US20160245992A1 - Optical device - Google Patents
Optical device Download PDFInfo
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- US20160245992A1 US20160245992A1 US15/045,645 US201615045645A US2016245992A1 US 20160245992 A1 US20160245992 A1 US 20160245992A1 US 201615045645 A US201615045645 A US 201615045645A US 2016245992 A1 US2016245992 A1 US 2016245992A1
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- 230000003287 optical effect Effects 0.000 title claims description 122
- 238000005253 cladding Methods 0.000 claims abstract description 71
- 239000000835 fiber Substances 0.000 claims description 121
- 230000008878 coupling Effects 0.000 claims description 70
- 238000010168 coupling process Methods 0.000 claims description 70
- 238000005859 coupling reaction Methods 0.000 claims description 70
- 238000005452 bending Methods 0.000 claims description 19
- 230000003247 decreasing effect Effects 0.000 claims description 13
- 238000010586 diagram Methods 0.000 description 46
- 230000001902 propagating effect Effects 0.000 description 42
- 238000004891 communication Methods 0.000 description 23
- 239000013307 optical fiber Substances 0.000 description 16
- 230000014509 gene expression Effects 0.000 description 14
- 239000011295 pitch Substances 0.000 description 13
- 238000000034 method Methods 0.000 description 6
- 230000005540 biological transmission Effects 0.000 description 3
- 230000005684 electric field Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 238000005094 computer simulation Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
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Classifications
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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
-
- 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
- G02B6/02004—Optical fibres with cladding with or without a coating characterised by the core effective area or mode field radius
- G02B6/02009—Large effective area or mode field radius, e.g. to reduce nonlinear effects in single mode fibres
- G02B6/02014—Effective area greater than 60 square microns in the C band, i.e. 1530-1565 nm
- G02B6/02019—Effective area greater than 90 square microns in the C band, i.e. 1530-1565 nm
-
- 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
- G02B6/02047—Dual mode fibre
-
- 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
- G02B6/02342—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by cladding features, i.e. light confining region
- G02B6/02376—Longitudinal variation along fibre axis direction, e.g. tapered holes
-
- 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
-
- 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
- G02B6/03644—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 - + -
-
- 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
- G02B6/24—Coupling light guides
- G02B6/36—Mechanical coupling means
- G02B6/3628—Mechanical coupling means for mounting fibres to supporting carriers
- G02B6/368—Mechanical coupling means for mounting fibres to supporting carriers with pitch conversion between input and output plane, e.g. for increasing packing density
-
- 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
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/262—Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
-
- 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
- G02B6/24—Coupling light guides
- G02B6/36—Mechanical coupling means
- G02B6/38—Mechanical coupling means having fibre to fibre mating means
- G02B6/3807—Dismountable connectors, i.e. comprising plugs
- G02B6/3873—Connectors using guide surfaces for aligning ferrule ends, e.g. tubes, sleeves, V-grooves, rods, pins, balls
- G02B6/3885—Multicore or multichannel optical connectors, i.e. one single ferrule containing more than one fibre, e.g. ribbon type
Definitions
- the disclosure relates to an optical device, which is preferred in the case of transmitting light in multiple modes.
- Optical fibers for use in widely available optical fiber communication systems have a structure in which the outer circumferential surface of one core is surrounded by a cladding. Optical signals propagate through the inside of this core, and thus information is transmitted. In these years, with the wide spread use of optical fiber communication systems, information volumes to be transmitted are dramatically increased.
- a multicore fiber includes a plurality of cores and a cladding surrounding the outer circumferential surface of the cores and this multicore fiber is used to transmit a plurality of signals with light propagating through each core.
- Patent Literature 1 discloses an optical device for transmitting light beams to and from a multicore fiber.
- a single-core optical fiber is inserted into each of a plurality of holes formed in a capillary to form an assembly, the assembly is drawn, and then the optical device is formed.
- the optical fiber is tapered in diameter from a first portion to a second portion of the optical fiber.
- Each of the optical fibers has a dual structure in which a core is formed of an inner core and an outer core surrounding the inner core with no gap.
- the refractive index of the inner core is set higher than the refractive index of the outer core.
- the refractive index of the cladding is set lower than the refractive index of the outer core.
- the diameter of the inner core and the refractive index difference between the inner core and the outer core are set so that a single-mode light beam easily propagates through the inner core.
- the outer diameter of the outer core and the refractive index difference between the outer core and the cladding are set so that a single-mode light beam easily spreads to the outer core and propagates through the entire core including the inner core and the outer core.
- a single-mode light beam propagating from the first portion to the second portion of each of the optical fibers propagates through the inner core in the first portion.
- the diameter of the inner core is below a predetermined diameter at the tapered second portion, and the leakage of light from the inner core to the outer core is increased. Consequently, after the diameter of the inner core is below a predetermined diameter, the light beam spreads to the outer core, and propagates through the core including the inner core and the outer core.
- MFD mode field diameter
- the premise of the optical device described in Patent Literature 1 is to transmit a single-mode light beam. Therefore, in the optical device, conditions, such as the refractive indexes and diameters of the inner core and the outer core, are set so that a single-mode light beam propagates as described above.
- optical communications there is known a method of few mode communications in which information is superposed on an LP 01 mode (fundamental mode) light beam and information is superposed on an LP 11 mode light beam for information communications. Therefore, also in few mode communications, an optical device for transmitting light beams to and from a multicore fiber is demanded.
- a concept is a configuration in which the refractive index in the center part of the inner core is more decreased than the refractive index of the outer circumferential portion of the inner core.
- the optical device is an optical device including: a plurality of cores each including an inner core and an outer core surrounding an outer circumferential surface of the inner core, the outer core having a refractive index lower than a refractive index of the inner core; and a cladding surrounding the outer circumferential surface of the core and having a refractive index lower than the refractive index of the outer core.
- a tapered portion is formed in which the each core is tapered in diameter from a first end to a second end of the core in a longitudinal direction and a pitch between the cores adjacent to each other is decreased.
- a bending loss of an LP 02 mode light beam and a bending loss of an LP 21 light beam at a wavelength of 1.53 ⁇ m are 1.0 dB/m or greater at a radius of 140 mm, and a bending loss of an LP 11 mode light beam at a wavelength of 1.625 ⁇ m is 0.5 dB/100 turns or less at a radius of 30 mm.
- a radius of the inner core before tapered in diameter is defined as r 1
- a radius of the outer core before tapered in diameter is defined as r 2
- a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding before tapered in diameter is defined as V 1
- a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding before tapered in diameter is defined as V 2 .
- each of the cores transmits the LP 01 and LP 11 mode light beams in the C band and the L band at the bending losses of the LP 02 and the LP 21 mode light beams.
- each of the cores is a two-stage core including an inner core and an outer core, and has a simpler configuration than in the previously existing optical devices.
- the optical device according to the disclosure can transmit light to and from a multicore fiber in few mode communications with a simple configuration.
- the radius r 2 of the outer core before tapered in diameter may be preferably 15 ⁇ m or more.
- the radius r 2 of the outer core before tapered in diameter may be more preferably 20 ⁇ m or more.
- a length of the tapered portion is 4 mm or longer, and a length of the core after tapered in diameter is 2 mm or longer.
- the crosstalk in the LP 11 mode light beam propagating through the cores adjacent to each other can be made ⁇ 30 dB or less.
- a length of the tapered portion is 6 mm or longer.
- the crosstalk in the LP 11 mode light beam propagating through the cores adjacent to each other can be made ⁇ 40 dB or less.
- a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding after tapered in diameter is defined as V 1 ′
- a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding after tapered in diameter is defined as V 2 ′.
- a refractive index volume formed of a product of a cross sectional area of the multicore fiber core and a relative refractive index difference of the multicore fiber core to a cladding surrounding an outer circumferential surface of the multicore fiber core is defined as V t .
- a coupling loss of an LP 01 mode light beam through the multicore fiber is equal to or greater than a coupling loss of an LP 11 mode light beam through the multicore fiber.
- an optical device that can transmit light to and from a multicore fiber in few mode communications with a simple configuration.
- FIG. 1 is a diagram of an optical device according to a first embodiment
- FIG. 2A is a diagram of a structure in a cross section perpendicular to the longitudinal direction at a position including a capillary of the optical device illustrated in FIG. 1 ;
- FIG. 2B is a diagram of a refractive index profile taken along line V-V in FIG. 2A ;
- FIG. 3A is a diagram of a core of a relay fiber
- FIG. 3B is a diagram of electric fields of an LP 01 mode light beam and an LP 11 mode light beam at a large-diameter portion and a small-diameter portion of the relay fiber;
- FIG. 4 is a diagram of an optical device according to a second embodiment
- FIG. 5A is a diagram of a structure in a cross section perpendicular to the longitudinal direction of the optical device in FIG. 4 ;
- FIG. 5B is a diagram of a refractive index profile taken along line V-V in FIG. 5A ;
- FIG. 6 is a diagram of a coupling loss and other parameters in Example 1.
- FIG. 7 is a diagram of the coupling loss of the LP 01 mode light beam and the coupling loss of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a circle in FIG. 6 ;
- FIG. 8 is a diagram of the coupling loss of the LP 01 mode light beam and the coupling loss of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a triangle in FIG. 6 ;
- FIG. 9 is a diagram of the coupling loss of the LP 01 mode light beam and the coupling loss of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a square in FIG. 6 ;
- FIG. 10 is a diagram of changes in the effective area of the LP 01 mode light beam and the effective area of the LP 11 mode light beam propagating through the core in the case in which the length of the tapered portion of the optical device that achieves parameters at the square in FIG. 6 is set to 5 mm;
- FIG. 11 is a diagram of changes in the effective area of the LP 01 mode light beam and the effective area of the LP 11 mode light beam propagating through the core in the case in which the length of the tapered portion of the optical device that achieves parameters at the square in FIG. 6 is set to 10 mm;
- FIG. 12 is a diagram of the size of the crosstalk in the LP 01 mode light beam propagating through cores adjacent to each other in the case of changing the length of the small-diameter portion of the optical device that achieves parameters at the square in FIG. 6 ;
- FIG. 13 is a diagram of the size of the crosstalk in the LP 11 mode light beam propagating through cores adjacent to each other in the case of changing the length of the small-diameter portion of the optical device that achieves parameters at the square in FIG. 6 ;
- FIG. 14 is a diagram of a coupling loss and other parameters in Example 2.
- FIG. 15 is a diagram of the coupling loss of the LP 01 mode light beam and the coupling loss of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a triangle in FIG. 14 ;
- FIG. 16 is a diagram of a coupling loss and other parameters in Example 3.
- FIG. 17 is a diagram of the coupling loss of the LP 01 mode light beam and the coupling loss of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a circle in FIG. 16 ;
- FIG. 18 is a diagram of the coupling loss of the LP 01 mode light beam and the coupling loss of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a triangle in FIG. 16 ;
- FIG. 19 is a diagram of the coupling loss of the LP 01 mode light beam and the coupling loss of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a square in FIG. 16 ;
- FIG. 20 is a diagram of the relationship between the radius of the outer core in the large-diameter portion and the values of the ratio of the refractive index volume of an inner core and the refractive index volume of an outer core 12 for the circle, the triangle, and the square in FIGS. 6, 14, and 16 .
- FIG. 1 is a diagram of an optical device according to a first embodiment of the disclosure. As illustrated in FIG. 1 , an optical device 1 according to the embodiment includes a plurality of relay fibers 10 and a capillary 20 as main components. In the embodiment, the number of the relay fibers 10 is seven.
- the relay fibers 10 are inserted into the capillary 20 from a first end to a second end of the capillary 20 .
- the relay fibers 10 and the capillary 20 are integrally formed with no gap.
- One end of the relay fiber 10 is exposed from the first end of the capillary 20 .
- the other end of the relay fiber 10 is flush with the second end of the capillary 20 . Therefore, the other end of each of the relay fibers 10 is seen at the second end of the capillary 20 .
- the capillary 20 has a circular in a cross section, and has a large-diameter portion 21 , a tapered portion 22 , and a small-diameter portion 23 along the longitudinal direction.
- the tapered portion 22 is tapered in diameter from the first end to the second end of the capillary 20 .
- This form is provided by a method below.
- a capillary is prepared.
- the capillary has through holes in the same number as the number of the relay fibers 10 to be inserted into the capillary, and the capillary has a constant thickness.
- the relay fibers 10 are individually inserted into the through holes.
- the capillary and the relay fibers 10 are heated and formed into a single product.
- each of the relay fibers 10 is tapered in diameter from the first end to the second end of the capillary 20 as the capillary 20 is tapered in diameter, and the pitch between the adjacent relay fibers 10 is decreased.
- the diameter of each of the relay fibers 10 is also decreased more than the diameter of the relay fiber 10 in the large-diameter portion.
- the pitch between the adjacent relay fibers 10 is also more decreased than the pitch between the adjacent relay fibers 10 in the large-diameter portion.
- FIG. 2A is a diagram of a structure in a cross section perpendicular to the longitudinal direction at a position including the capillary 20 of the optical device 1 .
- FIG. 2B is a diagram of a refractive index profile taken along line V-V on the cross section in FIG. 2A .
- the ratio of the outer diameter of the capillary 20 to the outer diameter of the relay fiber 10 is the same in the large-diameter portion 21 , the tapered portion 22 , and the small-diameter portion 23 of the capillary 20 in any cross sections perpendicular to the longitudinal direction. Therefore, it is unnecessary to identify cross sections and positions on the capillary 20 .
- the number of the relay fibers 10 is seven.
- One relay fiber 10 is disposed in the center of the capillary 20 .
- Six relay fibers 10 are disposed around the relay fiber 10 in the center. In this state, lines connecting the centers of the relay fibers 10 form a lattice of triangles, and the inter-center pitches of the relay fibers 10 are set equal.
- the relay fibers 10 are single-core optical fibers, each including a core 13 and a cladding 15 surrounding the outer circumferential surface of the core 13 with no gap.
- the core 13 includes an inner core 11 and an outer core 12 .
- each of the relay fibers 10 is tapered in diameter in the tapered portion 22 from the large-diameter portion 21 toward the small-diameter portion 23 . Consequently, the inner core 11 and the outer core 12 configuring the core 13 of the relay fiber 10 and the cladding 15 are tapered in diameter from the large-diameter portion 21 toward the small-diameter portion 23 as the ratios of the diameters are maintained. As illustrated in FIG.
- the radius of the inner core 11 is defined as r 1
- the radius of the outer core is defined as r 2 in the large-diameter portion 21 before tapered in diameter.
- the radius of the inner core 11 is defined as r 1 ′
- the radius of the outer core is defined as r 2 ′ in the small-diameter portion 23 after tapered in diameter.
- the refractive index of the inner core 11 is set higher than the refractive index of the outer core 12 .
- the refractive index of the cladding 15 is set lower than the refractive index of the outer core 12 .
- the refractive index of the capillary 20 is the same as the refractive index of the cladding 15 .
- the relative refractive index difference of the inner core 11 to the cladding 15 is defined as ⁇ 1
- the relative refractive index difference of the outer core to the cladding 15 is defined as ⁇ 2 .
- V 1 a refractive index volume formed of a product of the cross sectional area of the inner core 11 and a relative refractive index difference ⁇ 1 of the inner core 11 to the cladding 15 in the large-diameter portion 21
- V 2 a refractive index volume formed of a product of the cross sectional area of the outer core 12 and a relative refractive index difference ⁇ 2 of the outer core 12 to the cladding 15 in the large-diameter portion 21
- the outer diameter of the cladding of a typical optical fiber is 125 ⁇ m.
- a typical core pitch of a multicore fiber 5 is about 30 ⁇ m or more and 50 ⁇ m or less. Therefore, preferably, in the large-diameter portion 21 , the outer diameter of the relay fiber 10 is equal to the outer diameter of a typical optical fiber, and in the small-diameter portion 23 , the core pitch is the core pitch of a typical multicore fiber.
- the wall thickness between the through holes of the capillary 20 before tapered in diameter is 10 ⁇ m or more and 25 ⁇ m or less from the viewpoint of decreasing the size and obtaining strength.
- the draw ratio of the outer diameter of the capillary 20 in the large-diameter portion 21 before tapered in diameter to the outer diameter of the capillary 20 in the small-diameter portion 23 after tapered in diameter i.e., the draw ratio of the large-diameter portion 21 to the small-diameter portion 23
- the draw ratio is nearly equal to the draw ratio of the core 13 . Therefore, in order to match the diameter of the inner core 11 through which light propagates in the large-diameter portion 21 with the diameter of the outer core 12 through which light propagates in the small-diameter portion 23 , Expression 2 is satisfied.
- Expression 2 may be Expression 3.
- FIGS. 3A and 3B are diagrams each illustrating an LP 01 mode light beam and an LP 11 mode light beam propagating through the core 13 of each of the relay fibers 10 . More specifically, FIG. 3A is a diagram of the core 13 in the large-diameter portion 21 and the core 13 in the small-diameter portion 23 . FIG. 3B is a diagram of electric fields of the LP 01 and LP 11 mode light beams in the large-diameter portion 21 and the small-diameter portion 23 .
- the outer core 12 functions as the cladding for the inner core 11 , and the light beam in each mode propagates through the inner core 11 .
- the radius r 1 of the inner core 11 in the large-diameter portion 21 only has to be 6.47 ⁇ m, and a difference ⁇ 12 between the relative refractive index difference ⁇ 1 of the inner core 11 to the cladding 15 and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding only has to be 0.45%.
- the light beam in each mode propagating through the inner core 11 travels from the large-diameter portion 21 toward the small-diameter portion 23 , and then comes into the tapered portion 22 where the core 13 is tapered in diameter. Consequently, the light beam in each mode propagating through the inner core 11 leaks greatly from the inner core 11 to the outer core 12 . Therefore, in the small-diameter portion 23 , the light beam in each mode spreads to the outer core 12 , and propagates through the entire core 13 including the inner core 11 and the outer core 12 . However, the LP 01 and LP 11 mode light beams do not spread to the outer core 12 at the same place in the tapered portion 22 . The light beam in each mode spreads to the outer core 12 until the light beam in each mode reaches at least the small-diameter portion 23 , and then the light beam in each mode propagates through the core 13 including the inner core 11 and the outer core 12 .
- the LP 01 and LP 11 mode light beams propagate through the entire core 13 including the inner core 11 and the outer core 12 in the small-diameter portion 23 .
- the diameter of the core 13 is gradually increased from the small-diameter portion 23 to the large-diameter portion 21 .
- the light beam in each mode propagates through the inner core 11 .
- the outer core 12 functions as the cladding, and the light beam in each mode propagates through the inner core 11 .
- the radius r 2 of the outer core 12 only has to be 6.637 ⁇ m, and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding 15 only has to be 0.445%.
- the bending losses of an LP 02 mode light beam and an LP 21 light beam are 1.0 dB/m or greater at a radius of 140 mm.
- the bending loss of the LP 11 mode light beam at a wavelength of 1.625 ⁇ m is 0.5 dB/100 turns or less at a radius of 30 mm. Therefore, the relay fibers 10 are few mode optical fibers that substantially transmit the LP 01 and LP 11 mode light beams in the C and L bands and prevent light in higher modes than the LP 01 and LP 11 modes from propagating.
- the optical device 1 is used as the small-diameter portion 23 is connected to the multicore fiber 5 .
- the multicore fiber 5 includes a plurality of cores 53 and a cladding 55 surrounding the outer circumferential surfaces of the cores 53 with no gap.
- the refractive index of each of the cores 53 is set higher than the refractive index of the cladding 55 .
- the number of the relay fibers 10 of the optical device 1 is equal to the number of the cores 53 of the multicore fiber 5 .
- the relative position of the core 13 of each of the relay fibers 10 in the small-diameter portion 23 is the same as the relative position of each of the cores 53 of the multicore fiber 5 .
- the optical device 1 is connected to the multicore fiber 5 for use in the state in which in the optical device 1 , the cores 13 in the small-diameter portion 23 are opposed to the cores 53 on one end of the multicore fiber 5 . Therefore, light propagating through the cores 13 of the optical device 1 from the large-diameter portion 21 toward the small-diameter portion 23 as described above is entered to the cores 53 of the multicore fiber 5 , and propagates through the cores 53 . On the other hand, light propagating through the cores 53 of the multicore fiber 5 toward the optical device 1 is entered to the cores 13 of the optical device 1 , and propagates through the cores 13 from the small-diameter portion 23 toward the large-diameter portion 21 as described above. In other words, the optical device 1 is used as a device for transmitting light beams to and from the multicore fiber 5 .
- the optical device 1 is connected to the multicore fiber 5 , and then light is transmitted to and from the cores 53 of the multicore fiber 5 .
- the coupling loss of the LP 01 mode light beam is equal to or greater than the coupling loss of the LP 11 mode light beam.
- a refractive index volume formed of a product of the cross sectional area of the inner core 11 and the relative refractive index difference ⁇ 1 of the inner core 11 to the cladding 15 in the small-diameter portion 23 is defined as V 1 ′
- a refractive index volume formed of a product of the cross sectional area of the outer core 12 and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding 15 in the small-diameter portion 23 is defined as V 2 ′.
- a refractive index volume formed of a product of the cross sectional area of the cores 53 and a relative refractive index difference ⁇ t of the core 53 to the cladding 55 is defined as V t .
- Expression 4 is preferably satisfied.
- Expression 4 is satisfied, and thus the coupling loss of light reciprocating in the optical device 1 and the multicore fiber 5 can be decreased.
- the cores transmit the LP 01 and LP 11 mode light beams at least in the C and L bands. It has been found that in the transmission, Expressions 1 and 2 are satisfied, and thus the coupling loss of light can be made smaller in the case in which the optical device 1 is connected to the multicore fiber 5 .
- each of the cores 13 is a two-stage core including the inner core and the outer core 12 , which simplifies core configurations. Therefore, the optical device 1 according to the embodiment can transmit light to and from the multicore fiber 5 in few mode communications with a simple configuration.
- FIG. 4 is a diagram of an optical device according to the second embodiment of the disclosure.
- FIG. 5A is a diagram of a structure in a cross section perpendicular to the longitudinal direction of the optical device 2 in FIG. 4 .
- FIG. 5B is a diagram of a refractive index profile taken along line V-V in FIG. 5A .
- an optical device 2 according to the embodiment is different from the optical device 1 according to the first embodiment in that the outer circumferential surfaces of the cores 13 are surrounded with a cladding 25 made of glass with no gap similarly to the capillary 20 according to the first embodiment and the cores 13 are located only inside the cladding 25 .
- the optical device 2 according to the embodiment is equivalent to an optical device in which in the optical device 1 according to the first embodiment, the relay fibers 10 exposed from the capillary 20 are removed, the cladding 15 on each of the relay fibers 10 is removed, and spaces produced by removing the cladding 15 are filled with the capillary 20 .
- the optical device 2 thus configured has a structure in a cross section as illustrated in FIGS. 5A and 5B .
- the optical device 2 only has to be formed in which a multicore fiber having the same thickness as the thickness of the large-diameter portion 21 is prepared and the prepared multicore fiber is molten and drawn for forming the tapered portion 22 and the small-diameter portion 23 .
- the optical device 2 according to the embodiment also satisfies Expressions 1 and 2.
- optical device 2 using the multicore fiber thus formed can transmit light to and from the multicore fiber 5 in few mode communications similarly to the optical device 1 according to the first embodiment.
- the number of the relay fibers 10 according to the first embodiment and the number of the cores 13 according to the second embodiment can be appropriately modified.
- the refractive index of the cladding 15 is set equal to the refractive index of the capillary 20 .
- the refractive index of the cladding 15 may be different from the refractive index of the capillary 20 .
- Simulation was performed using a model in which the optical device 1 according to the first embodiment was connected to the multicore fiber 5 .
- a radius r t of the core 53 of the multicore fiber 5 was set to 6.47 ⁇ m
- the core pitch was set to 44.1 ⁇ m
- the relative refractive index difference ⁇ t of the core 53 to the cladding 55 was set to 0.45%.
- the diameter of the cladding 55 was set to 176.3 ⁇ m.
- the mode field diameter (MFD) of light at a wavelength of 1.55 ⁇ m propagating through the cores 53 of the multicore fiber 5 is 11.3 ⁇ m
- the effective area A eff is 110 ⁇ m 2 .
- the refractive index volume V t formed of a product of the cross sectional area of the cores 53 and the relative refractive index difference ⁇ t is 59.179.
- the radius r 1 of the inner core 11 in the large-diameter portion 21 was set to 6.47 ⁇ m, which is the same as the radius of the core 53 , and the core pitch in the large-diameter portion 21 was set to 176.4 ⁇ m.
- the difference ⁇ 12 between the relative refractive index difference ⁇ 1 of the inner core 11 to the cladding and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding was set to 0.45%, which is the same as the relative refractive index difference of the core 53 to the cladding 55 .
- the draw ratio was set to four, and the radius r 2 of the outer core 12 in the large-diameter portion 21 and the relative refractive index difference ⁇ 2 of the outer core to the cladding were changed.
- FIG. 6 is a diagram of the coupling loss of light at a wavelength of 1.55 ⁇ m propagating through the cores 13 of the optical device 1 and the cores 53 of the multicore fiber 5 .
- a solid line expresses the coupling loss of the LP 01 mode light beam
- a broken line expresses the coupling loss of the LP 11 mode light beam.
- Numerical characters denoted near the lines express a loss in the unit of dB. Simulation was calculated using a model in which the optical fiber was connected to the relay fiber 10 .
- the coupling loss of the optical fiber 1 to the relay fiber 10 was set to zero. Consequently, the main factor of the coupling loss in Example 1 is caused by the coupling loss of the optical device 1 to the multicore fiber 5 .
- An alternate long and short dash line in FIG. 6 is a line at which the bending loss of the LP 02 mode light beam at a wavelength of 1.53 ⁇ m is 1.0 dB/m at a radius of 140 mm.
- the propagation of light in higher modes than the LP 11 mode can be substantially reduced in the wavelength range at a wavelength of 1.53 ⁇ m or more (in the C and L bands).
- the LP 21 mode light beam is located on the upper side of the alternate long and short dash line at a wavelength of 1.530 ⁇ m. Therefore, since the LP 02 mode light beam is pumped instead of the LP 21 mode light beam, a line expressing the LP 21 mode light beam is not illustrated in Example 1.
- a long dashed double-short dashed line in FIG. 6 is a line at which the bending loss of the LP 11 mode light beam at a wavelength of 1.625 ⁇ m is 0.5 dB/100 turns at a radius of 30 mm. Therefore, in any regions including the bending losses on the long dashed double-short dashed line or greater, the LP 01 and LP 11 mode light beams in the C and L bands can be transmitted at low losses.
- a circle, a triangle, and a square express typical points at which such few mode communications are possible.
- the radius r 2 of the outer core 12 in the large-diameter portion 21 is about 26.547 ⁇ m (the radius r 2 ′ of the outer core 12 in the small-diameter portion 23 is about 6.637 ⁇ m), and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding is about 0.445%.
- the radius r 2 of the outer core 12 in the large-diameter portion 21 is about 28.069 ⁇ m (the radius r 2 ′ of the outer core 12 in the small-diameter portion 23 is about 7.017 ⁇ m), and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding is about 0.409%.
- the radius r 2 of the outer core 12 in the large-diameter portion 21 is about 29.592 ⁇ m (the radius r 2 ′ of the outer core 12 in the small-diameter portion 23 is about 7.398 ⁇ m), and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding is about 0.373%. From the conditions above, the radius r 1 ′ of the inner core 11 in the small-diameter portion 23 is 1.575.
- the refractive index volume formed of a product of the cross sectional area of the inner core 11 and the relative refractive index difference ⁇ 1 of the inner core 11 to the cladding 15 in the small-diameter portion 23 is defined as V 1 ′.
- the refractive index volume V 1 ′ is 7.357 ⁇ m 2 % at the circle, 7.062 ⁇ m 2 % at the triangle, and 6.767 ⁇ m 2 % at the square.
- the refractive index volume formed of a product of the cross sectional area of the outer core 12 and the relative refractive index difference ⁇ 2 of the outer core 12 after tapered in diameter is defined as V 2 ′.
- the refractive index volume V 2 ′ is 57.931 ⁇ m 2 % at the circle, 59.939 ⁇ m 2 % at the triangle, and 61.113 ⁇ m 2 % at the square. Therefore, at any of the circle, the triangle, and the square, Expression 4 is satisfied.
- Table 1 shows parameters in the case in which light at a wavelength of 1.55 ⁇ m propagates, an effective area A eff-LP01-21 of the LP 01 mode light beam in the large-diameter portion 21 , an effective area A eff-LP11-21 of the LP 11 mode light beam in the large-diameter portion 21 , a mode field diameter MFD 21 in the large-diameter portion 21 , an effective area A eff-LP01-23 of the LP 01 mode light beam in the small-diameter portion 23 , an effective area A eff-LP11-23 of the LP 11 mode light beam in the small-diameter portion 23 , and a mode field diameter MFD 23 in the small-diameter portion 23 .
- Table 1 shows parameters in the case in which light at a wavelength of 1.55 ⁇ m propagates through each cores, a coupling loss CL 01 of the LP 01 mode light beam and a coupling loss CL 11 of the LP 11 mode light beam at the connecting point of the optical device 1 to the multicore fiber 5 in each core.
- Table 1 shows parameters, the draw ratio TR, the radius r 1 of the inner core 11 in the large-diameter portion 21 , the radius r 2 of the outer core 12 in the large-diameter portion 21 , the radius r 1 ′ of the inner core 11 in the small-diameter portion 23 , the radius r 2 ′ of the outer core 12 in the small-diameter portion 23 , the difference A 12 between the relative refractive index difference ⁇ 1 and the relative refractive index difference ⁇ 2 , the relative refractive index difference ⁇ 2 , the refractive index volume V 1 ′, and the refractive index volume V 1 ′.
- FIG. 7 is a diagram of the coupling loss CL 01 of the LP 01 mode light beam and the coupling loss CL 11 of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of the optical device 1 that achieves parameters at the circle.
- FIG. 8 is a diagram of the coupling loss CL 01 of the LP 01 mode light beam and the coupling loss CL 11 of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of the optical device 1 that achieves parameters at the triangle.
- FIG. 8 is a diagram of the coupling loss CL 01 of the LP 01 mode light beam and the coupling loss CL 11 of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of the optical device 1 that achieves parameters at the triangle.
- FIGS. 7 to 9 are diagrams of the coupling loss CL 01 of the LP 01 mode light beam and the coupling loss CL 11 of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of the optical device 1 that achieves parameters at the square.
- a solid line expresses the coupling loss CL 01
- a broken line expresses the coupling loss CL 11 .
- any optical devices in the states expressed by the parameters at the circle, the triangle, and the square can reduce the coupling loss to 0.2 dB or less in optical communications in the C and L bands.
- FIG. 10 is a diagram of changes in an effective area A eff-LP01 of the LP 01 mode light beam propagating through the core 13 and an effective area A eff-LP11 of the LP 11 mode light beam in the case in which a length L t of the tapered portion 22 of the optical device 1 that achieves parameters at the square is set to 5 mm.
- FIG. 11 is a diagram of changes in the effective area A eff-LP01 of the LP 01 mode light beam propagating through the core 13 and the effective area A eff-LP11 of the LP 01 mode light beam in the case in which the length L t of the tapered portion 22 of the optical device 1 that achieves parameters at the square is set to 10 mm.
- FIGS. 10 is a diagram of changes in an effective area A eff-LP01 of the LP 01 mode light beam propagating through the core 13 and an effective area A eff-LP11 of the LP 11 mode light beam in the case in which a length L t of the tapered portion 22 of the optical device 1 that achieves parameters at the square is set
- a solid line expresses the effective area A eff-LP01 of the LP 01 mode light beam
- a broken line expresses the effective area A eff-LP11 of the LP 11 mode light beam.
- the horizontal axis expresses the distance from the boundary between the tapered portion and the large-diameter portion 21 . Therefore, the numeral zero on the horizontal axis is the boundary between the tapered portion 22 and the large-diameter portion 21 .
- the numeral five on the horizontal axis in FIG. 10 is the boundary between the tapered portion 22 and the small-diameter portion 23 .
- the numeral ten on the horizontal axis in FIG. 11 is the boundary between the tapered portion 22 and the small-diameter portion 23 .
- the length L t of the tapered portion 22 is 10 mm or longer, and thus it is possible to prevent light propagating through the core 13 from being coupled to light in higher modes than the LP 11 mode.
- FIG. 12 is a diagram of the size of the crosstalk in the LP 01 mode light beam propagating through the adjacent cores 13 in the case of changing a length L s of the small-diameter portion 23 of the optical device 1 that achieves parameters at the square.
- FIG. 13 is a diagram of the size of the crosstalk in the LP 11 mode light beam propagating through the adjacent cores 13 in the case of changing the length L s of the small-diameter portion 23 of the optical device 1 that achieves parameters at the square.
- FIGS. 12 and 13 illustrate the crosstalk in the case in which the length L t of the tapered portion 22 is 4.0 mm, 6.0 mm, 8.0 mm, and 10.0 mm.
- the size of the crosstalk in the LP 01 mode light beam was ⁇ 50 dB or less.
- the result was as follows.
- the length L t of the tapered portion 22 is 4.0 mm or longer and the length L s of the small-diameter portion 23 is 2 mm or longer, the size of the crosstalk in the LP 11 mode light beam can be decreased to ⁇ 30 dB or less.
- the length L t of the tapered portion 22 is 6.0 mm or longer, the size of the crosstalk can be decreased to ⁇ 40 dB or less.
- the radius r t of the core 53 was set to 6.63 ⁇ m
- the relative refractive index difference ⁇ t of the core 53 to the cladding 55 was set to 0.45%
- the core pitch was set to 45.5 ⁇ m
- the diameter of the cladding 55 was set to 181.8 ⁇ m.
- the mode field diameter (MFD) of light at a wavelength of 1.55 ⁇ m propagating through the cores 53 of the multicore fiber 5 is 11.5 ⁇ m
- the effective area A eff is 113.8 ⁇ m 2 .
- the refractive index volume V t formed of a product of the cross sectional area of the cores 53 and the relative refractive index difference ⁇ t is 62.143.
- the radius r 1 of the inner core 11 in the large-diameter portion 21 was set to 6.30 ⁇ m, and the core pitch in the large-diameter portion 21 was set to 144.2 ⁇ m.
- the difference A 12 between the relative refractive index difference ⁇ 1 of the inner core 11 to the cladding and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding was set to 0.50%.
- the draw ratio was set to 3.17, and then the radius r 2 of the outer core and the relative refractive index difference ⁇ 2 of the outer core to the cladding in the large-diameter portion 21 were changed.
- FIG. 14 is a diagram of the coupling loss of light at a wavelength of 1.55 ⁇ m propagating through the cores 13 of the optical device 1 and the cores 53 of the multicore fiber 5 .
- a dotted line expresses a line at which the bending loss of the LP 21 mode light beam at a wavelength of 1.53 ⁇ m is 1.0 dB/m at a radius of 140 mm.
- Example 1 in any regions including the bending losses on the alternate long and short dash line or below and on the long dashed double-short dashed line or above, few mode communications are possible in the C and L bands, in which the LP 01 and LP 11 mode light beams are transmitted and light in higher modes than the LP 01 and LP 11 modes is prevented from propagating.
- Example 1 also in Example 2, the result was that the coupling loss of the LP 01 mode light beam through the optical device 1 and the multicore fiber 5 was equal to or greater than the coupling loss of the LP 11 mode light beam through the optical device 1 and the multicore fiber 5 .
- a triangle expresses a typical point at which such few mode communications are possible.
- the radius r 2 of the outer core 12 in the large-diameter portion 21 is about 21.4354 ⁇ m (the radius r 2 ′ of the outer core 12 in the small-diameter portion 23 is about 6.762 ⁇ m), and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding is about 0.399%.
- the radius r 1 ′ of the inner core 11 in the small-diameter portion 23 is 1.987.
- the refractive index volume V 1 ′ is determined, and then the refractive index volume V 1 ′ is 11.153 at the triangle.
- the refractive index volume V 2 ′ is determined, and then the refractive index volume V 2 ′ is 52.337 at the triangle.
- Expression 4 is satisfied.
- Table 2 is parameters similar to Table 1.
- FIG. 15 is a diagram of the coupling loss CL 01 of the LP 01 mode light beam and the coupling loss CL 11 of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of the optical device 1 that achieves parameters at the triangle. As illustrated in FIG. 15 , it is revealed that any optical devices in the states expressed by the parameters at the triangle can reduce the coupling loss to 0.45 dB or less in optical communications in the C and L bands.
- Example 3 the configuration was the same as the configuration of Example 2 except that in the optical device 1 , the draw ratio was set to 4.01.
- FIG. 16 is the coupling loss of light at a wavelength of 1.55 ⁇ m propagating through the cores 13 of the optical device 1 and the cores 53 of the multicore fiber 5 .
- a dotted line in FIG. 16 expresses a line at which the bending loss of the LP21 mode light beam at a wavelength of 1.53 ⁇ m is 1.0 dB/m at a radius of 140 mm as in FIG. 14 .
- Example 3 in any regions including the bending losses on the alternate long and short dash line or below and on the long dashed double-short dashed line or above, few mode communications are possible in the C and L bands, in which the LP 01 and LP 11 mode light beams are transmitted and light in higher modes than the LP 01 and LP 11 modes is prevented from propagating.
- Example 1 also in Example 3, the result was that the coupling loss of the LP 01 mode light beam through the optical device 1 and the multicore fiber 5 was equal to or greater than the coupling loss of the LP 11 mode light beam through the optical device 1 and the multicore fiber 5 .
- a circle, a triangle, and a square express typical points at which such few mode communications are possible.
- the radius r 2 of the outer core 12 in the large-diameter portion 21 is about 26.921 ⁇ m (the radius r 2 ′ of the outer core 12 in the small-diameter portion 23 is about 6.730 ⁇ m), and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding is about 0.436%.
- the radius r 2 of the outer core 12 in the large-diameter portion 21 is about 27.938 ⁇ m (the radius r 2 ′ of the outer core 12 in the small-diameter portion 23 is about 6.967 ⁇ m), and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding is about 0.409%.
- the radius r 2 of the outer core 12 in the large-diameter portion 21 is about 28.888 ⁇ m (the radius r 2 ′ of the outer core 12 in the small-diameter portion 23 is about 7.204 ⁇ m), and the relative refractive index difference ⁇ 2 of the outer core 12 to the cladding is about 0.383%. From the conditions above, the radius r 1 ′ of the inner core 11 in the small-diameter portion 23 is 1.571.
- the refractive index volume V 1 ′ is determined, and then the refractive index volume V 1 ′ is 7.261 at the circle, 7.047 at the triangle, and 6.850 at the square.
- the refractive index volume V 2 ′ is determined, and then the refractive index volume V 2 ′ is 58.412 at the circle, 59.160 at the triangle, and 59.542 at the square. Therefore, at any of the circle, the triangle, and the square, Expression 4 is satisfied.
- Table 3 is parameters similar to Table 1.
- FIG. 17 is a diagram of the coupling loss CL 01 of the LP 01 mode light beam and the coupling loss CL 11 of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of the optical device 1 that achieves parameters at the circle.
- FIG. 18 is a diagram of the coupling loss CL 01 of the LP 01 mode light beam and the coupling loss CL 11 of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of the optical device 1 that achieves parameters at the triangle.
- FIG. 18 is a diagram of the coupling loss CL 01 of the LP 01 mode light beam and the coupling loss CL 11 of the LP 11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of the optical device 1 that achieves parameters at the triangle.
- FIGS. 17 to 19 are expressed by methods similar to the methods in FIGS. 7 to 9 .
- any optical devices in the states expressed by the parameters at the circle, the triangle, and the square can reduce the coupling loss to 0.25 dB or less in optical communications in the C and L bands.
- a ratio V 1 /V 2 of a refractive index volume V 1 of the inner core 11 to a refractive index volume V 2 of the outer core 12 was determined.
- the refractive index volume V 1 of the inner core 11 is expressed by a product of the cross sectional area of the inner core 11 and the relative refractive index difference ⁇ 1 of the inner core 11 in the large-diameter portion 21 .
- the refractive index volume V 2 of the outer core 12 is expressed by a product of the cross sectional area of the outer core 12 and the relative refractive index difference ⁇ 2 of the outer core 12 in the large-diameter portion 21 .
- the ratio V 1 /V 2 is the same value in any cross sections in the large-diameter portion 21 , the tapered portion 22 , and the small-diameter portion 23 .
- FIG. 20 is a diagram of the relationship between the radius r 2 of the outer core in the large-diameter portion 21 and the determined values of the ratio V 1 /V 2 for the circle, the triangle, and the square in FIGS. 6, 14 , and 16 , with quadrilaterals.
- FIGS. 6 and 16 in the case in which the radius r 2 ′ of the outer core in the small-diameter portion 23 is about 3.75 ⁇ m, or in FIG. 14 , in the case in which the radius r 2 ′ of the outer core in the small-diameter portion 23 is about 4.7 ⁇ m, the radius r 2 of the outer core in the large-diameter portion 21 is about 15 ⁇ m.
- the coupling loss will be about 0.5 dB or greater.
- the coupling loss can be reduced to about 0.5 dB.
- the optical device according to the disclosure can transmit light to and from a multicore fiber in few mode communications with a simple configuration, and can be used in the field of optical communications using multicore fibers, for example.
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Abstract
Description
- The disclosure relates to an optical device, which is preferred in the case of transmitting light in multiple modes.
- Optical fibers for use in widely available optical fiber communication systems have a structure in which the outer circumferential surface of one core is surrounded by a cladding. Optical signals propagate through the inside of this core, and thus information is transmitted. In these years, with the wide spread use of optical fiber communication systems, information volumes to be transmitted are dramatically increased.
- In order to achieve an increase in the transmission capacity of such optical fiber communication systems, there is known a method in which a multicore fiber includes a plurality of cores and a cladding surrounding the outer circumferential surface of the cores and this multicore fiber is used to transmit a plurality of signals with light propagating through each core.
- For example,
Patent Literature 1 below discloses an optical device for transmitting light beams to and from a multicore fiber. In the optical device, a single-core optical fiber is inserted into each of a plurality of holes formed in a capillary to form an assembly, the assembly is drawn, and then the optical device is formed. The optical fiber is tapered in diameter from a first portion to a second portion of the optical fiber. Each of the optical fibers has a dual structure in which a core is formed of an inner core and an outer core surrounding the inner core with no gap. The refractive index of the inner core is set higher than the refractive index of the outer core. The refractive index of the cladding is set lower than the refractive index of the outer core. In the first portion, which is not tapered in diameter, the diameter of the inner core and the refractive index difference between the inner core and the outer core are set so that a single-mode light beam easily propagates through the inner core. In the second portion, which is tapered in diameter, the outer diameter of the outer core and the refractive index difference between the outer core and the cladding are set so that a single-mode light beam easily spreads to the outer core and propagates through the entire core including the inner core and the outer core. - In the optical device, a single-mode light beam propagating from the first portion to the second portion of each of the optical fibers propagates through the inner core in the first portion. However, the diameter of the inner core is below a predetermined diameter at the tapered second portion, and the leakage of light from the inner core to the outer core is increased. Consequently, after the diameter of the inner core is below a predetermined diameter, the light beam spreads to the outer core, and propagates through the core including the inner core and the outer core. Thus, in the optical device, although the pitch between the cores is decreased in the tapered second portion, a change in the mode field diameter (MFD) of the light beam propagating through each of the cores is decreased in the first portion and the tapered second portion.
- The premise of the optical device described in
Patent Literature 1 is to transmit a single-mode light beam. Therefore, in the optical device, conditions, such as the refractive indexes and diameters of the inner core and the outer core, are set so that a single-mode light beam propagates as described above. - In optical communications, there is known a method of few mode communications in which information is superposed on an LP01 mode (fundamental mode) light beam and information is superposed on an LP11 mode light beam for information communications. Therefore, also in few mode communications, an optical device for transmitting light beams to and from a multicore fiber is demanded. For this demand, a concept is a configuration in which the refractive index in the center part of the inner core is more decreased than the refractive index of the outer circumferential portion of the inner core. However, there are requests to achieve the demand with optical devices in simple configurations.
- Therefore, it is an object of the disclosure to provide an optical device that can transmit light to and from a multicore fiber with a simple configuration in few mode communications.
- In order to achieve the object, the optical device according to the disclosure is an optical device including: a plurality of cores each including an inner core and an outer core surrounding an outer circumferential surface of the inner core, the outer core having a refractive index lower than a refractive index of the inner core; and a cladding surrounding the outer circumferential surface of the core and having a refractive index lower than the refractive index of the outer core.
- In the optical device, a tapered portion is formed in which the each core is tapered in diameter from a first end to a second end of the core in a longitudinal direction and a pitch between the cores adjacent to each other is decreased.
- When light propagates through the core tapered in diameter, a bending loss of an LP02 mode light beam and a bending loss of an LP21 light beam at a wavelength of 1.53 μm are 1.0 dB/m or greater at a radius of 140 mm, and a bending loss of an LP11 mode light beam at a wavelength of 1.625 μm is 0.5 dB/100 turns or less at a radius of 30 mm.
- In the optical device,
-
0.5377×r 2−7.7≦V 2 /V 1≦0.5377×r 2−5.7 3≦r 2 /r 1≦5 - are satisfied,
- where a radius of the inner core before tapered in diameter is defined as r1, a radius of the outer core before tapered in diameter is defined as r2, a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding before tapered in diameter is defined as V1, and a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding before tapered in diameter is defined as V2.
- In the optical device, the cores transmit the LP01 and LP11 mode light beams in the C band and the L band at the bending losses of the LP02 and the LP21 mode light beams. In the transmission, it was found that these two expressions are satisfied and thus optical coupling losses can be decreased in connecting an optical device to a multicore fiber. In addition to this, each of the cores is a two-stage core including an inner core and an outer core, and has a simpler configuration than in the previously existing optical devices.
- The optical device according to the disclosure can transmit light to and from a multicore fiber in few mode communications with a simple configuration.
- The radius r2 of the outer core before tapered in diameter may be preferably 15 μm or more. The radius r2 of the outer core before tapered in diameter may be more preferably 20 μm or more.
- Preferably, a length of the tapered portion is 4 mm or longer, and a length of the core after tapered in diameter is 2 mm or longer.
- With this configuration, the crosstalk in the LP11 mode light beam propagating through the cores adjacent to each other can be made −30 dB or less.
- Preferably, a length of the tapered portion is 6 mm or longer.
- With this configuration, the crosstalk in the LP11 mode light beam propagating through the cores adjacent to each other can be made −40 dB or less.
- In the optical device, a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding after tapered in diameter is defined as V1′, and a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding after tapered in diameter is defined as V2′. In a multicore fiber having a plurality of cores each to be coupled to each of the plurality of cores tapered in diameter, a refractive index volume formed of a product of a cross sectional area of the multicore fiber core and a relative refractive index difference of the multicore fiber core to a cladding surrounding an outer circumferential surface of the multicore fiber core is defined as Vt. In this case, preferably,
-
(V 1 ′+V 2′)/V t≧1 - is satisfied.
- Preferably, a coupling loss of an LP01 mode light beam through the multicore fiber is equal to or greater than a coupling loss of an LP11 mode light beam through the multicore fiber.
- As described above, according to the disclosure, there is provided an optical device that can transmit light to and from a multicore fiber in few mode communications with a simple configuration.
-
FIG. 1 is a diagram of an optical device according to a first embodiment; -
FIG. 2A is a diagram of a structure in a cross section perpendicular to the longitudinal direction at a position including a capillary of the optical device illustrated inFIG. 1 ; -
FIG. 2B is a diagram of a refractive index profile taken along line V-V inFIG. 2A ; -
FIG. 3A is a diagram of a core of a relay fiber; -
FIG. 3B is a diagram of electric fields of an LP01 mode light beam and an LP11 mode light beam at a large-diameter portion and a small-diameter portion of the relay fiber; -
FIG. 4 is a diagram of an optical device according to a second embodiment; -
FIG. 5A is a diagram of a structure in a cross section perpendicular to the longitudinal direction of the optical device inFIG. 4 ; -
FIG. 5B is a diagram of a refractive index profile taken along line V-V inFIG. 5A ; -
FIG. 6 is a diagram of a coupling loss and other parameters in Example 1; -
FIG. 7 is a diagram of the coupling loss of the LP01 mode light beam and the coupling loss of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a circle inFIG. 6 ; -
FIG. 8 is a diagram of the coupling loss of the LP01 mode light beam and the coupling loss of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a triangle inFIG. 6 ; -
FIG. 9 is a diagram of the coupling loss of the LP01 mode light beam and the coupling loss of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a square inFIG. 6 ; -
FIG. 10 is a diagram of changes in the effective area of the LP01 mode light beam and the effective area of the LP11 mode light beam propagating through the core in the case in which the length of the tapered portion of the optical device that achieves parameters at the square inFIG. 6 is set to 5 mm; -
FIG. 11 is a diagram of changes in the effective area of the LP01 mode light beam and the effective area of the LP11 mode light beam propagating through the core in the case in which the length of the tapered portion of the optical device that achieves parameters at the square inFIG. 6 is set to 10 mm; -
FIG. 12 is a diagram of the size of the crosstalk in the LP01 mode light beam propagating through cores adjacent to each other in the case of changing the length of the small-diameter portion of the optical device that achieves parameters at the square inFIG. 6 ; -
FIG. 13 is a diagram of the size of the crosstalk in the LP11 mode light beam propagating through cores adjacent to each other in the case of changing the length of the small-diameter portion of the optical device that achieves parameters at the square inFIG. 6 ; -
FIG. 14 is a diagram of a coupling loss and other parameters in Example 2; -
FIG. 15 is a diagram of the coupling loss of the LP01 mode light beam and the coupling loss of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a triangle inFIG. 14 ; -
FIG. 16 is a diagram of a coupling loss and other parameters in Example 3; -
FIG. 17 is a diagram of the coupling loss of the LP01 mode light beam and the coupling loss of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a circle inFIG. 16 ; -
FIG. 18 is a diagram of the coupling loss of the LP01 mode light beam and the coupling loss of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a triangle inFIG. 16 ; -
FIG. 19 is a diagram of the coupling loss of the LP01 mode light beam and the coupling loss of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the core of an optical device that achieves parameters at a square inFIG. 16 ; and -
FIG. 20 is a diagram of the relationship between the radius of the outer core in the large-diameter portion and the values of the ratio of the refractive index volume of an inner core and the refractive index volume of anouter core 12 for the circle, the triangle, and the square inFIGS. 6, 14, and 16 . - In the following, preferred embodiments of an optical device according to the disclosure will be described in detail with reference to the drawings.
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FIG. 1 is a diagram of an optical device according to a first embodiment of the disclosure. As illustrated inFIG. 1 , anoptical device 1 according to the embodiment includes a plurality ofrelay fibers 10 and a capillary 20 as main components. In the embodiment, the number of therelay fibers 10 is seven. - The
relay fibers 10 are inserted into the capillary 20 from a first end to a second end of the capillary 20. Therelay fibers 10 and the capillary 20 are integrally formed with no gap. One end of therelay fiber 10 is exposed from the first end of the capillary 20. The other end of therelay fiber 10 is flush with the second end of the capillary 20. Therefore, the other end of each of therelay fibers 10 is seen at the second end of the capillary 20. - The capillary 20 has a circular in a cross section, and has a large-
diameter portion 21, a taperedportion 22, and a small-diameter portion 23 along the longitudinal direction. The taperedportion 22 is tapered in diameter from the first end to the second end of the capillary 20. This form is provided by a method below. First, a capillary is prepared. The capillary has through holes in the same number as the number of therelay fibers 10 to be inserted into the capillary, and the capillary has a constant thickness. Therelay fibers 10 are individually inserted into the through holes. The capillary and therelay fibers 10 are heated and formed into a single product. The product formed of the capillary and the relay fibers is molten and drawn. The taperedportion 22 and the small-diameter portion 23 are formed by this drawing. Therefore, in the taperedportion 22 of the capillary 20, each of therelay fibers 10 is tapered in diameter from the first end to the second end of the capillary 20 as the capillary 20 is tapered in diameter, and the pitch between theadjacent relay fibers 10 is decreased. In the small-diameter portion 23, the diameter of each of therelay fibers 10 is also decreased more than the diameter of therelay fiber 10 in the large-diameter portion. The pitch between theadjacent relay fibers 10 is also more decreased than the pitch between theadjacent relay fibers 10 in the large-diameter portion. -
FIG. 2A is a diagram of a structure in a cross section perpendicular to the longitudinal direction at a position including thecapillary 20 of theoptical device 1.FIG. 2B is a diagram of a refractive index profile taken along line V-V on the cross section inFIG. 2A . In the case of the embodiment, the ratio of the outer diameter of the capillary 20 to the outer diameter of therelay fiber 10 is the same in the large-diameter portion 21, the taperedportion 22, and the small-diameter portion 23 of the capillary 20 in any cross sections perpendicular to the longitudinal direction. Therefore, it is unnecessary to identify cross sections and positions on the capillary 20. - As described above, in the embodiment, the number of the
relay fibers 10 is seven. Onerelay fiber 10 is disposed in the center of the capillary 20. Sixrelay fibers 10 are disposed around therelay fiber 10 in the center. In this state, lines connecting the centers of therelay fibers 10 form a lattice of triangles, and the inter-center pitches of therelay fibers 10 are set equal. - As illustrated in
FIGS. 1 and 2A , therelay fibers 10 are single-core optical fibers, each including acore 13 and acladding 15 surrounding the outer circumferential surface of the core 13 with no gap. Thecore 13 includes aninner core 11 and anouter core 12. As described above, each of therelay fibers 10 is tapered in diameter in the taperedportion 22 from the large-diameter portion 21 toward the small-diameter portion 23. Consequently, theinner core 11 and theouter core 12 configuring thecore 13 of therelay fiber 10 and thecladding 15 are tapered in diameter from the large-diameter portion 21 toward the small-diameter portion 23 as the ratios of the diameters are maintained. As illustrated inFIG. 2B , in the description below, the radius of theinner core 11 is defined as r1, and the radius of the outer core is defined as r2 in the large-diameter portion 21 before tapered in diameter. The radius of theinner core 11 is defined as r1′, and the radius of the outer core is defined as r2′ in the small-diameter portion 23 after tapered in diameter. - As illustrated in
FIG. 2B , the refractive index of theinner core 11 is set higher than the refractive index of theouter core 12. The refractive index of thecladding 15 is set lower than the refractive index of theouter core 12. In the embodiment, the refractive index of the capillary 20 is the same as the refractive index of thecladding 15. As illustrated inFIG. 2B , in the description below, the relative refractive index difference of theinner core 11 to thecladding 15 is defined as Δ1, and the relative refractive index difference of the outer core to thecladding 15 is defined as Δ2. - The
cores 13 satisfy Expression 1: -
0.5377×r 2−7.7≦V 2 /V 1≦0.5377×r 2−5.7 (1) - where a refractive index volume formed of a product of the cross sectional area of the
inner core 11 and a relative refractive index difference Δ1 of theinner core 11 to thecladding 15 in the large-diameter portion 21 is defined as V1, and a refractive index volume formed of a product of the cross sectional area of theouter core 12 and a relative refractive index difference Δ2 of theouter core 12 to thecladding 15 in the large-diameter portion 21 is defined as V2. - The outer diameter of the cladding of a typical optical fiber is 125 μm. On the other hand, a typical core pitch of a
multicore fiber 5 is about 30 μm or more and 50 μm or less. Therefore, preferably, in the large-diameter portion 21, the outer diameter of therelay fiber 10 is equal to the outer diameter of a typical optical fiber, and in the small-diameter portion 23, the core pitch is the core pitch of a typical multicore fiber. Preferably, the wall thickness between the through holes of the capillary 20 before tapered in diameter is 10 μm or more and 25 μm or less from the viewpoint of decreasing the size and obtaining strength. With this configuration, the draw ratio of the outer diameter of the capillary 20 in the large-diameter portion 21 before tapered in diameter to the outer diameter of the capillary 20 in the small-diameter portion 23 after tapered in diameter, i.e., the draw ratio of the large-diameter portion 21 to the small-diameter portion 23, is preferably three or more and five or less from the ratio (125+(10 to 25))/(30 to 50)=3 to 5, where the outer diameter of the capillary 20 in the small-diameter portion 23 is one. The draw ratio is nearly equal to the draw ratio of thecore 13. Therefore, in order to match the diameter of theinner core 11 through which light propagates in the large-diameter portion 21 with the diameter of theouter core 12 through which light propagates in the small-diameter portion 23,Expression 2 is satisfied. -
3≦r 2 /r 1≦5 (2) - Since the ratio of the diameter of the
inner core 11 to the diameter of theouter core 12 is the same at any positions on theoptical device 1 in the longitudinal direction,Expression 2 may beExpression 3. -
3≦r 2 ′/r 1′≦5 (3) - Light propagates through each of the
cores 13 of theoptical device 1 as described below.FIGS. 3A and 3B are diagrams each illustrating an LP01 mode light beam and an LP11 mode light beam propagating through thecore 13 of each of therelay fibers 10. More specifically,FIG. 3A is a diagram of the core 13 in the large-diameter portion 21 and the core 13 in the small-diameter portion 23.FIG. 3B is a diagram of electric fields of the LP01 and LP11 mode light beams in the large-diameter portion 21 and the small-diameter portion 23. - As illustrated in
FIG. 3 , in the large-diameter portion 21 where therelay fiber 10 is not tapered in diameter, theouter core 12 functions as the cladding for theinner core 11, and the light beam in each mode propagates through theinner core 11. In order that light propagates in this manner, in the case in which the wavelength range of used light ranges from 1.530 to 1.625 μm (in the C band and the L band), for example, the radius r1 of theinner core 11 in the large-diameter portion 21 only has to be 6.47 μm, and a difference Δ12 between the relative refractive index difference Δ1 of theinner core 11 to thecladding 15 and the relative refractive index difference Δ2 of theouter core 12 to the cladding only has to be 0.45%. - The light beam in each mode propagating through the
inner core 11 travels from the large-diameter portion 21 toward the small-diameter portion 23, and then comes into the taperedportion 22 where thecore 13 is tapered in diameter. Consequently, the light beam in each mode propagating through theinner core 11 leaks greatly from theinner core 11 to theouter core 12. Therefore, in the small-diameter portion 23, the light beam in each mode spreads to theouter core 12, and propagates through theentire core 13 including theinner core 11 and theouter core 12. However, the LP01 and LP11 mode light beams do not spread to theouter core 12 at the same place in the taperedportion 22. The light beam in each mode spreads to theouter core 12 until the light beam in each mode reaches at least the small-diameter portion 23, and then the light beam in each mode propagates through the core 13 including theinner core 11 and theouter core 12. - On the other hand, in the case in which light propagates through the core 13 from the small-
diameter portion 23 toward the large-diameter portion 21, the LP01 and LP11 mode light beams propagate through theentire core 13 including theinner core 11 and theouter core 12 in the small-diameter portion 23. In the taperedportion 22, the diameter of thecore 13 is gradually increased from the small-diameter portion 23 to the large-diameter portion 21. Thus, in the taperedportion 22, the light beam in each mode propagates through theinner core 11. Consequently, in the large-diameter portion 21, theouter core 12 functions as the cladding, and the light beam in each mode propagates through theinner core 11. In order that the light beam in each mode propagates in this manner, in the case in which the wavelength ranges of the light beams used are the C and L bands as described above, for example, in the small-diameter portion 23, the radius r2 of theouter core 12 only has to be 6.637 μm, and the relative refractive index difference Δ2 of theouter core 12 to thecladding 15 only has to be 0.445%. - In the case in which the light beam in each mode propagate through the
core 13 of each of the relay fibers in the small-diameter portion 23, in light at a wavelength of 1.53 μm, the bending losses of an LP02 mode light beam and an LP21 light beam are 1.0 dB/m or greater at a radius of 140 mm. In therelay fibers 10 in the small-diameter portion 23, the bending loss of the LP11 mode light beam at a wavelength of 1.625 μm is 0.5 dB/100 turns or less at a radius of 30 mm. Therefore, therelay fibers 10 are few mode optical fibers that substantially transmit the LP01 and LP11 mode light beams in the C and L bands and prevent light in higher modes than the LP01 and LP11 modes from propagating. - As illustrated in
FIG. 1 , theoptical device 1 is used as the small-diameter portion 23 is connected to themulticore fiber 5. Themulticore fiber 5 includes a plurality ofcores 53 and acladding 55 surrounding the outer circumferential surfaces of thecores 53 with no gap. The refractive index of each of thecores 53 is set higher than the refractive index of thecladding 55. The number of therelay fibers 10 of theoptical device 1 is equal to the number of thecores 53 of themulticore fiber 5. The relative position of thecore 13 of each of therelay fibers 10 in the small-diameter portion 23 is the same as the relative position of each of thecores 53 of themulticore fiber 5. Theoptical device 1 is connected to themulticore fiber 5 for use in the state in which in theoptical device 1, thecores 13 in the small-diameter portion 23 are opposed to thecores 53 on one end of themulticore fiber 5. Therefore, light propagating through thecores 13 of theoptical device 1 from the large-diameter portion 21 toward the small-diameter portion 23 as described above is entered to thecores 53 of themulticore fiber 5, and propagates through thecores 53. On the other hand, light propagating through thecores 53 of themulticore fiber 5 toward theoptical device 1 is entered to thecores 13 of theoptical device 1, and propagates through thecores 13 from the small-diameter portion 23 toward the large-diameter portion 21 as described above. In other words, theoptical device 1 is used as a device for transmitting light beams to and from themulticore fiber 5. - In this manner, the
optical device 1 is connected to themulticore fiber 5, and then light is transmitted to and from thecores 53 of themulticore fiber 5. In this case, in the embodiment, preferably, at the connecting point of theoptical device 1 to themulticore fiber 5, the coupling loss of the LP01 mode light beam is equal to or greater than the coupling loss of the LP11 mode light beam. - Here, a refractive index volume formed of a product of the cross sectional area of the
inner core 11 and the relative refractive index difference Δ1 of theinner core 11 to thecladding 15 in the small-diameter portion 23 is defined as V1′, and a refractive index volume formed of a product of the cross sectional area of theouter core 12 and the relative refractive index difference Δ2 of theouter core 12 to thecladding 15 in the small-diameter portion 23 is defined as V2′. In themulticore fiber 5, a refractive index volume formed of a product of the cross sectional area of thecores 53 and a relative refractive index difference Δt of the core 53 to thecladding 55 is defined as Vt. In this case,Expression 4 is preferably satisfied. -
(V 1 ′+V 2′)/V t≧1 (4) -
Expression 4 is satisfied, and thus the coupling loss of light reciprocating in theoptical device 1 and themulticore fiber 5 can be decreased. - As described above, in the
optical device 1 according to the embodiment, from the bending losses of the LP02 and the LP21 mode light beams, the cores transmit the LP01 and LP11 mode light beams at least in the C and L bands. It has been found that in the transmission,Expressions optical device 1 is connected to themulticore fiber 5. In addition, each of thecores 13 is a two-stage core including the inner core and theouter core 12, which simplifies core configurations. Therefore, theoptical device 1 according to the embodiment can transmit light to and from themulticore fiber 5 in few mode communications with a simple configuration. - Next, a second embodiment of the disclosure will be described. Noted that components the same as or equivalent to the components of the first embodiment are designated the same reference numerals and signs, and the overlapping description is omitted unless otherwise specified.
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FIG. 4 is a diagram of an optical device according to the second embodiment of the disclosure.FIG. 5A is a diagram of a structure in a cross section perpendicular to the longitudinal direction of theoptical device 2 inFIG. 4 .FIG. 5B is a diagram of a refractive index profile taken along line V-V inFIG. 5A . As illustrated inFIGS. 4, 5A, and 5B , anoptical device 2 according to the embodiment is different from theoptical device 1 according to the first embodiment in that the outer circumferential surfaces of thecores 13 are surrounded with acladding 25 made of glass with no gap similarly to the capillary 20 according to the first embodiment and thecores 13 are located only inside thecladding 25. In other words, theoptical device 2 according to the embodiment is equivalent to an optical device in which in theoptical device 1 according to the first embodiment, therelay fibers 10 exposed from the capillary 20 are removed, thecladding 15 on each of therelay fibers 10 is removed, and spaces produced by removing thecladding 15 are filled with the capillary 20. - The
optical device 2 thus configured has a structure in a cross section as illustrated inFIGS. 5A and 5B . Theoptical device 2 only has to be formed in which a multicore fiber having the same thickness as the thickness of the large-diameter portion 21 is prepared and the prepared multicore fiber is molten and drawn for forming the taperedportion 22 and the small-diameter portion 23. - The
optical device 2 according to the embodiment also satisfiesExpressions - Even the
optical device 2 using the multicore fiber thus formed can transmit light to and from themulticore fiber 5 in few mode communications similarly to theoptical device 1 according to the first embodiment. - The disclosure is described using the foregoing embodiments as examples. The disclosure is not limited to these embodiments.
- For example, the number of the
relay fibers 10 according to the first embodiment and the number of thecores 13 according to the second embodiment can be appropriately modified. - In the first embodiment, the refractive index of the
cladding 15 is set equal to the refractive index of the capillary 20. The refractive index of thecladding 15 may be different from the refractive index of the capillary 20. - In the following, the disclosure will be described more in detail with examples. The disclosure is not limited to the examples below. The examples below are based on computer simulation using a finite element method.
- Simulation was performed using a model in which the
optical device 1 according to the first embodiment was connected to themulticore fiber 5. - In the model, a radius rt of the
core 53 of themulticore fiber 5 was set to 6.47 μm, the core pitch was set to 44.1 μm, and the relative refractive index difference Δt of the core 53 to thecladding 55 was set to 0.45%. The diameter of thecladding 55 was set to 176.3 μm. In this case, the mode field diameter (MFD) of light at a wavelength of 1.55 μm propagating through thecores 53 of themulticore fiber 5 is 11.3 μm, and the effective area Aeff is 110 μm2. The refractive index volume Vt formed of a product of the cross sectional area of thecores 53 and the relative refractive index difference Δt is 59.179. - In the
optical device 1, the radius r1 of theinner core 11 in the large-diameter portion 21 was set to 6.47 μm, which is the same as the radius of the core 53, and the core pitch in the large-diameter portion 21 was set to 176.4 μm. The difference Δ12 between the relative refractive index difference Δ1 of theinner core 11 to the cladding and the relative refractive index difference Δ2 of theouter core 12 to the cladding was set to 0.45%, which is the same as the relative refractive index difference of the core 53 to thecladding 55. The draw ratio was set to four, and the radius r2 of theouter core 12 in the large-diameter portion 21 and the relative refractive index difference Δ2 of the outer core to the cladding were changed. -
FIG. 6 is a diagram of the coupling loss of light at a wavelength of 1.55 μm propagating through thecores 13 of theoptical device 1 and thecores 53 of themulticore fiber 5. InFIG. 6 , a solid line expresses the coupling loss of the LP01 mode light beam, and a broken line expresses the coupling loss of the LP11 mode light beam. Numerical characters denoted near the lines express a loss in the unit of dB. Simulation was calculated using a model in which the optical fiber was connected to therelay fiber 10. The coupling loss of theoptical fiber 1 to therelay fiber 10 was set to zero. Consequently, the main factor of the coupling loss in Example 1 is caused by the coupling loss of theoptical device 1 to themulticore fiber 5. - An alternate long and short dash line in
FIG. 6 is a line at which the bending loss of the LP02 mode light beam at a wavelength of 1.53 μm is 1.0 dB/m at a radius of 140 mm. In any regions including the bending losses on the alternate long and short dash line or below, the propagation of light in higher modes than the LP11 mode can be substantially reduced in the wavelength range at a wavelength of 1.53 μm or more (in the C and L bands). In the case of Example 1, the LP21 mode light beam is located on the upper side of the alternate long and short dash line at a wavelength of 1.530 μm. Therefore, since the LP02 mode light beam is pumped instead of the LP21 mode light beam, a line expressing the LP21 mode light beam is not illustrated in Example 1. - A long dashed double-short dashed line in
FIG. 6 is a line at which the bending loss of the LP11 mode light beam at a wavelength of 1.625 μm is 0.5 dB/100 turns at a radius of 30 mm. Therefore, in any regions including the bending losses on the long dashed double-short dashed line or greater, the LP01 and LP11 mode light beams in the C and L bands can be transmitted at low losses. - In other words, in
FIG. 6 , in any regions including the bending losses on the alternate long and short dash line or below and on the long dashed double-short dashed line or above, few mode communications are possible in the C and L bands, in which the LP01 and LP11 mode light beams are transmitted and light in higher modes than the LP01 and LP11 modes is prevented from propagating. In the regions inFIG. 6 , the result was that the coupling loss of the LP01 mode light beam through theoptical device 1 and themulticore fiber 5 was equal to or greater than the coupling loss of the LP11 mode light beam through theoptical device 1 and themulticore fiber 5. - In
FIG. 6 , a circle, a triangle, and a square express typical points at which such few mode communications are possible. At the circle, the radius r2 of theouter core 12 in the large-diameter portion 21 is about 26.547 μm (the radius r2′ of theouter core 12 in the small-diameter portion 23 is about 6.637 μm), and the relative refractive index difference Δ2 of theouter core 12 to the cladding is about 0.445%. At the triangle, the radius r2 of theouter core 12 in the large-diameter portion 21 is about 28.069 μm (the radius r2′ of theouter core 12 in the small-diameter portion 23 is about 7.017 μm), and the relative refractive index difference Δ2 of theouter core 12 to the cladding is about 0.409%. At the square, the radius r2 of theouter core 12 in the large-diameter portion 21 is about 29.592 μm (the radius r2′ of theouter core 12 in the small-diameter portion 23 is about 7.398 μm), and the relative refractive index difference Δ2 of theouter core 12 to the cladding is about 0.373%. From the conditions above, the radius r1′ of theinner core 11 in the small-diameter portion 23 is 1.575. - Here, the refractive index volume formed of a product of the cross sectional area of the
inner core 11 and the relative refractive index difference Δ1 of theinner core 11 to thecladding 15 in the small-diameter portion 23 is defined as V1′. The refractive index volume V1′ is 7.357 μm2% at the circle, 7.062 μm2% at the triangle, and 6.767 μm2% at the square. The refractive index volume formed of a product of the cross sectional area of theouter core 12 and the relative refractive index difference Δ2 of theouter core 12 after tapered in diameter is defined as V2′. The refractive index volume V2′ is 57.931 μm2% at the circle, 59.939 μm2% at the triangle, and 61.113 μm2% at the square. Therefore, at any of the circle, the triangle, and the square,Expression 4 is satisfied. - Table 1 shows parameters in the case in which light at a wavelength of 1.55 μm propagates, an effective area Aeff-LP01-21 of the LP01 mode light beam in the large-
diameter portion 21, an effective area Aeff-LP11-21 of the LP11 mode light beam in the large-diameter portion 21, a mode field diameter MFD21 in the large-diameter portion 21, an effective area Aeff-LP01-23 of the LP01 mode light beam in the small-diameter portion 23, an effective area Aeff-LP11-23 of the LP11 mode light beam in the small-diameter portion 23, and a mode field diameter MFD23 in the small-diameter portion 23. In addition to the parameters above, Table 1 shows parameters in the case in which light at a wavelength of 1.55 μm propagates through each cores, a coupling loss CL01 of the LP01 mode light beam and a coupling loss CL11 of the LP11 mode light beam at the connecting point of theoptical device 1 to themulticore fiber 5 in each core. In addition to the parameters above, Table 1 shows parameters, the draw ratio TR, the radius r1 of theinner core 11 in the large-diameter portion 21, the radius r2 of theouter core 12 in the large-diameter portion 21, the radius r1′ of theinner core 11 in the small-diameter portion 23, the radius r2′ of theouter core 12 in the small-diameter portion 23, the difference A12 between the relative refractive index difference Δ1 and the relative refractive index difference Δ2, the relative refractive index difference Δ2, the refractive index volume V1′, and the refractive index volume V1′. -
TABLE 1 Unit Circle Triangle Square TR — 4 4 4 r1 μm 6.47 6.47 6.47 r2 μm 26.547 28.069 29.592 r1′ μm 1.618 1.618 1.618 r2′ μm 6.637 7.017 7.398 Δ1 % 0.895 0.859 0.823 Δ12 % 0.45 0.45 0.45 Δ2 % 0.445 0.409 0.373 V1′ μm2 % 7.357 7.062 6.767 V2′ μm2 % 57.931 59.939 61.113 Aeff-LP01-21 μm2 109.130 109.179 109.229 Aeff-LP11-21 μm2 175.415 175.575 175.734 MFD21 μm 11.255 11.259 11.262 Aeff-LP01-23 μm2 66.328 71.595 77.083 Aeff-LP11-23 μm2 179.694 198.119 218.824 MFD23 μm 9.150 9.496 9.843 CL01 dB 0.191 0.141 0.111 CL11 dB 0.002 0.023 0.077 -
FIG. 7 is a diagram of the coupling loss CL01 of the LP01 mode light beam and the coupling loss CL11 of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of theoptical device 1 that achieves parameters at the circle.FIG. 8 is a diagram of the coupling loss CL01 of the LP01 mode light beam and the coupling loss CL11 of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of theoptical device 1 that achieves parameters at the triangle.FIG. 9 is a diagram of the coupling loss CL01 of the LP01 mode light beam and the coupling loss CL11 of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of theoptical device 1 that achieves parameters at the square. InFIGS. 7 to 9 , a solid line expresses the coupling loss CL01, and a broken line expresses the coupling loss CL11. - As illustrated in
FIGS. 7 to 9 , it is revealed that any optical devices in the states expressed by the parameters at the circle, the triangle, and the square can reduce the coupling loss to 0.2 dB or less in optical communications in the C and L bands. -
FIG. 10 is a diagram of changes in an effective area Aeff-LP01 of the LP01 mode light beam propagating through thecore 13 and an effective area Aeff-LP11 of the LP11 mode light beam in the case in which a length Lt of the taperedportion 22 of theoptical device 1 that achieves parameters at the square is set to 5 mm.FIG. 11 is a diagram of changes in the effective area Aeff-LP01 of the LP01 mode light beam propagating through thecore 13 and the effective area Aeff-LP11 of the LP01 mode light beam in the case in which the length Lt of the taperedportion 22 of theoptical device 1 that achieves parameters at the square is set to 10 mm. InFIGS. 10 and 11 , a solid line expresses the effective area Aeff-LP01 of the LP01 mode light beam, and a broken line expresses the effective area Aeff-LP11 of the LP11 mode light beam. InFIGS. 10 and 11 , the horizontal axis expresses the distance from the boundary between the tapered portion and the large-diameter portion 21. Therefore, the numeral zero on the horizontal axis is the boundary between the taperedportion 22 and the large-diameter portion 21. The numeral five on the horizontal axis inFIG. 10 is the boundary between the taperedportion 22 and the small-diameter portion 23. The numeral ten on the horizontal axis inFIG. 11 is the boundary between the taperedportion 22 and the small-diameter portion 23. - From
FIGS. 10 and 11 , the length Lt of the taperedportion 22 is 10 mm or longer, and thus it is possible to prevent light propagating through the core 13 from being coupled to light in higher modes than the LP11 mode. -
FIG. 12 is a diagram of the size of the crosstalk in the LP01 mode light beam propagating through theadjacent cores 13 in the case of changing a length Ls of the small-diameter portion 23 of theoptical device 1 that achieves parameters at the square.FIG. 13 is a diagram of the size of the crosstalk in the LP11 mode light beam propagating through theadjacent cores 13 in the case of changing the length Ls of the small-diameter portion 23 of theoptical device 1 that achieves parameters at the square.FIGS. 12 and 13 illustrate the crosstalk in the case in which the length Lt of the taperedportion 22 is 4.0 mm, 6.0 mm, 8.0 mm, and 10.0 mm. - As illustrated in
FIGS. 12 and 13 , the size of the crosstalk in the LP01 mode light beam was −50 dB or less. The result was as follows. When the length Lt of the taperedportion 22 is 4.0 mm or longer and the length Ls of the small-diameter portion 23 is 2 mm or longer, the size of the crosstalk in the LP11 mode light beam can be decreased to −30 dB or less. When the length Lt of the taperedportion 22 is 6.0 mm or longer, the size of the crosstalk can be decreased to −40 dB or less. - In the
multicore fiber 5, the radius rt of the core 53 was set to 6.63 μm, the relative refractive index difference Δt of the core 53 to thecladding 55 was set to 0.45%, the core pitch was set to 45.5 μm, and the diameter of thecladding 55 was set to 181.8 μm. In this case, the mode field diameter (MFD) of light at a wavelength of 1.55 μm propagating through thecores 53 of themulticore fiber 5 is 11.5 μm, and the effective area Aeff is 113.8 μm2. The refractive index volume Vt formed of a product of the cross sectional area of thecores 53 and the relative refractive index difference Δt is 62.143. - In the
optical device 1, the radius r1 of theinner core 11 in the large-diameter portion 21 was set to 6.30 μm, and the core pitch in the large-diameter portion 21 was set to 144.2 μm. The difference A12 between the relative refractive index difference Δ1 of theinner core 11 to the cladding and the relative refractive index difference Δ2 of theouter core 12 to the cladding was set to 0.50%. The draw ratio was set to 3.17, and then the radius r2 of the outer core and the relative refractive index difference Δ2 of the outer core to the cladding in the large-diameter portion 21 were changed. - Similarly to
FIG. 6 ,FIG. 14 is a diagram of the coupling loss of light at a wavelength of 1.55 μm propagating through thecores 13 of theoptical device 1 and thecores 53 of themulticore fiber 5. InFIG. 14 , a dotted line expresses a line at which the bending loss of the LP21 mode light beam at a wavelength of 1.53 μm is 1.0 dB/m at a radius of 140 mm. - Similarly to Example 1, also in Example 2, in any regions including the bending losses on the alternate long and short dash line or below and on the long dashed double-short dashed line or above, few mode communications are possible in the C and L bands, in which the LP01 and LP11 mode light beams are transmitted and light in higher modes than the LP01 and LP11 modes is prevented from propagating. Similarly to Example 1, also in Example 2, the result was that the coupling loss of the LP01 mode light beam through the
optical device 1 and themulticore fiber 5 was equal to or greater than the coupling loss of the LP11 mode light beam through theoptical device 1 and themulticore fiber 5. - In
FIG. 14 , a triangle expresses a typical point at which such few mode communications are possible. At the triangle, the radius r2 of theouter core 12 in the large-diameter portion 21 is about 21.4354 μm (the radius r2′ of theouter core 12 in the small-diameter portion 23 is about 6.762 μm), and the relative refractive index difference Δ2 of theouter core 12 to the cladding is about 0.399%. From the conditions above, the radius r1′ of theinner core 11 in the small-diameter portion 23 is 1.987. - Here, similarly to Example 1, the refractive index volume V1′ is determined, and then the refractive index volume V1′ is 11.153 at the triangle. Similarly to Example 1, the refractive index volume V2′ is determined, and then the refractive index volume V2′ is 52.337 at the triangle. At the triangle in
FIG. 14 ,Expression 4 is satisfied. For the triangle, Table 2 is parameters similar to Table 1. -
TABLE 2 Unit Triangle TR — 3.17 r1 μm 6.30 r2 μm 21.435 r1′ μm 1.987 r2′ μm 6.762 Δ1 % 0.899 Δ12 % 0.5 Δ2 % 0.399 V1′ μm2 % 11.153 V2′ μm2 % 52.337 Aeff-LP01-21 μm2 101.866 Aeff-LP11-21 μm2 161.323 MFD21 μm 10.849 Aeff-LP01-23 μm2 52.510 Aeff-LP11-23 μm2 189.560 MFD23 μm 8.293 CL01 dB 0.429 CL11 dB 0.010 - Similarly to
FIGS. 7 to 9 ,FIG. 15 is a diagram of the coupling loss CL01 of the LP01 mode light beam and the coupling loss CL11 of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of theoptical device 1 that achieves parameters at the triangle. As illustrated inFIG. 15 , it is revealed that any optical devices in the states expressed by the parameters at the triangle can reduce the coupling loss to 0.45 dB or less in optical communications in the C and L bands. - In Example 3, the configuration was the same as the configuration of Example 2 except that in the
optical device 1, the draw ratio was set to 4.01. - Similarly to
FIG. 6 ,FIG. 16 is the coupling loss of light at a wavelength of 1.55 μm propagating through thecores 13 of theoptical device 1 and thecores 53 of themulticore fiber 5. A dotted line inFIG. 16 expresses a line at which the bending loss of the LP21 mode light beam at a wavelength of 1.53 μm is 1.0 dB/m at a radius of 140 mm as inFIG. 14 . - Similarly to Examples 1 and 2, also in Example 3, in any regions including the bending losses on the alternate long and short dash line or below and on the long dashed double-short dashed line or above, few mode communications are possible in the C and L bands, in which the LP01 and LP11 mode light beams are transmitted and light in higher modes than the LP01 and LP11 modes is prevented from propagating. Similarly to Example 1, also in Example 3, the result was that the coupling loss of the LP01 mode light beam through the
optical device 1 and themulticore fiber 5 was equal to or greater than the coupling loss of the LP11 mode light beam through theoptical device 1 and themulticore fiber 5. - In
FIG. 16 , a circle, a triangle, and a square express typical points at which such few mode communications are possible. At the circle, the radius r2 of theouter core 12 in the large-diameter portion 21 is about 26.921 μm (the radius r2′ of theouter core 12 in the small-diameter portion 23 is about 6.730 μm), and the relative refractive index difference Δ2 of theouter core 12 to the cladding is about 0.436%. At the triangle, the radius r2 of theouter core 12 in the large-diameter portion 21 is about 27.938 μm (the radius r2′ of theouter core 12 in the small-diameter portion 23 is about 6.967 μm), and the relative refractive index difference Δ2 of theouter core 12 to the cladding is about 0.409%. At the square, the radius r2 of theouter core 12 in the large-diameter portion 21 is about 28.888 μm (the radius r2′ of theouter core 12 in the small-diameter portion 23 is about 7.204 μm), and the relative refractive index difference Δ2 of theouter core 12 to the cladding is about 0.383%. From the conditions above, the radius r1′ of theinner core 11 in the small-diameter portion 23 is 1.571. - Here, similarly to Example 1, the refractive index volume V1′ is determined, and then the refractive index volume V1′ is 7.261 at the circle, 7.047 at the triangle, and 6.850 at the square. Similarly to Example 1, the refractive index volume V2′ is determined, and then the refractive index volume V2′ is 58.412 at the circle, 59.160 at the triangle, and 59.542 at the square. Therefore, at any of the circle, the triangle, and the square,
Expression 4 is satisfied. Table 3 is parameters similar to Table 1. -
TABLE 3 Unit Circle Triangle Square TR — 4.01 4.01 4.01 r1 μm 6.3 6.3 6.3 r2 μm 26.921 27.938 28.888 r1′ μm 1.571 1.571 1.571 r2′ μm 6.730 6.967 7.204 Δ1 % 0.936 0.909 0.883 Δ12 % 0.5 0.5 0.5 Δ2 % 0.436 0.409 0.383 V1′ μm2 % 7.261 7.047 6.850 V2′ μm2 % 58.412 59.160 59.542 Aeff-LP01-21 μm2 101.820 101.854 101.885 Aeff-LP11-21 μm2 161.185 161.290 161.386 MFD21 μm 10.846 10.848 10.850 Aeff-LP01-23 μm2 64.084 67.225 70.380 Aeff-LP11-23 μm2 184.001 196.991 210.468 MFD23 μm 9.064 9.268 9.485 CL01 dB 0.238 0.200 0.170 CL11 dB 0.002 0.012 0.042 -
FIG. 17 is a diagram of the coupling loss CL01 of the LP01 mode light beam and the coupling loss CL11 of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of theoptical device 1 that achieves parameters at the circle.FIG. 18 is a diagram of the coupling loss CL01 of the LP01 mode light beam and the coupling loss CL11 of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of theoptical device 1 that achieves parameters at the triangle.FIG. 19 is a diagram of the coupling loss CL01 of the LP01 mode light beam and the coupling loss CL11 of the LP11 mode light beam in the case in which the wavelength of light changes, the light propagating through the cores of theoptical device 1 that achieves parameters at the square.FIGS. 17 to 19 are expressed by methods similar to the methods inFIGS. 7 to 9 . - As illustrated in
FIGS. 17 to 19 , it is revealed that any optical devices in the states expressed by the parameters at the circle, the triangle, and the square can reduce the coupling loss to 0.25 dB or less in optical communications in the C and L bands. - Next, for the
optical devices 1 achieving the parameters at the circle, the triangle, and the square inFIGS. 6, 14, and 16 , a ratio V1/V2 of a refractive index volume V1 of theinner core 11 to a refractive index volume V2 of theouter core 12 was determined. The refractive index volume V1 of theinner core 11 is expressed by a product of the cross sectional area of theinner core 11 and the relative refractive index difference Δ1 of theinner core 11 in the large-diameter portion 21. The refractive index volume V2 of theouter core 12 is expressed by a product of the cross sectional area of theouter core 12 and the relative refractive index difference Δ2 of theouter core 12 in the large-diameter portion 21. In the case of determining the ratio V1/V2, the ratio V1/V2 is the same value in any cross sections in the large-diameter portion 21, the taperedportion 22, and the small-diameter portion 23. - Next,
FIG. 20 is a diagram of the relationship between the radius r2 of the outer core in the large-diameter portion 21 and the determined values of the ratio V1/V2 for the circle, the triangle, and the square inFIGS. 6, 14 , and 16, with quadrilaterals. - As illustrated in
FIG. 20 , it was revealed that at the circle, the triangle, and the square inFIGS. 6, 14, and 16 , the correlation is present between the radius r2 of the outer core in the large-diameter portion 21 and the ratio V1/V2. FromFIG. 20 , it was revealed that the determined values of the ratio V1/V2 are all present in a range of 0.5377×r2−7.7 to 0.5377×r2−5.7. Therefore, it was revealed thatExpression 1 is held at the circle, the triangle, and the square inFIGS. 6, 14, and 16 . -
FIGS. 6 and 16 , in the case in which the radius r2′ of the outer core in the small-diameter portion 23 is about 3.75 μm, or inFIG. 14 , in the case in which the radius r2′ of the outer core in the small-diameter portion 23 is about 4.7 μm, the radius r2 of the outer core in the large-diameter portion 21 is about 15 μm. In this case, the coupling loss will be about 0.5 dB or greater. In the case in which the radius r2 of the outer core in the large-diameter portion 21 is about 15 μm, the coupling loss can be reduced to about 0.5 dB. - As described above, it was revealed that
Expression 1 is held, and thus the coupling loss of light through theoptical fiber 1 and themulticore fiber 5 can be reduced. - The optical device according to the disclosure can transmit light to and from a multicore fiber in few mode communications with a simple configuration, and can be used in the field of optical communications using multicore fibers, for example.
Claims (14)
0.5377×r 2−7.7≦V 2 /V 1≦0.5377×r 2−5.7 3≦r 2 /r 1≦5
(V 1 ′+V 2′)/V t≧1
(V 1 ′+V 2′)/V t≧1
(V 1 ′+V 2′)/V t≧1
(V 1 ′+V 2′)/V t≧1
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-
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