Microfilter convolution effects in Bragg grating sensor demodulation

摘要

Fabry-Perot microfilters are often used to demodulate the output from fibre Bragg grating sensor systems. The spectral output from such a system is a convolution of the interferometer effects and the reflection characteristics of the Bragg grating in question, thus introducing an unavoidable limit of achievable measurand resolution. However, in a practical situation noise will always be present and this will vary significantly the resolution attainable for different microfilters and can reduce the effectiveness of narrow band microfilters for these types of systems. The characteristic behaviour of a Fabry-Perot interferometer when utilized as a Bragg grating demodulator is analyzed under the realistic condition of noise. Results, in the form of calculated signal to noise ratios for a range of noise levels are shown.