Optical communications system

摘要

An optical communications system comprises a concatenated chain of amplifiers 14 disposed along a fibre transmission path 13. The signal to noise ratio is measured at each amplifier by selectively notch filtering a transmitted signal and measuring the power of the filtered and unfiltered signal within the notch bandwidth. A supervisory system 29 controls the gain of each amplifier whereby to maximise the aggregate signal to noise ratio of the system.