Patent Publication Number: US-2020285003-A1

Title: Photoelectric conversion module and active optical cable

Description:
TECHNICAL FIELD 
     The present invention relates to a photoelectric conversion module suitable for performing photoelectric conversion with high efficiency and an active optical cable. 
     BACKGROUND ART 
     As a photoelectric conversion module, there is a photoelectric conversion module in which a photoelectric conversion element performing conversion of light energy and electric energy and an optical fiber are fixed to each other and light propagates between the photoelectric conversion element and the optical fiber. In the photoelectric conversion module, a signal is converted from an optical signal to an electric signal or a signal is converted from an electric signal to an optical signal. Examples of the photoelectric conversion module can include a photoelectric conversion module in which an optical fiber is fixed to a laser diode (LD) and light emitted from the laser diode is propagated through an optical fiber and a photoelectric conversion module in which an optical fiber is connected to a photodiode (PD) and light emitted from the optical fiber is received by the photodiode. 
     Such an optical module is described in the following Patent Literature 1. In the optical module described in the following Patent Literature 1, an optical fiber is disposed at a predetermined interval on an optical semiconductor element to be a photoelectric conversion element, a transparent resin is filled between the optical semiconductor element and the optical fiber, and the optical fiber is fixed to an optical semiconductor. The transparent resin is also filled between a light receiving/emitting unit of the optical semiconductor element and an end face of the optical fiber and has an inclined surface inclined with respect to each of a longitudinal direction of the optical fiber and a direction perpendicular to a light receiving/emitting surface. The transparent resin is an optical coupling unit that reflects light by the inclined surface and optically couples the light receiving/emitting unit of the optical semiconductor element and a core of the optical fiber. Therefore, light emitted from the light receiving/emitting unit of the optical semiconductor element is incident on the core of the optical fiber through the optical coupling unit and light emitted from the core of the optical fiber is incident on the light receiving/emitting unit of the optical semiconductor element through the optical coupling unit. 
     [Patent Literature 1] WO 2011/083812 A 
     SUMMARY OF INVENTION 
     In the optical module described in the above Patent Literature 1, the optical coupling unit is formed of the resin, so that highly efficient optical transmission can be performed at a low cost. However, a photoelectric conversion module in which a loss of light is further reduced is required. 
     Accordingly, it is an object of the present invention to provide a photoelectric conversion module in which a loss of light is reduced and an active optical cable. 
     A photoelectric conversion module according to the present invention includes a photoelectric conversion element which has a light receiving/emitting unit to receive or emit light; an optical fiber which has one end portion fixed to the photoelectric conversion element; and a light transmitting resin which fixes the one end portion of the optical fiber and the photoelectric conversion element, reflects light by a predetermined region of a surface thereof, and optically couples a core of the optical fiber and the light receiving/emitting unit. An outer circumferential surface of a clad at the one end portion of the optical fiber contacts an element surface from which the light receiving/emitting unit is exposed at a position not overlapping a center of the light receiving/emitting unit in the photoelectric conversion element. 
     According to the photoelectric conversion module, because the outer circumferential surface of the clad at one end portion of the optical fiber fixed to the photoelectric conversion element contacts the element surface, a length of an optical path between the core of the optical fiber and the light receiving/emitting unit can be shortened in the light transmitting resin, as compared with the case where the optical fiber and the photoelectric conversion element are separated from each other as in the above Patent Literature 1. In the case where the photoelectric conversion element is a light emitting element, because light emitted from the light emitting element spreads, spreading of light is suppressed by shortening an optical path length to the optical fiber and an amount of light coupled to the core of the optical fiber can be increased. Also, because the light emitted from the optical fiber spreads, in the case where the photoelectric conversion element is a light receiving element, spreading of light is suppressed by shortening an optical path length to the light receiving element and an amount of light coupled to the light receiving element can be increased. In addition, the optical fiber is disposed at the position not overlapping the center of the light receiving/emitting unit. Preferably, the center of the light receiving/emitting unit is generally a position where the light intensity is highest and the center and the core of the optical fiber are optically coupled. Therefore, the optical fiber is disposed at the position not overlapping the center of the light receiving/emitting unit, so that it is possible to suppress loss of a part of the light with the highest intensity due to reflection or refraction in a side surface of the clad of the optical fiber or a side surface of the core. In this way, a coupling loss of light in the core of the optical fiber and the light receiving/emitting unit of the photoelectric conversion element can be suppressed. Therefore, according to the photoelectric conversion module according to the present invention, a loss of light can be reduced. 
     As described above, because the outer circumferential surface of the clad at one end portion of the optical fiber fixed to the photoelectric conversion element contacts the element surface, the end portion of the optical fiber hardly moves and moving of the end portion of the optical fiber in a direction perpendicular to the element surface in particular is suppressed, as compared with the case where the optical fiber and the photoelectric conversion element are separated from each other as in the photoelectric conversion module described in the above Patent Literature 1. The movement of the end portion of the optical fiber may tend to lead to an increase in the coupling loss of the light in the core of the optical fiber and the light receiving/emitting unit of the photoelectric conversion element. In addition, because the viscosity of the light transmitting resin tends to decrease under a high temperature environment, the coupling loss of the light due to the movement of the end portion of the optical fiber is more likely to increase. However, in the photoelectric conversion module according to the present invention, because the end portion of the optical fiber hardly moves as described above, optical coupling between the light receiving/emitting surface and the core of the optical fiber is stabilized and an increase in the coupling loss of the light in the core and the light receiving/emitting unit can be suppressed. 
     In addition, as described above, because the outer circumferential surface of the clad at one end portion of the optical fiber fixed to the photoelectric conversion element contacts the element surface, the photoelectric conversion module can realize height reduction, as compared with the case where the optical fiber and the photoelectric conversion element are separated from each other as in the photoelectric conversion module described in the above Patent Literature 1. 
     Preferably, a distance between an end face of the optical fiber and a center position of the light receiving/emitting unit in a longitudinal direction of the optical fiber is equal to a distance from the element surface to a center of the core. 
     By disposing the optical fiber in the photoelectric conversion element in such a manner, an optical path length of the light propagating through the light transmitting resin can be shortened and the coupling loss of the light in the core of the optical fiber and the light receiving/emitting unit of the photoelectric conversion element can be further reduced. 
     Preferably, the predetermined region of the surface of the light transmitting resin reflecting the light is inclined at 40 degrees to 50 degrees with respect to a direction perpendicular to the light receiving/emitting unit. 
     It has been found that, when the light is reflected at an angle within the above range and the core and a light receiving/emitting surface are optically coupled, the coupling loss of the light in the core of the optical fiber and the light receiving/emitting unit of the photoelectric conversion element can be sufficiently reduced, as compared with the case where the light is reflected at an angle outside the above range and the core and the light receiving/emitting unit are optically coupled. In addition, it has been found that, when the light is reflected at an angle within the above range, an increase in the coupling loss of the light in the core and the light receiving/emitting unit can be suppressed even if a position of a tip of the optical fiber deviates in the longitudinal direction. Therefore, the loss of the light can be further reduced by adopting the above configuration. 
     Preferably, the photoelectric conversion module further includes a substrate to which the photoelectric conversion element is fixed and a fixing resin which fixes the optical fiber to the substrate and the light transmitting resin is softer than the fixing resin. 
     According to this configuration, the optical fiber is firmly fixed to the substrate rather than the photoelectric conversion element. As a result, a movement of the optical fiber with respect to the substrate is strongly regulated and a movement of the optical fiber with respect to the photoelectric conversion element fixed to the substrate is also regulated. Therefore, a state in which the loss of the light is reduced can be maintained. Even if the fixing resin deforms due to some reason and the end portion of the optical fiber moves due to the deformation, the light transmitting resin softer than the fixing resin absorbs the movement, so that it is possible to suppress damage to the optical fiber or damage to the photoelectric conversion element. 
     Preferably, a plurality of the light receiving/emitting units, a plurality of the optical fibers, and a plurality of the light transmitting resins are provided, the plurality of optical fibers is gathered by a coating resin and is led out from the coating resin by a predetermined length so that the clad is exposed at the one end portion, each of the light transmitting resins individually fixes the one end portion of each of the optical fibers to the photoelectric conversion element, reflects light by the predetermined region of the surface thereof, and optically couples the core of each of the optical fibers and each of the light receiving/emitting units individually, and the outer circumferential surface of the clad at the one end portion of each of the optical fibers contacts the element surface at a position not overlapping the center of the light receiving/emitting unit. 
     In the photoelectric conversion module, the multicore optical fiber in which the plurality of optical fibers is gathered as described above is used. Even when the multicore optical fiber is used, as described above, each optical fiber contacts the element surface at the position not overlapping the center of the light receiving/emitting unit and each light transmitting resin optically connects the core of each optical fiber and the light receiving/emitting surface individually. Therefore, in the photoelectric conversion module, the loss of the light can be reduced while the multicore optical fiber is used. According to the photoelectric conversion module, because the movement of the end portion of the optical fiber is suppressed, an increase in the coupling loss of the light in the core and the light receiving/emitting unit can be suppressed and height reduction can be realized. As a form in which a plurality of light receiving/emitting units is provided, a form in which a plurality of photoelectric conversion elements is provided and a form in which the photoelectric conversion element has a plurality of light receiving/emitting units can be exemplified. 
     As described above, when the plurality of light receiving/emitting units, the plurality of optical fibers, and the plurality of light transmitting resins are provided, the photoelectric conversion module preferably further includes a substrate to which the photoelectric conversion element is fixed and a fixing resin which fixes each of the optical fibers to the substrate and the light transmitting resin is preferably softer than the fixing resin. 
     According to this configuration, each optical fiber is firmly fixed to the substrate rather than the photoelectric conversion element. As a result, a movement of the optical fiber with respect to the substrate is strongly regulated and a movement of the optical fiber with respect to the photoelectric conversion element fixed to the substrate is also regulated. Therefore, a state in which the loss of the light is reduced can be maintained. Even if the fixing resin deforms due to some reason and the end portion of the optical fiber moves due to the deformation, the light transmitting resin softer than the fixing resin absorbs the movement, so that it is possible to suppress damage to the optical fiber or damage to the photoelectric conversion element. 
     An active optical cable according to the present invention includes a light emitting element which has a light emitting unit to emit light; a light receiving element which has a light receiving unit to receive the light; an optical fiber which has one end portion fixed to the light emitting element and the other end portion fixed to the light receiving element; a first light transmitting resin which fixes the one end portion of the optical fiber and the light emitting element, reflects light by a predetermined region of a surface thereof, and optically couples a core of the optical fiber and the light emitting unit; and a second light transmitting resin which fixes the other end portion of the optical fiber and the light receiving element, reflects light by a predetermined region of a surface thereof, and optically couples the core of the optical fiber and the light receiving unit. An outer circumferential surface of a clad at the one end portion of the optical fiber contacts a light emitting element surface from which the light emitting unit is exposed at a position not overlapping a center of the light emitting unit in the light emitting element and an outer circumferential surface of the clad at the other end portion of the optical fiber contacts a light receiving element surface from which the light receiving unit is exposed at a position not overlapping a center of the light receiving unit in the light receiving element. 
     The active optical cable includes the photoelectric conversion module having the light emitting element, the optical fiber, and the first light transmitting resin and the photoelectric conversion module having the light receiving element, the optical fiber, and the second light transmitting resin. That is, the active optical cable includes a set of photoelectric conversion modules for transmitting and receiving light. In the active optical cable, because the loss of the light can be reduced in each photoelectric conversion module, efficient optical communication can be performed. In addition, in the active optical cable, the movement of the end portion of the optical fiber is suppressed in each photoelectric conversion module and an increase in the coupling loss of the light in the core and the light receiving/emitting unit can be suppressed, so that stable optical communication can be performed. In addition, in the active optical cable, because each photoelectric conversion module can realize the height reduction, miniaturization can be realized. 
     As described above, according to the present invention, a photoelectric conversion module in which a loss of light is reduced and an active optical cable are provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view showing a photoelectric conversion module according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the photoelectric conversion module of  FIG. 1 . 
         FIG. 3  is an enlarged view of an end portion of an optical fiber and a photoelectric conversion element in  FIG. 2 . 
         FIG. 4  is a diagram showing a relation of a ratio of an outer diameter D 1  of a clad of the optical fiber to a distance D 2  between an end face of the optical fiber along a longitudinal direction of the optical fiber and a center position of a light receiving/emitting unit and an increase amount of a coupling loss of light occurring between the optical fiber and the light receiving/emitting unit. 
         FIG. 5  is a plan view showing an active optical cable according to the first embodiment of the present invention. 
         FIG. 6  is a plan view showing a photoelectric conversion module according to a second embodiment of the present invention. 
         FIG. 7  is a plan view showing an active optical cable according to the second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, preferred embodiments of a photoelectric conversion module and an active optical cable according to the present invention will be described in detail with reference to the drawings. 
     First Embodiment 
     &lt;Photoelectric Conversion Module&gt; 
     First, a photoelectric conversion module according to this embodiment will be described.  FIG. 1  is a plan view showing a photoelectric conversion module according to a first embodiment of the present invention and  FIG. 2  is a cross-sectional view of the photoelectric conversion module of  FIG. 1 . 
     As shown in  FIGS. 1 and 2 , a photoelectric conversion module  1  according to this embodiment includes a substrate  10 , a photoelectric conversion element  20 , an optical fiber  30 , a light transmitting resin  41 , and a fixing resin  45  as a main configuration. 
     In this embodiment, the substrate  10  is a printed wiring board and includes a substrate body  11  and terminals  12  and lands  13  and  14  formed on the substrate body  11 . The substrate body  11  is a plate-like member made of an insulator such as glass epoxy or ceramic. In addition, each of the terminals  12  and the lands  13  and  14  is made of a conductor such as copper plating, the land  13  is a land to be connected to a signal terminal of the photoelectric conversion element  20 , the land  14  is a land to be connected to a ground terminal of the photoelectric conversion element  20 , and the terminals  12  are terminals to be connected to external devices. One terminal  12  and the land  13 , and the other terminal  12  and the land  14  are electrically connected to each other via wiring lines not shown in the drawings or other electronic components. 
     The photoelectric conversion element  20  is fixed to the substrate  10 . The photoelectric conversion element  20  is an element in which a light receiving/emitting unit  25  made of InGaP (indium gallium phosphide) or the like is provided on a base made of GaAs (gallium arsenide) or the like and may be called an optical semiconductor element. The photoelectric conversion element  20  is a light receiving element for performing conversion from an optical signal to an electric signal or a light emitting element for performing conversion from an electric signal to an optical signal. Since the photoelectric conversion element  20  performs light reception or light emission as described above, a light receiving/emitting surface  26  of the light receiving/emitting unit  25  is exposed from an element surface  21  to be a predetermined surface of the photoelectric conversion element  20 . The light receiving/emitting unit  25  performs light reception or light emission. 
     As an example of the case where the photoelectric conversion element  20  is a light receiving element, a photodiode or the like can be exemplified. In this case, the light receiving/emitting unit  25  is a light receiving unit, the element surface  21  is a light receiving element surface, and the light receiving unit is exposed from the light receiving element surface. In addition, as an example of the case where the photoelectric conversion element  20  is a light emitting element, a laser diode or the like can be exemplified. In this case, the light receiving/emitting unit  25  is a light emitting unit, the element surface  21  is a light emitting element surface, and the light emitting unit is exposed from the light emitting element surface. 
     In this embodiment, the photoelectric conversion element  20  has one light receiving/emitting unit  25 . In the photoelectric conversion element  20 , a signal terminal is formed on the element surface  21  and a ground terminal not shown in the drawings is formed on the side opposite to the element surface  21 . The terminal  23  and the land  13  of the substrate  10  are electrically connected via a wiring line  15  and the ground terminal not shown in the drawings and the land  14  of the substrate are electrically connected. The wiring line  15  is a conductive wiring line and is made of a metal such as gold, aluminum, and copper, for example. Although different from this embodiment, the ground terminal may be formed on the element surface  21 . In this case, a land electrically connected to the ground terminal is provided separately from the land  13  and the ground terminal and the land are electrically connected by a wiring line or the like. 
     In addition, the optical fiber  30  is fixed to the element surface  21  of the photoelectric conversion element  20 . The optical fiber  30  has a core  31 , a clad  32  surrounding an outer circumferential surface of the core  31 , and a protective layer  33  covering an outer circumferential surface of the clad  32 . A refractive index of the core  31  is higher than a refractive index of the clad  32 . Examples of the optical fiber can include a quartz optical fiber in which the core  31  and the clad  32  are formed of quartz, a plastic optical fiber in which the core  31  and the clad  32  are made of plastic, a polymer clad coated optical fiber in which the core is formed of quartz and the clad is formed of plastic, and the like. The protective layer  33  is formed of a photocurable resin or the like, for example. 
     The optical fiber  30  is, for example, a multimode fiber that propagates light of a plurality of modes. Although an outer diameter of the clad  32  is not particularly limited, the outer diameter is, for example, 125 μm and a diameter of the core  31  is, for example, 50 μm in the case of the multimode fiber. The optical fiber  30  may be a single mode fiber that propagates only light of a basic mode. In this case, the diameter of the core  31  is, for example, 10 μm. 
     The optical fiber  30  is led out by a predetermined length so that the clad  32  is exposed from the protective layer  33  at one end portion of the side fixed to the photoelectric conversion element  20 . In this embodiment, an end face of the optical fiber  30  is perpendicular to a longitudinal direction. As shown in  FIG. 2 , if this length is set to a lead-out length L, the lead-out length L is preferably 10 μm to 15 mm, more preferably, 1.5 mm to 2.5 mm. One end portion of the optical fiber  30  from which the clad  32  has been led out is disposed on the photoelectric conversion element  20  so that an outer circumferential surface of the clad  32  contacts the element surface  21  of the photoelectric conversion element  20 . The optical fiber  30  is disposed so that a center axis of the core  31  of the optical fiber  30  passes through a center of the light receiving/emitting unit  25  and at least a center of the light receiving/emitting surface  26  is exposed, when the element surface  21  is viewed in planar view. That is, one end portion of the optical fiber  30  is disposed on the photoelectric conversion element  20  to contact the element surface  21  at a position not overlapping the center of the light receiving/emitting unit  25 . As shown in  FIG. 2 , one end portion of the optical fiber  30  is more preferably disposed on the photoelectric conversion element  20  to contact the element surface  21  at a position not overlapping the entire light receiving/emitting unit  25 . 
     In a state in which one end portion of the optical fiber  30  is disposed on the photoelectric conversion element  20 , in this embodiment, the protective layer  33  of the optical fiber  30  and a part of the clad  32  exposed from the protective layer  33  are fixed to the substrate  10  by the fixing resin  45 . The fixing resin  45  is a hard resin and is, for example, a photocurable resin such as an acrylic resin, an epoxy resin, a silicon resin, or a resin obtained by mixing or synthesizing these resins. By the fixing resin  45 , a movement of the position of the optical fiber  30  is suppressed. 
     In addition, one end portion of the optical fiber  30  disposed on the photoelectric conversion element  20  is fixed to the photoelectric conversion element  20  by the light transmitting resin  41 . The light transmitting resin is made of a resin that transmits light propagating through the optical fiber  30 . Examples of the resin can include a photocurable resin such as an acrylic resin, an epoxy resin, a silicon resin, or a resin obtained by mixing or synthesizing these resins. 
     The light transmitting resin  41  is preferably softer than the fixing resin  45 . If the light transmitting resin  41  is harder than the fixing resin  45 , in the case where a vibration or the like is applied to the photoelectric conversion module  1  and the fixing resin is deformed, a stress may be applied to the optical fiber  30  to damage the led-out optical fiber  30  or the end portion of the optical fiber  30  may move and the stress due to the movement of the end portion may be applied to the photoelectric conversion element  20  to damage the photoelectric conversion element  20 . However, if the light transmitting resin  41  is softer than the fixing resin  45  as described above, in the case where the fixing resin  45  is deformed, the end portion of the optical fiber  30  can move due to the deformation and the stress for the optical fiber  30  can be alleviated by the movement or the light transmitting resin  41  can absorb the movement of the end portion of the optical fiber  30 , thereby suppressing the damage on the photoelectric conversion element  20 . 
     Next, a position relation of the optical fiber  30  and the light receiving/emitting unit  25 , a shape of the light transmitting resin  41 , and the like will be described in detail. 
       FIG. 3  is an enlarged view of the end portion of the optical fiber  30  and the photoelectric conversion element  20  shown in  FIG. 2 . As shown in  FIG. 3  in which an optical axis is shown by a broken line, light propagating between the optical fiber  30  and the light receiving/emitting unit  25  is reflected by a predetermined region  42  of a surface of the light transmitting resin  41  and propagates. The predetermined region  42  of the surface of the light transmitting resin  41  faces the core  31  at a predetermined inclination angle on the end face of the optical fiber  30  and faces the light receiving/emitting unit  25  at a predetermined inclination angle, to reflect the light as described above. Therefore, the predetermined region  42  of the surface of the light transmitting resin  41  can be understood as a reflection unit. 
     If the outer diameter of the clad of the optical fiber  30  is set to D 1 , the outer circumferential surface of the clad  32  contacts the element surface  21  as described above, so that a distance from the element surface  21  to the center of the core  31  of the optical fiber  30  is D 1 /2. In addition, a distance between the end face of the optical fiber  30  along the longitudinal direction of the optical fiber  30  and the center position of the light receiving/emitting unit  25  is set to D 2 . In this case, in this embodiment, the distance D 1 /2 and the distance D 2  are equal to each other. As such, because the distance D 1 /2 and the distance D 2  are equal to each other, an optical path length of the light that is reflected by the predetermined region  42  of the surface of the light transmitting resin  41  and propagates between the optical fiber  30  and the light receiving/emitting unit  25  can be minimized. 
       FIG. 4  is a diagram showing a relation between a ratio of the outer diameter D 1  to the distance D 2  and an increase amount of a coupling loss of light occurring between the optical fiber  30  and the light receiving/emitting unit  25 . Here, an angle of the predetermined region  42  reflecting light with respect to a direction perpendicular to the light receiving/emitting surface  26  of the light receiving/emitting unit  25  is set to θ. In  FIG. 4 , the above relation is shown every angle θ. 
     As shown in  FIG. 4 , the coupling loss of the light is smallest when the angle θ is 45 degrees and D 1 /D 2  is 0.5. If D 1 /D 2  is 0.5, it means that the distance D 2  in the longitudinal direction of the optical fiber  30  between the end face of the optical fiber  30  and the center position of the light receiving/emitting unit  25  is equal to the distance D 1 /2 from the element surface  21  to the center of the core  31  of the optical fiber  30 . In the case where the angle θ is 45 degrees, if the position of the end face of the optical fiber  30  deviates along the longitudinal direction of the optical fiber  30  and D 1 /D 2  deviates from 0.5, the coupling loss of the light increases. However, even in the case where D 1 /D 2  deviates from 0.5 by about 0.1 when the angle θ is 45 degrees, an increase amount of the coupling loss of the light is sufficiently small as less than 1 dB. If D 1 /D 2  deviates by about 0.1, it means that a deviation of about 20 μm occurs when the outer diameter of the clad is 125 μm as described above. 
     In addition, when θ is 40 degrees and D 1 /D 2  is about 0.6, the coupling loss of the light is smallest and a difference with the coupling loss of the light when the angle θ is 45 degrees and D 1 /D 2  is 0.5 is approximately 0.7 dB. However, even if D 1 /D 2  is 0.5, the coupling loss of the light does not change much as compared with the case when D 1 /D 2  is 0.6. In addition, even when D 1 /D 2  deviates from 0.5 by about 0.1, an increase amount of the coupling loss of the light is less than 1 dB and the coupling loss of the light is sufficiently suppressed. In addition, when 0 is 50 degrees and D 1 /D 2  is about 0.35, the coupling loss of the light is smallest and a difference with the coupling loss of the light in a case where the angle θ is 45 degrees and D 1 /D 2  is 0.5 is approximately 0.7 dB. However, even when D 1 /D 2  is 0.5, the coupling loss of the light does not change much as compared with the case where D 1 /D 2  is 0.35. In addition, even when D 1 /D 2  deviates from 0.5 by about 0.1, an increase amount of the coupling loss of the light is less than 1 dB and the coupling loss of the light is sufficiently suppressed. That is, in the case where θ is 40 to 50, when D 1 /D 2  deviates from 0.5 by about 0.1, that is, when D 1 /D 2  is about 0.4 to 0.6, the coupling loss of the light can be sufficiently suppressed. On the other hand, as apparent from  FIG. 4 , when θ is 35 degrees or 55 degrees, the coupling loss of the light increases by about 5 dB as compared with the coupling loss of the light when the angle θ is 45 degrees and D 1 /D 2  is 0.5. 
     As an example of forming the light transmitting resin  41 , in a state in which the clad  32  is disposed on the element surface  21  of the photoelectric conversion element  20 , a resin becoming the light transmitting resin  41  is dropped into the end portion of the optical fiber  30  and is cured. At this time, an amount, a viscosity, and the like of the resin to be dropped are controlled, so that it is possible to form the light transmitting resin  41  in which θ has been controlled. 
     Next, an operation of the photoelectric conversion module  1  will be described. 
     In the case where the photoelectric conversion element  20  of the photoelectric conversion module  1  is a light emitting element, an electric signal is input to the terminal  23  of the photoelectric conversion element  20  on the basis of an electric signal input to the terminal  12  of the photoelectric conversion module  1  and light is emitted from the light receiving/emitting unit  25 . The light emitted from the light receiving/emitting unit  25  is reflected by the predetermined region  42  of the surface of the light transmitting resin  41 , is incident on the core  31  of the optical fiber  30  from the end face, and propagates through the core  31  from one end portion to the other end portion. 
     On the other hand, in the case where the photoelectric conversion element  20  of the photoelectric conversion module  1  is a light receiving element, when light is emitted from the end face of the core  31  at one end portion of the optical fiber  30 , the emitted light is received by the predetermined region  42  of the surface of the light transmitting resin  41  and is received by the light receiving/emitting unit  25 . If the light is received by the light receiving/emitting unit  25 , an electric signal is output from the terminal  23  of the photoelectric conversion element  20  and an electric signal based on the electric signal is output from the terminal  12  of the photoelectric conversion module  1 . 
     As described above, in the photoelectric conversion module  1  according to this embodiment, the outer circumferential surface of the clad  32  at one end portion of the optical fiber  30  contacts the element surface  21  of the photoelectric conversion element  20  from which the light receiving/emitting unit  25  is exposed. Therefore, as compared with the case where the optical fiber  30  and the photoelectric conversion element  20  are separated from each other, the length of the optical path between the core  31  of the optical fiber  30  and the light receiving/emitting unit  25  in the light transmitting resin  41  can be shortened. In addition, because the optical fiber  30  is disposed at a position not overlapping the center of the light receiving/emitting unit  25 , a part of the light entering and leaving the center of the light receiving/emitting unit  25  can be suppressed from being lost due to reflection or refraction in a side surface of the clad  32  or a side surface of the core  31 . The light entering and leaving the center of the light receiving/emitting unit  25  is generally light with the highest intensity. Therefore, because the coupling loss of the light in the core  31  of the optical fiber  30  and the light receiving/emitting unit  25  of the photoelectric conversion element  20  can be suppressed, according to the photoelectric conversion module  1  according to this embodiment, a loss of the light can be reduced. 
     In addition, because the outer circumferential surface of the clad  32  at one end portion of the optical fiber  30  contacts the element surface  21 , as compared with the case where the optical fiber  30  and the photoelectric conversion element  20  are separated from each other, the end portion of the optical fiber  30  hardly moves and moving of the end portion of the optical fiber  30  in a direction perpendicular to the element surface  21  in particular is suppressed. The movement of the end portion of the optical fiber  30  tends to lead to an increase in the coupling loss of the light in the core  31  and the light receiving/emitting unit  25 . If the optical fiber  30  moves in the direction perpendicular to the element surface  21  in particular, the coupling loss of the light may further increase. In addition, because the viscosity of the light transmitting resin tends to decrease under a high temperature environment, the coupling loss of the light due to the movement of the end portion of the optical fiber is more likely to increase. However, in the photoelectric conversion module  1  according to this embodiment, because the end portion of the optical fiber  30  hardly moves as described above, optical coupling between the light receiving/emitting surface  26  and the core  31  of the optical fiber  30  is stabilized and an increase in the coupling loss of the light can be suppressed. 
     In addition, because the outer circumferential surface of the clad  32  at one end portion of the optical fiber  30  contacts the element surface  21  of the photoelectric conversion element  20 , the photoelectric conversion module  1  can realize height reduction as compared with the case where the optical fiber  30  and the photoelectric conversion element  20  are separated from each other. 
     &lt;Active Optical Cable&gt; 
     Next, an active optical cable according to this embodiment will be described. 
       FIG. 5  is a plan view showing the active optical cable according to this embodiment. As shown in  FIG. 5 , an active optical cable AC 1  according to this embodiment includes a photoelectric conversion module  1 A and a photoelectric conversion module  1 B. The photoelectric conversion module  1 A and the photoelectric conversion module  1 B use a common optical fiber  30 . 
     The photoelectric conversion module  1 A is a module in which the photoelectric conversion element  20  of the photoelectric conversion module  1  is replaced by a light emitting element  20 A. That is, the photoelectric conversion module  1 A is a light emitting module. 
     The light emitting element  20 A has a light emitting unit  25 A corresponding to the light receiving/emitting unit of the photoelectric conversion element  20  of the photoelectric conversion module  1  and the element surface  21  of the photoelectric conversion module  1  corresponds to a light emitting element surface  21 A of the light emitting element  20 A. One end portion of the optical fiber  30  is fixed to the light emitting element  20 A. Specifically, one end portion of the optical fiber  30  is led out in the same manner as one end portion of the optical fiber  30  of the photoelectric conversion module  1 . In addition, one end portion of the optical fiber  30  that has been led out is disposed to contact the light emitting element surface  21 A at a position where the outer circumferential surface of the clad  32  does not overlap the center of the light emitting unit  25 A of the light emitting element  20 A. One end portion of the optical fiber  30  disposed in this manner is fixed by a first light transmitting resin  41 A having the same configuration as the configuration of the light transmitting resin  41  of the photoelectric conversion module  1  in the same manner as the case where one end portion of the optical fiber  30  of the photoelectric conversion module  1  is fixed to the photoelectric conversion element  20  by the light transmitting resin  41 . One end portion of the optical fiber  30  is more preferably disposed to contact the light emitting element surface  21 A at a position not overlapping the entire light emitting unit  25 A of the light emitting element  20 A. 
     In addition, the photoelectric conversion module  1 B is a module in which the photoelectric conversion element  20  of the photoelectric conversion module  1  is replaced by a light receiving element  20 B. That is, the photoelectric conversion module  1 B is a light receiving module. 
     The light receiving element  20 B has a light receiving unit  25 B corresponding to the light receiving/emitting unit  25  of the photoelectric conversion element  20  of the photoelectric conversion module  1  and the element surface  21  of the photoelectric conversion module  1  corresponds to a light receiving element surface  21 B of the light receiving element  20 B. The other end portion of the optical fiber  30  is fixed to the light receiving element  20 B. Specifically, the other end portion of the optical fiber  30  is led out in the same manner as one end portion of the optical fiber  30  of the photoelectric conversion module  1 . In addition, the other end portion of the optical fiber  30  that has been led out is disposed to contact the light receiving element surface  21 B at a position where the outer circumferential surface of the clad  32  does not overlap a center of the light receiving unit  25 B of the light receiving element  20 B. The other end portion of the optical fiber  30  disposed in this manner is fixed by a second light transmitting resin  41 B having the same configuration as the configuration of the light transmitting resin  41  of the photoelectric conversion module  1  in the same manner as the case where one end portion of the optical fiber  30  of the photoelectric conversion module  1  is fixed to the photoelectric conversion element  20  by the light transmitting resin  41 . The other end portion of the optical fiber  30  is more preferably disposed to contact the light receiving element surface  21 B at a position not overlapping the entire light receiving unit  25 B of the light receiving element  20 B. 
     In the active optical cable AC 1  having the above configuration, an electric signal is input to the terminal  23  of the light emitting element  20 A on the basis of an electric signal input to the terminal  12  of the photoelectric conversion module  1 A and light is emitted from the light emitting unit  25 A. The light emitted from the light emitting unit  25 A is reflected by a predetermined region of a surface of the first light transmitting resin  41 A and is incident on the core  31  of the optical fiber  30 . The light then propagates through the core  31  from one end portion of the optical fiber  30  to the other end portion. The light emitted from the core  31  at the other end portion is reflected by a predetermined region of a surface of the second light transmitting resin  41 B and is received by the light receiving unit  25 B. When the light is received by the light receiving unit  25 B, an electric signal is output from the terminal of the light receiving element  20 B and an electric signal based on the electric signal is output from the terminal  12  of the photoelectric conversion module  1 B. 
     As described above, in the active optical cable AC 1 , the loss of the light can be reduced in each of the photoelectric conversion modules  1 A and  1 B in the same manner as the photoelectric conversion module  1 . Therefore, efficient optical communication can be performed. In addition, in the active optical cable AC 1 , the movement of the end portion of the optical fiber  30  in each of the photoelectric conversion modules  1 A and  1 B is suppressed in the same manner as the photoelectric conversion module  1  and an increase in the coupling loss of the light in the core  31  of the optical fiber  30  and the light receiving/emitting unit  25  of the photoelectric conversion element  20  can be suppressed. Therefore, stable optical communication can be performed. In addition, in the active optical cable AC 1 , because each of the photoelectric conversion modules  1 A and  1 B can realize height reduction in the same manner as the photoelectric conversion module  1 , miniaturization can be realized. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described in detail with reference to  FIGS. 6 and 7 . Components equal to or equivalent to those in the first embodiment are denoted by the same reference numerals and redundant explanation is omitted, unless particularly described. 
     &lt;Photoelectric Conversion Module&gt; 
       FIG. 6  is a plan view showing a photoelectric conversion module according to the second embodiment of the present invention. 
     A photoelectric conversion module  2  according to this embodiment is different from a photoelectric conversion module  1  according to the first embodiment in that a photoelectric conversion element  22  is used instead of a photoelectric conversion element  20  according to the first embodiment and a multicore optical fiber  35  is used instead of an optical fiber  30  according to the first embodiment. 
     The photoelectric conversion element  22  is different from the photoelectric conversion element  20  according to the first embodiment in that the photoelectric conversion element  22  includes a plurality of light receiving/emitting units  25  equal to a light receiving/emitting unit  25  according to the first embodiment and includes the number of terminals  23  based on the number of light receiving/emitting units  25 . Each of the terminals  23  is electrically connected to each of the lands  13  by a wiring line  15 , the number of lands being provided according to the number of terminals  23  provided in the substrate  10 . In the substrate  10  according to this embodiment, terminals  12  as the number corresponding to the number of lands  13  are provided. 
     The multicore optical fiber  35  includes a plurality of optical fibers  30  equal to the optical fiber according to the first embodiment and the plurality of optical fibers  30  is arranged in a planar shape and is integrally gathered by a coating resin  36 . At one end portion of the multicore optical fiber  35 , each optical fiber  30  is led out from the coating resin  36  and a protective layer  33  in the same manner as the optical fiber  30  according to the first embodiment. If a length of a lead-out portion is set to a lead-out length, the lead-out length is preferably 10 μm to 15 mm, more preferably, 1.5 mm to 2.5 mm. 
     One end portion of each of the optical fibers  30  that has been led out is disposed on an element surface  21  of the photoelectric conversion element  22  at a position not overlapping a center of the light receiving/emitting unit  25  in the same manner as the case where one end portion of the optical fiber  30  according to the first embodiment is disposed on an element surface  21  of the photoelectric conversion element  20 . One end portion of each of the optical fibers  30  that have been disposed corresponds to each of the light receiving/emitting units  25  one by one and a center line of each core  31  of each optical fiber  30  is located to substantially overlap the center of each light receiving/emitting unit  25 . One end portion of each optical fiber  30  is more preferably disposed on the element surface  21  of the photoelectric conversion element  22  at a position not overlapping the entire light receiving/emitting unit  25 . 
     In a state in which one end portion of each optical fiber  30  is disposed on the photoelectric conversion element  22 , one end portion of each optical fiber  30  is fixed to the photoelectric conversion element  22  by a plurality of light transmitting resins  41  each of which is disposed to correspond to each optical fiber  30  and which is separated from each other, in the same manner as the case where one end portion of the optical fiber  30  according to the first embodiment is fixed by the light transmitting resin  41 . 
     In the multicore optical fiber  35 , the coating resin  36  and a part of a clad  32  of each optical fiber  30  exposed from the coating resin  36  are fixed to the substrate  10  by a fixing resin  45 . 
     Here, if the multicore optical fiber  35  is cut by a fiber cutter, a position of an end face of each optical fiber  30  may deviate by about 20 μm in a longitudinal direction of the optical fiber  30  in a peak-to-peak manner. Here, when the clad  32  has a general outer diameter of 125 μm, as described above, a deviation of 20 μm corresponds to that D 1 /D 2  deviates by ±0.1. As described above, if an angle θ of a predetermined region of a surface of the light transmitting resin  41  on which light is reflected is 40 degrees to 50 degrees with respect to a line perpendicular to a photoelectric conversion element surface, a coupling loss of light of the core  31  and the light receiving/emitting unit  25  can be sufficiently suppressed even when D 1 /D 2  deviates by about ±0.1 from ±0.5. Therefore, by setting an inclination angle θ of the predetermined region of each light transmitting resin  41  to degrees to 50 degrees with respect to the line perpendicular to the photoelectric conversion element surface, an increase in the coupling loss of the light of the core  31  and the light receiving/emitting unit  25  can be suppressed even if the position of the end face of each optical fiber  30  deviates by about 20 μm in the longitudinal direction of the optical fiber  30  as described above. As such, when the position of the end face of the optical fiber  30  deviates in the longitudinal direction of the optical fiber  30 , the position of each light transmitting resin  41  is preferably deviated in the longitudinal direction of the optical fiber  30  according to the deviation of the end face. 
     In the photoelectric conversion module  2 , when the photoelectric conversion element  22  is a light emitting element, light is emitted from each light receiving/emitting unit  25 , on the basis of an electric signal input to the terminal  12  of the photoelectric conversion module  2 , in the same manner as the photoelectric conversion module  1  according to the first embodiment. The light emitted from each light receiving/emitting unit  25  is reflected by the predetermined region  42  of the surface of each light transmitting resin  41 , is incident on the core  31  of each optical fiber  30 , and propagates through each core  31  from one end portion to the other end portion. 
     On the other hand, in the case where the photoelectric conversion element  20  of the photoelectric conversion module  2  is a light receiving element, if light is emitted from one end portion of each optical fiber  30 , the light emitted from each core  31  is reflected by the predetermined region  42  of the surface of each light transmitting resin  41  and is received by each light receiving/emitting unit  25 . If the light is received by each light receiving/emitting unit  25 , an electric signal is output from the terminal  12  of the photoelectric conversion module  1  in the same manner as the photoelectric conversion module  1  according to the first embodiment. 
     As described above, in the photoelectric conversion module  2  according to this embodiment, even when the multicore optical fiber  35  is used, the outer circumferential surface of the clad  32  of each optical fiber  30  contacts the element surface  21  and each light transmitting resin  41  optically connects the core  31  of each optical fiber  30  and each light receiving/emitting unit  25  individually. Therefore, in the photoelectric conversion module  2 , the loss of the light can be reduced while the multicore optical fiber  35  is used. In addition, according to the photoelectric conversion module  2 , the movement of the end portion of each optical fiber  30  is suppressed in the same manner as the case where the movement of the end portion of the optical fiber  30  according to the first embodiment is suppressed. Therefore, an increase in the coupling loss of the light in the core  31  of the optical fiber  30  and the light receiving/emitting unit  25  of the photoelectric conversion element  20  can be suppressed and height reduction can be realized in the same manner as the photoelectric conversion module  1  according to the first embodiment. 
     &lt;Active Optical Cable&gt; 
     Next, an active optical cable according to this embodiment will be described. 
       FIG. 7  is a plan view showing the active optical cable according to this embodiment. As shown in  FIG. 7 , an active optical cable AC 2  according to this embodiment includes a photoelectric conversion module  2 A and a photoelectric conversion module  2 B. The photoelectric conversion module  2 A and the photoelectric conversion module  2 B use a common multicore optical fiber  35 . 
     The photoelectric conversion module  2 A is a module in which the photoelectric conversion element  22  of the photoelectric conversion module  2  is replaced by a light emitting element  22 A. That is, the photoelectric conversion module  2 A is a light emitting module. 
     The light emitting element  22 A has a plurality of light emitting units  25 A corresponding to the plurality of light receiving/emitting units  25  of the photoelectric conversion element  22  of the photoelectric conversion module  2  and the element surface  21  of the photoelectric conversion module  2  corresponds to a light emitting element surface  21 A of the light emitting element  22 A. In addition, one end portion of each optical fiber  30  is fixed to the light emitting element  22 A. Specifically, one end portion of each optical fiber  30  is led out in the same manner as one end portion of each optical fiber  30  of the photoelectric conversion module  2 . In addition, one end portion of each optical fiber  30  that has been led out is disposed to contact the light emitting element surface  21 A at a position where the outer circumferential surface of the clad  32  does not overlap the center of the light emitting unit  25 A of the light emitting element  22 A. One end portion of each optical fiber  30  disposed in this manner is fixed by a plurality of first light transmitting resins  41 A having the same configurations as the configurations of the plurality of light transmitting resins  41  of the photoelectric conversion module  2  in the same manner as the case where one end portion of each optical fiber  30  of the photoelectric conversion module  2  is fixed to the photoelectric conversion element  22  by each light transmitting resin  41 . One end portion of each optical fiber  30  is more preferably disposed to contact the light emitting element surface  21 A at a position not overlapping the entire portion of each light emitting unit  25 A of the light emitting element  22 A. 
     In addition, the photoelectric conversion module  2 B is a module in which the photoelectric conversion element  22  of the photoelectric conversion module  2  is replaced by a light receiving element  22 B. That is, the photoelectric conversion module  2 B is a light receiving module. 
     The light receiving element  22 B has a plurality of light receiving units  25 B corresponding to the plurality of light receiving/emitting units  25  of the photoelectric conversion element  22  of the photoelectric conversion module  2  and the element surface  21  of the photoelectric conversion module  2  corresponds to a light receiving element surface  21 B of the light receiving element  22 B. In addition, the other end portion of each optical fiber  30  is fixed to the light receiving element  22 B. Specifically, the other end portion of each optical fiber  30  is led out in the same manner as one end portion of each optical fiber  30  of the photoelectric conversion module  2 . The other end portion of each optical fiber  30  that has been led out is then disposed to contact the light receiving element surface  21 B at a position where the outer circumferential surface of the clad  32  does not overlap a center of the light receiving unit  25 B of the light receiving element  22 B. The other end portion of each optical fiber  30  disposed in this manner is fixed by a plurality of second light transmitting resins  41 B having the same configurations as the configurations of the plurality of light transmitting resins  41  of the photoelectric conversion module  1  in the same manner as the case where one end portion of each optical fiber  30  of the photoelectric conversion module  2  is fixed to the photoelectric conversion element  20  by each light transmitting resin  41 . The other end portion of each optical fiber  30  is more preferably disposed to contact the light receiving element surface  21 B at a position not overlapping the entire light receiving unit  25 B of the light receiving element  22 B. 
     In the active optical cable AC 2  having the above configuration, light is emitted from each light emitting unit  25 A, on the basis of an electric signal input to the terminal  12  of the photoelectric conversion module  2 A, in the same manner as the active optical cable AC 1  according to the first embodiment. Each light emitted from each light emitting unit  25 A is reflected by the predetermined region  42  of the surface of each first light transmitting resin  41 A and is incident on the core  31  of each optical fiber  30 . In addition, each light propagates through the core  31  from one end portion of each optical fiber  30  to the other end portion. The light emitted from each core  31  at the other end portion is reflected by the predetermined region  42  of the surface of each second light transmitting resin  41 B and is received by each light receiving unit  25 B. If the light is received by each light receiving unit  25 B, an electric signal is output from the terminal  12  of the photoelectric conversion module  2 B in the same manner as the active optical cable AC 1  according to the first embodiment. 
     As described above, in the active optical cable AC 1 , the loss of the light can be reduced between each optical fiber  30  and each light emitting element  22 A or each light receiving element  22 B in each of the photoelectric conversion modules  1 A and  1 B, in the same manner as the photoelectric conversion module  2 . Therefore, efficient optical communication can be performed. In addition, in the active optical cable AC 2 , the movement of the end portion of each optical fiber  30  in each of the photoelectric conversion modules  2 A and  2 B is suppressed in the same manner as the photoelectric conversion module  2  and an increase in the coupling loss of the light in the core  31  and the light receiving/emitting unit  25  can be suppressed. Therefore, stable optical communication can be performed. In addition, in the active optical cable AC 2 , because each of the photoelectric conversion modules  2 A and  2 B can realize height reduction in the same manner as the photoelectric conversion module  2 , miniaturization can be realized. 
     Although the present invention has been described using the first and second embodiments as the examples, the present invention is not limited thereto. 
     For example, in the second embodiment, each optical fiber  30  has the protective layer  33  and the protective layer  33  is covered by the coating resin  36 . However, the protective layer  33  is not an essential configuration. 
     In addition, in the second embodiment, the photoelectric conversion element  22  has the plurality of light receiving units  25 B. However, a form in which the plurality of light receiving/emitting units is provided is not limited to the second embodiment. Examples of the form can include a form in which the photoelectric conversion module includes a plurality of photoelectric conversion elements  20  equal to the photoelectric conversion element in the first embodiment. In this case, similar to the second embodiment, a plurality of light transmitting resins  41  may be provided and each light transmitting resin  41  may individually fix one end portion of each optical fiber  30  to each photoelectric conversion element  20  and reflect the light by the predetermined region  42  of the surface so that the core  31  of each optical fiber  30  and each light receiving/emitting unit  25  are optically coupled individually. In addition, the number of optical fibers  30  included in the multicore optical fiber  35  according to the second embodiment may be different from the number thereof in the above embodiments. 
     As described above, according to the present invention, the photoelectric conversion module in which the loss of the light is reduced and the active optical cable are provided and can be used as components in vehicles, home appliances, and other fields. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  1 A,  1 B,  2 ,  2 A,  2 B photoelectric conversion module 
           10  substrate 
           15  wiring line 
           20 ,  22  photoelectric conversion element 
           20 A,  22 A light emitting element 
           20 B,  22 B light receiving element 
           21  element surface 
           21 A light emitting element surface 
           21 B light receiving element surface 
           25  light receiving/emitting unit 
           25 A light emitting unit 
           25 B light receiving unit 
           26  light receiving/emitting surface 
           30  optical fiber 
           31  core 
           32  clad 
           33  protective layer 
           35  multicore optical fiber 
           36  coating resin 
           41  light transmitting resin 
           41 A first light transmitting resin 
           41 B second light transmitting resin 
         AC 1 , AC 2  active optical cable