Dot light source inscription apodized fiber grating system and method thereof

Abstract

The application provides a point light source inscription apodized fiber grating system and a method thereof. The system comprises: a laser for outputting inscription laser; a scanning reflection device for reflecting the laser output by the laser to an inscription area of an optical fiber and scanning the inscription area with the laser; an apodized inscription device for attenuating the power of the laser according to a predetermined attenuation curve; a laser focusing device for focusing the laser on the inscription area to form a grating pattern in the core of the inscription area; and a reference platform for mounting the laser, the scanning reflection device, the apodized inscription device and the laser focusing device. The system of the application effectively reduces the sidelobes on both sides of the resonance peak and improves the spectral characteristics of the fiber grating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber grating, in particular to a point light source writing apodized fiber grating system and a method thereof. BACKGROUND

[0002] Fiber grating is an important passive device of fiber, which has been widely used in fiber communication, fiber sensing, fiber laser and other fields. At present, a periodic refractive index modulation structure is directly formed on the fiber core by further expanding the rectangular spot output by an excimer laser and cooperating with a focusing system, a mask plate and the like at the back end, so as to form a fiber grating. However, the rectangular spot output by the excimer laser itself has certain unevenness, which causes the refractive index modulation distribution of the written fiber grating along the fiber core axis to be uneven, affecting the spectral type of the fiber grating.

[0003] The method of writing the fiber grating by point-by-point scanning along the fiber core axis with a point light source can effectively solve the problem of uneven refractive index modulation distribution, but it will bring a new problem, that is, the point light source writing fiber grating cannot use the traditional amplitude mask to realize apodized writing and the matching compensation process, resulting in more sidelobes on both sides of the reflection spectrum resonance peak of the written fiber grating, which seriously affects the application effect. SUMMARY

[0004] The present application provides a point light source writing apodized fiber grating system and a method thereof. The system comprises a laser, a scanning reflection device, an apodized writing device, a laser focusing device and a reference platform. By using the point-by-point scanning writing method, the problem of uneven refractive index modulation distribution in the traditional rectangular spot writing method is effectively solved, and the overall quality and performance of the fiber grating are improved. By using a mask plate and an apodized writing device, the attenuation curve of the laser power can be accurately controlled, and high-precision apodized writing can be realized. The apodized writing device has two functions of apodization and compensation, and the laser power is adjusted according to the predetermined attenuation curve through a gradient filter, which effectively reduces the sidelobes on both sides of the resonance peak, significantly improves the performance of the fiber grating, and overcomes the shortcomings of the prior art.

[0005] In the first aspect, the present application provides a point light source writing apodized fiber grating system, characterized in that the system comprises:

[0006] a laser for outputting laser for writing grating;

[0007] a scanning reflection device for reflecting the laser output by the laser to the writing area of the fiber and scanning the writing area with the laser;

[0008] an apodized writing device for attenuating the power of the laser according to a predetermined attenuation curve;

[0009] a laser focusing device for focusing the laser on the inscription region to form a grating pattern in the core of the inscription region;

[0010] a reference platform for mounting the laser, the scanning reflection device, the apodization inscription device and the laser focusing device.

[0011] In a second aspect, the present application also provides a point light source inscription apodization fiber grating method, characterized in that a point light source inscription apodization fiber grating system is provided, which comprises a laser, a scanning reflection device, an apodization inscription device, a laser focusing device and a reference platform; the method comprises:

[0012] the laser outputs laser for inscribing a grating;

[0013] the scanning reflection device reflects the laser output by the laser to an inscription region of an optical fiber and scans the inscription region with the laser;

[0014] the apodization inscription device attenuates the power of the laser according to a predetermined attenuation curve;

[0015] the laser focusing device focuses the laser on the inscription region to form a grating pattern in the core of the inscription region;

[0016] the reference platform mounts the laser, the scanning reflection device, the apodization inscription device and the laser focusing device.

[0017] The point light source inscription apodization fiber grating system and method provided by the present application have the following advantages: first, the point-by-point scanning inscription method with a point light source effectively solves the problem of uneven refractive index modulation distribution in the traditional rectangular light spot inscription method; second, the mask plate and the apodization inscription device can accurately control the attenuation curve of the laser power, realizing high-precision apodization inscription, wherein the apodization inscription device has the functions of apodization and compensation, and the gradual variable filter is used to adjust the laser power according to the predetermined attenuation curve, effectively reducing the sidelobes on both sides of the resonance peak, improving the spectral characteristics of the fiber grating and enhancing the application effect of the fiber grating in the fields of fiber communication, fiber sensing and fiber lasers; third, the gradual variable filter of the apodization inscription device can attenuate the laser power according to the predetermined attenuation curve, including Gaussian function, Sinc function and Tanh function, etc., meeting the requirements of various apodization functions and having high flexibility; fourth, the strip and ring gradual variable filters are designed with multiple attenuation curves, which can be switched between different gradual variable filter strips or filter rings according to requirements, reducing the frequency of replacing the filter and improving the work efficiency; fifth, the present application is compatible with multiple laser types, including nanosecond pulse laser and femtosecond pulse laser, and is suitable for different fiber grating inscription requirements, having a wide range of applications. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0019] Figure 1 is a schematic diagram of a point light source inscription apodized fiber grating system provided by the embodiments of the present application;

[0020] Figure 2a and 2b are an apodization curve and a compensation curve provided by the embodiments of the present application, respectively;

[0021] Figures 3a-3c are schematic diagrams of fiber grating transmission spectra inscribed by the embodiments of the present application without apodization compensation, only apodization without compensation, and both apodization and compensation, respectively;

[0022] Figure 4a and 4b are strip-shaped gradual change filters selected in the apodization process and gradually changed along the longitudinal direction of the filter and gradually changed in steps, respectively, provided by the embodiments of the present application;

[0023] Figure 5a and 5b are strip-shaped gradual change filters selected in the compensation process and gradually changed along the longitudinal direction of the filter and gradually changed in steps, respectively, provided by the embodiments of the present application;

[0024] Figure 6 is a ring-shaped gradual change filter gradually changed along the circumferential direction of the filter, provided by the embodiments of the present application;

[0025] Figure 7 is a ring-shaped gradual change filter gradually changed in steps along the circumferential direction of the filter, provided by the embodiments of the present application;

[0026] Figure 8 is a strip-shaped gradual change filter with multiple gradual change filter strips with different attenuation curves, provided by the embodiments of the present application;

[0027] Figure 9a and 9b are ring-shaped gradual change filters with multiple gradual change filter rings with different attenuation curves, provided by the embodiments of the present application;

[0028] Figure 10 is another schematic diagram of a point light source inscription apodized fiber grating system provided by the embodiments of the present application;

[0029] Figure 11The point light source inscription apodized fiber grating method flow chart is provided by the embodiment of the present application. DETAILED DESCRIPTION

[0030] The technical solutions of the present application are further described in detail below with reference to the drawings and embodiments. SUMMARY

[0032] As described above, the present application provides a point light source inscription apodized fiber grating system and method, which effectively reduces the sidelobes on both sides of the resonance peak and improves the spectral characteristics of the fiber grating.

[0033] Exemplary System

[0034] Figure 1 The point light source inscription apodized fiber grating system schematic diagram is provided by the embodiment of the present application, as shown in Figure 1 The system 100 provided by the embodiment includes a laser 2, a scanning reflection device 3, an apodized inscription device 4, a laser focusing device 5 and a reference platform 1.

[0035] Specifically, the laser 2 is used to output inscription grating laser.

[0036] The laser is a pulsed laser, which can be an ultraviolet nanosecond pulsed laser or an infrared femtosecond pulsed laser. The ultraviolet nanosecond pulsed laser can produce high-precision inscription effect on the optical fiber by releasing a short and intense energy pulse, while the infrared femtosecond pulsed laser can realize more precise micro-machining through extremely short pulse width.

[0037] The power of the laser 2 is adjustable, which can flexibly adjust the laser output power according to the actual inscription requirement and the characteristics of the fiber material, so as to optimize the inscription effect. At the same time, the output laser spot can be a uniformly distributed point spot to ensure the uniformity and consistency of inscription, or a Gaussian distributed point spot to meet the specific grating structure requirement.

[0038] The scanning reflection device 3 is used to reflect the laser output by the laser 2 to the inscription area of the optical fiber 8 and scan the inscription area with the laser.

[0039] Specifically, the scanning reflection device 3 is also used to scan the inscription area laterally with the laser, and adjust the scanning range according to the inscription parameters, so that the laser scanning edge is smaller than the two end points of the inscription area. The scanning reflection device 3 can be composed of a plane mirror, a total reflection prism or a concave mirror, which can be moved or rotated to change the direction of the laser beam and realize lateral scanning.

[0040] The rotating mechanism includes:

[0041] Galvo mirror: Uses electromagnetic drive for fast and precise angle adjustment, commonly used in high-precision scanning.

[0042] Rotary mirror: Driven by motor, changes the reflection direction of the laser beam, suitable for scenarios requiring large-scale scanning.

[0043] The translation mechanism includes:

[0044] X-Y scanning platform, used to provide horizontal and vertical movement to cover the entire writing area.

[0045] This includes linear guide rails to ensure smooth movement of the platform in the X and Y directions, as well as step motors or servo motors to drive the platform to move along the X and Y axes, ensuring precise positioning.

[0046] The movement mode includes X-Y plane movement, so that the platform can move in the horizontal plane, allowing the laser beam to scan the entire writing area.

[0047] The motor works synchronously through the control system to achieve precise scanning paths.

[0048] The scanning reflection device 3 also includes a control system to coordinate and control the movement of each component, achieving precise scanning and writing.

[0049] The control system also includes:

[0050] Microcontroller or industrial control computer as the control core, processing input and output signals, executing control algorithms.

[0051] Driver for providing driving signals to step motors or servo motors.

[0052] Sensor for monitoring the position and status of each component, providing feedback for closed-loop control.

[0053] Control of scanning path, speed and laser intensity is achieved through programming.

[0054] Utilize sensor feedback signals to adjust the actions of the motor and mirror in real time to maintain precision.

[0055] The laser can be collimated and incident on the scanning reflection device 3, or in a divergent state incident on the scanning reflection device 3, and collimated through the scanning reflection device 3 to the concave mirror.

[0056] The inscribed region is a bare fiber section with coating removed and cleaned. The distance between the two end points of the inscribed region and the edge of the coating layer near the inscribed region is not less than 2mm, so as to prevent the laser from scanning to the coating area and ensure that the laser energy is concentrated in the inscribed region, thereby avoiding thermal damage to the fiber coating.

[0057] The apodization inscribing device 4 is configured to attenuate the power of the laser according to a predetermined attenuation curve.

[0058] According to the attenuation mode, the attenuation curve includes a curve of power attenuation according to a mathematical function meeting the requirements of the apodization function and / or a stepwise broken line of power attenuation according to a certain step length (the power change of each step is discrete rather than continuous).

[0059] The mathematical function includes Gaussian function, super-Gaussian function, Sinc function, Tanh function, Hamming function, Blackman function and Cauchy function.

[0060] According to the use, the attenuation curve includes an apodization curve and / or a compensation curve. The attenuation degree of the apodization curve is first decreasing and then increasing, as shown in Figure 2a The attenuation degree of the compensation curve is first increasing and then decreasing, as shown in Figure 2b .

[0061] Specifically, the apodization inscribing device 4 attenuates the power of the laser according to a predetermined apodization curve in the apodization process and / or attenuates the power of the laser according to a predetermined compensation curve in the compensation process so that the sidelobes on both sides of the reflection spectrum resonance peak become smaller and even disappear. The initial point of the laser incident to the graded filter in the apodization process is a position with large attenuation, and the initial point of the laser incident to the graded filter in the compensation process is a position with small attenuation.

[0062] Apodization controls the refractive index modulation of the end of the fiber grating by applying gradually weakened light intensity at the end of the fiber grating, effectively reducing the sidelobes on the long wave side. Compensation is used to correct and optimize the non-uniformity of the fiber grating during the inscribing process, and compensate for the power loss caused by the non-uniformity, so as to make the reflection spectrum on the short wave side cleaner, i.e. compensation adjusts the laser power, compensates for the power loss of different positions of the fiber grating during the inscribing process, and ensures that the refractive index modulation of the entire fiber grating is more uniform.

[0063] In summary, apodization mainly acts on reducing the sidelobes on the long wave side, making the resonance peak on both sides (especially the long wave side) cleaner. Compensation mainly acts on ensuring that the reflection spectrum on the short wave side is cleaner, and the optimization of the overall reflection spectrum is realized by compensating for the non-uniformity during the inscribing process.

[0064] Figures 3a-3cThese are schematic diagrams of the fiber grating transmission spectra, showing the results with no apodization compensation, apodization without compensation, and both apodization and compensation. Figure 3a As shown, the transmission spectrum of a fiber grating without apodization and compensation is not clean because the refractive index modulation of the fiber grating is uneven at the ends and center, and there are many side lobes on both sides of the resonance peak. Figure 3b As shown, the transmission spectrum of a fiber grating that has undergone apodization but not compensation is compared to... Figure 3a The side lobes are reduced, and the long-wavelength side is much cleaner, but some side lobes remain on the short-wavelength side. Apodization effectively suppresses the side lobes on the long-wavelength side, but because no compensation is performed, the inhomogeneities present during the writing process are not corrected, and side lobes still exist on the short-wavelength side. Figure 3c As shown, the transmission spectrum of the fiber grating after apodization and compensation treatment has the fewest sidelobes, the cleanest spectral shape, and a significant reduction in clutter on both sides of the resonance peak. Apodization suppresses sidelobes on the long-wavelength side, compensates for and corrects inhomogeneities during the writing process, ensures more uniform refractive index modulation across the entire fiber grating, and also cleans the short-wavelength side.

[0065] The toe-cutting writing device 4 includes strip-shaped (as shown in Figure 4) or annular gradient filters (as shown in Figure 5), including continuous gradient filters and stepped gradient filters that gradually change along the longitudinal direction of the strip-shaped filter or the circumferential direction of the annular filter. Figure 4a and 5a A strip-shaped gradient filter that changes continuously and gradually along the longitudinal direction of the filter; Figure 4b and 5b It is a strip-shaped gradient filter with a stepped gradient along the longitudinal direction of the filter. Figure 6 It is a ring-shaped gradient filter that changes continuously and gradually along the circumference of the filter. Figure 7 It is an annular gradient filter with a stepped gradient along the circumference of the filter.

[0066] The strip-shaped gradient filter has one or more gradient filter strips with different attenuation curves; the annular gradient filter has one or more gradient filter rings with different attenuation curves.

[0067] Preferably, such as Figure 8 As shown, the strip-shaped graded filter can have multiple graded filter strips with different attenuation curves. By switching between different graded filter strips, different power attenuation curves are achieved, reducing the frequency of filter replacement compared to a strip-shaped graded filter with only one graded filter strip. Similarly, as... Figure 9a and 9b As shown, the annular graded filter can have multiple graded filter rings with different attenuation curves. By rotating the annular graded filter, different graded filter rings can be selected, thereby achieving different power attenuation curves and reducing the number of filter replacements.

[0068] The gradient filter can be rotated and / or translated to adjust the position of laser incidence on the filter, and the laser power is attenuated according to the predetermined attenuation curve by adjusting the position of laser incidence on the filter.

[0069] The apodization writing device 4 can include, in addition to the gradient filter,

[0070] A filter selection module automatically selects an appropriate gradient filter strip or gradient filter ring according to different attenuation curve parameters.

[0071] A moving mechanism, including a second translation mechanism and / or a rotation mechanism. The second translation mechanism provides the movement ability of the gradient filter in the horizontal direction to cover the entire writing area or achieve different light intensity distribution. The second translation mechanism can include an X-Y scanning platform, a linear guide rail, and a stepper motor or a servo motor, which are synchronized in translation motion through a control system. The rotation mechanism allows the gradient filter to rotate around its central axis to change the position and angle of laser incidence, thereby affecting the change of light intensity distribution. The rotation mechanism usually includes a rotating table and a motor drive system. The rotation angle is controlled by the motor to achieve the required light intensity adjustment. The adjustment of the rotation angle can accurately control the apodization compensation effect of the grating and optimize the grating performance.

[0072] A second control system coordinates and controls the rotation and translation of the gradient filter to achieve the predetermined light intensity attenuation curve. The second control system can include microcontrollers, industrial computers, and drivers, etc. The rotation angle, translation distance, and laser power are set by the program to achieve the required light intensity distribution. The second control system can adjust the position and angle of the filter in real time to ensure that the attenuation mode of the laser meets the design requirements.

[0073] A feedback adjustment system monitors the light intensity distribution in real time through sensors and adjusts the position and angle of the gradient filter according to the feedback signal to maintain the writing accuracy.

[0074] As an optional embodiment, as shown in Figure 1 The apodization writing device 4 is placed independently on the reference platform 1. The gradient filter selected for apodization is as shown in Figure 4a and 4b The gradient filter selected for compensation is as shown in Figure 5a and 5b

[0075] The overall position of the apodization writing device 4 can be fixed or not. The fixed position is easier to install and calibrate, reduces the complexity of synchronous adjustment, and simplifies the operation, but in order to meet the switching between the apodization curve and the compensation curve, the gradient filter needs to be selected as Figure 8 ​The graduated filter shown has at least two graduated filter strips; the non-fixed position can be flexibly adjusted according to different writing parameters such as the length of the writing area and the attenuation curve, but the installation and calibration are more complicated, and the requirement for the number of graduated filter strips of the graduated filter is low.

[0076] As another alternative embodiment, such as Figure 10 As shown, compared to the previous embodiment, the apodization writing device 4 is integrated into the scanning reflection device 3, while the positions of other components of the system 100 remain unchanged. During laser scanning, the gradient filter of the integrated apodization writing device 4 translates along with the incident point of the scanning laser and rotates simultaneously. The apodization and compensation processes require only one gradient filter ring, as shown... Figure 6 Alternatively, by rotating the graduated filter, the switching between the apodized and compensated curves can be achieved. To accommodate a wider selection of attenuation curves, a graduated filter with multiple graduated filter rings can also be used.

[0077] In the apodization process, the initial point of the laser incident on the graded filter is a position with greater attenuation, such as the center point with the greatest attenuation; in the compensation process, the initial point of the laser incident on the graded filter is a position with less attenuation, such as the center point with the least attenuation.

[0078] Compared to the first embodiment, in this embodiment, the apodization writing device 4 is built into the scanning reflection device 3. First, it reduces the space occupied by the system and has a higher degree of integration. Second, the gradient filter of the apodization writing device 4 moves synchronously with the laser scanning to ensure precise matching between the laser incident point and the filter. Third, it combines the advantages and disadvantages of the fixed and non-fixed positions in the first embodiment, which not only has low requirements for the number of gradient filter rings of the gradient filter, but also is simple and easy to operate.

[0079] In addition, in the second embodiment, the gradient filter can be either an annular gradient filter or a strip gradient filter. The position of the laser incident on the filter can be adjusted by translating the strip gradient filter.

[0080] The system 100 also includes a mask 6, which is used to form a grating pattern within the fiber core of the writing area using the laser.

[0081] The mask 6 is also used to split the laser into at least two coherent beams so that a grating pattern is formed in the fiber core of the writing area.

[0082] The coherent light is ±1st order diffraction light; the grating pattern is a periodic refractive index modulation structure.

[0083] The scanning reflection device 3 is also used to adjust the irradiation position of the laser on the mask 6 according to the writing parameters to adapt to different writing requirements.

[0084] The grating area of the mask plate 6 is located at the normal incidence position of the laser. In the apodization process, the laser passes through the grating area of the mask plate; in the compensation process, the laser does not pass through the grating area of the mask plate, but directly hits the inscription area, and the refractive index of the entire inscription area is improved by uniform irradiation, thereby compensating and ensuring that the reflection spectrum on the short wave side is cleaner.

[0085] The compensation process can be performed after the apodization process or before the apodization process.

[0086] It should be noted that if the laser is a femtosecond pulse laser, the mask plate 6 can not be included in the system 100. The femtosecond pulse laser has the characteristics of high peak power and extremely short pulse duration, and can directly form a high-quality grating pattern in the fiber core without the need for light splitting or light intensity modulation through the mask plate 6.

[0087] The laser focusing device 5 is used to focus the laser on the inscription area to form a grating pattern in the core of the inscription area.

[0088] The laser focusing device 5 is also used to accurately focus the laser longitudinally near the core of the inscription area.

[0089] The defocus distance of the core (the position deviation range of the laser focus point relative to the fiber core) is 0-25 mm, so as to adjust the focusing accuracy of the laser under different inscription requirements.

[0090] The focal length of the laser focusing device 5 is 50-300 mm. Different focal lengths can adapt to different inscription depth and spot size requirements.

[0091] The laser focusing device 5 can include:

[0092] A focusing lens is used to accurately focus the laser beam on the inscription area of the optical fiber 8. An appropriate focal length and aperture diameter are selected to ensure that the focusing effect of the laser beam in the optical fiber 8 is optimal.

[0093] A focal length adjuster includes mechanical or electric devices for adjusting the focal length to adapt to different inscription requirements. The focusing position of the laser beam can be accurately adjusted to optimize the inscription effect of the fiber grating.

[0094] A defocus distance controller adjusts the defocus distance (0-25 mm) to ensure the best focusing of the laser in the optical fiber 8, avoiding excessive beam spreading or insufficient focusing, which affects the inscription quality. In addition, Figure 10The position of the laser focusing device 5 in the system can be set not only directly below the scanning reflection device 3, but also behind the scanning reflection device 3, and the laser focusing device 5 can be replaced by a round lens instead of a cylindrical lens. However, the adjustment range of the focal length of the laser focusing device 5 is limited.

[0095] The reference platform 1 is used to mount other components in the system 100, and the material includes but is not limited to aluminum, stainless steel, marble, and the like.

[0096] The system 100 further comprises a microscopic imaging device 9 for measuring the distance between the optical fiber 8 and the mask plate 6, reducing the writing non-uniformity and grating performance instability caused by distance errors.

[0097] The distance between the optical fiber 8 and the mask plate 6 is 50-200 microns.

[0098] The microscopic imaging device 9 can include:

[0099] A microscope is used to observe the distance between the optical fiber 8 and the mask plate 6 in real time, to ensure that the distance (50-200 microns) between them meets the writing requirements. The microscope can include a high-resolution imaging system to facilitate accurate measurement and adjustment.

[0100] An image processing system is used to monitor the state of the writing area in real time through an image acquisition and processing system. It can include a high-resolution camera, image analysis software, etc., to detect and optimize the writing quality of the fiber grating.

[0101] The system 100 further comprises a clamping device 7 for fixing the optical fiber 8.

[0102] Specifically, the clamping device 7 is used to fix the two side fibers of the optical fiber 8 so that the optical fiber 8 is in a suspended state, and to apply an axial tension to the optical fiber 8 according to the writing parameters, to keep the position and tension of the optical fiber 8 stable, and to avoid writing errors caused by changes in the tension of the optical fiber 8.

[0103] The clamping device 7 comprises an X / Y / Z three-dimensional adjuster for adjusting the position of the optical fiber 8 so that the writing area is on the scanning path of the laser, to improve the writing accuracy. The operation of the adjuster can be manual or automatic to adapt to different writing requirements.

[0104] Exemplary Method

[0105] Correspondingly, the embodiment of the present application also provides a point light source writing apodized fiber grating method. The point light source writing apodized fiber grating system comprises a laser 2, a scanning reflection device 3, an apodization writing device 4, a laser focusing device 5, and a reference platform 1. Figure 11The point light source inscription apodization fiber grating method flow chart is provided by the embodiment of the present application, and the embodiment comprises the following steps:

[0106] S101: the laser 2 outputs inscription laser;

[0107] S102: the scanning reflection device 3 reflects the laser output by the laser 2 to the inscription area of the optical fiber 8 and scans the inscription area by using the laser;

[0108] S103: the apodization inscription device 4 attenuates the power of the laser according to a predetermined attenuation curve;

[0109] S104: the laser focusing device 5 focuses the laser on the inscription area to form a grating pattern in the core of the inscription area;

[0110] S105: the reference platform 1 installs the laser 2, the scanning reflection device 3, the apodization inscription device 4 and the laser focusing device 5.

[0111] The attenuation curve comprises an apodization curve and / or a compensation curve;

[0112] The attenuation degree of the apodization curve is to decrease first and then increase;

[0113] The attenuation degree of the compensation curve is to increase first and then decrease.

[0114] The step that the apodization inscription device 4 attenuates the power of the laser according to a predetermined attenuation curve specifically comprises:

[0115] The apodization inscription device 4 attenuates the power of the laser according to a predetermined apodization curve in the apodization process and / or according to a predetermined compensation curve in the compensation process.

[0116] The apodization inscription device 4 comprises a strip or ring-shaped gradual change filter, comprising a continuous gradual change filter and a stepped gradual change filter which gradually changes along the longitudinal direction or the circumferential direction of the filter;

[0117] The gradual change filter can be rotated and / or translated to adjust the position of the laser incident to the filter;

[0118] The step that the apodization inscription device 4 attenuates the power of the laser according to a predetermined apodization curve in the apodization process and / or according to a predetermined compensation curve in the compensation process specifically comprises:

[0119] The laser power is attenuated according to a predetermined attenuation curve by adjusting the position of the laser incident to the filter, wherein the initial point of the laser incident to the graded filter is a position with large attenuation in the apodization process, and the initial point of the laser incident to the graded filter is a position with small attenuation in the compensation process.

[0120] The attenuation curve includes a curve of power attenuation according to a mathematical function meeting the requirement of the apodization function and / or a stepped broken line of power attenuation according to a certain step.

[0121] The mathematical function includes a Gaussian function, a hyper-Gaussian function, a Sinc function, a Tanh function, a Hamming function, a Blackman function and a Cauchy function.

[0122] The laser is a pulsed laser.

[0123] The pulsed laser is a nanosecond pulsed laser or a femtosecond pulsed laser.

[0124] The power of the laser 2 is adjustable.

[0125] The spot of the laser is a uniform or Gaussian distributed point spot.

[0126] The step of reflecting the laser output by the laser 2 to the writing area of the optical fiber 8 and scanning the writing area by the laser by the scanning reflection device 3 specifically includes:

[0127] The scanning reflection device 3 scans the writing area laterally by the laser.

[0128] The scanning reflection device 3 adjusts the scanning range according to the writing parameters, so that the laser scanning edge is smaller than the two endpoints of the writing area.

[0129] The step of focusing the laser by the laser focusing device 5 in the writing area to form a grating pattern in the core of the writing area specifically includes:

[0130] The laser focusing device 5 is also used for longitudinally focusing the laser near the core of the writing area.

[0131] The defocus distance of the core is 0-25 mm.

[0132] The focal length of the laser focusing device 5 is 50-300 mm.

[0133] The system further comprises a mask plate 6, and the method further comprises:

[0134] The mask plate 6 forms a grating pattern in the core of the writing area by the laser.

[0135] The scanning reflection device 3 adjusts the irradiation position of the laser on the mask plate 6 according to the inscription parameters.

[0136] The mask plate 6 forms the grating pattern in the core of the inscription area by the laser.

[0137] The mask plate 6 divides the laser into at least two coherent lights to form the grating pattern in the core of the inscription area.

[0138] The coherent light is ±1 order diffraction light.

[0139] The grating pattern is a periodic refractive index modulation structure.

[0140] The system further comprises a microscopic imaging device 9; the method further comprises:

[0141] The microscopic imaging device 9 measures the distance between the optical fiber 8 and the mask plate 6.

[0142] The distance between the optical fiber 8 and the mask plate 6 is 50-200 microns.

[0143] The grating area of the mask plate 6 is located at the normal incidence position of the laser;

[0144] The laser passes through the grating area of the mask plate in the apodization process.

[0145] The laser does not pass through the grating area of the mask plate in the compensation process.

[0146] The system further comprises a clamping device 7; the method further comprises:

[0147] The clamping device 7 fixes the optical fiber 8.

[0148] The step of fixing the optical fiber 8 by the clamping device 7 specifically comprises fixing the two side pigtails of the optical fiber 8 by the clamping device 7 so that the optical fiber 8 is in a suspended state.

[0149] The step of fixing the optical fiber 8 by the clamping device 7 specifically comprises applying an axial tension to the optical fiber 8 by the clamping device 7 according to the inscription parameters.

[0150] The clamping device 7 comprises an X / Y / Z three-dimensional adjuster; the step of applying an axial tension to the optical fiber 8 by the clamping device 7 according to the inscription parameters specifically comprises:

[0151] The X / Y / Z three-dimensional adjuster adjusts the position of the optical fiber 8 so that the inscription area is on the scanning path of the laser.

[0152] The inscription area is a section of bare fiber with removed coating layer and cleaned.

[0153] The distance between the two endpoints of the writing area and the edge of the coating layer near the writing area is not less than 2 mm.

[0154] The apodization writing device 4 is independently placed on the reference platform 1.

[0155] The apodization writing device 4 is built in the scanning reflection device 3;

[0156] The step of adjusting the position of the laser incident to the filter to achieve the laser power according to the predetermined attenuation curve is specifically:

[0157] During the laser scanning process, the gradient filter of the apodization writing device 4 translates as a whole with the scanning laser incident point, and simultaneously rotates the gradient filter.

[0158] The strip-shaped gradient filter has a plurality of gradient filter strips with different attenuation curves.

[0159] The ring-shaped gradient filter has a plurality of gradient filter rings with different attenuation curves.

[0160] As an optional embodiment, the laser 2 is fixed to the reference platform 1, and the clamping device 7 is fixed to the reference platform 1 at a position convenient for operation. The tail fibers on both sides of the optical fiber 8 are fixed to the clamping device 7, and the bare fiber with the coating layer removed is in a suspended state, kept horizontal, and a certain tension is applied to the optical fiber 8 in the axial direction according to the requirement of the writing wavelength.

[0161] The distance between the optical fiber 8 and the mask plate 6 is measured by the microscopic imaging device 9, and is generally controlled between 50-200 microns according to the writing process adjustment.

[0162] The height of the mask plate 6 is adjusted so that the mask plate grating area is away from the position of the laser 2 output light. The laser 2 is turned on and runs at low power, the scanning reflection device 3 is used to reflect the laser output by the laser 2 to the writing area of the optical fiber 8, and a horizontal scanning mode is used to make the laser scan along the writing area with the coating layer removed. At this time, whether the optical fiber 8 is on the laser scanning path can be judged according to the laser spot shape behind the optical fiber 8, and the position of the optical fiber 8 is further adjusted by adjusting the X / Y / Z three-dimensional adjuster, so that the writing area of the optical fiber 8 is exactly on the laser scanning path. The scanning range of the scanning reflection device 3 is adjusted according to the grating writing parameter requirement, and the laser scanning edge is smaller than the stripping point at both ends of the writing area.

[0163] The laser after the scanning reflection device 3 is focused on the fiber core of the writing area of the optical fiber 8 by the laser focusing device 5, and the defocus distance of the fiber core is generally 0-25 mm.

[0164] The height of the mask plate 6 is adjusted so that the mask plate grating area is in the position of normal incidence of the laser 2 output light, the laser 2 is turned on, and the scanning reflection device 3 is operated to start the inscription of the fiber grating. During the inscription of the fiber grating, the apodization inscription device 4 is started synchronously. During the apodization, the laser 2 output laser power is attenuated according to the apodization curve, and the attenuation degree is gradually reduced and then gradually increased, as shown in FIG. 3. Figure 2a After the apodization inscription is completed, the height of the mask plate 6 is adjusted so that the mask plate grating area is away from the position of the laser 2 output light. During the compensation, the laser 2 output laser power is attenuated according to the compensation curve, and the attenuation degree is gradually increased and then gradually reduced, as shown in FIG. 4. Figure 2b

[0165] It should be noted that although several devices, units, or modules of the point light source inscription apodization fiber grating system are mentioned in the foregoing detailed description, such division is merely exemplary and not mandatory. In fact, according to the embodiments of the present application, the features and functions of two or more modules described above can be embodied in one module. Conversely, the features and functions of one module described above can be further divided into modules for embodiment.

[0166] In addition, although the operations of the point light source inscription apodization fiber grating method of the present application are described in a specific order in the accompanying drawings, this does not require or imply that the operations must be performed in this specific order, or that all of the shown operations must be performed to achieve the desired result. Additionally or alternatively, certain steps can be omitted, a plurality of steps can be combined into one step, and / or one step can be divided into a plurality of steps.

[0167] Although the spirit and principles of the present application have been described with reference to several specific embodiments, it should be understood that the present application is not limited to the disclosed specific embodiments, and the division of aspects does not mean that the features in these aspects cannot be combined for benefit, but is merely for the convenience of expression. The present application is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the appended claims.

[0168] The present application provides:

[0169] 1. A point light source inscription apodization fiber grating system, characterized in that the system comprises:

[0170] a laser for outputting inscription laser;

[0171] a scanning reflection device for reflecting the laser output by the laser to an inscription area of an optical fiber and scanning the inscription area with the laser;

[0172] an apodization inscription device for attenuating the power of the laser according to a predetermined attenuation curve.​

[0173] a laser focusing device for focusing the laser on the inscription region to form a grating pattern in the core of the inscription region;

[0174] a reference platform for mounting the laser, the scanning reflection device, the apodization inscription device and the laser focusing device.

[0175] 2. The system according to item 1, wherein the attenuation curve comprises an apodization curve and / or a compensation curve.

[0176] The apodization curve has a decreasing-then-increasing attenuation degree.

[0177] The compensation curve has an increasing-then-decreasing attenuation degree.

[0178] 3. The system according to item 2, wherein the apodization inscription device is further configured to attenuate the power of the laser according to a predetermined apodization curve during the apodization process, and / or to attenuate the power of the laser according to a predetermined compensation curve during the compensation process.

[0179] 4. The system according to item 3, wherein the apodization inscription device comprises a strip or ring-shaped gradual change filter, including a continuous gradual change filter and a stepped gradual change filter gradually changing along the longitudinal direction or the circumferential direction of the filter.

[0180] The gradual change filter can be rotated and / or translated to adjust the position of the laser incident on the filter, so as to achieve the laser power attenuated according to the predetermined attenuation curve.

[0181] In the apodization process, the initial point of the laser incident on the gradual change filter is a position with a large attenuation, and in the compensation process, the initial point of the laser incident on the gradual change filter is a position with a small attenuation.

[0182] 5. The system according to any one of items 1-4, wherein the attenuation curve comprises a curve for power attenuation according to a mathematical function meeting the requirements of an apodization function and / or a stepped broken line for power attenuation according to a certain step size.

[0183] 6. The system according to item 5, wherein the mathematical function comprises a Gaussian function, a super-Gaussian function, a Sinc function, a Tanh function, a Hamming function, a Blackman function and a Cauchy function.

[0184] 7. The system according to any one of items 1-4, wherein the laser is a pulsed laser.

[0185] The pulsed laser is a nanosecond pulsed laser or a femtosecond pulsed laser.

[0186] 8. The system according to any one of items 1-4, wherein the power of the laser is adjustable.

[0187] The spot of the laser is a uniform or Gaussian distributed point spot.

[0188] 9. The system according to any one of items 1-4, wherein the scanning reflection device is further configured to laterally scan the inscription region with the laser.

[0189] The scanning reflection device is further configured to adjust the scanning range according to inscription parameters, so that the laser scanning edge is smaller than the two end points of the inscription region.

[0190] 10. The system according to any one of items 1-4, wherein the laser focusing device is further configured to longitudinally focus the laser near the core of the inscription region.

[0191] 11. The system according to any one of items 1-4, wherein the defocus distance of the core is 0-25 mm.

[0192] 12. The system according to any one of items 1-4, wherein the focal length of the laser focusing device is 50-300 mm.

[0193] 13. The system according to any one of items 1-4, wherein the system further comprises a mask plate configured to form a grating pattern in the core of the inscription region with the laser.

[0194] The scanning reflection device is further configured to adjust the irradiation position of the laser on the mask plate according to inscription parameters.

[0195] 14. The system according to item 13, wherein the mask plate is further configured to divide the laser into at least two coherent lights to form a grating pattern in the core of the inscription region.

[0196] 15. The system according to item 14, wherein the coherent light is ±1 order diffracted light.

[0197] The grating pattern is a periodic refractive index modulation structure.

[0198] 16. The system according to item 13, wherein the system further comprises a microscopic imaging device configured to measure the distance between the optical fiber and the mask plate.

[0199] 17. The system of item 13, wherein the distance between the optical fiber and the mask is 50-200 microns.

[0200] 18. The system of item 13, wherein the grating area of the mask is located at the normal incidence position of the laser;

[0201] the laser passes through the grating area of the mask during the apodization process;

[0202] the laser does not pass through the grating area of the mask during the compensation process.

[0203] 19. The system of any one of items 1-4, wherein the system further comprises a clamping device for fixing the optical fiber.

[0204] 20. The system of item 19, wherein the clamping device is further used to fix the two side pigtails of the optical fiber so that the optical fiber is in a suspended state.

[0205] 21. The system of item 19, wherein the clamping device is further used to apply an axial tension to the optical fiber according to the inscription parameters.

[0206] 22. The system of item 21, wherein the clamping device comprises an X / Y / Z three-dimensional adjuster for adjusting the position of the optical fiber so that the inscription area is on the scanning path of the laser.

[0207] 23. The system of any one of items 1-4, wherein the inscription area is a section of bare fiber with removed coating and cleaned;

[0208] the distance between the two end points of the inscription area and the edge of the coating layer adjacent to the inscription area is not less than 2 mm.

[0209] 24. The system of any one of items 1-4, wherein the apodization inscription device is independently placed on the reference platform.

[0210] 25. The system of item 4, wherein the apodization inscription device is built into the scanning reflection device;

[0211] during the laser scanning process, the gradient filter of the apodization inscription device translates as a whole with the incident point of the scanning laser, and simultaneously rotates the gradient filter.

[0212] 26. The system of item 4, wherein the strip-shaped gradient filter has one or more gradient filter strips with different attenuation curves.

[0213] The annular gradual filter has one or more gradual filter rings with different attenuation curves.

[0214] 27. A method for point light source inscription apodized fiber grating, characterized in that a point light source inscription apodized fiber grating system comprises a laser, a scanning reflection device, an apodization inscription device, a laser focusing device and a reference platform; the method comprises:

[0215] the laser outputs inscription laser;

[0216] the scanning reflection device reflects the laser output by the laser to an inscription area of the fiber and scans the inscription area with the laser;

[0217] the apodization inscription device attenuates the power of the laser according to a predetermined attenuation curve;

[0218] the laser focusing device focuses the laser on the inscription area to form a grating pattern in the core of the inscription area;

[0219] the reference platform mounts the laser, the scanning reflection device, the apodization inscription device and the laser focusing device.

[0220] 28. The method according to item 27, characterized in that the attenuation curve comprises an apodization curve and / or a compensation curve;

[0221] the apodization curve has an attenuation degree of first decreasing and then increasing;

[0222] the compensation curve has an attenuation degree of first increasing and then decreasing.

[0223] 29. The method according to item 28, characterized in that the step of the apodization inscription device attenuating the power of the laser according to a predetermined attenuation curve specifically comprises:

[0224] the apodization inscription device attenuates the power of the laser according to a predetermined apodization curve during the apodization process and / or according to a predetermined compensation curve during the compensation process.

[0225] 30. The method according to item 29, characterized in that the apodization inscription device comprises a strip or annular gradual filter, including a continuous gradual filter and a stepped gradual filter gradually changing along the longitudinal direction or the circumferential direction of the filter;

[0226] the gradual filter can be rotated and / or translated to adjust the position of the laser incident to the filter;

[0227] The step of the apodizing and / or compensating device attenuating the power of the laser according to the predetermined apodization curve and / or compensation curve comprises:

[0228] The laser power is attenuated according to the predetermined attenuation curve by adjusting the position of the laser incident to the filter, and the initial point of the laser incident to the gradient filter is a position of larger attenuation in the apodization process and a position of smaller attenuation in the compensation process.

[0229] 31. The method of any one of claims 27-30, wherein the attenuation curve comprises a curve of power attenuation according to a mathematical function meeting the requirement of apodization function and / or a stepped broken line of power attenuation according to a certain step length.

[0230] 32. The method of claim 31, wherein the mathematical function comprises a Gaussian function, a super-Gaussian function, a Sinc function, a Tanh function, a Hamming function, a Blackman function and a Cauchy function.

[0231] 33. The method of any one of claims 27-30, wherein the laser is a pulsed laser.

[0232] The pulsed laser is a nanosecond pulsed laser or a femtosecond pulsed laser.

[0233] 34. The method of any one of claims 27-30, wherein the power of the laser is adjustable.

[0234] The spot of the laser is a uniform or Gaussian distributed point spot.

[0235] 35. The method of any one of claims 27-30, wherein the step of the scanning reflection device reflecting the laser output by the laser to a writing area of an optical fiber and scanning the writing area with the laser comprises:

[0236] The scanning reflection device scans the writing area with the laser in a transverse direction.

[0237] The scanning reflection device adjusts the scanning range according to the writing parameters, so that the scanning edge of the laser is smaller than the two end points of the writing area.

[0238] 36. The method of any one of claims 27-30, wherein the step of the laser focusing device focusing the laser on the writing area to form a grating pattern in the core of the writing area comprises:

[0239] The laser focusing device is also used to focus the laser longitudinally near the core of the inscription region.

[0240] 37. The method of any one of claims 27-30, wherein the core has a defocus distance of 0-25 mm.

[0241] 38. The method of any one of claims 1-4, wherein the laser focusing device has a focal length of 50-300 mm.

[0242] 39. The method of any one of claims 27-30, wherein the system further comprises a mask plate; and the method further comprises:

[0243] the mask plate forms a grating pattern of the laser within the core of the inscription region;

[0244] the scanning reflecting device adjusts the irradiation position of the laser on the mask plate according to inscription parameters.

[0245] 40. The method of claim 39, wherein the mask plate forms a grating pattern of the laser within the core of the inscription region by:

[0246] the mask plate divides the laser into at least two coherent lights to form a grating pattern within the core of the inscription region.

[0247] 41. The method of claim 40, wherein the coherent light is ±1 order diffraction light.

[0248] the grating pattern is a periodic refractive index modulation structure.

[0249] 42. The method of claim 39, wherein the system further comprises a microscopic imaging device; and the method further comprises:

[0250] the microscopic imaging device measures the distance between the optical fiber and the mask plate.

[0251] 43. The method of claim 39, wherein the distance between the optical fiber and the mask plate is 50-200 microns.

[0252] 44. The method of claim 39, wherein the grating region of the mask plate is located at the normal incidence position of the laser.

[0253] the laser passes through the grating region of the mask plate during the apodization process.

[0254] the laser does not pass through the grating region of the mask plate during the compensation process.

[0255] 45. The method of any of claims 27-30, wherein the system further comprises a clamping device; and the method further comprises:

[0256] The clamping device fixes the optical fiber.

[0257] 46. The method of claim 45, wherein the step of fixing the optical fiber by the clamping device comprises fixing both ends of the optical fiber by the clamping device so that the optical fiber is in a suspended state.

[0258] 47. The method of claim 45, wherein the step of fixing the optical fiber by the clamping device comprises applying an axial tension to the optical fiber according to the inscription parameters.

[0259] 48. The method of claim 47, wherein the clamping device comprises an X / Y / Z three- dimensional adjuster; and the step of applying an axial tension to the optical fiber by the clamping device according to the inscription parameters comprises:

[0260] The X / Y / Z three-dimensional adjuster adjusts the position of the optical fiber so that the inscription region is on the scanning path of the laser.

[0261] 49. The method of any of claims 27-30, wherein the inscription region is a section of bare fiber with removed coating and cleaned.

[0262] The distance between the two end points of the inscription region and the edge of the coating layer adjacent to the inscription region is not less than 2 mm.

[0263] 50. The method of any of claims 27-30, wherein the apodization inscription device is independently placed on the reference platform.

[0264] 51. The method of claim 30, wherein the apodization inscription device is built in the scanning reflection device.

[0265] The step of adjusting the position of the laser incident to the filter to achieve the laser power according to the predetermined attenuation curve comprises:

[0266] During the laser scanning, the gradient filter of the apodization inscription device translates as a whole with the scanning laser incident point, and simultaneously rotates the gradient filter.

[0267] 52. The method of claim 30, wherein the strip-shaped gradient filter has one or more gradient filter strips with different attenuation curves.

[0268] The ring-shaped gradient filter has one or more gradient filter rings with different attenuation curves.

Claims

1. A point light source system for writing apodized fiber optic gratings, characterized in that, The system includes: A point source laser, which is used to output a point-shaped laser for writing gratings; A scanning reflection device is used to reflect the laser output from the laser onto the marking area of ​​the optical fiber and to scan the marking area point by point using the laser. A toe-cutting writing apparatus includes a rotatable gradient filter having a predetermined attenuation curve for attenuating the power of the laser according to a first attenuation curve during the toe-cutting process and for power compensation according to a second attenuation curve during the compensation process. A laser focusing device for focusing the laser on the writing area to form a grating pattern within the fiber core of the writing area; A reference platform for mounting the laser, the scanning reflection device, the aponeurotic marking device, and the laser focusing device; Wherein, the first attenuation curve is a proximal curve, and the second attenuation curve is a compensation curve; The attenuation degree of the apophysis curve is first decrease and then increase, while the attenuation degree of the compensation curve is first increase and then decrease. The gradient filter is an annular gradient filter, including a continuous gradient filter or a stepped gradient filter that gradually changes along the circumference of the filter. The gradient filter can be rotated to adjust the position of the laser incident on the filter, and the laser power is attenuated according to a predetermined attenuation curve by adjusting the position of the laser incident on the filter. The same annular graded filter is used for both apodization and compensation, wherein during apodization, the initial point of the laser incident on the annular graded filter is a position with greater attenuation, and during compensation, the initial point of the laser incident on the annular graded filter is a position with less attenuation.

2. The system according to claim 1, characterized in that, The apotomizing writing device is also used to attenuate the power of the laser according to a predetermined apotomizing curve during the apotomizing process, and / or attenuate the power of the laser according to a predetermined compensation curve during the compensation process.

3. The system according to claim 1 or 2, characterized in that, The attenuation curve includes a curve that attenuates power according to a mathematical function that satisfies the requirements of the apodization function and / or a stepped broken line that attenuates power according to a certain step size.

4. The system according to claim 3, characterized in that, The mathematical functions include Gaussian function, super-Gaussian function, Sinc function, Tanh function, Hamming function, Blackman function, and Cauchy function.

5. The system according to claim 1, characterized in that, The laser is a pulsed laser; the pulsed laser is a nanosecond pulsed laser or a femtosecond pulsed laser.

6. The system according to claim 1, characterized in that, The power of the laser is adjustable; the laser spot is a uniform or Gaussian distributed dot-shaped spot.

7. The system according to claim 1, characterized in that, The scanning reflection device is also used to perform a lateral scan of the inscribed area using the laser; the scanning reflection device is also used to adjust the scanning range according to the inscription parameters so that the laser scanning edge is smaller than the two ends of the inscribed area.

8. The system according to claim 1, characterized in that, The laser focusing device is also used to longitudinally focus the laser near the fiber core of the inscribed area.

9. The system according to claim 1, characterized in that, The defocus distance of the fiber core is 0~25 mm.

10. The system according to claim 1, characterized in that, The focal length of the laser focusing device is 50~300 mm.

11. The system according to claim 1, characterized in that, The system also includes a photomask for forming a grating pattern within the fiber core of the writing area using the laser; the scanning reflection device is also used to adjust the irradiation position of the laser on the photomask according to the writing parameters.

12. The system according to claim 11, characterized in that, The mask is also used to split the laser into at least two coherent beams so that a grating pattern is formed within the fiber core of the writing area.

13. The system according to claim 12, characterized in that, The coherent light is ±1 order diffraction light; the grating pattern is a periodic refractive index modulation structure.

14. The system according to claim 11, characterized in that, The system also includes a microscopic imaging device for measuring the distance between the optical fiber and the mask.

15. The system according to claim 14, characterized in that, The distance between the optical fiber and the mask is 50-200 micrometers.

16. The system according to claim 11, characterized in that, The grid area of ​​the photomask is located at the normal incident position of the laser; during the toe cutting process, the laser passes through the grid area of ​​the photomask; during the compensation process, the laser does not pass through the grid area of ​​the photomask.

17. The system according to claim 1, characterized in that, The system also includes a clamping device for securing the optical fiber.

18. The system according to claim 17, characterized in that, The clamping device is also used to fix the pigtails on both sides of the optical fiber so that the optical fiber is in a suspended state.

19. The system according to claim 17, characterized in that, The clamping device is also used to apply axial tension to the optical fiber according to the inscription parameters.

20. The system according to claim 19, characterized in that, The clamping device includes an X / Y / Z three-dimensional adjuster, which is used to adjust the position of the optical fiber so that the writing area is on the scanning path of the laser.

21. The system according to claim 1, characterized in that, The writing area is a section of bare fiber with the coating removed and cleaned; the distance between the two ends of the writing area and the edge of the coating layer adjacent to the writing area is not less than 2 mm.

22. The system according to claim 1, characterized in that, The toe-cutting and writing device is placed independently on the reference platform.

23. The system according to claim 1, characterized in that, The toe-cutting and writing device is built into the scanning and reflecting device; during the laser scanning process, the gradient filter of the toe-cutting and writing device moves along with the incident point of the scanning laser and rotates at the same time.

24. The system according to claim 1, characterized in that, The annular gradient filter has one or more gradient filter rings with different attenuation curves.

25. A method for writing apodized fiber gratings using a point light source, characterized in that, A point-source laser writing apodized fiber grating system is provided, comprising a point-source laser, a scanning reflection device, an apodized writing device, a laser focusing device, and a reference platform; the method includes: The point source laser outputs a point-shaped laser for writing gratings; The scanning reflection device reflects the laser output from the laser onto the writing area of ​​the optical fiber, and uses the laser to scan the writing area point by point. The apodization writing device includes a rotatable gradient filter with a predetermined attenuation curve, which attenuates the power of the laser according to a first attenuation curve during the apodization process and performs power compensation according to a second attenuation curve during the compensation process. The laser focusing device focuses the laser on the writing area to form a grating pattern within the fiber core of the writing area; The reference platform is used to mount the laser, the scanning reflection device, the toe-cutting and marking device, and the laser focusing device; Wherein, the first attenuation curve is a proximal curve, and the second attenuation curve is a compensation curve; The attenuation degree of the apophysis curve is first decrease and then increase, while the attenuation degree of the compensation curve is first increase and then decrease. The gradient filter is an annular gradient filter, including a continuous gradient filter or a stepped gradient filter that gradually changes along the circumference of the filter. The gradient filter can be rotated to adjust the position of the laser incident on the filter, and the laser power is attenuated according to a predetermined attenuation curve by adjusting the position of the laser incident on the filter. The same annular graded filter is used for both apodization and compensation. During apodization, the initial point where the laser is incident on the annular graded filter is a position with greater attenuation, while during compensation, the initial point where the laser is incident on the annular graded filter is a position with less attenuation.

26. The method according to claim 25, characterized in that, The apotomizing writing device attenuates the power of the laser according to a predetermined apotomizing curve during the apotomizing process, and / or attenuates the power of the laser according to a predetermined compensation curve during the compensation process.

27. The method according to claim 25 or 26, characterized in that, The attenuation curve includes a curve that attenuates power according to a mathematical function that satisfies the requirements of the apodization function and / or a stepped broken line that attenuates power according to a certain step size.

28. The method according to claim 27, characterized in that, The mathematical functions include Gaussian function, super-Gaussian function, Sinc function, Tanh function, Hamming function, Blackman function, and Cauchy function.

29. The method according to claim 25, characterized in that, The laser is a pulsed laser; the pulsed laser is a nanosecond pulsed laser or a femtosecond pulsed laser.

30. The method according to claim 25, characterized in that, The power of the laser is adjustable; the laser spot is a uniform or Gaussian distributed dot-shaped spot.

31. The method according to claim 25, characterized in that, The scanning reflection device uses the laser to perform a horizontal scan of the inscribed area; and adjusts the scanning range according to the inscription parameters so that the laser scanning edge is smaller than the two ends of the inscribed area.

32. The method according to claim 25, characterized in that, The laser focusing device focuses the laser longitudinally near the core of the inscribed area.

33. The method according to claim 25, characterized in that, The defocus distance of the fiber core is 0~25 mm.

34. The method according to claim 25, characterized in that, The focal length of the laser focusing device is 50~300 mm.

35. The method according to claim 25, characterized in that, The system further includes a photomask; the method further includes: the photomask forming a grating pattern within the fiber core of the writing area using the laser; and the scanning reflection device adjusting the irradiation position of the laser on the photomask according to the writing parameters.

36. The method according to claim 35, characterized in that, The specific steps of the photomask forming a grating pattern within the fiber core of the writing area using the laser are as follows: The photomask splits the laser into at least two coherent beams to form a grating pattern within the fiber core of the writing area.

37. The method according to claim 36, characterized in that, The coherent light is ±1 order diffraction light; the grating pattern is a periodic refractive index modulation structure.

38. The method according to claim 35, characterized in that, The system further includes a microscopic imaging device; the method further includes: the microscopic imaging device is used to measure the distance between the optical fiber and the mask.

39. The method according to claim 38, characterized in that, The distance between the optical fiber and the mask is 50-200 micrometers.

40. The method according to claim 35, characterized in that, The grid area of ​​the photomask is located at the normal incident position of the laser; during the toe cutting process, the laser passes through the grid area of ​​the photomask; during the compensation process, the laser does not pass through the grid area of ​​the photomask.

41. The method according to claim 25, characterized in that, The system further includes a clamping device; the method further includes: the clamping device is used to fix the optical fiber.

42. The method according to claim 41, characterized in that, The clamping device is used to fix the two pigtails on both sides of the optical fiber so that the optical fiber is in a suspended state.

43. The method according to claim 41, characterized in that, The clamping device is also used to apply axial tension to the optical fiber according to the inscription parameters.

44. The method according to claim 43, characterized in that, The clamping device includes an X / Y / Z three-dimensional adjuster; the X / Y / Z three-dimensional adjuster is used to adjust the position of the optical fiber so that the writing area is on the scanning path of the laser.

45. The method according to claim 25, characterized in that, The writing area is a section of bare fiber with the coating removed and cleaned; the distance between the two ends of the writing area and the edge of the coating layer adjacent to the writing area is not less than 2 mm.

46. ​​The method according to claim 25, characterized in that, The toe-cutting and writing device is placed independently on the reference platform.

47. The method according to claim 25, characterized in that, The toe-cutting and writing device is built into the scanning and reflecting device; during the laser scanning process, the gradient filter of the toe-cutting and writing device moves along with the incident point of the scanning laser and rotates at the same time.

48. The method according to claim 25, characterized in that, The annular gradient filter has one or more gradient filter rings with different attenuation curves.

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