Improvements in and relating to the detection of analogue maintenance signals

摘要

The apparatus has an input (502) receiving an optical signal. The signal is split into two optical bands by a splitter (504). Photo detectors (510,512) receive the bands and output electrical signals proportional to total optical power of the respective band. An electrical filter strains one electrical signal to pass a frequency and block another frequency. Another filter passes the latter and blocks the former frequency of the other signal. Independent claims are also included for the following: (a) a node for an optical network (b) a method of offering a data transmission service over an optical network (c) a method of processing an optical signal.