JP2013041060A - Polymer-clad optical fiber and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer-clad optical fiber that has a high numerical aperture and also excellent moisture-resistance.SOLUTION: A polymer-clad optical fiber 11 includes an optical transmission path 11a formed of glass and a cladding 11b provided so as to coat it. The cladding material forming the cladding 11b contains a perfluoroether polymer cured by crosslinking caused by a hydrosilylation reaction.

Description

  The present invention relates to a polymer clad optical fiber and a manufacturing method thereof.

  As an optical fiber used in applications such as short distance data transfer, light guide, or fiber laser that requires a high numerical aperture (hereinafter referred to as “NA”), a glass core is formed by a polymer cladding. Polymer clad optical fibers coated with are known.

  For example, Patent Document 1 discloses that a core formed of glass has at least two silicon atoms bonded to at least two alkoxy groups in the molecule and at least a functional group capable of forming a chemical bond with an ultraviolet curable resin. A polymer-clad optical fiber coated with a clad formed of a resin composition containing one reactive compound is disclosed.

  Patent Document 2 discloses a polymer clad optical fiber in which a core formed of glass is covered with a clad formed of a cured product of a resin composition containing urethane di (meth) acrylate and a diluent.

  Patent Document 3 discloses a polymer clad optical fiber in which a core formed of glass is coated with a clad formed of a perfluoropolyether polymer having a urethane group at the end of the main chain and bonded with a (meth) acrylate group. It is disclosed.

  Patent Document 4 discloses a polymer clad optical fiber in which a core made of glass is covered with a clad formed of an ultraviolet curable fluororesin.

JP-A-5-112619 WO96 / 013739 JP 10-197731 A JP 2009-198706 A

  In a polymer clad optical fiber having a clad formed of a thermosetting silicone resin, the refractive index of the clad decreases only to about 1.41 due to the characteristics of the thermosetting silicone resin. is there.

  In polymer-clad optical fibers whose cladding is made of UV-curable fluorinated acrylate resin, it is necessary to increase the fluorine content in order to reduce the refractive index of the cladding. Although the refractive index of the cladding is lowered to about 1.38, the numerical aperture NA can still be increased only to about 0.47. Furthermore, since the acrylic group is hydrophilic, it is easy to absorb moisture. For example, when it is directly exposed to a high-humidity environment, such as when immersed in water, moisture easily enters, thereby the interface between the core and the cladding. If peeling occurs, light transmission loss increases. Moreover, since it is an ultraviolet curable type, depending on the type of glass forming the core, defects occur in the glass forming the core upon receiving ultraviolet light.

  An object of the present invention is to obtain a polymer clad optical fiber having high NA and excellent moisture resistance.

  The polymer-clad optical fiber of the present invention is a polymer-clad optical fiber having an optical transmission line formed of glass and a clad provided so as to cover the optical transmission line, the clad forming the clad The material includes a perfluoroether polymer cured by crosslinking through a hydrosilylation reaction.

  The method for producing a polymer-clad optical fiber according to the present invention includes an optical transmission line forming step of drawing a glass preform to form an optical transmission line, and a liquid on the surface of the optical transmission line formed in the optical transmission line formation step. A clad forming step of forming a clad by thermally curing by attaching and heating the clad forming material, and the clad forming material includes a perfluoroether polymer that is cured by cross-linking by a hydrosilylation reaction.

  According to the present invention, since the clad is formed of a clad material containing a perfluoroether polymer cured by crosslinking by hydrosilylation reaction, the clad is greatly reduced in refractive index. As a result, the polymer clad optical fiber of the present invention has High NA can be obtained with respect to the optical transmission line, and excellent moisture resistance can be obtained because the bonding portion between the carbon atom and the silicon atom, which serves as a crosslinking point of the cladding material, is hydrophobic.

1 is a perspective view showing a polymer-clad optical fiber core wire according to Embodiment 1. FIG. FIG. 3 is an explanatory view showing a method for manufacturing a polymer-clad optical fiber core wire according to the first embodiment. (A) And (b) is explanatory drawing of the measuring method of the glass transition temperature of a clad material. (A) And (b) is explanatory drawing of the measuring method of the hardening start temperature of a clad formation material. 6 is a perspective view showing a double clad optical fiber core wire according to Embodiment 2. FIG.

  The polymer clad optical fiber of this embodiment has an optical transmission line formed of glass and a clad provided so as to cover the optical transmission line. As an aspect of the optical transmission line, for example, a core made of a core having a higher refractive index than the clad and another clad made of glass having a refractive index lower than that of the core and higher than that of the clad on the surface of the core. (In this case, the clad is called the second clad and the other clad is called the first clad). Hereinafter, the former will be described as Embodiment 1 and the latter as Embodiment 2, and will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a polymer-clad optical fiber core wire 10 according to the first embodiment. The polymer-clad optical fiber core wire 10 according to the first embodiment is used for applications such as short distance data transfer and light guide.

  The polymer-clad optical fiber core wire 10 according to the first embodiment includes a polymer-clad optical fiber 11 having a circular cross section and an overcoat 12 that covers the polymer-clad optical fiber 11. The core wire diameter is, for example, 100 to 1000 μm.

  The polymer clad optical fiber 11 is composed of a core 11a (optical transmission line) having a circular cross section at the center of the fiber and a clad 11b provided so as to cover the core. The fiber diameter is, for example, 50 to 700 μm.

The core 11a is made of glass. The glass forming the core 11a may be pure quartz glass (SiO ₂ ), or a dopant that increases the refractive index such as Ge, a dopant that decreases the refractive index such as F, or a rare earth element (Er, Yb). , Nd) or other glass that is doped with other functional imparting dopants. The core diameter is, for example, 5 to 100 μm. The refractive index of the core 11a is, for example, 1.44 to 1.47. The refractive index of pure quartz glass is 1.459. The refractive index is measured by an Abbe refractometer according to JIS K 0062 (the same applies hereinafter).

  The clad 11b is formed of a clad material containing a perfluoroether polymer cured by crosslinking by a hydrosilylation reaction. The thickness of the clad 11b is, for example, 10 to 100 μm.

  The refractive index of the clad 11b is lower than the refractive index of the core 11a, for example, 1.37 or less, and preferably 1.35 or less when quartz glass is used for the core 11a. In this polymer clad optical fiber 11, when the clad 11b has such a low refractive index and the quartz glass is used for the core 11a, the NA with respect to the core 11a is, for example, 0.50 or more, preferably 0. 55 or more. When the light emitted from the light source is collected and incident on the core 11a, the higher the NA, the larger the incident angle. Therefore, the amount of incident light can be increased. NA is measured by the FFP method according to JIS C 6825.

  The density of the clad material forming the clad 11b is, for example, 1.70 to 1.80. The density of the cladding material is measured according to JIS K0061.

  The Young's modulus of the clad material forming the clad 11b is, for example, 0.5 to 50 MPa, and preferably 1 to 10 MPa from the viewpoint of buffering action against external force. The tensile strength of the clad material forming the clad 11b is, for example, 1 to 100 MPa, and is preferably 10 MPa or more from the viewpoint of resistance to external force. The elongation at the time of cutting of the clad material forming the clad 11b is, for example, 5 to 100%, and is 20 to 100% from the viewpoint of following the clad 11b to the core 11a when the polymer clad optical fiber 11 is bent. preferable. The Young's modulus of the clad material is in accordance with JIS K 6251, and the cross-sectional area is 2.5% when the clad material formed into a strip shape having a thickness of 200 μm and a width of 6 mm is stretched at a tensile speed of 1 mm / min. And elongation percentage (0.025). The tensile strength and elongation at break are measured under the conditions of a test piece shape dumbbell No. 2 and a test piece thickness of 200 μm in accordance with JIS K 6251 and a tensile speed of 50 mm / min.

  The Shore A hardness of the clad material forming the clad 11b is, for example, 10 to 80, and is preferably 25 to 80 from the viewpoint of resistance to the external force of the polymer clad optical fiber 11. The Shore A hardness of the clad material is measured with a type A durometer according to JIS K 6253.

  The glass transition temperature (Tg) of the clad material forming the clad 11b is, for example, 0 ° C. or lower, and is preferably −50 ° C. or lower from the viewpoint of reducing the characteristic change in the practical region of the polymer clad optical fiber 11. The glass transition temperature (Tg) of the cladding material is determined by the following procedure using a rigid pendulum type physical property tester 40A (for example, model number: RPT-3000W manufactured by A & D) as shown in FIG. Measured. The rigid pendulum type physical property tester 40A includes a sample stage 41A (for example, made of aluminum), and a pipe edge 42A (for example, model number: RPN160 manufactured by A & D Co., Ltd.) is provided on the specimen table 41A. (For example, model number: FRB100 manufactured by A & D Corporation) is hung and a pendulum is configured. In an air atmosphere at room temperature, a film F made of a clad material and having a thickness of about 100 μm is placed on the sample table 41A, and the sample table 41A is heated from −100 ° C. to 150 ° C. at a rate of 10 ° C./min for a certain period of time. Each time, the pendulum is vibrated and the vibration period is measured. When the viscoelasticity of the clad material changes, the logarithmic attenuation rate, which is a logarithmic value of the vibration period attenuation ratio, changes. Therefore, as shown in FIG. Indicates. The temperature indicating the maximum rate of change (that is, the temperature at which the first derivative curve of the logarithmic decay rate exhibits the maximum value) is defined as Tg. When Tg is present at -100 ° C or lower, measure using a device capable of measuring -100 ° C or lower on the same principle as described above, or use a dynamic viscoelasticity measuring device. The peak temperature of tan δ occurring at −100 ° C. or lower can be defined as Tg.

  The gel fraction of the clad material forming the clad 11b is, for example, 90 to 100%, and the viewpoint of preventing the characteristic change of the clad 11b caused by the evaporation of the low molecular weight component in a high temperature environment or the elution of the low molecular weight component in a high humidity environment. Therefore, it is preferably 96 to 100%. The gel fraction of the clad material is measured by mass change during solvent extraction. Specifically, Soxhlet extraction is performed on the clad material using methyl ethyl ketone (boiling point 79.5 ° C.) as a solvent at a circulation rate of about 10 times per hour for 5 hours, and the dry mass of the clad material after extraction is determined as the initial mass. The value expressed as a percentage is taken as the gel fraction.

  The 90 ° peeling force of the clad material, which serves as an index of the adhesion of the clad 11b to the core 11a, with respect to the glass is preferably 10 N / m or more. From the viewpoint of preventing the clad 11b from peeling from the core 11a, 20 N / m. More preferably. The 90 ° peel force for the glass of the clad material is in accordance with JISK 6854-1, and a clad forming material is applied on a glass substrate with a thickness of 100 to 200 μm and cured by crosslinking to obtain a clad material. Was cut into strips at intervals of 2.5 cm in width, and the tension was measured when one end of the strip-shaped clad material was pulled vertically from the glass substrate at a pulling speed of 100 mm / min, and the tension was measured. It can be obtained by dividing by the width of the strip-shaped clad material.

  The overcoat 12 is made of resin. Examples of the resin that forms the overcoat 12 include UV curable urethane acrylate resins, epoxy acrylate resins, and photo-curable resins such as silicone resins, thermoplastic resins such as nylon, polyimide resins, and thermosetting silicone resins. Examples thereof include thermosetting resins. When the polymer clad optical fiber 11 doped with a dopant such as a rare earth element is coated on the core 11a with an overcoat 12 of an ultraviolet curable resin, a wavelength shorter than 350 nm is used from the viewpoint of suppressing deterioration of the core 11a due to ultraviolet rays. It is preferable to select an ultraviolet curable resin that absorbs light.

  The thickness of the overcoat 12 is, for example, 10 to 100 μm. The refractive index of the overcoat 12 is, for example, 1.4 to 1.57, and is preferably higher than the refractive index of the cladding 11b from the viewpoint of suppressing the dissipation of the cladding mode light. The Young's modulus of the resin forming the overcoat 12 is, for example, 100 to 400 MPa, and is preferably higher than the Young's modulus of the clad material from the viewpoint of reducing the stress and transmission loss that occur during bending. The gel fraction of the resin forming the overcoat 12 is, for example, 80 to 100%, and is preferably lower than the gel fraction of the cladding material. Further, by reducing the difference in shrinkage due to the dissipative low molecular weight component that occurs when drying after water absorption, the occurrence of floating between the overcoat 12 and the clad 11b is restricted, thereby suppressing transmission loss. From the viewpoint of achieving this, the difference in gel fraction between the resin forming the overcoat 12 and the cladding material is preferably smaller than 5%.

  The polymer-clad optical fiber core wire 10 according to the first embodiment is configured to confine and transmit the light input to the core 11a within the core 11a due to the refractive index difference between the core 11a and the clad 11b. .

  Moreover, according to the polymer clad optical fiber core wire 10 according to the first embodiment, since the clad 11b is formed of a perfluoroether polymer cured by cross-linking by a hydrosilylation reaction, the clad 11b is greatly reduced in refractive index, As a result, a high NA can be obtained with respect to the core 11a, and excellent moisture resistance can be obtained because the bonding portion between the carbon atom and the silicon atom, which serves as a crosslinking point of the cladding material 11b, is hydrophobic. it can. Further, by introducing an alkoxy group bonded to the silicon atom of the clad 11b into the clad material 11b, the affinity between the clad 11b and the glass forming the core 11a is increased, resulting in high adhesion between them. More excellent moisture resistance can be obtained.

  Furthermore, the clad 11b formed by the perfluoroether polymer cured by crosslinking by hydrosilylation reaction is expected to have low temperature dependency of optical properties and excellent heat resistance, and can therefore be used in harsh environments. And long life can be expected. In addition, since it is a thermosetting resin, in the case of the polymer clad optical fiber 11 in which the core 11a is doped with a dopant such as a rare earth element, it is possible to prevent deterioration of the core 11a due to ultraviolet rays when the clad 11b is formed. it can.

  Next, a method for manufacturing the polymer-clad optical fiber core wire 10 according to the first embodiment will be described with reference to FIG. In the following, the case where the overcoat 12 is formed of an ultraviolet curable resin is taken as an example, but the present invention is not particularly limited thereto.

  First, a glass preform P for forming the core 11a is prepared. Examples of the method for producing the preform P include known methods such as a CVD method and a VAD method. The preform P is, for example, a cylindrical body having a length of 100 to 1000 mm and an outer diameter of 10 to 50 mm.

  Next, the preform P is set on the drawing machine 30.

  Here, the drawing machine 30 includes a spinning furnace 31 that heats the preform P, a subsequent clad forming portion 32, and a subsequent overcoat forming portion 33. The clad forming part 32 includes a first coating die 32a and a heating furnace 32b. The overcoat forming part 33 is composed of a second coating die 33a and a UV irradiator 33b.

  Then, the drawing machine 30 is operated, the core 11a is formed from the preform P in the spinning furnace 31, and then the core 11a is passed through the clad forming portion 32 to form the clad 11b to produce the polymer clad optical fiber 11. Then, the polymer clad optical fiber 11 is passed through the overcoat forming portion 33 to form the overcoat 12 to manufacture the polymer clad optical fiber core wire 10 according to the first embodiment.

  At this time, in the spinning furnace 31, the preform P is heated and drawn to form the core 11a (light transmission path forming step). Here, the set temperature (drawing temperature) of the spinning furnace 31 is, for example, 2000 to 2300 ° C. The drawing speed is, for example, 1 to 100 m / min.

  In the clad forming part 32, the drawn core 11a is passed through the first coating die 32a, and a liquid clad forming material is adhered to the surface thereof with a uniform thickness, and subsequently heated by passing through a heating furnace 32b. The clad 11b is formed by thermosetting (clad forming step).

  Here, the clad forming material includes a perfluoroether polymer which is cured by cross-linking by a C = C double bond and SiH hydrosilylation reaction. The clad forming material preferably contains C═C double bonds and SiH in a ratio of 1: 1.

  The clad forming material may be composed of a single component. A single component clad former is composed of a perfluoroether polymer having at least one C═C double bond and at least one SiH in the molecule, and when heated, the C═C double bond between the molecules. And SiH crosslink by hydrosilylation reaction.

  The clad forming material may be composed of a plurality of components. The multi-component clad forming material is composed of, for example, a perfluoroether polymer component having at least two C═C double bonds in the molecule and a fluorine-containing organosiloxane component having at least two SiH, and is heated. The C═C double bond and SiH are cross-linked by hydrosilylation reaction between both components.

  The C═C double bond may be contained in the main chain, may be contained in the side chain, and may be further contained at the end of the main chain or the side chain. The C═C double bond is preferably introduced as an alkenyl group in the molecule.

  Here, when an organosilicon compound having one or more silicon atoms directly bonded to an epoxy group and an alkoxy group in one molecule is added to the clad forming material, the epoxy group becomes C = An alkenyl group can be introduced into the clad forming material by reacting with a part of the C double bond and bonding with the clad forming material. Here, the alkoxy group directly bonded to the silicon atom reacts and bonds with the hydroxyl group on the surface of the quartz glass, thereby increasing the adhesion between the cladding material and the glass. The addition amount of the alkoxy group is, for example, 0.01 to 5%, and if it is 0.01% or more, the adhesion between the cladding material and the glass is extremely improved, and if it is 5% or less, the refraction of the cladding material is reduced. It has a low rate and is very suitable as a cladding.

  Examples of the alkenyl group include a vinyl group, a propenyl group, a styryl group, an isopropenyl group, a cyclopropenyl group, a butenyl group, a cyclobutenyl group, a cyclopentenyl group, a hexenyl group, and a cyclohexenyl group.

  The SiH may be contained in the main chain, may be contained in the side chain, and may be further contained at the end of the main chain or the side chain. SiH is a repeating structure of siloxane bonds in the molecule.

It is preferably introduced as The number of repeating siloxane bonds (n) is, for example, 2-5.

  The clad forming material may contain only a single kind of perfluoroether polymer, or may contain a plurality of kinds of perfluoroether polymers.

  The clad forming material may contain other polymer components as long as the high NA and excellent moisture resistance of the polymer clad optical fiber 11 are not impaired. The clad forming material may contain a platinum-based catalyst or the like.

  The clad forming material has a viscosity of, for example, 0.5 to 50 Pa · s, and preferably 1 to 10 Pa · s for the purpose of obtaining a coating film having a preferable thickness as the clad 11b. The viscosity of the clad forming material is measured by a cone-plate type rotational viscometer according to JIS Z 8803.

  The curing start temperature of the clad forming material is, for example, 70 to 150 ° C., and preferably 90 to 130 ° C. from the viewpoint of pot life and processing speed. The curing start temperature of the clad forming material is measured by the following procedure using a rigid pendulum type physical property tester 40B (for example, model number: RPT-3000W manufactured by A & D) as shown in FIG. The The rigid pendulum type physical property tester 40B includes a sample boat 41B (for example, made of aluminum), in which a knife edge 42B (for example, model number: RPN160 manufactured by A & D Co., Ltd.) is provided. (For example, model number: FRB100 manufactured by A & D Corporation) is hung and a pendulum is configured. In a room temperature air atmosphere, the clad forming material M is injected into the sample boat 41B to a depth of 0.5 mm, and the sample boat 41B is heated from room temperature to 200 ° C. at a rate of 10 ° C./min. In addition, the vibration period is measured by applying vibration to the pendulum at regular intervals. When the clad forming material M is cured by cross-linking, the elasticity of the liquid is increased and the vibration period is shortened. Therefore, as shown in FIG. The intersection point with the straight line portion where the cycle decreases is obtained, and this is set as the curing start temperature.

  The perfluoroether polymer contained in the clad forming material is, for example, SIFEL series manufactured by Shin-Etsu Chemical Co., Ltd. as a commercially available material.

    The set temperature of the heating furnace 32b is, for example, 100 to 500 ° C., and the furnace length is, for example, 300 to 300 cm.

  In the overcoat forming portion 33, the polymer clad optical fiber 11 in which the core 11a is coated with the clad 11b is passed through the second coating die 33a, and a liquid overcoat forming material is adhered to the surface thereof with a uniform thickness. The overcoat 12 is formed by being cured by being irradiated with ultraviolet rays through the UV irradiator 33b (overcoat forming step).

  Here, examples of the overcoat forming material include uncrosslinked ultraviolet curable urethane acrylate resin. The viscosity of the overcoat forming material is, for example, 0.5 to 5 Pa · s.

(Embodiment 2)
FIG. 5 shows a double-clad optical fiber 20 according to the second embodiment. The double clad optical fiber core wire 20 according to the second embodiment is used for applications such as a fiber laser.

  The double clad optical fiber core wire 20 according to the second embodiment is composed of a double clad optical fiber 21 (polymer clad optical fiber) having a circular cross section and an overcoat 22 covering the same. The core wire diameter is, for example, 100 to 1000 μm.

  The double clad optical fiber 21 includes a core 21a having a circular cross section at the center of the fiber, a first clad 21b provided so as to cover the core, and a second clad 21c provided so as to cover the core. . The cross-sectional shape of the first cladding 21b may be circular, but from the viewpoint of preventing the excitation light from becoming skew light that does not pass through the core 21a when the excitation light is input to the first cladding 21b. The cross-sectional shape is preferably a polygon or a non-geometric shape. The fiber diameter is, for example, 50 to 700 μm.

  The core 21a and the first cladding 21b are integrally formed of glass.

  The glass forming the core 21a is doped with, for example, a dopant that increases the refractive index such as Ge, a dopant that decreases the refractive index such as F, or other functionalizing dopants such as rare earth elements (Er, Yb, Nd). Quartz glass. The core diameter is, for example, 5 to 100 μm. The relative refractive index difference (Δ) between the core 21a and the first cladding 21b is, for example, 0.1 to 1.0%.

The glass forming the first cladding 21b may be pure quartz glass (SiO ₂ ), or may be quartz glass doped with a dopant that changes the refractive index, such as F or Ge. The thickness of the first cladding 21b is, for example, 25 to 350 μm. The refractive index of the first cladding 21b is lower than the refractive index of the core 21a, and the relative refractive index difference is, for example, 0.1 to 1.0%.

  The second clad 21c is formed of a clad material containing a perfluoroether polymer cured by crosslinking by a hydrosilylation reaction. The thickness of the second cladding 21c is, for example, 10 to 100 μm.

  The refractive index of the second cladding 21c is lower than the refractive index of the first cladding 21b, for example, 1.37 or less, and preferably 1.35 or less. In the double clad optical fiber 21, the second clad 21c has such a low refractive index, so that the NA with respect to the first clad 21b is, for example, 0.50 or more, preferably 0.55 or more.

  The other configuration of the second cladding 21c is the same as the configuration of the cladding 21b of the first embodiment.

  The overcoat 22 is formed of the same type of resin as the overcoat 12 of the first embodiment. The thickness of the overcoat 22 is, for example, 10 to 100 μm. The other configuration of the overcoat 22 is the same as the configuration of the clad 11b of the first embodiment.

  The double clad optical fiber core wire 20 according to the second embodiment transmits the excitation light input to the first cladding 21b while reflecting it at the interface between the first and second claddings 21b and 21c, and the excitation light. Is excited by the dopant doped in the core 21a when passing through the core 21a to form an inversion distribution between energy levels, so that the light input to the core 21a is amplified and transmitted by the stimulated emission. It is configured. Therefore, in the double clad optical fiber core wire 20 according to the second embodiment, the core 21a and the first clad 21b constitute an optical transmission line.

  In addition, according to the double clad optical fiber 20 according to the second embodiment, the second clad 21c is formed of a perfluoroether polymer cured by crosslinking by a hydrosilylation reaction. As a result, high NA can be obtained with respect to the first cladding 21b, and the bonding portion between the carbon atom and the silicon atom serving as a cross-linking point of the second cladding 21c is hydrophobic. Moisture resistance can be obtained. Further, by introducing an alkoxy group bonded to a silicon atom of the second clad 21c into the second clad 21c, the affinity with the glass forming the second clad 21c and the first clad 21b is increased. Adhesion occurs, and as a result, better moisture resistance can be obtained. Further, when the excitation light emitted from the light source is collected and incident on the first cladding 21b, the incident angle can be increased when the NA is high in this way, so that the amount of excitation light that can be incident can be increased. Therefore, since more excitation light can be confined in the first cladding 21b, high oscillation efficiency can be obtained.

  Further, the second clad 21c formed by the perfluoroether polymer cured by cross-linking by hydrosilylation reaction is expected to have low temperature dependency of optical characteristics and excellent heat resistance, and therefore is used in severe environments. Possibility and long life can be expected. In addition, since the second clad 21c is formed of a clad material cured by crosslinking a thermosetting resin by heating, in the case of the double clad optical fiber 21 in which the core 21a is doped with a dopant such as a rare earth element. In addition, it is possible to prevent the deterioration of the core 21a due to ultraviolet rays when forming the second cladding 21c.

  The manufacturing method of the double clad optical fiber core wire 20 according to the second embodiment is substantially the same as the manufacturing method of the polymer clad optical fiber core wire 10 according to the first embodiment. A preform having a two-layer structure of a material having a circular cross section for forming the first clad and a material for forming the first clad provided so as to cover the material is used, and the second clad 21c is formed from the clad forming material.

(Clad forming material)
<Example>
The clad forming material of the example was a perfluoroether polymer that was cured by cross-linking by a hydrosilylation reaction. The viscosity was 4 Pa · s. The curing start temperature of the clad forming material was 128 ° C. as measured by the method shown in FIGS. 4 (a) and 4 (b).

  This clad forming material was applied on a glass substrate and cured by thermal crosslinking under the conditions of a heating temperature of 150 ° C. and a heating time of 5 hours, thereby producing a sheet having a thickness of 200 μm. This is the cladding material of the example. The gel fraction of this clad material was 99%.

<Comparative example>
The clad forming material of the comparative example was an ultraviolet curable fluorinated acrylate resin that is cured by ultraviolet crosslinking. The viscosity was 2.4 Pa · s.

This clad forming material was applied onto a glass substrate and cured by ultraviolet crosslinking under a condition of an integrated light quantity of 1000 mJ / cm ² in a nitrogen atmosphere to produce a sheet having a thickness of 200 μm. This is the cladding material of the comparative example. The gel fraction of this clad material was 96%.

(Overcoat material)
The overcoat forming materials of Examples and Comparative Examples were UV curable urethane acrylate resins that were cured by UV crosslinking. The viscosity was 2.5 Pa · s.

This overcoat forming material was cured by UV crosslinking under a condition of a cumulative light quantity of 1000 mJ / cm ^{2 in} a nitrogen atmosphere to produce a sheet having a thickness of 200 μm. This is an overcoat material. The gel fraction of this overcoat material was 96%.

(Polymer-clad optical fiber core wire)
<Example>
Using the clad forming material of the above example and the overcoat forming material, a polymer clad optical fiber core having the same configuration as that of the first embodiment was produced, and this was used as the polymer clad optical fiber core of the example. At this time, the drawing conditions were a drawing speed of 20 m / min, and a set temperature of a heating furnace for curing the clad forming material was 400 ° C. The furnace length of the heating furnace was 1 m. The irradiation condition of the UV irradiator for curing the overcoat was 1000 mJ / cm ² .

  The core diameter of the polymer clad optical fiber core of the example was 350 μm. The fiber diameter of the polymer clad optical fiber was 260 μm. The core diameter was 200 μm.

  The core was made of pure quartz glass. The clad was formed of the clad material of the above example, that is, a perfluoroether polymer cured by crosslinking by a hydrosilylation reaction. The overcoat was formed of the above-described overcoat material, that is, an ultraviolet curable urethane acrylate resin cured by ultraviolet crosslinking.

<Comparative example>
A polymer-clad optical fiber core having the same structure as that of the example except that the clad was formed of a clad material of a comparative example, that is, an ultraviolet curable fluorinated acrylate resin cured by ultraviolet crosslinking, was prepared as a comparative example. The polymer-clad optical fiber core wire was used.

(Test evaluation method)
<Density of clad material>
Test pieces were prepared from the clad materials of Examples and Comparative Examples, and the density of the clad material was measured in accordance with JIS K0061.

<Shore A hardness of clad material>
The clad materials of the example and the comparative example were overlapped to prepare a test piece having a thickness of 6 mm, and the Shore A hardness of the clad material was measured with a type A durometer in accordance with JIS K 6253.

<90 ° peel strength of clad material to glass>
The clad forming material used in each of the examples and the comparative examples was applied on a glass substrate with a thickness of 100 to 200 μm, and cured by crosslinking to form a clad material. A test piece was prepared by cutting into a strip shape, and the tension when one end of the strip-shaped clad material was pulled up perpendicularly from the glass substrate at a pulling rate of 100 mm / min was measured, and the value was measured as a strip shape. By dividing by the width of the cladding material, the 90 ° peel force of the cladding material on the glass was measured.

The crosslinking conditions of the examples were a heating temperature of 150 ° C. and a heating time of 5 hours, and the crosslinking conditions of the comparative example were an integrated light quantity of 1000 mJ / cm ^{2 of} ultraviolet light irradiated for curing in a nitrogen atmosphere.

<Refractive index of clad material>
Test pieces were prepared from the clad materials of Examples and Comparative Examples, and the refractive index of the clad material was measured by the Abbe refractometer film sample measurement method according to JIS K0062.

<NA for the core of polymer-clad optical fiber>
For each of the polymer clad optical fiber cores of Examples and Comparative Examples, the NA with respect to the core of the polymer clad optical fiber was measured by the FFP method in accordance with JIS C 6825.

<Transmission loss after immersion of polymer-clad optical fiber core in hot water>
For each of the polymer-clad optical fiber cores of the example and the comparative example, 50 m is bundled, immersed in warm water adjusted to 85 ° C. in a water bath for 2 days, and signal light having a wavelength of 1.31 μm is transmitted. The transmission loss was measured by the cutback method.

(Test evaluation results)
Table 1 shows the test results.

The density of the clad material embodiment 1.77 g / cm ^3, and Comparative Examples was 1.65 g / cm ^3.

  The Shore A hardness of the clad material was 29 in the example and 41 in the comparative example.

  The 90 ° peeling force of the clad material on the glass was 21 N / m in the example and 11 N / m in the comparative example.

  The refractive index of the clad material was 1.34 in the example and 1.38 in the comparative example.

  The NA for the core of the polymer clad optical fiber core was 0.59 in the example and 0.45 in the comparative example.

  The transmission loss after immersion of the polymer-clad optical fiber in hot water was 5 dB / km in the example and 100 dB / km or more in the comparative example.

  The present invention is useful for a polymer clad optical fiber and a manufacturing method thereof.

10 Polymer-clad optical fiber core wire 11 Polymer-clad optical fiber 11a Core (optical transmission line)
11b Clad 12 Overcoat 20 Double clad optical fiber (polymer clad optical fiber)
21 Double clad optical fiber (polymer clad optical fiber)
21a Core 21b First clad 21c Second clad 22 Overcoat 30 Drawing machine 31 Spinning furnace 32 Clad formation part 32a First coating die 32b Heating furnace 33 Overcoat formation part 33a Second coating die 33b UV irradiation machines 40A, 40B Rigid body Pendulum type physical property tester 41A Sample stage 41B Sample boat 42A Pipe edge 42B Knife edge 43 Weight F Film M Clad forming material P Preform

Claims (6)

A polymer-clad optical fiber having an optical transmission line formed of glass and a clad provided to cover the optical transmission line,
The clad material forming the clad is a polymer clad optical fiber containing a perfluoroether polymer cured by cross-linking by a hydrosilylation reaction. The polymer-clad optical fiber according to claim 1,
A polymer clad optical fiber having a numerical aperture of 0.50 or more with respect to the optical transmission line. The polymer clad optical fiber according to claim 1 or 2,
A polymer clad optical fiber having a Shore A hardness of 10 to 80 of the clad material. The polymer clad optical fiber according to any one of claims 1 to 3,
A polymer clad optical fiber, wherein the clad material has a glass transition temperature of 0 ° C or lower.   A polymer-clad optical fiber, wherein the polymer-clad optical fiber according to any one of claims 1 to 4 is coated with an overcoat. An optical transmission line forming step of forming an optical transmission line by drawing a glass preform;
A clad forming step of forming a clad by thermosetting by attaching a liquid clad forming material to the surface of the optical transmission line formed in the optical transmission line forming step and heating;
A method for producing a polymer clad optical fiber comprising:
The said clad | crud forming material is a manufacturing method of the polymer clad optical fiber containing the perfluoroether polymer hardened | cured by bridge | crosslinking by hydrosilylation reaction.

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