The Submarine series of posts discusses the evolution of submarine networks alongside terrestrial ones over the past several decades. While there are similarities between these two network categories, such as the need to cover ultralong-haul distances and transport huge amounts of data, there are also important differences that have dictated their different evolutionary paths. The series focuses on space division multiplexing (SDM) as the ultimate solution to cover future capacity needs and overcome problems of both networks.
The introduction section provides a brief history of submarine cables, which were first submerged to transmit telegraphy data approximately one and a half centuries ago. Today, submarine cable systems have become a basic component of the whole global backbone network infrastructure and serve as the most crowded, yet isolated, of deep-water networks. The traffic generated by end-users has been boosted beyond the average 50% annual growth rate due to the COVID-19 pandemic, increasing the need for speed and more bandwidth.
We will review recent and future submarine technologies, focusing on all critical sectors: cable systems, amplifiers' technology, submarine network architectures, electrical power-feeding issues, economics, and security. The authors provide an overview of all recently announced SDM-based submarine cable systems, compare their performance (capacity-distance product), and analyze the reasons that led to the first SDM submarine deployment. They also report up-to-date experimental results of submarine transmission demonstrations and perform a qualitative categorization that relies on their features.
Based on all latest advances and their study findings, the authors try to predict the future of SDM submarine optical networks mainly in the fields of fiber types, fiber counts per cable, fiber-coating variants, modulation formats, as well as the type and layout structure of optical amplifiers. Results show that SDM can offer higher capacities (in order of Pb/s) compared to its counterparts, supported by novel network technologies: pump-farming amplification schemes, high counts up to 50 parallel fiber pairs, thinner fiber coating variants (200 µm), and optimum spectral efficiency (2-3 b/s/Hz).
Then we will conclude that tradeoffs between capacity and implementation complexity and cost will have to be carefully considered for future deployments of submarine cable systems. SDM can provide a solution to cover future capacity needs and overcome problems of both submarine and terrestrial networks.
Google Cloud Platform - Submarine Network
