MIT Lincoln Laboratory developed the multi-rate DPSK format, which uses a single, easy-to-implement transmitter and receiver design to achieve free-space optical communications (FSOC) over a wide range of data rates with nearly ideal performance. Optical differential-phase shift keying (DPSK) provides a desired modulation format that offers high receiver sensitivity, high tolerance to major nonlinear effects in high-speed transmissions, and high tolerance to coherent crosstalk. In DPSK, data information is carried by the optical phase. Space-qualified fiber and electro-optics hardware shown here generates and receives multi-rate DPSK waveforms. This tutorial includes references to project files that demonstrate some of the steps presented here. You should. An optical transmitter for RZ-DPSK coded optical signals (RZ-DPSK) has a single dual-drive Mach-Zehnder modulator (MZM), a data line for an electrical NRZ data signal (D) and a clock line for an electrical RZ clock signal (C).