JP3445718B2 - Fiber optic cable - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an SZ type optical fiber cable spacer rod which is repeatedly turned and turned while a groove for accommodating an optical fiber extends in a longitudinal direction.
The present invention relates to an optical fiber cable, and more particularly to an optical fiber cable for preventing an arrangement of an optical fiber tape from being disturbed. 2. Description of the Related Art A groove for accommodating optical fiber tapes in a stacked manner is formed on a spacer rod configured as a core structure of an SZ type optical fiber cable. FIG. 2 shows the layout of the grooves. The illustrated cylinder 1a represents the outer periphery of the spacer rod without the groove, and only the center line 2a of the opening of the groove is shown on the surface of the cylinder 1a.
The groove (center line 2a) turns from a predetermined circumferential angle to a predetermined opposite circumferential angle during a predetermined pitch in the longitudinal direction of the cylinder 1a, and reverses the direction to the predetermined circumferential angle. It is turning. The part where the turning direction of the groove is reversed is called a reversal part C,
Intermediate portions between two adjacent inverted portions are referred to as normal portions A and E (hereinafter, unified to A). The intermediate part between the reversing part C and the normal part A will be referred to as transition parts B and D for convenience. FIG. 3 shows a cross section of a normal part A, a transition part B, and a reversal part C of a spacer rod. As shown, the outer diameter d of the spacer rod 1 is 10 mm, and the depth of the groove is h.
Are 2 mm, the width w of the groove is 2 mm, and five grooves 2 are provided at equal intervals in the circumferential direction. The width w of these grooves 2 is continuously uniform irrespective of the position of the spacer rod 1 in the longitudinal direction. The distance between the adjacent reversing parts C, C,
The so-called inversion pitch is 150 mm, and the circumferential angle between both inversion parts C, C, the so-called inversion angle is 270 °. In an optical fiber cable, this groove 2
Inside, five optical fiber tapes 3 each having a width of 1.2 mm and a thickness of 0.3 mm are laminated and mounted. In the normal part A,
These five optical fiber tapes 3 are stacked neatly (with a relative twist of 0 °) in the groove, and the bottom of the groove and the lowermost optical fiber tape 3 are in full contact.
However, when the position is changed in the longitudinal direction, the position and the direction of the cross section of the groove 2 are changed. That is, the groove 2 is twisted. In contrast,
The four-fiber optical fiber tape 3 has a higher torsional rigidity than single-fiber or two-fiber optical fiber tapes, and therefore does not twist much.
Therefore, the torsion of the groove 2 and the torsion of each optical fiber tape 3 do not coincide with each other, and the two are relatively torsioned. Not done. For example, at transition B, the relative twist is about 45 °, and at reversal C, the relative twist is about 90 °. Since the twist of the groove 2 from the normal portion A to the reverse portion C is 135 °, the twist of the optical fiber tape 3 itself is the largest at the reverse portion C and is approximately 45 °. [0005] In the mounting state of FIG.
Even though the optical fiber tape 3 is twisted, the arrangement of the optical fiber tape 3 in the groove 2 is not lost, and thus the arrangement of the optical fiber tape 3 over the entire length of the optical fiber cable. If held, the transmission characteristics of the optical fiber will not be adversely affected. However, conventionally, the dimensions of the groove 2 are continuously uniform, and the maximum space is required when the relative twist with the optical fiber tape 3 at the transition portion B is about 45 °. Therefore, there is room in other parts. In particular, in the normal part A and the reversal part C,
A large amount of extra space occurs. For this reason, as shown in FIG. 4, the optical fiber tape 3, especially the upper optical fiber tape 3, may be separated from the lamination and the arrangement of the optical fiber tape may be disturbed. The optical fiber tape 3a thus separated from the lamination receives bending side pressure from the inner surface of the groove 2 or another optical fiber tape 3, so that transmission loss may increase. For example, an increase in transmission loss ranging from 1 dB / km to several dB / km may be observed in the wavelength band of 1.3 μm and 1.55 μm. Further, the optical fiber having an increased transmission loss tends to have a large loss variation even in a subsequent temperature characteristic test. An object of the present invention, the light to prevent the above problem was solved, an optical fiber ribbon array of disturbed
An object of the present invention is to provide a fiber cable . [0009] In order to achieve the above object, an optical fiber cable according to the present invention comprises an outer portion of a spacer rod.
It has a groove on the circumference, and this groove repeats at a predetermined pitch in the longitudinal direction.
This groove is formed by turning so that the turning direction is reversed.
Fiber optic cable housing optical fiber tape
In the case of the bull, the groove is opposite to the direction in which the turning direction is reversed.
A normal part located between the turning part and two adjacent turning parts.
The groove at the reversal part is formed
The width of the above is higher than the height of the laminated optical fiber tape
Larger than the thickness of the optical fiber tape alone, normal above
The width of the groove at the section is smaller than the width of the optical fiber tape.
It is larger than the thickness of the fiber tape alone . Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 2 shows the arrangement of grooves in the spacer rod of the SZ type optical fiber cable according to the present invention, as in the prior art. FIG. 1 is a sectional view of an optical fiber cable according to the present invention.
Shown in FIG. 1A is a cross section at a normal portion A of the spacer rod, FIG. 1B is a cross section at a transition portion B, and FIG.
(C) shows a cross section of the reversal part C. The spacer rod 1 has an outer diameter d of 10 mm as in the prior art, and is provided with five grooves 2 at equal intervals in the circumferential direction. The inversion pitch of the groove 2 is 150 mm, and the inversion angle is 270 °. In this groove, the width is 1.2
5 mm optical fiber tape 3 with a thickness of 0.3 mm
The sheets are stacked and mounted. FIG. 1 shows an optical fiber tape 3 mounted on only one groove 2. In the present invention, the size of the groove 2 differs depending on the position of the spacer rod 1 in the longitudinal direction. here,
The depth h of the groove 2 is uniformly 2.0 mm at any position, but is formed by changing the width w periodically and continuously. When the width w of the groove 2 is shown for a specific part, it is 2.0 mm in the transition parts B and D, but 1.4 m in the normal part A.
m, which is the narrowest between the transition part D and the transition part B. In the reversal part C, the distance is 1.7 mm, and is the narrowest between the transition part B and the transition part D. The width w of the groove 2 in the normal part A and the reverse part C is determined as follows. That is, the width w of the groove 2 at the reversal part C is
The width of the groove w at the normal portion A is larger than the height of the laminated optical fiber tape 3 by less than the thickness of the single optical fiber tape.
Is larger than the width of the optical fiber tape 3 by less than the thickness of the optical fiber tape alone. Therefore, in the inverted portion C, the groove width w−the tape stacking height <the tape thickness 0.3 mm. In the normal portion A, the groove width w−the tape width <the tape thickness 0.3 mm. Now, in the optical fiber cable of the present invention, in the normal portion A, since the optical fiber tape 3 is laminated neatly (with a relative twist of 0 °) to the groove 2, Although the width w is as small as 1.4 mm, the optical fiber tape 3 is accommodated with some margin. The gap between the optical fiber tape 3 and the groove 2 is 0.1 mm on one side and 0.2 mm on both sides. Since the gap is small as described above, there is no gap in which the optical fiber tape 3 detached from the lamination falls, and as a result, the arrangement of the optical fiber tape 3 is prevented from being disturbed. In the transition portions B and D, the optical fiber tape 3 is twisted by about 45 ° with respect to the groove 2 and requires the maximum space, so that the width of the groove is widened to 2.0 mm. At the reversal portion C, the point that the width w of the groove is narrow is the same as that of the normal portion A, but since the relative twist between the optical fiber tape 3 and the groove 2 is about 90 °, the groove w Is 1.7 mm, which has some margin for the lamination height of the optical fiber tape 3. Since the gap between the optical fiber tape 3 and the groove 2 is small, the optical fiber tape 3
Are not easily separated from the lamination, and as a result, the arrangement disorder of the optical fiber tape 3 is prevented. In the optical fiber cable of the present invention, the increase of the initial loss in the wavelength band of 1.3 μm and 1.55 μm in the step of forming a cable is 0.03 dB / km, which is extremely small as compared with the conventional one. Conventionally, a loss increase of several dB / km may occur due to an irregular arrangement of the optical fiber tape. However, in the present invention, since the groove width w is reduced in the normal portion A and the inversion portion C, The arrangement of the optical fiber tape 3 is not disturbed, and as a result, local side pressure and bending are not applied to the optical fiber tape 3, so that an increase in loss can be prevented. Also, when bending and lateral pressure are applied to the optical fiber tape 3 at room temperature due to misalignment, the linear expansion coefficient of the optical fiber is smaller than that of the spacer rod 1.
When the temperature becomes low, the bending applied to the optical fiber tape 3 increases, and when the temperature becomes high, the side pressure increases because the optical fiber tape 3 is stretched, so that the loss increases at both the low temperature and the high temperature. According to the present invention, since the arrangement disorder can be prevented,
The temperature characteristics of loss become stable. In the above embodiment, the width w of the groove is continuously changed. However, the following form can be used to simplify the groove processing. That is, in one groove, a width of 1.2
4 mm optical fiber tape 3 with a thickness of 0.3 mm and a thickness of 0.3 mm
The layers are stacked and mounted. As a result, since the tape stacking height matches the tape width, the normal portion A and the reverse portion C
And can make the width w of the groove the same. Since the width w of the groove in the normal part A and the reverse part C is the narrowest in the entire length of the groove, a groove having a constant width is formed first, and then the groove of the transition part B is enlarged. Grooves having a constant width can be formed by conventional existing equipment (such as an extruder). The groove 2 is enlarged by cutting or the like. In this case, in order to reduce the local side pressure applied to the side surface of the optical fiber tape 3,
It is preferable to continuously change the groove width. However, even if the groove width is changed in a stepwise manner by cutting, there is no practical problem as long as an extreme convex portion is removed by chamfering a corner. In the above embodiment, the groove 2 is formed symmetrically with respect to the diameter of the spacer rod 1 as an axis. However, the groove 2 is inclined leftward or rightward with respect to the diameter of the spacer rod 1. You may. The present invention exhibits the following excellent effects. (1) The increase in the initial loss in the step of forming the cable is extremely small, and the quality of the SZ type optical fiber cable is improved. (2) Since the temperature characteristics of the loss are stable, the environmental resistance of the SZ type optical fiber cable is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an SZ type optical fiber cable spacer rod showing one embodiment of the present invention. FIG. 2 is a perspective view showing a leading shape of a groove on a spacer rod. FIG. 3 is a cross-sectional view of a conventional SZ type optical fiber cable spacer rod. FIG. 4 is a cross-sectional view showing a defect of a conventional spacer rod for an SZ type optical fiber cable. [Description of Signs] 1 Spacer rod 2 Groove 3 Optical fiber tape A Normal part B Transition part C Inversion part

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hisanori Nakai 880 Sunazawa-cho, Hitachi City, Ibaraki Prefecture Inside the Takasago Plant, Hitachi Cable, Ltd. (56) References JP-A-8-234064 (JP, A) JP-A-8- 152545 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 6/44

Claims (1)

(57) [Claims 1] A groove is formed on the outer periphery of the spacer rod.
The groove repeatedly reverses the direction at a predetermined longitudinal pitch
It is formed by swiveling, and the optical fiber tape
In an optical fiber cable in which
A groove is formed between the reversing part where the direction of the rotation is reversed and the adjacent two
The width is narrowed at the normal part located between the two inversion parts
The width of the groove at the reversal part is
The above optical fiber tape unit is
Larger than the body thickness, the width of the groove at the normal part is
The above optical fiber tape alone than the width of the optical fiber tape
Fiber optic cable characterized by being less than the thickness of
Bull.