Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Optical direct comparison of two 87Sr lattice clocks using a >50km fiber link

T. Ido, Miho Fujieda, Atsushi Yamaguchi, M. Kumagai, Hidekazu Hachisu, Shigeo Nagano, T. Takano, Masao Takamoto, Hidetoshi Katori

Published Jan 1, 2011• 0 citations
Publisher

Abstract

>50km optical fiber link connecting NICT and Univ. of Tokyo has enabled direct comparison of 87Sr lattice clocks locating in each site. Transmission instability 2×10−14@1s unveils sub-10Hz fluctuations of recently developed NICT clock.

DOI
10.1364/cleo_si.2011.cfc4

Related papers

Optical direct comparison of87Sr optical lattice clocks using a >50 km telecommunication fiber link

Hidekazu Hachisu, Atsushi Yamaguchi, Miho Fujieda +7 more

An 87Sr-based-optical lattice clock in NICT is compared to that of The University of Tokyo using a >50 km fiber link. In this work, we have demonstrated for the first time that two distant Sr lattice clocks generate the same frequency with systematic uncertainty of 0.31 Hz (7.3 × 10-16 fractionally) for the 429 THz clock frequency.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Sep 8, 2011•1 citation

A 30-km-long optical fiber link for frequency comparison between distant strontium optical lattice clocks

Tomoya Akatsuka, Hitomi Ono, Keitaro Hayashida +4 more

We demonstrate a 30-km-long optical fiber link for frequency comparison between two strontium optical lattice clocks being developed at Riken and the University of Tokyo. We use a transfer laser at 1397 nm which is twice the wavelength of the clock transition of strontium clocks. The link stability is estimated to be 1×1017for an averaging time τ = 1 s, which is in good agreement with the theoretical limit calculated from the fiber noise spectrum. We discuss a remote clock comparison with stability of 10 (τ/s) by synchronously operating the two distant clocks.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Jul 1, 2013•1 citation

Remote Comparison of Two Sr Optical Lattice Clocks through a 58 km Fiber Link

Tang-Yin 堂银 Liao 廖, Hao 豪 Liu 刘, Fei Meng +9 more

Abstract Two 87Sr optical lattice clocks (OLCs) are being developed and operated at the National Institute of Metrology (NIM), located on different campuses that are 40 km apart. In order to compare the optical frequencies of these two Sr OLCs, a 58-km noise canceled fiber link is built to transfer both a 1542-nm transfer laser and a microwave reference from Changping campus to Hepingli campus. Two commercial optical frequency combs (OFCs) with adapted single-branch 698/1542 nm outputs coherently unite the two 698-nm clock lasers and the 1542-nm transfer laser. The fractional instability of the comparison yields 3.1 × 10−17 at 10000 s averaging time. The measured fractional frequency difference between these two Sr OLCs was evaluated to be 1.9(3.2) × 10−17, which is within their claimed uncertainties. This result demonstrates the consistency of their frequencies when they serve as optical frequency standards. Our remote comparison demonstrates the feasibility of optical clock comparison through a long-distance fiber link and contributes to the progress of redefinition of the SI second.

Chinese Physics Letters•Feb 17, 2025•3 citations

30-km-long optical fiber link at 1397 nm for frequency comparison between distant strontium optical lattice clocks

Tomoya Akatsuka, Hitomi Ono, Keitaro Hayashida +4 more

We demonstrate a 30-km-long optical fiber link for frequency comparison between two strontium optical lattice clocks being developed at RIKEN and the University of Tokyo. We use a transfer laser at 1397 nm, which is twice the wavelength of the clock transition of strontium clocks. The link stability is estimated to be 1 × 10−17 for an averaging time of τ = 1 s, which is in good agreement with the theoretical limit calculated from the fiber noise spectrum. We discuss a remote clock comparison with a stability of 1 × 10−17(τ/s)−1/2 by synchronously operating two distant clocks.

Japanese Journal of Applied Physics•Feb 5, 2014•30 citations

A Sr Lattice Clock at NICT and A Design of An Optical Cavity to Stabilize Clock Lasers

T. Ido, Atsushi Yamaguchi, Michi Koide

An 87Sr lattice clock has begun to work in NICT (National Institute of Information and Communications

The Review of Laser Engineering•Jan 1, 2010•1 citation

All-optical link for direct comparison of distant optical clocks

Miho Fujieda, Motohiro Kumagai, Shigeo Nagano +3 more

We developed an all-optical link system for making remote comparisons of two distant ultra-stable optical clocks. An optical carrier transfer system based on a fiber interferometer was employed to compensate the phase noise accumulated during the propagation through a fiber link. Transfer stabilities of 2 × 10(-15) at 1 second and 4 × 10(-18) at 1000 seconds were achieved in a 90-km link. An active polarization control system was additionally introduced to maintain the transmitted light in an adequate polarization, and consequently, a stable and reliable comparison was accomplished. The instabilities of the all-optical link system, including those of the erbium doped fiber amplifiers (EDFAs) which are free from phase-noise compensation, were below 2 × 10(-15) at 1 second and 7 × 10(-17) at 1000 seconds. The system was available for the direct comparison of two distant (87)Sr lattice clocks via an urban fiber link of 60 km. This technique will be essential for the measuring the reproducibility of optical frequency standards.

arXiv:1108.2775•Optics Express•Aug 11, 2011•93 citations
50km optical fiber link connecting NICT and Univ. of Tokyo has enabled direct comparison of 87Sr lattice clocks locating in each site. Transmission instability 2×10−14@1s unveils sub-10Hz fluctuations of recently developed NICT clock.
We demonstrate a 30-km-long optical fiber link for frequency comparison between two strontium optical lattice clocks being developed at Riken and the University of Tokyo. We use a transfer laser at 1397 nm which is twice the wavelength of the clock transition of strontium clocks. The link stability is estimated to be 1×1017for an averaging time τ = 1 s, which is in good agreement with the theoretical limit calculated from the fiber noise spectrum. We discuss a remote clock comparison with stability of 10 (τ/s) by synchronously operating the two distant clocks.
Abstract Two 87Sr optical lattice clocks (OLCs) are being developed and operated at the National Institute of Metrology (NIM), located on different campuses that are 40 km apart. In order to compare the optical frequencies of these two Sr OLCs, a 58-km noise canceled fiber link is built to transfer both a 1542-nm transfer laser and a microwave reference from Changping campus to Hepingli campus. Two commercial optical frequency combs (OFCs) with adapted single-branch 698/1542 nm outputs coherently unite the two 698-nm clock lasers and the 1542-nm transfer laser. The fractional instability of the comparison yields 3.1 × 10−17 at 10000 s averaging time. The measured fractional frequency difference between these two Sr OLCs was evaluated to be 1.9(3.2) × 10−17, which is within their claimed uncertainties. This result demonstrates the consistency of their frequencies when they serve as optical frequency standards. Our remote comparison demonstrates the feasibility of optical clock comparison through a long-distance fiber link and contributes to the progress of redefinition of the SI second.
We demonstrate a 30-km-long optical fiber link for frequency comparison between two strontium optical lattice clocks being developed at RIKEN and the University of Tokyo. We use a transfer laser at 1397 nm, which is twice the wavelength of the clock transition of strontium clocks. The link stability is estimated to be 1 × 10−17 for an averaging time of τ = 1 s, which is in good agreement with the theoretical limit calculated from the fiber noise spectrum. We discuss a remote clock comparison with a stability of 1 × 10−17(τ/s)−1/2 by synchronously operating two distant clocks.
We developed an all-optical link system for making remote comparisons of two distant ultra-stable optical clocks. An optical carrier transfer system based on a fiber interferometer was employed to compensate the phase noise accumulated during the propagation through a fiber link. Transfer stabilities of 2 × 10(-15) at 1 second and 4 × 10(-18) at 1000 seconds were achieved in a 90-km link. An active polarization control system was additionally introduced to maintain the transmitted light in an adequate polarization, and consequently, a stable and reliable comparison was accomplished. The instabilities of the all-optical link system, including those of the erbium doped fiber amplifiers (EDFAs) which are free from phase-noise compensation, were below 2 × 10(-15) at 1 second and 7 × 10(-17) at 1000 seconds. The system was available for the direct comparison of two distant (87)Sr lattice clocks via an urban fiber link of 60 km. This technique will be essential for the measuring the reproducibility of optical frequency standards.