Method for manufacturing optical connectors

Abstract

The present invention provides an optical connector and an optical connection structure that can suppress the increase in optical loss due to curing shrinkage of the adhesive. [Solution] The optical connector comprises a resin ferrule having a connecting end face and a fiber hole opening to the connecting end face, a plurality of optical fibers inserted into the fiber hole, and an adhesive disposed inside the ferrule for fixing the plurality of optical fibers to the ferrule. Each of the plurality of optical fibers has a small diameter portion located inside the fiber hole and a large diameter portion with a larger diameter than the small diameter portion. The ferrule does not have an injection hole formed in a region perpendicular to the longitudinal direction of the fiber hole from the small diameter portion for injecting the adhesive.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an optical connector.

Background Art

[0002] In a communication network using optical fibers, the transmission capacity has been increasing year by year. In the currently applied communication network using single-core fibers where each optical fiber has a single core, the transmission capacity is approaching its limit, and the application of multi-core fibers having multiple cores in a single optical fiber is expected.

[0003] In order to apply multi-core fibers to an already operating communication network, a fan-in / fan-out (FIFO) device serving as a conversion device between multi-core fibers and single-core fibers is required when connecting to existing communication devices and amplifiers using single-core fibers, and research and development are underway.

[0004] Non-Patent Document 1 discloses a FIFO device having an optical connector with a structure in which a plurality of optical fibers, which are single-core fibers, are inserted into one fiber hole of a ferrule. By connecting such an optical connector to a second optical connector having a multi-core fiber, a plurality of optical fibers can be connected to the multi-core fiber. In order to align the cores of the plurality of optical fibers with the arrangement of the cores of the multi-core fiber, the tip of the optical fiber is thinned by etching or the like.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] The fiber holes are filled with adhesive to fix multiple optical fibers to the ferrule. The small-diameter sections of the optical fibers, formed by miniaturizing the optical fibers, are susceptible to external stresses. For example, stress due to the curing shrinkage of the adhesive can easily cause minute bends (microbends). Such bending of the optical fiber (small-diameter section) leads to increased optical loss. In addition, injection holes for injecting adhesive are formed in the ferrule. If the injection holes are located near the small-diameter sections, the stress due to the curing shrinkage of the adhesive acting on these sections becomes large, making them more prone to bending and increasing optical loss.

[0007] This invention has been made in consideration of these circumstances and aims to provide a method for manufacturing an optical connector that can suppress the increase in optical loss due to curing shrinkage of the adhesive. [Means for solving the problem]

[0008] To solve the above problems, an optical connector according to embodiment 1 of the present invention comprises a resin ferrule having a connecting end face and a fiber hole opening to the connecting end face, a plurality of optical fibers inserted into the fiber hole, and an adhesive disposed inside the ferrule for fixing the plurality of optical fibers to the ferrule, wherein each of the plurality of optical fibers has a small diameter portion located inside the fiber hole and a large diameter portion with a larger diameter than the small diameter portion, and the ferrule does not have an injection hole formed in a region perpendicular to the longitudinal direction of the fiber hole from the small diameter portion for injecting the adhesive.

[0009] Furthermore, in embodiment 2 of the present invention, in the optical connector of embodiment 1, the injection hole is not formed in the region of the ferrule that is perpendicular to the longitudinal direction along the entire length of the ferrule.

[0010] Furthermore, in embodiment 3 of the present invention, in the optical connector of embodiment 1 or embodiment 2, the outer diameter of the small diameter portion is smaller than 80 μm.

[0011] Furthermore, in embodiment 4 of the present invention, in any one of embodiments 1 to 3, the fiber hole has a D shape in a cross-section perpendicular to the longitudinal direction.

[0012] Furthermore, in embodiment 5 of the present invention, in any one of embodiments 1 to 4, the ferrule has a plurality of fiber holes, including the fiber holes.

[0013] Furthermore, in embodiment 6 of the present invention, in the optical connector of embodiment 5, the ferrule is provided corresponding to each of the plurality of fiber holes and has a plurality of inlet holes opening on the rear end face opposite to the connection end face, wherein the plurality of inlet holes extend independently of each other and communicate with each of the plurality of fiber holes.

[0014] An optical connection structure according to aspect 7 of the present invention comprises an optical connector from any one of aspects 1 to 6, a second optical connector having a second connection end face that abuts the connection end face and a second fiber hole opening to the second connection end face, and a multicore fiber inserted into the second fiber hole and connected to the plurality of optical fibers. [Effects of the Invention]

[0015] According to the above aspects of the present invention, it is possible to provide a method for manufacturing an optical connector that can suppress the increase in optical loss due to curing shrinkage of the adhesive. [Brief explanation of the drawing]

[0016] [Figure 1] This is a perspective view of the optical connector according to the first embodiment. [Figure 2] This is a cross-sectional view taken along the line II-II arrow in Figure 1. [Figure 3]Of the optical connectors shown in FIG. 1, it is a perspective view in which a plurality of optical fibers are extracted. [Figure 4] It is a sectional view taken along the line IV-IV of FIG. 1 as viewed in the direction of the arrow. [Figure 5] It is a graph showing the relationship between microbend loss and the fiber diameter of an optical fiber. [Figure 6] It is a sectional view of an optical connection structure according to the first embodiment. [Figure 7] It is a sectional view of an optical connector according to the second embodiment. [Figure 8] It is a top view of an optical connection structure according to the third embodiment. [Figure 9] It is a sectional view of a conventional optical connector. [Figure 10] It is a graph showing the wavelength dependence of the insertion loss of the optical connector in Example 1. [Figure 11] It is a graph showing the wavelength dependence of the insertion loss of the optical connector in Comparative Example 1.

Mode for Carrying Out the Invention

[0017] Hereinafter, the optical connector and the optical connection structure of the present embodiment will be described based on the drawings. As shown in FIG. 1, the optical connector 1A includes a ferrule 10, a plurality of optical fibers 20, and an adhesive 30. The optical fiber 20 is a single-core fiber. In the present embodiment, the number of optical fibers 20 included in the optical connector 1A is four. However, the number of optical fibers 20 included in the optical connector 1A can be appropriately changed.

[0018] The ferrule 10 has a connecting end face 10a, a rear end face 10b, a fiber hole 11, an injection hole 12, two positioning holes 13, and an introduction hole 14 (see Figure 2). The connecting end face 10a is the surface that abuts against other connectors when the optical connector 1A is connected to other connectors. The fiber hole 11 and the two positioning holes 13 open to the connecting end face 10a. As shown in Figure 2, the introduction hole 14 opens to the rear end face 10b and communicates with the fiber hole 11. The optical fiber 20 is introduced into the fiber hole 11 through the introduction hole 14.

[0019] (direction definition) In this specification, the direction parallel to the central axis O of the fiber hole 11 is referred to as the Z direction, axial Z, or longitudinal direction Z. One direction perpendicular to the longitudinal direction Z is referred to as the first direction X. The first direction X is also the direction in which the two positioning holes 13 are aligned. The direction perpendicular to both the longitudinal direction Z and the first direction X is referred to as the second direction Y. Along the longitudinal direction Z, the direction from the rear end face 10b of the ferrule 10 toward the connecting end face 10a is referred to as the +Z direction, forward, or tip side. The direction opposite to the +Z direction is referred to as the -Z direction, rear, or base side. Viewed from the longitudinal direction Z, the direction perpendicular to the central axis O is referred to as the radial direction. Along the radial direction, the direction approaching the central axis O is referred to as the radially inward direction, and the direction moving away from the central axis O is referred to as the radially outward direction. The direction that circles around the central axis O when viewed from the longitudinal direction Z is called the circumferential direction. A cross-section perpendicular to the longitudinal direction Z is called a transverse surface. In other words, a transverse surface is a cross-section that extends along the first direction X and the second direction Y.

[0020] At the connection end face 10a, the fiber hole 11 is positioned between two positioning holes 13. Multiple optical fibers 20 are inserted into a single fiber hole 11. The illustrated optical connector 1A is the female side, and the relative positions of optical connector 1A and the other optical connectors are determined by inserting the positioning pins of the other optical connectors into the positioning holes 13. However, optical connector 1A may also be the male side; that is, optical connector 1A may have positioning pins.

[0021] As shown in Figure 2, the connecting end face 10a is inclined with respect to a virtual plane P that is perpendicular to the longitudinal direction Z when viewed from the first direction X. This inclined connecting end face 10a is formed, for example, by polishing the end face of the ferrule 10. The angle between the connecting end face 10a and the virtual plane P is, for example, 8°. However, this angle can be changed. By inclining the connecting end face 10a in this way, the amount of light reflected at the connection point can be reduced. However, the connecting end face 10a does not have to be inclined.

[0022] The ferrule 10 is made of resin. For example, the material of the ferrule 10 may be polyetheretherketone (PEEK) resin, polyarylene sulfide (PAS) resin, polyphenylene sulfide (PPS) resin, polyethersulfone (PES) resin, polyetherimide (PEI) resin, or liquid crystalline resin (LCP) with a melting point of 300°C or higher. The ferrule 10 has a substantially rectangular parallelepiped shape. The ferrule 10 is manufactured, for example, by resin molding. In this case, the ferrule 10 can be manufactured easily and with high precision. Furthermore, the design freedom for the shape and position of the fiber hole 11 and positioning hole 13 is increased, making the ferrule 10 suitable for use in, for example, multi-core connectors. In the case of a zirconia ferrule, alignment with other optical connectors is performed by the outer shape of the ferrule. On the other hand, in the case of a resin ferrule 10, as described above, alignment with other optical connectors is performed using the positioning hole 13. Therefore, high-precision alignment between optical connector 1 and other optical connectors can be achieved.

[0023] Figure 3 is a diagram showing multiple optical fibers 20 extracted from Figure 1. As shown in Figure 3, each optical fiber 20 has a bare fiber 21 and a sheath 22. The bare fiber 21 is made of, for example, quartz glass. The sheath 22 partially covers the bare fiber 21 and serves to protect it. The sheath 22 is made of a resin or the like. For example, the material of the sheath 22 may be a UV-curable resin. At the front end of each optical fiber 20, there is no sheath 22, and the bare fiber 21 is exposed. The exposed bare fiber 21 is inserted into the fiber hole 11 of the ferrule 10.

[0024] The bare fiber 21 has a small-diameter portion 21a, a large-diameter portion 21b, and a tapered portion 21c. The small-diameter portion 21a is located at the tip of the bare fiber 21. The outer diameter of the small-diameter portion 21a is smaller than the outer diameter of the large-diameter portion 21b. The tapered portion 21c is located between the small-diameter portion 21a and the large-diameter portion 21b. The tapered portion 21c has an outer diameter that gradually decreases as it extends forward. The small-diameter portion 21a and the tapered portion 21c can be formed by tapering the end of a bare fiber 21 that has a constant outer diameter in the longitudinal direction (the same outer diameter as the large-diameter portion 21b), for example, by etching. In this embodiment, the four small-diameter portions 21a of the four optical fibers 20 are inserted into one fiber hole 11 of the ferrule 10.

[0025] Figure 4 is a cross-sectional view of the vicinity of the fiber hole 11. As shown in Figure 4, the bare fiber 21 has a core 21d and a cladding 21e. The cladding 21e is arranged to surround the core 21d. The refractive index of the cladding 21e is lower than that of the core 21d. Therefore, the optical fiber 20 can confine light inside the core 21d.

[0026] In a cross-section perpendicular to the longitudinal direction Z, the fiber hole 11 is non-circular. Specifically, in the above cross-section, the fiber hole 11 is D-shaped. The fiber hole 11 has a curved portion 11a and a straight portion 11b. The curved portion 11a has an arc shape. Of the four bare fibers 21, two bare fibers 21 abut against both the curved portion 11a and the straight portion 11b. The remaining two bare fibers 21 abut against the curved portion 11a but not against the straight portion 11b. These four bare fibers 21 are positioned within the fiber hole 11 by abutting against the inner surface of the fiber hole 11 as described above.

[0027] The adhesive 30 has the function of fixing multiple optical fibers 20 to the ferrule 10. The adhesive 30 is filled in the gap between the inner surface of the fiber hole 11 and the outer surface of the optical fiber 20 (bare fiber 21). As the material of the adhesive 30, for example, a thermosetting resin can be used. More specifically, the material of the adhesive 30 may be an epoxy resin.

[0028] The adhesive 30 is injected into the ferrule 10 through the injection hole 12. As shown in Figure 2, the injection hole 12 opens into one end face of the ferrule 10 facing the second direction Y. The injection hole 12 communicates with the internal space of the ferrule 10 and the fiber hole 11. When the optical connector 1A is assembled, the adhesive 30 is injected into the ferrule 10 through the injection hole 12.

[0029] In this embodiment, the injection hole 12 is not formed in the region of the ferrule 10 from the small diameter portion 21a to the region perpendicular to the longitudinal direction Z. In the illustrated example, the injection hole 12 is formed at the base end of the ferrule 10. The injection hole 12 is positioned in the longitudinal direction Z at a location that overlaps with the large diameter portion 21b. The injection hole 12 is positioned in the longitudinal direction Z at a location that does not overlap with the small diameter portion 21a and the tapered portion 21c. The injection hole 12 may also be positioned in the longitudinal direction Z at a location that overlaps with the coating 22.

[0030] In this case, the small-diameter section of the optical fiber is susceptible to external stress, and for example, stress due to the curing shrinkage of the adhesive can easily cause minute bends (microbends). Such bending of the optical fiber (small-diameter section) leads to increased optical loss. Furthermore, if the injection hole for injecting the adhesive is located near the small-diameter section, the stress due to the curing shrinkage of the adhesive acting on the small-diameter section becomes large, making bending of the small-diameter section more likely and increasing optical loss.

[0031] In this embodiment, injection holes 12 are not formed in the region of the ferrule 10 that is perpendicular to the longitudinal direction Z, starting from the small-diameter portion 21a. Therefore, compared to, for example, the case where the injection holes are located near the small-diameter portion, the stress due to curing shrinkage of the adhesive 30 acting on the small-diameter portion 21a can be reduced. As a result, bending of the small-diameter portion 21a can be suppressed, and the increase in light loss can be suppressed.

[0032] Figure 5 shows the relationship between the fiber diameter of an optical fiber and the microbend loss. The relative microbend loss on the vertical axis of Figure 5 is the calculated value of the microbend loss for each fiber diameter, and is a reference value based on the microbend loss when the fiber diameter is 125 μm. As shown in Figure 5, the smaller the fiber diameter, the more susceptible the effects of microbend become. In the example shown, when the fiber diameter is 80 μm, the microbend loss is significantly higher compared to when the fiber diameter is 125 μm. Also, when the fiber diameter is 55 μm, the microbend loss is 10 times higher than when the fiber diameter is 125 μm. From the above results, it can be seen that when the diameter of the small-diameter portion 21a is smaller than 80 μm, optical loss due to microbending tends to increase. Therefore, when the diameter of the small-diameter portion 21a is smaller than 80 μm, it is more desirable to suppress the bending (microbending) of the small-diameter portion 21a in order to prevent an increase in optical loss. In this embodiment, by configuring the ferrule 10 so that the injection hole 12 is not formed in the region perpendicular to the longitudinal direction Z from the small-diameter portion 21a, the bending (microbending) of the small-diameter portion 21a can be suppressed. In other words, this embodiment is suitable for optical fibers 20 in which the diameter of the small-diameter portion 21a is smaller than 80 μm, and is even more suitable for optical fibers in which the diameter of the small-diameter portion 21a is smaller than 55 μm.

[0033] The assembly of optical connector 1A is performed, for example, by following the procedure below.

[0034] First, prepare multiple optical fibers 20 that have a coating 22. Next, the coating 22 is partially removed from each of the optical fibers 20 to expose the bare fiber 21. Next, a portion of the exposed bare fiber 21 is reduced in diameter by etching or the like. By varying the immersion time in the etching solution for each position along the longitudinal direction of the bare fiber 21, the small-diameter portion 21a and the tapered portion 21c can be made to any desired outer diameter.

[0035] Next, the bundled bare fibers 21 are inserted into the fiber holes 11 of the ferrule 10. Then, the fluid adhesive 30 is injected into the internal space of the ferrule 10 through the injection hole 12. The adhesive 30 may be actively forced into the fiber holes 11 by using a vacuum or the like to draw suction from the fiber holes 11 that open on the connecting end face 10a. Alternatively, the adhesive 30 may be forced into the fiber holes 11 by capillary forces or the like.

[0036] Next, the bare fiber 21 is fixed to the ferrule 10 by curing the adhesive 30. For example, if the adhesive 30 is a thermosetting resin such as epoxy resin, the adhesive 30 is heated to a temperature above its curing temperature. For example, if the adhesive 30 is a UV-curing resin, the adhesive 30 may be cured by irradiating it with UV light.

[0037] As described above, multiple optical fibers 20 can be fixed to the ferrule 10. If necessary, an optical connector 1A can be obtained by attaching other components to the ferrule 10.

[0038] Figure 6 is a cross-sectional view showing an optical connection structure C including an optical connector 1A. As shown in Figure 6, the optical connection structure C comprises an optical connector 1A, a second optical connector 100, and an adapter 2.

[0039] The second optical connector 100 comprises a second ferrule 110, a multicore fiber 120, and an adhesive 130. The second ferrule 110 has a second connection end face 110a and a second fiber hole 111 opening into the second connection end face 110a. The second connection end face 110a abuts against the connection end face 10a of the ferrule 10 of the optical connector 1A. The multicore fiber 120 has a bare fiber 121 and a sheath 122. At the front end of the multicore fiber 120, the sheath 122 is not provided, and the bare fiber 121 is exposed. The exposed bare fiber 121 is inserted into the second fiber hole 111. The multicore fiber 120 is connected to the multiple optical fibers 20 of the optical connector 1A. The adhesive 130 is injected into the second ferrule 110 to fix the multicore fiber 120 to the second ferrule 110.

[0040] The second optical connector 100 has positioning pins (not shown), and the relative positions of the optical connector 1A and the second optical connector 100 are determined by inserting the positioning pins of the second optical connector 100 into the positioning holes 13 of the optical connector 1A. The adapter 2 has the function of maintaining a state in which the connection end face 10a of the optical connector 1A and the second connection end face 110a of the second optical connector 100 are in contact with each other at an appropriate position. The adapter 2 has a through hole 2a that penetrates the adapter 2 in the longitudinal direction Z. The optical connector 1A and the second optical connector 100 are inserted into the through hole 2a, respectively.

[0041] As described above, the optical connector 1A according to this embodiment comprises a resin ferrule 10 having a connection end face 10a and a fiber hole 11 opening to the connection end face 10a, a plurality of optical fibers 20 inserted into the fiber hole 11, and an adhesive 30 disposed inside the ferrule 10 for fixing the plurality of optical fibers 20 to the ferrule 10. Each of the plurality of optical fibers 20 has a small diameter portion 21a located inside the fiber hole 11 and a large diameter portion 21b having a larger diameter than the small diameter portion 21a. Of the ferrule 10, there is no injection hole 12 formed from the small diameter portion 21a to a region perpendicular to the longitudinal direction Z of the fiber hole 11 into which the adhesive 30 is injected. Furthermore, the optical connection structure C according to this embodiment includes an optical connector 1A, a second optical connector 100 having a second connection end face 110a that abuts against the connection end face 10a, and a second fiber hole 111 that opens into the second connection end face 110a, and a multicore fiber 120 that is inserted into the second fiber hole 111 and connected to a plurality of optical fibers 20. With the optical connector 1A and optical connection structure C having such a configuration, it is possible to suppress the increase in optical loss due to curing shrinkage of the adhesive 30.

[0042] Furthermore, the outer diameter of the small-diameter portion 21a is less than 80 μm. In such an optical connector 1A, an injection hole 12 into which adhesive 30 is injected is not formed in the ferrule 10 from the small-diameter portion 21a to a region perpendicular to the longitudinal direction Z of the fiber hole 11, thereby suppressing the increase in optical loss due to curing shrinkage of the adhesive 30.

[0043] Furthermore, in a cross-section perpendicular to the longitudinal direction Z, the fiber hole 11 has a D shape. That is, the fiber hole 11 has a curved portion 11a and a straight portion 11b. In this case, it becomes easier to control the position of the optical fiber 20 inside the fiber hole 11. More specifically, for example, after injecting the adhesive 30 into the fiber hole 11, the optical fiber 20 can be aligned with respect to the straight portion 11b before the adhesive 30 hardens. The presence of the straight portion 11b, which serves as a position reference, makes it easier to control the position of the optical fiber 20 in the circumferential direction. As a result, rotational alignment of the optical fiber 20 is unnecessary when connecting the optical connector 1A to another optical connector (for example, a second optical connector 100), and the optical connector 1A can be easily connected to other optical connectors.

[0044] (Second Embodiment) Next, a second embodiment of the present invention will be described, which has the same basic configuration as the first embodiment. For this reason, the same reference numerals are used for similar components, and their descriptions are omitted; only the differences will be described.

[0045] As shown in Figure 7, in the optical connector 1B of this embodiment, the ferrule 10 does not have an injection hole. In other words, along the entire length of the ferrule 10 in the longitudinal direction Z, no injection holes are formed in the region of the ferrule 10 that is perpendicular to the longitudinal direction Z.

[0046] In assembling such an optical connector 1B, before inserting multiple bare fibers 21 into the fiber holes 11 of the ferrule 10, a fluid adhesive 30 is injected into the internal space of the ferrule 10 through an introduction hole 14. Then, the multiple bare fibers 21 are inserted into the fiber holes 11 through the introduction hole 14. As the multiple bare fibers 21 are inserted into the fiber holes 11, the adhesive 30 also enters the fiber holes 11. The adhesive 30 may be actively forced into the fiber holes 11 by suctioning the fiber holes 11 that open on the connection end face 10a using a vacuum or the like. After that, the bare fibers 21 are fixed to the ferrule 10 by curing the adhesive 30. In addition, any portion of the adhesive 30 that overflows from the fiber holes 11 towards the connection end face 10a may be removed by polishing the end face of the ferrule 10 after the adhesive 30 has cured.

[0047] As described above, in the optical connector 1B according to this embodiment, injection holes are not formed in the region of the ferrule 10 that is perpendicular to the longitudinal direction Z along the entire length of the ferrule 10 in the longitudinal direction Z. This configuration allows for a reduction in the amount of adhesive 30. Therefore, it is possible to more effectively suppress the increase in optical loss due to curing shrinkage of the adhesive 30. In addition, the structure of the ferrule 10 can be made simpler.

[0048] (Third embodiment) Next, a third embodiment of the present invention will be described, which has the same basic configuration as the first embodiment. For this reason, the same reference numerals are used for similar components, and their descriptions are omitted; only the differences will be described.

[0049] As shown in Figure 8, the optical connection structure C' of this embodiment includes an optical connector 1C, a second optical connector 100', and an adapter 2.

[0050] In the optical connector 1C of this embodiment, the ferrule 10 has a plurality of fiber holes 11. The plurality of fiber holes 11 are arranged in a first direction X. A plurality of optical fibers 20 are inserted through each of the plurality of fiber holes 11. The ferrule 10 is also provided with a plurality of inlet holes 14, each corresponding to the plurality of fiber holes 11. The plurality of inlet holes 14 extend independently of each other and communicate with each of the plurality of fiber holes 11. In addition, a single injection hole 12 is provided so as to communicate with the plurality of inlet holes 14.

[0051] The second optical connector 100' is equipped with multiple multicore fibers 120. The second ferrule 110 has multiple second fiber holes 111 through which each of the multiple multicore fibers 120 is inserted. The multiple second fiber holes 111 are provided in correspondence with each of the multiple fiber holes 11. The multicore fibers 120 are connected to multiple optical fibers 20 inserted through the corresponding fiber holes 11.

[0052] As described above, in the optical connector 1C according to this embodiment, the ferrule 10 has a plurality of fiber holes 11. In this case, a single ferrule 10 can have a plurality of fan-in / fan-out (FIFO) structures, and optical fibers 20 can be arranged at high density.

[0053] Furthermore, the ferrule 10 has multiple inlet holes 14 that are provided corresponding to each of the multiple fiber holes 11 and open on the rear end face 10b opposite to the connection end face 10a. The multiple inlet holes 14 extend independently of each other and communicate with each of the multiple fiber holes 11. In this case, for example, the amount of adhesive 30 can be reduced compared to the case where the multiple inlet holes 14 communicate with each other. Even when multiple fiber holes 11 are provided, it is possible to effectively suppress the increase in optical loss due to curing shrinkage of the adhesive 30.

[0054] (Examples) The above embodiments will be described below using specific examples. However, the present invention is not limited to the following embodiments.

[0055] Nine optical connectors were prepared, corresponding to Examples 1 to 5 and Comparative Examples 1 to 4. The insertion loss of each optical connector corresponding to Examples 1 to 5 and Comparative Examples 1 to 4 was measured.

[0056] The optical connector according to Examples 1 to 5 is the optical connector 1B (second embodiment) shown in Figure 7. That is, in optical connector 1B, injection holes are not formed in the region of the ferrule 10 that is perpendicular to the longitudinal direction Z along the entire length of the ferrule 10. The number of optical fibers 20 in optical connector 1B is four. The outer diameter of the small diameter portion 21a of the optical fiber 20 is 40 μm. The angle between the connection end face 10a of the ferrule 10 and the virtual plane P is 8°. The optical connectors relating to Comparative Examples 1 to 4 are the optical connector 200 (conventional example) shown in Figure 9. The optical connector 200 comprises a ferrule 210, a plurality of optical fibers 20, and an adhesive 30. The optical fibers 20 and adhesive 30 are the same as those in optical connector 1B. The number of optical fibers 20 in the optical connector 200 is four, the same as in optical connector 1B. The outer diameter of the small-diameter portion 21a of the optical fiber 20 is 40 μm. The ferrule 210 has a connecting end face 210a, a rear end face 210b, a fiber hole 211, an injection hole 212, two positioning holes (not shown), and an introduction hole 214. In the optical connector 200, the injection hole 212 formed in the ferrule 210 is positioned to overlap with the small-diameter portion 21a in the longitudinal direction Z. The other configurations are the same as the ferrule 10 of optical connector 1B. For example, the angle between the connecting end face 210a of the ferrule 210 and the virtual plane P was set to 8°, similar to the optical connector 1B.

[0057] The insertion loss (dB) was measured for each of the optical connectors according to Examples 1 to 5 and Comparative Examples 1 to 4. Table 1 shows the insertion loss of the optical connectors at a wavelength of 1310 nm. Table 1 also shows the insertion loss and its maximum value for each of the four optical fibers (ch1 to ch4).

[0058] [Table 1]

[0059] As shown in Table 1, it was confirmed that the insertion loss of the optical connectors in Examples 1 to 5 was reduced compared to the optical connectors in Comparative Examples 1 to 4.

[0060] Figures 10(a) to 10(d) are graphs showing the wavelength dependence of the insertion loss of the four optical fibers (ch1 to ch4) of the optical connector according to Example 1. Figures 11(a) to 11(d) are graphs showing the wavelength dependence of the insertion loss of the four optical fibers (ch1 to ch4) of the optical connector according to Comparative Example 1. As shown in Figures 10 and 11, it was confirmed that in the optical connector according to Example 1, the insertion loss was reduced for all four optical fibers (ch1 to ch4) compared to the optical connector according to Comparative Example 1, and the wavelength characteristics of the connection loss were also improved.

[0061] The technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

[0062] For example, in the optical connector 1C of the third embodiment, a plurality of injection holes 12 may be formed corresponding to each of the plurality of fiber holes 11. Also, similar to the second embodiment, in the optical connector 1C, injection holes may not be formed in the region of the ferrule 10 that is perpendicular to the longitudinal direction Z along the entire length of the ferrule 10.

[0063] Furthermore, without departing from the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments and modifications may be combined as appropriate. [Explanation of Symbols]

[0064] 1A, 1B, 1C…Optical connector 10…Ferrule 10a…Connecting end face 10b…Rear end face 11…Fiber hole 12…Injection hole 14…Inlet hole 20…Optical fiber 21a…Small diameter section 21b…Large diameter section 30…Adhesive 100, 100'…Second optical connector 110…Second ferrule 110a…Second connecting end face 111…Second fiber hole 120…Multicore fiber C, C'…Optical connection structure

Claims

1. A resin ferrule having a connecting end face, an introduction hole opening to the rear end face opposite the connecting end face, and a fiber hole opening to the connecting end face and communicating with the introduction hole, wherein, along the entire length of the fiber hole in the ferrule, in a region of the ferrule perpendicular to the longitudinal direction, an injection hole for injecting adhesive is not formed; An injection step in which adhesive is injected into the fiber hole from the introduction hole, Following the injection step, an insertion step is performed in which a plurality of bare fibers are inserted into the fiber holes into which the adhesive has been injected. A method for manufacturing an optical connector, comprising the features described above.

2. The method for manufacturing an optical connector according to claim 1, further comprising a suction step of suctioning the adhesive from the opening of the fiber hole opening on the connecting end face after the insertion step.

3. A method for manufacturing an optical connector according to claim 1 or 2, further comprising a bundling step, before the insertion step, of bundling the plurality of bare fibers so that, when viewed from the longitudinal direction, a plurality of fibers are arranged in a first direction perpendicular to the longitudinal direction and a plurality of fibers are arranged in a second direction perpendicular to both the longitudinal direction and the first direction.

4. The aforementioned plurality of bare fibers consist of four bare fibers, In the bundling process, the four bare fibers are bundled together such that, when viewed from the longitudinal direction, two are arranged in the first direction and two in the second direction. A method for manufacturing an optical connector according to claim 3.

5. The method for manufacturing an optical connector according to claim 1 or 2, wherein the fiber hole has a straight portion in a cross-section perpendicular to the longitudinal direction.

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