DARK PULSE TDMA OPTICAL NETWORK
The present invention relates to an optical network for carrying TDMA (Time Division Multiple Access) signals and to transmitters and receivers for use in nodes of such a network.
A network embodying the present invention might be used, for example, as a local area network (LAN) for interconnecting computer systems The increasing power of computer systems in terms of processor speeds and storage capacity has made it possible for conventional personal computers to handle multimedia applications involving real time video and animation and computer graphics. The high bandwidth data associated with such applications place heavy demands on the network and the performance of conventional LANs has failed to keep pace.
An optical network using synchronous TDMA potentially offers a far higher bandwidth, and so might be used as a high speed LAN to replace a conventional LAN. However, in existing optical networks, while signal transmission has been carried out in the optical domain, in practice some electronic circuits have been required for such functions as channel selection. It has been recognised that such electronic components of the network infrastructure constitute a bottleneck restricting the performance of the network.
"A High Speed Broadcast and Select TDMA network Using All-Optical Demultiplexing", L P Barry et al, ECOC '95 pp 437-440, describes an experimental OTDM network. At the receivers in the network nodes, an optical clock signal is detected and a variable delay applied in the electrical domain to the detected clock signal to select a particular TDMA channel. After pulse shaping, the signal is taken back into the optical domain by driving a local optical source, a DFB laser, which produces an optical signal for use in a subsequent all-optical switching stage
