Existing fiber networks can now carry both: quantum-secure communication and high-capacity data traffic
Fürth, Germany 2026-07-02
KEEQuant, together with consortium partners CESNET, EXATEL and PCSS, validated the system in a representative modern optical transport network environment, demonstrating quantum-secure communication alongside high-capacity transport traffic over distances of up to 75 km without dedicated dark fiber.
AI-generated Illustration: A visualization of QKD integration into existing transport infrastructure: QKD, shown as a purple quantum stream, joins classical high-capacity data traffic inside the same standard fiber.
The SEQRET consortium partners have validated that existing fiber networks can support quantum-secure communication alongside high-capacity data traffic on the same standard fiber pair. The system demonstrated quantum key distribution (QKD) together with up to 64 Tb/s of classical data traffic and reached distances of up to 75 km. The result directly addresses the dark-fiber bottleneck by showing that quantum-secure communication and high-capacity data traffic can coexist on the same fiber infrastructure used in optical transport networks.
This is particularly relevant for operators and infrastructure stakeholders because fiber scarcity is frequently the primary deployment obstacle. Reserving separate fiber for QKD can be costly and operationally difficult, especially in high-capacity transport networks. Coexistence changes that equation by allowing QKD to run on the same optical infrastructure as classical data traffic. This contributes to a reduction in deployment friction and enhances the practical fit of quantum-safe keying within telecom networks. The strategic consequence is clear: QKD can be introduced into installed transport infrastructure without a parallel dark-fiber build out or major network redesign.
“For operators serving critical-infrastructure and public-sector customers, trust depends on evidence. This validation provides exactly that: a concrete basis for evaluating how quantum-secure key distribution can be integrated into reliable, security-sensitive network services,” says Mateusz Ozimek, who leads the SEQRET project at EXATEL and works there as Head of the Space Technologies Team.
The validation was performed in a two-node setup over standard G.652.D fiber. To reflect representative network conditions, six optical transceivers were employed, while the rest of the optical transport environment was filled with noise loaded channels to emulate a fully populated DWDM line. In parallel, a KEEQuant QKD module generated cryptographic keys, which were delivered through the KEEQuant Key Management System (KMS) to an encryptor. A live encrypted video stream was transmitted using end-to-end encryption, showing a system-level implementation rather than an isolated component result.
Stable coexistence was demonstrated across three operating points:
- 80 × 800 Gb/s (64 Tb/s) across the C- and L-band over 60 km
- 40 × 800 Gb/s (32 Tb/s) in the C-band over 65 km
- 80 × 400 Gb/s (32 Tb/s) across the C- and L-band over 75 km
The result points to a practical route for integrating QKD into existing optical transport infrastructure with lower deployment friction and without reducing available payload capacity.
The demonstration brought together the complementary expertise of several project partners. KEEQuant (Germany) provided the QKD and key management systems and led the overall integration concept and end-to-end demonstration. EXATEL (Poland) contributed the telecommunications operator perspective, defining the operational requirements for real-world network deployment. CESNET (Czech Republic) provided an advanced testbed environment and supported the validation process, while PCSS (Poland) supplied the optical fibers used for range testing.
Funding
This work was carried out with the SEQRET project. The project is funded under the Digital Europe Programme within the framework of EuroQCI under the DIGITAL-2021-GCI-01-INDUSTRIAL call with the project ID 101091591.
Acknowledgements
KEEQuant thanks Ribbon for providing the encryption cards.
Consortium and Press Contacts
KEEQuant GmbH, develops deployable quantum-security technologies including quantum key distribution, key management and secure networking solutions for confidentiality-sensitive infrastructures (Germany)
E-Mail: press@keequant.com
CESNET, Czech Education and Scientific Network (Czech Republic)
E-Mail: marketing@cesnet.cz
EXATEL, leading provider of telecommunications, ICT, and cybersecurity technologies (Poland)
E-Mail: biuroprasowe@exatel.pl
PCSS, Poznan Supercomputing and Networking Center (Poland)
E-Mail: pr@man.poznan.pl