Fig. 1. Schematic diagram of coherent Raman amplification.

Fig. 2. (a) The dispersion curve of the PM-DC-EYDF. The relationship between gain and (b) pump power and (c) fiber length.

Fig. 3. Simulation evolution diagram of (a) the frequency domain and (b) time evolution.

Fig. 4. Schematic diagram of the coherent Raman amplification laser device. ISO, isolator; HWP, half wave plate; DM, dichroic mirror; GP, grating pair; LD, laser diode; LPF, long-pass filter; M, mirror.

Fig. 5. (a) Pulse train, (b) spectrum and (c) autocorrelation trace of the pump pulse.

Fig. 6. Schematic diagram of spectrum evolution (a) before and (b) after filtering. (c) 3D diagram of the spectrum evolution. (d) Raman spectrum when the pump power is 1.5 W (dot line), 2.5 W (dash line), 3.5 W (solid line), 4.5 W (dot dash line), respectively. (e) Measured autocorrelation trace and Gaussian fitting curve when the pump power is 4.5 W. (f) Radio-frequency spectrum of the Raman pulse. (g) Variations in the total output power and filtered Raman pulse power with the pump power. (h) Raman laser power fluctuation test curve with time.

Fig. 7. (a) Total spectrum evolution diagram in 3 m PM-DC-EYDF. (b) When the pump power is 9 W, measured Raman spectrum after filtering and (c) measured autocorrelation trace and Gaussian fitting curve. (d) Variations in the total output power and filtered Raman laser power with the pump power in 3 m PM-DC-EYDF.

Fig. 8. Variations in Raman pulse duration (circular point) and conversion efficiency (square point) with (a) pulse duration and (b) power of the 1560 nm pump.