KG -YDFA -B series ytterbium-doped fiber amplifier (YDFA) are based on double-clad fiber side-pump technology, the use of advanced "side-pump protection" technology, preferably high-performance Yb3 + doped double-clad fiber, pump laser, stability of the beam device, and a unique control and protection circuit to achieve 1064nm band signal low noise, high stability, high power stable output. It can be applied to laser radar, coherent synthesis and space optical communication systems and other