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WO2018168170A1 - Fibre multicœur - Google Patents

Fibre multicœur Download PDF

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Publication number
WO2018168170A1
WO2018168170A1 PCT/JP2018/000167 JP2018000167W WO2018168170A1 WO 2018168170 A1 WO2018168170 A1 WO 2018168170A1 JP 2018000167 W JP2018000167 W JP 2018000167W WO 2018168170 A1 WO2018168170 A1 WO 2018168170A1
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WO
WIPO (PCT)
Prior art keywords
core
eff
refractive index
elements
fiber
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PCT/JP2018/000167
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English (en)
Japanese (ja)
Inventor
雄佑 佐々木
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株式会社フジクラ
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Publication date
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Publication of WO2018168170A1 publication Critical patent/WO2018168170A1/fr

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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
    • 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

Definitions

  • the present invention relates to a multi-core fiber.
  • This application claims priority based on Japanese Patent Application No. 2017-053675 for which it applied to Japan on March 17, 2017, and uses the content here.
  • Patent Documents 1 and 2 propose providing a trench-shaped low refractive index portion outside the core. Also, a technique called heterogeneous core arrangement in which cores having different propagation constants are arranged alternately is used.
  • a multi-core fiber employing a heterogeneous core arrangement can suppress crosstalk to about 1/1000 compared to a multi-core fiber arranged with the same kind of core in an area larger than a certain bending radius.
  • a bending radius R pk at which crosstalk peaks is expressed by the following equation (1).
  • R pk (n eff / ⁇ n eff ) ⁇ ⁇ (1)
  • n eff represents the average effective refractive index of the modes propagating through the cores
  • ⁇ n eff represents the difference in effective refractive index of the modes propagating through the cores
  • ⁇ represents the inter-core distance.
  • the n eff at a wavelength of 1550 nm is about 1.4450 to 1.4500, which is a value approximated by Cellmeier.
  • the value of the effective refractive index n eff has little influence on the magnitude of R pk .
  • the inter-core distance ⁇ is determined so as to satisfy the crosstalk value required for the multi-core fiber.
  • ⁇ n eff can be largely changed by designing the refractive index distribution of each core. In order to suppress crosstalk between cores, it is desirable to increase ⁇ n eff as much as possible in order to reduce R pk . That, n eff of n eff is high core higher, it is required n eff of n eff is lower cores lower.
  • n eff tends to increase the refractive index of the core. Then, the cutoff wavelength becomes longer, and more modes propagate than the desired mode in the communication wavelength band. Also, the lower the n eff , the lower the refractive index of the core. Then, the cut-off wavelength is shortened and the bending loss is deteriorated. Therefore, ⁇ n eff cannot be increased so much, and there is a limit in reducing R pk .
  • the present invention has been made in view of the above circumstances, and provides a multi-core fiber capable of suppressing crosstalk between cores.
  • a first aspect of the present invention is a multi-core fiber comprising a plurality of core elements and an outer cladding surrounding the plurality of core elements, wherein the plurality of core elements have a higher refractive index than the outer cladding. And a low refractive index portion that surrounds the core and has a refractive index lower than that of the outer cladding, the inner radius r 2 of the low refractive index portion is equal to or greater than the outer radius r 1 of the core, and the effective refractive index is Two or more different core elements are included, and of the two or more core elements, r 2 / r 1 of the first core element having the highest effective refractive index is the second core element having the lowest effective refractive index. Greater than r 2 / r 1
  • the two or more types of core elements may have the same effective area within a range of ⁇ 3%.
  • the third aspect of the present invention may include a core element in which r 2 / r 1 is 1.0 in the multi-core fiber of the first aspect or the second aspect.
  • the 37 core elements are arranged in the center without causing vacancy at each lattice point of the hexagonal close-packed structure.
  • core elements of the highest effective refractive index are arranged at six lattice points farthest from the center, and the cutoff wavelength of the LP11 mode is 1530 nm or less in all the core elements. Also good.
  • the outer diameter of the outer cladding may be 250 ⁇ m or less and the inter-core distance may be 30 ⁇ m or less.
  • the difference in effective refractive index between adjacent core elements may be 0.0005 or more. .
  • the r 2 / r 1 is a graph showing an example of a dependency of the characteristics for r 1 and ⁇ in the case where a 1.7.
  • the r 2 / r 1 is a graph showing an example of a dependency of the characteristics for r 1 and ⁇ in the case where a 1.0. It is a graph which shows an example of the relationship between Tc and absorption loss.
  • FIG. 1 is an explanatory diagram illustrating the refractive index distribution of the core element.
  • the core element includes a core 11 having a refractive index higher than that of the outer cladding 14 and a low refractive index portion 13 surrounding the core 11 and having a refractive index lower than that of the outer cladding 14.
  • the inner radius r 2 of the low refractive index portion 13 is not less than the outer radius r 1 of the core 11.
  • the core 11 has a relative refractive index difference of ⁇ with respect to the outer cladding 14.
  • Low refractive index portion 13 has a relative refractive index difference of - [delta t to the outer cladding 14.
  • the low refractive index portion 13 has a width W as a difference between the outer radius and the inner radius.
  • the core element may have an inner cladding 12 between the core 11 and the low refractive index portion 13.
  • the refractive index of the inner cladding 12 may be equal to the refractive index of the outer cladding 14.
  • a core element having an inner cladding 12 between the core 11 and the low refractive index portion 13 is known as a core with a trench.
  • the core 11, the inner cladding 12, the low refractive index portion 13, and the outer cladding 14 can be made of quartz glass such as pure quartz or doped quartz, for example.
  • the refractive index of the glass can be adjusted depending on the presence / absence of doping, type (element), concentration, and the like.
  • the inner cladding 12 or outer cladding 14 may be composed of substantially undoped quartz glass.
  • a coating (not shown) made of resin or the like can be provided on the outer periphery of the outer cladding 14.
  • the multi-core fiber of this embodiment includes a plurality of core elements and an outer cladding that surrounds the plurality of core elements.
  • the plurality of core elements include two or more types of core elements having different effective refractive indexes n eff from each other.
  • the two or more types of core elements may be two or more types of cores with trenches, or may be a combination of one or more types of cores with trenches and one or more types of cores.
  • the n eff is high type of the core element (high n eff core), n eff is less kinds of core elements (low n eff core) but included. Furthermore, a core element having a middle n eff between the high n eff core and the low n eff core (medium n eff core) may be employed.
  • r 2 / r 1 is constant throughout all the cores with a trench in order to reduce manufacturing load (see Patent Documents 1 and 2).
  • r 2 / r 1 it becomes a constraint to increase ⁇ n eff and reduce R pk .
  • n eff decreases a cutoff wavelength of the core 11 are the same, r in 2 / r 1 is greater core element, also n eff a cutoff wavelength of the core 11 are the same Was found to be higher. Therefore, by designating a core element having a small r 2 / r 1 as a low n eff core and a core element having a large r 2 / r 1 as a high n eff core, a multi-core fiber having a large ⁇ n eff and a small R pk is designed. Can be made easier.
  • r 2 / r 1 high n eff core is greater than the low n eff core r 2 / r 1.
  • r 2 / r 1 of the medium n eff core may be equal to r 2 / r 1 high n eff core may be equivalent to the r 2 / r 1 low n eff core R 2 / r 1 between the two may be used.
  • FIGS. 2A to 2C schematically show cross-sectional views of a multi-core fiber in which a core element is arranged at each lattice point of a hexagonal close-packed structure.
  • a plurality of core elements are arranged in the outer cladding C without causing a space at each lattice point of the hexagonal close-packed structure.
  • Each core element is any one selected from three types: a high n eff core H, a medium n eff core M, and a low n eff core L.
  • the core elements adjacent to each other are selected from different types in any group.
  • FIG. 2A seven core elements are arranged in an allocation of one in the center and six in the first layer surrounding the outside of the center.
  • 19 core elements are arranged in an allocation of 1 in the center, 6 in the first layer, and 12 in the second layer surrounding the outside of the first layer.
  • FIG. 2C there are 37 core elements with one allocation in the center, 6 in the first layer, 12 in the second layer, and 18 in the third layer that surrounds the outside of the second layer. Has been placed.
  • the core elements are arranged so that the center is the high n eff core H and the types of adjacent core elements are different. It is also possible to arrange so that the center is the low n eff core L. It is also possible to arrange so that the center is the middle n eff core M.
  • the first layer two types of core elements different from the center are arranged.
  • three types of core elements may be sequentially arranged along the outer periphery of a substantially regular hexagon.
  • 3A to 3C schematically show cross-sectional views of a multi-core fiber in which a core element is arranged at each lattice point of a square lattice.
  • a plurality of core elements are arranged in the outer cladding C without causing a space at each lattice point of the square lattice.
  • Each core element is one selected from two types of a high n eff core H and a low n eff core L. High n eff cores and low n eff cores are alternately arranged, and the core elements adjacent to each other are of different types in any set.
  • FIGS. 4 and 5 show an example of the dependence of the characteristics on the outer radius r 1 [ ⁇ m] of the core 11 and the relative refractive index difference ⁇ [%] of the core 11.
  • FIG. 4 shows a calculation result when r 2 / r 1 is set to 1.7
  • FIG. 5 shows a calculation result when r 2 / r 1 is set to 1.0.
  • An alternate long and short dash line with n eff of 1.4480 to 1.4445 is a line connecting points (r 1 , ⁇ ) where n eff of the core element is equal to the value of each label.
  • the effective area A eff is the same from the viewpoint of uniformizing the connection loss and the optical S / N ratio (OSNR).
  • OSNR optical S / N ratio
  • Examples of the range in which A eff of two or more types of core elements are the same include within ⁇ 3%, within ⁇ 2%, and within ⁇ 1%.
  • ⁇ SC-L 1350 nm is set in consideration of the fact that the cut-off wavelength becomes long when the multi-core fiber is formed.
  • a short broken line labeled “ ⁇ SC-S ” gives a point (r 1 , ⁇ ) that gives the shortest value ( ⁇ SC-S ) of the calculated cutoff wavelength when the core element is singly disposed in the outer cladding. ).
  • Table 1 shows the parameters of core a to d and n eff .
  • W is the width of the low refractive index portion 13 in the radial direction, that is, the difference between the outer radius and the inner radius, as shown in FIG. ⁇ c22m is a 22 m cutoff wavelength.
  • r 2 / r 1 is constant, for example, the difference in n eff between core a and core b is 0.00076, and the difference in n eff between core c and core d is 0.00092.
  • the difference in n eff of core a and core d is 0.00109.
  • it r 2 / r 1 high n eff core is r 2 / r 1 is greater than the condition of low n eff core, a larger [Delta] n eff .
  • the A eff of all the core elements is the same in design under the same optical characteristic conditions, and when the cut-off wavelength range is set larger, ⁇ n eff can be realized.
  • the lower limit of r 2 / r 1 is 1.0 (W-type core) as described above. If r 2 / r 1 is too large, the crosstalk deteriorates or the core diameter becomes large.
  • the r 2 / r 1 of the high n eff core is in the range of 1.7 to 2.1. It is done.
  • a core element with a large r 2 / r 1 such as core a is a high n eff core
  • a core element with a small r 2 / r 1 is a low n eff core such as core d and a high n eff core.
  • a middle n eff core intermediate the core elements of the low-n eff core it is possible to design the multi-core fiber of heterogeneous core arrangement comprising three core elements.
  • n eff core between adjacent core elements, to reduce as much as possible all the R pk, preferably has an average n eff of high n eff core and a low n eff core. That, [Delta] n eff between the high n eff core and the middle n eff core is preferably equal to [Delta] n eff between the middle n eff core and low n eff core.
  • the minimum value of ⁇ n eff between adjacent core elements is about 0.0005.
  • (DELTA) neff can be 0.0005 or more by all the combinations between adjacent core elements.
  • Examples of ⁇ n eff between adjacent core elements include about 0.0005, about 0.0006, about 0.0007, about 0.0008, about 0.0009, and about 0.0010.
  • ⁇ n eff can be set in consideration of the cutoff wavelength, bending loss, and the like. Considering the cut-off wavelength, single mode transmission becomes possible by setting the mode used for transmission in all core elements to only the basic mode.
  • n eff core 1.44611.
  • core e As an example of a medium n eff core combined with core a and core d, for example, core e shown below can be cited.
  • the cladding thickness When designing the cladding thickness, a thickness that can suppress absorption loss from the outermost core element to the coating provided outside the outer cladding is required.
  • the core elements When the core elements are arranged without generating a space at each lattice point of the hexagonal close-packed structure, as described above, the 7-core fiber as shown in FIG. 2A, the 19-core fiber as shown in FIG. 2B, and the 37 as shown in FIG. A core fiber can be realized.
  • the cladding diameter of the multi-core fiber that is, the outer diameter of the outer cladding 14 is 250 ⁇ m or less, 37 cores are considered to be the limit of the number of cores.
  • the core elements located on the outermost side from the center are six of the outermost core elements arranged in a substantially regular hexagon, which are arranged at substantially the apexes of the regular hexagon.
  • the core elements located on the outermost side from the center are six of the outermost core elements arranged in a substantially regular hexagon, which are arranged at substantially the apexes of the regular hexagon.
  • the core elements located on the outermost side from the center there are two types of core elements located on the outermost side from the center.
  • the 37-core fiber shown in FIG. 2C only one type of core element is disposed on the outermost side from the center.
  • the 37-core fiber shown in FIG. 2C can be designed such that high n eff cores are arranged at six lattice points farthest from the center.
  • the 37-core fiber can make the cladding thickness the smallest.
  • the clad thickness Tc is the distance from the center of the core element arranged on the outermost side to the outer periphery of the outer clad. That is, the cladding thickness Tc is the minimum value of the distance from the center of the core element to the outer periphery of the outer cladding.
  • T c may be about 35 ⁇ m.
  • the inter-core distance can be determined in consideration of the increase in cutoff wavelength due to the low refractive index portions of a plurality of core elements surrounding a certain core element.
  • FIG. 7 shows the result of calculating the relationship of the bending loss [dB / m] with respect to the inter-core distance ⁇ [ ⁇ m] for the core H having the longest cutoff wavelength when one core element is arranged alone in the outer cladding. Shown in In the calculation of the graph of FIG. 7, the wavelength was set to 1530 nm and the bending radius was set to 140 mm. If the bending loss is 0.02 dB / m or more, the cutoff wavelength can be 1530 nm or less. From FIG.
  • the distance between the cores should be 28 ⁇ m or more.
  • the cutoff wavelength of the LP11 mode can be made 1530 nm or less.
  • An example of the inter-core distance for increasing the density is 30 ⁇ m or less.
  • FIG. 8 shows a cross-sectional photograph of this example
  • FIG. 9 shows a core layout diagram of this example.
  • the clad diameter D c was 248.3 ⁇ m
  • the clad thickness T c was 36.8 ⁇ m
  • the inter-core distance ⁇ was 29.1 ⁇ m.
  • a eff at three wavelengths 1550nm core is averaged for each type, 81.4 ⁇ m 2, 80.0 ⁇ m 2, were 80.4Myuemu 2 respectively.
  • the effective refractive index difference ⁇ n eff between adjacent core elements is 0.0005 or more.
  • FIG. 10 shows the measurement result of crosstalk (XT) [dB] between the cores.
  • the crosstalk was sufficiently small at 1550 nm at ⁇ 50 dB or less between core H and core M, between core M and core L, and between core H and core L.
  • the largest R pk among the combinations of the three types of core elements was as small as 71 mm or less.
  • C outer cladding
  • Dc cladding diameter
  • H high n eff core
  • L low n eff core
  • M medium n eff core
  • r 1 ... outer radius of the core
  • r 2 ... inner radius of the low refractive index portion
  • Tc Cladding thickness
  • W Width of low refractive index portion
  • ⁇ Specific refractive index difference of core
  • ⁇ t Specific refractive index difference of low refractive index portion
  • ⁇ Distance between cores, 11: Core, 12 ... Inner cladding, 13 ... low refractive index portion, 14 ... outer cladding.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
  • Lasers (AREA)

Abstract

Selon la présente invention, cette fibre multicœur est pourvue d'une pluralité d'éléments de cœur et d'une gaine externe entourant la pluralité d'éléments de cœur. La pluralité d'éléments de cœur ont chacun : un cœur ayant un indice de réfraction supérieur à celui de la gaine externe; et une partie à faible indice de réfraction entourant le cœur et ayant un indice de réfraction inférieur à celui de la gaine externe, un rayon interne r2 de la partie à faible indice de réfraction étant égal ou supérieur à un rayon externe r1 du noyau, et les éléments de cœur comprennent deux éléments de cœur ou plus ayant des indices de réfraction efficaces différents. Dans les deux éléments de cœur ou plus, r2/r1 d'un premier élément de cœur ayant l'indice de réfraction effectif le plus élevé est supérieur à r2/r1 d'un second cœur ayant l'indice de réfraction effectif le plus bas.
PCT/JP2018/000167 2017-03-17 2018-01-09 Fibre multicœur WO2018168170A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2017-053675 2017-03-17
JP2017053675A JP6623190B2 (ja) 2017-03-17 2017-03-17 マルチコアファイバ

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112969941A (zh) * 2018-11-21 2021-06-15 日本电信电话株式会社 多芯光纤、多芯光纤设计方法和光传输方法
WO2024166598A1 (fr) * 2023-02-08 2024-08-15 住友電気工業株式会社 Fibre optiques à âmes multiples et câble à fibres optiques à âmes multiples

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WO2020106463A1 (fr) * 2018-11-21 2020-05-28 Corning Incorporated Systèmes optiques comprenant des fibres optiques multi-coeur pour réaliser un couplage de coeur direct à coeur

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US20150160408A1 (en) * 2013-12-06 2015-06-11 Corning Incorporated Multicore optical fiber with multimode cores
WO2015133407A1 (fr) * 2014-03-07 2015-09-11 株式会社フジクラ Fibre multi-cœur
WO2016129650A1 (fr) * 2015-02-12 2016-08-18 株式会社フジクラ Fibre multicœur

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JP2013167861A (ja) * 2012-01-19 2013-08-29 Fujikura Ltd マルチコアファイバ
US20150160408A1 (en) * 2013-12-06 2015-06-11 Corning Incorporated Multicore optical fiber with multimode cores
WO2015133407A1 (fr) * 2014-03-07 2015-09-11 株式会社フジクラ Fibre multi-cœur
WO2016129650A1 (fr) * 2015-02-12 2016-08-18 株式会社フジクラ Fibre multicœur

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112969941A (zh) * 2018-11-21 2021-06-15 日本电信电话株式会社 多芯光纤、多芯光纤设计方法和光传输方法
CN112969941B (zh) * 2018-11-21 2023-08-25 日本电信电话株式会社 多芯光纤和光传输方法
WO2024166598A1 (fr) * 2023-02-08 2024-08-15 住友電気工業株式会社 Fibre optiques à âmes multiples et câble à fibres optiques à âmes multiples

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