Atul Kumar Gupta, Scientist-G, C-DOT
Achieving the performance promised by 6G, such as peak speeds of up to one terabit per second, will not be possible without fibre connectivity extending all the way to the end user.
Moreover, India’s digital landscape has evolved rapidly between 2020 and 2024 with internet usage increasing from 43 per cent to 58 per cent of the population. This growth, along with the increase in mobile data consumption (from 13.5 GB to 27.5 GB) and total mobile data traffic (9.6 EB to 21.5 EB), highlights the need for a robust optical fibre backbone to support continued digital expansion.
Fibre networks now form the foundation layer of the telecom infrastructure, supporting 4G/5G, broadband, data centres, cloud services and future 6G networks. Earlier, towers were connected using radio links, which are no longer sufficient. Fibre offers high capacity, low latency and scalability – key elements for the success of Digital India. As of March 2025, India has 4.21 million route km of OFC network.
C-DOT’s optical and quantum innovations
C-DOT is actively developing indigenous solutions across both core and access optical networks. In the core segment, it has built dense wavelength division multiplexing (DWDM) systems supporting 100G and 200G per wavelength and is working towards 400G. These solutions have passed field trials, received the Telecommunication Engineering Centre’s (TEC) approval, and have been transferred to manufacturers.
C-DOT has also developed optical transport network (OTN) cross-connects with 8-12 terabit capacity, along with essential software such as network planning tools and generalised multi protocol label switching-based control planes that support service restoration in case of failures.
Further, in the access segment, C-DOT already provides gigabit passive optical network (G-PON), 10 gigabit symmetric PON (XGS-PON) and next-generation PON 2 (NG-PON2) solutions. The system is designed around a central optical line terminal (OLT) connected through splitters to optical network terminals (ONTs) at the user premises. As demand increases, XGS-PON line cards can be added to the same fibre infrastructure at different wavelengths. A coexistence element manages this transition. To increase efficiency, C-DOT has started offering Combo PON, which enables both G-PON and XGS-PON to operate from a single line card, eliminating the need for separate coexistence elements. NG-PON2 can also be deployed on the same fibre using new wavelengths to deliver even higher bandwidths. Currently, more than 5,000 OLTs and 250,000 ONTs based on C-DOT designs are functional in live networks.
Furthermore, C-DOT has developed a wavelength division multiplexing-PON (WDM-PON)-based solution that reduces the fibre count by combining wavelengths for transmission over a single fibre. The system supports speeds of up to 25 Gbps over distances of 10 km, and is compliant with open radio access network specifications.
C-DOT offers a network planning tool that helps network operators plan and simulate networks with an automated control plane. In addition, a remote fibre monitoring system has been developed to detect fibre cuts and quality degradation in real time. This system can report fault locations and integrates with the geographic information system for precise mapping. However, given the sensitive nature of data transmitted over optical networks – from financial transactions to government communications – ensuring secure transmission is critical. While encryption is in place, evolving cyberthreats continue to attack vulnerabilities in current systems.
To address this, C-DOT has developed a quantum key distribution (QKD) system. This technology provides theoretically unbreakable keys for encrypting data. If eavesdropping is detected, the system can reroute or halt transmission. The QKD solution is based on European Telecommunications Standards Institute standards and can be overlaid on to existing networks. It supports differential phase shift and coherent one-way protocols. In addition, C-DOT has developed a 100G Layer 1 Quantum-Safe Encryptor by integrating post-quantum cryptographic engines into its DWDM platform.
Commercialisation of quantum communication
C-DOT is now shifting its focus from traditional optical systems to integrated quantum-secure networks and is capable of delivering customised solutions based on specific deployment needs. It has developed indigenous end-to-end telecom solutions encompassing wireless, optical, switching, post-quantum cryptography, QKD, 4G/5G, artificial intelligence, internet of things, machine-to-machine communication, etc. Indian Railways has issued a tender, which is currently under evaluation, and the Defence Research and Development Organisation has released a technical standard that has been awarded to one of the Department of Telecommunications’ partners.
Based on a presentation by Atul Kumar Gupta, Scientist-G, C-DOT
