A distributed fiber temperature measurement optical cable calibration device and calibration method

Abstract

The application discloses a kind of distributed optical fiber temperature measurement optical cable calibration device and calibration method, including distributed optical fiber temperature measurement optical cable, vertically arranged on a support body, and a plurality of gratings are arranged at intervals in the distributed optical fiber temperature measurement optical cable;Grating demodulator is arranged at the top of distributed optical fiber temperature measurement optical cable, and is used to collect the center wavelength data of all gratings;Electronic temperature and pressure gauge is arranged at the top of distributed optical fiber temperature measurement optical cable, and is used to measure the temperature data and pressure data of distributed optical fiber temperature measurement optical cable;Electronic temperature and pressure data acquisition equipment is connected with electronic temperature and pressure gauge, and is used to collect the temperature data and pressure data measured by electronic temperature and pressure gauge;Overall control device is connected with grating demodulator and electronic temperature and pressure data acquisition equipment, and based on the center wavelength data of grating and the temperature data and pressure data of distributed optical fiber temperature measurement optical cable, the calibration of the temperature sensitivity of all gratings is completed.

Description

Technical Field

[0001] This invention relates to a distributed optical fiber temperature measurement cable calibration device and calibration method, and belongs to the field of optical fiber sensing technology. Background Technology

[0002] Distributed fiber optic temperature sensing technology, especially that based on fiber Bragg gratings (FBGs), is widely used in fields such as oil and gas, geology, and environmental monitoring due to its advantages such as resistance to electromagnetic interference, intrinsic safety, long measurement distance, and multi-point measurement capability. In these applications, distributed fiber optic temperature sensing cables need to be deployed underground, on the seabed, or in other complex environments, and accurate temperature calibration is crucial for the normal operation of the system.

[0003] The temperature sensitivity of the grating in a distributed fiber optic temperature-sensing cable is relatively fixed in the bare fiber state. However, during the cabling process, due to stresses such as tension, bending, and compression, as well as differences in the thermal expansion coefficients of the protective materials, the temperature sensitivity of the grating may change. This change may vary depending on the position of the grating within the cable. Therefore, accurate temperature sensitivity calibration of the cable after cabling is crucial before use.

[0004] Existing methods for calibrating distributed fiber optic temperature-sensing cables typically involve laboratory testing, using methods such as constant-temperature water baths or temperature and humidity chambers. However, for long-distance cables reaching hundreds or even thousands of meters in length, overall calibration using large-scale constant-temperature equipment is neither practical nor economical. If the distributed fiber optic temperature-sensing cable is coiled and placed in a small constant-temperature device for segmented calibration, the additional stress generated by the coiling will affect the accuracy of the calibration results, failing to reflect the temperature sensitivity characteristics of the cable under actual deployment conditions. Furthermore, calibrating the distributed fiber optic temperature-sensing cable in the laboratory before transporting it to the field for installation means that the cable may still be subject to mechanical stress during transportation and installation, causing further changes in its temperature sensitivity characteristics and rendering the laboratory calibration results invalid.

[0005] Therefore, there is a lack of effective methods in the existing technology for conveniently and accurately calibrating the temperature sensitivity of long-distance distributed optical fiber temperature measurement cables under field conditions. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the prior art. Therefore, in response to the above-mentioned problems, the object of the present invention is to provide a distributed optical fiber temperature measurement cable calibration device and calibration method, which can accurately achieve temperature sensitivity calibration, thereby significantly improving the accuracy of temperature measurement.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0008] In a first aspect, the present invention provides a distributed optical fiber temperature-sensing cable calibration device, which includes a distributed optical fiber temperature-sensing cable, a grating demodulator, an electronic thermobarometer, an electronic thermobaric data acquisition device, and a central control device, wherein: the distributed optical fiber temperature-sensing cable is vertically mounted on a support, and a plurality of gratings are spaced apart inside the distributed optical fiber temperature-sensing cable; the grating demodulator is mounted at the top of the distributed optical fiber temperature-sensing cable and is used to collect the center wavelength data of all the gratings; the electronic thermobarometer is mounted at the top of the distributed optical fiber temperature-sensing cable and is used to measure the temperature and pressure data of the distributed optical fiber temperature-sensing cable; the electronic thermobarometer is connected to the electronic thermobarometer and is used to collect the temperature and pressure data measured by the electronic thermobarometer; the central control device is connected to the grating demodulator and the electronic thermobarometer, and, based on the center wavelength data of the gratings and the temperature and pressure data of the distributed optical fiber temperature-sensing cable, completes the calibration of the temperature sensitivity of all the gratings.

[0009] In some possible implementations, the distributed optical fiber temperature measurement cable includes an optical fiber, a grating, an inner steel tube, a filling layer, and an outer steel tube;

[0010] The filling layer is provided between the inner steel pipe and the outer steel pipe;

[0011] Multiple optical fibers are arranged inside the inner steel tube;

[0012] Each optical fiber is provided with a plurality of gratings at intervals.

[0013] In some possible implementations, the grating demodulator and / or the electronic temperature and pressure data acquisition device are fixedly mounted on the support or wellhead frame.

[0014] In some possible implementations, the support is a tubular column, and the distributed optical fiber temperature measuring cable and / or the electronic thermometer are fixed to the support using clamps.

[0015] Some possible implementations include:

[0016] Complete the installation of each component of the distributed optical fiber temperature measurement cable calibration device to ensure that the distributed optical fiber temperature measurement cable remains straight after installation and fixation, and avoids coiling or twisting.

[0017] The distributed optical fiber temperature measurement cable calibration device is placed vertically in seawater, and the center wavelength data of the grating and the temperature and pressure data of the distributed optical fiber temperature measurement cable are collected synchronously by the grating demodulator and the electronic thermobarometer.

[0018] Calculate using the pressure data collected from the distributed fiber optic temperature sensing cable k The depth of the top of the distributed fiber optic temperature measurement cable at that time ;

[0019] Will k The temperature T( of the distributed fiber optic temperature measurement cable collected at time) k ) and the corresponding depth data h( k By fitting the data, a profile model T(h() of seawater temperature variation with depth is obtained. k ));

[0020] Based on the depth of each grating, the profile model T(h) of the seawater temperature as a function of depth is used. k Estimate k Time of the first m The ambient temperature of the grating That is: for the first m The grating is based on the center wavelength of the acquisition. and the corresponding ambient temperature Obtain data pairs [ , Repeat this step to complete the temperature sensitivity calibration of all gratings.

[0021] Some possible implementations also include a process of pre-labeling the positions of the grating:

[0022] The locations of the electronic thermo-barometer and the grating are determined, and the location of the electronic thermo-barometer is recorded as 0 meters. m The location of grating number is denoted as m Rice, of which, m =1, 2, ..., M.

[0023] In some possible implementations, the center wavelength data of all the gratings and the temperature and pressure data of the electronic thermobarometer are collected at preset times, and all the collected data are stored in the central control device according to the collection time.

[0024] In some possible implementations, the pressure data collected from the distributed fiber optic temperature sensing cable is used to calculate... k The depth of the top of the distributed fiber optic temperature measurement cable at that time The process is as follows:

[0025] The deployment time of the distributed optical fiber temperature measurement cable calibration device is K minutes. k The pressure data from the electronic thermo-barometer at that time is P. (k ),in, k=1, 2, ..., K, then the depth of the top of the distributed optical fiber temperature measurement cable is... The calculation formula is:

[0026]

[0027] Where ρ is the density of seawater and g is the acceleration due to gravity;

[0028] At time k m The depth at which the grating is located is:

[0029] .

[0030] In some possible implementations, the seawater temperature varies with depth using a profile model T(h) based on the depth at which each grating is located. k Estimate k Time of the first m The ambient temperature of the grating :

[0031] .

[0032] In some possible implementations, [ , The formula for linear fitting of the data is: ;

[0033] in, For the first m The temperature sensitivity of the grating is given by b, which is a constant.

[0034] Because the present invention adopts the above technical solution, it has the following characteristics:

[0035] 1. Improved calibration accuracy: This invention performs calibration in a real deployment environment, taking into account the effects of factors such as cable stress, environmental pressure, and temperature gradient on the temperature sensitivity of the grating, resulting in more accurate and reliable sensitivity.

[0036] 2. Solving the problem of long-distance optical cable calibration: This invention overcomes the dependence of traditional laboratory calibration methods on large equipment and the errors caused by the coiling of long-distance optical cables, making it possible to accurately calibrate long-distance distributed optical fiber temperature measurement cables on site.

[0037] 3. Integration with the construction process: This invention integrates the calibration process with offshore drilling or production string lowering construction, eliminating the need for additional calibration steps and equipment, saving time and costs, and improving efficiency.

[0038] 4. Improve system measurement accuracy: By accurately calibrating the temperature sensitivity of each grating, this invention can significantly improve the temperature measurement accuracy of the entire distributed optical fiber temperature measurement cable.

[0039] 5. Strong applicability: This invention is applicable to various application scenarios that require the deployment of distributed optical fiber temperature measurement cables in long-distance environments with temperature and pressure gradients, especially deep-sea oil and gas exploration and development.

[0040] In summary, in addition to being applicable to offshore construction processes, this invention can also be applied to the scenario of deploying distributed optical fiber temperature measurement cables while drilling or in production tubing during oil and gas exploration. Attached Figure Description

[0041] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0042] Figure 1 This is a schematic diagram of the structure of the distributed optical fiber temperature measurement cable calibration device according to an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of the structure of a distributed optical fiber temperature measurement cable according to an embodiment of the present invention.

[0044] Figure 3 This is a schematic diagram of the cross-sectional structure of a distributed optical fiber temperature measurement cable according to an embodiment of the present invention.

[0045] Figure 4 This is a schematic diagram of the arrangement of the grating along the distributed optical fiber temperature measurement cable according to an embodiment of the present invention.

[0046] Figure 5 This is a schematic diagram of the distributed optical fiber temperature measurement cable calibration method of the present invention. Detailed Implementation

[0047] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude 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 construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0048] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0049] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "above," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure.

[0050] Because existing technologies make it difficult to accurately calibrate the temperature sensitivity of long-distance distributed optical fiber temperature-sensing cables under field conditions, this invention provides a calibration device and method for distributed optical fiber temperature-sensing cables. The device includes a distributed optical fiber temperature-sensing cable, a grating demodulator, an electronic thermobarometer, an electronic thermobaric data acquisition device, and a central control device. Specifically: the distributed optical fiber temperature-sensing cable is vertically mounted on a support structure, and several gratings are spaced apart inside the cable; the grating demodulator is located at the top of the cable and is used to collect the center wavelength data of all gratings; the electronic thermobarometer is located at the top of the cable and is used to measure the temperature and pressure data of the cable; the electronic thermobaric data acquisition device is connected to the thermobarometer and is used to collect the temperature and pressure data measured by the thermobarometer; the central control device is connected to the grating demodulator and the electronic thermobaric data acquisition device, and, based on the center wavelength data of the gratings and the temperature and pressure data of the distributed optical fiber temperature-sensing cable, completes the calibration of the temperature sensitivity of all gratings. Therefore, this invention combines the calibration process with the construction process of lowering offshore drill pipes or production tubing, enabling accurate acquisition of the temperature sensitivity of distributed fiber optic temperature measurement cables in actual deployment environments.

[0051] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0052] Example 1: As Figure 1 As shown, the distributed optical fiber temperature measurement cable calibration device provided in this embodiment includes: a tube column 1, a distributed optical fiber temperature measurement cable 2, a grating demodulator 3, an electronic thermobarometer 4, an electronic thermobaric data acquisition device 5, and a central control device 6, wherein:

[0053] The distributed optical fiber temperature measurement cable 2 is fixedly installed on the outside of the column 1. The distributed optical fiber temperature measurement cable 2 has multiple gratings integrated inside.

[0054] A grating demodulator 3 is installed at the top of the distributed optical fiber temperature measurement cable 2. The grating demodulator 3 is fixedly installed on the pipe column 1 or installed on the wellhead frame. The grating demodulator 3 is used to collect the center wavelength data of all gratings in the distributed optical fiber temperature measurement cable 2.

[0055] The electronic thermobarometer 4 is installed on top of the distributed optical fiber temperature measuring cable 2 to measure the temperature and pressure data of the distributed optical fiber temperature measuring cable 2.

[0056] The electronic temperature and pressure data acquisition device 5 is fixed on the tubing string 1 or installed on the wellhead frame, and is connected to the electronic temperature and pressure gauge 4 via cable 7, for acquiring temperature and pressure data measured by the electronic temperature and pressure gauge 4.

[0057] The central control device 6 connects to the grating demodulator 3 and the electronic temperature and pressure data acquisition device 5. Based on the center wavelength data of the grating and the temperature and pressure data of the distributed optical fiber temperature measurement cable 2, it completes the calibration of the temperature sensitivity of all gratings.

[0058] In a preferred embodiment of the present invention, such as Figure 2 , Figure 3 As shown, the distributed optical fiber temperature measurement cable 2 includes optical fibers 21, gratings 22, an inner steel tube 23, a filling layer 24, and an outer steel tube 25. A filling layer 24 is disposed between the inner steel tube 23 and the outer steel tube 25. Multiple optical fibers 21 (two optical fibers are used in this embodiment, but this is not a limitation) are disposed inside the inner steel tube 23. Multiple gratings 22 are engraved on each optical fiber 21. For example, in this embodiment, four gratings 22 are disposed on each optical fiber 21, but this is not a limitation.

[0059] Furthermore, such as Figure 4 As shown, the arrangement of the grating 22 along the distributed optical fiber temperature measurement cable 2 is schematic. The M gratings are numbered 1, 2...M from top to bottom.

[0060] Furthermore, in this implementation, the location of electronic thermobarometer 4 is recorded as 0 meters. m ( m The position of grating 22 (=1, 2, ..., M) is denoted as m rice.

[0061] In a preferred embodiment of the present invention, such as Figure 1 As shown, the tubing 1 can be a drill pipe or a production tubing, etc., and there are no restrictions here.

[0062] Furthermore, the distributed optical fiber temperature measurement cable 2 is fixed on the outside of the column 1. The fixing method can be by using clamps 8 or other special clamps, which are not limited here.

[0063] Furthermore, the electronic thermo-barometer 4 can also be fixed to the tubing 1 by clamps 8 or other special clamps, taking this as an example, but not limited to this.

[0064] Example 2: Figure 5 As shown, the calibration method for the distributed optical fiber temperature measurement cable calibration device provided in this embodiment includes:

[0065] S1. Installation of each module.

[0066] In this embodiment, according to Figure 1 The distributed fiber optic temperature measurement cable calibration device shown is equipped with various modules to ensure that the distributed fiber optic temperature measurement cable 2 remains straight after being fixed, avoiding coiling or twisting, so as to reduce the impact of additional stress on the grating 22.

[0067] In this embodiment, the locations of the electronic thermobarometer 4 and the grating 22 are predetermined, and the location of the electronic thermobarometer 4 is recorded as 0 meters. m ( m The positions of gratings (i.e., 1, 2, ..., M) are denoted as follows: m rice.

[0068] In this embodiment, the distributed optical fiber temperature measurement cable 2 is connected to the grating demodulator 3, and the electronic thermobarometer 4 is connected to the electronic thermobarometer data acquisition device 5. The grating demodulator 3 and the electronic thermobarometer data acquisition device 5 are connected to the central control device 6. The center wavelength data of all gratings 22 and the temperature and pressure data measured by the electronic thermobarometer 4 are collected at preset time intervals (e.g., every 1 minute, but not limited to this). All the collected data are stored in the central control device 6 according to the collection time.

[0069] S2, Lowering of Column 1 and Data Acquisition.

[0070] In this embodiment, the tube string 1 is slowly lowered into the seawater in a vertical position, while data from the grating 22 and the electronic thermobarometer 4 are collected simultaneously. In actual use, the lowering speed of the tube string 1 can be controlled to be slow enough to allow the distributed optical fiber temperature measurement cable 2 sufficient time to reach thermal equilibrium with the surrounding seawater. The lowering speed can be set based on experience and the site environment, and is not limited here.

[0071] Specifically, the total lowering time for tubing string 1 is K minutes. k The temperature data obtained by the electronic thermometer and barometer 4 is T( k The pressure data is P( k ); k Time of the first m ( m The center wavelength data of grating 22 (=1, 2, ..., M) is λ m ( k ),in, k =1, 2...K.

[0072] S3. Calculate depth using pressure data.

[0073] In this embodiment, the pressure data recorded by the electronic thermo-barometer 4 is used for calculation. k Depth of the top of the distributed fiber optic temperature measurement cable 2 :

[0074]

[0075] Where ρ is the density of seawater and g is the acceleration due to gravity. The density of seawater can be determined based on empirical formulas or actual measurement data.

[0076] Furthermore, at time k, the first m The depth at which the grating is located is:

[0077] (2).

[0078] S4. Establish a profile model of seawater temperature variation with depth.

[0079] In this embodiment, the temperature data T( measured by the electronic thermo-barometer 4 at different times) k ) and the corresponding depth data h( k The data points are summarized, and a profile model of seawater temperature variation with depth is fitted using these data points, which describes the functional relationship T(h( k During the fitting process, linear interpolation, polynomial fitting, exponential fitting, or more complex modeling combining historical ocean temperature data can be used, which will not be elaborated here.

[0080] S5. Estimate the ambient temperature of each grating 22.

[0081] In this embodiment, the calculation is performed according to formula (2). k Time of the first m The depth h of the grating m ( k Then, using the temperature profile model T(h( established in step S4) k ))getk Time of the first m The ambient temperature of the grating:

[0082] (3).

[0083] S6. Calibrate the temperature sensitivity of each grating 22.

[0084] In this embodiment, for the first m Grating 22 collects the center wavelength data λ acquired during the entire descent process. m ( k And the corresponding ambient temperature data T estimated in step S5. m ( k ), forming data pairs [ , Repeat this step to complete the temperature sensitivity calibration of all gratings 22.

[0085] Furthermore, , The formula for linear fitting of the data is: (4).

[0086] in, For the first m Temperature sensitivity of the grating b It is a constant.

[0087] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In the description of this specification, the terms "a preferred embodiment," "furthermore," "specifically," "in this embodiment," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments in this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A distributed optical fiber temperature measurement cable calibration device, characterized in that, The distributed optical fiber temperature measurement cable calibration device is placed vertically in seawater. The device includes a distributed optical fiber temperature measurement cable, a grating demodulator, an electronic thermobarometer, an electronic thermobaric data acquisition device, and a central control device, wherein: The distributed optical fiber temperature measurement cable is vertically mounted on a support body, wherein a number of gratings are spaced apart inside the distributed optical fiber temperature measurement cable. The grating demodulator is installed at the top of the distributed optical fiber temperature measurement cable and is used to collect the center wavelength data of all the gratings. The electronic thermobarometer is installed at the top of the distributed optical fiber temperature measurement cable and is used to measure the temperature and pressure data of the distributed optical fiber temperature measurement cable. The electronic temperature and pressure data acquisition device is connected to the electronic thermometer and is used to acquire the temperature and pressure data measured by the electronic thermometer and pressure. The central control device is connected to the grating demodulator and the electronic temperature and pressure data acquisition device. Based on the center wavelength data of the grating and the temperature and pressure data of the distributed optical fiber temperature measurement cable, it uses the pressure data to calculate the depth of the top of the distributed optical fiber temperature measurement cable, establishes a profile model of seawater temperature change with depth, estimates the ambient temperature of each grating, and completes the calibration of the temperature sensitivity of all the gratings.

2. The distributed optical fiber temperature measurement cable calibration device according to claim 1, characterized in that, The distributed optical fiber temperature measurement cable includes an optical fiber, a grating, an inner steel tube, a filling layer, and an outer steel tube; The filling layer is provided between the inner steel pipe and the outer steel pipe; Multiple optical fibers are arranged inside the inner steel tube; Each optical fiber is provided with a plurality of gratings at intervals.

3. The distributed optical fiber temperature measurement cable calibration device according to claim 1, characterized in that, The grating demodulator and / or the electronic temperature and pressure data acquisition device are fixedly mounted on the wellhead frame or the support body.

4. The distributed optical fiber temperature measurement cable calibration device according to claim 1, characterized in that, The support structure is a tubular column, and the distributed optical fiber temperature measurement cable and / or the electronic thermometer are fixed to the support structure with clamps.

5. A calibration method for the distributed optical fiber temperature measurement cable calibration device according to any one of claims 2 to 4, characterized in that, include: Complete the installation of each component of the distributed optical fiber temperature measurement cable calibration device to ensure that the distributed optical fiber temperature measurement cable remains straight after installation and fixation, and avoids coiling or twisting. The distributed optical fiber temperature measurement cable calibration device is placed vertically in seawater, and the center wavelength data of the grating and the temperature and pressure data of the distributed optical fiber temperature measurement cable are collected synchronously by the grating demodulator and the electronic thermobarometer. Calculate using the pressure data collected from the distributed fiber optic temperature sensing cable k The depth of the top of the distributed fiber optic temperature measurement cable at that time ; Will k The temperature T( of the distributed fiber optic temperature measurement cable collected at time) k ) and the corresponding depth data h( k By fitting the data, a profile model T(h() of seawater temperature variation with depth is obtained. k )); Based on the depth of each grating, the profile model T(h) of the seawater temperature as a function of depth is used. k Estimate k Time of the first m The ambient temperature of the grating That is: for the first m The grating is based on the center wavelength of the acquisition. and the corresponding ambient temperature Obtain data pairs [ , Repeat this step to complete the temperature sensitivity calibration of all gratings.

6. The calibration method according to claim 5, characterized in that, It also includes the process of pre-labeling the positions of the grating: The locations of the electronic thermo-barometer and the grating are determined, and the location of the electronic thermo-barometer is recorded as 0 meters. m The location of grating number is denoted as m Rice, of which, m =1, 2, ..., M.

7. The calibration method according to claim 5, characterized in that, The center wavelength data of all the gratings and the temperature and pressure data of the electronic thermobarometer are collected at preset times, and all the collected data are stored in the central control device according to the collection time.

8. The calibration method according to claim 6, characterized in that, Calculate using the pressure data collected from the distributed fiber optic temperature sensing cable k The depth of the top of the distributed fiber optic temperature measurement cable at that time The process is as follows: The deployment time of the distributed optical fiber temperature measurement cable calibration device is K minutes. k The pressure data from the electronic thermo-barometer at that time is P. (k ),in, k =1, 2, ..., K, then the depth of the top of the distributed optical fiber temperature measurement cable is... The calculation formula is: Where ρ is the density of seawater and g is the acceleration due to gravity; At time k m The depth at which the grating is located is: 。 9. The calibration method according to claim 8, characterized in that, Based on the depth of each grating, the profile model T(h) of the seawater temperature as a function of depth is used. k Estimate k Time of the first m The ambient temperature of the grating : 。 10. The calibration method according to claim 9, characterized in that, Will[ , The formula for linear fitting of the data is: ; in, For the first m The temperature sensitivity of the grating is given by b, which is a constant.

Images