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

arXiv:1008.0893 · Optics Express

Photon level crosstalk between parallel fibers installed in urban area

Mikio Fujiwara, Shigehito Miki, Taro Yamashita, Zhen Wang, Masahide Sasaki

Published Oct 5, 2010• 22 citations
arXivHTMLPDF

Abstract

We estimate the channel characteristics of field-installed dark fibers at single photon levels for quantum key distribution (QKD). Measured fibers are telecom single-mode dark fibers over 45 km connecting a center and suburbs of Tokyo. Their total losses are about 14dB, and 50% of the whole lengths are aerial lines. We find that stray light from other public internet fibers is dominant and crosstalk occurs at bending points in laying cables. These results mean the crosstalk from public networks can increase the bit error rate in the QKD system, and imply an underlying information leakage through an adjacent covered-fiber.

DOI
10.1364/oe.18.022199

Related papers

Effect of crosstalk on QBER in QKD in urban telecommunication fiber lines

V. L. Kurochkin, Yuriy V. Kurochkin, Alexander V. Miller +2 more

Quantum key distribution (QKD) as a technology is being actively implemented into existing urban telecommunication networks. QKD devices are commercially available products. While sending single photons through optical fiber, adjacent fibers, which are used to transfer classical information, might influence the amount of registrations of single photon detectors. This influence is registered, since it directly introduces a higher quantum bit error rate (QBER) into the final key [1-3]. Our report presents the results of the first tests of the QKD device, developed in the Russian Quantum Center. These tests were conducted in Moscow, and are the first of such a device in Russia in urban optical fiber telecommunication networks. The device in question is based on a two-pass auto-compensating optical scheme, which provides stable single photon transfer through urban optical fiber telecommunication networks [4,5]. The single photon detectors ID230 by ID Quantique were used. They operate in free-running mode, and with a quantum effectiveness of 10 % have a dark count ~10 Hz. The background signal level in the dedicated fiber was no less than 5.6∙10-14 W, which corresponds to 4.4∙104 detector clicks per second. The single mode fiber length in Moscow was 30.6 km, the total attenuation equal to 11.7 dB. The sifted quantum key bit rate reached values of 1.9 kbit/s with the QBER level equal to 5.1 %. Methods of lowering the influence of crosstalk on the QBER are considered.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Dec 30, 2016•3 citations

Performance of Long-Distance Quantum Key Distribution Over 90-km Optical Links Installed in a Field Environment of Tokyo Metropolitan Area

Kaoru Shimizu, Toshimori Honjo, Mikio Fujiwara +7 more

This paper reports experimental results for a long-term field trial of 1-GHz clock differential phase shift quantum key distribution that was incorporated in the test-bed optical fiber network installed in the Tokyo metropolitan area. A photon transmitter and a photon receiver were connected to a 90-km loop-back optical link with a 30-dB loss. Superconducting single photon detectors were employed to detect photons with a low dark count rate. Stable maintenance-free operation was achieved for 25 days, where the average sifted key generation rate and the quantum bit error rate were 11 kb/s and 2.6%, respectively. The average generation rate of a secure key after error correction and privacy amplification was 1.1 kb/s with a fluctuation of ± 0.5 kb/s. The achieved performance was examined using detailed bit error analysis. A comparison with meteorological data revealed the way in which the field environment influenced the key distribution performance.

Journal of Lightwave Technology•Nov 19, 2013•71 citations

Implementing QKD over Multi-Fiber Ribbon Cables: How Dark is the “Dark Fiber”?

Florian Honz, Vana Pezelj, Theodor Strobl +5 more

We identify inter-lane crosstalk as main cause for QKD degradation in 1×12 bend-loss insensitive fiber ribbon cables. Despite allocating QKD to unused fiber lanes, neighboring classical signals can lead to total saturation of single-photon detectors.

Optical Fiber Communication Conference•Jan 1, 2026•0 citations

Implementing QKD over Multi-Fiber Ribbon Cables: How Dark is the "Dark Fiber"?

Florian Honz, Vana Pezelj, Theodor Strobl +5 more

We identify inter-lane crosstalk as main cause for QKD degradation in 1×12 bend-loss insensitive fiber ribbon cables. Despite allocating QKD to unused fiber lanes, neighboring classical signals can lead to total saturation of single-photon detectors.

•Mar 13, 2026•0 citations

Quantum key distribution over 122 km of standard telecom fiber

C. Gobby, Yuan, ZL, Shields, AJ +1 more

A method for exceeding the 100 km barrier for quantum key distribution (QKD) over a standard telecom fiber was described. The system was based upon a time division Mach-Zender interferometer using phase modulation. The single photon detector was optimized by minimizing the contribution to the intrinsic error rate of detector dark count noise and stray photons. It was observed that a quantum bit error ratio (QBER) of 8.9% was achieved for a 122 km link, allowing a secure shared key to be formed after error correction and privacy amplification.

•May 10, 2004•448 citations

2 GHz clock quantum key distribution over 260 km of standard telecom fiber

Shuang Wang, Wei Chen, Jun-Fu Guo +5 more

We report a demonstration of quantum key distribution (QKD) over a standard telecom fiber exceeding 50 dB in loss and 250 km in length. The differential phase shift QKD protocol was chosen and implemented with a 2 GHz system clock rate. By careful optimization of the 1 bit delayed Faraday-Michelson interferometer and the use of the superconducting single photon detector (SSPD), we achieved a quantum bit error rate below 2% when the fiber length was no more than 205 km, and of 3.45% for a 260 km fiber with 52.9 dB loss. We also improved the quantum efficiency of SSPD to obtain a high key rate for 50 km length.

arXiv:1203.4323•Optics Letters•Mar 6, 2012•242 citations
We estimate the channel characteristics of field-installed dark fibers at single photon levels for quantum key distribution (QKD). Measured fibers are telecom single-mode dark fibers over 45 km connecting a center and suburbs of Tokyo. Their total losses are about 14dB, and 50% of the whole lengths are aerial lines. We find that stray light from other public internet fibers is dominant and crosstalk occurs at bending points in laying cables. These results mean the crosstalk from public networks can increase the bit error rate in the QKD system, and imply an underlying information leakage through an adjacent covered-fiber.
Quantum key distribution (QKD) as a technology is being actively implemented into existing urban telecommunication networks. QKD devices are commercially available products. While sending single photons through optical fiber, adjacent fibers, which are used to transfer classical information, might influence the amount of registrations of single photon detectors. This influence is registered, since it directly introduces a higher quantum bit error rate (QBER) into the final key [1-3]. Our report presents the results of the first tests of the QKD device, developed in the Russian Quantum Center. These tests were conducted in Moscow, and are the first of such a device in Russia in urban optical fiber telecommunication networks. The device in question is based on a two-pass auto-compensating optical scheme, which provides stable single photon transfer through urban optical fiber telecommunication networks [4,5]. The single photon detectors ID230 by ID Quantique were used. They operate in free-running mode, and with a quantum effectiveness of 10 % have a dark count ~10 Hz. The background signal level in the dedicated fiber was no less than 5.6∙10-14 W, which corresponds to 4.4∙104 detector clicks per second. The single mode fiber length in Moscow was 30.6 km, the total attenuation equal to 11.7 dB. The sifted quantum key bit rate reached values of 1.9 kbit/s with the QBER level equal to 5.1 %. Methods of lowering the influence of crosstalk on the QBER are considered.
This paper reports experimental results for a long-term field trial of 1-GHz clock differential phase shift quantum key distribution that was incorporated in the test-bed optical fiber network installed in the Tokyo metropolitan area. A photon transmitter and a photon receiver were connected to a 90-km loop-back optical link with a 30-dB loss. Superconducting single photon detectors were employed to detect photons with a low dark count rate. Stable maintenance-free operation was achieved for 25 days, where the average sifted key generation rate and the quantum bit error rate were 11 kb/s and 2.6%, respectively. The average generation rate of a secure key after error correction and privacy amplification was 1.1 kb/s with a fluctuation of ± 0.5 kb/s. The achieved performance was examined using detailed bit error analysis. A comparison with meteorological data revealed the way in which the field environment influenced the key distribution performance.
A method for exceeding the 100 km barrier for quantum key distribution (QKD) over a standard telecom fiber was described. The system was based upon a time division Mach-Zender interferometer using phase modulation. The single photon detector was optimized by minimizing the contribution to the intrinsic error rate of detector dark count noise and stray photons. It was observed that a quantum bit error ratio (QBER) of 8.9% was achieved for a 122 km link, allowing a secure shared key to be formed after error correction and privacy amplification.
We report a demonstration of quantum key distribution (QKD) over a standard telecom fiber exceeding 50 dB in loss and 250 km in length. The differential phase shift QKD protocol was chosen and implemented with a 2 GHz system clock rate. By careful optimization of the 1 bit delayed Faraday-Michelson interferometer and the use of the superconducting single photon detector (SSPD), we achieved a quantum bit error rate below 2% when the fiber length was no more than 205 km, and of 3.45% for a 260 km fiber with 52.9 dB loss. We also improved the quantum efficiency of SSPD to obtain a high key rate for 50 km length.