The Breaker Finder 5000

Interestingly I have a friend who is a structured cabling installer.
I have a few of his "fiber finder 5000" devices that he's constructed over the years.
Basically- it's hard to see if a fiber optic cable has "signal", and the higher the speed, the less the light shows up.
Sometimes it's also difficult to find pairs, especially with new construction.
He takes bright LED lights, and mounts them behind the connector of your choice- (ST, SC, LC, etc) and puts that into a project case with a battery.