Abstract:
There is provided a method of manufacturing an optical module comprises a component fixing step in which an optical waveguide and at least one optical device are detachably held by a fixing member capable of holding an uncured light curable resin in a required position, and a core forming step in which light of a wavelength for curing the light curable resin is emitted from the leading end of the optical waveguide to the light curable resin uncured and thus the light curable resin is cured to form a shaftlike core. According thereto, the optical waveguide and the optical device are connected by the core.

Description:
This application is based on Japanese Patent Application No. 2004-164084 and 2005-095568, which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optical module that has a core fabricated using a light curable resin solution and light, and to a method of and an apparatus for manufacturing the optical module. The invention is applicable to an inexpensive and low-loss optical module for use in optical fiber communications, such as an optical transmitter and receiver, an optical interconnection device, and an optical branching filter or coupler. 
   2. Description of the Related Art 
   The inventors, together with their coinventors, have developed and applied for patent on an optical waveguide having a so-called self-forming type core. The self-forming type core forms the optical waveguide in the following manner. That is, for example, a liquid light curable resin uncured is irradiated with curing wavelength light in a beam form from an optical fiber. Thereby, only the resin in an optical path portion irradiated in the beam form is cured to form a shaftlike cured material (core). Thereafter, the core is surrounded by a lower refractive index resin for example, thus forming the optical waveguide (see JP-A-2002-365459). Besides, the following is shown by using two light curable resins different in refractive index and curing wavelength. That is, when only the resin on the high refractive index side is cured for a long time (see JP-A-2002-169038) and when only the resin on the low refractive index side is cured for a short time (see JP-A-2004-149579), the remaining resin solution uncured is thereafter cured, thereby making it possible to form two kinds of optical waveguides each having a specific refractive index distribution. 
   The technology related to the invention will be described using  FIGS. 4A to 4E .  FIGS. 4A to 4E  are process diagrams showing a method of manufacturing an optical module having one light receiving device and one light emitting device. 
   As shown in  FIG. 4A , an open-topped casing  91  made of transparent resin is prepared, and a core end face  921  of an optical fiber  92  is introduced into the inside of the casing  91  and then fixed by a fixing member  93 . Next, a half mirror or dichroic mirror (wavelength selective mirror)  94  is fixed to the casing  91 . The half mirror or dichroic mirror (wavelength selective mirror)  94  is fixed inclined at 45 degrees to the bottom surface of the casing  91 . Thereafter, to form a core member, the inside of the casing  91  is filled with a high refractive index light curable resin solution  95  uncured. 
   Next, when the light curable resin solution  95  having filled the casing  91  from the end face  921  is irradiated with the curing wavelength light by the optical fiber  92 , then a cured material  95   c  is formed as being shaftlike along the optical path of the light ( FIG. 4B ). Since the half mirror or dichroic mirror (wavelength selective mirror)  94  is used this time, the cured material  95   c  will have branches. Thereafter, the light curable resin solution  95  uncured is removed ( FIG. 4C ). Next, the inside of the casing  91  is filled with a low refractive index curable resin solution  96  uncured that is to provide a cladding. Light curing, heat curing, or any other method may be adopted to cure the curable resin solution  96 . Thus, the curable resin solution  96  having filled the inside of the casing  91  is all cured into a cured material  96   c,  thereby forming optical waveguides, one of which has the high refractive index cured material  95   c  serving as the core and the other of which has the low refractive index cured material  96   c  serving as the cladding ( FIG. 4D ). 
   Thereafter, for example, a light emitting device  97  and a light receiving device  98  are attached to the vicinities of the junctions between the cured materials  95   c  serving as the cores and the casing  91  made of transparent resin. Thus, an optical module  900  capable of single-line two-way communication can be completed ( FIG. 4E ). 
   In the optical module  900  of  FIG. 4E , the light emitting device  97  and the light receiving device  98  face the cured materials  95   c  serving as the cores via the casing  91  made of transparent resin. With such a structure, it turns out, the following problem arises when a life and a deterioration in characteristics as a module are evaluated based on a so-called acceleration test. That is, in the state where the load of normal humidity at 85° C. or 95% relative humidity at 75° C. is applied, it turns out, the bonding between the cured material  95   c  serving as the core and the optical device  97 ,  98  is deteriorated in several hours, so that a light transmission loss is lost on the order of 40%. This is caused mainly by separation of the cured resin from the casing. 
   SUMMARY OF THE INVENTION 
   Thereupon, the inventors have earnestly examined an optical module having a self-forming type core in a different configuration from those of  FIGS. 4A to 4E  and have finally completed the invention. That is, an object of the invention is to provide an optical module in which the bonding between a core made of cured resin and an optical device is not easily deteriorated. 
   To solve the aforesaid problem, according to the invention, a method of manufacturing an optical module comprises holding detachably the optical waveguide and at least one optical devic by a mold, holding an uncured light curable resin in the mold, emitting light of a wavelength for curing the light curable resin from a leading end of the optical waveguide to the light curable resin and curing the light curable resin to form a core, and connecting the optical waveguide and the optical device by the core. Besides, the method further comprises removing an uncured part of the light curable resin from a surface of the core, and covering the leading end of the optical waveguide, an exposed surface of the core, and the optical device with a cladding material. Besides, the mold is detached after the core is formed. Besides, the core is formed after at least one optical component such as a mirror, half mirror is held on the mold. Here, an optical waveguide that is manufactured by any method. Besides, in the case of a plurality of the optical devices, it is derived that the core requires the number of branches smaller by one than the number of the optical devices. Besides, any number of curved portions can also be formed by using the mirrors. In the case of one optical device, the number of mirrors, half mirrors, and other optical components may be zero. The optical devices refer to a light emitting device, a light receiving device, an optical modulator, a coupler, and other devices. 
   Besides, the uncured resin removal step is carried out after the optical waveguide, the any number of mirrors, half mirrors, and other optical components, the one or plurality of optical devices, and the waveguide, which is formed so as to integrally connect them together and is branched and/or bent according to need, are detached from the mold. As aforesaid, in the case of one optical device, the number of mirrors, half mirrors, and other optical components may be zero. 
   Besides, the cladding material includes a light curable or heat curable resin, and the exposed surface of the core is covered with the light curable or heat curable resin uncured, which resin is thereafter cured. Besides, the optical component and the optical device are fixed as the cladding material covers main portions thereof and as the cladding material covers a vicinity of the emitting end of the optical waveguide. Here, that the cladding material covers the main portions of the optical components and optical devices means that the cladding material covers them to a sufficient extent to fix them, and is not limited to the state in which the cladding material fully covers them. 
   Besides, an optical module comprises an optical waveguide, a core that is formed in a self-forming manner by light curing as light is emitted from a leading end of the optical waveguide, an optical device connected to an other end of the core, and a cladding that, made of resin cured to integrally cover the leading end of the optical waveguide, the core, and the optical device. Besides, polymerization of the core and the cladding material proceeds due to heating, and the contraction ratio of the cladding material is higher than that of the core. 
   Besides, the mold comprises an opening in the upper side thereof, and a drain port which is provided in a bottom of the mold to drain an uncured resin, wherein an end of the optical waveguide is inserted into the mold in a horizontal direction, and wherein a formed resin component and the optical waveguide is detached from the mold in a state where the resin component and the optical wavegude are held connected. Besides, the method of manufacturing an optical module further comprises inserting one end of the optical waveguide into the mold in a horizontal direction, putting the optical device into the mold through an opening of the mold and fix the optical device temporarily, introducing the light curable resin into the mold, emitting a light beam at a wavelength adapted to harden the curable resin, from an other end of the optical waveguide into the mold, thereby to form the core which extends from the one end of the optical waveguide inserted into the mold, to the optical device, opening a drain port in a bottom of the mold, draining an uncured part of the light curable resin from the drain port, releasing a temporary fixation of the optical device connected by the core, and introducing a cladding material into the mold, curing the cladding material, and taking a optical module having the optical waveguide and the optical device integrated by the cladding material out of the mold. Besides, the curable resin is introduced after any desired number of reflective mirrors, semitransparent mirrors or other optical components have been put into the mold through the opening of the mold and have been temporarily fixed. Here, in the case where the plurality of optical devices exist, it is derived that the core requires a branch or branches the number of which is smaller by one than that of the optical devices. Also, any desired number of bent portions can be formed by employing the mirror or mirrors. In the case of the single optical device, none of the reflective mirror, semitransparent mirror and other optical component may well be disposed. The “optical device” signifies a light emitting device, a light receiving device, a light modulating device, a photocoupler, or the like. 
   Besides, an apparatus for manufacturing an optical module of the invention comprises a mold which has an opening and is capable of draining an uncured resin from a drain port that is provided in a bottom of the mold, wherein one end of the optical waveguide is insertable into the mold in a horizontal direction, and a formed resin component and the optical waveguide are detachable from the mold in a state where the resin component and the optical waveguide are connected to each other, a jig for putting at least one optical device into the mold through the opening of the mold so as to temporarily fix the optical device, means for introducing a light curable resin for forming a core into the mold, means for guiding a light beam at a wavelength adapted to cure the light curable resin, from an other end of the optical waveguide into the mold, means for introducing a cladding material into the mold, and means for curing the cladding material, wherein the optical waveguide and the optical device are connected by a core formed from the light curable resin, and covered with the cladding material. 
   The invention makes it possible to provide an optical module that uses a self-forming type core, wherein the core and optical devices are not easily separated. According to the invention, the optical devices can be pre-aligned in position, so that the process is simplified, thus enabling a reduction in cost. Besides, since a resin reservoir for a curable resin for core formation and a mold for clad formation are made common, the process can be simplified. Besides, the core can be bonded directly to the optical devices and not via the casing, thus improving bonding efficiency, so that a device life can be lengthened and a deterioration in characteristics can be suppressed. 
   The detachable fixing member may be detached at any step, but when it is detached before the uncured resin removal step, the uncured resin can be properly removed. When the cladding material uses a light or heat curable resin, especially a liquid one, the core can be fully covered therewith, thus making it possible to restrain light from leaking through a core surface. The cladding material also covers the mirrors, half mirrors, and other optical components, the main portions of the optical devices, and the vicinity of the emitting end of the optical waveguide, thereby making it possible to provide a strong optical module that is difficult to break. 
   Besides, the core can be bonded directly to the optical devices and not via the casing, thus improving bonding efficiency, so that a device life can be lengthened and a deterioration in characteristics can be suppressed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A to 1D  are process diagrams showing in conceptual form a manufacturing method of the invention 
       FIG. 2A  is a perspective oblique view showing a fixing member configured of two mold forms;  FIG. 2B  is an oblique view showing an optical module main portion having optical components connected by a core  6   c  made of a cured light curable resin; 
       FIG. 3A  is a graph chart showing a change in optical characteristics resulting from an acceleration test on bonding to a light emitting device;  FIG. 3B  is a graph chart showing a change in optical characteristics resulting from an acceleration test on bonding to a light receiving device; 
       FIGS. 4A to 4E  are process diagrams showing an optical module manufacturing method described in JP-A-2002-365459; 
       FIGS. 5A to 5D  are process diagrams (plan views) showing in conceptual form a manufacturing method of the invention; 
       FIG. 6  is a perspective view showing an example of a mold for use in the invention; and 
       FIGS. 7A to 7C  are process diagrams (side views) showing some steps of the manufacturing method in the case of using the mold in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Any optical components, etc. can be used to put the invention into practice. The pre-formed optical waveguide can suitably use an optical fiber such as a plastic optical fiber (POF) or a glass optical fiber (GOF). Other than the so-called fiber-shaped optical waveguide, however, any optical waveguides capable of emitting light in a beam form as described later are acceptable regardless of their shape. When an optical waveguide whose cladding portion is easy to process is used out of them, as described later, the processed cladding portion of the POF is covered with a cladding material of a self-forming type optical waveguide, whereby it is easy to make it difficult that the POF comes off the optical module. 
   Any available light curable resin can be used to form the core. For example, in JP-A-2002-169058 and JP-A-2002-149579, light curable resins and polymerization initiators of radical polymerization type and cationic polymerization type are listed as examples in which they are used as two-component mixtures. However, any one kind of the light curable resins described in JP-A-2002-169038 and JP-A-2004-149579 can be used independently as the light curable resin for forming the core of this application. To reinforce the adhesion between the core end face of the optical fiber and the device surfaces of the optical devices, as described in JP-A-2002-365459, a silane coupling agent may be used by dissolving or dispersing it in a light curable resign solution. The cladding material can similarly use any one kind of the light curable resins and polymerization initiators described in JP-A-2002-169038 and JP-A-2004-149579, or otherwise may use a heat curable resin. 
   First Embodiment 
     FIGS. 1A to 1D  are process diagrams showing in conceptual form a manufacturing method according to a first embodiment of the invention. First, a POF  1 , a green PD (light receiving device)  2 , a red LED (light emitting device)  3 , and a wavelength selective mirror  4  are prepared. The method uses the wavelength selective mirror  4  that reflects red light and transmits green light. These optical components are disposed on a fixing member  5  to which are fixed a core end face  11  of the POF  1 , a light receiving surface of the light receiving device  2 , a light emitting surface of the light emitting device  3 , and a reflective surface of the wavelength selective mirror  4 , and from which the optical components are detachable. The fixing member  5  is configured such that a light curable resin solution  6  to provide a core can be disposed thereon between the core end face  11  of the POF  1  and the lower left surface of the wavelength selective mirror  4 , between the upper right surface of the wavelength selective mirror  4  and the light receiving surface of the light receiving device  2 , and between the lower left surface of the wavelength selective mirror  4  and the light emitting surface of the light emitting device  3 . This configuration is conceptually shown as in  FIG. 1A . The shape of the entire fixing member  5  and the shape of a portion thereof in which the light curable resin solution  6  is disposed, an example of which shapes will be described in  FIG. 2  and the subsequent figures, are merely conceptually shown by broken lines in  FIGS. 1A to 1D . 
   A POF having a core diameter of 980 μm and an NA of 0.30 is used as the POF  1 . By using “UVX-4037” made by Toagosei Co., Ltd., which is an acrylic resin, as the light curable resin solution  6 , a laser beam of 458 nm wavelength is irradiated into the light curable resin solution  6  from the POF  1 , thereby forming a shaftlike cured material  6   c  that has branches in the vicinity of the wavelength selective mirror  4 . The shaftlike cured material  6   c  is formed to provide connections between the core end face  11  of the POF  1  and the lower left surface of the wavelength selective mirror  4 , between the upper right surface of the wavelength selective mirror  4  and the light receiving surface of the light receiving device  2 , and between the lower left surface of the wavelength selective mirror  4  and the light emitting surface of the light emitting device  3  ( FIG. 1B ). The factor of curing into a shaftlike form lies in that the light curable resin solution  6  is increased in refractive index by curing. In fact, the “UVX-4037” has a refractive index of 1.471 before curing and a refractive index of 1.491 after curing. 
   Thereafter, the fixing member  5  is detached and the light curable resin solution  6  uncured is removed ( FIG. 1C ). Thereafter, the formed module main portion is put in another mold for example, and the surrounding area thereof is covered with a cladding material  7 , which is cured. Thereby, an optical module  100  capable of single-line two-way communication can be formed with ease. Incidentally, “OP-38ZT”, which, made by Dainippon Ink and Chemicals, Inc., is a light curable fluorinated acrylic resin, is used as the cladding material  7 . The “OP-38ZT” has a refractive index of 1.380 after curing. 
   A combination of upper and lower two mold forms M 1  and M 2  as shown in  FIG. 2A  is adopted as the fixing member  5 . When the mold forms M 1  and M 2  are combined together, a portion  1   m  for fixing the POF  1 , a portion  2   m  for fixing the light receiving device  2 , a portion  3   m  for fixing the light emitting device  3 , a portion  4   m  for fixing the wavelength selective mirror  4 , and a portion  6   m  to be filled with the light curable resin solution  6  are formed as a continuous cavity. For example, since the shaftlike core  6   c  can be formed to have a diameter of 1 μm, the portion  6   m  to be filled with the light curable resin solution  6  is set to the size of the order of 2 μm in diameter. The reason is that, since the invention is not of injection molding type, the diameter of the portion  6   m  to be filled with the light curable resin solution  6  need be set larger than the designed diameter of the shaftlike core  6 . 
   By using the fixing member  5  as shown in  FIG. 2A , the core  6   c  is formed according to the process diagram of  FIGS. 1A to 1D , which then results in formation of an optical module main portion as shown in  FIG. 2B . It is apparent that the configuration of  FIG. 2B  is the same as that of  FIG. 1C . In  FIG. 2A , the cladding portion of the POF  1  is processed into a two-step flangelike form in order to prevent the POF  1  from coming off. This processing works effectively both when the POF  1  is fixed to the fixing member  5  as shown in  FIG. 2A  and when the entire module is covered with the cladding material shown in  FIG. 1D , thus making it possible to prevent the POF  1  from coming off. 
   As a comparative example of the optical module  100  of the invention formed as aforesaid, according to the process of  FIGS. 4A to 4E , a POF  91 , a red LED  97 , a green PD  98 , and a wavelength selective mirror  94  are prepared as the same optical components, and an optical module  900  is formed using the “UVX-4037” as a core and the “OP-38ZT” as a cladding. Then, an acceleration test is performed to the optical module  100  and the optical module  900 , thus evaluating a change in optical characteristics. The results are shown in  FIGS. 3A and 3B . The vertical axis of  FIGS. 3A and 3B  indicates 0 in the condition before the acceleration test, a positive when an optical loss occurs, and a negative when a gain occurs. 
   As shown in  FIG. 3A , as for red light from the red LED  3 ,  97  to the POF  1 ,  91 , in the optical module  100  of the invention, there is almost no change in optical characteristics at normal humidity at 85° C. On the contrary, in the conventional optical module  900 , the optical characteristics deteriorate 2 dB or more at normal humidity at 85° C. (a 40% decrease in the amount of light). Besides, in the optical module  100  of the invention, a gain occurs at 95% relative humidity at 75° C. The reason seems to be that heating allows polymerization to proceed in both the core  6   c  and the cladding  7 , thus improving the bonding to the red LED  3 . Besides, as shown in  FIG. 3B , the green LED  2  is also similar in the change of optical characteristics to the red LED  3 . Thus, according to the invention, it is possible to easily provide the optical module in which no separation between the core and the optical device occurs due to heating and no deterioration in characteristics occurs. 
   The gain is considered to occur at 95% relative humidity at 75° C. for various reasons and, for example, there is the following possibility. First, the core  6   c  is in the state where it includes some amount of unpolymerized material when being cured and formed in a self-forming manner. Next, when the cladding material  7  is light-cured, the unpolymerized material of the core  6   c  is polymerized. On the contrary, the cladding material  7 , merely light-cured, is still in the state where it includes an unpolymerized material. When the optical module  100  in such a state is placed in a heated state, curing of the cladding material  7  proceeds. Thereby, the contraction in volume of the cladding material  7  by polymerization of the unpolymerized material is made larger than that of the core  6   c  by polymerization of the remaining unpolymerized material. Thus, it is highly possible that compressive stress occurs between the core and the optical device. 
   The aforesaid embodiment shows an example in which the combination of upper and lower two mold forms M 1  and M 2  provides the fixing member  5 , which is detached at the uncured resin removal step. However, the fixing member of the invention is not limited to this configuration. The combinational fixing member can be modified in various ways so as to be capable of easy conception. For example, the configuration may be such that the mold forms used to cure the core  6   c  are used in curing the cladding material. In the aforesaid embodiment, to suppress the consumption of the light curable resin forming the core, the portion  6   m  to be filled with the light curable resin solution  6  is made small in volume. However, as shown in the conceptual diagram of  FIG. 1A , the portion  6   m  may be large in volume. 
   The aforesaid embodiment shows an example in which the optical components are not positionally aligned in the fixing member  5 . Alternatively, the configuration may be such that the optical components are positionally aligned using an optical jig. The aforesaid embodiment uses one wavelength selective filter, one light emitting device, and one light receiving device. Alternatively, the optical module may be configured in the following manners by using a plurality of the wavelength selective filters. That is, light from any number of light emitting devices is collected and led to the POF etc. through the wavelength selective filters. Besides, incident light is branched through the wavelength selective filters, from the POF etc. to any number of light receiving devices, by selecting or not selecting a wavelength. 
   Second Embodiment 
     FIGS. 5A to 5D  are process diagrams showing in conceptual form a manufacturing method according to a second embodiment of the invention. First, a POF  1 , a green PD  2 , a red LED  3 , and a wavelength selective mirror  4  are prepared. The method uses the wavelength selective mirror  4  that reflects red light and transmits green light. The individual components are arranged within a mold  105  in such a way that the core end face  11  of the POF  1  is fixed by the mold  105 , and that the light receiving face of the light receiving device  2 , the light emitting face of the light emitting device  3  and the reflective surface of the wavelength-selective mirror  4  are temporarily fixed by jigs not shown. By the way, whereas  FIG. 4  depicts side views showing the process in a horizontal direction, the respective views of  FIG. 5  are side views showing the process from above. Within the mold  105  indicated by a broken line in  FIG. 5 , a curable resin liquid  6  to become a core could be arranged. Incidentally, as will be indicated below, the core  6   c  to be hardened and formed in self-forming fashion is formed between the core end face  11  of the POF  1  and the left lower surface of the wavelength-selective mirror  4 , between the right upper surface of the wavelength-selective mirror  4  and the light receiving face of the light receiving device  2 , and between the left lower surface of the wavelength-selective mirror  4  and the light emitting face of the light emitting device  3 . This configuration is conceptually shown as in  FIG. 5A . The shape of the entire mold  105  and the shape of a portion thereof in which the light curable resin solution  6  is disposed, an example of which shapes will be described in  FIG. 6  and the subsequent figures, are merely conceptually shown by broken lines in  FIGS. 5A to 5D . 
   A POF having a core diameter of 980 μm and an NA of 0.30 is used as the POF  1 . By using “UVX-4037” made by Toagosei Co., Ltd., which is an acrylic resin, as the light curable resin solution  6 , a laser beam of 458 nm wavelength is irradiated into the light curable resin solution  6  from the POF  1 , thereby forming a shaftlike cured material  6   c  that has branches in the vicinity of the wavelength selective mirror  4 . The shaftlike cured material  6   c  is formed to provide connections between the core end face  11  of the POF  1  and the lower left surface of the wavelength selective mirror  4 , between the upper right surface of the wavelength selective mirror  4  and the light receiving surface of the light receiving device  2 , and between the lower left surface of the wavelength selective mirror  4  and the light emitting surface of the light emitting device  3  ( FIG. 5B ). The factor of curing into a shaftlike form lies in that the light curable resin solution  6  is increased in refractive index by curing. In fact, the “UVX-4037” has a refractive index of 1.471 before curing and a refractive index of 1.491 after curing. 
   Thereafter, a drain port in the bottom of the mold  105  is opened and the light curable resin solution  6  uncured is removed ( FIG. 5C ). Thereafter, the mold  105  is washed, and is filled up with a clad material  7 , which is subsequently hardened. In this way, an optical module  100  capable of single-wire two-way optical communications can be formed with ease ( FIG. 5D ). Incidentally, “OP-38ZT”, which, made by Dainippon Ink and Chemicals, Inc., is a light curable fluorinated acrylic resin, is used as the cladding material  7 . The “OP-38ZT” has a refractive index of 1.380 after curing. 
   Usable as the mold  105  is a substantially rectangular one which has no top surface and has an opening above as shown in  FIG. 6 . The mold  105  is so constructed that the bottom  105 B is slidable in the lengthwise direction of this mold, and that a bottom surface inside this mold can be entirely opened. A part  105 ′ of the front surface of the mold  105  is detachable. The front surface of the mold  105  is provided with a recess  1 H in the shape of the side surface of a semicircular column, and it forms a support portion for the POF  1  together with the recess  1 H′ of the part  105 ′ in the shape of the side surface of the semicircular column. The columnar side surfaces of the recesses  1 H and  1 H′ define a columnar side surface of radius R, and this columnar side surface is formed so as to agree with the outer peripheral surface of the POF  1 . Besides, the mold  105  and its part  105 ′ have their connection surfaces formed into a packing, and when they are combined, the resin liquid filling up the interior of the mold  105  is prevented from leaking out. 
   A process chart in the case of employing the mold  105  in  FIG. 6  is illustrated as side views (sectional views).  FIG. 7A  shows a state where the bottom  105 B of the mold  105  is closed, where the POF  1  is fixed by the detachable part  105 ′, where the green PD  2 , red LED  3  and wavelength-selective mirror  4  are temporarily fixed by the respective jigs  2 H,  3 H and  4 H, and where the mold  105  is filled up with the unhardened curable resin  6 .  FIG. 7A  corresponds to  FIG. 5A . Incidentally, the wiring electrodes of the green PD  2  and red LED  3  are omitted from illustration. 
     FIG. 7B  shows a state where the bottom  105 B of the mold  105  is slid and opened, and where the unhardened resin is removed.  FIG. 7B  corresponds to  FIG. 5C . 
     FIG. 7C  shows a state where the bottom  105 B of the mold  105  is slid and closed, and where this mold is filled up with the clad material  7 . When the clad material  7  is hardened in the state of  FIG. 7C , the optical module  100  in  FIG. 5D  could be formed. The detachable part  105 ′ is detached as shown in  FIG. 6 , whereby the optical module  100  could be easily taken out of the mold  105 . 
   In the above example, the mold  105  whose bottom  105 B is slidable is employed, but the mold may be provided with means capable of removing the unhardened curable resin, in its bottom. Incidentally, an alternative drain port may well be in such a shape that the unhardened curable resin is drawn out upwards from a nozzle. The jigs for the temporary fixations may be any articles which can position the optical devices and optical component. These jigs may be demounted either in advance of the removal of the unhardened curable resin, or midway of filling up the mold  105  with the clad material  7 . 
   The above example included one wavelength-selective filter, and one light emitting device as well as one light receiving device. It is also allowed, however, to construct an optical module in which a plurality of wavelength-selective filters are employed, whereby lights from any desired number of light emitting devices are collected and guided to a POF or the like, or input light is branched from a POF or the like into any desired number of light receiving devices with or without the selection of wavelengths. 
   In case of constructing an optical module in which a green LED and a red PD are respectively substituted for the green PD  2  and red LED  3  of the foregoing optical module  100 , and employing these optical modules in combination, a two-way optical communications module in which lights of two wavelengths are separately used for up and down communications can be formed with ease. Incidentally, the wavelength characteristics of the light receiving devices and light emitting devices and those of the wavelength-selective mirrors can be selected and applied at will.