WO2004021054A1

WO2004021054A1 - Optical fiber with island structure

Info

Publication number: WO2004021054A1
Application number: PCT/JP2003/010969
Authority: WO
Inventors: Hidenobu Murofushi
Original assignee: Asahi Glass Company, Limited
Priority date: 2002-08-29
Filing date: 2003-08-28
Publication date: 2004-03-11
Also published as: JP2004093639A; AU2003261812A1

Abstract

A high-transmission band optical transmission medium with low transmission loss. The medium is an optical fiber having an island structure, and is characterized in that a dispersion phase which is a component with a low index of refraction is dispersed in a continuous phase which is a component with a high index of refraction.

Description

Optical fiber with sea-island structure ''

The present invention relates to an optical transmission medium used as an optical fiber or the like, more specifically, an optical fiber having a sea-island structure having excellent heat resistance, flame retardancy, chemical resistance and solvent resistance, low transmission loss and a high transmission band. Related to the transmission body. Background art

An optical fiber has excellent characteristics as a light propagation medium, and an inorganic glass-based optical fiber having excellent light transmission properties over a particularly wide wavelength is conventionally used. In addition, these inorganic glass-based optical fibers are not only poor in workability, weak in bending stress, but also expensive, so that optical fibers (optical fiber wires) based on plastic have been developed and put into practical use. I have.

Conventionally, optical fibers have a graded-index structure in which a core material having a high refractive index is surrounded by a cladding material having a lower refractive index, and a core clad structure is formed using a combination of materials having different refractive indexes. (SI type) Optical fiber is common. Many plastic optical fibers having such a structure have been proposed and some of them have been put to practical use. A core (core) layer having a united body as a base material and a sheath (cladding) layer having a base material made of a substantially transparent fluoropolymer having a lower refractive index than these are used as basic constituent units. Japanese Patent Application Laid-Open No. 2-244007 also proposes using a fluorine-containing resin for both the core layer and the cladding layer.

As the optical fiber, a refractive index distribution type (GI type) optical fiber in which the refractive index is attenuated by distributing the material in the radial direction from the axis to the circumferential direction is known together with the above-mentioned refractive index step type optical fiber. (For example, “Chemistry and Industry,” Vol. 45, No. 7, 126, 1264 (1992), Japanese Unexamined Patent Publication (Kokai) No. 5-173030, WO94 / 044949, W094 / 1.505). In addition, Japanese Patent Application Laid-Open No. 5-241036 discloses a single case. Alternatively, a single mode (SM) plastic optical filter that transmits only a specific mode of light has been proposed. Further, Japanese Patent Application Laid-Open No. 9-33737 describes that at least seven cores having a diameter of 50 to 200 β πι made of a resin having a higher refractive index than the clad resin are contained in the clad resin. Embedded multi-core plastic optical fibers have been proposed.

An optical fiber (holey fiber) having a structure including holes is also known. For example, an optical fiber in which air is contained in a single material of silica glass is known as a total reflection type guided holey fiber in which light is guided by total reflection due to the presence of a low refractive index hole. ing.

In recent years, a photonic crystal fiber in which a photonic crystal structure is formed by periodically arranging holes in which the holes extend in parallel in the major axis direction has been receiving attention. One of the photonic crystal fibers has a core clad structure, and the presence of holes in the cladding lowers the effective refractive index of the cladding than that of the core, and guides light by total internal reflection. It is a total reflection type holey fiber.

Also, among photonic crystal fibers, a core which constitutes a defect with respect to the periodic arrangement of the holes constituting the photonic crystal structure as described above, and which exhibits particularly large wavelength dispersion, and leads the core to Attention has been paid to the principle of waveguiding, in which a photonic crystal fiber develops a photonic band gap (PBG) for the frequency of wave light.

In a fiber using the PBG as a waveguide principle, light having a frequency and a propagation constant belonging to the PBG exponentially attenuates in the cladding and cannot have a large amplitude, but a core having periodic defects can have a large amplitude. Therefore the light is localized in the core. In this PBG fiber, the core may have a hollow structure as long as it breaks the periodicity of the holes, and this point is significantly different from the conventional high refractive index core structure.

Photonic crystal fibers can achieve broadband single-mode operation depending on the size, number, and arrangement of holes.

The holey fiber comprising a photonic crystal fiber as described above, are known silica fibers of the inorganic glass system, as its production method, to prepare a cylindrical body made of a S i 0 ₂ mainly, the cylindrical body Penetrates in the long axis direction around the shaft core 969

There is a method (1) in which a preform having a solid structure is produced by providing a large number of three small holes, and the preform is stretched (drawn) in the longitudinal direction to form pores, thereby forming an optical fiber.

The bundling a large number of S i 0 ₂ made Kiyabirari the closest packing state, to prepare a preform by fusing integrated outer surfaces of adjacent Kiyabirari, production of the photonic crystal fiber to delineate the Purifu ohms A method (2) has also been proposed (Japanese Unexamined Patent Publication No. 2002-97034).

Although plastic optical fibers have characteristics that inorganic glass-based optical fibers do not have, practical grade optical fibers cannot be obtained with conventional graded-index plastic optical fibers because of their narrow transmission band. Japanese Unexamined Patent Publication No. Hei 9-133 737 describes that the difference in the refractive index between the core material and the clad material is reduced, and the bending loss reduced by that amount is bundled with a small core diameter while maintaining the incident light amount. Efforts have been made to improve the transmission bandwidth, but it has not been possible to achieve high-speed transmission of 1 GHz or more at 100 m. In addition, a graded-index plastic optical fiber has a large transmission loss in near-infrared light, and a practical optical fiber for communication has not been obtained. Furthermore, plastic optical fibers can only be used in a specific wavelength region due to wavelength absorption caused by vibration and bending motion of the C-H bond, that is, visible light (500-700 nm) It cannot be used in the near-infrared light (700 to 160 nm) region, and its use is limited.

In the method (1) for producing holey fibers including the photonic crystal fiber, since a large number of pores are provided close to the cylindrical body, the partition between adjacent small holes is extremely thin, and during processing, the partitioning portion is extremely thin. It is extremely difficult to create a preform because the partition may break. Furthermore, in the manufacturing method of the above (2), it is difficult to handle fine cavities and maintain cleanliness, and a process of fusing and integrating while maintaining the shape of a large number of cavities bundled in a close-packed state. Extremely difficult. Furthermore, since the fiber has many hollow portions, dust and water easily enter the gap, and the fiber strength is weak because the filling degree per fiber cross-sectional area is low.

In addition, conventional plastic optical fibers can provide mechanical strength, The heat resistance, moisture resistance, chemical resistance and nonflammability were not always satisfactory. The present invention relates to plastics mainly composed of polymers such as acrylic polymers represented by polymethyl methacrylate, polystyrene, polycarbonate and the like. It has the mechanical strength, heat resistance, moisture resistance, chemical resistance, and nonflammability required for LANs, apartments, medical equipment, automobiles, office automation (OA), home appliances, etc. that could not be achieved with optical fibers. It is another object of the present invention to provide an optical transmission medium that can be used as an optical fiber. Further, the present invention provides a method for producing visible light (500 to 700 nm) and near-infrared light (700 nm) which cannot be achieved by a plastic optical fiber mainly composed of a polymer such as an acrylic polymer, a polycarbonate, and norpolene. (0 to 160 nm) region, has mechanical strength not found in optical fibers containing holes (holey fibers including photonic crystal fibers), and a single core can be used if necessary. It is an object of the present invention to provide an optical transmission body that can be used as an optical fiber with a low transmission loss and a high transmission band that can provide ultra-high-speed transmission by setting a mode propagation condition.

Disclosure of the invention

The present invention provides an optical transmitter characterized by having a sea-island structure in which a low refractive index dispersed phase is dispersed in a high refractive index continuous phase in order to achieve the above object.

In the cross-sectional shape of the optical transmission body, it is preferable that the low-refractive-index dispersed phases are arranged so as to have a periodicity for forming an optical waveguide.

In the optical transmission body of the present invention, it is preferable that each of the component constituting the continuous phase having a high refractive index and the component constituting the dispersed phase having a low refractive index is a polymer of an organic compound.

The component constituting the high-refractive-index continuous phase is composed of a non-crystalline fluoropolymer (a) having substantially no C—H bond, and the component constituting the low-refractive-index dispersed phase is as described above. It is preferable that it is made of a fluoropolymer (b) having a refractive index lower than that of the fluoropolymer (a) by 0.01 or more.

The fluorinated polymer (a) preferably contains a fluorinated ring structure. The fluorinated ring structure may contain a ring member ether bond, and is preferably a fluorinated alicyclic structure.

In the optical transmission body of the present invention, the fluoropolymer having a fluorinated ring structure preferably has the fluorinated ring structure in the main chain.

In the optical transmitter of the present invention, both the fluoropolymers (a) and (b) have substantially no C—H bond, and may contain an ether bond in the main chain. It is preferably an amorphous fluoropolymer having an alicyclic structure.

The present invention is for producing an optical transmission body having the above-described sea-island structure, and comprises a long body made of a polymer of an organic compound having a high refractive index component, and an organic compound having a low refractive index component. The polymer is dispersed, and the polymer of the organic compound of the low refractive index component extends in the longitudinal direction in the elongated body, thereby providing a preform having a sea-island structure. Preferably, it is a preform from which a stretched molded article (light transmitting body) having a homogenous diameter cross section is obtained after stretching.

The present invention is also characterized in that a pre-divided strand-shaped polymer of an organic compound of a low refractive index component is placed in a tube made of a polymer of an organic compound of a high refractive index component, and co-spun. The present invention also provides a method for manufacturing an optical transmitter having a sea-island structure according to the present invention or a preform thereof.

In the present invention, a polymer of an organic compound, which is a low refractive index component, which is uniformly melted, is separated in an extrusion die, and after being finely divided, a polymer of an organic compound of a high refractive index component is supplied to a peripheral portion thereof. Then, the high-refractive-index component organic polymer is applied to the outer periphery of the low-refractive-index component organic polymer, and extruded from a common nozzle. The present invention provides a method for manufacturing an optical transmitter having the same or a preform thereof.

The present invention also provides an optical fiber code obtained by coating the optical transmission body with one or more layers.

The present invention also provides a long body made of a thermoplastic resin in which a tensile strength reinforcing member is buried having a hole extending in the longitudinal direction therein, and the optical fiber cord stored in the hole of the long body. And an optical fiber cable comprising:

The present invention also provides a band comprising a plurality of the above optical fiber cords bundled. Provide fiber optics. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view of an optical transmitter having a sea-island structure in which a dispersed phase is randomly dispersed in a continuous phase.

FIG. 2 is a cross-sectional view of an optical transmitter having a sea-island structure in which a dispersed phase is periodically dispersed throughout the continuous phase.

FIG. 3 is a cross-sectional view of an optical transmitter having a sea-island structure in which a disperse phase is periodically dispersed in a continuous phase in a mode different from that of FIG. 2. They are arranged concentrically.

FIG. 4 is a cross-sectional view of an optical transmitter that uses a photoband gap as a waveguide principle, in which a defect portion exists in a dispersed phase having a photonic crystal structure that is periodically arranged.

FIG. 5 is a cross-sectional view of the plastic optical fiber having the sea-island structure according to the present invention manufactured in the first embodiment.

FIG. 6 is a cross-sectional view of a plastic optical fiber having a sea-island structure according to the present invention manufactured in Example 2.

FIG. 7 is a cross-sectional view of a plastic optical fiber having a sindal mode duplex sea-island structure according to the present invention manufactured in Examples 4 and 5.

(Explanation of code)

1: optical transmitter (optical fiber), 2: continuous phase (sea part), 3: disperse phase (island part). BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described specifically.

In the present invention, the optical transmitter is specifically an optical fiber, an optical waveguide, a switch, a lens, or the like.

According to the optical fiber of the present invention, in the concept of the holey fiber including the photonic crystal fiber, a substance having a lower refractive index (dispersion) in the continuous phase than the substance forming the continuous phase is used instead of providing the porous portion. Phase) to form a sea-island structure It has the same function as holey fiber including photonic crystal fiber, and also has no voids in the fiber, thereby preventing dust and moisture from entering and improving the fiber strength. is there.

As long as the optical transmission body of the present invention has the above-described sea-island structure, the light guiding principle is not particularly limited, such as a total reflection type, a graded index type, and a PBG guiding principle.

In addition, the number, shape, arrangement, and size of the optical transmission medium, such as the diameter of the optical fiber, are not particularly limited, and the desired design can be appropriately performed according to the purpose of the optical transmission medium. If the guiding principle is of the total reflection type, the dispersed phase may be randomly dispersed in the continuous phase. FIG. 1 is a sectional view showing an example of the optical transmission body of the present invention. In FIG. 1, an optical transmitter 1 is a total reflection type optical transmitter in which a dispersed phase 3 is randomly dispersed in a continuous phase 2. However, in the present invention, in the cross-sectional shape of the optical transmission body, it is preferable that the disperse phase is dispersed with periodicity forming an optical waveguide. That is, in the optical transmission body of the present invention, the disperse phase has the same role as the porous portion of the hollow fiber including the photonic crystal fiber. It preferably has periodicity.

Specific examples of the periodicity for forming such an optical waveguide will be described below with reference to the drawings. FIGS. 2 and 3 show that, in the diameter cross section of the optical transmitter 1, the disperse phase 2 extends over the entire continuous phase 3. FIG. 4 is a radial cross-sectional view of an optical transmission body that is periodically arranged to form a photonic crystal structure. In the optical transmitter 1 shown in FIGS. 2 and 3, light is propagated by the principle of total reflection waveguide. In the case of such a total reflection type optical transmitter 1, it is not always necessary that the dispersed phases 3 are arranged periodically in a strict sense, and they may be arranged to some extent randomly.

Further, the disperse phase has a defect portion that breaks the photonic crystal structure in the periodically arranged photonic crystal structure as described above, so that a photonic band gap ( (PBG), and PBG may be a waveguide principle. 2003/010969

8

Fig. 4 shows an example of an embodiment using PBG as the guiding principle. In the optical transmitter 1 shown in FIG. 4, the dispersed phase 3 is periodically arranged in a honeycomb structure to form a photonic crystal structure, but the central portion of the honeycomb structure is not a dispersed phase 3 but a continuous phase 2. Has become. As a result, the continuous phase 2 in the central portion of the honeycomb structure forms a defect that breaks the periodicity of the structure.

In the optical transmission body of the present invention, the component constituting the high-refractive-index continuous phase and the component constituting the low-refractive-index dispersed phase preferably have a difference in refractive index between each other of 0.001 or more. The material is not particularly limited as long as it is suitable as a material of the optical transmission body. Therefore, for example, two inorganic glasses each having a difference in refractive index of 0.001 or more may be used, but preferably, the difference in refractive index of each other is 0.001 or more. It is a polymer of two organic compounds, and such a polymer of an organic compound widely includes a polymer of an organic compound used in the field of an optical transmitter. Examples of the polymer of the organic compound include an acrylic polymer represented by polymethyl methacrylate, polystyrene, polycarbonate, norportene, and some or all of the C-H bonds in the organic compound polymer. Fluorine-containing polymers substituted by C-F bonds are exemplified. In the present invention, the refractive index refers to a refractive index with respect to a sodium D line.

In addition, the present inventor has conducted intensive studies based on recognition of the above problems, and as a result, has been found to provide heat resistance, moisture resistance, chemical resistance, and nonflammability, and to cause light absorption by near-infrared light. — Prior to the finding that a fluoropolymer obtained by converting a C—H bond to a C—F bond (that is, a carbon-fluorine bond) is the best way to eliminate an H bond (ie, a carbon-hydrogen bond). I got it.

Therefore, in the optical transmission medium of the present invention, the continuous phase and the dispersed phase are preferably made of a non-crystalline fluorine-containing polymer having substantially no C—H bond.

In the present invention, the fluorinated polymer is not particularly limited as long as it is a non-crystalline fluorinated polymer having substantially no C—H bond, but a fluorinated polymer having a fluorinated ring structure is preferred. Specific examples of the fluorinated ring structure include a fluorinated alicyclic structure which may contain a ring member ether bond (hereinafter, may be simply referred to as a fluorinated alicyclic structure), a fluorinated imide ring structure, And a fluorine-containing triazine ring structure or a fluorine-containing aromatic ring structure. Among the above fluorinated ring structures, a fluorinated alicyclic structure and a fluorinated polyimide ring structure which may contain a ring member ether bond are preferable, and the former is more preferable. In particular, a fluoropolymer having the above-mentioned fluorinated ring structure in the main chain is preferable, and furthermore, the main chain constituent unit containing the ring structure can form a substantially linear structure and can be melt-molded. Are preferred. In particular, a fluorinated polymer having a fluorinated alicyclic structure in the main chain is preferable.

Next, in the present invention, a fluorine-containing polymer having a fluorine-containing alicyclic structure in the main chain, which is a particularly preferred fluorine-containing polymer, will be specifically described.

The fluoropolymer having a fluorinated alicyclic structure in the main chain is a fluorinated polymer having a main chain composed of a chain of carbon atoms and having a fluorinated alicyclic structure in the main chain. Having a fluorinated alicyclic structure in the main chain means that at least one of the carbon atoms forming the alicyclic ring is a carbon atom in the carbon chain forming the main chain, and at least one of the carbon atoms forming the alicyclic ring is present. It has a structure in which a fluorine atom or a fluorine-containing group is partially bonded.

Examples of the main chain constituent unit having a fluorinated alicyclic structure, which is a preferred embodiment of the fluorinated polymer according to the present invention, include the following structures.

0

In the above formulas, 1 is 0 to 5, m is 0 to 4, n is 0 to 1, l + m + r ^ ¾l to 6, o, p, and q are independently 0 to 5, o + p + q is 1-6, each RR ² and R ³ are independently, F, a _{_{C 1, CF 3, C 2}} F 5, C 3 F 7 or OCF _3, X ¹ and X ² are independently to F, a C 1 or CF _3. As the polymer having a fluorinated alicyclic structure, specifically,

(1) A monomer having a fluorinated alicyclic structure (a monomer having a polymerizable double bond between a carbon atom forming a ring and a carbon atom not forming a ring, or between two carbon atoms forming a ring) A monomer having a polymerizable double bond),

(2) A polymer having a fluorine-containing alicyclic structure in the main chain obtained by cyclopolymerization of a fluorine-containing monomer having two or more polymerizable double bonds is preferred.

The monomer having a fluorinated alicyclic structure is preferably a monomer having one polymerizable double bond, and the fluorinated monomer capable of undergoing cyclopolymerization has two polymerizable double bonds. Further, a monomer having no fluorinated alicyclic structure is preferable.

Hereinafter, a copolymerizable monomer other than a fluorine-containing monomer capable of undergoing cyclopolymerization with a monomer having a fluorine-containing alicyclic structure is referred to as “another radically polymerizable monomer”.

The carbon atoms constituting the main chain of the fluoropolymer are composed of two carbon atoms of the polymerizable double bond of the monomer. Therefore, in a monomer having a fluorine-containing alicyclic structure having one polymerizable double bond, one or both of the two carbon atoms constituting the polymerizable double bond constitute an alicyclic ring. Atom. A fluorine-containing monomer having no alicyclic ring and having two polymerizable double bonds is composed of one carbon atom of one polymerizable double bond and one carbon atom of the other polymerizable double bond. The carbon atoms combine to form a ring. An alicyclic ring is formed by the two bonded carbon atoms and the atoms between them (excluding atoms in the side chain), and an etheric oxygen atom is formed between the two polymerizable double bonds. When a is present, a fluorinated aliphatic ether ring structure is formed.

A polymer having a fluorinated alicyclic structure in the main chain obtained by polymerizing a monomer having a fluorinated alicyclic structure is perfluoro (2,2-dimethyl-1,3-dioxole)

(Abbreviated as PDD), perfluoro (2-methyl-1,3-dioxol), perfluoro (2-ethyl-2-propyl-1,3-dioxole), perfluoro mouth (2,2-dimethyl-4-methyl-1,3-) Peroxodioxoles having a fluorine-substituted alkyl group such as fluorine, trifluoromethyl group, penfluorofluorethyl group, or hepfluorofluoro group at ring carbon of peroxodioxole such as dioxol), perfluoro (4-methyl-2-methylene) Including 1,3 dioxolane (abbreviated as MMD) and perfluoro (2-methyl-1,4-dioxin) It is obtained by polymerizing a monomer having a nitrogen alicyclic structure.

Further, a polymer having a fluorinated alicyclic structure in the main chain obtained by copolymerizing this monomer with another radical polymerizable monomer containing no C—H bond may also be used. When the ratio of the polymerized unit of the other radical polymerizable monomer is increased, the light transmittance of the fluoropolymer may decrease.Therefore, the fluoropolymer may be a monomer having a fluoroalicyclic structure. Homopolymers and copolymers in which the ratio of the polymerized units of the monomers is 70 mol% or more are preferred.

Other radically polymerizable monomers that do not contain a C-H bond include tetrafluoroethylene, black trifluoroethylene, and perfluoro (methyl vinyl ether).

Examples of such commercially available amorphous fluorine-containing polymers having substantially no C—H bond include the above-mentioned perfluoro-2,2-dimethyl-1,3-dioxole polymer (trade name: Teflon (registered trademark) ) AF: manufactured by DuPont), perfluoro-4-methyl-1,3-dioxole polymer (trade name: HYFLON AD: manufactured by Audimont).

Further, a polymer having a fluorinated alicyclic structure in the main chain obtained by cyclopolymerization of a fluorinated monomer having two or more polymerizable double bonds is disclosed in JP-A-63-233. This is known from Japanese Patent Application Laid-Open No. 81111/1994 and Japanese Patent Application Laid-Open No. 63-238118 / 1988. That is, a monomer such as perfluoro (3-oxa-1,5_hexadiene) or perfluoro (3-oxa-11,6_hexadiene) (abbreviated as PBVE) is subjected to cyclopolymerization or a monomer thereof. The main chain is obtained by copolymerizing such a monomer with other radically polymerizable monomers that do not contain a C-H bond, such as tetrafluoroethylene, black trifluoroethylene, and perfluoro (methyl vinyl ether). Thus, a polymer having a fluorinated alicyclic structure is obtained. In the above-mentioned cyclopolymerization of PBVE, a polymerization unit having a 5-membered ring ether structure represented by the above formula (I) in the main chain is formed by the bond at the 2,6-position carbon.

Further, as the fluorine-containing monomer having two or more polymerizable double bonds, other than the above, for example, a monomer having a substituent on a saturated carbon of PBVE is also preferable. Oxa-1,6-butadiene) (PBVE— 4 Perfluoro (abbreviated as 4-black mouth-3-oxa-1, 6-butadiene) (PBVE-4 CL), perfluoro (5-methoxy-3-oxa1-1, 6-butadiene) (PBVE) — 5 MO), perfluoro (5-methyl-3-oxa-1,6-butadiene) and the like are also preferable. When the ratio of the polymerized unit of the other radical polymerizable monomer increases, the light transmittance of the fluoropolymer may decrease.Therefore, as the fluoropolymer, two or more polymerizable double bonds are used. Preferred is a homopolymer of a fluorine-containing monomer having the same or a copolymer having a ratio of polymerized units of the monomer of 40 mol% or more.

A commercial product of such a type of amorphous fluoropolymer having substantially no C—H bond is “CYTOP” (manufactured by Asahi Glass Co., Ltd.).

In addition, monomers having a fluorine-containing alicyclic structure, such as perfluoro (2,2-dimethyl-1,3-dioxol), perfluoro (3-oxa1-1,5-hexagen), perfluoro (3 -Oxa-1,6-butadiene) (PBVE) and other copolymers with a fluorine-containing monomer having two or more polymerizable double bonds also have a fluorine-containing alicyclic structure in the main chain. Is obtained. Also in this case, the light transmittance may be reduced depending on the combination. Therefore, the proportion of the polymerized unit of the fluorine-containing monomer having two or more polymerizable double bonds is preferably 30 mol% or more. Coalescence is preferred.

As the polymer having a fluorinated alicyclic structure, a polymer having a ring structure in the main chain is suitable. Those containing at least mol% are preferred in terms of transparency, mechanical properties and the like. Further, the polymer having a fluorinated alicyclic structure is preferably a perfluoropolymer. That is, the polymer is preferably a polymer in which all of the hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms.

However, some fluorine atoms of the perfluoropolymer may be replaced by atoms other than hydrogen atoms such as chlorine atoms and deuterium atoms. Since the presence of a chlorine atom has the effect of increasing the refractive index of the polymer, the polymer having a chlorine atom can be used particularly as a fluorine-containing polymer.

The above-mentioned fluoropolymers have a light transmitting body that exhibits heat resistance and softens even when exposed to high temperatures. It is desirable to have a sufficient molecular weight so as not to be difficult to reduce the light transmission performance. The molecular weight of the fluoropolymer for exhibiting such properties is limited to the molecular weight that can be melt-molded, but the intrinsic viscosity measured in 30 perfluoro (2-butylethyltrahydrofuran) (PBTHF) [ 7?], Usually 0.1 to Ld 1 / g, more preferably 0.2 to 0.5 dl / g. The number average molecular weight corresponding to the intrinsic viscosity is generally about 1 × 10 ^{4 to} 5 × 10 ⁶ , preferably about 5 × 10 ⁴ to 1 × 10 ⁶ .

In addition, in order to ensure the formability of the above-mentioned fluoropolymer during melt spinning or preform stretching, the melt viscosity of the fluoropolymer melted at 200 to 300 ° C is l x Preferably, it is about 10 ^{2 to} l X 10 ⁵ Pa's.

The fluorinated polymer having a fluorinated alicyclic structure described above is heat-stretched or stretched compared to a fluorinated polymer having a fluorinated imido ring structure, a fluorinated triazine ring structure or a fluorinated aromatic ring structure described below. This is particularly preferable because the polymer molecules are less likely to be oriented even when processed into fibers by melt spinning, and therefore, light scattering is less likely to occur. In particular, a fluorinated polymer having a fluorinated aliphatic ether ring structure is preferred.

The fluorinated polymer having a fluorinated alicyclic structure in the main chain is a preferred fluorinated polymer of the present invention, but as described above, the fluorinated polymer of the present invention is not limited thereto. .

For example, as described in JP-A-8-5848, a non-crystalline fluorine-containing polymer having substantially no C-H bond and having a fluorine-containing ring structure other than a fluorine-containing alicyclic structure in the main chain. Coalescing can be used. Specifically, for example, a non-crystalline fluorine-containing polymer having a fluorine-containing ring structure such as a fluorine-containing imide ring structure, a fluorine-containing triazine ring structure, or a fluorine-containing aromatic ring structure in a main chain can be used. The melt viscosity or molecular weight of these polymers is preferably in the same range as that of the above-mentioned fluorine-containing polymer having a fluorinated alicyclic structure in the main chain.

The fluorine-containing polymer having a fluorine-containing imide ring structure in the main chain, which is a preferred fluorine-containing polymer of the present invention, specifically has a repeating unit represented by the following general formula. Is illustrated

0

«

CNR ¹ N-R

\ / \ /

c c

0 o

(In the above formula, R ¹ is selected from the following,

R ² is selected from:

Here, R _f is selected from a fluorine atom, a perfluoroalkyl group, a perfluoroaryl group, a perfluoroalkoxy group, and a perfluorophenoxy group. You may. Y is selected from the following. ー 0-, -CO-, — S0 ₂ ―, one S-, one R *,-,-OR ', _Γ , R' _t 0- _r , ^ OR ', Of _r ,

-SR ', ^ _r ,', S _r , iSR "« S,,

Here, R ' _f is selected from a perfluoroalkylene group and a perfluoroarylene group, which may be the same or different. r is 1-10. Y and two R _f may form a ring across carbon, in which case the ring may be a saturated or unsaturated ring. )

Further, in the present invention, examples of the fluorine-containing polymer having a fluorine-containing aromatic ring structure include fluorine-substituted polymers of polymers having an aromatic ring in the side chain or main chain, such as polystyrene, polyacrylonitrile, and polyester. These may be perfluoro-substituted perfluorinated, or those obtained by substituting the remaining fluorine-substituted with chlorine or the like. Further, it may have a trifluoromethane substituent or the like.

Further, a fluorine atom in the fluoropolymer may be partially substituted with a chlorine atom in order to increase the refractive index. Although a substance for further increasing the refractive index may be contained in the fluorine-containing polymer of the present invention, it is preferable that the entire molding material of the present invention contains substantially no C—H bond.

In the above, the fluorinated polymer constituting the continuous phase and the dispersed phase of the light transmitting body has been described.In the present invention, the above polymer that has been polymerized in advance may be used as a molding material to form the fluorinated polymer. Polymerization may be performed at the time of molding using a polymerizable monomer that can be used.

Further, a preferred component constituting the continuous phase and the dispersed phase of the present invention is a non-crystalline fluoropolymer containing substantially no C—H bond. Since the refractive index needs to be 0.001 or lower, the fluorine-containing polymer constituting the dispersed phase may have a small amount of hydrogen atoms. However, the existence of hydrogen atoms is transmitted The fluoropolymer that constitutes the dispersed phase is also substantially different, because it may cause light absorption, and the presence of hydrogen atoms increases the refractive index of the polymer compared to fluorine atoms. A polymer having no hydrogen atom is preferred.

In the present invention, the production method is not particularly limited as long as the optical transmitter having the above-mentioned structure having a sea-island structure can be preferably obtained by using the above-mentioned fluoropolymer. Therefore, in the present invention, an optical transmission body having a sea-island structure may be directly manufactured, but the length of an organic compound having a high refractive index component is mixed with an organic compound having a low refractive index component. The coalesce is dispersed, and the polymer of the organic compound of the low refractive index component is produced by manufacturing a preform having a sea-island structure extending in the longitudinal direction in a long body and stretching and forming the preform. An optical transmission body having a desired diameter may be manufactured. Therefore, the present invention can also provide a preform having the above-mentioned sea-island structure.

The optical transmitter or preform having the sea-island structure of the present invention, more specifically, the optical transmitter or preform in which both the continuous phase and the dispersed phase constituting the sea-island structure are made of a polymer of an organic compound, Melt spinning and extrusion can be used as a technique for forming a sea-island structure by dispersing a dispersed phase therein.

For example, a pre-divided strand-shaped polymer of low refractive index organic compound (island material) is placed in a tube made of a polymer of high refractive index organic compound (sea material) and co-spun. Thereby, a sea-island structure can be formed.

In addition, a polymer (island material) of a low-refractive-index organic compound that has been uniformly melted is divided in an extrusion die, and after finely segmented, a polymer of a high-refractive-index organic compound (sea material) is placed around the periphery. The high-refractive-index organic compound polymer is supplied to the outer periphery of the low-refractive-index organic compound polymer, and then extruded from a common nozzle to form a sea-island structure.

According to the procedure of the present invention, an optical fiber having a sea-island structure can be obtained directly or by stretching a preform. The optical fiber thus obtained is usually coated with a thermoplastic resin or the like and used as an optical fiber cord. The coating may be made of materials commonly used for coating optical fiber, such as polyethylene, polyvinyl chloride, polymer methyl acrylate (PMMA), ethylene- What is necessary is just to select suitably from thermoplastic resins, such as a trafluoroethylene-type copolymer. Usually, a plurality of such optical fiber cable cords are provided on another covering in the form of a long body having a partition spacer and a hole for accommodating the optical fiber cable cords, For example, two cables are stored and used as an optical fiber cable. Such a long-shaped covering is usually buried with a tensile strength reinforcing member (tension member) for preventing tensile elongation of the optical fiber. The tension member may be appropriately selected from materials normally used for this purpose, for example, a wire such as a metal wire or an FRP wire, or a high-rigidity continuous filament such as aramid continuous filament. Further, a plurality of optical fiber cords obtained by coating optical fiber strands may be bundled and used as a bundle fiber. Such a bundle fiber includes a multi-core tape core constituted by arranging a plurality of optical fiber cords in parallel, in addition to a bundle of a plurality of optical fiber cords in an annular shape. In the case of the pandul fiber, another coating is formed so as to cover a plurality of bundled optical fiber cords. Further, in such a bundle fiber, various cushioning materials such as a tensile strength reinforcing yarn, a string, a paper, a plastic, and the like are usually arranged in a space between the optical fiber cords. Here, an optical fin is obtained. However, the present invention is not limited to this, and the present invention can be applied to an optical waveguide, an optical switch, a rod lens, and the like.

Since the light transmitting body of the present invention is preferably made of a fluoropolymer having substantially no CH bond, it is not affected by acidic chemicals such as sulfuric acid and hydrochloric acid and alkaline chemicals such as sodium hydroxide. In addition, it has the feature that it is not affected by organic solvents such as toluene, benzene and acetone, so it can be used in poor environments such as in sewer pipes or in factories where hydraulic oil is scattered. In addition, because of the sea-island structure in which the dispersed phase is dispersed in the continuous phase, bending loss is improved, and it can be used for movable parts such as mouth pots that are frequently bent.

Further, the optical fiber having the sea-island structure of the present invention can control the sea-island structure to have a single mode of light propagation in a continuous phase portion (core portion) surrounded by a disperse phase. An ultra-wide band of 4 GHz · km can be achieved, and the transmission loss at 100 m at wavelengths of 600 to 1,600 nm can be reduced to 50 dB or less. In particular, a fluoropolymer having an alicyclic structure in the main chain has a transmission loss of 100 Om at the same wavelength. Can be set to 20 dB or less. At a relatively long wavelength of 700 to 1,600 nm, such a low level of transmission loss is extremely advantageous. In other words, since the same wavelength as the quartz optical fiber can be used, the connection with the quartz optical fiber is easy, and the light source selection range is smaller than that of the conventional plastic optical fiber, which has to use a wavelength shorter than 650 nm. Has the advantage of being wide. The optical fiber having a sea-island structure of the present invention is used for LANs in public facilities such as subscriber communication lines, LANs in factories, LANs in hospitals, LANs in schools, LANs in sewer pipes, medical equipment, floor cables, and power lines. High-speed, high-bandwidth communication such as surveillance communication lines, automotive applications, monitor image transmission of train operating conditions, communication in large vessels on ocean routes, data transmission in aircraft, and amusement-related applications such as business game machines Necessary video transmission, high-quality video, transmission of stereoscopic images, wiring in equipment such as computers and automatic exchanges, general indoor communication networks, various sensor fields, lighting, illumination fields, energy transmission, and various other fields. Is available.

(Example)

Next, the present invention will be described more specifically with reference to Examples, but it goes without saying that these Examples do not limit the present invention.

Example 1

As the low-refractive-index fluoropolymer (a), a perfluoro (3-oxa-1,6-butadiene) cyclized polymer (refractive index: 1.34) was selected. The outer diameter was 20 mm and the length was 20 mm. A 500mm cylindrical island base material (c) was formed. On the other hand, 15% by mass of CTFE (clo-mouth trifluoroethylene) oligomer is added to the above perfluoro (3-oxa 1,6-butadiene) cyclized polymer, and heated to diffuse to obtain a high refractive index component (refractive index: 1. Prepare a fluorinated polymer of 355) and connect a hollow tube (sea base material: d) with an outer diameter of 40 mm, an inner diameter of 2 lmm, and a length of 550 mm, and a solid rod with an outer diameter of 20 mm. Molded. Only this solid rod was melt-spun to obtain a strand (e) having an outer diameter of 0.5 mm.

Insert the island base material (c) into the hollow part of the hollow tube (sea base material: d), melt-spun in a heating furnace heated to 220 mm, and have an outer diameter of 0.5 mm. 0.25 mm diameter Strand (f) was obtained.

In addition, the hollow tube (g) having an outer diameter of 20 mm, an inner diameter of 10 mm, and a length of 500 mm is formed by spin molding using the above perfluoro (3-oxa-1,6-butadiene) cyclized polymer. did. In the hollow part of the hollow tube (g), a strand (e) made of a high-refractive-index fluorine-containing compound is arranged at the center, and a low-length 480 mm length cut around the strand (e). 200 strands (f) made of a fluoropolymer having a refractive index were inserted concentrically into 200 strands, and the preform base material (h) prepared as the preform base material (h) was heated to 220 ° C. It is melt-spun in a furnace and has a diameter of 0.5 mm, which is a low-refractive-index fluorine-containing compound, in a continuous phase (sea material) 2 with an outer diameter of 0.5 mm and a high-refractive-index. An optical fiber 1 made of a fluoropolymer having a sea-island structure in which 200 dispersed phases (island materials) 3 of m were dispersed was obtained. In the optical fiber shown in Fig. 5, the dispersed phase 3 is linearly arranged from the center to the outside in the vertical and horizontal directions and diagonally so that the continuous phase 2 is divided into six parts. The dispersed phases 3 are dispersed with some periodicity between the arranged dispersed phases 3. Laser light with a numerical aperture (NA) of 0.1 and a wavelength of 850 nm was incident on the obtained optical fiber 1 made of a fluoropolymer, and a 200 m transmission test was performed. The transmission loss was 19 dBZkm and the bandwidth was 4 dB. GHz · km. When the fiber was bent at an R (curvature) of 10 and at an angle of 180 °, the loss was less than 0.1 dB.

Example 2

As a low refractive index fluoropolymer (a), a copolymer of perfluoro (2,2-dimethyl-1,3-dioxoxol) [PDD] and tetrafluoroethylene [TFE] (mole percentage ratio 65:35) (Refractive index: 1.31) was selected to produce a solid rod with an outer diameter of 20 mm and a length of 30 Omm. The solid rod (j) was heated and spun to obtain a strand (k) having an outer diameter of 2 mm.

At the same time, 30 rods made of polycarbonate with an outer diameter of 2 mm and a length of 30 Omm are concentrically placed in a concentric circle with a diameter of 2 Omm in a tube made of perfluoro (alkyl vinyl ether) -tetrafluoroethylene copolymer (PFA) with an inner diameter of 4 Omm. To make (Ie, no rods are placed at the center of the concentric circles), and in that state, a perfluoro (3- A cyclized polymer of 1,6-butadiene (refractive index: 1.34) was injected in a molten state to obtain a marine precursor (1). After cooling and solidification, the marine material precursor (1) was immersed in a dimethyl chloride solvent. In the construction of the marine material precursor (1), the fluoropolymer (a) was not affected at all, and only the polycarbonate rods were dissolved.

As a result, a sea material (m) having an outer diameter of 40 mm, a length of 300 mm, and 30 through-holes with an inner diameter of 2 mm formed so as to form a concentric circle with a diameter of 20 mm was obtained.

One island material obtained by cutting a strand (k) made of a fluorine-containing compound having a low refractive index into a length of 300 mm was inserted into the through hole of the obtained sea material (m). The sea material (m) and the island material (k) were integrated at the bottom so as not to slip, and melt-spun at 240.

As a result, the continuous phase (sea material) 2, which is a high-refractive-index fluorine-containing compound having an outer diameter of 0.5 mm as shown in Fig. 6, contains a low-refractive-index fluorine-containing compound, a dispersed phase (island material) ( Optical fiber 1 made of a fluoropolymer having a diameter of 25 lim) 3 and having 30 dispersed sea-island structures was obtained. In the optical fiber 1 shown in FIG. 6, the dispersed phase 3 is periodically and concentrically arranged with respect to the central axis of the optical fiber 1 in the continuous phase 2. A laser beam with a wavelength of 0.25 NA and a wavelength of 130 nm was injected into the obtained optical fiber, and a transmission test was performed at 500 m.The transmission loss was 17 dBZkm and the bandwidth was 1 GHzkm. Was. The loss when the fiber was bent at an angle of 180 ° at R10 was 0.1 dB.

Example 3

As the fluorinated polymer (a), a perfluoro (3-oxa-1,6-heptagene) cyclized polymer (refractive index: 1.34) was selected, and the outer diameter was 20 mm and the length was 20 mm. Formed a columnar body having a size of 500 mm. 7% by weight of perfluorotriphenylbenzene (TPB) was added to the mixture, and the mixture was heated and mixed at 250 ° C to produce a fluorine-containing compound having a high refractive index (refractive index: 1.355). A marine base material (n) having an outer diameter of 40 mm and a length of 500 mm was formed.

In addition, a cyclized polymer of the above perfluoro (3-oxa-1,6-butadiene) By using it as it is, a fluoropolymer with a low refractive index (refractive index: 1.34) was formed into a cylindrical body (o) for an island base material with an outer diameter of 20 mm and a length of 550 mm in a metal tube. .

Two corrosion-resistant 20 mm screw type extruders were prepared, and an extruder 1 for supplying an island base material and an extruder 2 for supplying a sea base material on the outer periphery thereof were connected via a crosshead. The island base material is divided into 19 streams in the crosshead, and the sea base material from the extruder 2 joins the outer periphery of each island base material.構造 Only the central part has a structure that does not supply island base material. A nozzle with a diameter of 3 mm was installed at the end of the crosshead.

The extruder 1 was charged with the island base material (o) and melted at 200 ° C. At the same time, the columnar body for a base material (n) was charged into the extruder 2 and melted at 220 ° C. Both merge in the crosshead and are guided to the nozzle with a multi-layer cross section in which 19 island base materials are dispersed as a dispersed phase in the continuous phase of the sea base material. The multilayer molten resin (P) extruded to the outside via the nozzle was stretched to an outer diameter of 5 mm to obtain the plastic optical filter shown in Fig. 3. In the optical fiber 1 shown in FIG. 3, 19 dispersed phases 3 (island material) having a diameter of 4 are periodically dispersed concentrically with respect to the central axis of the optical fiber 1 in a continuous phase (sea material) 2. Had a sea-island structure. When a laser beam with a NA of 0.25 and a wavelength of 850 nm was incident on the obtained optical fiber and a transmission test was performed at 1000 m, the transmission loss was 25 dBZkm and the bandwidth was 1.2 GHz · km. When the fiber was bent at R10 at an angle of 180 °, the loss was 0.2 dB.

Example 4

As a low refractive index fluoropolymer (a), a copolymer of perfluoro (2,2-dimethyl-1,3-dioxoxol) [PDD] tetrafluoroethylene [TFE] (mol percentage ratio 65:35) (refractive Index: 1.31) is selected as the island matrix, and high refractive index fluoropolymer is selected, and perfluoro (3-oxa-1,6-heppugen) (refractive index: 1.34) is selected as the sea matrix. Each was melted at 260 ° C. and solidified in a metal tube having an inner diameter of 20 mm to form a columnar body having an outer diameter of 40 mm and a length of 500 mm.

Prepare two 15 mm plunger type extruders with corrosion resistance and press The extruder (1) and the extruder (2) for supplying the marine base material on the outer periphery were connected via a crosshead. The island base material is split into two streams in the crosshead, and further split into 100 streams at each point. Then, the sea base material from the extruder (2) merges with the outer periphery of the island base material. Has become. However, the sea base material was arranged at the center of each of the 100 island base materials. At the end of the crosshead was a buzzard with an elliptical cross section of 3 mm long and 5 mm wide.

The island base material was put into the extruder (1) and melted at 220 ° C. At the same time, the columnar material for the base material was put into the extruder (2) and melted at 250 ° C.

Both merge in the crosshead, and a multi-layer cross-section in which two groups of 100 island base materials are dispersed in the sea matrix, which is a continuous phase, so that each group forms a concentric circle Is led to the nozzle. The multi-layered molten resin (o) extruded to the outside through the nozzle is stretched to an outer diameter of 0.3 x 0.5 mm, and the diameter of the dispersed phase (island material) 3 shown in Fig. 7 is 3 m each. A single-mode duplex (bidirectional) plastic optical fiber with a sea-island structure containing 100 dispersed phases (island materials) 3 per group was obtained. As shown in FIG. 7, the obtained optical fiber 1 has an elliptical cross-sectional shape, and includes two dispersed phases arranged concentrically in the continuous phase (sea material) 2 in the axial direction of the optical fiber 1. (Island lumber) There were three groups. A laser beam with a NA of 0.1 and a wavelength of 850 nm was incident on the obtained optical fiber, and a 200 m transmission test was performed.The transmission loss was 25 dBZkm and the bandwidth was 4.0 GHzkm. . In addition, bidirectional transmission could be performed with one fiber using the same fiber. The loss when bent at an angle of 180 ° with R10 was less than 0.01 dB.

Example 5

As the fluoropolymer (a), perfluoro (4-methylbutenyl vinyl ether), which is a low-refractive-index fluoropolymer (refractive index: 1.328), is used as an island base material, and a high-refractive-index fluorine-containing polymer is used. Perfluoro (3_oxa 1,6-butadiene), which is a coalescence (refractive index: 1.34), was selected as the marine base material, and each was melted at 250 ° C and solidified in a metal tube with an inner diameter of 2 Omm. Thus, a cylindrical body having an outer diameter of 3 Omm and a length of 50 Omm was formed.

Prepare two 15 mm plunger type extruders with corrosion-resistant specifications and press The extruder (1) and the extruder (2) for supplying the marine base material on the outer periphery were connected via a crosshead. The island base material is split into two streams in the crosshead, and further split into 100 streams at each point. Then, the sea base material from the extruder (2) merges with the outer periphery of the island base material. Has become. However, the sea base material was arranged at the center of each of the 100 island base materials. At the end of the crosshead is a nozzle with an elliptical cross section of 3 mm long and 5 mm wide.

The island base material was put into the extruder (1) and melted at 220 ° C. At the same time, a columnar body for marine base material was put into the extruder (2) and melted at 25 CTC.

The two converge in the crosshead, and the nozzles have a multi-layer cross section in which two groups of 100 islands are dispersed in a continuous phase in the marine base material so that each group forms a concentric circle. Led to. The multi-layered molten resin (o) extruded through the nozzle stretches to an outer diameter of 0.3 X 0.5 mm. As shown in Fig. 7, the diameter of the dispersed phase (island material) is 3 m each. Thus, a single-mode duplex (bidirectional) plastic optical fiber with a sea-island structure was obtained. The optical fiber 1 shown in FIG. 7 has an elliptical cross-sectional shape, and has a group of two dispersed phases (island materials) 3 arranged concentrically with respect to the axial direction of the optical fiber 1 in the continuous phase 2. Was. A 200 m transmission test was performed by injecting a laser beam with a NA of 0.1 and a wavelength of 850 nm into the obtained optical fiber.The transmission loss was 25 dB / km and the bandwidth was 4.0 GHz. km. In addition, bidirectional transmission could be performed with one fiber using the same fiber. The loss when bent at an angle of 180 ° with R10 was less than 0.01 dB. Industrial potential

According to the present invention, such as LAN, multi-family housing, medical equipment, automobile, OA (office automation), home electric appliance, etc., which cannot be achieved by conventional plastic optical transmission media such as polymethyl methacrylate, polystyrene, and polycarbonate. Thus, it is possible to provide an optical fiber product having low transmission loss, mechanical strength, heat resistance, moisture resistance, chemical resistance, and nonflammability required by the above. In addition, by making visible light (500-700 nm) and near-infrared light (700-1600 nm), which could not be achieved by conventional optical transmission media, available, and by using an optical fiber with a sea-island structure, the fiber was bent. of time Light with a low transmission loss and high transmission band type islands-in-the-sea structure that can provide ultra-high-speed transmission by reducing bending loss and providing single-mode propagation conditions as needed. it can.

Claims

The scope of the claims

1. An optical transmitter characterized by having a sea-island structure in which a low-refractive-index dispersed phase is dispersed in a high-refractive-index continuous phase.

2. The optical transmission body according to claim 1, wherein in the cross-sectional shape of the optical transmission body, the low-refractive-index dispersed phase is arranged to have a periodicity forming an optical waveguide.

3. The optical transmitter according to claim 1, wherein each of the component constituting the high-refractive-index continuous phase and the component constituting the low-refractive-index dispersed phase comprises a polymer of an organic compound.

4. The component constituting the high-refractive-index continuous phase is composed of an amorphous fluoropolymer (a) having substantially no C—H bond,

4. The component according to claim 3, wherein the component constituting the low-refractive-index dispersed phase is a fluoropolymer (b) having a refractive index lower than that of the fluoropolymer (a) by 0.0001 or more. 5. Optical transmitter.

5. The optical transmitter according to claim 4, wherein the fluoropolymer (a) has a fluorinated ring structure.

6. The optical transmitter according to claim 5, wherein the fluorinated ring structure is a fluorinated alicyclic structure which may contain a ring member ether bond.

7. The optical transmitter according to claim 5, wherein the fluorinated polymer having a fluorinated ring structure has the fluorinated ring structure in a main chain.

8. Both of the fluoropolymers (a) and (b) have substantially no C—H bond, and have a fluorinated alicyclic structure that may contain an ether bond in the main chain. The optical transmitter according to any one of claims 4 to 7, which is a crystalline fluoropolymer.

9. A method for producing the optical transmitter according to any one of claims 3 to 8, wherein the long body made of a polymer of an organic compound having a high refractive index has a low refractive index component. A preform having a sea-island structure, wherein a polymer of an organic compound is dispersed, and the polymer of the organic compound of the low refractive index component extends in the longitudinal direction in the elongated body.

10. A pre-divided strand-shaped polymer of an organic compound as a low-refractive-index component is placed in a tube made of a polymer of an organic compound as a high-refractive-index component, and co-spun. The method for producing an optical transmission body having a sea-island structure or a preform thereof according to any one of claims 3 to 9, wherein the optical transmission body is a yarn.

11. The polymer of the organic compound, which is a low-refractive-index component, which has been uniformly melted, is diverted in an extrusion die, and after being finely divided, an organic compound polymer, which is a high-refractive-index component, is supplied to the periphery thereof. 10. The polymer of the organic compound of the high refractive index component is applied to an outer peripheral portion of the polymer of the organic compound of the low refractive index component, and the polymer is extruded from a common nozzle. A method for producing an optical transmitter having a sea-island structure or a preform thereof according to any one of the above.

12. An optical fiber cord in which the optical transmission body according to claim 1 is coated with at least one layer.

13. A long body made of a thermoplastic resin having a hole extending in the longitudinal direction therein and having a tensile strength reinforcing member embedded therein, and the long body is housed in the hole of the long body. An optical fiber cable comprising:

14. A bundle fiber, wherein a plurality of the optical fiber cords according to claim 12 are bundled.