Japan to repair damaged undersea cables

Image caption KDDI will use deep water robots to repair the damaged undersea cables

Aftershocks are still preventing Japan's telecommunication companies from repairing undersea cables, damaged in the recent earthquake and tsunami.

To restore services, many providers have rerouted traffic to backup cables.

KDDI, Japan's second-largest telecoms operator, said it will send out a ship equipped with remotely-controlled robots as soon as the ground is still.

The robots can dive to a depth of 2,500m to repair the damaged cables - a task that may take months to complete.

In the mean-time, there is enough redundancy in the telecommunications infrastructure linking Japan to the rest of the world to keep the country connected.

KDDI spokesman Shin-ichiro Itoyama, speaking by phone from the company's headquarters in Tokyo, said that the deep water robots had previously only been used to lay cables on the seabed and not for any major repairs as there had never been much damage from previous earthquakes.

More than 5,400 people perished in Friday's 9.0-magnitude quake - the most powerful ever to hit Japan - and the ensuing tsunami.

Some 9,500 people are still missing.

Aftershock hits

At one point, during the interview, Mr Itoyama broke-off: "Oh wait a second, the ground is shaking again," he said.

Powerful aftershocks continue to rattle the devastated country, reaching magnitudes of 6.0 and higher.

Mr Itoyama said he was one of the few KDDI employees left working in the office. The majority were told to stay at home as long as the aftershocks last.

He explained that it was very difficult to assess the damage to the cables in the Pacific as many were buried in the seabed in those areas most affected by the disaster, including Ibaraki and Miyagi Prefectures.

Although there were serious service disruptions right after the earthquake and tsunami, with communications between Japan and US badly affected, that had since been restored, he added.

"On March 15, we solved all the problems by means of using other cables and back-up systems and we have recovered all the services between Japan and US," he said.

Mr Itoyama added that the traffic had been partially rerouted using the Russia-Japan cable network operated by KDDI and Russia's Rostelecom.

Other companies

KDDI is not the only telecommunications company in Japan badly affected by the disaster.

Image caption Many cables were damaged in the hardest-hit areas, such as Ibaraki Prefecture

The country's biggest operator, NTT, was hit hard as well.

"About half a million of telephone circuits are down," Kazuhiro Gomi, the head of the US branch of NTT, told the BBC.

"Nowadays, the Internet is as important as telephone lines - and about 150,000 internet circuits are down."

Mr Gomi added that mobile phone services have also suffered, especially in the north-east coastal area.

Other companies with undersea cables in the waters around Japan include Australian operator Telstra International, Taiwan's largest phone operator Chunghwa Telecom, and global telecommunications service provider Pacnet, headquartered in Singapore and Hong Kong.

While some of them say their services have been restored, others are still struggling.

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