WO2024166261A1 - Optical connector and method for manufacturing same - Google Patents

Abstract

This optical connector includes: a ferrule (10) that is removably connected to optical fibers (30) and holds the optical fibers (30) so that optical fiber end surfaces (31a) are exposed at a ferrule end surface (12); and a refractive index matching part (21) that is formed on the ferrule end surface (12) so as to cover the optical fiber end surfaces (31a). The optical fiber end surfaces (31a) are cleavage surfaces. The ferrule (10) includes optical fiber insertion holes (16) that guide optical fibers (31) to the ferrule end surface (12), and an optical fiber adhesion part (17) that is provided in a position spaced away from the optical fiber insertion holes (16) and fixes, with an adhesive (18), the optical fibers (30) facing the optical fiber insertion holes (16). The optical fiber end surfaces (31a) protrude from the ferrule end surface (12).

Description

Optical connector and manufacturing method thereof

This disclosure relates to optical connectors and methods for manufacturing the same.

Optical connectors are used in optical communication networks to connect optical fibers. SC connectors and LC connectors, which use cylindrical ferrules, are used as single-core optical connectors for connecting single-core optical fibers, while MT connectors or MPO connectors, which use rectangular MT ferrules, are used as multi-core optical connectors for connecting multi-core fibers within optical fiber cables.

The assembly process for these single-core and multi-core optical connectors is explained below. First, the coating of the optical fiber to which the optical connector is attached is removed to expose the cladding glass, which is then cut. Next, the cladding glass from which the coating has been removed is inserted into the optical fiber insertion hole of the ferrule, and the inserted optical fiber is fixed in the optical fiber insertion hole with an adhesive. After the optical fiber is glued and fixed in the ferrule, the optical fiber end face and the ferrule end face are polished using a polishing machine designed specifically for optical connectors.

In the polishing process, a polishing sheet is placed on top of a polishing pad, and the end face of the optical fiber and the end face of the ferrule are pressed against the polishing sheet while the polishing sheet is rotated to polish the end face. The end face of the optical fiber is polished first using a polishing sheet coated with coarse abrasive grains, then switched to a polishing sheet coated with finer abrasive grains, and the end face of the optical fiber that has simply been cut is processed into an optical fiber end face with a convex spherical shape. In the polishing process, the speed at which the polishing sheet is rotated and the polishing time are changed for each type of polishing sheet, and a polishing pad with a hardness suitable for each polishing sheet is used, so that the end face of the optical fiber can be processed into a convex spherical shape and the optical fiber end face can protrude slightly from the ferrule end face. After polishing, a housing is attached to the ferrule to complete the optical connector.

In commonly used optical connectors such as SC connectors, LC connectors, and MPO connectors, the cores of the optical fiber end faces are brought into contact with each other to achieve physical contact in order to achieve high return loss at the connection point. Polishing the optical fiber end face is necessary to form the optical fiber end face that achieves physical contact. In optical connectors, the ferrule to which the optical fiber is glued is pushed from the rear end of the ferrule by a spring, achieving physical contact with the optical fiber end face, which has a convex spherical shape.

In an MPO connector, the MT ferrule and the end face of the optical fiber are polished to form an oblique angle with respect to the optical axis of the optical fiber, and the MT ferrule is pressed from the rear end with a spring to physically contact the optical fiber with the oblique end face. In this configuration, when the MT ferrule with the oblique end face comes into contact, the force of the spring at the rear end of the MT ferrule causes the MT ferrule to slide in a direction that causes axial misalignment of the optical fiber within the clearance range between the guide pin and the guide pin hole. In order to suppress connection loss due to this axial misalignment, the MT ferrule used in the MPO connector offsets the position of the optical fiber hole in advance to anticipate the amount of sliding due to the force of the spring, thereby achieving a low-loss connection.

International Publication No. 2022/244039

Yoshiteru Abe, Yasushi Sakamoto, Kohei Kawasaki, Kengo Watanabe, Ryuichi Sugisaki, Kazuhide Nakajima, Kazunori Katayama, "Evaluation of 8-fiber multicore fiber connectors with different structures," IEICE Technical Report, vol. 121, no. 18, OFT2021-3, pp. 9-12, May 2021. Kota Shikama, Yoshiteru Abe, Shuichi Yanagi, Tetsuo Takahashi, "Design and Fabrication of PC Connection End Face of Optical Connector for Multicore Fiber," 2013 IEICE Society Conference, C-3-81, September 2013.

In multi-core optical connectors, as the number of cores in the optical fiber to be connected increases, it becomes difficult to physically contact all of the optical fiber cores. In an MPO connector, the amount of optical fiber protruding from the end face of the MT ferrule after polishing is not uniform, so the MT ferrule to which the optical fiber is glued is pushed from the rear end by a spring to achieve a physical contact connection even if the amount of protrusion differs. As the number of cores in the optical connector increases, the pressing force of the spring must be increased to compensate for the difference in the amount of protrusion.

The IEC, an international standardization organization, specifies the spring pressure according to the number of cores in an MPO connector. The IEC 61754-2-1 standard for 12-core MPO connectors specifies a spring pressure of about 10 N, while the IEC 61754-2-2 standard for 24-core MPO connectors specifies a spring pressure of about 20 N. In the future, it is expected that the spring pressure will be increased in accordance with the increase in the number of cores in MPO connectors. However, this will increase the difficulty of designing and manufacturing MPO connectors, making it difficult to achieve low-loss connections, as it will be necessary to adjust the offset of the optical fiber hole due to the increase in the sliding amount of the MT ferrule when connected due to the increase in spring pressure, and to deal with deformation of parts due to the increased spring pressure and changes to materials to provide resistance to the increased spring pressure.

In addition, in the polishing process of the optical fiber end face, the amount of protrusion of the optical fiber from the ferrule end face must be highly uniform, so the difficulty of the polishing process increases. Furthermore, when the optical fiber is a multicore fiber, the difficulty of achieving physical contact connection for all cores increases even more. In conventional optical connectors, the optical fiber end face shape and optical connector parts that realize physical contact connection are designed on the premise of a single-core fiber with only one core at the center of the clad glass. Since a multicore fiber has multiple cores, it is necessary to perform end face polishing suitable for multicore fibers in order to achieve high return loss for all multiple cores. For example, in an MT connector that connects an 8-core 4-core multicore fiber, an example has been reported in which the optical fiber end face is polished into a convex spherical shape, and then polished to flatten the end face to create an end face shape that allows physical contact connection for the 4 cores (see Non-Patent Document 1).

Even when connecting multicore fibers with a single-core optical connector, the range of allowable parameters for the end face shape is narrower than that for single-core fibers, and high-precision end face polishing is required to form an end face for physical contact connection of the multiple cores of the multicore fiber (see Non-Patent Document 2). In order to obtain high return loss with physical contact connection, it is also necessary to design the optical fiber end face shape after polishing and the pressing force for pressing the ferrule from the rear end according to the number of cores and type of optical fiber.

Research is being conducted on a multi-core optical connector that does not require loading of spring pressure even when the number of optical fiber cores increases (see Patent Document 1). However, Patent Document 1 is based on the premise that the optical fiber end faces are polished.

The present disclosure has been proposed in light of the above circumstances, and aims to provide an optical connector and a manufacturing method thereof that connects optical fibers with high return loss, regardless of the number of optical fiber cores or type of optical fiber, and without polishing the optical fiber end faces.

In order to solve the above problems, the optical connector disclosed herein is an optical connector that detachably connects an optical fiber, and includes a ferrule that holds the optical fiber so that the optical fiber end face is exposed from the ferrule end face, and a refractive index matching portion formed on the ferrule end face so as to cover the optical fiber end face, and the optical fiber end face is formed by cleavage.

The method of manufacturing an optical connector disclosed herein is for manufacturing an optical connector that detachably connects an optical fiber, and involves guiding the optical fiber along the optical fiber insertion hole of the ferrule, positioning it so that the optical fiber end face formed by cleavage is exposed on the ferrule end face, and forming a refractive index matching portion on the ferrule end face so as to cover the optical fiber end face.

According to the present disclosure, optical fibers can be connected with high return loss without polishing the end faces of the optical fibers, regardless of the number of cores or type of optical fiber.

FIG. 2 is an overhead view of an MT ferrule of the optical connector according to the first embodiment. FIG. 2 is a top view of an MT ferrule of the optical connector according to the first embodiment. FIG. 2 is a left side view of the MT ferrule according to the first embodiment. FIG. 2 is a cross-sectional view of an MT ferrule according to the first embodiment. FIG. 11 is a top view of an MT ferrule according to a first modified example of the first embodiment. FIG. 11 is a side view of an MT ferrule according to a second modified example of the first embodiment. FIG. 13 is an overhead view of an SC ferrule according to a second embodiment. FIG. 11 is a left side view of the SC ferrule according to the second embodiment. FIG. 13 is a left side view of an SC ferrule according to a modified example of the second embodiment.

The following describes in detail the embodiments of the present disclosure with reference to the drawings. In this embodiment, the first embodiment describes a multi-core optical connector using a rectangular ferrule, and the second embodiment describes a single-core optical connector using a cylindrical ferrule.

Note that this disclosure is not limited to the embodiments shown below. These embodiments are merely examples, and this disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Components with the same reference numerals in this specification and drawings are considered to be identical to each other.

(First embodiment)
In the first embodiment, a multi-fiber optical connector using an MT ferrule, which is a rectangular ferrule, will be described. The MT ferrule is used by being attached to the housing of an MT connector or an MPO connector. Fig. 1 is an overhead view showing an MT ferrule used in the optical connector of the first embodiment. Figs. 2, 3, and 4 are a top view, a left side view, and a cross-sectional view, respectively, of the MT ferrule used in the optical connector of the first embodiment. The cross-sectional view of Fig. 4 is taken along the section line IV-IV in Figs. 1, 2, and 3.

The optical connector of the first embodiment is a multi-core optical connector that detachably connects optical fibers 30, and has an approximately rectangular parallelepiped MT ferrule 10 that collectively holds the ends of the multi-core optical fiber 30, which is formed by arranging multiple optical fibers in a row and forming them into a tape, and a refractive index matching section 21 formed on the ferrule end face 12 that faces another optical connector to be connected. The MT ferrule 10 is provided with a boot 19 that extends from the rear end 13 that faces the ferrule end face 12 and covers and protects the multi-core optical fiber 30 toward the MT ferrule 10. The MT ferrule is made of an appropriate resin, and the boot 19 is made of an elastic material such as rubber. The illustrated multi-core optical fiber 30 is a four-core single-core fiber.

In the MT ferrule 10, the multi-core optical fiber 30 that reaches the internal space 15 of the MT ferrule 10 from the outside through the boot 19 and the opening at the rear end 13 of the MT ferrule 10 is a plurality of optical fibers 31 with the coating of the multi-core optical fiber 30 removed and the clad glass exposed. The optical fibers 31 are arranged so that each optical fiber end face 31a protrudes from the ferrule end face 12, guided from the internal space 15 by the optical fiber insertion hole 16. Each optical fiber 31 that faces the optical fiber insertion hole 16 in the internal space 15 is juxtaposed to the optical fiber adhesive part 17 provided at the bottom of the internal space 15 at a position away from the optical fiber insertion hole 16, and is fixed by adhesive 18. A window 14 that leads to the internal space 15 is formed on the upper surface 11 of the MT ferrule 10, so that adhesive 18 can be injected from the outside of the MT ferrule 10 into the optical fiber adhesive part 17 in the internal space 15.

The ferrule end face 12 is formed so as to be perpendicular to the optical axis of the optical fiber 31. The optical fiber end face 31a is a cleavage surface perpendicular to the optical axis of the optical fiber 31, forming a mirror surface without cracks or chips. A solid refractive index matching section 21 is formed with a predetermined thickness on the ferrule end face 12 to cover the optical fiber end face 31a. When the length of the optical fiber end face 31a protruding from the ferrule end face 12 is not uniform, the refractive index matching section 21 is formed with a thickness to cover the optical fiber 31 protruding the longest from the ferrule end face 12. The refractive index matching section 21 is formed in a rectangular area including the optical fiber 31 protruding from the ferrule end face 12 at the ferrule end face 12 so as not to reach the pair of guide pin holes 12a formed in the ferrule end face 12.

The refractive index matching section 21 is formed of a refractive index matching material and matches the refractive index with the multi-core optical fiber 30. When the multi-core optical fiber 30 is a quartz fiber, its refractive index is adjusted to be equivalent to that of quartz glass. For example, the refractive index at wavelengths of 1.31 μm and 1.55 μm used in communication is in the range of 1.440 to 1.450. For the refractive index matching material, for example, an acrylic silicone ultraviolet curing resin can be used. In addition, the refractive index matching section 21 has an appropriate hardness so that it can be deformed with a force of, for example, about 10 N so that when the MT ferrule 10 is attached to the MPO connector and the MPO connectors are connected to each other, they come into contact without forming any gaps and a good return loss can be ensured. The refractive index matching section 21 is bonded to the ferrule end face 12 and the optical fiber end face 31a, so it will not come off even if you touch it with your hand.

The optical connector of the first embodiment is manufactured by the following process. That is, the coating is removed from the tape-shaped multi-core optical fiber 30, and the multiple optical fibers 31 with the exposed cladding glass are cut by cleaving using an optical fiber cleaver or the like so that the optical fiber end face 31a is perpendicular to the optical axis of the optical fiber 31. A cleavage surface is formed on the optical fiber end face 31a. Then, the optical fiber 31 that has passed through the boot 19 is inserted from the opening of the rear end 13 of the MT ferrule 10, and the optical fiber 31 is guided by the optical fiber insertion hole 16 through the internal space 15 so that the optical fiber end face 31a protrudes from the ferrule end face 12. At this time, the optical fiber end face 31a protruding from the ferrule end face 12 is observed to confirm that the cleavage surface forms a mirror surface without cracks or chips. Then, each optical fiber 31 arranged side by side in the optical fiber adhesive section 17 provided at the bottom of the internal space 15 is fixed with adhesive 18, and a solid refractive index matching section 21 is formed using a refractive index matching material to cover the optical fiber end surface 31a protruding from the ferrule end surface 12.

The adhesive 18 used to fix the optical fiber 31 to the optical fiber adhesive portion 17 may have a higher viscosity than that used in normal optical connector assembly, so that it does not flow into the optical fiber insertion hole 16 through the internal space 15. The adhesive 18 may be injected through the window 14 from outside the MT ferrule 10 into the optical fiber adhesive portion 17 provided in the internal space 15. The refractive index matching portion 21 may be formed by applying an acrylic silicone ultraviolet curing resin to the ferrule end face 12 and then curing it by irradiating it with ultraviolet light. The boot 19 may be attached to the MT ferrule 10 after the optical fiber 31 is held in the MT ferrule 10.

In the first embodiment, a good return loss is ensured by the refractive index matching section 21 formed to cover the optical fiber end face 31a formed by the cleavage plane protruding from the ferrule end face 12. This eliminates the need for the high-precision optical fiber end face polishing process required in the manufacture of conventional optical connectors, making it possible to provide an optical connector that is easy to manufacture. In addition, a high return loss can be obtained at the connection point without polishing the optical fiber end face 31a.

In the first embodiment, the refractive index matching section 21 has an appropriate hardness so that when the MT ferrule 10 is attached to the MPO connector and the MPO connectors are connected to each other, they deform and come into contact without creating gaps, ensuring good return loss. This eliminates the need to design the optical fiber end face shape taking into account the fiber type and number of cores, or the force required to press the ferrule, in order to obtain high return loss, making it easier to design and manufacture the optical connector.

In the first embodiment, the MT ferrule 10 has an optical fiber adhesive section 17 that fixes the optical fiber 31 toward the optical fiber insertion hole 16 with adhesive 18, located at the bottom of the internal space 15 away from the optical fiber insertion hole 16. This prevents the adhesive 18 from flowing into the optical fiber insertion hole 16 and adhering to the optical fiber end face 31a. Therefore, the optical fiber end face 31a is not affected by the adhesion of the adhesive 18, and the refractive index can be appropriately matched by the refractive index matching section 21.

FIG. 5 is a top view showing the MT ferrule 10 of an optical connector of a first modified example of the first embodiment. The first modified example differs in that, whereas the optical fiber end face 31a protrudes from the ferrule end face 12 in the first embodiment, the optical fiber end face 31a is within the plane of the ferrule end face 12 or is pulled into the optical fiber insertion hole 16 opening in the ferrule end face 12. The other configurations are the same as those of the first embodiment.

Even in the first modified example, the optical fiber end face 31a located within the plane of the ferrule end face 12 is covered by the refractive index matching section 21 formed on the ferrule end face 12. The optical fiber end face 31a that is drawn from the ferrule end face 12 into the optical fiber insertion hole 16 is also covered by the refractive index matching section 21 that extends into the optical fiber insertion hole 16 without forming a gap. Therefore, even in the first modified example, the refractive index is appropriately matched by the refractive index matching section 21, ensuring good return loss.

The manufacturing method of the optical connector of the first modified example differs from that of the optical connector of the first embodiment in that, in the process of placing the optical fiber 31 through the internal space 15 and the optical fiber insertion hole 16 of the MT ferrule 10, the optical fiber end face 31a is prevented from protruding from the ferrule end face 12. In other respects, it is the same as the manufacturing method of the first embodiment.

In the first modified example, the optical fiber end face 31a is either within the plane of the ferrule end face 12 or is pulled into the optical fiber insertion hole 16 that opens into the ferrule end face 12, but the tip of each optical fiber 31 is covered by the refractive index matching section 21. Therefore, in the modified example, regardless of whether the optical fiber end face 31a is within the plane of the ferrule end face 12 or is pulled into the optical fiber insertion hole 16, the function of the refractive index matching section 21 to match the refractive index is ensured, and a good return loss is ensured.

FIG. 6 is a left side view showing the MT ferrule 10 of an optical connector of a second modified example of the first embodiment. The MT ferrule 10 of the second modified example differs in that it holds a 4-core, 4-core fiber, which is a multicore fiber, whereas the MT ferrule 10 of the first embodiment holds a 4-core single-core fiber 30. The other configurations are the same as those of the first embodiment.

The manufacturing method of the optical connector of the second modified example uses a four-core, four-core fiber instead of the four-core single-core fiber 30 of the first embodiment, and therefore differs from the first embodiment in that when the optical fiber 31 is inserted into the optical fiber insertion hole 16 so that each optical fiber end face 31a protrudes from the ferrule end face 12, the optical fiber end face 31a is observed to confirm that it forms a mirror surface without cracks or chips, and the optical fiber 30 is rotated relative to the MT ferrule 10 so that the four cores at each optical fiber end face 31a are aligned in the same direction. Other points are the same as the manufacturing method of the first embodiment.

In the second modified example, even for an optical fiber 31 made of a 4-core, 4-core multicore fiber, the refractive index matching portion 21 that covers each optical fiber end face 31a formed on the ferrule end face 12 enables connection with good return loss. Note that, although an example of a 4-core multicore fiber is shown in the second modified example, the number of cores can be increased in the same way to 7, 12, 19, etc. As the number of cores increases, it becomes more difficult to achieve physical contact connection of all cores, so the configuration of modified example 2 is more effective in terms of manufacturing yield the more cores there are.

Second Embodiment
In the second embodiment, a single-core optical connector using an SC ferrule, which is a cylindrical ferrule, will be described. The SC ferrule is used by being attached to a housing of the SC connector. In the second embodiment, an SC ferrule is exemplified as a cylindrical ferrule, but the present invention is not limited to this, and can be applied to an LC ferrule, which is also a cylindrical ferrule, in the same manner.

7 is a perspective view showing an SC ferrule used in an optical connector of the second embodiment. FIG. 8 is a left side view of an SC ferrule used in an optical connector of the second embodiment. The optical connector of the second embodiment is a single-core optical connector that detachably connects a single-core optical fiber 60, and has a substantially cylindrical SC ferrule member 40 that holds the end of the single-core optical fiber 60, and a refractive index matching portion 51 formed on a ferrule end face 42 that faces another optical connector to be connected. The SC ferrule member 40 has a cylindrical ferrule 41 in which a ferrule end face 42 is formed and an optical fiber insertion hole 45 is formed in the length direction, and a flange 49 into which the ferrule 41 is fitted and fixed. The flange 49 is fitted and fixed from the rear end of the ferrule 41 that faces the ferrule end face 42 in the length direction. The ferrule 41 is made of ceramic such as zirconia, and the flange 49 is made of metal. The illustrated single-core optical fiber 60 is a single-core four-core fiber that is a multicore fiber.

In the SC ferrule member 40, the single-core optical fiber 60 is an optical fiber 61 in which the coating has been removed from the optical fiber end face 61a over approximately the length of the ferrule 41, exposing the cladding glass. The optical fiber 61 is guided by the optical fiber insertion hole 45 and is positioned so that the optical fiber end face 61a protrudes from the ferrule end face 42 formed in the ferrule 41, and is fixed to the optical fiber insertion hole 45 at the rear end of the ferrule 41 with an adhesive.

The ferrule end face 42 is formed so as to be perpendicular to the optical axis of the optical fiber 61. The optical fiber end face 61a is a cleavage surface perpendicular to the optical axis of the optical fiber 61, forming a mirror surface without cracks or chips. A solid refractive index matching section 51 having a predetermined thickness that covers the optical fiber end face 61a is formed on the ferrule end face 42. The refractive index matching section 51 is formed in a circular area on the ferrule end face 42 that includes the optical fiber 61 protruding from the ferrule end face 42.

The refractive index matching section 51 is formed of a refractive index matching material and matches the refractive index with the multi-core optical fiber 60. When the multi-core optical fiber 60 is a quartz fiber, its refractive index is adjusted to be equal to that of quartz glass. For example, the refractive index at wavelengths of 1.31 μm and 1.55 μm used in communication is in the range of 1.440 to 1.450. For the refractive index matching material, for example, an acrylic silicone ultraviolet curing resin can be used. In addition, the refractive index matching section 21 has an appropriate hardness so that it can be deformed with a force of, for example, about 10 N so that when the SC ferrule member 40 is attached to the SC connector and the SC connectors are connected to each other, they come into contact without forming any gaps and a good return loss can be ensured. The refractive index matching section 51 is bonded to the ferrule end face 42 and the optical fiber end face 61a, so it will not come off even if you touch it with your hand.

The optical connector of the second embodiment is manufactured by the following process. That is, the coating is removed from the single-core optical fiber 60, and the optical fiber 61 with the exposed cladding glass is cut by cleaving using an optical fiber cleaver or the like so that the optical fiber end face 61a is perpendicular to the optical axis of the optical fiber 61. A cleavage surface is formed on the optical fiber end face 61a. Then, the optical fiber 61 that has passed through the sleeve 49 is guided by the optical fiber insertion hole 45 of the ferrule 41 so that the optical fiber end face 61a protrudes from the ferrule end face 12. At this time, the optical fiber end face 61a protruding from the ferrule end face 42 is observed, and it is confirmed that the cleavage surface forms a mirror surface without cracks or chips. After that, the optical fiber 61 is fixed to the optical fiber insertion hole 45 at the rear end of the ferrule 41 using an adhesive, and a solid refractive index matching part 51 is formed on the ferrule end face 42 using a refractive index matching material so as to cover the optical fiber end face 61a. Furthermore, the ferrule 41 is fitted into the flange 49 from the rear end.

In the second embodiment, a good return loss is ensured by the refractive index matching portion 51 formed to cover the optical fiber end face 61a formed by the cleavage plane protruding from the ferrule end face 42. This eliminates the need for the high-precision optical fiber end face polishing process required in the manufacture of conventional optical connectors, making it possible to provide an optical connector that is easy to manufacture. In addition, a high return loss can be obtained at the connection point without polishing the end face of the optical fiber 61.

In the second embodiment, the refractive index matching section 51 has an appropriate hardness so that when the SC ferrule member 40 is attached to the SC connector and the SC connectors are connected, they deform and come into contact without creating gaps, ensuring good return loss. This eliminates the need to design the optical fiber end face shape taking into account the fiber type and number of cores, or the force required to press the ferrule, in order to obtain high return loss, making it easier to design and manufacture the optical connector.

In the second embodiment, even for an optical fiber 61 made of a multi-core fiber of a single-core 4-core fiber, a refractive index matching portion 51 covering each optical fiber end face 61a formed on the ferrule end face 42 enables connection with good return loss. Note that, although an example of a 4-core multi-core fiber is shown in the second embodiment, the number of cores can be increased in the same way to 7, 12, 19, etc. As the number of cores increases, it becomes more difficult to achieve physical contact connection of all cores, so the configuration of the second embodiment is more effective in terms of manufacturing yield as the number of cores increases.

FIG. 9 is a left side view showing the SC ferrule member 40 of an optical connector according to a modified example of the second embodiment. The SC ferrule member 40 of the modified example differs in that, whereas the SC ferrule member 40 of the second embodiment holds a single-core four-core fiber 60, the SC ferrule member 40 of the modified example holds seven single-core fibers 65, and the inner diameter of the optical fiber insertion hole 45 is also larger. The other configurations are the same as those of the second embodiment.

The SC ferrule member 40 of the modified example is assumed to be connected to an SC ferrule that holds a seven-core multicore fiber. For this reason, the diameter of the single-core fiber 65 is equivalent to the distance between the cores of the multicore fiber. The outer diameter of the clad glass of the single-core fiber is usually about 0.125 mm, but the single-core fiber 65 of the modified example is reduced in outer diameter to the same as the inter-core distance of the multicore fiber by chemical etching or the like. In addition, the inner diameter of the optical fiber insertion hole 45 of the ferrule 41 of the modified example is about three times the inter-core distance of the multicore fiber so as to accommodate seven single-core fibers, and is larger than the inner diameter of the optical fiber insertion hole 45 of the second embodiment. The inner diameter of the optical fiber insertion hole 45 of the ferrule 41 of the corresponding other SC ferrule member 40 to which the modified SC ferrule member 40 is connected is slightly larger than the outer diameter of the clad glass of the multicore fiber.

The manufacturing method of the modified example is different from the manufacturing method of the second embodiment in that a process is added in which the clad glass of the seven single-core fibers 65 is processed to have an appropriate outer diameter in advance, instead of the single-core four-core fiber 60 of the first embodiment, and is assumed to be connected to a seven-core multicore fiber. The other processes are similar except that the optical fiber 61 is replaced with seven single-core fibers 65. In detail, the seven single-core fibers 65, whose coating has been removed and whose exposed clad glass has been processed to have an appropriate outer diameter, are cut by cleavage, and it is confirmed that the optical fiber end faces 65a of the seven single-core fibers protruding from the ferrule end face 42 by inserting them through the optical fiber insertion hole 45 form a mirror surface, and the seven single-core fibers 65 are fixed to the optical fiber insertion hole 45 at the rear end of the ferrule 41 with an adhesive, and a refractive index matching portion 51 is formed on the ferrule end face 42 so as to cover the optical fiber end faces 65a of the seven single-core fibers 65.

The modified SC ferrule member 40 can function as a fan-in fan-out for multicore fibers by connecting it to an SC ferrule with a 7-core multicore fiber attached. The modified SC ferrule has a refractive index matching portion 51 on the ferrule end face 42, so it can be connected to an SC ferrule with a multicore fiber attached while ensuring high return loss.

REFERENCE SIGNS LIST 10 MT ferrule 12 Ferrule end face 16 Optical fiber insertion hole 17 Optical fiber adhesive section 18 Adhesive 21 Refractive index matching section 31 Optical fiber 31a Optical fiber end face

Claims (8)

An optical connector for detachably connecting an optical fiber,
a ferrule for holding an optical fiber such that an end face of the optical fiber is exposed at an end face of the ferrule;
a refractive index matching portion formed on the ferrule end surface so as to cover the optical fiber end surface,
An optical connector, wherein the end face of the optical fiber is a cleavage face. The optical connector of claim 1, wherein the ferrule end face and the optical fiber end face are perpendicular to the optical axis of the optical fiber. The optical connector according to claim 1, wherein the ferrule includes an optical fiber insertion hole leading to the end face of the optical fiber, and an optical fiber adhesive part that is provided at a position away from the optical fiber insertion hole and fixes the optical fiber toward the optical fiber insertion hole with an adhesive. The optical connector of claim 1, wherein the optical fiber end face protrudes from the ferrule end face. The optical connector according to any one of claims 1 to 4, wherein the ferrule is used to connect a multi-fiber optical connector. The optical connector according to any one of claims 1 to 4, wherein the ferrule is used to connect a single-fiber optical connector. The optical connector according to any one of claims 1 to 4, wherein the optical fiber is a multicore fiber including multiple cores. A method for manufacturing an optical connector for detachably connecting optical fibers, comprising the steps of:
The optical fiber is guided along the optical fiber insertion hole of the ferrule so that the optical fiber end face formed by cleavage is exposed at the end face of the ferrule;
The optical fiber is fixed to the ferrule by an adhesive;
forming a refractive index matching portion on the ferrule end face so as to cover the optical fiber end face.

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