An optical bus system (1) having a start-up state and at least one operating state is disclosed. The optical bus system (1) includes a mechanical support structure (21) arranged to receive and hold a master module (2) having a downstream optical interface (3) and a set of slave modules (6) each having an upstream optical interface (7) and a downstream optical interface (8). The modules are attached to the mechanical support structure (21) such that optical interfaces of adjacent modules are aligned and in close proximity to each other in order to enable optical communication (24, 25) between adjacent modules. Each slave module (6) is further provided with circuitry to form one or two shunting signal paths (30, 31) depending on operating state after an addressing procedure is completed in the start-up state. Hereby, it is e.g. possible to realize a robust and cost-efficient optical bus system with high bandwidth capability.