Bus system with optical waveguides having collision detection

Abstract

Given a bus system comprising an optical waveguide, an electro-optical transmitter, and an opto-electrical receiver, the transmitter is constructed such that the light power coupled into the light waveguide and dependent on the information signal to be transmitted is variable in digital steps. The receiver is comprised of DC-coupled amplifiers without gain control. It contains a preliminary stage for generating a useful signal from the light signal, and has a first comparator stage for generating the information signal from the useful signal. The receiver also includes a second comparator stage to which a reference voltage variable in digital stages is supplied and which samples the level of the useful signal emitted by the preliminary stage. The second comparator stage emits a collision signal when the useful signal moves the reference voltage upwardly and thus indicates that at least two transmitters are coupling light into the optical waveguide. The structure of the transmitter and of the receiver enables a DC transmission circuit having the special advantages of the optical waveguide. By means of the adjustment of the transmitters and of the receivers, moreover it can be achieved that the simultaneous access of a plurality of transmitters to the optical waveguide can be determined from the height of the level of the useful signal emitted by the preliminary stage.