CN115752796A - A temperature sensor based on partial dual-core special optical fiber and its preparation method - Google Patents

Abstract

The invention relates to a temperature sensor based on a partial dual-core special optical fiber and a preparation method thereof, belonging to the technical field of optical fiber sensing, including single-mode optical fiber, multi-mode optical fiber and partial dual-core optical fiber; one end of the single-mode optical fiber is connected to a multi-core optical fiber One end of the mode fiber is connected, and the other end of the multimode fiber is connected to one end of the partial dual-core optical fiber; the partial dual-core optical fiber is composed of a first cylindrical structure, a tapered structure with a gradually decreasing diameter, and a second cylindrical structure. ; The end of the second cylindrical structure is provided with a spherical structure prepared from the same optical fiber as the second cylindrical structure. In the present invention, a cone structure with a gradually decreasing diameter is used to expose one core of the partial dual-core optical fiber, which increases the optical path difference of the transmitted light, and the spherical structure realizes the secondary interference of the transmitted light, thereby resulting in an effective refractive index of the transmission mode change. The temperature sensor has a compact and novel structure and high sensitivity, and has great application potential in the field of temperature measurement.

Description

A temperature sensor based on partial dual-core special optical fiber and its preparation method

technical field

The invention relates to a temperature sensor based on partial dual-core special optical fiber and a preparation method thereof, belonging to the technical field of optical fiber sensing.

Background technique

Conventional fiber optic temperature sensors are mainly divided into fiber grating temperature sensors and interferometric temperature sensors. The temperature measurement principle of the fiber grating temperature sensor is to use the photosensitive properties of the fiber material to form a spatial phase grating in the fiber core to measure the temperature. Zhou Zhi and others from the Harbin Institute of Technology in China package the FBG with a sensitive metal tube. While playing a protective role, it also improves its sensitivity; Yun Binfeng from Southeast University combined metal sleeves with polymers to increase the temperature sensitivity by five times compared with ordinary fiber gratings; foreign Jung et al. combined two materials with different thermal expansion coefficients It is packaged and made into a fiber grating temperature sensor with tunable sensitivity, etc. The fiber grating temperature sensor has little influence on it during use, with accurate measurement, high sensitivity and stable performance, but at the same time due to its packaging and signal resolution The adjustment process is complicated and the cost is relatively expensive, and it needs to be used with large instruments, which brings inconvenience to the use under some special conditions.

The interferometric fiber optic temperature sensor belongs to the phase modulation temperature sensor, which mainly uses the interference phenomenon of light and the generated phase difference to measure the temperature. At present, typical interferometric fiber optic temperature sensors include Mach-Zehnder fiber optic temperature sensor (MZI), Fabry-Perot fiber optic temperature sensor (FBI), Segnac fiber optic temperature sensor, etc. In 2021, Zhang et al. designed a Mach-Zehnder temperature-refractive index dual-parameter sensor based on a coreless-few-mode-coreless structure, achieving a maximum temperature sensing sensitivity of 0.0739nm/°C; in 2020, Sarah et al. For the first time, an all-fiber temperature sensor was proposed to corrode NCF with HF at a corrosion rate of 40%, and then coat a layer of copper oxide-polyvinyl alcohol (CuO-PVA) film as a sensitizing material in the corrosion area. Finally, the sensor was measured at In the range of 25℃～235℃, the maximum temperature sensitivity is 0.101nm/℃; the optical fiber temperature sensor is a new type of temperature sensor, which has anti-electromagnetic interference, high pressure resistance, corrosion resistance, explosion-proof and flame-proof, small size and light weight Etc. However, the sensitivity of the pure optical fiber structure in the existing interferometric temperature sensors is low, and most of them rely on temperature-sensitive materials to achieve the improvement of temperature sensitivity. Optical fiber temperature sensors such as Fabry-Perot structures that do not rely on temperature-sensitive materials but have high sensitivity , the sensor needs to be prepared in a microscopic environment, and the preparation process is complex and cumbersome.

Contents of the invention

The object of the present invention is to provide a temperature sensor based on partial dual-core special optical fiber and its preparation method. The temperature sensor has compact structure, convenient preparation and high sensitivity.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A temperature sensor based on partial dual-core special optical fiber, comprising: single-mode optical fiber, multi-mode optical fiber and partial dual-core optical fiber; one end of the single-mode optical fiber is connected to one end of the multi-mode optical fiber, and the other end of the multi-mode optical fiber connected with the first cylindrical structure end of partial duplex optical fiber;

The partially dual-core optical fiber includes a first cylindrical structure, a tapered structure with a gradually decreasing diameter, and a second cylindrical structure connected in sequence, and the other end of the second cylindrical structure is provided with a fiber made from the same fiber as the second cylindrical structure. Sphere structure.

The further improvement of the technical solution of the present invention is that: the single-mode optical fiber includes a first core and a first cladding wrapped outside the first core, and the first core is located at the center of the single-mode optical fiber;

The multimode optical fiber includes a second core and a second cladding wrapped outside the second core, and the second core is located at the center of the multimode optical fiber;

The partially dual-core optical fiber includes a third core, a fourth core and a third cladding wrapped outside the third core and the fourth core, the third core is located at the center of the partial dual-core optical fiber, The distance between the center of the fourth core and the center of the third core is 42.3 μm.

A further improvement of the technical solution of the present invention lies in that: the part of the fourth fiber core located in the second cylindrical structure is exposed in the air.

The further improvement of the technical solution of the present invention lies in that: the radius of the first core is 4.5 μm, and the radius of the first cladding is 62.5 μm.

The further improvement of the technical solution of the present invention lies in that: the radius of the second core is 52.5 μm, and the radius of the second cladding is 62.5 μm.

The further improvement of the technical solution of the present invention lies in that: the radius of the third fiber core is 4.2 μm, and the radius of the fourth fiber core is 3.8 μm.

The further improvement of the technical solution of the present invention lies in that: the diameter of the second cylindrical structure is 60-80 μm, and the length of the pyramidal structure is 3-5 mm.

The further improvement of the technical solution of the present invention lies in that: the diameter of the spherical structure is 100-200 μm.

A method for preparing a temperature sensor based on partial dual-core special optical fiber, comprising the following steps:

S1. Connect the single-mode optical fiber, multi-mode optical fiber and partial dual-core optical fiber through discharge cascade fusion in sequence;

S2. Corroding the other end of the partial dual-core optical fiber with a corrosive solution;

S3. Prepare a spherical structure by discharging the corroded end face of the partially dual-core optical fiber.

The further improvement of the technical solution of the present invention is that: the corrosion solution is 40% HF solution, the immersion length is 3-5 mm, and the immersion time is 30 minutes.

Owing to adopting above-mentioned technical scheme, the technical effect that the present invention obtains has:

The invention provides a temperature sensor based on partial dual-core special optical fiber and its preparation method. The tapered structure with gradually reduced diameter exposes one core of partial dual-core optical fiber, which increases the optical path difference of transmitted light. The structure enables secondary interference of the transmitted light, resulting in a change in the effective refractive index of the transmitted mode. The sensor of the invention has compact and novel structure, high sensitivity and great application potential in the field of temperature measurement.

Description of drawings

Fig. 1 is the overall structural representation of temperature sensor of the present invention;

Fig. 2 is the specific structural representation of temperature sensor of the present invention;

3a and 3b are schematic diagrams of the device before and after the preparation of the tapered structure of the temperature sensor and the second cylindrical structure of the present invention;

Fig. 4 is the flowchart of preparation method of the present invention;

Among them, 1. single-mode fiber, 2. multi-mode fiber, 3. first cylindrical structure, 4. cone structure, 5. second cylindrical structure, 6. spherical structure, 7. first cladding, 8. first Fiber core, 9, second cladding, 10, second fiber core, 11, third cladding, 12, fourth fiber core, 13, third fiber core.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The term "and/or" in the embodiments of the present invention describes the association relationship of associated objects, indicating that there may be three relationships, for example, A and/or B, which may mean: A exists alone, A and B exist simultaneously, and B exists alone These three situations. The character "/" generally indicates that the contextual objects are an "or" relationship.

The application scenarios described in the embodiments of the present invention are to illustrate the technical solutions of the embodiments of the present invention more clearly, and do not constitute limitations on the technical solutions provided by the embodiments of the present invention. It appears that the technical solutions provided by the embodiments of the present invention are also applicable to similar technical problems. Wherein, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

A temperature sensor based on a partial dual-core special optical fiber, as shown in Figures 1 and 2, comprising: a single-mode optical fiber 1, a multimode optical fiber 2 and a partial dual-core optical fiber; One end of the multi-mode fiber is connected to the other end of the multi-mode fiber with the first cylindrical structure 3 end of the partial dual-core fiber; the single-mode fiber 1 is used to receive the light emitted by the laser and transmit the light processed by the sensor to the spectrometer.

The single-mode optical fiber 1 includes a first core 8 and a first cladding 7 wrapped outside the first core 8, the first core 8 is located at the center of the single-mode optical fiber 1; the first core 8 has a radius of 4.5 μm, and the radius of the first cladding layer 7 is 62.5 μm.

The multimode fiber 2 includes a second core 10 and a second cladding 9 wrapped outside the second core 10, the second core 10 is located at the center of the multimode fiber 2; the second core 10 has a radius of 52.5 μm, and the second cladding 9 has a radius of 62.5 μm.

The partially dual-core optical fiber includes a first cylindrical structure 3, a tapered structure 4 with a gradually decreasing diameter, and a second cylindrical structure 5 connected in sequence, and the other end of the second cylindrical structure 5 is provided with a 5 The spherical structure 6 prepared with the same optical fiber. The radius of the first cylindrical structure 3 is 62.5 μm, the diameter of the second cylindrical structure 5 is 60-80 μm, the length of the cone structure 4 is 3-5 mm, and the diameter of the spherical structure 6 is 100-80 μm. 200 μm.

The partial dual-core optical fiber includes a third core 13, a fourth core 12, and a third cladding 11 wrapped outside the third core 13 and the fourth core 12, and the third cladding 11 forms a third cladding 11 externally. A cylindrical structure 3, a tapered structure 4 with a gradually decreasing diameter and a second cylindrical structure 5, the third core 13 is located at the center of the partial dual-core optical fiber, the center of the fourth core 12 is connected to the third core The distance between the centers of 13 is 42.3 μm, the radius of the third core 13 is 4.2 μm, and the radius of the fourth core 12 is 3.8 μm; the fourth core 12 is partially exposed in the second cylindrical structure 5 in the air.

A method for preparing a temperature sensor based on partial dual-core special optical fiber, as shown in Figure 4, comprises the following steps:

S1. Connect single-mode fiber 1, multi-mode fiber 2 and partial dual-core fiber through discharge cascade fusion in sequence

Before the single-mode optical fiber 1, multi-mode optical fiber 2 and partial dual-core optical fiber are discharged through the fusion splicing equipment, the optical fiber coating layer at one end is removed at a preset distance. The above-mentioned preset distance is determined by those skilled in the art according to the actual situation. Afterwards, cut the end face of the uncoated end flat, and place the end face of the single-mode fiber 1 and the multi-mode fiber 2 without the coating layer on the fiber fusion splicer, so that the end face of the optical fiber is aligned with the electrode rod, and the discharge fusion is performed. The discharge intensity and time They are 120bit and 3000ms respectively. Similarly, the other end of the multimode optical fiber 2 and the biased dual-core optical fiber also perform the same operation as above.

S2. Corroding the other end of the partial dual-core optical fiber with a corrosive solution to obtain a second cylinder and a tapered structure with a gradually decreasing diameter

Take the unfused end of the partial dual-core optical fiber to a length of 2 cm to remove the coating layer and cut the end face flat, and wipe it clean with alcohol cotton; then immerse it in a HF solution with a concentration of 40%, the immersion length is 3-5mm, and the immersion time is 30min . After the corrosion is completed, take it out and soak it in alcohol for 20 minutes to wash off the corrosion solution attached to the surface of the optical fiber, and dry it naturally to obtain the second cylinder 5 and the cone structure 4 with gradually decreasing diameter. 3a and 3b are schematic diagrams of the device before and after the preparation of the temperature sensor cone structure and the second cylinder structure, respectively. The etching solution may be, but not limited to, a 40% hydrofluoric acid solution.

S3. Prepare the end face of the partially dual-core optical fiber after being corroded by electric discharge to obtain a spherical structure 6

Put the second cylinder 5 obtained in step S2 and the tapered structure 4 whose diameter gradually decreases into the fusion splicing equipment so that the end face of the optical fiber is aligned with the electrode rod, push the partial dual-core optical fiber to the side without the optical fiber by 30 μm, and discharge to obtain Spherical structure, the discharge intensity and time are 80bit and 3000ms respectively to obtain the temperature sensor.

The following describes the steps to conduct a temperature sensing experiment and obtain spectral data through a temperature sensor:

Fix the temperature sensor on the glass plate and put it into the temperature control box. The single-mode jumper wire is sent out from the temperature control box to connect with the fiber grating demodulator. Turn on the switch of the temperature control box. From 25°C to 100°C, every 5 °C record the spectrogram data once. In the temperature sensor structure of the present invention, the light beam enters the multimode fiber from the single-mode fiber jumper at the input end. Since the second core diameter of the multimode fiber is relatively large, the light transmitted by the single-mode fiber jumper can be transmitted to the input bias Among the two cores of the dual-core fiber, the multimode fiber plays a role of "light beam expansion". Due to the distance between the two cores of the partial dual-core fiber, the weak coupling phenomenon is negligible. When the light enters the partial dual-core fiber, it is transmitted in the two cores, and the light transmitted in the fourth core is corroded. Reflected by the tapered structure, part of the light returns to the original path, and the other part of the fiber is lost in the air; the light transmitted in the third core reaches the spherical structure and interferes with the light transmitted in the third cladding, and then returns along the original path. Michelson interference occurs at the fusion joint between the mode fiber and partial dual-core fiber, and finally returns to the single-mode fiber jumper at the input end, and the fiber grating demodulator outputs the interference spectrum. Due to the effect of the corroded tapered structure and the spherical structure, the two beams of light in the partial dual-core optical fiber produce an optical path difference during transmission, which can realize the measurement of temperature.

The present invention proposes a temperature sensor based on a partial dual-core special optical fiber. The partial dual-core optical fiber uses a tapered structure with a gradually decreasing diameter to expose one core of the partial dual-core optical fiber, which increases the optical path difference of the transmitted light. The spherical structure A secondary interference of the transmitted light is achieved, resulting in a change in the effective refractive index of the transmitted mode. The temperature sensor has a compact and novel structure and high sensitivity, and has great application potential in the field of temperature measurement.

Claims (10)

1. A temperature sensor based on a double-core special optical fiber is characterized by comprising: the optical fiber comprises a single-mode optical fiber (1), a multimode optical fiber (2) and a bias double-core optical fiber; one end of the single-mode optical fiber (1) is connected with one end of a multimode optical fiber (2), and the other end of the multimode optical fiber (2) is connected with the end of a first cylindrical structure (3) of the eccentric twin-core optical fiber;

the inclined to one side double-core optical fiber comprises a first cylindrical structure (3), a cone structure (4) and a second cylindrical structure (5), wherein the cone structure (4) and the second cylindrical structure (5) are sequentially connected, the diameter of the cone structure is gradually reduced, and the other end portion of the second cylindrical structure (5) is provided with a sphere structure (6) which is made of the same optical fiber as the second cylindrical structure (5).

2. The temperature sensor based on the eccentric dual-core special optical fiber as claimed in claim 1, wherein: the single-mode optical fiber (1) comprises a first fiber core (8) and a first cladding (7) wrapping the first fiber core (8), wherein the first fiber core (8) is located at the central position of the single-mode optical fiber (1);

the multimode optical fiber (2) comprises a second fiber core (10) and a second cladding (9) wrapped outside the second fiber core (10), and the second fiber core (10) is located in the center of the multimode optical fiber (2);

the double-core fiber comprises a third fiber core (13), a fourth fiber core (12) and a third cladding (11) wrapping the third fiber core (13) and the fourth fiber core (12), wherein the third fiber core (13) is located at the center of the double-core fiber, and the distance between the center of the fourth fiber core (12) and the center of the third fiber core (13) is 42.3 mu m.

3. The temperature sensor based on the eccentric dual-core special optical fiber as claimed in claim 2, wherein: the fourth fiber core (12) is exposed in the air at the part of the second cylindrical structure (5).

4. The temperature sensor based on the eccentric dual-core special optical fiber as claimed in claim 3, wherein: the radius of the first core (8) is 4.5 μm, and the radius of the first cladding (7) is 62.5 μm.

5. The temperature sensor based on the eccentric dual-core special optical fiber as claimed in claim 3, wherein: the radius of the second core (10) is 52.5 mu m, and the radius of the second cladding (9) is 62.5 mu m.

6. The temperature sensor based on the eccentric dual-core special optical fiber as claimed in claim 3, wherein: the radius of the third fiber core (13) is 4.2 μm, and the radius of the fourth fiber core (12) is 3.8 μm.

7. The temperature sensor based on the eccentric dual-core special optical fiber as claimed in claim 3, wherein: the diameter of the second cylindrical structure (5) is 60-80 mu m, and the length of the cone structure (4) is 3-5 mm.

8. The temperature sensor based on the eccentric dual-core special optical fiber as claimed in claim 3, wherein: the diameter of the spherical structure (6) is 100-200 mu m.

9. The method for preparing the temperature sensor based on the double-core special optical fiber according to any one of claims 1 to 8, which is characterized by comprising the following steps: the method comprises the following steps:

s1, connecting a single-mode optical fiber (1), a multimode optical fiber (2) and a double-core fiber in a discharge cascade welding mode sequentially;

s2, corroding the other end of the eccentric twin-core optical fiber through a corrosive solution;

and S3, preparing the corroded end face of the eccentric twin-core optical fiber into a spherical structure (6) in a discharge mode.

10. The method for manufacturing the temperature sensor based on the eccentric dual-core special optical fiber according to claim 9, wherein the method comprises the following steps: the corrosion solution is a 40% HF solution, the immersion length is 3-5 mm, and the immersion time is 30min.

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