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Showing papers on "Fiber optic sensor published in 2003"


Journal ArticleDOI
TL;DR: Among the various fiber-optic sensor technologies, especially, technologies such as fiber grating sensors, fiber- Optic gyroscopes, and fiber-Optic current sensors are discussed with emphasis on the principles and current status.

1,610 citations


Journal ArticleDOI
TL;DR: In this paper, the authors reviewed recent research on fiber optic long-period gratings (LPGs) with emphasis placed upon the characteristics of LPGs that make them attractive for applications in sensing strain, temperature, bend radius and external index of refraction.
Abstract: Recent research on fibre optic long-period gratings (LPGs) is reviewed with emphasis placed upon the characteristics of LPGs that make them attractive for applications in sensing strain, temperature, bend radius and external index of refraction. The prospect of the development of multi-parameter sensors, capable of simultaneously monitoring a number of these measurands will be discussed.

1,203 citations


Journal ArticleDOI
TL;DR: This work reviews the use of fiber optic probes for optical spectroscopy, focusing on applications in turbid media, such as tissue, and covers universal design principles as well as technologies for beam deflecting and reshaping.
Abstract: Fiber optic probes are a key element for biomedical spectroscopic sensing. We review the use of fiber optic probes for optical spectroscopy, focusing on applications in turbid media, such as tissue. The design of probes for reflectance, polarized reflectance, fluorescence, and Raman spectroscopy is illustrated. We cover universal design principles as well as technologies for beam deflecting and reshaping.

464 citations


Journal ArticleDOI
TL;DR: In this paper, a novel long-period fiber grating (LPFG) fabricated by using a new writing technique that is mainly based on the thermal shock effect of focused high-frequency CO/sub 2/ laser pulses at several kilohertz was reported.
Abstract: In this paper, we report a novel long-period fiber grating (LPFG) fabricated by using a new writing technique that is mainly based on the thermal shock effect of focused high-frequency CO/sub 2/ laser pulses at several kilohertz. A number of unique characteristics of such a LPFG, such as bend, torsion, and transverse load, are observed by experiments, for the first time, to our knowledge. Based on these unique features, a novel bend-insensitive LPFG sensor that could solve the problem of cross-sensitivity between bend and other measurands, a novel torsion sensor that can realize absolute measurement of twist rate, and a load sensor that can achieve simultaneous measurement of transverse load and temperature using a single LPFG element are proposed and demonstrated. These unique features of the LPFGs are mainly due to the asymmetrical distribution of the refractive index on the cross section of the LPFG induced by high-frequency CO/sub 2/ laser pulses.

384 citations


Journal ArticleDOI
TL;DR: The modeling results of an all-fiber gas detector that uses photonic crystal fiber (PCF) and the relative sensitivity of the PCF as a function of the fiber parameters is calculated.
Abstract: We report the modeling results of an all-fiber gas detector that uses photonic crystal fiber (PCF). The relative sensitivity of the PCF as a function of the fiber parameters is calculated. Gas-diffusion dynamics that affect the sensor response time is investigated theoretically and experimentally. A practical PCF sensor aiming for high sensitivity gas detection is proposed.

306 citations


Journal ArticleDOI
TL;DR: This work describes what is to their knowledge the first use of fiber Bragg gratings written into three separate cores of a multicore fiber for two-axis curvature measurement.
Abstract: We describe what is to our knowledge the first use of fiber Bragg gratings written into three separate cores of a multicore fiber for two-axis curvature measurement. The gratings act as independent, but isothermal, fiber strain gauges for which local curvature determines the difference in strain between cores, permitting temperature-independent bend measurement.

266 citations


Journal ArticleDOI
TL;DR: In this article, a fiber-optic surface plasmon resonance (SPR) sensor was proposed which utilizes both polarization separation and broad band radiation depolarization in polarization-maintaining fibers to enhance sensor stability.
Abstract: A novel wavelength modulation-based fiber-optic surface plasmon resonance (SPR) sensor is reported which utilizes both polarization separation and broad band radiation depolarization in polarization-maintaining fibers to enhance sensor stability. Theoretical analysis of the sensing structure with ideally separated polarizations based on the mode of expansion and propagation method is presented. The effect of polarization cross-coupling was also analyzed in the approximation of an equivalent bulk optic structure. A laboratory prototype of the fiber-optic SPR sensor was characterized in terms of sensitivity and resolution. Experimental results indicate that this fiber-optic SPR sensor is able to resolve refractive index changes as low as 4×10−6 under moderate fiber deformations.

237 citations


Patent
26 Feb 2003
TL;DR: In this paper, the authors proposed a flexible "smart cable" which enables accurate measurement of local curvature and torsion along its length, which is then used to infer the position and attitude of one end of the cable relative to the other.
Abstract: The central system component of the present invention is a flexible “smart cable” which enables accurate measurement of local curvature and torsion along its length. These quantities are then used to infer the position and attitude of one end of the cable relative to the other. Sufficiently accurate measurements of the local curvature and torsion along the cable allow reconstruction of the entire cable shape, including the relative position and orientation of the end points. The smart cable for making these measurements comprises a multicore optical fiber, with individual fiber cores constructed to operate in the single mode regime, but positioned close enough to cause cross-talk (mode coupling) between cores over the length of the fiber. This cross-talk is very sensitive to the distribution of strains (curvature and torsion) along the cable.

231 citations


Journal ArticleDOI
TL;DR: The efficient generation of 100-W single-frequency radiation with diffraction-limited beam quality at the 1064-nm wavelength by use of a master-oscillator fiber power-amplifier system, consisting of a diode-pumped monolithic nonplanar ring laser as the master oscillator and an Yb-doped large-mode-area fiber as the power amplifier is reported.
Abstract: We report the efficient generation of 100-W single-frequency radiation with diffraction-limited beam quality at the 1064-nm wavelength by use of a master-oscillator fiber power-amplifier system, consisting of a diode-pumped monolithic nonplanar ring laser as the master oscillator and an Yb-doped large-mode-area fiber as the power amplifier. The emission spectrum, the intensity noise behavior, and further power-scaling possibilities to the >200-W level, which are determined by the threshold of stimulated Brillouin scattering in the fiber amplifier, are discussed.

224 citations


Journal ArticleDOI
TL;DR: In this article, a new concept for a multimode interference-based fiber-optic displacement sensor is investigated both theoretically and experimentally, and a displacement sensor consisting of only a section of multimode fiber fusion spliced to a singlemode fiber can be readily fabricated.
Abstract: A new concept for a multimode interference-based fiber-optic displacement sensor is investigated both theoretically and experimentally. By applying multimode interference and reimaging theory to optical fibers, a displacement sensor consisting of only a section of multimode fiber fusion spliced to a single-mode fiber can be readily fabricated. Observation and analysis of the power reflected off of a surface and back through the device over a finite wavelength range provides enough information to use the device as a calibrated displacement sensor over a large displacement range.

222 citations


Journal ArticleDOI
TL;DR: An overview of the intensity modulated and spectrometric fiber optic sensors and techniques to assess the condition of existing structures in order to enhance the durability of the new bridges, increasing lifetime and reliability and decreasing maintenance activities is provided.
Abstract: Advances in the production of optical fibers made possible the recent development of innovative sensing systems for the health monitoring of civil structures. The main reasons for this development are the reduced weight and dimensions of fiber optic sensors, the strong immunity to electromagnetic interference, the improved environmental resistance and the scale flexibility for small-gauge and long-gauge measurements. These systems can provide high-resolution and measurement capabilities that are not feasible with conventional technologies. In addition, they can be manufactured at a low cost and they offer a number of key advantages, including the ability to multiplex an appreciable number of sensors along a single fiber and interrogate such systems over large distances. For these reasons, it is evident that fiber optic sensors will change the instrumentation industry in the same way fiber optics has revolutionized communications. This paper provides an overview of the intensity modulated and spectrometric fiber optic sensors and techniques to assess the condition of existing structures in order to enhance the durability of the new bridges, increasing lifetime and reliability and decreasing maintenance activities. Application of these sensors to monitoring strain, temperature, inclination, acceleration, load measurements, ice detection, vehicles speeds and weights, and corrosion and cracking of reinforced and prestressed concrete structures will be described.

Journal ArticleDOI
Bing Yu1, Dae Woong Kim1, Jiangdong Deng1, Hai Xiao1, Anbo Wang1 
TL;DR: Test results indicate that these fiber optic acoustic sensors are capable of faithfully detecting acoustic signals propagating inside transformer oil with high sensitivity and wide bandwidth.
Abstract: A diaphragm-based interferometric fiber optic sensor that uses a low-coherence light source was designed and tested for on-line detection of the acoustic waves generated by partial discharges inside high-voltage power transformers The sensor uses a fused-silica diaphragm and a single-mode optical fiber encapsulated in a fused-silica glass tube to form an extrinsic Fabry-Perot interferometer, which is interrogated by low-coherence light Test results indicate that these fiber optic acoustic sensors are capable of faithfully detecting acoustic signals propagating inside transformer oil with high sensitivity and wide bandwidth

Journal ArticleDOI
TL;DR: A simple optical humidity sensor with fast response and high sensitivity, which is based on the plastic optical fiber structure change from leaky to guided, was easily fabricated and could be used for real-time humidity monitoring as mentioned in this paper.
Abstract: Certain kinds of cellulose, such as a hydroxyethylcellulose, swell in a humid atmosphere and show a decrease in refractive index. Using this effect, a simple optical humidity sensor with fast response and high sensitivity, which is based on the plastic optical fibre structure change from leaky to guided, was easily fabricated and could be used for real-time humidity monitoring.

Journal ArticleDOI
TL;DR: It is explained an observed spontaneous transition to the high-brightness, in-phase array state of a seven-core ytterbium-doped fiber laser array, which appears to be robust and scalable.
Abstract: We explain an observed spontaneous transition to the high-brightness, in-phase array state of a seven-core ytterbium-doped fiber laser array [IEEE Photonics Technol. Lett. 13, 439 (2001)]. The responsible mechanism is nonlinear refraction, and either in-phase or antiphase array modes can be selected by control of pump intensity. The phenomenon appears to be robust and scalable.

Journal ArticleDOI
TL;DR: In this article, a sensor scheme consisting of a combination of a polymer fibre Bragg grating and a silica fibre grating was proposed for temperature and strain discrimination. But it was not shown to provide a large sensitivity and dynamic range.

Patent
29 Aug 2003
TL;DR: In this article, a system and method to log a wellbore, comprising a logging tool adapted to be deployed in a well-bore environment, the logging tool including at least one sensor for taking a measurement of the wellbores flow, is presented.
Abstract: A system and method to log a wellbore, comprising a logging tool adapted to be deployed in a wellbore environment, the logging tool including at least one sensor for taking a measurement of the wellbore euviwwnent. The sensor is a fiber optic sensor and the system includes a fiber optic line in optical communication with the sensor. The data measured by the sensor is transmitted through the fiber optic line on a real time basis to the surface, Where the data is processed into a real time display. In one embodiment, the fiber optic sensor is a passive sensor not requiring electrical or battery power. In another embodiment, a continuous tube with one end at the earth's surface and the other end in the wellbore is attached to the logging tool and includes the fiber optic line disposed therein.

Journal ArticleDOI
TL;DR: The fabrication and modeling of single-mode tapered optical fiber sensors are reported and results indicate that sensor sensitivity can be adjusted with the taper waist diameter.
Abstract: We report the fabrication and modeling of single-mode tapered optical fiber sensors. The fabrication technique consists of stretching a section of fiber with an oscillating flame torch. Such a process allows controllable fabrication of lossless tapered fibers with a uniform waist. The sensor transmittance is modeled with a simple ray optics approach. In the model, all the taper parameters are taken into account. Our results indicate that sensor sensitivity can be adjusted with the taper waist diameter. As an example a gold-coated tapered fiber is theoretically and experimentally analyzed.

Journal ArticleDOI
TL;DR: Unambiguous simultaneous measurement of strain and temperature based on dual long-period fiber gratings by controlling their thermal and strain sensitivities is proposed and experimentally demonstrated.
Abstract: Unambiguous simultaneous measurement of strain and temperature based on dual long-period fiber gratings by controlling their thermal and strain sensitivities is proposed and experimentally demonstrated. The difference in the wavelength peak shift and the separation with the variation of strain and temperature allows discrimination between the strain and temperature effects, respectively.

Journal ArticleDOI
TL;DR: In this article, a fiber Bragg grating (FBG) sensor for detection of ultrasonic waves in liquids and solid structures is investigated, which contains a fiber probe with a FBG, a tunable narrowband laser source, and a photodetector.
Abstract: A fiber Bragg grating (FBG) sensor for detection of ultrasonic waves in liquids and solid structures is investigated. The sensor contains a fiber probe with a FBG, a tunable narrowband laser source, and a photodetector. When ultrasonic waves impinge on the fiber probe, the pitch of the grating is modulated through the elasto-optic effect. The corresponding changes in reflectivity of the grating are detected by a photodetector. The sensitivity of the sensor and its frequency and directional response in the 0.5 to 3.0 MHz range are measured. Some anomalous features of the FBG ultrasound sensor response are noted. It is shown that these features result from a combination of the sensor's response to the direct ultrasonic waves propagating through the medium and the signal generated by axially guided ultrasonic waves propagating through the fiber probe.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the transmission characteristics of the Single mode-Multimode-Single mode (SMS) fiber structures when the spot sizes of the fundamental modes of the single and multimode fibers do not match.

Journal ArticleDOI
TL;DR: In this paper, a fiber-optic hydrogen gas sensor using catalyst-supported tungsten trioxide (WO 3 ) was characterized, which utilizes the absorption of the evanescent field interaction in the clad of WO 3 thin film which was prepared by sol-gel process, coated on a silica core.
Abstract: A fiber-optic hydrogen gas sensor using catalyst-supported tungsten trioxide (WO 3 ) was characterized. This sensor utilizes the absorption of the evanescent field interaction in the clad of WO 3 thin film which was prepared by sol–gel process, coated on a silica core. The sensor using platinic acid as precursor and calcined at 500 °C showed fast response to hydrogen. The sensitivity was quite high even at room temperature. More than 75% reduction in optical power propagating through the fiber was attained by the exposure to 1 vol.% H 2 /99 vol.% N 2 . This resulted from the color change in cladding WO 3 region with the formation of tungsten bronze. The recovery of the sensor was achieved not in inert but in oxidizing atmosphere. The humidity strongly influenced the sensor responses. In both processes of the response to hydrogen and recovery with air, the reaction rate was accelerated by humidity. The sensitivity became smaller and the response speed got slower as ambient temperature lowered, but response of 4% decrease after 15 min, exposure to 1 vol.% H 2 /air was obtained at −30 °C. The observation guarantees the operations of wide temperature range. The high sensitivity in the low temperature range together with the line-sensing feature is very promising for the continuous monitoring of hydrogen leak for fuel-cell cars and other equipments utilizing hydrogen.

Journal ArticleDOI
Hai Xiao, Jiangdong Deng, Gary Pickrell1, Russell G. May, Anbo Wang1 
TL;DR: In this paper, a single-crystal sapphire fiber extrinsic Fabry-Perot interferometric strain sensors based on the white-light inter-ferometric spectrum demodulation technique is presented.
Abstract: Single-crystal sapphire fibers have a very high melting point (up to 2050/spl deg/C), which renders them a very good candidate for sensing applications at a very high temperature. We present in this paper the recent work of developing single-crystal sapphire fiber extrinsic Fabry-Perot interferometric strain sensors based on the white-light interferometric spectrum demodulation technique. Prototype sapphire strain sensors were fabricated and tested at high temperatures up to 1004/spl deg/C. The preliminary experimental results indicate that the sensors are promising to be used under high-temperature environments for making strain measurements with strain measurement resolution of 0.2-/spl mu/ strain.

Journal ArticleDOI
TL;DR: In this paper, a sensor for accurate and long-term fluid pressure monitoring in oil bore-holes based on optical fiber Bragg gratings (FBGs) is presented, which converts fluid pressure into optical fiber strain by means of a mechanical transducer designed to withstand downhole conditions.
Abstract: A sensor for accurate and long-term fluid pressure monitoring in oil bore-holes based on optical fiber Bragg gratings (FBGs) is presented The sensor converts fluid pressure into optical fiber strain by means of a mechanical transducer designed to withstand downhole conditions The sensor response is investigated as a function of pressure and temperature Effects of shock and vibration are also considered The expected stability and lifetime of the polyimide-coated gratings in a downhole environment are estimated by modeling and extended accelerated mechanical and thermal aging tests

Journal ArticleDOI
TL;DR: Chemical IR sensors can provide continuous information on the probed environment and are on the verge of taking the significant step from experiment to real-world applications.
Abstract: Chemical IR sensors can provide continuous information on the probed environment and are on the verge of taking the significant step from experiment to real-world applications.

Journal ArticleDOI
Ying Yang1, Liu Wu2, Yinqi Feng1, Yinqi Feng2, Ruikang K. Wang2 
TL;DR: In this article, a pig tendon was studied by the use of the conventional fibre-based optical coherence tomography (OCT) systems. And the results demonstrate that conventional OCT can be used to monitor the tissue birefringence.
Abstract: This paper addresses whether conventional fibre-based optical coherence tomography (OCT) is capable of obtaining birefringence information of well-organized tissues. For this purpose, a highly organized tissue, pig tendon, is studied by the use of the conventional fibre-based OCT systems. It is found that the tendons result in well-defined banded OCT images. The observed bands in the OCT images are sensitive to the wavelength of light source applied and phase retardation. The results demonstrate that conventional OCT can be used to monitor the tissue birefringence.

Journal ArticleDOI
TL;DR: In this article, the authors describe miniature Fabry-Perot cavity pressure sensors constructed by micromachining techniques in a turbine test application, which are embedded in the trailing edge of a nozzle guide vane installed upstream of a rotor in a full scale turbine stage transient test facility.
Abstract: Small size, high bandwidth pressure sensors are required for instrumentation of probes and test models in aerodynamic studies of complex unsteady flows. Optical-fiber pressure sensors promise potential advantages of small size and low cost in comparison with their electrical counterparts. We describe miniature Fabry-Perot cavity pressure sensors constructed by micromachining techniques in a turbine test application. The sensor bodies are 500 /spl mu/m squared, 300 /spl mu/m deep with a /spl sim/2 /spl mu/m-thick copper diaphragm electroplated on one face. The sensor cavity is formed between the diaphragm and the cleaved end of a single mode fiber sealed to the sensor by epoxy. Each sensor is addressed interferometrically in reflection by three wavelengths simultaneously, giving an unambiguous phase determination; a pressure sensitivity of 1.6 radbar/sup -1/ was measured, with a typical range of vacuum to 600 kPa. Five sensors were embedded in the trailing edge of a nozzle guide vane installed upstream of a rotor in a full-scale turbine stage transient test facility. Pressure signals in the trailing edge flow show marked structure at the 8 kHz blade passing frequency. To our knowledge, this is the first report of sensors located at the trailing edge of a normal-sized turbine blade.

Journal ArticleDOI
TL;DR: A new multiplexing method demonstrating the separation of two series of geometrically arranged fiber-optic distributed sensors in a Michelson interferometer (MI) configuration has been developed.
Abstract: A new multiplexing method demonstrating the separation of two series of geometrically arranged fiber-optic distributed sensors in a Michelson interferometer (MI) configuration has been developed. This method can acquire data from two sensors, then propagate the data into one channel, and finally separate the data by determining their working point, which is essential for some remote measurements. The working point of one sensor was deflected from the normal MI by introduction of two reference arms. The deflection was extracted electrically and employed to label the sensor. Verification with commercial piezoelectric transducers proves the efficiency of the method.

Journal ArticleDOI
TL;DR: Efficient optical carrier reduction of microwave signals with a single-mode 1.5-microm wavelength Brillouin all-fiber ring laser is experimentally demonstrated and evidence of generation of high-spectral-purity beatnotes is provided.
Abstract: We experimentally demonstrate efficient optical carrier reduction of microwave signals with a single-mode 1.5-microm wavelength Brillouin all-fiber ring laser. Because of the tunable optical coupling, the lasing threshold of the short-length (20-m) fiber cavity is lower than 5 mW, and high conversion efficiencies (up to 60%) are obtained at any pump power up to approximately 200 mW. Using the single-mode Stokes beam as a seed for the stimulated Brillouin scattering process allows up to 40-dB optical carrier depletion with almost no added noise for an optically carried microwave signal at 6 GHz. In addition, using this resonator, we provide evidence of generation of high-spectral-purity beatnotes.

Patent
24 Feb 2003
TL;DR: An optical thermal device and methods for monitoring temperature and detection of a vulnerable plaque of a patient comprising an elongate tubular element comprising at least one optical fiber, the fiber having at least 1 optical grating along an axis of the fiber; and a light source having a light beam that is coupled into the optical fiber as mentioned in this paper.
Abstract: An optical thermal device and methods for monitoring temperature and detection of a vulnerable plaque of a patient comprising an elongate tubular element comprising at least one optical fiber; the fiber having at least one optical grating along an axis of the fiber; and a light source having a light beam that is coupled into the at least one optical fiber; wherein the optical grating reflects a certain wavelength or intensity of the light beam, the certain wavelength or intensity of the reflected light beam being correlated to the temperature of the tissue regions.

Journal ArticleDOI
TL;DR: In this article, a novel hydrogel-coated singlemode fiber Bragg grating (FBG) sensor is investigated, which uses a swellable polymer material as the active sensing component.
Abstract: A novel hydrogel-coated single-mode fiber Bragg grating (FBG) sensor is investigated The sensor uses a swellable polymer material, hydrogel, as the active sensing component The sensing mechanism is based on the stress that is induced in the chemically sensitive swellable hydrogel coating The stress shifts the Bragg wavelength of the FBG By reducing the cladding diameter of FBG through etching with hydrofluoric acid, the tension tuning force of FBG can be lowered Therefore, the stress induced in hydrogel can shift the wavelength of FBG more and the sensitivity of the sensor is improved When the grating fiber is etched 375 μm in diameter, the sensitivity of sensor is approximately 10-fold larger than that without fiber etching