Patent ID: 7254326

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 being configured to send on said optical link at least a first optical signal having a first direction; at least a first pump source disposed along said optical link, said pump source being configured to send on said optical link a pump radiation in said first direction, so as to cause Raman amplification of said first optical signal; and at least one device disposed along said optical link; said device comprising: at least a first photodetector configured for converting a portion of said first optical signal in an electrical signal; and a first supervisory unit configured for amplifying said electrical signal, for extracting a first supervisory signal from said electrical signal, and for feeding said extracted amplified first supervisory signal to at least a first modulator connected to said optical link or to a driving circuit of said pump source, so as to superimpose said extracted amplified first supervisory signal on said first optical signal, wherein said first modulator is not said first pump source, and a network analyzer is coupled between said modulator and a photodiode.