Coherent Optical Frequency Transfer via a Fiber Link Laid Along a Railroad

Abstract

SummaryIn this paper, we measured and analyzed the phase noise and frequency instability of optical signal, which is transmitted via fiber links laying along railroad lines at different time periods. The frequency instability of the optical signal in terms of Allan Deviation (ADEV) is on the order of 10^−13 at an integration time of 1 s. The free-running phase noise PSD of the fiber link reached 10⁵ rad²/Hz at an offset frequency of 2 Hz. We demonstrated optical-carrier transfer over a fiber link by actively compensating for the phase noise. This paper analyzed phase noise characteristics of fiber link along the railway and explored the method to address the transmission of complex links in the future.