Submarine Network Series: Part 2- Past Evolution of Submarine Transmission Systems

The history of submarine cables can be traced back to the late 1840s when a newly discovered natural polymer called gutta percha provided the basic means for insulating cables for undersea use. In 1850, a relatively short-distance cable was submerged between the UK and France, but unfortunately, it lasted only for a few messages and was replaced by a more durable successor a year later. The first cable connecting Europe to the US became operational on August 16, 1858, but the deployment of cables across the Pacific Ocean proved to be more challenging, and transpacific telegraph cables only became operational in 1902.

It took approximately fifty more years for newer advanced cables to support voice and data communications to be deployed. TAT-1 was the first transatlantic cable used for telephony, which became operational on September 25, 1956, connecting Scotland to Clare Ville, initially supporting transmission of just 36 telephone channels. The first coaxial cables capable of transmitting frequency-multiplexed voice signals became operational in the 1960s, which eventually led to optical technology in 1986 and 1988, using optical fiber links for high-speed/capacity submarine communications.

Some significant milestones in the submarine era history include the first submarine cable supporting phone data (from San Francisco to Oakland) in 1884, the first submarine high-voltage direct current cable connecting the island of Gotland to mainland Sweden in 1954, and the first deployment of repeaters in the 1940s, boosting the TAT-1, which was the first telephone cable crossing Atlantic. The first transpacific submarine coaxial telephone cable linking Japan, Hawaii, and the US mainland was operational in 1964. The first submerged international fiber-optic cable that connected Belgium to the United Kingdom was in 1986, and the first submerged transoceanic fiber-optic cable, named TAT-8, that connected the USA to the United Kingdom and France, was in 1988.




Figure 1 depicts the historical evolution of submarine transmission systems leading to optical technology. In Figure 2, a transatlantic cable capacity comparison is illustrated from TAT-1 in 1956 to TAT-14 in 2001. Figure 3 shows the worldwide submarine cable map, which comprises 487 cables, stretching over 1.3 million km, and 1245 landing stations that are currently in service or under construction. These networks were deployed by consortia of major telecom network operators.

However, during the current century, major cloud service providers such as Google, Facebook, and Microsoft have become active investors in submarine networks. From 2016 to 2018, Google invested approximately $47 billion dollars in capital expenditure (capex) to expand and upgrade Google Cloud infrastructure. Nowadays, Google counts 134 points of presence (PoPs) and 14 major subsea cable investments globally, interconnecting all six continents. These investments have played a significant role in enabling Google to provide reliable and high-speed cloud services to customers globally.