nLight proposes the development of high efficiency, high average power 1550-nm laser transmitter system that is based on Er-doped fiber amplifier resonantly pumped by high efficiency 1532-nm fiber-coupled diode laser pumps. To meet the efficiency requirement for space communication, nLight proposes to improve overall laser transmitter efficiency by (1) optimizing diode laser and fiber coupling for maximum efficiency of 1532-nm pumps, (2) developing resonant pumping of the fiber amplifier for minimum quantum defect, and (3) design and development of Er-doped fiber amplifier capable of achieving high optical-to-optical efficiency. Under the proposed program, nLight will design and develop high efficiency 1532-nm diode lasers in conjunction with highly efficient fiber coupling techniques to achieve >40% conversion efficiency of the pump modules. By developing and utilizing novel fiber laser amplifier technologies, nLight anticipates achieving > 70% optical-to-optical efficiency for resonantly pumped Er-doped fiber amplifier. It is estimated that a high efficiency 1550-nm fiber laser transmitter will be developed to demonstrate >23 W average power and >23% WPE, the highest efficiency among eye-safe solid-state lasers.