A dual-parameter fiber optic sensor based on dual-core fiber and few-mode fiber grating

Abstract

This invention discloses a dual-parameter fiber optic sensor based on a dual-core fiber and a few-mode fiber grating, belonging to the field of fiber optic sensor technology. It comprises a broadband light source (BBS), a sensing structure, and an OSA spectrometer. This invention utilizes the beam splitting effect of the coreless fiber to couple more light into the cladding, thereby improving the sensing structure's sensitivity to temperature. The addition of a PDMS coating layer further enhances the sensing structure's temperature and strain sensitivity. Furthermore, the use of the few-mode fiber grating to decouple the characteristic peaks of different temperature and strain responses enables dual-parameter measurement of temperature and strain. It possesses advantages such as miniaturization, simple structure, and ease of fabrication, exhibiting high sensitivity in strain and temperature monitoring and the ability to simultaneously measure two parameters.

Description

Technical Field

[0001] This utility model relates to a dual-parameter fiber optic sensor, and more particularly to a dual-parameter fiber optic sensor based on a dual-core fiber and a few-mode fiber grating, belonging to the field of fiber optic sensor technology. Background Technology

[0002] Fiber optic sensing technology has been widely applied in temperature and strain monitoring due to its advantages such as resistance to electromagnetic interference, small size, long-distance transmission capability, and high sensitivity. In temperature measurement, fiber optic gratings, interferometers, and distributed fiber optic sensing technologies can achieve real-time sensing of ambient temperature through the thermo-optical and thermal expansion effects of fiber optic materials. In strain measurement, fibers rely on changes in grating periodicity, phase delay, or mode coupling to acquire strain information. However, temperature and strain often have a coupling effect on fiber optic sensing signals, meaning they simultaneously cause drift in optical characteristic parameters, leading to cross-sensitivity in the measurement results. Therefore, how to realize a highly sensitive fiber optic sensor that can independently demodulate temperature and strain has become an important research direction in this field. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a dual-parameter fiber optic sensor based on dual-core fiber and few-mode fiber grating. This sensor has the advantages of miniaturization, simple structure and easy fabrication, high sensitivity in strain and temperature monitoring, and the ability to measure two parameters simultaneously.

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

[0005] A dual-parameter fiber optic sensor based on a dual-core fiber and a few-mode fiber grating is characterized by comprising a broadband light source BBS (1), a sensing structure (2), and a spectrum analyzer OSA (3); a first single-mode fiber (201), a coreless fiber (202), a dual-core fiber (203), a PDMS coating layer (204), a few-mode fiber grating (205), and a second single-mode fiber (206); the broadband light source BBS (1) is connected to one end of the sensing structure (2), and the other end of the sensing structure (2) is connected to the spectrum analyzer. The OSA (3) is connected; wherein the sensing structure (2) is formed by discharge fusion of one end of the first single-mode fiber (201) and the coreless fiber (202), the other end of the coreless fiber (202) and the dual-core fiber (203) are discharged fused together, the PDMS coating layer (204) is coated onto the cladding surface of the dual-core fiber (203), the other end of the dual-core fiber (203) is discharged fused together with one end of the few-mode fiber grating (205), and the other end of the few-mode fiber grating (205) is discharged fused together with one end of the second single-mode fiber (206).

[0006] The beneficial effects of this utility model are:

[0007] 1. By using the beam splitting effect of coreless optical fiber, more light is coupled into the cladding, thereby improving the sensitivity response of the sensing structure to temperature.

[0008] 2. Improve the temperature and strain sensitivity of the sensing structure by adding a PDMS coating layer;

[0009] 3. By utilizing a few-mode fiber grating to decouple the characteristic peaks of different responses to temperature and strain, dual-parameter measurement of temperature and strain was achieved. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of a dual-parameter fiber optic sensor based on a dual-core fiber and a few-mode fiber grating according to this utility model. Figure 2 for Figure 1 A schematic diagram of the middle sensing structure 2.

[0011] 1 is a broadband light source (BBS); 2 is a sensing structure; 3 is an optical spectrum analyzer (OSA); 201 is the first single-mode fiber; 202 is a coreless fiber; 203 is a dual-core fiber; 204 is a PDMS coating layer; 205 is a few-mode fiber grating; and 206 is the second single-mode fiber.

[0012] Specific implementation methods

[0013] The following is a detailed description of the structure and working principle of this utility model:

[0014] A dual-parameter fiber optic sensor based on a dual-core fiber and a few-mode fiber grating is characterized by comprising a broadband light source BBS (1), a sensing structure (2), and a spectrum analyzer OSA (3); a first single-mode fiber (201), a coreless fiber (202), a dual-core fiber (203), a PDMS coating layer (204), a few-mode fiber grating (205), and a second single-mode fiber (206); the broadband light source BBS (1) is connected to one end of the sensing structure (2), and the other end of the sensing structure (2) is connected to the spectrum analyzer. The OSA (3) is connected; wherein the sensing structure (2) is formed by discharge fusion of one end of the first single-mode fiber (201) and the coreless fiber (202), the other end of the coreless fiber (202) and the dual-core fiber (203) are discharged fused together, the PDMS coating layer (204) is coated onto the cladding surface of the dual-core fiber (203), the other end of the dual-core fiber (203) is discharged fused together with one end of the few-mode fiber grating (205), and the other end of the few-mode fiber grating (205) is discharged fused together with one end of the second single-mode fiber (206).

[0015] Working principle of a dual-parameter fiber optic sensor based on dual-core fiber and few-mode fiber grating:

[0016] A dual-parameter fiber optic sensor based on dual-core fiber and few-mode fiber gratings is based on Figure 1All components are connected as shown; the broadband light emitted by the broadband light source BBS (1) first enters the sensing structure (2); in the sensing structure (2), the light sequentially enters the first single-mode fiber (201) and is then coupled to the coreless fiber (202); due to the mismatch in the core diameter, multiple higher-order modes are excited in the coreless fiber; then, the light is transmitted to the dual-core fiber (203), and after another core diameter mismatch, part of the light field is transmitted in the cladding in the form of cladding modes, wherein the refractive index of the cladding and the length of the dual-core fiber (203) will be determined. Under the influence of temperature and strain, the PDMS coating layer (204) causes part of the optical field to propagate in the dual-core region, including the fundamental mode and higher-order core modes. Subsequently, the light enters the few-mode fiber grating (205), where the cladding mode is coupled back to the core, interfering with the core mode and being reflected at a specific wavelength in the grating region. Finally, the transmitted light is output through the second single-mode fiber (206) and transmitted to the OSA (3) spectrometer for spectral detection and analysis. The temperature and strain responses are decoupled through the characteristic peaks of the few-mode fiber grating. Example

[0017] Figure 1 This is a schematic diagram of the structure of a dual-parameter fiber optic sensor based on a dual-core fiber and a few-mode fiber grating according to this utility model.

[0018] The broadband light source BBS (1) has a wavelength range of 600nm-1600nm, and the optical spectrum analyzer OSA (3) uses a Yokogawa AQ6370c. The coreless fiber (202) is 5mm long, the dual-core fiber (203) has a core diameter of 9μm, a core pitch of 12μm, and a length of 3cm, the PDMS coating layer (204) is 10μm thick, and the few-mode fiber grating (205) has a few-mode fiber length of 3cm, the grating area is written by a femtosecond laser, a length of 1cm, and a reflectivity of 80%-90%. The broadband light source BBS (1) is connected to one end of the sensing structure (2), and the other end of the sensing structure (2) is connected to the optical spectrum analyzer OSA (3). A(3) is connected; wherein the sensing structure (2) is formed by discharge fusion of one end of the first single-mode fiber (201) and the coreless fiber (202), the other end of the coreless fiber (202) and the dual-core fiber (203) are discharged fused together, the PDMS coating layer (204) is coated onto the cladding surface of the dual-core fiber (203), the other end of the dual-core fiber (203) is discharged fused together with one end of the few-mode fiber grating (205), and the other end of the few-mode fiber grating (205) is discharged fused together with one end of the second single-mode fiber (206).

[0019] The broadband light emitted from the broadband light source BBS (1) first enters the sensing structure (2); in the sensing structure (2), the light sequentially enters the first single-mode fiber (201) and is then coupled to the coreless fiber (202); due to the mismatch in the core diameter, multiple higher-order modes are excited in the coreless fiber; then, the light is transmitted to the dual-core fiber (203), and after another core diameter mismatch, part of the light field is transmitted in the cladding in the form of cladding modes, wherein the refractive index of the cladding and the length of the dual-core fiber (203) will be affected by the PDMS coating. Under the influence of temperature and strain, part of the light field is transmitted in the dual-core region under the action of the cladding (204), including the fundamental mode and the higher-order core mode; then, the light enters the few-mode fiber grating (205), where the cladding mode is coupled back to the core, interferes with the core mode, and is reflected at a specific wavelength in the grating region; finally, the transmitted light is output through the second single-mode fiber (206) and transmitted to the OSA (3) spectrometer for spectral detection and analysis, and the temperature and strain response are decoupled through the characteristic peaks of the few-mode fiber grating.

[0020] The above embodiments are only one of the preferred embodiments among all the solutions of this utility model. Other simple modifications to a dual-parameter fiber optic sensor based on dual-core fiber and few-mode fiber grating are all within the scope of protection of this utility model.

Claims

1. A dual-parameter optical fiber sensor based on dual-core fiber and few-mode fiber grating, characterized in that The system includes a broadband light source BBS (1), a sensing structure (2), and a spectrum analyzer OSA (3); a first single-mode fiber (201), a coreless fiber (202), a dual-core fiber (203), a PDMS coating layer (204), a few-mode fiber grating (205), and a second single-mode fiber (206); the broadband light source BBS (1) is connected to one end of the sensing structure (2), and the other end of the sensing structure (2) is connected to the spectrum analyzer OSA (3); wherein the sensing... Structure (2) consists of a first single-mode fiber (201) and a coreless fiber (202) with one end of discharge fusion, and the other end of the coreless fiber (202) and a dual-core fiber (203) with discharge fusion. A PDMS coating layer (204) is coated onto the cladding surface of the dual-core fiber (203). The other end of the dual-core fiber (203) is discharged fused to one end of a few-mode fiber grating (205). The other end of the few-mode fiber grating (205) is discharged fused to one end of a second single-mode fiber (206).

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