High bandwidth bend-insensitive multimode optical fiber

Abstract

The application relates to a high-bandwidth bending-insensitive multi-mode optical fiber which can be used for data communication and automobile communication, comprising a core layer and a cladding layer, the core layer has a parabolic refractive index profile, and the cladding layer comprises a first inner cladding layer, a second inner cladding layer, a sunken cladding layer and an outer cladding layer from inside to outside; the core layer distribution index alpha1 is 1.9-2.1, the core layer radius R1 is 12-28 mu m, the core layer center maximum relative refractive index difference Delta0 is 0.8%-1.2%, the relative refractive index difference Delta1 at the core layer edge R1 is-0.03%-0.03%, the width (R2-R1) of the first inner cladding layer is 0.4-3 mu m, the relative refractive index difference Delta2 at the outer side edge of the first inner cladding layer is-0.3%--0.04%, and the first inner cladding layer refractive index profile is a power exponential function distribution, and the width (R3-R2) of the second inner cladding layer is 0.5-4 mu m. The application realizes the optimization of optical transmission bandwidth performance.

Description

Technical Field

[0001] The invention relates to a high-bandwidth bend-insensitive multimode optical fiber, belongs to the technical field of optical communications, and can be used for transmission of data communications and automobile communications. Background Art

[0002] Multimode fiber, with its low system cost advantage, has become a high-quality solution for short-distance, high-speed transmission networks and has been widely used in data centers, office centers, high-performance computing centers, and storage area networks. The intermodal dispersion in multimode fiber greatly limits the transmission distance it can support. To reduce intermodal dispersion, the core refractive index profile of the multimode fiber needs to be designed to have a refractive index profile that continuously decreases from the center to the edge. We usually call this the "α profile." This means a refractive index profile that satisfies the following power exponential function:

[0003] r

[0004] Where n0 is the refractive index of the fiber axis; r is the distance from the fiber axis; a is the fiber core radius; α is the distribution index; ∆0 is the refractive index difference between the core center and the cladding, referred to as the relative refractive index difference.

[0005] Relative refractive index difference is ∆ i :

[0006]

[0007] in, is the refractive index at position i from the core center; Represents the refractive index of the optical fiber cladding, generally the refractive index of pure silica.

[0008] The core refractive index profile of multimode optical fiber is achieved by doping SiO2 with a certain concentration of refractive index-adjusting dopants (such as GeO2, F, B2O3, P2O5, TiO2, Al2O3, ZrO2, and SnO2). This precise control of the core refractive index profile allows multimode optical fiber to achieve high bandwidth performance, enabling high-speed transmission over hundreds of meters.

[0009] Multimode optical fiber is often used in integrated systems such as narrow cabinets, distribution boxes, and in-vehicle communications, where the fiber is subjected to very small bend radii. When conventional multimode optical fiber is bent at a small angle, high-order modes transmitted near the edge of the fiber core can easily leak out, resulting in signal loss. When designing the refractive index profile of bend-resistant multimode optical fiber, the method of adding low-refractive-index regions to the fiber cladding can be used to limit the leakage of high-order modes and minimize signal loss. However, the introduction of a depressed cladding will cause the propagation constant of high-order modes near the edge of the core layer to change, increasing the modal dispersion of the optical fiber. ​

[0010] Research has shown that when the refractive index profile of a multimode fiber is constant, it often exhibits high bandwidth performance only within a specific wavelength window. When the fiber's application window shifts to larger or smaller wavelengths, the bandwidth performance decreases significantly. Therefore, from an application perspective, the design of multimode fiber needs to be improved to ensure compatibility with existing OM3 / OM4 multimode fiber while also having low bandwidth-wavelength sensitivity to meet the application requirements of WDM technology within a certain wavelength range. Furthermore, it also requires excellent bend resistance to meet the new demands placed on multimode fiber by advances in transmission technology. By optimizing the type, concentration, and method of doping components, multi-component-doped fibers can achieve lower chromatic dispersion than the single-germanium-doped core layer of traditional multimode fibers, resulting in higher bandwidth over a wider range to meet the bandwidth requirements of wavelength division multiplexing (WDM) from 850 to 953 nm and transmission at 980 nm.

[0011] During the actual fabrication process, fluctuations in equipment and processes can cause the actual profile to deviate from the ideal profile, affecting the optical performance of the fiber and increasing the waste fiber rate. This is especially true in multi-element doping systems, where the composition of each doping layer varies significantly. Stress changes caused by element diffusion, thermal expansion coefficient, and viscosity differences during deposition, melting, and drawing processes can all lead to distortion of the refractive index profile. The core edge is particularly susceptible to the cladding structure and composition. To produce high-bandwidth, bend-insensitive multimode optical fibers, we need to minimize the impact of depressed cladding and profile distortion on the propagation modes within the core layer of the multimode fiber. Summary of the Invention

[0012] To facilitate the introduction of the present invention, some terms are defined:

[0013] Core rod: a preform containing the core layer and part of the cladding;

[0014] Radius: the distance between the outer boundary of the layer and the center point;

[0015] Refractive Index Profile: The relationship between the refractive index of the glass of an optical fiber or optical fiber preform (including the core rod) and its radius;

[0016] DMD: Differential Mode Delay, the difference in optical pulse delay between the fastest and slowest modes excited in a multimode fiber when using a laser light source. It is used to evaluate the bandwidth performance of a multimode fiber when using a laser light source.

[0017] DMD test: A single-mode probe with a mode field diameter of 5μm is used to continuously transmit light pulses to the fiber under test. The probe is simultaneously scanned from the fiber axis to the edge, moving 1μm at a time. At the receiving end, the light pulses at each position are recorded and superimposed on the same time domain diagram to form the DMD index.

[0018] Contribution of fluorine (F): The relative refractive index difference (ΔF) of fluorine-doped quartz glass relative to pure quartz glass is used to express the fluorine (F) doping amount;

[0019] Contribution of Germanium (Ge): The relative refractive index difference (ΔGe) of Germanium (Ge)-doped quartz glass relative to pure quartz glass is used to express the amount of Germanium (Ge) doping;

[0020] Contribution of phosphorus (P): The relative refractive index difference (ΔP) of phosphorus-doped quartz glass relative to pure quartz glass is used to express the amount of phosphorus (P) doping.

[0021] The technical problem to be solved by the present invention is to provide a high-bandwidth bend-insensitive multimode optical fiber with a reasonably designed core layer and cladding structure in view of the deficiencies in the above-mentioned prior art.

[0022] The technical solution adopted by the present 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 exponential function distribution), and the cladding layers are, from the inside to the outside, a first inner cladding layer, a second inner cladding layer, a depressed cladding layer and an outer cladding layer, characterized in that the core layer distribution index α1 is 1.9-2.1, the core layer radius R1 is 12-28 μm, the maximum relative refractive index difference Δ0 at the core layer center is 0.8%-1.2%, the relative refractive index difference Δ1 at the core layer edge R1 is -0.03%-0.03%, the width (R2-R1) of the first inner cladding layer is 0.4-3 μm, the relative refractive index difference Δ2 at the outer edge of the first inner cladding layer is -0.3%-0.04%, and the refractive index profile of the first inner cladding layer is a power exponential function distribution, and its relative refractive index difference Δ(r) is:

[0023] in , α2 is 0.5~2.0,

[0024] The width (R3-R2) of the second inner cladding is 0.5-4 μm, the relative refractive index difference Δ3 at the outer edge of the second inner cladding is -0.45%-0.03%, the width (R4-R3) of the depressed cladding is 3.0-9.0 μm, the relative refractive index difference Δ4 is ​​-0.9%-0.45%, and the outer cladding is a pure silica glass layer.

[0025] According to the above solution, the Δ2 of the first inner cladding is less than When α2 is 1~2, the first inner cladding Δ2> When , α2 ≥ 0.5 and < 1.

[0026] According to the above solution, the difference between the relative refractive index difference at the outer edge of the first inner cladding layer and the relative refractive index difference at the edge R1 of the core layer is Δ2-Δ1≤-0.04%.

[0027] According to the above scheme, the refractive index profile of the second inner cladding is distributed in a power exponential function, and its relative refractive index difference is

[0028] Δ(r) is:

[0029] in , α3 is 0.5~5.

[0030] According to the above solution, the difference between the relative refractive index difference between the outer edge of the second inner cladding and the relative refractive index difference between the outer edge of the first inner cladding is Δ3-Δ2<0.1%.

[0031] According to the above scheme, the core layer is a silica glass layer co-doped with germanium, fluorine or germanium, phosphorus and fluorine. The fluorine in the core layer serves as a negative dopant. The fluorine doping amount increases from the center of the core layer to the edge of the core layer. The fluorine doping contribution ΔF0 at the center of the core layer is -0.01% ~-0.1%, and the fluorine doping contribution ΔF1 at the edge of the core layer is -0.4% ~-0.1%.

[0032] According to the above scheme, the first inner cladding is a silica glass layer co-doped with germanium and fluorine or germanium, phosphorus and fluorine. The fluorine doping amount of the first inner cladding increases from the inner layer to the outer edge, wherein the fluorine doping contribution ΔF1 at the edge of the core layer is equal to the fluorine doping contribution ΔF1' at the inner layer of the first inner cladding, and the germanium doping contribution ΔGe1 at the edge of the core layer is equal to the germanium doping contribution ΔGe1' at the inner layer of the first inner cladding.

[0033] According to the above solution, the germanium doping contribution ΔGe2 at the outer edge of the first inner cladding is 0.02%~0.30%, and the fluorine doping contribution ΔF2 at the outer edge of the first inner cladding is -0.4%~-0.05%.

[0034] According to the above scheme, when the first inner cladding is co-doped with germanium, phosphorus and fluorine, the width of the first inner cladding is 1~3μm.

[0035] According to the above solution, the second inner cladding layer is a silica glass layer co-doped with fluorine or germanium, or fluorine or germanium, phosphorus and fluorine.

[0036] According to the above scheme, when the second inner cladding is co-doped with germanium, phosphorus and fluorine, the thickness of the second inner cladding (R3-R2) is ≥1.5μm, and the phosphorus doping contribution ΔP of the second inner cladding is <0.1%.

[0037] According to the above scheme, the optical fiber has a bandwidth of more than 6000 MHz-km at a wavelength of 850 nm, a bandwidth of more than 2600 MHz-km at a wavelength of 953 nm, and a bandwidth of more than 2000 MHz-km at a wavelength of 980 nm.

[0038] According to the above solution, the additional bending loss of the optical fiber caused by two turns with a bending radius of 7.5 mm at a wavelength of 850 nm is less than or equal to 0.1 dB; at a wavelength of 1300 nm, the additional bending loss caused by two turns with a bending radius of 7.5 mm is less than or equal to 0.3 dB.

[0039] The beneficial effects of the present invention are as follows: 1. The present invention improves the differential mode delay (DMD) performance of a multimode optical fiber by designing a power exponential function distribution structure of the first inner cladding, thereby optimizing the optical transmission bandwidth performance; 2. The double inner cladding design avoids the mutual influence between the core layer and the depressed cladding, as well as the refractive index distortion of the core layer caused by diffusion, stress, etc.; 3. The method of co-doping the first inner cladding with germanium and fluorine and doping the second inner cladding with fluorine avoids diffusion caused by the large difference in doping element concentration between the layers, thereby reducing the cross-sectional distortion caused by diffusion; 4. The reasonable germanium and fluorine concentration ratio and gradient change of the inner cladding improve the material viscosity matching of the inner cladding and the depressed cladding, making the stress change of the optical fiber smooth and reducing the cross-sectional distortion caused by stress; 5. The optical fiber of the present invention is not only compatible with existing OM3 / OM4 multimode optical fibers, but also supports wavelength division multiplexing technology in the wavelength range of 850nm~950nm; 6. The reasonable depressed cladding parameter design improves the bending insensitivity of the optical fiber, making it suitable for access networks, on-board optical communication networks and miniaturized optical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the refractive index profile of a comparative example of the present invention.

[0041] Figure 2 Schematic diagram of the refractive index profile of an embodiment of the present invention.

[0042] Figure 3 This is the DMD test result of a comparative example of the present invention.

[0043] Figure 4 This is a DMD test result of an embodiment of the present invention. DETAILED DESCRIPTION

[0044] Specific examples will be given below to further illustrate the present invention.

[0045] The embodiment of the present invention includes a core layer and a cladding layer, wherein the refractive index profile of the core layer is parabolic, and the cladding layers are sequentially composed of a first inner cladding layer, a second inner cladding layer, a depressed cladding layer, and an outer cladding layer from the inside to the outside. The refractive index profile of the multimode optical fiber core cladding layer needs to satisfy the following relationship:

[0046]

[0047] Wherein, Δ(r) is a function of the relative refractive index difference distribution along the radius, Δ0 is the relative refractive index difference at the center of the core layer, R1 is the radius of the core layer, Δ1 is the relative refractive index difference at R1, and α1 is the refractive index distribution index of the core layer; R2 is the outer diameter of the first inner cladding, Δ2 is the relative refractive index difference at the outer diameter (outer edge) of the first inner cladding, and α2 is the refractive index distribution index of the first inner cladding; R3 is the outer diameter of the second inner cladding, Δ3 is the relative refractive index difference at the outer diameter of the second inner cladding, and α3 is the refractive index distribution index of the second inner cladding; R4 is the outer diameter of the depressed cladding, Δ4 is ​​the relative refractive index difference of the depressed cladding; R5 is the outer diameter of the outer cladding, Δ5 is the relative refractive index difference of the outer cladding, and the outer cladding is a pure silica glass layer.

[0048] Relative refractive index difference, or ∆i:

[0049]

[0050] in, is the refractive index at position i from the core center; Represents the refractive index of the optical fiber cladding, generally the refractive index of pure silica.

[0051] The core layer of multimode optical fiber is a silica glass layer co-doped with germanium, fluorine or germanium, phosphorus and fluorine. Multi-element doping can effectively reduce the sensitivity of bandwidth to wavelength, so that multimode optical fiber has a higher bandwidth in a wider wavelength range.

[0052] The refractive index of the first inner cladding decreases gradually along the radial direction according to the distribution index to change the propagation constant of the core layer's high-order mode and compensate for the bandwidth deterioration caused by the depressed cladding and profile distortion. The refractive index of the first inner cladding is less than that of the outer cladding. , so that the propagation constant of the first inner cladding mode is This not only reduces the impact of the cladding and process on the high-order modes transmitted in the core layer, but also avoids the introduction of more new high-order modes that would reduce the fiber bandwidth.

[0053] The thickness and refractive index distribution parameters of the first inner cladding are related to the refractive index distribution of the core layer. By adjusting the relative refractive index difference Δ2, width R2-R1 and distribution index α2 at the outer diameter of the first inner cladding, the influence of the depressed cladding and profile distortion on the high-order mode of the core layer can be effectively reduced, thereby improving the mode bandwidth of the multimode optical fiber. When Δ2≤ When Δ2> When , α2≥0.5, <1.

[0054] In a comparative example, DMD Figure 3 In the middle, the high-order mode at the edge of the core layer is biased to the left, and the propagation constant of the high-order mode is small. In this case, Δ2 can be set to a larger value. large, the propagation constant of the high-order mode of the core layer is increased, the mode dispersion of the high-order mode is reduced, and α2 is adjusted to ensure that the change trend of the first inner cladding near the core layer region is similar to that of the core layer, thereby avoiding sudden changes in the refractive index profile. The DMD diagram of a certain embodiment after adjustment is shown in FIG. 8, and the intermodal dispersion between the high-order mode and the low-order mode is significantly reduced, and the fiber bandwidth is improved. Figure 4

[0055] The relative refractive index difference Δ2-Δ1 of the first inner cladding and the core layer edge is less than or equal to -0.04%, so as to ensure that the influence of the first inner cladding on the high-order mode of the core layer is large enough. However, when the refractive index Δ2 of the first inner cladding is too low or the width R2-R1 is too large, the number of leaky modes is too large, which reduces the bandwidth of the fiber. In order to limit the number of leaky modes, the width of the first inner cladding is between 0.2 and 2.5 μm, that is, the value of the relationship between the parameters inside and outside the first inner cladding should be between 0.2 and 2.5 μm. 2 2

[0056] At a high temperature in the drawing process, the doped germanium, phosphorus, fluorine and other elements in the core layer will diffuse, so that the refractive index of the core layer edge and the inner cladding of the fiber profile changes compared with the refractive index of the corresponding position of the preform. At the same time, the viscosity difference between the core layer and the cladding forms residual stress under the action of the drawing tension, and the refractive index profile is distorted under the photoelastic effect. The first inner cladding is a germanium, fluorine or germanium, phosphorus and fluorine co-doped silica glass layer. From the inside to the outside of the first inner cladding, the fluorine doping amount increases, wherein the fluorine doping contribution amount ΔF1 of the core layer edge is equal to the fluorine doping contribution amount ΔF1' of the inner diameter of the first inner cladding, and the germanium doping contribution amount ΔGe1 of the core layer edge is equal to the germanium doping contribution amount ΔGe1' of the inner diameter of the first inner cladding. Through reasonable allocation of the doping components, the profile distortion caused by diffusion and stress can be reduced.

[0057] In the preparation process of the multimode optical fiber, the flow meter is used to control the entry of the reactants. The flow meter is unstable when it is suddenly opened from the closed state, and the fluctuation in the small range is extremely large. When the multimode optical fiber is prepared by the tube method, the deposition starts from the cladding to the core, the refractive index of the first inner cladding gradually increases from outside to inside, and the flow meter of the germanium precursor also gradually increases. Therefore, before the core layer with the highest refractive index control precision is prepared, the flow meter of the germanium precursor has been gradually increased from a small opening to a target opening, and the slow change process is more controllable and stable compared with the sudden opening.

[0058] ​​​​​When the first inner cladding is co-doped with germanium and fluorine, the width of the first inner cladding is 0.4-2.5 μm, the germanium doping contribution ΔGe2 at the outer diameter of the first inner cladding is 0.02%-0.30%, and the fluorine doping contribution ΔF2 at the outer diameter of the first inner cladding is -0.4%--0.05%. When the first inner cladding is co-doped with germanium, phosphorus, and fluorine, the width of the first inner cladding is 1-3 μm.

[0059] The second inner cladding is used to compensate for the significant compositional differences between the core and depressed cladding, balancing the internal and external concentration differences and increasing the diffusion distance to minimize the impact of diffusion on the refractive index profile. Reasonable material composition, viscosity matching, and a smooth refractive index gradient minimize process-induced changes in the fiber's refractive index. The refractive index of the second inner cladding is graded, with a distribution index α3 ≥ 0.5 and ≤ 5.

[0060] The second inner cladding is a silica glass layer doped with fluorine or germanium, or fluorine or germanium, phosphorus, and fluorine. The fluorine doping contribution ΔF3 at the outer diameter of the second inner cladding is -0.5% to -0.1%. When the refractive index difference between the depressed cladding and the first inner cladding is large, such as when Δ4-Δ2 is less than -0.4%, the second inner cladding can be co-doped with germanium and fluorine, with the germanium doping contribution ΔGe3 at the outer diameter less than 0.15%. The germanium doping contribution of the second inner cladding decreases radially, resulting in a smooth change in viscosity and concentration between the first inner cladding and the depressed cladding, thereby minimizing diffusion of core germanium into the cladding.

[0061] Δ3 can be larger than Δ2, but Δ3-Δ2 needs to be less than 0.1%. When Δ3 is much larger than Δ2, the second inner cladding has too many high-order modes, which will lead to bandwidth degradation.

[0062] Compared to germanium, phosphorus significantly improves glass viscosity. Doping the second inner cladding with phosphorus can significantly reduce its viscosity, improving its viscosity match with the depressed cladding. When phosphorus is doped in the second inner cladding, its thickness must be ≥1.5μm. The phosphorus doping contribution ΔP to the second inner cladding is <0.1%.

[0063] The first and second inner cladding layers with negative refractive index can not only improve the modal dispersion of the core layer's higher-order modes, but also effectively improve the bending resistance of the optical fiber.

[0064] The outer cladding is a pure silica glass layer. The outer diameter of a conventional multimode optical fiber is generally 62.5±2.5μm. Multimode optical fibers with larger or smaller outer diameters, such as 40±2μm, 50±2μm, and 70±4μm, can also be prepared.

[0065] The refractive index profile of an actual optical fiber changes gradually between layers, not in steps. The boundaries between layers are determined as follows: The core edge R1 is the location where the relative refractive index difference drops to -0.03% to 0.03% within the R1 radius requirement range. The outer diameter R4 of the depressed cladding is the location where the relative refractive index difference increases to -0.03% to 0.03% within the R4-R3 width requirement range. Within the R2-R1 width requirement range, the outer diameter R2 of the first inner cladding is the vertex position determined by the first derivative of the relative refractive index difference with respect to the radius, or the inflection point position determined by the first derivative of the relative refractive index difference with respect to the radius. Within the R3-R2 width requirement range, the outer diameter R3 of the second inner cladding is the vertex position determined by the first derivative of the relative refractive index difference with respect to the radius, or the inflection point position determined by the first derivative of the relative refractive index difference with respect to the radius. When Δ2 is greater than Δ3, the inflection point determination is used; when Δ2 is less than Δ3, the vertex determination is used.

[0066] As described in this embodiment, a group of preform rods were prepared and drawn, using a double-layer coating of multimode optical fiber, such as a double-layer UV-curable acrylic resin. The structure and main performance parameters of the optical fiber are shown in Table 1.

[0067] Table 1: Main structural parameters and performance parameters of optical fiber

[0068]

Claims

1. A high-bandwidth bend-insensitive multimode optical fiber comprising a core layer and a cladding layer, wherein the refractive index profile of the core layer is distributed in a power exponential function, and the cladding layers are sequentially composed of a first inner cladding layer, a second inner cladding layer, a depressed cladding layer, and an outer cladding layer from the inside to the outside, characterized in that The core layer distribution index α1 is 1.9~2.1, the core layer radius R1 is 12~28μm, the maximum relative refractive index difference Δ0 at the core layer center is 0.8%~1.2%, the relative refractive index difference Δ1 at the core layer edge R1 is -0.03%~0.03%, the width of the first inner cladding (R2-R1) is 0.4~3μm, the relative refractive index difference Δ2 at the outer edge of the first inner cladding is -0.3%~-0.04%, and the refractive index profile of the first inner cladding is distributed in a power exponential function, and its relative refractive index difference Δ(r) is: in , α2 is 0.5~2.0, The width of the second inner cladding (R3-R2) is 0.5-4 μm, the relative refractive index difference Δ3 at the outer edge of the second inner cladding is -0.45%-0.03%, the width of the depressed cladding (R4-R3) is 3.0-9.0 μm, the relative refractive index difference Δ4 is ​​-0.9%-0.45%, and the outer cladding is a pure silica glass layer; the core layer is a silica glass layer doped with germanium, fluorine, or germanium, phosphorus, and fluorine. The fluorine in the core layer serves as a negative dopant, and the fluorine doping amount increases from the center of the core layer to the edge of the core layer. The fluorine doping contribution ΔF0 at the center of the core layer is -0.01%-0.1%, and the fluorine doping contribution ΔF1 at the edge of the core layer is -0.4%- -0.1%; the first inner cladding is a silica glass layer co-doped with germanium and fluorine or germanium, phosphorus and fluorine. The fluorine doping amount of the first inner cladding increases from the inner layer to the outer edge, wherein the fluorine doping contribution ΔF1 at the edge of the core layer is equal to the fluorine doping contribution ΔF1' at the inner layer of the first inner cladding, and the germanium doping contribution ΔGe1 at the edge of the core layer is equal to the germanium doping contribution ΔGe1' at the inner layer of the first inner cladding.

2. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, characterized in that The first inner cladding has a Δ2≤ When α2 is 1~2, the first inner cladding Δ2> When , α2 ≥ 0.5 and < 1.

3. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1 or 2, characterized in that The difference between the relative refractive index difference at the outer edge of the first inner cladding layer and the relative refractive index difference at the edge R1 of the core layer is Δ2-Δ1≤-0.04%.

4. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1 or 2, characterized in that The refractive index profile of the second inner cladding is distributed in a power exponential function, and its relative refractive index difference Δ(r) is: in , α3 is 0.5~5.

5. The high-bandwidth bend-insensitive multimode optical fiber according to claim 4, characterized in that The difference between the relative refractive index difference of the outer edge of the second inner cladding and the relative refractive index difference of the outer edge of the first inner cladding is Δ3-Δ2<0.1%.

6. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, characterized in that The germanium doping contribution ΔGe2 at the outer edge of the first inner cladding is 0.02% to 0.30%, and the fluorine doping contribution ΔF2 at the outer edge of the first inner cladding is -0.4% to -0.05%.

7. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, characterized in that When the first inner cladding is co-doped with germanium, phosphorus and fluorine, the width of the first inner cladding is 1-3 μm.

8. The high-bandwidth bend-insensitive multimode optical fiber according to claim 1, characterized in that The second inner cladding layer is a silica glass layer co-doped with fluorine or germanium, or fluorine or germanium, phosphorus and fluorine.

9. The high-bandwidth bend-insensitive multimode optical fiber according to claim 8, characterized in that When the second inner cladding is co-doped with germanium, phosphorus and fluorine, the thickness of the second inner cladding (R3-R2) is ≥1.5 μm, and the phosphorus doping contribution ΔP of the second inner cladding is <0.1%.

10. The bend-insensitive multimode optical fiber according to claim 1 or 2, characterized in that The optical fiber has a bandwidth of more than 6000 MHz-km at a wavelength of 850 nm, a bandwidth of more than 2600 MHz-km at a wavelength of 953 nm, and a bandwidth of more than 2000 MHz-km at a wavelength of 980 nm.

11. The bend-insensitive multimode optical fiber according to claim 1 or 2, characterized in that The additional bending loss of the optical fiber caused by winding two turns with a bending radius of 7.5 mm at a wavelength of 850 nm is less than or equal to 0.1 dB; and the additional bending loss caused by winding two turns with a bending radius of 7.5 mm at a wavelength of 1300 nm is less than or equal to 0.3 dB.

12. The bend-insensitive multimode optical fiber according to claim 1 or 2, characterized in that First inner cladding inside and outside - Between 0.2~2.5μm 2 between.

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