US Patent 8712247 Clock phase recovery apparatus

A clock phase recovery apparatus includes a clock estimator for estimating a first clock signal and a second clock signal upon the basis of an input signal, the input signal comprising a first sub-signal according to a first optical polarization and a second sub-signal according to a second optical polarization, the first clock signal comprising a first clock magnitude and a first clock phase, the second clock signal comprising a second clock magnitude and a second clock phase, and a selector for selecting the first clock phase to form the estimated clock phase if the first clock magnitude is greater than the second clock magnitude, or for selecting the second clock phase to form the estimated clock phase if the second clock magnitude is greater than the first clock magnitude.