OPTICAL CABLE STRUCTURE AND OPTICAL CABLE STRUCTURE PRODUCTION METHOD

An optical cable structure includes connector-equipped optical fibers, derived from an end portion of a sheath of an optical cable, that are accommodated in a tubular member. Each of the connector-equipped optical fibers includes a derivation optical fiber from the end portion of the sheath and an optical connector disposed at a distal portion of the derivation optical fiber. Lengths of at least some of the derivation optical fibers are different from each other. Each of the derivation optical fibers includes a proximal-side optical fiber on an end portion side of the sheath, a distal-side optical fiber on an optical connector side, and a connecting portion connecting the proximal-side optical fiber to the distal-side optical fiber. The connecting portions are disposed in the tubular member when the connector-equipped optical fibers are accommodated in the tubular member.

BACKGROUND

Technical Field

The present invention relates to an optical cable structure and a method for producing the optical cable structure.

Discussion of the Background

In the related art, when an optical cable is inserted into a duct to install optical wiring lines, a distal portion of the optical cable is protected by being accommodated in a tubular member (traction end). A plurality of optical fibers in which an optical connector is terminated at each distal portion are accommodated as the distal portion of the optical cable inside the tubular member.

Patent Document 1 discloses an optical cable structure in which the lengths of a plurality of optical fibers constituting a distal portion of an optical cable are made different from each other, and a plurality of optical connectors terminated at the plurality of optical fibers are disposed out of alignment in a length direction of the optical fiber (optical cable). In such an optical cable structure, it is possible to suppress the bulkiness of the plurality of optical connectors in a radial direction of the optical cable to maintain a small diameter dimension of the tubular member accommodating the plurality of optical connectors. For this reason, even if the number of optical fibers each having the optical connector at the distal portion is large, the optical cable can be inserted into a narrow duct.

Patent Document

Patent Document 1: Japanese Patent Publication No. 2002-333561

However, in a case where an attempt to produce the optical cable structure disclosed in Patent Document 1 is made, it is difficult to efficiently perform the termination work of the optical connector for the distal portion of each of the plurality of optical fibers. For example, in order to efficiently perform the termination work of the optical connector, it is preferable that the positions of the distal portions of the plurality of optical fibers are aligned. However, because the lengths of the plurality of optical fibers are different from each other, it is difficult to align the positions of the distal portions of the plurality of optical fibers.

SUMMARY

One or more embodiments provide an optical cable structure and a method for producing the optical cable structure capable of easily performing the termination work of optical connectors for a plurality of optical fibers constituting a distal portion of an optical cable accommodated in a tubular member.

An optical cable structure according to one or more embodiments is an optical cable structure including a plurality of connector-equipped optical fibers which are derived from an end portion of a sheath of an optical cable and accommodated in a tubular member having a predetermined length. Each of the plurality of connector-equipped optical fibers includes a derivation optical fiber derived from the end portion of the sheath, and an optical connector provided at a distal portion of the derivation optical fiber in a derivation direction. Lengths of at least some derivation optical fibers among a plurality of the derivation optical fibers derived from the end portion of the sheath are different from each other. Each of the plurality of derivation optical fibers has a proximal-side optical fiber located on an end portion side of the sheath, a distal-side optical fiber located on an optical connector side, and a connecting portion connecting the proximal-side optical fiber and the distal-side optical fiber to each other. The connecting portions of the plurality of derivation optical fibers are located inside the tubular member in a state where the plurality of connector-equipped optical fibers are accommodated in the tubular member.

A method for producing an optical cable structure according to one or more embodiments is a method for producing an optical cable structure including a plurality of connector-equipped optical fibers which are derived from an end portion of a sheath of an optical cable and accommodated in a tubular member having a predetermined length, the method comprising: a first step of terminating an optical connector at a first end portion of a distal-side optical fiber in a longitudinal direction; a second step of leading out a plurality of proximal-side optical fibers from the end portion of the sheath; and a third step of connecting a second end portion of each of a plurality of the distal-side optical fibers in the longitudinal direction to a distal portion of each of the plurality of proximal-side optical fibers after the first step and the second step to form the plurality of connector-equipped optical fibers each having a derivation optical fiber including the proximal-side optical fiber and a distal-side optical fiber, and the optical connector, and extending from the end portion of the sheath. At least one of lengths of the plurality of proximal-side optical fibers and lengths of the plurality of distal-side optical fibers is set before the third step such that lengths of at least some derivation optical fibers among a plurality of the derivation optical fibers derived from the end portion of the sheath are different from each other.

According to one or more embodiments, it is possible to easily perform the termination work of the optical connectors for the plurality of derivation optical fibers that constitute the distal portion of the optical cable and are accommodated in the tubular member.

DESCRIPTION OF THE EMBODIMENTS

First Example

Hereinafter, a first example of one or more embodiments will be described with reference toFIGS.1to8.

As shown inFIGS.1and2, an optical cable structure of the first example has a plurality of connector-equipped optical fibers1that are derived from an end portion of a sheath S of an optical cable C and constitute a distal portion of the optical cable C. In the shown example, the number of connector-equipped optical fibers1is three, but the present invention is not limited thereto. The plurality of connector-equipped optical fibers1are accommodated in a tubular member100having a predetermined length.

As shown inFIG.1, the tubular member100covers the plurality of connector-equipped optical fibers1. The tubular member100has the role of protecting the plurality of connector-equipped optical fibers1when the optical cable C passes through a duct or the like of a building. In addition, the tubular member100also has the role as a traction end that is tractioned when the optical cable C passes through the duct or the like. The tubular member100is removed from the optical cable C after the optical cable C passes through the duct or the like.

The tubular member100has a tubular main body101and a head102. The tubular main body101is formed in a tubular shape that accommodates the connector-equipped optical fibers1. The tubular main body101may have, for example, flexibility. The head102is provided at a distal portion of the tubular main body101and covers an opening on the distal side of the tubular main body101. A pulling eye103is provided at the distal end of the head102. By binding and pulling a rope or the like to the pulling eye103, the optical cable C can easily pass through the duct or the like.

The tubular member100is detachably attached to the optical cable C by accommodating the plurality of connector-equipped optical fibers1in the tubular main body101and then causing a proximal portion of the tubular main body101to be held by a holding tool105fixed to the end portion of the sheath S with a screw or the like.

As shown inFIGS.1to3, each connector-equipped optical fiber1of the optical cable C has a derivation optical fiber2derived from the end portion of the sheath S and an optical connector3provided at a distal portion of the derivation optical fiber2in a derivation direction.

The derivation optical fiber2has cores52and62(seeFIGS.4to6) for transmitting optical signals. Although the number of the cores52and62in the derivation optical fiber2may be, for example, one, the number thereof in the present example is more than one.

The derivation optical fiber2has a proximal-side optical fiber5, a distal-side optical fiber6, and a connecting portion7.

The proximal-side optical fiber5is a portion on the proximal side of the derivation optical fiber2located on the end portion side of the sheath S. As shown inFIG.4, the proximal-side optical fiber5in the present example is a multi-core fiber51having a plurality of (seven in the shown example) cores52. The plurality of cores52constituting the multi-core fiber51are disposed on the same circumference centered on an axis C1of the proximal-side optical fiber5when viewed from a longitudinal direction of the proximal-side optical fiber5, and are arranged at intervals around the axis C1. In addition, in the multi-core fiber51of the shown example, one core52is disposed on the axis C1of the proximal-side optical fiber5.

As shown inFIGS.1to3, the distal-side optical fiber6is a portion on the distal side of the derivation optical fiber2located on the optical connector3side. As shown inFIGS.5and6, the distal-side optical fiber6in the present example is configured by a plurality of (seven in the shown example) single-core fibers61each having one core62. The number of single-core fibers61constituting the distal-side optical fiber6corresponds to the number of cores52(seeFIG.4) of the multi-core fiber51constituting the proximal-side optical fiber5.

As shown inFIG.5, the plurality of single-core fibers61are arranged at a proximal portion (second end portion)6B, in the longitudinal direction, of the distal-side optical fiber6located on the proximal-side optical fiber5side as shown inFIG.3to correspond to the arrangement of the plurality of cores52of the proximal-side optical fiber5shown inFIG.4. Specifically, at the proximal portion of the distal-side optical fiber6, as shown inFIG.5, the plurality of single-core fibers61are disposed on the same circumference centered on a predetermined axis C2. In addition, one single-core fiber61is disposed to be located on the predetermined axis C2.

On the other hand, as shown inFIG.6, a plurality of single-core fibers61are arranged at a distal portion (first end portion)6A, in the longitudinal direction, of the distal-side optical fiber6located on the optical connector3side as shown inFIG.3to correspond to the optical connector3(ferrule). Specifically, as shown inFIG.6, the plurality of single-core fibers61are arranged in a line in a linear direction (left-right direction inFIG.6) perpendicular to the longitudinal direction thereof at a distal portion of the distal-side optical fiber6.

As shown inFIGS.1to3, the connecting portion7connects the proximal-side optical fiber5and the distal-side optical fiber6to each other. The connecting portion7has the role of optically coupling the plurality of cores52(seeFIG.4) of the proximal-side optical fiber5and the plurality of cores62(seeFIG.5) of the distal-side optical fiber6to each other individually. The connecting portion7of the present example is a connector connecting portion71that mechanically connects the proximal-side optical fiber5and the distal-side optical fiber6to each other.

As shown inFIGS.3and7, the connector connecting portion71has a proximal-side connector72, a distal-side connector73, and an adapter74.

The proximal-side connector72is provided at a distal portion of the proximal-side optical fiber5and has a connection surface721where the distal end of the proximal-side optical fiber5is exposed. Although not shown, an insertion hole is formed in the proximal-side connector72. The distal portion of the proximal-side optical fiber5is inserted through the insertion hole and is exposed from the connection surface721of the proximal-side connector72.

The distal-side connector73is provided at a proximal portion of the distal-side optical fiber6and has a connection surface731from which a proximal end of the distal-side optical fiber6is exposed. Although not shown, an insertion hole is formed in the distal-side connector73. The proximal portion of the distal-side optical fiber6is inserted through the insertion hole and is exposed from the connection surface731of the distal-side connector73.

The adapter74connects the proximal-side connector72and the distal-side connector73to each other to optically couple the cores52(seeFIG.4) of the proximal-side optical fiber5and the cores62(seeFIG.5) of the distal-side optical fiber6. The adapter74of the present example is formed in a tubular shape in which both ends in the axial direction are open. The proximal-side connector72and the distal-side connector73are inserted into openings at both ends of the adapter74such that the connection surfaces721and731of the proximal-side connector72and the distal-side connector73face each other. Accordingly, it is possible to butt the connection surfaces721and731of the proximal-side connector72and the distal-side connector73against each other to optically couple the cores52of the proximal-side optical fiber5and the cores62of the distal-side optical fiber6to each other.

As shown inFIGS.1and2, the lengths of the plurality of derivation optical fibers2derived from the end portion of the sheath S are different from each other. In the present example, the lengths of all the derivation optical fibers2are different from each other. In addition, the lengths of the plurality of proximal-side optical fibers5constituting the plurality of derivation optical fibers2are different from each other.

Moreover, the lengths of the plurality of distal-side optical fibers6constituting the plurality of derivation optical fibers2are equal to each other.

Since the lengths of the plurality of proximal-side optical fibers5constituting the plurality of derivation optical fibers2are different from each other, the plurality of connecting portions7(connector connecting portions71) located at the distal portions of the plurality of proximal-side optical fibers5are located out of alignment in the derivation direction of the derivation optical fibers2.

The optical connector3is provided at the distal portion of each derivation optical fiber2in the derivation direction, that is, provided at the distal portion of each distal-side optical fiber6. As shown inFIG.3, the optical connector3has a connection end face31where the distal end of the distal-side optical fiber6is exposed. Although not shown, an insertion hole is formed in the optical connector3. The distal portion of the distal-side optical fiber6is inserted through the insertion hole and is exposed from the connection end face31of the optical connector3. In the present example, the insertion hole of the optical connector3is formed such that the plurality of single-core fibers61are inserted therethrough in a state where the plurality of single-core fibers61(seeFIG.6) constituting the distal-side optical fiber6are arranged in a line in a linear direction perpendicular to the longitudinal direction thereof.

As described above, the lengths of the plurality of derivation optical fibers2derived from the end portion of the sheath S are different from each other. For this reason, the plurality of optical connectors3provided at the corresponding distal portions of the plurality of derivation optical fibers2are located out of alignment in the derivation direction of the derivation optical fibers2.

As shown inFIG.1, the connecting portions7of all the derivation optical fibers2are located inside the tubular member100in a state where the plurality of connector-equipped optical fibers1of the optical cable C configured are accommodated in the tubular member100.

In addition, the lengths of all of the connector-equipped optical fibers1are shorter than the length of the tubular member100.

Accordingly, the connector-equipped optical fibers1can be accommodated in the tubular member100without bending or the like of all the derivation optical fibers2.

Next, a method for producing the optical cable structure according to the present example will be described.

When producing the optical cable structure, first, as shown inFIGS.7and8, the optical connector3is terminated at a first end portion (distal portion)6A of the distal-side optical fiber6in the longitudinal direction (first step). The termination work of the optical connector3in the first step includes an insertion work of inserting the distal-side optical fiber6into the optical connector3, a polishing work of polishing the connection end face31of the optical connector3and the distal end of the distal-side optical fiber6exposed on the connection end face31, and an inspection work of inspecting an optical loss of the distal end of the distal-side optical fiber6exposed on the connection end face31. In addition, in the first step of the present example, the distal-side connector73is terminated at a second end portion (proximal portion)6B of the distal-side optical fiber6. The termination work of the distal-side connector73may include the same insertion work, polishing work, and inspection work as the above-described termination work of the optical connector3.

The first step is performed on the plurality of distal-side optical fibers6. In the present example, the lengths of the plurality of distal-side optical fibers6are preset before the first step such that the lengths of the plurality of distal-side optical fibers6are equal to each other.

In addition, when producing the optical cable structure, the plurality of proximal-side optical fibers5are derived from the end portion of the sheath S for the optical cable C (second step). In the second step of the present example, the lengths of the plurality of proximal-side optical fibers5are set such that the lengths of the plurality of proximal-side optical fibers5are different from each other. In addition, in the second step of the present example, the proximal-side connector72is terminated at the distal portion of the proximal-side optical fiber5. The termination work of the proximal-side connector72may include the same insertion work, polishing work, and inspection work as described above.

The second step may be performed, for example, before or after the first step, or simultaneously with the first step.

After the first step and the second step, as shown inFIGS.2and3, the second end portion (proximal portion)6B of each of the plurality of distal-side optical fibers6is connected to the distal portion of each of the plurality of proximal-side optical fibers5(third step). By performing the third step, the derivation optical fiber2having the proximal-side optical fiber5and the distal-side optical fiber6is configured. In addition, the connector-equipped optical fiber1having the derivation optical fiber2and the optical connector3and extending from the end portion of the sheath S is configured.

In the third step of the present example, the proximal-side optical fiber5and the distal-side optical fiber6are connected to each other by the connector connecting portion71. Specifically, the proximal-side optical fiber5and the distal-side optical fiber6are connected to each other by butting the proximal-side connector72provided at the distal portion of the proximal-side optical fiber5and the distal-side connector73provided at the second end portion (proximal portion)6B of the distal-side optical fiber6against each other by using the adapter74.

In the production method of the present example, as described above, before the first step, the lengths of the plurality of distal-side optical fibers6are set such that the lengths of the plurality of distal-side optical fibers6are equal to each other. In addition, in the second step, the lengths of the plurality of proximal-side optical fibers5are set such that the lengths of the plurality of proximal-side optical fibers5are different from each other. For this reason, in the state after the third step, the lengths of the plurality of derivation optical fibers2are different from each other.

As described above, the method for producing the optical cable structure is completed.

As described above, in the optical cable structure and the method for producing the optical cable structure according to the first example, the lengths of the plurality of derivation optical fibers2derived from the end portion of the sheath S are different from each other. For this reason, the plurality of optical connector3provided at the corresponding distal portions of the plurality of derivation optical fibers2can be located out of alignment in the derivation direction of the plurality of derivation optical fibers2. Accordingly, it is possible to suppress the bulkiness of the plurality of optical connectors3in the radial direction of the optical cable C. Therefore, the plurality of connector-equipped optical fibers1can be accommodated in the tubular member100having a small diameter dimension.

In addition, in the optical cable structure and the method for producing the optical cable structure according to the first example, the distal-side optical fiber6can be connected to the proximal-side optical fiber5after the optical connector3is terminated at the distal portion (first end portion)6A of the distal-side optical fiber6. That is, the termination work of the optical connector3can be performed before the distal-side optical fiber6is connected to the proximal-side optical fiber5. For this reason, even if the lengths of the plurality of derivation optical fibers2are different from each other in the optical cable structure after production, the termination work of the optical connectors3for the plurality of derivation optical fibers2accommodated in the tubular member100can be easily performed. Specifically, since the positions of the distal portions (first end portions)6A of the plurality of distal-side optical fibers6can be easily aligned, the termination work (particularly the polishing work and the inspection work) of the optical connector3for the distal-side optical fiber6can be easily performed.

In addition, in the optical cable structure and the method for producing the optical cable structure according to the first example, the lengths of the plurality of proximal-side optical fibers5extending from the end portion of the sheath S are different from each other. For this reason, the plurality of connecting portions7provided at the corresponding distal portions of the plurality of proximal-side optical fibers5can be located out of alignment in the longitudinal direction of the derivation optical fibers2. Accordingly, it is possible to suppress the bulkiness of the plurality of connecting portions7in the radial direction of the optical cable C. Therefore, the plurality of connector-equipped optical fibers1can be easily accommodated in the tubular member100having a small diameter dimension. In the first example, the above effect is particularly useful because the diameter dimension of the connector connecting portion71is larger than the diameter dimension of the derivation optical fiber2.

In addition, in the optical cable structure and the method for producing the optical cable structure according to the first example, the lengths of the plurality of distal-side optical fibers6are equal to each other. Accordingly, the optical cable structure can be produced by using the plurality of distal-side optical fibers6having the same length. Therefore, it is possible to efficiently produce the optical cable structure.

In addition, in the optical cable structure and the method for producing the optical cable structure according to the first example, the proximal-side optical fiber5and the distal-side optical fiber6are mechanically connected to each other by the connector connecting portion71. Accordingly, the proximal-side optical fiber5and the distal-side optical fiber6can be easily connected to each other without using a device such as a fusion splicer.

Second Example

Next, an optical cable structure and a method for producing the optical cable structure according to a second example of one or more embodiments will be described with reference toFIGS.9to12. In the following description, the configurations that are the same as those already described will be given the same reference signs, and duplicate descriptions thereof will be omitted.

As shown inFIG.9, similar to the first example, the optical cable structure of the second example is derived from the end portion of the sheath S of the optical cable C and has a plurality of connector-equipped optical fibers1B accommodated in the tubular member100. In addition, a derivation optical fiber2B of each connector-equipped optical fiber1B has a connecting portion7B that connects the proximal-side optical fiber5and the distal-side optical fiber6.

The connecting portion7B of the second example is a fusion-splicing portion71B that fusion-splices the proximal-side optical fiber5and the distal-side optical fiber6to each other. As shown inFIGS.10and11, the fusion-splicing portion71B of the second example is configured separately from the proximal-side optical fiber5and the distal-side optical fiber6.

The fusion-splicing portion71B has a proximal-side portion72B and a distal-side portion73B. The proximal-side portion72B includes a multi-core fiber having a plurality of cores. The cross-sectional shape of the proximal-side portion72B is the same as the cross-sectional shape of the proximal-side optical fiber5shown inFIG.4. The distal-side portion73B includes a plurality of single-core fibers each having one core. The cross-sectional shape of the distal-side portion73B is the same as the cross-sectional shape of the distal-side optical fiber6on the proximal portion side shown inFIG.5. The proximal-side portion72B and the distal-side portion73B are arranged in the longitudinal direction (left-right direction inFIG.10) of the cores and joined to each other by fusion or the like. Accordingly, the plurality of cores of the proximal-side portion72B and the plurality of cores of the distal-side portion73B are optically coupled to each other individually. According to such a configuration, when an optical connector (for example, MT ferrule) is wired to a terminal of an optical fiber, the alignment work in the rotation direction of the optical fiber (the direction around the axis of the optical fiber) is required in a case where the terminal of the optical fiber located on the optical connector side is a multi-core fiber, and the rotation directionality of the optical fiber is lost in a case where the terminal of the optical fiber is a single-core fiber. Therefore, the above-described alignment work becomes unnecessary.

The proximal-side portion72B of the fusion-splicing portion71B is fusion-spliced with the distal portion of the proximal-side optical fiber5. In addition, the distal-side portion73B of the fusion-splicing portion71B is fusion-spliced with the proximal portion of the distal-side optical fiber6. Accordingly, the cores52(seeFIG.4) of the proximal-side optical fiber5and the cores62(seeFIG.5) of the distal-side optical fiber6are optically coupled to each other via the core of the fusion-splicing portion71B (the proximal-side portion72B and the distal-side portion73B).

In the second example, the length of the fusion-splicing portion71B is shorter than the lengths of the proximal-side optical fiber5and the distal-side optical fiber6. In addition, in the second example, the lengths of the fusion-splicing portions71B are equal to each other between a plurality of the derivation optical fibers2B.

Although not shown, the fusion-splicing portion71B may have, for example, a protective sleeve that protects a fused portion between the proximal-side optical fiber5and the distal-side optical fiber6. In this case, the diameter dimension of the fusion-splicing portion71B is larger than the diameter dimension of the derivation optical fiber2.

Next, a method for producing the optical cable structure according to the second example will be described.

The production method of the second example is different from the production method of the first example in that the distal-side connector73(seeFIGS.7and8) is not terminated at the distal-side optical fiber6in the first step and the proximal-side connector72(seeFIGS.7and8) is not terminated at the proximal-side optical fiber5in the second step.

In addition, the production method of the second example is different from the production method of the first example in terms of a method of connecting the second end portion (proximal portion)6B of each of the plurality of distal-side optical fibers6to the distal portion of each of the plurality of proximal-side optical fibers5in the third step.

Hereinafter, the third step in the production method of the second example will be described.

As shown inFIGS.10to12, in the third step of the second example, the distal portion of the proximal-side optical fiber5and the proximal portion of the distal-side optical fiber6are fusion-spliced with each other by the fusion-splicing portion71B. Specifically, first, as shown inFIGS.11and12, the fusion-splicing portion71B is disposed between the distal portion of the proximal-side optical fiber5and the proximal portion of the distal-side optical fiber6. Thereafter, as shown inFIG.10, the distal portion of the proximal-side optical fiber5is fusion-spliced with the proximal-side portion72B of the fusion-splicing portion71B. In addition, the proximal portion of the distal-side optical fiber6is fusion-spliced with the distal-side portion73B of the fusion-splicing portion71B.

After the first step and the second step, the third step of the above-described second example is performed, thereby completing the production method of the second example.

According to the second example, the same effects as those of the first example are exhibited.

In addition, according to the second example, the proximal-side optical fiber5and the distal-side optical fiber6are fusion-spliced with each other. Accordingly, the proximal-side optical fiber5and the distal-side optical fiber6can be connected to each other with higher reliability.

In addition, in the second example, the fusion-splicing portion71B is configured separately from the proximal-side optical fiber5and the distal-side optical fiber6. In addition, the fusion-splicing portion71B has the proximal-side portion72B including multi-core fibers similar to the proximal-side optical fiber5, and the distal-side portion73B including a plurality of single-core fibers similar to the distal-side optical fiber6.

For this reason, the proximal-side optical fiber5and the distal-side optical fiber6can be connected to each other by the fusion-splicing between the multi-core fibers and the fusion-splicing between the plurality of single-core fibers. Here, the fusion-splicing between the same type of optical fibers can be performed more easily than the fusion-splicing between different types of optical fibers (that is, the fusion-splicing between the multi-core fibers and the plurality of single-core fibers). Accordingly, the proximal-side optical fiber5and the distal-side optical fiber6can be easily fusion-spliced with each other.

In addition, a large number of the fusion-splicing portions71B each having the proximal-side portion72B and the distal-side portion73B can be produced in advance before the proximal-side optical fiber5and the distal-side optical fiber6are fusion-spliced with each other. Accordingly, it is possible to efficiently perform the fusion-splicing between the plurality of proximal-side optical fibers5and the plurality of distal-side optical fibers6.

From the above, the optical cable structure can be efficiently produced.

In the second example, for example, the lengths of the fusion-splicing portions71B may be different from each other between the plurality of derivation optical fibers2B. For example, the lengths of the plurality of derivation optical fibers2B may be made different from each other by making the lengths of the fusion-splicing portions71B different from each other between the plurality of derivation optical fibers2B.

In the second example, for example, the length of the fusion-splicing portion71B may be equal to or longer than the lengths of the proximal-side optical fiber5and the distal-side optical fiber6.

In the second example, the fusion-splicing portion71B may be configured by, for example, the distal portion of the proximal-side optical fiber5and the proximal portion of the distal-side optical fiber6. That is, the proximal-side optical fiber5and the distal-side optical fiber6may be directly fusion-spliced with each other.

In one or more embodiments, for example, the plurality of proximal-side optical fibers5may have the same length. In this case, the lengths of the plurality of derivation optical fibers2and2B may be made different from each other, for example, by making the lengths of the plurality of distal-side optical fibers6different from each other.

In one or more embodiments, both the proximal-side optical fiber5and the distal-side optical fiber6may be, for example, the multi-core fibers51, or may be configured by, for example, the plurality of single-core fibers61. In addition, the proximal-side optical fiber5and the distal-side optical fiber6may be one single-core fiber61.

In the method for producing optical cable structure according to one or more embodiments, for example, in the first step, the lengths of the plurality of distal-side optical fibers6may be set such that the lengths of the plurality of distal-side optical fibers6are different from each other. In this case, in the second step, for example, similar to the above embodiments, the lengths of the plurality of proximal-side optical fibers5may be set such that the lengths of the plurality of proximal-side optical fibers5are different from each other, or for example, the lengths of the plurality of proximal-side optical fibers5may be set such that the lengths of the plurality of proximal-side optical fibers5are equal to each other. Even in a case where the lengths of the plurality of distal-side optical fibers6or the lengths of the plurality of proximal-side optical fibers5are set in this way, the lengths of the plurality of derivation optical fibers2and2B in the optical cable structure after production can be made different from each other.

In one or more embodiments, the lengths of all the derivation optical fibers2and2B extending from the end portion of the sheath S may not be different from each other. For example, the lengths of some derivation optical fibers2and2B among all the derivation optical fibers2and2B extending from the end portion of the sheath S may be equal to each other. For example, the plurality of derivation optical fibers2and2B extending from the end portion of the sheath S may be divided into a plurality of groups, the lengths of the plurality of derivation optical fibers2and2B constituting the same group are made equal to each other, and the lengths of the different groups of derivation optical fibers2and2B may be made different from each other. In this case, the plurality of optical connectors3provided at the distal ends of the plurality of derivation optical fibers2and2B constituting the same group are disposed at the same position in the derivation direction of the derivation optical fibers2and2B. In addition, the optical connectors3provided at the distal ends of the different groups of derivation optical fibers2and2B are located out of alignment in the derivation direction of the derivation optical fibers2and2B.

REFERENCE SIGNS LIST