JP2013125110A - Optical fiber cable and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber cable for securing the tear characteristic of a sheath by a notch formed on the sheath without needing an internal notch nor a tear string and enhancing the sealability of an introduction and derivation parts of a closure, and a method for manufacturing the optical fiber cable.SOLUTION: In an optical fiber cable having a plurality of notches 17 for sheath tearing on an external surface of a sheath in a longitudinal direction with the outer circumference of an assembled core 11 housing many optical fibers covered with a sheath 16, a remaining sheath thickness (t1, t2) from the bottom of a notch to a sheathe inner surface periodically changes in a longitudinal direction. In the remaining sheath thickness changing periodically, the thickness of the thinnest part is 0.3-0.6 mm, the thickness of the thickest part is 0.9-1.2 mm, and a length interval of the remaining sheath thickness changing periodically is 150-300 mm.

Description

  The present invention relates to an optical fiber cable in which a collection core in which a large number of optical fiber cores are assembled is covered with a sheath, and a method for manufacturing the same.

  With the recent expansion of broadband services such as video distribution, IP telephony, and data communications, the number of subscribers to home-use data communications services (FTTH: Fiber To The Home) using optical fibers is increasing. In this FTTH, a drop optical cable is used to drop a subscriber's house from a trunk optical cable. For example, the optical fiber can be pulled down to the subscriber's home by, for example, branching the optical fiber core from a trunk optical cable laid on a utility pole in a city with a connection box usually called a closure. A drop optical cable is connected to the fiber core using a fusion connection or an optical connector.

  In order to draw an optical fiber from the middle part of the trunk optical cable to a subscriber's house, etc., one to several optical fiber cores are selected from a plurality of optical fiber cores housed in the cable. A branching operation is performed. In this branching operation, it is necessary to peel off a sheath (also referred to as a jacket) mainly made of polyethylene when taking out the inner optical fiber core from the optical fiber cable.

When the sheath is peeled off, the sheath is cut with a blade or the like, and a few cm is cut in the longitudinal direction from the cut portion with a blade or the like, and a part of the sheath is partially removed. Then, by removing the tear string from the portion from which the sheath has been removed and pulling the tear string in the longitudinal direction, the sheath of several centimeters to several tens of centimeters can be peeled off.
However, in this case, since it is necessary to tear the sheath with a blade or the like, it takes time and cost because it requires a tear string.

On the other hand, for example, Patent Document 1 describes a slot-type optical cable that can easily remove a sheath and a press-wound tape. On the outer surface of the sheath of the slot type optical cable, two notches are formed as low-strength portions that extend in parallel with the overlapping portions at both ends of the press-wound tape. When taking out the optical fiber from the slot-type optical cable, the sheath can be cut out by holding and pulling the dedicated tool against the notch.
Patent Document 2 describes an optical fiber cable in which at least two external notches are provided on the outer surface of the sheath and an internal notch is formed as a sheath tearing means between the two external notches.

JP 2010-277062 A JP 2008-158368 A

  However, in the case of the slot-type optical cable disclosed in Patent Document 1, the two notches formed in the sheath as the low-strength portion are considered to have a width of about 1 to 2 mm and a depth of about 1 to 1.5 mm. Therefore, since the tip does not enter the notch with ordinary pliers or nippers, the notch cannot be gripped unless it is a special tweezer-shaped jig having a thickness of 1 mm or less. Moreover, even if the notch is grasped with such a jig, there is a risk that if a tearing force of 10 N or more is applied, it will slip because there is no catch.

  In addition, in the optical fiber cable described in Patent Document 2, a cutting edge such as a nipper is aligned with an external notch formed on the sheath so as to form a cut reaching the internal notch. If the internal notch is too small, the notch will not reach the internal notch. Conversely, if the internal notch is too large, the sheath will have insufficient strength. For this reason, it is necessary to form an internal notch having an appropriate size between the external notches or between the external protrusions, which is difficult to manufacture.

In addition, even if the size and depth of the notch are appropriately formed and the above points are improved, the sealing performance at the introduction and lead-out portion of the cable such as the closure is lowered, and the waterproofness due to the notch may be impaired. There is.
The present invention has been made in view of the above-described situation, and does not require an internal notch or a tear string, ensures the tearability of the sheath by the notch formed on the sheath, and introduces a closure etc. An object of the present invention is to provide an optical fiber cable with improved sealing performance and a method for manufacturing the same.

An optical fiber cable according to the present invention is an optical fiber cable in which the outer periphery of a collective core containing a large number of optical fibers is covered with a sheath, and the outer surface of the sheath has a plurality of notches for tearing the sheath along the longitudinal direction. The remaining sheath thickness from the bottom of the sheath to the inner surface of the sheath periodically changes in the longitudinal direction. Further, the thickness of the remaining sheath, which changes periodically, is 0.3 mm to 0.6 mm at the thinnest portion, 0.9 to 1.2 mm at the thickest portion, and The length interval of the remaining sheath thickness that changes periodically is preferably 150 to 300 mm.
In the above optical fiber cable manufacturing method, a notch is formed in the outer surface of the sheath by post-processing.

  According to the present invention, cutting with a nipper or the like is performed at a portion where the remaining sheath thickness is thin, and introduction and derivation of the sheath into a closure or the like is performed at a portion where the remaining sheath thickness is thick. Both can be secured.

It is a figure explaining the outline of the optical fiber cable by this invention. It is a figure explaining an example of the tearing method of the sheath of the optical fiber cable by this invention. It is a figure explaining the comparative evaluation example of the optical fiber cable by this invention.

  Embodiments of the present invention will be described with reference to the drawings. In the figure, 10 is a fiber cable, 11 is a collective core, 12 is a slot rod, 12a is a slot groove, 13 is a tension member, 14 is an optical fiber, 15 is an upper tape, 16 is a sheath, 17 is a notch, 17a and 17b Is a notch, 18 is a notch, 19 is a nipper, and 19a is an oblique blade.

  As shown in FIG. 1A, the optical fiber cable 10 according to the present invention is intended for an optical cable having a structure in which the outer periphery of a collective core 11 in which a plurality of optical fibers are accommodated and bundled is covered with a sheath 16. . The collective core 11 in the present invention is a collection of a plurality of optical fiber cores or optical fiber tape cores using interpositions, slots, etc., and the outer side thereof is an upper winding tape (also referred to as a presser winding tape). It shall be in a state of being bundled using.

  An optical fiber cable 10 shown in FIG. 1A shows an example of a slot-type optical fiber cable that is frequently used as an optical fiber cable for a trunk line. The optical fiber cable 10 includes a slot rod (also referred to as a spacer rod) 12 made of a plastic material in which a tension member (also referred to as a tensile body) 13 is embedded and integrated at the center and a plurality of slot grooves 12a are provided. The slot groove 12a of the slot rod 12 is formed in a spiral shape or an SZ shape. In the slot groove 12a, a plurality of optical fiber core wires or a tape-like optical fiber core wire 14 (hereinafter including a tape core wire) is formed. Simply referred to as an optical fiber).

  In the state where the optical fiber 14 is housed in the slot groove 12a, the upper winding tape 15 is applied to the outer periphery of the slot rod 12. The upper winding tape 15 holds the optical fiber 14 accommodated in the slot groove 12a so that it does not jump out, and absorbs water to stop the heat insulation layer when the sheath 16 is molded, or water in the optical cable. An agent may be added to function as a water absorbing layer. Further, the upper winding tape 15 can be either a horizontal winding wound in a spiral shape or a vertical winding in the longitudinal direction, and the above-described state is described with the upper winding tape 15 applied. Thus, the aggregate core 11 is formed.

  The outside of the collective core 11 is covered with a sheath 16 to form an optical fiber cable 10. The sheath 16 is formed by extruding, for example, low density polyethylene (LDPE) or flame retardant polyethylene resin on the outer periphery of the collective core 11 to have a sheath thickness of about 1.5 mm to 2 mm, for example. . A plurality of sheath tearing notches 17 having a V-shaped cross section are continuously formed along the longitudinal direction of the outer surface of the sheath.

  The present invention is characterized in that the thickness t (hereinafter referred to as the remaining notch thickness) from the bottom of the notch 17 having the V-shaped cross section to the inner surface of the sheath periodically changes in the longitudinal direction. . In the notch 17, for example, the notch portions 17 a having a thin remaining thickness t 1 and the notched portions 17 b having a thick thickness t 2 are alternately and periodically formed in the cable longitudinal direction. The remaining notch thickness t1 of the notch portion 17a is, for example, ½ or less than the remaining notch thickness t2 of the notch portion 17b. In other words, the groove depth of the notch portion 17a is the groove depth of the notch portion 17b. It is deeper than the depth of.

The notch portion 17a and the notch portion 17b may be changed stepwise as shown in the figure, but may be changed continuously to draw a sine curve, for example.
For example, when the thickness of the sheath 16 is 1.8 mm, the remaining notch thickness t is 0.3 to 0.3 mm when the thickness of the remaining sheath thickness t1 of the notch portion 17a is 0.1 mm. The thickness of the thickest portion of the remaining sheath thickness t2 of the notch portion 17b is preferably about 0.9 to 1.2 mm.

The length d1 of the notch portion 17a and the length d2 of the notch portion 17b are preferably about 150 to 300 mm. Further, the length d1 of the notch portion 17a and the length d2 of the notch portion 17b may be the same length, or may be different. That is, the notch portions 17a having a small remaining sheath thickness and the notch portions 17b having a large remaining sheath thickness are alternately formed.
The length interval of the remaining sheath thickness that changes periodically is the distance between the centers of the notch portion 17a and the notch portion 17b when the remaining sheath thickness changes stepwise, and the remaining sheath thickness. When continuously changing, the distance from the thinnest part to the thickest part is 150 to 300 mm.

  FIG. 2 is a diagram illustrating an example in which the sheath 16 of the above-described optical fiber cable 10 is peeled off using a general tool such as an oblique blade nipper. First, as shown in FIG. 2A, within the length range of the notch portion 17a where the remaining notch thickness of the notch 17 is thin, one end of the sheath to be peeled is set, and a ring-shaped notch 18 is cut with a cutter or the like. Insert. Next, adjacent to the notch 18, the oblique blade 19 a of the nipper 19 is inserted into two adjacent notch portions 17 a and cut. The notch portion 17a has a thin remaining sheath and can be easily cut with the slanted blade 19a of the nipper, and can easily form a gripping portion that serves as a starting point for sheath tearing.

Next, as shown in FIG. 2B, the gripping portion 17c, which is the starting point of tearing, is sandwiched between the diagonal blades 19a of the nipper 19 and pulled in the direction of the arrow so as to be cut (turned back) to the outer surface of the sheath 16. Tear. In addition, after a certain amount of tearing has been performed, the gripping portion 17c folded by the nipper's oblique blade 19a is sandwiched on both sides of the gripping portion 17c so as to be wound around the outer periphery or adjacent by hand. The sheath portion between the notches is pulled along the longitudinal direction to tear. In this case, the notch portion 17b having a thick remaining sheath can be easily torn.
Then, the notch portion 17b having a large remaining sheath thickness is used as a cable introduction / extraction portion such as a closure to ensure the sealing performance.

  In FIG. 3, the evaluation test result of the optical fiber cable mentioned above is shown. The optical fiber cables (samples 1 to 4) used in the evaluation test had a sheath outer diameter (cable outer diameter) of 10.5 mm, a sheath thickness of 1.8 mm, and a low-density polyethylene (LDPE) as the sheath material. ), V-shaped cross-sectional notches were formed evenly at four locations.

Sample 1 was a comparative example of the present invention, and the remaining sheath thickness was 1.2 mm and was made constant in the length direction. In this case, the sealing property to the closure was good and the waterproof property was good, but it was not possible to cut with a nipper, and it was difficult to tear the sheath.
Sample 4 was also a comparative example of the present invention, in which the remaining sheath thickness was 0.3 mm and constant in the length direction. In this case, it was possible to cut with a nipper and to tear the sheath well, but the sealing performance against the closure was low, and waterproofness could not be secured.

Sample 2 had a remaining sheath thickness of 1.2 mm and a remaining sheath thickness of 0.3 mm, and was alternately arranged with a length of 150 mm. In this case, cutting with a nipper was possible, the sheath was able to be teared well, the sealing property against the closure was good, and the waterproof property was good.
Sample 3 had a residual sheath thickness of 1.2 mm and a residual sheath thickness of 0.3 mm as in Sample 2, but both were alternately arranged with a length of 300 mm. In this case, although not as much as the sample 2, it was possible to cut with a nipper and to tear the sheath, and to have a good sealing property against the closure and a good waterproof property.

As a result of the evaluation test described above, in order to cut the sheath with a nipper and form a gripping portion that becomes the starting point of the sheath tearing, the remaining notch thickness is about 0.3 mm (the depth of the notch groove is 1.2 mm). Degree). However, if the remaining notch thickness is less than 0.3 mm, there is a problem that it is easy to tear due to insufficient strength, and it is desirable that the sheath portion having a thin remaining sheath thickness is 0.3 mm to 0.6 mm.
On the other hand, in order to ensure waterproofness against the closure, it is necessary that the remaining notch thickness is about 1.2 mm (notch groove depth is about 0.6 mm). However, if the remaining notch thickness exceeds 1.2 m, the tearing force is large, and it is difficult to tear by hand alone. Therefore, the sheath portion having a thick remaining sheath thickness is 0.9 mm to 1.2 mm. It is desirable to do.

  In addition, if the length of the sheath portion having a large remaining notch thickness is too long, tearing becomes difficult. In addition, if the length of the sheath part with a thin remaining notch thickness is too short, it may be difficult to form the sheath tear start end, and even in a sheath part with a thick residual notch thickness, a sealed part may be secured. Since it may be difficult, the length of each sheath portion is preferably 150 mm or more.

  As described above, the notch for stripping the sheath of the optical fiber cable is formed alternately in the longitudinal direction of the cable and the notch portion having a thin remaining notch thickness and the notch portion having a thick residual notch thickness. Then, tearing of the notch is started at the notch portion where the remaining notch thickness is reduced, and the sheath is torn safely and easily by introducing it into the closure at the notch portion where the remaining notch thickness is increased. At the same time, it is possible to improve waterproofness against the closure and the like.

In addition, as a method of alternately forming a notch portion with a thin remaining notch thickness and a notch portion with a thick residual notch thickness in the longitudinal direction of the cable, the shape of the die outlet of the extruded portion of the sheath is determined at a predetermined timing. It can be realized by controlling.
In addition to controlling the extrusion molding part, post-processing after forming the sheath, notches are formed by cutting, etc., the cutting depth of the cutting blade is periodically changed in the cable longitudinal direction, and the remaining sheath thickness is adjusted. Alternating can be formed.

DESCRIPTION OF SYMBOLS 10 ... Fiber cable, 11 ... Collective core, 12 ... Slot rod, 12a ... Slot groove, 13 ... Tension member, 14 ... Optical fiber, 15 ... Top wound tape, 16 ... Sheath, 17 ... Notch, 17a, 17b ... Notch part 17c: Grasping portion, 18: Incision, 19 ... Nipper, 19a ... Diagonal blade.

Claims (4)

An optical fiber cable having a plurality of notches for tearing the sheath along the longitudinal direction on the outer surface of the sheath, covering the outer periphery of the collective core containing a large number of optical fibers,
An optical fiber cable characterized in that the remaining sheath thickness from the bottom of the notch to the sheath inner surface periodically changes in the longitudinal direction.   The thickness of the remaining sheath that periodically changes is characterized in that the thickness of the thinnest part is 0.3 mm to 0.6 mm, and the thickness of the thickest part is 0.9 to 1.2 mm. The optical fiber cable according to claim 1.   The optical fiber cable according to claim 1 or 2, wherein a length interval of the remaining sheath thickness that changes periodically is 150 to 300 mm.   The method for manufacturing an optical fiber cable according to any one of claims 1 to 3, wherein a notch is formed in the outer surface of the sheath by post-processing.

Images