JP5412235B2 - Ferrule for optical fiber, connection method between optical waveguide and optical fiber - Google Patents

Description

  The present invention relates to an optical fiber ferrule, and more specifically to an optical fiber ferrule used to connect an optical waveguide formed on an optical circuit board and an optical fiber. The present invention also relates to a method for connecting an optical waveguide and an optical fiber.

To optical circuit components that include optical elements that use optical waveguides, such as Mach-Zehnder interferometers, in order to make light from a light source incident or to guide emitted light to an external light receiving element, An optical fiber is connected. As is well known, the optical waveguide is formed along the substrate surface by applying a technique such as titanium diffusion or proton exchange to an optical circuit substrate made of lithium niobate (LiNbO ₃ ) or the like. Then, by connecting the optical fiber to the optical waveguide that opens to the end face of the optical circuit board, it is possible to make light incident on the optical circuit component and to guide outgoing light from the optical circuit component.

  FIG. 17 shows a conventional example of a connection technique between the optical fiber 40 and the optical waveguide 110. As shown in FIG. 17A, in the optical circuit component 100, the end 111 of the optical waveguide 110 is opened on the end face 102 of the optical circuit substrate 101 on which the optical waveguide 110 is formed. Then, both the optical circuit board 101 and the ferrule 1 in which the optical fiber 40 is inserted are moved relative to each other while being held by mechanically holding or adsorbing using a jig such as a clamp or a vacuum chuck, Loss due to optical coupling between the end face (hereinafter referred to as fiber end face) 41 of the optical fiber 40 opening on the end face (hereinafter referred to as ferrule end face) 21 of the ferrule 1 and the end (hereinafter referred to as waveguide end face) 111 of the optical waveguide 110 is minimized. Adjust (align) so that The optical fiber 40 and the optical waveguide 110 are connected by adhering the ferrule end surface 21 and the end surface 102 of the optical circuit board 101 on the side where the optical waveguide 110 is opened.

  In general, the curing time of the adhesive is shortened as much as possible, or the positional relationship between the two is shifted from the aligned state due to the difference in thermal expansion between the optical circuit board 110 and the ferrule 1 during heating. In order to prevent this, the optical circuit board 101 and the ferrule 1 are bonded by a photo-curing adhesive 120. In order to use the photocurable adhesive 120, the ferrule 1 is made of a light transmissive material such as borosilicate glass. Then, as shown in FIG. 17B, after the optical fiber 40 and the optical waveguide 110 are correctly aligned, or while aligning, the photocurable adhesive 120 is applied, and the ferrule 1 and the optical waveguide are applied. When light 110 is properly aligned, light including wavelength components for curing the photocurable adhesive 120 from the back of the ferrule 1 toward the end face 102 of the optical circuit board 101 (visible light, ultraviolet light, etc.) , Hereinafter, curing light) 130 is irradiated.

  The curing light 130 passes through the ferrule 1 made of a light-transmitting material, and is irradiated to the photocurable adhesive 120 interposed between the ferrule end surface 21 and the end surface 102 of the optical circuit board 101, and the photocurable adhesive 120 is cured. As a result, the ferrule 1 and the optical circuit board 101 are bonded, and the optical fiber 40 and the optical waveguide 110 are connected in an aligned state.

  The curing light 130 is irradiated from a direction oblique to the normal direction of the end face 102 of the optical circuit board 101. This is because a jig for holding the ferrule 1 for alignment, a housing (wall surface) for housing the optical circuit component 100, the ferrule 1, and the like are installed in this normal direction. This is because a light source for irradiating the curing light 130 in the linear direction cannot be arranged. Even if a light source is installed in the normal direction and the curing light 130 can be irradiated from the back of the ferrule 1 along the extending direction of the ferrule 1, the curing light 130 passes through the ferrule 1 in the longitudinal direction. Until the end surface 21 of the optical circuit board 101 is reached, the energy of the irradiated curing light 130 is greatly attenuated, and the photocurable adhesive 120 may not be sufficiently cured.

  Further, since the optical waveguide 110 is usually disposed near the surface 103 of the optical circuit board 101, the optical waveguide 110 is disposed in the optical circuit board as shown in FIG. 17C. The holding block 140 is laminated on the surface 103 on the side, the holding block 140 is disposed so as to be flush with the end face 102 of the optical circuit board 101, and the end face 102 of the optical circuit board 101, the end face 102, In some cases, the ferrule end face 21 is bonded to both surfaces 141 of the holding block 140 that are flush with each other. The following Patent Document 1 describes a technique for connecting an optical fiber itself to an optical waveguide using a holding block without using a ferrule.

Japanese Patent No. 2764141

  As described above, the end faces of the optical fiber and the optical waveguide are adhered to each other while being maintained in a properly aligned state. A photo-curing adhesive is used for the bonding. However, in the technique described in Patent Document 1, since the thin fiber end face is directly bonded to the waveguide end face without using a ferrule, the bonding area is small and the bonding strength is insufficient. Therefore, there is a high possibility that a connection failure will occur due to vibration or the like. Therefore, as shown in FIG. 17, it is more reliable and common to connect the optical fiber 40 and the optical waveguide 110 using the ferrule 1. In addition, in order to ensure the adhesive strength of the ferrule end surface 21 and the end surface 102 of the optical circuit board 101, ie, the area of the ferrule end surface 21 is so preferable that it is large.

  By the way, as shown in FIGS. 17B and 17C, when the optical fiber 40 and the optical waveguide 110 are connected by bonding the ferrule 1 and the optical circuit board 101 with the photo-curing adhesive 120, Irradiation light 130 for curing is irradiated from an oblique direction behind the ferrule 1. In other words, the photocurable adhesive 120 applied between the ferrule end surface 21 and the end surface 102 of the optical circuit board 101 is irradiated with the curing light 130 that is transmitted obliquely through the ferrule 1. Therefore, the distance through which the curable light 130 passes through the ferrule 1 varies greatly depending on each position in the application region of the photocurable adhesive 120, and the energy of the light applied to the photocurable adhesive 120 is biased. That is, “irradiation unevenness” occurs. Due to this unevenness of irradiation, if a part of the photocurable adhesive 120 is not exposed with sufficient light energy and a part thereof is in an uncured state, the adhesive strength between the ferrule 1 and the optical circuit board 101 is lowered. However, the alignment state of the optical waveguide 110 and the optical fiber 40 may be shifted due to vibration or change with time.

  In addition, in order to irradiate with sufficient energy, when the illuminance is increased or the irradiation time is extended, even if all of the finally applied photocurable adhesive 120 is cured, the irradiation unevenness itself is Since it has not been solved, the time until curing varies depending on the location. In general, since the shrinkage ratio before and after curing in the photocurable adhesive 120 is about 10%, stress is generated at the interface between the rapidly cured portion and the uncured portion, and the curing light 130 is irradiated. There is a possibility that the positional relationship between the fiber end face 41 and the waveguide end face 111 in a correctly aligned state is deviated. Of course, not only the problem of uneven irradiation but also to increase the energy of the curing light 130, if the illuminance is increased, a high-performance and expensive light source is required, and if the irradiation time is increased, the time required for curing is increased. Become.

  Accordingly, an object of the present invention is to cure a photocurable adhesive when connecting an optical waveguide formed on the optical circuit board and an optical fiber by bonding the optical circuit board and a ferrule with a photocurable adhesive. It is to provide a ferrule that can reduce the unevenness of light irradiation and can be cured in a short time. Other purposes will be clarified in the following description.

The main invention for achieving the above object is an optical circuit ferrule for an optical fiber, which is bonded to an end face on the side where the optical waveguide is opened by a photocurable adhesive in an optical circuit board on which the optical waveguide is formed,
Formed of light transmissive material,
A flat portion having a flat surface on the front and back, and a wall portion whose front surface is an adhesive surface with the optical circuit board,
An optical fiber holding portion that is integrally formed on the rear surface of the wall portion, extends in the normal direction of the rear surface, and has a smaller front projection area than the wall portion,
An optical fiber insertion hole penetrating the front surface of the wall portion and the rear end surface of the optical fiber holding portion in the normal direction;
It is characterized by having.

  According to the ferrule for an optical fiber in the present invention, the ferrule end face and the end face of the optical circuit board are photocured in order to connect the optical fiber inserted therein and the optical waveguide formed in the optical circuit board. When bonding using an adhesive, unevenness of light irradiation for curing the photo-curing adhesive can be reduced and cured in a short time. Therefore, the reliability of various optical devices including a structure in which an optical fiber inserted in a ferrule is connected to an optical waveguide formed on an optical circuit board is improved, and the optical device is provided at a low cost. I can expect that.

It is an external view of the ferrule in the 1st Example of the present invention. It is a figure which shows the structure of the optical fiber penetration hole currently formed in the inside of the ferrule in the said 1st Example. It is a figure which shows the state at the time of adhere | attaching the ferrule in the said 1st Example to an optical circuit board. It is a figure which shows the modification of the ferrule in the said 1st Example. It is an external view of the ferrule in the 2nd Example of this invention. It is a figure which shows the state at the time of adhere | attaching the ferrule in the said 2nd Example to an optical circuit board. (A) is an external view of a ferrule in the third embodiment of the present invention, and (B) and (C) are views showing a method of bonding the ferrule and the optical circuit board in the third embodiment. is there. It is a figure which shows the other example of the adhesion method of the ferrule and optical circuit board in the said 3rd Example. (A) is a side view of the ferrule in the said 1st Example, (B) is an enlarged view in the circle | round | yen in (A), and is a figure for demonstrating the problem at the time of end surface grinding | polishing. It is the schematic of the ferrule in the 4th Example of this invention. It is a figure which shows the modification of the ferrule in the said 4th Example. It is a figure which shows an example in the state which edge-polished the ferrule in the said 4th Example. It is a figure which shows the modification of the ferrule in the said 4th Example. It is a figure which shows the modification of the ferrule in the said 4th Example. It is a figure which shows the grinding | polishing direction at the time of performing end surface grinding | polishing to the ferrule of the said 2nd Example. It is a figure which shows the ferrule in the other Example of this invention. It is a figure which shows the prior art example of the technique which connects an optical fiber and an optical waveguide.

=== Embodiment of the Invention ===
In addition to the embodiments corresponding to the main invention, the embodiments of the present invention include embodiments having the following features.

The shape of the boundary surface between the rear surface of the wall portion and the optical fiber holding portion is a flat shape that crosses the rear surface of the wall portion. Furthermore, the rear surface of the wall portion is bisected by the boundary surface.
The wall portion has a shape in which a straight line that is parallel to a reference line formed on the end face of the optical circuit board is formed. Furthermore, the optical fiber is a polarization maintaining optical fiber. In addition, the optical fiber holding section has a surface whose normal is a direction orthogonal or parallel to the polarization plane of the light propagating through the polarization maintaining optical fiber. Moreover, the said wall part is provided with the surface which made the normal line the direction orthogonal or parallel to the polarization plane of the light which the said polarization maintaining optical fiber propagates.
A flat wall reinforcing portion formed integrally with the rear surface of the wall portion and the optical fiber holding portion and extending rearward;
It must be molded from a light transmissive resin.

The present invention also extends to a method of connecting an optical waveguide and an optical fiber, and an embodiment corresponding to the invention according to the method opens to an end face of an optical circuit board on which the optical waveguide is formed. A method of connecting an optical waveguide and an optical fiber inserted in a ferrule,
The ferrule is formed of a light-transmitting material and has a flat plate shape having flat surfaces on the front and rear sides, a wall portion having a front surface as an opening end surface of the optical fiber and an adhesive surface with the optical circuit board, and the wall An optical fiber holding portion integrally formed on the rear surface of the portion and extending in the normal direction of the rear surface, and an optical fiber insertion passing through the front surface of the wall portion and the rear surface of the optical fiber holding portion in the normal direction With holes,
An alignment step of arranging the optical axis of the optical fiber and the optical axis of the optical waveguide on a straight line;
An adhesive application step of interposing a photo-curable adhesive between the front surface of the wall and the end surface of the optical circuit board;
A light irradiation step of irradiating light for curing the light curable adhesive,
In the light irradiation step, light is directly irradiated on the rear surface from an oblique direction with respect to the rear surface of the wall portion, and the light curable adhesive is cured by the light transmitted through the wall portion.

In an embodiment corresponding to the invention relating to a method for connecting an optical fiber and an optical waveguide, the optical fiber holding portion is a columnar shape having the optical fiber insertion hole as an axis, and a front end surface bisects a rear surface of the wall portion. It is a flat shape that traverses like
In the light irradiation step, light may be irradiated from two directions to each of the rear surfaces of the bisected wall portions.

  And the effect | action about each said embodiment, an effect, etc. are clarified by the following description.

=== First Embodiment ===
As specific examples of the present invention, some specific examples of the above embodiments will be given. FIG. 1 is an external view of a ferrule 1a according to the first embodiment of the present invention. Here, as shown in the figure, when the front and rear, left and right, and up and down directions are defined, (A) is a perspective view when the ferrule 1a is viewed from the front upper side, and (B) is from the rear upper side. FIG. The ferrule 1a is made of a light transmitting material such as optical plastic (for example, polymethyl methacrylate resin, polycarbonate) or optical glass (for example, borosilicate glass), and the two flat boxes (2, 3) are L It has an external shape that is formed in a letter shape. Specifically, from a box-shaped portion (wall portion) 2 that is flat in the front-rear direction and has a substantially rectangular projection shape from the front, and a box-shaped portion (optical fiber holding portion) 3 that is flat in the vertical direction and extends back and forth. Thus, the optical fiber holding portion 3 is formed integrally with the lower end of the rear surface 22 of the wall portion 2. A hole (optical fiber insertion hole) 4 through which an optical fiber is inserted is formed in the ferrule 1a. The optical fiber insertion hole 4 penetrates from the rear end surface 31 of the optical fiber holding portion 3 to the front surface 21 of the wall portion 2 in the front-rear direction. The front end side of the optical fiber 40 (for example, an optical fiber such as a single mode optical fiber (SMF), a multimode optical fiber (MMF), a dispersion compensating optical fiber (DCF), or a polarization maintaining optical fiber described later) is coated. The front end side is inserted into the optical fiber insertion hole 4 and is exposed so that the fiber end surface is flush with the front surface 21 of the wall portion 2. That is, the front surface 21 of the wall portion 2 becomes the ferrule end surface 21. Further, the front end opening 41 of the optical fiber insertion hole 4 is substantially a fiber end face. Therefore, in the description of each of the following embodiments including the first embodiment, the front surface 21 of the wall portion 2 and the front end opening 41 of the optical fiber insertion hole 4 are respectively a ferrule end surface 21, And the fiber end face 41.

  On the other hand, on the rear end opening 42 side of the optical fiber insertion hole 4, that is, on the rear end face 31 side of the optical fiber holding portion 3, there is a core wire (or strand) portion with a coating of the optical fiber 40 and a bare fiber portion. Near the boundary is inserted. Therefore, the diameter of the optical fiber insertion hole 4 gradually increases rearward on the rear end opening 42 side, and has a substantially trumpet shape. FIG. 2 illustrates a schematic structure of the optical fiber insertion hole 4. This figure shows a cross-sectional view taken along the line xx in FIG. (A) is an example in which the hole diameter gradually decreases from the rear end opening 42 of the optical fiber insertion hole 4 toward the front, and the narrow tube portion 43 through which the portion of the bare fiber is inserted from the front end opening 41 is rearward. In the course of the extension, the diameter gradually increases and reaches the rear end surface 31 of the optical fiber holding portion 3. (B) extends forward while maintaining the diameter of the rear end opening 42 that is slightly larger than the diameter of the core (or strand) of the optical fiber 40, and gradually reduces the diameter from the middle of the extension toward the front. , It continues to the narrow tube portion 43 through which the bare fiber is inserted.

  FIG. 3 shows a state in which the optical waveguide 110 formed on the optical circuit board and the optical fiber 40 are connected using the ferrule 1a in the first embodiment. Specifically, the arrangement relationship between the optical circuit board 101 and the ferrule 1a, the irradiation direction of the curing light 130 for curing the photocurable adhesive 120, and the like are shown. In FIG. 3, the optical circuit component 100 is mainly composed of an optical circuit board 101 on which an optical waveguide 110 is formed, and the optical waveguide 110 is provided near the surface layer of the surface 103 (the lower surface in this example) of the optical circuit board 101. It is arranged. The optical waveguide 110 opens in the end face (rear end face in this example) 102 on the side that is bonded to the ferrule 1a in the optical circuit board 101. The ferrule 1a is arranged so that the ferrule end surface 21 faces the rear end surface 102 of the optical circuit board 101 so that the fiber end surface 41 of the optical fiber 40 inserted therein and the waveguide end surface 111 are brought into contact with each other. .

  Next, a photocurable adhesive 120 is applied between the ferrule end face 21 and the rear end face 102 of the optical circuit board 101 while keeping the optical fiber 40 and the optical waveguide 110 properly aligned, and the wall portion 2 is irradiated with curing light 130 toward the rear surface 22. The curing light 130 mainly passes through the wall portion 2 to expose the photocurable adhesive 120. Since the wall portion 2 is a flat plate shape that is flat in the front-rear direction, the bonding area with the optical circuit board 101 is large, and high bonding strength can be obtained. Except for the boundary portion 32 with the optical fiber holding unit 3, the thickness in the front-rear direction is substantially constant over a wide area. Therefore, the curing light 130 is uniformly irradiated onto the photocurable adhesive 120. Further, since the curing light 130 passes through the thin wall portion 2 in the front and rear directions and is irradiated onto the light curing adhesive 120, the distance through which the light transmissive material constituting the ferrule 1a is transmitted is short. Therefore, the photocurable adhesive 120 can be sufficiently cured with a small amount of energy. That is, the bonding is completed by irradiation in a short time without using an expensive light source with high illuminance. Therefore, while ensuring sufficient adhesive strength, the time and cost required for the bonding process are reduced, and as a result, the optical fiber inserted in the ferrule is connected to the optical waveguide formed on the optical circuit board. It is possible to improve the reliability of various optical devices including the optical device and to provide the optical device at low cost.

  The optical fiber holding portion 3 is formed integrally with the rear surface 22 of the wall portion 2 and extends in the front-rear direction, and an optical fiber insertion hole 4 penetrating from the rear end surface 31 to the front surface 21 of the wall portion 2 is formed therein. It may be formed, for example, the shape which formed the cylindrical optical fiber holding | maintenance part 3 in the rear surface 22 of the flat wall part 2 like the ferrule 1b shown in FIG. Of course, the optical fiber holding part 3 can also be made into a columnar shape, and the wall part 2 can also be made into a disk shape.

  Further, the optical fiber holding unit 3 is often a part that is gripped or adsorbed by a jig such as a clamp or a vacuum chuck during alignment, and the shape of the optical fiber holding unit 3 is the type of the jig. The shape may be in accordance with the above. In any case, the front projection area of the optical fiber holder 3 is smaller than the front projection area of the wall 2, and when the curing light 130 irradiated from the rear of the wall 2 passes through the light transmissive material, If the transmission distance is substantially uniform, the shape of each part of the ferrule can be set appropriately. As for the ferrule material, it can be said that resin (optical plastic) is preferable to glass for reasons such as ease of molding and raw material costs. Of course, an appropriate material may be selected according to the specifications required for the optical device.

=== Second Embodiment ===
FIG. 5 shows the appearance of a ferrule 1c according to the second embodiment of the present invention. As shown in the figure, the front and rear, left and right, and up and down directions of the ferrule were defined. In the ferrule (1a, 1b) in the first embodiment shown in FIG. 1 and FIG. 4, the side shape when viewed from the left and right is L-shaped, but in the second embodiment, it is shown in FIG. As shown, it is T-shaped. In the example shown here, the optical fiber holding portion 3 bisects the rear surface 22 of the wall portion 2 in a vertically symmetrical manner at the boundary portion 32 with the wall portion 2. Of course, if the rear surface 22 of the wall portion 2 is divided into two parts up and down (or left and right) by the optical fiber holding unit 3, the planar shape from the front surface (rear surface) of the ferrule 1c is not necessarily vertically symmetrical (or left and right symmetrical). It does not have to be.

  When the optical fiber 40 and the optical waveguide 110 are connected using the ferrule 1c of the second embodiment, a holding block 140 may be used as shown in FIG. That is, the holding block 140 is laminated on the optical circuit board 101, and the holding block 140 is arranged so as to be flush with the end face (rear end face) 102 where the optical waveguide 110 is opened, and the optical circuit that is flush with it. What is necessary is just to adhere | attach in the state which made the ferrule end surface 21 face the both end surfaces (102, 141) of the board | substrate 101 and the holding block 140. FIG. In the example shown in FIG. 6A, the optical circuit board 101 and the holding block 140 are arranged so as to contact each other with respect to the ferrule 1c. The curing light 130 is applied to the ferrule 1c from the left or the right rear obliquely. In the first embodiment, the holding block 140 may be stacked on the optical circuit board 101. With the L-shaped ferrule 1a as in the first embodiment, the holding block 140 can be made thinner than in the second embodiment.

  Since the side surface shape of the optical fiber holding part 3 is formed so as to bisect the rear surface 22 of the wall part 2, as shown in FIG. You may irradiate each area | region of the rear surface 22 of the divided wall part 2 from two directions so that it may become symmetrical with respect to the extension direction. In the irradiation direction shown in FIG. 6A, the curing light 130 transmitted through the boundary portion 32 between the optical fiber holding portion 3 and the wall portion 2 has passed through the light-transmitting material for a long time. can do. Further, since the curing light 130 from the two directions overlaps at the boundary portion 32, the light energy is not insufficient, and the photocurable adhesive can be cured more reliably and in a short time. Of course, when the curing light is irradiated from one direction in the arrangement shown in FIG. 6B, the curing light 130 incident on the optical fiber holder 3 is once emitted from the optical fiber holder 3 and again incident on the wall 2. As a result, the curing light 130 is reflected or refracted inside and outside the light-transmitting material, and the loss increases. Therefore, when the optical fiber holding portion 3 is formed so as to bisect the rear surface 22 of the wall portion 2, it is desirable to irradiate from two directions when irradiating the curing light from the vertical direction.

  Note that the ferrule 1c of the second embodiment can increase the bonding area and increase the bonding strength with respect to the ferrule (1a, 1b) of the first embodiment. However, when the optical waveguide 110 is disposed in the vicinity of the surface layer of the optical circuit board 101, the holding block 140 is used for bonding. In the ferrule of the first embodiment, even if the optical waveguide 110 is disposed in the vicinity of the surface layer of the optical circuit board 101, it is only necessary to arrange the optical fiber holding portion 3 on the end face 111 side of the optical waveguide 110 at the time of bonding. There is an advantage that the optical circuit component can be easily miniaturized. In any case, the shape of the ferrule may be determined in consideration of the performance required for the optical circuit component.

=== Third embodiment ===
The optical fiber includes a polarization maintaining optical fiber that emits while maintaining the polarization direction of the incident light, such as a PANDA fiber (note that the polarization maintaining optical fiber is a polarization maintaining optical fiber or a polarization maintaining optical fiber). Etc.). The polarization maintaining optical fiber is used for the optical circuit component that handles the polarization, and the polarization having the polarization plane in the predetermined direction is input or the polarization plane of the polarization emitted from the optical circuit component is maintained. It will lead to an external light receiving element. Therefore, when connecting the optical waveguide to the polarization maintaining optical fiber, it is necessary to accurately match the polarization plane of the incident light to the optical waveguide or the output light from the optical waveguide with the polarization plane of the light propagating through the optical fiber. is there. The third embodiment is a ferrule having a structure suitable for connecting such a light holding optical fiber to an optical waveguide.

  7A to 7C show an outline of the ferrule 1d in the third embodiment. (A) is an external view of the ferrule 1d, and (B) is a perspective view showing an arrangement relationship when the optical circuit board 101 and the ferrule 1d are bonded together. (C) is a top view from the back in the arrangement | positioning relationship shown to (B). In the example shown in FIG. 7, the wall portion 2 is a flat plate shape whose front and rear surfaces (21, 22) are square, and the optical fiber holding portion 3 is a flat rectangular column shape having a flat hexagonal end surface. At the boundary surface with the rear surface 22 of the part 2, the rear surface 22 of the square is divided into two so as to be symmetric with respect to the diagonal direction 24. Here, the boundary surface between the optical fiber holding portion 3 and the rear surface 22 of the wall portion 2 is a flat hexagonal shape, but is not limited thereto, and may be a flat rectangular shape, a flat triangular shape, or the like. Or it may not be polygonal shape.

  In addition, a polarization maintaining optical fiber is inserted into the optical fiber insertion hole 4 of the ferrule 1d, and the polarization plane is parallel to or perpendicular to the normal direction of the flat surface 33 of the flat prismatic optical fiber holding unit 3. It shall be. That is, the polarization plane direction is expressed by the flat surface 33 of the optical fiber holding unit 3. Here, it is assumed that the polarization plane and the normal direction of the flat surface 33 of the optical fiber holding unit 3 are orthogonal to each other. That is, the flat surface 33 and the polarization plane of the optical fiber holding unit 3 are parallel to each other. The flat surface 33 of the optical fiber holding unit 3 is at an angle of 45 ° with respect to the upper surface 23 of the wall 2.

  In order to connect the optical fiber 40 inserted in the ferrule 1d shown in FIG. 7A and the optical waveguide 110 disposed on the optical circuit board 101 with their polarization planes coincident with each other. 7B, the upper surface 104 of the optical circuit board 101 is used as a reference surface, and the reference surface 104 and the upper surface 23 of the wall 2 of the ferrule 1d are maintained in a parallel relationship. Alignment is performed, and then the ferrule end face 21 and the rear end face 102 of the optical circuit board 101 are bonded. That is, the light propagating through the optical fiber 40 and the optical waveguide 110 oscillates in a direction inclined by 45 ° with respect to the reference plane 104.

  Specifically, as shown in FIG. 7C, the extension direction of the upper side of the rectangular end face 102 of the optical circuit board 101 is defined as a reference line 105, and the amplitude direction of light (polarization axis) with respect to the reference line 105 50 is inclined 45 °. On the other hand, the optical fiber holding portion 3 has a flat prismatic shape, and the flat surface 33 of the prism is inclined 45 ° with respect to the longitudinal direction 25 of the upper surface 23 of the wall portion 2 and coincides with the polarization axis 50 of the optical fiber. ing. Therefore, an operator who adheres the ferrule end surface 21 to the rear end surface 102 of the optical circuit board 101 can confirm the direction of the polarization axis 50 by the shape of the optical fiber holding unit 3.

  Next, the operator places the upper surface 23 of the wall 2 and the reference surface 104 of the optical circuit board 101, that is, the front edge 25 of the upper surface 23 of the wall 2 and the optical circuit board 101 so that the polarization axis 50 is in the correct direction. Alignment is performed while maintaining the reference line 105 in parallel, and then the wall portion 2 divided by the optical fiber holding portion 3 in the same manner as the ferrule 1c of the second embodiment shown in FIG. The rear surface 22 is irradiated with curing light from one direction along the longitudinal direction 33 of the end face 31 of the optical fiber holding unit 3 or from two directions so as to be symmetric with respect to the longitudinal direction. The rear end face 102 and the ferrule end face 22 may be bonded together. As shown in FIG. 8, when the front edge 25 of the upper surface 23 of the wall portion 2 is aligned with the reference line 105 in the optical circuit board 101, the optical circuit board is aligned substantially correctly. By designing the size of the rear end face 102 of the 101 and the wall 2 of the ferrule 1e, the time required for the alignment work can be shortened.

  Of course, if the ferrule 1d and the optical circuit board 101 can be bonded so that the polarization axes 50 of the optical fiber 40 and the optical waveguide 110 coincide with each other, the reference surface 104, the reference line 105, and the wall portion 2 of the optical circuit board 101 can be used. Some marks may be added in the vicinity of the upper surface 23 and the front edge 25 of the upper surface 23. Thereby, it can be recognized that these surfaces and lines (104, 105, 23, 25) should be arranged in parallel to each other. Further, the shape of the optical fiber holder 3 does not necessarily need to be able to confirm the polarization axis 50 of the optical fiber. That is, if the ferrule 1d and the optical circuit board 101 are bonded so that the reference surfaces and lines (104, 105, 23, 25) are parallel, the polarization axes 50 of both the optical fiber 40 and the optical waveguide 110 are naturally formed. As long as they match. In addition, the flat surface 33 of the optical fiber holding unit 3 is inclined 45 ° with respect to the upper surface 23 of the wall 2, but is not limited to 45 °, and the angle is changed according to the specifications required for the optical equipment. May be.

  Further, instead of making the flat surface of the optical fiber holding unit 3 orthogonal or parallel to the polarization plane, the side surface of the wall 2 may be orthogonal or parallel to the polarization plane. Even in this way, the operator can confirm the direction of the polarization axis 50 by the shape of the ferrule.

=== Fourth Embodiment ===
When the adhesive 120 or the like is interposed between the fiber end surface 41 and the waveguide end surface 111 and the both are separated from each other, the outgoing light from the opening end surface 41 of the optical fiber 40 is incident on the optical waveguide 110. In some cases, a part of the emitted light is reflected by the waveguide end face 111 and the reflected light returns to the fiber end face 41. At this time, when both the fiber end surface 41 and the waveguide end surface 111 are parallel to each other, that is, the ferrule end surface 21 and the rear end surface 102 of the optical circuit board 101 facing each other are facing each other, The reflected light enters the optical fiber 40 perpendicularly and propagates through the optical fiber 40 in the direction opposite to the outgoing light. As a result, the light source at the other end of the optical fiber 40 may be damaged. For this reason, the ferrule end face 21 is often subjected to end face polishing (so-called “oblique polishing”) so as to be inclined at a slight angle (for example, 6 ° to 8 °) with respect to the optical axis of the optical fiber 40. In the oblique polishing, the polishing is performed while pressing the abrasive so as to have a predetermined angle with respect to the original ferrule end face 21 orthogonal to the optical axis of the optical fiber 40.

  By the way, when performing oblique polishing on a ferrule made of a material having high hardness such as glass, it has been empirically found that the corner portion of the wall portion is likely to be chipped during the polishing. Also, in the case of end surface polishing (so-called “right angle polishing”) in which polishing is performed at an angle orthogonal to the optical axis of the optical fiber 40, the same problem may occur although it is less likely than in the case of oblique polishing. If the wall portion is chipped, the adhesion area with the optical circuit board is reduced, and the adhesion strength is lowered. Therefore, it is considered desirable to employ an optical plastic as the ferrule material because of the above-described advantages relating to ease of molding and raw material costs, as well as problems relating to this end face polishing.

  However, plastic is softer and more easily deformed than glass, and in the case of a ferrule made of the plastic, there is a possibility that the wall portion bends backward during end face polishing. FIG. 9 shows an example in which end face polishing is performed on the ferrule 1a previously shown as the first embodiment. (A) is a side view from the right side of the ferrule 1a, and (B) is an enlarged view in a circle in (A). For example, when the end surface is polished so that the surface inclined by the angle θ backward with respect to the left-right direction becomes the ferrule surface 21 and the abrasive is pressed from the front of the ferrule end surface 21, the ferrule 1a is made of a soft material. 9B, the wall portion 2 bends backward using the boundary portion 32 with the optical fiber holding portion 3 as a fulcrum and cannot be polished at an accurate angle θ. In addition, if the degree of bending differs at various locations on the ferrule end surface 21, the flatness of the ferrule end surface 21 is impaired. Therefore, the fourth embodiment of the present invention is a ferrule having a structure that takes into account that the ferrule end face 21 is polished.

  FIG. 10 shows the structure of the ferrule 1e in the fourth embodiment. (A) is a perspective view from the rear upper side, (B) is a side view from the right side. This ferrule 1e basically has a structure in which the optical fiber holding portion 3 is formed at the lower end of the rear surface 22 of the wall portion 2 in the same manner as the ferrule 1a of the first embodiment shown in FIG. The member (wall reinforcing portion) 5 is formed integrally on both the rear surface 22 of the wall portion 2 and the upper surface 34 of the optical fiber holding portion 3 so as to extend rearward.

  In the ferrule 1e according to the fourth embodiment, the rearward force applied to the front surface 21 of the wall portion 2 during end surface polishing is received at the front end 51 of the wall surface reinforcing portion 5 on the rear surface 22 of the wall portion 2, Finally, the rearward force is supported by the upper surface 34 of the optical fiber holding unit 3. Thereby, it is possible to prevent the wall portion 2 from being bent backward and to polish the ferrule end face 21 at an accurate angle and to be flat. In the end surface polishing, the angle of polishing is set with reference to a part of the surface of the ferrule 1e. In the example shown in FIG. 9, the lower surface 35 of the optical fiber holding portion 3 is used as the reference surface. That's fine.

  By the way, at the time of end face polishing, it is necessary to hold the ferrule 1e with a jig such as a clamp so that the reference surface 35 is at a predetermined angle with respect to the abrasive, and maintain the holding state during polishing. is there. Therefore, the wall surface reinforcing part 5 may become an obstacle depending on the place where the grip is held. In such a case, the wall surface reinforcing portion 5 does not have a substantially rectangular flat plate shape, and is directed from the upper surface 23 of the wall rear surface 22 toward the upper surface 34 of the optical fiber holding unit 3 as shown in FIG. A substantially triangular shape that draws a ridge line on the surface 52 may be formed into a flat plate shape.

  Moreover, even if it is the ferrule (1e, 1f) provided with the wall surface reinforcement part 5, depending on the material of the ferrule (1e, 1f), as shown in FIG. The portion where the wall reinforcing portion 5 is not in contact with the fulcrum 51 is bent backward relatively, and the ferrule end surface 21 has the wall reinforcing portion 5 and the optical fiber at the rear surface 22 of the wall portion 2. There is a possibility that the region corresponding to the portion with which the holding unit 3 is in contact is polished from the other region, and the ferrule end surface 21 is polished in a concave shape as shown in the figure. In such a case, like the ferrule 1g shown in FIG. 13, the wall surface reinforcing portions 5 may be provided at two locations so as to extend rearward from the left and right ends of the rear surface 22 of the wall portion 2.

  In the ferrule 1g shown in FIG. 13, since the optical fiber holding portion 3 is provided below the wall portion 2, the wall surface reinforcing portion 5 is provided above the optical fiber holding portion 3, and the optical fiber holding portion is provided. Although 3 and the wall surface reinforcement part 5 are U-shaped, it is not restricted to this. For example, when the optical fiber holding part 3 is at the center position in the vertical direction of the wall part 2 as in the ferrule 1c shown in FIG. 5, the wall surface reinforcing parts 5 are provided above and below the optical fiber holding part 3 to The fiber holding part 3 and the wall surface reinforcing part 5 may be H-shaped.

  Of course, the wall surface reinforcing portion 5 can be appropriately formed according to the basic structure of the ferrule. For reference, FIG. 14 shows a modified example (1h to 1j) of the ferrule provided with the wall surface reinforcing portion 5. (A) is an example of the ferrule 1h which provided the wall surface reinforcement part 5 in the ferrule 1c in a 2nd Example. (B) is the ferrule 1i which provided the wall surface reinforcement part 5 in the ferrule 1d in a 3rd Example. Here, the ferrule 1i provided with the substantially triangular wall reinforcing portion 5 is illustrated. (C) is an example of a ferrule 1j in which a substantially triangular wall reinforcing part 5 is provided on the ferrule 1b provided with the prismatic optical fiber holding part 3 shown in the drawing. In any case, the wall surface reinforcing portion 5 is integrally formed on both the rear surface 22 of the wall portion 2 of the ferrule (1e to 1j) and any one of the side surfaces 34 of the optical fiber holding portion 3, and extends rearward. It is flat.

  When the optical fiber holding portion 3 is formed so as to cross the rear surface 22 of the wall portion 2 as in the ferrules (1a, 1c, 1d) shown in FIGS. For example, as shown in FIG. 15, for example, a ferrule 1c having a T-shaped side surface from the left-right direction is a ferrule surface 21 obtained by rotating the vertical surface about the vertical direction by an angle θ. If the end face polishing is performed as described above, the optical fiber holding portion 3 itself exhibits the same function as the wall surface reinforcing portion 5 to some extent, and it may not be necessary to separately form the wall surface reinforcing portion 5. Therefore, whether or not the ferrules (1e to 1j) provided with the wall surface reinforcing portion 5 are employed, or the number and shape of the wall surface reinforcing portions 5 are added to the front surface 21 of the wall portion 2 when polishing the material of the ferrule itself and the end surface. What is necessary is just to determine according to the magnitude | size of a pressure, a grinding | polishing direction, the method of the holding | grip at the time of grinding | polishing operation, etc.

=== Other Embodiments ===
Modifications of the first to fourth embodiments are shown as other embodiments. FIGS. 16A to 16G illustrate some ferrules (1k to 1q) according to other examples. Ferrules (1k to 1m) shown in (A) to (C) are ferrules (1k to 1m) in which the shape of the front surface of the wall 2 is a circle, and (D) to (G) A part of the circle is cut out, and the shape of the front surface of the wall portion 2 is a D-cut type. The D-cut flat surface 23 connects, for example, the polarization maintaining optical fiber 40 to the optical waveguide 110. At this time, the optical circuit board 101 becomes a plane parallel to the reference plane 104. In (A) and (D), as in the second embodiment, the boundary surface between the rear surface 22 of the wall portion 2 and the optical fiber holding portion 3 bisects the rear surface 22. Further, in (A), (D), and (E) (G), a flat side surface 36 is formed on the optical fiber holding portion 3, and the flat side surface 36 is adsorbed by, for example, a vacuum chuck during alignment. It can be used as a surface to be used. In (C), (F), and (G), the optical fiber holding part 3 is located below the rear surface 22 of the wall part 2, but the optical fiber holding part 3 is separated depending on the grip during operation. You may arrange | position in the position of.

  In (D), (E), and (G), the flat surface 23 of the wall portion 2 and the side surface 36 of the optical fiber holding portion 3 are parallel to each other. You may cross at an angle of 45 °. In addition, when a polarization maintaining optical fiber is used, if at least one of the flat surface 23 of the wall 2 and the side surface 36 of the optical fiber holding unit 3 is orthogonal or parallel to the polarization plane, The person can confirm the direction of the polarization axis 50 according to the shape of the ferrule.

  As a matter of course, the ferrule (1k to 1q) shown in FIGS. 16A to 16G can be used as a basic structure to provide a ferrule including the wall surface reinforcing portion 5.

1, 1a-1q ferrule, 2 walls, 3 optical fiber holder,
4 optical fiber insertion hole, 5 wall reinforcement, 21 ferrule end face (front of wall),
22 rear surface of the wall portion, 31 rear end surface of the optical fiber holding portion,
32 Boundary between the wall portion and the optical fiber holding portion,
33 Flat surface of optical fiber holding part for confirming polarization plane, 40 optical fiber,
41 Front opening (fiber end face) of optical fiber insertion hole,
42 rear end opening of optical fiber insertion hole, 50 polarization axis, 51 front end of wall reinforcing part,
100 optical circuit components, 101 optical circuit board, 102 end face of optical circuit board,
103 optical circuit board side surface of the optical circuit board, 104 reference plane of the optical circuit board,
105 optical circuit board reference line, 110 optical waveguide,
111 Open end face of optical waveguide (waveguide end face), 120 photocurable adhesive,
130 Light (curing light) irradiated to the photo-curing adhesive, 140 Holding block

Claims (8)

A method of connecting an optical waveguide opened to an end face of an optical circuit board on which an optical waveguide is formed, and an optical fiber inserted in a ferrule,
(1) When the direction of the optical fiber inserted in the ferrule is the front-rear direction, in the ferrule, the optical circuit board side is the front, and the reverse side is the rear,
The ferrule is
A wall portion formed of a light transmissive material and having a flat surface on the front and rear, a front surface as an opening end surface of the optical fiber and an adhesive surface with the optical circuit board,
An optical fiber holding portion that is integrally formed on the rear surface of the wall portion, extends in the normal direction of the rear surface , and has a smaller front projection area than the wall portion ,
An optical fiber insertion hole that penetrates the front surface of the wall portion and the rear surface of the optical fiber holding portion in the normal direction, and the optical fiber extends later from the rear end opening of the optical fiber insertion hole;
(2) an alignment step of arranging the optical axis of the optical fiber and the optical axis of the optical waveguide on a straight line;
An adhesive application step of interposing a photo-curable adhesive between the front surface of the wall and the end surface of the optical circuit board;
A light irradiation step of irradiating light for curing the photocurable adhesive,
(3) In the light irradiation step, light is applied to the rear surface of the wall portion from an oblique direction, and the light curable adhesive is cured by light incident from the rear surface and transmitted through the wall portion. A method for connecting an optical fiber and an optical waveguide. The connection method according to claim 1 , wherein the optical fiber holding portion is a columnar shape having the optical fiber insertion hole as an axis, and has a flat shape that traverses so that a front end surface bisects a rear surface of the wall portion,
In the light irradiating step, light is irradiated from two directions to each of the rear surfaces of the bisected wall portion, and the method for connecting an optical fiber and an optical waveguide. Oite the connection method according to claim 1 or 2, wherein the wall, characterized in that it has a shape in which straight line is parallel to the reference line formed on the end face of the optical circuit board is formed A method of connecting the optical fiber and the optical waveguide . Oite the connection method according to claim 3, wherein the optical fiber connection method of the optical fiber and the optical waveguide, which is a polarization maintaining optical fiber. Oite the connection method according to claim 4, wherein the optical fiber holding portion, that said polarization maintaining optical fiber is provided with a surface perpendicular to the plane of polarization, or the direction parallel to the normal line of the light propagating A method for connecting an optical fiber and an optical waveguide . Oite the connection method according to claim 4, wherein the wall portion, characterized in that said polarization maintaining optical fiber comprises a plane perpendicular to the plane of polarization, or the direction parallel to the normal line of the light propagating A method of connecting the optical fiber and the optical waveguide . Includes Oite, the rear surface of the wall portion and said optical fiber holder a flat wall reinforcing portions extending rearward are integrally formed in the connecting method according to any one of claims 1 to 6 A method for connecting an optical fiber and an optical waveguide . Oite the connection method according to claim 1, connection between the optical fiber and the optical waveguide, characterized in that it is molded of transparent resin.

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