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.

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.

A Fiber Bragg grating (FBG) sensor structure, a method of fabricating a FBG sensor structure, and a method of employing a FBG sensor structure comprising an optical fiber portion having at least one FBG formed therein. The FBG sensor structure comprises an optical fiber portion having at least one FBG formed therein; and a sleeve structure capable of transferring vibrations and/or strain along a length thereof; wherein the optical fiber portion is coupled to the sleeve structure such that the central wavelength of the FBG, is variable under the transferred vibrations and/or strain.

Systems, arrangements, barriers and methods for detecting illicit attempts to compromise or penetrate a physical barrier are disclosed. The systems, arrangements, barriers and methods detect illicit attempts to pry, remove or compromise a security barrier from the surface or location it protects, by insider/outsider adversaries, when any type of cabled continuity sensor (optical, electrical) is woven, embedded, or interlaced through the security barrier.

An optical fiber sensing system for abnormal occurrence detection includes a receiving unit configured to receive an optical signal from an optical fiber for sensing. The system includes an identifying unit configured to identify an occurrence of an event and a type of the event that has occurred based on a vibration pattern included in the optical signal. The system includes an acquiring unit configured to acquire a detection condition pertaining to a period corresponding to the type of the event identified by the identifying unit. The system includes a determining unit configured to determine that the event identified by the identifying unit is an anomaly if the detection condition is satisfied.

A method using wavelength division multiplexing for reducing light diffusion and light reflection interference in an interference path, comprising: connecting a wavelength division multiplexer (10) serially at an end of a sensing optical fiber (6); using the wavelength division multiplexer (10) to extract a wavelength component from a working path for measuring an interfering signal caused by light diffusion and light reflection; using the signal as a reference to extract an effective signal component that has been interfered by light diffusion and light reflection, and obtaining a pure effective signal. Because the device connected at the end of the sensing optical fiber (6) is passive and requires no power, the system is easy to implement and is particularly suitable for situations in which power provision is difficult at the end of the sensing optical fiber (6). The method is suitable for long distance pipeline monitoring and a wide-range optical of fiber perimeter security. Also provided is a system using wavelength division multiplexing for reducing light diffusion and light reflection interference in an interference path.

A monitoring system using an optical line is disclosed. The monitoring system using an optical line according to the present invention comprises: a laser diode for generating an input optical signal; an optical element for receiving the input optical signal through a first port and outputting same through a second port, and for receiving a reflected optical signal through the second port and outputting same through a third port; an optical switch unit for receiving the input optical signal through an input port connected to the second port of the optical element, and for distributing same through at least two output ports; at least one optical monitoring line connected to the output ports of the optical switch unit; a photodiode connected to the third port of the optical element, for detecting the reflected optical signal; and a signal processing unit for processing the signal detected by the photodiode.

An optical fiber sensing system that includes an optical fiber provided in a monitor area, a detection unit that detects an anomaly that has occurred in the monitor area and identifies a location on the optical fiber where the anomaly is detected, based on a vibration pattern included in an optical signal received from the optical fiber, and a control unit that displays an arrangement situation of the optical fiber in an overlapping manner on a map of the monitor area, displays a mark indicating a location on the optical fiber where the anomaly is detected, in an overlapping manner on the map of the monitor area, and displays information indicating a detail of the anomaly.

A long-distance fiber optic monitoring system having a sensing unit and an analyzer that is remotely located from the sensing unit is provided. The sensing unit comprises a source of optical energy for injecting optical energy into the fiber optical cable and an optical detector configured to detect an optical return signal from the optical fiber. The detected optical return signal is associated with an acoustic signal impinging on the optical fiber. The analyzer receives a signal from the remote sensing unit via the optical fiber that is representative of the optical return signal, and determines a location of a disturbance based at least on the received signal. The representative signal can be transmitted from the remote sensing unit to the analyzer as an optical signal or via a metallic wired included with the optical fiber.

Various technologies described herein pertain to a sensored grate that can be utilized for various security fencing applications. The sensored grate includes a grate framework and an embedded optical fiber. The grate framework is formed of a molded polymer such as, for instance, molded fiber reinforced polymer. Further, the grate framework includes a set of elongated elements, where the elongated elements are spaced to define apertures through the grate framework. The optical fiber is embedded in the elongated elements of the grate framework. Moreover, bending or breaking of one or more of the elongated elements can be detected based on a change in a characteristic of input light provided to the optical fiber compared to output light received from the optical fiber.