JP2784077B2 - Adjustment method of extra length of optical fiber in cladding tube - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting an excess length of an optical fiber in a cladding tube.

INDUSTRIAL APPLICATION This invention is utilized for manufacture of the optical fiber cable covered with the metal or the non-metallic tube.

[Related Art] In recent years, optical communication cables widely used in recent years have been required to have a light weight and small diameter optical fiber cable which is covered with a metal tube or the like and has excellent environmental resistance.

There is a large difference in mechanical properties and thermal expansion coefficient between a cladding tube such as a metal tube and an optical fiber. Therefore, when the optical fiber cable is elongated or bent, the optical fiber may not be as elongated as the cladding tube. Further, when the optical fiber cable is exposed to a high temperature, the cladding tube may be stretched more than the optical fiber due to a difference in thermal expansion coefficient between the cladding tube and the optical fiber. In these cases, an excessive tension is applied to the optical fiber, and the optical fiber may be broken.

In order to solve such a problem, an extra length is given to an optical fiber. That is, the optical fiber is made somewhat longer than the cladding tube with the optical fiber cable at a uniform temperature over the entire length. This extra length is called extra length. If the extra length is given to the optical fiber, even if the cladding tube extends more than the optical fiber due to the difference in the coefficient of thermal expansion, if the cladding length is smaller than the extra length, no tension is applied to the optical fiber.

Regarding the extra length of the optical fiber, for example,
02 "Method of temperature compensation of cable containing optical fiber" and JP-A-59-191517 "Method of manufacturing metal tube containing extra-long wire body" are known. In the techniques disclosed therein, the moving speed and the hoop speed of the optical fiber are detected, and the speeds of the two are tuned at a fixed ratio, and the optical fiber is inserted into the tube to provide an extra length. Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 63-187209 "Method for manufacturing a tube containing a linear body", after the tube is vibrated and the linear body is inserted through the tube, the forward end of the linear body is advanced. Vibrating the tube again in the greeted state gives extra length.

[Problem to be Solved by the Invention] The conventional method has the following problems.

The extra length of the optical fiber must be of a sufficient length suitable for use conditions, and the variation of the extra length per unit length must be within a required range, that is, uniform. Further, when manufacturing an optical fiber cable, it is necessary that the surplus length can be adjusted accurately and easily.

In the methods disclosed in the above-mentioned JP-A-57-130002, JP-A-59-191517 and JP-A-63-187209, the amount of extra length is restricted, or the size of the extra length is accurately determined according to the use conditions. It is difficult to adjust freely.

That is, JP-A-57-130002 and JP-A-59-191517
According to the method disclosed in JP-A-2003-157, the moving speed of the optical fiber and the change in the hoop speed are detected, and tuning is performed at a constant speed. Therefore, it is difficult to provide the extra length uniformly. Further, in the method of Japanese Patent Application Laid-Open No. 63-187209, a rigid optical fiber is vibrated through a coiled tube, so that the difference between the tube inner diameter and the optical fiber diameter, that is, the clearance is important. In particular, since the clearance is small in a small-diameter tube, an optical fiber having high rigidity tends to be straight, and it is difficult to freely undulate in the tube. As a result, the adjustment range of the extra length is very narrow, it is difficult to secure the extra length according to the use conditions, and the extra length adjustment is not easy.

Therefore, the present invention can provide the required extra length to the optical fiber with high accuracy and uniformly along the length direction.
An object of the present invention is to provide a method for adjusting the length of an optical fiber in a cladding tube.

[Means for Solving the Problems] According to the method for adjusting the extra length of an optical fiber in a cladding tube of the present invention, a tension is applied to the cladding tube within its elastic range, and the cladding tube is stretched over the entire length by the required extra length of the optical fiber. Thereafter, the optical fiber is inserted into the cladding tube while the cladding tube is stretched. Then, the tension is released after the optical fiber is inserted.

As a method of extending a long cladding tube, the supply speed and the winding speed are synchronized between the supply side and the winding side of the cladding tube wound in a coil shape on a bobbin or a spool, and the supply side spool brakes. A method of controlling the force is used.
In order to provide the extra length uniformly, the supply side and the winding side are always kept at a constant tension. Alternatively, a method of controlling the winding speed by drawing a die may be used. When the cladding tube is short, the cladding tube may be extended linearly and both ends may be fixed in a state where tension is applied.

As a method of inserting the optical fiber into the cladding tube, a known vibration method, a pushing method, a fluid conveying method, or the like is adopted. When a lubricant such as graphite 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 is reduced, and the extra length can be given uniformly.

In order to give an accurate amount of extra length to the optical fiber, the relationship between the tensile force and the elongation of the cladding tube may be determined in advance by an experiment.

In the present invention, an optical fiber is an optical fiber consisting of a core and a cladding layer, a fiber coated with a synthetic resin, a metal, a ceramic, or the like; , Stranded and tape-shaped. The cladding tube is a cladding tube made of steel, copper, aluminum, titanium or other metal or plastic or other nonmetal.

[Operation] After the optical fiber is inserted through the cladding tube while the cladding tube is stretched, the tension is released. Since the cladding tube is stretched within its elastic range, the cladding tube contracts by the amount of extension when the tension is released. At this time, the optical fiber is dragged by the shrinkage of the cladding tube, is slightly curved, and has an extra length.

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

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

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

In the tension control device 21, a pair of fixed rollers 23 and a hydraulic cylinder 24 are attached to a mount 22. Hydraulic cylinder
A dancer roller 27 is rotatably supported at the tip of the rod 25. The dancer roller 27 moves up and down due to fluctuations in the tension of the steel pipe, and controls the tension to be a target value.

The winding device 31 includes a bobbin 32 for winding the steel pipe P,
34 rotatably supported. The lift 34 is moved up and down by a hydraulic cylinder 35. The bobbin 32 is driven to rotate by a DC motor 37. Further, the winding device 31 includes a traverser 41. The traverser 41 is movable in the direction perpendicular to the feed direction of the steel pipe P so that the bracket 42
Mounted on 39. A guide roller 44 is mounted near the lower end of the bracket 42. Bracket 42
Is reciprocated by a motor 46 and a screw mechanism (not shown).

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

The spool 13 around which the steel pipe P has been wound is attached to the gantry.
Next, the distal end portion of the steel pipe P is rewound to the bobbin 32 of the winding device via the fixed roller 23, the dancer roller 27, and the guide roller. Then, the tip of the steel pipe P is attached to the bobbin 32.
Fixed to Also, according to the bobbin 32 diameter, the hydraulic cylinder 35
The lifting table 34 is moved up and down to position the bobbin 32 at a predetermined height in advance.

In the above state, the spool 13 and the bobbin
32 is driven to rotate. Since the spool 13 is braked by the hydraulic brake, tension acts on the steel pipe P between the spool 13 and the bobbin 32. The braking force is set so that a predetermined tension acts on the steel pipe P. The magnitude of the tension can be measured by the pressure of the hydraulic oil of 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 by the bobbin 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. Since the relationship between the magnitude of the tension and the elongation of the steel pipe P is determined in advance by an experiment, by setting the magnitude of the tension, the steel pipe P is elongated by a required length, that is, a required extra length. Can be. FIG. 2 shows an example in which the relationship between the elongation and the tension of the steel pipe P is obtained by an experiment. The steel pipe P is spirally wound from one end of the bobbin 32 so as to be aligned along the axial direction of the bobbin 32. Therefore, as the winding progresses, the guide roller 44 is displaced in the axial direction according to the winding pitch of the steel pipe P.

Here, an example in which the steel pipe is stretched by the above-described device, an optical fiber is inserted, and an extra length is given to the optical fiber will be described.

Steel pipe: Stainless steel pipe (SUS304) with outer diameter 1.2mm, inner diameter 0.8mm, length 1000m (wrapped around bobbin 32 with body diameter 1200mm) Optical fiber: Quartz GI type fiber (core diameter 50μm, clad diameter 150μm) and UV resin (UV curable resin) coated optical fiber 0.4mm in diameter, graphite applied to the surface Extra length: 0.15% Applied tension: The load to give 0.15% elongation is 1 load from Fig. 2.
5kg is determined.

Optical fiber insertion method: vibration method An optical fiber was inserted by a vibration method in a state where tension was applied to the coiled steel pipe. Next, the steel pipe into which the optical fiber was inserted was wound around another bobbin with zero tension, and the tension was released.

For comparison, extra length was given to the coiled steel pipe and the optical fiber by the conventional method (vibration method). That is, after the optical fiber is inserted into the steel pipe by the vibration method, the vibration is stopped, and the optical fiber is fixed at the outlet end of the pipe. Next, the steel pipe is vibrated again with the optical fiber being free at the pipe inlet side. The extra length when the entry of the optical fiber is stopped on the tube entrance side is the maximum extra length.

Next, a total of 60 specimens of 5 m in length were collected from the steel pipe through which the optical fiber was inserted at the pipe inlet side, the pipe center, and the pipe outlet side, and the extra length was measured for each sample. As a result, the average value of the extra length is as follows.

Method of the present invention = 0.15% (x = 0.1495 to 0.1503%) Conventional method (maximum) = 0.034% (x = 0.031 to 0.036%) According to the method of the present invention, a target extra length rate of 0.15% could be obtained. .

With the conventional method of adding extra length by vibration, at most 0.034
%, But the target margin rate of 0.15% was not achieved.
In the conventional method, since the optical fiber has rigidity, it has a property of trying to maintain a straight shape, and swelling does not easily occur. For this reason, if 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 surplus length depends on the tube coil diameter and the tube diameter, and the adjustment range of the surplus length is narrow.

[Effects of the Invention] In the present invention, a surplus length is given by utilizing the shrinkage allowance of the elastic tube of the metal tube. It is easy to apply and release tension uniformly to the metal tube along the length of the tube. Further, the required extra length is within the range of the magnitude of the elastic deformation of the metal tube. Therefore, the required extra length can be given to the optical fiber with high accuracy and uniformly along the length direction. As a result, there is no possibility that microbending occurs in the optical fiber, and an increase in transmission loss can be prevented. The present invention is particularly effective when the metal tube has a small diameter.

[Brief description of the drawings]

FIG. 1 shows an example of an apparatus for carrying out the method of the present invention. FIG. 1 shows a schematic view of a cladding tube tension applying apparatus, and FIG. 2 shows an example in which the relationship between elongation and tension of a steel pipe is obtained by an experiment. It is a graph. 11 ... supply device, 13 ... spool, 14 ... DC motor,
21 ... tension control device, 23 ... fixed roller, 24 ... hydraulic cylinder, 27 ... dancer roller, 31 ... winding device, 32 ...
... bobbin, 34 ... elevator, 35 ... hydraulic cylinder, 37 ...
DC motor, 41… traverser, 42… bracket, 44
…… Guide roller, 46 …… Motor, P …… Steel pipe.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Shimizu Yokoi 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding Industry Co., Ltd. (56) References JP-A-61-284009 (JP, A) 58-117509 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 6/44 351 G02B 6/00 351

Claims (1)

(57) [Claims] In a method for adjusting the surplus length of an optical fiber inserted into a cladding tube, tension is applied to the cladding tube in an elastic range of the cladding tube, and the cladding tube is stretched over the entire length by a required extra length of the optical fiber. A method of adjusting the excess length of the optical fiber in the cladding tube, wherein the tension is released after inserting the optical fiber into the cladding tube in a state where the cladding tube is stretched.