Yuza-Tobishima: A Short Submarine Cable Connecting Japan’s Coast
The Yuza-Tobishima submarine cable is a 31-kilometer telecommunications link connecting the towns of
Yuza and
Tobishima, both located on Japan's coastline. Owned by NTT, one of Japan's leading telecommunications companies, this cable is listed as in service and was recorded as ready for service (RFS) in 2022 according to GeoCables' database. However, no design capacity, fiber pair count, supplier, or specific technological details have been disclosed publicly, leaving certain aspects of its construction and operation unclear.
What makes the Yuza-Tobishima cable notable is its relatively short length, which is uncommon for submarine cables that typically span hundreds or thousands of kilometers. Its role within the broader telecommunications infrastructure of Japan is likely localized, serving specific regional connectivity needs rather than acting as part of a transcontinental or international system. The absence of public data on its capacity and technology underscores the cable's niche function and raises questions about its exact operational scope.
Quick facts
| Cable name | Yuza-Tobishima |
| Length | 31 km |
| Ready for service (RFS) | 2022 (GeoCables database) |
| Owners | NTT |
| Status | In service |
| Design capacity | Not disclosed |
| Fiber pairs | Not disclosed |
| Supplier | Not disclosed |
| Technology | Not disclosed |
| Landing points | Tobishima (Japan); Yuza (Japan) |
Route
The Yuza-Tobishima cable connects two points on Japan's coastline: Tobishima and Yuza. Tobishima is a small island located in the Sea of Japan, while Yuza is a coastal town on the mainland in Yamagata Prefecture. The cable's route is entirely within Japanese territorial waters, reflecting its localized purpose. This short corridor likely serves to integrate Tobishima into the mainland's telecommunications network, improving connectivity for residents and businesses on the island.
Why it was built and what it carries
The specific motivations behind the Yuza-Tobishima cable's construction have not been publicly disclosed, but its short length and domestic scope suggest it was built to enhance regional connectivity rather than to support high-capacity international traffic. Tobishima, being an island, may have faced challenges in accessing reliable telecommunications infrastructure before the cable was installed. The cable likely provides essential internet and communication services to the island's population, facilitating local development and bridging the digital divide between Tobishima and the mainland.
History: what can be established
The Yuza-Tobishima cable was recorded as ready for service in 2022 according to GeoCables' database. No conflicting information from industry sources has been identified regarding its RFS date, making 2022 the most reliable estimate for when the cable became operational. NTT, the cable's owner, is a well-established player in Japan's telecom industry, known for both domestic and international submarine cable projects. However, no further historical details about the cable's planning, construction, or commissioning have been made publicly available.
Capacity and technology
Publicly available data does not disclose the Yuza-Tobishima cable's design capacity, fiber pair count, supplier, or specific technological features. Without documentation from NTT or other reliable sources, attributing these characteristics would be speculative. Given its short length and localized function, the cable is unlikely to feature cutting-edge high-capacity technology, but this cannot be confirmed without operator disclosures.
Latency: the physics
The theoretical one-way latency for light propagation over the 31-kilometer wet segment of the Yuza-Tobishima cable is approximately 0.2 milliseconds, with a round-trip time (RTT) floor of about 0.3 milliseconds. These values represent the absolute minimum latency achievable under ideal conditions, assuming light travels through the fiber at speeds between 200,000 and 204,000 kilometers per second. Real-world latency will be higher due to additional factors such as signal processing delays at terminal equipment, routing inefficiencies, and the latency introduced by land-based network segments at each landing point. No live measurements of the cable's latency have been reported.
Redundancy: what happens if it breaks
In the event of a failure, redundancy for the Yuza-Tobishima cable would depend on alternative connectivity options within the region. Given its short length and localized purpose, it is unlikely to have extensive redundancy built into its design. Repair logistics for submarine cables typically involve deploying specialized cable ships to locate and fix the fault. For a cable of this length, repairs would likely be straightforward compared to longer, more complex systems. However, the specific redundancy arrangements for Tobishima's connectivity are not documented in public sources.
Bottom line
- The Yuza-Tobishima cable is a 31-kilometer submarine link connecting Tobishima Island and Yuza on Japan's mainland.
- Owned by NTT, it was recorded as ready for service in 2022 and is listed as in service.
- Its design capacity, fiber pair count, supplier, and technology have not been disclosed publicly.
- Theoretical latency over the wet segment is approximately 0.2 milliseconds one-way, but real-world latency will be higher.
- Its localized function suggests it was built to improve regional connectivity rather than to handle high-capacity traffic.