I see what your saying BCD, but I can't say whether the optical part of POET is where the largest gains come from. Just the fact that GaAs is the base of the technology provides a huge increase in speed. It would be interesting to know whether those first chips that Dr Taylor produced had opticle elements, if anyone knows. I noticed on slide 24 of the CO on the web site both POET and PET are both attributed to having huge speed advantages, far more than the double you postulate. It is a good point you bring up though. Green