Improved high-speed adaptive equalization is presented that may involve
converting an optical signal into an electrical signal and performing equalization
by (i) filtering the electrical signal with an analog filter according to at least
one filter coefficient to produce a filtered output, (ii) generating an error signal
from the filtered output according to an error function, (iii) providing at least
one control signal to the analog filter for adjusting the at least one filter coefficient,
(iv) detecting a relationship between a change in the at least one filter coefficient
and a change in the error signal, and (v) adjusting the at least one filter coefficient
according to the relationship to minimize the error signal. The least one coefficient
may comprise a plurality of coefficients, and the relationship may be a gradient
estimate having multiple components, each determined by varying only one of the
coefficients and detecting a resulting change in the error signal.