CN211179526U

CN211179526U - Optical fiber hydrogen sensor based on single mode optical fiber probe type

Info

Publication number: CN211179526U
Application number: CN201922202950.3U
Authority: CN
Inventors: 杨智超; 孙雨阳; 何昊臻; 常冉; 徐贲
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2019-12-10
Filing date: 2019-12-10
Publication date: 2020-08-04
Anticipated expiration: 2029-12-10

Abstract

The utility model discloses an optic fibre hydrogen sensor based on single mode fiber probe formula, its characterized in that: the sensor is composed of a single-mode optical fiber, a PMMA cylinder made of polymethyl methacrylate material and a palladium-silver alloy film, wherein the end face of the single-mode optical fiber is cut flat, the fiber core at the tail end of the single-mode optical fiber is welded with the PMMA cylinder capable of completely covering the fiber core, the diameter of the PMMA cylinder is 10-15 mu m, and the thickness of the PMMA cylinder is 10-20 mu m; the side face of the PMMA material is coated with a palladium-silver alloy film, and the thickness of the PMMA material is 20-100 nm. When the device is applied, the sensor is placed in the space of the concentration of hydrogen to be measured, and the concentration of the hydrogen to be measured can be demodulated by measuring the output spectrum of the sensor through the optical fiber spectrometer. The invention has the characteristics of small volume, high sensitivity, simple preparation and probe type structure, and can be applied to the high-precision concentration measurement of hydrogen.

Description

Optical fiber hydrogen sensor based on single mode optical fiber probe type

Technical Field

The utility model belongs to the technical field of the optical fiber sensing, concretely relates to optic fibre hydrogen sensor based on single mode fiber probe formula.

Background

The resources such as coal, oil and natural gas are not renewable, the earth has limited stock, and the use of the fuel causes air pollution, so that the development of clean new energy without pollution is urgent. Thus, hydrogen is considered an important energy source in production activities in many fields. It is well known that hydrogen has the smallest and lightest molecular weight and is flammable and explosive. Since hydrogen is not good for breathing, it is colorless and tasteless, and cannot be detected by human nose, and its ignition point is 585 deg.C, and its explosion limit is 4% to 74.5% at room temperature and standard atmospheric pressure. Therefore, leak detection during storage and transportation of hydrogen is extremely important, and research on hydrogen sensors is an essential task.

Microlens-type optical fiber hydrogen sensors, proposed by m.a. butler in 1991, are coated with a hydrogen-sensitive film on the end face of the optical fiber, which is often made of Pd film. Light injected into the fiber is reflected at the output end face, and when the sensor is exposed to hydrogen, palladium reacts with hydrogen to cause a change in the refractive index of the palladium film, thereby causing a change in the light intensity. The structure and the manufacturing process are simple, only a film needs to be evaporated at the end part of the multimode optical fiber, the cost is low, the use is convenient, and the multimode optical fiber can be used for high voltage, electrical noise, high temperature, corrosion or other severe environments. But it is only suitable for point-type measurements and has limited multiplexing capability. And the sensitivity and the response time thereof interfere with each other and cannot be independently optimized. An evanescent field type optical fiber hydrogen sensor is a novel optical fiber hydrogen sensor, Tabib-Azar plates a layer of palladium film with the thickness of 10-20 nm on the surface of a multimode optical fiber in 1999 to form the evanescent field type optical fiber hydrogen sensor, and 0.6% of hydrogen can be detected in the air through the structure. Due to the uniqueness of the structure, the sensitivity and the response time of the sensor can be independently optimized by adjusting the length and the thickness of the palladium film, the sensor is not influenced by polarization, and distributed sensing can be realized through OTDR. The working mechanism of the optical fiber hydrogen sensor is mainly based on the evanescent field generated by the propagation of light in the optical fiber and the change of the optical property generated by the hydrogen adsorption of a palladium film. The evanescent field type optical fiber hydrogen sensor has high sensitivity but has high requirements on the manufacturing process, such as: the relevant technological parameters of optical fiber corrosion, tapering and the like need further research. The fiber grating hydrogen sensor is mainly based on the sensing process of the fiber grating, obtains sensing information by modulating the wavelength of fiber Bragg through external physical parameters, and is a wavelength modulation type fiber sensor. The working principle is that hydrogen acts on the sensing fiber grating plated with the Pd film, and the change of the hydrogen concentration can be reflected through the optical wavelength analysis of reflected light. The fiber grating hydrogen sensor is greatly influenced by temperature and mechanical stress, and is difficult to achieve good balance effect. And the preparation of the hydrogen sensor needs to use an expensive ultraviolet laser and the like, and more importantly, the sensitivity of the hydrogen sensor is limited by the low stress sensitivity (<2 pm/mu) of the Bragg grating, so that the hydrogen sensitivity is lower, and is generally 0.5-2 nm/% (volume specific concentration); polishing the Bragg grating can properly improve the sensitivity of hydrogen sensing, but simultaneously reduces the mechanical strength of the sensor, so that the sensor becomes fragile and easy to break. In addition, the length of the sensor reaches the centimeter magnitude, and the sensor is not suitable for being used in a small space. In conclusion, the currently used optical fiber hydrogen sensor has more or less contradictions between measurement sensitivity, environmental interference and device stability, and the exploration of the optical fiber hydrogen sensor with high sensitivity, simple preparation, low price, small volume and high stability has important practical significance.

Disclosure of Invention

In order to solve the defects of the prior art, the utility model provides an optic fibre hydrogen sensor based on single mode fiber probe formula has advantages such as sensitivity height, small, simple manufacture just have probe formula structure.

The utility model discloses the technical scheme who adopts: the utility model provides an optic fibre hydrogen sensor based on single mode fiber probe formula which characterized in that: the sensor is composed of a single-mode optical fiber, a polymethyl methacrylate (PMMA) cylinder and a palladium-silver alloy film, wherein the end face of the single-mode optical fiber is cut flat, the PMMA cylinder capable of completely covering the fiber core is welded at the fiber core at the tail end of the single-mode optical fiber, the diameter of the bottom of the single-mode optical fiber is 10-15 mu m, and the thickness of the single-mode optical fiber is 10-20 mu m; the side face of the PMMA material is coated with a palladium-silver alloy film, and the thickness of the PMMA material is 20-100 nm.

Compared with the prior art, the utility model beneficial effect be:

1. the preparation of the product only relates to the fusion of the single-mode optical fiber and the PMMA material, and the product has low cost and simple manufacturing process.

2. The utility model discloses the palladium-silver alloy film that uses in is more reliable and more stable than the quick material of likepowder hydrogen, can absorb a large amount of hydrogen, and the volume sharply expands simultaneously, produces longitudinal stress to the PMMA material, because on this kind of organic matter of film coating PMMA material, compare in general coating on optic fibre, PMMA material ductility is better, make its thickness increase more, and then arouse that the increase of its refracting index is more, interference spectrum center wavelength drift is more obvious, therefore, this sensor has very high hydrogen sensitivity.

3. The optical fiber hydrogen sensor is small in size, good in mechanical strength, provided with a probe type structure and convenient to use in a narrow space.

Drawings

The present invention will be further described with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a schematic structural diagram of a single-mode fiber probe type fiber hydrogen sensor;

in the figure: 1. the optical fiber comprises a single-mode optical fiber cladding, 2. a single-mode optical fiber core, 3. a PMMA material cylinder and 4. a palladium-silver alloy film.

Detailed Description

Fig. 1 is a schematic structural diagram of the present invention, wherein a polymethyl methacrylate (PMMA) cylinder is welded to a substrate by applying pressure in a semi-molten state under heating without any other adhesive substance. When the sensor is applied, the sensor is placed in a space with hydrogen concentration to be measured, the palladium-silver alloy film rapidly expands after absorbing hydrogen, longitudinal stress is generated on a PMMA material, the thickness of the PMMA material is increased, the cavity length of an F-P interferometer is increased (a single-mode optical fiber and the PMMA material are connected, the end surface of the material and air form a reflecting surface respectively to form an F-P interference cavity), and then the refractive index of the Polymethyl Methacrylate Material (PMMA) cylinder is increased, so that the central wavelength of the interference spectrum of the device drifts towards the long wavelength direction. Similarly, when the hydrogen concentration is decreased, the center wavelength of the interference spectrum of the device shifts to a short wavelength. The concentration of the hydrogen to be measured can be demodulated by measuring the output spectrum of the hydrogen by using the fiber spectrometer. The sensor in the utility model is composed of a single mode fiber, a polymethyl methacrylate (PMMA) cylinder and a palladium-silver alloy film, wherein the end surface of the single mode fiber is cut flat, and the end fiber core of the single mode fiber is welded with the PMMA cylinder which can completely cover the fiber core, the diameter of the PMMA cylinder is 10-15 mu m, and the thickness of the PMMA cylinder is 10-20 mu m; the side face of the PMMA material is coated with a palladium-silver alloy film, and the thickness of the PMMA material is 20-100 nm.

Claims

1. The single-mode fiber probe-based fiber hydrogen sensor comprises a single-mode fiber, a polymethyl methacrylate (PMMA) cylinder and a palladium-silver alloy film, wherein the end face of the single-mode fiber is flattened, and the polymethyl methacrylate cylinder capable of completely covering a fiber core is welded at the fiber core at the tail end of the single-mode fiber.

2. The single-mode fiber probe-based fiber-optic hydrogen sensor according to claim 1, wherein: the PMMA material cylinder is 10-15 microns in diameter and 10-20 microns in thickness.

3. The single-mode fiber probe-based fiber-optic hydrogen sensor according to claim 1, wherein: the side face of the PMMA material is coated with a palladium-silver alloy film, and the thickness of the PMMA material is 20-100 nm.