High-bandwidth bending insensitive vehicle-mounted multimode optical fiber and preparation method thereof

Abstract

The invention relates to a high-bandwidth bending insensitive vehicle-mounted multimode optical fiber and a preparation method thereof.The optical fiber comprises a core layer and cladding layers, the refractive index profile of the core layer is in a parabola shape, the distribution index ranges from 2.0 to 2.7, the radius R1 of the core layer ranges from 12 micrometers to 32 micrometers, delta 1max ranges from 0.85% to 1.5%, and the cladding layers are sequentially an inner cladding layer, a first sunken cladding layer, a second sunken cladding layer, a third sunken cladding layer and an outer cladding layer from inside to outside; the single-side width of the inner cladding layer is 0.5-3.0 [mu] m, the delta 2 is-0.24%-0.07%, the single-side width of the first sunken cladding layer is 1.5-6.0 [mu] m, the delta 3 is-1.1%-0.6%, the second sunken cladding layer comprises a first layer and a second layer which are sequentially arranged from inside to outside, the single-side width of the third sunken cladding layer is 1.5-12 [mu] m, the delta 6 is-1.0%-0.7%, the radius R7 of the outer cladding layer is 60-65 [mu] m, and the delta 7 is-0.12-0.15%. The optical fiber has the characteristics of high bandwidth, high bending resistance and the like, and can be applied to a vehicle-mounted optical communication network and a miniaturized optical device.

Description

Technical Field

[0001] This invention relates to a high-bandwidth, bend-insensitive automotive multimode optical fiber and its fabrication method. The optical fiber has characteristics such as high bandwidth and strong bending resistance, and belongs to the field of automotive communication technology. Background Technology

[0002] In recent years, multimode fiber has been widely used in large data centers, AI computing power network centers, local area office centers, high-performance computing centers, storage area networks, and vehicle optoelectronics due to its low system cost advantage and excellent characteristics of short-distance, high-speed transmission networks. With the widespread commercialization of 400Gb / s and the steady evolution towards 800Gb / s and even 1.6Tb / s, not only are the typical bandwidth values ​​of optical fibers being challenged, but also higher requirements are being placed on the deployment of larger capacity, smaller size, and higher density fiber-to-optical-cable integrated network interconnections.

[0003] Meanwhile, with the rapid development of automotive intelligence in recent years, the safety and driver assistance systems integrated into automotive electronic systems have deployed numerous sensors and processors within the vehicle. This necessitates higher-capacity data networks to support data exchange between these devices. This is especially true for autonomous vehicles, which are equipped with multiple lidar, millimeter-wave radars, high-definition cameras, and vehicle positioning systems. The data exchange between these sensors and the onboard computer is enormous. Traditional automotive information signal transmission systems, which primarily rely on metal media such as cables and copper wires for signal transmission, are ill-suited to meet the demands of large data volumes and high data capacity. Therefore, replacing traditional metal signal lines with fiber optic transmission has become an inevitable trend.

[0004] Multimode fiber has good compatibility with vehicle systems. However, when fiber is deployed in the confined space of a vehicle, it is subject to the influence of a very small bending radius within this extremely limited space. When conventional multimode fiber is bent at a small angle, higher-order modes transmitted near the fiber core edge are easily leaked out, resulting in signal loss and affecting transmission performance. The intermodal dispersion present in multimode fiber greatly limits the transmission distance it can support. To reduce intermodal dispersion, the refractive index profile of the multimode fiber core needs to be designed with a refractive index distribution that gradually decreases continuously from the center to the edge, which is usually called the "α profile".

[0005] Studies have shown that when the refractive index profile of a multimode fiber is constant, it often exhibits high bandwidth performance only for a specific wavelength window. When the application window of the fiber is shifted to a larger or smaller wavelength, the bandwidth performance will significantly decrease. Therefore, from an application perspective, it is necessary to improve the design of multimode fibers so that they are compatible with existing OM3 / OM4 (Pro / Ultra) / OM5 multimode fibers, have low bandwidth-wavelength sensitivity to meet the application requirements of WDM technology within a certain wavelength range, and also achieve excellent bending resistance at a smaller diameter. Summary of the Invention

[0006] To facilitate the explanation of this invention, some terms are defined as follows: Liner: A high-purity glass tube used in the preparation of mandrels; Mandrel: A prefabricated component containing a core layer and a partial cladding layer; Radius: The distance between the outer boundary of this layer and the center point; Core layer: The central part of the optical fiber's cross-section, i.e., the main light-guiding area of ​​the optical fiber; Cladding: includes inner cladding, recessed cladding and outer cladding. Inner cladding refers to the annular region in the cross-section of the optical fiber that is immediately adjacent to the core. Recessed cladding refers to the annular region in the cross-section of the optical fiber that is immediately adjacent to the inner cladding. Outer cladding refers to the annular region in the cross-section of the optical fiber that is immediately adjacent to the recessed cladding. Refractive index profile: The relationship between the refractive index of glass and its radius in an optical fiber or optical fiber preform (including the core rod), i.e., the α profile, which satisfies the following power-law function of refractive index distribution: r Where n1 is the refractive index of the fiber axis; r is the distance from the fiber axis; a is the fiber core radius; α is... Distribution index; 0 represents the refractive index of the fiber core relative to the outer cladding.

[0007] Relative refractive index difference i :

[0008] Where, n i n is the refractive index at a distance i from the center of the fiber core; n0 is the refractive index of pure silicon dioxide.

[0009] Numerical aperture: NA = n0 * (Δ1 - Δ2) 1 / 2 = n0*(2Δ) 1 / 2 .

[0010] The contribution of fluorine (F): The difference in refractive index (ΔF) between fluorine-doped (F) quartz glass and pure quartz glass, which represents the amount of fluorine (F) doping.

[0011] The contribution of boron (B): The difference in refractive index (ΔB) between fluorine-doped (F) quartz glass and pure quartz glass, which represents the amount of boron (B) doping.

[0012] Germanium (Ge) contribution: The amount of germanium (Ge) doping is expressed by the difference in refractive index (ΔGe) between germanium-doped quartz glass and pure quartz glass.

[0013] ​High-density cable: This usually refers to a high-core-count optical cable that can accommodate more cores per unit area or volume.

[0014] The technical problem to be solved by the present invention is to provide a high-bandwidth, bend-insensitive automotive multimode optical fiber and its preparation method, which addresses the shortcomings of the existing technology. The fiber has a reasonable core-cladding structure design and has excellent characteristics of high bandwidth and strong bend resistance.

[0015] The technical solution adopted by this invention to solve the above-mentioned problems is as follows: It includes a core layer and a cladding layer, the refractive index profile of the core layer is parabolic (α power function distribution), characterized in that the core layer distribution index α is 2.0~2.7, the core layer radius R1 is 12~32μm, and the maximum relative refractive index difference Δ at the center of the core layer is... 1max The relative refractive index difference (Δ1) at the core edge R1 is 0.15% to 0.05%. The cladding, from the inside out, consists of an inner cladding, a first depressed cladding, a second depressed cladding, a third depressed cladding, and an outer cladding. The width of one side of the inner cladding (R2-R1) is 0.5 to 3.0 μm, and the relative refractive index difference (Δ2) is -0.24% to 0.07%. The width of one side of the first depressed cladding (R3-R2) is 1.5 to 6.0 μm, and the relative refractive index difference (Δ3) is -1.1% to -0.6%. The second depressed cladding comprises a first layer and a second layer arranged sequentially from the inside out. The first layer exhibits a linearly increasing gradient, with a width of 0.5 to 2.5 μm on one side (R4-R3) and a relative refractive index difference (Δ4) of -1.0%. The two layers are flat or stepped, with a single-sided width (R5-R4) of 0.2~1.5μm and a relative refractive index difference Δ5 of -0.9%~-0.5%. The single-sided width (R6-R5) of the third cladding layer is 1.5~12μm, and the relative refractive index difference Δ6 of the third cladding layer is -1.0%~-0.7%. The radius of the outer cladding layer R7 is 60~65μm, and the relative refractive index difference Δ7 is -0.12~0.15%.

[0016] According to the above scheme, the relative refractive index difference Δ2 of the inner cladding is -0.18% to 0.02%.

[0017] According to the above scheme, the relative refractive index difference Δ3 of the first depressed cladding is -0.8% to -0.7%.

[0018] According to the above scheme, the relative refractive index difference Δ4 of the second sunken cladding layer is -0.8% to -0.5%.

[0019] According to the above scheme, the ratio of the width of the first layer to the width of the second layer of the second recessed cladding is 2 to 5.

[0020] According to the above scheme, the relative refractive index difference Δ6 of the third depressed cladding is -0.8% to -0.7%.

[0021] According to the above scheme, the core layer is a silicon dioxide glass layer co-doped with germanium and fluorine (Ge / F), or germanium, phosphorus, and fluorine (Ge / P / F), or germanium, boron, and fluorine (Ge / B / F). Fluorine in the core layer acts as a negative dopant, and the amount of fluorine doping increases from the center of the core layer to its edge. The contribution of fluorine doping at the center of the core layer is Δ. F0 The contribution of fluorine doping at the core edge is -0.1% to -0.04%, Δ. F1 The range is -0.6% to -0.08%.

[0022] According to the above scheme, the inner cladding layer is a silicon dioxide glass layer doped with germanium, fluorine, and phosphorus, or germanium, fluorine, and boron, or germanium, fluorine, phosphorus, and boron, and the radius R2 of the inner cladding layer is ≥15μm.

[0023] According to the above scheme, the single-side width (R2-R1) of the inner cladding layer is ≥1.8μm, and the phosphorus doping contribution ΔP is ≤0.12%.

[0024] According to the above scheme, the relative refractive index difference Δ2 of the inner cladding is less than or equal to the minimum relative refractive index difference Δ1 at the edge of the core layer, that is, Δ2≤Δ1.

[0025] According to the above scheme, the single-sided width (R3-R2) of the first recessed cladding layer is less than or equal to the single-sided width (R6-R5) of the third recessed cladding layer.

[0026] According to the above scheme, the ratio of the single-side width (R6-R5) of the third recessed cladding layer to the single-side width (R3-R2) of the first recessed cladding layer is 1.5 to 1.8.

[0027] According to the above scheme, the relative refractive index difference Δ5 between the two layers of the second recessed cladding is distributed as an upward convex curve, and the relative refractive index difference between the inner edge and the outer edge of the two layers is equal.

[0028] According to the above scheme, the second depressed cladding layer has a two-layer radius R5 ≥ 30 μm, and the relative refractive index difference Δ between the second depressed cladding layer and the second depressed cladding layer is... 4（5） Less than or equal to the relative refractive index difference Δ2 of the inner cladding, i.e., Δ 4（5） ≤Δ2.

[0029] According to the above scheme, the ratio of the single-side width (R6-R5) of the third depressed cladding to the single-side width (R5-R3) of the second depressed cladding is 2~3, the single-side width (R5-R3) of the second depressed cladding is ≥1μm, and the relative refractive index difference Δ6 of the third depressed cladding is less than or equal to the relative refractive index difference Δ6 of the second depressed cladding. 4（5） That is, Δ6≤Δ 4（5） .

[0030] According to the above scheme, the outer cladding layer is a pure silica glass layer, or a silica glass layer doped with one or more of the following dopants: aluminum, calcium, magnesium, titanium, zirconium, iron, cobalt, nickel, manganese, copper, lithium, sodium, potassium, boron, chlorine, etc. The aluminum (Al) content of the doped silica (SiO2) glass layer is 1~60ppm, the total metal element content is ≤80ppm, and the chlorine (Cl) content is 1300~2300ppm.

[0031] According to the above scheme, the numerical aperture of the optical fiber is 0.200~0.215.

[0032] According to the above scheme, the outer coating layer is coated with a resin coating layer. The resin coating layer includes an inner coating layer and an outer coating layer from the inside to the outside. The thickness of the inner coating layer on one side (R8-R7) is 10μm to 25μm, and the thickness of the outer coating layer on one side (R9-R8) is 10μm to 30μm.

[0033] According to the above scheme, the resin coating layer is a polyurethane acrylate coating layer. The inner coating layer has a Young's modulus ≤ 0.2 MPa and a glass transition temperature (Tg) ≤ -50°C. The outer coating layer has a Young's modulus ≥ 1100 MPa. The Young's modulus is measured using a D lamp cured in a nitrogen atmosphere at an energy of 1 J / cm² for a 75-micron film, under test conditions of 23°C and 50% relative humidity. Furthermore, the coating peel strength of the optical fiber is ≤ 0.8 N.

[0034] According to the above scheme, the thickness of the inner coating layer on one side (R8-R7) is 20μm ~ 25μm, and the thickness of the outer coating layer on one side (R9-R8) is 25μm ~ 30μm.

[0035] According to the above scheme, the DMD Inner Mask (5~18μm) and DMD Outer Mask (0~23μm) of the optical fiber are both less than or equal to 0.20 ps / m; the DMD Interval Mask is less than or equal to 0.15 ps / m; under preferred conditions, the DMD Inner Mask (5~18μm) and DMD Outer Mask (0~23μm) of the optical fiber are both less than or equal to 0.10 ps / m, and the DMD Interval Mask is less than or equal to 0.08 ps / m.

[0036] According to the above scheme, the full injection bandwidth (BW) of the optical fiber has 3500MHz at a wavelength of 850nm. km and above, with 2000MHz at a wavelength of 950nm. km and above, with 500MHz at a wavelength of 1300nm. km and above.

[0037] Furthermore, the fiber's full injection bandwidth (BW) has 6500MHz at a wavelength of 850nm. km and above, with 3500MHz at a wavelength of 950nm. km and above, with 700MHz at a wavelength of 1300nm. km and above.

[0038] According to the above scheme, the effective mode bandwidth (EMB) of the optical fiber has 6000MHz at a wavelength of 850nm. km or more; with 6500MHz at a wavelength of 860nm. km or more; with 6000MHz at a wavelength of 870nm. km or more; has 3600MHz at a wavelength of 910nm. km or more; with 2500MHz at a wavelength of 953nm. km or more; with 2400MHz at a wavelength of 980nm. km or more; with 2200MHz at a wavelength of 1060nm. km or more.

[0039] Furthermore, the effective mode bandwidth (EMB) of the optical fiber has 7000MHz at a wavelength of 850nm. km or more; with 7500MHz at a wavelength of 860nm. km or more; with 7000MHz at a wavelength of 870nm. km or more; has 4000MHz at a wavelength of 910nm. km or more; with 2800MHz at a wavelength of 953nm. km or more; with 2500MHz at a wavelength of 980nm. km or more; with 2300MHz at a wavelength of 1060nm. km or more.

[0040] According to the above scheme, the additional bending loss caused by bending the optical fiber twice with a bending radius of 7.5 mm at a wavelength of 850 nm is less than or equal to 0.08 dB; the additional bending loss caused by bending the optical fiber twice with a bending radius of 7.5 mm at a wavelength of 1300 nm is less than or equal to 0.08 dB; the additional bending loss caused by bending the optical fiber twice with a bending radius of 15 mm is less than or equal to 0.02 dB; and the additional bending loss caused by bending the optical fiber twice with a bending radius of 15 mm at a wavelength of 1300 nm is less than or equal to 0.03 dB.

[0041] According to the above scheme, the optical fiber has an attenuation value of less than or equal to 2.1dB at a wavelength of 850nm and an attenuation value of less than or equal to 0.37dB at a wavelength of 1300nm.

[0042] According to the above scheme, the fusion splice loss of the optical fiber at a wavelength of 850nm is less than or equal to 0.01dB, and the fusion splice loss at a wavelength of 1300nm is less than or equal to 0.01dB.

[0043] The technical solution of the optical fiber fabrication method of the present invention is as follows: A pure quartz glass liner is clamped and fixed at both ends on a plasma chemical vapor deposition (PCVD) lathe using rotating chucks. The liner is placed in a holding furnace at a temperature of 1000℃~1300℃ and passes through a high-frequency microwave resonant cavity. The process reactants required for core rod fabrication are evaporated into a stable gaseous state through a constant temperature and pressure (typically 45±2℃, 0.8±0.1 atm) evaporation system. This gaseous state is then introduced into the liner through a constant temperature (typically 20±2℃) pipe from one end of the lathe's rotating chuck, and is introduced into the liner amidst the gaseous reactants silicon tetrachloride (SiCl4) and O2. A certain amount of dopants such as germanium (GeCl4), fluorine (C2F6), phosphorus (POCl3), and boron (BCl3) are doped and deposited in a multi-element doping manner via high-energy plasma excited by a high-frequency microwave resonant cavity. The doping is then uniformly deposited in a glassy state on the inner wall of the liner tube. According to the optical fiber cross-sectional structure design requirements, the cladding and core layers are deposited sequentially. After deposition, the core is fused into a solid core rod by a high-temperature (1800℃~2300℃) fusion lathe. The core rod is then cleaned, etched, and dried, and combined with a matching ferrule to form a multimode optical fiber preform. Finally, the preform is drawn into an optical fiber using a drawing device.

[0044] According to the above scheme, the sequential deposition of the cladding and core layer includes the sequential deposition of a third depressed cladding, a second depressed cladding, a first depressed cladding, an inner cladding, and a core layer.

[0045] The beneficial effects of this invention are as follows: 1. By optimizing the material composition, cross-sectional structure design, and multi-element doping levels, the bandwidth performance of multimode optical fibers is improved, the differential mode delay (DMD) performance of multimode optical fibers is enhanced, and the bandwidth-wavelength sensitivity of optical fibers is reduced, thus achieving optimized improvement in optical transmission bandwidth performance; 2. By setting three recessed cladding layers, the mutual influence between the fiber core layer, inner cladding layer, first recessed cladding layer, second recessed cladding layer, and third recessed cladding layer, as well as refractive index distortion caused by diffusion and stress, is effectively avoided, thus improving the fiber's bending insensitivity performance; 3. By adopting a multi-element gradient doping method of germanium, fluorine, and phosphorus in the inner cladding layer, diffusion caused by the concentration difference of doping elements between layers is avoided, and the reasonable doping concentration of the inner cladding layer is achieved. Compared to variations, optimizing the viscosity matching of the inner cladding and the recessed cladding improves the smoothness of fiber stress changes, reduces fiber profile distortion caused by stress unevenness, and achieves compatibility between high-speed communication and small fiber diameter; 4. The fiber of this invention is not only compatible with existing OM3 / OM4 (Pro / ultra) / OM5 multimode fibers, but also supports wavelength division multiplexing technology in the 850nm~1060nm wavelength range; 5. Through coating material and thickness design, this invention reduces the outer diameter of the fiber, meeting the needs of miniaturized high-density cables, effectively saving the complex wiring problems in limited space. At the same time, the fiber has good stability and can maintain high transmission efficiency and strong stability under long-term working conditions. 6. The manufacturing method of this invention is simple, low-cost, highly feasible and operable, suitable for large-scale production, and applicable to vehicle-mounted optical communication networks and miniaturized optical devices. It can also adapt to the network demands of rapid data traffic growth, which is of great significance for the expansion of applications in the field of optical communication technology. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of a comparative refractive index profile structure of the present invention.

[0047] Figure 2 This is a schematic diagram of the radial cross-section structure of an optical fiber according to an embodiment of the present invention.

[0048] Figure 3 This is a schematic diagram of the refractive index profile of one embodiment of the present invention.

[0049] Figure 4 This is a schematic diagram of the refractive index profile of one embodiment of the present invention.

[0050] Figure 5 This is a schematic diagram of the refractive index profile of one embodiment of the present invention.

[0051] Figure 6 This is a schematic diagram of the refractive index profile of one embodiment of the present invention.

[0052] Figure 7 This is a differential mode delay diagram for a comparative example of the present invention.

[0053] Figure 8 This is a differential mode delay diagram according to an embodiment of the present invention. Detailed Implementation

[0054] Specific embodiments will be given below to further illustrate the present invention.

[0055] The preparation process of this invention is as follows: A high-purity quartz glass liner is clamped and fixed at both ends by rotating chucks on a plasma chemical vapor deposition (PCVD) lathe with a certain rotation angle. The liner is placed in a holding furnace at a certain temperature (usually 1000℃~1300℃) and passes through a high-frequency microwave resonant cavity. The process reactants required for mandrel preparation are formed into stable gaseous substances through a constant temperature and pressure (usually 45±2℃, 0.8±0.1atm) evaporation system. Then, the gaseous substances are introduced into the liner from one end of the lathe's rotating chuck through a constant temperature (usually 20±2℃) pipe. A certain amount of germanium (GeCl4), fluorine (C2F6), phosphorus (POCl3), and boron (BCl2) are introduced into the reaction gases silicon tetrachloride (SiCl4) and O2. 3) The refractive index is adjusted by using a multi-doping method to excite high-energy plasma through a high-frequency microwave resonant cavity for doping deposition. The gas flow rate is precisely controlled by a mass flow controller (MFC) throughout the process. Finally, the doping is deposited in a glassy state on the inner wall of the liner tube. The third depressed cladding, the second depressed cladding, the first depressed cladding, the inner cladding, and the core layer are deposited in sequence. After deposition, the core is shrunk into a solid core rod by a high-temperature (1800℃~2300℃) shrinking lathe. The solid core rod has the core layer, inner cladding, first depressed cladding, second depressed cladding, and third depressed cladding from the inside out. After cleaning, etching, and drying, the core rod is used to form an outer cladding through RIT sleeve process or OVD process to prepare a multimode optical fiber preform. The preform is then drawn into an optical fiber by a drawing equipment.

[0056] The resulting optical fiber consists of a core and a cladding. The refractive index profile of the core exhibits a parabolic distribution following an α-power exponential function, with a distribution exponent α1 ranging from 2.0 to 2.7. The core radius R1 ranges from 12 to 32 μm, and the maximum relative refractive index difference Δ at the core center is [not specified]. 1max The relative refractive index is 0.85% to 1.5%, and the relative refractive index difference Δ1 at the core edge R1 is -0.15% to 0.05%. The cladding layers, from the inside out, are an inner cladding layer, a first depressed cladding layer, a second depressed cladding layer, a third depressed cladding layer, and an outer cladding layer.

[0057] The width of one side (R2-R1) of the inner cladding is 0.5~3.0μm, and the relative refractive index difference Δ2 of the inner cladding is -0.24%~0.07%, preferably -0.18%~0.02%. The width of one side (R3-R2) of the first recessed cladding is 1.5~6.0μm, and the relative refractive index difference Δ3 of the first recessed cladding is -1.1%~-0.6%, preferably -0.8%~-0.7%. The second recessed cladding is provided with a first layer 21 and a second layer 22 from the inside to the outside. The relative refractive index difference of the first layer increases linearly with the increase of the fiber radius, and the relative refractive index difference of the second layer is equal to a flat or step curve. The relative refractive index difference at the beginning of the second layer is equal to the relative refractive index difference at the end of the first layer. The width of one side (R4-R3) of the first layer of the second recessed cladding 21 is 0.5~2.5μm, and the relative refractive index difference Δ4 is ​​-1.0%~-0.3%. Preferably, the relative refractive index difference Δ4 of the first layer of the second recessed cladding is -0.8%~-0.5%. The width of one side (R5-R4) of the second layer of the second recessed cladding 22 is 0.2~1.5μm, and the relative refractive index difference Δ5 is -0.9%~-0.5%. The ratio of the width of the first layer to the width of the second layer of the second recessed cladding is in the range of 2~5, which can effectively improve the bending insensitivity of the optical fiber. The width of the third cladding layer (R6-R5) is 1.5~12μm, and the relative refractive index difference Δ6 of the third cladding layer is -1.0%~-0.7%, preferably -0.8%~-0.7%. The outer cladding layer is a pure silica glass layer or a doped silica glass layer, with a radius R7 of 60~65μm and a relative refractive index difference Δ7 of -0.12~0.15%. The first cladding layer is designed with a deeper refractive index and a wider width than the first layer 21 of the second cladding layer, which can effectively increase the bending resistance. The second cladding layer 22 is designed with an equal-value straight line or a step curve, which can effectively alleviate defects such as microcracks caused by uneven stress between the cladding layer and the outer cladding layer, effectively offset the damage caused by external pressure on small-diameter optical fibers, and improve the service life in confined spaces and harsh environments. The triple-depressed cladding design optimizes the stress difference between the core, inner cladding, and depressed cladding, while reducing the fiber bandwidth's sensitivity to wavelength, giving the fiber good bend insensitivity while maintaining high bandwidth performance. Furthermore, the design where the refractive index at the beginning of the second layer 22 is equal to the refractive index at the end of the first section 21 improves the refractive index distortion caused by element diffusion between different layers of the core and depressed cladding, as well as the microcracks inside the fiber caused by stress inhomogeneity. This significantly improves the fiber's bend insensitivity, attenuation performance, and long-term stability.

[0058] The core layer of the optical fiber is a silicon dioxide glass layer co-doped with germanium and fluorine (Ge / F), or germanium, phosphorus, and fluorine (Ge / P / F), or germanium, boron, and fluorine (Ge / B / F). Multi-doping effectively reduces the bandwidth's sensitivity to wavelength, enabling the optical fiber to have high bandwidth over a wider wavelength range and improving high-speed communication performance. Fluorine acts as a negative dopant in the core layer, with the doping amount increasing from the core center to the edge. The fluorine doping contribution Δ at the core center is significant. F0 The contribution of fluorine doping at the core edge is -0.1% to -0.04%, Δ. F1 The range is -0.6% to -0.08%.

[0059] The inner cladding of the optical fiber is a silica glass layer co-doped with germanium, fluorine, and phosphorus (Ge / F / P), or germanium, fluorine, and boron (Ge / F / B), with a radius R2 ≥ 15 μm and a single-side width (R2-R1) ≥ 1.8 μm. The phosphorus doping contribution ΔP is ≤ 0.12%, and the boron doping contribution ΔB is ≤ 0.15%. Alternatively, it can be co-doped with germanium, fluorine, phosphorus, and boron. The relative refractive index difference Δ2 is less than or equal to the minimum relative refractive index difference Δ1 at the core edge, i.e., Δ2 ≤ Δ1. The design of the inner cladding's refractive index being lower than that at the core edge effectively prevents excessive mode leakage, improves the transmission performance of higher-order modes at the beginning of the core, effectively suppresses the propagation of higher-order modes in the core, and enhances both bandwidth stability and attenuation performance while improving the overall optical fiber communication transmission performance. Meanwhile, by doping with phosphorus or boron to significantly reduce its viscosity and improve its viscosity matching with the depressed cladding, the single-sided width (R3-R2) of the first depressed cladding is less than or equal to the single-sided width (R6-R5) of the third depressed cladding. Preferably, the ratio of the single-sided width (R6-R5) of the third depressed cladding to the single-sided width (R3-R2) of the first depressed cladding is in the range of 1.5 to 1.8. The relative refractive index difference Δ3 of the first depressed cladding is less than or equal to the relative refractive index difference Δ3 of the second depressed cladding. 4（5） That is, Δ3≤Δ 4（5） The relative refractive index difference Δ5 of the two layers 22 of the second recessed cladding exhibits an upward convex curve distribution, and the relative refractive index difference at the inner edge of the two layers 22 is equal to that at the outer edge. The refractive index gradient design of the first and second layers of the second recessed cladding effectively alters modal dispersion while possessing superior bending resistance, thus better preventing light leakage under deep trench conditions and ensuring stable and efficient energy transfer. The radius R5 of the second recessed cladding is ≥30μm, the ratio of the width of the third recessed cladding (R6-R5) to the width of the second recessed cladding (R5-R3) ranges from 2 to 3, preferably, the width of the second recessed cladding (R5-R3) is ≥1μm, and the relative refractive index difference Δ6 of the third recessed cladding is less than or equal to the relative refractive index difference Δ5 of the second recessed cladding. 4（5） That is, Δ6≤Δ 4（5）Preferably, the width R6 of the third recessed cladding layer is ≥33μm.

[0060] The first, second, and third depressed claddings have negative relative refractive index differences. In particular, the second depressed cladding has a negative relative refractive index difference Δ. 4（5） Greater than or equal to the relative refractive index difference Δ3 of the first depressed cladding, i.e., Δ 4（5） ≥Δ3. Besides improving high-level mode dispersion originating from the core layer, it can also effectively enhance the fiber's bending resistance and attenuation performance. The fiber's outer cladding is a pure silica glass layer or a silica glass layer doped with one or more of the following dopants: aluminum, calcium, magnesium, titanium, zirconium, iron, cobalt, nickel, manganese, copper, lithium, sodium, potassium, boron, and chlorine. The silica (SiO2) glass layer contains 1-60 ppm of aluminum (Al), ≤80 ppm of total metal elements, and 1300-2300 ppm of chlorine (Cl).

[0061] The outer cladding layer is coated with a resin coating layer, which includes an inner coating layer and an outer coating layer from the inside out. The inner coating layer is designed as a softer coating to buffer and dissipate fiber stress distortion caused by the forces from the outer coating layer and its outer surface, thereby minimizing the stress on the glass fiber. The outer coating layer is designed as a harder coating to buffer damage caused by external forces during cabling, handling, and installation. The inner coating layer is designed to maintain sufficient adhesion to the glass fiber while also having good peelability and no residue during thermal aging. The coating peel force of the fiber is ≤0.8N. The polymer material of the coating layer is polyurethane acrylate. The Young's modulus of the inner coating layer is ≤0.2MPa, and the glass transition temperature (Tg) is ≤-50°C. The Young's modulus of the outer coating layer is ≥1100MPa. The Young's modulus was measured using a D lamp to cure a 75-micron film at an energy of 1 J / cm² in a nitrogen atmosphere under test conditions of 23°C and 50% relative humidity. The coating layer is cured using ultraviolet lamps or LED light sources. The thickness of the inner coating layer (R8-R7) is 10μm to 25μm, and the thickness of the outer coating layer (R9-R8) is 10μm to 30μm. This dual-coating design ensures that the optical fiber has good mechanical properties while maintaining good high and low temperature performance during the fabrication of small-volume, high-density cables.

[0062] According to the present invention, an array of optical fiber preforms was prepared and drawn into optical fibers. The structural parameters and performance parameters of the optical fibers are shown in Table 1, where Δ4 represents the value around the center. Table 1: Core structure parameters and main performance parameters of optical fibers

[0063] The numerical aperture NA was measured according to the IEC 60793-1-43-2001 (NA) method.

[0064] The full injection bandwidth was measured according to the IEC60793-1-41 method, and the test was conducted under full injection conditions.

[0065] Differential mode delay (DMD) is measured according to IEC 60793-1-49. The length of the fiber under test is 1000m ± 20%. A probe single-mode fiber is connected between the fiber under test and the light source to limit the incident light mode of the fiber under test to single-mode. The incident light pulse width is less than or equal to 100ps. The light source is incident perpendicularly to the end face of the fiber under test, and the light is scanned radially along the end face. The time difference between the fastest and slowest light pulses arriving at the output end of the fiber under test is measured, which is the differential mode delay. At the same time, using these DMD data, calculations are performed to simulate a series of specified input modes to obtain the effective mode bandwidth (EMBc).

[0066] Macrobending loss is measured according to the FOTP-62 (IEC-60793-1-47) method. The fiber under test is wound with a certain diameter (e.g., 10mm, 15mm, 20mm, 30mm, etc.) once, and then the loop is released. The change in optical power before and after the loop is measured, and this is used as the macrobending loss of the fiber. During the test, an encircled flux injection condition is used. The encircled flux injection condition can be obtained by the following method: a 2-meter-long section of ordinary 50-micron core diameter multimode fiber is fused to the front end of the fiber under test, and a 25mm diameter loop is wound in the middle of this fiber. When full injection light is injected into this fiber, the fiber under test is in the encircled flux injection condition.

[0067] Attenuation and / or fusion loss are measured according to the IEC 60793-1-40-2001 method, which is the attenuation A(λ) and attenuation coefficient α(λ) between two cross sections 1 and 2 separated by a distance L on a fiber segment at wavelength λ.

[0068] Experiments show that the high-speed communication and narrow-diameter optical fiber manufactured according to the technical solution of the present invention has good compatibility with ordinary multimode optical fiber, and has high bandwidth and strong bending resistance. It has good high-speed communication and transmission performance in wavelengths of 850nm~980nm and 1060nm. In particular, due to its miniaturized design and performance advantages, it is widely used in vehicle systems and various complex and narrow spaces under long-term working conditions. The optical fiber has good stability.

Claims

1. A high-bandwidth, bend-insensitive automotive multimode optical fiber, comprising a core and a cladding, wherein the core has a parabolic refractive index profile, characterized in that... The core layer distribution index is 2.0~2.7, the core layer radius R1 is 12~32μm, and the maximum relative refractive index difference Δ at the core layer center is... 1max The relative refractive index difference (Δ1) at the core edge R1 is 0.15% to 0.05%. The cladding, from the inside out, consists of an inner cladding, a first depressed cladding, a second depressed cladding, a third depressed cladding, and an outer cladding. The width of one side of the inner cladding (R2-R1) is 0.5 to 3.0 μm, and the relative refractive index difference (Δ2) is -0.24% to 0.07%. The width of one side of the first depressed cladding (R3-R2) is 1.5 to 6.0 μm, and the relative refractive index difference (Δ3) is -1.1% to -0.6%. The second depressed cladding comprises a first layer and a second layer arranged sequentially from the inside out. The first layer exhibits a linearly increasing gradient, with a width of 0.5 to 2.5 μm on one side (R4-R3) and a relative refractive index difference (Δ4) of -1.0%. The two layers are flat or stepped, with a single-sided width (R5-R4) of 0.2~1.5μm and a relative refractive index difference Δ5 of -0.9%~-0.5%. The single-sided width (R6-R5) of the third cladding layer is 1.5~12μm, and the relative refractive index difference Δ6 of the third cladding layer is -1.0%~-0.7%. The radius of the outer cladding layer R7 is 60~65μm, and the relative refractive index difference Δ7 is -0.12~0.15%.

2. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1, characterized in that... The relative refractive index difference Δ2 of the inner cladding is -0.18% to 0.02%.

3. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The relative refractive index difference Δ3 of the first depressed cladding is -0.8% to -0.7%.

4. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The relative refractive index difference Δ4 between the second depressed cladding layer and the first layer is -0.8% to -0.5%.

5. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The ratio of the single-side width of the first layer to the single-side width of the second layer of the second recessed cladding is 2 to 5.

6. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The relative refractive index difference Δ6 of the third depressed cladding is -0.8% to -0.7%.

7. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The core layer is a silicon dioxide glass layer co-doped with germanium and fluorine, or germanium, phosphorus and fluorine, or germanium, boron and fluorine. Fluorine acts as a negative dopant in the core layer, and the amount of fluorine doping increases from the center to the edge. The contribution of fluorine doping at the center of the core layer is Δ. F0 The contribution of fluorine doping at the core edge is -0.1% to -0.04%, Δ. F1 The range is -0.6% to -0.08%.

8. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The inner cladding is a silica glass layer doped with germanium, fluorine, and phosphorus, or germanium, fluorine, and boron, or germanium, fluorine, phosphorus, and boron, and the radius R2 of the inner cladding is ≥15μm.

9. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The width of the inner cladding layer (R2-R1) is ≥1.8μm, the phosphorus doping contribution ΔP is ≤0.12%, and the relative refractive index difference Δ2 of the inner cladding layer is less than or equal to the minimum relative refractive index difference Δ1 at the edge of the core layer, i.e., Δ2≤Δ1.

10. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The ratio of the single-side width (R6-R5) of the third recessed cladding layer to the single-side width (R3-R2) of the first recessed cladding layer is 1.5 to 1.

8.

11. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The relative refractive index difference Δ5 between the two layers of the second recessed cladding exhibits an upward convex curve distribution, and the relative refractive index difference between the inner and outer edges of the two layers is equal.

12. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The second depressed cladding has a two-layer radius R5 ≥ 30 μm, and the relative refractive index difference Δ between the second depressed cladding and the second depressed cladding is... 4（5） Less than or equal to the relative refractive index difference Δ2 of the inner cladding, i.e., Δ 4（5） ≤Δ2.

13. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The ratio of the single-side width (R6-R5) of the third depressed cladding to the single-side width (R5-R3) of the second depressed cladding is 2-3, the single-side width (R5-R3) of the second depressed cladding is ≥1μm, and the relative refractive index difference Δ6 of the third depressed cladding is less than or equal to the relative refractive index difference Δ6 of the second depressed cladding. 4（5） That is, Δ6≤Δ 4（5） .

14. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The outer cladding layer is a pure silica glass layer, or a silica glass layer doped with one or more of the following dopants: aluminum, calcium, magnesium, titanium, zirconium, iron, cobalt, nickel, manganese, copper, lithium, sodium, potassium, boron, chlorine, etc. The aluminum content of the doped silica glass layer is 1~60ppm, the total metal content is ≤80ppm, and the chlorine content is 1300~2300ppm.

15. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The numerical aperture of the optical fiber is 0.200~0.

215.

16. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The outer coating is coated with a resin coating layer, which includes an inner coating layer and an outer coating layer from the inside to the outside. The thickness of the inner coating layer (R8-R7) on one side is 10μm to 25μm, and the thickness of the outer coating layer (R9-R8) on one side is 10μm to 30μm.

17. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 16, characterized in that... The resin coating is a polyurethane acrylate coating. The inner coating has a Young's modulus ≤ 0.2 MPa and a glass transition temperature Tg ≤ -50℃. The outer coating has a Young's modulus ≥ 1100 MPa. The coating peel force of the optical fiber is ≤ 0.8 N.

18. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 16, characterized in that... The thickness of the inner coating layer (R8-R7) on one side is 20μm ~ 25μm, and the thickness of the outer coating layer (R9-R8) on one side is 25μm ~ 30μm.

19. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The DMD Inner Mask (5~18μm) and DMD Outer Mask (0~23μm) of the optical fiber are both less than or equal to 0.20 ps / m; the DMD Interval Mask is less than or equal to 0.15 ps / m.

20. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The optical fiber has a full injection bandwidth of 3500MHz at a wavelength of 850nm. km and above, with 2000MHz at a wavelength of 950nm. km and above, with 500MHz at a wavelength of 1300nm. km and above.

21. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The effective mode bandwidth of the optical fiber is 6000MHz at a wavelength of 850nm. km or more; with 6500MHz at a wavelength of 860nm. km or more; with 6000MHz at a wavelength of 870nm. km or more; has 3600MHz at a wavelength of 910nm. km or more; with 2500MHz at a wavelength of 953nm. km or more; with 2400MHz at a wavelength of 980nm. km or more; with 2200MHz at a wavelength of 1060nm. km or more.

22. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The optical fiber exhibits a bending-induced additional loss of less than or equal to 0.08 dB at 850 nm wavelength due to two turns with a bending radius of 7.5 mm; less than or equal to 0.08 dB at 1300 nm wavelength due to two turns with a bending radius of 7.5 mm; less than or equal to 0.02 dB at 15 mm bending radius; and less than or equal to 0.03 dB at 1300 nm wavelength due to two turns with a bending radius of 15 mm.

23. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The optical fiber has an attenuation of less than or equal to 2.1 dB at a wavelength of 850 nm and an attenuation of less than or equal to 0.37 dB at a wavelength of 1300 nm.

24. The high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 1 or 2, characterized in that... The optical fiber has a fusion loss of less than or equal to 0.01 dB at a wavelength of 850 nm and a fusion loss of less than or equal to 0.01 dB at a wavelength of 1300 nm.

25. A method for fabricating any of the high-bandwidth, bend-insensitive automotive multimode optical fibers as described in claims 1-24, characterized in that... The pure quartz glass liner is clamped and fixed at both ends on a plasma chemical vapor deposition lathe using rotating chucks. The liner is placed in a holding furnace at a temperature of 1000℃~1300℃ and passes through a high-frequency microwave resonant cavity. The process reactants required for core rod preparation are converted into stable gaseous substances through a constant temperature and pressure evaporation system. Then, the gaseous substances are introduced into the liner through a constant temperature pipe from one end of the lathe's rotating chuck. One or more of the dopants GeCl4, C2F6, POCl3, and BCl3 are introduced into the gaseous reactants silicon tetrachloride and O2. Doping is carried out in a multi-element doping manner via high-energy plasma excited by the high-frequency microwave resonant cavity, and finally, the doping is uniformly deposited in a glassy state on the inner wall of the liner. According to the optical fiber cross-sectional structure design requirements, the cladding and core layers are deposited sequentially. After deposition, the core is shrunk into a solid core rod by a high-temperature shrinking lathe. The core rod is then cleaned, etched, and dried, and combined with a matching sleeve to form a multimode optical fiber preform. Finally, the preform is drawn into an optical fiber using a drawing device.

26. The method for fabricating high-bandwidth, bend-insensitive automotive multimode optical fiber according to claim 25, characterized in that... The sequential deposition of the coating and core layer includes the sequential deposition of a third depressed coating, a second depressed coating, a first depressed coating, an inner coating, and a core layer. The temperature and pressure of the process reactants in the constant temperature and pressure evaporation system are 45±2℃ and 0.8±0.1atm, respectively.

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