The objective of this program is to develop, demonstrate and implement an integrated optical transmitter for RZ-DPSK modulation for integration into modems for the international space station (ISS). Conventional optical transmitters are based on commercially available discrete components. These have several fiber interconnects which leads to increased optical loss, reduced reliability in a space environment and increased footprint in a an otherwise space constrained optical modem. Photonic integrated circuit technology promises to integrate these functions on a single monolithic chip implemented in rad hard Indium Phosphide technology. This will lead to a miniaturized compact implementation, compatible with wafer-scale manufacturing.