METHOD AND APPARATUS FOR COMMUNICATING AMPLITUDE MODULATED SIGNALS OVER AN OPTICAL COMMUNICATION PATH

摘要

A block of amplitude modulated television channel signals frequency modulates an optical communication path. In one embodiment, the AM modulated channel signals FM modulate an RF subcarrier which, in turn, is used to intensity modulate an optical carrier for transmission. Frequency modulation of the RF subcarrier by the amplitude modulated channel signals is advantageously performed at microwave frequencies. The FM modulated subcarrier signal is then converted down to a frequency range compatible with transmitter and receiver components used in the system. The frequency modulation and conversion can be performed by a pair of voltage controlled oscillators coupled in a push-pull mode of operation. The outputs of the oscillators are combined in a double balanced mixer to down convert the FM signal spectrum. In another embodiment, the optical frequency of an optical carrier is FM modulated by the block of AM signals. Receivers for the FM modulated band of AM channel signals are also disclosed.