| 摘要 |
Apparatus is provided for detecting losses in a branched optical fibre network c omprising a first optical fibre (17) and a plurality of second optical fibres (A, B) each of which is coupled to the first optical fibre. The first optical fibre (17) constitutes a main line, and the second optical fibres (A, B) constitute branch lines. The app aratus comprises launch means (13, 14, 16) for launching a carrier wave into the main line (17), respective modulating means (1 1a, 11b) in each of the branch lines (A, B) for modulation the carrier wave in that branch line, return means (12a, 12b) for ret urning the modulated signals along the branch lines to the main line, and monitoring means (20, 21a, 21b) for monitoring the m ain line for changes in the modulation of the returned signals. The modulation means (11a, 11b) are such that each modulates t he carrier wave differently.
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