Optical bus, and a signal processing unit

PROBLEM TO BE SOLVED: To provide an optical bus which freely attaches or removes a circuit substrate without requiring fine optical positioning during attaching plural circuit substrate to the optical bus to construct a signal processor, has high light availability, and can speedily transmit a signal, and provide a processor which performs signal processing such as data transmitting/receiving using the optical bus. SOLUTION: A signal processor includes a signal light incident part 15 where a signal light 70 is incoming into an optical bus 10, signal light outgoing parts 16a-16d which outgoes income and propagated signal light, a light diffuser 18 which diffuses signal light 70 toward a light transmitting layer 12, and light path changing part 19 which changes a light path of at least a part of the diffused signal light such that the light goes in the more parallel direction of the sheet plane of the optical bus 10.