Optical fiber sensing method, controller, optical fiber sensing system, and vehicle

Abstract

An optical fiber sensing method, a controller, an optical fiber sensing system, and a vehicle. The optical fiber sensing system comprises a controller, a light-emitting unit, a measurement optical path, and a receiving module. The controller is communicatively connected to the light-emitting unit and the receiving module, and the light-emitting unit and the receiving module are connected by means of the measurement optical path. The method comprises: a controller controls a light-emitting unit to send an optical pulse sequence to a measurement optical path, the optical pulse sequence comprising a plurality of optical pulses, and a time interval between two adjacent optical pulses among the plurality of optical pulses being adjustable; and the controller obtains a measurement result on the basis of a measurement electrical signal fed back by a receiving module, the measurement electrical signal being obtained by the receiving module on the basis of the plurality of optical pulses of the optical pulse sequence received by the measurement optical path.

Description

Optical fiber sensing method, controller, optical fiber sensing system and vehicle

[0001] This application claims priority to Chinese Patent Application No. 202411097966.1, filed on August 9, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of vehicles, and in particular to an optical fiber sensing method, a corresponding controller, a corresponding optical fiber sensing system, and a corresponding vehicle. BACKGROUND

[0003] In order to meet the requirement of timely detecting thermal runaway events of the battery cell, there is a need for real-time monitoring of the temperature of the battery cell. SUMMARY

[0004] The present disclosure provides an optical fiber sensing method, a corresponding controller, an optical fiber sensing system, and a corresponding vehicle.

[0005] In one aspect, an optical fiber sensing method is provided, applied to an optical fiber sensing system, the optical fiber sensing system comprising a controller, a light emitting unit, a measurement light path, and a receiving module, the controller being in communication connection with the light emitting unit and the receiving module respectively, the light emitting unit and the receiving module being connected through the measurement light path, the method comprising: the controller controlling the light emitting unit to send a light pulse sequence to the measurement light path, the light pulse sequence comprising a plurality of light pulses, a time interval between adjacent two light pulses in the plurality of light pulses being adjustable; the controller obtaining a measurement result according to a measurement electrical signal fed back by the receiving module, the measurement electrical signal being obtained by the receiving module from a plurality of light pulses of the light pulse sequence received from the measurement light path.

[0006] In some embodiments, the influencing factor of the time interval between the adjacent two light pulses comprises at least one of a length of the measurement light path, a working mode of the vehicle, a time requirement, and a user requirement.

[0007] In some embodiments, the influencing factor of the time interval between the adjacent two light pulses comprises the length of the measurement light path, and the time interval between the adjacent two light pulses in the plurality of light pulses is positively correlated with the length of the measurement light path.

[0008] In some embodiments, the working mode of the vehicle comprises an energy saving mode and a high efficiency mode, the influencing factor of the time interval between the adjacent two light pulses comprises the working mode of the vehicle, and the time interval between the adjacent two light pulses in the energy saving mode is greater than that in the high efficiency mode.

[0009] In some embodiments, the time interval between the two adjacent optical pulses is negatively related to a time requirement.

[0010] In some embodiments, the plurality of optical pulses comprises a first optical pulse and a second optical pulse adjacent to each other, the time interval between the two adjacent optical pulses comprises a first time interval between a sending time of the first optical pulse and a sending time of the second optical pulse, and the first time interval is greater than or equal to a time length of the first optical pulse transmitted in the measurement optical path.

[0011] In some embodiments, the sequence of optical pulses comprises n optical pulse subsequences, each of the n optical pulse subsequences comprises a plurality of optical pulses, an i-th optical pulse subsequence in the n optical pulse subsequences comprises a third optical pulse and a fourth optical pulse adjacent to each other, and a time interval between the two adjacent optical pulses is a time interval between a sending time of the third optical pulse and a sending time of the fourth optical pulse, where n is a positive integer, i is a positive integer, and i≤n.

[0012] In some embodiments, the plurality of optical pulses in the i-th optical pulse subsequence in the n optical pulse subsequences are respectively configured to measure an (a+n+i)-th measurement point in the measurement optical path, where a is a natural number.

[0013] In some embodiments, the n optical pulse subsequences comprise an optical pulse subsequence P and an optical pulse subsequence Q, an optical pulse p in the optical pulse subsequence P and an optical pulse q in the optical pulse subsequence Q are two optical pulses closest in time between two optical pulse subsequences, a time interval between the sending time of the optical pulse p and the sending time of the optical pulse q is less than a time interval between sending times of any two optical pulses in the optical pulse subsequence P.

[0014] In some embodiments, the sequence of optical pulses is generated by the optical emitting unit according to an optical pulse sequence control signal sent by the controller.

[0015] In some embodiments, the optical pulse sequence control signal is generated by the controller according to a laser optical pulse parameter requirement.

[0016] In some embodiments, the measurement optical path comprises a reference optical path segment and a sensing optical path segment.

[0017] In some embodiments, the measurement electrical signal comprises optical intensity information of a plurality of measurement points in the measurement optical path, and the measurement result is obtained by the controller according to the optical intensity information of the plurality of measurement points.

[0018] In some embodiments, the receiving module comprises a field programmable gate array (FPGA) and an optoelectronic conversion unit, the optoelectronic conversion unit is configured to convert the received optical pulses into digital electrical signals, and the FPGA is configured to process the digital electrical signals to obtain the light intensity information of the plurality of measurement points.

[0019] In some embodiments, the optoelectronic conversion unit comprises a diode, an amplification circuit filter, and an analog-to-digital converter, the diode is configured to convert the received optical pulses into analog electrical signals, the amplification circuit filter is configured to amplify and attenuate the analog electrical signals, and the analog-to-digital converter is configured to convert the analog electrical signals into the digital electrical signals.

[0020] In some embodiments, the light intensity information of each measurement point in the plurality of measurement points is obtained based on the accumulation of the electrical signals corresponding to the plurality of optical pulses in the optical pulse sequence.

[0021] In some embodiments, the measurement result is calculated by the controller based on the light intensity information of the plurality of measurement points in the reference light path segment and the sensing light path segment in the measurement light path.

[0022] In some embodiments, the method further comprises: if the number of the light intensity information of the measurement points in the measurement electrical signal is less than the number of the measurement points in the measurement light path, the controller determines that there is a breakpoint in the measurement light path.

[0023] In some embodiments, the method further comprises: the controller determines the position of the breakpoint based on the number of the light intensity information of the measurement points in the measurement electrical signal and the length of the measurement light path.

[0024] In some embodiments, the controller is a central controller or a domain controller of a vehicle.

[0025] In another aspect, a controller is provided, comprising a processor and a memory connected to the processor, the memory storing a computer program, and the processor being configured to execute the computer program to implement the above-described optical fiber sensing method.

[0026] In yet another aspect, an optical fiber sensing system is provided, comprising the above-described controller, the optical fiber sensing system further comprising a laser emission unit, a measurement light path, and a receiving module, the controller being communicatively connected to the laser emission unit and the receiving module respectively, and the laser emission unit and the receiving module being connected through the measurement light path.

[0027] In yet another aspect, a vehicle is provided, comprising the above-described controller or the above-described optical fiber sensing system.

[0028] In the embodiments of the present disclosure, the controller controls the light emitting unit to send a light pulse sequence to the measurement light path, and then the controller obtains a measurement result according to a measurement electrical signal fed back by the receiving module, wherein the measurement electrical signal is obtained by the receiving module according to a plurality of light pulses in the light pulse sequence received from the measurement light path, and the time interval between adjacent two light pulses in the plurality of light pulses is adjustable. The time interval between adjacent light pulses can be adjusted, so as to change the light pulse emission frequency per unit time by adjusting the time interval between light pulses, so as to adapt to different measurement requirements and conditions. Then, based on the change of the light pulse emission frequency per unit time, the number of accumulations of the same measurement point is increased, the measurement accuracy and stability of the measurement result are improved, the sampling frequency requirement of the sampling device is reduced, and the vehicle scene is applicable. BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is a block diagram of an optical fiber sensing system according to some embodiments;

[0030] FIG. 2 is another schematic diagram of an optical fiber sensing system according to some embodiments;

[0031] FIG. 3 is a flowchart of an optical fiber sensing method according to some embodiments;

[0032] FIG. 4 is a schematic diagram of a differential pulsation method according to some embodiments;

[0033] FIG. 5 is a process diagram of optical fiber sensing according to some embodiments;

[0034] FIG. 6 is a flowchart of photoelectric signal conversion according to some embodiments;

[0035] FIG. 7 is a block diagram of a vehicle according to some embodiments;

[0036] FIG. 8 is another block diagram of a vehicle according to some embodiments. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present disclosure more obvious and easy to understand, the present disclosure will be further described in detail below with reference to the drawings and specific embodiments.

[0038] In related technologies of battery pack temperature detection, a thermistor is usually used as a sensitive element for temperature detection. However, the thermistor is a small-volume single-point sensor, and thus a single thermistor can only detect temperature values in a very small range. When the distance between the thermistor and the point to be detected is relatively large or the thermistor is not closely attached, the reading accuracy will be affected. In addition, the thermistor has a self-heating phenomenon. With the extension of use time, the heat generated by the thermistor will continuously accumulate, resulting in temperature drift that is difficult to eliminate, and thus it is difficult to ensure the reliability of the reading. Moreover, the single-point sensor of the thermistor cannot be used in a series form to achieve distributed monitoring of the battery pack. The wiring harness cost and heat dissipation risk caused by densely arranging the single-point sensors of the thermistor make the distributed monitoring scheme of the thermistor not feasible for vehicle use.

[0039] The test distance of a traditional optical fiber demodulator is usually long, up to several kilometers or several hundred kilometers. Due to the large amount of data to be calculated, the hardware board used inside is usually a relatively expensive model, and a forced cooling device such as a thermoelectric cooler (TEC) needs to be used to prevent the temperature on the chip of the hardware board from being too high and causing damage to the hardware. That is, the traditional optical fiber demodulator has high requirements for the software and hardware of signal acquisition and signal processing, and the cost of the traditional optical fiber sensing demodulator is high, which is not suitable for vehicle use.

[0040] The optical fiber sensor detection points are highly dense, that is, the optical fiber can be used as a sensor everywhere, for example, hundreds to thousands of detection points can be arranged in a 100-meter-long optical fiber, and only one optical fiber can complete the full-vehicle temperature detection requirement or the complex task of three-dimensional battery pack temperature detection. Second, the optical fiber sensor is a sensing unit, and does not need to arrange a large number of wiring harnesses, which can save the cost of wiring harnesses, meet the development trend of lightweight vehicles, and help to reduce the overall weight of the vehicle and improve the cruising range. In addition, the optical fiber sensor has the characteristics of high precision and short response time, and can quickly and real-timely respond to temperature changes. That is, the highly dense optical fiber sensor has the characteristics of high precision and short response time, can quickly and real-timely respond to temperature changes, and the optical fiber sensor does not need to arrange a large number of wiring harnesses.

[0041] To solve the above problems, some embodiments of the present disclosure propose a temperature measurement system using an optical fiber as a sensing element, that is, an optical fiber sensing system.

[0042] Referring to FIG. 1, a block diagram of an optical fiber sensing system according to some embodiments is shown. The optical fiber sensing system 110 can include a controller 1101, an optical emission unit 1102, a measurement light path 1103, and a receiving module 1104.

[0043] In the optical fiber sensing system 110, the controller 1101 can be communicatively connected with the light emitting unit 1102 and the receiving module 1104, and the light emitting unit 1102 and the receiving module 1104 can be connected through the measurement optical path 1103.

[0044] For example, the controller 1101 can mainly control the light emitting unit 1102 to send a light pulse sequence to the measurement optical path 1103. The light pulse sequence includes a plurality of light pulses configured to measure the signals at specific points in the measurement optical path. The time interval between two adjacent light pulses is determined according to the length of the measurement optical path to ensure that the time of light pulse transmission in the optical path is properly compensated. The light emitting unit 1102 is mainly responsible for generating light pulses, and the generated light pulses are sent in a sequence, and the generated light pulses can usually be a stable laser beam configured to excite an optical intensity analog signal in the measurement optical path. The measurement optical path 1103 is the path of the light pulse sequence transmission. The receiving module 1104 is mainly responsible for receiving the light pulse sequence returned from the measurement optical path 1103, and converting the received light pulses into electrical signals containing information of each measurement point in the measurement optical path 1103, for example, the optical intensity information of each measurement point, so that the controller 1101 can obtain measurement results according to the measurement electrical signals fed back by the receiving module 1104.

[0045] In some embodiments, as shown in FIG. 2, the controller 1101 can be a central controller 18 or a domain controller of the vehicle, so as to multiplex the central controller 18 or the domain controller of the vehicle as a digital electrical signal processing unit to issue a light pulse sequence control signal, thereby controlling the light emitting unit 1102 to send a light pulse sequence to the measurement optical path 1103, and also multiplexing the central controller 18 or the domain controller of the vehicle as a digital electrical signal processing unit to obtain measurement results according to the measurement electrical signals fed back by the receiving module 1104. In this way, the digital electrical signal processing process of the optical fiber modulator with high cost can be replaced, and the cost can be reduced.

[0046] The light emitting unit 1102 can include an electrical modulator 1 and a laser 2, and the electrical modulator 1 can be mainly configured to control the output of the laser 2 to adjust the emitted light pulse sequence. The laser 2 is configured to generate a light pulse sequence.

[0047] The measurement light path 1103 can include a reference light path segment and a sensing light path segment. The reference light path segment can refer to the light path segment of the reference optical fiber 19, and the sensing light path segment can refer to the light path segment of the sensing optical cable 20. The reference optical fiber is usually configured to provide a stable reference signal to help system calibration and eliminate the influence of environmental factors on the sensing signal, thereby improving the measurement accuracy and stability of the system. The sensing optical cable serves as the actual sensing element, and can have a plurality of sampling points, such as sampling point 1, sampling point 2, sampling point 3,..., sampling point n, etc., which can serve as a plurality of measurement points for recording light intensity information at specific positions.

[0048] The receiving module 1104 can include a wavelength division multiplexing unit, an optoelectronic conversion unit, and a field-programmable gate array (FPGA).

[0049] The wavelength division multiplexing unit can mainly separate the light intensity analog signals corresponding to the optical pulses in the optical pulse sequence generated by the optical transmitting unit 1102 from the signals returned by the measurement light path 1103.

[0050] In some embodiments, as shown in FIG. 2, the wavelength division multiplexing unit can include a coupler 3 and a wavelength division multiplexing filter. The coupler 3 can effectively couple the optical pulse sequence generated by the optical transmitting unit 1102 into the measurement light path 1103, for example, so that the optical pulse sequence generates backscattered light in the measurement light path 1103. The wavelength division multiplexing filter can be configured to process the backscattered light to obtain the light intensity analog signals.

[0051] In some embodiments, the wavelength division multiplexing filter can include different types of wavelength division multiplexing filters, such as a Stokes light wavelength division multiplexing filter 4 and an anti-Stokes light wavelength division multiplexing filter 5, so that at least two light intensity analog signals with different central wavelengths can be generated based on the different types of wavelength division multiplexing filters. The Stokes light wavelength division multiplexing filter 4 can be configured to separate or combine light intensity analog signals of different wavelengths. Stokes light generally refers to light with lower energy in Raman scattering. The anti-Stokes light wavelength division multiplexing filter 5 can be configured for wavelength division multiplexing, i.e., separating or combining light intensity analog signals of different wavelengths. Anti-Stokes light refers to light with higher energy in Raman scattering.

[0052] In some embodiments, the optoelectronic conversion unit can be mainly configured to convert the received optical pulses into electrical signals.

[0053] For example, the photoelectric conversion unit can include a diode, an amplifier filter, an analog-to-digital converter 15 (ADC). The diode can be configured to convert the received light pulse into an analog electrical signal, the amplifier filter can be mainly configured to amplify and attenuate the analog electrical signal, and the ADC is configured to convert the analog electrical signal into a digital electrical signal.

[0054] As shown in FIG. 2, the diode can include a photodiode 8, 9, which can convert the light intensity analog signal into an analog electrical signal to detect and receive the light intensity analog signal in the measurement light path 1103.

[0055] The amplifier filter can include a preamplifier 10, 11, a multi-stage main amplifier 12, 13, and an anti-aliasing filter 14. The preamplifier 10, 11 can be mainly configured to amplify the weak electrical signal output by the photodiode for subsequent processing. The multi-stage main amplifier 12, 13 can be mainly configured to further amplify the signal to improve the strength and quality of the signal. The anti-aliasing filter 14 can be mainly configured to filter out frequency components higher than half the sampling rate to prevent aliasing.

[0056] In some embodiments, the diode and the amplifier filter can be referred to as an analog signal processing unit.

[0057] In addition, the receiving module 1104 can also include a temperature compensation circuit 7, which can be configured to cool the vehicle-mounted optical fiber sensing system. For example, the temperature compensation circuit 7 can adopt a temperature compensation circuit suitable for a medium and short distance measurement system to replace an expensive TEC semiconductor active cooling device in medium and short distance transmission, so that the wavelength shift effect of the laser due to temperature change can be solved, thereby realizing high-precision temperature detection and ensuring the stability and accuracy of the system. In some embodiments, the problem that the optical fiber sensing system is not suitable for vehicle-mounted temperature environment can also be solved by using a vehicle-grade chip, and the present disclosure is not limited thereto.

[0058] In some embodiments, a field programmable gate array (FPGA) 17 can be configured to process the digital electrical signal output by the digital-to-analog converter.

[0059] In some embodiments, the ADC can employ a dual-channel high-speed digital-analog signal converter. For example, the ADC can be configured to convert the analog electrical signal into a digital electrical signal, so that subsequent data analysis and processing can be performed, such as signal demodulation, data analysis, etc., to extract the effective sensing information. The FPGA 17 can be mainly configured to implement a complex digital signal processing algorithm to process the digital electrical signal through the digital signal processing algorithm to obtain the measurement electrical signal. For example, the digital signal processing performed can be cumulative processing of the digital electrical signal, which is not limited by the present disclosure.

[0060] In some embodiments, the FPGA 17 can include a global clock 16, and the FPGA 17 can issue a global clock signal to the electrical modulator 1 of the optical emission unit, the analog signal processing unit and the analog-digital signal converter described above, so as to determine the time information of the optical pulse when passing through a specific position based on the global clock signal.

[0061] In some embodiments, the FPGA 17 can further include a temperature calibration sensor 6, which can be configured to provide a temperature reference value, so that the FPGA 17 can help calibrate and compensate the influence of temperature change on the sensing system through the temperature reference value provided by the temperature calibration sensor 6 during processing of the digital electrical signal.

[0062] In actual application, as shown in FIG. 2, taking the controller 1101 as an example of the central controller 18 of the vehicle, the central controller 18 of the vehicle can be in communication connection with the electrical modulator 1 in the optical emission unit 1102 and the field programmable gate array 17 in the receiving module 1104, and the laser 2 in the optical emission unit 1102 and the coupler 3 of the wavelength division multiplexing unit in the receiving module 1104 can be connected through a measurement optical path, such as a reference optical fiber 19 and a sensing optical cable 20 containing multiple sampling points.

[0063] For example, the optical pulse sequence sent by the laser 2 can generate backscattering light on the measurement optical path through the coupler, and the backscattering light can pass through different types of wavelength division multiplexing filters to obtain at least two light intensity analog signals with different center wavelengths. The at least two light intensity analog signals with different center wavelengths can be converted into electrical signals based on a photodiode, a preamplifier, a multi-stage main amplifier, an anti-aliasing filter and a dual-channel high-speed digital-analog signal converter, respectively. The FPGA 17 can process the electrical signals to obtain the measurement electrical signal in combination with the temperature reference value provided by the temperature calibration sensor 6, and then the measurement electrical signal can be fed back to the controller, so that the controller can perform temperature solving processing based on the light intensity information of the multiple measurement points contained in the measurement electrical signal to obtain the measurement result. The measurement result can be output through a network port, which is not limited by the present disclosure.

[0064] The temperature compensation circuit 7 can compensate the influence of temperature change on the performance of the photodiode during the processing of the photodiode. Throughout the process, the global clock signal sent by the FPGA 17 to the electric modulator 1, the photodiode, and the dual-channel high-speed digital-to-analog signal converter can be controlled by the global clock 16 for clock synchronization.

[0065] The above optical fiber sensing system has the characteristics of medium and short distance transmission, high spatial resolution, and high signal signal-to-noise ratio, and is suitable for application in a vehicle-mounted scene.

[0066] Referring to FIG. 3, a flowchart of an optical fiber sensing method according to some embodiments is shown, which is applied to the optical fiber sensing system shown in FIGS. 1 and 2. For example, the method can include the following steps S301-S302.

[0067] Step S301: The controller controls the light emitting unit to send a light pulse sequence to the measurement light path, the light pulse sequence including a plurality of light pulses, and the time interval between adjacent two light pulses in the light pulse sequence being adjustable.

[0068] S302: The controller obtains a measurement result according to the measurement electrical signal fed back by the receiving module.

[0069] In this way, the time interval between adjacent two light pulses in the plurality of light pulses of the light pulse sequence is adjustable, so that the pulse time slot can be adjusted according to actual needs. In this way, the light pulse emission frequency per unit time can be changed, more light pulses can be emitted per unit time, and thus the accuracy can be improved without increasing the cost, the requirement for the analog-to-digital converter is reduced, and thus the system cost is reduced.

[0070] In some embodiments of the present disclosure, the digital electrical signal processing process of the traditional optical fiber demodulator can be realized by multiplexing the central controller or the domain controller of the vehicle as the digital electrical signal processing unit, and the demodulation cost of the optical fiber sensing system is reduced.

[0071] The controller can be a central controller or a domain controller of the vehicle.

[0072] The controller is responsible for controlling the light emitting unit to send a light pulse sequence to the measurement circuit, the light pulse sequence including a plurality of light pulses, and the time interval between adjacent two light pulses in the plurality of light pulses being adjustable to ensure that the time of the light pulse transmission in the light path is correctly compensated.

[0073] In some embodiments, the influencing factors of the time interval between adjacent two light pulses can include at least one of the length of the measurement light path, the working mode of the vehicle, the time requirement, and the user requirement.

[0074] For example, the time interval between two adjacent light pulses is positively correlated with the length of the measurement optical path, that is, the longer the measurement optical path, the longer the time interval between the light pulses.

[0075] The working mode of the vehicle also affects the time interval between the light pulses, that is, the time interval between two adjacent light pulses is positively correlated with the working mode of the vehicle, and the working mode of the vehicle includes an energy-saving mode and a high-efficiency mode. Generally, in the energy-saving mode, the system reduces the transmission frequency of the light pulses to save energy, and the time interval between two adjacent light pulses in the energy-saving mode is greater than that in the high-efficiency mode.

[0076] The time interval between two adjacent light pulses is negatively correlated with the time requirement, that is, the higher the time requirement, the shorter the time interval between the light pulses.

[0077] The user requirement can be embodied as the following laser light pulse parameter requirement, which is not described herein.

[0078] In actual application, the light pulse sequence is mainly generated by the light emitting unit according to the light pulse sequence control signal sent by the controller.

[0079] The light pulse sequence control signal is a signal for carrying information by changing the characteristics of the light pulse, and in the optical fiber sensing system, the light pulse sequence control signal can be sent by the controller, and the light pulse sequence control signal is configured to control and modulate the output of the light pulse.

[0080] In some embodiments, the light pulse sequence control signal is mainly generated by the controller according to the laser light pulse parameter requirement.

[0081] For example, the controller can generate a light pulse sequence control signal according to the laser light pulse parameter requirement by responding to the laser light pulse parameter requirement, and send the generated light pulse sequence control signal to the electro-modulator in the light emitting unit, so that the electro-modulator controls the laser in the light emitting unit to generate a light pulse sequence according to the light pulse sequence control signal.

[0082] The laser light pulse parameter requirement can be configured to indicate a parameter of a corresponding setting, which can affect the modulation of the light pulse sequence. The set parameter can include at least one of a spatial resolution requirement, a signal-to-noise ratio (SNR) requirement, and a light pulse sequence division requirement. The spatial resolution requirement refers to the minimum distance unit that the system can distinguish. In order to improve the spatial resolution, it is usually necessary to reduce the light pulse width, and shorter light pulse width means more accurate time measurement, thereby improving the distance resolution. The signal-to-noise ratio requirement refers to the ratio of signal strength to background noise strength, and in order to improve the signal-to-noise ratio, it can be necessary to increase the energy of the laser light pulse or adjust the light pulse width to ensure that the received signal is strong enough to be effectively identified from the noise. The light pulse sequence division requirement refers to the requirement setting of the transmission order and time interval of the light pulse, and the time interval can refer to the time interval between the transmission time of adjacent two light pulses in the plurality of light pulses, that is, the light pulse sequence division requirement affects the transmission time of the light pulse.

[0083] In some embodiments, the plurality of light pulses includes adjacent first and second light pulses, and when a time interval between the adjacent two light pulses is a first time interval between a transmission time of the first light pulse and a transmission time of the second light pulse, the first time interval is greater than or equal to a time length of the first light pulse in the measurement optical path.

[0084] The time length of the first light pulse in the measurement optical path, for example, can refer to the time experienced by the first light pulse from transmission to reception, which depends on the length of the optical path. The length of the measurement optical path determines the time required for the light pulse to transmit in the optical path. In order to ensure that the light pulse can be correctly received and processed when passing through the measurement optical path, when designing the light pulse sequence, it is necessary to ensure that the second light pulse adjacent to the first light pulse will not arrive before the first light pulse is completely transmitted, that is, the first time interval is greater than or equal to the time length of the first light pulse in the measurement optical path, so as to avoid interference or incorrect measurement results.

[0085] In some embodiments, the light pulse sequence includes n light pulse subsequences, each light pulse subsequence includes a plurality of light pulses, and a light pulse subsequence i in the n light pulse subsequences includes adjacent third and fourth light pulses, a time interval between the adjacent two light pulses is a time interval between a transmission time of the third light pulse and a transmission time of the fourth light pulse, and the aforementioned time interval is greater than or equal to a time length of the third light pulse in the measurement optical path. Wherein, n is a positive integer, i is a positive integer, and i≤n.

[0086] In order to achieve more precise control and higher measurement accuracy, the light pulse sequence can be divided into multiple subsequences, and each light pulse subsequence is controlled to accurately control the transmission time of each light pulse and the time interval between adjacent two light pulses, so as to assign a specific light pulse to each measurement point and achieve multi-point multi-dimensional measurement. In order to ensure that the light pulse can be correctly received and processed when passing through the measurement light path, when designing the light pulse sequence, it is necessary to ensure that the fourth light pulse adjacent to the third light pulse will not arrive before the third light pulse is completely transmitted, that is, the time interval between the transmission time of the third light pulse and the transmission time of the fourth light pulse is greater than or equal to the length of time that the third light pulse is transmitted in the measurement light path, so as to avoid interference or incorrect measurement results.

[0087] In some embodiments, the multiple light pulses in the light pulse subsequence i in the n light pulse subsequences included in the measurement light path are respectively configured to measure the an+i th measurement point in the measurement light path, where a is a natural number.

[0088] For example, the multiple light pulses in the light pulse subsequence i in the n light pulse subsequences included in the measurement light path can be configured to measure the an+i th measurement point in the measurement light path. a is a natural number, which can represent the position of the measurement point corresponding to each light pulse subsequence. In optical measurement, the natural number a can be used to represent the position of the measurement point corresponding to each light pulse subsequence. By using a, it can be ensured that the measurement points are numbered in a certain order, so as to realize ordered measurement. It can be understood that the measurement points measured by different light pulse subsequences are different, so that the strategy of measuring the measurement points in the measurement light path can be completed by the n light pulse subsequences together.

[0089] In order to improve the sampling accuracy of the analog-to-digital converter (ADC), a high sampling frequency and a sampling bit depth that meets the requirements are selected, for example, a sampling frequency of 500MS and a sampling bit depth of 14bits are commonly selected in the industry. Such high-speed sampling chips are expensive, which significantly increases the production cost of the entire system.

[0090] In some embodiments of the present disclosure, by measuring different measurement points through multiple light pulse subsequences, the sampling frequency can be reduced, so as to reduce the sampling frequency requirement of the ADC of the system, thereby reducing the system cost.

[0091] As shown in FIG. 4, for example, if the measurement light path includes 6 measurement points, if only a single light pulse sequence is included, as shown in FIG. 4(I), the single light pulse sequence needs to complete the measurement of the 6 measurement points.

[0092] For example, if the light pulse sequence includes two light pulse subsequences, one light pulse subsequence measures one half of the measurement points, and the other light pulse subsequence measures the other half of the measurement points. If one light pulse sequence measures all of the measurement points, the ADC needs to sample at a frequency of b, then the light pulse sequence includes two light pulse subsequences, one light pulse subsequence measures one half of the measurement points, and the other light pulse subsequence measures the other half of the measurement points, the sampling frequency can be reduced to b / 2.

[0093] As shown in FIG. 4(II), one light pulse subsequence can be configured to measure ① ③ ⑤, and the other light pulse subsequence can be configured to measure ② ④ ⑥. In combination of the two light pulse subsequences, all of the measurement points can be acquired.

[0094] In some embodiments, the frequency range of the light pulse sequence is 20000 Hz-200000 Hz, meaning that the number of light pulses transmitted per second by the light pulse sequence ranges between 20000 and 200000. The higher the frequency, the more the number of light pulses transmitted per second, and the lower the frequency, the less the number of light pulses transmitted per second.

[0095] In some embodiments, the cumulative duration of the light pulses in the light pulse sequence that measure the same measurement point ranges from 0.2 seconds to 1 second, meaning that the total duration of the light pulses that measure a particular point can range from 0.2 seconds to 1 second.

[0096] The longer the cumulative duration, the more the number of light pulses used for measurement, which can provide more accurate measurement results, but at the same time, increases the response time of the system. Therefore, in order to balance the measurement accuracy and the response time, in some embodiments of the present disclosure, the cumulative duration ranges from 0.2 seconds to 1 second. In some embodiments, the cumulative duration ranges from 0.4 seconds to 0.6 seconds. For example, the cumulative duration can be 0.4 seconds, 0.45 seconds, 0.5 seconds, 0.55 seconds, or 0.6 seconds.

[0097] In actual applications, each light pulse in each light pulse subsequence in the light pulse sequence can generate backscattering on the measurement light path. The measurement light path is the path of the light pulse sequence transmission, and the measurement light path includes a reference light path segment and a sensing light path segment. The reference light path segment can refer to the light path segment of the reference optical fiber, and the sensing light path segment can refer to the light path segment of the sensing optical cable, which can have a plurality of sampling points, and the plurality of sampling points can be used as a plurality of measurement points to record the light intensity information of a specific position.

[0098] Each light pulse can generate backscattered light at each measurement point on the reference optical fiber and the sensing optical cable. If the emission time of the light pulse is t1 and the time when the backscattered light returns to the receiving plane of the photodiode is t2, after determining the propagation speed of the light pulse in the optical fiber, the position where the scattered light is generated on the measurement light path can be determined using the following formula (1), and the light intensity information at a specific position can be recorded. For example, formula (1) can be as follows:

[0099] where c is the speed of light in a vacuum, n' is the refractive index of the sensing optical fiber, and the ratio of the two is the speed of the light pulse propagating in the optical fiber. In some embodiments of the present disclosure, the speed of the light pulse propagating in the optical fiber is about 2x10 8 m / s.

[0100] For example, after the light pulse enters the two sensing optical fibers as incident light into the reference optical fiber and the sensing optical cable, backscattered Raman scattering can occur at the sensing optical fiber to generate backscattered light.

[0101] In some embodiments, the n light pulse subsequences include a light pulse subsequence P and a light pulse subsequence Q, assuming that the light pulse p in the light pulse subsequence P and the light pulse q in the light pulse subsequence Q are the two light pulses closest in time between the two light pulse subsequences, then the time interval between the emission time of the light pulse p and the emission time of the light pulse q is less than the time interval between the emission times of any two light pulses in the light pulse subsequence P.

[0102] In some embodiments, the difference between the time interval between the emission time of the light pulse p and the emission time of the light pulse q and the time interval between the emission times of any two light pulses in the light pulse subsequence P is greater than or equal to Δt. Δt satisfies:

[0103] where c is the speed of light in a vacuum, n' is the refractive index of the sensing optical fiber, and Δx is the distance between adjacent two measurement points.

[0104] In order to transmit the light intensity information of the multiple measurement points obtained by the multiple light pulses based on the light pulse sequence to the controller for processing, the receiving module can return a measurement electrical signal to the controller, which can be obtained by the receiving module from the multiple light pulses of the light pulse sequence received from the measurement light path. The measurement electrical signal can include the light intensity information of the multiple measurement points in the measurement light path.

[0105] In actual application, the receiving module is responsible for receiving the light pulse sequence returned from the measurement light path, and the receiving module converts the received light pulse into an electrical signal.

[0106] The backscattered light generated by the light pulse in the measurement optical path can be generated at various measurement points on the reference optical fiber and the sensing optical cable, for example. For example, after the light pulse enters the sensing optical fiber as incident light, the light pulse generates backscattering at various points in the reference optical fiber and the sensing optical cable in turn via the coupler in the wavelength division multiplexing unit, so that the light pulse can act on two different optical fiber paths simultaneously or separately, thereby generating backscattered light, such as Rayleigh scattering, Raman scattering, Brillouin scattering, etc., on the two different paths.

[0107] For example, the backscattered light generated by the light pulse on the two different paths can be manifested as first backscattered light generated on the reference optical fiber and second backscattered light generated at various measurement points on the sensing optical cable. The first backscattered light generated in the reference optical fiber can provide a stable reference signal, and the second backscattered light generated at various measurement points on the sensing optical cable can contain information of the actual monitoring object, so that separation of reference measurement and sensing measurement can be achieved based on the backscattered light generated on different optical fiber paths.

[0108] The wavelength division multiplexing filter in the wavelength division multiplexing unit can process the backscattered light to obtain an optical intensity analog signal. The use of the wavelength division multiplexing filter enables selective transmission or reflection of light of a specific wavelength. For the light emitting unit, the wavelength division multiplexing filter can combine optical intensity analog signals of multiple different wavelengths and transmit them through the same optical fiber, thereby improving the transmission capacity and efficiency of the optical fiber. For the wavelength division multiplexing unit, the wavelength division multiplexing filter can separate the mixed optical intensity analog signals of different wavelengths, so that signals of each wavelength can be received and processed separately.

[0109] For example, the wavelength division multiplexing filter can include different types of wavelength division multiplexing filters, such as a wavelength division multiplexing filter for Stokes light and a wavelength division multiplexing filter for anti-Stokes light, so that at least two optical intensity analog signals with different central wavelengths can be generated based on the different types of wavelength division multiplexing filters.

[0110] For example, the light pulse undergoes elastic collision and inelastic collision with the molecules in the optical fiber, causing the light pulse to generate backscattering during propagation. Part of the scattered light is frequency-shifted. Based on the Raman scattering effect, the photons interact with the thermal vibration process of the optical fiber molecules, forming two kinds of scattered light that are centrally symmetric with respect to the frequency of the incident light. Among the two kinds of scattered light, the scattered light with a frequency lower than that of the incident light is called Stokes light, and the scattered light with a frequency higher than that of the incident light is called anti-Stokes light.

[0111] Suppose the light emitting unit is modulated by the light pulse sequence of the controller, generates and sends infrared light with a specific pulse width, frequency and intensity, for example, with a center wavelength of 1550 nm, the infrared light can return to the coupler in the opposite direction in the sensing optical fiber, and the infrared light is divided into two different optical fiber paths, i.e. the first backscattered light and the second backscattered light, then for each backscattered light, two different center wavelength light intensity analog signals can be obtained via two wave division multiplexing filters in front and behind. The center wavelength of one of the two wave division multiplexing filters should be the corresponding wavelength of the higher frequency anti-Stokes light, for example, 1650 nm, and the center wavelength of the other filter should be the corresponding wavelength of the lower frequency Stokes light, for example, 1450 nm.

[0112] In practical applications, photoelectric signal conversion can be completed by the photoelectric conversion unit, and the received light pulse can be converted into a digital electrical signal, so that the subsequent digital electrical signal can be processed to extract effective sensing information.

[0113] In some embodiments, the photoelectric conversion unit can include a diode, an amplifier circuit filter. The diode can be configured to convert the received light pulse into an analog electrical signal, and the amplifier circuit filter can be mainly configured to amplify and attenuate the analog electrical signal, and the analog-to-digital converter can be configured to convert the analog electrical signal into a digital electrical signal.

[0114] The diode can be a photodiode, and the amplifier circuit filter can include a preamplifier, a multi-stage main amplifier, and an anti-aliasing filter. The preamplifier 10 can be mainly configured to amplify the weak electrical signal output by the photodiode for subsequent processing. The multi-stage main amplifier can be mainly configured to further amplify the signal to improve the strength and quality of the signal. The anti-aliasing filter can be mainly configured to filter out frequency components higher than half the sampling rate to prevent aliasing and thus filter out high-frequency signals before converting to a digital electrical signal.

[0115] For the process of converting the electrical signal into a digital electrical signal, an analog-to-digital converter can be used, which can use but is not limited to a dual-channel high-speed digital-to-analog signal converter.

[0116] In practical applications, the process of optical fiber sensing can be as shown in FIG. 5. First, the sensor is powered on, i.e. the on-board low-voltage battery supplies power to the sensor. After the sensor is powered on, the field programmable gate array sends a global clock signal to the electric modulator, the photoelectric conversion unit and the analog-to-digital converter. For example, the field programmable gate array can use its internal clock as a reference to realize the distribution of the global clock signal, so as to unify the clock of the aforementioned components in the system and make them run at the same clock frequency. This is conducive to accurately measuring the return time of the optical intensity analog signal, determining the exact time of light return, and determining the position of light based on the time of light return, thereby ensuring the accuracy of the calculated position of the optical intensity analog signal. Then, the controller sends a light pulse sequence modulation signal, and the laser generates a light pulse sequence based on the electric modulator control. The light pulse can generate backscattered light at the reference optical fiber and the sensing optical cable in turn. Then, at least two optical intensity analog signals with different center wavelengths are obtained through the wavelength division multiplexing filter, and the optical intensity analog signal can be converted into an electrical signal through the photoelectric conversion unit.

[0117] For the complete process of signal conversion, as shown in FIG. 6, first, the optical intensity analog signal can be converted into an analog electrical signal through the photodiode in step S601. Then, the analog electrical signal can be amplified through the preamplifier and the multi-stage amplifier in step S602. In step S603, the high-frequency signal in the analog electrical signal is attenuated through the anti-aliasing filter. Then, the analog electrical signal can be converted into a digital electrical signal through the ADC in step S604.

[0118] For example, the first backscattered light of the reference optical fiber can generate a group of optical intensity analog signals after being processed by the two wavelength division multiplexing filters respectively, and the second backscattered light of the sensing optical cable can generate another group of optical intensity analog signals after being processed by the two wavelength division multiplexing filters respectively. Each group of optical intensity analog signals can be processed through the above-mentioned signal conversion process.

[0119] First, for each group of light intensity analog signals, it is assumed that there are two light intensity analog signals with different center wavelengths generated by Stokes optical filter and anti-Stokes optical filter in a group of light intensity analog signals, and each group of light intensity analog signals can be received by two photodiodes. After completing photoelectric conversion, the two photodiodes can respectively transmit the converted micro analog electrical signals to an operational amplifier circuit, which can be multi-stage amplification such as preamplifier, main amplifier, etc. In order to prevent aliasing when sampling the next stage analog signal, an anti-aliasing filter with low-pass effect can also be used to remove signals exceeding the upper limit of the dual-channel high-speed digital-to-analog signal converter to obtain electrical signals, so that the dual-channel high-speed digital-to-analog signal converter can subsequently convert the analog electrical signals into digital electrical signals to obtain each group of digital electrical signals for each group of light intensity analog signals.

[0120] It should be noted that the photodiode as a device for realizing photoelectric conversion has basic requirements for the optical detector, which can be high photoelectric conversion efficiency, low additional noise and fast response. In some embodiments, a PIN photodiode or avalanche photodiode with a working frequency of 100 MHz or more can be selected. In addition, the preamplifier should have low noise characteristics. In some embodiments, the preamplifier gain can be 10,000 times, and the single-stage main amplifier gain can be 10 times. The present disclosure does not limit this.

[0121] After converting the measurement electrical signal into a digital electrical signal via the dual-channel high-speed digital-to-analog signal converter, data analysis and processing can be performed at this time, such as signal demodulation, data analysis, etc., to extract effective sensing information. For example, after processing and analysis, accurate information about each point in the measurement optical path, such as distance, position, etc., can be obtained, and then accurate measurement of each point in the measurement optical path can be realized by accurately controlling the sending time and interval of the optical pulse and processing and analyzing the received optical pulse.

[0122] In an embodiment of the present disclosure, the digital electrical signal can be processed by the FPGA to obtain a measurement electrical signal containing light intensity information of a plurality of measurement points. For example, the light intensity information of each measurement point is obtained based on the accumulation of electrical signals corresponding to a plurality of optical pulses of the optical pulse sequence, for example, by accumulating the digital electrical signals corresponding to a plurality of optical pulses based on the FPGA.

[0123] The sensing optical cable has a plurality of measurement points (or sampling points), and the target digital electrical signal of the sensing optical cable can include a digital electrical signal accumulated by each measurement point based on the number of accumulations. The target digital electrical signal of the reference optical fiber can include a digital electrical signal accumulated by the reference optical fiber based on the number of accumulations.

[0124] As shown in step S508, the data can be accumulated by the field programmable gate array, which can be expressed as that the field programmable gate array receives the digital electrical signals obtained by the ADC sampling. At this time, in order to improve the signal-to-noise ratio, the preset number threshold times of fast and dense repeated collection can be performed on each single measurement point, and the equal weight accumulation can be performed. In addition, in order to obtain the reference measurement, the preset number threshold times of accumulation can also be performed on the digital electrical signals of the reference optical fiber.

[0125] For a certain group of digital electrical signals, when the digital electrical signals are converted, the converted digital electrical signals can be accumulated respectively, and the number of accumulations can be recorded. When the number of accumulations reaches the preset number threshold, the measurement electrical signals containing the optical intensity information of the plurality of measurement points in the group can be obtained.

[0126] In some embodiments, as shown in step S509, it can be judged whether the number of accumulations reaches the preset number threshold. If the number of accumulations does not reach the preset number threshold, the steps of the light emitting unit sending the light pulse, the light pulse generating backscattering in the reference optical path segment and the sensing optical path segment in turn through the coupler, the backscattering light obtaining two beams of optical intensity analog signals with different central wavelengths through the wavelength division multiplexing filter, the optical intensity analog signals being processed to obtain electrical signals through the photoelectric conversion unit, the electrical signals being processed to obtain digital electrical signals through the analog-digital signal converter, and the field programmable gate array accumulating the digital electrical signals can be continuously performed until the number of accumulations reaches the preset number threshold.

[0127] In actual application, for each group of digital electrical signals, the digital electrical signals converted from each beam of optical intensity analog signals can be subjected to separate equal weight accumulation operations. For example, for the first group of digital electrical signals of the reference optical fiber, assuming that it contains the digital electrical signals converted from the optical intensity analog signals based on the 1650 nm wavelength and the digital electrical signals converted from the optical intensity analog signals based on the 1450 nm wavelength, when accumulating, taking the digital electrical signals converted from the optical intensity analog signals based on the 1650 nm wavelength as an example, a plurality of digital electrical signals converted from the optical intensity analog signals based on the 1650 nm wavelength generated by the incident laser light pulses emitted according to the preset light pulse frequency in a single period can be accumulated. When accumulating the digital electrical signals of each measurement point on the sensing optical cable, the digital electrical signals converted from each beam of optical intensity analog signals need to be subjected to separate equal weight accumulation operations on the basis of the equal weight accumulation operations performed on the measurement points separately.

[0128] For example, assuming that the preset number threshold is p, when p times of fast and dense repeated collection are performed on each single measurement point, assuming that the signal amplitude obtained by each collection is Si and the noise amplitude is Ni, after accumulation, the signal-to-noise ratio can be represented by the following formula (3):

[0129] In this way, the signal-to-noise ratio can be expanded times, and further introduces a time-domain adjustable laser pulse time-sharing sampling method. By improving the time slot utilization rate of the optical pulse, the signal acquisition hardware requirement is reduced under the premise of ensuring good signal-to-noise ratio, so that the system cost is significantly optimized. In some embodiments, the number of accumulations can be 10000 to 60000, and the present disclosure is not limited thereto.

[0130] In an embodiment of the present disclosure, after the field programmable gate array (FPGA) obtains the measurement electrical signal, i.e., the number of accumulations reaches the preset number threshold, the measurement electrical signal can be fed back to the controller, so that the controller can obtain the measurement result according to the light intensity information of the multiple measurement points. For example, the measurement result is calculated by the controller according to the light intensity information of the multiple measurement points of the reference light path segment and the sensing light path segment in the measurement light path.

[0131] In an embodiment of the present disclosure, the single measurement point has a corresponding optical pulse sequence, and the single optical pulse sequence is configured to record the light intensity information generated by the optical pulse modulated by the optical pulse sequence modulation signal at the corresponding measurement point in the current period. At this time, the integrity of data transmission and reception can be ensured based on the count of the optical pulse sequence in the current period.

[0132] For example, the transmitted optical pulse sequence can be counted by the field programmable gate array (FPGA), and at this time, the controller can traverse each optical pulse sequence according to the count information of the transmitted optical pulse sequence, so that the light intensity information of each measurement point is obtained when the number of traversed optical pulse sequences is the same as the count information of the transmitted optical pulse sequence, to ensure complete data traversal.

[0133] That is, after the number of accumulations reaches the preset number threshold, S510 can be performed to traverse all optical pulse sequences in a single period. In one case, when the number of traversed optical pulse sequences is the same as the count information of the transmitted optical pulse sequence, i.e., all optical pulse sequences in a single period are completely traversed, S511 can be performed. The controller can perform digital filtering processing such as wavelet transform, and perform temperature drift calibration and temperature value calculation operations to obtain the measurement result. The measurement result can refer to the temperature value of the corresponding measurement point, and the calculated temperature data can be transmitted to the outside through the signal output interface.

[0134] In another case, if the number of traversed optical pulse sequences is different from the count information of the transmitted optical pulse sequences, i.e., in the case that the controller does not traverse all the optical pulse sequences in the current period, S512 can be executed to switch the optical pulse sequence by the controller, for example, by delaying or advancing the sending time of the next sequence optical pulse, so that the detection point positioning based on the principle of Optical Time Domain Reflectometer (OTDR) moves. In the OTDR system, the position of the measurement point can be changed by adjusting the sending time of the next optical pulse sequence. If the sending time is delayed, the next optical pulse can enter the optical fiber at a later time point, so that the detection point moves in a farther direction along the optical fiber. Conversely, if the sending time is advanced, the next optical pulse will enter the optical fiber at an earlier time point, so that the detection point moves in a closer direction, so that the controller traverses the switched optical pulse sequence.

[0135] It should be noted that the ratio of the backscattered light intensity to the incident light intensity of the OTDR optical fiber system based on Raman scattering is much smaller than that of Rayleigh scattering and Brillouin scattering, which makes the effective signal submerged in a complex noise environment when the signal-to-noise ratio is too low, resulting in abnormal demodulation. When the accumulation time is certain, the total sampling number of a single point in a reading period is multiplied with the increase of the optical pulse emission frequency, which further improves the signal-to-noise ratio. Considering that the introduction of the differential optical pulse method prolongs the accumulation time of a single measurement point group, which doubles the reading period, if the accumulation time is too long, the temperature of the sampling point may have changed significantly, which makes the temperature measurement value less real-time and deviates from the true value. In the actual measurement scene, it is not advisable to simply prolong the accumulation time to improve the signal-to-noise ratio. The optical fiber sensing scheme provided by some embodiments of the present disclosure is more suitable when the optical pulse emission frequency is 82000 Hz and the accumulation time is 0.4-0.6 seconds, and the present disclosure is not limited thereto.

[0136] In the case that the controller has completely traversed all the optical pulse sequences in the period, the controller can process the optical intensity information of the plurality of measurement points to obtain the measurement result.

[0137] Under the condition of spontaneous Raman scattering, the Stokes light intensity is independent of temperature, while the intensity of anti-Stokes light changes with temperature. The relationship between the ratio of the intensity of anti-Stokes light to the intensity of Stokes light and temperature can be expressed by formula (4):

[0138] where I AS is the anti-Stokes light intensity value, I Sdenoted as Stokes light intensity, α as a temperature-dependent coefficient, h as Planck's constant, c as the speed of light in vacuum, Δν as the Raman frequency shift, k as the Boltzmann constant, and T as the temperature to be measured at Kelvin.

[0139] From the above formula (4), the temperature at the point to be measured can be calculated based on the following formula (5):

[0140] Where T is the measured temperature value at Kelvin; I AS I represents the anti-Stokes light intensity value. S I is the Stokes light intensity value. AS / I S This represents the relationship between the intensity ratio of anti-Stokes light to Stokes light and temperature; α is the temperature-dependent coefficient; h is Planck's constant; c is the speed of light in vacuum; Δν is the Raman frequency shift; and k is Boltzmann's constant.

[0141] In some embodiments of this disclosure, digital filtering processes such as wavelet transform are performed on the controller to calibrate the sensor to a reference, and temperature drift calibration and temperature value calculation are performed.

[0142] Temperature drift refers to the measurement error in a fiber optic sensing system caused by temperature changes. To eliminate or reduce this error, temperature drift calibration can be performed. The controller can monitor the ambient temperature using a built-in temperature sensor or an external temperature measuring device and adjust the sensing data according to a pre-set calibration algorithm. For example, this can be achieved by using the ambient temperature calibrated by a digital temperature calibration sensor and a reference fiber optic cable as the reference temperature. It should be noted that the reference fiber optic cable and the digital temperature calibration sensor are calibrated identically.

[0143] In some embodiments, temperature calculation can be performed by comparing the intensity ratio of Stokes light and anti-Stokes light to determine the temperature characteristics of the corresponding measurement point. For example, assuming a reference fiber is used to collect the reference temperature value T0, that is, the selected digital temperature calibration sensor and the reference fiber reference temperature are T0, the temperature calculation formula for any measurement point can be derived from formula (5) to obtain formula (6), for example, formula (6) is shown below:

[0144] Where T can refer to the temperature value at a certain measurement point; Δν can refer to the frequency shift of the center wavelength; I AS (T) can refer to the anti-Stokes light intensity value at the corresponding measurement point at temperature T, I S (T) can refer to the Stokes light intensity value at temperature T at the corresponding measurement point, I AS (T0) can refer to the anti-Stokes light intensity value of the reference fiber at temperature T0, IS (T0) can refer to the stokes light intensity value of the reference optical fiber at the T0 temperature; h can refer to the Planck constant, k can refer to the Boltzmann constant, and both are similar to the accuracy coefficient, which are fixed values.

[0145] In actual application, after the temperature value of any measurement point is calculated, the corresponding temperature signal can be output through the network port to monitor the battery temperature in real time, and the vehicle-mounted optical fiber sensing can be realized.

[0146] In some embodiments of the present disclosure, the temperature calculation can be performed on the basis of the fast and dense repeated collection of the preset number threshold of each single measurement point, and the time-domain adjustable laser pulse time-sharing sampling method is introduced. In this way, by improving the time slot utilization rate of the optical pulse, the signal acquisition hardware demand is reduced under the premise of ensuring good signal-to-noise ratio, so that the system cost is significantly optimized.

[0147] In some embodiments of the present disclosure, the controller can further perform S513 to determine whether there is a breakpoint in at least one of the reference optical fiber or the sensing optical cable.

[0148] In some embodiments, the breakpoint determination can be obtained by comparing the actual total number of measurement points and the standard number of measurement points. For example, the controller can traverse the optical pulse sequence to obtain the number of light intensity information of the measurement points in the measurement electrical signal. If the number of light intensity information of the measurement points in the measurement electrical signal meets the number of measurement points in the measurement light path, it indicates that there is no breakpoint, and S514 can be performed to output the temperature signal through the network port. If the number of light intensity information of the measurement points in the measurement electrical signal is less than the number of measurement points in the measurement light path, the controller determines that there is a breakpoint in the measurement light path, and S515 can be performed to output the temperature signal through the network port, and the position of the breakpoint can be calculated and reported.

[0149] Suppose the number of light intensity information of the measurement points in the measurement electrical signal is the actual total number of measurement points n, and the number of measurement points in the measurement light path is the standard number of measurement points N. If the actual total number of measurement points n is less than the standard number of measurement points N, it indicates that the measurement points are insufficient, and it can be preliminarily determined that the optical fiber has a breakpoint. If the actual total number of measurement points n is greater than or equal to the standard number of measurement points N, it can be preliminarily determined that the optical fiber is complete.

[0150] The standard number of measurement points can be determined according to the length of the optical fiber, the resolution of the sensing system, and the expected monitoring accuracy, etc. For example, the length of the optical fiber in some embodiments of the present disclosure can refer to the effective length of the reference optical fiber and the sensing optical cable. Suppose the effective length of the reference optical fiber and the sensing optical cable is L1, and the system spatial resolution is Δx1. The calculation formula of the standard number of measurement points N can be as shown in the following formula (7):

[0151] In some embodiments, the controller further determines the location of the break point according to the number of light intensity information of the measurement points in the measurement electrical signal and the length of the measurement optical path, and carries the location of the break point when reporting the fiber break event.

[0152] In practical applications, in the case of preliminary determination that the optical fiber has a break point, OTDR or other sensing technology can be used to detect the discontinuous point in the optical fiber and calculate the location X of the break point. For example, the length L2 of the blind area at the incident end can be obtained, and the following calculation formula (8) can be used for calculation:

[0153] Wherein, X is the location of the break point; n is the actual total number of measurement points; N is the standard number of measurement points; L1 is the effective length of the reference optical fiber and the sensing optical cable; and L2 is the length of the blind area at the incident end.

[0154] It should be noted that, regardless of whether the reference optical fiber or the sensing optical cable has a break point, the temperature data can be transmitted to the outside through the signal output interface. When there is no break point, the output can be the temperature values of all the measurement points on the sensing optical fiber, and when there is a break point, the output can be the temperature values of the measurement points on the sensing optical fiber except the measurement point at the location of the break point, and the present disclosure does not limit this.

[0155] In some embodiments of the present disclosure, the controller controls the light emitting unit to send a light pulse sequence to the measurement optical path, and then the controller obtains the measurement result according to the measurement electrical signal fed back by the receiving module, the measurement electrical signal is obtained by the receiving module according to a plurality of light pulses of the light pulse sequence received from the measurement optical path, and the time interval between adjacent two light pulses in the plurality of light pulses is adjustable, so as to ensure that the time interval between adjacent light pulses is adjustable, thereby changing the light pulse emission frequency per unit time by adjusting the time interval between light pulses to adapt to different measurement requirements and conditions, and then increasing the number of accumulations of the same measurement point based on the change of the light pulse emission frequency per unit time, so as to improve the measurement accuracy and stability of the measurement result, reduce the sampling frequency requirement of the sampling device, and be suitable for vehicle-mounted scenes.

[0156] It should be noted that, for the method embodiments, in order to simply describe, they are all expressed as a series of action combinations, but those skilled in the art should know that the embodiments of the present disclosure are not limited by the order of the described actions, because according to the embodiments of the present disclosure, certain steps can be performed in other order or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification are all exemplary embodiments, and the actions involved are not necessarily required by the embodiments of the present disclosure.

[0157] Some embodiments of the present disclosure further provide a controller, comprising a processor, a memory connected with the processor, and the memory storing a computer program, the processor being configured to execute the computer program to implement the processes of the above-mentioned optical fiber sensing method embodiments and achieve the same technical effects. For the sake of brevity, the details are not repeated here.

[0158] As shown in FIG. 7 and FIG. 8, some embodiments of the present disclosure further provide a vehicle 1000, comprising the above-mentioned controller or the above-mentioned optical fiber sensing system. The provided vehicle 1000 can implement the processes of the above-mentioned optical fiber sensing method embodiments and achieve the same technical effects. For the sake of brevity, the details are not repeated here.

[0159] Some embodiments of the present disclosure further provide a computer readable storage medium, which stores a computer program. The computer program is executed by a processor to implement the processes of the above-mentioned optical fiber sensing method embodiments and achieve the same technical effects. For the sake of brevity, the details are not repeated here.

[0160] Each of the embodiments in the present specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0161] Those skilled in the art should understand that the embodiments of the present disclosure can be provided as a method, device, or computer program product. Therefore, the embodiments of the present disclosure can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the embodiments of the present disclosure can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, Compact Disc Read-Only Memory (CD-ROM), optical storage, etc.) containing computer-usable program code.

[0162] The embodiments of the present disclosure are described with reference to the flowcharts and / or block diagrams according to the method, terminal device (system), and computer program product of the embodiments of the present disclosure. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device produce a device for implementing the functions specified in one or more flows of the flowcharts and / or one or more blocks of the block diagrams.

[0163] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart or flowsheets and / or block or blocks of the block diagrams.

[0164] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart or flowsheets and / or block or blocks of the block diagrams.

[0165] Although preferred embodiments of the present disclosure have been described, those skilled in the art, once aware of the basic inventive concept, can make additional changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present disclosure.

[0166] Finally, it should be noted that the user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present disclosure are all information and data authorized by the user or authorized by all parties, and the collection, use and processing of related data need to comply with relevant laws, regulations and standards of relevant countries and regions, and provide corresponding operation portal for user to choose authorization or refusal.

[0167] It should also be noted that, in this document, relational terms such as first and second and the like can only be used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations exist in any such actual relationship or order. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed or inherent to such a process, method, article or terminal device. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article or terminal device including the element.

[0168] The above describes in detail the optical fiber sensing method, the corresponding controller, the corresponding optical fiber sensing system and the corresponding vehicle provided by the present disclosure. The principles and implementation manners of the present disclosure are described by using specific examples. The above description of the examples is only used to help understand the method of the present disclosure and its core idea. Meanwhile, for those skilled in the art, according to the idea of the present disclosure, the specific implementation manners and application ranges can be changed. In summary, the content of the present description should not be understood as a limitation of the present disclosure.

Claims

1. An optical fiber sensing method applied to an optical fiber sensing system, the optical fiber sensing system comprising a controller, a light emitting unit, a measurement light path and a receiving module, the controller being communicatively connected with the light emitting unit and the receiving module respectively, the light emitting unit and the receiving module being connected through the measurement light path, the method comprising: the controller controlling the light emitting unit to send a light pulse sequence to the measurement light path, the light pulse sequence comprising a plurality of light pulses, a time interval between adjacent two light pulses in the plurality of light pulses being adjustable; the controller obtaining a measurement result according to a measurement electrical signal fed back by the receiving module, the measurement electrical signal being obtained by the receiving module from a plurality of light pulses in the light pulse sequence received from the measurement light path.

2. The method of claim 1, wherein, The influencing factor of the time interval between the adjacent two light pulses comprises at least one of a length of the measurement light path, a working mode of a vehicle, a time effectiveness requirement, and a user requirement.

3. The method of claim 2, wherein, The influencing factor of the time interval between the adjacent two light pulses comprises the length of the measurement light path, and the time interval between the adjacent two light pulses in the plurality of light pulses is positively correlated with the length of the measurement light path.

4. The method of claim 2, wherein, The working mode of the vehicle comprises an energy saving mode and a high efficiency mode, the influencing factor of the time interval between the adjacent two light pulses comprises the working mode of the vehicle, and the time interval between the adjacent two light pulses in the energy saving mode is greater than that in the high efficiency mode.

5. The method of claim 2, wherein, The influencing factor of the time interval between the adjacent two light pulses comprises the time effectiveness requirement, and the time interval between the adjacent two light pulses in the plurality of light pulses is negatively correlated with the time effectiveness requirement.

6. The method of any one of claims 1-5, wherein, The plurality of light pulses comprises adjacent first and second light pulses, the time interval between the adjacent two light pulses is a first time interval between a sending time of the first light pulse and a sending time of the second light pulse, and the first time interval is greater than or equal to a time length of the first light pulse transmitted in the measurement light path.

7. The method of any one of claims 1-5, wherein, The light pulse sequence comprises n light pulse subsequences, each of the n light pulse subsequences comprises a plurality of light pulses, a light pulse subsequence i in the n light pulse subsequences comprises adjacent third and fourth light pulses, and the time interval between the adjacent two light pulses is a time interval between a sending time of the third light pulse and a sending time of the fourth light pulse, where n is a positive integer, i is a positive integer, and i≤n.

8. The method of claim 7, wherein, The plurality of light pulses in the light pulse subsequence i in the n light pulse subsequences comprised in the measurement light path are respectively configured to measure an an+i measurement point in the measurement light path, where a is a natural number.

9. The method of claim 7 or 8, wherein, The n optical pulse subsequences include an optical pulse subsequence P and an optical pulse subsequence Q, an optical pulse p in the optical pulse subsequence P and an optical pulse q in the optical pulse subsequence Q are two optical pulses closest in time between the two optical pulse subsequences, a time interval between a sending time of the optical pulse p and a sending time of the optical pulse q is less than a time interval between sending times of any two optical pulses in the optical pulse subsequence P.

10. The method of any one of claims 1-9, wherein, The optical pulse sequence is generated by the optical emitting unit according to an optical pulse sequence control signal sent by the controller.

11. The method of claim 10, wherein, The optical pulse sequence control signal is generated by the controller according to a laser optical pulse parameter requirement.

12. The method of any one of claims 1-11, wherein, The measurement optical path includes a reference optical path segment and a sensing optical path segment.

13. The method of any one of claims 1-12, wherein, The measurement electrical signal includes optical intensity information of a plurality of measurement points in the measurement optical path, and the measurement result is obtained by the controller according to the optical intensity information of the plurality of measurement points.

14. The method of claim 13, wherein, The receiving module includes a field programmable gate array (FPGA) and an optoelectronic conversion unit, the optoelectronic conversion unit is configured to convert the received optical pulse into a digital electrical signal, and the FPGA is configured to process the digital electrical signal to obtain the optical intensity information of the plurality of measurement points.

15. The method of claim 14, wherein, The optoelectronic conversion unit includes a diode, an amplification circuit filter, and an analog-to-digital converter, the diode is configured to convert the received optical pulse into an analog electrical signal, the amplification circuit filter is configured to amplify and attenuate the analog electrical signal, and the analog-to-digital converter is configured to convert the analog electrical signal into the digital electrical signal.

16. The method of any one of claims 13-15, wherein, The optical intensity information of each measurement point in the plurality of measurement points is obtained based on accumulation of electrical signals corresponding to a plurality of optical pulses in the optical pulse sequence.

17. The method of any one of claims 13-16, wherein, The measurement result is calculated by the controller according to the optical intensity information of a plurality of measurement points of the reference optical path segment and the sensing optical path segment in the measurement optical path.

18. The method of any one of claims 13-17, further comprising: If the number of optical intensity information of measurement points in the measurement electrical signal is less than the number of measurement points in the measurement optical path, the controller determines that there is a breakpoint in the measurement optical path.

19. The method of claim 18, further comprising: The controller determines the location of the breakpoint according to the number of optical intensity information of measurement points in the measurement electrical signal and the length of the measurement optical path.

20. The method of any one of claims 1-19, wherein, The controller is a central controller or a domain controller of a vehicle.

21. The method of any one of claims 1-20, wherein, The frequency range of the optical pulse sequence is 20000 Hz-200000 Hz, and the cumulative duration range of pulses measuring the same measurement point in the optical pulse sequence is 0.2 seconds-1 second.

22. A controller, comprising a processor and a memory connected with the processor, the memory storing a computer program, and the processor is configured to execute the computer program to implement the optical fiber sensing method according to any one of claims 1-21.

23. An optical fiber sensing system comprising the controller according to claim 22, the optical fiber sensing system further comprising a laser emitting unit, a measurement optical path and a receiving module, the controller being communicatively connected with the laser emitting unit and the receiving module, respectively, the laser emitting unit and the receiving module being connected through the measurement optical path.

24. A vehicle comprising the controller according to claim 22, or the optical fiber sensing system according to claim 23.

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