Abstract:
The present invention provides an optical module capable of achieving downsizing and high densification, and reducing crosstalk as compared to a conventional optical module. An optical module includes: an optical device including multiple light receiving elements; a control device which transmits and receives signals to and from the optical device; and a substrate including multiple lines which allow passage of the signals. Anode terminals of the multiple light receiving elements are connected to different lines by first wires, respectively. Cathode terminals of the multiple light receiving elements are connected to different lines by second wires, respectively. Each first wire and the corresponding second wire cross each other and are disposed out of contact with each other. The wires connecting each light receiving element and the control device, namely, the wires of each channel cross each other.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an optical module having a structure in which an optical device including multiple optical elements is connected to a control device by use of wiring. 
         [0003]    2. Description of the Related Art 
         [0004]    There have been growing demands for increases in speed and capacity of optical communication in recent years. To meet the demands, there has been used parallel optical transmission configured to transmit optical signals in parallel by using multiple optical fibers or optical waveguides. 
         [0005]    In an optical module used for the parallel optical transmission, an integrated, downsized, and high-density circuit is subject to an increase in mutual inductance between neighboring wires, which leads to crosstalk between signals traveling through the wires. The crosstalk further increases when high-frequency signals are used therein. For this reason, the occurrence of crosstalk is a major problem in an optical element which uses high-frequency signals. Accordingly, there has been a request for reducing crosstalk in order to pursue downsizing and higher densification of such an optical element. 
         [0006]    As a method of reducing crosstalk between signals, according to the technique described in Japanese Patent Application Publication No. Hei 5-251820, wiring for connecting a laser array to a printed board involves alternate arrangement of lines connected to p-type electrodes of lasers and lines connected to n-type electrodes of the lasers, in which the lines connected to the n-type electrodes are used as the ground. As a result, the wiring has a structure in which each signal line is sandwiched by ground lines, and crosstalk between the signal lines can thereby be reduced. 
         [0007]    Meanwhile, according to the technique described in Japanese Patent Application Publication No. 2002-261372, wiring for connecting an optical device and a driving device involves alternate arrangement of lines connected to anode electrodes of the optical device and lines connected to cathode electrodes of the optical device, in which the lines connected to the cathode electrodes are connected to a reference potential line. As a result, the wiring has a structure in which each signal line is sandwiched by ground lines, and crosstalk between the signal lines can thereby be reduced. 
         [0008]      FIG. 7  is a schematic diagram of an optical module used in the parallel optical transmission, and having a configuration in which signal lines and ground lines are alternately disposed as in the case of the techniques described in Japanese Patent Application Publications No. Hei 5-251820 and No. 2002-261372. The optical module includes: an optical device 2 having multiple optical elements 1; a control device 3 configured to control the optical device 2; and a substrate 4 having multiple lines 4a and 4b on its surface. The control device 3 is disposed on the substrate 4 in such a way as to be in contact with the multiple lines 4a and 4b. Each of the lines 4a and 4b is connected to one end of a wire 5 and the other end of the wire 5 is connected to a corresponding one of an anode terminal 6a and a cathode terminal 6b annexed to each of the multiple optical elements 1. The wires connecting the lines 4a to the anode terminals 6a and the wires connecting the lines 4b to the cathode terminals 6b are alternately disposed along the surface of the substrate 4. According to this configuration, the multiple optical elements 1 and the control device 3 transmit and receive signals therebetween through the lines 4a and 4b, the wires 5, and the terminals 6a and 6b. 
         [0009]    In this optical module, each line 4b connected to the corresponding cathode electrode 6b is connected to the ground on the control device 3 side. Accordingly, the optical module has a structure in which each signal line is sandwiched by ground lines. 
         [0010]    The configuration in which the signal lines and the ground lines are alternately disposed, as in the case of the techniques described in Japanese Patent Application Publications No. Hei 5-251820 and No. 2002-261372, may exhibit an insufficient crosstalk reduction effect along with further advances in the downsizing and the high densification. For this reason, there is a demand for another technique that can further reduce the crosstalk. 
       SUMMARY OF THE INVENTION 
       [0011]    An object of the present invention is to provide an optical module, which is capable of achieving downsizing and high densification, and reducing crosstalk as compared to a conventional optical module. 
         [0012]    A first aspect of the present invention is an optical module including: an optical element including an anode terminal and a cathode terminal; a control device configured to transmit and receive signals to and from the optical element; a first signal path electrically connecting the anode terminal to the control device, at least part of the first signal path being formed from a first conductive line; and a second signal path electrically connecting the cathode terminal to the control device, at least part of the second signal path being formed from a second conductive line. The first conductive line and the second conductive line cross each other and are out of contact with each other. 
         [0013]    A second aspect of the present invention is an optical including: an optical element; a control device including terminals electrically connected to the optical element, an input terminal configured to receive an input signal, and an output terminal configured to transmit an output signal; a first signal path through which the input signal travels to the input terminal, at least part of the first signal path being formed from a first conductive line; and a second signal path through which the output signal travels from the output terminal, at least part of the second signal path being formed from a second conductive line. The first conductive line and the second conductive line cross each other without being in contact with each other. 
         [0014]    The optical module according to the present invention can achieve downsizing and high densification, and reduce crosstalk as compared to a conventional optical module. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic diagram of an optical module according to a first embodiment. 
           [0016]      FIG. 2A  is a perspective view of wires according to the first embodiment. 
           [0017]      FIG. 2B  is a perspective view of wires according to a comparative example. 
           [0018]      FIG. 3A  is a graph showing output signals in an example. 
           [0019]      FIG. 3B  is a graph showing output signals in another example. 
           [0020]      FIG. 3C  is a graph showing output signals in the comparative example. 
           [0021]      FIG. 4A  is a graph showing crosstalk in the example. 
           [0022]      FIG. 4B  is a graph showing crosstalk in the other example. 
           [0023]      FIG. 4C  is a graph showing crosstalk in the comparative example. 
           [0024]      FIG. 5  is a schematic diagram of an optical module according to a second embodiment. 
           [0025]      FIG. 6  is a schematic diagram of an optical module according to a third embodiment. 
           [0026]      FIG. 7  is a schematic diagram of a conventional optical module. 
           [0027]      FIG. 8  is a schematic diagram of an optical module according to a fourth embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Embodiments of the present invention will be described below with reference to the drawings. It is to be noted, however, that the present invention is not limited only to the following embodiments. Meanwhile, in the drawings to be described below, constituents having similar functions will be denoted by the same reference numerals and duplicate description will be omitted when appropriate. 
       First Embodiment 
       [0029]      FIG. 1  is a schematic diagram of an optical module  100  of this embodiment. The optical module  100  includes: an optical device  102  having multiple light receiving elements  101 ; a control device  103  configured to transmit and receive signals to and from the optical device  102 ; and a substrate  104  having multiple lines  104   a  and  104   b  which allow passage of the signals. 
         [0030]    The optical device  102  includes the multiple light receiving elements  101 . Each light receiving element  101  is a photodiode which generates an electric signal upon receipt of light. An arbitrary light receiving element compatible with a high-frequency signal of 1 GHz or higher, or 10 GHz or higher, for example, can be used as the light receiving element  101 . Each light receiving element  101  includes an anode terminal  101   a  and a cathode terminal  101   b , which are located on a surface of the optical device  102 . In this specification, paths for signals related to each light receiving element  101  are called a channel. Although a total of three channels are illustrated in  FIG. 1 , the number of channels is not limited to the foregoing. 
         [0031]    In this embodiment, the optical device  102  is mounted on the substrate  104 . Instead, the optical device  102  may be integrated with the substrate  104 . The optical device  102  may adopt any arbitrary configuration as long as the configuration includes the multiple optical elements disposed in parallel so as to be able to realize the parallel optical transmission. 
         [0032]    The substrate  104  is a printed board, which includes the multiple conductive lines  104   a  and  104   b  on its surface. Each line  104   a  to be connected to a corresponding anode terminal  101   a  will be referred to as an anode line  104   a  and each line  104   b  to be connected to a corresponding cathode terminal  101   b  will be referred to as a cathode line  104   b . The anode lines  104   a  and the cathode lines  104   b  are alternately disposed in parallel with one another. Here, at least as many anode lines  104   a  as the anode terminals  101   a  are provided and at least as many cathode lines  104   b  as the cathode terminals  101   b  are provided. A pitch (an interval) between one of the anode lines  104   a  and the adjacent cathode line  104   b  is set equal to a pitch between one of the anode terminals  101   a  and the adjacent cathode terminal  101   b.    
         [0033]    The control device  103  is an integrated circuit (IC) configured to perform processing by receiving electric signals from the light receiving elements  101 . The control device  103  includes at least as many terminals (not shown) as a sum of the anode terminals  101   a  and the cathode terminals  101   b . The control device  103  is mounted on the substrate  104  in such a way that the terminals of the control device  103  are in contact with the lines  104   a  and  104   b , respectively. Instead, the control device  103  may be integrated with the substrate  104 . 
         [0034]    The control device  103  may adopt any arbitrary configuration as long as the control device  103  is connected to the anode terminals and the cathode terminals of the optical elements by way of wiring and configured to perform transmission and reception of the signals. 
         [0035]    The anode terminals  101   a  of the multiple light receiving elements  101  are connected to different anode lines  104   a  by using first wires  105   a , respectively. The anode terminals  101   a , the first wires  105   a , and the anode lines  104   a  thus connected collectively function as signal paths to transmit signals to the anode terminals  101   a , respectively. In the meantime, the cathode terminals  101   b  of the multiple light receiving elements  101  are connected to different cathode lines  104   b  by using second wires  105   b , respectively. The cathode terminals  101   b , the second wires  105   b , and the cathode lines  104   b  thus connected collectively function as signal paths to transmit signals from the cathode terminals  101   b , respectively. 
         [0036]    An anode terminal  101   a  and a cathode terminal  101   b  provided to one light receiving element  101 , i.e., related to the same channel, are respectively connected to two lines  104   a  and  104   b  that are adjacent to each other. 
         [0037]    In the state where the terminals are connected to the lines, each first wire  105   a  and the adjacent second wire  105   b  cross each other and are disposed out of contact with each other.  FIG. 2A  is a perspective view showing a three-dimensional layout of the first wires  105   a  and the second wires  105   b  of this embodiment. The first wire  105   a  connecting the anode terminal  101   a  to the anode line  104   a  is disposed in a crossing manner above and away from the second wire  105   b  connecting the cathode terminal  101   b  to the cathode line  104   b . This configuration establishes a crossing state of the wires connecting the respective light receiving elements  101  to the control device  103 , i.e., the wiring for the channels. In this specification, the above-described structure in which the wires for the same channel are connected in a crossing manner while avoiding the contact therebetween will be referred to as cross wiring. 
         [0038]    In this embodiment, the first wire  105   a  passes over the second wire  105   b . Instead, the first wire  105   a  may pass under the second wire  105   b  as long as the first wire  105   a  and the second wire  105   b  cross each other without coming into contact with each other. 
         [0039]    The wires in each of the same channels come close to each other by applying the cross wiring to the wiring between the light receiving elements  101  and the control device  103 . Accordingly, electromagnetic field coupling in each of the same channels is enhanced. In the meantime, coupling between different channels adjacent to each other is suppressed. As a result, crosstalk between the different channels is thought to be significantly reduced. 
         [0040]    In order to enhance the electromagnetic coupling in the same channel, it is desirable that the first wire  105   a  and the second wire  105   b  be located close to each other. To be more precise, a difference in height between the first wire  105   a  and the second wire  105   b  is preferably not more than 1.5 times the pitch (the interval between the anode terminal and the cathode terminal, and the interval between the lines) while keeping the first wire  105   a  and the second wire  105   b  away from each other at the crossing portion of the first wire  105   a  and the second wire  105   b . It is more preferable that the difference in height between the first wire  105   a  and the second wire  105   b  be about equal to or below the pitch. 
         [0041]    This embodiment employs the configuration in which all the pitches between the anode terminals  101   a  and the corresponding cathode terminals  101   b  are equal, and all the pitches between the anode lines  101   a  and the corresponding cathode lines  101   b  are equal. However, the pitches may vary in another applicable configuration. In this case, the pitch (hereinafter referred to as an intra-channel pitch) between the anode terminal  101   a  and the cathode terminal  101   b  in the same channel is preferably set equal to or below the pitch (hereinafter referred to as an inter-channel pitch) between the anode terminal  101   a  (or the cathode terminal  101   b ) of the aforementioned channel and the cathode terminal  101   b  (or the anode terminal  101   a ) of a channel adjacent to the aforementioned channel. 
         [0042]    In the configuration where the pitches vary, the difference in height between the first wire  105   a  and the second wire  105   b  is preferably not more than 1.5 times the inter-channel pitch while keeping the first wire  105   a  and the second wire  105   b  away from each other at the crossing portion of the first wire  105   a  and the second wire  105   b . It is more preferable that the difference in height between the first wire  105   a  and the second wire  105   b  be about equal to or below the inter-channel pitch. 
       EXAMPLES 
       [0043]    Crosstalk reduction effects according to the present invention were checked by means of simulation. In the simulation, AWR Microwave Office was used. 
         [0044]    Example 1 employed the configuration of the first embodiment. Conditions of the simulation were set as described below. In Example 1, the difference in height between the first wire  105   a  and the second wire  105   b  was set smaller than the pitch. 
         [0045]    Flat Surface Length: 0.3716 mm 
         [0046]    Height (First Wire): 0.175 mm 
         [0047]    Height (Second Wire): 0.1 mm 
         [0048]    Pitch: 0.125 mm 
         [0049]    Example 2 had a configuration in which only the height of the first wire was different from that in Example 1. Conditions of the simulation were set as described below. In Example 2, the difference in height between the first wire  105   a  and the second wire  105   b  was set equal to the pitch. 
         [0050]    Flat Surface Length: 0.3716 mm 
         [0051]    Height (First Wire): 0.225 mm 
         [0052]    Height (Second Wire): 0.1 mm 
         [0053]    Pitch: 0.125 mm 
         [0054]    Example 3 had a configuration in which only the height of the first wire was different from that in Example 1. Conditions of the simulation were set as described below. In Example 3, the difference in height between the first wire  105   a  and the second wire  105   b  was set about 1.5 times the pitch. 
         [0055]    Flat Surface Length: 0.3716 mm 
         [0056]    Height (First Wire): 0.275 mm 
         [0057]    Height (Second Wire): 0.1 mm 
         [0058]    Pitch: 0.125 mm 
         [0059]    Comparative Example had a configuration in which each first wire  105   a  and the corresponding second wire  105   b  did not cross each other (hereinafter referred to as straight wiring).  FIG. 2B  is a perspective view showing a three-dimensional layout of the first wires  105   a  and the second wires  105   b  in Comparative Example. Features other than the mode of connecting the wires were similar to those of Examples. Conditions of the simulation were set as described below. 
         [0060]    Flat Surface Length: 0.35 mm 
         [0061]    Height (First Wire): 0.1 mm 
         [0062]    Height (Second Wire): 0.1 mm 
         [0063]    Pitch: 0.125 mm 
         [0064]    The flat surface length is the length of each wire in a direction parallel to the substrate, and the height is the length of each wire in a direction perpendicular to the substrate. The pitch is the interval between the anode terminal and the cathode terminal, and is also the interval between the lines equal to the above. Here, distances between the line  104   a  or  104   b  and the corresponding terminal  101   a  or  101   b  were set equal in all Examples and Comparative Example. However, the flat surface length in each of Examples was longer than that in Comparative Example since Examples adopted the cross wiring. 
         [0065]    In general, a channel that brings about crosstalk is called an aggressor channel while a channel that suffers the crosstalk is called a monitor channel. The simulation was conducted by creating a model in which one monitor channel (B in  FIGS. 2A and 2B ) to which no voltage was applied was sandwiched between two aggressor channels (A and C in  FIGS. 2A and 2B ) to which voltages were applied. Then, voltages on the respective channels were measured by means of the simulation. 
         [0066]      FIGS. 3A to 3C  are graphs showing the voltages measured on the aggressor channels.  FIG. 3A  shows a result of Example 1,  FIG. 3B  shows a result of Example 2, and  FIG. 3C  shows a result of Comparative Example. In each of  FIGS. 3A to 3C , the horizontal axis indicates time and the vertical axis indicates the voltage. 
         [0067]    From  FIGS. 3A to 3C , it is clear that the voltages on the aggressor channels varied little among Examples and Comparative Example. In any of the aggressor channels of Examples and Comparative Examples, a peak-to-peak voltage Vpp was around 0.58 V. It was thus confirmed that the adoption of the cross wiring did not cause any deterioration of output signals as compared to the straight wiring, and that the cross wiring was able to achieve signal transmission equivalent to that of the straight wiring. 
         [0068]      FIGS. 4A to 4C  are graphs showing the voltages measured on the monitor channels.  FIG. 4A  shows a result of Example 1,  FIG. 4B  shows a result of Example 2, and  FIG. 4C  shows a result of Comparative Example. In each of  FIGS. 4A to 4C , the horizontal axis indicates the time and the vertical axis indicates the voltage. 
         [0069]    Since no voltage was applied to any of the monitor channels, the voltage measured on each monitor channel showed an amount of crosstalk from the aggressor channels. From  FIGS. 4A to 4C , it is clear that the amount of crosstalk in each Example was smaller than the amount of crosstalk in Comparative Example. 
         [0070]    Specifically, while the value Vpp in Comparative Example was about 0.019 V (−29.6 dB), the value Vpp in Example 1 was reduced to about 0.0080 V (−37.1 dB) and the value Vpp in Example 2 was reduced to about 0.0097 V (−35.5 dB). Meanwhile, the value Vpp in Example 3, which is not illustrated, was reduced to about 0.010 V (−35.2 dB). Accordingly, it was confirmed that the crosstalk was able to be significantly reduced, as compared to the straight wiring, by applying the cross wiring to micro circuits like those used in the simulation. 
       Second Embodiment 
       [0071]      FIG. 5  is a schematic diagram of an optical module  200  of this embodiment. In the optical module  100  of the first embodiment, the height of the first wire  105   a  is different from the height of the second wire  105   b , and the length (the total length) of the first wire  105   a  is therefore different from the length (the total length) of the second wire  105   b . On the other hand, the optical module  200  of this embodiment is configured to establish equal length wiring in which the length of the first wire  105   a  becomes equal to the length of the second wire  105   b . The establishment of the equal length wiring makes it possible to further enhance the crosstalk reduction effect and to achieve an additional effect that no signal delays occur between the wires. 
         [0072]    The optical module  200  has the same constituents as does the optical module  100  of the first embodiment, but only the layout of the constituents is different. 
         [0073]    In the optical module  200 , the first wire  105   a  connecting the anode terminal  101   a  to the anode line  104   a  is disposed in a crossing manner above and away from the second wire  105   b  connecting the cathode terminal  101   b  to the cathode line  104   b . At this time, the difference in height between the first wire  105   a  and the second wire  105   b  is compensated for by disposing the wires in such a way that a distance between the anode terminal  101   a  and the anode line  104   a  to be connected to the first wire  105   a  located above (i.e., a distance between the one end and the other end of the first wire  105   a ) becomes smaller than a distance between the cathode terminal  101   b  and the cathode line  104   b  to be connected to the second wire  105   b  located below (i.e., a distance between the one end and the other end of the second wire  105   b ). In the optical module  200 , the relative positions of the terminals  101   a ,  101   b  between the lines  104   a ,  104   b  are displaced in the direction of the surface of the substrate  104  such that the lengths of the first wire  105   a  and the second wire  105   b  become equal. 
         [0074]    On the other hand, when the first wire  105   a  passes under the second wire  105   b , the wires may be disposed in such a way that the distance between the anode terminal  101   a  and the anode line  104   a  to be connected to the first wire  105   a  located below becomes larger than the distance between the cathode terminal  101   b  and the cathode line  104   b  to be connected to the second wire  105   b  located above. 
       Third Embodiment 
       [0075]      FIG. 6  is a schematic diagram of an optical module  300  of this embodiment. The optical module  300  is characterized in that the optical module of the first embodiment further applies cross wiring to input-output wiring on the opposite side from the optical device  102  with respect to the control device  103 . This configuration can further enhance the crosstalk reduction effect. Only portions that are different from those of the first embodiment, i.e., the portions on the opposite side from the optical device  102  with respect to the control device  103  will be described herein. 
         [0076]    The control device  103  of the optical module  300  further includes input terminals  103   a  and output terminals  103   b . At least as many input terminals  103   a  and output terminals  103   b  as the optical elements  101  are provided. Each pair of the input terminal  103   a  and the output terminal  103   b  adjacent to each other perform the input and output of signals to and from one optical element  101  (i.e., one channel). 
         [0077]    The substrate  104  of the optical module  300  includes multiple conductive lines  107   a  and  107   b  located on the opposite side from the optical device  102  across the control device  103 . Each line  107   a  to be connected to its corresponding input terminal  103   a  will be referred to as an input line  107   a  while each line  107   b  to be connected to its corresponding output terminal  103   b  will be referred to as an output line  107   b . The input lines  107   a  and the output lines  107   b  are alternately provided in such a way as to be adjacent to one another. At least as many input lines  107   a  and output lines  107   b  as the optical elements  101  are provided. 
         [0078]    In this embodiment, the lines  104   a ,  104   b  and the lines  107   a ,  107   b  are provided on the same substrate. However, the lines  107   a  and  107   b  may be provided on a substrate different from the one provided with the lines  104   a  and  104   b.    
         [0079]    The input terminals  103   a  are connected to different input lines  107   a  by third wires  105   c , respectively. The input terminals  103   a , the third wires  105   c , and the input lines  107   a  thus connected collectively function as signal paths to transmit signals to the input terminals  103   a , respectively. In the meantime, the output terminals  103   b  are connected to different output lines  107   b  by fourth wires  105   d , respectively. The output terminals  103   b , the fourth wires  105   d , and the output lines  107   b  thus connected collectively function as signal paths to transmit signals from the output terminals  103   b , respectively. 
         [0080]    An input terminal  103   a  and an output terminal  103   b  related to each of the same channels are respectively connected to two lines  107   a  and  107   b  that are adjacent to each other. 
         [0081]    In the state where the terminals are connected to the lines, each third wire  105   c  and its adjacent fourth wire  105   d  cross each other and are disposed out of contact with each other. A three-dimensional layout of the third wires  105   c  and the fourth wires  105   d  is similar to the three-dimensional layout of the first wires  105   a  and the second wires  105   b  shown in  FIG. 2A . The third wire  105   c  connecting the input terminal  103   a  to the input line  107   a  is disposed in a crossing manner above and away from the fourth wire  105   d  connecting the output terminal  103   b  to the output line  107   b . This configuration establishes a crossing state of the wires connecting the respective terminals  103   a  and  103   b  to the corresponding lines  107   a  and  107   b , i.e., the wirings for the respective channels. 
         [0082]    In this embodiment, the third wire  105   c  passes over the fourth wire  105   d . Instead, the third wire  105   c  may pass under the fourth wire  105   d  as long as the third wire  105   c  and the fourth wire  105   d  cross each other without coming into contact with each other. 
         [0083]    The wires in each of the same channels come close to each other by applying the cross wiring to the wiring between the control device  103  and the input lines  107   a  as well as between the control device  103  and the output lines  107   b , whereby electromagnetic field coupling in each of the same channels is enhanced. In the meantime, coupling between different channels adjacent to each other is suppressed. As a result, crosstalk between the different channels is thought to be significantly reduced. 
         [0084]    In this embodiment, the optical device is connected to the control device by the cross wiring, and the input-output wiring of the control device on the opposite side from the optical device employs the cross wiring at the same time. It is to be noted, however, that the crosstalk reduction effect is obtainable by applying the cross wiring to any portion of the wiring in one channel. Accordingly, the crosstalk can be reduced by connecting the optical device to the control device by the straight wiring, and applying the cross wiring only to the input-output wiring of the control device on the opposite side from the optical device. 
       Fourth Embodiment 
       [0085]      FIG. 8  is a schematic diagram of an optical module  400  of this embodiment. The optical module  400  is characterized in that input terminals  103   c  and output terminals  103   d  are provided on the optical device  102  side of the control device  103 , instead of the lines  104   a  and  104   b , in the optical module of the third embodiment. Only portions that are different from those of the third embodiment, i.e., the portions on the optical device  102  side with respect to the control device  103  will be described herein. 
         [0086]    The control device  103  of the optical module  400  further includes input terminals  103   c  and output terminals  103   d . At least as many input terminals  103   c  and output terminals  103   d  as the optical elements  101  are provided. Each pair of the input terminal  103   c  and the output terminal  103   d  adjacent to each other perform the input and output of signals to and from one optical element  101  (i.e., one channel). 
         [0087]    The anode terminals  101   a  of the multiple optical elements  101  are connected to different input terminals  103   c  by first wires  105   a , respectively. The anode terminals  101   a , the first wires  105   a , and the input terminals  103   c  thus connected collectively function as signal paths to transmit signals to the anode terminals  101   a , respectively. In the meantime, the cathode terminals  101   b  of the multiple optical elements  101  are connected to different output terminals  103   d  by second wires  105   b , respectively. The cathode terminals  101   b , the second wires  105   b , and the output terminals  103   d  thus connected collectively function as signal paths to transmit signals from the cathode terminals  101   b , respectively. 
         [0088]    An anode terminal  101   a  and a cathode terminal  101   b  of one optical element  101 , or in other words related to the same channel, are respectively connected to two terminals  103   c  and  103   d  that are adjacent to each other. 
         [0089]    In this embodiment, the lines  104   a  and  104   b  of the third embodiment are not provided, and the first wires  105   a  and the second wires  105   b  are directly connected to the input terminals  103   c  and the output terminals  103   d  of the control device  103 , respectively. Accordingly, the lengths of signal paths can be configured short so that qualities of signals themselves are improved, while the effect of reducing crosstalk is obtained even more. 
         [0090]    Please note that the configuration of this embodiment can be applied to the first or second embodiments. This is achieved by providing the input terminals  103   c  and the output terminals  103   d  on the optical device  102  side of the control device  103 , instead of the lines  104   a  and  104   b.    
         [0091]    The present invention is not limited only to the above-described embodiments, and various changes are possible within the scope not departing from the gist of the present invention. 
         [0092]    The wiring connecting the terminals to the lines may use any conductive lines other than the wires as long as such conductive lines fulfill a connection method that can establish the cross wiring. The cross wiring may be established by: forming bumps on the terminals and lines; and joining the bumps by using conductive bodies. Meanwhile, the cross wiring may be established by: forming the wire passing on a lower side of the crossing portion as a wiring pattern on a printed board; and forming the wire passing on an upper side of the crossing portion as a wire or a bump. 
         [0093]    The cross wiring may be formed from wires directly connecting the terminals of the light receiving element and the terminals of the control device without the assistance of any lines on the substrate. 
         [0094]    When the optical module is caused to function as a light emission module, a light emitting element such as an edge emitting laser and a vertical cavity surface emitting laser (VCSEL) may be used in place of the light receiving element. In this case, the control device applies a voltage for causing light emission to the light emitting element through the wires and the terminals. 
         [0095]    The essence of the present invention is to apply the cross wiring to the wiring used in the optical module. Accordingly, the optical module of the present invention can use any optical element which is configured to perform at least any of light emission or light reception by transmission and reception of signals through an anode terminal and a cathode terminal.