Abstract:
An optical waveguide device includes a first substrate, where the first substrate includes a first plate and an optical waveguide region disposed on the first plate, and where the optical waveguide region includes a core for transmitting light and a cladding surrounding the core. The optical waveguide device further includes a second substrate, where the second substrate includes a second plate having a spacer. Additionally, a surface including the optical waveguide region of the first substrate opposes a surface including the spacer of the second substrate, the spacer is formed the region which is out of the core of the first substrate, a top surface of the spacer is in contact with the first substrate, the first substrate and the second substrate are bound with adhesive material, and the entire surface of the core is in contact with the adhesive material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This patent application is a continuation application of U.S. patent application Ser. No. 10/611,684, filed Jul. 1, 2003 now U.S. Pat. No, 7,013,055. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optical waveguide device which adds an optical fiber guide and an optical element placing portion for mounting an optical fiber, a light emitting element, a light receiving element, or the like and light modulating function to an optical waveguide for transmitting light in a core, a manufacturing method of the optical waveguide device, and an optical communication apparatus which uses the optical waveguide device. 
   2. Description of the Background Art 
   In a joint portion or an end portion of the optical fiber cable used for optical communication, the optical waveguide device is used in order to connect the optical fiber cable to other optical fiber cable, the light emitting element, or the light receiving element. In recent years, utilization of optical communication that can transmit large-capacity data at high speed has progressed. Thus, the manufacturing of an optical waveguide device that is inexpensive and suitable for mass production is desired. 
     FIG. 1  is a schematically perspective view of an optical waveguide device  1  which is conventionally used. As shown in  FIG. 2 , the optical waveguide device  1  includes an optical waveguide  6  and a supporting substrate  7 . The optical waveguide device  1  can be used in such a manner that the optical waveguide  6  is put on an optical waveguide placing portion  12  of the supporting substrate  7 , and a core  4  of the optical waveguide is connected to the optical fiber, a light emitting element  8 , light receiving element  10 , or the like. 
   The optical waveguide  6  includes a substrate  2 , the core  4  for transmitting a light therein, a lower cladding layer  3  and an upper cladding layer  5  which surround the core  4 , and a filter  13   d . The core  4 , the lower cladding layer  3 , and the upper cladding layer  5  are made of a substance, such as resin or glass, which has relatively large refractive index. So that the light is trapped in the core  4  and propagated, the refractive index of the core  4  need be large compared with the refractive indices of the lower cladding layer  3  and the upper cladding layer  5 . The filter  13   d  is the optical element having characteristics which transmit the light having a specific wavelength and reflect the light having the wavelengths except the specific wavelength. The filter  13   d  is used by placing it in a filter placing groove  13   c  which is formed in the optical waveguide  6  so that the core  4  is divided into a core  4   a  and cores  4   b  and  4   c.    
   An optical fiber guide  9  for positioning and placing the optical fiber, which has a V-shaped groove in cross section, and an optical fiber placing portion  12  for putting the optical waveguide  6  on it are formed on the supporting substrate  7  formed by etching a silicon substrate  11 . On the supporting substrate  7 , the light emitting element  8  such as a laser diode (LD) or a light emitting diode (LED), the light receiving element, and the like  10  are placed while an end face of the core  4  is aligned with an optical axis of the transmitting light. A lead and wire bonding pads  13   a  and  13   b  for applying electric power to the light emitting element  8  and the light receiving element  10  is formed on the supporting substrate  7 . 
   In the manufacturing of the optical waveguide device  1  in the conventional art, the optical waveguide  6  and the supporting substrate  7  were produced separately, and the optical waveguide  6  and the supporting substrate  7  were bonded one by one with the bonding resin to produce the optical waveguide device  1 . Accordingly, a manufacturing process became complicated, it took much time and cost for the manufacturing process, and the mass production could not be efficiently performed. Further, since the individual optical waveguide  6  and supporting substrate  7  are minute components, it took much time and cost to precisely align the optical waveguide  6  and supporting substrate  7  to assemble the optical waveguide device  1 , and it was difficult to improve net productivity. 
   On the other hand, a plurality of optical waveguides  6  and a plurality of supporting substrates  7  are formed on wafers or mother boards respectively, the two wafers or the two mother boards are bonded together, and then the bonded body is divided into the individual optical waveguide devices. As a result, the productivity is improved. However, in the optical waveguide device  1  in which the pad portion for mounting the light emitting element  8  or the light receiving element  10  and the optical fiber guide  9  are provided in the supporting substrate  7 , since the light emitting element and the light receiving element are finally mounted on the pad portion and the optical fiber need be fixed to the optical fiber guide  9 , it is necessary to expose the pad portion and the optical fiber guide  9 . Accordingly, in the method in which the plurality of optical waveguides  6  and the plurality of supporting substrates  7  are formed on the wafer or the mother board respectively and the both wafers or the both the mother boards are bonded over the surfaces, it is difficult to expose the optical fiber guide  9  or the pad portion, and possibility of the manufacturing method was low in the optical waveguide device having the optical fiber guide  9  or the pad portion. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing, it is an object of the invention to provide the manufacturing method of the optical waveguide device which simplifies the manufacturing process of the optical waveguide device and is suitable for the mass production. 
   A manufacturing method of an optical waveguide device according to a first aspect of the invention, including the steps of bonding a first substrate having an optical waveguide region, which includes a core transmitting light and a cladding surrounding the core, and a second substrate having a functional region over almost a whole surface, opposing at least a part of the functional region to an outside of the optical waveguide region in the first substrate, and removing an unnecessary part of the first substrate opposite to the functional region. At this point, the functional region provided in the second substrate is the region concerning the optical modulating function, in which the light emitting element or the light receiving element, an element mounting bench or the optical fiber guide for mounting the element such as the optical fiber or the component, a heater, or an electrode is formed. The optical waveguide region may include the filter or the heater element which influences the light propagating through the core. Further, the optical waveguide region may be provided in a whole of the first substrate, may be provided in a part of the first substrate, or may be the first substrate itself. 
   In the above-described manufacturing method of the optical waveguide device according to the first aspect of the invention, even if the first substrate and the second substrate are bonded over almost the whole surface, the functional region of the second substrate can be exposed to mount a predetermined element or component on the functional region in a manner that removes the unnecessary part opposite to the region where the functional region is formed in the first substrate. Accordingly, in bonding the first substrate and the second substrate, it is not necessary to apply the bonding resin onto a predetermined pattern except the unnecessary part of the first substrate, the bonding process of the first and second substrates can be simplified, and the manufacturing process of the optical waveguide device can be also simplified. 
   A manufacturing method of an optical waveguide device according to a second aspect of the invention, including the steps of bonding a first substrate having a plurality of optical waveguide regions, which include a core transmitting light and a cladding surrounding the core, and a second substrate having a plurality of functional regions over almost a whole surface, opposing at least a part of each of the functional regions to an outside of each optical waveguide region in the first substrate, and separating the first and the second substrates into individual optical waveguide devices including the optical waveguide region and the functional region, while an unnecessary part of the first substrate opposite to the functional region is removed. 
   In the above-described manufacturing method of the optical waveguide device according to the second aspect of the invention, even if the plurality of optical waveguide devices are simultaneously produced from the first substrate of the mother board and the second substrate of the mother board, after the first substrate of the mother board and the second substrate of the mother board are bonded over almost the whole surface, the unnecessary part of the first substrate can be removed to expose the functional region and the first and second substrates can be divided into the individual optical waveguide devices. Accordingly, after the first substrate of the mother board and the second substrate of the mother board are separately cut off, compared with the case in which the cut-off first and second substrates are bonded one by one, the manufacturing process of the optical waveguide device can be remarkably simplified and the productivity can be improved. 
   A manufacturing method of an optical waveguide device according to a third aspect of the invention, in which an uncured layer of a bonding resin is left between the first substrate and the second substrate in a region where the functional region is formed in bonding the first substrate and the second substrate, and the unnecessary part of the first substrate opposite to the functional region is removed by the uncured layer. In order to leave the uncured layer of the bonding resin between the first substrate and the second substrate, for example the photo-curing bonding resin such as a ultraviolet-curing resin is applied between the first and second substrates, then, the region which is left as the uncured layer may be covered with a mask, and the bonding resin may be irradiated with the light or an electron beam to partly cure the bonding resin. 
   In the above-described manufacturing method of the optical waveguide device according to the third aspect of the invention, in bonding the first substrate and the second substrate, the bonding resin is left at the uncured state in the region corresponding to the unnecessary part of the first substrate by partly curing the bonding resin, so that the unnecessary part can be simply removed to expose the functional region without injuring the functional region only by cutting off a periphery of the unnecessary part of the first substrate. 
   A manufacturing method of an optical waveguide device according to a forth aspect of the invention, in which a layer having low adhesive properties is formed in the unnecessary part of the first substrate opposite to the functional region or the region of the second substrate opposite to the unnecessary part before bonding the first substrate and the second substrate, and the unnecessary part of the first substrate opposite to the functional region is removed by the layer having low adhesive properties. At this point, the layer having low adhesive properties is not limited in particular, and the layer having the low adhesive properties may be the layer made of a metal film such as Ni or Au, an oxide film such as SiO 2 , or fluororesin such as PTFE, which is difficult material to be bonded by the bonding resin used, the layer having the bad adhesive properties with the substrate, or the layers in which the layers having the bad adhesive properties with each other are laminated. 
   In the above-described manufacturing method of the optical waveguide device according to the forth aspect of the invention, before the first substrate and the second substrate are bonded with the bonding resin, the layer having low adhesive properties is formed at the position corresponding to the unnecessary part of the first substrate in the first substrate or the second substrate, so that the unnecessary part can be removed to expose the functional region without injuring the functional region only by cutting off the periphery of the unnecessary part of the first substrate. 
   A manufacturing method of an optical waveguide device according to a fifth aspect of the invention, in which a boundary between the region to be removed in the first substrate and the region to be left is cut off by dicing to remove the unnecessary part of the first substrate, so that the unnecessary part of the first substrate can be easily removed. Particularly in the case that the plurality of optical waveguide devices are simultaneously produced, the process for removing the unnecessary part of the first substrate and the process for separating the first and second substrates into the individual optical waveguide devices can be performed at the same time and the manufacturing process of the optical waveguide device can be simplified. 
   A manufacturing method of an optical waveguide device according to a sixth aspect of the invention, including the steps of forming a first substrate by providing an optical waveguide region, which includes a core transmitting light and a cladding surrounding the core, on a substrate which transmits light, bonding the first substrate to a second substrate which does not sufficiently transmit the light, and removing the substrate which transmits light. In the above-described manufacturing method of the optical waveguide device according to the sixth aspect of the invention, the substrate which transmits the light is removed, so that the optical waveguide device can be thinned. 
   A manufacturing method of an optical waveguide device according to a seventh aspect of the invention, including the steps of forming a first substrate by providing an optical waveguide region, which includes a core transmitting light and a cladding surrounding the core, on a substrate which transmits light, bonding the first substrate to a second substrate, which has a functional region and does not sufficiently transmit the light, over almost a whole surface, opposing at least a part of the functional region to an outside of the optical waveguide region in the first substrate, removing the substrate which transmits the light, and removing an unnecessary part of the first substrate opposite to the functional region. 
   In the above-described manufacturing method of the optical waveguide device according to the seventh aspect of the invention, even if the first substrate and the second substrate have been bonded over almost the whole surface, by removing the unnecessary part opposite to the region in which the functional region is formed in the first substrate, the functional region of the second substrate can be exposed and the predetermined element or component can be mounted on the functional region. Accordingly, in bonding the first substrate and the second substrate, it is not necessary to apply the bonding resin onto the predetermined pattern except the unnecessary part of the first substrate, the bonding process of the first and second substrates can be simplified, and the manufacturing process of the optical waveguide device can be also simplified. Further, in the above-described manufacturing method of the optical waveguide device according to the seventh aspect of the invention, the substrate which transmits the light is removed, so that the optical waveguide device can be thinned. 
   In a manufacturing method of an optical waveguide device according to the invention according to the eighth aspect of the invention, in which the substrate transmitting the light on the sixth aspect or seventh aspect is removed by peeling off the substrate. In the above-described manufacturing method of the optical waveguide device according to the eighth aspect of the invention, the substrate transmitting the light is removed by peeling off the substrate, so that the substrate transmitting the light can be re-used and the cost of the manufacturing can be reduced. 
   A manufacturing method of an optical waveguide device according to a ninth aspect of the invention, further including a step of forming the optical waveguide region on the sixth aspect or seventh aspect in such a manner that a stamper is pressed to a photo-curing resin to transfer a shape of the stamper to the photo-curing resin and the photo-curing resin is irradiated with the light to cure the photo-curing resin. In the above-described manufacturing method of the optical waveguide device according to the ninth aspect of the invention, it is not necessary to take the time for heating in the case of the use of a thermal-curing resin, and the productivity of the optical waveguide region having the minute core can be increased. 
   A manufacturing method of an optical waveguide device according to a tenth aspect of the invention, in which a groove is formed in the first substrate so as to separate the core after removing the substrate which transmits the light, and a filter is inserted the groove. In the above-described manufacturing method of the optical waveguide device according to the tenth aspect of the invention, since the groove for the filter is provided after the excess substrate is removed, it is not necessary to provide the groove for the filter in the substrate transmitting the light, a blade can be prevented from cracking by the substrate transmitting the light in providing the groove with a dicing blade. Further, only the groove may be provided in the cladding or the like, so that the thinner groove can be formed. 
   A manufacturing method of an optical waveguide device according to the eleventh aspect of the invention, in which the first substrate and the second substrate are bonded with a bonding resin having almost the same refractive index as that of the cladding. In the above-described manufacturing method of the optical waveguide device according to the eleventh aspect of the invention, since the first substrate having the core and the cladding and the second substrate are bonded with the bonding resin having almost the same refractive index as that of the cladding, the bonding resin functions as the cladding after the optical waveguide device is completed. 
   According to the manufacturing method of the optical waveguide device according to the invention, the optical waveguide device can be produced. In the optical waveguide device, when the cross section of the core is formed in almost trapezoid-shaped, mold release characteristics can be held at good conditions in molding the core groove. Further, the optical waveguide device which is produced by the manufacturing method according to the invention can be used as the optical communication apparatus. 
   The above-described constituent components of the invention may be optionally combined as many as possible. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a schematically perspective view of an optical waveguide device of the related art. 
       FIG. 2  shows a schematically exploded perspective view of the optical waveguide device shown in  FIG. 1 . 
       FIG. 3  shows a schematically perspective view of the optical waveguide device according to an embodiment of the invention. 
       FIG. 4  shows a schematically exploded view of the optical waveguide device shown in  FIG. 3 . 
       FIG. 5  shows a schematically plane view illustrating a using mode of the optical waveguide device shown in  FIG. 3 . 
       FIG. 6  shows a view explaining a manufacturing method of the optical waveguide device of the invention. 
       FIG. 7  shows a continued view of  FIG. 6 . 
       FIG. 8  shows a continued view of  FIG. 7 . 
       FIGS. 9A to 9D  show sectional views taken on line A–A′ of  FIG. 8 , which explains a process to a manufacturing process of a core. 
       FIG. 10  shows a continued view of  FIG. 8 . 
       FIG. 11  shows a continued view of  FIG. 10 . 
       FIG. 12  shows a continued view of  FIG. 11 . 
       FIG. 13  shows a continued view of  FIG. 12 . 
       FIG. 14  shows a schematically perspective view of the optical waveguide device according to another embodiment of the invention. 
       FIG. 15  shows a schematically perspective view of a supporting substrate which is used for manufacturing the optical waveguide device shown in  FIG. 14 . 
       FIG. 16A  shows a plane view corresponding to a cross section taken on line D–D′ of  FIG. 14 , which explains the manufacturing method of the optical waveguide device shown in  FIG. 14 , and  FIG. 16B  shows a sectional view taken on line D–D′ of  FIG. 14 . 
       FIG. 17  is a schematically perspective view of the optical waveguide device according to still another embodiment of the invention. 
       FIGS. 18A to 18C  show views explaining the manufacturing process of the optical waveguide device shown in  FIG. 17 . 
       FIGS. 19A to 19C  show continued views of  FIG. 18 . 
       FIGS. 20A and 20B  show continued views of  FIG. 19 . 
       FIG. 21  shows a schematically exploded perspective view of the optical waveguide device according to still another embodiment of the invention. 
       FIG. 22  shows a view explaining the manufacturing method of the optical waveguide device shown in  FIG. 21 . 
       FIG. 23  shows a schematically perspective view of the optical waveguide device according to still another embodiment of the invention. 
       FIG. 24  shows a schematically exploded view of the optical waveguide device shown in  FIG. 23 . 
       FIG. 25  shows a schematic plane view of the optical waveguide device shown in  FIG. 23 . 
       FIGS. 26A to 26D  show views explaining the manufacturing process of the optical waveguide device shown in  FIG. 23 . 
       FIGS. 27A and 27B  show continued views of  FIG. 26 . 
       FIG. 28  shows a schematically perspective view of the optical waveguide device according to still another embodiment of the invention. 
       FIG. 29  shows a schematically exploded perspective view of the optical waveguide device shown in  FIG. 28 . 
       FIG. 30  shows a schematic plane view explaining the using mode of the optical waveguide device shown in  FIG. 28 . 
       FIG. 31  shows a perspective view illustrating the manufacturing method of the optical waveguide device shown in  FIG. 28 . 
       FIGS. 32A and 32B  show continued views of  FIG. 31 . 
       FIG. 33  shows a continued view of  FIG. 32 . 
       FIG. 34  shows a continued view of  FIG. 33 . 
       FIG. 35  shows a continued view of  FIG. 34 . 
       FIG. 36  shows a schematically sectional view of the optical waveguide device according to still another embodiment of the invention. 
       FIG. 37  shows an exploded perspective view of the optical waveguide device according to still another embodiment of the invention. 
       FIG. 38  shows a perspective view of the optical waveguide device according to still another embodiment of the invention. 
       FIG. 39  shows an exploded perspective view of the optical waveguide device shown in  FIG. 38 . 
       FIG. 40  shows a plane view of the optical waveguide device shown in  FIG. 38 . 
       FIG. 41  shows a schematically sectional view explaining the manufacturing method of the optical waveguide device shown in  FIG. 38 . 
       FIGS. 42A and 42B  show continued views of  FIG. 41 . 
       FIG. 43  shows a perspective view of the optical waveguide device according to still another embodiment of the invention. 
       FIG. 44  shows a sectional view of an optical transceiver which is constituted by the optical waveguide device shown in  FIG. 43 . 
       FIG. 45  shows a sectional view illustrating a comparative example to the optical waveguide device shown in  FIG. 43 . 
       FIGS. 46A and 46B  show schematically sectional views illustrating another comparative example. 
       FIG. 47  shows a view explaining an optical communication apparatus which utilizes the optical waveguide device according to the invention. 
       FIG. 48  shows a block diagram illustrating a configuration of an optical network unit. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   First Embodiment 
     FIG. 3  shows the schematically perspective view of an optical waveguide device  14   a  according to an embodiment of the invention.  FIG. 4  shows the schematically exploded perspective view of it. The optical waveguide device  14   a  of this embodiment includes a substrate for mounting  16  and an optical waveguide substrate  15 . The optical waveguide substrate  15  includes a cover glass  17 , a lower cladding layer  18  which is made of an optical material having high refractive index, cores  19   a ,  19   b , and  19   c  which are made of the optical material having the refractive index higher than that of the lower cladding layer  18  and transmit the light, a filter  29 , and an upper cladding layer  20  which is made of the same optical material for the lower cladding layer  18 . The filter  29  is an optical element which transmits only the light having a specific wavelength range but reflects the light having the wavelength range except the specific wavelength range. The filter  29  is placed inside a filter placing groove  31 . The cores  19   a  and  19   b  embedded in the lower cladding layer  18  are arranged in line, the filter  29  is inserted in the filter placing groove  31  so as to partition the cores  19   a  and  19   b  and to be disposed at a 45° angle relative to an optical axis of the cores  19   a  and  19   b , and the core  19   c  is arranged on a side face of the filter  29  so as to be disposed at a 90° angle relative to the optical axis of the cores  19   a  and  19   b.    
   In the substrate for mounting  16 , a waveguide fixing region  30  for laminating the waveguide substrate  15  is formed on a surface of a supporting substrate  21 , a V groove-shaped optical fiber guide  23   a  and concave optical element placing portions  24   a  and  24   b  are provided on a periphery of the waveguide fixing region  30 . The upper surface of the supporting substrate  21  except the waveguide fixing region  30  is thoroughly covered with a metallic thin film  22  such as Ni or Au. In the case that the supporting substrate  21  is made of a silicon substrate, the metallic thin film  22  may be formed onto a SiO 2  film which is formed by oxidizing the surface of the supporting substrate  21 . Element mounting benches (electrode pads)  33   a  and  33   b  for mounting a light receiving element or a light emitting element are formed in each optical element placing portions  24   a  and  24   b.    
   In the optical waveguide device  14   a  assembled as shown in  FIG. 3 , the optical waveguide substrate  15  is placed while the optical waveguide substrate  15  is vertically turned the other way round, the optical fiber guide  23   a  and the element mounting benches  33   a  and  33   b  are exposed from the optical waveguide substrate  15 . 
     FIG. 5  is a plane view showing a state in which the optical transceiver is constituted by mounting a light emitting element  28  and a light receiving element  27  on the optical waveguide device  14   a  and connecting an optical fiber  26 . The light receiving element  27  and the light emitting element  28  are mounted respectively on the element mounting benches  33   a  and  33   b  in the optical element placing portions  24   a  and  24   b  by die-bonding a lower surface electrode. The light receiving element  27  is opposed to an end face of the core  19   c  and the light emitting element  28  is opposed to the end face of the core  19   b . The upper surface electrodes of the light emitting element  28  and the light receiving element  27  are connected to a circuit board or the like with a bonding wire. In this state, though the element mounting bench  33   a  is electrically connected to the element mounting bench  33   b  with the metallic thin film  22 , there is no problem in the case that the sides of the element mounting benches  33   a  and  33   b  become ground electrodes. In the case that it is inconvenient that the element mounting bench  33   a  is electrically connected to the element mounting bench  33   b , the metallic thin film  22  may be electrically separated by cutting the metallic thin film  22  with a dicing blade between the element mounting benches  33   a  and  33   b . The optical fiber  26  is fixed with a bonding agent while the optical fiber  26  is contained in the optical fiber guide  23   a  to be positioned. Consequently, the optical axes of the core  19   a  and the optical fiber  26  are automatically aligned. 
   In the optical waveguide device  14   a , the filter  29  is used one having characteristics which transmit the light having the wavelength outgoing from the light emitting element  28  and reflect the light having the wavelength outgoing from the optical fiber  26 . Accordingly, when the light emitting element  28  emits the light to the core  19   b , the emitted light propagates through the core  19   b , transmits through the filter  29 , propagates through the core  19   a , and is incident to the optical fiber  26  to be transmitted through the optical fiber  26 . The light (receiving signal) propagating through the optical fiber  26  is incident to the core  19   a  and reflected by the filter  29 , and then the light propagates through the core  19   c  to be received by the light receiving element  27 . Thus, the optical waveguide device  14   a  can perform the transmission and reception of the signal with an external other device connected through the optical fiber. 
   As described above, the optical waveguide device  14   a  can be utilized as the optical transceiver for transmitting and receiving the signal. For example, like a personal computer connected to the Internet, the optical waveguide device  14   a  is used inside the apparatus which receives the signal from the outside and transmits the signal to the outside. 
   The manufacturing method of the optical waveguide device  14   a  will be described below referring to  FIGS. 6 to 13 . The surface of a silicon substrate (wafer)  21   a  which is a mother board of the supporting substrate  21  is etched, plural sets of the waveguide fixing region  30 , the optical element placing portions  24   a  and  24   b , and the optical fiber guide  23   a  are formed as shown in  FIG. 6 . Though the four substrates for mounting  16  can be made at once when the silicon substrate  21   a  of  FIG. 6  is used, mass production of the substrate for mounting  16 , i.e. the optical waveguide device  14   a  can be realized when the silicon substrate  21   a  having the larger area is used. 
   As shown in  FIG. 7 , the metallic thin film  22  is formed on the region except the waveguide fixing region  30  on the surface of the silicon substrate  21   a  by evaporating or sputtering the metal such as Ni or Au. Further, in the optical element placing portions  24   a  and  24   b , the element mounting benches  33   a  and  33   b  are formed on the metallic thin film  22  by an electrode material respectively. Hereinafter, the silicon substrate  21   a  on which the metallic thin film  22  is formed is referred to as a base substrate  16   a.    
   On the other hand, by using a glass substrate  17   a  having the area not lower than that of the silicon substrate  21   a , the mother board (optical waveguide mother board  15   a ) of the optical waveguide substrate  15   a  including the lower cladding layer  18  and cores  19   c  and  19   d , shown in  FIG. 8 , is formed by adopting a duplicating method (stamper method). The glass substrate (wafer)  17   a  is the motherboard of the cover glass  17  of the optical waveguide device  14   a.    
   The duplicating method (stamper method) using an ultraviolet-curing resin will be briefly described referring to  FIG. 9 .  FIGS. 9A to 9D  show the face corresponding to the cross section taken on line A–A′ of  FIG. 8 . As shown in  FIG. 9A , an uncured ultraviolet-curing resin (lower cladding resin)  18   a  is put onto the glass substrate  17   a , the surface of the uncured ultraviolet-curing resin  18   a  is pressed with a stamper (mold)  34   a  having the pattern of the same shape for the cores  19   c  and  19   d  to form a core groove  35 , and then the lower cladding layer  18  having the core groove  35 , as shown in  FIG. 9B , is formed in such a manner that the ultraviolet-curing resin  18   a  is irradiated with the ultraviolet ray to cure the ultraviolet-curing resin  18   a.    
   An uncured ultraviolet-curing resin (core resin)  19   e  having the refractive index larger than that of the lower cladding layer  18  is put into the inside of the core groove  35  formed in the lower cladding layer  18  and is pressed with a stamper  34   b  in order to flatten the surface of the lower cladding layer  18  and thin a thickness of a flash formed on the surface of the lower cladding layer  18  by the ultraviolet-curing resin  19   e  overflowing the core groove  35 , and then, as shown in  FIG. 9D , the cores  19   c  and  19   d  are formed in the core groove  35  in such a manner that the ultraviolet-curing resin  19   e  is irradiated with the ultraviolet ray to cure the ultraviolet-curing resin  19   e.    
   As shown in  FIG. 10 , an uncured resin  20   a  is put onto the surface of the optical waveguide mother board  15   a , and the optical waveguide mother board  15   a  and the base substrate  16   a  are bonded with the resin  20   a . Since the resin  20   a  becomes the upper cladding layer  20  when the resin  20   a  is cured, it is desirable that the resin  20   a  is the same ultraviolet-curing resin as the lower cladding layer  18  or the resin having the almost same refractive index for the lower cladding layer  18 , and the resin  20  has the refractive index lower than that of the cores  19   c  and  19   d.    
   It is necessary to precisely align the optical fiber guide  23   a , the optical element placing portions  24   a  and  24   b , and the cores  19   c  and  19   d , when the base substrate  16   a  is bonded to the optical waveguide motherboard  15   a . In order to align those components, the optical waveguide mother board  15   a  and the base substrate  16   a  may be bonded in such a manner that the alignment is precisely performed with alignment marks provided in the optical waveguide mother board  15   a  and the base substrate  16   a . If the alignment is performed with the base substrate  16   a  having the large area and the optical waveguide mother board  15   a  having the large area, a complicated procedure such as the alignment among the individual components is not required, and it is efficient because the plurality of cores are precisely aligned with the fiber guide and the like. 
   As shown in  FIG. 11 , the base substrate  16   a  is placed on the lower side and the optical waveguide mother board  15   a  is placed on the upper side, and separating grooves  25   a ,  25   b , and  25   c  are formed by making a cut in the optical waveguide mother board  15   a  with the dicing blade so as to pass through an edge of the waveguide fixing region  30 . The end face of the cores  19   c  and  19   d  are simultaneously formed by this cutting process to the separating grooves  25   a ,  25   b , and  25   c . Among the optical waveguide mother boards  15   a  divided by the separating grooves  25   a ,  25   b , and  25   c , because adhesion at an interface between the metallic thin film  22  and the upper cladding layer  20  is weak in the region (region outside the waveguide fixing region  30 ) where the metallic thin film  22  is formed on the surface of the base substrate  16   a , the unnecessary part can be easily peeled off from the base substrate  16   a  when force is applied to an unnecessary part (region corresponding to the outside of the waveguide fixing region) from the divided optical waveguide mother board  15   a . Accordingly, the optical fiber guide  23   a  of the base substrate  16   a  or the element mounting benches  33   a  and  33   b  in the optical element placing portions  24   a  and  24   b  can be exposed, while only the region in which the cores  19   c  and  19   d  are formed, shown by oblique lines in  FIG. 11 , remains. Each end face of the cores  19   c  and  19   d  is exposed on the surface of the outer periphery of the optical waveguide motherboard  15   a  which remains on the base substrate  16   a.    
   In the forming of the separating grooves  25   a ,  25   b , and  25   c  by dicing the optical waveguide mother board  15   a , as shown in  FIG. 11 , when the metallic thin film  22  is divided so that the separating grooves  25   a ,  25   b , and  25   c  are diced deeper than the metallic thin film  22 , the optical element placing portions  24   a  and  24   b , i.e., the element mounting benches  33   a  and  33   b , can be electrically insulated. 
   Then, the base substrate  16   a  and the optical waveguide mother board  15   a  are cut along line B–B′ and line C–C′ of  FIG. 11  to divide them into chips shown in  FIG. 12 , and the chip in which the optical waveguide substrate  15  is joined onto the substrate for mounting  16  is obtained. At this point, if the unnecessary part of the optical waveguide mother board  15   a  remains, the unnecessary part should be removed. As shown in  FIG. 13 , the filter placing groove  31  is formed by making the cut in the cover glass  17  and the lower cladding layer  18  with the dicing blade. At this point, the core  19   d  is divided to form the cores  19   a  and  19   b . Finally the optical waveguide device  14   a  shown in  FIG. 3  is completed by fitting the filter  29  using the multilayered reflecting film in a portion between the cores  19   a  and  19   b  of the filter placing groove  31 . The filter  29  may be projected from the upper surface of the cover glass  17 . 
   In the manufacturing method of the optical waveguide device of the embodiment, the optical waveguide mother board  15   a  having the large area and the base substrate  16   a  having the large area are bonded with the upper cladding layer  20  and it is divided into the individual chip of the optical waveguide device  14   a  in the final process, so that the optical waveguide device  14   a  can be efficiently manufactured compared with the bonding of the individual optical waveguide substrate  15  and the individual substrate for mounting  16  and the manufacturing method of the embodiment is fit to the mass production. Further, since the base substrate  16   a  and the optical waveguide mother board  15   a  having the large area having the large area are bonded, the alignment can be performed more precisely compared with the alignment between the small components. 
   In the optical waveguide device  14   a , it is necessary to expose finally the optical fiber guide  23   a  and the optical element placing portions  24   a  and  24   b . In the manufacturing method of the optical waveguide device of the embodiment, since the adhesion of the bonding resin  20   a  (upper cladding layer  20 ) is weakened by previously forming the metallic thin film  22  on the base substrate  16   a  in the region corresponding to the unnecessary part of the optical waveguide mother board  15   a , even if all the surfaces of the optical waveguide mother board  15   a  and the base substrate  16   a  are bonded, the unnecessary part of the optical waveguide mother board  15   a  can be easily removed and the manufacturing process can be further simplified. 
   In the embodiment, though the waveguide fixing region  30  is exposed from the metallic thin film  22 , the metallic thin film  22  may be also formed on the surface of the waveguide fixing region  30 . Though the unnecessary part of the optical waveguide mother board  15   a  can be easily removed from the metallic thin film  22  by applying force, since the bonding state between the unnecessary part and the supporting substrate  21  are held in the optical waveguide substrate  15  in which the cores  19   a ,  19   b , and  19   c  and the like are formed unless the peeling-off is performed by applying the force, the unnecessary part does not become an obstacle. 
   (Second Embodiment) 
     FIG. 14  shows the schematically perspective view of an optical waveguide device  14   b  according to another embodiment of the invention. The optical waveguide device  14   b  of the embodiment includes the supporting substrate  21 , the element mounting benches  33   a  and  33   b , a spacer  32 , the upper cladding layer  20 , the cores  19   a ,  19   b  and  19   c , the filter  29 , the lower cladding layer  18 , and the cover glass  17 . The cores  19   a  and  19   b  are arranged in line, and the core  19   c  is arranged at a 90° angle relative to the optical axis of the cores  19   a  and  19   b . The filter  29  is the optical element having characteristics which transmit the light having the specific wavelength range and reflect the light having the wavelengths except the specific one. The filter  29  is inserted into the filter placing groove  31 , which is formed at a 45° angle relative to the optical axis so as to partition the cores  19   a  and  19   b.    
   The optical fiber guide  23   a , the optical element placing portions  24   a  and  24   b , and the waveguide fixing region  30  are embedded in the surface of the supporting substrate  21 . The V-shaped optical fiber guide  23   a  is designed so that the optical axes of the core  19   a  and the optical fiber are automatically aligned when the optical fiber is placed on the optical fiber guide  23   a . In the element mounting benches  33   a  and  33   b  provided in the concave optical element placing portions  24   a  and  24   b , the light emitting element or the light receiving element which is connected to the cores  19   b  and  19   c  is placed to connect the external power supply. 
   In the manufacturing of the optical waveguide device of the invention, because almost all of the manufacturing processes are the same for the optical waveguide device described in the first embodiment, the processes different from the first embodiment will be mainly described below. 
   As shown in  FIG. 15 , the metal is deposited on a silicon substrate  21   b  in which the waveguide fixing region  30 , the optical element placing portions  24   a  and  24   b , and the optical fiber guide  23   a  are formed by the etching to form the spacer  32  and the element mounting benches  33   a  and  33   b , and this is used as a base substrate  16   b . As shown in  FIG. 8 , the optical waveguide mother board  15   a  includes the glass substrate  17   a , the lower cladding layer  18 , and the cores  19   c  and  19   d , and the optical waveguide mother board  15   a  is formed by the duplicating method (stamper method) as described in the first embodiment. In bonding the base substrate  16   b  and the optical waveguide mother board  15   a  together with the uncured ultraviolet-curing resin  20   a  which will be the upper cladding layer  20 , as described below, the resin  20   a  remains at uncured state in the region corresponding to the unnecessary part of the optical waveguide mother board  15   a  and the ultraviolet-curing resin  20   a  is cured only in the remaining region. 
     FIG. 16A  shows the plane corresponding to the cross section taken on line D–D′ of the optical waveguide device  14   b  shown in  FIG. 14  before forming the filter placing groove  31 , and  FIG. 16B  shows a sectional view taken on line D–D′ of the optical waveguide device  14   b  shown in  FIG. 14  after forming the filter placing groove  31 . In bonding the base substrate  16   b  and the optical waveguide mother board  15   a  together with the uncured ultraviolet-curing resin  20   a , as shown in  FIG. 16A , covering the unnecessary parts of the upper cladding layer  20  such as the surface of the optical element placing portions  24   a  and  24   b  and the surface of the optical fiber guide  23   a  with a mask  36   a  which block the ultraviolet ray, only the uncured ultraviolet-curing resin  20   a  of the necessary part (upper cladding layer  20 ) can be cured when the uncured ultraviolet-curing resin  20   a  is irradiated with the ultraviolet ray. 
   Then, similarly to the manufacturing process described in the first embodiment, the unnecessary glass substrate  17   a  and lower cladding layer  18  is taken off by using the dicing blade, and the end faces of the cores  19   c  and  19   d  are simultaneously formed. In this case, though a part of the spacer  32  or the supporting substrate  21  may be cut away, it is not always necessary to cut away the part. 
   Since frictional heat is generated in the operation of the dicing blade, the dicing blade is cooled by putting cooling water to it. At the same time, since the uncured ultraviolet-curing resin  20   a  is washed away with the cooling water, the cut unnecessary parts in the glass substrate  17   a  and the lower cladding  18  are easily removed. In the case that the uncured ultraviolet-curing resin  20   a  is not thoroughly washed away only with the cooling water of the dicing blade, the uncured ultraviolet-curing resin  20   a  may be thoroughly washed away with solvent. Then, the optical waveguide device  14   b  shown in  FIG. 16   b  is completed are divided into the individual waveguide chip with the dicing blade, the filter placing groove  31  is formed so that the core  19   d  is divided into the cores  19   a  and  19   b , and the filter  29  is placed. 
   In order to achieve the mass production or simplification of the manufacturing process, even for the unnecessary part for the optical waveguide device, the optical waveguide motherboard  15   a  and the base substrate  16   b  are once bonded over the whole surface in the manufacturing process of the optical waveguide device. According to the manufacturing method of the optical waveguide device of the invention, the upper cladding layer is made of the resin such as the ultraviolet-curing resin which is not cured unless specific conditions are given to the resin, the unnecessary part remains while the unnecessary part is not cured, and the unnecessary part can be easily removed. 
   According to the manufacturing method of the optical waveguide device  14   b  of the embodiment, since the remaining uncured resin is washed away in the process forming the end face of the core with the dicing blade and the unnecessary part is removed, it is not necessary to provide the additional process for removing the unnecessary part and the manufacturing process can be simplified. 
   Further, since the spacer  32  is provided in the base substrate  16   b  of the optical waveguide device of the invention, the thickness of the upper cladding layer  20  can be uniformed by the spacer  32 . For example, even if the amount or viscosity of the resin  20   a  which is dropped in order to form the upper cladding layer  20  is dispersed, since the core is not pressed below the height of the upper surface of the spacer  32  as shown in  FIG. 16B , the dispersion is hardly generated in the height at which the cores  19   a ,  19   b  and  19   c  are placed, and the alignment of the optical axis between the cores  19   a ,  19   b  and  19   c  and the light emitting element, the light receiving element, or the optical fiber which is connected to the cores  19   a ,  19   b  and  19   c  is precisely performed. 
   (Third Embodiment) 
     FIG. 17  is the schematically perspective view of an optical waveguide device  14   c  according to still another embodiment of the invention. The optical waveguide device  14   c  of the invention includes the supporting substrate  21 , a lead electrode  38  which is formed in a through hole  37  drilled through from the surface of the supporting substrate  21  to the backside, the element mounting benches  33   a  and  33   b  which covers the lead electrode  38 , the lower cladding layer  18 , the cores  19   a ,  19   b  and  19   c  which are formed inside the lower cladding layer  18 , the filter  29  which is inserted in the filter placing groove  31 , the upper cladding layer  20 , and the cover glass  17 . The V-shaped optical fiber guide  23   a  in which the optical fiber is placed is formed inside a concave groove  23   d  on the surface of the supporting substrate  21 . 
   The manufacturing method of the optical waveguide device  14   c  of the embodiment will be simply described below. As shown in  FIG. 18A , the concave groove  23   d  and the through hole  37  are formed in the supporting substrate  21  which is the glass substrate by the etching or the like. Then, as shown in  FIG. 18B , the inside of the through hole  37  is embedded with a material having the high electrical conductivity or the metallic film is formed inside the through hole  37  to form the lead electrode  38 , and the element mounting benches  33   a  and  33   b  are formed so as to cover the lead electrode  38 . The element mounting benches  33   a  and  33   b  may be formed by evaporation of the metal. 
   As shown in  FIG. 18C , in the surfaces opposite to the surface in which the element mounting benches  33   a  and  33   b  of the supporting substrate  21 , the region in which the lower cladding layer  18  and the optical fiber guide  23   a  are not formed on the supporting substrate  21  is covered with the mask  36   a  which does not transmits the ultraviolet ray. Then, the lower cladding layer  18  having the core groove  35  and the optical fiber guide  23   a  are formed in such a manner that the ultraviolet-curing resin  18   a  is dropped onto the supporting substrate  21  in order to form the lower cladding layer  18 , pressed with the stamper  34   a  having the same pattern as the optical fiber guide  23   a , the cores  19   c  and  19   d  and the optical fiber guide  23   a , and irradiated with the ultraviolet ray from the lower surface to cure the resin  18   a . At this point, the ultraviolet-curing resin  18   a  of a part which is covered with the mask  36   a  remains while the resin  18   a  is not cured. When the optical fiber guide  23   a  and the core groove  35  are simultaneously formed in the above-described way, the alignment of the optical axis between the core and the optical fiber connected to the core is more precisely performed. 
   A mask  36   b  covering a part in which the optical fiber guide  23   a  is formed is superimposed on the mask  36   a . As shown in  FIGS. 19A and 19B , the ultraviolet-curing resin  19   e  having the refractive index higher than that of the ultraviolet-curing resin  18   a  forming the lower cladding layer  18  is injected into the core groove  35 , pressed with the plane-shaped stamper  34   b , and irradiated with the ultraviolet ray from the lower surface side to form the cores  19   c  and  19   d . At this point, the formed cores  19   c  and  19   d  are those which intersect at right angles as described in the first embodiment and shown in  FIG. 8 . The ultraviolet-curing resins of parts which are covered with the masks  36   a  and  36   b  remain while the resin is not cured. 
   As shown in  FIG. 19C , an uncured ultraviolet-curing resin  20   a , which is the same type as that for the lower cladding layer  18 , is dropped onto the core  19   c  and  19   d  and lower cladding layer  18 . As shown in  FIG. 20A , the ultraviolet-curing resin  20   a  is pressed with a cover glass  17 , and ultraviolet rays are irradiated from the lower face side. At this point, there may be a problem that the ultraviolet-curing resin  20   a  also flows down to the surface of the supporting substrate  21 , the element mounting benches  33   a  and  33   b , or the optical fiber guide  23   a . However, since these regions are covered with the masks  36   a  and  36   b , there is no problem that the ultraviolet-curing resin  20   a  is cured. Then, the unnecessary cover glass  17  is cut away with the dicing blade and the end faces of the cores  19   c  and  19   d  are formed simultaneously. In doing so, the uncured ultraviolet-curing resin  20   a  is washed away with the cooling water of the dicing blade, and the unnecessary part can be removed as shown in  FIG. 19B . In the case that the ultraviolet-curing resin  20   a  is not thoroughly washed away with the cooling water of the dicing blade, the ultraviolet-curing resin  20   a  may be thoroughly removed by further using the solvent. In the case that the plurality of optical waveguide devices  14   c  are formed at once as the mother board, those are divided into waveguide chips by using the dicing blade. 
   Then, the cut is made into the cover glass  17 , the upper cladding layer  20 , and lower cladding layer  18  with the dicing blade to form the filter placing groove  31  so as to divide the core  19   d  into the cores  19   a  and  19   b . Finally, by placing the filter  29  between the cores  19   a  and  19   b  of the filter placing groove  31 , the optical waveguide device  14   c  shown in  FIG. 20B  is completed. 
   Even if the part is not required for the optical waveguide device, there is the part which is temporarily formed in the manufacturing process of the optical waveguide device in order to achieve the mass production or the simplification of the manufacturing process. In the manufacturing method of the optical waveguide device of the embodiment, the upper cladding layer is made of the resin such as the ultraviolet-curing resin which is not cured unless specific conditions are given to the resin, a boundary part between the necessary part and the unnecessary part remains while the boundary part is not cured, and the unnecessary part can be easily removed. 
   In the manufacturing method of the optical waveguide device of the invention, since the uncured resin is washed away in the process in which the end face of the core is formed with the dicing blade and the unnecessary part is removed, it is not necessary to provide the additional process for removing the unnecessary part, and the manufacturing process can be simplified. 
   (Fourth Embodiment) 
     FIG. 21  shows the schematically exploded perspective view of an optical waveguide device  14   d  according to still another embodiment of the invention. The optical waveguide device  14   d  includes the supporting substrate  21 , the lower cladding layer  18 , a core  19   f , the upper cladding layer  20 , and the cover glass  17 . Optical fiber guides  23   a ,  23   b  and  23   c  which automatically align the optical axis of the optical fiber connected to the end face of the core  19   f  are formed on the surface of the supporting substrate  21  made of glass. In the case that the supporting substrate  21  is used as the silicon substrate, the optical fiber guides  23   a ,  23   b , and  23   c  may be formed by the etching. The supporting substrate  21  may be also made in a manner that forms the transparent resin by injection molding, the stamper method, resin casting, or the like. 
   The optical waveguide device  14   d  of this embodiment can be produced by the same manufacturing method for the optical waveguide device shown in the third embodiment, as shown in  FIG. 22 . The supporting substrate  21  may be covered with the mask  36   a  so that only the region where the lower cladding layer  18 , the core  19   f , and the upper cladding layer  20  are formed is irradiated with the ultraviolet ray. 
   Even if the part is not required for the optical waveguide device, there is the part which is temporarily formed in the manufacturing process of the optical waveguide device in order to achieve the mass production or the simplification of the manufacturing process. In the manufacturing method of the optical waveguide device of the invention, the upper cladding layer is made of the resin such as the ultraviolet-curing resin which is not cured unless specific conditions are given to the resin, a boundary part between the necessary part and the unnecessary part remains while the boundary part is not cured, and the unnecessary part can be easily removed. 
   (Fifth Embodiment) 
     FIGS. 23 ,  24 , and  25  show the schematically perspective view, the schematically exploded view, and the schematic plane view of an optical waveguide device  14   e  (optical attenuator) according to still another embodiment of the invention respectively. The optical waveguide device  14   e  of the invention includes a base glass  39 , heaters  40   a  and  40   b , electrode lead pads  41   a  and  41   b , the upper cladding layer  20 , the cores  19   g ,  19   h    19   i ,  19   j , and  19   k , the lower cladding layer  18 , and the cover glass  17 . 
   In the cores  19   g  to  19   k  of the optical waveguide device  14   e  of the embodiment, though the core is the single core  19   g  at an entrance of light incident, the core branches off into the two cores  19   h  and  19   i  on its way, and then the two cores converge to the single core  19   j . The heaters  40   a  and  40   b  are placed on the surface of the base glass  39  lower the cores  19   i  and  19   h , the heater  40   a  can heat the core  19   i , and the heater  40   b  can heat the core  19   h.    
   When one of the heaters  40   a  and  40   b  conducts to heat one of the cores  19   i  and  19   h , the refractive index of heated one of the cores  19   i  and  19   h  is decreased and optical length of the light which is transmitted by the heated core  19   i  or  19   h  is changed, so that the phase difference between the light transmitted through the core  19   i  and the light transmitted through the core  19   h  is changed. Accordingly, the two lights having the different phases interfere with each other at a merging point of the two cores  19   i  and  19   h , and power of the light outputted from the core  19   k  is changed according to its phase difference. As a result, the amount of attenuation of the outputted light can be controlled by controlling a current value conducting the heater  40   a  or the heater  40   b  to change heat value of the heater  40   a  or the heater  40   b . Particularly, auto-power control can be performed so that the power of the light outputted from the core  19   k  becomes constant in such a manner that the light receiving element for monitoring is placed opposite to the core  19   j  for monitoring and the current value conducting the heaters  40   a  and  40   b  is feedback-controlled while the amount of receiving light is monitored with the light receiving element. 
   In the closest portion between the cores  19   j  and  19   k , the cores  19   j  and  19   k  are formed in parallel at intervals of about several times of the wavelength. The power of the light propagating through the core  19   j  can be transferred to the core  19   k  between the cores  19   j  and  19   k  which are close to such an extent, and a ration of the transferred light can be adjusted by setting the parallel portion to the proper length. In the optical waveguide device  14   e  of the embodiment, the 95% light is transferred to the core  19   k  and the remaining 5% light is outgoing from a light outgoing end of the core  19   j  in the light outputted from the merging point of the diverging cores  19   i  and  19   h . Since the core  19   k  is connected to the optical fiber or the light receiving element, the light outgoing from the core  19   k  cannot be directly examined. However, intensity of the light outgoing from the core  19   k  can be indirectly observed by monitoring the light outgoing from the core  19   j.    
   The manufacturing method of the optical waveguide device  14   e  of the invention will be described below. As shown in  FIG. 26A , A titanium thin film  40   c  is formed on the surface of the base glass  39  which is the glass substrate by depositing or sputtering titanium (Ti) having high thermal conductivity, and an aluminum thin film  41   c  is formed on the titanium thin film  40   c  by depositing aluminum (Al). 
   As shown in  FIG. 26B , the electrode lead pads  41   a  and  41   b  are formed by etching a part of the aluminum thin film  41   c , and then the heaters  40   a  and  40   b  are formed by etching a part of the exposed titanium thin film  40   c  as shown in  FIG. 26C . 
   As shown in  FIG. 26D , by adopting the duplicating method using the resin, which was described in the first embodiment, the base glass  39  in which the electrode lead pads  41   a  and  41   b  and the heaters  40   a  and  40   b  are formed is bonded in a manner that drops the uncured ultraviolet-curing resin  20   a , which has the same refractive index as that of the lower cladding layer  18  or the same level of the refractive index of the lower cladding layer  18 , onto the surface of the lower cladding layer  18  in the optical waveguide substrate  15  on which the lower cladding layer  18  and the cores  19   g  to  19   k  are formed on the cover glass  17 . 
   At this point, as shown in  FIG. 27A , a part where it is not necessary to form the upper cladding layer  20  is covered with the mask  36   a  from the lower surface of the cover glass  17 , and the upper cladding layer  20  is formed in such a manner that the ultraviolet-curing resin  20   a  is irradiated with the ultraviolet ray from the lower side of the mask  36   a  to cure it. 
   The unnecessary parts of the cover glass  17  and the lower cladding layer  18  are cut off with the dicing blade while the optical waveguide device is inversely turned the other way round so that the base glass  39  is placed on the lower side and the cover glass  17  is placed on the upper side, and the electrode lead pads  41   a  and  41   b  are exposed. As a result, the optical waveguide device  14   e  shown in  FIG. 27B  is completed. The cut-off cover glass  17  or lower cladding layer  18  and the remaining uncured resin  20   a  are washed away with the cooling water of the dicing blade. In the case that the ultraviolet-curing resin  20   a  is not thoroughly washed away with the cooling water of the dicing blade, the ultraviolet-curing resin  20   a  may be thoroughly removed by further using the solvent. 
   (Sixth Embodiment) 
     FIGS. 28 and 29  show the schematically perspective view and the schematically exploded perspective view of an optical waveguide device  14   f  according to still another embodiment of the invention respectively. The optical waveguide device  14   f  of the embodiment includes the substrate for mounting  16  and the optical waveguide substrate  15  and has the structure in which the cover glass  17  is removed from the optical waveguide device  14   a . That is, the optical waveguide substrate  15  includes the lower cladding layer  18  made of the optical material having the high refractive index and the upper cladding layer  20  which is made of the optical material having the refractive index higher than that of the lower cladding layer  18  and the same optical material for the cores  19   a ,  19   b , and  19   c , the filter  29 , and the lower cladding layer  18 , which transmit the light. The filter  29  is the optical element which transmits only the light having a certain wavelength range and reflects the light having the wavelength range except the certain wavelength range. The filter  29  is placed inside the filter placing groove  31 . The cores  19   a  and  19   b  embedded in the lower cladding layer  18  are arranged in line, the filter  29  is inserted in the filter placing groove  31  so as to partition the cores  19   a  and  19   b  and to be disposed at a 45° angle relative to the optical axis of the cores  19   a  and  19   b , and the core  19   c  is arranged on the side face of the filter  29  so as to be disposed at a 90° angle relative to the optical axis of the cores  19   a  and  19   b.    
   In the substrate for mounting  16 , the waveguide fixing region  30  for laminating the optical waveguide substrate  15  is formed on a surface of a supporting substrate  21 , the V groove-shaped optical fiber guide  23   a  and the concave optical element placing portions  24   a  and  24   b  are provided on a periphery of the waveguide fixing region  30 . The upper surface of the supporting substrate  21  except the waveguide fixing region  30  is thoroughly covered with the metallic thin film  22  such as Ni or Au. In the case that the supporting substrate  21  is made of the silicon substrate, the metallic thin film  22  may be formed onto a SiO 2  film which is formed by oxidizing the surface of the supporting substrate  21  (hereinafter referred to as silicon substrate). Element mounting benches (electrode pads)  33   a  and  33   b  for mounting the light receiving element and the light emitting element are formed in each optical element placing portions  24   a  and  24   b.    
   In the optical waveguide device  14   f  assembled as shown in  FIG. 28 , the optical waveguide substrate  15  is placed while the optical waveguide substrate  15  is vertically turned the other way round, the optical fiber guide  23   a  and the element mounting benches  33   a  and  33   b  are exposed from the optical waveguide substrate  15 . 
     FIG. 30  is the plane view showing a state in which the optical transceiver is constituted by mounting a light emitting element  28  and a light receiving element  27  on the optical waveguide device  14   f  and connecting the optical fiber  26 . The light receiving element  27  and the light emitting element  28  are mounted respectively on the element mounting benches  33   a  and  33   b  in the optical element placing portions  24   a  and  24   b  by die-bonding a lower surface electrode. The light receiving element  27  is opposed to an end face of the core  19   c  The light emitting element  28  is opposed to the end face of the core  19   b . The upper surface electrodes of the light emitting element  28  and the light receiving element  27  are connected to a circuit board or the like with a bonding wire. In this state, though the element mounting bench  33   a  is electrically connected to the element mounting bench  33   b  with the metallic thin film  22 , there is no problem in the case that the sides of the element mounting benches  33   a  and  33   b  become ground electrodes. In the case that it is inconvenient that the element mounting bench  33   a  is electrically connected to the element mounting bench  33   b , the metallic thin film  22  may be electrically separated by cutting the metallic thin film  22  with a dicing blade between the element mounting benches  33   a  and  33   b . The optical fiber  26  is fixed with a bonding agent while the optical fiber  26  is stored in the optical fiber guide  23   a  to be positioned. Consequently, the optical axes of the core  19   a  and the optical fiber  26  are automatically aligned. 
   In the optical waveguide device  14   f , the filter  29  is used one having characteristics which transmit the light having the wavelength outgoing from the light emitting element  28  and reflect the light having the wavelength outgoing from the optical fiber  26 . Accordingly, when the light emitting element  28  emits the light to the core  19 , the light propagates through the core  19   b , transmits through the filter  29 , propagates though the core  19   a , and is incident to the optical fiber  26  to be transmitted by the optical fiber  26 . The light (receiving signal) propagating through the optical fiber  26  is incident to the core  19   a , reflected by the filter  29 , propagates through the core  19   c , and is received by the light receiving element  27 . Thus, in the optical waveguide device  14   f , the transmission and reception of the signal can be performed between the optical waveguide device  14   f  and an external other device connected to the optical waveguide device  14   f  through the optical fiber. 
   The manufacturing method of the optical waveguide device  14   f  of the invention will be described below referring to  FIGS. 31 to 35 . The base substrate  16   a  shown in  FIG. 31  is produced through the processes (processes shown in  FIGS. 6 and 7 ) described in the first embodiment. The thickness of the silicon substrate  21   a  used is in the range of 500 to 1000 μm. The optical waveguide motherboard  15   a  shown in  FIG. 31  is produced on the glass substrate  17   a  through the processes (processes shown in  FIGS. 8 and 9 ) described in the first embodiment. The thickness of the glass substrate  17   a  is in the range of 500 to 1000 μm, the thickness of the lower cladding layer  18  is about 20 μm, and the cross section of the cores  19   c  and  19   d  is about 5 nm by 5 μm. After the base substrate  16   a  and the optical waveguide mother board  15   a  are produced in the above-described way, as shown in  FIG. 31 , the uncured ultraviolet-curing resin  20   a  is dropped onto the surface of the optical waveguide mother board  15   a , and the optical waveguide mother board  15   a  is integrally bonded to the base substrate  16   a  with the ultraviolet-curing resin  20   a  as shown in  FIG. 32A . The ultraviolet-curing resin  20   a  is cured in the waveguide fixing region  30  to become the upper cladding layer  20  having the thickness of about 20 μm. 
   It is necessary to precisely align the optical fiber guide  23   a , the optical element placing portions  24   a  and  24   b , and the cores  19   c  and  19   d , when the base substrate  16   a  is bonded to the optical waveguide motherboard  15   a . In order to align those components, the optical waveguide mother board  15   a  and the base substrate  16   a  may be bonded in such a manner that the alignment is precisely performed with alignment marks provided in the optical waveguide mother board  15   a  and the base substrate  16   a . When the alignment is performed with the base substrate  16   a  having the large area and the optical waveguide mother board  15   a  having the large area, a complicated procedure such as the alignment among the individual components is not required, and it is efficient because the plurality of cores are precisely aligned with the fiber guide and the like. 
   After the base substrate  16   a  and the optical waveguide mother board  15   a  are integrally bonded, the glass substrate  17   a  on the lower cladding layer  18  is removed as shown in  FIG. 32B . With reference to the method for removing the glass substrate  17   a , the glass substrate  17   a  may be physically peeled off from the lower cladding layer  18  by applying force to the glass substrate  17   a  or the glass substrate  17   a  may be dissolved by the etching or the like to remove it. In the case that the glass substrate  17   a  is peeled off, the material having low adhesion properties may be previously formed between the glass substrate  17   a  and the lower cladding layer  18  or processing which reduce the adhesion properties between the glass substrate  17   a  and the lower cladding layer  18  may be previously performed to the glass substrate  17   a . In the case that the adhesion properties of the glass substrate  17   a  and the lower cladding layer  18  are too low and surface treatment is performed in order to improve the adhesion properties, conditions for improving the adhesion properties may be released. In the case that the glass substrate  17   a  is removed by the etching, it is desirable to selectively etch the glass substrate  17   a  by using an etchant which could not etch the lower cladding layer  18 . 
   As shown in  FIG. 33 , the separating grooves  25   a ,  25   b , and  25   c  are formed by making the cut in the lower cladding layer  18  and the upper cladding layer  20  with the dicing blade so as to pass through the edge of the waveguide fixing region  30 . The end face of the cores  19   c  and  19   d  are simultaneously formed by this cutting process of the separating grooves  25   a ,  25   b , and  25   c . Among the lower cladding layer  18  or the upper cladding layer  20 , which is divided by the separating grooves  25   a ,  25   b , and  25   c , because the adhesion at the interface between the metallic thin film  22  and the upper cladding layer  20  is weak in the region (region outside the waveguide fixing region  30 ) where the metallic thin film  22  is formed on the surface of the base substrate  16   a , the unnecessary part can be easily peeled off from the base substrate  16   a  when the force is applied to the unnecessary part (region corresponding to the outside of the waveguide fixing region) of the lower cladding layer  18  or the upper cladding layer  20 . Accordingly, the optical fiber guide  23   a  of the base substrate  16   a  or the element mounting benches  33   a  and  33   b  in the optical element placing portions  24   a  and  24   b  can be exposed, while only the region in which the cores  19   c  and  19   d  are formed, shown by oblique lines in  FIG. 33 , remains. Each end face of the cores  19   c  and  19   d  is exposed on the surface of the outer periphery of the lower cladding layer  18  which remains on the base substrate  16   a.    
   In the forming of the separating grooves  25   a ,  25   b , and  25   c  by dicing the lower cladding layer  18  or the upper cladding layer  20 , as shown in  FIG. 33 , if the metallic thin film  22  is divided so that the separating grooves  25   a ,  25   b , and  25   c  are diced deeper than the metallic thin film  22 , the optical element placing portions  24   a  and  24   b , i.e. the element mounting benches  33   a  and  33   b  can be electrically insulated. 
   Then, the whole is cut along line E–E′ and line F–F′ of  FIG. 33  to divide it into chips shown in  FIG. 34 , and the chip in which the optical waveguide substrate  15  is joined onto the substrate for mounting  16  is obtained. In the case that the unnecessary part of the lower cladding layer  18  or the upper cladding layer  20  remains, the unnecessary part is removed. 
   Though the separating grooves  25   a ,  25   b , and  25   c  are formed by the dicing or the whole is divided into each chip by the dicing after the glass substrate  17   a  is removed, the sequence of the processes may be exchanged. That is, the glass substrate  17   a  may be removed after the separating grooves  25   a ,  25   b , and  25   c  are formed by the dicing or the whole is divided into each chip by the dicing. The glass substrate  17   a  may be removed at the same time when the separating grooves  25   a ,  25   b , and  25   c  are formed by the dicing or the whole is divided into each chip by the dicing. When the separating grooves  25   a ,  25   b , and  25   c  are formed by the dicing or the whole is divided into each chip by the dicing after the glass substrate  17   a  is removed, since the glass substrate  17   a  can be re-used, cost of the manufacturing can be reduced. 
   As shown in  FIG. 35 , the filter placing groove  31  is formed by making the cut in the lower cladding layer  18  with the dicing blade. At this point, the core  19   d  is divided to form the cores  19   a  and  19   b . Finally the optical waveguide device  14   f  shown in  FIG. 28  is completed by fitting the filter  29  using the multilayered reflecting film in the portion between the cores  19   a  and  19   b  of the filter placing groove  31 . The filter  29  may be projected from the upper surface of the lower cladding layer  18 . 
   In the manufacturing method of the optical waveguide device of the embodiment, the optical waveguide mother board  15   a  having the large area and the base substrate  16   a  having the large area are bonded with the upper cladding layer  20  and it is divided into the individual chip of the optical waveguide device  14   f  in the final process, so that the optical waveguide device  14   f  can be efficiently manufactured compared with the bonding of the individual optical waveguide substrate  15  and the individual substrate for mounting  16  and the manufacturing method of the embodiment is fit to the mass production. Since the base substrate  16   a  having the large area and the optical waveguide motherboard  1   5   a  having the large area are bonded, the alignment can be performed more precisely compared with the alignment between the small components. 
   In the optical waveguide device  14   f , it is necessary to expose finally the optical fiber guide  23   a  and the optical element placing portions  24   a  and  24   b . In the manufacturing method of the optical waveguide device of the embodiment, the adhesion of the bonding resin  20   a  (upper cladding layer  20 ) is weakened by previously forming the metallic thin film  22  on the base substrate  16   a  in the region corresponding to the unnecessary part of the optical waveguide mother board  15   a . Therefore, even if all the surfaces of the optical waveguide mother board  15   a  and the base substrate  16   a  are bonded, the unnecessary part of the lower cladding layer  18  or the upper cladding layer  20  can be easily removed and the manufacturing process can be further simplified. 
   In the embodiment, the waveguide fixing region  30  is exposed from the metallic thin film  22 . The other hand, the metallic thin film  22  may be also formed on the surface of the waveguide fixing region  30 . Though the unnecessary part of the lower cladding layer  18  or the upper cladding layer  20  can be easily removed from the metallic thin film  22  by applying force, since the bonding state between the unnecessary part and the supporting substrate  21  are held in the optical waveguide substrate  15  in which the cores  19   a ,  19   b , and  19   c  and the like are formed unless the peeling off is performed by applying the force, the unnecessary part does not become the obstacle. 
   In the above embodiments, the glass substrate  17   a  or the cover glass  17  is finally removed, so that only the waveguide region which does not include the cover glass  17  on the opaque supporting substrate  21  can be formed. That is, in the case that the cladding or the like is formed by using the ultraviolet-curing resin, the ultraviolet-curing resin can not be irradiated with the ultraviolet ray when the ultraviolet-curing resin is applied on the opaque substrate to hold it down with a metal mold, so that the waveguide region can not be formed. However, by adopting the method like the embodiment, the waveguide region can be also formed on the opaque substrate. 
   Accordingly, since the excess cover glass  17  is eliminated, the optical waveguide device  14   f  can be thinned. In the case that the filter placing groove  31  is provided, only the waveguide region such as the lower cladding layer  18  may be cut by the dicing in such a manner that the excess cover glass  17  is previously removed before the filter placing groove  31 . Thus, the groove having narrower width can be formed. That is, if the dicing is performed with the cover glass  17  attached, since the blade may be cracked in the case of the thin dicing blade (for example, the blade having the width not more than about 50 μm), the dicing cannot be performed. However, such restriction is eliminated by removing the cover glass  17 . Further, when the glass substrate  17   a  is removed by the peeling-off, the glass substrate  17   a  can be re-used and the cost of the manufacturing can be reduced. 
     FIG. 36  is the schematically sectional view showing a modification of the above-described embodiments. In the modification, the width is broad on the side close to the upper cladding layer  20  or the supporting substrate  21  and the width is narrow on the side far away from the upper cladding layer  20  or the supporting substrate  21  in the cross section of the cores  19   a ,  19   b , and  19   c , for example the cross section is a trapezoid shape. In case that the cross section of the cores  19   a ,  19   b , and  19   c  is formed in such a shape, the core groove  35  becomes broader in a direction in which a stamper  34   a  is drawn in forming the core groove  35  in the lower cladding layer  18  with the stamper  34   a  (see  FIG. 9 ). The nature of peel-off can be improved between the stamper  34  and the lower cladding layer  18 . 
   (Seventh Embodiment) 
   Similarly to the sixth embodiment, as to the optical waveguide devices mentioned after the second embodiment, the cover glass  17  can be also removed.  FIG. 37  is the exploded perspective view showing an optical waveguide device (two-branch coupler with optical fiber guide)  14   g  having the same structure for the fourth embodiment shown in  FIG. 21 . However, in the optical waveguide device  14   g , the opaque substrate such as the silicon substrate is used as the supporting substrate  21  having the optical fiber guides  23   a  to  23   c , and the lower cladding layer  18  in which the core  19   f  is formed is bonded to the supporting substrate  21  through the upper cladding layer  20 . 
   Similarly to the seventh embodiment, the optical waveguide device  14   g  is produced in such a manner that the core  19   f  is filled in the core groove of the lower cladding layer  18 , which is formed on the upper surface of the transparent cover glass  17 , the lower cladding layer  18  is bonded to the supporting substrate  21  with the ultraviolet-curing resin, similarly to  FIG. 22  the upper cladding layer  20  is formed by partly irradiating the ultraviolet-curing resin with the ultraviolet ray to cure it, and the cover glass  17  is removed before or after the unnecessary parts of lower cladding layer  18  and upper cladding layer  20  is removed. 
   (Eighth Embodiment) 
     FIGS. 38 ,  39 , and  40  show the schematically perspective view, the schematically exploded perspective view, and the schematic plane view of an optical waveguide device  14   h  (optical attenuator) according to still another embodiment of the invention respectively. The optical waveguide device  14   h  of the embodiment is one in which the cover glass  17  is eliminated from the structure of the optical waveguide device  14   e  according to the fifth embodiment shown in  FIGS. 23 to 25 . 
     FIGS. 41A and 41B  and  FIGS. 42A and 42B  describe the manufacturing method of the optical waveguide device  14   h  of the invention. An opaque silicon substrate  39   a  of which the heaters  40   a  and  40   b  and the pads  41   a  and  41   b  are formed on the lower surface, shown in  FIG. 41A , is produced in the same processes as those shown in  FIGS. 26A ,  26 B, and  26 C. In the optical waveguide substrate  15  shown in  FIG. 41A , similarly to the first embodiment, the lower cladding layer  18  and the cores  19   g  to  19   k  are formed on the transparent cover glass  17  by the duplicating method using the resin. As shown in  FIG. 41A , the uncured ultraviolet-curing resin  20   a , which has the same refractive index as that of the lower cladding layer  18  or the refractive index similar to that of the lower cladding layer  18 , is dropped onto the surface of the lower cladding layer  18  in the optical waveguide substrate  15  to bond the silicon substrate  39   a  on which the electrode lead pads  41   a  and  41   b  and the heaters  40   a  and  40   b  are formed. 
   At this point, as shown in  FIG. 41B , a part where it is not necessary to form the upper cladding layer  20  is covered with the mask  36   a  from the lower surface of the cover glass  17 , and the upper cladding layer  20  is formed in such a manner that the ultraviolet-curing resin  20   a  is irradiated with the ultraviolet ray from the lower side of the mask  36   a  to cure it. 
   As shown in  FIG. 42A , the cover glass  17  is cut off with the dicing blade while the optical waveguide device is inversely turned around so that the silicon substrate  39   a  is placed on the lower side and the cover glass  17  is placed on the upper side. Even in this case, with reference to the method for removing the cover glass  17 , the cover glass  17  may be mechanically peeled off from the lower cladding layer  18  by applying force to the cover glass  17  or the cover glass  17  may be dissolved by the etching or the like to remove it. In the case that the cover glass  17  is peeled off, the material having low adhesion properties may be previously formed between the cover glass  17  and the lower cladding layer  18  or processing which reduce the adhesion properties between the cover glass  17  and the lower cladding layer  18  may be previously performed to the cover glass  17 . In the case that the adhesion properties of the cover glass  17  and the lower cladding layer  18  is too low and the surface treatment is performed in order to improve the adhesion properties, the conditions for improving the adhesion properties may be released. In the case that the cover glass  17  is removed by the etching, it is desirable to selectively etch the cover glass  17  by using the etchant which could not etch the lower cladding layer  18 . 
   Further, as shown in  FIG. 42B , the optical waveguide device  14   h  shown in  FIG. 38  is completed in such a manner that the unnecessary part of the lower cladding layer  18  is cut off with the dicing blade and the electrode lead pads  41   a  and  41   b  are exposed. The cut-off lower cladding layer  18  and the remaining uncured resin  20   a  are washed away with the cooling water of the dicing blade. In the case that the ultraviolet-curing resin  20   a  is not thoroughly washed away with the cooling water of the dicing blade, the ultraviolet-curing resin  20   a  may be thoroughly removed by further using the solvent. 
   (Ninth Embodiment) 
     FIG. 43  is the perspective view showing the structure of an optical waveguide device  14   i  according to still another embodiment of the invention. In the substrate for mounting  16  of the optical waveguide device  14   i , the optical element placing portion  24   b  is provided in order to mount the light emitting element on the upper surface of the opaque supporting substrate  21  such as the silicon substrate, the element mounting bench  33   b  is provided inside the optical element placing portion  24   b , the V-groove shaped optical fiber guide  23   a  is provided on one end of the supporting substrate  21  so as to be opposite to the optical element placing portion  24   b , and the waveguide fixing region  30  is provided in the form of the concavity between the optical element placing portion  24   b  and the optical fiber guide  23   a . A line-shaped core  191  is embedded in the lower surface of the lower cladding layer  18  and the upper cladding layer  20  is provided on the lower surface of the lower cladding layer  18 . The optical waveguide substrate  15  is fixed on the substrate for mounting  16  so that the upper cladding layer  20  is embedded in the waveguide fixing region  30 . The optical waveguide device  14   i  is also produced by removing the cover glass  17  in the same way as the sixth embodiment. The filter placing groove  31  is obliquely cut by the dicing in the lower cladding layer  18  and the upper cladding layer  20 , and the filter  29  such as a WDM filter is inserted in the filter placing groove  31 . 
     FIG. 44  shows the state in which the optical waveguide device  14   i  is used as the optical transceiver. A light emitting element  8  is mounted on the element mounting bench  33   b  so that the light outgoing surface of the light emitting element  8  is opposite to the end face of the core  191 . A chip-shaped or package type of light receiving element  10  is fixed on the upper surface of the lower cladding layer  18  while a light receiving surface of the light receiving element  10  faces downward. The optical fiber  26  is fixed in the optical fiber guide  23   a  so as to be opposite to the end face of the core  191 . The light outgoing from the light emitting element  8  propagates in the core  191 , passes through the filter  29 , and reaches the optical fiber  26 . The light outgoing from the optical fiber  26  propagates through the core  191  to be reflected by the filter  29 , and then the light is transmitted by the lower cladding layer  18  to be received by the light receiving element  10 . 
     FIG. 45  is the comparative example for comparing to the optical waveguide device  14   i . In the optical waveguide device of the comparative example, the cover glass  17  remains on the lower cladding layer  18  and the light receiving element  10  is provided on the upper surface of the cover glass  17 . In the comparative example, while the thickness of the lower cladding layer  18  is about 20 μm, the thickness of the cover glass  17  is in the range of about 500 to about 1000 μm, so that the distance between the reflecting position of the light by the filter  29  and the light receiving element  10  becomes farther and the reflected light is widened. Consequently, the light quantity which is detected by the light receiving element  10  becomes very small and light receiving sensitivity is decreased. 
   On the other hand, in the optical waveguide device  14   i  of the invention, since the distance between the reflecting position of the light by the filter  29  and the light receiving element  10  can be reduced by the distance in which the cover glass  17  is absent, the light receiving sensitivity can be improved. 
   The comparison of the light receiving quantity in the optical waveguide device  14   i  according to the invention and the comparative example is as follows. Supposing that the thickness of the lower cladding layer  18  is 20 μm and the thickness of the cover glass  17  is 1000 μm (=1 mm) (for example, the oblique angle of the filter is set to 40°), the distance from the reflected point by the filter  29  to the light receiving element is 20.3 μm in the case that only the lower cladding layer  18  is provided, and the distance from the reflected point by the filter  29  to the light receiving element is 1036 μm in the case that the cover glass  17  is provided. Accordingly, the ration of the light receiving quantity is about 1/2601 (the ratio is about 1/676 in case that the thickness of the cover glass  17  is set to 500 μm). In order to obtain the same light receiving quantity, the light receiving element having the about 2600 times light receiving area is required in the case that the cover glass  17  is provided, so that the cost of the light receiving element  10  is quite increased. Further, capacitance of the light receiving element is increased as the light receiving area is increased. Since the communication speed is inversely proportional to the light receiving area, when the light receiving element  10  having such a large area is used, it is impossible to perform the high-speed communication, and it cannot be practically used. 
   With reference to the method for shortening the distance between the filter and the light receiving element while the cover glass  17  remains, as shown in  FIGS. 46A and 46B , it is considered that the waveguide fixing region  30  is provided in the form of the concavity in the supporting substrate  21  made of the silicon substrate, the cover glass  17  of the optical waveguide substrate  15  faces to the lower side, and the cover glass  17  is stored in the waveguide fixing region  30 . However, in such a structure, the waveguide fixing region  30  having the same depth as the thickness (500 to 1000 μm) of the cover glass  17  need to be provided in the supporting substrate  21  by the etching. Therefore, dispersion in accuracy of the depth of the waveguide fixing region  30  is too large, and it is absolutely impossible to adjust the height of the core of the optical fiber to the height of the core  191  of the waveguide. 
   For example, an average value of the amount of dispersion is about ±10% when the silicon substrate is etched with KOH having an etching rate of 0.5 to 1.0 μm/m for 17 to 33 hours. Supposing that the amount of dispersion in the etching is a normal distribution and standard deviation is set to σ, the average value is ±10% ±4σ, and it occupies the most part of the area in the normal distribution curve. On the other hand, when the amount of dispersion is suppressed within ±1 μm, the normal distribution has the width of ±1 μm=±0.04σ and it becomes about 3.2% of the area in the normal distribution. Yield becomes about 1/30, so that the cost is increased to about 30 times. Therefore, the structure shown in  FIG. 46  has no practicality. 
   (Tenth Embodiment) 
     FIG. 47  is the schematic view showing an apparatus for coupling and separating a light wave, in which the optical attenuators  129  and  133  according to still another embodiment of the invention are used (for example, the optical waveguide device shown in  FIGS. 23 and 24 ). The wave separator  127  and the wave coupler  128  are the device which is used in the wavelength division multiplexed (WDM) optical communication system which transmits the plurality of optical signals having the different wavelengths with one optical fiber  131 . The wave separator  127  is the device in which the optical signal transmitted with the one optical fiber  131  is separated in each wavelength to output each wavelength to the different optical fibers respectively. The wave coupler  128  is the device in which the optical signals having the different wavelengths inputted with the plurality of optical fibers are coupled to output it to the one optical fiber  132 . The optical waveguide device according to the invention may be used as an optical switch  110   e.    
   The optical switch  110   e  (2×2 optical switch) is the optical waveguide device which can switch a traveling direction of the light propagating through the core and radiate the light only from the selected core. The variable optical attenuators (VOA)  129  and  133  show the same as the one shown in the fifth embodiment. Two entrances of light incident are provided in each optical switch  110   e , one of the two entrances of light incident is connected to the wave separator  127  with an optical fiber  130   a , and the light beams having the wavelengths λ 1 , λ 2 , . . . , λN separated with the wave separator  127  is inputted to the one light incident end. The other is the entrance of incident of the light signal transmitted with an optical fiber  130   b  which in not connected to the wave separator  127 . The optical fiber  130   b  may be connected to other wave separator except the wave separator  127 . 
   Further, two light outgoing ends are provided in each optical switch  110   e , one of the two light outgoing ends is connected to the wave coupler  128  through the variable optical attenuators (VOA)  129  with an optical fiber  130   c , and the other of the two light outgoing ends is connected to an optical fiber  130   d  which in not connected to the wave coupler  128 . The optical fiber  130   d  may be connected to another wave coupler except the wave coupler  128 . 
   In the optical communication system using the wave coupler and separator, for example, the optical fibers  131  and  132  constitute a trunk network line in a network within city or an intercity network and transmit the wavelength division multiplexed signal. Supposing that all the optical switches  110   e  are connected to the side of the wave coupler  128 , after the wavelength division multiplexed signal transmitted through the trunk network line including the optical fiber  131  is separated into the light beams having the wavelengths λ 1 , λ 2 , . . . , λN by the wave separator  127 , the signal passes through each optical switch  110   e  to the side of the wave coupler, power of the signal of each wavelength is uniformed with the optical attenuator  129 , the signal of each wavelength λ 1 , λ 2 , . . . , λN is coupled again with the wave coupler  128 , the power of the whole wavelength division multiplexed signals is adjusted with the optical attenuator  133  so as to be set to a specified value, and the signal is transmitted to the trunk network line. 
   On the other hand, for example, if the optical switch  110   e  corresponding to the wavelength λ 1  is switched to the side different from the side of the wave coupler, only the signal of the wavelength λ 1  among the signals separated by the wave separator  127  is taken out to an access network line including the optical fiber  130   d . If the signal of the wavelength λ 1  has been transmitted from the access network line including the optical fiber  130   b , the signal of the wavelength λ 1  from the line is transmitted to the wave coupler  128  with the optical switch  110   e , superimposed on the wavelength division multiplexed signal transmitted from the optical fiber  131  to be outputted to the trunk network line including the optical fiber  132 . 
   In the optical network system, it is necessary that a user network in each home is connected to the trunk network with the access network (subscriber optical network), and an optical network unit for performing opto-electric conversion is required between the access network and the user network. Further, an optical line terminal for performing the opto-electric conversion is required at an exchange office (facilities center of telephone network operator) between the access network and trunk network. 
     FIG. 48  is a block diagram showing a configuration of the above-described optical network unit. A reference numeral of  136  indicates the optical fiber constituting the access network, and the optical fiber transmits the optical signal having the wavelength of 1550 nm and the optical signal having the wavelength of 1310 nm. WDM  137  is provided at the position opposite to the end face of the optical fiber  136 . In WDM  137 , the optical signal having the wavelength of 1550 nm transmitted through the optical fiber  136  is outputted from an outputting portion and the optical signal having the wavelength of 1310 nm inputted from an inputting portion is connected to the optical fiber  136 . 
   The optical signal having the wavelength of 1550 nm outputted from the outputting portion in WDM  137  is inputted into an opto-electric conversion module (PIN-AMP module)  138 . The opto-electric conversion module  138  includes a photo diode  139  and a preamplifier  140 . In the opto-electric conversion module  138 , the inputted optical signal is received with the photo diode  139  to convert it into the electric signal, amplified with the preamplifier  140 , and inputted to a data processing circuit  141 . Then, the electric signal processed with the data processing circuit  141  is transmitted to a telephone or a controller for home use, which is connected to the optical network unit. 
   On the other hand, an opto-electric conversion module  142  connected to the inputting portion in WDM  137  includes a laser diode  143  and a light receiving element for monitoring  144 . The laser diode  143  emits the light having the wavelength of 1310 nm, and the laser diode  143  is driven by a laser diode driving circuit  145 . The output is controlled so that the power of the optical signal emitted from the laser diode  143  becomes constant in such a manner that the optical signal emitted from the laser diode  143  is received with the light receiving element for monitoring  144 . Accordingly, the electric signal transmitted from the telephone or the home appliance is transmitted to the laser diode driving circuit  145 , the electric signal is converted into the optical signal in such a manner that the laser diode  143  is driven by the electric signal inputted into the laser diode driving circuit  145 , and the optical signal is transmitted to the optical fiber  136  through WDM  137 . 
   In the above-described optical network unit, the optical network unit can be miniaturized by using the optical waveguide device according to the invention. For example, the filter  29  and the cores  19   a ,  19   b , and  19   c  in the optical waveguide device (optical transceiver)  14   a  described from  FIG. 3  may be used as WDM  137 , the light receiving element  27  mounted on the optical waveguide device  14   a  may be used as the light receiving element  139  in the opto-electric conversion module  138 , and the light emitting element  28  mounted on the optical waveguide device  14   a  may be used as the laser diode  143  in the opto-electric conversion module  142 . The optical network unit can be formed in one-chip by mounting the preamplifier  140 , the data processing circuit  141 , the light receiving element for monitoring  144 , the laser diode driving circuit  145 , and the like on the supporting substrate  21  of the optical waveguide device  14   a.    
   Though the case of the optical network unit (ONU) was described here, the optical waveguide device of the invention can be also used for the optical line terminal (OLT). 
   According to the manufacturing method of the optical waveguide device of the invention, the unnecessary part generated in the mass production of the optical waveguide device can be easily removed. Further, since it is not necessary to provide the additional process for the removal of the unnecessary part, the manufacturing process can be simplified, the time taken for producing the optical waveguide device can be shortened, and the cost of the manufacturing can be suppressed. 
   According to the manufacturing method of other optical waveguide device of the invention, the optical waveguide device can be thinned. 
   While the invention has been described with respect to a limited number of embodiments, those who skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.