阅读说明：本技术 一种可温度补偿的光纤光栅紫外传感方法及装置 (Fiber bragg grating ultraviolet sensing method and device capable of compensating temperature ) 是由 沈涛 陈姣姣 代小爽 杨添宇 梁涵 于 2019-11-18 设计创作，主要内容包括：本发明公开了一种可温度补偿的光纤光栅紫外传感方法及装置,包括依次连接的光源、紫外传感头、光信号处理器,其中,紫外传感头包括单模光纤、多模光纤,塑料光纤光栅、ZnO复合氧化石墨烯；各器件之间通过光纤熔融连接的方式连接,采用溶胶-凝胶辅助水热法制备出的ZnO复合氧化石墨烯涂覆在塑料光纤光栅上,通过测量干涉光谱的改变来间接得到紫外光强的改变。本发明是为了解决在紫外传感领域中,现有紫外传感技术灵敏度低、结构复杂、生产成本高昂、操作复杂的问题。(The invention discloses a fiber bragg grating ultraviolet sensing method and a fiber bragg grating ultraviolet sensing device capable of temperature compensation, wherein the fiber bragg grating ultraviolet sensing method comprises a light source, an ultraviolet sensing head and an optical signal processor which are sequentially connected, wherein the ultraviolet sensing head comprises a single-mode optical fiber, a multi-mode optical fiber, a plastic fiber bragg grating and ZnO composite graphene oxide; all devices are connected in an optical fiber fusion connection mode, ZnO composite graphene oxide prepared by a sol-gel assisted hydrothermal method is coated on a plastic optical fiber grating, and the change of ultraviolet light intensity is indirectly obtained by measuring the change of an interference spectrum. The invention aims to solve the problems of low sensitivity, complex structure, high production cost and complex operation of the existing ultraviolet sensing technology in the field of ultraviolet sensing.)

1. The fiber bragg grating ultraviolet sensing method and device capable of temperature compensation are characterized in that the sensor comprises a light source (1), an ultraviolet sensing head (2) and an optical signal processor (3) which are sequentially connected, wherein:

the ultraviolet sensing head (2) is internally provided with a single mode fiber (2-1), a multimode fiber (2-2), a plastic fiber grating (2-3), ZnO composite graphene oxide (2-4), a second multimode fiber (2-5) and a second single mode fiber (2-6), and one end of the ultraviolet sensing head (2) is connected with the light source (1) and the other end is connected with the optical signal processor (3).

2. The method and the device for sensing the ultraviolet rays of the fiber bragg grating capable of temperature compensation according to claim 1, wherein the method comprises the following steps: the output center wavelength of the light source (1) is 1550nm, the frequency bandwidth is 40nm, and the light source is used for providing light signals.

3. The method and the device for sensing the ultraviolet rays of the fiber bragg grating capable of temperature compensation according to claim 1, wherein the method comprises the following steps: one side of the conical region of the plastic fiber grating (2-3) is used for writing a Bragg grating by utilizing a phase mask method.

4. The method and the device for sensing the ultraviolet rays of the fiber bragg grating capable of temperature compensation according to claim 1, wherein the method comprises the following steps: the surface of the conical area of the plastic fiber grating (2-3) is coated with ZnO composite graphene oxide (2-4), two ends of the plastic fiber grating (2-3) are connected with the first multimode fiber (2-2) and the second multimode fiber (2-5) in a melting mode, light beams are combined in the second multimode fiber (2-5) to form interference light, and interference signals are output from the second multimode fiber (2-6).

5. The method and the device for sensing the ultraviolet rays of the fiber bragg grating capable of temperature compensation according to claim 1, wherein the method comprises the following steps: the length of the plastic fiber grating (2-3) is set to be 2cm, the length of the Bragg grating is 9mm, and the surface of the plastic fiber grating is coated with ZnO composite graphene oxide (2-4).

6. The method and the device for sensing the ultraviolet rays of the fiber bragg grating capable of temperature compensation according to claim 1, wherein the method comprises the following steps: the lengths of the first multimode fiber (2-2) and the second multimode fiber (2-5) are set to be 1.5cm and 1.5cm respectively.

7. The method and the device for sensing the ultraviolet rays of the fiber bragg grating capable of temperature compensation according to claim 1, wherein the method comprises the following steps: the light source (1), the ultraviolet sensing head (2) and the optical signal processor (3) are connected with each other through single-mode optical fibers, and the single-mode optical fibers are connected with the devices in an optical fiber fusion connection mode.

8. The method and the device for sensing the ultraviolet rays of the fiber bragg grating capable of temperature compensation according to claim 1, wherein the method comprises the following steps: the optical signal processor (3) is a spectrometer, and the spectrometer (8) performs spectrum detection on the obtained interference signal and obtains corresponding sensing data.

9. The method and the device for sensing the ultraviolet rays of the fiber bragg grating capable of temperature compensation according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:

firstly, pretreating the plastic optical fiber, removing a cladding by using acetone, welding all sections of optical fibers together in a fusion connection mode, then fixing the welded sensing optical fiber on a tapering machine, placing the plastic optical fiber at a flame, and fixing two ends of the optical fiber by using a clamp; heating the optical fiber, and controlling the moving speed of the moving platform through a computer related program to obtain the tapered plastic optical fiber;

the U-shaped structure is manufactured by adopting a heat setting method: heating the metal rod to 70-90 ℃, then winding the conical plastic optical fiber part on the metal rod, and applying a proper pulling force to two ends of the metal rod to obtain a U-shaped plastic optical fiber with a stable structure;

utilizing a phase mask method to write a Bragg grating with the length of 9mm on one side of a U-shaped conical area of the plastic optical fiber;

preparing ZnO composite graphene oxide by a sol-gel assisted hydrothermal method: firstly, dispersing 3mL of graphene oxide solution with the concentration of 2mg/mL in 15mL of deionized water for 1h by ultrasonic; secondly, mixing the graphene oxide solution with 1.8g of zinc nitrate, 2.6g of citric acid and 35mL of deionized water, stirring at a constant temperature of 70 ℃ for 1h, and then slowly dropping 1mol/L of NaOH solution into the mixed solution until the pH value of the suspension is 9.6; then transferring the suspension into a reaction kettle, heating the reaction kettle in an electrothermal blowing drying oven at 120 ℃ for 17 hours, taking out and naturally cooling; finally, washing the product for 2 times by using deionized water, and centrifuging for 10min at the rotating speed of 6000 rmp/min;

coating ZnO composite graphene oxide on a plastic fiber grating by adopting a dropping-coating method: dropping the prepared material on a plastic fiber grating prepared in advance by using a rubber head dropper, and then putting the sensor into an electrothermal blowing drying oven at 60 ℃ for 5-7 hours to ensure that the ZnO composite graphene oxide and the plastic fiber grating are tightly attached together;

setting the parameters of the optical fiber fusion splicer as follows: in a manual mode, the discharge intensity is 4000bit, and the discharge time is 3000 ms; connecting a first single-mode fiber (2-1), a first multimode fiber (2-2), a plastic fiber grating (2-3), a second multimode fiber (2-5) and a second single-mode fiber (2-6) with each other in a fusion connection manner;

and connecting the completed ultraviolet sensing head (2) with the light source (1) and the optical signal processor (3) to further complete the manufacturing process of the whole ultraviolet sensing device.

Technical Field

The invention belongs to the technical field of optical fiber sensing, and particularly relates to a temperature-compensated optical fiber grating ultraviolet sensing method and device.

Background

The wide application of ultraviolet detection in the fields of civilian use, military industry and the like makes scientific researchers pay more and more attention to the development of ultraviolet detection. The earliest uv detectors were based on pure silicon but were not as accurate due to their response to visible light. With the continuous progress of the preparation process of semiconductor materials and devices, wide bandgap semiconductor ultraviolet detection has become a research hotspot in the technical field of ultraviolet detection at present. Compared with a narrow-band-gap semiconductor ultraviolet detector, the wide-bandgap material does not absorb visible light, has high response speed, high measurement precision and high visible light rejection ratio, can effectively make up the disadvantages of wide-bandgap materials such as Si and GaAs, and is widely applied to the field of ultraviolet detection. And the wide bandgap materials are various, such as ZnO, TiO and the like, and have the advantages of low cost, simple manufacture, large specific surface area, high stability and the like, so that the wide bandgap materials have important research significance.

The plastic optical fiber has the advantages of simple operation, good flexibility, firmness and durability, low loss window in visible light wave band and the like, so that the plastic optical fiber becomes an ideal choice for short-distance communication and sensing. Optical fiber sensing is a system that utilizes optical information generated by interaction of transmitted light waves and detected physical quantities in an optical fiber detection optical path. With the development of optical fibers in the sensing field, compared with the traditional quartz optical fiber, the plastic optical fiber has the advantages of low price, disposability, easy processing and connection and the like, and is widely applied. Compared with the traditional optical fiber detection device, the optical fiber grating detection device has the characteristics of high sensitivity and high ultraviolet detection precision. And the fiber grating can play a role in temperature compensation.

Disclosure of Invention

Aiming at the defects and improvement needs of the prior art, the invention provides a fiber grating ultraviolet sensing method and a fiber grating ultraviolet sensing device capable of temperature compensation, aiming at effectively solving the problems of difficult packaging and cross temperature sensitivity by researching the interference property of an optical fiber and designing a sensitive part and temperature compensation of the optical fiber, and simultaneously adopting a plastic optical fiber with a U-shaped structure and ZnO composite graphene oxide to achieve the purpose of enhancing the sensitivity to ultraviolet so as to prepare the fiber grating ultraviolet sensing device with high selectivity and high sensitivity.

According to one aspect of the invention, a temperature-compensated fiber grating ultraviolet sensing method and device are provided, wherein the sensor comprises a light source (1), an ultraviolet sensing head (2) and an optical signal processor (3) which are connected in sequence, wherein:

the ultraviolet sensing head (2) is internally provided with a single mode fiber (2-1), a multimode fiber (2-2), a plastic fiber grating (2-3), ZnO composite graphene oxide (2-4), a second multimode fiber (2-5) and a second single mode fiber (2-6), and one end of the ultraviolet sensing head (2) is connected with the light source (1) and the other end is connected with the optical signal processor (3).

The output center wavelength of the light source (1) is 1550nm, the frequency bandwidth is 40nm, and the light source is used for providing light signals.

One side of the conical region of the plastic fiber grating (2-3) is used for writing a Bragg grating by utilizing a phase mask method.

The surface of the conical area of the plastic fiber grating (2-3) is coated with ZnO composite graphene oxide (2-4), two ends of the plastic fiber grating (2-3) are connected with the first multimode fiber (2-2) and the second multimode fiber (2-5) in a melting mode, light beams are combined in the second multimode fiber (2-5) to form interference light, and interference signals are output from the second multimode fiber (2-6).

The length of the plastic fiber grating (2-3) is set to be 2cm, the length of the Bragg grating is 9mm, and the surface of the plastic fiber grating is coated with ZnO composite graphene oxide (2-4).

The lengths of the first multimode fiber (2-2) and the second multimode fiber (2-5) are set to be 1.5cm and 1.5cm respectively.

The light source (1), the ultraviolet sensing head (2) and the optical signal processor (3) are connected with each other through single-mode optical fibers, and the single-mode optical fibers are connected with the devices in an optical fiber fusion connection mode.

The optical signal processor (3) is a spectrometer, and the spectrometer (8) performs spectrum detection on the obtained interference signal and obtains corresponding sensing data.

According to another aspect of the present invention, there is provided a corresponding method for manufacturing an ultraviolet sensor head, the method comprising the steps of:

(1) firstly, pretreating the plastic optical fiber, removing a cladding by using acetone, welding all sections of optical fibers together in a fusion connection mode, then fixing the welded sensing optical fiber on a tapering machine, placing the plastic optical fiber at a flame, and fixing two ends of the optical fiber by using a clamp; heating the optical fiber, and controlling the moving speed of the moving platform through a computer related program to obtain the tapered plastic optical fiber;

(2) the U-shaped structure is manufactured by adopting a heat setting method: heating the metal rod to 70-90 ℃, then winding the conical plastic optical fiber part on the metal rod, and applying a proper pulling force to two ends of the metal rod to obtain a U-shaped plastic optical fiber with a stable structure;

(3) utilizing a phase mask method to write a Bragg grating with the length of 9mm on one side of a U-shaped conical area of the plastic optical fiber;

(4) preparing ZnO composite graphene oxide by a sol-gel assisted hydrothermal method: firstly, dispersing 3mL of graphene oxide solution with the concentration of 2mg/mL in 15mL of deionized water for 1h by ultrasonic; secondly, mixing the graphene oxide solution with 1.8g of zinc nitrate, 2.6g of citric acid and 35mL of deionized water, stirring at a constant temperature of 70 ℃ for 1h, and then slowly dropping 1mol/L of NaOH solution into the mixed solution until the pH value of the suspension is 9.6; then transferring the suspension into a reaction kettle, heating the reaction kettle in an electrothermal blowing drying oven at 120 ℃ for 17 hours, taking out and naturally cooling; finally, washing the product for 2 times by using deionized water, and centrifuging for 10min at the rotating speed of 6000 rmp/min;

(5) coating ZnO composite graphene oxide on a plastic fiber grating by adopting a dropping-coating method: dropping the prepared material on a plastic fiber grating prepared in advance by using a rubber head dropper, and then putting the sensor into an electrothermal blowing drying oven at 60 ℃ for 5-7 hours to ensure that the ZnO composite graphene oxide and the plastic fiber grating are tightly attached together;

(6) setting the parameters of the optical fiber fusion splicer as follows: in a manual mode, the discharge intensity is 4000bit, and the discharge time is 3000 ms; connecting a first single-mode fiber (2-1), a first multimode fiber (2-2), a plastic fiber grating (2-3), a second multimode fiber (2-5) and a second single-mode fiber (2-6) with each other in a fusion connection manner;

and connecting the completed ultraviolet sensing head (2) with the light source (1) and the optical signal processor (3) to further complete the manufacturing process of the whole ultraviolet sensing device.

In general, compared with the prior art, the method and the device for sensing the ultraviolet of the fiber bragg grating capable of temperature compensation according to the invention mainly have the following advantages:

1. the sensing unit is made of the plastic optical fiber and is tapered and heat-set to be U-shaped, the grating is added in the middle, and meanwhile, the surface of the optical fiber is coated with the ZnO composite graphene oxide material, so that the ultraviolet sensing effect can be effectively improved, and the temperature compensation effect is achieved;

2. the designed sensor structure is a five-section structure, and a multimode optical fiber is introduced into two sides of the plastic optical fiber to construct a Mach-Zehnder sensing structure, so that the sensitivity and the stability of the ultraviolet sensing head are improved;

3. the fiber grating ultraviolet sensor constructed according to the invention can complete the whole manufacturing process only by a sol-gel assisted hydrothermal method, a dripping coating method and an optical fiber fusion splicer which have simple manufacturing methods, is convenient to operate, has low manufacturing cost and high sensitivity, and is suitable for large-scale production and manufacturing.

Drawings

FIG. 1 is a schematic diagram of the overall structure of a temperature-compensated fiber grating UV sensing method and apparatus according to the present invention;

fig. 2 is an enlarged schematic view of the uv sensor head.

Detailed Description

The present invention will be further described with reference to the following examples.

Fig. 1 is a schematic diagram of the overall structure of a temperature-compensated fiber grating ultraviolet sensing method and device according to the invention. As shown in fig. 1, the method and apparatus for sensing ultraviolet light by using fiber bragg grating with temperature compensation according to the present invention mainly comprises a light source (1), an ultraviolet sensing head (2), and an optical signal processor (3), which are connected in sequence, wherein: the ultraviolet sensing head (2) comprises a first single-mode fiber (2-1), a first multi-mode fiber (2-2), a plastic fiber grating (2-3), ZnO composite graphene oxide (2-4), a second multi-mode fiber (2-5) and a second single-mode fiber (2-6), one end of the ultraviolet sensing head (2) is connected with the light source (1), and the other end of the ultraviolet sensing head is connected with the optical signal processor (3); the output center wavelength of the light source (1) is 1550nm, the frequency bandwidth is 40nm, and the light source is used for providing an optical signal; the first single-mode optical fiber (2-1) is used for receiving and transmitting the light of the light source (1) and transmitting the light to the first multi-mode optical fiber (2-2); the first single-mode fiber (2-1) and the first multimode fiber (2-2) are connected in a melting mode, and light beam splitting is formed in the first multimode fiber (2-2); the first multimode fiber (2-2) is connected with the plastic fiber grating (2-3) in a melting way, and light is split again in the plastic fiber grating (2-3); one side of the conical region of the plastic fiber grating (2-3) is used for writing a Bragg grating by using a phase mask method; the surface of a conical area of the plastic fiber grating (2-3) is coated with ZnO composite graphene oxide (2-4), two ends of the plastic fiber grating (2-3) are connected with the first multimode fiber (2-2) and the second multimode fiber (2-5) in a melting mode, light is combined in the second multimode fiber (2-5) to form interference light, and interference signals are output by the second multimode fiber (2-6); the spectrometer (8) performs spectral detection on the obtained interference signal and obtains corresponding sensing data.

Specifically, the fiber bragg grating ultraviolet detection device comprises five sections of optical fibers, namely a first single-mode optical fiber (2-1), a first multi-mode optical fiber (2-2), a plastic fiber bragg grating (2-3), ZnO composite graphene oxide (2-4), a second multi-mode optical fiber (2-5) and a second single-mode optical fiber (2-6). An optical signal sent by a light source (1) enters a first multimode fiber (2-2) through a first single mode fiber (2-1), then enters a plastic fiber grating (2-3), enters a second single mode fiber (2-6) through a second multimode fiber (2-5), and finally enters a spectrometer (8).

According to a preferred embodiment of the present invention, the lengths of the first multimode optical fiber (2-2) and the second multimode optical fiber (2-5) are set to 1.5cm and 1.5cm, respectively. The length of the plastic fiber grating (2-3) is set to 2 cm. More experimental data show that the length of the plastic fiber gratings (2-3) affects the light energy distribution and determines the coupling strength between fiber splices.

In order to improve the sensitivity of the sensor to ultraviolet intensity, in the implementation, the plastic optical fiber is tapered to be made into a U shape, and the plastic optical fiber grating (2-3) is coated with ZnO composite graphene oxide (2-4). The specific mode is as follows:

(1) firstly, pretreating the plastic optical fiber, removing a cladding by using acetone, welding all sections of optical fibers together in a fusion connection mode, then fixing the welded sensing optical fiber on a tapering machine, placing the plastic optical fiber at a flame, and fixing two ends of the optical fiber by using a clamp; heating the optical fiber, and controlling the moving speed of the moving platform through a computer related program to obtain the tapered plastic optical fiber;

(2) the U-shaped structure is manufactured by adopting a heat setting method: heating the metal rod to 70-90 ℃, then winding the conical plastic optical fiber part on the metal rod, and applying a proper pulling force to two ends of the metal rod to obtain a U-shaped plastic optical fiber with a stable structure;

(3) utilizing a phase mask method to write a Bragg grating with the length of 9mm on one side of a U-shaped conical area of the plastic optical fiber;

(4) preparing ZnO composite graphene oxide by a sol-gel assisted hydrothermal method: firstly, dispersing 3mL of graphene oxide solution with the concentration of 2mg/mL in 15mL of deionized water for 1h by ultrasonic; secondly, mixing the graphene oxide solution with 1.8g of zinc nitrate, 2.6g of citric acid and 35mL of deionized water, stirring at a constant temperature of 70 ℃ for 1h, and then slowly dropping 1mol/L of NaOH solution into the mixed solution until the pH value of the suspension is 9.6; then transferring the suspension into a reaction kettle, heating the reaction kettle in an electrothermal blowing drying oven at 120 ℃ for 17 hours, taking out and naturally cooling; finally, washing the product for 2 times by using deionized water, and centrifuging for 10min at the rotating speed of 6000 rmp/min;

(5) coating ZnO composite graphene oxide on a plastic fiber grating by adopting a dropping-coating method: dropping the prepared material on a plastic fiber grating prepared in advance by using a rubber head dropper, and then putting the sensor into an electrothermal blowing drying oven at 60 ℃ for 5-7 hours to ensure that the ZnO composite graphene oxide and the plastic fiber grating are tightly attached together;

(6) setting the parameters of the optical fiber fusion splicer as follows: in a manual mode, the discharge intensity is 4000bit, and the discharge time is 3000 ms; connecting a first single-mode fiber (2-1), a first multimode fiber (2-2), a plastic fiber grating (2-3), a second multimode fiber (2-5) and a second single-mode fiber (2-6) with each other in a fusion connection manner;

and connecting the completed ultraviolet sensing head (2) with the light source (1) and the optical signal processor (3) to further complete the manufacturing process of the whole ultraviolet sensing device.

The measurement principle is as follows:

when light of a light source (1) passes through a single mode fiber (2-1) and reaches a welding point of the single mode fiber (2-1) and a multimode fiber (2-2), light splitting is generated, the light is transmitted in the multimode fiber (4), when the light enters a plastic fiber grating (2-3), high-order modes of the plastic fiber grating (2-3) are excited due to the fact that fiber cores of the multimode fiber (2-2) and the plastic fiber grating (2-3) are not matched, due to the fact that transmission coefficients are different, the modes can interfere with each other when the light is recoupled to a second multimode fiber (2-5), and interference light is received by a spectrometer (8) through the single mode fiber (2-6).

When the external ultraviolet environment changes, the change can cause the change of the propagation constant of the plastic fiber grating (2-3), so that the mode interference phenomenon can occur, namely, the extreme value of the transmission spectrum can move, and the change of the characteristic wavelength is expressed as:

wherein, the characteristic wavelength is the effective refractive index, and L is the length of the plastic fiber grating. The shift of the characteristic wavelength can reflect the change of the external ultraviolet intensity.

When the external temperature changes, the effective refractive index and the period of the FBG change, which results in the central wavelength drift of the FBG, and the change of the central wavelength is expressed as:

wherein, the variation of the FBG effective refractive index is represented; is the FBG period. The shift in the center wavelength may reflect a change in the ambient temperature.

As can be seen from the above description, the fiber grating ultraviolet detection device according to the present invention can be manufactured by only using a hydrothermal method and a conventional optical fiber fusion splicer. Low cost, simple manufacture, high sensitivity and strong repeatability. In addition to the innovative use of plastic fibers to achieve good transmission spectra, U-bends and fiber gratings are also a major innovation in sensitivity and temperature compensation. The sensitivity of the sensing head is effectively improved, the cross sensitivity of temperature is effectively eliminated, and the method is suitable for large-scale production.