I'am running 2" EMT from an outside enclosure through the exterior wall into a switch room that is being attached with beam clamps, The EMT is carrying a Fiber optic cable feed to the switch room that converts to PVC upon entering the room, can I ground the EMT outside using a ground bushing with a ground rod or does it have to be grounded to the building ground? The EMT is dedicated to the fiber only.
You don't need to ground a hamster run, either.
Suppose you had a hamster habitat. And instead of fiber optic, you were using this EMT to extend the hamster habitat to an outdoor maze. Would this habitat run require grounding *solely due to using EMT as a building material? Of course not. That would be silly.
Well, as far as NEC is concerned, fiber-optic cable that has no DC wires running it counts the same as a hamster. It simply does not count for anything at all, and is completely out of its jurisdiction.
The only time fiber-optic cable is in NEC's jurisdiction is when you intermix it in a conduit with electrical wires. But even then, they consider it disregardable if there is nothing metallic in it.
To be code compliant you would ALSO bond the fiber at the service entrance with a intersystem bonding termination. NEC 250.94
Just driving a ground rod and not bonding it to the service supply w/ a intersystem bonding termination creates parallel paths and potential differences for voltages.
Edit: In light of the dielectric properties that some Fiber cables have, NEC 770.93 requires the bonding or grounding electrode of fiber only when in contact with electric light or power conductors. If you do decide to bond even though the fiber is not in contact, there are quite a few requirements. Some that may be relevant to your scenario is the use of non-corrosive material like copper or similar material for the bonding. Galvanized conduit would suffice but not regular EMT.