High-precision Fiber Bragg Grating Sensing Demodulation Method Insensitive to Polarization State Change

Abstract

The invention discloses a sensing modulating method for a high-precision fiber bragg grating insensitive to polarization state changes. The sensing modulating method comprises the steps that wavelet transformation is conducted on two paths of fiber bragg grating reflective spectrums S1 and S2 respectively, a wavelet transformation result WT1 and a wavelet transformation result WT2 are obtained, and thus a time-wavelet energy spectrum H1 of S1 and a time-wavelet energy spectrum H2 of S2 are calculated; the peak position of H1 and the peak position of H2 are detected, energy fusion is conducted on H1 and H2, and a new time-wavelet energy spectrum E1 and a new time-wavelet energy spectrum E2 are obtained; the peak position of E1 and the peak position of E2 are detected, the peak position P1 and the peak position P2 are obtained, subtraction is conducted on P1 and P2, and therefore the difference value of the two peak positions is obtained, in other words, the wavelength difference of the two paths of fiber bragg grating reflective spectrums is obtained. According to the sensing modulating method, the problem of modulation result errors caused by polarization state instability in single mode fibers can be effectively solved, the wavelet time frequency energy spectrums are used for replacing the reflective spectrums of the fiber bragg grating to achieve detection of the reflective peak of the fiber bragg grating, denoising can be conducted on sensing signals, and the strain measurement precision of a modulation system can be further improved.

Description

technical field [0001] The invention relates to the technical field of optical fiber sensing, in particular to a high-precision optical fiber grating sensing demodulation method that is insensitive to polarization state changes. Background technique [0002] With the rapid development of narrow linewidth laser and fiber Bragg grating sensing and demodulation technology, the ultra-high resolution static strain measurement scheme based on narrow linewidth laser and fiber Bragg grating has attracted the attention of researchers in the field of fiber optic sensing (Q.W.Liu.An ultra-high-resolution FBG static-strain sensor for geophysis applications. Proc. of SPIE, Vol.7653, 76530W, 2010). In order to further improve the strain measurement resolution of this technical solution, the fiber grating is required to have a narrower bandwidth. To this end, the University of Tokyo in Japan has proposed a variety of technical solutions, using the fiber grating method with a narrower band...

Images