Summary form only given. The authors discuss optical waveguiding at a wavelength of 1.3 microns in a separation by implantation of oxygen (SIMOX) sample with a silicon top layer about two microns thick on a buried SiO/sub 2/ layer about 4000 AA thick. The sample was formed using the standard SIMOX process with subsequent growth of epitaxial Si by chemical vapor deposition (CVD). The waveguide length was 1.1 cm. Very thin, very thick, and double-layer buried oxide structures have also been obtained with a multiple implantation process and growth of epitaxial Si by CVD. Optical waveguiding can be obtained in both silicon layers of a double-buried-layer SIMOX wafer. In addition, when the SiO/sub 2/ layer between 1 and 2 has a thickness of one micron, the guided optical signals in 1 will be independent of those in 2 because the guides are not coupled. Alternatively, optical signals can be transferred from one level to another at certain locations. For example, if the thickness of the 1-2 SiO/sub 2/ layer is reduced locally to 1000 AA, waveguide theory predicts that the waveguides in 1 will couple strongly to waveguides in 2 at that location. >