CN113218913A - Temperature-compensated chirped fiber grating sensor for measuring solution concentration - Google Patents
Temperature-compensated chirped fiber grating sensor for measuring solution concentration Download PDFInfo
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- CN113218913A CN113218913A CN202110589948.5A CN202110589948A CN113218913A CN 113218913 A CN113218913 A CN 113218913A CN 202110589948 A CN202110589948 A CN 202110589948A CN 113218913 A CN113218913 A CN 113218913A
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- fiber grating
- refractive index
- sensing unit
- solution concentration
- chirped fiber
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
Abstract
The invention discloses a chirp fiber grating sensor for measuring solution concentration by temperature compensation, which consists of a broadband light source, a filter, a sensing unit, liquid to be measured, a liquid container, a spectrometer and a single-mode fiber used for connection. The broadband laser output by the broadband light source is limited in a specific wavelength by the filter and then is input into the sensing unit, when the concentration of the solution changes, the refractive index of the solution changes simultaneously, so that the effective refractive index of the sensing unit changes, the spectral wavelength drifts, the graphene oxide film layer coated on the sensing unit can improve the sensing performance of the sensor, and the temperature and the concentration of the solution can be measured simultaneously, so that the sensor has the capability of temperature compensation under high sensitivity, and has a good application prospect.
Description
Technical Field
The invention provides a temperature-compensated chirp fiber grating sensor for measuring solution concentration, belonging to the technical field of fiber sensing.
Background
The chirped fiber grating is a kind of fiber grating, and is a special fiber grating with a period varying with the axial direction of the fiber; the transmission spectrum has wide bandwidth, so that band rejection of a plurality of wavelengths can be realized in the transmission spectrum, the method is suitable for multi-wavelength filtering, and has special advantages in the aspect of optical communication.
Generally, the existing solution concentration sensor can only measure a single parameter of solution concentration, and the measurement of the parameter of solution concentration is obtained by measuring a parameter of refractive index and then introducing the parameter into an empirical formula, so that the measurement of the solution concentration is really the measurement of the refractive index, the refractive index is usually not changed along with other environmental changes, but the change of temperature can cause the change of the refractive index, and therefore, in order to accurately measure the change of the refractive index, it is necessary to manufacture a temperature-compensated measurement refractive index sensor'.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a temperature-compensated chirp fiber grating sensor for measuring solution concentration, which is characterized in that broadband laser output by a broadband light source is limited in a specific wavelength by a filter and then is input into a sensing unit, when the solution concentration changes, the refractive index around the sensing unit changes, the corroded end of the sensed unit is more sensitive to the change of the refractive index, the non-corroded end can detect the change of the temperature, meanwhile, after a graphene oxide film is coated on the surface of a grating, small liquid molecules in a refractive index matching liquid can permeate into small gaps between graphene oxide films and are absorbed by the graphene oxide, the complex refractive index of the graphene itself can be influenced due to the change of the carrier concentration after absorption, and the existence of the graphene film enables the sensing unit to be more sensitive to the change of the external environment, therefore, when a sample coated with graphene is in an external environment with different refractive indexes, the spectrum of the sample is obviously changed, the solution concentration can be obtained by taking the measured refractive index change into the sample according to the solution concentration-solution refractive index empirical formula, the sensing unit is very sensitive to the ambient refractive index change, the temperature change condition can be detected in a temperature sensitive wavelength region, the temperature compensation effect is achieved, the stability of the sensor is improved, the sensitivity is good, and the application prospect is good.
1. The utility model provides a temperature compensation's measurement solution concentration chirp fiber grating sensor which characterized in that: the device comprises a broadband light source (1), a filter (2), a sensing unit (3), liquid to be measured (4), a liquid container (5), a spectrometer (6) and a single-mode optical fiber (7) for connection; the method is characterized in that: the sensing unit (3) consists of a corrosion chirped fiber grating refractive index sensing area (31), a non-corrosion chirped fiber grating temperature compensation area (32) and a graphene oxide film layer (33); the broadband light source (1) outputs light to the filter (2) to enable the spectrum to be limited to 1530 nm-1585 nm, then the light signal is input into the sensing unit (3), the liquid (4) to be detected is located in the liquid container (5), the sensing unit (3) is placed into the liquid (4) to be detected, the spectrum wave crest is moved due to the change of the environmental refractive index, the whole detection wavelength range is shifted due to the change of the environmental temperature, the sensitivity of the sensor can be improved due to the graphene oxide film layer (33), the corrosion chirped fiber grating refractive index sensing area (31) can detect the change of the environmental refractive index, the non-corrosion chirped fiber grating temperature compensation area (32) can play a role in temperature compensation, then the spectrum change is detected through the spectrometer (6), and the solution concentration empirical formula is brought into, the solution concentration change can be obtained, and all parts of the sensor are connected through the single-mode fiber (7), the sensor has high sensitivity and large detection range, can compensate temperature and has good application prospect.
Wherein the wavelength range of the broadband light source (1) is 1530 nm-1585 nm.
Wherein, the filter (2) is a band-pass filter.
Wherein the sensing unit (3) is a linear chirped fiber grating with a diameter of 100 μm and a length of 14mm, a fiber core refractive index of 1.45 and a refractive index modulation amplitude of 5 × 10-5The chirp coefficient was 2.5 nm/mm.
Wherein, the length of the corrosion chirped fiber grating refractive index sensing area (31) in the sensing unit (3) is 7mm, and the etching degree is 85%.
Wherein the length of the non-corrosion chirped fiber grating temperature compensation area (32) in the sensing unit (3) is 7 mm.
Wherein the thickness of the graphene oxide film layer (33) in the sensing unit (3) is 272nm, the thickness of a single layer is 6.8nm, and 40 layers are coated.
According to the inventionThe working principle is as follows: the corrosion chirped grating combines the wavelength selection characteristic of the Bragg grating and the transmission characteristic of the evanescent field of the corrosion optical fiber, is placed in different environments, the whole remaining corroded grating can be regarded as a fiber core, the environment medium around the optical fiber is regarded as a cladding, and the drifting condition of the Bragg wavelength caused by the difference of the diameters of the fiber cores is researched. When the period Λ of the grating is kept constant, the wavelength λ is known from the bragg conditionBWith effective refractive index neffExhibits a linear variation, since the phase factor beta of a single-mode fiber is closely related to the diameter of the fiber, thereby making the effective refractive index n of the gratingeff＝β/k0(wherein, k is02 pi/λ) also varies with the fiber diameter;
introducing fiber normalization frequency in calculation
And normalized transverse propagation constant
Thus the effective refractive index n can be adjustedeffExpressed as:
where a is the radius of the optical fiber and n1Is the refractive index of the core of the optical fiber, n2Is the refractive index of the cladding. And, the transverse propagation attempt U, the normalized frequency V satisfies the fiber eigenequation:
U2+W2＝V2 (2)
the process is simplified by adopting Gaussian field approximation, and the relationship of U and V can be represented by the following sub-formula:
the following can be obtained:
in fact, n1,k0Is constant, so that the effective refractive index n of the fiber Bragg gratingeffIs the fiber radius a and the cladding index n2When the radius a of the grating is changed, the fiber Bragg wavelength is changed along with the function of (A); when the refractive index n of the cladding is2When changed, the fiber bragg wavelength will also change accordingly.
The invention has the beneficial effects that: the corrosion part chirp fiber grating and the non-corrosion part chirp fiber grating coated with the graphene oxide are respectively used for detecting the refractive index at the temperature, so that the sensor is very sensitive to the change of the environmental refractive index, meanwhile, the sensitivity of the sensor can be obviously improved by temperature compensation, and a novel method which is simple, convenient, easy to build, reliable and high in sensitivity is provided for detecting the concentration of the solution.
Drawings
FIG. 1 is a schematic diagram of a temperature compensated chirped fiber grating sensor feature for measuring solution concentration according to the present invention.
Fig. 2 is a schematic diagram of a sensing unit structure of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
1. The utility model provides a temperature compensation's measurement solution concentration chirp fiber grating sensor which characterized in that: the device comprises a broadband light source (1), a filter (2), a sensing unit (3), liquid to be measured (4), a liquid container (5), a spectrometer (6) and a single-mode optical fiber (7) for connection; the method is characterized in that: the sensing unit (3) consists of a corrosion chirped fiber grating refractive index sensing area (31), a non-corrosion chirped fiber grating temperature compensation area (32) and a graphene oxide film layer (33); the broadband light source (1) outputs light and transmits the light to the filter (2), so that a spectrum is limited to 1530 nm-1585 nm, then an optical signal is input into the sensing unit (3), the sensing unit (3) is placed into liquid (4) to be detected, the dielectric constant of the graphene oxide film layer (33) changes along with environmental change, the overall effective refractive index of the fiber bragg grating is increased, the drift of the fiber bragg wavelength is further caused, meanwhile, the evanescent field strength of the grating surface is increased, the sensitivity of the sensor can be improved, the spectrum peak is moved due to the change of the environmental refractive index, the overall drift in the detection wavelength range is caused due to the change of the environmental temperature, the change of the environmental refractive index can be detected by the corrosion chirp fiber bragg grating refractive index sensing area (31), the change of the environmental refractive index can be detected by the non-corrosion chirp fiber bragg grating temperature compensation area (32), and the change of the environmental refractive index can be detected by the spectrometer (6) in the refractive index sensing area, the detected refractive index change is brought into a solution concentration empirical formula to obtain the solution concentration change, the change of the environmental temperature is detected in a temperature compensation area, so that the refractive index is detected and the temperature self-compensation effect is achieved, and all parts of the sensor are connected by a single-mode optical fiber (7).
Claims (7)
1. The utility model provides a temperature compensation's measurement solution concentration chirp fiber grating sensor which characterized in that: the device comprises a broadband light source (1), a filter (2), a sensing unit (3), liquid to be measured (4), a liquid container (5), a spectrometer (6) and a single-mode optical fiber (7) for connection; the method is characterized in that: the sensing unit (3) consists of a corrosion chirped fiber grating refractive index sensing area (31), a non-corrosion chirped fiber grating temperature compensation area (32) and a graphene oxide film layer (33); the broadband light source (1) outputs light to the filter (2) to enable the spectrum to be limited to 1530 nm-1585 nm, then the light signal is input into the sensing unit (3), the liquid (4) to be detected is located in the liquid container (5), the sensing unit (3) is placed into the liquid (4) to be detected, the spectrum wave crest is moved due to the change of the environmental refractive index, the whole detection wavelength range is shifted due to the change of the environmental temperature, the sensitivity of the sensor can be improved due to the graphene oxide film layer (33), the corrosion chirped fiber grating refractive index sensing area (31) can detect the change of the environmental refractive index, the non-corrosion chirped fiber grating temperature compensation area (32) can play a role in temperature compensation, then the spectrum change is detected through the spectrometer (6), and the solution concentration empirical formula is brought into, the solution concentration change can be obtained, and all parts of the sensor are connected through the single-mode fiber (7), the sensor has high sensitivity and large detection range, can compensate temperature and has good application prospect.
2. A temperature compensated measurement solution concentration chirped fiber grating sensor according to claim 1, wherein: the wavelength range of the broadband light source (1) is 1530 nm-1585 nm.
3. A temperature compensated measurement solution concentration chirped fiber grating sensor according to claim 1, wherein: the filter (2) is a band-pass filter.
4. A temperature compensated measurement solution concentration chirped fiber grating sensor according to claim 1, wherein: the sensing unit (3) is a linear chirped fiber grating with a diameter of 100 μm and a length of 14mm, a fiber core refractive index of 1.45 and a refractive index modulation amplitude of 5 × 10-5The chirp coefficient was 2.5 nm/mm.
5. A temperature compensated measurement solution concentration chirped fiber grating sensor according to claim 1, wherein: the length of a corrosion chirped fiber grating refractive index sensing area (31) in the sensing unit (3) is 7mm, and the corrosion degree is 85%.
6. A temperature compensated measurement solution concentration chirped fiber grating sensor according to claim 1, wherein: the length of a non-corrosive chirped fiber grating temperature compensation area (32) in the sensing unit (3) is 7 mm.
7. A temperature compensated measurement solution concentration chirped fiber grating sensor according to claim 1, wherein: the graphene oxide film layer (33) in the sensing unit (3) is 272nm thick, the single-layer film thickness is 6.8nm, and 40 layers are coated.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113945543A (en) * | 2021-09-02 | 2022-01-18 | 中国电子产品可靠性与环境试验研究所（（工业和信息化部电子第五研究所）（中国赛宝实验室）） | Optical fiber sensor and preparation method, detection system and detection method thereof |
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2021
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113945543A (en) * | 2021-09-02 | 2022-01-18 | 中国电子产品可靠性与环境试验研究所（（工业和信息化部电子第五研究所）（中国赛宝实验室）） | Optical fiber sensor and preparation method, detection system and detection method thereof |
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