JPH03267905A - Method for adjusting surplus length of optical fiber in coating pipe - Google Patents

Abstract

PURPOSE:To uniformly provide an optical fiber with a required surplus length along its longitudinal direction with high accuracy by inserting an optical fiber into a coating pipe P in an elongated state and releasing the tension after the optical fiber is inserted therein. CONSTITUTION:A device for imparting tension to the coating pipe consists of a feeder 11, a tension controller 21 and a coiler 31. The tension controller 21 is mounted with a pair of stationary rollers 23 and a hydraulic cylinder 24 on a stand 22 and the coiler 31 is rotatably supported to a bobbin 32 for coiling the coating pipe P on a lifting base 34. The tension is applied to the coating pipe P within the elastic region thereof to elongate the coating pipe P by as much as the required surplus length of the optical fiber when the steel pipe P is taken up while the tension is imparted thereto by the device constituted in such a manner. The optical fiber is inserted into the coating pipe P while the coating pipe P is held elongated. The tension is released after the optical fiber is inserted. The required surplus length is imparted to the optical fiber uniformly in its longitudinal direction with the high accuracy in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method for adjusting the extra length of an optical fiber within a cladding tube.

The invention is utilized in the manufacture of optical fiber cables coated with metal or non-metallic tubes.

[Conventional technology] Optical communication cables that have become widely used in recent years are
There is an increasing demand for optical fiber cables that are coated with metal tubes, have excellent environmental resistance, are lightweight, and have a small diameter.

There is a large difference in mechanical properties and coefficient of thermal expansion between coated tubes such as metal tubes and optical fibers. For this reason, when an optical fiber cable is stretched or bent, the optical fiber or cladding tube may not be able to fully stretch. Further, when an optical fiber cable is exposed to high temperatures, the cladding tube may stretch more than the optical fiber due to the difference in thermal expansion coefficient between the cladding tube and the optical fiber. In these cases, excessive tension is applied to the optical fiber, which may cause the optical fiber to break.

In order to solve such problems, attempts have been made to provide optical fibers with extra length. That is, the optical fiber is made to be longer than the cladding to some extent while the optical fiber cable is kept at a uniform temperature over its entire length. This extra length is called extra length. If the optical fiber is given extra length, even if the cladding tube stretches more than the optical fiber due to the difference in coefficient of thermal expansion, as long as the elongation is smaller than the extra length, no tension will be applied to the optical fiber.

Regarding the extra length of optical fiber, for example, Japanese Patent Application Laid-Open No. 57130
002 r Temperature Compensation Method J for Optical Fiber Diameter Cable and Japanese Unexamined Patent Publication No. 59-191517 r Manufacturing method of metal tube containing linear body with extra length" is known. These disclosed techniques detect the moving speed and hoop speed of the optical fiber, synchronize the two speeds at a fixed ratio, insert the optical fiber into the tube, and provide extra length. Also, JP-A-63-18720
In the technology disclosed in ``Method for manufacturing a tube containing a linear body'', the tube is vibrated and the linear body is inserted into the tube, and then the tube is inserted again with the tip of the linear body restrained from advancing. Vibrate to give extra length.

[Problem to be solved by the invention] The above conventional method has the following problems.

The extra length of the optical fiber must be long enough to suit the conditions of use, and the variation in the extra length per unit length must be within a required range, that is, it must be uniform.

Furthermore, when manufacturing an optical fiber cable, it is necessary to be able to easily adjust the extra length with high accuracy.

Said JP-A-57-130002, JP-A-59-1915
In the methods disclosed in No. 17 and JP-A-63-187209, the amount of extra length is limited, and it is difficult to freely adjust the amount of extra length with accuracy depending on usage conditions.

That is, JP-A-57-130002 and JP-A-59
-1915]7 detects the moving speed of the optical fiber and the change in hoop speed, and synchronizes at a constant speed. Therefore, it is difficult to provide the extra length uniformly. In addition, in the method of JP-A-63-187209, a rigid optical fiber is vibrated and inserted into a coiled tube.
The difference between the tube inner diameter and the optical fiber diameter, that is, the clearance, is important. In particular, in a small-diameter tube, the clearance is small, so a highly rigid optical fiber tends to be straight and difficult to freely undulate within the tube. As a result, the adjustment range for the amount of extra length is very narrow, making it difficult to ensure an amount of extra length that meets the conditions of use, and also making it difficult to adjust the extra length.

Therefore, the present invention makes it possible to provide the required extra length to the optical fiber with high precision and uniformly along the length direction.
The present invention provides a method for adjusting the extra length of an optical fiber within a cladding tube.

[Means for Solving the Problems] The method of adjusting the extra length of optical fiber in a cladding tube of the present invention involves applying tension to the cladding tube within its elastic range to stretch the cladding tube by a required amount of extra length of the optical fiber. Insert the optical fiber into the coated tube while the tube is stretched. After the optical fiber is inserted, the tension is released.

One way to stretch a long cladding tube is to synchronize the supply speed and winding speed between the supply side and the take-up side of the cladding tube wound into a coil on a hobbin or spool, and then A method of controlling braking force is used. In order to give the extra length uniformly, the tension on the supply side and the winding side should always be constant. Alternatively, a method may be used in which die wire drawing is performed and the winding speed is controlled. When the cladding tube is short, the cladding tube may be stretched linearly and both ends may be fixed under tension.

The method for inserting the optical fiber into the cladding tube is the known vibration method,
The indentation method, fluid conveyance method, etc. are adopted. If a lubricant such as chlorine or talc is applied to the inner surface of the cladding tube and the surface of the optical fiber and the optical fiber is inserted, the frictional resistance between both surfaces will be reduced and the extra length will be uniform.

In order to provide an accurate amount of extra length to the optical fiber, it is advisable to determine the relationship between the tensile force and elongation of the cladding tube through experiments.

In the present invention, the optical fiber includes an optical fiber consisting of a core and a crat layer, a coated optical fiber made of synthetic resin, metal, or ceramic, and a single core thereof. Refers to multi-core wires, stranded wire wires, and tape-shaped wires. In addition, cladding refers to cladding made of steel, copper, aluminum, titanium, or other metals, or plastic or other non-metals.

[Operation] After inserting the optical fiber into the cladding tube while the cladding tube is stretched, the tension is released. Since the cladding tube is stretched within its elastic range, the release of tension causes it to contract by the amount of stretch. At this time, the optical fiber is not stretched due to the shrinkage of the cladding tube, and is slightly bent, giving an extra length.

[Example] Fig. 1 shows an example of an apparatus for carrying out the method of the present invention, and shows a cladding tube tensioning apparatus.

The cladding tension applying device includes a supply device 11 and a tension control device 21.
and a winding device 31.

In the supply device 11, a spool 13 wound with a steel pipe (cladding pipe) is rotatably supported on a frame 12. Spool 13
is connected to a hydraulic brake (not shown) and rotated by a DC motor 14. The DC motor 14 is driven in synchronization with the DC motor 37 of the winding device 31 .

The tension control device 21 includes a pair of fixed rollers 23 on a pedestal 22.
and a hydraulic cylinder 24 are attached.

A dancer roller 27 is rotatably supported at the tip of a rod 25 of the hydraulic cylinder 24. dancer roller 27
moves up and down as the tension of the steel pipe changes, controlling the tension to the target value.

In the winding device 31, a pobbin 32 for winding up the steel pipe P is rotatably supported by a lifting platform 34. The lifting platform 34 is raised and lowered by a hydraulic cylinder 35. The pobbin 32 is rotationally driven by a DC motor 37. Further, the winding device 31 includes a traverser 41. The traverser 41 is mounted on the bracket 42 or the frame 39 so as to be movable in a direction perpendicular to the feeding direction of the steel pipe P. A kite roller 44 is attached near the lower end of the bracket 42. The bracket 42 is reciprocated by a motor 46 and a screw mechanism (not shown).

A method of winding up the steel pipe P while applying tension using the apparatus configured as described above will be described.

The spool 13 that takes up the steel pipe P is attached to the frame.

Then, the tip of the steel pipe P is rewound through the fixed roller 23, dancer roller 27, and guide roller until it reaches the pobbin 32 of the winding device. Then, the tip of the steel pipe P is fixed to the pobbin 32. In addition, the lifting platform 34 is raised and lowered by a hydraulic cylinder 35 according to the diameter of the pobbin 32, and the pobbin 32 is
is pre-positioned at a predetermined height.

In the above state, the spool 13 and the pobbin 32 are driven to rotate. Since the spool 13 is braked by a hydraulic brake, tension acts on the steel pipe P between the spool 13 and the pobbin 32. The braking force is set so that a predetermined tension is applied to the steel pipe P. The magnitude of the tension can be measured by the pressure of the hydraulic oil in the hydraulic cylinder 24 that supports the dancer roller 27. When the tension acting on the steel pipe P fluctuates while the steel pipe P is being wound up by the pobbin 32, the height position of the dancer roller 27 is changed to adjust the magnitude of the tension. For example, if the tension is smaller than the target value, the dancer roller 27 is pushed down. The relationship between the magnitude of the tension and the elongation of the steel pipe P has been determined in advance through experiments, so by setting the magnitude of the tension, the steel pipe P can be stretched by the required length, that is, the required extra length. I can do it. FIG. 2 shows an example of the relationship between elongation and tension of the steel pipe P obtained through experiments. The steel pipe P is spirally wound from one end of the pobbin 32 so as to be aligned along the axial direction of the pobbin 32. Therefore, as the winding progresses, the guide roller 44 is displaced in its axial direction in accordance with the winding pitch of the steel pipe P.

Here, an example will be described in which the above-mentioned device is used to stretch a steel pipe, insert an optical fiber, and give the optical fiber an extra length.

Steel pipe; outer diameter 1, 2 mm, inner diameter 0, 8 mm,
Stainless steel tube (SUS304) with a length of 1000 m (wound around a pobbin 32 with a body diameter of 1200 mm) Optical fiber double quartz Gl type fiber (core diameter 50 μm, crat diameter 15
An optical fiber with a diameter of 0.4 mm coated with UV resin (ultraviolet curable resin) on the surface of the optical fiber (0 μm), the surplus length ratio of graphite coating on the surface, 0.1596 applied tension O, ]Fd, the load that gives the elongation is From Figure 2, it is determined to be 15 kg.

Optical fiber insertion method: Vibration method The optical fiber was inserted into the above-mentioned coiled steel pipe by the vibration method while applying tension. Next, the steel pipe into which the optical fiber was inserted was wound around another bobbin with a tension of O, and the tension was released.

For comparison, extra length was given to the coiled steel pipe and optical fiber using the conventional method (vibration method). That is, after an optical fiber is inserted into a steel pipe by the vibration method, the vibration is stopped and the optical fiber is fixed at the exit side pipe end. Then, with the optical fiber free on the pipe entrance side, the steel pipe is vibrated again. The remaining length when the optical fiber stops advancing at the pipe entrance side is the maximum remaining length.

Next, a total of 60 specimens of 5 m length were prepared from the steel pipe with the optical fiber inserted, 20 each on the pipe entrance side, the pipe center, and the pipe exit side.
The remaining length of each specimen was measured. the result,
The average value of the extra length or as follows.

Method of the present invention x = 0.15% (x = 0.1495 to 0.150396) Conventional method (maximum) Ma = 0.03496 (x = 0.0:II to 0.036'1li) According to the method of the present invention In this case, we were able to obtain the target surplus length ratio of 0.15*.

The conventional method of adding extra length using vibration is at most 0.03
4% L, the target surplus length ratio is always 0.15! li was not obtained. In the conventional method, since the optical fiber has rigidity, it tends to maintain a straight shape, and undulations are less likely to occur. For this reason, when the cladding tube has a small diameter, the optical fiber tends to be located on the outer diameter side of the tube coil in the case of the maximum extra length. Therefore, in the conventional method, the extra length depends on the tube coil diameter and the tube diameter, and the adjustment range for the extra length is narrow.

[Effects of the Invention] In this invention, the extra length is provided by utilizing the shrinkage margin corresponding to the elastic strain of the metal tube. It is easy to uniformly apply and release tension to a metal tube along the length of the tube. moreover,
The required total length is within the range of elastic deformation of the metal tube. Therefore, the required extra length can be given to the optical fiber with high grain size and uniformly along the length direction. As a result, there is no risk of microventilation occurring in the optical fiber, and an increase in transmission loss can be prevented. This invention is particularly effective when the metal tube has a small diameter.

[Brief explanation of drawings]

Figure 1 shows an example of a device for carrying out the method of the present invention, and is a schematic diagram of a cladding tube tensioning device, and Figure 2 shows an example of the relationship between the elongation and tension of a steel pipe determined through experiments. It is a graph. 1]--supply device, I3... spool, 14...
DC motor, 21... Tension control device, 23-... Fixed roller, 24... Hydraulic cylinder, 27... Dancer roller, 31... Winding device, 32... Bobbin, 3
4... Lifting platform, 35... Hydraulic cylinder, 37...
DC motor, 4]... Traverser, 42... Bracket, 44-... Kite roller, 46... Motor, P
...Steel pipe.

Claims (1)

[Claims] 1. In a method of adjusting the extra length of an optical fiber inserted into a cladding tube, tension is applied to the cladding tube within its elastic range to stretch the cladding tube by the required extra length of the optical fiber, and the cladding tube is stretched. Insert the optical fiber into the cladding tube with
A method for adjusting the extra length of an optical fiber in a cladding tube, which comprises releasing the tension after the optical fiber is inserted.