Ferrule, optical connector and method for manufacturing optical connector

Abstract

The invention provides a ferrule, an optical connector, and a method for manufacturing the optical connector, which can handle high-speed large-capacity communication and are not easily damaged even when repeated stress is applied. A ferrule (10) for connecting a plurality of optical fibers is provided with: an optical fiber hole (100) which is provided in a connection end surface (11a) and into which an optical fiber is inserted; a protective jacket insertion hole (300) which is provided in the rear end surface (11b) and into which a protective jacket (60) through which a plurality of optical fibers can be inserted is inserted; an internal space (400) that connects the plurality of optical fiber holes (100) and the protective jacket insertion hole (300); a flange section (600) provided on the rear end surface (11b) side and protruding from a surface adjacent to the rear end surface (11b); the depth T of the protective sleeve insertion hole (300) is shorter than the length L of the flange portion (600) in the connection direction.

Description

Technical Field

[0001] The present invention relates to a ferrule for optically connecting optical fibers for transmitting optical signals, an optical connector having the ferrule mounted thereon, and a method for manufacturing the optical connector. Background Art

[0002] Optical cables using optical fibers are widely used for information communications in homes and industries because they enable high-speed communication of large amounts of information. For example, Patent Document 1 (Japanese Patent Laying-Open No. 2004-020962) discloses an optical connector that can uniformly inject adhesive resin into an optical fiber ribbon insertion hole of a ferrule without generating air bubbles when fixing an optical fiber ribbon to the ferrule of the optical connector.

[0003] The optical connector described in Patent Document 1 has a ferrule, which includes: a cylindrical protective cover for protecting an optical fiber ribbon formed by covering a plurality of optical fibers; a protective cover insertion hole for installing the protective cover; an optical fiber ribbon insertion hole, which is arranged in communication with the protective cover insertion hole; and a plurality of optical fiber holes for a plurality of optical fibers, which are arranged in communication with the optical fiber ribbon insertion hole; when a plurality of optical fibers are inserted into the optical fiber holes and the protective cover with the optical fiber ribbon inserted into the protective cover insertion hole, the optical connector is formed by filling a window hole provided at the top of the optical fiber ribbon insertion hole with a resin for bonding, and an inclined portion is provided at the optical fiber ribbon storage portion of the optical fiber ribbon insertion hole.

[0004] Patent Document 2 (Japanese Patent Laying-Open No. 2009-23015) discloses an optical ferrule capable of increasing the number of connectable optical fibers without changing the outer dimensions of the optical ferrule.

[0005] The optical ferrule described in Patent Document 2 uses an optical fiber with an outer diameter of 125 μm, for example, an optical fiber with a cladding diameter of 100 μm or less coated with a resin coating. The optical fiber is inserted into a protective cover fitted in an optical fiber insertion opening of the optical ferrule in a bundled state, and is bent inside the optical ferrule and guided to each optical fiber hole.

[0006] Patent document 3 (Japanese Patent Laying-Open No. 2021-101254) discloses an optical connector and a ferrule that can provide a gap between the ferrule and the housing when the ferrule is retracted, and configure the ferrule at a predetermined position relative to the housing before connecting the connector.

[0007] The optical connector described in Patent Document 3 includes a ferrule for fixing the end of an optical fiber, and a housing for housing the ferrule in a retractable manner. A pair of upper inclined surfaces are formed on the upper surface of the ferrule, and a pair of lower inclined surfaces are formed on the lower surface of the ferrule. The optical connector is characterized in that the pair of upper inclined surfaces are both oriented forward and upward, and are oriented in opposite directions to each other in the width direction. The pair of lower inclined surfaces are both oriented forward and downward, and are oriented in opposite directions to each other in the width direction. Prior art literature Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2004-020962 Patent Document 2: Japanese Patent Application Publication No. 2009-23015 Patent Document 3: Japanese Patent Application Publication No. 2021-101254 Summary of the invention Problem that the invention aims to solve

[0009] MT ferrules that enable high-density optical fiber communication are generally connected using specified optical connectors such as MPO connectors. In this case, a connector spring is provided inside the optical connector, and the elastic force of the connector spring applies a strong pressing force to the MT ferrule, thereby reducing the connection loss. In recent years, due to the demand for high-speed and high-capacity information communications, the number of optical fibers inserted into one ferrule has increased. As a result, since it is necessary to apply sufficient pressing force to each optical fiber, the pressing force applied to the ferrule will also increase. For example, in the case of an MPO connector based on PC connection, a pressing force of 10N or 20N or more is applied to the MT ferrule. Since the ferrule is the component that positions the end face of the optical fiber connection, it is also designed to be extremely precise in optical connectors, with its accuracy designed in sub-micron units. Here, in a state where the optical connector is connected, the two ferrules are accurately positioned by guide pins or the like, so that the pressing force of the connector spring is accurately applied to the connection end faces of the two ferrules. On the other hand, when the optical connector is disconnected, one ferrule is engaged with the connector housing and receives the pressing force of the coil spring. Therefore, a large mechanical load is applied to the ferrule, especially when the optical connector is attached or detached.

[0010] Optical cables are traditionally used to connect information communication devices that are far apart. Therefore, after the optical cables are laid and the optical connectors are connected, the optical connectors are not removed unless there are special circumstances such as abnormalities or re-laying. However, as information and communication equipment has become faster and more dense in recent years, optical cables are increasingly being used not only for long-distance communications but also for wiring of various information processing devices. For example, optical cables are being used for communication between servers or terminals in the same building, or for communication between boards in a server.

[0011] In this case, the optical connector is frequently installed and removed compared to the past, and a large mechanical load is applied to the ferrule each time it is installed and removed. As a result, the load on the ferrule is increased at a frequency not previously imagined, causing the problem of damage to the ferrule in the optical connector.

[0012] In the optical connector described in Patent Document 1, the ferrule in the protective cover insertion hole has a flange shape, so the height of the ferrule in the protective cover insertion hole becomes high (see Figure 1 and Figure 6 ). In addition, since the portion of the ferrule where the protective cover is inserted into the hole has a flange shape, the wall thickness of the portion of the ferrule where the protective cover is inserted into the hole becomes thicker, thereby preventing the generation of cracks in the ferrule and defects caused by the cracks. However, a general optical connector such as an MPO connector is configured so that the flange of the ferrule engages with the protrusion of the connector housing, so that the ferrule does not fall out of the connector forward. Therefore, when the optical connector is repeatedly assembled and disassembled, the mechanical load is concentrated near the flange and the window of the ferrule, causing cracks and damage to the ferrule.

[0013] In the optical ferrule of Patent Document 2, an optical ferrule having high density and excellent mechanical strength is realized by using an optical fiber with a small outer diameter and forming a special wiring structure inside the ferrule. However, in this case, the size of the internal space forming the window portion and the wiring structure is large, and even if the optical fiber is protected by a protective cover, the optical ferrule body may be damaged if the optical connector is disassembled and assembled many times.

[0014] In the optical connector of Patent Document 3, since an upper concave portion is provided on the upper surface of the ferrule and the upper convex portion engages with the upper concave portion, the problem of mechanical load being concentrated near the flange portion and the window portion as in the standardized MPO connector does not occur. However, in this case, since a special ferrule and optical connector need to be used, it is not universal, and since an upper concave portion needs to be provided in the ferrule body, there is a problem that it is difficult to achieve high density by arranging optical fibers in multiple stages.

[0015] An object of the present invention is to provide a ferrule, an optical connector, and a method for manufacturing the optical connector that can handle high-speed and large-capacity communications and is not easily damaged even when repeated stress is applied. Another object of the present invention is to provide a ferrule that has excellent durability and can be frequently attached and detached from an optical connector, an optical connector, and a method for manufacturing the optical connector. Means of solving the problem (1) The ferrule of the first invention is a ferrule for connecting multiple optical fibers, comprising: an optical fiber hole, which is arranged on the connection end face and is used to insert the optical fiber; a protective sleeve insertion hole, which is arranged on the rear end face and is used to insert a protective sleeve that can insert multiple optical fibers; an internal space that connects the multiple optical fiber holes and the protective sleeve insertion hole; a flange portion, which is arranged on the rear end face side and protrudes from the surface adjacent to the rear end face; the depth T of the protective sleeve insertion hole is shorter than the length L of the flange portion in the connection direction.

[0017] When the optical connector is connected, the pressing force of the connector spring is applied to the entire connection end surface of the ferrule. On the other hand, when the optical connector is disconnected, the protrusion of the connector housing engages with the flange of the ferrule, thereby preventing the ferrule from falling forward due to the pressing force of the coil spring. Therefore, when the optical connector is being assembled or disassembled, especially when the optical connector is disconnected, the flange of the ferrule and the protrusion of the connector housing collide, exerting a large impact stress on the ferrule. In addition, the design accuracy of the connector is generally lower than that of the ferrule, and when the protrusion of the connector housing and the flange of the ferrule are engaged, deformation stress is sometimes exerted on the ferrule due to the influence of flatness, etc., compared with when the ferrules are in contact with each other at the connection end faces 11a.

[0018] The ferrule is generally formed of a resin having excellent mechanical properties such as PPS (polyphenylene sulfide resin). However, with the recent increase in the density of optical communications, the pressing force applied by the connector spring is required to be 10N, 20N or more, and a large force is applied. In addition, with the diversification of optical communications in recent years, the need for frequent assembly and disassembly of optical connectors has increased. However, the increase in the number of assembly and disassembly applies repeated stress to the ferrule, causing durability problems such as damage to the ferrule in the optical connector.

[0019] According to the ferrule of the first invention, since the length L of the flange in the connection direction is longer than the depth T of the protective sleeve insertion hole, the wall thickness P on the front end side of the flange and / or the wall thickness M on the flange side of the internal space can be sufficiently ensured, and the strength to withstand the repeated stress applied to the flange when the optical connector is assembled and disassembled can be ensured. In addition, since the wall thickness near the front end of the flange, which is prone to load when the optical connector is assembled and disassembled, is continuously thickened, the stress borne by the resin per unit area is reduced, and fatigue due to repeated stress can be minimized. Therefore, even when the optical connector is frequently attached and detached, the ferrule can be prevented from being damaged and has excellent durability. (2) A ferrule according to a second aspect of the present invention is a ferrule according to one aspect, and may include a reinforcement portion between the deepest portion of the protective cover insertion hole and the front end portion of the flange portion.

[0021] If the optical connector with the ferrule installed is frequently disassembled and assembled, the ferrule in the optical connector will be damaged. In this case, cracks usually occur at the boundary part (corner part) between the flange part of the ferrule and the ferrule body, and the cracks spread to the protective cover insertion hole in the flange part, and eventually the ferrule may be broken (refer to Figure 7 This is considered to be because a large stress is generated on the front end surface side of the flange portion of the ferrule when the optical connector is disconnected. Therefore, by providing a reinforcement portion with a predetermined wall thickness between the front end surface of the flange portion and the bottom surface of the protective sleeve insertion hole, the portion that is prone to cracking can be reinforced to obtain strength to withstand stress associated with assembly and disassembly. Therefore, even when repeated stress is applied, the ferrule can be made less likely to be damaged. (3) The ferrule of the third invention is a ferrule according to any one of the first to second inventions, wherein the flange portion is formed in a manner covering the periphery of the protective cover insertion hole, a guide groove for guiding the optical fiber is formed on the rear end face side of the optical fiber hole, and a step can be provided on the bottom surface of the wall constituting the internal space between the rear end portion of the guide groove and the front end portion of the flange portion.

[0023] In recent years, as the density has increased, the diameter of the optical fiber has become thinner, and a guide groove is required to reliably insert the optical fiber into the optical fiber hole. In addition, when the optical fiber hole is arranged in multiple stages, the guide groove needs to be arranged in multiple stages, resulting in a larger size of the adhesive filling window, which is not conducive to the strength of the ferrule. Even in this case, by providing a predetermined distance Q between the rear end of the guide groove and the front end of the flange, it is possible to form an internal space having a predetermined wall thickness M between the rear end of the adhesive filling window and the front end of the flange. Therefore, the ferrule can achieve both high-density connection and high strength, and can be a ferrule that is not easily damaged even when repeated stress is applied. (4) The ferrule of the fourth invention is the ferrule according to any one of the first to third inventions, wherein the wall thickness M of the internal space on the front end surface side of the flange portion may be 0.8 to 1.5 times the wall thickness N of the protective cover insertion hole.

[0025] The inner space of the ferrule is filled with adhesive, and the protective cover is inserted into the protective cover insertion hole. However, since the strength of the adhesive and the protective cover is weaker than the strength of the ferrule body, when the optical connector is repeatedly assembled and disassembled, it will cause a load on the thin wall part of the ferrule body. In particular, as the optical connector is assembled and disassembled, stress tends to concentrate between the wall forming the internal space and the wall forming the protective sleeve insertion hole. In particular, when the ferrule body has a thin-walled portion, the portion cannot withstand repeated stress. Therefore, by configuring the wall thickness M of the internal space (the front end face side of the thinned flange portion) and the wall thickness N of the protective sleeve insertion hole to have a predetermined thickness range, the inner wall of the ferrule becomes continuous and integrated. Therefore, even when repeated stress is applied, the ferrule is not easily damaged. (5) The ferrule of the fifth invention is the ferrule according to any one of the first to fourth inventions, wherein a corner portion of an inner wall forming the protective cover insertion hole and / or a corner portion of an outer wall forming the flange portion may be provided with a curvature.

[0027] The corner edge portion forming the inner wall corner of the protective cover insertion hole and the corner edge portion forming the outer wall corner of the flange portion are portions where the shape of the component changes, so stress is easily concentrated and the maximum stress is greater than that of other portions. Therefore, by providing a curvature for relieving stress at each corner, it is possible to prevent the maximum stress from concentrating. Therefore, even when repeated stress is applied, the ferrule is not easily damaged. (6) The ferrule of the sixth invention is the ferrule according to any one of the first to fifth inventions, further comprising a pair of guide pin holes for inserting a pair of guide pins, and the distance between the guide pin holes and the protective cover insertion hole can be set to be greater than or equal to 0.1 mm and less than or equal to 0.2 mm.

[0029] In recent years, with the development of high speed and high capacity, the ferrule has been multi-core. However, when a large number of optical fibers are inserted into the ferrule, the size of the internal space and the protective cover insertion hole becomes larger, resulting in the problem of the thickness of the inner wall of the ferrule becoming thinner. Furthermore, since the pitch between a pair of guide pins is limited by the specification, when a large number of optical fibers are arranged, the thickness of the resin between the guide pin insertion hole and the protective cover insertion hole is likely to become thin, which may cause damage to this portion. Therefore, by setting the distance between the guide pin hole and the protective cover insertion hole to a predetermined distance, the thickness can be ensured even in the case of high density, so that the ferrule is not easily damaged even when repeated stress is applied. (7) An optical connector according to another invention is an optical connector to which the ferrule according to any one of the first to sixth inventions is mounted.

[0031] This allows the optical connector to have excellent durability and to be frequently assembled and disassembled. (8) Furthermore, according to another invention, a method for manufacturing an optical connector is provided with a ferrule according to any one of the first to sixth inventions, comprising: a fiber insertion step of inserting a plurality of optical fibers into fiber insertion holes, respectively; a protective cover insertion step of inserting a protective cover for the optical fiber into the protective cover insertion hole; and an installation step of installing the ferrule in a connector housing.

[0033] This allows the optical connector to have excellent durability and to be frequently assembled and disassembled. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic perspective view of the ferrule according to the first embodiment. Figure 2 It is a schematic cross-sectional view of the ferrule according to the first embodiment. Figure 3 (a) is a schematic front view of the ferrule of the first embodiment, Figure 3 (b) is a schematic top view, Figure 3 (d) is a schematic left view viewed from the left side, Figure 3 (c) is a schematic bottom view, Figure 3 (e) is a schematic right side view viewed from the right side. Figure 4 The ferrule of the first embodiment is inserted with a protective cover, Figure 4 (a) is a schematic cross-sectional view, Figure 4 (b) is a schematic left side view. Figure 5 yes Figure 2 Schematic enlarged view of the optical connector of the first embodiment shown in FIG. Figure 6 This is a schematic perspective view for explaining the internal structure of an optical connector. Figure 7 These are photos showing the results of a disassembly and assembly test using a common MT ferrule. Figure 8 It is a schematic cross-sectional view of the ferrule according to the second embodiment. Fig. 9 (a) is a schematic front view of the ferrule of the second embodiment, Fig. 9 (b) is a schematic top view, Fig. 9 (d) is a schematic left view viewed from the left side, Fig. 9 (c) is a schematic bottom view, Fig. 9 (e) is a schematic right side view viewed from the right side. Fig.10 It is a schematic cross-sectional view of a ferrule of a conventional example. Fig.11 (a) is a schematic front view of a ferrule according to a third embodiment, Fig.11 (b) is a schematic top view, Fig.11 (d) is a schematic left view viewed from the left side, Fig.11 (c) is a schematic bottom view, Fig.11 (e) is a schematic right side view viewed from the right side. Fig.12 (a) Yes Fig.11 (b) The cross-sectional view of the line a-a', Fig.12 (b) Yes Fig.11 (b) Cross-sectional view along line b-b'. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are used for the same components. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0036] <First Embodiment> (Insert 10) Figure 1 : is a schematic perspective view of the ferrule 10 of the first embodiment. Figure 2 is a schematic cross-sectional view of the ferrule 10 of the first embodiment, Figure 3 (b) is a cross-sectional view along line AA'. Figure 3 (a) is a schematic front view of the ferrule 10 of the first embodiment, Figure 3 (b) is a schematic top view, Figure 3 (d) is a schematic left view viewed from the left side, Figure 3 (c) is a schematic bottom view, Figure 3 (e) is a schematic right side view viewed from the right side.

[0037] like Figures 1 to 3 As shown, the main body of the ferrule 10 of this embodiment includes: a plurality of optical fiber holes 100, which are opened at the connection end face 11a (the front end face of the main body) and are used to insert and position the optical fiber (not shown) with the coating removed; and a plurality of semicircular, U-shaped or V-shaped guide grooves 110, which are connected to the rear ends of the plurality of optical fiber guide holes and are parallel to each other. The optical fiber hole 100 is formed by a plurality of optical fiber guide holes connected to the rear ends of the plurality of optical fiber holes 100 and are parallel to each other, and a reduced diameter portion 101 is provided inside. In addition, the main body of the ferrule 10 of the present embodiment comprises: a protective cover insertion hole 300 for installing a ferrule protective cover 60 for inserting the optical fiber; an adhesive filling window 500 for injecting an adhesive for fixing the plurality of optical fibers to the ferrule 10; and two guide holes 200, which are formed near the two end portions in the width direction parallel to the plurality of optical fiber holes 100 and are used for inserting guide pins 50.

[0038] The protective cover insertion hole 300 has an opening at the rear end face 11b of the ferrule 10, and the adhesive filling window 500 opens at the upper surface of the ferrule 10. In addition, in the main body of the ferrule 10, an internal space 400 is provided that connects the optical fiber hole 100, the protective cover insertion hole 300, and the adhesive filling window 500. When the adhesive is filled from the adhesive filling window 500, the internal space 400 is filled with the adhesive. Furthermore, the main body of the ferrule 10 may be appropriately provided with a mark indicating the manufacturer's name or model number, a mark indicating the ejector pin used during manufacturing, and the like. It should be noted that, in the description of this specification, the direction connecting the connecting end face 11a and the rear end face 11b ( Figure 3 The left-right direction of (a) can be called the connection direction or the front-back direction. Figure 3 The left and right direction of (e) can be called the width direction. Figure 3 The up-down direction (direction perpendicular to the connection direction) of (a) may be referred to as the up-down direction.

[0039] The ferrule 10 of this embodiment is usually accommodated in a Figure 6 In the illustrated optical connector 1 , by connecting two optical connectors 1 , the connection end faces 11 a of the ferrules 10 abut against each other, thereby optically connecting a plurality of optical fibers. The outer shape of the ferrule 10 of this embodiment is the same as the ferrule 10 of the shape generally called the MT ferrule. Generally, the MT ferrule is widely used in accordance with IEC, JIS, JPCA, etc. Figure 3 As shown, the ferrule 10 having the outer shape of a typical 12-core MT ferrule will be taken as an example for description. In addition, a standardized MPO connector is widely used as an optical connector 1 for connecting such an MT ferrule. Figure 6 The typical MPO connector shown is used as an example. It should be noted that the present invention is not only applicable to standardized MT ferrules and MPO connectors, but can also be applied to various ferrules 10 and optical connectors 1 whose dimensions and the like are appropriately changed according to the purpose of connection and the like.

[0040] When two optical fibers are connected for optical communication, a physical contact (PC) connection is generally adopted in which the end faces of the optical fibers are strongly pressed against each other. This is achieved by grinding the end faces of the optical fibers to be slightly curved into a convex shape and strongly pressing the end faces of such convex shapes against each other to eliminate air gaps, thereby achieving low-loss optical communication. When such a PC connection is performed, a prescribed pressing force needs to be applied to each optical fiber, so as the number of optical fibers corresponding to one ferrule 10 increases, the pressing force that the optical connector 1 has to apply to the MT ferrule also increases. In addition, since Fresnel reflection generated on the connection surface may have an adverse effect on optical communication, it is sometimes necessary to grind the connection end face 11a at an angle of about 8° relative to the connection direction. In this case, the end face of the optical fiber is inclined relative to the direction in which the pressing force is applied (connection direction). Therefore, considering the situation of performing inclined grinding, the pressing force of the connector spring 30 of the optical connector 1 is pre-designed to be large. From this point of view, for example, when connecting a standardized 12-core MT ferrule, the connector spring 30 of the MPO connector is standardized to apply a pressing force of 9.8N±2N to the MT ferrule. In addition, when connecting a 24-core MT ferrule, a pressing force of 20N±2N is usually applied.

[0041] Here, when the optical connector 1 is connected, the two ferrules 10 are accurately positioned by the guide pins 50, and the pressing force of the connector spring 30 is accurately applied to the connection end surface 11a of the ferrule 10. On the other hand, when the optical connector 1 is disconnected, as shown in FIG. Figure 6 As shown, the protrusion 21 of the connector housing 20 and the flange 600 of the ferrule 10 are engaged to prevent the ferrule 10 from falling forward. At this time, the pressing force of the connector spring 30 is received by the flange 600 of the ferrule 10, and a large impact stress may be applied to the ferrule 10 when the optical connector 1 is disconnected. Furthermore, although the ferrule 10 is extremely accurately designed, the connector housing 20 is not designed with high accuracy, so when the optical connector 1 is disconnected, a large pressing force is applied to a portion of the flange portion 600 , causing deformation stress to be applied to the ferrule 10 . Furthermore, optical communication is used in various information processing devices, and the frequency of attaching and detaching the optical connector 1 has increased in recent years. As a result, a large mechanical load is applied to the ferrule 10 each time it is attached and detached, causing a problem that the ferrule 10 is damaged inside the optical connector 1 . Furthermore, after the optical fiber is fixed, the connection end face 11a is optically polished, and the ferrule 10 is installed in the optical connector 1. When the connection end face 11a is polished, the flange portion 600 of the ferrule 10 is fixed and pressed on a high-speed polishing table using a jig. At this time, depending on the method of fixing the jig or the method of polishing the connection end face 11a (for example, oblique polishing, etc.), the flange portion 600 fixed to the jig may be subjected to a large load. Thus, when the connection end face 11a of the ferrule 10 is polished, a load may be applied near the flange portion 600 of the ferrule 10, causing damage.

[0042] (Insert 10) The ferrule 10 of this embodiment is as follows Figures 1 to 4 As shown, a ferrule having the same appearance as a standardized 12-core MT ferrule is shown as an example. That is, the total length of the MT ferrule body in the connection direction is 8.0 mm, the lateral width including the flange 600 is 7.0 mm, the longitudinal width including the flange 600 is 3.0 mm, the lateral width of the body excluding the flange 600 is 6.4 mm, and the longitudinal width of the body excluding the flange 600 is 2.5 mm. In addition, the protruding height of the flange 600 over the entire circumference is 0.25 mm, and the length L in the connection direction is 2.0 mm. In addition, the number of cores, cladding diameter, spacing, etc. of the optical fiber can be appropriately selected according to the purpose of the connection, but in the example of this embodiment, the diameter of the optical fiber hole 100 is 125μm and the spacing is 125μm. In addition, the diameter of the guide hole 200 is 0.7mm and the spacing is 4.6mm. In addition, the opening of the adhesive filling window 500 is 2.4mm in the connection direction and 3.0mm in the lateral width direction. It should be noted that the flange portion 600 is exemplified as being set from the rear end face 11b of the MT ferrule throughout the entire circumference (left and right sides and upper and lower sides), but it can also be set on a part of the side.

[0043] The ferrule 10 of this embodiment is formed, for example, by molding a resin material filled with an inorganic filler. The resin material is a thermosetting epoxy resin, PPS (polyphenylene sulfide), etc. Among them, from the viewpoint of position accuracy, dimensional accuracy, molding shrinkage, and thermal stability, polyphenylene sulfide (PPS) resin is preferably used. Thus, even if a small and high-density installation is performed, a ferrule 10 with low connection loss can be formed. In addition, the inorganic filler can be, for example, granular silica. By filling with inorganic fillers, the strength of the ferrule 10 can be improved. However, in recent years, when high density is required, the size of the internal space 400 and the protective cover insertion hole 300 tends to increase. In addition, as the frequency of assembly and disassembly of the optical connector 1 increases, the number of impacts applied to the ferrule 10 increases, causing the problem of cracks to become significant.

[0044] like Figure 4 As shown in FIG. 1 , a protective sleeve 60 for holding and protecting the optical fiber is inserted into a common MT ferrule. Figure 5 As shown, the ferrule 10 of the present embodiment is designed so that the depth T (depth in the connection direction) of the protective cover insertion hole 300 is shorter than the length L of the flange portion 600 in the connection direction. The depth T of the protective cover insertion hole 300 is preferably shorter than the length L of the flange portion 600 by more than 0.1 mm, more preferably shorter by more than 0.2 mm, and further preferably shorter by more than 0.4 mm. Thus, the reinforcing portion 610 described later can be ensured, and sufficient strength can be obtained. In addition, the depth T of the protective cover insertion hole 300 is preferably more than 1 / 2 of the length L of the flange portion 600 in the connection direction. Thus, the protective cover 60 can be reliably held in the protective cover insertion hole 300. The depth T of the protective cover insertion hole 300 of this embodiment is preferably 1.9 mm or less, more preferably 1.8 mm or less, and further preferably 1.6 mm or less. In addition, the depth T of the protective cover insertion hole 300 is preferably 1.0 mm or more. Thus, the protective cover 60 can be reliably held while maintaining strength.

[0045] The ferrule 10 of this embodiment is designed so that the depth T of the protective sleeve insertion hole 300 is shorter than the length L of the flange portion 600, and therefore a reinforcement portion 610 is provided as a wall constituting the internal space 400 between the deepest portion 301 of the protective sleeve insertion hole 300 (the bottom surface of the protective sleeve insertion hole 300) and the front end portion 601 of the flange portion 600 (the surface on the connection direction side). like Figure 5 As shown, the reinforcement part 610 is the wall of the main body of the ferrule 10 surrounding the internal space 400, and is also a part of the flange part 600. In the cross-sectional view in the connection direction, the wall thickness P of the reinforcement part 610 is preferably greater than 0.8 mm, more preferably greater than 0.9 mm, and further preferably greater than 0.95 mm. In addition, the length R of the reinforcement part 610 in the connection direction is preferably greater than 0.1 mm, more preferably greater than 0.2 mm, and further preferably greater than 0.4 mm. The thickness P of the reinforcement portion 610 is preferably 1.5 times or more and 2.5 times or less, more preferably 1.7 times or more and 2.3 times or less, and even more preferably 1.8 times or more and 2.2 times or less, the length R in the connection direction. Thereby, sufficient strength can be obtained.

[0046] The ferrule 10 of this embodiment is as follows Figure 5 As shown, among the walls constituting the internal space 400 , except for the reinforcement portion 610 , the wall on the front side of the front end surface of the flange portion 600 (the thinnest portion of the bottom surface constituting the internal space 400 ) has a predetermined wall thickness M. The thickness M of the wall on the front side of the front end surface of the flange portion 600 is preferably 0.5 mm or more, more preferably 0.6 mm or more, and even more preferably 0.7 mm or more. The thickness M of the wall on the front side of the front end surface of the flange portion 600 is preferably 0.8 to 1.5 times, more preferably 0.9 to 0.3 times, and even more preferably 0.95 to 0.2 times the thickness N of the boot insertion hole 300 . The wall of the internal space 400 is formed to cover the periphery of the internal space 400 , and the wall thickness M of the upper surface of the main body of the ferrule 10 (the surface constituting the frame of the adhesive filling window 500 ) is preferably the same thickness as described above.

[0047] The distance Q between the rear end 111 of the guide groove 110 and the front end 601 of the flange 600 is preferably 0.6 mm to 2.4 mm, more preferably 1.5 mm to 2.0 mm. Thus, the internal space having the wall thickness M can be sufficiently ensured, thereby achieving high-density connection and high-strength ferrule 10. The ferrule 10 of this embodiment is as follows Figure 2 and Figure 5 As shown in FIG. 1 , the bottom surface of the wall constituting the internal space 400 is composed of two sections: the bottom surface M' on the guide groove 110 side with a thicker wall thickness and the bottom surface M on the front end surface side of the flange portion 600 with a thinner wall thickness. Thus, even when the specified distance Q is ensured, the load on the mold during injection molding can be suppressed. Therefore, while having excellent mass productivity, it can also be a ferrule that is not easily damaged even when repeated stress is applied. In addition, since there is a predetermined step between the bottom surface of the guide groove 110 and the bottom surface M′ of the wall constituting the internal space 400 , the thickness of the coating layer of the optical fiber ribbon can be absorbed, so that the core wire of the optical fiber can be easily kept in a straight line.

[0048] The ferrule 10 of the present embodiment may form a curvature at a corner portion selected from the group consisting of corner portions 302 a and 302 b of the inner wall of the protective cover insertion hole 300 and corner portions 602 a and 602 b of the outer surface of the flange portion 600 . like Figure 5 As shown, the corner portion 302a is a corner formed between the wall of the protective cover insertion hole 300 in the insertion direction of the protective cover 60 and the deepest portion 301, and is composed of two surrounding sides in the width direction and two surrounding sides in the longitudinal direction. The corner portion 302b is a boundary portion between the internal space 400 and the protective cover insertion hole 300, and is composed of two surrounding sides in the width direction and two surrounding sides in the longitudinal direction. In addition, the corner portion 602a is a corner of two surfaces formed on the side of the front end portion 601 of the flange portion 600, and is composed of two surrounding sides in the width direction and two surrounding sides in the longitudinal direction. The corner portion 602b is a corner formed between the surface on the front side of the flange portion 600 and the outer surface of the wall constituting the internal space 400, and is composed of two surrounding sides in the width direction and two surrounding sides in the longitudinal direction. In this case, the curvature of the corner portions 302a, 302b, 602a, and 602b preferably has a curvature radius of 0.05 mm or more and 0.5 mm or less, and more preferably 0.08 mm or more and 0.2 mm or less. Thus, even when a pressing force is applied to the flange portion 600 when the optical connector 1 is attached or detached, stress that tends to concentrate on the corner portions 302a, 302b, 602a, and 602b can be reduced, thereby preventing the occurrence of cracks. Figure 5The example in which the curvature is formed only in the corner portion 302a and the corner portion 602b is shown. Thus, the influence on positioning when grinding the connection end face can be minimized. It should be noted that, it is not limited to this, and the curvature can be formed at least in the corner portion 302a and the corner portion 602a.

[0049] (Optical connector 1) Figure 6 This is a schematic three-dimensional diagram for explaining the internal structure of the optical connector 1 of this embodiment. The internal structure can be seen by removing 1 / 4 of the connecting device housing 20. The optical connector 1 is covered by a connector housing 20, and is configured so that internal components can be taken out from the rear of the connector housing 20 as needed. The inserted ferrule 10 is installed on the side (front end) closest to the connection surface of the optical connector 1, and is configured so as to engage with the protrusion 21 of the connector housing 20. When the optical connector 1 is connected to another optical connector 1, the ferrule 10 abuts against the connection end surface 11a and moves to the rear side, but when the connection of the optical connector 1 is released, the ferrule 10 is configured so that the protrusion 21 of the connector housing 20 engages with the ferrule 10 so that the ferrule 10 does not fall off the optical connector 1 forward.

[0050] In addition, the pin holder 40 is provided at the rear of the ferrule 10. The pin holder 40 holds a pair of guide pins 50, and the guide pins 50 penetrate the guide hole 200 of the ferrule 10 and protrude toward the connection surface side of the optical connector 1. It should be noted that, Figure 6 , an optical connector 1 (also referred to as a male side or a plug side) having guide pins 50 is illustrated. However, in this case, the other optical connector 1 to be connected generally does not have guide pins 50 (also referred to as a female side or a socket side). In addition, the connector spring 30 is provided behind the pin holder 40. The connector spring 30 applies a pressing force to the ferrule 10 by a strong elastic force. In this case, the optical fiber extending from the ferrule 10 passes through the pin holder 40 and the inside of the connector spring 30, and extends from the rear of the optical connector 1 to the outside. It should be noted that Figure 6 The internal structure of the MPO connector is illustrated as an example, but other connectors such as the MTP connector (registered trademark), SN connector (registered trademark), and MMCC connector (registered trademark) may be appropriately used depending on the purpose of the optical connection. Furthermore, the protective cover 60 inserted into the ferrule 10 may be appropriately designed according to the type of the optical connector 1 , the optical fiber wiring method, the purpose of the optical connection, and the like.

[0051] (Ferrule 10 of Second Embodiment) Figure 8 is a schematic cross-sectional view of a ferrule 10 according to a second embodiment, Fig. 9 (b) is a cross-sectional view along line BB'. Fig. 9 (a) is a schematic front view of the ferrule 10 of the second embodiment, Fig. 9 (b) is a schematic top view, Fig. 9 (d) is a schematic left view viewed from the left side, Fig. 9 (c) is a schematic bottom view, Fig. 9 (e) is a schematic right side view viewed from the right side. The ferrule 10 of the second embodiment is an example of a 36-core MT ferrule, and the optical fiber holes 100 of 12 fibers in a horizontal row are arranged in three rows. Thus, three times the amount of information can be communicated compared to the ferrule 10 of the first embodiment. On the other hand, the fiber holes 100 of this embodiment are arranged in three rows in the vertical direction. Figure 8 As shown, the guide groove 110 for inserting the optical fiber is configured in three sections. In addition, in order to accurately insert the optical fiber into each optical fiber hole 100, the opening of the adhesive filling window 500 needs to be enlarged. In addition, in order to connect the 36-core MT ferrule to the PC, the connector spring 30 needs a pressing force of 20N±2N, which applies a very large force to the MT ferrule. Thus, when the optical fiber becomes high-density, the openings of the internal space 400, the protective sleeve insertion hole 300 and the adhesive filling window 500 become larger than conventional ones, and a greater pressing force is applied to the ferrule 10, so the problem of damage due to assembly and disassembly of the optical connector 1 becomes more significant. It should be noted that, in this case, the rear end portion 111 of the guide groove 110 refers to the end portion of the guide groove 110 a on the rear end surface 11 b side.

[0052] (Ferrule 10 of the third embodiment) Fig.11 (a) is a schematic front view of the ferrule 10 of the third embodiment, Fig.11 (b) is a schematic top view, Fig.11 (d) is a schematic left view viewed from the left side, Fig.11 (c) is a schematic bottom view, Fig.11 (e) is a schematic right side view viewed from the right side. Fig.12 is a schematic cross-sectional view of a ferrule 10 according to a third embodiment, Fig.12 (a) Yes Fig.11 (b) The cross-sectional view of the line a-a', Fig.12 (b) Yes Fig.11 (b) Cross-sectional view along line b-b'. The ferrule 10 of the third embodiment is as follows: Fig.12 As shown in (a), the bottom surface of the wall constituting the internal space 400 is formed flat, and the wall thickness M' and the wall thickness M are configured to be the same wall thickness. That is, the ferrule 10 of the first embodiment, as Figure 2 and Figure 5 As shown, the bottom surface of the wall constituting the internal space 400 is composed of two sections, namely, the thick wall thickness M' on the guide groove 110 side and the thin wall thickness M on the front end surface side of the flange portion 600. On the other hand, the ferrule 10 of the third embodiment has no step on the bottom surface of the wall constituting the internal space 400 between the rear end portion 111 of the guide groove 110 and the front end portion 601 of the flange portion 600 and is formed flat. Thereby, the wall thickness M of the flange portion side of the internal space can be increased, and the strength can be further improved.

[0053] (Example and Comparative Example of Ferrule 10) Hereinafter, examples and comparative examples of the ferrule 10 will be described. [Example 1] As Example 1, Figure 8 and Fig. 9 The ferrule 10 of the second embodiment is shown. That is, the ferrule 10 of 36-core silica optical fiber with a cladding diameter φ of 125 μm, and the outer shape of the main body of the ferrule 10 (total length, lateral width, longitudinal width, flange size, etc.) is the same as that of the first embodiment. In addition, the diameter of the optical fiber hole 100 is set to 125 μm, the lateral spacing is set to 125 μm, the longitudinal spacing is set to 0.25 mm, the diameter of the guide hole 200 is set to 0.7 mm, and the spacing is set to 4.6 mm. In addition, the opening of the adhesive filling window 500 is set to 2.4 mm in the connection direction and 3.0 mm in the lateral width direction. The depth T of the protective cover insertion hole 300 is set to 1.5 mm, the opening in the lateral width direction is set to 3.6 mm, and the opening in the longitudinal width direction is set to 1.6 mm. In addition, the size of the internal space 400 is set to 3.24 mm in the lateral width direction, 1.2 mm in the longitudinal width direction, and 1.2 mm in the connection direction. In addition, the widths of the guide grooves 110a, 110b, and 110c in the connection direction are respectively set to 0.6 mm, and the total is 1.8 mm.

[0054] The length L of the flange portion 600 is set to 2 mm, the full circumferential protrusion height is set to 0.25 mm, and the wall thickness N of the protective cover insertion hole 300 is set to 0.65 mm. In addition, the wall thickness P of the reinforcement portion 610 is set to 1.0 mm, and the length R in the connection direction is set to 0.5 mm. In addition, the wall thickness M of the wall constituting the internal space 400 excluding the reinforcement portion 610 is set to 0.75 mm, and the distance Q between the rear end portion 111 and the front end portion 601 is set to 1.8 mm. Furthermore, the corner portion 302 a of the inner wall of the protective cover insertion hole 300 and the corner portion 602 b of the outer surface of the flange portion 600 are formed with a curvature having a curvature radius of 0.1 mm. It should be noted that, in this embodiment, the polyphenylene sulfide resin and the silica particles surface-treated with a silane coupling agent are melt-kneaded using a twin-screw extruder, and the ferrule 10 of the above-mentioned shape is formed by injection molding.

[0055] Thirty-six quartz optical fibers with a diameter of φ of 125 μm are inserted into the 36-core ferrule 10 obtained in this way and fixed with epoxy resin. The connecting end face 11a is polished to an inclination of 8° and installed in an MTP connector (manufactured by USCONEC), and a clamping force of 20 N is applied through the connector spring 30. Then, each connector was subjected to a disassembly and assembly test (Telcrdia-GR-1435-CORE, JIS C61300-2-2) 500 times. Furthermore, the above-mentioned disassembly and assembly test was performed 16 times to check the damage state of each ferrule 10 . As a result, no cracks occurred in the ferrule 10 of the example.

[0056] [Comparative Example 1] The assembly and disassembly test was performed in the same manner as in Example 1 except that a standardized general-purpose 36-core ferrule 10 (36MT-PA-S manufactured by Hakusan Corporation) was used. Fig.10 Schematic cross-sectional view of the ferrule 10 used in Comparative Example 1 is shown. The 36-core ferrule 10 used in Comparative Example 1 is different from that in Example 1 in the following points, and the ferrule 10 is the same as that in Example 1 otherwise. That is, the depth T of the protective cover insertion hole 300 is set to 3 mm, the opening in the lateral width direction is set to 3.6 mm, and the opening in the longitudinal width direction is set to 1.7 mm. In addition, the size of the internal space 400 is set to 3.24 mm in the lateral width direction, 1.2 mm in the longitudinal width direction, and 3.5 mm in the connection direction. The length L of the flange portion 600 is set to 2.0 mm, the full circumferential protrusion height is set to 0.25 mm, the wall thickness N of the protective cover insertion hole 300 is set to 0.65 mm, and the wall thickness M of the wall constituting the internal space 400 is set to 0.65 mm. In addition, no curvature is formed in the corner portion 302 a of the inner wall of the protective cover insertion hole 300 .

[0057] The result of subjecting the ferrule 10 of Comparative Example 1 obtained in this manner to the same assembly and disassembly test as in Example 1 was that the ferrules 10 of 5 out of 16 optical connectors 1 were damaged (3 on the female side and 2 on the male side). Figure 7 This is a photo of the damaged ferrule 10 after the disassembly test. Figure 7 (a) is a photograph of the ferrule 10 with damage on the female side, and (b) is a photograph of the ferrule 10 with damage on the male side. In both cases, it was confirmed that cracks occurred between the flange portion 600 of the ferrule 10 and the boot insertion hole 300, resulting in damage. On the other hand, it was confirmed that in the ferrule 10 of Example 1, since the wall thickness from the flange portion 600 to the boot insertion hole 300 is sufficiently ensured, cracks and damages are unlikely to occur even when the optical connector 1 is repeatedly attached and detached.

[0058] In the present invention, the ferrule 10 corresponds to the "ferrule", the connecting end face 11a corresponds to the "connecting end face", the optical fiber hole 100 corresponds to the "optical fiber hole", the protective cover 60 corresponds to the "protective cover", the protective cover insertion hole 300 corresponds to the "protective cover insertion hole", the internal space 400 corresponds to the "internal space", the rear end face 11b corresponds to the "rear end face", the flange portion 600 corresponds to the "flange portion", the deepest portion 301 corresponds to the "deepest portion", the reinforcement portion 610 corresponds to the "reinforcement portion", the guide grooves 110, 110a, 110b, 110c correspond to the "guide grooves", the corner edges 302a, 302b, 602a, 602b correspond to the "corner edges", the guide hole 200 corresponds to the "guide pin hole", and the optical connector 1 corresponds to the "optical connector".

[0059] A preferred embodiment of the present invention is described above, but the present invention is not limited thereto. It should be understood that various other embodiments may be provided without departing from the spirit and scope of the present invention. In addition, in this embodiment, the effects and effects of the structure of the present invention are described, but these effects and effects are only examples and do not limit the present invention. Description of Reference Numerals

[0060] 1: optical connector, 10: ferrule, 11a: connecting end face, 11b: rear end face, 20: connector housing, 30: connector spring, 50: guide pin, 60: protective cover, 100: optical fiber hole, 110, 110a, 110b, 110c: guide groove, 200: guide pin hole, 300: protective cover insertion hole, 301: deepest part, 302a, 302b: corner edge, 400: internal space, 600: flange part, 610: reinforcement part, 602a, 602b: corner edge.

Claims

1. A ferrule is a ferrule used to connect multiple optical fibers, characterized in that: have: An optical fiber hole, provided on the connection end surface, for inserting the optical fiber; A protective sleeve insertion hole is provided on the rear end surface and is used for inserting a protective sleeve capable of inserting a plurality of the optical fibers; An internal space connects the plurality of optical fiber holes and the protective sleeve insertion hole; as well as A flange portion is provided on the rear end surface side and protrudes from a surface adjacent to the rear end surface; A depth T of the protective cover insertion hole is shorter than a length L of the flange portion in the connecting direction.

2. The ferrule according to claim 1, characterized in that: A reinforcement portion is provided between the deepest portion of the protective cover insertion hole and the front end portion of the flange portion.

3. The ferrule according to claim 1, characterized in that: The flange portion is formed so as to cover the periphery of the protective cover insertion hole. A guide groove for guiding the optical fiber is formed on the rear end face side of the optical fiber hole. A bottom surface of a wall constituting the internal space is provided with a step between a rear end portion of the guide groove and a front end portion of the flange portion.

4. The ferrule according to claim 1, characterized in that: A wall thickness M of the internal space on the front end surface side of the flange portion is 0.8 times or more and 1.5 times or less of a wall thickness N of the protective cover insertion hole.

5. The ferrule according to claim 1, characterized in that: A curvature is provided to a corner portion of an inner wall forming the protective cover insertion hole and / or a corner portion of an outer surface forming the flange portion.

6. The ferrule according to claim 1, characterized in that: A pair of guide pin holes are also provided for inserting a pair of guide pins. The distance between the guide pin hole and the protective cover insertion hole is set to be greater than or equal to 0.1 mm and less than or equal to 0.2 mm.

7. An optical connector, characterized in that: The optical connector is equipped with the ferrule according to any one of claims 1 to 6.

8. A method for manufacturing an optical connector, which is a method for manufacturing an optical connector equipped with a ferrule according to any one of claims 1 to 6, characterized in that: include: An optical fiber insertion step of inserting the plurality of optical fibers into the optical fiber insertion holes respectively; a protective cover inserting step of inserting a protective cover for the optical fiber into the protective cover insertion hole; as well as The installation step is to install the ferrule in the connector housing.

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