Showing papers on "Fiber Bragg grating published in 1996"
TL;DR: A novel class of highly sensitive sensors based on long-period fiber gratings that can be implemented with simple and inexpensive demodulation schemes are presented.
Abstract: We present a novel class of highly sensitive sensors based on long-period fiber gratings that can be implemented with simple and inexpensive demodulation schemes. Temperature, strain, and refractive-index resolutions of 0.65 °C, 65.75 μ∈, and 7.69 × 10−5, respectively, are demonstrated for gratings fabricated in standard telecommunication fibers.
1,267 citations
TL;DR: In this paper, the difference in strain and temperature response of fiber Bragg gratings and a long period fiber grating was used to discriminate between strain induced and temperature induced wavelength shifts.
Abstract: We demonstrate a novel sensor which uses the difference in strain and temperature response of fiber Bragg gratings and a long period fiber grating to discriminate between strain and temperature induced wavelength shifts. Sensor interrogation is performed entirely on the fiber Bragg grating reflection signals. Strain and temperature were simultaneously measured to /spl plusmn/9 /spl mu/strain and /spl plusmn/1.5/spl deg/C over a wide range of conditions.
546 citations
TL;DR: The first experimental observation of nonlinear propagation effects in fiber Bragg gratings, resulting in nonlinear optical pulse compression and soliton propagation, is reported.
Abstract: We report the first experimental observation of nonlinear propagation effects in fiber Bragg gratings, resulting in nonlinear optical pulse compression and soliton propagation. The solitons occur at frequencies near the photonic band gap of the grating; they are due to a combination of the negative dispersion of the grating, which dominates the material dispersion, and self-phase modulation. The solitons propagate at velocities well below the speed of light in the uniform medium.
543 citations
TL;DR: Long-period fiber gratings are used to f latten the gain spectrum of erbium-doped fiber amplifiers and it is shown that a chain of amplifiers can be equalized, leading to a bandwidth enhancement by a factor of 3.
Abstract: Long-period fiber gratings are used to flatten the gain spectrum of erbium-doped fiber amplifiers. A broadband amplifier with <0.2-dB gain variation over 30 nm is presented. We also show that a chain of amplifiers can be equalized, leading to a bandwidth enhancement by a factor of 3.
500 citations
01 Jan 1996
475 citations
TL;DR: Some of the significant developments in fiber optic sensor technology which have occurred over the past 5 to 10 years are reviewed in this article, with particular emphasis given to advances in interferometric sensors, intrinsic distributed sensors, and Bragg grating based systems.
470 citations
TL;DR: In this paper, a detailed theoretical treatment of the effects of grating tilt on the spectral characteristics of a tilted optical-fiber phase grating is presented, compared with experimentally measured spectra of strong gratings.
Abstract: A detailed theoretical treatment is presented of bound-mode to bound-mode Bragg reflection and bound-mode to radiation-mode coupling loss in a tilted optical-fiber phase grating. Numerical predictions of the effects of grating tilt on the spectral characteristics of such a grating are calculated. These predictions are compared with experimentally measured spectra of strong gratings written by ultraviolet irradiation of deuterium-sensitized fiber with grating tilt angles ranging from 0° to 15°. Good agreement is obtained between the theoretical predictions and the experimental results.
428 citations
TL;DR: In this article, two Bragg gratings with closely spaced center wavelengths are written either side of a splice between two fibres of different diameter, showing similar temperature sensitivities but different strain responses to an applied stress.
Abstract: A new technique for the simultaneous, independent measurement of temperature and strain using in-fibre Bragg grating sensors is proposed and demonstrated. Two Bragg gratings with closely spaced centre wavelengths are written either side of a splice between two fibres of different diameter. The gratings show similar temperature sensitivities but different strain responses to an applied stress. Maximum errors of /spl plusmn/17 /spl mu//spl epsiv/ and /spl plusmn/1/spl deg/ are reported over 2500 /spl mu//spl epsiv/ and 120/spl deg/C measurement ranges.
374 citations
TL;DR: In this article, the authors demonstrated simultaneous continuous wave multiwavelength operation of an erbium-doped fiber laser using two types of recently developed in-fiber grating comb filters.
Abstract: Simultaneous continuous wave multiwavelength operation of an erbium-doped fiber laser has been demonstrated using two types of recently developed in-fiber grating comb filters. The lasing wavelengths and linewidths were determined by the comb filter, which was inserted in a ring cavity with a single inhomogeneously broadened gain medium.
345 citations
TL;DR: In this article, a fiber Bragg transducer was used for the measurement of acceleration using interferometric wavelength-shift detection with a demodulated signal output range of 50g rms with a minimum detectable signal of /spl sim/1 mg/spl radic/Hz.
Abstract: We report a fiber Bragg grating transducer for the measurement of acceleration. Results obtained using interferometric wavelength-shift detection demonstrate a demodulated signal output range of 50-g rms with a minimum detectable signal of /spl sim/1 mg//spl radic/Hz.
237 citations
02 Jun 1996
TL;DR: A self-starting passively mode-locked thulium-doped silica fiber laser capable of 190-fs pulses is reported, achieved with a band-gap-engineered saturable absorber fabricated monolithically along with the output coupler of the laser by MOCVD.
Abstract: Summary form only given. We report a self-starting passively mode-locked thulium-doped silica fiber laser capable of 190-fs pulses. Mode-locking of the fiber laser was achieved with a band-gap-engineered saturable absorber fabricated monolithically along with the output coupler of the laser by MOCVD. Stable, single-pulse-in-the-cavity mode-locking was observed for a 2-m-long fiber laser utilizing a nanosecond response strained InGaAs detector.
TL;DR: In this article, the techniques for fabrication and properties of periodic and aperiodic fibre Bragg gratings produced by UV exposure in photosensitive optical fibres are discussed with an emphasis on applications.
Abstract: The techniques for fabrication and the properties of periodic and aperiodic fibre Bragg gratings produced by UV exposure in photosensitive optical fibres are reviwwed with an emphasis on applications.
TL;DR: In this article, the effect of diametric load on the wavelength of the reflected light from a low-birefringence fiber Bragg grating was studied, and the experimental results showed very good correspondance with the theoretical predictions.
Abstract: The effect of diametric load on the wavelength of the reflected light from a low-birefringence fibre Bragg grating is studied. The effects of loads up to almost 90 N on a 2.5 cm length of fibre are examined. The experimental results show very good correspondance with the theoretical predictions.
TL;DR: An empirical scaling law is presented that models the increased energy required for launching a soliton into an optical system with sections of both normal and anomalous dispersion fiber and shows that the inclusion of periodic attenuation and amplification can be handled as separate problems.
Abstract: We present an empirical scaling law that models the increased energy required for launching a soliton into an optical system with sections of both normal and anomalous dispersion fiber. It is shown that the inclusion of periodic attenuation and amplification can be handled as separate problems, provided that the interval between optical amplifiers is substantially different from the period of the dispersion map. These concepts are illustrated by reference to an example system comprising dispersion-shifted fiber combined with anomalous standard fiber.
TL;DR: In this paper, a fiber Bragg grating pressure sensor with enhanced sensitivity was demonstrated, using a grating housed in a glass bubble, which increased the pressure sensitivity and effectively reduced the thermal crosstalk.
Abstract: A fibre Bragg grating pressure sensor with enhanced sensitivity has been demonstrated, using a grating housed in a glass bubble. This configuration increases the pressure sensitivity and effectively reduces the thermal crosstalk by a factor of 4. A pressure resolution of 0.5% over a full measurement range of 14 MPa has been achieved. This concept could lead to a range of sensors using fibre gratings with mechanical amplifiers to enhance sensitivity.
Patent•
25 Apr 1996
TL;DR: Disclosed as mentioned in this paper is a system for amplification of ultrashort optical pulses, where a compact stretcher is used with a bulk compressor, and compatibility between them is achieved by inserting a telescope in the path of the collimated beam.
Abstract: Disclosed is a system for amplification of ultrashort optical pulses. The disclosed system has reduced size and increased robustness, reliability and cost-effectiveness. The disclosed invention is particularly effective in chirped pulse amplification (CPA) systems wherein pulses are stretched, amplified, and re-compressed. According to one aspect of the invention a compact stretcher is used with a bulk compressor, and compatibility between them is achieved by inserting a telescope in the path of the collimated beam. Alternatively, compatibility between the stretcher and the compressor is achieved by creating nonlinearly chirped bragg grating in the fiber stretcher. According to another aspect of the invention, a fiber and a bulk amplifiers are used to amplify the pulse, and compatibility between them is achieved by inserting a doubling crystal in the path of the pulse between the two amplifiers. Another aspect of the disclosed amplification system is the pumping of a laser amplifier with a laser pump of the same material as the laser amplifier, but operating under different conditions.
TL;DR: In this article, the performance of a fiber grating interrogation system using an acousto-optic tunable filter (AOTF) was analyzed for both transmissive and reflective interrogation of FBGs.
Abstract: The performance of a fiber grating interrogation system using an acousto-optic tunable filter (AOTF) is analyzed. An equivalent linear circuit is presented to describe the system, which tracks the wavelength of a fiber Bragg grating (FBG) sensor in a FBG sensor array. From the model, the tracking resolution of a shot-noise-limited system has been determined for both transmissive and reflective interrogation of FBGs. An optimum ratio between the bandwidths of the FBG and the AOTF has been derived. Experimental results of a tracking system are presented to validate the theoretical predictions. The theory should also be suitable for interrogation systems using other forms of tunable bandpass filters for tracking the FBG wavelength.
TL;DR: In this paper, the use of wavelength division multiplexed fiber Bragg gratings for structural shape sensing and vibrational mode analysis is discussed, where the gratings are surface attached to a cantilever beam and demodulated by a scanning fibre Fabry-Perot filter to obtain strain information at different locations along the structure.
Abstract: This paper discusses the use of wavelength division multiplexed fibre Bragg gratings for structural shape sensing and vibrational mode analysis. The gratings are surface attached to a cantilever beam and demodulated by a scanning fibre Fabry - Perot filter to obtain strain information at different locations along the structure. Two demodulation schemes are used, namely a single-sensor locked mode interrogation technique which permits vibrational analysis and a scanning multi-sensor approach for beam shape determination. Static beam deformation prediction is performed using a Rayleigh - Ritz type analysis with three optimized trial functions and the strain information obtained from the fibre Bragg grating sensors. The strain information is read into a PC which performs the shape modelling of the beam.
TL;DR: A method of extracting the strain profile along a fiber Bragg grating from the intensity reflection spectrum is described, based on a filter synthesis theory that relates the aperiodicity of a grating with its reflection spectrum.
Abstract: A method of extracting the strain profile along a fiber Bragg grating from the intensity reflection spectrum is described The procedure is based on a filter synthesis theory that relates the aperiodicity of a grating with its reflection spectrum To illustrate the approach, we measured the strain profile near a hole in a plate and obtained a strain resolution of 80 μ∊ The spatial resolution depends on the strain gradient; ie, the higher the gradient, the better the resolution A resolution of 08 mm was achieved for a 5-mm grating with a gradient of 250 μ∊/mm
TL;DR: Temperature sensing to as low as 80 K was demonstrated with 1.55-μm fiber Bragg gratings and the temperature sensitivity values are smaller than those at room temperature because of the nonlinearity of both the thermal expansion and the thermo-optic effect.
Abstract: Temperature sensing to as low as 80 K was demonstrated with 1.55-μm fiber Bragg gratings. The gratings were bonded on substrates to increase sensitivity, and a shift of the reflection wavelength was measured. The temperature sensitivity was 0.02 nm/K at 100 K when an aluminum substrate was used and 0.04 nm/K at 100 K when a poly(methyl methacrylate) substrate was used. These values are smaller than those at room temperature because of the nonlinearity of both the thermal expansion and the thermo-optic effect. Extension to the liquid helium temperature is also discussed.
TL;DR: In this paper, the tension on the core of singlemode fibers is strongly increased by the formation of a Bragg grating and this tension increase lowers the refractive index because of the photoelastic effect.
Abstract: The tension on the core of single‐mode fibers is strongly increased by the formation of a Bragg grating. This tension increase lowers the refractive index because of the photoelastic effect. On the other hand, the compaction of the core network results in an increased refractive index. The two contributions are evaluated from axial stress measurements, from the determined index modulation amplitude, and from the mean index change of the Bragg gratings. The total Bragg grating index modulation is smaller than the compaction‐induced index modulation by 30%–35% because of the photoelastic effect.
TL;DR: In this article, a compact all-single-mode fiber add-drop multiplexer for dense wavelength-division-multiplexing systems is demonstrated, which consists of a polished fiber coupler with identical Bragg gratings within the interactive length.
Abstract: A novel compact all-single-mode fiber add-drop-multiplexer for dense wavelength-division-multiplexing systems is demonstrated. The device consists of a polished fiber coupler with identical Bragg gratings within the interactive length. The multiplexer operation has been theoretically analyzed and calculated transmission and reflection spectra are given. A fabricated prototype device shows good performance, but suffers from a high-insertion loss of 7 dB, which is due to the long but imperfect coupling region and can be drastically reduced in principle. A return loss >30 dB, coupling efficiency=99%, and bandwidth at FWHM /spl Delta//spl lambda/=1.2 mn was measured.
TL;DR: A method of measuring the complex modulation of a Bragg grating is derived from a one-dimensional model of light propagating in an optical fiber, using a Fourier transform of the interference fringes generated as a laser is swept through the wavelength.
Abstract: A method of measuring the complex modulation of a Bragg grating is derived from a one-dimensional model of light propagating in an optical fiber. Interference fringes between the Bragg grating and a reference air-gap reflector are measured, and a Fourier transform of the interference fringes generated as a laser is swept through the wavelength is used to compute the complex modulation function of the Bragg grating over a restricted domain. Supporting data, taken by temperature tuning a distributed feedback diode laser, are shown.
TL;DR: In this paper, a novel add/drop filter for use in WDM optical fiber systems based on a Bragg grating assisted mismatched coupler is presented. But it is not interferometric, unlike all similar devices demonstrated so far, and therefore does not need fine tuning of the interferometers during fabrication and does not have to maintain the balance of the interferer during its lifetime.
Abstract: We have demonstrated a novel add/drop filter for use in wavelength-division-multiplexing (WDM) optical fiber systems based on a Bragg grating assisted mismatched coupler. The device is potentially easy to fabricate and stable, because it is not interferometric, unlike all similar devices demonstrated so far, and, therefore, does not need fine tuning of the interferometers during fabrication and does not have to maintain the balance of the interferometers during its lifetime.
TL;DR: In this article, a novel multitap optical transversal signal processor based on wavelength multiplexed Bragg grating arrays is presented, which enables the realization of a large number of taps for obtaining sharp bandpass filtering with high resolution and also enables arbitrary tap weight profiles.
Abstract: A novel multitap optical transversal signal processor based on wavelength multiplexed Bragg grating arrays is presented. This structure enables the realization of a large number of taps for obtaining sharp bandpass filtering with high resolution and also enables arbitrary tap weight profiles to be obtained. Results on a 4-GHz, 29-tap filter demonstrates a sharp bandpass filter response, and windowing techniques on the tap profiles are demonstrated to enhance the sidelobe suppression characteristics.
Patent•
07 Nov 1996TL;DR: In this paper, a method for identifying a restriction in the flowline of a hydrocarbon production system, utilizes an optical fiber or optical fiber cable which is engaged along and preferably spirally wound around and along the flow line.
Abstract: A sensor apparatus and method for identifying a restriction in the flowline of a hydrocarbon production system, utilizes an optical fiber or optical fiber cable which is engaged along and preferably spirally wound around and along the flowline. Spaced apart strain gauges which are advantageously in the form of Bragg grating sensors, are engaged with the optical fiber at spaced locations along the flowline. The strain gauges are also engaged with the flowline to measure strain in the flowline. The hoop strain in particular indicates a change in pressure which can be measured by light signals supplied to and received from the optical fiber. Differences in strain along the flowline indicate pressure gradients in the flowline which in turn identify restrictions in the flowline.
02 Jun 1996
TL;DR: This paper reports a technique that transforms a FBG into a Bragg cell or acousto-optic modulator operating in reflection mode.
Abstract: Summary form only given. Fiber Bragg gratings (FBGs) written with ultraviolet light are becoming of increasing importance in fiber systems because of their high performance, versatility, and excellent physical characteristics. In this paper, we report a technique that transforms a FBG into a Bragg cell or acousto-optic modulator operating in reflection mode.
TL;DR: In this article, the authors report results of a system trial involving dispersion compensating chirped fiber gratings, demonstrating that transmission up to 537 km of standard telecommunications fiber is now feasible at 10 Gb/s, with a pair of 10-cm-long gratings cascaded together.
Abstract: We report on results of a system trial involving dispersion compensating chirped fiber gratings, demonstrating that transmission up to 537 km of standard telecommunications fiber is now feasible at 10 Gb/s, with a pair of 10-cm-long gratings cascaded together.
TL;DR: In this article, a variable fiber Bragg grating device using a segmented piezoelectric stack to combat chromatic dispersion is described, and it is shown that the dispersion can be varied from ~8770 to ~940 ps/nm with an increase in bandwidth.
Abstract: The authors describe novel dispersion variable fibre Bragg grating device using a segmented piezoelectric stack to combat chromatic dispersion. By applying appropriate voltages to the independently controlled constituent segments, it is shown that the dispersion can be varied from ~8770 to ~940 ps/nm with an increase in bandwidth from ~0.03 to ~0.32 nm.
Patent•
JDSU1
TL;DR: In this paper, the optical circulator, a plurality of bandpass wavelength division units and fiber Bragg gratings arranged in the optical fibers interconnecting the optical circuit and the bandpass division units are described.
Abstract: Multiplexer and demultiplexer devices for Dense WDM networks are described. The devices use an optical circulator, a plurality of bandpass wavelength division units and fiber Bragg gratings arranged in the optical fibers interconnecting the optical circulator and the bandpass wavelength division units. The optical circulator is connected to a network optical fiber and the bandpass wavelength division units are connected to a plurality of input/output optical fibers. Each fiber Bragg grating has a narrow wavelength reflection band about a predetermined wavelength and is arranged so that optical signals at wavelengths differing from predetermined wavelengths of the first optical fibers connected to a bandpass wavelength division unit are blocked and reflected. Depending upon the direction of the optical circulator, the device may be a multiplexer or a demultiplexer. Alternatively, a 3dB optical coupler may be used in place of the optical circulator with a corresponding rearrangement of the fiber Bragg gratings.