Abstract: A network system capable of delivering a large amount of data such as video data freely according to the intentions of the sender and the receiver alone is realized by a plurality of stations provided on at least one loop shaped optical network in which any one of the plurality of stations is capable of carrying out unidirectional communications with respect to any other one of the plurality of stations, where at least one wavelength is allocated to each station such that each station can transmit data by using a wavelength allocated to each station, receive data of any wavelengths transmitted from any other stations, and select only necessary wavelengths so as to select correspondent stations from which data are to be received.