JP2006276335A - Plastic optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable visually confirming a communication state of a plastic optical fiber. <P>SOLUTION: Visible light as an optical signal to be transmitted is made incident from an end face of the plastic optical fiber. A clad 22 has a scattering structure which scatters the visible light and emits it from the peripheral surface outside the plastic optical fiber. This scattering structure is a structure differing in density depending on positions in the clad 22. This structure is formed by partially changing, or the like, the crystal structure of a polymer. Thus, the core 21 transmits most of the visible light, and a part of the visible light is scattered in the clad 22 and is made to exit outside from the peripheral surface of the plastic optical fiber 11. Therefore, it is possible to visually check the 2nd wavelength light, and it can be judged whether or not communication is underway, and whether or not the plastic optical fiber 11 is disconnected on the way, and a disconnected point can be judged. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plastic optical fiber.

  Plastic optical fibers are superior to silica-based optical fibers in molding processability, weight reduction of members, cost reduction, flexibility, impact resistance, and the like. For example, a plastic optical fiber is not suitable for long-distance light transmission because its optical transmission loss is large compared to a silica-based optical fiber. However, due to the properties of plastic, the optical fiber core portion is several tens of μm or more. The so-called large diameter can be achieved. This increase in the diameter eliminates the need to increase the connection accuracy of various peripheral parts and devices used for branching and connection of the optical fiber with the optical fiber. Therefore, the plastic optical fiber has the merit that connection with peripheral parts and devices, ease of terminal processing, and high-precision alignment are unnecessary. In addition to the cost reduction of the connector part as described above, the plastic optical fiber has a low risk of puncture accidents on the human body due to the properties of the plastic, easy processability due to high flexibility, There are advantages such as easy installation, vibration resistance, and low price. Due to the above-described features, the demand for plastic optical fibers is increasing because they are particularly effective as on-site communication means in homes and offices.

  By the way, the communication status can be detected from the outside of a cable for telecommunications by using the dielectric effect, but the detection from the outside is not yet possible for an optical fiber. However, detection of the communication status is important not only for determining whether communication is in progress, but also for determining whether a disconnection has occurred. For example, it is necessary to grasp the state of the plastic optical fiber in a communication test performed immediately after installation or an inspection when communication is not possible. Therefore, in order to know the communication status, the present inventors have examined means for leaking a part of the light incident on the plastic optical fiber from the outer peripheral surface of the plastic optical fiber.

An example of leaking light incident on an optical fiber from the outer peripheral surface (light leakage) includes using an optical fiber as a light source, and the following proposals have been made. For example, Patent Document 1 is a light source device using an optical fiber as a light source, and in order to take out light incident from one end face of the optical fiber from the side surface, a scatterer is contained in the core of the optical fiber, An optical fiber that scatters incident light has been proposed. Further, in Patent Document 2, as a light used as an evacuation guide light or the like, a cable that allows light leakage to the side surface by arranging a light leakage type optical fiber (optical fiber strand) spirally on a spacer, Patent In Reference 3, an optical fiber cable for lateral illumination that guides light to the outside by providing a tube having a light-reflecting outer surface at the center. In Patent Document 4, a large number of optical fibers are bundled and transparent. Night-time warning lamps have been proposed that are covered with an outer skin so that light is emitted from the end of the optical fiber. Further, Patent Document 5 proposes a side-emitting optical fiber that leaks light by including a silica aerogel that is a scatterer in the clad, and Patent Document 6 describes an optical amplifier for grasping the communication status. A monitor structure has been proposed.
JP-A-5-27121 Japanese Utility Model Publication No. 7-10702 JP-T 8-510847 JP-A-11-119706 JP 2000-137119 A Japanese Patent Laid-Open No. 9-26379

  However, the proposals in Patent Documents 1 to 5 are all related to a light source using an optical fiber, and are not intended to grasp the communication status as described above, and do not have the effect. There is no suggestion. Furthermore, since light leaks from the side of the optical fiber, it deteriorates the communication performance, such as introducing a scatterer into the optical fiber or adding a spiral structure, and these proposals are not suitable for the purpose of grasping the communication situation. Is. According to the monitor structure of Patent Document 6, it is possible to grasp the communication state, but this is realized by devising the structure of the rare earth doped optical fiber amplifier, and the communication state is easily grasped. It does not satisfy the purpose. Further, the monitor structure proposed in Patent Document 6 has a problem that it is not necessarily applicable to communication wavelengths in plastic optical fibers.

  Therefore, in view of such a background, an object of the present invention is to propose a plastic optical fiber for easily detecting a communication state from the outside.

  In the present invention, in order to solve the above-mentioned problem, a linear member whose refractive index in the radial direction of the circular cross section is changed and the outer periphery of the linear member, the refractive index is the refractive index of the linear member. In the plastic optical fiber having an outer peripheral member, the outer peripheral member has a scattering structure that scatters a part of light incident from the end face of the plastic optical fiber and emits the light from the peripheral face to the outside. Has been.

  Further, the scattering structure is preferably a refractive index non-uniform structure having a refractive index different depending on a position in the outer peripheral member, and the non-refractive index non-uniform structure has a density non-uniform structure having a density different depending on a position in the outer peripheral member. It is preferable that

  In the plastic optical fiber of the present invention, (1) the outer peripheral member contains a polymer, and the crystal structure of the polymer is partially different to form the non-uniform structure. (2) the outer peripheral member Includes a polymer, and the density non-uniform structure is formed by molecular weight fluctuation of the polymer. (3) The outer peripheral member includes a polymer as a first component and a second component different from the first component, It is preferably at least one of the non-uniform structure due to the composition ratio fluctuation between the first component and the second component.

  Further, in the present invention, a linear member having a refractive index in the radial direction of a circular cross section, and an outer peripheral member provided on the outer periphery of the linear member and having a refractive index equal to or lower than the refractive index of the linear member. In the plastic optical fiber, the outer peripheral member includes a first layer on the inner side in the cross section, and a second layer provided on the outer periphery of the first layer and having a refractive index lower than that of the first layer. At least one of the layer and the second layer has a scattering structure in which a part of the light incident from the end face of the plastic optical fiber is scattered and emitted from the outer peripheral surface to the outside, and only the first layer is When it has a scattering structure, the second layer is constituted by a transmissive material that transmits the light.

  Furthermore, the present invention provides a linear member having a refractive index in the radial direction of a circular cross section, and an outer peripheral member provided on the outer periphery of the linear member, the refractive index being equal to or lower than the refractive index of the linear member. In the plastic optical fiber having the linear member and the outer peripheral member, the linear member and the outer peripheral member have a scattering structure in which a part of the light incident from the end face of the plastic optical fiber is scattered at the interface of each other and emitted from the outer peripheral surface of the outer peripheral member. Including as a feature. In addition, the present invention provides a linear member having a circular cross-sectional refractive index and a peripheral member provided on the outer periphery of the linear member, the refractive index being equal to or lower than the refractive index of the linear member. The outer peripheral member includes a first layer on the inner side in the cross section and a second layer provided on the outer periphery of the first layer and having a lower refractive index than the first layer, The first layer and the second layer have a scattering structure in which a part of the light incident from the end face of the plastic optical fiber is scattered at each interface and emitted to the outside from the outer peripheral surface of the second layer. Contains. In addition, the present invention provides a linear member having a circular cross-section in which the refractive index in the radial direction is changed, and an outer peripheral member provided on the outer periphery of the linear member, the refractive index being equal to or lower than the refractive index of the linear member. In the plastic optical fiber, the outer peripheral member includes a first layer on the inner side in the cross section, and a second layer provided on the outer periphery of the first layer and having a refractive index lower than that of the first layer. Concavities and convexities are formed on the outer periphery of the two layers to irregularly reflect a part of the light incident from the end face of the plastic optical fiber, and the irregularities are rough surfaces that emit light scattered in the second layer due to irregular reflection from the outer periphery to the outside of the layer. Is included as a feature.

  Furthermore, the present invention includes a plastic optical fiber cord comprising any one of the plastic optical fibers described above and a covering member that covers the outer periphery of the plastic optical fiber and transmits scattered light. It is configured.

  According to the present invention, the communication status can be easily detected from the outside.

  FIG. 1 is a flowchart for manufacturing a plastic optical fiber cord as an embodiment of the present invention. The manufacturing process of the plastic optical fiber cord of the present invention includes a preform manufacturing process 13 for manufacturing the preform 12 with the material constituting the plastic optical fiber 11, and the preform 12 is heated to have a predetermined outer diameter. A heating and stretching process 16 for producing the plastic optical fiber 11 by stretching, and a coating process for obtaining a plastic optical fiber cord (hereinafter sometimes simply referred to as a cord) 17 by providing a predetermined coating material on the plastic optical fiber 11. 18.

  2 is a cross-sectional view of the plastic optical fiber 11, and FIG. 3 is a graph showing the refractive index in the cross-sectional radial direction of the plastic optical fiber 11 shown in FIG. In FIG. 3, the horizontal axis indicates the cross-sectional radial direction of the plastic optical fiber, and the vertical axis indicates the refractive index, which means a higher value as it goes upward. As shown in FIG. 2, the plastic optical fiber 11 is provided on the outer periphery of the core 21 that transmits an optical signal and on the outer periphery of the core 21, and a part of the incident light is scattered and emitted from the outer periphery of the plastic optical fiber 11. The clad 22 has a tube shape with a constant outer diameter and an inner diameter in the longitudinal direction and a uniform thickness. Therefore, the diameter of the core 21 and the inner diameter of the clad 22 are equal.

  In FIG. 3, the range indicated by the symbol (A) on the horizontal axis is the refractive index of the cladding 22 in FIG. 2, and the range indicated by the symbol (B) is the refractive index of the core 21 in FIG. As shown in FIG. 3, the refractive index of the core 21 continuously increases from the boundary with the cladding 22 toward the center, and the refractive index of the cladding 22 is equal to or lower than the refractive index of the core 21. In the radial direction of the circular cross section, the difference between the maximum value and the minimum value of the refractive index is preferably 0.001 or more and 0.3 or less. With the structure as described above, the plastic optical fiber 11 exhibits a function as a GI (graded index) type optical transmission body. The clad 22 has a substantially constant refractive index as shown in FIG. 3, but the refractive index may increase as it approaches the core 21. It may be larger or continuously larger.

  In FIG. 2, the boundary between the core 21 and the clad 22 is shown for convenience of explanation. However, the clarity of the boundary differs depending on the material and manufacturing conditions of the core 21 and the clad 22, and the position indicated by this boundary line is It does not necessarily have to be a position showing the bending point in the refractive index graph. The preform 12 (see FIG. 1) has a cladding and a core larger in diameter than the plastic optical fiber 11, but the basic structure is the same as that of the plastic optical fiber 11, so that the illustration is omitted. There may be a space (hollow part) in the center. The present invention is applicable even if the core 21 has a concentric multilayer structure.

[Material of core 21]
The core 21 has a polymer as its main component, and other substances may be added for the purpose of expressing the refractive index distribution as described above or adjusting the state of the refractive index distribution. Examples of the substance to be added include a refractive index adjusting agent (dopant). As the polymer, a well-known polymer preferable as a plastic optical fiber can be used. Particularly preferably used is an organic material that has a high light transmittance and is preferably an amorphous polymer so as not to cause light scattering.

  Examples of polymers include (meth) acrylic acid esters (fluorine-free (meth) acrylic acid ester (a), fluorine-containing (meth) acrylic acid ester (b)), styrenic compounds (c), vinyl esters. (D), which is obtained by polymerizing bisphenol A, which is a raw material for polycarbonates, as a polymerizable compound. Examples include homopolymers obtained by polymerizing each of these as raw materials, copolymers obtained by combining two or more of these, and mixtures of various combinations of the above homopolymers and copolymers. it can. And among these, what contains (meth) acrylic acid esters or a fluorine-containing polymer as a component is more preferable when comprising an optical transmission body. Next, the above example will be described in more detail.

  Examples of (a) fluorine-free methacrylic acid ester and fluorine-free acrylic acid ester include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tert-butyl methacrylate, benzyl methacrylate, phenyl methacrylate, and methacrylic acid. Examples include cyclohexyl, diphenylmethyl methacrylate, tricyclo [5 · 2 · 1 · 02,6] decanyl methacrylate, adamantyl methacrylate, isobornyl methacrylate, norbornyl methacrylate, methyl acrylate, ethyl acrylate, acrylic acid- Examples thereof include tert-butyl and phenyl acrylate.

  In addition, (b) fluorine-containing acrylic acid ester and fluorine-containing methacrylate ester include 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3 , 3-pentafluoropropyl methacrylate, 1-trifluoromethyl-2,2,2-trifluoroethyl methacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 2,2, Examples include 3,3,4,4-hexafluorobutyl methacrylate.

  Furthermore, (c) styrene compounds include styrene, α-methylstyrene, chlorostyrene, bromostyrene, and the like. Furthermore, (d) vinyl esters include vinyl acetate, vinyl benzoate, vinyl phenyl acetate, vinyl chloroacetate and the like. Of course, the present invention is not limited to these, and the refractive index of a polymer composed of a polymerizable compound alone or a copolymer may have a predetermined refractive index distribution in the molded body when molded into an optical transmission body. In addition, it is preferable to determine the type and composition ratio.

  In addition, when the polymer of the core 21 and the clad 22 contains a hydrogen atom (H), it is preferable that the hydrogen atom is substituted with a deuterium atom (D), thereby reducing transmission loss, particularly It is possible to reduce transmission loss at wavelengths in the near infrared region.

  Furthermore, in order to use a plastic optical fiber for near-infrared light, an absorption loss caused by a C—H bond constituting the polymer occurs. Therefore, it is described in Japanese Patent No. 3332922 and Japanese Patent Application Laid-Open No. 2003-192708. By using a polymer in which C—H bond hydrogen atoms are substituted with deuterium atoms or fluorine, the wavelength region causing this transmission loss can be lengthened, and the loss of transmission signal light Can be reduced. Examples of such polymers include deuterated polymethyl methacrylate (PMMA-d8), polytrifluoroethyl methacrylate (P3FMA), polyhexafluoroisopropyl 2-fluoroacrylate (HFIP 2-FA), and the like. it can. In addition, in order not to impair the transparency after polymerization of the compound as a raw material, it is desirable that impurities and foreign substances serving as scattering sources are sufficiently removed before polymerization.

  In addition, the polymer that forms the core 21 is preferably 10,000 to 1,000,000, more preferably 30,000, from the viewpoint that it can be extruded into a linear body and can be suitably stretched as described below. ~ 500,000. Furthermore, suitability for stretching is also related to molecular weight distribution (MWD: weight average molecular weight / number average molecular weight). For example, if the MWD is too large, the stretchability may be deteriorated when components having an extremely large molecular weight are mixed, and stretching may be impossible. In the present invention, a preferred MWD range is 4 or less, and a more preferred range is 3 or less.

  Furthermore, among the above, the polymer is particularly preferably a fluorine-containing polymer. Fluorine-containing polymers have high heat resistance, moisture resistance, and chemical resistance, and light transmittance in the wavelength band from ultraviolet light to near infrared light is much higher than other polymers. The optical system can be effectively used.

  When a polymerizable compound is polymerized to obtain a polymer, a polymerization initiator may be used. As the polymerization initiator, for example, there are various types that generate radicals. For example, benzoyl peroxide (BPO), tert-butylperoxy-2-ethylhexanate (PBO), di-tert-butyl peroxide (PBD), tert-butylperoxyisopropyl carbonate (PBI) ) And peroxide compounds such as n-butyl-4,4-bis (tert-butylperoxy) valerate (PHV). 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2-methylpropane), 2,2′-azobis (2-methylbutane), 2,2′-azobis (2-methylpentane), 2,2′-azobis (2,3-dimethylbutane), 2,2 '-Azobis (2-methylhexane), 2,2'-azobis (2,4-dimethylpentane), 2,2'-azobis (2,3,3-trimethylbutane), 2,2'-azobis (2 , 4,4-trimethylpentane), 3,3′-azobis (3-methylpentane), 3,3′-azobis (3-methylhexane), 3,3′-azobis (3,4-dimethylpentane), 3,3'-azobis 3-ethylpentane), dimethyl-2,2′-azobis (2-methylpropionate), diethyl-2,2′-azobis (2-methylpropionate), di-tert-butyl-2,2 ′ -Azo compounds such as azobis (2-methylpropionate). In addition, a polymerization initiator is not limited to these, Moreover, you may use 2 or more types together.

  In order to keep various physical property values such as mechanical properties and thermophysical properties uniform when used as a polymer, it is preferable to adjust the degree of polymerization. A chain transfer agent can be used to adjust the degree of polymerization. About a chain transfer agent, according to the kind of polymeric compound used together, a kind and addition amount can be selected suitably. The chain transfer constant of the chain transfer agent for each polymerizable compound can be referred to, for example, Polymer Handbook 3rd Edition (J. BRANDRUP and EH IMMERGUT edition, published by JOHN WILEY & SON). The chain transfer constant can also be obtained by experiment with reference to Takayuki Otsu and Masaaki Kinoshita "Experimental Method for Polymer Synthesis", Kagaku Dojin, published in 1972.

  Examples of the chain transfer agent include alkyl mercaptans (for example, n-butyl mercaptan, n-pentyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, tert-dodecyl mercaptan, etc.), thiophenols (thiophenol, m-bromothio). Phenol, p-bromothiophenol, m-toluenethiol, p-toluenethiol, etc.) are preferably used. In particular, it is preferable to use an alkyl mercaptan such as n-octyl mercaptan, n-lauryl mercaptan, and tert-dodecyl mercaptan. A chain transfer agent in which a hydrogen atom of a C—H bond is substituted with a deuterium atom or a fluorine atom can also be used. Of course, the chain transfer agent is not limited to these, and two or more of these chain transfer agents may be used in combination.

  About each addition amount of the polymerization initiator mentioned above, a chain transfer agent, and a refractive index regulator, a preferable range can be suitably determined according to the kind etc. of the polymerizable compound for cores to be used. In this embodiment, the polymerization initiator is added so that it may become 0.005-0.050 mass% with respect to the polymeric compound for cores, and this addition rate is 0.010-0.020. It is more preferable to set it as the mass%. The chain transfer agent is added so as to be 0.10 to 0.40% by mass with respect to the polymerizable compound for the core, and the addition rate is 0.15 to 0.30% by mass. More preferably.

  Other additives can be added to the polymer as long as optical transmission performance is not deteriorated. For example, a stabilizer can be added for the purpose of improving weather resistance and durability. Further, for the purpose of improving optical transmission performance, a stimulated emission functional compound for optical signal amplification can be added. By adding the compound, the attenuated signal light can be amplified by the pumping light, and the transmission distance is improved. For example, it can be used as a fiber amplifier in a part of the optical transmission link. These additives can also be contained in the core polymer by polymerizing after being added to the various polymerizable compounds as the raw material.

  Further, a predetermined amount of a refractive index adjusting agent (dopant) is mixed in the core 21 in order to develop a refractive index distribution as shown in FIG. As this dopant, a non-polymerizable compound is preferable. When the dopant is added only to the inner core portion 25, the addition ratio is preferably 0.01 wt% or more and 25 wt% or less with respect to the polymer that is the main component of the inner core portion 25. % To 20% by weight or less is more preferable. This makes it easier to control the refractive index distribution coefficient in the radial direction of the circular cross section within the preferred range as described above.

  In this embodiment, a low molecular weight compound having a high refractive index, a large molecular volume, not participating in polymerization, and having a predetermined diffusion rate in a molten polymer is used as a dopant. The refractive index in the radial direction is changed. The dopant is not limited to a monomer, and may be an oligomer (including a dimer, a trimer, etc.). Therefore, even if it has a polymerization reactivity with the polymerizable compound for the inner core and the inner core in the monomer state, such an oligomer should be used as a dopant if it does not polymerize when it becomes an oligomer. Can do.

  Specific examples of the dopant include benzyl benzoate (BEN), diphenyl sulfide (DPS), triphenyl phosphate (TPP), benzyl-n-butyl phthalate (BBP), and diphenyl phthalate (DPP). , Diphenyl (DP), diphenylmethane (DPM), tricresyl phosphate (TCP), diphenyl sulfoxide (DPSO), etc., among which BEN, DPS, TPP, and DPSO are preferable. By adjusting the concentration and distribution of the dopant in the core 21, the refractive index of the POF 11 can be changed to a desired value.

[Clad 22 Material]
The clad 22 also has a polymer similar to the core 21. As the polymer and other materials, those obtained by removing the dopant from the above materials of the core can be used. In addition, polyvinylidene fluoride (PVDF) is also preferred. However, in this invention, it is set as the composition and mixing | blending which are demonstrated further after the following paragraph. In order to prevent moisture from entering the core 21 as much as possible, it is preferable that the water absorption is low. For example, the clad 22 is preferably composed mainly of a polymer having a saturated water absorption rate of less than 1.8%. More preferably, the outer core portion 24 is formed of a polymer having a saturated water absorption rate of less than 1.5%, more preferably a saturated water absorption rate of less than 1.0%. Here, the saturated water absorption is a value based on ASTM D570, and specifically, a value obtained by measuring the water absorption when a sample is immersed in water at 23 ° C. for 1 week.

  As will be described later, the plastic optical fiber of the present invention has an optical signal to be transmitted, and when light having a visible wavelength (referred to as visual light) enters from one end surface, the clad 22 emits one of visible light. A part has a scattering structure which is scattered and goes out from the outer peripheral surface. This scattering structure is a structure in which the material constituting the clad exhibits refractive index fluctuations, particularly density fluctuations. Fluctuation as used in the present invention is a non-uniformity in which the refractive index is partially different, especially the density is different when observed in a microscopic area large enough to scatter light, although the structure is macroscopically uniform. This means a state having a simple structure. Specifically, the micro area sufficiently large to scatter light is specifically the same size or larger than the wavelength of light, that is, 0.1 μm × 0.1 μm to 100 μm in the case of visible light. A region of about 100 μm is shown. Further, as the magnitude of the refractive index fluctuation, it is preferable that the difference in refractive index between different regions is 0.0005 to 0.05.

  Specifically, (1) a structure in which the constituting polymer has a partially different crystal structure, (2) a structure having a polymer whose molecular weight is fluctuated, that is, a molecular weight is non-uniform, (3) The first polymer and the second polymer are different from each other, and the composition ratio between the first polymer and the second polymer fluctuates, that is, the composition ratio indicated by the first polymer / second polymer for each micro area. (4) The polymer as the first component contains a second component different from this polymer, and the composition ratio of the polymer and the second component fluctuates, that is, the second component is divided into microscopic areas. (5) a structure in which impurities, a so-called migrating material that has migrated from the core 21 or the like is present in the clad 22, and the abundance ratio fluctuates. ) Structure in which the interface between the clad 22 and the core 21 is disturbed, or structure in which the interface between the first layer and the second layer is disturbed when the clad 22 has a multilayer structure of the first layer and the second layer. (7) A structure in which the outer surface of the cladding 22 has irregularities, and the like. Of these, (6) can be said to be a structure related to both the clad 22 and the core 21 in a strict sense, not just the structure of the clad 22. Moreover, the unevenness | corrugation of (7) reflects the light irregularly or permeate | transmits the exterior according to the wavelength of visible light, and the incident angle of the visible light with respect to an uneven surface.

  In the case of (1), the polymer of the clad 22 has a molecular structure including a crystal structure part and an amorphous structure part (amorphous part). Such a polymer may be a homopolymer that forms a crystal structure portion and an amorphous structure portion, respectively, or may be a copolymer in which a crystal structure unit and an amorphous structure unit are copolymerized. Good. Further, instead of the one having both the crystal structure portion and the amorphous structure portion in the molecule as described above, the main component of the clad 22 is obtained by dispersing the crystalline polymer in the polymer exhibiting the amorphous structure. It is good.

  As described above, the polymer has a molecular structure including the crystal structure portion and the amorphous structure portion, so that the visible light incident on the plastic optical fiber and transmitted through the amorphous structure portion is reflected by the crystal structure portion and clad. The light is scattered inside, passes through the amorphous structure portion, and exits to the outside, so that light can be detected visually. When the light is only visible halfway through the plastic optical fiber, it can be known that the plastic optical fiber may be broken at the visible end portion. The ratio of the crystal structure part to the total polymer weight of the clad 22 is preferably 1 to 100%.

  Moreover, in order to scatter light satisfactorily by the scattering structure of (1), it is preferable to determine the size of the crystal structure portion according to the wavelength of the light. That is, the size is the same scale size as the wavelength of light, specifically 0.1 μm or more. That is, if the crystal structure portion has a size greater than or equal to a predetermined value required for the wavelength of light, the object of the present invention cannot be achieved without light being scattered. In addition, when both communication light and visible light having different wavelengths are incident on the plastic optical fiber, and the wavelength of the communication light is longer than the wavelength of the visible light, the size of the crystal structure portion By setting the height between the two wavelengths, it can be expected that the visibility and the communication performance are more compatible.

  In the case of (2) above, when there are regions having different molecular weights, such as a sea-island sea portion and an island portion, the refractive index of light differs depending on each region. Can leak light. Therefore, it is possible to visually confirm the communication state and the presence or absence of disconnection. Such partial fluctuations in molecular weight may be caused by mixing (I) a first polymer and a second polymer having the same molecular structural unit but different molecular weights, or (II) a portion during polymerization. It can be formed due to the difference in the reactivity.

  In the case of the above (3), the first polymer and the second polymer having different molecular structural units are mixed and used as the main component of the clad, or two or more kinds of monomers are polymerized to form the area. A polymer having a different ratio of structural units may be formed every time, and this polymer may be used as a main component of the cladding. Thereby, a region having a partially different refractive index is formed, so that light can be scattered well and emitted to the outside, and the communication state and presence / absence of disconnection can be visually confirmed.

  In the case of the above (4), that is, the cladding 22 contains a polymer as the first component and another substance as the second component, and the volume ratio of the first component to the second component is mutually equal. If there are different areas, the refractive index will be different for each area, so as in the above-mentioned form, it is possible to scatter the visible light well and emit it to the outside, and visually check the communication state and the presence of disconnection. it can.

  In the case of (5) above, since the polymer in the cladding 22 and the impurities or the migrating substance coexist, the refractive index differs from region to region as in the cases of (2) and (4) above. The visible light can be scattered well and emitted to the outside, and the communication state and the presence or absence of disconnection can be confirmed visually.

  Furthermore, in the cases (6) and (7), any of the inner surface of the clad 22, the interface between the clad and the core, the outer surface of the clad 22, and the clad 22 having a multilayer structure of two or more layers. At least one of the first layer and the interface between the first layer and the other layer in contact with the first layer has a predetermined roughness according to the wavelength of the visible light. The roughness is not less than the same scale as the wavelength of visible light, specifically 0.1 μm or more. When this roughness is determined by the surface roughness Ra, a preferable Ra value is 0.1 μm or more and 100 μm or less. The Ra value can be obtained according to JIS B601: 2001 and JIS B651: 2001. In addition to the structures (1) to (7) described above, by adding a phosphor or a pigment to the cladding part, light having a wavelength different from the incident light is emitted to the outside, and the communication state and the like are visually observed from the outside. Can also be observed.

  Next, a method for manufacturing the plastic optical fiber will be described. As described above, since the plastic optical fiber is manufactured by stretching the preform 12 (see FIG. 1) having a larger outer diameter in the longitudinal direction, a method for manufacturing the preform will be described first. Further, the manufacturing method differs depending on whether the clad is any one of the above (1) to (7), so each case will be described.

  A method of manufacturing a preform cladding (hereinafter referred to as preform cladding) will be described. Among the above (1), when the crystal structure part and the amorphous structure part are respectively formed using one kind of homopolymer, there is a melt extrusion molding of a crystalline polymer as the simplest manufacturing method. In this case, the preform core (hereinafter referred to as a preform core) is preferably formed in a preformed hollow portion of a preform clad. In melt extrusion molding, a known melt extrusion molding machine is used to appropriately control the melting temperature, the drawing speed from the die, the cooling temperature after being taken out, the cooling speed, and the like. In the case of molding by extruding and cooling the crystalline polymer, the crystal structure portion is easily formed when the cooling rate is slow, and the amorphous structure portion is easily formed when the cooling is performed, that is, when the cooling rate is slow. Therefore, by controlling the cooling rate, the weight ratio of the crystal structure part to the total polymer volume and the size of the crystal structure part can be controlled. For example, when PVDF with a crystallization temperature of Tc is used as the polymer, crystallization is accelerated if the time required for the inner surface of the cladding to cool from (Tc + 30) ° C. to (Tc−30) ° C. is 6 seconds or longer. If the time is less than 6 seconds, the crystal structure can be reduced.

  Whether or not the crystal structure portion and the amorphous structure portion are formed together can be confirmed, for example, by microscopic observation.

  In the above (1), when the polymer of the clad of the plastic optical fiber is a copolymer of the crystalline structural unit and the amorphous structural unit, a copolymer for producing the preform clad is produced in advance. The method of extrusion molding with a melt extruder is the simplest, but is not limited to this, and there is also a method for producing a tubular preform clad while polymerizing a plurality of polymerizable compounds by a rotational polymerization method as described later. . The preform core is preferably formed in the hollow portion of the raw yarn clad formed in a tubular shape in advance. Copolymers for melt extrusion can be produced by copolymerizing monomers that form crystalline homopolymers and monomers that form amorphous homopolymers. It is also possible to produce a copolymer having a sea-island structure by once producing two types of polymers with both monomers and then further polymerizing them. Unlike the case of the homopolymer extrusion described above, the melt extrusion of such a copolymer is composed of a portion that is easy to crystallize and a portion that is difficult to crystallize. Therefore, precise control is not required for the melt extrusion conditions. Absent. Therefore, the melt extrusion conditions may be set according to the copolymer to be used, as in the general melt extrusion molding method.

  On the other hand, when a preform clad composed of the above copolymer is produced by a rotation polymerization method, a rotation polymerization apparatus and a rotation polymerization method in a preform core production method described later may be applied. However, in the production of the above-mentioned copolymer, when the monomers having a tendency of closer polymerization reactivity are combined, the resulting polymer molded product tends to be more uniform. Therefore, in order to scatter light moderately, the monomers are combined in consideration of the reactivity between the monomers.

  Of the above (1), when the cladding is formed by dispersing the crystalline polymer in the amorphous polymer, a polymer blend obtained by mixing the amorphous polymer and the crystalline polymer by, for example, melt kneading is previously prepared. It is preferable to produce a preform clad by extrusion molding after production. In the polymer blend to be obtained, it is preferable that the island portion has a crystalline polymer and the sea portion has an amorphous polymer sea-island structure. By using a polymer blend having such a sea-island structure, a clad exhibiting a suitable scattering state can be obtained.

  In the case of producing a preform clad for the above (2), in the polymerization reaction for producing the polymer, both in the case of extrusion molding of the polymer and in the case of polymerization formation by the rotational polymerization method The reaction rate should be increased. Thereby, molecular weight distribution becomes large and a scattering structure can be formed. As a method for increasing the polymerization reaction rate, (I) the polymerization temperature is increased. (II) Increasing the polymerization initiator.

  The preform clad for the above (3) can be produced by using two or more kinds of copolymerization monomers in the preform clad production method in the above (1). Similarly, the preform clad for the above (4) can be produced by adding a second component substance other than the monomer at the time of polymer polymerization production. Furthermore, the preform clad for the above (5) can be similarly manufactured according to the conditions at the time of forming other components such as impurities and cores at the time of polymer polymerization production.

  A method for forming the preform core in the hollow portion of the preform clad prepared in advance by the various methods described above will be described below. However, the present invention does not depend on the preform core forming method, and various known methods can be applied. In this embodiment, since the core of the plastic optical fiber exhibits the above-described refractive index profile (see FIG. 3), the rotating gel polymerization method is applied to the preform core manufacturing method. This rotating gel polymerization method can be applied to a method for producing a preform clad.

  FIG. 4 is a cross-sectional view of the polymerization vessel, FIG. 5 is a schematic perspective view of a rotary polymerization apparatus, and FIG. 6 is an explanatory view of a polymerization reaction by the polymerization apparatus. However, the present invention does not depend on the polymerization apparatus and the polymerization vessel shown in FIGS. 4 to 6, and this embodiment is an example as one aspect of the present invention.

  One end of the preform clad 32 is closed with a plug 37 made of a predetermined material. The stopper 37 is made of a material that does not dissolve in the polymerizable compound for forming the preform core, and does not include a substance that elutes a plasticizer or the like. An example of such a material is polytetrafluoroethylene (PTFE). After one end is closed with a plug 37, a preform core material 31 including a polymerizable compound is injected into the preform clad 32. Then, after the other end is also closed with the plug 37, the polymerizable compound is polymerized while rotating to produce a preform core. At the time of producing the preform core, the preform clad 32 is accommodated in a polymerization vessel 38 as shown in FIG. The superposition | polymerization container 38 has the cylindrical container main body 38a and the lid | cover 38b which each plugs up both ends of this container main body 38a, and is made from SUS in this embodiment. As shown in FIG. 10, the polymerization vessel 38 has an inner diameter slightly larger than the outer diameter of the preform clad 32, and the preform clad 32 rotates in synchronization with the rotation of the polymerization vessel 38 as described later. Have been able to. A support member or the like for supporting the preform cladding 32 may be provided on the inner surface of the polymerization container 38 or the like so that the preform cladding 32 can respond to the rotation of the polymerization container 38 as described above.

  The preform core is generated by setting the polymerization vessel 38 as described above in the rotary polymerization apparatus 41. As shown in FIG. 11, the rotation polymerization apparatus 41 detects a plurality of rotating members 43 in the apparatus main body 42, a drive unit 46 outside the apparatus main body 42, and the temperature in the apparatus main body 42, and the detection result. And a temperature controller 47 for controlling the internal temperature.

  The rotating member 43 has a cylindrical shape, and the longitudinal directions thereof are substantially parallel to each other and substantially horizontal so that at least one polymerization vessel 38 can be supported by two peripheral surfaces. One end of each rotating member 43 is rotatably attached to the side surface of the apparatus main body 42, and is rotated by the driving unit 46 under independent conditions. The drive unit 46 is provided with a controller (not shown), and the drive of the drive unit 46 is controlled by this controller. Then, at the time of a predetermined polymerization reaction, as shown in FIG. 6, the polymerization container 38 is placed on a trough formed by the peripheral surfaces of adjacent rotating members 43 and rotates according to the rotation of the rotating member 43. In FIG. 6, the rotation axis of the rotation member 43 is indicated by reference numeral 43a. Thus, in this embodiment illustrated here, rotation of the superposition | polymerization container 38 is made into the surface drive type, However, About this rotation system, it is not limited.

  In the present embodiment, as shown in FIG. 6, the lids 38 b at both ends of the polymerization vessel 38 are provided with magnets 38 c, respectively, and the magnet 45 is also provided between the two adjacent rotating members 43. Is provided. This prevents the polymerization container 38 from floating from the rotating member 43 during rotation. In addition to the above method using a magnet as a method of preventing the polymerization container 38 from floating from the rotation member 43, a rotation means similar to the rotation member 43 is further provided in contact with the upper part of the set polymerization container 38. The rotation of the polymerization vessel 38 may be prevented in the same manner, thereby preventing the polymerization vessel 38 from floating. In addition to this method, for example, there is a method of applying a predetermined load to the polymerization vessel 38 by providing a pressing means or the like above the polymerization vessel 38, but the present invention does not depend on the floating prevention method.

  Next, a preform core generation method will be described. The preform core raw material 31 to be used is preferably used after sufficiently removing a polymerization inhibitor, moisture, impurities, etc. in advance by filtration or distillation. After mixing the polymerizable compound and the polymerization initiator, it is preferable that the mixture is further subjected to ultrasonic treatment to remove dissolved gases and volatile components. In addition, before and after injecting the preform core raw material 31, the preform clad 32 and the preform core raw material 31 may be subjected to a decompression process by a known decompression device, if necessary.

  Thereafter, when the polymerization vessel 38 loaded with the preform clad 32 is rotated (horizontal rotation) with the longitudinal direction thereof being set in a substantially horizontal state, the polymerization core is generated and a preform core is generated. In this way, the preform core is generated by rotational polymerization in which polymerization is performed with the circular tube axis of the preform cladding 32 as the rotation center. Prior to the rotation polymerization, pre-polymerization may be performed with the preform clad 32 in an upright state. In this pre-polymerization, the circular tube of the preform clad 32 is used by a predetermined rotation mechanism as necessary. Rotate around the axis of rotation. In such rotation polymerization, the preform clad 32 is rotated while keeping the longitudinal direction thereof substantially horizontal, so that a preform core is easily formed on the entire inner surface of the preform clad 32. In the present invention, at the time of polymerization of the preform core, it is most preferable to make the longitudinal direction of the preform clad 32 horizontal in order to form the preform core on the entire inner surface of the preform clad 32. It is suitable if it is horizontal, and the allowable angle of the rotation axis is generally within 5 ° with respect to the horizontal.

  Then, the preform thus made is drawn by a known heat drawing method to obtain a plastic optical fiber.

  The present invention is not limited to the case where the clad has a single layer structure as in the above-described embodiment, and includes, for example, one having a multilayer structure of two or more layers concentrically. Here, a second embodiment of the present invention will be described. FIG. 7 is a manufacturing flow diagram of the plastic optical fiber 71 when the clad has a concentric two-layer structure. In the following description, of the two clad layers, the outer layer is referred to as an outer clad portion, and the inner layer is referred to as an inner clad portion. As in the first embodiment, the plastic optical fiber 71 is manufactured by first forming the preform 72 and then heating and stretching the preform 72 in the heating and stretching step 73. The preform 72 has a concentric two-layer structure and has a tubular preform clad and a preform core. First, the preform clad is formed and then the preform core is formed. A preform outer clad pipe 75 which is an outer layer of the two-layer structure of the preform clad is manufactured by the pipe manufacturing step 76, and the inner layer of the two-layer structure is formed in the preform outer clad pipe 75. The preform inner clad portion is formed in the preform inner clad portion forming step 77, and then the preform core is formed in the preform core forming step 78 to obtain the preform 72.

  FIG. 8 is a cross-sectional view of the plastic optical fiber 71, and FIG. 9 is a graph showing the refractive index in the cross-sectional radial direction of the plastic optical fiber 71. In FIG. 9, the horizontal axis indicates the cross-sectional radial direction of the plastic optical fiber 71, and the vertical axis indicates the refractive index, which means a higher value as it goes upward. As shown in FIG. 8, the plastic optical fiber 71 is provided on the outer periphery of the core 81 for transmitting an optical signal and on the outer periphery of the core 81, and a part of the incident light is scattered to be emitted from the outer periphery of the plastic optical fiber 11. And a cladding 82 for the purpose. The clad 82 has a concentric circular two-layer structure, and has an inner core portion 83 in contact with the outer periphery of the core 81 and an outer core portion 84 on the outer periphery of the inner core portion 83. The inner core portion 83 and the outer core portion 84 have a tube shape in which the outer diameter and the inner diameter are constant in the longitudinal direction and the thickness is uniform. The diameter of the cross-sectional circle of the core 81 is equal to the inner diameter of the inner clad portion 83.

  In FIG. 9, the range indicated by the symbol (C) on the horizontal axis is the refractive index of the outer cladding portion 84 in FIG. 8, and the range indicated by the symbol (D) is the refractive index of the inner cladding portion 83 in FIG. Yes, the range indicated by the symbol (E) is the refractive index of the core 81 in FIG. As shown in FIG. 9, the core 81 has a refractive index that continuously increases from the boundary with the inner cladding portion toward the center, and the refractive index of the inner cladding portion is equal to or lower than the refractive index of the core. . Moreover, although the refractive index of the outer clad part illustrated here is smaller than the refractive index of an inner clad, both may be the same value. In addition, both the inner clad portion 83 and the outer clad portion 84 of the present embodiment have a substantially constant refractive index as shown in FIG. 3, but even if the refractive index increases toward the core 21. The change in the refractive index may increase stepwise as it approaches the core 21 or may increase continuously.

  The preform 72 (see FIG. 7) has a larger cladding and core diameter than the plastic optical fiber 71, but the basic structure is the same as that of the plastic optical fiber 71, so illustration is omitted. In addition, the present invention is applied even if the core 81 has a concentric multilayer structure.

  The core 81 of the present embodiment has the same configuration as that of the core of the first embodiment, and the outer clad portion 84 scatters the visible light that is incident in the same manner as the clad of the first embodiment to externally. The material is the same as the cladding of the first embodiment. The inner cladding 83 excludes the configuration for light scattering from the configuration of the cladding of the first embodiment.

  With this configuration, the plastic optical fiber according to the present embodiment reflects most of the light incident from one end at the boundary between the core 81 and the inner clad portion 83 so that the core 81 can transmit the optical signal. Since a part of the incident light is scattered by the outer clad portion 84 and is emitted to the outside, the communication state of the plastic optical fiber can be visually confirmed from the outside. Further, in the present embodiment, since the refractive index of the outer cladding and the refractive index of the inner cladding are different from each other, the light scattered by the outer cladding portion 84 is prevented from entering the core. Light can be effectively used for the visual confirmation.

  And the manufacturing method of the plastic optical fiber 81 of this embodiment is as follows. That is, the outer clad pipe that becomes the preform outer clad portion is produced in the same manner as the clad of the first embodiment. And after a preform inner clad part is formed by the rotation gel polymerization method, the preform core is also formed by the rotation gel polymerization method.

  The preform 72 is heated and stretched to become a plastic optical fiber 71. The layer for scattering the visible light may be the inner clad portion 83 instead of or in addition to the outer clad portion 84 of the present embodiment. Also, the clad 82 has a multilayer structure of three or more layers, and any one of them is a plastic optical fiber that scatters incident visible light and emits it to the outside as in the clad of the first embodiment. Is also included in the present invention.

  Each plastic optical fiber 11 and 71 obtained by the above two embodiments is coated with a coating material by various known coating methods to form a cord. Note that the coating material at this time is a transparent material that allows light scattered by the cladding to pass outside. Next, how to use this code will be described.

  As described above, one end face of the obtained plastic optical cord is connected to a light source that emits light as an optical signal to be transmitted. The other end surface is connected to a light receiving element that receives the transmitted light.

  In addition, when the light receiving element cannot distinguish and receive the light emitted from the core and the scattered light from the clad, and the light to be transmitted and the visible light to be scattered have different wavelengths, It is preferable to provide an optical filter member that allows only light to be transmitted without passing scattered light between the light receiving element and the plastic optical cord. Thereby, it is possible to perform good communication while confirming the communication state. By using such an optical filter member, there is no need for the communication light to be transmitted and the visible light to be emitted independently from different light sources, and two lights can be emitted together from the same location. it can.

  A polymer mixture of PVDF and PMMA was melt-extruded to produce a tubular member that became the preform clad 32. At this time, the polymer ratio represented by (weight of PVDF) / (weight of PMMA) in the polymer mixture was changed in two ways, and the two types of preform clads in which the ratio of the crystal structure portion to the amorphous structure portion was different from each other 32 members were produced and designated as Experiment 1 and Experiment 2. In Experiment 1, the polymer ratio was 10/0, and by setting this value, the ratio of the crystal structure portion to the amorphous structure portion in the preform clad 32 was set to about 8/2. In Experiment 2, the polymer ratio was 8/2, and by setting this value, the ratio of the crystal structure portion in the preform clad 32 was made substantially zero.

  Next, a preform core raw material 31 made of a mixture of MMA, a polymerization initiator, a chain transfer agent, and a dopant having a higher refractive index than MMA is injected into the hollow portion of the preform clad 32 member obtained in advance, The inside of the polymerization vessel 38 was purged with nitrogen to carry out rotational gel polymerization. Thus, a raw yarn core was formed, and a preform 12 was obtained. The preform 12 was heated and stretched to obtain a plastic optical fiber 11. 650 nm light was incident on one end face of the plastic optical fiber 11 using a red laser diode (LD). And the confirmation evaluation of the communication state in Experiment 1 and Experiment 2 was implemented.

  As a result of Example 1, light was scattered in Experiment 1, and it was confirmed from the outside that light was scattered. On the other hand, in Experiment 2, the light scattered by the clad 22 was weak, and the communication state could not be confirmed visually.

  A preform outer clad pipe 75 was produced by melt extrusion molding. Experiments 3 and 4 were conducted by controlling the surface roughness of the inner surface of the preform outer clad pipe 75 by changing the cooling rate of the preform outer clad pipe 75 extruded from the extrusion die. In Experiment 3, the aforementioned cooling rate was 5 seconds / 60 ° C., and in Experiment 4, the cooling rate was 10 seconds / 60 ° C.

  A preform inner clad raw material, which is a mixture of MMA, a polymerization initiator, and a chain transfer agent, is injected into the hollow portion of the preform outer clad pipe 75, and then the preform outer clad pipe 75 is placed in the polymerization vessel 38. Nitrogen substitution was performed, and the polymerization reaction was caused to proceed while rotating and heating.

  A preform core raw material was filled in the hollow portion of the produced preform inner clad portion, and a preform core was formed by nitrogen substitution and rotating gel polymerization under heating. The preform core raw material is a mixture of MMA, a polymerization initiator, a chain transfer agent, and a dopant. And then. The preform 72 thus obtained was heated and stretched to form a plastic optical fiber 71, and the communication state was confirmed and evaluated in the same manner as in Example 1.

  As a result of Example 2, in Experiment 3, light was not scattered by the cladding, and the light could not be visually confirmed from the outside. On the other hand, in Experiment 4, a part of the incident light could be scattered by the clad 22, and the communication state could be confirmed visually.

  A preform outer clad pipe 75 was produced by melt extrusion molding. By making the aforementioned cooling rate of the preform outer clad pipe 75 extruded from the extrusion die 5 seconds / 60 ° C., the inner surface of the preform outer clad pipe 75 was made highly smooth. The surface roughness of the inner surface at this time is Ra = 0.11.

  A preform inner clad raw material, which is a mixture of MMA, a polymerization initiator, and a chain transfer agent, is injected into the hollow portion of the preform outer clad pipe 75, and then the preform outer clad pipe 75 is placed in the polymerization vessel 38. Nitrogen substitution was performed, and the polymerization reaction was caused to proceed while rotating and heating.

  A preform core raw material was filled into the hollow portion of the produced preform inner clad portion, and a raw yarn core was formed by rotational gel polymerization under nitrogen substitution and heating. The core raw material is a mixture of MMA, a polymerization initiator, a chain transfer agent, and a dopant. The conditions for this rotational gel polymerization were changed, and these were designated as Experiments 5 and 6. Specifically, in Experiment 5, the amount of polymerization initiator and the polymerization temperature were adjusted so that the core polymerization reaction was completed within 2 hours. On the other hand, in Experiment 6, the amount of polymerization initiator and the polymerization temperature were adjusted so that it would take 10 hours to complete the polymerization reaction of the core. Thereby, the permeability of the preform core raw material (MMA) with respect to the preform outer clad and the preform inner clad was made different between Experiment 5 and Experiment 6. Specifically, the amount of penetration in Experiment 6 was 9 times that in Experiment 5, and was 1.15 wt% with respect to the total polymer weight of the cladding. The preform 72 thus obtained was heated and stretched to form a plastic optical fiber 71, and the communication state was confirmed and evaluated in the same manner as in Example 1.

  As a result of Example 3, in Experiment 5, a large amount of light was scattered and emitted to the outside, and the light could be visually confirmed from the outside. On the other hand, in Experiment 6, light was not scattered by the clad 22, and the communication state could not be confirmed visually.

  A preform outer clad pipe 75 was produced by melt extrusion molding. By cooling the preform outer clad pipe 75 extruded from the extrusion die at the cooling rate of 5 seconds / 60 ° C., the inner surface of the preform outer clad pipe 75 was made highly smooth. The surface roughness of the inner surface at this time was Ra = 0.11.

  After injecting a raw material for inner clad, which is a mixture of MMA, a polymerization initiator, and a chain transfer agent, into the hollow portion of the preform outer clad pipe 75, the preform outer clad pipe 75 is placed in the polymerization vessel 38 and replaced with nitrogen. The polymerization reaction was caused to proceed while rotating and heating. In Example 4, Experiment 7 and Experiment 8 were carried out with different polymerization times for this polymerization reaction. Accordingly, in Experiment 7, a preform inner clad portion having a conversion rate of 80% was formed by shortening the polymerization time, and in Experiment 8, a preform inner clad having a conversion rate of 97% by increasing the polymerization time was formed. A clad portion was formed.

  Next, the core raw material was filled in the hollow portion of the preform inner clad portion, and a preform core was formed by nitrogen substitution and rotating gel polymerization under heating. The preform core raw material is a mixture of MMA, a polymerization initiator, a chain transfer agent, and a dopant. In Experiment 7, the materials of the preform inner clad part and the preform core are mixed at the interface between them, while in Experiment 8, the materials of the preform inner clad part and the preform core are mixed at the interface between them. Almost no mixing was confirmed. Then, the preform 72 obtained was heated and stretched to obtain a plastic optical fiber, and the communication state was confirmed and evaluated in the same manner as in Example 1.

  As a result of Example 4, in Experiment 7, it was possible to scatter a large amount of light to the outside, and it was possible to visually confirm the light from the outside. On the other hand, in Experiment 8, the light was not scattered by the clad 22, and the communication state could not be confirmed visually.

It is a manufacturing flow figure which manufactures the plastic optical cable using the plastic optical fiber of this invention. It is sectional drawing of a plastic optical fiber. It is a graph which shows the refractive index in the cross-sectional radial direction of the plastic optical fiber shown in FIG. It is a section schematic diagram of a polymerization container. It is the schematic of a rotation polymerization apparatus. It is explanatory drawing of a polymerization reaction method. It is a manufacturing flowchart of the plastic optical fiber as another embodiment. It is sectional drawing of a plastic optical fiber. It is a graph which shows the refractive index in the cross-sectional radial direction of the plastic optical fiber shown in FIG.

Explanation of symbols

11, 71 Plastic optical fiber 21, 81 Core 22, 82 Clad 83 Inner clad part 84 Outer clad part

Claims (11)

In a plastic optical fiber having a linear member having a refractive index in the radial direction of a circular cross section and an outer peripheral member provided on the outer periphery of the linear member and having a refractive index equal to or lower than the refractive index of the linear member ,
The outer peripheral member has a scattering structure in which a part of light incident from an end face of the plastic optical fiber is scattered and emitted from the peripheral face to the outside.   The plastic optical fiber according to claim 1, wherein the scattering structure is a non-uniform refractive index structure having a different refractive index depending on a position in the outer peripheral member.   3. The plastic optical fiber according to claim 2, wherein the refractive index non-uniform structure is a density non-uniform structure having different densities depending on positions in the outer peripheral member.   4. The plastic optical fiber according to claim 3, wherein the outer peripheral member includes a polymer, and the density nonuniform structure is obtained by partially different crystal structures of the polymer.   4. The plastic optical fiber according to claim 3, wherein the outer peripheral member includes a polymer, and the density non-uniform structure is formed by fluctuation in molecular weight of the polymer.   The outer peripheral member includes a polymer as a first component and a second component different from the first component, and has the density non-uniform structure due to a composition ratio fluctuation between the first component and the second component. The plastic optical fiber according to claim 3. In a plastic optical fiber having a linear member having a refractive index in the radial direction of a circular cross section and an outer peripheral member provided on the outer periphery of the linear member and having a refractive index equal to or lower than the refractive index of the linear member ,
The outer peripheral member includes a first layer on the inner side in a cross section and a second layer provided on the outer periphery of the first layer and having a refractive index lower than that of the first layer.
At least one of the first layer and the second layer has a scattering structure that scatters a part of light incident from the end face of the plastic optical fiber and emits the light from the outer peripheral surface to the outside.
When only the first layer has a scattering structure, the second layer is made of a transmissive material that transmits the light. In a plastic optical fiber having a linear member having a refractive index in the radial direction of a circular cross section and an outer peripheral member provided on the outer periphery of the linear member and having a refractive index equal to or lower than the refractive index of the linear member ,
The linear member and the outer peripheral member have a scattering structure in which a part of the light incident from the end face of the plastic optical fiber is scattered at the interface and emitted from the outer peripheral surface of the outer peripheral member to the outside. Characteristic plastic optical fiber. In a plastic optical fiber having a linear member having a refractive index in the radial direction of a circular cross section and an outer peripheral member provided on the outer periphery of the linear member and having a refractive index equal to or lower than the refractive index of the linear member ,
The outer peripheral member includes a first layer on the inner side in a cross section and a second layer provided on the outer periphery of the first layer and having a refractive index lower than that of the first layer.
The first layer and the second layer have a scattering structure in which a part of light incident from the end face of the plastic optical fiber is scattered at the interface between the first layer and the outer surface of the second layer. A plastic optical fiber characterized by that. In a plastic optical fiber having a linear member having a refractive index in the radial direction of a circular cross section and an outer peripheral member provided on the outer periphery of the linear member and having a refractive index equal to or lower than the refractive index of the linear member ,
The outer peripheral member includes a first layer on the inner side in a cross section and a second layer provided on the outer periphery of the first layer and having a refractive index lower than that of the first layer.
The outer periphery of the second layer is formed with irregularities for irregularly reflecting a part of the light incident from the end face of the plastic optical fiber,
The plastic irregularity is characterized in that the unevenness has a roughness for emitting light scattered in the second layer by the irregular reflection from the outer periphery to the outside of the layer. A plastic optical fiber according to any one of claims 1 to 10,
A covering member that covers an outer periphery of the plastic optical fiber and transmits the scattered light;
A plastic optical fiber cord characterized by comprising:

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