Enabling a multifunctional telecommunications fiber optic network: Ultrastable optical frequency transfer and attosecond timing in deployed multicore fiber

TL;DR

This paper demonstrates the use of multicore optical fibers to transfer ultrastable optical signals, enabling multifunctional telecom networks for applications like precise timing and quantum networking, with high stability over long distances.

Contribution

It introduces a method for faithful ultrastable optical signal transfer in multicore fibers compatible with existing telecom infrastructure, advancing multifunctional network capabilities.

Findings

Achieved fractional frequency instability of 3x10^-19 at 10,000 seconds

Demonstrated compatibility with unidirectional long-haul fiber systems

Enabled potential for intercontinental optical clock comparisons

Abstract

The telecommunications industry's deployment of billions of kilometers of optical fiber has created a vast global network that can be exploited for additional applications such as environmental sensing, quantum networking and international clock comparisons. However, for reasons such as the unidirectionality of long-haul fiber links, telecom fiber networks cannot always be adapted for important applications beyond data transmission. Fortunately, new multicore optical fibers create the opportunity for application coexistence with data traffic, creating expansive multifunctional networks. Towards that end, we propose and demonstrate the faithful transfer of ultrastable optical signals through multicore fiber in a way that is compatible with the unidirectionality of long-haul fiber optic systems, demonstrating a fractional frequency instability of 3x10-19 at 10,000 seconds. This opens the door towards intercontinental optical clock comparisons, with applications in fundamental physics and the redefinition of the second.