Telecommunication system and method for wavelength-division multiplexing transmissions with a controlled separation of the outgoing channels and capable of determining the optical signal/noise ratio

An optical telecommunication method comprising the steps of:

• generating at least one optical transmission signal, at a predetermined wavelength included in a predetermined wavelength band;
• transmitting said optical transmission signal through an optical fiber to a receiving station, comprising at least a receiving unit;
• feeding an optical signal comprising said optical transmission signal to a respective one of the receiving units in said receiving station, through a passband filter unit;
• receiving in said receiving unit the optical transmission signal passing through said filter unit;
• wherein said filter unit comprises a fixed filter and a tunable filter, said fixed filter having a predetermined passband including said predetermined wavelengths and said tunable filter being tunable to several wavelengths in said predetermined passband, by command means operable under several operating conditions, and in that said feeding step comprises:
• filtering said signal with said fixed filter;
• scanning said predetermined passband by varying said operating conditions of said tunable filter;
• recognizing said optical transmission signal in said passband and identifying the relevant operating conditions;
• and
• maintaining the operating conditions at said optical transmission signal.