Importance

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Abstract

Fault location apparatus is disclosed for use in an optical signal transmission network which comprises a main optical fibre having a plurality of branch fibres, and in which each final branch fibre of a chain of branches ends in a terminal unit. The fault location apparatus comprises OTDR equipment connected to the network so as to transmit an output signal through the main fibre and the branch fibres, and a filter incorporated in each of the final branch fibres. The filter is capable of reflecting back towards the OTDR equipment at least one wavelength in the OTDR band, but not traffic wavelengths. The OTDR equipment is operative to make measurements on the mirror or 'virtual' image of the path from the terminal unit incorporating the filter returning a signal to the equipment.

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First Claim