Phase-stabilized frequency transfer with arbitrary phase shift via optical fiber links

A phase-stabilized frequency transfer method with arbitrary phase shift is proposed, in which a tunable auxiliary RF signal is used for passive phase correction. The phase shift between the two sites can be adjusted by slight tuning the frequency of the auxiliary RF signal. A demonstration experiment is carried out. The frequencies of the local signal and the auxiliary signal are 4 GHz and 2 GHz, respectively. The frequency shift of the auxiliary signal is tuned from 0 to 50 kHz. Phase-stabilized frequency transfer is achieved via a 2-km fiber, in which the phase shift can be tuned from 0 to 360°. The Allan variances at all phase shifts meet well with each other. The proposed method can be used for phase synchronization with a specific phase shift for a distributed system.