JP2014182204A - Optical fiber connector with loose tube and manufacturing method for optical fiber connector with loose tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, at a low cost, a fiber connector with a loose tube, which is free from performance degradation and disconnection resulting from decentering.SOLUTION: An optical fiber connector with a loose tube comprises: a ferrule 2 having a front to which a capillary 3 is attached, the capillary 3 having an insertion hole 35 having an opening in the front end 33 thereof and used for inserting an optical fiber bare wire through it, the optical fiber bare wire extending toward the rear end 34 thereof along an optical axis 100, and the capillary 3 also having a cone part 31 reaching the rear end of the insertion hole while decreasing in diameter forward from the rear end, and in the rear end 42 of which a loose tube 5 is inserted; and an optical fiber 6. An optical fiber 6 is open in the front end of the capillary while an optical fiber core wire 61 is continuously inserted into the loose tube toward the rear of the optical fiber bare wire 62. Between the capillary and loose tube, a spacer 10 of length Ls in the forward and backward directions is interposed for bearing the optical fiber while keeping the distance L between the front end 32 of the cone part and the front end 51 of the loose tube constant. The length Ls is set such that the optical fiber has a predetermined curvature radius R or greater. The area where the spacer is interposed has the boundary 65 of the optical fiber core wire and optical fiber bare wire.

Description

  The present invention relates to an optical fiber connector with a loose tube in which an optical fiber is inserted into a loose tube and the loose tube is inserted into a ferrule.

  An optical fiber connector with a loose tube includes a ferrule, a loose tube inserted into the proximal end of the ferrule, and an optical fiber inserted through the loose tube, and the optical fiber inserted through the loose tube is attached to the ferrule. It has a structure that opens at the tip of the capillary. FIG. 1 shows a schematic structure of an optical fiber connector 1 with a loose tube. FIG. 1 is a longitudinal sectional view including the optical axis 100 when the direction of the optical axis 100 is the front-back (vertical) direction. The opening end 63 of the optical fiber 6 is the front.

  In the optical fiber connector 1 with a loose tube shown in FIG. 1, the ferrule 2 has a structure in which the rear end 34 side of the capillary 3 is coaxially held on the front end 41 side of a hollow cylinder (hereinafter referred to as flange) 4 called a flange or the like. The loose tube 5 is inserted on the rear end 42 side of the flange 4. The ferrule 2 is usually made of ceramic such as zirconia, and the flange 4 is made of metal such as stainless steel.

  The loose tube 5 is a plastic tube having an inner diameter φ1 larger than the outer diameter φ2 of the optical fiber 6, and an optical fiber core wire 61 such as a 0.25 mm strand is inserted therethrough. Thereby, the optical fiber core wire 61 is protected from mechanical load and impact from the outside. As is well known, the optical fiber core 61 is obtained by applying a resin coating 68 made of an ultraviolet curable resin or the like to an optical fiber itself (hereinafter referred to as an optical fiber bare wire) 62 in which a cladding is disposed around a core. . In addition, since the optical fiber 6 which comprises the optical fiber connector 1 with a loose tube has the part in the state of the optical fiber bare wire 62, and the part in the state of the optical fiber core wire 61, the following In the description, when it is not necessary to distinguish between the optical fiber core wire 61 and the bare optical fiber 62, the optical fiber core wire 61 and the bare optical fiber wire 62 are simply referred to as “optical fiber”, and the symbol “6” is also used.

  As a method of manufacturing (assembling) the optical fiber connector 1 with the loose tube having the above configuration, first, the optical fiber core wire 61 is protruded from the front end 51 of the loose tube 5 and the adhesive 7 is filled on the front end 51 side of the loose tube 5. Then, the optical fiber core wire 61 is fixed to the loose tube 5. Further, the resin coating 68 at the protruding portion is removed to leave the bare optical fiber 62. Then, the adhesive 8 is filled in the internal space 43 of the flange 4, and the loose tube 5 is inserted from the rear end 42 side of the flange 4.

  At the rear end 34 of the capillary 3, a conical hole (hereinafter referred to as a cone portion) 31 whose diameter is reduced toward the front is formed. When the loose tube 5 is inserted into the flange 4, an optical fiber bare wire is formed. The tip of 62 is inserted into the insertion hole 35 of the bare optical fiber 62 passing through the capillary 3 around the optical axis 100 while being guided by the inner surface 36 of the cone portion 31. The adhesive 8 filled in the internal space 43 of the flange 4 is also filled in the gap 44 between the outer surface of the loose tube 5 and the inner surface of the flange 4 as the loose tube 5 is inserted. Is pushed outward from the rear end 42 of the flange 4. Thereby, the rear end 42 of the flange 4 is sealed when the adhesive 8 is solidified. Then, after cutting the tip portion of the bare optical fiber 62 protruding from the front end 33 of the capillary 3 at the position of the front end 33 of the capillary 3, the tip of the bare optical fiber 62 together with the front end 33 of the capillary 3 is polished. An open end 63 of the optical fiber 6 is formed at the front end 33 of the capillary 3, and the optical fiber connector 1 with a loose tube is assembled.

  By the way, in the optical fiber connector 1 with the loose tube, since the inner diameter φ1 of the loose tube 5 is larger than the outer diameter φ2 of the optical fiber core 61, the optical fiber core 61 and the loose tube 5 are basically coaxial. is not. That is, it is eccentric. Further, the inner diameter φ3 of the flange 4 into which the loose tube 5 is inserted in the ferrule 2 is larger than the outer diameter φ4 of the loose tube in order to facilitate the insertion of the loose tube 5 when the optical fiber connector 1 with the loose tube is assembled. . Accordingly, the optical fiber 6 from the rear end 34 of the capillary 3 to the front end 51 of the loose tube 5 is bent in the ferrule 2. This bending causes disconnection. Even if the disconnection does not occur, it causes an increase in transmission loss and a decrease in long-term reliability. The following Patent Documents 1 to 7 describe techniques for reducing the eccentricity between the optical fiber and the capillary in the loose tube as much as possible in the optical fiber connector with the loose tube.

Japanese Patent No. 4117777 Japanese Patent No. 4128856 JP-A-11-231167. Japanese Patent Laid-Open No. 2003-066273 Japanese Patent No. 3723666 Japanese Patent Laid-Open No. 10-307233 JP 2004-020677 A

  As described above, in the optical fiber connector with the loose tube, there is basically a problem that the optical fiber is eccentric in the loose tube. And in the said patent documents 1-7, it is going to solve problems, such as characteristic deterioration of an optical fiber, a cutting | disconnection, by reducing the eccentricity as much as possible. However, it has been clarified by the inventor's research that there are various problems with the techniques described in the above patent documents. For example, in the technique described in Patent Document 1, the optical fiber core wire is uniformly reduced in diameter so as to be positioned substantially at the axial center of the loose tube with a caulking member from the outside of the loose tube and fixed. Therefore, there is a possibility that the optical fiber is disconnected during the caulking process.

  In the technique described in Patent Document 2, the heat-shrinkable tube that heats the heat-shrinkable tube so as to gradually reduce the diameter and gradually reduces the diameter is used as the loose tube. However, the hardness is different between a part that is sufficiently reduced in diameter by heat shrinkage and a part that is hardly thermally shrunk. That is, the hardness of the tube is different during the extension of one loose tube, and the loose tube does not bend uniformly when the optical fiber is routed, which makes it difficult to handle. Moreover, a complicated process for processing the heat-shrinkable tube so as to gradually reduce the diameter is necessary, resulting in an increase in cost. In the technique described in Patent Document 3, a jig having a stepped hole whose inner surface is a two-stage cylinder is used, and the loose tube and the optical fiber core wire are bonded in the jig so that the front end side of the loose tube is formed. The optical fiber and the loose tube are concentric. Therefore, the adhesive adheres to the jig every time the optical fiber core wire is bonded to the front end of the loose tube. Therefore, it is necessary to periodically clean the jig, and the time and cost for maintenance increase.

  In the technique described in Patent Document 4, the optical fiber core wire and the loose tube are bonded after the loose tube is inserted into the ferrule. However, the resin film is removed in a state where the loose tube and the optical fiber core are not bonded, and the optical fiber core cannot be held by holding the loose tube, so that the workability deteriorates. Further, in order to prevent the adhesive from protruding from the front end of the loose tube, it is necessary to increase the viscosity of the adhesive, and it is difficult to uniformly apply the adhesive into the loose tube. Therefore, the adhesive in the loose tube is actually unevenly distributed, and the optical fiber core wire is fixed at the position where the adhesive is unevenly distributed. Therefore, eccentricity cannot be reliably prevented.

  In the technique described in Patent Document 5, a hole having the same diameter as the optical fiber core wire including the resin coating is provided at the rear end of the capillary, and a hole through which only the bare optical fiber is inserted is continuous at the front end of the hole. As a result, the capillaries become longer, making it difficult to reduce the size of the optical fiber connector, and the general-purpose capillaries cannot be used. In the technique described in the cited document 6, a hole having the same diameter as the optical fiber core wire is provided in the flange. In many cases, the flange is made of metal, the end of the hole becomes sharp, and the core or bare wire of the optical fiber may touch the end of the hole and break.

  In the technique described in the cited document 7, the front end of the optical fiber core, that is, the resin coating portion is brought into contact with the capillary. However, the resin coating of the optical fiber is thin, and the end face of the coating layer is often deformed. If the deformed end face comes into contact with the capillary, the bare optical fiber is locally distributed along the shape of the end face. There is a possibility of bending.

  As described above, in the structure and manufacturing method of the conventional optical fiber connector based on the technical idea that the optical fiber is not bent, even if the eccentricity can be eliminated, the cost is high and the assembly workability is high. It may worsen or the expected effect may not actually be obtained. Accordingly, an object of the present invention is to provide a practical optical fiber connector that is inexpensive and has no performance deterioration or disconnection due to eccentricity.

In order to achieve the above object, the present invention provides a ferrule having a capillary attached to the front with the front-rear direction as the optical axis direction, a loose tube inserted on the rear end side of the ferrule, and inserted into the loose tube. An optical fiber connector with a loose tube comprising an optical fiber opened at the front end of the capillary while being,
In the optical fiber, an optical fiber core wire in which a resin coating is applied to the bare optical fiber is continuously extended behind the bare optical fiber composed of a core and a clad,
The capillary has an opening at the front end and extends through the optical axis to the rear end along the optical axis, and a rear end of the insertion hole while reducing the diameter from the rear end toward the front. A cone portion having a conical inner shape reaching the end is formed,
While the front end of the cone part and the front end of the loose tube are used as a bent region of the optical fiber, the front end of the capillary and the front end of the loose tube are brought into contact with each other while keeping the front and rear lengths of the bent region constant. A spacer that carries the optical fiber is interposed,
The longitudinal length of the spacer is set to be equal to or larger than a predetermined radius of curvature in which the optical fiber is allowed in the bent region,
In the intervening region of the spacer, there is a boundary between the optical fiber core wire and the bare optical fiber,
An optical fiber connector with a loose tube is provided.

  The spacer is more preferably an optical fiber connector with a loose tube in which a U-shaped groove that holds the optical fiber is formed by extending in the front-rear direction on the surface of a cylinder having a central axis in the front-rear direction.

The manufacturing method of the optical fiber connector with the loose tube is also within the scope of the present invention.
An optical fiber in a state of an optical fiber core coated with a resin coating is protruded from the front end of the loose tube while being inserted through the loose tube, and the optical fiber core is formed inward of the front end side of the loose tube. An optical fiber bonding step to bond the wires;
A resin film removing step of processing the optical fiber into a bare optical fiber state by removing the resin film from the middle of the extension of the optical fiber core protruding to the front end side of the loose tube to the front end;
An adhesive filling step of filling an adhesive into the rear end side inward of the ferrule;
While holding the optical fiber protruding to the front end side of the loose tube on the spacer, the spacer and the loose tube are inserted into the ferrule, and the front end of the bare optical fiber extends along the inner surface of the cone portion. A loose tube insertion step of inserting the capillary tube through the insertion hole of the capillary while guiding,
In the resin film removal step, for the optical fiber core protruding from the front end of the loose tube, the front resin film is removed from the front end from a position below the front and rear length of the spacer,
In the loose tube insertion step, the loose tube is inserted until the front end of the spacer contacts the rear end of the capillary while the rear end of the spacer is in contact with the front end of the loose tube.
This is a method for manufacturing an optical fiber connector with a roots tube.

  According to the present invention, a practical optical fiber connector free from performance deterioration and disconnection due to eccentricity can be provided at low cost.

It is a figure which shows the structure of the conventional optical fiber connector with a loose tube. It is a principal part enlarged view of the optical fiber connector with a loose tube shown in FIG. It is a figure for demonstrating the curvature radius of the optical fiber bent in the optical fiber connector with a loose tube It is a photograph which shows the disconnection state of the optical fiber in the optical fiber connector with a loose tube. It is a figure for demonstrating the mechanism in which an optical fiber breaks in the optical fiber connector with a loose tube. It is a figure which shows the structure of the optical fiber connector with a loose tube which concerns on the Example of this invention. It is arrow sectional drawing about each of the code | symbol bb, cc, and dd shown in FIG. It is a figure which shows the assembly procedure of the optical fiber connector with a loose tube shown in FIG.

=== Technical thought of the present invention ===
As described above, in an optical fiber connector with a loose tube (hereinafter referred to as an optical fiber connector), the optical fiber is decentered in principle. In the conventional technology, it has been dedicated to realizing a concentric state so that this eccentricity does not occur. And the technique which is going to implement | achieve the concentric state is substantially covered by the said patent documents 1-7. However, with the techniques described in these documents, it has been found that the assembly procedure and processing procedure of the optical fiber connector are complicated, and the cost required for maintenance of jigs used for assembly and processing increases. . In addition, the expected effect may not be obtained. With this, it is difficult to realize a practical optical fiber connector.

  Therefore, the present inventor changed the way of thinking and thought that the optical fiber may be decentered as long as the optical fiber does not deteriorate or break. The optical fiber has a specified radius of curvature that guarantees performance, and it is considered that the performance of the optical fiber connector can be secured if the optical fiber can be bent with a curvature larger than the specified radius of curvature with good reproducibility. Of course, if the assembly procedure and the processing procedure for achieving the desired radius of curvature are complicated, the cost increases. The present invention has been made as a result of intensive researches starting from the above-mentioned change of idea.

=== Eccentricity and radius of curvature ===
The technical idea of the present invention is to prevent performance deterioration and disconnection due to eccentricity by controlling the radius of curvature of the optical fiber in the optical fiber connector to be equal to or greater than an allowable value. FIG. 2 is a diagram for explaining the amount of eccentricity associated with the bending of the optical fiber 6 in the optical fiber connector 1, and illustrates the case where the amount of eccentricity d is maximized. 2A is an enlarged view inside the circle 101 in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line aa in FIG.

  As shown in FIG. 2A, the optical fiber 6 of the optical fiber connector 1 has a cone portion 31 formed from the front end 51 of the loose tube 5 to the rear end 34 of the capillary 3 in accordance with the amount of eccentricity d. Bend while drawing a curve gently up to the front end 32. 2B, the inner diameter φ1 of the loose tube 5 is larger than the outer diameter φ2 of the optical fiber core 61, and the loose tube 5 is inserted into the outer diameter φ4 of the loose tube 5. The inner diameter φ3 of the flange of the ferrule 2 is smaller. Accordingly, eccentricity occurs both between the loose tube 5 and the optical fiber 6 and between the loose tube 5 and the ferrule 2. Therefore, unless any processing or work is performed to correct the eccentricity between the loose tube 5 and the ferrule 2, the optical fiber 6 is in relation to the optical axis 100 that is also the central axis of the insertion hole 35 penetrating the capillary 3. Be sure to be eccentric. The eccentric amount d1 for the loose tube 5 and the optical fiber 6 is d1 = (φ1-φ2) / 2, and the eccentric amount d2 between the loose tube 5 and the ferrule 2 (or the optical axis 100) is d2. = (Φ3-φ4) / 2.

  Further, the final eccentricity d is the eccentricity between the optical axis 100 and the optical fiber 6, and this eccentricity d has the maximum value D as shown in FIG. 100, the center 52 of the loose tube 5 and the center 64 of the optical fiber 6 are on the same straight line, and the center 52 of the loose tube 5 and the center 64 of the optical fiber 6 are in the same direction with respect to the optical axis 100. . The maximum eccentric amount D is D = (φ3-φ4 + φ1-φ2) / 2. In the following, an eccentric state in which the eccentric amount d shown in FIG. 2 is the maximum value D is taken as an example, and a method for obtaining the curvature radius will be described based on the example. In this description, as shown in FIG. 2B, the direction of the straight line 110 connecting the optical axis 100, the center 52 of the loose tube 5 and the center 64 of the optical fiber 6 is the vertical direction, and the optical axis 100 is It is assumed that it is above the center 64 of the optical fiber 6.

FIG. 3 shows an example of how to find the curvature radius. As shown in FIG. 3, the bending state of the optical fiber 6 in the section from the front end 32 of the cone portion 31 of the capillary 3 to the distance L from the front end 51 of the loose tube 5 (hereinafter referred to as a bending region) The arcs (102, 103) can be treated as being continuous so as to be point-symmetric with respect to the intermediate position M of the distance (hereinafter referred to as a bending region length) L. The radius R of this arc (102, 103) becomes the curvature radius R. Here, if the crossing angle between the optical axis 100 and the straight line 104 connecting the front and rear ends of the continuous arc (102, 103) is θ, a circle (105, 106) having a radius R corresponding to the arc (102, 103). ) Is 2θ, the radius of curvature R is
R = (L ² −D ² ) / 4D Formula 1
It can be calculated by the following formula. Therefore, the radius of curvature R allowed in Equation 1, the inner diameter φ1 and outer diameter φ4 of the loose tube 5 shown in FIG. 2, the outer diameter φ2 of the optical fiber core 61, and the inner diameter φ3 of the flange 4 are as follows. If the maximum amount of eccentricity D required is substituted, the bending region length L is
L = {D ² + 4DR) ^1/2 Formula 2
It can be obtained by the following formula. That is, if the bending region length L is equal to or greater than the value of L obtained by Equation 2, the optical fiber 6 bends with an allowable curvature radius R or more.

=== About disconnection of optical fiber ===
As described above, the optical fiber 6 has an allowable range for the radius of curvature R when it is bent. Therefore, the present inventor considered that if the bending region length L is increased in the optical fiber connector 1 shown in FIG. 1, the radius of curvature R increases and the performance deterioration and disconnection of the optical fiber 6 can be prevented. However, it has been found that disconnection cannot be reliably prevented by simply increasing the bending region length L. Therefore, the present inventor examined the mechanism leading to the disconnection, and actually observed the inside of the optical fiber connector 1 in which the disconnection occurred in the optical fiber 6.

  FIG. 4 shows a photograph of the disconnected optical fiber connector 1. The photograph was taken when the surface of the optical fiber connector 1 was gradually polished along the front-rear direction and the insertion hole 35 of the optical fiber 6 in the capillary 3 was exposed. As shown in this photograph, the disconnection 66 is very often generated near the front end (vertex) 32 of the cone portion 31. Therefore, the present inventor made the following hypothesis about the mechanism of the disconnection from the fact that the position of the disconnection 66 is substantially constant.

  First, when the loose tube 5 is inserted into the ferrule 2, the bare optical fiber 62 on the front end side of the optical fiber 6 is inserted into the capillary 3 while being guided by the inner surface 36 of the cone portion 31, and the loose tube 5 is further inserted. Then, the front end 65 of the optical fiber core wire 61 comes into contact with the inner surface 36 of the cone portion 31 in the same manner. When the loose tube 5 is further inserted, the front end 65 of the optical fiber core wire 61 is bent without sliding well forward due to friction with the inner surface 36 of the cone portion 31, as shown in FIG. As a result, the position of the front end 65 of the optical fiber core 61 and the position of the front end 32 of the cone part 31 are greatly shifted, and a large stress is applied to the bare optical fiber 62 with the front end 32 of the cone part 31 as a fulcrum. Accordingly, it can be interpreted that a disconnection 66 has occurred at the front end 32 of the cone portion 31.

  Therefore, it is conceivable that the front end 65 of the optical fiber core wire 61 is further rearward. In this case, the resin coating 68 is removed and the optical fiber bare wire 62 having a low strength is connected to the flange 4 on the rear end side of the capillary 3. It will be exposed to the internal space 43. Since the bare optical fiber 62 is easily bent even by a slight stress or vibration, it is difficult to maintain a constant curvature radius in the flange 4. There is also a possibility that the bare optical fiber 62 contacts the inner wall of the flange 4 to cause a crack or the like. Therefore, it is desirable that the front end 65 of the optical fiber core wire 61 is as close as possible to the front end 32 of the cone portion 31 of the capillary 3. From the above, in order to maintain the curvature radius of the optical fiber 6 within the allowable range within the optical fiber connector 1, the bending region length L is set according to the allowable curvature radius, and the front end position of the loose tube, That is, it is necessary to adjust the bending region length L with high accuracy.

==== Embodiment of the Invention ====
In the optical fiber connector according to the embodiment of the present invention, in order to reliably prevent disconnection in the optical fiber connector, the front end position of the loose tube is extremely bent while the optical fiber core wire is bent at a specified radius of curvature or more in the bending region. It is adjusted with high accuracy. Moreover, the ease of the adjustment work is ensured.

  6 and 7 are structural views of the optical fiber connector 1a according to the embodiment of the present invention. 6 is a longitudinal sectional view of the optical fiber connector 1a, and FIGS. 7A to 7C are sectional views taken along arrows bb, cc, and dd in FIG. 6, respectively. The parts and members constituting the optical fiber connector 1a are indicated by hatching used in FIG. In addition, also in the optical fiber connector 1a according to the present embodiment, the optical fiber 6 has a portion in the state of the bare optical fiber 62 and a portion in the state of the optical fiber core 61, Similar to the optical fiber connector 1 shown in FIG. 1, when it is not necessary to distinguish between the optical fiber core 61 and the bare optical fiber 62, the optical fiber connector 61 is simply referred to as “optical fiber”, and the reference numeral is “6”. "Is used. As shown in these drawings, in the optical fiber connector 1a of this embodiment, the spacer 10 is interposed between the front end 51 of the loose tube 5 and the rear end 34 of the capillary 3. The spacer 10 in this embodiment has a shape in which a U-shaped groove 11 extending in the front-rear direction is formed on the surface of a hollow cylindrical stainless steel tube. The spacer 10 carries the optical fiber 6 between the front end 51 of the loose tube 5 and the rear end 34 of the capillary 3 while keeping the bent region length L constant.

  Thus, in the optical fiber connector 1a according to the present embodiment, the spacer 10 is interposed between the front end 51 of the loose tube 5 and the rear end 34 of the capillary 3, so that complicated adjustment work and high assembly accuracy are required. Without this, the radius of curvature R allowed for the optical fiber 6 can be secured. Further, when assembling the optical fiber connector 1a, the loose tube 5 is not excessively inserted, and the cutting of the bare optical fiber 62 at the front end 32 of the cone portion 31 can be reliably prevented.

  The longitudinal length Ls of the spacer 10 can be set based on the maximum value D of the eccentric amount and the allowable radius of curvature R. In the optical fiber connector 1a according to the present embodiment, the inner diameter φ1 and the outer diameter φ4 of the loose tube 5 are φ1 = 0.380 mm and φ4 = 0.910 mm, respectively, and the outer diameter φ2 of the optical fiber core wire 61 is The inner diameter φ3 of the flange 4 is φ2 = 0.242 mm and φ3 = 1.050 mm, respectively. Therefore, the maximum value D of the eccentric amount d is D = 0.139 mm. Further, the radius of curvature R allowed for the used optical fiber 6 is R ≧ 20 mm, and when the lower limit R = 20 mm is adopted, the bending region length L at this time is L≈2. 86 mm. The bending region length L obtained from this calculation is also the minimum value of the value obtained by adding the longitudinal length Lc of the cone portion and the longitudinal length Ls of the spacer 10, so the value of L obtained from the calculation of the longitudinal length Ls of the spacer 10 If it is set as above, the curvature radius of an optical fiber can be certainly made more than the lower limit of an allowable range. In the optical fiber connector 1a according to the present embodiment, Ls = 3.00 mm.

=== Method of Manufacturing Optical Fiber Connector ===
Next, a manufacturing method (hereinafter referred to as an assembling method) of the optical fiber connector 1a according to the present embodiment will be described. FIGS. 8A to 8F are longitudinal sectional views showing an example of a method for assembling the optical fiber connector 1a according to the present embodiment. The optical fiber core 61 is shown in a side view so that it can be easily distinguished from the bare optical fiber 62. First, as shown in (A), with the optical fiber core wire 61 protruding from the front end 51 of the loose tube 5, the adhesive 7 is filled inside the front end side of the loose tube 5 and the optical fiber 6 is attached. Fix to the loose tube 5. Next, as shown in (B), the front resin coating 68 is removed from an appropriate position of the optical fiber core wire 61 protruding from the front end 51 of the loose tube 5, so that a bare optical fiber 62 is obtained. It should be noted that the front end 65 of the optical fiber core 61 that is the removal position of the resin coating 68 need not be in the cone, and is behind the position that is the same distance as the length Ls of the spacer 10 from the front end 51 of the loose tube 5. I just need it.

  Next, as shown in (C), the optical fiber 6 protruding from the front end 51 of the loose tube 5 is carried by the spacer 10. That is, the optical fiber 6 is accommodated in the U-shaped groove 11 of the spacer 10. Then, as shown in (D), the inner space 43 of the flange 4 is filled with the adhesive 8, and the rear end 42 of the ferrule 2 is brought into contact with the rear end 12 of the spacer 10 against the front end 51 of the loose tube 5. Then, the tip 67 of the bare optical fiber 62, the spacer 10, and the loose tube 5 are inserted in this order. At the same time, the tip 67 of the bare optical fiber 62 is guided to the inner surface 36 of the cone portion 31, and the bare optical fiber 62 is inserted into the insertion hole 35 of the capillary 3. The adhesive 8 is also filled into the U-shaped groove 11 of the spacer 10. When the loose tube 5 is further inserted, the front end 13 of the spacer 10 comes into contact with the rear end 34 of the capillary 3 as shown in (E), and the loose tube 5 is not inserted any more. In this state, when the adhesive 8 is solidified, the loose tube 5 is fixed to the ferrule 2 and the optical fiber 6 carried by the spacer 10 is also fixed in a state where the periphery is filled with the adhesive 8. Finally, as shown in (F), the bare optical fiber 62 protruding from the front end 33 of the capillary 3 is cut at the position of the front end 33 and the front end 33 of the capillary 3 is polished. As a result, the opening end 63 of the optical fiber 6 is formed at the front end 33 of the capillary 3, and the assembly of the optical fiber connector 1a is completed.

=== Other Embodiments ===
The material of the spacer 10 is not limited to the above-described embodiment, and it is sufficient that the spacer 10 has a hardness that does not bend inside the ferrule 2 when it is inserted into the ferrule 2 together with the loose tube 5 and comes into contact with the rear end 34 of the capillary 3. . For example, glass, ceramics, hard resin, etc. can be considered.

  The shape of the spacer 10 is not limited to the above embodiment, and may be a tube shape, for example. However, in the case of the tube shape, when the ferrule 2 is filled with the adhesive 8 and inserted into the ferrule 2 together with the loose tube 5, there is no air escape space in the ferrule 2, and the tube-like spacer There is a slight possibility that bubbles will be generated. When bubbles are generated in the spacer 10, there is a concern that the optical fiber 6 carried by the spacer 10 is urged in the direction in which the adhesive 8 exists, and local bending occurs. Therefore, it is desirable that the spacer 10 has a shape in which a part of the tube is opened by opening a hole for connecting the inside and the outside. And if the U-shaped groove | channel 11 is formed over the length direction like the spacer 10 in the said Example, the escape route of air can be made over the full length of the spacer 10, and generation | occurrence | production of a bubble is reliably prevented. be able to.

  As a matter of course, the radius of curvature allowed for the optical fiber 6 differs depending on the thickness of the core wire or bare wire. Therefore, the length of the spacer 10 is appropriately changed according to the size of the optical fiber connector 1a to be incorporated and the thickness of the optical fiber 6. In the above embodiment, the optical fiber 6 is a single core type with a single bare optical fiber 62, but a plurality of bare optical fibers arranged in parallel are collectively covered with a resin coating. The so-called “tape core” type may be used. And what is necessary is just to form the insertion hole for inserting a some optical fiber bare wire in a capillary.

1,1a optical fiber connector with loose tube, 2 ferrule,
3 Capillary, 4 Flange, 5 Loose tube, 6 Optical fiber,
7,8 Adhesive, 10 Spacer, 11 U-shaped groove, 31 Cone part,
32 front end of cone part, 50 optical axis, 61 optical fiber core wire, 62 optical fiber bare wire,
63 Open end of optical fiber 68 Resin coating

Claims (3)

With the front-rear direction as the optical axis direction, a ferrule with a capillary attached to the front, a loose tube inserted into the rear end side of the ferrule, and an opening at the front end of the capillary while being inserted into the loose tube An optical fiber connector with a loose tube comprising an optical fiber comprising:
In the optical fiber, an optical fiber core wire in which a resin coating is applied to the bare optical fiber is continuously extended behind the bare optical fiber composed of a core and a clad,
The capillary has an opening at the front end and extends through the optical axis to the rear end along the optical axis, and a rear end of the insertion hole while reducing the diameter from the rear end toward the front. A cone portion having a conical inner shape reaching the end is formed,
While the front end of the cone part and the front end of the loose tube are used as a bent region of the optical fiber, the front end of the capillary and the front end of the loose tube are brought into contact with each other while keeping the front and rear lengths of the bent region constant. A spacer that carries the optical fiber is interposed,
The longitudinal length of the spacer is set to be equal to or larger than a predetermined radius of curvature in which the optical fiber is allowed in the bent region,
In the intervening region of the spacer, there is a boundary between the optical fiber core wire and the bare optical fiber,
An optical fiber connector with a loose tube.   An optical fiber connector with a loose tube, wherein the spacer is formed with a U-shaped groove for holding the optical fiber by extending in the front-rear direction on the surface of a cylinder having a central axis in the front-rear direction. It is a manufacturing method of the optical fiber connector with the loose tube according to claim 1 or 2,
An optical fiber in a state of an optical fiber core coated with a resin coating is protruded from the front end of the loose tube while being inserted through the loose tube, and the optical fiber core is formed inward of the front end side of the loose tube. An optical fiber bonding step to bond the wires;
A resin film removing step of processing the optical fiber into a bare optical fiber state by removing the resin film from the middle of the extension of the optical fiber core protruding to the front end side of the loose tube to the front end;
An adhesive filling step of filling an adhesive into the rear end side inward of the ferrule;
While holding the optical fiber protruding to the front end side of the loose tube on the spacer, the spacer and the loose tube are inserted into the ferrule, and the front end of the bare optical fiber extends along the inner surface of the cone portion. A loose tube insertion step of inserting the capillary tube through the insertion hole of the capillary while guiding,
In the resin film removal step, for the optical fiber core protruding from the front end of the loose tube, the front resin film is removed from the front end from a position below the front and rear length of the spacer,
In the loose tube insertion step, the loose tube is inserted until the front end of the spacer contacts the rear end of the capillary while the rear end of the spacer is in contact with the front end of the loose tube.
A method for manufacturing an optical fiber connector with a roots tube.