| 摘要 |
OPTICAL SIGNAL TRANSMISSION NETWORK An optical signal transmission network comprises a main optical fibre having a plurality of branch circuits, with each final branch circuit of a chain of branches ending in a terminal unit, and the network being associated with OTDR equipment connected so as to transmit an output signal through the main fibre and the branch circuits, wherein each said final branch circuit incorporates a filter which is capable of reflecting back towards the OTDR equipment at least one wavelength in the OTDR band, but not traffic wavelengths.
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