Does Wii's sensor bar send signals or is it just a source of "light"?

My Wii's sensor bar is standing at the top of the TV and when I sit in front of my TV, the sensor bar is about my head level. I know that the sensor bar emits infrared radiation for the Wii Remote, and if I look at the sensor bar with a camera, I see white lights in the camera screen. Does Wii's sensor bar send signals or is it just a kind of source of light for the Wii Remote to recognize?