CN106442340B - Device and method for detecting seawater salinity by long-period fiber gratings - Google Patents
Device and method for detecting seawater salinity by long-period fiber gratings Download PDFInfo
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Abstract
The invention discloses a seawater salinity detection device and method based on a long-period grating, wherein an optical fiber coupler (2) is input into an optical fiber connector P 0 Is connected with a light source (1); output optical fiber joint P of optical fiber coupler (2) 2 Is connected with a spectrometer (9) and is provided with an output optical fiber connector P 1 Is connected with one end face of the optical fiber carved with the long period grating (6); the optical fiber of the grating area part of the long period grating (6) is straightened and fixed on a bracket (3) comprising a concave liquid groove (5), and the flat end surface of the other end of the optical fiber carved with the long period grating (6) is plated with a reflecting film (8); the output port of the spectrometer (9) and the temperature sensor module (7) are respectively connected with the signal acquisition module (10), the signal acquisition module (10) is connected with the A/D conversion module (11), and the A/D conversion module (11) is connected with the singlechip (12). The device has the advantages of small volume, light weight, corrosion resistance, high sensitivity and electromagnetic interference resistance.
Description
Technical Field
The invention relates to the technical field of seawater salinity detection, in particular to a device and a method for detecting seawater salinity by a long-period fiber grating.
Background
Salinity is an important parameter of sea water, and many phenomena and processes occurring in the sea have a close relationship with the distribution variation of salinity. The method has the advantages that the method accurately detects the salinity of the seawater, has very important significance and guidance effects on researching a plurality of marine activities such as marine circulation, marine environment protection, marine climate prediction, marine resource exploration, marine resource development and utilization, mariculture, military channel measurement and the like and on marine scientific research, and can provide very important services and guarantees for economic activities on the ocean in China, particularly marine military activities.
Along with the continuous progress of ocean understanding and science and technology, various measurement technologies for detecting the salinity of the seawater are proposed, mainly including a conductivity method, a surface plasma resonance method, a microwave space remote sensing method, a Brillouin scattering method, a Raman spectroscopy, an ultraviolet spectroscopy, nuclear magnetic resonance and the like, as disclosed in instrument and meter journal 2005.26 (8), and published in a novel salinity optical sensor based on a surface plasma resonance principle such as Wu Yingcai, fu Yunliang and the like, photoelectric technology application 2011.07 (10) discloses a novel seawater salinity measuring technique by the combination of cunning and Liu Lanjun, a technical scheme for measuring the seawater salinity by a conductivity method is introduced, and ocean technology 2006.25 (3) discloses a pool experiment study of remote sensing of the seawater salinity by a microwave radiometer by the combination of Liu Zhaoshi, shi Jiuxin and the like. The conductivity method has high measurement precision and can be continuously detected on site, but the conductivity is obtained by taking salinity, temperature and pressure as parameters, errors caused by asynchronous three parameters exist, and the electrode is easy to damage and is easy to influence the measurement precision due to water quality pollution and electromagnetic interference; the microwave remote sensing method is convenient and quick, can continuously and dynamically monitor the salinity of the seawater in real time in a large area throughout the day, is only suitable for measuring the surface of the seawater due to weak microwave penetration capacity (a few millimeters), limits the application range of the method, is easily influenced by external factors, and has low measurement accuracy; the surface plasma resonance method, the Brillouin scattering+jet method, the ultraviolet absorption spectrometry, the nuclear magnetic resonance technology and other instruments have complex structures and huge volumes, and are difficult to be used for on-site real-time detection of the salinity of the seawater.
In view of the importance of seawater salinity detection, there have also appeared in recent years a number of patents for detecting seawater salinity.
Application number 201510412705.9 discloses a method for manufacturing rhodium electrodes on a sapphire substrate for detecting seawater salinity; the application No. 201310561955.X patent discloses a method of a contact pt four electrode salinity sensor based on MEMS technology; the application number 201410612672.8 patent discloses a salinity detection method which takes two parallel plates as polar plates and takes two gold fingers with brass gold-plated surfaces arranged in parallel as probes; the patent application number CN201210244182.8 discloses a seawater salinity measuring device comprising elements such as a conductivity cell, a constant temperature tank, a high-precision standard resistor, a sine wave generator, a voltage signal converter and the like. The methods of the patents are all conducted in an electrode mode, and the detection of the salinity of the seawater is realized through the acquisition of signals such as voltage, current, electric conduction and the like. The electrode type salinity sensor is easy to be corroded by seawater and interfered by electromagnetic, and polarization phenomenon is easy to occur in the long-term use process of the electrode, so that the accuracy of measurement is affected, and the service life of the electrode type salinity sensor is prolonged.
Application number 201310006396.6 discloses a method for measuring the salinity of seawater by utilizing the refractive index effect generated by a flow injection spectrophotometry, but the method which only depends on spectrophotometry is easily affected by substances with ultraviolet or fluorescence absorption characteristics, and the accuracy of seawater measurement needs to be further improved. Application number 201010603445.0 discloses a seawater salinity detection device with multiple refraction of prism models, which utilizes multiple refraction of light beams among optical glass of a group of prism models to test seawater salinity, and the structure is relatively complex due to multiple use of prism glass blocks. Application number 02117422.9 discloses a method and a device for detecting salinity of seawater by using optical fibers, wherein the principle is that salinity measurement is realized by detecting light spot position change on a CCD photosensitive surface caused by refractive index change of different salinity, but the device adopts a prism structure for measuring refractive index, so that the volume of the detection device is expanded intangibly, and the influence of temperature change on light deflection is not considered. Application number 201410425894.9 discloses a method for measuring seawater salinity by using a micro-nano optical fiber annular cavity sensor, but the tail end of a standard single-mode optical fiber is required to be thinned in the process of manufacturing the micro-nano optical fiber annular cavity, so that the capability of resisting mechanical interference of the optical fiber is reduced. Application number 201120543880.9 discloses a sensor for measuring seawater salinity based on FBG, in which a corroded bragg grating is used, so that the mechanical strength of the sensor is reduced, and the sensitivity of the bragg grating is far lower than that of a long-period grating.
The above patents and methods have some defects and limitations which are difficult to overcome, and the device and the system for detecting the salinity of the seawater cannot perform long-term reliable real-time monitoring in complex and changeable marine environments, and cannot meet the requirements of modern marine surveys. Therefore, the development of a novel salinity sensor which is firm, reliable, small in size, high in precision, capable of realizing long-distance signal transmission and strong in corrosion resistance and interference resistance is a current urgent problem to be solved.
Disclosure of Invention
The invention aims to provide a device and a method for detecting the salinity of seawater by a long-period fiber grating, which are used for solving the problems in the prior art, so that the device for detecting the salinity of the seawater has the advantages of small volume, light weight, corrosion resistance, high sensitivity and electromagnetic interference resistance.
In order to achieve the above object, the present invention provides the following solutions:
the invention provides a seawater salinity detection device based on a long-period grating, which comprises a light source, an optical fiber coupler, a liquid tank, a long-period grating, a temperature sensor module, a spectrometer, a signal acquisition module, an A/D conversion module, a singlechip and an output module, wherein the light source is connected with the optical fiber coupler; optical fiber connector P of input end of optical fiber coupler 0 Is connected with the light source; second output optical fiber joint P of the optical fiber coupler 2 A first output optical fiber connector P connected with the spectrometer 1 Is connected with one end face of the optical fiber carved with the long period grating; the optical fiber of the grating area part of the long period grating is straightened and fixed on a bracket containing a concave liquid tank capable of containing seawater, and the flat end surface of the other end of the optical fiber carved with the long period grating is plated with a reflecting film; the output port of the spectrometer and the temperature sensor module are respectively connected with the signal acquisition module, the signal acquisition module is connected with the A/D conversion module, the A/D conversion module is connected with the singlechip, and the singlechip is connected with the output module.
Optionally, the temperature sensor module is placed in a liquid tank of a bracket of the fixed long period grating.
Optionally, the fiber coupler is a 2×2 single mode fiber coupler.
Optionally, the long-period grating is a bare long-period grating which is not modified by a nano-film, a long-period grating etched by hydrofluoric acid or a long-period grating modified by various nano-film materials on the surface of the grating region cladding.
Optionally, the output module includes at least one of a liquid crystal display, a mobile phone, or a computer.
The invention also provides a seawater salinity detection method based on the long-period grating, which comprises the following steps:
firstly, an optical fiber connector P at the input end of an optical fiber coupler is connected 0 An optical fiber connector P connected with the light source and at the output end of the optical fiber coupler 2 Another optical fiber connector P at the output end of the optical fiber coupler connected with the spectrometer 1 Is connected with one end face of the optical fiber carved with the long period grating; the optical fiber of the grating area part of the long period grating is straightened and fixed on a bracket containing a concave liquid tank capable of containing seawater, and the flat end surface of the other end of the optical fiber carved with the long period grating is plated with a reflecting film; the output port of the spectrometer and the temperature sensor module are respectively connected with the signal acquisition module, then the signal acquisition module is connected with the A/D conversion module, the A/D conversion module is connected with the singlechip, and the salinity value is displayed through the liquid crystal display, or the salinity data is read and stored on a mobile phone or a computer through Bluetooth, WIFI or USB ports;
preparing a series of standard salinity solutions, then testing the prepared standard solution by using a fixed long-period grating at a certain constant temperature, and then carrying out algorithm processing on signals and data to prepare a standard curve of the variation relation between salinity and resonant wavelength and resonant intensity values;
step three, gradually increasing or reducing the temperature of the long-period grating, synchronously testing the resonance wavelength and the resonance intensity variation value of the fixed long-period grating in pure water, and then carrying out algorithm processing on the signals and the data to obtain a standard curve of the corresponding relation between the resonance wavelength and the resonance intensity variation value of the long-period grating and the temperature;
testing the seawater in the real seawater environment in real time by using a fixed long-period grating and a temperature sensor module, subtracting the resonance wavelength or the resonance intensity variation value of the long-period grating caused by temperature from the resonance wavelength and the resonance intensity value of the long-period grating measured in the real seawater, and comparing the resonance wavelength and the resonance intensity value obtained after correction with a standard curve of salinity to obtain the salinity value of the seawater;
and fifthly, displaying the numerical value of the seawater salinity through a liquid crystal display screen, or reading and storing the seawater salinity data on a mobile phone or a computer through a Bluetooth, WIFI or USB port.
Optionally, the long period grating in the second step estimates the salinity of the water by sensing the refractive index of the water.
Optionally, in the first step, the method adopted for plating the reflective film on the flat end surface of the optical fiber end of the long period grating is a sputtering method, an evaporation method, an atomic layer deposition method or a chemical wet method.
Compared with the prior art, the invention has the following technical effects:
(1) the electromagnetic interference is resisted, and the salinity of the seawater can be reflected more accurately and truly; (2) corrosion resistance, and is very suitable for long-term use in seawater; (3) the device has light weight, small volume and easy networking, and is beneficial to realizing online continuous automatic remote telemetry of the salinity of the seawater; (4) the application range is wide, the salinity near the sea level can be measured, and the method is particularly suitable for salinity detection in the deep ocean;
compared with other seawater salinity optical fiber sensing devices such as Bragg gratings, micro-nano optical fiber annular cavities and the like, the long-period grating seawater salinity sensor has higher sensitivity, and can more accurately distinguish the tiny change of the seawater salinity;
because the long period grating is easily influenced by the bending, the temperature and the salinity of the seawater, in practical application, the influence of the bending and the temperature in the seawater on the transmission spectrum of the long period grating is deducted, so that the real salinity of the seawater can be accurately measured. According to the invention, the long-period grating is straightened and fixed on the concave liquid tank bracket, so that the cross influence of bending on the transmission spectrum of the long-period grating is avoided; by adding a temperature sensor module and algorithm processing, the cross influence of temperature on the transmission spectrum of the long-period grating is eliminated; by utilizing the optical fiber coupler and the mode of preparing the reflecting film on the optical fiber end face of the long-period grating, the transmission spectrum display mode of the long-period grating is reserved, and the long-period grating is more beneficial to long-distance seawater salinity monitoring; the micro-nano filter membrane is coated on the outer ring layer of the long-period grating fixed support, so that solid biochemical substances in the seawater are prevented from adhering to the surface of the long-period grating region, and the accuracy of seawater salinity measurement is ensured.
The single-end-face transmission spectrum long-period grating seawater salinity sensor has the advantages of simple operation process, electromagnetic interference resistance and high detection sensitivity, has wide commercial application prospect, and is expected to be popularized and applied in the ocean field on a large scale.
Drawings
For a clearer description of an embodiment of the invention or of the technical solutions of the prior art, the drawings that are needed in the embodiment will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art;
FIG. 1 is a schematic diagram of an apparatus for detecting seawater salinity by a long period fiber grating of the present invention;
FIG. 2 is a graph showing the correspondence between the resonant wavelength and the salinity of the long period grating of the present invention;
FIG. 3 is a graph showing the correspondence between the resonant wavelength and the temperature of the long period grating according to the present invention;
reference numerals illustrate: 1 is a light source, 2 is an optical fiber coupler, 3 is a long period grating fixed support, 4 is a micro-nano filter film, 5 is a liquid tank, 6 is a long period optical fiber grating, 7 is a temperature reactor module, 8 is a reflecting film, 9 is a spectrometer, 10 is a signal acquisition module, 11 is an A/D conversion module, 12 is a singlechip, 13 is a liquid crystal display screen, and 14 is a mobile phone or a computer.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a device and a method for detecting the salinity of seawater by a long-period fiber grating, which are used for solving the problems in the prior art, so that the device for detecting the salinity of the seawater has the advantages of small volume, light weight, corrosion resistance, high sensitivity and electromagnetic interference resistance.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Example 1
The embodiment provides a seawater salinity detection device based on a long-period grating, which is shown in fig. 1 and comprises a light source 1, an optical fiber coupler 2 (the optical fiber coupler 2 is a 2 x 2 single-mode optical fiber coupler), a liquid tank 5, a long-period grating 6, a temperature sensor module 7, a spectrometer 9, a signal acquisition module 10, an A/D conversion module 11, a singlechip 12 and an output module; the optical fiber connector P0 at the input end of the optical fiber coupler 2 is connected with the light source 1; the second output optical fiber connector P2 of the optical fiber coupler 2 is connected with the spectrometer 9, the first output optical fiber connector P1 is connected with one end face of an optical fiber carved with a long period grating 6, and the long period grating 6 is a bare long period grating which is not modified by a nano film, a long period grating which is etched by hydrofluoric acid or a long period grating which is modified by various nano film materials on the surface of a grating region cladding; the optical fiber of the grating area part of the long-period grating 6 is straightened and fixed on a bracket 3 containing a concave liquid tank 5 capable of containing seawater, and the flat end surface of the other end of the optical fiber carved with the long-period grating 6 is plated with a reflecting film 8; the output port of the spectrometer 9 and the temperature sensor module 7 are respectively connected with the signal acquisition module 10, and the temperature sensor module 7 is arranged in the liquid tank 5 of the bracket 3 of the fixed long-period grating 6; the signal acquisition module 10 is connected with the A/D conversion module 11, the A/D conversion module 11 is connected with the singlechip 12, and the singlechip 12 is connected with the output module comprising at least one of a liquid crystal display 13, a mobile phone or a computer 14.
The embodiment also provides a seawater salinity detection method based on the long-period grating, which comprises the following steps:
firstly, an optical fiber connector P at the input end of an optical fiber coupler 2 is connected 0 An optical fiber connector P connected with the light source 1 and at the output end of the optical fiber coupler 2 2 Another optical fiber connector P at the output end of the optical fiber coupler 2 is connected with the spectrometer 9 1 Is connected with one end face of the optical fiber carved with the long period grating 6; the optical fiber of the grating area part of the long period grating 6 is straightened and fixed on a bracket 3 containing a concave liquid tank 5 capable of containing seawater, and the flat end surface of the other end of the optical fiber carved with the long period grating 6 is plated with a reflecting film 8 by adopting a sputtering method, an evaporation method, an atomic layer deposition method or a chemical wet method; the output port of the spectrometer 9 and the temperature sensor module 7 are respectively connected with the signal acquisition module 10, then the signal acquisition module 10 is connected with the A/D conversion module 11, the A/D conversion module 11 is connected with the singlechip 12, the numerical value of salinity is displayed through the liquid crystal display 13, or the salinity data is read and stored on the mobile phone or the computer 14 through Bluetooth, WIFI or USB ports;
preparing a series of standard salinity solutions, then testing the prepared standard solution at a certain constant temperature by using a fixed long-period grating 6, estimating the salinity of water by the long-period grating 6 through sensing the refractive index of the water, carrying out algorithm processing on signals and data, and preparing a standard curve of the variation relation between the salinity and the resonant wavelength as well as between the salinity and the resonant intensity value;
step three, gradually increasing or reducing the temperature of the long-period grating 6, synchronously testing the resonance wavelength and the resonance intensity variation value of the fixed long-period grating 6 in pure water, and then carrying out algorithm processing on signals and data to obtain a standard curve of the corresponding relation between the resonance wavelength and the resonance intensity variation value of the long-period grating 6 and the temperature;
testing the seawater in the real seawater environment in real time by using the fixed long-period grating 6 and the temperature sensor module 7 respectively, subtracting the resonance wavelength or the resonance intensity variation value of the long-period grating caused by the temperature from the resonance wavelength and the resonance intensity value of the long-period grating measured in the real seawater, and comparing the resonance wavelength and the resonance intensity value obtained after correction with a standard curve of the salinity to obtain the salinity value of the seawater;
and fifthly, displaying the seawater salinity value through the liquid crystal display 13, or reading and storing the seawater salinity data on the mobile phone or the computer 14 through Bluetooth, WIFI or USB ports.
The installation process and the detection process of the seawater salinity detection device based on the long-period grating are described in detail by specific examples:
first, an optical fiber connector P0 at the input end of an optical fiber coupler 2 is connected with a light source 1, and an optical fiber connector P at the output end of the optical fiber coupler 2 2 Another optical fiber connector P at the output end of the optical fiber coupler 2 is connected with the spectrometer 9 1 Is connected with one end face of the optical fiber carved with the long period grating 6; the optical fiber of the grating area part of the long-period grating 6 is straightened and fixed on a bracket 3 containing a concave liquid tank 5 capable of containing seawater, and the flat end surface of the other end of the optical fiber carved with the long-period grating 6 is plated with a reflecting film 8; the output port of the spectrometer 9 and the temperature sensor module 7 are respectively connected with the signal acquisition module 10, then the signal acquisition module 10 is connected with the A/D conversion module 11, the A/D conversion module 11 is connected with the singlechip 12, the numerical value of salinity is displayed through the liquid crystal display 13, or the salinity data is read and stored on the mobile phone or the computer 14 through Bluetooth, WIFI or USB ports, as shown in figure 1.
Secondly, preparing a series of sodium chloride standard solutions with the concentration of 0 per mill, 5 per mill, 10 per mill, 15 per mill, 20 per mill, 25 per mill, 30 per mill, 35 per mill and 40 per mill, and then respectively adding the standard solutions into a liquid tank of a fixed long-period grating at the constant temperature of 20 ℃, wherein the resonance wavelengths of the long-period grating are 1486.351nm, 1486.545nm, 1486.751nm, 1486.936nm, 1487.129nm, 1487.326nm, 1487.518nm, 1487.722nm and 1487.916nm, and the relation diagram of the salinity and the resonance wavelengths is shown in the attached figure 2 of the specification.
The pure water temperature of the liquid tank is respectively adjusted to be 5 ℃,10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃ and 50 ℃ of the temperature of the long-period grating, the resonance wavelength values of the fixed long-period grating which are tested synchronously are 1486.584nm, 1486.5064nm, 1486.428nm, 1486.351nm, 1486.273nm, 1486.196nm, 1486.118nm, 1486.041nm, 1485.963nm and 1485.885nm, and the standard curve of the corresponding relation between the resonance wavelength and the temperature of the long-period grating is shown in the specification and the figure 3.
The sea water in a certain area is tested in real time by using a fixed long-period grating and a temperature sensitive module, the result shows that the sea water temperature is 26 ℃, the resonance wavelength is 1486.862nm, the long-period grating resonance wavelength caused by the temperature is subtracted by carrying out algorithm processing on data, and the sea water salinity value is 10.74 per mill by comparing with a standard curve of salinity.
According to the invention, the long-period grating is straightened and fixed on the concave liquid tank bracket, so that the cross influence of bending on the transmission spectrum of the long-period grating is avoided; by adding a temperature sensor module and algorithm processing, the cross influence of temperature on the transmission spectrum of the long-period grating is eliminated; by utilizing the optical fiber coupler and the mode of preparing the reflecting film on the optical fiber end face of the long-period grating, the transmission spectrum display mode of the long-period grating is reserved, and the long-period grating is more beneficial to long-distance seawater salinity monitoring; the micro-nano filter membrane is coated on the outer ring layer of the long-period grating fixed support, so that solid biochemical substances in the seawater are prevented from adhering to the surface of the long-period grating region, and the accuracy of seawater salinity measurement is ensured.
The single-end-face transmission spectrum long-period grating seawater salinity sensor has the advantages of simple operation process, electromagnetic interference resistance and high detection sensitivity, has wide commercial application prospect, and is expected to be popularized and applied in the ocean field on a large scale.
The present specification has been presented in terms of specific examples to illustrate the principles and embodiments of the present invention, and the above examples are provided only to assist in understanding the method of the present invention and its core ideas; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (8)
1. Seawater salinity detection device based on long period grating, its characterized in that: the device comprises a light source (1), an optical fiber coupler (2), a liquid tank (5), a long-period grating (6), a temperature sensor module (7), a spectrometer (9), a signal acquisition module (10), an A/D conversion module (11), a singlechip (12) and an output module; the optical fiber connector P of the input end of the optical fiber coupler (2) 0 Is connected with the light source (1); a second output optical fiber joint P of the optical fiber coupler (2) 2 Connected to the spectrometer (9), a first output optical fiber connector P 1 Is connected with one end face of the optical fiber carved with the long period grating (6); the optical fiber of the grating area part of the long period grating (6) is straightened and fixed on a bracket (3) comprising a concave liquid tank (5) capable of containing seawater, and the flat end surface of the other end of the optical fiber carved with the long period grating (6) is plated with a reflecting film (8); the output port of the spectrometer (9) and the temperature sensor module (7) are respectively connected with the signal acquisition module (10), the signal acquisition module (10) is connected with the A/D conversion module (11), the A/D conversion module (11) is connected with the singlechip (12), and the singlechip (12) is connected with the output module.
2. The long-period grating-based seawater salinity detection device according to claim 1, wherein: the temperature sensor module (7) is arranged in the liquid groove (5) of the bracket (3) of the fixed long-period grating (6).
3. The long-period grating-based seawater salinity detection device according to claim 1, wherein: the optical fiber coupler (2) is a 2×2 single-mode optical fiber coupler.
4. The long-period grating-based seawater salinity detection device according to claim 1, wherein: the long-period grating (6) is a bare long-period grating which is not modified by a nano-film, a long-period grating etched by hydrofluoric acid or a long-period grating modified by a nano-film material on the surface of a grating region cladding.
5. The long-period grating-based seawater salinity detection device according to claim 1, wherein: the output module comprises at least one of a liquid crystal display (13), a mobile phone or a computer (14).
6. A seawater salinity detection method based on a long-period grating is characterized by comprising the following steps of: the method comprises the following steps:
firstly, an optical fiber connector P at the input end of an optical fiber coupler (2) is connected 0 An optical fiber connector P connected with the light source (1) and at the output end of the optical fiber coupler (2) 2 Another optical fiber connector P at the output end of the optical fiber coupler (2) is connected with the spectrometer (9) 1 Is connected with one end face of the optical fiber carved with the long period grating (6); the optical fiber of the grating area part of the long period grating (6) is straightened and fixed on a bracket (3) comprising a concave liquid tank (5) capable of containing seawater, and the flat end surface of the other end of the optical fiber carved with the long period grating (6) is plated with a reflecting film (8); the output port of the spectrometer (9) and the temperature sensor module (7) are respectively connected with the signal acquisition module (10), then the signal acquisition module (10) is connected with the A/D conversion module (11), the A/D conversion module (11) is connected with the singlechip (12), the salinity value is displayed through the liquid crystal display (13), or the salinity data is read and stored on the mobile phone or the computer (14) through Bluetooth, WIFI or USB ports;
preparing a series of standard salinity solutions, then testing the prepared standard solution by using a fixed long-period grating (6) at a certain constant temperature, and then carrying out algorithm processing on signals and data to prepare a standard curve of the variation relation between salinity and resonant wavelength and resonant intensity values;
step three, gradually increasing or reducing the temperature of the long-period grating (6), synchronously testing the resonance wavelength and the resonance intensity variation value of the fixed long-period grating (6) in pure water, and then carrying out algorithm processing on signals and data to obtain a standard curve of the corresponding relation between the resonance wavelength and the resonance intensity variation value of the long-period grating (6) and the temperature;
testing the seawater in the real seawater environment in real time by using a fixed long-period grating (6) and a temperature sensor module (7), subtracting the resonance wavelength or the resonance intensity variation value of the long-period grating caused by temperature from the resonance wavelength and the resonance intensity value of the long-period grating measured in the real seawater, and comparing the resonance wavelength and the resonance intensity value obtained after correction with a standard curve of salinity to obtain the salinity value of the seawater;
and fifthly, displaying the seawater salinity value through a liquid crystal display screen (13), or reading and storing the seawater salinity data on a mobile phone or a computer (14) through Bluetooth, WIFI or a USB port.
7. The long-period grating-based seawater salinity detection method according to claim 6, wherein: the long period grating (6) in the second step is used for estimating the salinity of water by sensing the refractive index of the water.
8. The long-period grating-based seawater salinity detection method according to claim 6, wherein: in the first step, a reflection film (8) is coated on the flat end surface of the optical fiber end of the long period grating (6) by a sputtering method, an evaporation method, an atomic layer deposition method or a chemical wet method.
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| CN201610852789.2A CN106442340B (en) | 2016-09-27 | 2016-09-27 | Device and method for detecting seawater salinity by long-period fiber gratings |
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| CN106442340B true CN106442340B (en) | 2023-06-13 |
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| CN108845387B (en) * | 2018-04-20 | 2019-12-17 | 东北大学 | Wedge-shaped micro-porous fiber grating capable of simultaneously measuring temperature, salinity and pressure of seawater |
| CN109030761B (en) * | 2018-06-15 | 2024-01-19 | 中国电建集团山东电力建设第一工程有限公司 | Seawater desalination detection device and use method |
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