Ds has got a cot toy that is a projected show onto the ceiling, birds going around. He knows exactly where it is in the cot. He'll wake up in the night, get upset, but as long as he can bang that button, and have a little light in his room, he settles down again.
I think it's pretty normal, I'm not sure he's exactly scared of the dark, more likely he's disorientated and unsure where he is. Can you get one of those little plug-in night lights, or a very soft light for his room? I'm paraniod about leaving doors open at night b/c of the increased risk of injury if there was a fire, so it'd be better if it was in his room.