Optical fiber

Abstract

To provide an optical fiber capable of reducing return light with a simple configuration.SOLUTION: The optical fiber 10 of the present disclosure includes a core 11 that is an optical transmission region. The core 11 includes at least one scattering source selected from the group consisting of particles and bubbles. When the optical fiber 10 is a glass optical fiber, the following (Ia) or (IIa) is satisfied, and when the optical fiber 10 is a plastic optical fiber, a specific condition is satisfied. (Ia) The refractive indices of the scattering sources at the wavelengths 850nm are 1.2 or more and 1.8 or less, the diameters of the scattering sources are more than 0.5 μm and 1.5 μm or less, and the total number of the scattering sources in the core is 396 or more and 1473 or less. (IIa) The refractive indices of the scattering sources at the wavelengths 850nm are less than 1.2 or more than 1.8, the diameters of the scattering sources are 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 149 or more and 491 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to optical fibers. [Background technology]

[0002] As the volume of communication over networks increases, communication methods are shifting from conventional binary signals (e.g., NRZ (Non Return to Zero)) to multilevel pulse amplitude modulation (PAM-X, where X = 3, 4, 6, 8, etc.). The use of multilevel amplitude modulation narrows the potential difference between each value, making the effects of amplitude noise a problem. In VCSELs (Vertical Cavity Surface Emitting Lasers), which are used as light sources for optical communications, emitted light is reflected off the end face of an optical fiber or the surface of a photodetector, and re-enters the VCSEL as returned light. It is known that this returned light generates noise.

[0003] Methods for reducing noise caused by optical feedback include intentionally misaligning the VCSEL, the optical components for coupling the light emitted from the VCSEL to the optical fiber, and the optical fiber, cutting the end face of the optical fiber at an angle, using an optical isolator, etc. Also under consideration is the reduction of noise caused by optical feedback using an optical transmission system that uses a photoreceiver equipped with a device for correcting the signal, as disclosed in Patent Document 1, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-151516 Summary of the Invention [Problem to be solved by the invention]

[0005] When using an optical isolator, it is necessary to properly position an optical crystal and a polarizer to rotate the polarization plane, which makes it unsuitable for communication transceivers that require compactness and increases costs.Methods that intentionally shift the alignment of the optical fiber, i.e., shifting the optical axis, can increase coupling loss and stray light, and also require strict positional accuracy between the light source and the optical fiber when mounting them.When correcting the signal, it is necessary to install a signal correction device in the optical receiver, which increases the size of the system due to the additional components.

[0006] The present disclosure has been made in view of the above, and aims to provide an optical fiber that can reduce return light with a simple configuration and can relax the positional accuracy required during installation. It is also an object of the present disclosure to provide an optical cord and an active optical cable including an optical fiber that can reduce return light with a simple configuration and can relax the positional accuracy required during installation. [Means for solving the problem]

[0007] The optical fiber according to the first aspect of the present disclosure is an optical fiber having a core which is an optical transmission region, the core comprises at least one scattering source selected from the group consisting of particles and bubbles; When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Ia) or (IIa): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IIIa), (IVa), or (Va): Optical fiber. (Ia) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 0.5 μm and less than 1.5 μm, and the total number of the scattering sources in the core is 396 or more and 1473 or less. (IIa) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 149 or more and 491 or less. (IIIa) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 149 or more and 982 or less. (IVa) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 4 μm and less than 8 μm, and the total number of the scattering sources in the core is 5 or more and 149 or less. (Va) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 10 μm or less, and the total number of the scattering sources in the core is greater than 248 and 1473 or less.

[0008] An optical cord according to a second aspect of the present disclosure includes the optical fiber according to the first aspect of the present disclosure.

[0009] An active optical cable according to a third aspect of the present disclosure includes: an optical code according to a second aspect of the present disclosure; an optoelectronic hybrid module; Equipped with. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide an optical fiber that can reduce return light with a simple configuration and can relax the positional accuracy required during installation. Furthermore, the present disclosure can provide an optical cord and an active optical cable including an optical fiber that can reduce return light with a simple configuration and can relax the positional accuracy required during installation. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a schematic diagram illustrating an example of a cross-sectional structure of an optical fiber according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a graph illustrating an example of a refractive index profile of a core of an optical fiber according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic diagram showing a modified example of the cross-sectional structure of the optical fiber according to the embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of a manufacturing apparatus that can be used to manufacture the optical fiber shown in FIG. [Figure 5] FIG. 5 is a schematic diagram illustrating an example of an optical cord including an optical fiber according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a schematic diagram illustrating an example of an active optical cable including an optical fiber according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Knowledge that forms the basis of this disclosure> As described in the [Background Art] section, returned light refers to light that is emitted from a light source, reflected by an end face of an optical fiber or the surface of a light-receiving element, and then returns to the light source. As a result of studying ways to reduce this returned light, the inventors found that, of the light reflected by the end face of an optical fiber or the surface of a light-receiving element, only the light corresponding to the spot size and divergence angle of the light emitted from the light source returns to the light source.

[0013] The optical fiber has a first end into which light emitted from a light source enters and a second end from which light that has passed through the optical fiber exits. In the optical fiber, the end from which reflected light that becomes returned light exits is the first end into which the light emitted from the light source enters. That is, as a result of extensive research, the inventors have found that, in order to reduce returned light, it is important to expand the beam width (i.e., beam diameter) of the reflected light that exits from the first end of the optical fiber toward the light source, and specifically, that the light that enters the light source as returned light can be reduced by expanding the beam width of the reflected light that exits from the first end of the optical fiber toward the light source more than the beam width of the incident light that enters the first end of the optical fiber from the light source.

[0014] Furthermore, the inventors have found that even if the beam width of reflected light emitted from the first end of the optical fiber toward the light source can be made wider than the beam width of incident light from the light source to the first end of the optical fiber, even a slight misalignment between the light source and the optical fiber when mounting the light source and the optical fiber may prevent the reduction of returned light. In such cases, strict positional accuracy between the light source and the optical fiber is required when mounting the light source and the optical fiber. If strict positional accuracy cannot be achieved, the returned light cannot be reduced. Therefore, the inventors have conducted further intensive research to obtain an optical fiber that can reduce returned light even when the positional accuracy during mounting is not so strict. As a result, they have found an optical fiber configuration that can reduce returned light even when the positional accuracy during mounting is not so strict, and have arrived at the optical fiber of the present disclosure.

[0015] <Embodiments of the present disclosure> (optical fiber) FIG. 1 is a schematic diagram illustrating an example of a cross-sectional structure of an optical fiber according to an embodiment of the present disclosure.

[0016] The optical fiber 10 according to this embodiment includes a core 11, which is a light transmitting portion. The optical fiber 10 according to this embodiment may further include a cladding 12 disposed around the core 11. The cladding 12 has the function of confining light that enters the core 11 within the core 11.

[0017] The optical fiber 10 according to this embodiment may be a glass optical fiber in which the core 11 is made of a glass material, or may be a plastic optical fiber in which the core is made of a plastic material.

[0018] The core 11 includes at least one scattering source selected from the group consisting of particles and bubbles. When the optical fiber 10 is a glass optical fiber, the optical fiber 10 satisfies the following (Ia) or (IIa). When the optical fiber 10 is a plastic optical fiber, the optical fiber 10 satisfies the following (IIIa), (IVa), or (Va).

[0019] (Ia) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 0.5 μm and 1.5 μm or less, and the total number of scattering sources in the core 11 is 396 or more and 1473 or less. (IIa) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or more than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of scattering sources in the core 11 is 149 or more and 491 or less. (IIIa) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of scattering sources in the core 11 is 149 or more and 982 or less. (IVa) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of scattering sources in the core 11 is 5 or more and 149 or less. (Va) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 10 μm or less, and the total number of scattering sources in the core 11 is greater than 248 and 1473 or less.

[0020] In this specification, the diameter of the scattering source and the particle diameter of the scattering source refer to the radius of the scattering source.

[0021] Under the above-described conditions, the optical fiber 10 according to this embodiment can widen the beam width of the reflected light at the first end face of the optical fiber 10, which emits reflected light from the optical fiber 10 toward the light source, by the scattering source contained in the core 11, to be greater than the beam width of the incident light incident from the light source to the first end of the optical fiber. This allows the optical fiber 10 according to this embodiment to reduce the amount of return light that returns to and enters the light source. Note that the first end of the optical fiber 10 is the end of the optical fiber 10 onto which the light emitted from the light source is incident, and the first end face refers to the incident surface of the optical fiber 10 onto which the light emitted from the light source is incident. The optical fiber 10 according to this embodiment can make the beam width (beam diameter) of the reflected light at the first end face, for example, five times or more, and even seven times or more, the beam width of the incident light incident from the light source to the first end of the optical fiber.

[0022] Furthermore, since the optical fiber 10 according to this embodiment includes a scattering source in the core 11 under the above-described conditions, even if the position of the optical fiber 10 is slightly misaligned with respect to the light source, the beam width of the reflected light at the first end face of the optical fiber 10 can be maintained, thereby reducing the amount of light returning to the light source. Therefore, the optical fiber 10 according to this embodiment can reduce the amount of light returning while relaxing the requirement for positional accuracy with respect to the light source during assembly. Note that in this specification, the misalignment of the optical fiber 10 with respect to the light source refers to the distance between the center of the light emitted from the light source and incident on the first end face of the optical fiber 10 (i.e., the center position of the beam diameter of the incident light at the first end face of the optical fiber 10) and the center of the core 11 at the first end face of the optical fiber 10.

[0023] When the optical fiber 10 according to this embodiment is a glass optical fiber, it is preferable that the optical fiber 10 satisfies the following (Ib) or (IIb), and when the optical fiber 10 according to this embodiment is a plastic optical fiber, it is preferable that the optical fiber 10 satisfies the following (IIIb), (IVb), or (Vb).

[0024] (Ib) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 0.5 μm and 1.5 μm or less, and the total number of scattering sources in the core 11 is 747 or more and 1228 or less. (IIb) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or more than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of scattering sources in the core 11 is 149 or more and 347 or less. (IIIb) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of scattering sources in the core 11 is 347 or more and 982 or less. (IVb) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of scattering sources in the core 11 is 75 or more and 149 or less. (Vb) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or more than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of scattering sources in the core 11 is 347 or more and 982 or less.

[0025] When the optical fiber 10 according to this embodiment satisfies the above (Ib), (IIb), (IIIb), (IVb), or (Vb), it is possible to further reduce the effect of misalignment of the optical fiber 10 with respect to the light source on the expansion of the beam width of the reflected light at the first end face of the optical fiber 10. Therefore, it is possible to achieve the expansion of the beam width of the reflected light at the first end face of the optical fiber 10 regardless of the misalignment of the optical fiber 10 with respect to the light source. In other words, it is possible to relax the positional accuracy required during mounting and stably reduce the return light to the light source.

[0026] When the optical fiber 10 according to this embodiment is a glass optical fiber, it is more preferable that the optical fiber 10 satisfies the following (Ic), and when the optical fiber 10 according to this embodiment is a plastic optical fiber, it is more preferable that the optical fiber 10 satisfies the following (IIIc), (IVc), or (Vc).

[0027] (Ic) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 0.5 μm and 1.5 μm or less, and the total number of scattering sources in the core 11 is 834 or more and 1129 or less. (IIIc) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of scattering sources in the core 11 is 347 or more and 982 or less. (IVc) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of scattering sources in the core 11 is 75 or more and 149 or less. (Vc) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or more than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of scattering sources in the core 11 is 347 or more and 982 or less.

[0028] When the optical fiber 10 according to this embodiment satisfies the above (Ic), (IIIc), (IVc), or (Vc), it is possible to further reduce the influence of misalignment of the optical fiber 10 with respect to the light source on the expansion of the beam width of the reflected light at the first end face of the optical fiber 10. Therefore, it is possible to more reliably achieve the expansion of the beam width of the reflected light at the first end face of the optical fiber 10, regardless of the misalignment of the optical fiber 10 with respect to the light source. In other words, it is possible to relax the positional accuracy required during mounting and more stably reduce the return light to the light source.

[0029] When the optical fiber 10 according to this embodiment is a glass optical fiber, it is more preferable that the optical fiber 10 satisfies the following (Id), and when the optical fiber 10 according to this embodiment is a plastic optical fiber, it is more preferable that the optical fiber 10 satisfies the following (IIId), (IVd), or (Vd).

[0030] (Id) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 0.5 μm and 1.5 μm or less, and the total number of scattering sources in the core 11 is 883 or more and 1080 or less. (IIId) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of scattering sources in the core 11 is 347 or more and 982 or less. (IVd) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of scattering sources in the core 11 is 75 or more and 149 or less. (Vd) The refractive index of the scattering source at a wavelength of 850 nm is greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of scattering sources in the core 11 is 347 or more and 982 or less.

[0031] When the optical fiber 10 according to this embodiment satisfies the above (Id), (IIId), (IVd), or (Vd), it is possible to further reduce the effect of misalignment of the optical fiber 10 with respect to the light source on the expansion of the beam width of the reflected light at the first end face of the optical fiber 10. Therefore, it is possible to more reliably achieve the expansion of the beam width of the reflected light at the first end face of the optical fiber 10, regardless of the misalignment of the optical fiber 10 with respect to the light source. In other words, it is possible to relax the positional accuracy required during mounting and more stably reduce the return light to the light source.

[0032] When the optical fiber 10 according to this embodiment is a glass optical fiber, it is particularly preferable that the optical fiber 10 satisfies the following (Ie), and when the optical fiber 10 according to this embodiment is a plastic optical fiber, it is particularly preferable that the optical fiber 10 satisfies the following (IVe).

[0033] (Ie) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 0.5 μm and 1.5 μm or less, and the total number of scattering sources in the core 11 is 933 or more and 1031 or less. (IVe) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of scattering sources in the core 11 is 75 or more and 149 or less.

[0034] When the optical fiber 10 according to this embodiment satisfies the above (Ie) or (IVe), it is possible to further reduce the effect of misalignment of the optical fiber 10 with respect to the light source on the expansion of the beam width of the reflected light at the first end face of the optical fiber 10. Therefore, it is possible to more reliably achieve the expansion of the beam width of the reflected light at the first end face of the optical fiber 10, regardless of the misalignment of the optical fiber 10 with respect to the light source. In other words, it is possible to relax the positional accuracy required during mounting and more stably reduce the return light to the light source.

[0035] Here, in this specification, the beam width of the reflected light at the first end face of the optical fiber 10 is specified by D4σ, which is calculated from the light intensity distribution (NFP image) measured by the NFP (Near Field Pattern) method. The D4σ width of the beam in the horizontal direction (x direction) or vertical direction (y direction) is four times the standard deviation σ of the light intensity distribution in the horizontal or vertical direction. The D4σ beam width in the x direction of the beam profile is expressed by the following formula (I):

number

[0036] In the above formula (I),

number

[0037] The D4σ beam width in the y direction can be calculated in the same way as the D4σ beam width in the x direction.

[0038] The scattering source having a refractive index of 1.2 or more and 1.8 or less at a wavelength of 850 nm may be, for example, at least one selected from the group consisting of GeO2, Al2O3, SiO2, MgF2, polystyrene, polymethyl methacrylate, poly(styrene-butadiene) copolymer, and polyphenylene sulfide, or at least one selected from the group consisting of GeO2, Al2O3, SiO2, and polystyrene. By using these materials as the scattering source, the beam width of the reflected light at the first end face of the optical fiber 10 can be more reliably widened, and as a result, the return light to the light source can be further reduced.

[0039] The scattering source having a refractive index greater than 1.8 at a wavelength of 850 nm may be, for example, at least one selected from the group consisting of TiO2, ZrO2, ZnO, and SrTiO3, or may be TiO2. By using these materials as the scattering source, the beam width of the reflected light at the first end face of the optical fiber 10 can be more reliably widened, and as a result, the return light to the light source can be further reduced.

[0040] In the optical fiber 10 according to this embodiment, the core 11 may have a refractive index profile. For example, the core 11 has the maximum refractive index in the central region of the core 11, and has a refractive index profile between the center 11a of the core 11 and the outer edge 11b of the core 11.

[0041] Fig. 2 is a graph showing an example of the refractive index profile of the core 11 of the optical fiber 10 according to this embodiment. The refractive index profile of the core 11 may have, for example, a parabolic profile with the refractive index n0 at the center 11a of the core 11 as a maximum value, as shown in Fig. 2. In this case, the refractive index decreases parabolically in the direction from the center 11a of the core 11 to the outer edge 11b of the core 11. When the refractive index profile of the core 11 has such a parabolic profile, the optical fiber 10 can reduce returned light and also achieve a good bandwidth.

[0042] Each component of the optical fiber 10 will be described in more detail below, taking as an example a case where the optical fiber 10 is a plastic optical fiber.

[0043] (Core 11) The core 11 is a region that transmits light. The core 11 is made of a material that has a higher refractive index than the cladding 12. With this configuration, light that enters the core 11 is confined within the core 11 by the cladding 12 and propagates through the optical fiber 10.

[0044] Core 11 includes, for example, a first resin. Core 11 may include the first resin as a main component. Here, "core 11 includes the first resin as a main component" means that the component contained in core 11 in the largest amount by mass is the first resin. Core 11 may include 75% by mass or more, 80% by mass or more, or 85% by mass or more of the first resin.

[0045] The core 11 further includes at least one scattering source selected from the group consisting of particles and bubbles. Examples of particles that can be used as scattering sources are as described above. The refractive index, diameter, and total number of scattering sources included in the core 11 are also as described above.

[0046] The core 11 may further contain an additive in addition to the first resin and the scattering source. The additive is, for example, a refractive index adjuster. That is, the core 11 may be formed from a resin composition containing the first resin, the scattering source, and an additive such as a refractive index adjuster. As the refractive index adjuster, for example, a known refractive index adjuster used in the material of the core 11 of the optical fiber 10 may be used. The material of the core 11 may contain an additive other than the refractive index adjuster.

[0047] The first resin contained in the core 11 is not particularly limited as long as it is a resin having high transparency. Examples of the first resin include fluorine-containing resins, acrylic resins such as methyl methacrylate, styrene-based resins, and carbonate-based resins.

[0048] The first resin contained in the core 11 may be at least one selected from the group consisting of a fully fluorinated resin, a partially fluorinated resin, a partially chlorinated resin, and a partially deuterated resin. The terms partially fluorinated resin, partially chlorinated resin, and partially deuterated resin refer to resins known in the art as core materials in which some of the hydrogen atoms in C-H bonds have been substituted with fluorine, chlorine, and deuterium, respectively. The term fully fluorinated resin refers to resins known in the art as core materials in which all of the hydrogen atoms in C-H bonds have been substituted with fluorine. Examples of resins known in the art as core materials include acrylic resins such as methyl methacrylate, styrene-based resins, and carbonate-based resins, as described above. Polymers having an alicyclic structure, such as a polymer having a dioxolane structure, may also be used.

[0049] The first resin is preferably at least one selected from the group consisting of fully fluorinated resins and partially fluorinated resins, that is, the first resin is preferably a fluorine-containing resin.

[0050] The first resin of core 11 is preferably a fluororesin containing a fluoropolymer. Hereinafter, the fluororesin contained in core 11 will be referred to as the first fluororesin, and the fluoropolymer contained in the first fluororesin will be referred to as the first fluoropolymer.

[0051] From the viewpoint of suppressing light absorption due to the stretching energy of C-H bonds, the first fluorine-containing polymer contained in the first fluorine-containing resin preferably contains substantially no hydrogen atoms, and particularly preferably has all hydrogen atoms bonded to carbon atoms substituted with fluorine atoms. That is, the first fluorine-containing polymer preferably contains substantially no hydrogen atoms and is perfluorinated. In this specification, "the fluorine-containing polymer contains substantially no hydrogen atoms" means that the content of hydrogen atoms in the fluorine-containing polymer is 1 mol% or less.

[0052] The first fluorine-containing polymer preferably has a fluorine-containing alicyclic structure. The fluorine-containing alicyclic structure may be contained in the main chain of the fluorine-containing polymer or in a side chain of the first fluorine-containing polymer. The first fluorine-containing polymer has, for example, a structural unit (A) represented by the following formula (1): [ka]

[0053] In formula (1), R ff 1 ~R ff 4 R each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 7 carbon atoms, or a perfluoroalkyl ether group having 1 to 7 carbon atoms. ff 1 and R ff 2 may be linked to form a ring. "Perfluoro" means that all hydrogen atoms bonded to a carbon atom are replaced with fluorine atoms.

[0054] In formula (1), the number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1. The perfluoroalkyl group may be linear or branched. Examples of the perfluoroalkyl group include a trifluoromethyl group, a pentafluoroethyl group, and a heptafluoropropyl group.

[0055] In formula (1), the number of carbon atoms in the perfluoroalkyl ether group is preferably 1 to 5, and more preferably 1 to 3. The perfluoroalkyl ether group may be linear or branched. Examples of the perfluoroalkyl ether group include a perfluoromethoxymethyl group.

[0056] R ff 1 and R ff 2 When these are linked to form a ring, the ring may be a 5-membered ring or a 6-membered ring. Examples of this ring include a perfluorotetrahydrofuran ring, a perfluorocyclopentane ring, and a perfluorocyclohexane ring.

[0057] Specific examples of the structural unit (A) include structural units represented by the following formulas (A1) to (A8). [ka]

[0058] Of the structural units represented by the above formulas (A1) to (A8), the structural unit (A) is preferably the structural unit (A2), ie, the structural unit represented by the following formula (2). [ka]

[0059] The first fluorine-containing polymer may contain one or more types of structural unit (A). In the first fluorine-containing polymer, the content of the structural unit (A) is preferably 20 mol % or more, more preferably 40 mol % or more, based on the total of all structural units. When the structural unit (A) is contained in an amount of 20 mol % or more, the first fluorine-containing polymer tends to have higher heat resistance. When the structural unit (A) is contained in an amount of 40 mol % or more, the first fluorine-containing polymer tends to have higher transparency and high mechanical strength in addition to high heat resistance. In the first fluorine-containing polymer, the content of the structural unit (A) is preferably 95 mol % or less, more preferably 70 mol % or less, based on the total of all structural units.

[0060] The structural unit (A) is derived from, for example, a compound represented by the following formula (3): ff 1 ~R ff 4 is the same as formula (1). The compound represented by formula (3) can be obtained by a known production method, such as the production method disclosed in JP-A-2007-504125. [ka]

[0061] Specific examples of the compound represented by the above formula (3) include compounds represented by the following formulae (M1) to (M8). [ka]

[0062] The fluorine-containing polymer may further contain other structural units in addition to the structural unit (A). Examples of the other structural units include the following structural units (B) to (D).

[0063] The structural unit (B) is represented by the following formula (4). [ka]

[0064] In formula (4), R 1 ~R 3 R each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. 4 represents a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

[0065] The fluorine-containing polymer may contain one or more types of structural unit (B). In the fluorine-containing polymer, the content of the structural unit (B) is preferably 5 to 10 mol % based on the total of all structural units. The content of the structural unit (B) may be 9 mol % or less, or may be 8 mol % or less.

[0066] The structural unit (B) is derived from, for example, a compound represented by the following formula (5): In formula (5), R 1 ~R 4 is the same as formula (4). The compound represented by formula (5) is a fluorine-containing vinyl ether such as perfluorovinyl ether. [ka]

[0067] The structural unit (C) is represented by the following formula (6). [ka]

[0068] In formula (6), R 5 ~R 8each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

[0069] The fluorine-containing polymer may contain one or more types of structural unit (C). In the fluorine-containing polymer, the content of the structural unit (C) is preferably 5 to 10 mol % based on the total of all structural units. The content of the structural unit (C) may be 9 mol % or less, or may be 8 mol % or less.

[0070] The structural unit (C) is derived from, for example, a compound represented by the following formula (7): 5 ~R 8 is the same as formula (6). The compound represented by formula (7) is a fluorine-containing olefin such as tetrafluoroethylene or chlorotrifluoroethylene. [ka]

[0071] The structural unit (D) is represented by the following formula (8). [ka]

[0072] In formula (8), Z is an oxygen atom, a single bond, or —OC(R 19 R 20 )O-, R 9 ~R 20each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkoxy group may be substituted with halogen atoms other than fluorine atoms. s and t each independently represent an integer of 0 to 5, and s+t is an integer of 1 to 6 (provided that Z is -OC(R 19 R 20 )O-, s+t may be 0).

[0073] The structural unit (D) is preferably represented by the following formula (9): The structural unit represented by the following formula (9) is the structural unit represented by the above formula (8) in which Z is an oxygen atom, s is 0, and t is 2. [ka]

[0074] In formula (9), R 141 , R 142 , R 151 , and R 152 each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkoxy group may be substituted with halogen atoms other than fluorine atoms.

[0075] The fluorine-containing polymer may contain one or more types of structural unit (D). In the fluorine-containing polymer, the content of the structural unit (D) is preferably 30 to 67 mol% based on the total of all structural units. The content of the structural unit (D) is, for example, 35 mol% or more, and may be 60 mol% or less, or may be 55 mol% or less.

[0076] The structural unit (D) is derived from a compound represented by the following formula (10): In formula (10), Z, R 9 ~R 18 , s and t are the same as in formula (8). The compound represented by formula (10) is a fluorine-containing compound which has two or more polymerizable double bonds and is capable of cyclopolymerization. [ka]

[0077] The structural unit (D) is preferably derived from a compound represented by the following formula (11): 141 , R 142 , R 151 , and R 152 is the same as equation (9). [ka]

[0078] Specific examples of the compound represented by formula (10) or formula (11) include the following compounds. CF2=CFOCF2CF=CF2 CF2=CFFOCF(CF3)CF=CF2 CF2=CFOCF2CF2CF=CF2 CF2=CFOCF2CF(CF3)CF=CF2 CF2=CFOCF(CF3)CF2CF=CF2 CF2=CFOCFClCF2CF=CF2 CF2=CFOCCl2CF2CF=CF2 CF2=CFOCF2OCF=CF2 CF2=CFOC(CF3)2OCF=CF2 CF2=CFOCF2CF(OCF3)CF=CF2 CF2=CFCF2CF=CF2 CF2=CFCF2CF2CF=CF2 CF2=CFCF2OCF2CF=CF2 CF2=CFOCF2CFClCF=CF2 CF2=CFOCF2CF2CCl=CF2 CF2=CFOCF2CF2CF=CFCl CF2=CFOCF2CF(CF3)CCl=CF2 CF2=CFOCF2OCF=CF2 CF2=CFOCCl2OCF=CF2 CF2=CClOCF2OCCl=CF2

[0079] The first fluorine-containing polymer may further contain other structural units than the structural units (A) to (D), but preferably does not substantially contain other structural units than the structural units (A) to (D). Here, "the fluorine-containing polymer does not substantially contain other structural units than the structural units (A) to (D)" means that the total of the structural units (A) to (D) is 95 mol % or more, preferably 98 mol % or more, of the total of all structural units in the fluorine-containing polymer.

[0080] The polymerization method for the first fluorine-containing polymer is not particularly limited, and for example, a general polymerization method such as radical polymerization can be used. The polymerization initiator for polymerizing the fluorine-containing polymer may be a perfluorinated compound.

[0081] The first fluorine-containing polymer constitutes a first fluorine-containing resin used as the first resin. The first resin has a first glass transition temperature of, for example, more than 105°C and not more than 140°C, and may be 120°C or higher.

[0082] The diameter (outer diameter) of the core is preferably 30 μm or more and 100 μm or less, and more preferably 40 μm or more and 70 μm or less.

[0083] (Clad 12) In the optical fiber 10 of this embodiment, the cladding 12 includes, for example, a second resin. The cladding 12 may include the second resin as a main component. Here, "the cladding 12 includes the second resin as a main component" means that the component that is contained in the cladding 12 in the largest amount by mass ratio is the second resin. The cladding 12 may include 80% by mass or more of the second resin, 90% by mass or more, or 95% by mass or more of the second resin. The cladding 12 may be composed only of the second resin. The cladding 12 may further include an additive in addition to the second resin.

[0084] The second resin contained in the clad 12 is not particularly limited as long as it is a resin having high transparency. Examples of the second resin are the same as those exemplified as the resin that can be used as the first resin. As with the first resin, a fluorine-containing resin is preferably used as the second resin.

[0085] The second resin of the clad 12 is preferably a fluororesin containing a fluoropolymer. Hereinafter, the fluororesin contained in the clad 12 will be referred to as the second fluororesin, and the fluoropolymer contained in the second fluororesin will be referred to as the second fluoropolymer.

[0086] As the second fluorine-containing resin, any of the fluorine-containing resins exemplified as the fluorine-containing resin that can be used as the first fluorine-containing resin can be used.

[0087] As the second fluorine-containing resin, a fluorine-containing resin containing a fluorine-containing polymer having an amorphous structure and further containing a constituent unit (E) represented by the following formula (12), and a fluorine-containing plasticizer may be used. [ka] (In formula (12), Z is an oxygen atom, a single bond, or —OC(R 31 R 32 )O-, R 21 ~R 32each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. "Perfluoro" means that all hydrogen atoms bonded to carbon atoms have been substituted with fluorine atoms. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkoxy group may be substituted with halogen atoms other than fluorine atoms. s and t each independently represent an integer of 0 to 5, and s+t is an integer of 1 to 6 (provided that Z is not -OC(R 31 R 32 ) In the case of O-, s+t may be 0. u and v are each independently 0 or 1.

[0088] The fluorine-containing polymer containing the structural unit (E) may further contain a structural unit (F) represented by the following formula (13). [ka] (In formula (13), R 33 ~R 36 each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

[0089] When the second fluorine-containing polymer is the above copolymer, the ratio of the structural unit (E) to the structural unit (F) is optional and is not particularly limited.

[0090] The second fluorine-containing polymer is preferably, for example, at least one selected from the group consisting of fluorine-containing polymer A and fluorine-containing polymer B shown below.

[0091] The fluorine-containing polymer A contains a structural unit (G) represented by the following formula (14) and a structural unit (H) represented by the following formula (15). 23 , R 24 , R 31 , and R 32 is the same as the above equation (12).

[0092] [ka] [ka] (In formula (15), R 37 ~R 40 each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 7 carbon atoms. The perfluoroalkyl group may have a ring structure. Some of the fluorine atoms may be substituted with halogen atoms other than fluorine atoms. Some of the fluorine atoms in the perfluoroalkyl group may be substituted with halogen atoms other than fluorine atoms.

[0093] The fluorine-containing polymer B contains a structural unit (I) represented by the following formula (16): 21 ~R 24 , R 27 ~R 30 , R 31 , and R 32 is the same as the above equation (12). [ka]

[0094] The above-mentioned fluorine-containing polymer A and fluorine-containing polymer B have very high transparency and can have a refractive index that is very low compared with the general refractive index of the first fluorine-containing resin used as the material for the core 11. Therefore, the second fluorine-containing resin containing at least one selected from the group consisting of fluorine-containing polymer A and fluorine-containing polymer B as the second fluorine-containing polymer can further reduce the refractive index while maintaining the high transparency of the cladding 12. As a result, the difference between the refractive index of the core 11 and the refractive index of the cladding 12 can be made even larger, which further improves the effect of confining light in the core 11 by the cladding 12 and makes it easier to achieve low transmission loss in the optical fiber 10.

[0095] The second fluorine-containing polymer preferably contains a structural unit (J) represented by the following formula (17). [ka] (In formula (17), m and n are any integers.)

[0096] The fluorine-containing plasticizer is preferably a fluorine-containing polyether, more preferably a perfluoropolyether.

[0097] Specific examples of perfluoropolyethers include organic compounds represented by the following formula (18) or (19): In the following formulas (18) and (19), p1, q1, p2, and q2 each represent an arbitrary integer. CF3-[(O(CF3)CFCF2) p1 -(OCF2) q1 ]OCF3(18) CF3-[(OCF2CF2) p2 -(OCF2) q2 ]OCF3(19)

[0098] The second fluorine-containing polymer constitutes a second fluorine-containing resin used as the second resin. The second glass transition temperature Tg2 of the second resin is not particularly limited and may be, for example, higher than 105°C and 170°C or lower, or 125°C or higher.

[0099] The outer diameter of the cladding 12 is preferably 40 μm or more and 120 μm or less, and more preferably 50 μm or more and 90 μm or less.

[0100] (Variation) FIG. 3 is a schematic diagram showing a modified cross-sectional structure of the optical fiber according to this embodiment. The optical fiber 20 shown in FIG. 3 has a configuration in which a coating layer 21 disposed on the outer periphery of the cladding 12 is further provided in addition to the optical fiber 10. The coating layer 21 is provided to improve the mechanical strength of the optical fiber 20. The coating layer 21 may be made of, for example, a material and configuration that are used as coating layers in known optical fibers. Examples of materials for the coating layer 21 include various engineering plastics such as polycarbonate, polyester, cycloolefin polymer, cycloolefin copolymer, polytetrafluoroethylene (PTFE), modified PTFE, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), as well as copolymers and mixtures thereof. The outer diameter of the coating layer 21 is preferably 150 μm or more and 400 μm or less, and more preferably 170 μm or more and 300 μm or less.

[0101] (Optical fiber manufacturing method) The optical fiber 10 according to this embodiment can be manufactured, for example, by the following method. An example of the manufacturing method will be described below, taking the case where the optical fiber 10 is a plastic optical fiber as an example.

[0102] The optical fiber 10 can be manufactured by, for example, a melt spinning method. That is, an example of a method for manufacturing the optical fiber 10 of this embodiment is as follows: melting a core material and extruding it into a fiber to produce a fiber-shaped molded body made of the core material; a clad material is melted and extruded to cover the surface of the molded body, thereby producing a laminate in which the core material and the clad material are concentrically laminated; The core material includes, for example, a material of particles that serve as scattering sources and a first resin, and the clad material includes, for example, a second resin.

[0103] When preparing a fiber-shaped molded body made of a core material, a first core material containing a refractive index adjuster may be extruded to form an inner core layer, and then a second core material may be extruded to cover the outer periphery of the inner core layer formed by the first core material. In this case, a refractive index distribution can be formed in the core 11 by diffusing the refractive index adjuster contained in the first core material toward the outer periphery of the core formed by the second core material. When preparing a core containing particles as scattering sources, for example, particles serving as scattering sources are dispersed in the first core material and the second core material. The total number of scattering sources in the core can be controlled, for example, by adjusting the concentration of the scattering source material dispersed in the core material. When preparing a core 11 containing bubbles as scattering sources, the degree of degassing of the core material during the process of melting the core material can be adjusted, for example, by interrupting the degassing process midway so that a predetermined number of bubbles are contained, and then extrusion molding can be performed to prepare the core 11 containing bubbles as scattering sources. Alternatively, the core 11 containing bubbles can be realized by irradiating the core material with laser light to generate bubbles in the core material.

[0104] FIG. 4 is a schematic cross-sectional view showing an example of a manufacturing apparatus that can be used to manufacture the optical fiber 20 shown in FIG.

[0105] The apparatus 1000 shown in FIG. 4 includes a first extrusion device 101a for extruding a first core material, a second extrusion device 101b for extruding a second core material, a third extrusion device 101c for extruding a cladding material, and a fourth extrusion device 101d for forming a coating layer.

[0106] The first extrusion device 101a has a first storage section 102a that stores the first core material 1a and a first extrusion section 103a that extrudes the first core material 1a stored in the first storage section 102a from the first storage section 102a. The first extrusion device 101a is further provided with a heating section (not shown) so that the first core material 1a can be melted in the first storage section 102a and the molten first core material 1a can be maintained in a molten state until it is molded. A rod-shaped first core material (preform) 1a is inserted into the first storage section 102a through an upper opening and is heated and melted in the first storage section 102a.

[0107] In the first extrusion device 101a, the first core material 1a is extruded by gas extrusion from the first storage section 102a through the first extrusion section 103a to form the inner core layer section 2. The first core material 1a extruded through the first extrusion section 103a to form the inner core layer section 2 then moves vertically downward and is supplied to the first chamber 110.

[0108] The second extrusion device 101b has a second storage section 102b that stores the second core material 1b and a second extrusion section 103b that extrudes the second core material 1b stored in the second storage section 102b from the second storage section 102b. The second extrusion device 101b extrudes the molten second core material so as to cover the outer periphery of the inner core layer section 2 formed from the first core material 1a extruded from the first extrusion device 101a. Specifically, the second core material extruded from the second extrusion device 101b is supplied to a first chamber 110. In the first chamber 110, the inner core layer section 2 formed from the first core material 1a is covered with the second core material, thereby forming an outer core section 3 that covers the outer periphery of the inner core layer section 2. The laminate 4 formed of the inner core layer portion 2 and the outer core portion 3 covering the outer periphery of the inner core layer portion 2 moves from the first chamber 110 to the diffusion tube 120 arranged vertically below the first chamber 110. A heater (not shown) for heating the laminate is arranged in the diffusion tube 120. The diffusion tube 120 diffuses dopants such as a refractive index adjuster contained in the inner core layer portion 2 of the laminate 4 passing through the inside of the diffusion tube 120 toward the outer core portion 3. In other words, the inner core layer portion 2 and the outer core portion 3 ultimately form a core.

[0109] The third extrusion device 101c has a third housing section 102c that houses the clad material 1c and a third extrusion section 103c that extrudes the clad material 1c housed in the third housing section 102c from the third housing section 102c. The third extrusion device 101c extrudes the molten clad material 1c so as to coat the outer periphery of the laminate 4 that has passed through the diffusion tube 120. Specifically, the clad material 1c extruded from the third extrusion device 101c is supplied to a second chamber 130. In the second chamber 130, the laminate 4 (i.e., the core) is coated with the clad material 1c, thereby forming a clad 5 that covers the outer periphery of the core. Hereinafter, the laminate 4 will be referred to as the core 4. The laminate formed of the core 4 and the clad 5 moves from the second chamber 130 to a third chamber 140 located vertically below the second chamber 130.

[0110] The fourth extrusion device 101d includes a fourth storage section 102d that stores the coating layer material 1d, a screw 104 disposed in the fourth storage section 102d, and a hopper 105 connected to the fourth storage section 102d. In the fourth extrusion device 101d, the coating layer material 1d, for example, in pellet form, is supplied to the fourth storage section 102d through the hopper 105. The coating layer material 1d supplied to the fourth storage section 102d is kneaded by the screw 104 while being heated, thereby softening and becoming flowable. The softened coating layer material 1d is extruded from the fourth storage section 102d by the screw 104.

[0111] The coating layer material 1d extruded from the fourth extrusion device 101d is supplied to the third chamber 140. In the third chamber 140, the surface of the laminate formed of the core 4 and the clad 5 is coated with the coating layer material 1d, thereby forming a coating layer 6 that covers the outer periphery of the clad 5.

[0112] The laminate 7, in which the core 4, the cladding 5, and the coating layer 6 are concentrically stacked, flows from the third chamber 140 into the internal flow path through the inlet of the nozzle 150. The laminate 7 is reduced in diameter as it passes through the internal flow path, and is discharged from the outlet of the nozzle 150 in the form of a fiber.

[0113] The laminate 7 discharged in the form of a fiber from the discharge port of the nozzle 150 flows into the internal space 161 of the cooling pipe 160, is cooled while passing through the internal space 161, and is discharged from the opening to the outside of the cooling pipe 160. The laminate 7 discharged from the cooling pipe 160 passes between two rolls 171 and 172 of the nip roll 170, and further passes through guide rolls 173 to 175 to be taken up around a take-up roll 176 as the optical fiber 10. A displacement meter 180 for measuring the outer diameter of the optical fiber may be further provided near the take-up roll 176, for example, between the guide roll 175 and the take-up roll 176.

[0114] Although the manufacturing method has been described above for the case where the optical fiber in this embodiment is a plastic optical fiber, the optical fiber in this embodiment can also be manufactured when the optical fiber is a glass optical fiber. For example, a glass material in which particle material that will become a scattering source is dispersed in advance can be prepared, and the glass can be melted and drawn to manufacture a glass optical fiber into which a scattering source has been introduced.

[0115] <Optical fiber simulation> The following shows the results of the study of the optical fiber 10 conducted by the present inventors, including simulations.

[0116] (Simulation environment) The simulation environment used in the simulation carried out by the present inventors was as follows. Ray tracing software: ZEMAX OpticStudio (premium edition) ver.21.2.2 PC: HP Elitebook 830 G7 Memory: 8GB

[0117] (Setting the optical fiber length and core radius) The length of the optical fiber in the simulation was set to 5 mm (0.5 cm) and the core radius was set to 0.0025 cm.

[0118] (Setting the refractive index of the optical fiber core) GRIN9.dll, which can be used for non-sequential ray tracing, was used to express the core refractive index distribution. GRIN9 is defined by the following equation (II): n(r) is the refractive index at the position of radius r. A(λ) and n0 are defined by the following equations (III) and (IV), respectively.

number

[0119] In the above formulas (II) to (IV), n0 is the refractive index at the center of the core 11, g is a refractive index distribution parameter, λ is the wavelength of the light used, B is a constant term that is independent of wavelength, C is a coefficient representing the wavelength dispersion of the refractive index, K0 is a constant for representing the radial refractive index distribution that depends on the refractive index of the core and cladding, and K1 and K2 are coefficients that respectively represent the wavelength dispersion.

[0120] In the refractive index setting in the simulations carried out by the present inventors, the maximum step size was set to 0.001. The g value in the above formula (II) was set to 2. Unused parameters C, K1, and K2 were set to 0. For B and K0, the values ​​in Table 1 below were used.

[0121] [Table 1]

[0122] (Scattering source settings) To simulate scattering within the core of an optical fiber, we adopted DLL-defined scattering (Mie.dll) as the volume physical property of the core, and set each parameter as shown in Table 2 below.

[0123] [Table 2]

[0124] The "total number of particles in the core" in Table 2 is a value calculated using the number density of scattering source particles in the core and the core volume calculated from the length and core radius of the optical fiber. However, the length of the optical fiber used to calculate the total number of scattering source particles is not the 5 mm length of the optical fiber set in the simulation, but half that length, or 2.5 mm. The reason for this is as follows: In this simulation, as described below, the D4σ beam width of the transmitted light through the optical fiber is calculated by analyzing the transmitted light, and the obtained D4σ beam width of the transmitted light through the optical fiber is considered to be the beam width of the reflected light at the first end face of the optical fiber, and the beam width of the reflected light at the first end face of the optical fiber is evaluated. However, considering that the actual reflected light travels a path twice the length of the optical fiber, the total number of scattering sources in the core is the number of scattering sources contained in the core volume of half the length of the optical fiber set in the simulation. Therefore, here, the core volume of 4.9 × 10 calculated from the optical fiber length of 0.25 cm and core radius of 0.0025 cm is used. -6 cm 3 The total number of scattering sources was calculated by multiplying this by the number density.

[0125] (Input light source setting) A Gaussian light source was used as a substitute for a light source with a small spot size and low NA, such as a VCSEL. Beam radius: 0.0028mm Position: 0.02317mm It was decided.

[0126] The number of analyses was 200,000.

[0127] Ray splitting and ray scattering were enabled.

[0128] (Analysis of light transmitted through optical fiber) Regarding the misalignment (x) of the optical fiber relative to the light source, the center position of the core of the optical fiber into which the light emitted from the light source is incident was set to x = 0 mm (i.e., no misalignment), x = 0.01 mm, and x = 0.02 mm relative to the center of the light emitted from the light source, and the NFP of the light transmitted through the optical fiber was evaluated for each. Using the obtained NFP image, the D4σ beam width was calculated using the method described above.

[0129] Table 3 shows the average D4σ beam width and standard deviation for the optical fiber positional offsets x = 0 mm, x = 0.01 mm, and x = 0.02 mm when the optical fiber is a glass optical fiber and GeO2 particles (refractive index: 1.5680) are used as the scattering source. When the optical fiber is a glass optical fiber and GeO2 particles are used as the scattering source, the D4σ beam width of the reflected light was 19 μm or more in all cases, which was wider than the beam width of the light emitted from the light source (beam radius × 2 = 2.8 × 2 = 5.6 μm).

[0130] Table 4 shows the average D4σ beam width and standard deviation of the D4σ beam width when the optical fiber was a glass optical fiber and Al2O3 particles (refractive index: 1.7589) were used as the scattering source, with the optical fiber being positioned at a misalignment of x = 0 mm, x = 0.01 mm, and x = 0.02 mm relative to the light source. When the optical fiber was a glass optical fiber and Al2O3 particles were used as the scattering source, the D4σ beam width of the reflected light was always 25 μm or more, which was wider than the beam width of the light emitted from the light source (beam radius × 2 = 2.8 × 2 = 5.6 μm).

[0131] Table 5 shows the average D4σ beam width and standard deviation for the optical fiber positional offset x = 0 mm, x = 0.01 mm, and x = 0.02 mm when the optical fiber was a glass optical fiber and TiO2 particles (refractive index: 2.3324) were used as the scattering source. When the optical fiber was a glass optical fiber and TiO2 particles were used as the scattering source, the D4σ beam width of the reflected light was 24 μm or more in all cases, which was wider than the beam width of the light emitted from the light source (beam radius × 2 = 2.8 × 2 = 5.6 μm).

[0132] Table 6 shows the average D4σ beam width and standard deviation for the optical fiber positional offset x = 0 mm, x = 0.01 mm, and x = 0.02 mm when the optical fiber was a glass optical fiber and an air bubble (refractive index: 1.0) was used as the scattering source. When the optical fiber was a glass optical fiber and an air bubble was used as the scattering source, the D4σ beam width of the reflected light was 20 μm or more in all cases, which was wider than the beam width of the light emitted from the light source (beam radius × 2 = 2.8 × 2 = 5.6 μm).

[0133] Table 7 shows the average D4σ beam width and standard deviation of the D4σ beam width when the optical fiber is a plastic optical fiber and SiO2 particles (refractive index: 1.45249) are used as the scattering source, with the optical fiber being positioned at a misalignment of x = 0 mm, x = 0.01 mm, and x = 0.02 mm relative to the light source. When the optical fiber is a plastic optical fiber and SiO2 particles are used as the scattering source, the D4σ beam width of the reflected light was 18 μm or more in all cases, which was wider than the beam width of the light emitted from the light source (beam radius × 2 = 2.8 × 2 = 5.6 μm).

[0134] Table 8 shows the average D4σ beam width and standard deviation of the D4σ beam width when the optical fiber is a plastic optical fiber and polystyrene particles (refractive index: 1.57622) are used as the scattering source, with the optical fiber being misaligned with the light source by x = 0 mm, x = 0.01 mm, and x = 0.02 mm. When the optical fiber is a plastic optical fiber and polystyrene particles are used as the scattering source, the D4σ beam width of the reflected light was always 21 μm or more, which was wider than the beam width of the light emitted from the light source (beam radius × 2 = 2.8 × 2 = 5.6 μm).

[0135] Table 9 shows the average D4σ beam width and standard deviation for the D4σ beam width when the optical fiber was a plastic optical fiber and TiO2 particles (refractive index: 2.3324) were used as the scattering source, with the optical fiber being positioned at a misalignment of x = 0 mm, x = 0.01 mm, and x = 0.02 mm relative to the light source. When the optical fiber was a plastic optical fiber and TiO2 particles were used as the scattering source, the D4σ beam width of the reflected light was 19 μm or more in all cases, which was wider than the beam width of the light emitted from the light source (beam radius × 2 = 2.8 × 2 = 5.6 μm).

[0136] Table 10 shows the average D4σ beam width and standard deviation of the D4σ beam width when the optical fiber was a plastic optical fiber and an air bubble (refractive index: 1.0) was used as the scattering source, with the optical fiber being misaligned relative to the light source by x = 0 mm, x = 0.01 mm, and x = 0.02 mm. When the optical fiber was a plastic optical fiber and an air bubble was used as the scattering source, the D4σ beam width of the reflected light was always 21 μm or more, which was wider than the beam width of the light emitted from the light source (beam radius × 2 = 2.8 × 2 = 5.6 μm).

[0137] The total number of scattering sources (total number of particles) in Tables 3 to 10 is calculated based on the number density of the scattering sources and the core volume of 4.9 × 10 calculated from the optical fiber length of 0.25 cm and the core radius of 0.0025 cm, as described above. -6 cm 3 This is the value calculated from the above.

[0138] Table 3

[0139] Table 4

[0140] Table 5

[0141] Table 6

[0142] Table 7

[0143] Table 8

[0144] Table 9

[0145] Table 10

[0146] From the above simulation results, it has been confirmed that the optical fiber 10 according to this embodiment satisfies the above (Ia) or (IIa) when the optical fiber 10 is a glass optical fiber, and satisfies the above (IIIa), (IVa), or (Va) when the optical fiber 10 is a plastic optical fiber, so that even if the position of the optical fiber 10 is slightly misaligned with respect to the light source (for example, about 10 μm), the expansion of the beam width of the reflected light at the first end face of the optical fiber 10 can be maintained, thereby making it possible to reduce the amount of light returning to the light source. In other words, it has been confirmed that the optical fiber 10 according to this embodiment can reduce the amount of light returning while relaxing the positional accuracy requirements with respect to the light source during assembly.

[0147] The optical fiber 10 (or optical fiber 20) according to this embodiment can also be used in optical cords, active optical cables, and the like.

[0148] Fig. 5 is a schematic diagram showing an example of an optical cord including the optical fiber 10 according to this embodiment. The optical cord 50 shown in Fig. 5 includes a cable 51 containing the optical fiber 10, and a connector 52 attached to at least one end of the cable 51.

[0149] Fig. 6 is a schematic diagram showing an example of an active optical cable including the optical fiber 10 according to this embodiment. The active optical cable 60 shown in Fig. 6 includes a cable 61 containing the optical fiber 10 according to this embodiment, a first connector 62 attached to a first end 61a of the cable 61 and including a first conversion unit (not shown) that converts an electrical signal into an optical signal, and a second connector 63 attached to a second end 61b of the cable 61 and including a second conversion unit (not shown) that converts an optical signal into an electrical signal.

[0150] [Note] To summarize the above, one aspect of the present disclosure is as follows.

[0151] (1) An optical fiber having a core that is an optical transmission region, the core comprises at least one scattering source selected from the group consisting of particles and bubbles; When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Ia) or (IIa): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IIIa), (IVa), or (Va): Optical fiber. (Ia) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 0.5 μm and less than 1.5 μm, and the total number of the scattering sources in the core is 396 or more and 1473 or less. (IIa) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 149 or more and 491 or less. (IIIa) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 149 or more and 982 or less. (IVa) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 4 μm and less than 8 μm, and the total number of the scattering sources in the core is 5 or more and 149 or less. (Va) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 10 μm or less, and the total number of the scattering sources in the core is greater than 248 and 1473 or less.

[0152] (2) When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Ib) or (IIb): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IIIb), (IVb), or (Vb): The optical fiber according to (1) above. (Ib) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 0.5 μm and less than 1.5 μm, and the total number of the scattering sources in the core is 747 or more and 1228 or less. (IIb) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 149 or more and 347 or less. (IIIb) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less. (IVb) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 4 μm and less than 8 μm, and the total number of the scattering sources in the core is 75 or more and 149 or less. (Vb) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less.

[0153] (3) When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Ic): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IIIc), (IVc), or (Vc): The optical fiber according to (1) or (2) above. (Ic) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 0.5 μm and less than 1.5 μm, and the total number of the scattering sources in the core is 834 or more and 1129 or less. (IIIc) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less. (IVc) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 4 μm and less than 8 μm, and the total number of the scattering sources in the core is 75 or more and 149 or less. (Vc) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less.

[0154] (4) When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Id): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IIId), (IVd), or (Vd): The optical fiber according to any one of (1) to (3) above. (Id) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 0.5 μm and less than 1.5 μm, and the total number of the scattering sources in the core is 883 or more and 1080 or less. (IIId) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less. (IVd) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 4 μm and less than 8 μm, and the total number of the scattering sources in the core is 75 or more and 149 or less. (Vd) The refractive index of the scattering source at a wavelength of 850 nm is greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less.

[0155] (5) When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Ie): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IVe): 10. The optical fiber according to claim 1. (Ie) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 0.5 μm and less than 1.5 μm, and the total number of the scattering sources in the core is 933 or more and 1031 or less. (IVe) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 4 μm and less than 8 μm, and the total number of the scattering sources in the core is 75 or more and 149 or less.

[0156] (6) The scattering source having a refractive index of 1.2 or more and 1.8 or less at a wavelength of 850 nm is at least one selected from the group consisting of GeO2, Al2O3, SiO2, MgF2, polystyrene, polymethyl methacrylate, poly(styrene-butadiene) copolymer, and polyphenylene sulfide. The optical fiber according to any one of (1) to (5) above.

[0157] (7) The scattering source having a refractive index greater than 1.8 at a wavelength of 850 nm is at least one selected from the group consisting of TiO2, ZrO2, ZnO, and SrTiO3. The optical fiber according to any one of (1) to (6) above.

[0158] (8) The optical fiber according to any one of (1) to (7) above is provided. Optical code.

[0159] (9) The optical code according to (8) above; an optoelectronic hybrid module; Active optical cable. [Industrial Applicability]

[0160] The optical fiber of the present disclosure can reduce returned light and suppress noise generation, and is therefore suitable as an optical fiber required for high speed and large capacity. [Explanation of symbols]

[0161] 1a First core material 1b Second core material 1c Cladding material 1d Covering layer material 2. Core inner layer 3 Core outer periphery 4 Laminate (core) 5. Clad 6 Covering layer 7 Laminate 10, 20 Optical fiber 11 cores 11a center 11b outer edge 12 Clad 21 Covering layer 50 Optical Cord 51 Cable 52 connectors 60 Active Optical Cable 61 Cable 61a First end 61b Second end 62 First Connector 63 Second Connector 101a First extrusion device 101b Second extrusion device 101c Third extrusion device 101d Fourth extrusion device 102a First storage section 102b Second storage section 102c Third Storage Unit 102d 4th Storage Unit 103a First extrusion section 103b Second extrusion section 103c Third extrusion section 104 Screw 105 Hopper 110 Room 1 120 Diffusion tube 130 Room 2 140 Room 3 150 nozzles 160 Cooling pipe 161 Interior Space 170 Nip Roll 171,172 rolls 173,174,175 Guide Roll 176 Winding Roll 180 Displacement Meter 1000 manufacturing equipment

Claims

1. An optical fiber having a core that is an optical transmission region, the core includes at least one scattering source selected from the group consisting of particles and bubbles; When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Ia) or (IIa): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IIIa), (IVa), or (Va): Optical fiber. (Ia) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 0.5 μm and 1.5 μm or less, and the total number of the scattering sources in the core is 396 or more and 1473 or less. (IIa) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 149 or more and 491 or less. (IIIa) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 149 or more and 982 or less. (IVa) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of the scattering sources in the core is 5 or more and 149 or less. (Va) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 10 μm or less, and the total number of the scattering sources in the core is greater than 248 and 1473 or less.

2. When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Ib) or (IIb): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IIIb), (IVb), or (Vb): The optical fiber of claim 1 . (Ib) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 0.5 μm and less than 1.5 μm, and the total number of the scattering sources in the core is 747 or more and 1228 or less. (IIb) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 149 or more and 347 or less. (IIIb) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less. (IVb) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of the scattering sources in the core is 75 or more and 149 or less. (Vb) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less.

3. When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Ic): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IIIc), (IVc), or (Vc): The optical fiber of claim 1 . (Ic) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 0.5 μm and less than 1.5 μm, and the total number of the scattering sources in the core is 834 or more and 1129 or less. (IIIc) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less. (IVc) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of the scattering sources in the core is 75 or more and 149 or less. (Vc) The refractive index of the scattering source at a wavelength of 850 nm is less than 1.2 or greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less.

4. When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Id): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IIId), (IVd), or (Vd): The optical fiber of claim 1 . (Id) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is greater than 0.5 μm and less than 1.5 μm, and the total number of the scattering sources in the core is 883 or more and 1080 or less. (IIId) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less. (IVd) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of the scattering sources in the core is 75 or more and 149 or less. (Vd) The refractive index of the scattering source at a wavelength of 850 nm is greater than 1.8, the diameter of the scattering source is 1.5 μm or more and 4 μm or less, and the total number of the scattering sources in the core is 347 or more and 982 or less.

5. When the optical fiber is a glass optical fiber in which the core is made of a glass material, the optical fiber satisfies the following (Ie): When the optical fiber is a plastic optical fiber in which the core is made of a plastic material, the optical fiber satisfies the following (IVe): The optical fiber of claim 1 . (Ie) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 0.5 μm and 1.5 μm or less, and the total number of the scattering sources in the core is 933 or more and 1031 or less. (IVe) The refractive index of the scattering source at a wavelength of 850 nm is 1.2 or more and 1.8 or less, the diameter of the scattering source is more than 4 μm and 8 μm or less, and the total number of the scattering sources in the core is 75 or more and 149 or less.

6. The scattering source having a refractive index of 1.2 or more and 1.8 or less at a wavelength of 850 nm is GeO 2 , Al 2 O 3 , SiO 2 , MgF 2 , at least one selected from the group consisting of polystyrene, polymethyl methacrylate, poly(styrene-butadiene) copolymer, and polyphenylene sulfide; The optical fiber of claim 1 .

7. The scattering source having a refractive index greater than 1.8 at a wavelength of 850 nm is TiO 2 , ZrO 2 , ZnO, and SrTiO 3 At least one selected from the group consisting of: The optical fiber of claim 1 .

8. An optical fiber according to any one of claims 1 to 7, Optical code.

9. The optical code according to claim 8; an optoelectronic hybrid module; Active optical cable.

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