Maintenance of Tonga stranded power optical cable

Tonga's submarine fibre-optic cable maintenance involves specialized repair ships, careful reconnection of severed ends, and adherence to international optical cable standards.

Background of the Cable Damage

Tonga's international internet connectivity was severely disrupted by the 2022 Hunga Tonga-Hunga Ha'apai volcanic eruption, which caused multiple breaks in the submarine fibre-optic cable connecting the islands to the global network. The eruption generated debris and underwater landslides, severing the cable in at least two locations, leaving the middle portion drifting in the ocean and the ends flailing on the seabed. This resulted in widespread communication outages, affecting internet, phone services, and critical infrastructure reliant on connectivity .

Repair Operations

Repairing a submarine cable requires a specialized cable repair ship equipped to locate, retrieve, and reconnect the damaged cable ends. For Tonga, ships such as the SubCom vessel Resilience and the Lodbrog have been deployed. The repair process involves:

• Locating the damaged sections using sonar and GPS mapping.
• Retrieving the cable ends from the seabed.
• Splicing and reconnecting the fibre-optic cores to restore signal continuity.
• Testing the repaired sections to ensure data transmission integrity before reburial or securing on the seabed . Delays can occur due to logistical challenges, such as ships needing to refuel or restock en route, as was the case with the vessel delayed in Fiji, which postponed repairs for affected islands like Vava'u and Ha'apai .

Maintenance Standards

While specific submarine cable maintenance is highly specialized, general optical fibre network maintenance follows ITU-T recommendations, such as ITU-T L.25, which outlines procedures for inspection, fault detection, and repair of fibre-optic networks. Although ITU-T L.25 primarily addresses terrestrial networks, principles like regular monitoring, fault localization, and adherence to splicing standards are applicable to submarine systems. For submarine cables, ITU-T G.979 provides guidance on monitoring systems for undersea optical cables .

Challenges and Considerations

• Environmental hazards: Underwater eruptions, earthquakes, and landslides can sever cables over long distances.
• Repair complexity: Submarine cable repair is time-consuming and requires precise handling to avoid further damage.
• Connectivity impact: Extended outages affect communications, banking, and emergency services, highlighting the critical nature of timely maintenance .
• Alternative solutions: Temporary satellite services, such as Starlink, have been used to provide interim connectivity during repair delays .

Conclusion

Maintaining and repairing Tonga's stranded submarine optical cable involves a combination of specialized vessels, technical expertise in fibre splicing, and adherence to international standards. The process is complex and sensitive to environmental and logistical factors, making timely restoration of connectivity a challenging but essential task for the islands' communication infrastructure.