Apparatus and method for monitoring losses in a branched optical fibre network

摘要

PCT No. PCT/GB91/00540 Sec. 371 Date Nov. 18, 1992 Sec. 102(e) Date Nov. 18, 1992 PCT Filed Apr. 8, 1991 PCT Pub. No. WO91/15744 PCT Pub. Date Oct. 17, 1991.Apparatus is provided for detecting losses in a branched optical fibre network comprising a first optical fibre and a plurality of second optical fibres each of which is coupled to the first optical fibre. The first optical fibre constitutes a main line, and the second optical fibres constitute branch lines. The apparatus comprises launch means for launching a carrier wave into the main line, respective modulators in each of the branch lines for modulating the carrier wave in that branch line, returns for returning the modulated signals along the branch lines to the main line, and monitors for monitoring the main line for changes in the modulation of the returned signals. The modulators are such that each modulates the carrier wave differently.