Double-parameter fiber laser sensor based on cascaded Sagnac ring and FMF-FBG

Abstract

The utility model discloses a double-parameter optical fiber laser sensor based on a cascade Sagnac ring and an FMF-FBG, which belongs to the technical field of optical fiber sensors and comprises an LD (laser diode) pumping laser source, a wavelength division multiplexer, a holmium-doped optical fiber, an optical isolator, a sensing structure, a coupler and a spectrum analyzer. According to the utility model, the polarization-maintaining photonic crystal fiber is adopted to form the Sagnac ring, so that the sensitivity of the sensing probe is effectively improved. The FMF-FBG is cascaded with the Sagnac ring, the Sagnac serves as a reference interferometer, the vernier effect is utilized, the sensitivity of the FMF-FBG sensor is improved, the few-mode fiber bragg grating has narrower line width and good polarization characteristic, temperature and strain sensing can be conducted on the few-mode fiber bragg grating, and double-parameter measurement is achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of optical fiber laser sensors, especially a kind of double-parameter optical fiber laser sensor based on cascade Sagnac ring and FMF-FBG, belong to optical fiber sensor technical field. BACKGROUND

[0002] In recent years, optical fiber sensing technology develops rapidly, and has wide application in aerospace, medicine, geological exploration and power system, and plays an irreplaceable role in various fields.Compared with traditional broadband light source optical fiber sensor, optical fiber laser sensor, which has good stability, narrow spectral width, high signal-to-noise ratio and other advantages, has become one of the research directions in the field of optical fiber sensing.However, in the process of researching high reliability and high sensitivity of optical fiber laser sensor, the existence of temperature and strain cross-sensitivity seriously affects the accuracy and judgment of sensing, so many sensing structures can only measure single parameter at present.The optical fiber laser sensor capable of measuring double parameters and having high sensitivity becomes the hotspot of next step research. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the purpose of the utility model provides a kind of double-parameter optical fiber laser sensor based on cascade Sagnac ring and FMF-FBG, and the laser has the characteristics of small volume, simple structure, easy to make, high temperature sensitivity.

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

[0005] 1. A kind of double-parameter optical fiber laser sensor based on cascade Sagnac ring and FMF-FBG, it is characterized by including LD pumped laser source (1), wavelength division multiplexer (2), holmium-doped optical fiber (3), optical isolator (4), first 3-dB coupler (5), polarization-maintaining photonic crystal fiber (6), few-mode Bragg fiber grating (7), second 3-dB coupler (8), optical spectrum analyzer (9);The L D Pump laser source (1) and wave division multiplexer (2) one port (201) are connected, wave division multiplexer (2) two ports (202) and holmium-doped optical fiber (3) one end are connected, holmium-doped optical fiber (3) the other end and optical isolator (4) one end are connected, optical isolator (4) the other end and first 3-dB coupler (5) one port (501) are connected, first 3-dB coupler (5) two ports (502) and polarization maintaining photonic crystal fiber (6) one end are connected, first 3-dB coupler (5) three ports (503) and polarization maintaining photonic crystal fiber (6) the other end are connected, first 3-dB coupler (5) four ports (504) and few-mode Bragg fiber grating (7) are connected, few-mode Bragg fiber grating (7) the other end and second 3-dB coupler (8) one port (801) are connected, second 3-dB coupler (8) two ports (802) and optical spectrum analyzer (9) are connected, second 3-dB coupler (8) three ports (803) and wave division multiplexer (2) three ports (203) are connected, wherein single-mode optical fiber and polarization maintaining photonic crystal fiber (6) are discharged and fused, single-mode optical fiber and few-mode Bragg fiber grating (7) are discharged and fused.

[0006] The beneficial effects of the present application are as follows:

[0007] 1. The polarization maintaining photonic crystal fiber is used to form a Sagnac ring, which effectively improves the sensitivity of the sensing probe.

[0008] 2. The FMF-FBG cascade Sagnac ring is used, Sagnac is used as a reference interferometer, and the sensitivity of the FMF-FBG sensor is improved by using the vernier effect.

[0009]

[0010] 3. The dual-parameter measurement of temperature and strain is realized. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is a structure diagram of a dual-parameter optical fiber laser sensor based on a cascade Sagnac ring and FMF-FBG.

[0012] 1 is an LD pump laser source; 2 is a wave division multiplexer; 3 is a holmium-doped optical fiber; 4 is an optical isolator; 5 is a 3-dB coupler; 6 is a polarization maintaining photonic crystal fiber; 7 is a few-mode Bragg fiber grating; 8 is a 3-dB coupler; and 9 is an optical spectrum analyzer.

[0013] DETAILED EMBODIMENT

[0014] The structure and working principle of the present application will be described in detail as follows:

[0015] ​1. A dual-parameter optical fiber laser sensor based on a cascade Sagnac ring and FMF-FBG, characterized by comprising an LD pumping laser source (1), a wavelength division multiplexer (2), a holmium-doped optical fiber (3), an optical isolator (4), a first 3-dB coupler (5), a polarization-maintaining photonic crystal fiber (6), a few-mode Bragg fiber grating (7), a second 3-dB coupler (8), and a spectrum analyzer (9); the LD pumping laser source (1) is connected to a port (201) of the wavelength division multiplexer (2), a second port (202) of the wavelength division multiplexer (2) is connected to one end of the holmium-doped optical fiber (3), the other end of the holmium-doped optical fiber (3) is connected to one end of the optical isolator (4), the other end of the optical isolator (4) is connected to a first port (501) of the first 3-dB coupler (5), a second port (502) of the first 3-dB coupler (5) is connected to one end of the polarization-maintaining photonic crystal fiber (6), a third port (503) of the first 3-dB coupler (5) is connected to the other end of the polarization-maintaining photonic crystal fiber (6), a fourth port (504) of the first 3-dB coupler (5) is connected to the few-mode Bragg fiber grating (7), the other end of the few-mode Bragg fiber grating (7) is connected to a first port (801) of the second 3-dB coupler (8), a second port (802) of the second 3-dB coupler (8) is connected to the spectrum analyzer (9), and a third port (803) of the second 3-dB coupler (8) is connected to a third port (203) of the wavelength division multiplexer (2); the single-mode optical fiber and the polarization-maintaining photonic crystal fiber (6) are discharge fusion spliced, and the single-mode optical fiber and the few-mode Bragg fiber grating (7) are discharge fusion spliced.

[0016] A working principle of a dual-parameter optical fiber laser sensor based on a cascade Sagnac ring and FMF-FBG:

[0017] A dual-parameter optical fiber laser sensor based on a cascade Sagnac ring and FMF-FBG according to Figure 1The shown components are connected, the 980m pump light output by the LD pump laser source (1) is coupled into the linear optical path by the port (201) of the wavelength division multiplexer (2), passes through the holmium-doped optical fiber (3), the holmium ions in the optical fiber absorb pump photons, particle inversion occurs, and stimulated radiation light is generated. The optical isolator (4) is connected to the holmium-doped optical fiber (3) at one end, and the light enters the first 3-dB coupler (5) through the optical isolator (4) at one end (501). After the input light enters the first 3-dB coupler (5), it is divided into two beams of equal intensity, one of which is output from the second port (502) of the first 3-dB coupler (5) and propagates in the counterclockwise direction, and the other is output from the third port (503) of the first 3-dB coupler (5) and propagates in the clockwise direction. Due to the birefringence effect of the polarization-maintaining photonic crystal fiber (6), the two beams of light will produce opposite phase differences, and after coupling, an interference spectrum can be formed at the fourth port (504) of the first 3-dB coupler (5). Changing the temperature and strain of the polarization-maintaining photonic crystal fiber (6) will cause the transmission spectrum of the Sagnac loop structure to shift, thereby realizing temperature and strain sensing. The light output from the fourth port (504) of the first 3-dB coupler (5) enters one end of the few-mode Bragg fiber grating (7), where the wavelengths of light that satisfy the fiber grating Bragg condition will be reflected, and the remaining wavelengths of light will continue to transmit through the few-mode Bragg fiber grating. The few-mode Bragg fiber grating has a narrower line width and good polarization characteristics, and can be used for temperature and strain sensing. The light passing through the few-mode Bragg fiber grating enters the second 3-dB coupler (8), which is divided into two beams of light. One beam of light is transmitted to the wavelength division multiplexer (2) through the third port (803) of the second 3-dB coupler (8); the other beam of light is transmitted to the optical spectrum analyzer (9) through the second port (802) of the second 3-dB coupler (8). Embodiment

[0018] Figure 1The utility model relates to a kind of double-parameter optical fiber laser sensor based on cascaded Sagnac ring and FMF-FBG structure schematic diagram of the utility model.The laser wavelength of LD pump source (1) is 980nm, wavelength division multiplexer (2) is 980nm / 1550nm, holmium-doped fiber (3) length is 2m, optical isolator (4) center wavelength is 1550nm, first 3-dB coupler (5) is 2x2, polarization-maintaining photonic crystal fiber (6) long is 20cm, first 3-dB coupler (5) and polarization-maintaining photonic crystal fiber (6) constitute Sagnac loop structure, few-mode fiber Bragg grating (7) length is 5cm.LD pump laser source (1) is connected with the one port (201) of wavelength division multiplexer (2), the two ports (202) of wavelength division multiplexer (2) are connected with the one end of holmium-doped fiber (3), the other end of holmium-doped fiber (3) is connected with the one end of optical isolator (4), the other end of optical isolator (4) is connected with the one port (501) of first 3-dB coupler (5), the two ports (502) of first 3-dB coupler (5) are connected with the one end of polarization-maintaining photonic crystal fiber (6), the three ports (503) of first 3-dB coupler (5) are connected with the other end of polarization-maintaining photonic crystal fiber (6), the four ports (504) of first 3-dB coupler (5) are connected with few-mode fiber Bragg grating (7), the other end of few-mode fiber Bragg grating (7) is connected with the one port (801) of second 3-dB coupler (8), the two ports (802) of second 3-dB coupler (8) are connected with optical spectrum analyzer (9), the three ports (803) of second 3-dB coupler (8) are connected with the three ports (203) of wavelength division multiplexer (2).Wherein single-mode fiber and polarization-maintaining photonic crystal fiber (6) carry out discharge fusion, single-mode fiber and few-mode fiber Bragg grating (7) carry out discharge fusion.

[0019] The 980m pump light outputted by the LD pump laser source (1) is coupled into the linear light path by one port (201) of the wavelength division multiplexer (2), passes through the holmium-doped optical fiber (3), the holmium ions in the optical fiber absorb the pump light, particle inversion occurs, and thus stimulated radiation light is generated. The optical isolator (4) is connected with the holmium-doped optical fiber (3) at one end, and the light enters one port (501) of the first 3-dB coupler (5) through the optical isolator (4). After the input light enters the first 3-dB coupler (5), it is divided into two beams with the same intensity, one of which is outputted from the second port (502) of the first 3-dB coupler (5) and propagates in the counterclockwise direction, and the other is outputted from the third port (503) of the first 3-dB coupler (5) and propagates in the clockwise direction. Due to the birefringence effect of the polarization-maintaining photonic crystal fiber (6), the two beams of light will produce opposite phase differences, and after coupling, an interference spectrum can be formed at the fourth port (504) of the first 3-dB coupler (5). Changing the temperature and strain of the polarization-maintaining photonic crystal fiber (6) will cause the transmission spectrum of the Sagnac loop structure to shift, so that the temperature and strain sensing can be realized. The light outputted from the fourth port (504) of the first 3-dB coupler (5) enters one end of the few-mode Bragg fiber grating (7), wherein the light of wavelengths satisfying the fiber grating Bragg condition will be reflected, and the rest of the wavelengths will be transmitted through the few-mode Bragg fiber grating. The few-mode Bragg fiber grating has a narrower line width and good polarization characteristics, and can be used for temperature and strain sensing. The light passing through the few-mode Bragg fiber grating enters the second 3-dB coupler (8), and is divided into two beams of light. One of the beams of light is transmitted to the wavelength division multiplexer (2) through the third port (803) of the second 3-dB coupler (8); the other beam of light is transmitted to the optical spectrum analyzer (9) through the second port (802) of the second 3-dB coupler (8).

[0020] The above embodiment is only one of the preferred schemes of all schemes of the present application, and other simple changes of the one kind of dual-parameter fiber laser sensor based on the cascaded Sagnac ring and FMF-FBG all belong to the scope of the present application.

Claims

1. A dual-parameter optical fiber laser sensor based on a concatenated Sagnac loop and FMF-FBG, characterized in that It includes LD pump laser source (1), wave division multiplexer (2), holmium-doped fiber (3), optical isolator (4), first 3-dB coupler (5), polarization maintaining photonic crystal fiber (6), few-mode Bragg fiber grating (7), second 3-dB coupler (8), optical spectrum analyzer (9); LD pump laser source (1) is connected with one port (201) of wave division multiplexer (2), two ports (202) of wave division multiplexer are connected with one end of holmium-doped fiber (3), the other end of holmium-doped fiber (3) is connected with one end of optical isolator (4), the other end of optical isolator (4) is connected with one port (501) of first 3-dB coupler (5), two ports (502) of first 3-dB coupler are connected with one end of polarization maintaining photonic crystal fiber (6), three ports (503) of first 3-dB coupler are connected with the other end of polarization maintaining photonic crystal fiber (6), four ports (504) of first 3-dB coupler (5) are connected with few-mode Bragg fiber grating (7), the other end of few-mode Bragg fiber grating (7) is connected with one port (801) of second 3-dB coupler (8), two ports (802) of second 3-dB coupler are connected with optical spectrum analyzer (9), three ports (803) of second 3-dB coupler are connected with three ports (203) of wave division multiplexer, wherein single-mode fiber and polarization maintaining photonic crystal fiber (6) are discharge fusion spliced, single-mode fiber and few-mode Bragg fiber grating (7) are discharge fusion spliced.

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