Frequency transfer over optical fiber based on photonic RF phase shifter

In this paper, an active phase drift cancellation scheme based on a photonic RF phase shifter for frequency transfer over optical fiber is proposed. By this scheme, a linear and stable photonic phase shifter, which is implemented with a dual parallel Mach-Zehnder modulator and an optical filter, is used to compensate the phase drift induced by the fiber transmission. A 1GHz reference signal transfer over 20 km single-mode fiber with sub picosecond timing jitters measured at the remote site is experimentally demonstrated using the proposed scheme.