Checking fiber cables for light without risking my eyes
Solution 1:
Something everyone carries around with them, a camera phone, can be a massive help. Even if the light is so faint that you can barely make it out, you should be able to tell the difference with a camera phone.
Here's an example of a rx cable (with no light coming from it):
Here's an example of a tx cable (with light coming from it):
It's really blurry because most camera phones won't focus a eighth of an inch from the lens, but it gets the job done without risking your eyes, and uses a tool that most everyone has.