Fiber array and optical connection structure

Abstract

A fiber array (11) according to the present invention optically connects to an optical element, the fiber array comprising: a substrate (116) having a plurality of V-grooves; a plurality of optical fibers (111 to 115) disposed in the plurality of V-grooves, respectively; and a lid (117) disposed to face the surface in which the V-grooves of the substrate are disposed. The optical fibers comprise core parts (1111, 1121, 1131, 1141, 1151) where cores are exposed and covered parts (1112, 1122, 1132, 1142, 1152) where the cores are covered. The substrate and the lid are transparent, and among the core parts of the plurality of optical fibers, a metal coating is applied to the outer peripheries of the core parts of at least two optical fibers in at least a portion located between the substrate and the lid.　This enables the present invention to provide a fiber array that can be easily aligned in an optical connection between the fiber array and an optical element.

Description

Fiber array and optical connection structure

[0001] The present invention relates to a fiber array and an optical connection structure for optically connecting a fiber array to an optical element.

[0002] In the fiber array 41, as shown in FIG. 8, optical fibers 411 to 415 are sandwiched between a V-groove substrate 416 and a lid 417, and are fixed in place with an adhesive (not shown). The input and output end faces of the fiber array 41 are polished. Here, an example using five optical fibers is shown, but there is no restriction on the number of fibers. Using the fiber array 41, optical fibers for inputting and outputting signals can be connected to optical element chips such as planar lightwave circuit (hereinafter referred to as "PLC") chips, SiPh (silicon photonics) chips, and LN (LiNbO3) chips.

[0003] 9 shows an example of an optical connection structure 50 between fiber arrays 51, 53 and a PLC chip 52. A splitter with one input and four outputs is used as an example of the PLC chip 52. The splitter splits input light from a single optical fiber into approximately four equal parts. For simplicity of explanation, a case will be described in which a PLC chip 52 has a single-core fiber array (input-side fiber array) 53 connected to its input side, and a four-core fiber array (output-side fiber array) 51 connected to its output side.

[0004] In each of the fiber arrays 51 and 53, optical fibers 531 and 511 to 514 arranged on a V-groove substrate are sandwiched between lids. The PLC chip 52 has a splitter (optical circuit) 525 with one input and four outputs, and is provided with glass plates 526 and 527 at its ends.

[0005] Light for alignment is input from the input-side fiber array 53, and the output-side fiber array 51 is aligned via the PLC chip 52 so that the light output from the output-side fiber array 51 is maximized. When the fiber array 51 has four optical fibers 511 to 514, the two optical fibers (two channels) arranged on the outside are aligned first. The spacing between the centers of the cores of the waveguides 521 to 524 of the PLC chip 52 and the spacing between the centers of the cores of the optical fibers 511 to 514 of the fiber array 51 are designed to be equivalent, so aligning the outer two optical fibers allows alignment of all the optical fibers.

[0006] For example, the output ports of the fiber array 51 are defined along the X axis as channel 1, channel 2, channel 3, and channel 4 in this order. All channels can be aligned by first aligning channel 1 and then aligning channel 4. Details will be described below.

[0007] The angles θx and θy around the x and y axes, other than the angle θz around the z axis, of the fiber array 51 are adjusted in advance relative to the PLC chip 52. The fiber array 51 is brought close to a position about 20 μm from the end face of the PLC chip 52, and in channel 1, the centers of the optical fiber cores in the fiber array 51 are visually aligned with the centers of the waveguide cores of the PLC chip 52 in the x-axis direction through a microscope.

[0008] Next, in channel 1, the optical fiber is moved in the y-axis direction to perform coarse alignment. Here, coarse alignment is a process of manually aligning the optical fiber so that light is incident from the PLC chip 52 to the fiber array 51. In this process, the centers of the optical fiber cores of the fiber array 51 and the waveguide cores of the PLC chip 52 are roughly aligned in the x-axis direction, so coarse alignment can be easily performed.

[0009] Next, the fiber array 51 is brought close to a position several μm away from the end face of the PLC chip 52, and automatic alignment is performed to perfectly align the centers of the optical fiber cores of the fiber array 51 with the centers of the waveguide cores of the PLC chip 52, i.e., the optical axes, so that the intensity (amount of light) of light incident from the waveguide cores of the PLC chip 52 to the cores of the fiber array 51 is maximized (fine alignment), thereby aligning channel 1. The coordinates of the stage at this time are recorded.

[0010] Next, rough alignment and fine alignment are performed on the waveguide core of the PLC chip 52 and the channel 4 of the optical fiber so that light is incident thereon in the same manner as described above, and the coordinates of the stage are recorded.

[0011] Next, the inclination of the fiber array 51 around the z-axis relative to the PLC chip 52 is calculated from the coordinates of channels 1 and 4, and θz is adjusted, and coarse and fine alignment of channel 1 is performed again.

[0012] Next, coarse and fine alignment is performed on channel 4. Next, fine alignment is performed on channel 1 again.

[0013] By these steps, the fiber center interval of the fiber array 51 and the interval between the waveguide cores of the PLC chip 52 are equal, so that channels 1 to 4 can be aligned.

[0014] Finally, an ultraviolet-curing adhesive is injected into the gap between the end face of the fiber array 51 and the end face of the PLC chip 52, and is cured by irradiating it with UV light. In this way, the fiber array 51 is fixed to the PLC chip 52.

[0015] Japanese Patent Application Publication No. 8-313744

[0016] The above-described connection method can be applied when the core diameter of the waveguide of an optical element (e.g., a PLC chip) or optical fiber is large, for example, a core diameter of approximately 8 μm or more. For light to enter the optical fiber from the PLC chip, the electric field of the waveguide core of the PLC chip and the electric field of the optical fiber must overlap. At this time, the width of the electric field of the light is approximately equal to the width of the waveguide core. In other words, when rough alignment is achieved, the waveguide core of the PLC chip and the core of the optical fiber must overlap in the direction perpendicular to the optical axis.

[0017] In recent years, waveguides and optical fibers with a large relative refractive index difference between the core and cladding have been used to miniaturize optical chips. As the relative refractive index difference increases, the core diameter must be reduced to maintain the sigmoid mode condition. When both core diameters are small, for example, when the waveguide core of a PLC chip is 3 μm and the core diameter of an optical fiber is 3 μm, it is difficult to visually align the centers of the two cores in the x-axis direction, making rough alignment difficult. For example, in a silicon photonics (SiPh) chip with a spot size converter integrated on the chip input / output side, the electric field of the input and output light is approximately 3 μm.

[0018] The most time-consuming step in the alignment process is the rough alignment process. Conventionally, the waveguide width is large, so the optical axis in the x-axis direction is aligned, and alignment in the y-axis direction is all that is required, so the rough alignment process did not take a long time.

[0019] However, when the waveguide diameter is about 3 μm, after visually aligning the optical axis in the x-axis direction, alignment in the y-axis direction is required, and then coarse alignment in the x-axis direction is required again. As a result, the stage needs to be moved in two axial directions, which poses the problem of taking a long time for coarse alignment.

[0020] In order to solve the above-mentioned problems, the fiber array of the present invention is a fiber array for optical connection to an optical element, and comprises a substrate having a plurality of V-grooves, a plurality of optical fibers arranged in each of the plurality of V-grooves, and a lid arranged opposite the surface of the substrate on which the V-grooves are arranged, wherein the optical fibers have a core portion where the core wire is exposed and a coating portion where the core wire is coated, the substrate and the lid are transparent, and of the core portions of at least two of the plurality of optical fibers, at least the outer periphery of the portion arranged between the substrate and the lid is metal coated.

[0021] According to the present invention, it is possible to provide a fiber array and an optical connection structure that allow easy alignment in optical connection between a fiber array and an optical element.

[0022] FIG. 1 is a schematic bird's-eye view showing the configuration of an optical connection structure according to a first embodiment of the present invention. FIG. 2 is a schematic bird's-eye view showing the configuration of a fiber array according to the first embodiment of the present invention. FIG. 3 is a schematic top view showing the configuration of a fiber array according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining the operation of the fiber array according to the first embodiment of the present invention. FIG. 5 is a schematic view showing the configuration of an end face of a fiber array according to a second embodiment of the present invention. FIG. 6 is a diagram for explaining the operation of the fiber array according to the second embodiment of the present invention. FIG. 7 is a schematic view showing the configuration of an end face of a fiber array according to a third embodiment of the present invention. FIG. 8 is a schematic bird's-eye view showing the configuration of a conventional fiber array. FIG. 9 is a schematic bird's-eye view showing the configuration of an optical connection structure including a conventional fiber array.

[0023] First Embodiment A fiber array and an optical connection structure according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG.

[0024] <Configuration of fiber array and optical connection structure> As an example, the optical connection structure 10 according to this embodiment includes a PLC chip 12, a fiber array 13 on the input side of the PLC chip 12, and a fiber array 11 on the output side of the PLC chip 12, as shown in FIG.

[0025] The PLC chip 12 has a splitter (optical circuit) 126 with one input and five outputs, and is provided with optical waveguides 121 to 125 on the output side, splitting input light from one optical fiber into five. It also has glass plates 127 and 128 at the ends of the input and output sides, respectively.

[0026] As shown in FIG. 2, the fiber array 11 according to this embodiment includes a V-groove substrate 116, a plurality of optical fibers 111 to 115, and a lid 117.

[0027] The V-groove substrate 116 has a plurality of V-grooves on its surface. The V-groove substrate 116 and the lid 117 are made of glass and are transparent. The V-groove substrate 116 and the lid 117 may be made of a transparent material other than glass. This allows the fiber array 11 to be seen through in the y-axis direction. It is desirable that the surfaces of the V-groove substrate 116 and the lid 117 perpendicular to the y-axis are flat.

[0028] The optical fibers 111 to 115 are arranged in each of the multiple V-grooves of the V-groove substrate 116, sandwiched between the lid (lid) 117 and the V-groove substrate 116, and adhesive is filled between the optical fibers 111 to 115, the lid (lid) 117, and the V-groove substrate 116, and they are adhesively fixed.

[0029] The five optical fibers are arranged at equal intervals (pitch). Three or more optical fibers may be arranged.

[0030] The fiber array 11 optically connects five optical fibers 111 to 115 to five waveguides 121 to 125 on the output side of the PLC chip 12 .

[0031] The fiber array 13 has a configuration similar to that of the fiber array 11, and comprises a V-groove substrate 116, one optical fiber, and a lid 117, and optically connects the optical fiber to one waveguide on the input side of the PLC chip 12.

[0032] 3 shows a schematic top view of the fiber array 11. The optical fibers 111, 112, 113, 114, and 115 have core portions 1111, 1121, 1131, 1141, and 1151 and coating portions 1112, 1122, 1132, 1142, and 1152, respectively. In the coating portions 1112, 1122, 1132, 1142, and 1152, the periphery of the core is coated (covered) with a resin or the like. In the core portions 1111, 1121, 1131, 1141, and 1151, the surrounding resin or the like has been removed, exposing the clad portion of the core and leaving it uncoated. The core portions 1111, 1121, 1131, 1141, and 1151 are sandwiched between a lid 117 and a V-groove substrate 116 and fixed with an adhesive or the like (not shown).

[0033] The diameter of the coating portions 1112, 1122, 1132, 1142, and 1152 is 250 μm for normal fibers and 165 μm for small-diameter fibers. The diameter of the core portions 1111, 1121, 1131, 1141, and 1151 is 125 μm for normal fibers and 80 μm for small-diameter fibers. The diameter of the core portions 1111, 1121, 1131, 1141, and 1151 (clad diameter of the optical fiber) can be reduced by wet etching or the like, so a diameter other than the above is not necessary.

[0034] In the core portions of the optical fibers 111 and 115, at least the outer periphery of the cores in the portions 1113 and 1153 sandwiched between the lid 117 and the V-groove substrate 116 (hereinafter also referred to as "coated portions") is metal coated.

[0035] The metal coating is applied using plating technology, electroforming technology, or the like. In the metal coating, nickel is applied as the first layer (inner layer), followed by gold as the second layer (outer layer). The total thickness of the first and second layers is 1 μm. The total thickness may be 1 to 5 μm. Coating the second layer (outer layer) with gold improves oxidation resistance and reliability. Here, the other three optical fibers 112, 113, and 114 do not need to be coated.

[0036] In the coating portions 1113, 1153 of the optical fibers 111, 115, the refractive index of the metal used in the coating differs from the refractive index of the glass member and adhesive. The refractive index of the glass member and adhesive is approximately 1.4 to 1.6 in the visible range. On the other hand, the refractive index of gold is approximately 0.2 for visible light, for example, a wavelength of 633 nm (red helium-neon laser). This difference in refractive index causes significant reflection between the metal (gold) of the coating and the adhesive used to secure the optical fiber.

[0037] In this way, the coating portions 1113 and 1153 generate significant reflection compared to the surrounding area (adhesive, etc.), so the reflected light can be easily observed on a monitor via a microscope. By analyzing the image obtained by monitor observation, the optical fibers 111 and 115 can be easily recognized as images.

[0038] 4 shows an enlarged view of the area near the optical fiber 111. The dotted lines in the figure indicate the edges of the V-groove in the V-groove substrate 116. The dashed-dotted line in the figure indicates the central axis of the core of the optical fiber 111. The coating portion 1113 of the optical fiber 111 is disposed in the V-groove in the V-groove substrate 116.

[0039] The boundary between the optical fiber 111 and other parts (glass members, adhesives, etc.) can be detected by performing a first or second order differential operation on the brightness distribution of pixels in the image near the optical fiber 111. This makes it possible to obtain the x coordinates of boundary points 1115 and 1116 of the optical fiber 111 at the end face of the fiber array 11.

[0040] Therefore, from the positions (x coordinates) of the boundary points 1115 and 1116, the position 1114 of the center of the optical fiber 111 on the end face of the fiber array 11, that is, the x coordinate of the center of the fiber core, can be obtained.

[0041] Using the acquired center position (x coordinate) of the fiber core, the stage on which the fiber array 11 is placed can be moved to match the x coordinate of the center position of the core at the end of the waveguide chip, which has been acquired in advance, and the optical fibers 111 can be optically connected (coarsely aligned) to the waveguide core. For example, when the coordinates (x, y, z) of the center position of the core at the end of the waveguide chip are (x1, Py, Pz), the fiber core is moved so that its center coordinates become (x1, Cy, Cz).

[0042] According to this embodiment, the process of rough alignment of optical fibers, which takes a long time, can be automated by image recognition, and therefore the alignment process can be speeded up.

[0043] In this embodiment, the coordinates 1114 indicate the position of the center of the core of the optical fiber 111 and also indicate the position of the end face of the fiber array 11. Therefore, by acquiring the central coordinates of the waveguide core at the end face of the PLC chip 12 in advance, it is possible to align the optical axes of the PLC chip 12 and the fiber array 11 in the x- and y-axis directions and to control the gap (spacing) between the PLC chip 12 and the fiber array 11 in the z-axis direction.

[0044] Furthermore, the end faces of the fiber array 11 are not limited to being polished at a right angle, but may also be polished at an angle. When the end faces of the fiber array 11 are polished at an angle, the ends (tips) of the optical fibers in the microscope field of view are either one end or the other end on the y-axis of the optical fiber end faces, resulting in a positional deviation in the z-direction from the core through which light propagates. However, when the fiber diameter is 80 μm or less, the positional deviation in the z-direction caused by polishing at an angle is a few μm or less, and the effect of this positional deviation on the alignment is small.

[0045] In this embodiment, an example in which the metal-coated optical fibers are arranged at both ends of the V-groove substrate has been shown, but this is not limiting. The metal-coated optical fibers may be arranged in two locations other than both ends of the V-groove substrate, or may be arranged in three or more locations.

[0046] In this embodiment, an example is shown in which the metal coating of the optical fiber uses a two-layer structure of gold and nickel, but this is not limiting. Metals other than gold and nickel, such as aluminum, may also be used. Also, a single-layer structure may be used for the metal coating.

[0047] Second Embodiment A fiber array and an optical connection structure according to a second embodiment of the present invention will be described with reference to FIGS.

[0048] <Configuration of Fiber Array> Similar to the first embodiment, the fiber array 21 according to this embodiment includes a V-groove substrate 216, a plurality of optical fibers, and a lid 117. At least the core portions of at least two of the plurality of optical fibers, for example, optical fibers 111 and 115, are metal-coated at least in the portions sandwiched between the lid 117 and the V-groove substrate 216 (coating portions 1113 and 1153).

[0049] 5 shows the end face of the fiber array 21. The optical fibers (core portions) 111 to 115 are sandwiched between a lid 117 and a V-groove substrate 216, and are bonded and fixed with an adhesive (not shown) filled between the optical fibers 111 to 115, the lid 117, and the V-groove substrate 216. The optical fibers (core portions) 111 and 115 have coating portions 1113 and 1153.

[0050] In the first embodiment, in the fiber array 11, the optical fibers 111 and 115 having the coatings 1113 and 1153 are positioned higher than the optical fibers 112 to 114 having no coatings due to the thickness of the metal coating.

[0051] As a result, even if the optical fibers 111 and 115 having the coatings 1113 and 1153 are aligned, the optical axes of the optical fibers 112 to 114 having no coatings are misaligned in the y-axis direction due to the thickness of the metal coating.

[0052] On the other hand, in this embodiment, the V-groove in which the metal-coated core wire portion (coating portion 1113, 1153) is arranged is formed deeper than the other V-grooves in consideration of the coating thickness, so that the centers of the multiple optical fibers 111 to 115 are arranged in an array with a constant height (y-axis direction).

[0053] As a result, when aligning the optical fibers 111 and 115 having the coating portions 1113 and 1153, the optical axes of the optical fibers 112 to 114 not having the coating portions are not misaligned in the y-axis direction, and the fiber array 21 can be aligned at the optimal position on the PLC chip 12.

[0054] The details of the configuration of the fiber array 21 will be described with reference to Fig. 6. In the V-groove substrate 216 of the fiber array 21, as shown in Fig. 6, the V-grooves in which the optical fibers 111 having the coating portion 1113 are arranged are deeper than the V-grooves in which the optical fibers 112 having no coating portion are arranged.

[0055] The difference in depth ΔD between the V-grooves is ΔD = t / cos(54.7) = 1.73t, since the inclination angle of the V-grooves is 54.7 degrees, where R is the diameter of the core wire and t is the thickness of the metal coating. For example, when t = 1 μm, the V-groove in which the core wire is located is about 2 μm (1.73 μm) deeper than the other V-grooves.

[0056] According to this embodiment, the process of coarse alignment of optical fibers, which takes a long time, can be automated by image recognition, thereby speeding up the alignment process and improving the accuracy of the aligned optical axis.

[0057] Third Embodiment A fiber array and an optical connection structure according to a third embodiment of the present invention will be described with reference to FIG.

[0058] <Configuration of Fiber Array> The fiber array 31 according to this embodiment includes a V-groove substrate 316, a plurality of optical fibers, and a lid 117, similar to the first embodiment.

[0059] In this embodiment, the core portions of all of the optical fibers 311 to 315 are metal-coated to the same thickness at the portions sandwiched between the lid 117 and the V-groove substrate 316. The depth of the V-grooves in the V-groove substrate 116 is also the same.

[0060] 7 shows the end face of the fiber array 31. In the fiber array 31, the core wires of all of the optical fibers 311 to 315 arranged on the V-groove substrate 316 are metal coated to the same thickness. Therefore, even though the V-grooves of the V-groove substrate 316 are all the same depth, the centers of the multiple optical fibers 311 to 315 are arranged in an array with a constant height (y-axis direction).

[0061] In this way, deviation of the optical axis in the y-axis direction can be avoided without forming V-grooves of different depths as in the second embodiment, and the fiber array can be aligned to the PLC chip at the optimum position.

[0062] According to this embodiment, the process of coarse alignment of optical fibers, which takes a long time, can be automated by image recognition, thereby speeding up the alignment process. Furthermore, the accuracy of the optical axis can be easily improved.

[0063] In the embodiment of the present invention, an example has been shown in which a fiber array is aligned with a PLC chip and optically connected to the chip, but the present invention is not limited to this.A fiber array may also be aligned with an optical element having an optical waveguide, such as a SiPh (silicon photonics) chip or an LN (LiNbO3) chip, other than a PLC chip, and optically connected to the chip.

[0064] In the embodiments of the present invention, examples of the structure, dimensions, materials, etc. of each component in the configuration of the fiber array and optical connection structure are shown, but the present invention is not limited to these examples. Any material may be used as long as the fiber array and optical connection structure can exhibit their functions and effects.

[0065] It should be noted that the present invention is not limited to the above-described embodiments, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention.

[0066] A part or all of the above-described embodiment or an example thereof can be described as, but is not limited to, the following supplementary notes.

[0067] (Supplementary Note 1) A fiber array for optical connection to an optical element, comprising: a substrate having a plurality of V-grooves; a plurality of optical fibers arranged in each of the plurality of V-grooves; and a lid arranged opposite the surface of the substrate on which the V-grooves are arranged, wherein the optical fibers have a core portion where the core wire is exposed and a coating portion where the core wire is coated, the substrate and the lid are transparent, and the core portions of at least two of the plurality of optical fibers are metal-coated at least on the outer periphery of the core portion located between the substrate and the lid.

[0068] (Appendix 2) A fiber array as described in Appendix 1, wherein the V-groove in which the metal-coated core wire portion is arranged is deeper than the V-groove in which the non-metal-coated core wire portion is arranged.

[0069] (Appendix 3) A fiber array as described in Appendix 1, wherein the outer periphery of the core portion of all of the optical fibers of the plurality of optical fibers is metal coated at least in the portion positioned between the substrate and the lid.

[0070] (Supplementary Note 4) An optical connection structure comprising the fiber array according to any one of Supplementary Note 1 to Supplementary Note 3, Supplementary Note 5, and Supplementary Note 6, and an optical element optically connected to the fiber array.

[0071] (Supplementary Note 5) A fiber array according to any one of Supplementary Notes 1 to 3, wherein the optical fibers are fixed to the substrate by an adhesive.

[0072] (Appendix 6) A fiber array described in any one of appendices 1 to 3 and appendices 5, wherein the metal coating has gold arranged on the surface side and nickel arranged on the core wire side.

[0073] The present invention can be applied to optical communication devices and optical communication systems that optically connect to optical fibers.

[0074] 11 Fiber array 111, 112, 113, 114, 115 Optical fiber 1111, 1121, 1131, 1141, 1151 Core portion 1112, 1122, 1132, 1142, 1152 Cover portion 1113, 1153 Coating portion 116 Substrate 117 Lid

Claims

1. A fiber array for optical connection to an optical element, comprising: a substrate having a plurality of V-grooves; a plurality of optical fibers arranged in each of the V-grooves; and a lid arranged opposite the surface of the substrate on which the V-grooves are arranged, wherein the optical fibers have a core portion where the core wire is exposed and a coating portion where the core wire is coated, the substrate and the lid are transparent, and the core portions of at least two of the plurality of optical fibers have a metal coating on the outer periphery of at least the portion of the core portion arranged between the substrate and the lid.

2. A fiber array according to claim 1, wherein the V-groove in which the metal-coated core wire portion is disposed is deeper than the V-groove in which the non-metal-coated core wire portion is disposed.

3. A fiber array according to claim 1, wherein the metal coating is applied to the outer periphery of at least the portion of the core wire portion of all of the optical fibers of the plurality of optical fibers that is disposed between the substrate and the lid.

4. An optical connection structure comprising: a fiber array according to claim 1 or 2; and an optical element optically connected to said fiber array.

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