used to trigger a suitable alarm indicative of the intrusion. 3 figs.

Concentric core optical fiber with multiple-mode signal transmission

DOEpatents

Muhs, Jeffrey D.

1997-01-01

A concentric core optical fiber provides for the simultaneous but independent transmission of signals over a single optical fiber. The concentric optical fiber is constructed of a single-mode or multimode inner optical fiber defined by a core and a cladding of a lower index of refraction than the core and an outer optical fiber defined by additional cladding concentrically disposed around the cladding and of an index of refraction lower than the first mentioned cladding whereby the latter functions as the core of the outer optical fiber. By employing such an optical fiber construction with a single-mode inner core or optical fiber, highly sensitive interferometric and stable less sensitive amplitude based sensors can be placed along the same length of a concentric core optical fiber. Also, by employing the concentric core optical fiber secure telecommunications can be achieved via the inner optical fiber since an intrusion of the concentric optical fiber will first cause a variation in the light being transmitted through the outer optical fiber and this variation of light being used to trigger a suitable alarm indicative of the intrusion.

Fiber optic in vivo imaging in the mammalian nervous system

PubMed Central

Mehta, Amit D; Jung, Juergen C; Flusberg, Benjamin A; Schnitzer, Mark J

2010-01-01

The compact size, mechanical flexibility, and growing functionality of optical fiber and fiber optic devices are enabling several new modalities for imaging the mammalian nervous system in vivo. Fluorescence microendoscopy is a minimally invasive fiber modality that provides cellular resolution in deep brain areas. Diffuse optical tomography is a non-invasive modality that uses assemblies of fiber optic emitters and detectors on the cranium for volumetric imaging of brain activation. Optical coherence tomography is a sensitive interferometric imaging technique that can be implemented in a variety of fiber based formats and that might allow intrinsic optical detection of brain activity at a high resolution. Miniaturized fiber optic microscopy permits cellular level imaging in the brains of behaving animals. Together, these modalities will enable new uses of imaging in the intact nervous system for both research and clinical applications. PMID:15464896

Characteristics of Extrinsic Fabry-Perot Interferometric (EFPI) Fiber-Optic Strain Gages

NASA Technical Reports Server (NTRS)

Hare, David A.; Moore, Thomas C., Sr.

2000-01-01

The focus of this paper is a comparison of the strain-measuring characteristics of one type of commercially available fiber-optic strain sensor with the performance of conventional resistance strain gages. Fabry-Perot type fiber-optic strain sensors were selected for this testing program. Comparative testing is emphasized and includes load testing at room temperature with apparent strain characterization cryogenically and at elevated temperatures. The absolute accuracy of either of these types of strain gages is not addressed.

LSPR and Interferometric Sensor Modalities Combined Using a Double-Clad Optical Fiber.

PubMed

Muri, Harald Ian; Bano, Andon; Hjelme, Dag Roar

2018-01-11

We report on characterization of an optical fiber-based multi-parameter sensor concept combining localized surface plasmon resonance (LSPR) signal and interferometric sensing using a double-clad optical fiber. The sensor consists of a micro-Fabry-Perot in the form of a hemispherical stimuli-responsive hydrogel with immobilized gold nanorods on the facet of a cleaved double-clad optical fiber. The swelling degree of the hydrogel is measured interferometrically using the single-mode inner core, while the LSPR signal is measured using the multi-mode inner cladding. The quality of the interferometric signal is comparable to previous work on hydrogel micro-Fabry-Perot sensors despite having gold nanorods immobilized in the hydrogel. We characterize the effect of hydrogel swelling and variation of bulk solution refractive index on the LSPR peak wavelength. The results show that pH-induced hydrogel swelling causes only weak redshifts of the longitudinal LSPR mode, while increased bulk refractive index using glycerol and sucrose causes large blueshifts. The redshifts are likely due to reduced plasmon coupling of the side-by-side configuration as the interparticle distance increases with increasing swelling. The blueshifts with increasing bulk refractive index are likely due to alteration of the surface electronic structure of the gold nanorods donated by the anionic polymer network and glycerol or sucrose solutions. The recombination of biotin-streptavidin on gold nanorods in hydrogel showed a 7.6 nm redshift of the longitudinal LSPR. The LSPR response of biotin-streptavidin recombination is due to the change in local refractive index (RI), which is possible to discriminate from the LSPR response due to changes in bulk RI. In spite of the large LSPR shifts due to bulk refractive index, we show, using biotin-functionalized gold nanorods binding to streptavidin, that LSPR signal from gold nanorods embedded in the anionic hydrogel can be used for label-free biosensing. These results demonstrate the utility of immobilizing gold nanorods in a hydrogel on a double-clad optical fiber-end facet to obtain multi-parameter sensing.

Theoretical Design of a Depolarized Interferometric Fiber-Optic Gyroscope (IFOG) on SMF-28 Single-Mode Standard Optical Fiber Based on Closed-Loop Sinusoidal Phase Modulation with Serrodyne Feedback Phase Modulation Using Simulation Tools for Tactical and Industrial Grade Applications

PubMed Central

Pérez, Ramón José; Álvarez, Ignacio; Enguita, José María

2016-01-01

This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h). This design presents two important properties: (1) an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2) a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM), so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type) realized by quadrupolar winding. The working wavelength will be 1310 nm. The theoretical calculated values of threshold sensitivity and dynamic range for this prototype are 0.052 °/h and 101.38 dB (from ±1.164 × 10−5 °/s up to ±78.19 °/s), respectively. The Scale-Factor (SF) non-linearity for this model is 5.404% relative to full scale, this value being obtained from data simulation results. PMID:27128924

Theoretical Design of a Depolarized Interferometric Fiber-Optic Gyroscope (IFOG) on SMF-28 Single-Mode Standard Optical Fiber Based on Closed-Loop Sinusoidal Phase Modulation with Serrodyne Feedback Phase Modulation Using Simulation Tools for Tactical and Industrial Grade Applications.

PubMed

Pérez, Ramón José; Álvarez, Ignacio; Enguita, José María

2016-04-27

This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h). This design presents two important properties: (1) an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2) a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM), so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type) realized by quadrupolar winding. The working wavelength will be 1310 nm. The theoretical calculated values of threshold sensitivity and dynamic range for this prototype are 0.052 °/h and 101.38 dB (from ±1.164 × 10(-5) °/s up to ±78.19 °/s), respectively. The Scale-Factor (SF) non-linearity for this model is 5.404% relative to full scale, this value being obtained from data simulation results.

Miniaturized fiber-optic Michelson-type interferometric sensors

NASA Technical Reports Server (NTRS)

Murphy, Kent A.; Miller, William V., III; Tran, Tuan A.; Vengsarkar, Ashish M.; Claus, Richard O.

1991-01-01

A novel, miniaturized Michelson-type fiber-optic interferometric sensor that is relatively insensitive to temperature drifts is presented. A fused-biconical tapered coupler is cleaved immediately after the coupled length and polished down to the region of the fused cladding, but short of the interaction region. The end of one core is selectively coated with a reflective surface and is used as the reference arm; the other core serves as the sensing arm. The detection of surface acoustic waves, microdisplacements, and magnetic fields is reported. The sensor is shown to be highly stable in comparison to a classic homodyne, uncompensated Michelson interferometer, and signal-to-noise ratios of 65 dB have been obtained.

Precision Laser Development for Interferometric Space Missions NGO, SGO, and GRACE Follow-On

NASA Technical Reports Server (NTRS)

Numata, Kenji; Camp, Jordan

2011-01-01

Optical fiber and semiconductor laser technologies have evolved dramatically over the last decade due to the increased demands from optical communications. We are developing a laser (master oscillator) and optical amplifier based on those technologies for interferometric space missions, including the gravitational-wave missions NGO/SGO (formerly LISA) and the climate monitoring mission GRACE Follow-On, by fully utilizing the matured wave-guided optics technologies. In space, where simpler and more reliable system is preferred, the wave-guided components are advantageous over bulk, crystal-based, free-space laser, such as NPRO (Nonplanar Ring Oscillator) and bulk-crystal amplifier.

Cost-effective optical fiber pressure sensor based on intrinsic Fabry-Perot interferometric micro-cavities

NASA Astrophysics Data System (ADS)

Domingues, M. Fátima; Rodriguez, Camilo A.; Martins, Joana; Tavares, Cátia; Marques, Carlos; Alberto, Nélia; André, Paulo; Antunes, Paulo

2018-05-01

In this work, a cost-effective procedure to manufacture optical fiber pressure sensors is presented. This has a high relevance for integration in robotic exoskeletons or for gait plantar pressure monitoring within the physical rehabilitation scenarios, among other applications. The sensing elements are based on Fabry-Perot interferometric (FPI) micro-cavities, created from the recycling of optical fibers previously destroyed by the catastrophic fuse effect. To produce the pressure sensors, the fiber containing the FPI micro-cavities was embedded in an epoxy resin cylinder used as pressure transducer and responsible to transfer the pressure applied on its surface to the optical fiber containing the FPI micro-cavity. Before the embedding process, some FPI sensors were also characterized to strain variations. After that, the effect of the encapsulation of the FPI structure into the resin was assessed, from which a slight decrease on the FPI interferogram fringes visibility was verified, indicating a small increase in the micro-cavity length. Up on the sensors characterization, a linear dependence of the wavelength shift with the induced pressure was obtained, which leads to a maximum sensitivity of 59.39 ± 1.7 pm/kPa. Moreover, direct dependence of the pressure sensitivity with the micro-cavity volume and length was found.

Dynamic Analysis with Fibre Optic Sensors for Structural Health Monitoring

DTIC Science & Technology

2006-10-01

cracked thick aluminum plate repaired with a bonded composite patch using transmission-type extrinsic Fabry – Perot interferometric optical fiber...and optical filtering have been used to demodulate returned Bragg signals. Due to the passive nature of the interrogation unit, system bandwidth is

Characterization of laser-driven shock waves in solids using a fiber optic pressure probe.

PubMed

Cranch, Geoffrey A; Lunsford, Robert; Grün, Jacob; Weaver, James; Compton, Steve; May, Mark; Kostinski, Natalie

2013-11-10

Measurement of laser-driven shock wave pressure in solid blocks of polymethyl methacrylate is demonstrated using fiber optic pressure probes. Three probes based on a fiber Fabry-Perot, fiber Bragg grating, and interferometric fiber tip sensor are tested and compared. Shock waves are generated using a high-power laser focused onto a thin foil target placed in close proximity to the test blocks. The fiber Fabry-Perot sensor appears capable of resolving the shock front with a rise time of 91 ns. The peak pressure is estimated, using a separate shadowgraphy measurement, to be 3.4 GPa.

Microstructured optical fiber interferometric breathing sensor.

PubMed

Favero, Fernando C; Villatoro, Joel; Pruneri, Valerio

2012-03-01

In this paper a simple photonic crystal fiber (PCF) interferometric breathing sensor is introduced. The interferometer consists of a section of PCF fusion spliced at the distal end of a standard telecommunications optical fiber. Two collapsed regions in the PCF caused by the splicing process allow the excitation and recombination of a core and a cladding PCF mode. As a result, the reflection spectrum of the device exhibits a sinusoidal interference pattern that instantly shifts when water molecules, present in exhaled air, are adsorbed on or desorbed from the PCF surface. The device can be used to monitor a person's breathing whatever the respiration rate. The device here proposed could be particularly important in applications where electronic sensors fail or are not recommended. It may also be useful in the evaluation of a person's health and even in the diagnosis and study of the progression of serious illnesses such as sleep apnea syndrome. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).

High-temperature optical fiber sensors for characterization of advanced composite aerospace materials

NASA Astrophysics Data System (ADS)

Wavering, Thomas A.; Greene, Jonathan A.; Meller, Scott A.; Bailey, Timothy A.; Kozikowski, Carrie L.; Lenahan, Shannon M.; Murphy, Kent A.; Camden, Michael P.; Simmons, Larry W.

1999-01-01

Optical fiber sensors have numerous advantages over conventional sensing technologies. One such advantage is that optical fiber sensors can operate in high temperature environments. While most conventional electrical-based sensors do not operate reliably over 300 degrees C, fused silica based optical fiber sensors can survive up to 900 degrees C, and sapphire based optical fiber sensors can survive up to 2000 degrees C. Using both fused silica and sapphire technologies, we present result for high temperature strain, pressure, and temperature sensors using Extrinsic Fabry-Perot INterferometric-based and Bragg grating sensors. High temperature strain and temperature sensors were used to conduct fatigue testing of composite coupons at 600 degrees C. The results from these specific high temperature applications are presented along with future applications and directions for these sensors.

Microstructured optical fiber interferometric breathing sensor

NASA Astrophysics Data System (ADS)

Favero, Fernando C.; Villatoro, Joel; Pruneri, Valerio

2012-03-01

In this paper a simple photonic crystal fiber (PCF) interferometric breathing sensor is introduced. The interferometer consists of a section of PCF fusion spliced at the distal end of a standard telecommunications optical fiber. Two collapsed regions in the PCF caused by the splicing process allow the excitation and recombination of a core and a cladding PCF mode. As a result, the reflection spectrum of the device exhibits a sinusoidal interference pattern that instantly shifts when water molecules, present in exhaled air, are adsorbed on or desorbed from the PCF surface. The device can be used to monitor a person's breathing whatever the respiration rate. The device here proposed could be particularly important in applications where electronic sensors fail or are not recommended. It may also be useful in the evaluation of a person's health and even in the diagnosis and study of the progression of serious illnesses such as sleep apnea syndrome.

Interferometric interrogation of π-phase shifted fiber Bragg grating sensors

NASA Astrophysics Data System (ADS)

Srivastava, Deepa; Tiwari, Umesh; Das, Bhargab

2018-03-01

Interferometric interrogation technique realized for conventional fiber Bragg grating (FBG) sensors is historically known to offer the highest sensitivity measurements, however, it has not been yet explored for π-phase-shifted FBG (πFBG) sensors. This, we believe, is due to the complex nature of the reflection/transmission spectrum of a πFBG, which cannot be directly used for interferometric interrogation purpose. Therefore, we propose here an innovative as well as simple concept towards this direction, wherein, the transmission spectrum of a πFBG sensor is optically filtered using a specially designed fiber grating. The resulting filtered spectrum retains the entire characteristics of a πFBG sensor and hence the filtered spectrum can be interrogated with interferometric principles. Furthermore, due to the extremely narrow transmission notch of a πFBG sensor, a fiber interferometer can be realized with significantly longer path difference. This leads to substantially enhanced detection limit as compared to sensors based on a regular FBG of similar length. Theoretical analysis demonstrates that high resolution weak dynamic strain measurement down to 4 pε /√{ Hz } is easily achievable. Preliminary experimental results are also presented as proof-of-concept of the proposed interrogation principle.

Micromachined fiber optic Fabry-Perot underwater acoustic probe

NASA Astrophysics Data System (ADS)

Wang, Fuyin; Shao, Zhengzheng; Hu, Zhengliang; Luo, Hong; Xie, Jiehui; Hu, Yongming

2014-08-01

One of the most important branches in the development trend of the traditional fiber optic physical sensor is the miniaturization of sensor structure. Miniature fiber optic sensor can realize point measurement, and then to develop sensor networks to achieve quasi-distributed or distributed sensing as well as line measurement to area monitoring, which will greatly extend the application area of fiber optic sensors. The development of MEMS technology brings a light path to address the problems brought by the procedure of sensor miniaturization. Sensors manufactured by MEMS technology possess the advantages of small volume, light weight, easy fabricated and low cost. In this paper, a fiber optic extrinsic Fabry-Perot interferometric underwater acoustic probe utilizing micromachined diaphragm collaborated with fiber optic technology and MEMS technology has been designed and implemented to actualize underwater acoustic sensing. Diaphragm with central embossment, where the embossment is used to anti-hydrostatic pressure which would largely deflect the diaphragm that induce interferometric fringe fading, has been made by double-sided etching of silicon on insulator. By bonding the acoustic-sensitive diaphragm as well as a cleaved fiber end in ferrule with an outer sleeve, an extrinsic Fabry-Perot interferometer has been constructed. The sensor has been interrogated by quadrature-point control method and tested in field-stable acoustic standing wave tube. Results have been shown that the recovered signal detected by the sensor coincided well with the corresponding transmitted signal and the sensitivity response was flat in frequency range from 10 Hz to 2kHz with the value about -154.6 dB re. 1/μPa. It has been manifest that the designed sensor could be used as an underwater acoustic probe.

Characterization of laser-driven shock waves in solids using a fiber optic pressure probe

DOE PAGES

Cranch, Geoffrey A.; Lunsford, Robert; Grun, Jacob; ...

2013-11-08

Measurement of laser-driven shock wave pressure in solid blocks of polymethyl methacrylate is demonstrated using fiber optic pressure probes. Three probes based on a fiber Fabry–Perot, fiber Bragg grating, and interferometric fiber tip sensor are tested and compared. Shock waves are generated using a high-power laser focused onto a thin foil target placed in close proximity to the test blocks. The fiber Fabry–Perot sensor appears capable of resolving the shock front with a rise time of 91 ns. As a result, the peak pressure is estimated, using a separate shadowgraphy measurement, to be 3.4 GPa.

Detecting ionizing radiation with optical fibers down to biomedical doses

NASA Astrophysics Data System (ADS)

Avino, S.; D'Avino, V.; Giorgini, A.; Pacelli, R.; Liuzzi, R.; Cella, L.; De Natale, P.; Gagliardi, G.

2013-10-01

We report on a passive ionizing radiation sensor based on a fiber-optic resonant cavity interrogated by a high resolution interferometric technique. After irradiation in clinical linear accelerators, we observe significant variations of the fiber thermo-optic coefficient. Exploiting this effect, we demonstrate an ultimate detection limit of 160 mGy with an interaction volume of only 6 × 10-4 mm3. Thanks to its reliability, compactness, and sensitivity at biomedical dose levels, our system lends itself to real applications in radiation therapy procedures as well as in radiation monitoring and protection in medicine, aerospace, and nuclear power plants.

Advanced Fiber-optic Monitoring System for Space-flight Applications

NASA Technical Reports Server (NTRS)

Hull, M. S.; VanTassell, R. L.; Pennington, C. D.; Roman, M.

2005-01-01

Researchers at Luna Innovations Inc. and the National Aeronautic and Space Administration s Marshall Space Flight Center (NASA MSFC) have developed an integrated fiber-optic sensor system for real-time monitoring of chemical contaminants and whole-cell bacterial pathogens in water. The system integrates interferometric and evanescent-wave optical fiber-based sensing methodologies with atomic force microscopy (AFM) and long-period grating (LPG) technology to provide versatile measurement capability for both micro- and nano-scale analytes. Sensors can be multiplexed in an array format and embedded in a totally self-contained laboratory card for use with an automated microfluidics platform.

Grating-assisted demodulation of interferometric optical sensors.

PubMed

Yu, Bing; Wang, Anbo

2003-12-01

Accurate and dynamic control of the operating point of an interferometric optical sensor to produce the highest sensitivity is crucial in the demodulation of interferometric optical sensors to compensate for manufacturing errors and environmental perturbations. A grating-assisted operating-point tuning system has been designed that uses a diffraction grating and feedback control, functions as a tunable-bandpass optical filter, and can be used as an effective demodulation subsystem in sensor systems based on optical interferometers that use broadband light sources. This demodulation method has no signal-detection bandwidth limit, a high tuning speed, a large tunable range, increased interference fringe contrast, and the potential for absolute optical-path-difference measurement. The achieved 40-nm tuning range, which is limited by the available source spectrum width, 400-nm/s tuning speed, and a step resolution of 0.4 nm, is sufficient for most practical measurements. A significant improvement in signal-to-noise ratio in a fiber Fabry-Perot acoustic-wave sensor system proved that the expected fringe contrast and sensitivity increase.

The effect of delay line on the performance of a fiber optic interferometric sensor

NASA Astrophysics Data System (ADS)

Lin, Yung-Li; Lin, Ken-Huang; Lin, Wuu-Wen; Chen, Mao-Hsiung

2007-09-01

The optical fiber has the features of low loss and wide bandwidth; it has replaced the coaxial cable as the mainstream of the communication system in recent years. Because of its high sensitivity characteristic, the interferometer is usually applied to long distance, weak signal detection. In general, if the area to be monitored is located far away, the weak signal will make it uneasy to detect. An interferometer is used for phase detection. Thus, the hydrophone which is based on interferometric fiber optic sensor has extremely high sensitivity. Sagnac interferometric hydrophone has low noise of marine environment, which is more suitably used to detect underwater acoustic signal than that of a Mach-Zehnder interferometer. In this paper, we propose the configuration of dual Sagnac interferometer, and use the mathematical methods to drive and design optimal two delay fiber lengths, which can enlarge the dynamic range of underwater acoustic detection. In addition, we also use software simulation to design optimal two delay fiber lengths. The experimental configuration of dual Sagnac interferometer with two optical delay line is shown as Fig. 1. The maximum and minimum measurable phase signal value of dual Sagnac interferometer (L II=2 km, L 4=222.2 m), shown in Fig. 3. The fiber optic sensor head is of mandrel type. The acoustic window is made of silicon rubbers. It was shown that we can increase their sensitivities by increasing number of wrapping fiber coils. In our experiment, the result shows that among all the mandrel sensor heads, the highest dynamic range is up to 37.6 +/- 1.4 dB, and its sensitivity is -223.3 +/-1.7 dB re V / 1μ Pa. As for the configuration of the optical interferometers, the intensity of the dual Sagnac interferometer is 20 dB larger than its Sagnac counterpart. Its dynamic range is above 66 dB where the frequency ranges is between 50 ~ 400 Hz, which is 24 dB larger than that of the Sagnac interferometer with the sensitivity of -192.0 dB re V / l μPa. In addition, by using software simulation to design optimal lengths of delay fibers, we can increase the dynamic range of interferometer on underwater acoustic detection. This paper verifies that, by means of adjusting the length of these two delay fibers, we can actually increase the dynamic range of acoustic signal detection.

High-sensitivity fiber optic acoustic sensors

NASA Astrophysics Data System (ADS)

Lu, Ping; Liu, Deming; Liao, Hao

2016-11-01

Due to the overwhelming advantages compared with traditional electronicsensors, fiber-optic acoustic sensors have arisen enormous interest in multiple disciplines. In this paper we present the recent research achievements of our group on fiber-optic acoustic sensors. The main point of our research is high sensitivity interferometric acoustic sensors, including Michelson, Sagnac, and Fabry-Pérot interferometers. In addition, some advanced technologies have been proposed for acoustic or acoustic pressure sensing such as single-mode/multimode fiber coupler, dual FBGs and multi-longitudinal mode fiber laser based acoustic sensors. Moreover, our attention we have also been paid on signal demodulation schemes. The intensity-based quadrature point (Q-point) demodulation, two-wavelength quadrature demodulation and symmetric 3×3 coupler methodare discussed and compared in this paper.

Surface-mount sapphire interferometric temperature sensor.

PubMed

Zhu, Yizheng; Wang, Anbo

2006-08-20

A fiber-optic high-temperature sensor is demonstrated by bonding a 45 degrees -polished single-crystal sapphire fiber on the surface of a sapphire wafer, whose optical thickness is temperature dependent and measured by white-light interferometry. A novel adhesive-free coupling between the silica and sapphire fibers is achieved by fusion splicing, and its performance is characterized. The sensor's interference signal is investigated for its dependence on angular alignment between the fiber and the wafer. A prototype sensor is tested to 1,170 degrees C with a resolution of 0.4 degrees C, demonstrating excellent potential for high-temperature measurement.

Fiber optic sensor based on Mach-Zehnder interferometer for securing entrance areas of buildings

NASA Astrophysics Data System (ADS)

Nedoma, Jan; Fajkus, Marcel; Martinek, Radek; Mec, Pavel; Novak, Martin; Bednarek, Lukas; Vasinek, Vladimir

2017-10-01

Authors of this article focused on the utilization of fiber optic sensors based on interferometric measurements for securing entrance areas of buildings such as windows and doors. We described the implementation of the fiber-optic interferometer (type Mach-Zehnder) into the window frame or door, sensor sensitivity, analysis of the background noise and methods of signal evaluation. The advantage of presented solution is the use of standard telecommunication fiber standard G.652.D, high sensitivity, immunity of sensor to electromagnetic interference (EMI) and passivity of the sensor regarding power supply. Authors implemented the Graphical User Interface (GUI) which offers the possibility of remote monitoring presented sensing solution.

Fiber optic smart structures and skins V; Proceedings of the Meeting, Boston, MA, Sept. 8, 9, 1992

NASA Technical Reports Server (NTRS)

Claus, Richard O. (Editor); Rogowski, Robert S. (Editor)

1993-01-01

The present conference discusses the materials used in applications of fiber-optics (F-O) to smart structures, extrinsic Fabry-Perot interferometric F-O sensors, sapphire F-O sensors, two-mode F-O sensors with photoinduced refractive index, an F-O accelerometer using two-mode fibers, and embedded F-O acoustic sensors for flaw detection. Also discussed are an optoelectronic smart structure interface, F-O sensors for simultaneous detection of strain and temperature, an optical Mach-Zehnder interferometer for smart skins, a split-cavity cross-coupled extrinsic fiber interferometer, and an embedded Bragg grating F-O sensor for composite flexbeams, an Er-doped ring-laser strain sensor.

Quasi-interferometric scheme improved by fiber Bragg grating written on macrostructure defect in silica multimode optical fiber operating in a few-mode regime

NASA Astrophysics Data System (ADS)

Evtushenko, Alexander S.; Faskhutdinov, Lenar M.; Kafarova, Anastasia M.; Kuznetzov, Artem A.; Minaeva, Alina Yu.; Sevruk, Nikita L.; Nureev, Ilnur I.; Vasilets, Alexander A.; Andreev, Vladimir A.; Morozov, Oleg G.; Burdin, Vladimir A.; Bourdine, Anton V.

2017-04-01

This work presents results of experimental approbation of earlier on proposed modified fiber optic stress sensor based on a few-mode effects occurring during laser-excited optical signal propagation over silica multimode optical fiber (MMF). Modification is concerned with a passage to quasi-interferometric scheme realized by two multimode Y-couplers with equalized arm lengths improved by fiber Bragg grating (FBG) written on preliminary formed precision macrostructure defects in silica multimode graded-index optical fibers and special offset launching conditions providing laser-based excitation of higher-order modes. The "arms" of quasi-interferometer are two equalized lengths of MMF Cat. OM2 with great central dip of refractive index profile and strong pulse splitting due to high differential mode delay (DMD). We tested FBGs with Bragg wavelength both 1310 nm and 1550 nm written over tapers or up-tapers preliminary formed in short pieces of MMF Cat. OM2+/OM3 and further jointed to the end of one of the arms before output Y-coupler. Researches were focused on comparison analysis of pulse responses under changing of selected excited mode mixing and power diffusion processes due to stress distributed action to sensor fiber depending. Here we considered FBGs not only as particular wavelength reflector during spectral response measurement but also as local periodic microstructure defect which strongly effects on few-mode signal components mixing process also improved by combination with macro-defect like taper or up-taper that should provide response variation. Some results pulse response measurements produced for different scheme configuration and their comparison analysis are represented.

Low-cost interferometric TDM technology for dynamic sensing applications

NASA Astrophysics Data System (ADS)

Bush, Jeff; Cekorich, Allen

2004-12-01

A low-cost design approach for Time Division Multiplexed (TDM) fiber-optic interferometric interrogation of multi-channel sensor arrays is presented. This paper describes the evolutionary design process of the subject design. First, the requisite elements of interferometric interrogation are defined for a single channel sensor. The concept is then extended to multi-channel sensor interrogation implementing a TDM multiplex scheme where "traditional" design elements are utilized. The cost of the traditional TDM interrogator is investigated and concluded to be too high for entry into many markets. A new design approach is presented which significantly reduces the cost for TDM interrogation. This new approach, in accordance with the cost objectives, shows promise to bring this technology to within the threshold of commercial acceptance for a wide range of distributed fiber sensing applications.

Closed-loop fiber optic gyroscope with homodyne detection

NASA Astrophysics Data System (ADS)

Zhu, Yong; Qin, BingKun; Chen, Shufen

1996-09-01

Interferometric fiber optic gyroscope (IFOG) has been analyzed with autocontrol theory in this paper. An open-loop IFOG system is not able to restrain the bias drift, but a closed-loop IFOG system can do it very well using negative feedback in order to suppress zero drift. The result of our theoretic analysis and computer simulation indicate that the bias drift of a closed-loop system is smaller than an open- loop one.

Interferometric fiber-optic temperature sensor with spiral polarization couplers

NASA Astrophysics Data System (ADS)

Cortés, R.; Khomenko, A. V.; Starodumov, A. N.; Arzate, N.; Zenteno, L. A.

1998-09-01

A fiber optic temperature sensor, for which the changes in modal birefringence of a short section of a long birefringent fiber are monitored remotely, is described. It employs a white light interferometer, which is formed by two concatenated spiral polarization mode couplers. A new method for white light interferometer output signal processing is described which provides a high accuracy absolute temperature measurement even in discontinuous operation of the sensor. Experimental results are presented for temperature measurements over a 100°C range with resolution of 3×10 -3 °C.

Fibre Optic Gyroscope Developments Using Integrated Optic Components

NASA Astrophysics Data System (ADS)

Minford, W. J.; DePaula, R. M.

1988-09-01

The sensing of rotation using counterpropagating optical beams in a fiber loop (the SAGNAC effect) has gone through extensive developments and demonstrations since first proved feasible by Vali and Shorthilll in 1976. The interferometric fiber gyroscope minimum configuration2 which uses a common input-output port and single-mode filter was developed to provide the extreme high stability necessary to reach the sensitivities at low rotation rates attainable with current state-of-the-art detectors. The simplicity and performance of this configuration has led to its acceptance and wide-spread use. In order to increase the mechanical stability of this system, all single-mode fiber components are employed and a further advancement to integrated optics has enabled most of the optical functions to be placed on a single mass-producible substrate. Recent improvements in the components (eg polarization maintaining fiber and low coherence sources) have further enhanced the performance of the minimum configuration gyro. This presentation focused on the impact of LiNbO3 integrated optic components on gyroscope developments. The use of Ti-indiffused LiNbO3 waveguide optical circuits in interferometric fiber optic gyroscopes has taken two directions: to utilize only the phase modulator, or to combine many of the minimum configuration optical functions on the electro-optic substrate. The high-bandwidth phase modulator is the driving force for using LiNbO3 waveguide devices. This device allows both biasing the gyro for maximum sensitivity and closing the loop via frequency shifting, for example, thus increasing the dynamic range of the gyro and the linearity of the scale factor. Efforts to implement most of the minimum configuration optical functions onto a single LiNbO3 substrate have been led by Thomson CSF.3 They have demonstrated an interferometric gyroscope with excellent performance using a LiNbO3 optical circuit containing a Y-splitter, phase modulator, and surface-resonant polarizer. JPL and AT&T-BL have an effort, under a NASA contract, to investigate other integrated optic gyro front-end circuits with the eventual goal of combining all minimum configuration functions on a single substrate. The performance of a gyroscope with a LiNbO3 polarizer, 3dB splitter, and phase modulator was discussed along with the waveguide device characteristics. The key advantages, future trends, and present issues involved with using LiNbO3 waveguide devices in a gyroscope were addressed.

Chronology of Fabry-Perot Interferometer Fiber-Optic Sensors and Their Applications: A Review

PubMed Central

Islam, Md. Rajibul; Ali, Muhammad Mahmood; Lai, Man-Hong; Lim, Kok-Sing; Ahmad, Harith

2014-01-01

Optical fibers have been involved in the area of sensing applications for more than four decades. Moreover, interferometric optical fiber sensors have attracted broad interest for their prospective applications in sensing temperature, refractive index, strain measurement, pressure, acoustic wave, vibration, magnetic field, and voltage. During this time, numerous types of interferometers have been developed such as Fabry-Perot, Michelson, Mach-Zehnder, Sagnac Fiber, and Common-path interferometers. Fabry-Perot interferometer (FPI) fiber-optic sensors have been extensively investigated for their exceedingly effective, simple fabrication as well as low cost aspects. In this study, a wide variety of FPI sensors are reviewed in terms of fabrication methods, principle of operation and their sensing applications. The chronology of the development of FPI sensors and their implementation in various applications are discussed. PMID:24763250

Novel Fiber-Optic Ring Acoustic Emission Sensor

PubMed Central

Han, Xiaole; Xia, Dong; Liu, Taolin; Lang, Hao

2018-01-01

Acoustic emission technology has been applied to many fields for many years. However, the conventional piezoelectric acoustic emission sensors cannot be used in extreme environments, such as those with heavy electromagnetic interference, high pressure, or strong corrosion. In this paper, a novel fiber-optic ring acoustic emission sensor is proposed. The sensor exhibits high sensitivity, anti-electromagnetic interference, and corrosion resistance. First, the principle of a novel fiber-optic ring sensor is introduced. Different from piezoelectric and other fiber acoustic emission sensors, this novel sensor includes both a sensing skeleton and a sensing fiber. Second, a heterodyne interferometric demodulating method is presented. In addition, a fiber-optic ring sensor acoustic emission system is built based on this method. Finally, fiber-optic ring acoustic emission experiments are performed. The novel fiber-optic ring sensor is glued onto the surface of an aluminum plate. The 150 kHz standard continuous sinusoidal signals and broken lead signals are successfully detected by the novel fiber-optic ring acoustic emission sensor. In addition, comparison to the piezoelectric acoustic emission sensor is performed, which shows the availability and reliability of the novel fiber-optic ring acoustic emission sensor. In the future, this novel fiber-optic ring acoustic emission sensor will provide a new route to acoustic emission detection in harsh environments. PMID:29342858

Novel Fiber-Optic Ring Acoustic Emission Sensor.

PubMed

Wei, Peng; Han, Xiaole; Xia, Dong; Liu, Taolin; Lang, Hao

2018-01-13

Acoustic emission technology has been applied to many fields for many years. However, the conventional piezoelectric acoustic emission sensors cannot be used in extreme environments, such as those with heavy electromagnetic interference, high pressure, or strong corrosion. In this paper, a novel fiber-optic ring acoustic emission sensor is proposed. The sensor exhibits high sensitivity, anti-electromagnetic interference, and corrosion resistance. First, the principle of a novel fiber-optic ring sensor is introduced. Different from piezoelectric and other fiber acoustic emission sensors, this novel sensor includes both a sensing skeleton and a sensing fiber. Second, a heterodyne interferometric demodulating method is presented. In addition, a fiber-optic ring sensor acoustic emission system is built based on this method. Finally, fiber-optic ring acoustic emission experiments are performed. The novel fiber-optic ring sensor is glued onto the surface of an aluminum plate. The 150 kHz standard continuous sinusoidal signals and broken lead signals are successfully detected by the novel fiber-optic ring acoustic emission sensor. In addition, comparison to the piezoelectric acoustic emission sensor is performed, which shows the availability and reliability of the novel fiber-optic ring acoustic emission sensor. In the future, this novel fiber-optic ring acoustic emission sensor will provide a new route to acoustic emission detection in harsh environments.

Application of optical interferometric techniques for non-destructive evaluation of novel "green" composite materials

NASA Astrophysics Data System (ADS)

Pagliarulo, Vito; Russo, Pietro; Bianco, Vittorio; Ferraro, Pietro; Simeoli, Giorgio; Cimino, Francesca; Ruggiero, Berardo

2018-04-01

Nowadays the use of advanced composite materials in aeronautics, both civil and military, in automotive and in sport applications, citing some, is well established. The characteristics of composite materials in terms of weight, fatigue resistance and corrosion resistance make them competitive with respect to conventional ones. On the other side, the fabrication process of the most employed composites reinforced by carbon fibers or glass fibers, needs of complex steps that not always are environmental complaisant. Moreover, such fibers are not themselves "green". For these reasons, in the last decades, the use of natural reinforcing fibers has gained an increasing attention allowing the development of new materials with the same advantages of composite systems but respecting the environment. Furthermore, such materials for their structural complexity are not always compatible with the use of standard non-destructive evaluation as the ultrasounds methods. In this work the efficiency of the employment of optical interferometric techniques as nondestructive evaluation methods in full field modality is proved on novel "green" composite materials. In particular, Electronic Speckle Pattern Interferometry has been tested on different kinds of specimens after flexural tests.

Demodulation System for Fiber Optic Bragg Grating Dynamic Pressure Sensing

NASA Technical Reports Server (NTRS)

Lekki, John D.; Adamovsky, Grigory; Floyd, Bertram

2001-01-01

Fiber optic Bragg gratings have been used for years to measure quasi-static phenomena. In aircraft engine applications there is a need to measure dynamic signals such as variable pressures. In order to monitor these pressures a detection system with broad dynamic range is needed. This paper describes an interferometric demodulator that was developed and optimized for this particular application. The signal to noise ratio was maximized through temporal coherence analysis. The demodulator was incorporated in a laboratory system that simulates conditions to be measured. Several pressure sensor configurations incorporating a fiber optic Bragg grating were also explored. The results of the experiments are reported in this paper.

Polymerization shrinkage of a dental resin composite determined by a fiber optic Fizeau interferometer

NASA Astrophysics Data System (ADS)

Arenas, Gustavo; Noriega, Sergio; Vallo, Claudia; Duchowicz, Ricardo

2007-03-01

A fiber optic sensing method based on a Fizeau-type interferometric scheme was employed for monitoring linear polymerization shrinkage in dental restoratives. This technique offers several advantages over the conventional methods of measuring polymerization contraction. This simple, compact, non-invasive and self-calibrating system competes with both conventional and other high-resolution bulk interferometric techniques. In this work, an analysis of the quality of interference signal and fringes visibility was performed in order to characterize their resolution and application range. The measurements of percent linear contraction as a function of the sample thickness were carried out in this study on two dental composites: Filtek P60 (3M ESPE) Posterior Restorer and Filtek Z250 (3M ESPE) Universal Restorer. The results were discussed with respect to others obtained employing alternative techniques.

Intrinsic polymer optical fiber sensors for high-strain applications

NASA Astrophysics Data System (ADS)

Kiesel, Sharon; Van Vickle, Patrick; Peters, Kara; Hassan, Tasnim; Kowalsky, Mervyn

2006-03-01

This paper presents intrinsic polymer fiber (POF) sensors for high-strain applications such as health monitoring of civil infrastructure systems subjected to earthquake loading or structures with large shape changes such as morphing aircraft. POFs provide a potential maximum strain range of 6-12%, are more flexible that silica optical fibers, and are more durable in harsh chemical or environmental conditions. Recent advances in the fabrication of singlemode POFs have made it possible to extend POFs to interferometric sensor capabilities. Furthermore, the interferometric nature of intrinsic sensors permits high accuracy for such measurements. However, several challenges, addressed in this paper, make the application of the POF interferometer more difficult than its silica counterpart. These include the finite deformation of the POF cross-section at high strain values, nonlinear strain optic effects in the polymer, and the attenuation with strain of the POF. In order to predict the response of the sensor a second-order (in strain) photoelastic effect is derived and combined with the second-order solution of the deformation of the optical fiber when loaded. It is determined that for the small deformation region four constants are required (two mechanical and two photoelastic properties) and for the large deformation region six additional constants are required (two mechanical and four photoelastic properties). This paper also presents initial measurements of the mechanical response of the sensor and comparison to previously reported POFs.

Study of the fusion point between PM-PCF and panda fiber and its influence to Interferometric fiber-optical gyroscope

NASA Astrophysics Data System (ADS)

Sun, Zuoming; Wang, Shuhua; Li, Junwei

2017-02-01

Microhole collapse property of polarization maintaining photonic crystal fibers (PM-PCF) and its effect on the splice loss and polarization cross-coupling during fusion splicing were investigated. The relationship between the microhole collapse and polarization cross-coupling are analyzed through simulation and experiment. Finally their influence to the phase error of the FOG is calculated and tested.

Fiber-linked interferometric pressure sensor

NASA Technical Reports Server (NTRS)

Beheim, G.; Fritsch, K.; Poorman, R. N.

1987-01-01

A fiber-optic pressure sensor is described which uses a diaphragm to modulate the mirror separation of a Fabry-Perot cavity (the sensing cavity). A multimode optical fiber delivers broadband light to the sensing cavity and returns the spectrally modulated light which the cavity reflects. The sensor's output spectrum is analyzed using a tunable Fabry-Perot cavity (the reference cavity) to determine the mismatch in the mirror separations of the two cavities. An electronic servo control uses this result to cause the mirror separation of the reference cavity to equal that of the sensing cavity. The displacement of the pressure-sensing diaphragm is then obtained by measuring the capacitance of the reference cavity's metal-coated mirrors. Relative to other fiber-optic sensors, an important advantage of this instrument is its high immunity to the effects of variations in both the transmissivity of the fiber link and the wavelength of the optical source.

Application of thin dielectric films in low coherence fiber-optic Fabry-Pérot sensing interferometers: comparative study

NASA Astrophysics Data System (ADS)

Hirsch, Marzena; Wierzba, Paweł; Jedrzejewska-Szczerska, Małgorzata

2016-11-01

We examine the application of selected thin dielectric films, deposited by atomic layer deposition (ALD), in a low coherence fiber-optic Fabry-Pérot interferometer designed for sensing applications. Such films can be deposited on the end-face of a single mode optical fiber (SMF-28) in order to modify the reflectivity of the Fabry-Pérot cavity, to provide protection of the fibers from aggressive environments or to create a multi-cavity interferometric sensor. Spectral reflectance of films made from zinc oxide (ZnO), titanium dioxide (TiO2), aluminum oxide (Al2O3) and boron nitride (BN) was calculated for various thickness of the films and compared. The results show that the most promising materials for use in fiber-optic Fabry-Pérot interferometer are TiO2 and ZnO, although Al2O3 is also suitable for this application.

Fiber Optic Sensor for Acoustic Detection of Partial Discharges in Oil-Paper Insulated Electrical Systems

PubMed Central

Posada-Roman, Julio; Garcia-Souto, Jose A.; Rubio-Serrano, Jesus

2012-01-01

A fiber optic interferometric sensor with an intrinsic transducer along a length of the fiber is presented for ultrasound measurements of the acoustic emission from partial discharges inside oil-filled power apparatus. The sensor is designed for high sensitivity measurements in a harsh electromagnetic field environment, with wide temperature changes and immersion in oil. It allows enough sensitivity for the application, for which the acoustic pressure is in the range of units of Pa at a frequency of 150 kHz. In addition, the accessibility to the sensing region is guaranteed by immune fiber-optic cables and the optical phase sensor output. The sensor design is a compact and rugged coil of fiber. In addition to a complete calibration, the in-situ results show that two types of partial discharges are measured through their acoustic emissions with the sensor immersed in oil. PMID:22666058

Interferometric system based on swept source-optical coherence tomography scheme applied to the measurement of distances of industrial interest

NASA Astrophysics Data System (ADS)

Morel, Eneas N.; Russo, Nélida A.; Torga, Jorge R.; Duchowicz, Ricardo

2016-01-01

We used an interferometric technique based on typical optical coherence tomography (OCT) schemes for measuring distances of industrial interest. The system employed as a light source a tunable erbium-doped fiber laser of ˜20-pm bandwidth with a tuning range between 1520 and 1570 nm. It has a sufficiently long coherence length to enable long depth range imaging. A set of fiber Bragg gratings was used as a self-calibration method, which has the advantage of being a passive system that requires no additional electronic devices. The proposed configuration and the coherence length of the laser enlarge the range of maximum distances that can be measured with the common OCT configuration, maintaining a good axial resolution. A measuring range slightly >17 cm was determined. The system performance was evaluated by studying the repeatability and axial resolution of the results when the same optical path difference was measured. Additionally, the thickness of a semitransparent medium was also measured.

Fiber Fabry-Perot sensors for detection of partial discharges in power transformers.

PubMed

Yu, Bing; Kim, Dae Woong; Deng, Jiangdong; Xiao, Hai; Wang, Anbo

2003-06-01

A diaphragm-based interferometric fiberoptic sensor that uses a low-coherence light source was designed and tested for on-line detection of the acoustic waves generated by partial discharges inside high-voltage power transformers. The sensor uses a fused-silica diaphragm and a single-mode optical fiber encapsulated in a fused-silica glass tube to form an extrinsic Fabry-Perot interferometer, which is interrogated by low-coherence light. Test results indicate that these fiber optic acoustic sensors are capable of faithfully detecting acoustic signals propagating inside transformer oil with high sensitivity and wide bandwidth.

Elasto-plastic bond mechanics of embedded fiber optic sensors in concrete under uniaxial tension with strain localization

NASA Astrophysics Data System (ADS)

Li, Qingbin; Li, Guang; Wang, Guanglun

2003-12-01

Brittleness of the glass core inside fiber optic sensors limits their practical usage, and therefore they are coated with low-modulus softer protective materials. Protective coatings absorb a portion of the strain, and hence part of the structural strain is sensed. The study reported here corrects for this error through development of a theoretical model to account for the loss of strain in the protective coating of optical fibers. The model considers the coating as an elasto-plastic material and formulates strain transfer coefficients for elastic, elasto-plastic and strain localization phases of coating deformations in strain localization in concrete. The theoretical findings were verified through laboratory experimentation. The experimental program involved fabrication of interferometric optical fiber sensors, embedding within mortar samples and tensile tests in a closed-loop servo-hydraulic testing machine. The elasto-plastic strain transfer coefficients were employed for correction of optical fiber sensor data and results were compared with those of conventional extensometers.

Studying the fundamental limit of optical fiber links to the 10-21 level.

PubMed

Xu, Dan; Lee, Won-Kyu; Stefani, Fabio; Lopez, Olivier; Amy-Klein, Anne; Pottie, Paul-Eric

2018-04-16

We present a hybrid fiber link combining effective optical frequency transfer and evaluation of performances with a self-synchronized two-way comparison. It enables us to detect the round-trip fiber noise and each of the forward and backward one-way fiber noises simultaneously. The various signals acquired with this setup allow us to study quantitatively several properties of optical fiber links. We check the reciprocity of the accumulated noise forth and back over a bi-directional fiber to the level of 3.1(±3.9) × 10 -20 based on a 160000s continuous data. We also analyze the noise correlation between two adjacent fibers and show the first experimental evidence of interferometric noise at very low Fourier frequency. We estimate redundantly and consistently the stability and accuracy of the transferred optical frequency over 43 km at 4 × 10 -21 level after 16 days of integration and demonstrate that a frequency comparison with instability as low as 8 × 10 -18 would be achievable with uni-directional fibers in urban area.

Diaphragm-Free Fiber-Optic Fabry-Perot Interferometric Gas Pressure Sensor for High Temperature Application.

PubMed

Liang, Hao; Jia, Pinggang; Liu, Jia; Fang, Guocheng; Li, Zhe; Hong, Yingping; Liang, Ting; Xiong, Jijun

2018-03-28

A diaphragm-free fiber-optic Fabry-Perot (FP) interferometric gas pressure sensor is designed and experimentally verified in this paper. The FP cavity was fabricated by inserting a well-cut fiber Bragg grating (FBG) and hollow silica tube (HST) from both sides into a silica casing. The FP cavity length between the ends of the SMF and HST changes with the gas density. Using temperature decoupling method to improve the accuracy of the pressure sensor in high temperature environments. An experimental system for measuring the pressure under different temperatures was established to verify the performance of the sensor. The pressure sensitivity of the FP gas pressure sensor is 4.28 nm/MPa with a high linear pressure response over the range of 0.1-0.7 MPa, and the temperature sensitivity is 14.8 pm/°C under the range of 20-800 °C. The sensor has less than 1.5% non-linearity at different temperatures by using temperature decoupling method. The simple fabrication and low-cost will help sensor to maintain the excellent features required by pressure measurement in high temperature applications.

Miniature all-silica optical fiber pressure sensor with an ultrathin uniform diaphragm.

PubMed

Wang, Wenhui; Wu, Nan; Tian, Ye; Niezrecki, Christopher; Wang, Xingwei

2010-04-26

This paper presents an all-silica miniature optical fiber pressure/acoustic sensor based on the Fabry-Perot (FP) interferometric principle. The endface of the etched optical fiber tip and silica thin diaphragm on it form the FP structure. The uniform and thin silica diaphragm was fabricated by etching away the silicon substrate from a commercial silicon wafer that has a thermal oxide layer. The thin film was directly thermally bonded to the endface of the optical fiber thus creating the Fabry-Perot cavity. Thin films with a thickness from 1microm to 3microm have been bonded successfully. The sensor shows good linearity and hysteresis during measurement. A sensor with 0.75 microm-thick diaphragm thinned by post silica etching was demonstrated to have a sensitivity of 11 nm/kPa. The new sensor has great potential to be used as a non-intrusive pressure sensor in a variety of sensing applications.

Two-wavelength quadrature multipoint detection of partial discharge in power transformers using fiber Fabry-Perot acoustic sensors

NASA Astrophysics Data System (ADS)

Dong, Bo; Han, Ming; Wang, Anbo

2012-06-01

A reliable and low-cost two-wavelength quadrature interrogating method has been developed to demodulate optical signals from diaphragm-based Fabry-Perot interferometric fiber optic sensors for multipoint partial discharge detection in power transformers. Commercial available fused-silica parts (a wafer, a fiber ferrule, and a mating sleeve) and a cleaved optical single mode fiber were bonded together to form an extrinsic Fabry-Perot acoustic sensor. Two lasers with center wavelengths separated by a quarter of the period of sensor interference fringes were used to probe acousticwave- induced diaphragm vibration. A coarse wavelength-division multiplexing (CWDM) add/drop multiplexer was used to separate the reflected two wavelengths before two photo detectors. Optical couplers were used to distribute mixed laser light to each sensor-detector module for multiplexing purpose. Sensor structure, detection system design and experiment results are presented.

Micro-structured optical fiber sensor for simultaneous measurement of temperature and refractive index

NASA Astrophysics Data System (ADS)

Liu, Ying-gang; Liu, Xin; Ma, Cheng-ju; Zhou, Yu-min

2018-03-01

Through using micro-machining method for optical fiber sensor, a kind of miniature, compact and composite structural all-fiber sensor is presented. Based on manufacturing two micro-holes with certain distance in ordinary single-mode fiber Bragg grating (FBG) by excimer laser processing technique, we fabricate a dual Fabry-Perot-FBG (FP-FBG) composite fiber interferometric sensor, which can be used in simultaneous measurement for liquid's refractive index (RI) and temperature change. Due to every micro-hole and the dual micro-holes in fiber acting as different Fabry-Perot (FP) cavities, this kind of sensor has not only different RI sensitivities but also different temperature sensitivities, which are corresponding to the wavelength shifts of the fine interference fringes and spectral envelope, respectively. The experimental results show that the spectral wavelength shift keep better linear response for temperature and RI change, so that we can select the higher temperature and RI sensitivities as well as the analyzed sensitivities of FBG to utilize them for constituting a sensitivity coefficients matrix. Finally, the variations of liquid's temperature and RI are detected effectively, and the resolutions can reach to 0.1 °C and 1.0 ×10-5 RIU. These characteristics are what other single-type sensors don't have, so that this kind of all-fiber dual FP-FBG composite fiber interferometric sensor can be used in extremely tiny liquid environment for measuring different physical quantities simultaneously.

Fiber optic strain and temperature sensor for power plant applications

NASA Astrophysics Data System (ADS)

Narendran, Nadarajah; Weiss, Joseph M.

1996-01-01

The applicability of fiber-optic strain and temperature sensors to monitor power plant structures was evaluated on a super-heated steam pipe operating at 1000 degree(s)F at the Tennessee Valley Authority power plant in Kingston, Tennessee. The potential applications of these fiber-optic sensors include health monitoring of high-temperature structures such as boilers, tube headers, and steam pipes, as well as many other power plant structures exposed to less severe environments. The sensor selected for this application is based on a white-light interferometric technique. The key features of this sensor include its ability for absolute measurements that are not affected by light loss along the fiber cable due to, for example, microbending effects and coupler loss, its compatibility with off-the-shelf fiber-optic components, and its low cost. The glass fiber-optic strain sensors were packaged in a rugged metal housing and were spot welded to the high-temperature steam pipe. Another set of gages was placed inside a thermowell for steam temperature measurement. Data collected during a routine start-up is very encouraging and the details are presented in this manuscript.

Performance limitations of a white light extrinsic Fabry-Perot interferometric displacement sensor

NASA Astrophysics Data System (ADS)

Moro, Erik A.; Todd, Michael D.; Puckett, Anthony D.

2012-06-01

Non-contacting interferometric fiber optic sensors offer a minimally invasive, high-accuracy means of measuring a structure's kinematic response to loading. The performance of interferometric sensors is often dictated by the technique employed for demodulating the kinematic measurand of interest from phase in the observed optical signal. In this paper a white-light extrinsic Fabry-Perot interferometer is implemented, offering robust displacement sensing performance. Displacement data is extracted from an estimate of the power spectral density, calculated from the interferometer's received optical power measured as a function of optical transmission frequency, and the sensor's performance is dictated by the details surrounding the implementation of this power spectral density estimation. One advantage of this particular type of interferometric sensor is that many of its control parameters (e.g., frequency range, frequency sampling density, sampling rate, etc.) may be chosen to so that the sensor satisfies application-specific performance needs in metrics such as bandwidth, axial displacement range, displacement resolution, and accuracy. A suite of user-controlled input values is investigated for estimating the spectrum of power versus wavelength data, and the relationships between performance metrics and input parameters are described in an effort to characterize the sensor's operational performance limitations. This work has been approved by Los Alamos National Laboratory for unlimited public release (LA-UR 12-01512).

A novel wavelength reused bidirectional RoF-WDM-PON architecture to mitigate reflection and Rayleigh backscattered noise in multi-Gb/s m-QAM OFDM SSB upstream and downstream transmission over a single fiber

NASA Astrophysics Data System (ADS)

Patel, Dhananjay; Dalal, U. D.

2017-05-01

A novel m-QAM Orthogonal Frequency Division Multiplexing (OFDM) Single Sideband (SSB) architecture is proposed for centralized light source (CLS) bidirectional Radio over Fiber (RoF) - Wavelength Division Multiplexing (WDM) - Passive Optical Network (PON). In bidirectional transmission with carrier reuse over the single fiber, the Rayleigh Backscattering (RB) noise and reflection (RE) interferences from optical components can seriously deteriorate the transmission performance of the fiber optic systems. These interferometric noises can be mitigated by utilizing the optical modulation schemes at the Optical Line Terminal (OLT) and Optical Network Unit (ONU) such that the spectral overlap between the optical data spectrum and the RB and RE noise is minimum. A mathematical model is developed for the proposed architecture to accurately measure the performance of the transmission system and also to analyze the effect of interferometric noise caused by the RB and RE. The model takes into the account the different modulation schemes employed at the OLT and the ONU using a Mach Zehnder Modulator (MZM), the optical launch power and the bit-rates of the downstream and upstream signals, the gain of the amplifiers at the OLT and the ONU, the RB-RE noise, chromatic dispersion of the single mode fiber and optical filter responses. In addition, the model analyzes all the components of the RB-RE noise such as carrier RB, signal RB, carrier RE and signal RE, thus providing the complete representation of all the physical phenomena involved. An optical m-QAM OFDM SSB signal acts as a test signal to validate the model which provides excellent agreement with simulation results. The SSB modulation technique using the MZM at the OLT and the ONU differs in the data transmission technique that takes place through the first-order higher and the lower optical sideband respectively. This spectral gap between the downstream and upstream signals reduces the effect of Rayleigh backscattering and discrete reflections.

Low-coherence interferometric tip-clearance probe

NASA Astrophysics Data System (ADS)

Kempe, Andreas; Schlamp, Stefan; Rösgen, Thomas; Haffner, Ken

2003-08-01

We propose an all-fiber, self-calibrating, economical probe that is capable of near-real-time, single-port, simultaneous blade-to-blade tip-clearance measurements with submillimeter accuracy (typically <100 μm, absolute) in the first stages of a gas turbine. Our probe relies on the interference between backreflected light from the blade tips during the 1-μs blade passage time and a frequency-shifted reference with variable time delay, making use of a low-coherence light source. A single optical fiber of arbitrary length connects the self-contained optics and electronics to the turbine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Wenhui; Jiang, Yi; Gao, Ran, E-mail: bitjy@bit.edu.cn

A photonic crystal fiber (PCF) based high-temperature fiber-optic sensor is proposed and experimentally demonstrated. The sensor head is a Fabry-Perot cavity manufactured with a short section of endless single-mode photonic crystal fiber (ESM PCF). The interferometric spectrum of the Fabry-Perot interferometer is collected by a charge coupled device linear array based micro spectrometer. A high-resolution demodulation algorithm is used to interrogate the peak wavelengths. Experimental results show that the temperature range of 1200 °C and the temperature resolution of 1 °C are achieved.

Complete chirp analysis of a gain-switched pulse using an interferometric two-photon absorption autocorrelation.

PubMed

Chin, Sang Hoon; Kim, Young Jae; Song, Ho Seong; Kim, Dug Young

2006-10-10

We propose a simple but powerful scheme for the complete analysis of the frequency chirp of a gain-switched optical pulse using a fringe-resolved interferometric two-photon absorption autocorrelator. A frequency chirp imposed on the gain-switched pulse from a laser diode was retrieved from both the intensity autocorrelation trace and the envelope of the second-harmonic interference fringe pattern. To verify the accuracy of the proposed phase retrieval method, we have performed an optical pulse compression experiment by using dispersion-compensating fibers with different lengths. We have obtained close agreement by less than a 1% error between the compressed pulse widths and numerically calculated pulse widths.

Fixing methods for the use of optical fibers in interferometric arrangements

NASA Astrophysics Data System (ADS)

Cubik, Jakub; Kepak, Stanislav; Fajkus, Marcel; Zboril, Ondrej; Nedoma, Jan; Davidson, Alan; Vasinek, Vladimir

2016-12-01

Today interferometric sensors are among the most accurate available thanks to their inherent high sensitivity. These highly versatile sensors may be used to measure phenomena such as temperature, strain, fluid level, flow, vibration, stress, etc. This article concentrates on the composition of fiber-optic interferometers, in particular the Mach-Zehnder type. The Mach-Zehnder type is composed of two arms, one for measurement and a second serving as a reference. When light enters the interferometer, ideally the phase of the light is shifted only in the measurement arm while the phase in the second arm remains unchanged. Interference occurs when the light recombining at the output and the resulting light intensity is proportional to the measurand. A major issue in the application of fiber based sensors is laying and fixing the fibers effectively in real life environments. Different approaches are necessary for both arms. The reference arm should as far as possible be isolated from the measurand. In this paper, various isolating materials are considered, however there are almost unlimited materials that may be used for isolation purposes. Conventional construction methods and materials were used such as aluminum tubing, flexible PVC tubing, double sided tape, steel clinches, superglue, PVC strips and PVC strips filled by silicon.

Applications for fiber optic sensing in the upstream oil and gas industry

NASA Astrophysics Data System (ADS)

Baldwin, Chris S.

2015-05-01

Fiber optic sensing has been used in an increasing number of applications in the upstream oil and gas industry over the past 20 years. In some cases, fiber optic sensing is providing measurements where traditional measurement technologies could not. This paper will provide a general overview of these applications and describe how the use of fiber optic sensing is enabling these applications. Technologies such as Bragg gratings, distributed temperature and acoustic sensing, interferometric sensing, and Brillouin scattering will be discussed. Applications for optic sensing include a range of possibilities from a single pressure measurement point in the wellbore to multizone pressure and flow monitoring. Some applications make use of fully distributed measurements including thermal profiling of the well. Outside of the wellbore, fiber optic sensors are used in applications for flowline and pipeline monitoring and for riser integrity monitoring. Applications to be described in this paper include in-flow profiling, well integrity, production monitoring, and steam chamber growth. These applications will cover well types such as injectors, producers, hydraulic fracturing, and thermal recovery. Many of these applications use the measurements provided by fiber optic sensing to improve enhanced oil recovery operations. The growing use of fiber optic sensors is providing improved measurement capabilities leading to the generation of actionable data for enhanced production optimization. This not only increases the recovered amount of production fluids but can also enhance wellbore integrity and safety.

Development of advanced seal verification

NASA Technical Reports Server (NTRS)

Workman, Gary L.; Kosten, Susan E.; Abushagur, Mustafa A.

1992-01-01

The purpose of this research is to develop a technique to monitor and insure seal integrity with a sensor that has no active elements to burn-out during a long duration activity, such as a leakage test or especially during a mission in space. The original concept proposed is that by implementing fiber optic sensors, changes in the integrity of a seal can be monitored in real time and at no time should the optical fiber sensor fail. The electrical components which provide optical excitation and detection through the fiber are not part of the seal; hence, if these electrical components fail, they can be easily changed without breaking the seal. The optical connections required for the concept to work does present a functional problem to work out. The utility of the optical fiber sensor for seal monitoring should be general enough that the degradation of a seal can be determined before catastrophic failure occurs and appropriate action taken. Two parallel efforts were performed in determining the feasibility of using optical fiber sensors for seal verification. In one study, research on interferometric measurements of the mechanical response of the optical fiber sensors to seal integrity was studied. In a second study, the implementation of the optical fiber to a typical vacuum chamber was implemented and feasibility studies on microbend experiments in the vacuum chamber were performed. Also, an attempt was made to quantify the amount of pressure actually being applied to the optical fiber using finite element analysis software by Algor.

Laser Development for Interferometry in Space

NASA Technical Reports Server (NTRS)

Numata, Kenji; Camp, Jordan

2012-01-01

We are developing a laser (master oscillator) and optical amplifier for interferometric space missions, including the gravitational-wave missions NGO and OpTIIX experiment on the international space station. Our system is based on optical fiber and semiconductor laser technologies, which have evolved dramatically in the past decade. We will report on the latest status of the development work, including noise measurements and space qualification tests.

Sparse aperture endoscope

DOEpatents

Fitch, J.P.

1999-07-06

An endoscope is disclosed which reduces the volume needed by the imaging part, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases it's utility. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing. 7 figs.

Sparse aperture endoscope

DOEpatents

Fitch, Joseph P.

1999-07-06

An endoscope which reduces the volume needed by the imaging part thereof, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases the utility thereof. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing.

Method and apparatus for monitoring and measuring the surface tension of a fluid using fiber optics

DOEpatents

Abraham, Bernard M.; Ketterson, John B.; Bohanon, Thomas M.; Mikrut, John M.

1994-01-01

A non-contact method and apparatus for measuring and monitoring the surface of a fluid using fiber optics and interferometric detection to permit measurement mechanical characteristics' fluid surfaces. The apparatus employs an alternating electric field gradient for generating a capillary wave on the surface of the fluid. A fiber optic coupler and optical fiber directs a portion of a laser beam onto the surface of the fluid, another portion of the laser beam onto the photo sensor, and directs light reflected from the surface of the fluid onto the photo sensor. The output of the photo sensor is processed and coupled to a phase sensitive detector to permit measurement of phase shift between the drive signal creating the capillary wave and the detected signal. This phase shift information is then used to determine mechanical properties of the fluid surface such as surface tension, surface elasticity, and surface inhomogeneity. The resulting test structure is easily made compact, portable, and easy to align and use.

A novel fiber optic geophone with high sensitivity for geo-acoustic detection

NASA Astrophysics Data System (ADS)

Zhang, Zhenhui; Yang, Huayong; Xiong, Shuidong; Luo, Hong; Cao, Chunyan; Ma, Shuqing

2014-12-01

A novel interferometric fiber optic geophone is introduced in this paper. This geophone is mainly used for geo-acoustic signal detection. The geophone use one of the three orthogonal components of mandrel type push-pull structure in mechanically and single-mode fiber optic Michelson interferometer structure with Faraday Rotation Mirror (FRM) elements in optically. The resonance frequency of the geophone is larger than 1000Hz. The acceleration sensitivity is as high as 56.6 dB (0dB re 1rad/g) with a slight sensitivity fluctuation of +/-0. 2dB within the frequency band from 20Hz to 200Hz. The geo-acoustic signals generated by underwater blasting are detected successfully. All the channels show good uniformity in the detected wave shape and the amplitudes exhibit very slight differences. The geo-acoustic signal excitated by the engine of surface vehicles was also detected successfully.

Optical system components for navigation grade fiber optic gyroscopes

NASA Astrophysics Data System (ADS)

Heimann, Marcus; Liesegang, Maximilian; Arndt-Staufenbiel, Norbert; Schröder, Henning; Lang, Klaus-Dieter

2013-10-01

Interferometric fiber optic gyroscopes belong to the class of inertial sensors. Due to their high accuracy they are used for absolute position and rotation measurement in manned/unmanned vehicles, e.g. submarines, ground vehicles, aircraft or satellites. The important system components are the light source, the electro optical phase modulator, the optical fiber coil and the photodetector. This paper is focused on approaches to realize a stable light source and fiber coil. Superluminescent diode and erbium doped fiber laser were studied to realize an accurate and stable light source. Therefor the influence of the polarization grade of the source and the effects due to back reflections to the source were studied. During operation thermal working conditions severely affect accuracy and stability of the optical fiber coil, which is the sensor element. Thermal gradients that are applied to the fiber coil have large negative effects on the achievable system accuracy of the optic gyroscope. Therefore a way of calculating and compensating the rotation rate error of a fiber coil due to thermal change is introduced. A simplified 3 dimensional FEM of a quadrupole wound fiber coil is used to determine the build-up of thermal fields in the polarization maintaining fiber due to outside heating sources. The rotation rate error due to these sources is then calculated and compared to measurement data. A simple regression model is used to compensate the rotation rate error with temperature measurement at the outside of the fiber coil. To realize a compact and robust optical package for some of the relevant optical system components an approach based on ion exchanged waveguides in thin glass was developed. This waveguides are used to realize 1x2 and 1x4 splitter with fiber coupling interface or direct photodiode coupling.

Temperature Dependence of Faraday Effect-Induced Bias Error in a Fiber Optic Gyroscope

PubMed Central

Li, Xuyou; Guang, Xingxing; Xu, Zhenlong; Li, Guangchun

2017-01-01

Improving the performance of interferometric fiber optic gyroscope (IFOG) in harsh environments, such as magnetic field and temperature field variation, is necessary for its practical applications. This paper presents an investigation of Faraday effect-induced bias error of IFOG under varying temperature. Jones matrix method is utilized to formulize the temperature dependence of Faraday effect-induced bias error. Theoretical results show that the Faraday effect-induced bias error changes with the temperature in the non-skeleton polarization maintaining (PM) fiber coil. This phenomenon is caused by the temperature dependence of linear birefringence and Verdet constant of PM fiber. Particularly, Faraday effect-induced bias errors of two polarizations always have opposite signs that can be compensated optically regardless of the changes of the temperature. Two experiments with a 1000 m non-skeleton PM fiber coil are performed, and the experimental results support these theoretical predictions. This study is promising for improving the bias stability of IFOG. PMID:28880203

Temperature Dependence of Faraday Effect-Induced Bias Error in a Fiber Optic Gyroscope.

PubMed

Li, Xuyou; Liu, Pan; Guang, Xingxing; Xu, Zhenlong; Guan, Lianwu; Li, Guangchun

2017-09-07

Improving the performance of interferometric fiber optic gyroscope (IFOG) in harsh environments, such as magnetic field and temperature field variation, is necessary for its practical applications. This paper presents an investigation of Faraday effect-induced bias error of IFOG under varying temperature. Jones matrix method is utilized to formulize the temperature dependence of Faraday effect-induced bias error. Theoretical results show that the Faraday effect-induced bias error changes with the temperature in the non-skeleton polarization maintaining (PM) fiber coil. This phenomenon is caused by the temperature dependence of linear birefringence and Verdet constant of PM fiber. Particularly, Faraday effect-induced bias errors of two polarizations always have opposite signs that can be compensated optically regardless of the changes of the temperature. Two experiments with a 1000 m non-skeleton PM fiber coil are performed, and the experimental results support these theoretical predictions. This study is promising for improving the bias stability of IFOG.

A development optical course based on optical fiber white light interference

NASA Astrophysics Data System (ADS)

Jiang, Haili; Sun, Qiuhua; Zhao, Yancheng; Li, Qingbo

2017-08-01

The Michelson interferometer is a very important instrument in optical part for college physics teaching. But most students only know the instrument itself and don't know how to use it in practical engineering problems. A case about optical fiber white light interference based on engineering practice was introduced in the optical teaching of college physics and then designed a development course of university physical optics part. This system based on low-coherence white light interferometric technology can be used to measure distribution strain or temperature. It also could be used in the case of temperature compensation mode.This teaching design can use the knowledge transfer rule to enable students to apply the basic knowledge in the university physics to the new knowledge domain, which can promote the students' ability of using scientific methods to solve complex engineering problems.

Nonlinear effects of a modal domain optical fiber sensor in a vibration suppression control loop for a flexible structure

NASA Technical Reports Server (NTRS)

Lindner, D. K.; Zvonar, G. A.; Baumann, W. T.; Delos, P. L.

1993-01-01

Recently, a modal domain optical fiber sensor has been demonstrated as a sensor in a control system for vibration suppression of a flexible cantilevered beam. This sensor responds to strain through a mechanical attachment to the structure. Because this sensor is of the interferometric type, the output of the sensor has a sinusoidal nonlinearity. For small levels of strain, the sensor can be operated in its linear region. For large levels of strain, the detection electronics can be configured to count fringes. In both of these configurations, the sensor nonlinearity imposes some restrictions on the performance of the control system. In this paper we investigate the effects of these sensor nonlinearities on the control system, and identify the region of linear operation in terms of the optical fiber sensor parameters.

Preliminary results of real-time in-vitro electronic speckle pattern interferometry (ESPI) measurements in otolaryngology

NASA Astrophysics Data System (ADS)

Conerty, Michelle D.; Castracane, James; Cacace, Anthony T.; Parnes, Steven M.; Gardner, Glendon M.; Miller, Mitchell B.

1995-05-01

Electronic Speckle Pattern Interferometry (ESPI) is a nondestructive optical evaluation technique that is capable of determining surface and subsurface integrity through the quantitative evaluation of static or vibratory motion. By utilizing state of the art developments in the areas of lasers, fiber optics and solid state detector technology, this technique has become applicable in medical research and diagnostics. Based on initial support from NIDCD and continued support from InterScience, Inc., we have been developing a range of instruments for improved diagnostic evaluation in otolaryngological applications based on the technique of ESPI. These compact fiber optic instruments are capable of making real time interferometric measurements of the target tissue. Ongoing development of image post- processing software is currently capable of extracting the desired quantitative results from the acquired interferometric images. The goal of the research is to develop a fully automated system in which the image processing and quantification will be performed in hardware in near real-time. Subsurface details of both the tympanic membrane and vocal cord dynamics could speed the diagnosis of otosclerosis, laryngeal tumors, and aid in the evaluation of surgical procedures.

Ultrasonic imaging of seismic physical models using a fringe visibility enhanced fiber-optic Fabry-Perot interferometric sensor.

PubMed

Zhang, Wenlu; Chen, Fengyi; Ma, Wenwen; Rong, Qiangzhou; Qiao, Xueguang; Wang, Ruohui

2018-04-16

A fringe visibility enhanced fiber-optic Fabry-Perot interferometer based ultrasonic sensor is proposed and experimentally demonstrated for seismic physical model imaging. The sensor consists of a graded index multimode fiber collimator and a PTFE (polytetrafluoroethylene) diaphragm to form a Fabry-Perot interferometer. Owing to the increase of the sensor's spectral sideband slope and the smaller Young's modulus of the PTFE diaphragm, a high response to both continuous and pulsed ultrasound with a high SNR of 42.92 dB in 300 kHz is achieved when the spectral sideband filter technique is used to interrogate the sensor. The ultrasonic reconstructed images can clearly differentiate the shape of models with a high resolution.

Silicon wafer temperature monitoring using all-fiber laser ultrasonics

NASA Astrophysics Data System (ADS)

Alcoz, Jorge J.; Duffer, Charles E.

1998-03-01

Laser-ultrasonics is a very attractive technique for in-line process control in the semiconductor industry as it is compatible with the clean room environment and offers the capability to inspect parts at high-temperature. We describe measurements of the velocity of laser-generated Lamb waves in silicon wafers as a function of temperature using fiber- optic laser delivery and all-fiber interferometric sensing. Fundamental anti-symmetric Lamb-wave modes were generated in 5 inches < 111 > silicon wafers using a Nd:YAG laser coupled to a large-core multimode fiber. Generation was also performed using an array of sources created with a diffraction grating. For detection a compact fiber-optic sensor was used which is well suited for industrial environments as it is compact, rugged, stable, and low-cost. The wafers were heated up to 1000 degrees C and the temperature correlated with ultrasonic velocity measurements.

Robust interferometric frequency lock between cw lasers and optical frequency combs.

PubMed

Benkler, Erik; Rohde, Felix; Telle, Harald R

2013-02-15

A transfer interferometer is presented which establishes a versatile and robust optical frequency locking link between a tunable single frequency laser and an optical frequency comb. It enables agile and continuous tuning of the frequency difference between both lasers while fluctuations and drift effects of the transfer interferometer itself are widely eliminated via common mode rejection. Experimental results will be presented for a tunable extended-cavity 1.5 μm laser diode locked to an Er-fiber based frequency comb.

Smart materials and structures

NASA Technical Reports Server (NTRS)

Rogowski, Robert S.; Heyman, Joseph S.

1993-01-01

Embedded optical fibers allow not only the cure-monitoring and in-service lifetime measurements of composite materials, but the NDE of material damage and degradation with aging. The capabilities of such damage-detection systems have been extended to allow the quantitative determination of 2D strain in materials by several different methods, including the interferometric and the numerical. It remains to be seen, what effect the embedded fibers have on the strength of the 'smart' materials created through their incorporation.

Speckle noise reduction in quantitative optical metrology techniques by application of the discrete wavelet transformation

NASA Astrophysics Data System (ADS)

Furlong, Cosme; Pryputniewicz, Ryszard J.

2002-06-01

Effective suppression of speckle noise content in interferometric data images can help in improving accuracy and resolution of the results obtained with interferometric optical metrology techniques. In this paper, novel speckle noise reduction algorithms based on the discrete wavelet transformation are presented. The algorithms proceed by: (a) estimating the noise level contained in the interferograms of interest, (b) selecting wavelet families, (c) applying the wavelet transformation using the selected families, (d) wavelet thresholding, and (e) applying the inverse wavelet transformation, producing denoised interferograms. The algorithms are applied to the different stages of the processing procedures utilized for generation of quantitative speckle correlation interferometry data of fiber-optic based opto-electronic holography (FOBOEH) techniques, allowing identification of optimal processing conditions. It is shown that wavelet algorithms are effective for speckle noise reduction while preserving image features otherwise faded with other algorithms.

Characteristics of a fiber-optical Fabry-Perot interferometric acoustic sensor based on an improved phase-generated carrier-demodulation mechanism

NASA Astrophysics Data System (ADS)

Mao, Xuefeng; Tian, Xiaoran; Zhou, Xinlei; Yu, Qingxu

2015-04-01

The characteristics of a fiber-optic Fabry-Perot interferometric acoustic sensor are investigated. An improved phase-generator carrier-demodulation mechanism is proposed for obtaining a high harmonic suppression ratio and stability of the demodulation results. A gold-coated polyethylene terephthalate membrane is used as the sensing diaphragm. By optimizing the parameters and the demodulation algorithm, the signal-to-noise ratio (SNR) and distortion ratio of 50.3 dB and the total harmonic distortion of 0.1% at 114 dB sound pressure level (SPL) (@ 1 kHz) are achieved, respectively. The sensor shows good temperature stability; the variation of the response is within 0.6 dB as the temperature changes from -10°C to 50°C. A sensitivity of 40 mV/Pa at 1 kHz and a frequency response range of 100 Hz to 12.5 kHz are reached, respectively. The SNR of the system is 60 dB (Re. 94 dB SPL). The sensor may be applied to photoacoustic spectrometers as a high-performance acoustic sensor.

Intrusion recognition for optic fiber vibration sensor based on the selective attention mechanism

NASA Astrophysics Data System (ADS)

Xu, Haiyan; Xie, Yingjuan; Li, Min; Zhang, Zhuo; Zhang, Xuewu

2017-11-01

Distributed fiber-optic vibration sensors receive extensive investigation and play a significant role in the sensor panorama. A fiber optic perimeter detection system based on all-fiber interferometric sensor is proposed, through the back-end analysis, processing and intelligent identification, which can distinguish effects of different intrusion activities. In this paper, an intrusion recognition based on the auditory selective attention mechanism is proposed. Firstly, considering the time-frequency of vibration, the spectrogram is calculated. Secondly, imitating the selective attention mechanism, the color, direction and brightness map of the spectrogram is computed. Based on these maps, the feature matrix is formed after normalization. The system could recognize the intrusion activities occurred along the perimeter sensors. Experiment results show that the proposed method for the perimeter is able to differentiate intrusion signals from ambient noises. What's more, the recognition rate of the system is improved while deduced the false alarm rate, the approach is proved by large practical experiment and project.

An Optical Interferometric Triaxial Displacement Sensor for Structural Health Monitoring: Characterization of Sliding and Debonding for a Delamination Process

PubMed Central

Chen, Yizheng; Zhuang, Yiyang; Du, Yang; Gerald, Rex E.; Tang, Yan

2017-01-01

This paper presents an extrinsic Fabry–Perot interferometer-based optical fiber sensor (EFPI) for measuring three-dimensional (3D) displacements, including interfacial sliding and debonding during delamination. The idea employs three spatially arranged EFPIs as the sensing elements. In our sensor, the three EFPIs are formed by three endfaces of three optical fibers and their corresponding inclined mirrors. Two coincident roof-like metallic structures are used to support the three fibers and the three mirrors, respectively. Our sensor was calibrated and then used to monitor interfacial sliding and debonding between a long square brick of mortar and its support structure (i.e., a steel base plate) during the drying/curing process. This robust and easy-to-manufacture triaxial EFPI-based 3D displacement sensor has great potential in structural health monitoring, the construction industry, oil well monitoring, and geotechnology. PMID:29165351

An Optical Interferometric Triaxial Displacement Sensor for Structural Health Monitoring: Characterization of Sliding and Debonding for a Delamination Process.

PubMed

Zhu, Chen; Chen, Yizheng; Zhuang, Yiyang; Du, Yang; Gerald, Rex E; Tang, Yan; Huang, Jie

2017-11-22

This paper presents an extrinsic Fabry-Perot interferometer-based optical fiber sensor (EFPI) for measuring three-dimensional (3D) displacements, including interfacial sliding and debonding during delamination. The idea employs three spatially arranged EFPIs as the sensing elements. In our sensor, the three EFPIs are formed by three endfaces of three optical fibers and their corresponding inclined mirrors. Two coincident roof-like metallic structures are used to support the three fibers and the three mirrors, respectively. Our sensor was calibrated and then used to monitor interfacial sliding and debonding between a long square brick of mortar and its support structure (i.e., a steel base plate) during the drying/curing process. This robust and easy-to-manufacture triaxial EFPI-based 3D displacement sensor has great potential in structural health monitoring, the construction industry, oil well monitoring, and geotechnology.

Graphene-oxide-coated interferometric optical microfiber ethanol vapor sensor.

PubMed

Zhang, Jingle; Fu, Haiwei; Ding, Jijun; Zhang, Min; Zhu, Yi

2017-11-01

A graphene-oxide-coated interferometric microfiber-sensor-based polarization-maintaining optical fiber is proposed for highly sensitive detecting for ethanol vapor concentration at room temperature in this paper. The strong sensing capability of the sensor to detect the concentration of ethanol vapor is demonstrated, taking advantage of the evanescent field enhancement and gas absorption of a graphene-oxide-coated microfiber. The transmission spectrum of the sensor varies with concentrations of ethanol vapor, and the redshift of the transmission spectrum has been analyzed for the concentration range from 0 to 80 ppm with sensitivity as high as 0.138 nm/ppm. The coated graphene oxide layer induces the evanescent field enhancement and gas selective adsorption, which improves sensitivity and selectivity of the microfiber gas sensor for ethanol vapor detection.

Method and apparatus for monitoring and measuring the surface tension of a fluid using fiber optics

DOEpatents

Abraham, B.M.; Ketterson, J.B.; Bohanon, T.M.; Mikrut, J.M.

1994-04-12

A non-contact method and apparatus are described for measuring and monitoring the surface of a fluid using fiber optics and interferometric detection to permit measurement of mechanical characteristics of fluid surfaces. The apparatus employs an alternating electric field gradient for generating a capillary wave on the surface of the fluid. A fiber optic coupler and optical fiber directs a portion of a laser beam onto the surface of the fluid, another portion of the laser beam onto the photo sensor, and directs light reflected from the surface of the fluid onto the photo sensor. The output of the photo sensor is processed and coupled to a phase sensitive detector to permit measurement of phase shift between the drive signal creating the capillary wave and the detected signal. This phase shift information is then used to determine mechanical properties of the fluid surface such as surface tension, surface elasticity, and surface inhomogeneity. The resulting test structure is easily made compact, portable, and easy to align and use. 4 figures.

Influence of fiber bending on wavelength demodulation of fiber-optic Fabry-Perot interferometric sensors.

PubMed

Liu, Guigen; Sheng, Qiwen; Hou, Weilin; Han, Ming

2016-11-14

In practical applications of fiber optic sensors based on Fabry-Perot interferometers (FPIs), the lead-in optical fiber often experiences dynamic or static bending due to environmental perturbations or limited installation space. Bending introduces wavelength-dependent losses to the sensors, which can cause erroneous readings for sensors based on wavelength demodulation interrogation. Here, we investigate the bending-induced wavelength shift (BIWS) to sensors based on FPIs. Partially explicit expressions of BIWSs for the reflection fringe peaks and valleys have been derived for sensors based on low-finesse FPI. The theoretical model predicts these findings: 1) provided that a fringe peak experiences the same modulation slope by bending losses with a fringe valley, BIWSs for the peak and valley have opposite signs and the BIWS for the valley has a smaller absolute value; 2) BIWS is a linear function of the length of the bending section; 3) a FPI with higher visibility and longer optical path length is more resistant to the influence of bending. Experiments have been carried out and the results agree well with the theoretical predictions.

Novel Fabry-Perot fiber optic sensor with multiple applications

NASA Astrophysics Data System (ADS)

Chen, Xiaopei; Shen, Fabin; Wang, Anbo; Wang, Zhuang; Zhang, Yan

2004-12-01

A novel Intrinsic Fabry-Perot fiber-optic sensor is presented in this paper. The sensors were made through two simple steps: wet chemical etch and fusion splice. Micro air-gaps were generated inside the fibers and functioned as reflective mirrors. This procedure not only provides a simple and cost effective technology for fabricating intrinsic Fabry-Perot Interferometric (IFPI) fiber sensors, but also provides two possible IFPI structures. Both of the fiber cavity between the air-gaps or the air-gap and cleaved fiber end can be used as sensing elements. With these two structures, this sensor can be used to measure the temperature, strain, pressure, refractive index of chemicals and the thin film thickness by itself. Multi-point measurements can also be achieved by multiplexing. Furthermore, it also can be multiplexed with other sensors such as Long Period Gratings (LPG) to provide compensations for other perturbation sensing. Theoretical and experimental studies of two sensor structures are described. Experimental results show that high resolution and high sensitivity can be obtained with appropriate signal processing.

Fabrication of Extremely Short Length Fiber Bragg Gratings for Sensor Applications

NASA Technical Reports Server (NTRS)

Wu, Meng-Chou; Rogowski, Robert S.; Tedjojuwono, Ken K.

2002-01-01

A new technique and a physical model for writing extremely short length Bragg gratings in optical fibers have been developed. The model describes the effects of diffraction on the spatial spectra and therefore, the wavelength spectra of the Bragg gratings. Using an interferometric technique and a variable aperture, short gratings of various lengths and center wavelengths were written in optical fibers. By selecting the related parameters, the Bragg gratings with typical length of several hundred microns and bandwidth of several nanometers can be obtained. These short gratings can be apodized with selected diffraction patterns and hence their broadband spectra have a well-defined bell shape. They are suitable for use as miniaturized distributed strain sensors, which have broad applications to aerospace research and industry as well.

Interferometric visualization and demodulation method for measuring quasi-static strain in fiber Bragg grating sensors by a simple rotating etalon filter

NASA Astrophysics Data System (ADS)

Rocco, Alessandra S.; Coppola, Giuseppe; Ferraro, Pietro; Foti, Giuseppe; Iodice, Mario

2004-09-01

Optical fiber sensors are the ideal system to monitor "smart structures" and on-site/real time stress measurements: they can be in fact easily embedded or attached to the structures under test and are not affected by electro- magnetic noise. In particular a signal from a Fiber Bragg grating sensor (FBG) may be processed such that its information remains immune to optical power fluctuations. Different interrogation methods can be used for reading out Bragg wavelength shifts. In this paper we propose a very simple interferometric method for interrogating FBG sensors, based on bi-polished silicon sample acting like an etalon tuneable filter (ETF). The Bragg wavelength shift can be evaluated by analyzing the spectral response of signal reflected by the FBG sensor and filtered by the ETF that is continuously and rapidly tuned. Tuning was obtained by rotating the ETF. Variation in the strain at the FBG causes a phase shift in the analyzed signal. The overall spectral signal, collected with time, consists in an interferometric figure which finesse and fringe contrast depending on the geometrical sizes and facets reflectivity of the silicon sample. The fringe pattern, expressed by the Airy's formula, depends on the wavelength l of the incident radiation and on the angle of incidence. The phase of fringe pattern can be retrieved by a standard FFT method giving quantitative measurements of the quasi-static strain variation sensed by the FBG. In this way, the method allows a valuable visualization of the time-evolution of the incremental strain applied to the FBG. Principle of functioning of this method is described and first results obtained employing such configuration, are reported.

Optical Fiber Sensors for Advanced Civil Structures

NASA Astrophysics Data System (ADS)

de Vries, Marten Johannes Cornelius

1995-01-01

The objective of this dissertation is to develop, analyze, and implement optical fiber-based sensors for the nondestructive quantitative evaluation of advanced civil structures. Based on a comparative evaluation of optical fiber sensors that may be used to obtain quantitative information related to physical perturbations in the civil structure, the extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor is selected as the most attractive sensor. The operation of the EFPI sensor is explained using the Kirchhoff diffraction approach. As is shown in this dissertation, this approach better predicts the signal-to-noise ratio as a function of gap length than methods employed previously. The performance of the optical fiber sensor is demonstrated in three different implementations. In the first implementation, performed with researchers in the Civil Engineering Department at the University of Southern California in Los Angeles, optical fiber sensors were used to obtain quantitative strain information from reinforced concrete interior and exterior column-to-beam connections. The second implementation, performed in cooperation with researchers at the United States Bureau of Mines in Spokane, Washington, used optical fiber sensors to monitor the performance of roof bolts used in mines. The last implementation, performed in cooperation with researchers at the Turner-Fairbanks Federal Highway Administration Research Center in McLean, Virginia, used optical fiber sensors, attached to composite prestressing strands used for reinforcing concrete, to obtain absolute strain information. Multiplexing techniques including time, frequency and wavelength division multiplexing are briefly discussed, whereas the principles of operation of spread spectrum and optical time domain reflectometery (OTDR) are discussed in greater detail. Results demonstrating that spread spectrum and OTDR techniques can be used to multiplex optical fiber sensors are presented. Finally, practical considerations that have to be taken into account when implementing optical fiber sensors into a civil structure environment are discussed, and possible solutions to some of these problems are proposed.

Miniature optical fiber temperature sensor based on FMF-SCF structure

NASA Astrophysics Data System (ADS)

Zhang, Chuanbiao; Ning, Tigang; Zheng, Jingjing; Gao, Xuekai; Lin, Heng; Li, Jing; Pei, Li; Wen, Xiaodong

2018-03-01

We proposed and experimentally demonstrated a miniature optical fiber temperature sensor consisting of a seven core fiber (SCF) and a few mode fiber (FMF). The device is fabricated by splicing a section of FMF with a segment of SCF to form a FMF-SCF based sensing structure, and during the FMF region, few modes can be excited and will propagate within the SCF. In experiment, the proposed device has good quality interferometric spectra, and the highest extinction ratio of 27 dB was achieved. When the temperature increases from room temperature to 110 °C, the temperature response properties of the sensor have been investigated, the wavelength sensitivity of about 91.8 pm/°C and the amplitude sensitivity of about 1.57 × 10-2 a.u./°C are obtained, respectively. Due to its easy and controllable fabrication, the sensor can be a suitable candidate in temperature sensing applications.

Method and apparatus for white-light dispersed-fringe interferometric measurement of corneal topography

NASA Technical Reports Server (NTRS)

Hochberg, Eric B. (Inventor); Baroth, Edmund C. (Inventor)

1994-01-01

An novel interferometric apparatus and method for measuring the topography of aspheric surfaces, without requiring any form of scanning or phase shifting. The apparatus and method of the present invention utilize a white-light interferometer, such as a white-light Twyman-Green interferometer, combined with a means for dispersing a polychromatic interference pattern, using a fiber-optic bundle and a disperser such as a prism for determining the monochromatic spectral intensities of the polychromatic interference pattern which intensities uniquely define the optical path differences or OPD between the surface under test and a reference surface such as a reference sphere. Consequently, the present invention comprises a snapshot approach to measuring aspheric surface topographies such as the human cornea, thereby obviating vibration sensitive scanning which would otherwise reduce the accuracy of the measurement. The invention utilizes a polychromatic interference pattern in the pupil image plane, which is dispersed on a point-wise basis, by using a special area-to-line fiber-optic manifold, onto a CCD or other type detector comprising a plurality of columns of pixels. Each such column is dedicated to a single point of the fringe pattern for enabling determination of the spectral content of the pattern. The auto-correlation of the dispersed spectrum of the fringe pattern is uniquely characteristic of a particular optical path difference between the surface under test and a reference surface.

Interferometric fiber optic displacement sensor

DOEpatents

Farah, J.

1999-04-06

A method is presented to produce a change in the optical path length in the gap between two single mode optical fibers proportional to the lateral displacement of either fiber end normal to its axis. This is done with the use of refraction or diffraction at the interface between a guiding and non-guiding media to change the direction of propagation of the light in the gap. A method is also presented for laying a waveguide on a cantilever so that the displacement of the tip of the cantilever produces a proportional path length change in the gap by distancing the waveguide from the neutral axis of the cantilever. The fiber is supported as a cantilever or a waveguide is deposited on a micromachined cantilever and incorporated in an interferometer which is made totally on a silicon substrate with the use of integrated-optic technology. A resonant element in the form of a micro-bridge is incorporated in the ridge waveguide and produces a frequency output which is readily digitizeable and immune to laser frequency noise. Finally, monolithic mechanical means for phase modulation are provided on the same sensor substrate. This is done by vibrating the cantilever or micro-bridge either electrically or optically. 23 figs.

Interferometric fiber optic displacement sensor

DOEpatents

Farah, J.

1995-05-30

A method is presented to produce a change in the optical path length in the gap between two single mode optical fibers proportional to the lateral displacement of either fiber end normal to its axis. This is done with the use of refraction or diffraction at the interface between a guiding and non-guiding media to change the direction of propagation of the light in the gap. A method is also presented for laying a waveguide on a cantilever so that the displacement of the tip of the cantilever produces a proportional path length change in the gap by distancing the waveguide from the neutral axis of the cantilever. The fiber is supported as a cantilever or a waveguide is deposited on a micromachined cantilever and incorporated in an interferometer which is made totally on a silicon substrate with the use of integrated-optic technology. A resonant element in the form of a micro-bridge is incorporated in the ridge waveguide and produces a frequency output which is readily digitizeable and immune to laser frequency noise. Finally, monolithic mechanical means for phase modulation are provided on the same sensor substrate. This is done by vibrating the cantilever or micro-bridge either electrically or optically. 29 figs.

Interferometric fiber optic displacement sensor

DOEpatents

Farah, John

1995-01-01

A method is presented to produce a change in the optical path length in the gap between two single mode optical fibers proportional to the lateral displacement of either fiber end normal to its axis. This is done with the use of refraction or diffraction at the interface between a guiding and non-guiding media to change the direction of propagation of the light in the gap. A method is also presented for laying a waveguide on a cantilever so that the displacement of the tip of the cantilever produces a proportional path length change in the gap by distancing the waveguide from the neutral axis of the cantilever. The fiber is supported as a cantilever or a waveguide is deposited on a micromachined cantilever and incorporated in an interferometer which is made totally on a silicon substrate with the use of integrated-optic technology. A resonant element in the form of a micro-bridge is incorporated in the ridge waveguide and produces a frequency output which is readily digitizeable and immune to laser frequency noise. Finally, monolithic mechanical means for phase modulation are provided on the same sensor substrate. This is done by vibrating the cantilever or micro-bridge either electrically or optically.

Interferometric fiber optic displacement sensor

DOEpatents

Farah, John

1999-01-01

A method is presented to produce a change in the optical path length in the gap between two single mode optical fibers proportional to the lateral displacement of either fiber end normal to its axis. This is done with the use of refraction or diffraction at the interface between a guiding and non-guiding media to change the direction of propagation of the light in the gap. A method is also presented for laying a waveguide on a cantilever so that the displacement of the tip of the cantilever produces a proportional path length change in the gap by distancing the waveguide from the neutral axis of the cantilever. The fiber is supported as a cantilever or a waveguide is deposited on a micromachined cantilever and incorporated in an interferometer which is made totally on a silicon substrate with the use of integrated-optic technology. A resonant element in the form of a micro-bridge is incorporated in the ridge waveguide and produces a frequency output which is readily digitizeable and immune to laser frequency noise. Finally, monolithic mechanical means for phase modulation are provided on the same sensor substrate. This is done by vibrating the cantilever or micro-bridge either electrically or optically.

An integrated optical sensor for measuring glucose concentration

NASA Astrophysics Data System (ADS)

Liu, Y.; Hering, P.; Scully, M. O.

1992-01-01

We used an optical sensor combined with a Mach-Zehnder interferometric waveguide and optical fibers to measure slight changes of aqueous sugar concentrations. The merits of this sensor are simplicity, reliability, high sensitivity and continuous monitoring. The technique is based on the fact that the refractive index of sugar solution changes with the concentration of sugar. In the experiment, one arm of the interferometer is clad with glue and is thus isolated from the sugar solution. The other one is exposed to the sugar solution. A single mode fiber is directly glued onto the interferometric waveguide, to guide the light into the interferometer. If the concentration of sugar covering the waveguide changes, the phase of propagating light in the exposed arm will be changed, while the phase in the other arm is fixed. Hence the output intensity from the interferometer is directly related to the concentration of the sugar solution. The result of this experiment yields the relation between the sugar concentration and output signal. From 0% to 1% concentration of sugar solution, there is only a 1.4×10-3 refractive index difference. Two sets of experimental data have been obtained, showing a linear relation between the sugar concentration and the output signal from our sensor. This sensor could be used for continuous monitoring of blood sugar in the human body.

Optical heterodyne accelerometry: passively stabilized, fully balanced velocity interferometer system for any reflector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buttler, William T.; Lamoreaux, Steven K.

2010-08-10

We formalize the physics of an optical heterodyne accelerometer that allows measurement of low and high velocities from material surfaces under high strain. The proposed apparatus incorporates currently common optical velocimetry techniques used in shock physics, with interferometric techniques developed to self-stabilize and passively balance interferometers in quantum cryptography. The result is a robust telecom-fiber-based velocimetry system insensitive to modal and frequency dispersion that should work well in the presence of decoherent scattering processes, such as from ejecta clouds and shocked surfaces.

Optical fiber sensors measurement system and special fibers improvement

NASA Astrophysics Data System (ADS)

Jelinek, Michal; Hrabina, Jan; Hola, Miroslava; Hucl, Vaclav; Cizek, Martin; Rerucha, Simon; Lazar, Josef; Mikel, Bretislav

2017-06-01

We present method for the improvement of the measurement accuracy in the optical frequency spectra measurements based on tunable optical filters. The optical filter was used during the design and realization of the measurement system for the inspection of the fiber Bragg gratings. The system incorporates a reference block for the compensation of environmental influences, an interferometric verification subsystem and a PC - based control software implemented in LabView. The preliminary experimental verification of the measurement principle and the measurement system functionality were carried out on a testing rig with a specially prepared concrete console in the UJV Řež. The presented system is the laboratory version of the special nuclear power plant containment shape deformation measurement system which was installed in the power plant Temelin during last year. On the base of this research we started with preparation other optical fiber sensors to nuclear power plants measurement. These sensors will be based on the microstructured and polarization maintaining optical fibers. We started with development of new methods and techniques of the splicing and shaping optical fibers. We are able to made optical tapers from ultra-short called adiabatic with length around 400 um up to long tapers with length up to 6 millimeters. We developed new techniques of splicing standard Single Mode (SM) and Multimode (MM) optical fibers and splicing of optical fibers with different diameters in the wavelength range from 532 to 1550 nm. Together with development these techniques we prepared other techniques to splicing and shaping special optical fibers like as Polarization-Maintaining (PM) or hollow core Photonic Crystal Fiber (PCF) and theirs cross splicing methods with focus to minimalize backreflection and attenuation. The splicing special optical fibers especially PCF fibers with standard telecommunication and other SM fibers can be done by our developed techniques. Adjustment of the splicing process has to be prepared for any new optical fibers and new fibers combinations. The splicing of the same types of fibers from different manufacturers can be adjusted by several tested changes in the splicing process. We are able to splice PCF with standard telecommunication fiber with attenuation up to 2 dB. The method is also presented. Development of these new techniques and methods of the optical fibers splicing are made with respect to using these fibers to another research and development in the field of optical fibers sensors, laser frequency stabilization and laser interferometry based on optical fibers. Especially for the field of laser frequency stabilization we developed and present new techniques to closing microstructured fibers with gases inside.

Optical Fiber Sensors for Infrasonic Wind Noise Reduction and Earth Strain Measurement

NASA Astrophysics Data System (ADS)

DeWolf, Scott

Fiber-based interferometers provide the means to sense very small displacements over long baselines, and have the advantage of being nearly completely passive in their operation, making them particularly well suited for geophysical applications. This work presents the development and results from four new systems: one in atmospheric acoustics and three in Earth strain. Turbulent pressure fluctuations (wind noise) are a significant limiting factor in low-frequency atmospheric acoustic measurements. The Optical Fiber Infrasound Sensor (OFIS) provides an alternative to traditional infrasonic wind noise reduction (WNR) techniques by providing an instantaneous average over a large spatial extent. This study shows that linear OFISs ranging in length from 30 to 270 m provide a WNR of up to 30 dB in winds up to 5 m/s, in good agreement with a new analytical model. Arrays of optical fiber strainmeters were deployed to measure sediment compaction at two sites in Bangladesh. One array at Jamalganj (in the north) consists of 20, 40, 60, and 100 m long strainmeters, while the second near Khulna (in the south) also includes lengths of 80 and 300 m. Two years of weekly measurements show a clear seasonal signal and subsidence at both sites that is in reasonable agreement with collocated GPS receivers. A new 250-meter, interferometric vertical borehole strainmeter has been developed based completely on passive optical components. Details of the prototyping, design, and deployment at the Pinon Flat Observatory (PFO) are presented. Power spectra show an intertidal noise level of -130 dB (re. 1 epsilon/Hz), consistent within 1-3 dB between redundant components. Examination of its response to Earth tides and earthquakes relative to the areal strain recorded by an orthogonal pair of collocated, 730 m horizontal laser strainmeters yield a Poisson's ratio of 0.26. Two prototype horizontal strainmeters were also developed to explore the use of similar interferometric optical fiber technology for near-surface, long baseline strain measurement. Both instruments are shown to faithfully record earthquakes and yield very good estimates of the M2 tidal constituent, despite unexplained 2-8% amplitude discrepancies between the 90 and 180 m long instruments relative to the collocated laser strainmeter and each other.

Fast and accurate read-out of interferometric optical fiber sensors

NASA Astrophysics Data System (ADS)

Bartholsen, Ingebrigt; Hjelme, Dag R.

2016-03-01

We present results from an evaluation of phase and frequency estimation algorithms for read-out instrumentation of interferometric sensors. Tests on interrogating a micro Fabry-Perot sensor made of semi-spherical stimuli-responsive hydrogel immobilized on a single mode fiber end face, shows that an iterative quadrature demodulation technique (IQDT) implemented on a 32-bit microcontroller unit can achieve an absolute length accuracy of ±50 nm and length change accuracy of ±3 nm using an 80 nm SLED source and a grating spectrometer for interrogation. The mean absolute error for the frequency estimator is a factor 3 larger than the theoretical lower bound for a maximum likelihood estimator. The corresponding factor for the phase estimator is 1.3. The computation time for the IQDT algorithm is reduced by a factor 1000 compared to the full QDT for the same accuracy requirement.

Fiber-Optic Temperature Sensor Using a Thin-Film Fabry-Perot Interferometer

NASA Technical Reports Server (NTRS)

Beheim, Glenn

1997-01-01

A fiber-optic temperature sensor was developed that is rugged, compact, stable, and can be inexpensively fabricated. This thin-film interferometric temperature sensor was shown to be capable of providing a +/- 2 C accuracy over the range of -55 to 275 C, throughout a 5000 hr operating life. A temperature-sensitive thin-film Fabry-Perot interferometer can be deposited directly onto the end of a multimode optical fiber. This batch-fabricatable sensor can be manufactured at a much lower cost than can a presently available sensor, which requires the mechanical attachment of a Fabry-Perot interferometer to a fiber. The principal disadvantage of the thin-film sensor is its inherent instability, due to the low processing temperatures that must be used to prevent degradation of the optical fiber's buffer coating. The design of the stable thin-film temperature sensor considered the potential sources of both short and long term drifts. The temperature- sensitive Fabry-Perot interferometer was a silicon film with a thickness of approx. 2 microns. A laser-annealing process was developed which crystallized the silicon film without damaging the optical fiber. The silicon film was encapsulated with a thin layer of Si3N4 over coated with aluminum. Crystallization of the silicon and its encapsulation with a highly stable, impermeable thin-film structure were essential steps in producing a sensor with the required long-term stability.

Fabrication of optical fiber sensor based on double-layer SU-8 diaphragm and the partial discharge detection

NASA Astrophysics Data System (ADS)

Shang, Ya-na; Ni, Qing-yan; Ding, Ding; Chen, Na; Wang, Ting-yun

2015-01-01

In this paper, a partial discharge detection system is proposed using an optical fiber Fabry-Perot (FP) interferometric sensor, which is fabricated by photolithography. SU-8 photoresist is employed due to its low Young's modulus and potentially high sensitivity for ultrasound detection. The FP cavity is formed by coating the fiber end face with two layers of SU-8 so that the cavity can be controlled by the thickness of the middle layer of SU-8. Static pressure measurement experiments are done to estimate the sensing performance. The results show that the SU-8 based sensor has a sensitivity of 154.8 nm/kPa, which is much higher than that of silica based sensor under the same condition. Moreover, the sensor is demonstrated successfully to detect ultrasound from electrode discharge.

Optical information processing at NASA Ames Research Center

NASA Technical Reports Server (NTRS)

Reid, Max B.; Bualat, Maria G.; Cho, Young C.; Downie, John D.; Gary, Charles K.; Ma, Paul W.; Ozcan, Meric; Pryor, Anna H.; Spirkovska, Lilly

1993-01-01

The combination of analog optical processors with digital electronic systems offers the potential of tera-OPS computational performance, while often requiring less power and weight relative to all-digital systems. NASA is working to develop and demonstrate optical processing techniques for on-board, real time science and mission applications. Current research areas and applications under investigation include optical matrix processing for space structure vibration control and the analysis of Space Shuttle Main Engine plume spectra, optical correlation-based autonomous vision for robotic vehicles, analog computation for robotic path planning, free-space optical interconnections for information transfer within digital electronic computers, and multiplexed arrays of fiber optic interferometric sensors for acoustic and vibration measurements.

Multimode excitation-induced phase shifts in intrinsic Fabry-Perot interferometric fiber sensor spectra.

PubMed

Ma, Cheng; Wang, Anbo

2010-09-01

We report the modal analysis of optical fiber single-mode-multimode-single-mode intrinsic Fabry-Perot interferometer sensors. The multimode nature of the Fabry-Perot cavity gives rise to an additional phase term in the spectrogram due to intermodal dispersion-induced wavefront distortion, which could significantly affect the cavity length demodulation accuracy. By using an exact model to analyze the modal behavior, this phase term is explained by employing a rotating vector approach. Comparison of the theoretical analysis with experimental results is presented.

Photonic Biosensor Assays to Detect and Distinguish Subspecies of Francisella tularensis

PubMed Central

Cooper, Kristie L.; Bandara, Aloka B.; Wang, Yunmiao; Wang, Anbo; Inzana, Thomas J.

2011-01-01

The application of photonic biosensor assays to diagnose the category-A select agent Francisella tularensis was investigated. Both interferometric and long period fiber grating sensing structures were successfully demonstrated; both these sensors are capable of detecting the optical changes induced by either immunological binding or DNA hybridization. Detection was made possible by the attachment of DNA probes or immunoglobulins (IgG) directly to the fiber surface via layer-by-layer electrostatic self-assembly. An optical fiber biosensor was tested using a standard transmission mode long period fiber grating of length 15 mm and period 260 μm, and coated with the IgG fraction of antiserum to F. tularensis. The IgG was deposited onto the optical fiber surface in a nanostructured film, and the resulting refractive index change was measured using spectroscopic ellipsometry. The presence of F. tularensis was detected from the decrease of peak wavelength caused by binding of specific antigen. Detection and differentiation of F. tularensis subspecies tularensis (type A strain TI0902) and subspecies holarctica (type B strain LVS) was further accomplished using a single-mode multi-cavity fiber Fabry-Perot interferometric sensor. These sensors were prepared by depositing seven polymer bilayers onto the fiber tip followed by attaching one of two DNA probes: (a) a 101-bp probe from the yhhW gene unique to type-A strains, or (b) a 117-bp probe of the lpnA gene, common to both type-A and type-B strains. The yhhW probe was reactive with the type-A, but not the type-B strain. Probe lpnA was reactive with both type-A and type-B strains. Nanogram quantities of the target DNA could be detected, highlighting the sensitivity of this method for DNA detection without the use of PCR. The DNA probe reacted with 100% homologous target DNA, but did not react with sequences containing 2-bp mismatches, indicating the high specificity of the assay. These assays will fill an important void that exists for rapid, culture-free, and field-compatible diagnosis of F. tularensis. PMID:22163782

Chromatic characterization of ion-exchanged glass binary phase plates for mode-division multiplexing.

PubMed

Prieto-Blanco, Xesús; Montero-Orille, Carlos; Moreno, Vicente; Mateo, Eduardo F; Liñares, Jesús

2015-04-10

Mode-division multiplexing (MDM) in few-mode fibers is regarded as a promising candidate to increase optical network capacity. A fundamental element for MDM is a modal transformer to LP modes which can be implemented in a free-space basis by using multiregion phase plates, that is, LP plates. Likewise, several wavelengths have to be used due to wavelength multiplexing purposes, optical amplification tasks, and so on. In this work we show that efficient monolithic binary phase plates for different wavelengths can be fabricated by ion-exchange in glass and used for MDM tasks. We introduce an optical characterization method of the chromatic properties of such phase plates which combines the inverse Wentzel-Kramers-Brillouin (IWKB) together with Mach-Zehnder and Michelson-based interferometric techniques. The interferometric method provides a measurement of the phase step for several wavelengths, which characterizes the chromatic properties of the phase plate. Consequently, it is shown that the IWKB method allows us to design and characterize the phase plates in an easy and fast way.

A novel lightweight Fizeau infrared interferometric imaging system

NASA Astrophysics Data System (ADS)

Hope, Douglas A.; Hart, Michael; Warner, Steve; Durney, Oli; Romeo, Robert

2016-05-01

Aperture synthesis imaging techniques using an interferometer provide a means to achieve imagery with spatial resolution equivalent to a conventional filled aperture telescope at a significantly reduced size, weight and cost, an important implication for air- and space-borne persistent observing platforms. These concepts have been realized in SIRII (Space-based IR-imaging interferometer), a new light-weight, compact SWIR and MWIR imaging interferometer designed for space-based surveillance. The sensor design is configured as a six-element Fizeau interferometer; it is scalable, light-weight, and uses structural components and main optics made of carbon fiber replicated polymer (CFRP) that are easy to fabricate and inexpensive. A three-element prototype of the SIRII imager has been constructed. The optics, detectors, and interferometric signal processing principles draw on experience developed in ground-based astronomical applications designed to yield the highest sensitivity and resolution with cost-effective optical solutions. SIRII is being designed for technical intelligence from geo-stationary orbit. It has an instantaneous 6 x 6 mrad FOV and the ability to rapidly scan a 6x6 deg FOV, with a minimal SNR. The interferometric design can be scaled to larger equivalent filled aperture, while minimizing weight and costs when compared to a filled aperture telescope with equivalent resolution. This scalability in SIRII allows it address a range of IR-imaging scenarios.

Neutron radiation effects on Fabry-Perot fiber optic sensors

NASA Astrophysics Data System (ADS)

Liu, Hanying; Talnagi, Joseph; Miller, Don W.

2003-07-01

Nuclear Power Plant operators and Generation IV plant designers are considering advanced data transmission and measurement systems to improve system economics and safety, while concurrently addressing the issue of obsolescence of instrumentation and control systems. Fiber optic sensors have advantages over traditional sensors such as immunity to electromagnetic interference or radio frequency interference, higher sensitivity and accuracy, smaller size and less weight, higher bandwidth and multiplexing capability. A Fabry-Perot fiber optic sensor utilizes a unique interferometric mechanism and data processing technique, and has potential applications in nuclear radiation environments. Three sensors with different gamma irradiation history were irradiated in a mixed neutron/gamma irradiation field, in which the total neutron fluence was 2.6×10 16 neutrons/cm 2 and the total gamma dose was 1.09 MGy. All of them experienced a temperature shift of about 34°F but responded linearly to temperature changes. An annealing phenomenon was observed as the environmental temperature increased, which reduced the offset by approximately 63%.

Signal processing of white-light interferometric low-finesse fiber-optic Fabry-Perot sensors.

PubMed

Ma, Cheng; Wang, Anbo

2013-01-10

Signal processing for low-finesse fiber-optic Fabry-Perot sensors based on white-light interferometry is investigated. The problem is demonstrated as analogous to the parameter estimation of a noisy, real, discrete harmonic of finite length. The Cramer-Rao bounds for the estimators are given, and three algorithms are evaluated and proven to approach the bounds. A long-standing problem with these types of sensors is the unpredictable jumps in the phase estimation. Emphasis is made on the property and mechanism of the "total phase" estimator in reducing the estimation error, and a varying phase term in the total phase is identified to be responsible for the unwanted demodulation jumps. The theories are verified by simulation and experiment. A solution to reducing the probability of jump is demonstrated. © 2013 Optical Society of America

An Extrinsic Fabry-Perot Interferometric Sensor using Intermodal Phase Shifting and Demultiplexing of the Propagating Modes in a Few-Mode Fiber

NASA Astrophysics Data System (ADS)

Chatterjee, Julius

This dissertation demonstrates a fiber-optic phase shifted Fabry-Perot interferometer (PS-FPI) as a sensor using modal demultiplexing. Single wavelength Fabry-Perot interferometers suffer from fringe ambiguity and loss of sensitivity at fringe extremes. These hindrances cause it to be a secondary choice when being selected for a measurement task at hand, and more often than not, white light based sensors are selected in favor of the single wavelength Fabry-Perot sensors. This work aims to introduce a technique involving the demultiplexing of the propagating linearly polarized (LP) modes in few mode fibers to obtain two fringe systems from the same sensing cavity. This results in a few-mode interferometer that effectively has two to three orders of magnitude higher perturbation sensitivity than a conventional few mode interferometer for the same sensing region. In this work, two different modal demultiplexing techniques (MD) are used to demodulate the propagating modes and to obtain two fringe sets. These output fringe sets are shifted in phase with respect to each other by a phase shift due to the propagation of the modes in the fiber-optic layout. A method of controlling this phase shift by straining a length of a two mode fiber located separate from the PS-FPI cavity is demonstrated and corresponding changes in phase shifts are shown. The results show a controllable phase shift for both the MD techniques, which is useful in sensing by permitting quadrature demodulation of interferometric fringes and also results in a novel few-mode sensing system having more than two orders of magnitude sensitivity than conventional few-mode devices.

A hybrid quantum eraser scheme for characterization of free-space and fiber communication channels

NASA Astrophysics Data System (ADS)

Nape, Isaac; Kyeremah, Charlotte; Vallés, Adam; Rosales-Guzmán, Carmelo; Buah-Bassuah, Paul K.; Forbes, Andrew

2018-02-01

We demonstrate a simple projective measurement based on the quantum eraser concept that can be used to characterize the disturbances of any communication channel. Quantum erasers are commonly implemented as spatially separated path interferometric schemes. Here we exploit the advantages of redefining the which-path information in terms of spatial modes, replacing physical paths with abstract paths of orbital angular momentum (OAM). Remarkably, vector modes (natural modes of free-space and fiber) have a non-separable feature of spin-orbit coupled states, equivalent to the description of two independently marked paths. We explore the effects of fiber perturbations by probing a step-index optical fiber channel with a vector mode, relevant to high-order spatial mode encoding of information for ultra-fast fiber communications.

Precision Laser Development for Gravitational Wave Space Mission

NASA Technical Reports Server (NTRS)

Numata, Kenji; Camp, Jordan

2011-01-01

Optical fiber and semiconductor laser technologies have evolved dramatically over the last decade due to the increased demands from optical communications. We are developing a laser (master oscillator) and optical amplifier based on those technologies for interferometric space missions, such as the gravitational-wave mission LISA, and GRACE follow-on, by fully utilizing the mature wave-guided optics technologies. In space, where a simple and reliable system is preferred, the wave-guided components are advantageous over bulk, crystal-based, free-space laser, such as NPRO (Non-planar Ring Oscillator) and bulk-crystal amplifier, which are widely used for sensitive laser applications on the ground.

Fiber optic systems for mobile platforms IV; Proceedings of the Meeting, San Jose, CA, Sept. 18, 1990

NASA Astrophysics Data System (ADS)

Lewis, Norris E.; Moore, Emery L.

The present conference on fiber-optic (FO) systems discusses topics in shipboard, automotive, spacecraft, and aeronautical FO applications. Attention is given to an FO interferometric ellipsoidal shell hydrophone, an FO backbone for a submarine combat system, EM environmental effects on shipboard FO installations, and recent developments in polymeric FO systems for automotive use. Also discussed are a wavelength-multiplexed FO position encoder for aircraft control systems, a code-division multiple-access system for integrated modular avionics, fly-by-light systems for commercial aircraft, FO temperature sensors for aerospace applications, a hybrid FO/electrical network for launch vehicles, the effects of ionizing radiation on FO systems, and FO systems in liquid propellant rocket environments.

Advanced ESPI-based medical instruments for otolaryngology

NASA Astrophysics Data System (ADS)

Castracane, James; Conerty, M.; Cacace, Anthony T.; Gardner, Glendon M.; Miller, Mitchell B.; Parnes, Steven M.

1993-05-01

Optical fibers have long been used for visual inspection inside the human body for medical diagnoses and treatment. By making use of sophisticated optical interferometric and ultra- small imaging techniques, combined with automated image processing, it is possible to extract significantly increased information for more accurate medical diagnoses. With support from NIH under the SBIR program, we have been developing a range of such instruments. One of these supported by the NIDCD is capable of providing detailed spatial information on the vibratory response of the tympanic membrane (TM). This instrument involves the examination of the TM by means of high speed electronic speckle pattern interferometry (ESPI). This provides a real time view of the vibration patterns of the TM for clinical diagnosis. This Interferometric Otoscope consists of mode conserving fiber optics, miniature diode lasers and high speed solid state detector arrays. We present the current status of the research including holography and ESPI of TM models and excised temporal bone preparations. A second instrument, also developed with support from NIDCD, is for application to the larynx. This system is also ESPI based but will incorporate features for direct vocal cord (VC) examination. By careful examination of the vibratory response of the VC during phonation, the characteristics of the mucosal wave may be examined. Adynamic regions of the cords can signal the start of lesions or cysts. Results of surgery can be evaluated in a quantitative manner. The design of a clinical prototype and preliminary electro-optic experiments on excised larynges and VC models will be presented.

A fiber-optic interferometer based on non-adiabatic fiber taper and long-period fiber grating for simultaneous measurement of magnetic field and temperature

NASA Astrophysics Data System (ADS)

Kang, Shouxin; Zhang, Hao; Liu, Bo; Lin, Wei; Zhang, Ning; Miao, Yinping

2016-01-01

A dual-parameter sensor based on a fiber-optic interferometer consisting of a non-adiabatic fiber taper and a long-period fiber grating (LPFG) integrated with magnetic nanoparticle fluids has been proposed and experimentally demonstrated. Due to the Mach-Zehnder interference induced by the concatenation of the fiber taper and long-period grating, an interferometric spectrum could be acquired within the transmission resonance spectral envelope of the LPFG. Thanks to different magnetic field and temperature sensitivities of difference interference dips, simultaneous measurement of the magnetic field intensity and environmental temperature could be achieved. Moreover, due to the variation in coupling coefficients of the fiber taper and the LPFG in response to the change of the applied magnetic field intensity, some of the interference dips would exhibit opposite magnetic-field-intensity-dependent transmission loss variation behavior. Magnetic field intensity and temperature sensitivities of 0.017 31 dB Oe-1 and 0.0315 dB K-1, and -0.024 55 dB Oe-1 and -0.056 28 dB K-1 were experimentally acquired for the experimentally monitored interference dips.

Strain Wave Acquisition by a Fiber Optic Coherent Sensor for Impact Monitoring

PubMed Central

Sbarufatti, Claudio; Beligni, Alessio; Gilioli, Andrea; Ferrario, Maddalena; Mattarei, Marco; Martinelli, Mario; Giglio, Marco

2017-01-01

A novel fiber optic sensing technology for high frequency dynamics detection is proposed in this paper, specifically tailored for structural health monitoring applications based on strain wave analysis, for both passive impact identification and active Lamb wave monitoring. The sensing solution relies on a fiber optic-based interferometric architecture associated to an innovative coherent detection scheme, which retrieves in a completely passive way the high-frequency phase information of the received optical signal. The sensing fiber can be arranged into different layouts, depending on the requirement of the specific application, in order to enhance the sensor sensitivity while still ensuring a limited gauge length if punctual measures are required. For active Lamb wave monitoring, this results in a sensing fiber arranged in multiple loops glued on an aluminum thin panel in order to increase the phase signal only in correspondence to the sensing points of interest. Instead, for passive impact identification, the required sensitivity is guaranteed by simply exploiting a longer gauge length glued to the structure. The fiber optic coherent (FOC) sensor is exploited to detect the strain waves emitted by a piezoelectric transducer placed on the aluminum panel or generated by an impulse hammer, respectively. The FOC sensor measurements have been compared with both a numerical model based on Finite Elements and traditional piezoelectric sensors, confirming a good agreement between experimental and simulated results for both active and passive impact monitoring scenarios. PMID:28773154

Detrecting and Locating Partial Discharges in Transformers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shourbaji, A.; Richards, R.; Kisner, R. A.

A collaborative research between the Oak Ridge National Laboratory (ORNL), the American Electric Power (AEP), the Tennessee Valley Authority (TVA), and the State of Ohio Energy Office (OEO) has been formed to conduct a feasibility study to detect and locate partial discharges (PDs) inside large transformers. The success of early detection of the PDs is necessary to avoid costly catastrophic failures that can occur if the process of PD is ignored. The detection method under this research is based on an innovative technology developed by ORNL researchers using optical methods to sense the acoustical energy produced by the PDs. ORNLmore » researchers conducted experimental studies to detect PD using an optical fiber as an acoustic sensor capable of detecting acoustical disturbances at any point along its length. This technical approach also has the potential to locate the point at which the PD was sensed within the transformer. Several optical approaches were experimentally investigated, including interferometric detection of acoustical disturbances along the sensing fiber, light detection and ranging (LIDAR) techniques using frequency modulation continuous wave (FMCW), frequency modulated (FM) laser with a multimode fiber, FM laser with a single mode fiber, and amplitude modulated (AM) laser with a multimode fiber. The implementation of the optical fiber-based acoustic measurement technique would include installing a fiber inside a transformer allowing real-time detection of PDs and determining their locations. The fibers are nonconductive and very small (core plus cladding are diameters of 125 μm for single-mode fibers and 230 μm for multimode fibers). The research identified the capabilities and limitations of using optical technology to detect and locate sources of acoustical disturbances such as in PDs in large transformers. Amplitude modulation techniques showed the most promising results and deserve further research to better quantify the technique’s sensitivity and its ability to characterize a PD event. Other sensing techniques have been also identified, such as the wavelength shifting fiber optics and custom fabricated fibers with special coatings.« less

Interferometric fiber-optic sensor embedded in a spark plug for in-cylinder pressure measurement in engines.

PubMed

Bae, Taehan; Atkins, Robert A; Taylor, Henry F; Gibler, William N

2003-02-20

Pressure sensing in an internal combustion engine with an intrinsic fiber Fabry-Perot interferometer (FFPI) integrated with a spark plug is demonstrated for the first time. The spark plug was used for the ignition of the cylinder in which it was mounted. The FFPI element, protected with a copper/gold coating, was embedded in a groove in the spark-plug housing. Gas pressure inthe engine induced longitudinal strain in this housing, which was also experienced by the fiber-optic sensing element. The sensor was monitored with a signal conditioning unit containing a chirped distributed-feedback laser. Pressure sensitivities as high as 0.00339 radians round-trip phase shift per pounds per square inch of pressure were observed. Measured pressure versus time traces showed good agreement with those from a piezoelectric reference sensor mounted in the same engine cylinder.

Interferometric Fiber-Optic Sensor Embedded in a Spark Plug for In-Cylinder Pressure Measurement in Engines

NASA Astrophysics Data System (ADS)

Bae, Taehan; Atkins, Robert A.; Taylor, Henry F.; Gibler, William N.

2003-02-01

Pressure sensing in an internal combustion engine with an intrinsic fiber Fabry-Perot interferometer (FFPI) integrated with a spark plug is demonstrated for the first time. The spark plug was used for the ignition of the cylinder in which it was mounted. The FFPI element, protected with a copper /gold coating, was embedded in a groove in the spark-plug housing. Gas pressure in the engine induced longitudinal strain in this housing, which was also experienced by the fiber-optic sensing element. The sensor was monitored with a signal conditioning unit containing a chirped distributed-feedback laser. Pressure sensitivities as high as 0.00339 radians round-trip phase shift per pounds per square inch of pressure were observed. Measured pressure versus time traces showed good agreement with those from a piezoelectric reference sensor mounted in the same engine cylinder.

Effect of MMF stub on the sensitivity of a photonic crystal fiber interferometer sensor at 1550 nm

NASA Astrophysics Data System (ADS)

Dhara, P.; Singh, Vinod K.

2015-01-01

A simple photonic crystal fiber (PCF) based Mach-Zehnder interferometric sensor is reported for sensing the refractive index and level of liquid. The sensing head is formed by all-fiber in-line single mode-multi mode-photonic crystal-single mode fiber structure using the fusion splicing method. The interferometric pattern, observed in the PCF interferometer using monochromatic source and temperature sensing arrangement, is novel and reported for the first time to the best of our knowledge. The refractive index sensitivity of the interferometric device is increased by using multimode fiber. The output intensity at the end of lead-out single mode fiber decreases with increase in refractive index of surrounding. The index sensitivities of the interferometric devices are 440.32 μw/RIU, 267.48 μw/RIU and 195.36 μw/RIU with sensing length 2.10 cm, 5.50 cm and 7.20 cm respectively. A 7.20 cm longed PCF sensor exhibits liquid level sensitivities -1.032 μw/cm, -1.197 μw/cm, and -1.489 μw/cm for three different liquid respectively.

A Fiber Optic Interferometric Sensor Platform for Determining Gas Diffusivity in Zeolite Films.

PubMed

Yang, Ruidong; Xu, Zhi; Zeng, Shixuan; Jing, Wenheng; Trontz, Adam; Dong, Junhang

2018-04-04

Fiber optic interferometer (FOI) sensors have been fabricated by directly growing pure-silica MFI-type zeolite (i.e., silicalite) films on straight-cut endfaces of single-mode communication optical fibers. The FOI sensor has been demonstrated for determining molecular diffusivity in the zeolite by monitoring the temporal response of light interference from the zeolite film during the dynamic process of gas adsorption. The optical thickness of the zeolite film depends on the amount of gas adsorption that causes the light interference to shift upon loading molecules into the zeolitic channels. Thus, the time-dependence of the optical signal reflected from the coated zeolite film can represent the adsorption uptake curve, which allows computation of the diffusivity using models derived from the Fick’s Law equations. In this study, the diffusivity of isobutane in silicalite has been determined by the new FOI sensing method, and the results are in good agreement with literature values obtained by various conventional macroscopic techniques. The FOI sensor platform, because of its robustness and small size, could be useful for studying molecular diffusion in zeolitic materials under conditions that are inaccessible to the existing techniques.

Improved Phase-Mask Fabrication of Fiber Bragg Gratings

NASA Technical Reports Server (NTRS)

Grant, Joseph; Wang, Ying; Sharma, Anup

2004-01-01

An improved method of fabrication of Bragg gratings in optical fibers combines the best features of two prior methods: one that involves the use of a phase mask and one that involves interference between the two coherent laser beams. The improved method affords flexibility for tailoring Bragg wavelengths and bandwidths over wide ranges. A Bragg grating in an optical fiber is a periodic longitudinal variation in the index of refraction of the fiber core. The spatial period (Bragg wavelength) is chosen to obtain enhanced reflection of light of a given wavelength that would otherwise propagate relatively unimpeded along the core. Optionally, the spatial period of the index modulation can be made to vary gradually along the grating (such a grating is said to be chirped ) in order to obtain enhanced reflection across a wavelength band, the width of which is determined by the difference between the maximum and minimum Bragg wavelengths. In the present method as in both prior methods, a Bragg grating is formed by exposing an optical fiber to an ultraviolet-light interference field. The Bragg grating coincides with the pattern of exposure of the fiber core to ultraviolet light; in other words, the Bragg grating coincides with the interference fringes. Hence, the problem of tailoring the Bragg wavelength and bandwidth is largely one of tailoring the interference pattern and the placement of the fiber in the interference pattern. In the prior two-beam interferometric method, a single laser beam is split into two beams, which are subsequently recombined to produce an interference pattern at the location of an optical fiber. In the prior phase-mask method, a phase mask is used to diffract a laser beam mainly into two first orders, the interference between which creates the pattern to which an optical fiber is exposed. The prior two-beam interferometric method offers the advantage that the period of the interference pattern can be adjusted to produce gratings over a wide range of Bragg wavelengths, but offers the disadvantage that success depends on precise alignment and high mechanical stability. The prior phase-mask method affords the advantages of compactness of equipment and relative insensitivity to both misalignment and vibration, but does not afford adjustability of the Bragg wavelength. The present method affords both the flexibility of the prior two-beam interferometric method and the compactness and stability of the prior phase-mask method. In this method (see figure), a laser beam propagating along the x axis is normally incident on a phase mask that lies in the (y,z) plane. The phase of light propagating through the mask is modulated with a spatial periodicity, p, along the y axis chosen to diffract the laser light primarily to first order at the angle . (The zero-order laser light propagating along the x axis can be used for alignment and thereafter suppressed during exposure of the fiber.) The diffracted light passes through a concave cylindrical lens, which converts the flat diffracted wave fronts to cylindrical ones, as though the light emanated from a line source. Then two parallel flat mirrors recombine the diffracted beams to form an interference field equivalent to that of two coherent line sources at positions A and B (virtual sources). The interference pattern is a known function of the parameters of the apparatus and of position (x,y) in the interference field. Hence, the tilt, wavelength, and chirp of the Bragg grating can be chosen through suitable adjustments of the apparatus and/or of the position and orientation of the optical fiber. In particular, the Bragg wavelength can be adjusted by moving the fiber along the x axis, and the bandwidth can be modified over a wide range by changing the fiber tilt angle or by moving the phase mask and/or the fiber. Alignment is easy because the zero-order beam defines the x axis. The interference is relatively stable and insensitive to the mechanical vibration because of the gh symmetry and compactness of the apparatus, the fixed positions of the mirrors and lens, and the consequent fixed positions of the two virtual line sources, which are independent of the translations of the phase mask and the laser relative to the lens.

Polar-interferometry: what can be learnt from the IOTA/IONIC experiment

NASA Astrophysics Data System (ADS)

Le Bouquin, Jean-Baptiste; Rousselet-Perraut, Karine; Berger, Jean-Philippe; Herwats, Emilie; Benisty, Myriam; Absil, Olivier; Defrere, Denis; Monnier, John; Traub, Wesley

2008-07-01

We report the first near-IR polar-interferometric observations, performed at the IOTA array using its integrated optics combiner IONIC. Fringes have been obtained on calibration stars and resolved late-type giants. Optical modeling of the array and dedicated laboratory measures allowed us to confirm the good accuracy obtained on the calibrated polarized visibilities and closure phases. However, no evidences for polarimetric features at high angular resolution have been detected. The simulations and the results presented here open several perspectives for polar-interferometry, especially in the context of fibered, single-mode combiners.

Fiber Fabry-Perot interferometer sensor for measuring resonances of piezoelectric elements

NASA Astrophysics Data System (ADS)

da Silva, Ricardo E.; Oliveira, Roberson A.; Pohl, Alexandre A. P.

2011-05-01

The development of a fiber extrinsic Fabry-Perot interferometer for measuring vibration amplitude and resonances of piezoelectric elements is reported. The signal demodulation method based on the use of an optical spectrum analyzer allows the measurement of displacements and resonances with high resolution. The technique consists basically in monitoring changes in the intensity or the wavelength of a single interferometric fringe at a point of high sensitivity in the sensor response curve. For sensor calibration, three signal processing techniques were employed. Vibration amplitude measurement with 0.84 nm/V sensitivity and the characterization of the piezo resonance is demonstrated.

Chemical-assisted femtosecond laser writing of lab-in-fibers.

PubMed

Haque, Moez; Lee, Kenneth K C; Ho, Stephen; Fernandes, Luís A; Herman, Peter R

2014-10-07

The lab-on-chip (LOC) platform has presented a powerful opportunity to improve functionalization, parallelization, and miniaturization on planar or multilevel geometries that has not been possible with fiber optic technology. A migration of such LOC devices into the optical fiber platform would therefore open the revolutionary prospect of creating novel lab-in-fiber (LIF) systems on the basis of an efficient optical transport highway for multifunctional sensing. For the LIF, the core optical waveguide inherently offers a facile means to interconnect numerous types of sensing elements along the optical fiber, presenting a radical opportunity for optimizing the packaging and densification of diverse components in convenient geometries beyond that available with conventional LOCs. In this paper, three-dimensional patterning inside the optical fiber by femtosecond laser writing, together with selective chemical etching, is presented as a powerful tool to form refractive index structures such as optical waveguides and gratings as well as to open buried microfluidic channels and optical resonators inside the flexible and robust glass fiber. In this approach, optically smooth surfaces (~12 nm rms) are introduced for the first time inside the fiber cladding that precisely conform to planar nanograting structures when formed by aberration-free focusing with an oil-immersion lens across the cylindrical fiber wall. This process has enabled optofluidic components to be precisely embedded within the fiber to be probed by either the single-mode fiber core waveguide or the laser-formed optical circuits. We establish cladding waveguides, X-couplers, fiber Bragg gratings, microholes, mirrors, optofluidic resonators, and microfluidic reservoirs that define the building blocks for facile interconnection of inline core-waveguide devices with cladding optofluidics. With these components, more advanced, integrated, and multiplexed fiber microsystems are presented demonstrating fluorescence detection, Fabry-Perot interferometric refractometry, and simultaneous sensing of refractive index, temperature, and bending strain. The flexible writing technique and multiplexed sensors described here open powerful prospects to migrate the benefits of LOCs into a more flexible and miniature LIF platform for highly functional and distributed sensing capabilities. The waveguide backbone of the LIF inherently provides an efficient exchange of information, combining sensing data that are attractive in telecom networks, smart catheters for medical procedures, compact sensors for security and defense, shape sensors, and low-cost health care products.

Simulating laser interferometers for missions such as (E)Lisa, Lisa pathfinder and Grace follow-on

NASA Astrophysics Data System (ADS)

Wanner, Gudrun; Kochkina, Evgenia; Mahrdt, Christoph; Müller, Vitali; Schuster, Sönke; Heinzel, Gerhard; Danzmann, Karsten

2017-11-01

Sensing tiny distance variations interferometrically will be a key task in several future space missions. Interferometric detectors such as (e)LISA will observe gravitational waves from cosmic events such as for instance super novae and extreme mass ratio inspirals. The detection principle of such detectors is sensing phase variations due to tiny distance variations between two free floating test masses aboard two remote spacecraft originating from passing gravitational waves. This detection principle will be tested for the first time by LISA Pathfinder (launch 2015), where the interferometric readout of two free floating test masses aboard one single spacecraft will be demonstrated. Future geodesy missions will map Earths Gravity field, by interferometrically measuring distance variations between two spacecraft in low Earth orbit. This will be tested for the first time by the Laser Ranging Instrument (LRI) aboard GRACE Follow-On (launch 2017). The low noise laser interferometry of all these missions provides a number of challenging tasks. We will present optical simulations performed for the missions above. The interferometry of LISA Pathfinder is purely local (there do not exist any received beams from remote spacecraft), such that all beams can be approximated by fundamental Gaussian beams. We will present simulations regarding the coupling of residual test mass jitter (longitudinal and lateral as well as angular) to the phase readout, including Monte Carlo simulations to predict how misalignment affects resulting phase noise and estimate in-flight alignment of the test masses. In all of the mentioned missions, the local laser beams are delivered to the optical bench by fibers, resulting in laser beams in fiber modes. Besides local laser beams, the interferometry of missions such as (e)LISA and LRI involves also received beams from remote spacecraft. These beams have diameters in the range of tens of meters (LRI) or kilometers (LISA / eLISA and alike), before being clipped down to centimeter scale by the receiving aperture. The resulting top hat beams show strong diffraction effects and are therefore imaged on the optical benches. Key elements for simulations are therefore the propagation with diffraction of top hat beams and fiber modes in vacuum, as well as imaging optics causing aberration and astigmatism, with the central task to characterize the coupling of test mass or spacecraft jitter to optical readout noise, in presence of realistic alignment errors. A recurring and often limiting noise in the length measurement originates from the cross coupling of angular component jitter. This cross coupling will be briefly introduced with strategies for its mitigation in the various missions. To overcome the limitations of existing and commercial software, we have written and used for the simulations above as well as for general interferometer design purposes a dedicated software package called IfoCAD which is publicly available and will be presented as well.

High-temperature optical fiber instrumentation for gas flow monitoring in gas turbine engines

NASA Astrophysics Data System (ADS)

Roberts, Adrian; May, Russell G.; Pickrell, Gary R.; Wang, Anbo

2002-02-01

In the design and testing of gas turbine engines, real-time data about such physical variables as temperature, pressure and acoustics are of critical importance. The high temperature environment experienced in the engines makes conventional electronic sensors devices difficult to apply. Therefore, there is a need for innovative sensors that can reliably operate under the high temperature conditions and with the desirable resolution and frequency response. A fiber optic high temperature sensor system for dynamic pressure measurement is presented in this paper. This sensor is based on a new sensor technology - the self-calibrated interferometric/intensity-based (SCIIB) sensor, recently developed at Virginia Tech. State-of-the-art digital signal processing (DSP) methods are applied to process the signal from the sensor to acquire high-speed frequency response.

Rotation Sensing with Trapped Ions

DTIC Science & Technology

2016-09-01

Sagnac effect can be used to measure the rotational velocity Ω of a reference frame by observing the phase shift of an interferometer in that frame whose...sensitivity of interferometric gyroscopes. For photons, optical fibers (or ring laser cavities) allow many effective round-trips through the Sagnac...interferometer, thereby increasing the effective area A by 2 times the number of round trips (M) without increasing the actual area of the apparatus. This

Single myelin fiber imaging in living rodents without labeling by deep optical coherence microscopy.

PubMed

Ben Arous, Juliette; Binding, Jonas; Léger, Jean-François; Casado, Mariano; Topilko, Piotr; Gigan, Sylvain; Boccara, A Claude; Bourdieu, Laurent

2011-11-01

Myelin sheath disruption is responsible for multiple neuropathies in the central and peripheral nervous system. Myelin imaging has thus become an important diagnosis tool. However, in vivo imaging has been limited to either low-resolution techniques unable to resolve individual fibers or to low-penetration imaging of single fibers, which cannot provide quantitative information about large volumes of tissue, as required for diagnostic purposes. Here, we perform myelin imaging without labeling and at micron-scale resolution with >300-μm penetration depth on living rodents. This was achieved with a prototype [termed deep optical coherence microscopy (deep-OCM)] of a high-numerical aperture infrared full-field optical coherence microscope, which includes aberration correction for the compensation of refractive index mismatch and high-frame-rate interferometric measurements. We were able to measure the density of individual myelinated fibers in the rat cortex over a large volume of gray matter. In the peripheral nervous system, deep-OCM allows, after minor surgery, in situ imaging of single myelinated fibers over a large fraction of the sciatic nerve. This allows quantitative comparison of normal and Krox20 mutant mice, in which myelination in the peripheral nervous system is impaired. This opens promising perspectives for myelin chronic imaging in demyelinating diseases and for minimally invasive medical diagnosis.

Single myelin fiber imaging in living rodents without labeling by deep optical coherence microscopy

NASA Astrophysics Data System (ADS)

Ben Arous, Juliette; Binding, Jonas; Léger, Jean-François; Casado, Mariano; Topilko, Piotr; Gigan, Sylvain; Claude Boccara, A.; Bourdieu, Laurent

2011-11-01

Myelin sheath disruption is responsible for multiple neuropathies in the central and peripheral nervous system. Myelin imaging has thus become an important diagnosis tool. However, in vivo imaging has been limited to either low-resolution techniques unable to resolve individual fibers or to low-penetration imaging of single fibers, which cannot provide quantitative information about large volumes of tissue, as required for diagnostic purposes. Here, we perform myelin imaging without labeling and at micron-scale resolution with >300-μm penetration depth on living rodents. This was achieved with a prototype [termed deep optical coherence microscopy (deep-OCM)] of a high-numerical aperture infrared full-field optical coherence microscope, which includes aberration correction for the compensation of refractive index mismatch and high-frame-rate interferometric measurements. We were able to measure the density of individual myelinated fibers in the rat cortex over a large volume of gray matter. In the peripheral nervous system, deep-OCM allows, after minor surgery, in situ imaging of single myelinated fibers over a large fraction of the sciatic nerve. This allows quantitative comparison of normal and Krox20 mutant mice, in which myelination in the peripheral nervous system is impaired. This opens promising perspectives for myelin chronic imaging in demyelinating diseases and for minimally invasive medical diagnosis.

Performance Enhancement of Bidirectional TWDM-PON by Rayleigh Backscattering Mitigation

NASA Astrophysics Data System (ADS)

Elewah, Ibrahim A.; Wadie, Martina N.; Aly, Moustafa H.

2018-01-01

A bidirectional time wavelength division multiplexing-passive optical network (TWDM-PON) with a centralized light source (CLS) is designed and evaluated. TWDM-PON is the promising solution for PON future expansion and migration. The most important issue that limits optical fiber transmission length is the interferometric noise caused by Rayleigh backscattering (RB). In this study, we demonstrate a TWDM-PON architecture with subcarrier at the remote node (RN) to mitigate the RB effect. A successful transmission with 8 optical channels is achieved using wavelength division multiplexing (WDM). Each optical channel is splitted into 8 time slots to achieve TWDM. The proposed scheme is operated over 20 km bidirectional single mode fiber (SMF). The proposed system has the advantage of expanding the downstream (DS) capacity to be 160 Gb/s (8 channels×20 Gb/s) and 20 Gb/s (8 channels×2.5 Gb/s) for the upstream (US) transmission capacity. This is accomplished by a remarkable bit error rate (BER) and low complexity.

Ultrafast Fabry-Perot fiber-optic pressure sensors for multimedia blast event measurements.

PubMed

Zou, Xiaotian; Wu, Nan; Tian, Ye; Zhang, Yang; Fitek, John; Maffeo, Michael; Niezrecki, Christopher; Chen, Julie; Wang, Xingwei

2013-02-20

A shock wave (SW) is characterized as a large pressure fluctuation that typically lasts only a few milliseconds. On the battlefield, SWs pose a serious threat to soldiers who are exposed to explosions, which may lead to blast-induced traumatic brain injuries. SWs can also be used beneficially and have been applied to a variety of medical treatments due to their unique interaction with tissues and cells. Consequently, it is important to have sensors that can quantify SW dynamics in order to better understand the physical interaction between body tissue and the incident acoustic wave. In this paper, the ultrafast fiber-optic sensor based on the Fabry-Perot interferometric principle was designed and four such sensors were fabricated to quantify a blast event within different media, simultaneously. The compact design of the fiber-optic sensor allows for a high degree of spatial resolution when capturing the wavefront of the traveling SW. Several blast event experiments were conducted within different media (e.g., air, rubber membrane, and water) to evaluate the sensor's performance. This research revealed valuable knowledge for further study of SW behavior and SW-related applications.

Towards Noise Tomography and Passive Monitoring Using Distributed Acoustic Sensing

NASA Astrophysics Data System (ADS)

Paitz, P.; Fichtner, A.

2017-12-01

Distributed Acoustic Sensing (DAS) has the potential to revolutionize the field of seismic data acquisition. Thanks to their cost-effectiveness, fiber-optic cables may have the capability of complementing conventional geophones and seismometers by filling a niche of applications utilizing large amounts of data. Therefore, DAS may serve as an additional tool to investigate the internal structure of the Earth and its changes over time; on scales ranging from hydrocarbon or geothermal reservoirs to the entire globe. An additional potential may be in the existence of large fibre networks deployed already for telecommunication purposes. These networks that already exist today could serve as distributed seismic antennas. We investigate theoretically how ambient noise tomography may be used with DAS data. For this we extend the theory of seismic interferometry to the measurement of strain. With numerical, 2D finite-difference examples we investigate the impact of source and receiver effects. We study the effect of heterogeneous source distributions and the cable orientation by assessing similarities and differences to the Green's function. We also compare the obtained interferometric waveforms from strain interferometry to displacement interferometric wave fields obtained with existing methods. Intermediate results show that the obtained interferometric waveforms can be connected to the Green's Functions and provide consistent information about the propagation medium. These simulations will be extended to reservoir scale subsurface structures. Future work will include the application of the theory to real-data examples. The presented research depicts the early stage of a combination of theoretical investigations, numerical simulations and real-world data applications. We will therefore evaluate the potentials and shortcomings of DAS in reservoir monitoring and seismology at the current state, with a long-term vision of global seismic tomography utilizing DAS data from existing fiber-optic cable networks.

Refractive index and strain sensor based on twin-core fiber with a novel T-shaped taper

NASA Astrophysics Data System (ADS)

Zhang, Chuanbiao; Ning, Tigang; Li, Jing; Zheng, JingJing; Gao, Xuekai; Pei, Li

2018-06-01

A compact in-fiber Mach-Zehnder interferometer (MZI) based on twin-core fiber (TCF) with a novel T-shaped taper is proposed and demonstrated. The taper was firstly fabricated by a short section of TCF, and then spliced with a section of cleaved single mode fiber (SMF). When the light transmit into the TCF, multiple modes will be excited and will propagate within the TCF. In experiment, the proposed device had a maximum interferometric extinction ratio about 17 dB. And the refractive index (RI), strain, and temperature response properties of the sensor have been investigated, which show a relatively high RI, strain sensitivity and low temperature cross sensitivity. Hence, the sensor can be a suitable candidate in the biochemical and physical sensing applications. And due to its easy and controllable fabrication, the novel drawing technology can be applied to more multicore optical fibers.

Ranging and Correlating Sensor Development Program.

DTIC Science & Technology

1983-11-01

environmental or man-made disturbance that imparts motion within the protected area. Examples include air turbulence, rotating or oscillating objects such as fans...passive magnetic, passive thermal, etc. All fiber- optic transducers may be categorized into either amplitude or phase (interferometric) types. In an...equivalent phase shifts of less than +/- 1800 for any target. The wavelength of a 20 kHz carrier in air is about 0.68 inches; at 50 kHz the wavelength is about

Optical fiber Fabry-Perot interferometry

NASA Astrophysics Data System (ADS)

Wang, Anbo

2014-06-01

Fiber Fabry-Perot (FP) interferometry is one of the most important tools for harsh environment sensing because of its great flexibility of sensor material selection, superior long-­-term stability, and nature of remote passive operation. Virginia Tech's Center for Photonics Technology has been involved in the research of this field for many years. After a quick review of the typical methods for the construction of F-P sensors, emphasis will be placed on the whitelight interferometry, which is perhaps the most robust interferometric sensor demodulation technique today. The recent discovery of an additional phase will be presented and its significance to the sensor demodulation will be discussed.

Interferometric measurement of refractive index modification in a single mode microfiber

NASA Astrophysics Data System (ADS)

Ahmed, Farid; Ahsani, Vahid; Jun, Martin B. G.

2017-02-01

Efficient and cost effective measurement of the refractive index profile in an optical fiber is a significant technical job to design and manufacture in-fiber photonic devices and communication systems. For instance, to design fiber gratings, it is required to estimate the refractive index modulation to be inscribed by the fabrication apparatus such as ultraviolet or infrared lasers. Mach-Zehnder interferometer (MZI) based quantification of refractive index change written in single mode microfiber by femtosecond laser radiation is presented in this study. The MZI is constructed by splicing a microfiber (core diameter: 3.75 μm, cladding diameter: 40 μm) between standard single mode fibers. To measure the RI inscribed by infrared femtosecond laser, 200 μm length of the core within the MZI was scanned with laser radiation. As the higher index was written within 200 μm length of the core, the transmission spectrum of the interferometer displayed a corresponding red shift. The observed spectral shift was used to calculate the amount of refractive index change inscribed by the femtosecond irradiation. For the MZI length of 3.25 mm, and spectral shift of 0.8 nm, the calculated refractive index was found to be 0.00022. The reported results display excellent agreement between theory and experimental findings. Demonstrated method provides simple yet very effective on-site measurement of index change in optical fibers. Since the MZI can be constructed in diverse fiber types, this technique offers flexibility to quantify index change in various optical fibers.

Detection of in-plane displacements of acoustic wave fields using extrinsic Fizeau fiber interferometric sensors

NASA Technical Reports Server (NTRS)

Dhawan, R.; Gunther, M. F.; Claus, R. O.

1991-01-01

Quantitative measurements of the in-plane particle displacement components of ultrasonic surface acoustic wave fields using extrinsic Fizeau fiber interferometric (EFFI) sensors are reported. Wave propagation in materials and the fiber sensor elements are briefly discussed. Calibrated experimental results obtained for simulated acoustic emission events on homogeneous metal test specimens are reported and compared to previous results obtained using piezoelectric transducers.

Improved vertical optical fiber borehole strainmeter design for measuring Earth strain.

PubMed

DeWolf, Scott; Wyatt, Frank K; Zumberge, Mark A; Hatfield, William

2015-11-01

Fiber-based interferometers provide the means to sense very small displacements over long baselines, and have the advantage of being nearly completely passive in their operation, making them particularly well suited for geophysical applications. A new 250 m, interferometric vertical borehole strainmeter has been developed based completely on passive optical components. Details of the design and deployment at the Piñon Flat Observatory are presented. Power spectra show an intertidal noise level of -130 dB (re. 1 ϵ(2)/Hz), consistent within 1-3 dB between redundant components. Examination of its response to Earth tides and earthquakes relative to the areal strain recorded by an orthogonal pair of collocated, 730 m horizontal laser strainmeters yield a Poisson's ratio for local near surface material of 0.25 that is consistent with previous results.

Nonadiabatic tapered optical fiber sensor for measuring interaction nicotine with DNA

NASA Astrophysics Data System (ADS)

Zibaii, M. I.; Latifi, H.; Pourbeyram, H.; Gholami, M.; Taghipour, Z.; Saeedian, Z.; Hosseini, S. M.

2011-05-01

A nonadiabatic tapered optical fiber sensor was utilized for studying of bimolecular interactions including DNA-DNA and DNA-Drug interaction. This work presents a simple evanescent wave sensing system based on an interferometric approach, suitable to meet the requirements of lable-free sensor systems for detecting biomolecular interactions. We have demonstrated the measuring refractive index and the real time detection of interactions between biomolecules. Furthermore basic experiments were carried out, for detecting the hybridization of 25-mer DNA with an immobilized counterpart on the surface. The overall shift after the successful DNA hybridization was 9.5 nm. In this work, a new approach for studying DNA-drug interactions was successfully tested. Nicotine as a carcinogenic compound in cigarette smoke plays an important role in interaction with DNA. Different concentrations of nicotine were applied to observe the Longmuir interaction with DNA.

Integrated-optics heralded controlled-NOT gate for polarization-encoded qubits

NASA Astrophysics Data System (ADS)

Zeuner, Jonas; Sharma, Aditya N.; Tillmann, Max; Heilmann, René; Gräfe, Markus; Moqanaki, Amir; Szameit, Alexander; Walther, Philip

2018-03-01

Recent progress in integrated-optics technology has made photonics a promising platform for quantum networks and quantum computation protocols. Integrated optical circuits are characterized by small device footprints and unrivalled intrinsic interferometric stability. Here, we take advantage of femtosecond-laser-written waveguides' ability to process polarization-encoded qubits and present an implementation of a heralded controlled-NOT gate on chip. We evaluate the gate performance in the computational basis and a superposition basis, showing that the gate can create polarization entanglement between two photons. Transmission through the integrated device is optimized using thermally expanded core fibers and adiabatically reduced mode-field diameters at the waveguide facets. This demonstration underlines the feasibility of integrated quantum gates for all-optical quantum networks and quantum repeaters.

High resolution signal-processing method for extrinsic Fabry-Perot interferometric sensors

NASA Astrophysics Data System (ADS)

Xie, Jiehui; Wang, Fuyin; Pan, Yao; Wang, Junjie; Hu, Zhengliang; Hu, Yongming

2015-03-01

In this paper, a signal-processing method for optical fiber extrinsic Fabry-Perot interferometric sensors is presented. It achieves both high resolution and absolute measurement of the dynamic change of cavity length with low sampling points in wavelength domain. In order to improve the demodulation accuracy, the reflected interference spectrum is cleared by Discrete Wavelet Transform and adjusted by the Hilbert transform. Then the cavity length is interrogated by the cross correlation algorithm. The continuous tests show the resolution of cavity length is only 36.7 pm. Moreover, the corresponding resolution of cavity length is only 1 pm on the low frequency range below 420 Hz, and the corresponding power spectrum shows the possibility of detecting the ultra-low frequency signals based on spectra detection.

Reflective SOA-based fiber Bragg grating ultrasonic sensing system with two wave mixing interferometric demodulation

NASA Astrophysics Data System (ADS)

Wei, Heming; Krishnaswamy, Sridhar

2017-04-01

Damages such as cracking or impact loading in civil, aerospace, and mechanical structures generate transient ultrasonic waves, which can be used to reveal the structural health condition. Hence, it is necessary to find a practical tool based on ultrasonic detection for structural health monitoring. In this work, we describe an intelligent fiber-optic ultrasonic sensing system, which is designed based on a fiber Bragg grating (FBG) and a reflective semiconductor optical amplifier (RSOA) used as an adaptive source, and demodulated by an adaptive photorefractive two wave mixing (TWM) technique without any active compensation of quasi-static strains and temperature. As the wavelength of the FBG shifts due to the excited ultrasonic waves, the wavelength of the optical output from the fiber cavity laser shifts accordingly. With regard to the shift of the FBG reflective spectrum, the adaptivity of the RSOA-based laser is analyzed theoretically and verified by the TWM demodulator. Additionally, due to the response time of the photorefractive crystal, the TWM demodulator is insensitive to low frequency-FBG spectral shift. The results demonstrate that this proposed FBG ultrasonic sensing system has high sensitivity and can respond the ultrasonic waves into the megahertz frequency range, which shows a potential for acoustic emission detection in practical applications.

All-optical, Three-axis Fiber Laser Magnetometer

DTIC Science & Technology

2012-04-16

into each core using an ultraviolet laser. Measurements of the differences in induced strain between the FBGs enables bending in two dimensions to...housing. This is repeated for multiple inclinations. The difference in strain between two FBGs as a function of rotation for three inclination...angles of 9°, 45°, and 81° is shown in Fig. 10(a). The FBG strain is measured using an interferometric method, and as such, the difference in strain is

Cost-efficient speckle interferometry with plastic optical fiber for unobtrusive monitoring of human vital signs.

PubMed

Podbreznik, Peter; Đonlagić, Denis; Lešnik, Dejan; Cigale, Boris; Zazula, Damjan

2013-10-01

A cost-efficient plastic optical fiber (POF) system for unobtrusive monitoring of human vital signs is presented. The system is based on speckle interferometry. A laser diode is butt-coupled to the POF whose exit face projects speckle patterns onto a linear optical sensor array. Sequences of acquired speckle images are transformed into one-dimensional signals by using the phase-shifting method. The signals are analyzed by band-pass filtering and a Morlet-wavelet-based multiresolutional approach for the detection of cardiac and respiratory activities, respectively. The system is tested with 10 healthy nonhospitalized persons, lying supine on a mattress with the embedded POF. Experimental results are assessed statistically: precisions of 98.8% ± 1.5% and 97.9% ± 2.3%, sensitivities of 99.4% ± 0.6% and 95.3% ± 3%, and mean delays between interferometric detections and corresponding referential signals of 116.6 ± 55.5 and 1299.2 ± 437.3 ms for the heartbeat and respiration are obtained, respectively.

A Thermal Performance Analysis and Comparison of Fiber Coils with the D-CYL Winding and QAD Winding Methods.

PubMed

Li, Xuyou; Ling, Weiwei; He, Kunpeng; Xu, Zhenlong; Du, Shitong

2016-06-16

The thermal performance under variable temperature conditions of fiber coils with double-cylinder (D-CYL) and quadrupolar (QAD) winding methods is comparatively analyzed. Simulation by the finite element method (FEM) is done to calculate the temperature distribution and the thermal-induced phase shift errors in the fiber coils. Simulation results reveal that D-CYL fiber coil itself has fragile performance when it experiences an axially asymmetrical temperature gradient. However, the axial fragility performance could be improved when the D-CYL coil meshes with a heat-off spool. Through further simulations we find that once the D-CYL coil is provided with an axially symmetrical temperature environment, the thermal performance of fiber coils with the D-CYL winding method is better than that with the QAD winding method under the same variable temperature conditions. This valuable discovery is verified by two experiments. The D-CYL winding method is thus promising to overcome the temperature fragility of interferometric fiber optic gyroscopes (IFOGs).

A Thermal Performance Analysis and Comparison of Fiber Coils with the D-CYL Winding and QAD Winding Methods

PubMed Central

Li, Xuyou; Ling, Weiwei; He, Kunpeng; Xu, Zhenlong; Du, Shitong

2016-01-01

The thermal performance under variable temperature conditions of fiber coils with double-cylinder (D-CYL) and quadrupolar (QAD) winding methods is comparatively analyzed. Simulation by the finite element method (FEM) is done to calculate the temperature distribution and the thermal-induced phase shift errors in the fiber coils. Simulation results reveal that D-CYL fiber coil itself has fragile performance when it experiences an axially asymmetrical temperature gradient. However, the axial fragility performance could be improved when the D-CYL coil meshes with a heat-off spool. Through further simulations we find that once the D-CYL coil is provided with an axially symmetrical temperature environment, the thermal performance of fiber coils with the D-CYL winding method is better than that with the QAD winding method under the same variable temperature conditions. This valuable discovery is verified by two experiments. The D-CYL winding method is thus promising to overcome the temperature fragility of interferometric fiber optic gyroscopes (IFOGs). PMID:27322271

Optical Fiber High Temperature Sensor Instrumentation for Energy Intensive Industries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooper, Kristie L.; Wang, Anbo; Pickrell, Gary R.

2006-11-14

This report summarizes technical progress during the program “Optical Fiber High Temperature Sensor Instrumentation for Energy Intensive Industries”, performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The objective of this program was to use technology recently invented at Virginia Tech to develop and demonstrate the application of self-calibrating optical fiber temperature and pressure sensors to several key energy-intensive industries where conventional, commercially available sensors exhibit greatly abbreviated lifetimes due primarily to environmental degradation. A number of significant technologies were developed under this program, including • a laser bonded silicamore » high temperature fiber sensor with a high temperature capability up to 700°C and a frequency response up to 150 kHz, • the world’s smallest fiber Fabry-Perot high temperature pressure sensor (125 x 20 μm) with 700°C capability, • UV-induced intrinsic Fabry-Perot interferometric sensors for distributed measurement, • a single crystal sapphire fiber-based sensor with a temperature capability up to 1600°C. These technologies have been well demonstrated and laboratory tested. Our work plan included conducting major field tests of these technologies at EPRI, Corning, Pratt & Whitney, and Global Energy; field validation of the technology is critical to ensuring its usefulness to U.S. industries. Unfortunately, due to budget cuts, DOE was unable to follow through with its funding commitment to support Energy Efficiency Science Initiative projects and this final phase was eliminated.« less

Fiber-optic three axis magnetometer prototype development

NASA Technical Reports Server (NTRS)

Wang, Thomas D.; Mccomb, David G.; Kingston, Bradley R.; Dube, C. Michael; Poehls, Kenneth A.; Wanser, Keith

1989-01-01

The goal of this research program was to develop a high sensitivity, fiber optic, interferometric, three-axis magnetometer for interplanetary spacecraft applications. Dynamics Technology, Inc. (DTI) has successfully integrated a low noise, high bandwidth interferometer with high sensitivity metallic glass transducers. Also, DTI has developed sophisticated signal processing electronics and complete data acquisition, filtering, and display software. The sensor was packaged in a compact, low power and weight unit which facilitates deployment. The magnetic field sensor had subgamma sensitivity and a dynamic range of 10(exp 5) gamma in a 10 Hz bandwidth. Furthermore, the vector instrument exhibited the lowest noise level when only one axis was in operation. A system noise level of 1 gamma rms was observed in a 1 Hz bandwidth. However, with the other two channels operating, the noise level increased by about one order of magnitude. Higher system noise was attributed to cross-channel interference among the dither fields.

Advances in sapphire optical fiber sensors

NASA Technical Reports Server (NTRS)

Wang, Anbo; Wang, George Z.; Gollapudi, Sridhar; May, Russell G.; Murphy, Kent A.; Claus, Richard O.

1993-01-01

We describe the development and testing of two sapphire fiber sensor designs intended for use in high temperature environments. The first is a birefringence-balanced polarimetric sapphire fiber sensor. In this sensor, two single crystal sapphire rods, acting as the birefringence sensing element, are connected to each other in such a way that the slow axis of the first rod is aligned along with the fast axis of the second rod, and the fast axis of the first rod is along the slow axis of the second rod. This sensor has been demonstrated for measurement of temperature up to 1500 C. The second is a sapphire-fiber-based intrinsic interferometric sensor. In this sensor, a length of uncoated, unclad, structural-graded multimode sapphire fiber is fusion spliced to a singlemode silica fiber to form a Fabry-Perot cavity. The reflections from the silica-to-sapphire fiber splice and the free endface of the sapphire fiber give rise to the interfering fringe output. This sensor has been demonstrated for the measurement of temperature above 1510 C, and a resolution of 0.1 C has been obtained.

A Low Temperature Scanning Force Microscope with a Vertical Cantilever and Interferometric Detection Scheme

NASA Astrophysics Data System (ADS)

Kim, Jeehoon; Williams, T. L.; Chu, Sang Lin; Korre, Hasan; Chalfin, Max; Hoffman, J. E.

2008-03-01

We have developed a fiber-optic interferometry system with a vertical cantilever for scanning force microscopy. A lens, mounted on a Pan-type walker, was used to collect the interference signal in the cavity between the cantilever and the single mode fiber. This vertical geometry has several advantages: (1) it is directly sensitive to lateral forces; (2) low spring constant vertical cantilevers may allow increased force sensitivity by solving the ``snap-in'' problem that occurs with soft horizontal cantilevers. We have sharpened vertical cantilevers by focused ion beam (FIB), achieving a tip radius of 20 nm. We will show test results of a magnetic force microscope (MFM) with this vertical cantilever system.

High resolution tiltmeters and strainmeters based on extrinsic fiber Fabbry-Perot interferometry: the LINES project

NASA Astrophysics Data System (ADS)

chery, J.; Boudin, F.; Cattoen, M.; Seat, H.; Suleiman, M.; Chawah, P.; Plantier, G.; Sourice, A.; Bernard, P.; Brunet, C.; Gaffet, S.; Boyer, D.

2011-12-01

Measurements of strain and vibrations due to seismic and volcanic processes are mandatory for the understanding and the monitoring of the behavior of these systems. In the future, risk mitigation will depend on our capability to detect in a reliable way small precursors of large seismic and volcanic events and to assess the seismic/aseismic spatial and temporal distribution and evolution of crustal strain in these unstable systems.The robustness of strain and motion detection is primary linked to measurement accuracy, but also to the number and repartition of instrument. This implies that instrument cost and maintenance are essential for the development of networks. To date, only GPS sensors are robust enough to be deployed for long periods of time with limited problems of maintenance. Tiltmeters and strainmeters capabilities are often plagued by numerous technical problems limiting their usefulness. On the basis of existing or prototype sensors, we develop new instruments (seismometers, tiltmeters, strainmeters) using an interferometric motion measurement. Both Laser source and fringe analysis are connected to the mechanical sensor with long optic fiber (100 m - 10 km) depending on applications (volcanoes, sea bottom, boreholes) The fiber signal transmission is a major improvement by comparison with usual electric wires (cost, data channels, lightning, weight). Also, the absence of embedded electronic on the sensor is a guarantee for reliability and toughness. The proposed optical cell is an extrinsic all-fiber Fabry-Perot type interferometer (EFFPI). While being intrinsically insensitive to external perturbations to the sensing arm such as from stress/strain and temperature variations, the EFFPI is, however, extremely sensitive to changes in its sensing cavity length caused by parameters such as displacement, strain, and mechanical deformation along the optical axis. Coupled to well-advanced associated technologies in terms of laser sources (stability, output power), optical fiber (quality, low losses, couplers, connectics), photodetection (bandwidth, gain, low-noise) and real-time interferometric signal demodulation, this interferometer is today a mature device whose performance potential can be exploited in in-situ environmental monitoring of seismic activities (earthquakes and volcanoes) and in predicting the related risks. In the framework of the LINES project, we develop three types of mechanical sensors: a long baseline tiltmeter based on hydrostatic levelling, a borehole tiltmeter based on a simple pendulum and a seismometer for detecting vibrations at frequencies higher than 1 Hz. A common building principle is an external laser source and phase detector: as this part of the tool is remotely connected through an optic fiber to the underground sensor, this overcomes most of electric, power and maintenance problem occurring with non-optical devices. Moreover, this allows simple analog data transmission for a real-time network monitoring. We will show preliminary results suggesting that a rapid transition between laboratory prototypes and field instruments is likely.

Highly compact fiber Fabry-Perot interferometer: A new instrument design

NASA Astrophysics Data System (ADS)

Nowakowski, B. K.; Smith, D. T.; Smith, S. T.

2016-11-01

This paper presents the design, construction, and characterization of a new optical-fiber-based, low-finesse Fabry-Perot interferometer with a simple cavity formed by two reflecting surfaces (the end of a cleaved optical fiber and a plane, reflecting counter-surface), for the continuous measurement of displacements of several nanometers to several tens of millimeters. No beam collimation or focusing optics are required, resulting in a displacement sensor that is extremely compact (optical fiber diameter 125 μm), is surprisingly tolerant of misalignment (more than 5°), and can be used over a very wide range of temperatures and environmental conditions, including ultra-high-vacuum. The displacement measurement is derived from interferometric phase measurements using an infrared laser source whose wavelength is modulated sinusoidally at a frequency f. The phase signal is in turn derived from changes in the amplitudes of demodulated signals, at both the modulation frequency, f, and its harmonic at 2f, coming from a photodetector that is monitoring light intensity reflected back from the cavity as the cavity length changes. Simple quadrature detection results in phase errors corresponding to displacement errors of up to 25 nm, but by using compensation algorithms discussed in this paper, these inherent non-linearities can be reduced to below 3 nm. In addition, wavelength sweep capability enables measurement of the absolute surface separation. This experimental design creates a unique set of displacement measuring capabilities not previously combined in a single interferometer.

Wavelength-switched phase interrogator for extrinsic Fabry-Perot interferometric sensors.

PubMed

Xia, Ji; Xiong, Shuidong; Wang, Fuyin; Luo, Hong

2016-07-01

We report on phase interrogation of extrinsic Fabry-Perot interferometric (EFPI) sensors through a wavelength-switched unit with a polarization-maintaining fiber Bragg grating (PMFBG). The measurements at two wavelengths are first achieved in one total-optical path. The reflected peaks of the PMFBG with two natural wavelengths are in mutually perpendicular polarization detection, and they are switched through an electro-optic modulator at a high switching speed of 10 kHz. An ellipse fitting differential cross multiplication (EF-DCM) algorithm is proposed for interrogating the variation of the gap length of the EFPI sensors. The phase demodulation system has been demonstrated to recover a minimum phase of 0.42  μrad/Hz at the test frequency of 100 Hz with a stable intensity fluctuation level of ±0.8  dB. Three EFPI sensors with different cavity lengths are tested at the test frequency of 200 Hz, and the results indicate that the system can achieve the demodulation of EFPI sensors with different cavity lengths stably.

Compact all-fiber interferometer system for shock acceleration measurement

NASA Astrophysics Data System (ADS)

Zhao, Jiang; Pi, Shaohua; Hong, Guangwei; Zhao, Dong; Jia, Bo

2013-08-01

Acceleration measurement plays an important role in a variety of fields in science and engineering. In particular, the accurate, continuous and non-contact recording of the shock acceleration profiles of the free target surfaces is considered as a critical technique in shock physics. Various kinds of optical interferometers have been developed to monitor the motion of the surfaces of shocked targets since the 1960s, for instance, the velocity interferometer system for any reflector, the fiber optic accelerometer, the photonic Doppler velocimetry system and the displacement interferometer. However, most of such systems rely on the coherent quasi-monochromatic illumination and discrete optic elements, which are costly in setting-up and maintenance. In 1996, L. Levin et al reported an interferometric fiber-optic Doppler velocimeter with high-dynamic range, in which fiber-coupled components were used to replace the discrete optic elements. However, the fringe visibility of the Levin's system is low because of the coupled components, which greatly limits the reliability and accuracy in the shock measurement. In this paper, a compact all-fiber interferometer system for measuring the shock acceleration is developed and tested. The advantage of the system is that not only removes the non-interfering light and enhances the fringe visibility, but also reduces polarization induced signal fading and the polarization induced phase shift. Moreover, it also does not require a source of long coherence length. The system bases entirely on single-mode fiber optics and mainly consists of a polarization beam splitter, a faraday rotator, a depolarizer and a 3×3 single-mode fiber coupler which work at 1310 nm wavelength. The optical systems of the interferometer are described and the experimental results compared with a shock acceleration calibration system with a pneumatic exciter (PneuShockTM Model 9525C by The Modal Shop) are reported. In the shock acceleration test, the interferometer system measured shock acceleration with peak accelerations of ~100,000 m/s2 and the durations of ~0.2 ms which are conformed to the results of the shock acceleration calibration system. The measured relative error of the acceleration is within 3%.

Fluoride glass fibers: applications and prospects

NASA Astrophysics Data System (ADS)

Poulain, Marcel

1998-09-01

Fluoride glass fibers have been intensively developed for the last 20 years. A major effort was devoted to the fabrication of low loss fibers for repeaterless long haul telecommunications. This step which ended in the late eighties provided the basic technology for the manufacturing of multimode and single mode fibers with minimum losses below 10 dB/km. Such fibers area now used for various passive applications requiring the handling of IR signal. In this respect, fluoride fibers are complementary to silica fibers when wavelength exceeds 2 micrometers . Some practical set ups are operating for IR imaging, remote spectroscopy and thermometry. Special fibers such as polarization maintaining fibers have been developed for interferometric astronomy, which could also apply to sensors. UV transmission has still to be developed. Laser power delivery is another field of application for these fibers. YAG:Er laser at 2.9 micrometers attracts a growing interest for medical applications, ophthalmology and dentistry, while prospects for CO laser are positive. Active fibers are based on rare earth doped single mode fibers. They lead to the definition of numerous new laser lines and emphasized the potential of up conversion for the generation of visible light using IR pumping laser diodes. High power output has been achieved in the blue and the red light, which open prospects for compact and all solid state fiber lasers for a wide range of applications, from displays to medical uses. Optical amplification makes another field of R and D centered on telecommunication needs. Pr3+ doped fluoride fibers have been used for the 1.3 micrometers band, and Er based fluoride fiber amplifiers exhibit wider and flatter gain than those made from silica. Optical amplification may be implemented at other wavelengths for more general purposes.

Proceedings of the Society of Photo-Optical Instrumentation Engineers, Optical Components: Manufacture & Evaluation, Volume 171

DTIC Science & Technology

1979-01-22

window locations at which interferometric measurements are gathered while the window is in motion. Figure 3 is an optical schematic and Figure 4 shows...imposed in system opera- tion although they have not been subjected to the interferometric analysis as presented here. Evaluation of Mirror #2 As...aberrations present. Introduction We present a technique for evaluating optical aberrations from interferometric data; a measured wavefront is

Optical Injection Locking of Vertical Cavity Surface-Emitting Lasers: Digital and Analog Applications

NASA Astrophysics Data System (ADS)

Parekh, Devang

With the rise of mobile (cellphones, tablets, notebooks, etc.) and broadband wireline communications (Fiber to the Home), there are increasing demands being placed on transmitters for moving data from device to device and around the world. Digital and analog fiber-optic communications have been the key technology to meet this challenge, ushering in ubiquitous Internet and cable TV over the past 20 years. At the physical layer, high-volume low-cost manufacturing of semiconductor optoelectronic devices has played an integral role in allowing for deployment of high-speed communication links. In particular, vertical cavity surface emitting lasers (VCSEL) have revolutionized short reach communications and are poised to enter more markets due to their low cost, small size, and performance. However, VCSELs have disadvantages such as limited modulation performance and large frequency chirp which limits fiber transmission speed and distance, key parameters for many fiber-optic communication systems. Optical injection locking is one method to overcome these limitations without re-engineering the VCSEL at the device level. By locking the frequency and phase of the VCSEL by the direct injection of light from another laser oscillator, improved device performance is achieved in a post-fabrication method. In this dissertation, optical injection locking of VCSELs is investigated from an applications perspective. Optical injection locking of VCSELs can be used as a pathway to reduce complexity, cost, and size of both digital and analog fiber-optic communications. On the digital front, reduction of frequency chirp via bit pattern inversion for large-signal modulation is experimentally demonstrated showing up to 10 times reduction in frequency chirp and over 90 times increase in fiber transmission distance. Based on these results, a new reflection-based interferometric model for optical injection locking was established to explain this phenomenon. On the analog side, the resonance frequency enhancement was exploited for millimeter-wave radio over fiber communications. Experimental demonstration of 4 Gb/s data transmission over 20 km of fiber and 3 m of wireless transmission at a 60 GHz carrier frequency was achieved. Additionally, optical injection of multi-transverse mode (MM) VCSELs was investigated showing record resonance frequency enhancement of > 54 GHz and 3-dB bandwidth of 38 GHz. Besides these applications, a number of other intriguing applications are also discussed, including an optoelectronic oscillator (OEO) and wavelength-division multiplexed passive optical networks (WDM-PON). Finally, the future of optical injection locking and its direction going forward will be discussed.

Solid State Research

DTIC Science & Technology

1988-11-15

Reduction of Intermodulation L.M. Johnson Opt. Lett. 13, 928 (1988) Distortion in Interferometric H.V. Roussell Optical Modulators * Author not at Lincoln...Engineering V, Proc. Niobate Interferometric Modulators SPIE 835, 29 (1988), DTIC AD-A198029 7553 Advanced Device Fabrication with W.D. Goodhue Proc...Colorado, 3 October 1988 7741 B Integrated-Optical Interferometric L.M. Johnson 2 X 2 Switches H.V.Roussell 7927B Free-Space Optical Interconnects

Components for IFOG based inertial measurement units using active and passive polymer materials

NASA Astrophysics Data System (ADS)

Ashley, Paul R.; Temmen, Mark G.; Diffey, William M.; Sanghadasa, Mohan; Bramson, Michael D.; Lindsay, Geoffrey A.; Guenthner, Andrew J.

2006-08-01

Highly accurate, compact, and low cost inertial measurement units (IMUs) are needed for precision guidance in navigation systems. Active and passive polymer materials have been successfully used in fabricating two of the key guided-wave components, the phase modulator and the optical transceiver, for IMUs based on the interferometric fiber optic gyroscope (IFOG) technology. Advanced hybrid waveguide fabrication processes and novel optical integration techniques have been introduced. Backscatter compensated low loss phase modulators with low half-wave drive voltage (V π) have been fabricated with CLD- and FTC- type high performance electro-optic chromophores. A silicon-bench architecture has been used in fabricating high gain low noise transceivers with high optical power while maintaining the spectral quality and long lifetime. Gyro bias stability of less than 0.02 deg/hr has been demonstrated with these components. A review of the novel concepts introduced, fabrication and integration techniques developed and performance achieved are presented.

Les Noyaux Actifs de Galaxies en interférométrie optique à très longue base - Projet 'OHANA

NASA Astrophysics Data System (ADS)

Woillez, Julien

2003-12-01

Recent progress in sensitivity achieved by the new generation of optical long baseline interfero- meters (VLTI & Keck) allows new fields of astronomy to benefit from very high angular resolution observations at near infrared wavelength. Extragalactic astronomy, through active galactic nuclei observations, is one of those fields. As a preparation to coming active nuclei interferometric observations, I present a toolbox designed for the in- terpretation of the first data, knowing that their amount will stay small at the beginning whereas the observed objects are known to be complex. I will also present one of the two first observations of active nuclei : the Seyfert 2 nucleus NGC 1068 observed with MIDI, the newly commissioned 10 μm instrument of the VLTI. With the Seyfert 1 nucleus NGC 4151 by Keck interferometer, those two observations confirm the forecasted need of higher angular resolution to study the inner parts of the molecular torus found in active galactic nuclei. The broad line region will be one of the next components to be observed with an interferometer, provided that the extra angular resolution becomes available. In order to study the 3D structure of the region, I present an innovative tomographic technique based on reverberation mapping and interferometry : interferometric reverberation. The 'OHANA project (Optical Hawaiian Array for Nanoradion Astronomy) is the topic of the second part of this work as it will provide the extra angular resolution. The project also aims at demonstrating the use of single mode fibers in J, H and K bands to coherently combine adaptive corrected telescopes, already present on top of Mauna Kea, into a very sensitive and resolving interferometer. I present the preparatory phase of the project (Phase I) where the coupling between adaptive optics and single mode fibers is studied on CFHT, Gemini and Keck telescopes. Those tests allow me to confirm the sensitivity of the final instrument as well as to propose a diagnostic on the different adaptive optics systems. Then I present the 'OHANA beam combiner that is about to be used in the demonstration phase (phase II). This combiner is based on a new concept where the two interferometric outputs of a single mode coaxial combination are combined in a multiaxial scheme in order to obtain a single output, with only one coupler. The interferogram is then temporally coded and the photometry spatially. I present the ongoing developments of pahse II, namely a gaussian beam delay line and 2×300 m long single mode fibers, in J, H and K bands, used for the coherent transport.

Design and characterization of MEMS interferometric sensing

NASA Astrophysics Data System (ADS)

Snyder, R.; Siahmakoun, A.

2010-02-01

A MEMS-based interferometric sensor is produced using the multi-user MEMS processing standard (MUMPS) micromirrors, movable by thermal actuation. The interferometer is comprised of gold reflection surfaces, polysilicon thermal actuators, hinges, latches and thin film polarization beam splitters. A polysilicon film of 3.5 microns reflects and transmits incident polarized light from an external laser source coupled to a multi-mode optical fiber. The input beam is shaped to a diameter of 10 to 20 microns for incidence upon the 100 micron mirrors. Losses in the optical path include diffraction effects from etch holes created in the manufacturing process, surface roughness of both gold and polysilicon layers, and misalignment of micro-scale optical components. Numerous optical paths on the chip vary by length, number of reflections, and mirror subsystems employed. Subsystems include thermal actuator batteries producing lateral position displacement, angularly tunable mirrors, double reflection surfaces, and static vertical mirrors. All mirror systems are raised via manual stimulation using two micron, residue-free probe tips and some may be aligned using electrical signals causing resistive heating in thermal actuators. The characterization of thermal actuator batteries includes maximum displacement, deflection, and frequency response that coincides with theoretical thermodynamic simulations using finite-element analysis. Maximum deflection of 35 microns at 400 mW input electrical power is shown for three types of actuator batteries as is deflection dependent frequency response data for electrical input signals up to 10 kHz.

Numerous applications of fiber optic evanescent wave Fourier transform infrared (FEW-FTIR) spectroscopy for subsurface structural analysis

NASA Astrophysics Data System (ADS)

Afanasyeva, Natalia I.; Welser, Leslie; Bruch, Reinhard F.; Kano, Angelique; Makhine, Volodymyr

1999-10-01

A new infrared (IR) interferometric method has been developed in conjunction with low-loss, flexible optical fibers, sensors, and probes. This combination of fiber optical sensors and Fourier Transform (FT) spectrometers can be applied to many fields, including (1) noninvasive medical diagnostics of cancer and other different diseases in vivo, (2) minimally invasive bulk diagnostics of tissue, (3) remote monitoring of tissue, chemical processes, and environment, (4) surface analysis of polymers and other materials, (5) characterization of the quality of food, pharmacological products, cosmetics, paper, and other wood-related products, as well as (6) agricultural, forensic, geological, mining, and archeological field measurements. In particular, our nondestructive, fast, compact, portable, remote and highly sensitive diagnostics tools are very promising for subsurface analysis at the molecular level without sample preparation. For example, this technique is ideal for different types of soft porous foams, rough polymers, and rock surfaces. Such surfaces, as well as living tissue, are very difficult to investigate by traditional FTIR methods. We present here FEW-FTIR spectra of polymers, banana and grapefruit peels, and living tissues detected directly at surfaces. In addition, results on the vibrational spectral analysis of normal and pathological skin tissue in the region of 850 - 4000 cm-1 are discussed.

Interferometric optical online dosimetry for selective retina treatment (SRT)

NASA Astrophysics Data System (ADS)

Stoehr, Hardo; Ptaszynski, Lars; Fritz, Andreas; Brinkmann, Ralf

2007-07-01

Selective retina treatment (SRT) is a new laser based method to treat retinal diseases associated with disorders of the retinal pigment epithelium (RPE). Applying microsecond laser pulses tissue damage spatially confined to the retinal pigment epithelium (RPE) is achieved. The RPE cell damage is caused by transient microbubbles emerging at the strongly absorbing melanin granules inside the RPE cells. Due to the spatial confinement to the RPE the photoreceptors can be spared and vision can be maintained in the treated retinal areas. A drawback for effective clinical SRT is that the laser induced lesions are ophthalmoscopically invisible. Therefore, a real-time feedback system for dosimetry is necessary in order to avoid undertreatment or unwanted collateral damage to the adjacent tissue. We develop a dosimetry system which uses optical interferometry for the detection of the transient microbubbles. The system is based on an optical fiber interferometer operated with a laser diode at 830nm. We present current results obtained with a laser slit lamp using porcine RPE explants in vitro and complete porcine eye globes ex vivo. The RPE cell damage is determined by Calcein fluorescence viability assays. With a threshold criterium for RPE cell death derived from the measured interferometric signal transients good agreement with the results of the viability assays is achieved.

Structural Health Monitoring Using Textile Reinforcement Structures with Integrated Optical Fiber Sensors

PubMed Central

Bremer, Kort; Weigand, Frank; Zheng, Yulong; Alwis, Lourdes Shanika; Helbig, Reinhard; Roth, Bernhard

2017-01-01

Optical fiber-based sensors “embedded” in functionalized carbon structures (FCSs) and textile net structures (TNSs) based on alkaline-resistant glass are introduced for the purpose of structural health monitoring (SHM) of concrete-based structures. The design aims to monitor common SHM parameters such as strain and cracks while at the same time acting as a structural strengthening mechanism. The sensor performances of the two systems are characterized in situ using Mach-Zehnder interferometric (MZI) and optical attenuation measurement techniques, respectively. For this purpose, different FCS samples were subjected to varying elongation using a tensile testing machine by carefully incrementing the applied force, and good correlation between the applied force and measured length change was observed. For crack detection, the functionalized TNSs were embedded into a concrete block which was then exposed to varying load using the three-point flexural test until destruction. Promising results were observed, identifying that the location of the crack can be determined using the conventional optical time domain reflectometry (OTDR) technique. The embedded sensors thus evaluated show the value of the dual achievement of the schemes proposed in obtaining strain/crack measurement while being utilized as strengthening agents as well. PMID:28208636

Quantum Noise Reduction with Pulsed Light in Optical Fibers.

NASA Astrophysics Data System (ADS)

Bergman, Keren

Optical fibers offer considerable advantages over bulk nonlinear media for the generation of squeezed states. This thesis reports on experimental investigations of reducing quantum noise by means of squeezing in nonlinear fiber optic interferometers. Fibers have low insertion loss which allows for long interaction lengths. High field intensities are easily achieved in the small cores of single mode fibers. Additionally, the nonlinear process employed is self phase modulation or the Kerr effect, whose broad band nature requires no phase matching and can be exploited with ultra-short pulses of high peak intensity. All these advantageous features of fibers result in easily obtained large nonlinear phase shifts and subsequently large squeezing parameters. By the self phase modulation process a correlation is produced between the phase and amplitude fluctuations of the optical field. The attenuated or squeezed quadrature has a lower noise level than the initial level associated with the coherent state field before propagation. The resulting reduced quantum noise quadrature can be utilized to improve the sensitivity of a phase measuring instrument such as an interferometer. Because the Kerr nonlinearity is a degenerate self pumping process, the squeezed noise is at the same frequency as the pump field. Classical pump noise can therefore interfere with the desired measurement of the quantum noise reduction. The most severe noise process is the phase noise caused by thermally induced index modulation of the fiber. This noise termed Guided Acoustic Wave Brillouin Scattering, or GAWBS, by previous researchers is studied and analyzed. Experiments performed to overcome GAWBS successfully with several schemes are described. An experimental demonstration of an interferometric measurement with better sensitivity than the standard quantum limit is described. The results lead to new understandings into the limitations of quantum noise reduction that can be achieved in the laboratory. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.).

Mode power distribution effect in white-light multimode fiber extrinsic Fabry-Perot interferometric sensor systems.

PubMed

Han, Ming; Wang, Anbo

2006-05-01

Theoretical and experimental results have shown that mode power distribution (MPD) variations could significantly vary the phase of spectral fringes from multimode fiber extrinsic Fabry-Perot interferometric (MMF-EFPI) sensor systems, owing to the fact that different modes introduce different extra phase shifts resulting from the coupling of modes reflected at the second surface to the lead-in fiber end. This dependence of fringe pattern on MPD could cause measurement errors in signal demodulation methods of white-light MMF-EFPI sensors that implement the phase information of the fringes.

Microwave Photonics Systems Based on Whispering-gallery-mode Resonators

PubMed Central

Coillet, Aurélien; Henriet, Rémi; Phan Huy, Kien; Jacquot, Maxime; Furfaro, Luca; Balakireva, Irina; Larger, Laurent; Chembo, Yanne K.

2013-01-01

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency. PMID:23963358

Microwave photonics systems based on whispering-gallery-mode resonators.

PubMed

Coillet, Aurélien; Henriet, Rémi; Phan Huy, Kien; Jacquot, Maxime; Furfaro, Luca; Balakireva, Irina; Larger, Laurent; Chembo, Yanne K

2013-08-05

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency.

The evolution and exploitation of the fiber-optic hydrophone

NASA Astrophysics Data System (ADS)

Hill, David J.

2007-07-01

In the late 1970s one of the first applications identified for fibre-optic sensing was the fibre-optic hydrophone. It was recognised that the technology had the potential to provide a cost effective solution for large-scale arrays of highly sensitive hydrophones which could be interrogated over large distances. Consequently both the United Kingdom and United States navies funded the development of this sonar technology to the point that it is now deployed on submarines and as seabed arrays. The basic design of a fibre-optic hydrophone has changed little; comprising a coil of optical fibre wound on a compliant mandrel, interrogated using interferometric techniques. Although other approaches are being investigated, including the development of fibre-laser hydrophones, the interferometric approach remains the most efficient way to create highly multiplexed arrays of acoustic sensors. So much so, that the underlying technology is now being exploited in civil applications. Recently the exploration and production sector of the oil and gas industry has begun funding the development of fibre-optic seismic sensing using seabed mounted, very large-scale arrays of four component (three accelerometers and a hydrophone) packages based upon the original technology developed for sonar systems. This has given new impetus to the development of the sensors and the associated interrogation systems which has led to the technology being adopted for other commercial uses. These include the development of networked in-road fibre-optic Weigh-in-Motion sensors and of intruder detection systems which are able to acoustically monitor long lengths of border, on both land and at sea. After two decades, the fibre-optic hydrophone and associated technology has matured and evolved into a number of highly capable sensing solutions used by a range of industries.

Coherently coupled high-power fiber arrays

NASA Astrophysics Data System (ADS)

Anderegg, Jesse; Brosnan, Stephen; Cheung, Eric; Epp, Paul; Hammons, Dennis; Komine, Hiroshi; Weber, Mark; Wickham, Michael

2006-02-01

A four-element fiber array has demonstrated 470 watts of coherently phased, linearly polarized light energy in a single far-field spot. Each element consists of a single-mode fiber-amplifier chain. Phase control of each element is achieved with a Lithium-Niobate phase modulator. A master laser provides a linearly polarized, narrow linewidth signal that is split into five channels. Four channels are individually amplified using polarization maintaining fiber power amplifiers. The fifth channel is used as a reference arm. It is frequency shifted and then combined interferometrically with a portion of each channel's signal. Detectors sense the heterodyne modulation signal, and an electronics circuit measures the relative phase for each channel. Compensating adjustments are then made to each channel's phase modulator. This effort represents the results of a multi-year effort to achieve high power from a single element fiber amplifier and to understand the important issues involved in coherently combining many individual elements to obtain sufficient optical power for directed energy weapons. Northrop Grumman Corporation and the High Energy Laser Joint Technology Office jointly sponsored this work.

A Fiber-Optic Sensor for Leak Detection in a Space Environment

NASA Technical Reports Server (NTRS)

Sinko, John E.; Korman, Valentin; Hendrickson, Adam; Polzin, Kurt A.

2009-01-01

A miniature fiber-optic, laser-based, interferometric leak detector is presented for application as a means to detect on-orbit gas leaks. The sensor employs a fiber-coupled modified Michelson interferometer to detect gas leaks by measuring an increase in gas density in the sensing region. Monitoring changes in the fringe pattern output by the interferometer allows for direct measurement of the gas density in the sensing region and, under the assumption of an equation of state, this can be used to obtain a pressure measurement. Measurements obtained over a pressure range from 20 mtorr to 760 torr using a prototypical interferometer on working gases of air, nitrogen, argon, and helium generally exhibit agreement with a theoretical prediction of the pressure increase required before an interference fringe completely moves over the detector. Additional measurements performed on various gases demonstrate the range of detectable species, measuring sub-torr pressure changes in the process. A high-fidelity measurement places the ultimate pressure resolution for this particular sensor configuration in the 10 mtorr range. Time-resolved data prove the capability of this sensor to detect fast gas flow phenomena associated with transients and pressure waves.

Optical fiber sensors for damage analysis in aerospace materials

NASA Technical Reports Server (NTRS)

Schindler, Paul; May, Russell; Claus, Richard

1995-01-01

Under this grant, fiber optic sensors were investigated for use in the nondestructive evaluation of aging aircraft. Specifically, optical fiber sensors for detection and location of impacts on a surface, and for detection of corrosion in metals were developed. The use of neural networks was investigated for determining impact location by processing the output of a network of fiberoptic strain sensors distributed on a surface. This approach employs triangulation to determine location by comparing the arrival times at several sensors, of the acoustic signal generated by the impact. For this study, a neural network simulator running on a personal computer was used to train a network using a back-propagation algorithm. Fiber optic extrinsic Fabry-Perot interferometer (EFPI) strain sensors are attached to or embedded in the surface, so that stress waves emanating from an impact can be detected. The ability of the network to determine impact location by time-or-arrival of acoustic signals was assessed by comparing network outputs with actual experimental results using impacts on a panel instrumented with optical fiber sensors. Using the neural network to process the sensor outputs, the impact location can be inferred to centimeter range accuracy directly from the arrival time data. In addition, the network can be trained to determine impact location, regardless of material anisotropy. Results demonstrate that a back-propagation network identifies impact location for an anisotropic graphite/bismaleimide plate with the same accuracy as that for an isotropic aluminum plate. Two different approaches were investigated for the development of fiber optic sensors for corrosion detection in metals, both utilizing optical fiber sensors with metal coatings. In the first approach, an extrinsic Fabry-Perot interferometric fiber optic strain sensor was placed under tensile stress, and while in the resulting strained position, a thick coating of metal was applied. Due to an increase in the quantity of material, the sensor does not return to its original position upon removal of the applied stress, and some residual strain is maintained within the sensor element. As the metal thickness decreases due to corrosion, this strain is released, providing the sensing mechanism for corrosion detection. In the second approach, photosensitive optical fibers with long period Bragg gratings in the core were coated with metal. The Bragg gratings serve to couple core modes at discrete wavelengths to cladding modes. Since cladding modes interact with the metal coating surrounding the fiber cladding, the specific wavelengths coupled from core to cladding depend on the refractive index of the metal coating. Therefore, as the metal corrodes, the resulting change in index of the coating may be measured by measuring the change in wavelength of the coupled mode. Results demonstrate that both approaches can be successfully used to track the loss in metal coating on the optical fiber sensors due to corrosion.

Interferometric architectures based All-Optical logic design methods and their implementations

NASA Astrophysics Data System (ADS)

Singh, Karamdeep; Kaur, Gurmeet

2015-06-01

All-Optical Signal Processing is an emerging technology which can avoid costly Optical-electronic-optical (O-E-O) conversions which are usually compulsory in traditional Electronic Signal Processing systems, thus greatly enhancing operating bit rate with some added advantages such as electro-magnetic interference immunity and low power consumption etc. In order to implement complex signal processing tasks All-Optical logic gates are required as backbone elements. This review describes the advances in the field of All-Optical logic design methods based on interferometric architectures such as Mach-Zehnder Interferometer (MZI), Sagnac Interferometers and Ultrafast Non-Linear Interferometer (UNI). All-Optical logic implementations for realization of arithmetic and signal processing applications based on each interferometric arrangement are also presented in a categorized manner.

High contrast stellar observations within the diffraction limit at the Palomar Hale telescope

NASA Astrophysics Data System (ADS)

Mennesson, B.; Hanot, C.; Serabyn, E.; Martin, S. R.; Liewer, K.; Loya, F.; Mawet, D.

2010-07-01

We report on high-accuracy, high-resolution (< 20mas) stellar measurements obtained in the near infrared ( 2.2 microns) at the Palomar 200 inch telescope using two elliptical (3m x 1.5m) sub-apertures located 3.4m apart. Our interferometric coronagraph, known as the "Palomar Fiber Nuller" (PFN), is located downstream of the Palomar adaptive optics (AO) system and recombines the two separate beams into a common singlemode fiber. The AO system acts as a "fringe tracker", maintaining the optical path difference (OPD) between the beams around an adjustable value, which is set to the central dark interference fringe. AO correction ensures high efficiency and stable injection of the beams into the single-mode fiber. A chopper wheel and a fast photometer are used to record short (< 50ms per beam) interleaved sequences of background, individual beam and interferometric signals. In order to analyze these chopped null data sequences, we developed a new statistical method, baptized "Null Self-Calibration" (NSC), which provides astrophysical null measurements at the 0.001 level, with 1 σ uncertainties as low as 0.0003. Such accuracy translates into a dynamic range greater than 1000:1 within the diffraction limit, demonstrating that the approach effectively bridges the traditional gap between regular coronagraphs, limited in angular resolution, and long baseline visibility interferometers, whose dynamic range is restricted to 100:1. As our measurements are extremely sensitive to the brightness distribution very close to the optical axis, we were able to constrain the stellar diameters and amounts of circumstellar emission for a sample of very bright stars. With the improvement expected when the PALM-3000 extreme AO system comes on-line at Palomar, the same instrument now equipped with a state of the art low noise fast read-out near IR camera, will yield 10-4 to 10-3 contrast as close as 30 mas for stars with K magnitude brighter than 6. Such a system will provide a unique and ideal tool for the detection of young (<100 Myr) self-luminous planets and hot debris disks in the immediate vicinity (0.1 to a few AUs) of nearby (< 50pc) stars.

Fiber optic interferometer as a security element

NASA Astrophysics Data System (ADS)

Nedoma, Jan; Zboril, Ondrej; Fajkus, Marcel; Cubik, Jakub; Zavodny, Petr; Novak, Martin; Bednarek, Lukas; Martinek, Radek; Vasinek, Vladimir

2016-04-01

Interferometric sensors can be categorized as highly sensitive and precise devices with series inconsiderable benefits from the possibility of using standard telecommunication fibers. They can be measured even small changes in the deformation of shapes in time, changes in temperature, pressure, voltage, vibration, electric field, etc. The basic idea, which is described in this article is the usage of the interferometer as a security and monitoring component, which offers a solution for securing of closed spaces, especially before unwanted entries. Its primary task is to detect intrusions - disrupting the integrity of the transparent window area due to vibration response. The base of the solution is a Mach-Zehnder interferometer, which consists of two arms in the power distribution ratio of 1:1, consisting of the SM optical fiber excited by a DFB laser. The interferometer is working on the wavelength of 1550 nm. The resulting signal is registered as a result of interference of optical beams from the reference and sensor arm. Realized measuring scheme was terminated optical receiver comprising PbSe detector. Below described experimental measurements have shown that implemented interferometer has a sufficient value of the signal to noise ratio (SNR) and is able to detect very weak signals in a wide frequency range from tens of Hz to kHz units. The signal was processed by applications developed for the amplitude-frequency spectrum. Evaluated was the maximum amplitude of the signal and compared to the noise. The results were verified by retesting the assembled prototype.

Experimental measurement and numerical analysis of group velocity dispersion in cladding modes of an endlessly single-mode photonic crystal fiber

NASA Astrophysics Data System (ADS)

Baselt, Tobias; Taudt, Christopher; Nelsen, Bryan; Lasagni, Andrés. Fabián.; Hartmann, Peter

2017-06-01

The optical properties of the guided modes in the core of photonic crystal fibers (PCFs) can be easily manipulated by changing the air-hole structure in the cladding. Special properties can be achieved in this case such as endless singlemode operation. Endlessly single-mode fibers, which enable single-mode guidance over a wide spectral range, are indispensable in the field of fiber technology. A two-dimensional photonic crystal with a silica central core and a micrometer-spaced hexagonal array of air holes is an established method to achieve endless single-mode properties. In addition to the guidance of light in the core, different cladding modes occur. The coupling between the core and the cladding modes can affect the endlessly single-mode guides. There are two possible ways to determine the dispersion: measurement and calculation. We calculate the group velocity dispersion (GVD) of different cladding modes based on the measurement of the fiber structure parameters, the hole diameter and the pitch of a presumed homogeneous hexagonal array. Based on the scanning electron image, a calculation was made of the optical guiding properties of the microstructured cladding. We compare the calculation with a method to measure the wavelength-dependent time delay. We measure the time delay of defined cladding modes with a homemade supercontinuum light source in a white light interferometric setup. To measure the dispersion of cladding modes of optical fibers with high accuracy, a time-domain white-light interferometer based on a Mach-Zehnder interferometer is used. The experimental setup allows the determination of the wavelengthdependent differential group delay of light travelling through a thirty centimeter piece of test fiber in the wavelength range from VIS to NIR. The determination of the GVD using different methods enables the evaluation of the individual methods for characterizing the cladding modes of an endlessly single-mode fiber.

Phase-generated carrier demodulation scheme for fiber Fabry-Pérot interferometric sensor with high finesse

NASA Astrophysics Data System (ADS)

Rao, Wei; Niu, Siliang; Zhang, Nan; Cao, Chunyan; Hu, Yongmin

2011-09-01

This paper presents a demodulation scheme using phase-generated carrier (PGC) for a fiber Fabry-Pérot interferometric (FFPI) sensor with high finesse. The FFPI is constructed by a polarization maintaining fiber ring resonator with dual-coupler (PMDC-FRR), which can eliminate the polarization induced fading phenomenon. Compared with the former phase demodulation methods, the PGC scheme in this paper does not assume a two-beam interferometric approximation for the Fabry-Pérot cavity, and can work at arbitrary value of finesse in theory. Two PMDC-FRRs with reflective coefficients of 0.5 and 0.9 are made in experiments for demodulation. Both the single-frequency and the wideband signals are successfully demodulated from the transmission intensities using the PGC demodulation scheme. The experimental results demonstrate that the PGC demodulation scheme is feasible for the FFPI sensor with high finesse. The effects of the reflective coefficient and the intensity loss to the finesse are also discussed.

Sol-gel nano-porous silica-titania thin films with liquid fill for optical interferometric sensors

NASA Astrophysics Data System (ADS)

Martin, Andrew J.; Green, Mino

1990-11-01

The production of thin films whose refractive index is measurand specific, for use in an interferometric fiber optic chemical sensor, is discussed. The problem of making such coatings has been tackled by a system we have termed the "guest-host" approach, in which an active liquid whose index varies with measurand, is contained within a porous glass host of fixed index. Suitable porous silica-titania glass films have been produced via the sol-gel process. The use of this system enables the index of the glass to be varied, so that the composite index of the liquid filled film can be tailored to that required by the optical system. The sol-gel method developed is based upon the hydrolysis and polymerisation of metal alkoxides, in an acidic aqueous/alcoholic solution. Thin film slab waveguides were deposited in order to measure the light scattering losses, which were found to be typically ''1dB/cm. The porosity of films was studied using a new technique developed in which water adsorption isotherms are plotted using ellipsometry. The pore size was found to be very small of pore diameter in the nanometer range, and the total porosity -1O%. Both of these factors were increased by the removal of residual organic material, using hydrogen peroxide. Finally the use of pH indicator dyes as a liquid fill is discussed, to produce a pH sensor.

SPECKLE INTERFEROMETRY AT THE U.S. NAVAL OBSERVATORY. XVI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mason, Brian D.; Hartkopf, William I.; Wycoff, Gary L., E-mail: bdm@usno.navy.mil, E-mail: wih@usno.navy.mil

2011-05-15

The results of 1031 speckle-interferometric observations of double stars, made with the 26 inch refractor of the U.S. Naval Observatory, are presented. Each speckle-interferometric observation of a system represents a combination of over two thousand short-exposure images. These observations are averaged into 457 mean relative positions and range in separation from 0.''15 to 16.''94, with a median separation of 3.''03. The range in V-band magnitudes for the primary (secondary) of observed targets is 3.1-12.9 (3.2-13.3). This is the sixteenth in a series of papers presenting measurements obtained with this system and covers the period 2009 January 12 through 2009 Decembermore » 17. Included in these data are 12 older measurements whose positions were previously deemed possibly aberrant, but are no longer classified this way following a confirming observation. Also, 10 pairs with a single observation are herein confirmed. This paper also includes the first data obtained using a new ICCD with fiber optic cables.« less

Digital signal processing for velocity measurements in dynamical material's behaviour studies.

PubMed

Devlaminck, Julien; Luc, Jérôme; Chanal, Pierre-Yves

2014-03-01

In this work, we describe different configurations of optical fiber interferometers (types Michelson and Mach-Zehnder) used to measure velocities during dynamical material's behaviour studies. We detail the algorithms of processing developed and optimized to improve the performance of these interferometers especially in terms of time and frequency resolutions. Three methods of analysis of interferometric signals were studied. For Michelson interferometers, the time-frequency analysis of signals by Short-Time Fourier Transform (STFT) is compared to a time-frequency analysis by Continuous Wavelet Transform (CWT). The results have shown that the CWT was more suitable than the STFT for signals with low signal-to-noise, and low velocity and high acceleration areas. For Mach-Zehnder interferometers, the measurement is carried out by analyzing the phase shift between three interferometric signals (Triature processing). These three methods of digital signal processing were evaluated, their measurement uncertainties estimated, and their restrictions or operational limitations specified from experimental results performed on a pulsed power machine.

M&A For Lithography Of Sparse Arrays Of Sub-Micrometer Features

DOEpatents

Brueck, Steven R.J.; Chen, Xiaolan; Zaidi, Saleem; Devine, Daniel J.

1998-06-02

Methods and apparatuses are disclosed for the exposure of sparse hole and/or mesa arrays with line:space ratios of 1:3 or greater and sub-micrometer hole and/or mesa diameters in a layer of photosensitive material atop a layered material. Methods disclosed include: double exposure interferometric lithography pairs in which only those areas near the overlapping maxima of each single-period exposure pair receive a clearing exposure dose; double interferometric lithography exposure pairs with additional processing steps to transfer the array from a first single-period interferometric lithography exposure pair into an intermediate mask layer and a second single-period interferometric lithography exposure to further select a subset of the first array of holes; a double exposure of a single period interferometric lithography exposure pair to define a dense array of sub-micrometer holes and an optical lithography exposure in which only those holes near maxima of both exposures receive a clearing exposure dose; combination of a single-period interferometric exposure pair, processing to transfer resulting dense array of sub-micrometer holes into an intermediate etch mask, and an optical lithography exposure to select a subset of initial array to form a sparse array; combination of an optical exposure, transfer of exposure pattern into an intermediate mask layer, and a single-period interferometric lithography exposure pair; three-beam interferometric exposure pairs to form sparse arrays of sub-micrometer holes; five- and four-beam interferometric exposures to form a sparse array of sub-micrometer holes in a single exposure. Apparatuses disclosed include arrangements for the three-beam, five-beam and four-beam interferometric exposures.

Modeling for IFOG Vibration Error Based on the Strain Distribution of Quadrupolar Fiber Coil

PubMed Central

Gao, Zhongxing; Zhang, Yonggang; Zhang, Yunhao

2016-01-01

Improving the performance of interferometric fiber optic gyroscope (IFOG) in harsh environment, especially in vibrational environment, is necessary for its practical applications. This paper presents a mathematical model for IFOG to theoretically compute the short-term rate errors caused by mechanical vibration. The computational procedures are mainly based on the strain distribution of quadrupolar fiber coil measured by stress analyzer. The definition of asymmetry of strain distribution (ASD) is given in the paper to evaluate the winding quality of the coil. The established model reveals that the high ASD and the variable fiber elastic modulus in large strain situation are two dominant reasons that give rise to nonreciprocity phase shift in IFOG under vibration. Furthermore, theoretical analysis and computational results indicate that vibration errors of both open-loop and closed-loop IFOG increase with the raise of vibrational amplitude, vibrational frequency and ASD. Finally, an estimation of vibration-induced IFOG errors in aircraft is done according to the proposed model. Our work is meaningful in designing IFOG coils to achieve a better anti-vibration performance. PMID:27455257

Wavelength interrogation of fiber Bragg grating sensors based on crossed optical Gaussian filters.

PubMed

Cheng, Rui; Xia, Li; Zhou, Jiaao; Liu, Deming

2015-04-15

Conventional intensity-modulated measurements require to be operated in linear range of filter or interferometric response to ensure a linear detection. Here, we present a wavelength interrogation system for fiber Bragg grating sensors where the linear transition is achieved with crossed Gaussian transmissions. This unique filtering characteristic makes the responses of the two branch detections follow Gaussian functions with the same parameters except for a delay. The substraction of these two delayed Gaussian responses (in dB) ultimately leads to a linear behavior, which is exploited for the sensor wavelength determination. Beside its flexibility and inherently power insensitivity, the proposal also shows a potential of a much wider operational range. Interrogation of a strain-tuned grating was accomplished, with a wide sensitivity tuning range from 2.56 to 8.7 dB/nm achieved.

A Fiber-Optic Interferometric Tri-Component Geophone for Ocean Floor Seismic Monitoring

PubMed Central

Chen, Jiandong; Chang, Tianying; Fu, Qunjian; Lang, Jinpeng; Gao, Wenzhi; Wang, Zhongmin; Yu, Miao; Zhang, Yanbo; Cui, Hong-Liang

2016-01-01

For the implementation of an all fiber observation network for submarine seismic monitoring, a tri-component geophone based on Michelson interferometry is proposed and tested. A compliant cylinder-based sensor head is analyzed with finite element method and tested. The operation frequency ranges from 2 Hz to 150 Hz for acceleration detection, employing a phase generated carrier demodulation scheme, with a responsivity above 50 dB re rad/g for the whole frequency range. The transverse suppression ratio is about 30 dB. The system noise at low frequency originated mainly from the 1/f fluctuation, with an average system noise level −123.55 dB re rad/Hz ranging from 0 Hz to 500 Hz. The minimum detectable acceleration is about 2 ng/Hz, and the dynamic range is above 116 dB. PMID:28036011

Measurement of the thickness of the lens with the use of all fiber low-coherence interferometer

NASA Astrophysics Data System (ADS)

Józwik, Michalina; Stepień, Karol; Lipiński, Stanisław; Budnicki, Dawid; Napierała, Marek; Nasiłowski, Tomasz

2015-12-01

In this paper we present experimental results of measurements of the lens thickness carried out using all fiber low coherence interferometer. A new interferometric device for measuring the thickness of the lens using optical fibers has been developed in response to market demand. It ensures fast, non-contact and accurate measurement. This work focuses above all on the conducting tests to determine the repeatability of the measurement and to verify the ability of using this method in industrial conditions. The system uses a Mach-Zehnder interferometer in which one of the arms is the reference part and the second arm containing the test element is the measurement part. The measurement rate and the easiness of placement of the test lens in the system give the possibility to automate the measurement process. We present the measurement results, which show that the use of low-coherence interferometry allows achieving high measurement accuracy and meeting other industrial needs.

Six-state phase modulation for reduced crosstalk in a fiber optic gyroscope.

PubMed

Zhang, Chunxi; Zhang, Shaobo; Pan, Xiong; Jin, Jing

2018-04-16

Electrical crosstalk in an interferometric fiber-optic gyroscope (IFOG) is regarded as the most significant factor influencing dead bands. Here, we present a six-state modulation (SSM) technique to reduce crosstalk. Compared to conventional four-state modulation (FSM) or square-wave modulation (SWM), the SSM reduces the correlation between modulation voltage and demodulation reference by separating their fundamental frequencies, and thus reduces the bias error induced by crosstalk. The measured dead band of a 1500-m IFOG is approximately 0.02 °/h using FSM and approximately 0.08 °/h using SWM, whereas there is no evidence of dead band using SSM. The IFOG using SSM also exhibits better angular random walk (ARW) and bias instability performance compared to the same IFOG using FSM or SWM. These results verify the crosstalk reduction effect of SSM. In theory, by using the relative intensity noise (RIN) suppressing technique with the optimal modulation depth of 2π/3, the SSM can eliminate the crosstalk, which offers the potential for a high-performance IFOG with low noise, high sensitivity, wide dynamic range, and no dead band.

Sensitivity distribution of a vibration sensor based on Mach-Zehnder interferometer designed inside the window system

NASA Astrophysics Data System (ADS)

Zboril, Ondrej; Nedoma, Jan; Cubik, Jakub; Novak, Martin; Bednarek, Lukas; Fajkus, Marcel; Vasinek, Vladimir

2016-04-01

Interferometric sensors are very accurate and sensitive sensors that due to the extreme sensitivity allow sensing vibration and acoustic signals. This paper describes a new method of implementation of Mach-Zehnder interferometer for sensing of vibrations caused by touching on the window panes. Window panes are part of plastic windows, in which the reference arm of the interferometer is mounted and isolated inside the frame, a measuring arm of the interferometer is fixed to the window pane and it is mounted under the cover of the window frame. It prevents visibility of the optical fiber and this arrangement is the basis for the safety system. For the construction of the vibration sensor standard elements of communication networks are used - optical fiber according to G.652D and 1x2 splitters with dividing ratio 1:1. Interferometer operated at a wavelength of 1550 nm. The paper analyses the sensitivity of the window in a 12x12 measuring points matrix, there is specified sensitivity distribution of the window pane.

Multidimensional gray-wavelet processing in interferometric fiber-optic gyroscopes

NASA Astrophysics Data System (ADS)

Yang, Yi; Wang, Zinan; Peng, Chao; Li, Zhengbin

2013-11-01

A multidimensional signal processing method for a single interferometric fiber-optic gyroscope (IFOG) is proposed, to the best of our knowledge, for the first time. The proposed method, based on a novel IFOG structure with quadrature demodulation, combines a multidimensional gray model (GM) and a wavelet compression technique for noise suppression and sensitivity enhancement. In the IFOG, two series of measured rotation rates are obtained simultaneously: an in-phase component and a quadrature component. Together with the traditionally measured rate, the three measured rates are processed by the combined gray-wavelet method. Simulations show that the intensity noise and non-reciprocal phase fluctuations are effectively suppressed by this method. Experimental comparisons with a one-dimensional GM(1, 1) model show that the proposed three-dimensional method achieves much better denoising performance. This advantage is validated by the Allan variance analysis: in a low-SNR (signal-to-noise ratio) experiment, our method reduces the angle random walk (ARW) and the bias instability (BI) from 1 × 10-2 deg h-1/2 and 3 × 10-2 deg h-1 to 1 × 10-3 deg h-1/2 and 3 × 10-3 deg h-1, respectively; in a high-SNR experiment, our method reduces the ARW and the BI from 9 × 10-4 deg h-1/2 and 5 × 10-3 deg h-1 to 4 × 10-4 deg h-1/2 and 3 × 10-3 deg h-1, respectively. Further, our method increases the dimension of the state-of-the-art IFOG technique from one to three, thus obtaining higher IFOG sensitivity and stability by exploiting the increase in available information.

Interferometric sensor based on the polarization-maintaining fibers

NASA Astrophysics Data System (ADS)

Cubik, Jakub; Kepak, Stanislav; Doricak, Jan; Vašinek, Vladimir; Liner, Andrej; Papes, Martin

2012-01-01

The interferometers composed of optical fibers are due to its high sensitivity capable of to measure various influences affecting the fiber. These influences may be bending or different sorts of fiber deformations, vibration, temperature, etc. In this case the vibration is the measured quantity, which is evaluated by analyzing the interference fringes representing changes in the fiber. Was used a Mach-Zehnder interferometer composed of the polarization maintaining elements. The polarization maintaining elements were used because of high sensitivity to polarization state inside the interferometer. The light was splitted into the two optical paths, where the first one is the reference fiber and it is separated from the actual phenomenon, and the second one is measuring fiber, which is directly exposed to vibration transmission from the underlying surface. The light source was narrowband DFB laser serating at a wavelength of 1550nm and as a detector an InGaAs PIN photodiode were used in this measurement. The electrical signal from the photodiode was amplified and fed into the measuring card. On the incoming signal the FFT was applied, which performs the transformation into the frequency domain and the results were further evaluated by software. We were evaluating the characteristic frequencies and their amplitude ratios. The frequency responses are unique for a given phenomenon, thus it is possible to identify recurring events by the characteristic frequencies and their amplitude ratios. The frequency range was limited by the properties of the used speaker, by the frequency characteristics of the filter in the amplifier and used resonant element. For the experiment evaluation the repeated impact of the various spherical objects on the surface board was performed and measured. The stability of amplitude and frequency and also the frequency range was verified in this measurement.

Optical fiber sensors-based temperature distribution measurement in ex vivo radiofrequency ablation with submillimeter resolution.

PubMed

Macchi, Edoardo Gino; Tosi, Daniele; Braschi, Giovanni; Gallati, Mario; Cigada, Alfredo; Busca, Giorgio; Lewis, Elfed

2014-01-01

Radiofrequency thermal ablation (RFTA) induces a high-temperature field in a biological tissue having steep spatial (up to 6°C∕mm) and temporal (up to 1°C∕s) gradients. Applied in cancer care, RFTA produces a localized heating, cytotoxic for tumor cells, and is able to treat tumors with sizes up to 3 to 5 cm in diameter. The online measurement of temperature distribution at the RFTA point of care has been previously carried out with miniature thermocouples and optical fiber sensors, which exhibit problems of size, alteration of RFTA pattern, hysteresis, and sensor density worse than 1 sensor∕cm. In this work, we apply a distributed temperature sensor (DTS) with a submillimeter spatial resolution for the monitoring of RFTA in porcine liver tissue. The DTS demodulates the chaotic Rayleigh backscattering pattern with an interferometric setup to obtain the real-time temperature distribution. A measurement chamber has been set up with the fiber crossing the tissue along different diameters. Several experiments have been carried out measuring the space-time evolution of temperature during RFTA. The present work showcases the temperature monitoring in RFTA with an unprecedented spatial resolution and is exportable to in vivo measurement; the acquired data can be particularly useful for the validation of RFTA computational models.

Spectral domain optical coherence tomography with dual-balanced detection

NASA Astrophysics Data System (ADS)

Bo, En; Liu, Xinyu; Chen, Si; Luo, Yuemei; Wang, Nanshuo; Wang, Xianghong; Liu, Linbo

2016-03-01

We developed a spectral domain optical coherence tomography (SD-OCT) system employing dual-balanced detection (DBD) for direct current term suppression and SNR enhancement, especially for auto-autocorrelation artifacts reduction. The DBD was achieved by using a beam splitter to building a free-space Michelson interferometer, which generated two interferometric spectra with a phase difference of π. These two phase-opposed spectra were guided to the spectrometer through two single mode fibers of the 8 fiber v-groove array and acquired by ultizing the upper two lines of a three-line CCD camera. We rotated this fiber v-groove array by 1.35 degrees to focus two spectra onto the first and second line of the CCD camera. Two spectra were aligned by optimum spectrum matching algorithm. By subtracting one spectrum from the other, this dual-balanced detection system achieved a direct current term suppression of ~30 dB, SNR enhancement of ~3 dB, and auto-autocorrelation artifacts reduction of ~10 dB experimentally. Finally we respectively validated the feasibility and performance of dual-balanced detection by imaging a glass plate and swine corneal tissue ex vivo. The quality of images obtained using dual-balanced detection was significantly improved with regard to the conventional single-detection (SD) images.

The beam combiners of Gravity VLTI instrument: concept, development, and performance in laboratory

NASA Astrophysics Data System (ADS)

Jocou, L.; Perraut, K.; Moulin, T.; Magnard, Y.; Labeye, P.; Lapras, V.; Nolot, A.; Perrin, G.; Eisenhauer, F.; Holmes, C.; Amorim, A.; Brandner, W.; Straubmeier, C.

2014-07-01

Gravity is one of the second-generation instruments of the Very Large Telescope Interferometer that operates in the near infrared range and that is designed for precision narrow-angle astrometry and interferometric imaging. With its infrared wavefront sensors, pupil stabilization, fringe tracker, and metrology, the instrument is tailored to provide a high sensitivity, imaging with 4-millisecond resolution, and astrometry with a 10μarcsec precision. It will probe physics close to the event horizon of the Galactic Centre black hole, and allow to study mass accretion and jets in young stellar objects and active galactic nuclei, planet formation in circumstellar discs, or detect and measure the masses of black holes in massive star clusters throughout the Milky Way. As the instrument required an outstanding level of precision and stability, integrated optics has been chosen to collect and combine the four VLTI beams in the K band. A dedicated integrated optics chip glued to a fiber array has been developed. Technology breakthroughs have been mandatory to fulfill all the specifications. This paper is focused on the interferometric beam combination system of Gravity. Once the combiner concept described, the paper details the developments that have been led, the integration and the performance of the assemblies.

Towards the LISA backlink: experiment design for comparing optical phase reference distribution systems

NASA Astrophysics Data System (ADS)

Isleif, Katharina-Sophie; Bischof, Lea; Ast, Stefan; Penkert, Daniel; Schwarze, Thomas S.; Fernández Barranco, Germán; Zwetz, Max; Veith, Sonja; Hennig, Jan-Simon; Tröbs, Michael; Reiche, Jens; Gerberding, Oliver; Danzmann, Karsten; Heinzel, Gerhard

2018-04-01

LISA is a proposed space-based laser interferometer detecting gravitational waves by measuring distances between free-floating test masses housed in three satellites in a triangular constellation with laser links in-between. Each satellite contains two optical benches that are articulated by moving optical subassemblies for compensating the breathing angle in the constellation. The phase reference distribution system, also known as backlink, forms an optical bi-directional path between the intra-satellite benches. In this work we discuss phase reference implementations with a target non-reciprocity of at most 2π μrad \\sqrtHz-1 , equivalent to 1 pm \\sqrtHz-1 for a wavelength of 1064 nm in the frequency band from 0.1 mHz to 1 Hz. One phase reference uses a steered free beam connection, the other one a fiber together with additional laser frequencies. The noise characteristics of these implementations will be compared in a single interferometric set-up with a previously successfully tested direct fiber connection. We show the design of this interferometer created by optical simulations including ghost beam analysis, component alignment and noise estimation. First experimental results of a free beam laser link between two optical set-ups that are co-rotating by  ±1° are presented. This experiment demonstrates sufficient thermal stability during rotation of less than 10‑4 K \\sqrtHz-1 at 1 mHz and operation of the free beam steering mirror control over more than 1 week.

Research on high-temperature sensing characteristics based on modular interference of single-mode multimode single-mode fiber

NASA Astrophysics Data System (ADS)

Peng, Zhaozhuang; Wang, Li; Yan, Huanhuan

2016-11-01

Application of high temperature fiber sensing system is very extensive. It can be mainly used in high temperature test aerospace, such as, materials, chemicals, and energy. In recent years, various on-line optical fiber interferometric sensors based on modular interference of single-mode-multimode-single-mode(SMS) fiber have been largely explored in high temperature fiber sensor. In this paper we use the special fiber of a polyimide coating, its sensor head is composed of a section of multimode fiber spliced in the middle of Single-mode fiber. When the light is launched into the multimode fiber(MMF) through the lead-in single-mode fiber(SMF), the core mode and cladding modes are excited and propagate in the MMF respectively. Then, at the MMF-SMF spliced point, the excited cladding modes coupled back into the core of lead-out SMF interfere with SMF core mode. And the wavelength of the interference dip would shift differently with the variation of the temperature. By this mean, we can achieve the measurement of temperature. The experimental results also show that the fiber sensor based on SMS structure has a highly temperature sensitivity. From 30° to 300°, with the temperature increasing, the interference dip slightly shifts toward longer wavelength and the temperature sensitivity coefficient is 0.0115nm/°. With high sensitivity, simple structure, immunity to electromagnetic interferences and a good linearity of the experimental results, the structure has an excellent application prospect in engineering field.

Pocket-Size Interferometric Systems

NASA Astrophysics Data System (ADS)

Waters, James P.; Fernald, Mark R.

1990-04-01

Optical sensors have the intrinsic advantages over electronic sensors of complete safety in hazardous areas and absolute immunity from both transmitting or picking up electromagnetic radiation. However, adoption of optical sensors in real-world applications requires a sensor design which has a sensitivity, resolution, and dynamic range comparable to an equivalent electronic sensor and at the same time must fulfill the practical considerations of small size and low cost. While sensitivity, resolution and dynamic range can be easily achieved with optical heterodyne sensors, the practical considerations make their near-term adoption unlikely. Significant improvements to optical heterodyne vibration and velocity sensors (flexibility, reliability and environmental immunity) have been realized with the use of semiconductor lasers, optical fibers and fiber-optic components. In fact, all of the discrete optical components in a heterodyne interferometer have been replaced with much smaller and more rugged devices except for the optical frequency shifter, acousto-optic modulator (AOM). The AOM and associated power supply, however, account for a substantial portion of both the size and cost. Previous work has shown that an integrated-optic, serrodyne phase modulator with an inexpensive drive circuit can be used for single sideband heterodyne detection. This paper describes the next step, design and implementation of a heterodyne interferometer using integrated-Optic technology to provide the polarization maintaining couplers and phase modulator. The couplers were made using a proton exchange process which produced devices with an extinction ratio of better than 40 dB. The serrodyne phase modulator had the advantage over an AOM of being considerably smaller and having a drive power of less than a milliwatt. The results of this work show that this technology is an effective way of reducing the size of the system and the cost of multiple units without sacarifying performance.

Comparative investigation of methods to determine the group velocity dispersion of an endlessly single-mode photonic crystal fiber

NASA Astrophysics Data System (ADS)

Baselt, Tobias; Popp, Tobias; Nelsen, Bryan; Lasagni, Andrés. Fabián.; Hartmann, Peter

2017-05-01

Endlessly single-mode fibers, which enable single mode guidance over a wide spectral range, are indispensable in the field of fiber technology. A two-dimensional photonic crystal with a silica central core and a micrometer-spaced hexagonal array of air holes is an established method to achieve endless single-mode guidance. There are two possible ways to determine the dispersion: measurement and calculation. We calculate the group velocity dispersion GVD based on the measurement of the fiber structure parameters, the hole diameter and the pitch of a presumed homogeneous hexagonal array and compare the calculation with two methods to measure the wavelength-dependent time delay. We measure the time delay on a three hundred meter test fiber with a homemade supercontinuum light source, a set of bandpass filters and a fast detector and compare the results with a white light interferometric setup. To measure the dispersion of optical fibers with high accuracy, a time-frequency-domain setup based on a Mach-Zehnder interferometer is used. The experimental setup allows the determination of the wavelength dependent differential group delay of light travelling through a thirty centimeter piece of test fiber in the wavelength range from VIS to NIR. The determination of the GVD using different methods enables the evaluation of the individual methods for characterizing the endlessly single-mode fiber.

Manufacturing Precise, Lightweight Paraboloidal Mirrors

NASA Technical Reports Server (NTRS)

Hermann, Frederick Thomas

2006-01-01

A process for fabricating a precise, diffraction- limited, ultra-lightweight, composite- material (matrix/fiber) paraboloidal telescope mirror has been devised. Unlike the traditional process of fabrication of heavier glass-based mirrors, this process involves a minimum of manual steps and subjective judgment. Instead, this process involves objectively controllable, repeatable steps; hence, this process is better suited for mass production. Other processes that have been investigated for fabrication of precise composite-material lightweight mirrors have resulted in print-through of fiber patterns onto reflecting surfaces, and have not provided adequate structural support for maintenance of stable, diffraction-limited surface figures. In contrast, this process does not result in print-through of the fiber pattern onto the reflecting surface and does provide a lightweight, rigid structure capable of maintaining a diffraction-limited surface figure in the face of changing temperature, humidity, and air pressure. The process consists mainly of the following steps: 1. A precise glass mandrel is fabricated by conventional optical grinding and polishing. 2. The mandrel is coated with a release agent and covered with layers of a carbon- fiber composite material. 3. The outer surface of the outer layer of the carbon-fiber composite material is coated with a surfactant chosen to provide for the proper flow of an epoxy resin to be applied subsequently. 4. The mandrel as thus covered is mounted on a temperature-controlled spin table. 5. The table is heated to a suitable temperature and spun at a suitable speed as the epoxy resin is poured onto the coated carbon-fiber composite material. 6. The surface figure of the optic is monitored and adjusted by use of traditional Ronchi, Focault, and interferometric optical measurement techniques while the speed of rotation and the temperature are adjusted to obtain the desired figure. The proper selection of surfactant, speed or rotation, viscosity of the epoxy, and temperature make it possible to obtain the desired diffraction-limited, smooth (1/50th wave) parabolic outer surface, suitable for reflective coating. 7. A reflective coat is applied by use of conventional coating techniques. 8. Once the final figure is set, a lightweight structural foam is applied to the rear of the optic to ensure stability of the figure.

Joint Services Electronics Program.

DTIC Science & Technology

1987-10-15

semiconductor perturb the index of refraction which can be detected in a Nomarski -type optical interferometer. For example, we have demonstrated the real-time...probe relies on a different physical effect and operates by interferometrically detecting the phase change induced in an optical beam by the presence of... interferometric diameter measurement system to monitor the growth process, has been in operation for . several years. The focussing optics and pulling mechanisms

Computational adaptive optics for broadband optical interferometric tomography of biological tissue

NASA Astrophysics Data System (ADS)

Boppart, Stephen A.

2015-03-01

High-resolution real-time tomography of biological tissues is important for many areas of biological investigations and medical applications. Cellular level optical tomography, however, has been challenging because of the compromise between transverse imaging resolution and depth-of-field, the system and sample aberrations that may be present, and the low imaging sensitivity deep in scattering tissues. The use of computed optical imaging techniques has the potential to address several of these long-standing limitations and challenges. Two related techniques are interferometric synthetic aperture microscopy (ISAM) and computational adaptive optics (CAO). Through three-dimensional Fourierdomain resampling, in combination with high-speed OCT, ISAM can be used to achieve high-resolution in vivo tomography with enhanced depth sensitivity over a depth-of-field extended by more than an order-of-magnitude, in realtime. Subsequently, aberration correction with CAO can be performed in a tomogram, rather than to the optical beam of a broadband optical interferometry system. Based on principles of Fourier optics, aberration correction with CAO is performed on a virtual pupil using Zernike polynomials, offering the potential to augment or even replace the more complicated and expensive adaptive optics hardware with algorithms implemented on a standard desktop computer. Interferometric tomographic reconstructions are characterized with tissue phantoms containing sub-resolution scattering particles, and in both ex vivo and in vivo biological tissue. This review will collectively establish the foundation for high-speed volumetric cellular-level optical interferometric tomography in living tissues.

Interferometric pump-probe characterization of the nonlocal response of optically transparent ion implanted polymers

NASA Astrophysics Data System (ADS)

Stefanov, Ivan L.; Hadjichristov, Georgi B.

2012-03-01

Optical interferometric technique is applied to characterize the nonlocal response of optically transparent ion implanted polymers. The thermal nonlinearity of the ion-modified material in the near-surface region is induced by continuous wave (cw) laser irradiation at a relatively low intensity. The interferometry approach is demonstrated for a subsurface layer of a thickness of about 100 nm formed in bulk polymethylmethacrylate (PMMA) by implantation with silicon ions at an energy of 50 keV and fluence in the range 1014-1017 cm-2. The laser-induced thermooptic effect in this layer is finely probed by interferometric imaging. The interference phase distribution in the plane of the ion implanted layer is indicative for the thermal nonlinearity of the near-surface region of ion implanted optically transparent polymeric materials.

Optical Sensors for Monitoring Gamma and Neutron Radiation

NASA Technical Reports Server (NTRS)

Boyd, Clark D.

2011-01-01

For safety and efficiency, nuclear reactors must be carefully monitored to provide feedback that enables the fission rate to be held at a constant target level via adjustments in the position of neutron-absorbing rods and moderating coolant flow rates. For automated reactor control, the monitoring system should provide calibrated analog or digital output. The sensors must survive and produce reliable output with minimal drift for at least one to two years, for replacement only during refueling. Small sensor size is preferred to enable more sensors to be placed in the core for more detailed characterization of the local fission rate and fuel consumption, since local deviations from the norm tend to amplify themselves. Currently, reactors are monitored by local power range meters (LPRMs) based on the neutron flux or gamma thermometers based on the gamma flux. LPRMs tend to be bulky, while gamma thermometers are subject to unwanted drift. Both electronic reactor sensors are plagued by electrical noise induced by ionizing radiation near the reactor core. A fiber optic sensor system was developed that is capable of tracking thermal neutron fluence and gamma flux in order to monitor nuclear reactor fission rates. The system provides near-real-time feedback from small- profile probes that are not sensitive to electromagnetic noise. The key novel feature is the practical design of fiber optic radiation sensors. The use of an actinoid element to monitor neutron flux in fiber optic EFPI (extrinsic Fabry-Perot interferometric) sensors is a new use of material. The materials and structure used in the sensor construction can be adjusted to result in a sensor that is sensitive to just thermal, gamma, or neutron stimulus, or any combination of the three. The tested design showed low sensitivity to thermal and gamma stimuli and high sensitivity to neutrons, with a fast response time.

Resolving the mystery of milliwatt-threshold opto-mechanical self-oscillation in dual-nanoweb fiber

NASA Astrophysics Data System (ADS)

Koehler, J. R.; Noskov, R. E.; Sukhorukov, A. A.; Butsch, A.; Novoa, D.; Russell, P. St. J.

2016-08-01

It is interesting to pose the question: How best to design an optomechanical device, with no electronics, optical cavity, or laser gain, that will self-oscillate when pumped in a single pass with only a few mW of single-frequency laser power? One might begin with a mechanically resonant and highly compliant system offering very high optomechanical gain. Such a system, when pumped by single-frequency light, might self-oscillate at its resonant frequency. It is well-known, however, that this will occur only if the group velocity dispersion of the light is high enough so that phonons causing pump-to-Stokes conversion are sufficiently dissimilar to those causing pump-to-anti-Stokes conversion. Recently it was reported that two light-guiding membranes 20 μm wide, ˜500 nm thick and spaced by ˜500 nm, suspended inside a glass fiber capillary, oscillated spontaneously at its mechanical resonant frequency (˜6 MHz) when pumped with only a few mW of single-frequency light. This was surprising, since perfect Raman gain suppression would be expected. In detailed measurements, using an interferometric side-probing technique capable of resolving nanoweb movements as small as 10 pm, we map out the vibrations along the fiber and show that stimulated intermodal scattering to a higher-order optical mode frustrates gain suppression, permitting the structure to self-oscillate. A detailed theoretical analysis confirms this picture. This novel mechanism makes possible the design of single-pass optomechanical oscillators that require only a few mW of optical power, no electronics nor any optical resonator. The design could also be implemented in silicon or any other suitable material.

Design and laboratory validation of a structural element instrumented with multiplexed interferometric fiber optic sensors

NASA Astrophysics Data System (ADS)

Zonta, Daniele; Pozzi, Matteo; Wu, Huayong; Inaudi, Daniele

2008-03-01

This paper introduces a concept of smart structural elements for the real-time condition monitoring of bridges. These are prefabricated reinforced concrete elements embedding a permanent sensing system and capable of self-diagnosis when in operation. The real-time assessment is automatically controlled by a numerical algorithm founded on Bayesian logic: the method assigns a probability to each possible damage scenario, and estimates the statistical distribution of the damage parameters involved (such as location and extent). To verify the effectiveness of the technology, we produced and tested in the laboratory a reduced-scale smart beam prototype. The specimen is 3.8 m long and has cross-section 0.3 by 0.5m, and has been prestressed using a Dywidag bar, in such a way as to control the preload level. The sensor system includes a multiplexed version of SOFO interferometric sensors mounted on a composite bar, along with a number of traditional metal-foil strain gauges. The method allowed clear recognition of increasing fault states, simulated on the beam by gradually reducing the prestress level.

Integrated optics prototype beam combiner for long baseline interferometry in the L and M bands

NASA Astrophysics Data System (ADS)

Tepper, J.; Labadie, L.; Diener, R.; Minardi, S.; Pott, J.-U.; Thomson, R.; Nolte, S.

2017-06-01

Context. Optical long baseline interferometry is a unique way to study astronomical objects at milli-arcsecond resolutions not attainable with current single-dish telescopes. Yet, the significance of its scientfic return strongly depends on a dense coverage of the uv-plane and a highly stable transfer function of the interferometric instrument. In the last few years, integrated optics (IO) beam combiners have facilitated the emergence of 4-telescope interferometers such as PIONIER or GRAVITY, boosting the imaging capabilities of the VLTI. However, the spectral range beyond 2.2 μm is not ideally covered by the conventional silica based IO. Here, we consider new laser-written IO prototypes made of gallium lanthanum sulfide (GLS) glass, a material that permits access to the mid-infrared spectral regime. Aims: Our goal is to conduct a full characterization of our mid-IR IO two-telescope coupler in order to measure the performance levels directly relevant for long-baseline interferometry. We focus in particular on the exploitation of the L and M astronomical bands. Methods: We use a dedicated Michelson-interferometer setup to perform Fourier transform spectroscopy on the coupler and measure its broadband interferometric performance. We also analyze the polarization properties of the coupler, the differential dispersion and phase degradation, as well as the modal behavior and the total throughput. Results: We measure broadband interferometric contrasts of 94.9% and 92.1% for unpolarized light in the L and M bands. Spectrally integrated splitting ratios are close to 50%, but show chromatic dependence over the considered bandwidths. Additionally, the phase variation due to the combiner is measured and does not exceed 0.04 rad and 0.07 rad across the L and M band, respectively. The total throughput of the coupler including Fresnel and injection losses from free-space is 25.4%. Furthermore, differential birefringence is low (<0.2 rad), in line with the high contrasts reported for unpolarized light. Conclusions: The laser-written IO GLS prototype combiners prove to be a reliable technological solution with promising performance for mid-infrared long-baseline interferometry. In the next steps, we will consider more advanced optical functions, as well as a fiber-fed input, and we will revise the optical design parameters in order to further enhance the total throughput and achromatic behavior.

A new method for determining the plasma electron density using optical frequency comb interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arakawa, Hiroyuki, E-mail: arakawa@fmt.teikyo-u.ac.jp; Tojo, Hiroshi; Sasao, Hajime

2014-04-15

A new method of plasma electron density measurement using interferometric phases (fractional fringes) of an optical frequency comb interferometer is proposed. Using the characteristics of the optical frequency comb laser, high density measurement can be achieved without fringe counting errors. Simulations show that the short wavelength and wide wavelength range of the laser source and low noise in interferometric phases measurements are effective to reduce ambiguity of measured density.

Common-Path Interferometric Wavefront Sensing for Space Telescopes

NASA Technical Reports Server (NTRS)

Wallace, James Kent

2011-01-01

This paper presents an optical configuration for a common-path phase-shifting interferometric wavefront sensor.1 2 This sensor has a host of attractive features which make it well suited for space-based adaptive optics. First, it is strictly reflective and therefore operates broadband, second it is common mode and therefore does not suffer from systematic errors (like vibration) that are typical in other interferometers, third it is a phase-shifting interferometer and therefore benefits from both the sensitivity of interferometric sensors as well as the noise rejection afforded by synchronous detection. Unlike the Shack-Hartman wavefront sensor, it has nearly uniform sensitivity to all pupil modes. Optical configuration, theory and simulations for such a system will be discussed along with predicted performance.

Tunable-optical-filter-based white-light interferometry for sensing.

PubMed

Yu, Bing; Wang, Anbo; Pickrell, Gary; Xu, Juncheng

2005-06-15

We describe tunable-optical-filter-based white-light interferometry for sensor interrogation. By introducing a tunable optical filter into a white-light interferometry system, one can interrogate an interferometer with either quadrature demodulation or spectral-domain detection at low cost. To demonstrate the feasibility of effectively demodulating various types of interferometric sensor, experiments have been performed using an extrinsic Fabry-Perot tunable filter to interrogate two extrinsic Fabry-Perot interferometric temperature sensors and a diaphragm-based pressure sensor.

Guide-star-based computational adaptive optics for broadband interferometric tomography

PubMed Central

Adie, Steven G.; Shemonski, Nathan D.; Graf, Benedikt W.; Ahmad, Adeel; Scott Carney, P.; Boppart, Stephen A.

2012-01-01

We present a method for the numerical correction of optical aberrations based on indirect sensing of the scattered wavefront from point-like scatterers (“guide stars”) within a three-dimensional broadband interferometric tomogram. This method enables the correction of high-order monochromatic and chromatic aberrations utilizing guide stars that are revealed after numerical compensation of defocus and low-order aberrations of the optical system. Guide-star-based aberration correction in a silicone phantom with sparse sub-resolution-sized scatterers demonstrates improvement of resolution and signal-to-noise ratio over a large isotome. Results in highly scattering muscle tissue showed improved resolution of fine structure over an extended volume. Guide-star-based computational adaptive optics expands upon the use of image metrics for numerically optimizing the aberration correction in broadband interferometric tomography, and is analogous to phase-conjugation and time-reversal methods for focusing in turbid media. PMID:23284179

Wavelength-division-multiplexing method of polarized low-coherence interferometry for fiber Fabry-Perot interferometric sensors.

PubMed

Yin, Jinde; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Wang, Shuang; Wu, Fan; Ding, Zhenyang

2013-10-01

We propose a new wavelength-division-multiplexing method for extrinsic fiber Fabry-Perot interferometric (EFPI) sensing in a polarized low-coherence interferometer configuration. In the proposed method, multiple LED sources are used with different center wavelengths, and each LED is used by a specific sensing channel, and therefore the spatial frequency of the low-coherence interferogram of each channel can be separated. A bandpass filter is used to extract the low-coherence interferogram of each EFPI channel, and thus the cavity length of each EFPI channel can be identified through demultiplexing. We successfully demonstrate the simultaneous demodulation of EFPI sensors with same nominal cavity length while maintaining high measurement precision.

A fast positioning algorithm for the asymmetric dual Mach-Zehnder interferometric infrared fiber vibration sensor

NASA Astrophysics Data System (ADS)

Jiang, Junfeng; An, Jianchang; Liu, Kun; Ma, Chunyu; Li, Zhichen; Liu, Tiegen

2017-09-01

We propose a fast positioning algorithm for the asymmetric dual Mach-Zehnder interferometric infrared fiber vibration sensor. Using the approximately derivation method and the enveloping detection method, we successfully eliminate the asymmetry of the interference outputs and improve the processing speed. A positioning measurement experiment was carried out to verify the effectiveness of the proposed algorithm. At the sensing length of 85 km, the experimental results show that the mean positioning error is 18.9 m and the mean processing time is 116 ms. The processing speed is improved by 5 times compared to what can be achieved by using the traditional time-frequency analysis-based positioning method.

Nonlinear Interferometric Vibrational Imaging (NIVI) with Novel Optical Sources

NASA Astrophysics Data System (ADS)

Boppart, Stephen A.; King, Matthew D.; Liu, Yuan; Tu, Haohua; Gruebele, Martin

Optical imaging is essential in medicine and in fundamental studies of biological systems. Although many existing imaging modalities can supply valuable information, not all are capable of label-free imaging with high-contrast and molecular specificity. The application of molecular or nanoparticle contrast agents may adversely influence the biological system under investigation. These substances also present ongoing concerns over toxicity or particle clearance, which must be properly addressed before their approval for in vivo human imaging. Hence there is an increasing appreciation for label-free imaging techniques. It is of primary importance to develop imaging techniques that can indiscriminately identify and quantify biochemical compositions to high degrees of sensitivity and specificity through only the intrinsic optical response of endogenous molecular species. The development and use of nonlinear interferometric vibrational imaging, which is based on the interferometric detection of optical signals from coherent anti-Stokes Raman scattering (CARS), along with novel optical sources, offers the potential for label-free molecular imaging.

Interferometry-based free space communication and information processing

NASA Astrophysics Data System (ADS)

Arain, Muzammil Arshad

This dissertation studies, analyzes, and experimentally demonstrates the innovative use of interference phenomenon in the field of opto-electronic information processing and optical communications. A number of optical systems using interferometric techniques both in the optical and the electronic domains has been demonstrated in the filed of signal transmission and processing, optical metrology, defense, and physical sensors. Specifically it has been shown that the interference of waves in the form of holography can be exploited to realize a novel optical scanner called Code Multiplexed Optical Scanner (C-MOS). The C-MOS features large aperture, wide scan angles, 3-D beam control, no moving parts, and high beam scanning resolution. A C-MOS based free space optical transceiver for bi-directional communication has also been experimentally demonstrated. For high speed, large bandwidth, and high frequency operation, an optically implemented reconfigurable RF transversal filter design is presented that implements wide range of filtering algorithms. A number of techniques using heterodyne interferometry via acousto-optic device for optical path length measurements have been described. Finally, a whole new class of interferometric sensors for optical metrology and sensing applications is presented. A non-traditional interferometric output signal processing scheme has been developed. Applications include, for example, temperature sensors for harsh environments for a wide temperature range from room temperature to 1000°C.

Light-pulse atom interferometric device

DOEpatents

Biedermann, Grant; McGuinness, Hayden James Evans; Rakholia, Akash; Jau, Yuan-Yu; Schwindt, Peter; Wheeler, David R.

2016-03-22

An atomic interferometric device useful, e.g., for measuring acceleration or rotation is provided. The device comprises at least one vapor cell containing a Raman-active chemical species, an optical system, and at least one detector. The optical system is conformed to implement a Raman pulse interferometer in which Raman transitions are stimulated in a warm vapor of the Raman-active chemical species. The detector is conformed to detect changes in the populations of different internal states of atoms that have been irradiated by the optical system.

Theoretical and experimental study of low-finesse extrinsic Fabry-Perot interferometric fiber optic sensors

NASA Astrophysics Data System (ADS)

Han, Ming

In this dissertation, detailed and systematic theoretical and experimental study of low-finesse extrinsic Fabry-Perot interferometric (EFPI) fiber optic sensors together with their signal processing methods for white-light systems are presented. The work aims to provide a better understanding of the operational principle of EFPI fiber optic sensors, and is useful and important in the design, optimization, fabrication and application of single mode fiber(SMF) EFPI (SMF-EFPI) and multimode fiber (MMF) EFPI (MMF-EFPI) sensor systems. The cases for SMF-EFPI and MMF-EFPI sensors are separately considered. In the analysis of SMF-EFPI sensors, the light transmitted in the fiber is approximated by a Gaussian beam and the obtained spectral transfer function of the sensors includes an extra phase shift due to the light coupling in the fiber end-face. This extra phase shift has not been addressed by previous researchers and is of great importance for high accuracy and high resolution signal processing of white-light SMF-EFPI systems. Fringe visibility degradation due to gap-length increase and sensor imperfections is studied. The results indicate that the fringe visibility of a SMF-EFPI sensor is relatively insensitive to the gap-length change and sensor imperfections. Based on the spectral fringe pattern predicated by the theory of SMF-EFPI sensors, a novel curve fitting signal processing method (Type 1 curve-fitting method) is presented for white-light SMF-EFPI sensor systems. Other spectral domain signal processing methods including the wavelength-tracking, the Type 2-3 curve fitting, Fourier transform, and two-point interrogation methods are reviewed and systematically analyzed. Experiments were carried out to compare the performances of these signal processing methods. The results have shown that the Type 1 curve fitting method achieves high accuracy, high resolution, large dynamic range, and the capability of absolute measurement at the same time, while others either have less resolution, or are not capable of absolute measurement. Previous mathematical models for MMF-EFPI sensors are all based on geometric optics; therefore their applications have many limitations. In this dissertation, a modal theory is developed that can be used in any situations and is more accurate. The mathematical description of the spectral fringes of MMF-EFPI sensors is obtained by the modal theory. Effect on the fringe visibility of system parameters, including the sensor head structure, the fiber parameters, and the mode power distribution in the MMF of the MMF-EFPI sensors, is analyzed. Experiments were carried out to validate the theory. Fundamental mechanism that causes the degradation of the fringe visibility in MMF-EFPI sensors are revealed. It is shown that, in some situations at which the fringe visibility is important and difficult to achieve, a simple method of launching the light into the MMF-EFPI sensor system from the output of a SMF could be used to improve the fringe visibility and to ease the fabrication difficulties of MMF-EFPI sensors. Signal processing methods that are well-understood in white-light SMF-EFPI sensor systems may exhibit new aspects when they are applied to white-light MMF-EFPI sensor systems. This dissertation reveals that the variations of mode power distribution (MPD) in the MMF could cause phase variations of the spectral fringes from a MMF-EFPI sensor and introduce measurement errors for a signal processing method in which the phase information is used. This MPD effect on the wavelength-tracking method in white-light MMF-EFPI sensors is theoretically analyzed. The fringe phases changes caused by MPD variations were experimentally observed and thus the MFD effect is validated.

Cryogenic Optical Performance of a Light-weight Mirror Assembly for Future Space Astronomical Telescopes: Optical Test Results and Thermal Optical Model

NASA Technical Reports Server (NTRS)

Eng, Ron; Arnold, William; Baker, Markus A.; Bevan, Ryan M.; Carpenter, James R.; Effinger, Michael R.; Gaddy, Darrell E.; Goode, Brian K.; Kegley, Jeffrey R.; Hogue, William D.;

Arrays of Regenerated Fiber Bragg Gratings in Non-Hydrogen-Loaded Photosensitive Fibers for High-Temperature Sensor Networks

PubMed Central

Lindner, Eric; Chojetztki, Christoph; Brueckner, Sven; Becker, Martin; Rothhardt, Manfred; Vlekken, Johan; Bartelt, Hartmut

2009-01-01

We report about the possibility of using regenerated fiber Bragg gratings generated in photosensitive fibers without applying hydrogen loading for high temperature sensor networks. We use a thermally induced regenerative process which leads to a secondary increase in grating reflectivity. This refractive index modification has shown to become more stable after the regeneration up to temperatures of 600 °C. With the use of an interferometric writing technique, it is possible also to generate arrays of regenerated fiber Bragg gratings for sensor networks. PMID:22408510

A miniature fiber optic pressure sensor for intradiscal pressure measurements of rodents

NASA Astrophysics Data System (ADS)

Nesson, Silas; Yu, Miao; Hsieh, Adam H.

2007-04-01

Lower back pain continues to be a leading cause of disability in people of all ages, and has been associated with degenerative disc disease. It is well accepted that mechanical stress, among other factors, can play a role in the development of disc degeneration. Pressures generated in the intervertebral disc have been measured both in vivo and in vitro for humans and animals. However, thus far it has been difficult to measure pressure experimentally in rodent discs due to their small size. With the prevalent use of rodent tail disc models in mechanobiology, it is important to characterize the intradiscal pressures generated with externally applied stresses. In this paper, a miniature fiber optic Fabry-Perot interferometric pressure sensor with an outer diameter of 360 μm was developed to measure intradiscal pressures in rat caudal discs. A low coherence interferometer based optical system was used, which includes a broadband light source, a high-speed spectrometer, and a Fabry-Perot sensor. The sensor employs a capillary tube, a flexible, polymer diaphragm coated with titanium as a partial mirror, and a fiber tip as another mirror. The pressure induced deformation of the diaphragm results in a cavity length change of the Fabry-Perot interferometer which can be calculated from the wavelength shift of interference fringes. The sensor exhibited good linearity with small applied pressures. Our validation experiments show that owing to the small size, inserting the sensor does not disrupt the annulus fibrosus and will not alter intradiscal pressures generated. Measurements also demonstrate the feasibility of using this sensor to quantify external load intradiscal pressure relationships in small animal discs.

Microphotonic devices for compact planar lightwave circuits and sensor systems

NASA Astrophysics Data System (ADS)

Cardenas Gonzalez, Jaime

2005-07-01

Higher levels of integration in planar lightwave circuits and sensor systems can reduce fabrication costs and broaden viable applications for optical network and sensor systems. For example, increased integration and functionality can lead to sensor systems that are compact enough for easy transport, rugged enough for field applications, and sensitive enough even for laboratory applications. On the other hand, more functional and compact planar lightwave circuits can make optical networks components less expensive for the metro and access markets in urban areas and allow penetration of fiber to the home. Thus, there is an important area of opportunity for increased integration to provide low cost, compact solutions in both network components and sensor systems. In this dissertation, a novel splitting structure for microcantilever deflection detection is introduced. The splitting structure is designed so that its splitting ratio is dependent on the vertical position of the microcantilever. With this structure, microcantilevers sensitized to detect different analytes or biological agents can be integrated into an array on a single chip. Additionally, the integration of a depolarizer into the optoelectronic integrated circuit in an interferometric fiber optic gyroscope is presented as a means for cost reduction. The savings come in avoiding labor intensive fiber pigtailing steps by permitting batch fabrication of these components. In particular, this dissertation focuses on the design of the waveguides and polarization rotator, and the impact of imperfect components on the performance of the depolarizer. In the area of planar lightwave circuits, this dissertation presents the development of a fabrication process for single air interface bends (SAIBs). SAIBs can increase integration by reducing the area necessary to make a waveguide bend. Fabrication and measurement of a 45° SAIB with a bend efficiency of 93.4% for TM polarization and 92.7% for TE polarization are presented.

Birefringence dispersion compensation demodulation algorithm for polarized low-coherence interferometry.

PubMed

Wang, Shuang; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Yin, Jinde; Wu, Fan

2013-08-15

A demodulation algorithm based on the birefringence dispersion characteristics for a polarized low-coherence interferometer is proposed. With the birefringence dispersion parameter taken into account, the mathematical model of the polarized low-coherence interference fringes is established and used to extract phase shift information between the measured coherence envelope center and the zero-order fringe, which eliminates the interferometric 2 π ambiguity of locating the zero-order fringe. A pressure measurement experiment using an optical fiber Fabry-Perot pressure sensor was carried out to verify the effectiveness of the proposed algorithm. The experiment result showed that the demodulation precision was 0.077 kPa in the range of 210 kPa, which was improved by 23 times compared to the traditional envelope detection method.

MONA, LISA and VINCI Soon Ready to Travel to Paranal

NASA Astrophysics Data System (ADS)

2000-11-01

First Instruments for the VLT Interferometer Summary A few months from now, light from celestial objects will be directed for the first time towards ESO's Very Large Telescope Interferometer (VLTI) at the Paranal Observatory (Chile). During this "First Light" event and the subsequent test phase, the light will be recorded with a special test instrument, VINCI (VLT INterferometer Commissioning Instrument). The main components of this high-tech instrument are aptly named MONA (a system that combines the light beams from several telescopes by means of optical fibers) and LISA (the infrared camera). VINCI was designed and constructed within a fruitful collaboration between ESO and several research institutes and industrial companies in France and Germany . It is now being assembled at the ESO Headquarters in Garching (Germany) and will soon be ready for installation at the telescope on Paranal. With the VLTI and VINCI, Europe's astronomers are now entering the first, crucial phase of an exciting scientific and technology venture that will ultimately put the world's most powerful optical/IR interferometric facility in their hands . PR Photo 31/00 : VINCI during tests at the ESO Headquarters in Garching. The VLT Interferometer (VLTI) ESO Press Photo 31/00 ESO Press Photo 31/00 [Preview; JPEG: 400 x 301; 43k] [Normal; JPEG: 800 x 602;208xk] [Full-Res; JPEG: 1923 x 1448; 2.2Mb] PR Photo 31/00 shows the various components of the complex VINCI instrument for the VLT Interferometer , during the current tests at the Optical Laboratory at the ESO Headquarters in Garching (Germany). It will later be installed in "clean-room" conditions within the Interferometric Laboratory at the Paranal Observatory. This electronic photo was obtained for documentary purposes. VINCI (VLT INterferometer Commissioning Instrument) is the "First Light" instrument for the Very Large Telescope Interferometer (VLTI) at the Paranal Observatory (Chile). Early in 2001, it will be used for the first tests of this very complex system. Subsequently, it will serve to tune this key research facility to the highest possible performance. The VLTI is based on the combination of light (beams) from the telescopes at Paranal. Of these, the four 8.2-m Unit Telescopes are already in operation - they will soon be joined by three 1.8-m telescopes that can be relocated on rails, cf. PR Photo 43b/99. By means of a system of mirrors, the light from two or more of these telescopes will be guided to the central Interferometric Laboratory , at the center of the observing platform on Paranal. Information about the heart of this complex system, the Delay Lines that are located in the underground Interferometric Tunnel, is available with the recent ESO PR Photos 26a-e/00. The VLTI will later receive other front-line instruments, e.g. AMBER , MIDI and PRIMA. When fully ready some years from now, the VLTI will produce extremely sharp images. This will have a major impact on different types of exciting astronomical observations, e.g.: * the direct discovery and imaging of extra-solar planets comparable to Jupiter, * the discovery and imaging of low-mass stars such as brown dwarfs, * observations of star-forming regions and to better understand the physical processes that give birth to stars, * spectral analysis of the atmospheres of nearby stars, and * imaging the objects of the very core of our Galaxy and the detection of black holes in active nuclei of galaxies. The VINCI test instrument The new instrument, VINCI , will soon be delivered to Paranal by the Département de Recherche Spatiale (Department for Space Research), a joint unit of the Centre Nationale de la Recherche Scientifique (French National Centre for Scientific Research) and the Paris Observatory. VINCI is a functional copy of the FLUOR instrument - now at the IOTA (Infrared Optical Telescope Array) interferometer - that has been upgraded and adapted to the needs of the VLTI. FLUOR was developed by the Département de Recherche Spatiale (DESPA) of the Paris Observatory. It was used in 1991 at the Kitt Peak National Observatory (Arizona, USA), for the first (coherent) combination of the light beams from two independent telescopes by means of optical fibers of fluoride glass. It has since been in operation for five years as a focal instrument at the IOTA Interferometer (Mount Hopkins, Arizona, USA) within a collaboration with the Harvard Smithsonian Center for Astrophysics), producing a rich harvest of scientific data. The VINCI partners The VINCI instrument is constructed in a collaboration between ESO (that also finances it) and the following laboratories and institutes: * DESPA (Paris Observatory) provides the expertise, the general concept, the development and integration of the optomechanics (with the exception of the camera) and the electronics, * Observatoire Midi-Pyrénées that produces the control software * The LISA infrared camera is developed by the Max-Planck-Institut für Extraterrestrische Physik (Garching, Germany), and * ESO provides the IR camera electronics and the overall observational software and is also responsible for the final integration. DESPA delivered VINCI to ESO in Garching on September 27, 2000, and is now assembling the instrument in the ESO optical workshop. It will stay here during three months, until it has been fully integrated and thoroughly tested. It will then be shipped to Paranal at the beginning of next year. After set-up and further tests, the first observations on the sky are expected in late March 2001. Fluoride fibers guide the light The heart of VINCI - named MONA - is a fiber optics beam combine unit. It is the outcome of a fertile, 10-year research partnership between Science (DESPA) and Industry ("Le Verre Fluoré" [2]). Optical fibers will be used to combine the light from two telescopes inside VINCI . Since the instrument will be working in the near-infrared region of the spectrum (wavelength 2-2.5 µm), it is necessary to use optical fibers made of a special type of glass that is transparent at these wavelengths. By far the best best material for this is fluoride glass . It was invented by one of the co-founders of the company "Le Verre Fluoré", the only manufacturer of this kind of highly specialized material in the world. Optical fibers of fluoride glass from this company are therefore used in VINCI . They are of a special type ("monomode") with a very narrow core measuring only 6.5 µm (0.065 mm) across. Light that is collected by one of the telescopes in the VLTI array (e.g., by the 50 m 2 mirror of a VLT Unit Telescope) is guided through the VLTI system of optics and finally enters this core. The fibers guide the light and at the same time "clean" the light beam by eliminating the errors introduced by the atmospheric turbulence, hereby improving the accuracy of the measurements by a factor of 10. DESPA has shown that this is indeed possible by means of real astronomical observations with the FLUOR experiment. Following this positive demonstration, it has been decided to equip the instrumentation of all interferometers currently under construction with fibers or equivalent systems.

Short-Range Six-Axis Interferometer Controlled Positioning for Scanning Probe Microscopy

PubMed Central

Lazar, Josef; Klapetek, Petr; Valtr, Miroslav; Hrabina, Jan; Buchta, Zdenek; Cip, Onrej; Cizek, Martin; Oulehla, Jindrich; Sery, Mojmir

2014-01-01

We present a design of a nanometrology measuring setup which is a part of the national standard instrumentation for nanometrology operated by the Czech Metrology Institute (CMI) in Brno, Czech Republic. The system employs a full six-axis interferometric position measurement of the sample holder consisting of six independent interferometers. Here we report on description of alignment issues and accurate adjustment of orthogonality of the measuring axes. Consequently, suppression of cosine errors and reduction of sensitivity to Abbe offset is achieved through full control in all six degrees of freedom. Due to the geometric configuration including a wide basis of the two units measuring in y-direction and the three measuring in z-direction the angle resolution of the whole setup is minimize to tens of nanoradians. Moreover, the servo-control of all six degrees of freedom allows to keep guidance errors below 100 nrad. This small range system is based on a commercial nanopositioning stage driven by piezoelectric transducers with the range (200 × 200 × 10) μm. Thermally compensated miniature interferometric units with fiber-optic light delivery and integrated homodyne detection system were developed especially for this system and serve as sensors for othogonality alignment. PMID:24451463

Solid State Research.

DTIC Science & Technology

1982-11-15

Optics Y-Junction and Mach-Zehnder Interferometric Modulator Using Four -Port Scattering Matrix 7 1.3 Heterodyne and Direct Detection at 10 om with High...and of the Mach-Zehnder interferometric modulator have been analyzed using the four -port scattering i- matrix. The interferometric properties of the Y...USING FOUR -PORT SCATTERING MATRIX The scattering matrix formalism for a lossless four -port device has been used to describe the performance of the

Interferometric source of multi-color, multi-beam entangled photons with mirror and mixer

DOEpatents

Dress, William B.; Kisner, Roger A.; Richards, Roger K.

2004-06-01

53 Systems and methods are described for an interferometric source of multi-color, multi-beam entangled photons. An apparatus includes: a multi-refringent device optically coupled to a source of coherent energy, the multi-refringent device providing a beam of multi-color entangled photons; a condenser device optically coupled to the multi-refringent device, the condenser device i) including a mirror and a mixer and ii) converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; a tunable phase adjuster optically coupled to the condenser device, the tunable phase adjuster changing a phase of at least a portion of the converged multi-color entangled photon beam to generate a first interferometeric multi-color entangled photon beam; and a beam splitter optically coupled to the condenser device, the beam splitter combining the first interferometeric multi-color entangled photon beam with a second interferometric multi-color entangled photon beam.

Optical Path Difference Fluctations at the CHARA Interferometric Array

NASA Astrophysics Data System (ADS)

Merand, A.; ten Brummelaar, T. A.; McAlister, H. A.; Ridgway, S. T.; Sturmann, J.; Sturmann, L.; Turner, N. H.; Bagnuolo, W. G.; Hrynevych, M.; Shure, M. A.

2001-05-01

Commissioning observations at the CHARA Array have been carried out with the two south telescopes, with a telescope separation of 34 meters. Due to the size of the array (>340 meters across) and the optical delay geometry, the beams travel horizontal distances of approximately 200 meters, with a number of reflections in the telescope coude area and the optical delay and beam combination areas. Stellar and laboratory observations have been analyzed to determine the variations of the optical path, as revealed by shifts in the interference pattern. The power spectra of the OPD variations are diagnostic of the atmospheric turbulence characteristics, and of any internal vibrations in the laboratory. Results of the OPD analysis will be compared to similar studies at other interferometric facilities. The CHARA Array, a six-telescope O/IR interferometric array operated by Georgia State University on Mt. Wilson, Calfornia, was funded by the National Science Foundation, the W.M. Keck Foundation, the David and Lucile Packard Foundation, and Georgia State University.

Cryogenic Optical Performance of a Lightweighted Mirror Assembly for Future Space Astronomical Telescopes: Correlating Optical Test Results and Thermal Optical Model

NASA Technical Reports Server (NTRS)

Eng, Ron; Arnold, William R.; Baker, Marcus A.; Bevan, Ryan M.; Burdick, Gregory; Effinger, Michael R.; Gaddy, Darrell E.; Goode, Brian K.; Hanson, Craig; Hogue, William D.;

Quantum dot-based local field imaging reveals plasmon-based interferometric logic in silver nanowire networks.

PubMed

Wei, Hong; Li, Zhipeng; Tian, Xiaorui; Wang, Zhuoxian; Cong, Fengzi; Liu, Ning; Zhang, Shunping; Nordlander, Peter; Halas, Naomi J; Xu, Hongxing

2011-02-09

We show that the local electric field distribution of propagating plasmons along silver nanowires can be imaged by coating the nanowires with a layer of quantum dots, held off the surface of the nanowire by a nanoscale dielectric spacer layer. In simple networks of silver nanowires with two optical inputs, control of the optical polarization and phase of the input fields directs the guided waves to a specific nanowire output. The QD-luminescent images of these structures reveal that a complete family of phase-dependent, interferometric logic functions can be performed on these simple networks. These results show the potential for plasmonic waveguides to support compact interferometric logic operations.

Generation and transmission of multilevel quadrature amplitude modulation formats using only one optical modulator: MATLAB Simulink simulation models

NASA Astrophysics Data System (ADS)

Binh, Le Nguyen

2009-04-01

A geometrical and phasor representation technique is presented to illustrate the modulation of the lightwave carrier to generate quadrature amplitude modulated (QAM) signals. The modulation of the amplitude and phase of the lightwave carrier is implemented using only one dual-drive Mach-Zehnder interferometric modulator (MZIM) with the assistance of phasor techniques. Any multilevel modulation scheme can be generated, but we illustrate specifically, the multilevel amplitude and differential phase shift keying (MADPSK) signals. The driving voltage levels are estimated for driving the traveling wave electrodes of the modulator. Phasor diagrams are extensively used to demonstrate the effectiveness of modulation schemes. MATLAB Simulink models are formed to generate the multilevel modulation formats, transmission, and detection in optically amplified fiber communication systems. Transmission performance is obtained for the multilevel optical signals and proven to be equivalent or better than those of binary level with equivalent bit rate. Further, the resilience to nonlinear effects is much higher for MADPSK of 50% and 33% pulse width as compared to non-return-to-zero (NRZ) pulse shaping.

42.8 Gb/s ASK homodyne receiver using standard DFB lasers

NASA Astrophysics Data System (ADS)

Becker, D.; Mohr, D.; Datta, S.; Wree, C.; Bhandare, S.; Joshi, A.

2009-05-01

Optical synchronous coherent detection is attracting greater attention within the defense and security community because it allows linear recovery both of the amplitude and phase of optical signals. Fiber-based transmission impairments such as chromatic dispersion and polarization mode dispersion can be compensated in the electrical domain. Additionally, synchronous detection offers the potential of improved receiver sensitivity and extended reach versus direct or interferometric detection schemes. 28 Gbaud/112 Gb/s and 42.8 Gbaud transmissions are now being considered in fiber networks worldwide. Due to the lack of broadband high frequency components centered at IF values of 56 GHz and 86 GHz, respectively, the coherent heterodyne approach is not viable for these baud rates. The homodyne approach remains one of the choices available to fully exploit the advantages of synchronous coherent detection at these transmission data rates. In order to implement the homodyne receiver, optical phase locking between the signal and local oscillator laser (LO) is required. Digital approaches for this task rely upon very complex, fast, and high power-consumption chips. A homodyne receiver using an analog approach for phase locking would allow for increased system simplicity at a lower cost. Use of commercial-off-the-shelf (COTS) DFB lasers embedded within the receiver would also increase system feasibility for defense applications. We demonstrate synchronous demodulation of a 42.8 Gbaud signal using an analog optical phase-locked loop. The homodyne system was optimized to use COTS DFB lasers having an aggregate linewidth of ~2 MHz. We also analyze the impact of uncompensated phase noise on receiver performance.

Interferometric phase measurement techniques for coherent beam combining

NASA Astrophysics Data System (ADS)

Antier, Marie; Bourderionnet, Jérôme; Larat, Christian; Lallier, Eric; Primot, Jérôme; Brignon, Arnaud

2015-03-01

Coherent beam combining of fiber amplifiers provides an attractive mean of reaching high power laser. In an interferometric phase measurement the beams issued for each fiber combined are imaged onto a sensor and interfere with a reference plane wave. This registration of interference patterns on a camera allows the measurement of the exact phase error of each fiber beam in a single shot. Therefore, this method is a promising candidate toward very large number of combined fibers. Based on this technique, several architectures can be proposed to coherently combine a high number of fibers. The first one based on digital holography transfers directly the image of the camera to spatial light modulator (SLM). The generated hologram is used to compensate the phase errors induced by the amplifiers. This architecture has therefore a collective phase measurement and correction. Unlike previous digital holography technique, the probe beams measuring the phase errors between the fibers are co-propagating with the phase-locked signal beams. This architecture is compatible with the use of multi-stage isolated amplifying fibers. In that case, only 20 pixels per fiber on the SLM are needed to obtain a residual phase shift error below λ/10rms. The second proposed architecture calculates the correction applied to each fiber channel by tracking the relative position of the interference finges. In this case, a phase modulator is placed on each channel. In that configuration, only 8 pixels per fiber on the camera is required for a stable close loop operation with a residual phase error of λ/20rms, which demonstrates the scalability of this concept.

Laser interferometer for space-based mapping of Earth's gravity field

NASA Astrophysics Data System (ADS)

Dehne, Marina; Sheard, Benjamin; Gerberding, Oliver; Mahrdt, Christoph; Heinzel, Gerhard; Danzmann, Karsten

2010-05-01

Laser interferometry will play a key role in the next generation of GRACE-type satellite gravity missions. The measurement concepts for future missions include a heterodyne laser interferometer. Furthermore, it is favourable to use polarising components in the laser interferometer for beam splitting. In the first step the influence of these components on the interferometer sensitivity has been investigated. Additionally, a length stability on a nm-scale has been validated. The next step will include a performance test of an interferometric SST system in an active symmetric transponder setup including two lasers and two optical benches. The design and construction of a quasi-monolithic interferometer for comparing the interferometric performance of non-polarising and polarising optics will be discussed. The results of the interferometric readout of a heterodyne configuration together with polarising optics will be presented to fulfil the phase sensitivity requirement of 1nm/√Hz-- for a typical SSI scenario.

Tuning fork enhanced interferometric photoacoustic spectroscopy: a new method for trace gas analysis

NASA Astrophysics Data System (ADS)

Köhring, M.; Pohlkötter, A.; Willer, U.; Angelmahr, M.; Schade, W.

2011-01-01

A photoacoustic trace gas sensor based on an optical read-out method of a quartz tuning fork is shown. Instead of conventional piezoelectric signal read-out, as applied in well-known quartz-enhanced photoacoustic spectroscopy (QEPAS), an interferometric read-out method for measurement of the tuning fork's oscillation is presented. To demonstrate the potential of the optical read-out of tuning forks in photoacoustics, a comparison between the performances of a sensor with interferometric read-out and conventional QEPAS with piezoelectric read-out is reported. The two sensors show similar characteristics. The detection limit (L) for the optical read-out is determined to be L opt=(2598±84) ppm (1 σ) compared to L elec=(2579±78) ppm (1 σ) for piezoelectric read-out. In both cases the detection limit is defined by the thermal noise of the tuning fork.

Automated interferometric synthetic aperture microscopy and computational adaptive optics for improved optical coherence tomography.

PubMed

Xu, Yang; Liu, Yuan-Zhi; Boppart, Stephen A; Carney, P Scott

2016-03-10

In this paper, we introduce an algorithm framework for the automation of interferometric synthetic aperture microscopy (ISAM). Under this framework, common processing steps such as dispersion correction, Fourier domain resampling, and computational adaptive optics aberration correction are carried out as metrics-assisted parameter search problems. We further present the results of this algorithm applied to phantom and biological tissue samples and compare with manually adjusted results. With the automated algorithm, near-optimal ISAM reconstruction can be achieved without manual adjustment. At the same time, the technical barrier for the nonexpert using ISAM imaging is also significantly lowered.

Interferometric fibre-optic curvature sensing for structural, directional vibration measurements

NASA Astrophysics Data System (ADS)

Kissinger, Thomas; Chehura, Edmon; James, Stephen W.; Tatam, Ralph P.

2017-06-01

Dynamic fibre-optic curvature sensing using fibre segment interferometry is demonstrated using a cost-effective rangeresolved interferometry interrogation system. Differential strain measurements from four fibre strings, each containing four fibre segments of gauge length 20 cm, allow the inference of lateral vibrations as well as the direction of the vibration of a cantilever test object. Dynamic tip displacement resolutions in the micrometre range over a 21 kHz interferometric bandwidth demonstrate the suitability of this approach for highly sensitive fibre-optic directional vibration measurements, complementing existing laser vibrometry techniques by removing the need for side access to the structure under test.

Photonic all-silicon microsensor for electromagnetic power in the microwave and millimeter-wave range

NASA Astrophysics Data System (ADS)

Rendina, Ivo; Bellucci, Marco; Cocorullo, Giuseppe; Della Corte, Francesco G.; Iodice, Mario

2000-03-01

A new type of non-perturbing electromagnetic power sensor for microwaves and millimeter-waves, based on the thermo- optical effect in a silicon interferometric etalon cavity is presented. The incident field power is partially dissipated into the all-silicon metal-less etalon, constituting the sensing element of the detector, so causing its temperature increase. This, in turn, induces the intensity modulation of a probe laser beam reflected by the cavity after a multiple beam interference process. The sensing element is directly connected to an optical fiber for remote interrogation, so avoiding the use of perturbing coaxial cables. The performances of such a new class of non-perturbing and wideband probes, in terms of sensitivity and resolution are discussed in detail. The experimental results concerning the characterization of a preliminary prototype sensor are presented and compared with theoretical data. The dependence of the sensor response on the electromagnetic frequency and on the sensing element characteristics is finally discussed.

Interferometric Gravity Darkening Observations of Vega with the CHARA Array

NASA Astrophysics Data System (ADS)

Aufdenberg, J. P.; Merand, A.; Coude Foresto, V.; Absil, O.; Di Folco, E.; Kervella, P.; Ridgway, S. T.; Sturmann, J.; Sturmann, L.; ten Brummelaar, T. A.; Turner, N. H.; Berger, D. H.; McAlister, H. A.

2005-12-01

We have obtained high-precision interferometric measurements of the A0 V standard star Vega with the Center for High Angular Resolution Astronomy (CHARA) Array and the Fiber Linked Unit for Optical Recombination (FLUOR) beam combiner in the K' band at projected baselines between 103 m and 273 m. The measured squared visibility amplitudes beyond the first lobe are significantly weaker than expected for a slowly rotating star and provide strong evidence for the model of Vega as a rapidly rotating star viewed very nearly pole on. We have constructed a Roche-von Zeipel gravity-darkened model atmosphere which is in generally good agreement with both our interferometric data and archival spectrophotometry. Our model indicates Vega is rotating at ˜92% of its angular break-up rate with an equatorial velocity of ˜275 km s-1. We find a polar effective temperature of ˜10150 K and a pole-to-equator effective temperature difference of ˜2500 K, much larger than the ˜300 K derived by Gulliver, Hill, and Adelman. Our model suggests that Vega's cool equatorial atmosphere may have significant convective flux and predicts a significantly cooler spectral energy distribution for Vega as seen by its surrounding debris disk. This work was performed in part under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Michelson Fellowship Program. JPL is managed for NASA by the California Institute of Technology. The CHARA Array is operated by the Center for High Angular Resolution Astronomy with support from Georgia State University and the National Science Foundation, the Keck Foundation and the Packard Foundation.

Fiber-optic hydrophone array for acoustic surveillance in the littoral

NASA Astrophysics Data System (ADS)

Hill, David; Nash, Phillip

2005-05-01

We describe a fibre-optic hydrophone array system architecture that can be tailored to meet the underwater acoustic surveillance requirements of the military, counter terrorist and customs authorities in protecting ports and harbours, offshore production facilities or coastal approaches. Physically the fibre-optic hydrophone array is in the form of a lightweight cable, enabling rapid deployment from a small vessel. Based upon an optical architecture of time and wavelength multiplexed interferometric hydrophones, the array is comprised of a series of hydrophone sub-arrays. Using multiple sub-arrays, extended perimeters many tens of kilometres in length can be monitored. Interrogated via a long (~50km) optical fibre data link, the acoustic date is processed using the latest open architecture sonar processing platform, ensuring that acoustic targets below, on and above the surface are detected, tracked and classified. Results obtained from an at sea trial of a 96-channel hydrophone array are given, showing the passive detection and tracking of a diver, small surface craft and big ocean going ships beyond the horizon. Furthermore, we describe how the OptaMarine fibre-optic hydrophone array fits into an integrated multi-layered approach to port and harbour security consisting of active sonar for diver detection and hull imaging, as well as thermal imaging and CCTV for surface monitoring. Finally, we briefly describe a complimentary land perimeter intruder detection system consisting of an array of fibre optic accelerometers.

Computational adaptive optics for broadband interferometric tomography of tissues and cells

NASA Astrophysics Data System (ADS)

Adie, Steven G.; Mulligan, Jeffrey A.

2016-03-01

Adaptive optics (AO) can shape aberrated optical wavefronts to physically restore the constructive interference needed for high-resolution imaging. With access to the complex optical field, however, many functions of optical hardware can be achieved computationally, including focusing and the compensation of optical aberrations to restore the constructive interference required for diffraction-limited imaging performance. Holography, which employs interferometric detection of the complex optical field, was developed based on this connection between hardware and computational image formation, although this link has only recently been exploited for 3D tomographic imaging in scattering biological tissues. This talk will present the underlying imaging science behind computational image formation with optical coherence tomography (OCT) -- a beam-scanned version of broadband digital holography. Analogous to hardware AO (HAO), we demonstrate computational adaptive optics (CAO) and optimization of the computed pupil correction in 'sensorless mode' (Zernike polynomial corrections with feedback from image metrics) or with the use of 'guide-stars' in the sample. We discuss the concept of an 'isotomic volume' as the volumetric extension of the 'isoplanatic patch' introduced in astronomical AO. Recent CAO results and ongoing work is highlighted to point to the potential biomedical impact of computed broadband interferometric tomography. We also discuss the advantages and disadvantages of HAO vs. CAO for the effective shaping of optical wavefronts, and highlight opportunities for hybrid approaches that synergistically combine the unique advantages of hardware and computational methods for rapid volumetric tomography with cellular resolution.

APTAMER CAPTURE AND OPTICAL INTERFEROMETRIC DETECTION OF CYANOBACTERIAL TOXINS

EPA Science Inventory

Cyanobacterial toxins have been identified as a health risk in source and finished waters passing through drinking water utilities in the United States. In this project, a rapid, sensitive and field usable sensor based on an aptamer modified planar waveguide interferometric se...

Optical fabrication and testing; Proceedings of the Meeting, Singapore, Oct. 22-27, 1990

NASA Astrophysics Data System (ADS)

Lorenzen, Manfred; Campbell, Duncan R.; Johnson, Craig W.

1991-03-01

Various papers on optical fabrication and testing are presented. Individual topics addressed include: interferometry with laser diodes, new methods for economic production of prisms and lenses, interferometer accuracy and precision, optical testing with wavelength scanning interferometer, digital Talbot interferometer, high-sensitivity interferometric technique for strain measurements, absolute interferometric testing of spherical surfaces, contouring using gratings created on an LCD panel, three-dimensional inspection using laser-based dynamic fringe projection, noncontact optical microtopography, laser scan microscope and infrared laser scan microscope, photon scanning tunneling microscopy. Also discussed are: combination-matching problems in the layout design of minilaser rangefinder, design and testing of a cube-corner array for laser ranging, mode and far-field pattern of diode laser-phased arrays, new glasses for optics and optoelectronics, optical properties of Li-doped ZnO films, application and machining of Zerodur for optical purposes, finish machining of optical components in mass production.

Optical fabrication and testing; Proceedings of the Meeting, Singapore, Oct. 22-27, 1990

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorenzen, M.; Campbell, D.R.; Johnson, C.W.

1991-01-01

Various papers on optical fabrication and testing are presented. Individual topics addressed include: interferometry with laser diodes, new methods for economic production of prisms and lenses, interferometer accuracy and precision, optical testing with wavelength scanning interferometer, digital Talbot interferometer, high-sensitivity interferometric technique for strain measurements, absolute interferometric testing of spherical surfaces, contouring using gratings created on an LCD panel, three-dimensional inspection using laser-based dynamic fringe projection, noncontact optical microtopography, laser scan microscope and infrared laser scan microscope, photon scanning tunneling microscopy. Also discussed are: combination-matching problems in the layout design of minilaser rangefinder, design and testing of a cube-corner arraymore » for laser ranging, mode and far-field pattern of diode laser-phased arrays, new glasses for optics and optoelectronics, optical properties of Li-doped ZnO films, application and machining of Zerodur for optical purposes, finish machining of optical components in mass production.« less

Radio-frequency unbalanced M-Z interferometer for wavelength interrogation of fiber Bragg grating sensors.

PubMed

Zhou, Jiaao; Xia, Li; Cheng, Rui; Wen, Yongqiang; Rohollahnejad, Jalal

2016-01-15

The optical unbalanced Mach-Zehnder interferometer (UMZI) has attracted significant interests for interrogation of FBG sensors owing to its excellent advantages in sensitivity, resolution, and demodulation speed. But this method is still limited to dynamic measurements due to its poor stability and reliability when used for quasi-static detections. Here, we propose for the first time, to the best of our knowledge, a radio-frequency unbalanced M-Z interferometer (RF-UMZI) for interrogation of FBG sensors, which, owing to its operation in an incoherent rather than a coherent regime, provides an ideal solution for the existing stability problem of the conventional UMZI, with remarkable features of adjustable resolution and potentially extremely high sensitivity. A dispersion compensation fiber (DCF) and single-mode fiber (SMF) with a small length difference are served as the two unbalanced arms of the RF interferometer. The induced differential chromatic dispersion transfers the wavelength shift of the FBG to the change of the RF phase difference between the two interferometric carriers, which ultimately leads to the variation of the RF signal intensity. An interrogation of a strain-turned FBG was accomplished and a maximum sensitivity of 0.00835  a.u./με was obtained, which can easily be further improved by more than two orders of magnitude through various fiber dispersion components. Finally, the stability of the interrogation was tested.

Advanced optical instruments technology

NASA Technical Reports Server (NTRS)

Shao, Mike; Chrisp, Michael; Cheng, Li-Jen; Eng, Sverre; Glavich, Thomas; Goad, Larry; Jones, Bill; Kaarat, Philip; Nein, Max; Robinson, William

1992-01-01

The science objectives for proposed NASA missions for the next decades push the state of the art in sensitivity and spatial resolution over a wide range of wavelengths, including the x-ray to the submillimeter. While some of the proposed missions are larger and more sensitive versions of familiar concepts, such as the next generation space telescope, others use concepts, common on the Earth, but new to space, such as optical interferometry, in order to provide spatial resolutions impossible with other concepts. However, despite their architecture, the performance of all of the proposed missions depends critically on the back-end instruments that process the collected energy to produce scientifically interesting outputs. The Advanced Optical Instruments Technology panel was chartered with defining technology development plans that would best improve optical instrument performance for future astrophysics missions. At this workshop the optical instrument was defined as the set of optical components that reimage the light from the telescope onto the detectors to provide information about the spatial, spectral, and polarization properties of the light. This definition was used to distinguish the optical instrument technology issues from those associated with the telescope, which were covered by a separate panel. The panel identified several areas for optical component technology development: diffraction gratings; tunable filters; interferometric beam combiners; optical materials; and fiber optics. The panel also determined that stray light suppression instruments, such as coronagraphs and nulling interferometers, were in need of general development to support future astrophysics needs.

Advanced optical instruments technology

NASA Astrophysics Data System (ADS)

Shao, Mike; Chrisp, Michael; Cheng, Li-Jen; Eng, Sverre; Glavich, Thomas; Goad, Larry; Jones, Bill; Kaarat, Philip; Nein, Max; Robinson, William

1992-08-01

The science objectives for proposed NASA missions for the next decades push the state of the art in sensitivity and spatial resolution over a wide range of wavelengths, including the x-ray to the submillimeter. While some of the proposed missions are larger and more sensitive versions of familiar concepts, such as the next generation space telescope, others use concepts, common on the Earth, but new to space, such as optical interferometry, in order to provide spatial resolutions impossible with other concepts. However, despite their architecture, the performance of all of the proposed missions depends critically on the back-end instruments that process the collected energy to produce scientifically interesting outputs. The Advanced Optical Instruments Technology panel was chartered with defining technology development plans that would best improve optical instrument performance for future astrophysics missions. At this workshop the optical instrument was defined as the set of optical components that reimage the light from the telescope onto the detectors to provide information about the spatial, spectral, and polarization properties of the light. This definition was used to distinguish the optical instrument technology issues from those associated with the telescope, which were covered by a separate panel. The panel identified several areas for optical component technology development: diffraction gratings; tunable filters; interferometric beam combiners; optical materials; and fiber optics. The panel also determined that stray light suppression instruments, such as coronagraphs and nulling interferometers, were in need of general development to support future astrophysics needs.

Fiber Fabry-Perot Interferometric Sensor for the Measurement of Electric Current Flowing through a Fuse

NASA Astrophysics Data System (ADS)

Park, Jaehee

2007-06-01

A fiber Fabry-Perot inteferometric sensor bonded close to a fusing element has been studied for the measurement of electric current flowing through a fuse. The phase shift of the sensor output signal is proportional to the square of the electric current passing through the fuse and the sensitivity is 0.827°/mA2.

Controlling the opto-mechanics of a cantilever in an interferometer via cavity loss

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidsfeld, A. von, E-mail: avonschm@uos.de; Reichling, M., E-mail: reichling@uos.de

2015-09-21

In a non-contact atomic force microscope, based on interferometric cantilever displacement detection, the optical return loss of the system is tunable via the distance between the fiber end and the cantilever. We utilize this for tuning the interferometer from a predominant Michelson to a predominant Fabry-Pérot characteristics and introduce the Fabry-Pérot enhancement factor as a quantitative measure for multibeam interference in the cavity. This experimentally easily accessible and adjustable parameter provides a control of the opto-mechanical interaction between the cavity light field and the cantilever. The quantitative assessment of the light pressure acting on the cantilever oscillating in the cavitymore » via the frequency shift allows an in-situ measurement of the cantilever stiffness with remarkable precision.« less

Noncontact acousto-ultrasonics using laser generation and laser interferometric detection

NASA Technical Reports Server (NTRS)

Green, Robert E., Jr.; Huber, Robert D.

1991-01-01

A compact, portable fiber-optic heterodyne interferometer designed to detect out-of-plane motion on surfaces is described. The interferometer provides a linear output for displacements over a broad frequency range and can be used for ultrasonic, acoustic emission, and acousto-ultrasonic (AU) testing. The interferometer in conjunction with a compact pulsed Nd:YAG laser represents a noncontact testing system. This system was tested to determine its usefulness for the AU technique. The results obtained show that replacement of conventional piezoelectric transducers (PZT) with a laser generation/detection system make it possible to carry out noncontact AU measurements. The waveforms recorded were 5 MHZ PZT-generated ultrasound propagating through an aluminum block, detection of the acoustic emission event, and laser AU waveforms from graphite-epoxy laminates and a filament-wound composite.

MEMS-based Optic Fiber Fabry-Perot Sensor for Underwater Acoustic Measurement with A Wavelength-switched System

NASA Astrophysics Data System (ADS)

Xia, J.; Y Wang, F.; Luo, H.; Hu, Y. M.; Xiong, S. D.

2017-12-01

In this paper, a MEMS-based extrinsic Farby-Perot Interferometric (EFPI) acoustic pressure acoustic sensor is presented. The diaphragm structure is used as the second reflected surface, and the sensitive surface to acoustic pressure. A wavelength-switched phase demodulation system for EFPI sensors is used for acoustic signal recovery. The modified phase demodulation system has been demonstrated to recover the signal to a stable intensity fluctuation level of ±0.5 dB at the test frequency of 2000 Hz. In the test depth of 50cm, the sensor has a resonant frequency of 3.7 kHz, a flat frequency range of 10-800Hz, and a corresponding acoustic pressure sensitivity of -159 dB re. 1/μPa.

Interferometric detection of nanoparticles

NASA Astrophysics Data System (ADS)

Hayrapetyan, Karen

Interferometric surfaces enhance light scattering from nanoparticles through constructive interference of partial scattered waves. By placing the nanoparticles on interferometric surfaces tuned to a special surface phase interferometric condition, the particles are detectable in the dilute limit through interferometric image contrast in a heterodyne light scattering configuration, or through diffraction in a homodyne scattering configuration. The interferometric enhancement has applications for imaging and diffractive biosensors. We present a modified model based on Double Interaction (DI) to explore bead-based detection mechanisms using imaging, scanning and diffraction. The application goal of this work is to explore the trade-offs between the sensitivity and throughput among various detection methods. Experimentally we use thermal oxide on silicon to establish and control surface interferometric conditions. Surface-captured gold beads are detected using Molecular Interferometric Imaging (MI2) and Spinning-Disc Interferometry (SDI). Double-resonant enhancement of light scattering leads to high-contrast detection of 100 nm radius gold nanoparticles on an interferometric surface. The double-resonance condition is achieved when resonance (or anti-resonance) from an asymmetric Fabry-Perot substrate coincides with the Mie resonance of the gold nanoparticle. The double-resonance condition is observed experimentally using molecular interferometric imaging (MI2). An invisibility condition is identified for which the gold nanoparticles are optically cloaked by the interferometric surface.

Simple online recognition of optical data strings based on conservative optical logic

NASA Astrophysics Data System (ADS)

Caulfield, H. John; Shamir, Joseph; Zavalin, Andrey I.; Silberman, Enrique; Qian, Lei; Vikram, Chandra S.

2006-06-01

Optical packet switching relies on the ability of a system to recognize header information on an optical signal. Unless the headers are very short with large Hamming distances, optical correlation fails and optical logic becomes attractive because it can handle long headers with Hamming distances as low as 1. Unfortunately, the only optical logic gates fast enough to keep up with current communication speeds involve semiconductor optical amplifiers and do not lend themselves to the incorporation of large numbers of elements for header recognition and would consume a lot of power as well. The ideal system would operate at any bandwidth with no power consumption. We describe how to design and build such a system by using passive optical logic. This too leads to practical problems that we discuss. We show theoretically various ways to use optical interferometric logic for reliable recognition of long data streams such as headers in optical communication. In addition, we demonstrate one particularly simple experimental approach using interferometric coinc gates.

3D interferometric shape measurement technique using coherent fiber bundles

NASA Astrophysics Data System (ADS)

Zhang, Hao; Kuschmierz, Robert; Czarske, Jürgen

2017-06-01

In-situ 3-D shape measurements with submicron shape uncertainty of fast rotating objects in a cutting lathe are expected, which can be achieved by simultaneous distance and velocity measurements. Conventional tactile methods, coordinate measurement machines, only support ex-situ measurements. Optical measurement techniques such as triangulation and conoscopic holography offer only the distance, so that the absolute diameter cannot be retrieved directly. In comparison, laser Doppler distance sensors (P-LDD sensor) enable simultaneous and in-situ distance and velocity measurements for monitoring the cutting process in a lathe. In order to achieve shape measurement uncertainties below 1 μm, a P-LDD sensor with a dual camera based scattered light detection has been investigated. Coherent fiber bundles (CFB) are employed to forward the scattered light towards cameras. This enables a compact and passive sensor head in the future. Compared with a photo detector based sensor, the dual camera based sensor allows to decrease the measurement uncertainty by the order of one magnitude. As a result, the total shape uncertainty of absolute 3-D shape measurements can be reduced to about 100 nm.

The Information Content of Interferometric Synthetic Aperture Radar: Vegetation and Underlying Surface Topography

NASA Technical Reports Server (NTRS)

Treuhaft, Robert N.

1996-01-01

This paper first gives a heuristic description of the sensitivity of Interferometric Synthetic Aperture Radar to vertical vegetation distributions and underlying surface topography. A parameter estimation scenario is then described in which the Interferometric Synthetic Aperture Radar cross-correlation amplitude and phase are the observations from which vegetation and surface topographic parameters are estimated. It is shown that, even in the homogeneous-layer model of the vegetation, the number of parameters needed to describe the vegetation and underlying topography exceeds the number of Interferometric Synthetic Aperture Radar observations for single-baseline, single-frequency, single-incidence-angle, single-polarization Interferometric Synthetic Aperture Radar. Using ancillary ground-truth data to compensate for the underdetermination of the parameters, forest depths are estimated from the INSAR data. A recently-analyzed multibaseline data set is also discussed and the potential for stand-alone Interferometric Synthetic Aperture Radar parameter estimation is assessed. The potential of combining the information content of Interferometric Synthetic Aperture Radar with that of infrared/optical remote sensing data is briefly discussed.

Optical design methods, applications, and large optics; Proceedings of the Meeting, Hamburg, Federal Republic of Germany, Sept. 19-21, 1988

NASA Astrophysics Data System (ADS)

Masson, Andre; Schulte In den Baeumen, J.; Zuegge, Hannfried

1989-04-01

Recent advances in the design of large optical components are discussed in reviews and reports. Sections are devoted to calculation and optimization methods, optical-design software, IR optics, diagnosis and tolerancing, image formation, lens design, and large optics. Particular attention is given to the use of the pseudoeikonal in optimization, design with nonsequential ray tracing, aspherics and color-correcting elements in the thermal IR, on-line interferometric mirror-deforming measurement with an Ar-ion laser, and the effect of ametropia on laser-interferometric visual acuity. Also discussed are a holographic head-up display for air and ground applications, high-performance objectives for a digital CCD telecine, the optics of the ESO Very Large Telescope, static wavefront correction by Linnik interferometry, and memory-saving techniques in damped least-squares optimization of complex systems.

Computer simulations of interferometric imaging with the VLT Interferometer and the AMBER instrument

NASA Astrophysics Data System (ADS)

Bloecker, Thomas; Hofmann, Karl-Heinz; Przygodda, Frank; Weigelt, Gerd

2000-07-01

We present computer simulations of interferometric imaging with the VLT interferometer and the AMBER instrument. These simulations include both the astrophysical modeling of a stellar object by radiative transfer calculations and the simulation of light propagation from the object to the detector (through atmosphere, telescopes, and the AMBER instrument), simulation of photon noise and detector read- out noise, and finally data processing of the interferograms. The results show the dependence of the visibility error bars on the following observational parameters: different seeing during the observation of object and reference star (Fried parameters r0,object equals 2.4 m, r0,ref. equals 2.5 m), different residual tip- tilt error ((delta) tt,object equals 2% of the Airy disk diameter, (delta) tt,ref. equals 0.1%), and object brightness (Kobject equals 3.5 mag and 11 mag, Kref. equals 3.5 mag). Exemplarily, we focus on stars in late stages of stellar evolution and study one of its key objects, the dusty supergiant IRC + 10420 that is rapidly evolving on human timescales. We show computer simulations of VLTI interferometry of IRC + 10420 with two ATs (wide-field mode, i.e. without fiber optics spatial filters) and discuss whether the visibility accuracy is sufficient to distinguish between different theoretical model predictions.

The VLT Interferometer and its AMBER Instrument: Simulations of Interferometric Imaging in the Wide-Field Mode

NASA Astrophysics Data System (ADS)

Blöcker, T.; Hofmann, K.-H.; Przygodda, F.; Weigelt, G.

We present computer simulations of interferometric imaging with the VLT interferometer and the AMBER instrument. These simulations include both the astrophysical modelling of a stellar object by radiative transfer calculations and the simulation of light propagation from the object to the detector (through atmosphere, telescopes, and the AMBER instrument), simulation of photon noise and detector read-out noise, and finally data processing of the interferograms. The results show the dependence of the visibility error bars on the following observational parameters: different seeing during the observation of object and reference star (Fried parameters r0,object and r0,ref. ranging between 0.9 m and 1.2 m), different residual tip-tilt error (δtt,object and δtt,ref. ranging between 0.1% and 20% of the Airy disk diameter), and object brightness (Kobject=3.5 mag to 13 mag, Kref.=3.5 mag). Exemplarily, we focus on stars in late stages of stellar evolution and study one of its key objects, the dusty supergiant IRC +10 420 that is rapidly evolving on human timescales. We show computer simulations of VLT interferometry of IRC +10 420 with two ATs (wide-field mode, i.e. without fiber optics spatial filters) and discuss whether the visibility accuracy is sufficient to distinguish between different theoretical model predictions.

Tightly Coupled Inertial Navigation System/Global Positioning System (TCMIG)

NASA Technical Reports Server (NTRS)

Watson, Michael D.; Jackson, Kurt (Technical Monitor)

2002-01-01

Many NASA applications planned for execution later this decade are seeking high performance, miniaturized, low power Inertial Management Units (IMU). Much research has gone into Micro-Electro-Mechanical System (MEMS) over the past decade as a solution to these needs. While MEMS devices have proven to provide high accuracy acceleration measurements, they have not yet proven to have the accuracy required by many NASA missions in rotational measurements. Therefore, a new solution has been formulated integrating the best of all IMU technologies to address these mid-term needs in the form of a Tightly Coupled Micro Inertial Navigation System (INS)/Global Positioning System (GPS) (TCMIG). The TCMIG consists of an INS and a GPS tightly coupled by a Kalman filter executing on an embedded Field Programmable Gate Array (FPGA) processor. The INS consists of a highly integrated Interferometric Fiber Optic Gyroscope (IFOG) and a MEMS accelerometer. The IFOG utilizes a tightly wound fiber coil to reduce volume and the high level of integration and advanced optical components to reduce power. The MEMS accelerometer utilizes a newly developed deep etch process to increase the proof mass and yield a highly accurate accelerometer. The GPS receiver consists of a low power miniaturized version of the Blackjack receiver. Such an IMU configuration is ideal to meet the mid-term needs of the NASA Science Enterprises and the new launch vehicles being developed for the Space Launch Initiative (SLI).

Computational adaptive optics for broadband optical interferometric tomography of biological tissue.

PubMed

Adie, Steven G; Graf, Benedikt W; Ahmad, Adeel; Carney, P Scott; Boppart, Stephen A

2012-05-08

Aberrations in optical microscopy reduce image resolution and contrast, and can limit imaging depth when focusing into biological samples. Static correction of aberrations may be achieved through appropriate lens design, but this approach does not offer the flexibility of simultaneously correcting aberrations for all imaging depths, nor the adaptability to correct for sample-specific aberrations for high-quality tomographic optical imaging. Incorporation of adaptive optics (AO) methods have demonstrated considerable improvement in optical image contrast and resolution in noninterferometric microscopy techniques, as well as in optical coherence tomography. Here we present a method to correct aberrations in a tomogram rather than the beam of a broadband optical interferometry system. Based on Fourier optics principles, we correct aberrations of a virtual pupil using Zernike polynomials. When used in conjunction with the computed imaging method interferometric synthetic aperture microscopy, this computational AO enables object reconstruction (within the single scattering limit) with ideal focal-plane resolution at all depths. Tomographic reconstructions of tissue phantoms containing subresolution titanium-dioxide particles and of ex vivo rat lung tissue demonstrate aberration correction in datasets acquired with a highly astigmatic illumination beam. These results also demonstrate that imaging with an aberrated astigmatic beam provides the advantage of a more uniform depth-dependent signal compared to imaging with a standard gaussian beam. With further work, computational AO could enable the replacement of complicated and expensive optical hardware components with algorithms implemented on a standard desktop computer, making high-resolution 3D interferometric tomography accessible to a wider group of users and nonspecialists.

Integrated-Optic Wavelength Multiplexer In Glass Fabricated By A Charge Controlled Ion Exchange

NASA Astrophysics Data System (ADS)

Klein, R.; Jestel, D.; Lilienhof, H. J.; Rottman, F.; Voges, E.

1989-02-01

Integrated-optic wavelength division multiplexing (WDM) is commonly used in communication systems. These WDM-devices are also well suited to build up optical fiber networks for both intensity and interferometric sensor types. The operation principle of our wavelength division multiplexing devise is based on the wavelength dependent two-mode interference in a two-moded waveguide, which is coupled adiabatically to the single-mode input and output strip waveguides. The single-mode input and output waveguides are connected via two Y-branches ( "'kJ- 1° branching angle ) with a two-moded intersection region. The ratio of the light powers in the single-mode output waveguides depends on wavelength . The two-mode interference within the two-moded center waveguide leads to an almost wavelength periodic transmission caracteristic . Dual-channel multiplexers/demultiplexers were fabricated by a charge controlled field assisted pottasium exchange in B-270 glass (Desag). The devices have a typical channel separation of 30 - 40 nm and a far-end crosstalk attenuation of better than 16 dB. The operation wavelength regions of the fabricated devices are 0.6 - 0.8 µm and 1.3 - 1.6 µm, respectively.

Control of Formation-Flying Multi-Element Space Interferometers with Direct Interferometer-Output Feedback

NASA Technical Reports Server (NTRS)

Lu, Hui-Ling; Cheng, H. L.; Lyon, Richard G.; Carpenter, Kenneth G.

2007-01-01

The long-baseline space interferometer concept involving formation flying of multiple spacecraft holds great promise as future space missions for high-resolution imagery. A major challenge of obtaining high-quality interferometric synthesized images from long-baseline space interferometers is to accurately control these spacecraft and their optics payloads in the specified configuration. Our research focuses on the determination of the optical errors to achieve fine control of long-baseline space interferometers without resorting to additional sensing equipment. We present a suite of estimation tools that can effectively extract from the raw interferometric image relative x/y, piston translational and tip/tilt deviations at the exit pupil aperture. The use of these error estimates in achieving control of the interferometer elements is demonstrated using simulated as well as laboratory-collected interferometric stellar images.

Control of Formation-Flying Multi-Element Space Interferometers with Direct Interferometer-Output Feedback

NASA Technical Reports Server (NTRS)

Lu, Hui-Ling; Cheng, Victor H. L.; Lyon, Richard G.; Carpenter, Kenneth G.

2007-01-01

The long-baseline space interferometer concept involving formation flying of multiple spacecrafts holds great promise as future space missions for high-resolution imagery. A major challenge of obtaining high-quality interferometric synthesized images from long-baseline space interferometers is to accurately control these spacecraft and their optics payloads in the specified configuration. Our research focuses on the determination of the optical errors to achieve fine control of long-baseline space interferometers without resorting to additional sensing equipment. We present a suite of estimation tools that can effectively extract from the raw interferometric image relative x/y, piston translational and tip/tilt deviations at the exit pupil aperture. The use of these error estimates in achieving control of the interferometer elements is demonstrated using simulated as well as laboratory-collected interferometric stellar images.

Pulse Holography: Review Of Applications

NASA Astrophysics Data System (ADS)

Smigielski, Paul

1990-04-01

Pulse Holography includes studies concerning time-varying phase objects as well as time-varying reflective objects involving the use of pulse ruby- and YAG-lasers. The paper is divided in two parts. One part concerns the direct use of 3-1) images reconstructed from holograms, i.e. applications to particle size analysis, 3-I) velocity measurements, 3-I) cinematography ... The second part describes applications using holographic interferometry in laboratory or in an industrial environment, i.e. applications to fluid mechanics, vibration analysis, non-destructive testing ... Recent developments including interferornetric cineholography, fiber optics, measurement of non-interferometric displacements ... , are also described. The future of holography depends to a great extent on data processing and interpretation of informations contained in holograms or holographic intericrograms. Therefore, we give the state of art in this field in Europe illustrated with some industrial applications.

How nonlinear optics can merge interferometry for high resolution imaging

NASA Astrophysics Data System (ADS)

Ceus, D.; Reynaud, F.; Tonello, A.; Delage, L.; Grossard, L.

2017-11-01

High resolution stellar interferometers are very powerful efficient instruments to get a better knowledge of our Universe through the spatial coherence analysis of the light. For this purpose, the optical fields collected by each telescope Ti are mixed together. From the interferometric pattern, two expected information called the contrast Cij and the phase information φij are extracted. These information lead to the Vij, called the complex visibility, with Vij=Cijexp(jφij). For each telescope doublet TiTj, it is possible to get a complex visibility Vij. The Zernike Van Cittert theorem gives a relationship between the intensity distribution of the object observed and the complex visibility. The combination of the acquired complex visibilities and a reconstruction algorithm allows imaging reconstruction. To avoid lots of technical difficulties related to infrared optics (components transmission, thermal noises, thermal cooling…), our team proposes to explore the possibility of using nonlinear optical techniques. This is a promising alternative detection technique for detecting infrared optical signals. This way, we experimentally demonstrate that frequency conversion does not result in additional bias on the interferometric data supplied by a stellar interferometer. In this presentation, we report on wavelength conversion of the light collected by each telescope from the infrared domain to the visible. The interferometric pattern is observed in the visible domain with our, so called, upconversion interferometer. Thereby, one can benefit from mature optical components mainly used in optical telecommunications (waveguide, coupler, multiplexer…) and efficient low-noise detection schemes up to the single-photon counting level.

Radiation effects in materials for optical interferometric devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koumvakalis, N.; Jani, M.G.; Halliburton, L.E.

The effects of ionizing radiation have been investigated in a series of materials commonly used in optical interferometric devices. Included in the study were three glass-ceramics (Zerodur, Cer-Vit 101, and Cer-Vit 142) and one Faraday-rotator glass (SF-57). Each glass-ceramic was irradiated at room temperature with 1.5-MeV electrons from a Van De Graaff accelerator. Similar irradiations were done on the Faraday-rotator glass at room temperature and 77 K. Optical absorption and electron spin resonance measurements provided a monitor of the radiation-induced point defects in all cases. The spectral characteristics and the production and thermal annealing behavior of these defects are described,more » and their possible effect on the performance of optical devices which incorporate these materials is considered.« less

Imaging Schwarzschild multilayer X-ray microscope

NASA Technical Reports Server (NTRS)

Hoover, Richard B.; Baker, Phillip C.; Shealy, David L.; Core, David B.; Walker, Arthur B. C., Jr.; Barbee, Troy W., Jr.; Kerstetter, Ted

1993-01-01

We have designed, analyzed, fabricated, and tested Schwarzschild multilayer X-ray microscopes. These instruments use flow-polished Zerodur mirror substrates which have been coated with multilayers optimized for maximum reflectivity at normal incidence at 135 A. They are being developed as prototypes for the Water Window Imaging X-Ray Microscope. Ultrasmooth mirror sets of hemlite grade sapphire have been fabricated and they are now being coated with multilayers to reflect soft X-rays at 38 A, within the biologically important 'water window'. In this paper, we discuss the fabrication of the microscope optics and structural components as well as the mounting of the optics and assembly of the microscopes. We also describe the optical alignment, interferometric and visible light testing of the microscopes, present interferometrically measured performance data, and provide the first results of optical imaging tests.

Squeezed pulsed light from a fiber ring interferometer

NASA Technical Reports Server (NTRS)

Bergman, K.; Haus, H. A.

1992-01-01

Observation of squeezed noise, 5 +/- 0.3 dB below the shot noise level, generated with pulses in a fiber ring interferometer is reported. The interferometric geometry is used to separate the pump pulse from the squeezed vacuum radiation. A portion of the pump is reused as the local oscillator in a homodyne detection. The pump fluctuations are successfully subtracted and shot noise limited performance is achieved at low frequencies (35-85 KHz). A possible utilization of the generated squeezed vacuum in improving a fiber gyro's signal to noise ratio is discussed.

Electro-optic modulation of a laser at microwave frequencies for interferometric purposes

NASA Astrophysics Data System (ADS)

Specht, Paul E.; Jilek, Brook A.

2017-02-01

A multi-point microwave interferometer (MPMI) concept was previously proposed by the authors for spatially-resolved, non-invasive tracking of a shock, reaction, or detonation front in energetic media [P. Specht et al., AIP Conf. Proc. 1793, 160010 (2017).]. The advantage of the MPMI concept over current microwave interferometry techniques is its detection of Doppler shifted microwave signals through electro-optic (EO) modulation of a laser. Since EO modulation preserves spatial variations in the Doppler shift, collecting the EO modulated laser light into a fiber array for recording with an optical heterodyne interferometer yields spatially-resolved velocity information. This work demonstrates the underlying physical principle of the MPMI diagnostic: the monitoring of a microwave signal with nanosecond temporal resolution using an optical heterodyne interferometer. For this purpose, the MPMI concept was simplified to a single-point construction using two tunable 1550 nm lasers and a 35.2 GHz microwave source. A (110) ZnTe crystal imparted the microwave frequency onto a laser, which was combined with a reference laser for determination of the microwave frequency in an optical heterodyne interferometer. A single, characteristic frequency associated with the microwave source was identified in all experiments, providing a means to monitor a microwave signal on nanosecond time scales. Lastly, areas for improving the frequency resolution of this technique are discussed, focusing on increasing the phase-modulated signal strength.

Electro-optic modulation of a laser at microwave frequencies for interferometric purposes.

PubMed

Specht, Paul E; Jilek, Brook A

2017-02-01

A multi-point microwave interferometer (MPMI) concept was previously proposed by the authors for spatially-resolved, non-invasive tracking of a shock, reaction, or detonation front in energetic media [P. Specht et al., AIP Conf. Proc. 1793, 160010 (2017).]. The advantage of the MPMI concept over current microwave interferometry techniques is its detection of Doppler shifted microwave signals through electro-optic (EO) modulation of a laser. Since EO modulation preserves spatial variations in the Doppler shift, collecting the EO modulated laser light into a fiber array for recording with an optical heterodyne interferometer yields spatially-resolved velocity information. This work demonstrates the underlying physical principle of the MPMI diagnostic: the monitoring of a microwave signal with nanosecond temporal resolution using an optical heterodyne interferometer. For this purpose, the MPMI concept was simplified to a single-point construction using two tunable 1550 nm lasers and a 35.2 GHz microwave source. A (110) ZnTe crystal imparted the microwave frequency onto a laser, which was combined with a reference laser for determination of the microwave frequency in an optical heterodyne interferometer. A single, characteristic frequency associated with the microwave source was identified in all experiments, providing a means to monitor a microwave signal on nanosecond time scales. Lastly, areas for improving the frequency resolution of this technique are discussed, focusing on increasing the phase-modulated signal strength.

Self-centering fiber alignment structures for high-precision field installable single-mode fiber connectors

NASA Astrophysics Data System (ADS)

Van Erps, Jürgen; Ebraert, Evert; Gao, Fei; Vervaeke, Michael; Berghmans, Francis; Beri, Stefano; Watté, Jan; Thienpont, Hugo

2014-05-01

There is a steady increase in the demand for internet bandwidth, primarily driven by cloud services and high-definition video streaming. Europe's Digital Agenda states the ambitious objective that by 2020 all Europeans should have access to internet at speeds of 30Mb/s or above, with 50% or more of households subscribing to connections of 100Mb/s. Today however, internet access in Europe is mainly based on the first generation of broadband, meaning internet accessed over legacy telephone copper and TV cable networks. In recent years, Fiber-To-The-Home (FTTH) networks have been adopted as a replacement of traditional electrical connections for the `last mile' transmission of information at bandwidths over 1Gb/s. However, FTTH penetration is still very low (< 5%) in most major Western economies. The main reason for this is the high deployment cost of FTTH networks. Indeed, the success and adoption of optical access networks critically depend on the quality and reliability of connections between optical fibers. In particular a further reduction of insertion loss of field- installable connectors must be achieved without a significant increase in component cost. This requires precise alignment of fibers that can differ in terms of ellipticity, eccentricity or diameter and seems hardly achievable using today's widespread ferrule-based alignment systems. In this paper, we present a field-installable connector based on deflectable/compressible spring structures, providing a self-centering functionality for the fiber. This way, it can accommodate for possible fiber cladding diameter variations (the tolerance on the cladding diameter of G.652 fiber is typically +/-0.7μm). The mechanical properties of the cantilever are derived through an analytical approximation and a mathematical model of the spring constant, and finite element-based simulations are carried out to find the maximum first principal stress as well as the stress distribution distribution in the fiber alignment structure. Elastic constants of the order of 104N=m are found to be compatible with a proof stress of 70 M Pa. We show the successful prototyping of 3-spring fiber alignment structures using deep proton writing and investigate their compatibility with replication techniques such as hot embossing and injection moulding. Fiber insertion in our self-centering alignment structures is achieved by means of a dedicated interferometric setup allowing assessment of the fiber facet quality, of the fiber's position in relation to the connector's front and of the spring deformation during fiber insertion. These self-centering structures have the potential to become the basic building blocks for a new generation of field-installable connectors, ultimately breaking the current paradigm of ferrule-based connectivity requiring extensive pre-engineering and highly specialized manpower for field deployment.

Astronomical Optical Interferometry. I. Methods and Instrumentation

NASA Astrophysics Data System (ADS)

Jankov, S.

2010-12-01

Previous decade has seen an achievement of large interferometric projects including 8-10m telescopes and 100m class baselines. Modern computer and control technology has enabled the interferometric combination of light from separate telescopes also in the visible and infrared regimes. Imaging with milli-arcsecond (mas) resolution and astrometry with micro-arcsecond (muas) precision have thus become reality. Here, I review the methods and instrumentation corresponding to the current state in the field of astronomical optical interferometry. First, this review summarizes the development from the pioneering works of Fizeau and Michelson. Next, the fundamental observables are described, followed by the discussion of the basic design principles of modern interferometers. The basic interferometric techniques such as speckle and aperture masking interferometry, aperture synthesis and nulling interferometry are disscused as well. Using the experience of past and existing facilities to illustrate important points, I consider particularly the new generation of large interferometers that has been recently commissioned (most notably, the CHARA, Keck, VLT and LBT Interferometers). Finally, I discuss the longer-term future of optical interferometry, including the possibilities of new large-scale ground-based projects and prospects for space interferometry.

Interferometric phase locking of two electronic oscillators with a cascade electro-optic modulator

NASA Astrophysics Data System (ADS)

Chao, C. H.; Chien, P. Y.; Chang, L. W.; Juang, F. Y.; Hsia, C. H.; Chang, C. C.

1993-01-01

An optical-type electrical phase-locked-loop system based on a cascade electro-optic modulator has been demonstrated. By using this technique, a set of optical-type phase detectors, operating at any harmonic frequencies of two applied phase-modulation signals, has been implemented.

Design, Fabrication, and Packaging of Mach-Zehnder Interferometers for Biological Sensing Applications

NASA Astrophysics Data System (ADS)

Novak, Joseph

Optical biological sensors are widely used in the fields of medical testing, water treatment and safety, gene identification, and many others due to advances in nanofabrication technology. This work focuses on the design of fiber-coupled Mach-Zehnder Interferometer (MZI) based biosensors fabricated on silicon-on-insulator (SOI) wafer. Silicon waveguide sensors are designed with multimode and single-mode dimensions. Input coupling efficiency is investigated by design of various taper structures. Integration processing and packaging is performed for fiber attachment and enhancement of input coupling efficiency. Optical guided-wave sensors rely on single-mode operation to extract an induced phase-shift from the output signal. A silicon waveguide MZI sensor designed and fabricated for both multimode and single-mode dimensions. Sensitivity of the sensors is analyzed for waveguide dimensions and materials. An s-bend structure is designed for the multimode waveguide to eliminate higher-order mode power as an alternative to single-mode confinement. Single-mode confinement is experimentally demonstrated through near field imaging of waveguide output. Y-junctions are designed for 3dB power splitting to the MZI arms and for power recombination after sensing to utilize the interferometric function of the MZI. Ultra-short 10microm taper structures with curved geometries are designed to improve insertion loss from fiber-to-chip without significantly increasing device area and show potential for applications requiring misalignment tolerance. An novel v-groove process is developed for self-aligned integration of fiber grooves for attachment to sensor chips. Thermal oxidation at temperatures from 1050-1150°C during groove processing creates an SiO2 layer on the waveguide end facet to protect the waveguide facet during integration etch processing without additional e-beam lithography processing. Experimental results show improvement of insertion loss compared to dicing preparation and Focused Ion Beam methods using the thermal oxidation process.

Direct Wafer Bonding and Its Application to Waveguide Optical Isolators

PubMed Central

Mizumoto, Tetsuya; Shoji, Yuya; Takei, Ryohei

2012-01-01

This paper reviews the direct bonding technique focusing on the waveguide optical isolator application. A surface activated direct bonding technique is a powerful tool to realize a tight contact between dissimilar materials. This technique has the potential advantage that dissimilar materials are bonded at low temperature, which enables one to avoid the issue associated with the difference in thermal expansion. Using this technique, a magneto-optic garnet is successfully bonded on silicon, III-V compound semiconductors and LiNbO3. As an application of this technique, waveguide optical isolators are investigated including an interferometric waveguide optical isolator and a semileaky waveguide optical isolator. The interferometric waveguide optical isolator that uses nonreciprocal phase shift is applicable to a variety of waveguide platforms. The low refractive index of buried oxide layer in a silicon-on-insulator (SOI) waveguide enhances the magneto-optic phase shift, which contributes to the size reduction of the isolator. A semileaky waveguide optical isolator has the advantage of large fabrication-tolerance as well as a wide operation wavelength range. PMID:28817020

Interferometric and nonlinear-optical spectral-imaging techniques for outer space and live cells

NASA Astrophysics Data System (ADS)

Itoh, Kazuyoshi

2015-12-01

Multidimensional signals such as the spectral images allow us to have deeper insights into the natures of objects. In this paper the spectral imaging techniques that are based on optical interferometry and nonlinear optics are presented. The interferometric imaging technique is based on the unified theory of Van Cittert-Zernike and Wiener-Khintchine theorems and allows us to retrieve a spectral image of an object in the far zone from the 3D spatial coherence function. The retrieval principle is explained using a very simple object. The promising applications to space interferometers for astronomy that are currently in progress will also be briefly touched on. An interesting extension of interferometric spectral imaging is a 3D and spectral imaging technique that records 4D information of objects where the 3D and spectral information is retrieved from the cross-spectral density function of optical field. The 3D imaging is realized via the numerical inverse propagation of the cross-spectral density. A few techniques suggested recently are introduced. The nonlinear optical technique that utilizes stimulated Raman scattering (SRS) for spectral imaging of biomedical targets is presented lastly. The strong signals of SRS permit us to get vibrational information of molecules in the live cell or tissue in real time. The vibrational information of unstained or unlabeled molecules is crucial especially for medical applications. The 3D information due to the optical nonlinearity is also the attractive feature of SRS spectral microscopy.

All-optical phase modulation for integrated interferometric biosensors.

PubMed

Dante, Stefania; Duval, Daphné; Sepúlveda, Borja; González-Guerrero, Ana Belen; Sendra, José Ramón; Lechuga, Laura M

2012-03-26

We present the theoretical and the experimental implementation of an all-optical phase modulation system in integrated Mach-Zehnder Interferometers to solve the drawbacks related to the periodic nature of the interferometric signal. Sensor phase is tuned by modulating the emission wavelength of low-cost commercial laser diodes by changing their output power. FFT deconvolution of the signal allows for direct phase readout, immune to sensitivity variations and to light intensity fluctuations. This simple phase modulation scheme increases the signal-to-noise ratio of the measurements in one order of magnitude, rendering in a sensor with a detection limit of 1.9·10⁻⁷ RIU. The viability of the all-optical modulation approach is demonstrated with an immunoassay detection as a biosensing proof of concept.

Diaphragm based long cavity Fabry-Perot fiber acoustic sensor using phase generated carrier

NASA Astrophysics Data System (ADS)

Liu, Bin; Lin, Jie; Liu, Huan; Ma, Yuan; Yan, Lei; Jin, Peng

2017-01-01

A diaphragm based long cavity Fabry-Perot interferometric fiber acoustic sensor is proposed. The Fabry-Perot cavity is formed by a flat fiber facet and an ultra-thin silver diaphragm with a 6-meter long fiber inserted in the cavity. A narrow-linewidth ring-cavity erbium-doped fiber laser is applied to demodulate the sensing signal in the phase generated carrier algorithm. Experimental results have demonstrated that the phase sensitivity is about -140 dB re 1 rad/μPa at 2 kHz. The noise equivalent acoustic signal level is 60.6 μPa/Hz1/2 and the dynamic range is 65.1 dB-SPL at 2 kHz. The sensor is suitable for sensing of weak acoustic signals.

Study on phase noise induced by 1/f noise of the modulator drive circuit in high-sensitivity fiber optic gyroscope

NASA Astrophysics Data System (ADS)

Teng, Fei; Jin, Jing; Li, Yong; Zhang, Chunxi

2018-05-01

The contribution of modulator drive circuit noise as a 1/f noise source to the output noise of the high-sensitivity interferometric fiber optic gyroscope (IFOG) was studied here. A noise model of closed-loop IFOG was built. By applying the simulated 1/f noise sequence into the model, a gyroscope output data series was acquired, and the corresponding power spectrum density (PSD) and the Allan variance curve were calculated to analyze the noise characteristic. The PSD curve was in the spectral shape of 1/f, which verifies that the modulator drive circuit induced a low frequency 1/f phase noise into the gyroscope. The random walk coefficient (RWC), a standard metric to characterize the noise performance of the IFOG, was calculated according to the Allan variance curve. Using an operational amplifier with an input 1/f noise of 520 nV/√Hz at 1 Hz, the RWC induced by this 1/f noise was 2 × 10-4°/√h, which accounts for 63% of the total RWC. To verify the correctness of the noise model we proposed, a high-sensitivity gyroscope prototype was built and tested. The simulated Allan variance curve gave a good rendition of the prototype actual measured curve. The error percentage between the simulated RWC and the measured value was less than 13%. According to the model, a noise reduction method is proposed and the effectiveness is verified by the experiment.

Chemical, biochemical, and environmental fiber sensors III; Proceedings of the Meeting, Boston, MA, Sept. 4, 5, 1991

NASA Astrophysics Data System (ADS)

Lieberman, Robert A.

Various papers on chemical, biochemical, and environmental fiber sensors are presented. Individual topics addressed include: fiber optic pressure sensor for combustion monitoring and control, viologen-based fiber optic oxygen sensors, renewable-reagent fiber optic sensor for ocean pCO2, transition metal complexes as indicators for a fiber optic oxygen sensor, fiber optic pH measurements using azo indicators, simple reversible fiber optic chemical sensors using solvatochromic dyes, totally integrated optical measuring sensors, integrated optic biosensor for environmental monitoring, radiation dosimetry using planar waveguide sensors, optical and piezoelectric analysis of polymer films for chemical sensor characterization, source polarization effects in an optical fiber fluorosensor, lens-type refractometer for on-line chemical analysis, fiber optic hydrocarbon sensor system, chemical sensors for environmental monitoring, optical fibers for liquid-crystal sensing and logic devices, suitability of single-mode fluoride fibers for evanescent-wave sensing, integrated modules for fiber optic sensors, optoelectronic sensors based on narrowband A3B5 alloys, fiber Bragg grating chemical sensor.

Nano-displacement sensor based on photonic crystal fiber modal interferometer.

PubMed

Dash, Jitendra Narayan; Jha, Rajan; Villatoro, Joel; Dass, Sumit

2015-02-15

A stable nano-displacement sensor based on large mode area photonic crystal fiber (PCF) modal interferometer is presented. The compact setup requires simple splicing of a small piece of PCF with a single mode fiber (SMF). The excitation and recombination of modes is carried out in a single splice. The use of a reflecting target creates an extra cavity that discretizes the interference pattern of the mode interferometer, boosting the displacement resolution to nanometer level. The proposed modal interferometric based displacement sensor is highly stable and shows sensitivity of 32  pm/nm.

Response of Solid He-4 to External Stress: Interdigital Capacitor Solid Level Detector and Optical Interferometer

NASA Technical Reports Server (NTRS)

Fay, J.; Wada, Y.; Masutomi, R.; Elkholy, T.; Kojima, H.

2003-01-01

Two experiments are being conducted to observe the liquid/solid interface of He-4 near 1 K. Interesting instabilities are expected to occur when the solid is non-hydrostatically stressed. (1)A compact interdigital capacitor is used as a level detector to observe solid He-4 to which stresses are applied externally. The capacitor consists of 38 interlaced 50 m wide and 3.8 mm long gold films separated by 50 m and deposited onto a 5 mm by 5 mm sapphire substrate. The capacitor is placed on one flat end wall of a cylindrical chamber (xx mm diameter and xx mm long). The solid is grown to a known height and a stress is applied by a tubular PZT along the cylindrical axis. The observed small change in height of the solid at the wall is linearly proportional to the applied stress. The solid height decreases under compressive stress but does not change under tensile stress. The response of the solid on compressive stress is consistent with the expected quadratic dependence on strain. (2)Interferometric techniques are being developed for observing the solid He-4 surface profile. A laser light source is brought into the low temperature region via single mode optical fiber. The interference pattern is transmitted back out of the low temperature apparatus via optical fiber bundle. The solid He-4 growth chamber will be equipped with two PZT's such that stress can be applied from orthogonal directions. Orthogonally applied stress is expected to induce surface instability with island-like deformation on a grid pattern. Apparatus design and progress of its construction are described.

Femtosecond frequency comb based distance measurement in air.

PubMed

Balling, Petr; Kren, Petr; Masika, Pavel; van den Berg, S A

2009-05-25

Interferometric measurement of distance using a femtosecond frequency comb is demonstrated and compared with a counting interferometer displacement measurement. A numerical model of pulse propagation in air is developed and the results are compared with experimental data for short distances. The relative agreement for distance measurement in known laboratory conditions is better than 10(-7). According to the model, similar precision seems feasible even for long-distance measurement in air if conditions are sufficiently known. It is demonstrated that the relative width of the interferogram envelope even decreases with the measured length, and a fringe contrast higher than 90% could be obtained for kilometer distances in air, if optimal spectral width for that length and wavelength is used. The possibility of comb radiation delivery to the interferometer by an optical fiber is shown by model and experiment, which is important from a practical point of view.

Development of high sensitivity eight-element multiplexed fiber laser acoustic pressure hydrophone array and interrogation system

NASA Astrophysics Data System (ADS)

Li, Ming; Sun, Zhihui; Zhang, Xiaolei; Li, Shujuan; Song, Zhiqiang; Wang, Meng; Guo, Jian; Ni, Jiasheng; Wang, Chang; Peng, Gangding; Xu, Xiangang

2017-09-01

Fiber laser hydrophones have got widespread concerns due to the unique advantages and broad application prospects. In this paper, the research results of the eight-element multiplexed fiber laser acoustic pressure array and the interrogation system are introduced, containing low-noise distributed feedback fiber laser (DFB-FL) fabrication, sensitivity enhancement packaging, and interferometric signal demodulation. The frequency response range of the system is 10Hz-10kHz, the laser frequency acoustic pressure sensitivity reaches 115 dB re Hz/Pa, and the equivalent noise acoustic pressure is less than 60μPa/Hz1/2. The dynamic range of the system is greater than 120 dB.

Shell-Type Micromechanical Oscillator

DTIC Science & Technology

2003-04-01

interferometric setup. A positive feedback loop was implemented by amplifying the red laser signal (related to the oscillator deflection) and using...resonator was actuated by a sharply focused, modulated Ar+ ion (blue) laser beam and detected by a red HeNe laser using an interferometric setup. A positive...top. Fig. 1 shows optical micrograph obtained by DIC (Differential Interference Contrast, known also as Nomarsky contrast). An array of three domes

The Spatially Resolved H(alpha)-Emitting Wind Structure of P Cygni

DTIC Science & Technology

2010-06-01

using radio and optical interferometry, as well as direct imaging with adaptive optics (AO). Radio interferometric observations detect the nebula around...to structures in the nebula of P Cyg that are more than an order of magnitude smaller. Therefore, optical interferometry provides a unique window of

Interferometric analysis of polishing surface with a petal tool

NASA Astrophysics Data System (ADS)

Salas-Sánchez, Alfonso; Leal-Cabrera, Irce; Percino Zacarias, Elizabeth; Granados-Agustín, Fermín S.

2011-09-01

In this work, we describe a phase shift interferometric monitoring of polishing processes produced by a petal tool over a spherical surface to obtain a parabolic surface. In the process, we used a commercial polishing machine; the purpose of this work is to have control of polishing time. To achieve this analysis, we used a Fizeau interferometer of ZYGO Company for optical shop testing, and the Durango software from Diffraction International Company. For data acquisition, simulation and evaluation of optical surfaces, we start polishing process with a spherical surface with 15.46 cm of diameter; a 59.9 cm of radius curvature and, with f/# 1.9.

Direct observation of crystal growth from solution using optical investigation of a growing crystal face

NASA Technical Reports Server (NTRS)

Lal, Ravindra

1994-01-01

The first technical report for the period 1 Jan. 1993 till 31 Dec. 1993 for the research entitled, 'Direct observation of crystal growth from solution using Optical Investigation of a growing crystal Face' is presented. The work on the project did not start till 1 June 1993 due to the non-availability of the required personnel. The progress of the work during the period 1 June 1993 till the end of 1993 is described. Significant progress was made for testing various optical diagnostic techniques for monitoring crystal solution. Some of the techniques that are being tested are: heterodyne detection technique, in which changes in phase are measured as a interferometric function of time/crystal growth; a conventional technique, in which a fringe brightness is measured as a function of crystal growth/time; and a Mach-Zehnder interferometric technique in which a fringe brightness is measured as a function of time to obtain information on concentration changes. During the second year it will be decided to incorporate the best interferometric technique along with the ellipsometric technique, to obtain real time in-situ growth rate measurements. A laboratory mock-up of the first two techniques were made and tested.

A New Optical Bench Concept for Space-Based Laser Interferometric Gravitational Wave Missions

NASA Astrophysics Data System (ADS)

Chilton, Andrew; Apple, Stephen; Ciani, Giacomo; Olatunde, Taiwo; Conklin, John; Mueller, Guido

2015-04-01

Space-based interferometric gravitational wave detectors such as LISA have been proposed to detect low-frequency gravitational wave sources such as the inspirals of compact objects into massive black holes or two massive black holes into each other. The optical components used to perform the high-precision interferometry required to make these measurements have historically been bonded to Zerodur optical benches, which are thermally ultrastable but difficult and time-consuming to manufacture. More modern implementations of LISA-like interferometry have reduced the length stability requirement on these benches from 30fm/√{Hz} to a few pm √{ Hz}. We therefore propose to alter the design of the optical bench in such a way as to no longer require the use of Zerodur; instead, we plan to replace it with more easily-used materials such as titanium or molybdenum. In this presentation, we discuss the current status of and future plans for the construction and testing of such an optical bench.

Surface slope metrology of highly curved x-ray optics with an interferometric microscope

NASA Astrophysics Data System (ADS)

Gevorkyan, Gevork S.; Centers, Gary; Polonska, Kateryna S.; Nikitin, Sergey M.; Lacey, Ian; Yashchuk, Valeriy V.

2017-09-01

The development of deterministic polishing techniques has given rise to vendors that manufacture high quality threedimensional x-ray optics. The surface metrology on these optics remains a difficult task. For the fabrication, vendors usually use unique surface metrology tools, generally developed on site, that are not available in the optical metrology labs at x-ray facilities. At the Advanced Light Source X-Ray Optics Laboratory, we have developed a rather straightforward interferometric-microscopy-based procedure capable of sub microradian characterization of sagittal slope variation of x-ray optics for two-dimensionally focusing and collimating (such as ellipsoids, paraboloids, etc.). In the paper, we provide the mathematical foundation of the procedure and describe the related instrument calibration. We also present analytical expression describing the ideal surface shape in the sagittal direction of a spheroid specified by the conjugate parameters of the optic's beamline application. The expression is useful when analyzing data obtained with such optics. The high efficiency of the developed measurement and data analysis procedures is demonstrated in results of measurements with a number of x-ray optics with sagittal radius of curvature between 56 mm and 480 mm. We also discuss potential areas of further improvement.

Digitally Enhanced Heterodyne Interferometry

NASA Technical Reports Server (NTRS)

Shaddock, Daniel; Ware, Brent; Lay, Oliver; Dubovitsky, Serge

2010-01-01

Spurious interference limits the performance of many interferometric measurements. Digitally enhanced interferometry (DEI) improves measurement sensitivity by augmenting conventional heterodyne interferometry with pseudo-random noise (PRN) code phase modulation. DEI effectively changes the measurement problem from one of hardware (optics, electronics), which may deteriorate over time, to one of software (modulation, digital signal processing), which does not. DEI isolates interferometric signals based on their delay. Interferometric signals are effectively time-tagged by phase-modulating the laser source with a PRN code. DEI improves measurement sensitivity by exploiting the autocorrelation properties of the PRN to isolate only the signal of interest and reject spurious interference. The properties of the PRN code determine the degree of isolation.

Metal-Coated Optical Fibers for High Temperature Applications

NASA Technical Reports Server (NTRS)

Zeakes, Jason; Murphy, Kent; Claus, Richard; Greene, Jonathan; Tran, Tuan

1996-01-01

This poster will highlight on-going research at the Virginia Tech Fiber & Electro-Optics Research Center (FEORC) in the area of thin films on optical fibers. Topics will include the sputter deposition of metals and metal; alloys onto optical fiber and fiber optic sensors for innovative applications. Specific information will be available on thin film fiber optic hydrogen sensors, corrosion sensors, and metal-coated optical fiber for high temperature aerospace applications.

Fiber optics: A research paper

NASA Technical Reports Server (NTRS)

Drone, Melinda M.

1987-01-01

Some basic aspects concerning fiber optics are examined. Some history leading up to the development of optical fibers which are now used in the transmission of data in many areas of the world is discussed. Basic theory of the operation of fiber optics is discussed along with methods for improving performance of the optical fiber through much research and design. Splices and connectors are compared and short haul and long haul fiber optic networks are discussed. Fiber optics plays many roles in the commercial world. The use of fiber optics for communication applications is emphasized.

Fiber optic connector

DOEpatents

Rajic, Slobodan; Muhs, Jeffrey D.

1996-01-01

A fiber optic connector and method for connecting composite materials within which optical fibers are imbedded. The fiber optic connector includes a capillary tube for receiving optical fibers at opposing ends. The method involves inserting a first optical fiber into the capillary tube and imbedding the unit in the end of a softened composite material. The capillary tube is injected with a coupling medium which subsequently solidifies. The composite material is machined to a desired configuration. An external optical fiber is then inserted into the capillary tube after fluidizing the coupling medium, whereby the optical fibers are coupled.

Mathematical model of a DIC position sensing system within an optical trap

NASA Astrophysics Data System (ADS)

Wulff, Kurt D.; Cole, Daniel G.; Clark, Robert L.

2005-08-01

The quantitative study of displacements and forces of motor proteins and processes that occur at the microscopic level and below require a high level of sensitivity. For optical traps, two techniques for position sensing have been accepted and used quite extensively: quadrant photodiodes and an interferometric position sensing technique based on DIC imaging. While quadrant photodiodes have been studied in depth and mathematically characterized, a mathematical characterization of the interferometric position sensor has not been presented to the authors' knowledge. The interferometric position sensing method works off of the DIC imaging capabilities of a microscope. Circularly polarized light is sent into the microscope and the Wollaston prism used for DIC imaging splits the beam into its orthogonal components, displacing them by a set distance determined by the user. The distance between the axes of the beams is set so the beams overlap at the specimen plane and effectively share the trapped microsphere. A second prism then recombines the light beams and the exiting laser light's polarization is measured and related to position. In this paper we outline the mathematical characterization of a microsphere suspended in an optical trap using a DIC position sensing method. The sensitivity of this mathematical model is then compared to the QPD model. The mathematical model of a microsphere in an optical trap can serve as a calibration curve for an experimental setup.

Initial Performance Evaluation of Optical Fibers and Sensors Under High-Energy Electron Beam Irradiation

NASA Astrophysics Data System (ADS)

Palmer, Matthew E.; Slusher, David; Fielder, Robert S.

2006-01-01

In this paper, recent work on the performance of optical fiber, fiber optic sensors, and fiber optic connectors under the influence of a high-energy electron beam is presented. Electron beam irradiation is relevant for the Jupiter Icy Moons Orbiter (JIMO) mission due to the high electron radiation environment surrounding Jupiter. As an initial feasibility test, selected optical fiber components were exposed to dose levels relevant to the Jupiter environment. Three separate fiber types were used: one series consisted of pure silica core fiber, two other series consisted of different levels of Germania-doped fiber. Additionally, a series of fused silica Extrinsic Fabry-Perot Interferometer (EFPI)-based fiber optic sensors and two different types of fiber optic connectors were tested. Two types of fiber coatings were evaluated: acrylate and polyimide. All samples were exposed to three different dose levels: 2 MRad, 20 MRad, and 50 MRad. Optical loss measurements were made on the optical fiber spools as a function of wavelength between 750 and 1750nm at periodic intervals up to 75 hrs after exposure. Attenuation is minimal and wavelength-dependent. Fiber optic sensors were evaluated using a standard EFPI sensor readout and diagnostic system. Optical connectors and optical fiber coatings were visually inspected for degradation. Additionally, tensile testing and minimum bend radius testing was conducted on the fibers. Initial loss measurements indicate a low-level of induced optical attenuation in the fiber which recovers with time. The fiber optic sensors exhibited no observable degradation after exposure. The optical fiber connectors and coatings also showed no observable degradation. In addition to harsh environment survivability, fiber optic sensors offer a number of intrinsic advantages for space nuclear power applications including extremely low mass, immunity to electromagnetic interference, self diagnostics / prognostics, and smart sensor capability. Deploying fiber optic sensors on future space exploration missions would provide a substantial improvement in spacecraft instrumentation.

Fiber distributed feedback laser

NASA Technical Reports Server (NTRS)

Elachi, C.; Evans, G. A.; Yeh, C. (Inventor)

1976-01-01

Utilizing round optical fibers as communication channels in optical communication networks presents the problem of obtaining a high efficiency coupling between the optical fiber and the laser. A laser is made an integral part of the optical fiber channel by either diffusing active material into the optical fiber or surrounding the optical fiber with the active material. Oscillation within the active medium to produce lasing action is established by grating the optical fiber so that distributed feedback occurs.

Development and applications of optical interferometric micrometrology in the Angstrom and subangstrom range

NASA Technical Reports Server (NTRS)

Lauer, James L.; Abel, Phillip B.

1988-01-01

The characteristics of the scanning tunneling microscope and atomic force microscope (AFM) are briefly reviewed, and optical methods, mainly interferometry, of sufficient resolution to measure AFM deflections are discussed. The methods include optical resonators, laser interferometry, multiple-beam interferometry, and evanescent wave detection. Experimental results using AFM are reviewed.

PCF-based Fabry-Perot interferometric sensor for strain measurement under high-temperature

NASA Astrophysics Data System (ADS)

Deng, Ming; Tang, Chang-Ping; Zhu, Tao; Rao, Yun-Jiang

2011-05-01

We report a simple and robust all-fiber in-line Fabry-Perot interferometer (FPI) with bubble cavity, which is fabricated by directly splicing a mutimode photonic crystal fiber to a conventional single mode fiber by using a commercial splicer. The fabrication process only involves fusion splicing and cleaving. The high-temperature strain characteristic of such a device is evaluated and experimental results shows that this FPI can be used as an ideal sensor for precise strain measurement under high temperatures of up to 750°C. Therefore, such a FPI sensor may find important applications in aeronautics or metallurgy areas.

Fiber optic monitoring device

DOEpatents

Samborsky, James K.

1993-01-01

A device for the purpose of monitoring light transmissions in optical fibers comprises a fiber optic tap that optically diverts a fraction of a transmitted optical signal without disrupting the integrity of the signal. The diverted signal is carried, preferably by the fiber optic tap, to a lens or lens system that disperses the light over a solid angle that facilitates viewing. The dispersed light indicates whether or not the monitored optical fiber or system of optical fibers is currently transmitting optical information.

Acoustic vibration sensor based on nonadiabatic tapered fibers.

PubMed

Xu, Ben; Li, Yi; Sun, Miao; Zhang, Zhen-Wei; Dong, Xin-Yong; Zhang, Zai-Xuan; Jin, Shang-Zhong

2012-11-15

A simple and low-cost vibration sensor based on single-mode nonadiabatic fiber tapers is proposed and demonstrated. The environmental vibrations can be detected by demodulating the transmission loss of the nonadiabatic fiber taper. Theoretical simulations show that the transmission loss is related to the microbending of the fiber taper induced by vibrations. Unlike interferometric sensors, this vibration sensor does not need any feedback loop to control the quadrature point to obtain a stable performance. In addition, it has no requirement for the coherence of the light source and is insensitive to temperature changes. Experimental results show that this sensing system has a wide frequency response range from a few hertz to tens of kilohertz with the maximal signal to noise ratio up to 73 dB.

Fiber optic connector

DOEpatents

Rajic, S.; Muhs, J.D.

1996-10-22

A fiber optic connector and method for connecting composite materials within which optical fibers are imbedded are disclosed. The fiber optic connector includes a capillary tube for receiving optical fibers at opposing ends. The method involves inserting a first optical fiber into the capillary tube and imbedding the unit in the end of a softened composite material. The capillary tube is injected with a coupling medium which subsequently solidifies. The composite material is machined to a desired configuration. An external optical fiber is then inserted into the capillary tube after fluidizing the coupling medium, whereby the optical fibers are coupled. 3 figs.

Characterization of light transmissions in various optical fibers with proton beam

NASA Astrophysics Data System (ADS)

Song, Young Beom; Kim, Hye Jin; Kim, Mingeon; Lee, Bongsoo; Shin, Sang Hun; Yoo, Wook Jae; Jang, Kyoung Won; Hwang, Sung Won

2017-12-01

As a feasibility study on the development of a fiber-optic radiation sensor for proton therapy dosimetry, we characterized light transmissions of various commercial optical fibers such as silica and plastic based optical fibers by the irradiation of proton beams. In this study, we measured light transmission spectra of optical fibers as a function of absorbed doses of proton beams using a deuterium & tungsten halogen lamps and a spectrometer. To be used as a fiber-optic radiation sensor, the optical fibers should have the radiation resistant characteristics and provide stable output signals during the proton beam irradiation. In this study, we could select suitable optical fibers to be used in the fiber-optic radiation sensor without quenching effects for proton therapy dosimetry. As a result, the light transmittance of the optical fibers had decreasing trends with increasing absorbed dose as expected.

Microstructure of the smart composite structures with embedded fiber optic sensing nerves

NASA Astrophysics Data System (ADS)

Liu, Jingyuan; Luo, Fei; Li, Changchun; Ma, Naibin

1997-11-01

The composite structures with embedded optical fiber sensors construct a smart composite structure system, which may have the characteristics of the in-service self-measurement, self- recognition and self-judgement action. In the present work, we studied the microstructures of carbon/epoxy composite laminates with embedded sensing optical fibers, and the integration of optical fiber with composites was also discussed. The preliminary experiment results show that because of the difference between the sensing optical fibers and the reinforcing fibers in their size, the microstructure of the composites with embedded optical fibers will produce partial local changes in the area of embedded optical fiber, these changes may affect the mechanical properties of composite structures. When the optical fibers are embedded parallel to the reinforcing fibers, due to the composite prepregs are formed under a press action during its curing process, the reinforcing fibers can be arranged equably around the optical fibers. But when the optical fibers are embedded perpendicularly to the reinforcement fibers, the resin rich pocket will appear in the composite laminates surrounding the embedded optical fiber. The gas holes will be easily produced in these zones which may produce a premature failure of the composite structure. The photoelastic experiments are also given in the paper.

Tunable optical assembly with vibration dampening

NASA Technical Reports Server (NTRS)

Allison, Sidney G. (Inventor); Shams, Qamar A. (Inventor); Fox, Robert L. (Inventor); Fox, legal representative, Christopher L. (Inventor); Fox Chattin, legal representative, Melanie L. (Inventor)

2009-01-01

An optical assembly is formed by one or more piezoelectric fiber composite actuators having one or more optical fibers coupled thereto. The optical fiber(s) experiences strain when actuation voltage is applied to the actuator(s). Light passing through the optical fiber(s) is wavelength tuned by adjusting the actuation voltage.

Inscription of first order fiber Bragg gratings in sapphire fibers by 400 nm femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Elsmann, Tino; Habisreuther, Tobias; Graf, Albrecht; Rothhardt, Manfred; Bartelt, Hartmut

2013-05-01

We demonstrate the inscription of fiber Bragg gratings in single crystalline sapphire using the second harmonic of a Ti:Sa-amplified femtosecond laser system. With the laser wavelength of 400 nm first order gratings were fabricated. The interferometric inscription was performed out using the Talbot interferometer. This way, not only single gratings but also multiplexed sensor arrays were realized. For evaluating of the sensor signals an adapted multimodal interrogation setup was build up, because the sapphire fiber is an extreme multimodal air clad fiber. Due to the multimodal reflection spectrum, different peak functions have been tested to evaluate the thermal properties of the grating. The temperature sensors were tested for high temperature applications up to 1200°C with a thermal sensitivity in the order of 25 pm/K which is more than the doubled of that one reached with Bragg gratings in conventional silica fibers.

Rapid constructions of microstructures for optical fiber sensors using a commercial CO2 laser system.

PubMed

Irawan, Rudi; Chuan, Tjin Swee; Meng, Tay Chia; Ming, Tan Khay

2008-06-27

Exposing an optical fiber core to the measurand surrounding the fiber is often used to enhance the sensitivity of an optical fiber sensor. This paper reports on the rapid fabrication of microstructures in an optical fiber using a CO₂ laser system which help exposing the optical fiber core to the measurand. The direct-write CO₂ laser system used is originally designed for engraving the polymeric material. Fabrications of microstructures such as in-fiber microhole, D-shaped fiber, in-fiber microchannel, side-sliced fiber and tapered fiber were attempted. The microstructures in the fibers were examined using a SEM and an optical microscope. Quality of microstructures shown by the SEM images and promising results from fluorescence sensor tests using in-fiber microchannels of 100μm width, 210μm depth and 10mm length show the prospect of this method for use in optical fiber sensor development. The direct-write CO₂ laser system is a flexible and fast machining tool for fabricating microstructures in an optical fiber, and can possibly be a replacement of the time consuming chemical etching and polishing methods used for microstructure fabrications of optical the fiber sensors reported in other literatures.

Rapid Constructions of Microstructures for Optical Fiber Sensors Using a Commercial CO2 Laser System

PubMed Central

Irawan, Rudi; Chuan, Tjin Swee; Meng, Tay Chia; Ming, Tan Khay

2008-01-01

Exposing an optical fiber core to the measurand surrounding the fiber is often used to enhance the sensitivity of an optical fiber sensor. This paper reports on the rapid fabrication of microstructures in an optical fiber using a CO2 laser system which help exposing the optical fiber core to the measurand. The direct-write CO2 laser system used is originally designed for engraving the polymeric material. Fabrications of microstructures such as in-fiber microhole, D-shaped fiber, in-fiber microchannel, side-sliced fiber and tapered fiber were attempted. The microstructures in the fibers were examined using a SEM and an optical microscope. Quality of microstructures shown by the SEM images and promising results from fluorescence sensor tests using in-fiber microchannels of 100μm width, 210μm depth and 10mm length show the prospect of this method for use in optical fiber sensor development. The direct-write CO2 laser system is a flexible and fast machining tool for fabricating microstructures in an optical fiber, and can possibly be a replacement of the time consuming chemical etching and polishing methods used for microstructure fabrications of optical the fiber sensors reported in other literatures. PMID:19662114

Fiber optic temperature sensor

NASA Technical Reports Server (NTRS)

Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor)

2000-01-01

A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

Fiber optic temperature sensor

NASA Technical Reports Server (NTRS)

Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor); Mattes, Brenton L. (Inventor); Charnetski, Clark J. (Inventor)

1999-01-01

A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

Magneto-Optic Field Coupling in Optical Fiber Bragg Gratings

NASA Technical Reports Server (NTRS)

Carman, Gregory P. (Inventor); Mohanchandra, Panduranga K. (Inventor); Emmons, Michael C. (Inventor); Richards, William Lance (Inventor)

2016-01-01

The invention is a magneto-optic coupled magnetic sensor that comprises a standard optical fiber Bragg grating system. The system includes an optical fiber with at least one Bragg grating therein. The optical fiber has at least an inner core and a cladding that surrounds the inner core. The optical fiber is part of an optical system that includes an interrogation device that provides a light wave through the optical fiber and a system to determine the change in the index of refraction of the optical fiber. The cladding of the optical fiber comprises at least a portion of which is made up of ferromagnetic particles so that the ferromagnetic particles are subject to the light wave provided by the interrogation system. When a magnetic field is present, the ferromagnetic particles change the optical properties of the sensor directly.

Micro-optical coherence tomography of the mammalian cochlea

PubMed Central

Iyer, Janani S.; Batts, Shelley A.; Chu, Kengyeh K.; Sahin, Mehmet I.; Leung, Hui Min; Tearney, Guillermo J.; Stankovic, Konstantina M.

2016-01-01

The mammalian cochlea has historically resisted attempts at high-resolution, non-invasive imaging due to its small size, complex three-dimensional structure, and embedded location within the temporal bone. As a result, little is known about the relationship between an individual’s cochlear pathology and hearing function, and otologists must rely on physiological testing and imaging methods that offer limited resolution to obtain information about the inner ear prior to performing surgery. Micro-optical coherence tomography (μOCT) is a non-invasive, low-coherence interferometric imaging technique capable of resolving cellular-level anatomic structures. To determine whether μOCT is capable of resolving mammalian intracochlear anatomy, fixed guinea pig inner ears were imaged as whole temporal bones with cochlea in situ. Anatomical structures such as the tunnel of Corti, space of Nuel, modiolus, scalae, and cell groupings were visualized, in addition to individual cell types such as neuronal fibers, hair cells, and supporting cells. Visualization of these structures, via volumetrically-reconstructed image stacks and endoscopic perspective videos, represents an improvement over previous efforts using conventional OCT. These are the first μOCT images of mammalian cochlear anatomy, and they demonstrate μOCT’s potential utility as an imaging tool in otology research. PMID:27633610

Local Leak Detection and Health Monitoring of Pressurized Tanks

NASA Technical Reports Server (NTRS)

Polzin, Kurt; Witherow, William; Korman, Valentin; Sinko, John; Hendrickson, Adam

2011-01-01

An optical gas-detection sensor safely monitors pressurized systems (such as cryogenic tanks) and distribution systems for leaks. This sensor system is a fiber-coupled, solid optical body interferometer that allows for the miniaturized sensing element of the device to be placed in the smallest of recesses, and measures a wide range of gas species and densities (leaks). The deflection of the fringe pattern is detected and recorded to yield the time-varying gas density in the gap. This technology can be used by manufacturers or storage facilities with toxic, hazardous, or explosive gases. The approach is to monitor the change in the index of refraction associated with low-level gas leaks into a vacuum environment. The completion of this work will provide NASA with an enabling capability to detect gas system leaks in space, and to verify that pressurized systems are in a safe (i.e. non-leaking) condition during manned docking and transit operations. By recording the output of the sensor, a time-history of the leak can be constructed to indicate its severity. Project risk is mitigated by having several interferometric geometries and detection techniques available, each potentially leveraging hardware and lessons learned to enhance detectability.

Improving the performance of interferometric imaging through the use of disturbance feedforward.

PubMed

Böhm, Michael; Glück, Martin; Keck, Alexander; Pott, Jörg-Uwe; Sawodny, Oliver

2017-05-01

In this paper, we present a disturbance compensation technique to improve the performance of interferometric imaging for extremely large ground-based telescopes, e.g., the Large Binocular Telescope (LBT), which serves as the application example in this contribution. The most significant disturbance sources at ground-based telescopes are wind-induced mechanical vibrations in the range of 8-60 Hz. Traditionally, their optical effect is eliminated by feedback systems, such as the adaptive optics control loop combined with a fringe tracking system within the interferometric instrument. In this paper, accelerometers are used to measure the vibrations. These measurements are used to estimate the motion of the mirrors, i.e., tip, tilt and piston, with a dynamic estimator. Additional delay compensation methods are presented to cancel sensor network delays and actuator input delays, improving the estimation result even more, particularly at higher frequencies. Because various instruments benefit from the implementation of telescope vibration mitigation, the estimator is implemented as a separate, independent software on the telescope, publishing the estimated values via multicast on the telescope's ethernet. Every client capable of using and correcting the estimated disturbances can subscribe and use these values in a feedforward for its compensation device, e.g., the deformable mirror, the piston mirror of LINC-NIRVANA, or the fast path length corrector of the Large Binocular Telescope Interferometer. This easy-to-use approach eventually leveraged the presented technology for interferometric use at the LBT and now significantly improves the sky coverage, performance, and operational robustness of interferometric imaging on a regular basis.

Towards coherent combination of 61 fiber amplifiers

NASA Astrophysics Data System (ADS)

Heilmann, Anke; Le Dortz, Jérémy; Daniault, Louis; Fsaifes, Ihsan; Bellanger, Séverine; Antier, Marie; Bourderionnet, Jérôme; Larat, Christian; Lallier, Eric; Durand, Eric; Brignon, Arnaud; Simon-Boisson, Christophe; Chanteloup, Jean-Christophe

2018-02-01

The XCAN project aims at the coherent combination of 61 fiber amplifiers in the femtosecond regime. An important intermediate step towards this goal is the implementation of a seven fiber test setup, which allows to address key scientific and technical challenges which might occur in the scaled version of 61 fibers. This work includes the design and characterization of a support unit able to hold 61 fibers with the high precision required for an efficient coherent combination in tiled aperture configuration. This configuration, in combination with an interferometric phase measurement and active phase control, is particularly well suited for the coherent combination of a very large number of beams. Our first preliminary results with seven fibers include a combination efficiency of 30 % and a residual phase error between two fibers as low as λ/40 rms. Experiments conducted with three fibers in order to evaluate technical improvements revealed an increase of efficiency to 54 %. The combined beam was temporally compressed to 225 fs, which is Fourier transform limited with respect to the measured spectrum.

Retinotopic and temporal organization of the optic nerve and tracts in the adult goldfish.

PubMed

Bunt, S M

1982-04-10

In order to investigate the role of the different factors controlling the pathways and termination sites of growing axons, selected optic fibers were traced from the eye to the tectum in adult goldfish either by filling them with HRP, or by severing a group of fibers and tracing their degeneration in 2 micrometers plastic sections stained with toluidine blue. Some fish received more than one lesion and others received both lesions and HRP applications. Two major rearrangements of the optic fibers were identified, one at the exit from the eye, the other within the optic tracts. Near the eye the optic fibers appear to be guided by the conformation of the underlying tissue planes that they encounter. The most recently added fibers, from the peripheral retina, grow over the vitread surface of the older fibers toward the blood vessel in the center of the optic nerve head. Behind the eye the fibers follow this blood vessel until it leaves the side of the optic nerve, and the fibers from peripheral retina are left as a single group on the ventral edge of the optic nerve cross section. As a consequence of this pattern of fiber growth the fibers form an orderly temporal sequence in the optic nerve, with the oldest fibers from the central retina on one side of the nerve and the youngest from peripheral retina on the other. In addition, the fibers are ordered topographically at right angles to this central-to-peripheral axis, with fibers from ventral retina on each edge of the nerve, dorsal fibers in the center, and nasal and temporal fibers in between. This arrangement of the optic fibers continues with only a little loss of precision up to the optic tracts. A more radical fiber rearrangement, seemingly incompatible with the fibers simply following tissue planes occurs within the optic tracts. Each newly arriving set of fibers grows over the surface of the optic tracts so that the older fibers come to lie deepest in the tracts. This segregation of fibers of different ages ensures that the rearrangement is limited to each layer of fibers. The abrupt reorganization of the fibers occurs as the tracts split around the nucleus rotundus to form the brachia of the optic tracts. The fibers are then arranged with temporal fibers nearest the nucleus rotundus and nasal fibers on the opposite edges of the brachia. From this point the fibers grow out over the tectal surface to their termination sites with only minimal rearrangements. Therefore the optic fiber rearrangements show evidence of several different sorts of constraints acting on the fibers at separate points in the optic pathway, each contributing to the final orderly arrangement of the fibers on the optic tectum.

Application of Nondestructive Testing Techniques to Materials Testing.

DTIC Science & Technology

1987-12-01

microscopy gives little quanti- image the center place of the Bragg cell to the back focal tative information on surface height. Nomarski differential...case we can write our technique in a shot-noise limited system, intensity (i2) f 2qloB = 2q 2 7PB measurements can yield interferometric accuracies. nh...comparable in sensitivity to OPTICAL AXIS phase-dependent interferometric techniques. Thedo--i thicknesses of photoresist films have been measured to f_

Method for optical and mechanically coupling optical fibers

DOEpatents

Toeppen, J.S.

1996-10-01

A method and apparatus are disclosed for splicing optical fibers. A fluorescing solder glass frit having a melting point lower than the melting point of first and second optical fibers is prepared. The solder glass frit is then attached to the end of the first optical fiber and/or the end of the second optical fiber. The ends of the optical fibers are aligned and placed in close proximity to each other. The solder glass frit is then heated to a temperature which is lower than the melting temperature of the first and second optical fibers, but which is high enough to melt the solder glass frit. A force is applied to the first and second optical fibers pushing the ends of the fibers towards each other. As the solder glass flit becomes molten, the layer of molten solder glass is compressed into a thin layer between the first and second optical fibers. The thin compressed layer of molten solder glass is allowed to cool such that the first and second optical fibers are bonded to each other by the hardened layer of solder glass. 6 figs.

Method for optical and mechanically coupling optical fibers

DOEpatents

Toeppen, John S.

1996-01-01

A method and apparatus for splicing optical fibers. A fluorescing solder glass frit having a melting point lower than the melting point of first and second optical fibers is prepared. The solder glass frit is then attached to the end of the first optical fiber and/or the end of the second optical fiber. The ends of the optical fibers are aligned and placed in close proximity to each other. The solder glass frit is then heated to a temperature which is lower than the melting temperature of the first and second optical fibers, but which is high enough to melt the solder glass frit. A force is applied to the first and second optical fibers pushing the ends of the fibers towards each other. As the solder glass flit becomes molten, the layer of molten solder glass is compressed into a thin layer between the first and second optical fibers. The thin compressed layer of molten solder glass is allowed to cool such that the first and second optical fibers are bonded to each other by the hardened layer of solder glass.

Refractive Index Compensation in Over-Determined Interferometric Systems

PubMed Central

Lazar, Josef; Holá, Miroslava; Číp, Ondřej; Čížek, Martin; Hrabina, Jan; Buchta, Zdeněk

2012-01-01

We present an interferometric technique based on a differential interferometry setup for measurement under atmospheric conditions. The key limiting factor in any interferometric dimensional measurement are fluctuations of the refractive index of air representing a dominating source of uncertainty when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of an over-determined interferometric setup where a reference length is derived from a mechanical frame made from a material with a very low thermal coefficient. The technique allows one to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range, acting as a tracking refractometer. The principle is demonstrated in an experimental setup. PMID:23202037

Refractive index compensation in over-determined interferometric systems.

PubMed

Lazar, Josef; Holá, Miroslava; Číp, Ondřej; Čížek, Martin; Hrabina, Jan; Buchta, Zdeněk

2012-10-19

We present an interferometric technique based on a differential interferometry setup for measurement under atmospheric conditions. The key limiting factor in any interferometric dimensional measurement are fluctuations of the refractive index of air representing a dominating source of uncertainty when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of an over-determined interferometric setup where a reference length is derived from a mechanical frame made from a material with a very low thermal coefficient. The technique allows one to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range, acting as a tracking refractometer. The principle is demonstrated in an experimental setup.

Multi-channel measurement for hetero-core optical fiber sensor by using CMOS camera

NASA Astrophysics Data System (ADS)

Koyama, Yuya; Nishiyama, Michiko; Watanabe, Kazuhiro

2015-07-01

Fiber optic smart structures have been developed over several decades by the recent fiber optic sensor technology. Optical intensity-based sensors, which use LD or LEDs, can be suitable for the monitor system to be simple and cost effective. In this paper, a novel fiber optic smart structure with human-like perception has been demonstrated by using intensity-based hetero-core optical fiber sensors system with the CMOS detector. The optical intensity from the hetero-core optical fiber bend sensor is obtained as luminance spots indicated by the optical power distributions. A number of optical intensity spots are simultaneously readout by taking a picture of luminance pattern. To recognize the state of fiber optic smart structure with the hetero-core optical fibers, the template matching process is employed with Sum of Absolute Differences (SAD). A fiber optic smart glove having five optic fiber nerves have been employed to monitor hand postures. Three kinds of hand postures have been recognized by means of the template matching process. A body posture monitoring has also been developed by placing the wearable hetero-core optical fiber bend sensors on the body segments. In order for the CMOS system to be a human brain-like, the luminescent spots in the obtained picture were arranged to make the pattern corresponding to the position of body segments. As a result, it was successfully demonstrated that the proposed fiber optic smart structure could recognize eight kinds of body postures. The developed system will give a capability of human brain-like processing to the existing fiber optic smart structures.

Optical fiber stripper positioning apparatus

DOEpatents

Fyfe, Richard W.; Sanchez, Jr., Amadeo

1990-01-01

An optical fiber positioning apparatus for an optical fiber stripping device is disclosed which is capable of providing precise axial alignment between an optical fiber to be stripped of its outer jacket and the cutting blades of a stripping device. The apparatus includes a first bore having a width approximately equal to the diameter of an unstripped optical fiber and a counter bore axially aligned with the first bore and dimensioned to precisely receive a portion of the stripping device in axial alignment with notched cutting blades within the stripping device to thereby axially align the notched cutting blades of the stripping device with the axis of the optical fiber to permit the notched cutting blades to sever the jacket on the optical fiber without damaging the cladding on the optical fiber. In a preferred embodiment, the apparatus further includes a fiber stop which permits determination of the length of jacket to be removed from the optical fiber.

A near-infrared interferometric survey of debris-disc stars. VI. Extending the exozodiacal light survey with CHARA/JouFLU

NASA Astrophysics Data System (ADS)

Nuñez, P. D.; Scott, N. J.; Mennesson, B.; Absil, O.; Augereau, J.-C.; Bryden, G.; ten Brummelaar, T.; Ertel, S.; Coudé du Foresto, V.; Ridgway, S. T.; Sturmann, J.; Sturmann, L.; Turner, N. J.; Turner, N. H.

2017-12-01

We report the results of high-angular-resolution observations that search for exozodiacal light in a sample of main sequence stars and sub-giants. Using the "jouvence" of the fiber linked unit for optical recombination (JouFLU) at the center for high angular resolution astronomy (CHARA) telescope array, we have observed a total of 44 stars. Out of the 44 stars, 33 are new stars added to the initial, previously published survey of 42 stars performed at CHARA with the fiber linked unit for optical recombination (FLUOR). Since the start of the survey extension, we have detected a K-band circumstellar excess for six new stars at the 1% level or higher, four of which are known or candidate binaries, and two for which the excess could be attributed to exozodiacal dust. We have also performed follow-up observations of 11 of the stars observed in the previously published survey and found generally consistent results. We do however detect a significantly larger excess on three of these follow-up targets: Altair, υ And and κ CrB. Interestingly, the last two are known exoplanet host stars. We perform a statistical analysis of the JouFLU and FLUOR samples combined, which yields an overall exozodi detection rate of . We also find that the K-band excess in FGK-type stars correlates with the existence of an outer reservoir of cold (≲100 K) dust at the 99% confidence level, while the same cannot be said for A-type stars.

Versatile generation of optical vector fields and vector beams using a non-interferometric approach.

PubMed

Tripathi, Santosh; Toussaint, Kimani C

2012-05-07

We present a versatile, non-interferometric method for generating vector fields and vector beams which can produce all the states of polarization represented on a higher-order Poincaré sphere. The versatility and non-interferometric nature of this method is expected to enable exploration of various exotic properties of vector fields and vector beams. To illustrate this, we study the propagation properties of some vector fields and find that, in general, propagation alters both their intensity and polarization distribution, and more interestingly, converts some vector fields into vector beams. In the article, we also suggest a modified Jones vector formalism to represent vector fields and vector beams.

Optical spatial heterodyne interferometric Fourier transform technique (OSHIFT) and a resulting interferometer

NASA Astrophysics Data System (ADS)

Georges, James A., III

2007-09-01

This article reports on the novel patent pending Optical Spatial Heterodyne Interferometric Fourier Transform Technique (the OSHIFT technique), the resulting interferometer also referred to as OSHIFT, and its preliminary results. OSHIFT was borne out of the following requirements: wavefront sensitivity on the order of 1/100 waves, high-frequency wavefront spatial sampling, snapshot 100Hz operation, and the ability to deal with discontinuous wavefronts. The first two capabilities lend themselves to the use of traditional interferometric techniques; however, the last two prove difficult for standard techniques, e.g., phase shifting interferometry tends to take a time sequence of images and most interferometers require estimation of a center fringe across wavefront discontinuities. OSHIFT overcomes these challenges by employing a spatial heterodyning concept in the Fourier (image) plane of the optic-under-test. This concept, the mathematical theory, an autocorrelation view of operation, and the design with results of OSHIFT will be discussed. Also discussed will be future concepts such as a sensor that could interrogate an entire imaging system as well as a methodology to create innovative imaging systems that encode wavefront information onto the image. Certain techniques and systems described in this paper are the subject of a patent application currently pending in the United States Patent Office.

Low-coherence interferometric sensor system utilizing an integrated optics configuration

NASA Astrophysics Data System (ADS)

Plissi, M. V.; Rogers, A. J.; Brassington, D. J.; Wilson, M. G. F.

1995-08-01

The implementation of a twin Mach-Zehnder reference interferometer in an integrated optics substrate is described. From measurements of the fringe visibilities, an identification of the fringe order is attempted as a way to provide an absolute sensor for any parameter capable of modifying the difference in path length between two interfering optical paths.

Fiber optic vibration sensor

DOEpatents

Dooley, Joseph B.; Muhs, Jeffrey D.; Tobin, Kenneth W.

1995-01-01

A fiber optic vibration sensor utilizes two single mode optical fibers supported by a housing with one optical fiber fixedly secured to the housing and providing a reference signal and the other optical fiber having a free span length subject to vibrational displacement thereof with respect to the housing and the first optical fiber for providing a signal indicative of a measurement of any perturbation of the sensor. Damping or tailoring of the sensor to be responsive to selected levels of perturbation is provided by altering the diameter of optical fibers or by immersing at least a portion of the free span length of the vibration sensing optical fiber into a liquid of a selected viscosity.

Fiber optic vibration sensor

DOEpatents

Dooley, J.B.; Muhs, J.D.; Tobin, K.W.

1995-01-10

A fiber optic vibration sensor utilizes two single mode optical fibers supported by a housing with one optical fiber fixedly secured to the housing and providing a reference signal and the other optical fiber having a free span length subject to vibrational displacement thereof with respect to the housing and the first optical fiber for providing a signal indicative of a measurement of any perturbation of the sensor. Damping or tailoring of the sensor to be responsive to selected levels of perturbation is provided by altering the diameter of optical fibers or by immersing at least a portion of the free span length of the vibration sensing optical fiber into a liquid of a selected viscosity. 2 figures.

Computer simulations of interferometric imaging with the Very Large Telescope Interferometer and its Astronomical Multibeam Recombiner instrument

NASA Astrophysics Data System (ADS)

Przygodda, Frank; Bloecker, Thomas; Hofmann, Karl-Heinz; Weigelt, Gerd

2001-05-01

We present computer simulations of interferometric imaging with the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory and the Astronomical Multibeam Recombiner (AMBER) phase-closure instrument. These simulations include both the astrophysical modeling of a stellar object by radiative-transfer calculations and the simulation of light propagation from the object to the detector (through atmosphere, telescopes, and the AMBER instrument), simulation of photon noise and detector readout noise, and finally data processing of the interferograms. The results show the dependence of the visibility error bars on the following observational parameters: different seeing during the observation of object and reference star (Fried parameters r0,object and r0,ref ranging between 0.9 and 1.2 m), different residual tip-tilt error ((delta) tt,object and (delta) tt,ref ranging between 0.1% and 20% of the Airy-disk diameter), and object brightness (Kobject equals 0.7 to 10.2 mag, Kref equals 0.7 mag). As an example, we focus on stars in late stages of stellar evolution and study one of the key objects of that kind, the dusty super-giant IRC + 10420, which is rapidly evolving on human time scales. We show computer simulations of VLT interferometer (visibility and phase-closure measurements) of IRC + 10420 with two and three auxiliary telescopes (in AMBER wide-field mode, i.e., without fiber optic spatial filters) and discuss whether the visibility accuracy is sufficient to distinguish between different theoretical model predictions.

Modal Filters for Infrared Interferometry

NASA Technical Reports Server (NTRS)

Ksendzov, Alexander; MacDonald, Daniel R.; Soibel, Alexander

2009-01-01

Modal filters in the approximately equal to 10-micrometer spectral range have been implemented as planar dielectric waveguides in infrared interferometric applications such as searching for Earth-like planets. When looking for a small, dim object ("Earth") in close proximity to a large, bright object ("Sun"), the interferometric technique uses beams from two telescopes combined with a 180 phase shift in order to cancel the light from a brighter object. The interferometer baseline can be adjusted so that, at the same time, the light from the dimmer object arrives at the combiner in phase. This light can be detected and its infrared (IR) optical spectra can be studied. The cancellation of light from the "Sun" to approximately equal to 10(exp 6) is required; this is not possible without special devices-modal filters- that equalize the wavefronts arriving from the two telescopes. Currently, modal filters in the approximately equal to 10-micrometer spectral range are implemented as single- mode fibers. Using semiconductor technology, single-mode waveguides for use as modal filters were fabricated. Two designs were implemented: one using an InGaAs waveguide layer matched to an InP substrate, and one using InAlAs matched to an InP substrate. Photon Design software was used to design the waveguides, with the main feature all designs being single-mode operation in the 10.5- to 17-micrometer spectral range. Preliminary results show that the filter's rejection ratio is 26 dB.

Design of fiber optic probes for laser light scattering

NASA Technical Reports Server (NTRS)

Dhadwal, Harbans S.; Chu, Benjamin

1989-01-01

A quantitative analysis is presented of the role of optical fibers in laser light scattering. Design of a general fiber optic/microlens probe by means of ray tracing is described. Several different geometries employing an optical fiber of the type used in lightwave communications and a graded index microlens are considered. Experimental results using a nonimaging fiber optic detector probe show that due to geometrical limitations of single mode fibers, a probe using a multimode optical fiber has better performance, for both static and dynamic measurements of the scattered light intensity, compared with a probe using a single mode fiber. Fiber optic detector probes are shown to be more efficient at data collection when compared with conventional approaches to measurements of the scattered laser light. Integration of fiber optic detector probes into a fiber optic spectrometer offers considerable miniaturization of conventional light scattering spectrometers, which can be made arbitrarily small. In addition static and dynamic measurements of scattered light can be made within the scattering cell and consequently very close to the scattering center.

Spectral interferometric microscopy reveals absorption by individual optical nanoantennas from extinction phase

PubMed Central

Gennaro, Sylvain D.; Sonnefraud, Yannick; Verellen, Niels; Van Dorpe, Pol; Moshchalkov, Victor V.; Maier, Stefan A.; Oulton, Rupert F.

2014-01-01

Optical antennas transform light from freely propagating waves into highly localized excitations that interact strongly with matter. Unlike their radio frequency counterparts, optical antennas are nanoscopic and high frequency, making amplitude and phase measurements challenging and leaving some information hidden. Here we report a novel spectral interferometric microscopy technique to expose the amplitude and phase response of individual optical antennas across an octave of the visible to near-infrared spectrum. Although it is a far-field technique, we show that knowledge of the extinction phase allows quantitative estimation of nanoantenna absorption, which is a near-field quantity. To verify our method we characterize gold ring-disk dimers exhibiting Fano interference. Our results reveal that Fano interference only cancels a bright mode’s scattering, leaving residual extinction dominated by absorption. Spectral interference microscopy has the potential for real-time and single-shot phase and amplitude investigations of isolated quantum and classical antennas with applications across the physical and life sciences. PMID:24781663

Fiber optic sensor and method for making

DOEpatents

Vartuli, James Scott; Bousman, Kenneth Sherwood; Deng, Kung-Li; McEvoy, Kevin Paul; Xia, Hua

2010-05-18

A fiber optic sensor including a fiber having a modified surface integral with the fiber wherein the modified surface includes an open pore network with optical agents dispersed within the open pores of the open pore network. Methods for preparing the fiber optic sensor are also provided. The fiber optic sensors can withstand high temperatures and harsh environments.

Optical-Fiber Fluorosensors With Polarized Light Sources

NASA Technical Reports Server (NTRS)

Egalon, Claudio O.; Rogowski, Robert S.

1995-01-01

Chemiluminescent and/or fluorescent molecules in optical-fiber fluorosensors oriented with light-emitting dipoles along transverse axis. Sensor of proposed type captures greater fraction of chemiluminescence or fluorescence and transmits it to photodetector. Transverse polarization increases sensitivity. Basic principles of optical-fiber fluorosensors described in "Making Optical-Fiber Chemical Sensors More Sensitive" (LAR-14525), "Improved Optical-Fiber Chemical Sensors" (LAR-14607), and "Improved Optical-Fiber Temperature Sensors" (LAR-14647).

All-optical clocked delay flip-flop using a single terahertz optical asymmetric demultiplexer-based switch: a theoretical study.

PubMed

Chattopadhyay, Tanay

2010-10-01

A flip-flop (FF) is a kind of latch and the simplest form of memory device, which stores various values either temporarily or permanently. Optical FF memories form a fundamental building block for all-optical packet switches in next-generation communication networks. An all-optical clocked delay FF using a single terahertz optical asymmetric demultiplexer-based interferometric switch is proposed and described. Numerical simulation results are also reported.

Refractive index retrieving of polarization maintaining optical fibers

NASA Astrophysics Data System (ADS)

Ramadan, W. A.; Wahba, H. H.; Shams El-Din, M. A.; Abd El-Sadek, I. G.

2018-01-01

In this paper, the cross-section images, of two different types of polarization maintaining (PM) optical fibers, are employed to estimate the optical phase variation due to transverse optical rays passing through these optical fibers. An adaptive algorithm is proposed to recognize the different areas constituting the PM optical fibers cross-sections. These areas are scanned by a transverse beam to calculate the optical paths for given values of refractive indices. Consequently, the optical phases across the PM optical fibers could be recovered. PM optical fiber is immersed in a matching fluid and set in the object arm of Mach-Zehnder interferometer. The produced interferograms are analyzed to extract the optical phases caused by the PM optical fibers. The estimated optical phases could be optimized to be in good coincidence with experimentally extracted ones. This has been achieved through changing of the PM optical fibers refractive indices to retrieve the correct values. The correct refractive indices values are confirmed by getting the best fit between the estimated and the extracted optical phases. The presented approach is a promising one because it provides a quite direct and accurate information about refractive index, birefringence and beat length of PM optical fibers comparing with different techniques handle the same task.

Fiber optic crossbar switch for automatically patching optical signals

NASA Technical Reports Server (NTRS)

Bell, C. H. (Inventor)

1983-01-01

A system for automatically optically switching fiber optic data signals between a plurality of input optical fibers and selective ones of a plurality of output fibers is described. The system includes optical detectors which are connected to each of the input fibers for converting the optic data signals appearing at the respective input fibers to an RF signal. A plurality of RF to optical signal converters are arranged in rows and columns. The output of each of the optical detectors are each applied to a respective row of optical signal converted for being converters back to an optical signal when the particular optical signal converter is selectively activated by a dc voltage.

Optical fiber end-facet polymer suspended-mirror devices

NASA Astrophysics Data System (ADS)

Yao, Mian; Wu, Jushuai; Zhang, A. Ping; Tam, Hwa-Yaw; Wai, P. K. A.

2017-04-01

This paper presents a novel optical fiber device based on a polymer suspended mirror on the end facet of an optical fiber. With an own-developed optical 3D micro-printing technology, SU-8 suspended-mirror devices (SMDs) were successfully fabricated on the top of a standard single-mode optical fiber. Optical reflection spectra of the fabricated SU- 8 SMDs were measured and compared with theoretical analysis. The proposed technology paves a way towards 3D microengineering of the small end-facet of optical fibers to develop novel fiber-optic sensors.

Optical Metrology for the Segmented Optics on the Constellation-X Spectroscopy X-Ray Telescope

NASA Technical Reports Server (NTRS)

Content, David; Colella, David; Fleetwood, Charles; Hadjimichael, Theo; Lehan, John; McMann, Joseph; Reid, Paul; Saha, Timo; Wright, Geraldine; Zhang, William

2004-01-01

We present the metrology requirements and metrology implementation necessary to prove out the reflector technology for the Constellation X(C-X) spectroscopy X-ray telescope (SXT). This segmented, 1.6m diameter highly nested Wolter-1 telescope presents many metrology and alignment challenges. In particular, these mirrors have a stringent imaging error budget as compared to their intrinsic stiffness; This is required for Constellation-X to have sufficient effective area with the weight requirement. This has implications for the metrology that can be used. A variety of contract and noncontact optical profiling and interferometric methods are combined to test the formed glass substrates before replication and the replicated reflector segments.The reflectors are tested both stand-alone and in-situ in an alignment tower.Some of these methods have not been used on prior X-ray telescopes and some are feasible only because of the segmented approach used on the SXT. Methods discussed include high precision coordinate measurement machines using very low force or optical probe axial interferometric profiling azimuthal circularity profiling and use of advanced null optics such as conical computer generated hologram (CGHs).

Improved Optical Fiber Chemical Sensors

NASA Technical Reports Server (NTRS)

Egalon, Claudio O.; Rogowski, Robert S.

1994-01-01

Calculations, based on exact theory of optical fiber, have shown how to increase optical efficiency sensitivity of active-core, step-index-profile optical-fiber fluorosensor. Calculations result of efforts to improve efficiency of optical-fiber chemical sensor of previous concept described in "Making Optical-Fiber Chemical Sensors More Sensitive" (LAR-14525). Optical fiber chemical detector of enhanced sensitivity made in several configurations. Portion of fluorescence or chemiluminescence generated in core, and launched directly into bound electromagnetic modes that propagate along core to photodetector.

Architectures of fiber optic network in telecommunications

NASA Astrophysics Data System (ADS)

Vasile, Irina B.; Vasile, Alexandru; Filip, Luminita E.

2005-08-01

The operators of telecommunications have targeted their efforts towards realizing applications using broad band fiber optics systems in the access network. Thus, a new concept related to the implementation of fiber optic transmission systems, named FITL (Fiber In The Loop) has appeared. The fiber optic transmission systems have been extensively used for realizing the transport and intercommunication of the public telecommunication network, as well as for assuring the access to the telecommunication systems of the great corporations. Still, the segment of the residential users and small corporations did not benefit on large scale of this technology implementation. For the purpose of defining fiber optic applications, more types of architectures were conceived, like: bus, ring, star, tree. In the case of tree-like networks passive splitters (that"s where the name of PON comes from - Passive Optical Network-), which reduce significantly the costs of the fiber optic access, by separating the costs of the optical electronic components. That's why the passive fiber optics architectures (PON represent a viable solution for realizing the access at the user's loop. The main types of fiber optics architectures included in this work are: FTTC (Fiber To The Curb); FTTB (Fiber To The Building); FTTH (Fiber To The Home).

Characterisation of a cryostat using simultaneous, single-beam multiple-surface laser vibrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kissinger, Thomas; Charrett, Thomas O. H.; James, Stephen W.

2016-06-28

A novel range-resolved interferometric signal processing technique that uses sinusoidal optical frequency modulation is applied to multi-surface vibrometry, demonstrating simultaneous optical measurements of vibrations on two surfaces using a single, collimated laser beam, with a minimum permissible distance of 3.5 cm between surfaces. The current system, using a cost-effective laser diode and a fibre-coupled, downlead insensitive setup, allows an interferometric fringe rate of up to 180 kHz to be resolved with typical displacement noise levels of 8 pm · Hz{sup −05}. In this paper, the system is applied to vibrometry measurements of a table-top cryostat, with concurrent measurements of the optical widowmore » and the sample holder target inside. This allows the separation of common-mode vibrations of the whole cryostat from differential vibrations between the window and the target, allowing any resonances to be identified.« less

Application Of Interferometry To Optical Components And Systems Evaluation

NASA Astrophysics Data System (ADS)

Houston, Joseph B., Jr.

1982-05-01

Interferometry provides opticians and lens designers with the ability to evaluate optical components and systems quantitatively. A variety of interferometers and interferometric test procedures have evolved over the past several decades. This evolution has stimulated an ever-increasing amount of interest in using a new generation of instrumentation and computer software for solving cost and schedule problems both in the shop and at field test sites. Optical engineers and their customers continue to gain confidence in their abilities to perform several operations such as assure component quality, analyze and optimize lens assemblies, and accurately predict end-item performance. In this paper, a set of typical test situations are addressed and some standard instrumentation is described, as a means of illustrating the special advantages of interferometric testing. Emphasis will be placed on the proper application of currently available hardware and some of the latest proven techniques.

Reflectance-mode interferometric near-infrared spectroscopy quantifies brain absorption, scattering, and blood flow index in vivo.

PubMed

Borycki, Dawid; Kholiqov, Oybek; Srinivasan, Vivek J

2017-02-01

Interferometric near-infrared spectroscopy (iNIRS) is a new technique that measures time-of-flight- (TOF-) resolved autocorrelations in turbid media, enabling simultaneous estimation of optical and dynamical properties. Here, we demonstrate reflectance-mode iNIRS for noninvasive monitoring of a mouse brain in vivo. A method for more precise quantification with less static interference from superficial layers, based on separating static and dynamic components of the optical field autocorrelation, is presented. Absolute values of absorption, reduced scattering, and blood flow index (BFI) are measured, and changes in BFI and absorption are monitored during a hypercapnic challenge. Absorption changes from TOF-resolved iNIRS agree with absorption changes from continuous wave NIRS analysis, based on TOF-integrated light intensity changes, an effective path length, and the modified Beer-Lambert Law. Thus, iNIRS is a promising approach for quantitative and noninvasive monitoring of perfusion and optical properties in vivo.

Eliminating crystals in non-oxide optical fiber preforms and optical fibers

NASA Technical Reports Server (NTRS)

LaPointe, Michael R. (Inventor); Tucker, Dennis S. (Inventor)

2010-01-01

A method is provided for eliminating crystals in non-oxide optical fiber preforms as well as optical fibers drawn therefrom. The optical-fiber-drawing axis of the preform is aligned with the force of gravity. A magnetic field is applied to the preform as it is heated to at least a melting temperature thereof. The magnetic field is applied in a direction that is parallel to the preform's optical-fiber-drawing axis. The preform is then cooled to a temperature that is less than a glass transition temperature of the preform while the preform is maintained in the magnetic field. When the processed preform is to have an optical fiber drawn therefrom, the preform's optical-fiber-drawing axis is again aligned with the force of gravity and a magnetic field is again applied along the axis as the optical fiber is drawn from the preform.

Lab-on-fiber electrophoretic trace mixture separating and detecting an optofluidic device based on a microstructured optical fiber.

PubMed

Yang, Xinghua; Guo, Xiaohui; Li, Song; Kong, Depeng; Liu, Zhihai; Yang, Jun; Yuan, Libo

2016-04-15

We report an in-fiber integrated electrophoretic trace mixture separating and detecting an optofluidic optical fiber sensor based on a specially designed optical fiber. In this design, rapid in situ separation and simultaneous detection of mixed analytes can be realized under electro-osmotic flow in the microstructured optical fiber. To visually display the in-fiber separating and detecting process, two common fluorescent indicators are adopted as the optofluidic analytes in the optical fiber. Results show that a trace amount of the mixture (0.15 μL) can be completely separated within 3.5 min under a high voltage of 5 kV. Simultaneously, the distributed information of the separated analytes in the optical fiber can be clearly obtained by scanning along the optical fiber using a 355 nm laser. The emission from the analytes can be efficiently coupled into the inner core and guides to the remote end of the optical fiber. In addition, the thin cladding around the inner core in the optical fiber can prevent the fluorescent cross talk between the analytes in this design. Compared to previous optical fiber optofluidic devices, this device first realizes simultaneously separating treatment and the detection of the mixed samples in an optical fiber. Significantly, such an in-fiber integrated separating and detecting optofluidic device can find wide applications in various analysis fields involves mixed samples, such as biology, chemistry, and environment.

Interferometric Methods of Measuring Refractive Indices and Double-Refraction of Fibres.

ERIC Educational Resources Information Center

Hamza, A. A.; El-Kader, H. I. Abd

1986-01-01

Presents two methods used to measure the refractive indices and double-refraction of fibers. Experiments are described, with one involving the use of Pluta microscope in the double-beam interference technique, the other employing the multiple-beam technique. Immersion liquids are discussed that can be used in the experiments. (TW)

Fiber optic coupled optical sensor

DOEpatents

Fleming, Kevin J.

2001-01-01

A displacement sensor includes a first optical fiber for radiating light to a target, and a second optical fiber for receiving light from the target. The end of the first fiber is adjacent and not axially aligned with the second fiber end. A lens focuses light from the first fiber onto the target and light from the target onto the second fiber.

Design of a space-based infrared imaging interferometer

NASA Astrophysics Data System (ADS)

Hart, Michael; Hope, Douglas; Romeo, Robert

2017-07-01

Present space-based optical imaging sensors are expensive. Launch costs are dictated by weight and size, and system design must take into account the low fault tolerance of a system that cannot be readily accessed once deployed. We describe the design and first prototype of the space-based infrared imaging interferometer (SIRII) that aims to mitigate several aspects of the cost challenge. SIRII is a six-element Fizeau interferometer intended to operate in the short-wave and midwave IR spectral regions over a 6×6 mrad field of view. The volume is smaller by a factor of three than a filled-aperture telescope with equivalent resolving power. The structure and primary optics are fabricated from light-weight space-qualified carbon fiber reinforced polymer; they are easy to replicate and inexpensive. The design is intended to permit one-time alignment during assembly, with no need for further adjustment once on orbit. A three-element prototype of the SIRII imager has been constructed with a unit telescope primary mirror diameter of 165 mm and edge-to-edge baseline of 540 mm. The optics, structure, and interferometric signal processing principles draw on experience developed in ground-based astronomical applications designed to yield the highest sensitivity and resolution with cost-effective optical solutions. The initial motivation for the development of SIRII was the long-term collection of technical intelligence from geosynchronous orbit, but the scalable nature of the design will likely make it suitable for a range of IR imaging scenarios.

Cable delay compensator for microwave signal distribution over optical fibers

NASA Astrophysics Data System (ADS)

Primas, Lori E.

1990-12-01

The basic principles of microwave fiber-optic systems are outlined with emphasis on fiber-optic cable delay compensators (CDC). Degradation of frequency and phase stability is considered, and it is pointed out that the long-term stability of a fiber-optic link is degraded by group delay variations due to temperature fluctuations in the optical fiber and low-frequency noise characteristics of the laser. A CDC employing a voltage-controlled oscillator to correct for phase variations in the optical fiber is presented, and the static as well as dynamic closed-loop analyses of the fiber-optic CDC are discussed. A constructed narrow-band fiber-optic CDC is shown to reduce phase variations caused by temperature fluctuations by a factor of 400. A wide-band CDC utilizing a temperature-controlled coil of fiber to compensate for phase delay is also proposed.

Omnidirectional fiber optic tiltmeter

DOEpatents

Benjamin, B.C.; Miller, H.M.

1983-06-30

A tiltmeter is provided which is useful in detecting very small movements such as earth tides. The device comprises a single optical fiber, and an associated weight affixed thereto, suspended from a support to form a pendulum. A light source, e.g., a light emitting diode, mounted on the support transmits light through the optical fiber to a group of further optical fibers located adjacent to but spaced from the free end of the single optical fiber so that displacement of the single optical fiber with respect to the group will result in a change in the amount of light received by the individual optical fibers of the group. Photodetectors individually connectd to the fibers produce corresponding electrical outputs which are differentially compared and processed to produce a resultant continuous analog output representative of the amount and direction of displacement of the single optical fiber.

Enhanced radiation resistant fiber optics

DOEpatents

Lyons, Peter B.; Looney, Larry D.

1993-01-01

A process for producing an optical fiber having enhanced radiation resitance is provided, the process including maintaining an optical fiber within a hydrogen-containing atmosphere for sufficient time to yield a hydrogen-permeated optical fiber having an elevated internal hydrogen concentration, and irradiating the hydrogen-permeated optical fiber at a time while the optical fiber has an elevated internal hydrogen concentration with a source of ionizing radiation. The radiation source is typically a cobalt-60 source and the fiber is pre-irradiated with a dose level up to about 1000 kilorads of radiation.

Enhanced radiation resistant fiber optics

DOEpatents

Lyons, P.B.; Looney, L.D.

1993-11-30

A process for producing an optical fiber having enhanced radiation resistance is provided, the process including maintaining an optical fiber within a hydrogen-containing atmosphere for sufficient time to yield a hydrogen-permeated optical fiber having an elevated internal hydrogen concentration, and irradiating the hydrogen-permeated optical fiber at a time while the optical fiber has an elevated internal hydrogen concentration with a source of ionizing radiation. The radiation source is typically a cobalt-60 source and the fiber is pre-irradiated with a dose level up to about 1000 kilorads of radiation. 4 figures.

Evaluation of insertion characteristics of less invasive Si optoneural probe with embedded optical fiber

NASA Astrophysics Data System (ADS)

Morikawa, Takumi; Harashima, Takuya; Kino, Hisashi; Fukushima, Takafumi; Tanaka, Tetsu

2017-04-01

A less invasive Si optoneural probe with an embedded optical fiber was proposed and successfully fabricated. The diameter of the optical fiber was completely controlled by hydrogen fluoride etching, and the thinned optical fiber can propagate light without any leakage. This optical fiber was embedded in a trench formed inside a probe shank, which causes less damage to tissues. In addition, it was confirmed that the optical fiber embedded in the probe shank successfully irradiated light to optically stimulate gene transfected neurons. The electrochemical impedance of the probe did not change despite the light irradiation. Furthermore, probe insertion characteristics were evaluated in detail and less invasive insertion was clearly indicated for the Si optoneural probe with the embedded optical fiber compared with conventional optical neural probes. This neural probe with the embedded optical fiber can be used as a simple and easy tool for optogenetics and brain science.

Tapered fiber nanoprobes: plasmonic nanopillars on tapered optical fiber tips for large EM enhancement.

PubMed

Savaliya, Priten; Dhawan, Anuj

2016-10-01

Employing finite difference time domain simulations, we demonstrate that electromagnetic field enhancement is substantially greater for tapered optical fibers with plasmonic nanostructures present on their tips as compared with non-tapered optical fibers having those plasmonic nanostructures, or with tapered optical fibers without the plasmonic nanostructures. We also carried out fabrication of plasmonic nanostructures on optical fiber tips.

Refractive-index profiling of embedded microstructures in optical materials

NASA Astrophysics Data System (ADS)

Dave, Digant P.; Milner, Thomas E.

2002-04-01

We describe use of a phase-sensitive low-coherence reflectometer to measure spatial variation of refractive index in optical materials. The described interferometric technique is demonstrated to be a valuable tool to profile the refractive index of optical elements such as integrated waveguides and photowritten optical microstructures. As an example, a refractive-index profile is mapped of a microstructure written in a microscope glass slide with an ultrashort-pulse laser.

Optical fibers and their applications 2012

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.; Wójcik, Waldemar

2013-01-01

XIVth Conference on Optical Fibers and Their Applications, Nałęczów 2012, which has been organized since more than 35 years, has summarized the achievements of the local optical fiber technology community, for the last year and a half. The conference specializes in developments of optical fiber technology, glass and polymer, classical and microstructured, passive and active. The event gathered around 100 participants. There were shown 60 presentations from 20 research and application groups active in fiber photonics, originating from academia and industry. Topical tracks of the Conference were: photonic materials, planar waveguides, passive and active optical fibers, propagation theory in nonstandard optical fibers, and new constructions of optical fibers. A panel discussion concerned teaching in fiber photonics. The conference was accompanied by a school on Optical Fiber Technology. The paper summarizes the chosen main topical tracks of the conference on Optical Fibers and Their Applications, Nałęczów 2012. The papers from the conference presentations will be published in Proc.SPIE. The next conference from this series is scheduled for January 2014 in Białowieża.

Interferometry On Grazing Incidence Optics

NASA Astrophysics Data System (ADS)

Geary, Joseph; Maeda, Riki

1988-08-01

A preliminary interferometric procedure is described showing potential for obtaining surface figure error maps of grazing incidence optics at normal incidence. The latter are found in some laser resonator configurations, and in Wolter type X-ray optics. The procedure makes use of cylindrical wavefronts and error subtraction techniques over subapertures. The surface error maps obtained will provide critical information to opticians in the fabrication process.

Fiber optic sensors

NASA Technical Reports Server (NTRS)

Hesse, J.; Sohler, W.

1984-01-01

A survey of the developments in the field of fiber optics sensor technology is presented along with a discussion of the advantages of optical measuring instruments as compared with electronic sensors. The two primary types of fiber optics sensors, specifically those with multiwave fibers and those with monowave fibers, are described. Examples of each major sensor type are presented and discussed. Multiwave detectors include external and internal fiber optics sensors. Among the monowave detectors are Mach-Zender interferometers, Michelson interferometers, Sagnac interferometers (optical gyroscopes), waveguide resonators, and polarimeter sensors. Integrated optical sensors and their application in spectroscopy are briefly discussed.

Demonstration of an ultra-wideband optical fiber inline polarizer with metal nano-grid on the fiber tip.

PubMed

Lin, Yongbin; Guo, Junpeng; Lindquist, Robert G

2009-09-28

Dramatic increase in the bandwidth of optical fiber inline polarizer can be achieved by using metal nano-grid on the fiber tip. However, high extinction ratio of such fiber polarizer requires high spatial frequency metal nano girds with high aspect ratio on the small area of optical fiber tip. We report the development of a nano-fabrication process on the optical fiber tip, and the design and realization of the first ultra-wideband fiber inline polarization device with Au nano gird fabricated on a single mode optical fiber end face.

Investigation of cladding and coating stripping methods for specialty optical fibers

NASA Astrophysics Data System (ADS)

Lee, Jung-Ryul; Dhital, Dipesh; Yoon, Dong-Jin

2011-03-01

Fiber optic sensing technology is used extensively in several engineering fields, including smart structures, health and usage monitoring, non-destructive testing, minimum invasive sensing, safety monitoring, and other advanced measurement fields. A general optical fiber consists of a core, cladding, and coating layers. Many sensing principles require that the cladding or coating layer should be removed or modified. In addition, since different sensing systems are needed for different types of optical fibers, it is very important to find and sort out the suitable cladding or coating removal method for a particular fiber. This study focuses on finding the cladding and coating stripping methods for four recent specialty optical fibers, namely: hard polymer-clad fiber, graded-index plastic optical fiber, copper/carbon-coated optical fiber, and aluminum-coated optical fiber. Several methods, including novel laser stripping and conventional chemical and mechanical stripping, were tried to determine the most suitable and efficient technique. Microscopic investigation of the fiber surfaces was used to visually evaluate the mechanical reliability. Optical time domain reflectometric signals of the successful removal cases were investigated to further examine the optical reliability. Based on our results, we describe and summarize the successful and unsuccessful methods.

Optical and mechanical response of high temperature optical fiber sensors

NASA Technical Reports Server (NTRS)

Sirkis, Jim

1991-01-01

The National Aerospace Plane (NASP) will experience temperatures as high as 2500 F at critical locations in its structure. Optical fiber sensors were proposed as a means of monitoring the temperature in these critical regions by either bonding the optical fiber to, or embedding the optical fiber in, metal matrix composite (MMC) components. Unfortunately, the anticipated NASP temperature ranges exceed the glass transition region of the optical fiber glass. The attempt is made to define the operating temperature range of optical fiber sensors from both optical and mechanical perspectives. A full non-linear optical analysis was performed by modeling the optical response of an isolated sensor cyclically driven through the glass transition region.

Fiber Optic Temperature Sensor Insert for High Temperature Environments

NASA Technical Reports Server (NTRS)

Black, Richard James (Inventor); Costa, Joannes M. (Inventor); Moslehi, Behzad (Inventor); Zarnescu, Livia (Inventor)

2017-01-01

A thermal protection system (TPS) test plug has optical fibers with FBGs embedded in the optical fiber arranged in a helix, an axial fiber, and a combination of the two. Optionally, one of the optical fibers is a sapphire FBG for measurement of the highest temperatures in the TPS plug. The test plug may include an ablating surface and a non-ablating surface, with an engagement surface with threads formed, the threads having a groove for placement of the optical fiber. The test plug may also include an optical connector positioned at the non-ablating surface for protection of the optical fiber during insertion and removal.

Liquid-filled hollow core microstructured polymer optical fiber.

PubMed

Cox, F M; Argyros, A; Large, M C J

2006-05-01

Guidance in a liquid core is possible with microstructured optical fibers, opening up many possibilities for chemical and biochemical fiber-optic sensing. In this work we demonstrate how the bandgaps of a hollow core microstructured polymer optical fiber scale with the refractive index of liquid introduced into the holes of the microstructure. Such a fiber is then filled with an aqueous solution of (-)-fructose, and the resulting optical rotation measured. Hence, we show that hollow core microstructured polymer optical fibers can be used for sensing, whilst also fabricating a chiral optical fiber based on material chirality, which has many applications in its own right.

Optical-fiber-to-waveguide coupling using carbon-dioxide-laser-induced long-period fiber gratings.

PubMed

Bachim, Brent L; Ogunsola, Oluwafemi O; Gaylord, Thomas K

2005-08-15

Optical fibers are expected to play a role in chip-level and board-level optical interconnects because of limitations on the bandwidth and level of integration of electrical interconnects. Therefore, methods are needed to couple optical fibers directly to waveguides on chips and on boards. We demonstrate optical-fiber-to-waveguide coupling using carbon-dioxide laser-induced long-period fiber gratings (LPFGs). Such gratings can be written in standard fiber and offer wavelength multiplexing-demultiplexing performance. The coupler fabrication process and the characterization apparatus are presented. The operation and the wavelength response of a LPFG-based optical-fiber-to-waveguide directional coupler are demonstrated.

Fiber Coupled Laser Diodes with Even Illumination Pattern

NASA Technical Reports Server (NTRS)

Howard, Richard T. (Inventor)

2007-01-01

An optical fiber for evenly illuminating a target. The optical fiber is coupled to a laser emitting diode and receives laser light. The la ser light travels through the fiber optic and exits at an exit end. T he exit end has a diffractive optical pattern formed thereon via etch ing, molding or cutting, to reduce the Gaussian profile present in co nventional fiber optic cables The reduction of the Gaussian provides an even illumination from the fiber optic cable.

Two classes of capillary optical fibers: refractive and photonic

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2008-11-01

This paper is a digest tutorial on some properties of capillary optical fibers (COF). Two basic types of capillary optical fibers are clearly distinguished. The classification is based on propagation mechanism of optical wave. The refractive, singlemode COF guides a dark hollow beam of light (DHB) with zero intensity on fiber axis. The photonic, singlemode COF carries nearly a perfect axial Gaussian beam with maximum intensity on fiber axis. A subject of the paper are these two basic kinds of capillary optical fibers of pure refractive and pure photonic mechanism of guided wave transmission. In a real capillary the wave may be transmitted by a mixed mechanism, refractive and photonic, with strong interaction of photonic and refractive guided wave modes. Refractive capillary optical fibers are used widely for photonic instrumentation applications, while photonic capillary optical fibers are considered for trunk optical communications. Replacement of classical, single mode, dispersion shifted, 1550nm optimized optical fibers for communications with photonic capillaries would potentially cause a next serious revolution in optical communications. The predictions say that such a revolution may happen within this decade. This dream is however not fulfilled yet. The paper compares guided modes in both kinds of optical fiber capillaries: refractive and photonic. The differences are emphasized indicating prospective application areas of these fibers.

Research and Development on Ultra-Lightweight Low-Loss Optical Fiber Communication Cable.

DTIC Science & Technology

FIBER OPTICS TRANSMISSION LINES, LIGHTWEIGHT), GLASS , FIBERS , ORGANIC COATINGS, POLYURETHANE RESINS, SOLUTIONS(GENERAL), POWDERS, ELECTROSTATICS...EXTRUSION, RUGGEDIZED EQUIPMENT, BROADBAND, OPTICAL COMMUNICATIONS, TACTICAL COMMUNICATIONS, FIBER OPTICS, LOSSES.

Forty-photon-per-pulse spectral phase retrieval by shaper-assisted modified interferometric field autocorrelation.

PubMed

Hsu, Chen-Shao; Chiang, Hsin-Chien; Chuang, Hsiu-Po; Huang, Chen-Bin; Yang, Shang-Da

2011-07-15

We retrieve the spectral phase of 400 fs pulses at 1560 nm with 5.2 aJ coupled pulse energy (40 photons) by the modified interferometric field autocorrelation method, using a pulse shaper and a 5 cm long periodically poled lithium niobate waveguide. The carrier-envelope phase control of the shaper can reduce the fringe density of the interferometric trace and permits longer lock-in time constants, achieving a sensitivity of 2.7×10(-9) mW(2) (40 times better than the previous record for self-referenced nonlinear pulse measurement). The high stability of the pulse shaper allows for accurate and reproducible measurements of complicated spectral phases. © 2011 Optical Society of America

Performance comparison of a fiber optic communication system based on optical OFDM and an optical OFDM-MIMO with Alamouti code by using numerical simulations

NASA Astrophysics Data System (ADS)

Serpa-Imbett, C. M.; Marín-Alfonso, J.; Gómez-Santamaría, C.; Betancur-Agudelo, L.; Amaya-Fernández, F.

2013-12-01

Space division multiplexing in multicore fibers is one of the most promise technologies in order to support transmissions of next-generation peta-to-exaflop-scale supercomputers and mega data centers, owing to advantages in terms of costs and space saving of the new optical fibers with multiple cores. Additionally, multicore fibers allow photonic signal processing in optical communication systems, taking advantage of the mode coupling phenomena. In this work, we numerically have simulated an optical MIMO-OFDM (multiple-input multiple-output orthogonal frequency division multiplexing) by using the coded Alamouti to be transmitted through a twin-core fiber with low coupling. Furthermore, an optical OFDM is transmitted through a core of a singlemode fiber, using pilot-aided channel estimation. We compare the transmission performance in the twin-core fiber and in the singlemode fiber taking into account numerical results of the bit-error rate, considering linear propagation, and Gaussian noise through an optical fiber link. We carry out an optical fiber transmission of OFDM frames using 8 PSK and 16 QAM, with bit rates values of 130 Gb/s and 170 Gb/s, respectively. We obtain a penalty around 4 dB for the 8 PSK transmissions, after 100 km of linear fiber optic propagation for both singlemode and twin core fiber. We obtain a penalty around 6 dB for the 16 QAM transmissions, with linear propagation after 100 km of optical fiber. The transmission in a two-core fiber by using Alamouti coded OFDM-MIMO exhibits a better performance, offering a good alternative in the mitigation of fiber impairments, allowing to expand Alamouti coded in multichannel systems spatially multiplexed in multicore fibers.

Use of 3000 Bragg Grating Strain Sensors Distributed on Four Eight-meter Optical Fibers During Static Load Tests of a Composite Structure

NASA Technical Reports Server (NTRS)

Childers, Brooks A.; Froggatt, Mark E.; Allison, Sidney G.; Moore, Thomas C., Sr.; Hare, David A.; Batten, Christopher F.; Jegley, Dawn C.

2001-01-01

This paper describes the use of a fiber optic system to measure strain at thousands of locations along optical fibers where weakly reflecting Bragg gratings have been photoetched. The optical fibers were applied to an advanced composite transport wing along with conventional foil strain gages. A comparison of the fiber optic and foil gage systems used for this test will be presented including: a brief description of both strain data systems; a discussion of the process used for installation of the optical fiber; comparative data from the composite wing test; the processes used for the location and display of the high density fiber optic data. Calibration data demonstrating the potential accuracy of the fiber optic system will also be presented. The opportunities for industrial and commercial applications will be discussed. The fiber optic technique is shown to be a valuable augmentation to foil strain gages providing insight to structural behavior previously requiring reliance on modeling.

Fiber optic sensors for gas turbine control

NASA Technical Reports Server (NTRS)

Shu, Emily Yixie (Inventor); Petrucco, Louis Jacob (Inventor); Daum, Wolfgang (Inventor)

2005-01-01

An apparatus for detecting flashback occurrences in a premixed combustor system having at least one fuel nozzle includes at least one photodetector and at least one fiber optic element coupled between the at least one photodetector and a test region of the combustor system wherein a respective flame of the fuel nozzle is not present under normal operating conditions. A signal processor monitors a signal of the photodetector. The fiber optic element can include at least one optical fiber positioned within a protective tube. The fiber optic element can include two fiber optic elements coupled to the test region. The optical fiber and the protective tube can have lengths sufficient to situate the photodetector outside of an engine compartment. A plurality of fuel nozzles and a plurality of fiber optic elements can be used with the fiber optic elements being coupled to respective fuel nozzles and either to the photodetector or, wherein a plurality of photodetectors are used, to respective ones of the plurality of photodetectors. The signal processor can include a digital signal processor.

Fiber optic sensors for gas turbine control

NASA Technical Reports Server (NTRS)

Shu, Emily Yixie (Inventor); Brown, Dale Marius (Inventor); Petrucco, Louis Jacob (Inventor); Lovett, Jeffery Allan (Inventor); Daum, Wolfgang (Inventor); Dunki-Jacobs, Robert John (Inventor)

2003-01-01

An apparatus for detecting flashback occurrences in a premixed combustor system having at least one fuel nozzle includes at least one photodetector and at least one fiber optic element coupled between the at least one photodetector and a test region of the combustor system wherein a respective flame of the fuel nozzle is not present under normal operating conditions. A signal processor monitors a signal of the photodetector. The fiber optic element can include at least one optical fiber positioned within a protective tube. The fiber optic element can include two fiber optic elements coupled to the test region. The optical fiber and the protective tube can have lengths sufficient to situate the photodetector outside of an engine compartment. A plurality of fuel nozzles and a plurality of fiber optic elements can be used with the fiber optic elements being coupled to respective fuel nozzles and either to the photodetector or, wherein a plurality of photodetectors are used, to respective ones of the plurality of photodetectors. The signal processor can include a digital signal processor.

Fiber optic sensors for gas turbine control

NASA Technical Reports Server (NTRS)

Shu, Emily Yixie (Inventor); Brown, Dale Marius (Inventor); Petrucco, Louis Jacob (Inventor); Lovett, Jeffery Allan (Inventor); Daum, Wolfgang (Inventor); Dunki-Jacobs, Robert John (Inventor)

1999-01-01

An apparatus for detecting flashback occurrences in a premixed combustor system having at least one fuel nozzle includes at least one photodetector and at least one fiber optic element coupled between the at least one photodetector and a test region of the combustor system wherein a respective flame of the fuel nozzle is not present under normal operating conditions. A signal processor monitors a signal of the photodetector. The fiber optic element can include at least one optical fiber positioned within a protective tube. The fiber optic element can include two fiber optic elements coupled to the test region. The optical fiber and the protective tube can have lengths sufficient to situate the photodetector outside of an engine compartment. A plurality of fuel nozzles and a plurality of fiber optic elements can be used with the fiber optic elements being coupled to respective fuel nozzles and either to the photodetector or, wherein a plurality of photodetectors are used, to respective ones of the plurality of photodetectors. The signal processor can include a digital signal processor.

Alternative Controller for a Fiber-Optic Switch

NASA Technical Reports Server (NTRS)

Peters, Robert

2007-01-01

A simplified diagram of a relatively inexpensive controller for a DiCon VX (or equivalent) fiber-optic switch -- an electromechanically actuated switch for optically connecting one or two input optical fibers to any of a number of output optical fibers is shown. DiCon VX fiber-optic switches are used primarily in research and development in the telecommunication industry. This controller can control any such switch having up to 32 output channels.

The comparison of two methods to manufacture fused biconical tapered optical fiber coupler

NASA Astrophysics Data System (ADS)

Wang, Yue; Liu, Hairong

2009-08-01

Optical fiber coupler is a directional coupler which is crucial component for optical fiber communication systems. The fused biconical taper is the most important method in facture of optical fiber coupler, with many advantages of low excess loss, precise coupling ratio, good consistency and stability. In this paper we have introduced a new method to manufacture optical fiber coupler. And more over the new manufacture process has been compared with the traditional manufacture method. In the traditional crafts, two optical fibers are parallel placed, and then use the method of tie a knot of the two optical fibers. In the new process, a new program of fiber placement is introduced. Two optical fibers are parallel placed in the middle of the fixture, and then in order to make the bare part of the optical fiber close as much as possible, the new plan using high temperature resistant material bind the both end of the fiber which are not removing the cladding. After many contrast tests, we can see that adopt the improved method of fiber placement, during the process of fiber pulling, the variation of optical power in the directional arm and the coupler arm are more smooth and steady. But the excess loss (EL) generated in the process of pulling is a bit higher than the traditional method of tie a knot. The tests show that the new method of optical fiber placement is feasible in the actual projects for the manufacture of coupler with low coupling ratio, but for the control of the EL still need further studying.

3D beam shape estimation based on distributed coaxial cable interferometric sensor

NASA Astrophysics Data System (ADS)

Cheng, Baokai; Zhu, Wenge; Liu, Jie; Yuan, Lei; Xiao, Hai

2017-03-01

We present a coaxial cable interferometer based distributed sensing system for 3D beam shape estimation. By making a series of reflectors on a coaxial cable, multiple Fabry-Perot cavities are created on it. Two cables are mounted on the beam at proper locations, and a vector network analyzer (VNA) is connected to them to obtain the complex reflection signal, which is used to calculate the strain distribution of the beam in horizontal and vertical planes. With 6 GHz swept bandwidth on the VNA, the spatial resolution for distributed strain measurement is 0.1 m, and the sensitivity is 3.768 MHz mɛ -1 at the interferogram dip near 3.3 GHz. Using displacement-strain transformation, the shape of the beam is reconstructed. With only two modified cables and a VNA, this system is easy to implement and manage. Comparing to optical fiber based sensor systems, the coaxial cable sensors have the advantage of large strain and robustness, making this system suitable for structure health monitoring applications.

The new 64m Sardinia Radio Telescope and VLBI facilities in Italy

NASA Astrophysics Data System (ADS)

Giovannini, Gabriele; Feretti, Luigina; Prandoni, Isabella; Giroletti, Marcello

2015-08-01

The Sardinia Radio Telescope (SRT) is a new major radio astronomical facility available in Italy for single dish and interferometric observations. It represents a flexible instrument for Radio Astronomy, Geodynamical studies and Space Science, either in single dish or VLBI mode. The SRT combines a 64m steerable collecting area, one of the largest all over the World with state-of-the-art technology (including an active surface) to enable high efficiency observations up to the 3-mm band.This new radio telescope together with the two 32m antennas in Noto and Medicina can be used for VLBI observations on a national basis (VLBIT). Data can be correlated in a short time (in real time soon) thanks to fiber-optics connection among the radio telescopes and the software correlator installed at the Radio Astronomy Institute in Bologna (IRA/INAF). In the poster I will present capabilities of the SRT telescope as well as the VLBIT project and I will shortly discuss the scientific prospects of the VLBIT.

Methods and apparatus for optical switching using electrically movable optical fibers

DOEpatents

Peterson, Kenneth A [Albuquerque, NM

2007-03-13

Methods and apparatuses for electrically controlled optical switches are presented. An electrically controlled optical switch includes a fixture formed using a laminated dielectric material, a first optical fiber having a fixed segment supported by the fixture and a movable segment extending into a cavity, a second optical fiber having a fixed segment supported by the fixture and an extended segment where an optical interconnect may be established between the first optical fiber and the second optical fiber, and a first electrical actuator functionally coupled to the fixture and the first fiber which alters a position of the moveable segment, based upon a control signal, for changing a state of the optical interconnect between one of two states.

Radial-firing optical fiber tip containing conical-shaped air-pocket for biomedical applications.

PubMed

Lee, Seung Ho; Ryu, Yong-Tak; Son, Dong Hoon; Jeong, Seongmook; Kim, Youngwoong; Ju, Seongmin; Kim, Bok Hyeon; Han, Won-Taek

2015-08-10

We report a novel radial-firing optical fiber tip containing a conical-shaped air-pocket fabricated by deforming a hollow optical fiber using electric arc-discharge process. The hollow optical fiber was fusion spliced with a conventional optical fiber, simultaneously deforming into the intagliated conical-shaped region along the longitudinal fiber-axis of the fiber due to the gradual collapse of the cavity of the hollow optical fiber. Then the distal-end of the hollow optical fiber was sealed by the additional arc-discharge in order to obstruct the inflow of an external bio-substance or liquid to the inner air surface during the surgical operations, resulting in the formation of encased air-pocket in the silica glass fiber. Due to the total internal reflection of the laser beam at the conical-shaped air surface, the laser beam (λ = 632.8 nm) was deflected to the circumferential direction up to 87 degree with respect to the fiber-axis.

VLT interferometer upgrade for the 2nd generation of interferometric instruments

NASA Astrophysics Data System (ADS)

Gonté, Frederic; Woillez, Julien; Schuhler, Nicolas; Egner, Sebastian; Merand, Antoine; Abad, José Antonio; Abadie, Sergio; Abuter, Roberto; Acuña, Margarita; Allouche, Fatmé; Alonso, Jaime; Andolfalto, Luigi; Antonelli, Pierre; Avila, Gerardo; Barriga, Pablo José; Beltran, Juan; Berger, Jean-Philippe; Bolados, Carlos; Bonnet, Henri; Bourget, Pierre; Brast, Roland; Bristow, Paul; Caniguante, Luis; Castillo, Roberto; Conzelmann, Ralf; Cortes, Angela; Delplancke, Françoise; Del Valle, Diego; Derie, Frederic; Diaz, Alvaro; Donoso, Reinaldo; Dorn, Reinhold; Duhoux, Philippe; Dupuy, Christophe; Eisenhauer, Frank; Elao, Christian; Fuenteseca, Eloy; Fernandez, Ruben; Gaytan, Daniel; Glindemann, Andreas; Gonzales, Jaime; Guieu, Sylvain; Guisard, Stephane; Haguenauer, Pierre; Haimerl, Andreas; Heinz, Volker; Henriquez, Juan Pablo; van der Heyden, P.; Hubin, Norbert; Huerta, Rodrigo; Jochum, Lieselotte; Leiva, Alfredo; Lévêque, Samuel; Lizon, Jean-Louis; Luco, Fernando; Mardones, Pedro; Mellado, Angel; Osorio, Juan; Ott, Jürgen; Pallanca, Laurent; Pavez, Marcus; Pasquini, Luca; Percheron, Isabelle; Pirard, Jean-Francois; Than Phan, Duc; Pineda, Juan Carlos; Pino, Andres; Poupar, Sebastien; Ramírez, Andres; Reinero, Claudio; Riquelme, Miguel; Romero, Juan; Rivinius, Thomas; Rojas, Chester; Rozas, Felix; Salgado, Fernando; Scheithauer, Silvia; Schmid, Christian; Schöller, Markus; Siclari, Waldo; Stephan, Christian; Tamblay, Richard; Tapia, Mario; Tristram, Konrad; Valdes, Guillermo; de Wit, Willem-Jan; Wright, Andrew; Zins, Gerard

2016-08-01

ESO is undertaking a large upgrade of the infrastructure on Cerro Paranal in order to integrate the 2nd generation of interferometric instruments Gravity and MATISSE, and increase its performance. This upgrade started mid 2014 with the construction of a service station for the Auxiliary Telescopes and will end with the implementation of the adaptive optics system for the Auxiliary telescope (NAOMI) in 2018. This upgrade has an impact on the infrastructure of the VLTI, as well as its sub-systems and scientific instruments.

Simultaneous off-axis multiplexed holography and regular fluorescence microscopy of biological cells.

PubMed

Nygate, Yoav N; Singh, Gyanendra; Barnea, Itay; Shaked, Natan T

2018-06-01

We present a new technique for obtaining simultaneous multimodal quantitative phase and fluorescence microscopy of biological cells, providing both quantitative phase imaging and molecular specificity using a single camera. Our system is based on an interferometric multiplexing module, externally positioned at the exit of an optical microscope. In contrast to previous approaches, the presented technique allows conventional fluorescence imaging, rather than interferometric off-axis fluorescence imaging. We demonstrate the presented technique for imaging fluorescent beads and live biological cells.

Trapping and Propelling Microparticles at Long Range by Using an Entirely Stripped and Slightly Tapered No-Core Optical Fiber

PubMed Central

Sheu, Fang-Wen; Huang, Yen-Si

2013-01-01

A stripped no-core optical fiber with a 125 μm diameter was transformed into a symmetric and unbroken optical fiber that tapers slightly to a 45-μm-diameter waist. The laser light can be easily launched into the no-core optical fiber. The enhanced evanescent wave of the slightly tapered no-core optical fiber can attract nearby 5-μm-diameter polystyrene microparticles onto the surface of the tapered multimode optical fiber within fast flowing fluid and propel the trapped particles in the direction of the light propagation to longer delivery range than is possible using a slightly tapered telecom single-mode optical fiber. PMID:23449118

[The design and application of domestic mid-IR fiber optics].

PubMed

Weng, Shi-fu; Gao, Jian-ping; Xu, Yi-zhuang; Yang, Li-min; Bian, Bei-ya; Xiang, Hai-bo; Wu, Jin-guang

2004-05-01

The combination of mid-IR fiber optics and FTIR has made the non-invasive determination of samples in situ, with long distances, and in vivo possible. In this paper domestic mid-IR fiber optics was improved to investigate the transmission ability of fiber optics and its application to the sample determination. New design was applied to obtaining one bare fiber optics, which has a minor energy loss and higher signal-to-noise ratio. The spectra of H2O/EtOH and tissue samples were measured using the new designed fiber optics and the results show that home-made mid-IR fiber optics can be applied to the field of determination of general and biological samples.

Trapping and propelling microparticles at long range by using an entirely stripped and slightly tapered no-core optical fiber.

PubMed

Sheu, Fang-Wen; Huang, Yen-Si

2013-02-28

A stripped no-core optical fiber with a 125 µm diameter was transformed into a symmetric and unbroken optical fiber that tapers slightly to a 45-µm-diameter waist. The laser light can be easily launched into the no-core optical fiber. The enhanced evanescent wave of the slightly tapered no-core optical fiber can attract nearby 5-µm-diameter polystyrene microparticles onto the surface of the tapered multimode optical fiber within fast flowing fluid and propel the trapped particles in the direction of the light propagation to longer delivery range than is possible using a slightly tapered telecom single-mode optical fiber.

Demonstration of theoretical and experimental simulations in fiber optics course

NASA Astrophysics Data System (ADS)

Yao, Tianfu; Wang, Xiaolin; Shi, Jianhua; Lei, Bing; Liu, Wei; Wang, Wei; Hu, Haojun

2017-08-01

"Fiber optics" course plays a supporting effect in the curriculum frame of optics and photonics at both undergraduate and postgraduate levels. Moreover, the course can be treated as compulsory for students specialized in the fiber-related field, such as fiber communication, fiber sensing and fiber light source. The corresponding content in fiber optics requires the knowledge of geometrical and physical optics as background, including basic optical theory and fiber components in practice. Thus, to help the students comprehend the relatively abundant and complex content, it is necessary to investigate novel teaching method assistant the classic lectures. In this paper, we introduce the multidimensional pattern in fiber-optics teaching involving theoretical and laboratory simulations. First, the theoretical simulations is demonstrated based on the self-developed software named "FB tool" which can be installed in both smart phone with Android operating system and personal computer. FB tool covers the fundamental calculations relating to transverse modes, fiber lasers and nonlinearities and so on. By comparing the calculation results with other commercial software like COMSOL, SFTool shows high accuracy with high speed. Then the laboratory simulations are designed including fiber coupling, Erbium doped fiber amplifiers, fiber components and so on. The simulations not only supports students understand basic knowledge in the course, but also provides opportunities to develop creative projects in fiber optics.

Characterization of a Fiber Optic Coupled Dosimeter for Clinical Electron Beam Dosimetry

DTIC Science & Technology

2010-04-29

2010 2. REPORT TYPE 3. DATES COVERED 00-00-2010 to 00-00-2010 4. TITLE AND SUBTITLE Characterization of a Fiber Optic Coupled Dosimeter for...Fiber Optic Coupled Dosimeter for Clinical Electron Beam Dosimetry. Abstract approved: Camille J. Lodwick Fiber-optic-coupled dosimeters ...Rights Reserved CHARACTERIZATION OF A FIBER OPTIC COUPLED DOSIMETER FOR CLINICAL ELECTRON

Energetic radiation influence on temperature dependency of Brillouin frequency in optical fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pheron, X.; Ouerdane, Y.; Delepine-Lesoille, S.

We present a post mortem study of the influence of energetic radiation on optical fiber Brillouin sensors, both Brillouin spectrum and its temperature dependency in two different fibers, a photosensitive optical fiber and a SMF28. The target application is nuclear wastes repository monitoring where optical fiber Brillouin sensors might be exposed to energetic radiation. UV exposure induced optical losses, Brillouin frequency shifts up to 28 MHz and even a variation of the temperature dependency. The photosensitive optical fiber resulted more sensitive than SMF28{sup TM}. (authors)

Method for the continuous processing of hermetic fiber optic components and the resultant fiber optic-to-metal components

DOEpatents

Kramer, D.P.

1994-08-09

Hermetic fiber optic-to-metal components and method for making hermetic fiber optic-to-metal components by assembling and fixturing elements comprising a metal shell, a glass preform, and a metal-coated fiber optic into desired relative positions and then sealing said fixtured elements preferably using a continuous heating process is disclosed. The resultant hermetic fiber optic-to-metal components exhibit high hermeticity and durability despite the large differences in thermal coefficients of expansion among the various elements. 3 figs.

Monitoring techniques for the manufacture of tapered optical fibers.

PubMed

Mullaney, Kevin; Correia, Ricardo; Staines, Stephen E; James, Stephen W; Tatam, Ralph P

2015-10-01

The use of a range of optical techniques to monitor the process of fabricating optical fiber tapers is investigated. Thermal imaging was used to optimize the alignment of the optical system; the transmission spectrum of the fiber was monitored to confirm that the tapers had the required optical properties and the strain induced in the fiber during tapering was monitored using in-line optical fiber Bragg gratings. Tapers were fabricated with diameters down to 5 μm and with waist lengths of 20 mm using single-mode SMF-28 fiber.

Optical Energy Transfer and Conversion System

NASA Technical Reports Server (NTRS)

Hogan, Bartholomew P. (Inventor); Stone, William C. (Inventor)

2015-01-01

An optical power transfer system comprising a fiber spooler, a fiber optic rotary joint mechanically connected to the fiber spooler, and an electrical power extraction subsystem connected to the fiber optic rotary joint with an optical waveguide. Optical energy is generated at and transferred from a base station through fiber wrapped around the spooler, through the rotary joint, and ultimately to the power extraction system at a remote mobility platform for conversion to another form of energy.

Fiber optically isolated and remotely stabilized data transmission system

DOEpatents

Nelson, Melvin A.

1992-01-01

A fiber optically isolated and remotely stabilized data transmission system s described wherein optical data may be transmitted over an optical data fiber from a remote source which includes a data transmitter and a power supply at the remote source. The transmitter may be remotely calibrated and stabilized via an optical control fiber, and the power source may be remotely cycled between duty and standby modes via an optical control fiber.

Fiber optically isolated and remotely stabilized data transmission system

DOEpatents

Nelson, M.A.

1992-11-10

A fiber optically isolated and remotely stabilized data transmission systems described wherein optical data may be transmitted over an optical data fiber from a remote source which includes a data transmitter and a power supply at the remote source. The transmitter may be remotely calibrated and stabilized via an optical control fiber, and the power source may be remotely cycled between duty and standby modes via an optical control fiber. 3 figs.

Harmonic demodulation and minimum enhancement factors in field-enhanced near-field optical microscopy.

PubMed

Scarpettini, A F; Bragas, A V

2015-01-01

Field-enhanced scanning optical microscopy relies on the design and fabrication of plasmonic probes which had to provide optical and chemical contrast at the nanoscale. In order to do so, the scattering containing the near-field information recorded in a field-enhanced scanning optical microscopy experiment, has to surpass the background light, always present due to multiple interferences between the macroscopic probe and sample. In this work, we show that when the probe-sample distance is modulated with very low amplitude, the higher the harmonic demodulation is, the better the ratio between the near-field signal and the interferometric background results. The choice of working at a given n harmonic is dictated by the experiment when the signal at the n + 1 harmonic goes below the experimental noise. We demonstrate that the optical contrast comes from the nth derivative of the near-field scattering, amplified by the interferometric background. By modelling the far and near field we calculate the probe-sample approach curves, which fit very well the experimental ones. After taking a great amount of experimental data for different probes and samples, we conclude with a table of the minimum enhancement factors needed to have optical contrast with field-enhanced scanning optical microscopy. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

Influence of stimulated Brillouin scattering on positioning accuracy of long-range dual Mach-Zehnder interferometric vibration sensors

NASA Astrophysics Data System (ADS)

He, Xiangge; Xie, Shangran; Cao, Shan; Liu, Fei; Zheng, Xiaoping; Zhang, Min; Yan, Han; Chen, Guocai

2016-11-01

The properties of noise induced by stimulated Brillouin scattering (SBS) in long-range interferometers and their influences on the positioning accuracy of dual Mach-Zehnder interferometric (DMZI) vibration sensing systems are studied. The SBS noise is found to be white and incoherent between the two arms of the interferometer in a 1-MHz bandwidth range. Experiments on 25-km long fibers show that the root mean square error (RMSE) of the positioning accuracy is consistent with the additive noise model for the time delay estimation theory. A low-pass filter can be properly designed to suppress the SBS noise and further achieve a maximum RMSE reduction of 6.7 dB.

The influence of underwater turbulence on optical phase measurements

NASA Astrophysics Data System (ADS)

Redding, Brandon; Davis, Allen; Kirkendall, Clay; Dandridge, Anthony

2016-05-01

Emerging underwater optical imaging and sensing applications rely on phase-sensitive detection to provide added functionality and improved sensitivity. However, underwater turbulence introduces spatio-temporal variations in the refractive index of water which can degrade the performance of these systems. Although the influence of turbulence on traditional, non-interferometric imaging has been investigated, its influence on the optical phase remains poorly understood. Nonetheless, a thorough understanding of the spatio-temporal dynamics of the optical phase of light passing through underwater turbulence are crucial to the design of phase-sensitive imaging and sensing systems. To address this concern, we combined underwater imaging with high speed holography to provide a calibrated characterization of the effects of turbulence on the optical phase. By measuring the modulation transfer function of an underwater imaging system, we were able to calibrate varying levels of optical turbulence intensity using the Simple Underwater Imaging Model (SUIM). We then used high speed holography to measure the temporal dynamics of the optical phase of light passing through varying levels of turbulence. Using this method, we measured the variance in the amplitude and phase of the beam, the temporal correlation of the optical phase, and recorded the turbulence induced phase noise as a function of frequency. By bench marking the effects of varying levels of turbulence on the optical phase, this work provides a basis to evaluate the real-world potential of emerging underwater interferometric sensing modalities.

Optical testing of aspheres based on photochromic computer-generated holograms

NASA Astrophysics Data System (ADS)

Pariani, Giorgio; Bianco, Andrea; Bertarelli, Chiara; Spanó, Paolo; Molinari, Emilio

2010-07-01

Aspherical optics are widely used in modern optical telescopes and instrumentation because of their ability to reduce aberrations with a simple optical system. Testing their optical quality through null interferometry is not trivial as reference optics are not available. Computer-Generated Holograms (CGHs) are efficient devices that allow to generate a well-defined optical wavefront. We developed rewritable Computer Generated Holograms for the interferometric test of aspheres based on photochromic layers. These photochromic holograms are cost-effective and the method of production does not need any post exposure process.

Measuring optical fiber length by use of a short-pulse optical fiber ring laser in a self-injection seeding scheme.

PubMed

Wang, Yi-Ping; Wang, Dong Ning; Jin, Wei

2006-09-01

A method for measuring the length of an optical fiber by use of an optical fiber ring laser pulse source is proposed and demonstrated. The key element of the optical fiber ring laser is a gain-switched Fabry-Perot laser diode operated in a self-injection seeding scheme. This method is especially suitable for measuring a medium or long fiber, and a resolution of 0.1 m is experimentally achieved. The measurement is implemented by accurately determining the pulse frequency that can maximize the output power of the fiber ring laser. The measurement results depend only on the refractive index of the fiber corresponding to this single wavelength, instead of the group index of the fiber, which represents a great advantage over both optical time-domain reflectometry and optical low-coherence reflectometry methods.

Fiber Optics: A New World of Possibilities in Light.

ERIC Educational Resources Information Center

Hutchinson, John

1990-01-01

The background and history of light and fiber optics are discussed. Applications for light passed either directly or indirectly through optical fibers are described. Suggestions for science activities that use fiber optics are provided. (KR)

Strain and dynamic measurements using fiber optic sensors embedded into graphite/epoxy tubes

NASA Technical Reports Server (NTRS)

Dehart, D. W.; Doederlein, T.; Koury, J.; Rogowski, R. S.; Heyman, J. S.; Holben, M. S., Jr.

1989-01-01

Graphite/epoxy tubes were fabricated with embedded optical fibers to evaluate the feasibility of monitoring strains with a fiber optic technique. Resistance strain gauges were attached to the tubes to measure strain at four locations along the tube for comparison with the fiber optic sensors. Both static and dynamic strain measurements were made with excellent agreement between the embedded fiber optic strain sensor and the strain gauges. Strain measurements of 10(exp -7) can be detected with the optical phase locked loop (OPLL) system using optical fiber. Because of their light weight, compatibility with composites, immunity to electromagnetic interference, and based on the static and dynamic results obtained, fiber optic sensors embedded in composites may be useful as the sensing component of smart structures.

A new fiber optic sensor for inner surface roughness measurement

NASA Astrophysics Data System (ADS)

Xu, Xiaomei; Liu, Shoubin; Hu, Hong

2009-11-01

In order to measure inner surface roughness of small holes nondestructively, a new fiber optic sensor is researched and developed. Firstly, a new model for surface roughness measurement is proposed, which is based on intensity-modulated fiber optic sensors and scattering modeling of rough surfaces. Secondly, a fiber optical measurement system is designed and set up. Under the help of new techniques, the fiber optic sensor can be miniaturized. Furthermore, the use of micro prism makes the light turn 90 degree, so the inner side surface roughness of small holes can be measured. Thirdly, the fiber optic sensor is gauged by standard surface roughness specimens, and a series of measurement experiments have been done. The measurement results are compared with those obtained by TR220 Surface Roughness Instrument and Form Talysurf Laser 635, and validity of the developed fiber optic sensor is verified. Finally, precision and influence factors of the fiber optic sensor are analyzed.

Fiber optic Cerenkov radiation sensor system to estimate burn-up of spent fuel: characteristic evaluation of the system using Co-60 source

NASA Astrophysics Data System (ADS)

Shin, S. H.; Jang, K. W.; Jeon, D.; Hong, S.; Kim, S. G.; Sim, H. I.; Yoo, W. J.; Park, B. G.; Lee, B.

2013-09-01

Cerenkov radiation occurs when charged particles are moving faster than the speed of light in a transparent dielectric medium. In optical fibers, the Cerenkov light also can be generated due to their dielectric components. Accordingly, the radiation-induced light signals can be obtained using optical fibers without any scintillating material. In this study, to measure the intensities of Cerenkov radiation induced by gamma-rays, we have fabricated the fiber-optic Cerenkov radiation sensor system using silica optical fibers, plastic optical fibers, multi-anode photomultiplier tubes, and a scanning system. To characterize the Cerenkov radiation generated in optical fibers, the spectra of Cerenkov radiation generated in the silica and plastic optical fibers were measured. Also, the intensities of Cerenkov radiation induced by gamma-rays generated from a cylindrical Co-60 source with or without lead shielding were measured using the fiberoptic Cerenkov radiation sensor system.

FIBER OPTICS: Polarization phase nonreciprocity in all-fiber ring interferometers

NASA Astrophysics Data System (ADS)

Andreev, A. Ts; Vasilev, V. D.; Kozlov, V. A.; Kuznetsov, A. V.; Senatorov, A. A.; Shubochkin, R. L.

1993-08-01

The polarization phase nonreciprocity in all-fiber ring interferometers based on single-mode optical fibers was studied experimentally. The results confirm existing theoretical models. Experimentally, it was possible to use fiber ring interferometers to measure the extinction coefficients of optical fiber polarizers. The largest extinction coefficients found for optical-fiber polarizers were 84 dB (for the wavelength 0.82 μm) and 86 dB (1.3 μm).

Removing the depth-degeneracy in optical frequency domain imaging with frequency shifting

PubMed Central

Yun, S. H.; Tearney, G. J.; de Boer, J. F.; Bouma, B. E.

2009-01-01

A novel technique using an acousto-optic frequency shifter in optical frequency domain imaging (OFDI) is presented. The frequency shift eliminates the ambiguity between positive and negative differential delays, effectively doubling the interferometric ranging depth while avoiding image cross-talk. A signal processing algorithm is demonstrated to accommodate nonlinearity in the tuning slope of the wavelength-swept OFDI laser source. PMID:19484034

The Space Infrared Interferometric Telescope (SPIRIT): Optical System Design Considerations

NASA Technical Reports Server (NTRS)

Wilson, Mark E.; Leisawitz, David; Martino, Anthony J.; Budinoff, Jason; Quijada, Manuel; Hyde, Tupper

2007-01-01

SPIRIT is a candidate NASA Origins Probe mission. It is a spatial and spectral interferometer operating at 4 K with an operating wavelength range 25 - 400 microns. This paper describes the various components of the candidate optical system, including telescopes, pointing and tracking optics, along with their functions. Some of the tradeoffs involved in selecting various components, with their particular characteristics, are described.

Using Optical Interferometry for GEO Satellites Imaging: An Update

DTIC Science & Technology

2016-05-27

of a geostationary satellite using the Navy Precision Optical Inter- ferometer (NPOI) during the glint season of March 2015. We succeeded in detecting...night. These baseline lengths correspond to a resolution of ∼4 m at geostationary altitude. This is the first multiple-baseline interferometric...detection of a satellite. Keywords: geostationary satellites, optical interferometry, imaging, telescope arrays 1. INTRODUCTION Developing the ability to

Photoacoustic-guided convergence of light through optically diffusive media.

PubMed

Kong, Fanting; Silverman, Ronald H; Liu, Liping; Chitnis, Parag V; Lee, Kotik K; Chen, Y C

2011-06-01

We demonstrate that laser beams can be converged toward a light-absorbing target through optically diffusive media by using photoacoustic-guided interferometric focusing. The convergence of light is achieved by shaping the wavefront of the incident light with a deformable mirror to maximize the photoacoustic signal, which is proportional to the scattered light intensity at the light absorber. © 2011 Optical Society of America

40-Gbit/s all-optical circulating shift register with an inverter.

PubMed

Hall, K L; Donnelly, J P; Groves, S H; Fennelly, C I; Bailey, R J; Napoleone, A

1997-10-01

We report what is believed to be the first demonstration of an all-optical circulating shift register using an ultrafast nonlinear interferometer with a polarization-insensitive semiconductor optical amplifier as the nonlinear switching element. The device operates at 40 Gbits/s, to our knowledge the highest speed demonstrated to date. Also, the demonstration proves the cascadability of the ultrafast nonlinear interferometric switch.

Microbend fiber-optic temperature sensor

DOEpatents

Weiss, J.D.

1995-05-30

A temperature sensor is made of optical fiber into which quasi-sinusoidal microbends have been permanently introduced. In particular, the present invention includes a graded-index optical fiber directing steady light through a section of the optical fiber containing a plurality of permanent microbends. The microbend section of the optical fiber is contained in a thermally expansive sheath, attached to a thermally expansive structure, or attached to a bimetallic element undergoing temperature changes and being monitored. The microbend section is secured to the thermally expansive sheath which allows the amplitude of the microbends to decrease with temperature. The resultant increase in the optical fiber`s transmission thus allows temperature to be measured. The plural microbend section of the optical fiber is secured to the thermally expansive structure only at its ends and the microbends themselves are completely unconstrained laterally by any bonding agent to obtain maximum longitudinal temperature sensitivity. Although the permanent microbends reduce the transmission capabilities of fiber optics, the present invention utilizes this phenomenon as a transduction mechanism which is optimized to measure temperature. 5 figs.

High pressure fiber optic sensor system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guida, Renato; Xia, Hua; Lee, Boon K

2013-11-26

The present application provides a fiber optic sensor system. The fiber optic sensor system may include a small diameter bellows, a large diameter bellows, and a fiber optic pressure sensor attached to the small diameter bellows. Contraction of the large diameter bellows under an applied pressure may cause the small diameter bellows to expand such that the fiber optic pressure sensor may measure the applied pressure.

Embedding Optical Fibers In Cast Metal Parts

NASA Technical Reports Server (NTRS)

Gibler, William N.; Atkins, Robert A.; Lee, Chung E.; Taylor, Henry F.

1995-01-01

Use of metal strain reliefs eliminates breakage of fibers during casting process. Technique for embedding fused silica optical fibers in cast metal parts devised. Optical fiber embedded in flange, fitting, or wall of vacuum or pressure chamber, to provide hermetically sealed feedthrough for optical transmission of measurement or control signals. Another example, optical-fiber temperature sensor embedded in metal structural component to measure strain or temperature inside component.

Optical fiber characteristics and standards; Proceedings of the Meeting, Cannes, France, November 25-27, 1985

NASA Technical Reports Server (NTRS)

Bouillie, Remy (Editor)

1986-01-01

Papers are presented on outside vapor deposition, the plasma activated CVD process for large scale production of telecommunication fibers, axial lateral plasma deposition technology from plastic clad silica, coatings for optical fibers, primary coating characterization, and radiation-induced time dependent attenuation in a fiber. Topics discussed include fibers with high tensile strength, the characteristics and specifications of airborne fiber optic components, the baseband frequency response of multimode fibers, and fibers for local and broadband networks. Consideration is given to industrial measurements for single mode and multimode fibers, the characterization of source power distribution in a multimode fiber by a splice offset technique, the measurement of chromatic dispersion in a single mode optical, and the effect of temperature on the refracted near-field optical fiber profiling technique.

Using a slightly tapered optical fiber to attract and transport microparticles.

PubMed

Sheu, Fang-Wen; Wu, Hong-Yu; Chen, Sy-Hann

2010-03-15

We exploit a fiber puller to transform a telecom single-mode optical fiber with a 125 microm diameter into a symmetric and unbroken slightly tapered optical fiber with a 50 microm diameter at the minimum waist. When the laser light is launched into the optical fiber, we can observe that, due to the evanescent wave of the slightly tapered fiber, the nearby polystyrene microparticles with 10 microm diameters will be attracted onto the fiber surface and roll separately in the direction of light propagation. We have also simulated and compared the optical propulsion effects on the microparticles when the laser light is launched into a slightly tapered fiber and a heavily tapered (subwavelength) fiber, respectively.

Photonic crystal fiber in-line Mach-Zehnder interferometer for explosive detection.

PubMed

Tao, Chuanyi; Wei, Heming; Feng, Wenlin

2016-02-08

We report a photonic crystal fiber (PCF) in-line Mach-Zehnder interferometer used as a gas sensor device which exhibits high sensitivity to the explosive trinitrotoluene (TNT). The interferometric sensor head is formed by embedding a segment of large-mode-area/grapefruit PCF between standard single-mode fibers via butt coupling, which produces two small air gaps in between terminated fiber ends with ceramic ferrule connectors as coupling regions, which also serve as inlet/outlet for the gas. The spectral response of the interferometer is investigated in terms of its wavelength spectrum. The selectivity to TNT vapor is achieved by immobilizing a molecular recognition ployallylamine layer on the inner surface of the holey region of the PCF. The TNT-induced variations of the interference fringes are measured and the sensing capability of the proposed sensor is demonstrated experimentally.

Selenium semiconductor core optical fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, G. W.; Qian, Q., E-mail: qianqi@scut.edu.cn; Peng, K. L.

2015-02-15

Phosphate glass-clad optical fibers containing selenium (Se) semiconductor core were fabricated using a molten core method. The cores were found to be amorphous as evidenced by X-ray diffraction and corroborated by Micro-Raman spectrum. Elemental analysis across the core/clad interface suggests that there is some diffusion of about 3 wt % oxygen in the core region. Phosphate glass-clad crystalline selenium core optical fibers were obtained by a postdrawing annealing process. A two-cm-long crystalline selenium semiconductor core optical fibers, electrically contacted to external circuitry through the fiber end facets, exhibit a three times change in conductivity between dark and illuminated states. Suchmore » crystalline selenium semiconductor core optical fibers have promising utility in optical switch and photoconductivity of optical fiber array.« less

7 CFR 1755.404 - Fiber optic cable telecommunications plant measurements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... performed on each optical fiber within the cable. (2) Method of measurement. For single mode fibers, the end-to-end attenuation measurements of each optical fiber at 1310 and/or 1550 nanometers in each...-end attenuation of each single mode optical fiber at 1310 and/or 1550 nanometers shall not exceed the...

7 CFR 1755.404 - Fiber optic cable telecommunications plant measurements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... performed on each optical fiber within the cable. (2) Method of measurement. For single mode fibers, the end-to-end attenuation measurements of each optical fiber at 1310 and/or 1550 nanometers in each...-end attenuation of each single mode optical fiber at 1310 and/or 1550 nanometers shall not exceed the...

7 CFR 1755.404 - Fiber optic cable telecommunications plant measurements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... performed on each optical fiber within the cable. (2) Method of measurement. For single mode fibers, the end-to-end attenuation measurements of each optical fiber at 1310 and/or 1550 nanometers in each...-end attenuation of each single mode optical fiber at 1310 and/or 1550 nanometers shall not exceed the...

Large core fiber optic cleaver

DOEpatents

Halpin, John M.

1996-01-01

The present invention relates to a device and method for cleaving optical fibers which yields cleaved optical fiber ends possessing high damage threshold surfaces. The device can be used to cleave optical fibers with core diameters greater than 400 .mu.m.

Optical fibers for the distribution of frequency and timing references

NASA Technical Reports Server (NTRS)

Lutes, G. F.

1981-01-01

An optical fiber communications link was installed for the purpose of evaluating the applicability of optical fiber technology to the distribution of frequency and timing reference signals. It incorporated a 1.5km length of optical fiber cable containing two multimode optical fibers. The two fibers were welded together at one end of the cable to attain a path length of 3km. Preliminary measurements made on this link, including Allan variance and power spectral density of phase noise are reported.

An interferometer having fused optical fibers, and apparatus and method using the interferometer

NASA Technical Reports Server (NTRS)

Hellbaum, Richard F. (Inventor); Claus, Richard O. (Inventor); Murphy, Kent A. (Inventor); Gunther, Michael F. (Inventor)

1992-01-01

An interferometer includes a first optical fiber coupled to a second optical fiber by fusing. At a fused portion, the first and second optical fibers are cut to expose respective cores. The cut or fused end of the first and second optical fibers is arranged to oppose a diaphragm or surface against which a physical phenomenon such as pressure or stress, is applied. In a first embodiment, a source light which is generally single-mode monochromatic, coherent light, is input to the first optical fiber and by evanescence, effectively crosses to the second optical fiber at the fused portion. Source light from the second optical fiber is reflected by the diaphragm or surface, and received at the second optical fiber to generate an output light which has an intensity which depends upon interference of reference light based on the source light, and the reflected light reflected from the diaphragm or surface. The intensity of the output light represents a positional relationship or displacement between the interferometer and the diaphragm or surface.

Development of self-sensing BFRP bars with distributed optic fiber sensors

NASA Astrophysics Data System (ADS)

Tang, Yongsheng; Wu, Zhishen; Yang, Caiqian; Shen, Sheng; Wu, Gang; Hong, Wan

2009-03-01

In this paper, a new type of self-sensing basalt fiber reinforced polymer (BFRP) bars is developed with using the Brillouin scattering-based distributed optic fiber sensing technique. During the fabrication, optic fiber without buffer and sheath as a core is firstly reinforced through braiding around mechanically dry continuous basalt fiber sheath in order to survive the pulling-shoving process of manufacturing the BFRP bars. The optic fiber with dry basalt fiber sheath as a core embedded further in the BFRP bars will be impregnated well with epoxy resin during the pulling-shoving process. The bond between the optic fiber and the basalt fiber sheath as well as between the basalt fiber sheath and the FRP bar can be controlled and ensured. Therefore, the measuring error due to the slippage between the optic fiber core and the coating can be improved. Moreover, epoxy resin of the segments, where the connection of optic fibers will be performed, is uncured by isolating heat from these parts of the bar during the manufacture. Consequently, the optic fiber in these segments of the bar can be easily taken out, and the connection between optic fibers can be smoothly carried out. Finally, a series of experiments are performed to study the sensing and mechanical properties of the propose BFRP bars. The experimental results show that the self-sensing BFRP bar is characterized by not only excellent accuracy, repeatability and linearity for strain measuring but also good mechanical property.

Fiber optic probes for laser light scattering: Ground based evaluation for micgrogravity flight experimentation. Integrated coherent imaging fiber optic systems for laser light scattering and other applications

NASA Technical Reports Server (NTRS)

Dhadwal, Harbans Singh

1994-01-01

The research work presented in this report has established a new class of backscatter fiber optics probes for remote dynamic light scattering capability over a range of scattering angles from 94 degrees to 175 degrees. The fiber optic probes provide remote access to scattering systems, and can be utilized in either a noninvasive or invasive configuration. The fiber optics create an interference free data channel to inaccessible and harsh environments. Results from several studies of concentrated suspension, microemulsions, and protein systems are presented. The second part of the report describes the development of a new technology of wavefront processing within the optical fiber, that is, integrated fiber optics. Results have been very encouraging and the technology promises to have significant impact on the development of fiber optic sensors in a variety of fields ranging from environmental monitoring to optical recording, from biomedical sensing to photolithography.

Fiber Optic Experience with the Smart Actuation System on the F-18 Systems Research Aircraft

NASA Technical Reports Server (NTRS)

Zavala, Eddie

1997-01-01

High bandwidth, immunity to electromagnetic interference, and potential weight savings have led to the development of fiber optic technology for future aerospace vehicle systems. This technology has been incorporated in a new smart actuator as the primary communication interface. The use of fiber optics simplified system integration and significantly reduced wire count. Flight test results showed that fiber optics could be used in aircraft systems and identified critical areas of development of fly-by-light technology. This paper documents the fiber optic experience gained as a result of this program, and identifies general design considerations that could be used in a variety of specific applications of fiber optic technology. Environmental sensitivities of fiber optic system components that significantly contribute to optical power variation are discussed. Although a calibration procedure successfully minimized the effect of fiber optic sensitivities, more standardized calibration methods are needed to ensure system operation and reliability in future aerospace vehicle systems.

Optical Fiber Chemical Sensor with Sol-Gel Derived Refractive Material as Transducer for High Temperature Gas Sensing in Clean Coal Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shiquan Tao

2006-12-31

The chemistry of sol-gel derived silica and refractive metal oxide has been systematically studied. Sol-gel processes have been developed for preparing porous silica and semiconductor metal oxide materials. Micelle/reversed micelle techniques have been developed for preparing nanometer sized semiconductor metal oxides and noble metal particles. Techniques for doping metal ions, metal oxides and nanosized metal particles into porous sol-gel material have also been developed. Optical properties of sol-gel derived materials in ambient and high temperature gases have been studied by using fiber optic spectroscopic techniques, such as fiber optic ultraviolet/visible absorption spectrometry, fiber optic near infrared absorption spectrometry and fibermore » optic fluorescence spectrometry. Fiber optic spectrometric techniques have been developed for investigating the optical properties of these sol-gel derived materials prepared as porous optical fibers or as coatings on the surface of silica optical fibers. Optical and electron microscopic techniques have been used to observe the microstructure, such as pore size, pore shape, sensing agent distribution, of sol-gel derived material, as well as the size and morphology of nanometer metal particle doped in sol-gel derived porous silica, the nature of coating of sol-gel derived materials on silica optical fiber surface. In addition, the chemical reactions of metal ion, nanostructured semiconductor metal oxides and nanometer sized metal particles with gas components at room temperature and high temperatures have also been investigated with fiber optic spectrometric methods. Three classes of fiber optic sensors have been developed based on the thorough investigation of sol-gel chemistry and sol-gel derived materials. The first group of fiber optic sensors uses porous silica optical fibers doped with metal ions or metal oxide as transducers for sensing trace NH{sub 3} and H{sub 2}S in high temperature gas samples. The second group of fiber optic sensors uses sol-gel derived porous silica materials doped with nanometer particles of noble metals in the form of fiber or coating for sensing trace H{sub 2}, NH{sub 3} and HCl in gas samples at for applications ambient temperature. The third classes of fiber optic sensors use sol-gel derived semiconductor metal oxide coating on the surface of silica optical fiber as transducers for selectively sensing H{sub 2}, CH{sub 4} and CO at high temperature. In addition, optical fiber temperature sensors use the fluorescence signal of rare-earth metal ions doped porous silica optical fiber or the optical absorption signal of thermochromic metal oxide materials coated on the surface of silica optical fibers have also been developed for monitoring gas temperature of corrosive gas. Based on the results obtained from this project, the principle of fiber optic sensor techniques for monitoring matrix gas components as well as trace components of coal gasification derived syngas has been established. Prototype sensors for sensing trace ammonia and hydrogen sulfide in gasification derived syngas have been built up in our laboratory and have been tested using gas samples with matrix gas composition similar to that of gasification derived fuel gas. Test results illustrated the feasibility of these sensors for applications in IGCC processes.« less

Effect of soil temperature on optical frequency transfer through unidirectional dense-wavelength-division-multiplexing fiber-optic links.

PubMed

Pinkert, T J; Böll, O; Willmann, L; Jansen, G S M; Dijck, E A; Groeneveld, B G H M; Smets, R; Bosveld, F C; Ubachs, W; Jungmann, K; Eikema, K S E; Koelemeij, J C J

2015-02-01

Results of optical frequency transfer over a carrier-grade dense-wavelength-division-multiplexing (DWDM) optical fiber network are presented. The relation between soil temperature changes on a buried optical fiber and frequency changes of an optical carrier through the fiber is modeled. Soil temperatures, measured at various depths by the Royal Netherlands Meteorology Institute (KNMI) are compared with observed frequency variations through this model. A comparison of a nine-day record of optical frequency measurements through the 2×298  km fiber link with soil temperature data shows qualitative agreement. A soil temperature model is used to predict the link stability over longer periods (days-months-years). We show that optical frequency dissemination is sufficiently stable to distribute and compare, e.g., rubidium frequency standards over standard DWDM optical fiber networks using unidirectional fibers.

Photonic arbitrary waveform generation applicable to multiband UWB communications.

PubMed

Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

2010-12-06

A novel photonic structure for arbitrary waveform generation (AWG) is proposed based on the electrooptical intensity modulation of a broadband optical signal which is transmitted by a dispersive element and the optoelectrical processing is realized by combining an interferometric structure with balanced photodetection. The generated waveform can be fully reconfigured through the control of the optical source power spectrum and the interferometric structure. The use of balanced photodetection permits to remove the baseband component of the generated signal which is relevant in certain applications. We have theoretically described and experimentally demonstrated the feasibility of the system by means of the generation of different pulse shapes. Specifically, the proposed structure has been applicable to generate Multiband UWB signaling formats regarding to the FCC requirements in order to show the flexibility of the system.

Non-interferometric phase retrieval using refractive index manipulation.

PubMed

Chen, Chyong-Hua; Hsu, Hsin-Feng; Chen, Hou-Ren; Hsieh, Wen-Feng

2017-04-07

We present a novel, inexpensive and non-interferometric technique to retrieve phase images by using a liquid crystal phase shifter without including any physically moving parts. First, we derive a new equation of the intensity-phase relation with respect to the change of refractive index, which is similar to the transport of the intensity equation. The equation indicates that this technique is unneeded to consider the variation of magnifications between optical images. For proof of the concept, we use a liquid crystal mixture MLC 2144 to manufacture a phase shifter and to capture the optical images in a rapid succession by electrically tuning the applied voltage of the phase shifter. Experimental results demonstrate that this technique is capable of reconstructing high-resolution phase images and to realize the thickness profile of a microlens array quantitatively.

Holographic Twyman-Green interferometer

NASA Technical Reports Server (NTRS)

Chen, C. W.; Breckinridge, J. B.

1982-01-01

A dichromated gelatin off-axis Fresnel zone plate was designed, fabricated, and used in a new type of interferometer for optical metrology. This single hologram optical element combines the functions of a beam splitter, beam diverger, and aberrated null lens. Data presented show the successful application for an interferometric test of an f/6, 200-mm diam parabolic mirror.

Symmetric periscope for concentric beam configuration in an ultra-high precision laser interferometric beam launcher

NASA Technical Reports Server (NTRS)

Ames, Lawrence L. (Inventor)

2006-01-01

An optical component especially suited for common path heterodyne interferometry comprises a symmetric dual-periscope configuration. Each periscope is substantially identical to the other with regard to certain design aspects. The resulting design is an optical component that is highly stable with variations in temperature and angular deviations.

Large core fiber optic cleaver

DOEpatents

Halpin, J.M.

1996-03-26

The present invention relates to a device and method for cleaving optical fibers which yields cleaved optical fiber ends possessing high damage threshold surfaces. The device can be used to cleave optical fibers with core diameters greater than 400 {micro}m. 30 figs.

Noninvasive blood pressure measurement scheme based on optical fiber sensor

NASA Astrophysics Data System (ADS)

Liu, Xianxuan; Yuan, Xueguang; Zhang, Yangan

2016-10-01

Optical fiber sensing has many advantages, such as volume small, light quality, low loss, strong in anti-jamming. Since the invention of the optical fiber sensing technology in 1977, optical fiber sensing technology has been applied in the military, national defense, aerospace, industrial, medical and other fields in recent years, and made a great contribution to parameter measurement in the environment under the limited condition .With the rapid development of computer, network system, the intelligent optical fiber sensing technology, the sensor technology, the combination of computer and communication technology , the detection, diagnosis and analysis can be automatically and efficiently completed. In this work, we proposed a noninvasive blood pressure detection and analysis scheme which uses optical fiber sensor. Optical fiber sensing system mainly includes the light source, optical fiber, optical detector, optical modulator, the signal processing module and so on. wavelength optical signals were led into the optical fiber sensor and the signals reflected by the human body surface were detected. By comparing actual testing data with the data got by traditional way to measure the blood pressure we can establish models for predicting the blood pressure and achieve noninvasive blood pressure measurement by using spectrum analysis technology. Blood pressure measurement method based on optical fiber sensing system is faster and more convenient than traditional way, and it can get accurate analysis results in a shorter period of time than before, so it can efficiently reduce the time cost and manpower cost.

Optical fiber strain sensor with improved linearity range

NASA Technical Reports Server (NTRS)

Egalon, Claudio Oliveira (Inventor); Rogowski, Robert S. (Inventor)

1995-01-01

A strain sensor is constructed from a two mode optical fiber. When the optical fiber is surface mounted in a straight line and the object to which the optical fiber is mounted is subjected to strain within a predetermined range, the light intensity of any point at the output of the optical fiber will have a linear relationship to strain, provided the intermodal phase difference is less than 0.17 radians.

High-power all-fiber ultra-low noise laser

NASA Astrophysics Data System (ADS)

Zhao, Jian; Guiraud, Germain; Pierre, Christophe; Floissat, Florian; Casanova, Alexis; Hreibi, Ali; Chaibi, Walid; Traynor, Nicholas; Boullet, Johan; Santarelli, Giorgio

2018-06-01

High-power ultra-low noise single-mode single-frequency lasers are in great demand for interferometric metrology. Robust, compact all-fiber lasers represent one of the most promising technologies to replace the current laser sources in use based on injection-locked ring resonators or multi-stage solid-state amplifiers. Here, a linearly polarized high-power ultra-low noise all-fiber laser is demonstrated at a power level of 100 W. Special care has been taken in the study of relative intensity noise (RIN) and its reduction. Using an optimized servo actuator to directly control the driving current of the pump laser diode, we obtain a large feedback bandwidth of up to 1.3 MHz. The RIN reaches - 160 dBc/Hz between 3 and 20 kHz.

High-accuracy fiber-optic shape sensing

NASA Astrophysics Data System (ADS)

Duncan, Roger G.; Froggatt, Mark E.; Kreger, Stephen T.; Seeley, Ryan J.; Gifford, Dawn K.; Sang, Alexander K.; Wolfe, Matthew S.

2007-04-01

We describe the results of a study of the performance characteristics of a monolithic fiber-optic shape sensor array. Distributed strain measurements in a multi-core optical fiber interrogated with the optical frequency domain reflectometry technique are used to deduce the shape of the optical fiber; referencing to a coordinate system yields position information. Two sensing techniques are discussed herein: the first employing fiber Bragg gratings and the second employing the intrinsic Rayleigh backscatter of the optical fiber. We have measured shape and position under a variety of circumstances and report the accuracy and precision of these measurements. A discussion of error sources is included.

[Optical-fiber Fourier transform spectrometer].

PubMed

Liu, Yong; Li, Bao-sheng; Liu, Yan; Zhai, Yu-feng; Wang, An

2006-10-01

A novel Fourier transform spectrum analyzer based on a single mode fiber Mach-Zehnder interferometer is reported. An optical fiber Fourier transform spectrometer, with bulk optics components replaced by fiber optical components and with the moving mirror replaced by a piezoelectric element fiber stretcher was constructed. The output spectrum of a LD below threshold was measured. Experiment result agrees with that by using grating spectrum analyzer, showing the feasibility of the optic fiber Fourier transform spectrometer for practical spectrum measurement. Spectrum resolution -7 cm(-1) was obtained in our experiment. The resolution can be further improved by increasing the maximum optical path difference.

Optical diffraction interpretation: an alternative to interferometers

NASA Astrophysics Data System (ADS)

Bouillet, S.; Audo, F.; Fréville, S.; Eupherte, L.; Rouyer, C.; Daurios, J.

2015-08-01

The Laser MégaJoule (LMJ) is a French high power laser project that requires thousands of large optical components. The wavefront performances of all those optics are critical to achieve the desired focal spot shape and to limit the hot spots that could damage the components. Fizeau interferometers and interferometric microscopes are the most commonly used tools to cover the whole range of interesting spatial frequencies. Anyway, in some particular cases like diffractive and/or coated and/or aspheric optics, an interferometric set-up becomes very expensive with the need to build a costly reference component or a specific to-the-wavelength designed interferometer. Despite the increasing spatial resolution of Fizeau interferometers, it may even not be enough, if you are trying to access the highest spatial frequencies of a transmitted wavefront for instance. The method we developed is based upon laser beam diffraction intermediate field measurements and their interpretation with a Fourier analysis and the Talbot effect theory. We demonstrated in previous papers that it is a credible alternative to classical methods. In this paper we go further by analyzing main error sources and discussing main practical difficulties.

Two-dimensional interferometric characterization of laser-induced refractive index profiles in bulk Topas polymer

NASA Astrophysics Data System (ADS)

Hessler, Steffen; Rosenberger, Manuel; Schmauss, Bernhard; Hellmann, Ralf

2018-01-01

In this paper we precisely determine laser-induced refractive index profiles created in cyclic olefin copolymer Topas 6017 employing a sophisticated phase shifting Mach-Zehnder interferometry approach. Beyond the usual one-dimensional modification depth measurement we highlight that for straight waveguide structures also a two-dimensional refractive index distribution can be directly obtained providing full information of a waveguide's exact cross section and its gradient refractive index contrast. Deployed as direct data input in optical waveguide simulation, the evaluated 2D refractive index profiles permit a detailed calculation of the waveguides' actual mode profiles. Furthermore, conventional one-dimensional interferometric measurements for refractive index depth profiles with varying total imposed laser fluence of a 248 nm KrF excimer laser are included to investigate the effect on refractive index modification depth. Maximum surface refractive index increase turns out to attain up to 1.86 ·10-3 enabling laser-written optical waveguide channels. Additionally, a comprehensive optical material characterization in terms of dispersion, thermo-optic coefficient and absorption measurement of unmodified and UV-modified Topas 6017 is carried out.

Wavefront Processing Through Integrated Fiber Optics.

NASA Astrophysics Data System (ADS)

Khan, Romel Rabiul

This thesis is devoted to the development of a new technology of integrated fiber optics. Through the use of fusion splicing and etching several dissimilar optical fibers can be integrated into a single fiber providing wave-front processing capabilities not previously possible. Optical fibers have been utilized for their unique capabilities; such as, remote beam delivery and immunity from electromagnetic noise. In this thesis, the understanding of integrated fiber optics through fusion splicing is furthered both theoretically and experimentally. Most of the common optical components such as lenses, apertures, and modulators can be implemented through the use of fiber optics and then integrated together through fusion splicing, resulting in an alignment-free, rugged and miniaturized system. For example, a short length of multimode graded-index fiber can be used as either a lens or a window to relay an image. A step-index multimode fiber provides a spacer or an aperture. Other special arrangements can be exploited to do in-line modulation in both amplitude and phase. The power of this technique is demonstrated by focusing on a few applications where significant advantages are obtained through this technology. In laser light scattering fiber optic systems, integrated fiber optics is used for delivering and receiving light from small scattering volumes in a spatially constrained environment. When applied for the detection of cataracts in the human eye lens, laser light scattering probes with integrated fiber optics could obtain a map of the eye lens and provide invaluable data for further understanding of cataractogenesis. Use of integrated fiber optics in the high resolution structural analysis of aircraft propeller blades is also presented. Coupling of laser diode to monomode fiber through integrated fiber optics is analyzed. The generation of nondiffracting Bessel-Gauss beams using integrated fiber optics is described. The significance of the Bessel-Gauss beam lies in the fact that it has a sharply defined main-lobe whose width can be designed to be as narrow as desired, while maintaining a long propagation-invariant range. Different methods of generation and properties of this beam are reviewed. Effects of misalignments in the input plane and discretization of the source are derived and evaluated.

Microstructured optical fiber-based luminescent biosensing: Is there any light at the end of the tunnel? - A review.

PubMed

Pidenko, Sergey A; Burmistrova, Natalia A; Shuvalov, Andrey A; Chibrova, Anastasiya A; Skibina, Yulia S; Goryacheva, Irina Y

2018-08-17

This review covers the current state of the art of luminescent biosensors based on various types of microstructured optical fiber. The unique optical and structural properties of this type of optical fiber make them one of the most promising integrated platforms for bioassays. The individual sections of this review are devoted to a) classification of microstructured optical fibers, b) microstructured optical fiber materials, c) aspects of biosensing based on the biomolecules incorporated into the microstructured optical fibers, and d) development of models for prediction of the efficiency of luminescent signal processing. The authors' views on current trends and limitations of microstructured optical fibers for biosensing as well as the most promising areas and technologies for application in analytical practice are presented. Copyright © 2017 Elsevier B.V. All rights reserved.

Algorithms and Array Design Criteria for Robust Imaging in Interferometry

NASA Astrophysics Data System (ADS)

Kurien, Binoy George

Optical interferometry is a technique for obtaining high-resolution imagery of a distant target by interfering light from multiple telescopes. Image restoration from interferometric measurements poses a unique set of challenges. The first challenge is that the measurement set provides only a sparse-sampling of the object's Fourier Transform and hence image formation from these measurements is an inherently ill-posed inverse problem. Secondly, atmospheric turbulence causes severe distortion of the phase of the Fourier samples. We develop array design conditions for unique Fourier phase recovery, as well as a comprehensive algorithmic framework based on the notion of redundant-spaced-calibration (RSC), which together achieve reliable image reconstruction in spite of these challenges. Within this framework, we see that classical interferometric observables such as the bispectrum and closure phase can limit sensitivity, and that generalized notions of these observables can improve both theoretical and empirical performance. Our framework leverages techniques from lattice theory to resolve integer phase ambiguities in the interferometric phase measurements, and from graph theory, to select a reliable set of generalized observables. We analyze the expected shot-noise-limited performance of our algorithm for both pairwise and Fizeau interferometric architectures and corroborate this analysis with simulation results. We apply techniques from the field of compressed sensing to perform image reconstruction from the estimates of the object's Fourier coefficients. The end result is a comprehensive strategy to achieve well-posed and easily-predictable reconstruction performance in optical interferometry.

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

Quantitative phase measurement for wafer-level optics

NASA Astrophysics Data System (ADS)

Qu, Weijuan; Wen, Yongfu; Wang, Zhaomin; Yang, Fang; Huang, Lei; Zuo, Chao

2015-07-01

Wafer-level-optics now is widely used in smart phone camera, mobile video conferencing or in medical equipment that require tiny cameras. Extracting quantitative phase information has received increased interest in order to quantify the quality of manufactured wafer-level-optics, detect defective devices before packaging, and provide feedback for manufacturing process control, all at the wafer-level for high-throughput microfabrication. We demonstrate two phase imaging methods, digital holographic microscopy (DHM) and Transport-of-Intensity Equation (TIE) to measure the phase of the wafer-level lenses. DHM is a laser-based interferometric method based on interference of two wavefronts. It can perform a phase measurement in a single shot. While a minimum of two measurements of the spatial intensity of the optical wave in closely spaced planes perpendicular to the direction of propagation are needed to do the direct phase retrieval by solving a second-order differential equation, i.e., with a non-iterative deterministic algorithm from intensity measurements using the Transport-of-Intensity Equation (TIE). But TIE is a non-interferometric method, thus can be applied to partial-coherence light. We demonstrated the capability and disability for the two phase measurement methods for wafer-level optics inspection.

Optical microscope using an interferometric source of two-color, two-beam entangled photons

DOEpatents

Dress, William B.; Kisner, Roger A.; Richards, Roger K.

2004-07-13

Systems and methods are described for an optical microscope using an interferometric source of multi-color, multi-beam entangled photons. A method includes: downconverting a beam of coherent energy to provide a beam of multi-color entangled photons; converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; transforming at least a portion of the converged multi-color entangled photon beam by interaction with a sample to generate an entangled photon specimen beam; and combining the entangled photon specimen beam with an entangled photon reference beam within a single beamsplitter. An apparatus includes: a multi-refringent device providing a beam of multi-color entangled photons; a condenser device optically coupled to the multi-refringent device, the condenser device converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; a beam probe director and specimen assembly optically coupled to the condenser device; and a beam splitter optically coupled to the beam probe director and specimen assembly, the beam splitter combining an entangled photon specimen beam from the beam probe director and specimen assembly with an entangled photon reference beam.

Specialty fibers for fiber optic sensor application

NASA Astrophysics Data System (ADS)

Bennett, K.; Koh, J.; Coon, J.; Chien, C. K.; Artuso, A.; Chen, X.; Nolan, D.; Li, M.-J.

2007-09-01

Over the last several years, Fiber Optic Sensor (FOS) applications have seen an increased acceptance in many areas including oil & gas production monitoring, gyroscopes, current sensors, structural sensing and monitoring, and aerospace applications. High level optical and mechanical reliability of optical fiber is necessary to guarantee reliable performance of FOS. In this paper, we review recent research and development activities on new specialty fibers. We discuss fiber design concepts and present both modeling and experimental results. The main approaches to enhancing fiber attributes include new index profile design and fiber coating modification.

Buying Fiber-Optic Networks.

ERIC Educational Resources Information Center

Fickes, Michael

2003-01-01

Describes consortia formed by college and university administrators to buy, manage, and maintain their own fiber-optic networks with the goals of cutting costs of leasing fiber-optic cable and planning for the future. Growth capacity is the real advantage of owning fiber-optic systems. (SLD)

Package for integrated optic circuit and method

DOEpatents

Kravitz, Stanley H.; Hadley, G. Ronald; Warren, Mial E.; Carson, Richard F.; Armendariz, Marcelino G.

1998-01-01

A structure and method for packaging an integrated optic circuit. The package comprises a first wall having a plurality of microlenses formed therein to establish channels of optical communication with an integrated optic circuit within the package. A first registration pattern is provided on an inside surface of one of the walls of the package for alignment and attachment of the integrated optic circuit. The package in one embodiment may further comprise a fiber holder for aligning and attaching a plurality of optical fibers to the package and extending the channels of optical communication to the fibers outside the package. In another embodiment, a fiber holder may be used to hold the fibers and align the fibers to the package. The fiber holder may be detachably connected to the package.

Package for integrated optic circuit and method

DOEpatents

Kravitz, S.H.; Hadley, G.R.; Warren, M.E.; Carson, R.F.; Armendariz, M.G.

1998-08-04

A structure and method are disclosed for packaging an integrated optic circuit. The package comprises a first wall having a plurality of microlenses formed therein to establish channels of optical communication with an integrated optic circuit within the package. A first registration pattern is provided on an inside surface of one of the walls of the package for alignment and attachment of the integrated optic circuit. The package in one embodiment may further comprise a fiber holder for aligning and attaching a plurality of optical fibers to the package and extending the channels of optical communication to the fibers outside the package. In another embodiment, a fiber holder may be used to hold the fibers and align the fibers to the package. The fiber holder may be detachably connected to the package. 6 figs.

Micro-LiDAR velocity, temperature, density, concentration sensor

NASA Technical Reports Server (NTRS)

Dorrington, Adrian A. (Inventor); Danehy, Paul M. (Inventor)

2010-01-01

A light scatter sensor includes a sensor body in which are positioned a plurality of optical fibers. The sensor body includes a surface, in one end of each of the optical fibers terminates at the surface of the sensor body. One of the optical fibers is an illumination fiber for emitting light. A plurality of second optical fibers are collection fibers for collecting scattered light signals. A light sensor processor is connected to the collection fibers to detect the scattered light signals.

Microstructured Optical Fiber for X-ray Detection

NASA Technical Reports Server (NTRS)

DeHaven, Stanton L.

2009-01-01

A novel scintillating optical fiber is presented using a composite micro-structured quartz optical fiber. Scintillating materials are introduced into the multiple inclusions of the fiber. This creates a composite optical fiber having quartz as a cladding with an organic scintillating material core. X-ray detection using these fibers is compared to a collimated cadmium telluride (CdTe) detector over an energy range from 10 to 40 keV. Results show a good correlation between the fiber count rate trend and that of the CdTe detector.

Model predictions of the results of interferometric observations for stars under conditions of strong gravitational scattering by black holes and wormholes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shatskiy, A. A., E-mail: shatskiy@asc.rssi.ru; Kovalev, Yu. Yu.; Novikov, I. D.

2015-05-15

The characteristic and distinctive features of the visibility amplitude of interferometric observations for compact objects like stars in the immediate vicinity of the central black hole in our Galaxy are considered. These features are associated with the specifics of strong gravitational scattering of point sources by black holes, wormholes, or black-white holes. The revealed features will help to determine the most important topological characteristics of the central object in our Galaxy: whether this object possesses the properties of only a black hole or also has characteristics unique to wormholes or black-white holes. These studies can be used to interpret themore » results of optical, infrared, and radio interferometric observations.« less

Fabrication of polymer microlenses on single mode optical fibers for light coupling

NASA Astrophysics Data System (ADS)

Zaboub, Monsef; Guessoum, Assia; Demagh, Nacer-Eddine; Guermat, Abdelhak

2016-05-01

In this paper, we present a technique for producing fibers optics micro-collimators composed of polydimethylsiloxane PDMS microlenses of different radii of curvature. The waist and working distance values obtained enable the optimization of optical coupling between optical fibers, fibers and optical sources, and fibers and detectors. The principal is based on the injection of polydimethylsiloxane (PDMS) into a conical micro-cavity chemically etched at the end of optical fibers. A spherical microlens is then formed that is self-centered with respect to the axis of the fiber. Typically, an optimal radius of curvature of 10.08 μm is obtained. This optimized micro-collimator is characterized by a working distance of 19.27 μm and a waist equal to 2.28 μm for an SMF 9/125 μm fiber. The simulation and experimental results reveal an optical coupling efficiency that can reach a value of 99.75%.

THUNDER Piezoelectric Actuators as a Method of Stretch-Tuning an Optical Fiber Grating

NASA Technical Reports Server (NTRS)

Allison, Sidney G.; Fox, Robert L.; Froggatt, Mark E.; Childers, Brooks A.

2000-01-01

A method of stretching optical fiber holds interest for measuring strain in smart structures where the physical displacement may be used to tune optical fiber lasers. A small, light weight, low power tunable fiber laser is ideal for demodulating strain in optical fiber Bragg gratings attached to smart structures such as the re-usable launch vehicle that is being developed by NASA. A method is presented for stretching optical fibers using the THUNDER piezoelectric actuators invented at NASA Langley Research Center. THUNDER actuators use a piezoelectric layer bonded to a metal backing to enable the actuators to produce displacements larger than the unbonded piezoelectric material. The shift in reflected optical wavelength resulting from stretching the fiber Bragg grating is presented. Means of adapting THUNDER actuators for stretching optical fibers is discussed, including ferrules, ferrule clamp blocks, and plastic hinges made with stereo lithography.

Optical fiber sensor having a sol-gel fiber core and a method of making

DOEpatents

Tao, Shiquan; Jindal, Rajeev; Winstead, Christopher; Singh, Jagdish P.

2006-06-06

A simple, economic wet chemical procedure is described for making sol-gel fibers. The sol-gel fibers made from this process are transparent to ultraviolet, visible and near infrared light. Light can be guided in these fibers by using an organic polymer as a fiber cladding. Alternatively, air can be used as a low refractive index medium. The sol-gel fibers have a micro pore structure which allows molecules to diffuse into the fiber core from the surrounding environment. Chemical and biochemical reagents can be doped into the fiber core. The sol-gel fiber can be used as a transducer for constructing an optical fiber sensor. The optical fiber sensor having an active sol-gel fiber core is more sensitive than conventional evanescent wave absorption based optical fiber sensors.

Study of fiber optics standardization, reliability, and applications

NASA Technical Reports Server (NTRS)

1980-01-01

The use of fiber optics in space applications is investigated. Manufacturers and users detailed the problems they were having with the use or manufacture of fiber optic components. The general consensus of all the companies/agencies interviewed is that fiber optics is a maturing technology and will definitely have a place in future NASA system designs. The use of fiber optics was found to have two main advantages - weight savings and increased bandwidth.

Three-dimensional image formation in fiber-optical second-harmonic-generation microscopy.

PubMed

Gu, Min; Fu, Ling

2006-02-06

Three-dimensional (3-D) image formation in fiber-optical second-harmonic-generation microscopy is revealed to be purely coherent and therefore can be described by a 3-D coherent transfer function (CTF) that exhibits the same spatial frequency passband as that of fiber-optical reflection-mode non-fluorescence microscopy. When the numerical aperture of the fiber is much larger than the angle of convergence of the illumination on the fiber aperture, the performance of fiber-optical second-harmonic-generation microscopy behaves as confocal second-harmonic-generation microscopy. The dependence of axial resolution on fiber coupling parameters shows an improvement of approximately 7%, compared with that in fiber-optical two-photon fluorescence microscopy.

Fabrication of Fiber Optic Grating Apparatus and Method

NASA Technical Reports Server (NTRS)

Wang, Ying (Inventor); Sharma, Anup (Inventor); Grant, Joseph (Inventor)

2005-01-01

An apparatus and method for forming a Bragg grating on an optical fiber using a phase mask to diffract a beam of coherent energy and a lens combined with a pair of mirrors to produce two symmetrical virtual point sources of coherent energy in the plane of the optical fiber. The two virtual light sources produce an interference pattern along the optical fiber. In a further embodiment, the period of the pattern and therefore the Bragg wavelength grating applied to the fiber is varied with the position of the optical fiber relative the lens.

Realization of fiber optic displacement sensors

NASA Astrophysics Data System (ADS)

Guzowski, Bartlomiej; Lakomski, Mateusz

2018-03-01

Fiber optic sensors are very promising because of their inherent advantages such as very small size, hard environment tolerance and impact of electromagnetic fields. In this paper three different types of Intensity Fiber Optic Displacement Sensors (I-FODS) are presented. Three configurations of I-FODS were realized in two varieties. In the first one, the cleaved multimode optical fibers (MMF) were used to collect reflected light, while in the second variety the MMF ended with ball lenses were chosen. To ensure an accurate alignment of optical fibers in the sensor head the MTP C9730 optical fiber ferrules were used. In this paper the influence of distribution of transmitting and detecting optical fibers on sensitivity and linear range of operation of developed I-FODS were investigated. We have shown, that I-FODS with ball lenses receive average 10.5% more reflected power in comparison to the cleaved optical fibers and they increase linearity range of I-FODS by 33%. In this paper, an analysis of each type of the realized sensor and detailed discussion are given.

Microbend fiber-optic temperature sensor

DOEpatents

Weiss, Jonathan D.

1995-01-01

A temperature sensor is made of optical fiber into which quasi-sinusoidal microbends have been permanently introduced. In particular, the present invention includes a graded-index optical fiber directing steady light through a section of the optical fiber containing a plurality of permanent microbends. The microbend section of the optical fiber is contained in a thermally expansive sheath, attached to a thermally expansive structure, or attached to a bimetallic element undergoing temperature changes and being monitored. The microbend section is secured to the thermally expansive sheath which allows the amplitude of the microbends to decrease with temperature. The resultant increase in the optical fiber's transmission thus allows temperature to be measured. The plural microbend section of the optical fiber is secured to the thermally expansive structure only at its ends and the microbends themselves are completely unconstrained laterally by any bonding agent to obtain maximum longitudinal temperature sensitivity. Although the permanent microbends reduce the transmission capabilities of fiber optics, the present invention utilizes this phenomenon as a transduction mechanism which is optimized to measure temperature.

Ultra-weak FBG and its refractive index distribution in the drawing optical fiber.

PubMed

Guo, Huiyong; Liu, Fang; Yuan, Yinquan; Yu, Haihu; Yang, Minghong

2015-02-23

For the online writing of ultra-weak fiber Bragg gratings (FBGs) in the drawing optical fibers, the effects of the intensity profile, pulse fluctuation and pulse width of the excimer laser, as well as the transverse and longitudinal vibrations of the optical fiber have been investigated. Firstly, using Lorentz-Loren equation, Gladstone-Dale mixing rule and continuity equation, we have derived the refractive index (RI) fluctuation along the optical fiber and the RI distribution in the FBG, they are linear with the gradient of longitudinal vibration velocity. Then, we have prepared huge amounts of ultra-weak FBGs in the non-moving optical fiber and obtained their reflection spectra, the measured reflection spectra shows that the intensity profile and pulse fluctuation of the excimer laser, as well as the transverse vibration of the optical fiber are little responsible for the inconsistency of ultra-weak FBGs. Finally, the effect of the longitudinal vibration of the optical fiber on the inconsistency of ultra-weak FBGs has been discussed, and the vibration equations of the drawing optical fiber are given in the appendix.

Distributed fiber-optic laser-ultrasound generation based on ghost-mode of tilted fiber Bragg gratings.

PubMed

Tian, Jiajun; Zhang, Qi; Han, Ming

2013-03-11

Active ultrasonic testing is widely used for medical diagnosis, material characterization and structural health monitoring. Ultrasonic transducer is a key component in active ultrasonic testing. Due to their many advantages such as small size, light weight, and immunity to electromagnetic interference, fiber-optic ultrasonic transducers are particularly attractive for permanent, embedded applications in active ultrasonic testing for structural health monitoring. However, current fiber-optic transducers only allow effective ultrasound generation at a single location of the fiber end. Here we demonstrate a fiber-optic device that can effectively generate ultrasound at multiple, selected locations along a fiber in a controllable manner based on a smart light tapping scheme that only taps out the light of a particular wavelength for laser-ultrasound generation and allow light of longer wavelengths pass by without loss. Such a scheme may also find applications in remote fiber-optic device tuning and quasi-distributed biochemical fiber-optic sensing.

Miniature mechanical transfer optical coupler

DOEpatents

Abel, Philip [Overland Park, KS; Watterson, Carl [Kansas City, MO

2011-02-15

A miniature mechanical transfer (MT) optical coupler ("MMTOC") for optically connecting a first plurality of optical fibers with at least one other plurality of optical fibers. The MMTOC may comprise a beam splitting element, a plurality of collimating lenses, and a plurality of alignment elements. The MMTOC may optically couple a first plurality of fibers disposed in a plurality of ferrules of a first MT connector with a second plurality of fibers disposed in a plurality of ferrules of a second MT connector and a third plurality of fibers disposed in a plurality of ferrules of a third MT connector. The beam splitting element may allow a portion of each beam of light from the first plurality of fibers to pass through to the second plurality of fibers and simultaneously reflect another portion of each beam of light from the first plurality of fibers to the third plurality of fibers.

Estimation of coupling efficiency of optical fiber by far-field method

NASA Astrophysics Data System (ADS)

Kataoka, Keiji

2010-09-01

Coupling efficiency to a single-mode optical fiber can be estimated with the field amplitudes at far-field of an incident beam and optical fiber mode. We call it the calculation by far-field method (FFM) in this paper. The coupling efficiency by FFM is formulated including effects of optical aberrations, vignetting of the incident beam, and misalignments of the optical fiber such as defocus, lateral displacements, and angle deviation in arrangement of the fiber. As the results, it is shown the coupling efficiency is proportional to the central intensity of the focused spot, i.e., Strehl intensity of a virtual beam determined by the incident beam and mode of the optical fiber. Using the FFM, a typical optics in which a laser beam is coupled to an optical fiber with a lens of finite numerical aperture (NA) is analyzed for several cases of amplitude distributions of the incident light.

All-optical, thermo-optical path length modulation based on the vanadium-doped fibers.

PubMed

Matjasec, Ziga; Campelj, Stanislav; Donlagic, Denis

2013-05-20

This paper presents an all-fiber, fully-optically controlled, optical-path length modulator based on highly absorbing optical fiber. The modulator utilizes a high-power 980 nm pump diode and a short section of vanadium-co-doped single mode fiber that is heated through absorption and a non-radiative relaxation process. The achievable path length modulation range primarily depends on the pump's power and the convective heat-transfer coefficient of the surrounding gas, while the time response primarily depends on the heated fiber's diameter. An absolute optical length change in excess of 500 µm and a time-constant as short as 11 ms, were demonstrated experimentally. The all-fiber design allows for an electrically-passive and remote operation of the modulator. The presented modulator could find use within various fiber-optics systems that require optical (remote) path length control or modulation.