JP3380392B2 - How to insert an optical fiber into a pipe - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of inserting an optical fiber into a tube, and more particularly, to an optical fiber core having an optical fiber inserted into a protective tube or a seam, and an optical fiber. A method for manufacturing a cord or fiber optic cable. 2. Description of the Related Art In recent years, optical communication cables that have been widely used have been required to have a metal-coated structure due to the low strength of optical fibers. Conventionally, as a method of manufacturing an optical fiber core wire in which an optical fiber is inserted through a tube such as a metal tube, a tape forming welding method (for example, see Japanese Patent Application Laid-Open No. Sho 60-46869) is known. In this method, an optical fiber is inserted while a metal tape is formed into a tubular shape and both side edges of the tape are welded to produce a tube. Disadvantages of this method include:-When the optical fiber passes through the welding point, the optical fiber is apt to deteriorate due to the effect of welding heat.-When the pipe diameter is as small as 2 mm or less, it is technically difficult to insert it. And the like. As another method of inserting an optical fiber, there is a method of inserting an optical fiber into a ready-made tube. However, this method has a limitation in the length of the tube and is limited to a short tube. As an improved system of this optical fiber insertion method, for example, Japanese Patent Laid-Open No. 58-2
There is a technique disclosed in Japanese Patent No. 5606. This technology is
First, after manufacturing an aluminum tube containing a steel wire, the tube is reduced in diameter, and then the steel wire in the tube is replaced with an optical fiber. This technique is superior to the conventional pipe insertion method in that the optical fiber is not deteriorated by welding heat and can be inserted into a small-diameter pipe, but has a drawback that the manufacturing process is complicated. . [0005] As still another method, a tube wound in a coil shape on a bobbin or the like is fixedly mounted on a vibration table, and the center axis of vibration of the vibration table is aligned with the coil axis so that the coil of the tube is rotated around the coil axis. There is a method of spirally vibrating and inserting an optical fiber into a tube (for example, see Japanese Patent Application Laid-Open No.
No. 44010). This method is disclosed in
Similarly to the technique disclosed in Japanese Patent No. 25606, there is an advantage that the optical fiber is not deteriorated by welding heat, can be inserted into a small-diameter tube, and the manufacturing process is simple. [0006] The above-mentioned JP-A-62-44
In the method disclosed in Japanese Patent Application Publication No. 010, there is a problem that it is difficult to insert a small-diameter, long tube. That is, because the friction between the optical fiber and the inner wall surface of the tube is not uniform along the tube, the traveling speed of the optical fiber is slowed along the tube. For this reason, the swell occurs in the optical fiber at a portion where the traveling speed is slow, and the swell tends to gradually increase. When the swell increases and the peaks and valleys of the swell contact and press against the inner wall surface of the pipe, the swell increases further. As a result, the frictional force between the optical fiber and the inner wall surface of the tube increases, and eventually exceeds the vibration carrying force, and the optical fiber stops moving. Further, in the case of a multi-turn coil of a tube, the pitch of the coil is reversed since the tube is folded at both ends of the coil and wound around a bobbin or the like. Therefore, for example, an optical fiber that has traveled upwards changes its direction downward at the end of the coil and travels. At this time, the optical fiber bends greatly and travels while changing its direction, so that the optical fiber may hit the inner wall of the tube and stop traveling. For these reasons, conventional insertion methods using vibration require a long time to insert an optical fiber into a small-diameter and long tube, and when the tube length reaches several hundred meters, the optical fiber Could not be passed through the tube. Japanese Patent Application Laid-Open No. 62-44010 discloses that a massive weight is attached to the tip of an optical fiber, and that the entry speed of the optical fiber is increased by attaching the weight. However, in this method, the rigidity of the weight may hinder the passage of a bent portion such as a folded portion (small radius of curvature) of the tube, and the applicable length is limited. On the other hand, when the optical fiber is vibrated and inserted, it is presumed that the entire optical fiber is not simultaneously subjected to the vibration conveying force from the inner wall of the tube, but is randomly received from a microscopic viewpoint. As a result, the optical fiber is traveling with waves. Of course, from a macro perspective, it is moving at a constant speed, receiving a uniform vibration force in the longitudinal direction. According to the experimental results of the inventor, the boundary is about 0.5 m. In other words, if it is less than that, the traveling speed is random, and if it exceeds it, the traveling speed becomes stable. As described above, the length of the weight has a limit. 0.
In the case of a 7 mm φ stainless steel wire, the limit is about 30 mm (stainless steel pipe outer diameter 1.8 mm φ, wall thickness 0.2
mm). Therefore, the weight shows a random progress. In addition, since the weight is generally short, the weight per unit length of the weight must be increased. It is effective to increase the outer diameter while increasing the density. However, there is a limit to the density increase, and if the outer diameter is large, it will come into contact with the top surface of the inner wall of the pipe during vibration transfer,
On the contrary, the traveling speed becomes slow. Therefore, the inner diameter of the pipe must be increased more than necessary. Therefore, the present invention enables an optical fiber to be inserted into a small-diameter and long tube in a short time, and furthermore, several hundreds.
It is an object of the present invention to provide a method of inserting an optical fiber into a tube through which an optical fiber can be inserted even if the length of the tube exceeds m. According to the optical fiber insertion method of the present invention, a tube wound in a coil shape is fixedly mounted on a vibration table, and a vibration center axis of the vibration table coincides with a tube coil axis. In the method of spirally vibrating the vibration table and inserting the optical fiber into the tube , the flexibility and the tube
It has the elasticity of trying to restore a straight line to the bending caused by the bending, the weight per unit length is larger than that of the optical fiber, and the lead wire having the same diameter as the optical fiber is connected to the tip of the optical fiber. The optical fiber is inserted into the tube by attaching to the part. Since the lead wire has a larger weight per unit length than that of the optical fiber, the traveling speed of the optical fiber is faster than that of the portion where the traveling speed is slow, and the portion where the speed is slow is pulled by the tip of the optical fiber. For this reason, excessive undulations caused by the low-speed portion are reduced. As a result, the frictional force between the optical fiber and the inner wall surface of the tube does not increase, and the progress of the optical fiber is stopped by friction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The lead wires used in the present invention must have flexibility and elasticity. That is, as described above, at both ends of the coil of the tube,
Since the tube is folded and wound around a bobbin,
The coil pitch is reversed. Thus, the lead must be flexible in order to smoothly progress along the tube bend at both ends of the tube coil. Further, if the lead wire is bent along the bend of the tube, the lead wire remains in contact with the inner wall surface of the tube. As a material having such properties, a stranded wire of a thin metal wire such as stainless steel or a plastic wire containing a metal powder such as iron is suitable. The lead wire has a weight of 50 m per unit length.
g / m or more, the diameter is 0.5 to 1.5 of the diameter of the optical fiber.
Desirably, the length is 0.5 to 100 m. If the weight per unit length is less than 50 mg / m, sufficient traction force cannot be applied to the optical fiber. The larger the weight per unit length, the better, but the upper limit is limited by the diameter and the specific gravity of the material of the lead wire. If the diameter of the lead wire is less than 0.5 times the diameter of the optical fiber, the strength becomes insufficient and the connection with the optical fiber becomes difficult. Conversely, if the diameter of the lead wire exceeds 1.5 times the diameter of the optical fiber, the difference from the inner diameter of the tube becomes smaller, and when the wire jumps up due to vibration, it immediately hits the inner wall surface of the tube, and the lead wire's forward distance decreases. Also, the flexibility of the lead wire decreases. If the length of the lead wire is less than 0.5 m, sufficient traction force will not be generated, and if it exceeds 100 m, the traction effect will be saturated and extra insertion time will be required by the length of the lead wire. Next, an apparatus embodying the present invention will be described with reference to the drawings. FIG. 1 is an overall side view showing an example of an apparatus for inserting an optical fiber into a steel pipe, FIG. 2 is a plan view of a vibration table, and FIG. 3 is an explanatory view of a method of attaching a vibration motor to the vibration table. The coil R of the steel pipe P is fixed to the outer peripheral edge of the lower flange and the shaft hole of the bobbin 1 with the fixing jig 9 of the vibration table 2 or the like, so that the vibration motors 3a, 3
It is placed and fixed on the vibration table 2 so as to reliably receive the vibration b. The vibration table 2 has a pair of vibration motors 3
a and 3b are integrally mounted at an angle of 12.5 ° from the vertical line, and a pair of vibration motors 3a and 3b are used to form the tube coil axis C.
To give a vibration around. The vibration table 2 is attached to the gantry 5 via the spring 4 so that the vibration of the vibration table 2 is not transmitted to the gantry 5. In this embodiment, as the vibration motors 3a and 3b, rotary vibrators that generate vibrations by using centrifugal force generated by rotation of unbalanced weights provided at both ends of the rotating shaft are used, and two rotary vibrators are used. 2 is mounted symmetrically with respect to the tube coil axis C. The angle α formed between the vibrating surfaces of the pair of vibration motors 3a and 3b with respect to the surface of the vibration table 2 installed horizontally is equal, and the other vibration conditions (frequency, amplitude, etc.) of the vibration motor are also changed. The vibration table 2 is configured to give a vibration obtained by combining vibrations of the pair of vibrators to the vibration table 2. When such a vibration is applied to the vibration table 2, the steel tube coil R on the table performs a circular motion with a constant angular velocity (a counterclockwise circular motion in the illustrated example) about the intermediate axis of the vibration motors 3a and 3b. By placing the coil R on the vibration table such that the intermediate axis and the tube coil axis C coincide, the axis of the coil R and the vibration center axis of the vibration table 2 can be matched. The vibration state of the vibration table will be described with reference to FIG. In FIG. 4, E denotes a vibration center axis C on the vibration table.
Is a circle after the movement of the circle E due to the vibration. In this manner, the circle spirally vibrates between the solid circle E and the broken circle E 'in the figure due to the vibration of the vibration table. The center of the circle P, vibrates vertically between P ', as the distance from the center, i.e. the horizontal plane of the respective points on the circle _{P 1, P 2, P 3} , P 4 according diameter of the circle becomes larger At the same time, the amplitudes P ₁ P ₁ ′ and P ₂
P ₂ ′, P ₃ P ₃ ′, and P ₄ P ₄ ′ gradually increase from PP ′. However, the vertical component of the amplitude is constant.
The coil of the steel pipe is placed on the vibration table so that the center axis of the coil coincides with the center axis of the vibration, and the circle corresponds to one turn of the steel pipe because the steel pipe is wound in a coil shape. A steel pipe having a diameter has the same vibration (same amplitude and vibration angle), and a steel pipe having an inner layer with a smaller diameter has a smaller amplitude and a larger vibration angle β. As shown in FIG. 5, a lead wire 13 is attached to the tip of the optical fiber 6 inserted into the steel pipe P. Before the insertion of the optical fiber, the lead wire 13 and the distal end of the optical fiber 6 are inserted into the steel pipe P in advance. In such a state, when the above-described spiral vibration is applied to the steel pipe coil R via the vibration table 2, the optical fiber 6 supplied from the pipe end 7 below the coil continuously enters the steel pipe P by the conveying force due to the vibration. Go. That is, the optical fiber 6 is unreeled from the spool 10 supported by the support 12, and the spool 10 → guide 11 → tube end 7 → coil tube P
→ It moves by the vibration of the coil R in the order of the tube end 8 and is loaded into the entire coil after a predetermined time. EXAMPLE In order to confirm the effect of the present invention, an optical fiber was inserted into a steel pipe by using the apparatus shown in FIG. 1 with and without a lead wire at the tip of the optical fiber. (1) Specimen steel tube coil: outer diameter (inner diameter) 1.4 mm φ (1.0 mm
φ), and 1.8 mmφ (1.4 mmφ), length 10
A stainless steel tube having a diameter of 00 m is wound on a steel bobbin having a winding drum diameter of 1200 mm. A coiled steel tube coil (three-layer winding): 4 quartz optical fibers (125 μm in diameter) coated with silicone resin and having a diameter of 0.4 × 1.1. mm optical fiber lead wire: 7 stainless steel wires with a diameter of 0.45 mm
The turning point of the metal tube is 410 points regardless of the tube diameter.
m point. (2) Vibration Conditions Since the steel tube coil used in this embodiment has three winding layers, all portions of the tube have substantially the same vibration conditions. Vibration angle of coil to horizontal plane 12.5 ° Frequency 25 Hz Vertical component of full amplitude 1.25 to 1.55 mm The insertion results are shown in FIG. FIG. 6 shows measurement results of the insertion stop point and the insertion end point every 50 minutes. The following is clear from FIG. In the steady state, (speed with lead wire) is about twice as long as (speed without lead wire). The insertion time of (with lead wire) is about ４ of that of (without lead wire) alone. In the case of (without lead wire), the insertion stopped at around 440m and 410m. When the insertion was stopped, the direction of vibration was reversed and the optical fiber was moved backward (see the mark) to reduce the contact force with the inner wall surface of the pipe which increased due to excessive undulation of the optical fiber. After reversing about 100 m to ease contact, insertion was resumed. In the case of a weight, an extremely low speed occurs when the pipe diameter is reduced (2.3 m / min → 1.2 m / min), but in the case of a lead wire, there is almost no change. As is clear from the above results, when an optical fiber is inserted through a small-diameter and long tube, the insertion stop occurs without a lead wire, and it is impossible to insert the optical fiber into the small-diameter and long tube. Impossible. Also, even if there is no insertion stop,
From the above results, it can be seen that the time for inserting (with lead wire) is shorter than the time for inserting with (lead wire) and (without lead wire) at the speed simply arithmetically added. According to the present invention, since the lead wire is attached to the tip of the optical fiber, the occurrence of excessive undulation can be suppressed, and the frictional force between the optical fiber and the inner wall surface of the tube increases. This prevents the optical fiber from stopping due to friction. Also, compared to the case of a weight, it is not necessary to increase the inner diameter of the tube. As a result, the optical fiber can be inserted into the small-diameter and long tube in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall side view showing an example of an apparatus for carrying out the present invention. FIG. 2 is a plan view of a vibration table. FIG. 3 is an explanatory diagram showing how to attach a vibration motor to a vibration table. FIG. 4 is an explanatory diagram of a vibration state. FIG. 5 is an explanatory diagram showing an example in which a lead wire is attached to a tip portion of an optical fiber. FIG. 6 is a diagram showing a result of inserting an optical fiber into a steel pipe. [Description of Signs] 1 bobbin 2 vibration table 3a, 3b vibration motor 6 optical fiber 7 pipe end 8 pipe end 10 spool 11 guide 13 lead wire R coil P steel pipe C vibration center axis

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noriyasu Funayama 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding Industry Co., Ltd. (72) Inventor Nobuyuki Fuse 3-5-2, Tsukiji, Chuo-ku, Tokyo (56) References JP-A-6-18722 (JP, A) JP-A-3-290604 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/44 G02B 6/00

Claims (1)

(57) [Claims] [Claim 1] A tube wound in a coil shape is fixedly mounted on a vibration table, and a vibration center axis of the vibration table coincides with a tube coil axis, and the vibration table is spirally vibrated. In the method of inserting an optical fiber into a tube, it is attempted to restore flexibility and straightness to bending due to bending of the tube.
The inside of the pipe is characterized in that the optical fiber has a high elasticity, a weight per unit length is greater than that of the optical fiber, and a lead wire having substantially the same diameter as the optical fiber is attached to the tip of the optical fiber and the optical fiber is inserted into the pipe. How to insert optical fiber through