| We present a novel single-mode-fiber-based multipoint spectroscopic chemical gas sensing system using frequency-shifted interferometry (FSI). The absorption spectra of gas cells in a network of serial and/or parallel topology can be measured with this multiplexing scheme. The principle of FSI and the implementation of the gas sensing system are explained. Experiments are performed on a three-sensor system and a minimum detectable concentration of 184 ppm for acetylene has been achieved. As an illustration of FSI's capability of interrogating large scale sensor networks, the same system incorporated 10 fiber Bragg grating sensors for strain measurement. A signal-to-noise ratio of 48 dB and crosstalk of less than -34 dB have been attained. Finally, the design considerations and trade-offs of a FSI sensing system are discussed. This thesis is the first demonstration of FSI's application in gas sensing. The high performance of the FSI technique has shown great potential in optical sensing. |
