Mjolner West: A Finland-Sweden Submarine Cable
Mjolner West is a submarine fiber optic cable connecting
Lokalahti in Finland to
Östhammar in Sweden. Spanning 250 kilometers, it is owned by GlobalConnect and is listed as in service. While its design capacity, fiber pair count, supplier, and specific technology are not publicly disclosed, the cable's importance lies in its role within the Baltic Sea region's telecommunications infrastructure.
What stands out about Mjolner West is the lack of clarity surrounding its operational details. While the GeoCables database records its ready-for-service (RFS) year as 2027, the cable is already listed as in service, suggesting either a discrepancy in the data or a potential early activation. Additionally, live latency measurements indicate significant variability, raising questions about routing, equipment, or other network factors impacting its real-world performance.
Quick facts
| Cable name | Mjolner West |
| Length | 250 km |
| Ready-for-service year | 2027 (GeoCables database) |
| Owner | GlobalConnect |
| Status | In service |
| Design capacity | Not disclosed |
| Fiber pairs | Not disclosed |
| Supplier | Not disclosed |
| Technology | Not disclosed |
| Landing points | Lokalahti (Finland), Östhammar (Sweden) |
| Other cables at Lokalahti | STO-HEL-One |
| Theoretical one-way latency | 1.2 ms |
| Theoretical round-trip latency | 2.5 ms |
| Measured Östhammar -> Lokalahti RTT | Min 10.4 ms, Avg 10.5 ms |
| Measured Lokalahti -> Östhammar RTT | Min 6.5 ms, Avg 24.9 ms |
Route
Mjolner West connects Lokalahti, Finland, to Östhammar, Sweden, across the Baltic Sea. Lokalahti is a known landing site for other cables, including STO-HEL-One, which links Stockholm and Helsinki. Östhammar, located on Sweden's eastern coast, provides a strategic point for connections to mainland Europe. The corridor is relatively short at 250 kilometers, making it a direct and efficient path between the two nations.
Why it was built and what it carries
The cable was likely built to enhance connectivity between Finland and Sweden, two countries with strong economic and technological ties. Submarine cables in this region typically support internet traffic, data center interconnection, and enterprise communications. While specific details about Mjolner West's capacity and technology are not disclosed, it is reasonable to assume that it serves as a high-capacity link to meet growing demand for bandwidth and low-latency connections in the Baltic region.
History: what can be established
The GeoCables database lists Mjolner West's ready-for-service year as 2027, but the cable is already marked as in service. This discrepancy could stem from an early activation or a misrecording in the database. Alternatively, the cable might have undergone partial commissioning before full operational status. Without operator documentation, the exact timeline remains unclear.
Capacity and technology
Publicly available sources do not disclose Mjolner West's design capacity, fiber pair count, supplier, or specific technology. This lack of transparency is not uncommon in the submarine cable industry, where commercial and competitive considerations often limit the release of technical specifications. Any attempt to attribute these details without documentation would be speculative.
Latency: the physics
Theoretical latency calculations for Mjolner West indicate a one-way light propagation time of approximately 1.2 milliseconds over its 250-kilometer length, with a round-trip time (RTT) floor of 2.5 milliseconds. However, live measurements from remote probes show significantly higher RTT values: Östhammar to Lokalahti ranges from 10.4 to 10.5 milliseconds, while Lokalahti to Östhammar ranges from 6.5 to 24.9 milliseconds. These discrepancies are likely due to additional delays introduced by land tails, terminal equipment, and routing inefficiencies. The asymmetry between the two directions suggests further complexities in the network path.
Redundancy: what happens if it breaks
In the event of a failure, redundancy for Mjolner West would depend on other cables in the region, such as STO-HEL-One, which also lands at Lokalahti. The Baltic Sea corridor is well-served by multiple submarine cables, ensuring alternative routes for data traffic. Standard industry practices for cable repair include deploying specialized ships to locate and fix faults, a process that can take days to weeks depending on weather and logistical factors.
Bottom line
- Mjolner West connects Lokalahti, Finland, to Östhammar, Sweden, across 250 kilometers.
- Owned by GlobalConnect, it is listed as in service despite a recorded RFS year of 2027.
- Design capacity, fiber pairs, supplier, and technology are not publicly disclosed.
- Theoretical latency is 1.2 ms one-way, but live measurements show higher and asymmetric RTTs.
- Redundancy is supported by other cables in the Baltic Sea corridor, such as STO-HEL-One.