CN220136519U - High-sensitivity temperature sensor - Google Patents

Abstract

The utility model discloses a high-sensitivity temperature sensor, wherein: the second single-mode optical fiber, the second multimode optical fiber, the fourth multimode optical fiber and the third single-mode optical fiber are coaxially connected, and the other optical fibers are in dislocation fusion connection, so that an S-shaped structure is formed in a plane of a top view; the single mode optical fibers, the multimode optical fibers and the single mode optical fibers are sequentially in staggered welding to form an SMF-MMF-SMF structure, and the multimode optical fibers are sensing areas of the optical fibers; forming a GIMMF-SIMMF-GIMMF structure in the step-type multimode optical fiber, the gradient-type multimode optical fiber and the step-type multimode optical fiber, so that the whole sensor presents periodicity, and the whole sensor is an LPFG optical fiber sensor structure; the first multimode optical fiber, the third multimode optical fiber and the fifth multimode optical fiber serve as first, second and third sensing zones, respectively. The structure is formed by simply welding and cascading common single-mode optical fibers, common gradient-type multimode optical fibers and common step-type multimode optical fibers, and has the advantages of simple manufacturing process, convenience in operation and convenience in popularization and use.

Description

A highly sensitive temperature sensor

Technical field

The utility model relates to the field of fiber grating sensors, specifically a high-sensitivity temperature sensor.

Background technique

Since the emergence of optical fiber sensing technology in 1977, new breakthroughs have been made in sensor preparation. With the vigorous development of optical fiber manufacturing technology, optical fiber communication technology and optical fiber sensing technology, fiber grating sensing technology has also made great progress. Fiber Bragg grating sensors have many advantages compared to capacitive inductive sensors, such as: small size, light weight, low cost, flameproof and explosion-proof, corrosion resistance, can work under high temperature and high pressure, anti-electromagnetic interference and high sensitivity, etc. Its sensing As an important symbol to measure the degree of informatization of a country, technology is widely used in various fields such as military, national defense, aerospace, industrial production, energy exploration, environmental protection, medicine and health, and building surveying. However, when measuring temperature, changes in the external environment will lead to changes in other factors, which will lead to problems of measurement cross-sensitivity and influence during the measurement process. Therefore, it is particularly important to develop a highly sensitive temperature sensor.

In 1999, Denis Donlagic and others invented the SMS optical fiber structure and produced the first quasi-distributed micro-bend sensor based on this structure, which led to the rapid development of optical fiber sensing technology. In 2014, SuJ et al. proposed a dual-parameter sensor based on MMF-MMF-MMF optical fiber structure and conducted experimental verification. However, they ignored the impact of refractive index on temperature, making it impossible to eliminate the impact of refractive index changes on temperature measurement when used. Impact. In 2021, Ma et al. used a layer of PDMS material to wrap the outside of a coreless optical fiber to achieve temperature sensing. However, this sensor needs to add expensive sensitive materials, resulting in increased production costs and low stability. The sensing test temperature Restricted.

Chinese patent CN1624441A discloses a slightly bent optical fiber sensor; Chinese patent CN10962603A discloses a fiber grating temperature sensor with a star-sensitive lens structure; Chinese patent CN216349216U discloses a cursor-based fiber grating temperature sensor and temperature sensing device , these disclosed sensors often have shortcomings such as complex manufacturing processes, high prices, poor sensor stability, and limited measurement accuracy range, making them inconvenient for practical promotion and application.

Utility model content

In view of the shortcomings pointed out in the above-mentioned prior art, the present utility model provides a cascade periodic structure based on SMF-MMF-SMF and MMF-MMF-MMF, and uses gradient multimode optical fiber and step multimode optical fiber in the sensing area. To improve the sensing sensitivity to prepare a highly sensitive temperature sensor.

The technical solution to achieve the purpose of this utility model is:

A highly sensitive temperature sensor, including a first single-mode optical fiber, a first multi-mode optical fiber, a second single-mode optical fiber, a second multi-mode optical fiber, a third multi-mode optical fiber and a fourth multi-mode optical fiber spliced with coaxial misalignment. The third single-mode optical fiber, the fifth multi-mode optical fiber and the fourth single-mode optical fiber, among which:

The second single-mode optical fiber, the second multi-mode optical fiber, the fourth multi-mode optical fiber and the third single-mode optical fiber are coaxially connected, and the remaining optical fibers are dislocated welding to form an S-shaped structure in the top view plane;

Each single-mode optical fiber, multi-mode optical fiber and single-mode optical fiber are dislocated and welded in sequence to form a SMF-MMF-SMF structure. The multi-mode optical fiber is the sensing area of the optical fiber;

The GIMMF-SIMMF-GIMMF structure is formed in step multimode optical fiber, gradient multimode optical fiber and step multimode optical fiber, so that the entire sensor is periodic, and the entire sensor forms a LPFG optical fiber sensor structure;

The first multimode optical fiber, the third multimode optical fiber and the fifth multimode optical fiber serve as the first, second and third sensing areas respectively.

The first single-mode optical fiber, the first multi-mode optical fiber, the second single-mode optical fiber, the second multi-mode optical fiber, the third multi-mode optical fiber, the fourth multi-mode optical fiber, the third single-mode optical fiber, the fifth multi-mode optical fiber and The fourth single-mode optical fiber has a cladding outer diameter of 125 μm.

The core diameter of the first, second, third, fourth and fifth single-mode optical fibers is 8-10 μm; the first and fifth multi-mode optical fibers have a core diameter of 8-10 μm. The fiber core diameter is 50 μm; the second and fourth multimode optical fiber core diameters are 62.5 μm; and the third multimode optical fiber core diameter is 105 μm.

Each sensing area of the optical fiber is dislocated and welded in different directions on the same plane, making the entire structure into an S-shaped structure, which can excite more modes of light and improve sensor sensitivity.

The sensor is divided into three different sensing areas, namely the first, third and fifth multi-mode optical fibers. When light is transmitted, different modes of light can be excited for coupling to increase the sensing sensitivity.

The sensor is an S-shaped periodic structure of SMF-MMF-SMF and GIMMF-SIMMF-GIMMF cascades.

The utility model provides a high-sensitivity temperature sensor, which has the following advantages compared with existing temperature measuring instruments:

1. It is made of ordinary multi-mode optical fiber and ordinary single-mode optical fiber. The raw materials are easy to obtain and the cost is low. It is made by coaxial dislocation welding. The production method is relatively mature and simple and efficient. It is conducive to Market creation and practical application.

2. Using fiber grating technology and utilizing the MZI interferometer principle, it not only retains the advantages of the traditional MZI interferometer, but also has high physical strength, wide measurement range, and cascades different structured lights for better coupling, making it Has better sensing effect.

3. Different types of optical fibers are used in the sensing area to enhance the temperature sensitivity of this area.

4. Use single-mode-multimode-single-mode fiber and step-type multi-mode-gradient multi-mode-step multi-mode misalignment welding to form an S-shaped structure in the coupling area of the optical fiber to prepare fiber grating to form LPFG, and misalignment weld S The LPFG-type structure forms the core temperature sensor structure, so that its spectral output has an obvious resonance peak suitable for sensing. By optimizing the geometric parameters and structural design of the core sensing element, the fiber mode can be selectively coupled, the output spectrum wavelength position and coupling depth can be determined, and core sensing elements with different center wavelengths can be designed. In the later stage, wavelength division multiplexing technology can be used to build a high-precision, omnidirectional, and fast-response distributed temperature fiber grating sensor measurement system.

5. Since the sensor has three different sensing areas, the transmitted light can stimulate more different modes of light to be coupled into the cladding and core of the optical fiber, so that the long-period sensing element produced has multiple modes. The effect of mutual coupling of light. By optimizing the design to make the mutual coupling parameters sensitive to a single parameter and realizing cross-sensitivity compensation, the purpose of decoupling is achieved, and the influence of other parameters on the resonance peak is reduced, which facilitates efficient and accurate measurement of the temperature of the external environment.

Description of drawings

Figure 1 is a schematic structural diagram of a high-sensitivity temperature sensor;

Figure 2 is a top view of an axial section of a highly sensitive temperature sensor;

Figure 3 is a right side view of an axial section of a high-sensitivity temperature sensor;

In the picture: 1. The first single-mode optical fiber 2. The first multi-mode optical fiber 3. The second single-mode optical fiber 4. The second multi-mode optical fiber 5. The third multi-mode optical fiber 6. The fourth multi-mode optical fiber 7. The third single-mode optical fiber Mode fiber 8. Fifth multi-mode fiber 9. Fourth single-mode fiber

Implementation

The content of the present utility model will be further elaborated below with reference to the accompanying drawings and examples, but the present utility model is not limited.

Example

As shown in Figure 1, a high-sensitivity temperature sensor includes a first single-mode optical fiber 1, a first multi-mode optical fiber 2, a second single-mode optical fiber 3, a second multi-mode optical fiber 4 and a third coaxial dislocation welded optical fiber. Multi-mode optical fiber 5, fourth multi-mode optical fiber 6, third single-mode optical fiber 7, fifth multi-mode optical fiber 8 and fourth single-mode optical fiber 9. Coaxial connection is used between the second single-mode optical fiber 3, the second multi-mode optical fiber 4 and the fourth multi-mode optical fiber 6 and the third single-mode optical fiber 7. The other optical fibers are dislocated and spliced to form an S-shaped structure in the top view plane. . Single-mode optical fiber, multi-mode optical fiber and single-mode optical fiber are sequentially fused to form a SMF-MMF-SMF periodic structure. The sensing area of the optical fiber is multi-mode optical fiber, so that the sensor forms a LPFG optical fiber sensor structure. In this structure, the first multimode optical fiber, the third multimode optical fiber and the fifth multimode optical fiber serve as the first, second and third sensing areas respectively.

The first single-mode optical fiber 1, the first multi-mode optical fiber 2, the second single-mode optical fiber 3, the second multi-mode optical fiber 4, the third multi-mode optical fiber 5, the fourth multi-mode optical fiber 6, the third single-mode optical fiber 7, The outer diameters of the fifth multimode optical fiber 8 and the fourth single-mode optical fiber 9 are both 125 μm.

The first single-mode optical fiber 1, the second single-mode optical fiber 3, the third single-mode optical fiber 7, the fourth single-mode optical fiber 9 and the fifth single-mode optical fiber have core diameters of 8-10 μm; the first multi-mode optical fiber 2 and the fifth single-mode optical fiber have core diameters of 8-10 μm; The core diameter of the multimode optical fiber 8 is 50 μm; the core diameter of the second multimode optical fiber 4 and the fourth multimode optical fiber 6 is 62.5 μm; and the core diameter of the third multimode optical fiber 5 is 105 μm.

The sensing areas of this sensor structure are dislocated and welded in different directions on the same plane, making the overall S-shaped structure, which can excite more modes of light and improve the sensor sensitivity.

The sensing structure has three different sensing areas, namely the first multimode optical fiber 2, the third multimode optical fiber 5 and the fifth multimode optical fiber 8. When light is transmitted, different modes of light can be excited for coupling to increase sensing. sensitivity.

The sensor is an S-shaped periodic structure of SMF-MMF-SMF and GIMMF-SIMMF-GIMMF cascade.

The manufacturing method of the above-mentioned high-sensitivity temperature sensor is:

First, use wire strippers to remove the coating layers of single-mode optical fibers and different multi-mode optical fibers. Then use dust-free paper dipped in alcohol to clean the location where the coating layer was removed. Then use a cutter to cut the tail of the multi-mode optical fiber flat. ;

Use a fiber grating cutting system and a CCD camera to observe the first single-mode optical fiber 1 and cut the right end face of the first single-mode optical fiber 1 flatly, and then use an optical fiber fusion splicer to perform fiber dislocation welding with the left end face of the first multi-mode optical fiber 2, and then The first multimode optical fiber 2 is cut flatly using a fiber grating cutting system and a CCD camera to observe the right end face of the first multimode optical fiber 2, and then is spliced with the left end of the second single mode optical fiber 3 using an optical fiber fusion splicer, while allowing The right end face of the first single-mode optical fiber 1 and the left end face of the second single-mode optical fiber 3 maintain a coaxial position;

Use the fiber grating cutting system and CCD camera to observe the second single-mode optical fiber 3 and cut it flatly to cut the right end face of the second single-mode optical fiber 3, and coaxially connect it to the left end of the second multi-mode optical fiber 4. Leave a suitable length and cut it flatly;

Use a fiber grating cutting system and a CCD camera to observe the third multimode optical fiber 5 and cut the left end face flatly, and then use an optical fiber fusion splicer to perform fiber dislocation splicing with the right end face of the second multimode optical fiber 4, and then fuse the third multimode optical fiber 5 5. Use the fiber grating cutting system and CCD camera to observe and cut the right end face of the third multi-mode optical fiber 5 flatly, and then use an optical fiber fusion splicer to perform optical fiber dislocation splicing with the left end part of the fourth multi-mode optical fiber 6. At the same time, let the second multi-mode optical fiber The right end face of 3 and the left end face of the fourth multimode optical fiber 6 maintain a coaxial position;

Use the fiber grating cutting system and CCD camera to observe the fourth multimode optical fiber 6 and cut it flatly to cut the right end face of the fourth multimode optical fiber 6, and coaxially connect it to the left end of the third single-mode optical fiber 7, leaving a suitable length and cut it flatly;

Use a fiber grating cutting system and a CCD camera to observe the third single-mode optical fiber 7 and cut it flatly to cut the right end face of the third single-mode optical fiber 7, and then use an optical fiber fusion splicer to perform fiber dislocation welding with the left end face of the fifth multi-mode optical fiber 8, and then Use a fiber grating cutting system and a CCD camera to observe the fifth multi-mode optical fiber 8 and cut the right end face of the fifth multi-mode optical fiber 8 flatly, and then use an optical fiber fusion splicer to perform optical fiber dislocation welding with the left end of the fourth single-mode optical fiber 9. Keep the right end face of the third single-mode optical fiber 7 and the left end face of the fourth single-mode optical fiber 9 in a coaxial position;

After the above operation, the sensor can form an LPFG structure. Finally, the fiber grating cutting system and CCD camera are used to observe and cut the right end face of the fourth single-mode optical fiber 9 flatly, forming an LPFG core sensing element.

When in use, connect the fiber core on the left side of the first single-mode fiber 1 to the supercontinuum light source (SC-5), so that the light source is input from the left side of the first single-mode fiber 1, and finally output from the fourth single-mode fiber, and Optical spectrum analysis (OSA) connection, the LPFG cascade core sensing element is clamped horizontally through fiber optic clamps, and the entire sensor is used to closely fit the stable temperature measurement platform; as for the constant temperature device, after the environmental system is stabilized, the spectral analysis ( OSA) data is imported into a computer (PC) and through a series of calculations, the optical relationship between the resonance peak and the linear change of the external ambient temperature is obtained. By adjusting the geometric parameters and optimizing the structure of the core sensing element, selectively coupling the fiber modes, and determining the output spectrum wavelength position and coupling depth, core sensing elements with different center wavelengths can be designed, which completes a high-sensitivity temperature sensor.

Claims (6)

1. The utility model provides a high-sensitivity temperature sensor, includes coaxial dislocation butt fusion's first single mode fiber, first multimode fiber, second single mode fiber, second multimode fiber, third multimode fiber, fourth multimode fiber, third single mode fiber, fifth multimode fiber and fourth single mode fiber, characterized by:

the second single-mode optical fiber, the second multimode optical fiber, the fourth multimode optical fiber and the third single-mode optical fiber are coaxially connected, and the other optical fibers are in dislocation fusion connection, so that an S-shaped structure is formed in a plane of a top view;

the single mode optical fibers, the multimode optical fibers and the single mode optical fibers are sequentially in staggered welding to form an SMF-MMF-SMF structure, and the multimode optical fibers are sensing areas of the optical fibers;

forming a GIMMF-SIMMF-GIMMF structure in the step-type multimode optical fiber, the gradient-type multimode optical fiber and the step-type multimode optical fiber, so that the whole sensor presents periodicity, and the whole sensor is an LPFG optical fiber sensor structure;

the first multimode optical fiber, the third multimode optical fiber and the fifth multimode optical fiber serve as first, second and third sensing zones, respectively.

2. A temperature sensor according to claim 1, characterized in that: the outer diameters of the cladding layers of the first single mode optical fiber, the first multimode optical fiber, the second single mode optical fiber, the second multimode optical fiber, the third multimode optical fiber, the fourth multimode optical fiber, the third single mode optical fiber, the fifth multimode optical fiber and the fourth single mode optical fiber are 125 mu m.

3. A temperature sensor according to claim 1, characterized in that: the diameters of fiber cores of the first single mode fiber, the second single mode fiber, the third single mode fiber, the fourth single mode fiber and the fifth single mode fiber are 8-10 mu m; the first multimode optical fiber and the fifth multimode optical fiber have core diameters of 50 μm; the second and fourth multimode optical fiber cores have diameters of 62.5 μm; the third multimode fiber core diameter was 105 μm.

4. A temperature sensor according to claim 1, characterized in that: and each sensing area of the optical fiber is in dislocation welding along different directions on the same plane, so that the whole optical fiber has an S-shaped structure.

5. A temperature sensor according to claim 1, characterized in that: the sensor is divided into three different sensing areas, namely a first multimode optical fiber, a third multimode optical fiber and a fifth multimode optical fiber, and when light is transmitted, light in different modes can be excited to be coupled so as to increase the sensing sensitivity.

6. A temperature sensor according to claim 1, characterized in that: the sensor is of a periodic structure of the S type of the cascade of SMF-MMF-SMF and GIMMF-SIMMF-GIMMF.