Kozushima, Japan

Kozushima: A Small Island Connected to Japan's Submarine Cable Network

Kozushima, a remote island in Japan's Izu archipelago, is home to a single submarine cable landing point. Despite its modest role in Japan's expansive cable infrastructure, Kozushima plays an important part in connecting the smaller islands of the region to the mainland. The cable landing here is part of the "5 Villages 6 Islands" system, a 355-kilometer domestic cable that links Kozushima to eight other landing points, including nearby islands such as Niijima, Mikurashima, and Hachijo.

The "5 Villages 6 Islands" Cable

The "5 Villages 6 Islands" cable, operational since 2019, is a domestic system designed to stitch together the Izu Islands, a chain of volcanic islands south of Tokyo. Unlike Japan's larger international cables, which connect the country to global hubs, this cable focuses entirely on regional connectivity. Kozushima is one of nine landing points in this chain, ensuring that even smaller, less populated islands have access to reliable telecommunications. This regional cable is critical for maintaining communication between the islands and the mainland, supporting local communities, tourism, and small-scale industries. While Kozushima itself does not host major industrial or research facilities, its inclusion in the cable network ensures that residents and businesses can access the same digital services as those on larger islands or the mainland.

Regional Context: Kozushima's Role in Japan's Cable Network

Japan is a global leader in submarine cable infrastructure, with 51 cables landing at 68 points across the country. Compared to major landing points like Shima (12 cables) or Maruyama (9 cables), Kozushima's single cable may seem modest. However, its role is specialized: it serves as a link in a domestic chain that prioritizes regional connectivity over international reach. This focus on local connections contrasts sharply with landing points like Chikura, which hosts eight cables, many of them international systems connecting Japan to the United States and other countries. Kozushima's cable, by comparison, does not extend beyond Japan's borders, emphasizing its role in supporting the Izu Islands rather than global telecommunications.

Latency Measurements: Kozushima's Performance

GeoCables has conducted 21 latency checks to Kozushima from nine source cities, with an average round-trip latency of 264 milliseconds. The best observed latency was 80 milliseconds, a solid performance for a remote island connected by a regional cable system. These measurements highlight the efficiency of the "5 Villages 6 Islands" cable in maintaining connectivity across the Izu Islands.

Conclusion

Kozushima may not stand out in Japan's vast submarine cable network, but its connection via the "5 Villages 6 Islands" cable is essential for regional integration. As one link in a chain that ties together the Izu Islands, Kozushima ensures that even smaller communities remain connected to the digital world. For residents and visitors alike, this single cable provides access to the services and communications that modern life depends on, bridging the gap between island life and mainland Japan.