| 摘要 |
An optical signal transmission network comprises a main optical fibre (8) having a plurality of branch circuits (11,12), with each final branch circuit of a chain of branches ending in a terminal unit (15,16,17), and the network being associated with OTDR equipment ( phi ) connected so as to transmit an output signal through the main fibre (8) and the branch circuits (11,12), wherein each said final branch circuit incorporates a filter (25,26,27) which is capable of reflecting back towards the OTDR equipment ( phi ) at least one wavelength in the OTDR band, but not traffic wavelengths. <IMAGE> |
