JPH02167510A - Optical cable and production thereof - Google Patents

Abstract

PURPOSE:To obtain specified mechanical strength by integrally winding a thermally expanding wire rod together with plural optical fibers. CONSTITUTION:The thermally expanding wire rod 9 is integrally wound together with the optical fibers 2, 2,.... The thermally expanding wire rod 9 is unitized to the same length as the length of the optical fibers 2, 2,... and is roughly wound by a wire rod member 10. This optical fiber unit 11 is assembled in the gap part of an external sheath 12 to constitute the optical cable. The thermally expanding wire rod 9 is cooled down to the temp. lower than the temp. at which the fibers is bundled in the stage when the optical fiber unit is housed in the optical cable. The thermally expanding wire rod 9 is shrunk and the optical fiber unit 11 is held curved in a wave shape along the thermally expanding wire rod 9. Excess tension, is, therefore, not exerted on the optical fibers 2, 2,... and the deterioration of the optical fibers 2, 2,... is prevented even if tension is applied on the optical cable. A surplus length is surely applied to the optical cable and cable is provided with the specified mechanical strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical cable in which integrated optical fiber units are accommodated in a gap, and a method for manufacturing the same.

[Conventional technology]

The original tensile strength of optical fibers, especially silica-based optical fibers, is approximately 300 Kg/m2, but it tends to deteriorate when tension is applied to the optical fibers due to external factors.

As methods for protecting optical fibers from external factors, there are two types: a loose type in which the strands or core fibers are housed freely in an air gap, and a tight type in which they are assembled together via a buffer layer that reduces the propagation of lateral pressure. (Current status and future of optical communications, Telecommunications technology deliberations, p.

211).

By the way, even if the tension applied to the optical cable is less than the tension that would immediately break the optical cable, if it is applied for a long time, the optical fiber will deteriorate and eventually break.

Therefore, while the optical cable is being pulled with tension within a predetermined allowable range, the optical cable is designed to provide extra length to the optical fiber to prevent abnormal tension from being applied to the optical fiber housed within the cable. It has been devised.

Figure 4 shows a conventional optical cable (
A New Simple Optical Cable
e Manufactured in a Single
Process, THE TRANSACTIO
NS 0FTHE IECE OF JAPAN, VO
L, E69. No. 4 APRIL 198B).

FIG. 5A is a perspective view showing the basic configuration of an optical cable. Optical cable] is a plurality of optical fibers 2.2,...
, is loosely wrapped with a colored yarn 3 to form an optical fiber unit 4 into a unit.
It is configured to be housed within a gap in the AP jacket 5. usually,
A plurality of optical fiber units are housed in this gap.

Note that a 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 an example of the structure of a conventional optical cable. An aluminum chip 8 is adhered to the inner surface of the cable core 7 of the optical cable 1. An optical fiber unit 4 is housed within this cable core. Note that two tensile strength members 6.6 are buried at eccentric positions of the optical cable 1.

In this way, since the tensile strength member is buried at an eccentric position within the cable, when the optical cable is bent at a predetermined curvature, tension is applied to the optical fiber unit.

Therefore, in the manufacturing process of optical cables, when winding the optical cable, the optical cable is bent at a predetermined curvature using a winding drum, etc., and the deviation between the neutral axis and the core position when bending the cable is utilized. This gives extra length to the optical fiber.

The ratio of the excess 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 middle position of the two tensile strength members 6.6 and the center of the cable. This ratio can be controlled by

[Problem to be solved by the invention]

However, in conventional optical cables, extra length is given to the optical fiber during the winding process, so when the optical cable is wound in multiple layers, the radius of curvature is different between the lower layer and the upper layer of optical cable that contact the winding drum. However, there was a problem in that the extra length given to the optical fiber was different. In this case, the extra length given to the optical fiber differs partially in the optical axis direction (longitudinal direction), resulting in a difference in mechanical strength in terms of tension resistance.

Furthermore, if an extra length is added in advance to accommodate the optical cable, the core wire may become slack, making manufacturing difficult.

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

Another object of the present invention is to provide a method for manufacturing an optical cable that can easily provide a desired extra length to the optical fiber unit within the cable.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an optical cable in which integrated optical fiber units are housed in a gap, a plurality of optical fibers in which the optical fiber units are assembled in the same direction, and a plurality of optical fibers in which the optical fiber units are assembled in the same direction. The present invention is characterized in that it is comprised of a thermally expandable wire layer, and coarse winding means for roughly winding the optical fiber and the thermally expandable wire at a predetermined pitch.

In addition, in a method for manufacturing an optical cable in which an integrated optical fiber unit is housed in a gap, a first step of concentrating a plurality of optical fibers together with a heated thermally expandable wire, and a step of connecting the thermally expandable wire and the optical fibers into a wire. a second step of roughly winding the optical fiber unit in a spiral shape with a shaped member; a third step of cooling the thermal expansion wire material and curving the optical fiber unit in a wavy manner along the thermal expansion wire material; The fourth unit is assembled into the cavity to form an optical cable.
It consists of the following steps.

[Effect]

Since the present invention is configured as described above, the heated thermal expansion wire is integrally wound with a plurality of optical fibers, so that when the thermal expansion wire contracts, the optical fiber becomes the thermal expansion wire. curve in a wavy manner.

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

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical cable and a method for manufacturing the same according to the present invention will be described below with reference to the accompanying drawings. In the description, the same elements are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is an exploded perspective view showing an embodiment of an 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 integrally wound together with the optical fibers 2, 2, . The thermal expansion wire 9 is formed into a unit with the same length as the optical fibers 2.2, . . . , and is roughly wound around a linear member 10 such as a colored string. This optical fiber unit 1
1 is assembled into the cavity of the outer sheath 12 to form an optical cable.

In addition, at the stage when it is stored in the optical cable, the thermal expansion wire 9
The optical fiber unit is cooled down from the temperature at which it is condensed, giving the optical fiber unit extra length. In other words, the thermal expansion wire 9 contracts, and the optical fiber unit 11 curves in a wavy manner 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 deterioration of the optical fibers 2.2, . . . can be prevented.

FIG. 2 is a side view for explaining the operation of the optical fiber unit described above. In the same figure (a), optical fiber 2.2,
... shows a state (heated state) in which the thermal expansion wire 9 is wound around the linear member 10, and a plurality of optical fibers 2.2, . . . are wrapped together with the heated thermal expansion wire 9. It is roughly wound by a shaped member 10.

FIG. 2(b) shows a state (cooled state) in which the optical fibers 2, 2, . Layer 9 shrinks. In this case, multiple optical fibers 2
．． Since the wires 2, . . . are tightly attached to the thermal expansion wire 9 by being wound with the linear member 10, they curve in a wavy manner along the thermal expansion wire 9. Therefore, optical fiber unit 1
] has an extra length in the longitudinal direction.

In this case, the linear expansion coefficient of the thermal expansion wire 9 is 1.4×10−
If it is 5℃-1, heat it to 100℃ in the wrapped state and bring it to room temperature (200C) while stored in the optical cable.
When cooled to 0.1%, an extra length of 0.1% can be provided.

However, when an optical fiber is bent, the optical transmission loss tends to increase, so it is desirable to set a limit on the radius of curvature in order to suppress the optical transmission loss to a range that does not cause any practical problems. For example, when using transmission light with a wavelength of 1.55 μm for a single mode optical fiber, lkm
In order to suppress the increase in loss per unit to 0.1 dB or less, it is necessary to maintain the radius of curvature of the optical fiber at 60 mm or more. 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 spirally wound around the thermal expansion wire 9 is P≧ 2πRJ ((60-R)/R) ... (1
)Must.

In this case, if the linear member contracts too much and the optical fiber comes out from the linear member, the above assumption will no longer hold.
For example, when using a temperature difference of 50°C to give an extra length to an optical fiber, the linear fat expansion coefficient σ of the thermal expansion wire is J(P 1) A, /(1+(2
If πR/P) 2) is B, then σ≦ (1-2πR
/ (P-A-B)) 150.

In addition, when using polyethylene material with a linear expansion coefficient of 7 x 105℃-1, by changing the thickness and adjusting the cooling efficiency until the optical fiber is wound, the optional extra length can be reduced by 0.5%. can be given up to.

Note that although this embodiment shows a loose type optical cable in which the optical fiber unit is freely housed in a gap, the present invention is not limited to loose type optical cables. For example, tight type optical cables may be used, which are integrated together via a buffer layer that reduces the propagation of lateral pressure. Any optical cable having at least a gap such as a groove in the longitudinal direction can be applied.

Furthermore, in order to reduce slippage between the thermal expansion wire 9 and the optical fibers 2.2, . .

For example, the surface may be poorly finished or coated with a material with a high coefficient of friction.

FIG. 3 shows a spacer that accommodates a spacer having a groove in the longitudinal direction.
1 shows an embodiment of a tight type optical cable manufacturing apparatus. The optical fibers 2.2, . . . supplied by the optical fiber supply devices 13, 13, . . In this case, a heater 16 is provided between the thermal expansion wire supply device 14 and the rough winding head 15.
is provided, and the thermal expansion wire 9 is fed into the rough winding head 15 in a heated state. In the coarse winding head 15, the thermal expansion wire 9 is roughly wound around the optical fibers 2, 2, .

This optical fiber unit 11 is inserted into a spacer 19 supplied from a spacer supply device 18 in a concentrator 17 . The spacer 19 is wrapped around the tape by a taping head 20. Note that in the case of a loose type optical cable, the process of storing it in the spacer 19 and taping it is unnecessary.

After that, one taped spacer is transferred to the extruder 21.
Sheathed with It is effective to cool the optical fiber unit 11 between the taping head 20 and the extruder 2]. The optical cable extruded by the extruder 21 is fed at a constant speed by a caterpillar 22 and wound around a winding drum 23.

Next, a method for manufacturing an optical cable according to the present invention will be explained based on the above-mentioned manufacturing apparatus. This invention basically consists of 4
It is composed of processes.

In the first step, a plurality of optical fibers 2.2,...
The wire is concentrated together with the heated thermal expansion wire. The heating temperature in this case is determined to be an optimum value, taking into consideration the number of optical fibers to be concentrated, the wire diameter, the material of the thermal expansion wire, the wire diameter, the feed speed, etc.

In the second step, the thermal expansion wire 9 and the optical fiber 2.2,
... is roughly wound spirally with a linear member (not shown),
An optical fiber unit 11 is formed. In this case, it is desirable to set the pitch interval for winding the wire portions based on 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 curved in a wave shape along the thermal expansion wire 9 (second step).
(See figure (b)). At this stage, the optical fiber unit 11
is given extra length.

In this case, if the pitch interval of the linear members is set based on equation (1), the radius of curvature of the optical fiber will be 60 mm or more, and the optical transmission loss will be 0.1 dB or less.

In the fourth step, the optical fiber unit 1=11 is sheathed by extrusion or the like and assembled into the gap of the optical cable.

In addition, in the case of tight type optical cable, the third and fourth steps
The process includes a step of storing the optical fiber unit 11 in a spacer and wrapping it with tape.

〔Effect of the invention〕

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

Furthermore, the optical cable manufacturing method according to the present invention can easily provide a desired extra length to the optical fiber unit within the cable. In this case, the surplus length ratio can be easily controlled by changing the temperature difference (heating temperature - cooling temperature) and the abrasiveness of the thermal expansion wire (by changing the coefficient of linear expansion). Therefore, a desired extra length can be easily provided to the optical cable.

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

[Brief explanation of the drawing]

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. 3 is a diagram showing an embodiment of the optical cable according to the present invention. FIG. 4, a block diagram showing an embodiment of an optical cable manufacturing apparatus, is a diagram showing an optical cable according to the prior art. 1... Optical cable 2... Optical fiber 3... Colored string 4.11... Optical fiber unit 5... LAP jacket 6... Tensile strength body 7... Cable core 8... Tape 9 . . . Thermal expansion fat wire 10 . . . Line member 12 . . . External sheath 13 . Heater 17... Line concentrator 18... One spacer supply device... Spacer 20... Taping head 21... Extruder 22... Caterpillar 23... Winding drum

Claims (1)

[Claims] 1. In an optical cable in which an integrated optical fiber unit is housed in a gap, the optical fiber unit has a plurality of optical fibers assembled in the same direction, and a plurality of optical fibers arranged in the same direction as the optical fibers. 1. An optical cable comprising: a collection of thermal expansion wires; and a coarse winding means for roughly winding the optical fiber and the thermal expansion wire at predetermined pitch intervals. 2. The outer diameter of the circumscribed circle that includes the optical fiber unit is d [mm], the outer diameter of the thermal expansion wire is D [mm], (d
+D)/2 is R, the pitch interval is 2πR
2. The optical cable according to claim 1, wherein the optical cable is equal to or larger than √((60-R)/R). 3. The pitch interval of the rough winding means is P [mm], √(P^
When 2-1) is A and √(1+(2πR/P)^2) is B, the coefficient of linear expansion of the thermal expansion wire is 1.4 x 10^- between 30°C and 100°C. ^5 or more, (1-2π
The optical cable according to claim 1, characterized in that R/(P・A・B))/50 or less. 4. A method for manufacturing an optical cable in which an integrated optical fiber unit is housed in a gap, including: a first step of concentrating a plurality of optical fibers together with a heated thermal expansion wire; and the thermal expansion wire and the optical fiber. a second step in which the optical fiber unit is roughly wound spirally with a linear member to form an optical fiber unit; and a third step in which the thermal expansion wire is cooled and the optical fiber unit is curved in a wavy manner along the thermal expansion wire. and a fourth step of assembling the optical fiber unit into a gap to form an optical cable.