A medical system includes a first electrical circuit, a second electrical circuit electrically isolated from the first electrical circuit, an optical isolator circuit coupled between the first and second electrical circuits, and a common-mode choke comprising a plurality of wires wound around a core and configured to reduce a voltage transient at an input of the optical isolator circuit to a level within a tolerance of the optical isolator circuit. A first end of the wires is conductively coupled to an output of the first electrical circuit and a second end of the wires is conductively coupled to the input of the optical isolator circuit.