WO2024111563A1 - Method for producing self-forming optical waveguide - Google Patents

Method for producing self-forming optical waveguide Download PDF

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Publication number
WO2024111563A1
WO2024111563A1 PCT/JP2023/041697 JP2023041697W WO2024111563A1 WO 2024111563 A1 WO2024111563 A1 WO 2024111563A1 JP 2023041697 W JP2023041697 W JP 2023041697W WO 2024111563 A1 WO2024111563 A1 WO 2024111563A1
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core
light
resin
forming
cores
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PCT/JP2023/041697
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French (fr)
Japanese (ja)
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興浩 杉原
英孝 寺澤
毅 行川
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国立大学法人宇都宮大学
Ｏｒｂｒａｙ株式会社
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Publication of WO2024111563A1 publication Critical patent/WO2024111563A1/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
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method
    • G02B6/138—Integrated optical circuits characterised by the manufacturing method by using polymerisation
    • 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

Definitions

  • the present invention relates to a method for manufacturing a self-written optical waveguide.
  • This optical waveguide has a core that is self-formed from photocurable resin.
  • the end of an optical fiber or the like is immersed in the photocurable resin, and light is irradiated from the optical fiber or the like into the photocurable resin, gradually hardening the photocurable resin, forming a self-forming optical waveguide at the end of the optical fiber or the like.
  • an optical connector comprises at least a ferrule and n self-forming optical waveguides (n: a natural number not including 0).
  • the ferrule has n optical fiber insertion holes, and an optical fiber is inserted into each optical fiber insertion hole.
  • the optical waveguide After the optical waveguide is formed, it is left for two minutes to promote mutual diffusion of the monomers at the boundary between the core and cladding, and then the cladding is formed by UV irradiation.
  • the core region of the photocurable resin only one of the monomers is consumed and polymerized, so a concentration gradient of the monomers occurs at the boundary between the core and cladding, promoting mutual diffusion and fulfilling the function of the cladding.
  • the entire photocurable resin by irradiating the entire photocurable resin with UV light, the entire core and cladding are cured and formed, resulting in the optical waveguide.
  • the present invention was made in consideration of the above problems, and aims to realize a method for manufacturing a self-written optical waveguide that can prevent poor coupling.
  • the photocurable resin includes a core-forming resin that is polymerized and hardened by light of a predetermined wavelength band being incident thereon and has a refractive index na, and a cladding-forming resin that is polymerized and hardened by light of an intensity equal to or greater than the intensity of the light incident on the core-forming resin and has a refractive index nb after hardening of nb ⁇ na, the two multi-core fibers are arranged opposite each other, and the photocurable resin is arranged between the multi-core fibers, and light of an intensity capable of polymerizing only the core-forming resin is incident on the photocurable resin in order from the cores of the two multi-core fibers, causing polymerization and hardening of the core
  • the method for manufacturing a self-forming optical waveguide according to the present invention can prevent the cores in each multicore fiber, which are formed by irradiating adjacent cores with light, from bonding with each other, thereby preventing poor bonding of the cores.
  • FIG. 1 is a front view showing a configuration of a multi-core fiber used in a method for manufacturing a self-written optical waveguide according to an embodiment of the present invention.
  • 1 is an explanatory diagram showing a part of a state in which a photocurable resin is disposed between two multi-core fibers in a manufacturing method of a self-written optical waveguide according to an embodiment of the present invention
  • FIG. 3 is an explanatory diagram showing a state in which light is incident from each core of two multi-core fibers into a photocurable resin to form a core portion of a self-written optical waveguide, starting from the state shown in FIG. 2 .
  • FIG. 4 is a perspective view showing the state of FIG. 3 excluding the photocurable resin and the transparent container.
  • FIG. 4 is an explanatory diagram showing a state in which light is made incident on and propagates through the core portions, starting from the state shown in FIG. 3, and leakage light is generated from each core portion.
  • FIG. FIG. 6 is an explanatory diagram showing a state in which each clad portion and a plurality of self-written optical waveguides are formed from the state shown in FIG. 5 .
  • 7 is a stereomicroscope image showing the state of FIG. 6.
  • a photocurable resin and two multicore fibers each having n cores are prepared, the photocurable resin includes a core-forming resin that is polymerized and hardened by light of a predetermined wavelength band being incident thereon and has a refractive index na, and a cladding-forming resin that is polymerized and hardened by light of an intensity equal to or greater than that of the light incident on the core-forming resin and has a refractive index nb after hardening of nb ⁇ na.
  • the two multicore fibers are arranged opposite each other, and a photocurable resin is arranged between the multicore fibers.
  • Light (hereinafter also simply referred to as "light") of an intensity capable of polymerizing only the core-forming resin is incident on the photocurable resin in order from the cores of the two multicore fibers, causing polymerization and hardening of the core-forming resin to form the core of the optical waveguide in the photocurable resin, and then a cladding is formed, thereby self-forming n optical waveguides in the photocurable resin.
  • the above manufacturing method makes it possible to prevent the cores in each multicore fiber from bonding together when they are formed by irradiating adjacent cores with light, thereby preventing poor bonding between the cores.
  • a photocurable resin 1 and a multicore fiber (3a, 3b) having n cores are prepared.
  • Two multicore fibers (3a, 3b) having the same structure are prepared.
  • n is a natural number of 2 or more, for example, 2 to 4.
  • n is not limited to the range exemplified here.
  • the transparent container 4 is filled with photocurable resin 1, and one end of each multicore fiber (3a, 3b) is immersed in the photocurable resin 1.
  • the photocurable resin 1 is disposed between the multicore fibers (3a, 3b), and the two multicore fibers (3a, 3b) are disposed facing each other with the photocurable resin 1 sandwiched between them.
  • the four cores (3a1-3a4, or 3b1-3b4) are arranged in two rows x two cores at equal angles (90° in FIG. 1) and equal intervals on the circumference of a circle centered on the center of the multicore fiber (3a, 3b).
  • the interval d between the cores (3a1-3a4, or 3b1-3b4) in the two multicore fibers (3a, 3b) is 50 ⁇ m.
  • the interval d is the distance between the centers of the two cores.
  • the cutoff wavelength is 1300 nm to 1500 nm
  • the mode field diameter is 7.4 ⁇ m to 8.5 ⁇ m (propagating light wavelength 1550 nm).
  • the end faces (3a5, 3b5) of the multicore fibers (3a, 3b) immersed in the photocurable resin 1 are formed to have a planar shape perpendicular to the optical axis direction of each core (3a1 to 3a4 or 3b1 to 3b4) as shown in FIG. 2.
  • the end faces (3a5, 3b5) are subjected to flat polishing.
  • the photocurable resin 1 includes a resin for forming the core portion and a resin for forming the cladding portion.
  • the resin for forming the core portion has a refractive index na as a result of being polymerized and cured when light of a specific wavelength band is incident on it.
  • the resin for forming the cladding portion is polymerized and cured when light of the same or different wavelength band as the wavelength band of the light incident on the resin for forming the core portion and of an intensity equal to or greater than that of the light incident on the resin for forming the core portion is incident on it.
  • the refractive index nb of the resin for forming the cladding portion after curing is nb ⁇ na.
  • the resin used to form the core and the resin used to form the cladding resins that undergo photopolymerization via different polymerization reactions are selected.
  • the resin used to form the core is an acrylic resin
  • the resin used to form the cladding is an epoxy resin.
  • the acrylic resin has a faster polymerization reaction rate than the epoxy resin, so only the acrylic resin is selectively polymerized by light of low intensity.
  • Acrylic resins and epoxy resins are solutions in which a photopolymerization initiator is added to a mixture of two or more types of monomers.
  • the light incident on the photocurable resin 1 is laser light with an intensity that allows polymerization of only the resin for forming the core portion.
  • the wavelength ⁇ w of the light can be set arbitrarily depending on the photopolymerization initiator, but one example is 365 nm to 1675 nm, and in this embodiment, ⁇ w is set to 405 nm. Additionally, the wavelength band to which the photopolymerization initiator is sensitive is also set to around 405 nm.
  • each multicore fiber (3a, 3b) When light is incident from the cores (3a1 to 3a4, or 3b1 to 3b4) to the photocurable resin 1, in each multicore fiber (3a, 3b), light is incident in sequence to the n cores.
  • “in sequence” means that when light is incident in sequence to the n cores in each multicore fiber (3a, 3b), during the time when light is incident on a certain core, light is not incident on any other cores of the same multicore fiber.
  • the multicore fiber 3a during the time when light is incident on the core 3a1, light is not incident on the cores 3a2, 3a3, and 3a4, and in the multicore fiber 3b, during the time when light is incident on the core 3b1, light is not incident on the cores 3b2, 3b3, and 3b4.
  • light may or may not be incident on the cores of the other multicore fiber.
  • cores are sequentially formed between each core in the order of core 3a1 (or 3b1) ⁇ 3a2 (or 3b4) ⁇ 3a3 (or 3b3) ⁇ 3a4 (or 3b2), and after the self-formation of the cores between each core is completed, the self-formation of the cores between the next cores is performed.
  • the reason for using such a light incidence process is that it is possible to prevent the cores formed by the light irradiation of adjacent cores in each multi-core fiber (3a, 3b) from bonding with each other, and thus prevent poor bonding of the cores.
  • the diameter of the cores (2a1, 2b1, 2c1, 2d1) is preferably the same as the diameter of each core (3a1-3a4, or 3b1-3b4) of the multicore fiber (3a, 3b), and it is preferable that each core (2a1, 2b1, 2c1, 2d1) has a uniform diameter in the optical axis direction. Furthermore, the mode field diameter of each core (2a1, 2b1, 2c1, 2d1) is the same (7.4 ⁇ m-8.5 ⁇ m) as the mode field diameter of each core (3a1-3a4, or 3b1-3b4) of the multicore fiber (3a, 3b).
  • the self-formation of the cladding portion will be described.
  • the interdiffusion of monomers is generated in the cladding portion forming resin in the photocurable resin 1 around the core portions (2a1, 2b1, 2c1, 2d1) (the boundary surface between the core portions 2a1, 2b1, 2c1, 2d1 and the other photocurable resin 1).
  • the monomers While the monomers are consumed and polymerized in the core portion (2a1, 2b1, 2c1, 2d1) region, the monomers in the photocurable resin 1 outside the core portions (2a1, 2b1, 2c1, 2d1) have not polymerized and are uncured and unconsumed, so a concentration gradient of the monomers is generated around the core portions (2a1, 2b1, 2c1, 2d1) and interdiffusion progresses.
  • the core portions (2a1, 2b1, 2c1, 2d1) were left to stand for 2 minutes after formation to promote interdiffusion of the monomers.
  • Light with an intensity equal to or greater than that of the light that polymerized the resin forming the core portion is made to enter the core portion (2a1, 2b1, 2c1, 2d1).
  • this intensity is set to be sufficient to polymerize the resin forming the cladding portion.
  • the light continues to propagate, causing light leakage from the cores (2a1, 2b1, 2c1, 2d1) to the uncured cladding resin surrounding the cores (2a1, 2b1, 2c1, 2d1).
  • the cladding resin surrounding the cores (2a1, 2b1, 2c1, 2d1) is then polymerized and cured by the leaking light shown by the arrows in FIG. 5, and the cladding (2a2, 2b2, 2c2, 2d2) is self-formed in a form that surrounds the surface of the cores (2a1, 2b1, 2c1, 2d1).
  • the arrows in FIG. 5 are only shown for one core 2a1, but light leakage also occurs in the other cores (2b1, 2c1, 2d1).
  • the cladding 2d2 is not shown, it is a self-formed cladding that surrounds the surface of the core 2d1.
  • the refractive index nb of the cladding (2a2, 2b2, 2c2, 2d2) self-formed shows nb ⁇ na, where na is the refractive index of the core (2a1, 2b1, 2c1, 2d1). Therefore, multiple self-formed optical waveguides (2a, 2b, 2c, 2d) are self-formed by the core (2a1, 2b1, 2c1, 2d1) and cladding (2a2, 2b2, 2c2, 2d2).
  • Self-formed optical waveguide 2a consists of core 2a1 and cladding 2a2.
  • Self-formed optical waveguide 2b consists of core 2b1 and cladding 2b2
  • self-formed optical waveguide 2c consists of core 2c1 and cladding 2c2
  • self-formed optical waveguide 2d consists of core 2d1 and cladding 2d2.
  • UV light is uniformly applied around the transparent container 4 to harden all of the unreacted photocurable resin 1 (see Figures 6 and 7).
  • the light for forming the cladding portions (2a2, 2b2, 2c2, 2d2) may be incident on all the core portions (2a1, 2b1, 2c1, 2d1) simultaneously from all the cores (3a1-3a4 or 3b1-3b4) of each multicore fiber (3a, 3b), or may be incident on each core portion (2a1, 2b1, 2c1, 2d1) one by one in sequence.
  • complex incident time control is not required, and the time required for forming the cladding portions (2a2, 2b2, 2c2, 2d2) can be shortened, which is preferable.
  • the cladding portions (2a2, 2b2, 2c2, 2d2) using light leakage from the core portions (2a1, 2b1, 2c1, 2d1), the occurrence of cure shrinkage of the entire photocurable resin 1 except for the core portions (2a1, 2b1, 2c1, 2d1) is prevented, and it is possible for the resin that cures when forming the cladding portions (2a2, 2b2, 2c2, 2d2) to be the only resin used to form the cladding portions. This prevents stress from occurring throughout the photocurable resin 1, making it possible to suppress deformation of the core portions (2a1, 2b1, 2c1, 2d1), and suppressing an increase in the light insertion loss into the core portions (2a1, 2b1, 2c1, 2d1).
  • the cladding portions (2a2, 2b2, 2c2, 2d2) by light leakage, it becomes possible to control the diameter and thickness of each cladding portion, and it is also possible to stabilize the optical and mechanical properties of the self-forming optical waveguides (2a, 2b, 2c, 2d).
  • the hardening of all clad portions (2a2, 2b2, 2c2, 2d2) can be completed without irradiating the photocurable resin 1 with UV light from the periphery when forming the clad portions (2a2, 2b2, 2c2, 2d2), so it is possible to prevent an increase in the optical insertion loss for each core portion (2a1, 2b1, 2c1, 2d1).
  • optical waveguide 2a is shown as channel 1
  • optical waveguide 2b is shown as channel 2
  • optical waveguide 2c is shown as channel 3
  • optical waveguide 2d is 500 ⁇ m.
  • the present invention is applicable not only to the manufacturing method of self-forming optical waveguides between multicore fibers, but also to the field of high-density optical packaging, such as the manufacturing method of self-forming optical waveguides between multicore fibers and silicon optical waveguides, or between multicore optical fibers and polymer optical waveguides.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Optical Couplings Of Light Guides (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
  • Optical Integrated Circuits (AREA)

Abstract

Provided is a method for producing a self-forming optical waveguide. A photocurable resin and two multi-core fibers (3a, 3b) having n cores (3a1 to 3a4, 3b1 to 3b4) (n: a natural number of 2 or more) are prepared. A photocurable resin (4) comprises: a core portion-forming resin that polymerizes and cures upon incidence of light in a predetermined wavelength band to have a refractive index na; and a cladding portion-forming resin that polymerizes and cures upon incidence of light having an intensity greater than or equal to that of the light incident on the core portion-forming resin to have a refractive index nb after curing of nb<na. The two multi-core fibers (3a, 3b) are arranged to face each other, and the photocurable resin (4) is arranged between the multi-core fibers (3a, 3b). Light is sequentially incident on the photocurable resin from the cores (3a1 to 3a4, 3b1 to 3b4) of the two multi-core fibers to form core portions (2a1 to 2d1). Subsequently, cladding portions (2a2 to 2d2) are formed.

Description

自己形成光導波路の製造方法Method for manufacturing self-written optical waveguide 関連出願の相互参照CROSS-REFERENCE TO RELATED APPLICATIONS
　本出願は、２０２２年１１月２１日出願の日本特願２０２２－１８５６５４号の優先権を主張し、その全記載は、ここに特に開示として援用される。 This application claims priority to Japanese Patent Application No. 2022-185654, filed November 21, 2022, the entire disclosure of which is expressly incorporated herein by reference.
　本発明は、自己形成光導波路の製造方法に関する。 The present invention relates to a method for manufacturing a self-written optical waveguide.
　光技術を利用した光通信、光情報処理、電子機器、或いは光学機器等の分野が進展しており、各種光デバイス間に於ける光導波路の開発が課題となっている。各種光デバイスは光ファイバ等の光導波路によって光学的に接続されるが、その接続には極めて高い位置精度が要求される。従来このような接続作業は、手作業若しくは高精度な調芯設備により行われている為、接続コストが上がってしまうという問題があった。 With the advancement of optical technology in the fields of optical communications, optical information processing, electronic devices, and optical devices, the development of optical waveguides between various optical devices has become an issue. Various optical devices are optically connected by optical waveguides such as optical fibers, but these connections require extremely high positional accuracy. Conventionally, such connection work has been performed manually or using high-precision alignment equipment, which has led to the problem of increased connection costs.
　そこでこのような問題を解決する為、自己形成光導波路が開発されている。この光導波路は、光硬化性樹脂から光導波路のコアを自己形成した光導波路である。光ファイバ等の端部を光硬化性樹脂に浸漬し、その光ファイバ等から光硬化性樹脂に光を入射して光硬化性樹脂を徐々に硬化させることで、光ファイバ等の端部に自己形成光導波路を形成する。 In order to solve these problems, a self-forming optical waveguide has been developed. This optical waveguide has a core that is self-formed from photocurable resin. The end of an optical fiber or the like is immersed in the photocurable resin, and light is irradiated from the optical fiber or the like into the photocurable resin, gradually hardening the photocurable resin, forming a self-forming optical waveguide at the end of the optical fiber or the like.
　このような自己形成光導波路として、例えば国際公開第２０２０／２０９３６４号（その全記載は、ここに特に開示として援用される）が挙げられる。国際公開第２０２０／２０９３６４号に依れば光コネクタが、少なくともフェルールと、ｎ本（ｎ：０を含まない自然数）の自己形成光導波路を備える。フェルールは、ｎ本の光ファイバ挿入孔を備え、各光ファイバ挿入孔に光ファイバが挿入されている。 An example of such a self-forming optical waveguide is International Publication No. 2020/209364 (the entire disclosure of which is expressly incorporated herein by reference). According to International Publication No. 2020/209364, an optical connector comprises at least a ferrule and n self-forming optical waveguides (n: a natural number not including 0). The ferrule has n optical fiber insertion holes, and an optical fiber is inserted into each optical fiber insertion hole.
　更に、光導波路の形成後２分間放置し、コアとクラッドとの境界面でのモノマーの相互拡散を促し、その後ＵＶ照射でクラッドを形成している。光硬化性樹脂のうち、コア領域中では一方のモノマーのみが消費されて重合するので、コアとクラッドとの境界面ではモノマーの濃度勾配が生じて相互拡散が進行し、クラッドの機能を果たす。また、光硬化性樹脂全体をＵＶ照射することで、コア及びクラッド全体が硬化形成されて、光導波路が得られる。 Furthermore, after the optical waveguide is formed, it is left for two minutes to promote mutual diffusion of the monomers at the boundary between the core and cladding, and then the cladding is formed by UV irradiation. In the core region of the photocurable resin, only one of the monomers is consumed and polymerized, so a concentration gradient of the monomers occurs at the boundary between the core and cladding, promoting mutual diffusion and fulfilling the function of the cladding. In addition, by irradiating the entire photocurable resin with UV light, the entire core and cladding are cured and formed, resulting in the optical waveguide.
　しかし、国際公開第２０２０／２０９３６４号の様な複数の自己形成光導波路を形成しようとすると、各光ファイバのコアから、同時に光を光硬化性樹脂内部に照射した場合、隣り合うコア同士の光照射で形成される、それぞれの自己形成光導波路が互いに結合して形成され、結合不良を招くおそれが有った。 However, when attempting to form multiple self-forming optical waveguides as in WO 2020/209364, if light is irradiated simultaneously from the cores of each optical fiber into the photocurable resin, the self-forming optical waveguides formed by irradiating adjacent cores with light may bond together, resulting in poor coupling.
　本発明は上記課題に鑑みてなされたものであり、結合不良が防止可能な、自己形成光導波路の製造方法の実現を目的とする。 The present invention was made in consideration of the above problems, and aims to realize a method for manufacturing a self-written optical waveguide that can prevent poor coupling.
　上記課題は、以下の本発明により解決される。即ち、本発明の自己形成光導波路の製造方法では、光硬化性樹脂とｎ本（ｎ：２以上の自然数）のコアを備えるマルチコアファイバを２つ用意し、光硬化性樹脂は、所定の波長帯域の光が入射されて重合及び硬化して屈折率ｎａを有するコア部形成用樹脂と、コア部形成用樹脂に入射する光の強度以上の光が入射されて重合及び硬化し、硬化後の屈折率ｎｂがｎｂ＜ｎａであるクラッド部形成用樹脂とを含み、２つのマルチコアファイバを互いに対向配置すると共に、マルチコアファイバの間に光硬化性樹脂を配置し、コア部形成用樹脂のみの重合が可能な強度の光を２つのマルチコアファイバのコアから順に光硬化性樹脂に入射し、コア部形成用樹脂の重合及び硬化を発生させて光硬化性樹脂内に光導波路のコア部を形成し、次にクラッド部を形成して、光硬化性樹脂内にｎ本の光導波路を自己形成する。 The above problem is solved by the present invention as described below. That is, in the manufacturing method of the self-forming optical waveguide of the present invention, a photocurable resin and two multi-core fibers having n cores (n: natural number of 2 or more) are prepared, the photocurable resin includes a core-forming resin that is polymerized and hardened by light of a predetermined wavelength band being incident thereon and has a refractive index na, and a cladding-forming resin that is polymerized and hardened by light of an intensity equal to or greater than the intensity of the light incident on the core-forming resin and has a refractive index nb after hardening of nb < na, the two multi-core fibers are arranged opposite each other, and the photocurable resin is arranged between the multi-core fibers, and light of an intensity capable of polymerizing only the core-forming resin is incident on the photocurable resin in order from the cores of the two multi-core fibers, causing polymerization and hardening of the core-forming resin to form the core of the optical waveguide in the photocurable resin, and then forming the cladding, thereby self-forming n optical waveguides in the photocurable resin.
　本発明に係る自己形成光導波路の製造方法に依れば、各マルチコアファイバに於いて、隣り合うコア同士の光照射で形成されるそれぞれのコア部が、互いに結合して形成されることを防止することができるので、コア部の結合不良が防止可能となる。 The method for manufacturing a self-forming optical waveguide according to the present invention can prevent the cores in each multicore fiber, which are formed by irradiating adjacent cores with light, from bonding with each other, thereby preventing poor bonding of the cores.
本発明の実施例に係る自己形成光導波路の製造方法で用いる、マルチコアファイバの構成を示す正面図である。1 is a front view showing a configuration of a multi-core fiber used in a method for manufacturing a self-written optical waveguide according to an embodiment of the present invention. 本発明の実施例に係る自己形成光導波路の製造方法に於ける、２つのマルチコアファイバ間に光硬化性樹脂を配置した状態の一部を示す説明図である。1 is an explanatory diagram showing a part of a state in which a photocurable resin is disposed between two multi-core fibers in a manufacturing method of a self-written optical waveguide according to an embodiment of the present invention; FIG. 図２の状態から、２つのマルチコアファイバの各コアから光硬化性樹脂内に光を入射し、自己形成光導波路のコア部を形態した状態を示す説明図である。FIG. 3 is an explanatory diagram showing a state in which light is incident from each core of two multi-core fibers into a photocurable resin to form a core portion of a self-written optical waveguide, starting from the state shown in FIG. 2 . 図３の状態から、光硬化性樹脂と透明容器を除外して示した斜視図である。FIG. 4 is a perspective view showing the state of FIG. 3 excluding the photocurable resin and the transparent container. 図３の状態から、コア部に光を入射及び伝搬させ、各コア部から漏光を発生させる状態を示す説明図である。4 is an explanatory diagram showing a state in which light is made incident on and propagates through the core portions, starting from the state shown in FIG. 3, and leakage light is generated from each core portion. FIG. 図５の状態から、各クラッド部と、複数本の自己形成光導波路を形態した状態を示す説明図である。FIG. 6 is an explanatory diagram showing a state in which each clad portion and a plurality of self-written optical waveguides are formed from the state shown in FIG. 5 . 図６の状態を示す、実体顕微鏡観察像である。7 is a stereomicroscope image showing the state of FIG. 6.
　本発明の自己形成光導波路の製造方法では、光硬化性樹脂とｎ本（ｎ：２以上の自然数）のコアを備えるマルチコアファイバを２つ用意し、光硬化性樹脂は、所定の波長帯域の光が入射されて重合及び硬化して屈折率ｎａを有するコア部形成用樹脂と、コア部形成用樹脂に入射する光の強度以上の光が入射されて重合及び硬化し、硬化後の屈折率ｎｂがｎｂ＜ｎａであるクラッド部形成用樹脂とを含み、２つのマルチコアファイバを互いに対向配置すると共に、マルチコアファイバの間に光硬化性樹脂を配置し、コア部形成用樹脂のみの重合が可能な強度の光（以下において、単に「光」とも記載する）を２つのマルチコアファイバのコアから順に光硬化性樹脂に入射し、コア部形成用樹脂の重合及び硬化を発生させて光硬化性樹脂内に光導波路のコア部を形成し、次にクラッド部を形成して、光硬化性樹脂内にｎ本の光導波路を自己形成する。 In the method for manufacturing a self-forming optical waveguide of the present invention, a photocurable resin and two multicore fibers each having n cores (n: a natural number of 2 or more) are prepared, the photocurable resin includes a core-forming resin that is polymerized and hardened by light of a predetermined wavelength band being incident thereon and has a refractive index na, and a cladding-forming resin that is polymerized and hardened by light of an intensity equal to or greater than that of the light incident on the core-forming resin and has a refractive index nb after hardening of nb < na. The two multicore fibers are arranged opposite each other, and a photocurable resin is arranged between the multicore fibers. Light (hereinafter also simply referred to as "light") of an intensity capable of polymerizing only the core-forming resin is incident on the photocurable resin in order from the cores of the two multicore fibers, causing polymerization and hardening of the core-forming resin to form the core of the optical waveguide in the photocurable resin, and then a cladding is formed, thereby self-forming n optical waveguides in the photocurable resin.
　上記製造方法では、コア部形成用樹脂のみの重合が可能な強度の光を、マルチコアファイバのコアから順に光硬化性樹脂に入射させることができる。 In the above manufacturing method, light with an intensity sufficient to polymerize only the resin used to form the core portion can be incident on the photocurable resin, starting from the core of the multicore fiber.
　上記製造方法に依れば、各マルチコアファイバに於いて、隣り合うコア同士の光照射で形成されるそれぞれのコア部が、互いに結合して形成されることを防止することができるので、コア部の結合不良が防止可能となる。 The above manufacturing method makes it possible to prevent the cores in each multicore fiber from bonding together when they are formed by irradiating adjacent cores with light, thereby preventing poor bonding between the cores.
　以下に本発明の一態様として、図１乃至図７を参照して、実施例に係る製造方法を説明するが、本発明は以下の実施例のみに限定されない。 As one embodiment of the present invention, a manufacturing method according to the embodiment will be described below with reference to Figs. 1 to 7, but the present invention is not limited to the following embodiment.
　本実施例の製造方法では、最初に光硬化性樹脂１とｎ本（ｎ：２以上の自然数）のコアを備えるマルチコアファイバ（３ａ、３ｂ）を用意する。マルチコアファイバ（３ａ、３ｂ）としては、同一構造の物を２つ用意する。ｎは２以上の自然数であり、例えば２以上４以下である。ただし、ｎはここに例示した範囲に限定されない。 In the manufacturing method of this embodiment, first, a photocurable resin 1 and a multicore fiber (3a, 3b) having n cores (n: natural number of 2 or more) are prepared. Two multicore fibers (3a, 3b) having the same structure are prepared. n is a natural number of 2 or more, for example, 2 to 4. However, n is not limited to the range exemplified here.
　透明容器４に光硬化性樹脂１を充たし、各マルチコアファイバ（３ａ、３ｂ）の片側の端部を、それぞれ光硬化性樹脂１内に浸漬させる。従って、マルチコアファイバ（３ａ、３ｂ）の間に光硬化性樹脂１を配置すると共に、光硬化性樹脂１を挟んで２つのマルチコアファイバ（３ａ、３ｂ）を互いに対向配置する。 The transparent container 4 is filled with photocurable resin 1, and one end of each multicore fiber (3a, 3b) is immersed in the photocurable resin 1. Thus, the photocurable resin 1 is disposed between the multicore fibers (3a, 3b), and the two multicore fibers (3a, 3b) are disposed facing each other with the photocurable resin 1 sandwiched between them.
　２つのマルチコアファイバ（３ａ、３ｂ）はどちらも、外形形状が図１に示す円形で、コア径が８．０μｍ、クラッド径が１２５μｍ、更にｎ＝４本のコア（３ａ１、３ａ２、３ａ３、３ａ４、又は３ｂ１、３ｂ２、３ｂ３、３ｂ４）を備える。また、４本のコア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）は図１に示すように、マルチコアファイバ（３ａ、３ｂ）の中央を中心とする円の円周上で等角度（図１では９０°）且つ等間隔に２列×２芯に配置されている。また、本実施例では、２つのマルチコアファイバ（３ａ、３ｂ）において、各コア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）の間隔ｄは、５０μｍである。間隔ｄは、２つのコアの中心間の距離である。 The two multicore fibers (3a, 3b) each have a circular outer shape as shown in FIG. 1, a core diameter of 8.0 μm, a cladding diameter of 125 μm, and n=4 cores (3a1, 3a2, 3a3, 3a4, or 3b1, 3b2, 3b3, 3b4). As shown in FIG. 1, the four cores (3a1-3a4, or 3b1-3b4) are arranged in two rows x two cores at equal angles (90° in FIG. 1) and equal intervals on the circumference of a circle centered on the center of the multicore fiber (3a, 3b). In this embodiment, the interval d between the cores (3a1-3a4, or 3b1-3b4) in the two multicore fibers (3a, 3b) is 50 μm. The interval d is the distance between the centers of the two cores.
　例えば、カットオフ波長は１３００ｎｍ～１５００ｎｍであり、モードフィールド径は７．４μｍ～８．５μｍ（伝搬光波長１５５０ｎｍ）である。 For example, the cutoff wavelength is 1300 nm to 1500 nm, and the mode field diameter is 7.4 μm to 8.5 μm (propagating light wavelength 1550 nm).
　光硬化性樹脂１に浸漬されるマルチコアファイバ（３ａ、３ｂ）の端面（３ａ５、３ｂ５）は、図２に示すように各コア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）の光軸方向に対して垂直に、平面形状となるように形成されている。端面（３ａ５、３ｂ５）には、平面研磨加工が施される。 The end faces (3a5, 3b5) of the multicore fibers (3a, 3b) immersed in the photocurable resin 1 are formed to have a planar shape perpendicular to the optical axis direction of each core (3a1 to 3a4 or 3b1 to 3b4) as shown in FIG. 2. The end faces (3a5, 3b5) are subjected to flat polishing.
　光硬化性樹脂１は、コア部形成用樹脂とクラッド部形成用樹脂とを含む。コア部形成用樹脂は、所定の波長帯の光が入射されて重合及び硬化することで、屈折率ｎａを有する。またクラッド部形成用樹脂は、コア部形成用樹脂に入射される光の波長帯域と同一又は異なる波長帯域であり、且つコア部形成用樹脂に入射される光の強度以上の光が入射されて、重合及び硬化する。更に、硬化後のクラッド部形成用樹脂の屈折率ｎｂは、ｎｂ＜ｎａである。 The photocurable resin 1 includes a resin for forming the core portion and a resin for forming the cladding portion. The resin for forming the core portion has a refractive index na as a result of being polymerized and cured when light of a specific wavelength band is incident on it. The resin for forming the cladding portion is polymerized and cured when light of the same or different wavelength band as the wavelength band of the light incident on the resin for forming the core portion and of an intensity equal to or greater than that of the light incident on the resin for forming the core portion is incident on it. Furthermore, the refractive index nb of the resin for forming the cladding portion after curing is nb<na.
　コア部形成用樹脂及びクラッド部形成用樹脂としては、互いに異なる重合反応を経て光重合が起こる樹脂を選択する。本実施例では、コア部形成用樹脂はアクリル系樹脂であり、クラッド部形成用樹脂はエポキシ系樹脂である。アクリル系樹脂とエポキシ系樹脂との組み合わせでは、アクリル系樹脂の方が、エポキシ系樹脂よりも重合反応速度が速い為、弱い強度の光によってアクリル系樹脂だけが選択的に重合する。 For the resin used to form the core and the resin used to form the cladding, resins that undergo photopolymerization via different polymerization reactions are selected. In this embodiment, the resin used to form the core is an acrylic resin, and the resin used to form the cladding is an epoxy resin. In a combination of acrylic and epoxy resins, the acrylic resin has a faster polymerization reaction rate than the epoxy resin, so only the acrylic resin is selectively polymerized by light of low intensity.
　またアクリル系樹脂とエポキシ系樹脂は、２種類以上のモノマーから成る混合液に光重合開始剤を添加した溶液である。 Acrylic resins and epoxy resins are solutions in which a photopolymerization initiator is added to a mixture of two or more types of monomers.
　次に、２つのマルチコアファイバ（３ａ、３ｂ）のコア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）から、所定の波長帯域の光を光硬化性樹脂１の内部に入射させる。光硬化性樹脂１に入射する光は、コア部形成用樹脂のみの重合が可能な強度のレーザ光である。光の波長λｗは光重合開始剤に応じて任意に設定可能であるが、一例として３６５ｎｍ～１６７５ｎｍが挙げられ、本実施例ではλｗ＝４０５ｎｍに設定する。併せて、光重合開始剤が感度を有する波長帯域も、４０５ｎｍ近辺とする。 Next, light in a predetermined wavelength band is incident on the inside of the photocurable resin 1 from the cores (3a1-3a4 or 3b1-3b4) of the two multicore fibers (3a, 3b). The light incident on the photocurable resin 1 is laser light with an intensity that allows polymerization of only the resin for forming the core portion. The wavelength λw of the light can be set arbitrarily depending on the photopolymerization initiator, but one example is 365 nm to 1675 nm, and in this embodiment, λw is set to 405 nm. Additionally, the wavelength band to which the photopolymerization initiator is sensitive is also set to around 405 nm.
　コア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）からの光の入射により、コア部形成用樹脂の重合及び硬化を発生させ、コア部形成用樹脂のモノマーがポリマーとなり、光硬化性樹脂１内に、図３及び図４に示す光導波路の複数本のコア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）が自己形成する。 Light incident on the cores (3a1-3a4 or 3b1-3b4) causes polymerization and hardening of the resin for forming the cores, the monomers of the resin for forming the cores become polymers, and multiple cores (2a1, 2b1, 2c1, 2d1) of the optical waveguide shown in Figures 3 and 4 are self-formed within the photocurable resin 1.
　コア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）から光硬化性樹脂１への光の入射の際に、各マルチコアファイバ（３ａ、３ｂ）において、ｎ本のコアに順に光を入射させる。ここで、「順に」とは、各マルチコアファイバ（３ａ、３ｂ）においてｎ本のコアへの光の入射を順次行う際、ある１本のコアに光を入射させている時間中、同じマルチコアファイバの他のいずれのコアにも光を入射させないことを意味する。例えば、マルチコアファイバ３ａにおいて、コア３ａ１に光を入射させている時間中にはコア３ａ２、３ａ３及び３ａ４には光を入射させず、マルチコアファイバ３ｂにおいて、コア３ｂ１に光を入射させている時間中にはコア３ｂ２、３ｂ３及び３ｂ４には光を入射させない。なお、２つのマルチコアファイバ（３ａ、３ｂ）の一方のマルチコアファイバのコアへの光の入射を行っている時間中、他方のマルチコアファイバのコアへの光の入射を行ってもよく、行わなくてもよい。図１～図３に示した例では、コア３ａ１（又は３ｂ１）→３ａ２（又は３ｂ４）→３ａ３（又は３ｂ３）→３ａ４（又は３ｂ２）の順に１本ずつのコア間でコア部を順次形成し、各コア間でコア部の自己形成が完了した後に次のコア間のコア部の自己形成を行う。このような光の入射工程とする理由は、各マルチコアファイバ（３ａ、３ｂ）に於いて、隣り合うコア同士の光照射で形成されるそれぞれのコア部が、互いに結合して形成されることを防止することが可能となり、コア部の結合不良が防止可能な為である。 When light is incident from the cores (3a1 to 3a4, or 3b1 to 3b4) to the photocurable resin 1, in each multicore fiber (3a, 3b), light is incident in sequence to the n cores. Here, "in sequence" means that when light is incident in sequence to the n cores in each multicore fiber (3a, 3b), during the time when light is incident on a certain core, light is not incident on any other cores of the same multicore fiber. For example, in the multicore fiber 3a, during the time when light is incident on the core 3a1, light is not incident on the cores 3a2, 3a3, and 3a4, and in the multicore fiber 3b, during the time when light is incident on the core 3b1, light is not incident on the cores 3b2, 3b3, and 3b4. Note that during the time when light is incident on the cores of one of the two multicore fibers (3a, 3b), light may or may not be incident on the cores of the other multicore fiber. In the example shown in Figures 1 to 3, cores are sequentially formed between each core in the order of core 3a1 (or 3b1) → 3a2 (or 3b4) → 3a3 (or 3b3) → 3a4 (or 3b2), and after the self-formation of the cores between each core is completed, the self-formation of the cores between the next cores is performed. The reason for using such a light incidence process is that it is possible to prevent the cores formed by the light irradiation of adjacent cores in each multi-core fiber (3a, 3b) from bonding with each other, and thus prevent poor bonding of the cores.
　コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）の径は、マルチコアファイバ（３ａ、３ｂ）の各コア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）径と同一とすることが望ましく、且つ、各コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）の光軸方向で一様な直径が望ましい。更に各コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）のモードフィールド径は、マルチコアファイバ（３ａ、３ｂ）の各コア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）のモードフィールド径と同一（７．４μｍ～８．５μｍ）とする。 The diameter of the cores (2a1, 2b1, 2c1, 2d1) is preferably the same as the diameter of each core (3a1-3a4, or 3b1-3b4) of the multicore fiber (3a, 3b), and it is preferable that each core (2a1, 2b1, 2c1, 2d1) has a uniform diameter in the optical axis direction. Furthermore, the mode field diameter of each core (2a1, 2b1, 2c1, 2d1) is the same (7.4 μm-8.5 μm) as the mode field diameter of each core (3a1-3a4, or 3b1-3b4) of the multicore fiber (3a, 3b).
　次に、クラッド部の自己形成について説明する。コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）の形成後、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）の周囲（コア部２ａ１、２ｂ１、２ｃ１、２ｄ１と、その他の光硬化性樹脂１との境界面）に於ける、光硬化性樹脂１内のクラッド部形成用樹脂に於いて、モノマーの相互拡散を発生させる。コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）領域中ではモノマーが消費されて重合しているのに対し、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）以外の光硬化性樹脂１のモノマーは重合反応しておらず、未硬化且つ未消費なので、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）の周囲でモノマーの濃度勾配が生じ、相互拡散が進行する。本実施例ではコア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）の形成後２分間放置して、モノマーの相互拡散を促した。 Next, the self-formation of the cladding portion will be described. After the core portions (2a1, 2b1, 2c1, 2d1) are formed, the interdiffusion of monomers is generated in the cladding portion forming resin in the photocurable resin 1 around the core portions (2a1, 2b1, 2c1, 2d1) (the boundary surface between the core portions 2a1, 2b1, 2c1, 2d1 and the other photocurable resin 1). While the monomers are consumed and polymerized in the core portion (2a1, 2b1, 2c1, 2d1) region, the monomers in the photocurable resin 1 outside the core portions (2a1, 2b1, 2c1, 2d1) have not polymerized and are uncured and unconsumed, so a concentration gradient of the monomers is generated around the core portions (2a1, 2b1, 2c1, 2d1) and interdiffusion progresses. In this example, the core portions (2a1, 2b1, 2c1, 2d1) were left to stand for 2 minutes after formation to promote interdiffusion of the monomers.
　次に、本実施例ではコア部形成樹脂を重合させた波長帯域と同一波長帯域（λｗ＝４０５ｎｍ）のレーザ光を、マルチコアファイバ（３ａ、３ｂ）の各コア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）からコア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）に入射させて、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）内部に伝搬させる。コア部形成樹脂を重合させた光の強度以上の光を、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）に入射させる。無論その強度は、クラッド部形成用樹脂を重合させることが可能な強度とする。 Next, in this embodiment, laser light of the same wavelength band (λw = 405 nm) as the wavelength band in which the resin forming the core portion is polymerized is made to enter the core portion (2a1, 2b1, 2c1, 2d1) from each core (3a1-3a4 or 3b1-3b4) of the multicore fiber (3a, 3b) and propagates inside the core portion (2a1, 2b1, 2c1, 2d1). Light with an intensity equal to or greater than that of the light that polymerized the resin forming the core portion is made to enter the core portion (2a1, 2b1, 2c1, 2d1). Of course, this intensity is set to be sufficient to polymerize the resin forming the cladding portion.
　更に光の伝搬を継続して、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）からコア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）周囲の未硬化のクラッド部形成用樹脂へと、漏光を発生させる。するとコア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）周囲のクラッド部形成用樹脂が、図５の矢印に示す漏光によって重合及び硬化して、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）表面を包囲する形態でクラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）が自己形成される。なお、図５の矢印は、１つのコア部２ａ１のみに図示しているが、漏光はその他のコア部（２ｂ１、２ｃ１、２ｄ１）でも発生する。また、クラッド部２ｄ２は図示していないが、コア部２ｄ１表面を包囲して自己形成されるクラッド部である。 The light continues to propagate, causing light leakage from the cores (2a1, 2b1, 2c1, 2d1) to the uncured cladding resin surrounding the cores (2a1, 2b1, 2c1, 2d1). The cladding resin surrounding the cores (2a1, 2b1, 2c1, 2d1) is then polymerized and cured by the leaking light shown by the arrows in FIG. 5, and the cladding (2a2, 2b2, 2c2, 2d2) is self-formed in a form that surrounds the surface of the cores (2a1, 2b1, 2c1, 2d1). Note that the arrows in FIG. 5 are only shown for one core 2a1, but light leakage also occurs in the other cores (2b1, 2c1, 2d1). Although the cladding 2d2 is not shown, it is a self-formed cladding that surrounds the surface of the core 2d1.
　硬化後に自己形成されたクラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）の屈折率ｎｂは、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）の屈折率ｎａに対してｎｂ＜ｎａを示す。よってコア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）とクラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）によって、複数本の自己形成光導波路（２ａ、２ｂ、２ｃ、２ｄ）が自己形成される。自己形成光導波路２ａがコア部２ａ１とクラッド部２ａ２から成る。また、自己形成光導波路２ｂがコア部２ｂ１とクラッド部２ｂ２から成り、自己形成光導波路２ｃがコア部２ｃ１とクラッド部２ｃ２から成り、自己形成光導波路２ｄがコア部２ｄ１とクラッド部２ｄ２から成る。 After curing, the refractive index nb of the cladding (2a2, 2b2, 2c2, 2d2) self-formed shows nb<na, where na is the refractive index of the core (2a1, 2b1, 2c1, 2d1). Therefore, multiple self-formed optical waveguides (2a, 2b, 2c, 2d) are self-formed by the core (2a1, 2b1, 2c1, 2d1) and cladding (2a2, 2b2, 2c2, 2d2). Self-formed optical waveguide 2a consists of core 2a1 and cladding 2a2. Self-formed optical waveguide 2b consists of core 2b1 and cladding 2b2, self-formed optical waveguide 2c consists of core 2c1 and cladding 2c2, and self-formed optical waveguide 2d consists of core 2d1 and cladding 2d2.
　最後に、透明容器４の周囲から紫外線（ＵＶ）を一様に照射して、全ての未反応の光硬化性樹脂１を硬化させる（図６、図７参照）。 Finally, ultraviolet (UV) light is uniformly applied around the transparent container 4 to harden all of the unreacted photocurable resin 1 (see Figures 6 and 7).
　なお、クラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）形成用の光を、各マルチコアファイバ（３ａ、３ｂ）の全てのコア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）から同時に全コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）に入射させても、各コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）に順に１本ずつ入射させてもよい。全てのコア（３ａ１～３ａ４、又は３ｂ１～３ｂ４）から同時に全コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）に入射させるにより、複雑な入射時間制御が必要無くなると共に、クラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）形成時間の短縮も図ることができるので好ましい。 The light for forming the cladding portions (2a2, 2b2, 2c2, 2d2) may be incident on all the core portions (2a1, 2b1, 2c1, 2d1) simultaneously from all the cores (3a1-3a4 or 3b1-3b4) of each multicore fiber (3a, 3b), or may be incident on each core portion (2a1, 2b1, 2c1, 2d1) one by one in sequence. By simultaneously incident on all the cores (3a1-3a4 or 3b1-3b4) on all the core portions (2a1, 2b1, 2c1, 2d1), complex incident time control is not required, and the time required for forming the cladding portions (2a2, 2b2, 2c2, 2d2) can be shortened, which is preferable.
　以上、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）からの漏光によりクラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）を形成することで、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）を除いた光硬化性樹脂１全体の硬化収縮の発生が防止され、クラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）形成時に硬化する樹脂をクラッド部形成用樹脂のみとすることが可能となる。従って、光硬化性樹脂１全体での応力の発生が防止され、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）の変形を抑制可能となり、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）への光挿入損失の増加を抑制することができる。 As described above, by forming the cladding portions (2a2, 2b2, 2c2, 2d2) using light leakage from the core portions (2a1, 2b1, 2c1, 2d1), the occurrence of cure shrinkage of the entire photocurable resin 1 except for the core portions (2a1, 2b1, 2c1, 2d1) is prevented, and it is possible for the resin that cures when forming the cladding portions (2a2, 2b2, 2c2, 2d2) to be the only resin used to form the cladding portions. This prevents stress from occurring throughout the photocurable resin 1, making it possible to suppress deformation of the core portions (2a1, 2b1, 2c1, 2d1), and suppressing an increase in the light insertion loss into the core portions (2a1, 2b1, 2c1, 2d1).
　更に、先に記載したように漏光によりクラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）を形成することで、各クラッド部の径や厚みを制御可能となり、自己形成光導波路（２ａ、２ｂ、２ｃ、２ｄ）の光学特性や機械的特性の安定化も図ることができる。 Furthermore, as described above, by forming the cladding portions (2a2, 2b2, 2c2, 2d2) by light leakage, it becomes possible to control the diameter and thickness of each cladding portion, and it is also possible to stabilize the optical and mechanical properties of the self-forming optical waveguides (2a, 2b, 2c, 2d).
　更に本実施例では、複数本の自己形成光導波路（２ａ、２ｂ、２ｃ、２ｄ）を形成する際、クラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）形成時に光硬化性樹脂１の周囲からのＵＶ照射を行わずに全てのクラッド部（２ａ２、２ｂ２、２ｃ２、２ｄ２）の硬化を完了させることができるので、コア部（２ａ１、２ｂ１、２ｃ１、２ｄ１）毎の光挿入損失の増加が防止可能となる。 Furthermore, in this embodiment, when forming multiple self-forming optical waveguides (2a, 2b, 2c, 2d), the hardening of all clad portions (2a2, 2b2, 2c2, 2d2) can be completed without irradiating the photocurable resin 1 with UV light from the periphery when forming the clad portions (2a2, 2b2, 2c2, 2d2), so it is possible to prevent an increase in the optical insertion loss for each core portion (2a1, 2b1, 2c1, 2d1).
　自己形成光導波路（２ａ、２ｂ、２ｃ、２ｄ）の形成後、マルチコアファイバ３ａの各コア（３ａ１～３ａ４）から各光導波路（２ａ、２ｂ、２ｃ、２ｄ）に１５５０ｎｍ波長の光を入射及び伝搬させ、入射光の光出力に対して出射される光出力をパワーメータで計測し、マルチコアファイバ（３ａ、３ｂ）間での光挿入損失を計測した。 After the self-forming optical waveguides (2a, 2b, 2c, 2d) were formed, light with a wavelength of 1550 nm was made to enter and propagate from each core (3a1-3a4) of the multicore fiber 3a into each optical waveguide (2a, 2b, 2c, 2d), and the optical output of the emitted light relative to the optical output of the incident light was measured with a power meter, and the optical insertion loss between the multicore fibers (3a, 3b) was measured.
　その損失値を表１に示す。表１に示すように、４本全ての光導波路（２ａ、２ｂ、２ｃ、２ｄ）に於いて、光挿入損失が０．２ｄＢ～１．２ｄＢの範囲内まで改善されていることが確認された。表１では、光導波路２ａをチャンネル１、光導波路２ｂをチャンネル２、光導波路２ｃをチャンネル３、光導波路２ｄをチャンネル４と示している。なお、２つのマルチコアファイバ（３ａ、３ｂ）の端面（３ａ５、３ｂ５）間での各光導波路（２ａ、２ｂ、２ｃ、２ｄ）の長さは、５００μｍである。 The loss values are shown in Table 1. As shown in Table 1, it was confirmed that the optical insertion loss was improved to within the range of 0.2 dB to 1.2 dB in all four optical waveguides (2a, 2b, 2c, 2d). In Table 1, optical waveguide 2a is shown as channel 1, optical waveguide 2b as channel 2, optical waveguide 2c as channel 3, and optical waveguide 2d as channel 4. The length of each optical waveguide (2a, 2b, 2c, 2d) between the end faces (3a5, 3b5) of the two multicore fibers (3a, 3b) is 500 μm.
　本発明はマルチコアファイバ間の自己形成光導波路の製造方法のみだけで無く、マルチコアファイバとシリコン光導波路間や、マルチコア光ファイバとポリマー光導波路間の自己形成光導波路の製造方法等の、高密度光実装分野にも適用可能である。 The present invention is applicable not only to the manufacturing method of self-forming optical waveguides between multicore fibers, but also to the field of high-density optical packaging, such as the manufacturing method of self-forming optical waveguides between multicore fibers and silicon optical waveguides, or between multicore optical fibers and polymer optical waveguides.
１　　　光硬化性樹脂
２ａ、２ｂ、２ｃ、２ｄ　　　自己形成光導波路
２ａ１、２ｂ１、２ｃ１、２ｄ１　　　自己形成光導波路のコア部
２ａ２、２ｂ２、２ｃ２、２ｄ２　　　自己形成光導波路のクラッド部
３ａ、３ｂ　　　マルチコアファイバ
３ａ１、３ａ２、３ａ３、３ａ４、３ｂ１、３ｂ２、３ｂ３、３ｂ４　　　マルチコアファイバのコア
３ａ５、３ｂ５　　　マルチコアファイバの端面
４　　　透明容器
ｄ　　　マルチコアファイバの各コアの間隔
  1 Photocurable resin 2a, 2b, 2c, 2d Self-forming optical waveguide 2a1, 2b1, 2c1, 2d1 Core portion 2a2, 2b2, 2c2, 2d2 Self-forming optical waveguide clad portion 3a, 3b Multicore fiber 3a1, 3a2, 3a3, 3a4, 3b1, 3b2, 3b3, 3b4 Core 3a5, 3b5 of multicore fiber End surface 4 of multicore fiber Transparent container d Spacing between each core of multicore fiber

Claims (1)

  1. 光硬化性樹脂とｎ本（ｎ：２以上の自然数）のコアを備えるマルチコアファイバを２つ用意し、
    前記光硬化性樹脂は、所定の波長帯域の光が入射されて重合及び硬化して屈折率ｎａを有するコア部形成用樹脂と、前記コア部形成用樹脂に入射する光の強度以上の光が入射されて重合及び硬化し、硬化後の屈折率ｎｂが前記ｎｂ＜前記ｎａであるクラッド部形成用樹脂とを含み、
    ２つの前記マルチコアファイバを互いに対向配置すると共に、前記マルチコアファイバの間に前記光硬化性樹脂を配置し、
    前記コア部形成用樹脂のみの前記重合が可能な強度の光を２つの前記マルチコアファイバの前記コアから順に前記光硬化性樹脂に入射し、前記コア部形成用樹脂の前記重合及び前記硬化を発生させて前記光硬化性樹脂内に光導波路のコア部を形成し、
    次にクラッド部を形成して、前記光硬化性樹脂内に前記ｎ本の光導波路を自己形成する自己形成光導波路の製造方法。
     
          Two multi-core fibers each having a photocurable resin and n cores (n: a natural number of 2 or more) are prepared.
    The photocurable resin includes a core portion forming resin which is polymerized and cured by light of a predetermined wavelength band being incident thereon and has a refractive index na, and a cladding portion forming resin which is polymerized and cured by light having an intensity equal to or greater than that of the light incident on the core portion forming resin and has a refractive index nb after curing such that nb<na,
    Two of the multi-core fibers are arranged to face each other, and the photocurable resin is arranged between the multi-core fibers;
    light having an intensity capable of polymerizing only the resin for forming the core portion is incident on the photocurable resin in sequence from the cores of the two multi-core fibers, thereby causing the polymerization and hardening of the resin for forming the core portion to occur, thereby forming a core portion of an optical waveguide in the photocurable resin;
    Next, a cladding portion is formed, and the n optical waveguides are self-formed in the photocurable resin.
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JP2010286718A (en) * 2009-06-12 2010-12-24 Sumitomo Electric Ind Ltd Multi-core fiber terminal and connection structure thereof
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