Optical Fiber Communication Conference

Towards international clock comparisons on a telecom network: ultrastable optical frequency transfer over deployed multi-core fiber

Nazanin Hoghooghi, Mikael Mazur, Nicolas K. Fontaine, Yifan Liu, Tetsuya Hayashi, Giammarco Di Sciullo, Divya Ann Shaji, Antonio Mecozzi, Cristian Antonelli, Franklyn Quinlan

Published Jan 1, 2024• 2 citations

Publisher

Abstract

We present optical frequency transfer over deployed multi-core fiber at levels that support the world’s best optical clocks for the first time, achieving fractional frequency stability better than 3 10-19 through 25.2 km of fiber.

DOI: 10.1364/ofc.2024.th4a.5

Related papers

Towards international clock comparisons on a telecom network: ultrastable optical frequency transfer over deployed multi-core fiber

Nazanin Hoghooghi, Mazur M., Nicolas K. Fontaine +7 more

We present optical frequency transfer over deployed multi-core fiber at levels that support the world's best optical clocks for the first time, achieving fractional frequency stability better than 3×10-19 through 25.2 km of fiber.

Jan 1, 20240 citations

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

Nazanin Hoghooghi, Mikael Mazur, Nicolas K. Fontaine +10 more

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.

arXiv:2410.13801Oct 17, 20240 citations

Ultrastable optical frequency transfer and attosecond timing in deployed multicore fiber

Nazanin Hoghooghi, Mikael Mazur, Nicolas K. Fontaine +10 more

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 multifunctional networks. Toward that end, we propose and demonstrate the faithful transfer of ultrastable optical signals through deployed multicore fiber in a way that is compatible with the unidirectionality of long-haul fiber optic systems, demonstrating fractional frequency instability of 3×10 −19 at 10,000 s. By supporting state-of-the-art optical atomic clocks, subsea multicore fibers can break the distance barrier for ultrastable optical frequency transfer, opening the door to intercontinental optical clock comparisons at the highest level, with applications in fundamental physics, relativistic geodesy, and the redefinition of the second.

OpticaMay 8, 20259 citations

Study of optical frequency transfer via fiber

Jie Liu, Jing Gao, Guanjun Xu +6 more

Optical clocks are considered as promising candidates for redefining the second in the International System of Units. Compared with microwave clocks, optical clocks are powerful tools for the fundamental research such as the constancy of the fundamental constants, the validity of Einstein’s theory of general relativity, and the predictions of quantum electrodynamics. Recently two research groups have demonstrated the optical clocks with an unprecedented precision level of 10-18, which is two orders better than the present primary frequency standard. Using two Sr optical clocks and three Cs fountain clocks, SYRTE group has demonstrated the definition of second with optical clocks.#br#For redefining the second with optical clocks in the future, the optical clocks from the remote laboratories should have a high precision and the frequency of the optical clocks need to be transferred over a long distance, with extremely high precision. Unfortunately the conventional means of frequency transfer such as two-way satellite time and frequency transfer can reach a 10-16 level in one day which is far below the requirement for an optical clocks. Various methods have been developed to transfer optical frequency signal via optical fibers. Especially a research group from Germany has achieved a frequency transfer stability of 10-19 level in hundreds of seconds with a fiber length of 1840 km.#br#We demonstrate the recent development of optical frequency transfer over a 70-km fiber spool at National Time Service Center. The measurement shows that the compensation for the fiber noise is close to the limitation induced by the fiber delay for the Fourier frequency from 1 Hz to 250 Hz. The transfer stability (Allan deviation) of the fiber link is 1.2×10-15 in 1 s averaging time, and 1.4×10-18 in 10000 s. A preliminary test of the optical frequency transfer over a 100-km spooled fiber is achieved with a stability of roughly one order worse than the 71 km result, 5×10-15 in 1 s.#br#We demonstrate a new scheme of remote compensation for optical frequency transfer via fibers against conventional local compensation method. This new scheme has the advantage of great simplification of the local site, which can find applications in massive extension of star network. The key feature is that we transfer the mixture of the round-trip signal and local reference to the remote user’s end via an auxiliary fiber. At remote site, the fiber noise is measured and compensated by AOM2 accordingly.#br#Transfer stabilities of 13×10-15 in 1 s averaging time and 4.8×10-18 in 10000 s are achieved with the remote fiber noise compensation via a 25 km fiber spool. The demonstrated transfer stability is comparable to that obtained by the local fiber noise compensation method.#br#The future star fiber network of optical frequency transfer can benefit from this method, because the simpler local setup is required and even can be shared in the central site for multitudinous remote users.

Acta Physica SinicaJan 1, 20158 citations

Record-breaking optical frequency dissemination over 2,067 km fiber network

Ziyang Chen, Xu KEmi, Hong Guo

Abstract A research team demonstrated a 2067-km field-deployed optical frequency dissemination link over standard telecommunications fiber. The system achieved a record fractional frequency instability of 2.9 × 10⁻ 21 at one day averaging time, and maintained continuous phase lock for more than four days, marking a major step toward large-scale optical clock networks and future precision timing infrastructure.

eLightAug 14, 20260 citations

Optical fiber link for ultra-stable frequency dissemination and atomic clock comparisons

Anne Amy‐Klein, Nicolas Quintin, N. Chiodo +42 more

The transfer of ultra-stable frequencies between distant laboratories is required by many applications from fundamental metrology to high-precision measurements. For that purpose, optical fibre links have been intensively studied over the last decade. They have demonstrated impressive results far beyond the GPS capabilities on distances up to 2000 km, thanks to an active compensation of the fiber propagation noise.Up to now, optical links has been mainly implemented between two labs, when future applications will require the development of metrological fiber networks. Towards this goal, we have developed a few techniques which allow us to distribute the ultrastable optical signal to many users simultaneously. We have designed repeater laser stations, which can be used to build a cascaded link or to distribute the ultrastable signal among two optical links [1]. These stations allow us also to compare the output end signals of two optical links. These versatile stations will be a key-component of the national metrological network currently being developed in France within the Refimeve+ project. To complete the network, we have demonstrated the extraction of the ultrastable signal from a main link and its seeding to a secondary link [2].Optical links are already been successfully used for clocks comparison. Recently we were able to compare the atomic clocks of the French and German National Metrology Institutes through two connected optical links of total length 1415-km [3]. We found that the two fully independent Sr lattice optical clocks at the two sites agreed to better than 5x10-17 limited only by the clocks uncertainties. A fractional statistical uncertainty of 3x10-17 was reached after only 1000 s averaging time, which is 10 times better, and more than four orders of magnitude faster than with any other existing frequency transfer method. The atomic fountain primary frequency standards from the two institutes were also compared and they were found to agree well within their combined uncertainties of a few 10-16 [4].

Jan 1, 20170 citations