TWI854865B - Optical fiber perimeter intrusion detection system and intrusion detection method - Google Patents

Abstract

An optical fiber perimeter intrusion detection system and an intrusion detection method are provided. The intrusion detection method includes: in response to a first phase of a first reflected light being changed, outputting a first interference of light by a first interference sensing module; in response to a second phase of a second reflected light being changed, outputting a second interference of light by a second interference sensing module; outputting a first alarm message corresponding to a first sensing fiber in response to a signal analyzer detecting the first interference of light, and outputting a second alarm message corresponding to a second sensing fiber in response to the signal analyzer detecting the second interference of light; and coupling an optical coupler in the first interference sensing module to an optical splitter, a first reflected mirror, the signal analyzer, and a light isolator.

Description

Optical fiber fence detection system and intrusion detection method

The present invention relates to an optical fiber fence detection system and an intrusion detection method.

Perimeter security is an important part of the "security" field. It can achieve a safe perimeter through environmental monitoring. The protection scope of perimeter security ranges from long-distance national border security, remote monitoring of oil pipelines or gas pipelines, to short-distance protection of government agencies, important facilities (such as airports, nuclear power plants, etc.) and home security, which has a significant impact on the overall national economy and people's livelihood.

Among the many perimeter security technologies, fiber optic sensing technology not only has the functions that traditional sensors can perform, including high-sensitivity detection of various physical quantities such as displacement, vibration, pressure, temperature, speed or flow, but also has the advantages of not being affected by weather, season or temperature, and being able to operate in corrosive and electromagnetic field environments. It is the main trend of future security technology development.

The fiber optic fence formed by the optical fiber inside the optical cable is a new type of perimeter security system. When there is an external intrusion, it will be accompanied by a vibration phenomenon. This vibration will be transmitted to the internal optical fiber through the optical cable sheath and detected by it. The optical fiber can be used as a detection element to detect external disturbances and determine whether it is an intrusion.

Vibration will change the light-guiding state of the optical fiber, causing the phase of the light being carried to change. Although the phase of light cannot be measured directly, it can be split into two paths by an optical splitter, and then the interference structure of the optical path can be used to make the light form constructive interference and destructive interference. The optical fiber fence can indirectly measure the phase change of the detection light through the change in light intensity generated after light interference, thereby knowing that vibration has occurred.

The measurement of optical fiber vibration phenomenon can obtain vibration information by collecting forward vibration detection light or backscattered vibration detection light. Forward vibration detection light provides vibration waveform information, which can be used to filter out interference caused by wind and small animals running and identify intrusion behavior. Backscattered vibration detection light provides vibration position information, which can be used to locate intrusion and assist in preventing intrusion. Although the provision of vibration position information is the main basis for preventing intrusion, the light intensity of backscattered vibration detection light is much smaller than that of forward vibration detection light, and the light intensity will decrease as the detection distance increases. Under this double limitation, it is more difficult to locate intrusion using backscattered vibration detection light. Furthermore, the components required to measure backscattered vibration detection light are more sophisticated than those required to measure forward vibration detection light, which will increase the cost of constructing the optical fiber fence and make it difficult to popularize the implementation of the optical fiber fence.

The present invention provides an optical fiber fence detection system and an intrusion detection method, which can use multiple pairs of optical fibers in the optical cable to perform vibration detection and signal transmission on different sections of the perimeter, and use multiple interference sensing modules to distinguish the detected sections, so that each section of the perimeter can be individually marked as an independent warning area. The optical fiber fence detection system can detect the phase change of the forward vibration detection light of each warning area to determine whether an intrusion behavior occurs in the warning area.

The present invention discloses an optical fiber fence detection system, comprising a light source, an optical cable, a signal analyzer and a spectrometer. The light source provides detection light. The optical cable comprises a first reflector, a first interference sensing module, a second reflector and a second interference sensing module. The first reflector generates a first reflected light of the detection light. The first interference sensing module is coupled to the light source, and is coupled to the first reflector through a first sensing optical fiber to receive the first reflected light, wherein the first interference sensing module outputs a first light interference in response to a change in a first phase of the first reflected light. The second reflector generates a second reflected light of the detection light. The second interference sensing module is coupled to the light source, and is connected to the second reflector through a second sensing optical fiber to receive a second reflected light, wherein the second interference sensing module outputs a second light interference in response to a change in a second phase of the second reflected light. The signal analyzer is coupled to the first interference sensing module and the second interference sensing module, wherein the signal analyzer outputs a first alarm message corresponding to the first sensing optical fiber in response to sensing the first optical interference, and outputs a second alarm message corresponding to the second sensing optical fiber in response to sensing the second optical interference. The optical splitter is coupled to the light source and the first interference sensing module, wherein the first interference sensing module includes an optical isolator and an optical splitter. The optical splitter includes a first input end, a first output end, a second input end, a second output end, a third input end, and a third output end. The first output end is coupled to the first input end through the first optical fiber. The second input end is coupled to the optical splitter. The second output end is coupled to the first reflector. The third input end is coupled to the signal analyzer. The third output end is coupled to the optical isolator.

In one embodiment of the present invention, the optical fiber fence detection system further includes a first photodetector and a second photodetector. The first photodetector is coupled to a first interference sensing module and a signal analyzer, wherein the signal analyzer senses the first light interference through the first photodetector. The second photodetector is coupled to a second interference sensing module and the signal analyzer, wherein the signal analyzer senses the second light interference through the second photodetector.

In an embodiment of the present invention, the first sensing optical fiber and the second sensing optical fiber are respectively distributed in different sections of the optical cable.

The present invention provides an intrusion detection method, comprising providing a detection light through a light source; generating a first reflected light of the detection light through a first reflector in an optical cable; coupling a first interference sensing module in the optical cable to the first reflector through a first sensing optical fiber to receive the first reflected light, wherein the first interference sensing module outputs a first light interference in response to a change in a first phase of the first reflected light; generating a second reflected light of the detection light through a second reflector in the optical cable; coupling a second interference sensing module in the optical cable to a second reflector through a second sensing optical fiber to receive the second reflected light, wherein the second interference sensing module outputs a first light interference in response to a change in a second phase of the second reflected light. Output a second optical interference; output a first alarm message corresponding to the first sensing optical fiber in response to the first optical interference sensed by the signal analyzer, and output a second alarm message corresponding to the second sensing optical fiber in response to the second optical interference sensed by the signal analyzer; and couple the first output end of the optical splitter in the first interference sensing module to the first input end of the optical splitter through the first optical fiber, couple the second input end of the optical splitter to the spectrometer, couple the second output end of the optical splitter to the first reflector, couple the third input end of the optical splitter to the signal analyzer, and couple the third output end of the optical splitter to the optical isolator in the first interference sensing module.

Based on the above, the present invention proposes a fiber optic fence detection system and an intrusion detection method, which can use an interference sensing module to segment the detected perimeter so that the range of the segment perimeter can be controlled for independent detection. The present invention can measure the vibration of the segment perimeter by collecting forward vibration detection light, and the obtained vibration waveform can be used to identify intrusion behavior. When vibration occurs at the segment perimeter and intrusion behavior has been identified, there is no need to locate the intrusion behavior on the entire perimeter. The entire segment perimeter can be regarded as a warning area and actions to stop the intrusion can be taken. Therefore, the detection system can be simplified and the construction cost of the system can be reduced.

In order to make the content of the present invention more clearly understood, the following embodiments are specifically cited as examples by which the present invention can be truly implemented. In addition, wherever possible, elements/components/steps with the same reference numerals in the drawings and embodiments represent the same or similar components.

FIG1 is a schematic diagram of an optical fiber fence detection system 100 according to an embodiment of the present invention. The optical fiber fence detection system 100 may include a light source 101, a spectrometer 102, a plurality of intrusion sensors (including intrusion sensors 111, 112, ..., 11n, etc., where n is a positive integer), a plurality of photodetectors (including photodetectors 151, 152, ..., 15n, etc., n photodetectors) and a signal analyzer 105.

The light source 101 is, for example, a continuous light source. The light source 101 can be used to provide detection light. The optical splitter 102 can have an input terminal and n output terminals, wherein the input terminal can be coupled to the light source 101, and the n output terminals can be coupled to the intrusion sensors 111, 112, ..., 11n respectively. The optical splitter 102 can receive the detection light from the light source 101 through the input terminal, and split the detection light into n components to transmit to the intrusion sensors 111, 112, ..., 11n respectively.

The n intrusion sensors mentioned above may be included in the same optical cable 103. Each of the n intrusion sensors may include an interference sensing module and a reflector, and the interference sensing module may be coupled to the reflector via a sensing optical fiber. For example, the intrusion sensor 111 may include an interference sensing module 121 and a reflector 141, wherein the interference sensing module 121 and the reflector 141 are coupled to each other via a sensing optical fiber 131. The intrusion sensor 112 may include an interference sensing module 122 and a reflector 142, wherein the interference sensing module 122 and the reflector 142 are coupled to each other via a sensing optical fiber 132. The intrusion sensor 11n may include an interference sensing module 12n and a reflective mirror 14n, wherein the interference sensing module 12n and the reflective mirror 14n are coupled to each other via a sensing optical fiber 13n. The structures and functions of the intrusion sensors 111, 112, ..., 11n may be similar to each other.

The sensing optical fiber of the intrusion sensor can be used to detect whether an intrusion event occurs in a specific section of the optical cable 103. The n sensing optical fibers can be distributed in different sections of the optical cable 103 to detect the vibration waves caused by the intrusion events corresponding to the sections. FIG. 2 shows a waveform diagram of the impact of vibration events on different sections according to an embodiment of the present invention. Assume that the optical cable 103 may include section I, section II and section III, and the sensing optical fibers 131, 132 and 13n may be distributed in section I, section II and section III, respectively. If an intrusion event occurs in section III, the amplitude of the vibration caused by the intrusion event on section III may be much greater than the amplitude of the vibration caused by the intrusion event on other sections, as shown in FIG. 2. Accordingly, the phase of the light transmitted in the sensing optical fiber 13n changes.

As shown in Fig. 1, the photodetectors 151, 152, ..., 15n can be coupled to the intrusion sensors 111, 112, ..., 11n, respectively, wherein the structures and functions of the photodetectors 151, 152, ..., 15n can be similar to each other. More specifically, the photodetectors 151, 152, ..., 15n can be coupled to the interference sensing modules 121, 122, ..., 12n, respectively.

The signal analyzer 105 is, for example, a central processing unit (CPU), or other programmable general-purpose or special-purpose micro control unit (MCU), microprocessor, digital signal processor (DSP), programmable controller, application specific integrated circuit (ASIC), graphics processing unit (GPU), image signal processor (ISP), image processing unit (IPU), arithmetic logic unit (ALU), complex programmable logic device (CPLD), field programmable gate array (FPGA), or other similar components or combinations of the above components.

The signal analyzer 105 may be coupled to the photodetectors 151, 152, ..., 15n, and may use the photodetectors 151, 152, ..., 15n to detect whether an intrusion event occurs in each section of the optical cable 103. The following uses the photodetector 151 and the intrusion sensor 111 corresponding to the photodetector 151 as an example to illustrate how the signal analyzer 105 detects an intrusion event.

The spectrometer 102 can divide the detection light provided by the light source 101 into n components, and transmit one of the n components to the reflector 141. The reflector 141 can generate corresponding reflected light according to the components of the detection light. The interference sensing module 121 can receive the reflected light from the reflector 141 through the sensing optical fiber 131. When an intrusion event occurs in the section of the optical cable 103 corresponding to the sensing optical fiber 131, the vibration caused by the intrusion event will cause the phase of the reflected light transmitted in the sensing optical fiber 131 to change. The interference sensing module 121 can output light interference to the detector 151 in response to the change in the phase of the reflected light. The detector 151 can sense light interference and output the sensing result of light interference to the signal analyzer 105. After the signal analyzer 105 receives the sensing result from the photodetector 151, the signal analyzer 105 can determine that the sensing optical fiber 131 corresponding to the photodetector 151 has detected an intrusion event based on the sensing result. If the signal analyzer 105 determines that the intensity of the optical interference is greater than the threshold value based on the sensing result, the signal analyzer 105 can determine that an intrusion event has occurred. Accordingly, the signal analyzer 105 can output an alarm message corresponding to the sensing optical fiber 131 to prompt the user that an intrusion event has occurred in the section of the optical cable 103 corresponding to the sensing optical fiber 131.

In a similar manner, the spectrometer 102 can divide the detection light provided by the light source 101 into n components, and transmit one of the n components to the reflector 14n. The reflector 14n can generate corresponding reflected light according to the components of the detection light. The interference sensing module 12n can receive the reflected light from the reflector 14n through the sensing optical fiber 13n. When an intrusion event occurs in the section of the optical cable 103 corresponding to the sensing optical fiber 13n, the vibration caused by the intrusion event will cause the phase of the reflected light transmitted in the sensing optical fiber 13n to change. The interference sensing module 12n can output optical interference to the detector 15n in response to the change in the phase of the reflected light. The detector 15n can sense the optical interference and output the sensing result of the optical interference to the signal analyzer 105. After the signal analyzer 105 receives the sensing result from the photodetector 15n, the signal analyzer 105 can determine that the sensing optical fiber 13n corresponding to the photodetector 15n has detected an intrusion event based on the sensing result. If the signal analyzer 105 determines that the intensity of the light interference is greater than the threshold value based on the sensing result, the signal analyzer 105 can determine that an intrusion event has occurred. Accordingly, the signal analyzer 105 can output an alarm message corresponding to the sensing optical fiber 13n to prompt the user that an intrusion event has occurred in the section of the optical cable 103 corresponding to the sensing optical fiber 13n.

FIG3 is a schematic diagram of an interference sensing module 121 according to an embodiment of the present invention. The interference sensing module 121 may include an optical splitter 210 and an optical splitter 220. The optical splitter 210 or the optical splitter 220 is, for example, a two-to-two optical splitter. The optical splitter 210 may include an input end 211, an input end 212, an output end 213, and an output end 214. The optical splitter 210 may divide an optical signal input to the input end 211 or the input end 212 into two components, and output the two components through the output end 213 and the output end 214, respectively. In addition, the optical splitter 210 may divide an optical signal input to the output end 213 or the output end 214 into two components, and output the two components through the input end 211 and the input end 212, respectively. On the other hand, the optical splitter 220 may include an input terminal 221, an input terminal 222, an output terminal 223, and an output terminal 224. The optical splitter 220 may split an optical signal input to the input terminal 221 or the input terminal 222 into two components, and output the two components respectively through the output terminal 223 and the output terminal 224. In addition, the optical splitter 220 may split an optical signal input to the output terminal 223 or the output terminal 224 into two components, and output the two components respectively through the input terminal 221 and the input terminal 222.

The input end 211, the input end 212, the output end 213, and the output end 214 of the optical splitter 210 may be coupled to the optical splitter 102, the photodetector 151, the input end 221 of the optical splitter 220, and the input end 222 of the optical splitter 220, respectively. The output end 223 of the optical splitter 220 may be coupled to the reflector 141. The output end 213 of the optical splitter 210 may be coupled to the input end 221 of the optical splitter 220 through the optical fiber 310, and the output end 214 of the optical splitter 210 may be coupled to the input end 222 of the optical splitter 220 through the optical fiber 320, wherein the optical fiber 310 may be longer than the optical fiber 320 to generate an optical path difference. The output end 223 of the optical splitter 220 can be coupled to the reflective mirror 141 through the sensing optical fiber 131 .

The optical splitter 210 can receive the detection light from the optical splitter 102 through the input end 211, and output the detection light to the optical splitter 220 through the output end 213 and the output end 214. The optical splitter 220 can receive the detection light from the optical splitter 210 through the input end 221 and the input end 222, and transmit the detection light to the reflector 141 through the output end 223. The reflector 141 can generate reflected light of the detection light, and transmit the reflected light to the optical splitter 220 through the sensing optical fiber 131. The splitter 220 may receive the reflected light from the reflector 141 through the output terminal 223, and divide the reflected light into two components, one of which is transmitted to the output terminal 213 of the optical splitter 210 through the optical fiber 310, and the other of which is transmitted to the output terminal 214 of the optical splitter 210 through the optical fiber 320. The optical splitter 210 may combine the two components of the reflected light from the optical splitter 220 to generate combined light, and output the combined light to the detector 151 through the input terminal 212.

The vibration caused by the intrusion event can change the phase of the reflected light transmitted in the sensing optical fiber 131. Therefore, the two components of the reflected light transmitted from the optical splitter 220 to the optical splitter 210 will also produce phase changes. Since the optical fiber 310 is longer than the optical fiber 320, the phase change of the component received by the output end 214 of the optical splitter 210 will be earlier than the phase change of the component received by the output end 214 of the optical splitter 210. When the phase of the component received by the output end 214 changes but the phase of the component received by the output end 213 has not changed, the combined light output from the input end 212 of the optical splitter 210 to the detector 151 will contain optical interference. The detector 151 can sense the optical interference and transmit the sensing result to the signal analyzer 105. The signal analyzer 105 can determine whether an intrusion event occurs based on the sensing results.

FIG4 is a schematic diagram of an interference sensing module 121 according to another embodiment of the present invention. The interference sensing module 121 may include an optical circulator 400 and an optical splitter 500. The optical circulator 400 is, for example, a three-port optical circulator, wherein the optical circulator 400 may include a terminal 410, a terminal 420, and a terminal 430. The optical circulator 400 may output an optical signal input to the terminal 410 through the terminal 420, and may output an optical signal input to the terminal 420 through the terminal 430. The optical splitter 500 is, for example, a two-to-two optical splitter, wherein the optical splitter 500 may include an input terminal 511, an input terminal 512, an output terminal 513, and an output terminal 514. The optical splitter 500 can separate the optical signal input to the input terminal 511 or the input terminal 512 into two components, and output the two components through the output terminal 513 and the output terminal 514. In addition, the optical splitter 500 can separate the optical signal input to the output terminal 513 or the output terminal 514 into two components, and output the two components through the input terminal 511 and the input terminal 512.

Ends 410, 420 and 430 of the optical circulator 400 may be coupled to the optical splitter 102, the input end 512 of the optical splitter 500 and the photodetector 151, respectively. The output end 514 of the optical splitter 500 may be coupled to the reflector 141. In addition, the input end 511 of the optical splitter 500 may be coupled to the output end 513 of the optical splitter 500 via the optical fiber 600 to generate an optical path difference.

The optical circulator 400 can receive the detection light from the optical splitter 102 through the end 410, and output the detection light to the optical splitter 500 through the end 420. The splitter 500 can receive the detection light from the optical circulator 400 through the input end 512, and can transmit the detection light to the reflector 141 through the output end 514. The reflector 141 can generate reflected light of the detection light, and transmit the reflected light to the optical splitter 500 through the sensing optical fiber 131. The optical splitter 500 can receive the reflected light from the reflector 141 through the output terminal 514 and split the reflected light into two components, one of which is transmitted to the output terminal 513 through the input terminal 511, and the other of which is transmitted to the terminal 420 of the optical circulator 400 through the input terminal 512. The optical circulator 400 can transmit the component of the reflected light received by the terminal 420 to the photodetector 151 through the terminal 430.

The vibration caused by the intrusion event can change the phase of the reflected light transmitted in the sensing optical fiber 131. Therefore, the two components received by the output end 513 and the output end 514 of the optical splitter 500 will also produce phase changes. Since the input end 511 and the output end 513 of the optical splitter 500 are connected to each other, the duration of the phase change of the component received by the output end 513 can be longer than the duration of the phase change of the component received by the output end 514. When the phase of the component received by the output end 513 changes but the phase of the component received by the output end 514 has been restored to its original state, the light output from the input end 512 of the optical splitter 500 to the optical circulator 400 will contain optical interference. Accordingly, the optical circulator 400 can transmit the optical interference to the detector 151 through the end 430. The photodetector 151 can sense light interference and transmit the sensing result to the signal analyzer 105. The signal analyzer 105 can determine whether an intrusion event occurs based on the sensing result.

FIG5 is a schematic diagram of an interference sensing module 121 according to another embodiment of the present invention. The interference sensing module 121 may include an optical splitter 700 and an optical isolator 800, wherein the optical splitter 700 is, for example, a three-to-three optical splitter. The optical splitter 700 may include an input end 710, an input end 720, an input end 730, an output end 740, an output end 750, and an output end 760. The optical splitter 700 may distinguish an optical signal input to the input end 710, the input end 720, or the input end 730 into three components, and output the three components through the output end 740, the output end 750, and the output end 760, respectively. In addition, the optical splitter 700 can separate the optical signal input to the output terminal 740, the output terminal 750 or the output terminal 760 into three components, and output the three components through the input terminal 710, the input terminal 720 and the input terminal 730 respectively.

The input end 720 and the input end 730 of the optical splitter 700 can be coupled to the beam splitter 102 and the photodetector 151, respectively. The output end 750 and the output end 760 of the optical splitter 700 can be coupled to the reflector 141 and the optical isolator 800, respectively. In addition, the input end 710 of the optical splitter 700 can be coupled to the output end 740 of the optical splitter 700 through the optical fiber 900 to generate an optical path difference.

The optical splitter 700 can receive the detection light from the optical splitter 102 through the input terminal 720, and output the detection light to the reflector 141 through the output terminal 750. The reflector 141 can generate reflected light of the detection light, and transmit the reflected light to the optical splitter 700 through the sensing optical fiber 131. The optical splitter 700 can receive the reflected light from the reflector 141 through the output terminal 750, and split the reflected light into three components, one of which is transmitted to the output terminal 740 through the input terminal 710, and another one of the three components is transmitted to the detector 151 through the input terminal 730.

The vibration caused by the intrusion event can change the phase of the reflected light transmitted in the sensing optical fiber 131. Therefore, the two components received by the output end 740 and the output end 750 of the optical splitter 700 will also produce phase changes. Since the input end 710 and the output end 740 of the optical splitter 700 are connected to each other, the duration of the phase change of the component received by the output end 740 can be longer than the duration of the phase change of the component received by the output end 750. When the phase of the component received by the output end 740 changes but the phase of the component received by the output end 750 has been restored to its original state, the light output from the input end 730 of the optical splitter 700 to the detector 151 will contain optical interference. Accordingly, the detector 151 can sense the optical interference and transmit the sensing result to the signal analyzer 105. The signal analyzer 105 can determine whether an intrusion event occurs based on the sensing results.

FIG6 is a flow chart of a method for detecting intrusion according to an embodiment of the present invention, wherein the method can be implemented by the optical fiber fence detection system 100 as shown in FIG1 . In step S601, a detection light is provided by a light source. In step S602, a first reflected light of the detection light is generated by a first reflector in the optical cable. In step S603, a first interference sensing module in the optical cable is coupled to a first reflector through a first sensing optical fiber to receive the first reflected light, wherein the first interference sensing module outputs a first light interference in response to a change in a first phase of the first reflected light. In step S604, a second reflected light of the detection light is generated by a second reflector in the optical cable. In step S605, a second interference sensing module in the optical cable is coupled to a second reflector through a second sensing optical fiber to receive a second reflected light, wherein the second interference sensing module outputs a second optical interference in response to a change in a second phase of the second reflected light. In step S606, a first alarm message corresponding to the first sensing optical fiber is output in response to the first optical interference being sensed by the signal analyzer, and a second alarm message corresponding to the second sensing optical fiber is output in response to the second optical interference being sensed by the signal analyzer.

In summary, the optical fiber fence detection system of the present invention can utilize multiple interference sensing modules in the optical cable to perform vibration detection and signal transmission for different alarm zones. The optical fiber fence detection system may include multiple interference sensing modules disposed in the optical cable, wherein the multiple interference sensing modules may be respectively connected to multiple optical fibers to become intrusion detection elements for independent alarm zones. When the optical signal in a specific optical fiber undergoes a phase change due to vibration, the corresponding interference sensing module may generate optical interference. When the signal analyzer detects optical interference of the interference sensing module, it may determine that an intrusion event has occurred in the alarm zone corresponding to the interference sensing module, thereby issuing an alarm message for the alarm zone. Accordingly, in addition to the optical cable, the optical fiber fence detection system can also locate the intrusion position without the need to build additional detection elements (such as elements for measuring backscattered vibration detection light). Therefore, the present invention can effectively reduce costs and simplify the complexity of system design.

100: Fiber optic fence detection system 101: Light source 102: Spectrometer 103: Fiber optic cable 105: Signal analyzer 111, 112, 11n: Intrusion sensor 121, 122, 12n: Interference sensing module 131, 132, 13n: Sensing fiber 141, 142, 14n: Reflector 151, 152, 15n: Photodetector 210, 220, 500, 700: Optical splitter 211, 212, 221, 222, 511, 512, 710, 720, 730: Input port 213, 214, 223, 224, 513, 514, 740, 750, 760: output end 310, 320, 600, 900: optical fiber 400: optical circulator 410, 420, 430: end 800: optical isolator S601, S602, S603, S604, S605, S606: steps

FIG. 1 is a schematic diagram of a fiber optic fence detection system according to an embodiment of the present invention. FIG. 2 is a waveform diagram of the impact of a vibration event on different sections according to an embodiment of the present invention. FIG. 3 is a schematic diagram of an interference sensing module according to an embodiment of the present invention. FIG. 4 is a schematic diagram of an interference sensing module according to another embodiment of the present invention. FIG. 5 is a schematic diagram of an interference sensing module according to another embodiment of the present invention. FIG. 6 is a flow chart of an intrusion detection method according to an embodiment of the present invention.

S601, S602, S603, S604, S605, S606: Steps

Claims (4)

A fiber optic fence detection system, comprising: A light source, providing detection light; An optical cable, comprising: A first reflector, generating a first reflected light of the detection light; A first interference sensing module, coupled to the light source, and coupled to the first reflector through a first sensing optical fiber to receive the first reflected light, wherein the first interference sensing module outputs a first light interference in response to a change in a first phase of the first reflected light; A second reflector, generating a second reflected light of the detection light; and A second interference sensing module, coupled to the light source, and connected to the second reflector through a second sensing optical fiber to receive the second reflected light, wherein the second interference sensing module outputs a second light interference in response to a change in a second phase of the second reflected light; A signal analyzer coupled to the first interference sensing module and the second interference sensing module, wherein the signal analyzer outputs a first alarm message corresponding to the first sensing optical fiber in response to sensing the first optical interference, and outputs a second alarm message corresponding to the second sensing optical fiber in response to sensing the second optical interference; and A spectrometer coupled to the light source and the first interference sensing module, wherein the first interference sensing module includes: An optical isolator; and An optical splitter, including: A first input end; A first output end, coupled to the first input end through a first optical fiber; A second input end, coupled to the spectrometer; A second output end, coupled to the first reflector; A third input end, coupled to the signal analyzer; and A third output end, coupled to the optical isolator. The optical fiber fence detection system as described in claim 1 further includes: a first photodetector coupled to the first interference sensing module and the signal analyzer, wherein the signal analyzer senses the first optical interference through the first photodetector; and a second photodetector coupled to the second interference sensing module and the signal analyzer, wherein the signal analyzer senses the second optical interference through the second photodetector. An optical fiber fence detection system as described in claim 1, wherein the first sensing optical fiber and the second sensing optical fiber are respectively distributed in different sections of the optical cable. An intrusion detection method includes: Providing detection light through a light source; Producing a first reflected light of the detection light through a first reflector in an optical cable; Coupling a first interference sensing module in the optical cable to the first reflector through a first sensing optical fiber to receive the first reflected light, wherein the first interference sensing module outputs a first light interference in response to a change in a first phase of the first reflected light; Producing a second reflected light of the detection light through a second reflector in the optical cable; Coupling a second interference sensing module in the optical cable to the second reflector through a second sensing optical fiber to receive the second reflected light, wherein the second interference sensing module outputs a second light interference in response to a change in a second phase of the second reflected light; In response to the first optical interference sensed by the signal analyzer, a first alarm message corresponding to the first sensing optical fiber is outputted, and in response to the second optical interference sensed by the signal analyzer, a second alarm message corresponding to the second sensing optical fiber is outputted; and The first output end of the optical splitter in the first interference sensing module is coupled to the first input end of the optical splitter through the first optical fiber, the second input end of the optical splitter is coupled to the optical splitter, the second output end of the optical splitter is coupled to the first reflector, the third input end of the optical splitter is coupled to the signal analyzer, and the third output end of the optical splitter is coupled to the optical isolator in the first interference sensing module.

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