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Showing papers on "Fiber Bragg grating published in 1997"


Journal ArticleDOI
TL;DR: In this paper, the authors review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings and intragrating sensing concepts.
Abstract: We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.

3,665 citations


Journal ArticleDOI
TL;DR: In this paper, the spectral properties of fiber reflection and transmission gratings are described and examples are given to illustrate the wide variety of optical properties that are possible in fiber gratings.
Abstract: In this paper, we describe the spectral characteristics that can be achieved in fiber reflection (Bragg) and transmission gratings. Both principles for understanding and tools for designing fiber gratings are emphasized. Examples are given to illustrate the wide variety of optical properties that are possible in fiber gratings. The types of gratings considered include uniform, apodized, chirped, discrete phase-shifted, and superstructure gratings; short-period and long-period gratings; symmetric and tilted gratings; and cladding-mode and radiation-mode coupling gratings.

3,330 citations


Journal ArticleDOI
TL;DR: Fiber Bragg grating (FBG) technology has been extensively studied in the literature as mentioned in this paper, where the basic techniques for fiber grating fabrication, their characteristics, and the fundamental properties of fiber gratings are described.
Abstract: The historical beginnings of photosensitivity and fiber Bragg grating (FBG) technology are recounted. The basic techniques for fiber grating fabrication, their characteristics, and the fundamental properties of fiber gratings are described. The many applications of fiber grating technology are tabulated, and some selected applications are briefly described.

2,905 citations


Journal ArticleDOI
Yun-Jiang Rao1
TL;DR: In-fibre Bragg grating (FBG) sensors are one of the most exciting developments in the field of optical fiber sensors in recent years as discussed by the authors, and significant progress has been made in applications to strain and temperature measurements.
Abstract: In-fibre Bragg grating (FBG) sensors are one of the most exciting developments in the field of optical fibre sensors in recent years. Compared with conventional fibre-optic sensors, FBG sensors have a number of distinguishing advantages. Significant progress has been made in applications to strain and temperature measurements. FBG sensors prove to be one of the most promising candidates for fibre-optic smart structures. This article presents a comprehensive and systematic overview of FBG sensor technology regarding many aspects including sensing principles, properties, fabrication, interrogation and multiplexing of FBG sensors. It is anticipated that FBG sensor systems will be commercialized and widely applied in practice in the near future due to the maturity of economical production of FBGs and the availability of cost effective interrogation and multiplexing techniques.

1,170 citations


Journal ArticleDOI
TL;DR: A theoretical model indicates that this mode of operation can be explained by the internal birefringence of the laser cavity combined with a nonlinear transmission element and the gain response of the fiber amplifier.
Abstract: An erbium-doped fiber laser that produces a train of intense noiselike pulses with a broadband spectrum and a short coherence length is reported. The noiselike behavior was observed in the amplitude as well as in the phase of the pulses. The maximum spectral width obtained was 44 nm. The high intensity and the short coherence length of the light were maintained even after propagation through a long dispersive fiber. A theoretical model indicates that this mode of operation can be explained by the internal birefringence of the laser cavity combined with a nonlinear transmission element and the gain response of the fiber amplifier.

457 citations


Journal ArticleDOI
Clinton Randy Giles1
TL;DR: Fiber Bragg gratings (FBGs) have emerged as important components in a variety of lightwave applications and their unique filtering properties and versatility as in-fiber devices is illustrated by their use in wavelength-stabilized lasers, fiber lasers, remotely pump amplifiers.
Abstract: Fiber Bragg gratings (FBGs) have emerged as important components in a variety of lightwave applications. Their unique filtering properties and versatility as in-fiber devices is illustrated by their use in wavelength-stabilized lasers, fiber lasers, remotely pump amplifiers. Raman amplifiers, phase conjugators, wavelength converters, passive optical networks, wavelength division multiplexers (WDMs) demultiplexers, add/drop multiplexers, dispersion compensators, and gain equalizers.

383 citations


Journal ArticleDOI
TL;DR: A new mechanism for passive Q switching of fiber lasers is discovered and 10-kW peak power pulses with ~2-ns pulse widths are reported from a diode-pumped ytterbium-doped fiber laser.
Abstract: We have discovered a new mechanism for passive Q switching of fiber lasers. 10-kW peak power pulses with ∼2-ns pulse widths are reported from a diode-pumped ytterbium-doped fiber laser. The laser generates a high-brightness Raman-dominated supercontinuum spectrum covering the complete window of transparency of silica fiber in the infrared from 1.06 to 2.3 µm

282 citations


Journal ArticleDOI
TL;DR: Fiber-optic Bragg grating strain sensors hold a great deal of potential for structural monitoring because of their exceptional stability and demonstrated potential for long-term monitoring as discussed by the authors, which results in measurement stability and lead/interconnect insensitivity which permit longterm and intermittent monitoring with high resolution and accuracy.
Abstract: Fiber-optic Bragg grating strain sensors hold a great deal of potential for structural monitoring because of their exceptional stability and demonstrated potential for long-term monitoring. This sensing technology takes advantage of a spectrally encoded signal which provides inherent immunity from signal intensity fluctuations which plague many other fiber-optic and electronic sensing techniques. This results in measurement stability and lead/interconnect insensitivity which permit longterm and intermittent monitoring with high resolution and accuracy. Fiber-optic grating sensors are intrinsic to the optical fiber, thus capitalizing on its extremely small size and inherent strength and durability. Recent results are provided from a sensor array installed in a road bridge. The strain sensors are attached to both steel and carbon-fiber-reinforced plastic prestressing tendons, which are embedded in the precast girders of the bridge. Measurements of traffic loads and the relaxation behaviour of the tendons are presented. The potential of fiber grating technology is briefly discussed including its application in long-gage strain-sensing and strain-distribution measurements.

249 citations


Journal ArticleDOI
TL;DR: A quasidistributed in-fiber Bragg grating (FBG) temperature sensor system has been developed for temperature proving in vivo in the human body for medical applications, e.g., hyperthermia treatment as mentioned in this paper.
Abstract: A novel quasidistributed in-fiber Bragg grating (FBG) temperature sensor system has been developed for temperature proving in vivo in the human body for medical applications, e.g., hyperthermia treatment. This paper provides the operating principle of FBG temperature sensors and then the design of the sensor head. High-resolution detection of the wavelength-shifts induced by temperature changes are achieved using drift-compensated interferometric detection while the return signals from the FBG sensor array are demultiplexed with a simple monochromator which offers crosstalk-free wavelength-division-multiplexing (WDM). A "strain-free" probe is designed by enclosing the FBG sensor array in a protection sleeve. A four FBG sensor system is demonstrated and the experimental results are in good agreement with those obtained by traditional electrical thermocouple sensors. A resolution of 0.1/spl deg/C and an accuracy of /spl plusmn/0.2/spl deg/C over a temperature range of 30-60/spl deg/C have been achieved, which meet established medical requirements.

229 citations


Journal ArticleDOI
TL;DR: In this paper, a general theoretical analysis of the influence of systematic errors associated with the measurement process is presented and applied to a range of techniques that are of current inter- est in the literature, including Bragg grating sensors, polarization-maintaining Fabry-Perot interfer- ometers, combined dual-mode interference/polarimetry sensors, and dis- persive Fourier transform spectroscopy measurements.
Abstract: Many optical fiber sensors designed to recover quasi-static strain fields in the presence of significant temperature changes have been reported in recent years. A general theoretical analysis of the influ- ence of systematic errors associated with the measurement process is presented and applied to a range of techniques that are of current inter- est in the literature. The performances of measurement methods based on Bragg grating sensors, polarization-maintaining Fabry-Perot interfer- ometers, combined dual-mode interference/polarimetry sensors, and dis- persive Fourier transform spectroscopy measurements are contrasted with respect to the influence of measurement error, calibration error, cross talk, and engineering practicality. © 1997 Society of Photo-Optical Instru- mentation Engineers.

229 citations


Patent
21 Feb 1997
TL;DR: In this article, a system-level optical measurement probe would include a laser, a spectrometer, a first optical fiber to carry energy from the laser to a sample, including a Bragg grating laser bandpass filter at its tip, and a second optical fiber, which would have included within it at its distal tip an optical filter to selectively reject energy associated with the nominal wavelength.
Abstract: Laser band-pass filter and/or band-reject filters are located at the end of an optical measurement probe by placing an appropriate Bragg grating proximate to the tip, and within, one or both of the optical fibers that make up the probehead. Thus, where an optical fiber is used to carry excitation energy of a nominal wavelength to a sample, the distal tip of this fiber will have included therein an optical filter to selectively pass energy of the nominal wavelength. Similarly, where an optical fiber is employed to carry stimulated emission from the sample to an analytical instrument such as a spectrometer, this fiber will have included within it at its distal tip an optical filter to selectively reject energy associated with the nominal wavelength. A disclosed system-level optical measurement probe would include a laser, a spectrometer, a first optical fiber to carry energy from the laser to a sample, including a Bragg grating laser bandpass filter at its tip, and a second optical fiber to carry energy collected from the sample to the spectrometer, including a Bragg grating laser band-reject filter at its tip.

Journal ArticleDOI
TL;DR: In this paper, a single sideband optical modulation at millimetre-wave frequencies using a fibre Bragg grating eliminates the dispersion-induced penalty over modulation frequency and fibre length.
Abstract: Dispersion causes a power penalty at certain fibre distances and frequencies in conventional millimetre-wave intensity modulation. Single sideband optical modulation at millimetre-wave frequencies using a fibre Bragg grating eliminates the dispersion-induced penalty over modulation frequency and fibre length.

Journal ArticleDOI
TL;DR: The differential modulation of the attenuation bands in a long-period grating is used for simultaneous sensing of axial strain and temperature in a grating fabricated in a conventional optical fiber.
Abstract: The differential modulation of the attenuation bands in a long-period grating is used for simultaneous sensing of axial strain and temperature. A grating fabricated in a conventional optical fiber is demonstrated for concurrent measurements of strain over a range of 2100 µ∊ and temperature over a range of 125 °C, with maximum errors of 58 µ∊ and 1 °C, respectively.

Journal ArticleDOI
TL;DR: In this paper, the thermal decay of fiber bragg gratings with and without hydrogen loading was examined over a period in excess of 5000 h and it was shown that the non-hydrogen loaded gratings do not obey the power law model.
Abstract: Fiber Bragg gratings (FBGs) have been written in silica fiber codoped with boron and germanium, using a continuous-wave (CW) 244-nm laser. The thermal decay of the gratings written with and without hydrogen loading is examined over a period in excess of 5000 h. It is shown that the thermal decay of the nonhydrogen loaded gratings is well explained by the power law model proposed by Erdogan. Gratings written in hydrogen loaded fiber, however, do not obey the power law model. A new model is presented based on a log time representation which can be used to predict the decay characteristics of gratings written in hydrogen loaded fiber.

Journal ArticleDOI
TL;DR: In this paper, a transmission-based dispersion compensator employing an apodized, unchirped fiber Bragg grating (FBG) was proposed for long-haul communication systems.
Abstract: We propose a transmission-based dispersion compensator employing an apodized, unchirped fiber Bragg grating (FBG). A theoretical model for dispersion compensation in transmission based on the dispersive properties of the periodic structure is developed. A figure of merit is defined for optimization of the grating parameters for maximum recompression of dispersion-broadened optical pulses in long-haul communication systems. Numerical examples confirm that nearly perfect compensation with very low insertion losses can be achieved for many practical cases of interest.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate the existence of Bragg grating solitons in fiber gratings at high intensities and demonstrate how trains of such solITons can be generated.
Abstract: We discuss experimental results that demonstrate the existence of Bragg grating solitons in fiber gratings at high intensities. These solitons can exist because of the balance of the nonlinearity in the glass and the group-velocity dispersion introduced by the grating. We show that Bragg grating solitons can travel at velocities substantially below that in bare fiber and also how trains of such solitons can be generated.

Journal ArticleDOI
TL;DR: In this article, a modified Sagnac interferometer-based fiber temperature sensor is proposed for temperature measurement, and a comparison of the proposed sensor with Bragg grating and long-period grating fiber sensors is derived.
Abstract: A modified Sagnac interferometer-based fiber temperature sensor is proposed. Polarization independent operation and high temperature sensitivity of this class of sensors make them cost effective instruments for temperature measurements. A comparison of the proposed sensor with Bragg grating and long-period grating fiber sensors is derived. A temperature-induced spectral displacement of 0.99 nm/K is demonstrated for an internal stress birefringent fiber-based Sagnac interferometer.

Patent
21 Apr 1997
TL;DR: In this paper, an optical system for detecting perturbations indicative of the performance of the piece of equipment being monitored is described, which consists of sensors (12), each of which uses Bragg gratings (12A-12N), induced by a preselected distribution and each Bragg grating returns, when subjected to incident light, a narrowbeam signal (22, 24, 26) identified by a predetermined wavelength.
Abstract: An optical system for detecting perturbations indicative of the performance of the piece of equipment being monitored is disclosed. The optical system comprises sensors (12), each of which uses Bragg gratings (12A-12N), induced therein and wherein the Bragg gratings (12A-12N) are arranged into a preselected distribution and each Bragg grating returns, when subjected to incident light, a narrowbeam signal (22, 24, 26) identified by a predetermined wavelength. The optical system utilizes at least one interferometer (56) whose operation is interlinked with optical multiplexing techniques, such as differentiate-cross-multiplying and time-division multiplexing.

Patent
27 Feb 1997
TL;DR: In this article, an apparatus and method for measuring strain of gratings written into an optical fiber is presented. Butts et al. measured the strain on the grating at each wavelength of optical radiation by determining the difference between the current wavelength and an earlier, zero-strain wavelength measurement.
Abstract: An apparatus and method for measuring strain of gratings written into an optical fiber. Optical radiation is transmitted over a plurality of contiguous predetermined wavelength ranges into a reference optical fiber network and an optical fiber network under test to produce a plurality of reference interference fringes and measurement interference fringes, respectively. The reference and measurement fringes are detected and sampled such that each sampled value of the reference and measurement fringes is associated with a corresponding sample number. The wavelength change of the reference optical fiber, for each sample number, due to the wavelength of the optical radiation is determined. Each determined wavelength change is matched with a corresponding sampled value of each measurement fringe. Each sampled measurement fringe of each wavelength sweep is transformed into a spatial domain waveform. The spatial domain waveforms are summed to form a summation spatial domain waveform that is used to determine location of each grating with respect to a reference reflector. A portion of each spatial domain waveform that corresponds to a particular grating is determined and transformed into a corresponding frequency spectrum representation. The strain on the grating at each wavelength of optical radiation is determined by determining the difference between the current wavelength and an earlier, zero-strain wavelength measurement.

Journal ArticleDOI
TL;DR: Both single-frequency Bragg-grating reflector and distributed-feedback lasers with slope efficiencies of 25% with respect to launched pump power have been realized in photosensitive Er/Yb-doped fibers.
Abstract: Boron- and germanium-doped highly photosensitive cladding is used in a novel design to achieve photosensitive Er/Yb-doped fibers, permitting short, strong gratings (length ≈1 cm, reflectivity >99%) to be written without hydrogenation. The high absorption at 980 nm in Er/Yb fibers permits efficient pump absorption over a short device length, which is ideal for achieving highly efficient single-frequency fiber lasers. Both single-frequency Bragg-grating reflector and distributed-feedback lasers with slope efficiencies of 25% with respect to launched pump power have been realized in such fibers.

Journal ArticleDOI
TL;DR: In this article, temperature and strain-insensitive long-period gratings can be fabricated in conventional optical fibers, where the former is employed to measure strain with resolution of 20 µ? under thermal fluctuations in the surroundings, while the latter is used to detect temperature variations as small as 0.8°C in the presence of axial strain.
Abstract: We demonstrate that temperature- and strain-insensitive long-period gratings can be fabricated in conventional optical fibers. The former is employed to measure strain with resolution of 20 µ? under thermal fluctuations in the surroundings, while the latter is used to detect temperature variations as small as 0.8°C in the presence of axial strain.

Journal ArticleDOI
TL;DR: In this paper, a novel approach of a true time-delay (TTD) optical feeder for phased-array antennas (PAAs) is presented and demonstrated by employing tunable lasers and a wide-bandwidth chirped fiber Bragg grating (FBG) as the dispersive element.
Abstract: In this paper, we present and demonstrate a novel approach of a true time-delay (TTD) optical feeder for phased-array antennas (PAAs). A continuously variable TTD is achieved by employing tunable lasers and a wide-bandwidth chirped fiber Bragg grating (FBG) as the dispersive element. The results show that a very high resolution performance (equivalent to a 6-b microwave phase shifter) is obtained for an L-band PAA employing narrow-tuning bandwidth lasers with a wavelength stability of 0.005 nm and a 4-nm bandwidth chirped grating with a dispersion of 835 ps/nm.

Journal ArticleDOI
TL;DR: In this paper, the use of fiber gratings in conjunction with erbium-doped fiber amplifiers (EDFAs), fiber lasers, and with semiconductor diode lasers is reviewed.
Abstract: The emergence of UV-written fiber gratings, both short and long period, as a reliable fiber technology has revolutionized the field of active fiber devices. The advantageous properties of spectral selectivity, low insertion loss, and component ruggedness have made devices possible that would not be viable without their use. The use of fiber gratings in conjunction with erbium-doped fiber amplifiers (EDFAs), fiber lasers, and with semiconductor diode lasers is reviewed.

Journal ArticleDOI
TL;DR: In this article, a simple and effective technique for the simultaneous measurement of temperature and strain using two closely spaced fiber gratings embedded in series in a silica glass capillary tube is described.

Journal ArticleDOI
TL;DR: In this article, the authors developed and demonstrated a novel technique to manufacture very long gratings with a nearly arbitrary reflectivity profile, based upon writing a set of consecutive subgratings with interferometric control of the relative position of each subgrating.
Abstract: We have developed and demonstrated a novel technique to manufacture very long gratings with a nearly arbitrary reflectivity profile. The technique is based upon writing a set of consecutive subgratings with interferometric control of the relative position of each subgrating.

Journal ArticleDOI
TL;DR: In this article, the authors examined the thermal stability of Bragg gratings with large and small index changes and compared the role of stabilization in enhancing the temperature stability of the grating.
Abstract: The phenomenon of decay in UV-induced Bragg gratings is examined. Thermal stability of gratings with large and small index changes are studied and compared. The role of stabilization in enhancing the thermal stability of gratings is explained. Approaches to analyzing and predicting grating decay are reviewed and compared.

Journal ArticleDOI
TL;DR: In this article, an active photonic signal processor which achieves a high-Q microwave bandpass response is presented, which comprises active fiber within a pair of fiber Bragg gratings, and produces multiple taps with precise delay-time characteristics.
Abstract: A new active photonic signal processor which achieves a high-Q microwave bandpass response is presented. It comprises active fiber within a pair of fiber Bragg gratings, and produces multiple taps with precise delay-time characteristics. The impulse response has demonstrated well in excess of 270 taps. The filter response demonstrates high resolution, having a narrow-band response with a Q of 325. The processor is also tunable, in both passband width and frequency.

Journal ArticleDOI
TL;DR: Numerical and experimental results show that there is an optimum Bragg wavelength difference between the two FBG's that maximizes the sensitivity for this demodulation technique.
Abstract: A technique for the demodulation of fiber Bragg grating (FBG) sensors based on the use of a second wavelength-matched FBG receiver to track wavelength shifts from the FBG sensor is analyzed, particularly regarding its sensitivity as determined by primary noise sources. Numerical and experimental results show that there is an optimum Bragg wavelength difference between the two FBG’s that maximizes the sensitivity for this demodulation technique.

Journal ArticleDOI
TL;DR: In this article, a comprehensive theoretical analysis of the compound phase-shifted uniform fiber Bragg grating (FBG) filter is presented, and the transmission characteristics are examined by a transfer matrix formulation.
Abstract: A comprehensive theoretical analysis of the compound phase-shifted uniform fiber Bragg grating (FBG) filter is presented. The transmission characteristics are examined by a transfer matrix formulation. It is shown that the transmission spectrum of such a filter is significantly controlled by the ratio of the grating lengths. By suitably choosing the ratio, a quasi-flat-top spectrum may be obtained. The general condition for the optimum case is derived. This characteristic makes the compound phase-shifted uniform FBG filter particularly advantageous for applications in wavelength-multiplexed optic-fiber communication systems.

Journal ArticleDOI
TL;DR: In this article, a new type of underwater acoustic sensor with an optical fiber Bragg grating (FBG) is proposed, which is able to operate with much larger dynamic range both at higher and lower pressure levels.
Abstract: A new type of underwater acoustic sensor is proposed with an optical fiber Bragg grating (FBG). Because of the photoelasticity with respect to the refractive index and the elasticity of the fiber, the sound pressure in water modulates the Bragg reflection wavelength and, in turn, the intensity of the laser light transmitted through the FBG fiber. Good linearity between the detected signal and the sound pressure is obtained in the range from 81 dB to 140 dB re 1 μPa. Since the upper and lower limits of the acoustic signal level for operation of the sensor are limited by the driving circuit and the transduction of the sound in water, the sensor is expected to operate with much larger dynamic range both at higher and lower pressure levels. Operation of the sensor is very stable with the insertion of optical isolators into the system, although without the isolators the output signal fluctuates at low frequency due to the Fabry-Perot interference effect between the FBG and the various facets.