Sensitivity enhanced all-fiber displacement sensor compatible with passive and intracavity system based on Lyot filter

Abstract

An all-fiber high-sensitivity displacement sensor based on 45°-spliced PM Lyot filter is proposed and its sensing performance is investigated experimentally. The transfer function of PM Lyot filter transmission spectrum is derived by the Jones matrix. It is indicated by the simulation results that the birefringence index and the splicing angle of the PM fiber have obvious influences on the displacement sensitivity and the spectral modulation depth, respectively. According to the relationship between the dips and the displacements, the Lyot-filter based sensing head has a good linearity. The sensitivity of 122.81 pm/μm is finally obtained in the range of 200μm displacement variation and its R square is larger than 0.997. Moreover, the sensing head can be compatible to the intracavity spectroscopy to narrow linewidth and enhance the high signal-to-noise ratio (SNR) so as to realize high-resolution sensing. It is demonstrated experimentally that the sensitivity of the intracavity displacement sensor can be 60 pm/μm with a linewidth narrower than 0.05 nm and a SNR higher than 55 dB. The excellent performance of the proposed sensor compatible with passive and intracavity system not only provides a new approach for optical fiber displacement sensor, but also further expands the application of Lyot filter in the sensing field.