A side-polished fiber optic packaging structure for stress relief of thermally induced phase change materials
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-24
- Publication Date
- 2026-08-11
Smart Images
Figure CN122546385A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical fiber packaging technology, specifically to a side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials. Background Technology
[0002] Side-polished optical fibers remove part of the cladding on one side, allowing the core light field to penetrate outward in the form of evanescent waves. In optoelectronic device manufacturing, these fibers need to be fixed in specific channels of the substrate and bonded using encapsulating adhesive. When the device experiences alternating ambient temperatures in actual operation, the quartz optical fiber, polymer encapsulating adhesive, and encapsulating substrate, which constitute the encapsulation body, have different coefficients of thermal expansion due to their different material compositions. This difference in physical properties causes thermal expansion mismatch during temperature rise and fall, inducing thermal stress at the encapsulation interface.
[0003] Due to the lack of cladding material, the polished area of the side-polished optical fiber exhibits an asymmetrical cross-section and a reduced overall thickness. Its bending modulus is at its lowest point throughout the fiber, making it a weak point in mechanical strength. Conventional encapsulating adhesive, after curing, exhibits fixed high-rigidity physical characteristics, failing to absorb and offset the thermal strain differences between materials. Thermal stress is conducted along the high-rigidity cured adhesive layer, leading to stress concentration at the interface of the structurally weak polished area. This stress concentration disrupts the original refractive index distribution of the fiber core through the elasto-optic effect, increasing polarization-dependent loss and additional attenuation during optical signal transmission. Simultaneously, mechanical stress acts directly on the thin polished surface edge, exceeding the yield limit of the quartz material, causing microcracks and physical fracture within the fiber, ultimately leading to optoelectronic device failure. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention provides a side-polished fiber packaging structure for stress relief of thermally induced phase change materials. This solves the problem that when side-polished fibers are subjected to alternating ambient temperatures, stress concentration in the weak polished area due to material thermal expansion mismatch leads to structural fracture and optical failure.
[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a side-polished fiber encapsulation structure for stress relief of thermally induced phase change materials, comprising a side-polished fiber, an encapsulation substrate, a fixative, and thermally induced phase change microcapsules dispersed in the fixative; The encapsulation substrate has a V-shaped groove for positioning the side-polished optical fiber. The side-polished optical fiber is embedded in the V-shaped groove, and the fixing adhesive is filled between the side-polished optical fiber and the V-shaped groove to fix the side-polished optical fiber to the encapsulation substrate. The side-polished optical fiber includes a polishing area and fixed sections located on both sides of the polishing area. The thermally induced phase change microcapsules are uniformly distributed in the fixative adhesive between the fixed section of the side-polished optical fiber and the V-groove; Within the encapsulation area corresponding to the polishing zone, the fixing adhesive is a pure adhesive layer, in which the thermally induced phase change microcapsules are not distributed, so as to avoid affecting the evanescent field coupling.
[0006] Preferably, the thermo-induced phase change microcapsules are paraffin-based microcapsules, with a core layer of paraffin and a shell layer of urea-formaldehyde resin.
[0007] Preferably, the thermo-induced phase change microcapsules are used to undergo a solid-liquid phase change during temperature changes, thereby changing the elastic modulus of the fixative to achieve the regulation and release of thermal stress.
[0008] Preferably, the core layer of the thermo-induced phase change microcapsule is paraffin wax, the melting point of which is 40–50°C, and the number of phase change cycles of the thermo-induced phase change microcapsule is not less than 10. 5 Second-rate.
[0009] Preferably, based on the adjustment and release of the thermal stress, stress concentration areas are avoided, and a uniform stress distribution area is formed.
[0010] Preferably, the thermo-induced phase change microcapsules are dispersed in the fixative, and the diameter of the thermo-induced phase change microcapsules is 15-25 μm.
[0011] Preferably, the thermo-induced phase change microcapsules are dispersed in the fixative, and the mass percentage of the thermo-induced phase change microcapsules in the fixative is 15% to 35%.
[0012] Preferably, the fixing adhesive is a high-transmittance UV-curable adhesive with a refractive index of 1.45 to 1.50.
[0013] Preferably, the encapsulation substrate is a silicon-based substrate or a ceramic substrate, and its coefficient of thermal expansion matches that of the side-polished optical fiber.
[0014] Preferably, the polishing zone length of the side-polished optical fiber is 5–20 mm, and the polishing depth of the polished surface is 1–3 μm.
[0015] This invention provides a side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials. It has the following beneficial effects: 1. This invention involves doping thermally induced phase change microcapsules into the fixative adhesive corresponding to the side-polished optical fiber fixing section. When the ambient temperature changes to the melting point of the microcapsules, a solid-liquid phase change occurs in the core layer, causing a change in the elastic modulus of the fixative adhesive. This absorbs the deformation caused by thermal expansion mismatch between the optical fiber, the fixative adhesive, and the encapsulation substrate. This feature adjusts the thermal stress distribution, transforming the original stress concentration area into a uniform stress distribution area, thereby reducing the risk of mechanical breakage at weak points in the optical fiber structure.
[0016] 2. This invention sets a pure adhesive layer at the corresponding position of the polishing area of the side-polished optical fiber. This structure strictly confines the microcapsule particles in the adhesive of a fixed section, so that no microcapsule particles are distributed around the polished surface of the optical fiber. This feature structurally avoids the interference of solid particles on the evanescent field coupling process of the side-polished optical fiber, and ensures the optical transmission performance of the device while realizing the stress release of the packaging structure.
[0017] 3. This invention uses a packaging substrate with a thermal expansion coefficient that matches the optical fiber, and the doped microcapsules have a phase transition cycle count of no less than 10. 5 Secondly, matching the thermal expansion coefficients between materials reduces the initial thermal strain amplitude caused by temperature changes from a fundamental level. Combined with the high phase transition lifetime of microcapsules, it maintains the stress adjustment capability of the encapsulation layer under multiple temperature cycles, thereby improving the long-term reliability of the device. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the overall three-dimensional structure of a side-polished optical fiber packaging structure for stress relief of thermally induced phase change material according to the present invention. Figure 2 This is a schematic diagram of the longitudinal cross-sectional structure of the present invention along the axial direction of the side-polished optical fiber; Figure 3 This is a schematic diagram of the cross-sectional structure of the present invention along the polishing zone direction; Figure 4 This is a schematic diagram of the cross-sectional structure of the present invention along the direction of the fixed segment; Figure 5 This is a schematic diagram showing the thermal stress distribution under high and low temperature alternating environment and a comparison between the traditional stress concentration area and the stress uniform distribution area of the present invention.
[0019] The components are: 1. Side-polished optical fiber; 11. Polished surface; 12. Polished area; 13. Fixing section; 2. Encapsulation substrate; 21. V-groove; 3. Fixing adhesive; 4. Thermally induced phase change microcapsule; 5. Pure adhesive layer; 6. Stress uniform distribution area; 7. Stress concentration area. Detailed Implementation
[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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. Example
[0021] Please see Figure 1This invention provides a side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials, the basic hardware architecture of which includes: The four main components—side-polished optical fiber 1, encapsulation substrate 2, fixative 3, and thermo-induced phase change microcapsules 4 suspended and dispersed in a specific area of the fixative 3—together constitute an optoelectronic device encapsulation system with adaptive thermal strain adjustment capability.
[0022] Please see Figure 2 The encapsulation substrate 2 has a V-groove 21 machined along the axial direction for positioning the side-polished optical fiber 1. In the assembly process, the cylindrical cladding outer wall of the side-polished optical fiber 1 is embedded in the V-groove 21. The V-shaped inclined surface is used to achieve high-precision self-alignment positioning constraint. The fixing adhesive 3 is filled in the micron-level gap between the outer surface of the side-polished optical fiber 1 and the inner wall of the V-groove 21. After curing, a polymer cross-linked network is formed, thereby realizing the physical bonding between the side-polished optical fiber 1 and the encapsulation substrate 2.
[0023] In terms of axial structure, the side-polished optical fiber 1 is divided into two functional areas: the polishing area 12 in the middle and the fixed sections 13 on both sides of the polishing area 12. The fixed sections 13 retain the complete optical fiber cladding structure and are used to bear the main mechanical anchoring force; the polishing area 12 is the core optical sensing or coupling area where part of the cladding is removed and the near-core area is exposed. In a preferred embodiment of the present invention, the encapsulation substrate 2 is made of silicon substrate or ceramic substrate. In this embodiment, the coefficient of thermal expansion of the metal substrate is 20 × 10⁻⁶. -6 The thermal expansion coefficient of the side-polished optical fiber 1 made of quartz material is only about 0.5×10 °C, while the thermal expansion coefficient of the side-polished optical fiber 1 is only about 0.5×10 °C. -6 / ℃; the coefficient of thermal expansion is approximately 2.6×10. -6 A silicon-based or similar ceramic substrate at a temperature of / ℃ allows the thermal expansion coefficient of the encapsulation substrate 2 to be more matched with that of the optical fiber at the base material level, thereby reducing the initial thermal strain amplitude caused by the difference in the expansion of the base components.
[0024] Please see Figure 3 In the encapsulation space corresponding to the polishing area 12 in the middle of the side-polished fiber 1, the filling fixative 3 is a pure adhesive layer 5 of a single material. No thermally induced phase change microcapsules 4 are distributed in this pure adhesive layer 5. The particle-free setting in this area is based on the requirements of optical transmission boundary conditions. In the side-polished fiber 1, there is an evanescent wave electromagnetic field on the surface of the polished surface 11 that penetrates into the external medium. Any heterogeneous particles with a size on the order of micrometers approaching this interface will cause Mie scattering due to the sudden change in refractive index, resulting in insertion loss of the transmitted beam.
[0025] By setting a pure adhesive layer 5, the contact between the phase change particles and the polished surface 11 is physically isolated, avoiding interference from the microcapsules on the evanescent field coupling. To ensure optical performance, the fixing adhesive 3 in this embodiment is a high-transmittance UV-curable adhesive, and its refractive index after curing is controlled between 1.45 and 1.50. Since the cladding refractive index of a single-mode silica fiber is about 1.446, matching the refractive index of the pure adhesive layer 5 within this range can maintain the fiber core's ability to limit total internal reflection of light waves and provide a stable refractive index transition interface for optical interaction with the external environment. At the same time, the polishing area 12 of the side-polished fiber 1 is processed to a length of 5 to 20 mm, and the polishing depth of the polished surface 11 is controlled between 1 and 3 μm. The residual cladding thickness of 1 to 3 μm allows some light energy to be exposed in the form of evanescent waves, meeting the optical field intensity required for device coupling, while retaining the basic waveguide constraint structure.
[0026] Please see Figure 4 Thermochromic phase change microcapsules 4 are uniformly distributed in the fixing adhesive 3 between the two fixed sections 13 and the V-groove 21 on both sides of the side-polished optical fiber 1. In a specific implementation scenario, the thermochromic phase change microcapsules 4 are core-shell structured paraffin-based microcapsules. The core layer is paraffin, a phase change energy storage material, and the shell layer is urea-formaldehyde resin synthesized by in-situ polymerization. The dense urea-formaldehyde resin shell layer has excellent mechanical compressive strength, can withstand the internal shrinkage stress during adhesive curing, and prevents leakage of internal liquefied paraffin under high temperature conditions. To meet the operating temperature standards of optical communication devices, the melting point of the paraffin core layer of the microcapsule was adjusted to be between 40 and 50°C, and the phase change cycle life of the thermally induced phase change microcapsule 4 was not less than 10. 5 Secondly, the setting of this melting point range corresponds to the temperature threshold at which the thermal stress of the encapsulation material begins to accumulate rapidly. In terms of process parameter control, the diameter of the thermo-induced phase change microcapsules 4 is selected to be 15-25 μm. If the particle size is less than 15 μm, the proportion of capsule wall material is too high, and the phase change molding efficiency is reduced. If the particle size is greater than 25 μm, the microparticles will agglomerate in the V-shaped groove gap with a width of hundreds of micrometers, resulting in local dispensing blockage. In addition, the mass percentage of the thermo-induced phase change microcapsules 4 in the fixing adhesive 3 is limited to 15%-35%. If the volume percentage is less than 15%, it is difficult to form a stress absorption network inside the adhesive. If it is higher than 35%, it will reduce the polymer crosslinking density of the UV-curable adhesive, causing a decrease in the interfacial adhesion of the fixing section 13.
[0027] Please see Figure 5 Based on the elastic modulus adjustment mechanism of phase change microcapsules, this invention optimizes the thermal stress distribution topology of the entire packaging system. When the ambient temperature rises, the high expansion of the fixative and the substrate in the traditional packaging structure will generate shear stress, which will be transmitted along the high rigidity colloid, forming a stress concentration area with a high peak value around the weakest polishing area of the optical fiber. In the structure of this invention, the thermo-induced phase change microcapsule 4 is used to cause the paraffin core layer to undergo a solid-liquid phase change when the temperature rises to the range of 40-50°C. The liquefied core layer has a reduced ability to resist external mechanical extrusion, causing the macroscopic elastic modulus of the fixing adhesive 3 in the area to decrease in a stepwise manner, exhibiting material softening characteristics. This softening characteristic allows the composite adhesive layer in the area where the fixing section 13 is located to obtain microscopic deformation tolerance. Based on this thermal stress regulation and release mechanism, some of the thermal strain energy generated by the expansion of the substrate is absorbed and unloaded by the small deformation of the softened microcapsules and composite adhesive when passing through the fixing section 13. Therefore, the thermal stress is greatly attenuated during the transmission to the central polishing zone 12, avoiding the generation of stress concentration zone 7, and instead forming a gentle stress uniform distribution zone 6 around the polishing zone. Example
[0028] This embodiment provides a method for fabricating a side-polished optical fiber encapsulation structure for stress relief of the above-mentioned thermally induced phase change material. The fabrication method includes the following steps: Urea and formaldehyde aqueous solution were mixed at a molar ratio of 1:1.5, and triethanolamine was added to adjust the pH of the system to 8.0. The mixture was mechanically stirred for 1 hour in a constant temperature water bath at 70℃ to obtain a urea-formaldehyde resin prepolymer solution. Nano-alumina particles accounting for 2% of the total mass of the shell were added to the solution and ultrasonically treated to make them evenly dispersed. Select paraffin wax with a melting point of 45℃ and heat it to 60℃ to melt it. Put the molten paraffin wax into an aqueous solution containing styrene-maleic anhydride copolymer emulsifier, turn on the high shear emulsifier and control the speed at 4000 rpm for homogenization emulsification, so that the paraffin wax droplet particle size is controlled at 20μm. Maintaining the emulsion temperature at a constant 60°C, the above prepolymer solution was slowly added dropwise to the emulsion. Dilute hydrochloric acid was added dropwise to adjust the pH of the system to 3.5, initiating a polycondensation and cross-linking reaction of the prepolymer on the surface of the paraffin droplets. Subsequently, the temperature was raised to 70°C and cured for 2.5 hours. After the reaction was completed, the prepolymer was filtered, washed with deionized water, and freeze-dried to obtain powdered thermo-induced phase change microcapsules, completing the in-situ encapsulation of the inner paraffin core layer and the outer thermally conductive shell layer. In a light-protected environment, 60% polyurethane acrylate prepolymer, 34% isobornyl acrylate, 4% 1-hydroxycyclohexylphenyl ketone photoinitiator, and 2% silane coupling agent were added to a reactor and mechanically stirred at 400 rpm for 2 hours at 40°C. After vacuum degassing to remove internal air bubbles, a base adhesive with a refractive index of 1.48 was obtained. The silane coupling agent was used to enhance the chemical bonding force of the interface at the subsequent curing and molding process. Measure 70% of the base adhesive, 28% of the thermo-induced phase change microcapsules and 2% of the dispersant by weight percentage. The dispersant is polyether-modified polydimethylsiloxane, CAS: 27306-78-1. First, dispersant is dissolved in base adhesive solution, then thermally induced phase change microcapsules are mixed in batches. The mixture is then transferred to a planetary centrifugal mixer and degasser, with the revolution speed set to 1500 rpm and the rotation speed set to 500 rpm for 10 minutes. Centrifugal force is used to achieve uniform dispersion of particles and remove microbubbles, thus preparing a liquid composite curing adhesive. The side-polished optical fiber is embedded in the V-groove of the encapsulation substrate, the polished surface is adjusted to face the preset coupling direction, and tension is applied to both ends of the optical fiber to keep it axially straight. Start the dual-head dispensing equipment and continuously inject the base adhesive into the 10mm long polishing area through the first dispensing needle. Simultaneously, inject the liquid composite curing adhesive into the fixed sections on both sides of the polishing area through the second dispensing needle, so that the two liquid phase colloids of the same matrix can be naturally fused at the interface. After the adhesive application is completed, the ultraviolet light source is turned on to irradiate the entire V-groove assembly area, controlling the surface irradiation energy to be 2500 mJ / cm². 2 This triggers the simultaneous free radical polymerization of the base adhesive and the liquid composite curing adhesive, completing the phase reconstruction of the continuous cross-linked network and the overall curing and molding of the optical fiber packaging structure. Example
[0029] This embodiment provides a method for fabricating a side-polished optical fiber encapsulation structure for stress relief of the above-mentioned thermally induced phase change material. The fabrication method includes the following steps: Urea and formaldehyde aqueous solution were mixed at a molar ratio of 1:1.5, and triethanolamine was added to adjust the pH of the system to 8.2. The mixture was mechanically stirred in a constant temperature water bath at 70℃ for 1 hour to obtain a urea-formaldehyde resin prepolymer solution. 1.5% of the total mass of the shell layer of nano boron nitride particles were added to the solution and ultrasonically treated to make them evenly dispersed. Select paraffin wax with a melting point of 42℃ and heat it to 60℃ to melt it. Put the molten paraffin wax into an aqueous solution containing styrene-maleic anhydride copolymer emulsifier. Control the mass ratio of paraffin wax to urea-formaldehyde resin material to be 2:1. Turn on the high shear emulsifier and control the speed to 5000 rpm for homogenization emulsification so that the paraffin wax droplet particle size is controlled at 15μm. The emulsion temperature was kept constant at 60°C. The above prepolymer solution was slowly added dropwise to the emulsion. Dilute hydrochloric acid was added to adjust the pH of the system to 3.2, which triggered the polycondensation and cross-linking reaction of the prepolymer on the surface of the paraffin droplets. The temperature was then raised to 70°C and cured for 3 hours. After the reaction was completed, the prepolymer was filtered, washed with deionized water and freeze-dried to obtain powdered thermo-induced phase change microcapsules. A high thermal conductivity network was constructed using nano-boron nitride and in-situ encapsulation was completed. In a light-protected environment, 55% polyurethane acrylate prepolymer, 38% isobornyl acrylate, 5% 1-hydroxycyclohexylphenyl ketone photoinitiator, and 2% silane coupling agent were added to a reaction vessel and mechanically stirred at 400 rpm for 2 hours at 40°C. After vacuum degassing to remove internal air bubbles, a base adhesive with a refractive index of 1.45 was obtained. Measure 80% of the base adhesive, 15% of the thermo-induced phase change microcapsules and 5% of the dispersant by mass percentage. First, dissolve the dispersant in the base adhesive, then mix in the thermo-induced phase change microcapsules in batches. Transfer the mixture into a planetary centrifugal mixer and deaerator, set the revolution speed to 1800 rpm and the rotation speed to 600 rpm and run for 8 minutes. Use centrifugal force to achieve uniform dispersion of particles and remove microbubbles to prepare a liquid composite curing adhesive. The side-polished optical fiber is embedded in the V-groove of the encapsulation substrate, the polished surface is adjusted to face the preset coupling direction, and tension is applied to both ends of the optical fiber to keep it axially straight. Start the dual-head dispensing equipment and continuously inject the base adhesive into the 5mm long polishing area through the first dispensing needle. Simultaneously, inject the liquid composite curing adhesive into the fixed sections on both sides of the polishing area through the second dispensing needle, so that the two liquid phase colloids of the same matrix can be naturally fused at the interface. After the adhesive application is completed, the ultraviolet light source is turned on to irradiate the entire V-groove assembly area, controlling the surface irradiation energy to be 2000 mJ / cm². 2 This triggers the simultaneous free radical polymerization of the base adhesive and the liquid composite curing adhesive, completing the phase reconstruction of the continuous cross-linked network and the overall curing and molding of the optical fiber packaging structure. Example
[0030] This embodiment provides a method for fabricating a side-polished optical fiber encapsulation structure for stress relief of the above-mentioned thermally induced phase change material. The fabrication method includes the following steps: Urea and formaldehyde aqueous solution were mixed at a molar ratio of 1:1.5, and triethanolamine was added to adjust the pH of the system to 7.8. The mixture was mechanically stirred for 1 hour in a constant temperature water bath at 70°C to obtain a urea-formaldehyde resin prepolymer solution. Graphene nanosheets accounting for 1% of the total mass of the shell were added to the solution and then ultrasonically treated to make them evenly dispersed. Select paraffin wax with a melting point of 50℃ and heat it to 60℃ to melt it. Put the molten paraffin wax into an aqueous solution containing styrene-maleic anhydride copolymer emulsifier. Control the mass ratio of paraffin wax to urea-formaldehyde resin material to be 5:1. Turn on the high shear emulsifier and control the speed to 3000 rpm for homogenization emulsification so that the paraffin wax droplet particle size is controlled at 25μm. The emulsion temperature was kept constant at 60°C. The above prepolymer solution was slowly added dropwise to the emulsion. Dilute hydrochloric acid was added to adjust the pH of the system to 4.0, which triggered the polycondensation and crosslinking reaction of the prepolymer on the surface of the paraffin droplets. Then the temperature was raised to 70°C and cured for 2 hours. After the reaction was completed, the prepolymer was filtered, washed with deionized water and freeze-dried to obtain powdered thermo-induced phase change microcapsules. Graphene was used to strengthen the mechanical strength and thermal conductivity of the capsule wall. In a light-protected environment, 70% polyurethane acrylate prepolymer, 28.5% isobornyl acrylate, 1% 1-hydroxycyclohexylphenyl ketone photoinitiator, and 0.5% silane coupling agent were added to a reactor and mechanically stirred at 400 rpm for 2 hours at 40°C. After vacuum degassing to remove internal air bubbles, a base adhesive with a refractive index of 1.50 was obtained. Measure 64.5% of the base adhesive, 35% of the thermo-induced phase change microcapsules, and 0.5% of the dispersant by mass percentage. First, dissolve the dispersant in the base adhesive, then mix in the thermo-induced phase change microcapsules in batches. Transfer the mixture into a planetary centrifugal mixer and deaerator, set the revolution speed to 1200 rpm and the rotation speed to 400 rpm and run for 12 minutes. Use centrifugal force to achieve uniform dispersion of particles and remove microbubbles to prepare a liquid composite curing adhesive with high microcapsule loading. The side-polished optical fiber is embedded in the V-groove of the encapsulation substrate, the polished surface is adjusted to face the preset coupling direction, and tension is applied to both ends of the optical fiber to keep it axially straight. Start the dual-head dispensing equipment and continuously inject the base adhesive into the 20mm long polishing area through the first dispensing needle. Simultaneously, inject the liquid composite curing adhesive into the fixed sections on both sides of the polishing area through the second dispensing needle, so that the two liquid phase colloids of the same matrix can be naturally fused at the interface. After the adhesive application is completed, the ultraviolet light source is turned on to irradiate the entire V-groove assembly area, controlling the surface irradiation energy to be 3000 mJ / cm². 2 This triggers the simultaneous free radical polymerization of the base adhesive and the liquid composite curing adhesive, completing the phase reconstruction of the continuous cross-linked network and the overall curing and molding of the optical fiber packaging structure.
[0031] Working principle: In the actual operation of the optoelectronic device containing the packaging structure of the present invention, when the ambient temperature changes drastically, significant thermal stress accumulates at the internal interface of the packaging substrate 2, the filling fixative 3, and the side polished optical fiber 1 due to the inherent difference in the coefficient of thermal expansion.
[0032] When the temperature rises and reaches the critical point of 40-50℃ for the thermally induced phase change microcapsule 4, the paraffin core material of the microcapsule 4, which is uniformly suspended in the fixing adhesive 3 where the fixing sections 13 at both ends of the side-polished optical fiber 1 are located, undergoes a phase change from solid to liquid. During the phase transition, paraffin absorbs latent heat to mitigate local temperature abrupt changes. At the same time, the liquefaction of the core layer weakens the microcapsule's ability to resist deformation. This change in the mechanical properties of the micromaterial reduces the macroscopic elastic modulus of the fixative 3, and a large number of flexible micro-deformation spaces are formed inside the fixative 3. When the interfacial shear and tensile stress generated by the thermal expansion of the encapsulation substrate 2 is transmitted axially to the fixed sections 13 at both ends of the optical fiber, it forces the softened composite adhesive layer to undergo slight deformation. The strain energy is absorbed by this flexible space, resulting in a significant stress relaxation phenomenon. This mechanism blocks the stress transmission path to the middle of the optical fiber 1.
[0033] Meanwhile, the polished area 12 located in the middle of the optical fiber 1 has a drastically reduced bending section modulus due to the side cladding being polished to a depth of 1-3 μm, making it the weakest area in terms of the overall optical fiber structure. In the structure of this invention, the area between the polished area 12 and the V-groove 21 is filled with only a single pure adhesive layer 5, without any micron-sized doped particles. This arrangement not only avoids the direct microscopic compressive stress on the fragile polished area 12 caused by the expansion of phase change particles, thus preventing the generation of micro-bending optical loss, but also eliminates the evanescent field scattering source caused by particle refractive index mismatch, ensuring efficient total internal reflection transmission of optical signals.
[0034] The synergistic effect of stress softening and absorption at both ends and particle-free physical protection in the middle eliminates the stress concentration zone 7 that is prone to occur in the weak polishing area in traditional rigid packaging structures. The stress field is redistributed, and finally a stress uniform distribution zone 6 with extremely low strain amplitude is formed around the polishing area 12. This structure completely solves the technical problems of mechanical brittle fracture and unstable optical signal transmission of side-polished optical fibers in harsh environments with wide temperature ranges from a rigorous physical and mechanical perspective.
[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A side-polished fiber encapsulation structure for stress relief of thermally induced phase change material, comprising a side-polished fiber (1), an encapsulation substrate (2), a fixative (3), and a thermally induced phase change microcapsule (4). Its features are: The encapsulation substrate (2) is provided with a V-groove (21) for positioning the side-polished optical fiber (1). The side-polished optical fiber (1) is embedded in the V-groove (21). The fixing adhesive (3) is filled between the side-polished optical fiber (1) and the V-groove (21) to fix the side-polished optical fiber (1) to the encapsulation substrate (2). The side-polished optical fiber (1) is divided into a polishing area (12) and fixed sections (13) located on both sides of the polishing area (12) along the axial direction. The thermo-induced phase change microcapsules (4) are uniformly dispersed in the fixing adhesive (3) located between the fixing section (13) and the V-groove (21); The fixing adhesive (3) located in the encapsulation area corresponding to the polishing zone (12) is a pure adhesive layer (5), which does not contain the thermally induced phase change microcapsules (4) to avoid affecting the evanescent field coupling.
2. The side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials according to claim 1, characterized in that, The thermally induced phase change microcapsule (4) is a paraffin-based microcapsule with a core layer of paraffin and a shell layer of urea-formaldehyde resin. The mass ratio of the core material to the shell material is 2-5:1; preferably, the shell is also doped with thermally conductive nanoparticles, which are one or more of nano-alumina particles, nano-boron nitride particles, or graphene nanosheets.
3. The side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials according to claim 1, characterized in that, The thermo-induced phase change microcapsules (4) are used to undergo a solid-liquid phase change during temperature changes, thereby changing the elastic modulus of the fixative (3) to achieve the adjustment and release of thermal stress.
4. The side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials according to claim 2, characterized in that, The core layer of the thermo-induced phase change microcapsule (4) is paraffin wax, the melting point of which is 40-50°C, and the phase change cycle number of the thermo-induced phase change microcapsule (4) is not less than 10. 5 Second-rate.
5. The side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials according to claim 3, characterized in that, Based on the adjustment and release of the thermal stress, stress concentration areas (7) are avoided, and a stress uniform distribution area (6) is formed.
6. The side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials according to claim 1, characterized in that, The thermo-induced phase change microcapsules (4) are dispersed in the fixative (3), and the diameter of the thermo-induced phase change microcapsules (4) is 15-25 μm.
7. The side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials according to claim 1, characterized in that, The thermally induced phase change microcapsules (4) are dispersed in the fixative (3) to form a composite curing adhesive; The composite curing adhesive comprises, by weight percentage: The base adhesive: 60%–80%; The thermally induced phase change microcapsules (4): 15%–35%; Dispersant: 0.5%–5%.
8. The side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials according to claim 1, characterized in that, The fixing adhesive (3) is a high-transmittance UV-curable adhesive with a refractive index of 1.45 to 1.50; The base adhesive of the fixative (3) comprises, by mass percentage: 50%–70% acrylate prepolymer, 20%–40% reactive diluent, 1%–5% photoinitiator, and 0.5%–2% silane coupling agent.
9. The side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials according to claim 1, characterized in that, The encapsulation substrate (2) is a silicon-based substrate or a ceramic substrate, and its coefficient of thermal expansion is matched with that of the side-polished optical fiber (1). When the encapsulation substrate (2) is a ceramic substrate, its material composition is one of alumina ceramic, aluminum nitride ceramic or zirconium oxide ceramic.
10. The side-polished optical fiber packaging structure for stress relief of thermally induced phase change materials according to claim 1, characterized in that, The polishing area (12) of the side-polished optical fiber (1) has a length of 5 to 20 mm, and the polishing area (12) has a polishing surface (11) with a polishing depth of 1 to 3 μm.