JPH0192704A - Connecting method for optical fiber-contained metallic tube - Google Patents

Abstract

PURPOSE:To attain connection by which an optical fiber-contained metallic tube can be wound to a reel or a spool without a hindrance, or can be rewound by the reel, etc. by bringing a covering tube into which an optical fiber is inserted through, to butt welding through a metallic connecting tube whose diameter is almost the same as that of said tube. CONSTITUTION:An optical fiber 1 is exposed from the end of a covering tube 5, a connecting tube 11 whose diameter is almost the same as that of the covering tube 5, and also, which has a slit so that the diameter can be expanded is fitted to the outside of one covering tube 5 by expanding the diameter, and in a state that the connecting tube 11 is moved backward from the tube end part, each exposed optical fiber 1 is connected. Subsequently, between the covering tubes 5 to be connected, the connecting tube 11 is positioned, the diameter of the connecting tube 11 is returned to its original state, the slit 12 is brought to seal welding S, and also, the end part of the covering tube 5 and the end part of the connecting tube 11 are brought to butt welding. In such a way, in case of winding an optical fiber contained metallic tube to a reel, etc., or rewinding it from the reel, etc., a connecting part 6 does not protrude and it does not occur that said part is caught in the optical fiber-contained metallic tube or an obstacle.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to a metal tube containing an optical fiber (that is, an optical fiber core, an optical fiber cord, or an optical fiber cable) in which an optical fiber is inserted into a metal cladding tube. Regarding connection method.

The optical fiber in this invention includes a fiber wire consisting of a core and a cladding layer, a fiber coated with synthetic resin, metal, ceramics, etc., and single-core fibers, multi-core fibers, and more. It refers to a line. In addition, cladding refers to steel, copper, lead, aluminum, and other metal tubes.

(Prior Art) Optical fibers that are extended over the air, under the sea, underground, etc. are sometimes covered with metal tubes or the like to prevent excessive tension or to provide environmental resistance. for example,
Optical communication cables that have become widely used in recent years are required to have optical fibers inserted through metal cladding tubes because the optical fibers are weak in strength.

In addition, in cables that are extended over long distances, such as submarine optical cables, metal tubes containing optical fibers are connected to each other. In such a connection, a slight gap is created between the cladding tubes at the connection portion, and in order to compensate for the gap, the cladding tubes are connected via a connecting tube or a connecting tube. As a connection between metal tubes containing optical fibers, for example, Utility Model Application No. 59-33015
There is an optical fiber connection portion disclosed in Japanese Utility Model Publication No. 59-136609.

The connection part disclosed in Utility Model Application Publication No. 59-33015 is
The connecting portion of the optical fiber cable is covered with a connecting tube, and the connecting portion of the connecting tube and the sheath of the optical fiber cable are integrated by welding or welding. In addition, the connection part disclosed in Japanese Utility Model Application Publication No. 59-136609 has an engaging part in which a metal sleeve having an inner diameter slightly larger than the outer diameter of the cladding tube to be connected is passed over the opposing connecting ends of the cladding tube. are placed on top of the cladding tube, the protrusion of the engaging portion bites into the cladding tube and fixed by pressure, and the joint between the cladding tube and the metal sleeve is sealed with solder.

(Problems to be solved by the invention) However, the conventional method of connecting metal tubes containing optical fibers has
There were the following problems.

Long metal tubes containing optical fibers are coiled onto reels or spools for ease of handling. At this time, in the above-mentioned conventional method for connecting a metal tube containing an optical fiber, the outer diameter is larger than that of the cladding tube. For this reason, when the optical fiber-containing metal tubes are arranged on a reel or the like and wound up, the connecting portion protrudes, which obstructs the winding operation. Furthermore, when a metal tube containing an optical fiber is stretched and reeled in from a reel or the like, the connecting portion gets caught on an obstacle, causing damage to the cladding tube or breakage.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for connecting a metal tube containing an optical fiber, which allows the metal tube containing an optical fiber to be wound onto a reel or spool without any trouble, or to be unwound from a reel.

(Means for Solving the Problems) A method for connecting metal tubes containing optical fibers according to the present invention exposes the optical fiber from the end of the cladding tube, so that the optical fiber has approximately the same diameter as the cladding tube and can be expanded. A connecting tube having a slit is enlarged in diameter and fitted onto the outside of one of the cladding tubes, and the exposed optical fibers are connected with the connecting tube retracted from the tube end. Next, a connecting tube is positioned between the cladding tubes to be connected, the diameter of the connecting tube is returned to its original value, the slit is sealed and welded, and the end of the tube to be connected and the end of the connecting tube are butt welded.

The connecting tube is preferably made of the same metal as the cladding tube through which the optical fiber is inserted. In addition, the connecting tube can be a connecting tube that has a linear slit along the tube axis, a connecting tube that has a spiral slit, a connecting tube that has a linear slit and the slit sides overlap, or a connecting tube that is divided into two by two linear slits. It is possible to use a connecting pipe etc.

If you take into account the exposed length of the optical fiber from the metal tube and the change in the length of the optical fiber due to joining the optical fibers, and standardize the connection tube length so that it is always constant, you can insert the optical fiber anywhere. It is possible to connect metal pipes.

Butt welds and seal welds are performed by conventional fusion welding, pressure welding, or brazing. Fusion welding includes plasma arc welding, laser welding, light beam welding, electron beam welding,
TIG arc welding, gas welding, resistance welding methods, etc. can be used.

The above-mentioned butt welding and seal welding may be performed by inserting a backing material into the cladding tube and the connecting tube. The shape of the backing material is preferably tubular, and the cladding material is
It is also advisable to line the connecting pipe with aluminum foil or the like to prevent the crushed backing material from scattering inside the pipe. Further, it is desirable that the backing material adhere closely to the welding area, and for this purpose, it is preferable to apply a thin layer of glass wool or the like to the surface of the backing material.

The backing material may be made of a mixture whose main component is a metal oxide such as silica sand, alumina, zircon sand, magnesia, or cordierite, or the surface of the aluminum tube or the like may be covered with a film of the mixture.

(Function) The connecting pipe has approximately the same diameter as the cladding pipe, and both pipes are connected by butt welding. Therefore, when winding the optical fiber-containing metal tube onto a reel or the like and unwinding it from the reel, the connecting portion does not protrude and does not get caught on the optical fiber-containing metal tube or obstacles.

The backing material also prevents molten metal from burning through and overheating the optical fiber during welding.

(Example) FIG. 1 shows an enlarged example of a connecting portion 6 of an optical fiber-containing metal tube connected by the method of the present invention.

The optical fiber 1 is a quartz glass wire (diameter 125 μm) that is coated primarily with silicone resin and secondarily coated with urethane resin, and has a diameter of 0.4 ma+. The left and right optical fibers 1 are heat-fused at a joint 2.

The cladding tube 5 into which the optical fiber 1 is inserted has an outer diameter of 1 and an In+
m, stainless steel tube (SUS30
4) and has a length of 5 km.

The connecting tube 11 is also made of stainless steel tube (SUS304) with an outer diameter of 1.1 m + n and an inner diameter of 0.8 + nm, and the length is 40 mm.
+n+n.

The length of the connecting tube II is equal to the length of the optical fiber 1 exposed from the covering tube 5 by the length necessary for connection. As shown in FIG. 2(a), a slit 12 is cut in the connecting tube 11 along the tube axis direction. This slit 12 will be seal welded S later.

The cladding tube 5 and the connecting tube 11 are butt welded B.

FIG. 3 shows another embodiment of the present invention, in which a connecting portion 6 of a metal tube containing an optical fiber is shown in an enlarged manner. Elements that are the same as those in the embodiment shown in FIG. 1 are given the same reference numerals, and their explanations will be omitted.

The backing tube 31 is inserted into the cladding tube 5 and the connecting tube 11.
The hook is inserted into the connecting pipe 11 so as to be passed across the hook. The backing tube 31 has a thickness of 0.02 mm and an outer diameter of 0.6
A heat insulating layer is formed by applying fine powder of a mixture containing alumina as a main component to the outside of a mm-thick aluminum tube and sintering it. The thickness of the backing tube 31 is 0.12 mm, and the outer diameter is 0.12 mm.
8vn, and the length is 80m, which is twice the length of the connecting pipe 11.
It is m.

Here, a method for connecting a metal tube containing optical fiber will be explained.

FIG. 4 shows a procedure for forming the connecting portion 6 shown in FIG. 3 (however, two wooden backing tubes 31a and 31b are used).

The optical fiber 1 is exposed from the cladding tube 5 by the length necessary for connection. Next, the slit 12 is opened, the connecting tube 11 is placed on one side of the cladding tube 5, and the connecting tube 11 is moved back and fitted into the cladding tube 5 so as not to cover the exposed portion. Next, while passing the optical fiber 1 through the insides of the backing tubes 31a and 31b, the backing tubes 31a and 31b are inserted into one side of the cladding tube 5,
This is also moved back so as not to cover the exposed portion of the optical fiber 1.

After the preparation for connection is completed as described above, the joint portion 2 of the optical fiber 1 is heated and the optical fibers are connected. Next, the backing tubes 31a and 31b are pulled out from the cladding tube 5, the ends of the backing tubes 31a and 31b are butted together, and the connecting tube 11
and fit it between the cladding tubes 5. After seal welding the slit 12 of the connecting pipe 11, the cladding pipe 5
and the connecting pipe 11 are butt welded B. In this example,
As shown in FIG. 5, seal welding and butt welding were performed by plasma arc welding while shielding gas G was supplied around the electrode 34 from the torch 33. The welding conditions are as follows.

Welding current: Average 0.68 A Pulse frequency: 3Hz Shield gas 28r+ 796 H25It/mtn
Electrode diameter: 1mm Welding heat input: 600 to 750 J/cm Welding speed:
2.5 to 3.5 cm/min Filler material: None Incidentally, the cladding tube 5 and the connecting tube 11 were held by a cooling chamber 36 as shown in FIG. cooling chuck 36
The main body 37 is cooled by passing cooling water through a flow path 38 provided inside. For this reason, the vicinity of the welded part is cooled, so that excessive welding heat does not cause holes or burn-through in the cladding tube 5 or the connecting tube 11, and overheating of the optical fiber 1 is also prevented. Ru.

Next, other embodiments will be described.

Although the connecting pipe 11 in the above embodiment is shown in FIG. 2(A), other connecting pipes 11 as shown below may also be used.

In the connecting pipe 3 shown in FIG. 2(B), the edges 15 overlap along the slit 14. In this connecting tube 13, since the slit 14 does not open toward the inside of the connecting tube, burn-through of the welded portion and overheating of the optical fiber 1 are prevented. Furthermore, by increasing the overlap, it can be applied to a wide range of pipe diameters. In the connecting pipe 16 shown in FIG. 2(C), the slit 17 is cut in a spiral shape. This connecting tube 16 requires less force to open the connecting tube. Further, the connecting pipe 18 shown in FIG. 2(d) has two slits 19 cut therein, and is vertically divided into two parts.

In this connecting tube 18, after connecting the optical fiber, the connecting tube 18 can be sandwiched between the facing cladding tubes '5.

The connecting tube 2I shown in FIG. 6(A) is provided with a ring-shaped fillet 22 at the tube end. The fillet 22 prevents burn-through. The connecting tube 23 shown in FIG. 6(b) has an annular fillet 24 formed by bending the tube end outward, and a linear fillet 25 formed by bending the edge of the slit 12 outward. These fillets 24 and 25 prevent welding heat input from concentrating on the joint, allowing for good welding. In addition, the fillets 24 and 25 are melted and become filler metal, thereby increasing the strength of the joint. Tube end or slit 1
A similar effect can be obtained by folding the edges of 2 inward.

The connecting pipe 26 shown in FIG. 7 consists of a pair of short pipes 27 and 29, one of which is provided with a fitting protrusion 28, and the other short pipe 29 is provided with a fitting recess 30.

The length of the connecting tube 26 can be freely changed, and even if the distance between the ends of the cladding tube 5 changes after the optical fiber 1 is connected, the length of the connecting tube 26 can be adjusted and fitted.

In the above embodiments, seal welding and butt welding were performed by plasma arc welding, but brazing may be used instead of these weldings.

FIG. 8 is an explanatory diagram of a connection method by brazing. This method uses electrical resistance heating to braze. That is, the heating current is supplied from the power source 41 while the cladding tube 5 is sandwiched between the electrodes 42 and the butt portion and the slit portion are pressurized. The brazing filler metal placed in the butt portions and slits melts and flows into the butt portions and slits by capillary action. In some cases, the area between the electrodes 42 may become red hot, so it is preferable to seal the butt portion and the slit portion with an inert gas. Furthermore, the electrodes, holding fittings, etc. may be cooled with water to prevent overheating. This brazing connection method has the advantage of being easy to use on-site.

The present invention is not limited to the above-mentioned embodiments, and for example, the supply of the optical fiber 1 into the tube is not limited to one, but may include a plurality of optical fibers depending on the inner diameter of the tube and the diameter of the optical fiber 1.

(Effects of the Invention) In the method for connecting metal tubes containing optical fibers according to the present invention, a cladding tube into which an optical fiber has been inserted is butt-welded through a metal connecting tube having approximately the same diameter. Therefore, unlike conventional connections in which a connecting tube is stacked on a cladding tube, there is no difference in tube diameter at the connection, and the connection is smooth. As a result, it becomes easy to handle the optical fiber-containing metal tube as a wire, especially if it is small in diameter and long. That is, when the optical fiber-containing metal tube is wound around a spool or the like and stored, it is possible to wind it in an aligned manner because there are no irregularities in the cladding tube. In addition, even if there is an obstacle when stretching the optical fiber-containing metal tube or pulling it up, it can be smoothly overcome, and there is no chance of the wire getting caught and broken, improving work efficiency.

Further, by providing a backing material at the connection part, burn-through and overheating of the optical fiber can be prevented during welding.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the first invention, and is an enlarged view of a method of connecting metal tubes containing optical fibers, and FIG. 2 is a perspective view 1 of a connecting tube.
Fig. 3 shows an embodiment of the second invention, and is an enlarged view of the method of connecting metal tubes containing optical fibers, Fig. 4 is a drawing explaining the method of connecting metal tubes containing optical fibers, and Fig. 5 shows the above-mentioned connection method. 6 is a perspective view showing another example of the connecting tube, FIG. 7 is a sectional view showing still another example of the connecting tube, and FIG. 8 is a metal tube containing optical fiber. It is an explanatory view of a method of connecting pipes by brazing. DESCRIPTION OF SYMBOLS 1... Optical fiber, 5... Covering tube, 6... Connection part, 11.13, 16, 13, 21.23.26-- Connection tube, 12, 14, 17.19- Slit, 31, 31
a, 31b = backing tube, 33-... welding torch, 36-
・Chuck, 41-・Power supply, 42-・Electrode, B・
...Butt welding (part), L-...brazing metal, S...seal welding (part).

Claims (2)

[Claims] (1) In a method of connecting metal tubes containing optical fibers inserted into a metal cladding tube with a gap through a metal connecting tube, the optical fiber is exposed from the end of the cladding tube, and the optical fiber is exposed from the end of the cladding tube, and A connecting tube with the same diameter and a slit so that it can be expanded is expanded in diameter and fitted to the outside of one of the cladding tubes, and the exposed optical fibers are connected with the connecting tube set back from the tube end. Then, the connecting tube is placed between the cladding tubes to be connected, the diameter of the connecting tube is returned to the original value, and the slit is sealed and welded,
A method for connecting metal tubes containing optical fibers, the method comprising butt welding an end of a cladding tube and an end of a connecting tube. (2) The method for connecting metal tubes containing optical fibers according to claim 1, characterized in that the seal welding and butt welding are performed by inserting a backing material into the cladding tube and the connecting tube.