2 input to 1 output Optical MIXER (not switcher)?

I have a PS3 connected to a Tritton AX Pro headset through optical. I would like to be able to mix in my laptop's optical signal with the PS3's though, and the headset only has one input. I have been looking around but I can't seem to find an adapter or anything that would MIX two signals into one. I do NOT want a switcher (of which there seems to be an abundance), but instead something that will simultaneously mix my laptop's signal with my PS3's signal. Is such a thing an inherent impossibility with this type of technology or can someone give me a link to something that does exist? All I can find are splitters or switchers, no passive (or even active) mixers. If anyone could help me out here, I would really appreciate it. Thanks in advance.