How data is routed from one landing point to another on submarine cables? On submarine optical cables with one trunk and several landing points, how does data that leaves one landing point be routed to a desired destination at another landing point? I have many hypotheses: \- The data is broadcasted to every other landing point. \- The data is always sent to a specific other landing point, as at the branching point only some fiber strands are branched from the trunk. Which one of them is true, or are all of them wrong?

As others have said, it goes from one point to another. Here are some explanations from manufacturers.

* Mistubish's info shows that the branching units really just split out pairs from the shielding, ie they always go from one point to a single other point. Photos and specs: <
* Nokia (formerly Alcatel-Lucent) underwater says can go 500 km without powered electronics (repeaters); branching units are powered or unpowered; cables have typically 8 pairs. <
* TE conference talk report covers end to end with good photos and some technical data <