ESAT-2: A Submarine Link Between Ireland and the United Kingdom
ESAT-2 is a submarine telecommunications cable connecting
Sandymount in Ireland to
Southport in the United Kingdom. With a total length of 245 km, it is owned by Esat BT and has been listed as in service since 2000 according to GeoCables records. This cable serves as one of the many links facilitating connectivity between Ireland and the UK, a corridor of significant importance for both nations' telecommunications infrastructure.
What makes ESAT-2 particularly interesting is the limited amount of publicly disclosed information about its technical specifications, such as design capacity, fiber pair count, supplier, and technology. Additionally, while GeoCables records indicate that ESAT-2 became ready for service in 2000, any conflicting industry sources would need to be surfaced for clarity. The cable's latency characteristics and its role in redundancy within the corridor also merit close examination.
Quick facts
| Name | ESAT-2 |
| Length | 245 km |
| Ready for Service | 2000 (GeoCables database) |
| Owners | Esat BT |
| Status | In service |
| Design Capacity | Not disclosed |
| Fiber Pairs | Not disclosed |
| Supplier | Not disclosed |
| Technology | Not disclosed |
| Landing Points | Sandymount (Ireland), Southport (United Kingdom) |
| Other Cables at Southport | EXA North and South, Rockabill |
Route
ESAT-2 spans 245 km across the Irish Sea, connecting Sandymount in Dublin, Ireland, to Southport in Merseyside, United Kingdom. Sandymount serves as a key landing point for Ireland's international connectivity, while Southport is a hub for multiple submarine cables, including EXA North and South and Rockabill. This geographic corridor is a well-established route for submarine cables, owing to the proximity of the two countries and their strong economic and digital ties.
Why it was built and what it carries
The ESAT-2 cable was built to enhance telecommunications connectivity between Ireland and the UK, supporting the increasing demand for international data exchange in the late 1990s and early 2000s. As Ireland's economy grew and its role in the global tech sector expanded, reliable connections to the UK became essential for businesses, internet service providers, and other stakeholders. While specific details about its data capacity and usage are not publicly disclosed, ESAT-2 likely plays a role in carrying internet traffic, private enterprise data, and other forms of digital communication between the two nations.
History: what can be established
GeoCables records indicate that ESAT-2 became ready for service in 2000. If industry sources suggest a different year, the discrepancy could arise from differences in the definition of "ready for service" (e.g., operational testing vs. commercial availability), delays in documentation, or errors in reporting. Esat BT, the cable's owner, is a telecommunications company with operations in Ireland and the UK, making it a logical operator for this trans-Irish Sea cable.
Capacity and technology
Publicly available information does not disclose ESAT-2's design capacity, fiber pair count, supplier, or specific technology. Without operator documentation, it is impossible to state these parameters definitively. Given its readiness date of 2000, ESAT-2 likely employs technology typical of that era, such as optical amplification and wavelength-division multiplexing (WDM). However, attributing specific features without evidence would be speculative.
Latency: the physics
Theoretical latency for light propagation over the 245 km wet segment is approximately 1.2 ms one-way, or 2.4 ms round-trip (RTT), assuming light travels at 200,000 to 204,000 km/s in fiber. Real-world latency measurements, however, are higher due to land tails, terminal equipment, and routing inefficiencies. GeoCables live measurements show minimum RTTs of 10.6 ms (Sandymount to Southport) and 19.5 ms (Southport to Sandymount), with averages of 49.9 ms and 20.3 ms, respectively. These figures reflect the full internet path, not the cable alone, and include additional network hops and processing delays.
Redundancy: what happens if it breaks
If ESAT-2 were to experience an outage, redundancy in the corridor is supported by other cables landing at Southport, such as EXA North and South and Rockabill. Repairing submarine cables typically involves deploying specialized ships equipped with remotely operated vehicles (ROVs) to locate and fix the fault, which can take weeks depending on weather conditions and the nature of the damage. The presence of multiple cables in this corridor mitigates the risk of prolonged connectivity disruptions.
Bottom line
- ESAT-2 is a 245 km submarine cable connecting Ireland and the UK, owned by Esat BT.
- GeoCables records its ready-for-service year as 2000; conflicting dates from industry sources should be investigated.
- Technical specifications such as design capacity, fiber pairs, supplier, and technology are not publicly disclosed.
- Theoretical latency over the wet segment is approximately 2.4 ms RTT, but real-world measurements are higher.
- Redundancy in the corridor is supported by other cables landing at Southport, including EXA North and South and Rockabill.