阅读说明：本技术 一种基于WO3的Sagnac干涉型光纤氢气传感器 (Based on WO3Sagnac interference type optical fiber hydrogen sensor ) 是由 俞建杰 刘姝仪 马才伟 张焱 胡传舟 高文元 梁正 于 2021-08-24 设计创作，主要内容包括：本发明公开了一种基于WO-(3)的Sagnac干涉型光纤氢气传感器,由宽带光源,光谱仪,单模光纤,光纤耦合器,FC光纤连接器,气室,气体流量控制器,氢气发生器,空气泵,掺催化剂的WO-(3)/SiO-(2)混合膜,PDMS,由飞秒激光刻写倾斜角为1.5°的光纤波导,无芯光纤组成。宽带光源发出的光通过单模光纤进入光纤耦合器,后被分成顺时针和逆时针方向的两列光波分别经FC光纤连接器传播,通过涂附掺催化剂的WO-(3)/SiO-(2)混合膜包裹的带有由飞秒激光刻写倾斜角为1.5°的光纤波导的无芯光纤,传输一周后,两列光波在光纤耦合器透射端处汇合并发生干涉。氢气浓度发生变化时,PDMS利用热膨胀性质改变无芯光纤表面折射率,通过计算产生的光程差,测得氢气浓度及其变化量。(The invention discloses a method based on WO 3 The Sagnac interference type optical fiber hydrogen sensor consists of a broadband light source, a spectrometer, a single-mode optical fiber, an optical fiber coupler, an FC optical fiber connector, an air chamber, a gas flow controller, a hydrogen generator, an air pump and WO doped with a catalyst 3 /SiO 2 The mixed film, PDMS, was composed of a femtosecond laser written fiber waveguide with an inclination angle of 1.5 degrees, and a coreless fiber. Light emitted by a broadband light source enters an optical fiber coupler through a single-mode optical fiber, is divided into two lines of light waves in clockwise and anticlockwise directions, is respectively transmitted through an FC optical fiber connector, and passes through WO coated with a doped catalyst 3 /SiO 2 After the coreless optical fiber wrapped by the mixed film and provided with the optical fiber waveguide with the inclination angle of 1.5 degrees is etched by femtosecond laser, two rows of light waves are converged at the transmission end of the optical fiber coupler and generate interference after being transmitted for one week. When the hydrogen concentration changes, the PDMS changes the refractive index of the surface of the coreless optical fiber by utilizing the thermal expansion property, and the hydrogen concentration and the change thereof are measured by calculating the generated optical path difference.)

1. Based on WO₃The Sagnac interference type optical fiber hydrogen sensor comprises a broadband light source (1), a spectrometer (2), a single-mode optical fiber (3), an optical fiber coupler (4), an FC optical fiber connector (5), an air chamber (6), a coreless optical fiber (7), a hydrogen flow controller (8), an air flow controller (9), a hydrogen generator (10), an air pump (11) and a WO doped with a catalyst₃/SiO₂The mixed film (12), PDMS (13), is made up of the fiber waveguide (14) with the inclination angle of 1.5 degrees of femtosecond laser inscription; the method is characterized in that: light emitted by a broadband light source (1) enters an optical fiber coupler (4) through a single-mode optical fiber (3), is divided into two lines of light waves in clockwise and anticlockwise directions, is respectively transmitted through an FC optical fiber connector (5), and passes through WO coated with a doped catalyst₃/SiO₂After the coreless optical fiber (7) which is wrapped by the mixed film (12) and is provided with the optical fiber waveguide (14) with the inclination angle of 1.5 degrees and is engraved by femtosecond laser is transmitted for a week, two rows of light waves are converged and interfered at the transmission end of the optical fiber coupler (4); the hydrogen flow controller (8) and the air flow controller (9) which are connected with the air chamber (6) are respectively connected with the hydrogen generator (10) and the air pump (11), when the hydrogen concentration changes, the PDMS (13) changes the surface refractive index of the coreless optical fiber (7) by utilizing the thermal expansion property, the generated optical path difference is calculated, and the hydrogen concentration and the change quantity thereof are measured.

2. WO-based according to claim 1₃The Sagnac interference type optical fiber hydrogen sensor is characterized in that WO adhered outside the PDMS is utilized₃/SiO₂The powder and hydrogen gas have oxidation-reduction reaction to change the WO coated with doped catalyst₃/SiO₂The surface refractive index of the core-less optical fiber wrapped by the mixed film and provided with the optical fiber waveguide with the inclination angle of 1.5 degrees is inscribed by femtosecond laser, the hydrogen concentration and the variation thereof are detected, and the chemical equation is as follows:

when hydrogen is absent, W0_3-xCan be oxidized into WO in air₃When WO is used₃When reacted with hydrogen, both the light absorption and the refractive index change.

Technical Field

The invention belongs to the technical field of optical fiber sensing, and particularly relates to a sensor based on WO₃The Sagnac interferometric fiber hydrogen sensor.

Background

In 1913, sagnac invented a ring interferometer, and summarized the working principle that a beam of light emitted from the same light source was split into two beams, which converged after traveling in the same loop for one circle in opposite directions, and then interfered on the screen, and when there was a rotation angular velocity in the loop plane, the interference fringes on the screen would move.

The optical fiber grating, especially the bragg grating, is widely applied to the field of optical fiber sensing with the advantages of low insertion loss, easy integration, good stability and the like, and becomes an indispensable optical element.

WO₃/SiO₂The powder acts as a sensitive area and when the sensor is exposed to air mixed with hydrogen, the redox reaction causes an increase in ambient temperature, resulting in a change in the shape of the sensing part due to thermal expansion of the PDMS.

The optical waveguide is a guiding structure composed of an optical transparent medium and used for transmitting optical frequency electromagnetic waves. The transmission principle of the optical waveguide is different from that of a metal closed waveguide, and the total reflection phenomenon of electromagnetic waves causes the optical waveguide to be limited in the waveguide and a limited region around the waveguide to be transmitted on a medium interface with different refractive indexes. Multimode and single mode optical fibers have been successfully used for communications. The transmission characteristics of the optical fiber are sensitive to external temperature factors, so that the optical fiber sensor can be manufactured to measure temperature.

Polydimethylsiloxane (PDMS), which is one of organic silicon, has been widely used in the field of optical fiber sensing because of its low cost, simple use, good adhesion with silicon wafers, good chemical inertness, and the like.

Disclosure of Invention

Aiming at the defects of the prior art, the inventionThe invention aims to use a Sagnac interference structure as a main structure of a sensor and utilize WO₃The hydrogen sensor is formed by carrying out oxidation-reduction reaction with hydrogen to release heat and changing the heated and easily expandable property of PDMS to change the environment of the inclined Bragg fiber grating cladding mold.

The invention is realized by the following technical scheme: based on WO₃The Sagnac interference type optical fiber hydrogen sensor comprises a broadband light source, a spectrometer, a single-mode optical fiber, an optical fiber coupler, an FC optical fiber connector, an air chamber, a coreless optical fiber, a hydrogen flow controller, an air flow controller, a hydrogen generator, an air pump and WO doped with a catalyst₃/SiO₂The mixed film is PDMS and consists of an optical fiber waveguide with the femtosecond laser writing inclination angle of 1.5 degrees; light emitted by a broadband light source enters an optical fiber coupler through a single-mode optical fiber, is divided into two lines of light waves in clockwise and anticlockwise directions, is respectively transmitted through an FC optical fiber connector, and passes through WO coated with a doped catalyst₃/SiO₂After the coreless optical fiber wrapped by the mixed film and provided with the optical fiber waveguide with the inclination angle of 1.5 degrees is etched by femtosecond laser, two rows of light waves are converged at the transmission end of the optical fiber coupler and generate interference after being transmitted for one week. The hydrogen flow controller and the air flow controller which are connected with the air chamber are respectively connected with the hydrogen generator and the air pump, when the hydrogen concentration changes, the PDMS changes the refractive index of the surface of the coreless optical fiber by utilizing the thermal expansion property, and the hydrogen concentration and the change quantity thereof are measured by calculating the generated optical path difference.

The working principle of the invention is as follows: based on the interference characteristic of the optical fiber Sagnac interference, WO adhered outside PDMS is utilized₃/SiO₂The powder and hydrogen gas have oxidation-reduction reaction to change the WO coated with doped catalyst₃/SiO₂The surface refractive index of the core-less optical fiber wrapped by the mixed film and provided with the optical fiber waveguide with the inclination angle of 1.5 degrees is inscribed by femtosecond laser, the hydrogen concentration and the variation thereof are detected, and the chemical equation is as follows:

when hydrogen is absent, WO_3-xCan be oxidized into WO in air₃. Hydrogen sensors based on these reactions can therefore be used for repeated measurements. When WO is₃When reacted with hydrogen, both the light absorption and the refractive index change.

The sensing part is composed of a single-mode-coreless-single-mode structure, an inner waveguide is written by femtosecond laser, and the laser beam is a Gaussian beam, namely the energy density of the center of the beam is higher than that of the edge of the beam. By adjusting the laser beam intensity, the central portion of the laser focus just satisfies the multiphoton ionization threshold of the medium, so that the region where the laser actually interacts with the material is limited to a small region around the center of the focus.

A portion of the light incident from the core of SMF1 is introduced into the waveguide where it propagates along the path defined by the waveguide structure and then returns to the core of SMF2 at the other end. The rest of the incident light diverges at the SMF-NCF interface and is partially collected by the SMF2 core at the other end. The recombined beams at the waveguide end produce a pattern of interference fringes. Let I₁And I₂Is constant, the output of MZI is

Where I is the intensity of the interference fringes, λ denotes the wavelength, n_C，n_N，Andcore refractive index of SMF, coreless fiber, waveguide in single mode fiber and wave in coreless fiberAnd (4) leading.

The invention has the beneficial effects that: the design of the invention is based on WO₃The Sagnac interference type optical fiber hydrogen sensor avoids the defect of complex manufacturing, can realize rapid and repeated measurement, greatly improves the measurement accuracy and sensitivity, has strong innovation and practical value, and has good application prospect.

Drawings

FIG. 1 is a diagram based on WO₃The Sagnac interference type optical fiber hydrogen sensor has a schematic structural diagram.

FIG. 2 is a schematic view of a coreless fiber with a fiber waveguide

Detailed Description

As shown in FIGS. 1 and 2, a WO-based material₃The Sagnac interference type optical fiber hydrogen sensor comprises a broadband light source 1, a spectrometer 2, a single-mode optical fiber 3, an optical fiber coupler 4, an FC optical fiber connector 5, an air chamber 6, a coreless optical fiber 7, a hydrogen flow controller 8, an air flow controller 9, a hydrogen generator 10, an air pump 11 and WO doped with a catalyst₃/SiO₂The mixed film 12, PDMS13, is composed of a fiber waveguide 14 with a femtosecond laser writing inclination angle of 1.5 degrees; light emitted by a broadband light source 1 enters an optical fiber coupler 4 through a single-mode optical fiber 3, is divided into two lines of light waves in clockwise and anticlockwise directions, is respectively transmitted through an FC optical fiber connector 5, and passes through WO coated with a doped catalyst₃/SiO₂After one week of transmission, the two arrays of light waves are converged and interfered at the transmission end of the optical fiber coupler 4 by the coreless optical fiber 7 which is wrapped by the mixed film 12 and is provided with the optical fiber waveguide 14 with the inclination angle of 1.5 degrees and is engraved by the femtosecond laser. The hydrogen flow controller 8 and the air flow controller 9 connected with the air chamber 6 are respectively connected with the hydrogen generator 10 and the air pump 11, when the hydrogen concentration changes, the PDMS13 changes the surface refractive index of the coreless optical fiber 7 by utilizing the thermal expansion property, and the hydrogen concentration and the change thereof are measured by calculating the generated optical path difference.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.