Linear analog optical communication system with two transmitted beams and phase modulation

Abstract

An optical communication system uses a radio frequency (RF) signal for communicating an analog communication signal. It comprises an optical transmitter and receiver. The optical transmitter comprises means for generating a first reference light beam, and means responsive to the analog communication signal to produce a communication light beam having phase modulation corresponding to the analog communication signal. The optical receiver comprises first means responsive to the reference light beam and the RF signal to develop a shifted light beam that is shifted in frequency by the RF frequency, second means to interferometrically combine the communication light beam with the shifted light beam to provide a heterodyne signal including information regarding the state of phase of the communication light beam, third means responsive to said heterodyne signal to produce an electrical signal at the optical beat frequency corresponding to the RF and with a phase corresponding to the state of phase of the communication light beam, and fourth means responsive to the RF signal and the electrical signals to provide an output signal that has a linear correspondence to the state of optical phase of the communication light beam and the analog communication signal. The optical transmitter and optical receiver are also invented.