Home / Blog / Rivers of bits under the oceans

Rivers of bits under the oceans

The map of fibre optical cables around the world. Existing cables are in dark blue, planned ones in pale blue. Image credit: Science News 2018

Our planet is encircled by optical fibre cables laid under the oceans and connecting continents. As of 2018 there were over 350 fibre optic cables under the oceans, for a total length exceeding 1 million km and a capacity in the Pbps range (total capacity).

Although the present capacity exceeds the demand several companies are laying other fibres, exploiting new under-ocean deployment technology, and have plans to lay several more. Whilst in the past Telecom Operators were the ones forming consortia and laying cables across the oceans, today the initiatives are led by the big “digital” companies, like Facebook and Google (that already have the biggest capacity share on transoceanic cables).

Google is building a trans-Atlantic optical fibre cable that will be breaking records in terms of capacity: 250Tbps, the whole Library of Congress content can be beamed through the cable in 3 tenth of a second.

For the record, the first trans-Atlantic optical fibre cable was the TAT-8, back in 1988 with a capacity of 40,000 voice channels – equivalent, broadly speaking, to 1.2Gbps. The cable being laid by Google has over 200,000 times more capacity.

Underwater submarine optical fibre cables. Image credit: SubCom

This increase in capacity has been fostered by better electronic-optical conversion, increased processing capacity (signal processing) and by more advanced repeaters (you need to amplify the optical  signal as it crosses the oceans at intervals of about 100km. Also, an important factor is the possibility of laying in a single cable (see the photo) several fibres. The cable being laid by Google contains 12 pairs, NEC recently announced a technology to pack 16 fibre pairs in a single cable and cables with 24 pairs are just around the corner.

Why are we laying more and more cables given that current cable capacity greatly exceed demand (notice that the cable being laid by Google is doubling the current capacity across the Atlantic)? Of course an obvious answer is to take care of the increasing traffic  but that is not the only reason. With an optical fibre, as termination point technology evolves (optoelectronics) one could replace the old termination point with new ones and double (roughly speaking) the fibre capacity. The real reason is that with the decrease in cost of laying cables (decrease per bit, the cost to deploy a cable has remained fairly constant in the last 20 years but today’s cable have a capacity that is thousands times the one their “ancestors” had, hence the cost per bit has decreased thousands fold) it is becoming affordable for the big “nines” to deploy their owns. Besides, today the traffic on those cables is no longer the one of Telcos (voice traffic) but, by far, it is the one of the big “nines” (plus Netflix, of course).  The traffic pattern is completely reversed: huge non-telco traffic and little traffic generated by telco services.
If before it made sense for Google to buy capacity from telcos, today it makes much more sense to have telcos buying capacity from Google (or processing/storage capacity from Amazon….).

Clearly this should ring a bell on telcos biz. They have (almost) completely lost the service revenues to the OTT, the appropriation of long distance infrastructures by the big nines casts a dark shadow on transport. Add to this the parallel growth of the edge by private (non telco) biz and the whole scenario turns sour.

Interestingly, it should be noted that this growing web of cables can also be used to monitor earthquakes (most of them occurring in the depth of the oceans floor).

About Roberto Saracco

Roberto Saracco fell in love with technology and its implications long time ago. His background is in math and computer science. Until April 2017 he led the EIT Digital Italian Node and then was head of the Industrial Doctoral School of EIT Digital up to September 2018. Previously, up to December 2011 he was the Director of the Telecom Italia Future Centre in Venice, looking at the interplay of technology evolution, economics and society. At the turn of the century he led a World Bank-Infodev project to stimulate entrepreneurship in Latin America. He is a senior member of IEEE where he leads the Industry Advisory Board within the Future Directions Committee and co-chairs the Digital Reality Initiative. He teaches a Master course on Technology Forecasting and Market impact at the University of Trento. He has published over 100 papers in journals and magazines and 14 books.