Mjolner West: planned submarine cable between Finland and Sweden
Mjolner West is a planned submarine cable project designed to connect
Lokalahti in Finland to
Östhammar in Sweden, spanning approximately 250 kilometers across the Baltic Sea. Owned by GlobalConnect, the cable is expected to be ready for service in 2027, as recorded in the GeoCables database. However, as of now, the cable is not operational, and details regarding its design capacity, fiber pair count, supplier, and specific technological features have not been publicly disclosed.
What makes Mjolner West particularly interesting is its role in enhancing connectivity between Finland and Sweden, a corridor that already hosts other submarine cables such as
STO-HEL-One at Lokalahti. This cable will likely contribute to the region's growing demand for high-capacity, low-latency connections, but its exact specifications and impact remain uncertain until further details are revealed by the operator.
Quick facts
| Name | Mjolner West |
| Length | 250 km |
| Ready for Service (RFS) | 2027 (planned) |
| Status | Planned - not yet in operation |
| Owners | GlobalConnect |
| Design Capacity | Not disclosed |
| Fiber Pairs | Not disclosed |
| Supplier | Not disclosed |
| Technology | Not disclosed |
| Landing Points | Lokalahti (Finland); Östhammar (Sweden) |
🗺 Show Mjolner West on the interactive cable map
Route
Mjolner West will traverse the Baltic Sea, connecting Lokalahti, Finland, to Östhammar, Sweden. Lokalahti is already a landing point for another submarine cable, STO-HEL-One, which links Stockholm and Helsinki. Östhammar, situated on Sweden's eastern coast, is less prominent as a cable landing site but is strategically located to facilitate connectivity between the two nations. The cable's route is expected to follow standard industry practices for surveying, laying, and burying submarine cables in shallow waters like the Baltic Sea.
Why it was built and what it carries
The primary motivation for building Mjolner West is to strengthen digital infrastructure between Finland and Sweden, two countries with significant economic and technological ties. The cable is expected to support increased data traffic, driven by the growing demand for cloud services, international connectivity, and low-latency applications in the region. While specific details about its design capacity and fiber pairs are not publicly available, it is reasonable to assume that the cable will be equipped to handle high-capacity data transmission to meet future requirements.
History: what can be established
According to the GeoCables database, Mjolner West is scheduled to be ready for service in 2027. As of now, no conflicting dates have emerged from industry sources, but it is worth noting that submarine cable projects often face delays due to permitting, environmental assessments, and logistical challenges. Until further updates from GlobalConnect or other stakeholders, the 2027 timeline remains the most reliable estimate.
Capacity and technology
Publicly available information does not disclose the design capacity, fiber pair count, or specific technology planned for Mjolner West. Without official documentation, it is impossible to confirm whether the cable will employ advanced technologies such as space-division multiplexing (SDM) or feature a specific number of fiber pairs. Such details are typically revealed closer to the cable's commissioning or through operator announcements.
Latency: the physics
The computed one-way light propagation latency for Mjolner West's 250-kilometer wet segment is approximately 1.2 milliseconds, with a theoretical round-trip time (RTT) floor of 2.5 milliseconds. However, real-world latency will be higher due to additional factors such as land-based cable segments, terminal equipment, and network routing.
Live measurements from remote probes, which capture the full internet path rather than the cable itself, report significantly higher RTTs between Östhammar and Lokalahti. These measurements range from a minimum of 10.4 ms to an average of 10.5 ms in one direction, and from a minimum of 6.5 ms to an average of 24.9 ms in the other direction. These values are well above the theoretical floor and reflect the influence of terrestrial network components and routing inefficiencies.
Any measured latency below the computed physical floor would be an artifact of the measurement method and not indicative of the cable's actual performance.
Redundancy: what happens if it breaks
If Mjolner West were to experience a fault, redundancy in the Finland-Sweden corridor would likely depend on other cables such as STO-HEL-One, which also lands at Lokalahti. This existing cable could provide alternative routes for data traffic, though the extent of its capacity and ability to absorb additional load is not publicly known. Repairing submarine cables typically involves deploying specialized cable ships to locate the fault, retrieve the damaged section, and replace it. In the Baltic Sea, repair operations are generally less complex than in deeper or more turbulent waters, but they can still be subject to weather delays and logistical challenges.
Bottom line
- Mjolner West is a planned submarine cable connecting Finland and Sweden, expected to be ready for service in 2027.
- The cable will span 250 kilometers between Lokalahti and Östhammar, enhancing connectivity in the Baltic Sea region.
- Details on design capacity, fiber pairs, supplier, and technology have not been disclosed.
- The theoretical latency floor is 2.5 ms RTT for the wet segment, but real-world latency will be higher due to additional network factors.
- Redundancy in the corridor may rely on existing cables like STO-HEL-One, though specifics are unclear.