A method and apparatus for the direct characterization of the phase of an optical signal includes measuring the interference between the optical signal and a sequence of optical pulses and processing the measured interference. The method and apparatus split and combine the optical signal and the sequence of optical pulses in order to measure the real and imaginary part of the interference signal for a least two pulses from the sequence of optical pulses. Processing steps are disclosed to obtain phase information on the optical signal from the measured interference.