CN117388979A - Multi-core microstructure optical fiber and preparation method thereof - Google Patents
Multi-core microstructure optical fiber and preparation method thereof Download PDFInfo
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 103
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 239000000835 fiber Substances 0.000 claims abstract description 176
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 42
- 239000010453 quartz Substances 0.000 claims abstract description 30
- 238000000034 method Methods 0.000 claims abstract description 24
- 230000002596 correlated effect Effects 0.000 claims abstract description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 20
- 229910002804 graphite Inorganic materials 0.000 claims description 20
- 239000010439 graphite Substances 0.000 claims description 20
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000005498 polishing Methods 0.000 claims description 6
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 6
- 150000002910 rare earth metals Chemical class 0.000 claims description 6
- 229910052732 germanium Inorganic materials 0.000 claims description 4
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 4
- 238000000227 grinding Methods 0.000 claims description 4
- 238000005491 wire drawing Methods 0.000 claims description 4
- 230000000875 corresponding effect Effects 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 7
- 238000013461 design Methods 0.000 abstract description 6
- 230000005540 biological transmission Effects 0.000 description 4
- 238000005253 cladding Methods 0.000 description 4
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 229920006240 drawn fiber Polymers 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
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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
- G02B6/02042—Multicore optical fibres
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
- C03B37/01208—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments for making preforms of microstructured, photonic crystal or holey optical fibres
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- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
- C03B37/01225—Means for changing or stabilising the shape, e.g. diameter, of tubes or rods in general, e.g. collapsing
- C03B37/0124—Means for reducing the diameter of rods or tubes by drawing, e.g. for preform draw-down
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- C—CHEMISTRY; METALLURGY
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- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
- C03B37/01225—Means for changing or stabilising the shape, e.g. diameter, of tubes or rods in general, e.g. collapsing
- C03B37/01251—Reshaping the ends
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
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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
- G02B6/02295—Microstructured optical fibre
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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
- G02B6/02295—Microstructured optical fibre
- G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
- G02B6/02319—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by core or core-cladding interface features
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2203/00—Fibre product details, e.g. structure, shape
- C03B2203/10—Internal structure or shape details
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2205/00—Fibre drawing or extruding details
- C03B2205/44—Monotoring or regulating the preform feed rate
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention relates to a multi-core microstructure optical fiber and a preparation method thereof, wherein the multi-core microstructure optical fiber comprises round fiber cores and quartz filling areas, the quartz filling areas are filled in areas among the round fiber cores, a plurality of layers of round fiber cores are arranged in the radial direction of the optical fiber, the distance between each round fiber core in each layer and the central position is the same, and the distance between the round fiber cores in each layer on the same circumference is the same or different; the arrangement mode of the prefabricated bars before the preparation of the multi-core microstructure optical fiber is as follows: for the core at the center position, the cross section is set to be circular, the cross sections of the cores at the rest of the positions deviating from the center position are set to be elliptical, and the ellipticity of each elliptical core is positively correlated with the distance of the position of the core deviating from the center position. The invention designs the cross section shape of the fiber core before starting preparation, counteracts the deformation influence on the fiber core in the drawing process, ensures that the fiber core is not out of round as much as possible, is easy to realize in process, and has good universality.
Description
Technical Field
The invention belongs to the technical field of special optical fiber preparation, and particularly relates to a multi-core microstructure optical fiber and a preparation method thereof.
Background
The multi-core optical fiber constructs a plurality of parallel space channels through a plurality of fiber cores contained in one optical fiber, namely, multiplexing is realized through a Space Division Multiplexing (SDM) technology, so that the shannon capacity limit of optical fiber transmission can be overcome, and the purpose of expanding the capacity of a transmission system is achieved.
As early as the 80 s of the 20 th century, fiber manufacturers in japan and the united states have explored the field of multi-core fiber manufacturing, and the number of cores of multi-core fibers used for system transmission capacity experiments has been increased from early 7 to 9 cores to 20 to 30 cores.
However, when actually drawing a multi-core fiber, there is a problem that the cores of the multi-core fiber are deformed and out of round. Because when drawing optical fiber, graphite furnace heats the optical fiber perform, the peripheral temperature of perform can rise earlier, takes place the tensile under the below traction force effect simultaneously, and the material of perform skin can fall earlier, and the material in perform central zone falls then slightly slowly for the lower surface of perform presents the indent shape. Therefore, the other cores, except the core located at the center of the preform, are deformed into an approximately elliptical shape after being drawn into an optical fiber, which seriously affects the beam transmission quality of the core and causes a large insertion loss when the multi-core optical fiber is coupled with other optical fibers or devices. Since most of the multi-core optical fiber preform is of a cylindrical structure, a cylindrical multi-core optical fiber preform is taken as an example. When the existing multi-core optical fiber preform is designed, the shapes of the preform and the fiber core are round, and after the preform is heated at high temperature by a graphite furnace and stretched by a traction mechanism, the lower surface of the preform is concave, as shown in figure 1. This phenomenon causes the cross-section of the core, which is offset from the center of the fiber, to deform into an approximately elliptical shape, the shape equation of which may be approximated byLong axis ofShort axisPointing to the center of the optical fiber. Wherein,is the long half-axis length of the fiber core,the included angle formed by the central axis of the fiber core and the tangent line at the intersection point of the lower surface of the drawn preform is related to the distance between the fiber core and the center of the fiber, and is influenced by the temperature of the graphite furnace and the drawing speed of the preform. Therefore, there is a need for a multi-core microstructured optical fiber and a method for manufacturing the same.
Disclosure of Invention
In order to overcome the above problems in the prior art, the present invention provides a multi-core microstructured optical fiber and a method for manufacturing the same, which are used for solving the above problems in the prior art.
The multi-core microstructure optical fiber comprises round fiber cores and quartz filling areas, wherein one round fiber core is arranged at a central position, the other round fiber cores are arranged at a certain distance from the central position, the quartz filling areas are filled in areas among the round fiber cores, the optical fiber is provided with at least one layer of round fiber cores along the radial direction, the distance between each round fiber core in each layer and the central position is the same, and the distance between the round fiber cores in each layer on the same circumference is the same or different; the arrangement mode of the prefabricated bars before the preparation of the multi-core microstructure optical fiber is as follows: for the core at the center position, the cross section is set to be circular, the cross sections of the cores at the rest of the positions deviating from the center position are set to be elliptical, and the ellipticity of each elliptical core is positively correlated with the distance of the position of the core deviating from the center position.
In the aspects and any possible implementation manner described above, there is further provided an implementation manner, where the number of cores of the multi-core microstructured optical fiber is greater than or equal to 2.
In aspects and any one of the possible implementations described above, there is further provided an implementation in which the quartz filling zone includes a plurality of capillary rods.
In aspects and any one of the possible implementations described above, there is further provided an implementation in which the number of cores of the fiber core is seven, thirteen or thirty-seven.
The invention also provides a preparation method of the multi-core microstructure optical fiber, which is used for preparing the multi-core microstructure optical fiber and comprises the following steps:
s1, setting fiber cores of multi-core microstructure optical fibers to be prepared, wherein the setting comprises the following steps: setting the cross section of the fiber core at the central position of the multi-core microstructure fiber to be prepared as a circle, setting the cross section of the fiber cores at the rest positions deviating from the central position as ovals, and positively correlating the ovality of each ovality fiber core with the distance of the position of the fiber core deviating from the central position;
s2, magnifying the cross section of the multi-fiber core formed by the center fiber core and all the elliptic fiber cores in equal proportion, and selecting a capillary rod and an outer sleeve with corresponding sizes according to the magnified shape;
s3, grinding, polishing and thinning the multi-fiber core to enable the outer diameter to reach a certain size, and taking the multi-fiber core as an elliptic cylinder fiber core;
s4, arranging the elliptic cylinder fiber cores, the plurality of capillary rods and the outer sleeve to obtain a multi-core optical fiber preform;
s5, drawing the multi-core optical fiber preform rod in a preparation tool at a high temperature to obtain the multi-core microstructure optical fiber.
In the aspect and any possible implementation manner described above, there is further provided an implementation manner, where the preparation tool is a drawing tower, and a graphite furnace is disposed in the drawing tower.
In aspects and any one of the possible implementations described above, there is further provided an implementation in which the circular core and the elliptical core are germanium-doped quartz cores or rare earth-doped cores.
In the foregoing aspect and any possible implementation manner, there is further provided an implementation manner, where the S5 specifically includes: and (3) placing the multi-core optical fiber preform into a wire drawing tower for high-temperature drawing, wherein the temperature of a graphite furnace is 1700-2000 ℃, and the rod feeding speed is 1-5 mm/min.
In the aspects and any possible implementation manner described above, there is further provided an implementation manner, wherein the graphite furnace temperature is set to 1900 ℃, the rod feeding speed is 2 mm/min, and the outer diameter of the drawn multi-core microstructure optical fiber is 100-500 micrometers.
In the aspect and any possible implementation manner as described above, there is further provided an implementation manner, where the outer diameter of the outer sleeve in S4 is 25-60 mm.
The beneficial effects of the invention are that
Compared with the prior art, the invention has the following beneficial effects:
the multi-core microstructure optical fiber comprises round fiber cores and quartz filling areas, wherein one round fiber core is arranged at a central position, the other round fiber cores are arranged at a certain distance from the central position, the quartz filling areas are filled in areas among the round fiber cores, the optical fiber is provided with at least one layer of round fiber cores along the radial direction, the distance between each round fiber core in each layer and the central position is the same, and the distance between the round fiber cores in each layer on the same circumference is the same or different; the arrangement mode of the prefabricated bars before the preparation of the multi-core microstructure optical fiber is as follows: for the core at the center position, the cross section is set to be circular, the cross sections of the cores at the rest of the positions deviating from the center position are set to be elliptical, and the ellipticity of each elliptical core is positively correlated with the distance of the position of the core deviating from the center position.
Compared with the prior art, the invention has the following advantages:
(1) The invention can effectively counteract the influence of the prefabricated rod on the ovalization deformation of the fiber core in the drawing process from the beginning design, so that the drawn multi-core fiber core is not out of round as much as possible, and the cross section of the drawn multi-core microstructure fiber is also round.
(2) The invention can be applied to the design of the multi-core optical fiber with the round fiber core, is easy to realize in the process and has good universality.
(3) The invention can obviously improve the fiber core of the multi-core fiber, in particular to the light beam propagation quality of the peripheral fiber core with obvious out-of-round, is favorable for ensuring the uniformity of signal transmission and provides support for multi-core fiber communication, in particular long-distance communication application.
Drawings
The left side of FIG. 1 is a perspective view of a preform, the upper right graph is a schematic cross-sectional view of the upper surface of the preform, and the lower right graph is a schematic cross-sectional view of a drawn fiber with deformed core;
FIG. 2 is a schematic cross-sectional view of a seven-core preform according to example 1 of the present invention;
FIG. 3 is a schematic cross-sectional view of a right circular core of a seven-core multi-core microstructured optical fiber according to embodiment 1 of the present invention;
FIG. 4 is a schematic cross-sectional view of a thirteen-core preform according to example 2 of the present invention;
FIG. 5 is a schematic cross-sectional view of a thirteen-core optical fiber of a twelve-core multi-core microstructured optical fiber according to embodiment 2 of the present invention;
FIG. 6 is a schematic cross-sectional view of a thirty-seven core preform according to embodiment 3 of the present invention;
FIG. 7 is a schematic cross-sectional view of a thirty-seven core optical fiber of the thirty-seven core multi-core microstructured optical fiber provided in embodiment 3 of the present invention;
FIG. 8 is a flow chart of the method of the present invention;
fig. 9 is a schematic view showing the shape of the lower surface of the preform after being drawn.
Detailed Description
For a better understanding of the present invention, the present disclosure includes, but is not limited to, the following detailed description, and similar techniques and methods should be considered as falling within the scope of the present protection. In order to make the technical problems, technical solutions and advantages to be solved more apparent, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.
It should be understood that the described embodiments of the invention are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The invention discloses a multi-core microstructure optical fiber, which comprises round fiber cores and quartz filling areas, wherein one round fiber core is arranged at a central position, the other round fiber cores are arranged at a certain distance from the central position, the quartz filling areas are filled in areas among the round fiber cores, the optical fiber is provided with at least one layer of round fiber cores along the radial direction, the distance between each round fiber core in each layer and the central position is the same, and the distance between the round fiber cores in each layer on the same circumference is the same or different; the arrangement mode of the prefabricated bars before the preparation of the multi-core microstructure optical fiber is as follows: for the core at the center position, the cross section is set to be circular, the cross sections of the cores at the rest of the positions deviating from the center position are set to be elliptical, and the ellipticity of each elliptical core is positively correlated with the distance of the position of the core deviating from the center position.
Preferably, the number of cores of the multi-core microstructured optical fiber is at least 2 cores, preferably 7 cores, 13 cores or 37 cores, wherein all cores of the drawn multi-core microstructured optical fiber are circular, and the elliptic cores are designed before the preparation of the optical fiber preform and are embodied in the optical fiber preform, so as to counteract the influence of deformation of the preform during the drawing on the ovalization of the cores
Further, the multi-core microstructure optical fiber comprises round fiber cores and quartz filling areas, wherein one round fiber core is arranged at the center position, the other round fiber cores are arranged at a certain distance from the center position, and the quartz filling areas are filled in the areas between the round fiber cores.
Further, the optical fiber is provided with a plurality of layers of circular fiber cores along the radial direction, the distance between each circular fiber core in each layer and the central position is the same, and the interval between the circular fiber cores in each layer on the same circumference (namely, the same radius) is the same or different.
Further, the quartz fill zone includes a plurality of capillary rods.
As a disclosed embodiment, as shown in fig. 8, the present invention further provides a method for preparing a multi-core microstructured optical fiber, the method comprising the steps of:
s1, setting fiber cores of multi-core microstructure optical fibers to be prepared, wherein the setting comprises the following steps: setting the cross section of the fiber core at the central position of the multi-core microstructure fiber to be prepared as a circle, setting the cross section of the fiber cores at the rest positions deviating from the central position as ovals, and positively correlating the ovality of each ovality fiber core with the distance of the position of the fiber core deviating from the central position;
s2, magnifying the cross section of the multi-fiber core formed by the center fiber core and all the elliptic fiber cores in equal proportion, and selecting a capillary rod and an outer sleeve with corresponding sizes according to the magnified shape;
s3, grinding, polishing and thinning the multi-fiber core to enable the outer diameter to reach a certain size, and taking the multi-fiber core as an elliptic cylinder fiber core;
s4, arranging the elliptic cylinder fiber cores, the plurality of capillary rods and the outer sleeve to obtain a multi-core optical fiber preform;
s5, drawing the multi-core optical fiber preform rod in a preparation tool at a high temperature to obtain the multi-core microstructure optical fiber.
Further, the core number of the fiber core is more than or equal to 2.
Further, the multi-core comprises a plurality of layers, wherein the circular core is arranged at the center position, and the other layers are all elliptical cores.
Further, the preparation tool is a graphite furnace, and a wire drawing tower is arranged in the graphite furnace.
Further, the round fiber core and the elliptic fiber core are germanium doped quartz fiber cores or rare earth doped fiber cores.
Further, the step S5 specifically includes: and (3) placing the multi-core optical fiber preform into a wire drawing tower for high-temperature drawing, wherein the temperature of a graphite furnace is 1700-2000 ℃, and the rod feeding speed is 1-5 mm/min.
According to the invention, the deformation condition of the fiber cores is reversed, and the fiber cores to be prepared are designed into an oval shape before the design of the preform, so that the deformation condition in the drawing process is counteracted, and each fiber core of the multi-core optical fiber obtained after the drawing process is round. Specifically, the core shapes of a plurality of groups of drawn multi-core fibers can be measured, and the core shapes required by the design of the preform can be reversely pushed out so as to offset the influence of the deformation of the cores.
In the method, the multi-fiber core prepared in advance is of a cylindrical structure, and the cylindrical structure consists of a plurality of elliptic cylindrical fiber cores and right circular cylindrical fiber cores with different ovality.
The ellipticity of the elliptic cylinder-shaped fiber core is determined by the concave degree of the lower surface of the prefabricated rod to be manufactured and the distance of the fiber core from the central axis of the prefabricated rod, wherein the concave degree of the lower surface of the prefabricated rod is related to the temperature of the graphite furnace. The shape equation of the fiber cores in the multi-core optical fiber preform is fitted by drawing a plurality of groups of multi-fiber cores with different core numbers, different core diameters and different core distances:
(1) Wherein ellipticity
（2）,The temperature of the graphite furnace is expressed as the unit of degrees centigrade,the ratio of the distance of the fiber core deviating from the central axis of the optical fiber preform to the radius of the optical fiber preform is beta, and the included angle formed by the cross section at the intersection point of the central axis of the fiber core and the lower surface of the optical fiber preform after being attenuated is beta.
Short axis (i.eA shaft),long axis (i.eAn axis) is directed toward the central axis of the preform, wherein,is the long half axis of the core (half of the long axis, i.e., the long half axis), as shown in figure 9,is related to the distance between the core and the center of the resulting fiber and is affected by the temperature of the graphite furnace and the preform drawing speed. The long axis extension line of the elliptic cylinder intersects with the central axis of the prefabricated rod.
The preparation method of the multi-core microstructure optical fiber is suitable for multi-core optical fibers with two cores or more than two cores.
Specifically, the preparation method of the invention comprises the following steps:
(1) According to the number of cores of the multi-core microstructure optical fiber and the distance of each core deviating from the central axis of the optical fiber, the weak coupling fiber cores are designed, the fiber cores are preferably at a distance of about 43um, the temperature and the drawing speed of a graphite furnace are used for designing the ellipticity of each fiber core, the ellipticity and the ellipticity are calculated according to the formulas (1) and (2), the cross section of the fiber core arranged at the central position of the multi-core microstructure optical fiber to be prepared is circular, the other fiber cores deviating from the center are designed as ellipses, the ellipticity is positively related with the distance of the fiber cores deviating from the center, and the circular fiber cores and the elliptical fiber cores form multi-fiber cores;
(2) Amplifying the multi-fiber core designed in the step (1) according to the equal proportion of the cross section of the multi-fiber core, and selecting a proper quartz capillary rod and an outer sleeve;
(3) Polishing and polishing the unground multi-fiber core according to the shape designed in the step (1) to enable the shape of the unground multi-fiber core to be in accordance with the elliptic cylinder body designed in the step (1), and then thinning the elliptic cylinder body until the diameter of the external diameter is 1-6 mm to serve as the elliptic cylinder multi-fiber core;
(4) The method comprises the following steps of arranging elliptic cylinder multi-fiber cores and quartz glass capillary rods, wherein an outer sleeve is arranged into the elliptic fiber core multi-fiber preform according to a designed structure by a stacking method, and the specific process of the stacking method is as follows: stacking quartz glass capillary rods and elliptic cylinder multiple fiber cores to form specific fiber core arrangement, fixing the fiber cores by using a clamp, and sleeving an outer sleeve on the outer surface to finally obtain the optical fiber preform, wherein the fiber cores are rare earth doped quartz rods or germanium doped quartz rods=.
(5) Placing the multi-core optical fiber preform with the elliptic fiber cores obtained in the step (4) into a drawing tower for high-temperature drawing, wherein a graphite furnace is arranged in the drawing tower, the temperature of the graphite furnace is 1700-2000 ℃, and the rod feeding speed is 1-5 mm/min.
In the step (4), the outer diameter of the outer sleeve is 25-60 mm, i.e. the outer diameter of the optical fiber preform.
The following are specific examples
Example 1
The present embodiment provides a seven-core multi-core optical fiber preform, as shown in fig. 2, having a cylindrical structure composed of a circular core 1, an elliptical core 2, and a quartz region 3; the round fiber core 1 and the elliptic fiber core 2 are germanium doped quartz fiber cores or rare earth doped fiber cores.
The quartz area 3 is composed of a quartz glass tube and a capillary high-purity quartz glass rod filled in the quartz glass tube.
The outer diameter of the quartz area 3 is 40 mm, namely the outer diameter size of the outer sleeve of the preform; the outer diameter of the circular core 1 is 3.1 mm.
The elliptic fiber core 2 has a long axis of 3.1 mm and a short axis of 2.7 mm, and the extension line of the long axis intersects with the central axis of the seven-core preform. Each core is arranged with a core spacing of 12 mm from its adjacent cores, for a total of 7 cores, consisting of a central circular core 1 and six outer elliptical cores 2. The six outer oval fiber cores 2 are arranged and combined in a regular hexagon to form a hexagon structure.
The preparation method of the multi-core microstructure optical fiber comprises the following steps:
(1) The ellipticity of each elliptic fiber core 2 is designed according to the core number of the seven-core microstructure fiber, the distance of each core deviating from the central axis of the fiber, the temperature of a graphite furnace and the drawing speed, and the elliptic shape and the ellipticity are calculated according to formulas (1) and (2).
(2) Amplifying the multi-fiber core structure designed in the step (1) according to the equal proportion of the sectional view, and selecting a proper quartz capillary rod and an outer sleeve.
(3) And (3) grinding and polishing the unground multi-fiber core according to the shape designed in the step (1) to enable the shape of the elliptic cylinder to meet the design requirement of the step (1), and then, thinning the elliptic cylinder to an elliptic cylinder with a long axis of 3.1 mm and a short axis of 2.7 mm to obtain the elliptic cylinder fiber core of the seven-core optical fiber preform.
(4) The elliptic cylinder fiber cores and the quartz glass capillary rods are arranged into the multi-core optical fiber preform by a stacking method according to a designed structure of an outer sleeve.
(5) And (3) placing the seven-core optical fiber preform obtained in the step (4) into a drawing tower for high-temperature drawing, wherein the temperature of a graphite furnace is about 1900 ℃, and the rod feeding speed is about 2 mm/min.
And finally, drawing the seven-core microstructure optical fiber, wherein each fiber core in the seven-core microstructure optical fiber is a perfect circular fiber core, the diameter of each fiber core of the drawn seven-core microstructure optical fiber is 11.1 micrometers, the core spacing is 43 micrometers, the diameter of the cladding (namely the outer cladding of the optical fiber, namely the outer diameter of the optical fiber) is 142 micrometers, and the structure is shown in figure 3.
Example 2
The embodiment provides a thirteen-core multi-core optical fiber preform, as shown in fig. 4, which is a cylindrical structure consisting of a circular fiber core 1, an inner elliptical fiber core 2, an outer elliptical fiber core 3 and a quartz region 4; the fiber cores are all rare earth doped fiber cores.
The quartz area 4 is composed of a quartz glass tube and a capillary high-purity quartz glass rod filled in the quartz glass tube.
The outer diameter of the preform to be prepared was 45 mm and the outer diameter of the circular core 1 was 1.54 mm.
The inner elliptical cores 2 have a major axis of 1.54 mm, a minor axis of 1.46 mm, and a core pitch of 7.52 mm. An extension line of the long axis is set to intersect with the central axis of the preform to be prepared.
The outer elliptical core 3 has a major axis of 1.54 mm and a minor axis of 1.38 mm, and the extension of the major axis is set to intersect with the central axis of the preform to be prepared.
Each core is disposed at a core spacing of 7.5 millimeters from its adjacent cores.
The number of cores is 13 in total, and consists of a central circular core, six inner elliptical cores and six outer elliptical cores, where the ellipticity of each core increases as the distance of the core from the central axis of the preform increases.
The fiber cores of all layers are arranged and combined in a regular hexagon to form a hexagon structure.
The preparation procedure is described in example 1.
The final drawn thirteen-core microstructure fiber has a core diameter of 8.8 microns, a core spacing of 43 microns, a cladding diameter of 257 microns, and a structure shown in fig. 5.
Example 3
The embodiment provides a thirty-seven core multi-core optical fiber preform, the structure of which is shown in fig. 6, and the multi-core optical fiber preform is a cylindrical structure consisting of a circular fiber core 1, a first layer of 6 elliptic fiber cores 2, a second layer of 12 elliptic fiber cores 3, a third layer of 18 elliptic fiber cores 4 and a quartz area 5; the fiber cores are all rare earth doped fiber cores. The quartz area 5 is composed of a quartz glass tube and a capillary high-purity quartz glass rod filled in the quartz glass tube.
The preform was set to have an outer diameter of 50 mm and the round core 1 to have an outer diameter of 1.37 mm.
The first elliptical cores 2 are the same size, with all major axes of 1.37 mm and minor axes of 1.31 mm. The extension line of the long axis intersects with the central axis of the preform.
The second elliptical cores 3 are all the same in size, all have a major axis of 1.37 mm and a minor axis of 1.26 mm, and the extension of the major axis intersects the central axis of the preform.
The dimensions of the third elliptical cores 4 are all the same, all having a major axis of 1.37 mm and a minor axis of 1.14 mm, the extension of the major axis intersecting the central axis of the preform.
The core spacing between each core of each layer and the adjacent core is 6 millimeters.
The cores were 37 in total, consisting of 1 central circular core, 6 first layer elliptical cores, 12 second layer elliptical cores and 18 third layer elliptical cores, where the ellipticity of the cores increased as the distance of the cores from the central axis of the preform increased.
The fiber cores of all layers are arranged and combined periodically to form a hexagonal structure.
The preparation method can be referred to in example 1.
The final drawn thirty-seven core microstructure fiber has a core diameter of 11 microns, a core spacing of 48 microns, a cladding diameter of 400 microns, and a structure shown in fig. 7.
It should be noted that the degree of ovalization of the core is also related to the drawing speed, and can be corrected according to the actual situation when the preform is actually drawn.
While the foregoing description illustrates and describes the preferred embodiments of the present invention, it is to be understood that the invention is not limited to the forms disclosed herein, but is not to be construed as limited to other embodiments, and is capable of numerous other combinations, modifications and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein, either as a result of the foregoing teachings or as a result of the knowledge or technology of the relevant art. And that modifications and variations which do not depart from the spirit and scope of the invention are intended to be within the scope of the appended claims.
Claims (10)
1. The multi-core microstructure optical fiber is characterized by comprising round fiber cores and quartz filling areas, wherein one round fiber core is arranged at a central position, the other round fiber cores are arranged at a certain distance from the central position, the quartz filling areas are filled in areas among the round fiber cores, the optical fiber is provided with at least one layer of round fiber cores along the radial direction, the distance between each round fiber core in each layer and the central position is the same, and the interval between the round fiber cores in each layer on the same circumference is the same or different; the arrangement mode of the prefabricated bars before the preparation of the multi-core microstructure optical fiber is as follows: for the core at the center position, the cross section is set to be circular, the cross sections of the cores at the rest of the positions deviating from the center position are set to be elliptical, and the ellipticity of each elliptical core is positively correlated with the distance of the position of the core deviating from the center position.
2. The multi-core microstructured optical fiber of claim 1, wherein the number of cores of the multi-core microstructured optical fiber is 2 or more.
3. The multi-core microstructured optical fiber of claim 1, wherein the quartz fill region comprises a plurality of capillary rods.
4. The multi-core microstructured optical fiber of claim 2, wherein the number of cores of the fiber core is seven, thirteen, or thirty-seven.
5. A method for preparing the multi-core microstructured optical fiber, wherein the method is used for preparing the multi-core microstructured optical fiber according to any one of claims 1 to 4, and comprises the following steps:
s1, setting fiber cores of multi-core microstructure optical fibers to be prepared, wherein the setting comprises the following steps: setting the cross section of the fiber core at the central position of the multi-core microstructure fiber to be prepared as a circle, setting the cross section of the fiber cores at the rest positions deviating from the central position as ovals, and positively correlating the ovality of each ovality fiber core with the distance of the position of the fiber core deviating from the central position;
s2, magnifying the cross section of the multi-fiber core formed by the center fiber core and all the elliptic fiber cores in equal proportion, and selecting a capillary rod and an outer sleeve with corresponding sizes according to the magnified shape;
s3, grinding, polishing and thinning the multi-fiber core to enable the outer diameter to reach a certain size, and taking the multi-fiber core as an elliptic cylinder fiber core;
s4, arranging the elliptic cylinder fiber cores, the plurality of capillary rods and the outer sleeve to obtain a multi-core optical fiber preform;
s5, drawing the multi-core optical fiber preform rod in a preparation tool at a high temperature to obtain the multi-core microstructure optical fiber.
6. The method for producing a multi-core microstructured optical fiber according to claim 5, characterized in that the production tool is a drawing tower in which a graphite furnace is provided.
7. The method of claim 5, wherein the circular core and the elliptical core are germanium doped quartz cores or rare earth doped cores.
8. The method for preparing a multi-core microstructured optical fiber according to claim 5, wherein said S5 specifically comprises: and (3) placing the multi-core optical fiber preform into a wire drawing tower for high-temperature drawing, wherein the temperature of a graphite furnace is 1700-2000 ℃, and the rod feeding speed is 1-5 mm/min.
9. The method of manufacturing a multi-core microstructured optical fiber according to claim 6, characterized in that,
the temperature of the graphite furnace is set to 1900 ℃, the rod feeding speed is 2 mm/min, and the outer diameter of the drawn multi-core microstructure optical fiber is 100-500 microns.
10. The method of manufacturing a multi-core microstructured optical fiber according to claim 5, wherein an outer diameter of said outer jacket tube in S4 is 25 to 60 mm.
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