Ferrule, optical connector, and method for manufacturing the ferrule

Abstract

To provide a ferrule which is thin and in which no crack is generated, and an optical connector which has the ferrule and a boot for a ferrule.SOLUTION: There is provided a ferrule 100 comprising on a front end face 100a, fiber holes 20, 25 into which a plurality of optical fibers is inserted, and on a rear end face 100b, a boot insertion hole 35 of a boot insertion part 30 into which a boot 102 for a ferrule is inserted, where the optical fibers are inserted into the boot for a ferrule. The ferrule 100 has an internal space for communicating the fiber hole 20 with the boot insertion hole 35, and has on one surface, an adhesive agent filling window 55 for an adhesive agent filling part 50 for filling an adhesive agent in the internal space, where a width of the ferrule 100 of the boot insertion part 30 is greater than a width of the ferrule body 10, a ratio of the width and a height of the ferrule 100 on the boot insertion part 30 is 5 times or greater, and a thinnest thickness of the ferrule 100 around the boot insertion hole 35 is 0.32 mm or greater.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an optical connector including a ferrule that optically connects optical fibers of an optical cable that transmits optical signals, and a ferrule boot that holds the optical fiber and is inserted and fixed into the ferrule, and a method for manufacturing the ferrule. [Background technology]

[0002] 2. Description of the Related Art Optical fiber cables using optical fibers are capable of transmitting large amounts of information at high speeds, and are therefore widely used for information communication in both domestic and industrial applications. For example, Patent Document 1 (JP 2004-020962 A) discloses an optical connector that, when fixing an optical fiber tape to the ferrule of the optical connector, can pour adhesive resin evenly into the optical fiber tape insertion hole of the ferrule without generating air bubbles.

[0003] The optical connector described in Patent Document 1 comprises a cylindrical boot for protecting an optical fiber tape covering multiple optical fibers, and a ferrule having a boot insertion hole for attaching the boot, an optical fiber tape insertion hole communicating with the boot insertion hole, and multiple optical fiber holes for multiple optical fibers communicating with the optical fiber tape insertion hole.The optical connector is formed by inserting multiple optical fibers into the optical fiber holes and inserting the boot with the optical fiber tape inserted into the boot insertion hole, and filling an adhesive resin through a window hole provided at the top of the optical fiber tape insertion hole, and a sloped portion is provided in the optical fiber tape storage portion of the fiber tape insertion hole.

[0004] Patent Document 2 (JP 2007-279576 A) discloses an optical connector that can reduce the bending force of an optical fiber by using a boot that has sufficient flexibility while preventing leakage of adhesive, and a manufacturing method for easily manufacturing this optical connector.

[0005] The optical connector described in Patent Document 2 is an optical connector in which an optical fiber is inserted into a fiber insertion hole of a ferrule and fixed with an adhesive, and is characterized by having a resin material portion that is injected in a liquid state into the rear end side of the ferrule and has elasticity when solidified.

[0006] Patent Document 3 (JP Patent Publication 2001-108867 A) discloses a ferrule for an MT optical connector that has high precision and shape stability.

[0007] The ferrule described in Patent Document 3 is a ferrule for a multi-core optical connector made of plastic and using a mating pin alignment system, with guide pin holes formed on both the left and right sides of multiple horizontally arranged optical fiber holes, and is characterized by the fact that the middle part between the left and right guide pin holes is thin-walled symmetrically from top to bottom.

[0008] Patent Document 4 (JP Patent Publication 2001-264585A) discloses a ferrule for an optical connector that is designed to improve the ease of assembly work.

[0009] The ferrule for optical connector described in Patent Document 4 has a guide hole for inserting a guide pin, and has an optical fiber insertion portion extending inward from an optical connection port formed on the front end face side, and is characterized in that convex portions are formed on the front end face side in correspondence with the number of optical connection ports, and the optical connection ports are located at the tops of the convex portions.

[0010] Patent Document 5 (Utility Model Registration No. 3222482) discloses a ferrule and optical connector that can prevent cracks from occurring in a boot insertion portion where a ferrule boot is inserted and chipping damage caused by cracks.

[0011] The ferrule described in Patent Document 5 is a ferrule having a front end face provided with a number of fiber holes for inserting a number of optical fibers respectively, and a boot insertion portion provided at the rear end for attaching a ferrule boot through which a number of optical fibers are inserted, the boot insertion portion being configured to open in communication with the rear end face and a portion of the top face of the ferrule, and boot holding portions for holding the ferrule boot are provided on both widthwise sides of the opening. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2004-020962 A [Patent Document 2] JP 2007-279576 A [Patent Document 3] JP 2001-108867 A [Patent Document 4] JP 2001-264585 A [Patent Document 5] Utility Model Registration No. 3222482 Summary of the Invention [Problem to be solved by the invention]

[0013] Optical cables were previously used to connect information and communication devices that were far apart, but as information and communication devices have become faster and more dense, optical cables are now often used for the internal wiring of information and communication devices.In such cases, the optical connectors that connect the optical cables together are often placed at the ends of the PC boards of the information and communication devices or on the PC boards themselves, which has made it necessary to make the optical connectors or the ferrules that make up the optical connectors thinner.

[0014] However, the optical fiber in the optical cable is weak against bending, and if it is bent at a sharp angle, the optical transmission loss increases and it may even be destroyed. For this reason, optical connectors are equipped with a boot made of flexible and elastic rubber or resin on the rear end side where the optical cable is connected, and the optical cable is inserted into this boot to prevent the increase in optical transmission loss and the destruction of the optical fiber. In this case, at the part of the optical connector at the rear end where the boot is provided, the optical cable must be inserted through the boot, and then the boot with the optical cable inserted through it must be inserted into the ferrule. This means that the height of the ferrule is inevitably large at the boot insertion part of the ferrule, making it difficult to realize a thin ferrule.

[0015] In the optical connector described in Patent Document 1, the ferrule in the boot insertion hole portion has a flange shape, and as a result, the height of the ferrule is high at the boot insertion hole (see Figures 1 and 6). And, by providing the ferrule in the boot insertion hole portion with a flange shape, the thickness of the ferrule in the boot insertion hole portion is increased, and the occurrence of cracks in the ferrule in this portion and chipping damage due to cracks are prevented. Optical connectors with this flange-shaped ferrule present no problem when used to connect optical cables to link information and communication devices that are far apart. However, when the optical connector is placed at the end of the PC board of the information and communication device or on the PC board itself, it can become an obstacle to increasing the density of information devices. Furthermore, even in the case of a ferrule with a flange, there is a thin portion of the ferrule between the flange and the adhesive filling window, which may cause cracks and chipping breakage due to the cracks.

[0016] The ferrule in the resin material filling area (corresponding to the boot insertion hole) of Patent Document 2 (see Figure 4), the flange portion of Patent Document 3 (see Figure 1), and the ferrule in the boot insertion hole of Patent Document 3 (see Figure 4) all have a flange shape, which is advantageous in preventing the occurrence of cracks in the ferrule in this area and chipping breakage due to cracks, but can sometimes be an obstacle to increasing the density of information equipment.

[0017] On the other hand, in the ferrule of Patent Document 5, the boot insertion portion has an opening at the top, and the boot is held in the boot insertion portion by forming a boot retaining portion consisting of a pair of protrusions on both widthwise sides of the opening. When the ferrule is made thinner and the flange shape of the boot insertion portion is eliminated, the ferrule structure tends to become thinner and its strength decreases. As a result, when the ferrule boot is inserted, cracks are likely to occur, especially between the boot insertion portion of the ferrule (boot window) and the adhesive filling portion, which can cause chipping and breakage. In contrast, in the ferrule of Patent Document 5, by opening the top surface of the boot insertion portion, it is possible to prevent cracks from occurring in the boot insertion portion and chipping damage caused by cracks when the ferrule boot is inserted. However, because the boot is made of flexible and elastic rubber or resin to prevent the optical fiber from being bent at a sharp angle, even if the side of the boot is held by the boot holding portion, when force is applied to the optical fiber cable, the boot may deform and the boot holding portion may not be able to hold it adequately.

[0018] An object of the present invention is to provide a thin ferrule that can accommodate the increasing density of information equipment and that does not generate cracks during the ferrule manufacturing process or when a ferrule boot is inserted, and a method for manufacturing the ferrule. Another object of the present invention is to provide an optical connector comprising a thin, crack-free ferrule, and a ferrule boot, through which a plurality of optical fibers can be inserted, which can protect the optical fibers from bending at sharp angles, and which can be inserted into the thin, crack-free ferrule. [Means for solving the problem]

[0019] (1) According to one aspect, a ferrule has a front end surface provided with a plurality of fiber holes for inserting a plurality of optical fibers respectively, and a rear end surface provided with a boot insertion hole of a boot insertion section for inserting a ferrule boot through which the plurality of optical fibers are passed, the ferrule has an internal space communicating with the plurality of fiber holes and the boot insertion hole, and is provided on one surface opposing in the vertical direction with an adhesive filling window of an adhesive filling section for filling the internal space with adhesive, the width of the ferrule at the boot insertion portion is greater than the width of the ferrule body, the ratio of the width to the height of the ferrule at the boot insertion portion is 5 times or more, and the thickness of the ferrule around the boot insertion hole is 0.32 mm or more at its thinnest part.

[0020] Here, the direction connecting the front end surface and the rear end surface is defined as the length direction, the direction perpendicular to the length direction is defined as the width direction, and the direction perpendicular to the length direction and the width direction is defined as the up-down direction. Moreover, it is preferable that the thickness of the ferrule around the boot insertion hole at its thinnest portion is 0.32 mm or more and 0.40 mm or less. In the case of a ferrule having a flange on its rear end face, the height of the ferrule at the boot insertion portion corresponds to the height of the ferrule other than the flange, the thinnest part of the ferrule corresponds to the thin part between the flange and the adhesive filling window, and the internal space corresponds to the combined part of the adhesive filling window and the boot insertion hole when viewed from above.

[0021] In recent optical communications, multi-core ferrules that are small and allow for high density have been widely used. In this case, in order to achieve further miniaturization and high density, it is preferable that the internal space of the ferrule is capable of storing high density multi-core fibers, and that the external dimensions of the ferrule are as small and flat as possible. However, when using a thin ferrule in which the ratio of width to height of the ferrule at the boot insertion portion is 5 times or more, in order to insert a ferrule boot into the boot insertion portion, it is necessary to make the ferrule as thin as possible in thickness to ensure the height of the boot insertion hole. However, when the ferrule thickness is thin, 1) Cracks occur when ultrasonically cleaning the resin after molding. 2) There is an issue that the ferrule may crack if you press the ferrule with your finger when inserting the ferrule boot with the fiber inserted through it. In a ferrule according to one aspect, by making the wall thickness of the ferrule 0.32 mm or more at the thinnest part, the occurrence of cracks can be preferably prevented even in a small, high-density ferrule.

[0022] (2) A ferrule according to a second aspect of the present invention may be made of PPS resin, the height of the ferrule may be 1.24 mm or more and 1.40 mm or less, and the height of the boot insertion hole of the boot insertion portion may be 0.50 mm or more and 0.70 mm or less.

[0023] Since small, high-density multi-fiber ferrules require extremely high positional and dimensional precision, it is preferable to use polyphenylene sulfide (PPS) resin. In this case, the thinning of the ferrule and the physical strength of the boot insertion part are contradictory issues, so it is important to select the optimal ferrule height and the height of the boot insertion hole of the ferrule. That is, in a thin ferrule made of PPS and having a height of 1.24 mm or more and 1.4 mm or less, it is preferable that the height of the boot insertion hole be 0.50 mm or more and 0.70 mm or less in order to make the wall thickness 0.32 mm or more. If the height of the boot insertion hole is less than the lower limit, the height of the boot inserted into the boot insertion hole will be too low, making it difficult to manufacture a boot that allows the optical fiber to be inserted smoothly.If the height of the boot insertion hole exceeds the upper limit, it will be difficult to ensure the wall thickness of the ferrule, which may cause problems.

[0024] (3) The ferrule according to the third invention may be the ferrule according to the first aspect to the second invention, wherein the ejection pin mark of the ferrule is located on the other surface facing in the vertical direction and in a portion that does not overlap with the internal space in top view.

[0025] Ferrules are formed, for example, by molding a resin material filled with an inorganic filler, but if the ejection pin during resin molding is provided at a position that corresponds to the internal space of the ferrule when viewed from above, the ferrule may crack when ejected because the ferrule at the portion that corresponds to the internal space is thin. Even if there are no obvious cracks on the outside of the ferrule, there may be internal cracks inside the ferrule, which may reduce the durability of the ferrule. In the ferrule of the third invention, the eject pin is positioned on the other surface facing upward and downward (the other surface facing the adhesive filling window) in a portion that does not overlap with the internal space when viewed from above, thereby preventing the occurrence of cracks during ejection.

[0026] (4) A ferrule according to a fourth aspect of the present invention is the ferrule according to any one of the first to third aspects of the present invention, wherein a corner of the adhesive filling window on the rear end face side may be provided with a radius of 0.3 mm or more.

[0027] When the ferrule is pressed with a finger or when the ferrule is ultrasonically cleaned, cracks are likely to occur at the corners on the rear end face of the adhesive filling window. In the ferrule according to the fourth invention, the corners on the rear end face of the adhesive filling window are rounded with a radius of 0.3 mm to avoid stress concentration and prevent cracks from occurring in this area.

[0028] (5) A ferrule according to a fifth aspect of the present invention is the ferrule according to any one of the first to fourth aspects of the present invention, wherein the boot insertion hole has four corners each having a radius of 0.1 mm or more.

[0029] The four corners of the boot insertion hole are prone to cracks during ultrasonic cleaning and when inserting the ferrule boot. In the ferrule according to the fifth aspect of the invention, the boot insertion hole has four corners each having a radius of 0.1 mm, thereby preventing cracks from occurring in this area.

[0030] (6) An optical connector according to another aspect includes a ferrule according to any one of the first to fifth aspects of the present invention, and a ferrule boot that holds a plurality of optical fibers arranged in the ferrule and is inserted and fixed into a boot insertion portion of the ferrule, the ferrule boot being formed from ABS resin.

[0031] Conventional ferrule boots are made of synthetic resins such as rubber and elastomers that have flexibility and elasticity. This is because the ferrule boot is placed around the outer periphery of the optical fiber cable, and prevents problems such as increased optical transmission loss caused by the optical fiber cable being bent at a steep angle or the optical fiber being broken due to a load in the bending direction imposed on the optical fiber cable when a connector is inserted or removed or the optical fiber cable is repeatedly bent. However, in a small and thin ferrule such as that of the present invention, the height of the boot insertion hole is low, so the height of the boot is also low. On the other hand, since the optical fiber needs to be inserted into the boot, a fiber insertion hole needs to be provided inside the boot. Therefore, the thickness of the ferrule boot is thin. In this case, it is difficult to mold a thin boot using conventional rubber, elastomer, etc. Even if a thin boot with a low height can be molded, the boot has an optical fiber insertion hole for inserting the optical fiber ribbon, and the walls of the insertion hole may adhere to each other, making it impossible to insert the optical fiber ribbon.

[0032] In an optical connector according to another aspect, ABS resin is used as a material having the flexibility required for protecting an optical fiber and the rigidity required for forming a thin boot. ABS resin has a tensile breaking strength of 40-50 MPa and a flexural modulus of 2000-2500 MPa, providing the rigidity and flexibility required for use as a boot material. This makes it possible to reliably mold a small, thin boot and prevent problems caused by adhesion of the insertion holes of the optical fiber ribbon.

[0033] (7) An optical connector according to a seventh aspect of the present invention is an optical connector according to another aspect, wherein the ferrule boot has an optical fiber insertion hole for inserting a plurality of optical fibers, and the thickness of the ferrule boot around the optical fiber insertion hole may be 0.15 mm or more at its thinnest part.

[0034] In this case, by setting the thickness to 0.15 mm, the height of the light insertion hole of the ferrule boot can be set to 0.3 mm. Also, by using ABS resin, a ferrule boot with a thickness of 0.15 mm can be stably molded.

[0035] (8) A method for manufacturing a ferrule according to still another aspect is a method for manufacturing a ferrule according to the first to fifth aspects of the present invention, and includes a resin molding step of molding a semi-finished ferrule having gates protruding from both widthwise ends of the boot insertion portion of the ferrule, an ejection step of ejecting the semi-finished ferrule by providing ejection pin positions on the other side of the gate and on the other side of a portion of the ferrule body that does not overlap with the internal space in a top view, and a cutting step of cutting off the gate from the semi-finished ferrule.

[0036] In order to prevent cracks from occurring during ejection, it is necessary to position the ejection pin in a portion that does not overlap with the internal space when viewed from above. However, because the area of ​​the portion that does not overlap with the internal space on the boot insertion side of the ferrule is small, it is difficult to position the ejection pin in a portion that does not overlap with the internal space. For this reason, in a ferrule manufacturing method according to another aspect, an ejection pin is positioned on the other side of the gate protruding from both widthwise ends of the boot insertion portion and on the other side of the ferrule body in a portion that does not overlap with the internal space (the adhesive filling window and the boot insertion hole in top view), thereby achieving an ejection process that enables smooth ejection and prevents the occurrence of cracks during ejection. [Brief description of the drawings]

[0037] [Figure 1] FIG. 2 is a schematic perspective view of a ferrule according to the first embodiment. [Diagram 2] FIG. 2(A) is a schematic top view of the ferrule of the first embodiment, FIG. 2(B) is a schematic side view seen from the left side, FIG. 2(C) is a schematic side view seen from the right side, and FIG. 2(D) is a schematic cross-sectional view of the A-A' plane in FIG. 2(A). [Diagram 3] FIG. 3(A) is a schematic top view of a ferrule of a modified example, FIG. 3(B) is a schematic side view as viewed from the left side, and FIG. 3(C) is a schematic side view as viewed from the right side. [Figure 4] FIG. 1 is a schematic exploded perspective view showing a configuration of an optical connector according to a first embodiment. [Diagram 5] 3 is a schematic cross-sectional view of the optical connector taken along a plane corresponding to the AA' plane in FIG. 2(A). [Figure 6] FIG. 6(A) is a schematic top view of the ferrule boot of the first embodiment, FIG. 6(B) is a schematic side view as viewed from the left side, and FIG. 6(C) is a schematic side view as viewed from the front side. [Figure 7] Figure 7(A) is a schematic top view of a modified ferrule boot, Figure 7(B) is a schematic side view seen from the left side, Figure 7(C) is a schematic side view seen from the right side, and Figure 7(D) is a schematic side view seen from the front. [Figure 8] 4 is a photograph of the ferrule of the embodiment taken from the rear end side. [Figure 9] 1 is a photograph of a ferrule of a comparative example taken from the rear end side. [Figure 10] FIG. 1 is a schematic diagram showing the position of an ejector pin on a top view of a semi-finished ferrule with a gate remaining. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals, and their names and functions are also the same, so detailed description thereof will not be repeated.

[0039] <First embodiment> (Ferrule 100) Fig. 1 is a schematic perspective view showing a ferrule 100 of the first embodiment. Also, Fig. 2(A) is a schematic top view of the ferrule 100 of the first embodiment, Fig. 2(B) is a schematic side view seen from the left side, Fig. 2(C) is a schematic side view seen from the right side, and Fig. 2(D) is a schematic cross-sectional view of the A-A' plane of Fig. 2(A).

[0040] 1 and 2, the ferrule 100 of this embodiment includes a ferrule body 10, a plurality of optical fiber holes 20 whose tips (connection end faces) open on a front end face 100a of the ferrule 100 and into which the portions of the optical fibers from which the coating has been removed are inserted, positioned, and fixed, a plurality of parallel fiber guide holes 25 that communicate with the rear ends of the plurality of optical fiber holes 20, and a plurality of parallel U-shaped or V-shaped fiber guide grooves 40 that communicate with the rear ends of the plurality of fiber guide holes 25 and are provided on the rear end side of the ferrule body 10. The ferrule 100 also includes a boot insertion section 30 for mounting a ferrule boot through which an optical fiber is inserted, an adhesive filling section 50 for injecting an adhesive for fixing the optical fiber to the ferrule body 10, and two guide pin holes 60 formed in the vicinity of both ends in the width direction parallel to the plurality of optical fiber holes 20 and for inserting guide pins.

[0041] The boot insertion section 30 has a boot insertion hole 35 opening in the rear end face 100b of the ferrule 100, and the adhesive filling section 50 has an adhesive filling window 55 opening in the upper face of the ferrule body 10. The ferrule 100 also has an internal space that communicates the optical fiber hole 20 and the fiber guide hole 25 with the boot insertion hole 35. The eject pin mark 36a in Fig. 2 is a mark that is generated when the ferrule 100 is ejected from the mold during the manufacturing process of the ferrule 100. The eject pin mark 36a may be one that can be confirmed visually from the outside, or one that can be ascertained from the internal structure (density, etc.) of the resin. In the description of this specification, the direction connecting the front end face 100a and the rear end face 100b (the left-right direction in FIG. 2(A)) is the length direction, the direction perpendicular to the length direction (the up-down direction in FIG. 2(A)) is the width direction, and the direction perpendicular to the length direction and the width direction is the up-down direction.

[0042] 1 and 2, the width of the ferrule 100 is greater in the boot insertion section 30 than in the ferrule body 10 in which the multiple optical fiber holes 20 and the fiber guide holes 25 are provided. This is because the boot insertion section 30 has a boot insertion hole 35 for inserting a ferrule boot 102 (see FIG. 3) therein, and stress is applied when the ferrule boot 102 is inserted. Many conventional ferrules 100 have a so-called brim shape, in which the thickness of the ferrule 100 is increased also in the vertical direction of the boot insertion portion 30 in order to increase the physical strength of the boot insertion portion 30. Providing a brim shape is effective as a measure against stress when inserting the ferrule boot 102, but even in the case of ferrules 100 with a brim shape, the thickness of the ferrule 100 is thin in the vicinity of the adhesive filling window 55, and cracks often occur in this portion during ultrasonic cleaning after resin molding, so it is not a sufficient measure against cracks.

[0043] The ferrule 100 is becoming thinner and more multi-core to accommodate the increasing density of information devices. The ferrule 100 of this embodiment has 12 cores, a maximum width of 7.00 mm, and a height of 1.25 mm. Therefore, the ratio of width to height is 5.6. The ferrule 100 having such a shape 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 these, it is preferable to use polyphenylene sulfide (PPS) resin from the viewpoints of positional accuracy, dimensional accuracy, molding shrinkage rate, and thermal stability. This makes it possible to make a ferrule with low connection loss even when compact and high-density mounting is performed. Also, the inorganic filler can be, for example, granular silica. Although the strength of the ferrule can be improved by filling it with an inorganic filler, in a thin ferrule 100 with a width-to-height ratio of 5 or more, the thickness of the ferrule 100 around the boot insertion hole 35 is thin, and cracks are likely to occur in this portion. Furthermore, among the thin parts of the ferrule 100, the corners of the opening are particularly prone to stress concentration and cracking. Therefore, a rounded shape with a radius of 0.3 mm is provided at the corner on the rear end face 100b side of the adhesive filling window 55, and the four corners of the boot insertion hole 35 are also provided with rounded shapes with a radius of 0.1 mm. This makes it possible to effectively disperse stress and other stresses while ensuring the wall thickness. In this embodiment, the parts with the thinnest wall thickness are the periphery of the opening of the boot insertion hole 35 and / or the periphery of the opening of the adhesive filling window 55, and cracks are particularly likely to occur near the four corners of the opening.

[0044] (Modification of Ferrule 100) FIG. 3(A) is a schematic top view of a modified ferrule 100, FIG. 3(B) is a schematic side view seen from the left side, and FIG. 3(C) is a schematic side view seen from the right side. The ferrule 100 in Fig. 2 is a so-called Slim & Short ferrule with a height of 1.25 mm and a length of 4 mm, while the ferrule 100 in Fig. 3 is a Slim ferrule with a height of 1.25 mm and a length of 8 mm. Also, the ferrule in Fig. 2 has 12 cores, while the ferrule in Fig. 3 has 16 cores. The present invention can also be applied to a 16-core Slim & Short ferrule or a 12-core Slim ferrule.

[0045] (Optical Connector 200) Fig. 4 is a schematic exploded perspective view of an optical connector 200 including a ferrule 100 and a ferrule boot 102 when an optical fiber cable 101 is inserted into the optical connector 200, and Fig. 5 is a schematic cross-sectional view of the optical connector 200 with the optical fiber cable 101 inserted therein, cut along a plane corresponding to the A-A' plane in Fig. 2(A). The ferrule boot 102 is inserted and fixed into the boot insertion portion 30 of the ferrule 100 while allowing the optical fiber cable 101 to pass through. The optical fiber cable 101 becomes a bare fiber 101a in the internal space of the ferrule 100 at a position where it has passed through the tip side of the ferrule boot 102, and reaches the front end face 100a of the ferrule 100 via the fiber guiding groove 40, the fiber guiding hole 25, and the optical fiber hole 20.

[0046] (Ferrule boots 102) Fig. 6(A) is a schematic top view of the ferrule boot 102, Fig. 6(B) is a schematic side view seen from the left side, and Fig. 6(C) is a schematic side view seen from the front side. The ferrule boot 102 has an optical fiber insertion hole 102a for inserting the optical fiber cable 101. The height of the optical fiber insertion hole 102a corresponds to the height of the optical fiber cable 101, and is about 0.3 mm. The thickness of the ferrule boot 102 is determined by the height of the ferrule boot 102, and the height of the ferrule boot 102 is approximately equal to the height of the boot insertion hole. For example, when the height of the boot insertion hole 35 is 0.80 mm, the thickness of the ferrule boot 102 is 0.25 mm, and when the height of the boot insertion hole 35 is 0.60 mm, the thickness of the ferrule boot 102 is 0.15 mm. Naturally, if the height of the boot insertion hole is low, the thickness of the ferrule boot 102 becomes thin, making it difficult to mold the ferrule boot 102. In addition, the larger the opening width and the lower the opening height of the optical fiber insertion hole 102a, the more likely the wall surfaces constituting the optical fiber insertion hole 102a will adhere to each other. Therefore, even if the ferrule boot 102 can be molded, the walls of the optical fiber insertion hole 102a may adhere over time, making it impossible to insert the optical fiber ribbon.

[0047] The conventional ferrule boot 102 is made of synthetic resin such as rubber or elastomer having flexibility and elasticity. This is because the ferrule boot 102 is disposed around the outer periphery of the optical fiber cable 101, and is intended to prevent inconveniences such as an increase in optical transmission loss caused by a load being applied to the optical fiber cable 101 in the bending direction due to insertion / removal operations of the optical connector 200 or repeated bending of the optical fiber cable 101, causing the optical fiber cable 101 to bend at a sharp angle or break. However, in a thin ferrule 100 such as that of the present invention, the height of the boot insertion hole 35 is low, and therefore the height of the ferrule boot 102 is also low. On the other hand, since the optical fiber cable 101 needs to be inserted into the ferrule boot 102, it is necessary to provide an optical fiber insertion hole 102a therein. Therefore, the thickness of the ferrule boot 102 is thin. In this case, it is difficult to form a thin boot using conventional rubber, elastomer, or the like.

[0048] In this embodiment, ABS resin is used as a material that has the flexibility required to protect the optical fiber and the rigidity required to form the thin ferrule boot 102. ABS resin has a tensile breaking strength of 40-50 MPa and a flexural modulus of 2000-2500 MPa, and thus has both the rigidity and flexibility required for the material of the ferrule boot 102. This makes it possible to reliably mold a small, thin boot and to prevent problems caused by adhesion of the insertion hole of the optical fiber ribbon.

[0049] Fig. 7 shows a modified example of the ferrule boot 102. Fig. 7(A) is a schematic top view of the ferrule boot 102, Fig. 7(B) is a schematic side view seen from the left side, Fig. 7(C) is a schematic side view seen from the right side, and Fig. 7(D) is a side view seen from the front side. The height of the optical fiber insertion hole 102a is about 0.3 mm. 7, the insertion portion 102b to be inserted into the boot insertion hole 35 of the ferrule 100 has a thickness of 0.15 mm, and can be inserted into the boot insertion hole 35 having a height of 0.60 mm. On the other hand, the protruding portion 102c protruding from the boot insertion hole 35 of the ferrule 100 may have a large thickness, for example, 0.25 mm. In the modified example of ferrule boot 102 in FIG. 7, the thickness of protrusion 102c is increased, thereby improving the physical strength of ferrule boot 102 when optical fiber cable 101 is bent.

[0050] (Examples and Comparative Examples of Ferrule 100) An example and a comparative example of the ferrule 100 will be described below. [Example 1] Fig. 8 is a photograph of the ferrule 100 of Example 1 viewed from the rear end side. The ferrule 100 in Fig. 8 is injection molded from PPS resin, and is a thin ferrule with a width of 7.0 mm at the boot insertion portion 30, a width of 6.40 mm at the ferrule body 10, and a height of 1.25 mm, with the width-to-height ratio being 5.6 times at the boot insertion portion 30 and 5.12 times at the ferrule body 10. The thickness of the ferrule 100 around the boot insertion hole 35 is 0.325 mm, and the height of the boot insertion hole 35 is 0.60 mm and the width is 3.60 mm. Furthermore, the four corners of boot insertion hole 35 are rounded with a radius of 0.1 mm. Although it cannot be seen in Fig. 8, in ferrule 100 of Example 1, the corners of adhesive filling window 55 on the rear end face 100b side are rounded with a radius of 0.3 mm.

[0051] 8, in the ferrule 100 of Example 1, no cracks were observed even at the four corners of the boot insertion hole 35 where cracks are likely to occur. Furthermore, although cracks often occur during ultrasonic cleaning, in the ferrules 100 of Example 1, even when the ferrules 100 were subjected to ultrasonic cleaning at 100% ultrasonic output for a total of 300 ferrules 100, not a single ferrule had a crack.

[0052] [Comparative Example 1] Fig. 9 is a photograph of the ferrule 100 of Comparative Example 1 as viewed from the rear end side. The ferrule 100 of Fig. 9 is molded in the same manner as the ferrule 100 of Example 1, and is a thin ferrule with a boot insertion portion 30 having a width of 7 mm, a ferrule body 10 having a width of 6.4 mm, and a height of 1.25 mm, with the ratio of width to height being 5.6 times for the boot insertion portion 30 and 5.12 times for the ferrule body 10. However, the height of the boot insertion hole 35 is high at 0.8 mm, and as a result, the thickness of the ferrule 100 around the boot insertion hole 35 is thin at 0.225 mm. The width of the boot insertion hole 35 is 3.6 mm. Further, neither the four corners of boot insertion hole 35 nor the corner of adhesive filling window 55 on the rear end surface 100b side is provided with a rounded shape.

[0053] 9, the ferrule 100 of Comparative Example 1 had a crack at the corner of the boot insertion hole 35 (arrow), and there is a high possibility that chipping and breakage due to the crack will occur during use. As in Example 1, ultrasonic cleaning was performed on a parameter set of 300 ferrules 100 of Comparative Example 1. However, since it was expected that the ferrules 100 of Comparative Example 1 would crack due to the ultrasonic cleaning, ultrasonic cleaning was performed with the ultrasonic output reduced to 50%. However, cracks were still observed in 46% of the ferrules 100 of Comparative Example 1.

[0054] When comparing Example 1 with Comparative Example 1, a) The wall thickness of the ferrule 100 around the boot insertion hole 35 is 0.1 mm thick. b) The difference is that the boot insertion hole 35 has four corners each having an R shape. Therefore, the reason why no cracks occur in the ferrule 100 of Example 1 is believed to be because the wall thickness of the ferrule 100 is 0.1 mm thick and / or because the four corners of the boot insertion hole 35 are rounded. As another comparative example, the inventors have also investigated the case where only the thickness of the ferrule 100 is increased, and in that case too, a significant improvement in crack occurrence was observed. Therefore, it is most effective to increase the thickness of the ferrule 100. Furthermore, by providing an R shape to the four corners of the boot insertion hole 35, it is possible to prevent stress concentration at the four corners and enhance the effect of preventing crack occurrence.

[0055] In addition, in the ferrule 100 of Example 1, the corner of the adhesive filling window 55 on the side of the rear end face 100b is rounded with a radius of 0.3 mm or more. By rounding this corner, the occurrence of cracks can be suppressed when the ferrule is pressed with a finger, for example. From the above results, in a thin ferrule with a height of 1.25 mm and a width-to-height ratio of ferrule 100 at boot insertion portion 30 of 5 or more, the thickness of ferrule 100 around boot insertion hole 35 must be 0.32 mm or more at its thinnest part. Furthermore, it is desirable to provide the four corners of boot insertion hole 35 with a R shape with a radius of 0.1 mm or more, and to provide the corner of adhesive filling window 55 on the rear end face 100b side with a R shape with a radius of 0.3 mm or more.

[0056] (Examples and Comparative Examples of Ferrule Boots 102) [Example 2] The shape of the ferrule boot 102 of the second embodiment is as shown in FIG. 6 or FIG. 7, and has a height of 0.6 mm, a thickness of the thinnest part of 0.15 mm, and an opening of the optical fiber insertion hole 102a of 0.3 mm so that it can be inserted into the boot insertion hole 35 having a height of 0.6 mm. The ferrule boot 102 of Example 2 is resin molded from ABS resin with higher rigidity. Specifically, Techno ABS350 from Techno Polymer Co., Ltd. is used as the molding resin. Techno ABS350 is a resin with higher rigidity than elastomers that have been used as resins for the ferrule boot 102 in the past. Techno ABS350 has, for example, a flexural modulus (ASTM D790) of 2350 MPa and a tensile breaking strength (ASTM D638) of 41.2 MPa. Note that ASTM is a standard established by ASTM International, the world's largest standardization organization. By using Techno ABS350 as the molding resin, it was possible to stably mold the ferrule boot 102 with a thickness of 0.15 mm at its thinnest point and an opening of 0.3 mm from the resin, and the optical fiber cable 101 could be reliably inserted even when assembling the optical connector 200.

[0057] [Comparative Example 2] The shape of the ferrule boot 102 of Comparative Example 2 is such that, in FIG. 6, the height is 0.8 mm, the thickness at the thinnest part is 0.25 mm, and the opening is 0.3 mm. The ferrule boot 102 of Comparative Example 2 can be resin molded using an elastomer as in the conventional case. For example, Pelprene (registered trademark) P90BD (manufactured by Toyobo) can be used as the resin. P90BD has physical properties such as a flexural modulus (ASTM D790) of 162 MPa and a tensile breaking strength (ASTM D638) of 31 MPa, making it easy to bend and somewhat prone to breaking. The ferrule boot 102 of Comparative Example 2 can be stably molded from resin, but since the height of the boot insertion hole 35 of the ferrule 100 of Example 2 is 0.6 mm, it cannot be combined with the ferrule 100 of the Example to form the optical connector 200.

[0058] [Comparative Example 3] The shape of the ferrule boot 102 in Comparative Example 3 is the same as that in the embodiment. However, in Comparative Example 3, Pelprene (registered trademark) P90BD was used as the molding resin, as in Comparative Example 2. However, when the resin was molded into the same shape as in Example 2, the shape after molding was not stable, and the optical fiber cable 101 could not be inserted reliably.

[0059] From the above results, a boot to be combined with a thin ferrule 100 having a boot insertion hole 35 with a height of 0.6 mm needs to have a wall thickness of 0.15 mm and be molded using a highly rigid resin such as ABS resin.

[0060] (Method of manufacturing ferrule 100) FIG. 10 is a schematic diagram showing an ejector pin position 36 on a top view of a semi-finished ferrule with a gate 37 remaining. The ferrule 100 is manufactured by resin molding. In this case, the injected resin is filled into the mold via the gate 37 and resin molded, and then the resin-molded semi-finished ferrule is ejected from the mold by an ejection pin, and finally the gate is cut off from the main body of the ferrule 100, completing the ferrule 100. In the conventional ferrule 100, all of these eject pin positions 36 were located in the main body of the ferrule 100. However, in the ferrule 100 of this embodiment, if the eject pin positions 36 overlap with the internal space that communicates between the fiber guide hole 25 and the boot insertion hole 35 in a top view, the wall thickness of the ferrule in the internal space is thin, and so a crack occurs in the semi-finished ferrule during ejection. Meanwhile, as can be seen from Fig. 10, it is difficult to locate the eject pin positions 36, particularly on the rear end face 100b side, in a portion that does not overlap with the internal space (outside the boot insertion hole 35 in Fig. 10).

[0061] In the manufacturing method of the ferrule 100 of this embodiment, the eject pin position 36 on the front end face 100a side is positioned on the other side of the ferrule body 10, and the eject pin position 36 on the rear end face 100b side is positioned not on the boot insertion portion 30 but on the other side of the gates 37 protruding from both ends of the width direction of the boot insertion portion 30. This prevents the eject pin position 36 from overlapping with the internal space when viewed from above, and prevents cracks from occurring in the semi-finished ferrule during ejection. Furthermore, in the ferrule 100 manufactured by this manufacturing method, the ejection pin mark 36a does not overlap with the internal space (corresponding to the adhesive filling window and the boot insertion hole) when viewed from above.

[0062] In the present invention, optical fiber hole 20 and fiber guiding hole 25 correspond to the "fiber hole", front end face 100a corresponds to the "front end face", ferrule boot 102 corresponds to the "ferrule boot", boot insertion portion 30 corresponds to the "boot insertion portion", boot insertion hole 35 corresponds to the "boot insertion hole", rear end face 100b corresponds to the "rear end face", ferrule 100 corresponds to the "ferrule", adhesive filling portion 50 corresponds to the "adhesive filling portion", adhesive filling window 55 corresponds to the "adhesive filling window", ferrule body 10 corresponds to the "ferrule body", eject pin mark 36a corresponds to the "eject pin mark", optical connector 200 corresponds to the "optical connector", optical fiber insertion hole 102a corresponds to the "optical fiber insertion hole", gate 37 corresponds to the "gate", and eject pin position 36 corresponds to the "eject pin position".

[0063] Although a preferred embodiment of the present invention is as described above, the present invention is not limited thereto. It is understood that various other embodiments can be made without departing from the spirit and scope of the present invention. Furthermore, although the actions and effects of the configuration of the present invention are described in this embodiment, these actions and effects are merely examples and do not limit the present invention. [Explanation of symbols]

[0064] 10 Ferrule body 20 Optical fiber hole 25 Fiber guide hole 30 Boot Insert 35 Boot insertion hole 36 Eject pin position 36a Eject pin mark Gate 37 50 Adhesive filling section 55 Adhesive-filled window 100 Ferrules 100a Front end surface 100b Rear end surface 102 Ferrule boots 102a Optical fiber insertion hole 200 Optical Connector

Claims

1. A ferrule having a front end surface provided with a plurality of fiber holes for respectively inserting a plurality of optical fibers, and a rear end surface provided with a boot insertion hole of a boot insertion portion for inserting a ferrule boot having a plurality of optical fibers inserted therethrough, the ferrule has an internal space communicating with the plurality of fiber holes and the boot insertion hole, and has adhesive filling windows on opposing surfaces in a vertical direction for filling the internal space with an adhesive, a width of the ferrule at the boot insertion portion is greater than a width of a ferrule body in which the plurality of fiber holes are provided, The ratio of the width to the height of the ferrule at the boot insertion portion is 5 times or more; The thickness of the ferrule around the boot insertion hole is 0.32 mm or more at the thinnest portion, The ferrule has an ejection pin mark located on the other surface facing the upper and lower sides, in a portion that does not overlap the internal space in top view and does not overlap the fiber hole.

2. The ferrule is made of PPS resin, 2. The ferrule according to claim 1, wherein the height of the ferrule at the boot insertion portion is 1.24 mm or more and 1.40 mm or less, and the height of the boot insertion hole at the boot insertion portion is 0.50 mm or more and 0.70 mm or less.

3. 3. The ferrule according to claim 1, wherein a corner of said adhesive filling window on the side of said rear end face is rounded with a radius of 0.3 mm or more.

4. 4. The ferrule according to claim 1, wherein the boot insertion hole has four corners each having a radius of 0.1 mm or more.

5. A ferrule according to any one of claims 1 to 4; a ferrule boot that holds a plurality of the optical fibers arranged in the ferrule and is inserted and fixed in the boot insertion portion of the ferrule, The optical connector, wherein the ferrule boot is made of ABS resin.

6. The ferrule boot has a thick portion and a thin portion, The optical connector according to claim 5 , wherein the thin portion is inserted and fixed to the boot insertion portion of the ferrule.

7. the ferrule boot has optical fiber insertion holes through which the optical fibers are inserted, 7. The optical connector according to claim 5, wherein the thickness of the ferrule boot around the optical fiber insertion hole is 0.15 mm or more at the thinnest portion.

8. A method for producing a ferrule according to any one of claims 1 to 4, comprising the steps of: a resin molding process for molding a semi-finished ferrule having gates protruding from both ends of the boot insertion portion of the ferrule in a width direction; an ejection step of ejecting the semi-finished ferrule by providing ejection pin positions on the other surface of the gate that faces the gate in the up-down direction and on the other surface of a portion of the ferrule body that does not overlap the internal space in a top view; and a cutting step of cutting off the gate from the semi-finished ferrule.

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