If anyone has told you there are "Tiers" in optical transceiver quality, you've been misinformed.
Optical transceivers are real workhorses in the world of modern business networks. These small plug-in devices are used in most brands of switches and controllers - most notably Cisco - and allow them to accept a far wider range of cable and fiber types than the switch could ever natively support.
If your switch has an SFP (Small-Form Pluggable) port, then it can be swapped out at will whenever you have a need for a new type of fiber run or distance. These ports are usually also plug-and-play, so that rebooting isn't necessary.
Sadly, some manufacturers want to nickle-and-dime you for their own matching brand of SFP transceivers, to the tune of hundreds of dollars, when realistically the components cost roughly 1/10th their list prices. To convince people to buy from them, rather than third-parties, they then engage in the age-old art of FUD: Fear, Uncertainty, and Doubt.
Companies like Cisco would desperately like you to believe that third-party transceivers are dangerous, or low quality, but it's simply not the case.