Study On Fiber Lasers Based On Chirped Phase-Shifted Fiber Grating

Compared with traditional solid state lasers, the fiber laser is in a special form and has more particular advantages. It is easily connected to fiber system with lower insertion loss and the laser obtained through it is in good quality. The fiber laser has been widely used in many areas, i.e. optical communication and sensing, radar, laser machining, laser medical and laser ranging areas. In this paper, under the national natural science fund project, the working theory and simulation analysis of wavelength tunable fiber laser and Q-switched fiber laser based on chirped phase-shifted fiber Bragg grating (CPSFBG) has been explored. The main content is as follows:1. Analyze the transmission characteristics of the Phase-Shifted Fiber Bragg Grating (PSFBG) and the Linearly Chirped Fiber Bragg Grating (LCFBG) using transfer matrix method. Make an introduction on the forming principle of the Chirped Phase-Shifted Fiber Bragg Grating (CPSFBG) and its application in wavelength tunable fiber laser and Q-Switched fiber laser.2. An implementation of wavelength tunable continued-output fiber laser based on the CPSFBG has been studied. In the implementation, the effect of the longitudinal tensile produced by piezoelectric ceramics (PZT) on the linear chirp fiber grating is used to induce phase-shift in the LCFBG. The transmission of the CPSFBG under two situations of PZT attached on the LCFBG in different positions and PZT powered with different voltages is been analyzed in simulation. The theoretical analysis and simulation have been made of this fiber laser in the article. In addition, the influence of pump power, the length of EDF and the ratio of coupler on the output power has been analyzed.3. An implementation of Q-Switched fiber laser based on the CPSFBG has been studied, which is performed by loading modulation signal on the PZT. In the simulation, a rectangular signal with duty cycle of 50% is used. When the modulation frequency is set to 10 KHz, a pulse with repetition frequency of 10 KHz, width of 1μs is obtained.4. The system model of wavelength tunable fiber laser based on CPSFBG has been set up. The LCFBG with center-wavelength of 1544.843nm and length of 9cm is obtained by phase mask and UV exposure technique. With PZT attached on the LCFBG in the center and powered by DC voltages, there is a peak in the transmission spectrum of CPSFBG. The center-wavelength and transmission of the peak of CPSFBG vary with the voltage. The working wavelength of the fiber laser based on that CPSFBG is red-shifted and the power of the laser increases with the increasing voltage, whose change trend is consistent with the theoretical analysis results. The results of the laser spectrum under a certain PZT voltage noted every 5 minutes in 30 minutes show that the designed fiber laser is in good stability.