Patent ID: 8493647
Filing Date: 2013-07-23
Classification: G02F,H04B

Abstract:
1. A method for compensating an operating point drift or a phase drift, which occurs in an optical device, by carrying out feedback control with use of a low frequency signal, said method comprising the steps of: (A) judging stability of the feedback control; and (B) switching a frequency of the low frequency signal from a first frequency to a second frequency which is different from the first frequency, in a case where the feedback control is determined to be unstable in the step (A), the step (A) including at least one of a first judging step and a second judging step, in the first judging step, the stability of the feedback control being determined by comparing (i) a moving average of phase differences between (a) low-frequency components contained in a signal generated by the optical device and (b) the low frequency signal with (ii) a predetermined threshold, and in the second judging step, the stability of the feedback control being determined by comparing (i) a variation in bias which is to be given to the optical device and is determined in accordance with the phase difference with (ii) a predetermined threshold.