JP2564836B2 - Method of coupling substrate of optical integrated circuit and optical fiber - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a gap between a tip of an optical fiber and an optical waveguide when the optical fiber is faced to a groove formed in a substrate of an optical integrated circuit and coupled. The present invention relates to a method of coupling a substrate of an optical integrated circuit and an optical fiber, which is capable of effectively suppressing optical transmission loss by preventing the above.

2. Description of the Related Art With the recent development of optoelectronics, optical transmission systems tend to be widely used as alternatives to conventional telecommunication systems. This optical transmission system uses an optical fiber made of, for example, quartz or multi-component glass as a medium for transmitting information by light, and therefore, does not suffer from electromagnetic induction interference and yet has a large capacity of information transmission density. It has many advantages, including: In the above-mentioned optical transmission technology, the optical fiber is coupled to a substrate of an optical integrated circuit in which a light emitting element, a waveguide, a light receiving element, etc. are integrated, and optical information is exchanged between the optical waveguide and the optical fiber of the substrate ( Light is incident and emitted.

For this reason, it is necessary to connect an optical fiber to the optical integrated circuit substrate, and as one of the methods for connecting the substrate and the optical fiber, an optical integrated circuit made of a glass material or a crystal of lithium niobate (LiNbO ₃ ) is used. A technique is known in which a groove having a required depth is formed on a substrate, the tip of an optical fiber is exposed in the groove, and the both are bonded by an ultraviolet curable resin. According to this coupling method, since the groove is formed in the optical integrated circuit board, there is an advantage that the optical fiber can be positioned with respect to the board with high accuracy. On the other hand, however, since the substrate is made of a highly brittle and difficult-to-cut material such as glass or lithium niobate, it is generally difficult to process the groove, and chipping such as cracking or chipping occurs during processing, resulting in defects. It has a high rate and a large loss due to light dispersion between the tip of the optical fiber and the groove.

As a proposal for solving these problems, the applicant of the present invention invented "a method for forming a groove in a brittle member" (Japanese Patent Application No. 61-28833).
No. 1) has been filed. The present invention is characterized in that a pyramidal tool having a pyramidal tip is fed in a horizontal direction while being rotated, and a groove having a V-shaped cross section is cut on the surface of the workpiece. The required groove can be formed on the optical integrated circuit board of the insulating member without chipping.

Problems to be Solved by the Invention As shown in FIG. 5, according to the invention of the above application,
A groove 12 having a V-shaped cross section can be formed on the surface of the substrate 10 to a required depth, and the optical waveguide 16 on the substrate 10 can be provided with the V-shaped groove 12 only by facing the tip of the optical fiber 14. The central axis of the optical fiber 14 can be positioned with high accuracy. However, in this method, since the V-shaped groove 12 is cut while rotating the pyramidal tool, the deepest portion 12a of the V-shaped groove 12 is, as shown in FIG. It is formed as a slope having an angle corresponding to the tip angle. Moreover, as the optical fiber 14 coupled to the V-shaped groove 12, a fiber processed so that the tip 14a thereof is perpendicular to the central axis C is used.

Therefore, when the optical fiber 14 is exposed to the fixed position of the V-shaped groove 12, the open end 16a of the optical waveguide 16 located above the innermost part 12a of the groove 12 and the tip 14a of the optical fiber 14 are separated from each other. A gap S is inevitably formed between the gaps, and the gap S causes a loss due to the dispersion of light, resulting in a problem of reducing the optical transmission efficiency.

SUMMARY OF THE INVENTION The present invention has been proposed in order to suitably solve the above problems that appear when coupling an optical fiber to a substrate of an optical integrated circuit. It is an object of the present invention to provide a means capable of realizing high-efficiency optical transmission by preventing loss due to light dispersion.

Means for Solving the Problems In order to overcome the problems and achieve the intended object, the present invention processes the tip of an optical fiber into a conical shape or a hemispherical shape, and forms the optical fiber into a substrate of an optical integrated circuit. It is characterized in that it is positioned in a groove portion having a V-shaped cross section processed into a deepest position and having an inclined end portion at the innermost side, and the tip of the optical fiber after the processing is directed and fixed to the inclined end portion.

Effects According to the method for coupling the substrate of the optical integrated circuit and the optical fiber according to the present invention, it becomes possible to couple the core portion of the optical fiber and the optical waveguide in a close contact state.

Embodiments Next, a method for coupling a substrate of an optical integrated circuit and an optical fiber according to the present invention will be described with reference to the accompanying drawings with reference to preferred embodiments. The same members as those already described with reference to FIG. 5 are designated by the same reference numerals.

A groove 12 having a V-shaped cross section is formed on the surface of an optical integrated circuit substrate 10 made of a glass material or lithium niobate by the method described in Japanese Patent Application No. 61-288331.
That is, a pyramidal tool made of cemented carbide is rotated and fed in the lateral direction on the surface of the optical integrated circuit substrate 10 to perform cutting, and the cutting is repeated a plurality of times so that the cross section is V-shaped.
The groove 12 having a V shape is machined in a good state without any chipping. In this case, the innermost portion 12a of the V-shaped groove 12 is formed with a slope having an angle corresponding to the tip angle of the pyramid tool, as described above.

In the present invention, the tip of the optical fiber 14 is processed into a conical shape or a hemispherical shape, and the processed core end 14a of the optical fiber 14 is processed.
Is fixed in a state of being directed to the inclined end portion 12a of the V-shaped groove 12 in the optical integrated circuit board 10 described above. That is, FIG. 2 shows an embodiment of means for processing the tip of the optical fiber 14 into a conical shape, in which the optical fiber 14 is held by a sheath-shaped holding body 18, and the tip 14a of the optical fiber 14 is held. Is slightly extended from this holder 18. Then, with respect to the grinding surface 22a of the disk-shaped grinding wheel 22 which is fixed to the vertical rotating shaft 20 and rotates horizontally, the holding body 18 is brought close to the grinding surface 22a at a required angle θ, and the tip 14a of the optical fiber 14 is moved to the grinding wheel Polish with 22. As a result, the tip 14a of the core portion of the optical fiber 14 is processed into a conical shape having an angle of 2θ, as shown in FIG.

FIG. 4 shows an embodiment of a method of processing the tip of the optical fiber 14 into a hemispherical shape. A high voltage is applied to the two discharge electrodes 24 and 26 facing each other, and the arc forming gap SG Generate an arc discharge inside. When the tip of the optical fiber 14 is placed in the electric arc forming gap SG and melted by arc discharge, the tip 14a of the core portion is processed into a hemispherical shape due to the surface tension during melting.

When the optical fiber 14 thus processed faces the V-shaped groove 12 of the optical integrated circuit board 10 according to the above-mentioned processing, the conical or hemispherical core tip 14a of the optical fiber 14 is processed.
As shown in FIG. 1, the light can be directed toward the open end 16a of the optical waveguide 16 in the optical integrated circuit board 10 and can be brought into close contact therewith. Therefore, no gap is formed between the optical fiber 14 and the optical waveguide 16, the loss due to the dispersion of light is effectively suppressed, and high optical transmission efficiency can be obtained. The V-shaped groove 12 and the optical fiber 14 are adhered and solidified with, for example, an ultraviolet curable resin. Further, due to the presence of the V-shaped groove 12, the optical fiber 14
The central axis of is positioned on the optical waveguide 16 on the substrate 10 with high accuracy.

As described above, in the method for coupling the substrate of the optical integrated circuit and the optical fiber according to the present invention, the optical fiber is positioned in the V-shaped groove formed in the substrate of the optical integrated circuit, and the conical or hemispherical shape is formed. The purpose is to fix the tip of the core processed into a V-shaped groove by directing it toward the slanted end portion of the V-shaped groove, and thus effectively suppressing the loss of light dispersion between the optical fiber and the optical waveguide to achieve high optical transmission. You can get efficiency. Further, only by exposing the optical fiber to the V-shaped groove formed on the surface of the substrate, the central axis line of the optical fiber can be positioned with high accuracy in the optical waveguide on the substrate.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a state in which a substrate of an optical integrated circuit and an optical fiber are coupled by the method according to the present invention, and FIG. 2 is an optical fiber used in the method shown in FIG. Explanatory diagram showing an example of means for processing the tip of the cone into a conical shape,
FIG. 3 is an explanatory view showing the tip shape of the optical fiber processed by the means shown in FIG. 2, and FIG. 4 shows a means for processing the tip of the optical fiber used in the method shown in FIG. FIG. 5 is an explanatory view showing an example, and FIG. 5 is a vertical cross-sectional view showing a coupling state between a groove portion and an optical fiber of an optical integrated circuit substrate according to a conventional technique. 10 …… Substrate, 12 …… V-shaped groove 12a …… Deepest part, 14 …… Optical fiber 14a …… Tip, 16 …… Optical waveguide 16a …… Open end, 18 …… Holder 20 …… Rotation axis, 22 …… Grinding wheel 22a …… Grinding surface, 24,26 …… Discharge electrode

Claims (3)

(57) [Claims] 1. A tip of an optical fiber is processed into a conical shape or a hemispherical shape, and the optical fiber is positioned in a groove portion having a V-shaped cross section formed on a substrate of an optical integrated circuit and having an inclined end portion at the innermost side,
A method for coupling a substrate of an optical integrated circuit and an optical fiber, characterized in that the tip of the processed optical fiber is directed and fixed to the inclined end portion. 2. The optical integrated circuit according to claim 1, wherein the tip of the optical fiber is brought into contact with a rotating grinding wheel at a required angle to thereby process the tip into a conical shape. Method of connecting the substrate to the optical fiber. 3. The method for coupling a substrate of an optical integrated circuit and an optical fiber according to claim 1, wherein the tip of the optical fiber is melted by arc discharge and processed into a hemispherical shape.