JPH04109206A - Connector fitting method for pipe containing optical fiber - Google Patents

Abstract

PURPOSE:To accurately and securely, easily insert an optical fiber into a ferrule by bending the optical fiber containing pipe so that the optical fiber is exposed from the pipe, holding a 2nd exposed part and inserting a 1st exposed part into the ferrule, and then putting the bent optical fiber containing pipe back into a straight state. CONSTITUTION:While the optical fiber containing pipe 1 is held linearly, an end part of the pipe is so removed as to expose the optical fiber from the pipe by at least the same length of the ferrule 17, thereby forming the 1st exposed part. Further, the optical fiber containing pipe 1 is so bent as to expose the optical fiber 3 from the pipe long enough at least to hold the optical fiber 3, which is drawn out of the pipe so that the optical fiber 3 is wound around the internal wall of the pipe 5 on the bending internal-diameter side, thereby forming the 2nd exposed part. The 2nd exposed part is held and the 1st exposed part is inserted into the ferrule 17; and then the bent optical fiber containing pipe 1 is put back into the straight state to return the 2nd exposed part into the pipe 5. Consequently, the optical fiber 3 of the optical fiber containing pipe 1 is securely and easily inserted into the ferrule 17 of the connector and fitted to the connector.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method for attaching an optical fiber tube, in which an optical fiber is inserted with a gap, to a connector having a ferrule.

In this invention, the optical fiber refers to a bare fiber consisting of a core and a cladding layer, a bare fiber coated with synthetic resin, metal, ceramics, etc.
Refers to core wire and cord. Also, metal tubes include seamless tubes made of steel (carbon steel, stainless steel, etc.), aluminum, copper, titanium, and other materials, metal tubes such as welded tubes, forge-welded tubes, plastic tubes and other non-metallic tubes, and flexible tubes. A tube. Note that the flexible tube refers to a thin metal or synthetic resin plate formed into a bellows shape or spirally wound, a synthetic resin tube such as vinyl chloride or polyethylene, or a rubber tube.

[Prior Art] Optical fibers that are extended over the air, under the sea, underground, etc. are coated with a metal tube to prevent excessive tension or to provide environmental resistance. Furthermore, if the covering is a metal tube, there is no need for a tension member, and since there is little slack in the overhead wire, it is possible to extend the wire with a larger span.

Optical communication cables that have become widely used in recent years require optical fibers coated with metal tubes because the optical fibers are weak in strength.

As such an optical fiber tube, for example, JP-A-63-
187208 is known. In this optical fiber tube, the optical fiber is inserted into the tube with a gap, and the remaining length is uniformly distributed in the longitudinal direction of the tube.

On the other hand, in optical communication equipment and optical application equipment, optical fiber
Alternatively, an optical fiber is connected to an optical device such as a light emitting/light receiving element. In these connections, optical fibers and connectors that accurately connect optical fibers and optical devices are widely used in order to reduce loss at the connections.

A connector consists of a plug with a ferrule, and an attacher or socket.

The ferrule holds and fixes the optical fiber with high dimensional accuracy. A method for attaching an optical fiber tube to such a connector is disclosed in Japanese Patent Application Laid-Open No. 1-312517.
Also known as a fiber optic connection. In this connection, an optical fiber is inserted into the ferrule by removing the distal end of the cladding of the optical fiber tube by the length of the ferrule, and the distal end of the tube is fixed to the rear end of the ferrule.

[Problem 5W to be solved by the invention] However, the conventional method of attaching an optical fiber tube to a connector disclosed in Japanese Patent Application Laid-Open No. 1-312517 has the following problems.

After fixing the tip of the optical fiber cladding tube and the rear end of the ferrule, the cladding tube is removed and the entire exposed tip of the optical fiber is inserted into the ferrule. In this case, the optical fiber is inserted after aligning the ferrule with the cladding tube in between, but since the optical fiber enters the cladding tube with a gap, the optical fiber swings, which causes the position of the ferrule to change. The alignment and insertion work was difficult.

Therefore, the present invention provides a method for attaching a connector to an optical fiber tube in which the optical fiber of the optical fiber tube inserted into the tube with a gap can be easily and reliably inserted into the ferrule of the connector and attached to the connector. This is what I am trying to do.

[Means for Solving the Problems] The method for attaching a connector to an optical fiber tube according to the present invention is as follows:
With the optical fiber-entering tube in a straight state, the end portion of the tube is removed so that the optical fiber is exposed from the tube by at least the length of the ferrule to form a first exposed portion. Next, bend the optical fiber tube so that the optical fiber is exposed from the tube by at least a length that can hold the optical fiber, and pull out the optical fiber from the tube so that the optical fiber wraps around the inner wall of the bent tube. This is the second exposed portion. Then, after holding the second exposed portion and inserting the first exposed portion into the ferrule, the bent optical fiber tube is returned to a straight shape 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.

Generally, a tube into which a bare optical fiber, a raw optical fiber, a cored optical fiber, or an optical fiber coat is inserted has an outer diameter of several mm or less. Therefore, even metal pipes can be easily bent with bare hands. The length of the second exposed portion is determined by the size of the means for holding the optical fiber, such as a holding jig or bare hands. The bending radius, bending center angle, or number of turns of the loop or coil is determined by the holding length, the difference between the inner diameter of the tube and the diameter of the optical fiber, and the permissible bending radius of the optical fiber. It is desirable that the bending radius is 30 mm or more. Furthermore, the lengths of the first exposed part and the second exposed part are:
From the viewpoint of workability, it is preferable to allow some leeway.

[Function] Since the optical fiber is inserted into the tube with a gap, even if 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 bent inner diameter side of the tube. Therefore, when the optical fiber is pulled in such a state, the optical fiber becomes wrapped around the bent inner diameter side of the tube. As a result,
The optical fiber is exposed from the tube end, that is, a second exposed portion is formed.

By adjusting the bending radius, center angle, or number of turns of the loop or coil, the length of the second exposed portion, that is, the holding allowance, can be set to an appropriate value.

Since the optical fiber is directly inserted into the ferrule while holding the optical fiber, it can be inserted accurately, reliably, and easily. When the optical fiber tube is returned to its straight state after insertion, the holding allowance returns to the inside of the tube. Therefore, no extra length of optical fiber is left in the connector. Furthermore, an optical fiber of an appropriate length is contained within the connector, and it is possible to avoid excessive tension or compressive stress from acting on the optical fiber due to the inclusion of an excessive length of optical fiber.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1(a) is a sectional view of the entire connector 11 and a portion of the attack 45.

The connector 11 includes a cylindrical holder 12.

A ferrule 17 is inserted into the front part of the halter 12, and a spacer 21 is inserted into the rear part. Ferrule 17
The tip protrudes from the holter 12, into which a ceramic capillary 18 is inserted. A coil spring 23 is inserted between the ferrule] 7 and the spacer 21. Inner circumference of Holter 12 and ferrule 1
A spline connection 25 is made to the ferrule 7, and the ferrule 17 is positioned by an annular stopper 13 within the halter 12. A clamper 27 is inserted into the rear part of the ferrule 17. A connecting nut 31 is loosely engaged with the front half of the halter 12. An annular stopper 32 is provided on the inner periphery of the connecting nut 3. When the connecting nut 31 is advanced relative to the holder 12, the stopper 32 hits the key 14 provided on the holder 12, and the stopper 32
moving forward as one. Further, a thread 15 is cut on the outer periphery of the halter 12 near the rear end, into which a fixing nut 35 is fitted. The spacer 21 is pressed against the fixing nut 35 by a coil spring 23. The rear half of the halter 12 and the fixing nut 35 are covered by a rubber hood 41.

A thread 46 is cut on the outer periphery of the adapter 45, into which the connection nut 31 is fitted. A key groove 47 is cut in the inner periphery of the attack 45, and the key 14 of the holder 12 is fitted into the key groove 47. Further, an alignment sleeve 48 is provided within the adapter 45. The outer circumference of the alignment sleeve 48 is attached to the holder 12, and the inner circumference is attached to the ferrule 1.
7 fit each other.

FIG. 1(b) shows the optical fiber entry tube 1, the lighting fiber 2, and the optical fiber core 3 in FIG. 1(a). The portion located inside the rear part of the clamper 27 and the front part of the fixing nut 35 is the optical fiber core 3 from which the metal tube 5 has been removed.
is in a state of Further, a portion of the ferrule 17 from the tip of the capillary 18 to the stopper portion 28 of the clamper 27 is in the state of a bare optical fiber 2 with the coating of the optical fiber core 3 removed. The length l of the bare optical fiber 2 section.

is about 2 to 5 mm. The optical fiber core wire 3 is moved from the rear end of the stopper portion 28 of the clamper 27 to the clamper 27.
It consists of a portion U2 up to the rear end and a portion I13 from the rear end of the clamper 27 to the tip of the metal tube 5. ! 2 is about 20 mm, and ρ3 is about 3 to 7 mm. In addition, the optical fiber core wire 3 is vertical. The part is the sum of the ferrule retraction allowance and the dimensional error margin when the ferrule tips are crimped and abutted together by the elastic force of the coil spring 23 during connector connection.

Here, regarding how to attach the optical fiber tube 1 to the connector 11, the installation process is shown in Figure 2 (A).
The following will be explained step by step.

(a) Cut the tip of the optical fiber-containing metal tube 1 to make it straight.

(b) α from the end of the metal tube 5 to the above 11+ρ2+J23
The metal tube 5 having a length of 1+α2 is removed to expose the optical fiber core 3, forming a fifteenth exit portion. Here, α is the tip confirmation distance for confirming that the lighting fiber 2 protrudes from the Chiyabirari 18, and is approximately 5 mm.

In addition, α2 is generated in the core and crat portion of the lighting fiber 2 at the cut point because when the metal tube 5 is cut along with the metal tube 5 in (a) above, the optical fiber core 3 is sandwiched between the metal tubes 5 and cut. The safety margin for removing cracks is approximately 5 mm.

(c) Pull out the optical fiber core 3 from the metal tube 5 of a predetermined length (bending length of the metal tube 5). A mark is made on the optical fiber core 3 at the end of the tube using, for example, water-based paint, and this point is designated as A. Also, calculate the necessary extra length β of the predetermined length, mark the position β1 on the tip side from point A of the optical fiber core 11!3,
Let this point be B. Note that due to the difference in mechanical and thermal properties between the optical fiber and the cladding, if excessive tension is applied to the optical fiber, the transmission characteristics will deteriorate. In order to avoid deterioration of transmission characteristics, the optical fiber is inserted into the tube with the length of the optical fiber being made longer than the length of the tube. The extra length that exceeds this pipe length is called the necessary extra length.

The surplus length ratio is usually predetermined at 0.02 to 0.5t. Here, the required extra length β1 is calculated by a predetermined length (bending length of the pipe) x extra length ratio.

(d) Push the optical fiber core 3 into the metal tube 5 until the tube end is positioned at point B. Then, cut the optical fiber core 3 by α2 (safety allowance) from the tip.

(f) Bend the optical fiber-containing metal tube 1 of a predetermined length, pull out the optical fiber core 3 from the metal tube 5, and
Let it be β2 (between BC). That is, the second exposed portion is the sum of the required extra length β and the extra bending length β2. The extra bending length refers to the extra length produced by winding the optical fiber core 3 around the inner wall surface of the tube 5 on the inner diameter side of the bend, which is shrunk due to compressive stress when the metal tube 5 is bent. Here, the extra bending length will be further explained with reference to FIGS. 3(a) and 3(b). Third
When the metal tube 5 is bent as shown in FIG.

stretches due to tensile stress. Next, when the optical fiber core wire 3 in the first exposed portion is stretched, the optical fiber core wire 3 in the metal tube 5 of a predetermined length is expanded into the shrunken metal tube 5 as shown in FIG. 3(b). It wraps around the inner wall surface on the inner diameter side of the bending to reduce the bending radius, and is thereby pulled out and exposed outside the tube by the extra bending length.

The extra bending length β2 is L/predetermined length, a: pipe outer diameter, t: wall thickness,
b: optical fiber diameter, d: bending radius (where L is the length of the center line of the bent tube).

In addition, in the case of a flexible tube in which the length of the bent outer diameter side of the bent pipe does not substantially change and only the bent inner diameter side shrinks, (T, the length of the bent pipe outer diameter side T) L). In this case, it is advantageous that the bending inner diameter side is greatly reduced, so that the extra bending length is long.

(f) In order to insert the tip end of the optical fiber core wire 3 into the capillary 18, the resin coating is removed by the length α1+ to form the lighting fiber 2. In this state, the optical fiber-containing metal tube is passed through the fixing nut 35 of the connector 11, the rubber hood 4, the coil spring 23, and the spacer 21, and while these are retracted, the bare optical fiber 2 is passed through the ferrule 17 and the clamper 27.

When passing the first exposed part of the optical fiber through the ferrule 17 and the clamper 27, hold the second exposed part (the optical fiber core 3 between BC) between your fingers and insert the ferrule and the clamper 27.
Since the optical fiber is passed through the capillary, the work can be done easily and accurately, and breakage of the optical fiber (particularly breakage of the bare optical fiber portion inserted into the capillary) can be prevented. This second exposed part is l
It is desirable that the thickness is 0 mm or more.

(g) Next, the bent metal tube 5 is returned to its original shape and made into a straight line, and the optical fiber core 3 (the part between AC) with an extra bending length β2 is drawn into the metal tube 5 to reduce the extra bending length. Eliminate.

(H) Further push the optical fiber core 3 of the required extra length β (the part between BA) into the metal tube 5.

In the states (S) and (H), the bare optical fiber 2 is connected to the capillary 1.
Since the tip of the bare optical fiber 2 and the tip of the capillary 18 are aligned at αl (tip confirmation type) height ratio, this protruding portion is polished to match the tip of the bare optical fiber 2 and the tip of the capillary 18. Next, the ferrule 17 is passed through the holder 12 with the connecting nut 31 loosely fitted, and the holter 12 and the ferrule 17 are spline connected 25. Here, the coil spring 23 that has been retreated
After inserting the spacer 21 into the halter 12,
Screw the fixing nut 35 into the bolt 15 of the halter 12.

Further, the fixing nut 35 is fixed to the metal tube 5 by caulking 36, and the fixing nut 35 is covered with a rubber foot 41.

Finally, when the connecting nut 31 is pulled out, the stopper 32 hits the key 14 of the holder 12 and moves forward together with the holder 12. Then, the connecting nut 31 is screwed into the screw 46 of the adapter 45. At this time, since the key 12 is fitted into the key groove 47 of the adapter 45, the holter 12 holding the ferrule 17 does not rotate. Holter 12 fits on the outside of alignment sleeve 48, and ferrule 17 fits on the inside of alignment sleeve 48. The ferrule 17 (not shown) of the optical fiber core 3 to be connected is inserted into the other side of the alignment sleeve 48 . The end surfaces of the capillaries 18 of both ferrules 17 come into contact within the alignment sleeve 48, and the left and right optical fiber core wires 3 are connected. Since the outer circumferential surface of the ferrule 17 and the inner circumferential surface of the alignment sleeve 48 are finished with a fine finish, both optical fiber cores 3 can be accurately connected. Furthermore, when the tip surfaces of the capillaries 18 of both ferrules 17 abut against each other, the coil spring 23 deforms and the ferrules 17 move backward, so that the tip surfaces of the capillaries 18 are reliably placed under appropriate surface pressure. contact.

(Specific Example 1) The optical fiber-containing metal tube used in Fig. 2 is an optical fiber core, core diameter 50μm, cladding diameter 125μm.
JJm, coated outer diameter 0.5■ Metal tube: outer diameter 1.2 mm, wall thickness 0.1511101,
Material 5US304 The specified length and other dimensions are: Predetermined length L: 1500mm Bending radius d: 100mm αI (tip confirmation type): 5mm ], :3non 1□20mm ]3: 5mm βI (required extra length): 3mm (extra) The length ratio is 0.2%).

The extra bending length β2 in this case was approximately 6 mm. The lengths β and +β2 of the second B protrusion were approximately 9 mm, and when this portion was held between fingers and the first exposed portion was inserted into the ferrule and clamper, it was possible to insert the first exposed portion easily and accurately.

(Specific Example 2) This specific example is a flexible tube in which 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 shrinks (as shown in Figures 4 to 6) This is the case of an optical fiber-containing metal tube with an optical fiber core inserted inside. The flexible tube used has an outer diameter of 4.2111 m, a thickness of 0.6 mm, and is made of 5US3 material.
It is 04. Other conditions are the same as in Example 1. The extra bending length in this case was as long as 93 mm, and the workability was sufficiently good.

The flexible tube used here was formed into a spiral shape by having hoops formed into an S-shaped cross section so that only adjacent hoops were engaged, and will be explained in more detail in FIGS. 4 to 6. do.

As shown in FIG. 4(a), one pitch block 52 of the optical fiber flexible tube 5j consists of a large diameter portion 53 and a small diameter portion 56. The large diameter portion 53 has a first annular end portion 54 at one end that protrudes inward. Similarly, the small diameter portion 56
is provided with a second annular end portion 57 projecting toward the outer diameter side at one end portion. The large diameter portion 53 and the small diameter portion 56 are connected via an annular connecting portion 58. As shown in FIG. 4(b), adjacent blocks 52 are movable in the tube axis direction and are connected in a spiral manner. At this connecting portion, the second annular end 57 is located within the large diameter portion 53 of the adjacent block 52 and is substantially in contact with the first annular end 54 .

In order to enable the adjacent blocks 52 to be displaced in the tube axis direction, the first annular end 54 and the second annular end 57 are located outside the small diameter portion 56 and the large diameter portion 53 of the adjacent block, respectively.
There is a gap 4 between the annular connecting portion 58 and the annular connecting portion 58. Further, the inner diameter of the first annular end portion 54 is smaller than the small diameter portion 5.
There is more clearance than the outer diameter of 6! 5, and the outer diameter of the second annular end portion 57 is smaller than the inner diameter of the large diameter portion 53 so as to create a gap I15. The magnitude of the deflection of the flexible tube 51 can also be adjusted by adjusting the magnitude of the deflection tube 51.

The flexible tube 51 configured in this manner has a property of trying to maintain straightness in the longitudinal direction. In the natural state where it extends straight, the first annular end 54 and the second annular end 57 of the flexible tube 51 are in contact as shown in FIG. 5, so when a compressive force is applied to the flexible tube 51, It shrinks, but does not stretch even when a tensile force is applied. In addition, when bent into a flexible tube 51,
As shown in FIG. 6, the first annular end 54 and the second annular end 57 of the flexible tube 51 are in strong contact with each other on the outer diameter side of the bend.
Bend away from each other on the inner diameter side. So, the flexible tube 51
can be contracted on the bending inner diameter side while maintaining 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 3 which is enclosed with a gap between the inner wall surface of the flexible tube 51 and the inner wall surface of the flexible tube 51. Of course, depending on the accuracy of forming the strip plate, the inner annular ends 54 and 57 may not be in complete contact due to the stretching force acting in the longitudinal direction, but the shrinkage on the inner diameter side of the bending will preferentially shrink. Substantially, there is almost no stretching on the outer diameter side of the bend.

[Effects of the Invention] According to the present invention, an extra bending length can be created by the simple operation of bending the optical fiber tube, and a sufficient holding margin for the optical fiber required when inserting the optical fiber into the ferrule can be obtained. Now, it is possible to insert an optical fiber into a ferrule accurately, reliably, and easily.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view showing the optical fiber inserted into the connector, FIG. 1(b) is an explanatory view of the first exposed part, and FIG.
Figures 3(a) and 3(b) are drawings showing the procedure for connecting optical fiber tubes with connectors according to the method of the present invention.
4 and 5 are cross-sectional views of a flexible tube covering an optical fiber, and FIG. 6 is a cross-sectional view of a portion of the flexible tube formed into a loop. 1... Optical fiber tube, 2... Bare optical fiber, 3
...Optical fiber core wire, 5...Tube, 11...Connector, I 2-...Holder, 13...Stopper, 14
... Key, 17 ... Ferrule, 18 ... Capillary, 21 ... Spacer, 23 ... Coil spring, 2
5... Spline, 27... Clamper, 28...
Stopper, 31... Connection nut, 32... Stopper, 35... Fixing nut, 36... Caulking, 41...
・Rubber foot, 45... Adapter, 47... Keyway, 48... Alignment sleeve, 51... Flexible pipe, 53
... Large diameter portion, 54... First annular end portion, 56... Small diameter portion, 57... Second annular end portion, 58... Connection portion.

Claims (1)

[Claims] 1. In a method of attaching an optical fiber tube in which the optical fiber is inserted with a gap in the tube to a connector with a ferrule, the optical fiber is exposed from the tube by at least the length of the ferrule while the optical fiber tube is kept in a straight line. remove the end of the tube to create a first exposed section, then bend the fiber-containing tube so that at least a length of the optical fiber that will hold the optical fiber is exposed from the tube, and the optical fiber is bent into the tube. Pull out the optical fiber from the tube so as to wrap it around the inner wall on the inner diameter side to form the second exposed section. After holding the second exposed section and inserting the first exposed section into the ferrule, bend the optical fiber tube into a straight line. A method for attaching a connector to an optical fiber tube, the method comprising: returning the second exposed portion to the inside of the tube.