Siemens Aktiengesellschaft

Rudolf Mittelmann

Hans Thinschmidt

An expansion network for increasing the number of subscriber terminations at a passive optical bus system comprising optical mixers is disclosed. The mixers are arranged in groups and the optical transmitters individually provided per subscriber are connected to the light receivers likewise individually provided per subscriber, being connected thereto in the manner of a mesh network via respectively only one of the mixers so that the attenuation of only one mixer is inserted into the optical path.

Expansion network for increasing the number of subscriber terminations

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.

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Ottobrunn, Germany

Rudolf Mittelmann