Method for manufacturing chirped fiber bragg grating based on asymmetric apodization

Abstract

The invention provides a chirped fiber bragg grating manufacturing method based on asymmetric apodization, which is applied to the technical field of fiber bragg grating preparation, and the method comprises the steps: determining a target asymmetric envelope function corresponding to a target chirped fiber bragg grating based on the parameter requirements of the target chirped fiber bragg grating; adjusting the pulse number of laser output by the femtosecond laser based on the target asymmetric envelope function; laser is controlled to irradiate a target area in the optical fiber, a target chirped fiber grating is formed, and the pulse number of the laser changes according to a target asymmetric envelope function and is gradually reduced from the center of the grating to the two ends. According to the method, the femtosecond laser pulse number is adjusted based on the asymmetric envelope function, so that the distribution gradient of refractive index modulation is finely adjusted, better reflection spectrum and time delay characteristics are obtained, the high-precision requirements for laser energy adjustment and displacement platform movement are reduced, and the apodization machining precision of the chirped fiber grating is effectively improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of fiber grating preparation, and more specifically, to a method for preparing a chirped fiber grating based on asymmetric apodization. Background Art

[0002] Chirped fiber grating is a fiber grating with non-uniform period characteristics, whose period changes slowly along the fiber axis. It is widely used in optical communication and sensing fields because it can achieve dispersion compensation and signal filtering. However, due to the Fabry-Perot effect caused by the sudden change of refractive index at both ends of the grating, the reflection spectrum and delay curve of the chirped fiber grating have significant oscillation or jitter within the bandwidth, which greatly restricts the performance and application of fiber grating devices.

[0003] In order to improve the performance of chirped fiber gratings, apodization technology is widely used. The apodization method can effectively suppress side lobes and delay jitter. Traditional symmetrical apodization methods usually symmetrically reduce the refractive index modulation depth at both ends of the grating to achieve apodization, mainly including apodization phase mask plate method, apodization plate method and scanning writing method, all of which rely on phase mask plates. In addition, symmetrical apodization causes the reflection wavelength at both ends of the grating to change gradually, resulting in a "self-chirp" effect, which in turn causes the reflection spectrum of the grating after apodization to have strong side lobes in the short wavelength direction and causes non-flat changes in the delay characteristics. Although it can improve the grating characteristics to a certain extent, it often has shortcomings in the smoothness and flexibility of the refractive index modulation depth.

[0004] For chirped fiber gratings, the amplitude of apodization in the long wavelength direction and the amplitude of apodization in the short wavelength direction have different effects on the reflection spectrum. Therefore, an asymmetric apodization method is proposed to further optimize the performance of the grating by asymmetrically adjusting the refractive index modulation depth at both ends of the grating. Studies have shown that increasing the apodization amplitude at the long wavelength end and reducing the apodization amplitude at the short wavelength end will obtain better reflection spectrum and delay characteristics. Existing asymmetric apodization methods mainly include asymmetric amplitude apodization plate method and multiple exposure apodization method. Both methods also rely on phase masks. The core parameters of the grating, such as the central wavelength, grating length and chirp coefficient, are all limited by the mask plate, and the flexibility is very poor.

[0005] How to improve the flexibility and accuracy of the fractionally symmetrical apodization method is a problem that needs to be solved urgently. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] The present disclosure provides a method for manufacturing a chirped fiber grating based on asymmetric apodization, which is used to at least partially solve one of the above technical problems.

[0008] (II) Technical solution

[0009] The present invention provides a method for manufacturing a chirped fiber grating based on asymmetric apodization, characterized in that the method comprises: determining a target asymmetric envelope function corresponding to the chirped fiber grating based on parameter requirements of the target chirped fiber grating; adjusting the number of pulses of the laser output by the femtosecond laser based on the asymmetric envelope function; controlling the laser to irradiate the target area in the optical fiber to form the target chirped fiber grating, wherein the number of laser pulses changes according to the target asymmetric envelope function and gradually decreases from the center of the grating to both ends.

[0010] According to an embodiment of the present disclosure, the target asymmetric envelope function is expressed as any one of a combination of symmetric envelope functions or a piecewise function, and the symmetric envelope function includes a Gaussian function, a Hamming function, a Blackman function, a raised cosine function, a Tanh function, a Cauchy function, and a sinc function.

[0011] According to an embodiment of the present disclosure, the optical fiber is placed on a translation stage, and the laser output positions are distributed according to the periodic intervals of the chirped grating.

[0012] According to an embodiment of the present disclosure, the energy of a single laser pulse is kept constant during the apodization process.

[0013] According to an embodiment of the present disclosure, the manufacturing method adopts a femtosecond laser direct writing method, and the femtosecond laser direct writing method includes any one of a point-by-point method, a line-by-line method, and a plane-by-plane method.

[0014] According to the embodiments of the present disclosure, the refractive index modulation depth of the central region of the target fiber grating is the largest, the refractive index modulation amplitude on both sides is smaller, and the toe-cutting ratio in the long wavelength direction is greater than that in the short wavelength direction.

[0015] According to an embodiment of the present disclosure, laser irradiation is controlled to target an area in an optical fiber to form a target chirped fiber grating, including: reflecting the laser output by a femtosecond laser to a beam expander through a high-reflection mirror to obtain an expanded laser beam; adjusting the parameters of the expanded laser beam to obtain a first laser; adjusting the diameter and shape of the first laser beam, and focusing the adjusted first laser to a target area in the optical fiber to adjust the refractive index of the optical fiber.

[0016] According to an embodiment of the present disclosure, the parameters of the expanded laser beam are adjusted to obtain a first laser, including: adjusting the laser power based on an electric laser power attenuator; and regulating the polarization state of the laser based on a polarizer group to obtain the first laser.

[0017] According to the embodiments of the present disclosure, during the production process of the chirped fiber grating, the grating structure and the reflection spectrum are monitored in real time by CCD and a spectrometer, and the production parameters of the fiber grating are adjusted based on the monitoring results to meet the parameter requirements of the target chirped fiber grating.

[0018] According to an embodiment of the present disclosure, the asymmetric envelope function can be expressed as:

[0019]

[0020] Among them, A is the modulation amplitude, which determines the maximum value of the modulation envelope; z0 is the position of the modulation point in the center of the grating, which is the dividing point between the left and right envelopes; σ left is the standard deviation on the left, controlling the width and slope of the left side of the grating, σ right Right standard deviation, controls the width and slope of the right side of the raster.

[0021] (III) Beneficial effects

[0022] The chirped fiber grating manufacturing method based on asymmetric apodization provided by the present disclosure has at least the following beneficial effects:

[0023] The femtosecond laser direct writing technology and asymmetric apodization design are used to precisely control the pulse number according to the envelope change, without the need for a phase mask, and support the design and preparation of high-quality chirped apodized fiber grating structures with different parameters, with better flexibility and consistency. The asymmetric apodization and precise femtosecond laser pulse number control method are introduced to precisely control the femtosecond laser pulse number according to the asymmetric envelope change, achieve subtle modulation of the refractive index modulation depth, effectively suppress the side lobes and delay oscillation of the spectrum, and significantly improve the dispersion characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0025] Figure 1 The flowchart of the method for manufacturing a chirped fiber grating based on asymmetric apodization according to an embodiment of the present disclosure is schematically shown;

[0026] Figure 2 The optical path diagram of the chirped fiber grating fabricated based on asymmetric apodization in the embodiment of the present disclosure is schematically shown;

[0027] Figure 3 The schematic diagram of the refractive index modulation depth of the asymmetric apodized chirped fiber grating according to the embodiment of the present disclosure is shown schematically;

[0028] Figure 4 The structural diagram of the chirped apodized fiber grating structure based on the femtosecond laser point-by-point method in an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

[0030] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0031] In the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0032] In the description of the present disclosure, it is necessary to understand that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the subsystem or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present disclosure.

[0033] Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure. The shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual size, proportion, and actual positional relationship. In addition, in the claims, any reference symbol between brackets shall not be construed as a limitation to the claims.

[0034] Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature. In the description of the present disclosure, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0036] The disclosed embodiment provides a method for manufacturing a chirped fiber grating based on asymmetric apodization, comprising: determining a target asymmetric envelope function corresponding to the chirped fiber grating based on parameter requirements of the target chirped fiber grating; adjusting the number of pulses of a laser output by a femtosecond laser based on the asymmetric envelope function; and controlling the laser to irradiate a target area in the optical fiber to form a target chirped fiber grating, wherein the number of laser pulses varies according to the target asymmetric envelope function and gradually decreases from the center of the grating to both ends.

[0037] Figure 1 The flowchart of the method for manufacturing a chirped fiber grating based on asymmetric apodization according to an embodiment of the present disclosure is schematically shown.

[0038] like Figure 1 As shown, the method for manufacturing a chirped fiber grating based on asymmetric apodization in this embodiment includes operations S110 to S130.

[0039] In operation S110, a target asymmetric envelope function corresponding to the chirped fiber grating is determined based on parameter requirements of the target chirped fiber grating.

[0040] In operation S120 , the number of pulses of the laser output by the femtosecond laser is adjusted based on the asymmetric envelope function.

[0041] In operation S130, the laser is controlled to irradiate a target area in the optical fiber to form a target chirped fiber grating, wherein the number of laser pulses varies according to a target asymmetric envelope function and gradually decreases from the center of the grating to both ends.

[0042] In some embodiments, the parameter requirements of the chirped fiber grating may include, for example, bandwidth, reflectivity, dispersion, group delay, and side mode suppression ratio. When manufacturing a chirped fiber grating with different parameter requirements, different envelope functions can be used according to the parameter requirements of the chirped fiber grating, and the number of pulses of the laser output by the femtosecond laser can be adjusted based on the envelope function, thereby achieving subtle modulation of the refractive index modulation depth, effectively suppressing the side lobes and delay oscillations of the spectrum, significantly improving the dispersion characteristics, and improving the flexibility and accuracy of the chirped fiber grating manufacturing.

[0043] Figure 2 The optical path diagram of the chirped fiber grating fabricated based on asymmetric apodization according to the embodiment of the present disclosure is schematically shown.

[0044] The following combination Figure 1 , Figure 2 The chirped fiber grating manufacturing method based on asymmetric apodization disclosed in the present invention is introduced in detail.

[0045] like Figure 2 As shown, the laser emitted by the femtosecond laser F1 is reflected by the high-reflection mirror F2 to the beam expander F3 to obtain an expanded laser beam. The expanded laser beam is attenuated by the electric laser power attenuator F4, and then transmitted to the polarizer group F6 and F7 through the high-reflection mirror F5. The laser polarization state is regulated based on the polarizer group F6 and F7. The regulated laser beam is reflected again by the high-reflection mirror F8, and after being limited by the aperture F9 and focused by the objective lens F10, it is irradiated to the specified area (i.e., the refractive index modulation point) on the optical fiber to perform refractive index modulation, thereby completing the production of asymmetric apodized chirped fiber gratings.

[0046] In some embodiments, a high-reflection mirror is used to change the propagation direction of the laser emitted by the femtosecond laser. The high-reflection mirror has a high reflectivity and can efficiently reflect the laser emitted by the femtosecond laser to the next optical element, reducing the energy loss of the laser during transmission. The laser is reflected to the beam expander by the high-reflection mirror, and the beam expander expands the diameter of the laser beam while reducing the divergence angle of the beam, so as to obtain a smaller focused spot to increase the power density of the laser, thereby producing a stronger refractive index modulation effect in the optical fiber. The electric laser power attenuator can adjust the power of the laser as needed to ensure the depth and uniformity of the refractive index modulation. The polarizer group includes a polarization converter F6 and a polarization controller F7, which regulate the polarization state of the laser based on the polarizer group to obtain the first laser. The aperture beam limiter is used to limit the diameter and shape of the first laser beam, and ensure that the laser beam is irradiated onto the optical fiber with a suitable size and shape by adjusting the size and position of the aperture. The objective lens is used to focus the first laser beam to the refractive index modulation point in the optical fiber. By precisely adjusting the focal length and position of the objective lens, it can be ensured that the laser beam is irradiated onto the optical fiber with extremely high power density, thereby generating a strong refractive index modulation effect in the optical fiber.

[0047] The chirped fiber grating manufacturing method based on asymmetric toe cutting proposed in the present disclosure is executed in a control system, which is used to design the structure to be engraved, set the grating parameters and motion-related parameters during the processing, and set the single-pulse laser energy and pulse code number.

[0048] The control system designs the structure to be engraved, sets the processing position and path, ensures that the laser engraving point is located in the middle of the fiber core, and controls the femtosecond laser pulse output position (refractive index modulation point) to be distributed according to the periodic interval of the chirped grating.

[0049] The control system sets a reasonable laser energy attenuation value and a maximum single pulse energy, determines the structural parameter requirements of the target chirped fiber grating, and determines the target asymmetric envelope function corresponding to the target chirped fiber grating according to the parameter requirements. The target asymmetric envelope function is the basis for adjusting the number of laser pulses, so that the number of laser pulses can modulate the refractive index of the fiber grating in a symmetrical manner. Among them, the target asymmetric envelope function can be composed of a combination of symmetric envelope functions, or it can be a piecewise function. The present disclosure does not limit the expression form of the asymmetric envelope function, which can be freely selected according to actual conditions. Among them, the symmetric envelope function can include, for example, a Gaussian function, a Hamming function, a Blackman function, a raised cosine function, a Tanh function, a Cauchy function, and a sinc function.

[0050] Figure 3 The schematic diagram of the refractive index modulation depth of the asymmetric apodized chirped fiber grating according to the embodiment of the present disclosure is shown schematically.

[0051] In some embodiments, the target refractive index variation function of the fiber Bragg grating is set to:

[0052]

[0053] Where z is the axial position of the optical fiber, n0 is the refractive index when not modulated, Δn is the amplitude of the refractive index change, and f(z) is the newly defined asymmetric envelope function.

[0054] The asymmetric envelope function can be expressed as:

[0055]

[0056] Among them, A is the modulation amplitude, which determines the maximum value of the modulation envelope; z0 is the position of the modulation point in the center of the grating, which is the dividing point between the left and right envelopes; σ left is the standard deviation on the left, controlling the width and slope of the left side of the grating, σ right is the right standard deviation, controlling the width and slope of the right side of the grating. left and σ rightThe broadening degree of the envelope function on both sides of the grating is theorized respectively, and different values ​​will lead to differences in the envelope slope, thus achieving asymmetry.

[0057] The asymmetric envelope function uses the Heaviside step function H(z) to simplify the formula. When z≤z0, H(z-z0)=0; when z≥z0, H(z-z0)=1, thereby achieving a smooth transition of f(z) at z=z0 and making the change of the refractive index modulation depth smoother, thereby effectively suppressing the sidelobes and ripple oscillations in the chirped grating reflection spectrum.

[0058] It should be noted that the expression of the asymmetric envelope function given in the present disclosure is only illustrative, and those skilled in the art can adjust it according to actual application conditions.

[0059] In addition, the control system will also set the grating parameters and parameters related to motion during the processing based on the target asymmetric envelope function, such as the processing speed of the translation stage, grating structure parameters (such as central wavelength, grating length, grating center period, chirp coefficient, refractive index modulation depth, etc.). The control system controls the translation stage to move at a certain speed, so that the output position of the femtosecond laser pulse (refractive index modulation point) is distributed according to the period interval of the chirped grating, and the femtosecond laser pulse is accurately controlled to change according to the asymmetric envelope to achieve the preparation of chirped toe-cut fiber gratings. In some embodiments, the displacement of the displacement platform is 1 nm, and the control system controls the translation stage to move along the axial direction of the optical fiber at a certain speed. By controlling the moving speed and moving distance of the displacement platform, the interaction time and area between the laser and the optical fiber can be accurately controlled, thereby making a grating structure with a specific refractive index distribution from the optical fiber.

[0060] In the process of making chirped fiber gratings, the energy of a single laser pulse remains unchanged, and the number of laser pulses is adjusted according to the target asymmetric envelope function to achieve arbitrary changes in the modulation depth of the fiber grating refractive index, thereby increasing the flexibility of chirped fiber grating preparation. The control system can, for example, adjust the change of the number of pulses through software system programming.

[0061] The chirped fiber grating manufacturing method provided by the embodiment of the present disclosure adopts a femtosecond laser direct writing method to write into the fiber grating structure, and the number of laser pulses is precisely controlled so that the number of laser pulses gradually decreases from the center of the grating to the two ends of the grating, and changes according to the asymmetric toe-cutting envelope, thereby effectively changing the refractive index modulation depth and achieving the effect of toe-cutting compensation. Among them, the femtosecond laser direct writing method can include, for example, a point-by-point method, a line-by-line method, a plane-by-plane method, etc. The refractive index modulation depth of the central area of ​​the target fiber grating is the largest, the refractive index modulation amplitude on both sides is small, and the toe-cutting ratio in the long wavelength direction is greater than the toe-cutting ratio in the short wavelength direction.

[0062] In some embodiments, an LED light source is further configured under the displacement platform. By adjusting the LED lighting source under the displacement platform, the image transmitted back by the image sensor (Harge Coupled Device, CCD) can be monitored in real time. The grating structure and the reflection spectrum can be monitored in real time through the CCD and the spectrometer to check whether the performance of the fiber grating meets the design requirements and ensure the quality of the manufactured fiber grating. Based on the monitoring results, the manufacturing parameters of the fiber grating are adjusted to meet the parameter requirements of the target chirped fiber grating, so as to achieve the precise manufacturing of the chirped fiber grating and improve the accuracy of the manufacturing of the target chirped fiber grating.

[0063] The chirped fiber grating manufacturing method provided by the present disclosure realizes apodization by precisely controlling the number of pulses according to the fine variation of any asymmetric apodization package, selecting the appropriate single pulse laser energy, the type of chirped fiber grating to be written, and the pulse variation parameters with the asymmetric apodization function. The femtosecond system accurately adjusts the distribution of the number of laser pulses according to the preset envelope function, realizes the fine regulation and arbitrary variation of the refractive index modulation depth in the fiber grating, and thus achieves the expected spectral characteristics. The chirped fiber grating is manufactured with high precision.

[0064] This production method is not limited by the phase mask plate, supports the design and preparation of high-quality chirped toe-cut fiber Bragg grating structures with different parameters, introduces asymmetric toe-cutting and precise femtosecond laser pulse number control methods, can finely adjust the distribution gradient of the refractive index modulation, obtain better reflection spectrum and time delay characteristics, and reduce the high-precision requirements for laser energy adjustment and displacement platform movement. It has better repeatability and consistency, and meets the needs of high-quality chirped fiber Bragg grating components in application fields such as multi-channel dispersion compensation and multi-channel filters.

[0065] In addition, before writing the fiber grating, the optical fiber is wiped with alcohol cotton and placed on the fiber clamping system on the XY translation stage, and then the area to be processed is immersed in the refractive index matching liquid, so that the refractive index difference of different layers of the optical fiber and the resulting cylindrical lens effect are reduced to a very low level.

[0066] Figure 4 The structural diagram of the chirped apodized fiber grating structure based on the femtosecond laser point-by-point method in an embodiment of the present disclosure is schematically shown.

[0067] like Figure 4As shown, the chirped apodized fiber grating structure includes a fiber core 1, a cladding 2 and a period 4. The number of pulses 3 of the femtosecond laser point-by-point method is set to change according to the asymmetric apodization envelope, and the chirped apodized fiber grating structure is obtained. The number of pulses of the chirped apodized fiber grating gradually decreases from the center of the grating to the two ends of the grating. The refractive index modulation depth is the largest in the central area of ​​the grating, and the refractive index modulation depth gradually decreases from the center of the grating to the two ends, wherein the apodization ratio in the long wavelength direction is greater than the apodization ratio in the short wavelength direction. Through the above steps, the required chirped apodized fiber grating based on the femtosecond laser system can be accurately manufactured to meet the application needs of different fields, with significant technical advantages and market potential.

[0068] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all be included in the scope of protection of the present disclosure.

Claims

1. A method for manufacturing a chirped fiber Bragg grating based on asymmetric apodization, characterized in that: The method comprises: Based on the parameter requirements of the target chirped fiber Bragg grating, determining the target asymmetric envelope function corresponding to the target chirped fiber Bragg grating; adjusting the number of pulses of the laser output by the femtosecond laser based on the target asymmetric envelope function; The laser is controlled to irradiate a target area in the optical fiber to form a target chirped fiber grating, wherein the number of pulses of the laser changes according to the target asymmetric envelope function and gradually decreases from the center of the grating to both ends.

2. The method for manufacturing an asymmetric apodized chirped fiber Bragg grating according to claim 1, characterized in that: The target asymmetric envelope function is expressed as any one of a combination of symmetric envelope functions or a piecewise function, and the symmetric envelope function includes a Gaussian function, a Hamming function, a Blackman function, a raised cosine function, a Tanh function, a Cauchy function, and a sinc function.

3. The method for manufacturing an asymmetric apodized chirped fiber Bragg grating according to claim 1, characterized in that: The optical fiber is placed on a displacement platform, and the laser output positions are distributed at intervals according to the chirped grating period.

4. The method for manufacturing an asymmetric apodized chirped fiber Bragg grating according to claim 1, characterized in that: The energy of the laser single pulse is kept constant during the apodization process.

5. The method for manufacturing an asymmetric apodized chirped fiber grating according to claim 1 adopts a femtosecond laser direct writing method, wherein the femtosecond laser direct writing method includes any one of a point-by-point method, a line-by-line method, and a plane-by-plane method.

6. The method for manufacturing an asymmetric apodized chirped fiber grating according to claim 5, wherein the refractive index modulation depth of the central region of the target fiber grating is the largest, the refractive index modulation amplitude on both sides is smaller, and the apodization ratio in the long wavelength direction is greater than the apodization ratio in the short wavelength direction.

7. The method for manufacturing an asymmetric apodized chirped fiber Bragg grating according to claim 1, characterized in that: The step of controlling the laser to irradiate a target area in the optical fiber to form a target chirped optical fiber grating comprises: The laser light outputted by the femtosecond laser is reflected to a beam expander through a high-reflection mirror to obtain an expanded laser beam; Adjusting the parameters of the expanded laser beam to obtain a first laser; The diameter and shape of the first laser beam are adjusted, and the adjusted first laser beam is focused to a target area in the optical fiber to adjust the refractive index of the optical fiber.

8. The method for manufacturing an asymmetric apodized chirped fiber Bragg grating according to claim 1, characterized in that: The step of adjusting the parameters of the expanded laser beam to obtain the first laser comprises: Adjusting the laser power based on an electric laser power attenuator; The polarization state of the laser is regulated based on the polarizer group to obtain the first laser.

9. The method for manufacturing an asymmetric apodized chirped fiber Bragg grating according to claim 1, characterized in that: During the production process of the chirped fiber grating, the grating structure and the reflection spectrum are monitored in real time by an image sensor and a spectrometer, and the production parameters of the fiber grating are adjusted based on the monitoring results to meet the parameter requirements of the target chirped fiber grating.

10. The method for manufacturing an asymmetric apodized chirped fiber Bragg grating according to claim 2, characterized in that: The asymmetric envelope function can be expressed as: Among them, A is the modulation amplitude, which determines the maximum value of the modulation envelope; z0 is the position of the modulation point in the center of the grating, which is the dividing point between the left and right envelopes; σ left is the standard deviation on the left, controlling the width and slope of the left side of the grating, σ right Right standard deviation, controls the width and slope of the right side of the raster.

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