JP2000131556A - Connection structure and connection method between optical waveguide and optical fiber - Google Patents

Abstract

(57) [Problem] To provide an end face connection adhesive for bonding an end face of an optical waveguide and an end face of an optical fiber, connection reliability was low. SOLUTION: An end face of an optical waveguide formed on a substrate 1 and an end face of an optical fiber 5 mounted on the optical fiber fixing groove 4 formed on the substrate 1 with the optical axis aligned with the optical axis. The optical fiber 5 is bonded together with the curable adhesive 7.
This is a connection structure between the optical fiber and the optical waveguide in which is fixed to the optical fiber fixing groove 4 by a thermosetting adhesive 8. The end faces of the optical waveguide and the optical fiber 5 are precisely joined together with a photocurable adhesive 7 and the optical fiber 5 is bonded to a thermosetting adhesive 8.
Accordingly, the connection strength can be improved by firmly fixing to the substrate, and good optical connection without causing optical axis shift can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure and a connection method between an optical waveguide and an optical fiber for connecting the optical waveguide and the optical fiber on a substrate such as an optical integrated circuit substrate by using an adhesive, and more particularly, to an optical fiber. The present invention relates to a connection structure and a connection method between an optical waveguide and an optical fiber in which the accuracy of optical axis adjustment between the fiber and the optical waveguide is improved and the connection strength of the optical fiber is increased.

[0002]

2. Description of the Related Art On a substrate for handling optical signals, such as an optical integrated circuit substrate or an opto-electronic mixed substrate, an optical signal is exchanged between a three-dimensional optical waveguide formed on the substrate and the outside. Optical connection structure for connecting to an optical fiber is required.

FIGS. 3 (a) and 3 (b) show a conventional example of such a connection structure between an optical waveguide and an optical fiber in a perspective view and a sectional view, respectively. In FIG. 3, 1 is a substrate, 2 and 3 are a core part and a clad part of a three-dimensional waveguide optical waveguide formed on the substrate 1, 4 is an optical fiber fixing groove formed on the substrate 1, and 5 is The optical fiber is fixed in the optical fiber fixing groove 4 with the optical axis aligned with the core 2 of the optical waveguide.

In such a connection structure between an optical waveguide and an optical fiber, first, as shown in FIG.
Optical fiber fixing groove 4 formed on the upper surface facing the optical waveguide
Then, the optical fiber 5 is inserted with its end face facing the end face of the optical waveguide. Next, after the insertion, the optical axes of the two are adjusted so that the core 6 as the optical axis of the optical fiber 5 and the core 2 as the optical axis of the optical waveguide are aligned. Then, a small amount of the end face connecting adhesive 7 is dropped between the inserted end face of the optical fiber 5 and the end face of the optical waveguide, and the end face is temporarily fixed. The agent 7 was added to increase the connection strength between the end faces, and both were securely bonded.

[0005]

However, in the conventional connection method as shown in FIG. 3, at the connection between the end faces of the optical waveguide and the optical fiber 5, the adhesive 7 which has been temporarily fixed is further bonded. When the agent 7 is added, the solvent or the like diffuses and permeates from the adhesive 7 before curing into the adhesive 7 cured in the temporary fixing, so that the cured adhesive 7 is loosened. There is a problem that the optical axis shift of No. 5 occurs.

Further, since the connection of the optical fiber 5 is performed at the end face of the tip, there is a problem that the connection strength of the optical fiber 5 is insufficient and the connection reliability is low.

The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to fix an optical fiber to an optical fiber when the optical fiber is fixed on a substrate having an optical waveguide formed thereon with an adhesive. By applying a fixing adhesive for fixing to the fixing groove, it is possible to securely fix the substrate to the substrate and improve the strength thereof, and the optical axis deviation caused by the curing of the end face connection adhesive and the fixing adhesive. An object of the present invention is to provide a connection structure and a connection method between an optical waveguide and an optical fiber, which are capable of optically connecting the optical axes with good positional accuracy by suppressing occurrence of the optical waveguide.

[0008]

According to the present invention, there is provided a connection structure between an optical waveguide and an optical fiber, wherein the optical waveguide is provided on an end face of the optical waveguide formed on a substrate and an optical fiber fixing groove formed on the substrate. And an end face of the optical fiber placed with the optical axis aligned with a light-curing adhesive, and the optical fiber is fixed to the optical fiber fixing groove with a thermosetting adhesive. It is.

Further, in the method for connecting an optical waveguide to an optical fiber according to the present invention, a substrate having an optical waveguide on an upper surface and an optical fiber fixing groove having an adhesive separating groove is prepared. The optical fiber is placed with the optical waveguide aligned with the optical axis in the fixing groove, and the end faces of the optical waveguide and the optical fiber are joined with a photocurable end face connection adhesive, and then the optical fiber fixing groove and The optical fiber is bonded with a thermosetting fixing adhesive.

[0010] According to the connection structure of the optical waveguide and the optical fiber of the present invention, the end faces of the optical waveguide and the optical fiber are joined to each other with an adhesive for connecting the end faces of a photocurable adhesive. Since the optical fiber is bonded and fixed to the optical fiber fixing groove with the adhesive for end face connection, the photocurable adhesive is bonded to the optical waveguide and the core portion (optical axis) of the optical fiber and the opposing optical fiber via the adhesive for end face connection. By irradiating the adhesive for end face connection with the light for curing the adhesive, the adhesive for end face connection between the optical axes and in the vicinity thereof can be light-cured, and the end faces can be joined with high positional accuracy, and the thermosetting can be performed. With the adhesive for fixing the conductive adhesive, the optical fiber can be firmly bonded to the optical fiber fixing groove of the substrate with a large connection strength while maintaining the alignment of the end faces with the optical waveguide, and can be fixed well and securely. .

According to the method for connecting an optical waveguide to an optical fiber according to the present invention, the optical fiber is placed in the optical fiber fixing groove so that the optical waveguide and the optical axis are aligned, and the end faces of the optical waveguide and the optical fiber are connected to each other. After bonding with the adhesive for end face connection of the photocurable adhesive, the optical fiber fixing groove and the optical fiber are joined with the adhesive for fixing of thermosetting adhesive different from the adhesive for end face connection. Even if a part of the fixing adhesive is in contact with the end face connection adhesive, the solvent or the like of the fixing adhesive diffuses and permeates into the end face connection adhesive and mixes. Looseness of the connection adhesive can be effectively suppressed. In addition, since the adhesive for connecting the end faces and the adhesive for fixing do not mix, the fixing of the end faces joined by the adhesive for connecting the end faces does not shift, and the fixing adhesive having a large adhesive strength is used. Since the optical fiber can be firmly fixed in the optical fiber fixing groove, the occurrence of optical axis shift between the optical waveguide and the optical fiber can be eliminated.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIGS. 1 (a) and 1 (b) are a perspective view and a sectional view, respectively, showing an embodiment of a connection structure between an optical waveguide and an optical fiber according to the present invention. In FIG.
Parts similar to those in FIG. 3 are denoted by the same reference numerals. Reference numeral 8 denotes a fixing adhesive for fixing the optical fiber 5 to the optical fiber fixing groove 4.

The connection structure between the optical waveguide and the optical fiber according to the present invention is fixed to the end face of the optical waveguide formed on the substrate 1 and the optical fiber fixing groove 4 formed on the substrate 1 by a fixing adhesive 8. With the end face of the optical fiber 5
That is, the core portion 2 of the optical waveguide and the core portion 6 of the optical fiber 5
And a bonding structure formed by joining with an end face connecting adhesive 7, wherein a light curable adhesive is used for the end face connecting adhesive 7, and a thermosetting adhesive is used for the fixing adhesive 8. The connection is characterized by using

As described above, since the end-face connecting adhesive 7 is made of a light-curing material and the fixing adhesive 8 is made of a thermosetting material, different types of adhesives are used. 5 contacts the fixing adhesive 8 along the end face and the side face near the end face, or the fixing adhesive 8 contacts the end face connecting adhesive 7 along the optical fiber 5 and the side face of the optical fiber fixing groove 4. Even if it does, the two will not be mixed, and the adhesive hardening of the adhesive, particularly the adhesive 7 for end face connection, will not be loosened, and the occurrence of optical axis deviation of the optical fiber 5 can be suppressed.

Here, since a photo-curable adhesive such as an ultraviolet-curable adhesive is used as the end face connecting adhesive 7, as shown in FIG. By irradiating the light L such as ultraviolet rays through the core 6 of the fiber 5, the adhesive 7 for connecting the end faces between the optical axes and in the vicinity thereof can be instantaneously cured. The position alignment with the optical fiber 5 is maintained as it is, and the optical connection without the optical axis shift can be performed.

As such an adhesive 7 for end face connection,
Those having the same refractive index as the core portion 2 of the optical waveguide and the core portion 6 of the optical fiber 5, that is, the refractive index difference between them is
A UV curable adhesive of 0.1% or less is desirable. By using such an ultraviolet-curable adhesive, light can be propagated between the end face of the optical waveguide and the end face of the optical fiber 5 without being scattered, and a good optical connection can be obtained. In addition, by using the ultraviolet curable adhesive, the state between the optical waveguide whose optical axis has been adjusted and the optical fiber 5 can be instantaneously fixed, so that the alignment characteristics are improved.

As a specific ultraviolet-curable adhesive, for example, an ultraviolet-curable epoxy resin or an ultraviolet-curable acrylic resin can be used. Above all, the use of an ultraviolet-curable epoxy resin is preferred in that shrinkage during curing is small.

On the other hand, since a thermosetting adhesive is used as the fixing adhesive 8, the adhesive strength of the optical fiber 5 to the optical fiber fixing groove 4 can be increased, so that the optical waveguide and the optical fiber are bonded to each other. Sufficient connection strength can be obtained, and good optical connection can be performed.

The thermosetting fixing adhesive 8 is not particularly limited as long as it has an effect of bonding the optical fiber 5 to the substrate 1. However, in order to reduce the influence on the optical axis deviation between the optical waveguide and the optical fiber 5, it is desirable that the adhesive does not mix with the photocurable end face connection adhesive 7 cured by temporary fixing. It is desirable that the thermal expansion coefficient and the shrinkage rate upon curing are as small as possible. For good and reliable adhesion of the optical fiber 5 to the substrate 1, it is necessary to consider the bonding area and the like.
It is desirable that the adhesive strength be at least kg.

As the fixing adhesive 8, for example, a thermosetting epoxy resin, an acrylic resin, a polyimide resin, a silicone adhesive or the like can be used. Above all, when a silicone adhesive is used, the adhesive strength is large,
It is also preferable in that the water absorption is low.

According to the connection structure of the present invention, when the end face connection adhesive 7 and the fixing adhesive 8 are not mixed with each other, the contact between them does not need to be a particular problem. Therefore, as shown in FIG.
Can be formed just below the end face of the optical waveguide. As a result, the end face of the optical fiber 5 is abutted against the end face of the optical waveguide while being supported by the optical fiber fixing groove 4, so that the alignment of the optical axis in the optical connection can be improved.

Further, according to the method for connecting an optical waveguide and an optical fiber of the present invention, after the optical fiber 5 is inserted and placed in the optical fiber fixing groove 4 formed on the substrate 1, the optical fiber 5 is connected to the optical fiber 5. The optical axis of the optical waveguide is adjusted to align the optical axes (core portion 2 and core portion 6) of the optical waveguide, and at the same time, a photocurable adhesive 7 for connecting the end surface between the optical waveguide and the end surface of the optical fiber 5.
Is dropped, and the core portion 2 of the optical waveguide or the optical fiber 5
Irradiation light L for curing is applied from the core portion 6 to cure the end face connection adhesive 7. At this time, the amount of the end face connection adhesive 7 to be dropped may be small, and the influence of shrinkage or the like generated during the curing is small, so that the occurrence of optical axis shift can be suppressed.

Thereafter, the optical fiber fixing groove 4 and the optical fiber 5 are joined by a fixing adhesive 8 of a thermosetting adhesive different from the photocurable end face connection adhesive 7. Although FIG. 1 shows an example in which the fixing adhesive 8 is provided around the optical fiber 5, the fixing adhesive 8 is interposed only between the optical fiber fixing groove 4 and the optical fiber 5. Needless to say, both may be bonded.

As a result, the optical fiber 5 can be firmly fixed to the optical fiber fixing groove 4 by the thermosetting fixing adhesive 8 having a large adhesive strength, and the optical axis deviation between the optical waveguide and the optical fiber 5 occurs. And a connection structure with high connection reliability that can eliminate the problem can be obtained. Further, since the types of the adhesive 7 for connecting the end face and the adhesive 8 for fixing are different, when the adhesive 8 for fixing is applied, a part of the adhesive 7 is spread and temporarily fixed. Even if they come into contact with each other, it is possible to effectively prevent the solvent and the like of the fixing adhesive 8 from diffusing and penetrating into and mixing with the end face connecting adhesive 7 to loosen the adhesion of the end face connecting adhesive 7 effectively. it can.

According to the connection structure and the connection method of the present invention, different adhesives of photo-curing and thermosetting are used for the adhesive 7 for end face connection and the adhesive 8 for fixing, respectively. The thermal and mechanical properties of the agent will be different. Therefore, taking into account the combination of the two properties, for example, even if one of the adhesives is likely to deteriorate with time under various environments, the other adhesive is unlikely to deteriorate with respect to the conditions. By selecting the above, the bonding effect between the optical waveguide and the optical fiber 5 can be maintained, and the connection reliability can be improved.

As a combination of such characteristics, for example, an ultraviolet-curing epoxy resin which has a small shrinkage at the time of curing and easily maintains the alignment and a glass transition temperature Tg which has low moisture absorption and high reliability after fixing are excellent. A combination with a thermosetting silicone resin is conceivable.

In the connection structure between the optical waveguide and the optical fiber according to the present invention, FIGS.
As shown in a sectional view similar to (b), between the end face of the optical fiber 5 and the fixing position by the fixing adhesive 8 with respect to the optical fiber fixing groove 4, the end face connecting adhesive 7 and the fixing adhesive are used. By forming an adhesive separating groove 9 for separating the adhesive 8 from the optical fiber 8, the end faces of the optical waveguide and the optical fiber 5 are connected to each other with an adhesive 7 for connecting the end faces, and then the adhesive 8 is fixed to the optical fiber fixing groove 4. , The two do not come into contact with each other due to the adhesive separating groove 9 formed between the two adhesives. Also, the fixing adhesive 8 and the end face connecting adhesive 7
Can be provided with a desired distance between the fixing adhesive 8 and the fixing adhesive 8.
Can be effectively prevented from affecting the end faces of the optical waveguide and the optical fiber 5 due to shrinkage and the like during the curing.
Therefore, it is possible to more effectively eliminate the optical axis deviation between the optical fiber 5 and the optical waveguide joined with the end face connecting adhesive 7 with the optical axes aligned, and the optical fiber 5 is fixed by the fixing adhesive 8. The optical fiber 5 can be securely fixed to the fiber fixing groove 4, and the connection reliability of the optical fiber 5 can be further improved.

Further, in the method for connecting an optical waveguide and an optical fiber according to the present invention, if the substrate in which the adhesive separating groove 9 is formed in the optical fiber fixing groove 4 is used, the optical fiber 5 is separated from the adhesive. After the optical waveguide and the optical fiber 5 are placed in the optical fiber fixing groove 4 having the groove 9 with the optical axis aligned and the end faces of the optical waveguide and the optical fiber 5 are joined with the end face connecting adhesive 7,
By joining the optical fiber 5 to the region of the optical fiber fixing groove 4 which sandwiches the adhesive separating groove 9 with respect to the end face of the optical fiber 5 with the fixing adhesive 8, the optical waveguide and the end face of the optical fiber 5 are joined together. Even if the fixing adhesive 8 is applied after connecting the two with the end face connecting adhesive 7, the two will not contact and mix due to the adhesive separating groove 9 formed between the two adhesives. Further, since a desired distance can be provided between the fixing adhesive 8 and the end face connecting adhesive 7, the influence when applying the fixing adhesive 8 or the fixing adhesive 8 is cured. It is possible to effectively prevent the influence of shrinkage or the like on the end face of the optical waveguide. Therefore, the optical waveguide and the optical fiber 5 which are aligned with the optical axis and bonded with the end face connection adhesive 7 are
Can be eliminated. Further, the optical fiber 5 can be securely fixed to the optical fiber fixing groove 4 by the fixing adhesive 8, and the connection strength of the optical fiber can be improved.

In addition, regarding the adhesive strength of the optical fiber 5 to the substrate 1, that is, the adhesive strength to the optical fiber fixing groove 4, after the end faces of the optical waveguide and the optical fiber 5 are joined together, Since the optical fiber fixing groove 4 and the optical fiber 5 are joined with the fixing adhesive 8 at a fixing position provided in a region sandwiching the adhesive separating groove 9 with respect to the end face of the optical fiber 5, sufficient An appropriate amount of the fixing adhesive 8 can be applied, and the adhesive strength of the optical fiber 5 can be improved. At this time, even if a large amount of the fixing adhesive 8 is applied and flows along the side surface of the optical fiber 5 due to the surface tension, the fixing adhesive 8 flowing to the end face side of the optical fiber 5 is fixed to the optical fiber. Since it stops at the adhesive separating groove 9 provided in the groove 4 and is separated from the end face connecting adhesive 7, there is no influence on the joint portion between the end face of the optical fiber 5 and the end face of the optical waveguide. Accordingly, the optical axis of the optical fiber 5 does not deviate due to shrinkage of the fixing adhesive 8 during curing.

Since the adhesive separating groove 9 is formed closer to the optical fiber 5 than the end face of the optical waveguide, the adhesive 7 for connecting the end face is spread over the entire end face of the optical waveguide. On the other hand, the end face can be expanded to the corner where the end face comes into contact with the end face of the optical waveguide. Therefore, the provision of the adhesive separating groove 9 allows the optical waveguide and the optical fiber 5 to be formed.
The bonding strength of the connection portion between the end faces can also be improved.

Further, since the adhesive separating groove 9 is formed closer to the optical fiber 5 than immediately below the end face of the optical waveguide, the optical fiber 5 is adjusted when the optical axis of the optical waveguide and the optical fiber 5 is adjusted.
Does not become unstable, and the optical axis can be easily adjusted.

Specifically, the position of the adhesive separating groove 9 is preferably 20 μm to 2 cm from the end face of the optical waveguide, and is located in a range between the end face of the optical fiber 5 and the fixed position.

In particular, if the position is 20 to 50 μm from the end face of the optical waveguide, it is preferable that the end face connection adhesive 7 and the fixing adhesive 8 can be effectively separated.

The dimensions such as the width, depth and length of the adhesive separating groove 9 are determined by a part of the end face connecting adhesive 7 spreading toward the adhesive separating groove 9 or the fixing adhesive 8. Occupies a volume larger than a part of the volume, and particularly preferably has a width of 10 μm or more that ensures the effect of separating the adhesive.

The shape of the adhesive separating groove 9 is to separate the end face connecting adhesive 7 applied between the optical waveguide and the end face of the optical fiber 5 and the fixing adhesive 8 applied to the optical fiber supporting groove 4. Any shape may be used as long as it is possible. For example, a groove having a rectangular cross section as shown in FIG.
Various shapes such as a V-shaped groove or a semicircular groove as shown in FIG. Above all, it is easy to manufacture by dicing, and if the volume is the same, the groove can be narrow or shallow. Therefore, a groove having a rectangular cross section is suitable for the connection structure of the present invention.

Further, not only one adhesive separating groove 9 but also a plurality of adhesive separating grooves 9 may be provided as shown in FIG. When a plurality of the adhesive separating grooves 9 are provided, not only can the adhesive function more reliably to separate the adhesive, but also the groove closest to the end face of the optical fiber 5 is the end face connecting adhesive. 7 is used as a groove for separating the fixing adhesive 8 from the fixing adhesive 8, and the fixing adhesive 8 is made to penetrate into the other grooves, and the effect of the surface tension is used to fix the optical fiber of the optical fiber 5. 4 can be further increased.

As the method for forming the adhesive separating groove 9, as in the case of the optical fiber fixing groove 4, a method using dicing, a method of performing reactive dry etching using a mask, and other methods are used. Good.

In the connection structure between an optical waveguide and an optical fiber according to the present invention, the substrate 1 may be any of various substrates used as substrates for handling optical signals, such as an optical integrated circuit substrate and an optoelectronic mixed substrate, such as a silicon substrate and an alumina substrate. Substrates, glass ceramic substrates, multilayer ceramic substrates, etc. can be used.

The optical waveguide formed on the substrate 1 is a three-dimensional waveguide-shaped optical waveguide in which a core 2 is formed in a cladding portion 3 and is made of silica, polyimide, fluororesin, or the like. A fluorinated polyimide / siloxane-based polymer or the like can be used. Among them, the use of an optical waveguide made of a siloxane-based polymer is preferable in terms of low-temperature formation and high heat resistance and low loss.

The optical fiber fixing groove 4 may be appropriately selected from various shapes, dimensions and forming methods according to the material and characteristics of the substrate 1 or the shape and dimensions of the optical fiber 5. Instead of the square groove shown in FIG. 1, a V-shaped groove or a semicircular groove may be used. For the formation, a method using dicing, a method for performing reactive dry etching using a mask, or another method may be used.

The optical fiber 5 is made of silica or P
A single-mode optical fiber or a multi-mode optical fiber made of MMA (polymethyl methacrylate) / fluororesin can be connected.

[0043]

Next, a specific example of a connection structure and a connection method between an optical waveguide and an optical fiber according to the present invention will be described.

Example 1 A step index type optical waveguide having a cladding portion made of siloxane polymer and a core portion made of titanium-containing siloxane polymer was formed on a substrate made of alumina ceramics. Next, a portion of the optical waveguide to be connected to the optical fiber was determined, and an end face of the optical waveguide was formed using a dicing blade. Further, an optical fiber fixing groove was formed at a position facing the end face by dicing. At this time, the depth from the upper surface of the optical waveguide to the bottom surface of the optical fiber fixing groove was 90 μm.

Next, a silica-based optical fiber having a diameter of 125 μm is inserted into the optical fiber fixing groove, and light incident from the end face of the optical fiber through the core of the optical waveguide is output from the other end face of the optical fiber. The optical axis of the optical waveguide and the optical fiber was adjusted while monitoring from above.

Next, an ultraviolet curable epoxy resin comprising a sulfonium salt-based photopolymerization initiator and an epoxy resin as an adhesive for end face connection having a refractive index similar to that of the core portion of the optical waveguide and the optical fiber is used. 0.245 μl of adhesive was dropped between the optical waveguide and the end face of the optical fiber, and
It was cured by irradiating ultraviolet rays from outside.

After that, a thermosetting adhesive of thermosetting silicone resin is applied as a fixing adhesive to the optical fiber fixing groove and the optical fiber, and the light is applied at 150 ° C. by a halogen lamp light.
By locally heating for 30 seconds, the fixing adhesive was cured to fix the optical fiber on the substrate.

When the connection loss between the optical waveguide and the optical fiber was measured by a cutback method for the connection structure between the optical waveguide and the optical fiber of the present invention, the LD (laser diode) light having a wavelength of 1.3 μm was obtained. It was confirmed that the connection loss with respect to was suppressed to 0.5 dB or less. Further, based on data representing the relationship between the positional deviation and the loss measured in advance, the optical axis deviation was evaluated by associating the minimum value of the loss, that is, the increase in the loss with respect to the positional deviation = 0, with the magnitude of the positional deviation. , Within 0.2 μm.

When the bonding strength of the optical fiber to the substrate was measured with a load tensile tester for this connection structure, the bonding strength of the optical fiber was 5 kg or more, and the substrate was sufficiently resistant to handling and handling after bonding the optical fiber. It was confirmed that it had good connection strength.

Further, this connection structure is kept at a high temperature of 85.degree.
Even after standing for a long time, no change was observed in various characteristics, and it was confirmed that the connection reliability was excellent.

Example 2 Next, using the same substrate as in Example 1, an adhesive separating groove was formed by dicing at a position 20 μm away from the end face of the optical waveguide on the bottom surface of the optical fiber fixing groove. Here, the adhesive separating groove is a rectangular cross-sectional shape with a depth of 30 μm and a width of 20 μm in the optical axis direction of the optical fiber, and the width in the direction perpendicular to the optical axis direction is formed as a terrace-shaped optical fiber fixing groove. Therefore, the width was the same as the width up to the end of the substrate.

Next, the end faces of the optical waveguide and the optical fiber were connected with an end face connecting adhesive in the same manner as in [Example 1].
Then, the optical fiber fixing groove and the optical fiber in the region where the adhesive separating groove is interposed between the end face of the optical fiber and the optical fiber [Example 1]
Apply the fixing adhesive in the same way as above, heat and cure,
The optical fiber was fixed on the substrate.

When this connection structure was evaluated in the same manner as in [Example 1], it was confirmed that all of them had the same or better characteristics.

It should be noted that the above is only an example of the embodiment of the present invention, and the present invention is not limited to these. Various modifications and improvements may be made without departing from the gist of the present invention. No problem.

[0055]

As described above, according to the connection structure for an optical waveguide and an optical fiber of the present invention, the end surfaces of the optical waveguide and the optical fiber are joined with a photocurable adhesive for connecting the end surfaces, and the heat is applied. Since the optical fiber is bonded and fixed to the optical fiber fixing groove with the curable adhesive for end face connection, the core (optical axis) of the optical waveguide and the optical fiber opposed to each other via the adhesive for end face connection is cured. Irradiating the adhesive for end face connection with the adhesive for end face connection, the adhesive for end face connection between the optical axes and the vicinity thereof can be light-cured, and the end faces can be joined with good positional accuracy, and the thermosetting fixing can be performed. With the adhesive for the optical fiber, the optical fiber can be firmly bonded to the optical fiber fixing groove of the substrate with a large connection strength while maintaining the alignment of the end faces with the optical waveguide,
It could be fixed well and reliably.

According to the method for connecting an optical waveguide and an optical fiber of the present invention, the optical fiber is placed in the optical fiber fixing groove so that the optical waveguide and the optical axis are aligned, and the end faces of the optical waveguide and the optical fiber are connected to each other. After joining with photo-curing adhesive for end face connection,
Since the optical fiber fixing groove and the optical fiber are joined with a thermosetting fixing adhesive different from the adhesive for the end face connection, when the fixing adhesive is applied, part of the adhesive is applied for the end face connection. Even if it comes into contact with the adhesive, it is possible to effectively prevent the solvent and the like of the fixing adhesive from diffusing and penetrating into and mixing with the end face connection adhesive and loosening the adhesion of the end face connection adhesive. Was. In addition, since the adhesive for connecting the end faces and the adhesive for fixing do not mix, the fixing of the end faces joined by the adhesive for connecting the end faces does not shift, and the fixing adhesive having a large adhesive strength is used. Since the optical fiber can be firmly fixed in the optical fiber fixing groove, the occurrence of optical axis shift between the optical waveguide and the optical fiber can be eliminated.

As described above, according to the present invention, when the optical fiber is fixed on the substrate on which the optical waveguide is formed, the fixing adhesive for fixing the optical fiber to the optical fiber fixing groove is used. By adding the resin to the substrate, it can be securely fixed to the substrate and its strength can be improved, and the occurrence of optical axis deviation caused by the curing of the adhesive for end face connection and the adhesive for fixing can be suppressed to achieve good positional accuracy. It is possible to provide a connection structure and a connection method between an optical waveguide and an optical fiber that can optically connect the optical axes.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are a perspective view and a sectional view, respectively, showing an example of an embodiment of a connection structure between an optical waveguide and an optical fiber according to the present invention.

FIGS. 2A to 2C are cross-sectional views showing another example of the embodiment of the connection structure between the optical waveguide and the optical fiber according to the present invention.

FIGS. 3A and 3B are a perspective view and a cross-sectional view, respectively, showing an example of a conventional connection structure between an optical waveguide and an optical fiber.

[Description of Signs] 1 ... Substrate 2 ... Core part of optical waveguide 3 ... Clad part of optical waveguide 4 ... Fixing groove for optical fiber 5 ... Optical fiber 6 ... Core of optical fiber Part 7: Adhesive for end face connection (photo-curable adhesive) 8: Adhesive for fixing (thermo-curable adhesive)

Claims (2)

[Claims] 1. An end face of an optical waveguide formed on a substrate,
The optical waveguide and the end face of the optical fiber placed in alignment with the optical axis are bonded to the optical fiber fixing groove formed on the substrate with a light-curing adhesive, and the optical fiber is connected to the optical fiber fixing groove. A connection structure between an optical waveguide and an optical fiber, wherein the optical waveguide and the optical fiber are fixed to each other with a thermosetting adhesive. 2. A substrate on which an optical waveguide and an optical fiber fixing groove having an adhesive separating groove are formed on the upper surface is prepared.
The optical fiber is placed with the optical axis aligned with the optical waveguide in the optical fiber fixing groove, and the end faces of the optical waveguide and the optical fiber are joined to each other with a photocurable end face connection adhesive, and then the optical fiber A method for connecting an optical waveguide and an optical fiber, wherein the fixing groove and the optical fiber are joined with a thermosetting fixing adhesive.