The Dubious Narrative That Modern Subsea Cables Rarely Have Outages

The Dubious Narrative That Modern Subsea Cables Rarely Have Outages

Earlier this year SMW5, which is a modern high capacity system RFS in 2016, experienced an outage in the Malacca Strait. It took the Indonesian ship almost a month to repair the cable because it could not find it. 😀 It happened because currents swept away the sediment in which cable was buried and it had drifted over 20 kilometers from the original burial path.

Some commentators in the Linked 01 submarine cable group have claimed that many systems rarely have outages or in some cases no outages over their entire operating life. I have no doubt that new cables have fewer outages due to deeper burial. Also cable construction companies today more consistently avoid geologically dangerous areas. In the past West African cables were knowingly deposited in unsafe areas like Congo Canyon because it was cheaper than going around them or building cable landing stations near better landings. Four cables land at the Abdijan CLS despite an undersea canyon known for debris slides right off shore. Penny wise, pound foolish. Current deployment is better because burial is deeper, physical surveys better, and the Big Three construction companies adhere more closely to best practices. Google and the other Digital Giants deserve credit in this regard.

But there is no silver bullet. Nature is Brutal. All deep sea TransAtlantic cables experience shunt faults because currents rub them against rocks. Slowly, but surely the protective polyethylene layer is worn away. Moreover, there is no alternative to lightweight cables. Deployment and repairs require it. Those requirements guarantee that currents can move them. EXA's Atlantic Express cable was buried in sections of the deep sea near the US, but at high cost. It is a practice unlikely to be emulated. Trawlers can penetrate the sea floor deeper than you might imagine - at least a meter down. Moreover, modern ships can operate in deeper waters such as 1500 or even 2000 meters. Many cables were laid without trenching in waters 1000 meters or greater in depth. 

The map below shows little yellow dots all over the cables. Those are repairs. A cable built in the last ten years will probably has far fewer yellow dots. But the claim that most modern cables have few or none seems dubious. Nature is not defeated that easily. Subsea cables are buried in muck, not rock. The carbon cycle dictates that living creatures such as plankton die and settle on the sea's floor. The floor is dynamic and constantly changing. It is not as stable as dry land. So it is best to keep expectations realistic. 

It is also an exaggeration to claim that unrepeatered cables can last indefinitely. Unrepeatered Irish sea cables have been retired because they accumulated too much optical loss due to numerous repairs. All cables will be shut down as they accumulate optical loss due to splicing and as new higher capacity technology becomes available. So I stick to my guns. The three new English Channel cables plus the Chunnel will dominate traffic flows over the next ten years with older systems like Concerto being retired. Physical assets depreciate. Modern technology has not abolished depreciation. Resistance is Futile.