A magnetic control end face protection device special for hollow core optical fiber and a preparation method thereof

Abstract

The application discloses a magnetic control end face protection device special for hollow optical fiber and a preparation method thereof. The device comprises a fixed base, which is used for sleeving and fixing the periphery of the end of the hollow optical fiber; a magnetic control hollow fiber ring, which is composed of a polymer matrix and pre-magnetized magnetic particles dispersed in the polymer matrix, and can be deformed in a radial contraction or radial expansion state under the action of an external magnetic field; the magnetic control hollow fiber ring is arranged on the fixed base and sleeved on the end of the hollow optical fiber, and is used for forming a physical barrier for the end face of the hollow optical fiber in the radial contraction state; and a flexible protective layer, which is arranged on the inner wall surface of the magnetic control hollow fiber ring. The end face protection device can realize remote reversible protection and zero power consumption standby for the end face of the hollow optical fiber.

Description

Technical Field

[0001] This invention relates to the field of optical fiber manufacturing technology, specifically to a magnetically controlled end-face protection device for hollow optical fibers and its preparation method. Background Technology

[0002] Hollow-core optical fiber, using air or gas as its light-guiding core, boasts significant advantages such as low transmission delay, low nonlinear coefficient, high laser damage threshold, and wide-band transmission. In recent years, it has achieved breakthroughs in cutting-edge fields such as high-speed optical interconnects in intelligent computing centers, high-power laser energy transmission, quantum state transmission, and high-precision sensing. However, the open hollow-core structure of its end face makes it extremely sensitive to contaminants such as dust, water vapor, oil, and radiation dust. End face contamination directly leads to optical path scattering, decreased coupling efficiency, and deterioration of sensing accuracy. Furthermore, in high-power laser transmission scenarios, contaminants absorb light energy and generate heat accumulation, easily causing end face damage and even system failure.

[0003] Currently, fiber optic end-face protection mainly relies on manually plugged-in rubber dust caps or disposable UV adhesive sealing solutions. Manual dust caps have the following inherent drawbacks: firstly, they require manual operation, which is inefficient and prone to loss in high-density deployment scenarios; secondly, they cannot be remotely controlled, posing a high risk of personnel intervention in hazardous environments such as nuclear radiation, deep sea, and underground mines; and thirdly, they lack status awareness capabilities, making it impossible to detect in real time whether the end face has been touched or contaminated. While UV adhesive sealing can achieve permanent hermetically sealed packaging, its low-viscosity adhesive is easily drawn into the micron-level air channels of hollow optical fibers due to capillary action, causing permanent blockage. Furthermore, the effect is irreversible after curing, making it unsuitable for connectors, sensor probes, and other applications requiring repeated opening and closing. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a dedicated magnetron sputtering end-face protection device for hollow optical fibers and its fabrication method. The end-face protection device of the present invention can achieve remote reversible protection of the hollow optical fiber end face and zero-power standby.

[0005] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: This invention provides a dedicated magnetron end-face protection device for hollow optical fibers, comprising: A fixing base is used to sleeve and fix the outer periphery of the end of the hollow optical fiber; Magnetically controlled hollow fiber rings are composed of a polymer matrix and pre-magnetized magnetic particles dispersed in the polymer matrix, and can undergo radial contraction or radial expansion deformation under the action of an external magnetic field. The magnetically controlled hollow fiber ring is disposed on the fixed base and sleeved on the end of the hollow fiber, which is used to form a physical barrier on the end face of the hollow fiber in the radially contracted state. A flexible protective layer is disposed on the inner wall surface of the magnetically controlled hollow fiber ring.

[0006] Furthermore, the magnetically controlled hollow fiber ring has a predetermined remanent magnetization intensity, which keeps it in a radially contracted state when there is no external magnetic field; by applying an external magnetic field with appropriate direction or intensity, the magnetically controlled hollow fiber ring is driven to switch to a radially expanded state.

[0007] When the optical path needs to be opened, an external magnetic field of suitable direction or intensity is applied. The pre-magnetized magnetic particles inside the magnetically controlled hollow fiber ring are magnetized by the external magnetic field, generating a magnetic torque that is opposite in direction to the remanent magnetization or sufficient to overcome the remanent magnetization attraction. This drives the magnetically controlled hollow fiber ring to undergo radial expansion deformation, causing the flexible protective layer to detach from the outer wall of the optical fiber, thus opening the optical path at the end face. After the external magnetic field is removed, the magnetically controlled hollow fiber ring returns to its contracted state by relying on the remanent magnetization.

[0008] Furthermore, in the magnetically controlled hollow fiber ring, the concentration of the pre-magnetized magnetic particles is distributed in a gradient, wherein the concentration in the outer wall region of the magnetically controlled hollow fiber ring is 40%~70wt%, and the concentration in the inner wall region is 10%~30wt%.

[0009] This design concentrates the driving force on the outer wall region of the magnetically controlled hollow fiber ring under the action of an external magnetic field. The inner wall region has a low magnetic powder concentration and good flexibility, which allows it to fit tightly against the outer wall of the optical fiber without damaging the fiber coating during shrinkage.

[0010] Furthermore, the pre-magnetized magnetic particles are oriented in the polymer matrix, with their easy magnetization axis oriented circumferentially along the magnetically controlled hollow fiber ring. This circumferentially oriented arrangement of the pre-magnetized magnetic particles ensures that the magnetostrictive force acts strictly radially, avoiding skewed deformation and improving driving efficiency and bonding uniformity.

[0011] Furthermore, the polymer matrix is ​​a piezoelectric polymer, and the magnetically controlled hollow fiber ring also includes an electrode layer disposed on its inner and outer walls. The electrode layer is used to draw out the electrical signal generated when the piezoelectric polymer is deformed or subjected to external force, so as to realize the self-sensing of the contact of the hollow fiber end face or the device status.

[0012] When the hollow fiber end face is impacted by dust, touched by foreign objects, or deformed by the device itself, the piezoelectric polymer generates a piezoelectric effect due to the force, forming a characteristic voltage signal between the electrode layers. This signal is led out through the electrode layers and transmitted to an external monitoring circuit to realize real-time sensing and alarm of end face touch events; at the same time, the waveform characteristics of the piezoelectric signals generated by different deformation states (contraction / expansion) are different, which can be used for self-monitoring of the device status.

[0013] Preferably, the piezoelectric polymer is β-crystalline enriched polyvinylidene fluoride or its copolymer; the electrode layer is a flexible transparent conductive layer selected from one or more of PEDOT:PSS, silver nanowires, carbon nanotubes or graphene.

[0014] Furthermore, the axial length of the magnetically controlled hollow fiber ring is 2~10mm, the wall thickness is 0.1~0.8mm, and the inner diameter in the radially contracted state is 0.05~0.3mm smaller than the outer diameter of the hollow fiber.

[0015] Preferably, the flexible protective layer is a black elastomer material or a radiation-resistant elastomer material, selected from one or more of polydimethylsiloxane, fluororubber, thermoplastic polyurethane or ethylene propylene diene monomer (EPDM) rubber, and its thickness is 10~100μm.

[0016] When the magnetically controlled hollow fiber ring shrinks, the flexible protective layer acts as an intermediate medium and is uniformly attached to the outer wall of the optical fiber. On the one hand, it compensates for the microscopic unevenness caused by the protrusion of magnetic particles and achieves effective physical barrier; on the other hand, it buffers the mechanical action of magnetic attraction on the optical fiber coating through elastic deformation, thus avoiding damage.

[0017] Another aspect of the present invention discloses a method for preparing a magnetron end-face protection device for hollow optical fibers, comprising the following steps: Step S1, preparing magnetic hollow fiber precursor: The polymer matrix, pre-magnetized magnetic particles and solvent are mixed to form a spinning solution, which is then extruded through a hollow fiber forming mold using a spinning process and formed in a coagulation bath to obtain the magnetic hollow fiber precursor; During the extrusion molding process, a circumferentially oriented external magnetic field is applied to the magnetic hollow fiber precursor to make the pre-magnetized magnetic particles align along the fiber circumference; Step S2: Stretching treatment: The magnetic hollow fiber precursor obtained in step S1 is subjected to stretching treatment. Step S3, Cutting and Magnetizing: The magnetic hollow fiber precursor obtained in step S2 is cut into fiber ring segments of predetermined length and placed in a pulsed magnetic field for magnetization treatment to impart a predetermined remanence to obtain a magnetically controlled hollow fiber ring. Step S4, forming a flexible protective layer: The inner wall surface of the magnetically controlled hollow fiber ring obtained in step S3 is coated or impregnated with a flexible material, and then cured to form a flexible protective layer; Step S5, Assembly and Fixing: The magnetically controlled hollow fiber ring with a flexible protective layer obtained in step S4 is fixed to the fixing base by adhesive bonding, and the fixing base is sleeved and fixed to the periphery of the hollow fiber end.

[0018] Further, in step S1, the mass fraction of the polymer matrix in the spinning solution is 12%~20%, and the mass fraction of the pre-magnetized magnetic particles is 30%~65%; the coagulation bath is a solution of water, ethanol, or a mixture of both, and the temperature is 30~70℃.

[0019] Furthermore, in step S1, the circumferentially oriented external magnetic field is provided by a ring-shaped permanent magnet or a ring-shaped electromagnetic coil, with a magnetic field strength of 0.5~2T, and the action time is the time it takes for the fiber to pass through the magnetic field region at the spinning traction linear speed.

[0020] Furthermore, the stretching process of the magnetic hollow fiber precursor includes: unidirectional or multi-stage stretching at a temperature of 60~100℃ with a stretching ratio of 2~10 times.

[0021] Furthermore, a polarization electric field of 5~30kV / mm is applied during the stretching process to induce the polymer matrix to transform into the β crystal form through polarization treatment.

[0022] Furthermore, the method also includes forming electrode layers on the inner and outer walls of the polarized magnetic hollow fiber precursor, respectively.

[0023] Further, in step S4, the flexible material is coated by dip coating or spray coating, and cured by heat curing or ultraviolet light curing; in step S5, the bonding method is ultraviolet curing adhesive bonding.

[0024] In the above preparation method, pre-magnetized magnetic particles are pre-arranged along the fiber circumference through online magnetic field orientation during the spinning process; precise and controllable remanence is imparted to the magnetically controlled hollow fiber rings through pulse magnetization after cutting; and piezoelectric β-crystals can be induced from β-crystal-enriched polyvinylidene fluoride or its copolymers through stretching polarization treatment. These process steps ensure the realization of the above-mentioned driving and sensing functions at the material level.

[0025] The beneficial effects of this invention are as follows: (1) Realize remote magnetic control and zero power consumption standby: By pre-magnetizing magnetic particles, the hollow fiber ring of the magnetic control is given a predetermined residual magnetism, realizing the zero power consumption protection state of radial contraction when there is no external magnetic field, and achieving zero energy consumption in standby; by applying an external magnetic field, it can be remotely switched to the expansion state and the optical path can be opened, thus solving the problem of inconvenience of manual operation in high-density or dangerous environments, and significantly reducing energy consumption.

[0026] (2) Improve driving efficiency through magnetic powder gradient distribution and directional arrangement: The concentration of pre-magnetized magnetic particles is distributed in a gradient of high on the outside and low on the inside, and the easy magnetization axis is oriented along the circumferential direction of the magnetically controlled hollow fiber ring, so that the magnetostrictive force is concentrated on the outer wall and the radial action is precise. The inner wall is compliant with the outer wall of the optical fiber, avoiding hard particles from scratching the coating and improving deformation uniformity and sealing performance.

[0027] (3) Realizes piezoelectric self-sensing intelligent monitoring: The present invention also uses a piezoelectric polymer matrix and sets inner and outer wall electrode layers, which can generate characteristic electrical signals when the end face is touched or when the magnetically controlled hollow fiber ring changes, and sense foreign object impact or device status in real time, providing a data basis for predictive maintenance and automated control without the need for additional sensors.

[0028] (4) Achieve flexible protective layer to adapt to extreme environment: The flexible protective layer in this invention can compensate for the micro-unevenness caused by the protrusion of magnetic particles and protect the fiber coating. At the same time, appropriate weather-resistant materials can be selected according to different scenarios such as ocean, nuclear radiation, and outdoor, so as to achieve long-term maintenance-free operation.

[0029] (5) Achieving synergistic performance through integrated preparation process: In the spinning process, the present invention applies a circumferential magnetic field to achieve the directional arrangement of pre-magnetized magnetic particles, combined with stretching polarization to induce the generation of piezoelectric β crystals, and then precisely controls the residual magnetism through pulse magnetization, so that the driving and sensing functions are integrated at the material level, with a wide process window and suitable for mass production.

[0030] (6) Realize reversible opening and closing and repeated use: The present invention remotely drives the magnetically controlled hollow fiber ring to reversibly switch between the contraction and expansion states through an external magnetic field. It can be opened and closed multiple times without the need for a damaging device, which can meet the needs of connectors, sensor probes and other devices that require repeated plugging and unplugging or switching of optical paths. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the magnetically controlled end-face protection device for hollow optical fibers according to the present invention.

[0032] The components include: 1. Fixed base; 2. Magnetically controlled hollow fiber ring; 3. Flexible protective layer; 4. Hollow fiber. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] like Figure 1 As shown, this invention provides a dedicated magnetron sputtering end-face protection device for hollow optical fibers. The device includes a fixed base 1, a magnetron sputtering hollow fiber ring 2, and a flexible protective layer 3.

[0035] The fixing base 1 is used to sleeve and fix the outer periphery of the end of the hollow optical fiber 4. The material of the fixing base 1 is not limited. For example, it can be made of photosensitive resin by 3D printing, or it can be made of other polymers or metal materials, as long as it can provide stable support and fixation.

[0036] The magnetically controlled hollow fiber ring 2 is disposed on the fixed base 1 and sleeved on the end of the hollow fiber 4, serving to physically block the end face of the hollow fiber 4 in a radially contracted state. The magnetically controlled hollow fiber ring 2 is composed of a polymer matrix and pre-magnetized magnetic particles dispersed within the polymer matrix, and is capable of radial contraction or radial expansion deformation under the action of an external magnetic field.

[0037] More specifically, the magnetically controlled hollow fiber ring 2 is sleeved on the end of the hollow fiber 4 and extends axially beyond its end face, and the flexible protective layer 3 is disposed on the inner wall surface of the magnetically controlled hollow fiber ring 2; in the radial contraction state, the magnetically controlled hollow fiber ring 2 drives the flexible protective layer 3 on its inner wall surface to retract inward, so that the flexible protective layer 3 adheres to the outer wall of the hollow fiber 4 and simultaneously covers or blocks the end face opening of the hollow fiber 4, forming a physical barrier to the end face area.

[0038] The magnetically controlled hollow fiber ring 2 has a predetermined remanent magnetization, allowing it to remain in a radially contracted state when no external magnetic field is applied. By applying an external magnetic field with appropriate direction or intensity, the magnetically controlled hollow fiber ring 2 is driven to switch to a radially expanded state. Specifically, when the optical path needs to be opened, an external magnetic field with appropriate direction or intensity is applied from the outside. The pre-magnetized magnetic particles inside the magnetically controlled hollow fiber ring 2 are magnetized by the external magnetic field, generating a magnetic torque that is opposite to the direction of the remanent magnetization or sufficient to overcome the remanent magnetization attraction. This drives the magnetically controlled hollow fiber ring 2 to undergo radial expansion deformation, causing the flexible protective layer 3 to detach from the outer wall of the optical fiber, thus opening the optical path at the end face. After the external magnetic field is removed, the magnetically controlled hollow fiber ring 2 returns to its contracted state due to the remanent magnetization, and the flexible protective layer 3 then re-attaches to the outer wall of the hollow fiber 4, restoring the physical barrier to the end face area.

[0039] Preferably, in the magnetized hollow fiber ring 2, the concentration of pre-magnetized magnetic particles is distributed in a gradient. For example, the concentration in the outer wall region of the magnetized hollow fiber ring 2 can be 40%~70wt%, and the concentration in the inner wall region can be 10%~30wt%. This gradient distribution allows the driving force to be concentrated in the outer wall region of the magnetized hollow fiber ring 2 under the action of an external magnetic field. The inner wall region has good flexibility due to the low magnetic powder concentration, and can tightly adhere to the outer wall of the optical fiber without damaging the optical fiber coating during shrinkage.

[0040] More preferably, the pre-magnetized magnetic particles are oriented in the polymer matrix, with their easy magnetization axis oriented circumferentially along the magnetically controlled hollow fiber ring 2. The circumferentially oriented magnetic powder arrangement ensures that the magnetostrictive contraction force acts strictly in the radial direction, avoiding skewed deformation and improving driving efficiency and bonding uniformity.

[0041] In another preferred embodiment, the polymer matrix is ​​a piezoelectric polymer, and the magnetically controlled hollow fiber ring 2 further includes electrode layers disposed on its inner and outer walls. The electrode layers are used to extract the electrical signals generated when the piezoelectric polymer is deformed or subjected to external force, thereby enabling self-sensing of the contact between the end face of the hollow fiber 4 and the device status. For example, when the end face of the hollow fiber 4 is impacted by dust, touched by a foreign object, or deformed by the device itself, the piezoelectric polymer generates a piezoelectric effect due to the force, forming a characteristic voltage signal between the electrode layers. This signal, after being extracted through the electrode layers, can be transmitted to an external monitoring circuit to achieve real-time sensing and alarm of end face contact events; simultaneously, the waveform characteristics of the piezoelectric signals generated by different deformation states (contraction / expansion) are different, which can be used for self-monitoring of the device status.

[0042] For example, the piezoelectric polymer may be β-crystalline enriched polyvinylidene fluoride (PVDF) or its copolymer; the electrode layer is a flexible transparent conductive layer, which may be selected from one or more of PEDOT:PSS, silver nanowires, carbon nanotubes or graphene, but is not limited thereto.

[0043] In embodiments of the present invention, the geometric parameters of the magnetically controlled hollow fiber ring 2 can be selected according to actual needs. For example, its axial length can be 2~10mm, its wall thickness can be 0.1~0.8mm, and its inner diameter in the radially contracted state is 0.05~0.3mm smaller than the outer diameter of the hollow fiber 4 to achieve an interference fit.

[0044] The flexible protective layer 3 is preferably a black elastomer material or a radiation-resistant elastomer material, such as one or more selected from polydimethylsiloxane (PDMS), fluororubber, thermoplastic polyurethane (TPU), or ethylene propylene diene monomer (EPDM), and its thickness can be 10~100μm. When the magnetically controlled hollow fiber ring 2 shrinks, the flexible protective layer 3 acts as an intermediate medium, uniformly adhering to the outer wall of the optical fiber. On the one hand, it compensates for the microscopic unevenness caused by the protrusion of magnetic particles, achieving effective physical barrier; on the other hand, it buffers the mechanical action of magnetic attraction on the optical fiber coating through elastic deformation, avoiding damage.

[0045] The preparation method of the above-mentioned magnetically controlled end-face protection device for hollow optical fibers includes the following steps: Step S1: Preparation of the magnetic hollow fiber precursor. A polymer matrix, pre-magnetized magnetic particles, and a solvent are mixed to form a spinning solution. The solution is extruded through a hollow fiber forming die (e.g., annular spinneret) using a spinning process (e.g., microfluidic spinning, melt spinning, or solution spinning), and then solidified in a coagulation bath to obtain the magnetic hollow fiber precursor. During the extrusion process, a circumferentially oriented external magnetic field is applied to the magnetic hollow fiber precursor, causing the pre-magnetized magnetic particles to align along the fiber circumference. The circumferentially oriented external magnetic field can be provided by a ring-shaped permanent magnet or a ring-shaped electromagnetic coil, with a magnetic field strength of 0.5~2T. The application time is adjusted according to the spinning traction speed to ensure sufficient time for the fiber to pass through the magnetic field region for the magnetic particles to complete their orientation. For example, the mass fraction of the polymer matrix in the spinning solution can be 12%~20%, and the mass fraction of the pre-magnetized magnetic particles can be 30%~65%; the coagulation bath can be water, ethanol, or a mixture of both, and the temperature can be 30~70℃.

[0046] Step S2: Stretching or Stretching Polarization Treatment. The magnetic hollow fiber precursor obtained in Step S1 is subjected to stretching treatment. For example, it can be unidirectional or multi-stage stretched at a stretching ratio of 2 to 10 times at a temperature of 60 to 100°C. When the polymer matrix is ​​a piezoelectric polymer, a polarization electric field of 5 to 30 kV / mm can be applied simultaneously with the stretching treatment to induce the polymer matrix to transform into a β-crystal form (when the polymer matrix is ​​a β-crystal enriched piezoelectric polymer such as PVDF), thereby imparting piezoelectric properties to the fiber.

[0047] For implementations requiring piezoelectric self-sensing functionality, electrode layers can be formed on the inner and outer surfaces of the magnetic hollow fiber precursor after stretching and polarization treatment. Exemplarily, conductive material can be uniformly coated onto the inner and outer surfaces of the magnetic hollow fiber precursor using methods such as screen printing, spraying, dip coating, or vapor deposition, and cured to form a flexible, transparent conductive layer, i.e., the electrode layer. The conductive material can be selected from one or more of PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrene sulfonate), silver nanowires, carbon nanotubes, or graphene. The thickness of the electrode layer is preferably 1~5 μm. Flexible wires can be led out from the electrode layer as needed for connecting to an external signal acquisition circuit.

[0048] Step S3: Cutting and Magnetizing. The magnetic hollow fiber obtained in step S2 is cut into fiber ring segments of predetermined length and placed in a pulsed magnetic field for magnetization treatment to impart a predetermined remanence, thereby obtaining a magnetically controlled hollow fiber ring 2.

[0049] Step S4: Forming a flexible protective layer. A flexible material is coated or impregnated onto the inner wall surface of the magnetron-controlled hollow fiber ring 2 obtained in step S3, and then cured to form a flexible protective layer 3. Exemplarily, the coating method can be dip coating or spray coating, and the curing method can be thermosetting or ultraviolet curing.

[0050] Step S5: Assembly and Fixing. The magnetically controlled hollow fiber ring 2 with flexible protective layer 3 obtained in step S4 is fixed to the fixing base 1 by an adhesive method (e.g., UV-curable adhesive bonding), and the fixing base 1 is sleeved and fixed to the periphery of the end of the hollow fiber 4.

[0051] The above preparation method utilizes online magnetic field orientation during spinning to achieve pre-arrangement of pre-magnetized magnetic particles along the fiber circumference. Pulse magnetization after cutting imparts precisely controllable remanence to the fiber rings. Furthermore, stretching polarization treatment induces the formation of piezoelectric β-crystals in the polymer matrix, thus ensuring the integrated realization of driving and sensing functions at the material level. This method has a wide process window and is suitable for mass production.

[0052] The present invention will be further described below through specific embodiments.

[0053] Example 1

[0054] like Figure 1 As shown, the magnetically controlled end-face protection device for hollow optical fiber in this embodiment 1 includes: a fixed base 1, which is made of photosensitive resin 3D printing, and its inner diameter matches the outer diameter of the hollow optical fiber 4 to be protected, with an axial length of 5mm; a magnetically controlled hollow fiber ring 2, which is disposed at the front end of the fixed base 1 and surrounds the outer wall of the optical fiber at the end of the hollow optical fiber 4; and a flexible protective layer 3, which is disposed on the inner wall surface of the magnetically controlled hollow fiber ring 2.

[0055] The operation of the device in this embodiment 1 can be divided into two basic states: Protection (Off) Status: In the absence of an external magnetic field, the magnetically controlled hollow fiber ring 2 maintains a radially contracted state due to the pre-existing remanent magnetism of its material. In this state, the magnetically controlled hollow fiber ring 2 causes its inner flexible protective layer 3 to tighten inwards, ensuring that the flexible protective layer 3 adheres tightly to the outer wall of the hollow fiber 4, effectively shielding and sealing the fiber end face. This state is the device's default standby state, with zero power consumption, providing long-term dust and contamination protection.

[0056] Open (Enabled) Status: When an open optical path is required for connection or signal transmission, an external magnetic field of appropriate direction and intensity is applied from outside the device (e.g., using a toroidal permanent magnet or electromagnetic coil). The external magnetic field magnetizes the pre-magnetized magnetic particles in the magnetically controlled hollow fiber ring 2, driving the fiber ring to undergo radial expansion deformation. The expanded magnetically controlled hollow fiber ring 2 causes its flexible protective layer 3 on its inner wall to detach from the outer wall of the hollow fiber 4, thereby creating space and opening the optical path. After the external magnetic field is removed, the magnetically controlled hollow fiber ring 2 automatically returns to its radially contracted protective state under the influence of its own residual magnetism.

[0057] The specific preparation steps of the dedicated magnetron end-face protection device for hollow optical fibers in this embodiment 1 are as follows: Step S1: Preparation of magnetic hollow fiber precursor. Polyvinylidene fluoride (PVDF, Arkema Kynar 761, France) was used as the polymer matrix, and pre-magnetized neodymium iron boron magnetic powder (NdFeB, average particle size 5 μm, Ningbo Yunsheng) was used as the pre-magnetized magnetic particles. By mass fraction: PVDF 15%, NdFeB magnetic powder 50%, solvent (DMF) 35%. After premixing PVDF and magnetic powder in a high-speed mixer, the solvent was added, and the mixture was stirred at 60°C for 12 hours until completely dissolved. After degassing, a spinning solution was obtained. Using a microfluidic spinning device, the spinning solution was extruded through an annular spinneret (outer diameter 2.0 mm, inner diameter 1.2 mm), and N2 was introduced into the core layer to form a hollow structure. The extruded fibers were then placed in a coagulation bath (water / ethanol volume ratio 1:1, temperature 45°C) for molding, with a winding speed of 8 m / min, to obtain the magnetic hollow fiber precursor.

[0058] Step S2: Orientation and Stretching Polarization of Magnetic Powder. During the extrusion molding process in Step S1, a ring-shaped permanent magnet (magnetic field strength 1.2T) is placed at the outlet of the coagulation bath, so that the magnetic hollow fiber precursor is subjected to a circumferential magnetic field when passing through, and the easy magnetization axis of the magnetic particles is oriented along the circumferential direction of the fiber. The oriented magnetic hollow fiber precursor is uniaxially stretched at 80℃ with a stretch ratio of 4 times, and a polarization electric field of 15kV / mm is applied simultaneously to induce the PVDF matrix to transform into the β crystal form, which can make the obtained magnetically controlled hollow fiber ring 2 have better rigidity, strength and fatigue resistance.

[0059] Step S3: Cutting and Magnetizing. The magnetic hollow fiber precursor obtained in step S2 is cut into fiber ring segments of 5 mm in length, placed in a pulsed magnetic field device, and magnetized by applying a 3T pulsed magnetic field to impart a predetermined residual magnetism to the magnetically controlled hollow fiber ring 2.

[0060] Step S4: Forming a flexible protective layer. Mix polydimethylsiloxane (PDMS, Dow Corning Sylgard 184) prepolymer and curing agent at a ratio of 10:1, add 5 wt% carbon black as a light-blocking agent, stir until homogeneous, and then degas. Centrifuge the mixture and remove excess liquid. Inject the homogeneous mixture into the core layer of the magnetic hollow fiber ring 2 using a syringe to form a uniform coating on the inner wall surface. Heat-cur at 80°C for 2 hours to form a flexible protective layer 3 with a thickness of approximately 30 μm.

[0061] Step S5: Assembly and Fixing. Take the photosensitive resin 3D printed fixing base 1 and coat its inner wall with UV-curable adhesive (NOA61). Fix the magnetically controlled hollow fiber ring 2 with the flexible protective layer 3 obtained in step S4 to the front end of the fixing base 1 and cure it with UV light for 30 seconds. Then, place the fixing base 1 around the end of the hollow fiber 4 (outer diameter 1.2mm), adjust its position so that the magnetically controlled hollow fiber ring 2 is located at the end face of the hollow fiber 4 and partially extends axially beyond its end face. Apply UV-curable adhesive to fix the fixing base 1 to the outer wall of the fiber, cure it with UV light, and complete the assembly.

[0062] Testing showed that the magnetron-controlled end-face protection device prepared in this embodiment maintained a radially contracted state in the absence of an external magnetic field, with the flexible protective layer 3 tightly adhering to the outer wall of the optical fiber, achieving a 98.5% blocking efficiency for dust particles smaller than 10μm. When a handheld annular neodymium iron boron magnet (surface magnetic field 0.3T) was brought near it, the magnetron-controlled hollow fiber ring 2 expanded within 0.3 seconds, fully opening the optical path; after the magnet was removed, it automatically returned to contraction within 0.2 seconds. After 1000 opening and closing cycle tests, the device functioned normally, and no visible wear was observed in the optical fiber coating.

[0063] Example 2

[0064] This embodiment is basically the same as Embodiment 1 in terms of preparation process and assembly method, the difference being: the flexible protective layer 3 is made of radiation-resistant fluororubber (FKM, DuPont Viton A) with a thickness of 50μm, suitable for nuclear radiation environments; the geometric parameters of the magnetron-controlled hollow fiber ring 2 are adjusted to an axial length of 8mm, a wall thickness of 0.5mm, and a shrinkage interference of 0.2mm, to accommodate a hollow fiber 4 with a larger outer diameter (outer diameter 1.8mm). After gamma ray irradiation testing (cumulative dose 1MGy), the device still functions normally.

[0065] Example 3

[0066] The preparation process and assembly method of this embodiment are basically the same as those of Embodiment 1. The difference lies in the gradient distribution of the magnetic particle concentration, which is achieved through a dual-channel liquid inlet of a microfluidic spinning device: the NdFeB concentration in the outer wall region is 60wt%, and the concentration in the inner wall region is 20wt%. Testing showed that the device in Embodiment 3 exhibits more uniform inner wall adhesion during shrinkage, and the surface pressure distribution on the fiber coating is reduced by 35% compared to the design with a uniform concentration (50wt%), further reducing the risk of coating wear.

[0067] Example 4

[0068] This embodiment is basically the same as Embodiment 1 in terms of preparation process and assembly method. The difference is that Embodiment 4 provides a device integrating piezoelectric self-sensing function. Based on Embodiment 1, a PEDOT:PSS electrode layer with a thickness of about 2μm is prepared on the inner and outer walls of the magnetically controlled hollow fiber ring 2 by screen printing, and a flexible wire is led out to connect to the signal acquisition circuit. Testing showed that when a dust particle with a diameter of 100μm impacts the end face area of ​​the optical fiber at a speed of 1m / s, the electrode layer can detect a voltage pulse of about 15mV; during the opening and closing of the device, the piezoelectric signal waveform characteristics corresponding to the contraction and expansion states are significantly different, which can be used for state self-monitoring.

[0069] Comparative Example 1 Commercially available rubber fiber optic dust caps (LC type, Shenzhen Feiyu Fiber Optic) were used to protect the end faces of hollow fiber optic cables of the same specifications. Compared with the embodiments of the present invention, Comparative Example 1 has the following shortcomings: it requires manual insertion and removal, which is time-consuming in the operation test of simulating a high-density port (100 ports) in a smart computing center; it cannot be remotely controlled, and cannot be used in the remote operation test simulating a nuclear radiation environment; and it does not have a status awareness function.

[0070] Comparative Example 2 The hollow fiber end face was permanently sealed using fiber-grade UV adhesive (Master Bond UV15-7LRI). The UV adhesive was applied to the fiber end face and cured by UV light irradiation for 60 seconds. Compared to the embodiments of this invention, Comparative Example 2 has the following shortcomings: it is irreversible, and once cured, it cannot be opened, failing to meet the requirements for intermittent use; the low-viscosity UV adhesive is drawn into the micron-level channels of the hollow fiber due to capillary action, affecting the fiber transmission channel; and it lacks remote control and self-sensing functions.

[0071] Performance tests were conducted on Examples 1-4 and Comparative Examples 1-2 above. Specific test methods are shown in Table 1, and test results are shown in Table 2. Table 1 Table 2 Through the above embodiments and comparative test data, it can be seen that without changing the original optical path structure of the hollow fiber, the hollow fiber protection device of the present invention can realize remote, reversible, and zero-power switching of the end-face protection state; on this basis, by further setting an electrode layer, the end-face state self-sensing function can also be integrated.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0073] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A magnetically controlled end-face protection device for hollow optical fibers, characterized in that, include: A fixing base is used to sleeve and fix the outer periphery of the end of the hollow optical fiber; Magnetically controlled hollow fiber rings are composed of a polymer matrix and pre-magnetized magnetic particles dispersed in the polymer matrix, and can undergo radial contraction or radial expansion deformation under the action of an external magnetic field. The magnetically controlled hollow fiber ring is disposed on the fixed base and sleeved on the end of the hollow fiber, which is used to form a physical barrier on the end face of the hollow fiber in the radially contracted state. A flexible protective layer is disposed on the inner wall surface of the magnetically controlled hollow fiber ring; The magnetically controlled hollow fiber ring has a predetermined remanence intensity, which keeps it in a radially contracted state when there is no external magnetic field; by applying an external magnetic field with appropriate direction or intensity, the magnetically controlled hollow fiber ring is driven to switch to a radially expanded state. The polymer matrix is ​​a piezoelectric polymer, and the magnetically controlled hollow fiber ring also includes an electrode layer disposed on its inner and outer walls. The electrode layer is used to draw out the electrical signal generated when the piezoelectric polymer is deformed or subjected to external force, so as to realize the self-sensing of the contact of the hollow fiber end face or the device status.

2. The magnetically controlled end-face protection device for hollow optical fibers according to claim 1, characterized in that, In the magnetically controlled hollow fiber ring, the concentration of the pre-magnetized magnetic particles is distributed in a gradient, with the concentration in the outer wall region of the magnetically controlled hollow fiber ring being 40%~70wt% and the concentration in the inner wall region being 10%~30wt%.

3. The magnetically controlled end-face protection device for hollow optical fibers according to claim 1, characterized in that, The pre-magnetized magnetic particles are oriented in the polymer matrix, with their easy magnetization axis oriented circumferentially along the magnetically controlled hollow fiber ring.

4. The magnetically controlled end-face protection device for hollow optical fibers according to claim 1, characterized in that, The piezoelectric polymer is β-crystalline enriched polyvinylidene fluoride or its copolymer; the electrode layer is a flexible transparent conductive layer selected from one or more of PEDOT:PSS, silver nanowires, carbon nanotubes or graphene.

5. The magnetically controlled end-face protection device for hollow optical fibers according to claim 1, characterized in that, The magnetically controlled hollow fiber ring has an axial length of 2~10mm, a wall thickness of 0.1~0.8mm, and an inner diameter in the radially contracted state that is 0.05~0.3mm smaller than the outer diameter of the hollow fiber.

6. The magnetically controlled end-face protection device for hollow optical fibers according to claim 1, characterized in that, The flexible protective layer is a black elastomer material or a radiation-resistant elastomer material, selected from one or more of polydimethylsiloxane, fluororubber, thermoplastic polyurethane or EPDM rubber, and its thickness is 10~100μm.

7. A method for preparing a magnetically controlled end-face protection device for hollow optical fibers as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1, Preparation of magnetic hollow fiber precursor: The polymer matrix, pre-magnetized magnetic particles and solvent are mixed to form a spinning solution, which is then extruded through a hollow fiber forming mold using a spinning process and formed in a coagulation bath to obtain the magnetic hollow fiber precursor; During the extrusion molding process, a circumferentially oriented external magnetic field is applied to the magnetic hollow fiber precursor, causing the pre-magnetized magnetic particles to align along the fiber circumference. Step S2, stretching treatment: The magnetic hollow fiber precursor obtained in step S1 is subjected to stretching treatment. Step S3, Cutting and Magnetizing: The magnetic hollow fiber precursor obtained in step S2 is cut into fiber ring segments of predetermined length and placed in a pulsed magnetic field for magnetization treatment to impart a predetermined remanence to obtain a magnetically controlled hollow fiber ring. Step S4, forming a flexible protective layer: The inner wall surface of the magnetically controlled hollow fiber ring obtained in step S3 is coated or impregnated with a flexible material, and then cured to form a flexible protective layer; Step S5, Assembly and Fixing: The magnetically controlled hollow fiber ring with a flexible protective layer obtained in step S4 is fixed to the fixing base by adhesive bonding, and the fixing base is sleeved and fixed to the periphery of the hollow fiber end.

8. The preparation method according to claim 7, characterized in that, In step S1, the mass fraction of the polymer matrix in the spinning solution is 12%~20%, and the mass fraction of the pre-magnetized magnetic particles is 30%~65%; the coagulation bath is a solution of water, ethanol, or a mixture of both, and the temperature is 30~70℃.

9. The preparation method according to claim 7, characterized in that, In step S1, the circumferentially oriented external magnetic field is provided by a ring permanent magnet or a ring electromagnetic coil, with a magnetic field strength of 0.5~2T and an action time of the fiber passing through the magnetic field region at the spinning traction linear speed.

10. The preparation method according to claim 7, characterized in that, The steps for stretching the magnetic hollow fiber precursor include: unidirectional or multi-stage stretching at a temperature of 60~100℃ with a stretching ratio of 2~10 times.

11. The preparation method according to claim 10, characterized in that, During the stretching process, a polarization electric field of 5~30kV / mm is applied to induce the polymer matrix to transform into the β crystal form through polarization treatment.

12. The preparation method according to claim 11, characterized in that, The preparation method also includes forming electrode layers on the inner and outer walls of the polarized magnetic hollow fiber precursor.

13. The preparation method according to claim 7, characterized in that, In step S4, the flexible material is coated by dip coating or spray coating, and cured by heat curing or ultraviolet light curing; in step S5, the bonding method is ultraviolet curing adhesive bonding.

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