High-precision Time-Frequency Signal Simultaneous Transfer System via a WDM-based Fiber Link

TL;DR

This paper presents a WDM-based fiber system capable of simultaneously transferring ultrastable optical frequency, microwave frequency, and time signals over 50 km with high precision, minimizing crosstalk and demonstrating excellent stability and accuracy.

Contribution

The study introduces a novel WDM-based system for simultaneous high-precision transfer of multiple time-frequency signals over a fiber link, with effective noise cancellation and crosstalk avoidance.

Findings

Optical frequency instability achieved 2E-17/s, scaling to 2E-20/10000 s.

Microwave frequency instability approaches 4E-15/s, decreasing to 1.4E-17/10000 s.

Time signal uncertainty is 2.08 ps over 50 km.

Abstract

In this paper, we demonstrate a wavelength division multiplexing (WDM) based system for simultaneously delivering ultrastable optical frequency reference, 10 GHz microwave frequency reference, and one pulse per second (1 PPS) time signal via a 50 km fiber network. For each signal, a unique noise cancellation technique is used to maintain the precision of them. After being compensated, the transfer frequency instability in terms of overlapping Allan deviation (OADEV) for the optical frequency achieves 2E-17/s and scales down to 2E-20/10000 s, which for the 10 GHz microwave reference approaches 4E-15/s and decreases to 1.4E-17/10000 s, and the time uncertainty of the 1 PPS time signal along the system is 2.08 ps. In this scheme, specific channels of WDM are respectively occupied for different signals to avoid the possible crosstalk interference effect between the transmitted reference signals. To estimate the performance of the above scheme, independent of these signals is also demonstrated in this 50 km link, the results are similar to that in the case of simultaneous delivery. This work shows that the WDM-based system is a promising method for building a nationwide time and frequency fiber transfer system with a communication optical network.