PURPOSE: To perform wavelength multiplex communication by using a netty optical communication network.

CONSTITUTION: The netty optical communication network is comprised of optical transmission lines 10a-10e coupled in net shape and optical communication equipment 121-126, and transmission routes for connecting the optical communication device of a transmission destination and that of transmission origin, for example, 1ab, 1be are comprised by the combination of one or plural optical transmission lines. Signal optical wavelength in use is decided in advance at every transmission line. As a result, it is possible to distinguish the transmission destination of signal light from the transmission origin based on two points with what signal light wavelength signal light is provided, and from which optical transmission line to be connected to the optical communication equipment input/output is performed. Therefore, the optical communication equipment can accurately perform the transmission, reception, and relay of the signal light in the netty optical communication network based on the transmission destination and the transmission origin distinguished by the above two points, and also, they are performed by using an optical multiplexer/demultiplexer.