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Anthony W. Brown

Bio: Anthony W. Brown is an academic researcher from University of New Brunswick. The author has contributed to research in topics: Brillouin scattering & Fiber optic sensor. The author has an hindex of 16, co-authored 38 publications receiving 1119 citations.

Papers
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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

Journal ArticleDOI
TL;DR: In this article, the structural strain measurement of tension and compression in the steel beam was demonstrated with a distributed fiber-optic sensor system based on Brillouin scattering, and the results were achieved with the introduction of a computer-controlled polarization controller, a fast digitizer-signal averager, a pulse duration control and the electrical optical modulator bias setting in software.
Abstract: The structural strain measurement of tension and compression in the steel beam was demonstrated with a distributed fiber-optic sensor system based on Brillouin scattering. The experiments were conducted both in the laboratory and outdoors. When it is in the outdoor environment, the temperature compensation has been taken into account for the strain measurement due to sunlight radiation. The compressive strain has been measured, without needing pretension on the fiber with a Brillouin scattering-based distributed sensor system, when the fiber is glued to the steel beam at every point. The dynamic range in the strain measurement has been increased, due to the elimination of the pretension requirement. The spatial resolution of the strain measurement is 0.5 m. The strain measurement accuracy is /spl plusmn/10 /spl mu//spl epsi/(/spl mu/m/m) in the laboratory environment with nonuniform-distributed strain. With uniform strain distribution, the strain accuracy for this system can be. /spl sim//spl plusmn/5 /spl mu//spl epsi/. These results were achieved with the introductions of a computer-controlled polarization controller, a fast digitizer-signal averager, a pulse duration control, and the electrical optical modulator bias setting in the software.

162 citations

Journal ArticleDOI
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

136 citations

Journal ArticleDOI
TL;DR: A new technique is reported that permits the simultaneous measurement of strain and temperature to resolutions of +/-178 microepsilon and +/-3.9 degrees C at a spatial resolution of 3.5 m by incorporation of the Brillouin-loss peak power with the conventional BrillouIn-frequency measurement.
Abstract: Brillouin-scattering-based sensors are capable of measuring either the strain or the temperature along the length of an optical fiber in a distributed fashion through measurement of the Brillouin-frequency shift. The cross sensitivity of the frequency shift to these two parameters makes it impossible to differentiate between them by measurement of the frequency shift alone. We report on a new technique that permits the simultaneous measurement of strain and temperature to resolutions of +/-178 microepsilon and +/-3.9 degrees C at a spatial resolution of 3.5 m by incorporation of the Brillouin-loss peak power with the conventional Brillouin-frequency measurement.

80 citations

Journal ArticleDOI
TL;DR: In this article, a novel dark-pulse-based technique has been used for the first time in a Brillouin scattering-based distributed fiber sensor, which is capable of strain and temperature measurement as conventional pulse-based systems but at much higher spatial resolution.
Abstract: A novel dark-pulse-based technique has been used for the first time in a Brillouin scattering-based distributed fiber sensor. Experimentally obtained Brillouin spectra demonstrate that the dark-pulse configuration is as capable of strain and temperature measurement as conventional pulse-based systems but at much higher spatial resolution. A spatial resolution of 50 mm is reported with a strain measurement accuracy of 6 /spl mu//spl epsiv/ on a 100-m sensing fiber.

79 citations


Cited by
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Journal ArticleDOI
26 Jun 2012-Sensors
TL;DR: A sensor with centimeter spatial resolution and high precision measurement of temperature, strain, vibration and birefringence can find applications in aerospace smart structures, material processing, and the characterization of optical materials and devices.
Abstract: Rayleigh, Brillouin and Raman scatterings in fibers result from the interaction of photons with local material characteristic features like density, temperature and strain. For example an acoustic/mechanical wave generates a dynamic density variation; such a variation may be affected by local temperature, strain, vibration and birefringence. By detecting changes in the amplitude, frequency and phase of light scattered along a fiber, one can realize a distributed fiber sensor for measuring localized temperature, strain, vibration and birefringence over lengths ranging from meters to one hundred kilometers. Such a measurement can be made in the time domain or frequency domain to resolve location information. With coherent detection of the scattered light one can observe changes in birefringence and beat length for fibers and devices. The progress on state of the art technology for sensing performance, in terms of spatial resolution and limitations on sensing length is reviewed. These distributed sensors can be used for disaster prevention in the civil structural monitoring of pipelines, bridges, dams and railroads. A sensor with centimeter spatial resolution and high precision measurement of temperature, strain, vibration and birefringence can find applications in aerospace smart structures, material processing, and the characterization of optical materials and devices.

1,011 citations

Journal ArticleDOI
23 May 2016-Sensors
TL;DR: The latest developments related with the improvement of these products are presented by presenting a wide range of laboratory experiments as well as an extended review of their diverse applications in civil engineering structures.
Abstract: The application of structural health monitoring (SHM) systems to civil engineering structures has been a developing studied and practiced topic, that has allowed for a better understanding of structures’ conditions and increasingly lead to a more cost-effective management of those infrastructures In this field, the use of fiber optic sensors has been studied, discussed and practiced with encouraging results The possibility of understanding and monitor the distributed behavior of extensive stretches of critical structures it’s an enormous advantage that distributed fiber optic sensing provides to SHM systems In the past decade, several R & D studies have been performed with the goal of improving the knowledge and developing new techniques associated with the application of distributed optical fiber sensors (DOFS) in order to widen the range of applications of these sensors and also to obtain more correct and reliable data This paper presents, after a brief introduction to the theoretical background of DOFS, the latest developments related with the improvement of these products by presenting a wide range of laboratory experiments as well as an extended review of their diverse applications in civil engineering structures

572 citations

Journal ArticleDOI
07 Apr 2011-Sensors
TL;DR: The progress on improving sensing performance parameters like spatial resolution, sensing length limitation and simultaneous temperature and strain measurement is reviewed.
Abstract: Brillouin scattering in optical fiber describes the interaction of an electro-magnetic field (photon) with a characteristic density variation of the fiber. When the electric field amplitude of an optical beam (so-called pump wave), and another wave is introduced at the downshifted Brillouin frequency (namely Stokes wave), the beating between the pump and Stokes waves creates a modified density change via the electrostriction effect, resulting in so-called the stimulated Brillouin scattering. The density variation is associated with a mechanical acoustic wave; and it may be affected by local temperature, strain, and vibration which induce changes in the fiber effective refractive index and sound velocity. Through the measurement of the static or dynamic changes in Brillouin frequency along the fiber one can realize a distributed fiber sensor for local temperature, strain and vibration over tens or hundreds of kilometers. This paper reviews the progress on improving sensing performance parameters like spatial resolution, sensing length limitation and simultaneous temperature and strain measurement. These kinds of sensors can be used in civil structural monitoring of pipelines, bridges, dams, and railroads for disaster prevention. Analogous to the static Bragg grating, one can write a moving Brillouin grating in fibers, with the lifetime of the acoustic wave. The length of the Brillouin grating can be controlled by the writing pulses at any position in fibers. Such gratings can be used to measure changes in birefringence, which is an important parameter in fiber communications. Applications for this kind of sensor can be found in aerospace, material processing and fine structures.

491 citations

Journal ArticleDOI
30 Jul 2015-Sensors
TL;DR: Recent research and applications in structural health monitoring of composite aircraft structures using FOS have been critically reviewed, considering both the multi-point and distributed sensing techniques.
Abstract: In-service structural health monitoring of composite aircraft structures plays a key role in the assessment of their performance and integrity. In recent years, Fibre Optic Sensors (FOS) have proved to be a potentially excellent technique for real-time in-situ monitoring of these structures due to their numerous advantages, such as immunity to electromagnetic interference, small size, light weight, durability, and high bandwidth, which allows a great number of sensors to operate in the same system, and the possibility to be integrated within the material. However, more effort is still needed to bring the technology to a fully mature readiness level. In this paper, recent research and applications in structural health monitoring of composite aircraft structures using FOS have been critically reviewed, considering both the multi-point and distributed sensing techniques.

461 citations

Journal ArticleDOI
TL;DR: A differential pulse-width pair Brillouin optical time domain analysis (DPP-BOTDA) for centimeter spatial resolution sensing using meter equivalent pulses is proposed.
Abstract: A differential pulse-width pair Brillouin optical time domain analysis (DPP-BOTDA) for centimeter spatial resolution sensing using meter equivalent pulses is proposed. This scheme uses the time domain waveform subtraction at the same scanned Brillouin frequency obtained from pulse lights with different pulse-widths (e.g. 50ns and 49ns) to form the differential Brillouin gain spectrum (BGS) at each fiber location. The spatial resolution is defined by the average of the rise and fall time equivalent fiber length for a small stress section rather than the pulse-width difference equivalent length. The spatial resolution of 0.18m for the 50/49ns pulse pair and 0.15m for 20/19ns pulse pair over 1km sensing length with Brillouin frequency shift accuracy of 2.6MHz are demonstrated.

376 citations