JP2008158406A - Fiber with optical transmission structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber with optical transmission structure that can be manufactured at low cost, that has very little transfer loss, since low-refractive index polymers are surrounded by high-refractive index polymers while these are arranged accurately, and that has superior reliability and general practicality. <P>SOLUTION: The fiber with optical transmission structure is formed, by dispersing a low refractive index dispersion phase comprising low refractive index fiber-forming polymers in a high-refractive index continuous phase comprising high-refractive index fiber-forming polymers, wherein the diameter of the low-refractive index dispersion phase is 10 μm or smaller, refractive index difference between the high and low refractive index fiber-forming polymers is 0.001 or larger, the number of the low refractive index dispersion phases is 100 or larger, and an optical transmission section is provided in the center of the fiber cross section, the optical transmission section which is a part of the high-refractive index continuous phase. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical transmission fiber used as an optical fiber and the like, and relates to an optical transmission fiber that has a low transmission loss and can be manufactured at a low cost because the disposition phase of the dispersed phase in the fiber cross section is extremely high. Is.

  An optical fiber has excellent characteristics as an optical transmission medium, and conventionally an inorganic glass fiber is used. In addition, these inorganic glass-based fibers are not only poor in workability, weak in bending stress but also expensive, so that optical fibers based on plastics have been developed and put to practical use.

  Conventionally, many refractive index stepped (SI type) optical fibers have been proposed in which a high refractive index core material is surrounded by a lower refractive index cladding material. Patent Document 1 also proposes using a fluorine-containing resin for both the core layer and the clad layer with low transmission loss. A refractive index distribution type (GI type) optical fiber is also known in which the refractive index is attenuated by distributing the material in the radial direction from the center of the fiber to the circumferential direction (for example, Patent Documents 2, 6, and 6). 7, Non-Patent Document 1, etc.). Further, Patent Document 3 proposes a multi-core plastic optical fiber in which seven or more cores having a diameter of 50 to 200 μm made of a resin having a refractive index higher than that of the clad resin are embedded in the clad resin. Yes.

In recent years, optical fibers having a structure including holes are known. A fiber having a photonic crystal structure has been proposed by arranging the holes periodically in parallel in the major axis direction.
Focusing on the waveguide principle of photonic crystal fibers, there are two categories. One is a total reflection type optical fiber that has a core-cladding structure and makes the effective refractive index of the clad lower than the refractive index of the core by making holes present in the clad, and guides light by total reflection. is there. The other is a photonic band gap type in which light is confined by a photonic band gap, and the structure requires strict periodicity and uniformity of hole size.

The following methods have been proposed for such a photonic crystal fiber. In Patent Document 4, using a material in which SiO ₂ is doped with GeO _2, a core part formed in a solid shape in the fiber axis direction and a large number in the fiber axis direction so as to cover the periphery of the core part are disclosed. A method of manufacturing a photonic crystal fiber having a porous portion in which fine pores are arranged in a fine shape is proposed. A cylindrical porous portion capillary having a hole that becomes the pore of the porous portion in the hole of the cylindrical support tube, and a rod shape having an outer diameter smaller than that of the porous portion capillary and serving as the core portion There have been proposed ones comprising a preform creating step in which the core part rods are respectively arranged to create a preform, and a step in which the preform is heated and stretched and drawn into a fiber shape.

  Patent Document 5 proposes a sea-island type photonic fiber using fluorine-based polymers having different refractive indexes. The island-island structure is obtained by placing a polymer of low-refractive-index organic compounds (island materials) in the form of strands divided in advance into a pipe made of a polymer of high-refractive-index organic compounds (sea materials) and co-spinning. A low refractive index polymer is divided and subdivided using an extrusion die in a molten state, and a high refractive index polymer is merged and fed to the periphery, and extruded from a common nozzle to create a preform. Further, a method for manufacturing a photonic crystal fiber by stretching has been proposed.

  However, in both Patent Documents 4 and 5, it is difficult to handle thin capillaries and maintain cleanliness in the method of creating an assembly-type photonic crystal fiber, and many capillaries that are bundled in a tightly packed state are retained. There is a problem in the stability of quality in which the process of fusing and integrating as it is and drawing the assembled preform uniformly. In both cases, it is difficult to reduce the pore diameters of the low refractive index phase and the pore phase in terms of manufacturing method and material processing, and it is difficult to form a photonic crystal structure with high accuracy, which leads to low loss. This has led to a decrease in performance.

JP-A-2-244007 Japanese Patent Laid-Open No. 5-173026 JP 9-33737 A JP 2002-326831 A JP 2004-93639 A WO94 / 04949 pamphlet WO94 / 1505 pamphlet “Chemistry and Industry” Vol. 45, No. 7, 1992, P1261-1264

  The present invention can be manufactured at a low cost, and a low refractive index polymer is surrounded by a high refractive index polymer and these are arranged with high precision, so there is very little transmission loss, and optical transmission with excellent reliability and general utility. An object is to provide a structural fiber.

  In order to achieve the above object, the present invention achieves the low refractive index by dispersing a low refractive dispersion phase composed of a low refractive index fiber-forming polymer in a high refractive index continuous phase composed of a high refractive index fiber forming polymer. The diameter of the refractive index dispersed phase is 10 μm or less, the refractive index difference between the high refractive index fiber forming polymer and the low refractive index fiber forming polymer is 0.001 or more, and the number of the low refractive index dispersed phases is There is provided an optical transmission structural fiber characterized in that there are 100 or more optical transmission sections provided at the center of the cross section of the fiber, and the optical transmission sections are part of the high refractive index continuous phase.

  According to the present invention, the low refractive index polymer can be manufactured at low cost, and the high refractive index polymer is surrounded by the high refractive index polymer so that the transmission loss is extremely low, and the reliability and general practicality are excellent. An optical transmission structural fiber can be provided.

  The optical transmission structure fiber of the present invention includes a low refractive index fiber-forming polymer (in a high refractive index continuous phase of a high refractive index fiber forming polymer (hereinafter sometimes simply referred to as a high refractive index polymer). Hereinafter, it is an optical transmission structure fiber in which a low refractive index dispersed phase (which may be simply referred to as a low refractive index polymer) is dispersed.

  In the present invention, the optical transmission structure fiber has the following diameter of the low refractive index dispersion phase, the refractive index difference between the high refractive index fiber forming polymer and the low refractive index fiber forming polymer, and the low refractive index dispersion. It is important that the number of phases is satisfied at the same time, and that an optical transmission part is provided at the center of the cross section of the fiber, and the optical transmission part has a structure that is a part of the high refractive index continuous phase. As a result, low-cost, high-refractive-index polymers are surrounded by high-refractive-index polymers, and these are arranged accurately, so that there is very little transmission loss, and light with excellent reliability and general practicality. Transmission structural fibers can be provided.

  That is, the diameter of the low refractive index continuous phase needs to be 10 μm or less. When the diameter of the low-refractive index continuous phase is larger than this, spots such as size and degree of orientation are generated in the fiber cross-section direction and fiber axis direction due to temperature spots and tension spots caused by it during the fiber manufacturing process. This causes transmission loss. The diameter of the low refractive index continuous phase is preferably 1 μm or less, more preferably 50 nm to 1 μm.

  Further, the difference in refractive index between the high refractive index fiber forming polymer and the low refractive index fiber forming polymer needs to be 0.001 or more. If the refractive index difference is smaller than this, transmission loss may be caused.

  The number of low refractive index dispersed phases needs to be 100 or more. When the number of low refractive index dispersed phases is less than 100, even in total reflection transmission / photonic band gap transmission, the central (core) portion which is an optical transmission portion and the low refractive index dispersion phase which is a non-optical transmission portion substantially. The difference in refractive index from the site of distribution is insufficient, causing transmission loss. Therefore, in order to ensure the boundary between the optical transmission unit and the non-optical transmission unit, the number of low refractive index dispersed phases is 100 or more, preferably 300 or more, more preferably 300 to 2000. There is a need.

  Furthermore, the optical transmission part is provided at the center of the cross section of the fiber, and the optical transmission part is provided as a part of the high refractive index continuous phase. It is also necessary to make a transmission body consisting of the transmission principle.

The photonic bandgap transmitter has the property of propagating light having a wavelength twice as long as a lossless portion in a defect portion in a structure in which minute phases having a diameter of about 0.1 μ to 1 μ are periodically arranged. That is, the refractive index n _i of the refractive index n _s and a low refractive index continuous phase distance Λ and a high refractive index the continuous phase between the low refractive index dispersion _phase, the volume ratio of the low refractive index dispersion phase phi, perpendicular angle of incidence (the periodic direction Angle) from θ), the propagation wavelength λ must satisfy the following relational expression.
λ = 2Λn _s sin θ (1 + ψ / sin ² θ) ^{−1/2
(Here, ψ = 3φ (m 2 -1} ) / (m 2 +2), it is _{m = n i / n s.} )
The incident angle θ and the propagation wavelength λ can be changed according to the light source and application.

  In the present invention, polycarbonate, isotactic polystyrene, syndiotactic polystyrene or the like is used as the high refractive index polymer, and an acrylic polymer represented by polymethyl methacrylate, polymethylpentene ( Poly 4-methylpentene-1) and the like can be preferably used.

  The optical transmission structure fiber of the present invention described above can be easily manufactured, for example, by the following method. That is, first, a low refractive index polymer and a high refractive index polymer are melt-spun so that the former is a dispersed phase (island component) and the latter is a continuous phase (sea component). As the spinneret used for melt spinning, any one such as a hollow pin group for forming an island component or a group having a fine hole group can be used. For example, any spinneret that forms an island-like cross-section by joining an island component extruded from a hollow pin or fine hole and an ocean component flow that is designed to fill the gap between them, and compressing this But you can. However, in order to form a core part forming a part of a high refractive index continuous phase composed of a sea component at the center of the fiber cross section, the specification is such that there is no island formation by hollow pins or fine holes. Examples of spinnerets that are preferably used are shown in FIGS. 1 and 2, but are not necessarily limited thereto. FIG. 1 shows a method in which hollow pins are discharged into a sea component resin reservoir portion and merged and compressed. FIG. 2 shows a method in which islands are formed by a fine hole method instead of hollow pins.

  The fiber melted and discharged from the above spinneret is solidified by cooling air and is preferably wound at 1000 to 3500 m / min. When a polymer having poor stretchability (solid plastic deformation) is used, the polymer may be wound up by only melt spinning and used as it is. If stretching is required, the obtained unstretched fiber may be temporarily wound up and separately stretched, or the unstretched fiber may be wound on a roller without being wound once, and then stretched and wound. Also good.

Hereinafter, the present invention will be described more specifically with reference to examples. Each evaluation item was measured by the following method.
(1) Distance between dispersed phases (islands), size of dispersed phase (islands) Diameter was measured by taking a fiber cross-sectional photograph at a magnification of 30000 with a transmission electron microscope TEM.
(2) Refractive index Atago Abbe refractometer type 1 was used and measured using sodium D at a constant temperature of 23 ° C.

[Example 1]
Polycarbonate (PC) is used as the high refractive index polymer and polymethyl methacrylate (PMMA) is used as the low refractive index polymer, and the melt is set to 280 ° C. using an extruder at a melting temperature of 290 ° C. and 250 ° C., respectively. It was introduced into a die forming a sea-island structure in which the number of refractive index dispersed phases (number of islands) was 500. The discharged sea-island cross-section fiber was wound at a winding speed of 2000 m / min.

  The diameter of the dispersed phase (island) of PMMA of the obtained fiber is 1 μm, the distance Λ between the low refractive index dispersed phases (islands) is 2.5 μm, the diameter of the optical transmission part (core part) is 5 μm, and the fiber diameter. Is 400 μm, the refractive index of the high refractive index continuous phase is 1.48, and the refractive index of the low refractive index dispersed phase is 1.38. A laser beam having an NA of 0.25 and a wavelength of 1300 nm was incident on the obtained optical transmission structure fiber (optical fiber), and a transmission test of 500 m was performed. The transmission loss was 25 dB / km, and the band was 4 GHz · km.

[Example 2]
The number of low-refractive-index dispersed phases set to 280 ° C. using PC as the high-refractive index polymer and PMMA as the low-refractive index polymer, with the melt and the melting temperature set at 290 ° C. and 250 ° C. respectively. The number of islands was introduced into a base forming a sea-island structure with 1000. The discharged sea-island cross-section fiber was wound up at 2000 m / min.

  The diameter of the low refractive index dispersed phase (island) of the obtained fiber PMMA is 700 nm, the distance between the low refractive index dispersed phases (islands) is 1.5 μm, the diameter of the optical transmission part (core part) is 3 μm, The fiber diameter is 480 μm, the refractive index of the high refractive index continuous phase is 1.48, and the refractive index of the low refractive index dispersed phase is 1.38. A laser beam having an NA of 0.25 and a wavelength of 1300 nm was incident on the obtained optical transmission structure fiber (optical fiber), and a transmission test of 500 m was performed. The transmission loss was 17 dB / km, and the band was 4 GHz · km. The loss when the fiber was bent at an angle of 180 ° with R10 was 0.2 dB.

[Example 3]
A low refractive index set to 260 ° C. using PMMA as the high refractive index polymer and poly-4-methylpentene-1 as the low refractive index polymer, and melted with an extruder at a melting temperature of 250 ° C. and 270 ° C., respectively. It was introduced into a die forming a sea-island structure in which the number of rate-dispersed phases (number of islands) was 500. The discharged sea-island cross-section fiber was wound at a winding speed of 2000 m / min.

  The diameter of the low refractive index dispersed phase (island) of the obtained fiber PMMA is 1 μm, the distance Λ between the low refractive index dispersed phases (islands) is 2.5 μm, and the diameter of the optical transmission part (core part) is 6 μm. The fiber diameter is 400 μm, the refractive index of the high refractive index continuous phase is 1.38, and the refractive index of the low refractive index dispersed phase is 1.36. A laser beam having an NA of 0.25 and a wavelength of 1300 nm was incident on the obtained optical transmission structure fiber (optical fiber), and a transmission test of 500 m was performed. The transmission loss was 31 dB / km, and the band was 4 GHz · km.

[Comparative Example 1]
The number of low-refractive index dispersed phases set to 280 ° C. using a high-refractive-index polymer PC and a low-refractive-index polymer PMMA using a melt temperature of 290 ° C. and 250 ° C., respectively. It was introduced into a base forming a sea-island structure with 25 islands). The discharged sea-island cross-section fiber was wound at a winding speed of 2000 m / min.

  The diameter of the low refractive index dispersed phase (island) of the obtained fiber PMMA is 15 μm, the distance Λ between the low refractive index dispersed phases (islands) is 40 μm, the diameter of the optical transmission part (core part) is 60 μm, the fiber The diameter is 320 μm, the refractive index of the high refractive index continuous phase is 1.48, and the refractive index of the low refractive index dispersed phase is 1.38. A laser beam having an NA of 0.25 and a wavelength of 1300 nm was incident on the obtained optical fiber, and a 500 m transmission test was performed. The transmission loss was 100 dB / km, and the band was 4 GHz · km.

[Example 4]
The number of low-refractive index dispersed phases set to 280 ° C. using a high refractive index polymer and PMMA as a low refractive index polymer and melted with an extruder at melting temperatures of 290 ° C. and 250 ° C., respectively. It was introduced into a base having a structure in which a low-refractive index dispersion phase (island) is not formed in the central part of the cross section, that is, an optical transmission part (core part) is formed in the central part. The discharged sea-island cross-section fiber was wound at a winding speed of 2000 m / min.

  The diameter of the low refractive index dispersed phase (island) of the obtained fiber PMMA is 100 nm, the distance Λ between the low refractive index dispersed phases (islands) is 300 nm, and the diameter of the optical transmission part (core part) is 800 nm. The outer diameter is 95 μm, the refractive index of the high refractive index continuous phase is 1.48, and the refractive index of the low refractive index dispersed phase is 1.38. When light of 250 to 1000 nm obtained by cutting light of NA 0.25 and infrared rays was incident on the obtained optical fiber, light of 650 nm was transmitted and a transmission test of 500 m was performed. The transmission loss was 40 dB / km and the band was 4 GHz · km.

  The optical transmission structure fiber of the present invention can be manufactured at low cost, has very little transmission loss, is excellent in reliability and general utility, and has extremely high industrial utility value.

1 is a schematic view of a spinneret used for spinning an optical transmission structure fiber of the present invention. Schematic of another spinneret used for spinning the optical transmission structure fiber of the present invention. Schematic which shows an example of the cross section of the optical transmission structure fiber of this invention.

Explanation of symbols

1: Dispersed phase (island component) polymer reservoir portion 2 before distribution: Dispersed phase (island component) distribution introduction hole 3: Continuous phase (sea component) introduction hole 4: Continuous phase (sea component) polymer reservoir portion before distribution 5: Individual continuous phase / dispersed phase (sea / island) structure forming part 6: Continuous phase / dispersed phase (sea / island) whole converging part 7: Dispersed phase (island component)
8: Continuous phase (sea component)
9: Optical transmission part (core part)
10: Optical transmission part (core part) Diameter 11: Fiber diameter 12: Dispersed phase (island) Diameter 13: Distance between dispersed phases (islands)

Claims (4)

  In a high refractive index continuous phase composed of a high refractive index fiber-forming polymer, a low refractive dispersion phase composed of a low refractive index fiber forming polymer is dispersed, and the diameter of the low refractive index dispersed phase is 10 μm or less, The refractive index difference between the high refractive index fiber forming polymer and the low refractive index fiber forming polymer is 0.001 or more, the number of the low refractive index dispersed phases is 100 or more, and the center part of the fiber cross section Is provided with an optical transmission part, and the optical transmission part is a part of the high refractive index continuous phase.   The optical transmission structure fiber according to claim 1, wherein the diameter of the low refractive index dispersed phase is 1 μm or less.   The optical transmission structure fiber according to claim 1, wherein the number of low refractive index dispersed phases is 300 or more. The distance Λ between the low refractive index dispersed phases, the refractive index ns of the high refractive index continuous phase and the refractive index ni of the low refractive index continuous phase, the volume ratio φ of the low refractive index dispersed phase, and the incident angle (angle from the normal in the period direction). The optical transmission structure fiber according to claim 1, wherein the propagation wavelength λ satisfies the following relational expression, where θ is:
λ = 2Λn _s sin θ (1 + ψ / sin ² θ) ^{−1/2
(Here, ψ = 3φ (m 2 -1} ) / (m 2 +2), it is _{m = n i / n s.} )

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