All-optical output power stabilization of double-clad Er:Yb amplifiers using 1064 nm signal injection

We present a novel technique for all-optical stabilization of the output power of telecom band amplifiers based on double-clad (DC) erbium-ytterbium (Er:Yb) doped fibers. The proposed method relies on the utilization of the undesirable energy back-transfer effect which occurs in DC Er:Yb active fibers. A feedback loop is built based on a low-power 1064 nm laser, which is coupled into the Er:Yb fiber along with the 1550 nm seed. The auxiliary 1 µm signal partially extracts the Yb-ion energy, altering the gain at the design wavelength. The stabilization technique was verified for two types of fibers, to demonstrate the feasibility of our approach regardless of the type of DC Er:Yb fiber used, its characteristics, and the amplifier configuration. A long-term stability improvement by a factor of 117 was achieved, reaching a deviation of 0.8 µ W, for 100 s integration time.