The 10 Longest Underwater Cables in the World

Ever sat and wondered what makes it possible for you to pick up your phone, dial the number of a friend or a family member who’s probably in several countries away from you, and almost immediately their face show up on your screen.

Several years ago this was impossible and we all know its possibility is attributed to the internet— but with that realization comes yet another question? What then makes the internet work? Chief amongst other things are the underwater cables. 

An underwater cable is a cable laid on the sea bed between land-based stations to carry signals across stretches of ocean and sea. 

Note that,  while underwater cables are mostly used for telecommunications signs, it is in no way limited to that.

In this article, a list of the longest underwater cables in the world in no particular order will be examined alongside every vital information about each of them. 


By J.P.Lon, CC BY 2.5, Link

The SEA-ME-WE3 cable, which connects Southeast Asia, the Middle East, and Western Europe, is the world’s longest optical submarine telecommunications connection.

It was completed in late 2000 and is managed by Singtel, a telecommunications company owned by the Singapore government. It is led by France Telecom and China Telecom.

The Consortium is made up of 92 additional telecom sector investors. In March of 2000, it was given the go-ahead.

It has a length of 39,000 kilometers (24,000 miles) and employs Wavelength Division Multiplexing (WDM) technology with Synchronous Digital Hierarchy (SDH) transmission to boost capacity and improve signal quality, particularly over long distances (this cable stretches from North Germany to Australia and Japan).

2. AAE-1

The Asia-Africa-Europe 1 (AAE-1) submarine communications cable system connects Hong Kong, Vietnam, Cambodia, Malaysia, Singapore, Thailand, Myanmar, India, Pakistan, Oman, UAE, Qatar, Yemen, Djibouti, Saudi Arabia, Egypt, Greece, Italy, and France over a distance of 25,000 kilometers.

To service the broadband market spanning Asia, Africa, and Europe, the AAE-1 cable has a capacity of at least 40 terabits per second (Tbit/s).

It became the longest underwater cable system in over a decade when it was launched for commercial use in July 2017.

The AAE-1 cable project was started by China Unicom in 2011 with the help and collaboration of Telecom Egypt.

3. Europe India Gateway

The Europe India Gateway (EIG) is an undersea communications cable system that connects the United Kingdom, Portugal, Gibraltar, Monaco, France, Libya, Egypt, Saudi Arabia, Djibouti, Oman, UAE, and India. 

The EIG stretches for about 15,000 kilometers. It was originally meant to deliver up to 3.84 terabits per second, but it was upgraded in 2015 and 2020 to deliver up to 3.84 terabits per second.

Alcatel-Lucent and TE Subcom (previously Tyco) collaborated on the cable system, which was expected to be finished in the second quarter of 2010.

The cable cost $700 million to construct and was launched in 2011. The EIG was the world’s first direct high-bandwidth optical fiber link connecting the United Kingdom and India.

FLAG FEA map.svg
GPLv3, Link

The Fibre-optic Link Around the Globe (FLAG) is a 28,000-kilometers long fiber-optic communications cable that connects the UK, Japan, India, and several other countries.

Global Cloud Xchange, and RCOM subsidiary, manages the cable. From the east coast of North America to Japan, the system runs.

In 2008, the Europe-Asia stretch was the world’s fourth-longest cable. 

In late 1997, the FLAG cable system was put into commercial use for the first time. FLAG uses synchronous digital hierarchy technology and has a speed of 10 Gbit/s.

Across 120,000 voice channels are carried over a distance of 27,000 kilometers (16,777 miles; 14,579 nautical miles) of primarily undersea cable.

5. I-ME-WE

CC BY-SA 4.0, Link

The I-ME-WE (India-Middle East-Western Europe) submarine communications cable system connects India and France and spans 13,000 kilometers (8,100 miles). 3.84 Terabits per second is the design capacity.

It has been active since 2009, with a connection to Tripoli, Lebanon, in November 2011. 

The extra bandwidth will be used by Internet Service Providers and Network Operators to provide high-bandwidth peer-to-peer IP-based broadband services like multimedia streaming, broadband Internet, and voice/video telephony.

6. SEA-ME-WE 4

CC BY 2.5, Link

The SEA-ME-WE 4 (South East Asia–Middle East–Western Europe 4) submarine communications cable system connects Singapore, Malaysia, Thailand, Bangladesh, India, Sri Lanka, Pakistan, the United Arab Emirates, Saudi Arabia, Sudan, Egypt, Italy, Tunisia, Algeria, and France.

It’s meant to be used in conjunction with, rather than as a substitute for, the SEA-ME-WE 3 cable. 

The cable runs for over 18,800 kilometers and serves as the key Internet backbone connecting Southeast Asia, India, the Middle East, and Europe.

7. SEA-ME-WE 5

The SEA-ME-WE 5 (South East Asia–Middle East–Western Europe 5) is an optical fiber undersea communications cable system that connects Singapore and France.

The cable is approximately 20,000 kilometers long and delivers broadband connectivity between Southeast Asia, South Asia, the Middle East, and Europe with a design capacity of 24 terabits per second. 

Alcatel-Lucent built the section from France to Sri Lanka, and NEC built the section from Sri Lanka to Singapore.

Construction began on June 6, 2014, and ended in December 2016. On January 16, 2017, an official launch event was conducted in Honolulu, Hawaii.

8. SAm-1

South America-1 (SAm-1) is a submarine optical communications cable. It began serving the United States, Puerto Rico, Brazil, Argentina, Chile, Peru, and Guatemala in 2000. SAm-1 was extended to Ecuador and Colombia in 2007. 

When it was approved in 2000, SAm-1 was to have four fiber pairs operating at 40 Gbit/s in a self-healing ring configuration, expandable to 48 channels at 10 Gbit/s each, for a total design capacity of 480 Gbit/s, and multiple upgrade capability using dense wave division multiplexing up to 1.92 terabits per second, with a total length of 25,00 kilometers and a total capacity of 480 Gbit/s.

9. Southern Cross Cable

Southern Cross Cable route.svg
CC BY-SA 3.0, Link

The Southern Cross Cable is a trans-Pacific telecommunications network that was launched in 2000. Southern Cross Cables Limited, a Bermuda-based corporation, manages the network. 

The network consists of 28,900 kilometers of underwater fiber-optic cables and 1,600 kilometers of terrestrial fiber optic cables, all of which are connected in a triple-ring configuration. Each cable had a bandwidth capacity of 120 gigabits per second at first.

This bandwidth was doubled in April 2008, and by the end of the year, it had been upgraded to 860 gigabit/s. In May 2010, Southern Cross upgraded the existing system to 1.2 Tbit/s.

10. SAT-3/WASC

CC BY 2.5, Link

SAT-3/WASC, or South Atlantic 3/West Africa, is an acronym for South Atlantic 3/West Africa.

The Submarine Line is a submarine communications cable that runs from Portugal to South Africa, with stops in numerous West African countries along the way.

It’s part of the SAT-3/WASC/SAFE cable system, which connects South Africa to Asia via the SAFE cable. 

The SAT-3/WASC/SAFE system provides an alternative to cable routes that traverse through the Middle East, such as SEA-ME-WE 3 and FLAG, for telecommunications traffic between Asia and Europe.

SAT-3 has a 340 Gbit/s capacity, while SAFE has a 440 Gbit/s capacity.

The length of this underwater cable is 28000 kilometers.