The fiber transceiver industry
When you buy transceivers for your switch, it is standard practice to order them from your network equipment manufacturer. However the switch vendor doesn’t actually manufacture these transceivers. There are a number of fiber interface transceiver manufacturers in the world, such as Finisar, Avago, JDSU, MRV, AOI, Delta and Wavesplitter.
These vendors will supply a variant of their standard transceiver to the switch vendor for resale. The switch vendor will perform testing of that transceiver against their switch, create a compatibility matrix and SKU for that transceiver and start selling the transceiver.