- long runs that are not that long. hdmi does not like long cables at all. even an overhead projector in a classroom requires super expensive cables (ever wondered why it's still mostly vga?)
- packing multiple displays in a single cable. fiber is so thin that with trunk cables you get a lot of strands in a single cable, capable of running a lot of displays
- just getting a really thin cable that can be run in existing conduits or hard to reach places
I did buy such a cable for home for the third reason, to run from the PC in the office to the TV in the living room. It runs on a bog standard OM3 MPO cable. The specific one I got comes from HeyOptics and their website already showcases a few usecases [1]. (not affiliated, just a great product that just works)
As for stadiums and more generally broadcast video, they're using SDI instead of HDMI. Those are indeed most of the time fiber, both for range and weight (think of the cameraman running along the terrain during a sport event, and their long tail of cables). When they use HDMI it's more in the control room.
8m or so is the limit for HDMI passive cables being 100% reliable.
If you want to go 15-30m--- using a video source from another part of your house, or to drive a projector in the middle of a classroom--- and you buy an "active cable", odds are it's fiber optic inside.
If you want to go hundreds of meters away, you'll get a purpose-built box that uses your own optical cables instead of a cable that hides the optical transceivers inside.
It's fairly thin, quite a bit thinner than most of my traditional copper cables I think. Apparently it's nominally 15m, they also have a 20m one: https://www.monoprice.com/product?p_id=43328
Copper thunderbolt cables are only good for 2-3m, after which you need active cables or repeaters and fiber is easily the best option at that point.
HDMI and DisplayPort are good for a bit longer than Thunderbolt over copper, but not by all that much. HDMI 2.1 can only go to around 3m as well now.
So we're in a world where "long" is a mere 5 meters / 15 feet. This is why so many VR headsets are using fiber cables - it has to be long to enable the movement and logistics of connecting a PC to someone freestanding in a room, but modern video signals are just too hard to drive over copper at that not really that long distances.
Are these used for very long runs - as in a video source to a projector (via hdmi) hundreds of meters away, like in a stadium..?
Thank you!