Patent ID: 7542673
Filing Date: 2009-06-02
Classification: H04B,H04J

Abstract:
1. A fault localization apparatus for an optical line in a wavelength division multiplexed passive optical network (WDM PON), the WDM PON comprising: a central office including a multiplexer connected to downstream transmitters and a demultiplexer connected to upstream receivers; a remote node including a multiplexer/demultiplexer connected to the multiplexer and the demultiplexer through a first optical line and passive elements; and optical network units connected to the multiplexer/demultiplexer through a plurality of second optical lines, respectively, the fault localization apparatus comprising: a pulse generator generating pulses; a 2×1 switch which is installed in each of the downstream transmitters, and connects a data signal generator or a pulse generator with a light source of the downstream transmitter; a passive element, installed between the multiplexer and a coupler, for changing paths of monitoring optical signals outputted through the multiplexer which are scattered or reflected backwards; a wavelength tunable band pass filter connected to the passive element; a controller checking whether the upstream receivers receive signals to check a channel exhibiting an abnormal receiving state, and controlling the 2×1 switch, such that a light source of a downstream transmitter which is selected from among the downstream transmitters is connected to the pulse generator when all of the upstream receivers do not receive signals, or such that a light source of a downstream transmitter which has the same channel of an upstream receiver not receiving a signal is connected to the pulse generator, when the upstream receiver does not receive the signal, and tuning the center wavelength of the wavelength tunable band pass filter to the wavelength of the monitoring optical signal; and a receiver for monitoring signals for inputting a monitoring optical signal from the wavelength tunable band pass filter, changing the inputted monitoring optical signal into an electrical signal, converting magnitude variation of the monitoring signal based on time lapse into optical loss values according to distance of the first optical line or one of the second optical lines, and then outputting the converted values, the fault localization apparatus performing such functions that: a channel exhibiting an abnormal receiving state of a signal received by one of the upstream receivers is checked, a monitoring optical signal is inputted to the multiplexer of the central office, in which the monitoring optical signal is generated by inputting a pulse to a light source of a downstream transmitter corresponding to the channel showing such an abnormal receiving state, such that, after the monitoring optical signal returns after being transmitted through the first optical line and one of the second optical lines, monitoring signal magnitude is measured in a time-domain to detect light loss and fault positions.