How do fiber Ethernet transmitters set their power output

Connect your replacement switches back-to-back with a fiber patch cable and verify for sure that their fiber ports work. If they do, then double check the patch cords you're using at each end in the same manner. If you really want to slog through it yourself and have the right patch cables you can use the switches as cheap testers to test at each of the splices (assuming you have connectors on the splices).

If the switches do work, get a better fiber contractor in there. It sounds like your contractor was dodgy. I agree w/ the other posters re: their meter. My experience with contractors testing fibers for me is that their meter knows far, far more than I do about a given fiber.

Pretty much don't bend them past 90 degrees under load, pinch them, step on them, or crush them. Fiber has a minimum bending radius and varies between fiber manufactures (check out their documentation on the specific fiber). Fiber has a lower tolerance to pulling tension so you should generally pull it by hand, steadily, and not jerky. For the final install keep the tensile load low. While they are not as tolerant to abuse as a cat5 cable, they are actually fairly resistant to abuse.