WO2014168040A1 - Optical coupling structure - Google Patents

Optical coupling structure Download PDF

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Publication number
WO2014168040A1
WO2014168040A1 PCT/JP2014/059558 JP2014059558W WO2014168040A1 WO 2014168040 A1 WO2014168040 A1 WO 2014168040A1 JP 2014059558 W JP2014059558 W JP 2014059558W WO 2014168040 A1 WO2014168040 A1 WO 2014168040A1
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WO
WIPO (PCT)
Prior art keywords
optical fiber
optical
core
face
light
Prior art date
Application number
PCT/JP2014/059558
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French (fr)
Japanese (ja)
Inventor
幸寛 土田
味村　裕
松浦　寛
康平 土井
航 熊谷
由紀子 白澤
佐々木　勇人
京平 吉田
雄介 大友
Original Assignee
古河電気工業株式会社
学校法人東北学院
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Application filed by 古河電気工業株式会社, 学校法人東北学院 filed Critical 古河電気工業株式会社
Priority to JP2015511216A priority Critical patent/JPWO2014168040A1/en
Publication of WO2014168040A1 publication Critical patent/WO2014168040A1/en

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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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H01S3/06729—Peculiar transverse fibre profile
    • H01S3/06737—Fibre having multiple non-coaxial cores, e.g. multiple active cores or separate cores for pump and gain

Definitions

  • the present invention relates to an optical coupling structure.
  • Patent Document 1 As an optical coupling structure for coupling light such as pumping light to a multi-core optical fiber having a plurality of core parts, a structure using an optical multiplexer as described in Patent Document 1, for example, and Non-Patent Document 1 are described. A structure using a lens is disclosed.
  • the present invention has been made in view of the above, and an object of the present invention is to provide an optical coupling structure capable of obtaining high coupling efficiency when coupling light to a multi-core optical fiber.
  • an optical coupling structure includes a multi-core optical fiber having a plurality of core portions and a cladding portion formed on an outer periphery of the plurality of core portions,
  • the multi-core optical fiber is arranged to be inclined, and an optical fiber that outputs light to be input to the end face of the multi-core optical fiber from the end face; and the light that is output from the end face of the optical fiber.
  • a light reflecting element for reflecting to an end face, and the end face of the multi-core optical fiber, the end face of the optical fiber, and the light reflecting element are arranged close to each other, and the light is output from the optical fiber after being output from the optical fiber. Input to the multi-core optical fiber only through a reflective element.
  • the end surface of the multi-core optical fiber is inclined with respect to the optical axis of the multi-core optical fiber so that the end surface has a normal line that is inclined opposite to the optical fiber. It is characterized by being.
  • the optical coupling structure according to the present invention is characterized in that, in the above invention, the multi-core optical fiber is inserted and fixed in a ferrule, and the optical fiber is held in a holding portion formed in the ferrule.
  • the optical coupling structure according to the present invention is characterized in that, in the above invention, the ferrule is made of a material transparent to the light output from the optical fiber.
  • the optical coupling structure according to the present invention is the above-described invention, wherein the multi-core optical fiber is a double-clad multi-core amplification optical fiber in which an optical amplification medium is added to at least one of the plurality of core portions.
  • the light output from the optical fiber is pumping light for optically pumping the optical amplification medium.
  • the optical coupling structure according to the present invention is disposed so as to face an end face of the multi-core amplification optical fiber with the light reflecting element interposed therebetween, and the signal light for performing optical amplification with the multi-core amplification optical fiber is provided.
  • a first lens configured to be input to the multi-core amplification optical fiber is further provided.
  • the optical coupling structure according to the present invention is characterized in that, in the above invention, the end surface of the multi-core amplification optical fiber is arranged at a position farther from the first lens than the focal length of the first lens.
  • the optical coupling structure according to the present invention is characterized in that, in the above invention, the end face of the multi-core amplification optical fiber is disposed at a position substantially at a focal length of the first lens.
  • the optical coupling structure according to the present invention further includes a first optical path displacement optical element disposed so as to face an end face of the multi-core amplification optical fiber with the first lens interposed therebetween, wherein the first optical path displacement is provided.
  • the optical element is configured to allow the plurality of signal lights input to the first optical path displacement optical element to be input to the multi-core amplification optical fiber via the lenses with optical axes parallel to each other. It is characterized by being.
  • the optical coupling structure according to the present invention is characterized in that, in the above invention, the first optical path displacement optical element is a lens or a prism.
  • the optical coupling structure according to the present invention is disposed so as to face the signal optical coupling optical fiber that outputs the plurality of signal lights to the multi-core amplification optical fiber, and the end face of the signal optical coupling optical fiber.
  • a second optical path displacement optical element disposed so as to face the end surface of the signal light coupling optical fiber with the second lens interposed therebetween, and the second lens includes the second lens,
  • a plurality of signal lights can be coupled to the multi-core amplification optical fiber, and the second optical path displacement optical element is input from the signal light coupling optical fiber via the second lens.
  • the plurality of signal lights are configured to be output with optical axes parallel to each other.
  • the optical coupling structure according to the present invention is characterized in that, in the above invention, the second optical path displacement optical element is a lens or a prism.
  • optical coupling structure is characterized in that, in the above invention, the optical coupling structure further includes an optical isolator disposed between the first and second optical path displacement optical elements.
  • the optical coupling structure according to the present invention is characterized in that, in the above invention, the optical fiber has a distributed refractive index type optical fiber portion disposed on the end face side of the optical fiber.
  • FIG. 1 is a schematic configuration diagram of an optical coupling structure according to the first embodiment.
  • FIG. 2 is a schematic cross-sectional view of the multi-core optical fiber shown in FIG.
  • FIG. 3 is a schematic side cutaway view of the optical coupling module according to the second embodiment.
  • 4 is a plan view of the optical coupling module shown in FIG.
  • FIG. 5 is a schematic configuration diagram of an optical coupling structure according to the third embodiment.
  • FIG. 6 is a schematic configuration diagram of an optical coupling structure according to the fourth embodiment.
  • FIG. 7 is a schematic configuration diagram of an optical coupling structure according to the fifth embodiment.
  • FIG. 8A is a schematic diagram of the prism shown in FIG.
  • FIG. 9 is a schematic configuration diagram of an optical coupling structure according to the sixth embodiment.
  • FIG. 10 is a diagram illustrating a configuration of an optical fiber bundle.
  • FIG. 11 is a schematic
  • FIG. 1 is a schematic configuration diagram of an optical coupling structure according to Embodiment 1 of the present invention.
  • the optical coupling structure 10 includes a multi-core optical fiber 1, an optical fiber 2, and an optical filter 3 that is a light reflecting element.
  • FIG. 2 is a schematic cross-sectional view of the multi-core optical fiber 1 shown in FIG.
  • the multi-core optical fiber 1 has seven core portions 1a made of, for example, quartz glass and a refractive index lower than that of, for example, the core portion 1a formed on the outer periphery of the seven core portions 1a.
  • This is a double-clad multi-core optical fiber.
  • the core portion 1a is arranged in a triangular lattice shape, and is composed of a core portion located substantially at the center of the multi-core optical fiber 1 and a core portion arranged so as to form a regular hexagon around the core portion.
  • the multi-core optical fiber 1 is a multi-core amplification optical fiber.
  • the multi-core optical fiber 1 has an end face 1d.
  • the end face 1d has a normal V that is inclined with respect to an axis X parallel to the optical axis of the core portion 1a and the inner cladding portion 1b of the multi-core optical fiber 1.
  • the core portion 1a receives, for example, signal light in the 1.0 ⁇ m wavelength band or 1.55 ⁇ m wavelength band from the outside, and the core diameter and the cladding so that the signal light can be transmitted in a single mode.
  • a relative refractive index difference with respect to the portion 1b is set.
  • the core diameter of the core part 1a is 2.0 ⁇ m or more and 5.5 ⁇ m or less
  • the interval between the core parts 1a is 30 ⁇ m or more and 60 ⁇ m or less.
  • the optical fiber 2 includes a core portion 2a made of, for example, silica-based glass, a clad portion 2b made of, for example, silica-based glass having a refractive index lower than that of the core portion 2a, and an end surface 2c.
  • the optical fiber 2 is arranged to be inclined with respect to the multi-core optical fiber 1 by an inclination angle A. Note that the normal V of the end face 1 d of the multicore optical fiber 1 is inclined to the side opposite to the optical fiber 2.
  • the optical filter 3 has a reflecting surface 3a, and the reflecting surface 3a is disposed so as to face the end surface 1d of the multicore optical fiber 1 and the end surface 2c of the optical fiber 2 in close proximity.
  • a dielectric multilayer film that totally reflects light having the wavelength of the light L1 output from the optical fiber 2 is formed.
  • the optical filter 3 is made of glass such as quartz glass, BK7, or SF6.
  • the optical fiber 2 outputs the light L1 from the end face 2c.
  • the light L1 is, for example, light having a wavelength that can optically pump the optical amplifying medium added to the core portion 1a of the multi-core optical fiber 1 (for example, excitation light having a wavelength band of 980 nm or 1480 nm).
  • the optical filter 3 reflects the light L ⁇ b> 1 output from the end surface 2 c to the end surface 1 d of the multicore optical fiber 1.
  • the reflected light L1 is optically coupled to the inner cladding portion 1b of the multi-core optical fiber 1, and the optical amplification medium added to the core portion 1a can be optically excited.
  • the optical coupling structure 10 after the light L1 is output from the optical fiber 2, it is input to the multi-core optical fiber 1 through the optical filter 3 only.
  • the reflection surface 3a is placed close to the end surface 1d and the end surface 2c, and the light L1 is coupled to the multicore optical fiber 1 without using a lens. Efficiency (for example, about 50% or more) can be realized.
  • the optical path length P of the light L1 from the end face 2c of the optical fiber 2 to the end face 1d of the multicore optical fiber 1 is preferably 1 mm or less, and is about several hundred ⁇ m. More preferred.
  • NA1 is about 0.15
  • d1 is about 150
  • NA2 is about 0.11
  • d2 is about 50 ⁇ m or 105 ⁇ m, for example.
  • the normal V of the end face 1d of the multicore optical fiber 1 is inclined to the side opposite to the optical fiber 2, the light L1 is incident in accordance with the optical axis of the inner cladding portion 1b according to Snell's law. Therefore, the incident angle to the end face 1d is inclined toward the optical fiber 2 side.
  • the inclination angle A can be increased, the optical filter 3 can be brought closer to the multi-core optical fiber 1 and the optical fiber 2, thereby realizing further higher coupling efficiency and downsizing.
  • the inclination angle of the normal line V can also be set as appropriate in order to achieve higher coupling efficiency.
  • the optical coupling structure 10 As described above, according to the optical coupling structure 10 according to the first embodiment, a sufficiently high coupling efficiency can be obtained when the light L1 is coupled to the multicore optical fiber 1.
  • An antireflection film may be formed on the end surface 1 d of the multicore optical fiber 1 or the end surface 2 c of the optical fiber 2.
  • Such an antireflection film is composed of, for example, a laminated film of a tantalum pentoxide film, a titanium oxide film, an alumina film, and a SiO 2 film.
  • the normal line V is not necessarily inclined and may be parallel to the axis X.
  • FIG. 3 is a schematic side cutaway view of an optical coupling module having an optical coupling structure according to Embodiment 2 of the present invention.
  • 4 is a plan view of the optical coupling module shown in FIG.
  • the optical coupling module 100 is obtained by modularizing the optical coupling structure 10 according to the first embodiment.
  • the optical coupling module 100 includes an optical coupling structure 10 including a multi-core optical fiber 1, an optical fiber 2, and an optical filter 3, a ferrule 101, a housing 102, a lens 103, and a lens holder 104. .
  • the housing 102 has a substantially cylindrical shape, and stores the ferrule 101 and also holds a lens holder 104 that stores the lens 103.
  • the housing 102 is formed with an opening 102a for taking out the optical fiber 2 to the outside. If the housing
  • the lens 103 is disposed so as to face the end face of the multi-core optical fiber 1 with the optical filter 3 interposed therebetween, and receives light input from the outside, for example, signal light in a 1.0 ⁇ m wavelength band or 1.55 ⁇ m wavelength band, as multi-core light.
  • the optical fiber 1 is configured to be input to the multi-core optical fiber 1 for optical amplification.
  • the lens holder 104 houses and holds the lens 103, and is made of, for example, stainless steel and is joined to the housing 102 by laser welding or the like.
  • the arrangement of the components of the optical coupling structure 10 according to the first embodiment can be set more suitably.
  • the multi-core optical fiber 1 When a structure in which the multi-core optical fiber 1 is inserted and fixed to the ferrule 101 is manufactured, first, the multi-core optical fiber 1 is inserted into the ferrule 101 in a state where the inclined surface 101b is not formed, and the ferrule 101 and the multi-core optical fiber are inserted. 1 is polished to form the inclined surface 101b and the inclined end surface 1d of the multi-core optical fiber 1 at the same time, and then the multi-core optical fiber 1 is pulled out from the inclined surface 101b to the rear side (right side of the paper) by a predetermined length, Therefore, it can be manufactured more easily by fixing.
  • FIG. 5 is a schematic configuration diagram of an optical coupling structure according to Embodiment 3 of the present invention, and an example of lens arrangement when a condensing optical system is configured when signal light is coupled to the multicore optical fiber 1.
  • FIG. 5 is a schematic configuration diagram of an optical coupling structure according to Embodiment 3 of the present invention, and an example of lens arrangement when a condensing optical system is configured when signal light is coupled to the multicore optical fiber 1.
  • the optical coupling structure 20A includes a multi-core optical fiber 1, an optical fiber 2, an optical filter 3, and a lens 4 corresponding to the lens 103 in FIGS.
  • the lens 4 as the first lens is disposed so as to face the end face of the multi-core optical fiber 1 with the optical filter 3 interposed therebetween, and light input from the outside, for example, signal light for communication is transmitted through the multi-core optical fiber 1. It is configured to be able to input to the multi-core optical fiber 1 for amplification.
  • the lens 4 is a spherical lens, an aspheric lens, a distributed refractive index lens, or the like, but is not particularly limited.
  • the reflective surface 3a (see FIG. 1) of the optical filter 3 totally reflects the light having the wavelength of the light L1 output from the optical fiber 2, and transmits the light having the wavelength band including the signal light. Is formed.
  • a dielectric multilayer film that transmits light in a wavelength band including signal light is also formed on the surface opposite to the reflecting surface 3a.
  • FIG. 5 two of the core portions 1a1 and 1a2 arranged on the outer peripheral side of the core portion 1a of the multi-core optical fiber 1 are shown as core portions 1a1 and 1a2, and the other core portions are not shown. is there.
  • the end face 1d of the multi-core optical fiber 1 is disposed at a position farther from the lens 4 than the focal length f of the lens 4. That is, if the distance between the end face 1d of the multi-core optical fiber 1 and the lens 4 is a, f ⁇ a holds. Then, when the beams B1 and B2 of the signal light input from the outside are condensed on the core portions 1a1 and 1a2 on the end face 1d by the lens 4, the beam waists W1 and W2 of the beams B1 and B2 are To the position of distance b.
  • the beam of signal light to be input to the other core portion 1a is also at a distance b from the lens 4 like the beams B1 and B2.
  • FIG. 6 is a schematic configuration diagram of an optical coupling structure according to the fourth embodiment, and illustrates a lens arrangement example 2 in a case where a parallel optical system is configured when signal light is coupled to the multi-core optical fiber 1.
  • FIG. 6 is a schematic configuration diagram of an optical coupling structure according to the fourth embodiment, and illustrates a lens arrangement example 2 in a case where a parallel optical system is configured when signal light is coupled to the multi-core optical fiber 1.
  • This optical coupling structure 20B is different from the optical coupling structure 20A shown in FIG. 5 in that the end face 1d of the multi-core optical fiber 1 is disposed at a position substantially at the focal length f of the lens 4, and the other configurations are as follows. It is the same. Then, when the externally input signal light beams B1 and B2 are input to the lens 4 as parallel light, they are condensed on the core portions 1a1 and 1a2 on the end face 1d. The beam of signal light to be input to the other core unit 1a is the same as the beams B1 and B2.
  • any arrangement of the lens arrangement examples 1 and 2 of the optical coupling structures 20A and 20B can be used.
  • FIG. 7 is a schematic configuration diagram of the optical coupling structure according to the fifth embodiment of the present invention, and is a diagram illustrating a configuration example 1 of the signal light input unit when the lens arrangement example 1 illustrated in FIG. 5 is employed. It is.
  • the multi-core optical fiber 5 is arranged in the same manner as the core portion 1a with the multi-core optical fiber 1 and is formed on the outer periphery of the seven core portions 5a made of quartz glass and the seven core portions 5a, for example, And a clad portion 5b made of quartz glass having a refractive index lower than that of the portion 5a.
  • a clad portion 5b made of quartz glass having a refractive index lower than that of the portion 5a.
  • FIG. 7 of the core portions 5 a of the multicore optical fiber 5 two core portions arranged on the outer peripheral side are shown as core portions 5 a 1 and 5 a 2, and the other core portions are not shown.
  • the multi-core optical fiber 5 is for inputting signal light for optical amplification by the multi-core optical fiber 1.
  • the lens 6 is disposed so as to face the end face of the multi-core optical fiber 5, and the optical axis and beam waist of the signal light output from the core portion 5 a of the multi-core optical fiber 5 have the signal light beam B 1, It is spatially propagated so as to substantially coincide with the optical axis of B2 and the beam waists W1 and W2, and is coupled to the core portions 1a1 and 1a2.
  • the prism 7 as the second optical path displacement optical element is disposed so as to face the end surface 5c of the multi-core optical fiber 5 with the lens 6 interposed therebetween.
  • the prism 8 as the first optical path displacement optical element is disposed so as to face the end surface 1 d of the multicore optical fiber 1 with the lens 4 interposed therebetween.
  • the prisms 7 and 8 have inclined surfaces 7a and 8a for displacing the optical path of incident light, and parallel surfaces 7b and 8b perpendicular to the optical axis, respectively.
  • FIG. 8A is a schematic diagram of the prism 7 (8) shown in FIG.
  • n 8
  • a regular octagonal pyramid shaped prism shown in FIG. 8B can be used.
  • the optical axis of the lens is placed on the central axis of the multi-core optical fiber and the focal position is set to the center of the multi-core optical fiber.
  • the traveling angle of the light output from the core portions 5a1 and 5a2 of the multi-core optical fiber 5 is determined.
  • the light traveling at this traveling angle is incident on one or two surfaces (parallel surface and inclined surface) of the regular n-pyramid and refracted according to Snell's law.
  • the angle of the positive n pyramid and the focal length of the lens are determined so that this refraction angle is parallel to the central axis of the optical fiber.
  • the inclined surfaces 7 a and 8 a are formed so as to correspond to the core portions on the outer peripheral side of the multi-core optical fibers 1 and 5.
  • Portions through which signal light input / output to / from the central core portion of the multi-core optical fibers 1 and 5 pass are parallel surfaces 7c and 8c parallel to the parallel surfaces 7b and 8b.
  • the prisms 7 and 8 are made of glass such as quartz glass or BK7 or SF6.
  • the lenses 4 and 6 are arranged so that the beam waists W1 and W2 of the beams B1 and B2 are formed at the position of the optical isolator 9.
  • the prism 7 is arranged so that each signal light is output from the core portions 5 a 1 and 5 a 2 of the multi-core optical fiber 5 and inputted through the lens 6.
  • the signal lights output from the prism 7 have their optical axes parallel to each other.
  • the prism 8 outputs the signal light beams B 1 and B 2 output from the core portions 5 a 1 and 5 a 2 of the multi-core optical fiber 5 and whose optical axes are made parallel by the prism 7 via the lens 4 to the core of the multi-core optical fiber 1.
  • the inclination angle of the inclined surface 8a is set so that the parts 1a1 and 1a2 can be input with optical axes parallel to each other. The same applies to the beam of signal light output from the other core portion of the multi-core optical fiber 5.
  • the prisms 7 and 8 can input signal light from the multi-core optical fiber 5 to the multi-core optical fiber 1 with low loss.
  • the signal light input to the multi-core optical fiber 1 is optically amplified while propagating through the core portion 1a optically pumped by the light L1 that is pumping light input from the optical fiber 2.
  • FIG. 9 is a schematic configuration diagram of the optical coupling structure according to the sixth embodiment of the present invention, and shows a configuration example 2 of the signal light input unit when the lens arrangement example 2 shown in FIG. 6 is adopted. It is.
  • any of the configurations 1 and 2 of the optical coupling structures 30A and 30B can be used.
  • the optical coupling structure 30A that employs the lens arrangement example 1 of the condensing optical system shown in FIG. 7 has a greater tolerance to the angular deviation of the beam, and therefore is free from manufacturing errors of the inclined surfaces 7a and 8a of the prisms 7 and 8. This is preferable because the tolerance value is large.
  • the optical coupling structure 30B adopting the parallel optical system lens arrangement example 2 shown in FIG. 9 is preferable in that it is easier to adjust the position of the optical element when it is manufactured.
  • the optical isolator 9 used in the present embodiment is a known one such as a one-stage structure using a wedge prism and a garnet crystal, or a two-stage structure having a structure for canceling polarization mode dispersion.
  • An optical isolator using a wedge-shaped prism is, for example, a birefringent optical crystal formed in a wedge shape so that the light incident / exit surfaces are not parallel to each other on the signal light incident / exit side.
  • the optical isolator is configured so that only the signal light in the optical transmission direction is coupled to the core portion of the optical fiber by including the 45-degree polarization plane rotation element and the 45-degree rotation Faraday element.
  • the optical axis of the return light is the signal light in the optical transmission direction. This is preferable because it has an angular deviation with respect to the optical axis of the optical axis and can effectively block the return light.
  • the condensing optical system as shown in FIG. 7 since the tolerance for the beam position deviation in the direction perpendicular to the optical axis is small, an optical isolator using a parallel plate type as a birefringent crystal is used.
  • the optical axis of the return light has a positional deviation with respect to the optical axis of the signal light in the optical transmission direction, which is preferable because the return light can be effectively blocked.
  • the prisms 7 and 8 are arranged so that the parallel surfaces 7b and 8b are opposed to each other, but the inclined surfaces 7a and 8a may be arranged so as to be opposed to each other. Further, instead of the prisms 7 and 8, a prism having no parallel surfaces 7b and 8b and inclined on both sides may be used. Alternatively, instead of the prisms 7 and 8, a lens as an optical path displacement optical element may be used.
  • the distance between the optical axes of the signal lights parallel to each other between the optical path displacement optical elements is larger than the distance between the cores of the multi-core optical fiber, so that the signal lights are less likely to interfere with each other.
  • this is realized by using a lens having a longer focal length than the lens 6 instead of the prism 7 and using a lens having a longer focal length than the lens 4 instead of the prism 8.
  • the signal lights parallel to each other between the optical path displacement optical elements are spaced so that the beam spreads in the plane perpendicular to the propagation direction do not overlap each other.
  • optical fiber bundle 5A as shown in FIG. 10 may be used in place of the multi-core optical fiber 5 in order to input signal light.
  • the optical fiber bundle 5A is formed by bundling and integrating seven optical fibers 5Aa including a core portion 5Aa1 and a cladding portion 5Aa2.
  • FIG. 11 is a schematic configuration diagram of an optical coupling structure according to Embodiment 7 of the present invention.
  • the optical coupling structure 10A is obtained by replacing the optical fiber 2 with the optical fiber 2A in the optical coupling structure 10 according to the first embodiment shown in FIG.
  • the optical fiber 2A includes an optical fiber portion 2A1 having a step index type refractive index distribution, and a distributed refractive index type optical fiber portion 2A2 disposed on the end face 2Aa side of the optical fiber 2A.
  • the coupling efficiency can be further increased.
  • the multi-core optical fiber 1 is a double-clad amplification optical fiber, but may be replaced with a multi-core optical fiber in which no optical amplification medium is added to the core portion.
  • the light L1 may not be excitation light.
  • the optical fiber 2 is not limited to a multimode optical fiber, and may be a single mode optical fiber.
  • signal light is input from the multi-core optical fiber 5 to the multi-core optical fiber 1, but the amplified signal light output from the multi-core optical fiber 1 is converted into multi-core optical fiber due to reciprocity of light.
  • the above-described embodiment can be applied to the case where the input is made to 5.
  • the present invention is not limited by the above embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention.
  • any of the optical coupling structures according to the above third to seventh embodiments may be configured like the optical coupling module according to the second embodiment. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.
  • the optical coupling structure according to the present invention is suitable mainly for use in optical communication.

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Abstract

An optical coupling structure is provided with: a multicore optical fiber having a plurality of core parts and a cladding part formed around the plurality of core parts; an optical fiber that is disposed at a slant with respect to the multicore optical fiber and outputs light for input to an end surface of the multicore optical fiber from an end surface thereof; and a light reflecting element for reflecting the light output from the end surface of the optical fiber to an end surface of the multicore optical fiber. The end surface of the multicore optical fiber, the end surface of the optical fiber, and the light reflecting element are disposed in proximity to each other, and after the light is output by the optical fiber, the same is input to the multicore optical fiber via only the light reflecting element. Thus, an optical coupling structure with which high coupling efficiency is obtained when light is coupled with the multicore optical fiber is provided.

Description

光結合構造Optical coupling structure
　本発明は、光結合構造に関するものである。 The present invention relates to an optical coupling structure.
　複数のコア部を有するマルチコア光ファイバに励起光などの光を結合させるための光結合構造として、たとえば特許文献１に記載されるような光合波器を用いる構造や、非特許文献１に記載されるようにレンズを用いた構造が開示されている。 As an optical coupling structure for coupling light such as pumping light to a multi-core optical fiber having a plurality of core parts, a structure using an optical multiplexer as described in Patent Document 1, for example, and Non-Patent Document 1 are described. A structure using a lens is disclosed.
特開平１０－１２５９８８号公報JP-A-10-125988
　しかしながら、公知の光結合構造では、マルチコア光ファイバに光を結合する際に十分に高い結合効率が得られないという問題があった。 However, the known optical coupling structure has a problem that a sufficiently high coupling efficiency cannot be obtained when light is coupled to the multi-core optical fiber.
　本発明は、上記に鑑みてなされたものであって、マルチコア光ファイバに光を結合する際に高い結合効率が得られる光結合構造を提供することを目的とする。 The present invention has been made in view of the above, and an object of the present invention is to provide an optical coupling structure capable of obtaining high coupling efficiency when coupling light to a multi-core optical fiber.
　上述した課題を解決し、目的を達成するために、本発明に係る光結合構造は、複数のコア部と前記複数のコア部の外周に形成されたクラッド部とを有するマルチコア光ファイバと、前記マルチコア光ファイバとは傾斜して配置されており、前記マルチコア光ファイバの端面に入力するための光を端面から出力する光ファイバと、前記光ファイバの端面から出力した前記光を前記マルチコア光ファイバの端面に反射させるための光反射素子と、を備え、前記マルチコア光ファイバの端面、前記光ファイバの端面、および前記光反射素子は近接して配置され、前記光は前記光ファイバから出力後に前記光反射素子のみを介して前記マルチコア光ファイバに入力することを特徴とする。 In order to solve the above-described problems and achieve the object, an optical coupling structure according to the present invention includes a multi-core optical fiber having a plurality of core portions and a cladding portion formed on an outer periphery of the plurality of core portions, The multi-core optical fiber is arranged to be inclined, and an optical fiber that outputs light to be input to the end face of the multi-core optical fiber from the end face; and the light that is output from the end face of the optical fiber. A light reflecting element for reflecting to an end face, and the end face of the multi-core optical fiber, the end face of the optical fiber, and the light reflecting element are arranged close to each other, and the light is output from the optical fiber after being output from the optical fiber. Input to the multi-core optical fiber only through a reflective element.
　本発明に係る光結合構造は、上記発明において、前記マルチコア光ファイバの端面は前記光ファイバとは反対側に傾斜する法線を有するように、前記マルチコア光ファイバの光軸に対して傾斜していることを特徴とする。 In the optical coupling structure according to the present invention, in the above invention, the end surface of the multi-core optical fiber is inclined with respect to the optical axis of the multi-core optical fiber so that the end surface has a normal line that is inclined opposite to the optical fiber. It is characterized by being.
　本発明に係る光結合構造は、上記発明において、前記マルチコア光ファイバと前記光ファイバとの傾斜角度が１５度～４５度であることを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, an inclination angle between the multi-core optical fiber and the optical fiber is 15 degrees to 45 degrees.
　本発明に係る光結合構造は、上記発明において、前記光ファイバの端面から前記マルチコア光ファイバの端面までの前記光の光路長が１ｍｍ以下であることを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, the optical path length of the light from the end face of the optical fiber to the end face of the multi-core optical fiber is 1 mm or less.
　本発明に係る光結合構造は、上記発明において、前記マルチコア光ファイバは、フェルールに挿通固定されており、前記光ファイバは前記フェルールに形成された保持部に保持されていることを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, the multi-core optical fiber is inserted and fixed in a ferrule, and the optical fiber is held in a holding portion formed in the ferrule.
　本発明に係る光結合構造は、上記発明において、前記フェルールは、前記光ファイバが出力する前記光に対して透明な材質からなることを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, the ferrule is made of a material transparent to the light output from the optical fiber.
　本発明に係る光結合構造は、上記発明において、前記マルチコア光ファイバは、前記複数のコア部の少なくともいずれか一つに光増幅媒体が添加されたダブルクラッド型のマルチコア増幅光ファイバであり、前記光ファイバが出力する前記光は前記光増幅媒体を光励起する励起光であることを特徴とする。 The optical coupling structure according to the present invention is the above-described invention, wherein the multi-core optical fiber is a double-clad multi-core amplification optical fiber in which an optical amplification medium is added to at least one of the plurality of core portions. The light output from the optical fiber is pumping light for optically pumping the optical amplification medium.
　本発明に係る光結合構造は、上記発明において、前記光反射素子を挟んで前記マルチコア増幅光ファイバの端面に対向するように配置され、前記マルチコア増幅光ファイバで光増幅をさせるための信号光を該マルチコア増幅光ファイバに入力できるように構成された第１レンズをさらに備えることを特徴とする。 In the above invention, the optical coupling structure according to the present invention is disposed so as to face an end face of the multi-core amplification optical fiber with the light reflecting element interposed therebetween, and the signal light for performing optical amplification with the multi-core amplification optical fiber is provided. A first lens configured to be input to the multi-core amplification optical fiber is further provided.
　本発明に係る光結合構造は、上記発明において、前記マルチコア増幅光ファイバの端面は、前記第１レンズから、該第１レンズの焦点距離よりも遠い位置に配置されていることを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, the end surface of the multi-core amplification optical fiber is arranged at a position farther from the first lens than the focal length of the first lens.
　本発明に係る光結合構造は、上記発明において、前記マルチコア増幅光ファイバの端面は、前記第１レンズの略焦点距離の位置に配置されていることを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, the end face of the multi-core amplification optical fiber is disposed at a position substantially at a focal length of the first lens.
　本発明に係る光結合構造は、上記発明において、前記第１レンズを挟んで前記マルチコア増幅光ファイバの端面に対向するように配置された第１光路変位光学素子をさらに備え、前記第１光路変位光学素子は、該第１光路変位光学素子に入力された複数の前記信号光を、前記レンズを介して前記マルチコア増幅光ファイバに、互いに平行な光軸で入力させることができるように構成されていることを特徴とする。 The optical coupling structure according to the present invention further includes a first optical path displacement optical element disposed so as to face an end face of the multi-core amplification optical fiber with the first lens interposed therebetween, wherein the first optical path displacement is provided. The optical element is configured to allow the plurality of signal lights input to the first optical path displacement optical element to be input to the multi-core amplification optical fiber via the lenses with optical axes parallel to each other. It is characterized by being.
　本発明に係る光結合構造は、上記発明において、前記第１光路変位光学素子はレンズまたはプリズムであることを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, the first optical path displacement optical element is a lens or a prism.
　本発明に係る光結合構造は、上記発明において、前記複数の信号光を前記マルチコア増幅光ファイバに出力する信号光結合用光ファイバと、前記信号光結合用光ファイバの端面に対向するように配置された第２レンズと、前記第２レンズを挟んで前記信号光結合用光ファイバの端面に対向するように配置された第２光路変位光学素子と、をさらに備え、前記第２レンズは、前記複数の信号光を前記マルチコア増幅光ファイバに結合させることができるように構成されており、前記第２光路変位光学素子は、前記信号光結合用光ファイバから、前記第２レンズを介して入力された前記複数の信号光が、互いに平行な光軸で出力するように構成されていることを特徴とする。 In the above invention, the optical coupling structure according to the present invention is disposed so as to face the signal optical coupling optical fiber that outputs the plurality of signal lights to the multi-core amplification optical fiber, and the end face of the signal optical coupling optical fiber. A second optical path displacement optical element disposed so as to face the end surface of the signal light coupling optical fiber with the second lens interposed therebetween, and the second lens includes the second lens, A plurality of signal lights can be coupled to the multi-core amplification optical fiber, and the second optical path displacement optical element is input from the signal light coupling optical fiber via the second lens. Further, the plurality of signal lights are configured to be output with optical axes parallel to each other.
　本発明に係る光結合構造は、上記発明において、前記第２光路変位光学素子はレンズまたはプリズムであることを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, the second optical path displacement optical element is a lens or a prism.
　本発明に係る光結合構造は、上記発明において、前記第１および第２光路変位光学素子の間に配置された光アイソレータをさらに備えることを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, the optical coupling structure further includes an optical isolator disposed between the first and second optical path displacement optical elements.
　本発明に係る光結合構造は、上記発明において、前記光ファイバは、該光ファイバの端面側に配置された分布屈折率型の光ファイバ部を有することを特徴とする。 The optical coupling structure according to the present invention is characterized in that, in the above invention, the optical fiber has a distributed refractive index type optical fiber portion disposed on the end face side of the optical fiber.
　本発明によれば、マルチコア光ファイバに光を結合する際に十分に高い結合効率が得られるという効果を奏する。 According to the present invention, there is an effect that a sufficiently high coupling efficiency can be obtained when light is coupled to a multi-core optical fiber.
図１は、実施の形態１に係る光結合構造の模式的な構成図である。FIG. 1 is a schematic configuration diagram of an optical coupling structure according to the first embodiment. 図２は、図１に示すマルチコア光ファイバの模式的な断面図である。FIG. 2 is a schematic cross-sectional view of the multi-core optical fiber shown in FIG. 図３は、実施の形態２に係る光結合モジュールの模式的な側面切り欠き図である。FIG. 3 is a schematic side cutaway view of the optical coupling module according to the second embodiment. 図４は、図３に示す光結合モジュールの平面図である。4 is a plan view of the optical coupling module shown in FIG. 図５は、実施の形態３に係る光結合構造の模式的な構成図である。FIG. 5 is a schematic configuration diagram of an optical coupling structure according to the third embodiment. 図６は、実施の形態４に係る光結合構造の模式的な構成図である。FIG. 6 is a schematic configuration diagram of an optical coupling structure according to the fourth embodiment. 図７は、実施の形態５に係る光結合構造の模式的な構成図である。FIG. 7 is a schematic configuration diagram of an optical coupling structure according to the fifth embodiment. 図８Ａは、図７に示すプリズムの模式図である。FIG. 8A is a schematic diagram of the prism shown in FIG. 図８Ｂは、ｎ＝８の場合に使用できるプリズムの模式図である。FIG. 8B is a schematic diagram of a prism that can be used when n = 8. 図９は、実施の形態６係る光結合構造の模式的な構成図である。FIG. 9 is a schematic configuration diagram of an optical coupling structure according to the sixth embodiment. 図１０は、光ファイババンドルの構成を示す図である。FIG. 10 is a diagram illustrating a configuration of an optical fiber bundle. 図１１は、実施の形態７に係る光結合構造の模式的な構成図である。FIG. 11 is a schematic configuration diagram of an optical coupling structure according to the seventh embodiment.
　以下に、図面を参照して本発明に係る光結合構造の実施の形態を詳細に説明する。なお、この実施の形態によりこの発明が限定されるものではない。また、各図面において、同一または対応する構成要素には適宜同一の符号を付している。また、図面は模式的なものであり、各要素の寸法の比率などは現実のものとは異なる場合があることに留意すべきである。また、図面相互間においても互いの寸法の関係や比率が異なる部分が含まれている場合がある。 Hereinafter, embodiments of an optical coupling structure according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Moreover, in each drawing, the same code | symbol is attached | subjected suitably to the same or corresponding component. In addition, it should be noted that the drawings are schematic and the ratio of dimensions of each element may be different from the actual one. In addition, there may be a case where the dimensional relationships and ratios are different between the drawings.
（実施の形態１）
　図１は、本発明の実施の形態１に係る光結合構造の模式的な構成図である。光結合構造１０は、マルチコア光ファイバ１と、光ファイバ２と、光反射素子である光フィルタ３とを備えている。 (Embodiment 1)
FIG. 1 is a schematic configuration diagram of an optical coupling structure according to Embodiment 1 of the present invention. The optical coupling structure 10 includes a multi-core optical fiber 1, an optical fiber 2, and an optical filter 3 that is a light reflecting element.
　図２は、図１に示すマルチコア光ファイバ１の模式的な断面図である。図１、２に示すように、マルチコア光ファイバ１は、たとえば石英系ガラスからなる７つのコア部１ａと、７つのコア部１ａの外周に形成された、たとえばコア部１ａよりも屈折率が低い石英系ガラスからなる内側クラッド部１ｂと、内側クラッド部１ｂの外周に形成された、たとえば内側クラッド部１ｂよりも屈折率が低い石英系ガラスや樹脂からなる外側クラッド部１ｃとを有しているダブルクラッド型のマルチコア光ファイバである。コア部１ａは、三角格子状に配置されており、マルチコア光ファイバ１の略中心に位置するコア部とその周囲に正六角形を形成するように配置されたコア部とからなる。 FIG. 2 is a schematic cross-sectional view of the multi-core optical fiber 1 shown in FIG. As shown in FIGS. 1 and 2, the multi-core optical fiber 1 has seven core portions 1a made of, for example, quartz glass and a refractive index lower than that of, for example, the core portion 1a formed on the outer periphery of the seven core portions 1a. An inner clad portion 1b made of quartz glass and an outer clad portion 1c made of quartz glass or resin having a lower refractive index than the inner clad portion 1b, for example, formed on the outer periphery of the inner clad portion 1b. This is a double-clad multi-core optical fiber. The core portion 1a is arranged in a triangular lattice shape, and is composed of a core portion located substantially at the center of the multi-core optical fiber 1 and a core portion arranged so as to form a regular hexagon around the core portion.
　また、マルチコア光ファイバ１のコア部１ａには、たとえば希土類元素であるエルビウム（Ｅｒ）やイッテルビウム（Ｙｂ）などの光増幅媒体が添加されている。したがって、マルチコア光ファイバ１はマルチコア増幅光ファイバである。マルチコア光ファイバ１は端面１ｄを有している。端面１ｄはマルチコア光ファイバ１のコア部１ａおよび内側クラッド部１ｂの光軸に平行な軸Ｘに対して傾斜した法線Ｖを有する。 Also, an optical amplification medium such as erbium (Er) or ytterbium (Yb), which are rare earth elements, is added to the core portion 1a of the multi-core optical fiber 1. Therefore, the multi-core optical fiber 1 is a multi-core amplification optical fiber. The multi-core optical fiber 1 has an end face 1d. The end face 1d has a normal V that is inclined with respect to an axis X parallel to the optical axis of the core portion 1a and the inner cladding portion 1b of the multi-core optical fiber 1.
　なお、コア部１ａは、後述するように、たとえば１．０μｍ波長帯や１．５５μｍ波長帯の信号光が外部から入力されるが、この信号光をシングルモードで伝送できるようにコア直径およびクラッド部１ｂに対する比屈折率差が設定されている。たとえば、コア部１ａのコア直径は２．０μｍ以上５．５μｍ以下であり、コア部１ａ同士の間隔は３０μｍ以上６０μｍ以下である。 As will be described later, the core portion 1a receives, for example, signal light in the 1.0 μm wavelength band or 1.55 μm wavelength band from the outside, and the core diameter and the cladding so that the signal light can be transmitted in a single mode. A relative refractive index difference with respect to the portion 1b is set. For example, the core diameter of the core part 1a is 2.0 μm or more and 5.5 μm or less, and the interval between the core parts 1a is 30 μm or more and 60 μm or less.
　光ファイバ２は、たとえば石英系ガラスからなるコア部２ａと、コア部２ａの外周に形成された、たとえばコア部２ａよりも屈折率が低い石英系ガラスからなるクラッド部２ｂと、端面２ｃとを有するマルチモード光ファイバである。光ファイバ２はマルチコア光ファイバ１とは傾斜角度Ａだけ傾斜して配置されている。なお、マルチコア光ファイバ１の端面１ｄの法線Ｖは、光ファイバ２とは反対側に傾斜している。 The optical fiber 2 includes a core portion 2a made of, for example, silica-based glass, a clad portion 2b made of, for example, silica-based glass having a refractive index lower than that of the core portion 2a, and an end surface 2c. A multimode optical fiber. The optical fiber 2 is arranged to be inclined with respect to the multi-core optical fiber 1 by an inclination angle A. Note that the normal V of the end face 1 d of the multicore optical fiber 1 is inclined to the side opposite to the optical fiber 2.
　光フィルタ３は、反射面３ａを有しており、反射面３ａがマルチコア光ファイバ１の端面１ｄおよび光ファイバ２の端面２ｃと近接して対向するように配置されている。光フィルタ３の反射面３ａは、光ファイバ２から出力される光Ｌ１の波長の光を全反射する誘電体多層膜が形成される。光フィルタ３はたとえば石英ガラスやＢＫ７、ＳＦ６等のガラスからなる。 The optical filter 3 has a reflecting surface 3a, and the reflecting surface 3a is disposed so as to face the end surface 1d of the multicore optical fiber 1 and the end surface 2c of the optical fiber 2 in close proximity. On the reflection surface 3a of the optical filter 3, a dielectric multilayer film that totally reflects light having the wavelength of the light L1 output from the optical fiber 2 is formed. The optical filter 3 is made of glass such as quartz glass, BK7, or SF6.
　光結合構造１０の光結合作用について説明する。光ファイバ２は、端面２ｃから光Ｌ１を出力する。光Ｌ１は、たとえばマルチコア光ファイバ１のコア部１ａに添加された光増幅媒体を光励起できる波長の光（たとえば９８０ｎｍ波長帯や１４８０ｎｍ波長帯の励起光）である。つぎに、光フィルタ３は、端面２ｃから出力された光Ｌ１をマルチコア光ファイバ１の端面１ｄに反射させる。反射された光Ｌ１はマルチコア光ファイバ１の内側クラッド部１ｂに光結合し、コア部１ａに添加された光増幅媒体を光励起することができる。 The optical coupling action of the optical coupling structure 10 will be described. The optical fiber 2 outputs the light L1 from the end face 2c. The light L1 is, for example, light having a wavelength that can optically pump the optical amplifying medium added to the core portion 1a of the multi-core optical fiber 1 (for example, excitation light having a wavelength band of 980 nm or 1480 nm). Next, the optical filter 3 reflects the light L <b> 1 output from the end surface 2 c to the end surface 1 d of the multicore optical fiber 1. The reflected light L1 is optically coupled to the inner cladding portion 1b of the multi-core optical fiber 1, and the optical amplification medium added to the core portion 1a can be optically excited.
　ここで、光結合構造１０では、光Ｌ１は光ファイバ２から出力後に、光フィルタ３のみを介してマルチコア光ファイバ１に入力する。このように、光結合構造１０では、反射面３ａを端面１ｄおよび端面２ｃと近接させて、レンズを介さずに光Ｌ１をマルチコア光ファイバ１に結合させているので、実用上好ましい程度の高い結合効率（たとえば５０％程度以上）を実現することができる。 Here, in the optical coupling structure 10, after the light L1 is output from the optical fiber 2, it is input to the multi-core optical fiber 1 through the optical filter 3 only. As described above, in the optical coupling structure 10, the reflection surface 3a is placed close to the end surface 1d and the end surface 2c, and the light L1 is coupled to the multicore optical fiber 1 without using a lens. Efficiency (for example, about 50% or more) can be realized.
　より高い結合効率を実現するためには、光ファイバ２の端面２ｃからマルチコア光ファイバ１の端面１ｄまでの光Ｌ１の光路長Ｐが１ｍｍ以下で有ることが好ましく、数百μｍ程度であることがより好ましい。 In order to realize higher coupling efficiency, the optical path length P of the light L1 from the end face 2c of the optical fiber 2 to the end face 1d of the multicore optical fiber 1 is preferably 1 mm or less, and is about several hundred μm. More preferred.
　また、マルチコア光ファイバ１の内側クラッド部１ｂのＮＡ（開口数）をＮＡ１、外径をｄ１とし、光ファイバ２のＮＡをＮＡ２、外径をｄ２とすると、ｄ１＞ｄ２、ＮＡ１＞ＮＡ２の関係が成り立つことが結合効率の向上の点から好ましい。ただし、これらの関係は、許容される結合効率によっては必ずしも満たさなくてもよい。ＮＡ１はたとえば約０．１５、ｄ１は約１５０μｍである。また、ＮＡ２はたとえば約０．１１、ｄ２は約５０μｍまたは１０５μｍである。 Further, assuming that the NA (numerical aperture) of the inner cladding portion 1b of the multi-core optical fiber 1 is NA1, the outer diameter is d1, the NA of the optical fiber 2 is NA2, and the outer diameter is d2, d1> d2 and NA1> NA2. Is preferable from the viewpoint of improving the coupling efficiency. However, these relationships may not necessarily be satisfied depending on the allowable coupling efficiency. For example, NA1 is about 0.15, and d1 is about 150 μm. NA2 is about 0.11, and d2 is about 50 μm or 105 μm, for example.
　また、マルチコア光ファイバ１、光ファイバ２、光フィルタ３の配置については、より高い結合効率を実現するように設定される。たとえは、マルチコア光ファイバ１、光ファイバ２、光フィルタ３の配置については、マルチコア光ファイバ１に入射される光Ｌ１の光軸が内側クラッド部１ｂの光軸と略一致し、かつ光Ｌ１がマルチコア光ファイバ１によってけられない（マルチコア光ファイバ１の端部などで光Ｌ１が遮られない）ような配置とすることが好ましい。また、光ファイバ２とマルチコア光ファイバ１との間の傾斜角度Ａは、上記結合効率が最大になるように設定すればよいが、たとえば１５度から４５度の範囲である。 Further, the arrangement of the multi-core optical fiber 1, the optical fiber 2, and the optical filter 3 is set so as to realize higher coupling efficiency. For example, regarding the arrangement of the multi-core optical fiber 1, the optical fiber 2, and the optical filter 3, the optical axis of the light L1 incident on the multi-core optical fiber 1 substantially matches the optical axis of the inner cladding portion 1b, and the light L1 is It is preferable that the arrangement is such that the multi-core optical fiber 1 is not blocked (the light L1 is not blocked by the end of the multi-core optical fiber 1 or the like). Further, the inclination angle A between the optical fiber 2 and the multi-core optical fiber 1 may be set so that the coupling efficiency is maximized, and is, for example, in the range of 15 to 45 degrees.
　また、マルチコア光ファイバ１の端面１ｄの法線Ｖが、光ファイバ２とは反対側に傾斜していると、スネルの法則によって、内側クラッド部１ｂの光軸に一致させて光Ｌ１を入射させるための端面１ｄへの入射角が、光ファイバ２側に傾斜することとなる。その結果、傾斜角度Ａを大きくすることができるので、光フィルタ３をマルチコア光ファイバ１および光ファイバ２とより近接させることができるので、さらに高い結合効率および小型化が実現される。法線Ｖの傾斜角度についても、より高い結合効率を実現するために適宜設定できる。 Further, when the normal V of the end face 1d of the multicore optical fiber 1 is inclined to the side opposite to the optical fiber 2, the light L1 is incident in accordance with the optical axis of the inner cladding portion 1b according to Snell's law. Therefore, the incident angle to the end face 1d is inclined toward the optical fiber 2 side. As a result, since the inclination angle A can be increased, the optical filter 3 can be brought closer to the multi-core optical fiber 1 and the optical fiber 2, thereby realizing further higher coupling efficiency and downsizing. The inclination angle of the normal line V can also be set as appropriate in order to achieve higher coupling efficiency.
　以上説明したように、本実施の形態１に係る光結合構造１０によれば、マルチコア光ファイバ１に光Ｌ１を結合する際に十分に高い結合効率を得ることができる。 As described above, according to the optical coupling structure 10 according to the first embodiment, a sufficiently high coupling efficiency can be obtained when the light L1 is coupled to the multicore optical fiber 1.
　なお、マルチコア光ファイバ１の端面１ｄや光ファイバ２の端面２ｃに反射防止膜を形成してもよい。このような反射防止膜は、たとえば５酸化タンタル膜、酸化チタン膜、アルミナ膜、およびＳｉＯ２膜の積層膜で構成される。また、法線Ｖは必ずしも傾斜していなくてもよく、軸Ｘに対して平行でもよい。 An antireflection film may be formed on the end surface 1 d of the multicore optical fiber 1 or the end surface 2 c of the optical fiber 2. Such an antireflection film is composed of, for example, a laminated film of a tantalum pentoxide film, a titanium oxide film, an alumina film, and a SiO 2 film. Further, the normal line V is not necessarily inclined and may be parallel to the axis X.
（実施の形態２）
　図３は、本発明の実施の形態２に係る光結合構造である光結合モジュールの模式的な側面切り欠き図である。図４は、図３に示す光結合モジュールの平面図である。光結合モジュール１００は、実施の形態１に係る光結合構造１０をモジュール化したものである。 (Embodiment 2)
FIG. 3 is a schematic side cutaway view of an optical coupling module having an optical coupling structure according to Embodiment 2 of the present invention. 4 is a plan view of the optical coupling module shown in FIG. The optical coupling module 100 is obtained by modularizing the optical coupling structure 10 according to the first embodiment.
　光結合モジュール１００は、マルチコア光ファイバ１と、光ファイバ２と、光フィルタ３とを備える光結合構造１０と、フェルール１０１と、筐体１０２と、レンズ１０３と、レンズホルダ１０４とを備えている。 The optical coupling module 100 includes an optical coupling structure 10 including a multi-core optical fiber 1, an optical fiber 2, and an optical filter 3, a ferrule 101, a housing 102, a lens 103, and a lens holder 104. .
　フェルール１０１は、略円柱状であって、マルチコア光ファイバ１を挿通固定する挿通孔１０１ａと、光フィルタ３が装着される傾斜面１０１ｂと、光ファイバ２を保持する保持部である溝１０１ｃとを有している。溝１０１ｃは、挿通孔１０１ａに対して傾斜角度Ａで傾斜した底面を有しており、挿通孔１０１ａに挿通固定されたマルチコア光ファイバ１と光ファイバ２との傾斜角度を傾斜角度Ａに保持することができる。また、傾斜面１０１ｂは、マルチコア光ファイバ１、光ファイバ２に対して光フィルタ３が適切な配置となるように傾斜角度が設定されている。このようなフェルール１０１の構造によって、マルチコア光ファイバ１、光ファイバ２、および光フィルタ３の配置が適切に保持される。なお、フェルール１０１は、ガラス等の光Ｌ１に対して透明な材質や、ジルコニア、金属等の材質で構成することができるが、透明な材質であれば、光Ｌ１のうちマルチコア光ファイバ１に結合できずに漏洩した光を透過し、光のエネルギーを外部に拡散できるので、光Ｌ１の強度が高いときには耐光強度性の点から好ましい。 The ferrule 101 is substantially cylindrical, and includes an insertion hole 101a for inserting and fixing the multi-core optical fiber 1, an inclined surface 101b to which the optical filter 3 is mounted, and a groove 101c that is a holding portion for holding the optical fiber 2. Have. The groove 101c has a bottom surface inclined at an inclination angle A with respect to the insertion hole 101a, and holds the inclination angle between the multicore optical fiber 1 and the optical fiber 2 inserted and fixed in the insertion hole 101a at the inclination angle A. be able to. In addition, the inclined surface 101 b is set to have an inclination angle so that the optical filter 3 is appropriately arranged with respect to the multi-core optical fiber 1 and the optical fiber 2. With such a structure of the ferrule 101, the arrangement of the multi-core optical fiber 1, the optical fiber 2, and the optical filter 3 is appropriately maintained. The ferrule 101 can be made of a material transparent to the light L1 such as glass, or a material such as zirconia or metal. However, if the material is transparent, the ferrule 101 is coupled to the multi-core optical fiber 1 in the light L1. Since the leaked light can be transmitted and the energy of the light can be diffused to the outside, it is preferable from the viewpoint of light resistance when the intensity of the light L1 is high.
　筐体１０２は、略円筒状であり、フェルール１０１を収容するとともに、レンズ１０３を収容したレンズホルダ１０４を保持する。筐体１０２には光ファイバ２を外部に取り出すための開口部１０２ａが形成されている。筐体１０２はたとえばステンレス鋼等の金属であれば、上述した漏洩光を受けたときに発生した熱を放熱することができる。これによって、光結合モジュール１００の温度上昇を抑制することができる。 The housing 102 has a substantially cylindrical shape, and stores the ferrule 101 and also holds a lens holder 104 that stores the lens 103. The housing 102 is formed with an opening 102a for taking out the optical fiber 2 to the outside. If the housing | casing 102 is metals, such as stainless steel, for example, it can thermally radiate the heat | fever which generate | occur | produced when receiving the leakage light mentioned above. Thereby, the temperature rise of the optical coupling module 100 can be suppressed.
　レンズ１０３は、光フィルタ３を挟んでマルチコア光ファイバ１の端面に対向するように配置され、外部から入力された光、たとえば１．０μｍ波長帯や１．５５μｍ波長帯の信号光を、マルチコア光ファイバ１で光増幅するためにマルチコア光ファイバ１に入力できるように構成されている。
　レンズホルダ１０４はレンズ１０３を収容し、保持するものであり、たとえばステンレス等からなり、筐体１０２にレーザ溶接等で接合されている。 The lens 103 is disposed so as to face the end face of the multi-core optical fiber 1 with the optical filter 3 interposed therebetween, and receives light input from the outside, for example, signal light in a 1.0 μm wavelength band or 1.55 μm wavelength band, as multi-core light. The optical fiber 1 is configured to be input to the multi-core optical fiber 1 for optical amplification.
The lens holder 104 houses and holds the lens 103, and is made of, for example, stainless steel and is joined to the housing 102 by laser welding or the like.
　この光結合モジュール１００によれば、実施の形態１に係る光結合構造１０の構成要素の配置をより好適に設定することができる。 According to the optical coupling module 100, the arrangement of the components of the optical coupling structure 10 according to the first embodiment can be set more suitably.
　なお、フェルール１０１にマルチコア光ファイバ１が挿通固定された構造を作製する場合には、まず傾斜面１０１ｂが形成されていない状態のフェルール１０１にマルチコア光ファイバ１を挿通し、フェルール１０１およびマルチコア光ファイバ１の端面を研磨して傾斜面１０１ｂとマルチコア光ファイバ１の傾斜した端面１ｄとを同時に形成し、その後マルチコア光ファイバ１を傾斜面１０１ｂから後方側（紙面右側）に所定長さだけ引き抜いて、そこで固定することによって、より簡易に作製することができる。 When a structure in which the multi-core optical fiber 1 is inserted and fixed to the ferrule 101 is manufactured, first, the multi-core optical fiber 1 is inserted into the ferrule 101 in a state where the inclined surface 101b is not formed, and the ferrule 101 and the multi-core optical fiber are inserted. 1 is polished to form the inclined surface 101b and the inclined end surface 1d of the multi-core optical fiber 1 at the same time, and then the multi-core optical fiber 1 is pulled out from the inclined surface 101b to the rear side (right side of the paper) by a predetermined length, Therefore, it can be manufactured more easily by fixing.
（実施の形態３）
　図５は、本発明の実施の形態３に係る光結合構造の模式的な構成図であって、マルチコア光ファイバ１に信号光を結合する際に集光光学系を構成する場合のレンズ配置例１を説明する図である。 (Embodiment 3)
FIG. 5 is a schematic configuration diagram of an optical coupling structure according to Embodiment 3 of the present invention, and an example of lens arrangement when a condensing optical system is configured when signal light is coupled to the multicore optical fiber 1. FIG.
　この光結合構造２０Ａは、マルチコア光ファイバ１と、光ファイバ２と、光フィルタ３と、さらに図３、４のレンズ１０３に対応するレンズ４とを備えている。第１レンズであるレンズ４は、光フィルタ３を挟んでマルチコア光ファイバ１の端面に対向するように配置され、外部から入力された光、たとえば通信用の信号光を、マルチコア光ファイバ１で光増幅するためにマルチコア光ファイバ１に入力できるように構成されている。レンズ４は球面レンズ、非球面レンズ、分布屈折率型レンズ等であるが、特に限定はされない。 The optical coupling structure 20A includes a multi-core optical fiber 1, an optical fiber 2, an optical filter 3, and a lens 4 corresponding to the lens 103 in FIGS. The lens 4 as the first lens is disposed so as to face the end face of the multi-core optical fiber 1 with the optical filter 3 interposed therebetween, and light input from the outside, for example, signal light for communication is transmitted through the multi-core optical fiber 1. It is configured to be able to input to the multi-core optical fiber 1 for amplification. The lens 4 is a spherical lens, an aspheric lens, a distributed refractive index lens, or the like, but is not particularly limited.
　また、光フィルタ３の反射面３ａ（図１参照）は、光ファイバ２から出力される光Ｌ１の波長の光を全反射し、信号光が含まれる波長帯の光を透過する誘電体多層膜が形成される。また、反射面３ａとは反対側の面も、信号光が含まれる波長帯の光を透過する誘電体多層膜が形成される。 The reflective surface 3a (see FIG. 1) of the optical filter 3 totally reflects the light having the wavelength of the light L1 output from the optical fiber 2, and transmits the light having the wavelength band including the signal light. Is formed. A dielectric multilayer film that transmits light in a wavelength band including signal light is also formed on the surface opposite to the reflecting surface 3a.
　なお、図５では、マルチコア光ファイバ１のコア部１ａのうち、外周側に配置されたコア部のうち２つをコア部１ａ１、１ａ２として示してあり、他のコア部は記載を省略してある。 In FIG. 5, two of the core portions 1a1 and 1a2 arranged on the outer peripheral side of the core portion 1a of the multi-core optical fiber 1 are shown as core portions 1a1 and 1a2, and the other core portions are not shown. is there.
　ここで、この光結合構造２０Ａでは、レンズ４の焦点距離をｆとすると、マルチコア光ファイバ１の端面１ｄは、レンズ４から、レンズ４の焦点距離ｆよりも遠い位置に配置されている。すなわち、マルチコア光ファイバ１の端面１ｄとレンズ４との距離をａとすると、ｆ＜ａが成り立つ。すると、外部から入力された信号光のビームＢ１、Ｂ２が、レンズ４によって、端面１ｄにおけるコア部１ａ１、１ａ２のそれぞれに集光するとき、ビームＢ１、Ｂ２のビームウエストＷ１、Ｗ２は、レンズ４から距離ｂの位置となる。ここで、ｂについては、１／ｆ＝１／ａ＋１／ｂの関係が成り立つ。なお、他のコア部１ａに入力されるべき信号光のビームも、ビームＢ１、Ｂ２と同様にレンズ４から距離ｂの位置となる。 Here, in this optical coupling structure 20A, when the focal length of the lens 4 is f, the end face 1d of the multi-core optical fiber 1 is disposed at a position farther from the lens 4 than the focal length f of the lens 4. That is, if the distance between the end face 1d of the multi-core optical fiber 1 and the lens 4 is a, f <a holds. Then, when the beams B1 and B2 of the signal light input from the outside are condensed on the core portions 1a1 and 1a2 on the end face 1d by the lens 4, the beam waists W1 and W2 of the beams B1 and B2 are To the position of distance b. Here, for b, the relationship 1 / f = 1 / a + 1 / b is established. The beam of signal light to be input to the other core portion 1a is also at a distance b from the lens 4 like the beams B1 and B2.
（実施の形態４）
　図６は、実施の形態４に係る光結合構造の模式的な構成図であって、マルチコア光ファイバ１に信号光を結合する際に平行光学系を構成する場合のレンズ配置例２を説明する図である。 (Embodiment 4)
FIG. 6 is a schematic configuration diagram of an optical coupling structure according to the fourth embodiment, and illustrates a lens arrangement example 2 in a case where a parallel optical system is configured when signal light is coupled to the multi-core optical fiber 1. FIG.
　この光結合構造２０Ｂは、図５に示す光結合構造２０Ａと比較すると、マルチコア光ファイバ１の端面１ｄが、レンズ４の略焦点距離ｆの位置に配置されている点が異なり、その他の構成は同様である。すると、外部から入力された信号光のビームＢ１、Ｂ２を平行光としてレンズ４に入力したときに、端面１ｄにおけるコア部１ａ１、１ａ２のそれぞれに集光する。なお、他のコア部１ａの入力されるべき信号光のビームも、ビームＢ１、Ｂ２と同様である。 This optical coupling structure 20B is different from the optical coupling structure 20A shown in FIG. 5 in that the end face 1d of the multi-core optical fiber 1 is disposed at a position substantially at the focal length f of the lens 4, and the other configurations are as follows. It is the same. Then, when the externally input signal light beams B1 and B2 are input to the lens 4 as parallel light, they are condensed on the core portions 1a1 and 1a2 on the end face 1d. The beam of signal light to be input to the other core unit 1a is the same as the beams B1 and B2.
　レンズ４の配置については、光結合構造２０Ａ、２０Ｂのレンズ配置例１、２のいずれの配置も利用できる。 As for the arrangement of the lens 4, any arrangement of the lens arrangement examples 1 and 2 of the optical coupling structures 20A and 20B can be used.
（実施の形態５）
　図７は、本発明の実施の形態５に係る光結合構造の模式的な構成図であって、図５に示すレンズ配置例１を採用した場合の信号光入力部の構成例１を示す図である。 (Embodiment 5)
FIG. 7 is a schematic configuration diagram of the optical coupling structure according to the fifth embodiment of the present invention, and is a diagram illustrating a configuration example 1 of the signal light input unit when the lens arrangement example 1 illustrated in FIG. 5 is employed. It is.
　この光結合構造３０Ａは、マルチコア光ファイバ１と、光ファイバ２と、光フィルタ３と、レンズ４と、信号光結合用マルチコア光ファイバとしてのマルチコア光ファイバ５と、第２レンズであるレンズ６と、光路変位光学素子としてのプリズム７、８と、光アイソレータ９とを備えている。 The optical coupling structure 30A includes a multi-core optical fiber 1, an optical fiber 2, an optical filter 3, a lens 4, a multi-core optical fiber 5 as a multi-core optical fiber for signal light coupling, and a lens 6 that is a second lens. , Prisms 7 and 8 as optical path displacement optical elements, and an optical isolator 9 are provided.
　マルチコア光ファイバ５は、マルチコア光ファイバ１とのコア部１ａと同様に配置された、石英系ガラスからなる７つの複数のコア部５ａと、７つのコア部５ａの外周に形成された、たとえばコア部５ａよりも屈折率が低い石英系ガラスからなるクラッド部５ｂとを備えている。なお、図７では、マルチコア光ファイバ５のコア部５ａのうち、外周側に配置された２つのコア部をコア部５ａ１、５ａ２として示してあり、他のコア部は記載を省略してある。マルチコア光ファイバ５はマルチコア光ファイバ１にて光増幅させるための信号光を入力するためのものである。 The multi-core optical fiber 5 is arranged in the same manner as the core portion 1a with the multi-core optical fiber 1 and is formed on the outer periphery of the seven core portions 5a made of quartz glass and the seven core portions 5a, for example, And a clad portion 5b made of quartz glass having a refractive index lower than that of the portion 5a. In FIG. 7, of the core portions 5 a of the multicore optical fiber 5, two core portions arranged on the outer peripheral side are shown as core portions 5 a 1 and 5 a 2, and the other core portions are not shown. The multi-core optical fiber 5 is for inputting signal light for optical amplification by the multi-core optical fiber 1.
　レンズ６は、マルチコア光ファイバ５の端面に対向するように配置されており、マルチコア光ファイバ５のコア部５ａから出力された信号光を、その光軸およびビームウエストが、信号光のビームＢ１、Ｂ２の光軸およびビームウエストＷ１、Ｗ２と略一致するように空間伝搬させて、コア部１ａ１、１ａ２に結合させるものである。 The lens 6 is disposed so as to face the end face of the multi-core optical fiber 5, and the optical axis and beam waist of the signal light output from the core portion 5 a of the multi-core optical fiber 5 have the signal light beam B 1, It is spatially propagated so as to substantially coincide with the optical axis of B2 and the beam waists W1 and W2, and is coupled to the core portions 1a1 and 1a2.
　第２光路変位光学素子としてのプリズム７は、レンズ６を挟んでマルチコア光ファイバ５の端面５ｃに対向するように配置されている。第１光路変位光学素子としてのプリズム８は、レンズ４を挟んでマルチコア光ファイバ１の端面１ｄに対向するように配置されている。プリズム７、８は、入射された光の光路を変位させるための傾斜面７ａ、８ａと、光軸に垂直な平行面７ｂ、８ｂをそれぞれ有する。図８Ａは、図７に示すプリズム７（８）の模式図である。プリズム７、８の傾斜面７ａ、８ａは、正ｎ角錐の頂部を中心軸に垂直な面で切断したような形状をしている。ここで、ｎはマルチコア光ファイバ１、５のコア部の数（ただし略同心円状に並んだコア部の数）に等しい。したがって、図８Ａの場合はｎ＝６である。なお、ｎ＝８の場合は、図８Ｂに示す正８角錐形状のプリズムを用いることができる。ここで、レンズの光軸をマルチコア光ファイバの中心軸上に置きかつ焦点位置をマルチコア光ファイバの中心にする。このとき、マルチコア光ファイバ５のコア部５ａ１、５ａ２から出力された光の進行角度が決まる。この進行角度で進んだ光が、正ｎ角錐の一面、二面（平行面と傾斜面）に入射し、スネルの法則に従って屈折する。この屈折角度が光ファイバの中心軸と平行になるように正ｎ角錐の角度、レンズの焦点距離を決める。傾斜面７ａ、８ａは、マルチコア光ファイバ１、５の外周側のコア部に対応させて形成されている。マルチコア光ファイバ１、５の中心のコア部に入出力される信号光が通過する部分は、平行面７ｂ、８ｂに平行な平行面７ｃ、８ｃとなっている。プリズム７、８はたとえば石英ガラスやＢＫ７、ＳＦ６等のガラスからなる。 The prism 7 as the second optical path displacement optical element is disposed so as to face the end surface 5c of the multi-core optical fiber 5 with the lens 6 interposed therebetween. The prism 8 as the first optical path displacement optical element is disposed so as to face the end surface 1 d of the multicore optical fiber 1 with the lens 4 interposed therebetween. The prisms 7 and 8 have inclined surfaces 7a and 8a for displacing the optical path of incident light, and parallel surfaces 7b and 8b perpendicular to the optical axis, respectively. FIG. 8A is a schematic diagram of the prism 7 (8) shown in FIG. The inclined surfaces 7a and 8a of the prisms 7 and 8 are shaped such that the tops of the regular n-pyramids are cut by a plane perpendicular to the central axis. Here, n is equal to the number of core portions of the multi-core optical fibers 1 and 5 (however, the number of core portions arranged substantially concentrically). Therefore, in the case of FIG. 8A, n = 6. When n = 8, a regular octagonal pyramid shaped prism shown in FIG. 8B can be used. Here, the optical axis of the lens is placed on the central axis of the multi-core optical fiber and the focal position is set to the center of the multi-core optical fiber. At this time, the traveling angle of the light output from the core portions 5a1 and 5a2 of the multi-core optical fiber 5 is determined. The light traveling at this traveling angle is incident on one or two surfaces (parallel surface and inclined surface) of the regular n-pyramid and refracted according to Snell's law. The angle of the positive n pyramid and the focal length of the lens are determined so that this refraction angle is parallel to the central axis of the optical fiber. The inclined surfaces 7 a and 8 a are formed so as to correspond to the core portions on the outer peripheral side of the multi-core optical fibers 1 and 5. Portions through which signal light input / output to / from the central core portion of the multi-core optical fibers 1 and 5 pass are parallel surfaces 7c and 8c parallel to the parallel surfaces 7b and 8b. The prisms 7 and 8 are made of glass such as quartz glass or BK7 or SF6.
　プリズム７、８の間には光アイソレータ９が配置されている。光アイソレータ９は、マルチコア光ファイバ５側から入力された光を透過し、マルチコア光ファイバ１側から入力された光をほとんど透過しないように構成されている。 An optical isolator 9 is disposed between the prisms 7 and 8. The optical isolator 9 is configured to transmit light input from the multi-core optical fiber 5 side and hardly transmit light input from the multi-core optical fiber 1 side.
　また、図７に示すように、光アイソレータ９の位置においてビームＢ１、Ｂ２のビームウエストＷ１、Ｗ２が形成されるように、レンズ４、６が配置される。 Further, as shown in FIG. 7, the lenses 4 and 6 are arranged so that the beam waists W1 and W2 of the beams B1 and B2 are formed at the position of the optical isolator 9.
　図７に示すように、プリズム７は、マルチコア光ファイバ５のコア部５ａ１、５ａ２から出力し、レンズ６を介して各信号光が入力されるように配置される。そして、プリズム７から出力した各信号光は、その各々の光軸が互いに平行になるようになっている。また、プリズム８は、マルチコア光ファイバ５のコア部５ａ１、５ａ２から出力され、プリズム７によって光軸が平行にされた信号光のビームＢ１、Ｂ２を、レンズ４を介してマルチコア光ファイバ１のコア部１ａ１、１ａ２に互いに平行な光軸で入力させることができるように、傾斜面８ａの傾斜角が設定されている。マルチコア光ファイバ５の他のコア部から出力された信号光のビームも同様である。このように、プリズム７、８によって、マルチコア光ファイバ５からマルチコア光ファイバ１への信号光の入力を低損失で行うことができる。このようにマルチコア光ファイバ１へ入力された信号光は、光ファイバ２から入力された励起光である光Ｌ１によって光励起されたコア部１ａを伝搬しながら、光増幅される。 7, the prism 7 is arranged so that each signal light is output from the core portions 5 a 1 and 5 a 2 of the multi-core optical fiber 5 and inputted through the lens 6. The signal lights output from the prism 7 have their optical axes parallel to each other. The prism 8 outputs the signal light beams B 1 and B 2 output from the core portions 5 a 1 and 5 a 2 of the multi-core optical fiber 5 and whose optical axes are made parallel by the prism 7 via the lens 4 to the core of the multi-core optical fiber 1. The inclination angle of the inclined surface 8a is set so that the parts 1a1 and 1a2 can be input with optical axes parallel to each other. The same applies to the beam of signal light output from the other core portion of the multi-core optical fiber 5. As described above, the prisms 7 and 8 can input signal light from the multi-core optical fiber 5 to the multi-core optical fiber 1 with low loss. Thus, the signal light input to the multi-core optical fiber 1 is optically amplified while propagating through the core portion 1a optically pumped by the light L1 that is pumping light input from the optical fiber 2.
（実施の形態６）
　図９は、本発明の実施の形態６に係る光結合構造の模式的な構成図であって、図６に示すレンズ配置例２を採用した場合の信号光入力部の構成例２を示す図である。 (Embodiment 6)
FIG. 9 is a schematic configuration diagram of the optical coupling structure according to the sixth embodiment of the present invention, and shows a configuration example 2 of the signal light input unit when the lens arrangement example 2 shown in FIG. 6 is adopted. It is.
　この光結合構造３０Ｂは、図７に示す光結合構造３０Ａと比較すると、図６に示すレンズ配置例２を採用した点が異なり、その他の構成は同様である。 This optical coupling structure 30B is different from the optical coupling structure 30A shown in FIG. 7 in that the lens arrangement example 2 shown in FIG. 6 is adopted, and other configurations are the same.
　信号光入力部の構成については、光結合構造３０Ａ、３０Ｂの構成例１、２のいずれの構成も利用できる。なお、図７に示す集光光学系のレンズ配置例１を採用した光結合構造３０Ａの方が、ビームの角度ずれに対するトレランスが大きいので、プリズム７、８の傾斜面７ａ、８ａの製造誤差に対する許容値が大きい点で好ましい。一方、図９に示す平行光学系のレンズ配置例２を採用した光結合構造３０Ｂの方が、作製するときの光学素子の位置調整がより容易である点で好ましい。 As for the configuration of the signal light input unit, any of the configurations 1 and 2 of the optical coupling structures 30A and 30B can be used. Note that the optical coupling structure 30A that employs the lens arrangement example 1 of the condensing optical system shown in FIG. 7 has a greater tolerance to the angular deviation of the beam, and therefore is free from manufacturing errors of the inclined surfaces 7a and 8a of the prisms 7 and 8. This is preferable because the tolerance value is large. On the other hand, the optical coupling structure 30B adopting the parallel optical system lens arrangement example 2 shown in FIG. 9 is preferable in that it is easier to adjust the position of the optical element when it is manufactured.
　本実施の形態で用いられる光アイソレータ９は、たとえば楔形プリズムとガーネット結晶とを用いた１段型構造、または偏波モード分散をキャンセルする構造を有する２段型構造のような公知のものであるが、特に限定はされない。楔形プリズムを用いた光アイソレータとは、たとえば、光入出射面が非平行になるように楔型に成形された複屈折光学結晶を信号光の入出射側に、その複数の複屈折光学結晶間に４５度偏波面回転素子および４５度回転ファラデー素子を備えることで、光伝送方向の信号光のみが光ファイバのコア部に結合するように構成された光アイソレータである。 The optical isolator 9 used in the present embodiment is a known one such as a one-stage structure using a wedge prism and a garnet crystal, or a two-stage structure having a structure for canceling polarization mode dispersion. However, there is no particular limitation. An optical isolator using a wedge-shaped prism is, for example, a birefringent optical crystal formed in a wedge shape so that the light incident / exit surfaces are not parallel to each other on the signal light incident / exit side. The optical isolator is configured so that only the signal light in the optical transmission direction is coupled to the core portion of the optical fiber by including the 45-degree polarization plane rotation element and the 45-degree rotation Faraday element.
　なお、図９のような平行光学系を用いた場合には、ビーム角度ずれに対するトレランスが小さいため、楔型プリズムを使用した光アイソレータを用いると、戻り光の光軸が光伝送方向の信号光の光軸に対し角度ずれを持つこととなり、戻り光を効果的に遮断できるので好ましい。 When the parallel optical system as shown in FIG. 9 is used, the tolerance against the beam angle deviation is small. Therefore, when an optical isolator using a wedge prism is used, the optical axis of the return light is the signal light in the optical transmission direction. This is preferable because it has an angular deviation with respect to the optical axis of the optical axis and can effectively block the return light.
　また、図７のような集光光学系を用いた場合には、光軸に垂直方向のビーム位置ずれに対するトレランスが小さいため、複屈折結晶として平行平板型のものを使用した光アイソレータを用いると、戻り光の光軸が光伝送方向の信号光の光軸に対し位置ずれを持つこととなり、戻り光を効果的に遮断できるので好ましい。 In addition, when the condensing optical system as shown in FIG. 7 is used, since the tolerance for the beam position deviation in the direction perpendicular to the optical axis is small, an optical isolator using a parallel plate type as a birefringent crystal is used. The optical axis of the return light has a positional deviation with respect to the optical axis of the signal light in the optical transmission direction, which is preferable because the return light can be effectively blocked.
　なお、光結合構造３０Ａ、３０Ｂでは、プリズム７、８は、平行面７ｂ、８ｂが対向するように配置されているが、傾斜面７ａ、８ａが対向するように配置してもよい。また、プリズム７、８に代えて、平行面７ｂ、８ｂが無く、両面が傾斜したプリズムを用いても良い。あるいは、プリズム７、８に代えて、光路変位光学素子としてのレンズを用いても良い。 In the optical coupling structures 30A and 30B, the prisms 7 and 8 are arranged so that the parallel surfaces 7b and 8b are opposed to each other, but the inclined surfaces 7a and 8a may be arranged so as to be opposed to each other. Further, instead of the prisms 7 and 8, a prism having no parallel surfaces 7b and 8b and inclined on both sides may be used. Alternatively, instead of the prisms 7 and 8, a lens as an optical path displacement optical element may be used.
　なお、プリズム７、８に代えてレンズを用いる場合は、該レンズの焦点距離がそれぞれレンズ４、６よりも長いものを用いることが好ましい。これにより、光路変位光学素子の間で互いに平行になった各信号光の光軸間の間隔がマルチコア光ファイバのコア間の間隔より大きくなるため、各信号光同士が干渉しにくくなる。これは、たとえば、プリズム７の代わりにレンズ６より焦点距離の長いレンズを、プリズム８の代わりにレンズ４より焦点距離の長いレンズを用いることで実現される。 In addition, when using a lens instead of the prisms 7 and 8, it is preferable to use a lens having a focal length longer than that of the lenses 4 and 6, respectively. Accordingly, the distance between the optical axes of the signal lights parallel to each other between the optical path displacement optical elements is larger than the distance between the cores of the multi-core optical fiber, so that the signal lights are less likely to interfere with each other. For example, this is realized by using a lens having a longer focal length than the lens 6 instead of the prism 7 and using a lens having a longer focal length than the lens 4 instead of the prism 8.
　更に、光路変位光学素子の間で互いに平行になった各信号光は、その伝搬方向と垂直な面内におけるビームの広がりが互いに重なり合わない程度の間隔にするとより好ましい。 Further, it is more preferable that the signal lights parallel to each other between the optical path displacement optical elements are spaced so that the beam spreads in the plane perpendicular to the propagation direction do not overlap each other.
　また、信号光を入力するために、マルチコア光ファイバ５の代わりに、図１０に示すような光ファイババンドル５Ａを使用しても良い。光ファイババンドル５Ａは、コア部５Ａａ１とクラッド部５Ａａ２とを備える７つの光ファイバ５Ａａを束ねて一体化したものである。 Further, an optical fiber bundle 5A as shown in FIG. 10 may be used in place of the multi-core optical fiber 5 in order to input signal light. The optical fiber bundle 5A is formed by bundling and integrating seven optical fibers 5Aa including a core portion 5Aa1 and a cladding portion 5Aa2.
（実施の形態７）
　図１１は、本発明の実施の形態７に係る光結合構造の模式的な構成図である。光結合構造１０Ａは、図１に示す実施の形態１に係る光結合構造１０において、光ファイバ２を光ファイバ２Ａに置き換えたものである。 (Embodiment 7)
FIG. 11 is a schematic configuration diagram of an optical coupling structure according to Embodiment 7 of the present invention. The optical coupling structure 10A is obtained by replacing the optical fiber 2 with the optical fiber 2A in the optical coupling structure 10 according to the first embodiment shown in FIG.
　光ファイバ２Ａは、ステップインデックス型の屈折率分布を有する光ファイバ部２Ａ１と、光ファイバ２Ａの端面２Ａａ側に配置された、分布屈折率型の光ファイバ部２Ａ２とを有する。この光ファイバ２Ａでは、分布屈折率型の光ファイバ部２Ａ２によって光Ｌ１をある程度集光させ、平行光または集光光として出力するので、結合効率をより高めることができる。 The optical fiber 2A includes an optical fiber portion 2A1 having a step index type refractive index distribution, and a distributed refractive index type optical fiber portion 2A2 disposed on the end face 2Aa side of the optical fiber 2A. In this optical fiber 2A, since the light L1 is condensed to some extent by the distributed refractive index type optical fiber portion 2A2 and output as parallel light or condensed light, the coupling efficiency can be further increased.
　なお、上記実施の形態では、マルチコア光ファイバ１はダブルクラッド型増幅光ファイバであるが、コア部に光増幅媒体が添加されていないマルチコア光ファイバに置き換えても良い。この場合、光Ｌ１は励起光でなくてもよい。また、光ファイバ２はマルチモード光ファイバにかぎられず、シングルモード光ファイバでもよい。 In the above embodiment, the multi-core optical fiber 1 is a double-clad amplification optical fiber, but may be replaced with a multi-core optical fiber in which no optical amplification medium is added to the core portion. In this case, the light L1 may not be excitation light. The optical fiber 2 is not limited to a multimode optical fiber, and may be a single mode optical fiber.
　また、上記実施の形態では、マルチコア光ファイバ５からマルチコア光ファイバ１へ信号光を入力させているが、光の相反性によって、マルチコア光ファイバ１から出力された増幅された信号光をマルチコア光ファイバ５に入力させる場合にも、上記実施の形態を適用できることは言うまでもない。 In the above embodiment, signal light is input from the multi-core optical fiber 5 to the multi-core optical fiber 1, but the amplified signal light output from the multi-core optical fiber 1 is converted into multi-core optical fiber due to reciprocity of light. Needless to say, the above-described embodiment can be applied to the case where the input is made to 5.
　なお、上記実施の形態により本発明が限定されるものではない。上述した各構成要素を適宜組み合わせて構成したものも本発明に含まれる。たとえば、上記実施の形態３～７に係る光結合構造のいずれについても、実施の形態２に係る光結合モジュールのように構成してもよい。また、さらなる効果や変形例は、当業者によって容易に導き出すことができる。よって、本発明のより広範な態様は、上記の実施の形態に限定されるものではなく、様々な変更が可能である。 The present invention is not limited by the above embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. For example, any of the optical coupling structures according to the above third to seventh embodiments may be configured like the optical coupling module according to the second embodiment. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.
　以上のように、本発明に係る光結合構造は、主に光通信の用途に利用して好適なものである。 As described above, the optical coupling structure according to the present invention is suitable mainly for use in optical communication.
　１、５　マルチコア光ファイバ
　１ａ、１ａ１、１ａ２、２ａ、５ａ、５ａ１、５ａ２、５Ａａ１　コア部
　１ｃ　外側クラッド部
　１ｂ　内側クラッド部
　１ｄ、２ｃ、２Ａａ、５ｃ　端面
　２、２Ａ、５Ａａ　光ファイバ
　２ｂ、５ｂ、５Ａａ２　クラッド部
　２Ａ１、２Ａ２　光ファイバ部
　３　光フィルタ
　３ａ　反射面
　４、６、１０３　レンズ
　５Ａ　光ファイババンドル
　７、８　プリズム
　７ａ、８ａ　傾斜面
　７ｂ、７ｃ、８ｂ、８ｃ　平行面
　９　光アイソレータ
　１０、１０Ａ、２０Ａ、２０Ｂ、３０Ａ、３０Ｂ　光結合構造
　１００　光結合モジュール
　１０１　フェルール
　１０１ａ　挿通孔
　１０１ｂ　傾斜面
　１０１ｃ　溝
　１０２　筐体
　１０２ａ　開口部
　１０４　レンズホルダ
　Ａ　傾斜角度
　Ｂ１、Ｂ２　ビーム
　Ｌ１　光
　Ｐ　光路長
　Ｖ　法線
　Ｗ１、Ｗ２　ビームウエスト
　Ｘ　軸 1, 5 Multi-core optical fiber 1a, 1a1, 1a2, 2a, 5a, 5a1, 5a2, 5Aa1 Core part 1c Outer cladding part 1b Inner cladding part 1d, 2c, 2Aa, 5c End face 2, 2A, 5Aa Optical fiber 2b, 5b, 5Aa2 Cladding portion 2A1, 2A2 Optical fiber portion 3 Optical filter 3a Reflecting surface 4, 6, 103 Lens 5A Optical fiber bundle 7, 8 Prism 7a, 8a Inclined surface 7b, 7c, 8b, 8c Parallel surface 9 Optical isolator 10, 10A, 20A, 20B, 30A, 30B Optical coupling structure 100 Optical coupling module 101 Ferrule 101a Insertion hole 101b Inclined surface 101c Groove 102 Housing 102a Opening 104 Lens holder A Inclination angle B1, B2 Beam L1 Light P Optical path length V Normal W1, W2 Beam waist X axis

Claims (16)

  1. 　複数のコア部と前記複数のコア部の外周に形成されたクラッド部とを有するマルチコア光ファイバと、
    　前記マルチコア光ファイバとは傾斜して配置されており、前記マルチコア光ファイバの端面に入力するための光を端面から出力する光ファイバと、
    　前記光ファイバの端面から出力した前記光を前記マルチコア光ファイバの端面に反射させるための光反射素子と、
    　を備え、前記マルチコア光ファイバの端面、前記光ファイバの端面、および前記光反射素子は近接して配置され、前記光は前記光ファイバから出力後に前記光反射素子のみを介して前記マルチコア光ファイバに入力することを特徴とする光結合構造。     A multi-core optical fiber having a plurality of core portions and a cladding portion formed on the outer periphery of the plurality of core portions;
    The multi-core optical fiber is arranged to be inclined, and an optical fiber that outputs light for inputting to the end face of the multi-core optical fiber from the end face;
    A light reflecting element for reflecting the light output from the end face of the optical fiber to the end face of the multi-core optical fiber;
    The end face of the multi-core optical fiber, the end face of the optical fiber, and the light reflecting element are disposed close to each other, and the light is output from the optical fiber to the multi-core optical fiber only through the light reflecting element. An optical coupling structure characterized by inputting.
  2. 　前記マルチコア光ファイバの端面は前記光ファイバとは反対側に傾斜する法線を有するように、前記マルチコア光ファイバの光軸に対して傾斜していることを特徴とする請求項１に記載の光結合構造。 2. The light according to claim 1, wherein an end face of the multi-core optical fiber is inclined with respect to an optical axis of the multi-core optical fiber so as to have a normal line that is inclined in a direction opposite to the optical fiber. Bond structure.
  3. 　前記マルチコア光ファイバと前記光ファイバとの傾斜角度が１５度～４５度であることを特徴とする請求項１または２に記載の光結合構造。 3. The optical coupling structure according to claim 1, wherein an inclination angle between the multi-core optical fiber and the optical fiber is 15 degrees to 45 degrees.
  4. 　前記光ファイバの端面から前記マルチコア光ファイバの端面までの前記光の光路長が１ｍｍ以下であることを特徴とする請求項１～３のいずれか一つに記載の光結合構造。 The optical coupling structure according to any one of claims 1 to 3, wherein an optical path length of the light from an end face of the optical fiber to an end face of the multi-core optical fiber is 1 mm or less.
  5. 　前記マルチコア光ファイバは、フェルールに挿通固定されており、前記光ファイバは前記フェルールに形成された保持部に保持されていることを特徴とする請求項１～４のいずれか一つに記載の光結合構造。 5. The light according to claim 1, wherein the multi-core optical fiber is inserted and fixed in a ferrule, and the optical fiber is held by a holding portion formed in the ferrule. Bond structure.
  6. 　前記フェルールは、前記光ファイバが出力する前記光に対して透明な材質からなることを特徴とする請求項５に記載の光結合構造。 The optical coupling structure according to claim 5, wherein the ferrule is made of a material transparent to the light output from the optical fiber.
  7. 　前記マルチコア光ファイバは、前記複数のコア部の少なくともいずれか一つに光増幅媒体が添加されたダブルクラッド型のマルチコア増幅光ファイバであり、前記光ファイバが出力する前記光は前記増幅媒体を光励起する励起光であることを特徴とする請求項１～６のいずれか一つに記載の光結合構造。 The multi-core optical fiber is a double-clad multi-core amplification optical fiber in which an optical amplification medium is added to at least one of the plurality of core portions, and the light output from the optical fiber optically pumps the amplification medium. 7. The optical coupling structure according to claim 1, wherein the optical coupling structure is excitation light.
  8. 　前記光反射素子を挟んで前記マルチコア増幅光ファイバの端面に対向するように配置され、前記マルチコア増幅光ファイバで光増幅をさせるための信号光を該マルチコア増幅光ファイバに入力できるように構成された第１レンズをさらに備えることを特徴とする請求項７に記載の光結合構造。 The multi-core amplification optical fiber is arranged so as to face the end surface of the multi-core amplification optical fiber with the light reflecting element interposed therebetween, and is configured to be able to input signal light for optical amplification with the multi-core amplification optical fiber to the multi-core amplification optical fiber. The optical coupling structure according to claim 7, further comprising a first lens.
  9. 　前記マルチコア増幅光ファイバの端面は、前記第１レンズから、該第１レンズの焦点距離よりも遠い位置に配置されていることを特徴とする請求項８に記載の光結合構造。 The optical coupling structure according to claim 8, wherein an end face of the multi-core amplification optical fiber is disposed at a position farther from the first lens than a focal length of the first lens.
  10. 　前記マルチコア増幅光ファイバの端面は、前記第１レンズの略焦点距離の位置に配置されていることを特徴とする請求項８に記載の光結合構造。 The optical coupling structure according to claim 8, wherein an end face of the multi-core amplification optical fiber is disposed at a position substantially at a focal length of the first lens.
  11. 　前記第１レンズを挟んで前記マルチコア増幅光ファイバの端面に対向するように配置された第１光路変位光学素子をさらに備え、前記第１光路変位光学素子は、該第１光路変位光学素子に入力された複数の前記信号光を、前記レンズを介して前記マルチコア増幅光ファイバに、互いに平行な光軸で入力させることができるように構成されていることを特徴とする請求項８～１０のいずれか一つに記載の光結合構造。 The optical system further includes a first optical path displacement optical element disposed to face an end face of the multi-core amplification optical fiber with the first lens interposed therebetween, and the first optical path displacement optical element is input to the first optical path displacement optical element 11. The apparatus according to claim 8, wherein the plurality of signal lights are input to the multi-core amplification optical fiber via the lenses with optical axes parallel to each other. The optical coupling structure according to any one of the above.
  12. 　前記第１光路変位光学素子はレンズまたはプリズムであることを特徴とする請求項１１に記載の光結合構造。 The optical coupling structure according to claim 11, wherein the first optical path displacement optical element is a lens or a prism.
  13. 　前記複数の信号光を前記マルチコア増幅光ファイバに出力する信号光結合用光ファイバと、
    　前記信号光結合用光ファイバの端面に対向するように配置された第２レンズと、
    　前記第２レンズを挟んで前記信号光結合用光ファイバの端面に対向するように配置された第２光路変位光学素子と、
    　をさらに備え、
    　前記第２レンズは、前記複数の信号光を前記マルチコア増幅光ファイバに結合させることができるように構成されており、
    　前記第２光路変位光学素子は、前記信号光結合用光ファイバから、前記第２レンズを介して入力された前記複数の信号光が、互いに平行な光軸で出力するように構成されていることを特徴とする請求項１１または１２に記載の光結合構造。     An optical fiber for signal light coupling that outputs the plurality of signal lights to the multi-core amplification optical fiber;
    A second lens disposed so as to face the end face of the signal light coupling optical fiber;
    A second optical path displacement optical element disposed so as to face the end face of the signal light coupling optical fiber with the second lens interposed therebetween;
    Further comprising
    The second lens is configured to be able to couple the plurality of signal lights to the multi-core amplification optical fiber,
    The second optical path displacement optical element is configured so that the plurality of signal lights input from the signal light coupling optical fiber via the second lens are output with optical axes parallel to each other. The optical coupling structure according to claim 11 or 12.
  14. 　前記第２光路変位光学素子はレンズまたはプリズムであることを特徴とする請求項１３に記載の光結合構造。 The optical coupling structure according to claim 13, wherein the second optical path displacement optical element is a lens or a prism.
  15. 　前記第１および第２光路変位光学素子の間に配置された光アイソレータをさらに備えることを特徴とする請求項１３または１４に記載の光結合構造。 The optical coupling structure according to claim 13 or 14, further comprising an optical isolator disposed between the first and second optical path displacement optical elements.
  16. 　前記光ファイバは、該光ファイバの端面側に配置された分布屈折率型の光ファイバ部を有することを特徴とする請求項１～１５のいずれか一つに記載の光結合構造。 The optical coupling structure according to any one of claims 1 to 15, wherein the optical fiber includes a distributed refractive index type optical fiber portion disposed on an end face side of the optical fiber.
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