Patent ID: 7164861

Claim:
An optical wavelength division multiplexing network having a multi-layer structure comprising at least three layers, said multi-layer structure comprising: a highest level network which is a ring network, said highest level network comprising at least one center node and two or more remote nodes which are joined by at least two optical fibers; at least one intermediate level network which is a ring network, said intermediate level network including one of the nodes belonging to the highest level network or to another intermediate level network immediately above said intermediate level network, as a center node thereof, nodes belonging to said ring network of said intermediate level network being joined by at least two optical fibers; and a lowest level network which is a star network centered around an access node which is a remote node belonging to said intermediate level network, said access node multiplexing traffic from one or a plurality of optical network units (ONU), said ONU and said access node being directly joined by at least one optical fiber, wherein said remote nodes amplify optical wavelength division multiplexing signals which are transmitted on an optical fiber of said highest level network to which said remote nodes belong, branch the amplified signals to an optical fiber of said intermediate level network, couple optical wavelength division multiplexing signals, which are input from an optical fiber of said intermediate level network, to optical wavelength division multiplexing signals transmitted on an optical fiber of said highest level network, and amplify the coupled signals; wherein said access node amplifies the optical wavelength division multiplexing signals transmitted from said optical fibers of said intermediate level network to which said access node is connected, selects optical signals having wavelengths which correspond to said ONU, outputs the selected signals to said ONU, multiplexes said optical signals transmitted from said ONU, divides the multiplexed signals in a plurality of directions, amplifies the divided signals, and transmits the amplified signals to an optical fiber of said intermediate level network to which said access node is connected; and wherein the center node belongs to said highest level network and said ONU establishes a direct communication path by using lights of different wavelengths, the optical signals being amplified, branched, and routed at said remote nodes and said access node provided therebetween.