TW202100640A - Plastic optical fiber - Google Patents

Abstract

This plastic optical fiber (10) is provided with a core (11) and a clad (12) disposed at the outer periphery of the core (11). At least part of the clad (12) comprises a resin having a porous structure. For example, it is also possible that the resin having the porous structure includes hollow particles, and the porous structure is formed by the hollow particles.

Description

Plastic optical fiber

The present invention relates to a plastic optical fiber.

The plastic optical fiber has a core as a central part of the light transmission part and a cladding covering the outer periphery of the core. The core is formed of a resin material with a high refractive index. In order to retain light in the core, the cladding is formed of a resin material having a lower refractive index than the resin material of the core.

Previously, various structures for reducing the transmission loss of plastic optical fibers were studied. For example, Patent Document 1 proposes a plastic optical fiber that reduces transmission loss by reducing the amount of foreign matter in the sheath, that is, in the cladding. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2016/063829

[The problem to be solved by the invention]

As a method to further reduce the transmission loss of plastic optical fiber, consider increasing the numerical aperture of the optical fiber. By increasing the numerical aperture of the optical fiber, for example, the bending loss is reduced, so the confinement effect of the light in the core is improved.

In order to increase the numerical aperture of the optical fiber, it is required to make the refractive index of the cladding lower. Previously, in order to reduce the refractive index of the cladding layer, it was implemented to reduce the refractive index of the resin material itself constituting the cladding layer. However, it is not easy to reduce the refractive index of the resin material itself, and it is limited to further reduce the refractive index of the cladding by developing resin materials.

Therefore, the object of the present invention is to provide a plastic optical fiber, which can increase the numerical aperture by reducing the refractive index of the cladding, and as a result, can achieve lower transmission loss. [Technical means to solve the problem]

The present invention provides a plastic optical fiber which is provided with a core and a cladding layer arranged on the outer periphery of the core, and at least a part of the cladding layer includes a resin having a porous structure. [Effects of Invention]

According to the present invention, a plastic optical fiber can be provided, which can increase the numerical aperture by further reducing the refractive index of the cladding, and as a result, can achieve lower transmission loss.

An embodiment of the plastic optical fiber (hereinafter referred to as "POF") of the present invention will be described. The POF of this embodiment includes a core and a clad layer arranged on the outer periphery of the core. At least a part of the clad layer contains a resin having a porous structure.

Figures 1 to 3 respectively show cross-sectional structures of examples of POF (the first to third examples) of the present embodiment.

The POF 10 of the first example shown in FIG. 1 includes a core 11 and a cladding 12 arranged on the outer periphery of the core 11. At least a part of the clad layer 12 contains a resin having a porous structure.

The POF 20 of the second example shown in FIG. 2 has a structure in which the cladding layer 12 is changed to the cladding layer 22 having a plurality of layers in the POF 10 shown in FIG. 1. Furthermore, in the POF 20, the cladding layer 22 has a two-layer structure including a first cladding layer 221 and a second cladding layer 222. The first cladding layer 221 is arranged in contact with the core 11, and the second cladding layer The coating layer 222 is arranged on the outer peripheral side than the first coating layer 221. In the case of this configuration, for example, the second coating layer 222 includes a resin having a porous structure. Furthermore, although FIG. 2 shows an example in which the clad layer 22 has a two-layer structure, the number of layers contained in the clad layer 22 is not limited to this, and may include three or more layers. When the cladding layer contains multiple layers, for example, even when the light incident on the core is not totally reflected by the interface between the core and the cladding layer and leaks out to the cladding layer, it can also be covered by the outer peripheral side. The layer is totally reflective, so light loss can be reduced.

The POF 30 of the third example shown in FIG. 3 has a configuration in which a coating layer 31 disposed on the outer periphery of the cladding layer 22 is further provided with respect to the POF 20. The coating layer 31 is provided to improve the mechanical strength of the POF 30.

Hereinafter, each configuration of the POF of this embodiment will be described in more detail.

(Fiber Core) The core is the area where light is transmitted. The core has a higher refractive index than the cladding. With this structure, the light incident into the core is enclosed in the core by the cladding and is transmitted in the POF.

The material of the core is not particularly limited as long as it is a resin with high transparency. Examples of the resin include acrylic resins such as fluorine-containing resins and methyl methacrylate, styrene resins, and carbonate resins. Among them, it is preferable to use a fluorine-containing resin in terms of achieving lower transmission loss in a wider wavelength region.

The fluorine-containing resin is, for example, a polymer using a fluorine-containing compound having a polymerizable double bond as a monomer. From the viewpoint of suppressing the light absorption caused by the expansion and contraction energy of the C-H bond, it is preferable that the fluorine-containing resin used as the core material does not contain the C-H bond. Therefore, it is preferable that the fluorine-containing resin contains substantially no hydrogen atoms, and it is particularly preferable that all H of the C-H bond is fluorinated. That is, it is preferable that the fluorine-containing resin contains substantially no hydrogen atoms and is perfluorinated. The fact that the fluorine-containing resin does not substantially contain hydrogen atoms means that the content of hydrogen atoms in the fluorine-containing resin is 1 mol% or less.

Examples of the fluorine-containing resin include polymers having a fluorine-containing aliphatic ring structure. As the polymer having a fluorine-containing aliphatic ring structure, it is preferable to use a fluorine-containing compound having a fluorine-containing aliphatic ring structure as a monomer and polymerize the monomer. It is preferable that the fluorine-containing polymer having a fluorine-containing aliphatic ring structure also contains substantially no hydrogen atoms. Here, the fluorine-containing compound having a fluorine-containing aliphatic ring structure means a fluorine-containing compound having a polymerizable double bond between the carbon atoms constituting the ring and the carbon atoms not constituting the ring, or between the two carbon atoms constituting the ring Fluorine-containing compound with polymerizable double bond. Examples of the fluorine-containing compound having a polymerizable double bond between carbon atoms constituting the ring and carbon atoms not constituting the ring include: perfluoro-2-methylene-4-methyl-1,3-dioxa Fluorinated compounds with 1,3-dioxolane structure such as cyclopentane. Examples of fluorine-containing compounds having a polymerizable double bond between two carbon atoms constituting the ring include: perfluoro-4-methyl-1,3-dioxole and perfluoro-4-methyl Fluorine-containing compounds with 1,3-dioxol structure such as 1,3-dioxole.

(式(1)中，R_ff ¹ ～R_ff ⁴ 分別獨立地表示氟原子、碳數1～7之全氟烷基、或碳數1～7之全氟烷基醚基；R_ff ¹ 及R_ff ² 亦可連結形成環)When the fluorine-containing resin is a perfluorinated fluorine-containing polymer having a fluorine-containing aliphatic ring structure, among the fluorine-containing compounds that form the monomers of the fluorine-containing polymer by polymerization, for example, the following The compound represented by formula (1). [化1]

(In formula (1), R _ff ¹ to R _ff ⁴ each independently represent a fluorine atom, a perfluoroalkyl group with 1 to 7 carbons, or a perfluoroalkyl ether group with 1 to 7 carbons; R _ff ¹ and R _ff ² can also be connected to form a ring)

As specific examples of the compound represented by the above formula (1), for example, compounds represented by the following formulas (A) to (H) can be cited. [化2]

As the fluorine-containing compound, it is preferable to use one refined so as not to contain impurities. Refining can be achieved by known methods. Particularly among impurities, since the acid component affects coloring, it is preferable not to include an acid component.

The fluorine-containing compound used as the monomer may be one type or two or more types. That is, the fluorine-containing resin used in this embodiment may be a fluorine-containing polymer obtained by homopolymerizing one fluorine compound, or a fluorine-containing copolymer obtained by copolymerizing two or more fluorine compounds. .

The fluorine-containing resin used in this embodiment may be, for example, a fluorine-containing compound having a fluorine-containing aliphatic ring structure (hereinafter referred to as a fluorine-containing compound (A)), and a fluorine-containing compound (A) Fluorine-containing copolymer obtained by copolymerization of other fluorine-containing compounds. Examples of other fluorine-containing compounds other than the fluorine-containing compound (A) include the following fluorine-containing compounds (B) to (D).

(式(2)中，R¹ ～R³ 分別獨立地表示氟原子、或碳數1～7之全氟烷基；R⁴ 表示碳數1～7之全氟烷基；全氟烷基可具有環結構；氟原子之一部分可被取代為氟原子以外之鹵素原子；全氟烷基中之氟原子之一部分可被取代為氟原子以外之鹵素原子)The fluorine-containing compound (B) is fluorine-containing vinyl ether such as perfluorovinyl ether. The fluorine-containing vinyl ether is represented by the following formula (2), for example. [化3]

(In formula (2), R ¹ to R ³ each independently represent a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms; R ⁴ represents a perfluoroalkyl group having 1 to 7 carbon atoms; the perfluoroalkyl group may It has a ring structure; part of the fluorine atoms can be substituted with halogen atoms other than fluorine atoms; part of the fluorine atoms in the perfluoroalkyl group can be substituted with halogen atoms other than fluorine atoms)

(式(3)中，R⁵ ～R⁸ 分別獨立地表示氟原子、或碳數1～7之全氟烷基；全氟烷基可具有環結構；氟原子之一部分可被取代為氟原子以外之鹵素原子；全氟烷基中之氟原子之一部分可被取代為氟原子以外之鹵素原子)The fluorine-containing compound (C) is a fluorine-containing olefin such as tetrafluoroethylene and chlorotrifluoroethylene. The fluorine-containing olefin is represented by the following formula (3), for example. [化4]

(In formula (3), R ⁵ to R ⁸ each independently represent a fluorine atom or a perfluoroalkyl group with 1 to 7 carbon atoms; the perfluoroalkyl group may have a ring structure; part of the fluorine atom may be substituted with a fluorine atom Halogen atoms other than fluorine atoms; part of the fluorine atoms in the perfluoroalkyl group can be substituted with halogen atoms other than fluorine atoms)

(式(4)中，Z表示氧原子、單鍵、或-OC(R¹⁹ R²⁰ )O-，R⁹ ～R²⁰ 分別獨立地表示氟原子、碳數1～5之全氟烷基、或碳數1～5之全氟烷氧基；氟原子之一部分可被取代為氟原子以外之鹵素原子；全氟烷基中之氟原子之一部分可被取代為氟原子以外之鹵素原子；全氟烷氧基中之氟原子之一部分可被取代為氟原子以外之鹵素原子；s及t分別獨立地為0～5且s＋t表示1～6之整數(其中，於Z為-OC(R¹⁹ R²⁰ )O-之情形時，s＋t亦可為0))The fluorine-containing compound (D) is a fluorine-containing compound that has two or more polymerizable double bonds and can be cyclized and polymerized. The fluorine-containing compound (D) is represented by the following formula (4), for example. [化5]

(In formula (4), Z represents an oxygen atom, a single bond, or -OC(R ¹⁹ R ²⁰ )O-, and R ⁹ to R ²⁰ each independently represent a fluorine atom, a perfluoroalkyl group with 1 to 5 carbon atoms, Or a perfluoroalkoxy group with 1 to 5 carbon atoms; part of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms; part of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms; all Part of the fluorine atoms in the fluoroalkoxy group may be substituted with halogen atoms other than fluorine atoms; s and t are each independently 0-5 and s+t represents an integer of 1-6 (wherein Z is -OC(R ^{19 In} the case of R ²⁰ )O-, s+t can also be 0))

(式(5)中，R¹⁴¹ 、R¹⁴² 、R¹⁵¹ 、及R¹⁵² 分別獨立地表示氟原子、碳數1～5之全氟烷基、或碳數1～5之全氟烷氧基；氟原子之一部分可被取代為氟原子以外之鹵素原子；全氟烷基中之氟原子之一部分可被取代為氟原子以外之鹵素原子；全氟烷氧基中之氟原子之一部分可被取代為氟原子以外之鹵素原子)As the fluorine-containing compound (D), a fluorine-containing compound represented by the following formula (5) can also be used. Furthermore, the structural unit represented by the following formula (5) is the case where Z is an oxygen atom, s is 0, and t is 2 in the above formula (4). [化6]

(In formula (5), R ¹⁴¹ , R ¹⁴² , R ¹⁵¹ , and R ¹⁵² each independently represent a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms; Part of fluorine atoms can be substituted with halogen atoms other than fluorine atoms; part of fluorine atoms in perfluoroalkyl groups can be substituted with halogen atoms other than fluorine atoms; part of fluorine atoms in perfluoroalkoxy groups can be substituted (Halogen atom other than fluorine atom)

As specific examples of the fluorine-containing compound (D), for example, the following compounds can be cited. CF ₂ =CFOCF ₂ CF=CF ₂ CF ₂ =CFOCF(CF ₃ )CF=CF ₂ CF ₂ =CFOCF ₂ CF ₂ CF=CF ₂ CF ₂ =CFOCF ₂ CF(CF ₃ )CF=CF ₂ CF ₂ =CFOCF (CF ₃ )CF ₂ CF=CF ₂ CF ₂ =CFOCFClCF ₂ CF=CF ₂ CF ₂ =CFOCCl ₂ CF ₂ CF=CF ₂ CF ₂ =CFOCF ₂ OCF=CF ₂ CF ₂ =CFOC(CF ₃ ) ₂ OCF= CF ₂ CF ₂ =CFOCF ₂ CF(OCF ₃ )CF=CF ₂ CF ₂ =CFCF ₂ CF=CF ₂ CF ₂ =CFCF ₂ CF ₂ CF=CF ₂ CF ₂ =CFCF ₂ OCF ₂ CF=CF ₂ CF ₂ = CFOCF ₂ CFClCF=CF ₂ CF ₂ =CFOCF ₂ CF ₂ CCl=CF ₂ CF ₂ =CFOCF ₂ CF ₂ CF=CFCl CF ₂ =CFOCF ₂ CF(CF ₃ )CCl=CF ₂ CF ₂ =CFOCF ₂ OCF=CF ₂ CF ₂ =CFOCCl ₂ OCF=CF ₂ CF ₂ =CClOCF ₂ OCCl=CF ₂

The fluorine-containing resin used in this embodiment is obtained by combining the fluorine-containing compound (A) with other fluorine-containing compounds other than the fluorine-containing compound (A) (for example, selected from the above-mentioned fluorine-containing compounds (B) to (D) ) In the case of a fluorine-containing copolymer obtained by copolymerization, in the fluorine-containing copolymer, the content of the structural unit (A) based on the fluorine-containing compound (A) is relative to the fluorine-containing copolymer (A) The total of all structural units in the copolymer is preferably 20 mol% or more, more preferably 40 mol% or more. By including the structural unit (A) at 20 mol% or more, the fluorinated copolymer can have higher heat resistance. By containing more than 40 mole% of the structural unit (A), the fluorinated copolymer can have higher heat resistance, higher transparency, and higher mechanical strength.

Furthermore, the fluorine-containing resin can be produced, for example, by using the fluorine-containing compound exemplified above as a monomer, and polymerizing the monomer by a known method using, for example, a known polymerization initiator. As the polymerization method, a known polymerization method can be used. For example, the fluorine-containing compound exemplified above can be subjected to radical polymerization according to conventional practice to produce a fluorine-containing resin. A perfluorinated fluorinated compound as a fluorinated compound is used as a monomer, and a polymerization initiator containing the perfluorinated compound is further used to produce a perfluorinated fluorinated resin.

In addition, when the fluorine-containing resin used in this embodiment is a polymer having a fluorine-containing aliphatic ring structure as described above, the polymer at the beginning of the polymerization may have an unstable functional group at the end. Therefore, in this case, it is preferable to perform terminal stabilization treatment for fluorinating the polymer with fluorine after the polymer is produced.

In addition to the above-mentioned resins, the core material may appropriately contain other components such as a refractive index modifier for increasing the refractive index.

When the POF of this embodiment is of a refractive index distribution type, for example, the core has a refractive index distribution in which the refractive index changes in the radial direction. Such a refractive index distribution can be formed, for example, by adding a refractive index adjusting agent to the fluorine-containing resin to diffuse (for example, thermally diffuse) the refractive index adjusting agent in the optical resin molded body.

The refractive index of the core only needs to be higher than the refractive index of the cladding, so it is not particularly limited. In order to achieve a higher numerical aperture in POF, it is preferable that the difference between the refractive index of the core and the refractive index of the cladding is larger. For example, the refractive index of the core can be set to 1.340 or more, preferably 1.360 or more. The upper limit of the refractive index of the core is not particularly limited, and is, for example, 1.4000 or less.

(wrapping) In this embodiment, at least a part of the clad layer contains a resin having a porous structure. The entire cladding layer may include a resin having a porous structure. In this way, since the cladding layer includes a porous structure, the refractive index of the cladding layer is lower than the refractive index of the resin itself used as the material of the cladding layer. Therefore, even when it is difficult to reduce the refractive index of the cladding by developing the resin itself, it is possible to lower the refractive index of the cladding. Thereby, since the difference between the refractive index of the core and the refractive index of the cladding can be made larger, a higher numerical aperture can be realized in the POF. As a result, a POF can be realized, which can reduce bending loss, improve the confinement effect of light in the core, and achieve lower transmission loss.

In the cladding layer, the refractive index of the portion including the resin having a porous structure is not particularly limited, and for example, it can be set to 1.310 or less, preferably 1.300 or less. The lower limit of the refractive index of the part including the resin having the porous structure is not particularly limited, and is, for example, 1.285 or more.

In the case where the cladding layer is composed of a single layer, for example, as shown in FIG. 1, the part having a porous structure in the cladding layer 12 is preferably a part located on the outer periphery. In order to reliably suppress the scattering of light leaking to the clad side, the inner peripheral portion, that is, the portion closer to the core 11, for example, the portion in contact with the core 11, preferably does not have a porous structure.

When the cladding layer is composed of a plurality of layers as shown in FIG. 2, for example, the second cladding layer 222 arranged on the outer peripheral side is more porous than the first cladding layer 221 arranged in contact with the core 11质结构。 Quality structure. In this case, in order that the light leaking from the core 11 to the first cladding layer 221 is completely reflected by the second cladding layer 222 and enclosed in the cladding layer 22, it is preferable that the second cladding layer 222 has Lower than the refractive index of the first cladding layer 221. For example, the first cladding layer 221 preferably has a refractive index in the range of 1.300 to 1.322. For example, the second cladding layer 222 preferably has a lower refractive index than the first cladding layer 221 and within a range of 1.290 to 1.300.

Furthermore, as described above, the clad layer 22 may have three or more clad layers. In this case, the second cladding layer 222 can be arranged at any position other than the innermost peripheral side of the cladding 22, but in order to further reduce the possibility of light scattering, it is preferably arranged on the outer peripheral side. The location. When the cladding 22 has three or more cladding layers, in order to securely confine the light leaking to the cladding 22 in the cladding 22, it is preferable to arrange the cladding 22 on the innermost peripheral side. The first cladding layer 221 has the highest refractive index, and the more the cladding layer is arranged on the outer peripheral side, the lower the refractive index. The coating layer having a porous structure can also design the refractive index by appropriately adjusting the pore conditions such as the pore size and porosity so that the refractive index falls within the required range.

The first coating layer 221 in contact with the core 11 may have a porous structure, but preferably does not have a porous structure. The reason is that when the first cladding layer 221 has a porous structure, light leaking to the cladding layer and incident to the first cladding layer 221 may be scattered. Therefore, in order to suppress loss due to light scattering, it is preferable that the first coating layer 221 does not have a porous structure.

The resin used as the material of the cladding layer is preferably a resin having a refractive index below the refractive index of the resin used as the material of the core. As the resin used for the material of the cladding layer, for example, acrylic resins such as fluorine-containing resins and methyl methacrylate, styrene resins, and carbonate resins can be cited. In order to prevent peeling at the interface between the clad and the core, the resin used as the material of the clad is preferably the same type as the resin used as the material of the core. For example, when a fluorine-containing resin is used as the material of the core, it is preferable that the resin used as the material of the cladding layer is also the same fluorine-containing resin. In addition, when the clad layer is composed of multiple layers as shown in FIG. 2, in order to prevent peeling between the layers, it is preferable that the resin used as the material of each clad layer is the same type of resin.

As described above, at least a part of the clad layer has a porous structure. In order to suppress light scattering, the pore size of the pores contained in the porous structure is preferably in the range of 10 nm to 200 nm, more preferably in the range of 10 nm to 150 nm, and more preferably in the range of 50 nm to 120 nm. Within range. Here, the pore diameter of the pores contained in the porous structure can be determined by measuring the maximum diameter of each pore using a transmission electron microscope (TEM) image.

The porous structure can also be realized by pores formed in the resin, or can be realized by making the resin contain hollow particles. From the viewpoint of easily controlling the size of the pores of the porous structure within a desired range, the porous structure is preferably formed by mixing hollow particles in a resin.

The hollow particles mixed in the resin preferably contain an inorganic compound. As the hollow particles, for example, hollow silica particles can be used. The hollow particles may be a mixture of hollow silica particles and other hollow particles, or may be composed of hollow silica particles only.

In the case where the cladding layer is formed by mixing hollow particles in the resin, it is preferable not to make the hollow particles become foreign matter in the cladding layer that increases transmission loss. Therefore, the diameter of the hollow particles is preferably in the range of 10 nm to 200 nm, and more preferably in the range of 50 nm to 120 nm. Here, the particle size of the hollow particles in the resin can be obtained by measuring the particle size of the hollow particles using a TEM image. In addition, in the resin having a porous structure, it is preferable to include hollow particles in the range of 10% by mass to 30% by mass, more preferably to include hollow particles in the range of 10% to 25% by mass, and more preferably The hollow particles are contained within the range of 15-25% by mass. The content of hollow particles in the cladding layer can be calculated from the ratio of the area of the cladding resin portion to the area of the hollow particle portion using a TEM image.

In the case where the pores of the porous structure are formed by hollow particles, the resin having the porous structure can be produced, for example, by mixing and dispersing the hollow particles in the resin as the base material. At this time, the hollow particles are preferably uniformly dispersed in the resin that becomes the base material, and preferably dispersed in the state of primary particles without forming aggregates (ie, secondary particles). In order to achieve such good dispersibility, it is preferable to perform surface treatment such as hydrophobic treatment on the hollow particles.

(Coating layer) As mentioned above, the coating layer is provided in order to improve the mechanical strength of the POF. As the coating layer, for example, the materials used as the coating layer in the well-known POF (for example, polycarbonate, etc.), various engineering plastics, cycloolefin polymers, PTFE (Polytetrafluoroethylene, polytetrafluoroethylene), modified PTFE, PFA ( Perfluoroalkoxy alkane, perfluoroalkoxy alkane) and its composition.

(Manufacturing method of POF) The POF of this embodiment can be manufactured by a known method of manufacturing POF. That is, the POF of the present embodiment can be manufactured by a method including: preparing the core and cladding resin materials used, and forming the POF using the resin materials. As a method of forming POF, for example, a melt spinning method can be used. The forming of the POF by the melt spinning method can be performed by, for example, melting the resin material for the core, the resin material for the cladding layer, and the resin material for the coating layer as necessary to perform composite spinning. wire.

When the porous structure of the cladding layer is formed by hollow particles, for example, a resin material for the cladding layer is prepared by mixing hollow particles with a resin as a base material. When the porous structure of the cladding layer is realized by the pores formed in the resin, the following method can be used. For example, the foaming agent is dispersed in the resin material in advance, and the foaming agent is heated during POF molding. Decompose, thereby generating bubbles. [Example]

(Example) For polyperfluoro-4-methyl 1,3-dioxolane, which is a fluororesin, add hollow nanosilica to 20% by mass, and use a biaxial kneading extruder to make it Evenly dispersed (mixture a).

For polyperfluoro-4-methyl 1,3-dioxolane, which is a fluororesin, melt and mix 2,4,6-triphenyltriphenyl as a refractive index adjuster so that it becomes 5 mass% (Mixture b).

Use mixture b as the core, use fluororesin polyperfluoro-4-methyl 1,3-dioxolane as the first coating layer, use the kneaded compound a as the second coating layer, and use polycarbonate The ester is used as a coating layer, and a multi-layer melt extrusion process is used to form four concentric fibers including a core, a first cladding layer, a second cladding layer, and a coating layer.

By the above method, the POF of the embodiment having the same configuration as that shown in FIG. 3 was manufactured. In the POF of the embodiment, the diameter of the core is 50 μm, the thickness of the first cladding layer is 70 μm, the thickness of the second cladding layer is 5 μm, and the thickness of the coating layer is 250 μm.

The evaluation of the POF of the embodiment can be performed by measuring the transmission loss after bending. The measurement of transmission loss is based on JIS C6823:2010. The measurement wavelength is 850 nm. The bending of the POF is performed by performing a 180-degree bending (U-shaped bending) with a bending radius of 2.5 mm. The transmission loss of the POF of the embodiment is 0.5 dB/km or less.

(Comparative example) The second coating layer was not formed. Except for this, the POF of the comparative example was produced under the same conditions as the POF of the example. Furthermore, the POF of the comparative example was also evaluated by the same method as the POF of the example. The transmission loss of the POF of the comparative example is more than 5 dB.

According to the results of the above examples and comparative examples, it can be confirmed that a POF with a cladding layer including a porous structure can achieve lower transmission loss. [Industrial availability]

The POF of the present invention can realize lower transmission loss and is suitable for high-speed communication purposes.

10:POF 11: fiber core 12: Cladding 20:POF 22: Cladding 30:POF 31: Coating layer 221: first coating 222: 2nd cladding layer

Fig. 1 is a schematic diagram showing an example of the cross-sectional structure of the plastic optical fiber of the present invention. Fig. 2 is a schematic diagram showing another example of the cross-sectional structure of the plastic optical fiber of the present invention. Fig. 3 is a schematic diagram showing another example of the cross-sectional structure of the plastic optical fiber of the present invention.

10:POF

11: fiber core

12: Cladding

Claims (9)

A plastic optical fiber, which is provided with a core and a cladding arranged on the outer periphery of the core, and At least a part of the cladding layer includes a resin having a porous structure. Such as the plastic optical fiber of claim 1, where The pore diameter of the pores contained in the above-mentioned porous structure is in the range of 10 nm to 200 nm. Such as the plastic optical fiber of claim 1, where The cladding layer includes a first cladding layer and a second cladding layer, The first cladding layer is arranged in contact with the core, and The second coating layer is arranged on the outer peripheral side than the first coating layer, and includes the resin having the porous structure. Such as the plastic optical fiber of claim 1, where The above resin contains hollow particles, and The porous structure is formed by the hollow particles. Such as the plastic optical fiber of claim 4, where The above-mentioned hollow particles contain an inorganic compound. Such as the plastic optical fiber of claim 4, where The above-mentioned hollow particles include hollow silica particles. Such as the plastic optical fiber of claim 4, where The diameter of the hollow particles is within the range of 50 nm or more and 120 nm or less. Such as the plastic optical fiber of claim 4, where The said resin contains the said hollow particle in the range of 10 mass% or more and 25 mass% or less. Such as the plastic optical fiber of claim 1, its It further includes a coating layer disposed on the outer periphery of the cladding layer.

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