An optical waveguide component and a manufacturing method therefor

Abstract: Provided is an optical waveguide component which has end faces to be connected with optical fiber connectors by means of guide pins, comprising an optical waveguide component body formed having an optical waveguide core portion, and a resin mold portion covering all the faces of the optical waveguide component body except the end faces, each end face of the resin mold portion being formed having guide pin holes with the optical waveguide core portion used as a positioning reference. Since the guide pin holes for connection with the optical fiber connectors are formed in the resin mold portion which covers the optical waveguide component body, the guide pin holes and a substrate can be restrained from being broken even though they are subjected to a load after connection. Marker portions for the arrangement of the guide pins, unlike conventional ones, need not be deep grooves in the upper surface of a cladding portion. Even in the case of a component whose optical waveguide core portion has a two-dimensional pattern, therefore, the marker portions can be formed without cutting the core pattern into pieces.

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. An optical connector similar to that shown in Fig. 1 is taught by JP-A-02-251 918. In the known optical connector disclosed in JP-A-02-251 918, guide pin holes are formed by resin molding, making use of large V-grooves cut on opposite sides of the upper surface of the substrate. In the known optical connector according to JP-A-02-251 918, the large grooves formed on the opposite sides of the upper surface of the substrate serve as reference positions for forming the guide pin holes. Therefore, when the guide pins are applied with external force, the resultant stress acts upon the large grooves, rather than the guide pin holes formed in the resin molding parts, because the large grooves have a much greater area of contact with the guide pins than the guide pin holes. Consequently, the stress acts upon the substrate via the large grooves, with the result that in the worst case, the substrate cracks at the large grooves. Moreover, the optical connector disclosed in JP-A-02-251 918 uses straight optical fibers, and therefore, it is not necessary to take account of two-dimensional expansibility of optical fibers. Accordingly, when forming the large grooves, attention need be focused only to an end face of the connector to ensure that there is a sufficient distance between each large groove and its adjacent small hole in which an optical fiber is inserted, since there is no possibility of the two grooves crossing each other. However, in the case of a substrate for optical waveguides which have two-dimensional expansibility, when forming the large grooves, attention should not be devoted only to a connection end face to ensure a predetermined distance between each large groove and its adjacent optical waveguide, because in the worst case, the large grooves cut off the optical waveguides. Avoiding this problem leads to an increased cost of groove cutting or an increased overall size of the optical waveguide component, as in the case of Fig. 1. EP-A-0 458 608 teaches an optical waveguide component with an end face to be connected with an optical fiber connector. The known component includes an integrated optical chip and a resin molded housing enclosing all but one face of the optical chip. The housing includes guide pins, the chip being positioned in respect to the guide pins. The optical fiber connector includes holes corresponding the guide pins and an optical fiber ribbon cable with fibers connectable to optical chip of the waveguide component. JP-A-62 276513 describes a structure of the multicore optical connector ferrule. V-grooves and optical fiber guide holes 13 are cut in a surface of the base plate 11, and a keeping plate 12 is placed on the same surface of the base plate, so that the V-grooves define guide pin holes 14, Namely, the guide pin holes are formed in the base plate itself. Moreover, in the case of JP-A-62 276513, two ferrules are connected to each other with respective end portions of guide pins received in the guide pin holes 14. Therefore, when the guide pins are inserted or removed, the base plate 11 may possibly be damaged. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical waveguide component and a manufacturing method therefor, in which grooves for guide pins for the connection of optical fiber connectors are formed without cutting a cladding portion or a substrate so as to range from the top of the cladding portion to the substrate. Another object of the present invention is to provide an optical waveguide component and a manufacturing method therefor, in which cracks, breakage, etc. cannot be easily caused in the vicinity of a substrate or guide pin holes of the component if a load is applied to the junction between the component and an optical fiber connector after they are connected. Still another object of the present invention is to provide an optical waveguide component and a manufacturing method therefor, in which guide pin holes can be formed without damaging an optical waveguide core portion with a two-dimensional expanse, if any, in the component. In order to achieve the above objects, according to the present invention, there is provided an optical waveguide component as defined in claims 1 or 2. According to the present invention, moreover, there is provided a method for manufacturing an optical waveguide component, comprising the steps of claim 4. 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 according to the present invention; Fig. 3 is a perspective view showing an optical waveguide component body 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 according to 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); and Fig. 9 is a perspective view showing a method for manufacturing the optical waveguide component body of the invention with use of orifices, positioned with respect to optical fibers, as marker portions. DETAILED DESCRIPTION OF THE INVENTION In an optical waveguide component according to the present invention, 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 according to the present invention, 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 according to the present invention. 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 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 µm, 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. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: An optical waveguide component which has end faces to be connected with optical fiber connectors by means of guide pins, comprising: an optical waveguide component body (A1) including: a substrate (1); a cladding portion (3) overlying a surface of the substrate (1); a plate member (8) extending over the cladding portion (3) and bonded thereto; and an optical waveguide core portion (2) embedded in the cladding portion (3), the optical waveguide core portion (2) comprising one or more cores (2a) which are arranged at predetermined pitches on the end faces of the cladding portion (3), and which can be butt jointed with an optical fiber connector (6) comprising one or more optical fibers to achieve optical coupling therebetween; and a resin mold portion (A2) formed covering all the faces of the body (A1) except the end faces, each end face of the resin mold portion (A2) being formed having guide pin holes (9a, 9b) and marker portions (8a, 8b), the marker portions (8a, 8b) being formed on the surface of the plate member (8) not bonded to the cladding portion (3) with the optical waveguide core portion (2) used as a positioning reference for positioning said marker portions, the marker portions being used as references for forming said guide pin holes during moulding of said resin mold portion. An optical waveguide component which has end faces to be connected with optical fiber connectors by means of guide pins, comprising: an optical waveguide component body (A1) including: a substrate (1); a cladding portion (3) overlying a surface of the substrate (1); a plate member (8) extending over the opposite surface of the substrate (1) and bonded thereto; and an optical waveguide core portion (2) embedded in the cladding portion (3), the optical waveguide core portion (2) comprising one or more cores (2a) which are arranged at predetermined pitches on the end faces of the cladding portion (3), and which can be butt jointed with an optical fiber connector (6) comprising one or more optical fibers to achieve optical coupling therebetween; and a resin mold portion (A2) formed covering all the faces of the body (A1) except the end faces, each end face of the resin mold portion (A2) being formed having guide pin holes (9a, 9b) and marker portions (8a, 8b), the marker portions (8a, 8b) being formed on the surface of the plate member (8) not bonded to said opposite surface of the substrate (1) with the optical waveguide core portion (2) used as a positioning reference for positioning said marker portions, the marker portions being used as references for forming said guide pin holes during moulding of said resin mold portion. The optical waveguide component of claims 1 or 2, wherein the plate member (8) is a glass plate. A method for manufacturing an optical waveguide component which has end faces connectable with optical fiber connectors, comprising the steps of: forming an optical waveguide component body (A1) by forming a cladding portion (3) on a surface of a substrate (1) and then bonding and fixing a plate member (8) on the other surface of the cladding portion (3) or on the opposite surface of the substrate (1), the cladding portion (3) having an optical waveguide core portion (2) embedded therein, the optical waveguide core portion (2) comprising one or more cores (2a) which can be butt jointed with one or more optical fibers (12) to achieve optical coupling therebetween; forming marker portions (8a, 8b, 8e, 8f) on the plate member (8) of the optical waveguide component body (A1) with the optical waveguide core portion (2) used as a positioning reference, the marker portions (8a, 8b, 8e, 8f) being formed on the surface of the plate member (8) not bonded to the cladding portion (3) or on the opposite surface of the substrate (1) ; injecting a molding resin into a mold after loading the optical waveguide component body (A1) into the mold, the mold having cores for guide pins positioned by using the marker portions (8a, 8b, 8e, 8f) as positioning references; and taking out the resulting cast article from the mold and removing the cores, thereby forming guide pin holes (9a, 9b) in each end face of a resin mold portion (A2) covering all the faces of the optical waveguide component body (A1) except both end faces thereof.

Inventors: NAKAMURA SHIRO, OHTA TOSHIHIKO, SHIGEMATSU TAKASHI, SHIMIZU TAKEO, NAKAMURA, SHIRO, OHTA, TOSHIHIKO, SHIGEMATSU, TAKASHI, SHIMIZU, TAKEO, Nakamura, Shiro, c/o The Furukawa Electric Co. Ltd, Ohta, Toshihiko, c/o The Furukawa Electric Co. Ltd, Shigematsu, Takashi, c/o The Furukawa Electric, Shimizu, Takeo, c/o The Furukawa Electric Co. Ltd.
Applicants: FURUKAWA ELECTRIC CO LTD, THE FURUKAWA ELECTRIC CO., LTD.
Application year: 1993
Main classification: G02B6
IPC codes: G02B6