listen to data traffic in fibre cables - how to intercept or tap a fibre

In general it is said, that data in fibre optic cables are safe from interception.
It's true, there is no electro magnetic way to "listen" to light pulses. And it is not possible to see the light pulses from outside without breaking or interrupting the cable. That sounds understandable. 

Why it is possible to listen to fibre cable data traffic: 
1. fibre optic cables can be very very long 1000 km and more this makes it difficult to protect it from foreign access.

2. even if cables lay on the ground of the sea or below earth, there are intersection points that allow to install devices for interception. As there are always several 100 fibre cores in one cable it is not easy to find the right one, but there are also ways to get it. For example by stealing cabling information documentation. 
2.a interception by cutting a fibre and splice a capture device in between the line. Done within a short interception of 1 hour that might not be suspicious. 
2.b use a Biegekopplerdevice to couple out the light without interruption (Einstein, SRF) 
2.c if there is an active device at an interception point, it is possible to hack such a network switch and then listen to the data 

be aware: The US submarine Jimmy Carter is said to be able to tap underwater fibre sea cables to eavesdrop communication (Washington Post, ARD).