A bandstop filter method and system for suppressing ASE noise is disclosed. In one embodiment of the bandstop filter system, there is provided a first switch, having an input port for receiving an optical signal, and two output ports; a bandstop filter coupled to a first of the two output ports of the first switch; and a second switch, having two input ports and one output port, wherein a first of the two input ports of the second switch is coupled to the bandstop filter and a second of the two input ports of the second switch is coupled to a second of the two output ports of the first switch.