High-bandwidth multimode optical fiber

Abstract

The present application provides a high-bandwidth multimode optical fiber. From the center of the high-bandwidth multimode optical fiber to the outer wall of the high-bandwidth multimode optical fiber, the high-bandwidth multimode optical fiber comprises a core layer, an inner cladding layer, a barrier layer, a depressed layer, and an outer cladding layer which are sequentially coated; the refractive index of the core layer from the center to the outer wall exhibits a power exponential function distribution, and the refractive index of the center of the core layer is the maximum; the refractive index of the inner cladding layer from the center to the outer wall gradually decreases; and the refractive index of the barrier layer is less than that of the inner cladding layer and greater than that of the depressed layer. The high-bandwidth multimode optical fiber provided in the present application has good bandwidth performance.

Description

High-bandwidth multimode fiber

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 5, 2023, with application number 202311648463.4 and application name “High-bandwidth multimode optical fiber”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of optical fiber technology, and more specifically, to a high-bandwidth multimode optical fiber. Background Art

[0003] Multimode fiber is a fiber that transmits multiple modes at a given operating wavelength. Due to its low system cost and high transmission capacity, multimode fiber is widely used in short- and medium-distance network systems, especially in data centers.

[0004] In related technologies, multimode optical fibers consist of a core layer, an inner cladding layer, a depression layer, and an outer cladding layer, extending from the center of the fiber outward. The refractive index of the core layer follows a power-exponential distribution from the center to the outer wall, while the refractive index of the inner cladding gradually decreases from the center to the outer wall.

[0005] However, the bandwidth performance of the above-mentioned multimode optical fibers is relatively poor.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a high-bandwidth multimode optical fiber with good bandwidth performance.

[0008] The present application provides a high-bandwidth multimode optical fiber, comprising a core layer, an inner cladding layer, a barrier layer, a depression layer and an outer cladding layer sequentially coated along the center of the high-bandwidth multimode optical fiber to the outer wall of the high-bandwidth multimode optical fiber;

[0009] The refractive index of the core layer from the center to the outer wall is distributed in a power exponential function. The refractive index at the center of the core layer is the largest, and the refractive index of the inner cladding gradually decreases from the center to the outer wall. The refractive index of the barrier layer is smaller than that of the inner cladding and larger than that of the depression layer.

[0010] In a possible implementation, in the high-bandwidth multimode optical fiber provided by the present application, the barrier layer includes a first barrier layer, and the first barrier layer is coated on the outer wall of the inner cladding.

[0011] In one possible implementation, the high-bandwidth multimode optical fiber provided in the present application comprises two barrier layers, the two barrier layers comprising a first barrier layer and a second barrier layer, the second barrier layer being coated on the outer wall of the inner cladding, and the first barrier layer being coated on the outer wall of the second barrier layer.

[0012] In a possible implementation, in the high-bandwidth multimode optical fiber provided by the present application, the refractive index of the first barrier layer is equal to the refractive index of the outer cladding layer.

[0013] In one possible implementation, the high-bandwidth multimode optical fiber provided by the present application has a first barrier layer with a cross-section that is annular along a direction perpendicular to the extension direction of the high-bandwidth multimode optical fiber, and a radial distance between an outer wall and an inner wall of the first barrier layer is 0-6 μm.

[0014] In a possible implementation, in the high-bandwidth multimode optical fiber provided by the present application, the difference between the refractive index of the second barrier layer and the refractive index of the outer cladding is no more than 0.2%, and the refractive index of the second barrier layer is no greater than the refractive index of the outer cladding.

[0015] In a possible implementation, in the high-bandwidth multimode optical fiber provided by the present application, the material of the second barrier layer includes silicon dioxide and fluorine, and the molar doping concentration of fluorine relative to silicon dioxide is 0.01%-0.5%.

[0016] In one possible implementation, the high-bandwidth multimode optical fiber provided by the present application has a second barrier layer with a cross-section that is annular along a direction perpendicular to the extension direction of the high-bandwidth multimode optical fiber, and a radial distance between the outer wall and the inner wall of the second barrier layer is 0.5-3 μm.

[0017] In a possible implementation, the high-bandwidth multimode optical fiber provided in the present application has a core layer with a cross-section that is circular along a direction perpendicular to the extension direction of the high-bandwidth multimode optical fiber, and a core layer radius of 22-32 μm.

[0018] In a possible implementation, the high-bandwidth multimode optical fiber provided by the present application has a refractive index difference between the core layer and the outer cladding layer of 0.9%-1.1%, and the refractive index of the core layer is greater than the refractive index of the outer cladding.

[0019] In one possible implementation, the high-bandwidth multimode optical fiber provided by the present application has a core layer material including silica, germanium dioxide, fluorine and phosphorus, wherein the molar doping concentration of fluorine relative to silica is 0.01%-0.35%, the molar doping concentration of phosphorus relative to silica is 0.01%-0.3%, and the molar doping concentration of germanium dioxide relative to silica is 3%-20%.

[0020] In one possible implementation, the high-bandwidth multimode optical fiber provided in the present application has an inner cladding with a cross-section that is annular along a direction perpendicular to the extension direction of the high-bandwidth multimode optical fiber, and a radial distance between the outer wall and the inner wall of the inner cladding is 0.5-6 μm.

[0021] In one possible implementation, the high-bandwidth multimode optical fiber provided by the present application has a refractive index difference between the inner wall of the inner cladding and the refractive index of the outer cladding of 0.001%-0.1%, and the refractive index of the inner wall of the inner cladding is greater than the refractive index of the outer cladding;

[0022] The difference between the refractive index of the outer wall of the inner cladding and the refractive index of the outer cladding is 0%-0.35%.

[0023] In one possible implementation, the high-bandwidth multimode optical fiber provided by the present application has an inner cladding material comprising silica, germanium dioxide, and fluorine, wherein the molar doping concentration of fluorine relative to silica is 0.01%-0.35%, and the molar doping concentration of germanium dioxide relative to silica is 0.2%-4%.

[0024] In one possible implementation, the high-bandwidth multimode optical fiber provided in the present application has a depressed layer with a cross-section that is annular along a direction perpendicular to the extension direction of the high-bandwidth multimode optical fiber, and a radial distance between the outer wall and the inner wall of the depressed layer is 2.5-6.5 μm.

[0025] In a possible implementation, in the high-bandwidth multimode optical fiber provided by the present application, the difference between the refractive index of the depressed layer and the refractive index of the outer cladding is 0.3%-0.6%, and the refractive index of the depressed layer is smaller than the refractive index of the outer cladding.

[0026] In a possible implementation, in the high-bandwidth multimode optical fiber provided by the present application, the material of the depressed layer includes silica and fluorine, and the molar doping concentration of fluorine relative to silica is 0.5%-1.5%.

[0027] In combination with the above technical solutions, the high-bandwidth multimode optical fiber provided by the present application is provided with an inner cladding and a barrier layer, and the refractive index of the inner cladding gradually decreases from the center to the outer wall. The refractive index of the barrier layer is less than that of the inner cladding and greater than that of the depression layer. This can gradually transition the refractive index between the core layer and the depression layer, avoiding a sudden change in the refractive index between the core layer and the depression layer, thereby reducing the interference of the core-cladding boundary on the high-order mode transmission rate, effectively controlling the core-cladding interface on the high-order mode transmission rate, reducing mode delay, thereby increasing the optical fiber transmission bandwidth and obtaining high-bandwidth characteristics. Moreover, by providing a barrier layer, the problem that fluorine in the depression layer will diffuse into the inner cladding under high temperature and affect the refractive index of the inner cladding can be solved, thereby improving bandwidth performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a DMD diagram of a multimode optical fiber in the related art;

[0029] FIG2 is a schematic diagram of the structure of a high-bandwidth multimode optical fiber provided in an embodiment of the present application;

[0030] FIG3 is a diagram showing a refractive index variation of a high-bandwidth multimode optical fiber provided in an embodiment of the present application along a cross section perpendicular to the extension direction;

[0031] FIG4 is a DMD diagram of a high-bandwidth multimode optical fiber provided in an embodiment of the present application;

[0032] FIG5 is a diagram showing a refractive index variation of a high-bandwidth multimode optical fiber provided in Example 1 of the present application along a cross section perpendicular to the extension direction;

[0033] FIG6 is a diagram showing the refractive index variation of a high-bandwidth multimode optical fiber provided in Example 2 of the present application along a cross section perpendicular to the extension direction.

[0034] Description of reference numerals:

[0035] 100-core layer;

[0036] 200-inner cladding;

[0037] 300-barrier layer;

[0038] 310-first barrier layer;

[0039] 320- second barrier layer;

[0040] 400-sag layer;

[0041] 500-outer cladding. DETAILED DESCRIPTION

[0042] In the description of this application, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to a fixed connection, an indirect connection via an intermediate medium, internal communication between two components, or an interaction between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0043] In the description of this application, the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limiting this application.

[0044] The terms "first," "second," and "third" (if any) in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in orders other than those illustrated or described herein.

[0045] In addition, the terms "comprises" and "having" and any variations thereof are intended to cover a non-exclusive inclusion. For example, a process, method, system, product or service tool that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, product or service tool.

[0046] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0047] In related technologies, a multimode optical fiber includes a core layer, an inner cladding, a depression layer, and an outer cladding from the center of the optical fiber to the outside. The refractive index of the core layer from the center to the outer wall is distributed in a power exponential function, the refractive index of the inner cladding gradually decreases from the center to the outer wall, and the refractive index of the depression layer is smaller than that of the outer cladding.

[0048] It can be understood that by adding a depressed layer, when macrobending occurs in the optical fiber, the high-order modes will be effectively confined to the depressed layer, reducing the leakage of the high-order modes, thereby reducing the bending loss of the optical fiber.

[0049] Furthermore, multimode optical fibers commonly have hundreds of transmission modes. Because each mode has a different transmission path within the fiber, the optical path lengths of pulse signal components in different modes are unequal, resulting in broadening of the pulse signals received at the output end and causing signal distortion. To reduce intermodal dispersion, the core refractive index profile is designed to adopt a power-exponential parabolic structure. This refractive index adjustment equalizes the optical path lengths of light pulses propagating in different modes, thereby reducing inter-pulse delay and increasing bandwidth.

[0050] Specifically, the relationship between the different radial refractive indices n of the core layer and the fiber radius r can be described by the following relationship:

[0051] Where n0 is the refractive index at the core center, b is the core radius, Δ is the difference between the refractive index at the core center and the refractive index at the core wall, and α is the core distribution index. The value of α directly determines the distribution of the core refractive index, thereby affecting the propagation speed of light in different modes. Therefore, by adjusting the value of α, intermodal dispersion can be effectively controlled, thereby optimizing bandwidth performance.

[0052] An inner cladding is set between the core layer and the depression layer, and the refractive index of the inner cladding is negatively correlated with the radius, which can make the refractive index between the core layer and the depression layer gradually transition, avoiding a sudden change in the refractive index between the core layer and the depression layer, thereby reducing the interference of the core-cladding boundary on the high-order mode transmission rate, effectively controlling the core-cladding interface on the high-order mode transmission rate, reducing mode delay, thereby increasing the optical fiber transmission bandwidth and obtaining high-bandwidth characteristics.

[0053] Multimode fiber bandwidth is a key parameter used to evaluate the signal rate capability of multimode transmission. Traditional multimode fiber uses LEDs (Light-Emitting Diodes) as its light source. The over-filled launch (OFL) bandwidth of a multimode fiber is an indicator of the fiber's bandwidth performance under the LED light source, typically measured using time-domain (pulse stretching) and frequency-domain (frequency sweep) methods. For high-speed transmission fibers with bandwidths above OM3, VCSELs (Vertical Cavity Surface Emitting Lasers) are used for fiber injection. These high-bandwidth light sources exhibit uneven emission along the radial plane, making effective mode bandwidth (EMB) more suitable. The EMB test method combines the measured DMD (Digital Micromirror Device) output delay response of the fiber with the typical light intensity distribution characteristics of a VCSEL laser operating at an 850nm wavelength. The bandwidth of the VCSEL fiber system, calculated through dispersion mode delay, is then used to determine the fiber's performance for 10Gbit / s Ethernet. The DMD test injects light pulses of a given wavelength λ at different radial offset positions. Due to the difference in radial refractive index, each pulse has a different transmission path. After transmitting through a given length L of fiber, the fiber's response to each pulse is measured to obtain a DMD graph. The pulse center delay is calculated as follows:

[0054] C i =T i -T0

[0055] i=0-25, i represents the first pulse, i=0 is the fiber center pulse. PW is the pulse test width, P i(t) is the power of the i-th pulse, T i is the pulse center of the i-th pulse, C i is the pulse center delay, P(t) is the power of the standard pulse, which is equal to P0(t), and t is time.

[0056] Figure 1 shows a DMD graph of a multimode fiber in the related art. As shown in Figure 1, the horizontal coordinates (pulse center delay) corresponding to the peak values ​​of each curve are poorly consistent under different radial offset conditions, and when the radial offset is greater than 20°, the curve has two distinct peaks.

[0057] In other words, the transmission speed of the high-order mode at the core layer boundary is affected by the refractive index difference at the core-clad boundary (the boundary between the core layer and the depression layer), resulting in an increase in the time delay at the core-clad boundary. How to effectively control the pulse rate at the core-clad boundary is a key issue that needs to be solved in the design of this application.

[0058] Analysis revealed that during the fabrication of multimode optical fibers in the related art, the fluorine concentration in the depressed layer is relatively high. Under high temperatures, the fluorine diffuses into the inner cladding, causing the interface between the inner cladding and the depressed layer to change due to the change in fluorine concentration, leading to a change in the refractive index. In other words, the actual refractive index at the interface between the inner cladding and the depressed layer after processing deviates from the target refractive index, resulting in limited accuracy in pulse delay control at the boundary. As a result, the inner cladding is less effective in improving the bandwidth of the multimode optical fiber, thus addressing the technical issue of poor bandwidth performance in the related art multimode optical fibers.

[0059] Based on this, the high-bandwidth multimode optical fiber provided in this application solves the problem that the fluorine in the depressed layer will diffuse into the inner cladding under high temperature and affect the refractive index of the inner cladding by setting a barrier layer between the inner cladding and the depressed layer, thereby improving the bandwidth performance.

[0060] Figure 2 is a schematic structural diagram of the high-bandwidth multimode optical fiber provided in an embodiment of the present application, Figure 3 is a refractive index change diagram of the high-bandwidth multimode optical fiber provided in an embodiment of the present application along a cross-section perpendicular to the extension direction, and Figure 4 is a DMD diagram of the high-bandwidth multimode optical fiber provided in an embodiment of the present application.

[0061] 2 to 4 , the high-bandwidth multimode optical fiber provided in the present application includes a core layer 100, an inner cladding 200, a barrier layer 300, a depression layer 400, and an outer cladding 500 sequentially coated along the center of the high-bandwidth multimode optical fiber to the outer wall of the high-bandwidth multimode optical fiber.

[0062] The refractive index of the core layer 100 from the center to the outer wall is distributed in a power exponential function, the refractive index at the center of the core layer 100 is the largest, the refractive index of the inner cladding 200 gradually decreases from the center to the outer wall, and the refractive index of the barrier layer 300 is smaller than the refractive index of the inner cladding 200 and greater than the refractive index of the depression layer 400.

[0063] It should be noted that the refractive index of the outer cladding layer 500 is equal to the refractive index of silicon dioxide, and the calculation formula of the refractive index difference is:

[0064] n1 is the difference between the refractive index N1 of the center of the core layer 100 and the refractive index of the outer cladding layer 500, n2 is the difference between the refractive index N2 of the outer wall of the core layer 100 and the refractive index of the outer cladding layer 500, n3 is the difference between the refractive index N3 of the second barrier layer and the refractive index of the outer cladding layer 500, n4 is the difference between the refractive index N4 of the depressed layer 400 and the refractive index of the outer cladding layer 500, and n g is the difference between the refractive index of the inner wall of the inner cladding 200 (point g in the figure) and the refractive index of the outer cladding 500, n u is the difference between the refractive index of the outer wall of the inner cladding 200 (the position indicated by point u in the figure) and the refractive index of the outer cladding 500

[0065] Among them, R0 is the radius of the core layer 100, R1 is the radius of the outer wall of the inner cladding layer 200, R2 is the radius of the outer wall of the second barrier layer, R3 is the radius of the outer wall of the first barrier layer, R4 is the radius of the outer wall of the depression layer 400, and R5 is the radius of the outer wall of the outer cladding layer 500.

[0066] It is understood that by providing the inner cladding 200 and the barrier layer 300, and by gradually decreasing the refractive index of the inner cladding 200 from the center to the outer wall, and by having the refractive index of the barrier layer 300 less than that of the inner cladding 200 and greater than that of the depressed layer 400, a gradual transition in the refractive index between the core layer 100 and the depressed layer 400 can be achieved, thereby avoiding a sudden change in the refractive index emission between the core layer 100 and the depressed layer 400. This reduces the interference of the core-cladding boundary (the boundary between the core layer 100 and the depressed layer 400) on the transmission rate of higher-order modes, effectively controls the transmission rate of higher-order modes at the core-cladding boundary, reduces mode delay, and thus improves the transmission bandwidth of the optical fiber, achieving high-bandwidth characteristics. Furthermore, the provision of the barrier layer 300 can solve the problem that fluorine in the depressed layer 400 can diffuse into the inner cladding 200 at high temperatures, affecting the refractive index of the inner cladding 200, thereby improving the bandwidth performance of the high-bandwidth multimode optical fiber.

[0067] The refractive index of the inner cladding 200 gradually decreases from the center to the outer wall, and its refractive index is linearly or approximately parabolically distributed, with an angle θ with the horizontal direction less than 90°.

[0068] The refractive index of the core layer 100 from the center to the outer wall is distributed in a power exponential function, and its parameter α depends on the operating wavelength. At an operating wavelength of 850 nm, α can ideally be 2-3. For example, α can be 2.08.

[0069] Furthermore, at a wavelength of 850 nm, the high-bandwidth multimode optical fiber has a bending loss of less than or equal to 0.2 dB when the fiber is loosely wound twice with a radius of 7.5 mm, and a bending loss of less than or equal to 0.1 dB when the fiber is loosely wound twice with a radius of 15 mm.

[0070] For high-bandwidth multimode optical fiber at a wavelength of 1300nm, the bending loss of 7.5mm radius loosely wound 2 turns is less than or equal to 0.5dB, and the bending loss of 15mm radius loosely wound 2 turns is less than or equal to 0.3dB.

[0071] The high-bandwidth multimode optical fiber provided in this embodiment comprises a core layer 100, an inner cladding 200, a barrier layer 300, a depressed layer 400, and an outer cladding 500, sequentially coated from the center of the high-bandwidth multimode optical fiber to its outer wall. The refractive index of the core layer 100 from the center to the outer wall follows a power exponential distribution, with the refractive index at the center of the core layer 100 being the highest. The refractive index of the inner cladding 200 gradually decreases from the center to the outer wall. The refractive index of the barrier layer 300 is lower than that of the inner cladding 200 and higher than that of the depressed layer 400. Thus, the high-bandwidth multimode optical fiber combines high bandwidth with excellent bending resistance.

[0072] In a possible implementation, the barrier layer 300 includes a first barrier layer 310 , and the first barrier layer 310 is coated on the outer wall of the inner cladding 200 .

[0073] Specifically, the first barrier layer 310 is a silicon dioxide layer, and the refractive index of the first barrier layer 310 is equal to that of the outer cladding 500. Thus, the first barrier layer 310 is provided to effectively prevent the fluorine in the depression layer 400 from diffusing into the inner cladding 200 under high temperature.

[0074] In another possible implementation, the barrier layer 300 includes a first barrier layer 310 and a second barrier layer 320. The second barrier layer 320 is coated on the outer wall of the inner cladding 200, and the first barrier layer 310 is coated on the outer wall of the second barrier layer 320. This provides a superior barrier effect for the barrier layer 300, further improving the bandwidth performance of high-bandwidth multimode optical fibers. The second barrier layer 320 can further assist in regulating the bandwidth of higher-order modes at the core-cladding boundary, compensating for the design precision of the inner cladding 200 due to rod manufacturing technology.

[0075] Specifically, the first barrier layer 310 is a silicon dioxide layer, and the refractive index of the first barrier layer 310 is equal to the refractive index of the outer cladding layer 500 .

[0076] In one possible implementation, the cross-section of the first barrier layer 310 is annular in shape, perpendicular to the extension direction of the high-bandwidth multimode optical fiber. The radial distance between the outer and inner walls of the first barrier layer 310 is 0-6 μm. In other words, R3 - R2 is 0-6 μm. For example, R3 - R2 can be 3 μm.

[0077] It can be understood that when R3 − R2 is 0 μm, the barrier layer 300 includes the second barrier layer 320 .

[0078] In this embodiment, the difference between the refractive index of the second barrier layer 320 and the refractive index of the outer cladding layer 500 is 0%-0.2%, and the refractive index of the second barrier layer 320 is not greater than the refractive index of the outer cladding layer 500 .

[0079] Exemplarily, the difference between the refractive index of the second barrier layer 320 and the refractive index of the outer cladding layer 500 is 0.1%.

[0080] In some embodiments, the material of the second barrier layer 320 includes silicon dioxide and fluorine, and the molar doping concentration of fluorine relative to silicon dioxide is 0.01%-0.5%. For example, the molar doping concentration of fluorine relative to silicon dioxide is 0.3%.

[0081] Specifically, the cross-section of the second barrier layer 320 is annular in shape, perpendicular to the extension direction of the high-bandwidth multimode optical fiber. The radial distance between the outer wall and the inner wall of the second barrier layer 320 is 0.5-3 μm. In other words, R2-R1 is 0.5-3 μm. For example, R2-R1 can be 2 μm.

[0082] In a possible implementation, along a direction perpendicular to the extension direction of the high-bandwidth multimode optical fiber, the cross-section of the core layer 100 is circular, and the radius of the core layer 100 is 22-32 μm, wherein the radius of the core layer 100 is 28 μm.

[0083] Specifically, the difference between the refractive index of the core layer 100 and the refractive index of the outer cladding layer 500 is 0.9%-1.1%, and the refractive index of the core layer 100 is greater than the refractive index of the outer cladding layer 500. For example, the difference between the refractive index of the core layer 100 and the refractive index of the outer cladding layer 500 is 1%.

[0084] The material of the core layer 100 includes silicon dioxide, germanium dioxide, fluorine and phosphorus, the molar doping concentration of fluorine relative to silicon dioxide is 0.01%-0.35%, the molar doping concentration of phosphorus relative to silicon dioxide is 0.01%-0.3%, and the molar doping concentration of germanium dioxide relative to silicon dioxide is 3%-20%.

[0085] It should be noted that the core layer 100 can be processed by using an MCVD (Modified Chemical Vapor Deposition) or PCVD (Plasma Chemical Vapor Deposition) in-tube rod making process.

[0086] In some embodiments, the cross-section of the inner cladding 200 is annular in shape, perpendicular to the extension direction of the high-bandwidth multimode optical fiber. The radial distance between the outer and inner walls of the inner cladding 200 is 0.5-6 μm. In other words, R1-R2 is 0.5-6 μm. For example, R1-R2 can be 3 μm.

[0087] 3 , the difference between the refractive index of the inner wall of the inner cladding 200 and the refractive index of the outer cladding 500 is 0.001%-0.1%, and the refractive index of the inner wall of the inner cladding 200 is greater than the refractive index of the outer cladding 500. For example, the difference between the refractive index of the inner wall of the inner cladding 200 and the refractive index of the outer cladding 500 is 0.05%.

[0088] The difference between the refractive index of the outer wall of the inner cladding 200 and the refractive index of the outer cladding 500 is 0%-0.35%. The refractive index of the outer wall of the inner cladding 200 may be greater than the refractive index of the outer cladding 500, the refractive index of the outer wall of the inner cladding 200 may be equal to the refractive index of the outer cladding 500, or the refractive index of the outer wall of the inner cladding 200 may be less than the refractive index of the outer cladding 500. Exemplarily, the difference between the refractive index of the outer wall of the inner cladding 200 and the refractive index of the outer cladding 500 is 0.2%.

[0089] Specifically, the material of the inner cladding 200 includes silicon dioxide, germanium dioxide and fluorine, the molar doping concentration of fluorine relative to silicon dioxide is 0.01%-0.35%, and the molar doping concentration of germanium dioxide relative to silicon dioxide is 0.2%-4%.

[0090] For example, the molar doping concentration of fluorine relative to silicon dioxide is 0.2%, and the molar doping concentration of germanium dioxide relative to silicon dioxide is 2%.

[0091] It should be noted that points g and u can be adjusted along four dimensions on the coordinate axis to achieve continuous adjustment of the bandwidth. The specific adjustment method is consistent with the adjustment method in the relevant technology and will not be described in detail in this embodiment.

[0092] In one possible implementation, the cross-section of the depressed layer 400 is annular in shape, perpendicular to the extension direction of the high-bandwidth multimode optical fiber. The radial distance between the outer and inner walls of the depressed layer 400 is 2.5-6.5 μm. In other words, R4-R3 is 2.5-6.5 μm. For example, R4-R3 is 4 μm.

[0093] Specifically, the difference between the refractive index of the depressed layer 400 and the refractive index of the outer cladding layer 500 is 0.3%-0.6%, and the refractive index of the depressed layer 400 is smaller than the refractive index of the outer cladding layer 500 .

[0094] For example, the difference between the refractive index of the trap layer and the refractive index of the outer cladding 500 is 0.45%.

[0095] The material of the recessed layer 400 includes silicon dioxide and fluorine, and the molar doping concentration of fluorine relative to silicon dioxide is 0.5%-1.5%.

[0096] Exemplarily, the molar doping concentration of fluorine relative to silicon dioxide is 1%.

[0097] The specific embodiments of the high-bandwidth multimode optical fiber are introduced below.

[0098] Example 1

[0099] FIG5 is a diagram showing the refractive index variation of a high-bandwidth multimode optical fiber provided in Example 1 of the present application along a cross section perpendicular to the extension direction.

[0100] As shown in Figure 5, the high-bandwidth multimode optical fiber includes a core layer 100, an inner cladding layer 200, a first barrier layer 310, a depression layer 400, and an outer cladding layer 500. The refractive index of the core layer 100 from the center to the outer wall is parabolic. The refractive index difference n1 between the center of the core layer 100 and the outer cladding 500 is 0.92%, and the refractive index difference n1 between the boundary point g between the inner cladding 200 and the core layer 100 and the outer cladding 500 is 0.92%. g is 0.07%, and the difference n between the boundary point u between the inner cladding 200 and the first barrier layer 310 and the refractive index of the outer cladding 500 is u The refractive index difference n4 between the depressed layer 400 and the outer cladding 500 is 0.41%. The radius R0 of the core layer 100 is 25 μm, and the width R1-R0 of the inner cladding 200 is 2.5 μm. This embodiment does not include a second barrier layer 320. The width of the first barrier layer 310, extending outward from the boundary of the inner cladding 200 to R3-R1, is 4.8 μm. The width of the depressed layer 400 is R4-R3, which is 4.5 μm. This embodiment can be produced using MCVD or PCVD processes.

[0101] Based on DMD test results, the effective modal bandwidth is calculated to be 1752 MHz / km, the full injection bandwidth at 850° is 1415 MHz / km, and the full injection bandwidth at 1300° is 579 MHz / km, meeting the OM2+ bandwidth standard. Bend loss for R7.5 (2 turns) at 850° is 0.028 dB, for R15 (2 turns) at 850° is 0.004 dB, for R7.5 (2 turns) at 1300° is 0.079 dB, and for R15 (2 turns) at 1300° is 0.018 dB.

[0102] Example 2

[0103] FIG6 is a diagram showing the refractive index variation of a high-bandwidth multimode optical fiber provided in Example 2 of the present application along a cross section perpendicular to the extension direction.

[0104] 6 , the high-bandwidth multimode optical fiber includes a core layer 100, an inner cladding layer 200, a second barrier layer 320, a first barrier layer 310, a depressed layer 400, and an outer cladding layer 500. The second barrier layer 320 is used to assist in compensating for high-order modes at the boundary.

[0105] The refractive index of the core layer 100 from the center to the outer wall is parabolic. The refractive index difference n1 between the center of the core layer 100 and the outer cladding 500 is 0.92%, and the refractive index difference n1 between the boundary point g between the inner cladding 200 and the core layer 100 and the outer cladding 500 is 0.92%. g is 0.07%, and the difference n between the boundary point u between the inner cladding 200 and the second barrier layer 320 and the refractive index of the outer cladding 500 is u The refractive index difference n3 between the second barrier layer 320 and the outer cladding 500 is -0.09%, and the refractive index difference n4 between the depressed layer 400 and the outer cladding 500 is 0.41%. The radius R0 of the core layer 100 is 25 μm, the width R1-R0 of the inner cladding 200 is 2.5 μm, the width R2-R1 of the second barrier layer 320 extending outward from the inner cladding 200 is 1 μm, the width R2-R1 of the first barrier layer 310 extending outward from the boundary of the inner cladding 200 is 4.8 μm, and the width R4-R3 of the depressed layer 400 is 4.5 μm. This embodiment can be produced using MCVD or PCVD processes.

[0106] Based on DMD test results, the effective mode bandwidth is calculated to be 2314 MHz / km, the full injection bandwidth @850 is 1695 MHz / km, and the full injection bandwidth @1300 is 604 MHz / km, meeting the OM3 bandwidth standard. The addition of the second barrier layer 320 can, to a certain extent, help mitigate the impact of the first barrier layer 310 on the bandwidth of the boundary higher-order modes. Bend loss is 0.102 dB for R7.5-2 turns @850, 0.073 dB for R15-2 turns @850, 0.418 dB for R7.5-2 turns @1300, and 0.111 dB for R15-2 turns @1300. Adding the second barrier layer 320 has minimal impact on multimode bending performance.

[0107] Example 3

[0108] Based on the design of the second embodiment, the parameters of the inner cladding 200 and the second barrier layer 320 are adjusted to increase the optical fiber bandwidth.

[0109] The high-bandwidth multimode optical fiber includes a core layer 100, an inner cladding layer 200, a second barrier layer 320, a first barrier layer 310, a depression layer 400, and an outer cladding layer 500. The refractive index of the core layer 100 is parabolically distributed from the center to the outer wall. The refractive index difference n1 between the center of the core layer 100 and the outer cladding 500 is 0.95%, and the refractive index difference n1 between the boundary point g between the inner cladding 200 and the core layer 100 and the outer cladding 500 is 0.95%.g is 0.085%, and the difference in refractive index between the boundary point u between the inner cladding 200 and the second barrier layer 320 and the outer cladding 500 is n u The refractive index difference n3 between the second barrier layer 320 and the outer cladding 500 is 0.02%, the refractive index difference n3 between the second barrier layer 320 and the outer cladding 500 is 0.12%, and the refractive index difference n4 between the depressed layer 400 and the outer cladding 500 is 0.41%. The radius R0 of the core layer 100 is 25.2 μm, the width R1-R0 of the inner cladding 200 is 3.2 μm, the width R2-R1 of the second barrier layer 320 extending outward from the inner cladding 200 is 1.8 μm, the width R3-R2 of the first barrier layer 310 extending outward from the boundary of the inner cladding 200 is 4.2 μm, and the width R4-R3 of the depressed layer 400 is 4.8 μm. This embodiment can be produced using MCVD or PCVD processes.

[0110] Based on DMD test results, the effective modal bandwidth is calculated to be 5726 MHz / km, the full injection bandwidth at 850° is 3961 MHz / km, and the full injection bandwidth at 1300° is 722 MHz / km, meeting the OM4 bandwidth standard. Bend loss for R7.5 (2 turns) at 850° is 0.095 dB, for R15 (2 turns) at 850° is 0.069 dB, for R7.5 (2 turns) at 1300° is 0.391 dB, and for R15 (2 turns) at 1300° is 0.103 dB.

[0111] Example 4

[0112] On the basis of the design of the third embodiment, the depth of the depressed layer is increased by 400, and the design parameters of other layers are adjusted to match, in order to improve the bending resistance of the high-bandwidth multimode optical fiber while having high bandwidth.

[0113] The high-bandwidth multimode optical fiber includes a core layer 100, an inner cladding layer 200, a second barrier layer 320, a first barrier layer 310, a depression layer 400, and an outer cladding layer 500. The refractive index of the core layer 100 is parabolically distributed from the center to the outer wall. The refractive index difference n1 between the center of the core layer 100 and the outer cladding 500 is 1.08%, and the refractive index difference n1 between the boundary point g between the inner cladding 200 and the core layer 100 and the outer cladding 500 is 1.08%. g is 0.09%, and the difference in refractive index between the boundary point u between the inner cladding 200 and the second barrier layer 320 and the outer cladding 500 is n uThe refractive index difference n3 between the second barrier layer 320 and the outer cladding 500 is 0.03%, the refractive index difference n3 between the second barrier layer 320 and the outer cladding 500 is 0.16%, and the refractive index difference n4 between the depressed layer 400 and the outer cladding 500 is 0.58%. The radius R0 of the core layer 100 is 25.5 μm, the width R1-R0 of the inner cladding 200 is 3.4 μm, the width R2-R1 of the second barrier layer 320 extending outward from the inner cladding 200 is 2.2 μm, the width R3-R2 of the first barrier layer 310 extending outward from the boundary of the inner cladding 200 is 4.3 μm, and the width R4-R3 of the depressed layer 400 is 5.2 μm. This embodiment can be produced using MCVD or PCVD processes.

[0114] Based on DMD test results, the effective modal bandwidth is calculated to be 4811 MHz / km, the full injection bandwidth at 850° is 3350 MHz / km, and the full injection bandwidth at 1300° is 783 MHz / km, meeting the OM3 bandwidth standard. Deepening the notch increases the impact on bandwidth. Bend loss is 0.063 dB for R7.5 (2 turns) at 850°, 0.055 dB for R15 (2 turns) at 850°, 0.207 dB for R7.5 (2 turns) at 1300°, and 0.044 dB for R15 (2 turns) at 1300°.

[0115] Example 5

[0116] Based on the design of the fifth embodiment, the parameters of the inner cladding layer 200, the second barrier layer 320 and the first barrier layer 310 are further adjusted to increase the bandwidth of the optical fiber.

[0117] The multimode optical fiber includes a core layer 100, an inner cladding layer 200, a second barrier layer 320, a first barrier layer 310, a depression layer 400, and an outer cladding layer 500. The refractive index of the core layer 100 is parabolically distributed from the center to the outer wall. The refractive index difference n1 between the center of the core layer 100 and the outer cladding 500 is 1.11%. The refractive index difference n1 between the boundary point g between the inner cladding 200 and the core layer 100 and the outer cladding 500 is 1.11%. g is 0.088%, and the difference in refractive index between the boundary point u between the inner cladding 200 and the second barrier layer 320 and the outer cladding 500 is n u The refractive index difference n3 between the second barrier layer 320 and the outer cladding 500 is 0.02%, the refractive index difference n3 between the second barrier layer 320 and the outer cladding 500 is 0.13%, and the refractive index difference n4 between the depressed layer 400 and the outer cladding 500 is 0.55%. The radius R0 of the core layer 100 is 26.2 μm, the width R1-R0 of the inner cladding 200 is 3 μm, the width R2-R1 of the second barrier layer 320 extending outward from the inner cladding 200 is 2.5 μm, the width R3-R2 of the first barrier layer 310 extending outward from the boundary of the inner cladding 200 is 4.6 μm, and the width R4-R3 of the depressed layer 400 is 5 μm. This embodiment can be produced using MCVD or PCVD processes.

[0118] Based on DMD test results, the effective modal bandwidth is calculated to be 7139 MHz / km, the full injection bandwidth at 850° is 4017 MHz / km, and the full injection bandwidth at 1300° is 892 MHz / km, meeting the OM4 bandwidth standard. Bend loss for R7.5 (2 turns) at 850° is 0.072 dB, for R15 (2 turns) at 850° is 0.061 dB, for R7.5 (2 turns) at 1300° is 0.239 dB, and for R15 (2 turns) at 1300° is 0.057 dB.

[0119] Table 1 shows the test performance of multimode optical fibers in different embodiments.

[0120] Table 2 shows the structural parameters of the multimode optical fiber in different embodiments.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-bandwidth multimode optical fiber, characterized in that: Along the center of the high-bandwidth multimode optical fiber to the outer wall of the high-bandwidth multimode optical fiber, including a core layer, an inner cladding layer, a barrier layer, a depression layer and an outer cladding layer covered in sequence; The refractive index of the core layer from the center to the outer wall is distributed in a power exponential function, the refractive index of the center of the core layer is the largest, the refractive index of the inner cladding gradually decreases from the center to the outer wall, and the refractive index of the barrier layer is smaller than the refractive index of the inner cladding and greater than the refractive index of the depression layer.

2. The high-bandwidth multimode optical fiber according to claim 1, characterized in that: The barrier layer includes a first barrier layer, and the first barrier layer is coated on the outer wall of the inner cladding layer.

3. The high-bandwidth multimode optical fiber according to claim 1, characterized in that: The barrier layer includes two layers, including a first barrier layer and a second barrier layer, the second barrier layer is coated on the outer wall of the inner envelope, and the first barrier layer is coated on the outer wall of the second barrier layer.

4. The high-bandwidth multimode optical fiber according to claim 2 or 3, characterized in that: The refractive index of the first barrier layer is equal to the refractive index of the outer cladding layer.

5. The high-bandwidth multimode optical fiber according to claim 3, characterized in that: Along the extending direction perpendicular to the high-bandwidth multimode optical fiber, the cross-section of the first barrier layer is annular in shape, and the radial distance between the outer wall and the inner wall of the first barrier layer is 0-6 μm.

6. The high-bandwidth multimode optical fiber according to claim 3, characterized in that: The difference between the refractive index of the second barrier layer and the refractive index of the outer cladding layer is no more than 2%, and the refractive index of the second barrier layer is no more than the refractive index of the outer cladding layer.

7. The high-bandwidth multimode optical fiber according to claim 3, characterized in that: The material of the second barrier layer includes silicon dioxide and fluorine, and the molar doping concentration of fluorine relative to silicon dioxide is 0.01%-0.5%.

8. The high-bandwidth multimode optical fiber according to claim 3, characterized in that: Along the extending direction perpendicular to the high-bandwidth multimode optical fiber, the cross-section of the second barrier layer is annular, and the radial distance between the outer wall and the inner wall of the second barrier layer is 0.5-3 μm.

9. The high-bandwidth multimode optical fiber according to any one of claims 5 to 8, characterized in that: Along a direction perpendicular to the extension direction of the high-bandwidth multimode optical fiber, the cross-section of the core layer is circular, and the radius of the core layer is 22-32 μm.

10. The high-bandwidth multimode optical fiber according to any one of claims 5 to 8, characterized in that: The difference between the refractive index of the core layer and the refractive index of the outer cladding layer is 0.9%-1.1%, and the refractive index of the core layer is greater than the refractive index of the outer cladding layer.

11. The high-bandwidth multimode optical fiber according to any one of claims 5 to 8, characterized in that: The core layer material includes silicon dioxide, germanium dioxide, fluorine and phosphorus, the molar doping concentration of fluorine relative to silicon dioxide is 0.01%-0.35%, the molar doping concentration of phosphorus relative to silicon dioxide is 0.01%-0.3%, and the molar doping concentration of germanium dioxide relative to silicon dioxide is 3%-20%.

12. The high-bandwidth multimode optical fiber according to any one of claims 5 to 8, characterized in that: Along the extending direction perpendicular to the high-bandwidth multimode optical fiber, the cross-section of the inner cladding is in the shape of a ring, and the radial distance between the outer wall and the inner wall of the inner cladding is 0.5-6 μm.

13. The high-bandwidth multimode optical fiber according to any one of claims 5 to 8, characterized in that: The difference between the refractive index of the inner wall of the inner cladding and the refractive index of the outer cladding is 0.001%-0.1%, and the refractive index of the inner wall of the inner cladding is greater than the refractive index of the outer cladding; The difference between the refractive index of the outer wall of the inner cladding and the refractive index of the outer cladding is 0%-0.35%.

14. The high-bandwidth multimode optical fiber according to any one of claims 5 to 8, characterized in that: The material of the inner cladding layer includes silicon dioxide, germanium dioxide and fluorine, the molar doping concentration of the fluorine relative to the silicon dioxide is 0.01%-0.35%, and the molar doping concentration of the germanium dioxide relative to the silicon dioxide is 0.2%-4%.

15. The high-bandwidth multimode optical fiber according to any one of claims 5 to 8, characterized in that: Along the extending direction perpendicular to the high-bandwidth multimode optical fiber, the cross-section of the depressed layer is in the shape of a ring, and the radial distance between the outer wall and the inner wall of the depressed layer is 2.5-6.5 μm.

16. The high-bandwidth multimode optical fiber according to any one of claims 5 to 8, characterized in that: The difference between the refractive index of the depressed layer and the refractive index of the outer cladding layer is 0.3%-0.6%, and the refractive index of the depressed layer is smaller than the refractive index of the outer cladding layer.

17. The high-bandwidth multimode optical fiber according to any one of claims 5 to 8, characterized in that: The material of the depressed layer includes silicon dioxide and fluorine, and the molar doping concentration of the fluorine relative to the silicon dioxide is 0.5%-1.5%.

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