A method for measuring and controlling the length of an optical fiber, a terminal and a storage medium

Abstract

The application discloses a kind of measurement control method of optical fiber length, terminal and storage medium, method includes: control single-mode laser generates continuous preset wavelength laser, and according to the input voltage of first acousto-optic modulator, first preset voltage is modulated, obtain single pulse laser;Pulse sequence is generated by preset proportion fiber coupler, and according to the input voltage of second acousto-optic modulator, second preset voltage is modulated, the intensity of part optical signal in pulse sequence is adjusted to preset intensity;The light signal after adjustment is converted into corresponding electrical signal by photoelectric detector, and according to pulse positioning rule, electrical signal is pulse positioned;According to the pulse electrical signal of positioning, oscilloscope sampling is carried out, and data fitting is carried out according to sampling data, the length of the optical fiber to be measured is calculated and output.The application carries out step modulation to light pulse intensity by acousto-optic modulator of optical fiber, and further improves measurement accuracy by expanding effective optical path length.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber technology, in particular to a method for measuring and controlling the length of an optical fiber, a terminal and a storage medium. BACKGROUND

[0002] In the field of optical fiber length measurement, there are several traditional methods such as time-of-flight (TOF), optical time domain reflectometer (OTDR), optical frequency domain reflectometer (OFDR), asymmetric Sagnac interferometer and laser mode locking method. The time-of-flight method requires a high-frequency pulse signal source and a high-time-stability high-speed oscilloscope, otherwise the measurement accuracy is difficult to guarantee, and the measurement accuracy of this method is usually in the order of centimeters; the optical time domain reflectometer utilizes the weak backscattering Rayleigh scattering light generated when light propagates in the optical fiber, which needs to be averaged to reduce detection noise, resulting in a longer measurement time, general measurement accuracy and a certain range of detection blind area; the optical frequency domain reflectometer requires a light source with low phase noise and large linear sweep range, which is difficult to guarantee the service life of the equipment and has very high cost, and at the same time, due to the limitation of the coherence length of the light source, it is not suitable for long distance measurement; the frequency shift asymmetric Sagnac interferometer is easily affected by the twist and disturbance of the optical fiber, which will cause changes in the polarization state of the light wave due to geometric effect and photoelastic effect, and further affect the measurement value of the measured optical fiber; the laser mode locking method cannot directly measure the length of the short optical fiber. In addition, many optical devices are large in size and have high requirements on the use environment, which are not suitable for on-site detection, so a detection device with high detection accuracy, low cost and convenient integration and carrying is needed.

[0003] Therefore, the prior art still needs to be improved. SUMMARY

[0004] The technical problem to be solved by the present application is that, in view of the defects of the prior art, the present application provides a method for measuring and controlling the length of an optical fiber, a terminal and a storage medium to solve the technical problems of low detection accuracy and high cost of traditional optical fiber length measurement control methods.

[0005] The technical solution adopted by the present application to solve the technical problem is as follows:

[0006] In a first aspect, the present application provides a method for measuring and controlling the length of an optical fiber, comprising:

[0007] controlling a single-mode laser to generate continuous laser of a preset wavelength, and modulating the input voltage of a first acousto-optic modulator according to a first preset voltage to convert the continuous laser of the preset wavelength into a single pulse laser;

[0008] generating a pulse sequence through a preset ratio optical fiber coupler, and modulating the input voltage of a second acousto-optic modulator according to a second preset voltage to adjust the intensity of part of the optical signals in the pulse sequence to a preset intensity;

[0009] The adjusted optical signal is converted into a corresponding electrical signal by a photoelectric detector, and the electrical signal is pulse-positioned according to a pulse positioning rule, to obtain a positioned pulse electrical signal;

[0010] An oscilloscope is sampled according to the positioned pulse electrical signal, and data fitting is performed according to the sampling data, to calculate the length of the optical fiber to be measured and output.

[0011] In an implementation manner, the control single-mode laser generates continuous laser of a preset wavelength, and the method comprises the following steps:

[0012] A simulation test is performed on a plurality of optical fiber couplers with different splitting ratios, and the optical fiber coupler with the preset ratio is selected according to the test result; wherein the preset ratio is 90:10.

[0013] In an implementation manner, the control single-mode laser generates continuous laser of a preset wavelength, and the input voltage of the first acousto-optic modulator is modulated according to a first preset voltage, to convert the continuous laser of the preset wavelength into single pulse laser, comprising:

[0014] The single-mode laser is controlled to generate continuous 1550nm laser;

[0015] The first acousto-optic modulator is controlled according to the first preset voltage, to open and close the optical path of the continuous 1550nm laser, to generate the single pulse laser.

[0016] In an implementation manner, the pulse sequence is generated by the optical fiber coupler with the preset ratio, and the input voltage of the second acousto-optic modulator is modulated according to a second preset voltage, to adjust the intensity of part of the optical signals in the pulse sequence to a preset intensity, comprising:

[0017] The single pulse is converted into the pulse sequence by the optical fiber coupler with the preset ratio;

[0018] The input voltage of the second acousto-optic modulator is modulated according to the second preset voltage;

[0019] The delay difference of the two arbitrary wave generators is adjusted, to adjust the intensity of part of the optical pulses in the pulse sequence to the same level.

[0020] In an implementation manner, the delay difference of the two arbitrary wave generators is adjusted, to adjust the intensity of part of the optical pulses in the pulse sequence to the same level, comprising:

[0021] The signal and the delay difference of the two arbitrary wave generators are controlled respectively, to control the input voltage of the corresponding acousto-optic modulator, to adjust the intensity of part of the optical pulses in the pulse sequence to the same level.

[0022] In an implementation manner, the converting the adjusted optical signal into corresponding electrical signals by the photodetector and the pulse positioning the electrical signals according to a pulse positioning rule to obtain a positioned pulse electrical signal, comprises:

[0023] The adjusted optical signal is converted into corresponding electrical signals by the photodetector.

[0024] The pulse sequence in all electrical signals is segmented according to a preset time period to obtain a maximum value in each time period.

[0025] The half-peak positions are searched on both sides of the maximum value in each time period, and a midpoint position is determined according to the searched two half-peak positions.

[0026] The midpoint position is set as a positioning point of the corresponding pulse electrical signal.

[0027] In an implementation manner, the oscilloscope sampling is performed according to the positioned pulse electrical signal, and data fitting is performed according to sampling data to calculate and output the length of the to-be-measured optical fiber, comprising:

[0028] The first time difference between the first pulse and the Nth pulse is calculated according to the positioning point of the pulse electrical signal.

[0029] The second time difference between the first pulse and the Nth pulse when the to-be-measured optical fiber is not placed is determined.

[0030] The round-trip time of flight of the optical signal in the to-be-measured optical fiber is calculated according to the first time difference and the second time difference.

[0031] The oscilloscope sampling is performed on the positioned pulse electrical signal according to the round-trip time of flight, and data fitting is performed according to sampling data to calculate and output the length of the to-be-measured optical fiber.

[0032] In an implementation manner, the first time difference between the first pulse and the Nth pulse is calculated according to the positioning point of the pulse electrical signal, comprising:

[0033] The optical path difference between the first pulse and the Nth pulse is calculated according to the optical path of the first pulse and the optical path of the Nth pulse.

[0034] The first time difference between the first pulse and the Nth pulse is calculated according to the optical path difference and the positioning point of the corresponding pulse signal.

[0035] In a second aspect, the present application also provides a terminal, comprising: a processor and a memory, the memory storing a fiber length measurement control program, the fiber length measurement control program being used to implement the operations of the fiber length measurement control method according to the first aspect when executed by the processor.

[0036] In a third aspect, the present application also provides a medium, which is a computer readable storage medium, the storage medium storing a fiber length measurement control program, the fiber length measurement control program being used to implement the operations of the fiber length measurement control method according to the first aspect when executed by a processor.

[0037] The present application has the following effects by adopting the above technical solutions:

[0038] The present application is based on the time-of-flight method, uses a fiber coupler structure to expand a single optical pulse into a pulse sequence, and increases the number of detectable pulses by stepwise modulation of the optical pulse intensity through a fiber acousto-optic modulator. Compared with the conventional time-of-flight method, the same length of the measured optical fiber is measured in a cyclic manner, the optical path length is expanded by a multiple, the error generated by the average measurement is divided by the number of pulses, and finally the sampling characteristics of the oscilloscope are used to collect the data in a special fitting manner, breaking through the limitation of the sampling speed of the oscilloscope, and realizing higher precision measurement. The present application has the characteristics of high precision, low cost and measurement stability. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from the structures shown in the drawings without creative labor.

[0040] Figure 1 is a flowchart of a fiber length measurement control method in an implementation manner of the present application.

[0041] Figure 2 is a schematic diagram of a fiber length measurement control system in an implementation manner of the present application.

[0042] Figure 3 is a schematic diagram of a pulse cycle generated by a fiber coupler in an implementation manner of the present application.

[0043] Figure 4 is a schematic diagram of input voltage modulation of a second acousto-optic modulator in an implementation manner of the present application.

[0044] Figure 5is a schematic diagram of the intensity modulation result of the optical pulse in an implementation of the present application.

[0045] Figure 6 is a schematic diagram of pulse positioning in an implementation of the present application.

[0046] Figure 7 is a schematic diagram of the variation of the pulse power with cycles under a single fiber coupler in an implementation of the present application.

[0047] Figure 8 is a schematic diagram of the variation of the pulse power with cycles under two fiber couplers in an implementation of the present application.

[0048] Figure 9 is a schematic diagram of the oscilloscope sampling an ideal pulse signal in an implementation of the present application.

[0049] Figure 10 is a schematic diagram of the relationship between the measured time of flight and the cycle number in an implementation of the present application.

[0050] Figure 11 is a functional schematic diagram of a terminal in an implementation of the present application.

[0051] The implementation of the present application, functional features and advantages will be further described with reference to the accompanying drawings and in conjunction with embodiments. DETAILED DESCRIPTION

[0052] To make the purpose, technical solutions and advantages of the present application more clear and explicit, the present application will be further described in detail below with reference to the accompanying drawings and in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0053] Exemplary method

[0054] In the existing optical fiber length measurement technology, most of the optical fiber length measurement technology usually has one or more of the problems of low measurement accuracy, limited measurement range, limited measurement environment, complex equipment and high cost.

[0055] In order to solve the above technical problems, the embodiment of the present application provides a kind of measurement control method of optical fiber length, the embodiment of the present application is based on time-of-flight method, utilize optical fiber coupler structure to expand single optical pulse to a set of pulse sequence, and the intensity of optical pulse is stepped modulated by optical fiber acousto-optic modulator to increase the number of detectable pulses.The embodiment of the present application measures the same length of the optical fiber to be measured in this cyclic way, can multiply the optical path length, the error generated by the continuous interval of pulse sequence is divided by the number of pulses to average measurement, finally, using the sampling characteristics of oscilloscope, the data collected is fitted in a special way, which breaks through the limitation of the sampling speed of oscilloscope, and realizes higher precision measurement.The embodiment of the present application has the characteristics of high precision, low cost and measurement stability.

[0056] As shown in Figure 1 The embodiment of the present application provides a kind of measurement control method of optical fiber length, comprising the following steps:

[0057] Step S100, control single mode laser to generate continuous preset wavelength laser, and modulate the input voltage of the first acousto-optic modulator according to the first preset voltage, convert the continuous preset wavelength laser into single pulse laser.

[0058] In the embodiment, the measurement control method of optical fiber length is applied to a terminal, and the terminal includes but is not limited to a computer, a mobile terminal and other devices.

[0059] In the embodiment, the measurement control method of optical fiber length is realized by a measurement control system of optical fiber length, and a new optical fiber length measurement system is adopted in the embodiment.On the one hand, the pulse sequence is generated by the circulation of the optical path, so as to expand the effective optical path length, reduce the error generated by the optical fiber length measurement, and further improve the measurement precision.On the other hand, according to the sampling characteristics of the oscilloscope, a fitting method is proposed to obtain more accurate values.

[0060] As shown in Figure 2 The measurement control system of optical fiber length includes a laser, a first acousto-optic modulator, an optical fiber coupler, a second acousto-optic modulator, a photodetector, an oscilloscope and a computer (i.e. a terminal) connected in sequence.The optical fiber coupler is provided with a fiber to be measured, and the X end of the fiber to be measured is connected to the F interface of the optical fiber coupler, and the Y end of the fiber to be measured is connected to the C interface of the optical fiber coupler.When the fiber to be measured is measured, the optical signal is transmitted from the F interface of the optical fiber coupler to the X end of the fiber to be measured, and then to the Y end of the fiber to be measured, and then to the C interface of the optical fiber coupler through the Y end of the fiber to be measured.

[0061] In one implementation manner of the embodiment, the optical fiber coupler needs to be modulated in advance to obtain the splitting ratio of the optical fiber coupler with the highest measurement precision.

[0062] Specifically, in one implementation of the embodiment, step S100 includes the following steps:

[0063] Step S001, simulate and test several different splitting ratio fiber couplers, and select the preset ratio fiber coupler according to the test results.

[0064] In the embodiment, the splitting ratio after simulation test is 90:10, that is, two 2x2 fiber couplers with a splitting ratio of 90:10 are used in the embodiment.

[0065] Specifically, in the process of simulation test, if only one fiber coupler is used to generate the optical pulse sequence, only the splitting ratio of the coupler is considered, and several common fiber couplers with different splitting ratios are simulated on MATLAB, and the pulse light power is obtained in each cycle as shown in the following table. Figure 7 It can be observed that in the pulse sequences generated by the fiber couplers with splitting ratios of 90:10, 99:1 and 75:25, the pulses after the first pulse are uniformly attenuated, but there is a significant drop between the power of the first pulse and the power of the second pulse. Therefore, when the power of the input laser is too small, the power of the pulse after the first pulse will drop significantly, and the corresponding waveform cannot be observed; if the power of the input laser is increased and the voltage display range of the oscilloscope is reduced, the power of the first pulse will be too large to exceed the voltage range selected by the oscilloscope, and the excessive power may cause permanent damage to the photodetector by the first pulse laser.

[0066] If two 2x2 fiber couplers are connected to generate the optical pulse sequence, only the splitting ratio of the coupler is considered, and several common fiber couplers with different splitting ratios are simulated on MATLAB, and the pulse light power is obtained in each cycle as shown in the following table. Figure 8 It can be seen that the optical power is uniformly attenuated. In this way, according to the loss existing in the actual system, the splitting ratio of the fiber coupler is reasonably selected, and the intensity of the pulse sequence is adjusted by the acousto-optic modulator, so that a better pulse sequence can be obtained; therefore, two 2x2 fiber couplers with a splitting ratio of 90:10 are used in the embodiment.

[0067] In the embodiment, after simulation test, the fiber to be measured is connected by the fiber coupler with the set splitting ratio, and then real-time measurement is performed by the fiber length measurement control system; in the process of real-time measurement, the single pulse laser signal required in the measurement process is generated by the laser and the first acousto-optic modulator.

[0068] Specifically, in one implementation of the embodiment, step S100 includes the following steps:

[0069] Step S101, controlling the single-mode laser to generate continuous 1550nm laser;

[0070] Step S102 : controlling the first acousto-optic modulator according to the first preset voltage to open and then close the optical path of the continuous 1550 nm laser to generate the single pulse laser.

[0071] In this embodiment, the laser is a single-mode laser that can generate a central wavelength of 1550 nm. The laser signal generated by the single-mode laser is a continuous laser. The single-mode laser generates a continuous 1550 nm laser that passes through a first acousto-optic modulator connected thereto. Under the modulation of the first acousto-optic modulator, a switching effect is generated on the optical path in which the laser is located, thereby generating a single pulse laser.

[0072] By controlling the input voltage of the first acousto-optic modulator, a switching effect is generated on the optical path. In the process of controlling the input voltage of the first acousto-optic modulator, the optical path is first controlled to be in an open state and then controlled to be in a closed state according to a first preset voltage, thereby generating a single pulse laser. The first preset voltage is the voltage when the optical path is in the open state (for example, 1V) and the voltage when the optical path is in the closed state (for example, 0V).

[0073] like Figure 1 As shown, in one implementation of the embodiment of the present invention, the method for measuring and controlling the length of an optical fiber further includes the following steps:

[0074] In step S200 , a pulse sequence is generated by a fiber coupler with a preset ratio, and an input voltage of a second acousto-optic modulator is modulated according to a second preset voltage to adjust the intensity of a portion of the optical signal in the pulse sequence to a preset intensity.

[0075] In this embodiment, after generating a single laser pulse, a pulse train is generated using two 2x2 fiber couplers with a 90:10 splitting ratio. The input voltage of a second acousto-optic modulator is then modulated to adjust the intensity of the optical signals in a portion of the pulse train to the same level (i.e., the same intensity).

[0076] Specifically, in one implementation of this embodiment, step S200 includes the following steps:

[0077] Step S201, converting the single pulse into the pulse sequence through the optical fiber coupler with the preset ratio;

[0078] Step S202, modulating the input voltage of the second acousto-optic modulator according to the second preset voltage;

[0079] Step S203, adjusting the time delay difference of the two arbitrary wave generators, adjusting the intensity of a part of the optical pulses in the pulse sequence to the same level.

[0080] In the embodiment, as shown in Figure 3 , a single optical pulse forms a pulse sequence through two 2x2 couplers, then the input voltage of the second acousto-optic modulator is modulated by a second preset voltage to obtain a modulated optical pulse signal; wherein, as shown in Figure 4 , the second preset voltage is a group of step voltages, the input voltage of the second acousto-optic modulator is gradually adjusted from 0V to 1V through the second preset voltage, and then the intensity of a part of the optical pulses in the pulse sequence is adjusted to the same level by adjusting the time delay difference of the two arbitrary wave generators.

[0081] Specifically, in an implementation manner of the embodiment, step S203 includes the following steps:

[0082] Step S203a, respectively controlling the signal and the time delay difference of the two arbitrary wave generators, controlling the input voltage of the corresponding acousto-optic modulator, and adjusting the intensity of a part of the optical pulses in the pulse sequence to the same level.

[0083] In the embodiment, the time delay difference of the two arbitrary wave generators can be adjusted on the computer using LabView software; specifically, the input voltage of the two acousto-optic modulators is controlled by simultaneously controlling the signal and the delay difference of the two arbitrary wave generators, and the intensity of a part of the optical pulses in the pulse sequence is finally adjusted to the same level by adjusting the time delay difference of the two arbitrary wave generators, as shown in the optical pulse intensity modulation result. Figure 5

[0084] Since the pulse laser circulates in the fiber coupler, the more the number of circulations, the more serious the energy attenuation of the optical pulse, resulting in that the pulse laser power generated after multiple circulations is too small to affect the detection effect of the oscilloscope on the signal.

[0085] As shown in Figure 1 , in an implementation manner of the embodiment, the optical fiber length measurement control method further includes the following steps:

[0086] Step S300, converting the adjusted optical signal into a corresponding electrical signal through a photodetector, and performing pulse positioning on the electrical signal according to a pulse positioning rule to obtain a positioned pulse electrical signal.

[0087] ​In this embodiment, after adjusting the intensity of a part of the light pulses in the pulse sequence to the same level, i.e. adjusting the power of the pulses after using the acousto-optic modulator, the light signal is converted into an electrical signal by a photodetector, then connected to an oscilloscope for observation and recording and exporting data to a computer (PC), and finally the data is processed offline using MATLAB.

[0088] Specifically, in an implementation form of this embodiment, step S300 includes the following steps:

[0089] Step S301, converting the adjusted light signal into a corresponding electrical signal by the photodetector;

[0090] Step S302, segmenting the pulse sequence in all electrical signals according to a preset time period to obtain the maximum value of each time period;

[0091] Step S303, finding the half-peak positions on both sides of the maximum value in each time period respectively, and determining the midpoint position according to the two found half-peak positions;

[0092] Step S304, setting the midpoint position as the positioning point of the corresponding pulse electrical signal.

[0093] In this embodiment, the pulse signal detected by the oscilloscope has been deformed in waveform and contains noise signals after passing through various optical and electrical devices. Determining the time interval between two rectangular pulses with a certain width is an important factor for accurately measuring the length of the optical fiber. In order to improve the measurement accuracy of the measured optical fiber, the obtained pulse signal needs to be positioned.

[0094] As shown in the positioning process as Figure 6 shown, the pulse sequence is first segmented in time, i.e. segmented according to a preset time period, wherein the preset time period can be 1 μs; then the maximum value (i.e. the peak value of the pulse signal intensity) of each time period is found. Due to the influence of noise and other factors, the maximum value point at this time has a certain randomness at the top of the rectangular pulse and cannot be used to position the position of the pulse.

[0095] Therefore, by finding the positions with a half amplitude (i.e. half-peak value positions) on both sides of the pulse maximum value point respectively, and determining the midpoint position of the two positions, the midpoint position is used as the positioning point of the corresponding pulse in the time period. Since the subsequent pulses are only subjected to several 2x2 fiber couplers and ordinary single-mode optical fibers compared to the previous pulses, there is almost no influence on the rising and falling edges of the rectangular pulse. The position of the pulse can be determined better by this method.

[0096] AsFigure 1 As shown in one implementation of the embodiment of the present application, the measurement control method of the optical fiber length further comprises the following steps:

[0097] In step S400, the oscilloscope sampling is performed according to the located pulse electrical signal, and the data fitting is performed according to the sampling data, so as to calculate and output the length of the optical fiber to be measured.

[0098] In the present embodiment, after the positions of the single pulse signals are located, the time points corresponding to the pulse signals are determined according to the located positions, and then the time difference between the two pulse signals is calculated by selecting the time point of the starting pulse signal and the time point of the ending pulse signal, and the length of the optical fiber to be measured can be obtained by combining the time difference when the optical fiber to be measured is not placed, the oscilloscope sampling and the fitting data, and outputting the calculated length of the optical fiber to be measured.

[0099] Specifically, in one implementation of the present embodiment, step S400 comprises the following steps:

[0100] In step S401, the first time difference between the first pulse and the Nth pulse is calculated according to the set location points of the pulse electrical signals.

[0101] In step S402, the second time difference between the first pulse and the Nth pulse when the optical fiber to be measured is not placed is determined.

[0102] In step S403, the round-trip time of flight of the optical signal in the optical fiber to be measured is calculated according to the first time difference and the second time difference.

[0103] In step S404, the oscilloscope sampling is performed on the located pulse electrical signal according to the round-trip time of flight, and the data fitting is performed according to the sampling data, so as to calculate and output the length of the optical fiber to be measured.

[0104] In the present embodiment, in the process of calculating the length of the optical fiber to be measured, the optical path (i.e. the optical path length value) of the first pulse and the optical path of the Nth pulse need to be determined first.

[0105] As shown in the present embodiment, the optical fiber to be measured (FUT) is placed in the system, and the optical path L1 of the first pulse can be represented as: Figure 2

[0106] L1=A→B→C→D→E→F→G→H

[0107] The optical path L N of the Nth pulse can be represented as:

[0108] L N =A→B→C→D→E→F→{(N-1)·(F→X→Y→C→D→E→F)}→G→H ​

[0109] Wherein, X→Y is the length L of the fiber to be measured FUT The optical path difference ΔL between the first pulse and the Nth pulse can be obtained from the above two equations FUT Which can be expressed as:

[0110] ΔL FUT = L N - L1= (N-1) · (F→X→Y→C→D→E→F)

[0111] The time difference Δt between the first pulse and the Nth pulse can be obtained after collecting the signal from the oscilloscope and processing the calculation FUT Which can be expressed as:

[0112]

[0113] Wherein, c is the speed of light, n eff is the effective refractive index of the fiber, σ FUT is the error caused by the measurement.

[0114] Similarly, when the fiber to be measured is not placed, the optical path difference ΔL0 between the first pulse and the Nth pulse and the time difference Δt0 can be expressed as:

[0115] ΔL0= (N-1) · (F→C→D→E→F)

[0116]

[0117] Therefore, by subtracting the two sets of data obtained by placing the fiber to be measured in the fiber coupler loop and not placing the fiber to be measured, the time of flight Δt of the light in the fiber to be measured can be obtained:

[0118]

[0119] Therefore, the length L of the fiber to be measured FUT can be derived from the above equation:

[0120]

[0121] As can be seen from the above equation, as the number of cycles increases, the more the number of pulse lasers obtained, the smaller the error σ caused by the measurement. Compared with the traditional time of flight method for measuring the length of the fiber, the measurement system used in this embodiment can multiply the effective optical path length, and does not need to use a photoelectric detector with very fast response speed. According to the actual number of cycles, the measurement error can be reduced by more than one order of magnitude, greatly improving the measurement accuracy.

[0122] In this embodiment, the length of the fiber to be measured can be calculated and output by the sampling characteristics of the oscilloscope and data fitting.

[0123] Since all oscilloscopes have a certain sampling speed and bandwidth, which means that the oscilloscope is not continuously sampled, so there is an error between the detected time domain signal and the ideal signal. This is used in this embodiment to analyze it and obtain the expression of the actual measured pulse interval, and the collected data is fitted to obtain the length of the fiber to be measured.

[0124] Assume that the oscilloscope samples an ideal pulse signal as shown in Figure 9 , where the black line is the ideal pulse signal, and the red dot is the sampling point of the oscilloscope. In this embodiment, the first sampling point before the rising edge of each pulse is used to represent the position of the pulse, and the time t(0) corresponding to the position of the rising edge of the first pulse is set as the starting point, that is:

[0125] t(0) = 0

[0126] The time t(1) corresponding to the position of the second rising edge can be derived from the added fiber length L, the effective refractive index n eff and the speed of light c:

[0127]

[0128] Due to the discrete sampling characteristics of the oscilloscope, the time position t0 of the first sampling point before the rising edge of the signal is a random position, which is determined by the start sampling time, and its random range is determined by the sampling time interval Δt s of the oscilloscope, that is:

[0129] t0 = -Δt s ·rand

[0130] randE(0, 1)

[0131] rand represents this random number, which will remain unchanged during the continuous sampling process of the oscilloscope. Then the time position of the seventh sampling point, that is, the first sampling point t1 before the rising edge of the second pulse, can be expressed as:

[0132]

[0133] Where, [] represents the floor function, as shown in the above formula, the time from the first sampling point to the second rising edge is divided by the sampling time interval Δt s , and then the floor function is taken and multiplied by the sampling time interval Δt s , that is, the time from the seventh sampling point to the second rising edge can be discarded. Since the time t(0) of the first rising edge position is set to 0 in this embodiment, finally subtract Δt srand to represent the position of the point. Similarly, in this embodiment, the time position t2 of the first sampling point before the second rising edge can be represented as:

[0134]

[0135] Finally, the time position t of the first sampling point before the (N+1)th rising edge is derived: N :

[0136]

[0137] Therefore, in this embodiment, the position of each pulse is represented by the first sampling point before the rising edge of the pulse, and the single flight time of light in the optical fiber under test can be represented by the positions of the (N+1)th pulse and the first pulse:

[0138]

[0139] In this embodiment, certain parameters are selected, and T N This expression is simulated, and the results are shown in Figure 10 The red line is the true value of the flight time of light T real derived directly from the length of the optical fiber, which is represented as:

[0140]

[0141] The blue line is the oscilloscope sampling, and the change in the measurement result with the increase in the number of cycles is calculated. It can be seen that with the increase in the number of cycles, the more cycles the light has in the loop, the more accurate the measurement is, and it is in an oscillation state near the true value, but overall it has a trend of converging to the true value.

[0142] T N is simplified and represented as:

[0143]

[0144] b=rand

[0145]

[0146] For measuring an optical fiber, it is known that the length of the optical fiber L, the effective refractive index n eff , the speed of light c, the oscilloscope sampling time interval Δt s , and the random number rand in a single measurement are constants. In a single measurement, a and b are unknown constants.

[0147] Since:

[0148]

[0149]

[0150]

[0151] T N Taking the limit, we have:

[0152]

[0153] Therefore, when N tends to infinity, T N will converge to the true value T real . However, due to the transmission loss of light in the optical fiber, the insertion loss of optical devices, and the loss caused by the splitting of the fiber coupler, it is actually not possible to achieve infinite cycles. Therefore, in this embodiment, the expression:

[0154]

[0155] is fitted with the measured data in a machine learning manner, where N, T N can be extracted from the measured data, and Δt s is the sampling time interval set by the oscilloscope, which is a known quantity. Through fitting, the values of a and b can be obtained, and finally the length L of the optical fiber can be deduced through the expression of a:

[0156]

[0157] In this way, the amount of data required for sampling is greatly reduced, and the requirement for the number of cycles of the system is also reduced, and very accurate measurement results can be obtained through a limited number of cycles. That is, by analyzing the sampling characteristics of the oscilloscope and fitting the data, the limitation of the sampling rate of the oscilloscope on the measurement of the length of the optical fiber based on the time-of-flight method is broken through.

[0158] It is worth mentioning that the measurement system in this embodiment is not only suitable for standard communication optical fibers, but also for special optical fibers such as single-mode photonic bandgap optical fibers, and can also be applied to the calculation of the effective refractive index of the optical fiber. For example, due to the variation of laser wavelength, environmental temperature, pressure, strain and production batch, the effective refractive index provided by the optical fiber manufacturer for the corresponding single-mode optical fiber usually has an error of 0.1%. If the measurement system in this embodiment is used, the actual length of a relatively short optical fiber (less than 2 meters) is measured by other equipment under the current environment, then the optical fiber is fused and connected to the measurement system, and finally the measurement is performed according to the above method, the effective refractive index of the optical fiber under the current environmental conditions can be deduced, and the length measurement of the long optical fiber can also be further calibrated.

[0159] The embodiment based on the time of flight method proposes a new optical fiber length measurement system, which has the advantages of simple structure, no restriction of the coherence length of the laser light source and the influence of the polarization of light, low cost, etc. In the embodiment, a new optical fiber length measurement system is used. On the one hand, the pulse sequence is generated by the circulation of the optical path, so as to expand the effective optical path length, reduce the error caused by the optical fiber length measurement, and further improve the measurement accuracy. On the other hand, according to the sampling characteristics of the oscilloscope, a fitting method is proposed to obtain more accurate numerical values.

[0160] The embodiment achieves the following technical effects through the above technical scheme.

[0161] The embodiment based on the time of flight method uses the optical fiber coupler structure to expand a single optical pulse into a set of pulse sequences, and increases the number of detectable pulses by stepwise modulation of the optical pulse intensity through the optical fiber acousto-optic modulator. Compared with the conventional time of flight method, the same length of the measured optical fiber is measured by this circulation method, which can expand the optical path length by several times. The error generated by the measurement is averaged by dividing the continuous interval of the pulse sequence by the number of pulses. Finally, by using the sampling characteristics of the oscilloscope and using a special fitting method for the collected data, the limitation of the sampling speed of the oscilloscope is broken through, and higher precision measurement is realized. The embodiment has the characteristics of high precision, low cost and measurement stability.

[0162] Exemplary device

[0163] Based on the above embodiment, the application further provides a terminal, comprising: a processor, a memory, an interface, a display screen and a communication module connected through a system bus; wherein the processor is used to provide calculation and control capability; the memory includes a storage medium and an internal memory; the storage medium stores an operating system and a computer program; the internal memory provides an environment for the operating system and the computer program in the storage medium to run; the interface is used to connect external devices, such as mobile terminals and computer devices; the display screen is used to display corresponding information; and the communication module is used to communicate with a cloud server or a mobile terminal.

[0164] The computer program is executed by the processor to implement the operation of the optical fiber length measurement control method.

[0165] Those skilled in the art can understand that, Figure 11 The principle block diagram shown in the figure is only a block diagram of part of the structure related to the application scheme, and does not constitute a limitation on the terminal to which the application scheme is applied. The specific terminal can include more or fewer components than those shown in the figure, or combine certain components, or have a different component arrangement.

[0166] In one embodiment, a terminal is provided, comprising: a processor and a memory, the memory storing a fiber length measurement control program, the fiber length measurement control program, when executed by the processor, being configured to implement the operations of the fiber length measurement control method described above.

[0167] In one embodiment, a storage medium is provided, the storage medium storing a fiber length measurement control program, the fiber length measurement control program, when executed by the processor, being configured to implement the operations of the fiber length measurement control method described above.

[0168] It can be understood by those skilled in the art that all or part of the processes in the above-mentioned embodiments can be completed by a computer program instructing related hardware, and the computer program can be stored in a non-volatile storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. Any reference to memory, storage, database or other medium used in the embodiments provided by the present application can include non-volatile and / or volatile memory.

[0169] In summary, the present application provides a fiber length measurement control method, a terminal and a storage medium. The method comprises: controlling a single-mode laser to generate continuous laser of a preset wavelength, and modulating the input voltage of a first acousto-optic modulator according to a first preset voltage to convert the continuous laser of the preset wavelength into single pulse laser; generating a pulse sequence through a preset proportion of a fiber coupler, and modulating the input voltage of a second acousto-optic modulator according to a second preset voltage to adjust the intensity of part of the optical signals in the pulse sequence to a preset intensity; converting the adjusted optical signals into corresponding electrical signals through a photodetector, and performing pulse positioning on the electrical signals according to a pulse positioning rule to obtain positioned pulse electrical signals; performing oscilloscope sampling according to the positioned pulse electrical signals, and performing data fitting according to the sampling data to calculate the length of the fiber to be measured and output. The present application further improves the measurement accuracy by extending the effective optical path length through the step modulation of the optical pulse intensity by the fiber acousto-optic modulator.

[0170] It should be understood that the application of the present application is not limited to the above examples, and those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present application.

Claims

1. A measurement control method of an optical fiber length, characterized by, The method comprises the following steps: controlling a single-mode laser to generate continuous laser of a preset wavelength, and modulating input voltage of a first acousto-optic modulator according to a first preset voltage to convert the continuous laser of the preset wavelength into single-pulse laser; generating a pulse sequence through a fiber coupler with a preset ratio, and modulating input voltage of a second acousto-optic modulator according to a second preset voltage to adjust intensity of part of optical signals in the pulse sequence to a preset intensity; converting the adjusted optical signals into corresponding electrical signals through a photodetector, and performing pulse positioning on the electrical signals according to a pulse positioning rule to obtain positioned pulse electrical signals; performing oscilloscope sampling on the positioned pulse electrical signals, and performing data fitting on sampling data to calculate a length of the optical fiber to be measured and output the length; the step of performing oscilloscope sampling on the positioned pulse electrical signals, and performing data fitting on sampling data to calculate a length of the optical fiber to be measured and output the length comprises: calculating a first time difference between a first pulse and an Nth pulse according to positioned points of the pulse electrical signals; determining a second time difference between the first pulse and the Nth pulse when the optical fiber to be measured is not placed; calculating a round-trip time of flight of the optical signals in the optical fiber to be measured according to the first time difference and the second time difference; performing oscilloscope sampling on the positioned pulse electrical signals according to the round-trip time of flight, and performing data fitting on sampling data to calculate a length of the optical fiber to be measured and output the length.

2. The measurement control method of the optical fiber length according to claim 1, characterized by, The step of controlling a single-mode laser to generate continuous laser of a preset wavelength comprises the following steps: performing simulation tests on fiber couplers with different splitting ratios, and selecting the fiber coupler with the preset ratio according to test results; wherein the preset ratio is 90:

10.

3. The measurement control method of the optical fiber length according to claim 1, characterized by, The step of controlling a single-mode laser to generate continuous laser of a preset wavelength, and modulating input voltage of a first acousto-optic modulator according to a first preset voltage to convert the continuous laser of the preset wavelength into single-pulse laser comprises: controlling the single-mode laser to generate continuous 1550nm laser; controlling the first acousto-optic modulator to open and close the optical path of the continuous 1550nm laser according to the first preset voltage to generate the single-pulse laser.

4. The measurement control method of the optical fiber length according to claim 1, characterized by, The step of generating a pulse sequence through a fiber coupler with a preset ratio, and modulating input voltage of a second acousto-optic modulator according to a second preset voltage to adjust intensity of part of optical signals in the pulse sequence to a preset intensity comprises: converting the single pulse into the pulse sequence through the fiber coupler with the preset ratio; modulating input voltage of the second acousto-optic modulator according to the second preset voltage; adjusting a delay difference of two arbitrary wave generators to adjust intensity of part of optical pulses in the pulse sequence to the same level.

5. The measurement control method of the optical fiber length according to claim 4, characterized by, The step of adjusting a delay difference of two arbitrary wave generators to adjust intensity of part of optical pulses in the pulse sequence to the same level comprises: controlling input voltage of the corresponding acousto-optic modulator by respectively controlling signals and delay differences of the two arbitrary wave generators to adjust intensity of part of optical pulses in the pulse sequence to the same level.

6. The measurement control method of the optical fiber length according to claim 1, characterized by, The adjusted optical signal is converted into a corresponding electrical signal by the photodetector, and the electrical signal is pulse-positioned according to a pulse positioning rule to obtain a positioned pulse electrical signal, including: The adjusted optical signal is converted into a corresponding electrical signal by the photodetector; The pulse sequence in all electrical signals is segmented according to a preset time period to obtain a maximum value of each time period; The half-peak positions are searched on both sides of the maximum value in each time period, and a midpoint position is determined according to the two searched half-peak positions; The midpoint position is set as a positioning point of the corresponding pulse electrical signal.

7. The measurement control method of the optical fiber length according to claim 1, characterized by, The first time difference between the first pulse and the Nth pulse is calculated according to the positioning point of the pulse electrical signal, including: The optical path difference between the first pulse and the Nth pulse is calculated according to the optical path of the first pulse and the optical path of the Nth pulse; The first time difference between the first pulse and the Nth pulse is calculated according to the optical path difference and the positioning point of the corresponding pulse signal.

8. A terminal, characterized by comprising: It includes: A processor and a memory, the memory stores an optical fiber length measurement control program, and the optical fiber length measurement control program is used to implement the operations of the optical fiber length measurement control method in any one of claims 1-7 when executed by the processor.

9. A medium characterized by, The medium is a computer readable storage medium, and the storage medium stores an optical fiber length measurement control program, and the optical fiber length measurement control program is used to implement the operations of the optical fiber length measurement control method in any one of claims 1-7 when executed by the processor.

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