A side-pump fiber coupler for high-power fiber amplifiers

A kind of side-pump fiber coupler for high-power fiber amplifiers is reported. Using the fused taper technics and a basic 21 coupling method, the side-pump fiber coupler of high coupling efficiency and high isolation was realized. Through the investigation of different fibers of the side-pump fiber couplers, the double-clad fiber with outside diameter 125 μm and numerical aperture(NA)0.46 was the best selection for the signal transmission and pump launched fiber. The side-pump fiber coupler integrating a 74% pump coupling efficiency, 95% signal transmission, with exceeding 50dB isolation between the signal input end and pump-light input end and 20 dB isolation between the pump-light input end and the signal output end was obtained. Using the side-pump fiber coupler, the narrow line-width all-fiber amplifier with an output power exceeding 1W was demonstrated.