JP2783390B2 - Optical cable and method for manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable for accommodating collectively integrated optical fiber units in a gap and a method for manufacturing the same.

[Conventional technology]

Although the original tensile strength of an optical fiber, particularly a silica-based optical fiber, is approximately 300 kg / mm ² , it tends to deteriorate when a tension is applied to the optical fiber by an external factor.

As a method of protecting the optical fiber from external factors, a loose type in which the wires or core wires are freely stored in the air gap, and a tight type in which the fibers are collectively integrated through a buffer layer that reduces the propagation of lateral pressure. Yes (the present and future of optical communication, Telecommunications Technology Council, p. 211).

By the way, even if the tension applied to the optical cable is less than the tension that immediately breaks the optical cable, if the tension is applied for a long time, the optical fiber deteriorates and eventually breaks.

Therefore, while the optical cable is being pulled with a predetermined allowable range of tension, an optical cable that gives an extra length to the optical fiber with respect to the cable length so that abnormal tension is not applied to the optical fiber housed in the optical cable. It has been devised.

FIG. 4 shows a conventional optical cable ("A
New Simple Optical Cable Manufactured in a Single
Process ", THE TRANSACTIONS OF THE IECE OF JAPAN, VO
L.E69, NO.4 APRIL 1986).

FIG. 1A is a perspective view showing a basic configuration of an optical cable. The optical cable 1 includes a plurality of optical fibers 2, 2,.
Is loosely wound by a colored yarn 3 and the unitized optical fiber unit 4 is housed in the gap of the LAP jacket 5. Usually, a plurality of optical fiber units are accommodated in this gap. The tensile strength member 6 is embedded in the LAP jacket 5 at an eccentric position.

FIG. 4 (b) is a cross-sectional view from the optical axis direction showing a structural example of a conventional optical cable. An aluminum tape 8 is adhered to the inner surface of the cable core 7 of the optical cable 1. The optical fiber unit 4 is housed in the cable core. In addition, two strength members 6 are buried at the eccentric position of the optical cable 1.

As described above, since the tensile strength member is buried at an eccentric position in the cable, when the optical cable is bent at a predetermined curvature, tension is applied to the optical fiber unit.

Therefore, in the optical cable manufacturing process, when winding the optical cable, the optical cable is bent at a predetermined curvature with a winding drum or the like, and the deviation between the neutral axis and the core wire position when bending the cable is used. This is to add extra length to the optical fiber.

The ratio of the extra length to the cable length is determined by the distance between the center of the cable and the center of the cable core, and the distance between the intermediate position between the two strength members 6, 6 and the center of the cable. Can control this ratio.

[Problems to be solved by the invention]

However, in the conventional optical cable, an extra length is given to the optical fiber in the winding process, so that when the optical cable is wound in multiple layers, the radius of curvature differs between the lower layer and the upper layer of the optical cable in contact with the winding drum. However, there is a problem that the extra lengths given to the optical fibers are different.
In this case, the extra length given to the optical fiber partially differs in the optical axis direction (longitudinal direction), and a difference occurs in mechanical strength in terms of tensile strength.

In addition, if the optical fiber is stored in the optical cable with an extra length in advance, the core wire becomes slack, which makes it difficult to manufacture.

Therefore, an object of the present invention is to provide an optical cable having at least a certain mechanical strength.

It is another object of the present invention to provide a method of manufacturing an optical cable that can easily provide a desired extra length to an optical fiber unit in the cable.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an optical cable in which an integrated optical fiber unit is housed, wherein the optical fiber unit has a plurality of optical fibers assembled in the same direction and an optical fiber in the same direction. The aggregated thermal expansion wire, the optical fiber and the thermal expansion wire are configured to have a linear member that is roughly wound at a predetermined pitch interval and is aggregated and integrated, and the optical fiber and the thermally expanded thermal expansion wire are provided. An optical fiber unit formed by integrating and integrating a linear member without loosening is housed in a curved state by cooling and shrinking a thermal expansion wire.

In the method of manufacturing an optical cable accommodating an optical fiber unit integrated and integrated therein, a first step of concentrating a plurality of optical fibers together with a heated thermal expansion wire, and an optical fiber and thermally expanded thermal expansion A second step of forming the optical fiber unit by loosely winding the wire material in a spiral shape with a linear member, and integrating and unifying the optical fiber and the heat-expanded thermal expansion wire material without loosening; A third step of cooling and shrinking the thermal expansion wire in a state where the optical fiber unit is gathered and integrated by the shape member, and bending the optical fiber unit into a wavy shape along the thermal expansion wire, and assembling the optical fiber unit curved into a wavy shape inside It comprises a fourth step of forming an optical cable.

[Action]

Since the present invention is configured as described above, the thermal expansion wire in the heated state is wound integrally with the plurality of optical fibers, so that the optical fiber contracts, and the optical fiber becomes the thermal expansion wire. Bends along the wave.

In addition, the extra length can be freely changed by changing the linear expansion coefficient and the wire diameter of the thermal expansion wire.

〔Example〕

Hereinafter, an embodiment of an optical cable and a method of manufacturing the same according to the present invention will be described with reference to the accompanying drawings. In the description, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is an exploded perspective view showing an embodiment of the optical cable according to the present invention. The difference from the prior art is that in the optical fiber unit, the thermal expansion wire 9 is wound integrally with the optical fibers 2, 2,. This thermal expansion wire 9 is unitized with the same length as the optical fibers 2, 2,... And is roughly wound by a linear member 10 such as a colored string. The optical fiber unit 11 is assembled in the gap of the outer sheath 12 to form an optical cable.

At the stage of being housed in the optical cable, the thermal expansion wire 9 has been cooled from the temperature at which it was condensed, and the optical fiber unit is given an extra length. In other words, the thermal expansion wire 9 contracts, and the optical fiber unit 11 is curved in a wavy shape along the thermal expansion wire 9. Therefore, even if tension is applied to the optical cable, excessive tension is not applied to the optical fibers 2, 2,..., And it is possible to prevent the optical fibers 2, 2,.

FIG. 2 is a side view for explaining the operation of the above-mentioned optical fiber unit. FIG. 3A shows an optical fiber 2,
.. Show a state (heated state) in which the thermal expansion wire 9 is wound around the linear member 10 (heated state), and the plurality of optical fibers 2, 2,. Coarsely wound by 10.

FIG. 2 (b) shows a state in which the optical fibers 2, 2,... Wound by the linear member 10 and the thermal expansion wire 9 are accommodated in the optical cable (cooled state). Shrink. In this case, the plurality of optical fibers 2,
2,... Are in close contact with the thermal expansion wire 9 by being wound around the linear member 10, so that they are wavyly curved along the thermal expansion wire 9. Therefore, the optical fiber unit 11 has an extra length in the longitudinal direction.

In this case, the coefficient of linear expansion of the thermal expansion wire 9 is 1.4 × 10 ^-5 ° C.
^-1 , the linear member 10 is wound around the optical fibers 2, 2,... And the thermal expansion member 9 in a state where the thermal expansion wire 9 is heated and expanded to 100 ° C., and is stored in an optical cable at room temperature (20 ° C.).
C) when cooled to 0.1%.

However, since the optical fiber tends to increase the optical transmission loss when it is bent, it is desirable to set a limit on the radius of curvature in order to suppress the optical transmission loss to a practically acceptable range. For example, if transmission light having a wavelength of 1.55 μm is used for a single-mode optical fiber, the radius of curvature of the optical fiber must be maintained at 60 mm or more in order to suppress the loss increase per km to 0.1 dB or less. is there. When the optical fiber draws a spiral with a radius R, in order to maintain the radius of curvature of the optical fiber at 60 mm or more, the pitch interval P of the linear member 10 wound spirally around the thermal expansion wire 9 is: Must.

In this case, if the linear member contracts too much and the optical fiber floats from the linear member, the above assumption is not satisfied.For example, when giving an extra length to the optical fiber using a temperature difference of 50 ° C., The linear expansion coefficient σ of the thermal expansion wire is Is B, it is necessary that σ ≦ (1-2πR / (PAB)) / 50.

When a polyethylene material having a linear expansion coefficient of 7 × 10 ^-5 ° C. ^-1 is used, an arbitrary extra length can be reduced by 0.5% by changing the thickness and adjusting the cooling efficiency until the optical fiber is wound. Can be given up to.

Although this embodiment shows a loose type optical cable in which an optical fiber unit is freely stored in a space, the present invention is not limited to a loose type optical cable. For example, a tight type optical cable that is assembled and integrated via a buffer tank in which propagation of lateral pressure is reduced may be used. At least, an optical cable having a gap such as a groove in the longitudinal direction can be applied.

Further, in order to reduce slippage between the thermal expansion wire 9 and the optical fibers 2, 2,..., The linear member 10, the surface of the thermal expansion wire 9 may be subjected to a surface treatment to increase a friction coefficient. For example, the surface finish is reduced, or a material having a high coefficient of friction is coated.

FIG. 3 shows an embodiment of an apparatus for manufacturing a tight type optical cable which accommodates a spacer having a groove in the longitudinal direction. The optical fibers 2, 2,... Supplied by the optical fiber supply devices 13, 13,.
The thermal expansion wire 9 supplied by 14 is sent to the coarse winding head 15 respectively. In this case, a heater 16 is provided between the thermal expansion wire supply device 14 and the coarse winding head 15,
The thermal expansion wire 9 is fed to the coarse winding head 15 in a heated state. In the coarsely wound head 15, a linear member (not shown)
, And the thermal expansion wire 9 are roughly wound to form an optical fiber unit 11.

The optical fiber unit 11 is put into a spacer 19 supplied from a spacer supply device 18 by a concentrator 17. The spacer 19 is wound up with a tape by a taping head 20. In the case of a loose-type optical cable, the step of storing the optical cable in the spacer 19 and taping it is unnecessary.

Thereafter, the taped spacer 19 is sheathed by the extruder 21. It is effective to cool the optical fiber unit 11 between the taping head 20 and the extruder 21.
The optical cable extruded by the extruder 21 is sent at a constant speed by a caterpillar 22 and wound up by a winding drum 23.

Next, a method for manufacturing an optical cable according to the present invention will be described based on the above-described manufacturing apparatus. The present invention basically includes four steps.

In the first step, the plurality of optical fibers 2, 2,... Are concentrated together with the heated thermal expansion wire 9. In this case, the optimum heating temperature is determined in consideration of the number of optical fibers to be condensed, the wire diameter, the material of the thermal expansion wire, the wire diameter, the feed speed, and the like.

In the second step, the thermal expansion wire 9 and the optical fibers 2, 2,.
Are roughly wound spirally with a linear member (not shown) to form the optical fiber unit 11. In this case, it is desirable that the pitch interval wound by the linear member is set based on the equation (1).

In the third step, the thermal expansion wire 9 of the optical fiber unit 11 formed in the second step is cooled, and the optical fiber unit 11 is bent in a wave shape along the thermal expansion wire 9 (FIG. 2 (b)). reference). At this stage, an extra length is given to the optical fiber unit 11. In this case, if the pitch interval between the linear members is set based on the expression (1), the radius of curvature of the optical fiber becomes
It becomes 60 mm or more, and the optical transmission loss becomes 0.1 dB or less.

In the fourth step, the optical fiber unit 11 is assembled in the gap of the optical cable by sealing it by extrusion or the like.

In the case of a tight type optical cable, a step of storing the optical fiber unit 11 in a spacer and winding the tape upward with a tape is included between the third step and the fourth step.

〔The invention's effect〕

Since the optical cable according to the present invention is configured as described above, the extra length can be given uniformly and reliably. Therefore, at least a certain mechanical strength can be provided.

Further, the method for manufacturing an optical cable according to the present invention can easily provide a desired extra length to an optical fiber unit in the cable. In this case, change the temperature difference (heating temperature → cooling temperature) or change the material of the thermal expansion wire (change the linear expansion coefficient)
By doing so, the surplus length ratio can be easily controlled. Therefore, a desired extra length can be easily provided to the optical cable.

As described above, according to the present invention, the optical fiber can be effectively protected from abnormal tension remaining during or after cable laying.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the optical cable according to the present invention, FIG. 2 is a process diagram for explaining the operation of the optical cable shown in FIG. 1, and FIG. FIG. 4 is a block diagram showing an embodiment of an optical cable manufacturing apparatus, and FIG. 4 is a view showing an optical cable according to the prior art. DESCRIPTION OF SYMBOLS 1 ... Optical cable 2 ... Optical fiber 3 ... Colored string 4, 11 ... Optical fiber unit 5 ... LAP jacket 6 ... Tensile body 7 ... Cable core 8 ... Tape 9 ... Thermal expansion wire 10 ... Wire member 12 External sheath 13 Optical fiber supply device 14 Thermal expansion wire supply device 15 Coarse winding head 16 Heater 17 Concentrator 18 Spacer supply device 19 Spacer 20 … Taping head 21… Extruder 22… Caterpillar 23… Winding drum

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G02B 6/44 366 G02B 6/44 391

Claims (4)

(57) [Claims] An optical cable accommodating an optical fiber unit which is assembled and integrated therein, wherein said optical fiber unit is composed of a plurality of optical fibers which are assembled in the same direction and a plurality of heat fibers which are assembled in the same direction as said optical fibers. An expansion wire, and a linear member that coarsely winds the optical fiber and the thermal expansion wire at a predetermined pitch interval and collectively integrates the optical fiber and the thermal expansion wire that has been heated and stretched; The optical fiber unit, formed by integrating the optical fiber unit without loosening with the linear member, is housed in a curved state by cooling and shrinking the thermal expansion wire. 2. An outer diameter of a circumscribed circle containing the optical fiber unit is d [mm], an outer diameter of the thermal expansion wire is D [mm],
When (d + D) / 2 is R, the pitch interval is The optical cable according to claim 1, wherein: 3. The method according to claim 1, wherein a pitch interval between the linear members is P [mm]. Where B is between 30 ° C. and 100 ° C., the thermal expansion wire has a linear expansion coefficient of 1.4 × 10 ⁻⁵ or more and (1-2πR / (P
A / B)) / 50 or less.
Optical cable as described. 4. A method of manufacturing an optical cable in which a collectively integrated optical fiber unit is housed inside, a first step of concentrating a plurality of optical fibers together with a heated thermal expansion wire, and said optical fiber and heating extension. A second step of forming the optical fiber unit by loosely winding the obtained thermal expansion wire spirally around a linear member and integrating the optical fiber and the thermally expanded thermal expansion wire without loosening; Cooling and shrinking the thermal expansion wire in a state where the thermal expansion wire and the optical fiber are gathered and integrated by the linear member,
An optical cable comprising: a third step of waving the optical fiber unit along the thermal expansion wire; and a fourth step of assembling the wavy optical fiber unit therein to form an optical cable. Manufacturing method.