This is typical detail and says there is a fault on SEA-ME-WE 3 (South East Asia-Middle East-Western Europe) Segment 7 Route 1 Fibre 2. This is a land segment, so easy to get to and quick to repair. In this case, less than two hours between first notice of fault and a clearance message.
Location can be determined by OTDR (optical time domain reflectometer), which is built-in on some systems or by internal systems in terminal equipment. Sometimes, the optical path is still intact but a fault develops in the power feeding system that powers the optical regenerators. This can be a open circuit or shunt fault. Using a Wheatstone or similar bridge can determine the distance to that kind of fault.
For the old copper lines, the Telegrapher’s Equations describe the voltage/current on transmission lines as a function of distance/time and are the basis for determining where the break is.
At a break, the circuit is open. In these cases, the signal essentially reflects right back, so you can measure the distance to the break based on what you get back. We did a week of lectures on this in college, and it was really neat to see just how much you could deduce based on a couple relatively simple measurements.
No indeed.
Within a few days of declaring war in WWI, Britain cut the undersea telegraph cables between Germany and North America. This restricted their communications, and forced them to use radio (which Britain could eavesdrop on, and decode).
And again in WWII, undersea cables going to Axis countries were cut.
During the Cold War, the USA was a bit smarter. Instead of cutting Soviet cables, they installed an electronic tap on the cables.
Wiki has a [list of international submarine communications cables.](List of international submarine communications cables)
Also, that lovely map of some of the (publicly reported only–right?) cables was produced by Nicola Rapp of Forbes magazine, with data from GeoTel Communications, according to the Daily Mail.
The access points are sometimes secret, right? I remember but can’t find an article about an English one that was discovered, to the consternation of someone or other.
If we’re talking about the Okhotsk tap, then it was blown by Robert Pelton. Interestingly, per the wiki, the Soviets did not remove the taps immediately upon learning of the operation. YGIAGAM how much intelligence from the tap was disinformation.
OTOH, I doubt that was the only submarine cable tapped either. An interesting article on the USN’s issues with Soviet spies in the 80s—mostly on the Walkers, but there’s a short blurb on Pelton----can be found here.
EDIT: The history, Spycraft, details a similar operation, this one directed at Soviet data lines going from Moscow to, IIRC, Arzamas. Worth your time, if you’re interested in the history of technical spying and the CIA.
The TPC-5 which Toshiba won the bid for the control system had repeaters every 200 km. You can see the growth in the amount of traffic possible in a figure in this paper (it’s in Japanese, but the vertical axis is the number of voice circuits possible, which is now meaningless except as a reference).
I worked on the bid product for Toshiba, and lead the translation and documentation team. Toshiba bid in dollars instead of yen and wound up losing over a million dollars on the project. They fired the director of the project, and I would have been happy to see him go, except I had already moved along.
