JP2000105324A - Structure and method for connecting optical waveguide with optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent optical axes from being misaligned from the result that an adhesive for end face connection for connecting the end face of an optical waveguide to that of an optical fiber and a fixing adhesive for connecting the optical fiber with an optical fiber fixing groove are mixed with each other. SOLUTION: This structure is formed by connecting an end face of an optical waveguide formed on a substrate 1 with that of an optical fiber 5 fixed with a fixing adhesive 8 by aligning the optical axis with that of the optical waveguide in the optical fiber fixing groove 4 formed on the substrate 1. Here, an adhesive separating groove 9 is arranged between the end face of the optical fiber 5 in the optical fiber fixing groove 4 and a fixing position by the fixing adhesive 8. Thus, it is possible to separate an end face connecting adhesive 7 from the fixing adhesive 8 by the groove 9, and prevent the optical axes from being misaligned from each other to achieve a satisfactory optical connection.

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 (a), 1 is a substrate, 2 and 3 are a core portion and a cladding portion of a three-dimensional waveguide optical waveguide formed on the substrate 1, and 4 is formed on the substrate 1. The optical fiber fixing grooves 5 and 5 are optical fibers fixed to 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, as shown in FIG. 3B, first, the optical fiber fixing groove 4 is provided with an optical axis, that is, a core 6 and an optical axis of the optical waveguide. An end face connection adhesive 7 made of an ultraviolet curable adhesive is filled between the end face of the optical fiber 5 and the end face of the optical waveguide inserted in alignment with a certain core portion 2. Next, the ultraviolet light L is passed through the core portion 2 of the optical waveguide and the core portion 6 of the optical fiber 5, and a part of the end face connection adhesive 7, that is, both core portions 2.7
By hardening the space between and the vicinity thereof, the end faces of the optical waveguide and the optical fiber 5 are temporarily fixed. afterwards,
The uncured portion of the end face connection adhesive 7 is cured by irradiating ultraviolet rays from the outside, so that the end faces of the optical waveguide and the optical fiber are securely bonded to each other.

Further, in order to securely fix the optical fiber 5 to the optical fiber fixing groove 4 of the substrate 1, a fixing adhesive 8 for fixing the optical fiber 5 to the optical fiber fixing groove 4 is applied. It was also fixed.

In the connection method shown in FIG. 3, the end face connection adhesive 7 first cures the portion where the core 2 of the optical waveguide and the core 6 of the optical fiber 5 face each other.
Next, since the periphery is cured, the alignment of the connection portion whose optical axis has been adjusted in advance is not affected by distortion such as shrinkage that occurs when the adhesive 7 for end face connection is cured, so that the optical axis may shift. Instead, the optical waveguide and the optical fiber 5 can be accurately connected.

FIGS. 4 (a) and 4 (b) show another example of a conventional connection structure between an optical waveguide and an optical fiber in a perspective view and a sectional view, respectively. In FIG. 4, the same parts as those in FIG. 3 are denoted by the same reference numerals.

In the connection structure shown in FIG. 4, first, the optical fiber is fixed such that the end face of the optical waveguide and the end face of the optical fiber 5 face the optical fiber fixing groove 4 formed on the substrate 1 so as to face the optical waveguide. The fiber 5 is inserted. After the insertion, the optical axes of the two are adjusted to align the core 2 of the optical waveguide and the core 6 of the optical fiber 5. Thereafter, a fixing adhesive 8 is dropped between the optical fiber 5 and the optical fiber fixing groove 4 at a position far away from the end face of the optical waveguide, and the optical fiber 5 is placed on the substrate 1.
Securely.

In the connection structure shown in FIG. 4, the fixing adhesive 8 flows between the optical fiber 5 and the optical fiber fixing groove 4 by the surface tension and flows therethrough.
All over the inside. As a result, since the amount and distribution of the fixing adhesive 8 can be easily controlled by using the optical fiber fixing groove 4, the optical axis deviation of the optical fiber 5 due to the application of the fixing adhesive 8 and the curing thereof can be prevented. It is possible to do.

[0011]

However, in the conventional connection method as shown in FIG. 3, the end-face connecting adhesive 7 for joining the end faces of the optical waveguide and the optical fiber 5 has the end face of the optical fiber 5 and the end face adhesive. The adhesive 8 is mixed with the fixing adhesive 8 applied to the optical fiber fixing groove 4 along the side surface near the end face, or is mixed with the adhesive 7 for connecting the end face along the side face of the optical fiber 5. Sometimes. Therefore, when the fixing adhesive 8 is cured after the end face connection adhesive 7 is cured, the end face connection adhesive 7 is pulled by the shrinkage accompanying the curing of the fixing adhesive 8, and as a result, the optical axis There has been a problem that displacement occurs.

Further, after the end face of the optical waveguide and the end face of the optical fiber 5 are connected by aligning the optical axis with the end face connecting adhesive 7, the fixing adhesive 8 is applied to connect the optical fiber 5 to the optical fiber fixing groove. When the optical fiber 5 is fixed to the optical fiber 5, the solvent or the like diffuses and permeates from the fixing adhesive 8 before curing into the cured end face connection adhesive 7, so that the adhesive effect is loosened.
However, there is also a problem that the optical axis is easily shifted.

Further, in the connection structure shown in FIG. 4, since the end face of the optical fiber 5 is merely abutted against the end face of the optical waveguide, the alignment of the optical axis in the optical connection is unstable. There was a point.

The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to fix an optical fiber on a substrate on which an optical waveguide is formed by using an adhesive. It is possible to improve the strength by improving the optical axis deviation caused by the application or curing and aligning the optical axis with good positional accuracy, and also securely fixing the optical fiber to the substrate with the fixing adhesive. It is an object of the present invention to provide a connection structure and a connection method between an optical waveguide and an optical fiber that can be performed.

[0015]

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 optical axis aligned with the optical axis and the end face of the optical fiber fixed by the fixing adhesive is connected by an end face connecting adhesive, the connection structure between the optical waveguide and the optical fiber, wherein the optical fiber fixing groove of the An adhesive separating groove is provided between an end face of the optical fiber and a fixing position by the fixing adhesive.

Further, according to the method for connecting an optical waveguide and an optical fiber of 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 fixed groove, and the end faces of the optical waveguide and the optical fiber are joined with an adhesive for end face connection. The optical fiber fixing groove in the region sandwiching the adhesive separating groove and the optical fiber are joined with a fixing adhesive.

According to the connection structure of the optical waveguide and the optical fiber of the present invention, the end face connecting adhesive is fixed between the end face of the optical fiber and the fixing position by the fixing adhesive with respect to the optical fiber fixing groove. Since the adhesive separating groove for separating the adhesive for the optical fiber is formed, after connecting the end faces of the optical waveguide and the optical fiber with the adhesive for connecting the end faces, the fixing adhesive is applied to the optical fiber fixing groove. Also, the two do not contact and mix due to the adhesive separating groove formed between the two adhesives. In addition, since a desired distance can be provided between the fixing adhesive and the end face connecting adhesive, an influence when applying the fixing adhesive, a contraction when the fixing adhesive is cured, and the like. Can be effectively prevented from affecting the end faces of the optical waveguide and the optical fiber. Accordingly, it is possible to eliminate the optical axis shift between the optical fiber and the optical fiber that are aligned with the optical axis and bonded with the end face connection adhesive. Further, the optical fiber can be securely fixed to the optical fiber fixing groove by the fixing adhesive, and the connection strength of the optical fiber can be improved.

Further, according to the method for connecting an optical waveguide to an optical fiber of the present invention, the optical fiber is placed in the optical fiber fixing groove having an adhesive separating groove with the optical axis aligned with the optical waveguide, and the optical fiber is connected to the optical waveguide. After joining the end faces of the optical fibers with an end face connecting adhesive, the area of the optical fiber fixing groove where the adhesive separating groove is interposed between the end faces of the optical fiber and the optical fiber are joined with the fixing adhesive. Therefore, even if the fixing adhesive is applied after the end faces of the optical waveguide and the optical fiber are connected to each other with the end face connecting adhesive, the two are contacted and mixed by the adhesive separating groove formed between the two adhesives. Nothing. In addition, since a desired distance can be provided between the fixing adhesive and the end face connecting adhesive, an influence when applying the fixing adhesive, a contraction when the fixing adhesive is cured, and the like. Can be effectively prevented from affecting the end face of the optical waveguide. Accordingly, it is possible to eliminate the optical axis shift between the optical fiber and the optical fiber that are aligned with the optical axis and bonded with the end face connection adhesive. Further, the optical fiber can be securely fixed in the optical fiber fixing groove by the fixing adhesive, and the connection strength of the optical fiber can be improved.

[0019]

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 example of an embodiment of a connection structure between an optical waveguide and an optical fiber according to the present invention. In FIG.
3 and 4 are denoted by the same reference numerals.

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 an end face of the optical fiber 5 fixed in the optical fiber fixing groove 4 and the optical fiber fixing groove 4. Between the fixing position where the optical fiber 5 is fixed to the groove 4 by the fixing adhesive 8, the end face connecting adhesive 7
An adhesive separating groove 9 for separating the fixing adhesive 8 from the fixing adhesive 8 is provided.

Since the adhesive separating groove 9 is provided as described above, the end face connecting adhesive 7 for joining the end faces of the optical waveguide and the optical fiber 5 is transmitted along the end face of the optical fiber 5 and the side face near the end face. It may be mixed with the fixing adhesive 8 applied to the optical fiber fixing groove 4 or the fixing adhesive 8 may travel along the side surface of the optical fiber 5 and be connected to the end face connecting adhesive 7.
Will not be mixed. Therefore, when the fixing adhesive 8 is hardened after the end face connection adhesive 7 is hardened, the end face connection adhesive 7 is pulled by the shrinkage accompanying the hardening of the fixing adhesive 8 so that the optical axis shift occurs. No more.

Also, after the end face of the optical waveguide and the end face of the optical fiber 5 are connected by aligning the optical axis with the end face connecting adhesive 7, the fixing adhesive 8 is applied to fix the optical fiber 5 to the optical fiber fixing groove. 4, a desired distance between the end face connection adhesive 7 and the fixing adhesive 8 can be easily secured, so that the cured end face connection adhesive 7 It is also possible to prevent the solvent or the like from diffusing or penetrating from the adhesive 8 to loosen the adhesive effect.

Moreover, since 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, the alignment of the optical axis in the optical connection can be improved.

According to the method for connecting an optical waveguide and an optical fiber of the present invention, first, the optical fiber 5 is inserted into the optical fiber fixing groove 4 having the adhesive separating groove 9 formed on the substrate 1.
After the optical fiber 5 and the optical waveguide 2 are inserted and placed in the optical fiber fixing groove 4, the optical axes of the optical fiber 5 and the optical waveguide 2 are adjusted to align the optical axes of the two. A small amount of adhesive 7 for dropping end face adhesive 7
To cure. At this time, the adhesive 7 for dropping the end face connection is dropped.
Is small, the influence of shrinkage or the like generated during the curing is small, and no optical axis shift occurs.

Here, if a photocurable adhesive such as an ultraviolet curable adhesive is used as the end face connecting adhesive 7, light such as ultraviolet rays is irradiated through the core 2 of the optical waveguide or the core 6 of the optical fiber. This makes it possible to instantly cure the adhesive 7 for connecting the end surfaces of the optical axis portion, so that the optical axis adjusted position alignment is maintained before the bonding, and a connection that does not cause an optical axis shift is preferable. It will be.

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, when the end face connection adhesive 7 is cured by a method such as heating using a thermosetting adhesive,
Resin-based adhesives generally have a large coefficient of thermal expansion and tend to cause optical axis deviation. However, even in this case, the adhesive 7 for end face connection is small and the absolute amount of expansion is small. There is no worry about axis deviation. Examples of the thermosetting adhesive suitable as the end face connection adhesive 7 include a thermosetting epoxy resin, an acrylic resin, a polyimide resin, and a silicone adhesive.

An adhesive 8 for fixing the optical fiber 5 to the substrate 1
There is no particular limitation as long as it has an effect of bonding to the surface. 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 thermal expansion coefficient and the contraction rate during curing are as small as possible. For secure bonding, it is desirable that a bonding strength of 1 kg or more be obtained in consideration of the bonding area and the like.

When a photocurable adhesive is used as the end face connection adhesive 7 and a thermosetting adhesive is used as the fixing adhesive 8, the thermosetting adhesive is used as compared with the photocurable adhesive. Since the adhesive strength of the agent is high, good optical connection can be performed in that the adhesive strength is further increased. As the thermosetting adhesive used for 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. Among them, the use of a silicone adhesive is preferred in that the adhesive strength is high and the water absorption is low.

It should be noted that even if a thermosetting adhesive is used for both the end face connecting adhesive 7 and the fixing adhesive 8, the fixing adhesive is used for the end face connecting adhesive 7 using a thermosetting adhesive. Needless to say, a photocurable adhesive may be used for 8. Also, when using a thermosetting adhesive or a photo-curing adhesive for both, by combining those having different curing conditions and light transmittance after curing, water absorption, adhesive strength, Tg, etc. A connection structure having good characteristics and high connection reliability can be obtained. The combination may be appropriately selected according to the specification of the connection structure.

Therefore, according to the connection method of the present invention, it is possible to obtain a connection between an optical waveguide and an optical fiber having high connection reliability without causing optical axis shift.

The bonding strength of the optical fiber 5 to the substrate 1, that is, the bonding strength to the optical fiber fixing groove 4, is determined after the end faces of the optical waveguide and the optical fiber 5 are joined to each other. 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 between the end face of the optical fiber 5 and a sufficient amount, Fixing adhesive 8
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 adhesive 7 for connecting the end face, 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.
The optical axis can be easily adjusted without the tip of the lens becoming unstable.

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 a substrate mixed with optoelectronics, 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.

The position of the adhesive separating groove 9 is preferably in the range between 20 μm and 2 cm from the end face of the optical waveguide and between the end face of the optical fiber 5 and the fixed position. Above all, it is preferable that the position is 20 to 50 μm from the end face of the optical waveguide because 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 occupy a larger volume than the volume of the adhesive 7 for connecting the end face of the optical waveguide and the end face of the optical fiber 5, especially , Width is 10μm to ensure the adhesive separation effect
It is desirable to have the above width.

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. 1, a V-shaped groove as shown in a sectional view similar to FIG. 1B in FIG. Various shapes are possible.
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 a plurality of adhesive separating grooves 9 may be provided as shown in FIG. 2 (b) in a sectional view similar to FIG. 1 (b). 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 and fixing adhesive 8
The fixing groove 8 is used for separating the optical fiber 5 from the optical fiber 5, and the adhesive strength of the optical fiber 5 to the optical fiber fixing groove 4 is further increased by utilizing the effect of the surface tension. It can also be increased.

As the method of 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.

[0046]

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 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.

Further, 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 separation groove is 30 μm deep
・ A cross section of a rectangular shape with a width of 20 μm in the optical axis direction of the optical fiber. The width in the direction perpendicular to the optical axis direction is the same as the width up to the end of the substrate because the optical fiber fixing groove is formed in a terrace shape. And

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 connecting an end face 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.

Thereafter, the same ultraviolet curable adhesive as the end face connection adhesive is applied to the end face of the optical fiber and the optical fiber fixing groove and the optical fiber in a region sandwiching the adhesive separation groove between the end faces of the optical fiber. And then cure by irradiating UV light,
The optical fiber was fixed on the substrate.

When the connection loss between the optical waveguide and the optical fiber of the present invention was measured by a cutback method, the LD (laser diode) light having a wavelength of 1.3 μm was measured. It was confirmed that the connection loss with respect to was suppressed to 0.5 dB or less.

Further, from the data representing the relationship between the positional deviation and the loss measured in advance, the minimum value of the loss, that is, the increase in the loss with respect to the positional deviation = 0, is evaluated according to the magnitude of the positional deviation. 0.2 μm
It was found that the deviation was within.

When the bonding strength of the optical fiber to the substrate was measured by a load tensile tester for this connection structure, the bonding strength of the optical fiber was 1 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.

Example 2 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 reactive ion etching device (RIE device). Further, an optical fiber fixing groove was formed at a position facing the end face by reactive ion etching. 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.

Further, an adhesive separating groove was formed by reactive ion etching 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 has a rectangular cross section having a depth of 30 μm and a width of 20 μm in the optical axis direction of the optical fiber, and has the same width as the optical fiber fixing groove in the direction perpendicular to the optical axis direction. It was a groove.

Next, a silica-based optical fiber having a diameter of 125 μm is inserted into the optical fiber fixing groove, passes through the core of the optical waveguide connected to the light emitting surface of the LD, and passes from the output end of the optical fiber connected to the optical waveguide to the LD. The optical axis of the optical waveguide and the optical fiber was adjusted while monitoring the emitted light.

Next, the same ultraviolet curable adhesive as in Example 1 was dropped on the optical waveguide and the end face of the optical fiber as an adhesive for end face connection having the same refractive index as that of the core portion of the optical waveguide and the optical fiber at 0.245 μl. Then, it was cured by irradiating ultraviolet rays from outside.

Thereafter, a thermosetting adhesive of a thermosetting silicone resin is applied to the end face of the optical fiber as a fixing adhesive to the optical fiber fixing groove and the optical fiber in a region sandwiching the adhesive separating groove therebetween. 150 by halogen lamp light
The fixing adhesive was cured by locally heating at 30 ° C. for 30 seconds, and the optical fiber was fixed on the substrate.

With respect to the connection structure between the optical waveguide and the optical fiber of the present invention thus manufactured, the connection loss between the optical waveguide and the optical fiber and the deviation of the optical axis were evaluated in the same manner as in [Example 1]. However, the connection loss between the optical waveguide and the optical fiber was 0.5 dB or less. Also, it was confirmed that the optical axis deviation in the connection of the optical fiber was 0.2 μm or less.

In this connection structure, the adhesive strength of the optical fiber to the substrate was measured by using a load tensile tester. As a result, it was confirmed that the adhesive strength was 5 kg or more, and that the adhesive strength was good. .

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 the embodiment. Various modifications and improvements can be made without departing from the gist of the present invention. No problem.

[0063]

As described above, according to the connection structure of the optical waveguide and the optical fiber of the present invention, the optical fiber fixing groove is provided between the end face of the optical fiber and the fixing position by the fixing adhesive. Due to the formation of the adhesive separation groove, the end face connection adhesive for joining the end faces of the optical waveguide and the optical fiber and the fixing adhesive for joining the optical fiber and the optical fiber fixing groove may come into contact with each other and mix. No, and because it is possible to provide a desired distance between the fixing adhesive and the end face connection adhesive, the effect when applying the fixing adhesive, or when the fixing adhesive is cured It is possible to effectively prevent the influence of contraction or the like from affecting the end faces of the optical waveguide and the optical fiber. Therefore, it is possible to eliminate the occurrence of optical axis deviation between the optical waveguide and the optical fiber, and to improve the connection strength of the optical fiber by securely fixing the optical fiber to the optical fiber fixing groove with a fixing adhesive. Can be.

Further, according to the method for connecting an optical waveguide to an optical fiber of the present invention, the optical fiber is placed on the optical fiber fixing groove having an adhesive separating groove so that the optical axis is aligned with the optical waveguide, and the optical waveguide is connected to the optical waveguide. After joining the end faces of the optical fibers with an end face connecting adhesive, the area of the optical fiber fixing groove where the adhesive separating groove is interposed between the end faces of the optical fiber and the optical fiber are joined with the fixing adhesive. Therefore, the adhesive for end face connection and the adhesive for fixing do not come into contact with each other due to the adhesive separating groove and do not mix, and a desired distance is provided between the adhesive for fixing and the adhesive for end face connection. Therefore, it is possible to effectively prevent the influence of applying the fixing adhesive or the effect of shrinkage when the fixing adhesive is cured from reaching the end face of the optical waveguide. Therefore, it is possible to eliminate the occurrence of optical axis deviation between the optical waveguide and the optical fiber, and to improve the connection strength of the optical fiber by securely fixing the optical fiber to the optical fiber fixing groove with a fixing adhesive. Can be.

Further, according to the connection structure and the connection method of the optical waveguide and the optical fiber of the present invention, the amount of the adhesive for connecting the end surface which joins the end surface of the optical waveguide and the end surface of the optical fiber can be reduced. Since the effects of shrinkage and expansion generated during curing of the adhesive can be suppressed to a small extent while the end faces are securely joined, an optical connection between the optical fiber and the optical waveguide with high reliability without optical axis shift is obtained. be able to.

Further, regarding the adhesive strength of the optical fiber to the substrate, a sufficient amount of the fixing adhesive can be applied to the optical fiber fixing groove while being separated from the end face connecting adhesive, so that the adhesive strength can be improved. Therefore, an optical connection having a high connection strength can be obtained. Therefore, it is possible to improve the accuracy of optical connection, and to obtain a highly reliable optical connection without the necessity of additional reinforcement of adhesive strength even when used in a situation where there is a slight temperature change. Can be.

Further, since the adhesive separating groove is not located immediately below the connection position between the optical waveguide and the end face of the optical fiber and the end face of the optical fiber can be supported by the optical fiber fixing groove, the position of the end face of the optical fiber can be adjusted. Good optical connection can be obtained by stabilizing.

As described above, according to the present invention, when an optical fiber is fixed on a substrate on which an optical waveguide is formed with an adhesive, an optical axis shift caused by the application of the fixing adhesive or the curing thereof is improved. The connection structure between the optical waveguide and the optical fiber, which can align the optical axis with good positional accuracy and optically connect the optical fiber, and can securely fix the optical fiber to the substrate with a fixing adhesive to improve the strength. A connection method could be provided.

[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 and 2B 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.

FIGS. 4A and 4B are a perspective view and a cross-sectional view, respectively, showing another example of a conventional connection structure between an optical waveguide and an optical fiber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Core part of optical waveguide 3 ... Cladding part of optical waveguide 4 ... Optical fiber fixing groove 5 ... Optical fiber 6 ... Core part of optical fiber 7 ... Adhesive for end face connection 8 ... Adhesive for fixing 9 ... Adhesive separation groove

Claims (2)

[Claims] 1. An end face of an optical waveguide formed on a substrate,
An optical waveguide and an optical fiber, wherein the optical fiber is fixed to the optical fiber fixing groove formed on the substrate by aligning the optical axis with the end face of the optical fiber fixed by the fixing adhesive, and bonded by the end face connecting adhesive; An optical waveguide and an optical fiber, wherein an adhesive separating groove is provided between an end face of the optical fiber of the optical fiber fixing groove and a fixing position by the fixing adhesive. Connection structure. 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.
Place the optical fiber in the optical fiber fixing groove with the optical waveguide aligned with the optical axis, and join the end faces of the optical waveguide and the optical fiber together with an end face adhesive, and then, with respect to the end face of the optical fiber. A method for connecting an optical waveguide and an optical fiber, wherein the optical fiber fixing groove in a region sandwiching the adhesive separating groove and the optical fiber are bonded with a fixing adhesive.