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.