Optical fibre cable

Also called: OFC, Optic fibre · Topic: World Transport and Communication · NCERT: Class 12, Ch 7 "Transport and Communication"

Meaning

Optical fibre cable (OFC) is a cable made of thin threads of glass that carry data as pulses of light, not as electric current.

• It matters because it was the first breakthrough of the digital age. Telephone companies replaced copper wire with it.
• Laid on the seabed as submarine cables, it carries about 99% of international internet traffic [8].

Explanation

How it works

• Old system: copper wire.
• It carried messages as electric current.
• It carried only a small amount of data and was slower.

• Electrical interference caused errors, and the wire was easy to tap (secretly listen in on).

• New system: optical fibre.

• A message is turned into light pulses.
• The light travels along very thin glass threads.
• The result is very large amounts of data, very high speed, strong security (hard to tap) and almost no errors.

Feature	Copper wire	Optical fibre
Signal	Electric current	Light pulses
Amount of data	Small	Very large
Speed	Slower	Very fast
Security	Easy to tap	Hard to tap
Errors	Affected by electrical interference	Almost error-free

How OFC helped create the internet

• Step 1: information became digital. In the 1990s, information began to be stored and sent as 0s and 1s.
• Step 2: one shared signal. Telecommunication (long-distance communication by electronic means) and computers could now use the same digital signal.
• Step 3: the two merged. Together they formed the internet. OFC is the high-capacity path that carries this digital traffic.

Submarine OFC: the world's data network

• Submarine communication cable: a fibre-optic cable laid on the seabed to carry data between countries and continents.
• Size of the network (2026): over 500 commercial cables, about 1.7 million km long in total. Together they carry hundreds of terabits of data every second [8].
• Lifespan and growth: cables were designed to last about 25 years. Cable capacity has grown by about 40% a year over the past 40 years [8].
• Cable landing station (CLS): the place on the shore where a submarine cable comes out of the sea and joins the land network.

Why cables still beat satellites

• Satellites are useful for remote places and for ships at sea.
• Cables carry much more data with less delay (latency, the time a signal takes to arrive).
• So most global traffic stays on the seabed, not in space.

Where it occurs

• India's main landing hubs:
• Mumbai: Arabian Sea coast, Maharashtra.
• Chennai: Bay of Bengal coast, Tamil Nadu.

• Kochi: Arabian Sea coast, Kerala.

• Chennai–Andaman & Nicobar Islands (CANI) cable (Bay of Bengal):

• Inaugurated in August 2020. It is about 2,313 km long [2].
• It links Port Blair and seven other islands: Little Andaman, Car Nicobar, Kamorta, Great Nicobar, Havelock, Long Island and Rangat [2].

• It has four fibre pairs. Each pair can carry up to 6.4 Tbps (terabits per second) [3].

• Kochi–Lakshadweep Islands (KLI-SOFC) cable (Arabian Sea):

• Inaugurated at Kavaratti on 3 January 2024. It is 1,868 km long and cost ₹1,072 crore plus taxes [4].
• It reaches 11 islands: Kavaratti, Agatti, Amini, Kadmat, Chetlet, Kalpeni, Minicoy, Androth, Kiltan, Bangaram and Bitra [4].

• It gives about 100 times faster internet than the earlier satellite links [4].

• World chokepoints and risk zones (a chokepoint is a narrow sea passage where many cables bunch together):

• Red Sea: cables pass through the Bab-el-Mandeb strait and along the Suez route. Cuts there in 2024 disrupted about 25% of Europe–Asia data traffic [8].
• Baltic Sea: there have been suspected deliberate cuts (sabotage).
• Tonga (Pacific Ocean): three major cuts since 2019, caused by natural hazards [8].

Don't confuse with

• Copper wire cable: carries electric current. It holds less data, is easy to tap and suffers from electrical interference. OFC carries light pulses.
• Transatlantic telegraph cable (1858, 1866): these first undersea cables carried coded electric signals (Morse code), not light. The 1858 cable failed after about three weeks. The first lasting one, laid in 1866, ran between Ireland and Newfoundland [9]. They were not optical fibre.
• Satellite links: they reach remote places and ships, but they carry far less data with more delay. Cables, not satellites, carry about 99% of international internet traffic [8].
• Telex: a network of teleprinters that sent typed messages over phone lines. It is now almost obsolete. OFC is the current backbone of communication.

Prelims Hooks

• OFC carries data as light pulses, not electric current. It is fast, secure (hard to tap) and almost error-free.
• About 99% of international internet traffic goes through submarine cables, not satellites [8].
• CANI = Chennai–Port Blair, Bay of Bengal, 2020, about 2,313 km [2]. KLI-SOFC = Kochi–Kavaratti, Arabian Sea, 2024, 1,868 km, 11 islands [4].
• Main cause of cable faults: about 80% come from human activity (ship anchors and fishing trawlers, boats that drag heavy nets along the seabed). Natural hazards like earthquakes, undersea landslides and volcanic eruptions cause fewer. There are usually 150–200 incidents a year [8].
• The International Advisory Body for Submarine Cable Resilience was formed by the ITU (International Telecommunication Union) and the ICPC (International Cable Protection Committee). It has 42 members, met first on 12 December 2024 and held a summit in Abuja, Nigeria, in February 2025 [7].
• Trap: the 1866 Ireland–Newfoundland cable was a telegraph cable, not an optical fibre cable [9].

Mains Points

• OFC as the base of the digital economy (GS-I, GS-III):
• OFC replaced copper and gave large, fast and secure data flow.
• Digital data in the 1990s merged telecommunication and computers into the internet.

• This made services trade and the quaternary sector (knowledge-based work) possible. Growth of India's data centres from 375 MW in 2020 to more than 1,500 MW needs more cable landings [6].

• Submarine OFC is critical infrastructure under threat (GS-III):

• About 99% of data runs through 500+ cables that bunch together at chokepoints like the Red Sea and Bab-el-Mandeb [8].
• Anchors, trawlers, earthquakes and suspected sabotage (Baltic Sea) can cut them. Few repair ships exist, so repairs can take weeks.

• So cable security is now part of geopolitics and maritime security.

• India's response:

• Island cables: CANI (2020) and KLI-SOFC (2024) narrow the digital divide. They support e-governance, telemedicine, online education, banking and tourism. They also tie strategic islands near the sea lanes to the mainland [2][4].
• TRAI recommendations, June 2023: study ways to fund Indian-flagged repair ships; set up cable depots on both west and east coasts; create two categories of landing station, Main CLS and CLS-PoP (CLS Point of Presence); encourage coastal states to offer incentives and waive Right-of-Way (RoW) charges for OFC links to landing stations [5].
• Building resilience: spread routes and landing points across both coasts to reduce dependence on Mumbai and Chennai, and work with other countries through the ITU–ICPC Advisory Body [7].

Related concepts

• Communication
• Telephone and telegraph
• Telecommunication
• Mass media
• Submarine communication cable

Read more

• Communication: telegraph and telephone to optical fibre and submarine cables