-1 km · 2 Landing Points · 1 Countries · Ready for Service: 2008
| Length | -1 km |
|---|---|
| Status | In Service |
| Ready for Service | 2008 |
| Landing Points | 2 |
| Countries | 1 |
| Location |
|---|
| Hachijo, Japan |
| Miura, Japan |
What each country and landing point keeps if Hachijojima-Mainland goes down. A calculation from our cable and landing-point database, not a forecast.
| Country | Other international cables | Land links | What remains |
|---|---|---|---|
| Japan | 34 | no | reserve of 34 cables |
Every landing point of this cable has another cable within 50 km.
No alerts from our monitoring on this cable in the last 180 days. Events feed →
Counted: other international cables landing in the same country (domestic cables between points of one country are not a way out), other cables at landing points within 50 km, and whether the country has land links. Not counted: cable capacity, operator contracts and satellite. Use as a first look at dependence, not as a statement of what would happen.
Monitored from 2026-07-21 through 2026-09-22 - live ICMP round-trip time measurements via our monitoring probes. All values below are recomputed daily from raw probe data. ✓ No anomalies detected in the monitored period.
| Probe | Location | Samples | Avg |
|---|---|---|---|
| #6410 own probe | Sao Paulo BR | 8 | 298.2 ms |
| own probe | Almaty KZ | 8 | 324.2 ms |
| #6487 | control probe | 6 | 93.3 ms |
| own probe | Moscow RU | 1 | 255.8 ms |
The Hachijojima-Mainland submarine cable is a key telecommunications link owned by NTT, connecting Hachijojima Island to mainland Japan. Operational since 2008, the cable ensures reliable communication between these two regions, supporting both local and international data traffic.
The cable spans between two landing points:
The Hachijojima-Mainland cable was ready for service in 2008, but detailed technical specifications such as its length, fiber pair count, and total capacity remain publicly undisclosed. The supplier responsible for its construction has also not been made available. Despite the lack of granular details, the cable plays a critical role in maintaining connectivity for Hachijojima Island.
This cable is vital for the connectivity of Hachijojima Island, providing a direct link to mainland Japan. It serves as a critical infrastructure component for redundancy and route diversity in the region. While it does not directly connect to international networks, it complements other regional cables such as Okinawa-Miyakojima-Ishigaki and Yuza-Tobishima, strengthening Japan’s domestic communication network. The cable helps mitigate risks associated with single points of failure and ensures uninterrupted communication for the island's residents and businesses.
Known facts about the Hachijojima-Mainland cable include its ownership by NTT, its operational status since 2008, and its landing points at Hachijo and Miura. However, several key details remain publicly undisclosed:
From a monitoring perspective, the Hachijojima-Mainland cable is an interesting subject due to its role in connecting a remote island to Japan’s mainland infrastructure. GeoCables could focus on monitoring BGP routing paths to identify potential latency issues or disruptions. Additionally, tracking vessel activity along the cable's route could provide insights into risks such as anchor dragging or accidental damage. Correlating network degradation with environmental or human activity could further enhance predictive maintenance strategies.
The Hachijojima-Mainland submarine cable is a crucial domestic link for Japan, connecting the remote Hachijojima Island to the mainland. While many technical details remain undisclosed, its importance in ensuring reliable connectivity cannot be overstated. For GeoCables, this cable offers an opportunity to enhance risk assessment and monitoring practices, contributing to the resilience of regional network infrastructure.
What next: Explore Hachijojima-Mainland on the interactive submarine cable map, browse the full catalog of submarine cables, or follow live network events and real-world internet latency.
| Status | ✓ Normal |
|---|---|
| RTT | 291.59 ms / base 284.44 ms |
| Last checked | 2026-09-22 10:32 |
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