As for common mode choke - what could that be?
What I don't get is this - sensors themself are digital. They output 1 (if IR light is detected) or 0. So the only way that the interrupt gets triggered is if somehow the voltage on the arduino pin drops (the interrupt is configured to trigger on falling voltage) when I turn on the light.
From your other postQuoteAs for common mode choke - what could that be? A common mode choke is two coils wound together on a single core but in opposite directions, any large transient signal on both lines will be suppressed as each line generates a magnetic field in opposite directions and they cancel out.
Try putting a 0.1uF capacitor from the arduino input to ground, that will help suppress pickup of interference signals.