Fibre optic techniques for remote spectroscopic methane detection - from concept to system realisation

Spectroscopic measurement of methane gas concentrations using absorption lines in the near infra red (the 1.67 mu m region) has been demonstrated by several research teams. The detection technique has the advantage of access through optical fibres which are very transparent in this spectral region and the disadvantage of relative insensitivity compared with the fundamental absorption lines in the 3-4 mu m area. This paper will describe a particular realisation of a fibre optic, highly multiplexed (up to 128 points) realisation of a methane gas detection system designed for safety monitoring applications and detection up to the lower explosive limit (5% by volume). This implementation is currently undergoing site trials and has combined advanced technological development especially in the signal processing domain with applications engineering, in particular with emphasis on the compatibility between the system performance, both technical and economic and potential applications. This approach which has involved close collaboration between the university research group and the specialist industrial provider of gas measurement systems promises to realise a cost effective and practical measurement system with state of the art technical performance. (C) 1998 Elsevier Science S.A. All rights reserved.