Computer-controlled multichannel heterodyne optical communication system

The described system consists of eight frequency-shift-keying (FSK) modulated channels multiplexed by a 16*16 optical star coupler. Six of these channels are generated by individual digitally tuned optical frequency synthesizers. The frequency of these six channels can be randomly selected from a set of equispaced frequencies (2.2 GHz). Two of the 16 multichannel signals coming out of the star coupler are demultiplexed by their individual digitally tuned heterodyne receivers. Each receiver can randomly select, from the computer keyboard, a desired channel. The computer can identify missing channels. More importantly, the digital tuning of the frequency synthesizers and of the receivers is insensitive to variations of the frequency-tuning current relationship of the lasers. These results show that the digital tuning capability of today's radio systems can be transposed to the optical domain.< >