Optical connector and method for manufacturing same

Abstract

An optical connector 10 includes: a substrate 12 in which a groove 24 is formed; an optical fiber 14 disposed in a groove 24 of the substrate 12 and having a predetermined outer diameter; a GRIN lens 16 disposed in the groove 24 of the substrate 12 and having the same outer diameter as that of the optical fiber 14; and a high transmittance member 18 disposed between the optical fiber 14 and the GRIN lens 16.

Description

Optical connector and manufacturing method thereof

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

[0002] 2. Description of the Related Art Conventionally, optical connectors have been known in which a GRIN lens is disposed at the tip of an optical fiber such as a single-mode fiber.

[0003] International Publication No. 2023 / 100607

[0004] In such optical connectors, alignment of the optical fiber and the GRIN lens is important to reduce optical loss, and if alignment of these components can be made easier, the manufacturing efficiency of optical connectors will improve.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical connector in which the alignment of components is easy, and a method for manufacturing the same.

[0006] In order to solve the above problems, an optical connector according to one embodiment of the present invention comprises a substrate having a groove formed therein, an optical fiber having a predetermined outer diameter and placed in the groove of the substrate, a GRIN lens having the same outer diameter as the optical fiber and placed in the groove of the substrate, and a high transmittance member placed between the optical fiber and the GRIN lens.

[0007] Another aspect of the present invention is a method for manufacturing an optical connector, comprising the steps of forming a groove in a substrate, forming a recess in the groove and arranging a high-transmittance member in the recess, arranging an optical fiber having a predetermined outer diameter in one of the grooves divided by the recess, and arranging a GRIN lens having the same outer diameter as the optical fiber in the other groove divided by the high-transmittance member.

[0008] Any combination of the above components and conversion of the present invention into a method, device, system, etc. are also valid aspects of the present invention.

[0009] According to the present invention, it is possible to provide an optical connector in which the alignment of components is easy, and a method for manufacturing the same.

[0010] FIGS. 1(a) to 1(c) are diagrams illustrating an optical connector according to an embodiment. They are enlarged views of a GRIN lens and a groove in the optical connector shown in FIG. 1(b). FIGS. 3(a) to 3(c) are diagrams illustrating a first step of a manufacturing method for an optical connector according to the embodiment. FIGS. 4(a) to 4(c) are diagrams illustrating a second step of a manufacturing method for an optical connector according to the embodiment. FIGS. 5(a) to 5(c) are diagrams illustrating a third step of a manufacturing method for an optical connector according to the embodiment. FIGS. 6(a) to 6(c) are diagrams illustrating a fourth step of a manufacturing method for an optical connector according to the embodiment. FIGS. 7(a) to 7(c) are diagrams illustrating a fifth step of a manufacturing method for an optical connector according to the embodiment. FIGS. 8(a) to 8(c) are diagrams illustrating a sixth step of a manufacturing method for an optical connector according to the embodiment. A right side view of an optical connector according to a modified example. A right side view of an optical connector according to another modified example. A plan view of an optical connector according to yet another modified example. FIGS. 12(a) to 12(d) are diagrams illustrating a method for manufacturing a high-transmittance member having a light-shielding wall. 1 is a diagram showing a calculation model in an optical simulation;

[0011] The present invention will be described below based on preferred embodiments with reference to the drawings. The following configurations are for illustrative purposes only to facilitate understanding of the present disclosure, and the scope of the present disclosure is defined solely by the appended claims. Identical or equivalent components and parts shown in each drawing are designated by the same reference numerals, and redundant explanations will be omitted where appropriate. Furthermore, the dimensions of the components in each drawing are enlarged or reduced as appropriate to facilitate understanding. Furthermore, some components that are not important for explaining the embodiments in each drawing are omitted.

[0012] 1(a) to 1(c) show an optical connector 10 according to an embodiment. Fig. 1(a) is a plan view, Fig. 1(b) is a front view, and Fig. 1(c) is a right side view. The same applies to the subsequent figures.

[0013] The optical connector 10 according to this embodiment is an optical connector array in which a plurality of optical connectors are integrated.

[0014] The optical connector 10 includes a substrate 12, a plurality of optical fibers 14, a plurality of GRIN lenses 16, a high transmittance member 18, a fiber cover member 20, and a lens cover member 22. The material of the fiber cover member 20 and the lens cover member 22 can be the same as that of the substrate 12 and the high transmittance member 18, such as glass.

[0015] The substrate 12 is rectangular in plan view. A plurality of linear grooves 24 are formed on the upper surface 12a of the substrate 12 in parallel with the short-side direction of the substrate 12. In this embodiment, the grooves 24 are so-called V-grooves, which have a V-shaped cross section perpendicular to the extension direction. The shape of the grooves 24 is not particularly limited, but considering the processing accuracy and the positioning accuracy of the optical fiber 14 and the GRIN lens 16, a V-groove is preferable.

[0016] In addition, a recess 26 is formed on the upper surface 12a of the substrate 12. The recess 26 is formed along the longitudinal direction of the substrate 12 so as to cross the middle of the groove 24. Therefore, each groove 24 is divided into two by the recess 26.

[0017] An optical fiber 14 having a circular cross section is placed in each of the divided grooves. The optical fiber 14 has a predetermined outer diameter. The optical fiber 14 may be a single-mode fiber having an outer diameter of 125 μm.

[0018] A GRIN lens 16 with a circular cross section is placed in each of the other divided grooves. The GRIN lens 16 is a lens for collimating the light emitted from the optical fiber 14. By using a GRIN lens as a collimating lens placed at the tip of the optical fiber 14, the emitted light can be collimated both in air and in liquid. With a normal convex lens, the difference in refractive index changes between air and liquid, causing the optical path to change. In addition, it is difficult to process a convex lens with an outer diameter of 125 μm, and it is extremely difficult to make it aspherical to reduce aberration rather than simply spherical.

[0019] The GRIN lens 16 has the same outer diameter as the optical fiber 14. When the optical fiber 14 is a single-mode fiber with an outer diameter of 125 μm, the GRIN lens 16 also has an outer diameter of 125 μm. The GRIN lens 16 may be a glass lens or a resin lens, but a glass lens is preferable from the viewpoint of transmittance and weather resistance.

[0020] The high transmittance member 18 is disposed between the plurality of optical fibers 14 arranged in the grooves 24 of the substrate 12 and the plurality of GRIN lenses 16. The high transmittance member 18 is disposed in a recess 26 formed in the upper surface 12a of the substrate 12.

[0021] The high-transmittance member 18 is formed in a block shape. By forming the high-transmittance member 18 in a block shape, as will be described later, the end faces of the optical fiber 14 and the GRIN lens 16 can be pressed against and fixed to the high-transmittance member 18 during manufacturing, making alignment easier. For this purpose, it is desirable that the surfaces of the high-transmittance member 18 that face the end face of the optical fiber 14 and the end face of the GRIN lens 16 be formed flat.

[0022] In this embodiment, instead of providing a separate high-transmittance member 18 for each pair of optical fiber 14 and GRIN lens 16, a single high-transmittance member 18 is provided that is common to multiple pairs of optical fiber 14 and GRIN lens 16. If the high-transmittance member 18 were not common but were provided separately for each pair, the high-transmittance member would be rod-shaped and have the same diameter as the optical fiber 14 and GRIN lens 16 so that it could be placed in the groove 24. In this case, the rod-shaped high-transmittance member has a very small outer diameter, for example, 125 μm, and precision and variation would be significant problems if it were cut and polished individually. By forming the high-transmittance member 18 into a block shape as in this embodiment, the high-transmittance member 18 can be made to a certain size, thereby improving the precision of cutting and polishing the high-transmittance member 18 itself.

[0023] The high-transmittance member 18 can be a glass block or a resin block, but a glass block is preferable from the viewpoint of transmittance and weather resistance. The high-transmittance member 18 may be a glass block with a refractive index n = 1.5 (@1.31 μm). The glass constituting the glass block is not particularly limited as long as it has satisfactory transparency (no absorption), flatness, and processability (ability to be formed into blocks). In addition, in the case of a resin block, a transparent resin such as acrylic or polycarbonate can be used.

[0024] 2 is an enlarged view of the GRIN lens 16 and groove 24 in the optical connector 10 shown in FIG. 1( b). As shown in FIG. 2, a GRIN lens 16 is disposed in each of a plurality of grooves 24 (V-grooves) formed in the upper surface 12a of the substrate 12. The plurality of GRIN lenses 16 are held down from above by a common lens cover member 22. The lens cover member 22 and the GRIN lenses 16 are fixed to the substrate 12 with adhesive 28. By using a V-groove as the groove 24, the position of the GRIN lens 16 within the groove 24 can be stabilized. Furthermore, the end face of the GRIN lens 16 abuts against the opposing surface of the high transmittance member 18.

[0025] The optical fibers 14 are fixed to the grooves 24 in the same manner as the grooves 24 of the GRIN lens 16 shown in FIG. 2 . That is, the optical fibers 14 are arranged in each of a plurality of grooves 24 (V-grooves) formed in the upper surface 12a of the substrate 12. The plurality of optical fibers 14 are held down from above by a common fiber cover member 20. The fiber cover member 20 and the optical fibers 14 are fixed to the substrate 12 with adhesive 28. By using a V-groove as the groove 24, the position of the optical fiber 14 within the groove 24 can be stabilized. Furthermore, the end face of the optical fiber 14 abuts against the opposing surface of the high transmittance member 18.

[0026] As in the optical connector 10 of this embodiment, by placing a high transmittance member 18 between the optical fiber 14 and the GRIN lens 16, the light emitted from the optical fiber 14 can be expanded before entering the GRIN lens 16, and the diameter of the collimated light emitted from the GRIN lens 16 can be increased.

[0027] As described above, in the optical connector 10 according to this embodiment, the outer diameter of the optical fiber 14 is the same as the outer diameter of the GRIN lens 16. This makes it possible to easily align the optical fiber 14 and the GRIN lens 16 simply by placing the optical fiber 14 and the GRIN lens 16 in one groove 24 (a groove having the same central axis), thereby improving manufacturing efficiency.

[0028] If the optical fiber 14 is a single-mode fiber with an outer diameter of 125 μm, the outer diameter of the GRIN lens 16 will be 125 μm. By making the optical fiber 14 and the GRIN lens 16 have the same outer diameter of 125 μm, it is possible to arrange many optical fibers 14 and GRIN lenses 16 in a very narrow width, and the optical connector 10 can be made smaller.

[0029] Next, a method for manufacturing the optical connector 10 according to this embodiment will be described. Figures 3(a) to 3(c) are diagrams for explaining the first step of the method for manufacturing the optical connector 10 according to this embodiment. In the first step, a plurality of grooves 24 are formed in the upper surface 12a of the substrate 12.

[0030] 4(a) to 4(c) are diagrams illustrating the second step of the manufacturing method for the optical connector 10 according to this embodiment. In the second step, a recess 26 is formed in the upper surface 12a of the substrate 12 so as to cross the middle of the multiple grooves 24. Note that the first and second steps may be reversed. That is, the multiple grooves 24 may be formed after the recess 26 is formed in the upper surface 12a of the substrate 12.

[0031] 5(a) to 5(c) are diagrams illustrating a third step in the manufacturing method of the optical connector 10 according to this embodiment. In the third step, an adhesive is applied to the recess 26 of the substrate 12, and then the high transmittance member 18 is placed and fixed in the recess 26. A UV-curable adhesive or a heat-curable adhesive can be used as the adhesive.

[0032] 6(a) to 6(c) are diagrams illustrating a fourth step in the manufacturing method of the optical connector 10 according to this embodiment. In the fourth step, an adhesive is applied to one of the grooves 24 divided by the recess 26, and then the optical fiber 14 is placed in the groove 24. The optical fiber 14 is then held down by the fiber cover member 20 and adhesively fixed. At this time, the optical fiber 14 is pressed against the high-transmittance member 18 so that there is no gap between the end face of the optical fiber 14 and the opposing surface of the high-transmittance member 18.

[0033] 7(a) to 7(c) are diagrams illustrating a fifth step in the manufacturing method for the optical connector 10 according to this embodiment. In the fifth step, an adhesive is applied to the other groove 24 separated by the recess 26, and then the GRIN lens 16 is placed in the other groove 24. The GRIN lens 16 is then pressed down with the lens cover member 22 and adhesively fixed in place. At this time, the GRIN lens 16 is pressed against the high transmittance member 18 so that there is no gap between the end face of the GRIN lens 16 and the opposing surface of the high transmittance member 18.

[0034] 8(a) to 8(c) are diagrams illustrating a sixth step in the manufacturing method of the optical connector 10 according to this embodiment. In this sixth step, the GRIN lens 16 is cut in one go and the cut surfaces are polished in one go to achieve the target length. By cutting and polishing the GRIN lens 16 in one go, handling is simplified, eliminating the need to handle small components, and precision and reduced variation can be achieved. The end face of the GRIN lens 16 may be flush with the end face of the substrate 12 or slightly uneven relative to the end face of the substrate 12, depending on the difference in hardness between the GRIN lens 16 and the substrate 12 and the polishing conditions.

[0035] Fig. 9 is a right side view showing an optical connector 30 according to a modified example. In the optical connector 30 shown in Fig. 9, the height of the high transmittance member 18 is smaller than that of the optical connector 10 described above. In this case, the fiber cover member and the lens cover member do not need to be separate members, but can be made into an integrated cover member 32. The cover member 32 has a recessed portion 34 formed therein into which a portion of the high transmittance member 18 fits.

[0036] Fig. 10 is a right side view showing an optical connector 40 according to another modification. In the optical connector 40 shown in Fig. 10, the height of the high transmittance member 18 is the same as the height of the optical fiber 14 and the GRIN lens 16. In this case, there is no need to provide a recess, and a flat cover member 42 can be used in which the fiber cover member and the lens cover member are integrated.

[0037] 11 is a plan view showing an optical connector 50 according to yet another modification. The optical connector 50 shown in FIG. 11 differs from the optical connector 10 described above in the configuration of the high transmittance member 52.

[0038] A pair of an optical fiber 14 and a GRIN lens 16 linearly arranged in one groove 24 constitutes one channel. The optical connector 50 includes a plurality of adjacently arranged channels. As shown in FIG. 11 , the high transmittance member 52 of the optical connector 50 has a light-shielding wall 54 between adjacent channels.

[0039] As shown by ray L1 in Figure 11 , when light traveling through the optical fiber 14 enters the high-transmittance member 52, the light may spread within the high-transmittance member 52. If the spacing between adjacent channels is narrow, part of the light may enter the GRIN lens 16 of the adjacent channel, resulting in crosstalk. Furthermore, as shown by ray L2 in Figure 11 , when light traveling through the high-transmittance member 52 exits the high-transmittance member 52, reflected light occurs due to the difference in refractive index between the high-transmittance member 52 and the GRIN lens 16 abutting the high-transmittance member 52 (Fresnel reflection). This reflected light may return toward the optical fiber 14 and enter the optical fiber 14 of an adjacent channel, resulting in crosstalk. Furthermore, Fresnel reflection may occur due to the difference in refractive index between the high-transmittance member 52 and the optical fiber 14 abutting the high-transmittance member 52, resulting in multiple reflections and the light entering the GRIN lens 16 of an adjacent channel, resulting in crosstalk.

[0040] By providing a light-shielding wall 54 between adjacent channels, as with the high-transmittance member 52 in this modified example, it is possible to block light directed toward the adjacent channel, thereby realizing a highly reliable optical connector that prevents the occurrence of crosstalk.

[0041] 12(a) to 12(d) are diagrams for explaining a method for manufacturing the high transmittance member 52 having the light-shielding wall 54. FIG.

[0042] In this method, a substrate 56 of a high transmittance member 52 is prepared. The substrate 56 is a plate-like body and may be formed from glass or resin. First, as shown in FIG. 12( a), a light-shielding film 58 is formed on one (or both) of the main surfaces of the substrate 56 using a method such as vapor deposition. Next, as shown in FIG. 12( b), multiple substrates 56 with the light-shielding film 58 are stacked and formed into a block using an adhesive. Next, as shown in FIG. 12( c), the multiple block-shaped substrates 56 are cut, and the cut surfaces are polished. This allows multiple high transmittance members 52 to be obtained, as shown in FIG. 12( d).

[0043] In the optical connector 10, the collimated light emitted from the GRIN lens 16 propagates through the air as a Gaussian beam. To minimize the divergence of the beam and make it as collimated as possible, it is necessary to maximize the mode field diameter (MFD) of the beam waist. By increasing the MFD, even if the positional relationship between the transmitting GRIN lens and the receiving GRIN lens is misaligned with respect to the optical axis (referred to here as optical axis misalignment), the amount of misalignment becomes smaller relative to the MFD, which has the effect of suppressing the decrease in coupling efficiency due to the amount of optical axis misalignment.

[0044] However, if the MFD of the collimated light is too large, some light cannot enter the GRIN lens on the receiving side when the optical axis is misaligned, resulting in a decrease in coupling efficiency. Therefore, when considering the optical axis misalignment, there is an optimal value for the MFD relative to the core diameter of the optical fiber 14 and the diameter of the GRIN lens 16.

[0045] The inventors performed a simulation of the relationship between optical axis misalignment and coupling efficiency. The simulation was performed using optical simulation software (ANSYS Zemax OpticStudio). The calculation model is shown in Figure 13. As shown in Figure 13, the output of a single-mode fiber (MFD 9.2 μm) was set at the left end, and the efficiency of light coupled into the single-mode fiber on the right end after propagating from glass (high-transmittance component) to a GRIN lens, then to a GRIN lens, and back to glass (high-transmittance component) was calculated. Figure 13 shows a calculation model with a gap between the GRIN lenses of 0 mm, an MFD of 40 μm, and an optical axis misalignment of 0 μm. The MFD was set to 10 μm to 110 μm by adjusting the lengths of the glass and GRIN lens (parallel to the optical axis direction). In an example model with a small MFD, the glass length was set to 0 and the GRIN lens length was set to 0.25P (+0.5P × N (N = 0, 1, 2, ...)). P denotes the pitch of the GRIN lens, which represents the meandering period of the light beam passing through the lens. On the other hand, an example of a model with a large MFD was set by increasing the length of the glass and shortening the length of the GRIN lens from 0.25P. The optical axis misalignment was modeled by shifting the position between the GRIN lenses. Figure 14 shows a calculation model with a gap between the GRIN lenses of 0 mm, an MFD of 40 μm, and an optical axis misalignment of 30 μm.

[0046] Table 1 below shows the simulation results of the light coupling efficiency with respect to the change in the amount of optical axis misalignment for each MFD.

[0047] Assuming that the optical axis misalignment during assembly is 5 μm, the MFD of the beam waist of the beam emitted from GRIN lens 16 is preferably 10 μm to 110 μm, at which the coupling efficiency is 70% or higher, more preferably 20 μm to 100 μm, at which the coupling efficiency is 80% or higher, and even more preferably 40 μm to 90 μm, at which the coupling efficiency is 90% or higher. The MFD of the beam waist of the beam emitted from GRIN lens 16 can be adjusted by the thickness of high transmittance member 18 and the length of GRIN lens 16.

[0048] The present invention has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications and changes are possible within the scope of the claims of the present invention, and that such modifications and changes also fall within the scope of the claims of the present invention. Therefore, the descriptions and drawings in this specification should be treated as illustrative rather than restrictive.

[0049] For example, although the above embodiment illustrates an optical connector array having multiple channels, the optical connector may have a single channel.

[0050] The present invention can be used in optical connectors.

[0051] 10, 30, 40, 50 Optical connector, 12 Substrate, 14 Optical fiber, 16 GRIN lens, 18, 52 High transmittance member, 20 Fiber cover member, 22 Lens cover member, 24 Groove, 26, 34 Recessed portion, 28 Adhesive, 32, 42 Cover member, 54 Light-shielding wall, 56 Base material, 58 Light-shielding film.

Claims

1. An optical connector comprising: a substrate having a groove formed therein; an optical fiber having a predetermined outer diameter placed in the groove of said substrate; a GRIN lens having the same outer diameter as said optical fiber placed in the groove of said substrate; and a high transmittance member placed between said optical fiber and said GRIN lens.

2. The optical connector according to claim 1, wherein said groove has a V-shaped cross section.

3. The optical connector according to claim 1, wherein the optical fiber is a single-mode fiber.

4. The optical connector according to claim 1, wherein the high transmittance member is in the form of a block.

5. An optical connector according to claim 4, wherein the high transmittance member is disposed in a recess provided midway in the groove of the substrate.

6. An optical connector according to claim 4, wherein the end face of said optical fiber and the end face of said GRIN lens abut against said high transmittance member.

7. An optical connector as described in claim 4, characterized in that a plurality of said grooves are formed in said substrate, said optical fiber and said GRIN lens are disposed in each of said plurality of grooves, and said common block-shaped high transmittance member is disposed between said plurality of optical fibers and said plurality of GRIN lenses.

8. An optical connector according to claim 1, wherein the mode field diameter of the beam waist of the beam emitted from said GRIN lens is 10 μm to 110 μm.

9. An optical connector according to any one of claims 1 to 8, wherein the high transmittance member has a light-shielding wall between adjacent channels.

10. A method for manufacturing an optical connector, comprising the steps of: forming a groove in a substrate; forming a recessed portion midway through the groove and placing a high transmittance member in the recessed portion; placing an optical fiber having a predetermined outer diameter in one of the grooves divided by the recessed portion; and placing a GRIN lens having the same outer diameter as the optical fiber in the other of the grooves divided by the high transmittance member.

11. The method for manufacturing an optical connector as described in claim 10, characterized in that the high transmittance member is block-shaped, and the method comprises the steps of: fixing the optical fiber placed in one of the grooves while pressing it against the high transmittance member; and fixing the GRIN lens placed in the other groove while pressing it against the high transmittance member.

12. A method for manufacturing an optical connector as described in claim 10 or 11, characterized in that the method further comprises a process for forming the high transmittance member, the process including the steps of: forming a light-shielding film on the main surface of the substrate of the high transmittance member; stacking a plurality of the substrates with the light-shielding film; and cutting the stacked plurality of substrates and polishing the cut surfaces.

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