AN ARCHITECTURE FOR FRAME INTEGRITY OPTICAL TDM SWITCHING

Future optical telecommunication networks will carry services such as high definition television (HDTV) and videophone, for which time division multiplexing (TDM) is a natural multiplexing format. The design of optical architectures for switching TDM data is therefore of great importance. For many applications, frame integrity is essential; a network has frame integrity if all the data entering on one frame leaves on one frame. Although this was considered in an earlier paper, a new architecture for optical TDM switching is presented here which makes more efficient use of hardware. The number of switches used is very close to the theoretical minimum. Lithium niobate switches, with fiber delay lines for storage, are used throughout, and the architecture allows the bitrate and wavelength transparency of these devices to be exploited. The networks are mathematically equivalent to Benes and Waksman networks, and they are constructed using recursive definitions which are justified mathematically. The use of ''feed-forward'' rather than ''feed-back'' delays produces superior crosstalk performance and more uniform attenuation than existing designs. The networks may be dilated in a similar way to dilated Benes networks, yielding vastly improved crosstalk performance at the expense of using roughly twice as many switches.