Since around the end of last year, there have been a number of subsea cable landings and service launches in Asia, such as the completion of the redundant leg of Asia Global Crossing's Pacific Crossing-1 trans-Pacific cable.
However, the same time period also saw select subsea cable consortia in high-profile repair mode. Earlier this year, the China-US Cable -- the first trans-Pacific cable directly connecting the US and China -- suffered a major blow as a section off the coast of Shanghai was snapped in two. The event cut off the majority of China's overseas 'Net connectivity and forced carriers with capacity booked on the system to reroute the traffic on to other systems.
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The second cut had less of an overall impact on regional traffic flows compared to the first one, but both episodes serve to illustrate that the business of building subsea cables is easy to take for granted -- especially when considering that it's been 153 years since someone first deployed a communications cable underwater.
Obviously, the business has come a long way since then in terms of technology and cost, but after a century and a half of trial and error, the actual act of deploying a subsea cable network has become a fairly straightforward procedure.
As Asia Global Crossing's MD for network development, David Milroy, puts it, "Deploying a submarine cable system isn't rocket science."
Of course, he adds, that doesn't mean it's child's play, either. Indeed, there is far more to deploying a fiber-optic cable system under a few kilometers of water than spooling it out off the back of a boat. In fact, comparatively speaking, that's the easy part.
Choose your armor
According to AGC's Milroy, just the initial planning of a subsea system involves a lot of legwork even before the ships start rolling out fiber into the sea.
"Before you even think about putting a cable system underwater, you have to take a number of things into account, such as the network engineering, what it's made of, where it goes, how it's manufactured," Milroy says. "For example, do you need single or double armor, and for which sections do you need it?
"Typically you'll need a double wrap [armor] for shallow water up to about 1,000 meters," explains Milroy, citing fishing trawlers and ship anchors as the most common hazards to be found at those depths. "If the water is deeper than that, you're pretty safe with single armor, since fishing nets and anchors typically don't reach that far."
K.F. Larm, regional director for Level 3's global submarine division, says that lightweight cables are okay for depths below 2,000 meters, but recommends light armor at depths of around 1,500 meters, where the danger isn't so much anchors and trawler, but sharks.
"If the cable becomes free-floating for some reason and isn't lying flat, the current will move it back and forth, and sharks will try to bite the cable."
(Those who wonder just how much damage a shark could possibly do to a fiber-optic cable are hereby reminded that (a) the optical fiber inside the cable is essentially made of glass, and (b) sharks are known to have a biting torque that measures in the range of several hundred pounds per square inch.)
Another reason for determining armor requirements in advance is that the type of armor used affects how much cable can be carried by a ship at one time.
Captain Frank Kitt of the CS Bold Endeavour -- part of the Global Marine fleet owned by Global Crossing - says that the two storage drums in the hold of his ship can carry between 4,000 and 6,000 km of fiber, depending on the armor thickness. "Obviously, a double-armor cable is thicker than single-armor -- about 46 mm compared to 31 mm," says Kitt. "That may not sound like a big difference, but it is when you coil it up in one drum."
Survey says
Another aspect of pre-planning a submarine system, says AGC's Milroy, is mapping out the undersea terrain.
"You have to do a marine survey, where you're taking a look at the sea bed and looking out for things like mountains and valleys and areas where earthquakes might pose a problem," Milroy explains. "You want to avoid natural and man-made formations and areas where there's plate movement activity. At the same time, you want the cable path to be as straight as possible. You don't want any bends because you risk breaking the fiber."
Even more potentially challenging are the things that most people outside the international carrier business might not associate with subsea systems at all, says Level 3's Larm, who offers a fairly long checklist of items.
"Oil exploration and exploitation areas, military zones, dumping zones, third-party territorial waters and political claim areas are all things to watch out for," Larm says. "You also want to avoid areas where there's heavy fishing activities or dredging. You also want to take things like water currents into account."
Then there's the matter of selecting a landing site. This is not to be confused with getting a license to land an international cable in a market -- which is certainly a key issue, but only for private systems like East Asia Crossing and Level 3's Tiger network, since club cables like SEA-ME-WE-3, APCN-2 and FLAG are the products of incumbent telcos who have had permission to land cables domestically since at least the start of the 20th century.
According to Su Weichou, VP for the Greater China market for Level 3, there are many issues to consider in deciding where to physically land a cable. He suggests keeping the cable away from the local shipping channels. "The reason is that you have to consider your future operation and maintenance plan," he says. "If you run the cable through a shipping channel and it breaks, you have to stop all ships from using that channel while you're repairing the cable."
Su offers Level 3's own experience with selecting landing sites for the Tiger system as an example. "In Taiwan, we couldn't land cable anywhere on most of the east coast because there's a lot of undersea volcano and earthquake activity just offshore," Su says. "Landing the cable on the southern tip presented a backhaul problem because it's too far away from the exchange. We also had to be careful with deploying cable in the Taiwan Straits, because it's a politically sensitive area."
By the book
The bright side is that by the time all of that gets sorted, deploying the cable itself is actually a relatively by-the-book affair. Once the cable itself has been manufactured according to spec, it's loaded onto the ship.
"After the shore ends are put in," says AGC's Milroy, "at both ends you run about 10 to 15 km of cable from the [beach] manhole and tie it off to a buoy, then you basically run the cable between the ends according to the survey."
That survey is loaded into the ship's computers, so the ship is in essence preprogrammed to follow the undersea route plotted out for the cable.
During this process, the cable isn't just lying on the sea bed -- at least not for the whole length of the system, although this was standard practice until at least the 1960s. Nowadays, the cable is buried under the sea bed, offering further protection from fishing boats, anchors and shark attacks.
Burial depth varies according to the situation. Burying the cable becomes optional at depths below 2,000 meters. For those who choose to bury the cable at those depths, a meter under the floor is usually sufficient. In shallower waters (from 1,000 meters and up), burial is virtually mandatory, and a burial depth of 10 meters is strongly recommended, especially as the system gets closer to shore.
The burial process is performed by the self-explanatory cable plow, which is remotely controlled from a bay onboard the ship. So is the ROV (remote operated vehicle), a track-mounted vehicle whose job is to guide the cable to the appropriate place mapped out for it on the sea bed. Both are bristling with video cameras so the remote operators can see the floor and make sure the burial is done properly. The cable plow is typically capable of plowing through solid rock as well as sediment.
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