#38 Light-emitting components

[Cousteau]

Would it be possible to add an LED and a light bulb that actually emit light, or make the already existing LEDs emit light? Since there are already photoresistors and phototransistors ("light sinks"), it would make sense that there were some light sources.
(I wanted to make an opto-coupler with an LED and an LDR, but it can't be simulated with precision unless a light source is implemented)