Demodulation Method of Distributed Fiber Bragg Grating Sensor Based on Whispering Gallery Mode Optical Microcavities

Abstract

A new system on demodulation of distributed fiber Bragg grating (FBG) sensor is built which is based on Whispering Gallery Modes Optical Microcavities. In order to eliminate the temperature effect on strian measurement two adjacent FBGs (one for sensing, the other for reference) with similar central wavelength and different lengths as a probe by parallel connection are utilized. Studies have shown that the Whispering Gallery Mode Optical Microcavities with special properties of selecting specific light, when the light couple into the cavity and shocking back and forth, only the specific light can couple out, it can be expressed as: 2πrn = kλ, where r is the cavity radius, n is the refractive index of the cavity, λ is the wavelength of the light coupled out, k is taken a positive integer. Using the fature of Whispering Gallery Modes Optical Microcavities to demodulate the spectral signal of the sensing probe, Combined with the light detector, signal amplifiers, computers and other devices to dispaly the detected strain in real time. Experiment result shows that it is feasible to demodulate action spectrum and the cross of FBG for temperature and the strain is solved. It is testified that the initial establishment of the laboratory system is stable, reliable, and less expensive.