Frequency multiplex system using injection locking of multiple laser

Abstract

An optical frequency division multiplex system including a transmitter, a receiver, and a transmission path connecting the transmitter to the receiver. In the transmitter a master laser is operated to produce a central peak at an optical frequency f.sub.o with side peaks separated by an amount .DELTA.f running to both sides of the central peak. The master laser output goes through an optical isolator to an optical coupler where it is split up into N+1 beams. Each optical output from the coupler is then positioned to be coupled into N slave lasers. Each slave laser is tuned to approximately coincide with one of the side peaks thus producing a single output frequency of (f.sub.o .+-.n.DELTA.f) from each slave laser diode. Electrical modulating signals for each of N information channels are applied separately to modulate the phase of each of the slave laser outputs. The outputs of the slave lasers are then recombined in a N.times.1 optical coupler, the output of which is transmitted over a single-mode fiber linking the transmitter to the receiver. One of the outputs of the 1.times.(N+1) coupler is transmitted to the receiver over a second single-mode fiber. At the receiver, the master laser carrier is split into N spatial components by a 1.times.N coupler. These are then filtered and amplified by a second group of N slave lasers. The output from this second unmodulated group of slave lasers is combined with the combined outputs from the modulated slave lasers in an array of 2.times.1 optical couplers. Finally, the light signals emerging from the couplers are converted to electrical signals for the N information channels by an array of photodetectors.