A method for estimating at least one
optical link parameter using a Viterbi
equalizer (1) generating averaged values (M) of
signal amplitudes of a distorted optical
signal transmitted through an
optical link (2) for a set of decided bit patterns (a, b, c, d, . . . ), the method comprising the following steps: forming a first parameter set (S) characteristic of a distorted
signal sequence using the averaged values (M(a), M(b), M(d), M(g)) for a given sequence (abdg) of bit patterns (a, b, c, d, . . . ), comparing the first parameter set (S) to a plurality of reference parameter sets (R1, R2, . . . ) characteristic for reference signal sequences of the same sequence (abdg) of bit patterns (a, b, c, d, . . . ), each of the reference parameter sets (R1, R2, . . . ) having a known value of the at least one
optical link parameter, and selecting the reference parameter set (R) with the closest correlation to the first parameter set (S), the known value of the at least one optical link parameter of the selected reference parameter set (R) being used as an estimate for the at least one optical link parameter. A
computer program product comprising a
software or a hardware implementing the method.