Patent ID: 7558477

Claim:
A communication recovering system for wavelength division a multiplexed passive optical network (WDM PON) comprising: a central office including: cyclic arrayed waveguide gratings (AWGs) C 1 and C 2 ; a first 1×2 optical switch which is installed at a multiplexed signal input and output lead of the cyclic AWG C 1 ; a second 1×2 optical switch which is installed at a multiplexed signal input and output lead of the cyclic AWG C 2 ; a first blue/red (B/R) band coupler which is connected to each of the first and the second 1×2 optical switches; a second B/R band coupler which is connected to each of the first and second 1×2 optical switches; a first optical fiber monitor which is installed on an optical fiber connecting the first 1×2 optical switch to the first B/R band coupler, and is connected to the first 1×2 optical switch; and a second optical fiber fault monitor which is installed on an optical fiber connecting the second 1×2 optical switch to the second B/R band coupler, and is connected to the second 1×2 optical switch; remote nodes including: a first remote node RN 1 which has a first cyclic AWG R 1 whose multiplexed signal input/output lead is connected to the first B/R band coupler and whose demultiplexed signal input/output leads are connected to first remote B/R band couplers, respectively; and a second remote node RN 2 which has a second cyclic AWG R 2 whose input/output lead is connected to the second B/R band coupler and whose demultiplexed signal input/output leads are connected to second remote B/R band couplers, respectively; and optical network units including: a plurality of transmitters/receivers; and star couplers which connect the plurality of transmitters/receivers to the first remote and second remote B/R band couplers, wherein when there in an fault in an optical fiber connecting the first B/R band coupler to the cyclic AWG R 1 or at an optical fiber connecting the first remote B/R band coupler to a corresponding star coupler of a corresponding ONU, optical signals are inputted/outputted through the first 1×2 optical switch and the second B/R band coupler, and when there is a fault in an optical fiber connecting the second B/R band coupler C 2 to the cyclic AWG R 2 or in an optical fiber connecting the second remote B/R band coupler to a corresponding star coupler of a corresponding ONU, optical signals are inputted/outputted through the second 1×2 optical switch and the first B/R band coupler.