An optimize delectroabsorption modulator structure is designed for high speed optical communication systems considering the extinction efficiency, operating bandwidth, polarization loss, and wavelength chirping. the operating wavelength region is $1.55mu extrm{m}$ and the deep ridge structure is adapted for th eminimum polarization loss. Simulations show that the absorption layer thickness larger than $0.25mu extrm{m}$, and the modulator length shorter than $200mu extrm{m}$ are required for the bandwidth over 10GHz. To obtain the modulatiron efficiency over 10dB/V, a wavelength detuning needs to be determined less than 40meV.