Hybrid Solution for Joint Transfer Time Signal With Both RF Frequency and Optical Frequency

Jialiang Wang,Nan Cheng,Jianfeng Sun,Youzhen Gui,Fei Yang,Fang Su,Haiwen Cai,Kang Ying,Yanguang Sun

doi:10.1109/jphot.2021.3104924

Abstract

We demonstrate a hybrid solution for simultaneous transfer of ultra-stable optical frequency, RF frequency and time signal on a 100 km fiber spool with the same wavelength based on coherent demodulation and optical phase-lock-loop (OPLL). The one pulse per second (1PPS) is encoded by phase and RF frequency is encoded with an intensity modulator. The noise caused by fiber link is compensated by the round-trip method. And the bad effect on optical frequency caused by optical phase modulation (PM) can be cleaned using OPLL. When the fiber link is stabilized, the transferred time deviation (TDEV) can be 2.4E-11@1s and 1.9E-12@104s, RF frequency stability can achieve 8.0E-14@1s and 2.5E-17@104s, the modified Allan deviation (MDEV) of cleaned optical frequency can be 1.4E-16@1s and 1.6E-19@104s.

Highlights

The dissemination of precise frequency and synchronization of accurate timescale between remote locations is very important for the most advanced scientific and industrial applications such as very long base line interferometry (VLBI) [1], deep space exploration, or mobile telecommunication [2]
We propose a simple scheme to jointly transfer radio frequency (RF) signal, 1PPS signal and optical frequency with the same wavelength, while keeping the stability of optical frequency being immune to the phase modulation (PM) process
The carrier is divided into two parts, one prepares to transfer to the remote site (RS) and the other one is used to beat with the returning signal

Summary

Introduction

The dissemination of precise frequency and synchronization of accurate timescale between remote locations is very important for the most advanced scientific and industrial applications such as very long base line interferometry (VLBI) [1], deep space exploration, or mobile telecommunication [2]. The process of the sinusoidal frequency signal converting may introduce electronics noises from digital circuits, those noises will cause a deterioration of frequency stability and make the short-term stability worse than 4.0E-13@1s [11]. To solve this problem, scientists have proposed the other scheme, in which a mode-locked laser is employed to transfer time signal with intensity modulation, where time deviation 300fs@5s is obtained and RF signal can be generated by optical frequency combs which can achieve the stability better than 1.0E-17 [12]. We propose a simple scheme to jointly transfer RF signal, 1PPS signal and optical frequency with the same wavelength, while keeping the stability of optical frequency being immune to the phase modulation (PM) process

Results

Discussion

Conclusion