Just a quick update, The sensors are prototyped but due to a few noise coupling and filter tuning issues, I don't have any conclusive results. The primary source of EMI was in the ribbon cable carrying the LED drive current which is parallel to the photodiode wires. As the current in the LED wires are orders of magnitudes greater than the photodiode wires, there is a lot of noise in the same frequency as the signal coupled in. Will look into shielding the wires.