The transverse load and temperature sensitivities of fibre Bragg gratings (FBGs) fabricated in a range commercially available stress geometrically induced high birefringent (HiBi) fibres have been experimentally investigated. wavelength reflected by the FBG each polarization eigenmode was measured independently simultaneously using custom designed interrogation system. highest sensitivity, 0.23 ± 0.02 nm/(N/mm), obtained with HiBi FBGs elliptically clad fibre. This higher than for any other...

The use of optical fibre Bragg grating (FBG) strain sensors to monitor the condition safety critical rail components is investigated. Fishplates, switchblades and stretcher bars on Stagecoach Supertram tramway in Sheffield UK have been instrumented with arrays FBG sensors. dynamic signatures induced by passage a tram over analysed identify features indicative changes components.

It is known that optical fiber long period gratings (LPGs) exhibit their highest sensitivity to environmental perturbation when the such phase matching condition satisfied at its turning point. The reproducible fabrication of LPGs with parameters satisfying this requires high resolution control over properties grating. performance an LPG system based on point-by-point UV exposure approach analyzed in paper, and factors influencing reproducibility, including period, duty cycle, environment...

Fibre optic based sensors are becoming increasingly viable as replacements for traditional flight test sensors. Here we present laboratory, wind tunnel and results of fibre Bragg gratings (FBG) used to measure surface strain an extrinsic Fabry–Perot interferometric (EFFPI) sensor unsteady pressure. The calibrated full scale resolution bandwidth the FBG EFFPI were shown be 0.29% at 2.5 kHz up 600 με 0.15% 10 respectively 400 Pa. tests, completed on a 30% model, allowed developed before...

Dynamic fiber-optic shape sensing, often also referred to as curvature or bend is demonstrated using fiber segment interferometry, where chains of segments, separated by broadband Bragg grating reflectors, are interrogated range-resolved interferometry. In this paper, the theory interferometric sensing segments developed in detail, including techniques infer lateral displacements from measured differential strain data and methods for directional calibration sensor. A proof-of-concept...

This paper compares two fibre optic sensing techniques for vibration characterisation: (a) optical Bragg grating (FBG) strain gauges and (b) a novel direct shape (DFOSS) approach based on differential interferometric measurements between multiple fibres within the same arrangement.Operational mode shapes frequency of an Airbus Helicopters H135 bearingless main rotor blade (5.1 m radius) were acquired during series ground tests undertaken in controlled laboratory environment.Data recorded by...

We report the development of a fibre Bragg grating (FBG) interrogation system that is capable detecting independently and simultaneously two orthogonally polarized signals reflected from polarization-maintaining (PM) FBG. This relaxes constraints on bandwidth FBG spectrum, allowing use shorter PM (larger bandwidth) for sensing applications where higher spatial resolution required. It imposes no limitation measurable strain range profile. The decoding complex spectral responses subjected to...

The performance of two complementary optical strain measurement techniques, speckle shearing interferometry (shearography) and fibre Bragg grating (FBG) sensors, is compared with that resistance foil gauges (RFSGs) theoretical predictions. test object used for the surface measurements was a hydrostatically loaded ABS pipe. A multi-component shearography instrument, capable full measurement, to determine displacement gradient components, from which components were calculated. Six mounted...

An effective-soil-pressure sensor for geotechnical applications based on Fibre Bragg Gratings is presented. The simultaneous measures total soil pressure and pore pressure, allowing the calculation of effective stress soil. Calibration using pressurised air demonstrated a sensitivity 2.02x10^-3 ± 2.84x10^-5nm/kPa 1.87x10^-3 6.88x10^-5nm/kPa respectively. This corresponds to resolution 4.95x10^-1kPa 5.46x10^-1kPa 1pm interrogation...

Abstract Optical fibre strain and shape measurement sensors were deployed on a 5-m long rotor blade during full-speed (rotation rate 6.6 Hz) helicopter ground run, with real-time data wirelessly streamed from hub-mounted sensor interrogators. In Part 1 of 2-part paper series, the sensing capabilities two optical fibre-based techniques, Bragg grating (FBG) segment interferometry (FSI), are compared, while 2 (Kissinger et al 2022 Smart Mater. Struct. accepted) specifically investigates based...

Dynamic loadings induced on a tufting needle during the of dry carbon fibre preform via commercial robot-controlled head were investigated in situ and real-time using optical Bragg grating (FBG) sensors bonded to shaft. The configured such that axial strain bending moments experienced by could be measured. A study influence thread type imparted revealed profiles which had equivalent trends but different magnitudes. mean maximum compression strains measured 4-ply quasi-isotropic − 499 ± 79...

The use of a range optical techniques to monitor the process fabricating fiber tapers is investigated. Thermal imaging was used optimize alignment system; transmission spectrum monitored confirm that had required properties and strain induced in during tapering using in-line Bragg gratings. Tapers were fabricated with diameters down 5 μm waist lengths 20 mm single-mode SMF-28 fiber.

Multiplexed optical fibre sensors were embedded into a carbon-fibre-reinforced-preform during the industrial production of full-sized, one-piece tail cone assembly for regional jet aircraft. Optical Fresnel monitored both infusion resin, via measurement refractive index-dependent attenuation in reflected light signal, and degree cure chemical reaction-dependent change index. The resin was also by Bragg gratings (FBGs) fabricated high linearly birefringent fibre, which measured...

Abstract Optical fibre strain and shape measurement sensors were deployed on a rotor blade during full-speed helicopter ground run, with real-time data wirelessly streamed from hub-mounted sensor interrogators. In part 2 of 2-part paper series, two-dimensional direct fibre-optic sensing (DFOSS), using segment interferometry-based interrogation is investigated. The concept change visualisation over one rotation period displacement surfaces introduced the usefulness DFOSS to gain additional...

The measurement of ground movement is an essential part many geotechnical engineering operations. For decades, inclinometer systems have traditionally been used for this purpose to provide crucial information engineers and researchers. However, conventional their limitations, such as high cost poor durability. In paper a fibre optic based system reported, which utilizes Bragg grating sensors attached the casing inclinometer. characterization sensor revealed good agreement with theory...

Langmuir-Blodgett (LB) films of omega-tricosenoic acid are deposited onto side-polished optical fibers, resulting in wavelength-selective elements. The wavelength response is shown to be strongly dependent on film thickness, giving a shift central with thickness Deltalambda(0)/Deltad = 2.4, agreement simple phasematching model. It demonstrated that an alternative polishing technique, requiring no substrates or epoxy, allows more repeatable LB deposition and produces devices similar...

A laser diode's junction voltage is a sensitive measure of its temperature and can be used in thermal control feedback loop. To compensate for the dependence laser's internal resistance, we have measured dynamic ∂V/∂I, by modulating injection current measuring demodulated voltage. The was thus controlled while operating at fixed DC current. Over an external range 15°C to 35°C, this stabilised centre frequency (wavelength) 1651 nm DFB diode with residual mean shift 60 MHz (0.5pm), less than...

Conventional singlemode semiconductor DFB and VCSEL lasers used in high resolution spectroscopy are often required to operate at specific, custom wavelengths, such as those associated with gas absorption lines. We present the results of work develop alternative sources 1550nm 1650nm regions, latter coinciding an line methane. Custom wavelength Bragg gratings have been stabilize output external cavity implemented both optical fiber planar silica-on-silicon integrated circuits, using...

A low loss in-fibre channel dropping filter is demonstrated by exploiting the evanescent coupling between a side polished monomode optical fibre and singlemode Langmuir-Blodgett (LB) film. The LB technique shown to provide precise film thickness control (~ 3 nm) for tight fabrication tolerances demanded this device.

The fabrication of an optical cavity at the distal end fiber has been achieved by Langmuir-Blodgett (LB) deposition tricosanoic acid. This technique allows nanometer-scale control over length to a total thickness ~0.5 microm . shown act interferometrically and, thus, potential sensing applications.

A novel suite of instrumentation for the characterisation materials held inside an air-tight tube furnace operated up to 250 °C has been developed. Real-time detection released gases (volatile organic compounds (VOCs), CO2, NO, NO2, SO2, CO and O2) was achieved combining commercial off-the-shelf (COTS) gas sensors sorbent tubes further qualitative semi-quantitative analysis by chromatography-mass spectrometry coupled thermal desorption (TD-GC-MS). The test system designed provide a...

Abstract Range resolved interferometry (RRI) applied to the interrogation of an extrinsic Fabry–Perot based pressure sensor in laboratory and wind tunnel environments is presented. A simple, compact head design was fabricated subsequently characterised using RRI, which shown have a sensitivity 1.627 <?CDATA $\times10^{-3}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo>...

Pile loading test plays an important role in the field of piling engineering. In order to gain further insight into load transfer mechanism, strain gauges are often used measure local strains along piles. This paper reports a case whereby FBG sensors was employed trial conducted on three different types pile tests glacial till. The instrumentation systems were configured suit specific characteristic each type test. Typical results presented. great potential using for testing is shown.

The CO2 laser based fabrication of tapered long period gratings (TLPGs) is optimized so that their transmission spectra are comparable with those made using the arc-discharge technique, which typically exhibits losses below 2 dB. reduction in loss was achieved by optimizing micro-taper geometry and duty-cycle device. A 6-period TLPG 378 μm exhibited a pass-band 0.6 dB, resonance band extinction values 3 dB had physical length 2.27 mm. average refractive index sensitivity 6 TPLG measured...

A differential extrinsic optical fiber Fabry-Perot based pressure sensor has been developed and benchmarked against a conventional piezoresistive Kulite sensor. The sensors were placed on the fuselage of 1:10/3 sub-scale model Scottish aviation Bulldog, which was in wind-tunnel. Pressure tappings that surrounded aided mapping distribution around this section fuselage. results obtained from fibre optic are good agreement with those tappings.