CN112577628B - A high-sensitivity temperature sensor with strong evanescent field interferometer cascaded optical reflection devices - Google Patents

Abstract

A high-sensitivity temperature sensor of a cascade light reflection device of a strong evanescent field interferometer comprises an outer wrapping layer, an interferometer and a light reflection device, wherein the interferometer comprises a wrapping layer and a plurality of fiber cores arranged in the wrapping layer, one end of the interferometer is connected with a light source, the other end of the interferometer is connected with the light reflection device in series, the outer wrapping layer is wrapped outside the middle of the wrapping layer and is made of a thermo-optic material, a capillary metal tube is wrapped outside the outer wrapping layer, and the thermo-optic material is polydimethylsiloxane, polyimide, magnesium fluoride or polyurethane. The design can not only monitor the temperature of the environment, has higher sensitivity, but also is convenient for demodulation and can monitor on line in real time.

Description

A high-sensitivity temperature sensor with strong evanescent field interferometer cascaded optical reflection devices

technical field

The invention relates to an optical fiber temperature sensor, which belongs to the field of optical fiber sensing technology, and also belongs to the intersecting field of material science and optoelectronic technology, in particular to a high-sensitivity temperature sensor of a strong evanescent field interferometer cascaded light reflection device.

Background technique

Temperature is a physical quantity that characterizes the degree of coldness and heat of an object. It is one of the basic detection parameters in industries such as industrial automation, household appliances, environmental protection, safety production and automobile industry. Especially with the rapid development of today's science and technology, people's requirements for the measurement accuracy of ambient temperature are getting higher and higher.

Currently widely used resistance and galvanic thermometers are commonly used in various environmental monitoring, and there are some other technologies to monitor changes in environmental temperature, including transistor temperature sensors, microwave temperature sensors, capacitance temperature sensors, etc. However, the above technologies are all or There are more or less the following shortcomings: weak anti-electromagnetic interference ability, large volume, high price, etc., and these shortcomings will inevitably affect the accuracy and sensitivity of monitoring.

The disclosure of information in this background section is only intended to increase the understanding of the general background of this patent application, and should not be considered as an acknowledgment or any form of suggestion that the information constitutes prior art known to those skilled in the art.

Contents of the invention

The purpose of the present invention is to overcome the defects and problems of low sensitivity in the prior art, and provide a high-sensitivity temperature sensor with strong evanescent field interferometer cascaded light reflection devices with high sensitivity.

To achieve the above objectives, the technical solution of the present invention is: a high-sensitivity temperature sensor of a strong evanescent field interferometer cascaded light reflection device, which includes an outer wrapping layer, an interferometer and a light reflection device, and the interferometer includes The cladding and multiple fiber cores arranged in it;

One end of the interferometer is connected to a light source, the other end of the interferometer is connected in series with a light reflection device, and the middle part of the interferometer is wrapped with an outer wrapping layer, and the outer wrapping layer is a thermo-optic material.

The absolute value of the thermo-optic coefficient of the thermo-optic material is greater than 3*10 ⁴ , the refractive index is 1.38-1.43, and the surface tension is 20.6-21.2 mN/m.

The thermo-optic material is polydimethylsiloxane, polyimide, magnesium fluoride or polyurethane.

The band selection width of the light reflection device is 1.1-1.6 times of the free spectrum width of the sensing peak of the interferometer.

The central wavelength range of the band of the light reflection device is 1.2-2.0 times the wavelength range of the sensing peak of the interferometer.

The light reflection device is a fiber Bragg grating, a broadband Bragg grating or a surface-modified nano-silver reflective film.

The interferometer includes a left optical fiber section, a left tapered section, a straight waist section, a right tapered section and a right optical fiber section, one end of the left optical fiber section is connected to a light source, and the other end of the left optical fiber section passes through the left cone in turn. Shaped section, straight waist section, right tapered section, right optical fiber section are connected in series with the light reflection device; 1/10 to 1/20 of the diameter;

The parts near the left tapered section on the left optical fiber section, the left tapered section, the straight waist section, the right tapered section, and the parts near the right tapered section on the right optical fiber section are jointly wrapped with the same outer wrapping layer .

There are seven fiber cores, including one central core and six peripheral cores, and all the peripheral cores are evenly distributed in a regular hexagon around the central core.

The diameter of the fiber core is 9 μm, the distance between adjacent fiber cores is 35 μm, the diameters of the left fiber section and the right fiber section are both 125 μm, and the diameter of the straight waist section is 6 μm-15 μm.

The outside of the outer wrapping layer is wrapped with a capillary metal tube.

Compared with prior art, the beneficial effect of the present invention is:

1. In the high-sensitivity temperature sensor of a strong evanescent field interferometer cascaded light reflection device of the present invention, it includes an outer cladding layer, an interferometer and a light reflection device, and the interferometer includes a cladding layer and multiple fiber cores arranged in it , where one end of the interferometer is connected to the light source, the other end of the interferometer is connected in series with the light reflection device, and the middle part of the interferometer is wrapped with an outer wrapping layer (that is, a thermo-optic material). When applied, the incident light emitted by the light source passes through The interferometer generates an interference spectrum. After the interference spectrum passes through the light reflection device, the sensing peak in the interference spectrum is reflected back to the interferometer. The advantages of this design are as follows:

First, the temperature change of the external environment will cause a corresponding linear change in the refractive index of the thermo-optic material, and the change in the refractive index of the thermo-optic material will cause the wavelength of the interference spectrum generated by the interferometer to shift, so that the external environment temperature, interference A linear relationship is constructed between the wavelengths of the spectrum, thereby overcoming the defect of low temperature sensitivity of the interferometer and realizing the sensitivity enhancement; secondly, when the interference spectrum is generated for the first time, the sensitivity enhancement of the thermo-optic material can be obtained, and when the interference spectrum After the sensing peak in the spectrum is reflected back into the interferometer, it will be sensitized by the thermo-optic material again, and the intensity of the sensing peak will be greatly increased, which can greatly improve the sensitivity. Therefore, the invention not only can monitor the temperature of the environment, but also has high sensitivity.

2. In the high-sensitivity temperature sensor of a strong evanescent field interferometer cascaded optical reflection device of the present invention, when the sensing peak in the interference spectrum is reflected back to the interferometer, due to the sensitization of the thermo-optic material, the sensing The peak intensity will be greatly increased, which is very beneficial to the subsequent demodulation of the sensing peak and facilitates real-time online monitoring. Therefore, the invention is convenient for demodulation and can monitor on-line in real time.

3. In the high-sensitivity temperature sensor of a strong evanescent field interferometer cascaded optical reflection device of the present invention, a capillary metal tube is wrapped outside the outer wrapping layer. When applied, the capillary metal tube can not only material) to protect the package, overcome the shortcomings of thermo-optic material flexibility, and can reduce the response time and avoid the interference of vibration or pressure on the sensor, which is conducive to the realization of online real-time high-precision demodulation. Therefore, the present invention is not only convenient for packaging and fixing, but also has strong anti-interference ability, which is beneficial to realize high-precision monitoring.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

FIG. 2 is a transverse sectional view of FIG. 1 .

FIG. 3 is a schematic structural diagram of the interferometer in FIG. 1 .

FIG. 4 is a transverse sectional view of FIG. 3 .

Fig. 5 is a schematic diagram of the application of the present invention.

Fig. 6 is a schematic diagram of temperature sensitivity comparison in Example 1 of the present invention.

In the figure: outer cladding layer 1, interferometer 2, cladding 21, fiber core 22, middle core 221, peripheral core 222, left fiber segment 23, left tapered segment 24, straight waist segment 25, right tapered segment 26 , right optical fiber section 27, light reflection device 3, capillary metal tube 4, light source 5, capping sleeve 6, thermo-optic material perfusion window 7, demodulator 8.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Referring to Fig. 1-Fig. 5, a high-sensitivity temperature sensor of a strong evanescent field interferometer cascaded light reflective device, which includes an outer cladding layer 1, an interferometer 2 and a light reflective device 3, and the interferometer 2 includes a cladding layer 21 and a plurality of fiber cores 22 arranged therein;

One end of the interferometer 2 is connected to the light source 5, the other end of the interferometer 2 is connected in series with the light reflection device 3, and the middle part of the cladding layer 21 is wrapped with an outer wrapping layer 1, and the outer wrapping layer 1 is a thermo-optic material .

The absolute value of the thermo-optic coefficient of the thermo-optic material is greater than 3*10 ⁴ , the refractive index is 1.38-1.43, and the surface tension is 20.6-21.2 mN/m.

The thermo-optic material is polydimethylsiloxane, polyimide, magnesium fluoride or polyurethane.

The band selection width of the light reflection device 3 is 1.1-1.6 times of the free spectrum width of the sensing peak of the interferometer 2 .

The central wavelength range of the band of the light reflection device 3 is 1.2-2.0 times the wavelength range of the sensing peak of the interferometer 2 .

The light reflection device 3 is a fiber Bragg grating, a broadband Bragg grating or a surface-modified nano-silver reflective film.

Described interferometer 2 comprises left optical fiber section 23, left tapered section 24, straight waist section 25, right tapered section 26 and right optical fiber section 27, and one end of described left optical fiber section 23 is connected with light source 5, left optical fiber The other end of the section 23 passes through the left tapered section 24, the straight waist section 25, the right tapered section 26, and the right optical fiber section 27 in series with the light reflection device 3; the left optical fiber section 23, the right optical fiber section 27 The diameters are consistent, and the diameter of the straight waist section 25 is 1/10 to 1/20 of the diameter of the left optical fiber section 23;

The outside of the position near the left tapered section 24 on the left optical fiber section 23, the left tapered section 24, the straight waist section 25, the right tapered section 26, and the position near the right tapered section 26 on the right optical fiber section 27 are common. The package has the same outer wrapping layer 1 .

The number of the fiber cores 22 is seven, including one central core 221 and six peripheral cores 222 , and all the peripheral cores 222 are uniformly distributed in a regular hexagon around the central core 221 .

The diameter of the fiber core 22 is 9 μm, the distance between adjacent fiber cores 22 is 35 μm, the diameters of the left fiber segment 23 and the right fiber segment 27 are both 125 μm, and the diameter of the straight waist segment 25 is 6 μm-15 μm .

A capillary metal tube 4 is wrapped around the outer wrapping layer 1 .

Principle of the present invention is described as follows:

In the present invention, the optical fiber is heated, melted and tapered into a micro-nano size, so that the surface of the optical fiber forms an evanescent field (including the left tapered section 24, the straight waist section 25, the right tapered section 26, especially in the straight waist section 25 surface to form a strong evanescent field) to obtain an interferometer, and then make the interferometer contact with the thermo-optic material (that is, the outer cladding layer), and finally package it with a capillary metal tube.

In application, when light passes through the interferometer, an interference spectrum will be generated. At this time, changes in the external temperature or refractive index will cause changes in the effective refractive index of the interferometer, resulting in a wavelength shift in the interference spectrum, thereby sensing the external temperature or refractive index. Variety. However, due to the small thermo-optic coefficient of silicon dioxide, the temperature sensitivity of the interferometer is low. Therefore, this design mainly focuses on the external refractive index change. Therefore, the thermo-optic material is wrapped outside the interferometer, that is, the thermal The relationship between the change of the refractive index of the optical material and the wavelength drift, and the change of the ambient temperature outside the thermo-optic material will cause the linear change of the refractive index of the thermo-optic material, thus establishing a relationship between the external ambient temperature and the wavelength drift linear correspondence.

In the present invention, the thermo-optic material preferably has a refractive index of 1.3907-1.4125 and a temperature of 10-60 degrees Celsius.

The light reflective device in the present invention is a band-selective light reflective device.

Example 1:

Referring to Fig. 1-Fig. 5, a high-sensitivity temperature sensor of a strong evanescent field interferometer cascaded light reflective device, which includes an outer cladding layer 1, an interferometer 2, a light reflective device 3 and a capillary metal tube 4, the interference The instrument 2 includes a cladding 21 and seven fiber cores 22 (comprising an intermediate core 221 and six peripheral cores 222, all of which are evenly distributed in a regular hexagon around the intermediate core 221) arranged in the interferometer. 2 comprises a left optical fiber section 23, a left tapered section 24, a straight waist section 25, a right tapered section 26 and a right optical fiber section 27, one end of the left optical fiber section 23 is connected to the light source 5, and the other end of the left optical fiber section 23 One end passes through the left tapered section 24, the straight waist section 25, the right tapered section 26, and the right optical fiber section 27 in series with the light reflection device 3; the diameters of the left optical fiber section 23 and the right optical fiber section 27 are consistent, so The diameter of the straight waist section 25 is 1/10 to 1/20 of the diameter of the left fiber section 23; 25. The outside of the right tapered section 26 and the right optical fiber section 27 near the right tapered section 26 are jointly wrapped with the same outer wrapping layer 1, and the outer wrapping layer 1 is a thermo-optic material (in this embodiment, poly methyl siloxane).

According to the experimental data, the sensitivity of the above-mentioned high-sensitivity temperature sensor can reach 14338pm/°C, which is 500 times higher than that of the bare fiber MZI, and the accuracy can reach up to 0.001°C.

In addition, please refer to FIG. 6 , which is a schematic diagram of the comparison of temperature sensitivity in Example 1. It can be seen from the figure that after being wrapped with polydimethylsiloxane, the sensitivity of the sensor to temperature is greatly increased.

Example 2:

Basic content is the same as embodiment 1, the difference is:

Magnesium fluoride is used as the thermo-optic material, and a tapered seven-core fiber Mach-Zehnder interferometer is used as the interferometer.

Example 3:

Basic content is the same as embodiment 1, the difference is:

The thermo-optic material is polyurethane, and the interferometer is a tapered single-mode fiber Mach-Zehnder interferometer.

The above descriptions are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments, but all equivalent modifications or changes made by those of ordinary skill in the art according to the disclosure of the present invention should be included within the scope of protection described in the claims.

Claims (9)

1. A high-sensitivity temperature sensor of a cascade light reflection device of a strong evanescent field interferometer is characterized in that: the high-sensitivity temperature sensor comprises an outer wrapping layer (1), an interferometer (2) and a light reflecting device (3), wherein the interferometer (2) comprises a wrapping layer (21) and a plurality of fiber cores (22) arranged in the wrapping layer;

one end of the interferometer (2) is connected with the light source (5), the other end of the interferometer (2) is connected with the light reflection device (3) in series, an outer wrapping layer (1) is wrapped outside the middle part of the interferometer (2), and the outer wrapping layer (1) is made of thermo-optic materials;

the interferometer (2) comprises a left optical fiber section (23), a left conical section (24), a straight waist section (25), a right conical section (26) and a right optical fiber section (27), one end of the left optical fiber section (23) is connected with the light source (5), and the other end of the left optical fiber section (23) sequentially passes through the left conical section (24), the straight waist section (25), the right conical section (26) and the right optical fiber section (27) and then is connected with the light reflection device (3) in series; the diameters of the left optical fiber section (23) and the right optical fiber section (27) are consistent, and the diameter of the straight waist section (25) is 1/10 to 1/20 of the diameter of the left optical fiber section (23);

the outer portions of the positions, close to the left conical section (24), on the left optical fiber section (23), the left conical section (24), the straight waist section (25), the right conical section (26) and the position, close to the right conical section (26), on the right optical fiber section (27) are wrapped with the same outer wrapping layer (1) together.

2. The high-sensitivity temperature sensor of the strong evanescent field interferometer cascade optical reflection device as claimed in claim 1, wherein: the absolute value of the thermo-optic coefficient of the thermo-optic material is more than 3 x 10 ⁴ The refractive index is 1.38-1.43, and the surface tension is 20.6-21.2 mN/m.

3. The high-sensitivity temperature sensor of the strong evanescent field interferometer cascade optical reflection device as claimed in claim 2, wherein: the thermo-optic material is polydimethylsiloxane, polyimide, magnesium fluoride or polyurethane.

4. A highly sensitive temperature sensor of a strong evanescent field interferometer cascade optical reflecting device as claimed in claim 1, 2 or 3, wherein: the wave band selection width of the light reflection device (3) is 1.1-1.6 times of the free spectrum width of a sensing peak of the interferometer (2).

5. The high-sensitivity temperature sensor of the strong evanescent field interferometer cascade optical reflection device as claimed in claim 4, wherein: the central wavelength range of the wave band of the light reflection device (3) is 1.2-2.0 times of the wavelength range of the sensing peak of the interferometer (2).

6. A highly sensitive temperature sensor of a strong evanescent field interferometer cascade optical reflection device as claimed in claim 1, 2 or 3, wherein: the light reflection device (3) is a fiber Bragg grating, a broadband Bragg grating or a nano silver reflection film with a modified surface.

7. A highly sensitive temperature sensor of a strong evanescent field interferometer cascade optical reflection device as claimed in claim 1, 2 or 3, wherein: the number of the fiber cores (22) is seven, the fiber cores comprise a middle core (221) and six peripheral cores (222), and all the peripheral cores (222) are uniformly distributed around the middle core (221) in a regular hexagon shape.

8. The highly sensitive temperature sensor of the strong evanescent field interferometer cascade optical reflection device as claimed in claim 7, wherein: the diameter of the fiber core (22) is 9 mu m, the distance between adjacent fiber cores (22) is 35 mu m, the diameters of the left fiber section (23) and the right fiber section (27) are both 125 mu m, and the diameter of the straight waist section (25) is 6 mu m-15 mu m.

9. A highly sensitive temperature sensor of a strong evanescent field interferometer cascade optical reflection device as claimed in claim 1, 2 or 3, wherein: the outer part of the outer wrapping layer (1) is wrapped with a capillary metal pipe (4).

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