Optical connector and method for manufacturing optical connector

Abstract

This optical connector (10) is provided with: a ferrule (11) having an end surface (15) in which at least one fiber hole (12) is open; at least one optical fiber (1) in which a core end surface (2a) is exposed from the end surface (15) via the fiber hole (12); a refractive index matching part (20) that is formed so as to be elastically deformable and is in contact with the core end surface (2a); and a protective part (21) that is provided on the end surface (15) and is formed to be harder than the refractive index matching part (20). The protection part (21) includes an accommodating recess (21) that accommodates the refractive index matching part (20).

Description

Optical connector and method for manufacturing optical connector

[0001] The present disclosure relates to optical connectors and methods of making optical connectors.

[0002] Patent Document 1 discloses an optical connector having a refractive index matching portion that covers the fiber end face of the optical fiber at the connecting end face of the ferrule. The refractive index matching portion is an elastically deformable solid, and is formed by applying a refractive index matching material to the connecting end face of the ferrule and then curing it.

[0003] International Publication No. 2022 / 244039

[0004] In the technology described in Patent Document 1, an elastically deformable refractive index matching section tightly contacts the connecting end faces of the ferrules without any gaps, thereby improving return loss. However, if the refractive index matching section is too hard, the above-mentioned sufficient contact cannot be achieved, and the return loss is likely to deteriorate. On the other hand, if the refractive index matching section is too soft, excessive deformation due to external force can easily cause tearing or peeling.

[0005] The present disclosure has been made in consideration of these circumstances, and aims to provide an optical connector and a method for manufacturing an optical connector that can achieve both improved return loss and durability of the refractive index matching material.

[0006] An optical connector according to a first aspect of the present disclosure comprises a ferrule having an end face with at least one fiber hole opened therein, at least one optical fiber having a core end face exposed from the end face through the fiber hole, a refractive index matching portion formed to be elastically deformable and in contact with the core end face, and a protective portion provided on the end face and formed to be harder than the refractive index matching portion, wherein the protective portion includes a housing portion for housing the refractive index matching portion.

[0007] An optical connector manufacturing method according to a second aspect of the present disclosure includes fixing at least one optical fiber having a core end face to a ferrule with the core end face exposed from the end face of the ferrule, applying a photocurable refractive index matching material to an area including the core end face, forming a refractive index matching portion in contact with the core end face by curing the refractive index matching material using light irradiation, removing portions of the refractive index matching material other than the portion where the refractive index matching portion is formed, applying a photocurable resin to the end face of the ferrule, and forming a protective portion by curing the resin using light irradiation, wherein the protective portion is formed to be harder than the refractive index matching portion.

[0008] According to the present disclosure, it is possible to provide an optical connector and a method for manufacturing an optical connector that can achieve both improved return loss and durability of the refractive index matching material.

[0009] FIG. 1 is a perspective view of an optical connector according to the present embodiment. FIG. 2A is a partial cross-sectional view of an example of an optical connector according to the present embodiment. FIG. 2B is a partial cross-sectional view of an example of an optical connector according to the present embodiment. FIG. 2C is a partial cross-sectional view of an example of an optical connector according to the present embodiment. FIG. 2D is a partial cross-sectional view of an example of an optical connector according to the present embodiment. FIG. 3A is a diagram showing a procedure for connecting a connector. FIG. 3B is a diagram showing a procedure for connecting a connector. FIG. 4A is a diagram for explaining steps in a method for manufacturing an optical connector according to the present embodiment. FIG. 4B is a diagram for explaining steps in a method for manufacturing an optical connector according to the present embodiment. FIG. 4C is a diagram for explaining steps in a method for manufacturing an optical connector according to the present embodiment. FIG. 4D is a diagram for explaining steps in a method for manufacturing an optical connector according to the present embodiment.

[0010] Hereinafter, an optical connector and an optical connector manufacturing method according to an embodiment of the present disclosure will be described with reference to the drawings. In the description of the drawings, identical parts are assigned the same reference numerals and description thereof will be omitted. For convenience of explanation, mutually orthogonal X, Y, and Z directions are defined. The X direction is the width direction of the ferrule. The Y direction is the height direction of the ferrule. The Z direction is the depth direction of the ferrule and the extension direction of the fiber hole (insertion hole). Furthermore, the direction in which the optical connector according to this embodiment faces the mating optical connector will be referred to as the front, and the opposite direction will be referred to as the rear.

[0011] Hereinafter, the optical connector 10 according to this embodiment will be referred to as the connector 10. Fig. 1 is an exploded perspective view of the connector 10. As shown in Fig. 1, the connector 10 according to this embodiment includes an optical fiber 1, a ferrule 11, a refractive index matching portion 20, and a protection portion 21.

[0012] The optical fiber 1 is inserted into the fiber hole 12 from the back surface 16 of the ferrule 11 via the groove 13. An end face 1a of the optical fiber 1 (hereinafter referred to as the fiber end face) includes an end face 2a of the core 2 (hereinafter referred to as the core end face) and is exposed at an end face 15 of the ferrule 11. The optical fiber 1 is, for example, a single mode fiber (SMF). In this case, a bare fiber with its coating removed is inserted into the fiber hole 12.

[0013] The ferrule 11 holds at least one optical fiber 1. That is, the ferrule 11 has at least one fiber hole 12 formed therein corresponding to the number and arrangement of the optical fibers 1. The fiber holes 12 may be arranged at intervals in the X direction, or multiple rows of fiber holes 12 arranged in the X direction may be arranged at intervals in the Y direction. However, the arrangement (disposition) of the multiple fiber holes 12 is not limited to that described above.

[0014] The type of ferrule 11 is appropriately selected according to the ferrule of the optical connector to be manufactured. For example, if the optical connector to be manufactured is a multi-fiber connector, the ferrule 11 is an MT ferrule as shown in Fig. 1. Also, if the optical connector to be manufactured is a multi-fiber connector, the ferrule 11 will be a cylindrical ferrule. However, the ferrule 11 is not limited to the two types of ferrules described above.

[0015] The ferrule 11 used in the connector 10 will be described using an MT ferrule, which is an example of a multi-fiber optical connector. However, as mentioned above, the ferrule 11 is not limited to an MT ferrule. The ferrule 11 includes a plurality of fiber holes 12 arranged in the X direction, grooves 13 that guide the optical fibers 1 into the fiber holes 12, and windows 14 that communicate with the grooves 13. The optical fibers 1 are held in the ferrule 11 by filling an adhesive through the windows 14.

[0016] The multiple fiber holes 12 extend along the Z direction within the ferrule 11 and open to an end face (front face) 15 of the ferrule 11. The end face 15 may be perpendicular to the Z direction (parallel to the XY plane) or may be inclined with respect to the Z and Y directions. In the latter case, the inclination angle is, for example, 8°.

[0017] Guide holes 17 are also formed in the end face 15. The guide holes 17 are located on both sides of a group of multiple fiber holes 12 aligned in the X direction. When the connector 10 and a mating connector 50 (see FIGS. 3A and 3B) are to be connected to each other, positioning guide pins (not shown) are inserted into the guide holes 17.

[0018] The refractive index matching section 20 is located in front of the fiber end face 1a. Light passes through the refractive index matching section 20 when the connector is connected. Therefore, the refractive index matching section 20 is formed of a resin 32 that is transparent to the light propagating through the optical fiber 1. The resin 32 is photocurable and remains elastic even after curing. That is, the refractive index matching section 20 is formed to be elastically deformable. Furthermore, the refractive index matching section 20 is softer than the protective section 21. That is, the hardness of the refractive index matching section 20 is less than the hardness of the protective section 21. The refractive index of the refractive index matching section 20 has a value corresponding to the refractive index of the core 2.

[0019] The refractive index matching portion 20 is a tubular member extending in the Z direction. The refractive index matching portion 20 has a front surface 20a facing the mating connector 50 (see FIGS. 3A and 3B ) and a back surface 20b in contact with at least the core end face 2a. The length L1 of the refractive index matching portion 20 along the Z direction may be longer than the length (thickness) L2 of the protection portion 21 along the same direction. In this case, the refractive index matching portion 20 is housed in the housing portion 22 of the protection portion 21 with a portion of the refractive index matching portion 20, including the front surface 20a, exposed from the protection portion 21.

[0020] As described above, the refractive index matching section 20 is in contact with at least the core end face 2a. That is, the refractive index matching section 20 may be in contact only with the core end face 2a, or may be in contact with the core end face 2a as well as the surface surrounding the core end face 2a. For example, the refractive index matching section 20 may be in contact with part or all of the fiber end face 1a (see FIG. 2B). Furthermore, the refractive index matching section 20 may also be in contact with the end face 15 of the ferrule 11 located around the fiber end face 1a (see FIG. 2C). That is, the size of the back surface 20b of the refractive index matching section 20 facing the end face 15 is arbitrary as long as the refractive index matching section 20 is in contact with the core end face 2a.

[0021] 2D , the refractive index matching section 20 may have a width (for example, a width along the Y direction) that increases toward the end face 15 of the ferrule 11 in a cross section including the central axis 4 of the fiber hole 12. In other words, the refractive index matching section 20 may have a tapered shape in which the width along a direction perpendicular to the Z direction decreases from the back surface 20 b toward the front surface 20 a.

[0022] The protective portion 21 is provided on the end surface 15 and surrounds the refractive index matching portion 20. The protective portion 21 is a tubular sheet-like member (plate-like member) having a length (thickness) L2 along the Z direction and extending parallel to the end surface 15. The protective portion 21 is formed, for example, from a photocurable resin 36. The refractive index of the resin 36 is arbitrary. The resin 36 may be transparent or colored. However, the protective portion 21 is harder than the refractive index matching portion 20. In other words, the hardness of the protective portion 21 is greater than the hardness of the refractive index matching portion 20.

[0023] The protective portion 21 is formed with a housing portion 22 that houses the refractive index matching portion 20. The housing portion 22 is a hole or window that penetrates the protective portion 21 in the Z direction. As described above, the length L1 of the refractive index matching portion 20 along the Z direction is longer than the length (thickness) L2 of the protective portion 21 along the same direction. Therefore, the housing portion 22 houses the refractive index matching portion 20 with a portion thereof, including the front surface 20 a, exposed from the protective portion 21.

[0024] The inner peripheral surface 22a of the accommodating portion 22 is in contact with the outer peripheral surface 20c of the refractive index matching portion 20. Therefore, as shown in FIGS. 2A to 2D, the accommodating portion 22 has a cross section complementary to the cross section of the refractive index matching portion 20 accommodated in the accommodating portion 22. For example, as shown in FIGS. 2A to 2C, if the refractive index matching portion 20 is formed in a cylindrical (disk-like) shape with a constant diameter, the inner peripheral surface 22a of the accommodating portion 22 also forms a cylindrical (disk-like) accommodation space with a constant diameter. On the other hand, as shown in FIG. 2D, if the refractive index matching portion 20 has a tapered shape toward the front of the ferrule 11, the inner peripheral surface 22a of the accommodating portion 22 also forms an accommodation space with a complementary tapered shape. That is, in a cross section including the central axis 4 of the fiber hole 12, the accommodating portion 22 has a width that increases toward the end face 15. By forming the refractive index matching portion 20 and the accommodation portion 22 each in a tapered shape, the accommodation portion 22 can hold the refractive index matching portion 20 more firmly, and the durability of the refractive index matching portion 20 is improved.

[0025] When multiple optical fibers 1 are fixed to the ferrule 11, the refractive index matching section 20 may be formed individually for each of the multiple optical fibers 1, or may extend so as to cover the fiber end faces 1 a of these optical fibers 1. In the former case, the multiple refractive index matching sections 20 are spaced apart from one another with protective sections 21 interposed therebetween. In the latter case, the refractive index matching section 20 extends along the arrangement direction of the optical fibers 1 and is formed in a band shape that covers each fiber end face 1 a. Furthermore, when a multi-stage optical fiber row is formed, a band-shaped refractive index matching section 20 may be formed for each stage. The accommodating section 22 is formed to match these shapes.

[0026] 3A and 3B are diagrams showing the procedure for connecting the connector 10 to a mating connector 50. For ease of explanation, an example will be given in which the connector shown in FIG. 2D is used as the connector 10. Also, FIGS. 3A and 3B show a conventional optical connector that does not have a protective portion 21 as the connector 50. However, the connector 50 may also be the optical connector according to this embodiment.

[0027] 3A, the end face 15 of the ferrule 11 and the end face 55 of the ferrule 51 of the connector 50 are brought into opposition to each other, and their positions are aligned using a guide pin (not shown). Next, as the end face 15 gradually approaches the end face 55, the refractive index matching section 20 first comes into contact with the end face (not shown) of the optical fiber on the connector 50 side. As the end face 15 is brought even closer to the end face 55 while maintaining this state, the length of the refractive index matching section 20 along the Z direction gradually contracts due to elastic deformation.

[0028] As shown in FIG. 3B , when the length of the refractive index matching portion 20 contracts to the thickness of the protective portion 21, the protective portion 21 comes into contact with the end face 55 (see FIG. 3B ). This restricts the movement of the ferrule 11 and connects the connector 10 and the connector 50 to each other. In this state, the refractive index matching portion 20 is in close contact with the connector 50. This eliminates air between the refractive index matching portion 20 and the connector 50, achieving an optical connection with good return loss. The protective portion 21 also contacts the end face 55 of the ferrule 51 of the connector 50. Therefore, if excessive force is applied to either the connector 10 or the connector 50 during connector connection, the protective portion 21 protects the refractive index matching portion 20. This prevents the refractive index matching portion 20 from peeling off or becoming loose from the ferrule 11.

[0029] The refractive index matching portion 20 does not have to protrude from the protective portion 21. Even in this case, the above-described effect can be obtained if the mating connector 50 has the shape shown in Fig. 2D. The same effect can also be obtained if the mating connector 50 has a connector in which a portion of the optical fiber in advance protrudes slightly from the end face of the ferrule.

[0030] Typically, before connecting an optical connector, the end face of the ferrule, where the fiber end face is exposed, must be cleaned with a dedicated cleaner. The cleaning method is specified in the International Electrotechnical Commission standard (IEC) TR 62627-01, and a dedicated cloth is used. The end face is cleaned by pressing the cloth against the ferrule end face and sliding the cloth or optical connector along the end face. In conventional connectors, the frictional force applied by the cloth during cleaning can cause the refractive index matching material to peel off or tear from the ferrule. In contrast, in the connector 10 according to this embodiment, the protective portion 21 is positioned relative to the refractive index matching portion 20 in the sliding direction of the cloth, protecting the refractive index matching portion 20. This makes the refractive index matching portion 20 less likely to peel off or tear. This means that the durability of the refractive index matching portion 20 can be improved.

[0031] Next, a method for manufacturing the connector 10 will be described. As an example, the manufacturing process for the configuration shown in Figure 2D will be described. Figures 4A to 4D are diagrams showing examples of the manufacturing process. For ease of explanation, these figures intentionally enlarge the periphery of the core end face 2a.

[0032] First, as shown in Figure 4A, at least one optical fiber 1 is fixed to the ferrule 11 with its core end face 2a exposed from the end face 15 of the ferrule 11. Next, a spacer 30 is placed on the end face 15. The spacer 30 has a through hole 31. The through hole 31 is formed in a position corresponding to the region 18 including the core end face 2a, and has a cross section complementary to the protective portion 21. Furthermore, the through hole 31 is filled with a resin 32, which is a photocurable refractive index matching material. That is, the resin 32 is applied to the region 18.

[0033] Next, a mask 33 is placed on the end face 15 of the ferrule 11 so that curing light 35, such as ultraviolet light, strikes only the core end faces 2a. Thereafter, curing light 35 is irradiated from a light source 34 toward the ferrule 11 to cure the resin 32. This cures the portion of the resin 32 that will become the refractive index matching section 20. In other words, the refractive index matching section 20 is formed. At this time, an optical lens may be placed in front of the curing light 35, or the curing light 35 may be irradiated to each core, so that a tapered refractive index matching section 20 is formed.

[0034] Next, uncured portions of the resin 32 are removed, and a photocurable resin 36, which will be the material for the protective portion 21, is applied to the end face 15. After curing, this resin 36 becomes harder than the refractive index matching portion 20. Furthermore, a plate 37 such as transparent glass is placed on top of the resin 36, and a predetermined pressure is applied toward the end face 15, compressing and deforming the refractive index matching portion 20. The predetermined pressure is equal to the value of the pressing force required when connecting the connector (see FIG. 3B ), for example.

[0035] Next, while the refractive index matching section 20 is maintained in a compressed and deformed state, the resin 36 is irradiated with curing light 35 to cure the resin 36. This cures the portion of the resin 36 that will become the protective section 21. That is, the protective section 21 is formed. The containing section 22 is also formed within the protective section 21.

[0036] Next, the plate 37 and the spacer 30 are removed, and excess (i.e., uncured) resin 36 is removed. By removing the plate 37, the compressively deformed refractive index matching portion 20 returns to its original shape. As a result, the refractive index matching portion 20 becomes thicker than the protective portion 21, and a portion of the refractive index matching portion 20 protrudes from the protective portion 21. In other words, the refractive index matching portion 20 is accommodated in the accommodation portion 22 with a portion of the refractive index matching portion 20 protruding from the protective portion 21.

[0037] If the refractive index matching portion 20 does not protrude from the protective portion 21, the pressing by the plate 37 is omitted. In this case, the protective portion 21 is formed without the refractive index matching portion 20 shrinking. Therefore, the refractive index matching portion 20 and the protective portion 21 have the same thickness.

[0038] REFERENCE SIGNS LIST 1 Optical fiber 2 Core 2a Core end face 10 Connector 11 Ferrule 12 Fiber hole 15 End face 20 Refractive index matching section 21 Protective section 22 Storage section

Claims

1. An optical connector comprising: a ferrule having an end face with at least one fiber hole opened therein; at least one optical fiber having a core end face exposed from the end face through the fiber hole; a refractive index matching section formed to be elastically deformable and in contact with the core end face; and a protective section provided on the end face and formed to be harder than the refractive index matching section, wherein the protective section includes a housing section that houses the refractive index matching section.

2. The optical connector according to claim 1, wherein the refractive index matching section is accommodated in the accommodating section with a portion of the refractive index matching section protruding from the protecting section.

3. An optical connector according to claim 1 or 2, wherein in a cross section including the central axis of said fiber hole, said refractive index matching section and said accommodating section have widths that increase toward said end face.

4. A method for manufacturing an optical connector, comprising: fixing at least one optical fiber having a core end face to the ferrule with the core end face exposed from the end face of the ferrule; applying a photo-curable refractive index matching material to an area including the core end face; forming a refractive index matching section in contact with the core end face by curing the refractive index matching material using light irradiation; removing portions of the refractive index matching material other than the section where the refractive index matching section is formed; applying a photo-curable resin to the end face of the ferrule; and forming a protective section by curing the resin using light irradiation; wherein the protective section is formed to be harder than the refractive index matching section.

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