OFS 22 Beijing, China

Steve, Fei and Thomas are attending the international conference on optical fibre sensors (OFS) this this week and are presenting a number of poster presentations of their work. If you are attending please go see them, they are only too happy to talk to people interested in the odd things we do!

Poster Session 1: Tuesday 16th October 2012

PO1‐4 Multiplexing tapered optical fibres using coherent optical frequency domain reflectometryRenata Jarzebinska, Edmon Chehura, Stephen W. James, Ralph P. Tatam, Cranfield Univ. (United Kingdom) [8421‐32]. Coherent optical frequency domain reflectometry is used to multiplex a serial array of tapered optical fibre sensors. By monitoring changes in the Rayleigh backscattered signal from tapered regions of a single mode optical fibre, the refractive index of the medium surrounding each taper can bedetermined. The approach is used to demonstrate a liquid flow sensor.

PO1‐43 Toward track component condition monitoring using optical fibre Bragg grating sensors, S. J. Buggy, S. W. James, S. Staines, Cranfield Univ. (United Kingdom); R. Carroll, Stagecoach Supertram (United Kingdom); P. Kitson, D. Farrington, L. Drewett, J. Jaiswal, Tata Steel RD&T (United Kingdom); R. P. Tatam, Cranfield Univ. (United Kingdom) [8421‐34]. Optical fibre Bragg grating sensors have been field‐trialed for the monitoring of dynamic loading of fish‐plates, stretcher bars and switchblades on a tram network, with the aim of developing a condition monitoring system. This paper provides preliminary data showing the ability to identify changes in track/component condition.

PO1‐109 A 1.65 um region external cavity laser diode using an InP gain chip and a fibre Bragg grating, F. Chen, J. Hodgkinson, S. Staines, S. James, R. Tatam, Cranfield Univ. (United Kingdom) [8421‐538] We present the construction of an external cavity laser (ECL) diode using an InP semiconductor gain chip and a fibre Bragg grating (FBG), designed to have an emission wavelength that coincides with an absorption line of methane, to be used for spectroscopic gas sensing. The FBG was employed as a wavelength selective and feedback element, which will potentially provide the laser with wavelength tuning capability. Narrow linewidth lasing output of less than 5 MHz was achieved. To our knowledge, this is the first FBG based ECL in the 1.65 μm region.

Poster Session 2: Wednesday 17th October 2012

PO2‐4 Optical coherence tomography for endoscopes, using imaging fibre bundles and a conical mirror, Helen D. Ford, Ralph P. Tatam, Cranfield Univ. (United Kingdom) [8421‐293] Imaging fibre bundles and a conical mirror have been used to construct a passive, endoscopic OCT probe with no scanning components at the probe tip. Circular scanning of the beam projected onto the proximal face of the imaging bundle results in a corresponding circular scan at the distal end of the probe. A 45o base‐angle conical mirror turns the output light to produce a radially‐directed beam that permits circumferential OCT scanning in quasi‐cylindrical ducts.

PO2‐107 Range‐resolved single‐sideband optical fibre interferometry for quasi‐distributed dynamic strain sensing, Thomas Kissinger, Thomas O. H. Charrett, Ralph P. Tatam, Cranfield Univ. (United Kingdom) [8421‐352] A novel optical signal processing scheme for fibre sensors is proposed, which combines interferometric phase measurements with range multiplexing. The scheme is based on single‐sideband signal processing and uses continuous‐wave pseudo‐random range encoding. The potential of the technique for cost‐effective dynamic quasi‐distributed strain sensing is explored by applying it to an array of fibre segments. In its current implementation dynamic strains in segments of 3.4 m gauge lengths can be measured with a resolution well below microstrains at a bandwidth of 100 kHz.

Poster Session 3: Thursday 18th October 2012

PO3‐63 On‐line load monitoring of a tufting needle using optical fibre Bragg grating sensors, Edmon Chehura, Giuseppe Dell’Anno, Tristan Huet, Stephen Staines, Stephen W. James, Ivana Partridge, Ralph P. Tatam, Cranfield Univ. (United Kingdom) [8421‐33] Optical fibre Bragg grating strain sensors are used to monitor the dynamic loads experienced by a tufting needle installed on a commercial robot‐controlled tufting tool during the tufting of a dry carbon fibre preform. The influence of the thread and thickness of the preform lay‐up were investigated. Maximum axial compression strains of ~‐250 microstrain, and bending strains of 1100 microstrain were measured during the tufting of a 4 ply quasi‐isotropic carbon fibre dry preform.

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