A method is provided for carrying out channel performance monitoring in an optical communication system. The method comprising: receiving an optical signal; obtaining digitized samples associated with the optical signal; storing the digitized samples; carrying out an off-line processing of the stored samples. The off-line processing includes: using the digitized samples to determine information characterizing the at least one optical channel used for conveying the optical signal; using the determined information to estimate a value of at least one optical channel performance parameter characterizing the at least one optical channel; and forwarding the value of the at least one optical channel performance parameter to a network management element; and wherein the at least one optical channel performance parameter is estimated without a prior knowledge of information on a modulation format associated with the optical channel.