Wavelength Division Multiplexing Passive Optical Network System Adopted Dual Central Office

Wavelength Division Multiplexing (WDM) Passive Optical Network (PON) system having a

• dual Central Office (CO), including:
• a ring type optical communication line;
• a CO including a plurality of optical transmission units for generating optical signals having different wavelengths, a plurality of optical reception units for forming pairs with respective optical transmission units, receiving optical signals having same wavelengths as the corresponding optical transmission units, converting the received optical signals into electrical signals and then outputting the converted electrical signals, a multiplexer/demultiplexer for multiplexing input optical signals having different wavelengths and then outputting a multiplexed optical signal to the optical communication line, and demultiplexing a multiplexed optical signal input through the optical communication line and then outputting demultiplexed optical signals, and a plurality of optical circulators for outputting an optical signal, output from an assigned optical transmission unit, to the multiplexer/demultiplexer, and outputting input optical signals, demultiplexed by the multiplexer/demultiplexer, to the assigned optical transmission unit;
• and
• at least one remote node having an optical add/drop multiplexer for dropping only signals having wavelengths in a specific band, from optical signals transmitted through the optical communication line and outputting to a subscriber side, and outputting optical signals transmitted from the subscriber side to the optical communication line, and an optical circulator for outputting the optical signals, dropped by the optical add/drop multiplexer, to optical reception units of subscribers' devices, and outputting the optical signals, received from optical transmission units of the subscribers' devices, to the optical add/drop multiplexer;
• the WDM PON system comprising:
• a plurality of COs;
• a first connection unit having a connection of an odd number of 1×2 couplers, the one side branched ends of one of which are alternately connected to one side branched ends of another 1×2 coupler, and which divide and transmit
• multiplexing signals, output from multiplexer/demultiplexers of the plurality of COs, and input signals, transmitted through branched paths, to the multiplexer/demultiplexers;
• a second connection unit having n signal compensation units, whose number is identical to a number of the 1×2 couplers of the first connection unit, which are connected to the branched paths of the first connection unit and compensate the signals transmitted and received through the multiplexer/demultiplexers;
• and
• a third connection unit for connecting the signal compensation units with at least one ring type optical communication line, thereby allowing signals to be transmitted and received between the multiplexer/demultiplexers and the ring type optical communication line.