A method for calibrating an optical fiber strain gauge

Abstract

The application discloses a kind of optical fiber strain tester calibration methods, it is related to optical fiber strain test technical field, comprising: taking the optical fiber sample of optical fiber to be measured;The physical length of optical fiber sample is directly measured based on mechanical measurement method;The actual group refractive index of optical fiber is input into phase shift method instrument, and phase shift method instrument is zeroed, then the measured optical fiber length of optical fiber sample is measured by phase shift method instrument, the length error is calculated by the measured optical fiber length and optical length of optical fiber sample, the strain test error is calculated by the optical length of two optical fiber samples respectively, the length of one optical fiber sample in two optical fiber samples is greater than the length of another optical fiber sample, and the phase shift method instrument is calibrated by length error and strain test error.The application provides a set of unified optical fiber strain tester calibration method, so that the test results of cross-device can be directly compared, and the credibility of test data of different manufacturers is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber strain testing, and in particular to a fiber strain tester calibration method. BACKGROUND

[0002] As the core carrier of information communication infrastructure, optical cables are widely used in various communication scenarios. Optical fiber strain testing is a key technology for evaluating the balance between mechanical and environmental performance of optical fibers and the reliability of communication network operation, and plays an important role in the design, manufacture, deployment and maintenance of optical fiber communication systems. With the evolution of optical fiber networks towards high speed, large capacity and long distance, accurate measurement and control of optical fiber strain characteristics have become a key link to ensure network performance - optical fiber strain not only directly affects transmission quality, but also is closely related to the service life of optical fiber and network reliability.

[0003] However, the current optical fiber strain testing field faces significant challenges:

[0004] Calibration traceability is not unified: different manufacturers' strain testers lack a unified calibration traceability method, making it difficult to directly compare test results across devices;

[0005] Measurement differences are significant: current global optical fiber strain measurement is mainly based on the phase shift method, but the industry has not established a unified method to evaluate the accuracy of instruments from different suppliers. Current precision verification relies only on manufacturers' internal verification methods at the time of factory delivery, without a unified calibration process and reference;

[0006] Data reliability is insufficient: the accuracy of test data is crucial for process change analysis, production parameter optimization and optical cable quality consistency, but due to the lack of a unified calibration verification method, when manufacturers use strain testers from two different suppliers, they cannot determine the reliability of the data.

[0007] Therefore, the present application develops a fiber strain tester calibration method to solve the above problems. SUMMARY

[0008] The present application proposes a fiber strain tester calibration method to solve the problems of current technology that cross-device test results cannot be directly compared, lack of a unified calibration method, and insufficient data reliability.

[0009] The present application achieves the above-mentioned purposes through the following technical solutions:

[0010] The present application is a fiber strain tester calibration method, characterized in that it comprises:

[0011] Taking the optical fiber sample of the optical fiber to be tested;

[0012] Directly measuring the physical length of the optical fiber sample based on mechanical measurement method;

[0013] The optical fiber sample is connected to the time delay test system, the optical length of the optical fiber sample is measured, the group refractive index of the optical fiber sample during the measurement process of the time delay test system is adjusted so that the optical length is equal to the physical length, and the group refractive index at this time is recorded as the actual group refractive index of the optical fiber;

[0014] The actual group refractive index of the optical fiber is input into the phase shift method instrument, the phase shift method instrument is zeroed, then the measured fiber length of the optical fiber sample is measured by the phase shift method instrument, the length error is calculated by the measured fiber length and the optical length of the optical fiber sample, the strain test error is calculated by the optical length and the measured fiber length of the two optical fiber samples, the length of one of the two optical fiber samples is greater than the length of the other optical fiber sample, and the phase shift method instrument is calibrated by the length error and the strain test error.

[0015] Further, the length error is calculated by the measured fiber length and the optical length of the optical fiber sample, and the phase shift method instrument is calibrated by the length error, comprising:

[0016] The measured fiber length of the optical fiber sample is measured by the zeroed phase shift method instrument;

[0017] The length error between the measured fiber length and the optical length thereof is calculated, and the calculation formula is as follows:

[0018] Length error = |L phase −L Time Delay Method | / L Time Delay Method × 100%;

[0019] L phase is the measured fiber length, and L Time Delay Method is the optical length thereof;

[0020] If the length error exceeds the preset length error threshold, the state of the phase shift method instrument needs to be checked.

[0021] Further, the length error threshold is 0.01%.

[0022] Further, the strain test error is calculated by the optical length and the measured fiber length of the two optical fiber samples, and the phase shift method instrument is calibrated by the strain test error, comprising:

[0023] The strain test standard value is calculated by the optical length of each of the two optical fiber samples, and the calculation formula is as follows:

[0024] Strain 测试标准值 = L2 / L1*100%;

[0025] Wherein, Strain 测试标准值 is the strain test standard value, L2 is the optical length of the shorter optical fiber, and L1 is the optical length of the longer optical fiber.

[0026] The lengths of the two long and short optical fiber samples are measured by the phase shift method instrument after zeroing to obtain the respective measured optical fiber lengths of the two optical fiber samples, and the strain test value is calculated according to the respective measured optical fiber lengths of the two optical fiber samples, and the calculation formula is as follows:

[0027] Strain 测试值 = L 2测 / L 1测 *100%;

[0028] Wherein, Strain 测试值 is the strain test value, L 2测 is the measured optical fiber length of the shorter optical fiber, and L 1测 is the measured optical fiber length of the longer optical fiber.

[0029] The error between the strain test standard value and the strain test value is calculated, and the calculation formula is as follows:

[0030] Strain test error value = Strain 测试值 - Strain 测试标准值 .

[0031] If the strain test error value exceeds the preset strain error threshold value, the phase shift method instrument does not meet the test requirements of the optical fiber tensile strain. The strain test error value is the corrected value after the instrument is calibrated.

[0032] Further, the lengths of the two optical fiber samples are measured by the phase shift method instrument after zeroing to obtain the respective measured optical fiber lengths of the two optical fiber samples, including:

[0033] The longer optical fiber in the optical fiber sample is connected to the phase shift method instrument after zeroing, and the measured optical fiber length of the longer optical fiber is measured by the phase shift method instrument;

[0034] The shorter optical fiber is continuously connected, and the total length of the longer optical fiber and the shorter optical fiber is tested;

[0035] The measured optical fiber length of the shorter optical fiber is obtained by subtracting the measured optical fiber length of the longer optical fiber from the total length.

[0036] Further, the preset strain error threshold value is 0.01%.

[0037] Further, when the physical length of the optical fiber sample is directly measured based on the mechanical measurement method, the following needs to be met: measurement environment: constant temperature (23±0.5°C); vibration interference is isolated by a shockproof table during measurement; repeat the measurement for ≥5 times, take the arithmetic mean of all measurement values, and the standard deviation is ≤0.5 mm.

[0038] Furthermore, the fiber optic sample is connected to the time delay testing system, the optical length of the fiber optic sample is measured, and the group refractive index of the fiber optic sample is adjusted during the measurement process to make the optical length equal to the physical length. The group refractive index at this point is recorded as the actual group refractive index of the fiber optic sample, including:

[0039] Connect the optical fiber sample to the time delay testing system, record the round-trip time t of the optical pulse, and calculate the optical length using the following formula:

[0040] L Time Delay Method =c*t / n group_nominal ;

[0041] L Time Delay Method n is the optical length. group_nominal is the nominal group refractive index of the optical fiber, and c is the speed of light in vacuum;

[0042] Adjust n group_nominal The value of L Time Delay Method =L mech L mech The physical length is used to connect the optical fiber into the optical path system for measurement and recording, which yields the actual group refractive index n of the optical fiber. group_actual The calculation formula is as follows:

[0043] n group_actual =L Time Delay Method / (n group_nominal *L mech ).

[0044] Furthermore, the measurement accuracy requirement for directly measuring the physical length of the optical fiber sample based on the mechanical measurement method is ≤1mm, and the measurement accuracy for measuring the optical length of the optical fiber sample using the time delay testing system is 0.01%.

[0045] The beneficial effects of this invention are as follows:

[0046] The fiber optic strain gauge calibration method proposed in this invention establishes a complete traceability system encompassing "mechanical reference → time-delay optical reference standard → dynamic group refractive index calibration → phase-shift instrument verification," enabling high-reliability strain testing. This invention provides a unified calibration method for fiber optic strain gauges, allowing for cross-device comparison of test data, ensuring reproducibility, improving the reliability of test data from different manufacturers, and providing technical assurance for process improvement and secure communication network operation. Attached Figure Description

[0047] Figure 1 This is a histogram of the phase-shift method for measuring the length of long optical fibers in the embodiments of this application;

[0048] Figure 2 This is a histogram showing the difference between the length of a long optical fiber measured by the phase-shift method and the length of a long optical fiber measured by the time-delay method in the embodiments of this application.

[0049] Figure 3 Histogram of the difference between the short fiber length measured by the phase shift method and the short fiber length measured by the time delay method in the embodiment of the present application.

[0050] Figure 4 Histogram of the difference between the ratio of the short fiber length and the long fiber length measured by the phase shift method and the ratio of the short fiber length and the long fiber length measured by the time delay method in the embodiment of the present application.

[0051] Figure 5 Histogram of the difference between the ratio of the short fiber length and the long fiber length measured by the phase shift method and the ratio of the short fiber length and the long fiber length measured by the time delay method in the embodiment of the present application. DETAILED DESCRIPTION

[0052] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments but not all of the present application. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0053] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0054] The specific embodiments of the present application will be described in detail below with reference to the drawings.

[0055] The specific implementation steps of the optical fiber strain tester calibration method of the present application are as follows:

[0056] Step 1: Mechanical reference length calibration

[0057] The physical length L of the optical fiber sample is measured using a precision mechanical measuring device as a reference value. The precision mechanical measuring device should be traced to the reference. The specific measurement method is to directly measure the physical length of the optical fiber by precision mechanical measurement (such as a micrometer or an optical microscope). mech

[0058] Test points:

[0059] Measurement environment: constant temperature (23±0.5°C), vibration interference isolation on a shockproof table.

[0060] Repeat the measurement ≥5 times and take the arithmetic mean value (standard deviation ≤0.5 mm).

[0061] Step 2: Time delay method optical length measurement and group refractive index correction​

[0062] Inversion of the actual group refractive index n of the optical fiber by the time delay method group_actual The specific operation is as follows:

[0063] 1. Time delay method optical length measurement

[0064] The optical fiber sample is connected to the time delay test system, the round trip time t of the light pulse is recorded, and the optical standard length is calculated. The formula is as follows:

[0065] L Time Delay Method =c*t / n group_nominal

[0066] n group_nominal is the nominal group refractive index of the optical fiber, L Time Delay Method is the optical length.

[0067] 2. Dynamic correction of the group refractive index

[0068] Adjust the value of n group_nominal , so that L Time Delay Method =L mech , L mech is the physical length, the connecting optical fiber is measured and recorded in the optical path system, and the actual group refractive index n group_actual of the optical fiber can be obtained. The calculation formula is as follows:

[0069] n group_actual =L Time Delay Method / (n group_nominal *L mech ).

[0070] The true group refractive index is derived by the proportional relationship. This method can measure the true group refractive index of unknown sample optical fiber or factory calibration error optical fiber.

[0071] Integrity of the traceability chain: the mechanical method provides a traceable physical length reference, and the mechanical method reference eliminates the systematic error caused by the uncertainty of the group refractive index in the optical method. The time delay method transmits it to the optical domain to obtain the accurate optical length L Time Delay Method , at this time the time delay test system for testing the length of the optical fiber must be traced to the reference.

[0072] The measurement accuracy requirement of the mechanical measurement method for directly measuring the physical length of the optical fiber sample is ≤1μm, and the measurement accuracy of the time delay test system for measuring the optical length of the optical fiber sample is ≤0.01%.

[0073] Use standard optical length optical fiber to verify the phase shift method / differential phase shift method instrument:

[0074] Length calibration of the phase shift method instrument

[0075] n group_actualInput phase shift method instrument, ensure the length calculation basis parameter accuracy.

[0076] Zero the instrument to eliminate the influence of the internal optical path and optical devices, then measure the fiber length L phase .

[0077] Comparison of the length test results of the time delay method (optical reference method) and the phase shift method / differential phase shift method:

[0078] Error = |L phase − L Time Delay Method | / L Time Delay Method × 100%

[0079] If the error exceeds the allowed range, the instrument state needs to be checked. The allowed error range is to be determined.

[0080] For example: the time delay method instrument, which is traced to the national reference, gives the long fiber length L1 traceable value as 12213.11 m, and the short fiber length L2 traceable value as 6.126 m, and the group refractive index is 1.4681.

[0081] The following is the test data of 17 instruments using L1 as 12213.11 m and L2 as 6.126 m. Figure 1 The length of the long fiber L1 measured by the 17 phase shift method instruments is shown, Figure 2 The difference between the length of the long fiber L1 measured by the phase shift method instrument and the reference length measured by the time delay method is shown. Figure 3 The length of the short fiber L2 measured by the 17 phase shift method instruments is shown, Figure 4 The difference between the length of the short fiber L2 measured by the phase shift method instrument and the reference length measured by the time delay method is shown.

[0082] As can be seen from the results, even with uniform settings, the absolute length obtained directly from the test also has differences, and the correction value of the strain test parameter of the instrument cannot be directly found.

[0083] Step 2: Calibration of the length change of the phase shift method / differential phase shift method test instrument, ensure temperature stability during testing.

[0084] Use the time delay method (set the fiber group refractive index as n group_actual ), respectively test the length of two fiber samples, where the length of the long fiber A is L1, and the length of the short fiber B is L2.

[0085] Strain 测试标准值 = L2 / L1*100%;

[0086] Use the phase shift method (or differential phase shift method) test instrument to test the length of the long fiber A L 1测After accessing the short optical fiber B, the length of the short optical fiber B is calculated as L 2测 .

[0087] Strain 测试值 = L 2测 / L 1测 *100%;

[0088] Comparison results:

[0089] Error value = Strain 测试值 -Strain 测试标准值 ;

[0090] The allowable error of the phase shift method instrument is determined (should be less than 0.01%), if the error exceeds the allowable range, the instrument does not meet the fiber tensile strain test requirements.

[0091] This error value is the corrected value after the instrument is calibrated.

[0092] Figure 5 The difference between the ratio of the phase shift method L2 (short fiber) and L1 (long fiber) and the ratio of the time delay method L2 (short fiber) / L1 (long fiber) is shown, and the upper and lower limit values ± 0.001% are the judgment range of the corresponding fiber strain gauge, if the data of the instrument is in this interval, the test requirements can be met.

[0093] The overall process of the application is as follows:

[0094] Mechanical method reference:

[0095] The physical length of the optical fiber / cable is measured by a high-precision laser interferometer or a national length reference ruler, as the starting point of the entire traceability chain (SI can be traced).

[0096] Time delay method optical reference:

[0097] The physical length is converted into an optical domain reference by using the time difference (time delay) of the propagation of the optical signal in the optical fiber, and the original value of the group refractive index is inverted. The time delay test device needs to be traced.

[0098] Dynamic calibration of group refractive index:

[0099] The group refractive index of the optical fiber sample is dynamically corrected in combination with environmental parameters such as temperature and air pressure, to obtain the calibrated group refractive index and eliminate environmental interference.

[0100] Phase shift method instrument verification:

[0101] The calibrated group refractive index is used to verify the measurement accuracy of the phase shift instrument.

[0102] The optical fiber strain tester calibration method provided by the application takes the mechanical method as the reference method for optical length test, reduces the optical length error to 0.01% through mechanical calibration, realizes the operability of long and short optical fiber standard parts, and combines optical fibers of different lengths as a transfer standard for strain test, so that the data of each strain tester is controlled. The optical fiber strain tester calibration method provided by the application establishes a "mechanical method reference time delay method optical reference standard group refractive index dynamic calibration phase shift method instrument verification" system through full-chain traceability, and can support high-reliability strain test. The application provides a unified optical fiber strain tester calibration method, so that the test results of cross-devices can be directly compared, and the reliability of test data of different manufacturers is improved.

[0103] The above only describes the preferred embodiments of the application, and it should be noted that those skilled in the art can make some improvements and refinements without departing from the technical principles of the application, and these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A calibration method for an optical fiber strain gauge, characterized in that, include: Take a sample of the optical fiber to be tested; The physical length of the optical fiber sample is directly measured using a mechanical measurement method. Connect the optical fiber sample to the time delay test system, measure the optical length of the optical fiber sample, adjust the group refractive index of the optical fiber sample during the measurement process of the time delay test system so that the optical length is equal to the physical length, and record the group refractive index at this time as the actual group refractive index of the optical fiber. The actual group refractive index of the optical fiber is input into the phase-shift instrument. The phase-shift instrument is then zeroed. The measurement fiber length of the optical fiber sample is measured using the phase-shift instrument. The length error is calculated by comparing the measurement fiber length with the optical length of the optical fiber sample. The strain test error is calculated by comparing the optical length and measurement fiber length of each of the two optical fiber samples. The length of one optical fiber sample is greater than that of the other optical fiber sample. The phase-shift instrument is calibrated using the length error and strain test error. The length error is calculated by measuring the fiber length and optical length of the fiber sample, and the phase-shift method instrument is calibrated using the length error, including: The length L of the measuring fiber sample was measured using a phase-shift method instrument after zeroing. phase ; Calculate the length L of the optical fiber phase Its optical length L Time Delay Method The length error between them is calculated using the following formula: Length error = |L phase -L Time Delay Method | / L Time Delay Method ×100%; L phase To measure the length of the optical fiber, L Time Delay Method Its optical length; If the length error exceeds the preset length error threshold, the status of the phase shift method instrument needs to be checked; The strain test error is calculated by measuring the optical length of each of the two fiber optic samples and the length of the measuring fiber. The phase-shifting instrument is then calibrated using the strain test error, including: The standard strain test value is calculated using the optical lengths of the two fiber optic samples, as shown in the following formula: Strain 测试标准值 = L2 / L1*100%; Among them, Strain 测试标准值 For strain testing standard values, L2 is the optical length of the shorter fiber, and L1 is the optical length of the longer fiber. The lengths of the two fiber optic samples were measured using a phase-shift method instrument after zeroing, obtaining the measured fiber lengths for each sample. The strain test values ​​were then calculated using the measured fiber lengths of the two samples, as shown in the following formula: Strain 测试值 = L 2测 / L 1测 *100%; Among them, Strain 测试值 L is the strain test value. 2测 For measuring the length of shorter optical fibers, L 1测 For measuring the length of longer optical fibers; The error between the standard strain test value and the strain test value is calculated using the following formula: Strain test error value = Strain 测试值 -Strain 测试标准值 ; If the strain test error value exceeds the preset strain error threshold, the phase shift method instrument does not meet the requirements for fiber optic tensile strain testing, and the strain test error value is the correction value after instrument calibration.

2. The calibration method for an optical fiber strain gauge according to claim 1, characterized in that, The length error threshold is 0.01%.

3. The calibration method for an optical fiber strain gauge according to claim 1, characterized in that, The lengths of the two fiber optic samples were measured using a phase-shift method instrument after zeroing, yielding the measured fiber lengths for each sample, including: The longer fiber in the optical fiber sample is connected to the phase-shift instrument after it has been zeroed, and the length of the longer fiber is measured by the phase-shift instrument. Continue connecting shorter optical fibers to test the total length of longer and shorter optical fibers; The measurement fiber length of the shorter fiber is obtained by subtracting the measurement fiber length of the longer fiber from the total length.

4. The calibration method for an optical fiber strain gauge according to claim 1, characterized in that, The preset strain error threshold is 0.01%.

5. The calibration method for an optical fiber strain gauge according to claim 1, characterized in that, When directly measuring the physical length of an optical fiber sample using mechanical measurement methods, the following conditions must be met: Measurement environment: stable temperature (23±0.5°C); vibration interference is isolated by using a vibration isolation table during measurement; repeated measurements ≥5 times, and the arithmetic mean of all measurements is taken, with a standard deviation ≤0.5 mm.

6. The calibration method for an optical fiber strain gauge according to claim 1, characterized in that, Connect the fiber optic sample to the time delay testing system, measure the optical length of the fiber optic sample, and adjust the group refractive index of the fiber optic sample during the measurement process so that the optical length equals the physical length. Record the group refractive index at this point as the actual group refractive index of the fiber optic sample, including: Connect the optical fiber sample to the time delay testing system, record the round-trip time t of the optical pulse, and calculate the optical length using the following formula: L Time Delay Method =c*t / n group_nominal ; L Time Delay Method n is the optical length. group_nominal is the nominal group refractive index of the optical fiber, and c is the speed of light in vacuum; Adjust n group_nominal The value of L Time Delay Method =L mech L mech The physical length is used to connect the optical fiber into the optical path system for measurement and recording, which yields the actual group refractive index n of the optical fiber. group_actual The calculation formula is as follows: n group_actual =L Time Delay Method / (n group_nominal *L mech )。 7. The calibration method for an optical fiber strain gauge according to claim 1, characterized in that, The measurement accuracy requirement for directly measuring the physical length of an optical fiber sample using mechanical measurement methods is ≤1mm, while the measurement accuracy for measuring the optical length of an optical fiber sample using a time delay testing system is 0.01%.

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