In this paper,a 4×4optical switch ma trix based on free carrier dispersion effect is designed and fabricated on silic on-on-insulator (SOI) water by a 0.8μm standard commercial CMOS line.It cons ists of four electro-optic 2×2multimode imaging-based Mach-Zehnder interfer ometers.As a basic unit,the proposed switch matrix can be extended to n×n matrix switch and used in both optical space-division and optical time-division switching networks.The two paired MMIs in each Mach-Zehn der structure are used as 3dB power splitters and combiners.Each switching elem ent is electrically driven with an independent extermal power supply.By injectin g free carriers into phase shifter with the active forward P-i-n diode,the π phase shift required for switching action is achieved.Experimental results show that the 4×4silicon photonic switch matrix has the crosstalk level lower tha n －8.02dB with a common spectral bandwidth as large as 35nm,which is from 1530nm to 1565nm.Furthermore,when a specif ic square-wave signal with 10%－90% transition time of 5ns is loaded,the switc hing response time is measured to be 17.4ns for the rising edge and 21ns for t he falling edge,respectively.