Applications of the optoelectronic matrix switch to communication systems

Because of their potential applications to satellite and other broadband switching systems, wideband matrix switches employing optical signal distribution and optoelectronic devices at the crosspoints have recently received considerable attention. Crosspoint isolation of more than 80 dB at signal frequencies up to 1 GHz and over 50 dB up to 4 GHz has been demonstrated with a silicon photodiode performing the switching. High speed switching with transition times less than 5 ns has also been demonstrated with GaAs devices. An optoelectronic matrix switch based on heterojunction photodiodes has been constructed for switching 400 Mb/s NRZ signals and a matrix switch for 10 MHz to 100 MHz signals is being developed commercially. With their features of high isolation, high crosstalk loss and short transition times, optoelectronic matrix switches lend themselves well to applications in satellite switched time division multiple-access (SS/TDMA) communication systems and the distribution of centrally-switched TV signals to subscribers in a fiber optic integrated service system.