Multiplexing of optical fibre gas sensors with an FMCW technique

Yu, H.B. and Jin, W. and Ho, H.L. and Chan, K.C. and Chan, C.C. and Demokan, M.S. and Stewart, G. and Culshaw, B. and Liao, Y.B. (2001) Multiplexing of optical fibre gas sensors with an FMCW technique. Applied Optics, 40 (7). pp. 1011-1020. ISSN 1539-4522

Abstract

We report on the use of a frequency-modulated continuous-wave technique for multiplexing optical fiber gas sensors. The sensor network is of a ladder topology and is interrogated by a tunable laser. The system performance in terms of detection sensitivity and cross talk between sensors was investigated and found to be limited by coherent mixing between signals from different channels. The system performance can be improved significantly by use of appropriate wavelength modulation -scanning coupled with low-pass filtering. Computer simulation shows that an array of 37 acetylene sensors with a detection accuracy of 2000 parts in 106 for each sensor may be realized. A two-sensor acetylene detection system was experimentally demonstrated that had a detection sensitivity of 165 parts in 106 for 2.5-cm gas cells (or a minimum detectable absorbance of 2.1 x 10-4 ) and a cross talk of -25 dB.

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