Fig. 1. Output longitudinal mode variation of DBR fiber laser under continuous temperature change. (a) Initial single longitudinal mode state; (b) About to enter the state of multi-longitudinal mode; (c) Multi-longitudinal mode state; (d) About to change back to the state of single longitudinal mode

Fig. 2. Structure of single frequency DBR fiber lase

Fig. 3. Longitudinal model characteristics of DBR fiber laser at 20 ℃. (a) Doped fiber 15 mm DBR; (b) Doped fiber 8 mm DBR

Fig. 4. Spectra of output laser at different temperatures

Fig. 5. Change of central wavelength of signal light within 30 minutes

Fig. 6. Laser pump-output relationship curve

Fig. 7. Structure of linewidth test system

Fig. 8. Result of linewidth test. (a) Linewidth of standard seed source; (b) Linewidth of DBR fiber laser

Fig. 9. Relative intensity noise of laser