Patent ID: 10380859

Abstract:
An intrusion detecting method using an intrusion detecting system which includes an optical fiber line installed in an area in which intrusion is to be detected, a laser diode inputting an optical signal to the optical fiber line, a photodiode detecting a reflected optical signal when the optical signal is reflected from the optical fiber line, an intrusion determining unit comparing a waveform of the reflected optical signal detected by the photodiode with a set reference waveform to determine whether an intrusion has occurred, and a laser diode temperature measuring unit measuring a temperature of the laser diode, includes designating, by the intrusion determining unit, a temperature of the laser diode at a first point in time as a first temperature and setting, to a reference waveform, a waveform of a first reflected optical signal caused by an input optical signal input by the laser diode at the first point in time, designating, by the intrusion determining unit, a temperature of the laser diode at a second point in time after the first point in time as a second temperature and determining whether the second temperature is within an allowable range with respect to the first temperature, and when it is determined that the second temperature exceeds the allowable range, resetting, by the intrusion determining unit, to the reference waveform, a waveform of a second reflected optical signal caused by an input optical signal input by the laser diode at the second point in time.