Awashima-Murakami

Awashima-Murakami: A Short Submarine Link Connecting Awashimaura and Murakami

The Awashima-Murakami submarine cable is a 66-kilometer optical fiber link connecting Awashimaura Village on Awashima Island to Murakami on the mainland of Japan. Owned by Awashimaura Village, this cable is listed as in service and was recorded as ready for service in 2022 according to GeoCables database records. It serves as a critical infrastructure element for the small island community, providing connectivity to mainland Japan. What makes this cable particularly interesting is its localized ownership and the absence of publicly disclosed technical specifications, such as design capacity, fiber pair count, or supplier details. This lack of transparency is not uncommon for smaller-scale submarine cables serving local or regional purposes, but it limits the ability to assess its full technological capabilities and operational significance.

Quick facts

Cable name	Awashima-Murakami
Length	66 km
Ready for service	2022 (GeoCables database value)
Owners	Awashimaura Village
Status	In service
Design capacity	Not disclosed
Fiber pairs	Not disclosed
Supplier	Not disclosed
Landing points	Awashimaura (Japan); Murakami (Japan)
Computed latency (one-way)	≈ 0.3 ms
Computed latency (RTT floor)	≈ 0.6 ms
Live latency measurements	None available

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Route

The Awashima-Murakami submarine cable connects two locations in Japan: Awashimaura Village on Awashima Island and Murakami City on the mainland. Awashima Island is situated in the Sea of Japan, approximately 30 kilometers off the coast of Niigata Prefecture. Murakami serves as the mainland landing point, providing access to larger national and regional networks. The cable's short length of 66 kilometers reflects its role as a localized infrastructure link rather than a long-haul intercontinental system.

Why it was built and what it carries

This cable was likely built to ensure reliable telecommunications connectivity for Awashima Island, a small and remote community with limited access to mainland infrastructure. Submarine cables are often the most practical solution for connecting islands to larger networks, offering higher bandwidth and lower latency compared to satellite-based systems. While specific details about the cable's data capacity and usage are not publicly disclosed, it is reasonable to assume that it supports internet, voice, and potentially other data services for residents, businesses, and public institutions on Awashima Island.

History: what can be established

GeoCables records the Awashima-Murakami cable as having been ready for service in 2022. No conflicting dates have been identified in publicly available industry sources, suggesting that this timeline is reliable. The cable’s ownership by Awashimaura Village indicates a localized initiative to improve connectivity for the island community. However, further details about the planning, construction, and commissioning phases are not publicly documented.

Capacity and technology

Publicly available data does not disclose the design capacity, fiber pair count, or the supplier of the Awashima-Murakami cable. Without operator documentation or reliable sources, attributing specific technological characteristics would be speculative. It is reasonable to assume that the cable uses standard optical fiber technology, but the exact specifications remain unknown.

Latency: the physics

Theoretical latency calculations for the Awashima-Murakami cable indicate a one-way light propagation time of approximately 0.3 milliseconds over its 66-kilometer length. This corresponds to a round-trip time (RTT) floor of approximately 0.6 milliseconds, assuming light travels through fiber at speeds between 200,000 and 204,000 kilometers per second. Real-world latency measurements would be higher due to additional factors such as land-based network segments, terminal equipment processing, and routing overhead. No live latency measurements are currently available for this cable.

Redundancy: what happens if it breaks

In the event of a cable break, redundancy options for Awashima Island would depend on alternative connectivity solutions, such as satellite links or other submarine cables in the region. Given the localized nature of the Awashima-Murakami cable, it is unlikely to have extensive redundancy built into its design. Repairs would likely follow standard industry practices, which involve deploying specialized cable repair ships to locate and fix the fault. The relatively short length of the cable could simplify repair logistics compared to longer systems.

Bottom line

• The Awashima-Murakami cable is a 66-kilometer submarine link connecting Awashima Island to mainland Japan.
• Owned by Awashimaura Village, it was recorded as ready for service in 2022.
• Technical specifications such as design capacity, fiber pairs, and supplier details are not publicly disclosed.
• Theoretical latency for the wet segment is approximately 0.6 ms RTT, but real-world latency would be higher.
• Redundancy options for Awashima Island are limited, and repairs would follow standard submarine cable practices.