Fig. 1. Schematic of FBG structure and test

Fig. 2. Schematic diagram of complete laser system with optical feedback

Fig. 3. Temperature fluctuations of two optical fibers under the conditions with and without temperature control

Fig. 4. The beat note of the laser during free-running spectrum

Fig. 5. The beat note spectrum of 0.130-nm bandwidth FBG at reflected power of 0.8 mW

Fig. 6. The reflectivity of two FBGs vary with wavelength

Fig. 7. The laser linewidth varies with the reflected power of two FBGs with different bandwidths (0.130 nm and 0.195 nm)

Fig. 8. Curve of phase noise conversion to intensity noise

Fig. 9. Frequency domain distribution of laser phase noise power