Compact cladding light filter and preparation method thereof

Abstract

The invention provides a compact cladding light filter and a preparation method thereof. The compact cladding light filter comprises an optical fiber body, an embedded optical fiber processing section and a packaging assembly, wherein the packaging assembly is arranged on the outer side of the processing section in a sleeving mode, and the two ends of the packaging assembly are fixedly connected with the optical fiber body. Wherein the length of the optical fiber processing section is 1.8-2.2 cm, the optical fiber processing section is sequentially provided with a fiber core and a first cladding from inside to outside in the radial direction, and the first cladding is of a non-total-reflection structure which cannot maintain total reflection. According to the compact cladding light filter, the ultra-short processing section is matched with the non-total-reflection first cladding, so that the filtering rate is larger than or equal to 90%, and the problems that a traditional filter needs to reach the standard in length and is easily limited by packaging are solved; and the reduction of the mechanical strength of the optical fiber can be avoided, and the reliability is ensured. Meanwhile, due to the ultra-short size, the ultra-short fiber laser can be flexibly integrated near an optical fiber in front of the input end of a laser output head, a mode field adapter, a beam combiner tail fiber and a fiber bragg grating, the packaging size of an original device is not affected, and finally support is provided for miniaturization and integrated upgrading of a whole laser.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber lasers, in particular to a compact cladding light filter and a preparation method thereof. BACKGROUND

[0002] High-power fiber lasers are widely used in industrial processing, medical treatment and other fields. In the output laser, in addition to the signal light in the fiber core, there is also non-ideal light (i.e. cladding light) transmitted in the cladding. The cladding light has high energy, and if not handled, it will burn the connectors of the laser system, cause the temperature of the system to be too high, and even damage the equipment. Therefore, a cladding light filter must be provided behind the laser output head to strip and dissipate this part of harmful light.

[0003] Traditional cladding light filters usually increase the leakage of cladding light through etching, grinding or bending, among which the etching method is often used because of its good effect. However, the cladding light filters of the prior art have some problems. In order to achieve a sufficient filtering rate (for example, >90%), the traditional etching type cladding light filter usually needs a long action distance (for example, more than 10 cm), which is too long in size, which is not conducive to the miniaturization and integration of the laser machine. In order to improve the filtering rate of a single etching, the optical fiber may be etched excessively, resulting in a sharp decrease in the mechanical strength of the optical fiber and a risk of breakage. If a mild etching is used, the filtering rate is not up to standard.

[0004] Therefore, there is a need for an integrated laser output head solution that can achieve high filtering rate in a short size and has a solid and reliable structure. SUMMARY

[0005] The present application aims to provide a compact cladding light filter and a preparation method thereof, which solve the technical problem that the existing cladding light filter needs a long size to achieve a high filtering rate.

[0006] To solve the above technical problems, the present application first provides a compact cladding light filter, which comprises an optical fiber body, an optical fiber processing section embedded in the optical fiber body, and a packaging assembly sleeved on the outside of the optical fiber processing section and fixedly connected to the optical fiber body at both ends. The length of the optical fiber processing section is 1.8-2.2 cm; the optical fiber processing section comprises a fiber core and a first cladding arranged in turn from the inside to the outside in the radial direction, and the first cladding is a non-total reflection structure that cannot maintain total reflection conditions.

[0007] Specifically, the compact cladding light filter of the present application, by virtue of the design of an ultra-short fiber processing section of 1.8-2.2 cm and a non-total reflection first cladding, can not only efficiently strip the cladding light, but also greatly reduce the device size, breaking through the size limitation of traditional filters; the embedded structure in combination with the fixed connection of the packaging assembly guarantees the structural stability and use reliability, and the ultra-short size makes it easier to integrate with various fiber devices, providing key support for the miniaturization and integration upgrade of the laser whole machine.

[0008] Preferably, the fiber body comprises, in sequence from the inside to the outside in the radial direction, a core, a second cladding and a coating layer, and the second cladding is a total reflection structure capable of maintaining the transmission of cladding light.

[0009] Specifically, the fiber body adopts a radial layered structure of a core, a total reflection second cladding and a coating layer, wherein the total reflection property of the second cladding can ensure stable transmission of the cladding light to the fiber processing section, providing a prerequisite for subsequent efficient filtering; at the same time, the complete layered structure guarantees the mechanical strength and signal light transmission stability of the fiber body, and does not increase the device size, meeting the compact design requirement.

[0010] Preferably, the fiber processing section comprises, in sequence along the signal light transmission direction, a first sub-section, a second sub-section and a third sub-section, the cladding light leakage amount of the first sub-section is less than that of the second sub-section, and the cladding light leakage amount of the second sub-section is less than that of the third sub-section.

[0011] Specifically, the fiber processing section adopts a three-section structure (first sub-section < second sub-section < third sub-section) with the cladding light leakage amount gradually increasing along the signal light transmission direction, which can realize gradient and efficient step-by-step filtering of the cladding light, avoiding the risk of local overheating caused by the one-time concentration of cladding light energy, and guaranteeing a high filtering rate of ≥90% in a short size of 1.8-2.2 cm; at the same time, the gradient leakage design can more evenly dissipate the cladding light energy, significantly improving the stability and service life of the device, and perfectly meeting the design requirements of the compact filter.

[0012] Preferably, the cladding light filtering rate of the fiber processing section is ≥90% when the through light power is 104 W.

[0013] Specifically, a high filtering rate of ≥90% can still be stably achieved under a high power condition of 104 W, which not only takes into account the use requirements of high-power laser application scenarios, but also improves the integration and adaptation of devices such as laser output heads and mode field adapters by virtue of the ultra-short size, providing strong support for the miniaturization and high-reliability operation of the laser whole machine.

[0014] Preferably, the length of the first sub-section is 0.4-0.6 cm, the length of the second sub-section is 0.4-0.6 cm, and the length of the third sub-section is 0.9-1.1 cm.

[0015] Specifically, the length ratio controls the total length of the fiber processing section in the ultra-short range of 1.8~2.2 cm, which precisely meets the compact design requirements. The shorter and similar first and second sub-sections can achieve preliminary and moderate gradient leakage of cladding light, and the longer third sub-section can meet the deep leakage requirement. The stepwise distribution effectively avoids local overheating caused by the concentration of cladding light energy.

[0016] Preferably, the fiber processing section comprises a tapered waist and at least one gradual transition part, one end of the gradual transition part is connected with the fiber body, and the other end of the gradual transition part is connected with the tapered waist; wherein the diameter of the gradual transition part decreases along the direction close to the tapered waist.

[0017] Specifically, the fiber processing section is matched with the tapered waist and the gradual transition part (both ends are connected with the tapered waist) whose diameter decreases along the direction close to the tapered waist. On the one hand, the diameter gradient change of the gradual transition part can guide the cladding light to leak gradually along the transmission direction, avoiding local overheating caused by energy concentrated leakage, and improving the safety of device operation. On the other hand, the cooperative structure of the tapered waist and the gradual transition part can efficiently destroy the cladding total reflection condition in the ultra-short size of 1.8~2.2 cm, guaranteeing the high filtering rate, and meeting the compact design requirements. At the same time, the smooth diameter gradient change can reduce the stress concentration caused by the sudden change of the fiber structure, enhance the mechanical strength of the fiber processing section, reduce the risk of fracture, and the overall structure is simple and controllable, without additional device volume, further improving the integration of the device with the packaging assembly and various fiber devices.

[0018] Preferably, the leakage amount of cladding light of the gradual transition part increases along the direction close to the tapered waist.

[0019] Specifically, the above design can guide the cladding light to leak gradually and uniformly along the transmission, avoiding local overheating caused by the energy concentrated in a certain section, and significantly improving the safety of device operation under high-power working conditions. At the same time, the gradient increase of the leakage amount can continuously and efficiently destroy the cladding total reflection condition in the ultra-short size of less than 1.8~2.2 cm, guaranteeing the cladding light filtering rate to meet the standard, and meeting the core requirements of compact design. In addition, the smooth leakage amount gradient change does not need to rely on the sudden change of the structure, can reduce the stress concentration caused by the sudden change of the performance of the fiber, enhance the mechanical strength of the processing section to reduce the risk of fracture, and the overall structure is simple and controllable, without additional space.

[0020] Correspondingly, the application also provides a preparation method of the compact cladding light filter according to any one of the above, the preparation method comprising the following steps: S10, using a stripping machine to strip the coating layer of the cladding light filtering area on the fiber body; S20, soaking the corresponding section of the cladding light filtering area in a hydrofluoric acid solution for preliminary corrosion, and then washing with deionized water after corrosion. S30, using a stripping machine to perform secondary processing on the stripped opening after preliminary corrosion, to strip the residual coating layer and the corrosion damaged layer at the stripped opening; S40, using a special corrosion paste to perform secondary corrosion processing on the section corresponding to the cladding light filtering area, to obtain a fiber processing section; wherein the fiber processing section comprises a core and a first cladding layer arranged in turn from the inside to the outside along the radial direction, and the first cladding layer is a non-total reflection structure that cannot maintain total reflection conditions; S50, sleeving a packaging assembly outside the fiber processing section, and fixing the two ends of the packaging assembly with the fiber body, to obtain a compact cladding light filter.

[0021] Specifically, the S10 step completely removes the coating layer of the cladding light filtering area, avoids the coating layer from shielding the subsequent corrosion and etching process, ensures that the subsequent processing can directly act on the cladding layer of the fiber processing section, and lays a foundation for precisely preparing the first cladding layer of the non-total reflection structure.

[0022] In the S20 step, the preliminary corrosion by hydrofluoric acid can pre-damage the total reflection structure of the part of the cladding layer corresponding to the cladding light filtering area, optimize the process parameters and improve the efficiency of the subsequent secondary corrosion processing; the deionized water cleaning can completely remove the residual acid, avoid continuous corrosion of the optical fiber by the acid, protect the fiber core from damage, and maintain the stability of signal light transmission.

[0023] In the S30 step, the residual coating layer and the corrosion damaged layer at the stripped opening are stripped, the interference of impurities on the subsequent process is eliminated, and the precision of the secondary corrosion processing is improved; at the same time, the shape of the stripped opening is modified, the stress concentration on the surface of the optical fiber is reduced, the mechanical strength of the fiber processing section is enhanced, and the risk of breakage during use is reduced.

[0024] In the S40 step, the secondary corrosion processing can precisely control the etching depth, range and shape, efficiently convert the cladding layer of the target section into the first cladding layer that cannot maintain total reflection conditions, and ensure that the fiber processing section realizes a cladding light filtering rate of ≥90% in an ultra-short size of 1.8~2.2 cm; the etching process is precisely controllable, can avoid the core area, does not damage the signal light transmission channel, protects the stable transmission of signal light, and has high process efficiency and good consistency, which is suitable for batch production requirements.

[0025] In the S50 step, the packaging assembly is sleeved and fixed at both ends, which can not only stabilize the position of the fiber processing section and avoid displacement affecting the filtering effect during use, but also isolate external interference such as dust and water vapor, and protect the stability of the structure and performance of the processing section; after packaging, the device size is not additionally increased, which is consistent with the compact design, and ensures the integration of the filter with various optical fiber devices.

[0026] Preferably, the encapsulation component is a thin glass tube, which encapsulates the optical fiber processing segment by dispensing adhesive. The small size of the thin glass tube matches the ultra-short design of the optical fiber processing segment, without increasing the overall size of the device, perfectly meeting the compact requirements. The dispensing encapsulation method can firmly fix the optical fiber processing segment, preventing it from shifting during use and affecting the cladding light filtering effect. At the same time, it can form a reliable seal, isolating external dust, moisture and other interference, protecting the structural and performance stability of the optical fiber processing segment.

[0027] Preferably, in step S20, the mass concentration of the hydrofluoric acid solution is 35%~45%, and the initial corrosion time is 28~32 min; in step S40, the specially prepared corrosion paste is made by mixing hydrofluoric acid solution and thickener, and the mass ratio of hydrofluoric acid solution to thickener is (1~3):1.

[0028] Specifically, the aforementioned hydrofluoric acid solution can gently and efficiently pre-destroy the total internal reflection structure of the cladding, laying the foundation for optimizing process parameters and shortening etching time in subsequent secondary etching. It also allows for precise control of etching depth and range, preventing damage to the fiber core and impacting signal transmission due to excessive concentration or duration. Furthermore, it is suitable for processing large cladding diameters of 400-800 μm, exhibiting strong process consistency and ensuring stable subsequent forming and filtration performance of the fiber processing section during mass production. Simultaneously, the specially formulated etching paste, with its viscosity adjusted by a thickener, allows for precise control of the etching range and depth, preventing the etching solution from flowing randomly and damaging non-target areas (especially the fiber core). This ensures targeted action only on the cladding to efficiently form a non-total internal reflection structure. This formulation combines flexibility and stability, improving the process controllability and consistency of secondary etching, helping to achieve high cladding light filtration rates within ultra-short dimensions, while also meeting the needs of mass production and ensuring stable performance of the fiber processing section.

[0029] Preferably, the secondary etching process in step S40 specifically includes: performing secondary etching on the section processed in step S20 in three segments along the signal light transmission direction; wherein, the length of the first segment is 0.4~0.6cm and the etching time is 14~16min; the length of the second segment is 0.4~0.6cm and the etching time is 24~26min; and the length of the third segment is 0.9~1.1cm and the etching time is 44~46min.

[0030] Specifically, this design can guide the cladding light to leak in a stepped manner and dissipate energy evenly by gradually increasing the etching depth, thus avoiding local overheating. It can also stably achieve a high filtration efficiency of ≥90% within an ultra-short overall size of 1.8~2.2cm. The etching parameters are precise and controllable, avoiding the fiber core area to ensure stable signal light transmission. At the same time, the process has strong consistency, is suitable for mass production, and perfectly matches the design requirements of compact filters and the integration compatibility with various fiber optic devices.

[0031] The beneficial effects of the present invention are as follows: Unlike the prior art, the present invention provides a compact cladding optical filter and its preparation method. The compact cladding optical filter includes an optical fiber body and an optical fiber processing segment embedded in the optical fiber body, as well as an encapsulation assembly sleeved on the outside of the optical fiber processing segment and fixedly connected to the optical fiber body at both ends. The length of the optical fiber processing segment is 1.8~2.2cm. The optical fiber processing segment includes a fiber core and a first cladding arranged radially from the inside to the outside. The first cladding is a non-total reflection structure that cannot maintain total reflection conditions. The compact cladding optical filter provided by this invention achieves a cladding optical filtration efficiency of ≥90% by using an ultra-short fiber processing segment of 1.8~2.2cm combined with a first cladding non-total reflection structure. This overcomes the problems of traditional filters requiring long dimensions to meet standards and being easily limited by packaging. Furthermore, it ensures filtration performance without excessive etching, effectively avoiding the risk of decreased fiber mechanical strength and ensuring structural reliability. Its ultra-short size allows for flexible integration near the front fiber of the laser output head input end, mode field adapter, combiner pigtail, and fiber Bragg grating, without affecting the original device packaging size. Finally, through adaptation and integration with various fiber optic devices, it provides strong support for the miniaturization and integration upgrade of the entire laser system. Attached Figure Description

[0032] Fig. 1 This is a schematic diagram of the compact cladding optical filter provided in Embodiment 1. Fig. 2 This is a schematic diagram of the fabrication method of the compact cladding optical filter provided in Embodiment 1; Fig. 3 This is a schematic diagram of the compact cladding optical filter provided in Embodiment 2; Fig. 4 This is a schematic diagram of the compact cladding optical filter provided in Embodiment 3; In the accompanying drawings: 100 – compact cladding optical filter; 10 – fiber body; 20 – fiber processing section; 21 – first sub-segment; 22 – second sub-segment; 23 – third sub-segment; 24 – gradient transition section; 25 – tapered waist. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] The purpose of this invention is to address the shortcomings of existing technologies by providing a compact cladding optical filter and its fabrication method. This device is a compact fiber optic device. It is compatible with large cladding diameters of 400µm, 600µm, and 800µm, shortening the length of the cladding optical filtering section to approximately 2cm. It can ensure a cladding optical filtering efficiency of over 90% when outputting high-power lasers, with a maximum optical power of up to 104W (further testing required). One fabrication process for the aforementioned compact cladding optical filter is as follows: First, the fiber processing section with the coating layer removed is etched using HF etching. Then, the etched section is treated with a stripping machine to prevent heat generation after light transmission. Subsequently, a secondary etching process is used to further etch this fiber section, destroying the total internal reflection structure of the cladding. To ensure device stability and easy integration, the fiber processing section is encapsulated in a thin glass tube.

[0035] The technical solution of the present invention will now be described in conjunction with specific embodiments.

[0036] Example 1: Please see Figs. 1-2 This embodiment 1 provides a compact cladding optical filter 100 and its preparation method. The compact cladding optical filter 100 includes an optical fiber body 10 and an optical fiber processing segment 20 embedded in the optical fiber body 10, as well as an encapsulation assembly sleeved on the outside of the optical fiber processing segment 20 and fixedly connected to the optical fiber body 10 at both ends. The length of the optical fiber processing segment 20 is 2 cm. The optical fiber processing segment 20 includes a fiber core and a first cladding arranged radially from the inside to the outside. The first cladding is a non-total reflection structure that cannot maintain total reflection conditions.

[0037] In Embodiment 1, the optical fiber body 10 includes a fiber core, a second cladding, and a coating layer arranged radially from the inside out. The second cladding is a total internal reflection structure that can maintain cladding light transmission. The optical fiber body 10 is a 20 / 400 optical fiber (the diameter of the fiber core is 20 μm, and the diameter of the second cladding is 400 μm) and its length is 0.98 m.

[0038] In Embodiment 1, the optical fiber processing segment 20 includes a first sub-segment 21, a second sub-segment 22, and a third sub-segment 23 connected sequentially along the signal light transmission direction. The cladding light leakage of the first sub-segment 21 is less than that of the second sub-segment 22, and the cladding light leakage of the second sub-segment 22 is less than that of the third sub-segment 23. The length of the first sub-segment 21 is 0.5 cm, the length of the second sub-segment 22 is 0.5 cm, and the length of the third sub-segment 23 is 1 cm.

[0039] The compact cladding light filter 100 fabrication method provided in this embodiment is simple to operate, has a good filtering effect, and only supports unidirectional light transmission, as detailed below: Step (1): Select a section of optical fiber, cut 1m, and use a stripping machine to remove the coating layer in the middle 2cm.

[0040] Step (2): Immerse the section with the coating removed in a 40wt% hydrofluoric acid solution for 30 minutes to corrode it, and then thoroughly clean it with deionized water.

[0041] Step (3): Use a peeling machine to treat the peeled area again (because the peeled area is damaged, a portion of the coating needs to be peeled off).

[0042] Step (4): A special etching paste was used to perform secondary etching treatment on the cladding light filtering area. The first sub-segment 21 (0.5cm) was etched for 15min, the second sub-segment 22 (0.5cm) was etched for 30min, and the third sub-segment 23 (1cm) was etched for 45min. The special etching paste was made by mixing 40wt% hydrofluoric acid solution with kaolin, and the mass ratio of 40wt% hydrofluoric acid solution to kaolin was 1:1.

[0043] Step (5): Place the processed fiber segment 20 into a thin glass tube and seal it with glue.

[0044] The cladding light filtering efficiency of the compact cladding optical filter 100 provided in Example 1 was tested. The test results showed that the cladding light filtering efficiency of the 2cm fiber processing section 20 reached 90% under 104W laser power. The device had good mechanical strength and the surface temperature of the housing was stable below 65°C.

[0045] Example 2: This embodiment 2 provides a compact cladding optical filter 100 and its preparation method. The structure of the compact cladding optical filter 100 is roughly the same as that of the compact cladding optical filter 100 provided in embodiment 1, with the only difference being: In embodiment 2, the optical fiber processing section 20 includes two gradient transition sections 24 (formed by secondary etching process) and a tapered waist section 25 located between the two gradient transition sections 24. The other end of each gradient transition section 24 away from the tapered waist section 25 is connected to the optical fiber body 10. The length of each gradient transition section 24 is 0.5 cm, and the length of the tapered waist section 25 is 1 cm.

[0046] The compact cladding light filter 100 provided in this embodiment 2 supports bidirectional light transmission, provides more uniform light filtering, and has a higher filtering rate for the same length, but the manufacturing process is relatively complex.

[0047] The cladding light filtering efficiency of the compact cladding optical filter 100 provided in Example 2 was tested. The test results showed that the cladding light filtering efficiency of the 2cm fiber processing section 20 reached 92% under 104W laser power. The device had good mechanical strength and the surface temperature of the housing was stable below 65°C.

[0048] Example 3: This embodiment 3 provides a compact cladding optical filter 100 and its preparation method. The structure of the above-mentioned compact cladding optical filter 100 is roughly the same as that of the compact cladding optical filter 100 provided in embodiment 1, the only difference being: In embodiment 3, the fiber processing section 20 includes a gradient transition section 24 (formed by secondary etching process) and a tapered waist section 25 connected to the gradient transition section 24. The other end of the gradient transition section 24 away from the tapered waist section 25 is connected to the fiber body 10. The length of the gradient transition section 24 is 0.5 cm, and the length of the tapered waist section 25 is 1.5 cm.

[0049] The compact cladding light filter 100 provided in this embodiment 3 adopts a single-sided gradient structure, with a longer waist for the same length; although it cannot transmit light in both directions, it can further improve the filtering efficiency.

[0050] The cladding light filtering efficiency of the compact cladding optical filter 100 provided in Example 3 was tested. The test results showed that the cladding light filtering efficiency of the 2cm fiber processing section 20 reached 91% under 104W laser power. The device had good mechanical strength and the surface temperature of the housing was stable below 65°C.

[0051] Comparative Example 1 (shorter hydrofluoric acid corrosion time): Comparative Example 1 provides a compact cladding optical filter 100 and its preparation method. The structure and preparation method of the above-mentioned compact cladding optical filter 100 are roughly the same as those of the compact cladding optical filter 100 provided in Example 1, except that the difference lies only in step (2) of the preparation method: Step (2): Immerse the section with the coating removed in hydrofluoric acid solution for 15 minutes to corrode it, and then thoroughly clean it with deionized water.

[0052] The cladding light filtering efficiency of the compact cladding optical filter 100 provided in Comparative Example 1 was tested. The test results showed that the cladding light filtering efficiency of the 2cm fiber processing section 20 reached 85% at a laser power of 104W.

[0053] Comparative Example 2 (Single Secondary Corrosion Treatment): Comparative Example 2 provides a compact clad optical filter 100 and its preparation method. The structure and preparation method of the above compact clad optical filter 100 are roughly the same as those of the compact clad optical filter 100 provided in Example 1. The only difference is that the preparation method does not include step (2) and only adopts a secondary etching process for segmented processing.

[0054] The cladding light filtering efficiency of the compact cladding optical filter 100 provided in Comparative Example 2 was tested. The test results showed that the cladding light filtering efficiency of the 2cm fiber processing section 20 reached 75% under a laser power of 104W, which was not optimal.

[0055] Comparative Example 3 (Traditional Cladding Optical Filter): Comparative Example 3 shows a cladding light filter with a length of 10.5 cm (the fiber processing section 20 used to filter out cladding light is 10.5 cm) prepared using conventional processes.

[0056] The cladding light filtering efficiency of the conventional cladding light filter provided in Comparative Example 3 was tested. The test results showed that the cladding light filtering efficiency of the 10.5cm fiber processing section 20 reached 90% at a laser power of 104W. However, the device size was too large, which severely limited the miniaturization of the laser.

[0057] Comparative Example 4 (corrosion with corrosive compound after tapering): Comparative Example 4 provides a compact cladding optical filter 100 and its preparation method. The structure and preparation method of the above-mentioned compact cladding optical filter 100 are roughly the same as those of the compact cladding optical filter 100 provided in Example 1, except that the difference lies only in step (4) of the preparation method: Step (4): First, the cladding light filtering area is subjected to overall tapering treatment. Then, a special etching paste is used to perform secondary etching treatment on the cladding light filtering area: the first sub-segment 21 (0.5cm) is subjected to secondary etching treatment for 15min, the second sub-segment 22 (0.5cm) is subjected to secondary etching treatment for 30min, and the third sub-segment 23 (1cm) is subjected to secondary etching treatment for 45min. The special etching paste is made by mixing 40wt% hydrofluoric acid solution with kaolin, and the mass ratio of 40wt% hydrofluoric acid solution to kaolin is 1:1.

[0058] The cladding light filtering efficiency of the conventional cladding light filter provided in Comparative Example 4 was tested. The test results showed that at a laser power of 104W, the cladding light filtering efficiency of the 10.5cm fiber processing section 20 reached 87%, which was not optimal and the core-cladding ratio changed.

[0059] As can be seen from the above comparison, the optical fiber processing segment 20 prepared by the present invention through "hydrofluoric acid etching + specially formulated etching paste etching" achieves a filtration rate far exceeding that of a single etching process within an extremely short dimension of only 2 cm, and successfully resolves the contradiction between high strength and high efficiency. Compared with traditional long-size solutions, the present invention achieves a significant reduction in device size (from 10.5 cm to 2 cm, a reduction of approximately 500%) while maintaining comparable performance, demonstrating outstanding technological progress.

[0060] In summary, unlike existing technologies, this invention utilizes a core process of "hydrofluoric acid etching + specially formulated etching paste etching." By employing a sequential cladding treatment method using hydrofluoric acid solution and specially formulated etching paste, along with control over process parameters, it achieves deep processing of the first cladding of the optical fiber processing section 20, thereby disrupting the total internal reflection structure of the first cladding. The ultra-short cladding optical filter unit manufactured using this process possesses the structural advantages of smaller length and a filtration efficiency greater than 90%. Furthermore, this small-sized cladding optical filter is not easily limited by the size of the packaging shell and can be integrated with various optical fiber devices (such as integration with a laser output head, integration on the optical fiber before the laser head input end, integration on a mode field adapter without affecting the packaging size, integration on a combiner pigtail, and integration near a fiber optic grating), exhibiting excellent integration adaptability.

[0061] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0062] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A compact cladding optical filter, characterized in that, It includes an optical fiber body and an optical fiber processing segment embedded in the optical fiber body, as well as an encapsulation assembly sleeved on the outside of the optical fiber processing segment and fixedly connected to the optical fiber body at both ends. The length of the fiber processing segment is 1.8~2.2cm; the fiber processing segment includes a fiber core and a first cladding arranged radially from the inside to the outside, and the first cladding is a non-total reflection structure that cannot maintain total reflection conditions.

2. The compact cladding optical filter according to claim 1, characterized in that, The optical fiber body includes a fiber core, a second cladding, and a coating layer arranged radially from the inside out. The second cladding is a total internal reflection structure that can maintain cladding light transmission.

3. The compact cladding optical filter according to claim 1, characterized in that, The optical fiber processing segment includes a first sub-segment, a second sub-segment, and a third sub-segment connected sequentially along the signal light transmission direction. The cladding light leakage of the first sub-segment is less than that of the second sub-segment, and the cladding light leakage of the second sub-segment is less than that of the third sub-segment.

4. The compact cladding optical filter according to claim 3, characterized in that, The cladding light filtering rate of the optical fiber processing section is ≥90% at an optical power of 104W.

5. The compact cladding optical filter according to claim 3, characterized in that, The length of the first sub-segment is 0.4~0.6cm, the length of the second sub-segment is 0.4~0.6cm, and the length of the third sub-segment is 0.9~1.1cm.

6. The compact cladding optical filter according to claim 1, characterized in that, The fiber processing section includes a tapered waist and at least one gradient transition section, one end of which is connected to the fiber body and the other end of which is connected to the tapered waist. The diameter of the gradual transition portion decreases in a gradient direction along the direction close to the waist of the cone.

7. The compact cladding optical filter according to claim 6, characterized in that, The cladding light leakage of the gradient transition section increases in a gradient direction towards the waist of the cone.

8. A method for fabricating a compact cladding optical filter as described in any one of claims 1 to 7, characterized in that, The preparation method includes the following steps: S10, use a stripping machine to strip the coating layer of the cladding light filtering area on the optical fiber body; S20, the corresponding section of the cladding light filtering area is immersed in hydrofluoric acid solution for preliminary corrosion, and then cleaned with deionized water after corrosion; S30, a stripping machine is used to perform secondary treatment on the peeled surface after the initial corrosion to remove the residual coating layer and corrosion damage layer at the peeled surface; S40, a specially formulated etching paste is used to perform a secondary etching treatment on the corresponding section of the cladding light filtering region to obtain the optical fiber processing section; wherein, the optical fiber processing section includes a fiber core and a first cladding arranged radially from the inside to the outside, and the first cladding is a non-total reflection structure that cannot maintain total reflection conditions; S50, the encapsulation component is sleeved on the outside of the optical fiber processing section, and both ends of the encapsulation component are fixedly connected to the optical fiber body to obtain the compact cladding optical filter.

9. The method for fabricating a compact cladding optical filter according to claim 8, characterized in that, In step S20, the mass concentration of the hydrofluoric acid solution is 35%~45%, and the initial corrosion time is 28~32 minutes; in step S40, the specially formulated corrosion paste is made by mixing the hydrofluoric acid solution and the thickener, and the mass ratio of the hydrofluoric acid solution to the thickener is (1~3):

1.

10. The method for fabricating a compact cladding optical filter according to claim 8, characterized in that, The secondary etching process in step S40 specifically includes: performing secondary etching on the section processed in step S20 in three segments along the signal light transmission direction; wherein, the first segment is 0.4~0.6cm long and the etching time is 14~16min; the second segment is 0.4~0.6cm long and the etching time is 24~26min; the third segment is 0.9~1.1cm long and the etching time is 44~46min.

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