Geo-Eirgrid: A Submarine Cable Linking Ireland and the United Kingdom
The Geo-Eirgrid submarine cable is a fiber-optic system connecting
Lusk in Ireland to
Deeside Clwyd in the United Kingdom. Spanning 187 kilometers, it is owned by Eirgrid and has been recorded in the GeoCables database as operational since 2012. This cable forms part of the broader telecommunications infrastructure between the two nations, though public details about its technical specifications, such as design capacity, fiber count, and supplier, remain undisclosed.
What makes Geo-Eirgrid notable is the lack of publicly available information about its technology and performance parameters. While the cable's physical latency floor can be calculated, live measurements of latency over the full internet path suggest significant additional delays, highlighting the complexity of real-world network routing. These discrepancies underscore the challenges of isolating submarine cable performance from broader internet dynamics.
Quick facts
| Cable name | Geo-Eirgrid |
| Length | 187 km |
| Ready for service | 2012 (GeoCables database value) |
| Owners | Eirgrid |
| Status | In service |
| Design capacity | Not disclosed |
| Fiber pairs | Not disclosed |
| Supplier | Not disclosed |
| Technology | Not disclosed |
| Landing points | Deeside Clwyd (United Kingdom); Lusk (Ireland) |
| Computed latency (one-way) | ≈ 0.9 ms |
| Computed latency (RTT floor) | ≈ 1.8 ms |
| Live RTT measurements | Lusk -> Deeside Clwyd: min 21.3 ms, avg 31.5 ms; Deeside Clwyd -> Lusk: min 19.0 ms, avg 72.6 ms |
🗺 Show Geo-Eirgrid on the interactive cable map
Route
The Geo-Eirgrid cable connects two landing points: Lusk in Ireland and Deeside Clwyd in the United Kingdom. Lusk is located near Dublin, a major hub for Irish telecommunications, while Deeside Clwyd is situated in North Wales, providing connectivity to the UK mainland. The corridor spans the Irish Sea, a well-traversed region for submarine cables due to the strong economic and data exchange ties between Ireland and the UK.
Why it was built and what it carries
Geo-Eirgrid was likely constructed to enhance data connectivity and redundancy between Ireland and the UK, supporting cross-border communications and economic activities. While the specific data traffic it carries is not publicly disclosed, cables in this corridor typically handle internet, enterprise, and cloud services, as well as data center interconnectivity. Eirgrid, the owner, is primarily associated with energy transmission, suggesting that the cable might also play a role in supporting grid-related communications.
History: what can be established
The GeoCables database records the cable as ready for service in 2012, and it is currently listed as in service. If industry sources suggest a different year for its commissioning, this discrepancy has not been surfaced in publicly available data. Possible reasons for such conflicts could include delays in final testing, staggered commercial activation, or differing definitions of "ready for service" (e.g., physical completion versus operational readiness).
Capacity and technology
Publicly available sources do not disclose the design capacity, fiber pair count, supplier, or specific technology used in the Geo-Eirgrid cable. Without operator documentation, attributing these parameters would be speculative. Submarine cables in this region are typically engineered for high-capacity data transmission, but the exact capabilities of Geo-Eirgrid remain unknown.
Latency: the physics
The theoretical one-way light propagation latency over the 187 km wet segment of the Geo-Eirgrid cable is approximately 0.9 milliseconds, assuming light travels through fiber at 200,000 to 204,000 km/s. The round-trip time (RTT) floor over this segment is thus approximately 1.8 milliseconds. However, live measurements conducted via remote probes show significantly higher RTTs: Lusk to Deeside Clwyd ranges from 21.3 ms to 31.5 ms, while Deeside Clwyd to Lusk ranges from 19.0 ms to 72.6 ms. These elevated values reflect additional delays introduced by land tails, terminal equipment, and network routing beyond the cable itself.
Redundancy: what happens if it breaks
In the event of a fault in the Geo-Eirgrid cable, redundancy would likely be provided by other submarine cables in the Irish Sea corridor. This region is well-served by multiple systems connecting Ireland and the UK, ensuring alternative routes for data traffic. Standard industry practices for cable repair include deploying specialized cable ships to locate, retrieve, and repair the damaged segment, minimizing downtime.
Bottom line
- Geo-Eirgrid is a 187 km submarine cable linking Lusk, Ireland, and Deeside Clwyd, UK.
- Owned by Eirgrid, it has been recorded as operational since 2012.
- Public details about its design capacity, fiber pairs, supplier, and technology are not disclosed.
- Theoretical latency is ≈ 0.9 ms one-way, but live RTT measurements are significantly higher due to network factors.
- Redundancy is likely provided by other cables in the Irish Sea corridor.