Passive Optical Phase Stabilization on a Ring Fiber Network

TL;DR

This paper introduces a passive phase stabilization technique for ring fiber networks that enables high spectral purity optical frequency transfer to multiple remote hubs without active stabilization, improving jitter and scalability.

Contribution

It presents a novel passive stabilization method for ring fiber networks that simplifies implementation and enhances phase jitter performance compared to active techniques.

Findings

Achieves a threefold reduction in phase jitter.

Automatically corrects fiber length fluctuations at multiple hubs.

Maintains delay-limited phase noise correction capability.

Abstract

Optical frequency transfer provides the means for high-fidelity frequency transfer across thousands of kilometers. A critical step in the further developing optical frequency transfer is its capability to transfer a high spectral purity feature from ultrastable lasers or optical clocks to any remote locations and, at the same time, its adaptability to incorporate the optical frequency transfer technique into any existing communication networks with different topologies. Here we for the first time report a technique that delivers optical-frequency signals to multiple independent remote hubs along a ring optical-fiber network with passive phase stabilization. The technique automatically corrects optical-fiber length fluctuations of arbitrary hubs along the loop by mixing and shifting optical signals. Without the help of an active phase tracker and a compensator, it could significantly mitigate some technical problems such as the limited compensation speed and phase recovery time, the phase jitter contamination caused by the servo bump in conventional phase noise cancellation. Moreover, by transmitting optical signals along both directions using the same optical source, it can improve the signal-to-noise ratio at each hub. This technique maintains the same delay-limited phase noise correction capability as in conventional techniques and, furthermore, improves the phase jitter by a factor of 3, opening a way to a broad distribution of an ultrastable frequency reference with high spectral purity and enabling a wide range of applications beyond metrology over a ring fiber network with the naturally impressive reliability and scalability.