Fiber optic transmission system with noise reduction using a non linear offset of the signals

摘要

The invention concerns a long distance transmission system wherein the signal to noise ratio is increased by noise filtering (1) outside the wavelength range of the transmitted signal, wavelength shifting (2) of the transmitted signal, and filtering of the transmitted wavelength shifted signals (5). The wavelength shifting of signals can be performed by widening the spectrum of the signals, or by optical phase conjugation.