Double-parameter optical fiber sensor based on vernier effect and Sagnac ring

Abstract

The utility model discloses a vernier effect and Sagnac ring-based dual-parameter optical fiber sensor, which belongs to the technical field of optical fiber sensors and comprises a broadband light source SLED (1), a coupler (2), a sensing structure A (3), a circulator (4), a sensing structure B (5) and a spectrum analyzer (6). The device comprises a first single-mode fiber (301), a polarization-maintaining photonic crystal fiber (302), a few-mode fiber (303), a fiber Bragg grating (304), a second single-mode fiber (501), a first hollow-core fiber (502) and a second hollow-core fiber (503). Parasitic interference is avoided by grinding the end face of the hollow-core optical fiber, and the reliability of the sensor is improved; two transmission peaks appear on the fiber bragg grating inscribed on the few-mode fiber through different mode numbers in the few-mode fiber, and gas concentration and temperature sensitivity of two signals can be calculated by observing drifting of the transmission peaks; an optical vernier effect can be formed through superposition of a Sagnac interferometer formed by polarization-maintaining photonic crystal fibers and an F-P interferometer formed by hollow core dislocation, and the gas concentration and the temperature sensitivity of the sensor are improved. The sensor has the characteristics of high sensitivity, wide measurement range, simple structure, small size and the like.

Description

Technical Field

[0001] This utility model relates to a dual-parameter sensor, and more particularly to a dual-parameter fiber optic sensor based on the vernier effect and Sagnac ring, belonging to the field of fiber optic sensor technology. Background Technology

[0002] In recent years, fiber optic sensing technology has developed rapidly. Fiber optic sensors, with their advantages of chemical corrosion resistance, small size, long transmission distance, and compact structure, have been widely used in bridge inspection, military engineering, biomedical engineering, and power systems, playing a vital role in each field. Common fiber optic sensor measurement parameters include temperature, gas concentration, strain, humidity, pressure, acceleration, and vibration. Gas concentration and temperature are particularly important parameters in many applications. However, in the pursuit of wide measurement range and high sensitivity in fiber optic sensors, the cross-sensitivity of gas concentration and temperature severely affects the accuracy and judgment of the sensing. Therefore, many current sensing structures can only measure a single parameter. Fiber optic sensors capable of measuring dual parameters with good sensitivity have become a hot research topic for the next stage. 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 the vernier effect and Sagnac ring. This sensor has the characteristics of high sensitivity to gas concentration and temperature, wide measurement range, simple structure, and small size.

[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 the vernier effect and Sagnac ring is characterized by comprising a broadband light source SLED (1), a coupler (2), a sensing structure A (3), a circulator (4), a sensing structure B (5), and a spectrometer (6); a first single-mode fiber (301), a polarization-maintaining photonic crystal fiber (302), a few-mode fiber (303), a fiber Bragg grating (304), a second single-mode fiber (501), a first hollow-core fiber (502), and a second hollow-core fiber (503); the broadband light source SLED (1) is connected to port one (201) of the coupler (2), port two (202) of the coupler (2) is connected to one end of the sensing structure A (3), the other end of the sensing structure A (3) is connected to port three (203) of the coupler (2), and port four (204) of the coupler (2). The circulator (4) is connected to port 1 (401), port 2 (402) is connected to one end of the sensing structure B (5), and port 3 (403) is connected to the spectrometer (6); the sensing structure A (3) is formed by discharge fusion of one end of the first single-mode fiber (301) and the polarization-maintaining photonic crystal fiber (302), and discharge fusion of the other end of the polarization-maintaining photonic crystal fiber (302) and one end of the few-mode fiber (303). A fiber Bragg grating (304) is written on the few-mode fiber (303) using a femtosecond laser; the sensing structure B (5) is formed by discharge fusion of one end of the second single-mode fiber (501) and the first hollow fiber (502), and misaligned fusion of the other end of the first hollow fiber (502) and one end of the second hollow fiber (503). The other end of the second hollow fiber (503) is ground with an 8° bevel.

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

[0007] 1. Parasitic interference is avoided by grinding the end face of the hollow fiber, which improves the reliability of the sensor;

[0008] 2. By using different modes in a few-mode fiber to create two transmission peaks in the fiber Bragg grating etched on it, and observing the drift of the transmission peaks, the sensitivity of the two signals to gas concentration and temperature can be calculated.

[0009] 3. The superposition of a Sagnac interferometer made of polarization-maintaining photonic crystal fiber and an FP interferometer made of hollow misalignment can form an optical vernier effect, which can improve the sensitivity of the sensor to gas concentration and temperature. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of a dual-parameter fiber optic sensor based on the vernier effect and Sagnac ring according to this utility model. Figure 2 This is a schematic diagram of the structure of sensor probe A. Figure 3 This is a schematic diagram of the structure of sensor probe B.

[0011] 1 is a broadband light source SLED; 2 is a coupler; 3 is a sensing structure A; 4 is a circulator; 5 is a sensing structure B; 6 is a spectrometer; 301 is a first single-mode fiber; 302 is a polarization-maintaining photonic crystal fiber; 303 is a few-mode fiber; 304 is a fiber Bragg grating; 501 is a second single-mode fiber; 502 is a first hollow-core fiber; 503 is a second hollow-core 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 the vernier effect and Sagnac ring is characterized by comprising a broadband light source SLED (1), a coupler (2), a sensing structure A (3), a circulator (4), a sensing structure B (5), and a spectrometer (6); a first single-mode fiber (301), a polarization-maintaining photonic crystal fiber (302), a few-mode fiber (303), a fiber Bragg grating (304), a second single-mode fiber (501), a first hollow-core fiber (502), and a second hollow-core fiber (503); the broadband light source SLED (1) is connected to port one (201) of the coupler (2), port two (202) of the coupler (2) is connected to one end of the sensing structure A (3), the other end of the sensing structure A (3) is connected to port three (203) of the coupler (2), and port four (204) of the coupler (2). The circulator (4) is connected to port 1 (401), port 2 (402) is connected to one end of the sensing structure B (5), and port 3 (403) is connected to the spectrometer (6); the sensing structure A (3) is formed by discharge fusion of one end of the first single-mode fiber (301) and the polarization-maintaining photonic crystal fiber (302), and discharge fusion of the other end of the polarization-maintaining photonic crystal fiber (302) and one end of the few-mode fiber (303). A fiber Bragg grating (304) is written on the few-mode fiber (303) using a femtosecond laser; the sensing structure B (5) is formed by discharge fusion of one end of the second single-mode fiber (501) and the first hollow fiber (502), and misaligned fusion of the other end of the first hollow fiber (502) and one end of the second hollow fiber (503). The other end of the second hollow fiber (503) is ground with an 8° bevel.

[0015] The working principle of a dual-parameter fiber optic sensor based on the vernier effect and Sagnac ring:

[0016] A dual-parameter fiber optic sensor based on vernier effect and Sagnac ring. Figure 1With all components connected, the broadband light output from the broadband light source SLED enters port one (401) of coupler (2). Port two (202) and port three (203) of coupler (2) split the light received from port one (201) of coupler (2) into two beams. The light output from port two (202) of coupler (2) first enters the first single-mode fiber (301) in the sensing structure A (3). Due to mode mismatch, when the light is transmitted to the interface between the first single-mode fiber (301) and the polarization-maintaining photonic crystal fiber (302), a higher-order mode is excited. When the light passes through the polarization-maintaining photonic crystal fiber (302), a higher-order mode is excited. 2) During transmission, due to the birefringence effect of the crystal, the light is split into two beams with different polarization states and different optical paths. When the light is transmitted from the polarization-maintaining photonic crystal fiber (302) to the few-mode fiber (303), the two polarized beams are coupled here, and the higher-order mode is also coupled into the core of the few-mode fiber. Furthermore, when the light is transmitted to the fiber Bragg grating (304), since the few-mode fiber allows more than one mode to propagate in the core, multiple different transmission characteristic peaks will appear. After the light is transmitted through port three (203) of coupler (2), it is output from port four (204) of coupler (2) and enters the circulator (4). Port 1 (401), circulator (4) and port 2 (402) output light to sensing structure B (5) and second single-mode fiber (501). When the light is transmitted to the end face of the second single-mode fiber (501) and the first hollow fiber (502), part of the light is reflected and part of the light is transmitted into the first hollow fiber (502). When the light is transmitted to the end face of the first hollow fiber (502) and the second hollow fiber (503), part of the light is reflected and part of the light is transmitted into the second hollow fiber (503). When the light is transmitted to the end of the second hollow fiber (503), parasitic interference is avoided due to the effect of the 8° inclined plane. The reflected light generated at the two end faces enters port two (402) of the circulator (4) and is output to the spectrometer (6) from port three (403) of the circulator (4). The Sagnac interference generated by the sensing structure A (3) and the FP interference generated by the sensing structure B (5) are finally characterized on the spectrometer (6). Then, through the calibration test experiment of gas concentration and temperature (selecting two different transmission characteristic peaks to reflect the drift of the interference spectrum envelope), based on the optical vernier effect and the drift of the transmission characteristic peak, the sensitivity coefficient matrix of gas concentration and temperature is finally obtained, realizing the simultaneous measurement of gas concentration and temperature. Example

[0017] Figure 1This is a schematic diagram of the structure of a dual-parameter fiber optic sensor based on the vernier effect and Sagnac ring of this utility model. In sensing structure A, the first single-mode fiber (201) is 3cm long, the polarization-maintaining photonic crystal fiber (202) is 40cm long, the few-mode fiber (203) is 5cm long, and the fiber Bragg grating (204) is 1cm long, written by a femtosecond laser. In sensing structure B, the second single-mode fiber (501) is 3cm long, the first hollow fiber (502) is 1cm long, and the second hollow fiber (503) is 1cm long. The broadband light source SLED (1) has a spectral range of 600-1600nm, the circulator (4) is a three-port circulator, the coupler (2) has a splitting ratio of 50:50, and the spectrometer (6) uses an OSA (Yokogawa) system. AQ6370c); the broadband light source SLED (1) is connected to port one (201) of coupler (2), port two (202) of coupler (2) is connected to one end of sensing structure A (3), the other end of sensing structure A (3) is connected to port three (203) of coupler (2), port four (204) of coupler (2) is connected to port one (401) of circulator (4), port two (402) of circulator (4) is connected to one end of sensing structure B (5), and port three (403) of circulator (4) is connected to the spectrometer (6); wherein sensing structure A ( 3) The first single-mode fiber (301) is fused to one end of the polarization-maintaining photonic crystal fiber (302) by discharge, and the other end of the polarization-maintaining photonic crystal fiber (302) is fused to one end of the few-mode fiber (303) by discharge. A fiber Bragg grating (304) is written on the few-mode fiber (303) by femtosecond laser. The sensing structure B (5) is fused to one end of the second single-mode fiber (501) by discharge, and the other end of the first hollow fiber (502) is fused to one end of the second hollow fiber (503) by misalignment. The other end of the second hollow fiber (503) is ground with an 8° bevel.

[0018] A dual-parameter fiber optic sensor based on vernier effect and Sagnac ring. Figure 1With all components connected, the broadband light output from the broadband light source SLED enters port one (401) of coupler (2). Port two (202) and port three (203) of coupler (2) split the light received from port one (201) of coupler (2) into two beams. The light output from port two (202) of coupler (2) first enters the first single-mode fiber (301) in the sensing structure A (3). Due to mode mismatch, when the light is transmitted to the interface between the first single-mode fiber (301) and the polarization-maintaining photonic crystal fiber (302), a higher-order mode is excited. When the light is transmitted in the polarization-maintaining photonic crystal fiber (302), due to the dual nature of the crystal... Due to the refraction effect, light is split into two beams with different polarization states and different optical paths. When the light is transmitted from the polarization-maintaining photonic crystal fiber (302) to the few-mode fiber (303), the two polarized beams are coupled here, and the higher-order mode is also coupled into the core of the few-mode fiber. Furthermore, when the light is transmitted to the fiber Bragg grating (304), since the few-mode fiber allows more than one mode to propagate in the core, multiple different transmission characteristic peaks will appear. After the light is transmitted through the third port (203) of the coupler (2), it is output from the fourth port (204) of the coupler (2) and enters the first port (401) of the circulator (4) and the second port (402) of the circulator (4). The output light is sent to the second single-mode fiber (501) of the sensing structure B (5). When the light is transmitted to the end face of the second single-mode fiber (501) and the first hollow fiber (502), part of the light is reflected and part of the light is transmitted into the first hollow fiber (502). In the sealed air chamber, the gas to be measured can enter the first hollow fiber (502) through the second hollow fiber (503) to achieve natural flow. When the light is transmitted to the end face of the first hollow fiber (502) and the second hollow fiber (503), part of the light is reflected and part of the light is transmitted into the second hollow fiber (503). When the light is transmitted to the end of the second hollow fiber (503), due to the 8° tilt... The surface effect avoids parasitic interference. The reflected light generated at the two end faces enters port two (402) of the circulator (4) and is output to the spectrometer (6) from port three (403) of the circulator (4). The Sagnac interference generated by the sensing structure A (3) and the FP interference generated by the sensing structure B (5) are finally characterized on the spectrometer (6). Then, through the calibration test experiment of gas concentration and temperature (selecting two different transmission characteristic peaks to reflect the drift of the interference spectrum envelope), based on the optical vernier effect and the drift of the transmission characteristic peak, the sensitivity coefficient matrix of gas concentration and temperature is finally obtained, realizing the simultaneous measurement of gas concentration and temperature.

[0019] 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 the vernier effect and Sagnac ring are all within the scope of protection of this utility model.

Claims

1. A dual-parameter fiber optic sensor based on the vernier effect and Sagnac ring, characterized in that... The system includes a broadband light source SLED (1), a coupler (2), a sensing structure A (3), a circulator (4), a sensing structure B (5), and a spectrometer (6); a first single-mode fiber (301), a polarization-maintaining photonic crystal fiber (302), a few-mode fiber (303), a fiber Bragg grating (304), a second single-mode fiber (501), a first hollow-core fiber (502), and a second hollow-core fiber (503); the broadband light source SLED (1) is connected to port one (201) of the coupler (2), port two (202) of the coupler (2) is connected to one end of the sensing structure A (3), the other end of the sensing structure A (3) is connected to port three (203) of the coupler (2), and port four (204) of the coupler (2) is connected to port one (401) of the circulator (4). The circulator (4) port 2 (402) is connected to one end of the sensing structure B (5), and the circulator (4) port 3 (403) is connected to the spectrometer (6); wherein the sensing structure A (3) is formed by discharge fusion of one end of the first single-mode fiber (301) and the polarization-maintaining photonic crystal fiber (302), and discharge fusion of the other end of the polarization-maintaining photonic crystal fiber (302) and one end of the few-mode fiber (303), and a fiber Bragg grating (304) is written on the few-mode fiber (303) by femtosecond laser; the sensing structure B (5) is formed by discharge fusion of one end of the second single-mode fiber (501) and the first hollow fiber (502), and discharge fusion of the other end of the first hollow fiber (502) and one end of the second hollow fiber (503) by misalignment, and the other end of the second hollow fiber (503) is ground with an 8° bevel.

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