Reseach Of FBG Sensing Characteristics Of Intra-cavity Fiber Optic Laser

Optical fiber bragg grating(FBG) sensors have advantages of small quality,resistance to electromagnetic interference, small size and high sensitivity, so they gotthe extensive attention. In some previous studies, broad band light sources or tunablelasers was often used in the FBG sensor system as the light source, however in theseschemes, their signal-to-noise ratios are not high, and the power consumption is too big,and at the same time if broadband light source is used as a sensor source, reflectionspectrum of3dB bandwidth is against demodulation.According to the research situation of present FBG sensor system, Schemes thatin-cavity FBG sensing system based on multi-wavelength erbium-doped fiber laserwavelength is demodulated using a cross-correlation algorithm have been proposed.First, this paper describes the FBG sensing theory, outlines working principle of themulti-wavelength fiber laser, and summarizes the advantages of in-cavity FBG sensingbased on multi-wavelength fiber laser.Secondly, in order to study the multi-wavelength laser output characteristics better,to study wavelength and intensity dynamic process in the multi-wavelengtherbium-doped fiber laser cavity, the paper constructs a theoretical model describingoscillation of fiber laser cavity. And study characteristics of the output laser in thesingle-wavelength laser and multi-wavelength laser.Thirdly, this paper presents a linear cavity structure of a dual-wavelengtherbium-doped fiber laser FBG sensing systems research program. Multi-wavelengtherbium-doped fiber laser is used as sensing light source, introducing two FBG as a filterelement for the laser cavity mirrors, and as a sensing element at the same time, and anFBG for strain sensing, the other for temperature compensation. Laser is introducedthrough using a nonlinear fiber environment (Nonlinear Optical Loop Mirror, NOLM)to suppress mode competition, to achieve the dual-wavelength output. For demodulatingsection, a resolution of0.01nm spectrometer is used to scan sensing signal, and usingthe cross-correlation algorithm to demodulate.The study showed that the design of fiber Bragg grating sensor system based onmulti-wavelength fiber lasers is feasible, can effectively improve the signal-to-noiseratio, lower power consumption, using the cross-correlation algorithm to demodulatecan suppress random noise to achieve the exact demodulation.