INTENSITY MODULATED OPTICAL CARRIER COMMUNICATION SYSTEM

摘要

A low-cost, reliable optical communications system and method, a feature of which is the use of an optical carrier beam which is intensity modulated at radio frequencies above one MHz and below the microwave range to produce a radio frequency subcarrier on the optical carrier. The radio frequency subcarrier is angle modulated, either in frequency or phase, for signal transmission. The frequency or phase modulation at radio frequencies insures high immunity to adverse atmospheric conditions, such as rain, snow, fog and turbulence. Other features include the maintenance of the subcarrier operating point by reversing the polarity of the voltage on the electro-optic crystal without changing the absolute magnitude of the voltage and the manner of locking the transmitter onto the receiver.