CN214584839U

CN214584839U - PH value measurement system based on micro-nano fiber Bragg grating

Info

Publication number: CN214584839U
Application number: CN202120821331.7U
Authority: CN
Inventors: 牛亚兰
Original assignee: Guangxi Science and Technology Normal University
Current assignee: Guangxi Science and Technology Normal University
Priority date: 2021-04-21
Filing date: 2021-04-21
Publication date: 2021-11-02
Anticipated expiration: 2031-04-21

Abstract

The utility model provides a pH value measurement system based on micro-nano fiber Bragg grating, which comprises a pumping light source, a first isolator, a wavelength division multiplexer, a micro-nano fiber Bragg grating, a pH sensitive film, a second isolator, a polarization controller, a polarizer, a photoelectric detector and a spectrum analyzer, wherein the pumping light source is connected with the input end of the first isolator; the output end of the first isolator is connected with the input port of the wavelength division multiplexer; the output port of the wavelength division multiplexer is connected with the micro-nano fiber Bragg grating; the pH sensitive film is coated outside the micro-nano fiber Bragg grating; the input end of the second isolator is connected with the reflection port of the wavelength division multiplexer, and the output end of the second isolator is connected with the input end of the polarization controller; the output end of the polarization controller is connected with the input end of the polarizer, the output end of the polarizer is connected with the input end of the photoelectric detector, and the output end of the photoelectric detector is connected with the spectrum analyzer. The sensitivity of pH value measurement can be improved, and the response time of detection is shortened.

Description

PH value measurement system based on micro-nano fiber Bragg grating

Technical Field

The utility model relates to an optical fiber sensing technology field, concretely relates to pH value measurement system based on receive optic fibre bragg grating a little.

Background

The pH value of the liquid is an important parameter reflecting the pH value of the liquid and is also one of important parameters reflecting the quality of water resources. The pH value measurement plays an important role in the fields of modern biopharmaceuticals, chemical engineering, environmental science, breeding and planting industry and the like, so that the pH value measurement device has important significance in accurately measuring and monitoring the pH value of liquid in real time.

The traditional liquid pH value measuring methods comprise a test paper comparison method, a spectrum analysis method, an indicator analysis method, an electrochemical method and the like, and the methods are technically mature and are applied for a long time. In the traditional methods, some methods are simple to operate, convenient and quick, and for example, a test paper comparison method has the defect of low measurement precision; some methods have complicated analysis processes and slow measurement response, such as spectroscopic analysis and indicator analysis. Therefore, the traditional pH value measuring method has the defects of low measuring precision, slow measuring response and the like, and is difficult to realize the requirements of accurate, quick, real-time and remote measurement on the pH value of the liquid.

Disclosure of Invention

The utility model discloses aim at solving one of the above-mentioned technical problem that proposes at least, provide a pH value measurement system based on receive optical fiber Bragg grating a little to improve the sensitivity of the measurement of pH value, reduce the response time that pH value detected.

In order to achieve the above purpose, the utility model adopts the technical proposal that:

a pH value measuring system based on a micro-nano fiber Bragg grating comprises a pumping light source, a first isolator, a wavelength division multiplexer, a micro-nano fiber Bragg grating, a pH sensitive film, a second isolator, a polarization controller, a polarizer, a photoelectric detector and a spectrum analyzer, wherein the output end of the pumping light source is connected with the input end of the first isolator; the output end of the first isolator is connected with the input port of the wavelength division multiplexer; an output port of the wavelength division multiplexer is connected with the micro-nano fiber Bragg grating; the pH sensitive film is coated on the outer surface of the micro-nano fiber Bragg grating; the input end of the second isolator is connected with the reflection port of the wavelength division multiplexer, and the output end of the second isolator is connected with the input end of the polarization controller; the output end of the polarization controller is connected with the input end of the polarizer, the output end of the polarizer is connected with the input end of the photoelectric detector, and the output end of the photoelectric detector is connected with the input end of the spectrum analyzer.

Furthermore, the micro-nano fiber bragg grating comprises a fiber core and a fiber cladding, wherein the fiber core and the fiber cladding respectively comprise a connecting area, a transition area and a detection area which are sequentially connected along the axial direction of the fiber core, the diameter of the connecting area is larger than that of the detection area, the diameter of the transition area is gradually reduced from the direction far away from the connecting area, the connecting area of the fiber cladding is coated outside the connecting area of the fiber core, the transition area of the fiber cladding is coated outside the transition area of the fiber core, and the detection area of the fiber cladding is coated outside the detection area of the fiber core; the detection area of the fiber core of the optical fiber is alternately inscribed with fiber Bragg grating pairs with submicron-sized diameters along the axial direction of the fiber core of the optical fiber; the pH sensitive film is coated outside the detection area of the optical fiber cladding; the connection area is connected with an output port of the wavelength division multiplexer.

Furthermore, the distance between the fiber Bragg grating pairs is 0.4-0.6 cm.

Further, the fiber core of the micro-nano fiber Bragg grating is erbium ytterbium co-doped fiber.

Furthermore, the pumping light source, the first isolator, the wavelength division multiplexer, the micro-nano fiber Bragg grating, the second isolator, the polarization controller, the polarizer and the photoelectric detector are all connected through transmission fibers, and the photoelectric detector is connected with the spectrum analyzer through a cable.

Further, the pH sensitive film is a pH sensitive hydrogel.

The utility model also provides another kind of pH value measurement system based on the optical fiber Bragg grating of receiving a little, including pumping light source, first isolator, wavelength division multiplexer, receive an optical fiber Bragg grating of receiving a little, pH sensitive membrane, second isolator and spectral analyser, pumping light source's output with the input of first isolator links to each other; the output end of the first isolator is connected with the input port of the wavelength division multiplexer; an output port of the wavelength division multiplexer is connected with the micro-nano fiber Bragg grating; the pH sensitive film is coated on the outer surface of the micro-nano fiber Bragg grating; the input end of the second isolator is connected with the reflection port of the wavelength division multiplexer, and the output end of the second isolator is connected with the input end of the spectrum analyzer.

Due to the adoption of the technical scheme, the utility model discloses following beneficial effect has:

1. according to the pH value measuring system based on the micro-nano fiber Bragg grating, the pH sensitive film and the micro-nano fiber Bragg grating are combined to form the optical fiber sensor for detecting the pH value of the liquid, the optical fiber sensor has the advantages of high measuring sensitivity, short response time, low transmission loss, strong anti-interference capability and the like, meets the monitoring and measuring requirements on the pH value of the liquid, improves the measuring sensitivity of the pH value, reduces the response time of pH value detection, is simple in structure, can also realize online and remote monitoring liquid pH value measurement, and is more convenient to use.

2. According to the pH value measuring system based on the micro-nano fiber Bragg grating, the polarization controller can keep the polarization state of the polarized light unchanged in the transmission process, and the accuracy of the detection result is further improved.

3. Above-mentioned pH value measurement system based on optical fiber Bragg grating receives a little is equipped with first isolator between pumping light source and wavelength division multiplexer to set up the second isolator between wavelength division multiplexer and spectral analyser, can prevent the light reflection through the cooperation of first isolator and second isolator, ensure unidirectional transmission.

4. According to the pH value measurement system based on the micro-nano fiber Bragg grating, the erbium-ytterbium co-doped fiber Bragg grating pair with the diameter of the submicron level is adopted, so that the erbium-ytterbium co-doped fiber Bragg grating pair is sensitive to the change of external stress, the detection precision is further improved, and the detection time is shortened.

Drawings

Fig. 1 is a schematic structural diagram of a pH value measurement system based on a micro-nano fiber bragg grating in embodiment 1 of the present invention.

Fig. 2 is a schematic structural diagram of a pH value measurement system based on a micro-nano fiber bragg grating in embodiment 2 of the present invention.

Fig. 3 is a schematic structural diagram of a micro-nano fiber bragg grating in embodiment 1 and embodiment 2 of the present invention.

Fig. 4 is a schematic structural diagram of the micro-nano fiber bragg grating after being wrapped with the pH sensitive film in embodiment 1 and embodiment 2 of the present invention.

Description of the main elements

2. A pump light source; 3. a first isolator; 4. a wavelength division multiplexer; 5. micro-nano fiber Bragg grating; 51. a fiber core; 52. a fiber cladding; 53. a connecting region; 54. a transition zone; 55. a detection zone; 56. a fiber Bragg grating pair; 6. a pH sensitive membrane; 7. a second isolator; 8. a polarization controller; 9. a polarizer; 10. a photodetector; 11. a spectrum analyzer; 12. a transmission optical fiber; 13. a spectrum analyzer; 14. a cable; 20. a liquid carrying tank; 30. a liquid.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or intervening components may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Example 1

Please refer to fig. 1 and fig. 4 together, a first embodiment of the present invention provides a pH value measuring system based on a micro-nano fiber bragg grating, which includes a pump light source 2, a first isolator 3, a wavelength division multiplexer 4, a micro-nano fiber bragg grating 5, a pH sensitive film 6, a second isolator 7, a polarization controller 8, a polarizer 9, a photodetector 10, and a spectrum analyzer 11.

The input end of the first isolator 3 is connected to the pump light source 2, and specifically, in the present embodiment, the input end of the first isolator 3 is connected to the pump light source 2 through the transmission fiber 12. Preferably, the transmission fiber 12 connecting the first isolator 3 and the pump light source 2 is a single-mode fiber, which has the characteristics of low cost, low loss, small intermodal dispersion, and the like, and is more favorable for realizing long-distance transmission.

The wavelength division multiplexer 4 is an optical passive device that combines two or more wavelength optical signals into the same optical fiber for transmission. In this embodiment, the wavelength division multiplexer 4 is a three-port optical fiber wavelength division multiplexer having three ports, namely an a port, a b port and a c port, wherein the a port is an input port, the b port is an output port, and the c port is a reflection port. The a port of the optical wavelength division multiplexer 4, that is, the input port of the optical wavelength division multiplexer 4, is connected to the output end of the first isolator 3, specifically, in the present embodiment, the input port of the optical wavelength division multiplexer 4 is connected to the output end of the first isolator 3 through a transmission fiber 12, and preferably, the transmission fiber 12 connecting the optical wavelength division multiplexer 4 and the first isolator 3 is a single mode fiber. The wavelength division multiplexer 4 preferably adopts a broadband high-isolation wavelength division multiplexer, and has the characteristics of stable performance, high isolation and the like. The wavelength division multiplexer 4 is a three-port optical fiber wavelength division multiplexer, and can better separate various laser lights with different wavelengths.

The micro-nano fiber bragg grating 5 is connected to a b port, i.e., an output port, of the wavelength division multiplexer 4, specifically, in this embodiment, the micro-nano fiber bragg grating 5 is connected to the b port, i.e., the output port, of the wavelength division multiplexer 4 through a transmission fiber 12, and preferably, the transmission fiber 12 connecting the micro-nano fiber bragg grating 5 to the wavelength division multiplexer 4 is a single mode fiber. In this embodiment, the micro-nano fiber bragg grating 5 includes a fiber bragg grating pair 56, which is written by erbium-ytterbium co-doped fiber through tapering and laser and has a diameter of a submicron level, specifically: referring to fig. 3, the micro-nano fiber bragg grating 5 includes a fiber core 51 and a fiber cladding 52, in this embodiment, the fiber core 51 is preferably an erbium-ytterbium co-doped fiber, which has a spectral width requirement on the pump laser that is greatly reduced compared with that before being undoped, and a commercially available, low-cost multimode high-power pump laser module can be used to meet the high-power signal light output requirement; the optical fiber core 51 and the optical fiber cladding 52 both comprise a connection region 53, a transition region 54 and a detection region 55 which are sequentially connected along the axial direction of the optical fiber core 51; the diameter of the connection region 53 is larger than that of the detection region 55, and the diameter of the detection region 55 of the optical fiber core 51 is in the micro-nano scale range; the diameter of the transition region 54 gradually decreases from the direction far away from the connection region 53, the connection region 53 of the optical fiber cladding 52 is coated outside the connection region 53 of the optical fiber core 51, the transition region 54 of the optical fiber cladding 52 is coated outside the transition region 54 of the optical fiber core 51, and the detection region 55 of the optical fiber cladding 52 is coated outside the detection region 55 of the optical fiber core 51; the detection regions 55 of the optical fiber core 51 are written with fiber bragg grating pairs 56 with a submicron diameter at intervals along the axial direction of the optical fiber core 51, and preferably, the distance between the fiber bragg grating pairs 56 is about 0.4-0.6 cm. The free end of the connection region 53 of the optical fiber core 51 and the free end of the connection region 53 of the optical fiber cladding 52 are both fusion-spliced to the transmission fiber 12.

When the micro-nano fiber bragg grating 5 is manufactured, the erbium-ytterbium co-doped fiber is processed by adopting a melting tapering method to form a transition region 54 and a detection region 55 with the diameter in a micro-nano scale, and then a fiber bragg grating pair 56 is formed in the detection region 55 of the fiber core 51 by adopting a laser writing method. The fiber cladding 52 is an outer portion of the fiber core 51, and is typically a layer of glass or other transparent material that covers the fiber core 51, and has a refractive index generally lower than that of the fiber core 51 to provide a reflective surface or optical isolation, while also providing some mechanical protection. In this embodiment, the pumping light source 2 is a high power semiconductor laser with output wavelength of 980nm, which has the characteristic of high power, and the output laser enables the micro-nano fiber bragg grating to absorb erbium and ytterbium ions in the 56 and then generates energy level transition, so as to generate new laser. The method of erbium ytterbium co-doped fiber belongs to the prior art, and the doping concentration of erbium ytterbium ion can be selected according to the actual need, which is not described herein for brevity. In the embodiment, the micro-nano fiber bragg grating 5 is of a single-ended structure, so that single-ended detection can be realized, and the use is more convenient.

The pH sensitive film 6 is coated on the outer surface of the micro-nano fiber Bragg grating 5, in the embodiment, the pH sensitive film 6 is coated on the outer surface of the detection area 55 of the fiber cladding 52, and the pH sensitive film 6 is pH sensitive hydrogel. The pH sensitive hydrogel is a material commonly used for measuring the pH value, when the pH value of the environment where the pH sensitive hydrogel is located is changed, the pH sensitive hydrogel can correspondingly shrink or expand, and the refractive index of the hydrogel can correspondingly change; the pH sensitive membrane 6 is sensitive to the response of pH, so that the detection sensitivity can be further improved; and the response range to pH is larger, so that the detection range can be further expanded.

The input of the second isolator 7 is connected to the c-port of the wavelength division multiplexer 4, i.e. the reflection port of the wavelength division multiplexer 4. In the present embodiment, the input end of the second isolator 7 and the c port of the wavelength division multiplexer 4 are connected by a transmission fiber 12, and preferably, the transmission fiber 12 connecting the second isolator 7 and the wavelength division multiplexer 4 is a single mode fiber. Preferably, the first isolator 3 and the second isolator 7 both use high-isolation isolators, which can limit the direction of light, so that light can only be transmitted in a single direction, and light reflected by the optical fiber echo can be better intercepted.

An input of the polarization controller 8 is connected to an output of the second isolator 7. In the present embodiment, the input end of the polarization controller 8 and the output end of the second isolator 7 are connected by a transmission fiber 12, and preferably, the transmission fiber 12 connecting the polarization controller 8 and the second isolator 7 is a single mode fiber. The output end of the polarization controller 8 is connected with the input end of the polarizer 9. In the present embodiment, the input end of the polarizer 9 and the output end of the polarization controller 8 are connected through a transmission fiber 12, and preferably, the transmission fiber 12 connecting the polarizer 9 and the polarization controller 8 is a single mode fiber. The output end of the polarizer 9 is connected to the input end of the photodetector 10, in this embodiment, the input end of the photodetector 10 is connected to the output end of the polarizer 9 through a transmission fiber 12, and preferably, the transmission fiber 12 connecting the photodetector 10 and the polarizer 9 is a single mode fiber. The output of the photodetector 10 is connected to the input of the spectrum analyzer 11, in this embodiment, the input of the spectrum analyzer 11 is connected to the output of the photodetector 10 through a cable 14, and preferably, the cable 14 connecting the spectrum analyzer 11 and the photodetector 10 is a high frequency cable.

Specifically, in this embodiment, the polarization controller 8 preferably adopts a three-ring optical fiber polarization controller, the polarizer 9 is an optical fiber polarizer, the photodetector 10 is a high-speed photodetector, and the spectrum analyzer 11 is a real-time spectrum analyzer, wherein the polarization controller 8 is selected to keep the polarization state of the polarized light unchanged during transmission; the polarizer 9 is selected to enable two polarization states which are perpendicular to each other to generate beat frequency; the photodetector 10 is capable of converting an optical signal in an optical fiber into an electrical signal; the spectrum analyzer 11 is a real-time spectrum analyzer, and the spectrum analyzer has a large measurement range and excellent performance. The structures of the pump light source 2, the first isolator 3, the wavelength division multiplexer 4, the pH sensitive film 6, the second isolator 7, the polarization controller 8, the polarizer 9, the photodetector 10, and the real-time spectrum analyzer 11 adopted in this embodiment all belong to the prior art, and are not described herein again for brevity.

When the pH value of the liquid is measured, the micro-nano fiber Bragg grating 5 coated with the pH sensitive film 6 is placed in the liquid 30 to be measured, in the embodiment, the liquid 30 of which the pH value needs to be measured is added into a liquid carrying pool 20, and the liquid 30 to be measured is added or replaced in the liquid carrying pool 20, so that the operation is simple and convenient. Laser emitted by the pumping light source 2 is incident into the micro-nano fiber bragg grating 5 wrapped with the pH sensitive film 6, and specifically, the laser emitted by the pumping light source 2 is incident into the micro-nano fiber bragg grating 5 wrapped with the pH sensitive film 6 after sequentially passing through an a port and a b port of the wavelength division multiplexer 4; after the micro-nano fiber bragg grating 5 coated with the pH sensitive film 6 is placed in the liquid 30 to be detected, the pH value of the liquid to be detected changes to promote the pH sensitive film 6 to shrink or expand, and at the moment, the characteristic wavelength of the micro-nano fiber bragg grating 5 changes. The light with the characteristic wavelength sequentially passes through the second isolator 7, the polarization controller 8, the polarizer 9 and the photoelectric detector 10 and then is converted into an electric signal, the relation between the electric signal and the characteristic wavelength of the micro-nano fiber bragg grating 5 is obtained through the spectrum analyzer 11, and the pH value of the liquid 30 to be measured can be obtained through a conversion method according to the relation between the characteristic wavelength of the micro-nano fiber bragg grating 5 and the characteristic wavelength returned by the pH standard liquid. The conversion method of pH value belongs to the prior art, and is not described herein for brevity.

According to the pH value measuring system based on the micro-nano fiber Bragg grating, the micro-nano fiber Bragg grating 5 is selected, so that the response is quicker and the measuring result is more accurate when the pH value is measured; the pumping light source 2 is selected to enable the output laser to be absorbed by erbium and ytterbium ions in the micro-nano fiber Bragg grating 5 and then to generate energy level transition, so that new laser is generated; the real-time spectrum analyzer 11 can display the characteristic frequency of the central wavelength of the returned micro-nano fiber Bragg grating 5. The pH value measuring system has the advantages of quick response, high measuring precision, capability of realizing remote and real-time measurement, single-ended detection and the like.

Example 2

Please refer to fig. 2 and fig. 4 simultaneously, a second embodiment of the present invention provides a pH value measuring system based on a micro-nano fiber bragg grating, which includes a pump light source 2, a first isolator 3, a wavelength division multiplexer 4, a micro-nano fiber bragg grating 5, a pH sensitive film 6, a second isolator 7 and a spectrum analyzer 13.

The input end of the first isolator 3 is connected to the pump light source 2, and specifically, in the present embodiment, the input end of the first isolator 3 is connected to the pump light source 2 through the transmission fiber 12. Preferably, the transmission fiber 12 connecting the first isolator 3 and the pump light source 2 is a single-mode fiber, which has the characteristics of low cost, low loss, small intermodal dispersion, and the like, and can realize long-distance transmission.

The wavelength division multiplexer 4 is an optical passive device that combines two or more wavelength optical signals into the same optical fiber for transmission, and in this embodiment, the wavelength division multiplexer 4 is a three-port optical fiber wavelength division multiplexer having three ports, which are an a port, a b port, and a c port, where the a port is an input port, the b port is an output port, and the c port is a reflection port. An input port, i.e., an a port, of the optical wavelength division multiplexer 4 is connected to an output end of the first isolator 3, and specifically, in the present embodiment, the input port of the optical wavelength division multiplexer 4 is connected to the output end of the first isolator 3 through a transmission fiber 12. The wavelength division multiplexer 4 preferably adopts a broadband high-isolation wavelength division multiplexer, and has the characteristics of stable performance, high isolation and the like. The wavelength division multiplexer 4 is a three-port optical fiber wavelength division multiplexer, and can better separate various laser lights with different wavelengths.

The micro-nano fiber bragg grating 5 is connected to an output port, i.e. a b port, of the wavelength division multiplexer 4, specifically, in this embodiment, the micro-nano fiber bragg grating 5 is connected to the output port of the wavelength division multiplexer 4 through a transmission fiber 12, and preferably, the transmission fiber 12 connecting the micro-nano fiber bragg grating 5 and the wavelength division multiplexer 4 is a single mode fiber. In this embodiment, the micro-nano fiber bragg grating 5 includes a fiber bragg grating pair 56, which is written by erbium-ytterbium co-doped fiber through tapering and laser and has a diameter of a submicron level, specifically: referring to fig. 3, the micro-nano fiber bragg grating 5 includes a fiber core 51 and a fiber cladding 52, in this embodiment, the fiber core 51 is preferably an erbium-ytterbium co-doped fiber, which has a spectral width requirement on the pump laser that is greatly reduced compared with that before being undoped, and a commercially available, low-cost multimode high-power pump laser module can be used to meet the high-power signal light output requirement; the optical fiber core 51 and the optical fiber cladding 52 both comprise a connection region 53, a transition region 54 and a detection region 55 which are sequentially connected along the axial direction of the optical fiber core 51; the diameter of the connection region 53 is larger than that of the detection region 55, and the diameter of the detection region 55 of the optical fiber core 51 is in the micro-nano scale range; the diameter of the transition region 54 gradually decreases from the direction far away from the connection region 53, the connection region 53 of the optical fiber cladding 52 is coated outside the connection region 53 of the optical fiber core 51, the transition region 54 of the optical fiber cladding 52 is coated outside the transition region 54 of the optical fiber core 51, and the detection region 55 of the optical fiber cladding 52 is coated outside the detection region 55 of the optical fiber core 51; the detection regions 55 of the optical fiber core 51 are written with fiber bragg grating pairs 56 with a submicron diameter at intervals along the axial direction of the optical fiber core 51, and preferably, the distance between the fiber bragg grating pairs 56 is about 0.4-0.6 cm. The free end of the connection region 53 of the optical fiber core 51 and the free end of the connection region 53 of the optical fiber cladding 52 are both fusion-spliced to the transmission fiber 12.

The pH sensitive film 6 is coated on the outer surface of the micro-nano fiber bragg grating 5, in the present embodiment, the pH sensitive film 6 is coated on the outer surface of the detection area 56 of the fiber cladding 52, and preferably, the pH sensitive film 6 is pH sensitive hydrogel. The pH-sensitive hydrogel is commonly used as a material for measuring pH value, when the pH value of the environment where the pH-sensitive hydrogel is located is changed, the pH-sensitive hydrogel correspondingly shrinks or expands, and the refractive index of the hydrogel also correspondingly changes; the pH sensitive membrane 6 is sensitive to the response of pH, so that the detection sensitivity can be further improved; and the response range to pH is larger, so that the detection range can be further expanded.

The input of the second isolator 7 is connected to the c-port of the wavelength division multiplexer 4, i.e. the reflection port of the wavelength division multiplexer 4. In the present embodiment, the input end of the second isolator 7 and the c port of the wavelength division multiplexer 4 are connected by a transmission fiber 12, and preferably, the transmission fiber 12 connecting the second isolator 7 and the wavelength division multiplexer 4 is a single mode fiber.

The input of the spectrum analyzer 13 is connected to the output of the second isolator 7. In the present embodiment, the input end of the spectrum analyzer 13 and the output end of the second isolator 7 are connected by the transmission fiber 12, and preferably, the transmission fiber 12 connecting the spectrum analyzer 13 and the second isolator 7 is a single mode fiber. Preferably, the first isolator 3 and the second isolator 7 both use high-isolation isolators, which can limit the direction of light, so that light can only be transmitted in a single direction, and light reflected by the optical fiber echo can be better intercepted. Preferably, the spectrum analyzer 13 is a wide bandwidth high resolution spectrum analyzer.

When the pH value of the liquid is measured, the micro-nano fiber Bragg grating 5 coated with the pH sensitive film 6 is placed into the liquid to be measured, in the embodiment, the liquid of which the pH value needs to be measured is added into a liquid carrying pool 20, and the liquid to be measured 30 is added or replaced in the liquid carrying pool 20, so that the operation is simple and convenient. Laser emitted by the pumping light source 2 is incident into the micro-nano fiber bragg grating 5 wrapped with the pH sensitive film 6, and specifically, the laser emitted by the pumping light source 2 is incident into the micro-nano fiber bragg grating 5 wrapped with the pH sensitive film 6 after sequentially passing through an a port and a b port of the wavelength division multiplexer 4; after the micro-nano fiber bragg grating 5 coated with the pH sensitive film 6 is placed in a liquid to be detected, when the pH value of the liquid around the micro-nano fiber bragg grating 5 changes, the pH sensitive hydrogel contracts or expands, the refractive index of the hydrogel correspondingly changes, the micro-nano fiber bragg grating 5 reflects the characteristic wavelength of the changed pH value, specifically, the transmission wave reflected by the micro-nano fiber bragg grating 5 enters the spectrum analyzer 13 through the port c of the wavelength division multiplexer 4, the spectrum analyzer 13 compares the characteristic wavelength of the changed pH value reflected by the micro-nano fiber bragg grating 5 with the characteristic wavelength of the pH standard liquid, and the pH value of the liquid to be detected can be obtained through a conversion method. The conversion method of pH value belongs to the prior art, and is not described herein for brevity.

When the pH value measuring system based on the micro-nano fiber Bragg grating is used, the micro-nano fiber Bragg grating 5 coated with the pH sensitive film 6 is placed into liquid to be detected, when the pH value of the environment where the pH sensitive film 6 is located changes, the pH sensitive film 6 can correspondingly contract or expand, the refractive index of the pH sensitive film can correspondingly change, the pH sensitive film 6 is combined with the micro-nano fiber Bragg grating 5, and the pH value can be accurately and quickly measured through the sensing effect of the strong evanescent field of the micro-nano fiber Bragg grating 5 on the refractive index.

According to the pH value measuring system based on the micro-nano fiber Bragg grating, the pH sensitive film and the micro-nano fiber Bragg grating are combined to form the optical fiber sensor for detecting the pH value of the liquid, the optical fiber sensor has the advantages of high measuring sensitivity, short response time, low transmission loss, strong anti-interference capability and the like, meets the monitoring and measuring requirements on the pH value of the liquid, improves the measuring sensitivity of the pH value, reduces the response time of pH value detection, is simple in structure, can also realize online and remote monitoring liquid pH value measurement, and is more convenient to use.

Above-mentioned pH value measurement system based on optical fiber Bragg grating receives a little is equipped with first isolator 3 between pumping light source 2 and wavelength division multiplexer 4 to set up second isolator 7 between wavelength division multiplexer 4 and spectral analyser 13, can prevent through the cooperation of first isolator 3 and second isolator 7 that the reverberation through wavelength division multiplexer 4 from getting into pumping light source 2, play the effect of protection pumping light source 2.

According to the pH value measurement system based on the micro-nano fiber Bragg grating, the erbium-ytterbium co-doped fiber Bragg grating pair 56 with the diameter of the submicron level is adopted, so that the erbium-ytterbium co-doped fiber Bragg grating pair is sensitive to the change of external stress, the detection precision is further improved, and the corresponding time is shortened.

According to the pH value measuring system based on the micro-nano fiber Bragg grating, the polarization controller 8 can keep the polarization state of the polarized light unchanged in the transmission process, and the accuracy of the detection result is further improved.

The above description is for the detailed description of the preferred possible embodiments of the present invention, but the embodiments are not intended to limit the scope of the present invention, and all equivalent changes or modifications accomplished under the technical spirit suggested by the present invention should fall within the scope of the present invention.

Claims

1. A pH value measuring system based on micro-nano fiber Bragg grating is characterized in that: the device comprises a pumping light source (2), a first isolator (3), a wavelength division multiplexer (4), a micro-nano fiber Bragg grating (5), a pH sensitive film (6), a second isolator (7), a polarization controller (8), a polarizer (9), a photoelectric detector (10) and a spectrum analyzer (11), wherein the output end of the pumping light source (2) is connected with the input end of the first isolator (3); the output end of the first isolator (3) is connected with the input port of the wavelength division multiplexer (4); the output port of the wavelength division multiplexer (4) is connected with the micro-nano optical fiber Bragg grating (5); the pH sensitive film (6) is coated on the outer surface of the micro-nano fiber Bragg grating (5); the input end of the second isolator (7) is connected with the reflection port of the wavelength division multiplexer (4), and the output end of the second isolator (7) is connected with the input end of the polarization controller (8); the output of polarization controller (8) with the input of polarizer (9) links to each other, the output of polarizer (9) with the input of photoelectric detector (10) links to each other, the output of photoelectric detector (10) with the input of spectral analyser (11) links to each other.

2. The pH value measurement system based on the micro-nano fiber Bragg grating is characterized in that: the micro-nano fiber Bragg grating (5) comprises a fiber core (51) and a fiber cladding (52), wherein the fiber core (51) and the fiber cladding (52) respectively comprise a connecting area (53), a transition area (54) and a detection area (55) which are sequentially connected along the axial direction of the fiber core (51), the diameter of the connecting area (53) is larger than that of the detection area (55), the diameter of the transition area (54) is gradually reduced from the direction far away from the connecting area (53), the connecting area (53) of the fiber cladding (52) is coated outside the connecting area (53) of the fiber core (51), the transition area (54) of the fiber cladding (52) is coated outside the transition area (54) of the fiber core (51), and the detection area (55) of the fiber cladding (52) is coated outside the detection area (55) of the fiber core (51); the detection area (55) of the optical fiber core (51) is engraved with a fiber Bragg grating pair (56) with the diameter of submicron level at intervals along the axial direction of the optical fiber core (51); the pH sensitive film (6) is coated outside the detection area (55) of the optical fiber cladding (52); the connection area (53) is connected to an output port of the wavelength division multiplexer (4).

3. The pH value measurement system based on the micro-nano fiber Bragg grating is characterized in that: the distance between the fiber Bragg grating pair (56) is 0.4-0.6 cm.

4. The pH value measurement system based on the micro-nano fiber Bragg grating is characterized in that: the fiber core (51) of the micro-nano fiber Bragg grating (5) is erbium-ytterbium co-doped fiber.

5. The pH value measurement system based on the micro-nano fiber Bragg grating is characterized in that: the pumping light source (2), the first isolator (3), the wavelength division multiplexer (4), the micro-nano fiber Bragg grating (5), the second isolator (7), the polarization controller (8), the polarizer (9) and the photoelectric detector (10) are connected through a transmission fiber (12), and the photoelectric detector (10) is connected with the spectrum analyzer (11) through a cable (14).

6. The pH value measurement system based on the micro-nano fiber Bragg grating is characterized in that: the pH sensitive film (6) is pH sensitive hydrogel.

7. A pH value measuring system based on micro-nano fiber Bragg grating is characterized in that: the device comprises a pumping light source (2), a first isolator (3), a wavelength division multiplexer (4), a micro-nano fiber Bragg grating (5), a pH sensitive film (6), a second isolator (7) and a spectrum analyzer (13), wherein the output end of the pumping light source (2) is connected with the input end of the first isolator (3); the output end of the first isolator (3) is connected with the input port of the wavelength division multiplexer (4); the output port of the wavelength division multiplexer (4) is connected with the micro-nano optical fiber Bragg grating (5); the pH sensitive film (6) is coated on the outer surface of the micro-nano fiber Bragg grating (5); the input end of the second isolator (7) is connected with the reflection port of the wavelength division multiplexer (4), and the output end of the second isolator (7) is connected with the input end of the spectrum analyzer (13).

8. The pH value measurement system based on the micro-nano fiber Bragg grating is characterized in that: the micro-nano fiber Bragg grating (5) comprises a fiber core (51) and a fiber cladding (52), wherein the fiber core (51) and the fiber cladding (52) respectively comprise a connecting area (53), a transition area (54) and a detection area (55) which are sequentially connected along the axial direction of the fiber core (51), the diameter of the connecting area (53) is larger than that of the detection area (55), the diameter of the transition area (54) is gradually reduced from the direction far away from the connecting area (53), the connecting area (53) of the fiber cladding (52) is coated outside the connecting area (53) of the fiber core (51), the transition area (54) of the fiber cladding (52) is coated outside the transition area (54) of the fiber core (51), and the detection area (55) of the fiber cladding (52) is coated outside the detection area (55) of the fiber core (51); the detection area (55) of the optical fiber core (51) is engraved with a fiber Bragg grating pair (56) with the diameter of submicron level at intervals along the axial direction of the optical fiber core (51); the pH sensitive film (6) is coated outside the detection area (55) of the optical fiber cladding (52); the connection area (53) is connected to an output port of the wavelength division multiplexer (4).

9. The pH value measurement system based on the micro-nano fiber Bragg grating is characterized in that: the distance between the fiber Bragg grating pair (56) is 0.4-0.6 cm.

10. The pH value measurement system based on the micro-nano fiber Bragg grating is characterized in that: the fiber core (51) adopts erbium ytterbium co-doped fiber.