Optical switching with directional coupler switches and delay lines

Optical time-division multiplexing is a technique that is suitable for future ultrafast optical communications networks. The paper describes some theoretical results on switching architectures which are equivalent to TST networks. They are constructed from 2×2 switches and delay lines. Here, implementation with lithium niobate switches and fibre delay lines is assumed, although other technologies could be used. The use of delay line memories allows block multiplexing to be used, where a block of several bits is held in each timeslot. A guard band between blocks allows each directional coupler switch to change state between timeslots. Also, delay lines imply bit-rate and coding format transparency