Continuous Variable QKD Coexists with Classical Data in the C-Band
Quantum-safe security solutions are rapidly evolving to enable the seamless adoption of next-generation technologies within today’s telecommunications networks. While Quantum Key Distribution (QKD) systems are already commercially available and mature, they still face significant challenges before widespread adoption by companies of all sizes becomes a reality.
At LuxQuanta, we are addressing one of the most critical challenges: integrating the quantum link—responsible for generating and distributing quantum keys—into existing optical infrastructure. We achieve this without displacing classical data channels, ensuring minimal impact and maximum compatibility with current network operations.
In a joint research effort between LuxQuanta, Telefónica, and the Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), recently published in a 2024 peer-reviewed paper, we demonstrate that this integration is not only possible—it is already viable using commercial technology and standard network infrastructure.
This result was validated through extensive experimentation in a metro network scenario, confirming that quantum and classical optical signals can share the same spectrum and physical infrastructure under real-world conditions.
The experimental setup included:
Importantly, all classical data channels remained within the C-band. No spectrum was shifted, and no classical traffic was removed to accommodate the quantum signal.
Infrastructure Compatibility
Cost-Effective Integration
Performance Optimization
Supporting a Quantum-Resilient Infrastructure
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Work funded by EU’s Horizon Europe research and innovation program, HE ALLEGRO (101092766) project and EC Digital QUARTER (101091588) project, and by the "Ministerio de Asuntos Económicos y Transformación Digital" and the European Union-NextGenerationEU in the frameworks of the "Plan de Recuperación, Transformación y Resiliencia" and of the "Mecanismo de Recuperación y Resiliencia" under reference 6G-OPENSEC-KEYS (TSI-063000- 2021-61).
At LuxQuanta, we are addressing one of the most critical challenges: integrating the quantum link—responsible for generating and distributing quantum keys—into existing optical infrastructure. We achieve this without displacing classical data channels, ensuring minimal impact and maximum compatibility with current network operations.
In a joint research effort between LuxQuanta, Telefónica, and the Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), recently published in a 2024 peer-reviewed paper, we demonstrate that this integration is not only possible—it is already viable using commercial technology and standard network infrastructure.
Coexistance in full-capacity C-band
LuxQuanta’s commercial CV-QKD system, branded as NOVA LQ®, successfully coexists with fully occupied C-band DWDM traffic, without displacing classical data channels or requiring dedicated optical fiber.This result was validated through extensive experimentation in a metro network scenario, confirming that quantum and classical optical signals can share the same spectrum and physical infrastructure under real-world conditions.
The experimental setup included:
- A 20 km amplified metro link based on FOADM architecture
- LuxQuanta’s NOVA LQ® CV-QKD platform, implementing the Gaussian Modulated Coherent State (GMCS) protocol with a true local oscillator
- 39 DWDM channels (100G and 400G), using off-the-shelf CFP2 and QSFP-DD transceivers from multiple vendors
- Standard telecom components, including EDFA amplifiers and 100 GHz multiplexers
Importantly, all classical data channels remained within the C-band. No spectrum was shifted, and no classical traffic was removed to accommodate the quantum signal.
Spectrum Efficiency
Full C-band utilization is preserved. Quantum security can be added without sacrificing classical capacity, making it fully compatible with current and future high-throughput network designs.
Infrastructure Compatibility
The CV-QKD system was deployed on a standard metro link using commercial transceivers and switching equipment, proving that quantum-secure upgrades can be achieved without any architectural changes.
Cost-Effective Integration
The use of just two standard filters simplifies deployment and reduces both cost and complexity. No dedicated fiber is required.
Performance Optimization
Experimental results showed improved secure key rates when the quantum channel was allocated to the anti-Stokes region of the C-band. This finding provides a practical guideline for minimizing noise—especially Raman scattering—in coexistence scenarios.
Supporting a Quantum-Resilient Infrastructure
This study was conducted as part of broader European initiatives focused on secure, future-proof communications, including the EU Horizon ALLEGRO project, the Digital QUARTER project, and Spain’s 6G-OPENSEC-KEYS initiative.
These programs aim to accelerate the adoption of quantum-safe technologies and reinforce Europe’s leadership in secure digital infrastructure.__
Work funded by EU’s Horizon Europe research and innovation program, HE ALLEGRO (101092766) project and EC Digital QUARTER (101091588) project, and by the "Ministerio de Asuntos Económicos y Transformación Digital" and the European Union-NextGenerationEU in the frameworks of the "Plan de Recuperación, Transformación y Resiliencia" and of the "Mecanismo de Recuperación y Resiliencia" under reference 6G-OPENSEC-KEYS (TSI-063000- 2021-61).
