The present invention discloses a Wavelength Division Multiplexing Filter which can satisfy coexistence requirements of different PON systems and an optical line detecting system. The Wavelength Division Multiplexing Filter comprises a plurality of filters that are configured: in a downlink direction, to receive a first optical pulse signal output by a first PON system, a second optical pulse signal output by a second PON system or gained by coupling an output signal of the second PON system and a video signal, and a third optical pulse signal sent from an Optical Time Domain Reflectometer, and to couple the first optical pulse signal, the second optical pulse signal and the third optical pulse signal into an Optical Division Network; and in an uplink direction, to split an uplink optical pulse signal according to wavelength bands, to transmit an optical pulse signal in a first uplink wavelength range to the first PON system, to transmit an optical pulse signal in a second uplink wavelength range to the second PON system, and to transmit an optical signal in a third uplink wavelength range to the Optical Time Domain Reflectometer.