Preparation method of optical fiber cladding light filter for high-power optical fiber laser

Abstract

The invention discloses an optical fiber cladding light filter for a high-power optical fiber laser and a preparation method thereof, and the method comprises the steps: preparing an optical fiber, removing a coating layer of the optical fiber according to a preset length, and enabling the optical fiber to form a structure in which the coating layers are reserved at the two ends and the surface of the optical fiber cladding is exposed in the middle region; the area, exposed out of the surface of the optical fiber cladding, of the optical fiber is divided into a first area and two second areas, the two second areas are connected to the two ends of the first area, and the second areas are spaced from the coating layer of the optical fiber; the first area is etched into a sharp granular shape to form a deep filtering area; the second area is etched into a smooth block shape, a transition area is formed, the length of the deep transition area is larger than that of the transition area, preparation is completed, and the finished optical fiber cladding light filter is obtained. The method is good in process consistency, stable and reliable, batch difference can be effectively reduced, and large-batch production is facilitated.

Description

Technical Field

[0001] The invention relates to the field of optical fiber lasers, in particular to an optical fiber cladding light filter applied to high-power optical fiber lasers and a preparation method thereof. Background Art

[0002] High-power fiber lasers require that the fiber cladding light filter has at least the ability to stably and continuously filter out hundreds of watts of fiber cladding light. Currently, the lowest-cost and most common way to prepare this level of fiber cladding light filter is to wet-etch the fiber cladding to form an uneven surface that destroys the cladding light waveguide. Compared with the wet etching process, the laser etching equipment investment cost is high, and the strength of the prepared device is low, and the overall cost-effectiveness is obviously not as good as wet etching; and the high-refractive index glue coating process is difficult to cope with cladding light above 100 watts, and is generally only used to filter out the residual cladding light in the pump fiber with a cladding light power of less than 20W, and cannot be used to prepare cladding light filters for high-power fiber lasers.

[0003] The existing wet etching process (CN 105372759 A) requires concentrated sulfuric acid, hydrofluoric acid and ammonium fluoride as a buffer in a specific implementation method, and is prepared into a corrosion paste with some hydrofluoric acid-resistant thickeners. It is obvious that the above chemicals are very harmful to the human body, and corresponding protective facilities and equipment need to be configured, which is not conducive to online operation. Especially when the ambient temperature is high, the operation is extremely unstable.

[0004] In the existing method based on frosting paste as an etchant (CN 118448968 A), hydrofluoric acid, a dangerous chemical substance, is always present in liquid form. It is still dangerous to the operator to operate, and the frosting paste is difficult to store for a long time: because the key formula hydrofluoric acid is easily volatile to toxic hydrogen fluoride gas, it has high requirements for storage conditions, and as the concentration of hydrogen fluoride continues to decrease, it will cause the stability of the etching process to deteriorate, the process yield is low, and it is impossible to accurately control the etching process to obtain high-quality etching morphology on the surface of the optical fiber cladding. Especially in the application field of pure air-cooled fiber lasers, because the end of the output optical cable removes the optical fiber cladding light filter to reduce heat generation, the cladding light filter inside the high-power air-cooled fiber laser needs to have a higher cladding light filtering ability, and because of the limitations of the air-cooled heat dissipation method, a relatively more balanced cladding light filtering is required. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a fiber cladding light filter for high-power fiber laser and a preparation method thereof.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The method for preparing a fiber cladding light filter for a high-power fiber laser comprises the following steps:

[0008] Prepare an optical fiber, remove the coating layer of the optical fiber according to a preset length, so that the optical fiber is formed into a structure in which the coating layer is retained at both ends and the surface of the optical fiber cladding is exposed in the middle area;

[0009] The area on the optical fiber where the optical fiber cladding surface is exposed is divided into a first area and a second area, wherein the second area has two areas, the two second areas are connected to two ends of the first area, and the second area is spaced apart from the coating layer of the optical fiber;

[0010] The first area is etched into a sharp granular morphology to form a deep filtering area; the second area is etched into a smooth block-like morphology to form a transition area. The length of the deep transition area is greater than the length of the transition area. The preparation is completed to obtain a finished optical fiber cladding light filter.

[0011] As a further improvement, the second region is etched using agent A, and the first region is etched using agent B;

[0012] Agent A is composed of the following raw materials in parts by weight: 15-25 parts of water-based frosting powder, 2-5 parts of soft sugar, 1-5 parts of aluminum oxide powder, 1-2 parts of barium sulfate powder or zirconium oxide powder of equal weight, after mixing, add 50-100 parts of hot water above 95°C and stir evenly, let stand for more than 10 minutes for use;

[0013] Agent B is composed of the following raw materials in parts by weight: 35-45 parts of water-based frosting powder, 2-3 parts of soft sugar, 1-3 parts of aluminum oxide powder, 1-2 parts of barium sulfate powder or zirconium oxide powder of equal weight, after mixing, add 50-100 parts of hot water above 95°C and stir evenly, let stand for more than 10 minutes for use;

[0014] Apply agent A on the surface of the second area and agent B on the surface of the first area, and leave them to stand at room temperature for 10 to 40 minutes;

[0015] Then clean and wash away the A and B agents.

[0016] As a further improvement, the mesh size of the aluminum oxide powder in the A agent is 20-40 meshes, and the mesh size of the aluminum oxide powder in the B agent is 70-90 meshes.

[0017] As a further improvement, the distance between the end of the first region and the coating layers at both ends of the optical fiber is greater than or equal to 25 mm, and the distance between the end of the second region and the coating layers at both ends of the optical fiber is greater than or equal to 10 mm.

[0018] As a further improvement, during cleaning, the optical fiber is first rinsed with hot water above 50°C, and the rinse liquid is collected; then the optical fiber is rinsed with anhydrous ethanol, and the anhydrous ethanol is analytically pure with a component fraction greater than or equal to 99.7%;

[0019] Add slaked lime powder to the flushing liquid, and mix the flushing liquid and slaked lime powder in a mass ratio of 10:3-5.

[0020] As a further improvement, when applying agent A and agent B, neither agent A nor agent B can contact the coating layer of the optical fiber.

[0021] As a further improvement, a tooling is provided for clamping the optical fiber, the tooling comprising a chassis, a guide rail and four sliding baffles, the guide rail being fixedly mounted on the chassis, the chassis being provided with a plurality of grooves for placing the optical fiber, the four sliding baffles being provided with perforations for the optical fiber to pass through, the guide rail being movable through the four sliding baffles, the four sliding baffles being adjusted at a distance on the guide rail to separate the optical fiber into an independent first area and two second areas, the chassis, the guide rail and the four sliding baffles being all made of plastic.

[0022] A fiber cladding light filter for a high-power fiber laser comprises an optical fiber. The optical fiber is provided with a first region and two second regions from which a coating layer is removed. The two second regions are connected to two ends of the first region. Both ends of the optical fiber are provided with a coating layer. There is a spacing distance between the second region and the coating layer. The first region presents a sharp granular morphology, the second region presents a smooth block morphology, and the length of the first region is greater than the length of the second region.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Low cost. No special protective facilities are required for implementation, and no expensive CO2 laser engraving machines or other additional equipment are required. The main raw materials used: frosting powder, auxiliary materials, soft white sugar, aluminum oxide powder, barium sulfate powder, zirconium oxide powder, and slaked lime are easy to obtain and low in cost.

[0025] 2. High safety. The operator does not need to prepare acid, especially concentrated sulfuric acid, high-concentration hydrofluoric acid and other dangerous acids;

[0026] 3. Easy to store, it can be stored in plastic or metal storage bottles, and there will be no problem of poor process stability due to volatilization;

[0027] 4. Environmental protection and low pollution. The manufacturing process provided by the present application does not need to consider the impact of acid leakage or volatilization on the environment, and effective neutralization measures are taken for dangerous fluoride ions during the process to avoid fluoride ion discharge and pollution of water bodies;

[0028] 5. Good process consistency. Since there is no process instability caused by acid volatilization, the process consistency is good, stable and reliable, which can effectively reduce batch differences. It is very suitable for mass production of fiber cladding light filters inside high-power air-cooled fiber lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the preparation method of the present invention;

[0030] Figure 2 It is a schematic diagram of the three-dimensional structure of the tooling in the present invention. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0032] In the description of the present invention, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like are involved, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" 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 or an electrical connection. It can be directly connected or 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 invention can be understood according to specific circumstances.

[0034] like Figure 1As shown, the preparation method of the optical fiber cladding light filter for high-power optical fiber laser comprises the following steps:

[0035] Prepare an optical fiber 1, remove the coating layer of the optical fiber 1 according to a preset length, so that the optical fiber is formed into a structure with coating layers 12 retained at both ends and the optical fiber cladding surface 11 exposed in the middle area. The length of the exposed optical fiber cladding surface 11 is controlled according to the actual situation of the power of the laser and the required filtering ability level. In this embodiment, the length of the optical fiber cladding surface is 90 to 100 mm.

[0036] The area on the optical fiber where the optical fiber cladding surface is exposed is divided into a first area 15 and a second area 16. The second area 16 has two areas, and the two second areas 16 are connected at both ends of the first area 15. The second area 16 is spaced apart from the coating layer 12 of the optical fiber, and the length of the first area 15 is greater than the length of the second area 16.

[0037] The first area 15 is etched into a sharp granular morphology, with a small and sharp shape, forming a deep filtering area; the second area is etched into a smooth block morphology, with a coarse shape, forming a transition area, and the length of the deep transition area is greater than the length of the transition area. The preparation is completed to obtain a finished optical fiber cladding light filter.

[0038] The second region is etched by using reagent A, and the first region is etched by using reagent B;

[0039] Agent A is composed of the following raw materials in parts by weight: 15-25 parts of water-based frosting powder, 2-5 parts of soft white sugar, 1-5 parts of 20-40 mesh aluminum oxide powder, 1-2 parts of barium sulfate powder or zirconium oxide powder of equal weight, after mixing, add 50-100 parts of hot water above 95°C and stir evenly, let stand for more than 10 minutes for use;

[0040] Agent B is composed of the following raw materials in parts by weight: 35-45 parts of water-based frosting powder, 2-3 parts of soft sugar, 1-3 parts of 70-90 mesh aluminum oxide powder, 1-2 parts of barium sulfate powder or zirconium oxide powder of equal weight, after mixing, add 50-100 parts of hot water above 95°C and stir evenly, let stand for more than 10 minutes for use;

[0041] Apply agent A on the surface of the second area and agent B on the surface of the first area, and leave them to stand at room temperature for 10 to 40 minutes;

[0042] Then, wash the A and B agents. When washing, first use hot water above 50°C to wash the optical fiber, and collect the washing liquid; then use anhydrous ethanol to wash the optical fiber, and the anhydrous ethanol should be analytically pure with a content fraction greater than or equal to 99.7%; add slaked lime powder to the washing liquid, and mix the washing liquid and slaked lime powder with the slaked lime powder in a mass ratio of 10:3-5 to fully neutralize the fluoride ions in the waste liquid to form environmentally friendly calcium fluoride precipitation.

[0043] The distance between the end of the first region and the coating layer at both ends of the optical fiber is greater than or equal to 25 mm, and the distance between the end of the second region and the coating layer at both ends of the optical fiber is greater than or equal to 10 mm. When applying agent A and agent B, neither agent A nor agent B can contact the coating layer of the optical fiber.

[0044] According to the above preparation method, a fiber cladding light filter for a high-power fiber laser is prepared, including an optical fiber 1, wherein the optical fiber 1 has a first area and two second areas where the coating layer 12 is removed, the two second areas are connected to the two ends of the first area, the two ends of the optical fiber have a coating layer, there is a spacing distance between the second area and the coating layer, the first area presents a sharp granular morphology, the second area presents a smooth block morphology, and the length of the first area is greater than the length of the second area.

[0045] The following is an explanation using a production example.

[0046] Take the production of 500 to 1000 fiber cladding light filters suitable for 2000W air-cooled fiber lasers as an example:

[0047] Prepare two 150ml polytetrafluoroethylene bottles A and B according to the amount required for preparing 500 to 1000 optical fiber cladding light filters, add 15 to 25g of aqueous frosting powder, 2 to 5g of soft sugar, 1 to 5g of 30-mesh aluminum oxide powder, and 1g to 2g of barium sulfate powder or zirconium oxide powder of equal mass into bottle A and set aside, and mark it as agent A; before starting production, pour 100ml of clean water above 96°C into bottle A, quickly stir it evenly with a plastic rod, and let it stand for 20 minutes.

[0048] Add 35-45g of water-based frosting powder, 2-3g of soft sugar, 1-3g of 80-mesh aluminum oxide powder, and 1g of barium sulfate powder or zirconium oxide powder of the same mass to bottle B, and mark it as agent B; before the production begins, pour 100ml of clean water above 96℃ into bottle B, stir quickly with a plastic stick, and let it stand for 20 minutes for use.

[0049] In the present application, a suitable proportion of soft white sugar, aluminum oxide powder, barium sulfate powder or zirconium oxide powder of equal mass can adjust the etching uniformity, viscosity, shorten the aging time, and ensure the uniformity and consistency between batches of agents. Agent A and Agent B can form different surface etching morphologies in the etching area of ​​the optical fiber cladding light filter due to the different frosting powder content and auxiliary material formula content. In particular, the auxiliary formula aluminum oxide powder, wherein the aluminum oxide powder with a particle fineness of 30 mesh can make the etching area of ​​the optical fiber cladding light filter form a larger block morphology. And the aluminum oxide powder with a particle fineness of 80 mesh can make the etching area form a sharp fine particle morphology.

[0050] According to the required optical fiber length (0.5m, 1m, 1.5m, etc.) and specifications (14 / 250, 20 / 400, 25 / 250, 30 / 400, 50 / 400, etc.) of the required optical fiber cladding light filter, 500 to 1000 optical fibers of corresponding length and specifications are cut out.

[0051] Press Attach Figure 1 As shown, the above-mentioned B agent is applied to the first area of ​​the optical fiber cladding surface 11, which is 25 mm away from the optical fiber coating layer 12; A agent is applied to the two ends of the B agent, i.e., the second area, and the A agent cannot contact the coating layer 12, and the distance is kept at least 10 mm; the coating length of the agent A at both ends is 10 to 15 mm.

[0052] In the actual batch production process, the application process of the above-mentioned A and B agents can be accelerated by a glue coating machine or simple tooling; Figure 2 The tooling shown can apply the agent more efficiently. Figure 2 In the middle is an acid- and alkali-resistant plastic tooling P, including a chassis P2, a guide rail P3 and a sliding baffle P1. The sliding baffle P1 is movably mounted on the guide rail P3. The guide rail P3 and the sliding baffle P1 can be disassembled. The chassis P2 is provided with a number of grooves, and the sliding baffle P1 is provided with perforations. The optical fiber is placed in the grooves and passes through the perforations. The four sliding baffles P1 can divide the thin chassis P2 into three independent areas for brushing medicine: PA1 corresponds to the second area for brushing medicine A, PB corresponds to the first area for brushing medicine B, and PA2 corresponds to the second area for brushing medicine A. After adjusting the intervals between PA1, PB, and PA2, brush the medicine into the above-divided areas respectively with a brush, so as to achieve precise control of the length of the medicine coating during batch production.

[0053] After the agent evenly covers the surface of the optical fiber cladding 11 to be applied, the entire cylindrical surface is evenly applied and left to stand at room temperature for 10 to 40 minutes; then rinse the agents A and B on the surface of the optical fiber cladding 11 and dry them. In the embodiment of the present application, the agent A and B on the surface of the optical fiber cladding 11, the flushing process is as follows: first spray with clean water to remove the agents A and B on the surface of the optical fiber cladding 11. The A agent and the B agent described in the present application can be easily removed by clean water. In order to remove the A agent and the B agent more efficiently, the clean water is selected to be hot water above 50°C. In order to reduce the harm of fluoride ion-containing wastewater to the environment, the flushing liquid generated during the cleaning process is collected, and slaked lime powder is added to the flushing liquid. The flushing liquid is mixed with slaked lime powder in a mass ratio of 10:3 to fully neutralize the fluoride ions in the waste liquid to form an environmentally harmless calcium fluoride precipitate.

[0054] After the agent on the surface of the optical fiber cladding 11 is removed by clean water until it is invisible to the naked eye, the surface is rinsed with 99.7% analytically pure anhydrous ethanol. The purpose of this step is to dehydrate and dry. Two different etching morphologies will be formed on the surface of the optical fiber cladding 11; the area etched by agent A is the transition zone 13. In this area, the surface of the optical fiber cladding 11 is a coarse and smooth block; the optical fiber cladding light generated during the operation of the laser is first filtered out in the transition zone 13, and a part of the light with a larger numerical aperture (NA) is filtered out. The coarse and smooth block etching morphology allows part of the cladding light to be filtered out more evenly, so as to effectively reduce the light energy released per unit area and improve reliability. Because of this, in this application, the cleanliness requirements for the etching area are low, and it only needs to be judged by the naked eye. The area etched by agent B is the deep filtering area 14. In this area, the surface of the optical fiber cladding 11 forms a fine and sharp granular etching morphology, which can effectively filter out the light with a smaller numerical aperture (NA) in the residual cladding.

[0055] Since the cladding light with a larger NA is very easy to be filtered out, a slight etching morphology on the surface can easily filter it out; therefore, the morphological features of the transition zone 13 must be coarse and smooth to suppress the filtering amount of the cladding light with a larger NA in this area. The transition zone 13 must not only filter out the cladding light with a larger NA, but also prevent these cladding lights with a larger NA from pouring out, but need to be filtered out as evenly as possible on the surface of the transition zone 13. The morphological features of the transition zone 13 directly determine whether the device can withstand higher cladding light, and accordingly determine whether the device can be used for higher-power fiber lasers. For general fiber lasers, the cladding light with a larger NA during operation is mainly the pump light that is not fully absorbed by the laser gain cavity, and this part of the energy accounts for the vast majority of the total energy of all cladding light. Therefore, the length of the transition zone 13 should not be too short, but also not too long. It needs to be adapted to the filtering ability of the cladding light and the power level of the laser cladding light according to the surface morphology formed after etching. Although the cladding light of small NA only occupies the entire cladding filter area 14, the surface morphology must be small and sharp, and the length of the deep filter area 14 must be significantly longer than the transition area 13, so that the deep filter area can fully filter the cladding light of small NA.

[0056] In the specific embodiment described in the present application, the transition zone 13 formed by the A agent has two positions located at the two ends of the deep filtering zone 14 respectively; the advantages of this approach are: on the one hand, it can ensure that the prepared optical cladding light filter has sufficient versatility, and the operator does not need to determine the input end of the device, and any end is the input end; on the other hand, the return light can be evenly filtered to improve the stability of the entire fiber laser optical path. Especially for air-cooled fiber lasers; because the output optical cable interface of the air-cooled fiber laser (generally QBH or QD) removes the cladding light filter. When this type of laser processes high-reflectivity materials such as copper and aluminum, the return light can only be filtered by the fiber cladding light filter inside the laser.

[0057] It should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. However, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a fiber cladding light filter for high-power fiber lasers, characterized in that: The following steps are involved: Prepare an optical fiber, remove the coating layer of the optical fiber according to a preset length, so that the optical fiber is formed into a structure in which the coating layer is retained at both ends and the surface of the optical fiber cladding is exposed in the middle area; The area on the optical fiber where the optical fiber cladding surface is exposed is divided into a first area and a second area, wherein the second area has two areas, the two second areas are connected to two ends of the first area, and the second area is spaced apart from the coating layer of the optical fiber; The first area is etched into a sharp granular morphology to form a deep filtering area; the second area is etched into a smooth block-like morphology to form a transition area. The length of the deep transition area is greater than the length of the transition area. The preparation is completed to obtain a finished optical fiber cladding light filter.

2. The method for preparing a fiber cladding light filter for a high-power fiber laser according to claim 1, characterized in that: The second region is etched by using reagent A, and the first region is etched by using reagent B; Agent A is composed of the following raw materials in parts by weight: 15-25 parts of water-based frosting powder, 2-5 parts of soft sugar, 1-5 parts of aluminum oxide powder, 1-2 parts of barium sulfate powder or zirconium oxide powder of equal weight, after mixing, add 50-100 parts of hot water above 95°C and stir evenly, let stand for more than 10 minutes for use; Agent B is composed of the following raw materials in parts by weight: 35-45 parts of water-based frosting powder, 2-3 parts of soft sugar, 1-3 parts of aluminum oxide powder, 1-2 parts of barium sulfate powder or zirconium oxide powder of equal weight, after mixing, add 50-100 parts of hot water above 95°C and stir evenly, let stand for more than 10 minutes for use; Apply agent A on the surface of the second area and agent B on the surface of the first area, and leave them to stand at room temperature for 10 to 40 minutes; Then clean and wash away the A and B agents.

3. The method for preparing the optical fiber cladding light filter for high-power optical fiber laser according to claim 2, characterized in that: The mesh size of the aluminum oxide powder in the A agent is 20-40 meshes, and the mesh size of the aluminum oxide powder in the B agent is 70-90 meshes.

4. The method for preparing a fiber cladding light filter for a high-power fiber laser according to claim 2, characterized in that: The distance between the end of the first region and the coating layers at both ends of the optical fiber is greater than or equal to 25 mm, and the distance between the end of the second region and the coating layers at both ends of the optical fiber is greater than or equal to 10 mm.

5. The method for preparing the optical fiber cladding light filter for high-power optical fiber laser according to claim 2, characterized in that: When cleaning, first use hot water above 50°C to rinse the optical fiber, and collect the rinse liquid; then use anhydrous ethanol to rinse the optical fiber, and the anhydrous ethanol is analytically pure with a component fraction greater than or equal to 99.7%; Add slaked lime powder to the flushing liquid, and mix the flushing liquid and slaked lime powder in a mass ratio of 10:3-5.

6. The method for preparing the optical fiber cladding light filter for high-power optical fiber laser according to claim 2, characterized in that: When applying agent A and agent B, neither agent A nor agent B can contact the coating layer of the optical fiber.

7. The method for preparing a fiber cladding light filter for a high-power fiber laser according to claim 2, characterized in that: A tool is provided for clamping optical fibers, the tool comprising a chassis, a guide rail and four sliding baffles, the guide rail is fixedly mounted on the chassis, a plurality of grooves for placing optical fibers are provided on the chassis, the four sliding baffles are provided with perforations for the optical fibers to pass through, the guide rail movably passes through the four sliding baffles, the four sliding baffles adjust the distance on the guide rail, and separate the optical fibers into an independent first area and two second areas, the chassis, the guide rail and the four sliding baffles are all made of plastic.

8. A fiber cladding light filter for a high power fiber laser, characterized in that: The optical fiber prepared by the preparation method according to any one of claims 1-7 includes a first area and two second areas where the coating is removed, the two second areas are connected to the two ends of the first area, the two ends of the optical fiber have a coating, there is a spacing distance between the second area and the coating, the first area has a sharp granular morphology, the second area has a smooth block morphology, and the length of the first area is greater than the length of the second area.

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