Patent ID: 7848643

Claim:
A communication recovering system for a wavelength division 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 installed at a multiplexed signal input/output lead of the cyclic AWG C 1 ; a second 1×2 optical switch installed at a multiplexed signal input/output lead of the cyclic AWG C 2 ; a first blue/red band coupler connected to each of the first and second 1×2 optical switches; a second blue/red band coupler connected to each of the first and second 1×2 optical switches; a first optical fiber fault monitor which is installed at an optical fiber connecting the first 1×2 optical switch to the first blue/red band coupler, and is connected to the first 1×2 optical switch; and a second optical fiber fault monitor which is installed at an optical fiber connecting the second 1×2 optical switch to the second blue/red band coupler, and is connected to the second 1×2 optical switch; remote nodes including: a first remote node and a second remote node, wherein the first remote node includes a blue/red band coupler R 11 connected to the first blue/red band coupler; a blue/red band coupler R 12 connected to a red lead of the blue/red band coupler R 11 ; a first 1×2 star coupler connected to a blue lead of each of the blue/red band couplers R 11 and R 12 , and a cyclic AWG R 1 whose multiplexed signal input/output lead is connected to the first 1×2 star coupler, and the second remote node includes a blue/red band coupler R 21 connected to the second blue/red band coupler, a blue/red band coupler R 22 connected to a blue lead of blue/red band coupler R 21 ; a second 1×2 star coupler connected to a red lead of each of the blue/red band couplers R 21 and R 22 ; and a cyclic AWG R 2 whose multiplexed signal input/output lead is connected to the second 1×2 star coupler, wherein the blue/red band coupler R 12 and the blue/red band coupler R 22 are connected to each other by an optical fiber, wherein when there is a fault in an optical fiber connecting the first blue/red band coupler to the blue/red band coupler R 11 , optical signals are inputted/outputted thereto/therefrom through the first 1×2 optical switch and the second blue/red band coupler, and when there is a fault in an optical fiber connecting the second blue/red band coupler to the blue/red band coupler R 21 , optical signals are inputted/outputted thereto/therefrom through the second 1×2 optical switch and the blue/red band coupler.