Patent ID: 7450849

Claim:
A wavelength-division multiplexing passive optical network (WDM-PON) comprising: a central office for generating a monitor light and multiplexed downstream optical signals to be output and detecting upstream optical signals, the central office including a signal monitoring unit monitoring based on a fed-back monitor light if wavelengths of the upstream optical signals and wavelengths of the downstream optical signals change; a plurality of subscriber units for detecting corresponding downstream optical signals and generating upstream optical signals; a remote node for reflecting the monitor light to the central office, de-multiplexing multiplexed downstream optical signals so as to output the downstream optical signals to the corresponding subscriber units, and multiplexing the upstream optical signals so as to output the upstream optical signals to the central office; a first optical path for linking the central office with the remote node; and a plurality of second optical paths for linking the remote node with the subscriber units, respectively, wherein the central office comprises: a downstream broadband light source for generating downstream light with a broad wavelength band; an upstream broadband light source for generating upstream light having a wavelength band different from the wavelength band of the downstream light; a plurality of downstream light sources for generating downstream optical signals having wavelengths locked by the downstream light; a plurality of upstream optical detectors for detecting upstream optical signals; a first multiplexer/de-multiplexer for multiplexing the downstream optical signals to be output, de-multiplexing multiplexed upstream optical signals to be output to the corresponding upstream optical detectors, and dividing the downstream light into a plurality of downstream channels to be output to the corresponding downstream light sources; a first wavelength selection reflection filter for selectively reflecting the monitor light having only a preset wavelength in the downstream light, the first wavelength selection reflection filter being positioned between the downstream broadband light source and the first multiplexer/de-multiplexer; and the signal monitoring unit for monitoring change of a wavelength of the monitor light reflected from the remote node so as to inspect a change in wavelengths of the upstream optical signals and the downstream optical signals and controlling the first multiplexer/de-multiplexer according to an inspection result.