Single Frequency Fiber laser with low Relative Intensity Noise (RIN) have wide application in quantum optics, pumping lasers, lidar, coherent optical communications, high-precision optical sensing, optical measurement, and precision spectroscopy. For example, the laser for trapping atoms in optical lattice demands not only high output power, but also low RIN to reduce the resonance between the lattice and atoms and low frequency noise (FN) to reduce the spatial vibration, which is quite important for the atoms lifetime in the lattice. In the atomic interferometer and atomic clock application, high power laser could lead to more atoms, uniform interaction area and high measurement SNR.