The invention relates to an electrical equalizer for equalizing an amplitude-modulated electrical signal derived from an optical signal in an Apol modulation format, preferably Apol-RZ-DPSK. Such electrical signal comprises a sequence of symbols subdivided in alternating even and odd symbols. The equalizer comprises first sampling means (11), configured for sampling the even symbols of the electrical signal. Further, the receiver comprises second sampling means (12), configured for sampling the odd symbols of the electrical signal. The equalizer comprises combining means (18, 19, 20, 21, 22, 23, 24, 30, 31, 32, 33, 34) for weightedly combining a first group of samples of adjacent symbols of the electrical signal and for weightedly combining a second group of samples of adjacent symbols of the electrical signal.