Fiber-optic joint time and frequency transfer with the same wavelength

Abstract

Optical fiber links have proven their powerful ability to transfer the ultrastable clock signals over a national and continental metrological optical network. In this Letter, we propose and demonstrate a new scheme that time and frequency signals are modulated on the same laser wavelength with phase and intensity modulation by an independent electro-optic modulator, respectively. Different wavelengths are used in two opposite directions to prevent Rayleigh scattering. The noise changes caused by the fluctuations of the transfer links are actively canceled at the local site by optical delay lines. Radio frequency with 1 GHz and time signal with one pulse per second (1 PPS) are transmitted over 110 km fiber spools. The experimental results demonstrate that frequency instabilities of 1.7 E − 14 at 1 s and 5.9 E − 17 at 10 4 s and time interval transfer of 1 PPS signal with sub-ps stability after 1000 s are obtained. This novel scheme offers advantages with respect to reduce the channel in the fiber network, and can keep the time and frequency signal free from interference with each other.