Multi-point grating optical cable temperature calibration device and calibration method

Abstract

The invention discloses a multipoint grating optical cable temperature calibration device and calibration method, and the device comprises a first optical cable disc which is used for winding and placing a multipoint grating optical cable to be calibrated; the second optical cable disc is used for receiving the multi-point grating optical cable which is released from the first optical cable disc and penetrates through the constant temperature box, and the released multi-point grating optical cable is wound on the second optical cable disc; at least two opposite sides of the constant temperature box are provided with through holes, so that the multi-point grating optical cable can penetrate into the box body from one through hole and penetrate out of the box body from the other through hole; the grating demodulator is connected with the multi-point grating optical cable and is used for collecting reflection spectrum or central wavelength change data of all gratings in the multi-point grating optical cable along with time in real time; and the computer is used for calculating and obtaining the temperature sensitivity and the thermal time constant of the gratings of all the multi-point grating optical cables. Therefore, calibration of the temperature sensitivity and the thermal time constant of each grating in the optical cable can be completed at a time, and more comprehensive grating temperature response characteristic parameters are provided.

Description

Technical Field

[0001] The present invention relates to a multi - point grating optical cable temperature calibration device and a calibration method, and relates to the technical field of fiber optic sensing. Background Art

[0002] Optical cables including multiple Fiber Bragg Gratings (FBGs) have wide applications in the field of temperature monitoring. To ensure accurate temperature measurement, it is necessary to calibrate the temperature sensitivity of each FBG in the optical cable, that is, to determine the relationship between the central wavelength of the FBG and temperature change (temperature sensitivity). In addition, when measuring rapidly changing temperatures, the structure and materials of the optical cable will affect the speed at which temperature is transmitted to the FBGs in the optical fiber, thereby affecting the response time of the FBGs. The thermal time constant is usually used to characterize this thermal dynamic response characteristic. In some applications (such as real - time monitoring of temperature transients), accurately understanding and compensating for the thermal time constant is crucial for improving measurement accuracy.

[0003] Existing FBG temperature sensitivity calibrations are usually carried out in a laboratory using constant - temperature equipment (such as an incubator or a water bath). The optical cable to be calibrated is placed in a constant - temperature environment, the environmental temperature is changed, the stable value of the FBG central wavelength after reaching thermal equilibrium is recorded, and then linear fitting is performed to obtain the temperature sensitivity. However, for an optical cable with a large number of FBGs and a long length, it is very difficult to calibrate the whole cable in a constant - temperature device. If segment - by - segment calibration is adopted, the optical cable needs to be coiled and placed in a small incubator, which is not only inefficient, but also the stress generated by coiling may affect the accuracy of the calibration result.

[0004] For the measurement of the thermal time constant, it is usually necessary to quickly place the FBG in a temperature - step environment, record the change curve of its central wavelength with time, and then perform fitting according to the exponential response model. Independently performing such temperature - step response measurements on each FBG in a long - distance optical cable to obtain the thermal time constant also faces problems of low efficiency and complex operation. In addition, when measuring the thermal time constant by coiling the optical cable, the thermal transfer characteristics of the coiled part of the optical cable may be different from those when it is deployed straight, affecting the accuracy of the measurement result.

[0005] Therefore, the prior art lacks a device and method that can efficiently and accurately calibrate the temperature sensitivity and thermal time constant of each FBG simultaneously for a long - distance optical cable containing multiple FBGs. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, in view of the above problems, the object of the present invention is to provide a multi-point grating optical cable temperature calibration device and a calibration method, so as to solve the problems of low calibration efficiency, complex operation and inaccurate results in the prior art for calibrating the temperature sensitivity and thermal time constant of a long-distance optical cable containing multiple FBGs, and to achieve accurate calibration of the temperature-sensitive characteristics and thermal dynamic response characteristics of each FBG in the multi-point grating optical cable.

[0007] In order to achieve the above object of the invention, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a multi-point grating optical cable temperature calibration device, which includes a first optical cable reel, a second optical cable reel, a constant temperature box, a grating demodulator, a multi-point grating optical cable and a computer, wherein: The first optical cable reel is used for winding and placing the multi-point grating optical cable to be calibrated; The second optical cable reel is used for receiving the multi-point grating optical cable released from the first optical cable reel and passing through the constant temperature box, and the released multi-point grating optical cable is wound on the second optical cable reel; The constant temperature box is provided with through holes at least on opposite sides, so that the multi-point grating optical cable can penetrate into the box body through one through hole and penetrate out of the box body through the other through hole; The grating demodulator is connected to the multi-point grating optical cable and is used for collecting in real time the data of the reflection spectrum or the central wavelength of all gratings in the multi-point grating optical cable changing with time; The computer is used for acquiring the data collected by the grating demodulator and performing fitting processing on the collected data to obtain the temperature sensitivity and thermal time constant of all gratings of the multi-point grating optical cable.

[0008] In some possible embodiments, the constant temperature box has an accurate temperature control ability and can stabilize the internal temperature of the box body at multiple preset target temperature points. The number of the constant temperature boxes is provided with a plurality of them, and the plurality of constant temperature boxes are connected in series and can be set at different temperatures respectively to achieve a more complex temperature profile or a faster temperature change.

[0009] In some possible embodiments, the grating demodulator is fixed on the side wall of the first optical cable reel and rotates synchronously with the first optical cable reel. The head end of the multi-point grating optical cable extends out to the side wall through the hole on the inner drum of the first optical cable reel and is connected to the grating demodulator, and the grating demodulator sends the collected data to the computer by wire or wirelessly.

[0010] In some possible embodiments, the through holes are also sealed with a flexible sealing material to reduce heat loss.

[0011] In some possible embodiments, both the first optical cable reel and the second optical cable reel use an electric optical cable reel or a manual optical cable reel in cooperation with a length measuring device to achieve precise movement and grating positioning of the multi-point grating optical cable.

[0012] In a second aspect, the present invention can also provide a calibration method for a multi-point grating optical cable temperature calibration device, including: Install and fix all components of the multi-point grating optical cable temperature calibration device as required; Set the temperature of the constant temperature chamber to the first target temperature T1, and wait for the temperature inside the constant temperature chamber to stabilize. The grating demodulator collects in real time the data of the change of the reflection spectrum or the central wavelength of the grating located inside the constant temperature chamber over time; rotate the second optical cable reel to take in the cable, so that the multi-point grating optical cable is released from the first optical cable reel and passes through the constant temperature chamber; set the temperature of the constant temperature chamber to the next target temperature T2, wait for stability, and then rotate the optical cable reel in the reverse direction to release the multi-point grating optical cable from the second optical cable reel and pass through the constant temperature chamber, and so on, set multiple target temperature points T N , and repeat the measurement for each target temperature to obtain the data of the change of the reflection spectrum or the central wavelength of all gratings over time at several target temperatures; Based on the data of the change of the reflection spectrum or the central wavelength of each grating over time at several target temperatures collected, perform single-point single-temperature wavelength-time curve fitting to obtain the fitting coefficients [b(T1), b(T2), ……, b(T N )] and [c(T1), c(T2), ……, c(T N )]; For each grating, use [T1, T2, ……, T N as the independent variable and the fitting coefficient [c(T1), c(T2), ……, c(T N )] as the dependent variable to perform linear fitting to obtain the temperature sensitivity of the grating; For each grating, based on the fitting coefficients [b(T1), b(T2), ……, b(T N )] and the measured temperature points [T1, T2, ……, T N , calculate the thermal time constant τ of the grating.

[0013] In some possible embodiments, installing and fixing all components of the multi-point grating optical cable temperature calibration device includes: Place the multi - point grating optical cable winding disc of the object to be determined on the first optical cable disc. The head end of the multi - point grating optical cable extends out to the side wall through the hole on the inner drum of the first optical cable disc. The grating demodulator is fixed on the side wall of the first optical cable disc. Connect the head end of the multi - point grating optical cable to the grating demodulator, release the tail end of the multi - point grating optical cable from the first optical cable disc and pass it through the constant temperature box and connect it to the second optical cable disc.

[0014] In some possible implementation manners, based on the time - varying data of the reflection spectra or central wavelengths of each grating at several target temperatures collected, perform single - point single - temperature wavelength - time curve fitting to obtain fitting coefficients. Specifically:

[0015] In the formula, λ B (T,t) represents the central wavelength of the grating at constant temperature T and time t. a(T), b(T), and c(T) are fitting coefficients at constant temperature T. Through fitting, the fitting coefficients of each grating at the target temperature can be obtained: [a(T1), a(T2), ……, a(T N )], [b(T1), b(T2), ……, b(T N )], and [c(T1), c(T2), ……, c(T N )].

[0016] In some possible implementation manners, for each grating, with [T1, T2, ……, T N as the independent variable and the fitting coefficient [c(T1), c(T2), ……, c(T N )] as the dependent variable, perform linear fitting to obtain the temperature sensitivity of the grating. The specific formula is: ; In the formula, S is the temperature sensitivity of the grating, and K is a constant.

[0017] In some possible implementation manners, for each grating, based on the fitting coefficient [b(T1), b(T2), ……, b(T N )] and the measured temperature points [T1, T2, ……, T N , calculate the thermal time constant τ of the grating. The specific formula is: ; In the formula, N is the number of measured temperature points, and T i is the measured temperature point.

[0018] Due to the adoption of the above - mentioned technical solutions, the present invention has the following characteristics: 1. Calibrate the temperature sensitivity and thermal time constant simultaneously: The present invention can complete the calibration of the temperature sensitivity and thermal time constant of each FBG in the optical cable at one time, providing more comprehensive FBG temperature response characteristic parameters.

[0019] 2. High efficiency: By means of the double optical cable reel cable guiding method, the present invention can efficiently perform batch calibration on long-distance optical cables containing multiple FBGs, greatly saving time and manpower.

[0020] 3. High precision: The calibration of the present invention is carried out in a controlled constant temperature oven environment, avoiding the interference of complex on-site environmental factors; the straightened optical cable state is closer to the actual deployment situation (compared with coiling), and the obtained sensitivity and time constant are more accurate.

[0021] 4. Characterize dynamic response: The present invention can accurately measure the thermal time constant affected by the optical cable structure, which helps to perform data compensation in dynamic temperature measurement applications and improve the measurement accuracy.

[0022] 5. Automatic control: The entire calibration process of the present invention can achieve automatic control, including the rotation of the optical cable reel, the temperature setting of the constant temperature oven, data acquisition and data processing.

[0023] In summary, the present invention has a wide range of applications and can be widely used in the temperature characteristic calibration of various long-distance optical cables containing FBGs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference numerals are used to represent the same components. In the drawings: Figure 1 It is a schematic structural diagram of a multi-point grating optical cable temperature calibration device according to an embodiment of the present invention.

[0025] Figure 2 It is a flowchart of a multi-point grating optical cable temperature calibration method according to an embodiment of the present invention.

[0026] Figure 3 It is the FBG central wavelength-temperature acquisition and fitting result according to an embodiment of the present invention.

[0027] Figure 4 It is the grating temperature sensitivity fitting result according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] It should be understood that the terms used herein are for the purpose of describing particular example embodiments only and are not intended to be limiting. Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" as used herein may also include the plural forms. The terms "comprising", "including", "containing", and "having" are inclusive and thus specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the particular order described or illustrated, unless an execution order is explicitly stated. It should also be understood that additional or alternative steps may be used.

[0029] Although the terms first, second, third, etc. may be used herein to describe multiple elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or section from another. Unless the context clearly dictates otherwise, terms such as "first", "second", and other numerical terms when used herein do not imply an order or sequence. Thus, a first element, component, region, layer, or section discussed below may be referred to as a second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0030] For ease of description, spatial relative relationship terms may be used herein to describe the relationship of one element or feature shown in the figures to another element or feature, such as "inner", "outer", "inside", "outside", "below", "above", etc. Such spatial relative relationship terms are intended to include different orientations of the device in use or operation other than the orientations depicted in the figures.

[0031] Since the prior art lacks a method for efficiently and accurately calibrating the temperature sensitivity and thermal time constant of each FBG in a long-distance optical cable containing multiple FBGs simultaneously, the present invention provides a multi-point grating optical cable temperature calibration device and a calibration method. The device includes a first optical cable reel, a second optical cable reel, a thermostat, a grating demodulator, a multi-point grating optical cable, and a computer, wherein: The first optical cable reel is used for winding and placing the multi-point grating optical cable to be calibrated; The second optical cable reel is used for receiving the multi-point grating optical cable released from the first optical cable reel and passing through the thermostat, and the released multi-point grating optical cable is wound on the second optical cable reel; The thermostat is provided with through holes on at least two opposite sides, so that the multi-point grating optical cable can penetrate into the box body through one through hole and penetrate out of the box body through the other through hole; The grating demodulator is connected to the multi-point grating optical cable and is used for collecting the change data of the reflection spectrum or the central wavelength of all the gratings in the multi-point grating optical cable in real time; The computer is used for obtaining the data collected by the grating demodulator and performing fitting processing on the collected data to obtain the temperature sensitivity and thermal time constant of the gratings of all the multi-point grating optical cables. Therefore, the present invention can complete the calibration of the temperature sensitivity and thermal time constant of each FBG in the optical cable at one time, and provides more comprehensive FBG temperature response characteristic parameters.

[0032] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art.

[0033] Example 1: As Figure 1 shown, the multi-point grating optical cable temperature calibration device provided in this embodiment includes: a first optical cable reel 1, a second optical cable reel 2, a thermostat 3, a grating demodulator 4, a multi-point grating optical cable 5, and a computer 6, wherein: The first optical cable reel 1 is used for winding and placing the multi-point grating optical cable 5 to be calibrated; The second optical cable reel 2 is used for receiving the multi-point grating optical cable 5 released from the first optical cable reel 1 and passing through the thermostat 3, and the released multi-point grating optical cable 5 is wound on the second optical cable reel 2.

[0034] The thermostat 3 is provided with through holes on at least two opposite sides, so that the multi-point grating optical cable 5 can penetrate into the box body through one through hole and penetrate out of the box body through the other through hole, wherein the thermostat 3 can stabilize the internal temperature of the box body at a plurality of preset target temperature points.

[0035] The grating demodulator 4 is connected to the multi-point grating optical cable 5 and is used for collecting the change data of the reflection spectrum or the central wavelength of all the FBGs in the multi-point grating optical cable 5 in real time at high speed.

[0036] A computer 6, which is used to acquire the data collected by the grating demodulator 4 and fit the collected data of the FBG reflection spectrum or the change data of the central wavelength over time, so as to obtain the temperature sensitivity and thermal time constant of each FBG.

[0037] In a preferred embodiment of the present invention, both the first optical cable reel 1 and the second optical cable reel 2 can use an electric optical cable reel or a manual optical cable reel in cooperation with a length measuring device to achieve precise movement of the multi-point grating optical cable 5 and FBG positioning.

[0038] In a preferred embodiment of the present invention, the constant temperature box 3 can use a high and low temperature box, a water bath box or a temperature control device capable of achieving a rapid temperature step, that is, it is ensured that the constant temperature box 3 needs to have precise temperature control ability.

[0039] Furthermore, the number of the constant temperature boxes 3 can be set to be multiple. When multiple constant temperature boxes 3 are set, the multiple constant temperature boxes 3 can be set in series and different temperatures can be set respectively to achieve a more complex temperature profile or a faster temperature change.

[0040] Furthermore, there are no requirements for the size of the constant temperature box body 3, but it is necessary to ensure that at least one grating is inside the constant temperature box body 3 within each time period.

[0041] Furthermore, measures should be taken at the through holes of the constant temperature box 3 to reduce heat dissipation, such as using a flexible sealing material for pore sealing.

[0042] In a preferred embodiment of the present invention, the grating demodulator 4 can collect the central wavelengths of all FBGs in the multi-point grating optical cable 5. The selection of the data acquisition frequency of the central wavelength depends on the size of the thermal time constant of the optical cable. Since the thermal time constant is related to the temperature gradient, for example, the thermal time constants for heating from 20 degrees to 30 degrees and from 20 degrees to 40 degrees are different, so a relatively suitable data acquisition frequency is set to capture the details of the thermal response.

[0043] In a preferred embodiment of the present invention, the grating demodulator 4 is fixed on the side wall of the first optical cable reel 1 and rotates synchronously with the first optical cable reel 1. The head end of the multi-point grating optical cable 5 extends through the hole on the inner drum of the first optical cable reel 1 to the side wall and is connected to the grating demodulator 4.

[0044] Furthermore, the grating demodulator 4 transmits the collected data to the computer 6 in real time through wireless means such as Bluetooth or WiFi. The grating demodulator 4 can also be connected to the computer 6 in a wired manner through a slip ring and transmit the collected data to the computer 6 in real time.

[0045] Embodiment 2: As Figure 2 shown, this embodiment also provides a method for calibrating the temperature of a multi-point grating optical cable, including: S1. Device connection and preparation.

[0046] In this embodiment, the multi-point grating optical cable 5 to be determined is wound around the first optical cable reel 1. The head end of the multi-point grating optical cable 5 extends through the hole on the inner drum of the first optical cable reel 1 to the side wall. The grating demodulator 4 is fixed on the side wall of the first optical cable reel 1. Connect the head end of the multi-point grating optical cable 5 to the grating demodulator 4. Release the tail end of the multi-point grating optical cable 5 from the first optical cable reel 1 and connect it to the second optical cable reel 2 after passing through the thermostat 3.

[0047] S2. Set the first target temperature and stabilize it.

[0048] In this embodiment, set the temperature of the thermostat 3 to the first target temperature T1 (for example, 30 °C), and wait for the temperature inside the box to stabilize, ensuring that the temperature fluctuation is within the allowable range, and record the current target temperature T1.

[0049] S3. Optical cable rotation and data acquisition.

[0050] In this embodiment, the optical cable rotation and data acquisition include: Rotate the second optical cable reel 2 to take in the cable, so that the multi-point grating optical cable 5 is released from the first optical cable reel 1 and enters the thermostat 3. Place the first FBG in the thermostat 3, and then turn on the grating demodulator 4 to record the central wavelength of this FBG (for example, record a central wavelength every 1 second, taking this as an example, not limited to this), and record for a long enough time (for example, 2 times or more of the estimated maximum thermal time constant) to ensure that the FBG reaches thermal equilibrium, where thermal equilibrium means that the temperature of the optical cable has reached the internal temperature of the thermostat. For example, the ambient temperature is 20 degrees, the temperature of the optical cable when it is just placed in the thermostat is 20 degrees, the thermostat is set to 30 degrees, the optical cable starts to heat up, and when the temperature of the optical cable itself reaches 30 degrees, it reaches thermal equilibrium.

[0051] Rotate the second optical cable reel 2 to take in the cable, so that the second FBG enters the thermostat 3, and then repeat the above data acquisition process, so that all FBGs on the optical cable are data acquired.

[0052] S4. Repeat temperature step and data acquisition.

[0053] In this embodiment, repeating the temperature step and data acquisition includes: First, set the temperature of the thermostat 3 to the next target temperature T2 (for example, 40 °C) and wait for it to stabilize.

[0054] Then, by rotating the optical cable reel in the reverse direction (for example, rotating the first optical cable reel 1 to take in the cable), make the multi-point grating optical cable 5 be released from the second optical cable reel 2 and pass through the thermostat 3, and repeat the data acquisition process in step S3. Multiple target temperature points T1, T2,..., T can be set.N (e.g., the operating temperature range of the covered optical cable), and repeat steps S2 and S3 for each target temperature.

[0055] In this embodiment, in addition to measuring the temperature rise of the FBG placed in the constant temperature chamber 3 as described above, the FBG can also be removed from the constant temperature chamber 3 to measure its dynamic response during the cooling process, which will not be elaborated here.

[0056] S5. Fitting of the single-point single-temperature wavelength-time curve.

[0057] In this embodiment, for each FBG collected during the process of stabilizing from room temperature to a certain temperature (e.g., entering T1 or T2 from room temperature, etc.), the change of its central wavelength over time is curve-fitted. For example, when entering T1 from room temperature, the grating demodulator records a set of central wavelength data every 1 second. The central wavelength at time t1 is λ B (T1, t1), and the central wavelength at time t2 is λ B (T2, t2), and so on. Curve fitting is performed on these data, with time t as the independent variable and λ B (T, t) as the dependent variable for fitting. The fitting uses the following formula: ; In the formula, λ B (T, t) represents the central wavelength of the FBG at constant temperature T and time t. a(T), b(T), and c(T) are fitting coefficients at constant temperature T. Through fitting, the fitting coefficients of each FBG at a specific temperature can be obtained: [a(T1), a(T2), ……, a(T N )], [b(T1), b(T2), ……, b(T N )], and [c(T1), c(T2), ……, c(T N )].

[0058] S6. Calibration of the grating temperature sensitivity.

[0059] In this embodiment, for each FBG, the stable central wavelength value c(T) after reaching thermal equilibrium at different target temperatures is extracted, and a linear fitting is performed with [T1, T2, ……, T N as the independent variable and [c(T1), c(T2), ……, c(T N )] as the dependent variable as follows: ; In the formula, S is the temperature sensitivity of this FBG, and K is a constant. By fitting each FBG, the temperature sensitivity of each FBG can be obtained.

[0060] S7. Calibration of the thermal time constant.

[0061] In this embodiment, for a specific FBG, its thermal time constant τ is calculated by the following formula: ; where N is the number of measured temperature points, b(T i ) is the fitting coefficient of formula (1), and T i is the measured temperature point.

[0062] As Figure 3 shown are the central wavelength data points of a certain FBG after reaching thermal equilibrium at different target temperatures and its linear fitting curve. A set of data is collected every 30 seconds, and the thermostat is stabilized at 29.5 °C, 39.0 °C, and 48.6 °C respectively. The parameter fitting results are shown in Table 1.

[0063]

[0064] Using formula (2) to fit the coefficient c, as Figure 4 shown, the fitting formula is, so the temperature sensitivity of this grating is 10.1 pm / °C. According to the coefficient b and formula (3), the thermal time constant of this grating can be calculated to be 6.79 s / °C.

[0065] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments. In the description of this specification, the descriptions with reference to terms such as "a preferred embodiment", "furthermore", "specifically", "in this embodiment", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of this specification. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0066] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-point grating optical cable temperature calibration device, characterized in that The device includes a first optical cable reel, a second optical cable reel, a thermostatic chamber, a grating demodulator, a multi-point grating optical cable, and a computer, where: The first optical cable reel is used for winding and placing the multi-point grating optical cable to be calibrated; The second optical cable reel is used for receiving the multi-point grating optical cable released from the first optical cable reel and passing through the thermostatic chamber, and the released multi-point grating optical cable is wound on the second optical cable reel; The thermostatic chamber is provided with through holes on at least two opposite sides, so that the multi-point grating optical cable can penetrate into the chamber through one through hole and penetrate out of the chamber through the other through hole; The grating demodulator is connected to the multi-point grating optical cable and is used for collecting in real time the data of the change of the reflection spectrum or the central wavelength of all gratings in the multi-point grating optical cable over time; The computer is used for obtaining the data collected by the grating demodulator and performing fitting processing on the collected data to obtain the temperature sensitivity and thermal time constant of the gratings of all the multi-point grating optical cables.

2. The multi-point grating optical cable temperature calibration device according to claim 1, wherein The thermostatic chamber has an accurate temperature control ability and can stabilize the internal temperature of the chamber at multiple preset target temperature points. A plurality of thermostatic chambers are arranged in series, and different temperatures can be set respectively to achieve a more complex temperature profile or a faster temperature change.

3. The multi-point grating optical cable temperature calibration device according to claim 1, characterized in that, The grating demodulator is fixed on the side wall of the first optical cable reel and rotates synchronously with the first optical cable reel. The head end of the multi-point grating optical cable extends to the side wall through the hole on the inner drum of the first optical cable reel and is connected to the grating demodulator. The grating demodulator sends the collected data to the computer by wired or wireless means.

4. The multi-point grating optical cable temperature calibration device according to claim 1, wherein The through holes are also sealed with a flexible sealing material to reduce heat loss.

5. The multi-point grating optical cable temperature calibration device according to claim 1, wherein, Both the first optical cable reel and the second optical cable reel use an electric optical cable reel or a manual optical cable reel in cooperation with a length measuring device to achieve the precise movement and grating positioning of the multi-point grating optical cable.

6. A calibration method for the multi-point grating optical cable temperature calibration device according to any one of claims 1 to 5, characterized in that, Including: Install and fix all the components of the multi-point grating optical cable temperature calibration device as required; Set the temperature of the thermostat to the first target temperature T1, and wait for the temperature inside the thermostat to stabilize. The grating demodulator continuously acquires the data of the reflection spectrum or the central wavelength of the grating inside the thermostat changing with time; Rotate the second cable reel to wind up the cable, so that the multi-point grating optical cable is released from the first cable reel and passes through the thermostat; Set the temperature of the thermostat to the next target temperature T2. After waiting for stability, rotate the cable reel in the reverse direction to release the multi-point grating optical cable from the second cable reel and pass through the thermostat, and so on, setting multiple target temperature points T N , and repeat the measurement for each target temperature to obtain the data of the reflection spectrum or the central wavelength of all gratings changing with time at several target temperatures; Based on the time-varying data of the reflection spectra or central wavelengths of each grating at several target temperatures collected, perform single-point and single-temperature wavelength-time curve fitting to obtain the fitting coefficients [b(T1), b(T2), ……, b(T N )] and [c(T1), c(T2), ……, c(T N )]; For each grating, with [T1, T2, ……, T N as the independent variable and the fitting coefficients [c(T1), c(T2), ……, c(T N )] as the dependent variable, a linear fit is performed to obtain the temperature sensitivity of the grating; For each grating, based on the fitting coefficients [b(T1), b(T2), ……, b(T N )] and the measured temperature points [T1, T2, ……, T N , the thermal time constant τ of the grating is calculated.

7. The calibration method according to claim 6, wherein Install and fix all the components of the multi-point grating optical cable temperature calibration device, including: Wind and place the multi-point grating optical cable to be calibrated on the first optical cable reel. The head end of the multi-point grating optical cable extends to the side wall through the hole on the inner drum of the first optical cable reel. The grating demodulator is fixed on the side wall of the first optical cable reel. Connect the head end of the multi-point grating optical cable to the grating demodulator, release the tail end of the multi-point grating optical cable from the first optical cable reel and pass it through the thermostatic chamber to connect to the second optical cable reel.

8. The calibration method according to claim 6, characterized in that Perform single-point single-temperature wavelength-time curve fitting based on the collected data of the change of the reflection spectrum or the central wavelength of each grating at several target temperatures over time to obtain fitting coefficients. Specifically: ； where λ B (T, t) represents the central wavelength of the grating at a constant temperature T and time t, and a(T), b(T), and c(T) are fitting coefficients at a constant temperature T. The fitting coefficients of each grating at the target temperature can be obtained through fitting: [a(T1), a(T2), ……, a(T N )], [b(T1), b(T2), ……, b(T N )], and [c(T1), c(T2), ……, c(T N )].

9. The calibration method according to claim 8, wherein For each grating, with [T1, T2, ……, T N as the independent variable and the fitting coefficients [c(T1), c(T2), ……, c(T N )] as the dependent variable, a linear fit is performed to obtain the temperature sensitivity of the grating. The specific formula is as follows: ; In the formula, S is the temperature sensitivity of this grating, and K is a constant.

10. The calibration method according to claim 9, wherein For each grating, based on the fitting coefficients [b(T1), b(T2), ……, b(T N )] and the measured temperature points [T1, T2, ……, T N , the thermal time constant τ of the grating is calculated, and the specific formula is: ； Where N is the number of measured temperature points, and T i is the measured temperature point.

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