| 摘要 |
Method and apparatus for acquiring information using a relative phase deviation between the phase of a receipt signal of an optical homodyne receiver and the phase of an optical signal of a local oscillator of the receiver. Previously information had to be taken from a control signal included in a larger DC signal. The compensation for the DC component is difficult. So as to make this unnecessary, the frequency FLo of the local oscillator is shifted by the frequency fH of a defined auxiliary carrier and the frequency-shifted optical signal is then superimposed on the optical receive signal and is detected. The detected signal is band-pass-filtered and is shifted to the baseband frequency by mixing with the same auxiliary carrier and then is low-passed filtered. The DC voltage obtained indicates the relative phase relationship between the local oscillator and the receive signal based on the sign of the signal and indicates the absolute phase deviation by its amplitude. The DC voltage signal can then be supplied to a control loop so as to make this signal as small as possible. |
