This proposal is for the development of an innovative compact, high power, and extremely reliable 1.26 micron Ho-doped single frequency fiber laser. The proposed single frequency seeder fiber laser consists of Raman pump laser and single frequency 1.26-micron fiber laser, which will be constructed by using Ho3+-doped fluoride glass fiber. A Raman fiber laser is used as a resonant pump laser source for Ho3+-doped fiber laser. High gain per unit length at 1.26 micron can be achieved in Ho-doped fluoride glass fiber due to the strong pump absorption and strong emission at 1.2 micron transition. 5 W single frequency 1.26-micron MOPA system with high-speed frequency modulation capability will be developed. It consists of a 1.26 micron single frequency seeder fiber laser and a 2-stage fiber amplifier. This type of fiber based seed laser is needed for remote sensing of O and O -N for measuring atmospheric pressure. The single frequency 1.26-micron fiber laser with high-speed frequency modulation capability and electronic control can be used to build coherent laser radar to perform instantaneous measurement. It offers much higher resolution compared to currently existing Raman fiber laser.