Undersea fibre-optic cable. Many layers. (Courtesy KCS)
Cables need armour (against sharks etc) and electical repeaters (signal boosters) (Courtesy several cable makers etc)
In connection with the New York Times article about the Russians not even contemplating cutting honest Western undersea cables - that article seems like another attempt of the US Navy and industry to boost the sales prospects of the US Unmanned Underwater Vehicles (UUVs).
Undersea cables were first laid in the 1850s between Britain and Europe and between Britain and US-Canada. Cables have been broken by human (fishing trawlers, poor leaky cable insulation material and anchors) and natural (earthquakes, currents, bitey sharks and whales) activity. A number of ports, such as Halifax, Canada, near important cable routes became homes to specialised cable repair ships.
The first CS Alert all you need to cut German Atlantic cables in 1914!
Surface ships have been more commonly used to cut undersea cables. In World War One, the British General Post Office Cable Ship CS Alert (above) was used to locate and cut five German cables heading into the Atlantic. A similar operation cut the German cables that connected Great Britain to the German coast. Successive missions by the CS Telconia and other ships later in the war eliminated the remainder of Germany's cable network and, in some instances, pulled the cables up with their grapples and relaid them into British and French ports for use by the Allied powers instead. Theft? See this source.
This useful book link indicates submarines, very early on, were also active in cable cutting. "The U-151 [in 1918] also cut the undersea cables between New York and Nova Scotia and New York and Colon, Panama."
U-151 (Photo courtesy http://www.steelnavy.com/HPww1UBoats.htm)
U-151 had an amazing performance then and now. It was built in 1916 (World War One) 1,500 tons (surfaced), 18 torpedos, 2 x 6 inch guns, 56 crew and a range of 25,000 nautical miles.
[As an aside - the century old U-151's specifications beg the question "Why does Australia in 2015 think an extra large 4,000 ton (surfaced) conventional submarine is necessary to give 11,000 nautical miles - less than half the range of U-151 a World War One submarine?]
At the beginning of World War Two Atlantic cables would have been cut in 1939, mainly by surface ships. In the Pacific the Japanese advance was so fast that allied cable cutting sometimes took until 1945. "/C" commented October 25, 2015 at 7:49 PM at http://gentleseas.blogspot.com.au/2015/10/south-korean-hhis-hds-400-small.html about British XE-class mini-submarines used to cut Japanese undersea cables in 1945 between Hong Kong and Saigon and between Hong Kong and Singapore.
One of the cutters was Max Shean from Western Australia doing very hazardous duty.
Since 1945 cables continue to be broken by fishing trawlers, anchors, earthquakes, currents, and bitey sharks. In response to this threat to the communications network, the practice of cable burial has developed. Still, cable breaks are by no means a thing of the past, with more than 50 repairs a year in the Atlantic alone, and significant breaks in 2006, 2008, and 2009.
The risk of fishing trawler nets causing cable faults was exploited during the Cold War. For example, in February 1959, a series of 12 breaks occurred in five American trans-Atlantic communications cables. In response, a United States naval vessel, the U.S.S. Roy O. Hale, detained and investigated the Russian trawler Novorosiysk. A review of Novorosiysk's log indicated it had been in the region of each of the cables when they broke. Broken sections of cable were also found on the deck of the Novorosiysk. It appeared that the cables had been dragged along by the ship's nets, and then cut once they were pulled up onto the deck to release the nets. The Russian stance on the investigation was that detaining Novorosiysk was unjustified, but the United States cited the Convention for the Protection of Submarine Telegraph Cables of 1884 to which Russia had signed as evidence of violation of international law.
Thus the Russians do have a record of cutting cables but they do not need dark ominous $Billion dollar submarines or UUVs to do it – just small cable ships or even trawlers.
Cable Landing Stations (see diagram second from top) can locate a break in a cable in less than a second. This is using electronic monitors and measurements, such as through spread-spectrum time-domain reflectometry (SSTDR).
In a major war cable cutting has three main advantages:
1. It immediately disrupts an enemy's international communications.
2. It also immediately disrupts domestic communications because, in the digital age, much of the internet AND telecommunications between major cities of the same country rely on international servers and links.
3. Having lost international cables an enemy is forced to use satellites, microwave links and other radio links. Since the beginning of World War One cables have been cut, in part, because subsequent reliance on radio links is much more easy to intercept - see https://en.wikipedia.org/wiki/Submarine_communications_cable#British_dominance_of_early_cable