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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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.
India's Quantum Future
"This initiative is a key milestone for India's telecom ecosystem. This achievement clearly establishes the feasibility of integrated quantum-classical networks over next-generation optical fibres saving costs for QKD deployments drastically," said Dr Rajkumar Upadhyay, CEO of C-DOT.
Rahul Puri, CEO of Optical Networking Business, STL said: "This breakthrough collaboration with C-DOT underscores India's growing prowess in pioneering next-gen digital infrastructure."
"By successfully integrating QKD with our indigenously developed MCF, we have demonstrated how cutting-edge optical innovations can revolutionise secure communication. We are committed to advancing India's quantum communication ambitions while driving global optical leadership," he said, noting that this milestone is a testament to the power of public-private partnerships in building a digitally sovereign and secure nation.
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C-DOT and STL
C-DOT is the R&D arm of the Department of Telecommunications (DoT). STL, an optical networking solutions company, has recently developed the MCF using Space Division Multiplexing, enabling ultra-high capacity data transmission within the same fibre diameter.
Both organisations reaffirmed their commitment to advancing India's capabilities in quantum communication and next-generation optical technologies.
