INTER-CHANNEL CROSSTALK PHENOMENA IN OPTICAL-TIME DIVISION MULTIPLEXED SWITCHING-NETWORKS

The nature of inter-channel crosstalk arising in OTDM switching networ ks formed from imperfectly isolated 2 x 2 crosspoints and optical dela y lines is investigated and a novel classification is identified. It i s shown that the mixing of crosstalk and signal waveforms which are ei ther, a) mutually coherent or, b) incoherent and (optical) frequency m atched to within the receiver bandwidth, may result in intensity noise and far greater performance degradation than for c) incoherent signal s whose optical beat frequency exceeds the receiver bandwidth. Initial experimental studies indicate that crosspoint isolation < -15 dB is r equired if undilated networks containing more than four crosspoints ar e to be realised.