Hokkaido-Rebun-Rishiri: connecting Japan's northern islands
The Hokkaido-Rebun-Rishiri submarine cable is a short but strategically significant telecommunications link operated by NTT, connecting three locations in Japan's northernmost region:
Rebun Island,
Rishirifuji on Rishiri Island, and
Wakkanai on the mainland of Hokkaido. With a total length of 64 kilometers, this cable plays an important role in providing connectivity to the remote islands of Rebun and Rishiri, which are known for their natural beauty but have limited infrastructure due to their geographic isolation.
What stands out about the Hokkaido-Rebun-Rishiri cable is the scarcity of publicly disclosed technical details. While its operational status and route are clear, information about its design capacity, fiber count, supplier, and specific technology has not been made available through public sources. This lack of transparency is not uncommon for smaller regional cables, especially when they are operated by a single entity like NTT, which may prioritize functionality over public disclosure.
Quick facts
| Cable name |
Hokkaido-Rebun-Rishiri |
| Length |
64 kilometers |
| Ready for service (RFS) |
2011 (GeoCables database value; other sources not surfaced) |
| Owners |
NTT |
| Status |
In service |
| Design capacity |
Not disclosed |
| Fiber pairs |
Not disclosed |
| Supplier |
Not disclosed |
| Technology |
Not disclosed |
| Landing points |
Rebun (Japan); Rishirifuji (Japan); Wakkanai (Japan) |
Route
The cable connects three landing points in Japan's northern region: Rebun Island, Rishirifuji on Rishiri Island, and Wakkanai on Hokkaido's mainland. Rebun and Rishiri are small, sparsely populated islands located in the Sea of Japan, northwest of Hokkaido. These islands are known for their unique ecosystems and serve as popular destinations for eco-tourism, but their remote location poses challenges for infrastructure development. Wakkanai, the northernmost city on Hokkaido, acts as the mainland hub for the cable, linking the islands to Japan's broader telecommunications network.
Why it was built and what it carries
The Hokkaido-Rebun-Rishiri cable was likely built to address the connectivity needs of Rebun and Rishiri Islands, ensuring reliable telecommunications services for residents, businesses, and local government operations. Given the islands' reliance on tourism, the cable also supports internet access for visitors. While specific data on its traffic capacity is not publicly available, the cable most likely carries a mix of voice, data, and internet services, typical for regional submarine cables serving remote areas.
History: what can be established
According to GeoCables data, the Hokkaido-Rebun-Rishiri cable was ready for service in 2011. No conflicting dates have been surfaced from other industry sources, suggesting that the 2011 RFS date is reliable. However, details about the planning, construction, and commissioning phases of the project are not publicly documented. As a regional cable operated by NTT, it may have been developed as part of broader efforts to improve connectivity in Japan's rural and remote areas.
Capacity and technology
Publicly available information does not disclose the design capacity, fiber pair count, supplier, or specific technology used in the Hokkaido-Rebun-Rishiri cable. Without operator documentation, attributing these characteristics would be speculative. Given its relatively short length and regional focus, it is likely that the cable was designed for modest capacity compared to larger international submarine cables.
Latency: the physics
The computed one-way light propagation latency over the 64-kilometer wet segment of the cable is approximately 0.3 milliseconds, with a theoretical round-trip time (RTT) floor of 0.6 milliseconds. However, real-world latency measurements would be higher due to additional factors such as land-based transmission distances, terminal equipment processing, and routing inefficiencies. No live latency measurements are currently available for this cable, and any attempt to estimate end-to-end RTT would require further data about its terrestrial connections.
Redundancy: what happens if it breaks
In the event of a cable fault, redundancy options for the Hokkaido-Rebun-Rishiri corridor would depend on alternative infrastructure in the region. While no specific alternatives are listed in the GeoCables database, Japan's strong domestic telecommunications network likely includes terrestrial and satellite links that could provide backup connectivity to Rebun and Rishiri Islands. Repair logistics for a cable of this length would follow standard industry practices, including fault localization, mobilization of repair vessels, and replacement of damaged segments. Given its short length, repair operations would likely be relatively straightforward compared to longer international cables.
Bottom line
- The Hokkaido-Rebun-Rishiri cable connects Rebun Island, Rishiri Island, and Wakkanai in northern Japan.
- It is 64 kilometers long and has been in service since 2011, according to GeoCables data.
- Operated by NTT, the cable's design capacity, fiber pairs, supplier, and technology are not publicly disclosed.
- Theoretical one-way latency over the wet segment is approximately 0.3 milliseconds, but real-world RTT is higher.
- No live latency measurements or redundancy specifics are available, but Japan's broader network likely provides backup options.