We present a fully integrated Mach-Zehnder interferometer in silicon-on-ins
ulator technology. Modulation of the index of refraction is achieved throug
h the plasma dispersion effect resulting in a bandwidth in the 10 MHz range
. A particular and innovative design makes this device completely compatibl
e with CMOS technology allowing electronic functions to be integrated on th
e same substrate. Measurement results, limitations due to thermooptic effec
t and absorption related to charge injection together with further improvem
ents are discussed.