Patent ID: 7738787

Claim:
An optical transmission line monitoring device comprising: a device which calculates a management amount based on an optical intensity of returning light; a reference data storage device which stores reference management amounts beforehand; a detecting device which in response to the calculated management amount being of poorer quality than the reference management amount stored in the reference data storage device detects a distance, creates detection data based on the calculated management amount, and stores the created detection data in a detection data storage device; an alarm outputting device that creates alarm data based on the detection data created by the detecting device, and displays the created alarm data on a screen; an inputting device that inputs selection command data indicating that the alarm data displayed on the screen will not be output; and a removal data adding device that adds, to the detection data stored in the detection data storage device corresponding to the alarm data of the selection command data input by the inputting device, output removal data indicating that it is not a target for outputting by the alarm outputting device; wherein the alarm outputting device changes a display of the alarm data corresponding to the detection data that the removal data adding device adds the output removal data to.