Optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF

Abstract

The utility model relates to an optical fiber temperature sensor, in particular to an optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF, which belongs to the technical field of optical fiber sensors and comprises a broadband light source, a structure a, a structure b and a spectrum analyzer. The structure a comprises a first single-mode optical fiber (201), a hollow-core optical fiber (202), a uv curing adhesive NOA68 (203) and a second single-mode optical fiber (204); the structure b comprises a third single-mode fiber (301), a coreless fiber NCF (302), a few-mode fiber FMF (303) and a fourth single-mode fiber (304); according to the utility model, the reference arm adopts the SMF-NCF-FMF structure, so that light of more single-mode optical fiber cores can be coupled into the cladding, and the interference effect of the reference arm is improved; a sensing arm FPI cavity is composed of a single-mode optical fiber end face and a uv curing adhesive NOA68, and the uv curing adhesive NOA68 is sensitive to temperature change and can improve the temperature sensitivity of the sensing arm. And by adopting the structure that the FPI is cascaded with the SMF-NCF-FMF, an optical vernier effect can be formed, and the temperature sensitivity of the sensor is improved. The sensor has the characteristics of high temperature sensitivity, strong anti-interference capability, small size, simplicity in manufacturing and the like.

Description

Technical Field

[0001] The utility model relates to an optical fiber temperature sensor, in particular to an optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF, belonging to the technical field of optical fiber sensors. Background Art

[0002] Optical fiber sensors are widely used in aerospace, petrochemical, medical, power transmission and other fields due to their strong anti-interference ability, small size, long transmission distance and safe transmission. At present, common optical fiber sensor measurement parameters include temperature, refractive index, strain, humidity, pressure, acceleration, vibration, etc., and temperature is a relatively important parameter in many application fields and has been a hot topic of research in recent years. In order to improve temperature sensitivity, researchers from various countries have proposed many new optical fiber sensing structures to improve temperature sensitivity, such as temperature sensors based on the combination of FBG and Mach-Zehnder interferometer, which have a relatively large measurement range but cannot meet the requirements of high sensitivity; FBG-based erbium-doped fiber laser structure can perform remote temperature sensing, but cannot meet the requirements of a large measurement range, etc. Summary of the invention

[0003] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the utility model is to provide an optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF, which has the characteristics of high temperature sensitivity, strong anti-interference ability, small size, simple production, etc.

[0004] The technical solution adopted by the utility model to solve the technical problem is:

[0005] An optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF is characterized by comprising a broadband light source SLED (1), a structure a (2), a structure b (3), and a spectrum analyzer (4); the structure a comprises a first single-mode optical fiber (201), a hollow-core optical fiber (202), a UV-curable adhesive NOA68 (203), and a second single-mode optical fiber (204); the hollow-core optical fiber (202) is filled with the UV-curable adhesive NOA68 (203); one end of the hollow-core optical fiber (202) with the adhesive is polished and flattened and fused with the second single-mode optical fiber (204); The other end of the hollow core optical fiber (202) is cut to a suitable length and fused with the first single-mode optical fiber (201); the structure b comprises a third single-mode optical fiber (301), a coreless optical fiber NCF (302), a few-mode optical fiber FMF (303), and a fourth single-mode optical fiber (304), and the above optical fibers are fused in sequence to form the structure b; the structure b is used as a reference arm of the optical vernier effect, and the structure a is used as a sensing arm of the optical vernier effect to measure temperature; the broadband light source SLED is connected to one end of the structure a, the other end of the structure a is connected to one end of the structure b, and the other end of the structure b is connected to a spectrum analyzer.

[0006] Beneficial effects of the utility model:

[0007] 1. The reference arm adopts the SMF-NCF-FMF structure, which can couple more light from the single-mode fiber core into the cladding, thereby improving the interference effect of the reference arm.

[0008] 2. The FPI cavity of the sensing arm is composed of the end face of the single-mode optical fiber and the UV-curing adhesive NOA68. The UV-curing adhesive NOA68 is more sensitive to temperature changes and can improve the temperature sensitivity of the sensing arm.

[0009] 3. The FPI cascade SMF-NCF-FMF structure can form an optical vernier effect and increase the temperature sensitivity of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural schematic diagram of an optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF of the utility model. Figure 2 for Figure 1 The structural diagram of 2 is shown in Figure 2. Figure 3 for Figure 1 Schematic diagram of the structure of 3.

[0011] 1 is a broadband light source SLED, 2 is structure a; 3 is structure b; 4 is a spectrum analyzer; 201 is a first single-mode optical fiber, 202 is a hollow-core optical fiber, 203 is a UV-curable adhesive NOA68, 204 is a second single-mode optical fiber; 301 is a third single-mode optical fiber, 302 is a coreless optical fiber NCF, 303 is a few-mode optical fiber FMF, and 304 is a fourth single-mode optical fiber. DETAILED DESCRIPTION

[0012] The following is a detailed description of the structure and working principle of the utility model:

[0013] An optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF is characterized by comprising a broadband light source SLED, structure a, structure b, a spectrum analyzer, a hollow-core optical fiber, UV curing adhesive NOA68, a few-mode optical fiber FMF, a coreless optical fiber NCF, and a single-mode optical fiber; the broadband light source SLED is connected to a first single-mode optical fiber (201), a second single-mode optical fiber (204) is connected to a third single-mode optical fiber (301), and a fourth single-mode optical fiber (304) is connected to the spectrum analyzer; wherein the manufacturing process of structure a is as follows: the hollow-core optical fiber (202) is immersed in the UV curing adhesive Adhesive NOA68 (204) is applied for 40 seconds, the glue will be absorbed into the hollow core optical fiber (202), and ultraviolet light is used for about 10 minutes to cure the glue, the end of the hollow core optical fiber (202) with glue is polished and smoothed and fused together with the second single-mode optical fiber (204), and the other end of the hollow core optical fiber (202) is cut to a suitable length and fused together with the first single-mode optical fiber (201); structure b is composed of the third single-mode optical fiber (301) and the coreless optical fiber NCF discharge fusion splicing, the coreless optical fiber NCF and the few-mode optical fiber FMF discharge fusion splicing, and the few-mode optical fiber FMF and the fourth single-mode optical fiber (304) discharge fusion splicing.

[0014] Working principle of a fiber optic temperature sensor based on FPI cascade SMF-NCF-FMF:

[0015] A fiber optic temperature sensor based on FPI cascade SMF-NCF-FMF is Figure 1 The components shown are connected well, and the light output by the broadband light source SLED enters the first single-mode optical fiber (201). The output light passes through the NOA68-air interface to generate Fresnel reflection, and the reflected light passes through the silica-air interface to generate a reflection again, thereby generating an optical path difference. Lights with different optical path differences at the NOA68-air interface generate interference. Then, the interference light passes through the second single-mode optical fiber (204) and passes through structure b, and the interference formed with structure b forms an optical cursor effect, that is, the two interference light beams are superimposed to form an interference envelope, and the light passing through structure b is transmitted to the spectrum analyzer. Example

[0016] Figure 1 It is a structural schematic diagram of an optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF of the utility model.

[0017] The air cavity in structure a has a length of 75 μm, the inner diameter of the hollow-core fiber is 80 μm, the outer diameter is 125 μm, and the length is 2 mm. The few-mode fiber FMF in sensing structure b is a four-mode fiber with a length of 22 cm, and the length of the coreless fiber NCF is 1 mm. The broadband light source SLED has a spectral range of 600-1600 nm, and the spectrum analyzer uses OSA (Yokogawa AQ6370c); a broadband light source SLED is connected to the first single-mode optical fiber (201), the second single-mode optical fiber (204) is connected to the third single-mode optical fiber (301), and the fourth single-mode optical fiber (304) is connected to the spectrum analyzer; wherein the manufacturing process of structure a is as follows: the hollow-core optical fiber (202) is immersed in UV curing adhesive NOA68 (204) for 40 seconds, the glue is absorbed into the hollow-core optical fiber (202), ultraviolet light is irradiated for about 10 minutes to cure the glue, the end of the hollow-core optical fiber (202) with glue is polished flat and fused with the second single-mode optical fiber (204), the hollow-core optical fiber (202) is cut to 2 mm and fused with the first single-mode optical fiber (201); the structure b is formed by discharge fusion splicing the third single-mode optical fiber (301) with the coreless optical fiber NCF, the coreless optical fiber NCF and the few-mode optical fiber FMF, and the few-mode optical fiber FMF and the fourth single-mode optical fiber (304).

[0018] The light output by the broadband light source SLED enters the first single-mode optical fiber (201), and the output light generates Fresnel reflection through the NOA68-air interface, and the reflected light is reflected again through the silica-air interface, thereby generating an optical path difference, and light with different optical path differences at the NOA68-air interface generates interference. Then, the interference light passes through the second single-mode optical fiber (204) and passes through structure b, and the interference formed with structure b forms an optical cursor effect, that is, two beams of interference light are superimposed to form an interference envelope, and the light passing through structure b is transmitted to the spectrum analyzer.

[0019] The above embodiment is only one of the preferred solutions among all the solutions of the utility model. Other simple changes to an optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF all fall within the scope of protection of the utility model.

Claims

1. An optical fiber temperature sensor based on FPI cascade SMF-NCF-FMF, characterized by The invention comprises a broadband light source SLED (1), a structure a (2), a structure b (3), and a spectrum analyzer (4); the structure a comprises a first single-mode optical fiber (201), a hollow-core optical fiber (202), a UV-curable adhesive NOA68 (203), and a second single-mode optical fiber (204); the hollow-core optical fiber (202) is filled with the UV-curable adhesive NOA68 (203); one end of the hollow-core optical fiber (202) with the adhesive is polished and flattened and fused with the second single-mode optical fiber (204); the other end of the hollow-core optical fiber (202) is cut to a suitable size; The structure b comprises a third single-mode optical fiber (301), a coreless optical fiber NCF (302), a few-mode optical fiber FMF (303), and a fourth single-mode optical fiber (304), and the above optical fibers are sequentially fused to form the structure b; the structure b is used as a reference arm of the optical vernier effect, and the structure a is used as a sensing arm of the optical vernier effect to measure temperature; the broadband light source SLED is connected to one end of the structure a, the other end of the structure a is connected to one end of the structure b, and the other end of the structure b is connected to a spectrum analyzer.

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