T2 and T1 are in fact physically connected between C gates and D gates, and you can walk that, but that's a long shlep. Instead, after arrival, follow signs to Terminal A (not "Baggage Claim" or "Exit", that takes you landside), take the train to "A/Z Gates" stop (you'll be in the airside carriage), through transfer security control next to the train stop, two levels down to A, through immigration and that's it, you're at deaprture gates A. Should be OK if your inbound isn't excessively delayed. I find transfer immigration and transfer security at FRA are not as bad as immigration and security are for those arriving/departing FRA.