CN107102400B - High-bandwidth bending insensitive multimode optical fiber - Google Patents
High-bandwidth bending insensitive multimode optical fiber Download PDFInfo
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- CN107102400B CN107102400B CN201710507899.XA CN201710507899A CN107102400B CN 107102400 B CN107102400 B CN 107102400B CN 201710507899 A CN201710507899 A CN 201710507899A CN 107102400 B CN107102400 B CN 107102400B
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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
- G02B6/03622—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 2 layers only
- G02B6/03627—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 2 layers only arranged - +
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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
- G02B6/03638—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 3 layers only
- G02B6/0365—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 3 layers only arranged - - +
Abstract
The invention relates to a high-bandwidth bending insensitive multimode fiber, which comprises a core layer and a cladding layer surrounding the core layer, wherein the refractive index profile of the core layer is parabolic, and the high-bandwidth bending insensitive multimode fiber is characterized in that the cladding layer sequentially comprises an inner cladding layer, a sunken cladding layer, a first outer cladding layer and a second outer cladding layer from inside to outside, the radius of the inner cladding layer is R2, the unilateral radial width (R2-R1) is 1-3 mu m, and the relative refractive index difference delta 2 is-0.2% -0.05%; the sunken cladding radius is R3, the unilateral radial width (R3-R2) is 4-8 μm, and the relative refractive index difference delta 3 is-0.8% -0.2%; the radius of the first outer cladding layer is R4, R4 is less than or equal to 58 mu m, and the relative refractive index difference delta 4 is 0.01-0.2%; the second outer cladding has a radius R5 of 60 to 65 μm and a relative refractive index difference Delta 5 of-0.1 to 0.1%. The optical fiber material has reasonable composition and structural design, can improve and reduce the internal stress distribution of the optical fiber, reduce the distortion of the section of the optical fiber and enhance the bending resistance and the bandwidth of the optical fiber.
Description
Technical Field
The invention relates to a high-bandwidth bending insensitive multimode optical fiber, belonging to the technical field of optical communication.
Background
The multimode fiber becomes a high-quality solution for a short-distance high-speed transmission network with the advantage of low system cost, and is widely applied to the fields of data centers, office centers, high-performance computing centers, storage area networks and the like. The application scenario of the multimode optical fiber is often narrow cabinet, distribution box and other integrated systems, and the optical fiber needs to withstand a small bending radius. When the conventional multimode optical fiber is bent at a small angle, high-order modes transmitted close to the edge of a fiber core are easy to leak out, so that signal loss is caused. This therefore places more stringent requirements on multimode optical fibres, where the bandwidth and bend resistance properties of the fibre are the two most important parameters.
Compared with the conventional multimode fiber, the high-bandwidth bending insensitive fiber not only has the characteristic of high bandwidth, but also has excellent bending resistance, and can exert the advantages of the high-bandwidth bending insensitive fiber under special arrangement conditions of a data center, a central computer room and the like. In the profile design and process design of the bend-insensitive multimode fiber, how to ensure the macrobending performance, DMD (Differential Mode Delay) performance and bandwidth performance of the fiber through the related design and achieve the requirements of the related standards and obtain the optimal value is the main difficulty.
In order to obtain a high bandwidth multimode optical fiber with good stability, the fiber refractive index profile, especially the core refractive index profile, must be precisely matched to the desired shape. The core design of the optical fiber preform is usually doped with one or more of germanium, fluorine, chlorine, phosphorus, etc. at a certain concentration to achieve a desired refractive index profile of the optical fiber core. However, after the optical fiber preform is melted at a high temperature and then drawn and cooled to form an optical fiber, the refractive index distribution of the cross section is distorted due to residual stress in the optical fiber. It is therefore important to try to reduce the effect of residual stress on the refractive index profile during the fiber production process. In the glass network structure, the dopant such as germanium, fluorine, chlorine, phosphorus and the like exists in the form of a network former, an intermediate or a modified body, which destroys the integrity of the original network structure and can reduce the viscosity of the glass at high temperature. The dopant ion concentration directly affects the high temperature viscosity of the fiber. The amount of the doping agent in the center of the multimode optical fiber core layer is larger than that of the doping agent at the edge of the core layer, so that the high-temperature viscosity mismatch of the optical fiber material components is caused, and the formation of the residual stress of the optical fiber core layer is aggravated.
Through relevant experimental research, for the bending insensitive multimode optical fiber, the viscosity design of the core layer and the inner cladding affects the DMD and the bandwidth of the optical fiber, and the viscosity design of the whole section of the optical fiber affects the DMD and the bandwidth of the optical fiber.
In document CN104360435, a bend insensitive multimode optical fiber is described, which uses a viscosity matching double inner cladding structure to reduce the influence of the drawing tension on the core portion of the optical fiber from the viscosity design and reduce the bend sensitivity of the optical fiber, but does not explain the influence of the viscosity of the cladding material on the performance of the optical fiber.
In order to obtain a multimode fiber with better bending resistance, the main method is to optimize the structure of the depressed cladding of the bending insensitive multimode fiber, namely the depth and the width of the depressed cladding of the fiber and the distance between the depressed cladding and the core layer. Theoretically, the larger depressed cladding width and depth can increase the bend resistance of the fiber, but it also makes it difficult for the higher-order modes of the multimode fiber to leak into the outer cladding, affecting the DMD and bandwidth performance of the fiber.
Disclosure of Invention
For convenience of introduction to the present disclosure, some terms are defined:
core rod: a preform comprising a core layer and a partial cladding layer;
radius: the distance between the outer boundary of the layer and the center point;
refractive index profile: the relationship between the refractive index of the glass of an optical fiber or an optical fiber preform (including a core rod) and the radius thereof;
sleeving a sleeve: quartz glass tubes meeting certain geometric and doping requirements;
the RIT process comprises the following steps: inserting the core rod into the sleeve to form an optical fiber preform;
relative refractive index difference, i.e. deltai：
Wherein n isiIs the refractive index i from the center of the fiber core; n is0Is the refractive index of pure silicon dioxide;
the refractive index profile of the core layer of the graded-mode multimode fiber satisfies the following power exponential function distribution:
wherein n is1Is the refractive index of the optical fiber axis; r is the distance from the axis of the fiber; a is the optical fiber core radius; alpha is a distribution index; Δ is the refractive index difference at the center of the core relative to pure silica.
DMD Differential Mode Delay.
The invention aims to solve the technical problem of providing a high-bandwidth bending-insensitive multimode optical fiber aiming at the defects in the prior art, the optical fiber has reasonable material composition and structural design, can improve and reduce the internal stress distribution of the optical fiber, reduces the distortion of the section of the optical fiber and enhances the bending resistance and the bandwidth of the optical fiber.
The technical scheme adopted by the invention for solving the problems is as follows: the core-layer refractive index profile is parabolic, the distribution index alpha is 1.9-2.2, the radius R1 of the core layer is 23-27 mu m, and the maximum relative refractive index difference delta 1 is 0.9% -1.2%, and the core-layer refractive index profile is characterized in that the cladding comprises an inner cladding, a sunken cladding, a first outer cladding and a second outer cladding from inside to outside in sequence, the radius of the inner cladding is R2, the unilateral radial width (R2-R1) is 1-3 mu m, and the relative refractive index difference delta 2 is-0.2% -0.05%; the radius of the sunken cladding is R3, the unilateral radial width (R3-R2) is 4-8 mu m, and the relative refractive index difference delta 3 is-0.8% -0.2%; the radius of the first outer cladding layer is R4, R4 is less than or equal to 58 mu m, and the relative refractive index difference delta 4 is 0.01-0.2%; the second outer cladding has a radius R5 of 60 to 65 μm and a relative refractive index difference Delta 5 of-0.1 to 0.1%.
According to the scheme, the second outer cladding is a silica glass layer doped with one or more of dopants such as aluminum, calcium, magnesium, titanium, zirconium, iron, cobalt, nickel, manganese, copper, lithium, sodium, potassium and boron, wherein the content of aluminum is 1-40 ppm, and the total content of metal elements is less than or equal to 60 ppm.
According to the scheme, the first outer cladding layer is a pure silica glass layer.
According to the scheme, the viscosity of the material of the second outer cladding is larger than that of the material of the first outer cladding.
According to the scheme, the numerical aperture of the optical fiber is 0.185-0.215.
According to the scheme, the optical fiber has an Effective Mode Bandwidth (EMB) of 3500MHz-km or more than 3500MHz-km at the wavelength of 850nm and has an Effective Mode Bandwidth (EMB) of 500MHz-km or more than 500MHz-km at the wavelength of 1300 nm.
According to the scheme, the optical fiber has an Effective Mode Bandwidth (EMB) of 4700MHz-km or more than 4700MHz-km at a wavelength of 850nm and an Effective Mode Bandwidth (EMB) of 500MHz-km or more than 500MHz-km at a wavelength of 1300 nm.
According to the scheme, the bending additional loss caused by winding the optical fiber for 2 circles at the wavelength of 850nm by the bending radius of 7.5 mm is less than 0.2 dB; bending additional losses of less than 0.5dB at 1300nm wavelength, caused by 2 turns with a 7.5 mm bending radius.
The technical scheme of the optical fiber manufacturing method of the invention is as follows: using a pure quartz glass tube as a deposition liner tube, carrying out doping deposition by using an in-tube deposition method, and sequentially depositing a sunken cladding layer, an inner cladding layer and a core layer on the inner wall of the deposition liner tube by changing the flow of doping gas in mixed gas according to the doping requirement of the optical fiber waveguide structure;
after deposition, the deposited liner tube is fused and contracted into a solid core rod by an electric heating furnace, and the solid core rod comprises a core layer, an inner cladding layer tightly wrapping the core layer, a sunken cladding layer tightly wrapping the inner cladding layer and a first outer cladding layer tightly wrapping the sunken cladding layer;
using a doped quartz glass tube as a sleeve to prepare a prefabricated rod by an RIT process, or depositing a second outer cladding layer by an OVD (over-all-glass deposition) or VAD (vapor-deposition) or APVD (advanced plasma chemical vapor deposition) outer cladding deposition process to prepare a prefabricated rod;
and (3) placing the prefabricated rod on an optical fiber drawing tower to be drawn into an optical fiber, and coating the surface of the optical fiber with a solidified polyacrylic acid resin layer.
The invention has the beneficial effects that: 1. through reasonable structure and material viscosity design and matching, in the design of the outer cladding part of the optical fiber, a mode of combining two materials with different viscosities is adopted, the viscosity of the first outer cladding is lower than that of the second outer cladding, the second outer cladding bears a larger proportion of wire drawing tension during wire drawing, the influence of the wire drawing tension on the section structure is reduced, the stress at the outer side of the fiber core, the inner cladding and the sunken part is reduced, the stress change is smooth, the section distortion is reduced, and the bandwidth is increased; 2. the stress makes the relative refractive index difference of the first outer cladding layer larger than that of the second outer cladding layer, which is equivalent to deepening the depth of the sunken cladding layer, thereby effectively enhancing the bending resistance of the multimode optical fiber, still ensuring that the high-order mode of the multimode optical fiber is leaked into the outer cladding layer, and avoiding influencing DMD and bandwidth performance while improving the bending resistance; 3. the viscosity of the second outer cladding is high, the tensile stress is increased, and the optical fiber strength is better; in addition, the viscosity of the material of the outer cladding can be properly adjusted by doping the outer cladding, so that the viscosity matching is more reasonable; 4. the invention has simple and convenient production control and high working efficiency, and is suitable for large-scale production.
Drawings
FIG. 1 is a schematic cross-sectional view of the refractive index of an optical fiber according to a first embodiment of the present invention.
FIG. 2 is a schematic stress profile of an example of the invention and a comparative example.
Detailed Description
Specific examples will be given below to further illustrate the present invention.
The invention comprises a core layer and a cladding layer surrounding the core layer, wherein the refractive index profile of the core layer is parabolic, the distribution index is alpha, the radius of the core layer is R1, and the maximum relative refractive index difference of the central position of the core layer is delta 1; the cladding comprises an inner cladding, a sunken cladding, a first outer cladding and a second outer cladding from inside to outside in sequence, the radius of the inner cladding is R2, the unilateral radial width is (R2-R1), and the relative refractive index difference is delta 2; the radius of the sunken cladding is R3, the unilateral radial width is (R3-R2), and the relative refractive index difference is delta 3; the first outer cladding has a radius of R4, a single-sided radial width of (R4-R3), and a relative refractive index difference of Δ 4; the first outer cladding has a radius R5 and a relative refractive index difference Δ 5. The structure and the main performance parameters of the fiber are shown in table 1.
Table 1: core structure parameters and main performance parameters of optical fiber
The macrobend additional loss is measured according to the IEC60793-1-47 method, the measured optical fiber is wound for two circles according to a certain diameter, then the circle is released, and the optical power change before and after the circle is measured, so that the macrobend additional loss of the optical fiber is obtained. During the test, the circular Flux (circular Flux) light injection condition is adopted. The Encircled Flux light injection conditions can be obtained by the following method: a section of common 50-micrometer core diameter multimode optical fiber with the length of 2m is welded at the front end of the measured optical fiber, a 25-mm diameter ring is wound in the middle of the optical fiber, and when full injection light is injected into the optical fiber, the measured optical fiber is annular flux light injection.
The full injection bandwidth is measured according to the IEC60793-1-41 method, and the test adopts the full injection condition. The Differential Mode Delay (DMD) is measured according to IEC60793-1-49 method, the length of the measured optical fiber is 1000m +/-20%, a probe single-mode optical fiber is connected between the measured optical fiber and a light source to limit the light mode entering the measured optical fiber to be a single mode, the pulse width of the incident light is less than or equal to 100ps, the light source vertically enters the end face of the measured optical fiber, scans along the end face in the radial direction, and the time difference between the fastest light pulse and the slowest light pulse reaching the output end of the measured optical fiber is measured, namely the differential mode delay. At the same time, the DMD data is used to perform a simulation of a series of calculations that specify the input mode, yielding the Effective Mode Bandwidth (EMB).
Claims (6)
1. A high-bandwidth bending insensitive multimode fiber comprises a core layer and a cladding layer surrounding the core layer, wherein the refractive index profile of the core layer is parabolic, the distribution index alpha is 1.9-2.2, the radius R1 of the core layer is 23-27 mu m, and the maximum relative refractive index difference delta 1 is 0.9-1.2 percent, and the multimode fiber is characterized in that the cladding layer sequentially comprises an inner cladding layer, a sunken cladding layer, a first outer cladding layer and a second outer cladding layer from inside to outside, the radius of the inner cladding layer is R2, the unilateral radial width (R2-R1) is 1-3 mu m, and the relative refractive index difference delta 2 is-0.2-0.05 percent; the radius of the sunken cladding is R3, the unilateral radial width (R3-R2) is 4-8 mu m, and the relative refractive index difference delta 3 is-0.8% -0.2%; the radius of the first outer cladding layer is R4, R4 is less than or equal to 58 mu m, and the relative refractive index difference delta 4 is 0.01-0.2%; the radius R5 of the second outer cladding is 60-65 μm, and the relative refractive index difference delta 5 is-0.1%; the second outer cladding is a silica glass layer doped with one or more of aluminum, calcium, magnesium, titanium, zirconium, iron, cobalt, nickel, manganese, copper, lithium, sodium, potassium and boron dopants, wherein the content of aluminum is 1-40 ppm, and the total content of metal elements is less than or equal to 60 ppm.
2. The high bandwidth bend insensitive multimode optical fiber of claim 1 wherein the second outer cladding is of a material having a viscosity greater than that of the first outer cladding.
3. The high bandwidth bend insensitive multimode optical fiber according to claim 1 or 2, wherein the numerical aperture of said fiber is between 0.185 and 0.215.
4. The high bandwidth bend insensitive multimode optical fiber according to claim 1 or 2, wherein said fiber has an effective modal bandwidth at a wavelength of 850nm of more than 3500MHz-km and an effective modal bandwidth at a wavelength of 1300nm of more than 500 MHz-km.
5. The high bandwidth bend insensitive multimode optical fiber according to claim 1 or 2, characterized in that said fiber has an effective modal bandwidth at a wavelength of 850nm of more than 4700MHz-km and an effective modal bandwidth at a wavelength of 1300nm of more than 500 MHz-km.
6. The high bandwidth bend insensitive multimode optical fiber according to claim 1 or 2, wherein said fiber has a bend additional loss of less than 0.2dB at a wavelength of 850nm resulting from 2 turns at a 7.5 mm bend radius; bending additional losses of less than 0.5dB at 1300nm wavelength, caused by 2 turns with a 7.5 mm bending radius.
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| CN108375815B (en) * | 2018-04-17 | 2020-08-25 | 长飞光纤光缆股份有限公司 | High-bandwidth bending insensitive multimode optical fiber |
| CN110780378A (en) * | 2019-11-13 | 2020-02-11 | 北京交通大学 | Multilayer refractive index gully gradient optical fiber leaking high-order mode |
| CN116577865B (en) * | 2023-07-14 | 2023-10-20 | 江苏永鼎股份有限公司 | Ultralow-loss bending insensitive optical fiber and optical fiber product |
| CN117434643B (en) * | 2023-12-15 | 2024-03-26 | 创昇光电科技(苏州)有限公司 | Radiation-resistant multi-cladding doped optical fiber |
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| CN105829928A (en) * | 2014-01-31 | 2016-08-03 | Ofs菲特尔有限责任公司 | Design and manufacture of multi-mode optical fibers |
| CN106324752A (en) * | 2016-11-08 | 2017-01-11 | 长飞光纤光缆股份有限公司 | High-bandwidth anti-radiation multimode optical fiber |
| CN106371167A (en) * | 2016-11-26 | 2017-02-01 | 长飞光纤光缆股份有限公司 | High-bandwidth multi-mode fiber |
| CN106383379A (en) * | 2016-11-26 | 2017-02-08 | 长飞光纤光缆股份有限公司 | High-bandwidth bending insensitive multi-mode fiber |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105829928A (en) * | 2014-01-31 | 2016-08-03 | Ofs菲特尔有限责任公司 | Design and manufacture of multi-mode optical fibers |
| CN106324752A (en) * | 2016-11-08 | 2017-01-11 | 长飞光纤光缆股份有限公司 | High-bandwidth anti-radiation multimode optical fiber |
| CN106371167A (en) * | 2016-11-26 | 2017-02-01 | 长飞光纤光缆股份有限公司 | High-bandwidth multi-mode fiber |
| CN106383379A (en) * | 2016-11-26 | 2017-02-08 | 长飞光纤光缆股份有限公司 | High-bandwidth bending insensitive multi-mode fiber |
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