Ultra-Accurate Time Dissemination in a Hybrid Fiber-Optic System with Frequency-Synchronized Lasers and λ-Swapping

Summary The accuracy of the wavelengths of lasers used in a fiber optic long-distance time transfer systems need to be at the level of some tens of MHz, if the transfer uncertainty at the level of picoseconds is expected at the distances spanning hundreds of kilometers. Such level of accuracy is difficult to obtain using a typical technology exploiting telecom-grade wavelength lockers based on Fabry-Perot etalons. We propose to solve this problem in a hybrid fiber optic transfer system, where the lasers used for time transfer are frequency-locked to a stable optical carrier, which also is simultaneously transmitted in the same fiber. Proposed method makes the time transfer uncertainty practically unaffected by the chromatic dispersion of the fiber link.