JPH08122562A - Optical connection system - Google Patents

Abstract

PURPOSE: To provide an optical connection system which easily performs alignment for connection between optical wirings, between an optical element and an optical wiring, or between optical elements and is suitable for miniaturization and has a low production cost. CONSTITUTION: A connection substrate 1 is provided with V grooves 4 and a subguide 6, and two optical fibers 2 and 3 are optically connected and fixed with an adhesive 5. Two optical fibers 2 and 3 are easily positioned in the axial direction with the subguide 6 and in the direction perpendicular to the axis with V grooves 4. A material having the same refractive index as cores of optical fibers 2 and 3 is used as the adhesive 5 to obtain a high coupling efficiency. Since the distance between optical fibers is unequivocally determined by the width of the subguide 6, effects of sure insertion of the adhesive 5 to the space between optical fibers 2 and 3, difficulty of an influence of end face shapes of optical fibers 2 and 3 upon the coupling characteristic, easier control of the amount of the adhesive 5, etc., are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to optical wiring, etc.
Optical element and optical wiring, or mutual connection of optical elements, etc.)
In particular, the present invention relates to a connection method that is easy to align, suitable for downsizing, and low in manufacturing cost.

[0002]

2. Description of the Related Art Known for connection of optical wiring,
Representative examples of various methods are given below. (1) Regarding the connection between the semiconductor optical device and the optical fiber,
A positioning mechanism in a direction perpendicular to the optical axis direction of an optical fiber is known, and a V groove provided on a wiring board is a typical example. This method has an advantage that the alignment of the optical fiber is easy. However, since the semiconductor optical device and the optical fiber are optically connected through an air gap, an optical system such as a lens is generally inserted between them to improve the coupling efficiency.

(2) Regarding connection between optical wirings, particularly between optical fibers, a connection method using an adhesive having a refractive index close to that of the core of the optical fiber is known. In this method, an adhesive is inserted between the optical fibers to be connected, and air with a small refractive index does not pass through the core (no air gap)
Therefore, it has the advantage of small coupling loss.

(3) Optical semiconductor devices, especially transmitters for optical communication
As an optical input / output structure at the package end of a receiving module, an optical fiber pigtail / hermetic seal system is well known in the past. This system is suitable for hermetically sealing a package, and is widely used for applications such as undersea cables and trunk lines for long-distance / large-capacity information transmission, where reliability is particularly important. This is an optical input / output structure at the end of the package, but is considered to be an optical connection in a broad sense.

[0005]

However, in the above-mentioned conventional system examples, the following points have not been taken into consideration.

(1) In the first method, the positioning of the optical fiber in the optical axis direction is not considered,
It takes time and effort to align in the optical axis direction, and has the drawback that it is difficult to reduce the cost. For example, in the case of aligning the semiconductor laser and the optical fiber in the optical axis direction, finely adjust the distance while monitoring the output light from the semiconductor laser with the optical fiber connected to him.
A method of fixing at a position where the fiber light output is maximum is known. In addition, since it is an optical connection via an air gap, it is necessary to process the tip shape of the optical fiber and insert an optical system such as a lens in order to improve the coupling efficiency. .

(2) The second method has a drawback that it is difficult to control the amount of adhesive. That is, when the amount of the adhesive is too small, air is likely to be mixed in, and the coupling loss becomes large. On the other hand, if the amount is too large, protrusion is likely to occur, which is an obstacle to device characteristics and reliability when used for connection with a semiconductor optical device or optical waveguide, and when used at the package end. Is an obstacle to hermetic sealing. The absolute amount of adhesive can be adjusted, for example, by adding a solution reservoir, but it is necessary to reliably fill the space between the adhesive optical wiring and control the amount of adhesive. It was difficult.

(3) In the third method, when the optical fiber is wound (bent), if the radius of curvature is made too small, light leaks out, which makes it difficult to miniaturize the package. Further, the cost of components such as hermetic seal is high, and the process of winding the optical fiber is difficult to automate, so that it is difficult to reduce the cost.

Considering the spread of optical information transmission to office buildings, homes, etc., which is currently being realized, the above-mentioned drawbacks are solved, alignment is easy, and an optical system suitable for downsizing and cost reduction is achieved. The creation of a connection method, particularly the creation of an optical input / output structure at the package end of an optical semiconductor device has been an important issue.

[0010]

According to the present invention, the above-mentioned problems can be solved by using the following means. In order to make the description easier to understand, the following description will be given using an example of optical fiber / optical fiber connection.

Optical connection is performed using the connection substrate 1 shown in FIG. The connection substrate 1 includes a V groove 4 and a sub guide 6, and an optical connection of two optical fibers 2 and 3 with an adhesive 5.
And fix. The adhesive 5 is made of a material having the same refractive index as the cores of the optical fibers 2 and 3.

[0012]

The means used in the present invention operates as follows.

Optical connection of the two optical fibers 2 and 3 and fixing of the two optical fibers in the connection board 1 shown in FIG. 1 facilitates positioning of the optical fibers. That is, the position in the direction perpendicular to the optical axis of the optical fiber is defined by the V groove 4.
This is because the position in the optical axis direction can be easily determined by the sub guide 6 without any difficult positioning operation. Further, by optically connecting both optical fibers via the adhesive 5 having the same refractive index as the cores 2 ′ and 3 ′ of the optical fibers 2 and 3, high coupling efficiency can be obtained. Furthermore, since the distance W between the optical fibers is uniquely determined by the width W of the sub-guide 6, the adhesive 5 can be reliably inserted into the gap between the optical fibers 2 and 3, and the bonding property is flat. The effects of being less susceptible to the influence of the end surface shape such as the flexibility and parallelism and facilitating the control of the amount of the adhesive 5 are provided. Further, when applied to optical connection of a semiconductor optical device or an optical waveguide, it also has an end face protection effect.

[0014]

【Example】

Example 1 An example of the present invention will be described with reference to FIG.
In this embodiment, the present invention is applied to optical connection between optical wirings,
Three types of studies were conducted: optical waveguide mutual, optical fiber mutual, optical waveguide and optical fiber. As an example, an example applied to the connection between the optical waveguide and the optical fiber will be described in detail.

As shown in the figure, in this embodiment, the optical waveguide 27 and the optical fiber 22 are optically connected in the connection board 21. Two
7'and 22 'show each core part. Here, the optical waveguide 27 is positioned at a position perpendicular to the optical axis in the rectangular groove 2.
8. The optical fiber 22 is easily determined by the V groove 24,
The position in the optical axis direction is easily determined by the sub guide 26. The distance between the optical waveguide 27 and the optical fiber 22 is determined by the width W of the sub guide 26. Both were fixed with an adhesive 25. The adhesive 25 also serves as a filler for the gap between the two and has a refractive index of about 1.4 to 1.6. Further, 29 is a solution reservoir for treating an excessive adhesive agent.

Here, depending on the width W of the sub guide 26,
The fact that the distance between the optical waveguide 27 and the optical fiber 22 is uniquely determined has some effects. The first is the effect of protecting the end face of the optical wiring, especially the end face of the optical waveguide. Since the upper surface (waveguide main surface) of the optical waveguide is weaker than that of the optical fiber, it is important to protect the upper surface of the end face as well.
For example, when the sub guide 26 is not provided, the optical waveguide 27 and the optical fiber 22 are directly contacted with each other, which is likely to cause damage. The second is the effect that the filler (adhesive 25) is reliably inserted between both optical wirings. If the sub-guide 26 was not provided, the filler did not enter well, and the bonding loss might increase due to bubbles. In this example, the width W was set as a parameter and was examined in the range of 5 μm to 100 μm, but in any case, the filling was ensured. The third is the effect of relaxing the dependence of the shape of the end face of the optical wiring on the coupling loss, which is related to the second effect of reliably inserting the filler. That is, in the air gap connection that does not use a filler, the shape of the end face of the optical wiring to be connected sensitively affects the coupling loss. This is due to the influence of reflection and the like due to light entering and leaving the core having a refractive index of about 1.46 and the air of about 1. Here, if the end surface of the optical wiring is a mirror surface, it is sufficient to consider about several percent of simple reflection. In the case of an optical fiber, a flat end surface can be obtained relatively easily by cleavage, but in the case of an optical waveguide. However, it is difficult to obtain a flat end face only by mechanical cutting, and an additional processing step such as polishing is required. But,
If the filler having the same refractive index as that of the core is securely inserted, even if the end face has some irregularities, there is almost no influence on the coupling loss. This is also related to the first end face protection effect, and even if the end face has some irregularities, if the gap is surely secured, there is no fear of damage.

In this embodiment, when a single mode fiber having a core diameter of 10 μm is used as the optical fiber 22 and the core of the optical waveguide 27 is set to about 6 μm × 10 μm, the distance W (width of the sub guide 26) between them is set. The coupling loss when the thickness was about 20 μm was 0.1 to 0.2 dB, and the coupling loss when it was about 50 μm was about 0.5 dB.

From the dependency of the coupling loss on the spacing W, it was found that the spacing W is within about 5 times the core diameter, and preferably within about 2 times the core diameter, although it depends on the required performance. Therefore, for a single mode fiber with a core diameter of 10 μm, it can be said that the standard value is within 50 μm, preferably within 20 μm. For a multimode fiber having a core diameter of 50 μm, it can be said that the value is within 100 μm.

The refractive index of the adhesive 25 is about 1.4.
˜1.6 was examined. ± for the refractive index of the core
When it was within about 3%, the coupling loss was about 0.2 dB, and within ± 1%, the coupling loss was about 0.1 dB.

Although the example applied to the connection between the optical waveguide and the optical fiber has been described in detail above, the same result has been obtained in the combination of the optical waveguides and the optical fibers. Therefore, it has been found that the present invention can be applied to the optical connection between the optical wirings and obtains a good result.

Embodiment 2 One embodiment of the present invention will be described with reference to FIG. In this embodiment, as an example applied to optical connection between an optical element and an optical wiring, a connection example between a waveguide type semiconductor light receiving element (hereinafter abbreviated as WGPD) and an optical fiber is shown.

FIG. 3 schematically shows an outline of the optical connection section. The WGPD 37 and the optical fiber 32 were optically connected in the connection board 31. Reference numeral 37 'indicates an optical waveguide portion of the WGPD 37, and reference numeral 32' indicates a core portion of the optical fiber 32. Here, the position in the direction perpendicular to the optical axis is WGPD37.
The square groove 38 and the optical fiber 32 are easily determined by the V groove 34, and the position in the optical axis direction is easily determined by the sub guide 36. The distance between the WGPD 37 and the optical fiber 32 is determined by the width W of the sub guide 36. Both were fixed with an adhesive 35. The filler 40 in the gap between the two is different from the adhesive 35 in terms of refractive index, and has a refractive index of about 2 to 2.4. Further, 39 is a solution reservoir for treating an excessive adhesive.

Here, depending on the width W of the sub guide 36,
The unique determination of the distance between the WGPD 37 and the optical fiber 32 has several advantages. Basically, it is the same as the first, second, and third effects described in detail in the first embodiment. This is because the WGPD 37 is a waveguide type, and thus the upper surface portion (waveguide main surface) is weak like the optical waveguide. On the other hand, since it is a semiconductor, it has an advantage that a cleavage plane can be used for the end face, but since the refractive index is greatly different from the core of the optical fiber 32, some improvement is required to improve the coupling efficiency with the filler.

In this embodiment, when a single mode fiber having a core diameter of 10 μm is used as the optical fiber 32, the coupling loss is 0.2 when the distance W between them (width of the sub guide 36) is set to about 20 μm. It was ~ 0.5 dB.

The refractive index of the filler 40 is about 2 to
I considered 2.4. For the refractive indices n1 (about 3.5) and n2 (about 1.46) of the core of the WGPD 37 and the optical fiber 32, the refractive index of the filler 40 to be inserted is
Centering on the square root n3 (about 2.26) of the product of n1 and n2, the coupling loss is about 0.5 dB within ± 5%, and the coupling loss is 0.2 dB within ± 3%.
It was about.

The example applied to the connection between the waveguide type semiconductor light receiving element and the optical fiber has been described above. It was found that the present invention can be applied to other semiconductor optical devices, for example, optical connection between a semiconductor laser and an optical wiring, and almost satisfactory results can be obtained. However, in the case of a semiconductor laser, it is possible to insert a filler for the time being because of the problem of burn-in due to the high density of emitted light and coating of the reflectance control coating on the end face of the semiconductor laser. It takes time to convert.

[0027]

As described above, according to the present invention, the positioning of the optical wiring or the like to be connected is facilitated by the positioning mechanism such as the sub guide in the optical axis direction and the V groove in the direction perpendicular to the optical axis. You can do it. Also, high bonding efficiency can be obtained by using an adhesive having the same refractive index as the core of the optical wiring or the like. In addition, the width of the sub-guide uniquely determines the spacing of the optical wiring, etc., so it can protect the end faces of semiconductor optical devices and optical waveguides, can be inserted securely into the gap of the optical wiring, etc. There are effects such as being less susceptible to the influence of the shape and facilitating the control of the amount of the adhesive. Therefore,
A compact, high coupling efficiency, easy-to-align optical connection system was realized. Moreover, the application has made it possible to realize an optical semiconductor device which is low in price and suitable for miniaturization.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an optical connection according to the present invention.

FIG. 2 is a diagram showing an outline of an embodiment of an optical connection according to the present invention.

FIG. 3 is a diagram showing an outline of another embodiment of the optical connection according to the present invention.

[Explanation of symbols]

 1, 21, 31: Connection substrate 2, 22, 32: Optical fiber 3: Other optical fiber 2 ', 3', 22 ', 32': Core part of optical fiber 4, 24, 34: V groove 5, 25 , 35: Adhesive 6,26, 36: Sub guide 27: Optical waveguide 27 ': Optical waveguide core portion 28, 38: Square groove 29: Solution reservoir 37: Waveguide type semiconductor light receiving element 37': Waveguide type semiconductor Optical waveguide part of light receiving element 40: Filler.

Claims (9)

[Claims] 1. A method of connecting optical lines to each other, optical elements to optical lines, or optical elements to each other (hereinafter abbreviated as "optical lines, etc."), a position in a three-dimensional direction including an optical axis direction. An optical connection system characterized by having a matching guide. 2. The optical connection system according to claim 1, wherein a filler having a refractive index larger than 1 is inserted into a gap between the optical wirings to be connected. 3. The optical connection system according to claim 1, wherein at least one of the optical wirings to be connected is an optical fiber. 4. The optical connection system according to claim 1, wherein at least one of the optical wirings to be connected is an optical waveguide. 5. The optical connection system according to claim 1, wherein at least one of the alignment guides for the optical wiring is a V groove. 6. The optical connection system according to claim 1, wherein at least one of the alignment guides for the optical wiring or the like is a square groove adapted to the size of the optical wiring or the like. . 7. The refractive index of the filler to be inserted is within ± 3%, preferably within ± 1% of the refractive index of the material forming at least one light propagation portion of the connecting optical wiring or the like. The optical connection system according to any one of claims 1 to 6, characterized in that. 8. The refractive index of a filler to be inserted is n2 with respect to the square root n3 of the product of n1 and n2, where n1 and n2 are the refractive indices of the materials constituting the light propagation portions such as mutual optical wirings to be connected. , ± 5% or less, preferably ± 3% or less, the optical connection system according to any one of claims 1 to 6. 9. A gap between optical wirings and the like which is determined by a guide for aligning the optical wirings and the like to be connected in the optical axis direction is 10.
9. The optical connection system according to claim 1, wherein the optical connection method is 0 μm or less, preferably 20 μm or less.