This series 1550nm Erbium ytterbium co-doped fiber amplifier is with low noise, high gain, wide bandwidth, efficient pump and stable working condition, etc. It takes advantage of envelope pump technology, which overcomes shortcomings of the single-mode fiber, and makes output power increased one to two orders of magnitude, and promotes the development of high-power fiber amplifier. We developed erbium ytterbium co-doped double-clad fiber amplifier which is fit to CATV system to adapt current require of FTTH and FTTB.