Modelling and design of an optical receiver

Dear all,

I am working on the design of an optical receiver consisting of a Transimpedance amplifier (TIA), a two stage variable gain amplifier (VGA) and an output buffer.

I am initially modelling both the TIA and the VGA using a simple verilogA behavioral model to gain some insights. I have a question regarding my behavioral model:

The TIA gives me input referred noise current and the VGA gives me input referred noise voltage. Is there any formula to convert these input referred noise quantities into an equivalent noise figure for the whole system?

Thanks!