Coral Sea Cable System (CS²)

The cable this site is named after

The Coral Sea Cable System — CS² to the people who built it — is a 4,700 km fibre-optic submarine cable connecting Sydney to Port Moresby (Papua New Guinea) and Honiara (Solomon Islands). Built by Alcatel Submarine Networks and delivered by Vocus, the four-fibre-pair international system was designed to deliver up to 20 Tbit/s to each country — 40 Tbit/s in total — replacing satellite links and a single ageing cable as the region's connection to the global internet.

The project also included the 730 km Solomon Islands Domestic Network (SIDN), extending connectivity from Honiara to Auki on Malaita, Noro on New Georgia, and Taro Island — the first domestic submarine network in the country's history.

Who paid, and who owns it

The Australian Government provided the majority of project funding, with the governments of Papua New Guinea and Solomon Islands together contributing up to one third of project costs. Ownership sits with the two Pacific nations: PNG DataCo and the Solomon Islands Submarine Cable Company majority-own the international system and receive its revenue, and Solomon Islands owns its domestic network outright. The decision for Australia to fund the system followed well-documented security concerns in Canberra about an earlier proposal for the Solomon Islands link to be built by a Chinese supplier.

Day-to-day, the system is operated through the Coral Sea Cable Company, jointly held by the Commonwealth of Australia, PNG DataCo and the Solomon Islands Submarine Cable Company.

The build

Marine survey work began in 2018, cable manufacture and loading followed at ASN's plants, and the main lay — including a deepest point of roughly 4,650 metres in the Solomon Sea — was completed through 2019. The final splice was made in September 2019 and the system entered commercial service in early 2020.

The complete build diary written by the original project team — from factory acceptance tests to the final splice — is preserved in [our archive](/archive), because before this site was an atlas, it was the project site for this very cable.

Why it matters

CS² is a textbook example of infrastructure diplomacy: a development-driven cable that doubled as strategic policy, delivered on an aggressive timeline, and transformed connectivity economics for two Pacific nations — World Bank-cited research at the time projected billions of dollars in additional regional GDP from improved connectivity. It is also this publication's reason for existing.