C-DOT, STL Demonstrate Quantum Key Distribution Transmission Over Multi-Core Fibre

The Centre for Development of Telematics (C-DOT), in collaboration with Sterlite Technologies Limited (STL), has successfully conducted India’s first Quantum Key Distribution (QKD) transmission over a 4-core Multi-Core Fibre (MCF), marking a major milestone in the nation’s journey towards quantum-secured communication networks.

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Also Read: C-DOT and IIT Bombay Collaborate on Optical Transceiver Chipset for 6G Wireless Links

What is Multi-Core Fibre?

Multi-Core Fibre (MCF) technology provides a powerful solution by enabling data transmission across multiple cores within a single fibre, significantly reducing physical space requirements and infrastructure costs. According to the Ministry of Communications, in the context of QKD — which typically requires a dedicated dark fibre for the quantum channel, MCF enables the physical separation of quantum and classical signals into distinct cores within a single fibre.

This allows for the simultaneous transmission of QKD and high-capacity data traffic on a single fibre without compromising quantum signal integrity thereby saving fibre cost, the Ministry announced on Thursday, April 19, 2025.

Simultaneous QKD and Data Transmission

In this demonstration, quantum signals for QKD were transmitted through one core, while the remaining three cores in the same fibre carried high-speed user data. A stable QKD link was established over a distance exceeding 100 km, validating the robustness and stability of quantum communication even amidst high-capacity classical data traffic, according to C-DOT.

C-DOT has successfully developed and deployed industry-grade Quantum Key Distribution (QKD) systems. Notably, C-DOT’s QKD systems have received Technology Approval from the Telecommunication Engineering Centre (TEC), a body under the DoT.