JP2005321425A - Ferrule opposition structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferrule opposition structure capable of reducing the number of components, improving productivity and reducing connection loss. <P>SOLUTION: The ferrule end part 14 of the ferrule 11 has functions of a convex lens and of an aligning. A convex lens 14a is integrally formed on the optical connection end part of the ferrule end part 14. Further, an engagement projection part 14b is integrally formed around the convex lens 14a. Respective ferrules 11 are optically connected by opposing the engagement projection parts 14b of the ferrule end part 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a facing structure between ferrules attached to a terminal of an optical fiber cable.

  Optical communication in automobiles has become widespread, and communication capacity has been increasing in recent years. Under such circumstances, optical fibers having a small core diameter and a large transmission band have begun to be used in recent optical communications. Regarding the connection between optical fibers in automobiles, there is a reason that the ends of the optical fiber cores cannot be brought into contact with each other due to the influence of vibration or impact. An optical coupling structure has been proposed in which one or two lenses are interposed between each ferrule to achieve optical coupling (see, for example, Patent Document 1).

  In FIG. 11, the optical coupling structure will be briefly described. Ferrules 2a and 2b are attached to the terminals of a pair of optical fibers 1a and 1b to be coupled. The flanges 3a and 3b are fitted and fixed to the outer peripheral surfaces of the ferrules 2a and 2b. Lenses 5a and 5b are held in hollow portions on one end sides of cylindrical lens holders 4a and 4b, and one end portions of ferrules 2a and 2b are inserted into hollow portions on the other end sides. Yes.

  The end surfaces of the optical fibers 1a and 1b are arranged at the centers of the opposite end surfaces of the ferrules 2a and 2b, and the optical axes of the optical fibers 1a and 1b and the optical axes of the lenses 5a and 5b are adjusted to coincide with each other. After that, the end surfaces of the flanges 3a and 3b and the end surfaces of the lens holders 4a and 4b are joined and fixed by welding or the like. In addition, the cylindrical sleeve 6 common to each outer peripheral surface is fitted and fixed to each outer peripheral surface of the lens holders 4a and 4b in a state where the end surfaces on the side holding the lenses 5a and 5b are abutted with each other. .

In the above configuration, the two lenses 5a and 5b are disposed between the end faces of the ferrules 2a and 2b, so that the connection loss due to the misalignment is reduced.
JP-A-8-271758 (2nd page, FIG. 1)

  Incidentally, the connection between the optical fibers 1a and 1b in the conventional optical coupling structure has a problem that the number of parts is large. In addition, there is a problem that the number of steps until the optical fibers 1a and 1b are connected to each other is large, and the productivity is poor. Regarding connection loss due to productivity and shaft misalignment, the lenses 5a and 5b are aligned by the lens holders 4a and 4b and the cylindrical sleeve 6, and the ferrules 2a and 2b are aligned by the flanges 3a and 3b and the lens holders 4a and 4b. Therefore, there is also a problem that high processing accuracy is required for all of the lens, lens holder, flange, and ferrule.

  This invention is made | formed in view of the situation mentioned above, and makes it a subject to provide the ferrule opposing structure which can aim at reduction of a number of parts, improvement of productivity, and reduction of a connection loss.

  The ferrule facing structure of the present invention according to claim 1 made to solve the above problems is a facing structure of ferrules attached to each end of a pair of optical fiber cables exposing an optical fiber, A convex lens is formed at the optical coupling tip portion of the ferrule, and a fitting protrusion that fits with the counterpart ferrule is formed around the convex lens.

  According to the present invention having such a feature, a ferrule having the function of a convex lens is obtained. In other words, since the lens and the ferrule are integrated, a member for holding the lens and a member for aligning the lens and the ferrule (aligning the optical axis) are not required. By using such a ferrule, the process until the optical fibers are connected is simplified. Furthermore, the portion requiring high machining accuracy is reduced. By providing the ferrule tip with the function of a convex lens, it contributes to reducing the number of parts, improving productivity, and reducing connection loss. Further, according to the present invention, since the opposing ferrules are fitted to each other, when the fitting protrusions are fitted, the alignment of the ferrules is performed easily and reliably, and the dedicated parts are It is possible to reduce the connection loss without using it.

  A ferrule facing structure according to a second aspect of the present invention is characterized in that, in the ferrule facing structure according to the first aspect, the tip of the fitting protruding portion protrudes from the top of the convex lens.

  According to the present invention having such characteristics, the convex lens is protected by the fitting protrusion, and for example, it is possible to prevent a problem that the convex lens is touched when the ferrules are fitted to each other.

  The ferrule facing structure of the present invention according to claim 3 is the ferrule facing structure according to claim 1 or 2, wherein the fitting protrusion of each ferrule is formed in a cylindrical shape, and a fitting recess is formed at the tip. And / or forming a convex part.

  According to the present invention having such a feature, the fitting of the ferrules is performed at the tip of the fitting protrusion. It becomes a structure which can suppress the size of the diameter direction of a ferrule.

  The ferrule facing structure according to a fourth aspect of the present invention is the ferrule facing structure according to the first or second aspect, wherein the fitting protrusion of each ferrule is formed in a cylindrical shape, and one of the fitting protrusions is formed. It is characterized in that the other is inserted into the part.

  According to the present invention having such a feature, the fitting of the ferrules is performed by inserting the fitting protrusion. One fitting protrusion has a function as a centering sleeve.

  A ferrule facing structure according to a fifth aspect of the present invention is characterized in that, in the ferrule facing structure according to any one of the first to fourth aspects, the convex lens is sealed when the fitting protrusions are fitted to each other. .

  According to the present invention having such characteristics, the opposing convex lenses are sealed by the fitting protrusions. In other words, when the fitting protrusion is fitted, the convex lens is dustproofed and waterproofed.

  A ferrule facing structure according to a sixth aspect of the present invention is the ferrule facing structure according to any one of the first to fifth aspects, wherein a pressing force from a pressing means is applied to each ferrule or one of the ferrules. It is said.

  According to the present invention having such characteristics, the ferrules are pressed from the pressing means in a state of facing each other. Generation of a gap at the contact portion between the fitting protrusions and an increase in the interval between the opposing convex lenses are prevented.

  According to the first aspect of the present invention, the number of parts can be reduced by providing a convex lens function at the optical coupling tip portion of the ferrule and by fitting the opposing ferrules together. There is an effect that productivity can be improved and connection loss can be reduced.

  According to the second aspect of the present invention, the convex lens can be protected by the fitting protrusion.

  According to the third aspect of the present invention, there is an effect that the size of the ferrule in the radial direction can be suppressed.

  According to the present invention described in claim 4, there is an effect that one of the fitting protrusions can function as a centering sleeve. Therefore, there is an effect that the number of parts can be reduced.

  According to the present invention described in claim 5, since it is a sealed structure, there is an effect that a dustproof or waterproof function can be added.

  According to the sixth aspect of the present invention, there is an effect that it is possible to prevent the generation of a gap at the contact portion between the fitting protrusions and the increase in the interval between the opposing convex lenses. Therefore, there is an effect that connection loss can be reduced. In addition, there is an effect that the sealing degree can be increased.

Hereinafter, description will be given with reference to the drawings.
FIG. 1 is a sectional view showing an embodiment of the ferrule facing structure of the present invention. 2 is a perspective view of the ferrule, and FIG. 3 is an explanatory diagram of the structure of the ferrule.

  1 to 3, reference numerals 11 and 11 indicate a pair of ferrules attached to the end of the optical fiber cable 12. Each ferrule 11 is entirely molded of a transparent synthetic resin material in this embodiment. Each ferrule 11 has a ferrule body portion 13 and a ferrule tip portion 14. Each ferrule 11 has a structure in which optical coupling can be achieved by attaching and facing fitting protrusions 14b, 14b, which will be described later, of the ferrule tip portion 14 to each other.

  Here, the transparent synthetic resin material will be described. Although not particularly limited, synthetic resin materials such as an acrylic resin, an alicyclic olefin resin, and an alicyclic acrylic resin are listed as examples. Needless to say, these synthetic resin materials are commercially available products that are easy to obtain and contribute to cost reduction.

  Prior to the description of the ferrule 11, the configuration of the optical fiber cable 12 will be described. The optical fiber cable 12 includes an optical fiber (optical fiber core wire) 15 and an optical fiber coating 16. Such an optical fiber cable 12 has an optical fiber coating 16 peeled off at a predetermined position on the terminal side. That is, the end of the optical fiber cable 12 is processed so that the optical fiber 15 is exposed by a predetermined length. The tip (end face) of the optical fiber 15 is formed on a flat surface.

  The optical fiber 15 has a core and a clad having a refractive index smaller than that of the core. The optical fiber 15 is not particularly limited in the present embodiment, but, for example, the core is formed of a transparent polycarbonate (PC). The clad is formed from transparent polymethyl methacrylate (PMMA). The optical fiber 15 may be a known glass optical fiber.

  The optical fiber coating 16 is a so-called sheath made of synthetic resin, and is provided to protect the optical fiber 15. In this embodiment, the optical fiber coating 16 includes a primary sheath 16a formed on the optical fiber 15 and a secondary sheath 16b formed on the primary sheath 16a. The secondary sheath 16b is peeled off so that the primary sheath 16a is exposed for a predetermined length.

  A ferrule tip portion 14 is coupled to one end of the ferrule body portion 13 of the ferrule 11 in a state where the optical axes are aligned. A flat surface 17 is formed on the other end of the ferrule body portion 13. A step portion 18 is formed outside the ferrule body portion 13. In this embodiment, the step portion 18 is formed to have a slight step. A ferrule hole 19 is formed in the ferrule body portion 13.

  The ferrule hole 19 is formed in a state where the other end of the ferrule body portion 13 is opened. Further, the ferrule hole 19 is formed so that its central axis coincides with the optical axis. In such a ferrule hole 19, a core wire guide portion 19a, a primary sheath guide portion 19b, and a secondary sheath guide portion 19c are formed in this order from the one end side. The ferrule hole 19 is filled with a filler (not shown) described later.

  The core wire guide portion 19 a is a portion into which the optical fiber 15 is inserted, and is formed in the same diameter shape as the optical fiber 15. Further, the core wire guide portion 19 a is formed so that a gap is formed between the innermost portion 19 a-1 and the tip of the optical fiber 15. The innermost part 19a-1 of the core wire guide part 19a is processed to have a surface roughness that can suppress light scattering. In addition, in this embodiment, the core wire guide portion 19a is formed so as to extend to a position straddling the ferrule tip end portion 14, but it is not limited to this.

  The primary sheath guide portion 19b is a portion into which the primary sheath 16a is inserted, and is formed in the same diameter shape as the primary sheath 16a. The secondary sheath guide portion 19c is a portion into which the secondary sheath 16b is inserted, and is formed in the same diameter shape as the secondary sheath 16b. Tapered portions 19d and 19e are formed between the core wire guide portion 19a and the primary sheath guide portion 19b and between the primary sheath guide portion 19b and the secondary sheath guide portion 19c due to the difference in diameter. The tapered portions 19d and 19e are appropriately set at an angle. The formation of the tapered portions 19d and 19e facilitates the insertion of the optical fiber cable 12.

  In the present embodiment, a curable transparent gel and a fixing adhesive are used as the filler (not shown). Examples of the transparent gel include silicone resins and epoxy resins (having a clear refractive index when cured). The transparent gel is larger than the refractive index of the ferrule material (the synthetic resin material described above), and is also referred to as the aperture angle (numerical aperture (NA)) of the optical fiber 15. NA: Numerical Aperture. Is selected so as to have a refractive index difference corresponding to (θmax: maximum acceptance angle) defined by NA = sin θmax (the light is reflected by the wall surface of the gap in the ferrule hole 19, and The gap portion functions as a light guide, and there is also an advantage that the lens design becomes easy).

  When the optical fiber cable 12 is inserted into the ferrule hole 19, the transparent gel fills the gap between the innermost part 19a-1 and the tip of the optical fiber 15 (if the optical fiber 15 is fixed, There is an advantage that pistoning due to a change in humidity (protrusion and dent of the optical fiber 15) can be prevented). The transparent gel has an advantage that fluidity can be suppressed.

  Examples of the fixing adhesive include an epoxy-based adhesive and an epoxy-mixed adhesive (having a viscosity that does not penetrate into the interior more than necessary). In addition to the above, the fixing adhesive may be a UV curable adhesive that is cured by ultraviolet irradiation from an ultraviolet irradiation device. The fixing of the optical fiber cable 12 is not limited to an adhesive, and may be welding such as laser welding, high frequency welding, ultrasonic welding, or the like.

  The ferrule tip portion 14 of the ferrule 11 has a function of a convex lens and a function for alignment. That is, the convex lens 14 a is integrally formed at the optical coupling tip portion of the ferrule tip portion 14. Further, a fitting protrusion 14b is integrally formed around the convex lens 14a.

  In this embodiment, the convex lens 14a is a convex lens that is processed into a spherical shape, and is shaped so that the light emitted from the optical fiber 15 is collimated and the parallel incident light is condensed toward the optical fiber 15. (The wavy line in FIG. 3 indicates the optical path). Such a convex lens 14a is designed including the distance from the innermost part 19a-1 of the core wire guide part 19a.

  The fitting protrusion 14b is a portion that fits with the counterpart ferrule 11 during optical coupling, and is formed in a cylindrical shape. At the tip of the fitting protrusion 14b, two fitting recesses 14b-1 and two protrusions 14b-2 are formed at an equal pitch, for example. The convex portion 14b-2 of the counterpart ferrule 11 is inserted into the concave portion 14b-1, and the concave portion 14b-1 of the counterpart ferrule 11 is inserted into the convex portion 14b-2.

  The tips of the fitting protrusions 14b come into contact with each other during optical coupling. The tip of the fitting protrusion 14b protrudes from the top of the convex lens 14a, and the convex lens 14a is protected by the fitting protrusion 14b. When the tips of the fitting protrusions 14b come into contact with each other at the time of optical coupling, the distance between the tops of the convex lenses 14a is kept constant.

  In the above configuration, when the optical fiber cable 12 is inserted into the ferrule hole 19 of the ferrule 11 and then the transparent gel and the fixing adhesive are cured, the ferrule 11 is attached to the end of the optical fiber cable 12. As shown in FIG. 1, when the ferrules 11 and 11 attached in this way are arranged to face each other using the fitting protrusions 14 b and 14 b, the optical fiber cables 12 and 12 are optically coupled (connected). Is completed.

  In this embodiment, one ferrule 11 is urged by a spring 20 (pressing means) as shown in FIG. That is, one ferrule 11 is pressed toward the other ferrule 11. By such pressing, in other words, by applying a pressing force, generation of a gap at the contact portion between the fitting protrusions 14b and 14b and an increase in the interval between the opposing convex lenses 14a and 14a are prevented. In FIG. 1, reference numeral 21 denotes a spring presser, and 22 denotes a ferrule presser. It is also possible to push the ferrules 11 together.

  Next, the lens effect of the ferrule 11 will be described with reference to FIG. FIG. 4 is a graph showing the off-axis characteristics (using an optical fiber having a core diameter of 200 μm and manufacturing a ferrule 11 with a suitable size. The ferrules 11 and 11 face each other as shown in FIG. Arranged to obtain off-axis characteristics). The solid line in the graph indicates the axis deviation characteristic of the ferrule 11. Also, the wavy line indicates the off-axis characteristic when there is no convex lens 14a, that is, when a conventional ferrule is used. In FIG. 4, the ferrule 11 has collimated output light due to the effect of the convex lens 14 a, so that the axis misalignment loss is small. However, it is difficult to process to an axial displacement of less than 50 μm due to relatively inexpensive resin molding, and an actual axial misalignment has occurred. 11 is better to use).

  As described above with reference to FIGS. 1 to 4, since the optical coupling tip portion of the ferrule tip portion 14 has the function of a convex lens, the number of parts can be reduced and the productivity can be reduced as compared with the conventional case. Can be improved and connection loss can be reduced. That is, since the ferrule 11 has a structure in which the lens and the ferrule are integrated, there is no need for a conventional member for holding the lens or a member for aligning the lens and the ferrule (aligning the optical axis). Can be. Further, as can be seen from the above, by using the ferrule 11, the process up to the connection between the optical fiber cables 12 and 12 can be remarkably simplified as compared with the prior art. Furthermore, by using the ferrule 11, it is possible to reduce the portion requiring high machining accuracy compared to the conventional case.

  Furthermore, by adopting a structure in which the opposing ferrules 11 are fitted together, it is possible to reduce the number of parts, improve productivity, and reduce connection loss. Furthermore, when the fitting protrusions 14b and 14b are fitted to each other, the ferrules 11 and 11 are aligned easily and reliably, and the connection loss can be reduced without using dedicated parts.

  In addition, since a gap is generated between the innermost portion 19a-1 of the ferrule hole 19a and the tip of the optical fiber 15, high processing accuracy for the optical fiber 15 and the ferrule 11 is not required, and productivity is improved. Can do. Further, since the gap formed is filled with an optically transparent transparent gel and the gap functions as a light guide, connection loss can be reduced.

  Next, another embodiment of the ferrule facing structure of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view showing another embodiment. Note that components that are basically the same as those described above are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 5, reference numerals 31 and 32 indicate a pair of ferrules attached to the ends of the optical fiber cables 12 and 12. Each of the ferrules 31 and 32 is formed entirely of the transparent synthetic resin material in this embodiment. The ferrule 31 has a ferrule body portion 33 and a ferrule tip portion 34. Similarly, the ferrule 32 has a ferrule body portion 13 and a ferrule tip portion 14 (here, it is assumed that there are no concave portions 14b-1 and convex portions 14b-2 of the ferrule tip portion 14). In this embodiment, the ferrule 32 is inserted into the ferrule tip portion 34 of the ferrule 31 so as to face the ferrule 32 so that optical coupling can be performed.

  A ferrule tip end portion 34 is coupled to one end of the ferrule main body portion 33 of the ferrule 31 with the optical axes thereof aligned. A flat surface 17 is formed on the other end of the ferrule body portion 33. A ferrule hole 19 is formed in the ferrule body portion 33.

  The ferrule tip portion 34 of the ferrule 31 has a function of a convex lens and a function for alignment. That is, the convex lens 14 a is integrally formed at the optical coupling tip portion of the ferrule tip portion 34. Further, a fitting protrusion 35 is integrally formed around the convex lens 14a.

  The fitting protrusion 35 is a portion that fits with the mating ferrule 32 during optical coupling, and is formed in a cylindrical shape and a shape into which the mating ferrule 32 can be inserted. The tip of the fitting protrusion 35 is shaped to abut against the stepped portion 18 of the mating ferrule 32. Alternatively, the tip of the fitting protrusion 14 b of the counterpart ferrule 32 is in contact with the outside of the convex lens 14 a of the ferrule 31. The tip of the fitting protrusion 35 protrudes from the top of the convex lens 14a, and the convex lens 14a is protected by the fitting protrusion 35. When the ferrule 32 is inserted into the ferrule tip portion 34 of the ferrule 31, that is, the fitting protrusion 35, and the above contact is made, the distance between the tops of the convex lenses 14 a is kept constant. It has become.

  In the above configuration, when the optical fiber cable 12 is inserted into the ferrule holes 19 of the ferrules 31 and 32 and then the transparent gel and the fixing adhesive are cured, the ferrules 31 and 32 are attached to the ends of the optical fiber cables 12. It is done. Then, when the ferrules 31 and 32 attached in this way are arranged to face each other using the fitting protrusions 35 and 14b, the optical coupling (connection) between the optical fiber cables 12 and 12 is completed. The effects of the other embodiment are the same as described above.

  6 and 7 are explanatory diagrams relating to the manufacture of ferrules. 6 and 7, the ferrules 11, 31, and 32 may be entirely formed of a transparent synthetic resin material as described above. However, depending on productivity and cost, the ferrules 11, 31, and 32 may be formed as lines L1 or L2. It may be changed to a structure to be added after the division. Further, only the convex lens 14a may be molded with a transparent synthetic resin material, and the other may be separately molded with an inexpensive synthetic resin material.

  8 to 10 are explanatory views of a sealing member attached to the ferrule. The sealing member is a member for adding a sealing structure to the ferrule facing structure of the present invention, and is effective for dustproofing and waterproofing to the convex lens 14a, and is attached as necessary.

  The sealing member 41 in FIG. 8 is formed in a shape that can be attached to the tip of the fitting protrusion 14b of the ferrule 11 (see the shape in FIG. 8). The sealing member 41 has flexibility and may be anything other than rubber, sponge or gel as long as the material can be molded (however, the degree of flexibility is sufficient when mating) A range in which the connection loss caused by the change in the distance between the tops of the convex lenses 14a and the axial displacement of the ferrules during vibration can be sufficiently reduced by the lens characteristics).

  The sealing member 42 in FIG. 9 is formed in a shape that can be attached to the tip of the fitting protrusion 14b of the ferrule 32 (see the shape in FIG. 9). The sealing member 42 in FIG. 9 is formed of the same material as the sealing member 41 in FIG. The sealing member 43 in FIG. 10 is formed in a shape that can be attached to the tip of the fitting protrusion 35 of the ferrule 31 or the step portion 18 of the ferrule 32 (see the shape in FIG. 10). The sealing member 43 in FIG. 10 is formed of the same material as the sealing member 41 in FIG.

  In addition, it goes without saying that the present invention can be variously modified without departing from the spirit of the present invention. In addition, this invention shall not be limited to the connection of the optical fibers in a motor vehicle. That is, it can be naturally applied to optical communication in other fields.

It is sectional drawing which shows one Embodiment of the ferrule opposing structure of this invention. It is a perspective view of a ferrule. It is structure explanatory drawing of a ferrule. It is a graph which shows an axial deviation characteristic. It is sectional drawing which shows other embodiment of the ferrule opposing structure of this invention. It is explanatory drawing which concerns on manufacture of a ferrule. It is explanatory drawing which concerns on manufacture of a ferrule. It is the member for sealing attached to the ferrule of FIG. 6 is a sealing member attached to the ferrule of FIG. It is another sealing member attached to the ferrule of FIG. It is sectional drawing which shows the optical coupling structure of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Ferrule 12 Optical fiber cable 13 Ferrule main-body part 14 Ferrule tip part 14a Convex lens 14b Fitting protrusion part 14b-1 Concave part 14b-2 Convex part 15 Optical fiber 16 Optical fiber coating | cover 19 Ferrule hole 20 Spring (pressing means)
21 Spring holder 22 Ferrule holder 31, 32 Ferrule 33 Ferrule main body part 34 Ferrule tip part 35 Fitting protrusion 41-43 Sealing member

Claims (6)

It is an opposing structure of ferrules attached to each end of a pair of optical fiber cables exposing an optical fiber,
A ferrule facing structure, wherein a convex lens is formed at an optical coupling tip portion of each ferrule, and a fitting protrusion is formed around the convex lens to be fitted with a counterpart ferrule. In the ferrule facing structure according to claim 1,
The ferrule facing structure, wherein the tip of the fitting protrusion protrudes from the top of the convex lens. In the ferrule facing structure according to claim 1 or 2,
The ferrule facing structure, wherein the fitting protrusion of each ferrule is formed in a cylindrical shape, and a concave and / or convex portion for fitting is formed at the tip. In the ferrule facing structure according to claim 1 or 2,
The ferrule facing structure, wherein the fitting protrusion of each ferrule is formed in a cylindrical shape, and the other is inserted into one of the fitting protrusions. In the ferrule facing structure according to any one of claims 1 to 4,
The ferrule facing structure, wherein the convex lens is sealed when the fitting protrusions are fitted to each other. In the ferrule facing structure according to any one of claims 1 to 5,
A ferrule facing structure, wherein a pressing force from pressing means is applied to each ferrule or one of the ferrules.

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