JP2693262B2 - Connector installation method for optical fiber tube - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of attaching an optical fiber-containing tube, in which an optical fiber is inserted with a gap in the tube, to a connector having a ferrule.

The optical fiber in the present invention refers to a bare fiber composed of a core and a clad layer, a fiber bare wire, a core wire and a cord obtained by coating the bare fiber with synthetic resin, metal, ceramics or the like. Metal pipes are seamless pipes made of steel (carbon steel, stainless steel, etc.), aluminum, copper, titanium and other materials, welded pipes, metal pipes such as forged pipes, plastic pipes and other non-metal pipes, and flexure. Says a tube. The flexible tube means a thin plate made of metal or synthetic resin formed into a bellows shape or spirally wound, a synthetic resin tube such as vinyl chloride or polyethylene, or a rubber tube.

[Prior Art] An optical fiber extended to the aerial, seabed, underground, etc. is used by being coated with a metal tube in order to prevent excessive tension or have environmental resistance. Further, if the coating is a metal tube, a tension member becomes unnecessary, and the slack of the overhead wire is small, so that the span can be extended and the wire can be extended. In optical communication cables that have been widely used in recent years, since the optical fiber is weak in strength, an optical fiber coated with a metal tube has been required. An example of such an optical fiber-containing tube is disclosed in Japanese Patent Laid-Open No. 63-1872.
The "tube containing a linear body" disclosed in 08 is known. In this optical fiber-containing tube, the optical fibers are inserted into the tube with a gap, and the extra length is evenly distributed in the longitudinal direction of the tube.

On the other hand, in optical communication devices and optical equipment, optical fibers are connected to each other, or optical fibers and optical devices such as light emitting / receiving elements are connected. In these connections, in order to reduce the loss at the connection portion, a connector that accurately connects the optical fibers or the optical fiber and the optical device is widely used.

The connector consists of a plug with a ferrule and an adapter or socket. The ferrule holds and fixes the optical fiber with high dimensional accuracy. "Optical fiber connection part" disclosed in Japanese Patent Laid-Open No. 1-312517 as a method for attaching a tube containing an optical fiber to such a connector
It has been known. For this connection part, an optical fiber obtained by removing the tip of the cladding of the optical fiber-containing tube by the length of the ferrule is inserted into the ferrule, and the tip of the tube is fixed to the rear end of the ferrule.

[Problems to be Solved by the Invention] However, the conventional method of attaching an optical fiber-containing tube disclosed in Japanese Patent Laid-Open No. 1-312517 to a connector has the following problems.

Since the front end of the coating tube of the optical fiber and the rear end of the ferrule are fixed, the coating tube is removed and all the exposed front end of the optical fiber is inserted into the ferrule. In this case, insert the optical fiber after aligning the optical fiber with the inlet of the ferrule with the cladding tube sandwiched between them, but since the optical fiber is inside the cladding tube with a gap, the optical fiber swings and therefore the position to the ferrule is increased. The work of fitting and inserting was difficult.

Therefore, the present invention provides a connector mounting method for an optical fiber-containing tube, by which the optical fiber of the optical fiber-containing tube inserted into the tube with a gap can be easily and surely inserted into the ferrule of the connector and attached to the connector. It is what

[Means for Solving the Problems] A connector mounting method for an optical fiber-containing tube according to the present invention is designed so that an optical fiber is exposed from the tube by at least the length of a ferrule in a state where the optical fiber-containing tube is linear. Is removed to form a first exposed portion. Then bend the tube containing the optical fiber so that the optical fiber is exposed from the tube at least as long as it can hold the optical fiber, and pull out the optical fiber from the tube so that the optical fiber is wrapped around the inner wall of the bent inner diameter side of the tube. The second exposed portion. Then, after holding the second exposed portion and inserting the first exposed portion into the ferrule, the bent optical fiber-containing tube is returned straight and the second exposed portion is returned into the tube. Here, bending the tube means forming the tube into an arc shape, a loop shape, or a coil shape.

In general, a tube into which a bare optical fiber, an optical fiber elemental wire, an optical fiber core wire or an optical fiber cord is inserted has an outer diameter of several mm or less. Therefore, even a metal pipe can be bent easily with bare hands. The length of the second exposed portion is determined by the size of a holding jig or a means for holding an optical fiber such as a bare hand. The bending radius, the bending center angle, or the number of turns of the loop or coil is determined by the holding length, the difference between the tube inner diameter and the optical fiber diameter, the allowable bending radius of the optical fiber, and the like. The bending radius is preferably 30 mm or more. In addition, it is preferable that the first exposed portion and the second exposed portion have a certain length in terms of workability.

[Operation] Since the optical fiber is inserted into the tube with a gap,
Even when the tube containing the optical fiber is bent, there is a gap between the bent inner diameter side of the optical fiber and the inner wall of the tube on the bent inner diameter side. Therefore, when the optical fiber is pulled in such a state, the optical fiber is wound around the bending inner diameter side of the tube. As a result, the optical fiber is exposed from the tube end, that is, the second exposed portion is formed.

By adjusting the bending radius, the central angle, or the number of turns of the loop or coil, the length of the second exposed portion, that is, the holding margin can be set to an appropriate value. Since the optical fiber is directly inserted into the ferrule while holding the holding margin of the optical fiber, the optical fiber can be inserted accurately, reliably and easily. When the tube containing the optical fiber is returned to the straight shape after insertion, the holding margin returns to the inside of the tube. Therefore, no extra length of optical fiber remains in the connector. In addition, since the optical fiber having an appropriate length is included in the connector, it is possible to avoid excessive tension or compressive stress acting on the optical fiber due to the inclusion of the optical fiber having an excessive length.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a sectional view of the entire connector 11 and a part of the adapter 45.

The connector 11 includes a cylindrical holder 12. The holder 12 has a ferrule 17 on the front and a spacer on the rear.
21 are inserted respectively. The tip of the ferrule 17 projects from the holder 12, and a capillary 18 made of ceramics is inserted therein. A coil spring 23 is inserted between the ferrule 17 and the spacer 21. holder
The inner circumference of 12 and the ferrule 17 are spline-connected 25, and the ferrule 17 is positioned by the annular stopper 13 in the holder 12. A clamper 27 is inserted in the rear part of the ferrule 17. In the first half of the holder 12,
Connection nut 31 is loose. An annular stopper 32 is provided on the inner circumference of the connection Nantes 31. When the connecting nut 31 is advanced with respect to the holder 12, the stopper 32 is
It hits the key 14 provided on the and moves forward together with the holder 12. Further, a screw 15 is cut on the outer periphery of the holder 12 near the rear end, and a fixing nut 35 is fitted therein. The spacer 21 is pressed against the fixed nut 35 by the coil spring 23. The rear half of the holder 12 and the fixing nut 35 are covered with a rubber hood 41.

A screw 46 is cut on the outer periphery of the adapter 45, and the connection nut 31 is fitted therein. A key groove 47 is cut on the inner periphery of the adapter 45, and the key of the holder 12 is inserted into the key groove 47.
14 fit together. There is also an alignment sleeve 48 inside the adapter 45.
Is provided. The outer circumference of the alignment sleeve 48 is the holder 12
On the inner circumference, ferrules 17 fit together.

FIG. 1 (b) shows the optical fiber-containing tube 1, the bare optical fiber 2 and the optical fiber core wire 3 in FIG. 1 (a). The rear part of the clamper 27 and the part inside the front part of the fixing nut 35 are in the state of the optical fiber core wire 3 with the metal tube 5 removed. Also, the ferrule 17 and the capillary 18
The part from the tip to the stopper portion 28 of the clamper 27 is in the state of the bare optical fiber 2 with the coating of the optical fiber core wire 3 removed. The length l ₁ of the bare optical fiber 2 is 2 to
It is about 5mm. The part of the optical fiber core wire 3 is the clamper 2
Part from the rear end of the stopper 28 of 7 to the rear end of the clamper 27 l ₂
It consists portion l ₃ from the clamper 27 rear end to the metal tube 5 tip and. l ₂ is about 20 mm and l ₃ is about ₃ to 7 mm. The l ₃ portion of the optical fiber core wire 3 should have the allowance such as dimensional error and the retreat allowance of the ferrule when the ends of the ferrules are pressed against each other by the elastic force of the coil spring 23 and brought into a butt state when the connector is connected. It is a thing.

Here, regarding the method of attaching the optical fiber-containing tube 1 to the connector 11, (a) to (a) of FIG.
It will be explained step by step with (i).

(B) The birth part of the metal tube 1 containing the optical fiber is cut into a linear shape.

(B) The metal tube 5 having a length obtained by adding α ₁ + α ₂ to the above l ₁ + l ₂ + l ₃ is removed from the end portion of the metal tube 5 to expose the optical fiber core wire 3 and form the first exposed portion. . Where α ₁ is capillary 1
It is about 5 mm as a tip confirmation margin for confirming that the bare optical fiber 2 is projected from 8. Further, α ₂ is the optical fiber core wire 3 when the metal tube 5 is cut together with the above (a).
Since it is sandwiched between the metal tubes 5 and cut, it is about 5 mm as a safety allowance for removing cracks generated in the core and the clad portion of the bare optical fiber 2 at this time.

(C) The optical fiber core wire 3 is pulled out from the metal tube 5 having a predetermined length (bending length of the metal tube 5). The optical fiber core wire 3 at the tube end portion is marked with, for example, an aqueous paint, and this point is designated as A. Also, the required extra length β ₁ of a predetermined length is calculated, and the position of β ₁ on the tip side from the point A of the optical fiber core wire 3 is marked, and this point is designated as B. It should be noted that if excessive tension is applied to the optical fiber due to the difference in the mechanical properties and the thermal properties of the optical fiber and the cladding tube, the transmission characteristics will deteriorate. In order to avoid deterioration of the transmission characteristics, the optical fiber is inserted into the tube with a length longer than the tube length in advance. Extra length beyond this pipe length,
It is called necessary extra length.

Surplus rate Is usually 0.02 to 0.5% and is predetermined. Here, the necessary extra length β ₁ is calculated by a predetermined length (bending length of the pipe) × surplus length ratio.

(D) The optical fiber core wire 3 is pushed into the metal tube 5 until B is located at the tube end. Then, the optical fiber core wire 3 is cut from the tip by α ₂ (safety allowance).

(E) Bending the metal tube 1 containing the optical fiber of a predetermined length, pulling out the optical fiber core wire 3 from the metal tube 5, and exposing the second exposed portion β ₁ + β ₂
(Between BC). That is, the second exposed portion has a required extra length β ₁
And the extra bending length β ₂ . The extra bending length refers to the extra length generated by winding the optical fiber core wire 3 around the inner wall surface of the metal tube 5 that is contracted by compressive stress on the inner diameter side of the metal tube 5 when it is bent. Here, regarding the extra bending length,
Further description will be given with reference to FIGS. When the metal pipe 5 is bent as shown in FIG.
T ₁ is shrinking working compressive stress, the outer diameter T ₀ extend working tensile stress. Next, when the optical fiber core wire 3 of the first exposed portion is pulled, the optical fiber core wire 3 inside the metal tube 5 of a predetermined length is bent on the bending inner diameter side of the metal tube 5 as shown in FIG. 3 (b). It will be wound around the inner wall surface of the to reduce the bending radius, and by that amount, it will be exposed outside the pipe by the extra bending length.

Bending margin β ₂ is L: predetermined length, a: pipe outer diameter, t: wall thickness, b: optical fiber core diameter, d: bending radius, (However, the length of the center line of the bent tube is L).

In addition, in the case of a flexible pipe in which the length on the outside diameter side of the bent pipe does not substantially change and only the inside diameter side bends, (However, the length of the bent pipe on the outer diameter side T ₀ is L). In this case, since the bending inner diameter side is greatly contracted, the bending margin is increased, which is advantageous.

(F) In order to insert the tip of the optical fiber core wire 3 into the capillary 18, the resin coating is removed by the length of α ₁ + l ₁ to obtain the bare optical fiber 2. In this state, the metal tube containing the optical fiber is attached to the fixing nut 35 of the connector 11, the rubber hood 41, the coil spring 23.
And the spacer 21, and these are retracted while the bare optical fiber 2 is passed through the ferrule 17 and the clamper 27.

When passing the first exposed portion of the optical fiber through the ferrule 17 and the clamper 27, the second exposed portion (the optical fiber core wire 3 between BCs) is pinched with fingers and passed through the ferrule 17 and the clamper 27, so the work is easy and accurate. It is possible to break the optical fiber (particularly the broken part of the bare optical fiber to be inserted into the capillary)
Can be prevented. The second exposed portion is preferably 10 mm or more.

(G) Next, the bent metal tube 5 is returned to its original shape to be a straight line, and the optical fiber core wire 3 (a portion between ACs) corresponding to the bend extra length β ₂ is drawn into the metal tube 5 to bend extra length. To eliminate.

(H) Further, the optical fiber core wire 3 having the required extra length β ₁ (the portion between BA) is pushed into the metal tube 5.

In the state of (r) and (h), the bare optical fiber 2 is a capillary 18
Since it is projected by α ₁ (tip confirmation margin) from the tip, the protruding portion is polished to match the tip of the bare optical fiber 2 with the tip of the capillary 18. Then, the ferrule 17 is passed through the holder 12 in which the connection nut 31 is loosely fitted, and the holder 12 and the ferrule 17 are spline-connected 25. Here, the coil spring 23 and the spacer 21 that have been retracted
After inserting into the holder 12, the fixing nut 35 is screwed into the screw 15 of the holder 12. Further, the fixing nut 35 is fixed to the metal pipe 5 by the caulking 36, and the fixing nut 35 is attached to the rubber hood.
Cover with 41. Next, when the connection nut 31 is pulled out, the stopper 32 hits the key 14 of the holder 12 and advances together with the holder 12. Then, the connection nut 31 is screwed into the screw 46 of the adapter 45. At this time, the key 12 is the adapter
Since it fits in the key groove 47 of 45, the holder 12 holding the ferrule 17 does not rotate. Holder 12 fits outside alignment sleeve 48, ferrule 17 aligns sleeve
Fit inside 48. The ferrule 17 (not shown) of the optical fiber core wire 3 on the other side to be connected is aligned with the alignment sleeve 48.
Is inserted on the other side of. The tip surfaces of the capillaries 18 of both ferrules 17 are in contact with each other in the alignment sleeve 48, and the left and right optical fiber core wires 3 are connected. Since the outer peripheral surface of the ferrule 17 and the inner peripheral surface of the alignment sleeve 48 are precisely finished, both optical fiber core wires 3 are accurately connected. Further, when the tip surfaces of the capillaries 18 of both ferrules 17 are brought into contact with each other, the coil spring 23 is deformed and the ferrule 17 is retracted.
And contact with appropriate surface pressure.

(Specific Example 1) The metal tube containing an optical fiber used in FIG. 2 is an optical fiber core wire: core diameter 50 μm, cladding diameter 125 μm,
Coated outer diameter 0.5 mm Metal tube: Outer diameter 1.2 mm, wall thickness 0.15 mm, material SUS304 Specified length and other dimensions are specified length L: 1500 mm Bending radius d: 100 mm α ₁ (tip confirmation allowance): 5 mm l ₁ : 3mm l ₂ : 20mm l ₃ : 5mm β ₁ (required surplus length): 3mm (surplus length ratio 0.2%). The bending margin β _{2 in} this case was about 6 mm. Second
The length β ₁ + β ₂ of the exposed portion was about 9 mm, and when this portion was sandwiched by fingers and the first exposed portion was inserted into the ferrule and the clamper, the insertion was easy and accurate.

(Specific Example 2) In this specific example, when the pipe is bent, the length on the outside diameter side of the bend does not substantially change, and only the inside diameter side of the bend contracts the flexible pipe (fourth example).
(Shown in FIGS. 6 to 6) in the case of an optical fiber-containing metal tube in which an optical fiber core wire is inserted. The flexible tube used has an outer diameter of 4.2 mm, a thickness of 0.6 mm, and a material of SUS304. Other conditions are the same as those in the first specific example. The bending margin in this case is 93
The length was as long as mm and the workability was sufficiently good.

The flexible tube used here is a hoop formed in an S-shaped cross section and formed in a spiral shape so that adjacent hoops are engaged with each other, which will be described in detail with reference to FIGS. 4 to 6. To do.

As shown in FIG. 4A, the one-pitch block 52 of the flexible tube 51 of the optical fiber comprises a large diameter portion 53 and a small diameter portion 56. The large-diameter portion 53 has a first annular end portion 54 protruding at the inner diameter side at one end. Similarly, the small-diameter portion 56 has a second annular end portion 57 at one end which projects to the outer diameter side. And
The large diameter portion 53 and the small diameter portion 56 are connected via an annular connecting portion 58. The adjacent blocks 52 are shown in FIG. 4 (b).
As shown in, the pipe is displaceable in the axial direction and connected in a spiral shape. At this connection, the second annular end
57 is in the large diameter portion 53 of the adjacent blocks 52 and is substantially in contact with the first annular end portion 54. In order for the adjacent blocks 52 to be displaceable in the pipe axis direction, the first annular end portion 54 and the second annular end portion 57 are located outside the small diameter portion 56 and inside the large diameter portion 53 of the adjacent blocks, respectively, A gap l ₄ is provided between the annular connecting portion 58 and the annular connecting portion 58. Further, the inner diameter of the first annular end portion 54 is larger than the outer diameter of the small diameter portion 56 so as to form a gap l _5, and the outer diameter of the second annular end portion 57 is larger than the inner diameter of the large diameter portion 53. l ₅ is small enough to produce this gap
the size of l _5, it is also possible to adjust the magnitude of deflection of the flexible tubing 51.

The flexible tube 51 thus configured has the property of maintaining straightness in the longitudinal direction. In the straight, natural state, the first annular end of the flexible tube 51 is shown in FIG.
Since the 54 and the second annular end portion 57 are in contact with each other, the flexible pipe 51
When a compressive force is applied, the material shrinks, but does not expand when a tensile force is applied. Also, when bent to the flexible pipe 51, the flexible pipe 51
The first annular end portion 54 and the second annular end portion 57 are in strong contact with each other on the bending outer diameter side and are separated from each other on the bending inner diameter side, as shown in FIG. Therefore, the flexible tube 51 can contract on the bending inner diameter side, and maintains substantially the same length on the bending outer diameter side. As a result, no tension or compression force is applied to the optical fiber core wire 3 which is enclosed with the inner wall surface of the flexible tube 51 having a gap. Of course, depending on the precision of the band-shaped plate molding, the two annular ends 54, 57 may not be in complete contact due to the stretching force acting in the longitudinal direction, but the shrinkage on the bending inner diameter side will be preferentially contracted, Substantially no extension occurs on the bending outside diameter side.

[Effects of the Invention] According to the present invention, a bending margin is generated by a simple operation of bending an optical fiber-containing tube, and a sufficient margin for holding the optical fiber when inserting the optical fiber into the ferrule can be taken. Therefore, the optical fiber can be inserted into the ferrule accurately, reliably and easily.

[Brief description of the drawings]

1 (a) is a sectional view showing a state in which an optical fiber is inserted into a connector, FIG. 1 (b) is an explanatory view of a first exposed portion, and FIG.
FIG. 3 is a drawing showing a procedure for connecting an optical fiber-containing tube with a connector by the method of the present invention, and FIGS. 3 (a) and 3 (b).
FIG. 4 is an explanatory view of the extra bending length, FIGS. 4 and 5 are sectional views of a flexible tube covering an optical fiber, and FIG. 6 is a sectional view showing a part of the flexible tube in a loop shape. 1 ... Tube with optical fiber, 2 ... Bare optical fiber, 3 ...
Optical fiber core wire, 5 ... Tube, 11 ... Connector, 12 ... Holder, 13 ... Stopper, 14 ... Key, 17 ... Ferrule, 18 ... Capillary, 21 ... Spacer, 23 ... Coil spring , 25 …… Spline, 27 …… Clamper, 28 …… Stopper, 31 …… Connection nut, 32 …… Stopper, 35 …… Fixing nut, 36 …… Caulking, 41 …… Rubber hood, 45 …… Adapter, 47… … Key groove, 48 …… Alignment sleeve, 51 …… Flexible tube, 53 …… Large diameter part, 54 …… First annular end part, 56 …… Small diameter part, 57 …… Second annular end part, 58 …… Connection.

Claims (1)

(57) [Claims] 1. A method of attaching an optical fiber-containing tube, in which an optical fiber is inserted with a gap in a tube, to a connector having a ferrule, wherein the optical fiber-containing tube is linear and the optical fiber is at least the length of the ferrule. The end of the tube is removed so that it is exposed from the tube to form the first exposed portion, and then the optical fiber-containing tube is bent so that the optical fiber is exposed from the tube by at least a length that can hold the optical fiber. The optical fiber is pulled out from the tube so as to be wound around the inner wall on the bending inner diameter side of the tube to form the second exposed portion.
A method of attaching a connector for an optical fiber-containing tube, comprising holding the exposed part and inserting the first exposed part into a ferrule, and then returning the bent optical fiber-containing tube to a straight line and returning the second exposed part into the tube. .