Multi-fiber optical ferrule and optical connector

Abstract

To provide a multi-fiber optical ferrule which is connection compatible with a conventional optical connector, and to provide a multi-fiber optical connector.SOLUTION: A multi-fiber optical ferrule 100 holds a plurality of optical fibers for optical connection. The ferrule 100 comprises: a coated fiber insertion hole 110 to which coated optical fibers 200 are inserted by being bundled in one row; and an end surface opening 120 which is formed at a connection end surface of the optical fibers, and communicates with the coated fiber insertion hole. In the end surface opening 120, two opposing sides are formed flat in parallel to a row direction of the optical fibers, and a coating 220 of the optical fibers and an adhesive material 300 are formed such that they can be exposed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multi-core optical ferrule that optically connects optical fibers of an optical cable that transmits optical signals. [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 Patent Publication No. 2006-163210) discloses an optical fiber positioning method and optical connecting parts that are also applicable to the case where a narrow-pitch optical fiber ribbon is connected to an optical connecting part.

[0003] The optical connection part described in Patent Document 1 is composed of a connector body and a cover member. The connector body has a guide section having a groove that guides the optical fiber and restricts its position in the width direction, and a fiber hole connected to this guide section into which the tip of the optical fiber is inserted. The cover member is fitted and attached from above the groove of the connector body, pressing the optical fiber toward the groove and being movable along the groove.

[0004] Patent Document 2 (JP Patent Publication 2009-229506 A) discloses a ferrule for an optical connector that does not require a precise mold and can precisely and easily hold a plurality of optical fibers in a high-density arrangement. The ferrule for an optical connector described in Patent Document 2 is for positioning and holding an optical fiber tape strand having its optical fiber exposed by removing its coating, and the first housing portion has an opening, and positions and holds each optical fiber by filling the opening with an optical fiber holding material while the optical fiber is positioned by an optical fiber positioning member, and the second housing portion is fixed to the first housing portion and holds the optical fiber tape strand.

[0005] Patent Document 3 (JP 2019-066634 A) discloses a boot that enables a ribbon wire with a small pitch between adjacent optical fibers to be attached to a ferrule with a large pitch for the holes into which the optical fibers are inserted.

[0006] The boot described in Patent Document 3 is a boot for an optical connector, and has first and second end faces facing each other, a tape bare wire holding hole provided between the first and second end faces into which a tape bare wire is introduced, and a plurality of separated fiber holding holes that communicate with the tape bare wire holding hole and into which a plurality of coated optical fibers are respectively inserted, the first end face having an opening as an introduction port for the tape bare wire holding hole and the second end face having a plurality of openings arranged in a line corresponding to the plurality of separated fiber holding holes, and the center-to-center distance between two adjacent openings of the plurality of openings is greater than the diameter of each of the plurality of openings. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-163210 A [Patent Document 2] JP 2009-229506 A [Patent Document 3] JP 2019-066634 A Summary of the Invention [Problem to be solved by the invention]

[0008] The optical connection part described in Patent Document 1 allows the attachment of optical fibers with their coatings, but since it is necessary to insert the tips of the optical fibers into the fiber holes, as the number of fibers increases and the density increases and the fiber diameter decreases, it becomes difficult to insert the optical fibers, which increases the burden on the worker. In addition, positioning the optical fiber requires complex operations such as repeatedly using a cover member to press the optical fiber while feeding it forward, and then positioning it by checking that the positioning protrusion is in contact with the contact surface.

[0009] In the optical connector ferrule described in Patent Document 2, the optical fiber is coated up to the first housing part, but it is necessary to remove the coating before positioning the optical connector ferrule. Therefore, the coating of all optical fibers must be stripped, and as the number of fibers increases and the density increases and the fiber diameter decreases, the burden on the worker increases. In addition, if some coating remains on the optical fiber or if the shavings are not sufficiently removed, the connection loss may increase.

[0010] In the boot described in Patent Document 3, coated optical fibers are inserted up to the boot of the optical connector, but optical fibers (bare fibers) are inserted into the ferrule. Therefore, it is necessary to strip the coating from all optical fibers, and as the number of fibers increases and the density increases and the fiber diameter decreases, the burden on the worker increases.

[0011] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a multi-core optical ferrule which allows easy high-density optical connection. Another object of the present invention is to provide a multi-core optical ferrule which allows high density optical connection and does not require stripping the coating of the optical fibers. It is still another object of the present invention to provide a multi-core optical ferrule which allows high-density optical connection and has low connection loss without stripping the coating of the optical fibers. [Means for solving the problem]

[0012] (1) A multi-core optical ferrule according to one aspect is a multi-core optical ferrule for holding and optically connecting a plurality of optical fibers, and includes a coated fiber insertion hole into which coated optical fibers are inserted in a row, and an end face opening formed in the connection end face of the optical fiber and communicating with the coated fiber insertion hole, wherein two opposing sides of the end face opening are formed flat and parallel to the row direction of the optical fibers, and the end face opening is formed so that the coating and adhesive of the optical fiber can be exposed.

[0013] The optical fiber ribbons that are mainly used today are made by bundling many optical fiber strands in a row, and each optical fiber strand is protected by a coating of several tens of micrometers of ultraviolet-curing resin or the like on an optical fiber cladding such as quartz glass. Therefore, in order to optically connect multiple optical fibers, the coating must be removed from the ends of all the optical fibers using a special tool to leave them as bare fibers, and then all the bare fibers must be inserted into each fiber hole of the multi-core ferrule, positioned, and fixed. Here, if some coating remains on the optical fiber or the removal of shavings is insufficient, local bending of the optical fiber may occur, resulting in high connection loss. Such operations such as inserting and positioning optical fibers on the order of microns are performed by skilled workers. However, in recent years, there has been a demand for even higher density, speed, and capacity in communications, and as optical wiring becomes more and more multi-core and denser, and as the fiber diameter becomes smaller, it becomes more difficult to remove the resin coating and also becomes more difficult to insert the multi-core ferrule into the fiber hole, resulting in problems such as an increased burden on workers.

[0014] According to the multi-core optical ferrule of the present invention, the end face opening has the same length and width dimensions as the coated optical fibers when aligned in a row, and is formed flat and parallel to the row direction, so that a bundle of coated optical fibers can be directly inserted through the coated fiber insertion hole for optical connection. This makes it possible to easily achieve high-density optical connection since there is no need to remove the coating from the optical fibers. In addition, since there are no fiber insertion holes through which the optical fibers pass one by one, the optical fibers can be easily fixed to the ferrule even when the number of cores and density are increased and the fiber diameter is reduced. In addition, in recent years, the design precision of optical fibers has improved and the uniformity of the thickness of the resin coating has been improved, so that by connecting strands of the same type of optical fiber ribbon, optical connections can be made with relatively little loss.

[0015] In particular, in recent years, with the on-boarding of optical wiring, the density of optical wiring is increasing, but in optical transmission within a computer, unlike conventional long-distance optical transmission (several hundred km, etc.), extremely low loss is not required in terms of connection loss. Therefore, based on the multi-core optical ferrule of the present invention, an optical connector that can easily achieve high density even when optically mounted on a board can be made. In this specification, an optical fiber consisting of a core and cladding made of quartz glass or the like may be referred to as a bare fiber, a bare fiber coated with a resin coating such as an ultraviolet-curable resin may be referred to as a fiber strand (or coated fiber), and multiple fiber strands arranged in a row and bundled into a tape shape with a tape coating of a thermoplastic resin or the like may be referred to as an optical fiber tape.

[0016] (2) A multi-core optical ferrule according to a second aspect of the present invention is a multi-core optical ferrule according to one aspect of the present invention, in which one end face opening is provided for one coated fiber insertion hole, and the coated fiber insertion hole has an insertion port for inserting an optical fiber into the multi-core optical ferrule, a diameter-reduced portion for positioning the optical fiber, and a guide portion for guiding the optical fiber to the end face opening, and the distance of the guide portion may be 0.7 mm or more and 2.0 mm or less.

[0017] The coated fiber insertion hole is formed with one smooth path from the insertion opening to the end face opening, and the coated fiber insertion hole allows the multiple optical fibers to be accurately aligned, and the guide section having a predetermined distance allows the multiple optical fibers to be positioned perpendicular to the connection end face. In addition, the guide section is filled with adhesive, so that the optical fiber can be fixed to the inner surface of the coated fiber insertion hole, and the accurately positioned optical fiber can be reliably fixed to the ferrule. Since the distance of the guide section is 0.7 mm to 2.0 mm, the optical fiber can be reliably fixed to the ferrule even if the connection end face of the multi-core optical ferrule is optically polished (and polished at an angle of 8° to further reduce reflection). Therefore, a multi-core optical ferrule with little connection loss can be obtained.

[0018] (3) A multi-core optical ferrule according to a third invention is the multi-core optical ferrule according to the second invention, wherein the opening width w in the row direction of the end face opening is 2.5 to 20 times the opening width h in the thickness direction, and the tapered portion may have a greater amount of diameter reduction in the row direction than in the thickness direction.

[0019] As a result, when multiple optical fiber strands are inserted into the end face opening from the insertion opening of the coated fiber insertion hole, each optical fiber strand is guided and aligned in a row by sliding against the inner surface of the coated fiber insertion hole. Therefore, even when a large number of optical fiber strands are used for high-density optical connection, the multiple optical fibers are accurately aligned, and a multi-core optical ferrule that is easy to insert into the coated fiber insertion hole can be formed.

[0020] (4) A multi-core optical ferrule according to a fourth aspect of the present invention is the multi-core optical ferrule according to any one of the first to third aspects of the present invention, Opening width in thickness direction h is the end opening 1 / w of the opening width in the row direction n times(n: Number of optical fibers ) may be smaller.

[0021] As a result, the opening width h in the thickness direction is designed to be narrower than the diameter d of the coated fiber. That is, in the process of inserting n coated fibers with diameter d into the ferrule, the coated fibers are compressed in the thickness direction (h direction), and as a result of the compression, the n coated fibers are deformed so as to expand in the row direction (w direction). As a result, the n coated fibers exert forces on each other in the row direction during the insertion process, and are evenly aligned in the row direction (w direction). In this way, the n coated fibers are fixed with adhesive in an evenly aligned state, allowing the n coated fibers to be positioned accurately, resulting in a multi-core optical ferrule with low connection loss.

[0022] (5) A multi-core optical ferrule according to a fifth aspect of the present invention is a multi-core optical ferrule according to any one of the first to fourth aspects of the present invention, wherein the opening width h in the thickness direction of the end face opening is 0.220 mm or more and 0.240 mm or less, and the opening width w in the row direction of the end face opening is n times (n: natural number) 0.24 mm or more and 0.26 mm or less.

[0023] As a result, the aperture width h is designed to be narrower than that of a coated fiber with a diameter d of 250 μm (optical fiber with a cladding diameter of 125 μm). In other words, in the process of inserting n coated fibers with a diameter d of 250 μm into the ferrule, the coated fibers are slightly compressed in the thickness direction (h direction), and as a result of the compression, the n coated fibers are deformed so as to expand in the row direction (w direction). As a result, the n coated fibers exert forces on each other in the row direction during the insertion process, and are evenly aligned in the row direction (w direction). In this way, the n coated fibers are fixed with adhesive while being evenly aligned, so that the n coated fibers can be positioned accurately and can be spliced ​​with minimal splice loss.

[0024] (6) A multi-core optical ferrule according to a sixth aspect of the present invention may be the multi-core optical ferrule according to the first or second aspect of the present invention, and may include two or more pairs of coated fiber insertion holes and end face openings.

[0025] This makes it possible to fix and optically connect two or more bundles of bare optical fiber wires.

[0026] (7) An optical connector according to another aspect is an optical connector comprising a multi-core optical ferrule according to any one of the first to sixth aspects of the present invention, a plurality of optical fibers, and an adhesive for fixing the optical fibers, and the end face opening may have an area ratio of exposed adhesive of 0.05 or more and 0.25 or less.

[0027] At the open end, the coated optical fiber is slightly compressed in the thickness direction (h direction) and slightly deformed from a perfect circle to an approximately rectangular shape. This allows each optical fiber to be accurately positioned at the connection end face while the adhesive securely fixes the optical fiber, resulting in an optical connector with low connection loss. Furthermore, since the adhesive covers the entire periphery of the optical fiber in a circularly symmetrical manner, a force acts evenly on the axial center of the optical fiber when the adhesive hardens, so that the optical fiber can be positioned accurately. The area ratio is the area of ​​the adhesive exposed at the end face opening divided by the area of ​​the end face opening. In this specification, the ferrule for the multi-fiber optical connector may be simply called a ferrule or an MT ferrule. The adhesive may be a thermosetting epoxy resin. [Brief description of the drawings]

[0028] [Figure 1] 1A is a left side view, FIG. 1B is a front view, FIG. 1C is a right side view, and FIG. 1D is a cross-sectional view taken along line B-B' of the multi-core optical ferrule of the present embodiment. [Diagram 2] 2 is a cross-sectional view taken along line AA' in FIG. [Diagram 3] 2 is a schematic diagram for explaining a connection end face of the multi-core optical ferrule of the present embodiment. FIG. [Figure 4] 13 is a photograph of a connection end face of a multi-fiber optical ferrule obtained as an example. [Diagram 5]FIG. 13 is a schematic diagram showing an example of a multi-core optical ferrule according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Although multiple embodiments of the present invention will be described, each of the embodiments may be implemented alone or in combination with one or more of the multiple embodiments. 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.

[0030] [Embodiment] Fig. 1(a), (b), (c) and (d) are respectively a left side view, a front view, a right side view and a cross-sectional view taken along line B-B' in Fig. 1(b) of the multi-core optical ferrule 100 of this embodiment, and Fig. 2 is a cross-sectional view taken along line A-A' in Fig. 1(a). Note that Fig. 1(b) shows the coated fiber insertion hole 110 by a dashed line. Fig. 2 also shows a state in which a coated fiber 200 is fixed to the multi-core optical ferrule 100 with an adhesive 300.

[0031] The multi-core optical ferrule 100 (hereinafter simply referred to as ferrule 100) is a main component that constitutes a multi-core optical connector, and is provided on both the end face of one optical fiber and the end face of the other optical fiber to precisely adjust the position of the connection end faces of each optical fiber and to apply a contact force to optically connect them. The ferrule 100 is capable of simultaneously connecting a plurality of optical fibers, and can be formed by injection molding a resin composition containing polyphenylene sulfide (hereinafter referred to as PPS) in a mold. The ferrule 100 has a coated fiber insertion hole 110 into which the coated fiber 200 is inserted, and a guide pin hole 130 into which a guide pin is inserted, and is an integral molded product (main body) made of a resin composition containing polyphenylene sulfide.

[0032] (Ferrule 100) 1 and 2, the ferrule 100 of this embodiment is provided with a coated fiber insertion hole 110 into which a coated fiber 200 (hereinafter also referred to as the bare optical fiber 200) without removing its coating is inserted as is. The coated fiber insertion hole 110 is provided with an insertion opening 111 for inserting the bare optical fiber 200 into the ferrule 100, a guide section 112 for guiding the bare optical fiber 200 and resin 300 to the splicing end face 101 side, a diameter-reducing section 113 for positioning the bare optical fiber 200, and a guide section 114 for guiding the bare optical fiber 200 to the end face opening 120.

[0033] The ferrule 100 of this embodiment has a shape called a thin ferrule, and has a thinner outer shape than a general MT ferrule. That is, as shown in FIG. 1(a), the connection end face 101 of the ferrule 100 shown in this embodiment is a substantially rectangular shape with curved surfaces R1 with a curvature radius of 0.3 mm at the four corners, and the long side is 6.4 mm long and the short side is 1.25 mm long. Also, as shown in FIG. 1(b), the main body of the ferrule 100 of this embodiment has a flange 140 on the insertion opening 111 side, and the length from the connection end face 101 to the insertion opening 111 is 8.0 mm, of which the flange 140 is 2.0 mm long. The flange 140 of this embodiment protrudes only in the long side direction of the connection end face 101 (the width direction of the ferrule 100), and the protruding amount is 0.2 mm. In this embodiment, an example of a thin ferrule having the flange 140 is shown, but the flange 140 may or may not be present, and the ferrule 100 may or may not be thin, and the size and the like of these can be appropriately selected or designed according to the purpose of the optical connection. Furthermore, an introduction window for the adhesive 300 may be appropriately provided as necessary.

[0034] The ferrule 100 of this embodiment is provided with a pair of guide pin holes 130 spaced a predetermined distance apart. When the ferrule 100 is to be optically connected to another ferrule (not shown), a guide pin (not shown) is inserted into the guide pin hole 130 to accurately position the ferrule 100 and the other ferrule. Since the end face opening 120 of the ferrule 100 is accurately positioned with respect to the pair of guide pin holes 130, the end face opening 120 of the ferrule 100 and the end face opening (not shown) of the other ferrule are accurately positioned, and the multiple optical fibers of the ferrule 100 can be optically connected to the multiple optical fibers of the ferrule with low loss. In this specification, the ferrule 100 into which the multiple optical fiber strands 200 are inserted and fixed with the adhesive 300 is also referred to as an optical connector 10.

[0035] (Coated fiber insertion hole 110) The ferrule 100 of this embodiment is provided with one coated fiber insertion hole 110, which communicates with an end face opening 120 of the connection end face 101. The inside of the coated fiber insertion hole 110 is formed with one smooth path so that a plurality of coated fibers 200 can be aligned and guided. The coated fiber insertion hole 110 is provided with an insertion port 111 for inserting the optical fiber 200 into the ferrule 100. As shown in FIG. 1(d), the opening of the coated fiber insertion port 110 is provided with a curved surface R2 with a curvature radius of 0.2 mm, and is formed so that the opening height gradually narrows toward the guide portion 112. In this embodiment, the length of the insertion port 111 (the distance for guiding the optical fiber 200) is 2.0 mm. As shown in FIG. 1(c), the opening of the coated fiber insertion port 110 is formed in a rectangular shape, with its long side (in the fiber row direction) being 3.1 mm or more and 3.2 mm or less, and its short side (in the ferrule thickness direction) being 0.26 mm or more and 0.27 mm or less. If the opening of this opening is too narrow, it becomes difficult to insert the optical fiber 200, and if it is too wide, the adhesive 300 is likely to leak out. In this embodiment, twelve coated fibers 200 with a diameter of 250 μm are inserted into the opening of the coated fiber insertion port 110 . This allows the multiple coated fibers 200 to be easily inserted into the ferrule 100 and to be accurately aligned in the thickness and width directions. The opening width h in the thickness direction of the end face opening 120 is preferably 0.220 mm or more and 0.248 mm or less, more preferably 0.230 mm or more and 0.245 mm or less, and even more preferably 0.230 mm or more and 0.235 mm or less.

[0036] The coated fiber insertion hole 110 is provided with a guide portion 112 that guides the optical fiber 200 and the resin 300 toward the connection end face 101 side. In the optical connector 10 of this embodiment, first, a plurality of coated fibers 200 are inserted into the ferrule 100 together, and the insertion port of the ferrule 100 is tilted upward to drip a thermosetting adhesive 300 into the insertion port 111. When the adhesive 300 is heated, the viscosity of the adhesive 300 gradually decreases, and the adhesive 300 passes through the guide portion 112 while running down the plurality of coated fibers 200 (dropping due to surface tension and its own weight). In this way, the adhesive 300 passes through the reduced diameter portion 113 and the guide portion 114 while wetting the plurality of coated fibers 200 inside the guide portion 112, and reaches the end face opening 120. Then, by continuing to heat the adhesive 300, the resin of the adhesive 300 that has reached the end face opening hardens, and the coated fibers 200 can be fixed to the ferrule 100.

[0037] Further, the coated fiber insertion hole 110 is provided with a reduced diameter portion 113 for positioning the optical fiber 200 . The diameter-reduced section 113 reduces the diameter mainly in the row direction (long side direction of the end face opening) of the optical fiber 200. The length of the diameter-reduced section 113 in this embodiment (the distance for guiding the optical fiber 200) is 1.0 mm, and the amount of diameter reduction in the row direction is 0.05 mm or more and 0.10 mm or less on one side. In the diameter-reduced section 113, the diameter is further reduced in the thickness direction, so that the optical fiber 200 is slightly compressed in the thickness direction (h direction) and deformed from a perfect circle to a substantially rectangular shape during the insertion process. The tapered portion 113 allows the multiple coated fibers 200 to be accurately aligned and positioned in the row direction. Also, the adhesive 300 supplied from the guide portion 112 can be gathered in the tapered portion 113 and can sufficiently fill the inside of the guide portion 114.

[0038] The coated fiber insertion hole 110 is provided with a guide portion 114 for guiding the optical fiber 200 to the end face opening 120 . The guide portion 114 is provided in the same shape (same size) as the opening of the end face opening 120, and is provided perpendicular to the connection end face 101. This allows the coated fiber 200 to be guided perpendicular to the end face opening 120 accurately. Moreover, the distance of the guiding portion 114 (the distance for guiding the optical fiber 200) is preferably 0.7 mm or more and 2.0 mm or less, and more preferably 0.8 mm or more and 1.5 mm or less. The distance of the guiding portion 114 in this embodiment is 1.0 mm. As a result, even if the connection end face of the multi-core optical ferrule is optically polished, and further polished at an angle of 8° to reduce reflection, the optical fiber can be reliably fixed and optically connected.

[0039] 3, it is preferable that the opening width w in the row direction of the end face opening 120 and the guide portion 114 is equal to the diameter d of the coated fiber 200 times the number n of the coated fibers 200. It is also preferable that the opening width h in the thickness direction of the end face opening 120 and the guide portion 114 is slightly smaller than the diameter d of the coated fiber 200, and the degree of this is preferably 0.01 mm or more and 0.03 mm or less, and more preferably 0.02±0.005 mm. In the present embodiment, the end face opening 120 and the guide portion 114 have an opening width w of 3.00 mm in the row direction and an opening width h of 0.230 mm in the thickness direction. This makes it possible to minimize the connection loss when connecting 12 coated fibers 200 each having a diameter d of 0.25 mm.

[0040] As a result of investigating variously changing each of the above dimensions, it was found that the dimensional accuracy of the aperture width h has a greater effect on the connection loss than the dimensional accuracy of the aperture width w. This is believed to be because, in the process in which the coated fiber 200 is compressed in the thickness direction (h direction), the n coated fibers 200 deform so as to spread in the row direction (w direction), exerting forces on each other in the row direction, and aligning evenly in the row direction (w direction).

[0041] FIG. 3(a) shows a schematic diagram of a connection end face 101 in this embodiment, and FIG. 3(b) shows a schematic diagram of a partially enlarged view of an end face opening 120. The coated fiber 200 is composed of an optical fiber 210 and a coating 220, and in a typical ferrule, the coating 220 is stripped off. The optical fiber 210 is composed of a glass cladding 212 and a core 211, and an optical signal is transmitted inside the core 211. Since the cladding 212 is set to have a lower refractive index than the core 211, the optical signal is totally reflected and is confined inside the core 211 and transmitted with extremely low loss. Furthermore, the optical fiber 210 is protected by a coating 220 having a silicone film 222 and a resin film 221 to improve the ease of handling. The silicone film 222 is in direct contact with the cladding 212, has high adhesion to glass, increases the stability of the interface, and disperses external forces. The silicone film 222 is coated on the outside with a resin film 221 made of an ultraviolet curing resin. This protects the optical fiber 210 and the silicone film 222, provides mechanical strength, and provides identification to the optical fiber 210 by coloring or the like. Usually, in a multi-core optical connector using an MT ferrule or the like, the coating 220 is carefully peeled off from the optical fiber 210, and the end faces of the optical fibers 210 are strongly abutted against each other to optically connect them.

[0042] In this case, polyester resin, epoxy resin, urethane resin, or fluorine resin can be used as the resin film 221, and among these, it is preferable to use a fluorine-based ultraviolet curing resin. Since the resin film 221 of the coating 220 is a fluorine resin, the optical fiber 200 can be smoothly inserted into the coated fiber insertion hole 110, and the circularity of the optical fiber 200 can be easily maintained. Among fluorine-based resins, PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) or FEP (tetrafluoroethylene-hexafluoropropylene copolymer resin) is more preferable. This makes it possible to obtain an optical fiber 200 with high moldability and circularity. Furthermore, the optical fiber 200 is smoothly inserted into the reduced diameter section 113 while being deformed during the insertion process. During deformation, the n coated fibers 200 can be smoothly aligned by exerting force on each other in the row direction due to the elastic force of the resin coating 221, thereby making it possible to further reduce connection loss.

[0043] In the ferrule 100 of this embodiment, the coated fiber 200 is inserted as is, so that the coating 220 and adhesive 300 appear in addition to the optical fiber 210 at the end face opening 120, as shown in Fig. 3. As described above, when the coated fiber 200 is first inserted into the coated fiber insertion hole 110 of the ferrule 100, the coated fiber 200 protrudes from the end face opening 120. When the thermosetting adhesive 300 is then introduced, the heated adhesive 300 runs along the coated fiber 200 in the guide portion 112, gathers at the funnel-shaped reduced diameter portion 113, fills the guide portion 114, and reaches the end face opening 120. When the adhesive 300 is further heated, it hardens and hardens so as to protrude in an arch from the end face opening 120. Thereafter, the coated fibers 200 and adhesive 300 protruding from the end face opening 120 are polished to eliminate the protruding height and become substantially flush with the connection end face 101, after which the connection end face is optically polished. In this case, 8° polishing may be performed as necessary to reduce reflected light. In this way, a pair of coated fibers 200 can be optically connected using a clip or the like, similar to a normal MT ferrule.

[0044] In this case, the adhesive 300 may be, for example, an epoxy-based adhesive, an acrylic-based adhesive, a urethane-based adhesive, a silicone-based adhesive, an olefin-based adhesive, or various hot melt adhesives (polyester-based, modified olefin-based), and the like. From the standpoint of stability during fixing, etc., an epoxy-based adhesive is preferred. The adhesive 300 is preferably a two-component thermosetting epoxy adhesive, with a viscosity of 2,000 to 6,000 CPS (23° C., 50 rpm) and a glass transition temperature of 80° C. to 200° C. This allows the coated fiber 200 to be reliably fixed to the guide portion 114. In addition, the linear expansion coefficient (below Tg) is 80×10 -6 in / in °C or less is preferable, and 60 × 10 -6 In terms of water resistance, the weight change after immersion in water for 360 hours is preferably 3% or less, and more preferably 1% or less. This makes it possible to maintain high positional accuracy of the optical fiber.

[0045] 3, the pitch of the optical fibers 210 coincides with the diameter of the coated fibers 200. In this embodiment, twelve coated fibers 200 with a diameter of 250 μm are used, so the pitch is 250 μm. The end face opening 120 of this embodiment opens in a rectangular shape, with two opposing long sides formed parallel to each other. The circular coated fibers 200 are closely arranged and aligned in this opening, and are filled with adhesive 300. In this case, it is preferable that the short side h of the end face opening 120 is 0.23 mm, which is slightly smaller than the diameter d of the optical fiber 210, and the long side w is equal to the diameter d x the number n. As a result, the resin coating 220 is compressed in the direction of the short side h, and the n coated fibers 200 exert force on each other in the direction of the long side w during the insertion process, aligning them evenly, thereby obtaining an accurate pitch and minimizing connection loss. In this case, the coated optical fiber 200 is compressed in the direction of the short side h and is slightly deformed from a perfect circle to a substantially rectangular shape. The area ratio of the adhesive 300 exposed to the end face opening 120 is preferably 0.05 to 0.25, more preferably 0.10 to 0.20, and even more preferably 0.14 to 0.15. It is also preferable that the optical fiber 210 to be connected is also of the same product (type) as the optical fiber 210. This makes it possible to minimize pitch deviations caused by differences in the thickness of the coating 220 between products.

[0046] [Example] The ferrule 100 of this embodiment was manufactured by injection molding using PPS resin. The size of the ferrule 100 was as described above, but the end face openings 120 were molded with an opening width w of 3.0 mm in the row direction and an opening width h of 0.230 mm in the thickness direction (Example 1). In Example 2, the opening width w in the row direction of the end face openings 120 was set to 3.0 mm, and the opening width h in the thickness direction was set to 0.240 mm, and the rest of the molding was performed in the same manner as in Example 1. In Example 3, the opening width w in the row direction of the end face openings 120 was set to 3.0 mm, and the opening width h in the thickness direction was set to 0.250 mm, and the rest of the molding was performed in the same manner as in Example 1.

[0047] An optical fiber ribbon (OM2 manufactured by Corning Corporation) was prepared in which 12 optical fiber strands with a diameter of 250 μm were bundled in a row, and the outer tape coating was removed to obtain an optical fiber strand. This optical fiber strand had a core diameter of 50 μm, a cladding diameter of 125 μm, and a coating of UV acrylate resin and silicone coating, giving it a diameter of 250 μm. Twelve optical fibers with their coatings still attached were inserted into the ferrule 100 of Examples 1 to 3, and an epoxy thermosetting adhesive (EPO-TEK353ND manufactured by EPOXY TECHNOLOGY) was applied thereto, followed by heating to 140°C. The coated fiber and adhesive protruding from the connection end face were then polished, and the end face of the ferrule was optically polished at an angle of 8° using a Domaille APM-HDC-5300. Fig. 4 is a photograph of the connection end face of the multi-core optical ferrule obtained in this example. Fig. 3 is a schematic diagram for explaining the photograph of the end face in Fig. 4. In this way, multiple examples were prepared and the central positions of the optical fiber cores were measured. It was found that the amount of positional deviation in the row direction (X direction in Fig. 4) was 1.43 μm on average in Example 1, while it was 1.89 μm on average in Example 3, and the amount of positional deviation from the design was the smallest in Example 1.

[0048] In addition, two ferrules of each example were prepared, fixed to an MPO connector, a guide pin was inserted, and the ferrules were brought into contact with each other with a force of 10 N applied, and optical loss was measured (JIS C 61300-3-4). As a result, it was found that Example 1 had the lowest connection loss and the highest positional accuracy of each optical fiber (small core misalignment). That is, it is preferable from the viewpoint of connection loss that the opening width h of the end face opening is slightly smaller than the diameter d of the optical fiber. Furthermore, a fluororesin is preferable as the resin coating of the optical fiber, and PFA or FEP is preferable. In this case, the 12 optical fibers are smoothly inserted into the ferrule 100 and aligned and positioned without load, deformation or gaps at the end face openings of the same size, so that the connection loss can be minimized.

[0049] (Modification) 5 is a schematic diagram showing an example of a multi-core optical ferrule 100' according to another embodiment. In this embodiment, the length of the body of the ferrule 100' is designed to be 3.4 mm, which is shorter than usual. In this case, it is provided with an insertion section 115 having the functions of an insertion port 111, a guide section 112, and a diameter-reducing section 113. That is, it is configured so that the diameter is gradually reduced in both the vertical direction and the width direction, so that even if the main body is short, multiple coated fibers 200 can be aligned and arranged. However, even in this case, the opening width h of the end face opening is designed to be slightly smaller than the diameter d of the optical fiber strand, and the length of the guide portion 114 is ensured to be 1.0 mm, thereby enabling the coated fiber 200 to be securely fixed at the connection end face. Further, the multi-core optical ferrule 100' of another embodiment shown in FIG. 5 is illustrated as having two coated fiber insertion holes 110, 110', but the number of coated fiber insertion holes 110 may be only one, or two.

[0050] In the present invention, optical connector 10 corresponds to the "optical connector", multi-core optical ferrule 100 corresponds to the "multi-core optical ferrule", coated fiber insertion hole 110 corresponds to the "coated fiber insertion hole", end face opening 120 corresponds to the "end face opening", coated fiber 200 corresponds to the "coated optical fiber", coating 220 corresponds to the "coating", adhesive 300 corresponds to the "adhesive", insertion port 111 corresponds to the "insertion port", reduced diameter section 113 corresponds to the "reduced diameter section", and guiding section 114 corresponds to the "guiding section".

[0051] 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]

[0052] 10 Optical Connector 100 Multi-core optical ferrule, ferrule 101 Connection end face 110 Coated fiber insertion hole 120 End opening 111 Insertion port 112 Information Department 113 Reduced diameter section 114 Guidance part 120 End opening 130 Guide pin hole 200 coated fiber 220 Covering 210 Optical Fiber 300 Adhesive

Claims

1. A multi-core optical ferrule for holding and optically connecting a plurality of optical fibers, a coated fiber insertion hole into which the coated optical fibers are inserted in a row; an end surface opening formed on the connection end surface of the optical fiber and communicating with the coated fiber insertion hole; the coated fiber insertion hole has, in this order, an insertion port facing the connection end face, an opening formed so as to narrow from the opening of the insertion port, a guide portion for guiding the coated fiber and adhesive, a diameter reducing portion for compressing the coated fiber in a thickness direction, and a guide portion provided to have the same size as the opening of the end face opening and for guiding the coated fiber; a multi-core optical ferrule in which the end face opening has two opposing sides formed flat and parallel to the row direction of the optical fibers, an opening width h in the thickness direction is smaller than 1 / n times the opening width w in the row direction (n: the number of the optical fibers), and the coating and adhesive of the optical fibers are formed so as to be exposed.

2. 2. The multi-core optical ferrule according to claim 1, wherein the end face opening has an opening width h in a thickness direction that is smaller than a diameter d of the coated fiber, an opening width w in a thickness direction that is n times the diameter d of the coated fiber (n: the number of the optical fibers), and the coated fiber is compressed only in the thickness direction.

3. one end face opening is provided for one of the coated fiber insertion holes, 3. The multi-core optical ferrule according to claim 1, wherein a distance of the guiding portion is 0.7 mm or more and 2.0 mm or less.

4. 4. A multi-core optical ferrule as claimed in claim 1, wherein an opening width h in a thickness direction of the end face opening is 0.220 mm or more and 0.240 mm or less, and an opening width w in a row direction of the end face opening is n times 0.24 mm or more and 0.26 mm or less (n: the number of the optical fibers).

5. 4. The multi-core optical ferrule according to claim 1, comprising two or more pairs of the coated fiber insertion hole and the end face opening.

6. 6. An optical connector comprising the multi-core optical ferrule according to claim 1, a plurality of optical fibers, and an adhesive for fixing the optical fibers, An optical connector, wherein an area ratio of the adhesive exposed at the end face opening is 0.05 or more and 0.25 or less.

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