CN115219455A - Interference type pH sensing device based on coreless optical fiber - Google Patents
Interference type pH sensing device based on coreless optical fiber Download PDFInfo
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- CN115219455A CN115219455A CN202210791214.XA CN202210791214A CN115219455A CN 115219455 A CN115219455 A CN 115219455A CN 202210791214 A CN202210791214 A CN 202210791214A CN 115219455 A CN115219455 A CN 115219455A
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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
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
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- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N21/7703—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator using reagent-clad optical fibres or optical waveguides
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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
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N21/78—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a change of colour
- G01N21/80—Indicating pH value
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- 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
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
- G01N2021/458—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods using interferential sensor, e.g. sensor fibre, possibly on optical waveguide
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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
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N2021/7769—Measurement method of reaction-produced change in sensor
- G01N2021/7779—Measurement method of reaction-produced change in sensor interferometric
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Abstract
The invention discloses an interference type pH sensing device based on coreless optical fibers. The optical fiber sensor is a single-mode-coreless-single-mode optical fiber sensor plated with a PAA/PAH film, and specifically consists of two sections of single-mode optical fibers and a coreless optical fiber plated with the PAA/PAH film, and the two ends of the coreless optical fiber are welded with the single-mode optical fibers; and measuring the wavelength shift condition corresponding to the interference peak value of the optical fiber sensor through spectral analysis, and determining the pH value by combining the relation between the pH value and the wavelength shift. The invention is suitable for high-precision pH value measurement in a liquid environment under the condition of known solution acidity and alkalinity, has the advantages of low price, simple manufacture, compact structure, high sensitivity and the like, and can be widely applied to the fields of food safety, industrial measurement, biomedicine and the like.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to an interference type optical fiber pH sensing device plated with a pH sensitive film and based on a coreless optical fiber structure.
Background
The pH value measurement of liquid is one of important parameters for characterizing the properties of solution, and is widely applied in the fields of chemical component analysis, biomedicine, food safety, agricultural production and the like. The traditional pH value measuring methods comprise pH test paper, a pH electrode and the like, but the methods have the problems of large detection error, slow response rate and the like, and can not meet the actual measurement requirements.
In recent years, with the continuous development of optical fiber sensing technology, optical fiber sensors are widely applied to various environmental parameter detection with the advantages of small volume, high sensitivity, simple structure, electromagnetic interference resistance, online real-time measurement and the like, such as: temperature, strain, bend, pH, and ambient refractive index, among others. The optical fiber pH sensor combines spectral analysis and optical fiber sensing technology, and utilizes the response of an acid-base indicator coated outside an optical fiber to pH to realize the measurement of the pH.
The types of acid-base indicators are various, and different acid-base indicators have different pH detection ranges and response times, for example, a fluorescent indicator taking salicylic acid as an example is mainly used for pH measurement in a neutral or acidic environment, and the response time is as long as 3-13min. Although the artificially synthesized acid-base indicator can realize the measurement in the full pH range, the indicator is high in manufacturing cost and can cause environmental pollution. In recent years, polymer films of interest have also been used as acid-base indicators. Among them, polyacrylate (PAH) and polyacrylic acid (PAA) films show good swelling shrinkage reaction when pH changes in solution, and the film thickness is the smallest in neutral environment, and increases with increasing or decreasing pH. In addition, the polymer film has good optical fiber adhesion, and optical fiber coating can be realized by utilizing a layer-by-layer self-assembly technology.
The optical fiber pH sensor is classified into an evanescent wave detection type, an optical fiber grating type and an interference type pH sensor according to the difference of the optical fiber structure types. Evanescent wave detection type pH sensors usually need to damage the mechanical structure of optical fibers, are not beneficial to long-term use of the sensors, and have low detection precision; although the fiber grating type pH sensor has high detection sensitivity, an expensive grating manufacturing platform is required, the manufacturing process is complex, and the cost is high. The interference type pH sensor based on the special optical fiber has the advantages of high detection sensitivity and simple manufacture. However, the current interference type pH sensor related to special optical fiber mainly utilizes the change of the refractive index of the thin film of the acid-base indicator in different pH environments to measure the pH value, and has the disadvantages of low identification and easy interference. Therefore, the invention has important significance in the aspect of the optical fiber pH value sensing device which is low in cost, simple to manufacture, high in sensitivity and high in identification.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides an interference type pH sensing device based on coreless optical fiber.
The optical fiber sensor is a single-mode-coreless-single-mode optical fiber sensor plated with a PAA/PAH film, and specifically consists of two sections of single-mode optical fibers and a coreless optical fiber plated with the PAA/PAH film, and the two ends of the coreless optical fiber are welded with the single-mode optical fibers; and measuring the wavelength shift condition corresponding to the peak value of the interference peak of the optical fiber sensor through spectral analysis, and determining the pH value by combining the relationship between the pH value and the wavelength shift amount.
The method is suitable for high-precision pH value measurement in a liquid environment under the known solution acid-base condition, and the high-precision pH value measurement is realized by determining the pH value change condition through the wavelength offset by utilizing the characteristic that the interference peak wavelength of the PAA/PAH film-plated coreless optical fiber sensing head changes along with the pH value.
The invention has the advantages of low price, simple manufacture, compact structure, high sensitivity and the like, and can be widely applied to the fields of food safety, industrial measurement, biomedicine and the like.
Drawings
FIG. 1 is a schematic view of the structure of the present invention;
FIG. 2 is a schematic diagram of a PAA/PAH film plated single mode-coreless-single mode fiber sensor;
FIG. 3 is a diagram of a theoretical simulation of beam transmission for a single-mode-coreless-single-mode fiber structure;
FIG. 4 is a schematic diagram of the spectrum measured by the apparatus of the present invention.
Detailed Description
The present invention is further described below in conjunction with the appended drawings to facilitate one skilled in the art in practicing the present invention.
As shown in fig. 1, the interferometric pH sensor device based on coreless fiber of the present invention includes a broadband light source 1, an unlimited length of single mode fiber 2, a single mode-coreless-single mode fiber sensor head 3 coated with PAA/PAH film, a second unlimited length of single mode fiber 4, and a spectrometer 5.
A broadband light source 1 covering a wave band of 1520-1620nm transmits light beams to a single-mode-coreless-single-mode optical fiber sensing head 3 coated with a PAA/PAH film through a single-mode optical fiber 2, and the light beams are output to a spectrometer 5 for spectrum monitoring through a single-mode optical fiber 4 after being tuned by the single-mode-coreless-single-mode optical fiber sensing head coated with the PAA/PAH film.
The basic structure of a single-mode-coreless-single-mode optical fiber sensor head coated with a PAA/PAH film is shown in FIG. 2. The basic components of the sensor include a single mode fiber 2 of unlimited length, a coreless fiber 6 coated with a PAA/PAH film 7, and a single mode fiber 4. In this embodiment, the length of the coreless fiber is L (1-3 cm), the diameter of the cladding is R (62.5 μm), and the thickness of the PAA/PAH film is d (200-600 nm), and the PAA/PAH is coated layer by layer outside the cladding of the coreless fiber by using a layer-by-layer self-assembly method after the coreless fiber is fusion-spliced with the positive core of the single-mode fiber.
When broadband light enters the coreless fiber through the single-mode fiber or enters the single-mode fiber from the coreless fiber, multimode interference occurs in the coreless fiber, and the mode of the interference is affected due to the fact that the thickness of the film changes according to pH, and therefore the interference spectrum is shifted. The peak wavelength of the interference peak of the spectrum can be expressed as
Wherein L is eff Is the length of the coreless optical fiber,
indicating that the difference in effective refractive index between the modes will be due to a change in pH in the liquid environment
And thus the peak wavelength of the interference peak shifts when the pH changes.
Referring to fig. 3, the result of the optical field energy distribution simulation result of the single-mode-coreless-single-mode fiber structure demonstrates that in the process that light beams are incident from the single-mode fiber and output to the single-mode fiber through the coreless fiber, due to different fiber structure parameters, light wave energy periodically diffuses out of the coreless fiber, and energy is exchanged in the single-mode-coreless-single-mode fiber structure to generate interference. The optical field energy will be affected by the PAA/PAH sensitive film coated outside the coreless fiber, and when the thickness of the sensitive film changes, the change of the interference spectrum will be caused.
The single mode-coreless-single mode optical fiber sensing head 3 coated with the PAA/PAH film is placed in standard solutions with different pH values, and the response of the spectrum recorded by the spectrometer to the pH values is shown in fig. 4. Therefore, the wavelength and the pH value corresponding to the loss peak value are analyzed, the response coefficient of the wavelength of the sensor to the pH value is solved, and the calibration is completed:
wherein λ is pH＝7 Is the peak wavelength of the reflection peak when the solution is a neutral solution with a pH value equal to 7; Δ pH is the difference between pH and pH 7 of a neutral solution.
Placing the PAA/PAH coated coreless fiber sensing head in a liquid environment with known pH value and unknown pH value, measuring the wavelength shift condition corresponding to the peak value of the interference peak by spectral analysis, and calculating the pH value by combining the formula between the pH value and the wavelength shift quantity
For the known solution with acid and alkali, selecting plus or minus in the formula, if the solution to be measured is in acid environment, selecting minus, that is, the formula is adjusted to be acid
If the solution to be measured is in an alkaline environment, "+" is selected, that is, the formula is adjusted to
In summary, the present invention utilizes the single-mode-coreless-single-mode fiber interference technology to achieve the acquisition of the interference spectrum, and utilizes the layer-by-layer self-assembly method to provide the spectral response characteristic of the pH sensor. The invention is suitable for high-precision measurement of the pH value of the known acid-base solution, has the advantages of electromagnetic interference resistance, simple manufacture, low price and the like, and is suitable for the application fields of food safety, medical treatment and health care and the like.
Claims (5)
1. The utility model provides an interference type pH sensing device based on coreless fiber, includes broadband light source, optical fiber sensor and spectrum appearance, optical fiber sensor set up between broadband light source and spectrum appearance, its characterized in that:
the optical fiber sensor is a single-mode-coreless-single-mode optical fiber sensor plated with a PAA/PAH film, and specifically comprises two sections of single-mode optical fibers and a coreless optical fiber plated with a PAA/PAH film, wherein the single-mode optical fibers are welded at two ends of the coreless optical fiber; and measuring the wavelength shift condition corresponding to the interference peak value of the optical fiber sensor through spectral analysis, and determining the pH value by combining the relation between the pH value and the wavelength shift.
2. The interference type pH sensing device based on the coreless optical fiber, according to claim 1, wherein: the coreless optical fiber is coated by adopting a layer-by-layer self-assembly method.
3. The interference type pH sensing device based on the coreless optical fiber as claimed in claim 2, wherein: the thickness of the coating is 200-600 nm.
4. The interference type pH sensing device based on the coreless optical fiber, according to claim 1 or 2, wherein: the response coefficient of the wavelength of the optical fiber sensor to the pH value needs to be calibrated in advance.
5. The interference type pH sensing device based on the coreless optical fiber, according to claim 1 or 2, wherein: the wavelength coverage range of the broadband light source is 1520-1620 nm.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117607100A (en) * | 2024-01-24 | 2024-02-27 | 河南师范大学 | Optical fiber sensing method for monitoring in-situ pH value in AZIBs secondary battery |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117607100A (en) * | 2024-01-24 | 2024-02-27 | 河南师范大学 | Optical fiber sensing method for monitoring in-situ pH value in AZIBs secondary battery |
| CN117607100B (en) * | 2024-01-24 | 2024-05-17 | 河南师范大学 | Optical fiber sensing method for monitoring in-situ pH value in AZIBs secondary battery |
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