Abstract: A node in an optical communications network receives optical packets at its input. It determines a priority assigned to each optical packet. When the optical packet is a transit packet destined for another node then, if the packet is determined to have a relatively higher priority, it is output from the node via a continuous-flow transmission path. Other transmit packets having relatively lower priorities are sent via an alternative transmission path that may include queues or buffers resulting in a variable delay.

Abstract: A clock signal at a divided clock rate is obtained from an optical signal stream at a higher clock rate. The optical signal stream at the higher clock rate is applied to an all-optical non- linear gate. There is feedback from the first output of the gate to its control input. The optical signal at a divided clock rate is present at a second output of the gate. The gate may comprise a non-linear loop mirror. A number of such gates may be cascaded in series to provide an output at a clock rate divided by 2n, where n is an integer.

Abstract: An optical network carrying TDMA (time division multiple access) signals includes an optical bus (1) and nodes (RN, TN) which are connected to the optical bus. The optical bus includes at least two co-located optical fiber waveguides (21, 22). At each node a receiver receives an optical data signal transmitted on one of the waveguides and an optical clock signal from another of the waveguides. The node may also include a transmitter, which may take a clock signal from one of the waveguides, modulate it, and output it as a data signal on another of the waveguides.

Abstract: A multi-bit packet carried on an optical network includes a marker pulse. A bit-rate clock for use in a bit-level operation on the packet is generated by replicating the marker pulse. The bit-level operation may comprise retiming, regeneration or demultiplexing. The marker pulse may be distinguished by a fixed, bit-asynchronous time relationship to the rest of the packet.

Abstract: 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.