An improved electro-optical system has a planar waveguide coupled to a photodetector through a transparent substrate. The planar waveguide is within a planar optical structure that can be part of optical communication network. The photodetector is positioned to receive light that passes from the waveguide through the transparent substrate. The photodetector can be electrically coupled to electrical circuitry along the transparent substrate for connection to a electrical apparatus. Corresponding methods for forming the electro-optical structure are described. These improved electro-optical systems can be used for terminating an optical transmission system at an end user or a local network associated with a group of end users.