STL (NSE: STLTECH), a global provider of optical and digital network solutions, in partnership with the Centre for Development of Telematics (C-DOT), the Department of Telecommunications’ research and development body, has successfully conducted India’s first Quantum Key Distribution (QKD) transmission over a 100-kilometre multi-core fibre (MCF) network. This achievement marks a significant advancement in establishing quantum-secure, next-generation communications infrastructure in India.
STL has developed and implemented India’s first multi-core fibre cabling solution as a complete end-to-end deployment, encompassing design, cabling, connectivity, installation, and field deployment. The MCF cabling system was implemented at the DoT-sponsored Advanced Optical Communications (AOC) Test Bed at IIT Madras and adheres to the Essential Requirements (ER) specified by the Telecommunication Engineering Centre (TEC). STL is recognised as the first global entity to operationalise MCF cabling across both underground and aerial networks and currently leads international efforts in standardisingfibre technologies and measurement protocols.
The multi-core fibre architecture enables parallel data transmission across multiple cores within a single optical fibre. This configuration optimises space and significantly reduces infrastructure costs. For quantum communication applications, particularly QKD—which traditionally requires separate dark fibre for the quantum channel—MCF allows quantum and classical signals to be physically separated across distinct cores within the same cable. This integration facilitates secure key distribution while maintaining high-speed data throughput without compromising the integrity of the quantum signals.
In the conducted demonstration, QKD signals were transmitted through one of the four cores, while the remaining three carried high-speed user data. STL and C-DOT successfully maintained a stable, error-free QKD transmission over 100 kilometres while concurrently supporting high-capacity classical data traffic. The demonstration validates the feasibility of implementing quantum-secured networks alongside conventional data networks, addressing the twin challenges of scalability and security.
This development supports national efforts to build quantum-resilient infrastructure aligned with future demands of 5G and 6G deployments. It reinforces India’s capability to develop sovereign, secure communication technologies that meet the growing requirements of data security and bandwidth.
Dr Rajkumar Upadhyay, Chief Executive Officer, C-DOT, stated that this demonstration represents a significant milestone for India’s telecommunications sector and highlights the importance of public-private collaboration in achieving critical technological breakthroughs. He noted the potential of integrated quantum-classical networks to reduce costs and accelerate QKD deployment at scale.
Rahul Puri, Chief Executive Officer of STL’s Optical Networking Business, emphasised the role of indigenous innovation in advancing secure communications. He described the project as a demonstration of STL’s technical leadership and a reflection of the country’s capacity to deliver next-generation, resilient digital infrastructure.
Sterlite Technologies Ltd (STL) is a global leader in digital technology and network solutions, known for its expertise in designing and delivering integrated digital networks. Headquartered in India, STL operates in over 100 countries, providing cutting-edge solutions across the telecom, cloud, and data center industries.
The company’s portfolio includes fiber optic cables, network design, and deployment services, as well as software solutions for network management and cybersecurity. STL is also deeply invested in driving digital transformation through its innovative 5G, AI, and IoT-enabled technologies. With a strong commitment to sustainability, STL is leading initiatives to build future-ready digital infrastructures while reducing environmental impact.
