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Proceedings Paper

Tunable diode laser spectroscopy over optical fibres for gas measurements in harsh industrial environments
Author(s): Walter Johnstone; Kevin Duffin; Andrew McGettrick; George Stewart; Amy Cheung; D. Moodie
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Paper Abstract

Near infra-red tuneable diode laser spectroscopy (TDLS) with wavelength modulation spectroscopy (WMS) is a powerful technique for the measurements of gas compositions, and its ability to address multiple sensing points over optical fibre networks is proving to be particularly useful. However, the complexity involved in compensating for errors arising from pressure fluctuations is a weakness. Indeed, it is desirable to develop the technique to be capable of measuring pressure. This requires the extraction of accurate linewidth information from the recovered signals, so far made difficult by the presence of a systematic distortion arising from the laser amplitude modulation. Here we report a simple detection technique to null the effects of laser amplitude modulation and recover undistorted signals from which the gas linewidth can be accurately measured. Firstly we demonstrate that the measurements of accurate gas linewidths and pressure can be made from direct detection TDLS, addressing an atmospheric water absorption line. Finally, we report the accurate and simple measurement of acetylene pressure from TDLS / WMS measurements.

Paper Details

Date Published: 24 September 2005
PDF: 8 pages
Proc. SPIE 5952, Optical Fibers: Applications, 595206 (24 September 2005); doi: 10.1117/12.622820
Show Author Affiliations
Walter Johnstone, Univ. of Strathclyde (United Kingdom)
Kevin Duffin, Univ. of Strathclyde (United Kingdom)
Andrew McGettrick, Univ. of Strathclyde (United Kingdom)
George Stewart, Univ. of Strathclyde (United Kingdom)
Amy Cheung, Univ. of Strathclyde (United Kingdom)
D. Moodie, Univ. of Strathclyde (United Kingdom)


Published in SPIE Proceedings Vol. 5952:
Optical Fibers: Applications
Leszek R. Jaroszewicz; Brian Culshaw; Anna Grazia Mignani, Editor(s)

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