It's possible to find the approximate location of a break by looking at its influence on reflections. A double break, as you're suggesting, would eventually be noticed.

(If that wasn't possible, then repairing cable breaks would be insanely expensive.)

Right. And if the US has been doing this for a decade or more, you'd think that at least one of the taps would have been discovered.

Who says they haven't?

As far as spying goes, the game has evolved to the point where it's not really embarrassing any more. Everybody knows that everybody does it, and there's pretty strong resistance to going public. If anything did get discovered it'd probably be used for disinformation or behind-the-scenes political capital if not just destroyed. Finding a box of electronics at the bottom of the sea isn't quite the same as capturing an enemy pilot in a spy plane [1] and it's gotten to the point that embarrassing yourself for being spied on is just as bad as embarrassing an adversary (or friend) for doing the spying. Plus, how are you going to attribute blame anyway?

1: https://en.wikipedia.org/wiki/Francis_Gary_Powers

Well, Russia did eventually exhibit the Ivy Bells one. And Google staff did react to news that NSA was tapping its traffic. I'm not arguing that cables aren't being tapped. It just seems odd that none of the major cable operators have revealed anything. But as you say, there's arguably resistance to going public.

I wonder how many reported cable breaks were in fact screwed up tap installs ;)

I would take with a grain of salt and publicity around espionage acts. Snowden's release is just about the only one I believe was genuine or not part of some back room dealings.

The first assumption is that any such announcement by any entity public or private is either calculated or forced with plenty of forces in the background pulling the stings. It would make the most sense that pieces of Google were in the know, being forced by secret orders, and begging to be able to feign outrage publicly to save face.

A person doesn't have to be a conspiracy nut to have reasonable doubt about any of this. Secret courts, secret orders, and massive NSA data collection are all general public knowledge. It's hard to believe there is any public disclosure that is not planned and carefully negotiated.

I don't doubt the US is capable of splicing - I think a lot of classified research was done to counter the detection of unauthorized taps. However, a huge number of cables pass through friendly countries and it's much easier to negotiate access. Another option is to electronically subvert the network equipment connected to the optic fiber. I imagine cable splicing is done sparingly, or when the easier options are not viable.

Discovered by who? I'm pretty sure the CIA/NSA will just "disappear" anyone who tries to report the anomaly.

You're pretty sure?

Let me rephrase that: I'm positive the CIA has in the past and will continue to make people disappear.

https://en.wikipedia.org/wiki/Black_site

Well, that's different than what you said. I agree with that completely.

yes https://theintercept.com/2015/09/28/death-athens-rogue-nsa-o...

Sounds fascinating but is there a tl;dr? I'm not doubting the CIA disappears people, I'm doubting that they would need to in the above scenario.

That is one way you can also passively tap a fiber without breaking it, I am not sure if it could be done deep undersea, I suppose it is possible with the right set up. Basically how it works is you have to open up all the cladding and get to the bare fiber (not always that easy) but assuming you can do that, then you can take another fiber and put it right next to, parallel with the main one and then apply a little heat, the proximity of the tapping fiber will pick up a small signal. It is called a fused biconical splitter, it is possible to do non-intrusively.