Bend insensitive high bandwidth multimode optical fiber

Abstract

The application discloses a bending-insensitive high-bandwidth multi-mode optical fiber, which comprises a core layer, an extension layer, an inner cladding layer, a sunken cladding layer and an outer cladding layer arranged in sequence from inside to outside, the refractive index profile of the core layer is parabolic, the distribution index is 1.9-2.2, the maximum relative refractive index difference of the core layer center position is 0.9%-1.2%, the relative refractive index difference of the extension layer is -0.03% to -0.02%, the difference between the highest relative refractive index difference and the lowest relative refractive index difference of the inner cladding layer is 0.005%-0.03%, the single-side radial width of the inner cladding layer is 0.5-4 mu m, the single-side radial width of the sunken cladding layer is 3-9 mu m, and the relative refractive index difference of the sunken cladding layer is -0.7% to -0.4%. In the application, the optical fiber viscosity is optimized, the sensitivity of the optical fiber bandwidth to wavelength is reduced, the optical fiber has good bending resistance and super high bandwidth performance by reasonably designing the waveguide structure and the doping system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical communication, and particularly relates to a bending-insensitive high-bandwidth multimode optical fiber. BACKGROUND

[0002] According to the TIA / EIA-492AAA standard, the multimode optical fiber can be divided into four types of OM1, OM2, OM3 and OM4. The high-bandwidth multimode optical fiber (such as OM3 / OM4) is widely used in the medium and short distance optical fiber network system due to relatively low system cost. The application scene of the multimode optical fiber is often a narrow cabinet, a distribution box and the like integrated system, and the optical fiber has many small bends. When the conventional multimode optical fiber is bent at a small angle, the high-order mode transmitted close to the edge of the fiber core is easily leaked out, thereby causing signal packet loss. When designing the refractive index profile of the bending-resistant multimode optical fiber, the method of adding a low refractive index region to the fiber cladding is generally used to limit the leakage of the high-order mode, so as to minimize the signal loss. In the profile design and process design of the bending-insensitive multimode optical fiber, the main difficulty is how to ensure the macro-bending performance, the DMD (Differential Mode Delay) performance and the bandwidth performance of the optical fiber through relevant design, and obtain the optimal value.

[0003] In order to obtain the high-bandwidth multimode optical fiber with good stability, the refractive index profile of the optical fiber, especially the refractive index profile of the core layer, must be accurately matched with the expected profile. Generally, a certain concentration of one or more of germanium, fluorine, chlorine and phosphorus is added to the core layer of the optical fiber preform to realize the desired refractive index distribution of the fiber core. The type and content of the doped elements in the fiber core will affect the material dispersion of the optical fiber, thereby affecting the wavelength sensitivity of the bandwidth of the optical fiber. The SiO2 doped with germanium has high material dispersion, and therefore, the wavelength range corresponding to the high bandwidth performance of the existing multimode optical fiber with a high germanium doping amount is very narrow, and a small change in the wavelength of the light source will cause a sharp decrease in the bandwidth performance. However, the multimode optical fiber applied in the wavelength division multiplexing system needs to maintain high bandwidth performance in a relatively wide wavelength range, and the transmission distance of the conventional multimode optical fiber with a high germanium doping amount in the wavelength division multiplexing system is often limited.

[0004] Not only the material dispersion but also the intermodal dispersion of the multimode optical fiber will affect the bandwidth performance, and in order to reduce the intermodal dispersion of the optical fiber, the refractive index profile of the core layer of the multimode optical fiber needs to be designed as a refractive index distribution that continuously and gradually decreases from the center to the edge, that is, a refractive index distribution of the following power function:

[0005]

[0006] r<a

[0007] Wherein, n1 is the refractive index of the optical fiber axis; r is the distance from the optical fiber axis; a is the optical fiber core radius; a is the distribution index; and Δ0 is the relative refractive index of the core center to the cladding.

[0008] The relative refractive index difference is Δ i The calculation formula is:

[0009]

[0010] Wherein, n i is the refractive index of the distance from the core center i position; n0 is the minimum refractive index of the optical fiber core layer, which is also the refractive index of the optical fiber cladding.

[0011] The related research shows that for the bend insensitive multimode optical fiber, the amount of doping, the viscosity after doping and the core layer profile refractive index design will affect the DMD and bandwidth of the optical fiber, therefore, in order to make the multimode optical fiber have good bend insensitive and high bandwidth performance, the doping system, viscosity ratio and optical fiber profile structure of the multimode optical fiber need to be optimized.

[0012] Chinese invention patent, publication number CN 106383379 A, discloses a kind of high bandwidth bend insensitive multimode optical fiber, which gradually increases in core layer fluorine-germanium co-doped fluorine-doped platform layer, it is also fluorine-germanium co-doped in inner cladding, but its fluorine-doped amount is not continuous with platform layer, it is easy to form stress mutation zone between core layer and sunken cladding, the viscosity of optical fiber will also change greatly, affect the bandwidth performance and attenuation performance of optical fiber.

[0013] In order to balance the stress and viscosity of core layer and sunken cladding, a platform layer is usually designed between the inner cladding of core layer and sunken cladding, the relative refractive index difference of the platform layer is a constant, but since the stress between core layer and sunken cladding changes with radius during the drawing process of multimode optical fiber, designing a platform layer with constant relative refractive index difference cannot well balance the stress and viscosity between the two. At the same time, due to different dopants, the platform layer will deform after drawing, therefore, when designing optical fiber, designing the inner cladding as a platform layer with constant relative refractive index difference cannot completely match the stress and viscosity of core layer and sunken cladding, and stress and viscosity compensation after drawing should be considered.

[0014] In order to solve the above problems of stress difference and viscosity difference, the application provides a kind of bend insensitive high bandwidth multimode optical fiber and its preparation method, a kind of inner cladding structure with inclined relative refractive index difference is designed, so that the stress and viscosity between sunken cladding and core layer can form continuity, eliminate the mutation area, thereby reducing the attenuation of optical fiber and improving the bandwidth performance. SUMMARY

[0015] In order to solve the technical problems in the prior art, the present application aims to provide a bending-insensitive high-bandwidth multimode optical fiber and a preparation method thereof.

[0016] In order to achieve the above-mentioned purposes and effects, the present application adopts the technical scheme of:

[0017] The bending-insensitive high-bandwidth multimode optical fiber comprises, from inside to outside, a core layer, an extension layer, an inner cladding layer, a sunken cladding layer and an outer cladding layer, the core layer has a parabolic refractive index profile, a distribution index α is 1.9-2.2, a maximum relative refractive index difference Δ1 at the center of the core layer is 0.9%-1.2%, a radius R1 of the core layer is 24-25 μm, a relative refractive index difference Δ2 of the extension layer is -0.03%- -0.02%, a difference between the radius R2 of the extension layer and the radius R1 of the core layer is 0.5-3 μm, a difference between the highest relative refractive index difference and the lowest relative refractive index difference of the inner cladding layer is 0.005%-0.03%, a single-side radial width of the inner cladding layer is 0.5-4 μm, a single-side radial width of the sunken cladding layer is 3-9 μm, and a relative refractive index difference Δ4 of the sunken cladding layer is -0.7%- -0.4%.

[0018] Further, the extension layer and the inner cladding layer are both silica glass layers doped with a dopant.

[0019] Further, the dopant comprises one or a combination of several of fluorine, aluminum, calcium, magnesium, titanium, zirconium, iron, cobalt, nickel, manganese, copper, lithium, sodium, potassium, boron, germanium, phosphorus.

[0020] Further, the outer cladding layer is a pure silica glass layer, and a radius R5 of the outer cladding layer is 62-63 μm.

[0021] Further, the optical fiber has a bending additional loss of less than 0.2 dB at a wavelength of 850 nm and a bending radius of 7.5 mm and 2 turns, and a bending additional loss of less than 0.5 dB at a wavelength of 1300 nm and a bending radius of 7.5 mm and 2 turns.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] The application discloses a bending-insensitive high-bandwidth multi-mode optical fiber, which comprises a core layer, an extension layer, an inner cladding layer, a sunken cladding layer and an outer cladding layer arranged in sequence from inside to outside, the core layer has a parabolic refractive index profile, a distribution index alpha is 1.9-2.2, a maximum relative refractive index difference Delta 1 of the core layer center position is 0.9%-1.2%, a radius R1 of the core layer is 24-25 mu m, a relative refractive index difference Delta 2 of the extension layer is -0.03% to -0.02%, a difference between the radius R2 of the extension layer and the radius R1 of the core layer is 0.5-3 mu m, a difference between the highest relative refractive index difference and the lowest relative refractive index difference of the inner cladding layer is 0.005%-0.03%, a single-side radial width of the inner cladding layer is 0.5-4 mu m, a single-side radial width of the sunken cladding layer is 3-9 mu m, and a relative refractive index difference Delta 4 of the sunken cladding layer is -0.7% to -0.4%. The optical fiber has good viscosity performance through reasonable doping, the profile of the optical fiber is optimized and designed, and the high-bandwidth performance of the multi-mode optical fiber is improved; the viscosity design and optimization of the fluorine / germanium doping of the extension layer and the inner cladding layer are highlighted, the extension layer (R2-R1) is co-doped with fluorine / germanium or other dopants (such as phosphorus), the fluorine doping ratio gradually increases from the core layer to the extension layer, the inner cladding layer (R3-R2) is co-doped with fluorine / germanium or other dopants (such as phosphorus), the doping amount (excluding fluorine) is consistent with the outermost end of the extension layer, the fluorine doping ratio is variable and gradually decreases with the increase of the radius, instead of only using fluorine doping and keeping the fluorine doping amount unchanged, the variable fluorine doping of the inner cladding layer can be adjusted according to the stress and viscosity test of the optical fiber, the appropriate variable fluorine doping amount and width can be selected, the optimal stress difference between the core layer, the extension layer and the sunken cladding layer is realized, the wavelength sensitivity of the optical fiber bandwidth is reduced, the optical fiber has good bending resistance and super high bandwidth performance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a refractive index profile schematic diagram of the application;

[0025] Figure 2 It is a fluorine doping amount schematic diagram of the application. DETAILED DESCRIPTION

[0026] The application will be described in detail below, so that the advantages and features of the application can be more easily understood by those skilled in the art, and the protection scope of the application can be more clearly and explicitly defined.

[0027] The following gives a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an extensive overview of all contemplated aspects, and is neither intended to identify key or critical elements of all aspects nor to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0028] As shown in Figures 1-2 A bending insensitive high-bandwidth multimode optical fiber, comprising a core layer, an extension layer, an inner cladding layer, a sunken cladding layer and an outer cladding layer arranged from inside to outside, the core layer has a parabolic refractive index profile, a distribution index α is 1.9-2.2, a radius R1 of the core layer is 24-25 μm, and a maximum relative refractive index difference Δ1 at the center of the core layer is 0.9%-1.2%; the extension layer has a radius R2, a single-side radial width (R2-R1) is 0.5-3 μm, and a relative refractive index difference Δ2 of the extension layer is -0.03%- -0.02%; a difference (Δ3-Δ2) between the highest relative refractive index difference and the lowest relative refractive index difference of the inner cladding layer is 0.005%-0.03%, and a single-side radial width (R3-R2) of the inner cladding layer is 0.5-4 μm; a single-side radial width (R4-R3) of the sunken cladding layer is 3-9 μm, and a relative refractive index difference Δ4 of the sunken cladding layer is -0.7%- -0.4%; the outer cladding layer is a pure silica glass layer, and a radius R5 of the outer cladding layer is 62-63 μm. By reasonably designing the waveguide structure and the doping system, the viscosity of the optical fiber is optimized, the sensitivity of the optical fiber bandwidth to wavelength is reduced, the optical fiber has good bending resistance and super-high bandwidth performance.

[0029] The extension layer and the inner cladding layer are silica glass layers doped with a dopant, wherein the dopant comprises one or a combination of fluorine, aluminum, calcium, magnesium, titanium, zirconium, iron, cobalt, nickel, manganese, copper, lithium, sodium, potassium, boron, germanium, phosphorus.

[0030] The viscosity design and optimization of the fluorine / germanium doping of the extension layer and the inner cladding layer are highlighted. For the extension layer, fluorine / germanium or other dopants (such as phosphorus) are co-doped, and the proportion of fluorine doping gradually increases from the core layer to the extension layer. For the inner cladding layer (R3-R2), fluorine / germanium or other dopants (such as phosphorus) are co-doped, and the doping amount (excluding fluorine) is consistent with the outermost end of the extension layer, and the proportion of fluorine doping is variable and gradually decreases with the increase of the radius, instead of only using fluorine doping with a constant fluorine doping amount. The variable fluorine doping of the inner cladding layer can be adjusted according to the stress and viscosity test of the optical fiber, and the appropriate variable fluorine doping amount and width can be selected to realize the optimal stress difference between the core layer, the extension layer and the sunken cladding layer, reduce the sensitivity of the optical fiber bandwidth to wavelength, and make the optical fiber have good bending resistance and super-high bandwidth performance.

[0031] The bending additional loss of the optical fiber of the present application caused by winding 2 turns at a bending radius of 7.5 mm at a wavelength of 850 nm is less than 0.2 dB, and the bending additional loss caused by winding 2 turns at a bending radius of 7.5 mm at a wavelength of 1300 nm is less than 0.5 dB.

[0032] Example 1

[0033] As shown in Figures 1-2As shown, a kind of bending insensitive high bandwidth multimode optical fiber, including the core layer, extension layer, inner cladding, sunken cladding and outer cladding arranged in order from inside to outside, wherein, core layer refractive index profile is parabolic, fluorine / germanium co-doped is carried out in core layer, so that the maximum relative refractive index difference Δ1 of core layer center position is 1.0%, distribution index α is 2.08, and core layer radius is 24.5 μm;Extension layer radius is R2, fluorine / germanium co-doped is carried out in extension layer, so that its single side radial width (R2-R1) is 2 μm, and the relative refractive index difference Δ2 of extension layer is-0.03%;Fluorine is doped in inner cladding, and the lowest relative refractive index difference Δ2 is-0.03%, the highest relative refractive index difference Δ3 is-0.02%, the difference (Δ3-Δ2) of the highest relative refractive index difference and the lowest relative refractive index difference of inner cladding is 0.01%, and the single side radial width (R3-R2) of inner cladding is 1.5 μm;Fluorine is doped in sunken cladding, and the relative refractive index difference Δ4 of sunken cladding is-0.6%, and the single side radial width (R4-R3) of sunken cladding is 6 μm.

[0034] Performance test is carried out to example 1, and the result is shown in table 1.

[0035] Table 1

[0036] Optical fiber bandwidth (MHz-km) Example 1 @ 850 nm full load bandwidth 4260 @ 1300 nm full load bandwidth 684 @ 850 nm effective modal bandwidth 7134 R = 7.5 mm, 2 turns @ 850 nm (dB) 0.046 R = 7.5 mm, 2 turns @ 1300 nm (dB) 0.153

[0037] The optical fiber of the application has a bending additional loss of less than 0.2 dB at 850 nm wavelength with 2 turns of 7.5 mm bending radius; and a bending additional loss of less than 0.5 dB at 1300 nm wavelength with 2 turns of 7.5 mm bending radius.

[0038] The part or structure not specifically described in the application can use prior art or existing product, and will not be described here.

[0039] The above only describes the embodiment of the application, and does not limit the patent scope of the application, and any equivalent structure or equivalent process transformation using the content of the application specification, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the application.

Claims

1. A bend-insensitive high-bandwidth multimode optical fiber, characterized by, The optical fiber comprises a core layer, an extension layer, an inner cladding layer, a sunken cladding layer and an outer cladding layer arranged from inside to outside, the core layer has a parabolic refractive index profile, a distribution index α is 1.9-2.2, a maximum relative refractive index difference Δ1 at the center of the core layer is 0.9%-1.2%, a radius R1 of the core layer is 24-25 μm, a relative refractive index difference Δ2 of the extension layer is -0.03%- -0.02%, a difference between the radius R2 of the extension layer and the radius R1 of the core layer is 0.5-3 μm, a difference between the highest relative refractive index difference and the lowest relative refractive index difference of the inner cladding layer is 0.005%-0.03%, a single-side radial width of the inner cladding layer is 0.5-4 μm, a single-side radial width of the sunken cladding layer is 3-9 μm, and a relative refractive index difference Δ4 of the sunken cladding layer is -0.7%- -0.4%; The extension layer is co-doped with fluorine / germanium or other dopants, and the proportion of fluorine doping gradually increases from the core layer to the extension layer. The inner cladding layer is co-doped with fluorine / germanium or other dopants, and the proportion of fluorine doping gradually decreases with the increase of the radius.

2. The bend-insensitive high-bandwidth multimode optical fiber of claim 1, wherein, The extension layer and the inner cladding layer are silica glass layers doped with dopants.

3. The bend-insensitive high-bandwidth multimode optical fiber of claim 1, wherein, The outer cladding layer is a pure silica glass layer, and the radius R5 of the outer cladding layer is 62-63 μm.

4. The bend-insensitive high-bandwidth multi-mode optical fiber of claim 1, wherein, The optical fiber has a bending additional loss of less than 0.2 dB at a wavelength of 850 nm and a bending radius of 7.5 mm and a bending additional loss of less than 0.5 dB at a wavelength of 1300 nm and a bending radius of 7.5 mm.

Images