Ile de Sein

Ile de Sein is one of the roughly sixty cable ships worldwide that keep the internet alive — laying new submarine cables and repairing broken ones, sailing for Alcatel Submarine Networks (ASN Marine).

Specifications

OperatorAlcatel Submarine Networks (ASN Marine)
Roleinstallation
FlagFrance
Built2001, Hyundai Mipo Dockyard, Ulsan
Length × beam140.36 m × 23.4 m
Cable capacity6,000 tonnes
DP classDP II
Base portMarseille, France (registry)

Equipment

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Overview

Ile de Sein is a dedicated cable installation vessel operated by Alcatel Submarine Networks (ASN Marine) under the French flag. Constructed in 2001 at Hyundai Mipo Dockyard in Ulsan, South Korea, the ship measures 140.36 metres in length with a beam of 23.4 metres — a hull form sized for the sustained deep-ocean passages that major installation projects demand.

Cable Handling and Capacity

The ship carries up to 6,000 tonnes of submarine cable distributed across four tanks: two main tanks holding 3,000 tonnes each, supplemented by two spare tanks of 250 tonnes apiece. Cable is loaded coiled into these tanks at a shore facility before departure, then paid out steadily over the stern as the vessel moves along the planned route.

Alongside the cable itself, Ile de Sein can accommodate up to 200 repeaters — the signal-amplifying housings spliced into the cable at regular intervals on long-haul fibre systems.

Positioning and Performance

The vessel holds DP II classification, meaning it uses an automated dynamic positioning system with redundant controls to hold station precisely without anchors — essential when hovering over a specific seabed location to make a splice or recover a fault. Maximum speed is 15.4 knots, with an economical transit speed of 11.5 knots.

Operator and Base

ASN Marine is the vessel-operating arm of Alcatel Submarine Networks, one of the principal contractors for submarine cable installation globally. Ile de Sein is registered at Marseille, France, positioning it with ready access to the Mediterranean and Atlantic approaches. Specific maintenance zone assignments for the vessel are not publicly documented.