British Telecommunications Public Limited Company

British Telecommunications Corporation

Danny Robert Pitcher

Kevin Smith

Julian Kazimierz Lucek

David Graham Moodie

Andrew David Ellis

Terence Widdowson

Terrence Widdowson

An optical network includes a number of nodes coupled to an optical transmission medium, such as an optical fiber bus. Each of the nodes includes a dark pulse generator. Different nodes output dark pulses in different time slots onto the transmission medium, forming a dark pulse OTDM (optical time division multiplexed) signal. The network may have a re-entrant bus topology.

Dark pulse TDMA optical network

A receiver at a node in an optical network receives an optical clock signal and an OTDM datastream. A detector converts the clock signal to the electrical domain. A variable delay stage applies a selected delay to the clock signal in the electrical domain. A non-linear electro-optic modulator which may be an electro-absorption modulator, receives the OTDM datastream at its optical input. An electrical control input of the modulator is connected to the output of the variable delay stage. The electro-optic modulator outputs an OTDM channel selected by setting the delay of the variable delay stage. The variable delay stage may include a number of logic gates, particularly AND gates, connected between a pair of microstrip delay lines. The gates are controlled to provide different paths with different corresponding delay times for the clock signal.

Optical network

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Danny Robert Pitcher