CN108760683B - Method for measuring solution refractive index by utilizing resonance in region with wavelength larger than fiber core mold wavelength - Google Patents
Method for measuring solution refractive index by utilizing resonance in region with wavelength larger than fiber core mold wavelength Download PDFInfo
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- CN108760683B CN108760683B CN201810407438.XA CN201810407438A CN108760683B CN 108760683 B CN108760683 B CN 108760683B CN 201810407438 A CN201810407438 A CN 201810407438A CN 108760683 B CN108760683 B CN 108760683B
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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Abstract
A method for measuring the refractive index of a solution using resonance at a wavelength greater than the wavelength of a core mode, comprising the steps of: a) building a measuring device; b) opening a temperature control table, setting the temperature to be 20 ℃, opening a light source and a spectrometer, and adjusting the measurement parameters of the spectrometer; c) inserting the tilted fiber bragg grating tail fiber into a standard solution; d) gradually changing the refractive index of the standard solution, recording the intensity of the resonance wave trough in a region with the wavelength being larger than that of the fiber core model, and drawing a change curve of the intensity of the resonance wave trough and the refractive index of the standard solution; d) and calculating the refractive index of the solution to be measured by measuring the resonance wave trough intensity of the solution to be measured by utilizing the variation curve of the resonance wave trough intensity and the refractive index of the standard solution. The invention can greatly improve the service life of the measuring device and improve the reliability of data; the operation is convenient and flexible, and the environmental adaptability is higher; the required spectrum range of acquisition is narrower, the response is faster, and the sensitivity and the resolution are higher.
Description
Technical Field
The invention belongs to the technical field of optical fiber sensing, and particularly relates to a method for measuring a solution refractive index.
Background
The refractive index measurement has very important significance in the fields of biochemistry, environmental detection, life science and the like. Therefore, researchers have conducted a great deal of research on refractive index measuring apparatuses and methods, in which optical fibers have attracted extensive research interest due to their advantages of small size, broad bandwidth, resistance to light intensity variations and electromagnetic interference, corrosion resistance, and the like.
At present, the apparatus and method for measuring refractive index by using optical fiber still have disadvantages, for example, most of them need to immerse their gate region or microstructure region in the solution to be measured when measuring refractive index by using optical fiber. Because these areas have low strength, they are easily broken during use and are difficult to repair, causing significant losses. Therefore, some researchers begin to measure the refractive index of the solution by using the tail fiber, but these methods have the disadvantages of wide monitoring range, slow response speed and low sensitivity.
Disclosure of Invention
The invention aims to provide a method for measuring the refractive index of a solution by utilizing resonance in a wavelength region which is longer than that of a fiber core model, aiming at the defects of the traditional device and method for measuring the refractive index of the solution by utilizing an optical fiber.
The invention is realized by the following technical scheme.
The invention relates to a method for measuring the refractive index of a solution by utilizing resonance in a wavelength region with a wavelength larger than that of a fiber core model, which comprises the following steps.
a) The measuring device required by the measuring method is built, and the device comprises an ASE light source, an OSA spectrometer, a light splitter, a Tilted Fiber Bragg Grating (TFBG), a fiber clamp and a temperature control table; one end of each of the two branches of the optical splitter is connected with an ASE light source, and the other end of each of the two branches of the optical splitter is connected with an OSA spectrometer; the optical splitter is connected with one end of the inclined fiber grating, and the tail of the other end of the inclined fiber grating is cut flat by an optical fiber cutter after a coating layer is removed; two sides of the grid region of the inclined fiber grating are respectively fixed by fiber clamps, and the grid region of the inclined fiber grating is arranged in the temperature control table.
b) And opening a temperature control table, setting the temperature to be 20 ℃, opening a light source and a spectrometer, and adjusting the measurement parameters of the spectrometer.
c) The tilted fiber grating pigtail was inserted into the standard solution.
d) Gradually changing the refractive index of the standard solution, recording the intensity of the resonance wave trough in the wavelength region of which the wavelength is greater than that of the fiber core model, and drawing a change curve of the intensity of the resonance wave trough and the refractive index of the standard solution.
d) And calculating the refractive index of the solution to be measured by measuring the resonance wave trough intensity of the solution to be measured by utilizing the variation curve of the resonance wave trough intensity and the refractive index of the standard solution.
The inclination angle of the inclined fiber grating is preferably 1-10 degrees.
The invention has the technical effects that: according to the method, the end surface Fresnel reflection of the TFBG tail fiber is utilized to measure the solution refractive index, the method well protects the grid region in the measurement process, and the service life of the measurement device can be greatly prolonged; meanwhile, the temperature of the grid region is controlled at constant temperature, so that the measurement error caused by cross sensitivity of the temperature and the refractive index can be avoided, and the reliability of data is improved. The method is used for measuring the solution, and the TFBG tail fiber is only required to be inserted into the solution, so that the refractive index of the solution can be measured, and the method is convenient and flexible to operate. Compared with a method for measuring the solution refractive index by using a gate region or a microstructure region, the method has the advantages that the used tail fiber has higher strength, is less prone to fracture and has higher environmental adaptability; even if the tail fiber is damaged, the damaged part can be cut off by the optical fiber cutter and can be measured again. The method utilizes resonance in a wavelength region with the wavelength larger than that of the fiber core model to measure the refractive index of the solution, has a narrower spectrum range, and has faster response, higher sensitivity and higher resolution compared with the prior method for measuring the refractive index by utilizing the tail fiber.
Drawings
FIG. 1 is a schematic view of an apparatus used in the present invention. Wherein, 1 is ASE light source, 2 is OSA spectrometer, 3 is optical splitter, 4 is inclined fiber grating, 5 is fiber clamp, 6 is temperature control platform.
FIG. 2 is the variation trend of the resonance trough spectrum of the present invention along with the refractive index of the standard solution in the region where the wavelength of the present invention is longer than that of the fiber core model.
FIG. 3 is a graph showing the variation of the intensity of the resonance valley in the wavelength region of the present invention which is longer than that of the core mode, and the refractive index of the standard solution.
Detailed Description
The invention will be further illustrated by the following examples in conjunction with the accompanying drawings.
Example 1.
FIG. 1 shows the measurement equipment required by the solution refractive index measurement method, such as FIG. 1, including an ASE light source 1, an OSA spectrometer 2, a beam splitter 3, a Tilted Fiber Bragg Grating (TFBG) 4, a fiber clamp 5, and a temperature control table 6; one end of each of two branches of the optical splitter 3 is connected with the ASE light source 1, and the other end is connected with the OSA spectrometer 2; the optical splitter is connected with one end of the inclined fiber grating 4, and the tail part of the other end of the inclined fiber grating 4 is cut and flattened by an optical fiber cutter after a coating layer is removed; two sides of the grid region of the inclined fiber grating 4 are respectively fixed by fiber clamps 5, and the grid region of the inclined fiber grating 4 is arranged in a temperature control table 6.
Example 2.
The method for measuring the refractive index of the glycerol solution to be measured by using the resonance measurement solution with the wavelength being larger than the wavelength region of the fiber core mold comprises the following steps.
According to the equipment installation steps, the equipment is installed, and the TFBG inclination angle used in the experiment is 6 degrees. Setting the temperature control table to 20 ℃, turning on the light source and the spectrometer, and adjusting the measurement parameters of the spectrometer. Inserting the tail fiber into the standard solution, gradually changing the refractive index of the standard solution, recording the intensity of the resonance wave trough in the wavelength region of which the wavelength is greater than that of the fiber core model, and drawing a change curve of the intensity of the resonance wave trough and the refractive index of the standard solution as shown in figure 3. As can be seen from FIG. 3, the sensitivity of the refractive index measurement method can reach 209.35dB/RIU at the maximum when the refractive index is 1.471, and the resolution of the spectrometer light intensity is 0.001dBm, so the resolution obtained by the measurement method can reach RIU and is higher than that of other intensity mode refractive index sensors. When a solution to be measured is measured, inserting the tail fiber into the solution to be measured to obtain a corresponding resonance wave trough with the intensity of-67.335 dBm, and obtaining the refractive index of the glycerol solution to be measured to be 1.385 through a curve of variation of the resonance wave trough intensity and the refractive index of the standard solution.
Example 3.
The method for measuring the refractive index of the glycerol solution to be measured by using the resonance measurement solution with the wavelength being larger than the wavelength region of the fiber core mold comprises the following steps.
According to the equipment installation steps, the equipment is installed, and the TFBG inclination angle used in the experiment is 8 degrees. Setting the temperature control table to 20 ℃, turning on the light source and the spectrometer, and adjusting the measurement parameters of the spectrometer. Inserting the tail fiber into the standard solution, gradually changing the refractive index of the standard solution, recording the intensity of the resonance wave trough in the wavelength region of which the wavelength is greater than that of the fiber core model, and drawing a change curve of the intensity of the resonance wave trough and the refractive index of the standard solution. And inserting the tail fiber into the solution to be detected to obtain a corresponding resonance wave trough with the intensity of-67.910 dBm, and obtaining the refractive index of the glycerol solution to be detected as 1.366 according to the variation curve of the resonance wave trough intensity and the refractive index of the standard solution.
Example 4.
The refractive index of a NaCl solution to be measured is measured by a method of measuring the refractive index of the solution by resonance in a wavelength region with a wavelength longer than that of the fiber core model, and the method comprises the following steps.
According to the equipment installation steps, the equipment is installed, and the TFBG inclination angle used in the experiment is 6 degrees. Setting the temperature control table to 20 ℃, turning on the light source and the spectrometer, and adjusting the measurement parameters of the spectrometer. Inserting the tail fiber into the standard solution, gradually changing the refractive index of the standard solution, recording the intensity of the resonance wave trough in the wavelength region of which the wavelength is greater than that of the fiber core model, and drawing a change curve of the intensity of the resonance wave trough and the refractive index of the standard solution. And inserting the tail fiber into the solution to be detected to obtain a corresponding resonance wave trough with the intensity of-64.821 dBm, and obtaining the refractive index of the glycerol solution to be detected to be 1.354 according to the variation curve of the resonance wave trough intensity and the refractive index of the standard solution.
Claims (2)
1. A method for measuring the refractive index of a solution by using resonance in a region with a wavelength greater than that of a fiber core model is characterized by comprising the following steps:
a) building a measuring device, wherein the device comprises an ASE light source, an OSA spectrometer, a light splitter, an inclined fiber grating, a fiber clamp and a temperature control table; one end of each of the two branches of the optical splitter is connected with an ASE light source, and the other end of each of the two branches of the optical splitter is connected with an OSA spectrometer; the optical splitter is connected with one end of the inclined fiber grating, and the tail of the other end of the inclined fiber grating is cut flat by an optical fiber cutter after a coating layer is removed; two sides of the grid region of the inclined fiber grating are respectively fixed by fiber clamps, and the grid region of the inclined fiber grating is arranged in the temperature control table;
b) opening a temperature control table, setting the temperature to be 20 ℃, opening a light source and a spectrometer, and adjusting the measurement parameters of the spectrometer;
c) inserting the tilted fiber bragg grating tail fiber into a standard solution;
d) gradually changing the refractive index of the standard solution, recording the intensity of a certain fixed resonance wave trough in a region with the wavelength being larger than that of the fiber core mold, and drawing a change curve of the intensity of the resonance wave trough and the refractive index of the standard solution;
e) and calculating the refractive index of the solution to be measured by measuring the resonance wave trough intensity of the solution to be measured by utilizing the variation curve of the resonance wave trough intensity and the refractive index of the standard solution.
2. The method of claim 1, wherein the tilt angle of the tilted fiber grating is 1 ° -10 ° in the region of the wavelength of the fiber core mode.
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| CN109443973A (en) * | 2018-12-12 | 2019-03-08 | 中国计量大学 | Steel reinforcement corrosion sensor in a kind of marine environment based on TFBG |
| CN111579534B (en) * | 2020-05-29 | 2023-06-27 | 重庆理工大学 | Optical fiber sensing detection device for detecting refractive index of solution and refractive index detection method |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014235007A (en) * | 2013-05-31 | 2014-12-15 | 国立大学法人 宮崎大学 | Device and method for detecting temperature and refractive index of medium |
| CN106053389A (en) * | 2016-05-25 | 2016-10-26 | 哈尔滨工程大学 | Micro-droplet sensing device and method using same to measure refractivity |
| CN107490561A (en) * | 2017-07-24 | 2017-12-19 | 温州大学 | A kind of highly sensitive inclined optical fiber grating low-refraction sensing detection device |
| CN107941753A (en) * | 2018-01-10 | 2018-04-20 | 南昌大学 | Device and the application of solution refractive index are surveyed in a kind of polished end faces reflection using TFBG tail optical fibers |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014235007A (en) * | 2013-05-31 | 2014-12-15 | 国立大学法人 宮崎大学 | Device and method for detecting temperature and refractive index of medium |
| CN106053389A (en) * | 2016-05-25 | 2016-10-26 | 哈尔滨工程大学 | Micro-droplet sensing device and method using same to measure refractivity |
| CN107490561A (en) * | 2017-07-24 | 2017-12-19 | 温州大学 | A kind of highly sensitive inclined optical fiber grating low-refraction sensing detection device |
| CN107941753A (en) * | 2018-01-10 | 2018-04-20 | 南昌大学 | Device and the application of solution refractive index are surveyed in a kind of polished end faces reflection using TFBG tail optical fibers |
Non-Patent Citations (1)
| Title |
|---|
| Simultaneous measurement of liquid level and surrounding refractive index using tilted fiber Bragg grating;Qi Jiang et al.;《Sensors and Actuators A 》;20110612;第170卷;62-65 * |
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