The original - unencrypted - data from a user, or sensor, pass through encryption layer before going to FHE system. I'm not sure I understand the question, but

The original - unencrypted - data from a user, or sensor, pass through encryption layer before going to FHE system. I'm not sure I understand the question, but to me FHE is purely computational thing - only CPU and RAM are involved, and also operations include input and output data. To prevent the system from learning anything about the data, all operations are of kind (RAM, encrypted output) = FHE(RAM, encrypted input) so all data in RAM get there in the encrypted form in the first place. Thus the FHE system never see unencrypted data. Coming back to an unhackable consumer device - if you measure a physical property, like temperature, or have a digital model of anything - you have to provide this data to FHE system only in the properly encrypted form. That encryption is on the consumer, not on FHE, as well as decryption of results of FHE operations. It's only the processing of data which FHE does.