ROVworld Subsea Information

Damaged phone cables get low-technology fix
Date: Wednesday, January 17, 2007 @ 17:40:47 EST

 Damaged phone cables get low-technology fixWorkers are relying on 19th century technology to fix a 21st century problem – disruption of the Internet traffic that tech-savvy Asia relies on. Crewmen on boats south of Taiwan are dragging the seabed with grappling hooks at the end of long ropes to recover fiber optic cables damaged in a 7.1-magnitude earthquake that struck the region on Dec. 26.

"No electronics involved," said John Walters, general manager of Global Marine, one of the firms engaged in the repairs. "It's an old and traditional technique."

Millions of people across the region in Taiwan, China, Hong Kong, Japan, Singapore, South Korea and as far away as Australia, suffered Internet and telephone blackouts when cables linking Asian countries with eachother and other regions were damaged.

Telecom operators have diverted the traffic to allow service to return to normal but the repair work continues.

"At this point none of those cables have been repaired," Walters told reporters in an interview.

"We are talking about cable that's lying on the surface of the seabed down to about 4,000 meters," Walters said.

Global Marine has two ships in the Bashi Channel and Luzon Strait between Taiwan and the Philippines, while other firms have provided four more ships, he said.

The vessels, specially designed to repair submarine cables, are more than 100m long and carry about 60 British officers and Filipino crewmen, he said.

They work 24 hours a day but the weather can hinder their progress. Walters said one ship is waiting for 48 to 64km per hour winds to die down in the Bashi Channel. The winds have stirred up 10 to 12m waves.

The second Global Marine vessel is closer to Taiwan and has been able to continue work, he said.

After arriving at the scene they survey the ocean bottom to assess whether the contour has changed, and the degree of sediment movement.

Then the traditional tools are brought out. A rope with a grapnel on the end is lowered into the depths and towed over the sea floor until tension registers on a graph on the ship, indicating contact has been made with the cable.

Today's fiber optic cables are just 21mm in diameter.

"You can understand the magnitude of the difficulty that we have," said Walters, who has 17 years' experience.

"What's key is the speed of the cable ship."

The grapnel is a metal tool about 46cm by 61cm with a cutter like a fine razor blade and a grabbing tool.

As tension increases and the cable is slowly pulled up, it is cut, grabbed, and half of it is hoisted to the surface.

Dropping the grapnel, dragging the sea bed and recovering the cable can take about 16 hours, Walters said.

"It is a tried and tested method," he said.


John Walters, general manager of Global Marine Singapore, stands on Thursday next to a model of a boat similar to those used to recover and fix fiber optic cables damaged in the 7.1-magnitude earthquake that struck Taiwan on Dec. 26.

Once the severed half of the cable is on board the boat, debris is cleared from the damaged end and the cable is tested, sealed and its end boiled off. Then it is attached to a buoy on the water surface while the process is repeated for the second half of the cable before both halves are spliced together and dropped back to the ocean floor.

Even before the Boxing Day earthquake, Global Marine had faced a busy year, with about 20 repairs after damage from fishermen or anchors. All those ruptures were fixed using the old grapnel method, he said.

Global Marine has remotely operated vehicles, a type of underwater robot, but they cannot operate below a depth of about 2,000m and are usually employed to bury a repaired cable in shallower water, he said.

They are not quicker than grapnels, either.

"We've learned our lessons, if you like, from history," said Walters, whose UK-based firm traces its origins back to 1850, when the first international submarine cable was laid between Britain and France.

Grapnel design has evolved over the past century, giving operators a variety of tools to choose from depending on the underwater terrain, he said.

A single cable repair can take about seven days, but on this mission most operators are quoting a 10-day repair period, he said. With about eight separate cable systems in the waters off Taiwan, and close to 18 faults caused by the earthquake, repairs will take time.

"We anticipate that all of these systems should be repaired – we're talking about end February," Walters said. 

This article comes from ROVworld Subsea Information

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