Compact fiber Bragg grating dynamic strain sensor cum broadband thermometer for thermally unstable ambience

Sreekumar, K and Asokan, S (2010) Compact fiber Bragg grating dynamic strain sensor cum broadband thermometer for thermally unstable ambience. In: Journal of optics a-pure and applied optics, 12 (1).

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Abstract

An instrument for simultaneous measurement of dynamic strain and temperature in a thermally unstable ambience has been proposed, based on fiber Bragg grating technology. The instrument can function as a compact and stand-alone broadband thermometer and a dynamic strain gauge. It employs a source wavelength tracking procedure for linear dependence of the output on the measurand, offering high dynamic range. Two schemes have been demonstrated with their relative merits. As a thermometer, the present instrumental configuration can offer a linear response in excess of 500 degrees C that can be easily extended by adding a suitable grating and source without any alteration in the procedure. Temperature sensitivity is about 0.06 degrees C for a bandwidth of 1 Hz. For the current grating, the upper limit of strain measurement is about 150 mu epsilon with a sensitivity of about 80 n epsilon Hz(-1/2). The major source of uncertainty associated with dynamic strain measurement is the laser source intensity noise, which is of broad spectral band. A low noise source device or the use of optical power regulators can offer improved performance. The total harmonic distortion is less than 0.5% up to about 50 mu epsilon, 1.2% at 100 mu epsilon and about 2.3% at 150 mu epsilon. Calibrated results of temperature and strain measurement with the instrument have been presented. Traces of ultrasound signals recorded by the system at 200 kHz, in an ambience of 100-200 degrees C temperature fluctuation, have been included. Also, the vibration spectrum and engine temperature of a running internal combustion engine has been recorded as a realistic application of the system.

Item Type:	Journal Article
Publication:	Journal of optics a-pure and applied optics
Publisher:	Institute of physics
Additional Information:	Copyright for this article belongs to Institute of physics.
Keywords:	fiber Bragg grating; temperature sensor; strain sensor; thermally unstable ambience; distributed feedback laser; ultrasound sensor; wavelength tracking; vibration analysis; internal combustion engine
Department/Centre:	Division of Physical & Mathematical Sciences > Instrumentation Appiled Physics
Date Deposited:	27 Jan 2010 09:54
Last Modified:	19 Sep 2010 05:54
URI:	http://eprints.iisc.ac.in/id/eprint/25457

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