Patent ID: 8660426

Claim:
A method for determining an OSNR (OSNR real ) of a real optical signal being carried in an optical network link, the method comprising: tapping a portion of the real optical signal; altering the tapped signal portion by adding to it an in-band artificial noise signal, thus obtaining a combined signal; scattering the combined signal by a stimulated Brillouin scattering (SBS) or a stimulated Raman scattering (SRS) in an optical element; extracting a signal back reflected by the SBS or the SRS from the optical element; determining an OSNR comb of the combined optical signal based on power of the reflected optical signal; and deriving the OSNR real from the OSNR comb by taking into account information on power of the added artificial noise, wherein the OSNR real is derived substantially according to the following equation: OSNR real =OSNR comb ×(OPcNR+1)/(OPcNR−OSNR comb ×( B ref /B eq )), where OPcNR=Pc/Padd, Pc is power of the real optical signal, Padd is power of the added artificial noise, and B ref /B eq is a coefficient.