Method for readjusting a phase or frequency modulation shift of an optical transmission signal

摘要

Apparatus and methods are disclosed for readjusting a modulation shift of a transmission light modulated optical signal. In these systems and methods, a first modulated portion of the modulated transmission light is removed to obtain a first modulated signal which is divided into first and second light beams. The first light beam is delayed by a specific delay time and the first and second light beams are coherently superimposed to obtain an optical superposition signal which is detected to produce a detector signal that is proportional to a power of the superposition signal. An error signal is subsequently generated from the detector signal which is representative of a modulation shift from a desired shift value which is used for substantially correcting a modulation of the transmission light.