| 摘要 |
A means for simplifying fault location in an optical signal transmission network in which a main optical fibre 8 is divided into a plurality of branch circuits 11 to 16, comprises optical time domain reflectrometry (OTDR) equipment 10 for transmitting an output signal along the main fibre, and for each branch circuit means 21 to 26 for causing the signal returned to the OTDR equipment from the branch to be modified in a manner unique to that branch. The branch circuit means 21 to 26 may each comprise a filter passing light at one or more distinctive frequency bands, a frequency modulator, or a polarizer. <IMAGE>
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