CN111221073B - Anti-bending multimode optical fiber - Google Patents
Anti-bending multimode optical fiber Download PDFInfo
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- CN111221073B CN111221073B CN201911347783.XA CN201911347783A CN111221073B CN 111221073 B CN111221073 B CN 111221073B CN 201911347783 A CN201911347783 A CN 201911347783A CN 111221073 B CN111221073 B CN 111221073B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/028—Optical fibres with cladding with or without a coating with core or cladding having graded refractive index
- G02B6/0288—Multimode fibre, e.g. graded index core for compensating modal dispersion
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
- G02B6/03616—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference
- G02B6/03661—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 4 layers only
Abstract
The invention discloses an anti-bending multimode optical fiber, which sequentially comprises a fiber core layer, an inner cladding layer, a depressed layer and an outer cladding layer from the center of the optical fiber to the outside, wherein the refractive index of the fiber core layer relative to the outer cladding layer is distributed in an alpha power exponential function along with the increase of the radius, alpha is a section distribution parameter of the refractive index of the fiber core layer, the refractive index of the center of the fiber core layer is the maximum, the refractive index of the inner cladding layer relative to the outer cladding layer is in negative correlation with the radius, and the refractive index of the depressed layer is smaller than that of the outer cladding layer. The multimode fiber is provided with the inner cladding between the fiber core layer and the depressed layer, the refractive index of the inner cladding is in negative correlation with the radius, the refractive index between the fiber core layer and the depressed layer can be gradually transited, the refractive index between the fiber core layer and the depressed layer is prevented from emitting sudden change, and therefore the interference of the core-cladding boundary to the transmission rate of a high-order mode is reduced, the transmission bandwidth of the multimode fiber is improved, and the influence of viscosity difference on the performance of the multimode fiber can be reduced due to the fact that the refractive index difference between the fiber core layer and the depressed layer is reduced.
Description
Technical Field
The embodiment of the invention relates to the technical field of optical fibers, in particular to an anti-bending multimode optical fiber.
Background
Multimode optical fibers are widely used in medium-short distance network systems, especially data centers, due to their advantages, such as low system cost and large transmission capacity. In recent years, with rapid development of new technologies such as FTTX, internet of things, cloud computing, cloud storage and the like, network data communication volume is in an exponential rising trend, and requirements for transmission performance of multimode optical fibers are continuously improved. In particular, in large lan systems such as data centers and super computing centers, high-speed data transmission requires more optical fiber links to be laid in a limited space, the optical fiber is often subjected to bending in different degrees, high-order modes transmitted in the multimode optical fiber are easily leaked out from a cladding when the optical fiber is bent, the attenuation of the optical fiber is increased, signal distortion may be caused, and the probability of error code of the system is increased.
At present, a commonly used method for reducing bending loss adopts a sunken layer design, and by adding a deep sunken layer, a high-order mode can be effectively limited in the sunken layer when the optical fiber is subjected to macrobending, so that leakage of the high-order mode is reduced, and the bending loss of the optical fiber is reduced. In addition, to achieve a high transmission capacity, multimode fibers should have as wide a bandwidth as possible, which for a given wavelength can be characterized both by "full injection" (only for light sources emitting uniformly radially) and by "effective mode", in which Dispersion Mode Delay (DMD) data is obtained by injecting at least 24 identical light pulses of a given wavelength successively at different radial positions, from which measurements the modal dispersion can be determined and the effective mode bandwidth calculated. The larger the mode delay, the higher the overlap ratio between adjacent pulses due to broadening, which reduces the transmission bandwidth of the fiber. 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 into a parabolic structure with power index distribution, so that the bandwidth performance is optimized by adjusting the distribution index of the core layer. However, some high-order modes in the actual transmission process cannot be completely limited in the core layer, and some high-order modes are transmitted in the depressed layer, and due to the abrupt change of the refractive index at the boundary of the core-package (the core layer and the depressed layer), the high-order modes cannot be properly compensated, so that the high-order modes at the boundary can show multiple pulses in Dispersion Mode Delay (DMD) measurement, and the signal response time is widened, the mode delay is increased, and the bandwidth performance is reduced. The core-cladding interface effect has an influence on bandwidth, and is particularly remarkable in bending-insensitive multimode fibers, the boundary refractive index difference between a deep depressed layer and a fiber core layer is large, and higher-order modes are transmitted faster or slower than other modes, so that serious pulse distortion is caused, and the bandwidth performance is influenced. In addition, the difference between the refractive index of the core layer and the depressed layer is large, and the difference between the light components is large, so that the problems of steam pocket or high stress and the like are easily generated on the interface due to large viscosity difference in the core rod manufacturing and wire drawing processes, and the product performance is influenced.
The effect of the core-cladding interface effect on the high-order modes is usually compensated by adding a terrace layer between the core layer and the depressed layer in the prior art, as shown in fig. 1, in which the refractive index of the terrace layer is a constant value, and the refractive index is equal to the refractive index at the interface between the terrace layer and the core layer. However, since the index difference between the mesa layer and the depressed layer is still large, the discontinuity in the index profile still affects the transmission rate of the higher order modes at the interface, affecting the bandwidth performance of the multimode fiber.
In view of the above, how to provide an anti-bending multimode optical fiber with high bandwidth is a problem to be solved by those skilled in the art.
Disclosure of Invention
The embodiment of the invention aims to provide an anti-bending multimode optical fiber, which can reduce the interference of a core-edge boundary on the transmission rate of a high-order mode in the use process, improve the transmission bandwidth of the optical fiber and reduce the influence of viscosity difference on the performance of the optical fiber.
In order to solve the above technical problems, an embodiment of the present invention provides an anti-bending multimode optical fiber, which sequentially includes a core layer, an inner cladding layer, a depressed layer, and an outer cladding layer from a center of the optical fiber to an outside, wherein a refractive index of the core layer relative to the outer cladding layer is distributed as an α power exponential function with an increase in radius, α is a refractive index profile distribution parameter of the core layer, the refractive index of the core layer is the largest, and the refractive index of the inner cladding layer relative to the outer cladding layer is negatively correlated with the radius.
Optionally, the refractive index of the inner cladding relative to the outer cladding is distributed as a linear function or a curve function with the increase of the radius.
Optionally, when the refractive index of the inner cladding relative to the outer cladding is distributed as a linear function with the increase of the radius, an included angle between any point on the linear function and the horizontal direction is smaller than a preset angle;
when the refractive index of the inner cladding relative to the outer cladding is distributed in a curve function along with the increase of the radius, the included angle between any point on the curve function and the horizontal direction is smaller than a preset angle.
Optionally, the preset angle is 45 °.
Optionally, the refractive index profile of the multimode optical fiber satisfies a first relation, where the first relation is:
wherein n (r) is the refractive index at radius r, n0Is the refractive index at the center r of the core layer equal to 0, Delta0Is the relative refractive index difference between the center of the core layer and the inner boundary of the inner cladding layer, RgIs the outer diameter of the core layer and the inner diameter of the inner cladding, n1Is RgRelative to the refractive index of the outer cladding, n2Is RuAn index of refraction relative to the outer cladding; r isuIs the outer diameter of the inner cladding and the inner diameter of the depressed layer, n3Is a constant number, n3Is the refractive index of the depressed layer, ncIs the refractive index, R, of the outer claddingfIs the outer diameter of the depressed layer and the inner diameter of the outer cladding layer, RmaxIs the outer diameter of the outer cladding.
Optionally, the refractive index of the center of the core layer relative to the outer cladding layer ranges from 0.013 to 0.016, and α is 1.90-2.10.
Optionally, the R isgIn the range of 22-32 μm.
Optionally, the R isgThe refractive index of the cladding layer relative to the cladding layer is in the range of 0.0005 to 0.002; said R isuWith respect to the outsourcingThe refractive index of the layer is in the range of-0.0005 to 0.0005.
Optionally, the width of the inner cladding is 3-5.5 μm; the outer diameter of the outer cladding is 62.5 +/-2.5 mu m.
Optionally, the fluorine-doped width of the subsidence layer is 2.5-5.5 μm; the depressed layer has a refractive index of-0.006 to-0.0025 relative to the outer cladding layer.
The embodiment of the invention provides an anti-bending multimode optical fiber which sequentially comprises a fiber core layer, an inner cladding layer, a depressed layer and an outer cladding layer from the center to the outside of the optical fiber, wherein the refractive index of the fiber core layer relative to the outer cladding layer is distributed in an alpha power exponential function along with the increase of the radius, alpha is a section distribution parameter of the refractive index of the fiber core layer, the refractive index of the fiber core layer is the maximum, the refractive index of the inner cladding layer relative to the outer cladding layer is in negative correlation with the radius, and the refractive index of the depressed layer is smaller than that of the outer cladding layer.
Therefore, the multimode fiber is provided with the inner cladding between the fiber core layer and the depressed layer, the refractive index of the inner cladding is in negative correlation with the radius, the refractive index between the fiber core layer and the depressed layer can be gradually transited, the refractive index between the fiber core layer and the depressed layer is prevented from emitting sudden change, and therefore interference of a core-cladding boundary to the transmission rate of a high-order mode is reduced, the transmission bandwidth of the multimode fiber is improved, and the influence of viscosity difference on the performance of the multimode fiber can be reduced due to the fact that the refractive index difference between the fiber core layer and the depressed layer is reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed in the prior art and the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic diagram of a connection structure of a core layer and a depressed layer in the prior art;
FIG. 2 is a schematic view of a section structure of an anti-bending multimode optical fiber according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of an anti-bending multimode optical fiber according to an embodiment of the present invention;
FIG. 4 is a schematic cross-sectional view of a bend-resistant multimode optical fiber according to an embodiment of the invention;
FIG. 5 is a schematic diagram of the central delay difference of the fiber pulse according to an embodiment of the present invention.
Detailed Description
The embodiment of the invention provides an anti-bending multimode optical fiber, which can reduce the interference of a core-edge boundary on the transmission rate of a high-order mode in the using process, improve the transmission bandwidth of the optical fiber and reduce the influence of viscosity difference on the performance of the optical fiber.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 2, fig. 2 is a schematic view of a section structure of a bend-resistant multimode optical fiber according to an embodiment of the present invention. The bending-resistant multimode optical fiber sequentially comprises a fiber core layer 1, an inner cladding layer 2, a depressed layer 3 and an outer cladding layer 4 from the center of the optical fiber to the outside, wherein the refractive index of the fiber core layer 1 relative to the outer cladding layer 4 is distributed along with the increase of the radius in an alpha power exponential function, alpha is a refractive index profile distribution parameter of the fiber core layer, the refractive index of the center of the fiber core layer 1 is maximum, and the refractive index of the inner cladding layer 2 relative to the outer cladding layer 4 is in negative correlation with the radius.
Specifically, the core layer 1 in the present embodiment may be a core layer having a radius R from the center (R ═ 0) of the multimode optical fibergAnd the refractive index of the core layer 1 relative to the outer cladding layer 4 is gradually changed, and the relative refractive index at the center of the core layer 1 is n0As shown in FIG. 3, the refractive index difference between the core layer 1 at the center and the outer cladding layer 4 is Δ 1, and the refractive index of the core layer 1 relative to the outer cladding layer 4 is distributed as an α -power exponential function with increasing R, which can be specifically referred to as 0 in FIG. 3<r≤RgCorresponding musicLine part from R to RgExtend a distance Ru-RgThe inner cladding 2 is formed, i.e. the boundary between the core layer 1 and the inner cladding 2 is R ═ RgWhere R isgHaving a refractive index n with respect to the outer cladding 41＝dng(RgRelative refractive index) of the inner cladding 2 relative to the outer cladding 4 is in negative correlation with the radius R, so that the sudden change of the refractive index between the core layer 1 and the depressed layer 3 can be relieved, and the continuous adjustability of the high-order mode transmission rate compensation is realized, wherein the inner diameter R of the inner cladding 2 isgThe relative refractive index is largest. The depressed layer 3 is R ═ RuTo R ═ RfThe refractive index of the depressed layer 3 relative to the outer cladding layer 4 is negative and the refractive index of the depressed layer 3 does not vary with radius, as can be seen in particular in the depressed portion of fig. 3, where the refractive index difference between the depressed layer 3 and the outer cladding layer 4 is Δ 2. The outer cladding 4 is from RfTo RmaxThe region in between, the outer cladding 4, is usually of pure quartz material with a refractive index ncWhich is the refractive index of SiO2, is distributed along the horizontal dashed line in fig. 3 as the refractive index of the outer cladding layer 4.
The fiber core layer 1 in the present application may be doped with GeO2 and F, or may be doped with a small amount of P2O5, and the relative refractive index distribution of the fiber core layer 1 is controlled by adjusting the doping amounts of GeO2 and F or P2O5, and the bandwidth of the optical fiber is adjusted by optimizing the refractive index profile distribution parameter of the fiber core layer.
Further, the refractive index of the inner cladding 2 relative to the outer cladding 4 in this embodiment is linearly or curvilinearly distributed as the radius increases. In particular, the distribution can be approximately parabolic when the distribution is curved, such as R in FIG. 3gTo RuIn order to better realize the continuous adjustment of the transmission rate of the high-order mode, when the refractive index of the inner cladding 2 relative to the outer cladding 4 is distributed in a linear function along with the increase of the radius, the included angle between any point on the linear function and the horizontal direction is smaller than a preset angle; when the refractive index of the inner cladding 2 relative to the outer cladding 4 is distributed in a curve function with the increase of the radius, the included angle between any point on the curve function and the horizontal direction is smaller than the preset angle theta, wherein, the embodimentThe preset angle θ in (1) may be 45 °. The transmission rate of a high-order mode at the boundary can be continuously adjusted by adjusting the refractive index curve distribution and the angle parameter change of the inner cladding 2 relative to the outer cladding 4, so that the core-cladding interface effect is effectively reduced or inhibited, and the bandwidth is improved.
In the present application, the interface R between the inner cladding layer 2 and the undercut layer 3 is RuHaving a refractive index n with respect to the outer cladding 42＝dnu(RuRelative refractive index) and the u point position can be continuously adjusted along the horizontal direction and the vertical direction according to the actual bandwidth requirement, as shown in the enlarged part of fig. 3, the position of the u point can be correspondingly compensated and adjusted in the up, down, left and right directions, wherein the g point is RgThe corresponding inflection point is positioned, and the radius of the point u and the n can be adjusted by adjusting the specific position of the point u2So as to adjust the delay of the higher order modes, with RuAnd refractive index dngThe compensation is increased, the higher-order mode delay is reduced, and the bandwidth of the optical fiber is increased.
Specifically, in the present application, the refractive index profile of the multimode optical fiber satisfies a first relation, where the first relation is:
wherein n (r) is the refractive index at radius r, n0The refractive index at the center r of the core layer is 0, Delta0Is the relative refractive index difference between the center of the core layer and the inner boundary of the inner cladding layer, RgThe outer diameter of the core layer and the inner diameter of the inner cladding layer, n1Is RgThe refractive index of (A) relative to the outer cladding, n2Is RuThe refractive index of the core relative to the outer cladding; r isuThe outer diameter of the inner cladding and the inner diameter of the depressed layer, n3Is a constant number, n3Is the refractive index of the depressed layer, ncIs the refractive index of the outer cladding, RfThe outer diameter of the depressed layer and the inner diameter of the outer cladding layer, RmaxThe outer diameter of the outer cladding. In particular, the method comprises the following steps of,
r is the radial distance from the core layer to the core axis.
Specifically, the refractive index of the center of the core layer 1 relative to the outer cladding layer 4 in the present application may be in the range of 0.013 to 0.016, that is, n0-n1The range of (2) is 0.013-0.016, the specific value can be determined according to actual needs, and the embodiment is not specially limited. In the application, the value range of the refractive index profile distribution parameter alpha of the fiber core layer can be 1.90-2.10, and the refractive index gradient region R of the fiber core layer 1gMay range from 22 to 32 μm. The width of the inner cladding in the application can be 3-5.5 mu m, and the inflection point g (namely R)g) The refractive index of the core relative to the outer cladding 4 may range from 0.0005 to 0.002; adjusted to u (i.e. R)u) The refractive index of the depressed layer 3 with respect to the outer cladding layer 4 may range from-0.0005 to 0.0005, the outer diameter of the outer cladding layer 4 may be 62.5 ± 2.5 μm, the depressed layer 3 may be realized by fluorine doping, the fluorine doping width may range from 2.5 to 5.5 μm, and the refractive index of the depressed layer 3 with respect to the outer cladding layer 4 (i.e., the refractive index depression difference) may range from-0.006 to-0.0025. As shown in fig. 3, the extension point R ═ R of the relative refractive index change curve corresponding to the core layer 1eRadius difference R between corner g and inflection point ge-RgThe range of (2) can be 0.2 to 1 μm, wherein the specific numerical value of each parameter can be determined according to actual needs, and the embodiment is not particularly limited.
The following is a detailed description of several examples through examples 1 to 5:
example 1, Ru-Rg3.4 μm; radius R at the inflection pointgIs 25.1 μm, corresponding to a refractive index dngIs 1.35 x 10-3(ii) a Radius R of adjustment point uuIs 27.0 μm, corresponding to a refractive index dnuIs-0.54 x 10-3A distance R from the extension point eu-ReIs 0.2 μm; the depth Δ 2 of the depressed F-doped layer (i.e., depressed layer) is-5.1 x 10-3(ii) a Calculating an Effective Mode Bandwidth (EMB) of 2750MHZ/km according to a DMD test result, a @850 full injection bandwidth of 6740MHZ/km, a @1300 full injection bandwidth of 470MHZ/km, and a B-level fiber; the bending loss R7.5-2 turns @850 of the optical fiber is 0.028dB, the bending loss R15-2 turns @850 of the optical fiber is 0.004dB, the bending loss R7.5-2 turns @1300 of the optical fiber is 0.079dB, and the bending loss R1 of the optical fiber is R15-2 turns @1300 is 0.018 dB; the time delay difference at the boundary (core-cladding boundary) was 0.0688ps/m, as shown in particular by curve 51 in FIG. 5, and the multimode fiber in this example was fabricated by MCVD or PCVD.
Example 2, Ru-RgIs 5.2 mu m; radius R at the inflection pointg24.6 μm, corresponding to a refractive index dngIs 1.1 x 10-3(ii) a Radius R of adjustment point uu25.9 μm, corresponding to a refractive index dnuIs 0.35 x 10-3A distance R from the extension point eu-Re0.7 μm; the depth delta 2 of the sunken F-doped layer is-4.9 x 10-3Calculating the Effective Mode Bandwidth (EMB) to be 5215MHZ/km according to the DMD test result, @850 full injection bandwidth 1509MHZ/km, @1300 full injection bandwidth 739MHZ/km, and meeting the OM3 bandwidth standard; the bending loss R7.5-2 turns @850 of the optical fiber is 0.007dB, the bending loss R15-2 turns @850 of the optical fiber is 0.005dB, the bending loss R7.5-2 turns @1300 of the optical fiber is 0.04dB, and the bending loss R15-2 turns @1300 of the optical fiber is 0.011 dB; the delay difference at the boundary was-0.2785 ps/m, wherein the profile of the test profile corresponding to the specific bend-resistant multimode optical fiber in the present embodiment is shown in fig. 4, and the delay difference curve at the center of the pulse is shown in fig. 5 as curve 52, and the multimode optical fiber of this example can be fabricated into a preform by MCVD or PCVD.
Example 3, Ru-Rg3.4 μm; radius R at turning pointg25.3 μm, corresponding to a refractive index dngIs 1.3 x 10-3(ii) a Radius R of adjustment point uuIs 27.1 μm, corresponding to a refractive index dnuIs-0.3 x 10-3A distance R from the extension point eu-ReIs 0.4 μm; the depth delta 2 of the sunken F-doped layer is-5.1 x 10-3Calculating the Effective Mode Bandwidth (EMB) to be 1840MHZ/km according to the DMD test result, the @850 full injection bandwidth 1633MHZ/km, the @1300 full injection bandwidth 734MHZ/km, and meeting the OM2+ bandwidth standard; the bending loss R7.5-2 turns @850 of the optical fiber is 0.04dB, the bending loss R15-2 turns @850 of the optical fiber is 0.032dB, the bending loss R7.5-2 turns @1300 of the optical fiber is 0.094dB, and the bending loss R15-2 turns @1300 of the optical fiber is 0.029 dB; the difference in the time delay at the boundary was-0.301 ps/m, as shown in particular by curve 53 in FIG. 5, and the multimode optical fiber of this example was fabricated by MCVD or PCVD.
Example 4, Ru-Rg5.1 μm; radius R at the inflection pointg24.5 μm, corresponding to a refractive index dngIs 1.1 x 10-3(ii) a Radius R of adjustment point uu26 μm, corresponding to a refractive index dnuIs-0.1 x 10-3A distance R from the extension point eu-Re0.3 μm; the depth delta 2 of the sunken F-doped layer is-4.9 x 10-3Calculating the Effective Mode Bandwidth (EMB) to be 4540MHZ/km according to the DMD test result, the @850 full injection bandwidth 3750MHZ/km and the @1300 full injection bandwidth 653MHZ/km, and meeting the OM3 bandwidth standard; the bending loss R7.5-2 circles @850 of the optical fiber is 0.043dB, the bending loss R15-2 circles @850 of the optical fiber is 0.009dB, the bending loss R7.5-2 circles @1300 of the optical fiber is 0.129dB, and the bending loss R15-2 circles @1300 of the optical fiber is 0.026 dB; the difference in the time delay at the boundary was-0.1613 ps/m, as shown in particular by curve 54 in FIG. 5, and the multimode fiber of this example was fabricated by MCVD or PCVD.
Example 5, Ru-RgIs 5.1 μm; radius R at the inflection pointg24.3 μm, corresponding to a refractive index dngIs 1.2 x 10-3(ii) a Radius R of adjustment point uu25.7 μm, corresponding to a refractive index dnuIs 0.4 x 10-3A distance R from the extension point eu-Re0.5 μm; the depth delta 2 of the sunken doped F layer is-3.4 x 10-3, the Effective Mode Bandwidth (EMB) is 8026MHZ/km according to DMD test results, the @850 full injection bandwidth 5090MHZ/km and the @1300 full injection bandwidth 555MHZ/km meet the OM4 bandwidth standard; the bending loss R7.5-2 turns @850 of the optical fiber is 0.137dB, the bending loss R15-2 turns @850 of the optical fiber is 0.028dB, the bending loss R7.5-2 turns @1300 of the optical fiber is 0.255dB, and the bending loss R15-2 turns @1300 of the optical fiber is 0.048 dB; the difference in time delay at the boundary was-0.0971 ps/m, as shown in particular by curve 55 in FIG. 5, and the multimode fiber of this example was used to prepare a preform by MCVD or PCVD.
It should be noted that the specific testing method for the DMD is the prior art, and the embodiment is not described in detail herein. Wherein, the parameters of examples 1 to 5 are shown in table 1:
TABLE 1
The bending-resistant multimode optical fiber in the application sequentially comprises a fiber core layer, an inner cladding layer, a sunken layer and an outer cladding layer from the center of the optical fiber to the outside, wherein the refractive index of the fiber core layer relative to the outer cladding layer is distributed along with the increase of the radius in an alpha power exponential function mode, alpha is a section distribution parameter of the refractive index of the fiber core layer, the refractive index of the fiber core layer is the largest, the refractive index of the inner cladding layer relative to the outer cladding layer is in negative correlation with the radius, and the refractive index of the sunken layer is smaller than the refractive index of the outer cladding layer.
Therefore, the multimode fiber is provided with the inner cladding between the fiber core layer and the depressed layer, the refractive index of the inner cladding is in negative correlation with the radius, the refractive index between the fiber core layer and the depressed layer can be gradually transited, the refractive index between the fiber core layer and the depressed layer is prevented from emitting sudden change, and therefore interference of a core-cladding boundary to the transmission rate of a high-order mode is reduced, the transmission bandwidth of the multimode fiber is improved, and the influence of viscosity difference on the performance of the multimode fiber can be reduced due to the fact that the refractive index difference between the fiber core layer and the depressed layer is reduced.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
1. An anti-bending multimode optical fiber is characterized by comprising a core layer, an inner cladding layer, a depressed layer and an outer cladding layer from the center of the optical fiber to the outside in sequence, wherein the refractive index of the core layer relative to the outer cladding layer is distributed in an alpha power exponential function along with the increase of the radius, alpha is a refractive index profile distribution parameter of the core layer, the refractive index of the center of the core layer is the maximum, the refractive index of the inner cladding layer relative to the outer cladding layer is in negative correlation with the radius, and the refractive index of the depressed layer is smaller than that of the outer cladding layer;
the refractive index of the inner cladding relative to the outer cladding is in a linear function distribution or a curve function distribution along with the increase of the radius;
the refractive index profile of the multimode optical fiber satisfies a first relation:
wherein n (r) is the refractive index at radius r, n0Is the refractive index at the center r of the core layer equal to 0, Delta0Is the relative refractive index difference between the center of the core layer and the inner boundary of the inner cladding layer, RgIs the outer diameter of the core layer and the inner diameter of the inner cladding layer, n1Is RgWith respect to the refractive index of the outer cladding, n2Is RuA fold in relation to the outer cover(ii) a refractive index; r isuIs the outer diameter of the inner cladding and the inner diameter of the depressed layer, n3Is a constant number, n3Is the refractive index of the depressed layer, ncIs the refractive index of the outer cladding, RfThe outer diameter of the depressed layer and the inner diameter of the outer cladding layer, RmaxIs the outer diameter of the outer cladding.
2. The bend-insensitive multimode optical fiber according to claim 1, wherein when the refractive index of the inner cladding relative to the outer cladding is linearly distributed as a function of increasing radius, an angle between any point on the linear function and a horizontal direction is smaller than a predetermined angle;
when the refractive index of the inner cladding relative to the outer cladding is distributed in a curve function along with the increase of the radius, the included angle between any point on the curve function and the horizontal direction is smaller than a preset angle.
3. The bend resistant multimode optical fiber of claim 2, wherein the predetermined angle is 45 °.
4. The bend-resistant multimode optical fiber according to claim 1, wherein the core layer has a refractive index in the range of 0.013 to 0.016 and α is 1.90 to 2.10 with respect to the outer cladding layer.
5. The bend resistant multimode optical fiber of claim 1, wherein R isgIn the range of 22-32 μm.
6. The bend resistant multimode optical fiber of claim 1, wherein R isgA refractive index range of 0.0005 to 0.002 with respect to the outer cladding; the R isuThe refractive index of the cladding layer is in the range of-0.0005 to 0.0005 relative to the refractive index of the cladding layer.
7. The bend-multimode optical fiber according to claim 1, wherein the width of the inner cladding is 3-5.5 μm; the outer diameter of the outer cladding is 62.5 +/-2.5 microns.
8. The bend-multimode optical fiber according to claim 1, wherein the fluorine-doped width of the depressed layer is 2.5 to 5.5 μm; the depressed layer has a refractive index of-0.006 to-0.0025 relative to the outer cladding layer.
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| CN116009141B (en) * | 2023-02-10 | 2024-01-12 | 烽火通信科技股份有限公司 | DMD (digital micromirror device) optimized gradient multimode optical fiber |
| CN116626805B (en) * | 2023-07-24 | 2023-10-13 | 中天科技光纤有限公司 | Ultra-low loss optical fiber and preparation method thereof |
| CN117348148B (en) * | 2023-12-05 | 2024-03-22 | 中天科技精密材料有限公司 | High bandwidth multimode optical fiber |
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| DE4127868A1 (en) * | 1991-08-22 | 1993-02-25 | Rheydt Kabelwerk Ag | Monomode optical fibre with ramped refractive index profile - has continuous linear increase in index of inner cladding up to intermediate value of core index |
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| DE4127868A1 (en) * | 1991-08-22 | 1993-02-25 | Rheydt Kabelwerk Ag | Monomode optical fibre with ramped refractive index profile - has continuous linear increase in index of inner cladding up to intermediate value of core index |
| CN101770051A (en) * | 2008-12-19 | 2010-07-07 | 三星光通信株式会社 | Low bend loss optical fiber |
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