Patent ID: 8301031

Claim:
A method for switching a Raman pump laser on and/or off in an optical transmission system, comprising the steps of: combining, at a transmitting end, a service signal in a form of a NRZ-modulated binary data signal with an optical useful signal and then transmitting a combined optical signal; extracting, at the receiving end, an extracted optical signal of the combined optical signal; demodulating and converting the extracted optical signal into a converted electrical signal; filtering, out of a corresponding electrical signal spectrum by a bandpass filter, a symmetrical signal spectrum with respect to the Nyquist frequency of the service signal having a plurality of spectral lines which are symmetrical with respect to the Nyquist frequency the service signal; squaring the symmetrical signal spectrum; filtering a clock line at the clock frequency of the service signal from the squared signal spectrum; and evaluating the amplitude of the clock line to detect the service signal in order to switch the Raman pump on and/or off.