Integrating quantum key distribution with classical communications in backbone fiber network.

Area of Science:

• Quantum communication
• Network security
• Fiber optics

Background:

• Quantum key distribution (QKD) offers information-theoretic security.
• Integrating QKD with high-capacity classical networks is challenging due to noise and power levels.
• Previous coexistence studies focused on metropolitan networks, not backbone infrastructure.

Purpose of the Study:

• To demonstrate the feasibility of integrating QKD with a commercial backbone network.
• To investigate the performance of QKD under high classical data traffic conditions.
• To advance the development of hybrid quantum-classical communication networks.

Main Methods:

• Integration of QKD with a 3.6 Tbps commercial backbone network over 66 km of fiber.
• Utilized 20 GHz pass-band filtering and large effective core area fibers.
• Tested both co-propagation and counter-propagation scenarios at 21 dBm launch power.

Main Results:

• Achieved real-time secure key rates of 4.5 kbps for co-propagation and 5.1 kbps for counter-propagation.
• Demonstrated successful coexistence despite high classical data traffic and optical power.
• Quantified the noise impact and filtering effectiveness in a real-world backbone network.

Conclusions:

• The integration of QKD with commercial backbone networks is feasible.
• This work represents a significant step towards building practical quantum networks alongside existing classical infrastructure.
• The achieved secure key rates highlight the potential for secure communication in future hybrid networks.