JP2011039298A - Optical coupling structure and optical transmission module using the optical coupling structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and satisfactorily connect an optical element and an optical transmission line to each other. <P>SOLUTION: The optical coupling structure includes a tip end of an optical fiber 1 in which a core is covered in the circumference with a clad 3, and an optical element 10 which is optically connected to the tip end of the optical fiber 1. With the optical fiber 1 held, the tip end of the optical fiber 1 is made a free end, which then is applied to a stiffness means 13 that prevents the free end from bending by weight. In a state where the tip end of the optical fiber 1 and the optical element 10 are oppositely arranged through a space and aligned, at least the tip end of the optical fiber 1 and the optical element 10 are fixed using a transparent resin whose refractive index is smaller than that of the core and larger than that of air. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical coupling structure that is applied to a mobile phone or the like and is used for optical communication or the like, and an optical transmission module using the optical coupling structure.

  As shown in FIG. 14, the optical fiber 1 used for optical communication or the like covers the periphery of the core 2 with a clad 3 having a refractive index smaller than that of the core 2, and surrounds the periphery with a protective coating (covering) such as resin. 4 is formed.

  FIG. 15 shows an example of an apparatus used when aligning (optical axis alignment) between the optical fiber 1 and the optical waveguide 5 (see, for example, Patent Document 1). This apparatus has a fixed base 6 on which the optical waveguide 5 is mounted and a moving table 7 on which the optical fiber 1 is placed. The moving table 7 is movable in the X, Y, and Z directions orthogonal to each other. Is formed. This movement is performed manually or by driving an electric motor.

  When the alignment is performed, light from the light emitting unit 8 is incident from one end side (left side in the drawing) of the optical fiber 1 and is emitted from the other end side of the optical fiber 1, and the emitted light is emitted from one end of the optical waveguide 5. The optical fiber 1 is moved relative to the optical waveguide 5 so as to enter from the side (opposite side to the optical fiber 1). Reference numeral 9 denotes a photodetector that detects light emitted from the optical waveguide 5.

Japanese Patent Laid-Open No. 5-196831

  By the way, as shown in FIG. 15, when the optical fiber 1 is aligned so as not to protrude from the moving table 7, the operation of fixing the optical fiber 1 and the optical waveguide 5 using an adhesive or the like after alignment is performed. Since it is difficult, the fixing work may not be successful, and the combined optical axes may be displaced with great effort.

  Further, in the configuration in which the optical fiber 1 is aligned so that it does not protrude from the moving table 7, for example, as shown in FIG. 16, the connection partner side is an optical element 10 such as a light emitting element, and the optical fiber 1 is optically mounted on the fixed base 6. When the element 10 is arranged and the moving table 7 is moved to the optical element 10 side, the moving table 7 comes into contact with the fixed base 6 on which the optical element 10 is mounted, thereby bringing the optical fiber 1 closer to the optical element 10. There is a possibility that it is not possible.

  Note that the moving table 7 may come into contact with the optical element and peripheral components depending on the shape of the optical element and the arrangement and shape of other components arranged around the optical element. There is a possibility that the tip portion of the optical fiber 1 cannot be brought close to an appropriate distance from the optical element.

  Therefore, when aligning, as shown in FIG. 17, it is conceivable to place the optical fiber 1 in a state where the tip portion of the optical fiber 1 protrudes further forward than the end of the moving table 7. However, since the diameter of the optical fiber 1 is very thin, for example, about 70 μm, the tip of the optical fiber 1 is placed when the tip of the optical fiber 1 is placed in a state where it protrudes further forward than the end of the moving table 7. The portion bends due to the weight of the optical fiber 1 and hangs down. Then, the tip surface of the optical fiber 1 is tilted from the optical axis, and the alignment of the optical axis of the tilt angle (θx) in the X direction and the tilt angle (θy) in the Y direction is necessary. End up.

  Further, even if the tip end side of the optical fiber 1 does not sag during alignment, if the diameter of the optical fiber 1 to be used is small, as shown in FIG. 18, the optical fiber 1 and the connection partner side (here, When the optical waveguide 5) is fixed using the adhesive 11 or the like after alignment, the optical fiber 1 may hang down due to the weight of the adhesive 11. In that case, there is a possibility that the optical axis that has been combined is shifted.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to easily and accurately align an optical transmission line such as an optical fiber and an optical element, or between optical transmission lines. An object of the present invention is to provide an optical coupling structure capable of optical coupling with loss and an optical transmission module using the optical coupling structure.

In order to achieve the above object, the present invention has the following configuration as means for solving the above problems. That is, the optical coupling structure of the present invention is
In an optical coupling structure comprising a tip of an optical transmission line that is covered with a clad around the core, and an optical element optically coupled to the tip of the optical transmission line,
Holding the optical transmission line, the tip of the transmission line is a free end,
Applying a rigid means for preventing the free end from bending due to its own weight at the free end of the optical transmission line;
In a state in which the tip of the optical transmission path and the optical element are arranged to face each other with a gap between them, at least the tip of the optical transmission path and the optical element are smaller in refractive index than the core and less than air. It is characterized by being fixed using a transparent resin having a large refractive index.

The optical coupling structure of the present invention is
In the optical coupling structure formed by optically coupling the tips of the first and second optical transmission lines that cover the core with the cladding,
Holding each optical transmission line, the tip of the transmission line is a free end,
Stiffening means for preventing the free end from bending due to its own weight is applied to the free end of each optical transmission line;
A transparent resin having a refractive index smaller than that of the core and higher than that of air is used at least at the tip of each of the optical transmission paths in a state where the distal ends of the optical transmission paths are opposed to each other with an interval and aligned. It is also characterized by being fixed.

Furthermore, the optical transmission module of the present invention includes:
An optical coupling structure of the present invention including an optical element, and a mother substrate on which an electric circuit for optical transmission is formed, wherein the optical element and the electric circuit are electrically connected. .

  In the present invention, the optical transmission path is held and the tip of the optical transmission path is a free end, and stiffening means for preventing the free end from being bent by its own weight is provided. Therefore, even when the tip of the optical transmission path and the optical element are aligned to face each other with a gap between them, both when the optical transmission path is aligned with the tip of the tip facing each other with a gap between them. Alignment can be performed easily and accurately without being affected by the bending of the tip region of the optical transmission path due to its own weight.

  Then, with the optical transmission line and the optical element aligned, at least the tip of the optical transmission line and the optical element are fixed with a transparent resin, so that the optical transmission line such as an optical fiber and the optical element are Easy and accurate optical coupling. In addition, the optical transmission lines such as optical fibers can be optically coupled easily and accurately by fixing at least the tip of each optical transmission line with a transparent resin in a state where the optical transmission lines are aligned. .

  In addition, by making the transparent resin a resin having a refractive index smaller than that of the core of the optical transmission path and a refractive index higher than that of air, the transparent resin plays a role like a clad of the optical transmission path. The transmitted light can be prevented from diffusing from the outer peripheral side of the core to the transparent resin side. Also, in the gap between the core end face of the optical transmission path and the optical element, and the gap between the core end face of the optical transmission path, the light confinement action works, the light spreading angle can be suppressed, and the light at the interface Can also be reduced. Therefore, the optical coupling loss between the core end surface and the optical element and the optical coupling loss between the core end surfaces can be reduced.

  Furthermore, the free end cladding of the optical transmission path is removed to expose the core, or the free end cladding of the optical transmission path is formed thin toward the tip of the optical transmission path, and only the core is formed at the tip of the optical transmission path. The following effects can be achieved by forming a shape in which is exposed. In other words, with these configurations, the core exposed in the tip region of the optical transmission line is obtained by using optical means that can be observed from at least two directions of the upper and side surfaces of the optical transmission line, such as an optical fiber, by image observation. Can be aligned with the optical axis of the optical element. Therefore, it is possible to align the optical transmission line and the optical element more easily and accurately in a shorter time.

  In addition, when the cladding of the tip region of the optical transmission line is removed and the core is protruded and exposed, and a rigid means using resin is applied around the protruding core, the diameter of the tip region of the optical transmission line is set to the light Can be equivalent to the diameter of the transmission line. That is, since the stiffening means is provided in place of the cladding in the tip region of the optical transmission line, the height of the optical coupling portion with the optical element can be reduced. Further, the curing means can be easily and appropriately subjected to the curing means by curing by heat and the ultraviolet curing resin by curing by ultraviolet rays.

  Furthermore, in the optical transmission module assembled by electrically connecting the optical coupling structure described above and the mother substrate on which the optical circuit for optical transmission is formed, alignment as an optical transmission module is not necessary, so the production time is reduced. Shortening can be achieved and cost reduction can be achieved by reducing the defect rate.

It is typical sectional drawing (a) for demonstrating the optical coupling structure of 1st Example, and typical front view (b) of the front end surface of the optical fiber currently applied. It is explanatory drawing of the alignment process of the optical fiber and optical element which are applied to 1st Example. It is typical sectional drawing for demonstrating the optical coupling structure of 2nd Example. It is explanatory drawing of the manufacturing process of the optical fiber applied to 2nd Example. It is typical sectional drawing for demonstrating the optical coupling structure of 3rd Example. It is a schematic diagram for demonstrating the alignment process of the optical fiber and optical element in optical coupling structure formation of 3rd Example. It is typical sectional drawing for demonstrating the optical coupling structure of 4th Example. It is explanatory drawing of the manufacturing process of the optical fiber applied to 4th Example. It is typical sectional drawing for demonstrating the optical coupling structure of 5th Example. It is typical sectional drawing for demonstrating the optical coupling structure formed by providing a light shielding member. It is typical sectional drawing for demonstrating the optical transmission module of 6th Example. It is a typical top view for demonstrating the optical transmission module of another Example. It is a schematic diagram for demonstrating the example of the formation method which freezes the front end side of an optical fiber and forms an optical coupling structure. It is a schematic diagram for demonstrating the structure of an optical fiber. It is a schematic diagram for demonstrating the example of an optical fiber, an optical waveguide, and an alignment apparatus. It is a schematic diagram for demonstrating the problem at the time of mounting so that the front end side may not protrude from a table at the time of alignment. It is a schematic diagram for demonstrating the problem at the time of mounting so that the front end side of an optical fiber may protrude from a table at the time of alignment. It is a schematic diagram for demonstrating the problem at the time of fixing an optical fiber and an optical waveguide after alignment.

  Embodiments according to the present invention will be described below with reference to the drawings. In the description of the embodiments, the same components as those in the conventional example are denoted by the same reference numerals, and the same reference numerals are denoted by the same reference numerals among the embodiments, and the duplicate description is omitted or simplified. .

  FIG. 1A is a schematic cross-sectional explanatory view showing a first embodiment of an optical coupling structure according to the present invention. As shown in the figure, a tip end portion (optical coupling end portion) of an optical fiber 1 serving as an optical transmission line and an optical element 10 optically coupled to the optical fiber 1 are arranged to face each other with a gap therebetween. An optical connector may be provided at the end of the optical fiber 1 opposite to the optical element 10. The optical element 10 is a light emitting element and is mounted on the optical element substrate 12. The optical element substrate 12 may be provided with a simple amplifier circuit. Although not shown, the optical coupling structure has a wiring pattern electrically connected to the optical element 10 (may be patterned on the optical element substrate 12 or may be a lead wire). And an mother board on which an electric circuit used for optical transmission is formed is provided with an interface.

  The optical fiber 1 is formed of a quartz fiber. Stiffening means 13 is provided to prevent the tip region, which is the free end of the optical fiber 1 from being bent by its own weight when held at a position inside the tip so that the tip of the optical fiber 1 becomes a free end. Yes. The stiffening means 13 is applied by, for example, applying an epoxy-based thermosetting resin to the outer periphery of the clad 3 so as to have a thickness of, for example, about 20 μm, followed by curing. Thermosetting resins have material properties that are irreversible to heat and do not remelt.

  When forming the optical coupling structure of this embodiment, the tip side of the optical fiber 1 is immersed in a thermosetting resin, and then at least the tip side of the optical fiber 1 is heated to cure the thermosetting resin. The stiffening means 13 is provided. When excess resin adheres to the front end surface of the optical fiber 1, for example, as shown in FIG. 1B, the front end portion of the optical fiber 1 is cut to form a thermoset resin on the front end surface of the optical fiber 1. It is assumed that no is attached.

  Then, for example, as shown in FIG. 2, the optical fiber 1 provided with the stiffening means 13 and stiffened at the tip side is placed on the moving table 7, and the optical fiber 1 and the optical element 10 are aligned. At this time, the optical fiber 1 is placed in a state in which the tip portion of the optical fiber 1 protrudes beyond the end of the moving table 7. In this embodiment, since the stiffening means 13 is provided as described above, the tip side of the optical fiber 1 is not bent by its own weight.

  In addition, the optical fiber 1 and the optical element 10 fixed on the fixing base 6 are arranged to face each other with a space therebetween, and for example, light emitted from the optical element 10 is incident on the optical fiber 1 from the distal end side of the optical fiber 1, The light emitted from the other end of the fiber 1 is measured by an optical power meter (not shown) or the like. The optical fiber 1 is appropriately moved in the three directions X, Y, and Z together with the moving table 7 so that the measured value is maximized, and the optical axis A1 of the optical fiber 1 and the optical axis A2 of the optical element 10 are accurately set. Align. FIG. 2 schematically shows a state in which the optical fiber 1 side is moved in the Y direction.

  The tip region of the aligned optical fiber 1 and the optical element 10 are fixed using a transparent resin 14 as shown in FIG. As the transparent resin 14, for example, an optical characteristic having a value equivalent to the refractive index of the cladding 3, that is, an optical characteristic in which the refractive index after curing is smaller than that of the core 2 and larger than that of air, An acrylic UV curable adhesive is used. The transparent resin 14 is not limited to the ultraviolet curable adhesive, and the refractive index may be larger than the refractive index of the clad 3 as long as it has a function of confining light propagating through the core 2. It may be good or small.

  In this embodiment, the optical element 10, the distal end side of the optical fiber 1, and the transparent resin 14 may be accommodated in the package 15 together with the optical element substrate 12. Further, the formation portion of the protective coating 4 of the optical fiber 1 may be provided in the package 15 and fixed. In these cases, the inside of the package 15 is potted with the thermosetting resin used when the stiffening means 13 is applied or the sealing resin 16 having physical properties close to that of the transparent resin 14 and accommodated in the package 15. This makes it difficult to break when an external force is applied, and the influence of humidity and the like can be avoided. The material of the sealing resin 16 is not particularly limited, and is appropriately set. In addition, only the bottom plate 15a of the package 15 is provided, and the sealing resin 16 is exposed. Also good.

  Next, the optical coupling structure of the second embodiment will be described. The second embodiment has the configuration shown in the sectional view of FIG. In the second embodiment, as shown in FIG. 4A, for example, by applying a chemical treatment, the cladding 3 in the tip region of the optical fiber 1 is removed, and the tip of the core 2 protrudes and is exposed. As shown in FIG. 4B, the stiffening means 13 is applied only around the protruding core 2 by applying and curing an ultraviolet curable resin.

  Next, the optical coupling structure of the third embodiment will be described with reference to FIG. In the third embodiment, as in the second embodiment, the cladding 3 in the tip region of the optical fiber 1 is removed, and the core 2 is projected beyond the end of the cladding 3 to be exposed. The exposed core 2 is formed with a length that does not bend due to its own weight even if the inside of the exposed core 2 is held, for example, as short as about 1 to 2 mm.

  In the third embodiment, alignment of the optical fiber 1 and the optical element 10 can be performed in the same manner as in the first embodiment. However, in the third embodiment, the core 2 in the tip region of the optical fiber 1 is exposed. Therefore, alignment can be performed using optical means that can be observed from at least two directions of the upper surface and the side surface of the optical fiber 1. That is, for example, as shown in FIG. 6, the optical fiber 1 and the optical element 10 are mounted on the mounting table 17, and the exposed core 2 and the optical element 10 are imaged by the camera 18 from the side surface direction of the optical fiber 1. The image is displayed on the display 19. While observing the image, at least one of the optical fiber 1 and the optical element 10 is moved to align the optical axes of the optical fiber 1 and the optical element 10 (alignment), and align from the side direction. Similarly, the exposed core 2 and the optical element 10 are observed from the upper surface direction of the optical fiber 1 and aligned from the upper surface direction of the optical fiber 1.

  In the first and second embodiments as well, if the stiffening means 13 is provided uniformly and thinly, the distal end side of the optical fiber 1 and the optical element 10 are observed from at least two directions of the upper surface and the side surface of the optical fiber 1. Using the optical means that can be used, alignment can be performed by the alignment method described in the third embodiment. However, as described above, it is preferable to use the method of measuring the light intensity because alignment can be performed with high accuracy.

  Next, the optical coupling structure of the fourth embodiment will be described with reference to FIGS. As shown in FIG. 8, the fourth embodiment removes the cladding 3 in the tip region of the optical fiber 1 so that the thickness decreases toward the tip by, for example, chemical liquid treatment. Only the core 2 is exposed. The length for removing the clad 3 is as short as 0.5 to 1.0 mm, for example. For this reason, even if it holds the inner side so that the area | region where the clad 3 was removed becomes a free end, the area | region where the clad 3 was removed does not bend by its own weight. For this reason, the stiffening means 13 is not applied to this portion as shown in FIG.

  Next, the optical coupling structure of the fifth embodiment will be described with reference to FIG. The fifth embodiment is an optical coupling structure formed by optically coupling the tips of optical fibers 1 and 20 as first and second optical transmission lines in which the core 2 is covered with a clad 3. The optical fibers 1 and 20 are held and the ends of the optical fibers 1 and 20 are formed as free ends, and stiffening means 13 for preventing the free ends from being bent by its own weight is applied to the free ends of the optical fibers 1 and 20, The optical fibers 1 and 20 are fixed using a transparent resin 14 in a state in which the tips of the optical fibers 1 and 20 are arranged to face each other with a gap and aligned. Although not shown, the fourth embodiment also has an interface for connecting to the outside.

  In each of the first to fifth embodiments, a thermosetting resin is used as the stiffening means 13, but an ultraviolet curable resin may be used. The optical element 10 may be covered with the transparent resin 14 only at the tip side. Furthermore, for example, as shown in FIG. 10, a light blocking member 21 that covers the transparent resin 14 and blocks the transmission of light from the outside to the outside may be provided. As described above, when the light blocking member 21 is provided, light from the outside enters the optical fiber 1 or the optical element 10 from the tip region of the optical fiber 1 or the optical element 10, or the tip region of the optical fiber 1 or the optical element 10. It is possible to prevent light from being emitted from the outside.

  The sixth embodiment is an example of an optical transmission module according to the present invention, and its configuration is schematically shown in FIG. FIG. 11A is a cross-sectional view of the optical transmission module according to the sixth embodiment (see the BB line in FIG. 11B), and FIG. 11B is a vertical cross-sectional view (FIG. 11). (Refer to line AA in (a)).

  The optical transmission module of the sixth embodiment includes an optical coupling structure 22 having the same basic configuration as that of the first embodiment, and a mother substrate 24 on which an electric circuit 23 for optical transmission is formed. The electrical circuit 23 is electrically connected. On the mother board 24, an electrical I / F (electric interface) unit for connecting the optical transmission module and an external circuit is provided.

  There are various configurations in the optical coupling structure according to the present invention including the first to fifth embodiments, and various optical coupling structures according to the present invention can be applied to the optical transmission module according to the present invention. Is. The optical transmission line such as the optical fiber 1 and the optical element are optically connected (see, for example, the first to fourth embodiments), the electric circuit 23 formed on the mother substrate 25, and the optical element 10. Can be electrically connected to each other, or the electric circuit 23 can be provided on the optical element substrate 12, and the electric circuit 23 can be electrically connected to the optical element 10 to form an optical transmission module. Alternatively, the electrical circuit 23 may be formed separately from the optical coupling structure 22 and electrically connected via an interface.

  For example, as a modification of the light transmission module of the sixth embodiment, a light transmission module may be formed by using a light receiving element as the optical element 10 instead of the light emitting element provided in the light transmission module of the sixth embodiment. it can. Also, as shown in FIG. 12, when the optical transmission module of the sixth embodiment is 25a and the optical transmission module of the modification (using the light receiving element as the optical element 10) is 25b, these optical transmission modules An optical transmission module 26 in which 25a and 25b are connected can also be formed. In the light transmission module 26, light emitted from the light emitting element of the light transmission module 25a can be transmitted through the optical fiber 1 and received by the light receiving element of the light transmission module 25b.

  The present invention is not limited to the above embodiments, and can take various forms. For example, as shown in FIG. 13, the stiffening means 13 is applied so that the tip end side of the optical transmission line such as the optical fiber 1 is frozen and the tip region of the optical transmission line is prevented from being bent by its own weight. May be. In this case, preparation of a solvent or the like is not necessary, and the tip region of the frozen optical transmission path returns to the original state over time, so that workability is good.

  Further, in each of the above embodiments, the quartz fiber is used as the optical transmission line. However, the optical transmission line has a structure of plastic fiber, organic optical waveguide, quartz, plastic, and organic optical waveguide, for example, the core 2 is quartz, The clad 3 may be formed by a resin structure.

  The optical coupling structure and the optical transmission module according to the present invention can be applied to a FOT (Fiber Optical Transceiver) or the like because the optical element and the optical transmission path and the optical transmission paths can be optically connected with a simple configuration.

DESCRIPTION OF SYMBOLS 1,20 Optical fiber 2 Core 3 Clad 10 Optical element 12 Optical element board 13 Rigid means 14 Transparent resin 22 Optical coupling structure 23 Electric circuit 24 Mother board 25a, 25b, 26 Optical transmission module

Claims (7)

In an optical coupling structure comprising a tip of an optical transmission line that is covered with a clad around the core, and an optical element optically coupled to the tip of the optical transmission line,
Holding the optical transmission line, the tip of the transmission line is a free end,
Applying a rigid means for preventing the free end from bending due to its own weight at the free end of the optical transmission line;
In a state in which the tip of the optical transmission path and the optical element are arranged to face each other with a gap between them, at least the tip of the optical transmission path and the optical element are smaller in refractive index than the core and less than air. An optical coupling structure characterized by being fixed using a transparent resin having a large refractive index. In the optical coupling structure formed by optically coupling the tips of the first and second optical transmission lines that cover the core with the cladding,
Holding each optical transmission line, the tip of the transmission line is a free end,
Stiffening means for preventing the free end from bending due to its own weight is applied to the free end of each optical transmission line;
A transparent resin having a refractive index smaller than that of the core and higher than that of air is used at least at the tip of each of the optical transmission paths in a state where the distal ends of the optical transmission paths are opposed to each other with an interval and aligned. An optical coupling structure characterized by being fixed.   An optical element is optically coupled to at least one of the first and second optical transmission lines at an end opposite to the optical coupling end of the first and second optical transmission lines. The optical coupling structure according to claim 2.   4. The light according to claim 1, wherein the core is exposed by removing the clad at the free end of the optical transmission line, and the tip of the exposed core and the optical element are aligned by optical means. Bond structure.   The clad is formed thinly toward the tip of the optical transmission line, and the shape is such that only the core is exposed at the tip of the optical transmission line, and the exposed tip of the core and the optical element are aligned by optical means. The optical coupling structure according to claim 1 or claim 3, wherein   5. The curing means obtained by curing a thermosetting or ultraviolet curable resin applied to the exposed tip of the core and forming the same thickness and the same refractive index as the clad. Optical coupling structure.   An optical coupling structure according to claim 1 or any one of claims 3 to 6 and a mother substrate on which an electric circuit for optical transmission is formed, wherein the optical element and the electric circuit are electrically connected. Optical transmission module, characterized in that the optical transmission module is connected.

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