Dense FDM Coherent Optical Switching System
We report the results obtained with a dense FDM coherent optical star network operated as a computer-controlled high capacity switch. The system provides switching connectivity between the input signals modulating the transmitting lasers and the output signals demodulated by optical receivers. It consists of eight FSK-modulated channels multiplexed by a 16×16 optical star coupler. Six of these channels arc generated by individual digitally tuned optical frequency synthesizers. The frequency of these six channels can be randomly selected from a set of equi-spaced frequencies (2.2 GHz). Two of the sixteen multi-channel signals, coming out of the star coupler, arc demultiplexed by their individual digitally tuned heterodyne receivers. Each receiver can randomly select a desired channel by computer command. Switching is performed by rerouting, from the computer keyboard, the transmitted channels between the receivers. The receivers can identify missing channels. More importantly, the digital tuning of the frequency synthesizers and of the receivers is insensitive to variation of the frequency-tuning current relationship of the lasers.
KeywordsMilO Coupler Demultiplexing
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