RF Frequency Stacking over Fibre/Fiber Optic

I am an Electronics Engineering student and for a large project, I am looking into satellite TV distribution over a Fibre Optic network. To do this, a Fibre LNB has to be used to capture and convert the incoming RF to IF to send down the Fibre Optic cabling. To enable the full frequency spectrum to go down a single fibre cable, the technology used by the manufacturer is 'frequency stacking' and this ultimately allows multiple users on the same 'line', watch different channels (as opposed to a traditional coax system where each user generally needs their own coax link to the LNB or a multiswitch needs to be used).

As part of my study I am trying to simulate the system (in Optsim) as best I can and I wondered how the 'frequency stacking' might be done. My thought is that as the incoming signal is modulated using QPSK, I wondered if frequency stacking is achieved through the use of PM-QPSK/DP-QPSK utilising dual polarisation? I know that the signal is transported over 4 'sub bands', being Vertical High, Vertical Low, Horizontal High and Horizontal Low (referring to polarisation and high/low voltage level) as stated by the manufacturer.

Is this the likely method or is 'frequency stacking' a different thing altogether?