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Low Thermal Sensitivity Hollow Core Fiber for Optically-Switched Data Centers

Low Thermal Sensitivity Hollow Core Fiber for Optically-Switched Data Centers
Low Thermal Sensitivity Hollow Core Fiber for Optically-Switched Data Centers

Optical switches offer several benefits over electronic switches, including better scalability, lower power consumption, and lower latency. The end-to-end switching latency in optical switching systems is the sum of the optical switching time and the clock and data recovery (CDR) locking time. In short packet dominated data center networks, the CDR locking time limits the end-to-end switching latency. It has been shown that sub-nanosecond CDR locking time is required to achieve high network throughput. Recent research shows that scalable and sub-nanosecond CDR can be achieved by synchronizing the clock frequency and phase of all end-points connected to an optical switch. In such a system, the clock phases must be tracked because of the thermally-induced change of propagation time through standard single mode fiber (SMF-28). Hollow core fiber has been shown to have a 20 times smaller thermal coefficient of delay than SMF-28, offering the potential to simplify clock phase tracking. In this article, we investigate the benefits of the low thermal coefficient of delay of hollow core fiber for clock-synchronized data center networks, showing under 625 ps CDR locking time in both a point-to-point and a 2-to-1 optically switched system, using real-time 60-ns packets operating at 25.6 Gb/s. Based on our results, we estimate that sub-nanosecond CDR locking time can be achieved for a 100 m size data center cluster interconnected by an optical switch using hollow core fiber, without active tracking of clock phase.

Clock and data recovery (CDR), Data centers, Optical fiber communication, Optical fibers, Optical switching
0733-8724
2703-2709
Clark, Kari A.
d354d373-db12-4016-9245-8de43ca568bb
Chen, Yong
0bfb3083-4cd2-4463-a7a4-f48c4158b15a
Numkam Fokoua, Eric R.
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Bradley, Tom
d4cce4f3-bb69-4e14-baee-cd6a88e38101
Poletti, Francesco
9adcef99-5558-4644-96d7-ce24b5897491
Richardson, David J.
ebfe1ff9-d0c2-4e52-b7ae-c1b13bccdef3
Bayvel, Polina
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Slavík, Radan
2591726a-ecc0-4d1a-8e1d-4d0fd8da8f7d
Liu, Zhixin
01f60f1d-54b7-4c19-b3f3-9550f9d77733
Clark, Kari A.
d354d373-db12-4016-9245-8de43ca568bb
Chen, Yong
0bfb3083-4cd2-4463-a7a4-f48c4158b15a
Numkam Fokoua, Eric R.
cca13dcd-4443-4638-b9b4-d2dcb1dd100a
Bradley, Tom
d4cce4f3-bb69-4e14-baee-cd6a88e38101
Poletti, Francesco
9adcef99-5558-4644-96d7-ce24b5897491
Richardson, David J.
ebfe1ff9-d0c2-4e52-b7ae-c1b13bccdef3
Bayvel, Polina
0f0922e3-b79a-490f-8e50-e2e098b3e102
Slavík, Radan
2591726a-ecc0-4d1a-8e1d-4d0fd8da8f7d
Liu, Zhixin
01f60f1d-54b7-4c19-b3f3-9550f9d77733

Clark, Kari A., Chen, Yong, Numkam Fokoua, Eric R., Bradley, Tom, Poletti, Francesco, Richardson, David J., Bayvel, Polina, Slavík, Radan and Liu, Zhixin (2020) Low Thermal Sensitivity Hollow Core Fiber for Optically-Switched Data Centers. Journal of Lightwave Technology, 38 (9), 2703-2709, [9026763]. (doi:10.1109/JLT.2020.2979143).

Record type: Article

Abstract

Optical switches offer several benefits over electronic switches, including better scalability, lower power consumption, and lower latency. The end-to-end switching latency in optical switching systems is the sum of the optical switching time and the clock and data recovery (CDR) locking time. In short packet dominated data center networks, the CDR locking time limits the end-to-end switching latency. It has been shown that sub-nanosecond CDR locking time is required to achieve high network throughput. Recent research shows that scalable and sub-nanosecond CDR can be achieved by synchronizing the clock frequency and phase of all end-points connected to an optical switch. In such a system, the clock phases must be tracked because of the thermally-induced change of propagation time through standard single mode fiber (SMF-28). Hollow core fiber has been shown to have a 20 times smaller thermal coefficient of delay than SMF-28, offering the potential to simplify clock phase tracking. In this article, we investigate the benefits of the low thermal coefficient of delay of hollow core fiber for clock-synchronized data center networks, showing under 625 ps CDR locking time in both a point-to-point and a 2-to-1 optically switched system, using real-time 60-ns packets operating at 25.6 Gb/s. Based on our results, we estimate that sub-nanosecond CDR locking time can be achieved for a 100 m size data center cluster interconnected by an optical switch using hollow core fiber, without active tracking of clock phase.

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Low Thermal Sensitivity Hollow Core Fiber for Optically-Switched Data Centers - Accepted Manuscript
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Accepted/In Press date: 29 February 2020
e-pub ahead of print date: 6 March 2020
Published date: 1 May 2020
Additional Information: Funding Information: Manuscript received November 15, 2019; revised February 24, 2020; accepted February 29, 2020. Date of publication March 6, 2020; date of current version May 6, 2020. This work was supported in part by EPSRC Grants AirGuide Photonics EP/P030181/1, in part by TRANSNET EP/R035342/1, in part by EP/R041792/1, in part by the ERC Lightpipe Project 682724, and in part by Royal Society PIF\R1\180001. (Corresponding author: Zhixin Liu.) Kari A. Clark, Polina Bayvel, and Zhixin Liu are with the Department of Electronic and Electrical Engineering, University College London, London WC1E 6BT, U.K. (e-mail: kari.clark.14@ucl.ac.uk; p.bayvel@ucl.ac.uk; zhixin.liu@ucl.ac.uk). Publisher Copyright: © 1983-2012 IEEE.
Keywords: Clock and data recovery (CDR), Data centers, Optical fiber communication, Optical fibers, Optical switching

Identifiers

Local EPrints ID: 441659
URI: http://eprints.soton.ac.uk/id/eprint/441659
ISSN: 0733-8724
PURE UUID: 7af4e6c3-4d03-44e9-8828-4b8f1b4506d1
ORCID for Yong Chen: ORCID iD orcid.org/0000-0003-0383-6113
ORCID for Tom Bradley: ORCID iD orcid.org/0000-0001-6568-5811
ORCID for Francesco Poletti: ORCID iD orcid.org/0000-0002-1000-3083
ORCID for David J. Richardson: ORCID iD orcid.org/0000-0002-7751-1058
ORCID for Radan Slavík: ORCID iD orcid.org/0000-0002-9336-4262

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Date deposited: 23 Jun 2020 16:46
Last modified: 05 Oct 2022 01:46

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Contributors

Author: Kari A. Clark
Author: Yong Chen ORCID iD
Author: Eric R. Numkam Fokoua
Author: Tom Bradley ORCID iD
Author: Polina Bayvel
Author: Radan Slavík ORCID iD
Author: Zhixin Liu

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