A silicon p-i-n diode Mach-Zehnder optical modulator integrated with grating couplers is fabricated in 0.18-mu m complementary metal oxide semiconductor technology. The device has an ultracompact length of 200 mu m. High modulation efficiency with a figure of merit of V(pi)L = 0.22 V mm is demonstrated. A novel pre-emphasis technique is introduced to achieve high-speed modulation, and a data transmission rate of 3 Gbps is present. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3560264]