OCEAN NETWORKS, INC.
THE HISTORY OF
SUBMARINE TELECOMMUNICATIONS CABLES
From Telegraph Wire to Global Fiber-Optic Infrastructure
The Atlantic Telegraph Cable Fleet at Berehaven, 1866. Robert Charles Dudley, The Metropolitan Museum of Art. Public domain.
OCEAN NETWORKS, INC. | ENGINEERING & TRAINING SERIES
August 2026
Executive Summary
Submarine telecommunications cables are among the foundational infrastructures of the modern world. Their history begins with the nineteenth-century electrical telegraph, when engineers learned to insulate copper conductors against seawater and protect them mechanically for installation on the seabed. The first practical cross-Channel service between Britain and France began in 1851, and the first transatlantic telegraph cable operated briefly in 1858. A durable Atlantic connection followed in 1866, when the cable-laying ship Great Eastern completed the route between Ireland and Newfoundland.[1][2]
The technology then evolved through several distinct eras: global telegraph networks, coaxial telephone cables, early digital transmission, fiber optics, optical amplification, wavelength-division multiplexing, coherent transmission, and today’s high-fiber-pair systems. Each transition increased capacity by orders of magnitude while preserving the same basic system challenge: build a route that can survive decades underwater, monitor it from shore, and repair it when a fault occurs.
Today, submarine fiber-optic cables carry more than 99 percent of intercontinental data traffic, supporting financial markets, cloud computing, government communications, enterprise networks, and consumer Internet services.[7] Their strategic importance is therefore both a continuation of cable history and a direct consequence of it.
Figure 1. Major milestones in the development of submarine telecommunications cables. Original illustration.
Central theme: The transmission medium changed from copper to glass, and signaling changed from electrical pulses to optical wavelengths, but the engineering lifecycle—route design, manufacture, marine installation, testing, monitoring, fault localization, repair, and restoration—has remained remarkably consistent.
Contents
1. Origins: Telegraphy, Insulation, and the First Sea Crossings
2. The 1858 Transatlantic Cable: Proof of Possibility
3. 1866: The Great Eastern and the First Durable Atlantic Link
4. The Global Telegraph Network and the Cable Empires
5. Cables as Strategic Infrastructure: 1900–1945
6. The Coaxial Telephone Era and TAT-1
7. The Fiber-Optic Revolution and TAT-8
8. Optical Amplification, WDM, and the Internet Build-Out
9. The Cloud Era, Coherent Optics, and Spatial Division Multiplexing
10. The Parallel History of Cable Installation, Protection, and Repair
11. What the History Teaches Modern Cable Developers
Appendix A. Milestone Timeline
Appendix B. Glossary
References and Image Credits
Introduction: A Network Hidden Beneath the Sea
Long-distance communications once moved only as fast as ships. The electrical telegraph changed that on land, but oceans remained a physical barrier until engineers could create a conductor that would transmit a signal reliably while submerged. The key nineteenth-century breakthrough was not merely the telegraph instrument; it was the ability to combine a conductive core, electrical insulation, mechanical protection, and specialized marine installation methods into a practical submarine system.
That combination created a new class of infrastructure. Submarine cables shortened diplomatic and commercial communications from days or weeks to minutes, transformed news and finance, created new geopolitical dependencies, and eventually became the physical transport layer for the global Internet. The history is therefore simultaneously a story of materials science, electrical and optical engineering, marine operations, finance, regulation, and geopolitics.
1. Origins: Telegraphy, Insulation, and the First Sea Crossings
The 1840s and early 1850s established the basic materials and marine practices of cable engineering.
The commercial electrical telegraph spread rapidly across Europe and North America during the 1840s. Extending telegraphy across water required a cable that would conduct the signal while preventing seawater from acting as an electrical path. Gutta-percha—a natural latex obtained from trees in Southeast Asia—became the critical insulating material for early submarine telegraph conductors because it could form a continuous waterproof layer around copper wire.
In 1850, an experimental telegraph cable was laid between Britain and France across the English Channel. It did not remain in service, but an improved armored cable was installed the following year and supported regular service. The ITU identifies the Britain–France cable of 1850 and the regular service begun in 1851 as the beginning of practical international submarine telegraphy.[1]
Figure 2. Simplified comparison of an 1850s telegraph cable and a modern optical cable. Original illustration; construction varies by cable type.
The early engineering vocabulary remains recognizable today. Cable designers had to balance electrical performance, tensile strength, flexibility, abrasion resistance, manufacturability, and the mechanical loads imposed during paying out from a ship. Near shore, where anchors, fishing activity, surf, and seabed movement posed greater risk, heavier protection was needed. In deep water, cable weight and installation tension became dominant constraints.
Continuity with modern systems: Modern fiber-optic cables use radically different transmission technology, but still vary armor, protection, and installation methods according to water depth and external threat.
2. The 1858 Transatlantic Cable: Proof of Possibility
A technical failure that nevertheless proved that continents could be electrically connected beneath the ocean.
The Atlantic posed a much harder problem than the English Channel. The route was thousands of kilometers long, deep-ocean pressure was extreme, cable manufacture had to be highly consistent, and electrical signaling over such a long insulated conductor suffered from resistance and capacitance. The Atlantic Telegraph Company, associated most prominently with Cyrus W. Field, organized repeated attempts beginning in the 1850s.
Figure 3. Historical map of the 1858 Atlantic cable route. Public-domain historical map; reproduced via Brewminate.
In August 1858, a cable between Ireland and Newfoundland successfully carried transatlantic telegraph traffic. The event was celebrated internationally because it demonstrated that near-instantaneous electrical communication across an ocean was possible. However, the cable performed poorly and failed after only a few weeks. The failure exposed weaknesses in cable manufacture, electrical testing, signaling practice, and system operation.[1][2]
One important lesson was that submarine cable engineering had to be treated as a complete system discipline. A cable could be mechanically intact but electrically degraded; an aggressive signaling method could damage insulation; and shore-terminal decisions could determine the life of thousands of kilometers of wet plant. The 1858 project therefore became both a landmark achievement and a case study in why design margins, testing, and operational discipline matter.
3. 1866: The Great Eastern and the First Durable Atlantic Link
Improved cable design, better instruments, and a purpose-adapted cable-laying platform converted the Atlantic experiment into reliable infrastructure.
Figure 4. Great Eastern and support vessels at Berehaven before the 1866 Atlantic cable expedition. Robert Charles Dudley, The Metropolitan Museum of Art. Public domain.
The 1866 expedition succeeded because several lessons from earlier failures had been incorporated. Cable manufacturing and handling improved, electrical theory and measurement advanced, and the enormous Great Eastern provided an unusually stable platform with sufficient capacity to carry the cable. The ship could pay out long continuous lengths while engineers monitored electrical continuity and mechanical tension.
The Great Eastern completed a working Atlantic cable in July 1866. The expedition then recovered the end of the cable lost during the 1865 attempt and completed that line as well, leaving two working transatlantic connections. The Metropolitan Museum of Art’s documentation of the expedition notes that the 1866 fleet reached Newfoundland after laying roughly 1,960 miles of working cable and that two functioning cables were established that year.[2]
Figure 5. Landing the Shore End of the Atlantic Cable, 1866. Robert Charles Dudley, The Metropolitan Museum of Art. Public domain.
The 1866 success marked the point at which oceanic telegraphy moved from heroic experiment toward dependable commercial infrastructure. The economics changed immediately: governments, news organizations, banks, trading houses, and large commercial enterprises could now move information across the Atlantic on a time scale fundamentally different from physical transportation.
Why 1866 matters: The cable was not simply “another attempt.” It demonstrated a repeatable technical and commercial model for long-haul submarine telecommunications and established many practices that later became standard in route engineering, cable manufacture, laying, testing, and repair.
4. The Global Telegraph Network and the Cable Empires
From the 1870s to the early twentieth century, submarine cables became a global network rather than a collection of individual crossings.
After the Atlantic breakthrough, submarine telegraph routes expanded rapidly through the Mediterranean, around Africa, to India and Asia, across the Pacific, and to South America. Cable stations were established at geographically strategic landing points and islands, and large cable companies developed specialized fleets and maintenance organizations. By the turn of the twentieth century, U.S. Navy historical material describes a world with close to 200,000 nautical miles of submarine telegraph cable.[3]
Figure 6. The “All Red Line,” 1902–1903, depicting a British imperial communications concept built around submarine and land telegraph routes. George Johnson. Public domain via Wikimedia Commons.
The “All Red Line” is a useful illustration of how cable routes became instruments of political economy and imperial strategy. The objective was not merely to connect places; it was to connect them through routes and territories considered politically reliable. Cable landing rights, relay stations, concessions, ownership, and access to repair capacity therefore became strategic issues as well as commercial ones.
This era also produced the institutional foundations of modern international telecommunications. Cross-border telegraph systems had incompatible operating practices and tariffs, prompting international agreements and ultimately the creation of the International Telegraph Union in 1865, the predecessor of today’s ITU.[1]
5. Cables as Strategic Infrastructure: 1900–1945
The same networks that accelerated commerce became targets, intelligence sources, and instruments of state power.
By the early twentieth century, submarine cables were recognized as critical national infrastructure. Control of routes affected diplomatic communications, military command, commercial intelligence, and the ability to communicate with overseas territories. Cable cutting had already been used in nineteenth-century conflicts, and it became a deliberate wartime strategy in the twentieth century.
At the opening of the First World War, Britain moved rapidly against German trans-oceanic telegraph cables, forcing more German long-distance traffic onto routes that could be intercepted. U.S. Naval History and Heritage Command sources describe British cable-cutting operations as part of the communications-intelligence environment surrounding the Zimmermann Telegram and other wartime traffic.[3]
The strategic lesson has persisted: physical diversity, route diversity, ownership, landing rights, repair access, and operational security are not secondary matters. They are fundamental features of network resilience. Modern debates about cable security are therefore not entirely new; they are the latest form of questions that have existed since cables first became essential to national communications.
Historical pattern: As soon as submarine cables became economically indispensable, they also became strategically significant. Commercial resilience and national-security resilience have been intertwined for more than a century.
6. The Coaxial Telephone Era and TAT-1
In 1956, submarine cables crossed from telegraph-dominated communications into reliable transatlantic voice service.
Figure 7. Section of TAT-1 cable with layers stripped back. Photo by Geni, Wikimedia Commons, CC BY-SA 4.0.
7. The Fiber-Optic Revolution and TAT-8
The move from copper to glass transformed the capacity, economics, and architecture of submarine systems.
Optical fiber offered a fundamentally different transmission medium: light rather than electrical current, much lower attenuation over useful wavelengths, enormous bandwidth, and immunity to electromagnetic interference. During the 1970s and 1980s, rapid progress in semiconductor lasers, low-loss fiber, optical detectors, digital multiplexing, and undersea repeater technology made transoceanic fiber systems practical.
TAT-8 entered service in 1988 as the first transatlantic fiber-optic cable. IEEE historical sources identify it as the first transatlantic optical-fiber system and commonly cite an initial transmission rate of approximately 280 Mb/s.[5] In retrospect, that capacity is tiny compared with modern systems, but the architectural transition was decisive: the future of long-haul submarine communications had moved from coaxial copper to optical fiber.
Early optical submarine systems still relied on submerged repeaters that regenerated the digital signal electronically. That approach worked, but each repeater was tied to a specific line rate and signal format. The next breakthrough—optical amplification—would remove much of that electronic rigidity and enable a much more scalable transmission architecture.
Technology inflection point: TAT-8 mattered less for its absolute capacity than for the medium it validated. Once glass fiber became the wet-plant transmission path, subsequent advances could multiply capacity without changing the basic seabed route.
8. Optical Amplification, WDM, and the Internet Build-Out
The 1990s converted submarine fiber from a fast digital pipe into a scalable optical platform.
The erbium-doped fiber amplifier (EDFA) was one of the most important developments in optical communications. Instead of converting each optical signal back to electronics at every submerged repeater, an EDFA could amplify light directly in the optical domain. ITU historical material describes the arrival of fiber amplifiers around 1989 and their commercial availability around 1990 as the beginning of a new phase of optical-system development.[6]
Optical amplification enabled wavelength-division multiplexing (WDM), in which many optical carriers at different wavelengths share the same fiber. Dense WDM then increased the number of usable wavelengths and made capacity upgrades progressively more dependent on terminal equipment rather than wholesale replacement of the wet plant. This separation between long-life submerged infrastructure and upgradable terminal technology became a defining economic characteristic of modern submarine systems.
During the late 1990s and early 2000s, Internet and telecommunications growth drove a large wave of private cable construction. The boom produced extensive new route diversity and capacity, followed by a severe industry correction when projected demand and financing assumptions proved too aggressive. Nevertheless, much of the infrastructure installed during that period became part of the platform on which subsequent global Internet growth was built.
Figure 8. Simplified architecture of a modern repeatered optical submarine cable system. Original illustration.
9. The Cloud Era, Coherent Optics, and Spatial Division Multiplexing
Modern systems optimize the entire electrical-optical-mechanical chain rather than relying only on faster transponders.
From the 2010s onward, large cloud and content providers became direct investors and consortium participants in submarine cable systems. Their traffic profiles—data-center replication, cloud services, video distribution, search, social platforms, AI workloads, and enterprise connectivity—rewarded high-capacity routes between major data-center regions and encouraged new ownership and commercial models.
At the same time, coherent optical transmission brought sophisticated digital signal processing to submarine terminal equipment. Coherent receivers recover both amplitude and phase information and can support advanced modulation, polarization multiplexing, and powerful forward-error correction. This allows operators to extract much more information from the finite optical signal-to-noise budget of a transoceanic fiber pair.
Modern design has increasingly emphasized spatial division multiplexing (SDM): using more fiber pairs, often at lower optical power per fiber, to increase total cable capacity while remaining within the power-feed and repeater constraints of the wet plant. “Open cable” approaches also seek to define wet-plant interfaces so that terminal equipment can be selected or upgraded with greater flexibility.
The resulting system is best understood as an integrated energy and information budget. Power feeding equipment supplies constant current through the cable conductor; repeaters convert that electrical power into pump light for optical amplifiers; each fiber pair carries many wavelengths; and coherent SLTE at the landing stations continually evolves to use the available optical spectrum more efficiently.
Modern optimization: The design target is no longer simply “maximum bits per fiber.” It is maximum useful system capacity, reliability, upgradeability, and economic value across the full cable lifetime.
10. The Parallel History of Cable Installation, Protection, and Repair
Every generation of cable technology has depended on marine operations capable of installing and restoring the wet plant.
Cable ships were specialized almost as soon as submarine telegraph networks expanded. Early operations relied on grapnels, visual navigation, mechanical paying-out equipment, and electrical continuity tests. Over time, cable ships added increasingly precise navigation, dynamic positioning, deep-water grappling systems, plows, remotely operated vehicles (ROVs), acoustic positioning, side-scan and multibeam survey tools, and computerized cable-engine control.
Figure 9. ROV being launched during work on the TAT-14 cable system, 2005. Photo by Tom Jervis, Wikimedia Commons, CC BY 2.0.
11. What the History Teaches Modern Cable Developers
The strongest modern projects reflect lessons learned repeatedly over 175 years of submarine cable engineering.
Treat the cable as a system, not a product.
Wet plant, terminal equipment, power feed, landing infrastructure, terrestrial backhaul, monitoring, spares, repair capability, permits, and commercial structure must be engineered together.
Reliability is designed before installation.
The inability to access submerged equipment economically makes component qualification, factory acceptance, integration testing, and installation quality central to system value.
Route diversity has commercial and strategic value.
The global telegraph era demonstrated that route ownership and landing geography can matter as much as raw transmission capacity.
The wet plant must outlive several generations of terminal technology.
From WDM through coherent optics, many of the largest capacity gains have come from terminal upgrades applied to an existing cable system.
Repairability is part of design.
Cable type transitions, jointing plans, spares, vessel access, fault-localization capability, and maintenance agreements determine real-world restoration performance.
Demand forecasts must be paired with financing discipline.
The history of cable booms and busts shows that technical need does not automatically produce a financeable project; timing, customers, ownership structure, and capital cost matter.
Standards and interoperability reduce risk.
International standards evolved because submarine systems cross borders and combine equipment, marine operations, and operating practices from many parties.
Enduring lesson: Submarine cables are long-life infrastructure deployed in an environment that is difficult and expensive to access. Successful projects therefore reward conservative engineering, disciplined execution, and long-term operational planning.
Appendix A. Milestone Timeline
Appendix B. Glossary of Common Submarine Cable Terms
BMH — Beach Manhole — A shore-side chamber where submarine cable is transitioned, jointed, or connected to terrestrial cable infrastructure.
Cable Landing Station (CLS) — Facility housing the terminal and support equipment associated with a submarine cable landing.
Coherent transmission — Optical transmission using coherent detection and digital signal processing to recover advanced modulation formats and improve spectral efficiency.
EDFA — Erbium-Doped Fiber Amplifier — Optical amplifier that boosts signals near the 1550-nm transmission window without converting them to electronics.
PFE — Power Feeding Equipment — Terminal equipment that supplies constant electrical current through the cable conductor to power submerged repeaters and certain branching units.
Repeater — Pressure-resistant submerged unit that amplifies or regenerates signals. Modern long-haul systems generally use optical amplifiers.
SDM — Spatial Division Multiplexing — Capacity scaling approach that increases the number of spatial paths—typically fiber pairs—rather than relying only on more capacity per individual fiber.
SLTE — Submarine Line Terminal Equipment — Optical terminal equipment that transmits and receives wavelength channels over the submarine wet plant.
Wet plant — The submerged portion of the system: submarine cable, repeaters, branching units, joints, and related undersea components.
WDM / DWDM — Wavelength-division multiplexing / dense wavelength-division multiplexing: multiple optical wavelengths transmitted simultaneously through the same fiber.
Selected References
[1] International Telecommunication Union (ITU), “Overview of ITU’s History.” https://www.itu.int/en/history/pages/ITUsHistory.aspx
[2] The Metropolitan Museum of Art, Robert Charles Dudley works documenting the 1866 Atlantic cable expedition. https://www.metmuseum.org/art/collection/search/383832
[3] Naval History and Heritage Command, “Telegraphy and Cable Cutting” and related World War I communications history. https://www.history.navy.mil/research/publications/documentary-histories/united-states-navy-s/telegraphy-and-cable.html
[4] Engineering and Technology History Wiki / IEEE Milestone, “The First Submarine Transatlantic Telephone Cable System (TAT-1), 1956.” https://ethw.org/Milestones:The_First_Submarine_Transatlantic_Telephone_Cable_System_(TAT-1),_1956
[5] IEEE historical literature on TAT-8 and the transition to transoceanic optical fiber systems. https://ieeexplore.ieee.org/document/16377/
[6] ITU-T G-series Supplement 42, historical phases of optical fiber transmission, including optical amplification and WDM. https://www.itu.int/rec/T-REC-G.Sup42-201404-S/en
[7] International Telecommunication Union, “Building resilient connectivity,” noting that submarine cables carry over 99% of intercontinental data traffic. https://www.itu.int/160/vision/building-resilient-connectivity/
[8] ITU-T Recommendation G.972, definitions and architecture for optical fiber submarine cable systems. https://www.itu.int/rec/T-REC-G.972/en
Image Credits and Licensing
Cover / Figure 4: Robert Charles Dudley, “The Atlantic Telegraph Cable Fleet Assembled at Berehaven,” 1866. The Metropolitan Museum of Art. Public Domain.Source
Figure 3: Historical map of the 1858 Atlantic cable route; public-domain historical map reproduced via Brewminate.Source
Figure 5: Robert Charles Dudley, “Landing the Shore End of the Atlantic Cable,” 1866. The Metropolitan Museum of Art. Public Domain.Source
Figure 6: George Johnson, “All Red Line,” 1903. Wikimedia Commons. Public Domain.Source
Figure 7: Geni, “TAT 1 cable.JPG,” 2016. Wikimedia Commons. CC BY-SA 4.0 (also offered under other listed licenses).Source
Figure 9: Tom Jervis, “Launching the ROV, TAT-14,” 2005. Wikimedia Commons. CC BY 2.0.Source
Figures 1, 2, and 8: Original illustrations created for this document.
Note: Historical dimensions, capacities, and dates are presented at the level appropriate for a general engineering history. Specific systems often had multiple commissioning milestones, later capacity upgrades, or differing contemporary descriptions.
Courtesy of Ocean Networks
Download a Submarine Cable System History Map HERE
TAT-1, the first transatlantic telephone cable system, entered service in September 1956.
It used coaxial cable and submerged electronic repeaters to overcome attenuation across the Atlantic. The system initially provided 36 voice-frequency channels and represented a major step in reliability and bandwidth compared with earlier telegraph cables.[4]
TAT-1 consisted of two directional cable paths and demonstrated that active undersea electronics could operate reliably for years in deep water. This was an extraordinary reliability requirement: a failed submerged repeater could not be serviced in place; the cable had to be located, recovered, repaired, and relaid.
The achievement created the engineering culture that still characterizes repeatered submarine systems—extreme component qualification, conservative reliability design, rigorous factory testing, and detailed system acceptance procedures.
Through the 1960s and 1970s, submarine telephone cables expanded in capacity and geographic reach. Communications satellites also became an important part of the international network, especially for broadcast and certain long-distance services. Rather than eliminate cables, satellites and cables developed complementary roles. As digital traffic grew, the superior bandwidth economics and lower propagation delay of optical fiber would eventually make submarine cables the dominant infrastructure for bulk intercontinental data.
Repair remains a physical marine operation. A fault must be localized electrically or optically, a repair vessel mobilized, and the cable recovered from the seabed or accessed by ROV. Damaged cable is removed, new cable and joints are installed and tested, and the repaired section is relaid—often with burial or other protection in shallow water.
The methods are more precise than in the nineteenth century, but the basic operational sequence is recognizable: locate, recover, test, splice, verify, and redeploy.
Modern maintenance agreements and regional repair arrangements exist because faults are time-critical and specialized vessels are scarce assets. Cable resilience therefore depends not only on cable design but also on access to crews, spares, permits, ports, and repair ships.
Shallow-water protection has likewise evolved. Armored cable, route engineering, burial by plow or jetting, articulated pipe, rock placement, horizontal directional drilling at selected landings, and cable awareness programs all address the same historic reality: most practical cable threats are concentrated where human activity is greatest.
