JP2008134492A - Optical transmission system and optical module equipped with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission system in which the optical path between the face direction of a substrate and the vertical optical transmission direction is converted with high efficiency, and a first optical transmission substrate and a second optical transmission substrate can easily be positioned. <P>SOLUTION: The optical transmission system includes: a first optical transmission substrate 1 provided with an optical transmission hole 3 having open parts on both main faces; and a second optical transmission substrate 2 provided with an optical waveguide 5 disposed on one of the main faces of the substrate 2, an optical path conversion part 4 which converts the optical transmission direction between the optical transmission hole 3 of the first optical transmission substrate 1 and the optical waveguide 5; and a lens 6 which is optically coupled to the optical transmission hole 3 and optically coupled to the optical path 5 via the optical path conversion part 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical transmission system including a plurality of optical transmission boards and an optical module including the optical transmission system.

  In recent years, with the improvement of information processing capability of computers, in an integrated circuit (IC) such as a semiconductor large scale integrated circuit element (LSI, VLSI) used as a microprocessor, the degree of integration of transistors has been increased. The operating speed of the IC has reached the GHz level at the clock frequency. Along with this, there has been a demand for higher density and finer electrical wiring for electrically connecting electrical elements.

  However, increasing the density and miniaturization of electrical wiring tends to cause crosstalk and propagation loss of electrical signals. Therefore, electrical signals input to and output from semiconductor devices are converted to optical signals, and the optical signals are mounted. An optical transmission technique in which an optical wiring such as an optical waveguide formed on a substrate is transmitted has been studied.

  As such an optical transmission technology, light is transmitted by optical waveguides formed on the front and back surfaces of the circuit board, or through holes (optical transmission holes) provided between the front and back surfaces of the circuit board. It is known to transmit light. Such an optical transmission hole is obtained by penetrating the circuit board perpendicularly to the optical waveguide, and can be used in combination with the optical waveguide to transmit three-dimensional light.

For example, Patent Document 1 discloses a three-dimensional optical transmission technique having an optical transmission hole 13 and an optical waveguide 15. According to this, the optical waveguide 15 is provided in the second optical transmission board 12 serving as the motherboard, and the optical transmission hole 13 is provided in the first optical transmission board 11 serving as the daughter board for mounting on the motherboard, The optical waveguide 15 and the light transmission hole 13 are optically coupled (see FIG. 7).
JP 2003-215372 A

  However, in the technique disclosed in Patent Document 1, in order to optically couple the optical waveguide 15 and the optical transmission hole 13, the first optical transmission substrate 11 and the second optical transmission substrate 12 are connected via the solder connection portion 19. Since they are connected, the optical transmission hole 13 in the first optical transmission substrate 11 and the optical waveguide 15 in the second optical transmission substrate 12 cannot be sufficiently aligned.

  Further, when the sealing resin is filled between the first optical transmission board 11 and the second optical transmission board 12, the sealing resin has a uniform refractive index. Light diffuses between the optical transmission hole 13 and the optical waveguide 15, and high-efficiency optical transmission conversion cannot be performed.

  In this way, optical transmission that achieves both easy alignment between the first optical transmission substrate and the second optical transmission substrate and conversion of the highly efficient optical transmission direction between the optical transmission hole and the optical waveguide. The technology has not been obtained so far.

  The present invention has been devised to solve the above-described problems in the prior art, and its purpose is to suppress light scattering between the optical transmission hole and the optical waveguide and to perform the first optical transmission. It is an object of the present invention to provide an optical transmission system that allows easy alignment between a substrate and a second optical transmission substrate.

  An optical transmission system according to the present invention includes a first optical transmission board that includes an optical transmission hole that passes through from one main surface to the other main surface and has openings on both main surfaces, and one main surface. A second optical transmission board having the first optical transmission board mounted on a surface thereof; an optical waveguide disposed on the one main surface; the optical transmission hole of the first optical transmission board; A second optical transmission board having an optical path conversion unit for changing an optical transmission direction between the optical waveguide and an opening in the other main surface of the first optical transmission board. A convex curved surface and a second convex curved surface aligned with the optical path conversion unit, optically coupled to the optical transmission hole, and optically coupled to the optical waveguide via the optical path conversion unit. Coupled lenses.

  The first optical transmission board is preferably mounted by a spherical conductive member arranged in a lattice pattern with respect to the second optical transmission board with respect to the second optical transmission board.

  The lens is preferably spherical.

  It is preferable that a transparent resin capable of transmitting light is provided in the light transmission hole.

  It is preferable that the transparent resin includes a core portion having a refractive index higher than that of the surrounding portion in the radial direction of the light transmission hole.

  The optical transmission system according to the present invention may include a step of arranging the lens between the first optical transmission substrate and the second optical transmission substrate, and the second optical transmission substrate based on an outer shape of the lens. Preferably, the method includes a step of mounting the first optical transmission board.

  The optical module of the present invention includes the optical transmission system and an optical semiconductor element mounted on the one main surface of the first optical transmission board and optically coupled to the optical transmission hole. .

  According to the optical transmission system of the present invention, the first optical transmission board having optical transmission holes penetrating from one main surface to the other main surface and having openings on both main surfaces, A second optical transmission board having the first optical transmission board mounted on the main surface thereof, an optical waveguide disposed on the one main surface, and the optical transmission hole of the first optical transmission board A second optical transmission board comprising: an optical path changing part for changing an optical transmission direction between the first optical transmission board and an opening in the other main surface of the first optical transmission board. 1 convex curved surface and a second convex curved surface aligned with the optical path changing unit, optically coupled to the light transmission hole, and to the optical waveguide via the optical path changing unit. And optically coupled lenses to scatter light between the light transmission hole and the optical waveguide. It is possible to suppress.

  Specifically, the lens has a first convex curved surface that enters into the opening of the first optical transmission board and a second convex curved surface enters into the recess formed in the optical waveguide. Thus, since the mounting position of the lens with respect to the optical axis connecting the center of the optical transmission hole and the optical path changing unit is uniquely determined, the positions of the first optical transmission substrate and the second optical transmission substrate with respect to the outer shape of the lens Enables matching.

  The first optical transmission board is free from the second optical transmission board by using a spherical conductive member arranged in a lattice pattern with respect to the second optical transmission board, as compared with the case where other mounting means are used. A high degree of alignment is possible.

  Since the lens has a spherical shape, it is possible to improve both the condensing effect and the alignment effect on the optical path reflecting surface by the lens.

  The light transmission hole is provided with a transparent resin capable of transmitting light, thereby reducing light reflection at the opening of the light transmission hole and further scattering light at the optical path changing unit. It is possible to reduce the crosstalk of light with other adjacent core portions.

  The transparent resin includes a core part having a refractive index higher than that of the surrounding part in the radial direction of the optical transmission hole, so that an optical signal is confined and propagated in the core part, and high-efficiency optical signal propagation is achieved. Can be realized.

  The method of manufacturing an optical transmission system according to the present invention includes the step of arranging the lens between the first optical transmission substrate and the second optical transmission substrate, and the second light with reference to the outer shape of the lens. Including the step of mounting the first optical transmission board on the transmission board, the lens serves as a reference, and the first optical transmission board and the second optical transmission board can be aligned.

  The optical transmission system and the optical module including the optical transmission system according to the present invention will be described with reference to the drawings. However, the drawings are only examples of the embodiments, and the present invention is not limited to them.

  FIG. 1 is a cross-sectional view schematically showing an example of an embodiment of an optical transmission system of the present invention. In FIG. 1, 1 is a first optical transmission substrate, 2 is a second optical transmission substrate, 3 is an optical transmission hole, 4 is an optical path conversion unit, 5 is an optical waveguide, 6 is a lens, 7 is an optical semiconductor element, and 8 is a ball. A grid array (hereinafter referred to as BGA) is shown. The lens 6 in FIG. 1 has a spherical shape. The optical semiconductor element is not included in the configuration of the optical transmission system.

  In FIG. 1, the first optical transmission board 1 is used as a daughter board, and the second optical transmission board 2 is used as a mother board on which the first optical transmission board 1 is mounted. The daughter board here means a board that is mounted on the mother board to give the mother board a function.

  Each configuration will be described below.

<First optical transmission board>
As the first optical transmission board 1, for example, a printed wiring board made of generally used epoxy resin or ceramic is used. Among them, a printed wiring board having a symmetrical layer structure in which a resin insulating layer having the same thickness is formed on both sides is preferable because the mechanical strength is large and it is possible to effectively prevent the warpage of the board due to heat. It is more preferable that the resin insulating layers on both sides have the same thickness. The thickness of the substrate can be 0.5 to 1.5 mm.

  Further, a multilayer wiring board may be used as the first optical transmission board 1. Here, the multilayer wiring substrate may be any substrate in which a plurality of electrical wiring layers and insulating layers are alternately laminated, for example, a substrate composed of a core substrate and a buildup layer formed on the wiring substrate surface side. Is also included. Here, the build-up layer is a multilayer substrate in which electrical wiring layers and insulating layers are alternately stacked, and the core substrate is a single layer on which the build-up layer is provided and supports the build-up layer. Say.

  The first optical transmission board 1 is provided with an optical transmission hole 3. In FIG. 1, the optical transmission hole 3 is perpendicular to one main surface of the first optical transmission substrate 1 and the other main surface, and one main surface of the first optical transmission substrate 1 It refers to a through-hole that transmits light by penetrating from one surface to the other main surface and making openings on the two main surfaces. For example, as shown in FIG. 1, when a light emitting element is installed as an optical semiconductor element 7 on one main surface to form an optical module, light emitted from the optical semiconductor element 7 propagates to the optical transmission hole 3. The light is transmitted to the other main surface.

  For the formation of the light transmission hole 3, a drill or laser used in a normal printed circuit board drilling process is preferably used. And the optical transmission hole 3 is formed by letting the 1st optical transmission board | substrate 1 penetrate from one main surface to the other main surface. The light transmission hole 3 preferably has a circular cross section and a diameter of 50 to 200 μm.

On the other main surface side, the optical transmission hole 3 is inserted into and engaged with a part of the curved surface of the lens, which will be described later, so as to contact the opening of the optical transmission hole 3. It can be used for positioning with the substrate 1.

  It is preferable that a transparent resin capable of transmitting light is provided in the light transmission hole 3. The reason for this is that light reflection at the opening of the light transmission hole 3 is reduced, light scattering at the optical path changing portion can be reduced, and light crosstalk with other adjacent core portions can be reduced. This is because it can be made smaller. In that case, the transparent resin preferably has a refractive index distribution that is high in the central portion and low in the peripheral portion in the radial direction. Thus, the part where the refractive index is higher than the peripheral part is referred to as a core part. Such a concentric refractive index distribution has an optical confinement effect for confining an optical signal in the center.

  When a transparent resin is provided in the light transmission hole 3, polysilane that causes a photo bleaching phenomenon in which the refractive index decreases when irradiated with light, or a photosensitive acrylic resin or epoxy resin that can be removed by developing the irradiated portion. Can be used. For example, when the photo bleaching phenomenon is used, the light transmission hole 3 is filled with polysilane, heated and cured, and then passed through a photomask (having a light shielding part with a circular pattern having a smaller diameter than the light transmission hole). The refractive index distribution is formed in the transparent resin in the light transmission hole 3 by irradiating the ultraviolet light to lower the refractive index of the ultraviolet light irradiating portion and finally performing the post baking.

  In the case of using an ultraviolet curable acrylic resin or epoxy resin, the light transmission hole 3 is filled with these photosensitive polymer materials and cured by heating, and then a photomask (having a diameter smaller than that of the light transmission hole 3). A portion (light) removed by development in the light transmission hole 3 after removing the resin of the ultraviolet light irradiation portion by performing development by irradiating the ultraviolet light through a circular pattern light-transmitting portion) The center of the transmission hole) is filled with a material having a higher refractive index than that of the material first filled, irradiated with ultraviolet light without using a photomask, and finally cured by post-baking. A refractive index distribution is formed in the transparent resin.

  The first optical transmission board 1 is mounted on the second optical transmission board 2 on the other main surface side of the first optical transmission board 1, that is, on the main surface side to be mounted on the second optical transmission board 2. Mounting means are provided for this purpose. As this mounting means, for example, it is formed as an electrode formed of a metal such as Cu, Ni, Ag, W, Mo, Al, Au. Similar electrodes are provided as mounting means at positions corresponding to one main surface of the second optical transmission board, and the first optical transmission board 1 is mounted on the second optical transmission board 2 via solder or the like. . The electrodes of these mounting means may form an electric circuit with the second optical transmission board 2 as an exposed portion of the electric wiring layer of the multilayer wiring board described above, or anywhere. You may form as a floating electrode which is not connected.

<Second optical transmission board>
The material of the second optical transmission board 2, the thickness of the board, the mounting structure, and the like are the same as those of the first optical transmission board 1 described above.

  The second optical transmission board 2 is provided with an optical path conversion unit 4 and an optical waveguide 5.

  When the first optical transmission board 1 described above is mounted on the second optical transmission board 2, the optical path conversion unit 4 applies to both the optical transmission hole 3 of the first optical transmission board 1 and the optical waveguide 5. Optically coupled to each other, and has a function of changing the light transmission direction between the light transmission hole 3 and the optical waveguide 5. Specifically, since the optical path conversion unit 4 is a light reflecting surface having a certain inclination angle, the incident direction of light can be converted into the reflecting direction, and the optical transmission hole 3 and the optical waveguide having different optical path directions, respectively. 5 can be optically coupled.

  In FIG. 1, it is formed at a position corresponding to the opening position of the light transmission hole 3 of the first light transmission substrate 1, and the optical path conversion unit 4 is provided after the optical waveguide 5 is formed. Here, the “location corresponding to the opening position of the light transmission hole 4” is a position located below the opening 1a of the light transmission hole 3 when the substrates are mounted, and the lens 6 and the optical waveguide. 5 is a portion where the optical path conversion unit 4 can perform highly efficient optical coupling.

  As a method of forming the optical path conversion unit 4, generally, a part of the optical waveguide is cut obliquely by grooving with a dicing saw using a diamond blade whose tip is processed at 45 degrees or 90 degrees. It is formed. In addition, there are a method of forming a slope by patterning the optical waveguide 5 using a gray mask, oblique exposure, or the like, or a method of using a marking machine used for cutting a printed circuit board. Further, a penetration that is positioned on the optical path of the optical path conversion unit 4 by bringing a part of a curved surface of a lens described later into contact with and engaging with the position of one main surface of the second optical transmission board 2. It is desirable to provide a hole or a recess. Using this through hole or recess, the lens and the second optical transmission board 2 can be used for positioning. Such a through-hole or a recessed part can be formed by laser processing etc., for example. It is necessary to form these through-holes and recesses in contact with the lens with high accuracy so that the lens can be optically coupled with the optical path conversion unit 4 satisfactorily.

  In FIG. 1, a configuration in which the optical path conversion unit 4 is formed in the optical waveguide 5 is given as a specific example. However, the optical path conversion unit 4 in the present invention is not limited thereto, and for example, a configuration different from the optical waveguide 5 It may be.

  The optical path conversion unit 4 may be an inclined surface formed on the middle surface of the optical waveguide 5, or gold (Au), silver (Ag), platinum (Pt), aluminum (Al), copper (Cu), or the like. As described above, a film having a high reflectance with respect to the light guided through the optical waveguide 5 can be formed on the surface thereof.

  The optical waveguide 5 is disposed on one main surface of the second optical transmission board 2 and plays a role of transmitting light.

As shown in FIG. 1, the optical waveguide 5 is preferably composed of a core portion (a hatched portion in the optical waveguide 5 in FIG. 1) and a cladding portion that surrounds the core portion and has a refractive index smaller than that of the core portion. By adjusting the refractive indexes of the core part and the clad part, good light propagation is possible.
Examples of a method for producing the optical waveguide 5 having the core part include a direct exposure method, a refractive index change method (photo bleaching method), and a reactive ion etching method.

  Examples of materials that can be manufactured by the direct exposure method include photosensitive epoxy resins, acrylic resins, and polyimide resins. In the direct exposure method, a necessary pattern can be obtained by applying, exposing, and developing materials corresponding to the core portion and the clad portion. For example, if a negative photosensitive epoxy resin is used, the exposed portion of the resin is cured and exposed by applying a material and preparing and exposing a photomask that exposes the necessary areas. By removing the unexposed resin by development, a desired pattern can be obtained. By applying this method to both the lower clad part and the upper clad part and the core part, the optical waveguide 5 can be formed only at a necessary place in the entire substrate. For example, in the case of a multi-mode optical waveguide, the shape and dimensions of the core portion and the clad portion of the optical waveguide are set so that the thickness of the lower clad portion and the upper clad portion is the core when the thickness of the core portion is about 50 μm. The optical waveguide 5 having a thickness of about 100 μm can be obtained as about 25 μm, which is half of the portion.

<Lens>
In the present invention, the lens 6 has an effect of suppressing light scattering between the optical transmission hole 3 and the optical waveguide 5 and an effect of aligning the positions of the first optical transmission substrate 1 and the second optical transmission substrate 2. Is.

  The lens 6 includes a convex curved surface (hereinafter referred to as a first convex curved surface) aligned with an opening in the other main surface of the first optical transmission board, and a convex curved surface (hereinafter referred to as a first convex curved surface) aligned with the optical path changing unit 4. The above-mentioned effect can be satisfied by providing the second convex curved surface.

  Here, a specific example of the lens 6 will be described with reference to FIGS. 2 and 3 are enlarged views of the main part of FIG. 1, respectively. In FIGS. 2 and 3, A indicated by a dotted line indicates an optical axis, and B indicates an optical signal. 4 is a top view of the opening 1a on the other main surface of the first optical transmission board 1, the lens 6, and the opening 5b of the recess 5a formed in the optical waveguide 5 in FIG. It is a figure which shows the shape when doing. In addition, although the recessed part 5a in FIG. 4 has the opening part 5b by laser processing etc., it is not limited to it in this invention.

  In FIG. 2, the first convex curved surface is in contact with the peripheral edge portion 1b of the opening 1a, and the first convex curved surface enters the opening 1a. Further, the second convex curved surface is in contact with the peripheral edge portion 5c of the opening 5b, and the second convex curved surface enters the concave portion 5a.

  Then, alignment between the vertex of the first convex curved surface that is inserted into the bay and the center of the opening 1a is performed, and alignment between the vertex of the second convex curved surface that is inserted into the bay and the center of the opening 5b is performed. Made.

  As a result, as shown in FIG. 4, the centers of the opening 1a, the lens 6 and the opening 5b all coincide, and the first optical transmission board 1, the lens 6 and the second optical transmission board are aligned. .

  In FIG. 4, the shape of the opening 1a is a circle (radius r).

  In FIG. 4, the shape of the opening 5b is a square (perpendicular from the center to the side), but other examples include a rectangle such as a rectangle and a rhombus, and a polygon such as a triangle and a pentagon.

  Even when a transparent resin capable of transmitting light is provided in the light transmission hole 3, the transparent resin is flexible, so that the convex curved surface of the lens 6 is connected to the opening of the light transmission hole. The same effect can be obtained.

  The lens 6 is formed between the first optical transmission board 1 and the second optical transmission board 2 through a mounting process of the first optical transmission board 1 and the second optical transmission board 2. Specifically, as shown in FIG. 1, as a mounting means, spherical conductive members (hereinafter referred to as a ball grid array (registered trademark) or BGA) arranged in a lattice pattern with respect to the second optical transmission board 2. By using self-alignment at the time of reflow, the first optical transmission board 1 and the second optical transmission board 2 are naturally aligned using the lens 6 as a reference. The lens 6 may be bonded to the first optical transmission board 1 before mounting or may be bonded to the second optical transmission board 2.

  Other mounting means include a pin grid array and the like, but BGA is particularly preferable because it is not necessary to perform mechanical alignment.

  Examples of the lens 6 include a spheroid lens 9 (see FIG. 5) or a cylindrical lens 10 (see FIG. 6) whose both end surfaces are convex curved surfaces, in addition to the spherical lens described above. In the latter two lenses, it is required to precisely align and fix the optical axis with respect to the light transmission hole 3, but the spherical lens does not depend on the position at the time of fixing and the optical axis does not depend on the position. Since it is formed, the effect of suppressing the scattering of light and the effect of positioning can be obtained repeatedly.

  The lens 6 is formed of various optical glasses, resins such as acrylic and epoxy.

The optical module in the present invention includes the optical transmission system of the present invention and the optical semiconductor element 7. As the optical semiconductor element 7, a light emitting element such as a surface emitting laser (VCSEL),
A surface light receiving type semiconductor light receiving element (PD: Photo Diode) or the like may be used.

  In the method of manufacturing an optical transmission system according to the present invention, first, a step of arranging the lens 6 between the first optical transmission substrate 1 and the second optical transmission substrate 2 (hereinafter, step 1) is performed, and then the lens 6 The step of mounting the first optical transmission board 1 on the second optical transmission board 2 (hereinafter, step 2) is performed on the basis of the outer shape.

  In step 1, the lens 6 may be positioned between the first light transmission board 1 and the second light transmission board 2, and may be bonded to the first light transmission board 1, for example. The second optical transmission board 2 may be adhered.

  In step 2, in the mounting step, the first optical transmission board 1 moves to a position where it fits with the outer shape of the lens 6 at the time of self-alignment. , And positioning can be performed uniquely.

  In FIG. 3, transmission of light in the optical module is performed as follows.

  When the optical semiconductor element 7 is a light emitting element such as a surface emitting laser (VCSEL), an optical signal emitted from the light emitting point is coupled to the light transmission hole 3 while spreading radially. Inside the light transmission hole 3, it propagates to the other end by the light condensing action or the light guiding action, exits radially from the end, and enters the lens 6. Then, the light is condensed in the optical axis direction on the first convex curved surface of the lens 6 and propagates inside the lens 6. Then, on the second convex curved surface, the optical signal is further condensed in the direction of the optical axis A, reflected by the optical path conversion unit 4 before reaching the condensing point, and the optical path is converted by approximately 90 degrees, and the optical waveguide 5 Reach the end of the.

FIG. 1 is a cross-sectional view schematically showing an example of an embodiment of an optical transmission system of the present invention. FIG. 2 is a partially enlarged sectional view of FIG. FIG. 3 is a partially enlarged sectional view of FIG. FIG. 4 is a top view of the particular configuration in FIG. FIG. 5 is a sectional view schematically showing an example of the embodiment of the optical transmission system of the present invention. FIG. 6 is a cross-sectional view schematically showing an example of the embodiment of the optical transmission system of the present invention. FIG. 7 is a cross-sectional view schematically showing an example of an embodiment of a conventional optical transmission system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 1st optical transmission board | substrate 1a The opening part 1b in the other main surface of the 1st optical transmission board | substrate 1 The peripheral part 2 of the opening part 1a, 12 2nd optical transmission board | substrate 3, 13 Optical transmission hole 4 Optical path conversion part 4a Optical path Ends 5 and 15 of conversion unit 4 Optical waveguide 5a Recessed part 5b of optical waveguide 5 Opening part 5c of recessed part 5a Peripheral part 6 of opening part 5b Spherical lens 7, 17 Optical semiconductor element 8 BGA
9 Rotating Ellipsoidal Lens 10 Cylindrical Lens with Both Ends Convex Curved 19 Solder Connection A Optical Axis B Optical Signal

Claims (7)

A first optical transmission board that penetrates between one main surface and the other main surface, and has optical transmission holes each having an opening on both main surfaces;
A second optical transmission board having the first optical transmission board mounted on one main surface, the optical waveguide disposed on the one main surface, and the optical transmission of the first optical transmission board A second optical transmission board comprising: an optical path conversion unit that converts an optical transmission direction between the hole and the optical waveguide;
A first convex curved surface aligned with an opening in the other main surface of the first optical transmission board; and a second convex curved surface aligned with the optical path changing portion, and the optical transmission hole. A lens optically coupled to the optical waveguide via the optical path changing unit,
An optical transmission system comprising:   2. The optical transmission system according to claim 1, wherein the first optical transmission board is mounted by a spherical conductive member arranged in a lattice pattern with respect to the second optical transmission board.   The optical transmission system according to claim 1, wherein the lens has a spherical shape.   The optical transmission system according to claim 1, wherein a transparent resin capable of transmitting light is provided in the optical transmission hole.   The optical transmission system according to claim 4, wherein the transparent resin includes a core portion having a refractive index higher than that of a peripheral portion in a radial direction of the optical transmission hole. An optical transmission system according to any one of claims 1 to 5,
An optical semiconductor element mounted on the one main surface of the first optical transmission board and optically coupled to the optical transmission hole;
An optical module comprising: A method for manufacturing an optical transmission system according to any one of claims 1 to 5,
Disposing the lens between the first optical transmission substrate and the second optical transmission substrate;
Mounting the first optical transmission board on the second optical transmission board based on the outer shape of the lens;
A method of manufacturing an optical transmission system including:

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