To output sample values of a number required for demodulation, without raising the sampling frequency.
A clock timing recovery unit 12 comprises: an interpolation unit 21 for outputting a sample value r with an interpolation period Tint, based on a sample value d obtained by sampling a modulation signal with a sampling period Ts less than the symbol period Tsym of the modulation signal, in a digital coherent receiver 1 receiving the modulation signal; a squaring device 23 generating a time series signal having clock frequency components based on a re-sample value r; a deflection angle calculation unit 26 for calculating the deflection angle α of clock frequency components included in the time series signal; and an interpolation period correction unit for correcting a reference period Tref, i.e., a period obtained by multiplying the symbol period Tsym of time reference in the digital coherent receiver 1 by the inverse of the number of times of interpolation, based on the deflection angle α, and outputting it as the interpolation period Tint.
Yoshiki Kuroki
Ichira Kondo
Atsushi Umekage