JP4770551B2 - Optical module - Google Patents

Description

  The present invention relates to an optical module used in optical communication.

  Conventionally, in order to perform optical communication, an optical module having a light emitting element and / or a light receiving element mounted on a substrate, an optical fiber, a receptacle for positioning and fixing the optical fiber, and the like as main components has been used ( For example, see Patent Documents 1 and 2).

  Patent Document 1 describes an optical module in which an optical semiconductor element and an optical fiber are optically coupled, fixed to a substrate, and sealed with a transparent resin material so as to cover the tip of the optical semiconductor element and the optical fiber. ing.

  Patent Document 2 discloses a light-emitting element that converts an electrical signal into an optical signal and transmits the optical signal to an optical fiber, and has a through-insertion hole at a position that is determined based on the mounting position of the light-emitting element. A lead frame, a protrusion that is fitted into the through-insertion hole and relatively fixes the position of the lead frame, and a sleeve that is fitted with the end of the optical fiber and relatively fixes the position of the optical fiber, and emits light A photoelectric transmission device is described that includes a receptacle for optically coupling an element and an optical fiber.

JP 2005-284015 A JP 2005-062842 A

  However, the optical module and the photoelectric transmission device described above have a problem that the optical semiconductor element cannot be sufficiently radiated because the optical semiconductor element such as the light emitting element and the light receiving element is directly sealed with resin.

  In the optical module described above, it is necessary to select a resin having a small refractive index as a resin for sealing the optical fiber and the optical semiconductor element. However, since such a resin is rare and very expensive, there is a problem that the cost of the entire optical module increases.

  Furthermore, the above-described optical module has a problem that the optical axes of the optical semiconductor element and the optical fiber shift due to the shrinkage of the resin accompanying the solidification of the sealing resin. That is, when the position of the tip of the optical fiber is shifted in a direction perpendicular to the optical axis, there arises a problem that the light amount from the optical semiconductor element or the light amount transmitted to the optical semiconductor element is reduced.

  In addition, if the position of the tip of the optical fiber is shifted in the optical axis direction, the lens is shifted from the focal position of the lens, which causes a problem that the amount of light from the optical semiconductor element or the amount of light transmitted to the optical semiconductor element is reduced. Such a problem becomes more prominent as the diameter of the core of the optical fiber becomes smaller.

  In this respect, in the photoelectric transmission device described above, the optical fiber is relatively positioned by the receptacle, the photoelectric transmission connector, and the ferrule with respect to the optical semiconductor element fixed to the substrate, and the optical semiconductor element and the optical fiber are positioned. It can be easily done.

  However, it is necessary to process parts such as a receptacle, a ferrule, and a photoelectric transmission connector with high accuracy, and there is a problem that the cost of each part is increased, and consequently, the cost of the photoelectric transmission device is increased.

  In addition, even if each part such as a receptacle, ferrule, and photoelectric connector is processed with high accuracy, each part has a processing error, so that when the photoelectric device is assembled, the processing error accumulates. is there. Therefore, there is a limit to positioning of the optical semiconductor element and the optical fiber. Considering the technical level of the processing technology for each component, it is considered that the technology is applied to an optical fiber having a core diameter of 50 μm or more. That is, there is a problem that it is difficult to apply to an optical fiber having a core diameter of 50 μm or less only by mechanical positioning.

Moreover, although the above-described photoelectric transmission device positions an optical fiber and an optical semiconductor element by a ferrule, the optical fiber here is a core of the optical fiber. This is because, unlike the core coating, the optical fiber core has high processing accuracy, so that the ferrule can be used for highly accurate positioning.
For this reason, there exists a problem that the apparatus which fixes separately so that the primary coating | coated (and secondary coating | coated) of an optical fiber may not move with respect to a photoelectric sending device occurs.

  Because, only the core at the tip of the optical fiber is fixed to the photoelectric transmission device, the primary coating (and secondary coating) of the optical fiber is not fixed, and the optical fiber is free, the fixed core portion is fixed. This is because the fracture occurs at the boundary between the core portions that are not formed.

  The present invention has been made to solve such problems, while simplifying and downsizing the optical connecting element between the optical semiconductor element and the optical fiber, which has conventionally been composed of a plurality of parts, and reducing costs, An object of the present invention is to provide an optical module that facilitates work associated with optical coupling.

The present invention provides an optical module comprising a substrate on which an optical semiconductor element is mounted and a receptacle attached on the substrate, wherein the substrate has a plurality of attachment holes, and the receptacle has a plurality of protrusions inserted into the attachment holes, A housing recess for housing the optical semiconductor element, an insertion hole having a distal end surface into which the distal end of the optical fiber is inserted, and light or an optical semiconductor emitted from the distal end of the optical fiber between the distal end surface and the housing recess The reflective surface that reflects the light emitted from the element is formed integrally with a transparent resin, and a clearance for positioning the receptacle is provided between the inner peripheral surface of the mounting hole and the outer peripheral surface of the protrusion. Thus, an adjustment function capable of finely adjusting the positions of the optical fiber and the optical semiconductor element is provided. The clearance for adjustment is preferably in the range of 0.1 mm to 0.3 mm.
The optical fiber includes a core and a coating provided on an outer periphery of the core, and the insertion hole is provided on the distal end surface side and has a diameter larger than the core and a diameter smaller than the coating. The small-diameter portion that is set and holds the core and the large-diameter portion that is provided on the side opposite to the tip surface and has a diameter larger than that of the coating and that holds the coating are connected to each other. A tip of the core held by the core abuts the tip surface, and a concave groove having a depth reaching the large-diameter portion constituting the insertion hole is formed in the large-diameter portion in plan view on the outer surface of the receptacle. It is formed so that it may overlap, and the above-mentioned covering of the above-mentioned optical fiber is fixed to the above-mentioned receptacle by filling the above-mentioned concave groove with an adhesive and solidifying it.

A plurality of pairs of optical semiconductor elements and optical fibers may be provided. That is, a plurality of optical semiconductor elements may be mounted on the substrate, and the receptacle may be provided with insertion holes for inserting the same number of optical fibers as the number of optical semiconductor elements.
In this case, in order to eliminate the influence of the stray light coming from the pair of the adjacent optical semiconductor element and the optical fiber, there is one optical path from the distal end surface of the insertion hole to the accommodating recess in which the optical semiconductor element is accommodated, It is desirable to provide a groove between other adjacent optical paths and to isolate both optical paths by the groove.
Further, this isolation may be performed by providing a member that reflects or absorbs light between both optical paths.

  In addition, a convex lens may be provided on the optical axis of the optical semiconductor element in the receiving recess of the receptacle that stores the optical semiconductor element.

Further, the reflecting surface provided on the receptacle may be mirror-coated, or the reflecting surface may be a condensing mirror.
Further, a control element for controlling the operation of the optical semiconductor element may be mounted on the substrate.

  The insertion hole in the receptacle may be formed by connecting a plurality of holes having different diameters, and the optical fiber may be inserted into the insertion hole with the primary coating attached. Further, the insertion hole may be formed by connecting a plurality of holes having different diameters, and the optical fiber may be inserted into the insertion hole with the secondary coating and the primary coating attached.

  According to the present invention, it is possible to provide an optical module that facilitates the work associated with optical connection while simplifying and downsizing the optical connection component between the optical semiconductor element and the optical fiber to reduce the cost.

  Hereinafter, the present invention will be described in detail using examples.

A first embodiment according to the present invention will be described with reference to FIGS.
1 and 2 are side sectional views of an optical module according to the present invention.

  As shown in FIG. 1, an optical module 1 includes an optical semiconductor element 2 such as a light receiving element that receives light and converts it into an electric signal and / or a light emitting element that emits light according to the electric signal, and the optical semiconductor element. 2 and a receptacle 4 fixed to the substrate 3.

  The receptacle 4 is inserted into an accommodating recess 5 for accommodating the optical semiconductor element 2, an insertion hole 7 for inserting the optical fiber 6, and an attachment hole 31 provided in the substrate 3, so as to fix the receptacle 4 to the substrate 3. The projection 8 and the reflecting surface 9 are integrally formed using a transparent resin (for example, acrylic resin, polycarbonate resin, etc.).

  The insertion hole 7 formed in the receptacle 6 is set to have a large diameter portion set to a diameter slightly larger than the diameter of the primary coating 62 of the optical fiber 6 and a diameter slightly larger than the core 61 of the optical fiber 6. The small-diameter portion is formed to be connected.

  Since the insertion hole 7 has the distal end surface 71, the optical fiber 6 is inserted into the insertion hole 7 with the primary coating 62 attached, and the distal end of the core 61 is abutted against the distal end surface 71. The optical fiber 6 can be easily positioned in the optical axis direction.

  If the optical fiber 6 is inserted into the insertion hole 7 with the primary coating with poor surface accuracy attached, and then the receptacle 4 and the optical fiber 6 are fixed by the adhesive 10, the optical fiber 6 is firmly attached to the receptacle 4. Fixed.

  That is, the receptacle 4 has a function of fixing not only the core 61 of the optical fiber 6 but also the optical fiber 6 itself. For this reason, since the instrument which fixes the optical fiber 6 is unnecessary, the cost required for positioning of the optical fiber 6 can be reduced. However, the present invention does not directly fix the core 61 of the optical fiber 6 to the component as in the prior art described above, and there is a gap between the inner peripheral surface of the insertion hole 7 and the outer peripheral surface of the core 61. Therefore, the position of the core 61 varies.

  For this reason, as shown in FIG. 1, the clearance between the mounting hole 31 of the substrate 3 and the protrusion 8 formed on the receptacle 4 is set to 0.1 to 0.3 mm, and adjustment work is performed using this clearance. There is a need to do.

  In this embodiment, since the clearance is set to 0.2 mm, the receptacle 4 can be adjusted with respect to the substrate 3 by ± 0.1 mm. Then, the variation in the relative position between the outer peripheral surface of the core 61 of the optical fiber 6 and the inner peripheral surface of the insertion hole 7 can be sufficiently absorbed.

  When the optical semiconductor element 2 is a light receiving element, the operation of adjusting the position of the receptacle 4 is performed by connecting a light emitting device to a rear end (not shown) of the optical fiber 6 and passing the optical fiber 6 from the light emitting device to the light receiving element. A general method of searching the position where the light quantity of the transmitted light is maximum by moving the receptacle 4 while observing a light quantity monitor (not shown) connected to the light receiving element 2 can be employed.

  In the case where the optical semiconductor element 2 is a light emitting element, a light receiving device is connected to the rear end (not shown) of the optical fiber 6, and the position where the amount of light transmitted from the light emitting element through the optical fiber 6 is maximized. The general method of moving the receptacle 4 while observing the light amount monitor connected to the light receiving device can be employed.

As a result of such adjustment work, as soon as a position where the light quantity becomes maximum is found, the receptacle 4 can be firmly fixed to the substrate 2 by heating and melting the protrusion 8 as shown in FIG.
Thus, in the present invention, after the optical fiber 6 is fixed to the receptacle 4, the receptacle 4 is moved to adjust the positioning with the optical semiconductor element 2 mounted on the substrate 2. Even an optical fiber having a core 61 with a diameter of 50 μm or less, specifically a core with a diameter of 10 μm, can be used as an optical module.

Another embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 3 is a perspective view of the optical module, and FIG. 4 is a plan view of the optical module.
In addition, about the part same as the optical module concerning 1st Example, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The optical module according to the second embodiment differs from the first embodiment in that a light receiving element 22 and a light emitting element 21 are provided as the optical semiconductor element 2 and the tip of one optical fiber 6 (insertion hole 7). Between the receptacle portion in the optical path (light path) from the distal end surface 71 of the optical fiber 6 to the light receiving element 22 and the receptacle portion in the optical path from the distal end of the other optical fiber 6 (tip surface 71 of the insertion hole 7) to the light emitting element 21. In addition, a point where the groove 11 is provided, a point where not only the primary coating 62 of the optical fiber but also the secondary coating is inserted into the insertion hole 7 of the receptacle, and a concave groove extending from the top surface of the receptacle to the insertion hole 7 are formed on the top surface of the receptacle. It is a point provided in.

  As shown in FIG. 3, a light receiving element 21 and a light emitting element 22 as optical semiconductor elements 2 are mounted on the substrate 3 of the optical module 1, and these are disconnected from the outside by an accommodation recess 5 formed in the receptacle 4. Has been.

  The receptacle 4 has a small diameter portion 72 into which the core 61 of the optical fiber 6 is inserted, a medium diameter portion 73 into which the primary coating 62 of the optical fiber 6 is inserted, and a large diameter portion into which the secondary coating 63 of the optical fiber 6 is inserted. An insertion hole 7 formed by connecting 74 is provided.

  In the receptacle 4, a groove 11 is formed between the optical path from the tip of the core 61 of the optical fiber 6 to the light emitting element 21 and the optical path from the tip of the core 61 of the other optical fiber 6 to the light receiving element 22. ing. That is, the groove 11 is provided in a portion of the receptacle approximately in the middle of the two optical paths from the distal end surface 71 of the insertion hole 7 to the accommodating recess 5 in which the optical semiconductor element 2 is accommodated. Since the receiving recess 5 has a function of disconnecting the optical semiconductor element 2 from the outside, the groove 11 is formed with a depth up to just before reaching the receiving recess.

  In this embodiment, the groove 11 has two optical semiconductor elements 2 and the receptacle 4 is formed of a transparent resin. Therefore, stray light generated in one optical path enters the other optical path, and the other optical path. This is provided in order to prevent the optical signal from being adversely affected.

  That is, a part of the light emitted from the light emitting element 21 enters the light receiving element 22 as stray light, or a part of the light transmitted to the light receiving element 22 enters the light emitted from the light emitting element 21 as stray light. Although there is a possibility, by providing the groove 11 between the two optical paths, a space having a refractive index different from that of the resin constituting the receptacle can be formed, so that the entry of stray light can be effectively prevented.

Further, the receptacle 4 is further provided with a concave groove 19 from the upper surface.
The concave groove 19 is formed by inserting the two optical fibers 6 into the insertion hole 7 of the receptacle 4 and abutting the core 61 against the bottom 71 of the insertion hole 7 and then filling the concave groove 19 with an adhesive (not shown). The optical fiber 6 is firmly fixed to the receptacle 4.

As shown in FIG. 4, the concave groove 19 is formed to a depth reaching the insertion hole 73 for inserting the primary coating 62 of the optical fiber 6 and the insertion hole 74 for inserting the secondary coating 63. Then, the UV adhesive is poured into the concave groove 19 and the UV adhesive is cured by applying ultraviolet rays to the UV adhesive, thereby firmly fixing the primary coating and the secondary coating of the optical fiber 6 to the receptacle 4 in a short time. can do.

The optical fiber 6 shown in the present embodiment is a glasses-type two-core optical fiber, and the cost of the optical module 1 can be reduced in that such a multi-core optical fiber 6 can be directly fixed to the receptacle 4. Can do.
Note that the method for adjusting the amount of received light and the amount of emitted light in the two optical semiconductor elements 2 is the same as that described in the first embodiment, and a description thereof will be omitted.

Another embodiment of the present invention will be described in detail with reference to FIG.
FIG. 5 is a side sectional view of the optical module.
The same parts as those of the optical module according to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The difference of the optical module according to this embodiment from the first embodiment is that the reflecting surface 9 of the receptacle 4 is mirror-coated and the concave portion 5 on the optical axis of the optical semiconductor element 2 is provided with a lens 12. The only point is that they are integrally molded and the point that the UV adhesive 20 is used when fixing the protrusions 8 to the substrate 3.

  The reflection surface 9 of the receptacle 4 reflects most of the light transmitted from the optical fiber 6 and reaches the optical semiconductor element 2 due to the difference in refractive index between the resin constituting the receptacle 4 and air. Further, most of the light emitted from the optical semiconductor element 2 is reflected and enters the optical fiber 6.

  However, as shown in the present embodiment, the light reflectance can be increased by applying the mirror coating 13 to the surface of the reflecting surface 9.

  Then, the convex lens 12 is integrally formed on the optical axis of the optical semiconductor element 2 in the housing recess 5 of the receptacle 4, thereby condensing the light transmitted from the optical fiber 6 on the light receiving point of the optical semiconductor element 2. be able to. Conversely, the light emitted from the optical semiconductor element 2 can be condensed or collimated to enter the optical fiber 6.

  This convex lens does not have to be integrally molded, and may be a separate part. In this case, the convex lens may be fixed to the upper surface of the housing recess 5 with an adhesive or the like.

Another embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a side sectional view of the optical module.
In addition, about the part same as the optical module concerning 1st Example, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The only difference from the first embodiment of the optical module according to this embodiment is that the reflecting surface 9 of the receptacle 4 is provided with a mirror coating 14 serving as a condenser mirror.

That is, a convex portion is provided in the optical path on the reflecting surface 9, and the mirror coating 14 is applied to the surface of the convex portion.
With this configuration, the same effect as in the third embodiment can be obtained.

Another embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7 is a side sectional view of the optical module.
In addition, about the part same as the optical module concerning 1st Example, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The difference of the optical module according to this embodiment from the first embodiment is only that the primary coating 62 of the optical fiber 6 is extended to the vicinity of the tip of the core 61.

  With this configuration, the processing of the insertion hole 7 can be facilitated, and stray light can hardly enter the core 61.

Another embodiment of the present invention will be described in detail with reference to FIG.
FIG. 8 is a schematic view of a device 18 using the optical module according to the present invention.
In addition, about the part same as the optical module 1 concerning 1st Example, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The main difference of the optical module 1 according to this embodiment from the first embodiment is that a substrate 3 is mounted with a control element 15 of a light receiving element as an optical semiconductor element 2 and a control element 17 of a light emitting element. It is only a point surrounded by the body 16. For ease of explanation, only the outline of the housing 16 is shown.

  As shown in FIG. 8, in the optical module 1 according to the present embodiment, the substrate 3 protrudes in the direction opposite to the optical fiber 6, and the control elements 15 and 17 of the optical semiconductor element 2 are mounted on the protruding portion. ing.

  Here, the control elements 15 and 17 are in a chip state, and are electrically connected to the wiring of the substrate 3 by wire bonding after being fixed to the substrate 3 with an adhesive or the like.

Thus, by using the optical module 1 according to the present invention, the entire device 18 used for optical communication can be reduced in size.
In the present embodiment, the width and height of the housing 15 can be set to 6 mm.

  Therefore, the present invention can be used as a small optical communication module by mounting other functional components on the substrate 3.

Another embodiment of the present invention will be described in detail with reference to FIG.
FIG. 10 is a perspective view of an optical module according to the present invention.
In addition, about the part same as the optical module 1 concerning 2nd Example, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The main difference of the optical module 1 according to this embodiment from the second embodiment is that a member that absorbs light or a member that reflects light is provided at the position of the groove 11 in FIG. 3, as shown in FIG. It is a point.

  Specifically, the member may be a metal plate that has been subjected to surface treatment, an opaque plate such as a black resin, or an antireflection flocking treatment plate. Such an opaque plate or the like may be inserted in advance when the receptacle 4 is integrally formed of a transparent resin, or may be press-fitted into the groove 11 after forming the groove 11 in FIG. Further, the opaque plate or the like may have a high light absorption rate, or conversely, may not absorb light and reflect light.

  Further, opaque resin may be filled and molded by the two-color molding method at the position of the groove 11 in FIG. 3 (between the optical paths). As the opaque resin, a black resin having a high light absorption rate is desirable.

  The above-described embodiments are merely illustrative and are not intended to limit the present invention. The present invention can be recognized by those skilled in the art from the claims, the detailed description of the invention, and the drawings. Modifications and additions can be made without departing from the technical idea of the invention.

  For example, in the above-described embodiments, one or two optical semiconductor elements 2 are shown, but three or more optical fibers 6 may be used. In this case, since there are three or more optical paths, in the second embodiment, two or more grooves 11 are provided in the receptacle 4.

  Moreover, the fixing of the receptacle 4 to the substrate 3 is not limited to the dissolution, deformation, and UV adhesive of the protrusions 8, and may be fixed by screws.

  Further, the groove 11 in FIG. 3 may be black-plated with a high light absorption rate. When the surface treatment of the reflective surface 9 is performed, the groove 11 is also made of the same material (for example, reflective plating). Surface treatment may be performed at the same time. Examples of thin film coatings for increasing the reflectivity include vapor deposition, sputtering, and CVD.

  In addition, as shown in FIG. 9, the present invention has a diameter of about 6 mm by mounting components other than the components described in the sixth embodiment, for example, the camera 23, the camera control component 24, and the like on the substrate 3. It can be applied to small in-vehicle cameras, security cameras, endoscopes and the like.

  The present invention is applied to an optical module used for optical communication.

(Example 1) which is side sectional drawing of the optical module which concerns on this invention. (Example 1) which is side sectional drawing of the optical module which concerns on this invention. (Example 2) which is a perspective view of the optical module which concerns on this invention (Example 2) which is a top view of the optical module which concerns on this invention (Example 3) which is side sectional drawing of the optical module which concerns on this invention. (Example 4) which is side sectional drawing of the optical module which concerns on this invention. (Example 5) which is side sectional drawing of the optical module which concerns on this invention. (Example 6) which is a schematic diagram of the optical module which concerns on this invention. It is a schematic diagram of the optical module which concerns on this invention. (Example 7) which is a perspective view of the optical module which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical module 2 Optical semiconductor element 3 Board | substrate 4 Receptacle 5 Recessed part 6 Optical fiber 7 Insertion hole 8 Protrusion 9 Reflecting surface 31 Mounting hole 71 Bottom

Claims (8)

A substrate on which an optical semiconductor element is mounted;
In an optical module comprising a receptacle attached on the substrate,
The substrate is formed with a plurality of mounting holes,
The receptacle includes a plurality of protrusions that are inserted into the mounting holes,
A housing recess for housing the optical semiconductor element;
Inserting an optical fiber, an insertion hole having a tip surface with which the tip of the optical fiber abuts,
A reflection surface that reflects light emitted from the tip of the optical fiber or light emitted from the optical semiconductor element between the tip surface and the housing recess is integrally formed of a transparent resin,
A clearance for positioning adjustment of the receptacle is provided between the inner peripheral surface of the mounting hole and the outer peripheral surface of the protrusion,
The optical fiber has a core and a coating provided on an outer periphery of the core,
The insertion hole has a small diameter portion for holding the core is set smaller in diameter than and the covering larger in diameter than said core is provided on the front-end surface side, from the coating provided on the opposite side to the front end face The diameter is also set to be large and the large-diameter portion that holds the coating is connected to each other .
Tip of the core held in the small diameter portion is in contact with the tip surface,
A concave groove having a depth reaching the large diameter portion of the insertion hole is formed on the outer surface of the receptacle so as to overlap the large diameter portion in plan view.
The optical module is characterized in that the coating of the optical fiber is fixed to the receptacle by filling the concave groove with an adhesive and solidifying . A plurality of the optical semiconductor elements are mounted on the substrate,
The receptacle is provided with the same number of insertion holes as the optical semiconductor element,
2. The light according to claim 1, wherein a groove or a member that reflects or absorbs light is provided between one optical path from the distal end surface of the insertion hole to the housing recess and another optical path adjacent to the optical path. module.   The optical module according to claim 1, wherein a convex lens is attached on the optical axis of the optical semiconductor element in the housing recess.   The optical module according to claim 1, wherein the reflective surface is mirror-coated.   The optical module according to claim 4, wherein the reflecting surface is a condensing mirror.   A plurality of the insertion holes are formed side by side,
  The concave groove is formed across the large diameter portion of the plurality of insertion holes,
  The optical module according to claim 1.   The coating has a primary coating provided on the outer periphery of the core, and a secondary coating provided on the outer periphery of the primary coating,
  The large-diameter portion constituting the insertion hole is formed on the small-diameter portion side, on a first large-diameter portion on which the primary coating is inserted and held, and on the opposite side of the first large-diameter portion to the small-diameter portion side. The second large diameter portion that is formed and inserted and held by the secondary coating is connected,
  The concave groove is formed across the first large diameter portion and the second large diameter portion,
  The optical module of any one of Claims 1-6.   The end portion on the small diameter portion side of the first large diameter portion that holds the primary coating is formed with a tapered taper toward the small diameter portion side.
  The optical module according to claim 7.

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