Patent Description:
The present application claims priority from <CIT>.

<CIT> and <CIT> disclose an optical fiber ribbon in which a connecting portion at which adjacent optical fibers are connected to each other and a non-connecting portion at which adjacent optical fibers are not connected to each other are intermittently provided in a longitudinal direction between a part or all of the optical fibers.

A further example of the prior art can be found in document <CIT>.

An optical fiber ribbon according to an aspect of the present invention is defined in claim <NUM>.

An optical fiber cable according to an aspect of the present invention is defined in claim <NUM>.

A connector-equipped optical fiber cord according to an aspect of the present invention is defined in claim <NUM>.

In order to further increase a density of an optical fiber cable, an optical fiber ribbon using an optical fiber having a core wire diameter smaller than <NUM> in the related art may be used. When a bending pressure is generated in a direction (width direction) in which the optical fiber ribbons are arranged side by side in the optical fiber cable, bending strain in the optical fibers particularly positioned at an endmost end of the optical fiber ribbons increases. A thin optical fiber has low rigidity. Therefore, a transmission loss may increase due to the optical fibers meandering in the optical fiber cable. In particular, when the number of optical fiber ribbons increases, the transmission loss may significantly increase.

An object of the present disclosure is to provide an optical fiber ribbon, an optical fiber cable, and a connector-equipped optical fiber cord that prevent an increase in transmission loss.

According to the present disclosure, it is possible to provide an optical fiber ribbon, an optical fiber cable, and a connector-equipped optical fiber cord that can prevent an increase in transmission loss.

First, embodiments of the present disclosure will be listed and described.

In an optical fiber ribbon according to an aspect of the present disclosure,.

When the optical fiber ribbon is mounted on an optical fiber cable, the optical fiber cable may be bent and a bending pressure may be applied thereto. According to the optical fiber ribbon having the above-described configuration, even when the optical fibers (in particular, optical fibers at a position where a curvature radius is the largest when the optical fiber ribbon is bent) constituting the optical fiber ribbon meander in the above-described case, the bending strain is less likely to occur. As a result, the increase in transmission loss may be reduced.

Optical fibers at a position where a curvature radius is the largest is, for example, optical fibers at an endmost end of the optical fiber ribbon that bends outward when the optical fiber ribbons bend in a direction in which the optical fiber ribbons are arranged in parallel (such that one end of the optical fiber is on an inner side and the other end of the optical fiber is on an outer side while maintaining the ribbon in a planar state).

In addition, in a case where the optical fiber ribbons bend in the direction in which the optical fiber ribbons are arranged in parallel at a bending radius R (a radius of a curve line passing through a center in the direction in which the optical fiber ribbons are arranged in parallel), when a distance from a curve line passing through a center to the optical fibers at the endmost end of the optical fiber ribbon that bends outward is r, the bending strain S in the optical fibers at the endmost end is expressed as follows, <MAT>.

When the optical fiber ribbons bend in the direction along which the optical fiber is arranged in parallel, the bending strain S becomes the largest.

(<NUM>) The optical fiber ribbon described above may be an intermittent connection-type optical fiber ribbon in which a connecting portion at which adjacent optical fibers are connected to each other and a non-connecting portion at which adjacent optical fibers are not connected to each other are intermittently provided in a longitudinal direction between a part or all of the optical fibers.

According to the optical fiber ribbon having the above-described configuration, when the optical fiber ribbon is mounted on an optical fiber cable, the optical fiber ribbon is easily gathered in a manner of being rounded in a cross-sectional view. That is, the distance r from the curve line passing through the center to the optical fibers at the endmost end of the optical fiber ribbon tends to be smaller than the distance r when the optical fiber ribbons bend in the parallel direction. Accordingly, since the bending strain S is reduced, the increase in transmission loss of the optical fibers constituting the optical fiber ribbon may be further reduced.

(<NUM>) In the optical fibers, when a bending diameter ϕ is <NUM> with <NUM> turn, a bending loss at a wavelength of <NUM> may be <NUM> dB or less, and when the bending diameter ϕ is <NUM> with <NUM> turns, the bending loss at the wavelength of <NUM> may be <NUM> dB or less.

According to the optical fiber ribbon having the above-described configuation, by using the optical fibers having a small bending loss, the increase in transmission loss may be more reliably reduced.

(<NUM>) In the optical fibers at both ends of the optical fiber ribbon in the parallel direction, when the bending diameter ϕ is <NUM> with <NUM> turn, the bending loss at the wavelength of <NUM> is <NUM> dB or less, and when the bending diameter ϕ is <NUM> with <NUM> turns, the bending loss at the wavelength of <NUM> is <NUM> dB or less.

Since the increase in transmission loss due to the meandering of the optical fibers becomes more remarkable in the optical fibers at both ends of the optical fiber ribbon, by using the optical fibers having a smaller bending loss for the optical fibers at both ends of the optical fiber ribbon, the increase in transmission loss can be more reliably reduced.

(<NUM>) When an outer diameter of the optical fibers is set to D, the number of optical fibers is set to N, and a thickness of a connecting resin covering peripheries of the optical fibers at both ends of the optical fiber ribbon is set to RT, a width W of the optical fiber ribbon in the parallel direction may be equal to or less than a value calculated by following expression, <MAT>.

By reducing the width W of the optical fiber ribbon in the parallel direction, the bending strain S may be reduced.

(<NUM>) The number of optical fibers may be a multiple of eight.

Since the optical fibers are generally used in units of eight optical fibers, versatility is easily obtained according to the above-described configuration.

(<NUM>) The optical fibers each includes a glass fiber, and two coating layers covering a periphery of the glass fiber,.

According to the optical fiber ribbon having the above-described configuation, since the Young's modulus of the primary resin is lower than that of the optical fiber in the related art and the Young's modulus of the secondary resin is higher than that of the optical fiber in the related art, a shell effect is improved, and lateral pressure resistance may be improved.

(<NUM>) The optical fiber ribbon includes one layer or more of the connecting resin, and
a Young's modulus of an outermost connecting resin at <NUM> may be <NUM> MPa or less, and a breaking elongation may be <NUM>% or more.

According to the optical fiber ribbon having the above-described configuation, since the Young's modulus of the outermost connecting resin at <NUM> is <NUM> MPa or less, and the breaking elongation is <NUM>% or more, the optical fiber ribbon is easy to deform, and the bending strain may be alleviated.

An optical fiber cable according to an aspect of the present disclosure is.

According to the optical fiber ribbon having the above-described configuation, even if the optical fiber cable in which the optical fiber ribbons having an optical fiber density of <NUM> optical fibers/mm<NUM> or more are mounted at a high density, when the optical fibers constituting the optical fiber ribbon meander in the optical fiber cable, the bending strain is less likely to occur, and thus, the increase in transmission loss may be reduced.

In addtion, a connector-equipped optical fiber cord according to an aspect of the present disclosure includes
(<NUM>) an optical fiber cord including the optical fiber ribbon according to any one of (<NUM>) to (<NUM>) covered with a sheath, and a connector connected to the optical fiber cord.

According to the connector-equipped optical fiber cord, when the optical fibers constituting the optical fiber ribbon included in the optical fiber cord meander, the bending strain is less likely to occur, and thus, the increase in transmission loss may be reduced.

Specific examples of an optical fiber ribbon, an optical fiber cable, and a connector-equipped optical fiber cord according to an embodiment of the present disclosure will be described below with reference to the drawings.

The invention is not limited to these examples, and is defined by the scope of the claims, and is intended to include all modifications within the scope the claims.

<FIG> is a cross-sectional view perpendicular to a longitudinal direction of an optical fiber ribbon <NUM> (1A, 1B) according to a first embodiment.

As shown in <FIG>, in the optical fiber ribbon <NUM>, sixteen optical fibers <NUM> (11A to 11P) are arranged in parallel. The optical fibers 11A to 11P are arranged in a state in which adjacent optical fibers are at least partially in contact with each other, and the entire optical fibers 11A to 11P are collectively covered and connected by a connecting resin <NUM>.

The optical fibers <NUM> each includes, for example, a glass fiber <NUM> including a core and cladding, and two coating layers covering a periphery of the glass fiber <NUM>. An inner coating layer of the two coating layers on an inner side is formed of a primary resin <NUM>. An outer coating layer of the two coating layers on an outer side is formed of a secondary resin <NUM>. A colored layer or the like may be provided outside the two coating layers.

A soft resin having a relatively low Young's modulus is used in the primary resin <NUM> that is in contact with the glass fiber <NUM> as a buffer layer. Further, a hard resin having a relatively high Young's modulus is used in the secondary resin <NUM> as a protective layer. The Young's modulus of the primary resin <NUM> at, for example, <NUM> is <NUM> MPa or less. The Young's modulus of the secondary resin <NUM> at, for example, <NUM> is <NUM> MPa or more, and preferably <NUM> MPa or more. The primary resin <NUM> and the secondary resin <NUM> are formed of an ultraviolet curable resin, a thermosetting resin, and the like.

In the optical fibers <NUM>, when a bending diameter ϕ is <NUM> with <NUM> turn, a bending loss at, for example, a wavelength of <NUM> is <NUM> dB or less, and when the bending diameter ϕ is <NUM> with <NUM> turns, the bending loss at the wavelength of <NUM> is <NUM> dB or less. In the optical fibers 11A, 11P disposed at both ends of the optical fiber ribbon <NUM> in a direction in which the optical fibers <NUM> are arranged in parallel, when the bending diameter ϕ is <NUM> with <NUM> turn, the bending loss at, for example, the wavelength of <NUM> is <NUM> dB or less, and when the bending diameter ϕ is <NUM> with <NUM> turn, the bending loss at the wavelength of <NUM> is <NUM> dB or less.

The connecting resin <NUM> is provided in a manner of forming a shape having recessed portions between the optical fibers <NUM> corresponding to depressions formed between adjacent optical fibers <NUM>. A Young's modulus of the connecting resin <NUM> at a room temperature (for example, <NUM>) is <NUM> MPa or less. Further, a breaking elongation of the connecting resin <NUM> at a room temperature (for example, <NUM>) is <NUM>% or more. As the connecting resin <NUM>, an ultraviolet curable resin, a thermosetting resin, or the like is used. In addition, the connecting resin <NUM> is preferably formed of a resin containing a silicon-based lubricant, in order to reduce friction with other members disposed around the connecting resin <NUM>. In addition, it is preferable that the connecting resin <NUM> is a resin having good peelability, in order to facilitate an operation of separating single optical fiber from the optical fibers 11A to 11P.

In the first embodiment, an outer diameter D1 of the optical fibers <NUM> (11A to 11P) is in a range of <NUM> or more and <NUM> or less. Each thickness RT1 of the connecting resin <NUM> covering peripheries of the optical fibers 11A, 11P at both ends of the optical fiber ribbon <NUM> (1A, 1B) is, for example, <NUM>.

For example, when an average value of the outer diameters D1 of the optical fibers <NUM> is <NUM>, a center-to-center distance P1 between the adjacent optical fibers <NUM> is <NUM>, a thickness T1 of the optical fiber ribbon <NUM> is <NUM>, and a width W1 of the optical fiber ribbon <NUM> in the direction in which the optical fibers <NUM> are arranged in parallel is <NUM>.

Further, when the outer diameter D1 is set to an upper limit value <NUM> of the range, the width W1 is <NUM>.

In the first embodiment, the D1 corresponds to D of the present disclosure, and the RT1 corresponds to RT of the present disclosure.

<FIG> is a plan view showing an example of the optical fiber ribbon <NUM> (optical fiber ribbon 1A).

As shown in <FIG>, the optical fiber ribbon 1A is an intermittent connection-type optical fiber ribbon in which a connecting portion <NUM> in which adjacent optical fibers are connected to each other and a non-connecting portion <NUM> in which adjacent optical fibers are not connected to each other are intermittently provided in the longitudinal direction for each of two optical fibers. In the optical fiber ribbon 1A, the connecting portions <NUM> and the non-connecting portions <NUM> are provided between the optical fibers 11B and 11C, between the optical fibers 11D and 11E, between the optical fibers 11F and <NUM>, between the optical fibers <NUM> and 11I, between the optical fibers 11J and <NUM>, between the optical fibers <NUM> and <NUM>, and between the optical fibers 11N and 11O.

<FIG> shows the optical fiber ribbon 1A in a state in which the non-connecting portions <NUM> are expanded in the direction in which the optical fibers 11A to 11P are arranged in parallel. In addition, <FIG> shows a cross-sectional view taken along, for example, a line A-A of the optical fiber ribbon 1A in a state in which the non-connecting portions <NUM> are not expanded.

<FIG> is a plan view showing another example of the optical fiber ribbon <NUM> (optical fiber ribbon 1B).

As shown in <FIG>, the optical fiber ribbon 1B is an intermittent connection-type optical fiber ribbon in which the connecting portions <NUM> in which adjacent optical fibers are connected to each other and the non-connecting portions <NUM> in which adjacent optical fibers are not connected to each other are intermittently provided in the longitudinal direction for all of the optical fibers. The configuration of the optical fiber ribbon 1B is the same as the configuration of the optical fiber ribbon 1A described above except for the positions where the connecting portions <NUM> and the non-connecting portions <NUM> are provided.

<FIG> is a cross-sectional view perpendicular to a longitudinal direction of an optical fiber ribbon <NUM> according to a second embodiment.

As shown in <FIG>, the optical fiber ribbon <NUM> includes sixteen optical fibers <NUM> (21A to 21P).

The sixteen optical fibers 21Ato 21P are provided as eight double-core optical fiber ribbons <NUM> (28A to <NUM> in this example) integrated by bringing two optical fibers <NUM> into contact with each other. The double-core optical fiber ribbon 28A includes optical fibers 21A and 21B, and similarly, the double-core optical fiber ribbon 28B includes optical fibers 21C and 21D, the double-core optical fiber ribbon 28C includes optical fibers 21E and 21F, the double-core optical fiber ribbon 28D includes optical fibers <NUM> and <NUM>, the double-core optical fiber ribbon 28E includes optical fibers 21I and 21J, the double-core optical fiber ribbon 28F includes optical fibers <NUM> and <NUM>, the double-core optical fiber ribbon <NUM> includes optical fibers <NUM> and 21N, and the double-core optical fiber ribbon <NUM> includes optical fibers <NUM> and 21P.

The double-core optical fiber ribbons 28A to <NUM> are integrated by applying a connecting resin 25a to surfaces of the two optical fibers 21A and 21B, 21C and 21D, 21E and 21F, <NUM> and <NUM>, 21I and 21J, <NUM> and <NUM>, <NUM> and 21N, and <NUM> and 21P, which are arranged in contact with each other.

The optical fiber ribbon <NUM> is integrally formed by arranging eight double-core optical fiber ribbons 28A to <NUM> in parallel and collectively being covered with the connecting resin 25b.

As described above, the connecting resin <NUM> is formed of two layers including the inner connecting resin 25a covering peripheries of the two optical fibers <NUM> arranged in contact with each other and an outer connecting resin 25b covering periphery of the inner connecting resin 25a. In the connecting resin <NUM>, a Young's modulus of the outer connecting resin 25b as an outermost layer at a room temperature (for example, <NUM>) is <NUM> MPa or less, and a breaking elongation at a room temperature (for example, <NUM>) is <NUM>% or more. Other configurations of the connecting resin <NUM> are the same as those of the connecting resin <NUM> of the optical fiber ribbon 1A.

The optical fibers <NUM> each includes a glass fiber <NUM>, a primary resin <NUM>, and a secondary resin <NUM>. Configurations of the glass fiber <NUM>, the primary resin <NUM>, and the secondary resin <NUM> are the same as the configurations of the glass fiber <NUM>, the primary resin <NUM>, and the secondary resin <NUM> in the optical fiber ribbon 1A according to the first embodiment. In addition, a bending loss of the optical fibers <NUM> is the same as the bending loss of the optical fibers <NUM> of the optical fiber ribbon 1A.

An outer diameter D2 of the optical fibers <NUM> (21A to 21P) in the second embodiment is in the range of <NUM> or more and <NUM> or less, similarly to the outer diameter of the optical fibers <NUM> according to the first embodiment. Each thickness RT2 of the connecting resin <NUM> covering peripheries of the optical fibers 21A, 21P at both ends of the optical fiber ribbon <NUM> is, for example, <NUM>.

For example, when an average value of the outer diameters D2 of the optical fibers <NUM> is <NUM>, a center-to-center distance P21 between the optical fibers <NUM> constituting each of the double-core optical fiber ribbons <NUM> is <NUM>, and a center-to-center distance P22 between the optical fibers <NUM> of the adjacent double-core optical fiber ribbons <NUM> is <NUM>. In this case, a thickness T2 of the optical fiber ribbon <NUM> is <NUM>, and a width W2 of the optical fiber ribbon <NUM> is <NUM>.

Further, when the outer diameter D2 is set to an upper limit value <NUM> of the range, the width W2 of the optical fiber ribbon <NUM> is <NUM>.

The center-to-center distance P21 is a center-to-center distance between the optical fibers 21A and 21B, 21C and 21D, 21E and 21F, <NUM> and <NUM>, 21I and <NUM>, <NUM> and <NUM>, <NUM> and 21N, and <NUM> and 21P in <FIG>.

The center-to-center distance P22 is a center-to-center distance between the optical fibers 21B and 21C, 21D and 21E, 21F and <NUM>, <NUM> and <NUM>, 21J and <NUM>, <NUM> and <NUM>, and 21N and <NUM> in <FIG>.

In the second embodiment, the D2 corresponds to the D of the present disclosure, and the RT2 corresponds to the RT of the present disclosure.

The optical fiber ribbon <NUM> is an intermittent connection-type optical fiber ribbon in which the connecting portion <NUM> in which adjacent optical fibers <NUM> are connected to each other and the non-connecting portion <NUM> in which adjacent double-core optical fiber ribbons <NUM> are not connected to each other are intermittently provided in the longitudinal direction for each double-core optical fiber ribbon <NUM>.

<FIG> is a cross-sectional view perpendicular to a longitudinal direction of an optical fiber ribbon <NUM> according to a third embodiment. <FIG> is a plan view of the optical fiber ribbon <NUM>. <FIG> shows the optical fiber ribbon <NUM> in a state in which non-connecting portions <NUM> are expanded in a direction in which optical fibers 31A to 31P are arranged in parallel. In addition, <FIG> is the cross-sectional view of the optical fiber ribbon <NUM> taken along a line B-B in a state in which the non-connecting portions <NUM> are closed.

As shown in <FIG> and <FIG>, the optical fiber ribbon <NUM> includes sixteen optical fibers <NUM> (31A to 31P). As shown in <FIG>, the optical fiber ribbon <NUM> is an intermittent connection-type optical fiber ribbon in which connecting portions <NUM> in which adjacent optical fibers are connected to each other and the non-connecting portions <NUM> in which adjacent optical fibers are not connected to each other are intermittently provided in the longitudinal direction for all of the optical fibers. The connecting portions <NUM> of the optical fiber ribbon <NUM> are formed of a connecting resin 35b.

As shown in <FIG>, the sixteen optical fibers 31A to 31P are arranged in parallel in a state in which adjacent optical fibers <NUM> are spaced apart from each other by a certain distance. Accordingly, the optical fibers <NUM> arranged in the state in which adjacent optical fibers <NUM> are spaced apart from each other by the certain distance are connected to each other by a connecting resin 35a provided in a manner of covering a periphery of each optical fiber <NUM> and the connecting resin 35b provided in a manner of filling a gap between adjacent optical fibers. The connecting resin 35b constitutes a bridge portion that bridges the adjacent optical fibers <NUM>.

As described above, the optical fiber ribbon <NUM> is integrated by connecting the optical fibers arranged in parallel and spaced apart from each other by the certain distance by the connecting resins 35a, 35b.

Young's moduli, breaking elongations, and other configurations of the connecting resins 35a, 35b are the same as those of the connecting resin <NUM> of the optical fiber ribbon 1A.

An outer diameter D3 of the optical fibers <NUM> (31A to 31P) in the third embodiment is in the range of <NUM> or more and <NUM> or less, similarly to the outer diameters of the optical fibers <NUM> according to the first embodiment and the optical fibers <NUM> according to the second embodiment. Each thickness RT3 of the connecting resin 35a covering peripheries of the optical fibers 31A, 11P at both ends of the optical fiber ribbon <NUM> is, for example, <NUM>.

In the third embodiment, a center-to-center distance P3 between adjacent optical fibers <NUM> is approximately <NUM> in any case in which the outer diameter D3 is in the range of <NUM> or more and <NUM> or less. Therefore, a width of the connecting resin 35b provided between adjacent optical fibers <NUM> (a length in a direction in which the optical fibers <NUM> are arranged in parallel) varies depending on a value of the outer diameter D3 of the optical fibers <NUM>.

When the outer diameter D3 of the optical fibers <NUM> is set to an upper limit value <NUM> of the range, a width W3 of the optical fiber ribbon <NUM> is <NUM>.

In the third embodiment, the D3 corresponds to the D of the present disclosure, and the RT3 corresponds to the RT of the present disclosure.

In each of the embodiments, the optical fiber ribbon constituted by sixteen optical fibers is described, but the optical fiber ribbon according to the present disclosure may be formed of <NUM> or more and <NUM> or less optical fibers.

Since the optical fiber is generally used in units of eight optical fibers in many cases, the number of optical fibers may be a multiple of eight, such as, <NUM>, <NUM>, <NUM>, and <NUM>.

The optical fiber ribbon according to the present disclosure is not limited to the intermittent connection-type optical fiber ribbon.

When an optical fiber cable on which the optical fiber ribbons are mounted with a high density is bent, a bending pressure is applied to the mounted optical fiber ribbons. The bending pressure becomes maximum when the optical fiber ribbons are bent in a width direction (the direction in which the optical fibers are arranged in parallel), strain due to the bending occurs in each of the optical fibers by the bending pressure, and an increase in transmission loss due to the bending loss may occur.

When the optical fiber ribbons are bent in the direction in which the optical fibers are arranged in parallel, and with reference to a bending strain of an optical fiber arranged in a center of the optical fiber ribbons in the parallel direction, as the optical fiber is arranged away from the center, the strain (hereinafter, referred to as bending strain) generated when the optical fiber ribbons are bent increases. Since a tape width of the optical fiber ribbon increases as the number of optical fibers increases, the bending strain generated in the optical fibers arranged at both ends of the optical fiber ribbon increases as the number of optical fibers increases. When the bending strain generated in the optical fibers arranged at both ends increases, the optical fibers meander by a bending strain to a compression direction that is generated in an optical fiber arranged on an innermost side when the bending occurs in the parallel direction, and the transmission loss due to the bending loss increases. In addition, when the optical fibers have a small diameter of <NUM> or the like, since a rigidity is lower than that of the optical fibers having a diameter of <NUM> in the related art, the meandering of the optical fibers is likely to occur.

The present inventors have studied conditions under which, when the bending pressure is applied to the optical fiber ribbons <NUM> (<NUM>, <NUM>) of the respective embodiments in the direction in which the optical fibers are arranged in parallel, even when the optical fibers <NUM> (<NUM>, <NUM>) meander, the bending strain can be made less likely to occur.

<FIG> is a diagram schematically showing the state in which the optical fiber ribbon <NUM> (<NUM>, <NUM>) is bent in a direction in which the sixteen optical fibers <NUM> (<NUM>, <NUM>) constituting the optical fiber ribbon <NUM> (<NUM>, <NUM>) are arranged in parallel, and the sixteen optical fibers <NUM> (<NUM>, <NUM>) maintain in the state of being parallel. In <FIG>, in order to simplify the drawing, the number of optical fibers is reduced to illustrate.

<FIG> shows a state in which when the optical fiber ribbon <NUM> (<NUM>, <NUM>) is bent in the parallel direction, the optical fiber 11P (21P, 31P) at one end corresponds to an optical fiber on an inner side of the bending. Although each optical fiber ribbon <NUM> (<NUM>, <NUM>) is the intermittent connection-type optical fiber ribbon, in the present study, it is assumed that the state in which the optical fibers are arranged in parallel is maintained when the optical fiber ribbon <NUM> (<NUM>, <NUM>) is bent in the parallel direction (it is not considered that the optical fiber ribbon is rounded in a cross-sectional view).

In this study, as shown in <FIG>, in the bent optical fiber ribbon <NUM> (<NUM>, <NUM>), a radius of a curve line C passing through a center in the direction in which the optical fibers <NUM> (<NUM>, <NUM>) are arranged in parallel is defined as a bending radius R. Further, a distance (displacement amount) from the curve line C to the optical fiber 11A (21A, 31A) arranged at an endmost end of the optical fiber ribbon <NUM> (<NUM>, <NUM>) that bends outward is defined as a maximum displacement r.

In this case, when the strain generated in the optical fiber 11A (21A, 31A) by the bending in the parallel direction is referred to as a bending strain S, the bending strain S can be expressed by an equation S = <NUM> × r/R (%) using the maximum displacement r and the bending radius R. The bending strain S is a bending strain generated in the optical fiber at an endmost end in a direction in which the optical fiber ribbon bends outward, and is a maximum value of the bending strain applied to the optical fiber of the optical fiber ribbon.

Next, the bending strain S in the optical fiber ribbon <NUM> (<NUM>, <NUM>) is calculated. In the optical fiber ribbon <NUM>, the maximum displacement is represented by ra, and the bending strain is represented by Sa. In the optical fiber ribbon <NUM>, the maximum displacement is represented by rb, and the bending strain is represented by Sb. In the optical fiber ribbon <NUM>, the maximum displacement is represented by rc, and the bending strain is represented by Sc.

Since each of the maximum displacements ra to rc is the distance from the curve line C to the optical fiber 11A (21A, 31A), each of the maximum displacements ra to rc is ½ of the tape width W1 (W2, W3) of the optical fiber ribbon <NUM> (<NUM>, <NUM>).

In this study, the bending radius R is <NUM>. A value of the bending radius R is assumed to be a bending radius applied to the optical fiber ribbon mounted on the optical fiber cable as compared with a bending radius of bending occured when general installation is performed in the optical fiber cable.

Calculation results of the maximum displacement and the bending strain of the optical fiber ribbon in each embodiment are as follows.

According to the calculation results of the bending strain S, the bending strain in the optical fiber ribbon <NUM> according to the third embodiment is the largest value (Sc = <NUM> (%)). In the optical fiber cable using sixteen optical fiber ribbons, the problem of the increase in transmission loss does not occur as compared with the case in which the bending (maximum bending radius is about <NUM>) occurs when the general installation is performed. Therefore, the value of the bending strain of the optical fiber ribbon <NUM> is set to a maximum value of bending strains S16 in the optical fiber ribbons according to the present disclosure.

Next, based on the bending strains S16 of the sixteen optical fiber ribbons calculated as described above, a value of the bending strains S corresponding to the number of optical fibers constituting the optical fiber ribbon is obtained. Therefore, a value is obtained by dividing the maximum value (Sc = <NUM> (%)) of the bending strain S16 by the number (<NUM>) of optical fibers from a center of the optical fiber ribbon <NUM> to the optical fiber 31A at the endmost end.

Then, when a bending pressure is applied to the optical fiber ribbon <NUM> (<NUM>, <NUM>) of the respective embodiments in the parallel direction, even the optical fibers <NUM> (<NUM>, <NUM>) meander, a value obtained by multiplying the obtained value (<NUM> (%)/<NUM> = <NUM> (%)) by N/<NUM>, which is the maximum displacement r of the optical fiber, is set as an upper limit value of the bending strain capable of reducing the transmission loss (N is the number of optical fibers).

Since the optical fiber ribbon <NUM> (<NUM>, <NUM>) is the intermittent connection-type optical fiber ribbon, the optical fiber ribbon <NUM> (<NUM>, <NUM>) is gathered in a manner of being rounded in a cross-sectional view when being mounted on the optical fiber cable. Therefore, the distance r from the curve line C passing through the center of the optical fiber ribbon <NUM> (<NUM>, <NUM>) to the optical fiber 11A (21A, 31A) at the endmost end is reduced. Accordingly, since the bending strain S of the optical fiber ribbon <NUM> (<NUM>, <NUM>) is reduced, the optical fibers <NUM> (<NUM>, <NUM>) constituting the optical fiber ribbon <NUM> (<NUM>, <NUM>) may be further reduced from meandering, and the increase in transmission loss may be further reduced.

In addtion, in the optical fibers <NUM> (<NUM>, <NUM>) of the optical fiber ribbon <NUM> (<NUM>, <NUM>), when a bending diameter ϕ is <NUM> with <NUM> turn, a bending loss at a wavelength of <NUM> is <NUM> dB or less, and when the bending diameter ϕ is <NUM> with <NUM> turns, the bending loss at the wavelength of <NUM> is <NUM> dB or less. In this way, by using the optical fibers <NUM> (<NUM>, <NUM>) having a small bending loss, the increase in transmission loss may be more reliably reduced.

In addtion, in the optical fibers 11A, 11P (21A, 21P, 31A, 31P) at both ends of the optical fiber ribbon <NUM> (<NUM>, <NUM>) in the width direction, when a bending diameter ϕ is <NUM> with <NUM> turn, the bending loss at the wavelength of <NUM> is <NUM> dB or less, and when the bending diameter ϕ is <NUM> with <NUM> turns, the bending loss at the wavelength of <NUM> is <NUM> dB or less. The increase in transmission loss due to the meandering of the optical fibers <NUM> (<NUM>, <NUM>) becomes more remarkable in the optical fibers 11A, 11P (21A, 21P, 31A, 31P) at both ends of the optical fiber ribbon <NUM> (<NUM>, <NUM>). Therefore, by using the optical fibers having a smaller bending loss for the optical fibers 11A, 11P (21A, 21P, 31A, 31P) at both ends, the increase in transmission loss is further reliably reduced.

Further, when the outer diameter of the optical fibers <NUM> (<NUM>, <NUM>) is D, the number of optical fibers <NUM> (<NUM>, <NUM>) is N, and the thickness of the connecting resin (<NUM>, <NUM>, 35a) covering the peripheries of the optical fibers 11A, 11P (21A, 21P, 31A, 31P) at both ends of the optical fiber ribbon <NUM> (<NUM>, <NUM>) is RT, the width W of the optical fiber ribbon <NUM> (<NUM>, <NUM>) in the parallel direction may be equal to or less than <MAT>.

As a result, the bending strain S in the optical fiber ribbon <NUM> (<NUM>, <NUM>) can be reduced.

In a core alignment fusion splicer, since the optical fiber ribbons are collectively connected in a state of being arranged in parallel, a size of a fusion portion thereof is a size corresponding to the width of the optical fiber ribbons. As the core alignment fusion splicer, a core alignment fusion splicer in which a width of an optical fiber ribbon including twelve optical fibers having a core wire diameter of <NUM> is adjusted to <NUM> to <NUM> is generally used. Even in an optical fiber ribbon including sixteen optical fibers as in the optical fiber ribbon <NUM> (<NUM>), as long as the width W1 (W2) is <NUM> or less, a commonly used core alignment fusion splicer as described above can be used without preparing a new core alignment fusion splicer.

In addition, since the optical fibers <NUM> (<NUM>, <NUM>) are generally used in units of eight optical fibers in many cases, versatility is easily obtained by setting the number of optical fibers <NUM> (<NUM>, <NUM>) in the optical fiber ribbon <NUM> (<NUM>, <NUM>) to a multiple of eight.

According to the optical fiber ribbon <NUM> (<NUM>, <NUM>), in the optical fibers <NUM> (<NUM>, <NUM>), the Young's modulus of the primary resin <NUM> (<NUM>, <NUM>) at <NUM> is <NUM> MPa or less, and the Young's modulus of the secondary resin <NUM> (<NUM>, <NUM>) at <NUM> is <NUM> MPa or more. According to this configuration, since the Young's modulus of the primary resin is lower than that of the optical fiber in the related art and the Young's modulus of the secondary resin is higher than that of the optical fiber in the related art, a shell effect is improved, and lateral pressure resistance of the optical fibers <NUM> (<NUM>, <NUM>) can be improved.

According to the optical fiber ribbon <NUM> (<NUM>, <NUM>), the Young's modulus of the outermost connecting resin <NUM> (25b, 35a, 35b) at <NUM> is <NUM> MPa or less, and the breaking elongation is <NUM>% or more. Therefore, the optical fiber ribbon <NUM> (<NUM>, <NUM>) is easy to deform, and the bending strain can be alleviated.

Next, an optical fiber cable according to the present embodiment will be described with reference to <FIG> and <FIG>.

<FIG> is a view showing an example of a slotless type optical fiber cable using the optical fiber ribbon <NUM> (<NUM>, <NUM>) according to the present embodiment. <FIG> is a view showing an example of a slot type optical fiber cable using the optical fiber ribbon <NUM> (<NUM>, <NUM>) according to the present embodiment.

A slotless type optical fiber cable <NUM> shown in <FIG> includes a cylindrical tube <NUM> and a plurality of optical fiber ribbons <NUM> (<NUM>, <NUM>) mounted in the tube <NUM>. The optical fiber ribbons <NUM> (<NUM>, <NUM>) are gathered in a manner of being rounded, and strand without stranding the optical fiber ribbons <NUM> (<NUM>, <NUM>) back. In addition, a plurality of fillers <NUM> (tension fibers or the like) are mounted in the tube <NUM> so as to fill gaps among the optical fiber ribbons <NUM> (<NUM>, <NUM>). A periphery of the tube <NUM> is covered with a sheath <NUM>. Tension members <NUM> and tearing strings <NUM> are embedded inside the sheath <NUM>. Since the optical fiber ribbons <NUM> (<NUM>, <NUM>) are gathered in the manner of being rounded and strand without stranding the optical fiber ribbons <NUM> (<NUM>, <NUM>) back, bending in the width direction of the optical fiber ribbons <NUM> (<NUM>, <NUM>) is less likely to occur.

In the optical fiber cable <NUM>, an optical fiber density of the optical fibers <NUM> (<NUM>, <NUM>) per unit area in a cable cross section is <NUM> optical fibers/mm<NUM> or more. When the optical fiber cable is the slotless type optical fiber cable, the optical fiber density is calculated by dividing the number of optical fibers by a cross-sectional area of the optical fiber cable. For example, the slotless type optical fiber cable <NUM> shown in <FIG> includes <NUM> optical fibers, and when an outer diameter of the optical fiber cable <NUM> is prepared as <NUM>, the optical fibers <NUM> (<NUM>, <NUM>) can be mounted in the optical fiber cable <NUM> at an optical fiber density of <NUM> optical fibers/mm<NUM>.

A slot type optical fiber cable <NUM> shown in <FIG> includes a slot rod <NUM> having a plurality of slot grooves <NUM>, and a plurality of optical fiber ribbons <NUM> (<NUM>, <NUM>) mounted in the slot grooves <NUM>. The slot rod <NUM> includes a tension member <NUM> at a center, and has a structure in which the plurality of slot grooves <NUM> are provided radially. The optical fiber ribbons <NUM> (<NUM>, <NUM>) are gathered in the manner of being rounded, and strand without stranding the optical fiber ribbons <NUM> (<NUM>, <NUM>) back, so as to be mounted in the slot grooves <NUM>. A press winding tape <NUM> is wound around the slot rod <NUM>, and a sheath <NUM> is formed around the press winding tape <NUM>. Since the optical fiber ribbons <NUM> (<NUM>, <NUM>) are gathered in the manner of being rounded and strand without stranding the optical fiber ribbons <NUM> (<NUM>, <NUM>) back, bending in the width direction of the optical fiber ribbons <NUM> (<NUM>, <NUM>) is less likely to occur.

An optical fiber density of the optical fiber cable <NUM> is <NUM> optical fibers/mm<NUM> or more. For example, the slot type optical fiber cable <NUM> shown in <FIG> includes <NUM> optical fibers, and when an outer diameter of the optical fiber cable <NUM> is prepared as <NUM>, the optical fibers <NUM> (<NUM>, <NUM>) can be mounted in the optical fiber cable <NUM> at an optical fiber density of <NUM> optical fibers/mm<NUM>.

According to the optical fiber cable <NUM> (<NUM>), the optical fiber ribbons <NUM> (<NUM>, <NUM>) described above are mounted in the optical fiber cable <NUM> (<NUM>). Therefore, even when the optical fiber ribbon <NUM> (<NUM>, <NUM>) has an optical fiber density of <NUM> optical fibers/mm<NUM> or more, even the optical fibers <NUM> (<NUM>, <NUM>) constituting the optical fiber ribbon <NUM> (<NUM>, <NUM>) meander in the optical fiber cable <NUM> (<NUM>), the bending strain is less likely to occur. Therefore, the increase in transmission loss due to the meandering of the optical fibers <NUM> (<NUM>, <NUM>) may be reduced. In the optical fiber cable <NUM> (<NUM>), the optical fiber ribbons <NUM> (<NUM>, <NUM>) are rounded and gathered, and the optical fiber ribbons <NUM> (<NUM>, <NUM>) may be gathered in a state of being arranged in a row without being rounded.

Next, a connector-equipped optical fiber cord according to the present embodiment will be described with reference to <FIG> and <FIG>. <FIG> is a view showing an example of a connector-equipped optical fiber cord using the optical fiber ribbon <NUM> (<NUM>, <NUM>) according to the present embodiment. <FIG> is a front view showing a connector insertion/removal portion of the connector-equipped optical fiber cord shown in <FIG>.

A connector-equipped optical fiber cord <NUM> shown in <FIG> includes an optical fiber cord <NUM> in which the optical fiber ribbons <NUM> (<NUM>, <NUM>) are mounted, and a connector portion <NUM> connected to the optical fiber cord <NUM>. For example, two optical fiber ribbons including sixteen optical fibers or one optical fiber ribbon including thirty-two optical fibers are mounted in the optical fiber cord <NUM>. The connector portion <NUM> is formed of a multi-fiber push-on (MPO) connector that can collectively connect a plurality of optical fibers. As shown in <FIG>, the connector portion <NUM> includes an insertion/removal portion <NUM> to be inserted into or removed from another connector, adapter, or the like. The insertion/removal portion <NUM> is provided with thirty-two (<NUM> holes × <NUM> rows) through holes <NUM> into which tip portions of the respective optical fibers <NUM> (<NUM>, <NUM>) of the optical fiber ribbon <NUM> (<NUM>, <NUM>) are inserted.

Claim 1:
An optical fiber ribbon (<NUM>, 1A, 1B, <NUM>, <NUM>) comprising:
<NUM> or more and <NUM> or less optical fibers (<NUM>) arranged in parallel; and
a connecting resin (<NUM>, <NUM>, 25a, 25b, 35a, 35b) that connects adjacent optical fibers of the optical fibers (<NUM>), wherein
an outer diameter of each of the optical fibers (<NUM>) is <NUM> or more and <NUM> or less,
characterized in that
in a case where the number of optical fibers (<NUM>) is set to N, and a bending strain of the optical fibers (<NUM>) is set to S, S = <NUM> × N/<NUM> (%) or less;
wherein, in the optical fibers (<NUM>), in a case where a bending diameter ϕ is <NUM> with <NUM> turn, a bending loss at a wavelength of <NUM> is <NUM> dB or less, and when the bending diameter ϕ is <NUM> with <NUM> turns, the bending loss at the wavelength of <NUM> is <NUM> dB or less;
wherein, in the optical fibers (<NUM>) at both ends of the optical fiber ribbon in a parallel direction, in a case where the bending diameter ϕ is <NUM> with <NUM> turn, the bending loss at the wavelength of <NUM> is <NUM> dB or less, and when the bending diameter ϕ is <NUM> with <NUM> turn, the bending loss at the wavelength of <NUM> is <NUM> dB or less;
wherein the bending loss of the optical fibers (<NUM>) at both ends of the optical fiber ribbon in the parallel direction is lower than the bending loss of the optical fibers other than the optical fibers at both ends of the optical fiber ribbon in the parallel direction.