C-DOT and Sterlite Technologies Ltd. (STL) achieve India’s  First Quantum Key Distribution (QKD) over Multi-Core Fibre

17 April 2025: In a landmark achievement, C-DOT, jointly with Sterlite Technologies Limited (STL), has successfully tested India’s first QKD transmission over a 4-core Multi-Core Fibre (MCF) — marking a major milestone in the nation’s journey towards quantum-secured communication networks.

Multi-Core Fibre (MCF) technology provides a powerful solution by enabling data transmission  across multiple cores within a single fibre, significantly saving physical space and infrastructure costs. In the context of QKD — which typically requires a dedicated dark fibre for the quantum  channel, MCF offers a significant advantage: it enables the physical separation of quantum  and classical signals into distinct cores within 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.

In this activity, the quantum signals of QKD were transmitted through one core, while simultaneously, the other three cores on the same fibre were used to carry 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.

The Centre for Development of Telematics (C-DOT), India’s premier telecom R&D centre under the Department of Telecommunications (DoT), Ministry of Communications, Government of  India, has emerged as a key player in advancing India’s quantum communication ecosystem.  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. 

Sterlite Technologies Limited (STL) is a leading global provider of integrated digital networks, specialising in optical fibre manufacturing and network designs, with 10+ global manufacturing plants and a customer base spanning 100+ countries. As a trailblazer in Optical  Networking, Optical Connectivity, Data Centres, and Enterprise solutions, STL has recently developed Multi-Core Fibre (MCF), positioning it at the forefront of building future-ready,  scalable fibre networks. STL’s Multicore fibre leverages Space Division Multiplexing in 7 and 4  core fibre to achieve ultra-high transmission capacity per fibre within the same diameter. 

Speaking at the occasion, Dr. Rajkumar Upadhyay, CEO of C-DOT, stated, “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”.

Rahul Puri, CEO, 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 revolutionized secure communication. We are committed to advancing India’s quantum communication ambitions while driving global optical leadership. This milestone is a testament to the power of public-private partnerships in building a digitally sovereign and secure nation.”

Both C-DOT and Sterlite Technologies (STL) reaffirm their commitment to advancing India’s capabilities in quantum communication and optical network innovations. This achievement is a foundational step toward realizing a cost effective, secure and resilient national quantum communication infrastructure.