5 Villages 6 Islands: connecting Tokyo's remote archipelago
The 5 Villages 6 Islands submarine cable is a regional telecommunications system owned by the Tokyo Metropolitan Government, designed to link remote islands in the Izu archipelago with reliable connectivity. Spanning 355 kilometers, the cable connects eight landing points across six islands and one village in Japan. It has been listed as in service since 2019, according to GeoCables records, although public information about its technical specifications remains sparse.
What sets this cable apart is its focus on serving smaller, isolated communities rather than major urban centers. While it is not a high-capacity international system, its role in enabling local communication and internet access is significant for the residents of these islands. However, many details about its design, technology, and capacity are not publicly disclosed, leaving room for speculation about its engineering and operational performance.
Quick facts
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Route
The cable connects eight landing points across six islands and one village in the Izu archipelago, a chain of volcanic islands stretching southward from the Japanese mainland. The landing points include Aogashima, Hachijo, Kozushima, Mikurashima, Miyake, Niijima, Oshima, Shikinejima, and Toshima. These locations are part of the Tokyo Metropolitan area but are geographically remote, making submarine cables essential for reliable communication.
Hachijo serves as a critical node, as it hosts three other submarine cables: the
Hachijojima-Mainland cable, the
Izu Islands Cable System, and the
Ogasawara Cable Network. Similarly, Miyake and Oshima are connected to the Izu Islands Cable System, providing some redundancy in the region.
Why it was built and what it carries
The 5 Villages 6 Islands cable was built to provide telecommunications services to the remote communities of the Izu archipelago. These islands have limited infrastructure and rely heavily on submarine cables for internet and voice communication. The Tokyo Metropolitan Government's involvement suggests a focus on public service rather than commercial profit, aiming to improve connectivity for residents and support local development.
Publicly available data does not confirm the cable's design capacity or the type of traffic it carries. It is likely that the cable supports general internet access, voice communication, and possibly government services, but attributing specific applications without operator documentation would be speculative.
History: what can be established
GeoCables records the cable as ready for service in 2019, and it is currently listed as operational. No conflicting industry sources have been identified regarding its RFS year. The Tokyo Metropolitan Government's ownership aligns with its jurisdiction over the Izu islands, emphasizing the cable's role in regional connectivity rather than international data transmission.
Details about the cable's construction, supplier, and initial testing phases are not publicly available, which is common for smaller regional systems.
Capacity and technology
The design capacity of the 5 Villages 6 Islands cable has not been disclosed in public sources, nor has information about its fiber count, supplier, or specific technology. Without operator documentation, it cannot be stated whether the cable uses advanced technologies like coherent optical transmission or simpler legacy systems. Such omissions are not unusual for regional cables serving smaller populations.
Latency: the physics
The computed one-way light propagation latency over the cable's 355 km wet segment is approximately 1.7 milliseconds, with a theoretical round-trip time (RTT) floor of 3.5 milliseconds. However, real-world latency is higher due to additional factors like land tails, terminal equipment, and routing inefficiencies.
Live measurements from remote probes show significantly higher RTTs to Shikinejima, ranging from 74.6 ms (Singapore) to 392.3 ms (Cape Town). These values reflect the full internet path, including terrestrial networks and intercontinental links, rather than the cable itself.
Redundancy: what happens if it breaks
If the 5 Villages 6 Islands cable were to experience a fault, redundancy is partially available through other cables in the region. Hachijo, Miyake, and Oshima are connected to the Izu Islands Cable System, while Hachijo also links to the Hachijojima-Mainland and Ogasawara Cable Network systems. These alternative routes could mitigate disruptions, but the extent of redundancy for smaller landing points like Aogashima and Toshima is unclear.
Repair logistics for submarine cables typically involve specialized vessels equipped with remotely operated vehicles (ROVs) for fault detection and cable recovery. Repairs in the Izu archipelago would likely follow standard industry practices, but specific arrangements for this cable are not publicly documented.
Bottom line
- Regional submarine cable connecting eight landing points in Japan's Izu archipelago.
- Owned by the Tokyo Metropolitan Government, operational since 2019.
- Design capacity, fiber pairs, supplier, and technology are not publicly disclosed.
- Computed RTT floor ≈ 3.5 ms; live internet path RTTs significantly higher.
- Partial redundancy available through other cables at Hachijo, Miyake, and Oshima.