In 1985, the University of Southampton in the UK reported the production of low-loss rare earth-doped silica fiber by using the MCVD method [1]. Within the fellowing two years, Payne et al. [2, 3] reported the first fiber laser and amplifier (EDFA) near 1.54 μm based on erbium-doped silica fiber. Due to its good mechanical properties, high tensile strength, and ease of fusion with communication fibers, erbium-doped silica fiber can meet the high reliabilityrequirements of optical amplifiers, thus becoming the preferred gain medium for commercial EDFAs. Since then, erbium-doped fiber amplifiers have undergone rapid development, with research work continuously achieving significant progress, perfectly solving the limitation of communication fiber loss on optical transmission distance, and truly realizing long-distance optical communication. Today, EDFA has become the most widely used optical module in optical communication systems, mainly used for device insertion loss compensation, long-distance transmission relay, and as a power amplifier or preamplifier, amplifying the signal energy output by optical transmitter or recevied by optical receiver. Due to the strong demand, erbium-doped fiber, as the core component of EDFA, is currently the most deeply researched and widely used rare earth-doped fiber. With the development of the research, erbium-doped silica fiber in the field of high-power lasers has also made significant progress, represented by ytterbium-erbium co-doped double-clad fiber, which has important applications in 1.5 μm LIDAR and laser communication .