Undersea Cables: Importance & Threats

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Disruptions to SEA-ME-WE 4 and IMEWE undersea cables in the Red Sea increased India-Europe latency, straining cross-regional connectivity.

What are Undersea Cables?

Undersea cables are fibre-optic cables laid on the ocean floor, carrying over 95% of international internet traffic. They form the backbone of the global internet, enabling cloud services, digital trade, and international communications.
They use total internal reflection, transmitting terabits of data as light pulses.
They connect internet service providers and telecom operators everywhere with those in other countries.
There are more than 600 active and planned submarine cables (Jan 2025) lying on the ocean floor.

Fibre optics refers to the technology and method of transmitting data as light pulses along a glass or plastic strand or fibre.

Data Transmission: Fibre optics transmits data in the form of light particles, or photons, that pulse through a fibre optic cable.
Total Internal Reflection: When light signals are sent through the fiber optic cable, they reflect off the core and cladding in a series of zig-zag bounces, following a process called total internal reflection.
- The glass fibre core and the cladding each have a different refractive index that bends incoming light at a certain angle.
Optical Transmitters & Receivers: Convert electrical signals into light (transmitters) and back into data (receivers).

Backbone of the global Communication: Carrying approximately 99% of internet traffic and supporting critical services such as commerce, finance, government operations, digital health, and education.
Enable fast and reliable Internet: They ensure seamless, low-latency data exchange, smooth browsing, streaming, and communication.
Cost-Effective Long-Term Connectivity: Despite high initial costs, subsea cables offer more reliable and affordable connectivity over time.
Geopolitical Leverage: Control over subsea cable routes is increasingly seen as a national security and strategic asset.
- China is expanding undersea cables via its Digital Silk Road, highlighting need for alternatives.
Digital Resilience: Enhances redundancy and reduces vulnerabilities to sabotage, cyberattacks, or natural disasters (e.g., Red Sea cable disruptions in 2024).

While satellite internet (e.g., Starlink) is useful in remote areas, undersea cables are preferred due to following reasons:

Lower Latency: Satellites have much higher latency compared to undersea cables.
- Latency refers to the time delay in data transmission from one point to another.
Higher Bandwidth: Limited bandwidth of Satellites makes them unsuitable for large-scale AI and cloud applications.
Less Expensive: Satellites are more expensive and less reliable than fibre-optic networks.

Damage from Anchors & Earthquakes: Ships dropping anchors and natural disasters can snap cables, disrupting global connectivity.
- E.g., an estimated 150-200 faults occur globally every year due to fishing, anchoring, natural hazards, and equipment failure.
Sabotage: E.g., in 2023, Taiwan accused two Chinese vessels of cutting the only two submarine cables to the Matsu Islands, leaving 14,000 residents without internet for six weeks.
Maintenance Issues: Repairs require deep-sea robots and specialised ships, making them time-consuming and costly.
- Multiple cable failures off the coast of West Africa in March 2024 led to significant internet disruptions affecting at least 10 nations.
Geopolitical Concerns: Countries compete for control over strategic cable routes, leading to security and regulatory challenges.
- Laying and maintaining subsea cables involves billions of dollars, limiting expansion in some regions.
Cybersecurity Threats: Undersea cables are vulnerable to espionage, hacking, and sabotage, posing risks to data security.

International Cable Protection Committee (ICPC): Founded in 1958, ICPC is the world’s leading organisation promoting submarine cable protection and resilience.
International Advisory Body for Submarine Cable Resilience: Launched by the International Telecommunication Union (ITU) and ICPC in 2024 to strengthen the resilience of submarine cables.
International Telecommunication Union (ITU): ITU is at the forefront of efforts to enhance the resilience of these cables through cooperation, standard-setting, and technical guidance.

The Department of Telecommunications is the nodal authority for undersea cable licensing.
Installed Base: India hosts 17 international cables across 14 landing stations in five coastal cities.
- Concentration: Cable landings are heavily concentrated in Mumbai and Chennai.
Capacity Surge: Since 2016, activated capacity rose ninefold, reaching 132 Tbps by 2023.
Next-Gen Networks: 2Africa Pearls, IAX, and IEX are major upcoming undersea cable projects.

Digital Economy growth: India’s bandwidth requirement is projected to grow at 38% between 2021-28, fuelled by rising consumption and data centre investments, making it a natural landing point for future global cable networks.
Geostrategic Location: Positioned between Europe, Southeast Asia, and Africa, India sits near key maritime choke points — the Strait of Hormuz, the Strait of Malacca and Bab-el-Mandeb making the country a natural hub for global cable networks.

Meagre Number: India hosts only 17 international subsea cables (Singapore – 26). 15 of 17 cables land in a 6-km stretch in Mumbai, creating vulnerability and regional bottlenecks.
Cumbersome Licensing Process: Requires 50+ clearances from multiple ministries.
No Domestic Repair Fleet: Dependent on foreign-flagged ships (from Dubai and Singapore), with 3–5 month delays for repairs due to slow customs, naval, and crew approvals.
Limited Cable Landing Locations: Cable landing stations are concentrated in 5 cities, i.e. Mumbai, Chennai, Kochi, Tuticorin, and Thiruvananthapuram poses single-point failure risk in the event of sabotage or natural disasters.