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The Strathprints institutional repository is a digital archive of University of Strathclyde research outputs.

Strathprints serves world leading Open Access research by the University of Strathclyde, including research by the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS), where research centres such as the Industrial Biotechnology Innovation Centre (IBioIC), the Cancer Research UK Formulation Unit, SeaBioTech and the Centre for Biophotonics are based.

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Tuneable diode laser spectroscopy over optical fibres for gas measurements in harsh industrial environments

Johnstone, Walter and Duffin, Kevin and Mcgettrick, Andrew James and Stewart, George and CHEUNG, Amy and Moodie, D. (2005) Tuneable diode laser spectroscopy over optical fibres for gas measurements in harsh industrial environments. Proceedings of SPIE: The International Society for Optical Engineering, 5952. p. 595206.

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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.