Fig. 1. Schematic of a π phase-shifted fiber Bragg grating

Fig. 2. Simulation of π phase-shifted fiber Bragg grating at temperatures of 5, 35, 65, 95 ℃

Fig. 3. Experimental setup of temperature tuning and test of π phase-shifted fiber Bragg grating

Fig. 4. Transmission spectra of π phase-shifted fiber Bragg grating at temperatures of 5, 35, 65, 95 ℃

Fig. 5. Central wavelength changing curve of π phase-shifted fiber Bragg grating with temperature

Fig. 6. Experimental setup of narrow linewidth fiber laser based on π phase FBG-shifted fiber Bragg grating

Fig. 7. Output spectra of laser at different temperatures of π phase-shifted fiber Bragg grating