Patent ID: 7274871

Claim:
An optical transmission system comprising: at least a first and a second terminal station, optically connected with each other by an optical link, said first or said second terminal station configured to send on said optical link at least a first optical signal having a first direction, said system further comprising: a first supervisory unit associated to a device disposed along said optical link, said first supervisory unit being configured for generating a first supervisory signal, said first supervisory unit coupled to at least one modulator that is configured to superimpose on said first optical signal said first supervisory signal; and at least one pump source disposed along said optical link, said pump source configured to send on said optical link a pump radiation in a second direction opposite to said first direction, and configured to cause Raman amplification of said first optical signal and of said first supervisory signal superimposed on said first optical signal, wherein said at least one modulator is not said pump source.