Frequency and phase control loop synchronisation method - using auxiliary signal with low intensity and orthogonal polarisation w.r.t. main transmission signal during new synchronisation phase

摘要

During the new synchronisation phase an auxiliary signal is transmitted in addition to the main transmission signal which is modulated by the input signal. The auxiliary signal has a low intensity and orthogonal polarisation w.r.t. the main transmission signal and as little modulation as possible. The polarisation control loop of the optical superposition receiver is switched during the new synchronisation phase so that the IF-amplitude yielded from the main transmission signal is minimised. The IF-amplitude yielded from the auxiliary signal is maximised. USE/ADVANTAGE - Optical superposition receiver. Avoids false synchronisation of optical control loop both in region of ground signal and of sidebands.