JP3425091B2 - Optical cable and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable for a subscriber who is connected to a subscriber such as a general household from an outdoor optical cable line, and in particular, distortion caused by a bending tendency of a supporting wire of the optical fiber core. The present invention relates to an optical cable having improved reliability by eliminating an influence on a wire and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, as an optical cable for a subscriber, a support wire such as a steel wire arranged in parallel and an outer circumference of an optical fiber core wire are externally coated with plastic or the like, for example, as shown in FIG. There has been proposed an optical cable having a structure as exemplified in JP-A-10-010384 and JP-A-3-156410.

[0003]

However, in the case where the supporting line of the optical cable for the subscriber has a bending tendency, the optical cable is exposed to waste heat from electric equipment due to environmental conditions after being laid. When the outer coating layer is softened due to high temperature, the bending tendency of the supporting wire becomes apparent and creep deformation occurs, which causes stress strain on the optical fiber core wire to increase transmission loss or breakage. Harm occurs.

Specifically, when the outer coating layer 4 of the optical cable illustrated in FIG. 4 (a) is heated and softened, the bending tendency of the support wire 1 becomes apparent and the deformation illustrated in FIGS. 4 (b) and 4 (c). Occurs.

That is, as shown in FIG. 4 (b), the optical fiber core wire 2 is provided inside the arc of the support wire 1 in which the bending tendency becomes apparent.
When is pushed, the optical transmission loss increases due to the strain caused by the irregular shrinkage deformation. Further, as shown in FIG. 4C, when the optical fiber core wire 2 is pushed to the outside of the arc of the support wire 1 in which the bending habit is manifested, tension acts on the optical fiber core wire 2 to break it. There is a case.

Typical types of bending tendency of the support line 1 of the optical cable are shown in FIGS. 6 (a), 6 (b) and 6 (c). Here, the bending habit of the support line 1 is represented by the direction → R, which is the direction from the support line 1a in which the bending habit becomes apparent in a natural state in which the support line 1a is released from restraint by an external force, toward the center of curvature O. Is represented by the radius of curvature R. Direction of curl by this definition → R is naturally its supporting line 1
And the center of curvature O.

If the bending habit is the same over the entire length of the supporting wire 1, the direction of the bending habit of all parts of the supporting wire 1 → R
Will have the same direction of the center of curvature O, and the size R will have the same value. The bending tendency of the support wire 1 is usually restrained by an external force applied by being wound on a bobbin or being covered with an outer coating layer, but this bending tendency is largely restrained after the optical cable is laid. When the layer is heated and softened, this bending tendency becomes apparent and the above-mentioned adverse effect occurs.

Further, the bending tendency of the support wire 1 is completely hidden by tension being applied to the support wire in the horizontal direction during manufacturing of the optical cable. Hereinafter, when the support line 1 is not particularly referred to, it means a state in which the bending habit is restrained by some external force and it is completely hidden.

In the type of bending habit shown in FIG. 6 (a), the optical fiber core wire 2 is adjacent to a plane 2 parallel to a plane 200 including the support wire 1 and the direction of the bending habit → R and the center of curvature O.
20 shows a case in which the support line 1 is arranged on a position 20 and projected in a direction orthogonal to the surface thereof. Incidentally, this type of bending tendency corresponds to the optical cable shown in FIG.

In the figure, reference numerals 1 and 11 represent support wires in which the bending habit is restrained, and 2 and 12b represent optical fiber core wires in that case, and 1a is a support wire 1 in which the bending habit is actualized, 11 and 2a are optical fiber core wires 2 and 1 in that case.
2b is represented. FIG. 6 (b), the same is true if the (c).

In the type of bending habit shown in FIG. 6B, the optical fiber core wire 2 is on the plane 300 including the support wire 1 and the direction of the bending habit → R and the center of curvature O, and 1 shows a case in which the wire is arranged in parallel with the support line 1 in the direction of the bending tendency of 1 → Ra. By the way, in this type of bending habit, the direction of the bending habit of the support line 1 in FIG.
This is a case corresponding to the case of Ra and the case of FIG. 4B showing the state in which the bending habit is revealed and the optical cable is deformed.

In the type of bending habit shown in FIG. 6 (c), the optical fiber core wire 2 is on a plane 400 including the supporting wire 1 and the direction of the bending habit → R and the center of curvature O, and the supporting wire is 1 shows the case of being arranged in parallel with the support line 1 in the direction of the curving tendency of 1 → the direction opposite to Rb. By the way, this type of bending habit corresponds to the case where the direction of the bending habit of the support line 1 in Fig. 4 (a) is → Rb and the case where the bending habit is manifested and the optical cable is deformed as shown in Fig. 4 (c). This is the case.

A conventional optical cable is manufactured by a method as illustrated in FIG. For example, the supporting wire 11 is bent downward by the supporting wire supply 20, and the supporting wire 11 is supplied to the extrusion coating device in a state where the optical fiber 12b is arranged below the supporting wire 1. In the extrusion coating device, the same figure (c)
The outer coating layer is coated and integrated by a cross head 40 having a die device 40a having a daruma-shaped opening 40 (b) illustrated in FIG. 1 and wound by a winding drum 60 to complete an optical cable.

Therefore, the conventional optical cable is usually shown in FIG.
It has the type of bending habit shown in (b). Further, if either the supporting wire supply 20 or the die device 40 (a) illustrated in FIG. 7 is turned upside down, the direction of the bending tendency of the supporting wire 1 and the positional relationship between the optical fiber 2 become opposite.
An optical cable having the type of curl shown in (c) is manufactured. This is also a type of bending habit often seen in conventional optical cables.

The type of bending habit of the optical cable shown in FIG. 6 is typical, and the optical fiber core wire 2 and the support wire 1 are shown.
There may be innumerable intermediates depending on the positional relationship with the direction of the bending tendency. Even with the same optical cable, different bending habits may be mixed depending on the position in the longitudinal direction. The type of bending habit of the support wire 1 shown in FIGS. 6B and 6C is as shown in FIG. 4B when the bending habit becomes apparent.
As illustrated in (c), the optical fiber core wire 2 is adversely affected. The type of bending habit of the support wire 1 shown in FIG. 6A hardly affects the optical fiber core wire 2.

In the conventional optical cable, as shown in FIG.
Although there is a possibility that the type of bending habit shown in Fig. 4 may be accidentally included, the technical idea of proactively imparting this type of bending habit to the support line 1 over the entire length of the optical cable to protect the optical fiber core wire is proposed. It has not been. In the following, the vertical direction means a downward direction in which gravity acts, and the horizontal direction means a direction orthogonal to the vertical direction.

[0017]

In order to overcome the above-mentioned problems, according to the present invention, the system having the type of bending tendency of the support wire shown in FIG. 6 (a) is positively adopted over the entire length of the optical cable. By avoiding the influence on the optical fiber core wire when the bending tendency becomes apparent, an optical cable with high reliability is realized.

More specifically, an optical cable in which an outer coating layer is formed on the outer circumference of support wires arranged in parallel and an optical fiber core wire to form an integrated structure, wherein the optical fiber core wire is the support wire and its bend. It is characterized in that the support line is arranged on a plane adjacent to the plane including the center of curvature of the habit and in a direction orthogonal to the plane.

Further, the present invention, as illustrated in FIG.
An outer coating layer is formed by an extrusion coating device on a state in which a support wire 1 having a bending tendency in the horizontal direction and an optical fiber core wire 2 are arranged adjacent to each other in the horizontal direction on a vertical plane and integrated. It is a method of manufacturing an optical cable characterized by the above.

That is, in the optical cable of the present invention, as shown in FIGS. 1 (a) and 6 (a), after the supporting wire 1 is positively bent in the horizontal direction with a constant radius of curvature R, In a state where the supporting wire 1 is stretched in the horizontal direction, the optical fiber core wire 2 is placed on the plane 220 adjacent to the plane 300 including the supporting wire 1 and the center of curvature O of the bending tendency in parallel with the supporting wire 1. 1 is arranged at a position projected in the direction orthogonal to the surface, and the outer coating layer 4 is formed on these and integrated.

According to the optical cable of the present invention, even if the bending tendency of the supporting wire 1 becomes apparent after the optical cable is manufactured and the optical cable is bent with a constant curvature, the direction of the bending tendency of the supporting wire becomes → Due to the relationship with R, the entire optical cable bends as illustrated in FIG.

In this case, tension or compressive stress is applied to the outer coating layer inside or outside the arc of the bent optical cable, but these stresses are canceled at the central position where the optical fiber core wire exists. Therefore, these influences hardly affect the optical fiber core wire. In the case of an optical cable including the optical fiber ribbon, in addition to these requirements, a straight line connecting the centers of the two optical fibers at the ends of the cross-section of the optical fiber ribbon (hereinafter, simply light (Referred to as the axis of the fiber tape core wire) in a direction orthogonal to the plane 200 formed by the support wire 1 and the center of curvature O of the bending tendency (see FIGS. 2B and 6A). This avoids the influence when the bending tendency becomes apparent.

Of course, according to the configuration of the present invention, FIG.
It is possible to avoid deformation that gives strains of extension and contraction to the entire optical fiber core wire as exemplified in (c). Therefore, even if the bending tendency of the support wire becomes apparent due to the heat source of the environment after laying the optical cable according to the present invention, the adverse effects such as increase in transmission loss and disconnection of the optical fiber core wire are avoided, and reliability is improved. A high optical cable can be realized.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 to 3 and 6. It should be noted that the same parts are denoted by the same reference numerals and redundant description will be omitted.

[0025]

(Embodiment 1) This embodiment is a case in which the bending habit shown in FIG. That is, the optical fiber core wire 2 is provided with a plane 22 parallel to the surface 200 including the support wire 1 and the center of curvature O of the bending tendency.
This is a case in which the support line 1 is arranged on 0 and at a position projected in a direction orthogonal to the surface thereof.

The structure of the optical cable of this embodiment is shown in FIG.
Shown in. Reference numeral 1 is a support wire made of a steel wire having an outer diameter of 1.2 mm. 2 is an outer diameter of 250 μm coated with UV curable resin
Is an optical fiber core wire. Support wire 1 and optical fiber core wire 2
The center-to-center distance between and is 2.5 mm. 3 is a copper wire with an outer diameter of 0.4 mm for telephone lines.

An outer coating layer 4 made of polyvinyl chloride resin has a function of coating the outer circumferences of the support wire 1 and the optical fiber core wire 2 to be integrated with each other and protecting them from the environment. The outer coating layer 4 has a thickness of 0.
It has a thickness of 4 mm. Reference numeral 5 denotes a neck portion that connects a portion including the support wire and a portion including the optical fiber core wire 2 and has a thickness of 0.2.
The length is 0.3 mm in mm. Reference numeral 6 is a notch for facilitating the work of taking out and exposing the optical fiber core wire 2 of the terminal at the time of construction. The size of the cross section of the entire optical cable is such that the height h is 5 mm and the width w is 2 mm.

(Manufacturing method) The supporting wire 1 is wound around the outer circumference of a rotating cylinder having a radius of curvature of 0.8 m and heat-treated to remove the irregular bending habit and to positively increase the total length of the supporting wire 1. A bending tendency with a horizontal direction and a radius of curvature R of 1 m is positively applied.

In a state where the support wire 1 is linearly stretched by tensioning the support wire 1 in the horizontal direction, the support wire 1, the optical fiber core wire 2 and the two optical fiber core wires 2 arranged at positions sandwiching the support wire 1 are arranged. All of the copper wires 3 were arranged in parallel in a vertical plane, supplied to an extrusion coating apparatus having a die device having a cross-section of the opening that matches the cross-sectional outer shape of the optical cable shown in FIG. Polyvinyl chloride resin coated with resin, cooled,
An optical cable having a cross-sectional structure as shown in the figure was manufactured.
The manufactured optical cable is wound on a bobbin with an outer diameter of 50 cm whose central axis is located in the same vertical direction as the rotating cylinder so that a new bending habit in a direction different from that of the support wire 1 is not added. I took it.

The transmission loss of a laser beam bundle having a wavelength of 1.55 μm was measured with this optical cable wound on a bobbin, and the result was 0.19 dB / km. Regarding the manufactured optical cable, the radius of curvature at room temperature in a natural state unwound from the bobbin is about 5 m, and the bending radius R of the support wire 1 is 1 m. It was restrained considerably by the material strength of the resin.

A heat cycle was applied to the optical cable 500m in this state to reveal the bending tendency of the support wire 1.
That is, this optical cable was heated to + 70 ° C. at a rate of 1 ° C./min, left for 2 hours, and then -30 at a rate of 1 ° C./min.
The cycle of dropping to 0 ° C. and leaving for 2 hours was repeated 3 times.

As shown in FIG. 1 (b), the optical cable after the heat cycle has a portion including the supporting wire 1 and a portion including the optical fiber core wire 2 due to the bending tendency of the supporting wire 1, respectively. It was deformed into concentric circles with the same radius of curvature. The radius of curvature of the entire optical cable in this state was about 2.5 m with respect to the bending radius R of the support wire 1 having a radius of curvature of 1 m.

The transmission loss of the optical cable in this state was measured under the same conditions as described above, and the increase in the optical loss due to the thermal deformation when the heat cycle was applied was obtained. The result was 0.03 dB / k.
The size was extremely small and was negligible. this is,
When the optical cable bends as shown in FIG. 1B, compressive strain acts on the outer coating layer 4 inside the arc of the optical cable, and tensile strain acts on the outer coating layer 4 outside the arc. However, it is considered that these strains are just canceled at the position of the optical fiber core wire 2 located at the center, and the lateral pressure is hardly applied to the optical fiber core wire 2.

(Comparative Example 1) In Comparative Example 1, an optical cable having the same cross-sectional structure as that of Example 1 is shown in FIG.
This is a case in which the bending tendency shown in (b) is added. Specifically, as shown in FIG. 4B, an optical cable in which the bending tendency of the support wire 1 is given in the direction of the optical fiber core wire 2 → Ra shown in FIG. 4A is manufactured and a heat cycle is added. The effects of the present invention will be clarified by causing such deformation and comparing the magnitude of the increase in optical loss due to thermal deformation with the case of the first embodiment.

That is, the optical fiber core wire 2 is arranged parallel to the lower side of the supporting wire 1 in a state in which the supporting wire 1 is bent downward and then stretched in the horizontal direction. As in the case of Example 1, by forming the outer coating layer 4 made of polyvinyl chloride resin on them and integrating them, the same direction as that of the optical fiber core wire 2 illustrated in FIG. → An optical cable having a bending property of Ra was manufactured and wound on a bobbin having a radius of 50 cm as in Example 1.

Regarding the optical cable of this Comparative Example 1, the radius of curvature at room temperature in a natural state unwound from the bobbin is about 7.
The radius of curvature was 5 m, which was larger than the radius of curvature of 5 m of the optical cable of Example 1. This is because the influence of the shape of the cross section of the optical cable is larger than that in the first embodiment due to the direction of the bending tendency → Ra, and thus the bending tendency of the support 1 is restrained relatively strongly. Under the same heat cycle load conditions and the same transmission loss measurement conditions as in Example 1, a heat cycle was applied to this optical cable to reveal the bending tendency and the transmission loss was measured.

The optical cable after the heat cycle was subjected to compressive deformation as shown in FIG. 4 (b), and the radius of curvature of the entire optical cable was about 4 m. The transmission loss in the state wound on the bobbin before the heat cycle is 0.1
No difference from Example 1 was observed at 9 dB / km. It is considered that this is because the optical cable wound on the bobbin is kept in the same shape as in the first embodiment and the bending tendency is restricted. The increase in transmission loss due to the addition of heat cycle is 0.33 dB / k
It was m. This is 10 as compared with the case of the first embodiment.
It is twice as large.

The result of comparison between this Comparative Example 1 and the above Example 1 is due to the heat source of the environment after the application of the optical cable by adopting the system of the bending tendency shown in FIG. 6 (a) adopted in Example 1. It is shown that the increase in transmission loss can be suppressed remarkably.

(Example 2) Example 2 is a case where the present invention is applied to an optical cable using an optical fiber ribbon instead of the optical cable of Example 1. That is, as illustrated in FIG. 2A, the optical cable of the second embodiment uses four optical fiber tape core wires 12b instead of the optical fiber core wire 2 as compared with the optical cable of the first embodiment. The fiber optic cable
In this case, the axis of the core wire is arranged in a direction orthogonal to the plane formed by the center of the support wire 11 and the center of curvature of the bending tendency.

That is, for an optical cable using the optical fiber ribbon 12b, the above-mentioned conditions required for an optical cable having a normal linear optical fiber 2 are weighted to determine the axis of the optical fiber ribbon 12b. The direction is a plane 2 including the center of the support line 11 and the center of curvature O of the bending tendency.
00 (see FIG. 6 (a)). still,
The “orthogonal direction” used here is not a mathematically strict one, and when actually manufacturing an optical cable, a manufacturing error of up to about 5 degrees with respect to this orthogonal direction is included, so that it is used in the present invention. The "orthogonal direction" includes this meaning including the case of the first embodiment.

By arranging the axis of the optical fiber ribbon 12b in such a direction, the optical fiber ribbon 12b is oriented in a direction orthogonal to the surface thereof even when the bending tendency of the support wire 11 becomes apparent. Since it bends, it is hardly affected by the stress strain due to the bending tendency of the support wire 11.

In the optical cable of FIG. 2 (a), 11 is a supporting wire made of a steel wire having an outer diameter of 2.6 mm, and has a bending tendency with a radius of curvature R of 3 m in the horizontal direction, that is, the → R direction in FIG. 2 (a). Have. Reference numeral 12b is an optical fiber ribbon having a thickness of 0.3 mm and a width of 1.1 mm of four cores including four optical fiber cores 2 having the same outer diameter of 250 μm as in Example 1.

Reference numeral 10a denotes 4 of the optical fiber ribbon core wire 2.
It is an optical cable core having an outer diameter of 5 mm formed by stacking a plurality of the polypropylene fiber layers 13a. As described above, the optical cable core 10a is arranged in a direction in which the axis of the optical fiber tape core wire 12b contained therein is orthogonal to the support wire 11 and the plane 200 including the curvature center O of the bending tendency thereof.

Reference numeral 14 denotes an outer coating layer made of polyethylene, which has a thickness of 1.5 mm on the outer circumference of the support wire 11 and a thickness of 1.5 mm on the outer circumference of the optical cable core 10a. And are integrated via a neck portion 15 having a thickness of 2 mm and a length of 2.4 mm. The distance between the center of the support wire 11 and the center of the optical cable core 10a is 9.2 mm. The overall size of this optical cable has a height h of 16 mm and a maximum width w of 8 mm.

(Manufacturing Method) Optical Cable 10 of the Second Embodiment
As illustrated in FIG. 3, the manufacturing method of No.
Support wire supply 2 which is a drum containing a 6 mm steel wire
From 0, the supporting wire 11 is supplied, wound around the outer circumference of the turntable 30 having a radius of 2.5 m, whose central axis is oriented in the vertical direction, and subjected to heat treatment, and the radius of curvature R in the horizontal direction
Is applied to the cross head 40 of the extrusion coating device in a tense state.

At the same time, the four-fiber optical fiber ribbon 12
Optical fiber supply 20a consisting of a bobbin accommodating b
4 are arranged, and four optical fiber tape core wires 12b are supplied from the optical fiber supply 20a in a state where the axis of the optical fiber core wire 12b is oriented in the vertical direction, and a bobbin accommodating a polypropylene fiber 13a is provided on the outer periphery thereof. The polypropylene fiber 13a is fed from the fiber supply 30a and wound so as to have an outer diameter of 5 mm.
0a is formed.

The optical cable core 10a is connected to the support wire 11
3 (c), which is aligned in parallel to the lower position of the optical fiber so that the center-to-center distance is 9.2 mm, matches the external dimensions of the cross section of the optical cable of FIG. 2 (a). It is supplied to a crosshead 40 of an extrusion coating apparatus equipped with a die device 40a having a mold opening 40b, and polyethylene is coated on the outer periphery thereof to form an outer coating 14 to be integrated.

The die device 40a of the crosshead 40
From the above, the optical cable 100 extruded with the polyethylene coated thereon is loaded with tension, and the cooling water tank 50 is in a tense state.
It is then cooled to room temperature and then wound up on a winding drum 60 having a radius of 1 m. In this case, the central axis of the winding drum 60 is directed in the same vertical direction as the turntable so that a new bending tendency is not given to the manufactured optical cable in a direction different from the bending tendency of the supporting wire 11, The optical cable was wound in the same direction as the bending tendency of 11.

(Transmission loss) When the optical cable was wound around a drum 60 having a radius of 1 m and the transmission loss was measured under the same measurement conditions as in Example 1, the result was 0.20 dB / km, which was the same as the value of an ordinary optical cable. It was about the same. The radius of curvature of the manufactured optical cable was 7 m at room temperature in a natural state of being unwound from the winding drum 60. This is because the bending strength of the support wire 11 having a radius of curvature R of 3 m was restricted by the material strength of polyethylene of the outer coating layer 14. The optical cable 500m in this state was subjected to heat cycle under the same conditions as in Example 1, and as a result, the deformation illustrated in FIG. The radius of curvature of the optical cable after the heat cycle was about 5 m.

As a result of measuring the transmission loss of the optical cable in this state by the same method as in Example 1, a slight increase of 0.03 dB / km in optical loss, which was negligible as in Example 1, was observed due to the addition of heat cycle. It was only observed.

Comparative Example 2 In this Comparative Example 2, an optical cable having the same cross-sectional structure as that of Example 2 is given the same bending habit as shown in FIG. This is the case.

Specifically, an optical cable having a structure in which the optical cable core 10a is arranged in the bending direction of the support wire 11 → Ra in FIG. 5A is manufactured by the method according to the second embodiment. A heat cycle is applied to the manufactured optical cable to cause thermal deformation as illustrated in FIG. 6B, the magnitude of increase in transmission loss is clarified, and comparison is made with the case of the second embodiment. In this case, as can be seen from FIGS. 5 (a) and 6 (b), the support wire 11 and the direction of its bending tendency → R
The center of the optical cable core 10a is included in a plane 300 including a and the center of curvature O, and the axes of the four optical fiber ribbons 12b are arranged in parallel to this plane.

The optical cable of this comparative example 2 is manufactured by using the optical cable manufacturing apparatus shown in FIG. 3 in which the axial direction of the turntable 30 is oriented horizontally and the steel wire 1 is provided on the outer periphery thereof.
Is different from that of the second embodiment in that a bending tendency having a radius of curvature R of 3 m is applied to the support wire 11 in a downward direction. Other manufacturing conditions are the same as those in the second embodiment.

The radius of curvature of the optical cable of Comparative Example 2 was about 10 m at room temperature in the natural state of being unwound from the winding drum 60. This value is larger than in the case of the optical cable of Example 2 having a radius of curvature of 7 m, but this value is in addition to the material strength of polyethylene of the outer coating layer 4, the bending direction of the supporting wire 11 and the crossing of the optical cable. Due to the influence of the shape of the surface, the bending tendency of the support wire 11 having the radius of curvature R of 3 m is more strongly restrained than in the second embodiment.

A heat cycle was applied to this optical cable under the same heat cycle load conditions as in Example 2, and the transmission loss of the optical cable before and after the heat cycle was measured under the same measurement conditions. After the heat cycle, the optical cable was deformed as shown in Fig. 5 (b),
The radius of curvature was about 6 m.

The transmission loss in the state of being wound on the winding drum 60 before applying the heat cycle was 0.20 dB / km, and no difference from the case of Example 2 was recognized. However, the increase of the transmission loss due to the addition of the heat cycle is 0.8 times as large as that in the case of the second embodiment.
A value of 53 dB / km was obtained.

From the results of comparison between this Comparative Example 2 and Example 2,
The same conclusions as the comparison results of Example 1 and Comparative Example 1 are obtained. That is, it can be seen that by adopting the system of the bending tendency shown in FIG. 6A adopted in Example 2, it is possible to remarkably suppress the increase of transmission loss due to the heat source of the environment after the application of the optical cable. However, in the case of the second embodiment, the cross-sectional area of the optical cable is large, so that the effect of the present invention is more remarkable than that of the first embodiment.

In the case of the second embodiment, the direction of the axis of the optical fiber ribbon 12b is set to the plane 200 (see FIG. 6 (a)) which includes the center of the support wire 11 and the center of curvature O of the bending tendency. However, the effect of the present invention is not limited to this range, and it is also effective when the axial direction is arranged in a direction that forms an acute angle with the direction orthogonal to this plane.

In the first and second embodiments, the bending tendency of the supporting wire is given before the outer coating of the optical cable by the extrusion coating device, but the present invention is not limited to this, and an electric current is applied to the supporting wire after the optical cable is manufactured. It is also possible to wind the turntable while heating it by flowing it to give a certain bending tendency. Further, in the above-mentioned Examples 1 and 2, single steel wires were used as the support wires 1 and 11, but the present invention is not limited to this, and twisted steel wires and other metal wires can also be used.

[0060]

According to the optical cable of the present invention, the optical fiber is located on a plane adjacent to the plane including the support line and the center of curvature of the bending tendency of the support line, and at a position where the support line is projected in a direction orthogonal to the plane. Since the core wire is arranged, the external coating layer softens due to the heat source of the environment during use, the outer coating layer softens, and even if the bending tendency of the supporting wire becomes apparent and the entire optical cable bends, The optical fiber core only bends with the same curvature, and the optical fiber core is not subject to any distortion due to compression or tensile stress, which may increase optical transmission loss or cause disconnection. It is possible to realize a highly reliable optical cable.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structure of an optical cable of the present invention and a state after thermal deformation. FIG. 1A shows the cross section of the optical cable and the direction of the bending tendency of the supporting wire → R, and FIG. 1B shows the state where the bending tendency of the supporting wire becomes apparent and the optical cable is deformed.

FIG. 2 is a cross-sectional view showing the structure of another optical cable of the present invention and a perspective view showing a state after thermal deformation. FIG. 1A shows the cross section of the optical cable and the direction of the bending tendency of the supporting wire → R, and FIG. 1B shows the state where the bending tendency of the supporting wire becomes apparent and the optical cable is deformed.

FIG. 3 is a side view and a plan view showing the optical cable manufacturing apparatus of the present invention. 3A shows a side surface of the optical cable manufacturing apparatus of the present invention, FIG. 3B shows a plane, and FIG. 3C shows a shape of an opening of a die device of an extrusion coating apparatus.

FIG. 4 is a cross-sectional view showing a structure of a conventional optical cable and a perspective view showing a state after thermal deformation. FIG. 4A shows the cross-sectional structure of the optical cable and the bending direction of the supporting wire → Ra and → Rb, and FIG. 4B shows the bending direction of the supporting wire → Ra. The state of the optical cable after thermal deformation is shown in (c) of the figure.
The respective states after thermal deformation of the optical cable in which the optical fiber core wires are arranged in the direction opposite to Rb are shown.

5A and 5B are a cross-sectional view of an optical cable of Comparative Example 2 and a perspective view showing a state after thermal deformation. FIG. 5A shows the cross section of the optical cable and the direction of the bending tendency of the support line → Ra, and FIG. 5B shows the state after the thermal deformation of the optical cable of FIG. 5A.

FIG. 6 is a perspective view for explaining a type of bending tendency of a support wire in an optical cable. FIG. 6A shows a plane 220 in which the support wire has a bending direction → R in the horizontal direction, and the optical fiber core wire is adjacent to the plane 200 including the support wire and the curvature center O of the bending bow in parallel. The support wire is arranged above and in a position where the support wire is projected in a direction orthogonal to the plane. In FIG. 6B, the support wire has a bending tendency from downward to Ra, and the optical fiber core wire bends. It is arranged in parallel with the support line in the direction of the habit, and the support line bends downward in the figure (c).
FIG. 4b shows a system of optical cables in which the optical fiber core wire is arranged in parallel with the support wire in the direction opposite to the direction of its bending tendency.

FIG. 7 is a side view and a plan view showing a conventional optical cable manufacturing apparatus. FIG. 7A shows a side surface of a conventional optical cable manufacturing apparatus, FIG. 7B shows a plane, and FIG. 7C shows an opening shape of a die device of an extrusion coating apparatus.

[Explanation of symbols]

1, 11: Supporting wire 1a: Supporting wire in a state where the bending tendency is manifested 1, 112 2, 12b: Optical fiber core wire, optical fiber tape core wire 2a: Optical fiber in a state where the bending tendency of the supporting wire is manifested Core wire 1, optical fiber tape core wire 12b 3: Copper wires 4, 14: Outer coating layers 5, 15: Neck part 6: Notch 10, 100: Optical cable 10a: Optical cable core 20: Support wire supply 13a: Fiber layer 20a: Optical Fiber supply 30: Turntable 30a: Fiber supply 40: Cross-head 40a of extrusion coating device: Die device 40b of extrusion coating device: Opening 50: Cooling tank 60: Winding drums 200, 300, 400: Support wire and its A plane 220 including the center of curvature of the bending tendency: a plane adjacent to the support line in parallel with the plane including the center of curvature of the bending tendency.

Front page continuation (72) Inventor Masakazu Watanabe 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Seigo 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Yuji Sera 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Kimio Ando 3-19-3 Nishishinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (56) Reference JP-A-11-223750 (JP, A) JP-A-10-48487 (JP, A) JP-A-9-281368 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) G02B 6/44 H01B 13/22 H01B 13/24

Claims (5)

(57) [Claims] 1. An optical cable in which an outer coating layer is formed on the outer circumference of a support wire arranged in parallel and an optical fiber core wire, and the optical fiber core wire comprises the support wire and a curvature of its bending tendency. An optical cable arranged on a plane parallel to a plane including the center and at a position where the support line is projected in a direction orthogonal to the plane. 2. The optical fiber core wire is an optical fiber tape core wire, and an axis line connecting the centers of two optical fibers at both ends of a cross section of the optical fiber core wire is the support wire and the center of curvature of its bending tendency. The optical cable according to claim 1, wherein the optical cable is arranged in a direction orthogonal to a plane formed by the optical cable. 3. Place the said optical fiber and said supporting wire imparted with bending tendency in the horizontal plane vertically, that are integrated to form the outer coating layer by extrusion coating device on its outer circumference The method for manufacturing an optical cable according to claim 1, wherein the optical cable is manufactured. 4. The optical fiber core wire is an optical fiber tape core wire, and an axis connecting the centers of two optical fibers at both ends of a cross section of the optical fiber core wire is the support wire and the center of curvature of its bending tendency. The method of manufacturing an optical cable according to claim 3, wherein the optical cable is arranged in a direction orthogonal to a plane that forms the optical cable. 5. The method of manufacturing an optical cable according to claim 3, wherein the supporting wire is provided with a bending tendency in a fixed direction by winding the supporting wire around an outer circumference of a disk or a columnar body.