Run an INFRARED repeater,
photocell here, emitter here, easy-peasy.
The Big Bang Theory Season 1, Episode 2
What's up with the INFRARED cameras?
The Big Bang Theory Season 4, Episode 18
The optics are great.
It's got INFRARED technology.
The Big Bang Theory Season 6, Episode 21
Now, inside we've got motion detectors,
INFRARED sensors...
The Big Bang Theory Season 3, Episode 13