TWI761978B - Device and method for preventing digging of optical cable - Google Patents

Abstract

The invention provides a detection device and method for preventing digging damage of an optical cable, in particular to using the optical fiber in the optical cable to detect the vibration point, and coupling the optical splitter to form a Sagnac ring double-nested interference structure device, so that the phase changes due to vibration The detection light from the vibration point returns to the measurement point to produce a time difference, so as to locate the vibration point.

Description

Device and method for preventing digging damage of optical cable

The present invention relates to an optical cable detection device and method, and in particular to an optical cable damage prevention detection device and method. The optical fiber in the optical cable is used as a sensing element and combined with an optical splitter and a delay optical fiber to form a Sagnac The ring double-nested interference structure is used to actively detect the audio frequency generated by vibration and calculate the position of the vibration point, so that the optical cable maintenance operator can immediately stop the construction before the optical cable is damaged by construction, and has an early warning protection effect on the optical cable.

In response to the ever-increasing demand for bandwidth for high-speed broadband services, the number of optical cables used as communication lines has gradually increased, resulting in increased workload and difficulty in managing and maintaining these optical cables. Among them, the failure of the optical cable is the most distressing for the on-site maintenance personnel: the reasons for the failure of the optical cable can be divided into construction excavation, man-made damage, typhoon, flood, earthquake, earth-rock flow, and material reliability. Natural disasters are difficult to predict and prevent, and man-made damage can be prevented through some mechanisms. At present, the anti-excavation of optical cable mainly relies on regular inspections by personnel and keeps in touch with pipeline units and construction workers. However, these measures are still insufficient: for example, the time for piling at the construction site, weather, traffic, and manpower constraints cannot fully cooperate with the construction time of the construction site. Due to factors that are difficult to grasp, such as surveys, optical cables are cut every year, resulting in a large number of communication interruptions and heavy economic losses.

Optical fiber is a medium for carrying optical signals. The cable core is formed by a specific method. The cable core is assembled into a bundle and covered with several layers of protective structures to form an optical cable. In addition to the advantages of being free from electromagnetic interference, small size, and wide frequency, the optical fiber itself can be used for signal transmission purposes, and can also sense external environmental changes such as strain, temperature, and pressure. The use of the optical fiber in the optical cable can be used as a sensing element, which is especially suitable for long-distance continuous detection. Before the optical cable is excavated and damaged by construction, the equipment will generate vibration audio during the construction process. This vibration audio will be transmitted to the internal optical fiber through the optical cable The sensing through the optical fiber can send back the vibration audio and the location information to produce early warning protection for the optical cable.

Vibration and audio will change the light-guiding state of the optical fiber, causing the phase of the light to be changed. However, the phase of the light cannot be directly measured. The light must be divided into two paths by an optical splitter, and then the interference structure of the optical path is used to make the light form constructive. Interference and destructive interference, the vibration audio is obtained by indirectly measuring the phase change of the carrier light through the change of light intensity after light interference.

There are two main forms of typical interference architectures, Sagnac and Mach-Zehnder. The Sagnac architecture uses two lights passing through the same path but in opposite directions to perform dual-light interference due to the photometric phase difference generated by the time difference between the sensing points passing through. In the application case, however, the detection of the leak position adopts the zero-point frequency location method of the signal spectrum. In this method, the signal must not only undergo complex demodulation processing, but also the detection distance is limited by the spectral width of the leak signal. The Mach-Zehnder architecture utilizes two paths of light passing through different paths. The phase of the light passing through the sensing point path changes and produces double light interference with the light passing through the other path. This dual-light interference structure with different paths has high requirements on the coherence of the light source, thus increasing the cost of the sensing system and easily causing system noise interference.

In view of this, the inventor of the present case is eager to improve and innovate, and proposes an optical cable damage prevention detection device and method, which uses the optical fiber in the optical cable as a sensing element, and combines it with an optical splitter and a delay optical fiber to form a Sagnac ring double-embedded. Set the interference device to measure the vibration audio, and calculate the location of the vibration point by sensing the time difference between the vibration point and the measurement point, so that the optical cable maintenance operator can immediately stop the construction before the optical cable is damaged by construction. Produce early warning protection.

The invention provides an optical cable damage prevention detection device, comprising: two 2x2 optical splitters used for interference on the same side of the optical output end and the two ends of the optical fiber used for sensing in the optical cable to form two Sagnac rings, two Sagnac rings, two Sagnac rings. Two other 2x2 optical splitters are used for coupling to form a Sagnac ring double-nested interference structure, which makes the sensing fiber a common part of the two Sagnac interference rings. The nested coupling method is to connect the two light output ends of the same side of the optical splitter with the light output ends of the interference optical splitter in the Sagnac ring respectively, and to connect the other side 2 of the optical splitter. One of the light output ends is connected to a sensing fiber, and the other is connected to an anti-reflection element to avoid measurement interference caused by unexpected reflected light. In the Sagnac ring, there are two light output ends on the other side of the interference light splitter. One light output end is connected to the light source generator for generating sensing light, and the other light output end is connected to the photodetector for receiving the sensing light and converting it into electrical energy. Signal. A signal analyzer is connected to the individual photodetectors of the two Sagnac interference rings and receives the electrical signals of the photodetectors, thereby analyzing the vibration audio and calculating the location of the vibration point. The two delay fibers are respectively connected in the Sagnac ring between the interference optical splitter and the coupling optical splitter, so that the corresponding photodetector receives the sensing light time difference, and the difference time is used to make the signal analyzer calculate out the vibration point position.

The present invention provides a detection method for preventing digging damage of an optical cable. The method is as follows: first, the light source generators of the two Sagnac rings generate sensing light respectively, and then divide the sensing light into two lights through the corresponding optical splitter. The two sensing beams travel around the Sagnac ring in a clockwise direction and a counterclockwise direction, respectively, and travel through the sensing fiber and the delay fiber to sense the vibration audio from the vibration point and return to the measurement point. When the two sensing lights are mixed at the measurement point, an interference signal is generated. The photodetector converts the interference signal into an electrical signal, and the electrical signal enters the signal analyzer for analysis. Due to the different coupling positions of the delay fibers of the two Sagnac rings relative to the sensing fibers, the corresponding optical path lengths from the vibration point to the measurement point are different, thus resulting in the difference in time when the photodetector receives the interference signal. The time difference of the electrical signals generated by the two Sagnac rings can calculate the location of the vibration point.

Therefore, the present invention provides an optical cable damage prevention detection device and method, which uses the existing optical fiber in the optical cable as a sensing element, not only does not need to build a sensing element but also can perform continuous position detection, which can effectively reduce costs and simplify System design complexity. In addition, under the Sagnac ring double-nested interference structure, the system can reduce the coherence requirements of the light source to avoid measurement noise caused by scattering, and can use the time difference of the received sensing light generated by the delay fiber to calculate The vibration point position, the method provided by the device is simple and fast, and has an early warning protection effect on the prevention of digging damage of the optical cable.

The purpose of the present invention is to provide a kind of optical fiber in the optical cable as the sensing element, which can transmit the vibration audio and the position information back to the optical cable to produce an early warning protection effect, so that the optical cable maintenance operator can immediately prevent the construction of the optical cable before it is damaged by construction. A detection device and method for preventing digging damage of an optical cable.

FIG. 1 is a diagram of the optical cable damage prevention and detection device of the present invention. As shown in FIG. 1 , the first optical splitter 12a (which is in the form of 2x2, that is, has two optical output ends on both sides), the first delay optical fiber 20a, the optical cable 10 and the (one core) sensing optical fiber 11 are connected to form a first optical fiber. Sagnac ring. The second optical splitter 12b (in the form of 2x2), the second delay fiber 20b, the optical cable 10 and the sensing fiber 11 are connected to form a second Sagnac ring, and are connected by the third optical splitter 13 and the fourth optical splitter 14 ( Both in the form of 2x2) coupling the first Sagnac ring and the second Sagnac ring into a double Sagnac ring nested interference architecture.

In one embodiment, the nested coupling method of the double Sagnac ring nested interference structure includes: connecting the light output end L point of the third optical splitter 13 to the light output of the first optical splitter 12a of the first Sagnac ring The end C is connected; the light output end K of the third optical splitter 13 is connected to the light output end J of the second optical splitter 12b through the second delay fiber 20b; the light output end P of the third optical splitter 13 is connected. Then it is connected to the sensing fiber 11; the light output end O of the third optical splitter 13 is connected to the anti-reflection element 17 to avoid measurement interference caused by unexpected reflected light.

Similarly, the light output end Q of the fourth optical splitter 14 is connected to the light output end D of the first optical splitter 12a through the first delay fiber 20a; the light output end R of the fourth optical splitter 14 is connected to the first optical splitter 12a. The light output terminal I of the second optical splitter 12b of the two Sagnac rings is connected to point I; the optical output terminal S of the fourth optical splitter 14 is connected to the sensing fiber 11 ; the optical output terminal T of the fourth optical splitter 14 The point-connected anti-reflection element 18 avoids measurement disturbance caused by unintended reflected light.

The first light source generator 15a is connected to the light output end point E of the first light splitter 12a, and can be used to generate a first sensing light. In one embodiment, the first light splitter 12a can divide the first sensing light generated by the first light source generator 15a into two paths, and output them from the light output ends C and D of the first light splitter 12a. The first photodetector 16a is connected to the light output end point F of the first optical splitter 12a. The first photodetector 16a receives and measures the sensing light output from the light output end point F of the first optical splitter 12a, and The sensing light is converted into an electrical signal and output to the signal analyzer 19 .

Similarly, the second light source generator 15b is connected to the light output end point H of the second light splitter 12b, and can be used to generate a second sensing light. In one embodiment, the second light splitter 12b can divide the second sensing light generated by the second light source generator 15b into two and output them to the light output terminals I and J of the second light splitter 12b. The second light detector 16b is connected to point G of the light output end of the second light splitter 12b. The second light detector 16b receives and measures the sensing light output from the light output end point G of the second light splitter 12b, and The sensing light is converted into an electrical signal and output to the signal analyzer 19 .

When the sensing light emitted by the first light source generator 15a and the second light source generator 15b respectively passes through the vibration point X of the optical cable 10, the pressure of the vibration point sensed by the sensing fiber 11 will cause the phase of the light to change. In this case, due to the different optical paths from the vibration point to the measurement point caused by the first delay fiber 20a and the second delay fiber 20b, the phase-changed sensing light returns to the first photodetector 16a and the second photodetector The timing of the device 16b is different. Therefore, the signal analyzer 19 can calculate the position of the vibration point X by analyzing the difference in the time when the first photodetector 16a and the second photodetector 16b receive the sensing light.

To calculate the position of the vibration point X of the optical cable 10, it is necessary to know whether the above-mentioned optical path meets the conditions of optical interference, so further analysis of the optical path is required. For the sensing light emitted by the first light source generator 15a, after it enters the light output point E of the first optical splitter 12a, the first optical splitter 12a bisects the sensing light. The sensing light is divided into two equal parts and then output from the light output ends C and D of the first optical splitter 12a respectively, wherein the output light from the C point is clockwise around the first Sagnac ring, and the output light from the D point is the inverse direction. Clockwise around the first Sagnac ring.

Clockwise light starts from point C of the light output end of the first optical splitter 12a, enters from point L of the light output end of the third optical splitter 13, and exits from point P, passes through the sensing fiber 11 of the optical cable 10, and then passes through the light output end of the third optical splitter 13. The light output end S of the four-optical splitter 14 enters and exits from point Q, and then returns to point D of the light output end of the first optical splitter 12a through the first delay fiber 20a, enters and exits from point F, and reaches the first detection light device 16a. On the other hand, the light in the counterclockwise direction starts from point D of the light output end of the first optical splitter 12a, passes through the first delay fiber 20a, enters from point Q of the light output end of the fourth optical splitter 14, and exits from point S, through the first delay fiber 20a. The sensing fiber 11 of the optical cable 10 enters and exits from point L from point P of the light output end of the third optical splitter 13, and returns to point C of the light output end of the first optical splitter 12a, enters and exits from point F, and reaches the first point. A photodetector 16a.

Both the clockwise light and the counterclockwise light are generated by the first light source generator 15a, so their wavelengths (or frequencies) are the same, and they respectively reach the vibration point X of the optical cable 10, and then return to the light source. The first photodetector 16a. Therefore, the phase difference (optical path difference) of the light traveling in the clockwise direction and the light traveling in the counterclockwise direction is fixed, which meets the conditions for interference, so interference can occur.

Similarly, for the sensing light emitted by the second light source generator 15b, after it enters point H of the light output end of the second light splitter 12b, the second light splitter 12b bisects the light. The bisected sensing light is then output from the light output ends I and J of the second optical splitter 12b respectively, wherein the output light from the J point is clockwise around the second Sagnac ring, and the output light from the I point is: Go around the second Sagnac ring counterclockwise.

The light in the clockwise direction starts from point J of the light output end of the second optical splitter 12b, passes through the second delay fiber 20b, enters from point K of the light output end of the third optical splitter 13, and exits from point P, and passes through the sensor of the optical cable 10. The detection fiber 11 enters and exits from point R from point S of the light output end of the fourth optical splitter 14, then returns to point I of the light output end of the second optical splitter 12b, enters and exits from point G, and reaches the second detection light device 16b. On the other hand, the light in the counterclockwise direction starts from point I of the light output end of the second optical splitter 12b, enters from point R of the light output end of the fourth optical splitter 14, and exits from point S, and passes through the sensing fiber 11 of the optical cable 10. , then enter from point P of the light output end of the third optical splitter 13 and exit from point K, and then pass through the second delay fiber 20b, return to point J of the light output end of the second optical splitter 12b, enter and exit from point G, reach The second photodetector 16b.

Both the clockwise light and the counterclockwise light are generated by the second light source generator 15b, so their wavelengths (or frequencies) are the same, and they reach the vibration point X of the optical cable 10 successively, and then return to The second photodetector 16b. Therefore, the phase difference (optical path difference) of the light traveling in the clockwise direction and the light traveling in the counterclockwise direction is fixed, which meets the conditions for interference, so interference can occur.

、

、

、

、

、

、

。 FIG. 2 is a light path diagram of the optical cable damage prevention detection device of the present invention. When the optical cable is vibrated, the sensing optical fiber is vibrated and the phase of the sensing light changes. According to the analysis of the path of the phase-changed sensing light back to the detector, it can be found that the optical cable damage prevention detection device of the present invention has a total of There are 4 paths, including: (1) Path I clockwise back to the first photodetector 16a; (2) Path II clockwise back to the second photodetector 16b; (3) Path III counterclockwise back To the first photodetector 16a; (4) Path IV goes counterclockwise back to the second photodetector 16b. In Figure 2, it is assumed that

,

,

,

,

,

,

.

。路徑II：光從X點出發，經S點、R點、I點到達G點，其路徑II的長度為

。路徑III：光從X點出發，經P點、L點、C點到達F點，其路徑III的長度為

。路徑IV：光從X點出發，經P點、K點、J點到達G點，其路徑IV的長度為

。由於

遠大於

，所以從震動點X到第一檢光器16a路徑III光程將小於路徑I光程，行走路徑III的光將先到達第一檢光器16a。同理，從震動點X到第二檢光器16b路徑II光程將小於路徑IV光程，行走路徑II的光將先到達第二檢光器16b。感測光被第一檢光器16a和第二檢光器16b所接收將轉變成為電氣信號，然後再進入訊號分析儀分析19處理。 When the vibration source occurs at point X of the optical cable, the path I: The light starts from point X, passes through point S, point Q, and point D to point F, and the length of the path I is

. Path II: The light starts from point X, passes through point S, point R, and point I to point G, and the length of path II is

. Path III: The light starts from point X, goes through point P, point L, point C to point F, and the length of path III is

. Path IV: The light starts from point X and reaches point G through point P, K, and J. The length of the path IV is

. because

much larger than

, so the optical length of the path III from the vibration point X to the first photodetector 16a will be smaller than the optical length of the path I, and the light traveling in the path III will reach the first photodetector 16a first. Similarly, the optical length of path II from the vibration point X to the second photodetector 16b will be smaller than the optical length of path IV, and the light traveling in the path II will reach the second photodetector 16b first. The sensed light received by the first photodetector 16a and the second photodetector 16b will be converted into electrical signals, and then entered into the signal analyzer for analysis 19 for processing.

，其會造成第一檢光器16a與第二檢光器16b接收光信號有時間差異，經訊號分析儀可分析出差異時間

。已知光纜長度

（下稱方程式(1)），透過差異時間

，

（下稱方程式(2)），其中c表示真空中光速，n表示光纖的折射率。解方程式(1)與(2)，則可以分別得到

與

之值，因而得知震動點X位置。 Path II and Path III have optical path difference

, which will cause the time difference between the first photodetector 16a and the second photodetector 16b to receive the optical signal, and the difference time can be analyzed by the signal analyzer

. Known cable length

(hereafter referred to as equation (1)), through the difference time

,

(hereinafter referred to as equation (2)), where c represents the speed of light in vacuum, and n represents the refractive index of the fiber. Solving equations (1) and (2), we can get

and

The value of , so the position of the vibration point X is known.

FIG. 3 is a flow chart of the method for preventing digging damage of an optical cable according to the present invention. To measure the position of the vibration point X on the optical cable, the first light source generator 15a and the second light source generator 15b in FIG. 1 are used to generate a sensing light (step S30 ) by using the optical cable damage prevention detection device of the present invention, respectively. The first optical splitter 12a and the second optical splitter 12b divide each into two sensing beams (step S31), and the bisected sensing beams travel clockwise and counterclockwise respectively corresponding to the first Sagnac ring and the The second Sagnac ring (step S32).

When the external construction equipment generates vibration audio through the optical cable, it is sensed by the internal optical fiber. At the vibration point X, the phase-changed sensing light will return to the first photodetector 16a for measurement in the original clockwise and counterclockwise directions in the first Sagnac ring according to path I and path III, and in the second Sagnac ring according to the path II and path IV return to the second detector 16b for measurement.

When the length of the first delay fiber 20a and the second delay fiber 20b is longer than the sensing cable, no matter where the vibration point X occurs in the cable, the optical paths of paths II and III can be made smaller than paths IV and I, respectively, so that the phase changes The sensed light first reaches the second photodetector 16b (step S34) or the first photodetector 16a (step S33), respectively. The sensing light received by the first photodetector 16a and the second photodetector 16b will be converted into an electrical signal, and then entered into the signal analyzer 19 for analysis and processing.

，其會造成第一檢光器16a與第二檢光器16b接收光信號有時間差異，經訊號分析儀可分析出時間差異

(步驟S35)。訊號分析儀將差異時間

轉換成為實際光程差

(步驟S36)，並代入光纜長度

則可計算出

與

之值，因而得知震動點X位置(步驟S37)。 Path II and Path IV have an optical path difference

, which will cause a time difference between the optical signals received by the first photodetector 16a and the second photodetector 16b, and the time difference can be analyzed by the signal analyzer

(step S35). The signal analyzer will discrepancy time

Convert to actual optical path difference

(step S36), and substitute the cable length

can be calculated

and

The value of , thus the position of the vibration point X is known (step S37 ).

In FIG. 4, it is assumed that the length of the sensing fiber in the optical cable is 7000 meters, and when there is no vibration on the optical cable, the sensing light circles the first Sagnac ring and the second Sagnac ring and returns to the first detector 16a and the second detector respectively. The optical device 16b, after being converted into an electrical signal, is analyzed and processed by the signal analyzer 19, and then the electrical signal corresponding to the sensing light with no phase change is displayed.

FIG. 5 is a diagram showing the electrical signal of the optical cable damage prevention detection device of the present invention having vibration induction in the optical cable. When there is vibration on the optical cable, the phase of the sensing light changes, and after detouring the first Sagnac ring and the second Sagnac ring, it returns to the first photodetector 16a and the second photodetector 16b, respectively, and is converted into an electrical signal. The instrument 19 shows that the electrical signal corresponding to the phase change sensing light has a time delay (6.8 microseconds). After conversion, the corresponding length is 1360 meters, and the total length of the sensing fiber in the optical cable is 7000 meters. Using the delay time rule, it can be calculated The vibration point is located at 4180 meters from one end of the cable.

The present invention provides an optical cable damage prevention detection device and method, which uses the existing optical fiber in the optical cable as a sensing element, not only does not need to build a sensing element, but also can perform continuous position detection, which can effectively reduce costs and simplify the system. Design complexity. In addition, under the Sagnac ring double-nested interference structure, the system can use low-coherence light, such as light-emitting diodes, super-optical diodes and spontaneous light sources as light sources to avoid measurement noise caused by scattering The vibration point position can be calculated by using the time delay of the received sensing light generated by the delayed optical fiber, and the method is simple and fast, and has an early warning protection effect on the optical cable.

Although the present invention has been disclosed above by the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, The protection scope of the present invention shall be determined by the scope of the appended patent application.

10: Optical cable 11: Sensing fiber 12a: First Optical Splitter 12b: Second optical splitter 13 The third optical splitter 14: Fourth optical splitter 15a: The first light source generator 15b: Second light source generator 16a: First photodetector 16b: Second photodetector 17, 18: Anti-reflection elements 19: Signal Analyzer 20a: First Delay Fiber 20b: Second Delay Fiber C, D, E, F, G, H, I, J, K, L, O, P, Q, R, S, T: Optical output terminals X: Vibration point S30~S37: Steps

FIG. 1 is a diagram of the optical cable damage prevention detection device of the present invention; 2 is a diagram showing the light path of the optical cable damage prevention detection device of the present invention; FIG. 3 is a flow chart showing the method for preventing digging damage detection of an optical cable according to the present invention; 4 is a diagram showing the electrical signal diagram of the optical cable damage prevention detection device of the present invention without vibration induction in the optical cable; and FIG. 5 is a diagram showing the electrical signal of the optical cable damage prevention detection device of the present invention having vibration induction in the optical cable.

10: Optical cable 11: Sensing fiber 12a: First Optical Splitter 12b: Second optical splitter 13 The third optical splitter 14: Fourth optical splitter 15a: The first light source generator 15b: Second light source generator 16a: First photodetector 16b: Second photodetector 17, 18: Anti-reflection elements 19: Signal Analyzer 20a: First Delay Fiber 20b: Second Delay Fiber C, D, E, F, G, H, I, J, K, L, O, P, Q, R, S, T: Optical output terminals X: Vibration point

Claims (12)

An optical cable damage prevention detection device uses optical fibers in optical cables as sensing elements, and is combined with optical splitters and delay optical fibers to form a Sagnac ring double-nested interference structure to detect vibrations. Return to the time difference generated by the measurement point to calculate the position of the vibration point, wherein the optical cable damage prevention detection device includes: a sensing fiber for sensing environmental vibration; a first delay fiber; a second delay an optical fiber; a first optical splitter, wherein the first optical splitter, the sensing fiber, the first delay fiber form a first Sagnac ring; a second optical splitter, wherein the second optical splitter, the first optical splitter The sensing fiber and the second delay fiber form a second Sagnac ring; a third optical splitter; a fourth optical splitter, wherein the third optical splitter and the fourth optical splitter cooperate to connect the first Sagnac ring and a second Sagnac ring coupled to form the Sagnac ring double-nested interference structure; a first light source generator for generating a first sensing light to the first light splitter; a second light source generator for generating A second sensing light is sent to the second light splitter, wherein the first light splitter and the second light splitter respectively bisect the first sensing light and the second sensing light into two sensing lights, and after the bisect These sensing light points of respectively circling the first Sagnac ring and the second Sagnac ring clockwise and counterclockwise; a first photodetector for receiving and measuring the sensed light circling the first Sagnac ring and converting it become a first electrical signal; a second photodetector for receiving and measuring the sensing light passing around the second Sagnac ring and converting it into a second electrical signal; a signal analyzer connected to the first a photodetector and the second photodetector for receiving and analyzing the first electrical signal and the second electrical signal, and comparing the sensed light between the first Sagnac ring and the second Sagnac ring Go back to the respective time of the measurement point, analyze the time difference Δt and convert it into an optical path difference and calculate the position of the vibration point according to the optical path difference and the total length of the optical cable. The optical cable breakage prevention and detection device as described in claim 1, wherein the first optical splitter and the second optical splitter respectively comprise two light output ends on one side and two light output ends on the other side Output ends, the light output ends on the side of the first light splitter are respectively connected to the first light source generator and the first light detector, and the first sensing light generated by the first light source generator is divided into two, and then output from the light output ends on the other side of the first light splitter; the light output ends on the side of the second light splitter are respectively connected to the second light source generator and the second detector an optical device, and the second sensing light generated by the second light source generator is equally divided into two, and then output from the light output ends on the other side of the second optical splitter. The optical cable damage prevention detection device as described in claim 2, wherein the first sensing light bisected by the first optical splitter is respectively clockwise Direction and counter-clockwise around the first Sagnac ring or the second Sagnac ring, and back to the first optical splitter to be received and measured by the first photodetector; wherein by the second optical splitter The bisected second sensed light circles the first Sagnac ring or the second Sagnac ring in a clockwise direction and a counterclockwise direction, respectively, and returns to the second optical splitter to be received by the second photodetector and measurement. The optical cable breakage prevention and detection device as described in claim 1, wherein the third optical splitter and the fourth optical splitter respectively comprise two light output ends on one side and two light output ends on the other side Output ends, the light output ends on the side of the first optical splitter are respectively coupled to the first Sagnac ring and the second Sagnac ring, and the light output ends on the other side of the first optical splitter are respectively coupled The sensing fiber and a first anti-reflection element are connected, the light output ends on the same side of the second optical splitter are respectively coupled to the first Sagnac ring and the second Sagnac ring, the second optical splitter is another The light output ends on the side are respectively coupled to the sensing fiber and a second anti-reflection element. The optical cable damage prevention detection device as described in item 4 of the claimed scope, wherein the first anti-reflection element and the second anti-reflection element are used to reduce measurement interference caused by unexpected reflected light. The optical cable damage prevention detection device as described in claim 1, wherein the lengths of the first delay optical fiber and the second delay optical fiber are greater than the coupling between the first optical splitter and the third optical splitter The coupling distance between the coupling distance and the coupling distance between the second optical splitter and the fourth optical splitter and the length of the sensing fiber. The optical cable damage prevention detection device as described in claim 6, wherein the first delay optical fiber is located in the first Sagnac ring and is connected between the first optical splitter and the third optical splitter, The counterclockwise light path from the vibration point to the measurement point is smaller than the clockwise light path. The optical cable damage prevention detection device as described in claim 6, wherein the second delay optical fiber is located in the second Sagnac ring and is connected between the second optical splitter and the fourth optical splitter, The clockwise light path from the vibration point to the measurement point is smaller than the counterclockwise light path. An optical cable damage prevention detection method, using the optical cable damage prevention detection device as claimed in claim 1, comprising: generating the first sensing light and the second sensing light; the first sensing light and the first sensing light The two sensing lights are divided equally into two sensing lights; the bisected sensing lights circle the first Sagnac ring and the second Sagnac ring in a clockwise direction and a counterclockwise direction respectively; Sensing light, traveling through the vibration point and returning to the measuring point according to the clockwise light path and the counterclockwise light path, and measuring the sensing light at the measuring point; the sensing light traveling around the second Sagnac ring, traveling through The vibration point returns to the measurement point according to the clockwise light path and the counterclockwise light path, and the sensing light is measured at the measuring point; compare the sensing light in the first Sagnac ring and the second Sagnac The respective time of the loop returning to the measurement point, and then analyze the time difference Δt and convert it into light Path difference: Calculate the position of the vibration point according to the optical path difference and the total length of the optical cable. The detection method for preventing digging damage of optical cables as described in item 9 of the scope of the application, wherein the respective time of returning to the measurement point means that the sensing lights return from the vibration point to the measurement point in a clockwise direction and Counterclockwise, respectively, the time required to travel the shortest light path in the first Sagnac ring and the second Sagnac ring. The detection method for preventing digging damage of optical cable as described in item 9 of the scope of the patent application, wherein the time difference Δt refers to the difference between the shortest optical paths in the clockwise direction and the counterclockwise direction, causing the sensed light to travel from the vibration point Returning to the measurement point to generate a time difference, the optical path difference obtained by converting the time difference Δt is Δt . c / n , where c is the speed of light in vacuum and n is the refractive index of the fiber. The detection method for preventing digging of optical cables as described in item 9 of the patent application scope, wherein the length of the sensing optical fiber is

and light path difference

c / n , and the method includes: calculating the position of the vibration point based on the length of the sensing fiber and the optical path difference, wherein

and

are the distances of the vibration point from both ends of the sensing fiber, respectively.

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