We present a technique for dynamic strain measurements in optical fibers based on the stimulated Brillouin scattering interaction between two counterpropagating pulses. The allows high sampling rate and permits to addressing dynamically randomly position at which vibration is measured. Preliminary experimental results carried out with perturbation frequency up 98 Hz demonstrate validity of proposed technique.

In this paper, we demonstrate high spatial (≈3 cm) and spectral (≈30 MHz) resolution Brillouin sensing by use of optical frequency-domain analysis (BOFDA) signal processing. An iterative method is employed to correct the acquired data from spurious effects associated acoustic wave modulation relevant in regime. Experimental tests that proposed algorithm allows reconstruct shift profile with full allowed system bandwidth.

We demonstrate a Brillouin optical frequency-domain reflectometry (BOFDR) technique, which can measure the strain and/or temperature along an fiber with one-end access, by detecting spontaneous scattering from sinusoidally modulated pump light. Compared to analysis (BOFDA), we show that BOFDR measurements are free distorting components related acoustic wave modulation, thus simplifying data processing.

In the last years, fiber optic sensors have been widely exploited for several sensing applications, including static and dynamic strain measurements up to acoustic detection. Among these, Bragg grating indicated as ideal candidate practical structural health monitoring in light of their unique advantages over conventional devices. Although this class has successfully tested low-frequency measurements, identification sensor performances high-frequency detection, emission ultrasonic...

Distributed temperature measurements in a perfluorinated graded-index polymer optical fiber (POF) with 50- μm core diameter are reported for the first time, to best of our knowledge. Brillouin frequency-domain analysis is shown be able resolve spatially temperature-dependent frequency shift profile along 20-m POF sample, at nominal spatial resolution 4 m. The results indicate that POFs potentially useful distributed based on stimulated scattering.

In this paper, we show some recent experimental applications of Brillouin optical time-domain analysis (BOTDA) based sensors for geotechnical monitoring. particular, how these can be applied to detecting early movements soil slopes by the direct embedding suitable fiber cables in ground is presented. Furthermore, same technology used realize innovative inclinometers, as well smart foundation anchors.

We present a technical solution, capable of alleviating the problem pump depletion in long-range Brillouin distributed fiber sensor. This solution takes advantage presence two sidebands probe wave to generate dual gain-loss interaction, giving rise reduced depletion. Experimental results, carried out by using optical frequency-domain analysis configuration, demonstrated improvement offered technique.

Abstract The mechanics of rainfall-induced flowslides in pyroclastic soils have yet to be completely clarified. complexity phenomena (rainfall-induced failure initially unsaturated granular deposits, post-failure transition flow-like landslide) requires the use a well-equipped small-scale flume. To this aim, flume experiments at Second University Naples were performed analyze fundamental aspects such phenomena. A new experimental program is now being carried out assess performance time...

We report the results of a static load test performed on road-bridge with span length 44.40 m. The tests were by portable prototype instrument exploiting stimulated Brillouin scattering in optical fibers for deformation and temperature measurements. fiber sensor was able to provide strain distribution along supporting beam bridge spatial resolution 3 meters ±15 με. Comparison fiber-optic measurements finite-elements-method (FEM) simulations, as well data collected vibrating wire gauges,...

The application of a Brillouin distributed sensor for the monitoring railway traffic is presented in this work. field test performed on Italian regional line San Severo-Peschici, operated by Ferrovie del Gargano. A single-mode optical fiber was attached along rail length about 60 m. strain associated with train passage acquired monitored at 31 Hz acquisition rate and 1 m spatial resolution. data demonstrates its capability retrieving useful information monitoring, such as identification,...

This work reports on the application of a distributed fiber-optic strain sensor for long-term monitoring railway tunnel affected by an active earthflow. The has been applied to detect distribution along optical fiber attached two walls tunnel. experimental results, relative two-year campaign, demonstrate that is able localized strains, identify their location walls, and follow temporal evolution.

In this paper, we demonstrate automatic vehicle detection and counting by processing data acquired using a phase-sensitive optical time-domain reflectometer ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>ϕ</mml:mi> </mml:math> -OTDR) distributed fiber sensor. The are processed the Hough transform, which detects lines in images formed representing space–time domain. A rough classification of vehicles (heavy versus light vehicles) is also proposed, based...

Although landsliding is the macroscopic effect of slope failure, it only final stage an often time-consuming process soil deformation. In many cases, movement remains extremely slow and undetected for a long time; in other failure abrupt, preceded by small deformations followed rapid, destructive movements. This case granular soils pyroclastic nature, which involve extensive mountainous area surrounding Mt. Vesuvius southern Italy. Given that around highly urbanized densely populated,...

We present a hybrid Brillouin/Rayleigh sensor for multiparameter sensing in optical fibers. The system makes use of single laser pulse to excite both Rayleigh and Brillouin backscattering the same fiber. In detection path, backscattered signals are separated based on their different wavelengths. is capable determining simultaneously frequency shift (BFS) fiber, as well contents any vibration acting fiber recovered by phase sensitive OTDR (ϕ-OTDR) measurements. reported experiments show...

The experimental validation of a numerical technique for temperature/strain profile reconstruction based on Brillouin optical-fibre time-domain analysis (BOTDA) sensors is presented. In this approach, we search directly the frequency shift along fibre that matches measured data. algorithm harmonic expansion unknown profile, whose coefficients are determined by means multidimensional minimization. Experimental measurements have been carried out in order to reveal influence nonlocalities...

Stimulated Brillouin scattering (SBS) has been recently shown to offer a mechanism for generating tunable all-optical delays in room-temperature single-mode optical fibers at telecommunication wavelengths. This technique makes use of the rapid variation refractive index that occurs vicinity gain resonance. When slow light pulse delay is subject constraint on allowable distortion, it pair closely-spaced lines can increase distortion-constrained delay, with respect single-line configuration....

Numerical and experimental results on stimulated Brillouin scattering (SBS) in a graded-index multimode silica fiber are reported. The Gain Spectrum (BGS) is shown to strongly depend the pump probe modal content. By use of numerical model, BGS at varying launching conditions both beams computed. show that intramodal intermodal SBS contribute overall BGS. Experiments confirm predictions.

We report the results of a long term structural health monitoring (SHM) test campaign performed on concrete bridge. A one-year was by portable prototype instrument based stimulated Brillouin scattering in single-mode optical fibre. The fibre sensor attached along one arch bridge using two types adhesive for comparison purposes. able to provide strain distribution structure during campaign, with spatial resolution 1 m. crack revealed and correctly localized distributed sensor.

We demonstrate a two-wavelength differential-phase-measuring OTDR sensor that uses perfect periodic correlation phase codes to enhance the measurement performance. The technique extends range of sensors by synthesizing virtual longer-wavelength from two simultaneous measurements using different lasers. This increases free unwrapping errors. However, we find application this greatly relative noise. To compensate for issue, introduce use optical pulse compression increase signal-to-noise ratio...

Nowadays, the development of simple, fast, and low-cost selective sensors to detect substances interest is great importance in several application fields. Among this kind sensors, those based on surface plasmon resonance (SPR) represent a promising category, since they are highly sensitive, versatile, label-free. In work, an SPR probe, poly(methyl methacrylate) (PMMA) slab waveguide covered by gold nanofilm, combined with specific molecularly imprinted polymer (MIP) receptor for bovine serum...

Abstract All structures during operating life can be affected by faults induced accidental events and operational conditions. Structural health monitoring systems provide quasi-real-time diagnosis of the structure, thus enabling condition-based maintenance approach. By means piezoelectric transducers (PZTs) ultrasonic guided waves (UGW), structural integrity easily interrogated, even though laborious post-processing techniques are required to correctly interpret sensed data. This work aims...

In this paper, we propose and demonstrate a network analysis optical frequency domain reflectometer (NA-OFDR) for distributed temperature measurements at high spatial (down to 3 cm) resolution. The system makes use of frequency-stepped, continuous-wave (cw) laser, whose output light is modulated using vector analyzer. latter also used demodulate the amplitude beat signal obtained by coherently mixing Rayleigh backscattered with local oscillator. capable measurand resolution (50 mK 3-cm...

We present a distributed optical fiber sensor based on hybrid Brillouin frequency/correlation-domain analysis (BOFDA/BOCDA) configuration for both static and dynamic strain measurements. Distributed (or temperature) measurements are realized using the conventional BOFDA method, i.e., acquiring baseband transfer function of through vector network analyzer (VNA). With little modifications, same setup can perform dynamic, position-selective synthesizing correlation peak frequency modulation...