Patent ID: 7433594

Claim:
A node apparatus in an optical wavelength division multiplexing network having a multi-level structure, said node apparatus being connected to a lowest level network and a network higher than the lowest level network (hereinafter referred to as a “higher level network”), the higher level network including a bidirectional primary fiber path and a bidirectional protection fiber path, the lowest level network including a plurality of optical network units (ONUs) connected thereto, each ONU being allocated with a respective wavelength and capable of de-multiplexing, said node apparatus comprising: a first passive optical component configured to receive and branch optical signals from the bidirectional primary fiber path, and couple optical signals received from the lowest level network to the bidirectional primary fiber path; a second passive optical component configured to receive and branch optical signals from the bidirectional protection fiber path, and couple optical signals received from the lowest level network to the bidirectional protection fiber path; an optical switch configured to select and output optical signals received from the bidirectional primary fiber path if the optical signals are being input from the bidirectional primary fiber path, and select and output optical signals received from the bidirectional protection fiber path if severance of the optical signals is detected in input from the bidirectional primary fiber path; an optical divider configured to divide optical signals received from the ONUs into a plurality of directions, the divided optical signals being coupled to the first and second passive optical components; bidirectional optical amplifiers configured to amplify the optical signals input to and output from said first and second passive optical components; an optical star coupler connected to the ONUs; and an optical circulator provided between said optical switch and said optical star coupler, said optical circulator being coupled to said optical divider, wherein said node apparatus provides an optical communication path between the higher level network and the lowest level network without converting the optical signals into electrical signals.