Phase-coherent frequency comparison of optical clocks using a telecommunication fiber link

Schnatz, H.; Terra, Osama; Predehl, Katharina; Feldmann, Thorsten; Legero, Thomas; Lipphardt, B.; Sterr, U.; Grosche, G.; Holzwarth, Ronald; Hänsch, Theodor W.; Udem, Th.; Lu, Zehuang; Wang, L.J.; Ertmer, W.; Friebe, J.; Pape, A.; Rasel, Ernst M.; Riedmann, M.; Wübbena, T.

doi:10.1109/tuffc.2010.1395

Cited by 18 publications

(2 citation statements)

References 34 publications

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“…Due to their bulky size and complex structure, optical clocks can only be developed and operated in a few laboratories. Therefore, it is necessary to establish a high-precision transmission system to realize the frequency distribution and comparison of optical clocks [4,5]. With the characteristics of low attenuation, high reliability, and immunity to electromagnetic interference [6], fibers have become a common medium for high-precision distribution of frequency standards.…”

Section: Introductionmentioning

confidence: 99%

Remote Residual Instability Evaluation of Comb-Based Precise Frequency Transmission for Optical Clock

Li,

Gui,

et al. 2023

Photonics

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Optical clocks can be used as the absolute frequency reference due to their high accuracy and stability. In a precise optical clock transmission system, the instability loss of the link is usually evaluated by beating the remote optical signal with the reference clock, which is not suitable for real frequency distribution applications. Therefore, it is necessary to assess the performance directly at the remote site for the optical frequency transfer, because the two sites of the link are usually not co-located. In this paper, we proposed a comb-based remote residual instability evaluation scheme. Two coherent optical combs with different wavelengths were extracted from a frequency stable comb and transmitted after multiplexing. The residual instability was evaluated directly at the remote site by measuring the phase fluctuation difference between the two combs. We achieved 8.61 × 10−19 at 40,000 s over a 10 km fiber link, reaching the instability of optical clocks. These results revealed that our scheme can evaluate optical clock frequency transmission directly at the remote site, which made the method truly practical.

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Section: Introductionmentioning

confidence: 99%

Remote Residual Instability Evaluation of Comb-Based Precise Frequency Transmission for Optical Clock

Li,

Gui,

et al. 2023

Photonics

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“…At present, two types of heterodyne OPLLs, including discrete space optics [6] and PIC optics [7,8], have been developed. Tremendous attention has been paid to PIC-based OPLLs, owing to their advantages of compact structure, short signal delay, convenient packaging, and low power consumption [9,10].…”

Section: Introductionmentioning

confidence: 99%

Simulation and Design of a PIC-Based Heterodyne Optical Phase Locked Loop

et al. 2023

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In this paper, we report on our simulation and design of a photonic integrated circuits (PIC)-based heterodyne optical phase-locked loop (OPLL). Our simulation reveals that the OPLL operation can be in one of three states, i.e., absolutely stable, metastable, and unstable states, depending on the relative position of the initial phase reversal point to the loop bandwidth. By systematically optimizing all of the loop parameters involved, the loop bandwidth of 247.8 MHz and the residual phase noise variance of 0.012 rad2 are theoretically obtained in such a PIC-OPLL system, which are better than any reported counterparts. In addition, the lowest required power of the master laser is also evaluated, assuming that the largest acceptable residual phase noise variance is 0.02 rad2, and it is found that the lowest master laser power is −54 dBm in our current OPLL system, and this value can be reduced to −56 dBm, providing that the summed linewidth is reduced to 10 kHz.

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Comparing ultrastable lasers at 7 × 10−17 fractional frequency instability through a 2220 km optical fibre network

et al. 2022

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Ultrastable lasers are essential tools in optical frequency metrology enabling unprecedented measurement precision that impacts on fields such as atomic timekeeping, tests of fundamental physics, and geodesy. To characterise an ultrastable laser it needs to be compared with a laser of similar performance, but a suitable system may not be available locally. Here, we report a comparison of two geographically separated lasers, over the longest ever reported metrological optical fibre link network, measuring 2220 km in length, at a state-of-the-art fractional-frequency instability of 7 × 10−17 for averaging times between 30 s and 200 s. The measurements also allow the short-term instability of the complete optical fibre link network to be directly observed without using a loop-back fibre. Based on the characterisation of the noise in the lasers and optical fibre link network over different timescales, we investigate the potential for disseminating ultrastable light to improve the performance of remote optical clocks.

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Phase-coherent frequency comparison of optical clocks using a telecommunication fiber link

Cited by 18 publications

References 34 publications

Remote Residual Instability Evaluation of Comb-Based Precise Frequency Transmission for Optical Clock

Remote Residual Instability Evaluation of Comb-Based Precise Frequency Transmission for Optical Clock

Simulation and Design of a PIC-Based Heterodyne Optical Phase Locked Loop

Comparing ultrastable lasers at 7 × 10−17 fractional frequency instability through a 2220 km optical fibre network

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