An exemplary medical system includes a first electrical circuit (204-1) on a PCB (206), a second electrical circuit (204-2) on the PCB and electrically isolated from the first electrical circuit, and a free space optics interface assembly (302) on the PCB. The free space optics assembly includes a housing (402) defining a free space chamber (404) in the housing, an optical transmitter (416) having an input (426) that is electrically coupled to the first electrical circuit, and an optical receiver (418) in optical communication with the optical transmitter via the free space chamber and having an output (432) that is electrically coupled to the second electrical circuit. The optical transmitter and the optical receiver are hermetically sealed within the housing.