Silicon based integrated optics is attracting an increasing amount of interest due to low inherent loss at 1.3 μm and 1.5 μm and to the potential for transforming VLSI techniques from microelectronics to integrated optics. Different schemes for waveguides based on silicon technology have been proposed and examined [1-3]. Kurdi et al. [4] proposed SOI and low losses of rib waveguides in different SOI-material (BESOI: bond and etch back SOI, SIMOX-SOI: separation by implantation of oxygen, ZMR: zone melting recrystallisation) have been reported [5], The losses depend mainly on the Si top layer thickness (Fig. la).