We propose an all-fiber based 2.05-micron single frequency, narrow linewidth seeder laser with 10 nm tuning range and 5GHz frequency modulation for next generation LIDAR system. Highly Tm-doped fiber laser is used as a resonant pump source in order to reduce the phase noise and laser linewidth. An environment insensitive package will be used to minimize the laser phase noise and linewidth. Ho3+-doped fiber is used for seed laser generation, due to its strong emission at 2.05 micron. A Piezo attached to the laser cavity is used to modulate the frequency to 5 GHz with speed up to 10KHz. The laser can be continuously tuned over 10 nm range. The single frequency 2.05-micron fiber laser can be used to build coherent laser radars and Differential Absorption Lidars (DIALs) to perform instant measurement of velocity and concentration of CO2 and other gases , aerosols, clouds. The high-speed frequency modulation (5 GHz) of single frequency fiber laser used as local oscillator covers tuning over a selected CO2 absorption line. The large wavelength tuning range (10 nm) also enable scientists and engineers to explore the feasibility of using such laser for other remote sensing applications.