Fig. 1. Schematic configuration of a typical fiber MOPA system.

Fig. 2. (a) Applied strain distribution along the gain fiber. (b) Calculated effective SBS gain spectra with and without strain^[23].

Fig. 3. Beam quality (M² factor) versus the output power of a typical SFFA. Insets: beam profiles at selected output powers^[35].

Fig. 4. TMI threshold as a function of the relative intensity noise (RIN) of the pump and the seed. The artificially imprinted noise contains frequencies from 1 Hz up to 2 kHz. The impact of the pump intensity noise (blue dots) on the TMI threshold is significantly stronger than that of the seed intensity noise (red dots)^[61].

Fig. 5. Output power evolution of the CW single-frequency amplifiers in an all-fiber format operating in 1 µm, 1.5 µm, and 2 µm regions (an updated version of Fig. 7 in Ref. [13]).

Fig. 6. Experimental setup of the tapered YDF-based SFFA at 1030 nm. P-A, pre-amplifier; BPF, bandpass filter; LD, laser diode; PM, polarization maintaining; YDF, Yb-doped fiber^[35].

Fig. 7. Example of a transfer function for the pump and seed power modulation^[110].

Fig. 8. Phase-noise measurements of the fiber amplifier scaled as frequency noise^[114].

Fig. 9. Relative power noise of the combined beam in comparison with the single amplifier performance. Relative power noise variations are caused by the amplifier pumps^[133].