VARIABLE RATE DPSK SYSTEM ARCHITECTURE

PROBLEM TO BE SOLVED: To provide a variable rate differential phase shift keying modulation communication system without power or performance loss. SOLUTION: This invention includes a transmitter 38 that is provided with a carrier source 42, a phase modulator 44, and a DPSK encoder 46. An optical amplifier 54 such as a rare-earth element doped fiber amplifier amplifies a modulation carrier signal. A signal is continuously transmitted to a multi-rate receiver 40 through a communication channel such as free space. The multi-rate receiver includes a single demodulator 80 such as a photo interferometer used at frequency division data rates. A modulation signal is detected by a photodiode array and detected data are applied to a clock and data recovery circuit 122 tuned by a switched filter circuit 106 as a function of a data rate.