80km Stretch of Tonga Cable In Pieces From Eruption

The explosion blew the cable to pieces, and some have been recovered, but a major 55km section and expensive repeater are still missing.By Mary Lyn Fonua, Matangi, Tonga Online
February 16, 2022

An 80 km stretch of Tonga's telecommunications cable, was blown to bits by a volcanic eruption on Jan. 15 and there's no easy fix. Short pieces have been recovered, while a major section of the fibre optic cable, about 55 km long, including an expensive repeater, has yet to be recovered from the seabed.

“It is obvious that the eruption/shockwaves/tsunami caused major havoc under water,’ James Panuve, Tonga Cable Ltd. CEO, told Matangi Tonga yesterday.

While Tonga Cable Ltd. hopes the cable ship Reliance will find the missing pieces, the biggest challenge now is bridging the 80+km between the Fiji end of the cable that was recovered on Saturday and the Tonga end of the cable. He said TCL does not have enough cable spare on the ship to bridge this gap.

“We have had to ask other cable owners in the region, who have cable spares on the Reliance and who are willing to allow us to use their cable spares. We will have to either replace or pay for what we use later.”

He agrees that this exercise will probably be remembered as one of their most difficult endeavours.

“The main obstacle last week was the bad weather and big swells out at open sea.  Now, it is the water depth (~2-2.5km) and, now understanding, that the cable is no longer following the path where it was supposed to be in the affected area.

“We have found some parts of the cable to be buried and/or displaced…One section was found to be buried under around 30cm of sand/sediment and one section was found broken and 5km north of where it should have been,” he said.

The Fiji-Tonga cable is 839km long. The Tonga end of the cable is broken 36km offshore from Sopu base station, while the Fiji end of the cable is broken 691km (linear distance) from Fiji. Between these two points are the bits and pieces.

Eight attempts at recovery

“There have been a total of eight attempts to recover the Fiji end of the cable.  The eighth being the successful attempt,” he said.

“The first attempt resulted in recovery of 1.2km of cable; attempt no. 7 resulted in recovery of 9.3km.

“The last attempt, no. 8, resulted in recovery of the Fiji end of the cable, but tests showed that there was a break 2km further on in the cable. Therefore, the cable was recovered up to that point and the bad section was cut out, resulting in a 2km section,” he said.

“There is a major section of the cable still down there at the sea bed, which we think will be about 55+km long, including our expensive repeater unit. This is the cable section we are hoping to recover.”

James said that there are six repeater units between Fiji and Tonga, roughly 130km apart, and this ‘lost’ repeater is the last one before the cable reaches Tonga. The function of the repeater is to boost the communications signal.

“Mini system” to bridge gap

So are we still on track for repair by Feb. 20, or what is the plan now?

“Yes. We have recovered the Fiji end on Feb. 12, and have secured this end. …But tests run on the current recovered end shows clear run to the Fiji cable station, indicating the rest of the cable is in good shape,” James said

“The amount of new cable to be laid is in excess of 80km and, hopefully, not beyond 90km. Actual length will depend on contour of the ocean bed, which may have been affected or changed by the disaster.

“We have only just recovered the Fiji end on Saturday. While they are trying to put together the ‘mini system’ to bridge the gap between the two cable ends, they are also trying to recover some of our cable that is still missing and laying on the ocean bed somewhere.

“A major component in this ‘lost’ cable is our repeater which on its own costs around US$230k. So we are hopeful we can retrieve this unit and that it is still functional.”

Meanwhile, James said the cost of the repair was mounting.

“Of course, the longer the ship stays out here, the higher our ship invoice will be at the end of the job. So, it is a bit difficult to put a definitive figure on it at this stage. We are hoping to have a better picture in the next couple of days,” he said.

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