JP3071403B2 - Optical fiber unit - 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 fiber unit used for an optical fiber cable on which optical fibers are mounted at a high density, and more particularly, to an optical fiber unit in which a plurality of optical fibers are twisted and used.

[0002]

2. Description of the Related Art As an optical fiber cable in which optical fibers are mounted at a high density, for example, a structure as shown in FIG. The optical fiber cable shown in FIG. 1 has a spiral spacer 1 arranged at the center and a plurality of optical fiber units 2 arranged around the spiral spacer 1.

An optical fiber 3 is provided around the outer periphery of the spiral spacer 1.
Are formed, and in each of the spiral grooves 4, an optical fiber 3 is accommodated in a stepped manner, and a holding tape 5 is wound around the outer periphery thereof.

The optical fiber unit 2 has a unit body 6 having a concave shape formed in a spiral shape, and a unit body 6 having a concave shape.
And the optical fibers 7 are stacked and housed in a stepped manner in the optical fiber unit 2. The optical fiber units 2 are twisted so as to be adjacent to each other along the outer peripheral surface of the press-winding tape 5. The presser winding tape 8 is wound around the outer periphery, and the outer periphery of the tape 8 is covered with a sheath 9 to form a hierarchical structure.

An optical fiber cable having such a structure is
Recently, adoption as a subscriber optical cable has been considered, and a spiral spacer 1 and an optical fiber unit 2 are provided so that branching can be performed without cutting the optical fiber cable itself.
Have been put to practical use.

Incidentally, the raw material of the spiral spacer 1 used for this type of optical fiber cable includes impact resistance,
In addition to physical properties such as rigidity and strength, environmental resistance performance such as low-temperature embrittlement performance and stress tracking performance is required.
T) A resin is used.

However, when the unit main body 6 of the optical fiber unit 2 is formed using such a resin, there are technical problems described below.

[0008]

That is, when the optical fiber unit 2 is twisted in an SZ shape around the spiral spacer 1 and the tension member, a PC / PB blended with a PBT resin or a polycarbonate (PC) resin.
When the T resin is used, the rigidity of the unit main body 6 increases, and there is a problem that when the unit main body 6 is bent in the groove width direction at the SZ inversion portion or the like, the side wall portion falls down into the groove.

When there is a large temperature change in the environment where the optical fiber cable is laid, the unit body 6 using HDPE undergoes recrystallization, so that the unit body 6 contracts in the longitudinal direction. This has caused a problem that the SZ inversion angle and the twist pitch are disturbed.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to prevent the side wall from falling down due to lateral bending and to reduce the longitudinal length due to environmental temperature change. An object of the present invention is to provide an optical fiber unit capable of suppressing a contraction in a direction and obtaining stable optical transmission characteristics.

[0011]

In order to achieve the above object, the present invention provides an optical fiber or an optical fiber tape having a plurality of SZ-shaped optical fibers or optical fiber tape cores which are housed around the center of a spiral slot or a tensile strength wire. a twisted synthetic resin optical fiber units are combined in the optical fiber unit has a unit body where the optical fiber storage groove is provided, it said unit main body includes a bottom portion defining the optical fiber receiving groove And a cross section having a pair of side walls formed upright at both ends of the bottom is substantially U-shaped, and the unit main body is made of PBT resin or a mixed resin of PC resin / PBT resin and HDPE resin. Formed in front
The PBT resin or PC resin / PB in the mixed resin.
The proportion occupied by the T resin was 70 to 30% by volume . According to the optical fiber unit configured as described above, the unit main body is made of PBT resin or PC resin / PBT resin and HD.
It is formed of a mixed resin with PE resin, and the volume ratio of these resins
Since the ratio is set within a specific range, the side wall has an appropriate rigidity according to the mixing ratio of these resins,
This part is prevented from falling down. On the other hand, when the environmental temperature change is large, the shrinkage of the HDPE resin is suppressed by the mixed PBT resin or PC resin / PBT resin. Further, the PBT resin or the PBT resin in the mixed resin is used.
PC resin / PBT resin accounts for 70-30 % by volume
, The effect of suppressing shrinkage with respect to rigidity and temperature changes can be more effectively exerted.

[0012]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a unit body 10 of an optical fiber unit according to the present invention. The unit main body 10 has a substantially concave optical fiber housing groove 12 formed in the center.

The unit main body 10 includes the optical fiber housing groove 1.
2 and a pair of side wall portions 16 formed upright at both ends of the bottom portion 14, and has a substantially U-shaped cross section.

On the central axis of the bottom portion 14, one or a plurality of tensile members 18 made of organic fibers, glass fibers, steel wires or the like are buried along the longitudinal direction. The unit main body 10 is formed of a PBT resin or a PBT resin or a mixed resin of a PC / PBT resin and an HDPE resin in the following mixing ratio.

Next, the unit body 10 having such a shape will be described.
A brief description will be given of a method of manufacturing the device. Unit body 10
When molding the tensile strength member, the tensile strength member 18 is sent out to a crosshead die to which a U-shaped die plate is attached, and the HDPE resin and the PBT resin or PC / PB
This is performed by extruding a mixed resin with the T resin.

The blend of HDPE resin and PBT resin is
After dry blending with a blender, supply to a crosshead die. In this case, HDPE resin and PB
The T resin or the PC / PBT resin may be blended as it is, but if an additive such as a wax having compatibilizing performance is slightly added, the mixing of both resins becomes easy,
And it can be uniformly dispersed.

The shape of the manufactured unit main body 10 is such that the dimensions of the optical fiber housing groove 12 are 4.6 mm in outer width and 3. mm in inner width.
The thickness was 8 mm, the groove depth was 4.7 mm, and the thickness of the bottom portion 14 and the side wall portion 16 was about 1 mm.

Example 1 An HDPE resin and a PBT resin were blended, and a mixed resin having a volume ratio of the PBT resin of 30% was extruded to obtain a unit body 10 having a sectional shape shown in FIG.

Example 2 An HDPE resin and a PBT resin were blended, and a mixed resin having a volume ratio of the PBT resin of 50% was extruded to obtain a unit body 10 having a sectional shape shown in FIG.

Example 3 An HDPE resin and a PBT resin were blended, and a mixed resin having a volume ratio of the PBT resin of 70% was extruded to obtain a unit body 10 having a sectional shape shown in FIG.

Comparative Example 1 An HDPE resin and a PBT resin were blended, and a mixed resin having a volume ratio of the PBT resin of 15% was extruded to obtain a unit body 10 having a sectional shape shown in FIG.

Comparative Example 2 An HDPE resin and a PBT resin were blended, and a mixed resin having a volume ratio of the PBT resin of 85% was extruded to obtain a unit body 10 having a sectional shape shown in FIG.

Comparative Example 3 A single HDPE resin was extruded to obtain a unit body 10 having a sectional shape shown in FIG.

[0025]Comparative Example 4  Extrusion molding of PBT resin alone, the cross-sectional shape shown in Figure 1
Was obtained.

The heat shrinkage, bending stiffness,
When the bending buckling diameter was examined, the results shown in Table 1 below were obtained.

[0027]

[Table 1]

The heat shrinkage is the shrinkage when a 1 m sample is left in an atmosphere at 100 ° C. for one hour. The bending rigidity is the rigidity when the unit body is bent in the width direction.
The bending buckling diameter is a diameter at which the unit main body is bent in the width direction and the groove width of the unit starts to change.

As can be seen from the results in Table 1, Example 1
In Comparative Examples 1 to 3, the heat shrinkage was smaller than that of Comparative Examples 1 and 3, the bending rigidity was smaller than that of Comparative Example 4, and the bending buckling diameter was smaller when the unit body 10 was bent in the width direction. While the diameter at the beginning of the change was as large as 800 mm, in Examples 1 to 3, it was as small as 600 to 700 mm.

Next, a non-woven fabric tape is pressed and wound around the outer periphery of a spacer on which an 800-core optical fiber having an outer diameter of 24.5 Φmm is mounted, and the core material is placed around the inside of the unit body 10 of the embodiment and comparative example. After assembling 10 pieces of 8-core optical fiber tape having a thickness of 0.3 mm and a width of 2.1 mm, 15 pieces were twisted in an SZ shape, further wrapped around the outer circumference with a nonwoven tape, and then covered with a PE sheath. A 200-core optical fiber cable having an outer diameter of 45 mm was manufactured in a length of 200 m.

The twist reversal angle of the unit is 3
00 ° and the inversion pitches were 450 mm and 350 mm. In each of the obtained optical fiber cables, the transmission performance of the optical fiber of each unit was measured.

For an optical fiber cable having an inverted pitch of 350 mm, a transmission loss was measured at a wavelength of 1.55 μm, and a heat cycle test at −30 ° C. to 70 ° C. was performed five times, and then the transmission characteristics were measured again. Table 2 shows the measurement results.

[0033]

[Table 2]

As can be seen from the results shown in Table 2, in Examples 1 to 3, the transmission loss was smaller than that of each of the comparative examples. In particular, in the case of the comparative example, the transmission loss after the heat cycle test was small. Although it becomes very large, it hardly changes in Examples 1 to 3.

In the above embodiment, the case where the optical fiber unit is twisted and assembled in an SZ shape around the outer periphery of the spiral spacer is exemplified. However, the embodiment of the present invention is not limited to this configuration. The present invention is also applicable to a configuration in which the units are directly twisted and assembled on the outer periphery of the tension member.

[0036]

As described in detail in the above embodiments, according to the optical fiber unit of the present invention, by combining different resins, it is possible to prevent disturbance such as environmental temperature change.
It can suppress the longitudinal shrinkage of the unit,
When twisted in the SZ shape, the phenomenon that the unit side surface portion falls into the groove is eliminated, so that stable and high transmission characteristics can be secured for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a unit main body of an optical fiber unit according to the present invention.

FIG. 2 is a sectional view showing an example of the present invention and a conventional optical fiber cable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Unit main body 12 Optical fiber accommodation groove 14 Bottom part 16 Side wall part

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nori Ishii 2-1-1, Yabuta Nishi, Gifu City, Gifu Prefecture Ube Nitto Kasei Co., Ltd. Gifu Research Laboratory (72) Inventor Hideyuki Iwata 3-chome Nishishinjuku, Shinjuku-ku, Tokyo No. 19-2 Nippon Telegraph and Telephone Corporation (72) Inventor Hiroki Ishikawa 1 Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Inside Yokohama Works (72) Inventor Yoshiyuki Suetsugu 1 Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Address Sumitomo Electric Industries, Ltd. Yokohama Works (56) References JP-A-8-5878 (JP, A) JP-A-7-294784 (JP, A) JP-A-6-331866 (JP, A) 6-331864 (JP, A) JP-A-5-261843 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/44

Claims (1)

(57) [Claims] The outer periphery of 1. A centrally located spiral slot or tensile strength wire, a plurality of accommodating the optical fiber or optical fiber ribbon core is a synthetic resin optical fiber units twisted SZ form, The optical fiber unit has a unit main body provided with an optical fiber housing groove, and the unit main body has a bottom defining the optical fiber housing groove and a pair of side walls formed to rise at both ends of the bottom. And the unit body is made of PBT resin or PC resin / PB
Forming a mixed resin of T resin and HDPE resin, the PBT resin or PC resin / P of the mixed resin
An optical fiber unit wherein the ratio of the BT resin is 70 to 30% by volume .