Optical wavelength division multiplexing transmission network system using transmitting/receiving apparatuses having 2-input and 2-output optical path switching elements

An optical wavelength division multiplexing transmission network system comprising:

• an arrayed-waveguide grating type multiplexing/demultiplexing circuit having N input ports and N output ports, where N is a plural number;
• and
• N transmitting/receiving apparatuses, each apparatus being optically connected to a predetermined input port and a predetermined output port of the arrayed-waveguide grating type multiplexing/demultiplexing circuit, wherein:
• the arrayed-waveguide grating type multiplexing/demultiplexing circuit has a wavelength response having a cyclic input/output relationship;
• and
• each transmitting/receiving apparatus comprises:
• a demultiplexer for demultiplexing an optical signal input from the predetermined output port of the arrayed-waveguide grating type multiplexing/demultiplexing circuit into signals of N wavelengths, and respectively outputting the demultiplexed optical signals from N output ports;
• a transmitter for respectively transmitting optical signals of N wavelengths from N output ports;
• a receiver for respectively receiving optical signals of N wavelengths from N input ports;
• a multiplexer for multiplexing optical signals of N wavelengths input from N input ports, and outputting the multiplexed signal to the predetermined input port of the arrayed-waveguide grating type multiplexing/demultiplexing circuit;
• and
• N 2-input and 2-output optical path switching elements corresponding to N wavelengths, each switching element being independently switched between first and second connective conditions, wherein:
• in the first connective condition, the output port corresponding to a specific wavelength of the demultiplexer is connected to the input port corresponding to the specific wavelength of the receiver, and the output port corresponding to a specific wavelength of the transmitter is connected to the input port corresponding to the specific wavelength of the multiplexer;
• and
• in the second connective condition, the output port corresponding to a specific wavelength of the transmitter is connected to the input port corresponding to the specific wavelength of the receiver, and the output port corresponding to a specific wavelength of the demultiplexer is connected to the input port corresponding to the specific wavelength of the multiplexer.