Destructively interfering the output of a modulated slave laser with a signal derived from a master laser to achieve carrier suppression

摘要

An optical transmitter includes a master laser device 12 for generating a master signal and a slave laser device 14, injected with the master signal 13 such that a signal generated by the slave laser 15 is phase-locked with the master signal. A data stream to be transmitted modulates the slave laser device such that the signal generated by the slave laser device 15 comprises a modulated part and a carrier part. The transmitter also includes an interfering arrangement 16 for destructively interfering the signal generated by the slave laser device 15 with a signal 21 derived from the master signal, so as to generate an output signal 24 in which the carrier part is at least partially cancelled. The signal derived from the master signal may be obtained by reflecting the master signal off a mirror 18 and passing the reflected signal through a phase shift device 20 and an attenuation or amplification device 22. In embodiments, the transmitter comprises multiple slave laser devices (114a, 114b, Fig. 2), each injection locked with a common master laser and modulated with respective data signals. The outputs of the slave lasers can be coherently multiplexed together (130, Fig. 2) to generate multiple-bit output signals.