JPH06138340A - Optical coupling structure of optical waveguide and optical fiber - Google Patents

Abstract

PURPOSE:To allow the optical waveguide and the optical fiber to be subjected to optical coupling in the lump and with high accuracy even if they are plural, respectively, so that as for the optical waveguide, its core layer only is subjected to film thickness control with high accuracy in order to secure the alignment of high accuracy in the height direction. CONSTITUTION:An optical fiber 14 is fixed to an optical fiber fixing groove 20 formed on the substrate surface 19a of an optical fiber fixing substrate 19 so that a distance extending from its optical axis center to the substrate surface 19a becomes equal to a distance extending from the upper face of an optical waveguide 12 to the center of an optical waveguide core 15, and in the optical fiber fixing substrate 19, two alignment projections 18 are formed on both sides of the optical fiber fixing groove 20, and on an optical waveguide substrate 11, an alignment guide 13 having the guide face 13a and a guide groove 13b of the same height as the upper face of the optical waveguide 12 is formed, and in a state that the tip of the optical fiber 14 and the tip of the optical waveguide 12 are brought into contact closely with each other, two alignment projections 18 are inserted into the guide groove 13b, and the substrate surface 19a is allowed to adhere closely and fixed to the guide face 13a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coupling structure for an optical waveguide and an optical fiber for optically coupling the optical waveguide and the optical fiber formed on a substrate in an optical communication device or the like. The present invention relates to an optical coupling structure of an optical waveguide and an optical fiber for optically coupling between modules, between an optical waveguide module and an optical waveguide board, or between optical waveguide boards.

[0002]

2. Description of the Related Art An optical coupling structure for optically coupling an optical waveguide and an optical fiber is provided with a guide groove in series with the optical waveguide on the surface of the substrate on which the optical waveguide is formed for easy adjustment of the optical axis. , A structure in which an optical fiber is inserted into this guide groove to optically couple is reported (eg Y.Yamada
et.al., "High-silica multimode channel waveguides
tructure for minimizing fiber-waveguide-fiber coup
Ling loss "; J. Lightwave Tech LT-4,277 (1986)). Fig. 2 shows a conventional optical coupling structure using this guide groove. In the figure, 21 is a substrate, 22 is an optical waveguide, and 23 is. An optical fiber insertion guide, and a guide groove 24 is formed between two optical fiber insertion guides 23. 25 is an optical fiber, 26 is an optical waveguide core, 27 is an optical waveguide clad, and 28 is an optical fiber. It is the core (circle part of the dotted line).
In this optical coupling structure, the width of the guide groove 24 is set to the optical fiber 2
5, the height of the optical fiber insertion guide 23 (or the depth of the guide groove 24) is controlled so that the position of the optical fiber core 28 matches the position of the optical waveguide core 26. Thus, by simply inserting the optical fiber 25 into the guide groove 24, optical coupling can be performed without requiring a complicated alignment operation.

[0003]

In the prior art, the precision of the width and depth of the guide groove 24 must be 1 micron or less in order to perform optical coupling with high precision. Guide groove 24
Since it is formed by reactive ion etching (RIE), the groove width can be controlled to 1 micron or less within the range of mask accuracy. However, regarding the groove depth, particularly in the case of an organic optical waveguide material such as a polyimide material, after spin-coating the optical waveguide clad 27 layer and the optical waveguide core 26 layer on the substrate 21, the optical waveguide 22 film is formed through a curing process. Therefore, the film thickness error of the spin coating and the film contraction error of the curing are superimposed to set the film thickness of the optical waveguide core 26 and the optical waveguide clad 27 to the set values (for example, 50 μm and 40 μm, respectively).
On the other hand, it is difficult to control the error to be 1 micron or less, and thus it is difficult to accurately align the optical fiber core 28 and the optical waveguide core 26 in the height direction. Further, conventionally, the optical fiber 25 and the optical waveguide 22 are aligned and fixed one by one, so that the assembly is complicated. Furthermore, since two optical fiber insertion guides 23 are required on both sides of the optical fiber 25 for positioning and fixing one optical fiber 25, the optical fibers 25 are optically coupled to the optical waveguides 22. Optical fiber 2
It is difficult to shorten the pitch between 5 and high density,
In other words, it was difficult to reduce the size of the optical coupling structure.

The present invention has been made in view of such a conventional problem, and in order to ensure accurate alignment in the height direction, the optical waveguide is capable of controlling the film thickness of only the core layer with high accuracy. Even if there are multiple optical waveguides and optical fibers, they can be optically coupled together with high precision, and the guide groove does not require high-precision depth machining.
It is another object of the present invention to provide an optical coupling structure of an optical waveguide and an optical fiber which can be further miniaturized.

[0005]

In order to solve the above problems, the present invention provides an optical coupling structure of an optical waveguide and an optical fiber for optically coupling the optical waveguide and the optical fiber formed on an optical waveguide substrate, The optical fiber in the optical fiber fixing groove formed on the substrate surface of the optical fiber fixing substrate, the distance from the optical axis center of the optical fiber to the substrate surface from the upper surface of the optical waveguide to the center of the optical waveguide core It is inserted and fixed so as to be equidistant from the distance, two alignment protrusions are formed on both sides of the optical fiber fixing groove in the optical fiber fixing substrate, and the upper surface of the optical waveguide is formed in the optical waveguide substrate. Forming a positioning guide having a guide surface at the same height as the above and a guide groove corresponding to the two positioning protrusions, and the optical fiber tip and the optical waveguide tip are in close contact with each other. One of the positioning protrusions is inserted into the guide groove, contact the substrate surface of the optical fiber fixing substrate to said guide surface, and gist to become fixed.

[0006]

In the above structure, the optical fiber has the optical fiber fixing groove formed on the substrate surface of the optical fiber fixing substrate, and the distance from the optical axis center to the substrate surface is from the upper surface of the optical waveguide to the center of the optical waveguide core. It is inserted and fixed so that it is equidistant from the distance. In this way, the tip of the optical fiber fixed to the optical fiber fixing board is brought into close contact with the tip of the optical waveguide, and the two positioning protrusions on the optical fiber fixing board side are inserted into the guide groove of the positioning guide. By doing so, the lateral alignment between the optical waveguide and the optical fiber is performed. Then, the substrate surface of the optical fiber fixing substrate is brought into close contact with and fixed to the guide surface of the alignment guide, whereby the alignment in the height direction is performed, and the optical waveguide and the optical fiber are optically coupled with high accuracy. In this way, by setting the alignment reference in the height direction of the optical coupling between the optical waveguide and the optical fiber to be the guide surface that is at the same height as the upper surface of the optical waveguide, the optical waveguide accurately forms only the core layer. It is sufficient to control the thickness, and it is not necessary to control the film thickness of the cladding layer in addition to the core layer with high precision as in the conventional case. A plurality of optical waveguides are formed on the optical waveguide substrate at required intervals, and correspondingly, a plurality of optical fiber fixing grooves are formed between the two alignment protrusions on the optical fiber fixing substrate. By inserting and fixing the optical fiber, it becomes possible to collectively optically couple the plurality of optical waveguides and the plurality of optical fibers with high accuracy.
Further, in this case, it is not necessary to provide optical fiber insertion guides on both sides of each optical fiber as in the conventional case, so that the pitch between the plurality of optical fibers can be shortened and the optical coupling structure can be miniaturized. Further, the depth of the guide groove may be set to be equal to or larger than the depth at which the optical fiber comes into contact with the groove bottom when positioning the optical fiber fixed substrate on the alignment guide. Therefore, highly accurate groove depth machining is unnecessary. Become.

[0007]

Embodiments of the present invention will be described in detail below with reference to FIG. In the figure, 11 is an optical waveguide substrate on which an optical waveguide 12 is formed.
Positioning guides 13 each having a guide surface 13a having the same height as the upper surface of the optical waveguide 12 and guide grooves 13b corresponding to two positioning protrusions described later are formed on both sides of the two forming portions. . 14 is an optical fiber, 15
Is an optical waveguide core, 16 is an optical waveguide clad, 17 is an optical fiber core (circle of dotted line), 19 is an optical fiber fixing substrate, and the optical fiber fixing groove 20 is provided on the substrate surface 19a.
And two alignment protrusions 18 are formed on both sides of the optical fiber fixing groove 20.

The optical waveguide substrate 11 is made of, for example, Si or alumina. The optical waveguide 12 formed on the optical waveguide substrate 11 is coated with, for example, polyimide or polymethylmethacrylate (PMMA) by spin coating, and then reactive ions are formed. It is formed by etching. The width and height of the optical waveguide core 15 and the optical waveguide cladding 16 are, for example, 50 × 50 microns and 50 × 40 microns, respectively. Further, since the alignment guide 13 is formed on the optical waveguide substrate 11 at the same time as the optical waveguide 12, the height of the guide surface 13a is equal to the height of the upper surface of the optical waveguide 12, and the guide groove 13 is formed.
The width and depth of b is, for example, 500 × 90 microns.
The optical fiber fixing substrate 19 is made of, for example, glass, and the optical fiber fixing groove 20 is formed by, for example, chemical etching or machining. The depth, width and shape of the optical fiber fixing groove 20 are, for example, when the optical fiber 14 having a fiber diameter of 125 μm and a core diameter of 50 μm is closely attached and inserted from the center of the optical fiber core 17 to the substrate of the optical fiber fixing substrate. The V-shaped groove is, for example, 65 μm deep and 130 μm wide so that the distance to the surface 19a is 25 μm. After the optical fiber 14 is inserted in close contact with the optical fiber fixing groove 20, it is fixed by, for example, an ultraviolet curable adhesive. The alignment protrusions 18 each have, for example, a width of 50 μm and a height of 50 μm, and the distance between the outer sides of the two protrusions 18 is 500 μm.

Next, alignment and assembly of the optical coupling structure will be described. First, by inserting the two alignment protrusions 18 into the guide groove 13b under an optical microscope,
The plurality of optical waveguides 12 and the plurality of optical fibers 14 are aligned in the x-axis direction. When glass is used as the material of the optical fiber fixing substrate 19, alignment in the x-axis direction can be easily performed visually under an optical microscope. S as material
When an i substrate or the like is used, a marker may be attached to a surface opposite to the substrate surface 19a, that is, a position corresponding to the alignment protrusion 18 on the upper surface. Next, after pressing the end surface of the optical fiber 14 against the end surface of the optical waveguide 12, the substrate surface 19a of the optical fiber fixing substrate 19 is brought into close contact with the guide surface 13a by using a jig (not shown), so that the y axis and z Perform axial alignment. In the aligned state of each axis, the optical waveguide 12 and the optical fiber 14 can be optically coupled with high accuracy by subsequently fixing them using, for example, an ultraviolet curable adhesive. The optical waveguide may be made of a silica glass material.

[0010]

As described above, according to the present invention,
The optical fiber is fixed in the optical fiber fixing groove formed on the substrate surface so that the distance from the optical axis center to the substrate surface is equal to the distance from the upper surface of the optical waveguide to the optical waveguide core center. An optical fiber fixing substrate provided with two alignment protrusions on both sides of the groove was used, and the optical waveguide substrate corresponded to the guide face having the same height as the upper surface of the optical waveguide and the two alignment protrusions. A positioning guide having a guide groove is formed, and two positioning protrusions are inserted into the guide groove while the optical fiber tip and the optical waveguide tip are in close contact with each other, and the substrate surface of the optical fiber fixed substrate is a guide surface. Since the contact reference and the fixing in the height direction serve as a guide surface having the same height as the upper surface of the optical waveguide, the optical waveguide layer only needs to have high accuracy in controlling the film thickness of the core layer. Conventional It is not necessary to the thickness control is also clad layer with high precision in addition to the core layer as. If there are a plurality of optical waveguides on the optical waveguide substrate, and correspondingly, a plurality of optical fiber fixing grooves are formed between two alignment protrusions on the optical fiber fixing substrate to fix a plurality of optical fibers. The optical waveguide and the plurality of optical fibers can be collectively optically coupled with high precision. Further, in this case, since it is not necessary to provide the optical fiber insertion guides on both sides of each optical fiber as in the conventional case, the pitch between the optical fibers can be shortened and the optical coupling structure can be miniaturized. Further, the depth of the guide groove may be set to be equal to or larger than the depth at which the optical fiber comes into contact with the groove bottom when positioning the optical fiber fixed substrate on the alignment guide. Therefore, highly accurate groove depth machining is unnecessary. Become.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an optical coupling structure between an optical waveguide and an optical fiber according to the present invention.

FIG. 2 is a configuration diagram showing an optical coupling structure of a conventional optical waveguide and an optical fiber.

[Explanation of symbols]

 11 Optical Waveguide Substrate 12 Optical Waveguide 13 Positioning Guide 13a Guide Surface 13b Guide Groove 14 Optical Fiber 15 Optical Waveguide Core 17 Optical Fiber Core 18 Positioning Protrusion 19 Optical Fiber Fixed Substrate 20 Optical Fiber Fixed Groove

Claims (1)

[Claims] 1. In an optical coupling structure of an optical waveguide and an optical fiber for optically coupling the optical waveguide and the optical fiber formed on the optical waveguide substrate, the optical fiber is formed on the substrate surface of the optical fiber fixing substrate. In the optical fiber fixing groove, inserted and fixed so that the distance from the optical axis center of the optical fiber to the substrate surface is the same distance as the distance from the upper surface of the optical waveguide to the center of the optical waveguide core, Two positioning protrusions are formed on both sides of the optical fiber fixing groove on the fiber fixing substrate, and a guide surface having the same height as the upper surface of the optical waveguide and the two positioning protrusions are formed on the optical waveguide substrate. Forming a positioning guide having a guide groove corresponding to, and inserting the two positioning protrusions into the guide groove in a state where the optical fiber tip and the optical waveguide tip are in close contact with each other, An optical coupling structure between an optical waveguide and an optical fiber, characterized in that a substrate surface of an optical fiber fixing substrate is in close contact with and fixed to the guide surface.