An optical waveguide component and a manufacturing method therefor

Abstract: The invention concerns a method for manufacturing an optical waveguide component which has end faces connectable with optical fiber connectors. The method comprises the steps of: arranging guide pins (4a, 4b) and optical fiber ferrules (15), having optical fibers (12) set therein, at the upper portion of a mold (14) so as to be positioned with respect to one another, the mold (14) having at least three pin rods (16) capable of fine motion at the bottom thereof; placing an optical waveguide component body (A1), having an optical waveguide core portion (2) embedded therein, on the at least three pin rods (16) in a manner such that the end faces of the optical waveguide core portion (2) are opposed to the respective end faces of the optical fiber ferrules (15), the optical waveguide core portion (2) comprising cores (2a) which can be butt jointed with the optical fibers (12) to achieve optical coupling therebetween; injecting a molding resin into the mold (14) after finely adjusting the motion of the pin rods (16) to align the optical waveguide core portion (2) with the optical fibers (12) in the optical fiber ferrules (15); and taking out the resulting cast article from the mold (14) and removing the guide pins (4a, 4b), thereby forming guide pin holes (9a, 9b) in each end face of a resin mold portion covering all the faces of the optical waveguide component body except both end faces thereof.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an optical waveguide component used with optical fiber connectors connected to the end faces thereof and a manufacturing method therefor, and more particularly, to an optical waveguide component used with optical fiber connectors connected thereto without alignment, and a manufacturing method therefor. Description of the Prior Art An optical waveguide component, which has an optical waveguide core portion of a predetermined pattern embedded in a cladding portion, is used with single- or multi-core optical fiber connectors connected to both end faces thereof. There are two methods for connecting the optical fiber connectors. In one method, the end face of each optical fiber connector is butted to an end face of the optical waveguide component, the respective optical axes of optical waveguide cores are aligned individually with those of optical fibers, and thereafter, the connector and the component are fixed by bonding or welding. The other method is a non-alignment connecting method, which will be described below. The non-alignment connection is applied to an optical waveguide component, such as the one shown in Fig. 1, for example. In an optical waveguide component A, as shown in Fig. 1, an optical waveguide core portion 2 is formed on an optical waveguide substrate 1, such as a silicon substrate with a predetermined thickness. The core portion 2, which is composed of optical waveguide cores 2a of quartz glass arranged at predetermined pitches in the crosswise direction of the substrate 1, is embedded in a cladding portion 3 of quartz glass (with a lower refractive index than that of the core material). Two grooves 3a and 3b, which have a predetermined width and depth and extend in the lengthwise direction of the substrate 1, are marked in the cladding portion 3 and the substrate 1, ranging from the top of the cladding portion to the near portion of the bottom of the substrate, by means of a dicer, for example. In doing this, the optical waveguide core portion 2 is used as a positioning reference. Guide pins 4a and 4b with a predetermined diameter are arranged in the grooves 3a and 3b, respectively, and the whole resulting structure is pressed by means of a hold-down plate 5 so that the pins 4a and 4b are fixed in the grooves 3a and 3b. On the other hand, optical fiber connectors 6 each contain optical fibers which are arranged at the same pitches as the cores 2a of the core portion 2 of the optical waveguide component A. Further, pin holes 6a and 6b are formed on either side so as to be coaxial with the guide pins 4a and 4b, respectively. In connecting each optical fiber connector 6 to the optical waveguide component A, the guide pins 4a and 4b are inserted into the pin holes 6a and 6b, respectively, of the connector 6, and the respective end faces of the component A and the connector 6 are brought into contact with each other. Then, the component and the connector are pressed against each other by means of, for example, a spring clip 7. Thereupon, the respective optical axes of the cores 2a of the optical waveguide core portion 2 are individually in alignment with the optical fibers of the optical fiber connector 6. Thus, the optical connection is completed without requiring alignment operation. According to the non-alignment connecting method described above, however, cracks may possibly be caused at the junction between the optical waveguide component A and the optical fiber connector 6, in the vicinity of the grooves 3a and 3b of the component, as the guide pins are inserted or removed, or if the smallest load is applied on the junction after the component and the connector are connected. The grooves 3a and 3b of the optical waveguide component A are cut in the top face of the cladding portion 3 to a depth such that they can receive the guide pins 4a and 4b, respectively. If the substrate 1 is about 1 mm thick, for example, the depth of the grooves 3a and 3b in the substrate is great relative to the thickness of the substrate, so that the strength of the substrate may be lowered in some cases. In an optical waveguide component designed so that the pattern of the cores 2a of the optical waveguide core portion 2 is freely formed with a two-dimensional expanse, the two-dimensional core pattern sometimes may be cut into pieces as the grooves 3a and 3b are formed. Avoiding this situation entails an increase in cost for groove cutting or in the overall size of the optical waveguide component A. Similar conventional connectors are disclosed in EP-A-0 458 608, JP-A-62276513, JP-A-01291204, JP-A-02251918. SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing an optical waveguide component as defined in claim 1. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view illustrating the way optical fiber connectors are connected to a conventional optical waveguide component; Fig. 2 is a perspective view showing an optical waveguide component not part of the present invention; Fig. 3 is a perspective view showing an optical waveguide component body not part of the invention; Fig. 4 is a perspective view showing an optical waveguide component body formed of a quartz glass plate (hold-down plate member) engraved with V-grooves (marker portions); Fig. 5 is a perspective view showing a method for manufacturing the optical waveguide component body of the invention directly on a silicon wafer (substrate); Fig. 6 is a sectional view taken along line VI-VI of Fig. 5; Fig. 7 is a perspective view showing an alternative optical waveguide component not part of the invention; Fig. 8 is a perspective view showing an alternative method for manufacturing the optical waveguide component body of the invention directly on the silicon wafer (substrate) not part of the invention; Fig. 9 is a perspective view showing a method of manufacturing the optical waveguide component body of the invention with use of orifices, positioned with respect to optical fibers, as marker portions, not part of the invention; Fig. 10 is a perspective view showing an example of a mold used in a method of manufacturing the optical waveguide component of the invention according to the invention; and Fig. 11 is a perspective view showing a state in which the optical waveguide component body is held in midair over the mold of Fig. 10. DETAILED DESCRIPTION OF THE INVENTION In an optical waveguide component, all the faces of its body except both end faces which are to be connected with optical fiber connectors, that is, the top and bottom faces and both side faces, are encapsulated in an elastic resin, thus forming a resin mold portion. Each end face of this resin mold portion is formed having guide pin holes, which are positioned with reference to an optical waveguide core portion of the optical waveguide component. In connecting an optical fiber connector to the optical waveguide component, guide pins are inserted individually into the guide pin holes, and an end face of the component body and the end face of the connector are butted, with the guide pins in pin holes of the connector. Then, the component body and the connector are pressed against and fixed to each other by means of, for example, a spring clip. Thus, in the optical waveguide component, a substrate 1 is not engraved with the deep grooves 3a and 3b which are provided for the case shown in Fig. 1, so that its strength is not low. Further, the resin mold portion, which is formed having the guide pin holes, is so elastic that it can absorb a load, if any, acting on the junction between the component and the connector after their connection. As a result, the substrate and the guide pin holes can be restrained from being cracked or broken. In forming the guide pin holes in the resin mold portion, moreover, references for positioning the holes in a resin molding process should only be marks on the surface of a hold-down plate member, and need not be deep grooves in the upper surface of a cladding, such as the ones required in the conventional case. Even though the optical waveguide core portion is a two-dimensional pattern, therefore, there is no possibility of its being cut into pieces, so that the size of the optical waveguide component can be reduced correspondingly. The following is a detailed description of illustrative embodiments of the optical waveguide component and a manufacturing method therefor according to the present invention. Embodiment 1 Fig. 2 is a perspective view showing an embodiment of the optical waveguide component. In Fig. 2, an optical waveguide component A comprises an optical waveguide component body A1 and a resin mold portion A2 which covers all the faces of the body A1 except the end faces. The optical waveguide component body A1 includes a substrate 1 formed of e.g. silicon, a cladding portion 3 overlying the substrate, and an optical waveguide core portion 2 composed of cores 2a which are embedded in the cladding portion 3 and arranged at predetermined pitches on the end faces. A hold-down plate member, e.g., a quartz glass plate 8 with a desired thickness, is bonded to the upper surface of the cladding portion 3 by means of an adhesive. Two V-grooves 8a and 8b with a suitable depth are cut in the upper surface of the quartz glass plate 8 using the optical waveguide core portion 2 as a positioning reference. The grooves 8a and 8b serve as positioning references or marker portions for guide pin holes (described below) in a resin molding process. Guide pin holes 9a and 9b with a predetermined diameter and length are formed in each end face of the resin mold portion A2 which covers the optical waveguide component body A1. In connecting an optical fiber connector to the optical waveguide component A, guide pins are inserted individually into the guide pin holes 9a and 9b, and. the remaining parts of the guide pins are inserted into pin holes formed in the end face of the connector, corresponding in position to the guide pin holes, so that the connector and the component are butted. The guide pin holes 9a and 9b are formed using the V-grooves 8a and 8b as their positioning references, while the grooves 8a and 8b are cut using the optical waveguide core portion 2 as their positioning reference. Equivalently, therefore, the guide pin holes 9a and 9b are formed with the optical waveguide core portion 2 used as their positioning reference. Thus, each of optical fibers of the optical fiber connector and its corresponding core 2a of the core portion 2 are connected to each other with their respective optical axes in alignment. The optical waveguide component A can be manufactured in the following manner. First, the cladding portion 3 of e.g. quartz glass and the optical waveguide core portion 2 therein are formed on the surface of the substrate 1 by a conventional method, as shown in Fig. 3. Then, the quartz glass plate 8, for use as the hold-down plate member, is bonded and fixed to the cladding portion 3 by means of the adhesive composed of, for example, heat resisting epoxy resin. In this case, the thickness of the glass plate 8 may be adjusted to any suitable value. For example, it may be about 0.5 mm if the thicknesses of the substrate 1 and the cladding portion 3 are about 1 mm and 50 µ m, respectively. Subsequently, the two V-grooves 8a and 8b are cut in the upper surface of the quartz glass plate 8 using the optical waveguide core portion 2 as the positioning reference, by means of a dicer or other machining means. Since the V-grooves are used as the positioning references for the guide pin holes in the resin molding process (mentioned later), it is necessary only that the positional relation with the core portion 2 be indicated. Thus, the V-grooves should only be shallow enough not to reach the upper surface of the cladding portion 3, for example. The optical waveguide component body A1 is manufactured in the following manner. This manufacturing method will be described with reference to Fig. 5 and the sectional view of Fig. 6 taken along line VI-VI of Fig. 5. The cladding portion 3, which has the optical waveguide core portion 2, composed of the cores 2a, embedded therein, is formed on the substrate 1, such as a silicon wafer, by the conventional flame deposition method. In doing this, no cladding is formed on some of the cores 2a of the optical waveguide core portion 2 with respect to the lengthwise direction so that the core portion 2 can indicate its own position. Then, the quartz glass plate 8 as the hold-down plate member, having a thickness of e.g. 1 mm, is pasted on the whole surface of the cladding portion 3 by means of a thermosetting adhesive. Thereafter, the two V-grooves 8a and 8b, which extend in the lengthwise direction of the optical waveguide core portion 2 and have a depth of about 0.2 mm, are cut as marker portions in the surface of the quartz glass plate 8 with use of some of the cores of the core portion 2, which are seeable through the plate 8, as references. The depth of the V-grooves 8a and 8b may be adjusted by utilizing height-direction markers 10a and 10b which are marked so as to extend at right angles to the core portion 2. Thereafter, the substrate 1 is cut along the lengthwise direction using the V-grooves 8a and 8b as the positioning references, by means of a dicer or the like, whereby the optical waveguide component bodies A1, such as the one shown in Fig. 4, are cut out individually. Then, each obtained optical waveguide component body is set in a mold. At this time, pins with a diameter of e.g. about 0.3 mm are previously arranged in the mold, in positions corresponding to the V-grooves 8a and 8b of the component body, the pins are pressed against the grooves 8a and 8b, and the component body is set in the mold. Further, cores for guide pins with a diameter of e.g. about 0.7 mm are arranged in the mold with use of the aforesaid pins as positioning references, and a molding resin is then filled into the mold. After the resin is set, the whole resulting structure is taken out of the mold, and the core is removed. Thereupon, the optical waveguide component A is obtained with the V-grooves 8a and 8b filled up, comprising the optical waveguide component body A1 and the resin mold portion A2, which surrounds the component body A1 and has the guide pin holes 9a and 9b opening in each end face thereof, in predetermined positions relative to the optical waveguide core portion 2, as shown in Fig. 2. Embodiment 2 Fig. 7 is a perspective view showing another embodiment. In this case, the quartz glass plate 8 for use as the hold-down plate member is bonded to the back of the substrate 1, the V-grooves 8a and 8b are cut in the plate 8, and the whole structure is resin-molded. Embodiment 3 Fig. 8 shows a state in which the quartz glass plate 8 of Embodiment 1 to be pasted on the cladding portion 3 is divided into two quartz glass plates 8c and 8d, which are separately pasted on the optical waveguide core portion 2 with a space between them in the lengthwise direction of the core portion 2. In this case, the aimed optical waveguide component can be manufactured in the same manner as in Embodiment 1. In the case of Embodiment 3, the two quartz glass plates 8c and 8d bite into the molding resin when they are resin-molded in the mold, thereby effectively preventing the optical waveguide component body from being disengaged. In Embodiments 1 to 3, the quartz glass plate 8, pasted as the hold-down plate member on the surface of the cladding portion 3, is provided to prevent the V-grooves 8a and 8b as the marker portions, which function as the positioning references for the optical waveguide component body set in the mold, from being cut to the depth of the optical waveguide core portion 2, that is, to protect the core portion 2. Therefore, there are no special restrictions on the thickness and material of the hold-down plate member, provided that the press member can achieve this purpose. Moreover, the hold-down plate member is not limited to a plate such as the one described above, and may be formed by applying water glass to the surface of the cladding portion 3 to a desired thickness or depositing a cladding thick by the conventional flame deposition method, for example. Although the V-grooves are used as the marker portions in the embodiments described above, the configuration of the marker portions according to the present invention is not limited to this. Alternatively, a plurality of conical recesses may be arranged in the extending direction of the optical waveguide core portion, for example. In short, the marker portions may be any suitable signs which are positioned with respect to the optical waveguide core portion. Embodiment 4 Fig. 9 is a perspective view showing an alternative manufacturing method. In Fig. 9, the optical waveguide component body A1 is prepared having the optical waveguide core portion 2 formed in the same manner as in Embodiment 1. This component body A1 is set on a fine adjustment table (not shown) which can finely move in X, Y, Z, x, y, and z directions. The hold-down plate member, such as the quartz glass plate 8, is pasted on the optical waveguide component body A1 by means of an ultraviolet-curing adhesive 11. Orifices 8e and 8f are bored as marker portions in the surface of the quartz glass plate 8. As orifice hold-down pins 13, which are in alignment with optical fibers 12 to be aligned, are fitted individually into the holes 8a and 8b, the plate 8 is positioned with respect to the optical fibers 12. Hereupon, the fine adjustment table is activated. The quartz glass plate 8, which is fixed to the optical waveguide component body A1 by means of the orifice hold-down pins 13, is kept immovable with respect to the optical fibers 12, although it is movable with respect to the component body A1. After the respective optical axes of the optical fibers 12 are aligned individually with the cores 2a of the optical waveguide core portion 2 in this manner, ultraviolet rays are applied to the ultraviolet-curing adhesive to cure the resin, thereby fixing the quartz glass plate 8 to the optical waveguide component body A1. Then, the orifice hold-down pins 13 are drawn out, the optical waveguide component body A1, having only the quartz glass plate 8 fixed thereon, is put into the mold, and cores for the guide pins are arranged for resin molding with use of the orifices 8e and 8f as positioning references. After the molding resin is cured, the core is removed. As a result, an optical waveguide component is obtained having guide pin holes which are formed with reference to the orifices 8e and 8f as the marker portions which are formed with use of the optical waveguide core portion 2 as the positioning reference. Embodiment 5 Figs. 10 and 11 are perspective views for illustrating a method for manufacturing the optical waveguide component according to the present invention, in which the optical waveguide component body is set directly in the mold without forming the marker portions. First, the top portions of both side walls of a open-topped mold 14 are notched to form two pairs of large V-grooves 14a and 14b and two pairs of small V-grooves 14c and 14d between the large ones. A pair of guide pins 4a and 4b are fixed to the large V-groove pairs 14a and 14b, respectively, in a suspended manner. Four optical fiber ferrules 15 for optical input and output are. fixed individually to the small V-grooves 14c and 14d. The individual V-grooves are cut so that the respective axes of the guide pins 4a and 4b and the optical fiber ferrules 15 are arranged in predetermined positional relations. Three or more (six in the drawings) pin rods 16 protrude from the bottom of the mold 14. Each rod 16, like a pointer of a dial gauge, for example, can finely move in the X, Y, Z, and y directions. In the mold 14 in this state, the optical waveguide component body A1, having the optical waveguide core portion 2 embedded therein, is placed on the pin rods 16 to be held in midair so that the respective end faces of the cores of the core portion 2 are opposed to the end faces of the optical fiber ferrules 15, as shown in Fig. 11. Thereafter, the respective axes of the optical fibers 12, set individually in the optical fiber ferrules 15, are aligned with those of their corresponding cores 2a of the core portion 2 by finely adjusting the length of projection of each pin rod 16. After the alignment is finished, the molding resin is injected into the mold 14 with the optical waveguide component body A1 softly pressed down lest it move. After the resin is cured, the resulting cast article is released from the mold 14, and the guide pins 4a and 4b and the optical fiber ferrules 15 are removed. As a result, the optical waveguide component body A1 is encapsulated in the molding resin, and guide pin holes, positioned with respect to the optical waveguide core portion 2, are formed in the molding resin portion. Where technical features mentioned in claim 1 are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of claim 1 and accordingly, such reference signs do not have any limiting effect on the scope of claim 1.

Claims: A method of manufacturing an optical waveguide component which has end faces connectable with optical fiber connectors, comprising the steps of: arranging guide pins (4a, 4b) and optical fibre ferrules (15), having optical fibers (12) set therein, at the upper lateral portion of a mould (14) so that the optical fibre ferrules are positioned with respect to one another so as to form pairs of opposed optical fibre ferrules, the mould (14) having at least three pin rods (16) capable of fine motion at the bottom thereof; placing an optical waveguide component body (A1), having an optical waveguide core portion (2) embedded therein, on the at least three pin rods (16) so as to be held in midair in a manner such that the end faces of the optical waveguide core portion (2) are opposed to the respective end faces of the optical fibre ferrules (15), the optical waveguide core portion (2) comprising cores (2a) which can be butt jointed with the optical fibres (12) in said ferrules to achieve optical coupling therebetween; finely adjusting the length of the pin rods (16) to align the cores of the optical waveguide core portion (2) with the optical fibres (12) in the optical fibre ferrules (15); injecting a molding resin into the mould (14) taking out the resulting cast article from the mould (14); and removing the guide pins (4a, 4b), thereby forming guide pin holes (9a, 9b) in each end face of a resin mold portion covering all the faces of the optical waveguide component body except both end faces thereof.

Inventors: NAKAMURA SHIRO, OHTA TOSHIHIKO, SHIGEMATSU TAKASHI, SHIMIZU TAKEO, NAKAMURA, SHIRO, OHTA, TOSHIHIKO, SHIGEMATSU, TAKASHI, SHIMIZU, TAKEO
Applicants: FURUKAWA ELECTRIC CO LTD, THE FURUKAWA ELECTRIC CO., LTD.
Application year: 1993
Main classification: G02B6
IPC codes: G02B6