Abstract:
An optically coupled device and an optical module including the optically coupled device are provided that can appropriately and efficiently perform position measurement of an optical surface, and allow a product having superior overall efficiency to be stably manufactured at a low cost. 
     An optically coupled device main body  15  is formed having a shape that allows both first lens surface  5  and second lens surface  8  to be viewed simultaneously from a surface normal direction of at least one of a first surface portion  2   a  and a second surface portion  3   a.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optically coupled device and an optical module including the optically coupled device. In particular, the present invention relates to an optically coupled device and an optical module including the optically coupled device suitable for optically coupling a photoelectric conversion device and a multi-mode optical fiber. 
     2. Description of the Related Art 
     In recent years, with increasing speed and capacity of data communication, the need is further rising for an optical fiber communication technology using an optical fiber. 
     An optical fiber communication technology such as this uses an optically coupled device to which an optical fiber and a photoelectric conversion device (such as a semiconductor laser or a photodetector) are attached. In many optically coupled devices, a surface facing a photoelectric conversion element (light-emitting unit or light-receiving unit) of the photoelectric conversion device and a surface facing an end surface of the optical fiber are formed into lens surfaces. 
     In this type of optically coupled device, for example, light emitted from a semiconductor laser is coupled to the end surface of the optical fiber using transmittance and refraction of light by the lens surfaces. 
     Among optically coupled devices, some include a lens array structure in which a plurality of lens surfaces are arranged to correspond to a plurality of optical fibers (multi-core optical fiber and the like) 
       FIG. 8  is a front view of an example of a conventional optically coupled device  1  having a lens array structure such as this.  FIG. 9  is a planar view of  FIG. 8 .  FIG. 10  is a right side view of  FIG. 8 . 
     In the optically coupled device  1  in  FIG. 8 , a photoelectric conversion device can be attached from the front to a front end surface (front end surface in  FIG. 8 )  2 . A plurality of optical fibers can be attached from above to a front end surface  3 . A plurality of photoelectric conversion elements that emit or receive light are formed in an array along a lateral direction in  FIG. 8 . The optical fibers are arrayed in the lateral direction in  FIG. 8 . A substrate-mounted photoelectric conversion device functioning as at least one of a vertical cavity surface emitting laser (VCSEL) and a photodetector, for example, is attached as the photoelectric conversion device. The plurality of optical fibers are housed within a connector and attached with the connector. 
     As shown in  FIG. 8 , on the front end surface  2  of the optically coupled device  1 , a plurality of first lens surfaces  5  are formed on a surface portion  2   a  in an array, such as to be adjacent to one another along the lateral direction. The first lens surfaces  5  are convex towards the front (the front side in  FIG. 8 ). The surface portion  2   a  is formed in a center portion and has a planar, roughly rectangular shape that is long in the lateral direction. The first lens surfaces  5  can form optical paths connecting each photoelectric conversion element of the photoelectric conversion device and each end surface of the optical fibers. 
     As shown in  FIG. 8 , on the front end surface  2  of the optically coupled device, an outer side surface portion  2   b  of the surface portion  2   a  on which the first lens surfaces  5  are formed is formed parallel to the surface portion  2   a  and higher towards the photoelectric conversion device side (front) in a surface normal direction of the surface portion  2   a  in relation to the surface portion  2   a . When the photoelectric conversion device is attached to the optically coupled device  1 , a semiconductor substrate of the photoelectric conversion device comes into contact with the outer side surface portion  2   b.    
     Moreover, as shown in  FIG. 8 , a pair of circular positioning holes  7  is formed on positions near both outer sides of the surface portion  2   a  on which the first lens surfaces  5  are formed, in a direction in which the first lens surfaces  5  are arrayed. The positioning holes  7  are used for positioning the photoelectric conversion device when the photoelectric conversion device is attached to the optically coupled device  1 . Specifically, when the photoelectric conversion device is attached, a pair of positioning pins (not shown) passing through the substrate of the photoelectric conversion device respectively engage with each positioning hole  7 , thereby positioning the photoelectric conversion device. 
     On the other hand, as shown in  FIG. 9 , on a top end surface  3  of the optically coupled device  1 , a plurality of second lens surfaces  8  are formed on a surface portion  3   a  in an array, such as to be adjacent to one another along the lateral direction. The second lens surfaces  8  are convex towards the front side in  FIG. 9  (upward in  FIG. 8 ). The surface portion  3   a  is formed in a center portion and has a planar, roughly rectangular shape that is long in the lateral direction. Each second lens surface  8  forms a pair with a first lens surface  5 . With the first lens surfaces  5 , the second lens surfaces  8  can form optical paths connecting each of the photoelectric conversion elements of the photoelectric conversion device and each end surface of the optical fibers. A distance between center points of the second lens surfaces  8  that are adjacent to each other is formed to match a distance between the center points of the first lens surfaces  5  that are adjacent to each other. 
     As shown in  FIG. 9 , on the upper end surface  3  of the optically coupled device, an outer side surface portion  3   b  of the surface portion  3   a  on which the second lens surfaces  8  are formed is formed parallel to the surface portion  3   a  and higher towards the optical fiber side (front side in  FIG. 9  and upwards in  FIG. 8 ) in a surface normal direction of the surface portion  3   a  in relation to the surface portion  3   a . When the optical fibers are attached to the optically coupled device  1 , the connector of the optical fibers comes into contact with the outer side surface portion  3   b.    
     Moreover, as shown in  FIG. 9 , a pair of columnar positioning pins  10  is formed on positions near both outer sides of the surface portion  3   a  on which the second lens surfaces  8  are formed, in a direction in which the second lens surfaces  8  are arrayed. The positioning pins  10  are used for positioning the optical fibers when the optical fibers are attached to the optically coupled device  1 . Specifically, when the optical fibers are attached, the positioning pins  10  engage with a pair of positioning holes (not shown) formed on the connector of the optical fibers, thereby positioning the optical fibers. 
     As shown in  FIG. 10 , a reflection surface  12  is formed on a rear end surface  11  of the optically coupled device  1  in a recessing manner. The reflection surface  12  is at an angle of about 45° to both an optical axis OA 1  of the first lens surfaces  5  and an optical axis OA 2  of the second lens surfaces  8 . The reflection surface  12  can switch between an optical path of light traveling on the optical axis OA 1  of the first lens surfaces  5  and an optical path of light traveling on the optical axis OA 2  of the second lens surfaces  8 , through reflection of the light. Therefore, the reflection surface  12 , with the plurality of first lens surfaces  5  and the plurality of second lens surfaces  8 , can form optical paths connecting each of the plurality of photoelectric conversion elements of the photoelectric conversion device and each end surface of the plurality of optical fibers. 
     In an optically coupled device  1  such as this, the optical fibers can be pulled out in parallel with the semiconductor substrate of the photoelectric conversion device. Therefore, the optically coupled device  1  has an advantage of requiring less physical space. 
     In an optically coupled device  1  such as this, to allow the first lens surfaces  5  and the second lens surfaces  8  to form a desired optical path, it is important that each lens surface  5  and  8  is formed with significant precision at a targeted position. 
     However, depending on manufacturing conditions, such as dimensional accuracy of a mold used to form the optically coupled device, positional accuracy of each lens surface  5  and  8  may not be sufficiently achieved, initially. 
     Therefore, conventionally, when the optically coupled device  1  is manufactured, at a product inspection stage, the position of each lens surface  5  and  8  in a product is measured. Based on measurement results, manufacturing conditions, such as adjustment of the mold, are adjusted accordingly, thereby ensuring the positional accuracy of the lens surfaces  5  and  8 . 
     In a positional measurement of the lens surfaces, such as this, aiming to ensure the positioning accuracy of the lens surfaces, various measurement methods can be considered, such as a contact-type measurement method in which the lens surfaces are stroked by a probe, and a non-contact-type optical measurement method in using a tool microscope and an image measurement device. However, in terms of performing the positional measurement without damaging the lens surfaces that have small dimensions, the optical measurement method is preferred. 
     An example of an optical lens surface position measurement method is as follows. First, as shown in  FIG. 11A , the optically coupled device  1  is set on the tool microscope in a state allowing the planar shape of the first lens surfaces  5  to be visible. At this time, the second lens surfaces  8  are not visible. 
     Then, after an outline of the upper end surface  3  extending in the lateral direction in  FIG. 11A  is recognized, two points, P 1  and P 2 , that are separated from each other are taken on the outline. A line connecting the two points P 1  and P 2  is assumed. The line is defined as a Y axis of an XY coordinate system (two-dimensional Cartesian coordinate system). 
     Next, respective center lines L 1  and L 2 of the two positioning pins  10  are determined. A line at an equal distance from the two center lines L 1  and L 2  and parallel to both center lines L 1  and L 2  is determined. The line is defined as an X axis of the XY coordinate system. 
     Then, after an intersection between the X axis and the Y axis is determined to be a point of origin (0,0) in the XY coordinate system, the position measurement of the first lens surfaces  5  is performed by the X coordinate and the Y coordinate of a center point of each first lens surface  5  being determined. 
     Next, as shown in  FIG. 11B , the optically coupled device  1  is set on the tool microscope in a state allowing the planar shape of the second lens surfaces  8  to be visible. At this time, the first lens surfaces  5  are not visible. 
     Then, after an outline of a portion (lower side edge in  FIG. 11B ) of the upper end surface  3  extending in the lateral direction in  FIG. 11B  is recognized, two points, P 1 ′ and P 2 ′, that are separated from each other are taken on the outline. A line connecting the two points P 1 ′ and P 2 ′ is assumed. The line is defined as a Y axis of an XY coordinate system. 
     Next, respective center points S 1  and S 2  of the two positioning pins  10  are determined. Center lines L 1 ′ and L 2 ′ passing through the two center points S 1  and S 2  and perpendicular to the Y axis are determined. A line at an equal distance from the two center lines L 1 ′ and L 2 ′ and parallel to both center lines L 1 ′ and L 2 ′ is determined. The line is defined as an X axis of the XY coordinate system. 
     Then, after an intersection between the X axis and the Y axis is determined to be a point of origin (0,0) in the XY coordinate system, the position measurement of the second lens surfaces  8  is performed by the X coordinate and the Y coordinate of a center point of each second lens surface  8  being determined. 
     In this way, conventionally, the position measurement of the lens surfaces  5  and  8  using the tool microscope is performed by an XY coordinate system being defined, with a predetermined area (such as the positioning pins  10 ) of the optically coupled device  1  as a reference. 
     Patent Literature 1: Japanese Patent Laid-open Publication No. 2005-31556 
     In the above-described optically coupled device  1 , to allow an arbitrary first lens surface  5  and a corresponding second lens surface  8  to appropriately form an optical path, the Y coordinates of the center points of both lens surfaces  5  and  8  are required to match. 
     On the other hand, conventionally, during position measurement of the first lens surface  5 , the XY coordinate system is defined based on a side surface shape of the positioning pins  10 . During position measurement of the second lens surface  8 , the XY coordinate system is defined based on a planar shape of the positioning pins  10 . Therefore, even when the same positioning pins  10  serve as the reference for the XY coordinate system, depending on the dimensional accuracy of the positioning pins  10 , high-precision position measurement of ht lens surfaces  5  and  8  is impeded. 
     In other words, when the positioning pins  10  are formed having an accurate columnar shape, the center lines L 1  and L 2  of the side surface shape of the positioning pins  10  shown in  FIG. 11A  passes through the center points S 1  and S 2  of the planar shape of the positioning pins  10  shown in  FIG. 11B . In this case, shifting in the Y-axis direction does not occur between the center lines L 1  and L 2  in  FIG. 11A  and the lines L 1 ′ and L 2 ′ passing through the center points S 1  and S 2  in  FIG. 11B . The Y coordinate of the point of origin in the XY coordinate system defined in  FIG. 11A  and the Y coordinate of the point of origin in the XY coordinate system defined in  FIG. 11B  match. In this case, when the Y coordinate of an arbitrary first lens surface  5  measured using the XY coordinate system defined in  FIG. 11A  matches the Y coordinate of the second lens surface  8  corresponding to the arbitrary first lens surface  5  measured using the XY coordinate system defined in  FIG. 11B , the positions of both lens surfaces  5  and  8  can be judged to be appropriate. 
     However, when the positioning pins  10  are not formed having an accurate columnar shape, the center lines L 1  and L 2  in  FIG. 11A  do not pass through the center points S 1  and S 2  in  FIG. 11B . In this case, misalignment in the Y-axis direction occurs between the center lines L 1  and L 2  in  FIG. 11A  and the lines L 1 ′ and L 2 ′ passing through the center points S 1  and S 2  in  FIG. 11B . The Y coordinate of the point of origin in the XY coordinate system defined in  FIG. 11A  and the Y coordinate of the point of origin in the XY coordinate system defined in  FIG. 11B  do not match. In this case, when the positions of both lens surfaces  5  and  8  are judged to be appropriate because the Y coordinate of an arbitrary first lens surface  5  measured using the XY coordinate system defined in  FIG. 11A  matches the Y coordinate of the second lens surface  8  corresponding to the arbitrary first lens surface  5  measured using the XY coordinate system defined in  FIG. 11B , an erroneous judgment is made. 
     Moreover, conventionally, the XY coordinate system used for the position measurement of the first lens surfaces  5  and the XY coordinate system used for the position measurement of the second lens surfaces  8  are required to be separately defined by a same procedure. Therefore, the position measurement of the lens surfaces cannot be efficiently performed. 
     In other words, conventionally, a problem occurs in that an appropriate and efficient position measurement of the lens surfaces is difficult to perform. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention has been achieved in light of the above-described issues. An object of the present invention is to provide an optically coupled device and an optical module including the optically coupled device that can appropriately and efficiently perform position measurement of an optical surface, and allow a product having superior overall efficiency to be stably manufactured at a low cost. 
     In order to achieve the aforementioned object, an optically coupled device according to a first aspect of the present invention is an optically coupled device to which a photoelectric conversion device and a multi-mode optical fiber can be attached. A photoelectric conversion element that emits or receives light is formed on the photoelectric conversion device. The optically coupled device can optically couple the photoelectric conversion element and an end surface of the optical fiber. The optically coupled device includes a first lens surface formed on a first surface portion of an end surface on the photoelectric conversion device side of an optically coupled device main body. The first surface portion faces the,photoelectric conversion element when the photoelectric conversion device is attached. The first lens surface forms an optical path connecting the photoelectric conversion element and an end surface of the optical fiber. The optically coupled device also includes a second lens surface formed on a second surface portion of an end surface on the optical fiber side of an optically coupled device main body. The second surface portion faces the end surface of the optical fiber when the optical fiber is attached. The second lens surface forms an optical path connecting the photoelectric conversion element and the end surface of the optical fiber. In the optically coupled device, the optically coupled device main body is formed having a shape in which the end surface on the photoelectric conversion device side and the end surface on the optical fiber side are adjacent to each other, and the first surface portion and the second surface portion are perpendicular to each other. Moreover, the optically coupled device main body is formed having a shape allowing both the first lens surface and the second lens surface to be viewed simultaneously from a surface normal direction of at least one of the first surface portion and the second surface portion. 
     In the first aspect of the present invention, the optically coupled device main body is formed having a shape allowing both the first lens surface and the second lens surface to be viewed simultaneously from the surface normal direction of at least one of the first surface portion and the second surface portion. Therefore, when position measurement of one lens surface is performed, a two-dimensional coordinate system used for the position measurement of the lens surface can be directly used to measure a coordinate of a predetermined coordinate axis component of the other lens surface. Therefore, a relative positional relationship between one lens surface and the other lens surface can be accurately grasped at the same time using a common two-dimensional coordinate system. As a result, lens surface position measurement can be appropriately and efficiently performed. 
     An optically coupled device according to a second aspect is the optically coupled device according to the first aspect in which the optically coupled device is formed such that a device on which a plurality of photoelectric conversion elements are formed in an array can be attached as the photoelectric conversion device. The optically coupled device is formed such that a plurality of optical fibers can be attached to correspond to the plurality of photoelectric conversion elements. A plurality of first lens surfaces and a plurality of second lens surfaces are respectively formed in an array to correspond to the plurality of photoelectric conversion elements and the plurality of optical fibers. An array direction of the plurality of first lens surfaces and an array direction of the plurality of second lens surfaces are formed parallel to each other. 
     In the second aspect of the invention, a positional relationship of lens surface array directions of the plurality of first lens surfaces and the plurality of second lens surfaces respectively corresponding to the first lens surfaces can be grasped using the common two-dimensional coordinate system. Therefore, position measurement of the plurality of first lens surfaces and the plurality of second lens surfaces can be appropriately and efficiently performed. 
     An optically coupled device according to a third aspect is the optically coupled device according to the first aspect in which the end surface on the optical fiber side of the optically coupled device main body includes a third surface portion formed at a peripheral position of the second surface portion. The third surface portion is formed such as to be higher towards the optical fiber side in the surface normal direction of the second surface portion in relation to the second surface portion. The end surface on the optical fiber side of the optically coupled device main body also includes a fourth surface portion formed in a position adjacent to both the second surface portion and the end surface on the photoelectric conversion device side of the optically coupled device main body. The fourth surface portion is formed such as to have a same planar shape as the second surface portion or such as to be lower towards a side heading away from the optical fiber in the surface normal direction of the second surface portion in relation to the second surface portion. The optically coupled device is formed such that the fourth surface portion allows the second lens surface to be viewed simultaneously with the first lens surface from the surface normal direction of the first surface portion. 
     In the third aspect of the invention, the second lens surface can be viewed simultaneously with the first lens surface from the surface normal direction of the first surface portion through use of a simple shape. Therefore, cost is further reduced. 
     An optically coupled device according to a fourth aspect is the optically coupled device according to the third aspect in which at least one portion of the third surface portion is formed to allow contact with a connector of the optical fiber when the optical fiber is attached. 
     In the fourth aspect of the invention, the third surface portion allows a focal distance to be appropriately secured between the end surface of the optical fiber and the second lens surface, thereby maintaining favorable overall efficiency. 
     An optically coupled device according to a fifth aspect is the optically coupled device according to the first aspect in which the end surface on the photoelectric conversion device side of the optically coupled device main body includes a fifth surface portion formed at a peripheral position of the first surface portion. The fifth surface portion is formed such as to be higher towards the photoelectric conversion device side in the surface normal direction of the first surface portion in relation to the first surface portion. The end surface on the photoelectric conversion device side of the optically coupled device main body also includes a sixth surface portion formed in a position adjacent to both the first surface portion and the end surface on the optical fiber side of the optically coupled device main body. The sixth surface portion is formed such as to have a same planar shape as the first surface portion or such as to be lower towards a side heading away from the photoelectric conversion device in the surface normal direction of the first surface portion in relation to the first surface portion. The optically coupled device is formed such that the sixth surface portion allows the first lens surface to be viewed simultaneously with the second lens surface from the surface normal direction of the second surface portion. 
     In the fifth aspect of the present invention, the first lens surface can be viewed simultaneously with the second lens surface from the surface normal direction of the second surface portion through use of a simple shape. Therefore, cost is further reduced. 
     An optically coupled device according to a sixth aspect is the optically coupled device according to the fifth aspect in which at least one portion of the fifth surface portion is formed to allow contact with the photoelectric conversion device when the photoelectric conversion device is attached. 
     In the sixth aspect of the invention, the fifth surface portion allows a focal distance to be appropriately secured between the photoelectric conversion elements of the photoelectric conversion device and the first lens surface, thereby maintaining favorable overall efficiency. 
     An optical module according to a seventh aspect is an optical module including an optically coupled device according to the first aspect and a photoelectric conversion device corresponding to the optically coupled device. A photoelectric conversion element that emits or receives light is formed on the photoelectric conversion device. 
     In the seventh aspect of the invention, both the first lens surface and the second lens surface can be viewed simultaneously from the surface normal direction of at least one of the first surface portion and the second surface portion. Therefore, when position measurement of one lens surface is performed, a two-dimensional coordinate system used for the position measurement of the lens surface can be directly used to measure a coordinate of a predetermined coordinate axis component of the other lens surface. Therefore, a relative positional relationship between one lens surface and the other lens surface can be accurately grasped at the same time using a common two-dimensional coordinate system. 
     EFFECT OF THE INVENTION 
     The optically coupled device and the optical module of the present invention can appropriately and efficiently perform position measurement of an optical surface, and allow a product having superior overall efficiency to be stably manufactured at a low cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of an optically coupled device according to an embodiment of the present invention; 
         FIG. 2  is a planar view of  FIG. 1 ; 
         FIG. 3  is a rear view of  FIG. 1 ; 
         FIG. 4  is a right side view of  FIG. 1 ; 
         FIG. 5  is a cross-sectional view taken along line A-A in  FIG. 1 ; 
         FIG. 6  is an exploded view of an optical module according to the embodiment of the present invention; 
         FIG. 7A  is a diagram of a lens surface position measurement state allowing a relative positional relationship between first lens surfaces and second lens surfaces to be grasped, and an XY coordinate system used when the position measurement is performed, in the optically coupled device according to the embodiment of the present invention; 
         FIG. 7B  is a diagram of a position measurement state of only the second lens surfaces and an XY coordinate system used when the position measurement is performed, in the optically coupled device according to the embodiment of the present invention; 
         FIG. 8  is a front view of an example of a conventional optically coupled device; 
         FIG. 9  is a planar view of  FIG. 8 ; 
         FIG. 10  is a right side view of  FIG. 8 ; 
         FIG. 11A  is a diagram of a position measurement state of only first lens surfaces and an 
       XY coordinate system used when the position measurement is performed, in a conventional lens surface position measurement method; 
         FIG. 11B  is a diagram of a position measurement state of only second lens surfaces and an XY coordinate system used when the position measurement is performed, in the conventional lens surface position measurement method and 
         FIG. 12  is a right side elevational view of an optical module according to another embodiment of the present invention, corresponding to  FIG. 4 ; 
         FIG. 13  is a cross-sectional view thereof, corresponding to  FIG. 5 ; 
         FIG. 14  is a right side elevational view of an optical module according to still another embodiment of the present invention, corresponding to  FIGS. 4 and 12 ; and 
         FIG. 15  is a cross-sectional view thereof, corresponding to  FIGS. 5 and 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     (First Embodiment) 
     An optically coupled device and an optical module according to an embodiment of the present invention will be described below with reference to  FIG. 1  to  FIG. 7 . 
       FIG. 1  is a front view of an optically coupled device  15  according to the embodiment.  FIG. 2  is a planar view of  FIG. 1 .  FIG. 3  is a rear view of  FIG. 1 .  FIG. 4  is a right-side view of  FIG. 1 .  FIG. 5  is a cross-sectional view taken along line A-A in  FIG. 1 .  FIG. 6  is an exploded right-side view of an optical module  16  according to the embodiment. 
     Like a conventional optically coupled device, the optically coupled device  15  according to the embodiment is formed in a manner allowing each of a plurality of photoelectric conversion elements formed in an array on a photoelectric conversion device and respective end surfaces of a plurality (for example, the same number as the photoelectric conversion elements) of multi-mode optical fibers corresponding to the photoelectric conversion elements to be optically coupled. The photoelectric conversion elements emit or receive light. 
     In other words, as shown in  FIG. 6 , the optically coupled device  15  according to the embodiment is formed such that a photoelectric conversion device  18  can be attached to a front end surface  2  (a left end surface in  FIG. 6 ) that serves as a photoelectric conversion device-side end surface of the optically coupled device  15 . A plurality of photoelectric conversion elements  17  are formed in an array on a semiconductor substrate  20  in the photoelectric conversion device  18 . Because  FIG. 6  is a diagram of the photoelectric conversion device  18  viewed from a direction in which the photoelectric conversion elements  17  are arrayed, only a single photoelectric conversion element  17  is shown. In actuality, a plurality of photoelectric conversion elements  17  are arrayed along a direction perpendicular to a surface of the paper on which  FIG. 6  is printed. A photoelectric conversion device  18  such as this is attached to the optically coupled device  15  such that the photoelectric conversion elements  17  face the front end surface  2  side of the optically coupled device  15 . When the photoelectric conversion device  18  is attached, the photoelectric conversion device  18  is positioned by a pair of positioning pins  23  passing through the semiconductor substrate  20  being respectively engaged with a pair of positioning holes  7  of the optically coupled device  15 . The photoelectric conversion device  18  is then fixed by a fixing means, such as press-fitting, at the position at which the photoelectric conversion device  18  is positioned. In a photoelectric conversion device  18  such as this, when a light-emitting unit that emits light and a light-receiving unit that receives light are both disposed as the photoelectric conversion element  17 , the present invention can be applied to bi-directional communication. 
     As shown in  FIG. 6 , a plurality of optical fibers  19  can be attached with a connector  21  to an upper end surface  3  adjacent to the front end surface  2 . The upper end surface  3  serves as an optical fiber-side end surface of the optically coupled device  15 . Because  FIG. 6  is a diagram of the optical fibers  19  viewed from a direction in which the optical fibers  19  are arrayed, only a single optical fiber  19  is shown. In actuality, a plurality of optical fibers  19  are arrayed along a direction perpendicular to a surface of the paper on which  FIG. 6  is printed. Optical fibers  19  such as these are attached to the optically coupled device  15  such that end surfaces  19   a  of the optical fibers  19  face the upper end surface  3  of the optically coupled device  15 . When the optical fibers  19  are attached, the optical fibers  19  are positioned by a pair of positioning holes  24  formed on the connector  21  being respectively engaged with a pair of positioning pins  10  of the optically coupled device  15 . The optical fibers  19  are then fixed by a fixing means, such as press-fitting, at the position at which the optical fibers  19  are positioned. 
     As shown in  FIG. 1 ,  FIG. 4 , and  FIG. 5 , a roughly rectangular shaped area that is long in the lateral direction of  FIG. 1 , formed in a center portion of the front end surface  2  of the optically coupled device  15 , is a first surface portion  2   a . A plurality (for example, the same number as the photoelectric conversion elements  17 ) of first lens surfaces  5 , similar to those in  FIG. 8 , are formed in an array along the lateral direction of  FIG. 1 . The first lens surfaces  5  serve as first lens surfaces. When the photoelectric conversion device  18  is attached to the optically coupled device  15 , the first surface portion  2   a  and the first lens surfaces  5  face the plurality of photoelectric conversion elements  17  of the photoelectric conversion device  18 . The first lens surfaces  5  can form optical paths connecting each photoelectric conversion element  17  of the photoelectric conversion device  18  and each end surface  19   a  of the optical fibers  19 . 
     As shown in  FIG. 1 ,  FIG. 4 , and  FIG. 5 , on the front end surface  2  of the optically coupled device  15 , a surface portion  25  is formed on an outer position adjacent to the first surface portion  2   a , such as to surround the overall periphery of the first surface portion  2   a . The surface portion  25  is formed parallel to the first surface portion  2   a  and higher towards the photoelectric conversion device  18  side (front) in a surface normal direction of the first surface portion  2   a  in relation to the first surface portion  2   a . A pair of positioning holes  7 , similar to those in  FIG. 8 , are respectively formed near both ends in the lateral direction within the surface portion  25 . The surface portion  25  serves as a surface portion  25  for burr clearance, preventing burrs formed within the first surface portion  2   a  (such as on an outer circumferential end of the surface portion  2   a ) from projecting further towards the photoelectric conversion device  18  side than a fifth surface portion  26 , described hereafter. 
     The fifth surface portion  26  is formed in a peripheral position of the first surface portion  2   a  that is an outer position adjacent to the surface portion  25  for burr clearance. The fifth surface portion  26  is formed parallel to the surface portion  2 a and the surface portion  25  for burr clearance and higher towards the photoelectric conversion device  18  side (front) in a surface normal direction of the first surface portion  2   a  in relation to the surface portion  2   a  and the surface portion  25  for burr clearance. When the photoelectric conversion device  18  is attached to the optically coupled device  15 , the semiconductor substrate  20  of the photoelectric conversion device  18  comes into contact with the fifth surface portion  26 . As a result of the semiconductor substrate  20  coming into contact with the fifth surface portion  26 , a constant interval equivalent to a focal distance can be secured between the photoelectric conversion elements  17  and the first lens surfaces  5 . The constant interval can be more appropriately secured as a result of the burrs being prevented from projecting from the fifth surface portion  26  beforehand by the surface portion  25  for burr clearance, even when the burrs are formed within the first surface portion  2   a.    
     On the other hand, as shown in  FIG. 2 ,  FIG. 4 , and  FIG. 5 , a roughly rectangular shaped area that is long in the lateral direction of  FIG. 2 , formed in a center portion of the upper end surface  3  of the optically coupled device  15 , is a second surface portion  3   a . A plurality (for example, the same number as the first lens surfaces  5 ) of second lens surfaces  8 , similar to those in  FIG. 9 , are formed in an array along the lateral direction of  FIG. 3 . The second lens surfaces  8  serve as second lens surfaces. When the optical fibers  19  are attached to the optically coupled device  15 , the second surface portion  3   a  and the second lens surfaces  8  face the end surfaces  19   a  of the optical fibers  19 . The second lens surfaces  8  can form optical paths connecting each photoelectric conversion element  17  of the photoelectric conversion device  18  and each end surface  19   a  of the optical fibers  19 . 
     As shown in  FIG. 2 , on the upper end surface  3  of the optically coupled device  15 , a surface portion  28  is formed on an outer position adjacent to the second surface portion  3   a , such as to partially surround the periphery of the second surface portion  3   a  (from mainly three directions, the back [above in  FIG. 2 ], the left, and the right). The surface portion  28  is formed parallel to the second surface portion  3   a  and higher towards the optical fiber  19  side in a surface normal direction of the second surface portion  3   a  in relation to the second surface portion  3   a . A pair of positioning pins  10 , similar to those in  FIG. 9 , are formed near both ends in the lateral direction within the surface portion  28 . The surface portion  28  serves as a surface portion  28  for burr clearance, preventing burrs formed within the second surface portion  3   a  (such as on an outer circumferential end of the surface portion  3   a ) and burrs formed on a base-end outer circumference of the positioning pins  10  from projecting further towards the optical fiber  19  side than a third surface portion  29 , described hereafter. 
     The third surface portion  29  is formed in a peripheral position of the second surface portion  3   a  that is an outer position adjacent to the surface portion  28  for burr clearance. The third surface portion  29  is formed parallel to the second surface portion  3   a  and higher towards the optical fiber  19  side in a surface normal direction of the second surface portion  3   a  in relation to the second surface portion  3   a , such as to surround the outer circumference of the surface portion  28 . When the optical fibers  19  are attached to the optically coupled device  15 , the connector  21  comes into contact with the third surface portion  29 . As a result of the connector  21  coming into contact with the third surface portion  29 , a constant interval equivalent to a focal distance can be secured between the end surfaces  19   a  of the optical fibers  19  and the second lens surfaces  8 . The constant interval can be more appropriately secured as a result of the burrs being prevented from projecting from the third surface portion  29  beforehand by the surface portion  28  for burr clearance, even when the burrs are formed within the second surface portion  3   a.    
     As shown in  FIG. 1 ,  FIG. 2 ,  FIG. 4 , and  FIG. 5 , the optically coupled device  15  of the embodiment has a fourth surface portion  30  at a position on the upper end surface  3  adjacent to both the second surface portion  3   a  on the upper end surface  3  and the fifth surface portion  26  of the front end surface  2 . The fourth surface portion  30  is formed having a same planar shape as the second surface portion  3   a.    
     As shown in  FIG. 2 , the fourth surface portion  30  is formed such that dimensions in the lateral direction in  FIG. 2  is slightly smaller than the second surface portion  3   a  along the second surface portion  3   a . The fourth surface portion  30  is formed to positions reaching further outward in the direction in which the plurality of second lens surfaces  8  are arrayed than a pair of second lens surfaces  8  positioned on both ends in the direction in which the second lens surfaces  8  are arrayed. 
     According to the embodiment, as a result of a fourth surface portion  30  such as this, as shown in  FIG. 1 , a side surface shape of the second lens surfaces  8  from the surface normal direction of the first surface portion  2   a  can be viewed simultaneously with a planar surface shape of the first lens surfaces  5 . 
     As shown in  FIG. 3  to  FIG. 6 , a reflection surface  12  is formed on a rear end surface  11  of the optically coupled device  15  in a recessing manner, similar to that in  FIG. 10 . The reflection surface  12  is at an angle of about 45° to both an optical axis OA 1  (see  FIG. 6 ) of the first lens surfaces  5  and an optical axis OA 2  (see  FIG. 6 ) of the second lens surfaces  8 . The reflection surface  12 , with the first lens surfaces  5  and the second lens surfaces  8 , can form a plurality of optical paths connecting each of the plurality of photoelectric conversion elements  17  of the photoelectric conversion device  18  and each end surface  19   a  of the plurality of optical fibers  19 . 
     An upper-side tilted surface  32  is formed connected to an upper end of the reflection surface  12  in  FIG. 3  to  FIG. 6 . The upper-side tilted surface  32  is slightly tilted upwards from the surface normal direction of the rear end surface  11 . An orthogonal surface  33  is formed connected to a lower end of the reflection surface  12  in  FIG. 3  to  FIG. 6 . The orthogonal surface  33  is perpendicular to the surface normal direction of the rear end surface  11 . Moreover, a lower-side tilted surface  34  is formed connected to a lower end of the orthogonal surface  33 . The lower-side tilted surface  34  is slightly tilted downwards from the surface normal direction of the rear end surface  11 . 
     When the tilting angle of the reflection surface  12  is measured during a product manufacturing process, for example, it is important that a measuring device such as a non-contact-type, three-dimensional measuring device irradiate a laser beam for measurement towards both upper and lower ends of the reflection surface  12  from the rear of the optically coupled device  15  (right in  FIG. 4  to  FIG. 6 ), appropriately recognize both upper and lower ends of the reflection surface  12  by receiving a reflection light of the light beam, and accurately grasp positions of both upper and lower ends. In this case, because attachment positions of a light-emitting unit and a light-receiving unit of the measuring device are misaligned in the vertical direction, when the reflection surface  12  is measured, the laser beam is forced to be irradiated and the reflection light is forced to be reflected at an angle to the surface normal direction of the rear end surface  11 . However, when each tilted surface  32  and  34  are formed as shown in  FIG. 3  to  FIG. 6 , both irradiation of the laser beam to both upper and lower ends of the reflection surface  12  and reception of the reflection light from both upper and lower ends can be appropriately performed. Moreover, at this time, a borderline between the reflection surface  12  and the upper-side tilted surface  32  and a borderline between the reflection surface  12  and the orthogonal surface  33  can each be recognized. Therefore, the positions of both upper and lower ends of the reflection surface  12  can be grasped with certainty. As a result, measurement of the tilting angle of the reflection surface  12  can be performed with high precision. 
     Next, operations according to the embodiment will be described. 
     When the position measurement of the first lens surfaces  5  and the second lens surfaces  8  is performed on the optically coupled device  15  according to the embodiment, first, as shown in  FIG. 7A , the optically coupled device  15  is placed on the tool microscope such that the planar shape of the first lens surfaces  5  is visible. 
     At this time, according to the embodiment, because the fourth surface portion  30  is formed, the side surface shape of the second lens surfaces  8  can also be viewed with the planar shape of the first lens surfaces  5 . 
     Then, in this state, after an outline of the upper end surface  3  extending in the lateral direction in  FIG. 7A  is recognized, two points, P 1  and P 2 , that are separated from each other are taken on the outline. A line connecting the two points P 1  and P 2  is assumed. The line is defined as a Y axis of an XY coordinate system (two-dimensional Cartesian coordinate system) 
     Next, respective center lines L 1  and L 2  of the two positioning pins  10  are determined. A line at an equal distance from the two center lines L 1  and L 2  and parallel to both center lines L 1  and L 2  is determined. The line is defined as an X axis of the XY coordinate system. 
     Then, after an intersection between the X axis and the Y axis is determined to be a point of origin (0,0) in the XY coordinate system, the position measurement of the first lens surfaces  5  is performed by the X coordinate and the Y coordinate of a center point of each first lens surface  5  being determined. 
     Moreover, at this time, because the second lens surfaces  8  are visible, the XY coordinate system in  FIG. 7A  can be directly used to measure Y coordinates of center point of the second lens surfaces  8 . Here, the Y coordinates of the center points of the second lens surfaces  8  are determined, for example, as follows. After a line that passes through a surface peak of the second lens surface  8  and is parallel to the X axis is determined, an intersection between the line and the Y axis is a Y coordinate. 
     As a result, relative positional relationship between the first lens surfaces  5  and the second lens surfaces  8  or, in other words, whether the Y coordinates of the center points of the first lens surfaces  5  and the Y coordinates of the center points of the second lens surfaces  8  match can be accurately grasped at the same time using a common XY coordinate system. 
     At this time, because the side surface shape of the second lens surfaces  8  are visible, X coordinates of surface peak points of the second lens surfaces  8  can be measured, and whether all surface peak points of the plurality of second lens surfaces  8  have a same height can be judged. 
     Next, as shown in  FIG. 7B , the optically coupled device  15  is placed on the tool microscope such that the planar shape of the second lens surfaces  8  is visible. At this time, the first lens surfaces  5  are not visible. 
     Then, after an outline of a portion (lower side edge in  FIG. 7B ) of the upper end surface  3  extending in the lateral direction in  FIG. 7B  is recognized, two points, P 1 ′ and P 2 ′, that are separated from each other are taken on the outline. A line connecting the two points P 1 ′ and P 2 ′ is assumed. The line is defined as a Y axis of an XY coordinate system. 
     According to the embodiment, the X axis defined in  FIG. 7A  is used as is. 
     Then, as shown in  FIG. 7B , after determining an intersection between the X axis and the Y axis to be a point of origin (0,0) in the XY coordinate system, the X coordinate of each center point of the second lens surfaces  8  is determined, thereby performing the position measurement of the second lens surfaces  8 . At this time, the Y coordinates of the center points of the second lens surfaces  8  are already measured in the operation in  FIG. 7A . Therefore, measurement is not necessary. 
     As described above, according to the embodiment, the fourth surface portion  30  having a simple shape allows the second lens surfaces  8  to be viewed from the surface normal direction of the first surface portion  2   a , simultaneously with the first lens surfaces  5 . Therefore, the relative positional relationship between the first lens surfaces  5  and the second lens surfaces  8  can be accurately grasped at the same time using a common XY coordinate system. As a result, the positional measurement of the lens surfaces can be appropriately and efficiently performed at a low cost. 
     The present invention is not limited to the above-described embodiment. Various modifications can be made as required. 
     For example, according to the above-described embodiment, the fourth surface portion  30  is formed having a same planar shape as the second surface portion  3   a . However, the present invention is not limited thereto. For example, the fourth surface portion  30  can be formed to become lower towards a side heading away from the optical fibers  19  in the surface normal direction of the second surface portion  3   a  in relation to the second surface portion  3   a.  In this case as well, the second lens surfaces  8  can be viewed from the surface normal direction of the first surface portion  2   a , simultaneously with the first lens surfaces  5 . Therefore, similar effects as those according to the above-described embodiment can be achieved. 
     As shown in  FIGS. 12 and 13 , in place of the fourth surface portion  30  or, as shown in  FIGS. 14 and 15 , in addition to the fourth surface portion  30 , a sixth surface portion  38  can be provided in a potion on the front end surface  2  adjacent to both the first surface portion  2   a  and the upper end surface  3  of the optically coupled device  15 . The sixth surface portion  38  is formed so as to have a same planar shape as the first surface portion  2   a  or formed to be lower on a side heading away from the photoelectric conversion device  18  in the surface normal direction of the first surface portion  2   a  in relation to the first surface portion  2   a.    
     In this structure, the sixth surface portion  38  allows the planar shape of the second lens surfaces  8  and the side surface shape of the first lens surfaces  5  to be simultaneously viewed from the surface normal direction of the second surface portion  3   a . Therefore, the relative positional relationship between the first lens surfaces  5  and the planar shape of the second lens surfaces  8  is viewed. As a result, the positional measurement of the lens surfaces  5  and  8  can be appropriately and efficiently performed.