A method for measuring salinity

Abstract

An embodiment of the present application provides a salinity measurement method. The method utilizes the characteristic that strain in an optical frequency domain reflectometer system causes changes in the collected signal. The method obtains the signal of a first optical fiber not immersed in a target area and the signal of the first optical fiber after immersion in the target area, and establishes a relationship between the signal change of the first optical fiber and the strain of the first optical fiber. Based on the correspondence between shape and salinity, a correspondence between the signal change and the salinity is then established. By obtaining the signal change of the first optical fiber at each position immersed in the area to be detected, the salinity of each position of the first optical fiber immersed in the area to be detected can be obtained. The signal change of the first optical fiber at each position immersed in the area to be detected can be obtained all at once, reducing the time spent on obtaining salinity and improving the efficiency of salinity detection.

Description

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 11, 2022, with application number 202211412914.X and invention name “A Method for Measuring Salinity”, the entire contents of which are incorporated into this application by application. Technical Field

[0002] The present application relates to the technical field of salinity measurement, and in particular to a salinity measurement method. Background Art

[0003] Salinity is a measure of the total amount of dissolved salts in a solution. In environmental protection settings, determining whether water pollutants meet discharge standards requires obtaining salinity data for each region. Similarly, in marine life research, determining the survival and activity of marine organisms requires obtaining salinity data for each region.

[0004] Currently, there are two ways to obtain the salinity of a solution. First, the salinity of a solution is measured using an electrical sensor. In this method, the salinity of the solution to be detected in each area is obtained based on the conductivity of the solution to be detected in each area where multiple electrical sensors are located. Second, the salinity of a solution is measured using an optical sensor with a prism structure. In this method, the refractive index of the solution to be detected in each area is obtained by using the corresponding prism structure when multiple optical sensors with a prism structure are located in each area where the solution to be detected is distributed. Then, based on the refractive index of the solution to be detected in each area, the salinity of the solution to be detected in each area is obtained.

[0005] However, both of the above methods for obtaining the salinity of any solution require sequentially measuring the salinity of the solution to be measured at multiple different positions. Therefore, obtaining the salinity takes a long time and is inefficient. Summary of the Invention

[0006] The present application provides a salinity measurement method to solve the technical problem that obtaining salinity is time-consuming and inefficient.

[0007] In order to solve the above technical problems, the embodiments of the present application disclose the following technical solutions:

[0008] In a first aspect, embodiments of the present application disclose a salinity measurement method, which is applied to a processor, the processor being connected to an optical frequency domain reflectometry system, wherein a sensing optical fiber of the optical frequency domain reflectometry system includes an optical fiber coated with polyimide, and includes obtaining an initial shape, where the initial shape is the shape of a first optical fiber when not immersed in a target area, the target area being the area where a solution whose salinity has been tested is located, and the target area includes at least one, and the first optical fiber is an optical fiber coated with polyimide;

[0009] Acquiring a reference signal by collecting a signal from the first optical fiber through an optical frequency domain reflectometry system;

[0010] After the first optical fiber is immersed in the target area, a signal of the first optical fiber immersed in the target area is collected by an optical frequency domain reflectometry system to obtain a measurement signal;

[0011] determining, based on the reference signal and the measurement signal, the strain of the first optical fiber when the first optical fiber is immersed in each target area;

[0012] determining a functional relationship between the shape of the first optical fiber and the salinity based on the strain, the initial shape, and the salinity of the solution in each target area;

[0013] The salinity of the solution in each position of the area to be detected is obtained according to the shape of the first optical fiber immersed in the area to be detected and the functional relationship.

[0014] Optionally, determining, based on the reference signal and the measurement signal, the strain of the first optical fiber when the first optical fiber is immersed in each target area, includes:

[0015] Performing fast Fourier transform on the reference signal and the measurement signal respectively;

[0016] determining a length of the first optical fiber;

[0017] scaling the reference signal and the measurement signal after fast Fourier transformation according to the length of the first optical fiber;

[0018] The scaled reference signal and the measured signal are divided into N parts, where N is a preset positive integer, and each part of the reference signal and the measured signal corresponds to the same position in the target area;

[0019] Performing fast inverse Fourier transform on the divided reference signal and measurement signal respectively;

[0020] The strain of the first optical fiber when the first optical fiber is immersed in the target area is determined based on the reference signals and the measurement signal after the fast inverse Fourier transform.

[0021] Optionally, determining the strain of the first optical fiber when the first optical fiber is immersed in the target area based on the reference signals and the measurement signals after fast inverse Fourier transform includes:

[0022] Obtaining back Rayleigh scattering spectrum shift information of the first reference signal and the first measurement signal by performing cross-correlation calculation on the first reference signal and the first measurement signal after fast inverse Fourier transform, where the first reference signal is any one of N reference signals, the first measurement signal is any one of the N measurement signals, and the first reference signal and the first measurement signal correspond to the same position of the target area;

[0023] Determining the strain at each position where the first optical fiber is immersed in the target area based on backscattered Rayleigh scattering spectrum shift information of each first reference signal and the first measurement signal;

[0024] An average value of strains at various positions where the first optical fiber is immersed in the target area is obtained, and the strain of the first optical fiber when immersed in the target area is determined based on the average value.

[0025] Optionally, determining a functional relationship between the shape of the first optical fiber and salinity includes:

[0026] Determine the Lingdon coefficient based on the strain, initial shape, and salinity of each target area;

[0027] According to the sensitivity coefficient, a functional relationship between the shape of the first optical fiber immersed in the target area and the salinity is determined.

[0028] Optionally, determining the length of the first optical fiber includes:

[0029] Acquire the reference signal or the measurement signal after the fast Fourier transform according to the preset acquisition frequency, and obtain the number of signal points corresponding to the reference signal or the number of signal points corresponding to the measurement signal;

[0030] The length of the first optical fiber is determined according to the distance formula of two adjacent signal points, the spatial resolution formula and the length formula of the first optical fiber. The two adjacent signal points are signal points corresponding to two adjacent reference signals or two adjacent measurement signals.

[0031] Optionally, the distance formula between two adjacent signal points is:

[0032] Wherein, ΔZ is the distance between two adjacent signal points, λ represents the central wavelength of the swept tunable light source in the optical frequency domain reflectometry system, n represents the effective refractive index of the first optical fiber, and Δλ represents the scanning range of the swept tunable light source.

[0033] Optionally, the spatial resolution formula is:

[0034] Among them, ΔX is the spatial resolution, M is the number of signal points contained in the spatial resolution, is the distance between two adjacent signal points.

[0035] Optionally, the length formula of the first optical fiber is:

[0036] Where L is the length of the first optical fiber, N is the number of spatial resolutions contained in the first optical fiber, is the spatial resolution.

[0037] Optionally, the optical frequency domain reflectometry system includes a frequency-sweeping tunable light source and an acquisition card, the frequency-sweeping tunable light source is communicatively connected to the acquisition card, and the signal of the first optical fiber is collected through the optical frequency domain reflectometry system to obtain a reference signal, including:

[0038] After the frequency-swept tunable light source emits a frequency-swept laser and the acquisition card acquires the reference signal of the first optical fiber, the reference signal is acquired based on the interaction with the acquisition card.

[0039] Optionally, after the first optical fiber is immersed in the target area, a signal of the first optical fiber immersed in the target area is collected by an optical frequency domain reflectometry system to obtain a measurement signal, including:

[0040] When the first optical fiber is immersed in the target area, the swept frequency tunable light source emits a swept frequency laser, and after the measurement signal of the first optical fiber immersed in the target area is collected by the acquisition card, the measurement signal is obtained according to the interaction with the acquisition card.

[0041] The beneficial effects of the present application are as follows: utilizing the characteristic of an optical frequency domain reflectometry system that strain affects the collected signal, the signal of the first optical fiber before immersion in the target area and the signal of the first optical fiber after immersion in the target area are acquired, and the signal change of the first optical fiber is associated with the strain of the first optical fiber. Based on the correspondence between shape and salinity, a correspondence between the signal change and the salinity is then established. By acquiring the signal change of the first optical fiber at each position immersed in the area to be detected, the salinity of the first optical fiber at each position immersed in the area to be detected can be acquired. The signal change of the first optical fiber at each position immersed in the area to be detected can be acquired in a uniform manner, reducing the time required to acquire salinity and improving the efficiency of salinity detection.

[0042] Furthermore, the optical frequency domain reflection system itself has a high spatial resolution characteristic. The higher the spatial resolution, the smaller the distance between each position of the area to be detected in which the first optical fiber is immersed, and the more detailed the salinity of the area to be detected in which the first optical fiber is immersed. Therefore, the present application improves the detail of obtaining the salinity of the solution distributed at each position of the area to be detected by utilizing the optical frequency domain reflection system when detecting salinity.

[0043] Furthermore, in the scenario of environmental protection, it is convenient to obtain the salinity of water pollutants distributed in various regions based on the salinity distribution, so that it is easy to judge whether the water pollutants meet the emission standards; in the scenario of marine life research, it is convenient to obtain the salinity of seawater distributed in various regions based on the salinity distribution, so that it is easy to judge the survival and activity conditions of marine organisms.

[0044] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0046] Figure 1 A schematic diagram of a salinity measurement method provided in an embodiment of the present application;

[0047] Figure 2 A schematic flow chart of another salinity measurement method provided in an embodiment of the present application;

[0048] Figure 3 A schematic diagram of the structure of the optical frequency domain reflectometry system provided in an embodiment of the present application;

[0049] Figure 4 A schematic diagram of the cross-correlation principle provided in an embodiment of the present application;

[0050] Figure 5 This is a structural schematic diagram of a salinity measurement device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0052] To facilitate the technical solution of the application, some concepts involved in this application are first explained below.

[0053] The reference signal is the backscattered Rayleigh signal of the first optical fiber in the initial shape, the measurement signal is the backscattered Rayleigh signal of the first optical fiber after being immersed in the target area, and the signal point is the reference signal point or measurement signal point obtained by collecting the reference signal or measurement signal after fast Fourier transformation according to a preset acquisition frequency.

[0054] See also Figure 1 and Figure 2 The embodiment of the present application provides a salinity measurement method, which is applied to a processor, the processor is connected to an optical frequency domain reflectometry system, and the sensing optical fiber of the optical frequency domain reflectometry system includes an optical fiber coated with polyimide, including the following steps:

[0055] Step S110: obtaining an initial shape, which is the shape of the first optical fiber when it is not immersed in the target area. The target area is the area where the solution with detected salinity is located, and the target area includes at least one. The first optical fiber is an optical fiber coated with polyimide.

[0056] Step S120: collecting the signal of the first optical fiber through an optical frequency domain reflectometry system to obtain a reference signal.

[0057] In some embodiments, see Figure 3 The optical frequency domain reflection system includes a tunable light source, three couplers, a Mach-Zehnder interferometer, an acquisition card, two polarization controllers, a polarization beam splitter, a detector, a circulator and a sensing fiber. The three couplers are respectively a first coupler, a second coupler and a third coupler, and the two polarization controllers are respectively a first polarization controller and a second polarization controller. The tunable light source can be optionally a tunable laser.

[0058] When the tunable light source is a tunable laser, the continuous laser output of the tunable light source is split into two parts by a first coupler (10 / 90 optical coupler). 10% of the laser light is incident on an unbalanced Mach-Zehnder interferometer, providing a trigger signal for the acquisition card, while the remaining 90% of the laser light enters a second coupler. A second coupler (1 / 99 optical coupler) splits the 90% of the laser light into two parts: a 1% portion and a 99% portion. The 99% portion passes through a circulator and a second polarization controller and enters the sensing fiber for detection. Furthermore, the 1% portion undergoes polarization adjustment via the first polarization controller. The Rayleigh scattered signal and the polarization-adjusted 1% portion are then input into a third coupler (50 / 50 optical coupler). The Rayleigh scattered signal and the polarization-adjusted 1% portion are combined within the third coupler (50 / 50 optical coupler) to generate an interference signal. This interference signal is then decomposed into a "p" light component and an "s" light component by a polarization beam splitter. Finally, the "p" and "s" light components are captured by the acquisition card. The polarization adjustment of the first polarization controller is used to ensure that the “p” light component and the “s” light component decomposed by the polarization beam splitter have the same power.

[0059] In some embodiments, the optical frequency domain reflection system includes a swept-frequency tunable light source and an acquisition card. The swept-frequency tunable light source is communicatively connected to the acquisition card. After the swept-frequency tunable light source emits a swept-frequency laser and the acquisition card acquires the reference signal of the first optical fiber, the reference signal is obtained based on the interaction with the acquisition card.

[0060] Step S130: After the first optical fiber is immersed in the target area, the signal of the first optical fiber immersed in the target area is collected by an optical frequency domain reflectometry system to obtain a measurement signal.

[0061] In some embodiments, after the first optical fiber is immersed in the target area, the swept frequency tunable light source emits a swept frequency laser, and the measurement signal of the first optical fiber immersed in the target area is collected by the acquisition card, the measurement signal is obtained based on the interaction with the acquisition card.

[0062] Step S140: determining the strain of the first optical fiber when the first optical fiber is immersed in each target area according to the reference signal and the measurement signal.

[0063] In some embodiments, the strain of the first optical fiber when the first optical fiber is immersed in each target area can be determined by the following steps:

[0064] Performing fast Fourier transform on the reference signal and the measurement signal respectively;

[0065] determining a length of the first optical fiber;

[0066] scaling the reference signal and the measurement signal after fast Fourier transformation according to the length of the first optical fiber;

[0067] The scaled reference signal and the measured signal are divided into N parts, where N is a preset positive integer, and each part of the reference signal and the measured signal corresponds to the same position in the target area;

[0068] Performing fast inverse Fourier transform on the divided reference signal and measurement signal respectively;

[0069] The strain of the first optical fiber when the first optical fiber is immersed in the target area is determined based on the reference signals and the measurement signal after the fast inverse Fourier transform.

[0070] In some embodiments, the reference signal and the measurement signal are mapped from the optical frequency domain to the distance domain using a fast Fourier algorithm through data processing software, and the reference signal and the measurement signal after fast Fourier transformation are scaled according to the length of the first optical fiber until the length of the reference signal and the measurement signal in the distance domain is equal to the length of the first optical fiber.

[0071] A sliding window is used in the distance domain to divide the reference signal and the measurement signal in the distance domain into N parts, where N is a preset positive integer. Each part of the reference signal and the measurement signal corresponds to a position in the target area. The size of the sliding window is determined by the spatial resolution of the optical frequency domain reflection system, and the size of the sliding window is the same as the spatial resolution of the optical frequency domain reflection system.

[0072] In some embodiments, the length of the first optical fiber may be determined according to the following steps:

[0073] Acquire the reference signal or the measurement signal after the fast Fourier transform according to the preset acquisition frequency, and obtain the number of signal points corresponding to the reference signal or the number of signal points corresponding to the measurement signal;

[0074] The length of the first optical fiber is determined according to the distance formula of two adjacent signal points, the spatial resolution formula and the length formula of the first optical fiber. The two adjacent signal points are signal points corresponding to two adjacent reference signals or two adjacent measurement signals.

[0075] In some embodiments, the distance formula between two adjacent signal points is:

[0076] Wherein, ΔZ is the distance between two adjacent signal points, λ represents the central wavelength of the swept tunable light source in the optical frequency domain reflectometry system, n represents the effective refractive index of the first optical fiber, and Δλ represents the scanning range of the swept tunable light source.

[0077] In some embodiments, the spatial resolution formula is:

[0078] Among them, ΔX is the spatial resolution, M is the number of signal points contained in the spatial resolution, is the distance between two adjacent signal points.

[0079] In some embodiments, the length of the first optical fiber is calculated as follows:

[0080] Where L is the length of the first optical fiber, N is the number of spatial resolutions contained in the first optical fiber, is the spatial resolution.

[0081] In some embodiments, the strain of the first optical fiber when the first optical fiber is immersed in the target area may be determined by the following steps:

[0082] Obtaining back Rayleigh scattering spectrum shift information of the first reference signal and the first measurement signal by performing cross-correlation calculation on the first reference signal and the first measurement signal after fast inverse Fourier transform, where the first reference signal is any one of N reference signals, the first measurement signal is any one of the N measurement signals, and the first reference signal and the first measurement signal correspond to the same position of the target area;

[0083] Determining the strain at each position where the first optical fiber is immersed in the target area based on backscattered Rayleigh scattering spectrum shift information of each first reference signal and the first measurement signal;

[0084] An average value of strains at various positions where the first optical fiber is immersed in the target area is obtained, and the strain of the first optical fiber when immersed in the target area is determined based on the average value.

[0085] In some embodiments, as Figure 2 As shown, the tunable light source of the optical frequency domain reflectometer system performs a scan, including a reference scan when the first optical fiber is not immersed in the target area and a test scan after the first optical fiber is immersed in the target area. Raw data corresponding to the reference scan is acquired through the reference scan, including a reference signal acquired based on the reference scan. Raw data corresponding to the test scan is acquired through the test scan, including a measurement signal acquired based on the reference scan. A fast Fourier transform is performed on these two types of raw data to determine the length of the first optical fiber. Based on the length of the first optical fiber, these two types of raw data are scaled and divided into n segments, where n is a preset positive integer. Each segment of the raw data corresponds to a location in the target area. Each segment contains m data points, which are reference signal points or measurement signal points acquired by acquiring the fast Fourier transformed raw data at a preset acquisition frequency. Perform a fast inverse Fourier transform on any segment of the raw data i, and obtain a spectrum offset obtained by cross-correlation calculation between the reference signal and the measurement signal for each segment of the raw data after the fast inverse Fourier transform. Determine the strain of the first optical fiber when the first optical fiber is immersed in the target area based on the spectrum offset.

[0086] In some embodiments, as Figure 4 As shown, when the shape of the first optical fiber does not change, the central peak obtained by cross-correlating the reference signal and the measurement signal will not change, as shown by the solid line; when the shape of the first optical fiber changes, the central peak obtained by cross-correlating the reference signal and the measurement signal will shift, as shown by the dotted line.

[0087] Step S150: determining a functional relationship between the shape of the first optical fiber and the salinity according to the strain, the initial shape, and the salinity of the solution in each target area.

[0088] In some embodiments, the function relationship between the shape of the first optical fiber and the salinity is determined by the following steps:

[0089] Determine the Lingdon coefficient based on the strain, initial shape, and salinity of each target area;

[0090] According to the Salinity coefficient, a functional relationship between the shape of the first optical fiber immersed in the target area and the salinity is determined.

[0091] Step S160: obtaining the salinity of the solution at each position in the area to be detected based on the shape and functional relationship of the first optical fiber immersed in the area to be detected.

[0092] As can be seen from the above embodiments, the embodiments of the present application provide a salinity measurement method. The method utilizes the characteristic that the optical frequency domain reflection system is affected by strain, which causes changes in the collected signal. The method obtains the signal of the first optical fiber that is not immersed in the target area and the signal of the first optical fiber after being immersed in the target area, and establishes a relationship between the signal change of the first optical fiber and the strain of the first optical fiber. Then, based on the correspondence between shape and salinity, a correspondence between the signal change and the salinity is established. By obtaining the signal change of the first optical fiber at each position immersed in the area to be detected, the salinity of the first optical fiber at each position immersed in the area to be detected can be obtained. The signal change of the first optical fiber at each position immersed in the area to be detected can be obtained at one time, which reduces the time spent on obtaining salinity and improves the efficiency of detecting salinity.

[0093] Furthermore, the optical frequency domain reflection system itself has a high spatial resolution characteristic. The higher the spatial resolution, the smaller the distance between each position of the area to be detected in which the first optical fiber is immersed, and the more detailed the salinity of the area to be detected in which the first optical fiber is immersed. Therefore, the present application improves the detail of obtaining the salinity of the solution distributed at each position of the area to be detected by utilizing the optical frequency domain reflection system when detecting salinity.

[0094] Furthermore, in the scenario of environmental protection, it is convenient to obtain the salinity of water pollutants distributed in various regions based on the salinity distribution, so that it is easy to judge whether the water pollutants meet the emission standards; in the scenario of marine life research, it is convenient to obtain the salinity of seawater distributed in various regions based on the salinity distribution, so that it is easy to judge the survival and activity conditions of marine organisms.

[0095] like Figure 5 As shown, corresponding to the aforementioned embodiment of a salinity measurement method, the present application also provides an embodiment of a salinity measurement device. The device is applied to a processor, the processor being connected to an optical frequency domain reflectometry system, the optical frequency domain reflectometry system having a sensing optical fiber comprising an optical fiber coated with polyimide, and includes: an initial shape acquisition module, a reference signal acquisition module, a measurement signal acquisition module, a strain determination module, a functional relationship determination module, and a salinity acquisition module. The reference signal acquisition module and the measurement signal acquisition module are both communicatively connected to the strain determination module, the initial shape acquisition module and the strain determination module are both communicatively connected to the functional relationship determination module, and the functional relationship determination module is communicatively connected to the salinity acquisition module.

[0096] The initial shape acquisition module is used to acquire an initial shape, where the initial shape is the shape of the first optical fiber when it is not immersed in a target area. The target area is the area where the solution with detected salinity is located, and the target area includes at least one. The first optical fiber is the optical fiber coated with polyimide.

[0097] The reference signal acquisition module is used to collect the signal of the first optical fiber through the optical frequency domain reflectometry system to obtain a reference signal.

[0098] In some embodiments, the optical frequency domain reflection system includes a swept-frequency tunable light source and an acquisition card, the swept-frequency tunable light source is communicatively connected to the acquisition card, and the reference signal acquisition module is specifically used to obtain the reference signal based on the interaction with the acquisition card after the swept-frequency tunable light source emits a swept-frequency laser and the acquisition card acquires the reference signal of the first optical fiber.

[0099] The measurement signal acquisition module is configured to collect a signal of the first optical fiber immersed in the target area through the optical frequency domain reflectometry system to acquire a measurement signal after the first optical fiber is immersed in the target area.

[0100] In some embodiments, the measurement signal acquisition module is specifically used to, after the first optical fiber is immersed in the target area, emit a swept-frequency laser from a swept-frequency tunable light source, and collect the measurement signal of the first optical fiber after being immersed in the target area through an acquisition card, and then obtain the measurement signal based on the interaction with the acquisition card.

[0101] The strain determination module is configured to determine the strain of the first optical fiber when the first optical fiber is immersed in each of the target areas according to the reference signal and the measurement signal.

[0102] In some embodiments, the strain determination module is specifically configured to obtain backscattered Rayleigh scattering spectrum shift information of the first reference signal and the first measurement signal by performing cross-correlation calculation on the first reference signal and the first measurement signal after fast inverse Fourier transform, where the first reference signal is any one of N reference signals, the first measurement signal is any one of the N measurement signals, and the first reference signal and the first measurement signal correspond to the same position of the target area;

[0103] Determining the strain at each position where the first optical fiber is immersed in the target area based on backscattered Rayleigh scattering spectrum shift information of each first reference signal and the first measurement signal;

[0104] An average value of strains at various positions where the first optical fiber is immersed in the target area is obtained, and the strain of the first optical fiber when immersed in the target area is determined based on the average value.

[0105] The functional relationship determination module is configured to determine the functional relationship between the shape of the first optical fiber and the salinity according to the strain, the initial shape, and the salinity of the solution in each of the target areas.

[0106] In some embodiments, the functional relationship determination module is specifically configured to determine the Ringdon coefficient based on the strain, the initial shape, and the salinity of each target area; and determine the functional relationship between the shape of the first optical fiber and the salinity based on the sensitivity coefficient.

[0107] The salinity acquisition module is used to acquire the salinity of the solution at various positions in the area to be detected based on the shape of the first optical fiber immersed in the area to be detected and the functional relationship.

[0108] As can be seen from the above embodiments, the salinity measurement device provided in the embodiments of the present application utilizes the characteristic that strain in an optical frequency domain reflectometry system causes changes in the collected signal. A reference signal acquisition module is used to acquire the signal of a first optical fiber that is not immersed in a target area. A measurement signal acquisition module is used to acquire the signal of the first optical fiber after immersion in the target area. An initial shape acquisition module, a strain determination module, and a functional relationship determination module are used to establish a relationship between the signal change of the first optical fiber and the strain of the first optical fiber. Based on the correspondence between shape and salinity, a correspondence between the signal change and salinity is established. The salinity acquisition module is used to acquire the salinity of each position of the first optical fiber immersed in the area to be detected by acquiring the signal change of the first optical fiber at each position of the area to be detected. The signal change of the first optical fiber at each position of the area to be detected can be acquired all at once, reducing the time required to acquire salinity and improving the efficiency of salinity detection.

[0109] Furthermore, the optical frequency domain reflection system itself has a high spatial resolution characteristic. The higher the spatial resolution, the smaller the distance between each position of the area to be detected in which the first optical fiber is immersed, and the more detailed the salinity of the area to be detected in which the first optical fiber is immersed. Therefore, the present application improves the detail of obtaining the salinity of the solution distributed at each position of the area to be detected by utilizing the optical frequency domain reflection system when detecting salinity.

[0110] Furthermore, in the scenario of environmental protection, it is convenient to obtain the salinity of water pollutants distributed in various regions based on the salinity distribution, so that it is easy to judge whether the water pollutants meet the emission standards; in the scenario of marine life research, it is convenient to obtain the salinity of seawater distributed in various regions based on the salinity distribution, so that it is easy to judge the survival and activity conditions of marine organisms.

[0111] Since the above embodiments are all described by reference in combination with other embodiments, different embodiments have the same parts, and the same and similar parts between the various embodiments in this specification can be referred to each other. No further detailed explanation is given here.

[0112] It should be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a circuit structure, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such circuit structure, article or device. In the absence of further restrictions, the presence of an element defined by the phrase "includes a..." does not exclude the presence of other identical elements in the circuit structure, article or device comprising the element.

[0113] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the disclosure of the invention herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0114] The above-described embodiments of the present application do not constitute a limitation on the scope of protection of the present application.

Claims

1. A salinity measurement method, characterized in that: Applied to a processor, the processor is connected to an optical frequency domain reflectometry system, the sensing optical fiber of the optical frequency domain reflectometry system includes an optical fiber coated with polyimide, and the salinity measurement method includes: Acquiring an initial shape, where the initial shape is the shape of the first optical fiber when it is not immersed in a target area, where the target area is an area where a solution of known salinity is located, and the target area includes at least one, and the first optical fiber is the optical fiber coated with polyimide; collecting the signal of the first optical fiber by the optical frequency domain reflectometry system to obtain a reference signal; After the first optical fiber is immersed in the target area, a signal of the first optical fiber immersed in the target area is collected by the optical frequency domain reflectometry system to obtain a measurement signal; determining, based on the reference signal and the measurement signal, the strain of the first optical fiber when the first optical fiber is immersed in each of the target areas; determining a functional relationship between the shape of the first optical fiber and the salinity according to the strain, the initial shape, and the salinity of the solution in each of the target areas; obtaining the salinity of the solution at each position in the area to be detected based on the shape of the first optical fiber immersed in the area to be detected and the functional relationship; The determining, based on the reference signal and the measurement signal, the strain of the first optical fiber when the first optical fiber is immersed in each of the target areas, includes: performing fast Fourier transform on the reference signal and the measurement signal respectively; determining a length of the first optical fiber; Scaling the reference signal and the measurement signal after fast Fourier transformation according to the length of the first optical fiber; Dividing the scaled reference signal and the measurement signal into N parts, where N is a preset positive integer, and each part of the reference signal and the measurement signal corresponds to the same position of the target area; performing fast inverse Fourier transform on the divided reference signal and the measurement signal respectively; determining, based on each of the reference signals and the measurement signal after fast inverse Fourier transformation, a strain of the first optical fiber when the first optical fiber is immersed in the target area; The determining, based on each of the reference signals and the measurement signal after fast inverse Fourier transform, the strain of the first optical fiber when the first optical fiber is immersed in the target area includes: Obtaining back Rayleigh scattering spectrum shift information of a first reference signal and a first measurement signal by performing cross-correlation calculation on a first reference signal and a first measurement signal after fast inverse Fourier transform, where the first reference signal is any one of N reference signals, the first measurement signal is any one of the N measurement signals, and the first reference signal and the first measurement signal correspond to the same position of the target area; determining the strain at each position where the first optical fiber is immersed in the target area based on backscattered Rayleigh scattering spectrum shift information of each of the first reference signal and the first measurement signal; obtaining an average value of strains at various positions of the first optical fiber immersed in the target area, and determining the strain of the first optical fiber when immersed in the target area based on the average value; Determining the functional relationship between the shape of the first optical fiber and the salinity includes: determining a sensitivity coefficient according to the strain, the initial shape, and the salinity of each of the target areas; A functional relationship between the shape of the first optical fiber immersed in the target area and the salinity is determined according to the sensitivity coefficient.

2. The salinity measurement method according to claim 1, characterized in that: Determining the length of the first optical fiber includes: Acquire the reference signal or the measurement signal after fast Fourier transformation according to a preset acquisition frequency, and obtain the number of signal points corresponding to the reference signal or the number of signal points corresponding to the measurement signal; The length of the first optical fiber is determined according to the distance formula of the two adjacent signal points, the spatial resolution formula and the length formula of the first optical fiber, where the two adjacent signal points are signal points corresponding to the two adjacent reference signals, or signal points corresponding to the two adjacent measurement signals.

3. The salinity measurement method according to claim 2, characterized in that: The distance formula between two adjacent signal points is: Wherein, ΔZ is the distance between two adjacent signal points, λ represents the central wavelength of the swept tunable light source in the optical frequency domain reflection system, n represents the effective refractive index of the first optical fiber, and Δλ represents the scanning range of the swept tunable light source.

4. The salinity measurement method according to claim 2, characterized in that: The spatial resolution formula is: Wherein, ΔX is the spatial resolution, M is the number of signal points contained in the spatial resolution, is the distance between two adjacent signal points.

5. The salinity measurement method according to claim 2, characterized in that: The length formula of the first optical fiber is: Where L is the length of the first optical fiber, N is the number of spatial resolutions contained in the first optical fiber, is the spatial resolution.

6. The salinity measurement method according to claim 1, characterized in that: The optical frequency domain reflectometry system includes a frequency-sweeping tunable light source and an acquisition card, wherein the frequency-sweeping tunable light source is communicatively connected to the acquisition card. The optical frequency domain reflectometry system is used to collect the signal of the first optical fiber to obtain a reference signal, including: After the frequency-sweeping tunable light source emits frequency-sweeping laser light and the acquisition card acquires the reference signal of the first optical fiber, the reference signal is acquired based on interaction with the acquisition card.

7. The salinity measurement method according to claim 6, characterized in that: After the first optical fiber is immersed in the target area, collecting a signal of the first optical fiber immersed in the target area by the optical frequency domain reflectometry system to obtain a measurement signal includes: After the first optical fiber is immersed in the target area, the swept tunable light source emits a swept laser, and the acquisition card collects the measurement signal of the first optical fiber immersed in the target area, the measurement signal is obtained based on the interaction with the acquisition card.

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