The present invention discloses a passive optical network system based on
wavelength protection and the protection backup method thereof. It
comprises an optical line terminal (OLT) with two interface circuits, two
trunk lines, an optical splitter network, multiple branch lines and
optical network units (ONU), each of which is with two interface
circuits. The two interface circuits of the OLT transmit downlink optical
signals with different wavelengths, while the two interface circuits of
the ONU transmit uplink optical signals with different wavelengths. Each
trunk line is set with a wavelength division multiplexing (WDM) device
and it can only pass the uplink and downlink signals of the connected
interface circuits. Each branch line includes a branch optical fiber and
a WDM device that is used to transmit two downlink signals to the
corresponding interface circuits respectively and meanwhile transmit
uplink signals from the two interface circuits as well, so as to form two
active/backup bidirectional optical paths between the corresponding
interface circuits of the OLT and the ONU. The cost of setting up the
system in the present invention is low, but the system can provide hot
backup protection for the trunk optical fiber and the OLT.