Fig. 1. Schematic diagram of experimental setup. HR-FBG, high-reflectivity FBG; MFA, mode field adapter; BPF, band-pass filter; WDM, wavelength division multiplexer; P4, extra port of WDM.

Fig. 2. Characteristics of the amplified RFL. (a) Detailed spectrum varying with different output powers. (b) Temporal stability at full power.

Fig. 3. Characteristics of the idler laser. (a) Output power as a function of the pump power. (b) Temporal stability.

Fig. 4. Spectra details of (a) signal laser and (b) idler laser.

Fig. 5. (a) Beam quality measurement. (b) Near-field intensity distribution of the idler laser.