I have no idea what plasmon signal is, so I think about it as a train. Then, plasmon guide acts as rails, plurality of signals as a traffic light, and the waveguide as an electric wire that runs along the rails toward the traffic light. That's all.
The whole patent is a great illustration of how people keep reinventing the railway system even when they think they invent some fancy new technology.
On the system level, the key to understanding a patent is to figure out which element plays the role of Payload. In this case it's "plasmon signal".