A method and device for preparing optical fiber grating with adjustable birefringence

Abstract

The present invention provides a method and device for preparing an optical fiber grating with adjustable birefringence, comprising the following steps: step S1: arranging an optical fiber on a displacement platform; step S2: focusing the laser on a certain area on the optical fiber after being shaped by a laser shaping device; the displacement platform drives the optical fiber to move, so that the laser induces the formation of a refractive index modulation area on the optical fiber to form an optical fiber grating; step S3: testing the birefringence of the optical fiber grating by a polarization analysis and demodulation device, and comparing the difference between the feedback value of the birefringence data and the preset target value; step S4: if there is a difference between the feedback value of the birefringence data and the preset target value, obtaining the adjustment parameters required by the laser shaping device according to the difference between the feedback value of the birefringence data and the preset target value; adjusting the laser shaping device according to the adjustment parameters, and executing step S2 to achieve the regulation of the birefringence of the optical fiber grating.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber grating preparation, and in particular to a method and a device for preparing an optical fiber grating with adjustable birefringence. Background Art

[0002] Fiber Bragg gratings have a series of excellent properties such as strong anti-electromagnetic interference ability, corrosion resistance, small size, and large-scale networking. They are important devices in the fields of fiber optic communication and fiber optic sensing.

[0003] Polarization-dependent loss refers to the maximum change in the transmission power of the input optical signal under all polarization states. It is mainly used to measure the sensitivity of optical devices or optical systems to the polarization state of the transmitted light and is an important parameter of fiber Bragg gratings. In the field of optical fiber communications, excessive polarization-dependent loss will increase the bit error rate; in the field of optical fiber sensing, polarization-dependent loss will affect the stability of the reflection spectrum of the fiber Bragg grating, thereby affecting the measurement accuracy of the grating; the polarization-dependent loss of the fiber Bragg grating is mainly caused by birefringence. When the laser-induced refractive index modulation area is not circularly symmetrical, the birefringence of the fiber Bragg grating will increase greatly.

[0004] The fiber Bragg grating is written on the fiber core by using the phase mask plate method based on ultraviolet continuous laser. The refractive index modulation area formed completely covers the core, and a lower birefringence coefficient can be obtained, thereby reducing the polarization-dependent loss of the fiber Bragg grating. However, the fiber Bragg grating prepared based on ultraviolet continuous laser needs to be sensitized to the optical fiber. The obtained grating is usually a type I grating, which cannot work stably for a long time in a high temperature environment and is greatly limited in the field of high-temperature sensing. The femtosecond laser phase mask plate method can be used to prepare type II gratings, which greatly improves the temperature tolerance of the fiber Bragg grating, and there is no need to sensitize the optical fiber. However, when writing the fiber Bragg grating wavelength division multiplexing array, phase masks of different periods are required, which greatly reduces the flexibility. The femtosecond laser point-by-point method can flexibly prepare high-temperature resistant fiber Bragg gratings of different periods. However, after the femtosecond laser is focused by the objective lens, an elliptical focal point is formed on the cross section of the optical fiber core, not a circular focal point, which induces birefringence and increases polarization-dependent loss, thereby affecting the application of fiber Bragg grating in optical fiber sensing and optical fiber communication.

[0005] In addition, in certain specific scenarios, high birefringence fiber Bragg gratings also have significant application value. With the development of science and technology and the widespread deployment and application of 5G technology, the era of artificial intelligence is coming. Intelligent robots can replace manual work in some extreme environments and avoid some dangerous things from happening, so they have great development value.

[0006] High birefringence fiber Bragg grating sensors can be used in intelligent robot fingers as pressure sensors. When the robot fingers feel different pressures, the sensors can get real-time perception and feedback. When external pressure is applied in different directions along the high birefringence fiber Bragg grating sensor, the sensor will have different spectral responses. Through a spectrometer or a polarization analysis and demodulation system, the changes in the polarization spectrum of the high birefringence fiber Bragg grating can be demodulated to obtain lateral pressure responses in different directions. High birefringence fiber Bragg grating sensor is an excellent lateral pressure sensor. Summary of the invention

[0007] In view of the above requirements, the purpose of the present invention is to provide a method and device for preparing an adjustable birefringence fiber Bragg grating, aiming to achieve the regulation of the birefringence of the fiber Bragg grating, so as to obtain the required high birefringence fiber Bragg grating or low birefringence fiber Bragg grating.

[0008] The present application provides a method for preparing a fiber grating with adjustable birefringence, comprising the following steps:

[0009] Step S1: placing the optical fiber on a displacement platform;

[0010] Step S2: the laser emitted by the laser device is shaped by the laser shaping device to change the circular spot into a linear spot; the shaped laser is focused to a certain area on the optical fiber;

[0011] The displacement platform drives the optical fiber to move, so that the laser induces the formation of a refractive index modulation area on the optical fiber, forming a fiber grating;

[0012] Step S3: testing the birefringence of the fiber Bragg grating by a polarization analysis and demodulation device, and comparing the difference between the feedback value of the birefringence data and the preset target value;

[0013] Step S4: if there is a difference between the feedback value of the birefringence data and the preset target value, the adjustment parameters required for the laser shaping device are obtained according to the difference between the feedback value of the birefringence data and the preset target value; the laser shaping device is adjusted according to the adjustment parameters, and step S2 is executed to achieve regulation of the birefringence of the fiber grating.

[0014] According to a method for preparing a fiber Bragg grating with adjustable birefringence provided in an embodiment of the present application, the method for testing the birefringence of the fiber Bragg grating by a polarization analysis and demodulation device in step S3 includes:

[0015] After the tunable light enters the polarization analyzer, two orthogonal polarization states with the same wavelength are output; the two orthogonal polarization states enter the fiber grating, and the birefringence of the fiber grating causes the wavelengths of the two orthogonal polarization states to shift;

[0016] The intelligent terminal obtains the difference between the central wavelengths of the two polarization states according to the power values ​​of the fiber Bragg grating at different wavelengths detected by the optical power meter, and calculates the birefringence of the fiber Bragg grating.

[0017] According to a method for preparing a fiber Bragg grating with adjustable birefringence provided in an embodiment of the present application, in step S4, the intelligent terminal obtains the adjustment parameters required for the laser shaping device based on the correspondence between the difference between the feedback value of the calculated birefringence data and the preset target value and the adjustment parameters of the laser shaping device.

[0018] According to a method for preparing a fiber Bragg grating with adjustable birefringence provided in an embodiment of the present application, the laser shaping device is a slit shaping device, and the slit shaping device shapes the laser into a linear spot;

[0019] In step S4, the ellipticity of the cross section of the fiber Bragg grating refractive index modulation region is changed by adjusting the width of the slit, thereby achieving regulation of the birefringence of the fiber Bragg grating.

[0020] According to a method for preparing a fiber Bragg grating with adjustable birefringence provided in an embodiment of the present application, the laser shaping device is a spatial light modulator, and the spatial light modulator shapes the laser into a linear spot;

[0021] In step S4, the ellipticity of the cross section of the fiber Bragg grating refractive index modulation region is changed by adjusting the phase distribution of the spatial light modulator, thereby achieving regulation of the birefringence of the fiber Bragg grating.

[0022] According to a method for preparing a fiber Bragg grating with adjustable birefringence provided in an embodiment of the present application, the laser shaping device is a double-cylindrical lens, and the double-cylindrical lens shapes the laser into a linear spot;

[0023] In step S4, the ellipticity of the cross section of the fiber Bragg grating refractive index modulation region is changed by adjusting the relative position of the double cylindrical lenses, thereby achieving regulation of the birefringence of the fiber Bragg grating.

[0024] The present application also provides a device for preparing a fiber grating with adjustable birefringence, comprising: a laser processing optical path system, a displacement platform, and a polarization analysis and demodulation device; the laser processing optical path system comprises a laser device and a laser shaping device;

[0025] The laser shaping device is used to shape the laser emitted by the laser device, and the shaped laser is focused on the optical fiber;

[0026] The displacement platform is used to drive the optical fiber to move so that the laser can induce a refractive index modulation region on the optical fiber, thereby forming a fiber grating;

[0027] The polarization analysis and demodulation device is used to test the birefringence of the optical fiber grating, and obtain the adjustment parameters required by the laser shaping device according to the difference between the feedback value of the birefringence data and the preset target value.

[0028] According to an embodiment of the present application, a device for preparing a fiber grating with adjustable birefringence further includes a control device, which is connected to the laser shaping device and adjusts the laser shaping device according to adjustment parameters.

[0029] According to a device for preparing a fiber grating with adjustable birefringence provided in an embodiment of the present application, the polarization analysis and demodulation device includes a tunable laser, a polarization analyzer, an optical power meter and an intelligent terminal;

[0030] The tunable laser is connected to the input port of the polarization analyzer, and the output port of the polarization analyzer is connected to the first end of the fiber grating; the second end of the fiber grating is connected to the optical power meter; the polarization analyzer and the optical power meter are both connected to the intelligent terminal;

[0031] The intelligent terminal obtains the difference between the two polarization state wavelengths according to the power values ​​of the fiber Bragg grating at different wavelengths detected by the optical power meter, and calculates the birefringence of the fiber Bragg grating;

[0032] The intelligent terminal obtains the adjustment parameters required for the laser shaping device according to the correspondence between the difference between the calculated feedback value of the birefringence data and the preset target value and the adjustment parameters of the laser shaping device.

[0033] According to an apparatus for preparing a fiber grating with adjustable birefringence provided in an embodiment of the present application, the laser shaping device is a slit shaping device, a spatial light modulator, or a double cylindrical lens.

[0034] The present invention has the following beneficial effects:

[0035] The present application provides a method and device for preparing a fiber grating with adjustable birefringence, which can not only prepare a low-birefringence fiber grating, reduce polarization-related loss in the light transmission process, and improve the transmission quality of optical devices, but also have high utilization value in both fiber optic communication and fiber optic sensing; it can also prepare a high-birefringence fiber grating, which can be used as a lateral pressure sensor for autonomous perception of intelligent robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a simplified structural diagram of a device for preparing a fiber grating with adjustable birefringence according to the present application;

[0037] Figure 2 It is a structural schematic diagram of a device for preparing a fiber Bragg grating with adjustable birefringence according to the present application;

[0038] Figure 3 It is a partial structural schematic diagram of a preparation device corresponding to the first embodiment of the method for preparing a controllable birefringence fiber grating of the present application;

[0039] Figure 4 It is a partial structural schematic diagram of a preparation device corresponding to the second embodiment of the method for preparing a controllable birefringence fiber grating of the present application;

[0040] Figure 5 It is a partial structural schematic diagram of a preparation device corresponding to the third embodiment of the method for preparing a controllable birefringence fiber grating of the present application;

[0041] Figure 6 It is a schematic diagram of the ellipticity of the cross section of the refractive index modulation region of the fiber grating obtained by the method for preparing the adjustable birefringence fiber grating of the present application.

[0042] Figure annotation:

[0043] Laser device 10, laser shaping device 20, laser focusing device 30, clamping and moving device 40, polarization analysis and demodulation device 50, femtosecond laser 101, frequency multiplier 102, optical component 103, CCD 104, dichroic mirror 105, tunable laser 501, polarization analyzer 502, power meter 503, intelligent terminal 504, slit shaping device 31, optical fiber 601, fiber grating 602, spatial light modulator 32, beam splitter 33, double cylindrical lens 34. DETAILED DESCRIPTION

[0044] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0045] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the present invention will be further described in detail in conjunction with the following referenced drawings and exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in different forms. The essence of the description is only to help technicians in the relevant field to comprehensively understand the specific details of the present invention.

[0046] The present application provides a device for preparing a fiber grating with adjustable birefringence.

[0047] like Figure 1 , Figure 2 As shown,

[0048] The present invention provides a device for preparing a fiber grating 602 with adjustable birefringence, which includes a laser processing optical path system, a displacement platform, and a polarization analysis and demodulation device 50.

[0049] The laser processing optical path system includes a laser device 10 , a laser shaping device 20 , a laser focusing device 30 , and a clamping and moving device 40 .

[0050] The laser device 10 is used to emit laser light to the laser shaping device 20, and the laser device 10 includes a femtosecond laser, a frequency multiplier 102, corresponding optical components 103, a CCD 104, and a dichroic mirror 105. The optical component 103 includes an attenuator and a shutter device for controlling the laser light; the attenuator can be composed of a half-wave plate and a Glan prism.

[0051] The laser shaping device 20 is used to shape the laser emitted by the laser device 10. The laser shaping device 20 in the specific embodiment of the present application is a slit shaping device 31, a spatial light modulator 32, or a double cylindrical lens.

[0052] The shaped laser is focused onto the optical fiber 601 by the laser focusing device 30. The laser focusing device 30 is an objective lens 30.

[0053] The clamping and moving device 40 includes an optical fiber 601 fixture and a displacement platform 40. The displacement platform is, for example, a high-precision three-dimensional electric platform. The displacement platform is used to drive the optical fiber 601 to move so that the laser induces the formation of a refractive index modulation region on the optical fiber 601, thereby forming a fiber grating 602.

[0054] The polarization analysis and demodulation device 50 is used to test the birefringence of the fiber grating 602 and obtain the adjustment parameters required by the laser shaping device 20 according to the difference between the feedback value of the birefringence data and the preset target value.

[0055] The fiber grating 602 preparation device also includes a control device. The control device is connected to the laser shaping device 20 and adjusts the laser shaping device 20 according to the adjustment parameters. When the laser shaping device 20 is a slit shaping device 31, the control device is, for example, an electric control knob. Every time it rotates an angle, the width of the slit will change to a certain extent. When the laser shaping device 20 is a spatial light modulator 32, the control device directly encodes and generates a corresponding hologram. After the light passes through the spatial light modulator, the light will be modulated. When the laser shaping device 20 is a double-column lens, the two lenses can be installed on the electric moving device of the control device, and the positions of the two lenses are changed by the control device to adjust the light.

[0056] The polarization analysis and demodulation device 50 of the specific embodiment of the present application includes a tunable laser 501 , a polarization analyzer 502 , an optical power meter 503 and an intelligent terminal 504 .

[0057] The tunable laser 501 is connected to the input port of the polarization analyzer 502, and the output port of the polarization analyzer 502 is connected to the first end of the fiber grating 602. The second end of the fiber grating 602 is connected to the optical power meter 503, and the polarization analyzer 502 and the optical power meter 503 are both connected to the intelligent terminal 504.

[0058] The intelligent terminal 504 is used to obtain the difference between the two polarization state wavelengths according to the power values ​​of the fiber Bragg grating 602 at different wavelengths detected by the optical power meter 503, and calculate the birefringence of the fiber Bragg grating 602;

[0059] The intelligent terminal 504 further obtains the adjustment parameters required for the laser shaping device 20 according to the correspondence between the difference between the calculated feedback value of the birefringence data and the preset target value and the adjustment parameters of the laser shaping device 20. The intelligent terminal 504 is, for example, a computer. The computer is connected to the control device.

[0060] The present application also provides a method for preparing a fiber grating 602 with adjustable birefringence, comprising the following steps:

[0061] Step S1: placing the optical fiber 601 on a displacement platform;

[0062] Step S2: the laser emitted by the laser device 10 is shaped by the laser shaping device 20 to change the circular spot into a linear spot; the shaped laser is focused to a certain area on the optical fiber 601;

[0063] The displacement platform drives the optical fiber 601 to move, so that the laser induces a refractive index modulation region on the optical fiber 601 to form a fiber grating 602;

[0064] Step S3: testing the birefringence of the fiber Bragg grating 602 by the polarization analysis demodulation device 50, and comparing the difference between the feedback value of the birefringence data and the preset target value;

[0065] Step S4: if there is a difference between the feedback value of the birefringence data and the preset target value, the adjustment parameter required for the laser shaping device 20 is obtained according to the difference between the feedback value of the birefringence data and the preset target value; the laser shaping device 20 is adjusted according to the adjustment parameter, and step S2 is executed to achieve regulation of the birefringence of the fiber Bragg grating 602.

[0066] In step S4, after adjusting the laser shaping device 20 according to the adjustment parameters, step S2 is executed to write the next grating, and the fiber grating 602 with the required birefringence can be obtained.

[0067] Steps S2 to S4 may also be performed multiple times until the feedback value of the birefringence data in step S3 is the same as the preset target value, and the desired grating is obtained.

[0068] In a specific embodiment of the present application, in step S3, the method for testing the birefringence of the fiber grating 602 by the polarization analysis demodulation device 50 includes:

[0069] After the tunable light enters the polarization analyzer 502, two orthogonal polarization states with the same wavelength are output; the two orthogonal polarization states enter the fiber grating 602, and the birefringence of the fiber grating 602 causes the wavelengths of the two orthogonal polarization states to shift;

[0070] The intelligent terminal 504 obtains the difference between the central wavelengths of the two polarization states according to the power values ​​of the fiber Bragg grating 602 at different wavelengths detected by the optical power meter 503 , and calculates the birefringence of the fiber Bragg grating 602 .

[0071] In a specific embodiment of the present application, in step S4, the intelligent terminal 504 obtains the adjustment parameters required for the laser shaping device 20 according to the correspondence between the difference between the calculated feedback value of the birefringence data and the preset target value and the adjustment parameters of the laser shaping device 20.

[0072] In step S1, the optical fiber 601 to be processed is placed on a high-precision three-dimensional electric platform, one end is clamped and fixed with a clamp, and prestress is applied to the other end to make it horizontal and straight, and then clamped and fixed with a clamp.

[0073] In step S2, the structure of the laser shaping device 20 is adjusted and the corresponding parameters are set, so that the circular laser spot before entering the objective lens becomes a linear spot, and the spot is parallel to the axial direction of the optical fiber 601. The objective lens is used for observation, and the position of the optical fiber 601 is continuously adjusted so that the axial direction of the optical fiber 601 is perpendicular to the femtosecond laser, so that the femtosecond laser is focused on a certain area on the optical fiber 601, for example, at the center of the core of the optical fiber 601. After setting the appropriate laser energy and other related parameters. The displacement platform is controlled to start uniform motion, and the linear spot induces a refractive index modulation area on the core of the optical fiber 601 to form a fiber grating 602.

[0074] In step S3, the output end of the tunable laser 501 is connected to the input end of the polarization synthesizer through a single-mode jumper. The light enters the polarization analyzer 502 and is decomposed into various polarization states. The polarization states of the two modes TE and TM required are synthesized according to the Mueller matrix. The two polarization states are orthogonal polarization states with the same wavelength. The output end of the polarization synthesizer is connected to the fiber grating 602 sample to be tested, and the two polarization states are output to the fiber grating 602 sample.

[0075] Originally, the wavelengths of the two polarization states are the same, but due to the birefringence of the sample, the two polarization states have an offset after passing through the fiber grating 602 sample to be tested. The optical power meter 503 can detect the power value of the fiber grating 602 sample at different wavelengths, and the intelligent terminal 504 displays the spectrum of the two polarization states, and it can be known that the two polarization states have changed after passing through the fiber grating 602 sample; the intelligent terminal 504 can calculate the birefringence of the fiber grating 602 sample based on the difference in the wavelengths of the two polarization states and the offset of the two wavelengths. The calculated birefringence feedback value is compared with the size of the birefringence target value we preset, and the difference between the two can be obtained.

[0076] In a specific embodiment of the present application, the computer software in the intelligent terminal 504 is used to generate control parameters for the laser shaping device 20 according to the difference between the feedback value of the birefringence data and the preset target value, and the corresponding relationship between the specific difference amount and the adjustment parameters of the laser shaping device 20.

[0077] For example, the slit is calibrated in advance, and the birefringence can be increased or decreased by how much the slit width changes, so that the difference between the feedback value of the birefringence data and the preset target value is established with the adjustment parameter of the laser shaping device 20, and the corresponding data can be pre-stored in the intelligent terminal 504.

[0078] The present application can automatically calculate the corresponding adjustment data through computer software. The calculation process or implementation method of calculating the required adjustment data using the obtained birefringence of the fiber grating 602 is a prior art and will not be described in detail in the present invention.

[0079] In step S4, the parameters of the laser shaping device 20 are further adjusted according to the adjustment parameters. By changing the parameters of the laser shaping device 20, the ellipticity of the cross section of the refractive index modulation region of the laser-induced fiber Bragg grating 602 can be changed, thereby realizing the correction of the ellipticity of the cross section of the refractive index modulation region of the fiber Bragg grating 602 and preparing the desired fiber Bragg grating 602.

[0080] First embodiment

[0081] like Figure 3 As shown, it is a first embodiment of a method for preparing a fiber Bragg grating with adjustable birefringence. In this embodiment, the laser shaping device 20 is a slit shaping device 31. By adjusting the position and width of the slit shaping device 31 and other parameters, the femtosecond laser passes through the slit to form a linear light spot, and the linear light spot is parallel to the axial direction of the optical fiber 601. In step S4, the parameters of the slit are adjusted, for example, by adjusting the width of the slit, the ellipticity of the cross section of the refractive index modulation region of the fiber Bragg grating 602 can be changed, so as to achieve the regulation of the birefringence of the fiber Bragg grating 602.

[0082] The parameters of the slit can be adjusted by electric control to change the ellipticity of the cross section of the refractive index modulation region of the fiber Bragg grating 602, thereby achieving Figure 6 The ellipticity control shown is: from a larger grating ellipticity A (the ratio of the major and minor axes of the ellipse is greater than 1) to a smaller grating ellipticity B (the ratio of the major and minor axes of the ellipse is close to or equal to 1), and then to a larger grating ellipticity C (the ratio of the major and minor axes of the ellipse is greater than 1).

[0083] The control device is connected to the slit shaping device 31, and the control device can realize automatic regulation of the parameters of the slit.

[0084] The method for preparing the adjustable birefringent fiber grating 602 is simple, convenient and low-cost, but the laser energy utilization rate is low.

[0085] Second embodiment

[0086] Figure 4 As shown, a second embodiment of a method for preparing a fiber Bragg grating with adjustable birefringence is shown. In this embodiment, the laser shaping device 20 is a spatial light modulator 32, and the spatial light modulator 32 shapes the laser into a linear spot.

[0087] Different from the first embodiment, this embodiment adjusts the positions of the spatial light modulator 32 and the beam splitter 33 to change the parameters of the spatial light modulator 32, such as the amplitude, intensity and phase of the light distribution on the spatial light modulator 32, so that the femtosecond laser passes through the beam splitter 33 and is reflected by the spatial light modulator 32 and the beam splitter 33 to form a linear light spot.

[0088] Different from the first embodiment, in step S4 of this embodiment, the amplitude, intensity and phase of the light distribution on the spatial light modulator 32 are changed according to the adjustment data to adjust the ellipticity of the cross section of the refractive index modulation area of ​​the modified fiber Bragg grating 602, thereby regulating the birefringence of the fiber Bragg grating 602.

[0089] The method is used to prepare an adjustable birefringent fiber grating 602, which is flexible and can shape the laser into various desired shapes by changing the amplitude, intensity and phase of the light distribution on the spatial light modulator 32.

[0090] Third embodiment

[0091] Figure 5 FIG. 1 is a third embodiment of a method for preparing a fiber Bragg grating with adjustable birefringence. In this embodiment, the laser shaping device 20 is a double cylindrical lens.

[0092] Different from the first embodiment, in this embodiment, in step S3, when the laser shaping device 20 shapes the laser, the position between the two cylindrical lenses of the double cylindrical lens is adjusted so that the femtosecond laser forms a linear spot of appropriate width after passing through the double cylindrical lens.

[0093] Different from the first embodiment, in step S4 of this embodiment, the position between the two cylindrical lenses of the double cylindrical lens is changed according to the adjustment data to adjust the ellipticity of the cross section of the refractive index modulation region of the modified fiber Bragg grating 602, thereby regulating the birefringence of the fiber Bragg grating 602.

[0094] The method is used to prepare the controllable birefringence fiber grating 602, and the laser energy utilization rate is high.

[0095] Obviously, the embodiments described above are only some embodiments of the present application, rather than all embodiments. The preferred embodiments of the present application are given in the accompanying drawings, but they do not limit the scope of patent protection of the present application. The present application can be implemented in many different forms. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive. Although the present application is described in detail with reference to the aforementioned embodiments, for those skilled in the art, it is still possible to modify the technical solutions recorded in the aforementioned specific implementation methods, or to perform equivalent replacement of some of the technical features therein. Any equivalent structure made using the contents of the specification and drawings of this application, directly or indirectly used in other related technical fields, is also within the scope of patent protection of this application.

Claims

1. A method for preparing a fiber Bragg grating with adjustable birefringence, characterized in that: The preparation method comprises the following steps: Step S1: placing the optical fiber on a displacement platform; Step S2: the laser emitted by the laser device is shaped by the laser shaping device to change the circular spot into a linear spot; the shaped laser is focused to a certain area on the optical fiber; the displacement platform drives the optical fiber to move, so that the laser induces the formation of a refractive index modulation area on the optical fiber to form a fiber grating; Step S3: testing the birefringence of the fiber Bragg grating by a polarization analysis and demodulation device, and comparing the difference between the feedback value of the birefringence data and the preset target value; Step S4: if there is a difference between the feedback value of the birefringence data and the preset target value, the adjustment parameters required for the laser shaping device are obtained according to the difference between the feedback value of the birefringence data and the preset target value; the laser shaping device is adjusted according to the adjustment parameters, and step S2 is executed to achieve regulation of the birefringence of the fiber grating.

2. The method for preparing a fiber Bragg grating according to claim 1, wherein: The method for testing the birefringence of the fiber grating by the polarization analysis demodulation device in step S3 includes: After the tunable light enters the polarization analyzer, two orthogonal polarization states with the same wavelength are output; the two orthogonal polarization states enter the fiber grating, and the birefringence of the fiber grating causes the wavelengths of the two orthogonal polarization states to shift; The intelligent terminal obtains the difference between the central wavelengths of the two polarization states according to the power values ​​of the fiber Bragg grating at different wavelengths detected by the optical power meter, and calculates the birefringence of the fiber Bragg grating.

3. The method for preparing a fiber Bragg grating according to claim 2, characterized in that: In step S4, the intelligent terminal obtains the adjustment parameters required for the laser shaping device according to the correspondence between the difference between the calculated feedback value of the birefringence data and the preset target value and the adjustment parameters of the laser shaping device.

4. The method for preparing a fiber Bragg grating according to claim 1, characterized in that: The laser shaping device is a slit shaping device, and the slit shaping device shapes the laser into a linear spot; In step S4, the ellipticity of the cross section of the fiber Bragg grating refractive index modulation region is changed by adjusting the width of the slit, thereby achieving regulation of the birefringence of the fiber Bragg grating.

5. The method for preparing a fiber Bragg grating according to claim 1, characterized in that: The laser shaping device is a spatial light modulator, and the spatial light modulator shapes the laser into a linear spot; In step S4, the ellipticity of the cross section of the fiber Bragg grating refractive index modulation region is changed by adjusting the phase distribution of the spatial light modulator, thereby achieving regulation of the birefringence of the fiber Bragg grating.

6. The method for preparing a fiber Bragg grating according to claim 1, characterized in that: The laser shaping device is a double-column lens, which shapes the laser into a linear spot; In step S4, the ellipticity of the cross section of the fiber Bragg grating refractive index modulation region is changed by adjusting the relative position of the double cylindrical lenses, thereby achieving regulation of the birefringence of the fiber Bragg grating.

7. A device for preparing a fiber Bragg grating with adjustable birefringence, comprising: Laser processing optical path system, displacement platform, polarization analysis and demodulation device; the laser processing optical path system includes a laser device and a laser shaping device; The laser shaping device is used to shape the laser emitted by the laser device, and the shaped laser is focused on the optical fiber; The displacement platform is used to drive the optical fiber to move so that the laser can induce a refractive index modulation region on the optical fiber, thereby forming a fiber grating; The polarization analysis and demodulation device is used to test the birefringence of the fiber grating, and obtain the adjustment parameters required by the laser shaping device according to the difference between the feedback value of the birefringence data and the preset target value; A control device, the control device is connected to the laser shaping device and adjusts the laser shaping device according to the adjustment parameters; The polarization analysis and demodulation device includes a tunable laser, a polarization analyzer, an optical power meter and an intelligent terminal; The tunable laser is connected to the input port of the polarization analyzer, and the output port of the polarization analyzer is connected to the first end of the fiber grating; the second end of the fiber grating is connected to the optical power meter; the polarization analyzer and the optical power meter are both connected to the intelligent terminal; The intelligent terminal obtains the difference between the central wavelengths of the two polarization states according to the power values ​​of the fiber Bragg grating at different wavelengths detected by the optical power meter, and calculates the birefringence of the fiber Bragg grating; The intelligent terminal obtains the adjustment parameters required for the laser shaping device according to the correspondence between the difference between the calculated feedback value of the birefringence data and the preset target value and the adjustment parameters of the laser shaping device; The laser shaping device is a slit shaping device, a spatial light modulator or a double-column lens.

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