Method and system for measuring cable strain based on optical fiber stretching

Abstract

A method and system for measuring cable strain based on optical fiber stretching relates to the field of on-line monitoring of cables with optical fibers, and the method comprises the following steps: modulating a correlation sequence to a detection wavelength to form a detection optical signal, and sending the detection optical signal to an optical fiber line of a cable to be measured; receiving a reflected signal or a loopback signal in the optical fiber line, performing correlation operation on the reflected signal or the loopback signal and the correlation sequence, and determining the time delay of a correlation peak of the reflected signal or the loopback signal; according to the time delay of the reflection signal, determining the length of an optical fiber through which the optical signal passes from the transmitting end to each reflection point; or determining the optical fiber length of the optical fiber line from one end to the other end according to the time delay of the loopback signal; comparing the length of the optical fiber with a corresponding reference record to obtain the strain of the optical fiber; and obtaining the strain of the cable according to the corresponding relation between the strain of the optical fiber and the strain of the cable. According to the invention, the interference on the measurement result under temperature and dynamic conditions can be avoided, and the technical problem that the cable strain cannot be accurately measured in the prior art is solved.

Description

Technical Field

[0001] The present application relates to the field of online monitoring of optical fiber cables, and in particular to a method and system for measuring cable strain based on optical fiber stretching. Background Art

[0002] Due to the influence of complex factors such as weather, topography, and topography, the management of overhead transmission lines is difficult for high-voltage power grids, and the stability, power supply capacity, and disaster resistance of power grids are facing severe tests. Real-time monitoring of long-distance high-voltage transmission lines has always been a difficult problem faced by power companies. In the past, transmission line inspections were mainly carried out by manpower, which not only consumed a lot of manpower, material and financial resources, but also failed to obtain accurate real-time data. At present, high-voltage transmission lines use cables with optical fibers for transmission. Through optical fiber distributed sensing technology, based on the characteristics of optical fiber perception and transmission integration, workers can monitor the status of optical fibers through optical fiber sensors and understand the strain of high-voltage transmission lines on the same line in real time.

[0003] The basic parameters of power transmission lines are temperature and stress. Only by measuring the temperature and stress values ​​of the cables of the power transmission lines at the same time can the strain of the cables be analyzed. However, due to the cross-sensitivity of temperature and stress in the optical fiber sensor itself, the wavelength changes caused by temperature and stress cannot be distinguished based on wavelength demodulation in actual measurements. In addition, overhead cables also need to be specially monitored for complex dynamic conditions such as dancing and breeze vibration. These conditions can cause serious damage to the cables, but unlike static stretching, it is impossible to simply measure dynamically changing stress in this shaking condition. These complex conditions reduce the accuracy of optical fiber sensing in measuring cable strain, bringing new challenges to practical applications. Summary of the invention

[0004] The present application provides a method and system for measuring cable strain based on optical fiber stretching, which can solve the technical problem that the cable strain cannot be accurately measured in the prior art.

[0005] In a first aspect, an embodiment of the present application provides a method for measuring cable strain based on optical fiber stretching, the method comprising:

[0006] Modulate the correlation sequence onto the detection wavelength to form a detection optical signal, and send it to the optical fiber line of the cable to be tested;

[0007] Receiving a reflected signal or a loopback signal in the optical fiber line, and performing a correlation operation with the correlation sequence to determine a time delay of a correlation peak of the reflected signal or the loopback signal;

[0008] Determine the length of the optical fiber that the optical signal passes through from the transmitting end to each reflection point based on the time delay of the reflected signal; or determine the length of the optical fiber from one end to the other end of the optical fiber line based on the time delay of the loopback signal;

[0009] Comparing the optical fiber length with a corresponding reference record to obtain the strain of the optical fiber;

[0010] The strain of the cable is obtained according to the corresponding relationship between the strain of the optical fiber and the strain of the cable.

[0011] In combination with the first aspect, in one implementation, determining the length of the optical fiber that the optical signal passes through from the transmitting end to each reflection point according to the time delay of the reflected signal includes:

[0012] Based on the time delay of the reflected signal and the transmission speed of light in the optical fiber, the optical path distance of the optical signal from emission to reception is calculated. Half of this optical path distance is the length of the optical fiber from the emission end to each reflection point.

[0013] In combination with the first aspect, in one implementation, determining the length of an optical fiber from one end to the other end of an optical fiber line according to a time delay of a loopback signal includes:

[0014] Based on the time delay of the loopback signal and the transmission speed of light in the optical fiber, the optical path distance of the optical signal from transmission to reception is calculated. Half of this optical path distance is the length of the optical fiber from one end to the other end of the optical fiber line.

[0015] In combination with the first aspect, in one embodiment, the reference record is: after the cable is installed for the first time, in the absence of external force, the optical fiber length is determined based on the reflection signal or the loopback signal according to the method of measuring the cable strain by optical fiber stretching.

[0016] In combination with the first aspect, in one implementation, obtaining the strain of the cable according to the correspondence between the strain of the optical fiber and the strain of the cable includes:

[0017] In the tensile load and strain curve of the optical fiber, find the tensile load of the optical fiber corresponding to the optical fiber strain;

[0018] On the tensile load and strain curve of the cable, find the state point that is the same as the tensile load of the optical fiber, and then determine the strain of the cable based on this state point.

[0019] In combination with the first aspect, in one implementation, the refresh rate of measuring the cable strain is increased by increasing the frequency at which the detection light signal is sent to the optical fiber line.

[0020] In a second aspect, an embodiment of the present application provides a device for measuring optical fiber strain, which is used to measure the strain of an optical fiber in any of the methods for measuring cable strain based on optical fiber stretching, and the device includes:

[0021] A transmitting end, which is used to modulate the correlation sequence onto a detection wavelength to form a detection optical signal, and send it to the optical fiber line of the cable to be tested;

[0022] A receiving end, which is used to receive a reflection signal or a loopback signal of an optical fiber line, and perform a correlation operation with the correlation sequence to determine the delay of a correlation peak of the reflection signal or the loopback signal; determine the optical fiber length from the transmitting end to each reflection point of the optical signal according to the delay of the reflection signal; or determine the optical fiber length from one end to the other end of the optical fiber line according to the delay of the loopback signal; and compare the optical fiber length with a corresponding reference record to obtain the strain of the optical fiber;

[0023] The coupler is used to couple the detection light signal emitted by the transmitting end into the optical fiber line, and is also used to separate the light signal reflected or looped back in the optical fiber line.

[0024] In conjunction with the second aspect, in one implementation, the sending end includes:

[0025] A sequence generation module, which is used to generate a correlation sequence with autocorrelation;

[0026] A digital-to-analog conversion module, which is used to convert the relevant sequence from a digital signal into a corresponding analog electrical signal;

[0027] An electro-optical modulator, which is used to modulate the analog electrical signal onto an optical carrier to form a detection optical signal;

[0028] The first optical amplifier is used for amplifying the detection optical signal and then sending it to the coupler.

[0029] In conjunction with the second aspect, in one implementation, the receiving end includes:

[0030] A second optical amplifier, which is used to amplify the reflected signal or the loopback signal in the optical fiber line;

[0031] A filter, for a reflected signal, for filtering optical signals other than the reflected wavelength; for a loopback signal, for filtering optical signals other than the loopback signal;

[0032] A photodetector, which is used to detect the optical signal filtered by the filter and convert it into an electrical signal;

[0033] A signal processing module is used to sample the electrical signal and perform correlation operations with the correlation sequence to determine the time delay of the correlation peak of the reflection signal or loopback signal detected by the photodetector; determine the optical fiber length from the transmitting end to each reflection point of the optical signal according to the time delay of the reflection signal; or determine the optical fiber length from one end to the other end of the optical fiber line according to the time delay of the loopback signal; and compare the optical fiber length with the corresponding reference record to obtain the strain of the optical fiber.

[0034] In combination with the second aspect, in one implementation, the transmitting end and the receiving end are hardware installed together, and the coupler is a power splitter or an optical circulator.

[0035] The beneficial effects brought by the technical solution provided in the embodiments of the present application include:

[0036] Through the correlation operation of the reflected signal or loopback signal in the optical fiber line, the corresponding delay of the signal can be obtained. According to the delay of the reflected signal, the length of the optical fiber that the optical signal passes through from the transmitting end to each reflection point can be determined; or according to the delay of the loopback signal, the length of the optical fiber from one end to the other end of the optical fiber line can be determined, and then the strain of the optical fiber can be obtained by comparing the optical fiber length with the corresponding reference record; according to the corresponding relationship between the strain of the optical fiber and the strain of the cable, the strain of the cable can be obtained. Through the above method, the strain of the optical fiber in the cable can be obtained dynamically and accurately, and then according to the corresponding relationship, the strain of the cable can be obtained through conversion, avoiding the interference of temperature and dynamic conditions on the measurement results, and solving the technical problem that the cable strain cannot be accurately measured in the prior art.

[0037] In addition, since the accuracy of measuring optical fiber length can reach centimeter level, by sending related sequences at high speed and modulating them to the detection wavelength to form a detection light signal, the duration of each bit of the related sequence can be reduced, thereby obtaining high resolution. At the same time, high resolution also ensures that related sequences of limited length can be sent quickly, and multiple measurements can be quickly achieved to obtain a high dynamic refresh rate. The measurement frequency can reach hundreds of times per second, so the changes in the cable can be dynamically and accurately grasped. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of an embodiment of a method for measuring cable strain based on optical fiber stretching of the present application;

[0039] Figure 2 A schematic diagram of the reflection of an optical signal in an optical fiber line according to an embodiment of the present application;

[0040] Figure 3 A schematic diagram of looping back an optical signal in an optical fiber line according to an embodiment of the present application;

[0041] Figure 4 This is a schematic diagram of the corresponding relationship between the strain of the optical fiber and the strain of the cable in which it is located in this application;

[0042] Figure 5 FIG. 1 is a schematic diagram of an embodiment of a device for measuring optical fiber strain of the present application.

[0043] In the figure:

[0044] 1. Transmitter, 11. Sequence generation module, 12. Digital-to-analog conversion module, 13. Electro-optical modulator, 14. First optical amplifier,

[0045] 2. receiving end, 21. second optical amplifier, 22. filter, 23. photodetector, 24. signal processing module,

[0046] 3. Coupler. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0048] First, some technical terms in the present application are explained to facilitate those skilled in the art to understand the present application.

[0049] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0050] In a first aspect, an embodiment of the present application provides a method for measuring cable strain based on optical fiber stretching.

[0051] In one embodiment, referring to Figure 1 , Figure 1 This is a flow chart of an embodiment of the method for measuring cable strain based on optical fiber stretching in this application. Figure 1 As shown, the method for measuring cable strain based on optical fiber stretching includes the following steps:

[0052] S1. Modulate the correlation sequence to the detection wavelength to form a detection optical signal, and send it to the optical fiber line of the cable to be tested.

[0053] S2. Receive a reflected signal or a loopback signal in the optical fiber line, and perform a correlation operation with the aforementioned correlation sequence to determine a time delay of a correlation peak corresponding to the reflected signal or the loopback signal.

[0054] S3. Determine the length of the optical fiber that the optical signal passes through from the transmitting end to each reflection point based on the time delay of the reflected signal; or determine the length of the optical fiber from one end to the other end of the optical fiber line based on the time delay of the loopback signal.

[0055] S4, comparing the optical fiber length determined in S3 with the corresponding reference record to obtain the strain of the optical fiber;

[0056] S5. Obtain the strain of the cable according to the corresponding relationship between the strain of the optical fiber and the strain of the cable.

[0057] The above-mentioned benchmark record is: after the cable is installed for the first time, in the absence of external force, the optical fiber length is determined for the first time based on the reflection signal or loopback signal according to the above-mentioned method of measuring the cable strain by optical fiber stretching, in order to provide a basis for comparison later.

[0058] Through the above method, the strain of the optical fiber in the cable can be obtained dynamically and accurately, and then the strain of the cable can be obtained through conversion according to the corresponding relationship, avoiding the interference of temperature and dynamic conditions on the measurement results, and solving the technical problem that the cable strain cannot be accurately measured in the prior art.

[0059] There are two ways to implement the above method of measuring cable strain based on optical fiber stretching. Figure 2 As shown, in one embodiment, the optical fiber line is a single-fiber bidirectional line, and the detection light signal is transmitted along the optical fiber of the cable to be tested, passing through each reflection point in the optical fiber line (such as reflection point 1 and reflection point 2) in turn to form a reflection signal.

[0060] In this embodiment, the above step S2 receives the reflected signal in the optical fiber line, performs correlation operation on the reflected signal and the correlation sequence modulated to the detection wavelength in step S1, and obtains the time delay and peak value of the correlation peak corresponding to the reflected signal.

[0061] According to the time delay of the reflected signal obtained in step S2, the optical path distance △D that each optical signal travels from the transmitting end to the reflection point and then reflected back to the receiving end is calculated according to the formula △D=ct, where c is the transmission speed of light in the optical fiber, and t is the time delay from the emission to the reception of the optical signal carrying the relevant sequence, which is the time delay of the reflected signal in this embodiment. When the length of the optical fiber is fixed, in the above step S3, half of the optical path distance △D can be determined by the time delay of the reflected signal, which is the length of the optical fiber that the optical signal travels from the transmitting end to each reflection point, that is, When there are multiple reflection points, the distance between each reflection point and the monitoring device (the receiving end in this embodiment) can be determined by monitoring different reflection signals of each reflection point.

[0062] like Figure 3 As shown, in another embodiment, the optical fiber line is a loop line, and the detection optical signal returns through two optical fibers in the same cable and may pass through an optical amplifier in the middle of the optical fiber line.

[0063] In this embodiment, the above step S2 receives the loopback signal in the optical fiber line, performs correlation operation on the loopback signal and the correlation sequence modulated onto the detection wavelength in step S1, and obtains the delay and peak value of the correlation peak corresponding to the loopback signal.

[0064] According to the time delay of the loopback signal obtained in step S2, the same calculation method as in the previous embodiment is used, and according to the formula △D=ct, the optical path distance △D that the optical signal travels from the time it is emitted to the time it is looped back can be calculated, where c is the transmission speed of light in the optical fiber, and t is the time delay from the time the optical signal carrying the relevant sequence is emitted to the time it is received, which in this embodiment is the time delay of the loopback signal. When the length of the optical fiber is fixed, in the above step S3, the optical fiber length from one end to the other end of the optical fiber line can be determined by the time delay of the loopback signal to be half of the optical path distance △D, that is,

[0065] In the above step S4, for each reflected signal, the strain of the optical fiber (in this embodiment, the stretched length of the optical fiber) can be obtained by comparing the length of each optical fiber segment determined in S3 with the corresponding reference record. For the loopback signal, the optical fiber strain (in this embodiment, the stretched length of the optical fiber) can be obtained by directly comparing it with the reference record.

[0066] Further, in one embodiment, in the above step S5, the strain of the cable is obtained according to the correspondence between the strain of the optical fiber and the strain of the cable, which specifically includes the following contents:

[0067] like Figure 4 As shown, it is a schematic diagram of the corresponding relationship between the strain of the optical fiber and the strain of the cable in which it is located. Figure 4 The horizontal axis represents the tensile load (i.e. stress), and the vertical axis represents the strain. Figure 4 It includes the tensile load and strain curve of the optical fiber, as well as the tensile load and strain curve of the cable. The relationship between the tensile load and strain can be determined by the cable cabling process and the cable overhead laying conditions, and can be measured in the actual environment. When the cable is subjected to "long-term tension under the design meteorological conditions load", the reserve margin of the optical fiber is completely released and the optical fiber is stretched. Since there is a linear correspondence between the tensile length of the optical fiber and the strain of the optical fiber, the strain of the cable, and the tensile load of the cable, the actual deformation of the cable and the stress (i.e., tensile load) it bears can be determined based on the tensile length of the optical fiber.

[0068] Specifically, in the tensile load and strain curve of the optical fiber, find the tensile load of the optical fiber corresponding to the strain of the optical fiber; on the tensile load and strain curve of the cable, find the state point with the same tensile load of the optical fiber, and then determine the strain of the cable according to the state point. For example, the strain of the optical fiber obtained in S4 is i, and in the tensile load and strain curve of the optical fiber, find the point E with the ordinate i, and then obtain the abscissa j of point E, where j is the tensile load. Then, on the tensile load and strain curve of the cable, find the point F (state point) with the tensile load j, and obtain the ordinate k according to point F, where k is the strain of the cable.

[0069] The spatial resolution that can be achieved by the above method can be determined according to the formula △d = c△t, where c is the transmission speed of light in the optical fiber, and △t is the duration of each bit of the correlation sequence. By sending the correlation sequence at high speed, a very short △t can be achieved, and then a very small △d can be achieved to obtain high resolution. At the same time, the extremely short △t also ensures that the correlation sequence of limited length is sent quickly, and multiple measurements can be quickly achieved, the frequency is increased, and a high dynamic refresh rate is obtained, so the changes of the cable can be dynamically and accurately grasped.

[0070] In a second aspect, an embodiment of the present application further provides a device for measuring optical fiber strain, which is used to measure the optical fiber strain in any of the above-mentioned embodiments of the method for measuring cable strain based on optical fiber stretching.

[0071] In one embodiment, referring to Figure 5 , Figure 5 This is a functional module diagram of an embodiment of the optical fiber strain measurement device of the present application. Figure 5 As shown, the measuring device includes a transmitting end 1, a receiving end 2 and a coupler 3.

[0072] The transmitting end 1 is used to modulate the correlation sequence onto the detection wavelength to form a detection optical signal, and send it to the optical fiber line of the cable to be tested.

[0073] The receiving end 2 is used to receive the reflected signal or loopback signal of the optical fiber line, and perform correlation operation with the aforementioned correlation sequence to determine the delay of the correlation peak of the reflected signal or loopback signal; determine the optical fiber length from the transmitting end to each reflection point of the optical signal according to the delay of the reflected signal; or determine the optical fiber length from one end to the other end of the optical fiber line according to the delay of the loopback signal; compare the determined optical fiber length with the corresponding reference record to obtain the strain of the optical fiber.

[0074] The coupler 3 is used to couple the detection optical signal sent by the transmitting end 1 into the optical fiber line, and is also used to separate the optical signal reflected or looped back in the optical fiber line.

[0075] Furthermore, in one embodiment, the transmitting end 1 includes: a sequence generating module 11 , a digital-to-analog conversion module 12 , an electro-optical modulator 13 and a first optical amplifier 14 .

[0076] The sequence generation module 11 is used to generate a correlation sequence with good autocorrelation.

[0077] The digital-to-analog conversion module 12 is used to convert the relevant sequence from a digital signal into a corresponding analog electrical signal.

[0078] The electro-optic modulator 13 is used to modulate the analog electrical signal onto an optical carrier to form a detection optical signal.

[0079] The first optical amplifier 14 is used to amplify the detection optical signal and send it to the coupler 3 for long-distance optical fiber transmission and detection.

[0080] Furthermore, in one embodiment, the receiving end 2 includes: a second optical amplifier 21 , a filter 22 , a photodetector 23 and a signal processing module 24 .

[0081] The second optical amplifier 21 is used to amplify the reflected signal or the loopback signal in the optical fiber line.

[0082] The filter 22 is used for filtering optical signals other than the reflected wavelength for the reflected signal and the loopback signal.

[0083] The photodetector 23 is used to detect the optical signal filtered by the filter and convert it into an electrical signal.

[0084] The signal processing module 24 is used to sample the electrical signal, average and reduce noise, and then perform correlation operations. Specifically, the noise-reduced signal is correlated with the correlation sequence to determine the delay of the correlation peak of the reflection signal or loopback signal detected by the photodetector; according to the delay of the reflection signal, the optical fiber length from the transmitting end to each reflection point is determined; or according to the delay of the loopback signal, the optical fiber length from one end to the other end of the optical fiber line is determined; and it is also used to compare the optical fiber length with the corresponding reference record to obtain the strain of the optical fiber.

[0085] For the convenience of use, the above optical fiber strain measurement device has the hardware of the transmitting end 1 and the receiving end 2 installed together and can be placed in a central machine room or the like. The downlink optical signal is coupled to the optical fiber line through the coupler 3, and the uplink optical signal is separated from the optical fiber line through the coupler 3. The coupler 3 can be a power splitter or an optical circulator.

[0086] Through the above-mentioned embodiments of the measuring device, the strain of the optical fiber in the cable can be obtained dynamically and accurately.

[0087] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are only for description and do not represent the advantages or disadvantages of the embodiments.

[0088] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit "first", "second" and "third" to different types.

[0089] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[0090] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; the “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0091] In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0092] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, disk, CD) as described above, and includes a number of instructions for a terminal device to execute the methods described in each embodiment of the present application.

[0093] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for measuring cable strain based on optical fiber stretching, characterized in that: The method comprises: Modulate the correlation sequence onto the detection wavelength to form a detection optical signal, and send it to the optical fiber line of the cable to be tested; Receiving a reflected signal or a loopback signal in the optical fiber line, and performing a correlation operation with the correlation sequence to determine a time delay of a correlation peak of the reflected signal or the loopback signal; Determine the length of the optical fiber that the optical signal passes through from the transmitting end to each reflection point based on the time delay of the reflected signal; or determine the length of the optical fiber from one end to the other end of the optical fiber line based on the time delay of the loopback signal; Comparing the optical fiber length with a corresponding reference record to obtain the strain of the optical fiber; The strain of the cable is obtained according to the corresponding relationship between the strain of the optical fiber and the strain of the cable.

2. The method for measuring cable strain based on optical fiber stretching according to claim 1, characterized in that: According to the time delay of the reflected signal, determine the length of the optical fiber that the optical signal passes from the transmitting end to each reflection point, including: Based on the time delay of the reflected signal and the transmission speed of light in the optical fiber, the optical path distance of the optical signal from emission to reception is calculated. Half of this optical path distance is the length of the optical fiber from the emission end to each reflection point.

3. The method for measuring cable strain based on optical fiber stretching according to claim 1, characterized in that: Determine the length of the optical fiber from one end to the other end of the optical fiber line based on the delay of the loopback signal, including: Based on the time delay of the loopback signal and the transmission speed of light in the optical fiber, the optical path distance of the optical signal from transmission to reception is calculated. Half of this optical path distance is the length of the optical fiber from one end to the other end of the optical fiber line.

4. The method for measuring cable strain based on optical fiber stretching according to claim 1, characterized in that: The reference record is: after the cable is installed for the first time, in the absence of external force, the optical fiber length is determined based on the reflection signal or loopback signal according to the method of measuring the cable strain by optical fiber stretching.

5. The method for measuring cable strain based on optical fiber stretching according to claim 1, characterized in that: According to the correspondence between the optical fiber strain and the cable strain, the strain of the cable is obtained, including: In the tensile load and strain curve of the optical fiber, find the tensile load of the optical fiber corresponding to the optical fiber strain; On the tensile load and strain curve of the cable, find the state point that is the same as the tensile load of the optical fiber, and then determine the strain of the cable based on this state point.

6. The method for measuring cable strain based on optical fiber stretching according to claim 1, characterized in that: By increasing the frequency at which the detection light signal is sent to the optical fiber line, the refresh rate of measuring the cable strain is increased.

7. An optical fiber strain measuring device, used for measuring the strain of an optical fiber in the method for measuring cable strain based on optical fiber stretching as described in any one of claims 1 to 6, characterized in that: The device comprises: A transmitting end, which is used to modulate the correlation sequence onto a detection wavelength to form a detection optical signal, and send it to the optical fiber line of the cable to be tested; A receiving end, which is used to receive a reflection signal or a loopback signal of an optical fiber line, and perform a correlation operation with the correlation sequence to determine the delay of a correlation peak of the reflection signal or the loopback signal; determine the optical fiber length from the transmitting end to each reflection point of the optical signal according to the delay of the reflection signal; or determine the optical fiber length from one end to the other end of the optical fiber line according to the delay of the loopback signal; and compare the optical fiber length with a corresponding reference record to obtain the strain of the optical fiber; The coupler is used to couple the detection light signal emitted by the transmitting end into the optical fiber line, and is also used to separate the light signal reflected or looped back in the optical fiber line.

8. The optical fiber strain measuring device according to claim 7, characterized in that: The transmitting end comprises: A sequence generation module, which is used to generate a correlation sequence with autocorrelation; A digital-to-analog conversion module, which is used to convert the relevant sequence from a digital signal into a corresponding analog electrical signal; An electro-optical modulator, which is used to modulate the analog electrical signal onto an optical carrier to form a detection optical signal; The first optical amplifier is used for amplifying the detection optical signal and then sending it to the coupler.

9. The optical fiber strain measuring device according to claim 7, characterized in that: The receiving end comprises: A second optical amplifier, which is used to amplify the reflected signal or the loopback signal in the optical fiber line; A filter, for the reflected signal and the loopback signal, which is used to filter the optical signal outside the reflected wavelength; A photodetector, which is used to detect the optical signal filtered by the filter and convert it into an electrical signal; A signal processing module is used to sample the electrical signal and perform correlation operations with the correlation sequence to determine the time delay of the correlation peak of the reflection signal or loopback signal detected by the photodetector; determine the optical fiber length from the transmitting end to each reflection point of the optical signal according to the time delay of the reflection signal; or determine the optical fiber length from one end to the other end of the optical fiber line according to the time delay of the loopback signal; and compare the optical fiber length with the corresponding reference record to obtain the strain of the optical fiber.

10. The optical fiber strain measuring device according to claim 7, characterized in that: The transmitting end and the receiving end hardware are installed together, and the coupler is a power splitter or an optical circulator.

Images