The present invention relates to an optical fiber, specifically, an optical fiber that can be used in an optical fiber cable.
Background technology
[0002]
　In recent years, the traffic of communication infrastructure constructed by optical fiber cables and the like has been increasing due to the maturity of Fiber To The Home (FTTH) services, the spread of mobile terminals, the expansion of cloud service usage, and the increase in video traffic. .. Therefore, it is required to construct a communication infrastructure more economically and efficiently than before. Against this background, there is a demand to increase the number of mounting cores and mounting density of optical fibers mounted on optical fiber cables.
[0003]
　As a means for increasing the number of mounting cores and the mounting density of the optical fiber, it is conceivable to reduce the diameter of the optical fiber. However, in this case, the optical fiber is easily affected by the lateral pressure, and the microbend loss, which is the optical loss caused by the so-called minute bending in which the axis of the optical fiber is slightly bent, can be increased. In Patent Document 1 below, the coating thickness of the optical fiber is reduced by adjusting the elastic coefficient of the coating of the optical fiber and the glass transition point, thereby suppressing microbend loss even when the diameter of the optical fiber is reduced. It is stated that it can be done.
[0004]
Patent Document 1: Japanese Patent Application Laid-Open No. 2012-508395
Outline of the invention
[0005]
　However, the microbend loss propagates the optical fiber with parameters related to the optical fiber geometry such as the coating thickness of the optical fiber, the outer diameter of the glass forming the core and the clad, the Young ratio of the glass, and the Young ratio of the coating. It tends to be affected by parameters related to the optical characteristics of the optical fiber, such as the propagation constant of light. In Patent Document 1, the coating thickness is taken into consideration as the above parameter in terms of suppressing microbend loss, but parameters other than the coating thickness are not taken into consideration. Therefore, there is a demand for an optical fiber capable of suppressing microbend loss in consideration of various parameters that affect microbend loss.
[0006]
　Therefore, an object of the present invention is to provide an optical fiber capable of suppressing microbend loss.
[0007]
　In order to achieve the above object, the present invention is an optical fiber including a core and a glass portion including a clad surrounding the core, a primary coating layer covering the clad, and a secondary coating layer covering the primary coating layer. The spring coefficient of the primary coating layer is κs (MPa), the bending rigidity of the glass portion is H f (MPa · μm 4 ), the deformation resistance of the secondary coating layer is D 0 (MPa), and the bending rigidity of the secondary coating layer. H 0 (MPa · μm 4 ), the Young ratio of the glass portion is E g (GPa), the Young ratio of the primary coating layer is E p (MPa), and the Young ratio of the secondary coating layer is E s (MPa). The outer diameter of the glass portion is d f (μm), the radius of the outer peripheral surface of the primary coating layer is R p (μm), the radius of the outer peripheral surface of the secondary coating layer is R s (μm), and the primary coating layer is When the thickness of the secondary coating layer is t p (μm) and the thickness of the secondary coating layer is t s (μm),

In represented by geometry microbend loss characteristic F of the optical fiber MyuBL_G (GPa -1 · [mu] m -10.5 · 10 -27 propagation constant and), the propagation constant and the radiation mode in the waveguide mode propagating through the optical fiber If the difference and the propagation constant difference Δβ (rad / m), and

in the optical fiber of the optical microbend loss characteristic F represented MyuBL_derutabeta (1 / (rad / [mu] m) 8 and),
with,

in The value of the microbend loss characteristic factor F μBL_GΔβ ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) expressed is 6.1 ([GPa -1 · μm -2.5 / rad 8] ] ・ 10-12 ) It is characterized by being less than or equal to.
[0008]
　Microbend loss of optical fiber is described in Non-Patent Document 1 (J. Baldauf, et al., “Relationship of Mechanical Characteristics of Dual Coated Single Mode Optical Fibers and Microbending Loss,” IEICE Trans. Commun., Vol. E76-B, No. 4, 1993.), Non-Patent Document 2 (K. Petermann, et al., “Upper and Lower Limits for the Microbending Loss in Arbitrary Single-Mode Fibers,” J. Lightwave technology, vol. LT-4, no .1, pp. 2-7, 1986.), Non-Patent Document 3 (Ogoshi et al., “Optical Fiber,” Ohm, pp.235-239, 1989.), and Non-Patent Document 4 (P. Sillard, et. Effects of both fiber optic geometry and optical properties, as described in al., “Micro-Bend Losses of Trench-Assisted Single-Mode Fibers,” ECOC2010, We.8.F.3, 2010.) Tend to receive.
[0009]
　Here, the geometry of the optical fiber is a parameter related to the structure of the optical fiber, and in the present invention, the spring coefficient κs of the primary coating layer in the optical fiber, the flexural rigidity H f of the glass portion, and the deformation resistance D of the secondary coating layer D. 0 , flexural rigidity of the secondary coating layer H 0 , Young's modulus E g of the glass part, Young 's modulus E p of the primary coating layer, Young's modulus E s of the secondary coating layer , outer diameter d f of the glass part (diameter of the glass part) , The radius R p of the primary coating layer, the radius R s of the secondary coating layer, the thickness t p of the primary coating layer , and the thickness t s of the secondary coating layer .
[0010]
　By the way, according to the above-mentioned Non-Patent Documents 2 to 4, microbend loss is a phenomenon caused by mode coupling in which the waveguide mode propagating in the optical fiber is coupled with the radiation mode. Such mode coupling is considered to occur due to the above-mentioned minute bending, and the propagation constant difference, which is the difference between the propagation constant of the light propagating in the optical fiber in the waveguide mode and the propagation constant in the radiation mode. It is said to be determined by (Δβ). The above-mentioned optical characteristics of the optical fiber are parameters related to the characteristics of light propagating in the optical fiber, and in the present invention, the above-mentioned propagation constant difference Δβ (rad / m) is meant.
[0011]
　The microbend loss of such an optical fiber is a transmission loss measured in a state where the optical fiber is wound in one layer with a predetermined tension around the body portion of the roughened bobbin, and the optical fiber is unwound from the bobbin. It may be represented by the value of sandpaper tension winding loss increase, which is the difference from the transmission loss measured with almost no tension applied. The smaller the value of such sandpaper tension winding loss increase, the smaller the microbend loss of the optical fiber.
[0012]
　By the way, as an optical fiber cable constituting a communication infrastructure, a so-called tape slot type cable (RSCC:) configured by accommodating a plurality of tape core wires in each of a plurality of slots formed in a holder for holding the tape core wire. Ribbon Slotted Core Cable) and a small-diameter high-density cable (UHDC: Ultra-High Density Cable) configured by densely arranging tape core wires inside the cable without using the above-mentioned holder are known. Of these, since the tape slot type cable has a structure in which a plurality of tape core wires are accommodated in the slots as described above, lateral pressure is applied to the optical fibers constituting the tape core wires, which may cause microbend loss. .. Therefore, in the tape slot type cable, in consideration of such microbend loss, it is preferable to use an optical fiber in which the value of the increase in sandpaper tension winding loss is suppressed to 0.6 dB / km or less.
[0013]
　The present inventor has diligently studied the relationship between the increase in sandpaper tension winding loss and the above-mentioned various parameters in the optical fiber used for the optical fiber cable. As a result, it was found that the value of the microbend loss characteristic factor F μBL_GΔβ represented by the above formula has a high correlation with the value of the increase in sandpaper tension winding loss. That is, the present inventor has found that the value of the microbend loss characteristic factor has a substantially positive proportional relationship with the value of the increase in sandpaper tension winding loss.
[0014]
　As a result of further research, the present inventor conducted sandpaper when the value of the microbend loss characteristic factor was 6.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ). It was found that the value of the increase in tension winding loss was slightly smaller than 0.6 dB / km. As described above, the value of the microbend loss characteristic factor and the value of the sandpaper tension winding loss increase are generally in a positive proportional relationship with each other. Therefore, by setting the value of the microbend loss characteristic factor of the optical fiber to 7183 GPa 3 · nm 2.5 · rad 8 or less, the microbend loss can be suppressed to the extent that it can be applied to the tape slot type cable.
[0015]
　As described above, according to the optical fiber of the present invention, microbend loss can be suppressed.
[0016]
　Further, it is more preferable that the value of the microbend loss characteristic factor is 4.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ) or less.
[0017]
　Among the optical fiber cables constituting the communication infrastructure, the tape core wires are densely arranged as described above in the small diameter high density cable. Therefore, similarly to the tape slot type cable, the optical fiber constituting the tape core wire receives lateral pressure, and microbend loss may occur. In addition, the small-diameter high-density cable is slotless as described above, and since all the tape core wires are densely arranged inside the cable, the tape core wires are arranged in a plurality of grooves. The optical fiber tends to be subjected to a large lateral pressure. Therefore, it is recommended to use an optical fiber having a smaller microbend loss than the optical fiber used for the tape slot type cable in the small diameter high density cable. From this point of view, it is preferable to use an optical fiber in which the value of the increase in sandpaper tension winding loss is suppressed to 0.34 dB / km or less in the small-diameter high-density cable.
[0018]
　According to the present inventor, the value of the microbend loss characteristic factor corresponding to the value of the increase in sandpaper tension winding loss (0.34 dB / km) is 4.1 ([GPa -1 · μm -2.5 / km). rad 8 ] ・ 10-12 ) was found. Therefore, by setting the value of the microbend loss characteristic factor of the optical fiber to 4.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less, it can be applied to small-diameter high-density cables. Microbend loss can be suppressed to the extent possible.
[0019]
　Further, in the above-mentioned optical fiber, the coating thickness obtained by adding the thickness of the primary coating layer and the thickness of the secondary coating layer is preferably 42.0 μm or less.
[0020]
　The larger the coating thickness, the larger the outer diameter of the optical fiber tends to be, and the smaller the coating thickness, the smaller the outer diameter of the optical fiber tends to be. The optical fiber used for the optical fiber cable constituting the communication infrastructure generally has a coating thickness of about 60 μm. Therefore, if the coating thickness is 42.0 μm or less, it is possible to realize an optical fiber having a smaller diameter than a general optical fiber constituting a communication infrastructure. By the way, the value of the microbend loss characteristic factor is determined by various parameters as described above, and the parameters include the thickness of the primary coating layer and the thickness of the secondary coating layer. Therefore, according to the present invention, even if the thickness of the primary coating layer or the thickness of the secondary coating layer is reduced, the value of the microbend loss characteristic factor can be set to 6.1 ([GPa] by adjusting other parameters. -1 · μm -2.5 / rad 8 ] · 10-12 ) or less, and 4.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less It can also be. Therefore, even if the coating thickness of the optical fiber of the present invention is 42.0 μm or less, microbend loss can be suppressed to such an extent that it can be used for a tape slot type cable or a small diameter high density cable.
[0021]
　Further, it is more preferable that the coating thickness is 38.0 μm or less.
[0022]
　Further, it is more preferable that the coating thickness is 36.5 μm or less.
[0023]
　Further, it is more preferable that the coating thickness is 34.5 μm or less.
[0024]
　Further, it is more preferable that the coating thickness is 34.0 μm or less.
[0025]
　By reducing the coating thickness in this way, microbend loss can be suppressed to the extent that it can be used for tape slot type cables and small-diameter high-density cables, and an optical fiber with a smaller diameter can be realized. ..
[0026]
　Further, when the coating thickness is 42.0 μm or less, the outer diameter of the glass portion may be 65 μm or more and 100 μm or less.
[0027]
　The larger the outer diameter of the glass portion, the larger the outer diameter of the optical fiber tends to be, and the smaller the outer diameter of the glass portion, the smaller the outer diameter of the optical fiber tends to be. The optical fiber used for the optical fiber cable constituting the communication infrastructure is generally formed so that the outer diameter of the glass portion is 125 μm. Therefore, if the coating thickness is 42.0 μm or less and the outer diameter of the glass portion is 100 μm or less, an optical fiber having a smaller diameter than the general optical fiber constituting the communication infrastructure can be realized. .. By the way, the value of the microbend loss characteristic factor is determined by various parameters as described above, and the parameters include the coating thickness and the outer diameter of the glass portion. Therefore, according to the present invention, even if the coating thickness is reduced and the outer diameter of the glass portion is reduced, the value of the microbend loss characteristic factor is set to 6.1 ([GPa] by adjusting other parameters. -1 · μm -2.5 / rad 8 ] · 10-12 ) or less, and 4.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less It can also be. Therefore, even if the coating thickness of the optical fiber of the present invention is 42.0 μm or less and the outer diameter of the glass portion is 100 μm or less, microbend loss is suppressed to the extent that it can be used for tape slot type cables and small diameter high density cables. Can be done.
[0028]
　If the outer diameter of the brittle glass portion is as thin as about 65 μm, the mechanical bending resistance of the optical fiber can be increased by the amount that the brittle glass is thinned.
[0029]
　Further, it is more preferable that the outer diameter of the glass portion is 90 μm or less.
[0030]
　Further, it is more preferable that the outer diameter of the glass portion is 80 μm or less.
[0031]
　Further, it is more preferable that the outer diameter of the glass portion is 75 μm or less.
[0032]
　Further, it is more preferable that the outer diameter of the glass portion is 70 μm or less.
[0033]
　By reducing the outer diameter of the glass part in this way, microbend loss is suppressed to the extent that it can be used for tape slot type cables and small diameter high density cables, and an optical fiber with a smaller diameter is realized. Can be done.
[0034]
　When the coating thickness is 42.0 μm or less, the mode field diameter at a wavelength of 1310 nm is 7.6 μm or more and 8.7 μm or less, the cable cutoff wavelength is 1260 nm or less, and the zero dispersion wavelength is 1300 nm or more and 1324 nm. The zero dispersion slope may be 0.073 ps / km / nm or more and 0.092 ps / km / nm.
[0035]
　In this case, the macrobend loss at a wavelength of 1625 nm when bent at a radius of 10 mm may be 1.5 dB / turn or less.
[0036]
　Alternatively, the macrobend loss at a wavelength of 1625 nm when bent at a radius of 10 mm may be 0.2 dB / turn or less.
[0037]
　Alternatively, the macrobend loss at a wavelength of 1625 nm when bent at a radius of 10 mm may be 0.1 dB / turn or less.
[0038]
　As described above, according to the present invention, there is provided an optical fiber capable of suppressing microbend loss.
A brief description of the drawing
[0039]
FIG. 1 is a diagram schematically showing a structure having a cross section perpendicular to the longitudinal direction of the optical fiber cable according to the first embodiment of the present invention.
FIG. 2 is a perspective view schematically showing an example of an optical fiber tape core wire included in the optical fiber cable shown in FIG.
FIG. 3 is a diagram schematically showing a structure of a cross section perpendicular to the longitudinal direction of the optical fiber included in the optical fiber tape core wire shown in FIG.
FIG. 4 is a diagram showing a structure having a cross section perpendicular to the longitudinal direction of the optical fiber cable according to the second embodiment of the present invention.
FIG. 5 is a diagram showing the relationship between the value of the microbend loss characteristic factor and the increase in sandpaper tension winding loss in the optical fiber shown in FIG.
Mode for carrying out the invention
[0040]
　Hereinafter, embodiments for carrying out the optical fiber according to the present invention will be illustrated together with the accompanying drawings. The embodiments illustrated below are for facilitating the understanding of the present invention, and are not for limiting the interpretation of the present invention. The present invention can be modified or improved from the following embodiments without departing from the spirit of the present invention. Further, in the present specification, the dimensions of each member may be exaggerated for ease of understanding.
[0041]
(First Embodiment)
　FIG. 1 is a diagram schematically showing a structure of a cross section perpendicular to the longitudinal direction of the optical fiber cable 1 according to the first embodiment. As shown in FIG. 1, the optical fiber cable 1 is a so-called tape slot type cable (RSCC: Ribbon Slotted Core Cable). The optical fiber cable 1 mainly includes a sheath 3, a plurality of tape core wires 4, a holding body 5, and a tensile strength body 6.
[0042]
　The sheath 3 is a tubular member and may be formed of a thermoplastic resin such as polyethylene. The holding body 5 is housed in the internal space of the sheath 3. In this way, the sheath 3 houses the holding body 5 inside and protects the holding body 5.
[0043]
　The holding body 5 is a member that holds a plurality of tape core wires 4. A plurality of slots 5S are formed in the holding body 5, and a plurality of tape core wires 4 are accommodated in each of the slots 5S. By increasing the number of tape core wires 4 accommodated in the slot 5S, the number of optical fiber cores included in the optical fiber cable 1 can be increased.
[0044]
　In the present embodiment, the tensile strength body 6 is embedded in the substantially center of the holding body 5 in the cross-sectional view of FIG. Such a tensile strength body 6 can prevent the tape core wire 4 from being stretched more than necessary when tension is applied in the longitudinal direction of the tape core wire 4.
[0045]
　FIG. 2 is a perspective view schematically showing an example of the tape core wire 4. As shown in FIG. 2, the tape core wire 4 of the present embodiment is a so-called intermittent adhesive type tape core wire. The tape core wire 4 has a configuration in which a plurality of optical fibers 10 are arranged along a direction perpendicular to the longitudinal direction, and the arranged optical fibers 10 are bonded to each other. The tape core wire 4 includes an adhesive portion 4A and a single core portion 4B. The adhesive portion 4A is a portion where adjacent optical fibers 10 are adhered to each other, and is provided intermittently at a constant pitch along the longitudinal direction. The single core portion 4B is a portion located between the adhesive portions 4A, and is a portion where the optical fibers 10 are not adhered to each other. With such a configuration, the tape core wire 4 can be easily deformed, for example, twisted or bundled in a substantially cylindrical shape. FIG. 1 schematically shows a state in which each tape core wire 4 is bundled in a substantially cylindrical shape.
[0046]
　Note that FIG. 2 shows an example in which the tape core wire 4 is composed of four optical fibers 10, but this is an example. That is, the number of optical fibers 10 constituting the tape core wire 4 is not particularly limited, and may be less than 4 or more than 4. For example, the tape core wire 4 may be composed of a 12-core optical fiber 10. Further, the tape core wire 4 is not limited to the intermittent adhesive type.
[0047]
　FIG. 3 is a diagram showing a structure of a cross section perpendicular to the longitudinal direction of the optical fiber 10 constituting the tape core wire 4. The optical fiber 10 of this embodiment is a single mode optical fiber. As shown in FIG. 3, the optical fiber 10 includes a core 11, a clad 12 that surrounds the core 11 without gaps, a primary coating layer 14 that covers the clad 12, and a secondary coating layer 15 that covers the primary coating layer 14. Is provided as the main configuration. In the optical fiber 10, the clad 12 has a lower refractive index than the core 11.
[0048]
　The core 11 may be formed from pure quartz to which no dopant is added, or may be formed from quartz to which germanium (Ge) or the like that increases the refractive index is added as a dopant.
[0049]
　As mentioned above, the clad 12 has a lower refractive index than the core 11. For example, when the core 11 is formed of pure quartz, the clad 12 may be formed of quartz to which fluorine (F), boron (B), or the like that lowers the refractive index is added as a dopant. When it is formed from quartz to which germanium (Ge) or the like which increases the refractive index is added as a dopant, it may be formed from pure quartz to which no dopant is added. Further, the clad 12 may be formed of quartz to which chlorine (Cl2) has been added. Further, the clad 12 may be a single layer, may be composed of a plurality of layers having different refractive indexes, or may be a pore-assisted type.
[0050]
　As described above, the core 11 and the clad 12 are both formed of quartz (glass). Therefore, the core 11 and the clad 12 are collectively referred to as the glass portion 13. That is, the glass portion 13 includes the core 11 and the clad 12, and the glass portion 13 is covered with the primary coating layer 14. The glass portion 13 may also be referred to as an optical fiber bare wire portion. The outer diameter (diameter) d f of such a glass portion 13 is generally 125 μm. However, in the present embodiment, the outer diameter d f of the glass portion 13 can be made smaller than this. For example, it can be 65 μm or more and 100 μm or less, 65 μm or more and 90 μm or less, 65 μm or more and 80 μm or less, 65 μm or more and 75 μm or less, or 65 μm or more and 70 μm or less. be able to. The reason why the outer diameter d f of the glass portion 13 can be reduced in this way will be described later.
[0051]
　The outer diameter d of the glass portion having a brittle f is if fineness of about 65 .mu.m, minute glass brittle becomes thinner, the mechanical bending resistance of the optical fiber may be higher.
[0052]
　Primary coating layer 14 is formed, for example, an ultraviolet curable resin or a thermosetting resin, the thickness on the outside of the glass portion 13 of t p is formed by ([mu] m). In the present embodiment, the Young's modulus E g of the primary coating layer 14 is lower than the Young's modulus E s of the secondary coating layer 15 . By setting the primary coating layer 14 in direct contact with the glass portion to have a low Young's modulus in this way, the primary coating layer 14 acts as a cushioning material, and the external force acting on the glass portion 13 can be reduced. Assuming that the radius of the outer peripheral surface of the primary coating layer 14 is R p (μm), the outer diameter of the primary coating layer 14 is represented by 2 R p , and the radius of the glass portion (d f × 1/2) is R. Assuming g (μm), the thickness t p of the primary coating layer 14 is expressed by the following equation.
t p = R p- R g
[0053]
　In the present embodiment, the secondary coating layer 15 is a layer forming the outermost layer of the optical fiber 10, and is formed of, for example, an ultraviolet curable resin or a thermosetting resin different from the resin forming the primary coating layer 14, and is a primary. It is formed on the outside of the coating layer 14 with a thickness of t s (μm). For example, when the primary coating layer 14 is formed of an ultraviolet curable resin, the secondary coating layer 15 may be formed of an ultraviolet curable resin different from the ultraviolet curable resin forming the primary coating layer 14, and the primary coating layer 14 may be formed of an ultraviolet curable resin. Is formed from a thermosetting resin, it may be formed from a thermosetting resin different from the primary coating layer 14. In the present embodiment, the Young's modulus E s of the secondary coating layer 15 is higher than the Young's modulus E g of the primary coating layer 14 . As described above, the secondary coating layer 15 forming the outermost layer of the optical fiber 10 has a high Young's modulus, so that the glass portion 13 can be appropriately protected from an external force. Assuming that the radius of the outer peripheral surface of the secondary coating layer 15 is R s , the outer diameter of the secondary coating layer 15, that is, the outer diameter of the optical fiber 10 is represented by 2 R s , and the thickness of the secondary coating layer 15 is described above. t s is expressed by the following equation.
t s = R s- R p
[0054]
　By the way, the outer diameter of the optical fiber used for the optical fiber cable is generally about 240 μm to 250 μm. Therefore, the outer diameter of the secondary coating layer 15 may be approximately 240 μm. However, in the present embodiment, the outer diameter of the secondary coating layer 15 can be made smaller than 240 μm. For example, it can be about 190 μm, about 150 μm to about 160 μm, or about 125 μm. The reason why the outer diameter of the secondary coating layer 15, that is, the outer diameter of the optical fiber 10 can be reduced in this way will be described later.
[0055]
　Further, assuming that the sum of the thickness t p of the primary coating layer 14 and the thickness t s of the secondary coating layer 15 is the coating thickness t, the coating thickness of the optical fiber used for the optical fiber cable is generally 60 μm. Degree. Therefore, the coating thickness t of the optical fiber 10 may be about 60 μm. However, in the present embodiment, the coating thickness t of the optical fiber 10 can be made smaller than 60 μm. For example, it can be 42.5 μm or less, 38.0 μm or less, 36.5 μm or less, 34.5 μm or less, or 34.0 μm or less. be able to. The reason why the coating thickness of the optical fiber 10 can be reduced in this way will be described later.
[0056]
　As described above, in the optical fiber cable 1 of the present embodiment, the tape core wire 4 including a plurality of such optical fibers 10 is densely housed in the slot 5S of the holder 5. As a result, the optical fiber cable 1 can accommodate a large number of optical fibers. For example, the optical fiber cable 1 accommodates 1000 or more optical fibers. Further, as described above, in the optical fiber 10 of the present embodiment, the glass portion 13 can be formed to have an outer diameter smaller than that of the glass portion of the general optical fiber, and the coating thickness is the coating of the general optical fiber. It can be formed smaller than the thickness. Therefore, the outer diameter of the optical fiber 10 can be made smaller than the outer diameter of a general optical fiber, and the diameter of the optical fiber 10 can be reduced. By reducing the diameter of the optical fiber 10 in this way, the size of the tape core wire 4 can be made smaller than the size of a general tape core wire. Therefore, by accommodating the tape core wire 4 having such a small size in the slot 5S, the number of optical fiber cores accommodated in the optical fiber cable 1 can be further increased. Alternatively, the size of the optical fiber cable 1 can be reduced by accommodating the tape core wire 4 having such a small size in the slot 5S.
[0057]
　On the other hand, as the accommodation density of the tape core wire in the slot increases, the lateral pressure acting on the optical fiber tends to increase. When the optical fiber receives lateral pressure in this way, the shaft of the optical fiber is slightly bent, and microbend loss may occur. Further, if the outer diameter of the glass portion of the optical fiber or the coating thickness of the optical fiber is reduced, the glass portion is susceptible to lateral pressure, and microbend loss may also occur.
[0058]
　However, in the optical fiber 10 of the present embodiment, the value of the microbend loss characteristic factor F μBL_GΔβ , which will be described later, is 6.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ) or less. Is formed in. Therefore, even when the outer diameter and the coating thickness of the glass portion are reduced and the number of cores of the optical fiber 10 accommodated in the slot 5S is increased, the microbend loss can be suppressed. The reason for this will be described in detail below.
[0059]
　Microbend loss of optical fiber is described in Non-Patent Document 1 (J. Baldauf, et al., “Relationship of Mechanical Characteristics of Dual Coated Single Mode Optical Fibers and Microbending Loss,” IEICE Trans. Commun., Vol. E76-B, No. 4, 1993.), Non-Patent Document 2 (K. Petermann, et al., “Upper and Lower Limits for the Microbending Loss in Arbitrary Single-Mode Fibers,” J. Lightwave technology, vol. LT-4, no .1, pp. 2-7, 1986.), Non-Patent Document 3 (Ogoshi et al., “Optical Fiber,” Ohm, pp.235-239, 1989.), and Non-Patent Document 4 (P. Sillard, et. Effects of both fiber optic geometry and optical properties, as described in al., “Micro-Bend Losses of Trench-Assisted Single-Mode Fibers,” ECOC2010, We.8.F.3, 2010.) Tend to receive.
[0060]
　Here, the geometry of the optical fiber is a parameter related to the structure of the optical fiber, and in the present embodiment, the spring coefficient κs of the primary coating layer in the optical fiber, the flexural rigidity H f of the glass portion, and the deformation resistance of the secondary coating layer. D 0 , flexural rigidity H of the secondary coating layer 0 , the Young's modulus of the glass portion E g , the Young's modulus E of the primary coating layer p , Young's modulus E of the secondary coating layer s , the outer diameter d of the glass portion f of the (glass portion diameter ), The radius R p of the primary coating layer, the radius R s of the secondary coating layer, the thickness t p of the primary coating layer , and the thickness t s of the secondary coating layer .
[0061]
　By the way, according to the above-mentioned Non-Patent Documents 2 to 4, microbend loss is a phenomenon caused by mode coupling in which the waveguide mode propagating in the optical fiber is coupled with the radiation mode. This waveguide mode is, for example, LP01 mode. It is said that such mode coupling is caused by so-called minute bending in which the axis of the optical fiber is slightly bent, and the propagation constant is the difference between the propagation constant in the waveguide mode and the propagation constant in the radiation mode. It is believed to be determined by the difference (Δβ). The above-mentioned optical characteristics of the optical fiber are parameters related to the characteristics of light propagating in the optical fiber, and in the present invention, the above-mentioned propagation constant difference Δβ (rad / m) is meant.
[0062]
　The microbend loss of such an optical fiber is a transmission loss measured in a state where the optical fiber is wound in one layer with a predetermined tension around the body portion of the roughened bobbin, and the optical fiber is unwound from the bobbin. It may be represented by the value of sandpaper tension winding loss increase, which is the difference from the transmission loss measured with almost no tension applied. The smaller the value of such sandpaper tension winding loss increase, the smaller the microbend loss of the optical fiber.
[0063]
　By the way, a tape slot type cable (RSCC) such as the optical fiber cable 1 of the present embodiment may cause microbend loss as described above. Therefore, the tape slot type cable has a required characteristic that the value of the increase in sandpaper tension winding loss is 0.6 dB / km or less in consideration of such microbend loss.
[0064]
　The present inventor has diligently studied the relationship between the increase in sandpaper tension winding loss and the above-mentioned various parameters in the optical fiber used for the optical fiber cable. As a result, the spring coefficient κs of the primary coating layer, the bending rigidity H f of the glass portion, the deformation resistance D 0 of the secondary coating layer, the bending rigidity H 0 of the secondary coating layer, and the Young's modulus E g of the glass portion, which are parameters related to the geometry. , Young's modulus E of the primary coating layer p , Young's modulus E of the secondary coating layer s outer diameter d of the glass portion f the radius R of the outer peripheral surface of the primary coating layer p radius R of the outer peripheral surface of the secondary coating layer s , primary The geometry microbend loss characteristic F μBL_G determined by the following equation (1) regarding the coating layer thickness t p and the secondary coating layer thickness t s, and the following equation (2) regarding the propagation constant difference Δβ, which is a parameter related to the optical characteristics. Optical microbend loss characteristic determined by F μBL_Δβ

And, it was found that the value of the microbend

loss characteristic factor F μBL_GΔβ represented by the following formula (3) has a high correlation with the value of the sandpaper tension winding loss increase. That is, the present inventor has found that the value of the microbend loss characteristic factor has a substantially positive proportional relationship with the value of the increase in sandpaper tension winding loss.
[0065]
　According to Non-Patent Document 5 (K. Kobayashi, et al., “Study of Microbending loss in thin coated fibers and fiber ribbons,” IWCS, pp.386 & # 8211; 392, 1993.) The typical value of the constant μ in 1) is “3”. Therefore, the above equation (1) becomes the following equation (4).

[0066]
　In addition, Non-Patent Document 2 and Non-Patent Document 6 (CD Hussey, et al., “characterization and design of single-mode optical fiber,” Optical and Quantum Electronics, vol. 14, no. 4, pp. 347 & # According to 8211; 358, 1982.), The typical value of the constant p in the above equation (2) is "4". Therefore, the above equation (2) becomes the following equation (5).

[0067]
　Further, as a result of further research, the present inventor found that the value of the microbend loss characteristic factor was 6.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ). It was found that the value of the increase in sandpaper tension winding loss was slightly smaller than 0.6 dB / km. As described above, the value of the microbend loss characteristic factor and the value of the sandpaper tension winding loss increase are generally in a positive proportional relationship with each other. Therefore, by setting the value of the microbend loss characteristic factor of the optical fiber to 6.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less, the required characteristics of the tape slot type cable can be obtained. Microbend loss can be suppressed to the extent that it is satisfied.
[0068]
　As described above, in the optical fiber 10 of the present embodiment, the value of the microbend loss characteristic factor F μBL_GΔβ is 6.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ) or less. Is formed as follows. Therefore, in the optical fiber 10 of the present embodiment, the microbend loss can be suppressed to the extent that the required characteristics of the tape slot type cable are satisfied. Therefore, the optical fiber cable 1 using the optical fiber 10 can exhibit good optical characteristics.
[0069]
　Further, as described above, the optical fiber 10 of the present embodiment, the outer diameter d of the glass portion 13 f to or smaller than 125 [mu] m, the coating thickness t even when or smaller than 60 [mu] m, the glass portion Parameters other than the outer diameter d f and the coating thickness t are adjusted so that the value of the microbend loss characteristic factor F μBL_GΔβ is 6.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less. Therefore, the microbend loss can be suppressed to the extent that the required characteristics of the tape slot type cable are satisfied. Here, as shown in FIG. 3, the outer diameter 2R of the optical fiber 10 s , the outer diameter d of the glass portion f with the, and the coating thickness
t, 2R s = d f + 2t
represented by. Therefore, as described above, the coating thickness t is reduced, and the outer diameter d f of the glass portion is reduced. The diameter of the optical fiber can be reduced by reducing the diameter of the optical fiber. Therefore, by using the optical fiber 10 having such a small diameter and suppressed microbend loss, a tape slot type cable having excellent optical characteristics that realizes an increase in the number of cores and a small size is configured. obtain.
[0070]
(Second Embodiment)
　Next, the second embodiment will be described with reference to FIG. FIG. 4 is a diagram schematically showing a structure having a cross section perpendicular to the longitudinal direction of the optical fiber cable 2 of the present embodiment. The same or equivalent components as those in the first embodiment are designated by the same reference numerals and duplicated description will be omitted unless otherwise specified.
[0071]
　As shown in FIG. 4, the optical fiber cable 2 of the first embodiment is the optical fiber cable 1 of the first embodiment in that a tape core wire 4 having substantially the same configuration as that of the first embodiment is housed therein. It has the same configuration as. However, the optical fiber cable 2 is mainly different from the optical fiber cable 1 in the following points.
[0072]
　The optical fiber cable 1 is a tape slot type cable (RSCC) as described above. On the other hand, as shown in FIG. 4, the optical fiber cable 2 of the present embodiment does not have the holding body 5. That is, the optical fiber cable 2 is a so-called small-diameter high-density cable (UHDC: Ultra-High Density Cable) in which the tape core wire is not accommodated in the slot of the holder but is directly accommodated in the sheath. That is, an accommodation space 3S is formed inside the sheath 3 of the optical fiber cable 2, and a plurality of tape core wires 4 are arranged in the accommodation space 3S. The tensile strength body 6 may be embedded in the sheath 3 of the optical fiber cable 2 at positions facing each other with the center of the optical fiber cable 2 interposed therebetween.
[0073]
　Further, as described above, the tape core wire 4 of the present embodiment has substantially the same configuration as the tape core wire 4 of the first embodiment. However, the value of the microbend loss characteristic factor F μBL_GΔβ of the optical fiber 10 included in the tape core wire 4 of the present embodiment is 4.1 ([GPa -1 · μm −2.5 / rad 8 ] for the reason described later. ] ・ 10-12 ) The following.
[0074]
　Since the small-diameter high-density cable such as the optical fiber cable 2 does not have the holding body 5 as described above and is slotless, the tape core wires 4 are densely arranged in the accommodation space 3S of the sheath 3. Can be done. Therefore, a large number of tape core wires can be accommodated as compared with a tape slot type cable such as the optical fiber cable 1.
[0075]
　On the other hand, in the small-diameter high-density cable, since many tape core wires are densely arranged in one place as described above, a large lateral pressure tends to be applied to the optical fiber as compared with the tape slot type cable. Therefore, it is recommended to use an optical fiber having a smaller microbend loss than the optical fiber used for the tape slot type cable in the small diameter high density cable. From this point of view, the small-diameter high-density cable has a required characteristic that the value of the sandpaper tension winding loss increase is 0.34 dB / km or less.
[0076]
　The present inventor calculated the value of the microbend loss characteristic factor F μBL_GΔβ corresponding to the value of the increase in sandpaper tension winding loss (0.34 dB / km) based on the above equations (3) to (5). As a result, it was found that the value was 4.1 ([GPa- 1 · μm −2.5 / rad 8 ] · 10-12 ). That is, by setting the value of the microbend loss characteristic factor F μBL_GΔβ to 4.1 ([GPa -1・ μm- 2.5 / rad 8 ] ・ 10-12 ) or less, the required characteristics of the small-diameter high-density cable can be obtained. It was found that the microbend loss can be suppressed to the extent that it is satisfied.
[0077]
　As described above, the optical fiber 10 of the present embodiment has a microbend loss characteristic factor F μBL_GΔβ of 4.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ) or less. As described above, the various parameters are adjusted and configured. Therefore, the microbend loss can be suppressed to the extent that the required characteristics of the small-diameter high-density cable are satisfied. Therefore, the optical fiber cable 2 using the optical fiber 10 can exhibit good optical characteristics.
[0078]
　Further, as described above, the optical fiber 10 of the present embodiment, the outer diameter d of the glass portion 13 f to or smaller than 125 [mu] m, the optical fiber 10 the coating thickness t to or less than 60μm fine Even when the diameter is increased, the microbend loss can be suppressed to the extent that the required characteristics of the small diameter high density cable are satisfied. Therefore, by using the optical fiber 10 having a reduced diameter in this way, it is possible to construct a small-diameter high-density cable having excellent optical characteristics that realizes an increase in the number of cores and a reduction in size.
[0079]
　Next, the reason why the outer diameter d f of the glass portion 13 can be reduced, the reason why the coating thickness of the optical fiber 10 can be reduced, the reason why the outer diameter of the optical fiber 10 can be reduced, and the like will be described.
[0080]
　The present inventor performed the following Examples 1 to 48 in order to verify the relationship between the value of the microbend loss characteristic factor F μBL_GΔβ and the value of the sandpaper tension winding loss increase αμBL . The embodiment of the present invention is not limited to Examples 1 to 48.
[0081]
(Examples 1 to 22) The
　present inventor prepares optical fiber samples 1 to 22 in which the above various parameters are changed, and measures the value of sandpaper tension winding loss increase for each sample 1 to 22. , The value of the microbend loss characteristic factor F μBL_GΔβ was calculated based on the above formulas (3) to (5) . The optical fiber of Sample 1 is the optical fiber of Example 1, and the optical fiber of Sample 2 is the optical fiber of Example 2. As described above, the sample numbers of the optical fibers correspond to the numbers of the examples. The optical fiber of sample 8 is an optical fiber generally used for an optical fiber cable constituting a communication infrastructure, and has an outer diameter of a glass portion of 125 μm and a coating thickness of 57.5 μm. An optical fiber such as this sample 8 is sometimes referred to as a "general optical fiber".
[0082]
　The sandpaper tension winding loss increase test was performed as follows. That is, first, sandpaper (SiC having an average particle diameter of 50 μm (for example, model number # 360)) is wound around the bobbin having a body diameter of 380 mm, and one layer of an optical fiber wire is wound around the bobbin at 100 gf. Propagates light with a wavelength of 1550 nm. The transmission loss at this time is measured. After that, the optical fiber wire is unwound from the bobbin, light having a wavelength of 1550 nm is propagated with almost no tension applied, and the transmission loss is measured. Then, the difference between these transmission losses was obtained, and the value of this difference was defined as the sandpaper tension winding loss increase α μBL .
[0083]
　Tables 1 to 5 below show the parameter specifications for each of the samples 1 to 22, the value of the microbend loss characteristic factor F μBL_GΔβ for each of the samples 1 to 22, and the increase in sandpaper tension winding loss for each of the samples 1 to 22. The value of α μBL is shown.
[0084]
　In Tables 1 to 5 below and Tables 7 to 10 described later, the mode field diameter (MFD), cutoff wavelength, macro bend loss, and the like are as follows. The mode field diameter is the mode field diameter of the LP01 mode light when the light having a wavelength of 1310 nm is propagated through the optical fiber.
[0085]
The mode field diameter is determined by the ITU-T recommendation G.I. In 650.1, it is represented by the definition formula of Petermann II (the following formula (6)). Here, E (r) represents the electric field strength at the point where the distance from the central axis of the optical fiber is r.

[0086]
　Further, the cutoff wavelength indicates the minimum wavelength at which the higher-order mode is sufficiently attenuated. This higher-order mode refers to, for example, the LP11 mode. Specifically, it is the minimum wavelength at which the loss in the higher-order mode is 19.3 dB. The cutoff wavelength includes a fiber cutoff wavelength and a cable cutoff wavelength. For example, the ITU-T recommendation G.I. It can be measured by the measuring method described in 650. The cutoff wavelengths shown in Tables 1 to 5 are cable cutoff wavelengths. The MAC value is the ratio of the mode field diameter of light having a wavelength of 1310 nm to the cable cutoff wavelength. If the mode field diameter is 2w and the cable cutoff wavelength is λ cc , it is 2w / λ cc.Is defined as. Further, the macro bend loss is a bending loss caused by light having a wavelength of 1625 nm propagating through the bent portion when the optical fiber is bent with a radius of 10 mm. “/ Turn” in the unit of macrobend loss means “per turn of optical fiber”. The propagation constant difference is the difference between the propagation constant of light having a wavelength of 1550 nm in the waveguide mode and the propagation constant of light having a wavelength of 1550 nm in the radiation mode. In this experiment, the propagation constant of light having a wavelength of 1550 nm in LP01 mode. It is the difference between the propagation constant and the propagation constant in the LP11 mode. The propagation constant is based on the refractive index distribution of the prototype optical fiber, and is based on Non-Patent Document 7 (K. Saitoh and M. Koshiba, “Full-Vectorial Imaginary-Distance Beam Propagation Method Based on a Finite Element Scheme: Application to Photonic Crystal). It was calculated using the two-dimensional finite element method described in Fibers, ”IEEE J. Quant. Elect. Vol. 38, pp. 9 27-933, 2002.). Further, the zero dispersion wavelength refers to a wavelength at which the value of the wavelength dispersion becomes zero. Here, the wavelength dispersion is the sum of the material dispersion and the waveguide dispersion. The zero dispersion slope refers to the rate of change of wavelength dispersion with respect to the wavelength at the zero dispersion wavelength.
[0087]

[0088]

[0089]

[0090]

[0091]

[0092]
　The present inventor has a coordinate system in which the value of the microbend loss characteristic factor F μBL_GΔβ is on the horizontal axis (X-axis) and the value of sandpaper tension winding loss increase αμBL is on the vertical axis (Y-axis). The values of each of the 22 microbend loss characteristic factors F μBL_GΔβ and the sandpaper tension winding loss increase α μBL were plotted. As a result, a scatter plot as shown in FIG. 5 was obtained. When the function was obtained from this scatter plot using the method of least squares, a linear function having a positive slope represented by the following equation (7) was obtained. Moreover, the correlation coefficient of the data of FIG. 5 was 94% or more.

That is, the value of the microbend loss characteristic factor F μBL_GΔβ and the value of the sandpaper tension winding loss increase αμBL have a high correlation. Specifically, the value of the microbend loss characteristic factor F μBL_GΔβ is the sandpaper tension winding. It was found that there is a proportional relationship with the value of loss increase α μBL , which has a generally positive slope.
[0093]
　By the way, as described above, the tape slot type cable (RSCC) has a required characteristic that the value of the sandpaper tension winding loss increase α μBL is 0.60 (dm / km) or less. Further, the small-diameter high-density cable (UHDC) has a required characteristic that the value of the sandpaper tension winding loss increase α μBL is 0.34 (dm / km) or less. Therefore, Table 6 below shows the values ​​of the microbend loss characteristic factor F μBL_GΔβ , the value of sandpaper tension winding loss increase αμBL , the pass / fail of the required characteristics of the tape slot type cable (RSCC), and the small diameter in each of Examples 1 to 22. Shows pass / fail for the required characteristics of high-density cable (UHDC). In Table 6, Y means that the required characteristics are satisfied, and N means that the required characteristics are not satisfied.
[0094]

[0095]
　From Table 6, if the value of the microbend loss characteristic factor F μBL_GΔβ is 6.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less, the sandpaper tension winding loss increase α When the value of μBL is approximately 0.60 or less and the value of the microbend loss characteristic factor F μBL_GΔβ is larger than 6.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ), sand It was found that the value of the paper tension winding loss increase α μBL tends to exceed 0.60. That is, the value of the microbend loss characteristic factor F μBL_GΔβ is 6.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12.) It was found that the required characteristics of the tape slot type cable can be satisfied by adjusting the values ​​of the parameters listed in Tables 1 to 5 above so as to be as follows.
[0096]
　Also, the microbend loss characteristic factor F MyuBL_jiderutabeta value of 4.1 ([GPa -1 · [mu] m -2.5 / rad 8 ] · 10 -12 if) or less, sandpaper tension winding loss increase alpha MyuBL of When the value becomes about 0.34 or less and the value of the microbend loss characteristic factor F μBL_GΔβ becomes larger than 4.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ), the sandpaper It was found that the value of the tension winding loss increase α μBL tended to exceed 0.34. That is, the value of the microbend loss characteristic factor F μBL_GΔβ is 4.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12.) It was found that by adjusting the values ​​of the parameters listed in Tables 1 to 5 above so as to be as follows, the required characteristics of the small-diameter high-density cable can be satisfied in addition to the required characteristics of the tape slot type cable. ..
[0097]
　Specifically, among the samples 1 to 22, the samples satisfying the required characteristics of the tape slot type cable were the samples excluding the samples 1, 5, and 6. Further, the samples satisfying the required characteristics of the small-diameter high-density cable in addition to the required characteristics of the tape slot type cable were the samples excluding Examples 1, 2, 5, 6, 13, and 18.
[0098]
　Further, among the samples satisfying at least the required characteristics of the tape slot type cable in Samples 1 to 22, the samples other than Samples 4, 7, and 8 are smaller than the outer diameter (125 μm) of the glass portion of a general optical fiber. It has an outer diameter of 80 μm or 90 μm glass part. Specifically, Samples 2, 3, 9 to 14, and 18 to 22 have an outer diameter of a glass portion of 80 μm, and Samples 15 to 17 have an outer diameter of a glass portion of 90 μm. That is, by adjusting the parameters as in Samples 2, 3, and 9 to 22, light that at least satisfies the required characteristics of the tape slot type cable and has an outer diameter of the glass portion smaller than that of a general optical fiber. It has been found that fibers can be formed.
[0099]
　Further, it was found that the samples satisfying at least the required characteristics of the tape slot type cable in Samples 1 to 22 have a coating thickness smaller than the coating thickness of a general optical fiber (approximately 60 μm) except for Sample 8. rice field. Specifically, Samples 3, 9, and 12 have a coating thickness of 42.0 μm, and Samples 10, 11, 13, 14, 18, and 20-22 have a coating thickness of 36.5 μm. It was found that Sample 2 had a coating thickness of 36.0 μm, Samples 15 to 17 had a coating thickness of 34.5 μm, and Samples 4 and 7 had a coating thickness of 34.0 μm. That is, by adjusting the parameters as in Samples 2 to 4, 7, and 9 to 22, light that at least satisfies the required characteristics of the tape slot type cable and has a coating thickness smaller than that of a general optical fiber. It has been found that fibers can be formed.
[0100]
　As described above, among the samples 1 to 22, the samples other than the samples 1, 5, 6 and 8 satisfy at least the required characteristics of the tape slot type cable and are outside the glass portion smaller than the general optical fiber. It was found to have a diameter and a coating thickness. By forming both the outer diameter and the coating thickness of the glass portion to be smaller than the outer diameter and the coating thickness of the glass portion of a general optical fiber, it is possible to effectively reduce the diameter of the optical fiber.
[0101]
　Further, the optical fibers of Samples 1 to 22 have an MFD of 7.6 μm or more. If the MFD is too small, a mismatch of the MFD when connected to a general-purpose optical fiber may occur. However, if the MFD of the optical fiber is 7.6 μm or more, the mismatch of the MFD when connected to the general-purpose optical fiber can be reduced. Therefore, the occurrence of connection loss can be effectively suppressed.
[0102]
　Further, the optical fibers of Samples 5 to 8 satisfy the international standard ITU-. G.657.A1. That is, the MFD having a wavelength of 1310 nm is 8.2 μm or more and 9.6 μm or less, the cable cutoff wavelength is 1260 nm or less, the zero dispersion wavelength is 1300 nm or more and 1324 nm or less, and the zero dispersion slope is 0.073 ps / km / nm. It is 0.092 ps / km / nm or less, and the macrobend loss at a wavelength of 1625 nm when bent at a radius of 10 mm is 1.5 dB / turn or less. Further, the optical fibers of Samples 1 to 4 satisfy ITU-T G657.A2. That is, the MFD having a wavelength of 1310 nm is 8.2 μm or more and 9.6 μm or less, the cable cutoff wavelength is 1260 nm or less, the zero dispersion wavelength is 1300 nm or more and 1324 nm or less, and the zero dispersion slope is 0.073 ps / km / nm. It is 0.092 ps / km / nm or less, and the macrobend loss at a wavelength of 1625 nm when bent at a radius of 10 mm is 0.2 dB / turn or less. Further, the optical fibers of Samples 13 to 15 satisfy ITU-T G657.B3. That is, the MFD having a wavelength of 1310 nm is 8.26 μm or more and 9.6 μm or less, the cable cutoff wavelength is 1260 nm or less, the zero dispersion wavelength is 1300 nm or more and 1324 nm, and the zero dispersion slope is 0.073 ps / km / nm or more. It is 0.092 ps / km / nm or less, and the macrobend loss at a wavelength of 1625 nm when bent at a radius of 10 mm is 0.1 dB / turn or less.
[0103]
(Examples 23 to 28) Further
　, the present inventor has the same optical characteristics as the samples 16, 17, and 19, specifically, the same MFD, cable cutoff wavelength, MAC value, and macrobend loss as those of these samples. It has (bending loss), propagation constant difference, zero dispersion wavelength, and zero dispersion slope, has the same primary coating layer thickness and secondary coating layer thickness as sample 19, and has an outer diameter of the glass part of 65 μm. The values ​​of the microbend loss characteristic factor F μBL_GΔβ of the optical fiber samples 23 to 28 adjusted as shown in Table 7 below were obtained.
[0104]

[0105]
　As shown in Table 7, each of the samples 23 to 28 has an outer diameter of a glass portion of 65 μm and a coating thickness of 42 μm. The values ​​of the microbend loss characteristic factor F μBL_GΔβ of samples 25 to 28 are all 6.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less, and samples 25 to 28 are tapes. It was found that the required characteristics of the slot type cable were satisfied. In addition, the values ​​of the microbend loss characteristic factor F μBL_GΔβ of the samples 27 and 28 are 4.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ) or less, and the samples 27 and 28 are tapes. It was found that in addition to the required characteristics of the slot type cable, the required characteristics of the small diameter high density cable were satisfied. Similar to the samples 25 to 28, the samples 23 and 24 have an outer diameter of the glass portion of 65 μm and a coating layer thickness of 42 μm, but the value of the microbend loss characteristic factor F μBL_GΔβ is 6.1 ([[ GPa -1 · μm -2.5 / rad 8] ・ 10-12 ) was exceeded, and neither the required characteristics of the tape slot type cable nor the required characteristics of the small diameter high density cable were satisfied.
[0106]
(Examples 29 to 36) Further
　, the present inventor has the same optical characteristics as the samples 15, 16, 17, and 19, specifically, the same MFD, cable cutoff wavelength, MAC value, and macro as those of these samples. Light having bend loss, propagation constant difference, zero dispersion wavelength, and zero dispersion slope, having the same primary coating layer thickness and secondary coating layer thickness as sample 19, and having an outer diameter of 70 μm in the glass portion. Assuming a fiber, the value of the microbend loss characteristic factor F μBL_GΔβ of the optical fiber samples 29 to 36 adjusted as shown in Tables 8 and 9 was determined.
[0107]

[0108]

[0109]
　As shown in Tables 8 and 9, each of the samples 29 to 36 has an outer diameter of a glass portion of 70 μm and a coating thickness of 42 μm. The values ​​of the microbend loss characteristic factor F μBL_GΔβ of samples 26 to 28 are all 6.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less, and samples 29 to 36 are tapes. It was found that the required characteristics of the slot type cable were satisfied. In addition, the values ​​of the microbend loss characteristic factor F μBL_GΔβ of samples 31, 33, 35 and 36 are all 4.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less. It was found that the samples 31, 33, 35 and 36 satisfy the required characteristics of the small diameter high density cable in addition to the required characteristics of the tape slot type cable.
[0110]
(Examples 37 to 42) Further
　, the present inventor has the same optical characteristics as the samples 15, 17, and 19, specifically, the same MFD, cable cutoff wavelength, MAC value, and macrobend loss as those of these samples. An optical fiber having the same propagation constant difference, zero dispersion wavelength, and zero dispersion slope, the same primary coating layer thickness and secondary coating layer thickness as sample 19, and an outer diameter of a glass portion of 75 μm. Assuming, the values ​​of the microbend loss characteristic factor F μBL_GΔβ of the optical fiber samples 37 to 42 adjusted as shown in Table 10 below were obtained.
[0111]

[0112]
　As shown in Table 10, each of the samples 37 to 42 has an outer diameter of a glass portion of 75 μm and a coating thickness of 42 μm. The values ​​of the microbend loss characteristic factor F μBL_GΔβ of samples 37 to 42 are all 4.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less, and samples 37 to 42 are tapes. It was found that in addition to the required characteristics of the slot type cable, the required characteristics of the small diameter high density cable were satisfied.
[0113]
(Examples 43 to 48) Further
　, the present inventor has the same optical characteristics as the samples 15, 17, and 19, specifically, the same MFD, cable cutoff wavelength, MAC value, and macrobend loss as those of these samples. An optical fiber having the same propagation constant difference, zero dispersion wavelength, and zero dispersion slope, the same primary coating layer thickness and secondary coating layer thickness as sample 19, and an outer diameter of 80 μm in the glass portion. Assuming, the values ​​of the microbend loss characteristic factor F μBL_GΔβ of the optical fiber samples 43 to 48 adjusted as shown in Table 11 below were obtained.
[0114]

[0115]
　As shown in Table 11, each of the samples 45 to 48 has an outer diameter of the glass portion of 80 μm, an outer diameter of the secondary coating layer of 125 μm, and a thickness of the coating layer of 22.5 μm. The values ​​of the microbend loss characteristic factor F μBL_GΔβ of samples 45 to 48 are all 6.1 ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) or less, and samples 45 to 48 are tapes. It was found that the required characteristics of the slot type cable were satisfied. The value of the microbend loss characteristic factor F μBL_GΔβ of sample 47 is 4.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ) or less, and sample 47 is of a tape slot type cable. In addition to the required characteristics, it was found to meet the required characteristics of the small diameter high density cable. Similar to the samples 45 to 48, the samples 43 and 44 have an outer diameter of the glass portion of 80 μm, an outer diameter of the secondary coating layer of 125 μm, and a thickness of the coating layer of 22.5 μm, but microbend. The value of the loss characteristic factor F μBL_GΔβ is 6.1 ([GPa -1 · μm] -2.5 / rad 8 ] · 10-12 ) was exceeded, and neither the required characteristics of the tape slot type cable nor the required characteristics of the small diameter high density cable were satisfied.
[0116]
　Although the present invention has been described above by taking the above-described embodiment as an example, the present invention is not limited thereto.
[0117]
　For example, in the first and second embodiments, the example in which the secondary coating layer is the outermost layer of the optical fiber has been described. However, even when a colored layer is provided as a third coating layer on the outer periphery of the secondary coating layer, the secondary coating layer and the colored layer are used as long as the Young's modulus of the colored layer is not significantly different from the Young's modulus of the secondary coating layer. It is possible to apply it to the present invention by regarding it as a second coating layer, that is, a secondary coating layer.
[0118]
　According to the present invention, an optical fiber capable of suppressing microbend loss is provided, and can be used in a field such as a communication infrastructure.
The scope of the claims
[Claim 1]
　An optical fiber including a core and a glass portion containing a clad surrounding the core, a primary coating layer covering the clad, and a secondary coating layer covering the
　primary coating layer , wherein the spring coefficient of the primary coating layer is κs (MPa). The bending rigidity of the glass portion is H f (MPa · μm 4 ), the deformation resistance of the secondary coating layer is D 0 (MPa), and the bending rigidity of the secondary coating layer is H 0 (MPa · μm 4 ). the Young's modulus of the glass portion E g (GPa), the Young's modulus of the primary coating layer E p (MPa), the Young's modulus of the secondary coating layer E s (MPa), the outer diameter of the glass portion d f ( μm), the radius of the outer peripheral surface of the primary coating layer is R p (μm), the radius of the outer peripheral surface of the secondary coating layer is R s (μm), the thickness of the primary coating layer is t p (μm), and When the thickness of the secondary coating layer is t s (μm),

The geometry microbend loss characteristic F μBL_G ([GPa -1 · μm -2.5 / rad 8 ] · 10-12 ) of the
optical fiber represented by, and the propagation constant in the waveguide mode propagating the optical fiber. When the difference from the propagation constant in the radiation mode is the propagation constant difference Δβ (rad / m),

the optical microbend loss characteristic F μBL_Δβ (1 / (rad / μm) 8 ) of the optical fiber represented by The value of the microbend

loss characteristic factor F μBL_GΔβ ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ) represented by is 6.1 ([GPa -1 · μm -2) .5 / rad 8 ] ・ 10-12)
An optical fiber characterized by the following .
[Claim 2]
The optical fiber according to claim 1, 　wherein the value of the microbend loss characteristic factor is 4.1 ([GPa -1 · μm −2.5 / rad 8 ] · 10-12 ) or less
.
[Claim 3]

The optical fiber according to claim 1 or 2, 　wherein the coating thickness obtained by adding the thickness of the primary coating layer and the thickness of the secondary coating layer is 42.0 μm or less .
[Claim 4]

The optical fiber according to claim 3, 　wherein the coating thickness is 38.0 μm or less .
[Claim 5]

The optical fiber according to claim 4, 　wherein the coating thickness is 36.5 μm or less .
[Claim 6]

The optical fiber according to claim 5, 　wherein the coating thickness is 34.5 μm or less .
[Claim 7]

The optical fiber according to claim 6, 　wherein the coating thickness is 34.0 μm or less .
[Claim 8]

The optical fiber according to any one of claims 3 to 7, 　wherein the outer diameter of the glass portion is 65 μm or more and 100 μm or less .
[Claim 9]

The optical fiber according to claim 8, 　wherein the outer diameter of the glass portion is 90 μm or less .
[Claim 10]

The optical fiber according to claim 9, 　wherein the outer diameter of the glass portion is 80 μm or less .
[Claim 11]

The optical fiber according to claim 10, 　wherein the outer diameter of the glass portion is 75 μm or less .
[Claim 12]

The optical fiber according to claim 11, 　wherein the outer diameter of the glass portion is 70 μm or less .
[Claim 13]
　The mode field diameter of light at a wavelength of 1310 nm is 7.6 μm or more and 8.7 μm or less, the cable cutoff wavelength is 1260 nm or less, the zero dispersion wavelength is 1300 nm or more and 1324 nm or less, and the zero dispersion slope is 0.073 ps / km.
The optical fiber according to any one of claims 3 to 11, wherein the optical fiber is / nm or more and 0.092 ps / km / nm .
[Claim 14]

The optical fiber according to claim 13, wherein the 　macrobend loss at a wavelength of 1625 nm when bent at a radius of 10 mm is 1.5 dB / turn or less .
[Claim 15]

The optical fiber according to claim 13, wherein the 　macrobend loss at a wavelength of 1625 nm when bent at a radius of 10 mm is 0.2 dB / turn or less .
[Claim 16]

The optical fiber according to claim 13, wherein the 　macrobend loss at a wavelength of 1625 nm when bent at a radius of 10 mm is 0.1 dB / turn or less .