A bit like a spider web attached to a tree, New Zealand’s internet network hangs off just 20 strands of glass fibre, each about the thickness of a human hair. Tom Pullar-Strecker explains.
You read that right. Those glass fibres, contained in four submarine cables connecting New Zealand to the United States and Australia, carry virtually all communications to and from the country.
Cut them all, and InternetNZ chief security officer Sam Sargeant says most of the modern technology systems we rely on for work and play would stop working.
Because so many systems and services are hosted overseas in the era of cloud computing, even sending an email to your next-door neighbour would probably be impossible.
The “weird interconnected” nature of modern systems means no-one knows exactly what services might survive and that would be hard to test without pulling the plug, Sargeant says.
“The systems we use to buy gas at the petrol station may require a global corporate connection and, if that goes down, can you buy petrol? Let’s hope so.”
How long have we relied on these cables?
Submarine cables are not an engineering achievement that came in the order one might expect.
The first transcontinental cable was laid between Britain and the United States in 1858, allowing telegrams to be sent between the countries for the first time using Morse code along its seven twisted copper wires.
Queen Victoria and United States president James Buchanan used it to exchange telegrams several years before the invention of the humble stapler in 1877, and 18 years before anyone stepped into anything resembling a motor car.
Now the world’s oceans are criss-crossed by more than a million kilometres of submarine cables, linking billions of kilometres of fibre on land.
The more modern submarine cables, laid after about 1988, contain several strands of glass fibre, rather than a copper wire, to carry their traffic.
How do they work?
The way fibre-optic cables transmit information is by having light shone down them that can be detected at the other end, in the same way that you might communicate with someone using a torch across a darkened field at night.
The modern miracle is not so much the cables themselves but the lasers and switching equipment at either end of the cables that can flick on and off and detect those flashes of light, in different wavelengths, at mind-boggling speeds.
It is those optical electronics, along with the number of strands of fibre, that determine how much information a cable can carry.
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At the moment, the highest-capacity submarine cables have transfer rates in the tens of terabits but as faster switching equipment is developed and commercialised that should further increase, allowing both new and sometimes also existing cables to carry more data.
This year, researchers in Japan reportedly sent a petabit (1000 terabits) of data down a single optical fibre in a second.
That is enough bandwidth in theory to transfer all the works of William Shakespeare to 250,000 different people in a hundredth of a second (uncompressed), or to simultaneously stream Netflix in HD to 200 million people.
If they are glass, will they last forever?
If a few strands of glass fibre were all that submarine cables were comprised of, then they might last almost forever but sadly that is not the case.
The light signals they carry need a boost about every 60km, using “repeaters” that are attached to every undersea cable, just as you might need a plug-in device to extend a wi-fi signal to a distant corner of your home.
The repeaters need power to provide that boost, which means every submarine fibre-optic cable also carries a copper power cable alongside its fibre strands.
That equipment limits the working life of cables to a few decades.
Power for the repeaters is usually provided by diesel generators at landing stations along the way, which has the practical effect that undersea cables need to come ashore about every 10,000km.
How are they laid?
A few things have not changed much since the 19th century.
As there is no machine to do it, cables – sometimes thousands of kilometres long – are wound by hand around huge spools in special cable-laying ships, like giant spools of cotton, in a process that can take several laborious weeks, before they are lowered on to the seabed.
The final few kilometres before they come ashore are usually buried, to protect them from being dragged up and cut by ship anchors.
What is their economic significance?
The most meaningful measure perhaps is that submarine cables underpin pretty much all international communications that take place today and most have large amounts of “unlit” excess capacity.
That capacity is the reason Kiwis can now video-call friends and relatives on the other side of the world for free, using services such as Skype and WhatsApp.
Without fibre-optic submarine cables, that just would not be possible.
Phone calls, internet traffic and television pictures can be relayed from one continent to another by satellites in space but not nearly as cheaply or efficiently, so subsea cables are here to stay.
Subsea cables can cost tens of millions to many hundreds of millions of dollars, depending on their length.
So traditionally they have been laid by large telecommunications companies such as – in this neck of the woods – Telstra, Optus, TGP and Spark.
But cloud computing giants such as Google, Microsoft and Amazon have increasingly been getting in on the act to help link their global data centres.
Who is behind NZ’s cables?
The first modern fibre-optic network connecting New Zealand with Australia and the US, the Southern Cross Cable Network, shaped in a figure of eight centred on Hawaii, was completed by a Spark-led joint venture in 2000 at a cost of US$1.3 billion (NZ$1.8b).
For many years it held a near monopoly on the flow of traffic to and from New Zealand.
But in the past few years there has been a flurry of activity.
In 2017, Spark, Vodafone and Telstra clubbed together to build an extra fibre line, the Tasman Global Access cable, to Australia.
The following year, independent operator Hawaiki Cable completed a $500m cable to the US and Australia.
Hawaiki is now hoping to lay the first international submarine cable from the South Island, to Sydney and Melbourne, to support its investment in a huge data centre near Invercargill.
And Southern Cross is refreshing its network with its new Next trans-Pacific cable due to be in service next year.
Are they reliable?
After the first transatlantic telegrams were sent in 1858, there was a large street parade on Broadway in New York to celebrate and unused sections of the cable were chopped up to make popular souvenirs.
Nowadays, people are only likely to pay much attention to submarine cables if they suddenly stop working, which is a very rare occurrence.
And that is just as well, as it could take weeks to send a specialist repair ship to fix a cable if it broke far out to sea.
Earthquakes, as well as ship anchors, have damaged and broken submarine cables but that is unusual, and New Zealand now has enough cables coming ashore in different places, with enough excess capacity, for no single outage to risk sending us back to the pre-internet age.
If a single cable was knocked out of action, communications traffic could quite easily be rerouted, though it might run slower.
But if they were all suddenly cut, that would be pretty much it for the internet until they were fixed.
What are the risks of that?
According to Britain’s English Historical Review, Britain’s very first military action after declaring war on Germany in World War I was to cut five cables linking Germany with France, Spain and the Azores.
And in recent years, concerns have grown that subsea cable could become an easy target in a global conflict that perhaps fell short of an actual war.
There is evidence also that subsea cables have been spied on, or at least that the ability to interfere with them has been tested.
The Russian spy ship Yantar and the US nuclear submarine Jimmy Carter are two of the vessels that are believed to have been modified specifically for such operations.
Surprisingly, it can be possible to “read” the data on a fibre-optic cable by bending it and detecting the tiny amount of light that will travel straight ahead and leak out through its plastic casing.
But then any submarine spy has got the challenge of how to make sense of all those terabits of encrypted data, deep under the ocean.
InternetNZ’s Sargeant has another concern.
The ransomware attack on the Colonial Pipeline, a fuel pipeline in the US, earlier this month shows how critical infrastructure can be attacked by “talented criminal groups”, he says.
The implications of submarine cable operators suffering a similar fate are reducing as the number of cables to New Zealand increases and the risk of a successful attack is remote, he says.
“But having said that, it is not impossible.”
