Thank you for the message. Yes, I made error in the description.  I feed in one of the  data from loader into FCNN (to be trained) network . Then ,  concatenate its output with another data from data loader, and feed the concatenated one to the  “model” (which is trained). The output from “model” is used to calculate error . This error is to be backpropagated through (FCNN).
Again, thanks a lot for your precious time here.