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Journal ArticleDOI

Pulse width dependance of the Brillouin loss spectrum

15 Sep 1999-Optics Communications (North-Holland)-Vol. 168, pp 393-398
TL;DR: In this article, the dependance of the Brillouin loss spectrum on the pump pulse width was studied. And the authors showed the nonlinear variations in the peak power and linewidth over a range of pulse widths from 10 to 4000 ns.
About: This article is published in Optics Communications.The article was published on 1999-09-15. It has received 30 citations till now. The article focuses on the topics: Brillouin scattering & Brillouin zone.
Citations
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Patent
01 Nov 2002
TL;DR: In this paper, a distribution optical fiber sensor system was proposed to measure distortion and temperature of a structure with a high spatial resolution, where a light source emits a first pulse light having a pulse width longer than a transient response of an acoustic phonon and a second pulse light after a time interval during which vibration of the acoustic phonons is maintained thereby supplying the pulse lights to the optical fiber.
Abstract: A distribution optical fiber sensor system measures distortion and temperature of a structure with a high spatial resolution. The system has an optical fiber on an object to be measured. A light source emits a first pulse light having a pulse width longer than a transient response of an acoustic phonon and a second pulse light after a time interval during which vibration of the acoustic phonon is maintained thereby supplying the pulse lights to the optical fiber. A detector detects scattering gain spectra of a Brillouin-scattered light created in the optical fiber by the second pulse light at intervals corresponding to twice the time obtained by equally dividing the pulse width of the second pulse light. A controlling/calculating unit calculates distortion and/or temperature based on the scattering gain spectra for sections of the optical fiber corresponding to the scattering gain spectra at the respective time intervals.

84 citations

Patent
17 May 2002
TL;DR: In this paper, the authors used the Brillouin scattering spectrum analysis to measure strain, displacement, temperature or other physical quantities at any location along an optical fiber attached to a structure.
Abstract: Brillouin scattering spectrum analysis is used to measure strain, displacement, temperature or other physical quantities at any location along an optical fiber attached to a structure. The fiber can be interrogated with different pulse widths for coarse and fine scans. The fiber can also have multiple sensors, either formed in a single fiber or branching off from a backbone fiber, in which case other segments of the fiber can be used for temperature compensation.

71 citations

DissertationDOI
01 Jan 2011
TL;DR: In this article, the authors identified, developed and implemented innovative applications of distributed fiber-optic sensing for use in geotechnical engineering projects and considered one dimensional, two dimensional and three dimensional problems.
Abstract: This study identified, developed and implemented innovative applications of distributed fiber-optic sensing for use in geotechnical engineering projects. The study considered one dimensional, two dimensional and three dimensional problems. Strain distributions in soil-embedded cables were monitored. Road-embedded sensors and borehole-embedded sensors were also studied.

62 citations


Cites methods from "Pulse width dependance of the Brill..."

  • ...By fitting a Lorentzian curve to the backscatter spectrum and calculating the peak of the Lorentzian curve, the peak power of the Brillouin spectrum is obtained (Smith et al., 1999)....

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Journal ArticleDOI
TL;DR: In this paper, the effect of Fresnel reflection on BOTDR measurement was discussed and the authors showed that the theoretical detection sensitivity is limited by the pulse modulation effect and phase noise of the light source that is incorporated into the Brillouin spectrum by way of the Fresnel reflections, when the sensor is located near the reflection point.
Abstract: We discuss the effect of Fresnel reflection on BOTDR measurement. We show that the theoretical detection sensitivity with respect to Brillouin scattering is limited by the pulse modulation effect and phase noise of the light source that is incorporated into the Brillouin spectrum by way of the Fresnel reflection, when the Brillouin sensor is located near the Fresnel reflection point. We describe the detection sensitivity in the presence of Fresnel reflection in terms of the minimum detectable sensor length. In regard to the pulse modulation effect, we find that when the pulsewidth is short, the noise in the Brillouin spectrum is large and the detection sensitivity deteriorates. We derive quantitative equations and confirm the equations experimentally. When the pulsewidth is 10 ns with a 1-MHz linewidth laser, the boundary Fresnel reflection determining whether or not we can measure a 1-m sensor fiber near the Fresnel reflection is about 30 dB lower than that for a 100 ns pulsewidth. A 1-m sensor fiber near the Fresnel reflection could be measured with a 10-ns pulse only when the Fresnel reflection was very low at about . Moreover, the effect of the laser linewidth is also discussed analytically. The analysis suggests that a laser with a narrower linewidth will provide better sensitivity.

37 citations


Cites background or methods from "Pulse width dependance of the Brill..."

  • ...The pulse modulation also broadens the Brillouin scattering spectrum [7]....

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  • ...The power spectrum of the Brillouin scattering in the BOTDR measurement (W/Hz) is the convolution of the Brillouin scattering spectrum and pulse spectrum [7] and the light source spectrum...

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Journal ArticleDOI
TL;DR: In this paper, a technique for the accurate processing of experimental data measured with the distributed Brillouin sensor at centimeter spatial resolution is proposed, which uses analytical solutions of the steady-state-coupled intensity equations for stimulated BrillOUin scattering.
Abstract: A technique for the accurate processing of experimental data measured with the distributed Brillouin sensor at centimeter spatial resolution is proposed. It uses analytical solutions of the steady-state-coupled intensity equations for stimulated Brillouin scattering. This technique includes experimental parameters such as pulsewidth and extinction ratio, pulse (Stokes) and pump powers, and sensing fiber characteristics. This approach also accounts for the effects induced by the ac and dc parts of the pulse. It is capable of extracting strain components hidden in a distorted single-peak spectrum by the implementation of form factors to analyze the shape of the spectrum. This signal processing technique has been validated by experimental data obtained under controlled laboratory conditions. The good agreement between reconstructed and measured spectra reflects the Brillouin frequency shift and the strain affecting the fiber.

36 citations


Cites background from "Pulse width dependance of the Brill..."

  • ...with the distribution Ip(0)f(ν) of the power spectrum of the pulse [13], [14]...

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References
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Book
Govind P. Agrawal1
01 Jan 1989
TL;DR: The field of nonlinear fiber optics has advanced enough that a whole book was devoted to it as discussed by the authors, which has been translated into Chinese, Japanese, and Russian languages, attesting to the worldwide activity in the field.
Abstract: Nonlinear fiber optics concerns with the nonlinear optical phenomena occurring inside optical fibers. Although the field ofnonlinear optics traces its beginning to 1961, when a ruby laser was first used to generate the second-harmonic radiation inside a crystal [1], the use ofoptical fibers as a nonlinear medium became feasible only after 1970 when fiber losses were reduced to below 20 dB/km [2]. Stimulated Raman and Brillouin scatterings in single-mode fibers were studied as early as 1972 [3] and were soon followed by the study of other nonlinear effects such as self- and crossphase modulation and four-wave mixing [4]. By 1989, the field ofnonlinear fiber optics has advanced enough that a whole book was devoted to it [5]. This book or its second edition has been translated into Chinese, Japanese, and Russian languages, attesting to the worldwide activity in the field of nonlinear fiber optics.

15,770 citations

Journal ArticleDOI
TL;DR: In this paper, a pump and probe based method for Brillouin gain spectrum measurements in optical fibers is presented, which uses a single laser source together with an external modulator to generate the interacting lightwaves.
Abstract: A novel method for Brillouin gain spectrum measurements in optical fibers is presented. It is based on the pump and probe technique with the specificity to use a single laser source together with an external modulator to generate the interacting lightwaves. The high accuracy and inherent stability of the technique makes it suitable for calibration and reference measurements. Different fibers with different refractive index profiles have been tested and characterized. The problem of the evolution of the polarization of the interacting waves is addressed in the article and a polarization insensitive determination of the actual Brillouin gain coefficient is made possible through two successive measurements with different polarizations. The effects of strain and temperature on the Brillouin gain spectrum are also fully characterized.

848 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical model of the interaction of the pulsed and CW beams is described and compared with experiments, and issues related to the variation within the sensing fiber of the polarizations of the two beams are investigated.
Abstract: Results are reported from recent research on the use of the Brillouin gain/loss mechanism for distributed sensing. A theoretical model of the interaction of the pulsed and CW beams is described and compared with experiments. Results from a system with a 51 km sensing length are presented. We finally investigate issues related to the variation within the sensing fiber of the polarizations of the two beams. >

302 citations

Journal ArticleDOI
TL;DR: A novel distributed temperature sensor that uses the temperature dependence of the frequency at which the loss is maximized in the interaction between a cw laser and a pulsed laser with a 32-km sensing length is presented.
Abstract: We present a novel distributed temperature sensor that uses the temperature dependence of the frequency at which the loss is maximized in the interaction between a cw laser and a pulsed laser. With a 32-km sensing length, a temperature resolution of 1°C has been achieved; it is also shown that a spatial resolution of 5 m may be obtained.

229 citations

Journal ArticleDOI
TL;DR: It was found that the Brillouin-loss signal intensity is linearly related to the duration of the pump pulse used to obtain the spectrum, and three distinct behaviors were observed in the spectral linewidth.
Abstract: The characterization of the Brillouin-loss spectrum of single-mode fibers with very short (<10-ns) pulses has been studied. It was found that the Brillouin-loss signal intensity is linearly related to the duration of the pump pulse used to obtain the spectrum. In contrast with the uniform trend of the signal, three distinct behaviors were observed in the spectral linewidth. At long pulse durations the linewidth was constant at approximately 40 MHz. Pulse durations of the order of the phonon lifetime resulted in a broader spectrum, reaching a maximum width of ~100 MHz at 5 ns. Reducing the pulse duration further resulted in a sudden narrowing of the Brillouin line.

162 citations