Patent ID: 7003228

Claim:
An apparatus for processing an optical signal comprising: an optical-to-electrical conversion module for receiving the optical signal and converting the optical signal into an electrical signal; and an adaptive equalizer module coupled to the optical-to-electrical conversion module for performing equalization on the electrical signal to produce an equalized signal, the adaptive equalization module comprising: i. an analog filter adapted to receive and filter the electrical signal to produce a filtered output according to at least one filter coefficient, ii. an error generator adapted to receive the filtered output and generate an error signal from the filtered output according to an error function, and iii. a controller adapted to receive the error signal and provide at least one control signal to the analog filter for adjusting the at least one filter coefficient, the controller further adapted to detect a relationship between a change in the at least one filter coefficient and a change in the error signal and adjust the at least one filter coefficient according to the relationship to minimize the error signal, wherein the error function involves: performing a first sign-removal operation on the filtered output to produce a first sign-removed signal; generating a difference signal representing difference between the first sign-removed signal and a steady signal; and performing a second sign-removal operation on the difference signal to produce a second sign-removed signal; outputting the second sign-removed signal as the error signal.