Showing papers on "Fiber optic sensor published in 2007"
TL;DR: A detailed mechanism of the surface plasmon resonance (SPR) technique for sensing purposes has been discussed in this paper, where different new techniques and models in this area that have been introduced are discussed in quite a detail.
Abstract: Since the introduction of optical fiber technology in the field of sensor based on the technique of surface plasmon resonance (SPR), fiber-optic SPR sensors have witnessed a lot of advancements. This paper reports on the past, present, and future scope of fiber-optic SPR sensors in the field of sensing of different chemical, physical, and biochemical parameters. A detailed mechanism of the SPR technique for sensing purposes has been discussed. Different new techniques and models in this area that have been introduced are discussed in quite a detail. We have tried to put the different advancements in the order of their chronological evolution. The content of the review article may be of great importance for the research community who are to take the field of fiber-optic SPR sensors as its research endeavors.
824 citations
TL;DR: In this article, a fiber-optic strain sensor is demonstrated by using a short length of polarization-maintaining photonic crystal fiber (PM-PCF) as the sensing element inserted in a Sagnac loop interferometer.
Abstract: A fiber-optic strain sensor is demonstrated by using a short length of polarization-maintaining photonic crystal fiber (PM-PCF) as the sensing element inserted in a Sagnac loop interferometer. Spectrum shift in response of strain with a sensitivity of 0.23pm∕μe is achieved, and the measurement range, by stretching the PM-PCF only, is up to 32me. Due to the ultralow thermal sensitivity of the PM-PCF, the proposed strain sensor is inherently insensitive to temperature, eliminating the requirement for temperature compensation.
415 citations
TL;DR: In this article, the capability of different bimetallic combinations to be used in a fiber optic sensor based on the technique of surface plasmon resonance has been investigated and compared numerically.
Abstract: In the present work, we have investigated the capability of different bimetallic combinations to be used in a fiber optic sensor based on the technique of surface plasmon resonance. The metals considered for the present analysis are silver, gold, copper, and aluminum. The performance of the sensor with different bimetallic combinations is evaluated and compared numerically. The performance is analyzed in terms of three parameters: sensitivity, signal-to-noise ratio (SNR), and operating range. On the basis of the comparison and some logical criteria, the best possible bimetallic combination along with requisite thickness distribution is predicted. The bimetallic combination is capable of simultaneously providing the larger values of sensitivity, SNR, and operating range, which is not possible with any single metallic layer.
275 citations
TL;DR: In this paper, the phase matching between a plasmon and a core mode can be enforced by introducing air-filled microstructures into the fiber core, where the effective refractive index can be lowered to match that of a plasmus by introducing a small central hole into the fibre core.
Abstract: Design strategies for microstructured-optical-fiber (MOF-) based surface-plasmon-resonance (SPR) sensors are presented. In such sensors, plasmons on the inner surface of the large metallized channels containing analyte can be excited by a fundamental mode of a single-mode microstructured fiber. Phase matching between a plasmon and a core mode can be enforced by introducing air-filled microstructures into the fiber core. Particularly, in its simplest implementation, the effective refractive index of a fundamental mode can be lowered to match that of a plasmon by introducing a small central hole into the fiber core. Resolution of the MOF-based sensors is demonstrated to be as low as 3×10−5 RIU, where RIU means refractive index unit. The ability to integrate large-size microfluidic channels for efficient analyte flow together with a single-mode waveguide of designable modal refractive index is attractive for the development of integrated highly sensitive MOF-SPR sensors operating at any designable wavelength.
261 citations
TL;DR: The transmission spectrum of fiber Bragg gratings with gratings planes tilted at a small angle relative to the fiber axis shows a large number of narrowband cladding mode resonances within a 100 nm wide spectrum.
Abstract: The transmission spectrum of fiber Bragg gratings with gratings planes tilted at a small angle (2°-10°) relative to the fiber axis shows a large number of narrowband cladding mode resonances within a 100 nm wide spectrum. When a gold coating with a thickness between 10 and 30 nm is deposited on the fiber, the transmission spectrum shows anomalous features for values of the outside medium refractive index between 1.4211 and 1.4499. These features are shown to correspond to the excitation of surface plasmon resonances at the external surface of the gold film.
251 citations
TL;DR: Field tests in desert terrain of a distributed sensor system for detecting and locating intruders based on the phase-sensitive optical-time-domain reflectometer (phi-OTDR) are described, with high sensitivity and consistent detection of intruders on foot and of vehicles traveling down a road near the cable line.
Abstract: Field tests in desert terrain of a distributed sensor system for detecting and locating intruders based on the phase-sensitive optical-time-domain reflectometer (phi-OTDR) are described. The sensing element is a single-mode telecommunications fiber in a 4.5 mm diameter cable buried in a trench filled with loose sand. Light pulses from a continuous-wave Er:fiber Fabry-Perot laser with a narrow (<3 kHz) instantaneous linewidth and low (few kilohertz per second) frequency drift are injected into one end of the fiber, and the orthogonal polarizations of the backscattered light are monitored with separate receivers. Localized phase changes in the optical carrier are sensed by subtracting a phi-OTDR trace from an earlier stored trace. High sensitivity and consistent detection of intruders on foot and of vehicles traveling down a road near the cable line was realized over a cable length of 8.5 km and a total fiber path of 19 km in real time.
249 citations
TL;DR: Investigation of the strain and temperature characteristics of the two MFPIs with an identical cavity length show that the strain sensitivity of the PCF- based MFPI is smaller than that of the SMF-based M FPI due to their different waveguide structures, while the twoMFPIs have close temperature sensitivities due to the similar host materials.
Abstract: Micro Fabry-Perot (F-P) interferometers (MFPIs) are machined in a single-mode fiber (SMF) and a photonic crystal fiber (PCF) by using a near-infrared femtosecond laser, respectively. The strain and temperature characteristics of the two MFPIs with an identical cavity length are investigated and the experimental results show that the strain sensitivity of the PCF-based MFPI is smaller than that of the SMF-based MFPI due to their different waveguide structures, while the two MFPIs have close temperature sensitivities which are much smaller than that of an in-line SMF etalon sensor reported previously. These MFPIs in silica fibers are compact, stable, inexpensive, capable for mass-production and easy fabrication, offering great potentials for wide sensing applications.
247 citations
TL;DR: The experimental results show that the wavelength separation between selected resonances allows the measurement of the refractive index of the medium surrounding the fiber for values between 1.25 and 1.44 with an accuracy approaching 1x10(-4).
Abstract: Short-period fiber Bragg gratings with weakly tilted grating planes generate multiple strong resonances in transmission. Our experimental results show that the wavelength separation between selected resonances allows the measurement of the refractive index of the medium surrounding the fiber for values between 1.25 and 1.44 with an accuracy approaching 1x10(-4). The sensor element is 10 mm long and made from standard single-mode telecommunication grade optical fiber by ultraviolet light irradiation through a phase mask.
245 citations
TL;DR: In this article, the authors report a highly sensitive (∼2.8pm∕μe) wavelength-encoded strain sensor made from a piece of photonic crystal fiber (PCF) spliced to standard fibers.
Abstract: The authors report a highly sensitive (∼2.8pm∕μe) wavelength-encoded strain sensor made from a piece of photonic crystal fiber (PCF) spliced to standard fibers. The authors intentionally collapse the PCF air holes over a short region to enlarge the propagating mode of the lead-in fiber which allows the coupling of only two modes in the PCF. The transmission spectrum of the interferometer is stable and sinusoidal over a broad wavelength range. The sensor exhibits linear response to strain over a large measurement range, its temperature sensitivity is very low, and for its interrogation a battery-operated light emitting diode and a miniature spectrometer are sufficient.
228 citations
TL;DR: A novel refractometric sensor based on a coated all-coupling optical-fiber-nanowire microcoil resonator which is robust, compact, and comprises an intrinsic fluidic channel is presented.
Abstract: We present a novel refractometric sensor based on a coated all-coupling optical-fiber-nanowire microcoil resonator which is robust, compact, and comprises an intrinsic fluidic channel. We calculate the device sensitivity and find its dependence on the nanowire diameter and coating thickness. A sensitivity as high as 700 nm/RIU and a refractive index resolution as low as 10 are predicted. (See also erratum, doi:10.1364/OE.15.009385)
223 citations
TL;DR: Experimental results show that smaller core diameter graded-index fibers display greater strain-induced peak wavelength shifts than larger core diameter fibers.
Abstract: We report a low-loss, low-cost high-sensitivity all-fiber strain and temperature sensor based on mode interference in graded-index multimode fibers. Blueshifts with strain and temperature sensitivities of 18.6 pm/microstrain and 58.5 pm/ degrees C have been observed. Experimental results show that smaller core diameter graded-index fibers display greater strain-induced peak wavelength shifts than larger core diameter fibers.
TL;DR: In this article, the authors provide a summary of basic principles pertaining to practical health monitoring of civil engineering structures with optical fiber sensors, including sensor principles, strain transfer mechanism, sensor packaging, sensor placement in construction environment, and reliability and survivability of the sensors.
Abstract: Implementation of successful civil structural health monitoring strategies requires selection and placement of sensors suitable for measurement of key parameters that influence the performance and health of the structural system. Optical fiber sensors have been successfully implemented in aeronautics, mechanical systems, and medical applications. Civil structures pose further challenges in monitoring mainly due to their large dimensions, diversity as well as heterogeneity of materials involved, and hostile construction environment. This article provides a summary of basic principles pertaining to practical health monitoring of civil engineering structures with optical fiber sensors. The issues discussed include basic sensor principles, strain transfer mechanism, sensor packaging, sensor placement in construction environment, and reliability and survivability of the sensors.
Patent•
21 Mar 2007TL;DR: In this paper, the authors propose an apparatus to interrogate one or more fiber optic sensors to make high-resolution measurements at long distances between the sensor and the interrogator apparatus.
Abstract: An apparatus to interrogate one or more fiber optic sensors to make high-resolution measurements at long distances between the sensor and the interrogator apparatus. The apparatus comprises a tunable light source, an optical switch for pulsing the light source, at least one sensor (e.g., a Fabry-Perot sensor) for reflecting the laser light, a fiber optic cable interconnecting the sensor with the light source, a coupler for directing the reflected light from the sensor to a detector in order to generate a digital output, and a control logic for tuning the laser light source based on the digital output from the detector. Use of a fiber Bragg grating temperature sensor is also contemplated.
TL;DR: It is shown that the optical fiber channel model can be treated as a special kind of multiple-input multiple- output (MIMO) model, namely, a two-input two-output (TITO) models which is intrinsically represented by a two -element Jones vector familiar to the optical communications community.
Abstract: In this paper, we conduct theoretical and experimental study on the PMD-supported transmission with coherent optical orthogonal frequency-division multiplexing (CO-OFDM). We first present the model for the optical fiber communication channel in the presence of the polarization effects. It shows that the optical fiber channel model can be treated as a special kind of multiple-input multiple-output (MIMO) model, namely, a two-input two-output (TITO) model which is intrinsically represented by a two-element Jones vector familiar to the optical communications community. The detailed discussions on various coherent optical MIMO-OFDM (CO-MIMO-OFDM) models are presented. Furthermore, we show the first experiment of polarization-diversity detection in CO-OFDM systems. In particular, a CO-OFDM signal at 10.7 Gb/s is successfully recovered after 900 ps differential-group-delay (DGD) and 1000-km transmission through SSMF fiber without optical dispersion compensation. The transmission experiment with higher-order PMD further confirms the immunity of the CO-OFDM signal to PMD in the transmission fiber. The nonlinearity performance of PMD-supported transmission is also reported. For the first time, nonlinear phase noise mitigation based on receiver digital signal processing is experimentally demonstrated for CO-OFDM transmission.
TL;DR: In this article, the first microstructured polymer optical fiber (mPOF) fabricated from Topas cyclic olefin copolymer has been presented, which allows for a novel type of fiber-optic biosensor where localized sensor layers may be activated on the inner side of the air holes in a predetermined section of the mPOF.
Abstract: We present what is believed to be the first microstructured polymer optical fiber (mPOF) fabricated from Topas cyclic olefin copolymer, which has attractive material and biochemical properties. This polymer allows for a novel type of fiber-optic biosensor, where localized sensor layers may be activated on the inner side of the air holes in a predetermined section of the mPOF. The concept is demonstrated using a fluorescence-based method for selective detection of fluorophore-labeled antibodies.
TL;DR: The proposed device can calculate the first time derivative of the complex field of an arbitrary narrowband optical waveform with a very high accuracy and efficiency and demonstrate the high performance of this device by processing gigahertz-bandwidth phase and intensity optical temporal variations.
Abstract: We propose and experimentally demonstrate an all-optical (all-fiber) temporal differentiator based on a simple π-phase-shifted fiber Bragg grating operated in reflection. The proposed device can calculate the first time derivative of the complex field of an arbitrary narrowband optical waveform with a very high accuracy and efficiency. Specifically, the experimental fiber grating differentiator reported here offers an operation bandwidth of ≈ 12 GHz. We demonstrate the high performance of this device by processing gigahertz-bandwidth phase and intensity optical temporal variations.
TL;DR: A beam profile characterization of different variations of graded-index (GRIN) fiber lenses, which were recently proposed for biomedical imaging probes, is presented.
Abstract: The quality and parameters of probing optical beams are extremely important in biomedical imaging systems both for image quality and light coupling efficiency considerations. For example, the shape, size, focal position, and focal range of such beams could have a great impact on the lateral resolution, penetration depth, and signal-to-noise ratio of the image in optical coherence tomography. We present a beam profile characterization of different variations of graded-index (GRIN) fiber lenses, which were recently proposed for biomedical imaging probes. Those GRIN lens modules are made of a single mode fiber and a GRIN fiber lens with or without a fiber spacer between them. We discuss theoretical analysis methods, fabrication techniques, and measured performance compared with theory.
TL;DR: A photonic device, a plasmonic optical antenna fiber probe, is proposed that can potentially be used for in-situ chemical and biological detection and surface-enhanced Raman scattering.
Abstract: We present a systematic study of optical antenna arrays, in which the effects of coupling between the antennas, as well as of the antenna length, on the reflection spectra are investigated and compared. Such arrays can be fabricated on the facet of a fiber, and we propose a photonic device, a plasmonic optical antenna fiber probe, that can potentially be used for in-situ chemical and biological detection and surface-enhanced Raman scattering.
TL;DR: A novel Mach-Zehnder interferometer based on a fiber multimode interference structure combined with a long-period fiber grating (LPG) is proposed and demonstrated as a bending sensor.
Abstract: A novel Mach-Zehnder interferometer based on a fiber multimode interference structure combined with a long-period fiber grating (LPG) is proposed. The multimode interference is achieved through the use of a MMF section spliced between two single-mode fibers, with a length adjusted to couple a fraction of light into the cladding modes. A LPG placed after the MMF couples light back into the fiber core, completing the Mach-Zehnder interferometer. This novel configuration was demonstrated as a bending sensor.
TL;DR: In this article, a fiber-optic current sensor for direct currents up to 500 kA is presented, which makes use of the Faraday effect in an optical fiber loop around the current-carrying bus bars.
Abstract: A highly accurate fiber-optic current sensor for direct currents up to 500 kA is presented. Applications include the control of the electrolysis process for the production of metals such as aluminum, copper, zinc, magnesium, and others. The sensor offers significant advantages with regard to performance and ease of use compared to state-of-the-art Hall-effect-based current transducers. The sensor makes use of the Faraday effect in an optical fiber loop around the current-carrying bus bars. A novel scheme of a polarization-rotated reflection interferometer and fiber gyroscope technology is used to measure the magneto-optic phase shifts. An appropriate technique has been developed for packaging the sensing fiber in a flexible strip of fiber-reinforced epoxy for loop diameters of up to several meters. Sensor accuracy and repeatability are well within 0.1% over a wide range of currents and temperatures. The sensor calibration is valid, regardless of the given magnetic field distribution, and remains stable under repeated manipulation of the flexible sensing strip.
TL;DR: In this article, a hybrid configuration of Mach-Zehnder and Sagnac interferometers was proposed as a sensing frame for a gas or liquid pipeline leak, in which there are two light paths that have the same optical length but travel different sequence paths.
Abstract: When a gas or liquid pipeline leaks, it will generate broadband acoustic signal This acoustic pressure will induce an optical phase signal of the optical fiber fixed on the surface of pipes In this paper, we propose a hybrid configuration of Mach-Zehnder and Sagnac interferometer as sensing frame In this interferometer, there are two light paths that have the same optical length but travel different sequence paths Because the propagation lights of the two light paths pass through the leaking point at different times, the resulting phase signals differ respectively After interference, we demodulate the sensing phase signal by a broadband phase generated carrier (PGC) circuit and then the leaking point can be acquired from null frequency of the output spectrum This system has many advantages, such as its in-line configuration, all fiber structural design and polarization-insensitive for sensing fiber This system also has very wide dynamic range which can be greater than 76 dB with the minimum detectable phase signal about 33 × 10 − 4 ( rad / Hz )
TL;DR: In this paper, the authors presented a BOTDA system based on dark-pulse scattering that provides improved resolution, accuracy, and acquisition time over conventional BOTSDA systems, without the severe limitations on sensing length often imposed by other high-resolution techniques.
Abstract: Brillouin scattering-based distributed fiber-optic sensing is a powerful measurement tool that uses the inelastic scattering of incident light by an acoustic wave (phonon) to determine strain and/or temperature conditions of the fiber. Since the original Brillouin-time-domain-analysis (BOTDA) technique was proposed, several other analysis methods have been introduced to improve sensing performance in four key areas: spatial resolution; measurement accuracy; total sensing length; and measurement-acquisition time. The four factors are generally interrelated and improvements to one factor often come at the cost of one or more of the others. For example, one system might sacrifice spatial resolution for total sensing length, while another might sacrifice accuracy to gain acquisition speed. We present a BOTDA system based on dark-pulse scattering that provides improved resolution, accuracy, and acquisition time over conventional BOTDA systems, without the severe limitations on sensing length often imposed by other high-resolution techniques. Theoretical validation of the method is given, and experimental results are presented that demonstrate 20-mm resolution strain measurements with an accuracy of plusmn20 muepsiv, which is the highest spatial resolution yet reported for a BOTDA system
TL;DR: In this article, the core and cladding modes exhibit different thermal sensivities, while the strain sensivities are approximately equal, while monitoring the core-core mode coupling resonance and the corecladding modes coupling resonance of the TFBG spectrum allows the separation of the temperature and strain induced wavelength shifts.
TL;DR: In this article, a single-mode tapered fiber with a [PDDA/Poly R-478] nanostructured overlay was used for humidity sensor for human breathing monitoring.
Abstract: Electrostatic self-assembly has been used in this work to fabricate a new optical fiber humidity sensor. Said sensor consists of a single-mode tapered fiber coated with a [PDDA/Poly R-478] nanostructured overlay, in such a way that the thickness can be controlled in order to optimize the sensor sensitivity, by stopping the deposition process at the maximum slope of the transmitted optical power. The same tapered optical fiber tested with an overlay coating at the optimal working point achieves 26.8 times better sensitivity than with a double thickness overlay. A variation of 16 dB in optical power is achieved with responses time of 300 ms for changes in relative humidity from 75% to 100%. The high dynamic performance and low temperature cross-sensitivity allows this sensor to be used for human breathing monitoring.
TL;DR: The paper analyses and compares different types of high-birefringence fiber loop mirror sensors using conventional and microstructured optical fibers, for simultaneous measurement of physical parameters when combined with others optical devices.
Abstract: Recent advances in devices and applications of high-birefringence fiber loopmirror sensors are addressed. In optical sensing, these devices may be used as strain andtemperature sensors, in a separate or in a simultaneous measurement. Other describedapplications include: refractive index measurement, optical filters for interrogate gratingsstructures and chemical etching control. The paper analyses and compares different types ofhigh-birefringence fiber loop mirror sensors using conventional and microstructured opticalfibers. Some configurations are presented for simultaneous measurement of physicalparameters when combined with others optical devices, for example with a long periodgrating.
TL;DR: Simulations demonstrate the potential for a fiber designed to suppress stimulated Brillouin scattering through a reduction in the overlap of the optical and acoustic fields to achieve greater than 1000 Watts of output power.
Abstract: High power operation of narrow linewidth optical fiber amplifiers is usually limited by the onset of stimulated Brillouin scattering. In this paper, we present results demonstrating over 500 Watts of power in a single mode beam from a fiber designed to suppress stimulated Brillouin scattering through a reduction in the overlap of the optical and acoustic fields. Simulations demonstrate the potential for this fiber to achieve greater than 1000 Watts of output power.
TL;DR: The study of the Stokes emission evolution with pressure shows that highly efficient Raman amplification is still possible even at atmospheric pressure.
Abstract: We report on what is, to our knowledge, the first cw pumped Raman fiber-gas laser based on a hollow-core photonic crystal fiber filled with hydrogen. The high efficiency of the gas-laser interaction inside the fiber allows operation in a single-pass configuration. The transmitted spectrum exhibits 99.99% of the output light at the Stokes wavelength and a pump power threshold as low as 2.25 W. The study of the Stokes emission evolution with pressure shows that highly efficient Raman amplification is still possible even at atmospheric pressure. The addition of fiber Bragg gratings to the system, creating a cavity at the Stokes wavelength, reduces the Raman threshold power below 600 mW.
TL;DR: In this paper, a surface plasmon resonance based fiber-optic sensor for the detection of organophosphate pesticide, chlorphyrifos, has been reported.
Abstract: Fabrication and characterization of a surface plasmon resonance based fiber-optic sensor for the detection of organophosphate pesticide, chlorphyrifos, have been reported. The probe is prepared by immobilizing acetylcholinesterase (AChE) enzyme on the silver coated core of a plastic-cladded silica (PCS) fiber. The detection is based on the principle of competitive binding of the pesticide (acting as inhibitor) for the substrate (acetlythiocholine iodide) to the enzyme AChE. The spectral interrogation method has been used to characterize the sensor. It has been observed that the SPR wavelength decreases with the increase in the concentration of the pesticide for the fixed concentration of substrate in the fluid around the probe. Further, the effect of the concentration of the substrate in the fluid on the resonance wavelength has been studied. The sensitivity, detection accuracy, reproducibility and stability of the sensor have been also determined. It has been found that the sensitivity decreases with the increase in the concentration of the pesticide while reverse is the case for detection accuracy.
TL;DR: In this paper, an optical sensor based on a highly birefringent photonic crystal fiber (Hi-Bi PCF) loop mirror was presented, and the length of the sensing head was 380 mm and its corresponding wavelength spacing between two interferometer minima was 8 nm.
Abstract: This work presents an optical sensor based on a highly birefringent photonic crystal fiber (Hi-Bi PCF) loop mirror. The length of the sensing head is 380 mm and its corresponding wavelength spacing between two interferometer minima is 8 nm. The optical sensor was characterized in strain and in temperature with an uncoated Hi-Bi PCF and with an acrylate coated Hi-Bi PCF. Different results for strain and temperature sensitivity were obtained. Relatively to the strain measurement, the sensor with the uncoated Hi-Bi PCF presents slightly less sensitivity (1.11 ) when compared with coated Hi-Bi PCF (1.21 ). For the temperature measurement and with the uncoated Hi-Bi PCF, the optical sensor is insensitive to temperature (0.29 pm/K).
TL;DR: In this article, a fiber Bragg grating (FBG) pressure sensor with a metal tube was developed, which can be applied in the measurement of hydraulic pressure and vibration.