Optical waveguide device and optical transmitter

Abstract

The present invention improves the mechanical strength of a lens for optically coupling an optical waveguide and an optical fiber provided on a substrate.　This lens unit is for optically coupling an optical waveguide and an optical fiber provided on a substrate, and comprises: a lens part; and a holding part that holds the lens part. The holding part has, along one lateral surface through which the optical axis does not pass, a thick section in which the thickness measured in the optical axis direction is greater than that of other sections of the holding part.

Description

[Technical Field]

[0001] The present invention relates to a lens unit that optically couples an optical waveguide with an optical fiber, an optical waveguide device using the lens unit, and an optical transmitter using the optical waveguide device. [Background technology]

[0002] In high-speed / large-capacity optical fiber communication systems, optical transmitters incorporating waveguide-type optical elements (hereinafter referred to as optical modulation elements) that perform optical modulation are widely used. Among them, optical modulation elements using LiNbO3 (hereinafter also referred to as LN) substrates that have electro-optic effects are widely used in high-speed / large-capacity optical fiber communication systems because they can achieve low optical loss and broadband optical modulation characteristics compared to modulation elements using semiconductor materials such as indium phosphide (InP), silicon (Si), or gallium arsenide (GaAs).

[0003] Patent Document 1 describes an optical element module in which an optical waveguide formed on a substrate is optically coupled to an optical fiber using a lens means having one surface with a convex curved surface and the other surface opposite to the other surface processed to be flat.

[0004] Furthermore, in recent years, in order to achieve even lower voltage driving and higher speed modulation while miniaturizing the optical modulator itself, optical modulators using rib-type optical waveguides or ridge-type optical waveguides (hereinafter collectively referred to as convex optical waveguides) configured by forming strip-shaped convex portions on the surface of a thin-film (or thin-plate) LN substrate (for example, a thickness of 20 μm or less) are being put into practical use in order to further strengthen the interaction between the signal electric field and the guided light in the substrate (for example, Patent Documents 2 and 3).

[0005] Furthermore, in addition to miniaturizing the optical modulation element itself, efforts are also being made to house an electronic circuit and an optical modulation element in a single housing and integrate them as an optical modulation module. For example, an optical modulation module has been proposed that achieves miniaturization and integration by integrating an optical modulation element and a high-frequency driver amplifier that drives the optical modulation element in a single housing and arranging optical input / output units in parallel on one surface of the housing. In the optical modulation element used in such an optical modulation module, the optical waveguide is formed on the substrate so that the optical input terminal and optical output terminal of the optical waveguide are located on one side of the substrate constituting the optical modulation element, and the optical propagation direction is folded back on the substrate (e.g., Patent Document 4). Hereinafter, an optical modulation element configured with an optical waveguide including such a folded portion of the optical propagation direction is referred to as a folded-back optical modulation element. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-173594 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-264548 [Patent Document 3] International Publication No. 2018 / 031916 [Patent Document 4] Japanese Patent Application Publication No. 2019-152732 Summary of the Invention [Problem to be solved by the invention]

[0007] Fig. 9 is a three-view diagram showing an example of the configuration of a lens unit similar to the conventional lens means described in Patent Document 1. Fig. 10 is a diagram showing an example of an arrangement when an optical waveguide and an optical fiber are optically coupled using the lens unit shown in Fig. 9.

[0008] The diagram on the bottom right of Figure 9 is a front view of the lens unit 90, the diagram on the left is a side view of the lens unit 90 seen from the left of the front view, and the diagram on the top is a side view of the lens unit 90 seen from above the front view.

[0009] The lens unit 90 includes a lens portion 91 and a holder 92 that holds the lens portion 91. The lens portion 91 is a curved convex portion formed on a lens surface 921, which is one surface of the holder 92. A support surface 922, which is the surface of the holder 92 that faces the lens surface 921, is adhesively fixed to and supported by an end surface of a substrate 94 on which an optical waveguide 93 is formed, as shown in FIG. 10 . Both the lens surface 921 and the support surface 922 can serve as a light entrance surface or a light exit surface of the lens unit 90, depending on how the lens unit 90 is used.

[0010] 10, when optically coupling an optical waveguide 93 and an optical fiber 95 using a lens unit 90, for example, a substrate 94 on which the optical waveguide 93 is formed is fixed inside a housing (not shown). Then, both ends of the lens unit 90 (for example, the hatched portions on the left and right in the front view shown in FIG. 9) are held in the thickness direction of the lens unit 90 by clamp jigs 97a and 97b, and 97c and 97d (hereinafter collectively referred to as clamp jigs 97), respectively, and the position of the lens unit 90 is aligned to an appropriate position so that the optical power incident on the optical waveguide 93 and output from the optical fiber 95 is maximized.

[0011] After alignment, a support surface 922 of the lens unit 90 is fixed to the end surface of the substrate 94 with an optical adhesive or the like. Here, a lens 952 that focuses light emitted from the lens unit 90 is fixed to an end portion 951 of the optical fiber 95 according to conventional technology, for example, at a position that has been adjusted in advance with respect to the optical fiber 95. Note that the lens unit 90 can be held not only in the thickness direction of the lens unit 90 as with a clamp jig 97, but also from side surfaces 925 and 924 of the lens unit 90 in a direction perpendicular to the optical axis direction of the lens unit 90 as with clamp jigs 98a and 98b (hereinafter referred to as clamp jig 98) shown by dotted lines in the figure.

[0012] As another means for holding the lens unit 90 during the alignment work, in addition to the clamping jig described above, a method of using a suction jig to hold one side surface 923 of the lens unit 90 by suction may be considered.

[0013] Here, the thickness L90 of the holding part 92 depends on the NA (Numerical Aperture) of the optical waveguide 93, and needs to be smaller as the NA increases, that is, as the divergence angle φ of the beam emitted from the optical waveguide 93 increases. Also, the NA of the optical waveguide 93 increases as the mode field diameter of the optical waveguide 93 decreases.

[0014] For example, in the above-mentioned folded optical modulation element, a convex waveguide with a small mode field diameter and strong optical confinement characteristics is used as the optical waveguide to reduce the optical radiation loss of the optical waveguide at the folded portion in the light propagation direction. As an example, in an optical modulator using an LN substrate, the mode field diameter of such a convex waveguide is approximately 3 to 5 μm, which is smaller than the mode field diameter of a diffusion-type waveguide formed by diffusing titanium metal into an LN substrate, which is 6 to 10 μm. Therefore, the NA of the convex waveguide is approximately twice as large as the NA of the diffusion-type waveguide, and the thickness L90 of the holding portion 92 of the lens unit 90 used to couple the convex waveguide to the optical fiber can be as thin as, for example, approximately 0.5 μm, half that of the diffusion-type waveguide.

[0015] If such a thin holding portion 92 is held by clamp jig 97 or clamp jig 98, the holding force will apply stress to lens unit 90, which may result in deformation or damage to holding portion 92. Furthermore, if side surface 923 of holding portion 92 of lens unit 90 is held by a suction jig, the diameter of the suction hole in the suction jig needs to be reduced in accordance with the thickness of side surface 923, weakening the suction force used to suction lens unit 90. As a result, lens unit 90 may fall off the suction jig during alignment, or slippage may occur at the suction position on side surface 923, making high-precision adjustment difficult.

[0016] In view of the above background, an object of the present invention is to improve the mechanical strength of a lens that optically couples an optical waveguide provided on a substrate with an optical fiber. [Means for solving the problem]

[0017] One aspect of the present invention is an optical waveguide element having an optical waveguide provided on a substrate; optical waveguide and light fiber and Optically coupled lens unit and , a housing for accommodating the optical waveguide element, the housing comprising a case having an opening on one side and a cover covering the opening on the one side of the case, and the lens unit The lens unit has a lens section and a holding section that holds the lens section, and the holding section has a lens section through which an optical axis of the lens section passes. a third surface different from the first and second surfaces of the lens unit; The thickness of the holding portion measured in the direction of the optical axis along the thick With thick part The lens unit is arranged so that the first surface faces an end of the optical waveguide element and the third surface faces one of the opening surfaces of the case, and the thick portion forms a convex portion on the second surface opposite the first surface facing the end of the optical waveguide element, and the end of the convex portion does not come into contact with other objects. According to another aspect of the present invention, The lens unit comprises: The lens portion includes a plurality of lens portions arranged in one direction, and the thick portion of the holding portion extends in the direction in which the lens portions are arranged. According to another aspect of the present invention, the holding portion further includes: 3rd page Opposite to Side 4 The holding portion has a thick portion whose thickness measured in the direction of the optical axis is greater than the thickness of the other portion of the holding portion. According to another aspect of the present invention, the holding portion is Side 4 The thickness of the thick portion in 3rd page The thickness is thinner than the thick part in the According to another aspect of the present invention, the thick portion has a sloped portion whose thickness decreases continuously toward the lens portion. According to another aspect of the present invention, the optical fiber includes an input optical fiber that propagates input light to the optical waveguide, and an output optical fiber that propagates output light from the optical waveguide; The optical waveguide element has an optical input end of the optical waveguide that receives the input light and an optical output end of the optical waveguide that outputs the output light, both of the input optical fiber and the output optical fiber being fixed to one surface of the housing, and the lens unit disposed between the optical waveguide element and the input optical fiber and the output optical fiber is the number of said input light beams and the number of said output light beams; The lens portion includes a number of lens portions equal to the sum of According to another aspect of the present invention, the optical waveguide element includes an optical assembly arranged between the input optical fiber and the output optical fiber, and the optical assembly and the thick portion on the one side of the lens unit have overlapping portions when viewed in a plan view from the opening of the case. According to another aspect of the present invention, the optical waveguide element ,light and an electronic circuit for driving the optical waveguide element is provided inside the housing. According to still another aspect of the present invention, there is provided an optical waveguide device, It is a light modulation element and an electronic circuit that generates an electrical signal for causing the optical waveguide element to perform a modulation operation. [Effects of the Invention]

[0018] According to the present invention, the mechanical strength of a lens disposed between an optical waveguide and an optical fiber can be improved. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing the configuration of a lens unit according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of an arrangement in which an optical waveguide and an optical fiber are optically coupled using the lens unit shown in FIG. [Figure 3] FIG. 3 is a diagram showing the configuration of a lens unit according to a first modified example. [Figure 4] FIG. 4 is a diagram showing the configuration of a lens unit according to a second modified example. [Figure 5] FIG. 5 is a diagram showing the configuration of an optical waveguide device according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view of the optical waveguide device shown in FIG. 5 taken along the line XI-XI. [Figure 7] FIG. 7 is a diagram showing the configuration of an optical waveguide device according to a third embodiment of the present invention. [Figure 8]FIG. 8 is a diagram showing the configuration of an optical transmitting device according to the fourth embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing an example of the configuration of a conventional lens unit. [Figure 10] FIG. 10 is a diagram showing an example of an arrangement in which an optical waveguide and an optical fiber are optically coupled using the conventional lens unit shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [1. First embodiment] First, a first embodiment of the present invention will be described. Fig. 1 is a three-view diagram showing the configuration of a lens unit 10 according to the first embodiment of the present invention. In Fig. 1, the diagram on the lower right is a front view of the lens unit 10, the diagram on the left is a side view of the lens unit 10 as seen from the left of the front view, and the diagram on the upper side is a side view of the lens unit 10 as seen from above the front view.

[0021] The lens unit 10 is disposed, for example, between an optical waveguide element having an optical waveguide provided on a substrate and an optical fiber, and focuses or collimates input light or output light of the optical waveguide to optically couple the optical waveguide and the optical fiber.

[0022] Similar to the conventional lens unit 90 described above, the lens unit 10 has a lens portion 11 and a holder portion 12 that holds the lens portion 11. The lens unit 10 can be formed by, for example, pressing glass heated to a temperature above its softening point, so that the lens portion 11 and the holder portion 12 are integrally made of the same material.

[0023] Lens portion 11 is a curved convex portion formed on lens surface 121, which is one surface of holding portion 12. Of holding portion 12, support surface 122 facing lens surface 121 on which lens portion 11 is formed is adhesively fixed to and supported by an end surface of a substrate on which an optical waveguide is formed. Both lens surface 121 and support surface 122 can serve as a light entrance surface or a light exit surface of lens unit 10, depending on how lens unit 10 is used.

[0024] In particular, in the lens unit 10 according to this embodiment, the holder 12 has, in an area that does not include the lens portion 11, a thick portion 12a (hatched portion in the illustration) along one side surface 123 that is not a surface through which the optical axis 13 of the lens portion 11 passes (i.e., not the lens surface 121 or the support surface 122), where the thickness L11 measured in the direction of the optical axis 13 is greater than the thickness L10 of the other portion of the holder 12. The thick portion 12a is configured to include, for example, the entire side surface 123.

[0025] As a result, in lens unit 10, thickness L10 of holding portion 12, which is the distance from support surface 122 to lens portion 11, is maintained at a constant value, while thick portion 12a, which has a thickness L11 greater than thickness L10, can improve the mechanical strength of lens unit 10 as a whole. Therefore, in lens unit 10, for example, during alignment work when using this lens unit to optically couple an optical waveguide and an optical fiber, by holding thick portion 12a with a clamping jig, it is possible to prevent damage such as deformation or breakage of lens unit 10.

[0026] Furthermore, since the size of side surface 123 is enlarged by the presence of thick portion 12a, when a suction jig is used in the alignment work, sufficient suction force can be ensured by suctioning side surface 123 along thick portion 12a. This prevents lens unit 10 from slipping or falling off the suction jig, enabling highly accurate position adjustment.

[0027] Fig. 2 is a diagram showing an example of an arrangement when an optical waveguide and an optical fiber are optically coupled using the lens unit 10 shown in Fig. 1. In Fig. 2, an optical waveguide element 14, in which an optical waveguide is formed on a substrate, is fixed to a case 15. Furthermore, a terminal portion 161 of an optical fiber 16 is fixed to a position on the case 15 opposite the end portion of the optical waveguide element 14. A lens 162, the position of which is adjusted in advance with respect to the optical fiber 16, is disposed on the terminal portion 161. Furthermore, an optical assembly 17, which includes, for example, an optical filter, is disposed between the end portion of the optical waveguide element 14 and the optical fiber 16.

[0028] Lens unit 10 is mounted, for example, with side surface 123 along thick portion 12a facing the opening direction of case 15 (upward in the figure). For example, lens unit 10 is gripped by clamping jigs 18a and 18b at thick portion 12a and inserted into case 15 from above in the figure. Alternatively, lens unit 10 may be gripped from side surfaces 125 and 126 of lens unit 10 in a direction perpendicular to the direction of optical axis 13 of lens unit 10, similar to clamping jigs 98a and 98b shown in FIG.

[0029] During the alignment process, the position of lens unit 10 is adjusted using clamping jigs 18a and 18b, and after adjustment, support surface 122 is adhesively fixed to the end of optical waveguide element 14. In particular, in lens unit 10, the thickness of the portions other than thick portion 12a is thinner than that of thick portion 12a, so that optical assembly 17 can be inserted under thick portion 12a, as shown in Fig. 2. This prevents case 15 from becoming larger in size due to thick portion 12a.

[0030] From the viewpoint of the mechanical strength of the lens unit 10, it is desirable that the thick portion 12a is configured to include the entire side surface 123 as shown in Fig. 1. In addition, in this embodiment, the thick portion 12a is formed so as not to create a step on the support surface 122 as shown in Fig. 1, but the thick portion 12a may be provided so as to create a step on the support surface 122 as long as it does not interfere with fixing the support surface 122 to the optical waveguide.

[0031] 1, thick portion 12a is preferably configured to have inclined portion 124 whose thickness continuously decreases toward lens portion 11 so that light entering or exiting lens portion 11 is not blocked by thick portion 12a. From the viewpoint of sufficiently preventing blocking of light entering or exiting lens portion 11, it is desirable that inclination angle θ of inclined portion 124 with respect to optical axis 13 of lens portion 11 be equal to or greater than 20 degrees and equal to or less than 45 degrees.

[0032] In addition, when the thick portion 12a and the lens portion 11 are formed sufficiently apart, the inclined portion 124 may not be provided, and the holding portion 12 may be configured so that the thickness changes in a stepwise manner between the thick portion 12a and the portion other than the thick portion 12a (i.e., the inclination angle θ = 90 degrees).

[0033] Next, a modified example of the lens unit 10 will be described. [1.1 First Modification] Fig. 3 is a diagram showing the configuration of lens unit 20 according to a first modified example. In Fig. 3, the diagram on the lower right is a front view of lens unit 20, the diagram on the left is a side view of lens unit 20 seen from the left of the front view, and the diagram on the upper side is a side view of lens unit 20 seen from above the front view. In Fig. 3, the same components as those in lens unit 10 shown in Fig. 1 are designated by the same reference numerals as in Fig. 1, and the above-mentioned explanation of Fig. 1 is incorporated herein by reference.

[0034] Lens unit 20 has a configuration similar to that of lens unit 10 shown in Figure 1, but multiple lens portions 11 are arranged in one direction (left and right direction in the front view shown), and thick portion 22a of holding portion 22 extends along the arrangement direction of lens portions 11.

[0035] Similar to lens unit 10, lens portion 11 and holder 22 of lens unit 20 are integrally formed, for example, from the same material, and lens portion 11 is formed on lens surface 221, which is one surface of holder 22. Of holder 22, support surface 222 facing lens surface 221 is supported by being adhesively fixed to an end surface of a substrate on which an optical waveguide is formed (hereinafter also referred to as an optical waveguide substrate), for example. Furthermore, thick portion 22a is formed along one side surface 223 that is not a surface through which optical axis 13 of lens portion 11 passes (i.e., not lens surface 221 or support surface 222), such that thickness L21 measured in the direction of optical axis 13 is greater than thickness L20 of the remaining portion of holder 22, and is provided in a portion that does not include lens portion 11.

[0036] 1, the lens unit 20 maintains a constant thickness L20 of the holding portion 22, which is the distance from the support surface 222 to the lens portions 11, while the thick portions 22a, which have a thickness L21 greater than the thickness L20, improves the mechanical strength of the entire lens unit 20. In particular, the thick portions 22a of the lens unit 20 are formed to extend in the arrangement direction of the lens portions 11, improving the bending strength along the arrangement direction. This makes it possible to prevent the lens unit 20 from deteriorating its adhesion to the optical waveguide substrate due to bending of the support surface 222 caused by stress from a clamping jig during alignment, for example.

[0037] Although the number of lens portions 11 arranged is three in the example of FIG. 2, it is not limited to this and may be any number equal to or greater than two.

[0038] [1.2 Second Modification] Fig. 4 is a diagram showing the configuration of a lens unit 30 according to a second modified example. In Fig. 4, the diagram on the lower right is a front view of the lens unit 30, the diagram on the left is a side view of the lens unit 30 seen from the left of the front view, and the diagram on the upper side is a side view of the lens unit 30 seen from above the front view. In Fig. 4, the same components as those shown in Figs. 1 and 3 are indicated by the same reference numerals as in Figs. 1 and 3, and the above-mentioned explanations for Figs. 1 and 3 are incorporated herein by reference.

[0039] The lens unit 30 has a similar configuration to the lens unit 20 shown in FIG. 3, but differs in that it includes a holding portion 22-1 instead of the holding portion 22. The holding portion 22-1 has a similar configuration to the holding portion 22, but in addition to the thick portion 22a provided along the side surface 223, a thick portion 22b is provided along another side surface 224 that faces the side surface 223 with the lens portion 11 in between. In the example shown in FIG. 4, the thickness L22 of the thick portion 22b is thinner than the thickness L21 of the thick portion 22a (L22 <L21)。

[0040] In the lens unit 30 having the above configuration, similar to the lens unit 10 shown in FIG. 1, the thickness L20 is maintained at a constant value, while the thick portions 22a and 22b can further improve the mechanical strength of the lens unit 30 as a whole.

[0041] Furthermore, in the lens unit 30, the thickness L22 of the thick portion 22b is formed to be thinner than the thickness L21 of the thick portion 22a. Therefore, for example, if it is necessary to arrange an optical assembly 17 as shown in FIG. 2 between the lens unit 30 and the optical fiber, a location for arranging such an optical assembly 17 can be secured on the side of the thick portion 22b, as in the configuration shown in FIG. 2.

[0042] In addition, if no optical component such as optical assembly 17 is used between the substrate and the optical fiber, or if sufficient space can be secured between the substrate and the optical fiber to place an optical component, thick portion 22a and thick portion 22b can be formed to have the same thickness (L21 = L22).

[0043] [2. Second Embodiment] Next, a second embodiment of the present invention will be described. The second embodiment is an optical waveguide device configured using the lens unit 20 or 30 according to the modification of the first embodiment described above.

[0044] Fig. 5 is a diagram showing an example of the configuration of an optical waveguide device 50 according to the second embodiment. Fig. 6 is a cross-sectional view taken along line XI-XI of the optical waveguide device 50 shown in Fig. 5. The optical waveguide device 50 shown in Fig. 5 includes, as an example, the lens unit 30 shown in Fig. 4. In Figs. 5 and 6, the same components as those shown in Fig. 4 are designated by the same reference numerals as those shown in Fig. 4, and the above description of Fig. 4 is incorporated herein.

[0045] The optical waveguide device 50 includes an optical waveguide element 51 having an optical waveguide 51b provided on a substrate 51a, a housing 52 that houses the optical waveguide element 51, and an input optical fiber 53 and an output optical fiber 54 that propagate input light and output light of the optical waveguide element 51. In addition, a lens unit 30 is disposed between the optical waveguide element 51 and the input optical fiber 53 and output optical fiber 54.

[0046] Housing 52 is configured, for example, with a hexahedral case 521 having one open face (the face shown in FIG. 5), and a cover 522 that covers the open face of case 521. Note that while only a portion of cover 522 is depicted in FIG. 5, it should be understood that cover 522 is configured to cover the entire opening of case 521.

[0047] The optical waveguide element 51 is a folded optical modulation element that performs DP-QPSK modulation, and has an optical waveguide 51b, which is a convex waveguide, formed on a substrate 51a made of, for example, LN. Such a DP-QPSK modulator can be configured using a so-called nested Mach-Zehnder optical waveguide. In the optical waveguide element 51, which is an optical modulation element, signal electrodes (not shown) that control light waves propagating through the optical waveguide 51b are formed on the substrate 51a according to conventional technology. These signal electrodes are connected to signal pins 57 provided on the case 521 via a relay substrate 56 disposed within the case 521.

[0048] The light propagation direction of optical waveguide 51b of optical waveguide element 51 is folded back on substrate 51a, and one light input end and two light output ends of optical waveguide 51b are arranged on one end face of substrate 51a. The sum of the number of incident light beams entering optical waveguide element 51 and the number of output light beams output from optical waveguide element 51 is three, and lens unit 30 has the same number of lens portions 11.

[0049] The input optical fiber 53 and the output optical fiber 54 are both fixed to one surface (the surface on the right side in the figure) of the housing 52 via terminal portions 531 and 541, respectively. Lenses 532 and 542 are fixed to the terminal portions 531 and 541, respectively, and their positions are adjusted with respect to the input optical fiber 53 and the output optical fiber 54.

[0050] Light incident from input optical fiber 53 is collimated by lens 532, and then collected by one lens portion 11 of lens unit 30, and coupled to the optical input end of optical waveguide element 51. Two light beams emitted from the optical output end of optical waveguide element 51 are two linearly polarized light beams, which are collimated by the other two lens portions 11 of lens unit 30, and then polarization-combined by optical assembly 55 to become one optical beam.

[0051] According to conventional technology related to DP-QPSK modulators, the optical assembly 55 may include a beam shift prism that translates the optical axis of the input light from the input optical fiber 53, and a half-wave plate and a polarization combining prism that polarization combine the two output light beams from the optical waveguide 51b. The polarization combined light beam output from the optical assembly 55 is collected by a lens 542 and coupled to the output optical fiber 54.

[0052] The lens unit 30 is arranged so that the side surface 223 along the thick portion 22a faces the opening of the case 521 (i.e., the upward direction in FIG. 6). As a result, during the alignment process in the manufacturing process of the optical waveguide device 50, the lens unit 30 is held and its position adjusted by a clamping jig or a suction jig lowered through the opening of the case 521. Thereafter, the support surface 222 of the lens unit 30 is fixed to the end face of the optical waveguide element 51 with an optical adhesive.

[0053] The optical assembly 55 is disposed close to the lens unit 11 to a position where it fits under the thick portion 22a of the lens unit 30. That is, the optical assembly 55 and the thick portion 22a along the side surface 223 of the lens unit 30 have overlapping portions in a plan view of the case 521 seen from its opening (the hatched portion shown in FIG. 5 and the range indicated by the symbol A in FIG. 6).

[0054] The optical waveguide device 50 having the above configuration is configured using the lens unit 30, and therefore it is possible to prevent deformation or damage to the lens unit 30 during alignment of the optical system during manufacturing, thereby improving manufacturing yield. Furthermore, in the optical waveguide device 50, the optical assembly 55 can be mounted so that it has a portion that overlaps with the thick portion 22a of the lens unit 30 in a plan view seen from the opening of the case 521, and therefore it is possible to suppress an increase in the length dimension of the case 521 even if the thick portion 22a is present.

[0055] The optical waveguide device 50 may be configured using the lens unit 20 instead of the lens unit 30. When the lens unit 20 is used, the same effects as those of the optical waveguide device 50 described above can be achieved.

[0056] [Third embodiment] Next, a third embodiment of the present invention will be described. Fig. 7 is a diagram showing the configuration of an optical waveguide device 60 according to the third embodiment. In Fig. 7, the same components as those in the optical waveguide device 50 shown in Figs. 5 and 6 are designated by the same reference numerals as in Figs. 5 and 6, and the above explanations for Figs. 5 and 6 are incorporated herein.

[0057] The optical waveguide device 60 shown in Fig. 7 has a similar configuration to the optical waveguide device 50 shown in Fig. 5, but a driver circuit 61 for driving the optical waveguide element is mounted on the relay substrate 56. As explained in Fig. 5, the optical waveguide element 51 is an optical modulation element, such as a DP-QPSK modulator, that modulates and outputs input light from an input optical fiber 53. The driver circuit 61 is mounted in the form of, for example, an integrated circuit (IC).

[0058] The driving circuit 61 generates a high-frequency electrical signal for driving the optical waveguide element 51 based on, for example, a modulation signal supplied from the outside via the signal pin 57, and outputs the generated high-frequency electrical signal to a signal electrode (not shown) formed on the substrate 51 a of the optical waveguide element 51.

[0059] The optical waveguide device 60 having the above configuration uses a lens unit 30 having a thick portion 22a, similar to the optical waveguide device 50 according to the second embodiment, and therefore can prevent deformation or breakage of the lens unit 30 during manufacturing while suppressing an increase in the length dimension of the case 521, thereby improving manufacturing yield.

[0060] 5, the optical waveguide device 60 may also use the lens unit 20 instead of the lens unit 30. When the lens unit 20 is used, the same effects as those described above can be achieved.

[0061] 3. Fourth Embodiment Next, a fourth embodiment of the present invention will be described. This embodiment is an optical transmitter 70 equipped with the optical waveguide device 50 according to the second embodiment. Fig. 8 is a diagram showing the configuration of the optical transmitter 70 according to this embodiment. This optical transmitter 70 includes the optical waveguide device 50, a light source 71 that inputs light to the optical waveguide device 50, a modulator driver 72, and a modulation signal generator 73.

[0062] The modulation signal generation unit 73 is an electronic circuit that generates an electric signal for causing the optical waveguide element 51 of the optical waveguide device 50 to perform a modulation operation. Based on transmission data provided from the outside, the modulation signal generation unit 73 generates a modulation signal, which is a high-frequency signal for causing the optical waveguide element 51 to perform an optical modulation operation in accordance with the modulation data, and outputs the modulation signal to the modulator drive unit 72.

[0063] The modulator driver 72 amplifies the modulation signal input from the modulation signal generator 73 and outputs a high-frequency electrical signal (drive signal) for driving the signal electrode of the optical waveguide element 51 included in the optical waveguide device 50. Note that instead of the optical waveguide device 50 and the modulator driver 72, an optical waveguide device 60 including a drive circuit 61 equivalent to the modulator driver 72 can also be used.

[0064] The optical transmitter 70 having the above configuration uses the optical waveguide device 50 or 60 according to the second or third embodiment described above, in which the lens unit 20 or 30 prevents an increase in the size of the housing 52 while improving the manufacturing yield, and therefore costs can be reduced without increasing the size.

[0065] The present invention is not limited to the configurations of the above-described embodiments and their alternative configurations, and can be implemented in various forms without departing from the spirit of the present invention.

[0066] For example, in the lens units 10, 20, and 30 according to the first embodiment and its modified examples, the lens portion 11 is configured with a convex curved surface, but is not limited to this. The lens portion 11 may be a Fresnel lens having a sawtooth cross section or a gradient index lens configured with a refractive index that changes depending on the distance from the center of the optical axis. Furthermore, the lens portion 11 may be configured with a concave curved surface depending on the optical design between the optical waveguide and the optical fiber.

[0067] In the first embodiment and its modified examples described above, the lens units 10, 20, and 30 are formed by pressing glass heated to a softening point or higher, thereby integrating the lens portion 11 and the holder 12, 22, or 22-1. However, the present invention is not limited to this configuration. For example, the lens units 10, 20, and 30 may be formed by pressing transparent plastic. Furthermore, for example, the lens units 10, 20, and 30 may be formed by combining the lens portion 11 and the holder 12, 22, or 22-1, which are separately formed.

[0068] Furthermore, in the above-described lens units 10, 20, and 30, each holding portion has a thick portion on one or two sides thereof, but the thick portions may be provided independently or connected to three or more sides of the holding portion.

[0069] 4. Configurations supported by the above embodiments The above embodiment and modifications support the following configurations.

[0070] (Configuration 1) A lens unit that optically couples an optical waveguide provided on a substrate with an optical fiber, the lens unit having a lens portion and a holding portion that holds the lens portion, the holding portion having a thick portion along one side that is not a plane through which the optical axis of the lens portion passes, where the thickness of the holding portion measured in the direction of the optical axis is greater than other portions of the holding portion. According to the lens unit of configuration 1, the mechanical strength can be increased, and deformation or damage to the lens unit can be prevented during operations such as alignment.

[0071] (Configuration 2) A lens unit according to configuration 1, including a plurality of the lens portions arranged in one direction, wherein the thick portion of the holding portion extends along the arrangement direction of the lens portions. According to the lens unit of configuration 2, bending of the lens unit along the arrangement direction of the lens portions can be prevented, and, for example, a decrease in adhesion between the lens unit and the end face of the optical waveguide substrate can be prevented.

[0072] (Configuration 3) A lens unit according to configuration 1 or 2, wherein the holding portion further has a thick portion on another side opposite the one side across the lens portion, the thickness measured in the direction of the optical axis being greater than the thickness of the other part of the holding portion. According to the lens unit of configuration 3, the mechanical strength of the lens unit can be further increased.

[0073] (Configuration 4) The lens unit according to Configuration 3, wherein the thickness of the thick portion of the holding portion on the other side surface is thinner than the thickness of the thick portion on the one side surface. According to the lens unit of configuration 4, the mechanical strength is further improved by providing two thick portions, and when other components such as an optical assembly are arranged between the optical waveguide and the optical fiber inside the housing, for example, the other components can be arranged near the thinner thick portions, thereby suppressing an increase in the size of the housing due to the provision of the thick portions.

[0074] (Configuration 5) The lens unit according to any one of configurations 1 to 4, wherein the thick portion has an inclined portion whose thickness continuously decreases toward the lens portion. According to the lens unit of configuration 5, it is possible to prevent a portion of the light incident on or emitted from the lens portion from being blocked by the thick portion.

[0075] (Configuration 6) An optical waveguide device comprising: an optical waveguide element having an optical waveguide provided on a substrate; a housing for accommodating the optical waveguide element; input optical fibers and output optical fibers for propagating input light and output light of the optical waveguide element; and a lens unit according to any one of configurations 1 to 5, arranged between the optical waveguide element and the input optical fibers and the output optical fibers. According to the optical waveguide device of configuration 6, it is possible to prevent deformation or damage to the lens unit during manufacturing while suppressing an increase in the housing size, thereby improving manufacturing yield.

[0076] (Configuration 7) An optical waveguide device according to configuration 6, wherein the housing is composed of a hexahedral case with one open side and a cover that covers the open side of the case, and the lens unit is arranged so that the one side on which the thick portion is provided faces the open side of the case. According to the optical waveguide device of configuration 7, for example, a clamping tool can be used to grip the thick portion of the lens unit through the opening of the case, making it easy to align the lens unit.

[0077] (Configuration 8) The optical waveguide device according to Configuration 7, wherein the optical waveguide element has, on one end face of the substrate, an optical input end of the optical waveguide that receives the input light and an optical output end of the optical waveguide that outputs the output light, the input optical fiber and the output optical fiber are both fixed to one face of the housing, and the lens unit arranged between the optical waveguide element and the input optical fiber and the output optical fiber includes the lens portions in a number equal to the sum of the number of incident light beams that enter the optical waveguide element and the number of output light beams that output from the optical waveguide element. According to the optical waveguide device of configuration 8, an optical waveguide element having an optical input end and an optical output end on one end surface of a substrate, an input optical fiber, and an output optical fiber are optically coupled by a single lens unit with improved mechanical strength, thereby improving the manufacturing yield.

[0078] (Configuration 9) An optical waveguide device according to configuration 7 or 8, including an optical assembly arranged between the optical waveguide element and the input optical fiber and / or the output optical fiber, wherein the optical assembly and the thick portion on the one side of the lens unit have overlapping portions when the case is viewed in a plan view from the opening. According to the optical waveguide device of configuration 9, the optical assembly can be placed under the thick portion on one side surface, thereby suppressing an increase in the housing size due to the provision of the thick portion.

[0079] (Configuration 10) An optical waveguide device according to any one of configurations 6 to 9, wherein the optical waveguide element is an optical modulation element that modulates and outputs input light from the input optical fiber, and the housing has an electronic circuit inside that drives the optical waveguide element. According to the optical waveguide device of configuration 10, the electronic circuit that drives the optical waveguide element, which is an optical modulation element, is housed in the housing, so that good optical modulation characteristics can be realized.

[0080] (Configuration 11) An optical transmitter comprising the optical waveguide device according to any one of configurations 6 to 10, and an electronic circuit that generates an electrical signal for causing the optical waveguide element to perform a modulation operation. According to the optical transmitting device of configuration 11, an optical waveguide device is used that uses a lens unit of any one of configurations 1 to 5 to suppress an increase in the housing size while improving the manufacturing yield, thereby making it possible to reduce costs while avoiding an increase in the device size. [Explanation of symbols]

[0081] 10, 20, 30, 90... Lens unit, 11, 91... Lens portion, 12, 22, 22-1, 92... Holding portion, 12a, 22a, 22b... Thick portion, 121, 221, 921... Lens surface, 122, 222, 922... Support surface, 123, 125, 126, 223, 224, 923, 924, 925... Side, 124... Inclined portion, 13... Optical axis, 14, 51... Optical waveguide element, 15, 521... Case, 16, 95... Optical fiber, 161, 531, 541, 951... Terminal portion, 1 62, 532, 542, 952...lenses, 17, 55...optical assembly, 18a, 18b, 97a, 97b, 97c, 97d, 98a, 98b...clamping jigs, 50, 60...optical waveguide device, 51a, 94...substrate, 51b, 93...optical waveguide, 52...housing, 522...cover, 53...input optical fiber, 54...output optical fiber, 56...relay board, 57...signal pin, 61...driver circuit, 70...optical transmitter, 71...light source, 72...modulator driver, 73...modulation signal generator.

Claims

1. An optical waveguide element having an optical waveguide provided on a substrate; a lens unit that optically couples the optical waveguide and an optical fiber; a housing for accommodating the optical waveguide element, the housing including a case having an opening on one side and a cover covering the opening on the case; Equipped with The lens unit comprises: a lens portion and a holding portion that holds the lens portion, the holding portion has a thick portion, the thickness of which is thicker than other portions of the holding portion as measured in the direction of the optical axis, along a third surface, which is different from the first surface and the second surface of the lens unit and through which the optical axis of the lens portion passes, and the lens unit is arranged so that the first surface faces an end of the optical waveguide element and the third surface faces the one open surface of the case, the thick portion forms a convex portion on the second surface opposite to the first surface facing an end of the optical waveguide element, and an end of the convex portion does not come into contact with another object; Optical waveguide devices.

2. The lens unit includes a plurality of the lens portions arranged along one direction, The thick portion of the holding portion extends along the arrangement direction of the lens portions.

2. The optical waveguide device according to claim 1.

3. the holding portion further has a thick portion on a fourth surface facing the third surface with the lens portion interposed therebetween, the thick portion having a thickness measured in the optical axis direction that is greater than the thickness of other portions of the holding portion.

3. The optical waveguide device according to claim 1.

4. the thickness of the thick portion of the holding portion on the fourth surface is thinner than the thickness of the thick portion of the thick portion on the third surface; 4. The optical waveguide device according to claim 3.

5. The thick portion has a sloped portion whose thickness continuously decreases toward the lens portion.

5. The optical waveguide device according to claim 1.

6. The optical fiber includes an input optical fiber that propagates input light to the optical waveguide, and an output optical fiber that propagates output light from the optical waveguide, the optical waveguide element has, on one end surface of the substrate, an optical input end of the optical waveguide that receives the input light and an optical output end of the optical waveguide that outputs the output light, the input optical fiber and the output optical fiber are both fixed to one surface of the housing; the lens unit disposed between the optical waveguide element and the input optical fiber and the output optical fiber includes the lens portions in a number equal to the sum of the number of the input light beams and the number of the output light beams; 6. The optical waveguide device according to claim 1.

7. an optical assembly disposed between the optical waveguide element and the input optical fiber and / or the output optical fiber; the optical assembly and the thick portion on the one side surface of the lens unit have portions that overlap with each other in a plan view of the case seen from the opening; 7. The optical waveguide device according to claim 6.

8. the optical waveguide element is an optical modulation element that modulates and outputs light, an electronic circuit for driving the optical waveguide element is disposed inside the housing; 8. The optical waveguide device according to claim 1.

9. The optical waveguide device according to any one of claims 1 to 8, an electronic circuit that generates an electrical signal for causing the optical waveguide element, which is an optical modulation element, to perform a modulation operation; An optical transmitting device comprising:

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