Fig. 1. Structural diagram of linearly polarized narrow-linewidth all-fiber laser system

Fig. 2. Characterizations of backscattered light power and laser output spectra. (a) Curve of backscattered light power varying with laser output power; (b) backscattered light spectra at different laser output powers

Fig. 3. WNS₁ phase modulation. (a) Curves of backscattered light power versus laser output power; (b) spectra of backscattered light at different laser output powers; (c) time-domain characteristics of backscattered light

Fig. 4. WNS phase modulation with different modulation frequencies. (a) Laser output spectra; (b) curves of backscattered optical power versus laser output power; (c) change trends of linewidth and SBS threshold

Fig. 5. WNS phase modulations with different modulation depths. (a) Laser output spectra; (b) curves of backscattered optical power versus laser output power; (c) change trends of linewidth and SBS threshold

Fig. 6. Cascaded WNS phase modulation. (a) Laser output spectra; (b) curves of backscattered optical power versus laser output power; (c) change trends of linewidth and SBS threshold

Fig. 7. PRBS 9 phase modulation. (a) Curve of backscattered light power versus laser output power; (b) backscattered light spectra at different laser output powers

Fig. 8. PRBS phase modulations with different code lengths. (a) Laser output spectra; (b) curves of backscattered optical power versus laser output power; (c) change trends of linewidth and SBS threshold

Fig. 9. PRBS phase modulations with different modulation frequencies. (a) Laser output spectra; (b) curves of backscattered optical power versus laser output power; (c) change trends of linewidth and SBS threshold

Fig. 10. PRBS phase modulations with different modulation depths. (a) Laser output spectra; (b) curves of backward scattered light power versus laser output power (inset shows enlarged plot of curves of backward scattered light power versus laser output power at 50‒200 mV); (c) change trends of linewidth and SBS threshold

Fig. 11. Curve of laser output power versus pump power

Fig. 12. Spectra of different laser output powers. (a) Forward spectra; (b) backscattered light spectra

Fig. 13. Laser output characteristics. (a) Output spectra at laser output power of 1254 W; (b) PER characteristics at different laser powers