method and apparatus for frequency domain modulation 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 provided with means modulating the output radiations of said laser sources responsive to individual signal inputs , thereby establishing , for each signal input , an individual optical information wave train , a collimating lens , an acousto - optical modulator means introducing a sub - carrier signal developing a beat frequency with said optical information wave train , an optical fiber coupler transmitting the resulting signal through an optical fiber to a common square law detector and an 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 .