A packaging structure based on quadratic Bessel function simple branch modulation, an anti-vibration fiber laser and a packaging method

Abstract

The application provides a packaging structure based on secondary Bessel function simple branch modulation, an anti-vibration fiber laser and a packaging method, and belongs to the technical field of fiber laser packaging. The packaging structure comprises a metal base, the metal base is provided with a groove, the groove is provided with a fiber grating area near the neutral axis of the bottom of the groove, the bottom of the groove is provided with a convex structure, the shape of the convex structure is an asymmetric arc shape, and the curve of the arc shape is generated by a secondary Bessel curve. The groove is provided with a fiber, and the two ends of the fiber are fixed on the bottom of the groove. The fiber remains in a relaxed state in the middle segment area of the groove. A gap is left around the middle segment of the groove, or low modulus material is filled in the gap. The application effectively improves the lateral equivalent stiffness, multi-step improves the structure natural frequency in multiple directions, and further improves the overall first-order natural frequency, so that excellent frequency noise suppression capability is shown in the vibration test, and the stability of the fiber laser under acceleration disturbance is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of fiber laser packaging technology, specifically relating to a packaging structure based on simply supported modulation of a second-order Bessel function, an anti-vibration fiber laser, and a packaging method. Background Technology

[0002] Distributed feedback fiber lasers (DFLS) are narrow-linewidth fiber lasers that use a single active phase-shifting fiber grating (APFG) as the gain medium and resonant cavity. They offer advantages such as narrow linewidth, low noise, and simple structure. However, they are extremely sensitive to external sound waves, vibrations, and temperatures, and have long been studied as active fiber optic sensors in applications such as seismic detectors and hydrophones. In recent years, with the development of distributed fiber optic sensing technology, narrow-linewidth lasers as system light sources have received increasing attention. DFLS, as an important type of narrow-linewidth laser, has attracted widespread research attention, but its excellent environmental sensitivity has become a negative factor affecting laser stability. Therefore, effective sound and vibration isolation encapsulation of the APFG is essential to meet the application requirements of the laser. In-depth research on related encapsulation structures and materials is crucial for improving the overall performance of fiber lasers.

[0003] A common packaging method for fiber lasers typically employs a convex simply supported beam structure, fixed at both ends using a curing process. The basic principle involves creating a groove from the top center of the material to the neutral axis of the structure. Based on beam bending theory, the neutral axis maintains its length during bending deformation. The groove bottom is not of uniform depth but rather a convex arc with a radius of 1m. This convex structure breaks the fiber's "string" vibration mode. The "string" structure becomes more sensitive to acoustic waves, leading to more drastic changes in laser linewidth. However, when bent and attached to a smooth surface, the "string" structure is broken, creating tangential tension at various points on the grating. This significantly reduces the effects of string vibration, micro-bending, and standing waves caused by acoustic wave vibration, thus preventing drastic changes in laser wavelength and linewidth. However, in a convex simply supported beam structure, when subjected to external acceleration disturbances, the natural frequency under transverse acceleration excitation often differs significantly from that under longitudinal acceleration excitation. This results in a higher degree of coupling between lateral acceleration and fiber laser frequency noise when an acceleration load is applied, and the frequency disturbance it introduces is also significantly greater than the noise generated by longitudinal acceleration, leading to poor overall structural vibration resistance. Summary of the Invention

[0004] The purpose of this invention is to provide a packaging structure based on simply supported modulation of a quadratic Bessel function, an anti-vibration fiber laser, and a packaging method, which significantly reduces frequency noise coupling caused by acceleration and improves the frequency stability of the laser under non-closed-loop conditions.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A simply supported modulation packaging structure based on a quadratic Bessel function includes: a metal base with a groove on the metal base, an optical fiber grating region near the neutral axis at the bottom of the groove, and a protruding structure at the bottom of the groove. The protruding structure is asymmetrically arc-shaped, and the curve of the arc is generated by a quadratic Bessel curve.

[0007] Furthermore, an optical fiber is installed at the bottom of the groove, and both ends of the optical fiber are fixed at the bottom of the groove.

[0008] Furthermore, the optical fiber remains in a relaxed state in the middle section region of the groove.

[0009] Furthermore, the optical fiber has a gap around the middle section of the groove, or is filled with a low-modulus material.

[0010] Furthermore, the quadratic Bézier curve satisfies the quadratic Bézier curve function. :

[0011] ,

[0012] in, It is the starting point of the curve. These are the control points of the curve. It is the endpoint of the curve. It is a parameter.

[0013] Furthermore, the arc shape is achieved by adjusting the intermediate control point of the quadratic Bézier curve. This gives it an asymmetric curvature distribution.

[0014] Furthermore, the two ends of the optical fiber are fixed with adhesive, and the groove area where the middle section of the optical fiber is located is filled with low-modulus silicone grease.

[0015] The present invention also includes:

[0016] A vibration-resistant fiber laser includes the above-described packaging structure.

[0017] The present invention may also include:

[0018] A packaging method based on the above-mentioned quadratic Bessel function simply supported modulation packaging structure, the method includes the following steps:

[0019] Step 1: Fix the end point of the groove and set the arc length of the arc curve;

[0020] Step 2: Iteratively solve for the control points of the quadratic Bézier curve to ensure that the curve meets the design arc length;

[0021] Step 3: Machining the groove according to the arc curve;

[0022] Step 4: Arrange the fiber optic grid area near the neutral axis of the groove and encapsulate it by fixing both ends.

[0023] Furthermore, the method for machining the groove according to the arc curve includes:

[0024] First, fix the starting point of the groove. and the finish line And set the target arc length to establish a quadratic Bézier curve function. ,right The velocity vector function is obtained by differentiation. The magnitude of the velocity vector is numerically solved using adaptive Simpson integral, thereby obtaining the arc length of the curve. The bisection method or Newton's iteration method is then used to determine the control points. The position is optimized and adjusted so that the error between the final curve arc length and the target arc length does not exceed 0.01%. Through control point optimization, the generated Bézier curve has an asymmetric curvature distribution, realizing controllable adjustment of the groove geometry.

[0025] After obtaining the final arc curve, it is output as a machining path, and the groove is machined and formed on the metal base using CNC machining or micro-machining technology.

[0026] The beneficial effects of this invention are as follows:

[0027] The fiber laser packaging structure of this invention significantly improves the natural frequency under the same acceleration excitation. Under the same acceleration impact, the frequency noise suppression capability of the fiber laser packaging structure is stronger than that of the traditional convex simply supported beam.

[0028] This invention employs an asymmetric, convex, simply supported arc structure, placing the fiber grating region near the neutral axis. Simultaneously, a packaging method with fixed ends and a relaxed middle section significantly reduces the axial strain transmitted to the fiber by external acceleration. The curvature of the arc-shaped beam structure is optimized using a quadratic Bessel function. By fixing the endpoints and numerically solving for the intermediate control points, the arc length, curvature distribution, and effective stress transmission path satisfy specific natural frequency design targets. The asymmetric, convex structure geometrically introduces axial and bending coupling effects, effectively improving the transverse equivalent stiffness. This allows for multi-step enhancement of the structure's natural frequency in multiple dimensions, thereby increasing the overall first-order natural frequency. Consequently, it exhibits excellent frequency noise suppression capabilities in vibration testing, significantly improving the stability of the fiber laser under acceleration disturbances. Attached Figure Description

[0029] Appendix Figure 1 This is a schematic diagram of the packaging structure of the present invention;

[0030] Appendix Figure 2For the appendix Figure 1 The left view;

[0031] Appendix Figure 3 This is a comparison diagram of the natural frequencies of the symmetrical convex beam structure of the present invention and the prior art under two-dimensional acceleration excitation;

[0032] Appendix Figure 4 This is a comparison diagram of the frequency noise of two encapsulation structures, namely the symmetrical convex beam structure of the present invention and the prior art, under the same acceleration conditions. Detailed Implementation

[0033] The present invention will now be further described with reference to the accompanying drawings.

[0034] This invention provides a simply supported modulation encapsulation structure based on a quadratic Bessel function, as shown in the attached figure. Figure 1-2 As shown, it includes: a metal base 1, a groove 2, and a fiber optic grid region 3 placed near the neutral axis of the groove;

[0035] The metal base 1 is preferably made of materials with good mechanical stability, such as aluminum alloy, copper alloy, or stainless steel.

[0036] The bottom of the groove 2 has a raised structure, the shape of which is an asymmetrical arc, and the curve of the arc is generated by a quadratic Bézier curve.

[0037] The arc shape is generated by a quadratic Bézier curve. By adjusting the control point in the middle of the Bézier curve, while keeping the encapsulation length of the fiber laser grating region constant (i.e., the arc lengths of the asymmetric circular arc and the symmetrical convex arc are consistent), the groove has an asymmetric curvature distribution. The optical fiber is fixed at both ends and free in the middle. Point bonding is performed at both ends of the groove, and the middle section is left with a gap or filled with low-modulus material to weaken the transmission of axial strain. Under vibration, the asymmetric protrusion structure will increase the vibration modes of the overall structure under high-frequency acceleration excitation, making its modes richer, thereby increasing the effective stiffness and raising the first natural frequency.

[0038] The quadratic Bézier curve starts from the starting point. Control points and the end point The curve arc length is obtained through numerical integration, and control points are used. Iterative optimization is performed to ensure that the overall arc length of the resulting curve remains consistent with that of a traditional symmetrical convex arc structure, but the curvature exhibits an asymmetrical distribution. This asymmetrical curvature design of the invention causes the structure to generate a significant axial-bending coupling effect when subjected to external acceleration excitation, effectively improving the lateral equivalent stiffness.

[0039] In this embodiment, the fiber grating region 3 is arranged near the neutral axis of the groove to minimize the impact of bending deformation on stress coupling. The fiber adopts a fixed-end, loose-center fixation method, that is, UV adhesive is used for spot bonding at both ends of the groove to fix the fiber ends; the middle section of the groove is kept in a loose state, or filled with flexible materials such as low-modulus silicone grease, to weaken the efficiency of the encapsulation structure in transferring external stress to the fiber grating region. This structure can significantly reduce the axial strain response of the fiber grating under acceleration disturbance, thereby reducing the frequency noise of the fiber laser.

[0040] As attached Figure 3 As shown, through finite element natural frequency analysis, the first-order transverse natural frequency of the asymmetric convex arc structure described in this embodiment under acceleration excitation conditions is increased to about 181 kHz, which is about 8 kHz higher than that of the symmetric convex beam structure. This proves that the structure has higher transverse geometric stiffness and better anti-acceleration coupling capability.

[0041] Furthermore, the method of constructing an arc-shaped groove using a quadratic Bezier function includes: fixing the end position of the groove, setting the target arc length, calculating the arc length of the quadratic Bezier curve through numerical integration, and adjusting the position of the intermediate control point through an iterative method to make the actual arc length meet the design requirements; using the obtained curve as the bottom shape of the groove to process an asymmetric convex arc structure.

[0042] Compared to traditional symmetrical convex beams, this invention features an asymmetrical convex arc, causing the curvature at the bottom of the groove to be unevenly distributed along its length. This geometric asymmetry introduces a significant axial-bending coupling effect when the structure is subjected to lateral acceleration. When lateral inertial forces act on this asymmetrical structure, some of these forces generate additional traction or compression along the beam's axial direction, causing the structure to be simultaneously constrained axially during lateral deformation, resulting in additional geometric stiffness. This increase in geometric stiffness directly boosts the lateral equivalent bending stiffness, making the overall first-order natural frequency of the structure higher than that of a symmetrical convex beam. Under the same material and arc length, this results in stronger vibration resistance and a higher natural frequency. Furthermore, the asymmetrical curvature alters the effective mass distribution involved in the structure's dynamics, reducing the effective modal mass corresponding to the main vibration modes, thereby further increasing the natural frequency. This increase in natural frequency makes the encapsulated structure less susceptible to being driven to the resonance region under acceleration disturbances, effectively suppressing the transfer of excitation energy to the fiber optic grating region. Based on the aforementioned structural characteristics, in actual frequency noise tests, the asymmetric convex arc encapsulation structure exhibited a significantly lower frequency noise power spectral density than the symmetrical convex structure under acceleration loading, indicating lower sensitivity to acceleration disturbances and stronger vibration resistance. Under the same acceleration amplitude, the frequency noise response amplitude of the structure of this invention was significantly reduced, proving that the asymmetric convex arc not only enhances the natural frequency but also achieves superior vibration and noise reduction performance in actual vibration and noise environments.

[0043] Example 2:

[0044] Based on the packaging structure described in Example 1, this embodiment provides a method for constructing a groove curve based on simply supported modulation of a quadratic Bessel function:

[0045] First, fix the starting point of the groove. and the finish line The target arc length is set so that the constructed curve is consistent with the general convex simply supported beam encapsulation structure in terms of total length, so as to avoid affecting the encapsulation length of the fiber optic grating region.

[0046] The quadratic Bézier curve function B(t) is expressed as follows:

[0047] ,

[0048] in, It is the starting point of the curve. These are the control points of the curve. It is the endpoint of the curve. It's a parameter, specifically, It refers to the progress of the movement from the starting point to the end point.

[0049] right The velocity vector function is obtained by differentiation. The magnitude of the velocity vector is numerically solved using an adaptive Simpson integral, thus yielding the arc length of the curve. The bisection method or Newton's iteration method is then used to determine the control points. The position is optimized and adjusted so that the error between the final curve arc length and the target arc length does not exceed 0.01%. Through control point optimization, the generated Bézier curve has an asymmetric curvature distribution, enabling controllable adjustment of the groove geometry.

[0050] After obtaining the final curve, it can be output as a machining path, and the groove can be machined and formed on the metal base using CNC machining or micro-machining technology.

[0051] Example 3:

[0052] Based on the packaging structure described in Example 1, this example provides a method for preparing the packaging structure and testing its vibration and noise performance. The metal substrate is processed according to the asymmetric convex arc curve obtained in Example 2 to prepare the target groove. Subsequently, a fiber grating containing a π phase shift is arranged near the neutral axis of the groove. The ends of the fiber are fixed using UV-curable adhesive, and the middle section is filled with low-modulus silicone grease to keep the grating region in a near-free state, thereby reducing the coupling efficiency of the structure's strain towards the fiber. After packaging, the structure is mounted on a vibration testing platform, and acceleration excitation is applied using a PZT (piezoelectric ceramic plate). The PZT excitation frequency range is set from 100Hz to 10kHz to cover the low-to-mid-frequency band where fiber lasers are most susceptible to vibration interference in practical applications.

[0053] In the test, the experimental data were obtained by measuring the frequency noise power spectrum of the fiber laser output, as shown in the attached figure. Figure 4 As shown, the structure's ability to suppress acceleration disturbances was evaluated. Experimental results show that, throughout the entire excitation frequency band from 100 Hz to 10 kHz, the vibration-resistant structure based on simply supported modulation of a quadratic Bessel function, as used in this invention, exhibits significantly better frequency noise suppression performance than the traditional symmetrical convex package structure under acceleration. Due to the inherent frequency boost caused by the asymmetric curvature and the axial-bending coupling effect, the excitation energy is more difficult to transfer to the grating region, thus significantly reducing the peak amplitude of the frequency noise. Comprehensive frequency domain test results show that the frequency noise robustness of the structure of this invention is significantly improved in vibration environments, fully verifying the vibration resistance and noise reduction advantages of the asymmetric convex arc package design under wideband vibration noise conditions.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A simply supported modulation packaging structure based on a quadratic Bessel function, characterized in that, include: A metal base (1) has a groove (2) on it. A fiber optic grid region (3) is located near the neutral axis at the bottom of the groove (2). The bottom of the groove (2) has a protrusion structure. The protrusion structure is asymmetrically arc-shaped, and the curve of the arc is generated by a quadratic Bezier curve.

2. The simply supported modulation encapsulation structure based on a quadratic Bessel function according to claim 1, characterized in that, An optical fiber is installed at the bottom of the groove (2), and both ends of the optical fiber are fixed at the bottom of the groove.

3. The simply supported modulation encapsulation structure based on a quadratic Bessel function according to claim 1 or 2, characterized in that, The optical fiber remains in a relaxed state in the middle section of the groove (2).

4. The simply supported modulation encapsulation structure based on a quadratic Bessel function according to claim 1 or 2, characterized in that, The optical fiber has a gap around the middle section of the groove, or is filled with a low-modulus material.

5. The simply supported modulation encapsulation structure based on a quadratic Bessel function according to claim 1, characterized in that, The quadratic Bézier curve satisfies the quadratic Bézier curve function. : , in, It is the starting point of the curve. These are the control points of the curve. It is the endpoint of the curve. It is a parameter.

6. The simply supported modulation encapsulation structure based on a quadratic Bessel function according to claim 1 or 5, characterized in that, The arc shape is achieved by adjusting the midpoint of the quadratic Bézier curve. This gives it an asymmetric curvature distribution.

7. The simply supported modulation encapsulation structure based on a quadratic Bessel function according to claim 4, characterized in that, The two ends of the optical fiber are fixed with adhesive, and the groove area where the middle section of the optical fiber is located is filled with low-modulus silicone grease.

8. A vibration-resistant fiber laser, characterized in that, Includes the packaging structure as described in any one of claims 1-7.

9. A packaging method based on a simply supported modulation packaging structure of a quadratic Bessel function as described in any one of claims 1-7, characterized in that, The method includes the following steps: Step 1: Fix the end point of the groove and set the arc length of the arc curve; Step 2: Iteratively solve for the control points of the quadratic Bézier curve to ensure that the curve meets the design arc length; Step 3: Machining the groove according to the arc curve; Step 4: Arrange the fiber optic grid area near the neutral axis of the groove and encapsulate it by fixing both ends.

10. The packaging method based on a simply supported modulation packaging structure of a quadratic Bessel function according to claim 9, characterized in that, The method for machining grooves according to the arc curve includes: First, fix the starting point of the groove (2). and the finish line And set the target arc length to establish a quadratic Bézier curve function. ,right The velocity vector function is obtained by differentiation. The magnitude of the velocity vector is numerically solved using adaptive Simpson integral, thereby obtaining the arc length of the curve. The bisection method or Newton's iteration method is then used to determine the control points. The position is optimized and adjusted so that the error between the final curve arc length and the target arc length does not exceed 0.01%. Through control point optimization, the generated Bézier curve has an asymmetric curvature distribution, realizing the controllable adjustment of the geometry of the groove (2). After obtaining the final arc curve, it is output as a processing path, and the groove is formed on the metal base (1) by using CNC machining or micro-machining technology.

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