JP7760417B2 - Optical fiber cable manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing an optical fiber cable .

As a technology for imparting tension resistance to optical fiber cables, Patent Document 1 proposes a technique in which a linear or band-shaped flexible tensile strength material is attached along the longitudinal direction of the tube on the outer surface of a flexible tube, such as a metal tube, through which the optical fiber is inserted.

In addition, Patent Document 2 presents a technology for quickly inserting optical fibers into thin, long tubes.

Japanese Patent Application Publication No. 11-174293 Japanese Patent Application Publication No. 9-281364

In optical fiber cables, the metal tube through which the optical fiber is inserted has high radial strength but low longitudinal tensile strength, so a material that provides tensile strength along the longitudinal axis of the metal tube's outer periphery is sometimes applied. However, applying such a material to the outer periphery of the metal tube inevitably increases the outer diameter of the cable. On the other hand, the fiber material used to provide tensile strength has lower rigidity than glass optical fiber, making it extremely difficult to insert into a long metal tube.

The objective of this embodiment of the present application is to provide a method for manufacturing an optical fiber cable in which tensile strength fibers with lower rigidity than optical fibers are inserted into a long metal tube (hereinafter referred to as a "closed tube") that has no communication between the interior space and the outside world except at both ends, and an optical fiber cable manufactured using this method that has high tensile strength in the longitudinal direction.

The method for manufacturing an optical fiber cable according to an embodiment of the present application is characterized in that a coiled closed tube is fixedly placed on a vibration table, the optical fiber and high-tensile strength fiber are bundled and tied together at their tips, the tied tips are inserted into one end of the closed tube, and the vibration center axis of the vibration table is aligned with the tube coil axis to vibrate the vibration table in a spiral motion, and the optical fiber and high-tensile strength fiber are inserted into the closed tube.

Here, it is desirable that the optical fiber and the tensile strength fiber are bound together with a binding band wrapped around the ends of each other. Furthermore, it is desirable that a lead wire that is flexible and elastic, has a weight per unit length greater than the weight per unit length of the optical fiber, and has a diameter equal to or smaller than the diameter of the bundle of optical fiber and tensile strength fiber, is attached to the binding band and inserted into the closed tube.

The above manufacturing method produces an optical fiber cable characterized by an optical fiber and a tensile strength fiber inserted into a closed tube.

The embodiments of the present application are configured as described above, making it possible to provide a method for manufacturing an optical fiber cable in which tensile strength fibers with lower rigidity than optical fibers are inserted into a closed tube, and an optical fiber cable manufactured using this method that has high longitudinal tensile strength.

1 is a schematic diagram showing the structure of an optical fiber cable according to an embodiment of the present application. FIG. 1 is a side view schematically showing an example of an apparatus for inserting a fiber bundle into a closed tube. FIG. 2 is a plan view schematically showing a vibration table. FIG. 10 is a schematic diagram showing how a vibration motor is attached to a vibration table. FIG. An example in which the tip of a fiber bundle is bound with a binding band is shown in a partial cross section. An example in which a lead wire is attached to the tip of a fiber bundle is shown in a partial cross section.

Embodiments of the present application will be described below with reference to the drawings. Please note that the drawings described below are schematic diagrams, and the positional relationships between components and size ratios may not be the same as those in the actual product.

Figure 1 is a schematic diagram showing the structure of an optical fiber cable 20 according to this embodiment. The closed tube P is a flexible metal tube (e.g., a steel tube) formed to a long length (e.g., a total length of 10 m or more), and its outer periphery is covered with a synthetic resin coating layer C. The internal space of the closed tube P is not in communication with the outside except at both ends. In other words, there are no holes or gaps on the side of the closed tube P that would allow communication with the outside world.

A fiber bundle 6 consisting of optical fibers 6a and tensile strength fibers 6b is inserted throughout the entire length of the internal space of the closed tube P. The number of optical fibers 6a inserted varies depending on the application of the optical fiber cable 20, and may be multiple as shown in this figure, or may be just one.

The tensile strength fibers 6b are inserted into the closed tube P to improve the tensile strength of the optical fiber cable 20. Suitable tensile strength fibers 6b include synthetic resin fibers with excellent tensile strength, such as aromatic polyamide fibers, and especially aramid fibers. While these tensile strength fibers 6b have excellent tensile strength, they are less rigid than the glass optical fibers 6a and have a lower weight per unit length, making it extremely difficult to insert them alone into the long closed tube P. Therefore, by bundling the tensile strength fibers 6b with the optical fibers 6a to form a fiber bundle 6, it becomes possible to insert the tensile strength fibers 6b together with the optical fibers 6a into the long closed tube P.

Next, the manufacturing method of the optical fiber cable 20 of this embodiment will be described with reference to the drawings. Figure 2 is an overall side view showing an example of a device for inserting a fiber bundle 6 into the internal space of a closed pipe P formed as a steel pipe, Figure 3 is a plan view of the vibration table 2, and Figure 4 is an explanatory diagram of how vibration motors 3a and 3b are attached to the vibration table 2.

The coil R of the closed tube P is placed and fixed on the vibration table 2 by fixing the outer periphery of the lower flange of its bobbin 1 and the axial hole with a fixture 9 or the like on the vibration table 2 so that it can reliably receive the vibrations of the vibration motors 3a and 3b. A pair of vibration motors 3a and 3b are integrally attached to the vibration table 2, tilted, for example, by 12.5° from the vertical, and the pair of vibration motors 3a and 3b apply vibrations centered on the tube coil axis X. The vibration table 2 is attached to the stand 5 via springs 4, so that the vibrations of the vibration table 2 are not transmitted to the stand 5.

In this example, the vibration motors 3a and 3b are rotary vibrators that generate vibrations by utilizing centrifugal force generated by the rotation of unbalanced weights attached to both ends of the rotation shaft. Two of these are attached symmetrically to the vibration table 2 with respect to the tube coil axis X. The vibration planes of the pair of vibration motors 3a and 3b form the same angle α with the horizontally installed surface of the vibration table 2. Furthermore, other vibration conditions of the vibration motors (frequency, amplitude, etc.) and the rotation direction of the vibrators are also the same, so that the vibrations from the pair of vibrators are combined and applied to the vibration table 2. When such vibrations are applied to the vibration table 2, the coil R of the closed tube P on the table performs circular motion at a constant angular velocity (counterclockwise in the illustrated example) around the intermediate axis of the vibration motors 3a and 3b. By placing the coil R on the vibration table so that this intermediate axis coincides with the tube coil axis X, the axis of the coil R can be aligned with the vibration center axis of the vibration table 2.

The vibration state of the vibration table will be explained using Figure 5. In Figure 5, E is a circle drawn on the vibration table with the tube coil axis X (the vibration central axis) as its center, and E' is the circle after circle E has moved due to vibration. Thus, the circle vibrates spirally between the solid-line circle E and the dashed-line circle E' due to the vibration of the vibration table. The center of the circle vibrates vertically between _P and _P '. As the distance from the center increases, i.e., as the diameter of the _circle increases, the vibration angle β of each point _P1 , _P2 , _P3 , and _P4 on the circumference relative to the horizontal plane decreases, and the amplitudes _P1P'1 , _P2P'2 , _P3P'3 , _{and P4P'4} gradually increase from PP'. However, the vertical component of the amplitude remains constant. The closed tube coil is placed on a vibration table so that the tube coil axis X coincides with the vibration center axis. Since the closed tube is wound in a coil shape, the above circle corresponds to one turn of the closed tube. Therefore, closed tubes of the same diameter of the coil exhibit the same vibration (same amplitude and vibration angle), while the smaller the diameter of the inner closed tube, the smaller the amplitude and the larger the vibration angle β.

As shown in Figure 6, multiple optical fibers 6a inserted into the closed tube P are bundled with tensile strength fibers 6b to form a fiber bundle 6, and their ends are bound together by wrapping a binding band 6c around them. The binding band 6c can be, for example, adhesive tape. First, the ends of the fiber bundle 6 bound with the binding band 6c are inserted into the tube start end 7 of the closed tube P. In this state, when the spiral vibration described above is applied to the coil R of the closed tube P via the vibration table 2, the fiber bundle 6 is supplied from the tube start end 7, which is the lower end of the coil, by the conveying force of the vibration and continuously enters the closed tube P. That is, the fiber bundle 6 is unwound from the spool 10 axially supported by the support 12 and moves due to the vibration of the coil R in the following order: spool 10 → guide 11 → tube start end 7 → closed tube P of the coil R → tube end 8. After a predetermined time, it is inserted through the entire coil R.

As shown in Figure 7, a lead wire 13 may be attached to the tie band 6c that ties the tip of the fiber bundle 6. The lead wire 13 is made of a flexible and elastic material, for example, a strand of thin metal wire such as stainless steel, or a plastic wire containing metal powder such as iron, and is formed with a diameter equal to or smaller than that of the fiber bundle 6. This lead wire 13 is inserted into the tube start end 7 of the closed tube P, and then spiral vibrations are applied to the coil R of the closed tube P via the vibration table 2 as described above, allowing the fiber bundle 6 to be inserted into the closed tube P of the coil R following the lead wire 13.

The closed tube P used in this application does not have to be a simple, long cylindrical tube as shown in the above embodiment, but may also be, for example, a long tube formed as a stacked spiral tube to increase flexibility.

REFERENCE SIGNS LIST 1 bobbin 2 vibration table 3a, 3b vibration motor 4 spring 5 stand 6 fiber bundle 6a optical fiber 6b tensile strength fiber 6c binding band 7 tube start end 8 tube end 9 fixing jig 10 spool 11 guide 12 support 13 lead wire 20 optical fiber cable C coating layer P closed tube R coil X tube coil axis

Claims (3)

The closed tube wound into a coil is fixed and placed on a vibration table,
The optical fiber and the tensile strength fiber are bundled and bound together at only the tips of the fibers.
A method for manufacturing an optical fiber cable, characterized in that the bundled tip is inserted into one end of the closed tube, the vibration center axis of the vibration table is aligned with the tube coil axis, which is the center axis of the coiled portion of the closed tube, and the vibration table is vibrated spirally, and the optical fiber and the tensile strength fiber are inserted into the closed tube. The method for manufacturing an optical fiber cable according to claim 1, characterized in that the optical fiber and the tensile strength fiber are bound together with a binding band wound around each other's ends. 3. The method for manufacturing an optical fiber cable according to claim 2, characterized in that a lead wire having flexibility and elasticity, a weight per unit length greater than the weight per unit length of the optical fiber, and a diameter equal to or smaller than the diameter of the optical fiber and the bundle of tensile strength fibers is attached to the bundle tie and inserted into the closed tube .