Northern Lights: a short domestic submarine cable in the United Kingdom
The Northern Lights submarine cable is a 67-kilometer fiber-optic system connecting
Dunnet Head and
Skaill, both located in the United Kingdom. Owned by BT and listed as in service, the cable has been operational since 2008 according to GeoCables data. Its short length and domestic routing make it a relatively modest system compared to transcontinental submarine cables, but it serves as a key link in the UK's telecommunications infrastructure.
What is particularly interesting about Northern Lights is the scarcity of publicly disclosed technical details. Information about its design capacity, fiber pair count, supplier, and technology has not been made available in public sources, making it challenging to assess its full capabilities or role within BT's network. Additionally, while GeoCables records its ready-for-service year as 2008, no conflicting dates have surfaced in industry sources, leaving this timeline undisputed.
Quick facts
| Cable name | Northern Lights |
| Length | 67 km |
| Ready-for-service year | 2008 (GeoCables database) |
| Owner | BT |
| Status | In service |
| Design capacity | Not disclosed |
| Fiber pairs | Not disclosed |
| Supplier | Not disclosed |
| Technology | Not disclosed |
| Landing points | Dunnet Head (United Kingdom), Skaill (United Kingdom) |
Route
The Northern Lights cable connects Dunnet Head, located at the northern tip of mainland Scotland, to Skaill, situated on the Orkney Islands. This short route spans just 67 kilometers across the Pentland Firth, a strait that separates the Scottish mainland from the Orkney archipelago. The geographic corridor is notable for its challenging marine conditions, including strong tidal currents, which are common in the Pentland Firth. While these conditions can complicate cable installation and maintenance, they are standard considerations for submarine cable projects in such environments.
Why it was built and what it carries
Northern Lights was likely built to enhance connectivity between the Scottish mainland and the Orkney Islands, providing reliable telecommunications services to the region. While specific details about its traffic profile are not disclosed, cables of this type typically carry a mix of voice, data, and internet traffic. Given BT's ownership, it is reasonable to assume that Northern Lights serves both residential and business customers, as well as supporting BT's broader network operations in the UK.
History: what can be established
GeoCables records the Northern Lights cable as ready for service in 2008, and no alternative dates have been identified in industry sources. This timeline aligns with BT's ongoing investments in its domestic network during the early 2000s, a period marked by efforts to modernize and expand connectivity across the UK. The cable's continued listing as in service suggests that it remains operational and maintained to this day.
Capacity and technology
Publicly available data does not disclose the design capacity, fiber pair count, supplier, or specific technology used in the Northern Lights cable. Without operator documentation or reliable third-party sources, these aspects cannot be confidently stated. Submarine cables of this scale typically employ standard fiber-optic technology, but attributing specific features to Northern Lights without evidence would be speculative.
Latency: the physics
The computed one-way light propagation latency for Northern Lights is approximately 0.3 milliseconds over its 67-kilometer wet segment. The theoretical round-trip time (RTT) floor is therefore around 0.7 milliseconds. However, real-world latency is higher due to factors such as land tails (connections to terrestrial networks), terminal equipment delays, and routing inefficiencies. Live measurements from remote probes show significantly higher RTTs, ranging from 34.9 milliseconds (Minsk to Dunnet Head) to 247.7 milliseconds (Sydney to Dunnet Head). These results reflect the full internet path, including intermediate routing and terrestrial links, rather than the cable itself.
Redundancy: what happens if it breaks
In the event of a failure, redundancy for Northern Lights would likely depend on other domestic submarine cables or terrestrial networks serving the region. While specific alternatives are not listed in the FACTS block, the UK's telecommunications infrastructure includes multiple routes connecting the mainland to the Orkney Islands and other remote areas. Repairing a cable in the Pentland Firth would involve standard industry practices, including fault localization, mobilization of repair vessels, and deployment of remotely operated vehicles (ROVs) for cable recovery and splicing.
Bottom line
- Northern Lights is a 67-kilometer submarine cable connecting Dunnet Head and Skaill in the United Kingdom.
- Owned by BT and listed as in service, it has been operational since 2008 according to GeoCables data.
- Technical details such as design capacity, fiber pairs, supplier, and technology are not publicly disclosed.
- Theoretical latency over the wet segment is approximately 0.7 ms RTT, but real-world measurements reflect higher values due to routing and terrestrial factors.
- Redundancy would rely on other domestic cables or terrestrial networks, with repairs following standard industry practices.