British Telecommunications Public Limited Company

David M Spirit

Andrew David Ellis

Lutz C Blank

Robert John Manning

Peter J Keeble

Christopher J Rowe

David Arthur Davies

David M Patrick

David Arthur Owen Davies

Optical signals used for telecommunications in time division multiplexed format are processed to remove channels for local demodulation and to replace the removed channels with locally modulated data. The received signals are subjected to a wavelength modulation so that signals in selected channels are given distinctive wavelengths. After wavelength modulation, the time division multiplexed signals are separated using wavelength sensitive splitters and the various channels are sent to their correct destinations. In one embodiment, one channel is selected and given a distinctive wavelength and all the non-selected channels retain their original wavelength. The channels with the original wavelength are provided to an output terminal for onward transmission whereas the selected channel is provided for local demodulation.

Optical switch

Optical switching device

A waveguide carrying system signals at a first wavelength and OTDR signals at a second wavelength is provided with an optical amplifier and an isolator. The isolator has a high isolation factor at the first wavelength and a low isolation factor at the second wavelength.

Optical time domain reflectometry

Apparatus and a method for increasing the optical measurement range in optical time domain reflectometers in which a fibre laser amplifier is used to amplify the optical time domain reflectometer pulses launched into a waveguide. This apparatus and method have particular usefulness for branched local networks. The signal returning to the optical time domain reflectometer is amplified as well as the outbound signal.

Optical time domain relectometry with optical amplifier for extended

OTDR having optically switched amplified output onto test fibre to

OTDR using distributed optical amplification in optical waveguide under

Growing community of inventors

Woodbridge, United Kingdom

David M Spirit