WDM optical network with passive pass-through at each node

An interface device for use in an optical network employing wavelength division multiplexing, comprising a demultiplexer for dropping a predetermined waveband from the network at a node, means for converting optical input signals from said demultiplexer to electrical output signals, means for generating optical output signals from electrical input signals, a multiplexer for adding a said optical output signals in a predetermined waveband to the network, said demultiplexer and multiplexer being arranged to forward passively optical signals in bands other than said band that is dropped.

A fiber optic wavelength division multiplexed ring comprising a plurality of switching nodes, means for generating a plurality of wavelengths organized in to bands on said ring, and means for transmitting maintenance channel data on at least one of said wavelengths as a pilot tone.

A distributed-high speed packet switch comprising a plurality of switching components distributed over a geographic area;

• a fiber optic wavelength division multiplexed ring interconnecting said switching components, said fiber optic ring carrying a plurality of wavelengths organized into bands;
• and means for adding/dropping a band at each switching component associated therewith, said adding/dropping means passively forwarding other bands, and pairs of said switching components forming part of said switch directly communicating on wavelengths in bands associated therewith.

In a communications network employing wavelength division multiplexing comprising a plurality of nodes, and an optical transmission medium interconnecting said nodes via individual links, a method of optimizing the individual link performance (received signal quality, power level, bit error rate) between any communicating nodes in the network comprising sending data over maintenance channel links.

In a communications network employing wavelength division multiplexing comprising a plurality of nodes, and an optical transmission medium interconnecting said nodes via individual links, a method of determining whether a data channel is carrying valid traffic or noise comprising verifying the consistency of the bit rate of the data channel.

In a communications network employing wavelength division multiplexing comprising a plurality of nodes, and an optical transmission medium interconnecting said nodes via individual links, a method of determining whether pulse retiming is required and controlling a frequency agile clock recovery and jitter filter circuit comprising measuring the bit rate of a data channel.