High-Sensitivity Fiber-Optic Ultrasound Sensors for Medical Imaging Applications

PubMed Central

Wen, H.; Wiesler, D.G.; Tveten, A.; Danver, B.; Dandridge, A.

2010-01-01

This paper presents several designs of high-sensitivity, compact fiber-optic ultrasound sensors that may be used for medical imaging applications. These sensors translate ultrasonic pulses into strains in single-mode optical fibers, which are measured with fiber-based laser interferometers at high precision. The sensors are simpler and less expensive to make than piezoelectric sensors, and are not susceptible to electromagnetic interference. It is possible to make focal sensors with these designs, and several schemes are discussed. Because of the minimum bending radius of optical fibers, the designs are suitable for single element sensors rather than for arrays. PMID:9691368

Graphene enhanced optical fiber SPR sensor for liquid concentration measurement

NASA Astrophysics Data System (ADS)

Zhou, Xue; Li, Xuegang; Cheng, TongLei; Li, Shuguang; An, Guowen

2018-07-01

A high sensitivity optical fiber Surface Plasmon Resonance (SPR) sensor which based on coreless optical fiber, silver film and graphene, has been designed and implemented for liquid concentration detection. In this paper, Graphene is firstly verified that it can be used to enhance the evanescent field of traditional optical fiber and thus increasing sensitivity in experiment. The sensitivity of proposed sensor is 6.417 nm/%, which is higher than that of the traditional optical fiber SPR sensor according to the comparative experiments. In addition, the proposed sensor is extremely easy to make and the silver film could be protected from oxidation and damage due to the existence of graphene. Moreover, the sensor has pretty small size, immunity to electromagnetic interference, quick response speed and thus can suitable a variety of severe environments and real-time measurement.

Sensitivity enhancement of fluorescence detection in CE by coupling and conducting excitation light with tapered optical fiber.

PubMed

Yang, Xiupei; Huo, Feng; Yuan, Hongyan; Zhang, Bo; Xiao, Dan; Choi, Martin M F

2011-01-01

This paper reports the enhancement of sensitivity of detection for in-column fiber optic-induced fluorescence detection system in CE by tapered optical fiber (TOF). Two types of optical fiber, TOF and conventional cylindrical optical fiber (COF), were employed to construct the CE (TOF-CE and COF-CE) and were compared for sensitivity to riboflavin (RF). The fluorescence intensities from a RF sample with excitation light sources and fibers at various coupling angles were investigated. The fluorescence signal from TOF-CE was ca. ten times that of COF-CE. In addition, the detection performance of four excitation light source-fiber configurations including Laser-TOF, Laser-COF, LED-TOF, and LED-COF were compared. The LODs for RF were 0.21, 0.82, 0.80, and 7.5 nM, respectively, for the four excitation light source-fiber configurations. The results demonstrate that the sensitivity obtained by LED-TOF is close to that of Laser-COF. Both Laser-TOF and LED-TOF can greatly improve the sensitivity of detection in CE. TOF has the major attribute of collecting and focusing the excitation light intensity. Thus, the sensitivity obtained by LED-TOF without focusing lens is just same as that of LED-COF with a focusing lens. This demonstrates that the CE system can be further simplified by eliminating the focusing lens for excitation light. LED-TOF-CE and LED-COF-CE system were applied to the separation and determination of RF in real sample (green tea), respectively. The tapered fiber optic-induced fluorescence detection system in CE is an ideal tool for trace analysis. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Control systems using modal domain optical fiber sensors for smart structure applications

NASA Technical Reports Server (NTRS)

Lindner, Douglas K.; Reichard, Karl M.

1991-01-01

Recently, a new class of sensors has emerged for structural control which respond to environmental changes over a significant gauge length; these sensors are called distributed-effect sensors. These sensors can be fabricated with spatially varying sensitivity to the distributed measurand, and can be configured to measure a variety of structural parameters which can not be measured directly using point sensors. Examples of distributed-effect sensors include piezoelectric film, holographic sensors, and modal domain optical fiber sensors. Optical fiber sensors are particularly attractive for smart structure applications because they are flexible, have low mass, and can easily be embedded directly into materials. In this paper we describe the implementation of weighted modal domain optical fiber sensors. The mathematical model of the modal domain optical fiber sensor model is described and used to derive an expression for the sensor sensitivity. The effects of parameter variations on the sensor sensitivity are demonstrated to illustrate methods of spatially varying the sensor sensitivity.

Fiber optic SERS-based plasmonics nanobiosensing in single living cells

NASA Astrophysics Data System (ADS)

Scaffidi, Jonathan P.; Gregas, Molly K.; Seewaldt, Victoria; Vo-Dinh, Tuan

2009-05-01

We describe the development of small molecule-sensitive plasmonics-active fiber-optic nanoprobes suitable for intracellular bioanalysis in single living human cells using surface-enhanced Raman scattering (SERS) detection. The practical utility of SERS-based fiber-optic nanoprobes is illustrated by measurements of intracellular pH in HMEC- 15/hTERT immortalized "normal" human mammary epithelial cells and PC-3 human prostate cancer cells. The results indicate that fiber-optic nanoprobe insertion and interrogation provide a sensitive and selective means to monitor biologically-relevant small molecules at the single cell level.

Overview of Fiber-Optical Sensors

NASA Technical Reports Server (NTRS)

Depaula, Ramon P.; Moore, Emery L.

1987-01-01

Design, development, and sensitivity of sensors using fiber optics reviewed. State-of-the-art and probable future developments of sensors using fiber optics described in report including references to work in field. Serves to update previously published surveys. Systems incorporating fiber-optic sensors used in medical diagnosis, navigation, robotics, sonar, power industry, and industrial controls.

Radio-over-fiber using an optical antenna based on Rydberg states of atoms

NASA Astrophysics Data System (ADS)

Deb, A. B.; Kjærgaard, N.

2018-05-01

We provide an experimental demonstration of a direct fiber-optic link for RF transmission ("radio-over-fiber") using a sensitive optical antenna based on a rubidium vapor cell. The scheme relies on measuring the transmission of laser light at an electromagnetically induced transparency resonance that involves highly excited Rydberg states. By dressing pairs of Rydberg states using microwave fields that act as local oscillators, we encoded RF signals in the optical frequency domain. The light carrying the information is linked via a virtually lossless optical fiber to a photodetector where the signal is retrieved. We demonstrate a signal bandwidth in excess of 1 MHz limited by the available coupling laser power and atomic optical density. Our sensitive, non-metallic and readily scalable optical antenna for microwaves allows extremely low-levels of optical power (˜1 μW) throughput in the fiber-optic link. It offers a promising future platform for emerging wireless network infrastructures.

Chemiluminescent optical fiber immunosensor for the detection of anti-West Nile virus IgG.

PubMed

Herrmann, Sebastien; Leshem, Boaz; Landes, Shimi; Rager-Zisman, Bracha; Marks, Robert S

2005-03-31

An ELISA-based optical fiber methodology developed for the detection of anti-West Nile virus IgG antibodies in serum was compared to standard colorimetric and chemiluminescent ELISA based on microtiter plates. Colorimetric ELISA was the least sensitive, especially at high titer dilutions. The fiber-optic immunosensor based on the same ELISA immunological rationale was the most sensitive technique.

Thermal and chemical treatment of polymer optical fiber Bragg grating sensors for enhanced mechanical sensitivity

NASA Astrophysics Data System (ADS)

Pospori, A.; Marques, C. A. F.; Sáez-Rodríguez, D.; Nielsen, K.; Bang, O.; Webb, D. J.

2017-07-01

An investigation of the thermal annealing effects on the strain, stress, and force sensitivities of polymer optical fiber Bragg grating sensors is performed. We demonstrate for the first time that the fiber annealing can enhance both stress and force sensitivities of Bragg grating sensors, with the possible cause being the molecular relaxation of the polymer when fiber is raised above the β -transition temperature. A simple, cost-effective, but well controlled method for fiber annealing is also presented in this work. In addition, the effects of chemical etching on the strain, stress, and force sensitivities have been investigated. Results show that fiber etching too can increase the force sensitivity, and it can also affect the strain and stress sensitivities of the Bragg grating sensors.

Highly Sensitive Temperature Sensors Based on Fiber-Optic PWM and Capacitance Variation Using Thermochromic Sensing Membrane.

PubMed

Khan, Md Rajibur Rahaman; Kang, Shin-Won

2016-07-09

In this paper, we propose a temperature/thermal sensor that contains a Rhodamine-B sensing membrane. We applied two different sensing methods, namely, fiber-optic pulse width modulation (PWM) and an interdigitated capacitor (IDC)-based temperature sensor to measure the temperature from 5 °C to 100 °C. To the best of our knowledge, the fiber-optic PWM-based temperature sensor is reported for the first time in this study. The proposed fiber-optic PWM temperature sensor has good sensing ability; its sensitivity is ~3.733 mV/°C. The designed temperature-sensing system offers stable sensing responses over a wide dynamic range, good reproducibility properties with a relative standard deviation (RSD) of ~0.021, and the capacity for a linear sensing response with a correlation coefficient of R² ≈ 0.992 over a wide sensing range. In our study, we also developed an IDC temperature sensor that is based on the capacitance variation principle as the IDC sensing element is heated. We compared the performance of the proposed temperature-sensing systems with different fiber-optic temperature sensors (which are based on the fiber-optic wavelength shift method, the long grating fiber-optic Sagnac loop, and probe type fiber-optics) in terms of sensitivity, dynamic range, and linearity. We observed that the proposed sensing systems have better sensing performance than the above-mentioned sensing system.

Comment on "Optical-fiber-based Mueller optical coherence tomography".

PubMed

Park, B Hyle; Pierce, Mark C; de Boer, Johannes F

2004-12-15

We comment on the recent Letter by Jiao et al. [Opt. Lett. 28, 1206 (2003)] in which a polarization-sensitive optical coherence tomography system was presented. Interrogating a sample with two orthogonal incident polarization states cannot always recover birefringence correctly. A previously presented fiber-based polarization-sensitive system was inaccurately characterized, and its method of eliminating the polarization distortion caused by single-mode optical fiber was presented earlier by Saxer et al. [Opt. Lett. 25, 1355 (2000)].

Distributed phase birefringence measurements based on polarization correlation in phase-sensitive optical time-domain reflectometers.

PubMed

Soto, Marcelo A; Lu, Xin; Martins, Hugo F; Gonzalez-Herraez, Miguel; Thévenaz, Luc

2015-09-21

In this paper a technique to measure the distributed birefringence profile along optical fibers is proposed and experimentally validated. The method is based on the spectral correlation between two sets of orthogonally-polarized measurements acquired using a phase-sensitive optical time-domain reflectometer (ϕOTDR). The correlation between the two measured spectra gives a resonance (correlation) peak at a frequency detuning that is proportional to the local refractive index difference between the two orthogonal polarization axes of the fiber. In this way the method enables local phase birefringence measurements at any position along optical fibers, so that any longitudinal fluctuation can be precisely evaluated with metric spatial resolution. The method has been experimentally validated by measuring fibers with low and high birefringence, such as standard single-mode fibers as well as conventional polarization-maintaining fibers. The technique has potential applications in the characterization of optical fibers for telecommunications as well as in distributed optical fiber sensing.

Fiber optic choline biosensor

NASA Astrophysics Data System (ADS)

Wang, Hong; Cao, Xiaojian; Jia, Ke; Chai, Xueting; Lu, Hua; Lu, Zuhong

2001-10-01

A fiber optic fluorescence biosensor for choline is introduced in this paper. Choline is an important neurotransmitter in mammals. Due to the growing needs for on-site clinical monitoring of the choline, much effect has been devoted to develop choline biosensors. Fiber-optic fluorescence biosensors have many advantages, including miniaturization, flexibility, and lack of electrical contact and interference. The choline fiber-optic biosensor we designed implemented a bifurcated fiber to perform fluorescence measurements. The light of the blue LED is coupled into one end of the fiber as excitation and the emission spectrum from sensing film is monitored by fiber-spectrometer (S2000, Ocean Optics) through the other end of the fiber. The sensing end of the fiber is coated with Nafion film dispersed with choline oxidase and oxygen sensitive luminescent Ru(II) complex (Tris(2,2'-bipyridyl)dichlororuthenium(II), hexahydrate). Choline oxidase catalyzes the oxidation of choline to betaine and hydrogen peroxide while consuming oxygen. The fluorescence intensity of oxygen- sensitive Ru(II) are related to the choline concentration. The response of the fiber-optic sensor in choline solution is represented and discussed. The result indicates a low-cost, high-performance, portable choline biosensor.

Rugged fiber optic probe for raman measurement

DOEpatents

O'Rourke, Patrick E.; Toole, Jr., William R.; Nave, Stanley E.

1998-01-01

An optical probe for conducting light scattering analysis is disclosed. The probe comprises a hollow housing and a probe tip. A fiber assembly made up of a transmitting fiber and a receiving bundle is inserted in the tip. A filter assembly is inserted in the housing and connected to the fiber assembly. A signal line from the light source and to the spectrometer also is connected to the filter assembly and communicates with the fiber assembly. By using a spring-loaded assembly to hold the fiber connectors together with the in-line filters, complex and sensitive alignment procedures are avoided. The close proximity of the filter assembly to the probe tip eliminates or minimizes self-scattering generated by the optical fiber. Also, because the probe can contact the sample directly, sensitive optics can be eliminated.

Field test investigation of high sensitivity fiber optic seismic geophone

NASA Astrophysics Data System (ADS)

Wang, Meng; Min, Li; Zhang, Xiaolei; Zhang, Faxiang; Sun, Zhihui; Li, Shujuan; Wang, Chang; Zhao, Zhong; Hao, Guanghu

2017-10-01

Seismic reflection, whose measured signal is the artificial seismic waves ,is the most effective method and widely used in the geophysical prospecting. And this method can be used for exploration of oil, gas and coal. When a seismic wave travelling through the Earth encounters an interface between two materials with different acoustic impedances, some of the wave energy will reflect off the interface and some will refract through the interface. At its most basic, the seismic reflection technique consists of generating seismic waves and measuring the time taken for the waves to travel from the source, reflect off an interface and be detected by an array of geophones at the surface. Compared to traditional geophones such as electric, magnetic, mechanical and gas geophone, optical fiber geophones have many advantages. Optical fiber geophones can achieve sensing and signal transmission simultaneously. With the development of fiber grating sensor technology, fiber bragg grating (FBG) is being applied in seismic exploration and draws more and more attention to its advantage of anti-electromagnetic interference, high sensitivity and insensitivity to meteorological conditions. In this paper, we designed a high sensitivity geophone and tested its sensitivity, based on the theory of FBG sensing. The frequency response range is from 10 Hz to 100 Hz and the acceleration of the fiber optic seismic geophone is over 1000pm/g. sixteen-element fiber optic seismic geophone array system is presented and the field test is performed in Shengli oilfield of China. The field test shows that: (1) the fiber optic seismic geophone has a higher sensitivity than the traditional geophone between 1-100 Hz;(2) The low frequency reflection wave continuity of fiber Bragg grating geophone is better.

Turbidimeter Design and Analysis: A Review on Optical Fiber Sensors for the Measurement of Water Turbidity

PubMed Central

Omar, Ahmad Fairuz Bin; MatJafri, Mohd Zubir Bin

2009-01-01

Turbidimeters operate based on the optical phenomena that occur when incident light through water body is scattered by the existence of foreign particles which are suspended within it. This review paper elaborates on the standards and factors that may influence the measurement of turbidity. The discussion also focuses on the optical fiber sensor technologies that have been applied within the lab and field environment and have been implemented in the measurement of water turbidity and concentration of particles. This paper also discusses and compares results from three different turbidimeter designs that use various optical components. Mohd Zubir and Bashah and Daraigan have introduced a design which has simple configurations. Omar and MatJafri, on the other hand, have established a new turbidimeter design that makes use of optical fiber cable as the light transferring medium. The application of fiber optic cable to the turbidimeter will present a flexible measurement technique, allowing measurements to be made online. Scattered light measurement through optical fiber cable requires a highly sensitive detector to interpret the scattered light signal. This has made the optical fiber system have higher sensitivity in measuring turbidity compared to the other two simple turbidimeters presented in this paper. Fiber optic sensors provide the potential for increased sensitivity over large concentration ranges. However, many challenges must be examined to develop sensors that can collect reliable turbidity measurements in situ. PMID:22408507

Realization of a fiber optic sensor detecting the presence of a liquid

NASA Astrophysics Data System (ADS)

Guzowski, B.; Łakomski, M.; Nowogrodzki, K.

2016-11-01

Over the past thirty years, optical fibers have revolutionized the telecommunication market. Fiber optics play also important roles in other numerous applications. One of these applications is fiber sensing - very fast developing area. In this paper, realization of different configurations of a fiber optic sensor detecting the presence of liquid is presented. In the presented sensor, two multimode fibers (MMF) are placed opposite each other, where the first one transmits the light radiation, while the second one is a receiver. Due to the small size of the core (50 μm diameter), they had to be precisely positioned. Therefore the optical fibers were placed in the etched channels in the silicon substrate. In order to make sensors more sensitive, ball-lensed optical fibers were used. Four different diameters of lenses were examined. Sensitivity to the presence of liquids was compared in all realized sensors. Moreover, the influence of distance between the transmitting and receiving optical fiber on the received optical power is also described in this paper. All developed sensors were tested at 1300 nm wavelength. In the last part of this paper the detailed discussion is given.

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)

Non-enzymatic glucose detection based on phenylboronic acid modified optical fibers

NASA Astrophysics Data System (ADS)

Sun, Xiaolan; Li, Nana; Zhou, Bin; Zhao, Wei; Liu, Liyuan; Huang, Chao; Ma, Longfei; Kost, Alan R.

2018-06-01

A non-enzymatic, sensitive glucose sensor was fabricated based on an evanescent wave absorbing optical fiber probe. The optical fiber sensor was functionalized by fixing a poly (phenylboronic acid) (polyPBA) film onto the conical region of the single mode fiber. The reflected light intensity of the polyPBA-functionalized fiber sensor increased proportionally with glucose concentration in the range of 0-60 mM, and the sensor showed good reproducibility and stability. The developed sensor possessed a high sensitivity of 0.1787%/mM and good linearity. The measurement of glucose concentration in human serum was also demonstrated.

Nanoparticles based fiber optic SPR sensor

NASA Astrophysics Data System (ADS)

Shah, Kruti; Sharma, Navneet K.

2018-05-01

Localized surface plasmon resonance based fiber optic sensor using platinum nanoparticles is proposed and theoretically analyzed. Increase in thickness of nanoparticles layer increases the sensitivity of sensor. 50 nm thick platinum nanoparticles layer based sensor reveals highest sensitivity.

Comparison of sensitivity and resolution load sensor at various configuration polymer optical fiber

NASA Astrophysics Data System (ADS)

Arifin, A.; Yusran, Miftahuddin, Abdullah, Bualkar; Tahir, Dahlang

2017-01-01

This study uses a load sensor with a macro-bending on polymer optical fiber loop model which is placed between two plates with a buffer spring. The load sensor with light intensity modulation principle is an infrared LED emits light through the polymer optical fiber then received by the phototransistor and amplifier. Output voltage from the amplifier continued to arduino sequence and displayed on the computer. Load augment on the sensor resulted in an increase of curvature on polymer optical fibers that can cause power losses gets bigger too. This matter will result in the intensity of light that received by phototransistor getting smaller, so that the output voltage that ligable on computer will be getting smaller too. The sensitivity and resolution load sensors analyzed based on configuration with various amount of loops, imperfection on the jacket, and imperfection at the cladding and core of polymer optical fiber. The results showed that the augment on the amount of load, imperfection on the jacket and imperfection on the sheath and core polymer optical fiber can improve the sensitivity and resolution of the load sensor. The best sensors resolution obtained on the number of loops 4 with imperfection 8 on the core and cladding polymer optical fiber that is 0.037 V/N and 0,026 N. The advantages of the load sensor based on polymers optical fiber are easy to make, low cost and simple to use measurement methods.

Gas refractometry based on an all-fiber spatial optical filter.

PubMed

Silva, Susana; Coelho, L; André, R M; Frazão, O

2012-08-15

A spatial optical filter based on splice misalignment between optical fibers with different diameters is proposed for gas refractometry. The sensing head is formed by a 2 mm long optical fiber with 50 μm diameter that is spliced with a strong misalignment between two single-mode fibers (SMF28) and interrogated in transmission. The misalignment causes a Fabry-Perot behavior along the reduced-size fiber and depending on the lead-out SMF28 position, it is possible to obtain different spectral responses, namely, bandpass or band-rejection filters. It is shown that the spatial filter device is highly sensitive to refractive index changes on a nitrogen environment by means of the gas pressure variation. A maximum sensitivity of -1390 nm/RIU for the bandpass filter was achieved. Both devices have shown similar temperature responses with an average sensitivity of 25.7 pm/°C.

φ-OTDR sensing system with bidirectional pumped fiber Raman amplifier and unbalanced MZ interferometer

NASA Astrophysics Data System (ADS)

Zhang, Liang; Tian, Ming; Dong, Lei

2017-10-01

In order to improve the detection distance and the sensitivity, we propose a novel distributed optical fiber sensing system. This system is composed of bidirectional pumping fiber Raman amplifier and unbalanced fiber Mach-Zehnder interferometer. Based on the interference mechanism of phase sensitive optical time domain reflectometer (φ-OTDR), the system can get the sensing information of the whole optical fiber by analyzing the backward scattered light. The interferometer is used as the demodulator of the sensing system, which consists of a 3×3 coupler and two faraday rotator mirrors. By means of the demodulator, the signal light is divided into three beams with fixed phase difference. To deal with these three signals, we can get the vibration information directly on the optical fiber. Through experimental study, this system has a high sensitivity. The maximum sensing length and the spatial resolution of the φ-OTDR system are 100 km and 10 m. The signal to noise ratio about 18 dB is achieved.

Optical fiber strain sensor for application in intelligent intruder detection systems

NASA Astrophysics Data System (ADS)

Stańczyk, Tomasz; Tenderenda, Tadeusz; Szostkiewicz, Lukasz; Bienkowska, Beata; Kunicki, Daniel; Murawski, Michal; Mergo, Pawel; Nasilowski, Tomasz

2017-10-01

Nowadays technology allows to create highly effective Intruder Detection Systems (IDS), that are able to detect the presence of an intruder within a defined area. In such systems the best performance can be achieved by combining different detection techniques in one system. One group of devices that can be applied in an IDS, are devices based on Fiber Optic Sensors (FOS). The FOS benefits from numerous advantages of optical fibers like: small size, light weight or high sensitivity. In this work we present a novel Microstructured Optical Fiber (MOF) characterized by increased strain sensitivity dedicated to distributed acoustic sensing for intelligent intruder detection systems. By designing the MOF with large air holes in close proximity to a fiber core, we increased the effective refractive index sensitivity to longitudinal strain. The presented fiber can be easily integrated in a floor system in order to detect any movement in the investigated area. We believe that sensors, based on the presented MOF, due to its numerous advantages, can find application in intelligent IDS.

State-of-the-art fiber optics for short distance frequency reference distribution

NASA Astrophysics Data System (ADS)

Lutes, G. F.; Primas, L. E.

1989-05-01

A number of recently developed fiber-optic components that hold the promise of unprecedented stability for passively stabilized frequency distribution links are characterized. These components include a fiber-optic transmitter, an optical isolator, and a new type of fiber-optic cable. A novel laser transmitter exhibits extremely low sensitivity to intensity and polarization changes of reflected light due to cable flexure. This virtually eliminates one of the shortcomings in previous laser transmitters. A high-isolation, low-loss optical isolator has been developed which also virtually eliminates laser sensitivity to changes in intensity and polarization of reflected light. A newly developed fiber has been tested. This fiber has a thermal coefficient of delay of less than 0.5 parts per million per deg C, nearly 20 times lower than the best coaxial hardline cable and 10 times lower than any previous fiber-optic cable. These components are highly suitable for distribution systems with short extent, such as within a Deep Space Communications Complex. Here, these new components are described and the test results presented.

State-of-the-art fiber optics for short distance frequency reference distribution

NASA Technical Reports Server (NTRS)

Lutes, G. F.; Primas, L. E.

1989-01-01

A number of recently developed fiber-optic components that hold the promise of unprecedented stability for passively stabilized frequency distribution links are characterized. These components include a fiber-optic transmitter, an optical isolator, and a new type of fiber-optic cable. A novel laser transmitter exhibits extremely low sensitivity to intensity and polarization changes of reflected light due to cable flexure. This virtually eliminates one of the shortcomings in previous laser transmitters. A high-isolation, low-loss optical isolator has been developed which also virtually eliminates laser sensitivity to changes in intensity and polarization of reflected light. A newly developed fiber has been tested. This fiber has a thermal coefficient of delay of less than 0.5 parts per million per deg C, nearly 20 times lower than the best coaxial hardline cable and 10 times lower than any previous fiber-optic cable. These components are highly suitable for distribution systems with short extent, such as within a Deep Space Communications Complex. Here, these new components are described and the test results presented.

Birefringence measurement of retinal nerve fiber layer using polarization-sensitive spectral domain optical coherence tomography with Jones matrix based analysis

NASA Astrophysics Data System (ADS)

Yamanari, Masahiro; Miura, Masahiro; Makita, Shuichi; Yatagai, Toyohiko; Yasuno, Yoshiaki

2007-02-01

Birefringence of retinal nerve fiber layer is measured by polarization-sensitive spectral domain optical coherence tomography using the B-scan-oriented polarization modulation method. Birefringence of the optical fiber and the cornea is compensated by Jones matrix based analysis. Three-dimensional phase retardation map around the optic nerve head and en-face phase retardation map of the retinal nerve fiber layer are shown. Unlike scanning laser polarimetry, our system can measure the phase retardation quantitatively without using bow-tie pattern of the birefringence in the macular region, which enables diagnosis of glaucoma even if the patients have macular disease.

All-optical non-mechanical fiber-coupled sensor for liquid- and airborne sound detection.

NASA Astrophysics Data System (ADS)

Rohringer, Wolfgang; Preißer, Stefan; Fischer, Balthasar

2017-04-01

Most fiber-optic devices for pressure, strain or temperature measurements are based on measuring the mechanical deformation of the optical fiber by various techniques. While excellently suited for detecting strain, pressure or structure-borne sound, their sensitivity to liquid- and airborne sound is so far not comparable with conventional capacitive microphones or piezoelectric hydrophones. Here, we present an all-optical acoustic sensor which relies on the detection of pressure-induced changes of the optical refractive index inside a rigid, millimeter-sized, fiber-coupled Fabry-Pérot interferometer (FPI). No mechanically movable or deformable parts take part in the signal transduction chain. Therefore, due to the absence of mechanical resonances, this sensing principle allows for high sensitivity as well as a flat frequency response over an extraordinary measurement bandwidth. As a fiber-coupled device, it can be integrated easily into already available distributed fiber-optic networks for geophysical sensing. We present characterization measurements demonstrating the sensitivity, frequency response and directivity of the device for sound and ultrasound detection in air and water. We show that low-frequency temperature and pressure drifts can be recorded in addition to acoustic sensing. Finally, selected application tests of the laser-based hydrophone and microphone implementation are presented.

U-bent plastic optical fiber based plasmonic biosensor for nucleic acid detection

NASA Astrophysics Data System (ADS)

Gowri, A.; Sai, V. V. R.

2017-05-01

This study presents the development of low cost, rapid and highly sensitive plasmonic sandwich DNA biosensor using U-bent plastic optical fiber (POF) probes with high evanescent wave absorbance sensitivity and gold nanoparticles (AuNP) as labels. Plastic optical fiber (PMMA core and fluorinated polymer as cladding) offer ease in machinability and handling due to which optimum U-bent geometry (with fiber and bend diameter of 0.5 and 1.5 mm respectively) for high sensitivity could be achieved. A sensitive fiber optic DNA biosensor is realized by (i) modifying the PMMA surface using ethylenediamine (EDA) in order to maximize the immobilization of capture oligonucleotides (ONs) and (ii) conjugating probe ONs to AuNP labels of optimum size ( 35 nm) with high extinction coefficient and optimal ON surface density. The sandwich hybridization assay on U-bent POF probes results in increase in optical absorbance through the probe with increase in target ON concentration due to the presence of increased number of AuNPs. The absorbance of light passing through the U-bent probe due to the presence of AuNP labels on its surface as result of sandwich DNA hybridization is measured using a halogen lamp and a fiber optic spectrometer. A picomolar limit of detection of target ON (0.2 pM or 1 pg/ml or 5 attomol in 25 μL) is achieved with this biosensing scheme, indicating its potential for the development of a highly sensitive DNA biosensor.

Groove micro-structure optical fiber refractive index sensor with nanoscale gold film based on surface plasmon resonance

NASA Astrophysics Data System (ADS)

Zhang, Zhen; Li, Shuguang; Liu, Qiang; Feng, Xinxing; Zhang, Shuhuan; Wang, Yujun; Wu, Junjun

2018-07-01

A groove micro-structure optical fiber refractive index sensor with nanoscale gold film based on surface plasmon resonance (SPR) is proposed and analyzed by the finite element method (FEM). Numerical results show that the average sensitivity is 15,933 nm/refractive index unit (RIU) with the refractive index of analyte ranging from 1.40 to 1.43 and the maximum sensitivity is 28,600 nm/RIU and the resolution of the sensor is 3.50 × 10-8 RIU. The groove micro-structure optical fiber refractive index sensor do some changes on the D-shaped fiber sensor, compared with conventional D-shaped fiber sensor, it has a higher sensitivity and it is easier to produce than the traditional SPR sensor.

Improved optical axis determination accuracy for fiber-based polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Lu, Zenghai; Matcher, Stephen J.

2013-03-01

We report on a new calibration technique that permits the accurate extraction of sample Jones matrix and hence fast-axis orientation by using fiber-based polarization-sensitive optical coherence tomography (PS-OCT) that is completely based on non polarization maintaining fiber such as SMF-28. In this technique, two quarter waveplates are used to completely specify the parameters of the system fibers in the sample arm so that the Jones matrix of the sample can be determined directly. The device was validated on measurements of a quarter waveplate and an equine tendon sample by a single-mode fiber-based swept-source PS-OCT system.

Spatial Frequency Multiplexing of Fiber-Optic Interferometric Refractive Index Sensors Based on Graded-Index Multimode Fibers

PubMed Central

Liu, Li; Gong, Yuan; Wu, Yu; Zhao, Tian; Wu, Hui-Juan; Rao, Yun-Jiang

2012-01-01

Fiber-optic interferometric sensors based on graded-index multimode fibers have very high refractive-index sensitivity, as we previously demonstrated. In this paper, spatial-frequency multiplexing of this type of fiber-optic refractive index sensors is investigated. It is estimated that multiplexing of more than 10 such sensors is possible. In the multiplexing scheme, one of the sensors is used to investigate the refractive index and temperature responses. The fast Fourier transform (FFT) of the combined reflective spectra is analyzed. The intensity of the FFT spectra is linearly related with the refractive index and is not sensitive to the temperature.

Sensitive liquid refractive index sensors using tapered optical fiber tips.

PubMed

Tai, Yi-Hsin; Wei, Pei-Kuen

2010-04-01

An optical fiber sensor based on the change of optical confinement in a subwavelength tip is presented. The optical spot is substantially increased when the environmental refractive index (RI) increases from 1.3 to 1.4. By measuring the intensity of low angular spectral components, an intensity sensitivity up to 8000% per RI unit is achieved. The fiber tip sensors take advantage of the small detection volume and real-time responses. We demonstrate the application of the nanofiber sensors for measuring concentrations of acids and evaporation rates of aqueous mixtures.

All-fiber hybrid photon-plasmon circuits: integrating nanowire plasmonics with fiber optics.

PubMed

Li, Xiyuan; Li, Wei; Guo, Xin; Lou, Jingyi; Tong, Limin

2013-07-01

We demonstrate all-fiber hybrid photon-plasmon circuits by integrating Ag nanowires with optical fibers. Relying on near-field coupling, we realize a photon-to-plasmon conversion efficiency up to 92% in a fiber-based nanowire plasmonic probe. Around optical communication band, we assemble an all-fiber resonator and a Mach-Zehnder interferometer (MZI) with Q-factor of 6 × 10(6) and extinction ratio up to 30 dB, respectively. Using the MZI, we demonstrate fiber-compatible plasmonic sensing with high sensitivity and low optical power.

Fiber cavity ring-down using an optical time-domain reflectometer

NASA Astrophysics Data System (ADS)

Passos, D. J.; Silva, S. O.; Fernandes, J. R. A.; Marques, M. B.; Frazão, O.

2014-12-01

This work presented a demonstration of the potential for a fiber based cavity ring-down (CRD) using an optical time-domain reflectometer (OTDR). The OTDR was used to send the impulses down into about 20 km of a standard single optical fiber, at the end of which the fiber cavity ring-down was placed. The OTDR measured no appreciable losses, so other CRDs multiplexed could be spliced in parallel along the same optical fiber. To demonstrate the behavior and sensitivity of the proposed configuration, a displacement sensor based on a fiber taper with a diameter of 50 μm was placed inside the fiber loop, and the induced losses were measured on the CRD signal — a sensitivity of 11.8 ± 0.5 μs/mm was achieved. The dynamic range of the sensing head used in this configuration was about 2 mm. Finally, this work was also compared with different works published in the literature.

Long-Period Gratings in Highly Germanium-Doped, Single-Mode Optical Fibers for Sensing Applications

PubMed Central

Schlangen, Sebastian; Bremer, Kort; Zheng, Yulong; Böhm, Sebastian; Steinke, Michael; Wellmann, Felix; Neumann, Jörg; Overmeyer, Ludger

2018-01-01

Long-period fiber gratings (LPGs) are well known for their sensitivity to external influences, which make them interesting for a large number of sensing applications. For these applications, fibers with a high numerical aperture (i.e., fibers with highly germanium (Ge)-doped fused silica fiber cores) are more attractive since they are intrinsically photosensitive, as well as less sensitive to bend- and microbend-induced light attenuations. In this work, we introduce a novel method to inscribe LPGs into highly Ge-doped, single-mode fibers. By tapering the optical fiber, and thus, tailoring the effective indices of the core and cladding modes, for the first time, an LPG was inscribed into such fibers using the amplitude mask technique and a KrF excimer laser. Based on this novel method, sensitive LPG-based fiber optic sensors only a few millimeters in length can be incorporated in bend-insensitive fibers for use in various monitoring applications. Moreover, by applying the described inscription method, the LPG spectrum can be influenced and tailored according to the specific demands of a particular application. PMID:29702600

Optofluidic in-fiber interferometer based on hollow optical fiber with two cores.

PubMed

Yuan, Tingting; Yang, Xinghua; Liu, Zhihai; Yang, Jun; Li, Song; Kong, Depeng; Qi, Xiuxiu; Yu, Wenting; Long, Qunlong; Yuan, Libo

2017-07-24

We demonstrate a novel integrated optical fiber interferometer for in-fiber optofluidic detection. It is composed of a specially designed hollow optical fiber with a micro-channel and two cores. One core on the inner surface of the micro-channel is served as sensing arm and the other core in the annular cladding is served as reference arm. Fusion-and-tapering method is employed to couple light from a single mode fiber to the hollow optical fiber in this device. Sampling is realized by side opening a microhole on the surface of the hollow optical fiber. Under differential pressure between the end of the hollow fiber and the microhole, the liquids can form steady microflows in the micro-channel. Simultaneously, the interference spectrum of the interferometer device shifts with the variation of the concentration of the microfluid in the channel. The optofluidic in-fiber interferometer has a sensitivity of refractive index around 2508 nm/RIU for NaCl. For medicine concentration detection, its sensitivity is 0.076 nm/mmolL -1 for ascorbic acid. Significantly, this work presents a compact microfluidic in-fiber interferometer with a micro-channel which can be integrated with chip devices without spatial optical coupling and without complex manufacturing procedure of the waveguide on the chips.

Two-Channel SPR Sensor Combined Application of Polymer- and Vitreous-Clad Optic Fibers

PubMed Central

Wei, Yong; Su, Yudong; Liu, Chunlan; Nie, Xiangfei; Liu, Zhihai; Zhang, Yu; Zhang, Yonghui

2017-01-01

By combining a polymer-clad optic fiber and a vitreous-clad optic fiber, we proposed and fabricated a novel optic fiber surface plasmon resonance (SPR) sensor to conduct two-channel sensing at the same detection area. The traditional optic fiber SPR sensor has many disadvantages; for example, removing the cladding requires corrosion, operating it is dangerous, adjusting the dynamic response range is hard, and producing different resonance wavelengths in the sensing area to realize a multi-channel measurement is difficult. Therefore, in this paper, we skillfully used bare fiber grinding technology and reverse symmetry welding technology to remove the cladding in a multi-mode fiber and expose the evanescent field. On the basis of investigating the effect of the grinding angle on the dynamic range change of the SPR resonance valley wavelength and sensitivity, we combined polymer-clad fiber and vitreous-clad fiber by a smart design structure to realize at a single point a two-channel measurement fiber SPR sensor. In this paper, we obtained a beautiful spectral curve from a multi-mode fiber two-channel SPR sensor. In the detection range of the refractive rate between 1.333 RIU and 1.385 RIU, the resonance valley wavelength of channel Ⅰ shifted from 622 nm to 724 nm with a mean average sensitivity of 1961 nm/RIU and the resonance valley wavelength of channel Ⅱ shifted from 741 nm to 976 nm with a mean average sensitivity of 4519 nm/RIU. PMID:29232841

Two-Channel SPR Sensor Combined Application of Polymer- and Vitreous-Clad Optic Fibers.

PubMed

Wei, Yong; Su, Yudong; Liu, Chunlan; Nie, Xiangfei; Liu, Zhihai; Zhang, Yu; Zhang, Yonghui

2017-12-09

By combining a polymer-clad optic fiber and a vitreous-clad optic fiber, we proposed and fabricated a novel optic fiber surface plasmon resonance (SPR) sensor to conduct two-channel sensing at the same detection area. The traditional optic fiber SPR sensor has many disadvantages; for example, removing the cladding requires corrosion, operating it is dangerous, adjusting the dynamic response range is hard, and producing different resonance wavelengths in the sensing area to realize a multi-channel measurement is difficult. Therefore, in this paper, we skillfully used bare fiber grinding technology and reverse symmetry welding technology to remove the cladding in a multi-mode fiber and expose the evanescent field. On the basis of investigating the effect of the grinding angle on the dynamic range change of the SPR resonance valley wavelength and sensitivity, we combined polymer-clad fiber and vitreous-clad fiber by a smart design structure to realize at a single point a two-channel measurement fiber SPR sensor. In this paper, we obtained a beautiful spectral curve from a multi-mode fiber two-channel SPR sensor. In the detection range of the refractive rate between 1.333 RIU and 1.385 RIU, the resonance valley wavelength of channel Ⅰ shifted from 622 nm to 724 nm with a mean average sensitivity of 1961 nm/RIU and the resonance valley wavelength of channel Ⅱ shifted from 741 nm to 976 nm with a mean average sensitivity of 4519 nm/RIU.

Characteristic Analysis Light Intensity Sensor Based On Plastic Optical Fiber At Various Configuration

NASA Astrophysics Data System (ADS)

Arifin, A.; Lusiana; Yunus, Muhammad; Dewang, Syamsir

2018-03-01

This research discusses the light intensity sensor based on plastic optical fiber. This light intensity sensor is made of plastic optical fiber consisting of two types, namely which is cladding and without cladding. Plastic optical fiber used multi-mode step-index type made of polymethyl metacrylate (PMMA). The infrared LED emits light into the optical fiber of the plastic and is subsequently received by the phototransistor to be converted to an electric voltage. The sensor configuration is made with three models: straight configuration, U configuration and gamma configuration with cladding and without cladding. The measured light source uses a 30 Watt high power LED with a light intensity of 0 to 10 Klux. The measured light intensity will affect the propagation of light inside the optical fiber sensor. The greater the intensity of the measured light, the greater the output voltage that is read on the computer. The results showed that the best optical fiber sensor characteristics were obtained in U configuration. Sensors with U-configuration without cladding had the best sensitivity and resolution values of 0.0307 volts/Klux and 0.0326 Klux. The advantages of this measuring light intensity based on the plastic optical fiber instrument are simple, easy-to-make operational systems, low cost, high sensitivity and resolution.

Sensitivity, accuracy, and precision issues in opto-electronic holography based on fiber optics and high-spatial- and high-digitial-resolution cameras

NASA Astrophysics Data System (ADS)

Furlong, Cosme; Yokum, Jeffrey S.; Pryputniewicz, Ryszard J.

2002-06-01

Sensitivity, accuracy, and precision characteristics in quantitative optical metrology techniques, and specifically in optoelectronic holography based on fiber optics and high-spatial and high-digital resolution cameras, are discussed in this paper. It is shown that sensitivity, accuracy, and precision dependent on both, the effective determination of optical phase and the effective characterization of the illumination-observation conditions. Sensitivity, accuracy, and precision are investigated with the aid of National Institute of Standards and Technology (NIST) traceable gages, demonstrating the applicability of quantitative optical metrology techniques to satisfy constantly increasing needs for the study and development of emerging technologies.

Single mode tapered fiber-optic interferometer based refractive index sensor and its application to protein sensing.

PubMed

Yadav, T K; Narayanaswamy, R; Abu Bakar, M H; Kamil, Y Mustapha; Mahdi, M A

2014-09-22

We demonstrate refractive index sensors based on single mode tapered fiber and its application as a biosensor. We utilize this tapered fiber optic biosensor, operating at 1550 nm, for the detection of protein (gelatin) concentration in water. The sensor is based on the spectroscopy of mode coupling based on core modes-fiber cladding modes excited by the fundamental core mode of an optical fiber when it transitions into tapered regions from untapered regions. The changes are determined from the wavelength shift of the transmission spectrum. The proposed fiber sensor has sensitivity of refractive index around 1500 nm/RIU and for protein concentration detection, its highest sensitivity is 2.42141 nm/%W/V.

Textile Pressure Sensor Made of Flexible Plastic Optical Fibers

PubMed Central

Rothmaier, Markus; Luong, Minh Phi; Clemens, Frank

2008-01-01

In this paper we report the successful development of pressure sensitive textile prototypes based on flexible optical fibers technology. Our approach is based on thermoplastic silicone fibers, which can be integrated into woven textiles. As soon as pressure at a certain area of the textile is applied to these fibers they change their cross section reversibly, due to their elastomeric character, and a simultaneous change in transmitted light intensity can be detected. We have successfully manufactured two different woven samples with fibers of 0.51 and 0.98 mm diameter in warp and weft direction, forming a pressure sensitive matrix. Determining their physical behavior when a force is applied shows that pressure measurements are feasible. Their usable working range is between 0 and 30 N. Small drifts in the range of 0.2 to 4.6%, over 25 load cycles, could be measured. Finally, a sensor array of 2 × 2 optical fibers was tested for sensitivity, spatial resolution and light coupling between fibers at intersections. PMID:27879938

Ultrafast time-stretch imaging at 932 nm through a new highly-dispersive fiber

PubMed Central

Wei, Xiaoming; Kong, Cihang; Sy, Samuel; Ko, Ho; Tsia, Kevin K.; Wong, Kenneth K. Y.

2016-01-01

Optical glass fiber has played a key role in the development of modern optical communication and attracted the biotechnology researcher’s great attention because of its properties, such as the wide bandwidth, low attenuation and superior flexibility. For ultrafast optical imaging, particularly, it has been utilized to perform MHz time-stretch imaging with diffraction-limited resolutions, which is also known as serial time-encoded amplified microscopy (STEAM). Unfortunately, time-stretch imaging with dispersive fibers has so far mostly been demonstrated at the optical communication window of 1.5 μm due to lack of efficient dispersive optical fibers operating at the shorter wavelengths, particularly at the bio-favorable window, i.e., <1.0 μm. Through fiber-optic engineering, here we demonstrate a 7.6-MHz dual-color time-stretch optical imaging at bio-favorable wavelengths of 932 nm and 466 nm. The sensitivity at such a high speed is experimentally identified in a slow data-streaming manner. To the best of our knowledge, this is the first time that all-optical time-stretch imaging at ultrahigh speed, high sensitivity and high chirping rate (>1 ns/nm) has been demonstrated at a bio-favorable wavelength window through fiber-optic engineering. PMID:28018737

Ultrafast time-stretch imaging at 932 nm through a new highly-dispersive fiber.

PubMed

Wei, Xiaoming; Kong, Cihang; Sy, Samuel; Ko, Ho; Tsia, Kevin K; Wong, Kenneth K Y

2016-12-01

Optical glass fiber has played a key role in the development of modern optical communication and attracted the biotechnology researcher's great attention because of its properties, such as the wide bandwidth, low attenuation and superior flexibility. For ultrafast optical imaging, particularly, it has been utilized to perform MHz time-stretch imaging with diffraction-limited resolutions, which is also known as serial time-encoded amplified microscopy (STEAM). Unfortunately, time-stretch imaging with dispersive fibers has so far mostly been demonstrated at the optical communication window of 1.5 μm due to lack of efficient dispersive optical fibers operating at the shorter wavelengths, particularly at the bio-favorable window, i.e., <1.0 μm. Through fiber-optic engineering, here we demonstrate a 7.6-MHz dual-color time-stretch optical imaging at bio-favorable wavelengths of 932 nm and 466 nm. The sensitivity at such a high speed is experimentally identified in a slow data-streaming manner. To the best of our knowledge, this is the first time that all-optical time-stretch imaging at ultrahigh speed, high sensitivity and high chirping rate (>1 ns/nm) has been demonstrated at a bio-favorable wavelength window through fiber-optic engineering.

Optical fiber interferometer for the study of ultrasonic waves in composite materials

NASA Technical Reports Server (NTRS)

Claus, R. O.; Zewekh, P. S.; Turner, T. M.; Wade, J. C.; Rogers, R. T.; Garg, A. O.

1981-01-01

The possibility of acoustic emission detection in composites using embedded optical fibers as sensing elements was investigated. Optical fiber interferometry, fiber acoustic sensitivity, fiber interferometer calibration, and acoustic emission detection are reported. Adhesive bond layer dynamical properties using ultrasonic interface waves, the design and construction of an ultrasonic transducer with a two dimensional Gaussian pressure profile, and the development of an optical differential technique for the measurement of surface acoustic wave particle displacements and propagation direction are also examined.

Design of Oil Viscosity Sensor Based on Plastic Optical Fiber

NASA Astrophysics Data System (ADS)

Yunus, Muhammad; Arifin, A.

2018-03-01

A research of plastic optical fiber based sensors have been studied for measurement of oil viscosity. This sensor was made with straight configuration, U configuration, and gamma configuration have two types, there are optical fiber sensor with cladding and without cladding. Viscosity sensor was made, dipped into an oil sample with a concentration of viscosity percentage about 270 mPa.s - 350 mPa.s. The light from the LED propagated into the optical fiber, then it was received by the photodetector converted to output power. When plastic optical fiber dipped into an oil sample, viscosity of oil affect increase of refractive index on optical fiber resulting in a bigger loss of power so the light intensity will be smaller, consequences the measured output power will be smaller. Sensitivity and resolution viscosity sensor without cladding peel showed the best result rather than viscosity sensor with cladding peel. The best result in the measurement showed in gamma configuration with 3 cm length of cladding peel and the diameter of bending 0,25 cm is the range 103,090 nWatt, sensitivity 1,289 nWatt/mPa.s, and resolution 0,776 mPa.s. This method is effectively and efficiently used as an oil viscosity sensor with high sensitivity and resolution.

Multimode-singlemode-multimode optical fiber sensor coated with novolac resin for detecting liquid phase alcohol

NASA Astrophysics Data System (ADS)

Marfu'ah, Amalia, Niza Rosyda; Hatta, Agus Muhamad; Pratama, Detak Yan

2018-04-01

Alcohol sensor based on multimode-singlemode-multimode (MSM) optical fiber with novolac resin as the external medium is proposed and demonstrated experimentally. Novolac resin swells when it is exposed by the alcohol. This effect causes a change in the polymer density leading to the refractive index's variation. The transmission light of the sensor depends on the refractive index of external medium. Based on the results, alcohol sensor based on MSM optical fiber structure using novolac resin has a higher sensitivity compared to the sensor without using novolac resin in the mixture of alcohol and distilled water. Alcohol sensor based on MSM optical fiber structure using novolac resin in the mixture of alcohol and distilled water with a singlemode fiber length of 5 mm has a sensitivity of 0.028972 dBm per % V/V, and in the mixture of alcohol and sugar solution of 10% w/w has a sensitivity of 0.005005 dBm per % V/V.

In-situ growth of AuNPs on WS2@U-bent optical fiber for evanescent wave absorption sensor

NASA Astrophysics Data System (ADS)

Zhang, Suzhen; Zhao, Yuefeng; Zhang, Chao; Jiang, Shouzhen; Yang, Cheng; Xiu, Xianwu; Li, Chonghui; Li, Zhen; Zhao, Xiaofei; Man, Baoyuan

2018-05-01

The sensitivity of the evanescent wave absorption sensor is always a hot topic which has been attracted researchers' discussion. It is still a challenge for developing the effective sensor to sensitively detect some biochemical molecules solution in a simple and low-cost way. In this paper, an evanescent wave absorption (EWA) sensor has been presented based on the U-bent multimode fiber coated with tungsten disulfide (WS2) film and in-situ growth of gold nanoparticles (AuNPs) for the detection of ethanol solution and sodium chloride (NaCl) solution. Benefitted from the effective light coupling produced between U-bent probe and AuNPs, we attained the optimal size of the AuNPs by changing the reaction time between WS2 and tetrachloroauric acid (HAuCl4). With the AuNPs/WS2@U-bent optical fiber, we discussed the behaviors of EWA sensor, such as sensitivity, reproducibility, fast response-recovery time and stability. The sensitivity (△A/△C) of the proposed AuNPs/WS2@U-bent optical fiber EWA sensor is 0.65 for the detection of the ethanol solution. Besides, the AuNPs/WS2@U-bent optical fiber EWA sensor exhibits high sensitivity in detection of the sodium chloride (NaCl), which can reach 1.5 when the proposed sensor was immersed into NaCl solution. Our work demonstrates that the U-bent optical fiber EWA sensor may have promising applications in testing the solution of concentration.

Partially reduced graphene oxide based FRET on fiber-optic interferometer for biochemical detection

NASA Astrophysics Data System (ADS)

Yao, B. C.; Wu, Y.; Yu, C. B.; He, J. R.; Rao, Y. J.; Gong, Y.; Fu, F.; Chen, Y. F.; Li, Y. R.

2016-03-01

Fluorescent resonance energy transfer (FRET) with naturally exceptional selectivity is a powerful technique and widely used in chemical and biomedical analysis. However, it is still challenging for conventional FRET to perform as a high sensitivity compact sensor. Here we propose a novel ‘FRET on Fiber’ concept, in which a partially reduced graphene oxide (prGO) film is deposited on a fiber-optic modal interferometer, acting as both the fluorescent quencher for the FRET and the sensitive cladding for optical phase measurement due to refractive index changes in biochemical detection. The target analytes induced fluorescence recovery with good selectivity and optical phase shift with high sensitivity are measured simultaneously. The functionalized prGO film coated on the fiber-optic interferometer shows high sensitivities for the detections of metal ion, dopamine and single-stranded DNA (ssDNA), with detection limits of 1.2 nM, 1.3 μM and 1 pM, respectively. Such a prGO based ‘FRET on fiber’ configuration, bridging the FRET and the fiber-optic sensing technology, may serve as a platform for the realization of series of integrated ‘FRET on Fiber’ sensors for on-line environmental, chemical, and biomedical detection, with excellent compactness, high sensitivity, good selectivity and fast response

Partially reduced graphene oxide based FRET on fiber-optic interferometer for biochemical detection

PubMed Central

Yao, B. C.; Wu, Y.; Yu, C. B.; He, J. R.; Rao, Y. J.; Gong, Y.; Fu, F.; Chen, Y. F.; Li, Y. R.

2016-01-01

Fluorescent resonance energy transfer (FRET) with naturally exceptional selectivity is a powerful technique and widely used in chemical and biomedical analysis. However, it is still challenging for conventional FRET to perform as a high sensitivity compact sensor. Here we propose a novel ‘FRET on Fiber’ concept, in which a partially reduced graphene oxide (prGO) film is deposited on a fiber-optic modal interferometer, acting as both the fluorescent quencher for the FRET and the sensitive cladding for optical phase measurement due to refractive index changes in biochemical detection. The target analytes induced fluorescence recovery with good selectivity and optical phase shift with high sensitivity are measured simultaneously. The functionalized prGO film coated on the fiber-optic interferometer shows high sensitivities for the detections of metal ion, dopamine and single-stranded DNA (ssDNA), with detection limits of 1.2 nM, 1.3 μM and 1 pM, respectively. Such a prGO based ‘FRET on fiber’ configuration, bridging the FRET and the fiber-optic sensing technology, may serve as a platform for the realization of series of integrated ‘FRET on Fiber’ sensors for on-line environmental, chemical, and biomedical detection, with excellent compactness, high sensitivity, good selectivity and fast response PMID:27010752

Optical fiber curvature sensor based on MMF-SCF-MMF structure

NASA Astrophysics Data System (ADS)

Wang, Qi; Liu, Yu

2018-07-01

A sensitive curvature sensor based on MMF-SCF-MMF (MMF: multimode fiber; SCF: seven core fiber) structure is proposed. The multimode fiber (MMF) are used to improve the light coupling efficiency between the input singlemode fiber (SMF) and the seven-core fiber (SCF), and the seven-core fiber is used as the main element for curvature measurement. Experimental results show that the best curvature sensitivity reaches 41.46453 nm/m-1 in the range of 0.094 m-1-0.567 m-1. The temperature sensitivity is up to 59.02 pm/°C in the range of 20 °C-55 °C. The optical curvature sensors are widely used for buildings structure health monitoring and mechanical engineering due to the advantages of compact structure, anti-electromagnetic interference, and low cost.

Improved Optical-Fiber Temperature Sensors

NASA Technical Reports Server (NTRS)

Rogowski, Robert S.; Egalon, Claudio O.

1993-01-01

In optical-fiber temperature sensors of proposed type, phosphorescence and/or fluorescence in temperature-dependent coating layers coupled to photodetectors. Phosphorescent and/or fluorescent behavior(s) of coating material(s) depend on temperature; coating material or mixture of materials selected so one can deduce temperature from known temperature dependence of phosphorescence and/or fluorescence spectrum, and/or characteristic decay of fluorescence. Basic optical configuration same as that of optical-fiber chemical detectors described in "Making Optical-Fiber Chemical Detectors More Sensitive" (LAR-14525).

Fiber Optic Fabry-Perot Current Sensor Integrated with Magnetic Fluid Using a Fiber Bragg Grating Demodulation

PubMed Central

Xia, Ji; Wang, Qi; Liu, Xu; Luo, Hong

2015-01-01

An optical fiber current sensor based on Fabry-Perot interferometer using a fiber Bragg grating demodulation is proposed. Magnetic fluid is used as a sensitive medium in fiber optical Fabry-Perot (F-P) cavity for the optical characteristic of magnetic-controlled refractive index. A Fiber Bragg grating (FBG) is connected after the F-P interferometer which is used to reflect the optical power at the Bragg wavelength of the interference transmission spectrum. The corresponding reflective power of the FBG will change with different external current intensity, due to the shift on the interference spectrum of the F-P interferometer. The sensing probe has the advantages of convenient measurement for its demodulation, low cost and high current measurement accuracy on account of its sensing structure. Experimental results show that an optimal sensitivity of 0.8522 nw/A and measurement resolution of 0.001 A is obtained with a FBG at 1550 nm with 99% reflectivity. PMID:26184201

Fiber Optic Fabry-Perot Current Sensor Integrated with Magnetic Fluid Using a Fiber Bragg Grating Demodulation.

PubMed

Xia, Ji; Wang, Qi; Liu, Xu; Luo, Hong

2015-07-09

An optical fiber current sensor based on Fabry-Perot interferometer using a fiber Bragg grating demodulation is proposed. Magnetic fluid is used as a sensitive medium in fiber optical Fabry-Perot (F-P) cavity for the optical characteristic of magnetic-controlled refractive index. A Fiber Bragg grating (FBG) is connected after the F-P interferometer which is used to reflect the optical power at the Bragg wavelength of the interference transmission spectrum. The corresponding reflective power of the FBG will change with different external current intensity, due to the shift on the interference spectrum of the F-P interferometer. The sensing probe has the advantages of convenient measurement for its demodulation, low cost and high current measurement accuracy on account of its sensing structure. Experimental results show that an optimal sensitivity of 0.8522 nw/A and measurement resolution of 0.001 A is obtained with a FBG at 1550 nm with 99% reflectivity.

Exposed-core chalcogenide microstructured optical fibers for chemical sensing

NASA Astrophysics Data System (ADS)

Troles, Johann; Toupin, Perrine; Brilland, Laurent; Boussard-Plédel, Catherine; Bureau, Bruno; Cui, Shuo; Mechin, David; Adam, Jean-Luc

2013-05-01

Chemical bonds of most of the molecules vibrate at a frequency corresponding to the near or mid infrared field. It is thus of a great interest to develop sensitive and portable devices for the detection of specific chemicals and biomolecules for various applications in health, the environment, national security and so on. Optical fibers define practical sensing tools. Chalcogenide glasses are known for their transparency in the infrared optical range and their ability to be drawn as fibers. They are consequently good candidates to be used in biological/chemical sensing. For that matter, in the past decade, chalcogenide glass fibers have been successfully implemented in evanescent wave spectroscopy experiments, for the detection of bio-chemical species in various fields of applications including microbiology and medicine, water pollution and CO2 detection. Different types of fiber can be used: single index fibers or microstructured fibers. Besides, in recent years a new configuration of microstructured fibers has been developed: microstructured exposed-core fibers. This design consists of an optical fiber with a suspended micron-scale core that is partially exposed to the external environment. This configuration has been chosen to elaborate, using the molding method, a chalcogenide fiber for chemical species detection. The sensitivity of this fiber to detect molecules such as propan-2-ol and acetone has been compared with those of single index fibers. Although evanescent wave absorption is inversely proportional to the fiber diameter, the result shows that an exposed-core fiber is much more sensitive than a single index fiber having a twice smaller external diameter.

Optical fiber Fabry-Perot interferometer with pH sensitive hydrogel film for hazardous gases sensing

NASA Astrophysics Data System (ADS)

Zheng, Yangzi; Chen, Li Han; Chan, Chi Chiu; Dong, Xinyong; Yang, Jingyi; Tou, Zhi Qiang; So, Ping Lam

2015-09-01

An optical fiber Fabry-Perot interferometer (FPI) coated with polyvinyl alcohol/poly-acrylic acid (PVA/PAA) hydrogel film for toxic gases measurement has been developed. Splicing a short section of hollow core fiber between two single mode fibers forms the FPI. Dip-coated pH-sensitive PVA/PAA hydrogel film on the fiber end performs as a receptor for binding of volatile acids or ammonia, which makes the sensing film swelling or shrinking and results in the dip wavelength shift of the FPI. By demodulating the evolution of reflection spectrum for various concentrations of volatile acids, a sensitivity of 20.8 nm/ppm is achieved with uniform linearity.

Vibration sensitivity of the scanning near-field optical microscope with a tapered optical fiber probe.

PubMed

Chang, Win-Jin; Fang, Te-Hua; Lee, Haw-Long; Yang, Yu-Ching

2005-01-01

In this paper the Rayleigh-Ritz method was used to study the scanning near-field optical microscope (SNOM) with a tapered optical fiber probe's flexural and axial sensitivity to vibration. Not only the contact stiffness but also the geometric parameters of the probe can influence the flexural and axial sensitivity to vibration. According to the analysis, the lateral and axial contact stiffness had a significant effect on the sensitivity of vibration of the SNOM's probe, each mode had a different level of sensitivity and in the first mode the tapered optical fiber probe was the most acceptive to higher levels of flexural and axial vibration. Generally, when the contact stiffness was lower, the tapered probe was more sensitive to higher levels of both axial and flexural vibration than the uniform probe. However, the situation was reversed when the contact stiffness was larger. Furthermore, the effect that the probe's length and its tapered angle had on the SNOM's probe axial and flexural vibration were significant and these two conditions should be incorporated into the design of new SNOM probes.

Improved Fiber-Optic-Coupled Pressure And Vibration Sensors

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J.; Cuomo, Frank W.

1994-01-01

Improved fiber-optic coupler enables use of single optical fiber to carry light to and from sensor head. Eliminates problem of alignment of multiple fibers in sensor head and simplifies calibration by making performance both more predictable and more stable. Sensitivities increased, sizes reduced. Provides increased margin for design of compact sensor heads not required to contain amplifier circuits and withstand high operating temperatures.

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.

High-precision micro-displacement optical-fiber sensor based on surface plasmon resonance.

PubMed

Zhu, Zongda; Liu, Lu; Liu, Zhihai; Zhang, Yu; Zhang, Yaxun

2017-05-15

We propose and demonstrate a novel optical-fiber micro-displacement sensor based on surface plasmon resonance (SPR) by fabricating a Kretschmann configuration on graded-index multimode fiber (GIMMF). We employ a single-mode fiber to change the radial position of the incident beam as the displacement. In the GIMMF, the angle between the light beam and fiber axis, which is closely related to the resonance angle, is changed by the displacement; thus, the resonance wavelength of the fiber SPR shifts. This micro-displacement fiber sensor has a wide detection range of 0-25 μm, a high sensitivity with maximum up to 10.32 nm/μm, and a nanometer resolution with minimum to 2 nm, which transcends almost all of other optical-fiber micro-displacement sensors. In addition, we also research that increasing the fiber polishing angle or medium refractive index can improve the sensitivity. This micro-displacement sensor will have a great significance in many industrial applications and provide a neoteric, rapid, and accurate optical measurement method in micro-displacement.

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

Indium oxide based fiber optic SPR sensor

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

Shukla, Sarika; Sharma, Navneet K., E-mail: navneetk.sharma@jiit.ac.in

2016-05-06

Surface plasmon resonance based fiber optic sensor using indium oxide layer is presented and theoretically studied. It has been found that with increase in thickness of indium oxide layer beyond 170 nm, the sensitivity of SPR sensor decreases. 170 nm thick indium oxide layer based SPR sensor holds maximum sensitivity.

Noninvasive encapsulated fiber optic probes for interferometric measurement

NASA Astrophysics Data System (ADS)

Zboril, O.; Cubik, J.; Kepak, S.; Nedoma, J.; Fajkus, M.; Zavodny, P.; Vasinek, V.

2017-10-01

This article focuses on the sensitivity of encapsulated interferometric probes. These probes are used mainly for BioMed and security applications. Fiber-optic sensors are interesting for these applications, as they are resistant to electromagnetic interference (EMI) and that also do not affect the surrounding medical and security equipment. Using a loop of the optical fiber with is not a suitable for these measurements. The optical fiber should be fixed to one position, and should not significantly bend. For these reasons, the optical fiber is encapsulated. Furthermore, it is necessary that the encapsulated measuring probes were flexible, inert, water resistant and not toxic. Fiber-optic sensors shouldn't be magnetically active, so they can be used for example, in magnetic resonance environments (MR). Probes meeting these requirements can be widely used in health care and security applications. Encapsulation of interferometric measuring arm brings changes in susceptibility of measurements in comparison with the optical fiber without encapsulation. To evaluate the properties of the encapsulated probes, series of probes made from different materials for encapsulation was generated, using two types of optical fibers with various degrees of protection. Comparison of the sensitivity of different encapsulated probes was performed using a series of measurements at various frequencies. The measurement results are statistically compared in the article and commented. Given the desired properties polydimethylsiloxane (PDMS) polymer has been proven the most interesting encapsulating material for further research.

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

Optical electric field sensor sensitivity direction rerouting and enhancement using a passive integrated dipole antenna.

PubMed

Seng, Frederick; Yang, Zhenchao; King, Rex; Shumway, LeGrand; Stan, Nikola; Hammond, Alec; Warnick, Karl F; Schultz, Stephen

2017-06-10

This work introduces a passive dipole antenna integrated into the packaging of a slab-coupled optical sensor to enhance the directional sensitivity of electro-optic electric field measurements parallel to the fiber axis. Using the passive integrated dipole antenna described in this work, a sensor that can typically only sense fields transverse to the fiber direction is able to sense a 1.25 kV/m field along the fiber direction with a gain of 17.5. This is verified through simulation and experiment.

Lamping process and application of ultra small U-shaped, whispery gallery mode (WGM) based optic fiber sensors

NASA Astrophysics Data System (ADS)

Chang, Yuan Cheng; Chiang, Chia Chin

2015-07-01

This study success to smaller and control the diameter of single mode optical fiber whispery gallery mode (WGM) to diameter 0.8 mm nonetching and nontaping treated. The sensitivity of this type ultra-small U-shape WGM strengthens neither etching nor taping fibre. The sensitivity we apply to thermo test depends on wavelength shift from 40 ~ 96°C (R2 = 0.99 ). The specially characteristics of the optical fiber could be tested for temperature, refraction, vibration, concussion, and CO2 detection.

Fiber-optic refractometer based on an etched high-Q π-phase-shifted fiber-Bragg-grating.

PubMed

Zhang, Qi; Ianno, Natale J; Han, Ming

2013-07-10

We present a compact and highly-sensitive fiber-optic refractometer based on a high-Q π-phase-shifted fiber-Bragg-grating (πFBG) that is chemically etched to the core of the fiber. Due to the p phase-shift, a strong πFBG forms a high-Q optical resonator and the reflection spectrum features an extremely narrow notch that can be used for highly sensitivity refractive index measurement. The etched πFBG demonstrated here has a diameter of ~9.3 μm and a length of only 7 mm, leading to a refractive index responsivity of 2.9 nm/RIU (RIU: refractive index unit) at an ambient refractive index of 1.318. The reflection spectrum of the etched πFBG features an extremely narrow notch with a linewidth of only 2.1 pm in water centered at ~1,550 nm, corresponding to a Q-factor of 7.4 × 10(5), which allows for potentially significantly improved sensitivity over refractometers based on regular fiber Bragg gratings.

Jones matrix analysis for a polarization-sensitive optical coherence tomography system using fiber-optic components.

PubMed

Park, B Hyle; Pierce, Mark C; Cense, Barry; de Boer, Johannes F

2004-11-01

We present an analysis for polarization-sensitive optical coherence tomography that facilitates the unrestricted use of fiber and fiber-optic components throughout an interferometer and yields sample birefringence, diattenuation, and relative optic axis orientation. We use a novel Jones matrix approach that compares the polarization states of light reflected from the sample surface with those reflected from within a biological sample for pairs of depth scans. The incident polarization alternated between two states that are perpendicular in a Poincaré sphere representation to ensure proper detection of tissue birefringence regardless of optical fiber contributions. The method was validated by comparing the calculated diattenuation of a polarizing sheet, chicken tendon, and muscle with that obtained by independent measurement. The relative importance of diattenuation versus birefringence to angular displacement of Stokes vectors on a Poincaré sphere was quantified.

Ultrahigh resolution radiation imaging system using an optical fiber structure scintillator plate.

PubMed

Yamamoto, Seiichi; Kamada, Kei; Yoshikawa, Akira

2018-02-16

High resolution imaging of radiation is required for such radioisotope distribution measurements as alpha particle detection in nuclear facilities or high energy physics experiments. For this purpose, we developed an ultrahigh resolution radiation imaging system using an optical fiber structure scintillator plate. We used a ~1-μm diameter fiber structured GdAlO 3 :Ce (GAP) /α-Al 2 O 3 scintillator plate to reduce the light spread. The fiber structured scintillator plate was optically coupled to a tapered optical fiber plate to magnify the image and combined with a lens-based high sensitivity CCD camera. We observed the images of alpha particles with a spatial resolution of ~25 μm. For the beta particles, the images had various shapes, and the trajectories of the electrons were clearly observed in the images. For the gamma photons, the images also had various shapes, and the trajectories of the secondary electrons were observed in some of the images. These results show that combining an optical fiber structure scintillator plate with a tapered optical fiber plate and a high sensitivity CCD camera achieved ultrahigh resolution and is a promising method to observe the images of the interactions of radiation in a scintillator.

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.

Preliminary design of land displacement-optical fiber sensor and analysis of observation during laboratory and field test

NASA Astrophysics Data System (ADS)

Bayuwati, Dwi; Waluyo, Tomi B.; Widiyatmoko, Bambang

2015-01-01

An optical fiber optic sensor for detecting land displacement is discussed in this paper. The sensor system consists of a laser at wavelength 1.3 um, optical fiber coupler, optical fiber as sensor and light transmitting media, PIN photodiodedetector system, data logger and personal computer. Sensor was made from a curved optical fiber with diameter 35 mm, which will be changed into a heart-shape fiber if it is pulled. The heart-shape fiber sensor is the modification of the earlier displacement fiber sensor model which was in an ellipse form. Light to and from the optical fiber sensor was transmitted into a length of a multi core, single mode optical fiber cable. The scheme of the optical displacement sensor system has been described here. Characterization in the laboratory has been done by applying a series of pulling mechanism, on the heart-shape fiber sensor; which represents the land displacement process. Characterization in the field was carried out by mounting the sensor system on a scaled-down model of a land slope and artificially reproducing the landslide process using a steady-flow of artificial rainfall as the trigger. The voltage sensor output was recorded during the artificial landslide process. The displacement occurence can be indicated from the declining of the sensor signal received by the detector while the reference signal is steady. Characterization in the laboratory resulted in the performance of the optical fiber land displacement, namely, sensitivity 0.027(mV/mV)/mm, resolution 0.37 mm and measurement range 30 mm; compared with earlier optical fiber sensor performance with similar sensitivity and resolution which works only in 8 mm displacement range. Based on the experiment of landslides simulation in the field, we can define a critical condition in the real situation before landslides occurence to take any measures to prevent more casualties and losses.

An integrated micro-volume fiber-optic sensor for oxygen determination in exhaled breath based on iridium(III) complexes immobilized in fluorinated xerogels.

PubMed

Xiong, Yan; Ye, Zhongbin; Xu, Jing; Zhu, Yuanqiang; Chen, Chen; Guan, Yafeng

2013-03-21

A novel integrated fiber-optic sensor with micro detection volume is developed and evaluated for O(2) determination on a breath-by-breath basis in human health monitoring applications. The sensing element was fabricated by dip-coating an uncladded optical fiber with [Ir(piq)(2)(acac)]-doped hybrid fluorinated ORMOSIL (organically modified silicate) film, which was prepared from 3,3,3-trifluoropropyltrimethoxysilane (TFP-TriMOS) and n-propyltrimethoxysilane (n-propyl-TriMOS). The sensor was then constructed by inserting the prepared optical fiber into a transparent capillary. A microchannel formed between the optical fiber and the capillary inner wall acted as a flow cell for the sample flowing through. The evanescent wave (EW) field produced on the fiber core surface can excite the O(2)-sensitive fluorophores of [Ir(piq)(2)(acac)] to produce emission fluorescence. O(2) can be sensed by its quenching effect on the emission fluorescence intensity. Spectroscopic properties have been characterized by FTIR and fluorescence measurements. Stern-Volmer and Demas models were both employed to analyse the sensor sensitivity, which is 13.0 with the LOD = 0.009% (3σ) and the response time is about 1 s. By integrating the sensing and detection elements on the optical fiber, the novel configuration showed advantages of easy fabrication and low cost. Parameters of sensitivity, response time, repeatability, humidity effect and temperature effect were discussed in detail. The proposed sensor showed potential for practical in-breath O(2) analysis application due to its advantages of easy fabrication, low cost, fast response, excellent hydrophobicity, negligible temperature interference and suitable sensitivity.

151-km single-end phase-sensitive optical time-domain reflectometer assisted by optical repeater

NASA Astrophysics Data System (ADS)

Song, Muping; Zhu, Weiji; Xia, Qiaolan; Yin, Cong; Lu, Yan; Wu, Ying; Zhuang, Shouwang

2018-02-01

A phase-sensitive optical time-domain reflectometry (ϕOTDR) system that can detect intrusion over 150 km is presented. The ϕOTDR system uses nonbalanced optical repeaters to extend the sensing distance. The repeater consists of two erbium-doped optical fiber amplifiers (EDFAs) and one Raman amplifier (RA). One EDFA power amplifier amplifies the forward-transmitting pulse, and one EDFA preamplifier is used for the backscattering signal, respectively. The RA helps keeping the power along the fiber stable. The optical repeater is installed at the connection of two adjacent fibers to compensate the power decline due to fiber loss. It is easy to install the repeater midway among the fiber links in the system for longer-distance sensing since there is no need of modifying the original sensing system. The theoretical analysis of the repeater is given to describe its effect on the distributed sensing. In experiments, several ϕOTDR traces show a good agreement with theoretical results. Using the optical repeater, 35-Hz vibration at 151 km is successfully measured with signal-to-noise ratio of 8 dB without extra signal processing.

Small-volume cavity cell using hollow optical fiber for Raman scattering-based gas detection

NASA Astrophysics Data System (ADS)

Okita, Y.; Katagiri, T.; Matsuura, Y.

2011-03-01

The highly sensitive Raman cell based on the hollow optical fiber that is suitable for the real-time breath analysis is reported. Hollow optical fiber with inner coating of silver is used as a gas cell and a Stokes light collector. A very small cell whose volume is only 0.4 ml or less enables fast response and real-time measurement of trace gases. To increase the sensitivity the cell is arranged in a cavity which includes of a long-pass filter and a high reflective mirror. The sensitivity of the cavity cell is more than two times higher than that of the cell without cavity.

Distributed Fiber Optic Sensors for Earthquake Detection and Early Warning

NASA Astrophysics Data System (ADS)

Karrenbach, M. H.; Cole, S.

2016-12-01

Fiber optic cables placed along pipelines, roads or other infrastructure provide dense sampling of passing seismic wavefields. Laser interrogation units illuminate the fiber over its entire length, and strain at desired points along the fiber can be determined from the reflected signal. Single-mode optical fibers up to 50 km in length can provide a distributed acoustic sensing system (DAS) where the acoustic bandwidth of each channel is limited only by the round-trip time over the length of the cable (0.0005 s for a 50 km cable). Using a 10 m spatial resolution results in 4000 channels sampled at 2.5 kHz spanning a 40 km-long fiber deployed along a pipeline. The inline strain field is averaged along the fiber over a 10 m section of the cable at each desired spatial sample, creating a virtual sensor location. Typically, a dynamic strain sensitivity of sub-nanometers within each gauge along the entire length of the fiber can be achieved. This sensitivity corresponds to a particle displacement figure of approximately -90 dB ms-2Hz-½. Such a fiber optic sensor is not as sensitive as long-period seismometers used in earthquake networks, but given the large number of channels, small to medium-sized earthquakes can be detected, depending on distance from the array, and can be located with precision through arrival time inversions. We show several examples of earthquake recordings using distributed fiber optic arrays that were deployed originally for other purposes. A 480 km long section of a pipeline in Turkey was actively monitored with a DAS fiber optic system for activities in the immediate vicinity of the pipeline. The densely spaced sensor array along the pipeline detected earthquakes of 3.6 - 7.2 magnitude range, centered near Van, Turkey. Secondly, a fiber optic system located along a rail line near the Salton Sea in California was used to create a smaller scale fiber optic sensor array, on which earthquakes with magnitudes 2.2 - 2.7 were recorded from epicenters up to 65 km away. Our analysis shows that existing fiber optic installations along infrastructure could be combined to form a large aperture array with tens of thousands of channels for epicenter estimation and for early warning purposes, augmenting existing earthquake sensor networks.

High-sensitivity stress sensor based on Bragg grating in BDK-doped photosensitive polymer optical fiber

NASA Astrophysics Data System (ADS)

Wang, Tongxin; Luo, Yanhua; Peng, Gang-Ding; Zhang, Qijin

2012-02-01

Bragg grating in a single-mode photosensitive polymer optical fiber (POF) with benzil dimethyl ketal (BDK)-doped in core has been inscribed through the Sagnac ring interference method. The Bragg wavelength of grating is about 1570nm. The stress and strain response of fiber Bragg grating (FBG) has been studied respectively. By fitting the experimental result, the strain sensitivity of FBG in POF has been found to be almost same to that of conventional silica fiber Bragg gratings. However, the stress sensitivity of FBG in POF is measured to be 421pm/MPa, which is 28 times higher than FBG in silica fiber. And such high stress sensitivity makes Bragg grating in a single-mode BDK-doped POF appear to be very attractive for constructing stress sensor with high resolution.

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 sensitivity cascaded preamplifier with an optical bridge structure in Brillouin distributed fiber sensing system

NASA Astrophysics Data System (ADS)

Bi, Weihong; Lin, Hang; Fu, Xinghu; Fu, Guangwei

2013-12-01

Fiber amplifiers such as Erbium-doped fiber amplifier (EDFA) played a key role in developing long-haul transmission system and have been an important element for enabling the development of optical communication system. EDFA amplifies the optical signal directly, without the optical-electric-optical switch and has the advantages such as high gain, broad band, low noise figure. It is widely used in repeaterless submarine system, smart grid and community antenna television system. This article describe the application of optical-fiber amplifiers in distributed optical fiber sensing system, focusing on erbium-doped fiber preamplifiers in modern transmission optical systems. To enhance the measurement range of a spontaneous Brillouin intensity based distributed fiber optical sensor and improve the receiver sensitivity, a two cascaded EDFAs C-band preamplifier with an optical bridge structure is proposed in this paper. The first cascaded EDFA is consisted of a length of 4.3m erbium-doped fiber and pumped in a forward pump light using a laser operating at 975nm. The second one made by using a length of 16m erbium-doped fiber is pumped in a forward pump light which is the remnant pump light of the first cascaded EDFA. At the preamplifier output, DWDM, centered at the signal wavelength, is used to suppress unwanted amplified spontaneous emission. The experimental results show that the two cascade preamplifier with a bridge structure can be used to amplify for input Brillouin backscattering light greater than about -43dBm. The optical gain is characterized and more than 26dB is obtained at 1549.50nm with 300mW pump power.

Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing.

PubMed

Klantsataya, Elizaveta; François, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M

2015-09-29

Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33-1.37) suitable for biosensing applications.

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

Temperature-strain discrimination in distributed optical fiber sensing using phase-sensitive optical time-domain reflectometry.

PubMed

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

2017-07-10

A method based on coherent Rayleigh scattering distinctly evaluating temperature and strain is proposed and experimentally demonstrated for distributed optical fiber sensing. Combining conventional phase-sensitive optical time-domain domain reflectometry (ϕOTDR) and ϕOTDR-based birefringence measurements, independent distributed temperature and strain profiles are obtained along a polarization-maintaining fiber. A theoretical analysis, supported by experimental data, indicates that the proposed system for temperature-strain discrimination is intrinsically better conditioned than an equivalent existing approach that combines classical Brillouin sensing with Brillouin dynamic gratings. This is due to the higher sensitivity of coherent Rayleigh scatting compared to Brillouin scattering, thus offering better performance and lower temperature-strain uncertainties in the discrimination. Compared to the Brillouin-based approach, the ϕOTDR-based system here proposed requires access to only one fiber-end, and a much simpler experimental layout. Experimental results validate the full discrimination of temperature and strain along a 100 m-long elliptical-core polarization-maintaining fiber with measurement uncertainties of ~40 mK and ~0.5 με, respectively. These values agree very well with the theoretically expected measurand resolutions.

Optical fiber-based fluorescent viscosity sensor

NASA Astrophysics Data System (ADS)

Haidekker, Mark A.; Akers, Walter J.; Fischer, Derek; Theodorakis, Emmanuel A.

2006-09-01

Molecular rotors are a unique group of viscosity-sensitive fluorescent probes. Several recent studies have shown their applicability as nonmechanical fluid viscosity sensors, particularly in biofluids containing proteins. To date, molecular rotors have had to be dissolved in the fluid for the measurement to be taken. We now show that molecular rotors may be covalently bound to a fiber-optic tip without loss of viscosity sensitivity. The optical fiber itself may be used as a light guide for emission light (external illumination of the tip) as well as for both emission and excitation light. Covalently bound molecular rotors exhibit a viscosity-dependent intensity increase similar to molecular rotors in solution. An optical fiber-based fluorescent viscosity sensor may be used in real-time measurement applications ranging from biomedical applications to the food industry.

Optical fiber-based fluorescent viscosity sensor.

PubMed

Haidekker, Mark A; Akers, Walter J; Fischer, Derek; Theodorakis, Emmanuel A

2006-09-01

Molecular rotors are a unique group of viscosity-sensitive fluorescent probes. Several recent studies have shown their applicability as nonmechanical fluid viscosity sensors, particularly in biofluids containing proteins. To date, molecular rotors have had to be dissolved in the fluid for the measurement to be taken. We now show that molecular rotors may be covalently bound to a fiber-optic tip without loss of viscosity sensitivity. The optical fiber itself may be used as a light guide for emission light (external illumination of the tip) as well as for both emission and excitation light. Covalently bound molecular rotors exhibit a viscosity-dependent intensity increase similar to molecular rotors in solution. An optical fiber-based fluorescent viscosity sensor may be used in real-time measurement applications ranging from biomedical applications to the food industry.

Microstructured Optical Fiber Sensors Embedded in a Laminate Composite for Smart Material Applications

PubMed Central

Sonnenfeld, Camille; Sulejmani, Sanne; Geernaert, Thomas; Eve, Sophie; Lammens, Nicolas; Luyckx, Geert; Voet, Eli; Degrieck, Joris; Urbanczyk, Waclaw; Mergo, Pawel; Becker, Martin; Bartelt, Hartmut; Berghmans, Francis; Thienpont, Hugo

2011-01-01

Fiber Bragg gratings written in highly birefringent microstructured optical fiber with a dedicated design are embedded in a composite fiber-reinforced polymer. The Bragg peak wavelength shifts are measured under controlled axial and transversal strain and during thermal cycling of the composite sample. We obtain a sensitivity to transversal strain that exceeds values reported earlier in literature by one order of magnitude. Our results evidence the relevance of using microstructured optical fibers for structural integrity monitoring of composite material structures. PMID:22163755

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.

A Small U-Shaped Bending-Induced Interference Optical Fiber Sensor for the Measurement of Glucose Solutions.

PubMed

Fang, Yu-Lin; Wang, Chen-Tung; Chiang, Chia-Chin

2016-09-09

The study proposes a small U-shaped bending-induced interference optical fiber sensor; this novel sensor is a probe-type sensor manufactured using a mechanical device, a heat source, optical fiber and a packaging module. This probe-type sensor overcomes the shortcomings of conventional optical fibers, including being difficult to repair and a tendency to be influenced by external forces. We manufactured three types of sensors with different curvature radiuses. Specifically, sensors with three radiuses (1.5 mm, 2.0 mm, and 3.0 mm) were used to measure common water and glucose solutions with concentrations of between 6% and 30% (the interval between concentrations was 4%). The results show that the maximal sensitivity was 0.85 dB/% and that the linearly-dependent coefficient was 0.925. The results further show that not only can the small U-shaped bending-induced interference optical fiber sensor achieve high sensitivity in the measurement of glucose solutions, but that it can also achieve great stability and repeatability.

Fiber-optic beam control systems using microelectromechanical systems

NASA Astrophysics Data System (ADS)

Sumriddetchkajorn, Sarun

This dissertation, for the first time, proposes, studies, and experimentally demonstrated novel fiber-optic beam control systems based on the use of microelectromechanical system (MEMS) technology in which the miniaturized versions of mechanical systems can be obtained. Beam control modules include optical add/drop filters, optical switches, variable photonic delay lines (VPDLs), and variable optical attenuators (VOAs). The optical add/drop filter functions as a multiwavelength optical switch that offers the ability to drop and add a certain number of desired wavelengths at an intermediate location where access to all the propagating optical channels is not required between transmission terminals. The VOA can also be used in networks where stocking and tracking of fixed attenuators is difficult. Other specific applications of the VOA are optical gain equalization and polarization dependent loss and gain compensation required in high data-rate wavelength division multiplexed (WDM) lightwave systems. A VPDL can be used to adjust timing amongst multiwavelength optical signals in order to reduce timing jitter and burst traffic in photonic packet switching and parallel signal processing systems. In this dissertation, a small tilt micromirror device is proposed for the implementation of all fiber-optic beam control modules. In particular, the macro-pixel approach where several micromirrors are used to manipulate the desired optical beam is introduced to realize high speed and fault tolerant beam control modules. To eliminate the need of careful optical alignment, an all fiber-connectorized multiwavelength optical switch structure is presented and experimentally demonstrated by using a fiber-loop mirror concept with polarization control. In addition, liquid crystal (LC) devices are studied and are used to implement a compact retro- reflective 2 x 2 fiber-optic switch. Compared to MEMS- based mirror technology, the LC technology is more sensitive to temperature, thereby inappropriate to deploy in a harsh environment. With the benefit provided by WDM systems, wavelength sensitive fiber-optic beam controllers are proposed, offering wavelength sensitive time delay and amplitude controls that can be applied in several applications ranging from optical communications to high speed parallel signal processing. (Abstract shortened by UMI.)

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.

Reflection based Extraordinary Optical Transmission Fiber Optic Probe for Refractive Index Sensing.

PubMed

Lan, Xinwei; Cheng, Baokai; Yang, Qingbo; Huang, Jie; Wang, Hanzheng; Ma, Yinfa; Shi, Honglan; Xiao, Hai

2014-03-31

Fiber optic probes for chemical sensing based on the extraordinary optical transmission (EOT) phenomenon are designed and fabricated by perforating subwavelength hole arrays on the gold film coated optical fiber endface. The device exhibits a red shift in response to the surrounding refractive index increases with high sensitivity, enabling a reflection-based refractive index sensor with a compact and simple configuration. By choosing the period of hole arrays, the sensor can be designed to operate in the near infrared telecommunication wavelength range, where the abundant source and detectors are available for easy instrumentation. The new sensor probe is demonstrated for refractive index measurement using refractive index matching fluids. The sensitivity reaches 573 nm/RIU in the 1.333~1.430 refractive index range.

SWCNTs-based nanocomposites as sensitive coatings for advanced fiber optic chemical nanosensors

NASA Astrophysics Data System (ADS)

Consales, M.; Crescitelli, A.; Penza, M.; Aversa, P.; Giordano, M.; Cutolo, A.; Cusano, A.

2008-04-01

In this work, the feasibility of exploiting novel Cadmium Arachidate (CdA)/single-walled carbon nanotubes (SWCNTs) based composites as sensitive coatings for the development of robust and high performances optoelectronic chemosensors able to work in liquid environments has been investigated and proved. Here, nano-composite sensing layers have been transferred upon the distal end of standard optical fibers by the Langmuir-Blodgett (LB) technique. Reflectance measurements have been carried out to monitor ppm concentration of chemicals in water through the changes in the optical and geometrical features of the sensing overlay induced by the interaction with the analyte molecules. Preliminary experimental results evidence that such nanoscale coatings integrated with the optical fiber technology offers great potentialities for the room temperature detection of chemical traces in water and lead to significant improvements of the traditional fiber optic sensors based on SWCNTs layers.

Study of Optical Fiber Sensors for Cryogenic Temperature Measurements.

PubMed

De Miguel-Soto, Veronica; Leandro, Daniel; Lopez-Aldaba, Aitor; Beato-López, Juan Jesus; Pérez-Landazábal, José Ignacio; Auguste, Jean-Louis; Jamier, Raphael; Roy, Philippe; Lopez-Amo, Manuel

2017-11-30

In this work, the performance of five different fiber optic sensors at cryogenic temperatures has been analyzed. A photonic crystal fiber Fabry-Pérot interferometer, two Sagnac interferometers, a commercial fiber Bragg grating (FBG), and a π-phase shifted fiber Bragg grating interrogated in a random distributed feedback fiber laser have been studied. Their sensitivities and resolutions as sensors for cryogenic temperatures have been compared regarding their advantages and disadvantages. Additionally, the results have been compared with the given by a commercial optical backscatter reflectometer that allowed for distributed temperature measurements of a single mode fiber.

Study of Optical Fiber Sensors for Cryogenic Temperature Measurements

PubMed Central

Leandro, Daniel; Lopez-Aldaba, Aitor; Beato-López, Juan Jesus; Pérez-Landazábal, José Ignacio; Auguste, Jean-Louis; Jamier, Raphael; Roy, Philippe; Lopez-Amo, Manuel

2017-01-01

In this work, the performance of five different fiber optic sensors at cryogenic temperatures has been analyzed. A photonic crystal fiber Fabry-Pérot interferometer, two Sagnac interferometers, a commercial fiber Bragg grating (FBG), and a π-phase shifted fiber Bragg grating interrogated in a random distributed feedback fiber laser have been studied. Their sensitivities and resolutions as sensors for cryogenic temperatures have been compared regarding their advantages and disadvantages. Additionally, the results have been compared with the given by a commercial optical backscatter reflectometer that allowed for distributed temperature measurements of a single mode fiber. PMID:29189755

Optic axis determination accuracy for fiber-based polarization-sensitive optical coherence tomography.

PubMed

Park, B Hyle; Pierce, Mark C; Cense, Barry; de Boer, Johannes F

2005-10-01

We present a generalized analysis of fiber-based polarization-sensitive optical coherence tomography with an emphasis on determination of sample optic axis orientation. The polarization properties of a fiber-based system can cause an overall rotation in a Poincaré sphere representation such that the plane of possible measured sample optic axes for linear birefringence and diattenuation no longer lies in the QU-plane. The optic axis orientation can be recovered as an angle on this rotated plane, subject to an offset and overall indeterminacy in sign such that only the magnitude, but not the direction, of a change in orientation can be determined. We discuss the accuracy of optic axis determination due to a fundamental limit on the accuracy with which a polarization state can be determined as a function of signal-to-noise ratio.

Meeting Future C3I (Command-Control-Communications-Intelligence) Needs with Fiber Optics,

DTIC Science & Technology

1985-05-01

Frequency dependence of the sensitivity of fibers with hard coatings is relatively small. Nylon gives the weakest dependence, while the soft UV -cured...elastomer gives the strongest. Maximum sensitivity is obtained with Teflon TFE, while the minimum is achieved with the soft UV coating. With the latter...fiber-optics systems: the LED (Light Emitting Diode) and ILD (Injection Laser Diode). These devices emit light when an electric current is applied. The

On-line tritium production monitor

DOEpatents

Mihalczo, John T.

1993-01-01

A scintillation optical fiber system for the on-line monitoring of nuclear reactions in an event-by-event manner is described. In the measurement of tritium production one or more optical fibers are coated with enriched .sup.6 Li and connected to standard scintillation counter circuitry. A neutron generated .sup.6 Li(n )T reaction occurs in the coated surface of .sup.6 Li-coated fiber to produce energetic alpha and triton particles one of which enters the optical fiber and scintillates light through the fiber to the counting circuit. The coated optical fibers can be provided with position sensitivity by placing a mirror at the free end of the fibers or by using pulse counting circuits at both ends of the fibers.

On-line tritium production monitor

DOEpatents

Mihalczo, J.T.

1993-11-23

A scintillation optical fiber system for the on-line monitoring of nuclear reactions in an event-by-event manner is described. In the measurement of tritium production one or more optical fibers are coated with enriched {sup 6}Li and connected to standard scintillation counter circuitry. A neutron generated {sup 6}Li(n)T reaction occurs in the coated surface of {sup 6}Li-coated fiber to produce energetic alpha and triton particles one of which enters the optical fiber and scintillates light through the fiber to the counting circuit. The coated optical fibers can be provided with position sensitivity by placing a mirror at the free end of the fibers or by using pulse counting circuits at both ends of the fibers. 5 figures.

Cadmium arachidate single-walled carbon nanotubes composites as sensitive coatings for high sensitivity fiber optic chemo-sensors

NASA Astrophysics Data System (ADS)

Consales, M.; Crescitelli, A.; Cutolo, A.; Penza, M.; Aversa, P.; Giordano, M.; Cusano, A.

2007-07-01

In this work, the feasibility to exploit optoelectronic chemo-sensors based on cadmium arachidate (CdA)/single-walled carbon nanotubes (SWCNTs) composites for detection of chemical pollutants both in air and water environments has been investigated. The nanocomposite sensing layers have been transferred upon the distal end of standard optical fibers by the Langmuir-Blodgett (LB) technique. Single wavelength reflectance measurements (λ=1310 nm) have been carried out to monitor chemicals concentration through changes in the optical length of the Fabry-Pérot (FP) cavity induced by the interaction of the sensitive layer with the analyte molecules. The preliminary experimental results evidence the good potentiality of these fiber optic nanosensors to detect toluene and xylene at ppm level both in air and water environments at room temperature.

Modeling the action-potential-sensitive nonlinear-optical response of myelinated nerve fibers and short-term memory

NASA Astrophysics Data System (ADS)

Shneider, M. N.; Voronin, A. A.; Zheltikov, A. M.

2011-11-01

The Goldman-Albus treatment of the action-potential dynamics is combined with a phenomenological description of molecular hyperpolarizabilities into a closed-form model of the action-potential-sensitive second-harmonic response of myelinated nerve fibers with nodes of Ranvier. This response is shown to be sensitive to nerve demyelination, thus enabling an optical diagnosis of various demyelinating diseases, including multiple sclerosis. The model is applied to examine the nonlinear-optical response of a three-neuron reverberating circuit—the basic element of short-term memory.

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.

Portable evanescent wave fiber biosensor for highly sensitive detection of Shigella

NASA Astrophysics Data System (ADS)

Xiao, Rui; Rong, Zhen; Long, Feng; Liu, Qiqi

2014-11-01

A portable evanescent wave fiber biosensor was developed to achieve the rapid and highly sensitive detection of Shigella. In this study, a DNA probe was covalently immobilized onto fiber-optic biosensors that can hybridize with a fluorescently labeled complementary DNA. The sensitivity of detection for synthesized oligonucleotides can reach 10-10 M. The surface of the sensor can be regenerated with 0.5% sodium dodecyl sulfate solution (pH 1.9) for over 30 times without significant deterioration of performance. The total analysis time for a single sample, including the time for measurement and surface regeneration, was less than 6 min. We employed real-time polymerase chain reaction (PCR) and compared the results of both methods to investigate the actual Shigella DNA detection capability of the fiber-optic biosensor. The fiber-optic biosensor could detect as low as 102 colony-forming unit/mL Shigella. This finding was comparable with that by real-time PCR, which suggests that this method is a potential alternative to existing detection methods.

Sensitive zone parameters and curvature radius evaluation for polymer optical fiber curvature sensors

NASA Astrophysics Data System (ADS)

Leal-Junior, Arnaldo G.; Frizera, Anselmo; José Pontes, Maria

2018-03-01

Polymer optical fibers (POFs) are suitable for applications such as curvature sensors, strain, temperature, liquid level, among others. However, for enhancing sensitivity, many polymer optical fiber curvature sensors based on intensity variation require a lateral section. Lateral section length, depth, and surface roughness have great influence on the sensor sensitivity, hysteresis, and linearity. Moreover, the sensor curvature radius increase the stress on the fiber, which leads on variation of the sensor behavior. This paper presents the analysis relating the curvature radius and lateral section length, depth and surface roughness with the sensor sensitivity, hysteresis and linearity for a POF curvature sensor. Results show a strong correlation between the decision parameters behavior and the performance for sensor applications based on intensity variation. Furthermore, there is a trade-off among the sensitive zone length, depth, surface roughness, and curvature radius with the sensor desired performance parameters, which are minimum hysteresis, maximum sensitivity, and maximum linearity. The optimization of these parameters is applied to obtain a sensor with sensitivity of 20.9 mV/°, linearity of 0.9992 and hysteresis below 1%, which represent a better performance of the sensor when compared with the sensor without the optimization.

Escherichia coli Fiber Sensors Using Concentrated Dielectrophoretic Force with Optical Defocusing Method.

PubMed

Tai, Yi-Hsin; Lee, Chia-Wei; Chang, Dao-Ming; Lai, Yu-Sheng; Huang, Ding-Wei; Wei, Pei-Kuen

2018-05-25

A sensitive tapered optical fiber tip combined with dielectrophoretic (DEP) trapping was used for rapid and label-free detection of bacteria in water. The angular spectrum of the optical field at the fiber tip was changed with the surrounding refractive index (RI). By measuring far-field intensity change at the defocus plane, the intensity sensitivity was up to 95 200%/RIU (RI unit), and the detection limit was 5.2 × 10 -6 RIU at 0.5% intensity stability. By applying an AC voltage to a Ti/Al coated fiber tip and an indium-tin-oxide glass, the DEP force effectively trapped the Escherichia coli ( E. coli) near the fiber tip. Those bacteria can be directly measured from optical intensity change due to the increase of surrounding RI. By immobilizing the antibody on the Ti/Al fiber tip, the tests for specific K12 bacteria and nonspecific BL21 bacteria verified the specificity. The antibody-immobilized Ti/Al coated fiber tip with DEP trapping can detect bacteria at a concentration about 100 CFU/mL.

Effective light coupling in reflective fiber optic distance sensors using a double-clad fiber

NASA Astrophysics Data System (ADS)

Werzinger, Stefan; Härteis, Lisa; Köhler, Aaron; Engelbrecht, Rainer; Schmauss, Bernhard

2017-04-01

Many fiber optic distance sensors use a reflective configuration, where a light beam is launched from an optical fiber, reflected from a target and coupled back into the fiber. While singlemode fibers (SMF) provide low-loss, high-performance components and a well-defined output beam, the coupling of the reflected light into the SMF is very sensitive to mechanical misalignments and scattering at the reflecting target. In this paper we use a double-clad fiber (DCF) and a DCF coupler to obtain an enhanced multimodal coupling of reflected light into the fiber. Increased power levels and robustness are achieved compared to a pure SMF configuration.

Phase shift of TE and TM modes in an optical fiber due to axial strain (exact solution)

NASA Technical Reports Server (NTRS)

Egalon, Claudio O.; Rogowski, Robert S.

1992-01-01

Axial strain may be determined by monitoring the phase shift of modes of a variety of optical fiber sensors. In this paper, the exact solution of a circular optical fiber is used to calculate the phase shift of the TE and TM modes. Whenever an optical fiber is stressed, the optical path length, the index of refraction, and the propagation constants of each fiber mode change. In consequence, the modal phase term, beta(ln)z, of the fields is shifted by an amount Delta phi. In certain cases, it is desirable to control the phase shift term in order to make the fiber either more or less sensitive to certain kinds of strain. It is shown that it can be accomplished by choosing appropriate fiber parameters.

Pressure sensitivity analysis of fiber Bragg grating sensors

NASA Astrophysics Data System (ADS)

Mrad, Nezih; Sridharan, Vasant; Kazemi, Alex

2014-09-01

Recent development in fiber optic sensing technology has mainly focused on discrete sensing, particularly, sensing systems with potential multiplexing and multi-parameter capabilities. Bragg grating fiber optic sensors have emerged as the non-disputed champion for multiplexing and simultaneous multi-parameter sensing for emerging high value structural components, advanced processing and manufacturing capabilities and increased critical infrastructure resilience applications. Although the number of potential applications for this sensing technology is large and spans the domains of medicine, manufacturing, aerospace, and public safety; critical issues such as fatigue life, sensitivity, accuracy, embeddability, material/sensor interface integrity, and universal demodulation systems still need to be addressed. The purpose of this paper is to primarily evaluate Commercial-Of-The-Shelf (COTS) Fiber Bragg Grating (FBG) sensors' sensitivity to pressure, often neglected in several applications. The COTS fiber sensitivity to pressure is further evaluated for two types of coatings (Polyimide and Acrylate), and different arrangements (arrayed and single).

Evanescent-wave photoacoustic spectroscopy with optical micro/nano fibers.

PubMed

Cao, Yingchun; Jin, Wei; Ho, Lut Hoi; Liu, Zhibo

2012-01-15

We demonstrate gas detection based on evanescent-wave photoacoustic (PA) spectroscopy with tapered optical fibers. Evanescent-field instead of open-path absorption is exploited for PA generation, and a quartz tuning fork is used for PA detection. A tapered optical fiber with a diameter down to the wavelength scale demonstrates detection sensitivity similar to an open-path system but with the advantages of easier optical alignment, smaller insertion loss, and multiplexing capability.

Simulation and performance evaluation of fiber optic sensor for detection of hepatic malignancies in human liver tissues

NASA Astrophysics Data System (ADS)

Sharma, Anuj K.; Gupta, Jyoti; Basu, Rikmantra

2018-01-01

A fiber optic sensor is proposed for the identification of healthy and cancerous liver tissues through determination of their corresponding refractive index values. Existing experimental results describing variation of complex refractive index of liver tissues in near infrared (NIR) spectral region are considered for theoretical calculations. The intensity interrogation method with chalcogenide fiber is considered. The sensor's performance is closely analyzed in terms of its sensitivity at multiple operating wavelengths falling in NIR region. Operating at shorter NIR wavelengths leads to greater sensitivity. The effect of design parameters (sensing region length and fiber core diameter), different launching conditions, and fiber glass materials on sensor's performance is examined. The proposed sensor has the potential to provide high sensitivity of liver tissue detection.

Tuning operating point of extrinsic Fabry-Perot interferometric fiber-optic sensors using microstructured fiber and gas pressure.

PubMed

Tian, Jiajun; Zhang, Qi; Fink, Thomas; Li, Hong; Peng, Wei; Han, Ming

2012-11-15

Intensity-based demodulation of extrinsic Fabry-Perot interferometric (EFPI) fiber-optic sensors requires the light wavelength to be on the quadrature point of the interferometric fringes for maximum sensitivity. In this Letter, we propose a novel and remote operating-point tuning method for EFPI fiber-optic sensors using microstructured fibers (MFs) and gas pressure. We demonstrated the method using a diaphragm-based EFPI sensor with a microstructured lead-in fiber. The holes in the MF were used as gas channels to remotely control the gas pressure inside the Fabry-Perot cavity. Because of the deformation of the diaphragm with gas pressure, the cavity length and consequently the operating point can be remotely tuned for maximum sensitivity. The proposed operating-point tuning method has the advantage of reduced complexity and cost compared to previously reported methods.

Fiber-Optic Refractometer Based on an Etched High-Q π-Phase-Shifted Fiber-Bragg-Grating

PubMed Central

Zhang, Qi; Ianno, Natale J.; Han, Ming

2013-01-01

We present a compact and highly-sensitive fiber-optic refractometer based on a high-Q π-phase-shifted fiber-Bragg-grating (πFBG) that is chemically etched to the core of the fiber. Due to the π phase-shift, a strong πFBG forms a high-Q optical resonator and the reflection spectrum features an extremely narrow notch that can be used for highly sensitivity refractive index measurement. The etched πFBG demonstrated here has a diameter of ∼9.3 μm and a length of only 7 mm, leading to a refractive index responsivity of 2.9 nm/RIU (RIU: refractive index unit) at an ambient refractive index of 1.318. The reflection spectrum of the etched πFBG features an extremely narrow notch with a linewidth of only 2.1 pm in water centered at ∼1,550 nm, corresponding to a Q-factor of 7.4 × 105, which allows for potentially significantly improved sensitivity over refractometers based on regular fiber Bragg gratings. PMID:23845932

Optimization of a fiber optic flexible disk microphone

NASA Astrophysics Data System (ADS)

Zhang, Gang; Yu, Benli; Wang, Hui; Liu, Fei; Peng, Jun; Wu, Xuqiang

2011-11-01

An optimized design of a fiber optic flexible disk microphone is presented and verified experimentally. The phase sensitivity of optical fiber microphone (both the ideal model with a simply supported disk (SSD) and the model with a clamped disk (CLD)) is analyzed by utilizing theory of plates and shells. The results show that the microphones have an optimum length of the sensing arm when inner radius of the fiber coils, radius and Poisson's radio of the flexible disk have been determined. Under a typical condition depicted in this paper, an optimum phase sensitivity for SSD model of 27.72 rad/Pa (-91.14 dB re 1 rad/μPa) and an optimum phase sensitivity for CLD model of 3.18 rad/Pa (-109.95 dB re 1 rad/μPa), can be achieved in theory. Several sample microphones are fabricated and tested. The experimental results are basically consistent with the theoretical analysis.

Scintillator fiber optic long counter

DOEpatents

McCollum, Tom; Spector, Garry B.

1994-01-01

A flat response position sensitive neutron detector capable of providing neutron spectroscopic data utilizing scintillator fiber optic filaments embedded in a neutron moderating housing having an open end through which neutrons enter to be detected.

High-temperature fiber optic pressure sensor

NASA Technical Reports Server (NTRS)

Berthold, J. W.

1984-01-01

Attention is given to a program to develop fiber optic methods to measure diaphragm deflection. The end application is intended for pressure transducers capable of operating to 540 C. In this paper are reported the results of a laboratory study to characterize the performance of the fiber-optic microbend sensor. The data presented include sensitivity and spring constant. The advantages and limitations of the microbend sensor for static pressure measurement applications are described. A proposed design is presented for a 540 C pressure transducer using the fiber optic microbend sensor.

Alcohol sensor based on u-bent hetero-structured fiber optic

NASA Astrophysics Data System (ADS)

Patrialova, Sefi N.; Hatta, Agus M.; Sekartedjo, Sekartedjo

2016-11-01

A sensor based on a fiber optic hetero-structure to determine the concentration of alcohol has been proposed. The structure of the sensing probe in this research is a singlemode-multimode-singlemode (SMS) which bent into Ushaped and soon called as SMS u-bent. The SMS structure was chosen to get a higher sensitivity. This research utilizes the principle of multimode interference and evanescent field by modifying the cladding with various alcohol concentration. Testing of the sensor's performance has been done by measuring the sensor's power output response to the length of the SMS fiber optic, bending diameter, and alcohol concentration. Based on the experiment result, the ubent SMS fiber optic with 50 mm bending diameter and 63 mm MMF lenght has the highest sensitivity, 3.87 dB/% and the minimum resolution, 0.26 x 10-3 %.

Fiber Surface Modification Technology for Fiber-Optic Localized Surface Plasmon Resonance Biosensors

PubMed Central

Zhang, Qiang; Xue, Chenyang; Yuan, Yanling; Lee, Junyang; Sun, Dong; Xiong, Jijun

2012-01-01

Considerable studies have been performed on the development of optical fiber sensors modified by gold nanoparticles based on the localized surface plasmon resonance (LSPR) technique. The current paper presents a new approach in fiber surface modification technology for biosensors. Star-shaped gold nanoparticles obtained through the seed-mediated solution growth method were found to self-assemble on the surface of tapered optical fibers via amino- and mercapto-silane coupling agents. Transmitted power spectra of 3-aminopropyltrimethoxy silane (APTMS)-modified fiber were obtained, which can verify that the silane coupling agent surface modification method is successful. Transmission spectra are characterized in different concentrations of ethanol and gentian violet solutions to validate the sensitivity of the modified fiber. Assembly using star-shaped gold nanoparticles and amino/mercapto silane coupling agent are analyzed and compared. The transmission spectra of the gold nanoparticles show that the nanoparticles are sensitive to the dielectric properties of the surrounding medium. After the fibers are treated in t-dodecylmercaptan to obtain their transmission spectra, APTMS-modified fiber becomes less sensitive to different media, except that modified by 3-mercaptopropyltrimethoxy silane (MPTMS). Experimental results of the transmission spectra show that the surface modified by the gold nanoparticles using MPTMS is firmer compared to that obtained using APTMS. PMID:22736974

Tapered Optical Fiber Probe Assembled with Plasmonic Nanostructures for Surface-Enhanced Raman Scattering Application.

PubMed

Huang, Zhulin; Lei, Xing; Liu, Ye; Wang, Zhiwei; Wang, Xiujuan; Wang, Zhaoming; Mao, Qinghe; Meng, Guowen

2015-08-12

Optical fiber-Raman devices integrated with plasmonic nanostructures have promising potentials for in situ probing remote liquid samples and biological samples. In this system, the fiber probe is required to simultaneously demonstrate stable surface enhanced Raman scattering (SERS) signals and high sensitivity toward the target species. Here we demonstrate a generic approach to integrate presynthesized plasmonic nanostructures with tapered fiber probes that are prepared by a dipping-etching method, through reversed electrostatic attraction between the silane couple agent modified silica fiber probe and the nanostructures. Using this approach, both negatively and positively charged plasmonic nanostructures with various morphologies (such as Au nanosphere, Ag nanocube, Au nanorod, Au@Ag core-shell nanorod) can be stably assembled on the tapered silica fiber probes. Attributed to the electrostatic force between the plasmonic units and the fiber surface, the nanostructures do not disperse in liquid samples easily, making the relative standard deviation of SERS signals as low as 2% in analyte solution. Importantly, the detection sensitivity of the system can be optimized by adjusting the cone angle (from 3.6° to 22°) and the morphology of nanostructures assembled on the fiber. Thus, the nanostructures-sensitized optical fiber-Raman probes show great potentials in the applications of SERS-based environmental detection of liquid samples.

High sensitivity refractive index sensor based on adiabatic tapered optical fiber deposited with nanofilm by ALD.

PubMed

Zhu, Shan; Pang, Fufei; Huang, Sujuan; Zou, Fang; Dong, Yanhua; Wang, Tingyun

2015-06-01

Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractive index sensor based on an adiabatic tapered optical fiber. Different thickness of Al₂O₃ nanofilm is coated around fiber taper precisely and uniformly under different deposition cycles. Attributed to the high refractive index of the Al₂O₃ nanofilm, an asymmetry Fabry-Perot like interferometer is constructed along the fiber taper. Based on the ray-optic analysis, total internal reflection happens on the nanofilm-surrounding interface. With the ambient refractive index changing, the phase delay induced by the Goos-Hänchen shift is changed. Correspondingly, the transmission resonant spectrum shifts, which can be utilized for realizing high sensitivity sensor. The high sensitivity sensor with 6008 nm/RIU is demonstrated by depositing 3000 layers Al₂O₃ nanofilm as the ambient refractive index is close to 1.33. This high sensitivity refractive index sensor is expected to have wide applications in biochemical sensors.

Depth-resolved birefringence and differential optical axis orientation measurements with fiber-based polarization-sensitive optical coherence tomography.

PubMed

Guo, Shuguang; Zhang, Jun; Wang, Lei; Nelson, J Stuart; Chen, Zhongping

2004-09-01

Conventional polarization-sensitive optical coherence tomography (PS-OCT) can provide depth-resolved Stokes parameter measurements of light reflected from turbid media. A new algorithm that takes into account changes in the optical axis is introduced to provide depth-resolved birefringence and differential optical axis orientation images by use of fiber-based PS-OCT. Quaternion, a convenient mathematical tool, is used to represent an optical element and simplify the algorithm. Experimental results with beef tendon and rabbit tendon and muscle show that this technique has promising potential for imaging the birefringent structure of multiple-layer samples with varying optical axes.

Strain distribution in thin concrete pavement panels under three-point loading to failure with pre-pulse-pump Brillouin optical time domain analysis (Presentation Video)

NASA Astrophysics Data System (ADS)

Bao, Yi; Cain, John; Chen, Yizheng; Huang, Ying; Chen, Genda; Palek, Leonard

2015-04-01

Thin concrete panels reinforced with alloy polymer macro-synthetic fibers have recently been introduced to rapidly and cost-effectively improve the driving condition of existing roadways by laying down a fabric sheet on the roadways, casting a thin layer of concrete, and then cutting the layer into panels. This study is aimed to understand the strain distribution and potential crack development of concrete panels under three-point loading. To this end, six full-size 6ft×6ft×3in concrete panels were tested to failure in the laboratory. They were instrumented with three types of single-mode optical fiber sensors whose performance and ability to measure the strain distribution and detect cracks were compared. Each optical fiber sensor was spliced and calibrated, and then attached to a fabric sheet using adhesive. A thin layer of mortar (0.25 ~ 0.5 in thick) was cast on the fabric sheet. The three types of distributed sensors were bare SM-28e+ fiber, SM-28e+ fiber with a tight buffer, and concrete crack cable, respectively. The concrete crack cable consisted of one SM-28e+ optical fiber with a tight buffer, one SM-28e+ optical fiber with a loose buffer for temperature compensation, and an outside protective tight sheath. Distributed strains were collected from the three optical fiber sensors with pre-pulse-pump Brillouin optical time domain analysis in room temperature. Among the three sensors, the bare fiber was observed to be most fragile during construction and operation, but most sensitive to strain change or micro-cracks. The concrete crack cable was most rugged, but not as sensitive to micro-cracks and robust in micro-crack measurement as the bare fiber. The ruggedness and sensitivity of the fiber with a tight buffer were in between the bare fiber and the concrete crack cable. The strain distribution resulted from the three optical sensors are in good agreement, and can be applied to successfully locate cracks in the concrete panels. It was observed that the three types of fibers were functional until the concrete panels have experienced inelastic deformation, making the distributed strain sensing technology promising for real applications in pavement engineering.

Embedded fiber optic ultrasonic sensors and generators

NASA Astrophysics Data System (ADS)

Dorighi, John F.; Krishnaswamy, Sridhar; Achenbach, Jan D.

1995-04-01

Ultrasonic sensors and generators based on fiber-optic systems are described. It is shown that intrinsic fiber optic Fabry-Perot ultrasound sensors that are embedded in a structure can be stabilized by actively tuning the laser frequency. The need for this method of stabilization is demonstrated by detecting piezoelectric transducer-generated ultrasonic pulses in the presence of low frequency dynamic strains that are intentionally induced to cause sensor drift. The actively stabilized embedded fiber optic Fabry-Perot sensor is also shown to have sufficient sensitivity to detect ultrasound that is generated in the interior of a structure by means of a high-power optical fiber that pipes energy from a pulsed laser to an embedded generator of ultrasound.

Research on dual-parameter optical fiber sensor based on few-mode fiber with two down-tapers

NASA Astrophysics Data System (ADS)

Wang, Xue; Tong, Zhengrong; Zhang, Weihua; Xue, Lifang

2017-10-01

A dual-parameter optical fiber sensor, which is fabricated by sandwiching a segment of few-mode fiber (FMF) with two down-tapers between two segments of standard single-mode fibers (SMFs), is investigated theoretically and experimentally. The two down-tapers on the FMF can enhance the evanescent field, making the sensor more sensitive to changes in the external environment. The refractive index (RI) and temperature are measured simultaneously using the different sensitivities of the two dips in this experimental interference spectrum. The measured temperature sensitivities are 0.097 and 0.114 nm/°C, and the RI sensitivities are -97.43 and -108.07 nm/RIU, respectively. Meanwhile, the simple SMF-FMF-SMF structure is also measured. By comparing the experimental results of the two structures, the sensitivities of the proposed structure based on the dual-taper FMF are significantly improved. In addition, the sensor is easy to fabricate and cost effective.

Mechanical and optical characteristics of a new fiber optical system used for cardiac contraction measurement.

PubMed

Kloppe, A; Hoeland, K; Müller, S; Hexamer, M; Nowack, G; Mügge, A; Werner, J

2004-10-01

In order to obtain a better physiological performance and a closer restoration of the regular rhythm of failing hearts, a new fiber optical sensor system for the measurement of cardiac contraction has been developed. It consists of an opto-electrical unit and a sensing fiber which has to be positioned in the heart. The objective of this new fiber optic sensor system is to use the inotropic information to adjust a stimulation algorithm in single or multichamber pacing or to detect arrhythmia in insufficient heart function. In this study, the mechanical and optical characteristics of different fibers are investigated. The relationship between the attenuation (with an achieved numerical maximum of 0.3 dB), the bending diameter and the angle of bending is determined in a range of 20-160 mm. The most suitable fiber for the application in cardiological problems is determined (WT8 fiber), for which the sensitivity is analyzed. Additionally, power spectra are calculated from WT8 fiber signals obtained from pig hearts, working under physiological conditions. The maximal frequency response was 23 Hz. It is concluded that the fiber optical measurement of cardiac contraction is not only feasible and reproducible, but the WT8 fiber also shows optimal behavior in the range of parameters occurring in the heart chambers. Nevertheless, in order to restrict the measured signal reliably to bending processes within the chambers only, it is concluded that a special combined fiber has to be constructed with a high sensitivity only at its terminal section within the heart.

Optical Fiber Grating Hydrogen Sensors: A Review

PubMed Central

Dai, Jixiang; Zhu, Li; Wang, Gaopeng; Xiang, Feng; Qin, Yuhuan; Wang, Min; Yang, Minghong

2017-01-01

In terms of hydrogen sensing and detection, optical fiber hydrogen sensors have been a research issue due to their intrinsic safety and good anti-electromagnetic interference. Among these sensors, hydrogen sensors consisting of fiber grating coated with sensitive materials have attracted intensive research interests due to their good reliability and distributed measurements. This review paper mainly focuses on optical fiber hydrogen sensors associated with fiber gratings and various materials. Their configurations and sensing performances proposed by different groups worldwide are reviewed, compared and discussed in this paper. Meanwhile, the challenges for fiber grating hydrogen sensors are also addressed. PMID:28287499

Optical Fiber Grating Hydrogen Sensors: A Review.

PubMed

Dai, Jixiang; Zhu, Li; Wang, Gaopeng; Xiang, Feng; Qin, Yuhuan; Wang, Min; Yang, Minghong

2017-03-12

In terms of hydrogen sensing and detection, optical fiber hydrogen sensors have been a research issue due to their intrinsic safety and good anti-electromagnetic interference. Among these sensors, hydrogen sensors consisting of fiber grating coated with sensitive materials have attracted intensive research interests due to their good reliability and distributed measurements. This review paper mainly focuses on optical fiber hydrogen sensors associated with fiber gratings and various materials. Their configurations and sensing performances proposed by different groups worldwide are reviewed, compared and discussed in this paper. Meanwhile, the challenges for fiber grating hydrogen sensors are also addressed.

Fiber Optic Microphone

NASA Technical Reports Server (NTRS)

Cho, Y. C.; George, Thomas; Norvig, Peter (Technical Monitor)

1999-01-01

Research into advanced pressure sensors using fiber-optic technology is aimed at developing compact size microphones. Fiber optic sensors are inherently immune to electromagnetic noise, and are very sensitive, light weight, and highly flexible. In FY 98, NASA researchers successfully designed and assembled a prototype fiber-optic microphone. The sensing technique employed was fiber optic Fabry-Perot interferometry. The sensing head is composed of an optical fiber terminated in a miniature ferrule with a thin, silicon-microfabricated diaphragm mounted on it. The optical fiber is a single mode fiber with a core diameter of 8 micron, with the cleaved end positioned 50 micron from the diaphragm surface. The diaphragm is made up of a 0.2 micron thick silicon nitride membrane whose inner surface is metallized with layers of 30 nm titanium, 30 nm platinum, and 0.2 micron gold for efficient reflection. The active sensing area is approximately 1.5 mm in diameter. The measured differential pressure tolerance of this diaphragm is more than 1 bar, yielding a dynamic range of more than 100 dB.

Passive-quadrature demodulated localized-Michelson fiber-optic strain sensor embedded in composite materials

NASA Astrophysics Data System (ADS)

Valis, Tomas; Tapanes, Edward; Liu, Kexing; Measures, Raymond M.

1991-04-01

A strain sensor embedded in composite materials that is intrinsic, all fiber, local, and phase demodulated is described. It is the combination of these necessary elements that represents an advance in the state of the art. Sensor localization is achieved by using a pair of mirror-ended optical fibers of different lengths that are mechanically coupled up until the desired gauge length for common-mode suppression has been reached. This fiber-optic sensor has been embedded in both thermoset (Kevlar/epoxy and graphite/epoxy) and thermoplastic (graphite/PEEK) composite materials in order to make local strain measurements at the lamina level. The all-fiber system uses a 3 x 3 coupler for phase demodulation. Parameters such as strain sensitivity, transverse strain sensitivity, failure strain, and frequency response are discussed, along with applications.

Fiber-Optic Thermal Sensor for TiN Film Crack Monitoring

PubMed Central

Hsu, Hsiang-Chang; Hsieh, Tso-Sheng; Chen, Yi-Chian; Chen, Hung-En; Tsai, Liren

2017-01-01

The study focuses on the thermal and temperature sensitivity behavior of an optical fiber sensor device. In this article, a titanium nitride (TiN)-coated fiber Bragg grating (FBG) sensor fabricated using an ion beam sputtering system was investigated. The reflection spectra of the FBG sensor were tested using R-soft optical software to simulate the refractive index sensitivity. In these experiments, the temperature sensitivity of the TiN FBG was measured at temperatures ranging from 100 to 500 °C using an optical spectrum analyzer (OSA). The results showed that the temperature sensitivity of the proposed TiN FBG sensor reached 12.8 pm/°C for the temperature range of 100 to 300 °C and 20.8 pm/°C for the temperature range of 300 to 500 °C. Additionally, we found that the produced oxidation at temperatures of 400–500 °C caused a crack, with the crack becoming more and more obvious at higher and higher temperatures. PMID:29137131

Investigating the Strain, Temperature and Humidity Sensitivity of a Multimode Graded-Index Perfluorinated Polymer Optical Fiber with Bragg Grating

PubMed Central

Zheng, Yulong; Bremer, Kort

2018-01-01

In this work we investigate the strain, temperature and humidity sensitivity of a Fiber Bragg Grating (FBG) inscribed in a near infrared low-loss multimode perfluorinated polymer optical fiber based on cyclic transparent optical polymer (CYTOP). For this purpose, FBGs were inscribed into the multimode CYTOP fiber with a core diameter of 50 µm by using a krypton fluoride (KrF) excimer laser and the phase mask method. The evolution of the reflection spectrum of the FBG detected with a multimode interrogation technique revealed a single reflection peak with a full width at half maximum (FHWM) bandwidth of about 9 nm. Furthermore, the spectral envelope of the single FBG reflection peak can be optimized depending on the KrF excimer laser irradiation time. A linear shift of the Bragg wavelength due to applied strain, temperature and humidity was measured. Furthermore, depending on irradiation time of the KrF excimer laser, both the failure strain and strain sensitivity of the multimode fiber with FBG can be controlled. The inherent low light attenuation in the near infrared wavelength range (telecommunication window) of the multimode CYTOP fiber and the single FBG reflection peak when applying the multimode interrogation set-up will allow for new applications in the area of telecommunication and optical sensing. PMID:29734734

Investigating the Strain, Temperature and Humidity Sensitivity of a Multimode Graded-Index Perfluorinated Polymer Optical Fiber with Bragg Grating.

PubMed

Zheng, Yulong; Bremer, Kort; Roth, Bernhard

2018-05-05

In this work we investigate the strain, temperature and humidity sensitivity of a Fiber Bragg Grating (FBG) inscribed in a near infrared low-loss multimode perfluorinated polymer optical fiber based on cyclic transparent optical polymer (CYTOP). For this purpose, FBGs were inscribed into the multimode CYTOP fiber with a core diameter of 50 µm by using a krypton fluoride (KrF) excimer laser and the phase mask method. The evolution of the reflection spectrum of the FBG detected with a multimode interrogation technique revealed a single reflection peak with a full width at half maximum (FHWM) bandwidth of about 9 nm. Furthermore, the spectral envelope of the single FBG reflection peak can be optimized depending on the KrF excimer laser irradiation time. A linear shift of the Bragg wavelength due to applied strain, temperature and humidity was measured. Furthermore, depending on irradiation time of the KrF excimer laser, both the failure strain and strain sensitivity of the multimode fiber with FBG can be controlled. The inherent low light attenuation in the near infrared wavelength range (telecommunication window) of the multimode CYTOP fiber and the single FBG reflection peak when applying the multimode interrogation set-up will allow for new applications in the area of telecommunication and optical sensing.

Real-time dosimetry in radiotherapy using tailored optical fibers

NASA Astrophysics Data System (ADS)

Rahman, A. K. M. Mizanur; Zubair, H. T.; Begum, Mahfuza; Abdul-Rashid, H. A.; Yusoff, Z.; Omar, Nasr Y. M.; Ung, N. M.; Mat-Sharif, K. A.; Bradley, D. A.

2016-05-01

Real-time dosimetry plays an important role for accurate patient-dose measurement during radiotherapy. A tiny piece of laboratory fabricated Ge-doped optical fiber has been investigated as a radioluminescence (RL) sensor for real-time dosimetry over the dose range from 1 Gy to 8 Gy under 6 MV photon beam by LINAC. Fiber-coupled software-based RL prototype system was used to assess essential dosimetric characteristics including dose response linearity, dose rate dependency, sensitivity, repeatability and output dependence on field sizes. The consistency level of RL photon counts versus dose rate was also compared with that of standard Al2O3:C chips. Sensitivity of Ge-doped fiber were found to be sufficiently sensitive for practical use and also provided linear dose responses for various dose rates from 100 cGy/min to 600 cGy/min using both 6 MV photon and 6 MeV electron beams. SEM-EDX analysis was performed to identify Ge-dopant concentration level within the optical fiber RL material. Accumulated doses were also estimated using simple integral technique and the error was found to be around less than 1% under dissimilar dose rates or repeat measurements. The evaluation of the Ge-doped optical fiber based RL dosimeter system indicates its potential in medical dosimetry.

Retinal nerve fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes.

PubMed

El Beltagi, Tarek A; Bowd, Christopher; Boden, Catherine; Amini, Payam; Sample, Pamela A; Zangwill, Linda M; Weinreb, Robert N

2003-11-01

To determine the relationship between areas of glaucomatous retinal nerve fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. Retrospective observational case series. Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >-8 dB were included. Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. The location and number of optical coherence tomography clock hour retinal nerve fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography-measured retinal nerve fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression (R(2)). The retinal nerve fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results (R(2)) showed that deviation from the normal retinal nerve fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions (R(2) range, 0.34-0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region (R(2) = 0.01). Localized retinal nerve fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.

Hybrid Raman/Brillouin-optical-time-domain-analysis-distributed optical fiber sensors based on cyclic pulse coding.

PubMed

Taki, M; Signorini, A; Oton, C J; Nannipieri, T; Di Pasquale, F

2013-10-15

We experimentally demonstrate the use of cyclic pulse coding for distributed strain and temperature measurements in hybrid Raman/Brillouin optical time-domain analysis (BOTDA) optical fiber sensors. The highly integrated proposed solution effectively addresses the strain/temperature cross-sensitivity issue affecting standard BOTDA sensors, allowing for simultaneous meter-scale strain and temperature measurements over 10 km of standard single mode fiber using a single narrowband laser source only.

Tolerancing the alignment of large-core optical fibers, fiber bundles and light guides using a Fourier approach.

PubMed

Sawyer, Travis W; Petersburg, Ryan; Bohndiek, Sarah E

2017-04-20

Optical fiber technology is found in a wide variety of applications to flexibly relay light between two points, enabling information transfer across long distances and allowing access to hard-to-reach areas. Large-core optical fibers and light guides find frequent use in illumination and spectroscopic applications, for example, endoscopy and high-resolution astronomical spectroscopy. Proper alignment is critical for maximizing throughput in optical fiber coupling systems; however, there currently are no formal approaches to tolerancing the alignment of a light-guide coupling system. Here, we propose a Fourier alignment sensitivity (FAS) algorithm to determine the optimal tolerances on the alignment of a light guide by computing the alignment sensitivity. The algorithm shows excellent agreement with both simulated and experimentally measured values and improves on the computation time of equivalent ray-tracing simulations by two orders of magnitude. We then apply FAS to tolerance and fabricate a coupling system, which is shown to meet specifications, thus validating FAS as a tolerancing technique. These results indicate that FAS is a flexible and rapid means to quantify the alignment sensitivity of a light guide, widely informing the design and tolerancing of coupling systems.

Tolerancing the alignment of large-core optical fibers, fiber bundles and light guides using a Fourier approach

PubMed Central

Sawyer, Travis W.; Petersburg, Ryan; Bohndiek, Sarah E.

2017-01-01

Optical fiber technology is found in a wide variety of applications to flexibly relay light between two points, enabling information transfer across long distances and allowing access to hard-to-reach areas. Large-core optical fibers and light guides find frequent use in illumination and spectroscopic applications; for example, endoscopy and high-resolution astronomical spectroscopy. Proper alignment is critical for maximizing throughput in optical fiber coupling systems, however, there currently are no formal approaches to tolerancing the alignment of a light guide coupling system. Here, we propose a Fourier Alignment Sensitivity (FAS) algorithm to determine the optimal tolerances on the alignment of a light guide by computing the alignment sensitivity. The algorithm shows excellent agreement with both simulated and experimentally measured values and improves on the computation time of equivalent ray tracing simulations by two orders of magnitude. We then apply FAS to tolerance and fabricate a coupling system, which is shown to meet specifications, thus validating FAS as a tolerancing technique. These results indicate that FAS is a flexible and rapid means to quantify the alignment sensitivity of a light guide, widely informing the design and tolerancing of coupling systems. PMID:28430250

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.

Highly sensitive evanescent wave combination tapered fiber optic fluorosensor for protein detection

NASA Astrophysics Data System (ADS)

Nardone, Vincent; Kapoor, Rakesh

2008-02-01

In this paper we are reporting the development of a highly sensitive evanescent wave combination tapered fiber optic fluorosensor. We have demonstrated detection of 5 pM Bovine Serum Albumin (BSA) protein using these fiber optic sensors. The sensor can be easily adopted for detection of other proteins. Six identical probes were prepared and affinity pure Goat anti-BSA antibodies were immobilized on the probe surface. We could detect signal from all the probes kept in 5 pM to 1 nM BSA solution while no signal was detected from the probes kept in 20 nM labeled ESA solution.

Active polymer materials for optical fiber CO2 sensors

NASA Astrophysics Data System (ADS)

Wysokiński, Karol; Filipowicz, Marta; Stańczyk, Tomasz; Lipiński, Stanisław; Napierała, Marek; Murawski, Michał; Nasiłowski, Tomasz

2017-04-01

CO2 optical fiber sensors based on polymer active materials are presented in this paper. Ethyl cellulose was proven to be a good candidate for a matrix material of the sensor, since it gives porous, thick and very sensitive layers. Low-cost sensors based on polymer optical fibers have been elaborated. Sensors have been examined for their sensitivity to CO2, temperature and humidity. Response time during cyclic exposures to CO2 have been also determined. Special layers exhibiting irreversible change of color during exposure to carbon dioxide have been developed. They have been verified for a possible use in smart food packaging.

Ultra-sensitive near-infrared fiber-optic gas sensors enhanced by metal-organic frameworks

NASA Astrophysics Data System (ADS)

Chong, Xinyuan; Kim, Ki-Joong; Li, Erwen; Zhang, Yujing; Ohodnicki, Paul R.; Chang, Chih-Hung; Wang, Alan X.

2016-03-01

We demonstrate ultra-sensitive near-infrared (NIR) fiber-optic gas sensors enhanced by metalorganic framework (MOF) Cu-BTC (BTC=benzene-1,3,5- tricarboxylate), which is coated on a single-mode optical fiber. For the first time, we obtained high-resolution NIR spectroscopy of CO2 adsorbed in MOF without seeing any rotational side band. Real-time measurement showed different response time depending on the concentration of CO2, which is attributed to the complex adsorption and desorption mechanism of CO2 in Cu-BTC. The lowest detection limit of CO2 we achieved is 20 ppm with only 5-cm long Cu-BTC film.

Experimental study of optical fibers influence on composite

NASA Astrophysics Data System (ADS)

Liu, Rong-Mei; Liang, Da-Kai

2010-03-01

Bending strength and elasticity modulus of composite, with and without embedded optical fibers, were experimentally studied. Two kinds of laminates, which were denoted as group 1 and group 2, were fabricated from an orthogonal woven glass/epoxy prepreg. Since the normal stress value becomes the biggest at the surface of a beam, the optical fibers were embedded at the outmost layer and were all along the loading direction. Four types of materials, using each kind of laminated prepreg respectively, were manufactured. The embedded optical fibers for the 4 material types were 0, 10, 30 and 50 respectively. Three-point bending tests were carried out on the produced specimens to study the influence of embedded optical fiber on host composite. The experimental results indicated that the materials in group 2 were more sensitive to the embedded optical fibers.

Thermo-optic characteristic of DNA thin solid film and its application as a biocompatible optical fiber temperature sensor.

PubMed

Hong, Seongjin; Jung, Woohyun; Nazari, Tavakol; Song, Sanggwon; Kim, Taeoh; Quan, Chai; Oh, Kyunghwan

2017-05-15

We report unique thermo-optical characteristics of DNA-Cetyl tri-methyl ammonium (DNA-CTMA) thin solid film with a large negative thermo-optical coefficient of -3.4×10^-4/°C in the temperature range from 20°C to 70°C without any observable thermal hysteresis. By combining this thermo-optic DNA film and fiber optic multimode interference (MMI) device, we experimentally demonstrated a highly sensitive compact temperature sensor with a large spectral shift of 0.15 nm/°C. The fiber optic MMI device was a concatenated structure with single-mode fiber (SMF)-coreless silica fiber (CSF)-single mode fiber (SMF) and the DNA-CTMA film was deposited on the CSF. The spectral shifts of the device in experiments were compared with the beam propagation method, which showed a good agreement.

High-temperature fiber-optic lever microphone

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J.; Cuomo, Frank W.; Nguyen, Trung D.; Rizzi, Stephen A.; Clevenson, Sherman A.

1995-01-01

The design and construction of a fiber-optic lever microphone, capable of operating continuously at temperatures up to 538 C (1000 F) are described. The design is based on the theoretical sensitivities of each of the microphone system components, namely, a cartridge containing a stretched membrane, an optical fiber probe, and an optoelectronic amplifier. Laboratory calibrations include the pistonphone sensitivity and harmonic distortion at ambient temperature, and frequency response, background noise, and optical power transmission at both ambient and elevated temperatures. A field test in the Thermal Acoustic Fatigue Apparatus at Langley Research Center, in which the microphone was subjected to overall sound-pressure levels in the range of 130-160 dB and at temperatures from ambient to 538 C, revealed good agreement with a standard probe microphone.

Enhancing the performance of coherent OTDR systems with polarization diversity complementary codes.

PubMed

Dorize, Christian; Awwad, Elie

2018-05-14

Monitoring the optical phase change in a fiber enables a wide range of applications where fast phase variations are induced by acoustic signals or by vibrations in general. However, the quality of the estimated fiber response strongly depends on the method used to modulate the light sent to the fiber and capture the variations of the optical field. In this paper, we show that distributed optical fiber sensing systems can advantageously exploit techniques from the telecommunication domain, as those used in coherent optical transmission, to enhance their performance in detecting mechanical events, while jointly offering a simpler setup than widespread pulse-cloning or spectral-sweep based schemes with acousto-optic modulators. We periodically capture an overall fiber Jones matrix estimate thanks to a novel probing technique using two mutually orthogonal complementary (Golay) pairs of binary sequences applied simultaneously in phase and quadrature on two orthogonal polarization states. A perfect channel response estimation of the sensor array is achieved, subject to conditions detailed in the paper, thus enhancing the sensitivity and bandwidth of coherent ϕ-OTDR systems. High sensitivity, linear response, and bandwidth coverage up to 18 kHz are demonstrated with a sensor array composed of 10 fiber Bragg gratings (FBGs).

Enhancing the performance of coherent OTDR systems with polarization diversity complementary codes

NASA Astrophysics Data System (ADS)

Dorize, Christian; Awwad, Elie

2018-05-01

Monitoring the optical phase change in a fiber enables a wide range of applications where fast phase variations are induced by acoustic signals or vibrations in general. However, the quality of the estimated fiber response strongly depends on the method used to modulate the light sent to the fiber and capture the variations of the optical field. In this paper, we show that distributed optical fiber sensing systems can advantageously exploit techniques from the telecommunication domain, as those used in coherent optical transmission, to enhance their performance in detecting mechanical events, while jointly offering a simpler setup than widespread pulse-cloning or spectral-sweep based schemes with acousto-optic modulators. We periodically capture an overall fiber Jones matrix estimate thanks to a novel probing technique using two mutually orthogonal complementary (Golay) pairs of binary sequences applied simultaneously in phase and quadrature on two orthogonal polarization states. A perfect channel response estimation of the sensor array is achieved, subject to conditions detailed in the paper, thus enhancing the sensitivity and bandwidth of coherent phase-OTDR systems. High sensitivity, linear response, and bandwidth coverage up to 18 kHz are demonstrated with a sensor array composed of 10 fiber Bragg gratings (FBGs).

Respiration and body movement analysis during sleep in bed using hetero-core fiber optic pressure sensors without constraint to human activity.

PubMed

Nishyama, Michiko; Miyamoto, Mitsuo; Watanabe, Kazuhiro

2011-01-01

We describe respiration monitoring in sleep using hetero-core fiber optic pressure sensors. The proposed hetero-core fiber optic sensor is highly sensitive to macrobending as a result of the core diameter difference due to stable single-mode transmission. Pressure sensors based on hetero-core fiber optics were fabricated to have a high sensitivity to small pressure changes resulting from minute body motions, such as respiration, during sleep and large pressure changes, such as those caused by a rollover. The sensors are installed in a conventional bed. The pressure characteristic performance of all the fabricated hetero-core fiber optic pressure sensors is found to show a monotonic response with weight changes. A respiration monitoring test in seven subjects efficiently demonstrates the effective use of eight hetero-core pressure sensors installed in a bed. Additionally, even in the case of different body postures, such as lying on one's side, a slight body movement due to respiration is detected by the hetero-core pressure sensors.

Respiration and body movement analysis during sleep in bed using hetero-core fiber optic pressure sensors without constraint to human activity

NASA Astrophysics Data System (ADS)

Nishyama, Michiko; Miyamoto, Mitsuo; Watanabe, Kazuhiro

2011-01-01

We describe respiration monitoring in sleep using hetero-core fiber optic pressure sensors. The proposed hetero-core fiber optic sensor is highly sensitive to macrobending as a result of the core diameter difference due to stable single-mode transmission. Pressure sensors based on hetero-core fiber optics were fabricated to have a high sensitivity to small pressure changes resulting from minute body motions, such as respiration, during sleep and large pressure changes, such as those caused by a rollover. The sensors are installed in a conventional bed. The pressure characteristic performance of all the fabricated hetero-core fiber optic pressure sensors is found to show a monotonic response with weight changes. A respiration monitoring test in seven subjects efficiently demonstrates the effective use of eight hetero-core pressure sensors installed in a bed. Additionally, even in the case of different body postures, such as lying on one's side, a slight body movement due to respiration is detected by the hetero-core pressure sensors.

Evaluation of Aerogel Clad Optical Fibers Final Report CRADA No. TSB-1448-97

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

Maitland, Duncan; Droege, M. W.

Fiber-optic based sensors will be needed for in situ monitoring of degradation products in various components of nuclear weapons. These sensors typically consist of a transducer located at the measurement site whose optical properties are modulated by interaction with the targeted degradation product. The interrogating light source and the detector for determining sensor response are located remotely. These two subsystems are connected by fiber optic cables. LLNL has developed a new technology, aerogel clad optical fibers, that have the advantage of accepting incident rays over a much wider angular range than normal glass clad fibers. These fibers are also capablemore » of transmitting light more efficiently. These advantages can lead to a factor of 2-4 improvement in sensitivity and detection limit.« less

Temperature sensor based on an isopropanol-sealed photonic crystal fiber in-line interferometer with enhanced refractive index sensitivity.

PubMed

Qiu, Sun-jie; Chen, Ye; Xu, Fei; Lu, Yan-qing

2012-03-01

We fabricate a simple, compact, and stable temperature sensor based on a liquid-sealed photonic crystal fiber (PCF) in-line nonpolarimetric modal interferometer. Different from other reported PCF devices, it does not need expensive polarimetric devices, and the liquid is sealed in one fiber. The device consists of a stub of isopropanol-filled PCF spliced between standard single-mode fibers. The temperature sensitivity (-166 pm/°C) increases over an order of magnitude compared with those of the previous sensors based on air-sealed PCF interferometers built via fusion splicing with the same mechanism. In addition, the refractive index sensitivity also increases. Higher temperature sensitivity can be realized by infiltrating some liquid having a higher thermo-optic coefficient into the microholes of the PCF. © 2012 Optical Society of America

A Highly Sensitive Fiber Optic Sensor Based on Two-Core Fiber for Refractive Index Measurement

PubMed Central

Guzmán-Sepúlveda, José Rafael; Guzmán-Cabrera, Rafael; Torres-Cisneros, Miguel; Sánchez-Mondragón, José Javier; May-Arrioja, Daniel Alberto

2013-01-01

A simple and compact fiber optic sensor based on a two-core fiber is demonstrated for high-performance measurements of refractive indices (RI) of liquids. In order to demonstrate the suitability of the proposed sensor to perform high-sensitivity sensing in a variety of applications, the sensor has been used to measure the RI of binary liquid mixtures. Such measurements can accurately determine the salinity of salt water solutions, and detect the water content of adulterated alcoholic beverages. The largest sensitivity of the RI sensor that has been experimentally demonstrated is 3,119 nm per Refractive Index Units (RIU) for the RI range from 1.3160 to 1.3943. On the other hand, our results suggest that the sensitivity can be enhanced up to 3485.67 nm/RIU approximately for the same RI range. PMID:24152878

Sensitivity Enhancement in Low Cutoff Wavelength Long-Period Fiber Gratings by Cladding Diameter Reduction.

PubMed

Del Villar, Ignacio; Partridge, Matthew; Rodriguez, Wenceslao Eduardo; Fuentes, Omar; Socorro, Abian Bentor; Diaz, Silvia; Corres, Jesus Maria; James, Stephen Wayne; Tatam, Ralph Peter

2017-09-13

The diameter of long-period fiber gratings (LPFGs) fabricated in optical fibers with a low cutoff wavelength was be reduced by hydrofluoric acid etching, enhancing the sensitivity to refractive index by more than a factor of 3, to 2611 nm/refractive index unit in the range from 1.333 to 1.4278. The grating period selected for the LPFGs allowed access to the dispersion turning point at wavelengths close to the visible range of the optical spectrum, where optical equipment is less expensive. As an example of an application, a pH sensor based on the deposition of a polymeric coating was analyzed in two situations: with an LPFG without diameter reduction and with an LPFG with diameter reduction. Again, a sensitivity increase of a factor of near 3 was obtained, demonstrating the ability of this method to enhance the sensitivity of thin-film-coated LPFG chemical sensors.

FIBER OPTIC BIOSENSOR FOR DNA DAMAGE

EPA Science Inventory

This paper describes a fiber optic biosensor for the rapid and sensitive detection of radiation-induced or chemically-induced oxidative DNA damage. The assay is based on the hybridization and temperature-induced dissociation (melting curves) of synthetic oligonucleotides. The...

Scintillator fiber optic long counter

DOEpatents

McCollum, T.; Spector, G.B.

1994-03-29

A flat response position sensitive neutron detector capable of providing neutron spectroscopic data utilizing scintillator fiber optic filaments embedded in a neutron moderating housing having an open end through which neutrons enter to be detected is described. 11 figures.

A fiber-optic sensor based on no-core fiber and Faraday rotator mirror structure

NASA Astrophysics Data System (ADS)

Lu, Heng; Wang, Xu; Zhang, Songling; Wang, Fang; Liu, Yufang

2018-05-01

An optical fiber sensor based on the single-mode/no-core/single-mode (SNS) core-offset technology along with a Faraday rotator mirror structure has been proposed and experimentally demonstrated. A transverse optical field distribution of self-imaging has been simulated and experimental parameters have been selected under theoretical guidance. Results of the experiments demonstrate that the temperature sensitivity of the sensor is 0.0551 nm/°C for temperatures between 25 and 80 °C, and the correlation coefficient is 0.99582. The concentration sensitivity of the device for sucrose and glucose solutions was found to be as high as 12.5416 and 6.02248 nm/(g/ml), respectively. Curves demonstrating a linear fit between wavelength shift and solution concentration for three different heavy metal solutions have also been derived on the basis of experimental results. The proposed fiber-optic sensor design provides valuable guidance for the measurement of concentration and temperature.

Demodulation of an optical fiber MEMS pressure sensor based on single bandpass microwave photonic filter.

PubMed

Wang, Yiping; Ni, Xiaoqi; Wang, Ming; Cui, Yifeng; Shi, Qingyun

2017-01-23

In this paper, a demodulation method for optic fiber micro-electromechanical systems (MEMS) extrinsic Fabry-Perot interferometer (EFPI) pressure sensor exploiting microwave photonics filter technique is firstly proposed and experimentally demonstrated. A single bandpass microwave photonic filter (MPF) which mainly consists of a spectrum-sliced light source, a pressurized optical fiber MEMS EFPI, a phase modulator (PM) and a length of dispersion compensating fiber (DCF) is demonstrated. The frequency response of the filter with respect to the pressure is studied. By detecting the resonance frequency shifts of the MPF, the pressure can be determined. The theoretical and experimental results show that the proposed EFPI pressure demodulation method has a higher resolution and higher speed than traditional methods based on optical spectrum analysis. The sensitivity of the sensor is measured to be as high as 86 MHz/MPa in the range of 0-4Mpa. Moreover, the sensitivity can be easily adjusted.

A Novel Mach-Zehnder Interferometer Using Eccentric-Core Fiber Design for Optical Coherence Tomography.

PubMed

Xiong, Qiao; Tong, Xinglin; Deng, Chengwei; Zhang, Cui; Wang, Pengfei; Zheng, Zhiyuan; Liu, Fang

2018-05-13

A novel Mach-Zehnder interferometer using eccentric-core fiber (ECF) design for optical coherence tomography (OCT) is proposed and demonstrated. Instead of the commercial single-mode fiber (SMF), the ECF is used as one interference arm of the implementation. Because of the offset location of the eccentric core, it is sensitive to directional bending and the optical path difference (OPD) of two interference arms can be adjusted with high precision. The birefringence of ECF is calculated and experimentally measured, which demonstrates the polarization sensitivity of the ECF proposed in the paper is similar to that of SMF. Such a structure can replace the reference optical delay line to form an all-fiber passive device. A mirror is used as a sample for analyzing the ECF bending responses of the system. Besides, four pieces of overlapping glass slides as sample are experimentally measured as well.

[The Research on Optic Fiber FBG Corrosion Sensor Based on the Analysis of the Spectral Characteristics].

PubMed

Zhang, Jun; Zeng, Jie; Wang, Bo; Wang, Wen-juan; Liang, Da-kai; Liu, Xiao-ying

2016-03-01

Aiming at meeting the need of aluminum corrosion monitoring in aerospace field, a pre-load type fiber grating corrosion sensor based on an aluminum thin tube structure is proposed. The corrosion sensor of aluminum alloy structure in-service monitoring mechanism is studied, a theoretical model about the relation of FBG reflection spectral characteristics and aluminum thickness variation is also obtained. Optical fiber grating corrosion monitoring test system based on the capillary structure of aluminum alloy is constructed by acid-base environment. The problem of cross sensitivity of temperature and strain is solved by configuring an optical fiber grating which is not affected by strain and only sensitive to temperature inside the aluminum alloy tube. The results shows that he aluminum tube packaging design not only can sense the effects of corrosion on the mechanical properties, but also can interference shielding effect of corrosion on the tube optical fiber sensing device. With the deepening of the metal tube corrosion and aluminum alloy tube thickness gradually thinning, fiber grating reflective spectrum gradually shift to the short wavelength and the wall thickness and the grating center wavelength offset has a good monotonic relation. These characteristics can provide useful help to further research corrosion online monitoring based on optic fiber sensor.

Fiber optic-based biosensor

NASA Technical Reports Server (NTRS)

Ligler, Frances S.

1991-01-01

The NRL fiber optic biosensor is a device which measures the formation of a fluorescent complex at the surface of an optical fiber. Antibodies and DNA binding proteins provide the mechanism for recognizing an analyze and immobilizing a fluorescent complex on the fiber surface. The fiber optic biosensor is fast, sensitive, and permits analysis of hazardous materials remote from the instrumentation. The fiber optic biosensor is described in terms of the device configuration, chemistry for protein immobilization, and assay development. A lab version is being used for assay development and performance characterization while a portable device is under development. Antibodies coated on the fiber are stable for up to two years of storage prior to use. The fiber optic biosensor was used to measure concentration of toxins in the parts per billion (ng/ml) range in under a minute. Immunoassays for small molecules and whole bacteria are under development. Assays using DNA probes as the detection element can also be used with the fiber optic sensor, which is currently being developed to detect biological warfare agents, explosives, pathogens, and toxic materials which pollute the environment.

Thermal Strain Analysis of Optic Fiber Sensors

PubMed Central

Her, Shiuh-Chuan; Huang, Chih-Ying

2013-01-01

An optical fiber sensor surface bonded onto a host structure and subjected to a temperature change is analytically studied in this work. The analysis is developed in order to assess the thermal behavior of an optical fiber sensor designed for measuring the strain in the host structure. For a surface bonded optical fiber sensor, the measuring sensitivity is strongly dependent on the bonding characteristics which include the protective coating, adhesive layer and the bonding length. Thermal stresses can be generated due to a mismatch of thermal expansion coefficients between the optical fiber and host structure. The optical fiber thermal strain induced by the host structure is transferred via the adhesive layer and protective coating. In this investigation, an analytical expression of the thermal strain and stress in the optical fiber is presented. The theoretical predictions are validated using the finite element method. Numerical results show that the thermal strain and stress are linearly dependent on the difference in thermal expansion coefficients between the optical fiber and host structure and independent of the thermal expansion coefficients of the adhesive and coating. PMID:23385407

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.

Distributed Fiber-Optic Sensors for Vibration Detection

PubMed Central

Liu, Xin; Jin, Baoquan; Bai, Qing; Wang, Yu; Wang, Dong; Wang, Yuncai

2016-01-01

Distributed fiber-optic vibration sensors receive extensive investigation and play a significant role in the sensor panorama. Optical parameters such as light intensity, phase, polarization state, or light frequency will change when external vibration is applied on the sensing fiber. In this paper, various technologies of distributed fiber-optic vibration sensing are reviewed, from interferometric sensing technology, such as Sagnac, Mach–Zehnder, and Michelson, to backscattering-based sensing technology, such as phase-sensitive optical time domain reflectometer, polarization-optical time domain reflectometer, optical frequency domain reflectometer, as well as some combinations of interferometric and backscattering-based techniques. Their operation principles are presented and recent research efforts are also included. Finally, the applications of distributed fiber-optic vibration sensors are summarized, which mainly include structural health monitoring and perimeter security, etc. Overall, distributed fiber-optic vibration sensors possess the advantages of large-scale monitoring, good concealment, excellent flexibility, and immunity to electromagnetic interference, and thus show considerable potential for a variety of practical applications. PMID:27472334

Distributed Fiber-Optic Sensors for Vibration Detection.

PubMed

Liu, Xin; Jin, Baoquan; Bai, Qing; Wang, Yu; Wang, Dong; Wang, Yuncai

2016-07-26

Distributed fiber-optic vibration sensors receive extensive investigation and play a significant role in the sensor panorama. Optical parameters such as light intensity, phase, polarization state, or light frequency will change when external vibration is applied on the sensing fiber. In this paper, various technologies of distributed fiber-optic vibration sensing are reviewed, from interferometric sensing technology, such as Sagnac, Mach-Zehnder, and Michelson, to backscattering-based sensing technology, such as phase-sensitive optical time domain reflectometer, polarization-optical time domain reflectometer, optical frequency domain reflectometer, as well as some combinations of interferometric and backscattering-based techniques. Their operation principles are presented and recent research efforts are also included. Finally, the applications of distributed fiber-optic vibration sensors are summarized, which mainly include structural health monitoring and perimeter security, etc. Overall, distributed fiber-optic vibration sensors possess the advantages of large-scale monitoring, good concealment, excellent flexibility, and immunity to electromagnetic interference, and thus show considerable potential for a variety of practical applications.

Neurotransmitter measurement with a fiber optic probe using pulsed ultraviolet resonance Raman spectroscopy

NASA Astrophysics Data System (ADS)

Schulze, H. Georg; Greek, L. Shane; Blades, Michael W.; Bree, Alan V.; Gorzalka, Boris B.; Turner, Robin F. B.

1997-05-01

Many techniques have been developed to investigate the chemistry associated with brain activity. These techniques generally fall into two categories: fast techniques with species restricted sensitivity and slow techniques with generally unrestricted species sensitivity. Therefore, a need exists for a fast non-invasive technique sensitive to a wide array of biologically relevant compounds in order to measure chemical brain events in real time. The work presented here describes the progress made toward the development of a novel neurotransmitter probe. A fiber-optic linked Raman and tunable ultraviolet resonance Raman system was assembled with custom designed optical fiber probes. Probes of several different geometries were constructed and their working curves obtained in aqueous mixtures of methyl orange and potassium nitrate to determine the best probe configuration given particular sample characteristics. Using this system, the ultraviolet resonance Raman spectra of some neurotransmitters were measured with a fiber-optic probe and are reported here for the first time. The probe has also been used to measure neurotransmitter secretions obtained from depolarized rat pheochromocytoma cells.

Highly sensitive lidar with a thumb-sized sensor-head built using an optical fiber preamplifier

NASA Astrophysics Data System (ADS)

Inoue, Daisuke; Ichikawa, Tadashi; Matsubara, Hiroyuki; Mao, Xueon; Maeda, Mitsutoshi; Nagashima, Chie; Kagami, Manabu

2011-06-01

We developed a LIDAR system with a sensor head as small as 22 cc, in spite of the inclusion of a scanning mechanism. This LIDAR system not only has a small body, but is also highly sensitive. Our LIDAR system is based on time-of-flight measurements, and it incorporates an optical fiber. The main feature of our system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enabled us to exceed the detection limit of thermal noise. In conventional LIDAR systems the detection limit is determined by thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use detect the received signals directly. In the case of our LIDAR system, received signal is amplified by an optical fiber amplifier in front of the photo diode and the TIA. Therefore, our LIDAR system can boost the signal level before the weak incoming signal is depleted by thermal noise. There are conditions under which the noise figure for the combination of an optical fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode. We optimized the gain of the optical fiber amplifier and TIA in our LIDAR system such that it is capable of detecting a single photon. As a result, the detection limit of our LIDAR system is determined by shot noise. This small and highly sensitive measurement technology shows great potential for use in LIDAR with an optical preamplifier.

Phase-sensitive fiber-based parametric all-optical switch.

PubMed

Parra-Cetina, Josué; Kumpera, Aleš; Karlsson, Magnus; Andrekson, Peter A

2015-12-28

We experimentally demonstrate, for the first time, an all-optical switch in a phase-sensitive fiber optic parametric amplifier operated in saturation. We study the effect of phase variation of the signal and idler waves on the pump power depletion. By changing the phase of a 0.9 mW signal/idler pair wave by π/2 rad, a pump power extinction ratio of 30.4 dB is achieved. Static and dynamic characterizations are also performed and time domain results presented.

Photoinduced Electron Transfer Based Ion Sensing within an Optical Fiber

PubMed Central

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

2011-01-01

We combine suspended-core microstructured optical fibers with the photoinduced electron transfer (PET) effect to demonstrate a new type of fluorescent optical fiber-dip sensing platform for small volume ion detection. A sensor design based on a simple model PET-fluoroionophore system and small core microstructured optical fiber capable of detecting sodium ions is demonstrated. The performance of the dip sensor operating in a high sodium concentration regime (925 ppm Na+) and for lower sodium concentration environments (18.4 ppm Na+) is explored and future approaches to improving the sensor’s signal stability, sensitivity and selectivity are discussed. PMID:22163712

The family of micro sensors for remote control the pollution in liquids and gases

NASA Astrophysics Data System (ADS)

Tulaikova, Tamara; Kocharyun, Gevorg; Rogerson, Graham; Burmistrova, Ludmyla; Sychugov, Vladimir; Dorojkin, Peter

2005-10-01

There are the results for the 3 groups of fiber-optical sensors. First is the fiber-optical sensor with changed sensitive heads on the base on porous polymer with clamped activated dye. Vibration method for fiber-optical sensors provides more convenient output measurements of resonant frequency changes, in comparison with the first device. The self-focusing of the living sells into optical wave-guides in laser road in water will be considered as a new touch method for environment remote sensing.

Pressure-sensitive optrode

DOEpatents

Hirschfeld, T.B.

1985-04-09

An apparatus and method are disclosed for sensing changes in pressure and for generating optical signals related to changes in pressure. Light from a fiber optic is directed to a movable surface which is coated with a light-responsive material, and which moves relative to the end of the fiber optic in response to changes in pressure. The same fiber optic collects a portion of the reflected or emitted light from the movable surface. Changes in pressure are determined by measuring changes in the amount of light collected. 5 figs.

A consideration of the use of optical fibers to remotely couple photometers to telescopes

NASA Technical Reports Server (NTRS)

Heacox, William D.

1988-01-01

The possible use of optical fibers to remotely couple photometers to telescopes is considered. Such an application offers the apparent prospect of enhancing photometric stability as a consequence of the benefits of remote operation and decreased sensitivity to image details. A properly designed fiber optic coupler will probably show no significant changes in optical transmisssion due to normal variations in the fiber configuration. It may be more difficult to eliminate configuration-dependent effects on the pupil of the transmitted beam, and thus achieve photometric stability to guiding and seeing errors. In addition, there is some evidence for significant changes in the optical throughputs of fibers over the temperature range normally encountered in astronomical observatories.

Optical fibre PH sensor based on immobilized indicator

NASA Astrophysics Data System (ADS)

Cai, Defu; Cao, Qiang; Han, JingHong; Cai, Jine; Li, YaTing; Zhu, ZeMin; Fan, Jie; Gao, Ning

1991-08-01

An optical fiber pH sensor which has the immobilized pH sensitive indicator dye reagents on the tip of the optical fiber has been studied. The probe is made by covalently immobilizing the phenol red, bromine phenol blue, or bromothymol blue on the polyacrylamide microsphere fixed by polyterafluoroethylene (PTFE) film. A gap between the dye and optical fiber was used to make the diffusion of the hydrogen ions easier. The parameters of the optical fiber pH sensor have been given completely. The ranges of measurement are 3.0 - 5.0 pH, 7.0 - 8.5 pH, and 8.0 - 10.0 pH for bromine phenol blue, phenol red, and bromothymol blue, respectively. The sensitivity is 66.6 mV/pH. The probe has a precision of better than 0.55 pH. The linear correlation coefficient is 0.999. The response time is 1 - 2 min. The hysteresis is 0.52%. The repeatability is 0.013 mV, while the stability is 0.015 pH/h.

Fabrication of fiber-optic localized surface plasmon resonance sensor and its application to detect antibody-antigen reaction of interferon-gamma

NASA Astrophysics Data System (ADS)

Jeong, Hyeon-Ho; Erdene, Norov; Lee, Seung-Ki; Jeong, Dae-Hong; Park, Jae-Hyoung

2011-12-01

A fiber-optic localized surface plasmon (FO LSPR) sensor was fabricated by gold nanoparticles (Au NPs) immobilized on the end-face of an optical fiber. When Au NPs were formed on the end-face of an optical fiber by chemical reaction, Au NPs aggregation occurred and the Au NPs were immobilized in various forms such as monomers, dimers, trimers, etc. The component ratio of the Au NPs on the end-face of the fabricated FO LSPR sensor was slightly changed whenever the sensors were fabricated in the same condition. Including this phenomenon, the FO LSPR sensor was fabricated with high sensitivity by controlling the density of Au NPs. Also, the fabricated sensors were measured for the resonance intensity for the different optical systems and analyzed for the effect on sensitivity. Finally, for application as a biosensor, the sensor was used for detecting the antibody-antigen reaction of interferon-gamma.

Analysis of multimode fiber bundles for endoscopic spectral-domain optical coherence tomography

PubMed Central

Risi, Matthew D.; Makhlouf, Houssine; Rouse, Andrew R.; Gmitro, Arthur F.

2016-01-01

A theoretical analysis of the use of a fiber bundle in spectral-domain optical coherence tomography (OCT) systems is presented. The fiber bundle enables a flexible endoscopic design and provides fast, parallelized acquisition of the OCT data. However, the multimode characteristic of the fibers in the fiber bundle affects the depth sensitivity of the imaging system. A description of light interference in a multimode fiber is presented along with numerical simulations and experimental studies to illustrate the theoretical analysis. PMID:25967012

Magnetic field sensor based on the magnetic-fluid-clad combined with singlemode-multimode-singlemode fiber and large core-offset splicing structure

NASA Astrophysics Data System (ADS)

Lv, Ri-qing; Qian, Jun-kai; Zhao, Yong

2018-03-01

A simple, compact optical fiber magnetic field sensor is proposed and experimentally demonstrated in this paper. It is based on the magnetic-fluid-clad combined with singlemode-multimode-singlemode fiber structure and large core-offset splicing structure. It was protected by a section of capillary tube and was sealed by UV glue. A sensing property study of the combined optical fiber structure and the proposed sensor were carried out. The experimental results show that the sensitivity of the refractive index of the optical fiber sensing structure is up to 156.63 nm/RIU and the magnetic field sensitivity of the proposed sensor is up to -97.24 pm/Oe in the range from 72.4 Oe to 297.8 Oe. The proposed sensor has several other advantages, such as simple structure, small size, easy fabrication and low cost.

Surface plasmon resonance based fiber optic detection of chlorine utilizing polyvinylpyrolidone supported zinc oxide thin films.

PubMed

Tabassum, Rana; Gupta, Banshi D

2015-03-21

A highly sensitive chlorine sensor for an aqueous medium is fabricated using an optical fiber surface plasmon resonance (OFSPR) system. An OFSPR-based chlorine sensor is designed with a multilayer-type platform by zinc oxide (ZnO) and polyvinylpyrollidone (PVP) film morphology manipulations. Among all the methodologies of transduction reported in the field of solid state chemical and biochemical sensing, our attention is focused on the Kretschmann configuration optical fiber sensing technique using the mechanism of surface plasmon resonance. The optical fiber surface plasmon resonance (SPR) chlorine sensor is developed using a multimode optical fiber with the PVP-supported ZnO film deposited over a silver-coated unclad core of the fiber. A spectral interrogation mode of operation is used to characterize the sensor. In an Ag/ZnO/PVP multilayer system, the absorption of chlorine in the vicinity of the sensing region is performed by the PVP layer and the zinc oxide layer enhances the shift in resonance wavelength. It is, experimentally, demonstrated that the SPR wavelength shifts nonlinearly towards the red side of the visible region with an increase in the chlorine concentration in an aqueous medium while the sensitivity of the sensor decreases linearly with an increase in the chlorine concentration. As the proposed sensor utilizes an optical fiber, it possesses the additional advantages of fiber such as less signal degradation, less susceptibility to electromagnetic interference, possibility of remote sensing, probe miniaturization, probe re-usability, online monitoring, small size, light weight and low cost.

Improved vibration sensor based on a biconical tapered singlemode fiber, using in-fiber Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Wonko, R.; Moś, J. E.; Stasiewicz, K. A.; Jaroszewicz, L. R.

2017-05-01

Optical fiber vibration sensors are an appropriate alternative for piezoelectric devices, which are electromagnetic sensitive to the external conditions. Most of the vibration sensors demonstrated in previous publications resist to different interferometers or Bragg's gratings. Such sensors require a long time of stabilization of an optical signal, because they are vulnerable to undesirable disturbance. In majority, time response of an optical sensor should be instantaneous, therefore we have proposed an in- line vibration sensing passive element based on a tapered fiber. Micrometer sized optical fiber tapers are attractive for many optical areas due to changes process of boundary conditions. Such phenomena allow for a sensitive detection of the modulation phase. Our experiment shows that a singlemode, adiabatic tapered fiber enables detecting an acoustic vibration. In this study, we report on Mach- Zehnder (MZ) interferometer as a vibration sensor which was composed of two 50/50 couplers at 1550 nm. In the reference arm we used a 4 meter singlemode optical fiber (SMF28), while in the arm under test we placed tapered optical fibers attached to a metal plate, put directly on speaker. Researches carried out on different tapered fibers which diameter of a taper waist was in the range from 5 μm to 25 μm, and each taper was characterized by optical losses less than 0,5 dB. The measured phase changes were over a frequency from 100 Hz to 1 kHz and an amplitude in the range from 100 mVpp to 1 Vpp. Although on account of a limited space we have showed only the results for 100 Hz. Nevertheless, experimental results show that this sensing system has a wide frequency response range from a few hertz to one of kilohertz, however for some conditions, a standard optical fiber showed better result.

Diaphragm size and sensitivity for fiber optic pressure sensors

NASA Technical Reports Server (NTRS)

He, Gang; Cuomo, Frank W.; Zuckerwar, Allan J.

1991-01-01

A mechanism which leads to a significant increase in sensitivity and linear operating range in reflective type fiber optic pressure transducers with minute active dimensions is studied. A general theoretical formalism is presented which is in good agreement with the experimental data. These results are found useful in the development of small pressure sensors used in turbulent boundary layer studies and other applications.

Improvement of highly sensitive lidar with a thumb-sized sensor-head built using an optical fiber preamplifier

NASA Astrophysics Data System (ADS)

Inoue, Daisuke; Ichikawa, Tadashi; Matsubara, Hiroyuki; Mao, Xueon; Maeda, Mitsutoshi; Nagashima, Chie; Kagami, Manabu

2012-06-01

We have developed a LIDAR system with a sensor head which, although it includes a scanning mechanism, is less than 20 cc in size. The system is not only small, but is also highly sensitive. Our LIDAR system is based on time-of-flight measurements, and incorporates an optical fiber. The main feature of our system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enable us to exceed the detection limit set by thermal noise. In conventional LIDAR systems the detection limit is determined by the thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use detect the received signals directly. In the case of our LIDAR system, the received signal is amplified by an optical fiber amplifier before reaching the photo diode and the TIA. Therefore, our LIDAR system boosts the signal level before the weak incoming signal is depleted by thermal noise. There are conditions under which the noise figure for the combination of an optical fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode. We optimized the gains of the optical fiber amplifier and the TIA in our LIDAR system such that it would be capable of detecting a single photon. As a result, the detection limit of our system is determined by shot noise. We have previously demonstrated optical pre-amplified LIDAR with a perfect co-axial optical system[1]. For this we used a variable optical attenuator to remove internal reflection from the transmission and receiving lenses. However, the optical attenuator had an insertion loss of 6dB which reduced the sensitivity of the LIDAR. We re-designed the optical system such that it was semi-co-axial and removed the variable optical attenuator. As a result, we succeeded in scanning up to a range of 80 m. This small and highly sensitive measurement technology shows great potential for use in LIDAR.

Slab-coupled optical sensor fabrication using side-polished Panda fibers.

PubMed

King, Rex; Seng, Frederick; Stan, Nikola; Cuzner, Kevin; Josephson, Chad; Selfridge, Richard; Schultz, Stephen

2016-11-01

A new device structure used for slab-coupled optical sensor (SCOS) technology was developed to fabricate electric field sensors. This new device structure replaces the D-fiber used in traditional SCOS technology with a side-polished Panda fiber. Unlike the D-fiber SCOS, the Panda fiber SCOS is made from commercially available materials and is simpler to fabricate. The Panda SCOS interfaces easier with lab equipment and exhibits ∼3  dB less loss at link points than the D-fiber SCOS. The optical system for the D-fiber is bandwidth limited by a transimpedance amplifier (TIA) used to amplify to the electric signal. The Panda SCOS exhibits less loss than the D-fiber and, as a result, does not require as high a gain setting on the TIA, which results in an overall higher bandwidth range. Results show that the Panda sensor also achieves comparable sensitivity results to the D-fiber SCOS. Although the Panda SCOS is not as sensitive as other side-polished fiber electric field sensors, it can be fabricated much easier because the fabrication process does not require special alignment techniques, and it is made from commercially available materials.

All fiber optics circular-state swept source polarization-sensitive optical coherence tomography.

PubMed

Lin, Hermann; Kao, Meng-Chun; Lai, Chih-Ming; Huang, Jyun-Cin; Kuo, Wen-Chuan

2014-02-01

A swept source (SS)-based circular-state (CS) polarization-sensitive optical coherence tomography (PS-OCT) constructed entirely with polarization-maintaining fiber optics components is proposed with the experimental verification. By means of the proposed calibration scheme, bulk quarter-wave plates can be replaced by fiber optics polarization controllers to, therefore, realize an all-fiber optics CS SSPS-OCT. We also present a numerical dispersion compensation method, which can not only enhance the axial resolution, but also improve the signal-to-noise ratio of the images. We demonstrate that this compact and portable CS SSPS-OCT system with an accuracy comparable to bulk optics systems requires less stringent lens alignment and can possibly serve as a technology to realize PS-OCT instrument for clinical applications (e.g., endoscopy). The largest deviations in the phase retardation (PR) and fast-axis (FA) angle due to sample probe in the linear scanning and a rotation angle smaller than 65 deg were of the same order as those in stationary probe setups. The influence of fiber bending on the measured PR and FA is also investigated. The largest deviations of the PR were 3.5 deg and the measured FA change by ~12 to 21 deg. Finally, in vivo imaging of the human fingertip and nail was successfully demonstrated with a linear scanning probe.

Hollow optical fiber induced solar cells with optical energy storage and conversion.

PubMed

Ding, Jie; Zhao, Yuanyuan; Duan, Jialong; Duan, Yanyan; Tang, Qunwei

2017-11-09

Hollow optical fiber induced dye-sensitized solar cells are made by twisting Ti wire/N719-TiO 2 nanotube photoanodes and Ti wire/Pt (CoSe, Pt 3 Ni) counter electrodes, yielding a maximized efficiency of 0.7% and good stability. Arising from optical energy storage ability, the solar cells can generate electricity without laser illumination.

Fiber-optic photoelastic pressure sensor with fiber-loss compensation

NASA Technical Reports Server (NTRS)

Beheim, G.; Anthan, D. J.

1987-01-01

A new fiber-optic pressure sensor is described that has high immunity to the effects of fiber-loss variations. This device uses the photoelastic effect to modulate the proportion of the light from each of two input fibers that is coupled into each of two output fibers. This four-fiber link permits two detectors to be used to measure the sensor's responses to the light from each of two independently controlled sources. These four detector outputs are processed to yield a loss-compensated signal that is a stable and sensitive pressure indicator.

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

A low-power, high-sensitivity micromachined optical magnetometer

NASA Astrophysics Data System (ADS)

Mhaskar, R.; Knappe, S.; Kitching, J.

2012-12-01

We demonstrate an optical magnetometer based on a microfabricated 87Rb vapor cell in a micromachined silicon sensor head. The alkali atom density in the vapor cell is increased by heating the cell with light brought to the sensor through an optical fiber, and absorbed by colored filters attached to the cell windows. A second fiber-optically coupled beam optically pumps and interrogates the atoms. The magnetometer operates on 140 mW of heating power and achieves a sensitivity below 20 fT/√Hz throughout most of the frequency band from 15 Hz to 100 Hz. Such a sensor can measure magnetic fields from the human heart and brain.

Fiber optic refractive index monitor

DOEpatents

Weiss, Jonathan David

2002-01-01

A sensor for measuring the change in refractive index of a liquid uses the lowest critical angle of a normal fiber optic to achieve sensitivity when the index of the liquid is significantly less than the index of the fiber core. Another embodiment uses a liquid filled core to ensure that its index is approximately the same as the liquid being measured.

Fiber temperature sensor with nanostructured cladding by TiO2 nanoparticles self-assembled onto a side polished optical fiber

NASA Astrophysics Data System (ADS)

Yang, Bing; Chen, Zhe; Wang, Yiting; Zhang, Jun; Liao, Guozhen; Tian, Zhengwen; Yu, Jianhui; Tang, Jieyuan; Luo, Yunhan; Lu, Huihui

2015-07-01

A temperature fiber sensor with nanostructured cladding composed ted by titanium dioxide (TiO2) nanoparticles was demonstrated. The nanoparticles self-assembled onto a side polished optical fiber (SPF). The enhancement of interaction between the propagating light and the TiO2 nanoparticles (TN) can be obtained via strong evanescent field of the SPF. The strong light-TN interaction gives rise to temperature sensing with a optical power variation of ~4dB in SPF experimentally for an environment temperature ranging from -7.8°C to 77.6°C. The novel temperature sensor shows a sensitivity of ~0.044 dB/°C. The TN-based fiber-optic temperature sensor is facile to manufactured, compatible with fiber-optic interconnections and high potential in photonics applications.

Nanoimprinting on optical fiber end faces for chemical sensing

NASA Astrophysics Data System (ADS)

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

2008-04-01

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

Fiber optic oxygen sensor leak detection system for space applications

NASA Astrophysics Data System (ADS)

Kazemi, Alex A.; Goswami, Kish; Mendoza, Edgar A.; Kempen, Lothar U.

2007-09-01

This paper describes the successful test of a multi-point fiber optic oxygen sensor system during the static firing of an Evolved Expandable Launch Vehicle (EELV)/Delta IV common booster core (CBC) rocket engine at NASA's Stennis Flight Center. The system consisted of microsensors (optrodes) using an oxygen gas sensitive indicator incorporated onto an optically transparent porous substrate. The modular optoelectronics and multiplexing network system was designed and assembled utilizing a multi-channel opto-electronic sensor readout unit that monitored the oxygen and temperature response of the individual optrodes in real-time and communicated this information via a serial communication port to a remote laptop computer. The sensor packaging for oxygen consisted of two optrodes - one doped with an indicator sensitive to oxygen, and the other doped with an indicator sensitive to temperature. The multichannel oxygen sensor system is fully reversible. It has demonstrated a dynamic response to oxygen gas in the range of 0% to 100% with 0.1% resolution and a response time of <=10 seconds. The sensor package was attached to a custom fiber optic ribbon cable, which was then connected to a fiber optic trunk communications cable (standard telecommunications-grade fiber) that connected to the optoelectronics module. Each board in the expandable module included light sources, photo-detectors, and associated electronics required for detecting oxygen and temperature. The paper illustrates the sensor design and performance data under field deployment conditions.

Thermoluminescence characteristics of Ge-doped optical fibers with different dimensions for radiation dosimetry.

PubMed

Begum, Mahfuza; Rahman, A K M Mizanur; Abdul-Rashid, H A; Yusoff, Z; Begum, Mahbuba; Mat-Sharif, K A; Amin, Y M; Bradley, D A

2015-06-01

Important thermoluminescence (TL) properties of five (5) different core sizes Ge-doped optical fibers have been studied to develop new TL material with better response. These are drawn from same preform applying different speed and tension during drawing phase to produce Ge-doped optical fibers with five (5) different core sizes. The results of the investigations are also compared with most commonly used standard TLD-100 chips (LiF:Mg,Ti) and commercial multimode Ge-doped optical fiber (Yangtze Optical Fiber, China). Scanning Electron Microscope (SEM) and EDX analysis of the fibers are also performed to map Ge distribution across the deposited region. Standard Gamma radiation source in Secondary Standard Dosimetry Lab (SSDL) was used for irradiation covering dose range from 1Gy to 10Gy. The essential dosimetric parameters that have been studied are TL linearity, reproducibility and fading. Prior to irradiation all samples ∼0.5cm length are annealed at temperature of 400°C for 1h period to standardize their sensitivities and background. Standard TLD-100 chips are also annealed for 1h at 400°C and subsequently 2h at 100°C to yield the highest sensitivity. TL responses of these fibers show linearity over a wide gamma radiation dose that is an important property for radiation dosimetry. Among all fibers used in this study, 100μm core diameter fiber provides highest response that is 2.6 times than that of smallest core (20μm core) optical fiber. These fiber-samples demonstrate better response than commercial multi-mode optical fiber and also provide low degree of fading about 20% over a period of fifteen days for gamma radiation. Effective atomic number (Zeff) is found in the range (13.25-13.69) which is higher than soft tissue (7.5) however within the range of human-bone (11.6-13.8). All the fibers can also be re-used several times as a detector after annealing. TL properties of the Ge-doped optical fibers indicate promising applications in ionizing radiation dosimetry. Copyright © 2014 Elsevier Ltd. All rights reserved.

Holograms for laser diode: Single mode optical fiber coupling

NASA Technical Reports Server (NTRS)

Fuhr, P. L.

1982-01-01

The low coupling efficiency of semiconductor laser emissions into a single mode optical fibers place a severe restriction on their use. Associated with these conventional optical coupling techniques are stringent alignment sensitivities. Using holographic elements, the coupling efficiency may be increased and the alignment sensitivity greatly reduced. Both conventional and computer methods used in the generation of the holographic couplers are described and diagrammed. The reconstruction geometries used are shown to be somewhat restrictive but substantially less rigid than their conventional optical counterparts. Single and double hologram techniques are examined concerning their respective ease of fabrication and relative merits.

Humidity Sensor Based on Bragg Gratings Developed on the End Facet of an Optical Fiber by Sputtering of One Single Material.

PubMed

Ascorbe, Joaquin; Corres, Jesus M; Arregui, Francisco J; Matias, Ignacio R

2017-04-29

The refractive index of sputtered indium oxide nanocoatings has been altered just by changing the sputtering parameters, such as pressure. These induced changes have been exploited for the generation of a grating on the end facet of an optical fiber towards the development of wavelength-modulated optical fiber humidity sensors. A theoretical analysis has also been performed in order to study the different parameters involved in the fabrication of this optical structure and how they would affect the sensitivity of these devices. Experimental and theoretical results are in good agreement. A sensitivity of 150 pm/%RH was obtained for relative humidity changes from 20% to 60%. This kind of humidity sensors shows a maximum hysteresis of 1.3% relative humidity.

Vibration sensing in flexible structures using a distributed-effect modal domain optical fiber sensor

NASA Technical Reports Server (NTRS)

Reichard, Karl M.; Lindner, Douglas K.; Claus, Richard O.

1991-01-01

Modal domain optical fiber sensors have recently been employed in the implementation of system identification algorithms and the closed-loop control of vibrations in flexible structures. The mathematical model of the modal domain optical fiber sensor used in these applications, however, only accounted for the effects of strain in the direction of the fiber's longitudinal axis. In this paper, we extend this model to include the effects of arbitrary stress. Using this sensor model, we characterize the sensor's sensitivity and dynamic range.

U-Shaped and Surface Functionalized Polymer Optical Fiber Probe for Glucose Detection.

PubMed

Azkune, Mikel; Ruiz-Rubio, Leire; Aldabaldetreku, Gotzon; Arrospide, Eneko; Pérez-Álvarez, Leyre; Bikandi, Iñaki; Zubia, Joseba; Vilas-Vilela, Jose Luis

2017-12-25

In this work we show an optical fiber evanescent wave absorption probe for glucose detection in different physiological media. High selectivity is achieved by functionalizing the surface of an only-core poly(methyl methacrylate) (PMMA) polymer optical fiber with phenilboronic groups, and enhanced sensitivity by using a U-shaped geometry. Employing a supercontinuum light source and a high-resolution spectrometer, absorption measurements are performed in the broadband visible light spectrum. Experimental results suggest the feasibility of such a fiber probe as a low-cost and selective glucose detector.

High Sensitivity Refractometer Based on TiO₂-Coated Adiabatic Tapered Optical Fiber via ALD Technology.

PubMed

Zhu, Shan; Pang, Fufei; Huang, Sujuan; Zou, Fang; Guo, Qiang; Wen, Jianxiang; Wang, Tingyun

2016-08-15

Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractometer based on an adiabatic tapered optical fiber. Different thicknesses of titanium dioxide (TiO₂) nanofilm were coated around the tapered fiber precisely and uniformly under different deposition cycles. Attributed to the higher refractive index of the TiO₂ nanofilm compared to that of silica, an asymmetric Fabry-Perot (F-P) resonator could be constructed along the fiber taper. The central wavelength of the F-P resonator could be controlled by adjusting the thickness of the TiO₂ nanofilm. Such a F-P resonator is sensitive to changes in the surrounding refractive index (SRI), which is utilized to realize a high sensitivity refractometer. The refractometer developed by depositing 50.9-nm-thickness TiO₂ on the tapered fiber shows SRI sensitivity as high as 7096 nm/RIU in the SRI range of 1.3373-1.3500. Due to TiO₂'s advantages of high refractive index, lack of toxicity, and good biocompatibility, this refractometer is expected to have wide applications in the biochemical sensing field.

Crescent shaped Fabry-Perot fiber cavity for ultra-sensitive strain measurement.

PubMed

Liu, Ye; Wang, D N; Chen, W P

2016-12-02

Optical Fabry-Perot interferometer sensors based on inner air-cavity is featured with compact size, good robustness and high strain sensitivity, especially when an ultra-thin air-cavity is adopted. The typical shape of Fabry-Perot inner air-cavity with reflection mode of operation is elliptic, with minor axis along with and major axis perpendicular to the fiber length. The first reflection surface is diverging whereas the second one is converging. To increase the visibility of the output interference pattern, the length of major axis should be large for a given cavity length. However, the largest value of the major axis is limited by the optical fiber diameter. If the major axis length reaches the fiber diameter, the robustness of the Fabry-Perot cavity device would be decreased. Here we demonstrate an ultra-thin crescent shaped Fabry-Perot cavity for strain sensing with ultra-high sensitivity and low temperature cross-sensitivity. The crescent-shape cavity consists of two converging reflection surfaces, which provide the advantages of enhanced strain sensitivity when compared with elliptic or D-shaped FP cavity. The device is fabricated by fusion splicing an etched multimode fiber with a single mode fiber, and hence is simple in structure and economic in cost.

Crescent shaped Fabry-Perot fiber cavity for ultra-sensitive strain measurement

NASA Astrophysics Data System (ADS)

Liu, Ye; Wang, D. N.; Chen, W. P.

2016-12-01

Optical Fabry-Perot interferometer sensors based on inner air-cavity is featured with compact size, good robustness and high strain sensitivity, especially when an ultra-thin air-cavity is adopted. The typical shape of Fabry-Perot inner air-cavity with reflection mode of operation is elliptic, with minor axis along with and major axis perpendicular to the fiber length. The first reflection surface is diverging whereas the second one is converging. To increase the visibility of the output interference pattern, the length of major axis should be large for a given cavity length. However, the largest value of the major axis is limited by the optical fiber diameter. If the major axis length reaches the fiber diameter, the robustness of the Fabry-Perot cavity device would be decreased. Here we demonstrate an ultra-thin crescent shaped Fabry-Perot cavity for strain sensing with ultra-high sensitivity and low temperature cross-sensitivity. The crescent-shape cavity consists of two converging reflection surfaces, which provide the advantages of enhanced strain sensitivity when compared with elliptic or D-shaped FP cavity. The device is fabricated by fusion splicing an etched multimode fiber with a single mode fiber, and hence is simple in structure and economic in cost.

High Sensitive Temperature Sensor Using a Liquid-core Optical Fiber with Small Refractive Index Difference Between Core and Cladding Materials.

PubMed

Xu, Yonghao; Chen, Xianfeng; Zhu, Yu

2008-03-17

An intensive temperature sensor based on a liquid-core optical fiber has been demonstrated for the measuring the temperature of the environment. The core of fiber is filled with a mixture of toluene and chloroform in order to make the refractive index of the liquid-core and the cladding of the fiber close. The experiment shows that a temperature sensitivity of about 5 dB/K and a tunable temperature range (from 20 o C to 60 o C) can be achieved. Based on the dielectric-clad liquid core fiber model, a simulation was carried out and the calculated results were in good accord with the experimental measurement.

Thermoluminescence properties of Yb-Tb-doped SiO2 optical fiber subject to 6 and 10 MV photon irradiation

NASA Astrophysics Data System (ADS)

Sahini, M. H.; Wagiran, H.; Hossain, I.; Saeed, M. A.; Ali, H.

2014-08-01

This paper reports thermoluminescence characteristics of thermoluminescence dosimetry 100 chips and Yb-Tb-doped optical fibers irradiated with 6 and 10 MV photons. Thermoluminescence response of both dosimeters increases over a wide photon dose range from 0.5 to 4 Gy. Yb-Tb-doped optical fibers demonstrate useful thermoluminescence properties and represent a good candidate for thermoluminescence dosimetry application with ionizing radiation. The results of this fiber have been compared with those of commercially available standard thermoluminescence dosimetry-100 media. Commercially available Yb-Tb-doped optical fibers and said standard media are found to yield a linear relationship between dose- and thermoluminescence signal, although Yb-Tb-doped optical fibers provide only 10 % of the sensitivity of thermoluminescence dosimetry-100. With better thermoluminescence characteristics such as small size (125 μm diameter), high flexibility, easy of handling and low cost, as compared to other thermoluminescence materials, indicate that commercial Yb-Tb-doped optical fiber is a promising thermoluminescence material for variety of applications.

In vivo thickness and birefringence determination of the human retinal nerve fiber layer using polarization-sensitive optical coherence tomography.

PubMed

Cense, B; Chen, T C; de Boer, J F

2006-01-01

Thinning of the retinal nerve fiber layer and changes in retinal nerve fiber layer birefringence may both precede clinically detectable glaucomatous vision loss. We present in vivo thickness and depth-resolved birefringence measurements of the human retinal nerve fiber layer (RNFL) by use of polarization-sensitive optical coherence tomography (PS-OCT). Using a fiber-based PS-OCT setup real-time images of the human retina in vivo were recorded, co-registered with retinal video images of the location of PS-OCT scans. PS-OCT scans around the optic nerve head (ONH) of two healthy young volunteers were made using 10 concentric circles of increasing radius. Both the mean retinal nerve fiber layer thickness and mean retinal nerve fiber birefringence for each of 48 sectors on a circle were determined. The retinal nerve fiber layer thickness and birefringence varied as a function of sector around the ONH. Measured double pass phase retardation per unit depth values around the ONH range between 0.10 and 0.35 degrees/microm. The retinal nerve fiber layer becomes thinner with increasing distance from the ONH. In contrast, the birefringence does not vary significantly with increasing distance from the ONH.

Toxin detection using a fiber-optic-based biosensor

NASA Astrophysics Data System (ADS)

Ogert, Robert A.; Shriver-Lake, Lisa C.; Ligler, Frances S.

1993-05-01

Using an evanescent wave fiber optic-based biosensor developed at Naval Research Laboratory, ricin toxin can be detected in the low ng/ml range. Sensitivity was established at 1 - 5 ng/ml using a two-step assay. The two-step assay showed enhanced signal levels in comparison to a one-step assay. A two-step assay utilizes a 10 minute incubation of an immobilized affinity purified anti-ricin antibody fiber optic probe in the ricin sample before placement in a solution of fluorophore-labeled goat anti-ricin antibodies. The specific fluorescent signal is obtained by the binding of the fluorophore-labeled antibodies to ricin which is bound by the immobilized antibodies on the fiber optic probe. The toxin can be detected directly from urine and river water using this fiber optic assay.

Quasi-distributed sol-gel coated fiber optic oxygen sensing probe

NASA Astrophysics Data System (ADS)

Zolkapli, Maizatul; Saharudin, Suhairi; Herman, Sukreen Hana; Abdullah, Wan Fazlida Hanim

2018-03-01

In the field of aquaculture, optical sensor technology is beginning to provide alternatives to the conventional electrical sensor. Hence, the development and characterization of a multipoint quasi-distributed optical fiber sensor for oxygen measurement is reported. The system is based on 1 mm core diameter plastic optical fiber where sections of cladding have been removed and replaced with three metal complexes sol-gel films to form sensing points. The sensing locations utilize luminophores that have emission peaks at 385 nm, 405 nm and 465 nm which associated with each of the sensing points. Interrogation of the optical sensor system is through a fiber optic spectrometer incorporating narrow bandpass emission optical filter. The sensors showed comparable sensitivity and repeatability, as well as fast response and recovery towards oxygen.

Fiber-based free-space optical coherent receiver with vibration compensation mechanism.

PubMed

Zhang, Ruochi; Wang, Jianmin; Zhao, Guang; Lv, Junyi

2013-07-29

We propose a novel fiber-based free-space optical (FSO) coherent receiver for inter-satellite communication. The receiver takes advantage of established fiber-optic components and utilizes the fine-pointing subsystem installed in FSO terminals to minimize the influence of satellite platform vibrations. The received beam is coupled to a single-mode fiber, and the coupling efficiency of the system is investigated both analytically and experimentally. A receiving sensitivity of -38 dBm is obtained at the forward error correction limit with a transmission rate of 22.4 Gbit/s. The proposed receiver is shown to be a promising component for inter-satellite optical communication.

New properties of a fiber optic sensor in application of a composite fence for critical infrastructure protection

NASA Astrophysics Data System (ADS)

Zyczkowski, M.; Szustakowski, M.; Markowski, P.

2015-09-01

This paper presents a new solution of using the composite fence with a novel fiber optic modalmetric sensor integrated within its structure. The modalmetric sensor is based on changes in a transverse modal field which is generated at the output of a multimode fiber. By a spatial limitation of the transverse modal field observation to its fragment thereof, changes' transformation in the modal distribution into changes of the output signal amplitude is made. Due to a constant analysis of the structure output signal, detection of an external disorder is possible. Integration of optical fibers with the fence structure allows for an accurate reproduction of the fence movement onto the optical fiber by significantly improving sensitivity of the modalmetric fiber sensor structure.

Moiré phase-shifted fiber Bragg gratings in polymer optical fibers

NASA Astrophysics Data System (ADS)

Min, Rui; Marques, Carlos; Bang, Ole; Ortega, Beatriz

2018-03-01

We demonstrate a simple way to fabricate phase-shifted fiber Bragg grating in polymer optical fibers as a narrowband transmission filter for a variety of applications at telecom wavelengths. The filters have been fabricated by overlapping two uniform fiber Bragg gratings with slightly different periods to create a Moiré grating with only two pulses (one pulse is 15 ns) of UV power. Experimental characterization of the filter is provided under different conditions where the strain and temperature sensitivities were measured.

Fiber optic pressure sensors in skin-friction measurements

NASA Technical Reports Server (NTRS)

Cuomo, F. W.

1986-01-01

A fiber optic lever sensing technique that can be used to measure normal pressure as well as shear stresses is discussed. This method uses three unequal fibers combining small size and good sensitivity. Static measurements appear to confirm the theoretical models predicted by geometrical optics and dynamic tests performed at frequencies up to 10 kHz indicate a flat response within this frequency range. These sensors are intended for use in a low speed wind tunnel environment.

Theoretical modeling of a coupled plasmon waveguide resonance sensor based on multimode optical fiber

NASA Astrophysics Data System (ADS)

Liu, Kun; Xue, Meng; Jiang, Junfeng; Wang, Tao; Chang, Pengxiang; Liu, Tiegen

2018-03-01

A coupled plasmon waveguide resonance (CPWR) sensor based on metal/dielectric-coated step index multimode optical fiber is proposed. Theoretical simulations using the four-layer Fresnel equations based on a bi-dimensional optical fiber model were implemented on four structures: Ag-ZnO, Au-ZnO, Ag-TiO2 and Au-TiO2. By controlling the thickness of dielectric layer, we managed to manipulate the CPWR resonance wavelengths. When a CPWR resonance dip is in the short wavelength region, it is insensitive to the change of surrounding refractive index (SRI) and can be used as a reference to improve the sensing accuracy of surface plasmon resonance (SPR) mode. With the increase of the thickness of the dielectric layer, the CPWR resonance dips shift to longer wavelength and the corresponding sensitivities increase. When the 1st CPWR resonance wavelength is near 1550 nm and SRI is around 1.333, the sensitivities of four structures reach 1360.61 nm/RIU, 1375.76 nm/RIU, 1048.48 nm/RIU and 1015.15 nm/RIU, respectively. The values are close to that of the conventional SPR optical fiber sensor while the spectral bandwidths of the optical fiber CPWR sensors are narrower.

Surface Plasmon Resonance-Based Fiber Optic Sensors Utilizing Molecular Imprinting

PubMed Central

Gupta, Banshi D.; Shrivastav, Anand M.; Usha, Sruthi P.

2016-01-01

Molecular imprinting is earning worldwide attention from researchers in the field of sensing and diagnostic applications, due to its properties of inevitable specific affinity for the template molecule. The fabrication of complementary template imprints allows this technique to achieve high selectivity for the analyte to be sensed. Sensors incorporating this technique along with surface plasmon or localized surface plasmon resonance (SPR/LSPR) provide highly sensitive real time detection with quick response times. Unfolding these techniques with optical fiber provide the additional advantages of miniaturized probes with ease of handling, online monitoring and remote sensing. In this review a summary of optical fiber sensors using the combined approaches of molecularly imprinted polymer (MIP) and the SPR/LSPR technique is discussed. An overview of the fundamentals of SPR/LSPR implementation on optical fiber is provided. The review also covers the molecular imprinting technology (MIT) with its elementary study, synthesis procedures and its applications for chemical and biological anlayte detection with different sensing methods. In conclusion, we explore the advantages, challenges and the future perspectives of developing highly sensitive and selective methods for the detection of analytes utilizing MIT with the SPR/LSPR phenomenon on optical fiber platforms. PMID:27589746

Study on the effect of carbon nanotube coating on the refractive index sensing sensitivity of fiber modal interferometer

NASA Astrophysics Data System (ADS)

Zhang, Ya-nan; Xie, Wen-ge; Wang, Jianzhang; Wang, Pengzhao

2018-01-01

Refractive index sensing of liquid is important in the domain of chemistry and biology. Fiber optical sensors provide an excellent way to measure the refractive index due to their feasible integration to other fiber optics components, high sensitivity, small size, and distributed sensing. However, conventional optical sensors have different shortages. To find a practical way to measure the refractive index of liquid, this paper intended to combine Carbon Nanotube (CNT) with non-core fiber (NCF) to prepare a kind of modal interferometer sensor and to explore the effect of CNT coating on refractive index sensing properties of the modal interferometer. Firstly, a structure of single mode non-core single mode (SNS) fiber with a CNT film coating was proposed and simulated. The simulation results showed that the CNT coating could improve the refractive index sensitivity of the interferometer sensor. Then in the experiment part, the CNT solution was fabricated and deposited onto the NCF, and a refractive index sensing system was built to examine the property of the CNT-coated SNS interferometer sensor. During the experiment, the influence factors of sensitivity were summarized by testing the sensing performance under different conditions, and it was demonstrated that the CNT coating could improve the contrast of the interference spectrum, and also had the possibility to increase the refractive index sensitivity of the interferometer sensor.

Temperature-sensitive optrode

DOEpatents

Hirschfeld, T.B.

1985-09-24

Method and apparatus are provided for measuring temperature and for generating optical signals related to temperature. Light from a fiber optic is directed to a material whose fluorescent response varies with ambient temperature. The same fiber optic delivering the excitation beam also collects a portion of the fluorescent emission for analysis. Signal collection efficiency of the fiber optic is enhanced by requiring that the fluorescent probe material be in the shape of an oblong parabolically tapered solid. Reproducibility is enhanced by using Raman backscatter to monitor excitation beam fluctuations, and by using measurements of fluorescence lifetime. 10 figs.

Temperature-sensitive optrode

DOEpatents

Hirschfeld, Tomas B.

1985-01-01

Method and apparatus are provided for measuring temperature and for generating optical signals related to temperature. Light from a fiber optic is directed to a material whose fluorescent response varies with ambient temperature. The same fiber optic delivering the excitation beam also collects a portion of the fluorescent emission for analysis. Signal collection efficiency of the fiber optic is enhanced by requiring that the fluorescent probe material be in the shape of an oblong parabolically tapered solid. Reproducibility is enhanced by using Raman backscatter to monitor excitation beam fluctuations, and by using measurements of fluorescence lifetime.

Refractive-index dispersion measurement of bulk optical materials using a fiber raman laser widely tunable in the visible and near-infrared

NASA Astrophysics Data System (ADS)

Ilev, Ilko K.; Kumagai, Hiroshi; Toyoda, Koichi

1997-01-01

We propose a simple, highly sensitive fiber-optic autocollimation method for refractive-index dispersion measurement of solid-state and liquid bulk optical materials using a double-pass fiber Raman laser with Littrow-prism-tuned emission. The optical fiber is a key element of the scheme and serves simultaneously as a point laser source for the test, as a highly sensitive point receiver (or spatial filter) of the autocollimation backreflectance signal and as a medium for nonlinear frequency conversion and generation of a broadband continuum spectrum. When the Raman medium is a graded-index multimode fiber with powerful pumping (over 100 kW) using the second harmonic of a Q-switched Nd:YAG laser (λp=532nm), we obtain widely tunable (0.54-1.01 μm) generation in both the visible and near-IR ranges. The results obtained in the refractive-index dispersion measurements are fitted to the Sellmeier dispersion equation and the standard deviation of the experimental data from the analytical curve does not exceed 5x10-5.

Power modulation based fiber-optic loop-sensor having a dual measurement range

NASA Astrophysics Data System (ADS)

Nguyen, Nguyen Q.; Gupta, Nikhil

2009-08-01

A fiber-optic sensor is investigated in this work for potential applications in structural health monitoring. The sensor, called fiber-loop-sensor, is based on bending an optical fiber beyond a critical radius to obtain intensity losses and calibrating the losses with respect to the applied force or displacement. Additionally, in the present case, the use of single-mode optical fibers allows the appearance of several resonance peaks in the transmitted power-displacement graph. The intensity of one of these resonances can be tracked in a narrow range to obtain high sensitivity. Experimental results show that the resolution of 10-4 N for force and 10-5 m for displacement can be obtained in these sensors. The sensors are calibrated for various loop radii and for various loading rates. They are also tested under loading-unloading conditions for over 104 cycles to observe their fatigue behavior. The sensors show very repeatable response and no degradation in performance under these test conditions. Simple construction and instrumentation, high sensitivity, and low cost are the advantages of these sensors.

Strain Insensitive Optical Phase Locked Loop

NASA Technical Reports Server (NTRS)

Egalon, Claudio Oliviera (Inventor); Rogowski, Robert S. (Inventor)

1996-01-01

An apparatus is provided to allow for quasi distributed sensing of strain within a test object. Strain insensitive fiber is used to deliver a light signal to a strain sensitive fiber in an optical phase locked loop sensor configuration. The use of strain insensitive delivery fiber allows for non-integrated measurements of strain without the use of expensive electronics such as those employed in ODTR techniques. The novelty of the present invention lies in the use of strain insensitive multimode fiber. The inventors had previously developed a similar sensor with strain insensitive fiber, however it was restricted to the use of single or few mode fibers. The use of an optical phase locked loop arrangement allows for the use of multimode strain insensitive fiber.

Two Fiber Optical Fiber Thermometry

NASA Technical Reports Server (NTRS)

Jones, Mathew R.; Farmer, Jeffery T.; Breeding, Shawn P.

2000-01-01

An optical fiber thermometer consists of an optical fiber whose sensing tip is given a metallic coating. The sensing tip of the fiber is essentially an isothermal cavity, so the emission from this cavity will be approximately equal to the emission from a blackbody. Temperature readings are obtained by measuring the spectral radiative heat flux at the end of the fiber at two wavelengths. The ratio of these measurements and Planck's Law are used to infer the temperature at the sensing tip. Optical fiber thermometers have high accuracy, excellent long-term stability and are immune to electromagnetic interference. In addition, they can be operated for extended periods without requiring re-calibration. For these reasons. it is desirable to use optical fiber thermometers in environments such as the International Space Station. However, it has recently been shown that temperature readings are corrupted by emission from the fiber when extended portions of the probe are exposed to elevated temperatures. This paper will describe several ways in which the reading from a second fiber can be used to correct the corrupted temperature measurements. The accuracy and sensitivity to measurement uncertainty will be presented for each method.

Loss-compensation technique using a split-spectrum approach for optical fiber air-gap intensity-based sensors

NASA Astrophysics Data System (ADS)

Wang, Anbo; Miller, Mark S.; Gunther, Michael F.; Murphy, Kent A.; Claus, Richard O.

1993-03-01

A self-referencing technique compensating for fiber losses and source fluctuations in air-gap intensity-based optical fiber sensors is described and demonstrated. A resolution of 0.007 micron has been obtained over a measurement range of 0-250 microns for an intensity-based displacement sensor using this referencing technique. The sensor is shown to have minimal sensitivity to fiber bending losses and variations in the LED input power. A theoretical model for evaluation of step-index multimode optical fiber splice is proposed. The performance of the sensor as a displacement sensor agrees well with the theoretical analysis.

A Polymer Optical Fiber Fuel Level Sensor: Application to Paramotoring and Powered Paragliding

PubMed Central

Montero, David Sánchez; Lallana, Pedro Contreras; Vázquez, Carmen

2012-01-01

A low-cost intensity-based polymer optical fiber (POF) sensor for fuel level measurements in paramotoring and powered paragliding is presented, exploiting the advantages of the optical fiber sensing technology. Experimental results demonstrate that the best option can be performed by stripping the fiber at the desired discrete points to measure the fuel level as well as with a gauge-shape fiber bending. The prototype has a good linearity, better than 4% full scale (F.S.), and sensitivity around 0.5 V per bend are obtained. Hysteresis due to residual fluid at the sensing points is found to be less than 9% F.S. PMID:22778637

Low cost fiber optic sensing of sugar solution

NASA Astrophysics Data System (ADS)

Muthuraju, M. E.; Patlolla, Anurag Reddy; Vadakkapattu Canthadai, Badrinath; Pachava, Vengalrao

2015-03-01

The demand for highly sensitive and reliable sensors to assess the refractive index of liquid get many applications in chemical and biomedical areas. Indeed, the physical parameters such as concentration, pressure and density, etc., can be found using the refractive index of liquid. In contrast to the conventional refractometer for measurement, optical fiber sensor has several advantages like remote sensing, small in size, low cost, immune to EMI etc., In this paper we have discussed determination of refractive index of sugar solution using optical fiber. An intensity modulated low cost plastic fiber optic refractive index sensor has been designed for the study. The sensor is based on principle of change in angle of reflected light caused by refractive index change of the medium surrounding the fiber. The experimental results obtained for the sugar solution of different refractive indices prove that the fiber optic sensor is cable of measuring the refractive indices as well as the concentrations.

The measurement system of birefringence and Verdet constant of optical fiber

NASA Astrophysics Data System (ADS)

Huang, Yi; Chen, Li; Guo, Qiang; Pang, Fufei; Wen, Jianxiang; Shang, Yana; Wang, Tingyun

2013-12-01

The Faraday magneto-optical effect of optical fiber has many applications in monitoring magnetic field and electric current. When a linearly polarized light propagates in the direction of a magnetic field, the plane of polarization will rotate linearly proportional to the strength of the applied magnetic field, which following the relationship of θF =VBl. θF is the Faraday rotation angle, which is proportional to the magnetic flux density B and the Verdet constant V . However, when the optical fiber contains the effect of linear birefringence, the detection of Faraday rotation angle will depend on the line birefringence. In order to determine the Verdet constant of an optical fiber under a linear birefringence, the fiber birefringence needs to be accurately measured. In this work, a model is applied to analyze the polarization properties of an optical fiber by using the Jones matrix method. A measurement system based on the lock-in amplifier technology is designed to test the Verdet constant and the birefringence of optical fiber. The magnetic field is produced by a solenoid with a DC current. A tunable laser is intensity modulated with a motorized rotating chopper. The actuator supplies a signal as the phase-locked synchronization reference to the signal of the lock-in amplifier. The measurement accuracy is analyzed and the sensitivity of the system is optimized. In this measurement system, the Verdet constant of the SMF-28 fiber was measured to be 0.56±0.02 rad/T·m at 1550nm. This setup is well suitable for measuring the high signal-to-noise ratio (SNR) sensitivity for lock-in amplifier at a low magnetic field strength.

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-speed polarization sensitive optical frequency domain imaging with frequency multiplexing

PubMed Central

Yun, S.H.; Vakoc, B.J.; Shishkov, M.; Desjardins, A.E.; Park, B.H.; de Boer, J.F.; Tearney, G.J.; Bouma, B.E.

2009-01-01

Polarization sensitive optical coherence tomography (PS-OCT) provides a cross-sectional image of birefringence in biological samples that is complementary in many applications to the standard reflectance-based image. Recent ex vivo studies have demonstrated that birefringence mapping enables the characterization of collagen and smooth muscle concentration and distribution in vascular tissues. Instruments capable of applying these measurements percutaneously in vivo may provide new insights into coronary atherosclerosis and acute myocardial infarction. We have developed a polarization sensitive optical frequency domain imaging (PS-OFDI) system that enables high-speed intravascular birefringence imaging through a fiber-optic catheter. The novel design of this system utilizes frequency multiplexing to simultaneously measure reflectance of two incident polarization states, overcoming concerns regarding temporal variations of the catheter fiber birefringence and spatial variations in the birefringence of the sample. We demonstrate circular cross-sectional birefringence imaging of a human coronary artery ex vivo through a flexible fiber-optic catheter with an A-line rate of 62 kHz and a ranging depth of 6.2 mm. PMID:18542183

FIBER AND INTEGRATED OPTICS: Multiplexed optical-fiber sensors with autodyne detection

NASA Astrophysics Data System (ADS)

Potapov, V. T.; Mamedov, A. M.; Shatalin, S. V.; Yushkaĭtis, R. V.

1993-09-01

A method is proposed for multiplexing optical-fiber interference sensors. The method involves autodyne reception of frequency-modulated radiation reflected back to the laser. The response of a He-Ne laser with a linearly varying generation frequency to radiation reflected back from a single-mode fiber is studied. The spectrum of beats caused in the laser radiation by the reflection is shown to be governed by the distribution of reflectors along the fiber. The phases of the spectral components contain information about the phase shift of the reflected optical signal. A hydrophone array with a sensitivity of 30 μrad/Hz1/2 is described. A distributed temperature sensor with a spatial resolution of 1 m is also described.

Sensitivity of corneal biomechanical and optical behavior to material parameters using design of experiments method.

PubMed

Xu, Mengchen; Lerner, Amy L; Funkenbusch, Paul D; Richhariya, Ashutosh; Yoon, Geunyoung

2018-02-01

The optical performance of the human cornea under intraocular pressure (IOP) is the result of complex material properties and their interactions. The measurement of the numerous material parameters that define this material behavior may be key in the refinement of patient-specific models. The goal of this study was to investigate the relative contribution of these parameters to the biomechanical and optical responses of human cornea predicted by a widely accepted anisotropic hyperelastic finite element model, with regional variations in the alignment of fibers. Design of experiments methods were used to quantify the relative importance of material properties including matrix stiffness, fiber stiffness, fiber nonlinearity and fiber dispersion under physiological IOP. Our sensitivity results showed that corneal apical displacement was influenced nearly evenly by matrix stiffness, fiber stiffness and nonlinearity. However, the variations in corneal optical aberrations (refractive power and spherical aberration) were primarily dependent on the value of the matrix stiffness. The optical aberrations predicted by variations in this material parameter were sufficiently large to predict clinically important changes in retinal image quality. Therefore, well-characterized individual variations in matrix stiffness could be critical in cornea modeling in order to reliably predict optical behavior under different IOPs or after corneal surgery.

Research on dual-parameter optical fiber sensor based on thin-core fiber and spherical structure

NASA Astrophysics Data System (ADS)

Tong, Zhengrong; Wang, Xue; Zhang, Weihua; Xue, Lifang

2018-04-01

A novel dual-parameter optical fiber sensor is proposed and experimentally demonstrated. The proposed sensor is based on a fiber in-line Mach-Zehnder interferometer, which is fabricated by sandwiching a section of thin-core fiber between two spherical structures made of single-mode fibers. The transmission spectrum exhibits the response of the interference between the core and the different cladding modes. Due to the different wavelength shifts of the two selected dips, the simultaneous measurement of temperature and the surrounding refractive index can be achieved. The measured temperature sensitivities are 0.067 nm/°C and 0.050 nm/°C, and the refractive index sensitivities are  -119.9 nm/RIU and  -69.71 nm/RIU, respectively. In addition, the compact size, simple fabrication and cost-effectiveness of the fiber sensor are also advantages.

Novel fiber optic sensor probe with a pair of highly reflected connectors and a vessel of water absorption material for water leak detection.

PubMed

Cho, Tae-Sik; Choi, Ki-Sun; Seo, Dae-Cheol; Kwon, Il-Bum; Lee, Jung-Ryul

2012-01-01

The use of a fiber optic quasi-distributed sensing technique for detecting the location and severity of water leakage is suggested. A novel fiber optic sensor probe is devised with a vessel of water absorption material called as water combination soil (WCS) located between two highly reflected connectors: one is a reference connector and the other is a sensing connector. In this study, the sensing output is calculated from the reflected light signals of the two connectors. The first reflected light signal is a reference and the second is a sensing signal which is attenuated by the optical fiber bending loss due to the WCS expansion absorbing water. Also, the bending loss of each sensor probe is determined by referring to the total number of sensor probes and the total power budget of an entire system. We have investigated several probe characteristics to show the design feasibility of the novel fiber sensor probe. The effects of vessel sizes of the probes on the water detection sensitivity are studied. The largest vessel probe provides the highest sensitivity of 0.267 dB/mL, while the smallest shows relatively low sensitivity of 0.067 dB/mL, and unstable response. The sensor probe with a high output value provides a high sensitivity with various detection levels while the number of total installable sensor probes decreases.

An optical fiber spool for laser stabilization with reduced acceleration sensitivity to 10-12/g

NASA Astrophysics Data System (ADS)

Hu, Yong-Qi; Dong, Jing; Huang, Jun-Chao; Li, Tang; Liu, Liang

2015-10-01

Environmental vibration causes mechanical deformation in optical fibers, which induces excess frequency noise in fiber-stabilized lasers. In order to solve such a problem, we propose an ultralow acceleration sensitivity fiber spool with symmetrically mounted structure. By numerical analysis with the finite element method, we obtain the optimal geometry parameters of the spool with which the horizontal and vertical acceleration sensitivity can be reduced to 3.25 × 10-12/g and 5.38 × 10-12/g respectively. Moreover, the structure features the insensitivity to the variation of geometry parameters, which will minimize the influence from numerical simulation error and manufacture tolerance. Project supported by the National Natural Science Foundation of China (Grant Nos. 11034008 and 11274324) and the Key Research Program of the Chinese Academy of Sciences (Grant No. KJZD-EW-W02).

Highly sensitive detection of molecular interactions with plasmonic optical fiber grating sensors.

PubMed

Voisin, Valérie; Pilate, Julie; Damman, Pascal; Mégret, Patrice; Caucheteur, Christophe

2014-01-15

Surface Plasmon resonance (SPR) optical fiber biosensors constitute a miniaturized counterpart to the bulky prism configuration and offer remote operation in very small volumes of analyte. They are a cost-effective and relatively straightforward technique to yield in situ (or even possibly in vivo) molecular detection. The biosensor configuration reported in this work uses nanometric-scale gold-coated tilted fiber Bragg gratings (TFBGs) interrogated by light polarized radially to the optical fiber outer surface, so as to maximize the optical coupling with the SPR. These gratings were recently associated to aptamers to assess their label-free biorecognition capability in buffer and serum solutions. In this work, using the well-acknowledged biotin-streptavidin pair as a benchmark, we go forward in the demonstration of their unique sensitivity. In addition to the monitoring of the self-assembled monolayer (SAM) in real time, we report an unprecedented limit of detection (LOD) as low as 2 pM. Finally, an immunosensing experiment is realized with human transferrin (dissociation constant Kd~10(-8) M(-1)). It allows to assess both the reversibility and the robustness of the SPR-TFBG biosensors and to confirm their high sensitivity. © 2013 Published by Elsevier B.V.

Simultaneous measurement of temperature and strain based on composite long-period fiber grating

NASA Astrophysics Data System (ADS)

Tong, Chengguo; Hu, Qihao; He, Jiang; Chen, XuDong; Geng, Tao; Bao, Zhanjing; Li, Zixuan; Yang, Wenlei; Sun, Weimin

2016-11-01

Long period fiber grating is a kind of transmission type optical fiber grating. Due to the advantages such as low insertion loss, wide bandwidth, low-level reflection, high sensitivity, low cost and ease of compactness, LPFGs have been widely applied in optical fiber sensing and optical fiber communication. The Mode coupling of LPFG is the coupling between the fiber core mode and the cladding mode in the same transmission direction. If the ordinary LPFG is combined with bitaper or taper, we can effectively change the original LPFG's transmission spectrum to obtain the composite LPFG, which can stimulate new resonant peaks in the original wavelength-dependent transmission loss of the grating basis, thus applying to the dual-parameter simultaneously measuring field. We report a novel all-fiber narrow-bandwidth intermodal Mach- Zehnder interferometer (MZI) based on a long-period fiber grating (LPFG) combined with a fiber bitaper. The LPFG is written by high-frequency CO2 laser pulses, and the bitaper is connected in series with the LPFG, forming the Mach- Zehnder interferometer (MZI). Experimental results indicate that the MZI has good temperature sensitivity, The temperature sensitivity of the two loss peaks are 55.35pm/°C and 48.18pm/°C respectively. The strain sensitivity of the two loss peaks are 3.35pm/μɛ and -4.925pm/μɛ respectively. By using the different temperature and strain response characteristics of the loss peaks, the temperature and strain measurement can be realized simultaneously. the proposed device has good repeatability and stability, which would be a promising candidate for precise dual-parameter sensing application.

Extrinsic optical-fiber ultrasound sensor using a thin polymer film as a low-finesse Fabry-Perot interferometer

NASA Astrophysics Data System (ADS)

Beard, P. C.; Mills, T. N.

1996-02-01

Theoretical and experimental aspects of an extrinsic optical-fiber ultrasound sensor are described. The sensor is based on a thin transparent polymer film acting as a low-finesse Fabry-Perot cavity that is mounted at the end of a multimode optical fiber. Performance was found to be comparable with that of a piezoelectric polyvinylidene difluoride-membrane (PVDF) hydrophone with a sensitivity of 61 mV/MPa, an acoustic noise floor of 2.3 KPa over a 25-MHz bandwidth, and a frequency response to 25 MHz. The wideband-sensitive response and design flexibility of the concept suggests that it may find application as an alternative to piezoelectric devices for the detection and measurement of ultrasound.

Fabry-Perot interferometer fiber tip sensor based on a glass microsphere glued at the etched end of multimode fiber

NASA Astrophysics Data System (ADS)

Chen, Weiping P.; Wang, Dongning N.; Xu, Ben; Wang, Zhaokun K.; Zhao, Chun-Liu

2017-05-01

We demonstrate an optical Fabry-Perot interferometer fiber tip sensor based on a glass microsphere glued at the etched end of a multimode fiber. The fiber device is miniature and robust, with a convenient reflection mode of operation, a high temperature sensitivity of 202.6 pm/°C within the range from 5°C to 90°C, a good refractive index sensitivity of ˜119 nm/RIU within the range from 1.331 to 1.38, and a gas pressure sensitivity of 0.19 dB/MPa.

Piezo-phototronic UV/visible photosensing with optical-fiber-nanowire hybridized structures.

PubMed

Wang, Zhaona; Yu, Ruomeng; Pan, Caofeng; Liu, Ying; Ding, Yong; Wang, Zhong Lin

2015-03-04

An optical-fiber-nanowire hybridized UV-visible photodetector (PD) is reported. The PD is designed to allow direct integration in optical communication systems without requiring the use of couplers via fiber-welding technology. The PD works in two modes: axial and off-axial illumination mode. By using the piezo-phototronic effect, the performance of the PD is enhanced/optimized by up to 718% in sensitivity and 2067% in photoresponsivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

pH Optrode Instrumentation

NASA Technical Reports Server (NTRS)

Tabacco, Mary Beth; Zhou, Quan

1995-01-01

pH-sensitive chromophoric reagents immobilized in porous optical fibers. Optoelectronic instrumentation system measures acidity or alkalinity of aqueous nutrient solution. Includes one or more optrodes, which are optical-fiber chemical sensors, in sense, analogous to electrodes but not subject to some of spurious effects distorting readings taken by pH electrodes. Concept of optrodes also described in "Ethylene-Vapor Optrodes" (KSC-11579). pH optrode sensor head, with lead-in and lead-out optical fibers, convenient for monitoring solutions located away from supporting electronic equipment.

Stability of a pH-sensitive polymer matrix

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

Northrup, M.A.; Langry, K.; Angel, S.M.

1990-03-01

A ratiometric pH-sensitive fluorescent dye (hydroxypyrenetrisulfonic acid) was covalently attached to an acrylamide polymer. These pH-sensitive copolymers were either covalently bonded to the end of an optical fiber or polymerized into separate gels. Long-term, accelerated aging studies were performed on the fibers and gels in 43{degree}C distilled H{sub 2}O. The fiber-immobilized optrodes gave good pH responses for up to 2 months. The pH-sensitive gels were physically attached to optical fibers and gave very good pH responses for over one year. These physically immobilized, one-year-old, pH-sensitive copolymers provided optrodes with linear pH responses between pH 6 and 8 and resolution greatermore » than 0.25 pH unit. A simple photostability experiment on these optrodes showed that they were very photostable. The results of this study indicate that pH-sensitive copolymers in a simple optrode design can be employed as pH sensors with useful lifetimes exceeding one year. 11 refs., 6 figs.« less

Efferent control of temporal response properties of the Limulus lateral eye

PubMed Central

1990-01-01

The sensitivity of the Limulus lateral eye exhibits a pronounced circadian rhythm. At night a circadian oscillator in the brain activates efferent fibers in the optic nerve, inducing multiple changes in the physiological and anatomical characteristics of retinal cells. These changes increase the sensitivity of the retina by about five orders of magnitude. We investigated whether this increase in retinal sensitivity is accompanied by changes in the ability of the retina to process temporal information. We measured the frequency transfer characteristic (FTC) of single receptors (ommatidia) by recording the response of their optic nerve fibers to sinusoidally modulated light. We first measured the FTC in the less sensitive daytime state and then after converting the retina to the more sensitive nighttime state by electrical stimulation of the efferent fibers. The activation of these fibers shifted the peak of the FTC to lower frequencies and reduced the slope of the low-frequency limb. These changes reduce the eye's ability to detect rapid changes in light intensity but enhance its ability to detect dim flashes of light. Apparently Limulus sacrifices temporal resolution for increased visual sensitivity at night. PMID:2307958

Modeling of Distributed Sensing of Elastic Waves by Fiber-Optic Interferometry

PubMed Central

Agbodjan Prince, Just; Kohl, Franz; Sauter, Thilo

2016-01-01

This paper deals with the transduction of strain accompanying elastic waves in solids by firmly attached optical fibers. Stretching sections of optical fibers changes the time required by guided light to pass such sections. Exploiting interferometric techniques, highly sensitive fiber-optic strain transducers are feasible based on this fiber-intrinsic effect. The impact on the actual strain conversion of the fiber segment’s shape and size, as well as its inclination to the elastic wavefront is studied. FEM analyses show that severe distortions of the interferometric response occur when the attached fiber length spans a noticeable fraction of the elastic wavelength. Analytical models of strain transduction are presented for typical transducer shapes. They are used to compute input-output relationships for the transduction of narrow-band strain pulses as a function of the mechanical wavelength. The described approach applies to many transducers depending on the distributed interaction with the investigated object. PMID:27608021

Clinical in vivo dosimetry using optical fibers.

PubMed

Gripp, S; Haesing, F W; Bueker, H; Schmitt, G

1998-01-01

Discoloring of glass due to ionizing radiation depends on the absorbed dose. The radiation-induced light attenuation in optical fibers may be used as a measure of the dose. In high-energy photon beams (6 MV X rays), a lead-doped silica fiber can be calibrated. A dosimeter based on an optical fiber was developed for applications in radiation therapy. The diameter of the mounted fiber is 0.25 mm, whereas the length depends on the sensitivity required. To demonstrate the applicability, a customized fiber device was used to determine scattered radiation close to the lens of the eye. Measurements were compared with TLDs (LiF) in an anthropomorphic phantom. The comparison with TLD measurements shows good agreement. In contrast to TLD, optical fibers provide immediate dose values, and the readout procedure is much easier. Owing to its small size and diameter, interesting invasive dose measurements are feasible.

Modeling of Distributed Sensing of Elastic Waves by Fiber-Optic Interferometry.

PubMed

Agbodjan Prince, Just; Kohl, Franz; Sauter, Thilo

2016-09-06

This paper deals with the transduction of strain accompanying elastic waves in solids by firmly attached optical fibers. Stretching sections of optical fibers changes the time required by guided light to pass such sections. Exploiting interferometric techniques, highly sensitive fiber-optic strain transducers are feasible based on this fiber-intrinsic effect. The impact on the actual strain conversion of the fiber segment's shape and size, as well as its inclination to the elastic wavefront is studied. FEM analyses show that severe distortions of the interferometric response occur when the attached fiber length spans a noticeable fraction of the elastic wavelength. Analytical models of strain transduction are presented for typical transducer shapes. They are used to compute input-output relationships for the transduction of narrow-band strain pulses as a function of the mechanical wavelength. The described approach applies to many transducers depending on the distributed interaction with the investigated object.

Vibro-Perception of Optical Bio-Inspired Fiber-Skin.

PubMed

Li, Tao; Zhang, Sheng; Lu, Guo-Wei; Sunami, Yuta

2018-05-12

In this research, based on the principle of optical interferometry, the Mach-Zehnder and Optical Phase-locked Loop (OPLL) vibro-perception systems of bio-inspired fiber-skin are designed to mimic the tactile perception of human skin. The fiber-skin is made of the optical fiber embedded in the silicone elastomer. The optical fiber is an instinctive and alternative sensor for tactile perception with high sensitivity and reliability, also low cost and susceptibility to the magnetic interference. The silicone elastomer serves as a substrate with high flexibility and biocompatibility, and the optical fiber core serves as the vibro-perception sensor to detect physical motions like tapping and sliding. According to the experimental results, the designed optical fiber-skin demonstrates the ability to detect the physical motions like tapping and sliding in both the Mach-Zehnder and OPLL vibro-perception systems. For direct contact condition, the OPLL vibro-perception system shows better performance compared with the Mach-Zehnder vibro-perception system. However, the Mach-Zehnder vibro-perception system is preferable to the OPLL system in the indirect contact experiment. In summary, the fiber-skin is validated to have light touch character and excellent repeatability, which is highly-suitable for skin-mimic sensing.

Multiplexed neural recording along a single optical fiber via optical reflectometry

PubMed Central

Rodriques, Samuel G.; Marblestone, Adam H.; Scholvin, Jorg; Dapello, Joel; Sarkar, Deblina; Mankin, Max; Gao, Ruixuan; Wood, Lowell; Boyden, Edward S.

2016-01-01

Abstract. We introduce the design and theoretical analysis of a fiber-optic architecture for neural recording without contrast agents, which transduces neural electrical signals into a multiplexed optical readout. Our sensor design is inspired by electro-optic modulators, which modulate the refractive index of a waveguide by applying a voltage across an electro-optic core material. We estimate that this design would allow recording of the activities of individual neurons located at points along a 10-cm length of optical fiber with 40-μm axial resolution and sensitivity down to 100  μV using commercially available optical reflectometers as readout devices. Neural recording sites detect a potential difference against a reference and apply this potential to a capacitor. The waveguide serves as one of the plates of the capacitor, so charge accumulation across the capacitor results in an optical effect. A key concept of the design is that the sensitivity can be improved by increasing the capacitance. To maximize the capacitance, we utilize a microscopic layer of material with high relative permittivity. If suitable materials can be found—possessing high capacitance per unit area as well as favorable properties with respect to toxicity, optical attenuation, ohmic junctions, and surface capacitance—then such sensing fibers could, in principle, be scaled down to few-micron cross-sections for minimally invasive neural interfacing. We study these material requirements and propose potential material choices. Custom-designed multimaterial optical fibers, probed using a reflectometric readout, may, therefore, provide a powerful platform for neural sensing. PMID:27194640

Optical-fiber strain sensors with asymmetric etched structures.

PubMed

Vaziri, M; Chen, C L

1993-11-01

Optical-fiber strain gauges with asymmetric etched structures have been analyzed, fabricated, and tested. These sensors are very sensitive with a gauge factor as high as 170 and a flat frequency response to at least 2.7 kHz. The gauge factor depends on the asymmetry of the etched structures and the number of etched sections. To understand the physical principles involved, researchers have used structural analysis programs based on a finite-element method to analyze fibers with asymmetric etched structures under tensile stress. The results show that lateral bends are induced on the etched fibers when they are stretched axially. To relate the lateral bending to the optical attenuation, we have also employed a ray-tracing technique to investigate the dependence of the attenuation on the structural deformation. Based on the structural analysis and the ray-tracing study parameters affecting the sensitivity have been studied. These results agree with the results of experimental investigations.

Fiber-Optic Pressure Sensor With Dynamic Demodulation Developed

NASA Technical Reports Server (NTRS)

Lekki, John D.

2002-01-01

Researchers at the NASA Glenn Research Center developed in-house a method to detect pressure fluctuations using a fiber-optic sensor and dynamic signal processing. This work was in support of the Intelligent Systems Controls and Operations project under NASA's Information Technology Base Research Program. We constructed an optical pressure sensor by attaching a fiber-optic Bragg grating to a flexible membrane and then adhering the membrane to one end of a small cylinder. The other end of the cylinder was left open and exposed to pressure variations from a pulsed air jet. These pressure variations flexed the membrane, inducing a strain in the fiber-optic grating. This strain was read out optically with a dynamic spectrometer to record changes in the wavelength of light reflected from the grating. The dynamic spectrometer was built in-house to detect very small wavelength shifts induced by the pressure fluctuations. The spectrometer is an unbalanced interferometer specifically designed for maximum sensitivity to wavelength shifts. An optimum pathlength difference, which was determined empirically, resulted in a 14-percent sensitivity improvement over theoretically predicted path-length differences. This difference is suspected to be from uncertainty about the spectral power difference of the signal reflected from the Bragg grating. The figure shows the output of the dynamic spectrometer as the sensor was exposed to a nominally 2-kPa peak-to-peak square-wave pressure fluctuation. Good tracking, sensitivity, and signal-to-noise ratios are evident even though the sensor was constructed as a proof-of-concept and was not optimized in any way. Therefore the fiber-optic Bragg grating, which is normally considered a good candidate as a strain or temperature sensor, also has been shown to be a good candidate for a dynamic pressure sensor.

Metal-Organic Framework Thin Film Coated Optical Fiber Sensors: A Novel Waveguide-Based Chemical Sensing Platform.

PubMed

Kim, Ki-Joong; Lu, Ping; Culp, Jeffrey T; Ohodnicki, Paul R

2018-02-23

Integration of optical fiber with sensitive thin films offers great potential for the realization of novel chemical sensing platforms. In this study, we present a simple design strategy and high performance of nanoporous metal-organic framework (MOF) based optical gas sensors, which enables detection of a wide range of concentrations of small molecules based upon extremely small differences in refractive indices as a function of analyte adsorption within the MOF framework. Thin and compact MOF films can be uniformly formed and tightly bound on the surface of etched optical fiber through a simple solution method which is critical for manufacturability of MOF-based sensor devices. The resulting sensors show high sensitivity/selectivity to CO 2 gas relative to other small gases (H 2 , N 2 , O 2 , and CO) with rapid (

Correction for frequency-dependent hydrophone response to nonlinear pressure waves using complex deconvolution and rarefactional filtering: application with fiber optic hydrophones.

PubMed

Wear, Keith; Liu, Yunbo; Gammell, Paul M; Maruvada, Subha; Harris, Gerald R

2015-01-01

Nonlinear acoustic signals contain significant energy at many harmonic frequencies. For many applications, the sensitivity (frequency response) of a hydrophone will not be uniform over such a broad spectrum. In a continuation of a previous investigation involving deconvolution methodology, deconvolution (implemented in the frequency domain as an inverse filter computed from frequency-dependent hydrophone sensitivity) was investigated for improvement of accuracy and precision of nonlinear acoustic output measurements. Timedelay spectrometry was used to measure complex sensitivities for 6 fiber-optic hydrophones. The hydrophones were then used to measure a pressure wave with rich harmonic content. Spectral asymmetry between compressional and rarefactional segments was exploited to design filters used in conjunction with deconvolution. Complex deconvolution reduced mean bias (for 6 fiber-optic hydrophones) from 163% to 24% for peak compressional pressure (p+), from 113% to 15% for peak rarefactional pressure (p-), and from 126% to 29% for pulse intensity integral (PII). Complex deconvolution reduced mean coefficient of variation (COV) (for 6 fiber optic hydrophones) from 18% to 11% (p+), 53% to 11% (p-), and 20% to 16% (PII). Deconvolution based on sensitivity magnitude or the minimum phase model also resulted in significant reductions in mean bias and COV of acoustic output parameters but was less effective than direct complex deconvolution for p+ and p-. Therefore, deconvolution with appropriate filtering facilitates reliable nonlinear acoustic output measurements using hydrophones with frequency-dependent sensitivity.

Axial strain insensitivity of weakly guiding optical fibers

NASA Technical Reports Server (NTRS)

Egalon, Claudio O.; Rogowski, Robert S.

1993-01-01

A numerical model has been developed to calculate the modal phase shift of circular step index profile weakly guiding fibers under axial strain. Whenever an optical fiber is under stress, the optical path length, the index of refraction, and the propagation constants of each mode change. In consequence, the phase of each mode is also modified. A relationship for the modal phase shift is presented. This relation is applied to both single mode and two-mode fibers in order to determine the sensitivity characteristics of strained fibers. It was found that the phase shift is strongly dependent on the core refractive index, n(co). It was also found that it is possible to design fibers which are insensitive to axial strain. Practical applications of strain insensitive fibers are discussed.

High Sensitivity Refractometer Based on TiO2-Coated Adiabatic Tapered Optical Fiber via ALD Technology

PubMed Central

Zhu, Shan; Pang, Fufei; Huang, Sujuan; Zou, Fang; Guo, Qiang; Wen, Jianxiang; Wang, Tingyun

2016-01-01

Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractometer based on an adiabatic tapered optical fiber. Different thicknesses of titanium dioxide (TiO2) nanofilm were coated around the tapered fiber precisely and uniformly under different deposition cycles. Attributed to the higher refractive index of the TiO2 nanofilm compared to that of silica, an asymmetric Fabry–Perot (F-P) resonator could be constructed along the fiber taper. The central wavelength of the F-P resonator could be controlled by adjusting the thickness of the TiO2 nanofilm. Such a F-P resonator is sensitive to changes in the surrounding refractive index (SRI), which is utilized to realize a high sensitivity refractometer. The refractometer developed by depositing 50.9-nm-thickness TiO2 on the tapered fiber shows SRI sensitivity as high as 7096 nm/RIU in the SRI range of 1.3373–1.3500. Due to TiO2’s advantages of high refractive index, lack of toxicity, and good biocompatibility, this refractometer is expected to have wide applications in the biochemical sensing field. PMID:27537885

Analysis of the mechanics and deformation characteristics of optical fiber acceleration sensor

NASA Astrophysics Data System (ADS)

Liu, Zong-kai; Bo, Yu-ming; Zhou, Ben-mou; Wang, Jun; Huang, Ya-dong

2016-10-01

The optical fiber sensor holds many advantages such as smaller volume, lighter weight, higher sensitivity, and stronger anti-interference ability, etc. It can be applied to oil exploration to improve the exploration efficiency, since the underground petroleum distribution can be obtained by detecting and analyzing the echo signals. In this paper, the cantilever beam optical fiber sensor was mainly investigated. Specifically, the finite element analysis method is applied to the numerical analysis of the changes and relations of the optical fiber rail slot elongation on the surface of the PC material fiber winding plate along with the changes of time and power under the action of sine force. The analysis results show that, when the upper and lower quality blocks are under the action of sine force, the cantilever beam optical fiber sensor structure can basically produce synchronized deformation along with the force. And the optical fiber elongation length basically has a linear relationship with the sine force within the time ranges of 0.2 0.4 and 0.6 0.8, which would be beneficial for the subsequent signal acquisition and data processing.

Apparatus for weighing and identifying characteristics of a moving vehicle

DOEpatents

Muhs, Jeffrey D.; Jordan, John K.; Tobin, Jr., Kenneth W.; LaForge, John V.

1993-01-01

Apparatus for weighing a vehicle in motion is provided by employing a plurality of elongated fiber-optic sensors defined by an optical fiber embedded in an encasement of elastomeric material and disposed parallel to each other on the roadway in the path of moving vehicles. Each fiber-optic sensor is provided with contact grid means which can be selectively altered to provide the fiber-optic sensors with sensitivities to vehicular weight different from each other for weighing vehicles in an extended weight range. Switch means are used in conjunction with the fiber-optic sensors to provide signals indicative of the speed of the moving vehicle, the number of axles on the vehicle, weight distribution, tire position, and the wheelbase of the vehicle. The use of a generally N-shaped configuration of switch means also provides a determination of the number of tires on each axle and the tire footprint. When switch means in this configuration are formed of optical fibers, the extent of light transmission through the fibers during contact with the tires of the vehicle is indicative of the vehicle weight.

Calibration and Deployment of a Fiber-Optic Sensing System for Monitoring Debris Flows

PubMed Central

Huang, Ching-Jer; Chu, Chung-Ray; Tien, Tsung-Mo; Yin, Hsiao-Yuen; Chen, Ping-Sen

2012-01-01

This work presents a novel fiber-optic sensing system, capable of monitoring debris flows or other natural hazards that produce ground vibrations. The proposed sensing system comprises a demodulator (BraggSCOPE, FS5500), which includes a broadband light source and a data logger, a four-port coupler and four Fiber Bragg Grating (FBG) accelerometers. Based on field tests, the performance of the proposed fiber-optic sensing system is compared with that of a conventional sensing system that includes a geophone or a microphone. Following confirmation of the reliability of the proposed sensing system, the fiber-optic sensing systems are deployed along the Ai-Yu-Zi and Chu-Shui Creeks in Nautou County of central Taiwan for monitoring debris flows. Sensitivity test of the deployed fiber-optic sensing system along the creek banks is also performed. Analysis results of the seismic data recorded by the systems reveal in detail the frequency characteristics of the artificially generated ground vibrations. Results of this study demonstrate that the proposed fiber-optic sensing system is highly promising for use in monitoring natural disasters that generate ground vibrations. PMID:22778616

Apparatus for weighing and identifying characteristics of a moving vehicle

DOEpatents

Muhs, J.D.; Jordan, J.K.; Tobin, K.W. Jr.; LaForge, J.V.

1993-11-09

Apparatus for weighing a vehicle in motion is provided by employing a plurality of elongated fiber-optic sensors defined by an optical fiber embedded in an encasement of elastomeric material and disposed parallel to each other on the roadway in the path of moving vehicles. Each fiber-optic sensor is provided with contact grid means which can be selectively altered to provide the fiber-optic sensors with sensitivities to vehicular weight different from each other for weighing vehicles in an extended weight range. Switch means are used in conjunction with the fiber-optic sensors to provide signals indicative of the speed of the moving vehicle, the number of axles on the vehicle, weight distribution, tire position, and the wheelbase of the vehicle. The use of a generally N-shaped configuration of switch means also provides a determination of the number of tires on each axle and the tire footprint. When switch means in this configuration are formed of optical fibers, the extent of light transmission through the fibers during contact with the tires of the vehicle is indicative of the vehicle weight. 15 figures.

Glucose Sensor Using U-Shaped Optical Fiber Probe with Gold Nanoparticles and Glucose Oxidase

PubMed Central

Chen, Kuan-Chieh; Li, Yu-Le; Wu, Chao-Wei

2018-01-01

In this study, we proposed a U-shaped optical fiber probe fabricated using a flame heating method. The probe was packaged in glass tube to reduce human factors during experimental testing of the probe as a glucose sensor. The U-shaped fiber probe was found to have high sensitivity in detecting the very small molecule. When the sensor was dipped in solutions with different refractive indexes, its wavelength or transmission loss changed. We used electrostatic self-assembly to bond gold nanoparticles and glucose oxidase (GOD) onto the sensor’s surface. The results over five cycles of the experiment showed that, as the glucose concentration increased, the refractive index of the sensor decreased and its spectrum wavelength shifted. The best wavelength sensitivity was 2.899 nm/%, and the linearity was 0.9771. The best transmission loss sensitivity was 5.101 dB/%, and the linearity was 0.9734. Therefore, the proposed U-shaped optical fiber probe with gold nanoparticles and GOD has good potential for use as a blood sugar sensor in the future. PMID:29659536

Glucose Sensor Using U-Shaped Optical Fiber Probe with Gold Nanoparticles and Glucose Oxidase.

PubMed

Chen, Kuan-Chieh; Li, Yu-Le; Wu, Chao-Wei; Chiang, Chia-Chin

2018-04-16

In this study, we proposed a U-shaped optical fiber probe fabricated using a flame heating method. The probe was packaged in glass tube to reduce human factors during experimental testing of the probe as a glucose sensor. The U-shaped fiber probe was found to have high sensitivity in detecting the very small molecule. When the sensor was dipped in solutions with different refractive indexes, its wavelength or transmission loss changed. We used electrostatic self-assembly to bond gold nanoparticles and glucose oxidase (GOD) onto the sensor’s surface. The results over five cycles of the experiment showed that, as the glucose concentration increased, the refractive index of the sensor decreased and its spectrum wavelength shifted. The best wavelength sensitivity was 2.899 nm/%, and the linearity was 0.9771. The best transmission loss sensitivity was 5.101 dB/%, and the linearity was 0.9734. Therefore, the proposed U-shaped optical fiber probe with gold nanoparticles and GOD has good potential for use as a blood sugar sensor in the future.

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

PubMed

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

2015-05-04

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

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

PubMed Central

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

2015-01-01

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

Detection of Ultrasonic Stress Waves in Structures Using 3D Shaped Optic Fiber Based on a Mach-Zehnder Interferometer.

PubMed

Lan, Chengming; Zhou, Wensong; Xie, Yawen

2018-04-16

This work proposes a 3D shaped optic fiber sensor for ultrasonic stress waves detection based on the principle of a Mach–Zehnder interferometer. This sensor can be used to receive acoustic emission signals in the passive damage detection methods and other types of ultrasonic signals propagating in the active damage detection methods, such as guided wave-based methods. The sensitivity of an ultrasonic fiber sensor based on the Mach–Zehnder interferometer mainly depends on the length of the sensing optical fiber; therefore, the proposed sensor achieves the maximum possible sensitivity by wrapping an optical fiber on a hollow cylinder with a base. The deformation of the optical fiber is produced by the displacement field of guided waves in the hollow cylinder. The sensor was first analyzed using the finite element method, which demonstrated its basic sensing capacity, and the simulation signals have the same characteristics in the frequency domain as the excitation signal. Subsequently, the primary investigations were conducted via a series of experiments. The sensor was used to detect guided wave signals excited by a piezoelectric wafer in an aluminum plate, and subsequently it was tested on a reinforced concrete beam, which produced acoustic emission signals via impact loading and crack extension when it was loaded to failure. The signals obtained from a piezoelectric acoustic emission sensor were used for comparison, and the results indicated that the proposed 3D fiber optic sensor can detect ultrasonic signals in the specific frequency response range.

Detection of Ultrasonic Stress Waves in Structures Using 3D Shaped Optic Fiber Based on a Mach–Zehnder Interferometer

PubMed Central

Xie, Yawen

2018-01-01

This work proposes a 3D shaped optic fiber sensor for ultrasonic stress waves detection based on the principle of a Mach–Zehnder interferometer. This sensor can be used to receive acoustic emission signals in the passive damage detection methods and other types of ultrasonic signals propagating in the active damage detection methods, such as guided wave-based methods. The sensitivity of an ultrasonic fiber sensor based on the Mach–Zehnder interferometer mainly depends on the length of the sensing optical fiber; therefore, the proposed sensor achieves the maximum possible sensitivity by wrapping an optical fiber on a hollow cylinder with a base. The deformation of the optical fiber is produced by the displacement field of guided waves in the hollow cylinder. The sensor was first analyzed using the finite element method, which demonstrated its basic sensing capacity, and the simulation signals have the same characteristics in the frequency domain as the excitation signal. Subsequently, the primary investigations were conducted via a series of experiments. The sensor was used to detect guided wave signals excited by a piezoelectric wafer in an aluminum plate, and subsequently it was tested on a reinforced concrete beam, which produced acoustic emission signals via impact loading and crack extension when it was loaded to failure. The signals obtained from a piezoelectric acoustic emission sensor were used for comparison, and the results indicated that the proposed 3D fiber optic sensor can detect ultrasonic signals in the specific frequency response range. PMID:29659540

Study on the mechanical analysis and the testing technology of the optical fiber cables released from the bobbin

NASA Astrophysics Data System (ADS)

Wang, Rong; Li, Zhen-hua; Bian, Bao-min; Liu, Cheng-lin; Ji, Yun-jing

2014-12-01

Accurate measurements of forces applied to the optical cable reels with high spinning speeds, will render information on the breakdown of optical fibers, and thus improve the odds of success and un-winding efficiency. In this paper we analyze and deduce the cable wire stress at high pay-off speeds. A high-sensitive opti-mechanical testing sensory device is designed to measure both the axial tension of the cables and the radial pressure of the cable reels at varying stress points simultaneously. The time resolution of this new device is less than 0.015ms, the response time is up to 15μs, and its sensitivity is about 500pc/N, which satisfies the mechanical testing requirements at high spinning speeds. In addition, the spinning speed of 260m/s led to the break-down of the optical fibers, and the spinning speed of 250m/s tested finally led to a deceleration near the end of the broken fibers. It is obvious that this kit can meet the requirement to obtain the periodic signals of the varying forces for each layer and each turn of optical fiber cables. Moreover, we found that the pay-off fiber cable is safe with the unwinding speed of 250m/s and the break-down of optical cables happens during the deceleration process. However, it is under the unwinding speed of 260m/s that pay-off fiber cables broke during the experiment. The abnormal breakdown signals are captured at these unwinding speeds, respectively.

Sensitivity and Specificity of Cardiac Tissue Discrimination Using Fiber-Optics Confocal Microscopy.

PubMed

Huang, Chao; Sachse, Frank B; Hitchcock, Robert W; Kaza, Aditya K

2016-01-01

Disturbances of the cardiac conduction system constitute a major risk after surgical repair of complex cases of congenital heart disease. Intraoperative identification of the conduction system may reduce the incidence of these disturbances. We previously developed an approach to identify cardiac tissue types using fiber-optics confocal microscopy and extracellular fluorophores. Here, we applied this approach to investigate sensitivity and specificity of human and automated classification in discriminating images of atrial working myocardium and specialized tissue of the conduction system. Two-dimensional image sequences from atrial working myocardium and nodal tissue of isolated perfused rodent hearts were acquired using a fiber-optics confocal microscope (Leica FCM1000). We compared two methods for local application of extracellular fluorophores: topical via pipette and with a dye carrier. Eight blinded examiners evaluated 162 randomly selected images of atrial working myocardium (n = 81) and nodal tissue (n = 81). In addition, we evaluated the images using automated classification. Blinded examiners achieved a sensitivity and specificity of 99.2 ± 0.3% and 98.0 ± 0.7%, respectively, with the dye carrier method of dye application. Sensitivity and specificity was similar for dye application via a pipette (99.2 ± 0.3% and 94.0 ± 2.4%, respectively). Sensitivity and specificity for automated methods of tissue discrimination were similarly high. Human and automated classification achieved high sensitivity and specificity in discriminating atrial working myocardium and nodal tissue. We suggest that our findings facilitate clinical translation of fiber-optics confocal microscopy as an intraoperative imaging modality to reduce the incidence of conduction disturbances during surgical correction of congenital heart disease.

A high sensitivity fiber optic macro-bend based gas flow rate transducer for low flow rates: Theory, working principle, and static calibration

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

Schena, Emiliano; Saccomandi, Paola; Silvestri, Sergio

2013-02-15

A novel fiber optic macro-bend based gas flowmeter for low flow rates is presented. Theoretical analysis of the sensor working principle, design, and static calibration were performed. The measuring system consists of: an optical fiber, a light emitting diode (LED), a Quadrant position sensitive Detector (QD), and an analog electronic circuit for signal processing. The fiber tip undergoes a deflection in the flow, acting like a cantilever. The consequent displacement of light spot center is monitored by the QD generating four unbalanced photocurrents which are function of fiber tip position. The analog electronic circuit processes the photocurrents providing voltage signalmore » proportional to light spot position. A circular target was placed on the fiber in order to increase the sensing surface. Sensor, tested in the measurement range up to 10 l min{sup -1}, shows a discrimination threshold of 2 l min{sup -1}, extremely low fluid dynamic resistance (0.17 Pa min l{sup -1}), and high sensitivity, also at low flow rates (i.e., 33 mV min l{sup -1} up to 4 l min{sup -1} and 98 mV min l{sup -1} from 4 l min{sup -1} up to 10 l min{sup -1}). Experimental results agree with the theoretical predictions. The high sensitivity, along with the reduced dimension and negligible pressure drop, makes the proposed transducer suitable for medical applications in neonatal ventilation.« less

Development and evaluation of optical fiber NH3 sensors for application in air quality monitoring

NASA Astrophysics Data System (ADS)

Huang, Yu; Wieck, Lucas; Tao, Shiquan

2013-02-01

Ammonia is a major air pollutant emitted from agricultural practices. Sources of ammonia include manure from animal feeding operations and fertilizer from cropping systems. Sensor technologies with capability of continuous real time monitoring of ammonia concentration in air are needed to qualify ammonia emissions from agricultural activities and further evaluate human and animal health effects, study ammonia environmental chemistry, and provide baseline data for air quality standard. We have developed fiber optic ammonia sensors using different sensing reagents and different polymers for immobilizing sensing reagents. The reversible fiber optic sensors have detection limits down to low ppbv levels. The response time of these sensors ranges from seconds to tens minutes depending on transducer design. In this paper, we report our results in the development and evaluation of fiber optic sensor technologies for air quality monitoring. The effect of change of temperature, humidity and carbon dioxide concentration on fiber optic ammonia sensors has been investigated. Carbon dioxide in air was found not interfere the fiber optic sensors for monitoring NH3. However, the change of humidity can cause interferences to some fiber optic NH3 sensors depending on the sensor's transducer design. The sensitivity of fiber optic NH3 sensors was found depends on temperature. Methods and techniques for eliminating these interferences have been proposed.

Intensity insensitive one-dimensional optical fiber tilt sensor

NASA Astrophysics Data System (ADS)

Vadakkapattu Canthadai, Badrinath; Sengupta, Dipankar; Pachava, Vengalrao; Kishore, P.

2014-06-01

The paper presents a proximity sensor based on plastic optical fiber as tilt sensor. Discrete and continuous response of the sensor against change in tilt angle of the setup is studied. The sensor can detect tilt angles up to 5.70 and the achieved sensor sensitivity is 97mV/0 .

New methods of multimode fiber interferometer signal processing

NASA Astrophysics Data System (ADS)

Vitrik, Oleg B.; Kulchin, Yuri N.; Maxaev, Oleg G.; Kirichenko, Oleg V.; Kamenev, Oleg T.; Petrov, Yuri S.

1995-06-01

New methods of multimode fiber interferometers signal processing are suggested. For scheme of single fiber multimode interferometers with two excited modes, the method based on using of special fiber unit is developed. This unit provides the modes interaction and further sum optical field filtering. As a result the amplitude of output signal is modulated by external influence on interferometer. The stabilization of interferometer sensitivity is achieved by using additional special modulation of output signal. For scheme of single fiber multimode interferometers with excitation of wide mode spectrum, the signal of intermode interference is registered by photodiode matrix and then special electronic unit performs correlation processing. For elimination of temperature destabilization, the registered signal is adopted to multimode interferometers optical signal temperature changes. The achieved parameters for double mode scheme: temporary stability--0.6% per hour, sensitivity to interferometer length deviations--3,2 nm; for multimode scheme: temperature stability--(0.5%)/(K), temporary nonstability--0.2% per hour, sensitivity to interferometer length deviations--20 nm, dynamic range--35 dB.

Research on fiber-optic cantilever-enhanced photoacoustic spectroscopy for trace gas detection

NASA Astrophysics Data System (ADS)

Chen, Ke; Zhou, Xinlei; Gong, Zhenfeng; Yu, Shaochen; Qu, Chao; Guo, Min; Yu, Qingxu

2018-01-01

We demonstrate a new scheme of cantilever-enhanced photoacoustic spectroscopy, combining a sensitivity-improved fiber-optic cantilever acoustic sensor with a tunable high-power fiber laser, for trace gas detection. The Fabry-Perot interferometer based cantilever acoustic sensor has advantages such as high sensitivity, small size, easy to install and immune to electromagnetic. Tunable erbium-doped fiber ring laser with an erbium-doped fiber amplifier is used as the light source for acoustic excitation. In order to improve the sensitivity for photoacoustic signal detection, a first-order longitudinal resonant photoacoustic cell with the resonant frequency of 1624 Hz and a large size cantilever with the first resonant frequency of 1687 Hz are designed. The size of the cantilever is 2.1 mm×1 mm, and the thickness is 10 μm. With the wavelength modulation spectrum and second-harmonic detection methods, trace ammonia (NH3) has been measured. The gas detection limits (signal-to-noise ratio = 1) near the wavelength of 1522.5 nm is achieved to be 3 ppb.

Low-temperature sensitivity periodically tapered photonic crystal-fiber-based refractometer.

PubMed

Wang, Pengfei; Bo, Lin; Guan, Chunying; Semenova, Yuliya; Wu, Qiang; Brambilla, Gilberto; Farrell, Gerald

2013-10-01

In this Letter, an all-fiber refractometer with a simple configuration of periodical tapers on a photonic crystal fiber (PCF) is proposed and investigated experimentally. The proposed fiber refractive index (RI) sensor consists of a PCF sandwiched between two standard single-mode fibers, with tapers periodically fabricated along the PCF using a CO(2) laser beam focused by a ZnSe cylindrical lens. The proposed fiber sensor can be used for RI sensing by measuring the wavelength shift of the multimode interference dip over the transmission spectrum. An average sensitivity of 222 nm/RIU has been experimentally achieved over a RI range from 1.33 to 1.38. The proposed refractometer is also significantly less sensitive to temperature, and an experimental demonstration of this reduced sensitivity is presented. The proposed RI sensor benefits from simplicity and low-cost and achieves a competitive sensitivity compared with other existing fiber-optic sensors.

In-line optical fiber sensors based on cladded multimode tapered fibers.

PubMed

Villatoro, Joel; Monzón-Hernández, David; Luna-Moreno, Donato

2004-11-10

The use of uniform-waist cladded multimode tapered optical fibers is demonstrated for evanescent wave spectroscopy and sensors. The tapering is a simple, low-loss process and consists of stretching the fiber while it is being heated with an oscillating flame torch. As examples, a refractive-index sensor and a hydrogen sensor are demonstrated by use of a conventional graded-index multimode optical fiber. Also, absorbance spectra are measured while the tapers are immersed in an absorbing liquid. It is found experimentally that the uniform waist is the part of the taper that contributes most to the sensor sensitivity. The taper waist diameter may also be used to adjust the sensor dynamic range.

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.

Glucose-Sensitive Hydrogel Optical Fibers Functionalized with Phenylboronic Acid.

PubMed

Yetisen, Ali K; Jiang, Nan; Fallahi, Afsoon; Montelongo, Yunuen; Ruiz-Esparza, Guillermo U; Tamayol, Ali; Zhang, Yu Shrike; Mahmood, Iram; Yang, Su-A; Kim, Ki Su; Butt, Haider; Khademhosseini, Ali; Yun, Seok-Hyun

2017-04-01

Hydrogel optical fibers are utilized for continuous glucose sensing in real time. The hydrogel fibers consist of poly(acrylamide-co-poly(ethylene glycol) diacrylate) cores functionalized with phenylboronic acid. The complexation of the phenylboronic acid and cis-diol groups of glucose enables reversible changes of the hydrogel fiber diameter. The analyses of light propagation loss allow for quantitative glucose measurements within the physiological range. © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

All-optical fiber anemometer based on laser heated fiber Bragg gratings.

PubMed

Gao, Shaorui; Zhang, A Ping; Tam, Hwa-Yaw; Cho, L H; Lu, Chao

2011-05-23

A fiber-optic anemometer based on fiber Bragg gratings (FBGs) is presented. A short section of cobalt-doped fiber was utilized to make a fiber-based "hot wire" for wind speed measurement. Fiber Bragg gratings (FBGs) were fabricated in the cobalt-doped fiber using 193 nm laser pulses to serve as localized temperature sensors. A miniature all-optical fiber anemometer is constructed by using two FBGs to determine the dynamic thermal equilibrium between the laser heating and air flow cooling through monitoring the FBGs' central wavelengths. It was demonstrated that the sensitivity of the sensor can be adjusted through the power of pump laser or the coating on the FBG. Experimental results reveal that the proposed FBG-based anemometer exhibits very good performance for wind speed measurement. The resolution of the FBG-based anemometer is about 0.012 m/s for wind speed range between 2.0 m/s and 8.0 m/s.

Dopants concentration effects on the wavelength shift of long-period fiber gratings used as liquid level detectors

NASA Astrophysics Data System (ADS)

Mao, Barerem-Melgueba; Zhou, Bin

2011-12-01

Two liquid level sensors based on different long-period fiber gratings are proposed and compared. The long-period gratings have the same characteristics (length, grating period) but are fabricated in different optical fibers (photosensitive B-Ge codoped optical fibers with different dopants concentrations). The principle of this type of sensor is based on the refractive index sensitivity of long-period fiber gratings. By monitoring the resonant wavelength shifts of a given attenuation band, one can measure the immersed lengths of long-period fiber gratings and then the liquid level. The levels of two different solutions are measured. The maximum shift (7.69 nm) of the investigated resonance wavelength was observed in LPG1 (fabricated in Fibercore PS1250/1500). By controlling the fiber dopants concentrations one can improve the readouts of a fiber-optic liquid level sensor based on long-period fiber gratings.

Sensitivity optimization of ZnO clad-modified optical fiber humidity sensor by means of tuning the optical fiber waist diameter

NASA Astrophysics Data System (ADS)

Azad, Saeed; Sadeghi, Ebrahim; Parvizi, Roghaieh; Mazaheri, Azardokht; Yousefi, M.

2017-05-01

In this work, the multimode optical fiber size effects on the performances of the clad-modified fiber with ZnO nanorods relative humidity (RH) sensor were experimentally investigated. Simple and controlled chemical etching method through on line monitoring was used to prepare different fiber waist diameter with long length of 15 mm. More precisely, the competition behavior of sensor performances with varying fiber waist diameter was studied to find appropriate size of maximizing evanescent fields. The obtained results revealed that evanescent wave absorption coefficient (γ) enhanced more than 10 times compare to bare fiber at the proposed optimum fiber diameter of 28 μm. Also, high linearity and fast recovery time about 7 s was obtained at the proposed fiber waist diameter. Applicable features of the proposed sensor allow this device to be used for humidity sensing applications, especially to be applied in remote sensing technologies.

Fiber-Optic Sensor-Based Remote Acoustic Emission Measurement in a 1000 °C Environment.

PubMed

Yu, Fengming; Okabe, Yoji

2017-12-14

Recently, the authors have proposed a remote acoustic emission (AE) measurement configuration using a sensitive fiber-optic Bragg grating (FBG) sensor. In the configuration, the FBG sensor was remotely bonded on a plate, and an optical fiber was used as the waveguide to propagate AE waves from the adhesive point to the sensor. The previous work (Yu et al., Smart Materials and Structures 25 (10), 105,033 (2016)) has clarified the sensing principle behind the special remote measurement system that enables accurate remote sensing of AE signals. Since the silica-glass optical fibers have a high heat-resistance exceeding 1000 °C, this work presents a preliminary high-temperature AE detection method by using the optical fiber-based ultrasonic waveguide to propagate the AE from a high-temperature environment to a room-temperature environment, in which the FBG sensor could function as the receiver of the guided wave. As a result, the novel measurement configuration successfully achieved highly sensitive and stable AE detection in an alumina plate at elevated temperatures in the 100 °C to 1000 °C range. Due to its good performance, this detection method will be potentially useful for the non-destructive testing that can be performed in high-temperature environments to evaluate the microscopic damage in heat-resistant materials.

Near-field fluorescence thermometry using highly efficient triple-tapered near-field optical fiber probe.

PubMed

Fujii, T; Taguchi, Y; Saiki, T; Nagasaka, Y

2012-12-01

A novel local temperature measurement method using fluorescence near-field optics thermal nanoscopy (Fluor-NOTN) has been developed. Fluor-NOTN enables nanoscale temperature measurement in situ by detecting the temperature-dependent fluorescence lifetime of CdSe quantum dots (QDs). In this paper, we report a novel triple-tapered near-field optical fiber probe that can increase the temperature measurement sensitivity of Fluor-NOTN. The performance of the proposed probe was numerically evaluated by the finite difference time domain method. Due to improvements in both the throughput and collection efficiency of near-field light, the sensitivity of the proposed probe was 1.9 times greater than that of typical double-tapered probe. The proposed shape of the triple-tapered core was successfully fabricated utilizing a geometrical model. The detected signal intensity of dried layers of QDs was greater by more than two orders than that of auto-fluorescence from the fiber core. In addition, the near-field fluorescence lifetime of the QDs and its temperature dependence were successfully measured by the fabricated triple-tapered near-field optical fiber probe. These measurement results verified the capability of the proposed triple-tapered near-field optical fiber probe to improve the collection efficiency of near-field fluorescence.

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.

High-quality fiber fabrication in buffered hydrofluoric acid solution with ultrasonic agitation.

PubMed

Zhong, Nianbing; Liao, Qiang; Zhu, Xun; Wang, Yongzhong; Chen, Rong

2013-03-01

An etching method for preparing high-quality fiber-optic sensors using a buffered etchant with ultrasonic agitation is proposed. The effects of etching conditions on the etch rate and surface morphology of the etched fibers are investigated. The effect of surface roughness is discussed on the fibers' optical properties. Linear etching behavior and a smooth fiber surface can be repeatedly obtained by adjusting the ultrasonic power and etchant pH. The fibers' spectral quality is improved as the ratio of the pit depth to size decreases, and the fibers with smooth surfaces are more sensitive to a bacterial suspension than those with rough surfaces.

Fiber-optic miniature sensor for in situ temperature monitoring of curing composite material

NASA Astrophysics Data System (ADS)

Sampath, Umesh; Kim, Dae-gil; Kim, Hyunjin; Song, Minho

2018-04-01

This study proposes a fiber-optic temperature sensor with a single-mode fiber tip covered with a thermo-sensitive polymer resin. The temperature is sensed by measuring the Fresnel reflection from the optical fiber/polymer interface. Because the thermo-optic coefficients differ between the optical fiber and the polymer, the in situ temperature can be measured even in curing composite materials. In initial experiments, the proposed sensor successfully measured and recovered the temperature information. The measured sensor data were linearly correlated, with an R2 exceeding 0.99. The standard deviation in the long-term measurements of constant temperature was 2.6%. The durability and stability of the sensor head material in long-term operation was validated by Fourier transform infrared spectroscopy and X-ray diffraction analysis. In further experiments, the suggested miniature temperature sensor obtained the internal temperatures of curing composite material over a wide range (30-110 °C).

Single-mode optical fiber design with wide-band ultra low bending-loss for FTTH application.

PubMed

Watekar, Pramod R; Ju, Seongmin; Han, Won-Taek

2008-01-21

We propose a new design of a single-mode optical fiber (SMF) which exhibits ultra low bend sensitivity over a wide communication band (1.3 microm to 1.65 microm). A five-cladding fiber structure has been proposed to minimize the bending loss, estimated to be as low as 4.4x10(-10) dB/turn for the bend radius of 10 mm.

Multimode fiber tip Fabry-Perot cavity for highly sensitive pressure measurement.

PubMed

Chen, W P; Wang, D N; Xu, Ben; Zhao, C L; Chen, H F

2017-03-23

We demonstrate an optical Fabry-Perot interferometer fiber tip sensor based on an etched end of multimode fiber filled with ultraviolet adhesive. The fiber device is miniature (with diameter of less than 60 μm), robust and low cost, in a convenient reflection mode of operation, and has a very high gas pressure sensitivity of -40.94 nm/MPa, a large temperature sensitivity of 213 pm/°C within the range from 55 to 85 °C, and a relatively low temperature cross-sensitivity of 5.2 kPa/°C. This device has a high potential in monitoring environment of high pressure.

Guided wave and damage detection in composite laminates using different fiber optic sensors.

PubMed

Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Shirai, Takehiro

2009-01-01

Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG) and Doppler effect-based fiber optic (FOD) sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber reinforced plastic (CFRP) laminate and acquired by these fiber optic sensors. Characteristics of these fiber optic sensors in ultrasonic guided wave detection were systematically compared. Results demonstrated that both the FBG and FOD sensors can be applied in guided wave and damage detection for the CFRP laminates. The signal-to-noise ratio (SNR) of guided wave signal captured by an FOD sensor is relatively high in comparison with that of the FBG sensor because of their different physical principles in ultrasonic detection. Further, the FOD sensor is sensitive to the damage-induced fundamental shear horizontal (SH(0)) guided wave that, however, cannot be detected by using the FBG sensor, because the FOD sensor is omnidirectional in ultrasound detection and, in contrast, the FBG sensor is severely direction dependent.

Fiber optic chemical sensors: The evolution of high- density fiber-optic DNA microarrays

NASA Astrophysics Data System (ADS)

Ferguson, Jane A.

2001-06-01

Sensors were developed for multianalyte monitoring, fermentation monitoring, lactate analysis, remote oxygen detection for use in bioremediation monitoring and in a fuel spill clean-up project, heavy metal analysis, and high density DNA microarrays. The major focus of this thesis involved creating and improving high-density DNA gene arrays. Fiber optic sensors are created using fluorescent indicators, polymeric supports, and optical fiber substrates. The fluorescent indicator is entrapped in a polymer layer and attached to the tip of the optical fiber. The tip of the fiber bearing the sensing layer (the distal end) is placed in the sample of interest while the other end of the fiber (the proximal end) is connected to an analysis system. Any length of fiber can be used without compromising the integrity or sensitivity of the system. A fiber optic oxygen sensor was designed incorporating an oxygen sensitive fluorescent dye and a gas permeable polymer attached to an optical fiber. The construction simplicity and ruggedness of the sensor enabled its deployment for in situ chemical oxidation and bioremediation studies. Optical fibers were also used as the substrate to detect biomolecules in solution. To monitor bioprocesses, the production of the analyte of interest must be coupled with a species that is optically measurable. For example, oxygen is consumed in many metabolic functions. The fiber optic oxygen sensor is equipped with an additional sensing layer. Upon contact with a specific biochemical in the sample, a reaction occurs in the additional sensing layer that either consumes or produces oxygen. This dual layer system was used to monitor the presence of lactate, an important metabolite for clinical and bioprocess analysis. In many biological and environmental systems, the generation of one species occurs coincidentally with the generation or consumption of another species. A multianalyte sensor was prepared that can monitor the simultaneous activity of pH, CO2 and O2. This sensor is useful for monitoring bioprocesses such as (beer) fermentation and for clinical situations such as blood gas analysis. DNA sensors were created by attaching short single strands of DNA (probes) to the fiber tip. A matching single strand (target) forms a strong interacting pair with the probe upon contact. The target strands in a sample are labeled with a fluorescent dye. When a probe-target pair is formed and excitation light is sent down the fiber, the fiber bearing the pair emits light that is captured and detected. A high density DNA array was created by isolating thousands of discrete DNA sensors on the tip of an imaging optical fiber. This array was made possible by the formation of microwells on the imaging fiber tip. Microspheres functionalized with DNA were placed in the wells of the fiber and each microsphere was independently and simultaneously monitored. (Abstract shortened by UMI.)

Long-range distributed optical fiber hot-wire anemometer based on chirped-pulse ΦOTDR.

PubMed

Garcia-Ruiz, Andres; Dominguez-Lopez, Alejandro; Pastor-Graells, Juan; Martins, Hugo F; Martin-Lopez, Sonia; Gonzalez-Herraez, Miguel

2018-01-08

We demonstrate a technique allowing to develop a fully distributed optical fiber hot-wire anemometer capable of reaching a wind speed uncertainty of ≈ ±0.15m/s (±0.54km/h) at only 60 mW/m of dissipated power in the sensing fiber, and within only four minutes of measurement time. This corresponds to similar uncertainty values than previous papers on distributed optical fiber anemometry but requires two orders of magnitude smaller dissipated power and covers at least one order of magnitude longer distance. This breakthrough is possible thanks to the extreme temperature sensitivity and single-shot performance of chirped-pulse phase-sensitive optical time domain reflectometry (ΦOTDR), together with the availability of metal-coated fibers. To achieve these results, a modulated current is fed through the metal coating of the fiber, causing a modulated temperature variation of the fiber core due to Joule effect. The amplitude of this temperature modulation is strongly dependent on the wind speed at which the fiber is subject. Continuous monitoring of the temperature modulation along the fiber allows to determine the wind speed with singular low power injection requirements. Moreover, this procedure makes the system immune to temperature drifts of the fiber, potentially allowing for a simple field deployment. Being a much less power-hungry scheme, this method also allows for monitoring over much longer distances, in the orders of 10s of km. We expect that this system can have application in dynamic line rating and lateral wind monitoring in railway catenary wires.

Towards a Uniform Metrological Assessment of Grating-Based Optical Fiber Sensors: From Refractometers to Biosensors

PubMed Central

Chiavaioli, Francesco; Gouveia, Carlos A. J.; Jorge, Pedro A. S.; Baldini, Francesco

2017-01-01

A metrological assessment of grating-based optical fiber sensors is proposed with the aim of providing an objective evaluation of the performance of this sensor category. Attention was focused on the most common parameters, used to describe the performance of both optical refractometers and biosensors, which encompassed sensitivity, with a distinction between volume or bulk sensitivity and surface sensitivity, resolution, response time, limit of detection, specificity (or selectivity), reusability (or regenerability) and some other parameters of generic interest, such as measurement uncertainty, accuracy, precision, stability, drift, repeatability and reproducibility. Clearly, the concepts discussed here can also be applied to any resonance-based sensor, thus providing the basis for an easier and direct performance comparison of a great number of sensors published in the literature up to now. In addition, common mistakes present in the literature made for the evaluation of sensor performance are highlighted, and lastly a uniform performance assessment is discussed and provided. Finally, some design strategies will be proposed to develop a grating-based optical fiber sensing scheme with improved performance. PMID:28635665

Fiber optic refractive index and magnetic field sensors based on microhole-induced inline Mach-Zehnder interferometers

NASA Astrophysics Data System (ADS)

Chen, Feifei; Jiang, Yi; Zhang, Liuchao; Jiang, Lan; Wang, Sumei

2018-04-01

A compact microhole-induced fiber optic inline Mach-Zehnder interferometer (MZI) is demonstrated for measurements of refractive index (RI) and magnetic field. Inline MZIs with different etched diameters, different interaction lengths and different sizes of microholes are fabricated and assessed. The optical transmission spectra of the inline MZIs immersed into a series of liquids are characterized and analysed. Experimental results show that liquid RI sensitivity as high as 539.8436 nm RIU-1 in the RI range of 1.3352-1.4113 RIU is achieved and also exhibits good linearity with a correlation coefficient  >93%. An inline MZI is also fabricated to be a magnetic field sensor by using magnetic fluid material. The experimental results show that this magnetic field sensor has a high sensitivity of  -275.6 pm Oe-1. The inline MZI-based fiber optic sensors possess many advantages, such as small size, simple fabrication, high sensitivity and good linearity, which has a wide application potential in chemical, biological and environmental sensing fields.

Towards a Uniform Metrological Assessment of Grating-Based Optical Fiber Sensors: From Refractometers to Biosensors.

PubMed

Chiavaioli, Francesco; Gouveia, Carlos A J; Jorge, Pedro A S; Baldini, Francesco

2017-06-21

A metrological assessment of grating-based optical fiber sensors is proposed with the aim of providing an objective evaluation of the performance of this sensor category. Attention was focused on the most common parameters, used to describe the performance of both optical refractometers and biosensors, which encompassed sensitivity, with a distinction between volume or bulk sensitivity and surface sensitivity, resolution, response time, limit of detection, specificity (or selectivity), reusability (or regenerability) and some other parameters of generic interest, such as measurement uncertainty, accuracy, precision, stability, drift, repeatability and reproducibility. Clearly, the concepts discussed here can also be applied to any resonance-based sensor, thus providing the basis for an easier and direct performance comparison of a great number of sensors published in the literature up to now. In addition, common mistakes present in the literature made for the evaluation of sensor performance are highlighted, and lastly a uniform performance assessment is discussed and provided. Finally, some design strategies will be proposed to develop a grating-based optical fiber sensing scheme with improved performance.

Optical power-based interrogation of plasmonic tilted fiber Bragg grating biosensors

NASA Astrophysics Data System (ADS)

González-Vila, Á.; Lopez-Aldaba, A.; Kinet, D.; Mégret, P.; Lopez-Amo, M.; Caucheteur, C.

2017-04-01

Two interrogation techniques for plasmonic tilted fiber Bragg grating sensors are reported and experimentally tested. Typical interrogation methods are usually based on tracking the wavelength shift of the most sensitive cladding mode, but for biosensing applications, spectrometer-based methods can be replaced by more efficient solutions. The proposed techniques thus rely on the measurement of the induced changes in optical power. The first one consists of a properly polarized tunable laser source set to emit at the wavelength of the sensor most sensitive mode and an optical power meter to measure the transmitted response. For the second method, a uniform fiber Bragg grating is photo-inscribed beyond the sensor in such a way that its central wavelength matches the sensor most sensitive mode, acting as an optical filter. Using a LED source, light reflected backwards by this grating is partially attenuated when passing through the sensor due to plasmon wave excitation and the power changes are quantified once again with an optical power meter. A performance analysis of the techniques is carried out and they both result competitive interrogation solutions. The work thus focuses on the development of cost-effective alternatives for monitoring this kind of biosensors in practical situations.

Optical fiber evanescent absorption sensors for high-temperature gas sensing in advanced coal-fired power plants

NASA Astrophysics Data System (ADS)

Buric, Michael P.; Ohodnicky, Paul R.; Duy, Janice

2012-10-01

Modern advanced energy systems such as coal-fired power plants, gasifiers, or similar infrastructure present some of the most challenging harsh environments for sensors. The power industry would benefit from new, ultra-high temperature devices capable of surviving in hot and corrosive environments for embedded sensing at the highest value locations. For these applications, we are currently exploring optical fiber evanescent wave absorption spectroscopy (EWAS) based sensors consisting of high temperature core materials integrated with novel high temperature gas sensitive cladding materials. Mathematical simulations can be used to assist in sensor development efforts, and we describe a simulation code that assumes a single thick cladding layer with gas sensitive optical constants. Recent work has demonstrated that Au nanoparticle-incorporated metal oxides show a potentially useful response for high temperature optical gas sensing applications through the sensitivity of the localized surface plasmon resonance absorption peak to ambient atmospheric conditions. Hence, the simulation code has been applied to understand how such a response can be exploited in an optical fiber based EWAS sensor configuration. We demonstrate that interrogation can be used to optimize the sensing response in such materials.

High spatial resolution distributed optical fiber dynamic strain sensor with enhanced frequency and strain resolution.

PubMed

Masoudi, Ali; Newson, Trevor P

2017-01-15

A distributed optical fiber dynamic strain sensor with high spatial and frequency resolution is demonstrated. The sensor, which uses the ϕ-OTDR interrogation technique, exhibited a higher sensitivity thanks to an improved optical arrangement and a new signal processing procedure. The proposed sensing system is capable of fully quantifying multiple dynamic perturbations along a 5 km long sensing fiber with a frequency and spatial resolution of 5 Hz and 50 cm, respectively. The strain resolution of the sensor was measured to be 40 nε.

DNA based thin solid films and its application to optical fiber temperature sensor

NASA Astrophysics Data System (ADS)

Hong, Seongjin; Jung, Woohyun; Kim, Taeoh; Oh, Kyunghwan

2017-04-01

Temperature dependent refractive index of DNA-cetyltrimethylammonium chloride (CTMA) thin-solid-film was measured 20 to 90° to obtain its thermo-optic coefficient of -3.6×10-4 (dn/dT). DNA- CTMA film has high thermosoptic coefficient than other polymers. The film was deposited on coreless silica fiber (CSF) to serve as a multimode interferometer optical fiber temperature sensor. It is immersed in a water that changed temperature from 40 to 90°. It has sensitivity of 0.25nm/℃.

High sensitivity optical fiber liquid level sensor based on a compact MMF-HCF-FBG structure

NASA Astrophysics Data System (ADS)

Zhang, Yunshan; Zhang, Weigang; Chen, Lei; Zhang, Yanxin; Wang, Song; Yan, Tieyi

2018-05-01

An ultra-high sensitivity fiber liquid level sensor based on wavelength demodulation is proposed and demonstrated. The sensor is composed of a segment of multimode fiber and a large aperture hollow-core fiber assisted by a fiber Bragg grating (FBG). Interference occurs due to core mismatching and different modes with different effective refractive indices. The experimental results show that the liquid level sensitivity of the sensor is 1.145 nm mm‑1, and the linearity is up to 0.996. The dynamic temperature compensation of the sensor can be achieved by cascading an FBG. Considering the high sensitivity and compact structure of the sensor, it can be used for real-time intelligent monitoring of tiny changes in liquid level.

Evanescent field refractometry in planar optical fiber.

PubMed

Holmes, Christopher; Jantzen, Alexander; Gray, Alan C; Gow, Paul C; Carpenter, Lewis G; Bannerman, Rex H S; Gates, James C; Smith, Peter G R

2018-02-15

This Letter demonstrates a refractometer in integrated optical fiber, a new optical platform that planarizes fiber using flame hydrolysis deposition (FHD). The unique advantage of the technology is survivability in harsh environments. The platform is mechanically robust, and can survive elevated temperatures approaching 1000°C and exposure to common solvents, including acetone, gasoline, and methanol. For the demonstrated refractometer, fabrication was achieved through wet etching an SMF-28 fiber to a diameter of 8 μm before FHD planarization. An external refractive index was monitored using fiber Bragg gratings (FBGs), written into the core of the planarized fiber. A direct comparison to alternative FBG refractometers is made, for which the developed platform is shown to have comparable sensitivity, with the added advantage of survivability in harsh environments.

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.

Fiber optic temperature sensor gives rise to thermal analysis in complex product design

NASA Astrophysics Data System (ADS)

Cheng, Andrew Y. S.; Pau, Michael C. Y.

1996-09-01

A computer-adapted fiber-optic temperature sensing system has been developed which aims to study both the theoretical aspect of fiber temperature sensing and the experimental aspect of such system. The system consists of a laser source, a fiber sensing element, an electronic fringes counting device, and an on-line personal computer. The temperature measurement is achieved by the conventional double beam fringe counting method with optical path length changes in the sensing beam due to the fiber expansion. The system can automatically measure the temperature changes in a sensing fiber arm which provides an insight of the heat generation and dissipation of the measured system. Unlike the conventional measuring devices such as thermocouples or solid state temperature sensors, the fiber sensor can easily be wrapped and shaped to fit the surface of the measuring object or even inside a molded plastic parts such as a computer case, which gives much more flexibility and applicability to the analysis of heat generation and dissipation in the operation of these machine parts. The reference beam is being set up on a temperature controlled optical bench to facilitate high sensitivity and high temperature resolution. The measuring beam has a motorized beam selection device for multiple fiber beam measurement. The project has been demonstrated in the laboratory and the system sensitivity and resolution are found to be as high as 0.01 degree Celsius. It is expected the system will find its application in many design studies which require thermal budgeting.

Tapered optical fiber tip probes based on focused ion beam-milled Fabry-Perot microcavities

NASA Astrophysics Data System (ADS)

André, Ricardo M.; Warren-Smith, Stephen C.; Becker, Martin; Dellith, Jan; Rothhardt, Manfred; Zibaii, M. I.; Latifi, H.; Marques, Manuel B.; Bartelt, Hartmut; Frazão, Orlando

2016-09-01

Focused ion beam technology is combined with dynamic chemical etching to create microcavities in tapered optical fiber tips, resulting in fiber probes for temperature and refractive index sensing. Dynamic chemical etching uses hydrofluoric acid and a syringe pump to etch standard optical fibers into cone structures called tapered fiber tips where the length, shape, and cone angle can be precisely controlled. On these tips, focused ion beam is used to mill several different types of Fabry-Perot microcavities. Two main cavity types are initially compared and then combined to form a third, complex cavity structure. In the first case, a gap is milled on the tapered fiber tip which allows the external medium to penetrate the light guiding region and thus presents sensitivity to external refractive index changes. In the second, two slots that function as mirrors are milled on the tip creating a silica cavity that is only sensitive to temperature changes. Finally, both cavities are combined on a single tapered fiber tip, resulting in a multi-cavity structure capable of discriminating between temperature and refractive index variations. This dual characterization is performed with the aid of a fast Fourier transform method to separate the contributions of each cavity and thus of temperature and refractive index. Ultimately, a tapered optical fiber tip probe with sub-standard dimensions containing a multi-cavity structure is projected, fabricated, characterized and applied as a sensing element for simultaneous temperature and refractive index discrimination.

Temperature measurement and damage detection in concrete beams exposed to fire using PPP-BOTDA based fiber optic sensors

NASA Astrophysics Data System (ADS)

Bao, Yi; Hoehler, Matthew S.; Smith, Christopher M.; Bundy, Matthew; Chen, Genda

2017-10-01

In this study, Brillouin scattering-based distributed fiber optic sensor is implemented to measure temperature distributions and detect cracks in concrete structures subjected to fire for the first time. A telecommunication-grade optical fiber is characterized as a high temperature sensor with pulse pre-pump Brillouin optical time domain analysis (PPP-BODTA), and implemented to measure spatially-distributed temperatures in reinforced concrete beams in fire. Four beams were tested to failure in a natural gas fueled compartment fire, each instrumented with one fused silica, single-mode optical fiber as a distributed sensor and four thermocouples. Prior to concrete cracking, the distributed temperature was validated at locations of the thermocouples by a relative difference of less than 9%. The cracks in concrete can be identified as sharp peaks in the temperature distribution since the cracks are locally filled with hot air. Concrete cracking did not affect the sensitivity of the distributed sensor but concrete spalling broke the optical fiber loop required for PPP-BOTDA measurements.

MEMS fiber-optic Fabry-Perot pressure sensor for high temperature application

NASA Astrophysics Data System (ADS)

Fang, G. C.; Jia, P. G.; Cao, Q.; Xiong, J. J.

2016-10-01

We design and demonstrate a fiber-optic Fabry-Perot pressure sensor (FOFPPS) for high-temperature sensing by employing micro-electro-mechanical system (MEMS) technology. The FOFPPS is fabricated by anodically bonding the silicon wafer and the Pyrex glass together and fixing the facet of the optical fiber in parallel with the silicon surface by glass frit and organic adhesive. The silicon wafer can be reduced through dry etching technology to construct the sensitive diaphragm. The length of the cavity changes with the deformation of the diaphragm due to the loaded pressure, which leads to a wavelength shift of the interference spectrum. The pressure can be gauged by measuring the wavelength shift. The pressure experimental results show that the sensor has linear pressure sensitivities ranging from 0 kPa to 600 kPa at temperature range between 20°C to 300°C. The pressure sensitivity at 300°C is approximately 27.63 pm/kPa. The pressure sensitivities gradually decrease with increasing the temperature. The sensor also has a linear thermal drift when temperature changes from 20°C - 300°C.

Improved fiber-optic chemical sensor for penicillin

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

Healy, B.G.; Walt, D.R.

An optical penicillin biosensor is described, based on the enzyme penicillinase. The sensor is fabricated by selective photodeposition of analyte-sensitive polymer matrices on optical imaging fibers. The penicillin-sensitive matrices are fabricated by immobilizing the enzyme as micrometer-sized particles in a polymer hydrogel with a covalently bound pH indicator. An array of penicillin-sensitive and pH-sensitive matrices are fabricated on the same fiber. This array allows for the simultaneous, independent measurement of pH and penicillin. Independent measurement of the two analytes allows penicillin to be quantitated in the presence of a concurrent pH change. An analysis was conducted of enzyme kinetic parametersmore » in order to model the penicillin response of the sensor at all pH values. This analysis accounts for the varying activity of the immobilized penicillinase at different pH values. The sensor detects penicillin in the range 0.25-10.0 mM in the pH range 6.2-7.5. The sensor was used to quantify penicillin concentration produced during a Penicillium chrysogenum fermentation. 27 refs., 7 figs., 1 tab.« less

[INVITED] Recent advances in surface plasmon resonance based fiber optic chemical and biosensors utilizing bulk and nanostructures

NASA Astrophysics Data System (ADS)

Gupta, Banshi D.; Kant, Ravi

2018-05-01

Surface plasmon resonance has established itself as an immensely acclaimed and influential optical sensing tool with quintessential applications in life sciences, environmental monitoring, clinical diagnostics, pharmaceutical developments and ensuring food safety. The implementation of sensing principle of surface plasmon resonance employing an optical fiber as a substrate has concomitantly resulted in the evolution of fiber optic surface plasmon resonance as an exceptionally lucrative scaffold for chemical and biosensing applications. This perspective article outlines the contemporary studies on fiber optic sensors founded on the sensing architecture of propagating as well as localized surface plasmon resonance. An in-depth review of the prevalent analytical and surface chemical tactics involved in configuring the sensing layer over an optical fiber for the detection of various chemical and biological entities is presented. The involvement of nanomaterials as a strategic approach to enhance the sensor sensitivity is furnished concurrently providing an insight into the diverse geometrical blueprints for designing fiber optic sensing probes. Representative examples from the literature are discussed to appreciate the latest advancements in this potentially valuable research avenue. The article concludes by identifying some of the key challenges and exploring the opportunities for expanding the scope and impact of surface plasmon resonance based fiber optic sensors.

Influence of the composite material thermal expansion on embedded highly birefringent polymer microstructured optical fibers

NASA Astrophysics Data System (ADS)

SzelÄ g, M.; Lesiak, P.; Kuczkowski, M.; Domański, A. W.; Woliński, T. R.

2013-05-01

Results of our research on embedded highly birefringent polymer microstructured fibers are presented. A composite material sample with fibers embedded between two layers of a multi-layer composite structure is fabricated and characterized. Temperature sensitivities of the polymer fibers are measured in a free space and compared with the fibers embedded in the composite material. It appeared that highly birefringent polymer microstructured fibers exhibit a strong increase in temperature sensitivity when embedded in the composite material, which is due to the stress-induced changes in birefringence created by thermally-induced strain.

Ultrahigh-sensitive multimode interference-based fiber optic liquid-level sensor realized using illuminating zero-order Bessel-Gauss beam

NASA Astrophysics Data System (ADS)

Saha, Ardhendu; Datta, Arijit; Kaman, Surjit

2018-03-01

A proposal toward the enhancement in the sensitivity of a multimode interference-based fiber optic liquid-level sensor is explored analytically using a zero-order Bessel-Gauss (BG) beam as the input source. The sensor head consists of a suitable length of no-core fiber (NCF) sandwiched between two specialty high-order mode fibers. The coupling efficiency of various order modes inside the sensor structure is assessed using guided-mode propagation analysis and the performance of the proposed sensor has been benchmarked against the conventional sensor using a Gaussian beam. Furthermore, the study has been corroborated using a finite-difference beam propagation method in Lumerical's Mode Solutions software to investigate the propagation of the zero-order BG beam inside the sensor structure. Based on the simulation outcomes, the proposed scheme yields a maximum absolute sensitivity of up to 3.551 dB / mm and a sensing resolution of 2.816 × 10 - 3 mm through the choice of an appropriate length of NCF at an operating wavelength of 1.55 μm. Owing to this superior sensing performance, the reported sensing technology expedites an avenue to devise a high-performance fiber optic-level sensor that finds profound implication in different physical, biological, and chemical sensing purposes.

Highly sensitive LIDAR with a thumb-sized sensor-head built using an optical fiber preamplifier (3)

NASA Astrophysics Data System (ADS)

Inoue, Daisuke; Ichikawa, Tadashi; Matsubara, Hiroyuki; Kagami, Manabu

2013-05-01

We have developed a LIDAR system with a sensor head which, although it includes a scanning mechanism, is less than 20 cc in size. The system is not only small, but is also highly sensitive. Our LIDAR system is based on time-of-flight measurements, and incorporates an optical fiber. The main feature of our system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enable us to exceed the detection limit set by thermal noise. In conventional LIDAR systems the detection limit is determined by the thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use detect the received signals directly. In the case of our LIDAR system, the received signal is amplified by an optical fiber amplifier before reaching the photo diode and the TIA. Therefore, our LIDAR system boosts the signal level before the weak incoming signal is depleted by thermal noise. There are conditions under which the noise figure for the combination of an optical fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode. We optimized the gains of the optical fiber amplifier and the TIA in our LIDAR system such that it would be capable of detecting a single photon. As a result, the detection limit of our system is determined by shot noise. We have previously demonstrated scanning up to a range of 80 m with this LIDAR system with a 2 mm diameter of receiving lens. We improved the optical amplifier and the peak output power of LIDAR was over 10KW. We redesigned the sensor-head and improved coupling efficiency. As a result, we succeeded in scanning over a range of 100 m. This small and highly sensitive measurement technology shows great potential for use in LIDAR.

Research on a new fiber-optic axial pressure sensor of transformer winding based on fiber Bragg grating

NASA Astrophysics Data System (ADS)

Liu, Yuan; Li, Lianqing; Zhao, Lin; Wang, Jiqiang; Liu, Tongyu

2017-12-01

Based on the principle of the fiber Bragg grating, a new type of fiber-optic pressure sensor for axial force measurement of transformer winding is designed, which is designed with the structure of bending plate beam, the optimization of the packaging process, and material of the sensor. Through the calibration experiment to calibrate the sensor, the field test results of the Taikai transformer factory show that the sensitivity of the sensor is 0.133 pm/kPa and the repeatability error is 2.7% FS. The data of the fiber-optic pressure sensor in different positions maintain consistent and repeatable, which can meet the requirement of the real-time monitoring of the axial force of transformer winding.

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands

PubMed Central

Vasconcelos, Helena

2018-01-01

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO2) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency. PMID:29677108

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands.

PubMed

de Almeida, José M M M; Vasconcelos, Helena; Jorge, Pedro A S; Coelho, Luis

2018-04-20

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO₂) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency.

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.

Toward Optical Sensors: Review and Applications

NASA Astrophysics Data System (ADS)

Sabri, Naseer; Aljunid, S. A.; Salim, M. S.; Ahmad, R. B.; Kamaruddin, R.

2013-04-01

Recent advances in fiber optics (FOs) and the numerous advantages of light over electronic systems have boosted the utility and demand for optical sensors in various military, industry and social fields. Environmental and atmospheric monitoring, earth and space sciences, industrial chemical processing and biotechnology, law enforcement, digital imaging, scanning, and printing are exemplars of them. The ubiquity of photonic technologies could drive down prices which reduced the cost of optical fibers and lasers. Fiber optic sensors (FOSs) offer a wide spectrum of advantages over traditional sensing systems, such as small size and longer lifetime. Immunity to electromagnetic interference, amenability to multiplexing, and high sensitivity make FOs the sensor technology of choice in several fields, including the healthcare and aerospace sectors. FOSs show reliable and rigid sensing tasks over conventional electrical and electronic sensors. This paper presents an executive review of optical fiber sensors and the most beneficial applications.

Optical bending sensor using distributed feedback solid state dye lasers on optical fiber.

PubMed

Kubota, Hiroyuki; Oomi, Soichiro; Yoshioka, Hiroaki; Watanabe, Hirofumi; Oki, Yuji

2012-07-02

Novel type of optical fiber sensor was proposed and demonstrated. The print-like fabrication technique fabricates multiple distributed feedback solid state dye lasers on a polymeric optical fiber (POF) with tapered coupling. This multi-active-sidecore structure was easily fabricated and provides multiple functions. Mounting the lasers on the same point of a multimode POF demonstrated a bending radius sensitivity of 20 m without any supports. Two axis directional sensing without cross talk was also confirmed. A more complicated mounting formation can demonstrate a twisted POF. The temperature property of the sensor was also studied, and elimination of the temperature influence was experimentally attained.

Refractive-index-sensing fiber comb using intracavity multi-mode interference fiber sensor

NASA Astrophysics Data System (ADS)

Oe, Ryo; Minamikawa, Takeo; Taue, Shuji; Fukano, Hideki; Nakajima, Yoshiaki; Minoshima, Kaoru; Yasui, Takeshi

2018-02-01

Refractive index measurement is important for evaluation of liquid materials, optical components, and bio sensing. One promising approach for such measurement is use of optical fiber sensors such as surface plasmonic resonance or multi-mode interference (MMI), which measure the change of optical spectrum resulting from the refractive index change. However, the precision of refractive index measurement is limited by the performance of optical spectrum analyzer. If such the refractive index measurement can be performed in radio frequency (RF) region in place of optical region, the measurement precision will be further improved by the frequency-standard-based RF measurement. To this end, we focus on the disturbance-to-RF conversion in a fiber optical frequency comb (OFC) cavity. Since frequency spacing frep of OFC depends on an optical cavity length nL, frep sensitively reflects the external disturbance interacted with nL. Although we previously demonstrated the precise strain measurement based on the frep measurement, the measurable physical quantity is limited to strain or temperature, which directly interacts with the fiber cavity itself. If a functional fiber sensor can be installed into the fiber OFC cavity, the measurable physical quantity will be largely expanded. In this paper, we introduce a MMI fiber sensor into a ring-type fiber OFC cavity for refractive index measurement. We confirmed the refractive-index-dependent frep shift.

SU-E-T-159: Characteristics of Fiber-Optic Radiation Sensor for Proton Therapeutic Beam

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

Son, J; Kim, M; Hwang, U

Purpose: A fiber-optic radiation sensor using Cerenkov radiation has been widely studied for use as a dosimeter for proton therapeutic beam. Although the fiber-optic radiation sensor has already been investigated for proton therapeutic, it has been examined relatively little work for clinical therapeutic proton beams. In this study, we evaluated characteristics of a fiber-optic radiation sensor for clinical therapeutic proton beams. We experimentally evaluated dose-rate dependence, dose response and energy dependence for the proton beam. Methods: A fiber-optic radiation sensor was placed in a water phantom. Beams with energies of low, middle and high were used in the passively-scattered protonmore » therapeutic beam at the National Cancer Center in Korea. The sensor consists of two plastic optical fibers (POF). A reference POF and 2 cm longer POF were used to utilize the subtraction method for having sensitive volume. Each POF is optically coupled to the Multi-Anode Photo Multiplier Tube (MAPMT) and the MAPMT signals are processed using National Instruments Data Acquisition System (NI-DAQ). We were investigated dosimetric properties including dose-rate dependence, dose response and energy dependence. Results: We have successfully evaluated characteristics of a fiber optic radiation sensor using Cerenkov radiation. The fiber-optic radiation sensor showed the dose response linearity and low energy dependence. In addition, as the dose-rate was increased, Cerenkov radiation increased linearly. Conclusion: We evaluated the basic characteristics of the fiber optic radiation sensor, the dosimetry tool, to raise the quality of proton therapy. Based on the research, we developed a real time dosimetry system of the optic fiber to confirm the real time beam position and energy for therapeutic proton pencil beam.« less

Metal–Organic Framework Thin Film Coated Optical Fiber Sensors: A Novel Waveguide-Based Chemical Sensing Platform

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

Kim, Ki-Joong; Lu, Ping; Culp, Jeffrey T.

Integration of optical fiber with sensitive thin films offers great potential for the realization of novel chemical sensing platforms. In this study, we present a simple design strategy and high performance of nanoporous metal–organic framework (MOF) based optical gas sensors, which enables detection of a wide range of concentrations of small molecules based upon extremely small differences in refractive indices as a function of analyte adsorption within the MOF framework. Thin and compact MOF films can be uniformly formed and tightly bound on the surface of etched optical fiber through a simple solution method which is critical for manufacturability ofmore » MOF-based sensor devices. The resulting sensors show high sensitivity/selectivity to CO 2 gas relative to other small gases (H 2, N 2, O 2, and CO) with rapid (< tens of seconds) response time and excellent reversibility, which can be well correlated to the physisorption of gases into a nanoporous MOF. We propose a refractive index based sensing mechanism for the MOF-integrated optical fiber platform which results in an amplification of inherent optical absorption present within the MOF-based sensing layer with increasing values of effective refractive index associated with adsorption of gases.« less

Metal–Organic Framework Thin Film Coated Optical Fiber Sensors: A Novel Waveguide-Based Chemical Sensing Platform

DOE PAGES

Kim, Ki-Joong; Lu, Ping; Culp, Jeffrey T.; ...

2018-01-18

Integration of optical fiber with sensitive thin films offers great potential for the realization of novel chemical sensing platforms. In this study, we present a simple design strategy and high performance of nanoporous metal–organic framework (MOF) based optical gas sensors, which enables detection of a wide range of concentrations of small molecules based upon extremely small differences in refractive indices as a function of analyte adsorption within the MOF framework. Thin and compact MOF films can be uniformly formed and tightly bound on the surface of etched optical fiber through a simple solution method which is critical for manufacturability ofmore » MOF-based sensor devices. The resulting sensors show high sensitivity/selectivity to CO 2 gas relative to other small gases (H 2, N 2, O 2, and CO) with rapid (< tens of seconds) response time and excellent reversibility, which can be well correlated to the physisorption of gases into a nanoporous MOF. We propose a refractive index based sensing mechanism for the MOF-integrated optical fiber platform which results in an amplification of inherent optical absorption present within the MOF-based sensing layer with increasing values of effective refractive index associated with adsorption of gases.« less

Multimode-singlemode-multimode fiber sensor for alcohol sensing application

NASA Astrophysics Data System (ADS)

Rofi'ah, Iftihatur; Hatta, A. M.; Sekartedjo, Sekartedjo

2016-11-01

Alcohol is volatile and flammable liquid which is soluble substances both on polar and non polar substances that has been used in some industrial sectors. Alcohol detection method now widely used one of them is the optical fiber sensor. In this paper used fiber optic sensor based on Multimode-Single-mode-Multimode (MSM) to detect alcohol solution at a concentration range of 0-3%. The working principle of sensor utilizes the modal interference between the core modes and the cladding modes, thus make the sensor sensitive to environmental changes. The result showed that characteristic of the sensor not affect the length of the single-mode fiber (SMF). We obtain that the sensor with a length of 5 mm of single-mode can sensing the alcohol with a sensitivity of 0.107 dB/v%.

D-Shaped Polarization Maintaining Fiber Sensor for Strain and Temperature Monitoring.

PubMed

Qazi, Hummad Habib; Mohammad, Abu Bakar; Ahmad, Harith; Zulkifli, Mohd Zamani

2016-09-15

A D-shaped polarization-maintaining fiber (PMF) as fiber optic sensor for the simultaneous monitoring of strain and the surrounding temperature is presented. A mechanical end and edge polishing system with aluminum oxide polishing film is utilized to perform sequential polishing on one side (lengthwise) of the PMF in order to fabricate a D-shaped cross-section. Experimental results show that the proposed sensor has high sensitivity of 46 pm/µε and 130 pm/°C for strain and temperature, respectively, which is significantly higher than other recently reported work (mainly from 2013) related to fiber optic sensors. The easy fabrication method, high sensitivity, and good linearity make this sensing device applicable in various applications such as health monitoring and spatial analysis of engineering structures.

D-Shaped Polarization Maintaining Fiber Sensor for Strain and Temperature Monitoring

PubMed Central

Qazi, Hummad Habib; Mohammad, Abu Bakar; Ahmad, Harith; Zulkifli, Mohd Zamani

2016-01-01

A D-shaped polarization-maintaining fiber (PMF) as fiber optic sensor for the simultaneous monitoring of strain and the surrounding temperature is presented. A mechanical end and edge polishing system with aluminum oxide polishing film is utilized to perform sequential polishing on one side (lengthwise) of the PMF in order to fabricate a D-shaped cross-section. Experimental results show that the proposed sensor has high sensitivity of 46 pm/µε and 130 pm/°C for strain and temperature, respectively, which is significantly higher than other recently reported work (mainly from 2013) related to fiber optic sensors. The easy fabrication method, high sensitivity, and good linearity make this sensing device applicable in various applications such as health monitoring and spatial analysis of engineering structures. PMID:27649195

Measurement Sensitivity Of Liquid Droplet Parameters Using Optical Fibers

NASA Astrophysics Data System (ADS)

Das, Alok K.; Mandal, Anup K.

1990-02-01

A new clad probing technique is used to measure the size, number, refractive index and viscosity of liquid droplets sprayed from a pressure nozzle on an uncoated core-clad fiber. The probe monitors the clad mode power loss within the leaky ray zone represented as a three region fiber. Liquid droplets measured are Glycerine, commercial grade Turpentine, Linseed oil and some oil mixtures. The measurement sensitivity depends on probing conditions and clad diameter which is observed experimentally and verified analytically. A maximum sensitivity is obtained for the tapered probe-fiber diameter made equal to the clad thickness. A slowly tapered probe-fiber and a small end angle as well as separation of the sensor-fiber and the probe-fiber further improve the sensitivity. Under the best probing condition for 90-percent Glycerine droplets of - 50 micron diameter and a 50/125 micron sensor fiber with clad refractive index of 1.465 and 0.2 NA, the measured sensitivity per drop is 0.015 and 0.006 dB, respectively, for (10-20) and (100-200) droplets. Sensitivities for different systems are shown. The sensitivity is optimized by choosing proper fiber for known liquids.

A Portable Array-Type Optical Fiber Sensing Instrument for Real-Time Gas Detection

PubMed Central

Hung, San-Shan; Chang, Hsing-Cheng; Chang, I-Nan

2016-01-01

A novel optical fiber array-type of sensing instrument with temperature compensation for real-time detection was developed to measure oxygen, carbon dioxide, and ammonia simultaneously. The proposed instrument is multi-sensing array integrated with real-time measurement module for portable applications. The sensing optical fibers were etched and polished before coating to increase sensitivities. The ammonia and temperature sensors were each composed of a dye-coated single-mode fiber with constructing a fiber Bragg grating and a long-period filter grating for detecting light intensity. Both carbon dioxide and oxygen sensing structures use multimode fibers where 1-hydroxy-3,6,8-pyrene trisulfonic acid trisodium salt is coated for carbon dioxide sensing and Tris(2,2′-bipyridyl) dichlororuthenium(II) hexahydrate and Tris(bipyridine)ruthenium(II) chloride are coated for oxygen sensing. Gas-induced fluorescent light intensity variation was applied to detect gas concentration. The portable gas sensing array was set up by integrating with photo-electronic measurement modules and a human-machine interface to detect gases in real time. The measured data have been processed using piecewise-linear method. The sensitivity of the oxygen sensor were 1.54%/V and 9.62%/V for concentrations less than 1.5% and for concentrations between 1.5% and 6%, respectively. The sensitivity of the carbon dioxide sensor were 8.33%/V and 9.62%/V for concentrations less than 2% and for concentrations between 2% and 5%, respectively. For the ammonia sensor, the sensitivity was 27.78%/V, while ammonia concentration was less than 2%. PMID:27941636

A Portable Array-Type Optical Fiber Sensing Instrument for Real-Time Gas Detection.

PubMed

Hung, San-Shan; Chang, Hsing-Cheng; Chang, I-Nan

2016-12-08

A novel optical fiber array-type of sensing instrument with temperature compensation for real-time detection was developed to measure oxygen, carbon dioxide, and ammonia simultaneously. The proposed instrument is multi-sensing array integrated with real-time measurement module for portable applications. The sensing optical fibers were etched and polished before coating to increase sensitivities. The ammonia and temperature sensors were each composed of a dye-coated single-mode fiber with constructing a fiber Bragg grating and a long-period filter grating for detecting light intensity. Both carbon dioxide and oxygen sensing structures use multimode fibers where 1-hydroxy-3,6,8-pyrene trisulfonic acid trisodium salt is coated for carbon dioxide sensing and Tris(2,2'-bipyridyl) dichlororuthenium(II) hexahydrate and Tris(bipyridine)ruthenium(II) chloride are coated for oxygen sensing. Gas-induced fluorescent light intensity variation was applied to detect gas concentration. The portable gas sensing array was set up by integrating with photo-electronic measurement modules and a human-machine interface to detect gases in real time. The measured data have been processed using piecewise-linear method. The sensitivity of the oxygen sensor were 1.54%/V and 9.62%/V for concentrations less than 1.5% and for concentrations between 1.5% and 6%, respectively. The sensitivity of the carbon dioxide sensor were 8.33%/V and 9.62%/V for concentrations less than 2% and for concentrations between 2% and 5%, respectively. For the ammonia sensor, the sensitivity was 27.78%/V, while ammonia concentration was less than 2%.

Design and evaluation of capillary coupled with optical fiber light-emitting diode induced fluorescence detection for capillary electrophoresis.

PubMed

Ji, Hongyun; Li, Meng; Guo, Lihong; Yuan, Hongyan; Wang, Chunling; Xiao, Dan

2013-09-01

A new detector, capillary coupled with optical fiber LED-induced fluorescence detector (CCOF-LED-IFD, using CCOF for short), is introduced for CE. The strategy of the present work was that the optical fiber and separation capillary were, in the parallel direction, fastened in a fixation capillary with larger inner diameter. By employing larger inner diameter, the fixation capillary allowed the large diameter of the optical fiber to be inserted into it. By transmitting an enhanced excitation light through the optical fiber, the detection sensitivity was improved. The advantages of the CCOF-CE system were validated by the detection of riboflavin, and the results were compared to those obtained by the in-capillary common optical fiber LED-induced fluorescence detector (IC-COF-LED-IFD, using COF for short). The LODs of CCOF-CE and COF-CE were 0.29 nM and 11.0 nM (S/N = 3), respectively. The intraday (n = 6) repeatability and interday (n = 6) reproducibility of migration time and corresponding peak area for both types of CE were all less than 1.10 and 3.30%, respectively. The accuracy of the proposed method was judged by employing standard addition method, and recoveries obtained were in the range of 98.0-102.4%. The results indicated that the sensitivity of the proposed system was largely improved, and that its reproducibility and accuracy were satisfactory. The proposed system was successfully applied to separate and determine riboflavin in real sample. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nondestructive surface analysis for material research using fiber optic vibrational spectroscopy

NASA Astrophysics Data System (ADS)

Afanasyeva, Natalia I.

2001-11-01

The advanced methods of fiber optical vibrational spectroscopy (FOVS) has been developed in conjunction with interferometer and low-loss, flexible, and nontoxic optical fibers, sensors, and probes. The combination of optical fibers and sensors with Fourier Transform (FT) spectrometer has been used in the range from 2.5 to 12micrometers . This technique serves as an ideal diagnostic tool for surface analysis of numerous and various diverse materials such as complex structured materials, fluids, coatings, implants, living cells, plants, and tissue. Such surfaces as well as living tissue or plants are very difficult to investigate in vivo by traditional FT infrared or Raman spectroscopy methods. The FOVS technique is nondestructive, noninvasive, fast (15 sec) and capable of operating in remote sampling regime (up to a fiber length of 3m). Fourier transform infrared (FTIR) and Raman fiber optic spectroscopy operating with optical fibers has been suggested as a new powerful tool. These techniques are highly sensitive techniques for structural studies in material research and various applications during process analysis to determine molecular composition, chemical bonds, and molecular conformations. These techniques could be developed as a new tool for quality control of numerous materials as well as noninvasive biopsy.

Design of a multimodal fibers optic system for small animal optical imaging.

PubMed

Spinelli, Antonello E; Pagliazzi, Marco; Boschi, Federico

2015-02-01

Small animals optical imaging systems are widely used in pre-clinical research to image in vivo the bio-distribution of light emitting probes using fluorescence or bioluminescence modalities. In this work we presented a set of simulated results of a novel small animal optical imaging module based on a fibers optics matrix, coupled with a position sensitive detector, devoted to acquire bioluminescence and Cerenkov images. Simulations were performed using GEANT 4 code with the GAMOS architecture using the tissue optics plugin. Results showed that it is possible to image a 30 × 30 mm region of interest using a fiber optics array containing 100 optical fibers without compromising the quality of the reconstruction. The number of fibers necessary to cover an adequate portion of a small animal is thus quite modest. This design allows integrating the module with magnetic resonance (MR) in order to acquire optical and MR images at the same time. A detailed model of the mouse anatomy, obtained by segmentation of 3D MRI images, will improve the quality of optical 3D reconstruction. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

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

Phase sensitive distributed vibration sensing based on ultraweak fiber Bragg grating array using double-pulse

NASA Astrophysics Data System (ADS)

Liu, Tao; Wang, Feng; Zhang, Xuping; Zhang, Lin; Yuan, Quan; Liu, Yu; Yan, Zhijun

2017-08-01

A distributed vibration sensing technique using double-optical-pulse based on phase-sensitive optical time-domain reflectometry (ϕ-OTDR) and an ultraweak fiber Bragg grating (UWFBG) array is proposed for the first time. The single-mode sensing fiber is integrated with the UWFBG array that has uniform spatial interval and ultraweak reflectivity. The relatively high reflectivity of the UWFBG, compared with the Rayleigh scattering, gains a high signal-to-noise ratio for the signal, which can make the system achieve the maximum detectable frequency limited by the round-trip time of the probe pulse in fiber. A corresponding experimental ϕ-OTDR system with a 4.5 km sensing fiber integrated with the UWFBG array was setup for the evaluation of the system performance. Distributed vibration sensing is successfully realized with spatial resolution of 50 m. The sensing range of the vibration frequency can cover from 3 Hz to 9 kHz.

DNA-Aptamer optical biosensors based on a LPG-SPR optical fiber platform for point-of-care diagnostic

NASA Astrophysics Data System (ADS)

Coelho, L.; Queirós, R. B.; Santos, J. L.; Martins, M. Cristina L.; Viegas, D.; Jorge, P. A. S.

2014-03-01

Surface Plasmon Resonance (SPR) is the base for some of the most sensitive label free optical fiber biosensors. However, most solutions presented to date require the use of fragile fiber optic structure such as adiabatic tapers or side polished fibers. On the other hand, long-period fiber gratings (LPG) present themselves as an interesting solution to attain an evanescent wave refractive index sensor platform while preserving the optical fiber integrity. The combination of these two approaches constitute a powerful platform that can potentially reach the highest sensitivities as it was recently demonstrated by detailed theoretical study [1, 2]. In this work, a LPG-SPR platform is explored in different configurations (metal coating between two LPG - symmetric and asymmetric) operating in the telecom band (around 1550 nm). For this purpose LPGs with period of 396 μm are combined with tailor made metallic thin films. In particular, the sensing regions were coated with 2 nm of chromium to improve the adhesion to the fiber and 16 nm of gold followed by a 100 nm thick layer of TiO2 dielectric material strategically chosen to attain plasmon resonance in the desired wavelength range. The obtained refractometric platforms were then validated as a biosensor. For this purpose the detection of thrombin using an aptamer based probe was used as a model system for protein detection. The surface of the sensing fibers were cleaned with isopropanol and dried with N2 and then the aminated thrombin aptamer (5'-[NH2]- GGTTGGTGTGGTTGG-3') was immobilized by physisorption using Poly-L-Lysine (PLL) as cationic polymer. Preliminary results indicate the viability of the LPFG-SPR-APTAMER as a flexible platforms point of care diagnostic biosensors.

A wide range and highly sensitive optical fiber pH sensor using polyacrylamide hydrogel

NASA Astrophysics Data System (ADS)

Pathak, Akhilesh Kumar; Singh, Vinod Kumar

2017-12-01

In the present study we report the fabrication and characterization of no-core fiber sensor (NCFS) using smart hydrogel coating for pH measurement. The no-core fiber (NCF) is stubbed between two single-mode fibers with SMA connector before immobilizing of smart hydrogel. The wavelength interrogation technique is used to calculate the sensitivity of the proposed sensor. The result shows a high sensitivity of 1.94 nm/pH for a wide range of pH values varied from 3 to 10 with a good linear response. In addition to high sensitivity, the fabricated sensor provides a fast response time with a good stability, repeatability and reproducibility.

A Micro Bubble Structure Based Fabry–Perot Optical Fiber Strain Sensor with High Sensitivity and Low-Cost Characteristics

PubMed Central

Yan, Lu; Gui, Zhiguo; Wang, Guanjun; An, Yongquan; Gu, Jinyu; Zhang, Meiqin; Liu, Xinglin; Wang, Zhibin; Wang, Gao; Jia, Pinggang

2017-01-01

A high-sensitivity, low-cost, ultrathin, hollow fiber micro bubble structure was proposed; such a bubble can be used to develop a high-sensitivity strain sensor based on a Fabry–Perot interferometer (FPI). The micro bubble is fabricated at the fiber tip by splicing a glass tube to a single mode fiber (SMF) and then the glass tube is filled with gas in order to expand and form a micro bubble. The sensitivity of the strain sensor with a cavity length of about 155 μm and a bubble wall thickness of about 6 μm was measured to be up to 8.14 pm/με. PMID:28282960

A Micro Bubble Structure Based Fabry-Perot Optical Fiber Strain Sensor with High Sensitivity and Low-Cost Characteristics.

PubMed

Yan, Lu; Gui, Zhiguo; Wang, Guanjun; An, Yongquan; Gu, Jinyu; Zhang, Meiqin; Liu, Xinglin; Wang, Zhibin; Wang, Gao; Jia, Pinggang

2017-03-09

A high-sensitivity, low-cost, ultrathin, hollow fiber micro bubble structure was proposed; such a bubble can be used to develop a high-sensitivity strain sensor based on a Fabry-Perot interferometer (FPI). The micro bubble is fabricated at the fiber tip by splicing a glass tube to a single mode fiber (SMF) and then the glass tube is filled with gas in order to expand and form a micro bubble. The sensitivity of the strain sensor with a cavity length of about 155 μm and a bubble wall thickness of about 6 μm was measured to be up to 8.14 pm/μϵ.

Combined imaging and chemical sensing using a single optical imaging fiber.

PubMed

Bronk, K S; Michael, K L; Pantano, P; Walt, D R

1995-09-01

Despite many innovations and developments in the field of fiber-optic chemical sensors, optical fibers have not been employed to both view a sample and concurrently detect an analyte of interest. While chemical sensors employing a single optical fiber or a noncoherent fiberoptic bundle have been applied to a wide variety of analytical determinations, they cannot be used for imaging. Similarly, coherent imaging fibers have been employed only for their originally intended purpose, image transmission. We herein report a new technique for viewing a sample and measuring surface chemical concentrations that employs a coherent imaging fiber. The method is based on the deposition of a thin, analyte-sensitive polymer layer on the distal surface of a 350-microns-diameter imaging fiber. We present results from a pH sensor array and an acetylcholine biosensor array, each of which contains approximately 6000 optical sensors. The acetylcholine biosensor has a detection limit of 35 microM and a fast (< 1 s) response time. In association with an epifluorescence microscope and a charge-coupled device, these modified imaging fibers can display visual information of a remote sample with 4-microns spatial resolution, allowing for alternating acquisition of both chemical analysis and visual histology.

Highly Sensitive Liquid Core Temperature Sensor Based on Multimode Interference Effects

PubMed Central

Fuentes-Fuentes, Miguel A.; May-Arrioja, Daniel A.; Guzman-Sepulveda, José R.; Torres-Cisneros, Miguel; Sánchez-Mondragón, José J.

2015-01-01

A novel fiber optic temperature sensor based on a liquid-core multimode interference device is demonstrated. The advantage of such structure is that the thermo-optic coefficient (TOC) of the liquid is at least one order of magnitude larger than that of silica and this, combined with the fact that the TOC of silica and the liquid have opposite signs, provides a liquid-core multimode fiber (MMF) highly sensitive to temperature. Since the refractive index of the liquid can be easily modified, this allows us to control the modal properties of the liquid-core MMF at will and the sensor sensitivity can be easily tuned by selecting the refractive index of the liquid in the core of the device. The maximum sensitivity measured in our experiments is 20 nm/°C in the low-temperature regime up to 60 °C. To the best of our knowledge, to date, this is the largest sensitivity reported for fiber-based MMI temperature sensors. PMID:26512664

A comprehensive review of lossy mode resonance-based fiber optic sensors

NASA Astrophysics Data System (ADS)

Wang, Qi; Zhao, Wan-Ming

2018-01-01

This review paper presents the achievements and present developments in lossy mode resonances-based optical fiber sensors in different sensing field, such as physical, chemical and biological, and briefly look forward to its future development trend in the eyes of the author. Lossy mode resonances (LMR) is a relatively new physical optics phenomenon put forward in recent years. Fiber sensors utilizing LMR offered a new way to improve the sensing capability. LMR fiber sensors have diverse structures such as D-shaped, cladding-off, fiber tip, U-shaped and tapered fiber structures. Major applications of LMR sensors include refraction sensors and biosensors. LMR-based fiber sensors have attracted considerable research and development interest, because of their distinct advantages such as high sensitivity and label-free measurement. This kind of sensor is also of academic interest and many novel and great ideas are continuously developed.

Collection of Light From an Optical Fiber With a Numerical Aperture Greater Than One

NASA Technical Reports Server (NTRS)

Egalon, Claudio O. (Inventor); Rogowski, Robert S. (Inventor)

1996-01-01

In an optical fiber having NA greater than 1, light may be internally reflected when it strikes the fiber end at a fiber-air interface. This problem may be overcome by modification of the fiber by reverse tapering the core. Light is redirected by the taper to strike the interface at an angle closer to normal. This allows light to exit the fiber end that would by internally reflected in an untapered fiber of NA greater than 1. The novelty of the present invention lies in the tapering of the fiber core for increased through transmission of light. Prior art devices have made use of fiber tapers to achieve mode control or fiber coupling. The problem of internal reflection has not been addressed as it is one that is not as important in fibers having NA less than 1, which are more common. In chemical sensing it is advantageous to make use of fibers having higher NA due to an increased sensitivity. However the advantages in sensitivity are diminished due to the loss of signal at the fiber-air interface. The present invention overcomes the problem of loss at the interface, thus facilitating the use of high NA fibers for chemical sensing.

Sensitive Leptospira DNA detection using tapered optical fiber sensor.

PubMed

Zainuddin, Nurul H; Chee, Hui Y; Ahmad, Muhammad Z; Mahdi, Mohd A; Abu Bakar, Muhammad H; Yaacob, Mohd H

2018-03-23

This paper presents the development of tapered optical fiber sensor to detect a specific Leptospira bacteria DNA. The bacteria causes Leptospirosis, a deadly disease but with common early flu-like symptoms. Optical single mode fiber (SMF) of 125 μm diameter is tapered to produce 12 μm waist diameter and 15 cm length. The novel DNA-based optical fiber sensor is functionalized by incubating the tapered region with sodium hydroxide (NaOH), (3-Aminopropyl) triethoxysilane and glutaraldehyde. Probe DNA is immobilized onto the tapered region and subsequently hybridized by its complementary DNA (cDNA). The transmission spectra of the DNA-based optical fiber sensor are measured in the 1500 to 1600 nm wavelength range. It is discovered that the shift of the wavelength in the SMF sensor is linearly proportional with the increase in the cDNA concentrations from 0.1 to 1.0 nM. The sensitivity of the sensor toward DNA is measured to be 1.2862 nm/nM and able to detect as low as 0.1 fM. The sensor indicates high specificity when only minimal shift is detected for non-cDNA testing. The developed sensor is able to distinguish between actual DNA of Leptospira serovars (Canicola and Copenhageni) against Clostridium difficile (control sample) at very low (femtomolar) target concentrations. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical refractometer based on an asymmetrical twin-core fiber Michelson interferometer.

PubMed

Zhou, Ai; Zhang, Yanhui; Li, Guangping; Yang, Jun; Wang, Yuzhuo; Tian, Fengjun; Yuan, Libo

2011-08-15

We report and demonstrate an optical refractometer based on a compact fiber Michelson interferometer. The Michelson interferometer is composed of an asymmetrical twin-core fiber containing a central core and a side core. By chemically etching a segment of the twin-core fiber until the side core is exposed, the effective index of the side core in the etched region is sensitive to the environmental refractive index, which leads to a shift of the transmission spectrum of the Michelson interferometer. The experimental results show that such a device has a refractive index resolution of more than 800 nm/refractive index unit in the range of 1.34-1.37. © 2011 Optical Society of America

Highly sensitive rotation sensing based on orthogonal fiber-optic structures

NASA Astrophysics Data System (ADS)

Yang, Yi; Wang, Zi-nan; Xu, Lian-yu; Wang, Cui-yun; Jia, Lei; Yu, Xiao-qi; Shao, Shan; Li, Zheng-bin

2011-08-01

In traditional fiber-optic gyroscopes (FOG), the polarization state of counter propagating waves is critically controlled, and only the mode polarized along one particular direction survives. This is important for a traditional single mode fiber gyroscope as the requirement of reciprocity. However, there are some fatal defects such as low accuracy and poor bias stability in traditional structures. In this paper, based on the idea of polarization multiplexing, a double-polarization structure is put forward and experimentally studied. In highly birefringent fibers or standard single mode fibers with induced anisotropy, two orthogonal polarization modes can be used at the same time. Therefore, in polarization maintaining fibers (PMF), each pair of counter propagating beams preserve reciprocity within their own polarization state. Two series of sensing results are gotten in the fast and slow axes in PMF. The two sensing results have their own systematic drifts and the correlation of random noise in them is approximately zero. So, beams in fast and slow axes work as two independent and orthogonal gyroscopes. In this way, amount of information is doubled, providing opportunity to eliminate noise and improve sensitivity. Theoretically, this double-polarization structure can achieve a sensitivity of 10-18 deg/h. Computer simulation demonstrates that random noise and systematic drifts are largely reduced in this novel structure. In experiment, a forty-hour stability test targeting the earth's rotation velocity is carried out. Experiment result shows that the orthogonal fiber-optic structure has two big advantages compared with traditional ones. Firstly, the structure gets true value without any bias correction in any axis and even time-varying bias does not affect the acquisition of true value. The unbiasedness makes the structure very attractive when sudden disturbances or temperature drifts existing in working environment. Secondly, the structure lowers bias for more than two orders and enhances bias stability for an order higher (compared with single axis result), achieving a bias stability of 0.01 deg/h. The evidences from all aspects convincingly show that the orthogonal fiber-optic structure is robust against environmental disturbance and material defects, achieving high stability and sensitivity.

Optic axis determination by fiber-based polarization-sensitive swept-source optical coherence tomography

NASA Astrophysics Data System (ADS)

Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

2011-03-01

We describe a fiber-based variable-incidence-angle (VIA) polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) system to determine the 3-D optical axis of birefringent biological tissues. Single-plane VIAPS- OCT is also explored which requires measurement of the absolute fast-axis orientation. A state-of-the-art PS-SS-OCT system with some improvements both in hardware and software was used to determine the apparent optical birefringence of equine tendon for a number of different illumination directions. Polar and azimuthal angles of cut equine tendon were produced by VIA method and compared with the nominal values. A quarter waveplate (QWP) and equine tendon were used as test targets to validate the fast-axis measurements using the system. Polar and azimuthal angles of cut equine tendon broadly agreed with the expected values within about 8% of the nominal values. A theoretical and experimental analysis of the effect of the sample arm fiber on determination of optical axis orientation using a proposed definition based on the orientation of the eigenpolarization ellipse experimentally confirms that this algorithm only works correctly for special settings of the sample arm fiber. A proposed algorithm based on the angle between Stokes vectors on the Poincaré sphere is confirmed to work for all settings of the sample arm fiber. A calibration procedure is proposed to remove the sign ambiguity of the measured orientation and was confirmed experimentally by using the QWP.

High resolution, high sensitivity, dynamic distributed structural monitoring using optical frequency domain reflectometry

NASA Astrophysics Data System (ADS)

Kreger, Stephen T.; Sang, Alex K.; Garg, Naman; Michel, Julia

2013-05-01

Fiber-optic ultrasonic transducers are an important component of an active ultrasonic testing system for structural health monitoring. Fiber-optic transducers have several advantages such as small size, light weight, and immunity to electromagnetic interference that make them much more attractive than the current available piezoelectric transducers, especially as embedded and permanent transducers in active ultrasonic testing for structural health monitoring. In this paper, a distributed fiber-optic laser-ultrasound generation based on the ghost-mode of tilted fiber Bragg gratings is studied. The influences of the laser power and laser pulse duration on the laser-ultrasound generation are investigated. The results of this paper are helpful to understand the working principle of this laser-ultrasound method and improve the ultrasonic generation efficiency.

Mixed C18 and C1 modification on an optical fiber for chromatographic sensing.

PubMed

Zhou, Leiji; Wang, Kemin; Zuo, Xinbing; Choi, Martin M F; Chen, Yunqing; Huang, Shasheng

2003-09-01

An optical fiber-chromatographic sensor, aiming at simultaneous and selective response to multiple components following a chromatographic separation, is described. We report an improved approach for immobilization of octadecyl (C(18)) and methyl (C(1)) moieties as stationary phase on an optical fiber suitable as a sensing phase for organic solutes. By this approach, the stability and lifetime of the sensing layer as well as the detectability and retention behavior of the chromatographic sensor could be improved. Infrared spectroscopy was employed to confirm the presence of C(18) and C(1) moieties on the modified surface of the optical fiber. The chromatographic sensor was applied, with good sensitivity and chemical selectivity, to the simultaneous separation and detection of bromobenzene and toluene, using water as the mobile phase.

Acceleration Strain Transducer with Increased Sensitivity

DTIC Science & Technology

2009-09-22

utilizing a fiber laser sensor. The fiber laser accelerometer 10 includes a fiber laser 12. Fiber laser 12 can be either a Fabry - Perot type cavity...fiber laser or a distributed feedback fiber laser. In a Fabry - Perot type fiber laser, the laser cavity is a length of erbium- doped optical fiber...designs can produce the same type of signal. A receiver 26 receives the phase shifted signal. Receiver 26 is capable of demodulating and detecting

Enhancement of the sensitivity of gas sensor based on microstructure optical fiber

NASA Astrophysics Data System (ADS)

Morshed, Monir; Hasan, Md. Imran; Razzak, S. M. Abdur

2015-12-01

This paper proposes the design and characterization of microstructure optical fiber for gas sensing applications. The aim is to detect toxic and colorless gases over a wide transmission band covering 0.80 µm to 2.00 µm wavelength. Numerical investigation is carried out by using the finite element method (FEM). The numerical study shows that sensitivity of the proposed sensor is moderately increased by introducing four non-circular holes around the defected core of photonic crystal fiber and the confinement loss is also reduced. Furthermore, we confirm that increasing the diameter of central air core and size of the non-circular holes can improve the relative sensitivity and the confinement loss is reduced by increasing the diameter of air holes in the cladding. The enhancement of the relative sensitivity is more than 27.58% (0.1323 to 0.1688) at the wavelength λ=1.33µm that is the absorption line of methane (CH4) and hydrogen fluoride (HF) gases. The confinement loss of the fiber is 1.765×10-8 dB/m.

Dual-core optical fiber based strain sensor for remote sensing in hard-to-reach areas

NASA Astrophysics Data System (ADS)

MÄ kowska, Anna; Szostkiewicz, Łukasz; Kołakowska, Agnieszka; Budnicki, Dawid; Bieńkowska, Beata; Ostrowski, Łukasz; Murawski, Michał; Napierała, Marek; Mergo, Paweł; Nasiłowski, Tomasz

2017-10-01

We present research on optical fiber sensors based on microstructured multi-core fiber. Elaborated sensor can be advantageously used in hard-to-reach areas by taking advantage of the fact, that optical fibers can play both the role of sensing elements and they can realize signal delivery. By using the sensor, it is possible to increase the level of the safety in the explosive endangered areas, e.g. in mine-like objects. As a base for the strain remote sensor we use dual-core fibers. The multi-core fibers possess a characteristic parameter called crosstalk, which is a measure of the amount of signal which can pass to the adjacent core. The strain-sensitive area is made by creating the tapered section, in which the level of crosstalk is changed. Due to this fact, we present broadened conception of fiber optic sensor designing. Strain measurement is realized thanks to the fact, that depending on the strain applied, the power distribution between the cores of dual-core fibers changes. Principle of operation allows realization of measurements both in wavelength and power domain.

Applications of fiber-optics-based nanosensors to drug discovery.

PubMed

Vo-Dinh, Tuan; Scaffidi, Jonathan; Gregas, Molly; Zhang, Yan; Seewaldt, Victoria

2009-08-01

Fiber-optic nanosensors are fabricated by heating and pulling optical fibers to yield sub-micron diameter tips and have been used for in vitro analysis of individual living mammalian cells. Immobilization of bioreceptors (e.g., antibodies, peptides, DNA) selective to targeting analyte molecules of interest provides molecular specificity. Excitation light can be launched into the fiber, and the resulting evanescent field at the tip of the nanofiber can be used to excite target molecules bound to the bioreceptor molecules. The fluorescence or surface-enhanced Raman scattering produced by the analyte molecules is detected using an ultra-sensitive photodetector. This article provides an overview of the development and application of fiber-optic nanosensors for drug discovery. The nanosensors provide minimally invasive tools to probe subcellular compartments inside single living cells for health effect studies (e.g., detection of benzopyrene adducts) and medical applications (e.g., monitoring of apoptosis in cells treated with anticancer drugs).

A High Sensitivity and Wide Dynamic Range Fiber-Optic Sensor for Low-Concentration VOC Gas Detection

PubMed Central

Khan, Md. Rajibur Rahaman; Kang, Shin-Won

2014-01-01

In this paper, we propose a volatile organic compound (VOC) gas sensing system with high sensitivity and a wide dynamic range that is based on the principle of the heterodyne frequency modulation method. According to this method, the time period of the sensing signal shift when Nile Red containing a VOC-sensitive membrane of a fiber-optic sensing element comes into contact with a VOC. This sensing membrane produces strong, fast and reversible signals when exposed to VOC gases. The response and recovery times of the proposed sensing system were less than 35 s, and good reproducibility and accuracy were obtained. PMID:25490592

Sensitive Detection of Small Particles in Fluids Using Optical Fiber Tip with Dielectrophoresis

PubMed Central

Tai, Yi-Hsin; Chang, Dao-Ming; Pan, Ming-Yang; Huang, Ding-Wei; Wei, Pei-Kuen

2016-01-01

This work presents using a tapered fiber tip coated with thin metallic film to detect small particles in water with high sensitivity. When an AC voltage applied to the Ti/Al coated fiber tip and indium tin oxide (ITO) substrate, a gradient electric field at the fiber tip induced attractive/repulsive force to suspended small particles due to the frequency-dependent dielectrophoresis (DEP) effect. Such DEP force greatly enhanced the concentration of the small particles near the tip. The increase of the local concentration also increased the scattering of surface plasmon wave near the fiber tip. Combined both DEP effect and scattering optical near-field, we show the detection limit of the concentration for 1.36 μm polystyrene beads can be down to 1 particle/mL. The detection limit of the Escherichia coli (E. coli) bacteria was 20 CFU/mL. The fiber tip sensor takes advantages of ultrasmall volume, label-free and simple detection system. PMID:26927128

Adaptable Optical Fiber Displacement-Curvature Sensor Based on a Modal Michelson Interferometer with a Tapered Single Mode Fiber

PubMed Central

Salceda-Delgado, G.; Martinez-Rios, A.; Selvas-Aguilar, R.; Álvarez-Tamayo, R. I.; Castillo-Guzman, A.; Ibarra-Escamilla, B.; Durán-Ramírez, V. M.; Enriquez-Gomez, L. F.

2017-01-01

A compact, highly sensitive optical fiber displacement and curvature radius sensor is presented. The device consists of an adiabatic bi-conical fused fiber taper spliced to a single-mode fiber (SMF) segment with a flat face end. The bi-conical taper structure acts as a modal coupling device between core and cladding modes for the SMF segment. When the bi-conical taper is bent by an axial displacement, the symmetrical bi-conical shape of the tapered structure is stressed, causing a change in the refractive index profile which becomes asymmetric. As a result, the taper adiabaticity is lost, and interference between modes appears. As the bending increases, a small change in the fringe visibility and a wavelength shift on the periodical reflection spectrum of the in-fiber interferometer is produced. The displacement sensitivity and the spectral periodicity of the device can be adjusted by the proper selection of the SMF length. Sensitivities from around 1.93 to 3.4 nm/mm were obtained for SMF length between 7.5 and 12.5 cm. Both sensor interrogations, wavelength shift and visibility contrast, can be used to measure displacement and curvature radius magnitudes. PMID:28574421

Adaptable Optical Fiber Displacement-Curvature Sensor Based on a Modal Michelson Interferometer with a Tapered Single Mode Fiber.

PubMed

Salceda-Delgado, G; Martinez-Rios, A; Selvas-Aguilar, R; Álvarez-Tamayo, R I; Castillo-Guzman, A; Ibarra-Escamilla, B; Durán-Ramírez, V M; Enriquez-Gomez, L F

2017-06-02

A compact, highly sensitive optical fiber displacement and curvature radius sensor is presented. The device consists of an adiabatic bi-conical fused fiber taper spliced to a single-mode fiber (SMF) segment with a flat face end. The bi-conical taper structure acts as a modal coupling device between core and cladding modes for the SMF segment. When the bi-conical taper is bent by an axial displacement, the symmetrical bi-conical shape of the tapered structure is stressed, causing a change in the refractive index profile which becomes asymmetric. As a result, the taper adiabaticity is lost, and interference between modes appears. As the bending increases, a small change in the fringe visibility and a wavelength shift on the periodical reflection spectrum of the in-fiber interferometer is produced. The displacement sensitivity and the spectral periodicity of the device can be adjusted by the proper selection of the SMF length. Sensitivities from around 1.93 to 3.4 nm/mm were obtained for SMF length between 7.5 and 12.5 cm. Both sensor interrogations, wavelength shift and visibility contrast, can be used to measure displacement and curvature radius magnitudes.

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.

Fiber optic hydrogen sensors: a review

NASA Astrophysics Data System (ADS)

Yang, Minghong; Dai, Jixiang

2014-12-01

Hydrogen is one of the next generation energies in the future, which shows promising applications in aerospace and chemical industries. Hydrogen leakage monitoring is very dangerous and important because of its low ignition energy, high combustion efficiency, and smallest molecule. This paper reviews the state-of-art development of the fiber optic hydrogen sensing technology. The main developing trends of fiber optic hydrogen sensors are based on two kinds of hydrogen sensitive materials, i.e. palladium-alloy thin films and Pt-doped WO3 coatings. In this review work, the advantages and disadvantages of these two kinds of sensing technologies will be evaluated.

A Temperature Sensor Based on a Polymer Optical Fiber Macro-Bend

PubMed Central

Moraleda, Alberto Tapetado; García, Carmen Vázquez; Zaballa, Joseba Zubia; Arrue, Jon

2013-01-01

The design and development of a plastic optical fiber (POF) macrobend temperature sensor is presented. The sensor has a linear response versus temperature at a fixed bend radius, with a sensitivity of 1.92·10−3 (°C)−1. The sensor system used a dummy fiber-optic sensor for reference purposes having a resolution below 0.3 °C. A comprehensive experimental analysis was carried out to provide insight into the effect of different surrounding media on practical macro-bend POF sensor implementation. Experimental results are successfully compared with bend loss calculations. PMID:24077323

Optic fiber pulse-diagnosis sensor of traditional Chinese medicine

NASA Astrophysics Data System (ADS)

Ni, J. S.; Jin, W.; Zhao, B. N.; Zhang, X. L.; Wang, C.; Li, S. J.; Zhang, F. X.; Peng, G. D.

2013-09-01

The wrist-pulse is a kind of signals, from which a lot of physiological and pathological status of patients are deduced according to traditional Chinese medicine theories. This paper designs a new optic fiber wrist-pulse sensor that based on a group of FBGs. Sensitivity of the optic fiber wrist-pulse measurement system reaches 0.05% FS and the range reaches 50kPa. Frequency response is from 0 Hz to 5 kHz. A group of typical pulse signal is given out in the paper to compare different status of patient. It will improve quantification of pulse diagnosis greatly.

Compact and cost-effective multi-channel optical spectrometer for fine FBG sensing in IoT technology

NASA Astrophysics Data System (ADS)

Konishi, Tsuyoshi; Yamasaki, Yu

2018-02-01

Optical fiber sensor networks have attracted much attention in IoT technology and a fiber Bragg grating is one of key sensor devices there because of their advantages in a high affinity for optical fiber networks, compactness, immunity to electromagnetic interference and so on. Nevertheless, its sensitivity is not always satisfactory so as to be usable together with widespread cost-effective multi-channel spectrometers. In this paper, we introduce a new cost-effective approach for a portable multi-channel spectrometer with high spectral resolution and demonstrates some preliminary experimental results for fine FBG sensing.

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.

Self-Referenced Fiber Optic System For Remote Methane Detection

NASA Astrophysics Data System (ADS)

Zientkiewicz, Jacek K.

1989-10-01

The paper discusses a fiber optic multisensor methane detection system matched to topology and environment of the underground mine. The system involves time domain multiplexed (TDM) methane sensors based on selective absorption of source radiation by atomic/molecular species in the gas sensing heads. A two-wavelength ratiometric approach allows simple self-referencing, cancels out errors arising from other contaminants, and improves the measurement contrast. The laboratory system consists of a high radiance LED source, multimode fiber, optical sensing head, optical bandpass filters, and involves synchronous detection with low noise photodiodes and a lock-in amplifier. Detection sensitivity versus spectral resolution of the optical filters has also been investigated and described. The system performance was evaluated and the results are presented.

Ultrafast optics. Ultrafast optical control by few photons in engineered fiber.

PubMed

Nissim, R; Pejkic, A; Myslivets, E; Kuo, B P; Alic, N; Radic, S

2014-07-25

Fast control of a strong optical beam by a few photons is an outstanding challenge that limits the performance of quantum sensors and optical processing devices. We report that a fast and efficient optical gate can be realized in an optical fiber that has been engineered with molecular-scale accuracy. Highly efficient, distributed phase-matched photon-photon interaction was achieved in the fiber with locally controlled, nanometer-scale core variations. A three-photon input was used to manipulate a Watt-scale beam at a speed exceeding 500 gigahertz. In addition to very fast beam control, the results provide a path to developing a new class of sensitive receivers capable of operating at very high rates. Copyright © 2014, American Association for the Advancement of Science.

Graphene based chalcogenide fiber-optic evanescent wave sensor for detection of hemoglobin in human blood

NASA Astrophysics Data System (ADS)

Sharma, Anuj K.; Gupta, Jyoti

2018-03-01

Fiber optic evanescent wave sensor with graphene as an absorption-enhancing layer to measure hemoglobin concentration in human blood is proposed. Previous modal functions and experimental results describing the variation of optical constants of human blood with different hemoglobin concentrations in the near-infrared spectral region are considered for sensor design simulation. The sensor's performance is closely analyzed in terms of its absorption coefficient, sensitivity, and detection limit. It is found that the proposed sensor should be operated at longer light wavelength to get more enhanced sensitivity and smaller detection limit. At 1000 nm wavelength, a detection limit of 18 μg/dL and sensitivity of 6.71 × 10-4 per g/dL is achievable with the proposed sensor. The sensitivity is found to be better for larger hemoglobin concentrations. The results are correlated with the evanescent wave penetration depth.

Sensitivity-enhanced optical temperature sensor with cascaded LPFGs

NASA Astrophysics Data System (ADS)

Tsutsumi, Yasuhiro; Miyoshi, Yuji; Ohashi, Masaharu

2011-12-01

We propose a new structure of optical fiber temperature sensor with cascaded long-period fiber gratings (LPFGs) and investigate the temperature dependent loss of cascaded LFPGs. Each of the cascaded LPFGs has the same resonance wavelength with the same temperature change, because the cascaded LPFGs are made of a heat-shrinkable tube and a screw. The total resonance loss of proposed cascaded LPFGs shows higher temperature sensitivity than that of a single LPFG. The thermal coefficient of 4-cascaded LPFG also shows more than 4 times larger than that of a single one.

The detection of organophosphonates by polymer films on a surface acoustic wave device and a micromirror fiber optic sensor

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

Hughes, R.C.; Ricco, A.J.; Butler, M.A.

There is a need for sensitive detection of organophosphonates by, inexpensive, portable instruments. Two kinds of chemical sensors, based on surface acoustic wave (SAW) devices and fiber optic micromirrors, show promise for such sensing systems. Chemically sensitive coatings are required for detection and data for thin films of the polymer polysiloxane are reported for both kinds of physical transducers. Both kinds of sensor are shown to be capable of detecting concentrations of diisopropylmethylphosphonate (DIMP) down to 1 ppM.

Label-Free Detection of Cancer Biomarkers Using an In-Line Taper Fiber-Optic Interferometer and a Fiber Bragg Grating

PubMed Central

Sun, Dandan; Wang, Guanjun

2017-01-01

A compact and label-free optical fiber sensor based on a taper interferometer cascaded with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for detection of a breast cancer biomarker (HER2). The tapered fiber-optic interferometer is extremely sensitive to the ambient refractive index (RI). In addition, being insensitive to the RI variation, the FBG can be applied as a temperature thermometer due to its independent response to the temperature. Surface functionalization to the sensor is carried out to achieve specific targeting of the unlabeled biomarkers. The result shows that the proposed sensor presents a low limit-of-detection (LOD) of 2 ng/mL, enabling its potentials of application in early diagnosis on the breast cancer. PMID:29113127

A fusion-spliced near-field optical fiber probe using photonic crystal fiber for nanoscale thermometry based on fluorescence-lifetime measurement of quantum dots.

PubMed

Fujii, Takuro; Taguchi, Yoshihiro; Saiki, Toshiharu; Nagasaka, Yuji

2011-01-01

We have developed a novel nanoscale temperature-measurement method using fluorescence in the near-field called fluorescence near-field optics thermal nanoscopy (Fluor-NOTN). Fluor-NOTN enables the temperature distributions of nanoscale materials to be measured in vivo/in situ. The proposed method measures temperature by detecting the temperature dependent fluorescence lifetimes of Cd/Se quantum dots (QDs). For a high-sensitivity temperature measurement, the auto-fluorescence generated from a fiber probe should be reduced. In order to decrease the noise, we have fabricated a novel near-field optical-fiber probe by fusion-splicing a photonic crystal fiber (PCF) and a conventional single-mode fiber (SMF). The validity of the novel fiber probe was assessed experimentally by evaluating the auto-fluorescence spectra of the PCF. Due to the decrease of auto-fluorescence, a six- to ten-fold increase of S/N in the near-field fluorescence lifetime detection was achieved with the newly fabricated fusion-spliced near-field optical fiber probe. Additionally, the near-field fluorescence lifetime of the quantum dots was successfully measured by the fabricated fusion-spliced near-field optical fiber probe at room temperature, and was estimated to be 10.0 ns.

Sensitivity-enhanced Tm3+/Yb3+ co-doped YAG single crystal optical fiber thermometry based on upconversion emissions

NASA Astrophysics Data System (ADS)

Yu, Lu; Ye, Linhua; Bao, Renjie; Zhang, Xianwei; Wang, Li-Gang

2018-03-01

Optical thermometry based on Y3Al5O12 (YAG) single crystal optical fiber with end Tm3+/Yb3+ co-doped is presented. The YAG crystal fiber with end Tm3+/Yb3+ co-doped was grown by laser heated pedestal growth (LHPG) method. Under a 976 nm laser diode excitation, the upconversion (UC) emissions, originating from 3F2,3 →3H6 and 3H4 →3H6 transitions of Tm3+ ions, were investigated in the temperature range from 333 K to 733 K. Interestingly, the UC emission intensity of 3F2,3 →3H6 transition was significantly enhanced with increase of temperature, as compared with the other Tm3+/Yb3+ co-doped materials. The temperature dependence of fluorescence intensity ratio (FIR) of these two emission bands (3F2,3/3H4 →3H6) suggests that this doped YAG crystal fiber can be used as a highly sensitive optical thermal probe, which demonstrates a high absolute sensitivity with the maximum value of 0.021 K-1 at 733 K. In addition, due to the compact structure, strong mechanical strength and high thermal stability, such thermal probe may be a more promising candidate for temperature sensor with a high spatial resolution.

A double-taper optical fiber-based radiation wave other than evanescent wave in all-fiber immunofluorescence biosensor for quantitative detection of Escherichia coli O157:H7.

PubMed

Zhang, Zhonghuan; Hua, Fei; Liu, Ting; Zhao, Yong; Li, Jun; Yang, Ruifu; Yang, Changxi; Zhou, Lei

2014-01-01

Cylindrical or taper-and-cylinder combination optical fiber probe based on evanescent wave has been widely used for immunofluorescence biosensor to detect various analytes. In this study, in contrast to the contradiction between penetration depth and analyte diameter of optical fiber probe-based evanescent wave, we demonstrate that double-taper optical fiber used in a radiation wave-based all-fiber immunofluorescence biosensor (RWAIB) can detect micron-scale analytes using Escherichia coli O157:H7 as representative target. Finite-difference time-domain method was used to compare the properties of evanescent wave and radiation wave (RW). Ray-tracing model was formulated to optimize the taper geometry of the probe. Based on a commercial multi-mode fiber, a double-taper probe was fabricated and connected with biosensor through a "ferrule connector" optical fiber connector. The RWAIB configuration was accomplished using commercial multi-mode fibers and fiber-based devices according to the "all-fiber" method. The standard sample tests revealed that the sensitivity of the proposed technique for E. coli O157:H7 detection was 10(3) cfu · mL(-1). Quantitation could be achieved within the concentration range of 10(3) cfu · mL(-1) to 107 cfu · mL(-1). No non-specific recognition to ten kinds of food-borne pathogens was observed. The results demonstrated that based on the double-taper optical fiber RWAIB can be used for the quantitative detection of micron-scale targets, and RW sensing is an alternative for traditional evanescent wave sensing during the fabrication of fiber-optic biosensors.

Evanescent wave absorbance based fiber optic biosensor for label-free detection of E. coli at 280 nm wavelength.

PubMed

Bharadwaj, Reshma; Sai, V V R; Thakare, Kamini; Dhawangale, Arvind; Kundu, Tapanendu; Titus, Susan; Verma, Pradeep Kumar; Mukherji, Soumyo

2011-03-15

A novel label-free technique for the detection of pathogens based on evanescent wave absorbance (EWA) changes at 280 nm from a U-bent optical fiber sensor is demonstrated. Bending a decladded fiber into a U-shaped structure enhances the penetration depth of evanescent waves and hence sensitivity of the probe. We show that the enhanced EWA response from such U-bent probes, caused by the inherent optical absorbance properties of bacterial cells or biomolecules specifically bound to the sensor surface, can be exploited for the detection of pathogens. A portable optical set-up with a UV light emitting diode, a spectrometer and U-bent fiber optic probe of 200 μm core diameter, 0.75 mm bend radius and effective probe length of 1cm demonstrated an ability to detect less than 1000 cfu/ml. Copyright © 2011. Published by Elsevier B.V.

Temperature Measurement and Damage Detection in Concrete Beams Exposed to Fire Using PPP-BOTDA Based Fiber Optic Sensors.

PubMed

Bao, Yi; Hoehler, Matthew S; Smith, Christopher M; Bundy, Matthew; Chen, Genda

2017-10-01

In this study, distributed fiber optic sensors based on pulse pre-pump Brillouin optical time domain analysis (PPP-BODTA) are characterized and deployed to measure spatially-distributed temperatures in reinforced concrete specimens exposed to fire. Four beams were tested to failure in a natural gas fueled compartment fire, each instrumented with one fused silica, single-mode optical fiber as a distributed sensor and four thermocouples. Prior to concrete cracking, the distributed temperature was validated at locations of the thermocouples by a relative difference of less than 9 %. The cracks in concrete can be identified as sharp peaks in the temperature distribution since the cracks are locally filled with hot air. Concrete cracking did not affect the sensitivity of the distributed sensor but concrete spalling broke the optical fiber loop required for PPP-BOTDA measurements.

Variable angle-of-incidence polarization-sensitive optical coherence tomography: its use to study the 3D collagen structure of equine articular cartilage

NASA Astrophysics Data System (ADS)

Ugryumova, Nadya; Gangnus, Sergei V.; Matcher, Stephen J.

2006-02-01

Polarization-sensitive optical coherence tomography has been used to spatially map the birefringence of equine articular cartilage. The polar orientation of the collagen fibers relative to the plane of the joint surface must be taken into account if a quantitative measurement of true birefringence is required. Using a series of images taken at different angles of illumination, we determine the fiber polar angle and true birefringence at one site on a sample of equine cartilage, on the assumption that the fibers lie within the plane of imaging. We propose a more general method based on the extended Jones matrix formalism to determine both the polar and azimuthal orientation of the collagen fibers as well as the true birefringence as functions of depth.

Plasmonic nanoshell functionalized etched fiber Bragg gratings for highly sensitive refractive index measurements.

PubMed

Burgmeier, Jörg; Feizpour, Amin; Schade, Wolfgang; Reinhard, Björn M

2015-02-15

A novel fiber optical refractive index sensor based on gold nanoshells immobilized on the surface of an etched single-mode fiber including a Bragg grating is demonstrated. The nanoparticle coating induces refractive index dependent waveguide losses, because of the variation of the evanescently guided part of the light. Hence the amplitude of the Bragg reflection is highly sensitive to refractive index changes of the surrounding medium. The nanoshell functionalized fiber optical refractive index sensor works in reflectance mode, is suitable for chemical and biochemical sensing, and shows an intensity dependency of 4400% per refractive index unit in the refractive index range between 1.333 and 1.346. Furthermore, the physical length of the sensor is smaller than 3 mm with a diameter of 6 μm, and therefore offers the possibility of a localized refractive index measurement.

Measuring electrically charged particle fluxes in space using a fiber optic loop sensor

NASA Technical Reports Server (NTRS)

1992-01-01

The purpose of this program was to demonstrate the potential of a fiber optic loop sensor for the measurement of electrically charged particle fluxes in space. The key elements of the sensor are a multiple turn loop of low birefringence, single mode fiber, with a laser diode light source, and a low noise optical receiver. The optical receiver is designed to be shot noise limited, with this being the limiting sensitivity factor for the sensor. The sensing element is the fiber optic loop. Under a magnetic field from an electric current flowing along the axis of the loop, there is a non-vanishing line integral along the fiber optic loop. This causes a net birefringence producing two states of polarization whose phase difference is correlated to magnetic field strength and thus, current in the optical receiver electronic processing. The objectives in this program were to develop a prototype laser diode powered fiber optic sensor. The performance specification of a minimum detectable current density of 1 (mu)amp/sq m-(radical)Hz, should be at the shot noise limit of the detection electronics. OPTRA has successfully built and tested a 3.2 m diameter loop with 137 turns of low birefringence optical fiber and achieved a minimum detectable current density of 5.4 x 10(exp-5) amps/(radical)Hz. If laboratory space considerations were not an issue, with the length of optical fiber available to us, we would have achieved a minimum detectable current density of 4 x 10(exp -7) amps/(radical)Hz.

10-Gbps optical duobinary signal generated by bandwidth-limited reflective semiconductor optical amplifier in colorless optical network units and compensated by fiber Bragg grating-based equalizer in optical line terminal

NASA Astrophysics Data System (ADS)

Fu, Meixia; Zhang, Min; Wang, Danshi; Cui, Yue; Han, Huanhuan

2016-10-01

We propose a scheme of optical duobinary-modulated upstream transmission system for reflective semiconductor optical amplifier-based colorless optical network units in 10-Gbps wavelength-division multiplexed passive optical network (WDM-PON), where a fiber Bragg grating (FBG) is adopted as an optical equalizer for better performance. The demodulation module is extremely simple, only needing a binary intensity modulation direct detection receiver. A better received sensitivity of -16.98 dBm at bit rate error (BER)=1.0×10-4 can be achieved at 120 km without FBG, and the BER at the sensitivity of -18.49 dBm can be up to 2.1×10-5 at the transmission distance of 160 km with FBG, which demonstrates the feasibility of our proposed scheme. Moreover, it could be a high cost-effectiveness scheme for WDM-PON in the future.

Optical bio-sniffer for ethanol vapor using an oxygen-sensitive optical fiber.

PubMed

Mitsubayashi, Kohji; Kon, Takuo; Hashimoto, Yuki

2003-11-30

An optical bio-sniffer for ethanol was constructed by immobilizing alcohol oxidase (AOD) onto a tip of a fiber optic oxygen sensor with a tube-ring, using an oxygen sensitive ruthenium organic complex (excitation, 470 nm; fluorescent, 600 nm). A reaction unit for circulating buffer solution was applied to the tip of the device. After the experiment in the liquid phase, the sniffer-device was applied for gas analysis using a gas flow measurement system with a gas generator. The optical device was applied to detect the oxygen consumption induced by AOD enzymatic reaction with alcohol application. The sensor in the liquid phase was used to measure ethanol solution from 0.50 to 9.09 mmol/l. Then, the bio-sniffer was calibrated against ethanol vapor from 0.71 to 51.49 ppm with good gas-selectivity based on the AOD substrate specificity. The bio-sniffer with the reaction unit was also used to monitor the concentration change of gaseous ethanol by rinsing and cleaning the fiber tip and the enzyme membrane with buffer solution.

Refractive index sensor based on plastic optical fiber with tapered structure.

PubMed

De-Jun, Feng; Guan-Xiu, Liu; Xi-Lu, Liu; Ming-Shun, Jiang; Qing-Mei, Sui

2014-04-01

This work reports a refractive index sensor made of plastic optical fiber (POF) with tapered structure. Transmission loss is measured when the external environment's refractive index changes from 1.33 to 1.41. Three wavelengths (532, 633, and 780 nm) are used to evaluate the sensitivity of the sensor, and results indicate that 633 nm is the best sensing wavelength due to the increased levels of sensitivity achieved at this wavelength. A biconical sensing structure is designed to enhance the sensitivity of the sensor. A sensitivity of 950 μW/RIU at 633 nm is obtained for a biconical sensing structure when launched power is 1 mW. Due to its sensitivity to the refractive index and simple construction, POF with tapered structure has potential applications in the biosensing field.

A Fiber Optic Ammonia Sensor Using a Universal pH Indicator

PubMed Central

Rodríguez, Adolfo J.; Zamarreño, Carlos R.; Matías, Ignacio R.; Arregui, Francisco. J.; Domínguez Cruz, Rene F.; May-Arrioja, Daniel. A.

2014-01-01

A universal pH indicator is used to fabricate a fiber optic ammonia sensor. The advantage of this pH indicator is that it exhibits sensitivity to ammonia over a broad wavelength range. This provides a differential response, with a valley around 500 nm and a peak around 650 nm, which allows us to perform ratiometric measurements. The ratiometric measurements provide not only an enhanced signal, but can also eliminate any external disturbance due to humidity or temperature fluctuations. In addition, the indicator is embedded in a hydrophobic and gas permeable polyurethane film named Tecoflex®. The film provides additional advantages to the sensor, such as operation in dry environments, efficient transport of the element to be measured to the sensitive area of the sensor, and prevent leakage or detachment of the indicator. The combination of the universal pH indicator and Tecoflex® film provides a reliable and robust fiber optic ammonia sensor. PMID:24583969

Thermoluminescence response of flat optical fiber subjected to 9 MeV electron irradiations

NASA Astrophysics Data System (ADS)

Hashim, S.; Omar, S. S. Che; Ibrahim, S. A.; Hassan, W. M. S. Wan; Ung, N. M.; Mahdiraji, G. A.; Bradley, D. A.; Alzimami, K.

2015-01-01

We describe the efforts of finding a new thermoluminescent (TL) media using pure silica flat optical fiber (FF). The present study investigates the dose response, sensitivity, minimum detectable dose and glow curve of FF subjected to 9 MeV electron irradiations with various dose ranges from 0 Gy to 2.5 Gy. The above-mentioned TL properties of the FF are compared with commercially available TLD-100 rods. The TL measurements of the TL media exhibit a linear dose response over the delivered dose using a linear accelerator. We found that the sensitivity of TLD-100 is markedly 6 times greater than that of FF optical fiber. The minimum detectable dose was found to be 0.09 mGy for TLD-100 and 8.22 mGy for FF. Our work may contribute towards the development of a new dosimeter for personal monitoring purposes.

A Silver Nanoparticle-Modified Evanescent Field Optical Fiber Sensor for Methylene Blue Detection

PubMed Central

Luo, Ji; Yao, Jun; Lu, Yonggang; Ma, Wenying; Zhuang, Xuye

2013-01-01

A silver nanoparticle-modified evanescent field optical fiber sensor based on a MEMS microchannel chip has been successfully fabricated. Experimental results show that the sensor response decreases linearly with increasing concentration of analyte. Over a range of methylene blue concentrations from 0 to 0.4 μmol/mL, the sensor response is linear (R = 0.9496). A concentration variation of 0.1 μmol/mL can cause an absorbance change of 0.402 dB. Moreover, the optical responses of the same sensing fiber without decoration and modified with silver nanoparticles have also been compared. It can be observed that the output intensity of the Ag nanoparticle-modified sensor is enhanced and the sensitivity is higher. Meanwhile, the absorbance spectra are found to be more sensitive to concentration changes compared to the spectra of the peak wavelength. PMID:23519353

Alpha-fetoprotein detection by using a localized surface plasmon coupled fluorescence fiber-optic biosensor

NASA Astrophysics Data System (ADS)

Chang, Ying-Feng; Chen, Ran-Chou; Li, Ying-Chang; Yu, Chih-Jen; Hsieh, Bao-Yu; Chou, Chien

2007-11-01

Alpha-fetoprotein (AFP) detection by using a localized surface plasmon coupled fluorescence (LSPCF) fiber-optic biosensor is setup and experimentally demonstrated. It is based on gold nanoparticle (GNP) and coupled with localized surface plasmon wave on the surface of GNP. In this experiment, the fluorophores are labeled on anti-AFP which are bound to protein A conjugated GNP. Thus, LSPCF is excited with high efficiency in the near field of localized surface plasmon wave. Therefore, not only the sensitivity of LSPCF biosensor is enhanced but also the specific selectivity of AFP is improved. Experimentally, the ability of real time measurement in the range of AFP concentration from 0.1ng/ml to 100ng/ml was detected. To compare with conventional methods such as enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay (RIA), the LSPCF fiber-optic biosensor performs higher or comparable detection sensitivity, respectively.

Multi-event waveform-retrieved distributed optical fiber acoustic sensor using dual-pulse heterodyne phase-sensitive OTDR.

PubMed

He, Xiangge; Xie, Shangran; Liu, Fei; Cao, Shan; Gu, Lijuan; Zheng, Xiaoping; Zhang, Min

2017-02-01

We demonstrate a novel type of distributed optical fiber acoustic sensor, with the ability to detect and retrieve actual temporal waveforms of multiple vibration events that occur simultaneously at different positions along the fiber. The system is realized via a dual-pulse phase-sensitive optical time-domain reflectometry, and the actual waveform is retrieved by heterodyne phase demodulation. Experimental results show that the system has a background noise level as low as 8.91×10^-4  rad/√Hz with a demodulation signal-to-noise ratio of 49.17 dB at 1 kHz, and can achieve a dynamic range of ∼60  dB at 1 kHz (0.1 to 104 rad) for phase demodulation, as well as a detection frequency range from 20 Hz to 25 kHz.

BPM analysis of all-optical fiber interferometric sensor based on a U-shape microcavity

NASA Astrophysics Data System (ADS)

Wu, Hongbin; Yuan, Lei; Wang, Sumei; Zhao, Longjiang; Cao, Zhitao

2014-02-01

Reflectivity spectrum of beam propagation method (BPM), for the first time to the best of our knowledge, is realized and utilized to model all-optical fiber interferometric sensor formed by a U-shape microcavity embedded in a single mode optical fiber and illustrate the principle of sensor structures varied by the length and the depth of U-shape microcavity. BPM analysis gives a constructive guideline to get a high interferometric fringe visibility which is most important for sensing application. The simulated results are completely in agreement with the interferometric sensor principle of Fabry-Perot interferometer (FPI) theory. With the conclusion of FPI sensor, refractive index (RI) sensitivity and temperature sensitivity are then simulated and obtained as 1049+/-5.2nm/RIU (refractive index unit) within RI range of solutions and 1.04+/-0.03pm/°C respectively.

In situ fluorescence imaging of localized corrosion with a pH-sensitive imaging fiber

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

Panova, A.A.; Pantano, P.; Walt, D.R.

1997-12-01

A fiber optic pH-sensor capable of both visualizing corrosion sites and measuring local chemical concentrations is applied to real-time corrosion monitoring. The imaging fiber`s distal face containing an immobilized pH-sensitive fluorescent dye is brought into contact with metal surfaces submerged in aqueous buffers and fluorescence images are acquired as a function of time. The observed changes in fluorescence due to increases in pH at cathodic sites and decreases in pH at anodic sites are indicative of localized corrosion rates.

[INVITED] Tilted fiber grating mechanical and biochemical sensors

NASA Astrophysics Data System (ADS)

Guo, Tuan; Liu, Fu; Guan, Bai-Ou; Albert, Jacques

2016-04-01

The tilted fiber Bragg grating (TFBG) is a new kind of fiber-optic sensor that possesses all the advantages of well-established Bragg grating technology in addition to being able to excite cladding modes resonantly. This device opens up a multitude of opportunities for single-point sensing in hard-to-reach spaces with very controllable cross-sensitivities, absolute and relative measurements of various parameters, and an extreme sensitivity to materials external to the fiber without requiring the fiber to be etched or tapered. Over the past five years, our research group has been developing multimodal fiber-optic sensors based on TFBG in various shapes and forms, always keeping the device itself simple to fabricate and compatible with low-cost manufacturing. This paper presents a brief review of the principle, fabrication, characterization, and implementation of TFBGs, followed by our progress in TFBG sensors for mechanical and biochemical applications, including one-dimensional TFBG vibroscopes, accelerometers and micro-displacement sensors; two-dimensional TFBG vector vibroscopes and vector rotation sensors; reflective TFBG refractometers with in-fiber and fiber-to-fiber configurations; polarimetric and plasmonic TFBG biochemical sensors for in-situ detection of cell, protein and glucose.

An embedded fibre optic sensor for impact damage detection in composite materials

NASA Astrophysics Data System (ADS)

Glossop, Neil David William

1989-09-01

A structurally embedded fiber optic damage detection sensor for composite materials is described. The system is designed specifically for the detection of barely visible damage resulting from low velocity impacts in Kevlar-epoxy laminates. By monitoring the light transmission properties of optical fiber embedded in the composite, it was shown that the integrity of the material can be accurately determined. The effect of several parameters on the sensitivity of the system was investigated, including the effect of the optical fiber orientation and depth of embedding within the composite. A novel surface was also developed for the optical fibers to ensure they will fracture at the requisite damage level. The influence of the optical fiber sensors on the tensile and compressive material properties and on the impact resistance of the laminate was also studied. Extensive experimental results from impact tests are reported and a numerical model of the impact event is presented which is able to predict and model the damage mechanism and sensor system. A new and powerful method of nondestructive evaluation for translucent composite materials based on image enhanced backlighting is also described.

[INVITED] Porphyrin-nanoassembled fiber-optic gas sensor fabrication: Optimization of parameters for sensitive ammonia gas detection

NASA Astrophysics Data System (ADS)

Korposh, Sergiy; Kodaira, Suguru; Selyanchyn, Roman; Ledezma, Francisco H.; James, Stephen W.; Lee, Seung-Woo

2018-05-01

Highly sensitive fiber-optic ammonia gas sensors were fabricated via layer-by-layer deposition of poly(diallyldimethylammonium chloride) (PDDA) and tetrakis(4-sulfophenyl)porphine (TSPP) onto the surface of the core of a hard-clad multimode fiber that was stripped of its polymer cladding. The effects of film thickness, length of sensing area, and depth of evanescent wave penetration were investigated to clearly understand the sensor performance. The sensitivity of the fiber-optic sensor to ammonia was linear in the concentration range of 0.5-50 ppm and the response and recovery times were less than 3 min, with a limit of detection of 0.5 ppm, when a ten-cycle PDDA/TSPP film was assembled on the surface of the core along a 1 cm-long stripped section of the fiber. The sensor's response towards ammonia was also checked under different relative humidity conditions and a simple statistical data treatment approach, principal component analysis, demonstrated the feasibility of ammonia sensing in environmental relative humidity ranging from dry 7% to highly saturated 80%. Penetration depths of the evanescent wave for the optimal sensor configuration were estimated to be 30 and 33 nm at wavelengths of 420 and 706 nm, which are in a good agreement with the thickness of the 10-cycle deposited film (ca. 30 nm).

A Multi-D-Shaped Optical Fiber for Refractive Index Sensing

PubMed Central

Chen, Chien-Hsing; Tsao, Tzu-Chein; Tang, Jaw-Luen; Wu, Wei-Te

2010-01-01

A novel class of multi-D-shaped optical fiber suited for refractive index measurements is presented. The multi-D-shaped optical fiber was constructed by forming several D-sections in a multimode optical fiber at localized regions with femtosecond laser pulses. The total number of D-shaped zones fabricated could range from three to seven. Each D-shaped zone covered a sensor volume of 100 μm depth, 250 μm width, and 1 mm length. The mean roughness of the core surface obtained by the AFM images was 231.7 nm, which is relatively smooth. Results of the tensile test indicated that the fibers have sufficient mechanical strength to resist damage from further processing. The multi-D-shaped optical fiber as a high sensitive refractive-index sensor to detect changes in the surrounding refractive index was studied. The results for different concentrations of sucrose solution show that a resolution of 1.27 × 10−3–3.13 × 10−4 RIU is achieved for refractive indices in the range of 1.333 to 1.403, suggesting that the multi-D-shaped fibers are attractive for chemical, biological, and biochemical sensing with aqueous solutions. PMID:22399908

Effect of Surface Coverage of Gold Nanoparticles on the Refractive Index Sensitivity in Fiber-Optic Nanoplasmonic Sensing.

PubMed

Wu, Wei-Te; Chen, Chien-Hsing; Chiang, Chang-Yue; Chau, Lai-Kwan

2018-05-31

A simple theoretical model was developed to analyze the extinction spectrum of gold nanoparticles (AuNPs) on the fiber core and glass surfaces in order to aid the determination of the surface coverage and surface distribution of the AuNPs on the fiber core surface for sensitivity optimization of the fiber optic particle plasmon resonance (FOPPR) sensor. The extinction spectrum of AuNPs comprises of the interband absorption of AuNPs, non-interacting plasmon resonance (PR) band due to isolated AuNPs, and coupled PR band of interacting AuNPs. When the surface coverage is smaller than 12.2%, the plasmon coupling effect can almost be ignored. This method is also applied to understand the refractive index sensitivity of the FOPPR sensor with respect to the non-interacting PR band and the coupled PR band. In terms of wavelength sensitivity at a surface coverage of 18.6%, the refractive index sensitivity of the coupled PR band (205.5 nm/RIU) is greater than that of the non-interacting PR band (349.1 nm/RIU). In terms of extinction sensitivity, refractive index sensitivity of the coupled PR band (-3.86/RIU) is similar to that of the non-interacting PR band (-3.93/RIU). Both maximum wavelength and extinction sensitivities were found at a surface coverage of 15.2%.

Window flaw detection by backscatter lighting

NASA Technical Reports Server (NTRS)

Crockett, L. K.; Minton, F. R.

1978-01-01

Portable fiber-optic probe detects tiny flaws in transparent materials. Probe transmits light through surface to illuminate interior of material by backscattering off its edges. Light-sensitive contact paper records scratch pattern. Technique can be used for rapid visual checks. Flexible fiber optics are safely used in explosive or flammable areas; they present no hazard of breakage or contamination in controlled environments.

Tapered GRIN fiber microsensor.

PubMed

Beltrán-Mejía, Felipe; Biazoli, Claudecir R; Cordeiro, Cristiano M B

2014-12-15

The sensitivity of an optical fiber microsensor based on inter-modal interference can be considerably improved by tapering a short extension of the multimode fiber. In the case of Graded Index fibers with a parabolic refractive index profile, a meridional ray exhibits a sinusoidal path. When these fibers are tapered, the period of the propagated beam decrease down-taper and increase up-taper. We take advantage of this modulation -along with the enhanced overlap between the evanescent field and the external medium- to substantially increase the sensitivity of these devices by tuning the sensor's maximum sensitivity wavelength. Moreover, the extension of this device is reduced by one order of magnitude, making it more propitious for reduced space applications. Numerical and experimental results demonstrate the success and feasibility of this approach.

The Sagnac-configured fiber optic calorimeter: An investigation of an improved non-destructive methodology for determining the thermal power output of heat-producing nuclear materials

NASA Astrophysics Data System (ADS)

Bayliss, Stephen Carlton

An essential component in an ever-expanding global nuclear economy is the nondestructive assay (NDA) of nuclear materials. Accurate accounting of these materials helps to insure the safe handling and disposal of them and the accurate monitoring of these materials can help prevent their diversion. A particularly useful and important NDA technique has proven to be isothermal calorimetry. With state-of-the-art calorimeters, heat rates as low as a few milliwatts can be measured, which correspond to approximately one gram of plutonium or one milligram of tritium; two materials of particular interest. In addition, calorimetry is relatively insensitive to the matrix of the sample. This work reports on the development of a calorimeter technique based on fiber optics, which can greatly increase the sensitivity of the calorimeter compared with present day devices. Specifically, this device uses an optical fiber configuration based on the Sagnac interferometer. Fundamentally, the optical fiber is replacing the resistive wire used in conventional calorimeters. The optical fiber is wrapped around two "thermels;" a reference and a sample thermel; the thermal sample to be measured is placed in the sample thermel. The light within the optical fiber of the sample arm experiences a change in phase due to the change in the index of refraction caused by the thermal load. When this light mixes with the light from the reference arm, a change in the light intensity results. An electro-optic receiver converts the time-varying light intensity to a time-varying voltage output. It is this voltage output that is stored and analyzed. A prototype fiber calorimeter has been built and proved capable of measuring heat loads in the microwatt regime. This sensitivity represents a factor of a one thousand-fold improvement over conventional calorimeters. This would allow plutonium samples as small as one milligram to be measured and microgram quantities of tritium. In addition, gram quantities of 93% enriched uranium could be measured for the first time using calorimetry. This device has not been optimized with respect to background interferences (room thermal loads and acoustics), but indications are that the sensitivity could be improved further with more development.

In situ simultaneous strain and temperature measurement of adaptive composite materials using a fiber Bragg grating based sensor

NASA Astrophysics Data System (ADS)

Yoon, Hyuk-Jin; Costantini, Daniele M.; Michaud, Veronique; Limberger, Hans G.; Manson, Jan-Anders; Salathe, Rene P.; Kim, Chun-Gon; Hong, Chang-Sun

2005-05-01

An optical fiber sensor to simultaneously measure strain and temperature was designed and embedded into an adaptive composite laminate which exhibits a shape change upon thermal activation. The sensor is formed by two fiber Bragg gratings, which are written in optical fibers with different core dopants. The two gratings were spliced close to each other and a sensing element resulted with Bragg gratings of similar strain sensitivity but different response to temperature. This is due to the dependence of the fiber thermo-optic coefficient on core dopants and relative concentrations. The sensor was tested on an adaptive composite laminate made of unidirectional Kevlar-epoxy pre-preg plies. Several 150μm diameter pre-strained NiTiCu shape memory alloy wires were embedded in the composite laminate together with one fiber sensor. Simultaneous monitoring of strain and temperature during the curing process and activation in an oven was demonstrated.

Uncertainty quantification of fiber orientation distribution measurements for long-fiber-reinforced thermoplastic composites

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

Sharma, Bhisham N.; Naragani, Diwakar; Nguyen, Ba Nghiep

Here, we present a detailed methodology for experimental measurement of fiber orientation distribution in injection-molded discontinuous fiber composites using the method of ellipses on two-dimensional cross sections. Best practices to avoid biases occurring during surface preparation and optical imaging of carbon-fiber-reinforced thermoplastics are discussed. We developed a marker-based watershed transform routine for efficient image segmentation and the separation of touching fiber ellipses. The sensitivity of the averaged orientation tensor to the image sample size is studied for the case of long-fiber thermoplastics. A Mori–Tanaka implementation of the Eshelby model is then employed to quantify the sensitivity of elastic stiffness predictionsmore » to biases in the fiber orientation distribution measurements.« less

Uncertainty quantification of fiber orientation distribution measurements for long-fiber-reinforced thermoplastic composites

DOE PAGES

Sharma, Bhisham N.; Naragani, Diwakar; Nguyen, Ba Nghiep; ...

2017-09-28

Here, we present a detailed methodology for experimental measurement of fiber orientation distribution in injection-molded discontinuous fiber composites using the method of ellipses on two-dimensional cross sections. Best practices to avoid biases occurring during surface preparation and optical imaging of carbon-fiber-reinforced thermoplastics are discussed. We developed a marker-based watershed transform routine for efficient image segmentation and the separation of touching fiber ellipses. The sensitivity of the averaged orientation tensor to the image sample size is studied for the case of long-fiber thermoplastics. A Mori–Tanaka implementation of the Eshelby model is then employed to quantify the sensitivity of elastic stiffness predictionsmore » to biases in the fiber orientation distribution measurements.« less

Graphene Oxide in Lossy Mode Resonance-Based Optical Fiber Sensors for Ethanol Detection.

PubMed

Hernaez, Miguel; Mayes, Andrew G; Melendi-Espina, Sonia

2017-12-27

The influence of graphene oxide (GO) over the features of an optical fiber ethanol sensor based on lossy mode resonances (LMR) has been studied in this work. Four different sensors were built with this aim, each comprising a multimode optical fiber core fragment coated with a SnO₂ thin film. Layer by layer (LbL) coatings made of 1, 2 and 4 bilayers of polyethyleneimine (PEI) and graphene oxide were deposited onto three of these devices and their behavior as aqueous ethanol sensors was characterized and compared with the sensor without GO. The sensors with GO showed much better performance with a maximum sensitivity enhancement of 176% with respect to the sensor without GO. To our knowledge, this is the first time that GO has been used to make an optical fiber sensor based on LMR.

Impact and vibration detection in composite materials by using intermodal interference in multimode optical fibers

NASA Astrophysics Data System (ADS)

Malki, Abdelrafik; Gafsi, Rachid; Michel, Laurent; Labarrère, Michel; Lecoy, Pierre

1996-09-01

An optical fiber sensor based on the intermodal interference principle is integrated in a composite material to detect impacts and vibrations. Six fibers are integrated at the top of a carbon/epoxy composite panel so as to form a grid into the structure. Spectral and temporal responses to impacts and acoustic vibrations of the sensor are compared with a piezoelectric accelerometer. The tests proved the facility of integration and the high sensitivity of the device. The location of impacts is performed with this arrangement by measuring the arrival times of the front waves to the fibers.

Fiber optic micro sensor for the measurement of tendon forces

PubMed Central

2012-01-01

A fiber optic sensor developed for the measurement of tendon forces was designed, numerically modeled, fabricated, and experimentally evaluated. The sensor incorporated fiber Bragg gratings and micro-fabricated stainless steel housings. A fiber Bragg grating is an optical device that is spectrally sensitive to axial strain. Stainless steel housings were designed to convert radial forces applied to the housing into axial forces that could be sensed by the fiber Bragg grating. The metal housings were fabricated by several methods including laser micromachining, swaging, and hydroforming. Designs are presented that allow for simultaneous temperature and force measurements as well as for simultaneous resolution of multi-axis forces. The sensor was experimentally evaluated by hydrostatic loading and in vitro testing. A commercial hydraulic burst tester was used to provide uniform pressures on the sensor in order to establish the linearity, repeatability, and accuracy characteristics of the sensor. The in vitro experiments were performed in excised tendon and in a dynamic gait simulator to simulate biological conditions. In both experimental conditions, the sensor was found to be a sensitive and reliable method for acquiring minimally invasive measurements of soft tissue forces. Our results suggest that this sensor will prove useful in a variety of biomechanical measurements. PMID:23033868

Enhancement of the sensitivity of a temperature sensor based on fiber Bragg gratings via weak value amplification.

PubMed

Salazar-Serrano, L J; Barrera, D; Amaya, W; Sales, S; Pruneri, V; Capmany, J; Torres, J P

2015-09-01

We present a proof-of-concept experiment aimed at increasing the sensitivity of Fiber-Bragg-gratings temperature sensors by making use of a weak-value-amplification scheme. The technique requires only linear optics elements for its implementation and appears as a promising method for increasing the sensitivity than state-of the-art sensors can currently provide. The device implemented here is able to generate a shift of the centroid of the spectrum of a pulse of ∼0.035  nm/°C, a nearly fourfold increase in sensitivity over the same fiber-Bragg-grating system interrogated using standard methods.

Highly sensitive refractive index fiber inline Mach-Zehnder interferometer fabricated by femtosecond laser micromachining and chemical etching

NASA Astrophysics Data System (ADS)

Sun, Xiao-Yan; Chu, Dong-Kai; Dong, Xin-Ran; Zhou, Chu; Li, Hai-Tao; Luo-Zhi; Hu, You-Wang; Zhou, Jian-Ying; Cong-Wang; Duan, Ji-An

2016-03-01

A High sensitive refractive index (RI) sensor based on Mach-Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed, which is fabricated by femtosecond laser transversal-scanning inscription method and chemical etching. A rectangular cavity structure is formed in part of fiber core and cladding interface. The MZI sensor shows excellent refractive index sensitivity and linearity, which exhibits an extremely high RI sensitivity of -17197 nm/RIU (refractive index unit) with the linearity of 0.9996 within the refractive index range of 1.3371-1.3407. The experimental results are consistent with theoretical analysis.

Radiation hardening of optical fibers and fiber sensors for space applications: recent advances

NASA Astrophysics Data System (ADS)

Girard, S.; Ouerdane, Y.; Pinsard, E.; Laurent, A.; Ladaci, A.; Robin, T.; Cadier, B.; Mescia, L.; Boukenter, A.

2017-11-01

In these ICSO proceedings, we review recent advances from our group concerning the radiation hardening of optical fiber and fiber-based sensors for space applications and compare their benefits to state-of-the-art results. We focus on the various approaches we developed to enhance the radiation tolerance of two classes of optical fibers doped with rare-earths: the erbium (Er)-doped ones and the ytterbium/erbium (Er/Yb)-doped ones. As a first approach, we work at the component level, optimizing the fiber structure and composition to reduce their intrinsically high radiation sensitivities. For the Erbium-doped fibers, this has been achieved using a new structure for the fiber that is called Hole-Assisted Carbon Coated (HACC) optical fibers whereas for the Er/Ybdoped optical fibers, their hardening was successfully achieved adding to the fiber, the Cerium element, that prevents the formation of the radiation-induced point defects responsible for the radiation induced attenuation in the infrared part of the spectrum. These fibers are used as part of more complex systems like amplifiers (Erbium-doped Fiber Amplifier, EDFA or Yb-EDFA) or source (Erbium-doped Fiber Source, EDFS or Yb- EDFS), we discuss the impact of using radiation-hardened fibers on the system radiation vulnerability and demonstrate the resistance of these systems to radiation constraints associated with today and future space missions. Finally, we will discuss another radiation hardening approach build in our group and based on a hardening-by-system strategy in which the amplifier is optimized during its elaboration for its future mission considering the radiation effects and not in-lab.

Experimental demonstration of the switching dose-rate method on doped optical fibers

NASA Astrophysics Data System (ADS)

Thomas, J.; Myara, M.; Troussellier, L.; Régnier, E.; Burov, E.; Gilard, O.; Sottom, M.; Signoret, P.

2017-11-01

Optical technology developed for ground and submarine telecommunications is becoming of strong interest for next generation satellites. In addition to inter-satellite laser communications and LIDAR's, new applications are being considered such as on-board distribution and processing of microwave signals, fiber sensors or gyroscopes as well. Whereas common optical / optoelectronic components are known to be weakly sensitive to radiations, the essential optical amplifiers are strongly degraded in such an environment because of the RIA (Radio-Induced-Absorption) experienced by the Erbium-Doped Fiber (EDF) itself [1-3]. This degradation is mainly caused by the presence of co-doping ions, such as Aluminium or Germanium, inserted in the fibre to assist the inclusion of the Erbium ions in the silica matrix or to provide to the optical fibre its guiding properties.

Optical trapping and control of nanoparticles inside evacuated hollow core photonic crystal fibers

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

Grass, David, E-mail: david.grass@univie.ac.at; Fesel, Julian; Hofer, Sebastian G.

2016-05-30

We demonstrate an optical conveyor belt for levitated nanoparticles over several centimeters inside both air-filled and evacuated hollow-core photonic crystal fibers (HCPCF). Detection of the transmitted light field allows three-dimensional read-out of the particle center-of-mass motion. An additional laser enables axial radiation pressure based feedback cooling over the full fiber length. We show that the particle dynamics is a sensitive local probe for characterizing the optical intensity profile inside the fiber as well as the pressure distribution along the fiber axis. In contrast to some theoretical predictions, we find a linear pressure dependence inside the HCPCF, extending over three ordersmore » of magnitude from 0.2 mbar to 100 mbar. A targeted application is the controlled delivery of nanoparticles from ambient pressure into medium vacuum.« less

Fiber Sensor Systems Based on Fiber Laser and Microwave Photonic Technologies

PubMed Central

Fu, Hongyan; Chen, Daru; Cai, Zhiping

2012-01-01

Fiber-optic sensors, especially fiber Bragg grating (FBG) sensors are very attractive due to their numerous advantages over traditional sensors, such as light weight, high sensitivity, cost-effectiveness, immunity to electromagnetic interference, ease of multiplexing and so on. Therefore, fiber-optic sensors have been intensively studied during the last several decades. Nowadays, with the development of novel fiber technology, more and more newly invented fiber technologies bring better and superior performance to fiber-optic sensing networks. In this paper, the applications of some advanced photonic technologies including fiber lasers and microwave photonic technologies for fiber sensing applications are reviewed. FBG interrogations based on several kinds of fiber lasers, especially the novel Fourier domain mode locking fiber laser, have been introduced; for the application of microwave photonic technology, examples of microwave photonic filtering utilized as a FBG sensing interrogator and microwave signal generation acting as a transversal loading sensor have been given. Both theoretical analysis and experimental demonstrations have been carried out. The comparison of these advanced photonic technologies for the applications of fiber sensing is carried out and important issues related to the applications have been addressed and the suitable and potential application examples have also been discussed in this paper. PMID:22778591

Real-time distributed fiber optic sensor for security systems: Performance, event classification and nuisance mitigation

NASA Astrophysics Data System (ADS)

Mahmoud, Seedahmed S.; Visagathilagar, Yuvaraja; Katsifolis, Jim

2012-09-01

The success of any perimeter intrusion detection system depends on three important performance parameters: the probability of detection (POD), the nuisance alarm rate (NAR), and the false alarm rate (FAR). The most fundamental parameter, POD, is normally related to a number of factors such as the event of interest, the sensitivity of the sensor, the installation quality of the system, and the reliability of the sensing equipment. The suppression of nuisance alarms without degrading sensitivity in fiber optic intrusion detection systems is key to maintaining acceptable performance. Signal processing algorithms that maintain the POD and eliminate nuisance alarms are crucial for achieving this. In this paper, a robust event classification system using supervised neural networks together with a level crossings (LCs) based feature extraction algorithm is presented for the detection and recognition of intrusion and non-intrusion events in a fence-based fiber-optic intrusion detection system. A level crossings algorithm is also used with a dynamic threshold to suppress torrential rain-induced nuisance alarms in a fence system. Results show that rain-induced nuisance alarms can be suppressed for rainfall rates in excess of 100 mm/hr with the simultaneous detection of intrusion events. The use of a level crossing based detection and novel classification algorithm is also presented for a buried pipeline fiber optic intrusion detection system for the suppression of nuisance events and discrimination of intrusion events. The sensor employed for both types of systems is a distributed bidirectional fiber-optic Mach-Zehnder (MZ) interferometer.

Fiber optic FTIR instrument for in vivo detection of colonic neoplasia

NASA Astrophysics Data System (ADS)

Van Nortwick, Matthew; Hargrove, John; Wolters, Rolf; Crawford, James M.; Arroyo, May; Mackanos, Mark; Contag, Christopher H.; Wang, Thomas D.

2009-02-01

We demonstrate the proof of concept for use of a fiber optic FTIR instrument to perform in vivo detection of colonic neoplasia as an adjunct to medical endoscopy. FTIR is sensitive to the molecular composition of tissue, and can be used as a guide for biopsy by identifying pre-malignant tissue (dysplasia). First, we demonstrate the use of a silver halide optical fiber to collect mid-infrared absorption spectra in the 950 to 1800 cm-1 regime with high signal-to-noise from biopsy specimens of colonic mucosa tissue ex vivo. We observed subtle differences in wavenumber and magnitude of the absorbance peaks over this regime. We then show that optimal sub-ranges can be defined within this spectral regime and that spectral pre-processing can be performed to classify the tissue as normal, hyperplasia, or dysplasia with high levels of performance. We used a partial least squares discriminant analysis and a leave-one-subject-out crossvalidation strategy to classify the spectra. The results were compared with histology, and the optimal thresholds resulted in an overall sensitivity, specificity, accuracy, and positive predictive value of 96%, 92%, 93%, and 82%, respectively for this technique. We demonstrate that mid-infrared absorption spectra can be collected remotely with an optical fiber and used to identify colonic dysplasia with high accuracy. We are now developing an endoscope compatible optical fiber to use this technique clinically for the early detection of cancer.

Integrating Fiber Optic Strain Sensors into Metal Using Ultrasonic Additive Manufacturing

NASA Astrophysics Data System (ADS)

Hehr, Adam; Norfolk, Mark; Wenning, Justin; Sheridan, John; Leser, Paul; Leser, Patrick; Newman, John A.

2018-03-01

Ultrasonic additive manufacturing, a rather new three-dimensional (3D) printing technology, uses ultrasonic energy to produce metallurgical bonds between layers of metal foils near room temperature. This low temperature attribute of the process enables integration of temperature sensitive components, such as fiber optic strain sensors, directly into metal structures. This may be an enabling technology for Digital Twin applications, i.e., virtual model interaction and feedback with live load data. This study evaluates the consolidation quality, interface robustness, and load sensing limits of commercially available fiber optic strain sensors embedded into aluminum alloy 6061. Lastly, an outlook on the technology and its applications is described.

Application of distributed optical fiber sensing technologies to the monitoring of leakage and abnormal disturbance of oil pipeline

NASA Astrophysics Data System (ADS)

Yang, Xiaojun; Zhu, Xiaofei; Deng, Chi; Li, Junyi; Liu, Cheng; Yu, Wenpeng; Luo, Hui

2017-10-01

To improve the level of management and monitoring of leakage and abnormal disturbance of long distance oil pipeline, the distributed optical fiber temperature and vibration sensing system is employed to test the feasibility for the healthy monitoring of a domestic oil pipeline. The simulating leakage and abnormal disturbance affairs of oil pipeline are performed in the experiment. It is demonstrated that the leakage and abnormal disturbance affairs of oil pipeline can be monitored and located accurately with the distributed optical fiber sensing system, which exhibits good performance in the sensitivity, reliability, operation and maintenance etc., and shows good market application prospect.

Fiber-optic sensors for aerospace electrical measurements: An update

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Rose, A. H.; Tang, D.; Day, G. W.

1991-01-01

Fiber-optic sensors are being developed for electrical current, voltage, and power measurements in aerospace applications. These sensors are presently designed to cover ac frequencies from 60 Hz to 20 kHz. The current sensor, based on the Faraday effect in optical fiber, is in advanced development after some initial testing. Concentration is on packaging methods and ways to maintain consistent sensitivity with changes in temperature. The voltage sensor, utilizing the Pockels effect in a crystal, has excelled in temperature tests. This paper reports on the development of these sensors, the results of evaluation, improvements now in progress, and the future direction of the work.

A hydrostatic leak test for water pipeline by using distributed optical fiber vibration sensing system

NASA Astrophysics Data System (ADS)

Wu, Huijuan; Sun, Zhenshi; Qian, Ya; Zhang, Tao; Rao, Yunjiang

2015-07-01

A hydrostatic leak test for water pipeline with a distributed optical fiber vibration sensing (DOVS) system based on the phase-sensitive OTDR technology is studied in this paper. By monitoring one end of a common communication optical fiber cable, which is laid in the inner wall of the pipe, we can detect and locate the water leakages easily. Different apertures under different pressures are tested and it shows that the DOVS has good responses when the aperture is equal or larger than 4 mm and the inner pressure reaches 0.2 Mpa for a steel pipe with DN 91cm×EN 2cm.

Optical fiber endface biosensor based on resonances in dielectric waveguide gratings

NASA Astrophysics Data System (ADS)

Wawro, Debra D.; Tibuleac, Sorin; Magnusson, Robert; Liu, Hanli

2000-05-01

A new fiber optic sensor integrating dielectric diffraction gratings and thin films on optical fiber endfaces is prosed for biomedical sensing applications. This device utilizes a resonant dielectric waveguide grating structure fabricated on an optical fiber endface to probe reactions occurring in a sensing layer deposited on its surface. The operation of this sensor is based upon a fundamental resonance effect that occurs in waveguide gratings. An incident broad- spectrum signal is guided within an optical fiber and is filtered to reflect or transmit a desired spectral band by the diffractive thin film structure on its endface. Slight changes in one or more parameters of the waveguide grating, such as refractive index or thickness, can result in a responsive shift of the reflected or transmitted spectral peak that can be detected with spectroscopic instruments. This new sensor concept combines improved sensitivity and accuracy with attractive features found separately in currently available fiber optic sensors, such as large dynamic range, small sensing proximity, real time operation, and remote sensing. Diffractive elements of this type consisting of a photoresist grating on a Si3N4 waveguide have been fabricated on multimode optical fiber endfaces with 100 micrometers cores. Preliminary experimental tests using a tunable Ti:sapphire laser indicate notches of 18 percent in the transmission spectrum of the fiber endface guided-mode resonance devices. A theoretical analysis of the device performance capabilities is presented and applied to evaluate the feasibility and potential advantages of this bioprobe.

A sensitivity-enhanced refractive index sensor using a single-mode thin-core fiber incorporating an abrupt taper.

PubMed

Shi, Jie; Xiao, Shilin; Yi, Lilin; Bi, Meihua

2012-01-01

A sensitivity-enhanced fiber-optic refractive index (RI) sensor based on a tapered single-mode thin-core diameter fiber is proposed and experimentally demonstrated. The sensor head is formed by splicing a section of tapered thin-core diameter fiber (TCF) between two sections of single-mode fibers (SMFs). The cladding modes are excited at the first SMF-TCF interface, and then interfere with the core mode at the second interface, thus forming an inter-modal interferometer (IMI). An abrupt taper (tens of micrometers long) made by the electric-arc-heating method is utilized, and plays an important role in improving sensing sensitivity. The whole manufacture process only involves fiber splicing and tapering, and all the fabrication process can be achieved by a commercial fiber fusion splicer. Using glycerol and water mixture solution as an example, the experimental results show that the refractive index sensitivity is measured to be 0.591 nm for 1% change of surrounding RI. The proposed sensor structure features simple structure, low cost, easy fabrication, and high sensitivity.

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.

Side illuminated optical fiber as a multiplexing element for spectroscopic systems

NASA Astrophysics Data System (ADS)

Egalon, Claudio O.; Matta, Michael P.; Lavezzari, Delbert C.; Insley, Robert Y.; Jaring, Carolyn C.; Quiday, Marie F.

2013-09-01

A new type of colorimeter with multiple channels was demonstrated using a side illuminated optical fiber. When different spots of a properly modified fiber are side illuminated, multiple signals are generated and guided by the waveguide: the essence of multiplexing. This configuration is simple, low cost, does not require a sensitive coating and can analyze several samples along the fiber with a single detector: the most expensive component. Since regular colorimeters use one detector per sample, our new configuration considerably lowers the cost of analyzing multiple samples. This system consists of a fiber mounted over a support, three LEDs, an LED driver, a photo diode and a read-out: to increase the signal, the fiber was tapered. For calibration purposes, six solutions of different concentrations of food dye were prepared, placed inside cuvettes along the fiber length and illuminated by the LEDs. This light passes through the solution, strikes the fiber and is guided to the detector: the darker the solution the lower the signal intensity. Several calibration curves were obtained using different light intensities: it was found that the greater the intensity, the higher the colorimeter sensitivity. This simple capability can be used to easily control the device's sensitivity and its resolution. Although built for three samples only, this device can be modified to accommodate more. With cuvettes measuring 1 cm, it is possible to accommodate one sample per cm of fiber. Also, with minor modifications, this colorimeter can be used for fluorescence, scattering and index of refraction measurements.

Extraction of natural weight shift and foot rolling in gait based on hetero-core optical fiber load sensor

NASA Astrophysics Data System (ADS)

Otsuka, Yudai; Koyama, Yuya; Nishiyama, Michiko; Watanabe, Kazuhiro

2016-03-01

Gait in daily activity affects human health because it may cause physical problems such as asymmetric pelvis, flat foot and bowlegs. Monitoring natural weight shift and foot rolling on plantar has been employed in order for researchers to analyze gait characteristics. Conventional gait monitoring systems have been developed using camera, acceleration sensor, gyro sensor and electrical load sensors. They have some problems such as limited measurement place, temperature dependence and electric leakage. On the other hand, a hetero-core optical fiber sensor has many advantages such as high sensitivity for macro-bending, light weight sensor element, independency on temperature fluctuations, and no electric contact. This paper describes extraction of natural weight shift and foot rolling for gait evaluation by using a sensitive shoe, in the insole of which hetero-core optical load sensors are embedded for detecting plantar pressure. Plantar pressure of three subjects who wear the sensitive shoe and walk on the treadmill was monitored. As a result, weight shift and foot rolling for three subjects were extracted using the proposed sensitive shoe in terms of centroid movement and positions. Additionally, these extracted data are compared to that of electric load sensor to ensure consistency. For these results, it was successfully demonstrated that hetero-core optical fiber load sensor performed in unconstraint gait monitoring as well as electric load sensor.

U-shaped micro-groove fiber based on femtosecond laser processing for humidity sensing

NASA Astrophysics Data System (ADS)

Fu, Gui; Ma, Li-li; Su, Fu-fang; Shi, Meng

2018-05-01

A novel optical fiber sensor with a U-shaped micro-groove structure ablated by femtosecond laser on single-mode fiber for measuring air relative humidity (RH) is reported in this paper. In order to improve the accuracy of sensor, a graphene oxide (GO)/polyvinyl alcohol (PVA) composite film is coated on the surface of micro-groove structure. In the U-shaped micro-groove structure, the remaining core and micro-cavity in the micro-groove make up two major optical propagation paths, forming a Mach-Zehnder interferometer (MZI). The sensor has a good linear response within the RH range of 30%—85%, and the maximum sensitivity can reach 0.638 1 nm/%RH. The effect of temperature on the overall performance of the humidity sensor is also investigated. As a new type of all-fiber device, the sensor shows excellent sensitivity and stability.

Plasmonic fiber-optic vector magnetometer

NASA Astrophysics Data System (ADS)

Zhang, Zhaochuan; Guo, Tuan; Zhang, Xuejun; Xu, Jian; Xie, Wenping; Nie, Ming; Wu, Qiang; Guan, Bai-Ou; Albert, Jacques

2016-03-01

A compact fiber-optic vector magnetometer based on directional scattering between polarized plasmon waves and ferro-magnetic nanoparticles is demonstrated. The sensor configuration reported in this work uses a short section of tilted fiber Bragg grating (TFBG) coated with a nanometer scale gold film and packaged with a magnetic fluid (Fe3O4) inside a capillary. The transmission spectrum of the sensor provides a fine comb of narrowband resonances that overlap with a broader absorption of the surface plasmon resonance (SPR). The wavelength of the SPR attenuation in transmission shows high sensitivity to slight perturbations by magnetic fields, due to the strong directional scattering between the SPR attenuated cladding modes and the magnetic fluid near the fiber surface. Both the orientation (2 nm/deg) and the intensity (1.8 nm/mT) of magnetic fields can be determined unambiguously from the TFBG spectrum. Temperature cross sensitivity can be referenced out by monitoring the wavelength of the core mode resonance simultaneously.

Optical fiber F-P magnetic field sensor based on magnetostrictive effect of magnetic fluid

NASA Astrophysics Data System (ADS)

Shi, Fuquan; Luo, Yan; Che, Jiajia; Ren, Zhijun; peng, Baojin

2018-07-01

magnetic field sensor of air-gap Fabry-Perot fiber interferometersis proposed based on magnetostrictive effect. The sensor is consisted of single-model fiber (SMF), air-gap, no-core fiber (NCF) and magnetic fluid. Those are sealed in the capillary, SMF and NCF are connect with air chamber and magnetic fluid column. With the presence of an external magnetic field, air chamber cavity length changes because of the magneto-volume variation of magnetic fluids. This situation causes a change in the optical path difference. Detection of the drift of interference spectrum leads to the detection of the change in magnetic field. When the magnetic field is parallel to the direction in which the capillary is placed, the sensitivity is 0.2347 nm/mT; when the magnetic fluid is perpendicular to the direction in which the capillary is placed, the sensitivity is 0.325 nm/http://mT.%20In.

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.

Temperature-independent refractometer based on fiber-optic Fabry-Perot interferometer

NASA Astrophysics Data System (ADS)

Li, Jiacheng; Qiao, Xueguang; Wang, Ruohui; Rong, Qiangzhou; Bao, Weijia; Shao, Zhihua; Yang, Tingting

2016-04-01

A miniature fiber-optic refractometer based on Fabry-Perot interferometer (FPI) has been proposed and experimentally demonstrated. The sensing head consists of a short section of photonics crystal fiber (PCF) spliced to a single mode fiber (SMF), in which the end-face of the PCF is etched to remove holey structure with hydrofluoric (HF) acid. A Fabry-Perot interference spectrum is achieved based on the reflections from the fusion splicing interface and the end-face of the core of PCF. The interference fringe is sensitive to the external refractive index (RI) with an intensity-referenced sensitivity of 358.27 dB/RIU ranging from 1.33 to 1.38. The sensor has also been implemented for the concentration measurement of λ-phage DNA solution. In addition, the dip intensity is insensitive to the ambient temperature variation, making it a good candidate for temperature-independent bio-sensing area.

Broadband Vibration Detection in Tissue Phantoms Using a Fiber Fabry-Perot Cavity.

PubMed

Barnes, Jack; Li, Sijia; Goyal, Apoorv; Abolmaesumi, Purang; Mousavi, Parvin; Loock, Hans-Peter

2018-04-01

A fiber optic vibration sensor is developed and characterized with an ultrawide dynamic sensing range, from less than 1 Hz to clinical ultrasound frequencies near 6 MHz. The vibration sensor consists of a matched pair of fiber Bragg gratings coupled to a custom-built signal processing circuit. The wavelength of a laser diode is locked to one of the many cavity resonances using the Pound-Drever-Hall scheme. A calibrated piezoelectric vibration element was used to characterize the sensor's strain, temperature, and noise responses. To demonstrate its sensing capability, an ultrasound phantom with built-in low frequency vibration actuation was constructed. The fiber optic senor was shown to simultaneously capture the low frequency vibration and the clinical ultrasound transmission waveforms with nanostrain sensitivity. This miniaturized and sensitive vibration sensor can provide comprehensive information regarding strain response and the resultant ultrasound waveforms.

Fiber Fabry-Perot tip sensor based on multimode photonic crystal fiber

NASA Astrophysics Data System (ADS)

Wu, Di; Huang, Yu; Fu, Jian-Yu; Wang, Guo-Yin

2015-03-01

We propose a novel Fabry-Perot interferometer (FPI) sensor for simultaneous measurement of refractive index (RI) and temperature based on Fresnel reflection and the thermo-optic effect of silica. The sensor head consists of a short section of multimode photonic crystal fiber (MPCF) and a conventional single mode fiber (SMF), where two thin films are formed by collapsing the air holes of MPCF with a commercialized fusion splicer. Experimental results show that such a device has a linear RI sensitivity of ~21.52 dB/RIU (RI unit) and a linear optical path difference (OPD) temperature sensitivity of ~25 nm/°C. In addition, a high RI resolution of about ~1.7×10-5 is obtained by using the Fourier transformation to decompose the spectral response in different spatial frequencies. Low-cost, easy fabrication and high resolution make it appropriate for practical applications.

No-core fiber-based highly sensitive optical fiber pH sensor.

PubMed

Bhardwaj, Vanita; Pathak, Akhilesh Kumar; Singh, Vinod Kumar

2017-05-01

The present work describes the fabrication and characterization of an optical fiber pH sensor using a sol–gel technique. The sensing head configuration is incorporated using a short section of no-core fiber, coated with tetraethyl orthosilicate and spliced at the end of a single mode fiber with a bulge. Different types of indicators (bromophenol blue, cresol red, and chlorophenol red) were used to achieve a wide pH range from 2 to 13. High sensitivities of the fabricated device were found to be 1.02 and ? 0.93 ?? nm / pH for acidic and alkaline solutions, respectively. From the characterization results, it was noted that there is an impact of ionic strength and an effect of the temperature of liquid on the response characteristic, which is an advantage of the existing device over the other pH sensors. The fabricated sensor exhibited good reflection spectrum, indicating a blueshift in resonance wavelength for alkaline solutions and a redshift for acidic solutions.

Asymmetrical dual tapered fiber Mach-Zehnder interferometer for fiber-optic directional tilt sensor.

PubMed

Lee, Cheng-Ling; Shih, Wen-Cheng; Hsu, Jui-Ming; Horng, Jing-Shyang

2014-10-06

This work proposes a novel, highly sensitive and directional fiber tilt sensor that is based on an asymmetrical dual tapered fiber Mach-Zehnder interferometer (ADTFMZI). The fiber-optic tilt sensor consists of two abrupt tapers with different tapered waists into which are incorporated a set of iron spheres to generate an asymmetrical strain in the ADTFMZI that is correlated with the tilt angle and the direction of inclination. Owing to the asymmetrical structure of the dual tapers, the proposed sensor can detect the non-horizontal/horizontal state of a structure and whether the test structure is tilted to clockwise or counterclockwise by measuring the spectral responses. Experimental results show that the spectral wavelengths are blue-shifted and red-shifted when the sensor tilts to clockwise (-θ) and counterclockwise ( + θ), respectively. Tilt angle sensitivities of about 335 pm/deg. and 125 pm/deg. are achieved in the -θ and + θ directions, respectively, when the proposed sensing scheme is utilized.

Experimental design rules for implementing biconically tapered single mode optical fibre displacement sensors

NASA Astrophysics Data System (ADS)

Arregui, Francisco J.; Matias, Ignacio R.; Bariain, Candido; Lopez-Amo, Manuel

1998-06-01

Tapered optical fibers are used to design couplers, wavelength division multiplexers, near field scanning optical microscopy, just to mention a few. Moreover, and due to its strong transmission dependence to external medium the tapered fiber may also be used to sense distinct parameters such as temperature, humidity, PH, etc. In this work bending effects in tapers are exploited to achieved displacement sensors and to present design rules for implementing these sensors according to the desired both range and sensitivity.

Fiber-optic sensors for aerospace electrical measurements - An update

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Rose, A. H.; Tang, D.; Day, G. W.

1991-01-01

The authors report the progress made on the development of aerospace current and voltage sensors which use fiber-optic and optical sensing heads. These sensors are presently designed to cover ac frequencies from 60 Hz to 20 kHz. The current sensor, based on the Faraday effect in optical fiber, is in advanced development after some initial testing. The emphasis is on packaging methods and ways to maintain consistent sensitivity with changes in temperature. The voltage sensor, utilizing the Pockels effect in a crystal, has excelled in temperature tests. The authors report on the development of these sensors. The authors also relate the technology used in the sensors, the results of evaluation, improvements being made, and the future direction of the work.

Widely tunable asymmetric long-period fiber grating with high sensitivity using optical polymer on laser-ablated cladding.

PubMed

Chen, Nan-Kuang; Hsu, Der-Yi; Chi, Sien

2007-08-01

We demonstrate high-efficiency, wideband-tunable, laser-ablated long-period fiber gratings that use an optical polymer overlay. Portions of the fiber cladding are periodically removed by CO(2) laser pulses to induce periodic index changes for coupling the core mode into cladding modes. An optical polymer with a high thermo-optic coefficient with a dispersion distinct from that of silica is used on a deep-ablated cladding structure so that the effective indices of cladding modes become dispersive and the resonant wavelengths can be efficiently tuned. The tuning efficiency can be as high as 15.8 nm/ degrees C, and the tuning range can be wider than 105 nm (1545-1650 nm).

Uncertainty quantification of fiber orientation distribution measurements for long-fiber-reinforced thermoplastic composites

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

Sharma, Bhisham N.; Naragani, Diwakar; Nguyen, Ba Nghiep

We present a detailed methodology for experimental measurement of fiber orientation distribution (FOD) in injection-molded discontinuous fiber composites using the method of ellipses on 2D cross sections. Best practices to avoid biases occurring during surface preparation and optical imaging of carbon-fiber-reinforced thermoplastics are discussed. A marker-based watershed transform routine for efficient image segmentation and the separation of touching fiber ellipses is developed. The sensitivity of the averaged orientation tensor to the image sample size is studied for the case of long-fiber thermoplastics. A Mori-Tanaka implementation of the Eshelby model is then employed to quantify the sensitivity of elastic stiffness predictionsmore » to biases in the FOD measurements.« less

Uncladded sensing fiber for refractive index measurement

NASA Astrophysics Data System (ADS)

Bhardwaj, V.; Gangwar, R. K.; Pathak, A. K.; Singh, V. K.

2016-05-01

The formation of chemically etched optical fiber for use in refractive index sensor is addressed. This presented design of a refractive index (RI) sensor is based on recording the power loss exhibited by radiation propagating through an etched multimode fiber (MMF) immersed in the liquid under study. The decreasing diameters of fibers are found to be strongly dependent on the temperature and etchant composition. This experiment was performed for different unclad etched fibers for same sensing length and the RI changes from 1.33 RIU to 1.38 RIU. When the multimode fiber (MMF) is etched for 12 hours the sensitivity of the sensor is approximately 204.25dBm/RIU, which is larger than without etched fiber having sensitivity 127.2dBm/RIU.

Tilted Fiber Bragg Grating photowritten in microstructured optical fiber for improved refractive index measurement.

PubMed

Phan Huy, Minh Châu; Laffont, Guillaume; Dewynter, Véronique; Ferdinand, Pierre; Labonté, Laurent; Pagnoux, Dominique; Roy, Philippe; Blanc, Wilfried; Dussardier, Bernard

2006-10-30

We report what we believe to be the first Tilted short-period Fiber Bragg Grating photowritten in a microstructured optical fiber for refractive index measurement. We investigate the spectral sensitivity of Tilted Fiber Bragg Grating to refractive index liquid inserted into the holes of a multimode microstructured fiber. We measure the wavelength shift of the first four modes experimentally observed when calibrated oils are inserted into the fiber holes, and thus we determine the refractive index resolution for each of these modes. Moreover, a cross comparison between experimental and simulation results of a modal analysis is performed. Two simulation tools are used, respectively based on the localized functions method and on a finite element method. All results are in very good agreement.

Fiber-Optic Based Compact Gas Leak Detection System

NASA Technical Reports Server (NTRS)

deGroot, Wim A.

1995-01-01

A propellant leak detection system based on Raman scattering principles is introduced. The proposed system is flexible and versatile as the result of the use of optical fibers. It is shown that multiple species can be monitored simultaneously. In this paper oxygen, nitrogen, carbon monoxide, and hydrogen are detected and monitored. The current detection sensitivity for both hydrogen and carbon monoxide is 1% partial pressure at ambient conditions. The sensitivity for oxygen and nitrogen is 0.5% partial pressure. The response time to changes in species concentration is three minutes. This system can be used to monitor multiple species at several locations.

Experimental results for characterization of a tapered plastic optical fiber sensor based on SPR

NASA Astrophysics Data System (ADS)

Cennamo, N.; Galatus, R.; Zeni, L.

2015-05-01

The experimental results obtained with two different Plastic Optical Fiber (POF) geometries, tapered and not-tapered, for a sensor based on Surface Plasmon Resonance (SPR) are presented. SPR is used for determining the refractive index variations at the interface between a gold layer and a dielectric medium (aqueous medium). In this work SPR sensors in POF configurations, useful for bio-sensing applications, have been realized for the optimization of the sensitivity and experimentally tested. The results show as the sensitivity increases with the tapered POF configuration, when the refractive index of aqueous medium increases.

Theoretical investigation on multilayer nanocomposite-based fiber optic SPR sensor

NASA Astrophysics Data System (ADS)

Shojaie, Ehsan; Madanipour, Khosro; Gharibzadeh, Azadeh; Abbasi, Shabnam

2017-06-01

In this work, a multilayer nanocomposite based fiber optic SPR sensor is considered and especially designed for CO2 gas detection. This proposed fiber sensor consists of fiber core, gold-silver alloy and the absorber layers. The investigation is based on the evaluation of the transmitted-power derived under the transfer matrix method and the multiple-reflection in the sensing area. In terms of sensitivity, the sensor performance is studied theoretically under various conditions related to the metal layer and its gold and silver nanoparticles to form a single alloy film. Effect of additional parameters such as the ratio of the alloy composition and the thickness of the alloy film on the performance of the SPR sensor is studied, as well. Finally, a four-layer structure is introduced to detect carbon dioxide gas. It contains core fiber, gold-silver alloy layer, an absorbent layer of carbon dioxide gas (KOH) and measurement environment. Lower price and size are the main advantages of using such a sensor in compare with commercial (NDIR) gas sensor. Theoretical results show by increasing the metal layer thickness the sensitivity of sensor is increased, and by increasing the ratio of the gold in alloy the sensitivity is decreased.

Continuous glucose determination using fiber-based tunable mid-infrared laser spectroscopy

NASA Astrophysics Data System (ADS)

Yu, Songlin; Li, Dachao; Chong, Hao; Sun, Changyue; Xu, Kexin

2014-04-01

Wavelength-tunable laser spectroscopy in combination with a small-sized fiber-optic attenuated total reflection (ATR) sensor (fiber-based evanescent field analysis, FEFA) is reported for the continuous measurement of the glucose level. We propose a method of controlling and stabilizing the wavelength and power of laser emission and present a newly developed mid-infrared wavelength-tunable laser with a broad emission spectrum band of 9.19-9.77 μm (1024-1088 cm-1). The novel small-sized flow-through fiber-optic ATR sensor with long optical sensing length was used for glucose level determination. The experimental results indicate that the noise-equivalent concentration of this laser measurement system is as low as 3.8 mg/dL, which is among the most precise glucose measurements using mid-infrared spectroscopy. The sensitivity, which is three times that of conventional Fourier transform infrared spectrometer, was acquired because of the higher laser power and higher spectral resolution. The best prediction of the glucose concentration in phosphate buffered saline solution was achieved using the five-variable partial least-squares model, yielding a root-mean-square error of prediction as small as 3.5 mg/dL. The high sensitivity, multiple tunable wavelengths and small fiber-based sensor with long optical sensing length make glucose determination possible in blood or interstitial fluid in vivo.

In-line open-cavity Fabry-Pérot interferometer formed by C-shaped fiber fortemperature-insensitive refractive index sensing.

PubMed

Wu, Chuang; Liu, Zhengyong; Zhang, A Ping; Guan, Bai-Ou; Tam, Hwa-Yaw

2014-09-08

We report an open-cavity optical fiber Fabry-Pérot interferometer (FPI) capable of measuring refractive index with very low temperature cross-sensitivity. The FPI was constructed by splicing a thin piece of C-shaped fiber between two standard single-mode fibers. The refractive index (RI) response of the FPI was characterized using water-ethanol mixtures with RI in the range of 1.33 to 1.36. The RI sensitivity was measured to be 1368 nm/RIU at the wavelength of 1600 nm with good linearity. Thanks to its all-glass structure, the FPI exhibits very low temperature cross-sensitivity of 3.04 × 10⁻⁷ RIU/°C. The effects of cavity length on the performance of the sensor were also studied. A shorter cavity gives rise to broader measurement range while offering larger detection limit, and vice versa. What's more, the effect of material dispersion of analyte on the sensitivity of open-cavity FPIs was identified for the first time. The sensor is compact in size and easy to fabricate. It is potentially useful for label-free optical sensing of chemical and biological samples.

First clinical evaluation of a new percutaneous optical fiber glucose sensor for continuous glucose monitoring in diabetes.

PubMed

Müller, Achim Josef; Knuth, Monika; Nikolaus, Katharina Sibylle; Krivánek, Roland; Küster, Frank; Hasslacher, Christoph

2013-01-01

This article describes a new fiber-coupled, percutaneous fluorescent continuous glucose monitoring (CGM) system that has shown 14 days of functionality in a human clinical trial. The new optical CGM system (FiberSense) consists of a transdermal polymer optical fiber containing a biochemical glucose sensor and a small fluorescence photometer optically coupled to the fiber. The glucose-sensitive optical fiber was implanted in abdominal and upper-arm subcutaneous tissue of six diabetes patients and remained there for up to 14 days. The performance of the system was monitored during six visits to the study center during the trial. Blood glucose changes were induced by oral carbohydrate intake and insulin injections, and capillary blood glucose samples were obtained from the finger tip. The data were analyzed using linear regression and the consensus error grid analysis. The FiberSense worn at the upper arm exhibited excellent results during 14 wearing days, with an overall mean absolute relative difference (MARD) of 8.3% and 94.6% of the data in zone A of the consensus error grid. At the abdominal application site, FiberSense resulted in a MARD of 11.4 %, with 93.8% of the data in zone A. The FiberSense CGM system provided consistent, reliable measurements of subcutaneous glucose levels in human clinical trial patients with diabetes for up to 14 days. © 2013 Diabetes Technology Society.

Fiber optic vibration sensor using bifurcated plastic optical fiber

NASA Astrophysics Data System (ADS)

Abdullah, M.; Bidin, N.; Yasin, M.

2016-11-01

An extrinsic fiber optic vibration sensor is demonstrated for a fiber optic displacement sensor based on a bundled multimode fiber to measure a vibration frequency ranging from 100 until 3000 Hz. The front slope has a sensitivity of 0.1938mV/mm and linearity of 99.7% within a measurement range between 0.15-3.00 mm. By placing the diaphragm of the concave load-speaker within the linear range from the probe, the frequency of the vibration can be measured with error percentage of less than 1.54%. The graph of input against output frequency for low, medium and high frequency range show very high linearity up to 99%. Slope for low, medium, and high frequency range are calculated as 1.0026, 0.9934, and 1.0007 respectively. Simplicity, long term stability, low power consumption, wide dynamic and frequency ranges, noise reduction, ruggedness, linearity and light weight make it promising alternative to other well-establish methods for vibration frequency measurement.

NDT of fiber-reinforced composites with a new fiber-optic pump–probe laser-ultrasound system☆

PubMed Central

Pelivanov, Ivan; Buma, Takashi; Xia, Jinjun; Wei, Chen-Wei; O’Donnell, Matthew

2014-01-01

Laser-ultrasonics is an attractive and powerful tool for the non-destructive testing and evaluation (NDT&E) of composite materials. Current systems for non-contact detection of ultrasound have relatively low sensitivity compared to contact peizotransducers. They are also expensive, difficult to adjust, and strongly influenced by environmental noise. Moreover, laser-ultrasound (LU) systems typically launch only about 50 firings per second, much slower than the kHz level pulse repetition rate of conventional systems. As demonstrated here, most of these drawbacks can be eliminated by combining a new generation of compact, inexpensive, high repetition rate nanosecond fiber lasers with new developments in fiber telecommunication optics and an optimally designed balanced probe beam detector. In particular, a modified fiber-optic balanced Sagnac interferometer is presented as part of a LU pump–probe system for NDT&E of aircraft composites. The performance of the all-optical system is demonstrated for a number of composite samples with different types and locations of inclusions. PMID:25302156

Conformal Regge theory

NASA Astrophysics Data System (ADS)

Goncalves, Vasco David Fonseca

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Analytical Applications of Fluorescent Carbon Dots

NASA Astrophysics Data System (ADS)

Goncalves, Helena Maria Rodrigues

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Nanostructured Photoanodes for Solar Cells

NASA Astrophysics Data System (ADS)

Apolinario, Arlete Ondina Alves da Silva

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Chemoselectivity of Immobilized Transition Metal Catalysts

NASA Astrophysics Data System (ADS)

Teixeira, Filipe

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Sources and diagnostics for attosecond science

NASA Astrophysics Data System (ADS)

Miranda, Miguel Nicolau da Costa Ribeiro de

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Photonic crystal fiber heat sensors

NASA Astrophysics Data System (ADS)

Twigg, S.; Coompson, J.; Colalillo, A.; Wynne, R.

2011-04-01

A sensing configuration based on commercially available triple-core photonic crystal fiber (PCF) for the image-based collection of thermal information is presented. Detection of thermal phenomena on the micro and nano scale is important for monitoring thermodynamic processes including cooling mechanisms for industry and basic research in both civil and mechanical systems. The thermal characteristics of the PCF combined with coupled-mode theory principles are used to construct a three core PCF with a 1-D core arrangement to simultaneously measure heat flux and temperature. The PCF sensor demonstrated high detection sensitivity (<1°C) and fast response times (<30μs), which is a significant improvement to current commercial standards. PCFs are specialty optical fibers that contain carefully spaced micronsized cavities that provide extraordinary waveguide characteristics not demonstrated by standard optical fiber. The three core PCF has a core diameter of 3.9μm, outer diameter of 132.5μm and varied inter core spacing. A single mode fiber is fusion spliced with the multi-core PCF such that the optical field is confined and launched into the PCF core. The output end of the fiber is inspected and imaged with a CCD camera. A 25mm section of the PCF is surrounded by a guarded hotplate configuration to control the thermal conditions for sensor characterization. Evanescent wave coupling occurs whereby power is transferred from the central core to a neighboring core. Minimum detection sensitivities of 0.2 °C were recorded. Theoretical sensitivities on the order of 10-2 °C are possible. Experimental results were in agreement with coupled-mode theoretical results.

Development of active and sensitive material systems based on composites

NASA Astrophysics Data System (ADS)

Asanuma, Hiroshi

2002-07-01

This paper describes new concepts proposed by the author to realize active and sensitive structural material systems. Two examples of multifunctional composites were fabricated and evaluated in this study as follows: (1) An active laminate of aluminum plate (works as muscle), epoxy film (as insulator), unidirectional CFRP prepreg (as bone and blood vessel) and copper foil electrode (to apply voltage on CFRP) was made with an embedded optical fiber multiply fractured in the CFRP layer (works as nerve), of which curvature change could be effectively monitored with the fractured optical fiber. (2) A stainless steel fiber/aluminum active composite with embedded Ti oxide/Ti composite fiber was fabricated. The Ti oxide/Ti fiber could work as a sensor for temperature by removing a part of the oxide before embedment to make a metallic contact between the embedded titanium fiber and aluminum matrix to be able to generate thermal electromotive force, and also could work as a sensor for strain and as a heater for actuation. In the both cases, the outputs from their embedded sensors can be used to control their actuations.

Simple fiber-optic confocal microscopy with nanoscale depth resolution beyond the diffraction barrier.

PubMed

Ilev, Ilko; Waynant, Ronald; Gannot, Israel; Gandjbakhche, Amir

2007-09-01

A novel fiber-optic confocal approach for ultrahigh depth-resolution (

Optical fiber spectroscopy: A study of the luminescent properties of the europium ion for thermal sensors

NASA Technical Reports Server (NTRS)

Buoncristiani, A. Martin

1992-01-01

Recently, there has been interest in developing a distributed temperature sensor integrated into an optical fiber. Such a system would allow embedding of the optical fiber within or on a structural material to provide for continuous monitoring of the material's temperature. Work has already begun on the development of a temperature sensor using the temperature dependent emission spectra from the lanthanide rare earths doped into crystalline hosts. The lifetime, the linewidth and the integrated intensity of this emission are each sensitive to changes in the temperature and can provide a basis for thermometry. One concept for incorporating this phenomena into an optical fiber based sensor involves bonding the optically active material to the cladding of an optical fiber and allowing the luminescent light to couple into the the fiber by the evanescent wave. Experimental work developing this concept has already been reported. Measurements of the linewidth of Eu3+:Y2O3, diffused into a fiber, made by Albin clearly show a strong and regular dependence on temperature over the range of 300 to 1000 K. We report here on a study of the temperature dependence of the lineshape of the emission at 611 nm using the data in references. We focus attention on understanding the general behavior of the Eu3+:Y2O3 system. Building upon understanding of this system we will be able to establish the physical criterial for a good optical fiber based temperature sensor and then to examine available data on other lanthanide rare earths and transition metal ions to determine the best luminescent system for temperature sensing in an optical fiber.

Ultraviolet spectroscopic breath analysis using hollow-optical fiber as gas cell

NASA Astrophysics Data System (ADS)

Iwata, T.; Katagiri, T.; Matsuura, Y.

2017-02-01

For breath analysis on ultraviolet absorption spectroscopy, an analysis system using a hollow optical fiber as gas cell is developed. The hollow optical fiber functions as a long path and extremely small volume gas cell. Firstly, the measurement sensitivity of the system is evaluated by using NO gas as a gas sample. The result shows that NO gas with 50 ppb concentration is measured by using a system with a laser-driven, high intensity light source and a 3-meter long, aluminum-coated hollow optical fiber. Then an absorption spectrum of breath sample is measured in the wavelength region of around 200-300 nm and from the spectrum, it is found that the main absorbing components in breath were H2O, isoprene, and O3 converted from O2 by radiation of ultraviolet light. Then the concentration of isoprene in breath is estimated by using multiple linear regression analysis.

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.

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

PubMed

Liehr, Sascha; Breithaupt, Mathias; Krebber, Katerina

2017-03-31

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

Photonic crystal fiber Fabry-Perot interferometers with high-reflectance internal mirrors

NASA Astrophysics Data System (ADS)

Fan, Rong; Hou, Yuanbin; Sun, Wei

2015-06-01

We demonstrated an in-line micro fiber-optic Fabry-Perot interferometer with an air cavity which was created by multi-step fusion splicing a muti-mode photonic crystal fiber (MPCF) to a standard single mode fiber (SMF). The fringe visibility of the interference pattern was up to 20 dB by reshaping the air cavity. Experimental results showed that such a device could be used as a highly sensitive strain sensor with the sensitivity of 4.5 pm/μɛ. Moreover, it offered some other outstanding advantages, such as the extremely compact structure, easy fabrication, low cost, and high accuracy.

A novel optical fiber displacement sensor of wider measurement range based on neural network

NASA Astrophysics Data System (ADS)

Guo, Yuan; Dai, Xue Feng; Wang, Yu Tian

2006-02-01

By studying on the output characteristics of random type optical fiber sensor and semicircular type optical fiber sensor, the ratio of the two output signals was used as the output signal of the whole system. Then the measurement range was enlarged, the linearity was improved, and the errors of reflective and absorbent changing of target surface are automatically compensated. Meantime, an optical fiber sensor model of correcting static error based on BP artificial neural network(ANN) is set up. So the intrinsic errors such as effects of fluctuations in the light, circuit excursion, the intensity losses in the fiber lines and the additional losses in the receiving fiber caused by bends are eliminated. By discussing in theory and experiment, the error of nonlinear is 2.9%, the measuring range reaches to 5-6mm and the relative accuracy is 2%.And this sensor has such characteristics as no electromagnetic interference, simple construction, high sensitivity, good accuracy and stability. Also the multi-point sensor system can be used to on-line and non-touch monitor in working locales.

Verification of the windings axial clamping forces for high voltage power transformers by using passively mode-locked fiber lasers

NASA Astrophysics Data System (ADS)

Şchiopu, IonuÅ£ Romeo; ǎgulinescu, Andrei, Dr; Iordǎnescu, Raluca; Marinescu, Andrei

2015-02-01

The current paper describes an optoelectronic method for direct monitoring of the axial clamping forces both in static and in dynamic duty. As advantages of this method we can state that it can be applied both to new and refurbished transformers without performing constructive changes or affecting in any way the transformer safety in operation. For monitoring the axial clamping forces for high-voltage (HV) power transformers, we use an optical fiber that we integrate into the laser cavity of a passively mode-locked fiber laser (PMFL). To each axial clamp corresponds a solitonic optical spectrum that is changed at the periodical passing of the fundamental soliton pulse through the sensitive fiber inside the transformer. Moreover, as a specific characteristic, the laser stability is unique for each set of axial clamping forces. Other important advantages of using an optical fiber as compared to the classical approach in which electronic sensors are used consist in the good reliability and insulator properties of the optical fiber, avoiding any risk of fire or damage of the transformer.

Photonic crystal nanofiber air-mode cavity with high Q-factor and high sensitivity for refractive index sensing

NASA Astrophysics Data System (ADS)

Ma, Xiaoxue; Chen, Xin; Nie, Hongrui; Yang, Daquan

2018-01-01

Recently, due to its superior characteristics and simple manufacture, such as small size, low loss, high sensitivity and convenience to couple, the optical fiber sensor has become one of the most promising sensors. In order to achieve the most effective realization of light propagation by changing the structure of sensors, FOM(S •Q/λres) ,which is determined by two significant variables Q-factor and sensitivity, as a trade-off parameter should be optimized to a high value. In typical sensors, a high Q can be achieved by confining the optical field in the high refractive index dielectric region to make an interaction between analytes and evanescent field of the resonant mode. However, the ignored sensitivity is relatively low with a high Q achieved, which means that the resonant wavelength shift changes non-obviously when the refractive index increases. Meanwhile, the sensitivity also leads to a less desirable FOM. Therefore, a gradient structure, which can enhance the performance of sensors by achieving high Q and high sensitivity, has been developed by Kim et al. later. Here, by introducing parabolic-tapered structure, the light field localized overlaps strongly and sufficiently with analytes. And based on a one-dimensional photonic-crystal nanofiber air-mode cavity, a creative optical fiber sensor is proposed by combining good stability and transmission characteristics of fiber and strengths of tapered structure, realizing excellent FOM {4.7 x 105 with high Q-factors (Q{106) and high sensitivities (<700 nm/RIU).

Magnetic resonance-coupled fluorescence tomography scanner for molecular imaging of tissue

NASA Astrophysics Data System (ADS)

Davis, Scott C.; Pogue, Brian W.; Springett, Roger; Leussler, Christoph; Mazurkewitz, Peter; Tuttle, Stephen B.; Gibbs-Strauss, Summer L.; Jiang, Shudong S.; Dehghani, Hamid; Paulsen, Keith D.

2008-06-01

A multichannel spectrally resolved optical tomography system to image molecular targets in small animals from within a clinical MRI is described. Long source/detector fibers operate in contact mode and couple light from the tissue surface in the magnet bore to 16 spectrometers, each containing two optical gratings optimized for the near infrared wavelength range. High sensitivity, cooled charge coupled devices connected to each spectrograph provide detection of the spectrally resolved signal, with exposure times that are automated for acquisition at each fiber. The design allows spectral fitting of the remission light, thereby separating the fluorescence signal from the nonspecific background, which improves the accuracy and sensitivity when imaging low fluorophore concentrations. Images of fluorescence yield are recovered using a nonlinear reconstruction approach based on the diffusion approximation of photon propagation in tissue. The tissue morphology derived from the MR images serves as an imaging template to guide the optical reconstruction algorithm. Sensitivity studies show that recovered values of indocyanine green fluorescence yield are linear to concentrations of 1nM in a 70mm diameter homogeneous phantom, and detection is feasible to near 10pM. Phantom data also demonstrate imaging capabilities of imperfect fluorophore uptake in tissue volumes of clinically relevant sizes. A unique rodent MR coil provides optical fiber access for simultaneous optical and MR data acquisition of small animals. A pilot murine study using an orthotopic glioma tumor model demonstrates optical-MRI imaging of an epidermal growth factor receptor targeted fluorescent probe in vivo.

A hetero-core fiber optic smart mat sensor for discrimination between a moving human and object on temporal loss peaks

NASA Astrophysics Data System (ADS)

Hosoki, Ai; Nishiyama, Michiko; Choi, Yongwoon; Watanabe, Kazuhiro

2011-05-01

In this paper, we propose discrimination method between a moving human and object by means of a hetero-core fiber smart mat sensor which induces the optical loss change in time. In addition to several advantages such as flexibility, thin size and resistance to electro-magnetic interference for a fiber optic sensor, a hetero-core fiber optic sensor is sensitive to bending action of the sensor portion and independent of temperature fluctuations. Therefore, the hetero-core fiber thin mat sensor can have a fewer sensing portions than the conventional floor pressure sensors, furthermore, can detect the wide area covering the length of strides. The experimental results for human walking tests showed that the mat sensors were reproducibly working in real-time under limiting locations the foot passed in the mat sensor. Focusing on the temporal peak numbers in the optical loss, human walking and wheeled platform moving action induced the peak numbers in the range of 1 - 3 and 5 - 7, respectively, for the 10 persons including 9 male and 1 female. As a result, we conclude that the hetero-core fiber mat sensor is capable of discriminating between the moving human and object such as a wheeled platform focusing on the peak numbers in the temporal optical loss.

Localized surface plasmon resonance-based fiber-optic sensor for the detection of triacylglycerides using silver nanoparticles.

PubMed

Baliyan, Anjli; Usha, Sruthi Prasood; Gupta, Banshi D; Gupta, Rani; Sharma, Enakshi Khular

2017-10-01

A label-free technique for the detection of triacylglycerides by a localized surface plasmon resonance (LSPR)-based biosensor is demonstrated. An LSPR-based fiber-optic sensor probe is fabricated by immobilizing lipase enzyme on silver nanoparticles (Ag-NPs) coated on an unclad segment of a plastic clad optical fiber. The size and shape of nanoparticles were characterized by high-resolution transmission electron microscopy and UV-visible spectroscopy. The peak absorbance wavelength changes with concentration of triacylglycerides surrounding the sensor probe, and sensitivity is estimated from shift in the peak absorbance wavelength as a function of concentration. The fabricated sensor was characterized for the concentration of triacylglyceride solution in the range 0 to 7 mM. The sensor shows the best sensitivity at a temperature of 37°C and pH 7.4 of the triacylglycerides emulsion with a response time of 40 s. A sensitivity of 28.5  nm/mM of triacylglyceride solution is obtained with a limit of detection of 0.016 mM in the entire range of triacylglycerides. This compact biosensor shows good selectivity, stability, and reproducibility in the entire physiological range of triacylglycerides and is well-suited to real-time online monitoring and remote sensing. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

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

NASA Astrophysics Data System (ADS)

Yamazaki, Hiroshi; Koyama, Yuya; Watanabe, Kazuhiro

2014-05-01

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

Spectral domain polarization-sensitive optical coherence tomography at 850 nm

NASA Astrophysics Data System (ADS)

Cense, Barry; Chen, Teresa C.; Mujat, Mircea; Joo, Chulmin; Akkin, Taner; Park, B. H.; Pierce, Mark C.; Yun, Andy; Bouma, Brett E.; Tearney, Guillermo J.; de Boer, Johannes F.

2005-04-01

Spectral-Domain Polarization-Sensitive Optical Coherence Tomography (SD-PS-OCT) is a technique developed to measure the thickness and birefringence of the nerve fiber layer in vivo as a tool for the early diagnosis of glaucoma. A clinical SD-PS-OCT system was developed and scans were made around the optic nerve head (ONH) using ten concentric circles of increasing diameter. One healthy volunteer was imaged. Retinal nerve fiber layer thickness and birefringence information was extracted from the data. Polarization-sensitive OCT images were acquired at video rate (29 frames per second (fps), 1000 A-lines / frame) and at 7 fps (1000 A-lines / frame). The last setting improved the signal to noise ratio by approximately 6 dB. Birefringence measurements on the healthy volunteer gave similar results as earlier reported values that were obtained with a time-domain setup. The measurement time was reduced from more than a minute to less than a second.

Toward athermal silicon-on-insulator (de)multiplexers in the O-band.

PubMed

Hassan, Karim; Sciancalepore, Corrado; Harduin, Julie; Ferrotti, Thomas; Menezo, Sylvie; Ben Bakir, Badhise

2015-06-01

We report on the design, fabrication, and characterization of a 1×4 silicon-on-insulator (SOI) demultiplexer exhibiting a significant reduction of its thermo-optical sensitivity in the O-band. The optical filtering is achieved by cascading several Mach-Zehnder interferometers (MZIs) fabricated on a 300-nm-thick SOI platform. Owing to an asymmetric design of the confinement for each MZIs, we found an athermal criterium that satisfies the spectral requirements. The thermal sensitivity of the structure is analyzed by a semi-analytical model in order to create an athermal multiplexer. Fiber-to-fiber thermo-optical testing reveals a thermal sensitivity of around 17  pm/°C reduced by 75% compared to the standard devices with promising performances for both the crosstalk (15 dB), the insertion losses (4 dB), and absolute lambda registration (<0.25  nm).

A FBG pulse wave demodulation method based on PCF modal interference filter

NASA Astrophysics Data System (ADS)

Zhang, Cheng; Xu, Shan; Shen, Ziqi; Zhao, Junfa; Miao, Changyun; Bai, Hua

2016-10-01

Fiber optic sensor embedded in textiles has been a new direction of researching smart wearable technology. Pulse signal which is generated by heart beat contains vast amounts of physio-pathological information about the cardiovascular system. Therefore, the research for textile-based fiber optic sensor which can detect pulse wave has far-reaching effects on early discovery and timely treatment of cardiovascular diseases. A novel wavelength demodulation method based on photonic crystal fiber (PCF) modal interference filter is proposed for the purpose of developing FBG pulse wave sensing system embedded in smart clothing. The mechanism of the PCF modal interference and the principle of wavelength demodulation based on In-line Mach-Zehnder interferometer (In-line MZI) are analyzed in theory. The fabricated PCF modal interferometer has the advantages of good repeatability and low temperature sensitivity of 3.5pm/°C from 25°C to 60°C. The designed demodulation system can achieve linear demodulation in the range of 2nm, with the wavelength resolution of 2.2pm and the wavelength sensitivity of 0.055nm-1. The actual experiments' result indicates that the pulse wave can be well detected by this demodulation method, which is in accordance with the commercial demodulation instrument (SM130) and more sensitive than the traditional piezoelectric pulse sensor. This demodulation method provides important references for the research of smart clothing based on fiber grating sensor embedded in textiles and accelerates the developments of wearable fiber optic sensors technology.

Preparation Of Small Diameter Sensors For Continuous Clinical Monitoring

NASA Astrophysics Data System (ADS)

Walt, David R.; Munkholm, Christiane; Jordan, David; Milanovich, Fred P.; Daley, Paul F.

1987-04-01

We have prepared fluorescence-based fiber optic sensors which give rapid and reversible responses. Other investigators have previously prepared sensors in which a membrane, tubing, or a hollow fiber is used to contain a specific reagent near the distal end of the fiber. Such an approach produces fibers with limited signal magnitudes and slow response times. Furthermore, these sensors are cumbersome to assemble, and are difficult to miniaturize and calibrate. We have developed a technique for the covalent chemical modification of the fiber's distal surface which is easily adapted to the smallest diameter glass optical fiber (100 μm). The sensing layer is attached directly to the fiber surface. The layer is extremely thin and highly porous and provides high fluorescence intensity with nearly instantaneous response times. The fibers are moderately stable against bleaching and have long shelf-lives. Our initial efforts have concentrated on the preparation of pH-sensitive optical sensors that are useful in the pH range 4.0 to 8.0. These sensors are reversible in response to pH variation and possess signal-to-noise ratios over 250/1. The fibers are prepared using a glass surface modification followed by a polymerization step for dye immobilization. Both fluorescence and absorbance-based sensors have been prepared using this technique. The absorbance-based pH sensors have 100% response times of less than 3 seconds, are sensitive in the region of pH 6.0 to 8.0, and provide reliable measurement of pH with precision of better than 0.03 pH units.

Displacement sensing based on modal interference in polymer optical fibers with partially applied strain

NASA Astrophysics Data System (ADS)

Mizuno, Yosuke; Hagiwara, Sonoko; Kawa, Tomohito; Lee, Heeyoung; Nakamura, Kentaro

2018-05-01

Strain sensing based on modal interference in multimode fibers (MMFs) has been extensively studied, but no experimental or theoretical reports have been given as to how the system works when strain is applied not to the whole MMF but only to part of the MMF. Here, using a perfluorinated graded-index polymer optical fiber as the MMF, we investigate the strain sensing characteristics of this type of sensor when strain is partially applied to fiber sections with different lengths. The strain sensitivity dependence on the length of the strained section reveals that this strain sensor actually behaves as a displacement sensor.

Welding-fume-induced transmission loss in tapered optical fibers

NASA Astrophysics Data System (ADS)

Yi, Ji-Haeng

2015-09-01

This paper presents a method for sensing welding fumes in real time. This method is based on the results of nanoparticle-induced optical-fiber loss experiments that show that the losses are determined by the nanoparticle density and the taper waist. The tapered fiber is obtained by applying heat radiated from hot quartz, and monitoring is done in real time. First, the durability of the tapered fiber during the welding process is proven. Then, the loss is categorized by using the sizes of welding fume particles. The sensitivity to welding fumes increases with increasing size of the particles; consequently, the dimension of the taper waist decreases.

Evaluation of an optical fiber probe for in vivo measurement of the photoacoustic response of tissues

NASA Astrophysics Data System (ADS)

Beard, Paul C.; Mills, Timothy N.

1995-05-01

A miniature (1 mm diameter) all-optical photoacoustic probe for generating and detecting ultrasonic thermoelastic waves in biological media at the tip of an optical fiber has been developed. The probe provides a compact and convenient means of performing pulsed photoacoustic spectroscopy for the characterization of biological tissue. The device is based upon a transparent Fabry Perot polymer film ultrasound sensor mounted directly over the end of a multimode optical fiber. The optical fiber is used to deliver nanosecond laser pulses to the tissue producing thermoelastic waves which are then detected by the sensor. Detection sensitivities of 53 mv/MPa and a 10 kPa acoustic noise floor have been demonstrated giving excellent signal to noise ratios in a strong liquid absorber. Lower, but clearly detectable, signals in post mortem human aorta have also been observed. The performance and small physical size of the device suggest that it has the potential to perform remote in situ photoacoustic measurements in tissue.

All fiber magnetic field sensor with Ferrofluid-filled tapered microstructured optical fiber interferometer.

PubMed

Deng, Ming; Huang, Can; Liu, Danhui; Jin, Wei; Zhu, Tao

2015-08-10

An ultra-compact optical fiber magnetic field sensor based on a microstructured optical fiber (MOF) modal interference and ferrofluid (FF) has been proposed and experimentally demonstrated. The magnetic field sensor was fabricated by splicing a tapered germanium-doped index guided MOF with six big holes injected with FF to two conventional single-mode fibers. The transmission spectra of the proposed sensor under different magnetic field intensities have been measured and theoretically analyzed. Due to an efficient interaction between the magnetic nanoparticles in FF and the excited cladding mode, the magnetic field sensitivity reaches up to117.9pm/mT with a linear range from 0mT to 30mT. Moreover, the fabrication process of the proposed sensor is simple, easy and cost-effective. Therefore, it will be a promising candidate for military, aviation industry, and biomedical applications, especially, for the applications where the space is limited.

Fast detection of humidity with a subwavelength-diameter fiber taper coated with gelatin film.

PubMed

Zhang, Lei; Gu, Fuxing; Lou, Jingyi; Yin, Xuefeng; Tong, Limin

2008-08-18

A subwavelength-diameter tapered optical fiber coated with gelatin layer for fast relative humidity (RH) sensing is reported. The sensing element is composed of a 680-nm-diameter fiber taper coated with a 80-nm-thickness 8-mm-length gelatin layer, and is operated at a wavelength of 1550 nm. When exposed to moisture, the change in refractive index of the gelatin layer changes the mode field of the guided mode of the coated fiber, and converts a portion of power from guided mode to radiation mode, resulting in RH-dependent loss for optical sensing. The sensor is operated within a wide humidity range (9-94% RH) with high sensitivity and good reversibility. Measured response time is about 70 ms, which is one or two orders of magnitude faster than other types of RH sensors relying on conventional optical fibers or films.

How to specify and measure sensitivity in Distributed Acoustic Sensing (DAS)?

NASA Astrophysics Data System (ADS)

Gabai, Haniel; Eyal, Avishay

2017-04-01

In Rayleigh-scattering-based Distributed Acoustic Sensing (DAS) an optical fiber is transformed into an array of thousands of 'virtual microphones'. This approach has gained tremendous popularity in recent years and is one of the most successful examples of a fiber-optic sensing method which made its way from the academia to the market. Despite the great amount of work done in this field, sensitivity, which is ones of the most critical parameters of any sensing technique, was rarely investigated in this context. In particular, little attention was given to its random characteristics. Without careful consideration of the random aspects of DAS, any attempt to specify its sensitivity or to compare between different DAS modalities is of limited value. Recently we introduced a new statistical parameter which defines DAS sensitivity and enables comparison between the performances of different DAS systems. In this paper we generalize the previous parameter and give a broader, simple and intuitive definition to DAS sensitivity. An important attribute of these parameters is that they can be easily extracted from the static backscatter profile of the sensing fiber. In the paper we derive the relation between DAS sensitivity and the static backscatter profile and present an experimental verification of this relation.

In-Fiber Magneto-Optic Devices Based on Ultrahigh Verdet Constant Organic Materials and Holey Fibers

DTIC Science & Technology

2009-02-02

protocols and a noise equivalent magnetic field sensitivity of ~ 100 pT/ VHz has been demonstrated. • Magneto-optic properties of magnetite - PMMA composite...nanoparticle - PMMA nanocomposite. We have used both transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) to...we expect to enhance it in our devices by their proper symmetrization as described above. Passive Poking core ^^ direction Magnetic AA

Fiber-based polarization-sensitive OCT of the human retina with correction of system polarization distortions

PubMed Central

Braaf, Boy; Vermeer, Koenraad A.; de Groot, Mattijs; Vienola, Kari V.; de Boer, Johannes F.

2014-01-01

In polarization-sensitive optical coherence tomography (PS-OCT) the use of single-mode fibers causes unpredictable polarization distortions which can result in increased noise levels and erroneous changes in calculated polarization parameters. In the current paper this problem is addressed by a new Jones matrix analysis method that measures and corrects system polarization distortions as a function of wavenumber by spectral analysis of the sample surface polarization state and deeper located birefringent tissue structures. This method was implemented on a passive-component depth-multiplexed swept-source PS-OCT system at 1040 nm which was theoretically modeled using Jones matrix calculus. High-resolution B-scan images are presented of the double-pass phase retardation, diattenuation, and relative optic axis orientation to show the benefits of the new analysis method for in vivo imaging of the human retina. The correction of system polarization distortions yielded reduced phase retardation noise, and better estimates of the diattenuation and the relative optic axis orientation in weakly birefringent tissues. The clinical potential of the system is shown by en face visualization of the phase retardation and optic axis orientation of the retinal nerve fiber layer in a healthy volunteer and a glaucoma patient with nerve fiber loss. PMID:25136498

Feasibility study for distributed dose monitoring in ionizing radiation environments with standard and custom-made optical fibers

NASA Astrophysics Data System (ADS)

Van Uffelen, Marco; Berghmans, Francis; Brichard, Benoit; Borgermans, Paul; Decréton, Marc C.

2002-09-01

Optical fibers stimulate much interest since many years for their potential use in various nuclear environments, both for radiation tolerant and EMI-free data communication as well as for distributed sensing. Besides monitoring temperature and stress, measuring ionizing doses with optical fibers is particularly essential in applications such as long-term nuclear waste disposal monitoring, and for real-time aging monitoring of power and signal cables installed inside a reactor containment building. Two distinct options exist to perform optical fiber dosimetry. First, find an accurate model for a restricted application field that accounts for all the parameters that influence the radiation response of a standard fiber, or second, develop a dedicated fiber with a response that will solely depend on the deposited energy. Using various models presented in literature, we evaluate both standard commercially available and custom-made optical fibers under gamma radiation, particularly for distributed dosimetry applications with an optical time domain reflectometer (OTDR). We therefore present the radiation induced attenuation at near-infrared telecom wavelengths up to MGy total dose levels, with dose rates ranging from about 1 Gy/h up to 1 kGy/h, whereas temperature was raised step-wise from 25 °C to 85 °C. Our results allow to determine and compare the practical limitations of distributed dose measurements with both fiber types in terms of temperature sensitivity, dose estimation accuracy and spatial resolution.

Design of a Pressure Sensor Based on Optical Fiber Bragg Grating Lateral Deformation

PubMed Central

Urban, Frantisek; Kadlec, Jaroslav; Vlach, Radek; Kuchta, Radek

2010-01-01

This paper describes steps involved in the design and realization of a new type of pressure sensor based on the optical fiber Bragg grating. A traditional pressure sensor has very limited usage in heavy industrial environments, particularly in explosive or electromagnetically noisy environments. Utilization of optics in these environments eliminates all surrounding influences. An initial motivation for our development was the research, experimental validation, and realization of a complex smart pressure sensor based on the optical principle. The main benefit of this solution consists of increasing sensitivity, resistance to electromagnetic interference, dimensions, and potential increased accuracy. PMID:22163521

Humidity sensor based on intracavity sensing of fiber ring laser

NASA Astrophysics Data System (ADS)

Shi, Jia; Xu, Wei; Xu, Degang; Wang, Yuye; Zhang, Chao; Yan, Chao; Yan, Dexian; He, Yixin; Tang, Longhuang; Zhang, Weihong; Yao, Jianquan

2017-10-01

A humidity sensor based on the intracavity sensing of a fiber ring laser is proposed and experimentally demonstrated. In the fiber ring laser, a humidity-sensitive fiber-optic multimode interferometer (MMI), fabricated by the single-mode-no-core-single-mode (SNCS) fiber coated with Agarose, works as the wavelength-selective filter for intracavity wavelength-modulated humidity sensing. The experiment shows that the lasing wavelength of the fiber laser has a good linear response to ambient humidity from 35%RH to 95%RH. The humidity sensitivity of -68 pm/%RH is obtained with a narrow 3 dB bandwidth less than 0.09 nm and a high signal-to-noise ratio (SNR)  ˜60 dB. The time response of the sensor has been measured to be as fast as 93 ms. The proposed sensor possesses a good stability and low temperature cross-sensitivity.

Detection of bacteria using bacteriophage with hollow gold nanostructures immobilized fiber optic sensor

NASA Astrophysics Data System (ADS)

Halkare, Pallavi; Punjabi, Nirmal; Wangchuk, Jigme; Kondabagil, Kiran; Mukherji, Soumyo

2016-04-01

Hollow gold nanostructures (HGNS) have been used in variety of optical biosensors due to their inherent advantage of operating at near infra red (NIR) wavelength, large extinction coefficient and high dielectric sensitivity. The absorption wavelength of these nanostructures can be modulated by changing the ratio of hollow region to the core shell thickness. The aim of the present study is to incorporate the properties of HGNS, to develop LSPR based U-bent fiber optic sensor for detection of pathogens. The detection was carried out using an experimental set up consisting of a white light source, 200 μm diameter optical fiber having bend diameter of 1.6 mm +/- 0. 2 mm and a spectrometer. The HGNS were immobilized on the decladded portion of the fiber optic probe by chemisorptions. The effective plasmon penetration depth of the HGNS immobilized fiber optic sensor was approximated by using alternating layers of positively and negatively charged polyelectrolytes. The HGNS immobilized U-bent fiber optic sensor was used for detection of E.coli B40 strain using bacteriophage T4. The preliminary experiments were carried out with 104 cfu/ml of E.coli B40 and the change in absorbance obtained was approx. 0.042 +/- 0.0045 abs. units (n = 3). The response of this sensor was found to be better than spherical gold nanoparticle immobilized sensing platforms.

Amylin Detection with a Miniature Optical-Fiber Based Sensor

NASA Astrophysics Data System (ADS)

Liu, Zhaowen; Ann, Matsko; Hughes, Adam; Reeves, Mark

We present results of a biosensor based on shifts in the localized surface plasmon resonance of gold nanoparticles self-assembled on the end of an optical fiber. This system allows for detection of protein expression in low sensing volumes and for scanning in cell cultures and tissue samples. Positive and negative controls were done using biotin/avidin and the BSA/Anti-BSA system. These demonstrate that detection is specific and sensitive to nanomolar levels. Sensing of amylin, an important protein for pancreatic function, was performed with polyclonal and monoclonal antibodies. The measured data demonstrates the difference in sensitivity to the two types of antibodies, and titration experiments establish the sensitivity of the sensor. Further experiments demonstrate that the sensor can be regenerated and then reused.

Optical Fiber Thermometer Based on Fiber Bragg Gratings

NASA Astrophysics Data System (ADS)

Rosli, Ekbal Bin; Mohd. Noor, Uzer

2018-03-01

Fiber Bragg grating has generated much interest in use as sensors to measure strain, temperature, and other physical parameters. It also the most common component used to develop this sensor with the advantages of simple, intrinsic sensing elements, electrically passive operation, EMI immunity, high sensitivity, compact size and potentially low cost [6]. This paper reports the design of an optical fiber thermometer based on fiber Bragg gratings. The system was developed for detecting temperature and strain by monitoring the shift of Bragg wavelength. The shifting of Bragg wavelength is used to indicate the temperature and strain due to the change in the surrounding temperature and strain. When the temperature and strain reach the exact wavelength level of the system, the temperature and strain value will display on the Arduino liquid crystal display (LCD). The optical fiber will provide the broadband light source and after passing the FBG the Bragg wavelength into the optical spectrum analyzer (OSA). The system is based on FBG as a physical quantity sensor. The temperatures measured is taken from the water bath and that of the strain is provided by amount of slotted mass used. The outcome of this project is to characterize the Bragg wavelength shifting from the fiber Bragg grating output. As the conclusion, this project provides an efficient optical fiber thermometer in measuring temperature and strain in order to replace the use of conventional electrical instruments.

Fiber Grating Environmental Sensing System

DOEpatents

Schulz, Whitten L.; Udd, Eric

2003-07-29

Fiber grating environmental measurement systems are comprised of sensors that are configured to respond to changes in moisture or chemical content of the surrounding medium through the action of coatings and plates inducing strain that is measured. These sensors can also be used to monitor the interior of bonds for degradation due to aging, cracking, or chemical attack. Means to multiplex these sensors at high speed and with high sensitivity can be accomplished by using spectral filters placed to correspond to each fiber grating environmental sensor. By forming networks of spectral elements and using wavelength division multiplexing arrays of fiber grating sensors may be processed in a single fiber line allowing distributed high sensitivity, high bandwidth fiber optic grating environmental sensor systems to be realized.

Real-time, ultrahigh-resolution, optical coherence tomography with an all-fiber, femtosecond fiber laser continuum at 1.5 microm.

PubMed

Nishizawa, N; Chen, Y; Hsiung, P; Ippen, E P; Fujimoto, J G

2004-12-15

Real-time, ultrahigh-resolution optical coherence tomography (OCT) is demonstrated in the 1.4-1.7-microm wavelength region with a stretched-pulse, passively mode-locked, Er-doped fiber laser and highly nonlinear fiber. The fiber laser generates 100-mW, linearly chirped pulses at a 51-MHz repetition rate. The pulses are compressed and then coupled into a normally dispersive highly nonlinear fiber to generate a low-noise supercontinuum with a 180-nm FWHM bandwidth and 38 mW of output power. This light source is stable, compact, and broadband, permitting high-speed, real-time, high-resolution OCT imaging. In vivo high-speed OCT imaging of human skin with approximately 5.5-microm resolution and 99-dB sensitivity is demonstrated.

OPTOELECTRONICS, FIBER OPTICS, AND OTHER ASPECTS OF QUANTUM ELECTRONICS: Interference-threshold storage of optical data

NASA Astrophysics Data System (ADS)

Efimkov, V. F.; Zubarev, I. G.; Kolobrodov, V. V.; Sobolev, V. B.

1989-08-01

A method for the determination of the spatial characteristics of a laser beam is proposed and implemented. This method is based on the interaction of an interference field of two laser beams, which are spatially similar to the one being investigated, with a light-sensitive material characterized by a sensitivity threshold.

Fabrication and mechanical behavior of dye-doped polymer optical fiber

NASA Astrophysics Data System (ADS)

Jiang, Changhong; Kuzyk, Mark G.; Ding, Jow-Lian; Johns, William E.; Welker, David J.

2002-07-01

The purpose of this article is to study the materials physics behind dye-doped polymethyl metharcylate (PMMA) that is important for the optical fiber drawing process. We report effects of the fabrication process on the mechanical properties of the final fiber. The qualitative degree of polymer chain alignment is found to increase with the drawing force, which in turn decreases with the drawing temperature and increases with the drawing ratio. The chain alignment relaxes when the fibers are annealed at 95 degC with a commensurate decrease in fiber length and increase in diameter. The annealed fiber has higher ductility but lower strength than the unannealed fiber. Both the yield and tensile strengths are dependent on the strain rate. The relationship between tensile strength, sigmab, and fiber diameter, d, is found empirically to be sigmab[is proportional to]d-0.5. The yield strength appears to be less sensitive to the fiber diameter than the tensile strength. For PMMA doped with disperse red 1 azo dye, the yield strength, tensile strength, and Young's modulus peak at a dye concentration of 0.0094 wt %. These results are useful for designing polymer optical fibers with well-defined mechanical properties.

Continuous liquid level detection based on two parallel plastic optical fibers in a helical structure

NASA Astrophysics Data System (ADS)

Zhang, Yingzi; Hou, Yulong; Zhang, Yanjun; Hu, Yanjun; Zhang, Liang; Gao, Xiaolong; Zhang, Huixin; Liu, Wenyi

2018-02-01

A simple and low-cost continuous liquid-level sensor based on two parallel plastic optical fibers (POFs) in a helical structure is presented. The change in the liquid level is determined by measuring the side-coupling power in the passive fiber. The side-coupling ratio is increased by just filling the gap between the two POFs with ultraviolet-curable optical cement, making the proposed sensor competitive. The experimental results show that the side-coupling power declines as the liquid level rises. The sensitivity and the measurement range are flexible and affected by the geometric parameters of the helical structure. A higher sensitivity of 0.0208 μW/mm is acquired for a smaller curvature radius of 5 mm, and the measurement range can be expanded to 120 mm by enlarging the screw pitch to 40 mm. In addition, the reversibility and temperature dependence are studied. The proposed sensor is a cost-effective solution offering the advantages of a simple fabrication process, good reversibility, and compensable temperature dependence.

Uncladded sensing fiber for refractive index measurement

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

Bhardwaj, V., E-mail: bhardwajphyism@gmail.com; Gangwar, R. K.; Pathak, A. K.

2016-05-06

The formation of chemically etched optical fiber for use in refractive index sensor is addressed. This presented design of a refractive index (RI) sensor is based on recording the power loss exhibited by radiation propagating through an etched multimode fiber (MMF) immersed in the liquid under study. The decreasing diameters of fibers are found to be strongly dependent on the temperature and etchant composition. This experiment was performed for different unclad etched fibers for same sensing length and the RI changes from 1.33 RIU to 1.38 RIU. When the multimode fiber (MMF) is etched for 12 hours the sensitivity ofmore » the sensor is approximately 204.25dBm/RIU, which is larger than without etched fiber having sensitivity 127.2dBm/RIU.« less

Fiber-Laser-Based Ultrasound Sensor for Photoacoustic Imaging

PubMed Central

Liang, Yizhi; Jin, Long; Wang, Lidai; Bai, Xue; Cheng, Linghao; Guan, Bai-Ou

2017-01-01

Photoacoustic imaging, especially for intravascular and endoscopic applications, requires ultrasound probes with miniature size and high sensitivity. In this paper, we present a new photoacoustic sensor based on a small-sized fiber laser. Incident ultrasound waves exert pressures on the optical fiber laser and induce harmonic vibrations of the fiber, which is detected by the frequency shift of the beating signal between the two orthogonal polarization modes in the fiber laser. This ultrasound sensor presents a noise-equivalent pressure of 40 Pa over a 50-MHz bandwidth. We demonstrate this new ultrasound sensor on an optical-resolution photoacoustic microscope. The axial and lateral resolutions are 48 μm and 3.3 μm. The field of view is up to 1.57 mm2. The sensor exhibits strong resistance to environmental perturbations, such as temperature changes, due to common-mode cancellation between the two orthogonal modes. The present fiber laser ultrasound sensor offers a new tool for all-optical photoacoustic imaging. PMID:28098201

Hollow fiber optics with improved durability for high-peak-power pulses of Q-switched Nd:YAG lasers.

PubMed

Matsuura, Yuji; Tsuchiuchi, Akio; Noguchi, Hiroshi; Miyagi, Mitsunobu

2007-03-10

To improve the damage threshold of hollow optical waveguides for transmitting Q-switched Nd:YAG laser pulses, we optimize the metallization processes for the inner coating of fibers. For silver-coated hollow fiber as the base, second, and third Nd:YAG lasers, drying silver films at a moderate temperature and with inert gas flow is found to be effective. By using this drying process, the resistance to high-peak-power optical pulse radiation is drastically improved for fibers fabricated with and without the sensitizing process. The maximum peak power transmitted in the fiber is greater than 20 MW. To improve the energy threshold of aluminum-coated hollow fibers for the fourth and fifth harmonics of Nd:YAG lasers, a thin silver film is added between the aluminum film and the glass substrate to increase adhesion of the aluminum coating. By using this primer layer, the power threshold improves to 3 MW for the fourth harmonics of a Q-switched Nd:YAG laser light.

Simultaneous measurement of breathing rate and heart rate using a microbend multimode fiber optic sensor

NASA Astrophysics Data System (ADS)

Chen, Zhihao; Lau, Doreen; Teo, Ju Teng; Ng, Soon Huat; Yang, Xiufeng; Kei, Pin Lin

2014-05-01

We propose and demonstrate the feasibility of using a highly sensitive microbend multimode fiber optic sensor for simultaneous measurement of breathing rate (BR) and heart rate (HR). The sensing system consists of a transceiver, microbend multimode fiber, and a computer. The transceiver is comprised of an optical transmitter, an optical receiver, and circuits for data communication with the computer via Bluetooth. Comparative experiments conducted between the sensor and predicate commercial physiologic devices showed an accuracy of ±2 bpm for both BR and HR measurement. Our preliminary study of simultaneous measurement of BR and HR in a clinical trial conducted on 11 healthy subjects during magnetic resonance imaging (MRI) also showed very good agreement with measurements obtained from conventional MR-compatible devices.

Intruder signature analysis from a phase-sensitive distributed fiber-optic perimeter sensor

NASA Astrophysics Data System (ADS)

Madsen, C. K.; Bae, T.; Snider, T.

2007-09-01

Using a phase-sensitive optical time-domain reflectometer developed at Texas A&M University, this paper reports on recent advances in intruder detection and classificatoin for long perimeters or borders. The system uses light pulses from a narrow linewidth CW laser with low frequency drift to interrogate an optical fiber. The backscattered light is detected, and real-time processing of the received signal is performed. Signatures from single and multiple humans on foot, nearby vehicle traffic on a road, construction-like vehicle activity, and animals have been obtained. Individual footsteps are clearly identified and the cadence readily observed. Time-frequency plots are used to compare the signatures. The detected signal contains information regarding the weight of the intruder as well. An adult weighing around 60kg may produce several π-radian shifts in the optical phase, which is detected by the system. While distances up to 20km have been monitored in previous remote field tests, we report measurements on a local test site with a total fiber length of 12km. A 3-mm diameter fiber cable is buried at a depth of 20-46 cm over a distance of 44m, with a 2km spool of fiber attached prior to the buried fiber and a 10km fiber spool connected in series after the buried section. Recent advances in data acquisition and signal processing allow us to avoid false alarms due to drifts in the laser center frequency and greatly improve the probability of detection. With these advancements, this technology is prime for low-cost perimeter monitoring of high-value and high-security installations such as nuclear power plants and military bases as well as national borders.

Femtosecond laser inscription of optical circuits in the cladding of optical fibers

NASA Astrophysics Data System (ADS)

Grenier, Jason R.

The aim of this dissertation was to address the question of whether the cladding of single-mode fibers (SMFs) could be modified to enable optical fibers to serve as a more integrated, highly functional platform for optical circuit devices that can efficiently interconnect with the pre-existing fiber core waveguide. The approach adopted in this dissertation was to employ femtosecond laser direct writing (FLDW), an inherently 3D fabrication technique that harnesses non-linear laser-material interactions to modify the fused silica fiber cladding. A fiber mounting and alignment technique was developed along with oil-immersion focusing to address the strong aberrations caused by the cylindrical fiber shape. The development of real-time device monitoring during the FLDW was instrumental to overcome the acute coupling sensitivity to laser alignment errors of +/-1 ?m positional uncertainty, and thereby opened a new practical direction for the precise fabrication of optical devices inside optical fibers. These powerful and flexible laser fabrication and characterization techniques were successfully employed to optimize optical waveguiding devices positioned within the core and cladding of optical fibers. X-, S-Bend, and directional couplers were developed to enable efficient coupling between the laser-formed cladding devices and the pre-existing core waveguide, enabling up to 62% power transfer over bandwidths up to 300 nm at telecommunication wavelengths. Precise alignment of femtosecond laser modification tracks were positioned inside or near the core waveguide of SMFs was further shown to enable a flexible reshaping of the optical properties to create multimode guiding sections arbitrarily along the fiber length. This core waveguide modification facilitated the precise formation of multimode interferometers along the core waveguide to precisely tailor the modal profiles, and control the spectral and polarization response. In-fiber multimode interference (MMI) splitters and couplers were fabricated with coupling ratios from 2% to 50% over a broad 350 nm bandwidth across the telecommunication band. Laser-induced birefringence was harnessed to generate polarization dependent MMI devices for strong polarization filtering (24 dB isolation), or polarization selective taps with up to 50% tapping efficiency over a 25 nm bandwidth. This dissertation is therefore the first demonstration of femtosecond laser direct writing as a flexible and monolithic means of embedding and integrating highly functional optical circuit devices within the cladding of optical fibers that can interconnect efficiently with the pre-existing fiber core waveguide. These developments represent a significant technological advancement for creating new 3D photonic integrated microsystems within the cladding of optical fibers and underpins a new technological platform of fiber cladding photonics.

Investigation on a fiber optic accelerometer based on FBG-FP interferometer

NASA Astrophysics Data System (ADS)

Lin, Chongyu; Luo, Hong; Xiong, Shuidong; Li, Haitao

2014-12-01

A fiber optic accelerometer based on fiber Bragg grating Fabry-Perot (FBG-FP) interferometer is presented. The sensor is a FBG-FP cavity which is formed with two weak fiber Bragg gratings (FBGs) in a single-mode fiber. The reflectivity of the two FBGs is 9.42% and 7.74% respectively, and the fiber between them is 10 meters long. An optical demodulation system was set up to analyze the reflected light of FBG-FP cavity. Acceleration signals of different frequencies and intensities were demodulated correctly and stably by the system. Based on analyzing the optical spectrum of weak FBG based FBG-FP cavity, we got the equivalent length of FBG-FP cavity. We used a path-matching Michelson interferometer (MI) to demodulate the acceleration signal. The visibility of the interference fringe we got was 41%~42% while the theory limit was 50%. This indicated that the difference of interferometer's two arms and the equivalent length of FBG-FP cavity were matched well. Phase generated carrier (PGC) technology was used to eliminate phase fading caused by random phase shift and Faraday rotation mirrors (FRMs) were used to eliminate polarization-induced phase fading. The accelerometer used a compliant cylinder design and its' sensitivity and frequency response were analyzed and simulated based on elastic mechanics. Experiment result showed that the accelerometer had a flat frequency response over the frequency range of 31-630Hz. The sensitivity was about 31dB (0dB=1rad/g) with fluctuation less than 1.5dB.

[Spectral characteristics of refractive index based on nanocoated optical fiber F-P sensor].

PubMed

Jiang, Ming-Shun; Li, Qiu-Shun; Sui, Qing-Mei; Jia, Lei; Peng, Peng

2013-01-01

An optical fiber Fabry-Perot (F-P) interferometer end surface was modified using layer-by-layer assembly and chemical covalent cross linking method, and the refractive index (RI) response characteristics of coated optical fiber F-P sensor were experimentally studied. Poly diallyldimethylammonium chloride (PDDA) and sodium polystyrene sulfonate (PSS) were chosen as nano-film materials. With the numbers of layers increasing, the reflection spectral contrast of optical fiber F-P sensor presents from high to low, then to high regularity. And the reflection spectral contrast has good temperature stability. The reflection spectra of the optical F-P sensor coated with 20 bilayers for a series of concentration of sucrose and inorganic solution were measured. Experimental results show that the inflection point extends from 1.457 to 1.462 3, and the reflection spectral contrast sensitivity to low RI material and high RI material is 24.53 and 3.60 dB x RI(-1), respectively, with good linearity. The results demonstrate that the functional coated optical F-P sensor provides a new method for biology and chemical material test.

Miniature fiber Fabry-Perot sensors based on fusion splicing

NASA Astrophysics Data System (ADS)

Zhu, Jia-li; Wang, Ming; Yang, Chun-di; Wang, Ting-ting

2013-03-01

Fiber-optic Fabry-Perot (F-P) sensors are widely investigated because they have several advantages over conventional sensors, such as immunity to electromagnetic interference, ability to operate under bad environments, high sensitivity and the potential for multiplexing. A new method to fabricate micro-cavity Fabry-Perot interferometer is introduced, which is fusion splicing a section of conventional single-mode fiber (SMF) and a section of hollow core or solid core photonic crystal fiber (PCF) together to form a micro-cavity at the splice joint. The technology of fusion splicing is discussed, and two miniature optical fiber sensors based on Fabry-Perot interference using fusion splicing are presented. The two sensors are completely made of fused silica, and have good high-temperature capability.

Towards a fully integrated optical gyroscope using whispering gallery modes resonators

NASA Astrophysics Data System (ADS)

Amrane, T.; Jager, J.-B.; Jager, T.; Calvo, V.; Léger, J.-M.

2017-11-01

Since the developments of lasers and the optical fibers in the 70s, the optical gyroscopes have been subject to an intensive research to improve both their resolution and stability performances. However the best optical gyroscopes currently on the market, the ring laser gyroscope and the interferometer fiber optic gyroscope are still macroscopic devices and cannot address specific applications where size and weight constraints are critical. One solution to overcome these limitations could be to use an integrated resonator as a sensitive part to build a fully Integrated Optical Resonant Gyroscope (IORG). To keep a high rotation sensitivity, which is usually degraded when downsizing this kind of optical sensors based on the Sagnac effect, the resonator has to exhibit a very high quality factor (Q): as detailed in equation (1) where the minimum rotation rate resolution for an IORG is given as a function of the resonator characteristics (Q and diameter D) and of the global system optical system characteristics (i.e. SNR and bandwidth B), the higher the Q×D product, the lower the resolution.

Optical fiber sensors technology for supervision, control and protection of high power systems

NASA Astrophysics Data System (ADS)

Nascimento, Ivo Maciel

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Analysis of Plasmonics Based Fiber Optic Sensing Structures

NASA Astrophysics Data System (ADS)

Moayyed, Hamed

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.