An optical measuring apparatus, includes an
optical branch element for splitting a measured light into plural lights, a time
delay processing portion for giving a predetermined time
delay to one split light of the measured light, an optical
phase diversity circuit for outputting an in-phase
signal component and an quadrature-phase
signal component of the measured light by virtue of an interference between the measured light and a reference light between which a relative
time difference corresponds to a time give by the time
delay, while using other split light of the measured light or the measured light to which a process is applied by the time delay
processing portion as the reference light, a
data processing circuit for calculating at least one of an amount of change of an amplitude and an amount of change of a phase of the measured light, based on the in-phase
signal component and the quadrature-phase signal component, and an optical
time gate processing portion or an electric
time gate processing portion provided on a
route extending from the
optical branch element to the
data processing circuit, for extracting at least one of split lights of the measured light every predetermined
bit time while shifting a timing, wherein changes of amplitude / phase distributions in time are measured.