Apparatus for optical fiber communications using standing wave acousto-optical modulator

Claim 1

A frequency domain modulation system for optical fiber communication particularly useful for digital and analog signal transmission comprising, in the order recited, a plurality of parallel-connected signal input units each incorporating individual laser sources of unique frequency F o provided with individual means modulating the output radiations of said laser sources responsive to individual signals input to thereby impose an information signal onto said output radiations thereby establishing an individual optical information wave train, a collimating lens, a separate standing wave type acousto-optical modulator means driven at a frequency Fc/2 which interacts with said optical information wave train to produce two optical frequency components equal to Fo±Fc/2 and an optical fiber coupler transmitting the resulting modulated wave train through an optical fiber to a common square law detector where the sub-carrier frequency, Fc, is detected as the unique beat frequency of said two optical frequency components, said information signal thereby being recovered at the output of said square law detector by an information receiver, said information receiver isolating a preselected individual signal input according to its associated individual sub-carrier frequency, said individual sub-carrier frequencies being spaced one from another by a frequency interval forestalling interference in the reception of said individual signal inputs.