Research On Devices Based On Chirped Phase Shift Fiber Bragg Grating

Fiber gratings are one of the most common optical devices.Optoelectronic devices based on fiber gratings have the advantages of small size,easy integration and easy connection with fiber communication systems.Optoelectronic devices based on fiber gratings are important component of optical networks.Chirped phase-shifted fiber grating(PS-CFBG)is made by introducing phase shifts on chirped fiber Bragg grating(CFBG)to open one or more extremely narrow "windows" in the spectrum of CFBG,which make the PS-CFBG has obvious advantages in multi-channel narrowband filtering.PS-CFBG can be widely used in the fields of wavelength division multiplexing,multi-wavelength modulation and multi-parameter sensing.In this paper,the spectral characteristics of PS-CFBG are analyzed with the V-I transmission matrix method,and on this basis,tunable filter,high-energy pulse laser,and micron-level precise positioning sensor are studied.The main research contents and innovative results as follow:1.Theoretical models of phase-shifted fiber gratings based on V-I transfer matrix formalism is established.The research results show that,in terms of the spectral characteristics of the shifted fiber grating,the model based on V-I transfer matrix formalism has higher calculation efficiency under the premise of ensuring the calculation accuracy,compared with the three common analysis methods(transmission matrix method,F-P cavity equivalent method and multilayer film method).2.Two types of tunable filters based on PS-CFBG and polarization-maintaining PS-CFBG are studied.The filtering strength,filtering wavelength,wavelength interval and number can be adjusted by changing the magnitude,position and number of induced phase shifts.When the filtering strength reaches to the maximum,the smallest narrowband bandwidth of 0.008 nm is obtained.Using piezoelectric ceramics(PZT)to introduce phase shift on CFBG and polarization maintaining CFBG.By adjusting the driving voltage on PZT to change the magnitude of phase shift,filtering strength of two filters are tuned.The experiment provides a new idea for the research of tunable narrowband filters.3.An erbium-doped fiber ring laser with PZT based PS-CFBG has been built.When the PZT is driven by DC voltage and square-wave signal,continuous and pulse laser output are obtained,respectively.Set the pump power of the laser at 107 m W,when amplitude of DC voltage is 75 V,a continuous laser output with signal-to-noise ratio(SNR)of 60 d B is obtained;when the amplitude of square wave signal is 75 V and the frequency is 1 k Hz and 2 k Hz,pulse laser outputs with energy of 1.67 ?J(1 k Hz)and 2.77 ?J(2k Hz)were obtained.4.A dual-wavelength erbium-doped fiber ring laser based on polarization-maintaining PS-CFBG is proposed and built.A PZT is pasted to polarization-maintaining CFBG to achieve narrow-band in the spectrum of CFBG.When the pump power of the laser is 135 m W and the driven DC voltage of PZT is 60 V,the dual-wavelength laser with interval of 0.384 nm and SNR more than 40 d B is obtained.Besides,single-wavelength output and switching can be realized by adjusting the polarization state of laser cavity.5.A strain and strain point precise positioning sensor based on cascaded CFBGs is researched.The research results show that,the sensor can theoretically realize the strain point positioning to the micron level.PZT is used to introduce micro-strain on the cascade CFBG,and the magnitude of the micro-strain is changed by adjusting its driven voltage.Under the two situations of,multiple strain points on one single CFBG and one single strain point on each CFBG,the sensor based on cascaded CFGBs is used in strain sensing,and the maximum strain sensitivity of 0.19 pm / ?? is obtained.