JP2564837B2 - Method of coupling substrate of optical integrated circuit and optical fiber - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention connects an optical fiber to a surface other than an end portion of a substrate of an optical integrated circuit and allows light to enter and exit in the middle of an optical waveguide at low cost. The present invention relates to a method of coupling a substrate of an optical integrated circuit and an optical fiber, which is realized and improves the degree of freedom in circuit design.

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.

Problems to be Solved by the Invention The methods of making light incident on an optical integrated circuit substrate are roughly classified into the following two forms. The first form is
As shown in FIG. 10, on the surface of the optical integrated circuit substrate 10, a groove 12 having a required depth to be opened at the end 10a of the substrate is formed,
This is a joining method in which the tip of the optical fiber 14 is exposed in the groove 12 and both are adhered by an ultraviolet curable resin or the like. According to this coupling method, the core 14a at the tip of the optical fiber 14 is
Is the end 18a of the optical waveguide 18 located at the deepest part of the groove 12.
There is an advantage that the positioning can be performed with high accuracy. However, since the substrate 10 is made of a highly brittle material such as a glass material or lithium niobate, it is generally difficult to process the groove portion 12,
It has a defect that cracking and chipping occur during processing and the defect rate is high.

The second form is as shown in FIG.
This is a method in which the light from 14 is focused by a condenser lens 16 and the focused light is made incident on the polishing end face 18a of the optical waveguide 18 on the substrate 10. Since this method uses the condenser lens 16, there is a drawback in that the structure is large and the manufacturing cost is high.

Moreover, the disadvantages common to both methods described above are that the optical fiber 14 is orthogonally connected to the end face 18a of the optical waveguide 18 on the substrate 10, or the optical axis of the focused light from the condenser lens 16 is changed to the end face 18a of the optical waveguide 18. It is necessary to make it orthogonal to. For this reason, in the conventional coupling method, it was not possible to allow light to enter or emit light in the middle of the optical waveguide 18 at an arbitrary position of the optical waveguide 18 on the substrate 10.

In this way, in order to allow the light to enter and exit in the middle of the optical waveguide 18, as shown in FIG. 12, titanium oxide (TiO ₂ )
A rutile prism 20 made of a material is attached to the optical waveguide 18 of the substrate 10, light is made incident on the middle of the optical waveguide 18 through the rutile prism 20, or from the middle of the optical waveguide 18 through the prism 20. A method of emitting light has been implemented. However, the rutile prism 20 is not general because it uses an expensive material, and there is a problem that the optical system is complicated as well as protruding and bulky on the optical integrated circuit board 10. It impaired the degree of freedom.

An object of the present invention is that, in the conventional method of coupling an optical fiber to an optical integrated circuit substrate, light cannot be incident or emitted in the middle of the optical waveguide, or even if it is possible, the manufacturing cost can be reduced. In view of the above-mentioned problems such as increase in size, it has been proposed to preferably solve this problem, in the middle of the optical waveguide in the optical integrated circuit substrate, light incidence and light emission at low cost. It is an object of the present invention to provide a means capable of improving the degree of freedom in circuit design.

Means for Solving the Problems In order to overcome the above problems and achieve the intended purpose, the present invention provides a substrate of an optical integrated circuit having a V-shaped cross section and a bottom having a relatively gentle radius of curvature. Is formed, the optical fiber is flexibly positioned along the bottom slope of the V-shaped groove, and the conical or hemispherical end of the optical fiber is formed into the V-shaped groove in cross section. It is characterized in that it is oriented and fixed to the innermost part of.

According to the method for coupling the substrate of the optical integrated circuit and the optical fiber according to the present invention, the light is input and the light is emitted in the middle of the optical waveguide on the optical integrated circuit substrate at a simple and low cost. It will be possible.

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. 10 are designated by the same reference numerals.

First, in the bonding method according to the present embodiment, as shown in FIGS. 1 to 5, the surface of the optical integrated circuit board 10 made of a glass material or lithium niobate is V-shaped in cross section and relatively gentle. A groove 12 having a bottom surface having a gradient of radius of curvature is formed. As means for forming the groove 12, for example, a second
As shown in the figure, the tip blade part
A pyramid tool 22 obtained by processing 22a into a quadrangular pyramid shape is used. That is, when the tip angle of the pyramidal blade portion 22a is 60 °, the shank diameter is 5
mm pyramidal tool 22, 40,000 rpm rotation and speed 1 mm / min
And the feed are simultaneously performed to make a required cut in the surface of the optical integrated circuit board 10. Since the processing start position by the pyramid tool 22 is not from the end of the optical integrated circuit substrate 10 but from a required position on the surface of the substrate 10, the tool 22 includes the rotation and the feed in addition to the above. , Vertical descent and climb control should also be provided. Therefore, the blade portion 22a makes a cutting movement with a swing as shown by an arrow A with respect to the vertical plane. Further, since the substrate 10 is the brittle member as described above, it is necessary to perform the cutting with the pyramid tool 22 in a reciprocating manner in a plurality of times, and the number of times of cutting is, for example, 12 times. It is suitable.

As a result, as shown in FIGS. 3 to 5, the bottom surface of the bottom of the ship 10 has a V-shaped cross section that matches the tip angle of the pyramid tool 22 and has a relatively gentle radius of curvature on the arbitrary surface of the substrate 10. A groove 12 having is formed. Processing end 12 of this groove 12
a has a sloped surface corresponding to the tip angle of the pyramid tool 22 and the tilt angle of the tool 22, and the substrate 1 at the processing end 12a
0 The end surface 18a of the optical waveguide 18 is located near the upper surface.

In the groove 12 thus processed, the optical fiber 14 is faced and coupled, but in the present invention, the optical fiber 14 is flexibly positioned along the bottom slope of the groove 12, and The core axial center portion of the tip portion of the optical fiber 14 processed into a conical shape or a hemispherical shape is fixed so as to be oriented parallel to the surface of the substrate 10. For example, FIG. 8 shows an embodiment of means for processing the tip of the optical fiber 14 into a conical shape,
The optical fiber 14 is held by a sheath-shaped holder 24, and the tip 14a of the optical fiber 14 is slightly extended from the holder 24. Then, with respect to the grinding surface 28a of the disk-shaped grinding wheel 28 that is fixed to the vertical rotation shaft 26 and rotates horizontally, the holder 2
4 are brought close to each other at a required angle θ, and the tip 14a of the optical fiber 14 is polished by the grinding stone 28. 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.

FIG. 9 shows an embodiment of a means for processing the tip of the optical fiber 14 into a hemispherical shape. A high voltage is applied to the two discharge electrodes 30 and 32 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.

As shown in FIG. 1, the optical fiber 14 processed in this manner is flexibly positioned along the bottom slope having the required radius of curvature in the V-shaped groove 12 according to the above-described processing. The conical or hemispherical core tip 14 of the optical fiber 14
The a is oriented parallel to the surface of the substrate 10 and is brought into close contact with the light incident surface 18a of the optical waveguide 18. In this state, the V-shaped groove 12 and the optical fiber 14 are bonded and fixed by, for example, an ultraviolet curable resin. As a result, no gap is formed between the optical fiber 14 and the optical waveguide 18, the loss due to the dispersion of light is effectively suppressed, and high optical transmission efficiency can be obtained.

FIG. 7 shows an application example of the present invention, in which the output lines 34a and 36a of the two X-type branch switches 34 and 36 formed in the optical waveguide 18 of the optical integrated circuit board 10 are separated from each other. It can be suitably used when it is desired to input to the X-type branch switch 38. That is, the above-mentioned V-shaped groove 12 is processed in the portion of the output line 34a of the optical waveguide 18 and the portion of the input line 38a of the X-type branch switch 38, respectively, and the optical fiber 1 is provided between both V-shaped grooves 12, 12.
By coupling with 4, it is possible to easily enter and exit light from the middle of the optical waveguide 18.

EFFECTS OF THE INVENTION As described above, according to the method for coupling the substrate of the optical integrated circuit and the optical fiber according to the present invention, the light is incident on the optical waveguide and the optical waveguide is provided at a position other than the end portion of the substrate of the optical integrated circuit. It is possible to emit light from the device at a low cost and improve the degree of freedom in designing the optical integrated circuit.

[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 coupled by the method according to the present invention are coupled, and FIG. 2 is an optical integrated circuit used in the method shown in FIG. FIG. 3 is an explanatory view showing an example of means for forming a groove having a bottom surface with a V-shaped cross section and a relatively gentle gradient of curvature radius on the circuit board; FIG. 3 is formed by the means shown in FIG. A plan view of the groove, FIG. 4 is a vertical sectional view taken along line IV-IV of FIG. 3, FIG. 5 is a vertical sectional view taken along line VV of FIG. 3, FIG. 6 is a plan view of FIG. 1, and FIG. FIG. 8 is a schematic perspective view showing an application example of the present invention, showing an X-type branch switch formed in an optical waveguide of an optical integrated circuit substrate, and FIG. 8 shows an end of an optical fiber used in the method shown in FIG. Explanatory drawing showing an example of means for processing into a conical shape,
FIG. 9 is an explanatory view showing an example of a means for processing the tip of an optical fiber used in the method according to the present invention into a hemispherical shape, and FIG. 10 is a groove portion of an optical integrated circuit substrate and an optical fiber which have been conventionally implemented. Fig. 11 is a perspective view showing a coupling relationship with Fig. 11, Fig. 11 is a perspective view of a prior art in which light is incident on an optical integrated circuit board by using a condenser lens, and Fig. 12 is a rutile prism for the optical integrated circuit board. FIG. 3 is a perspective view of a conventional technique in which light is made incident and emitted. 10: substrate, 12: V-shaped groove 12a: innermost part, 14: optical fiber 14a: tip, 16: condenser lens 18: optical waveguide 18a: open end (light incident surface) 20 ...... Rutile prism, 22 …… Pyramid tool 22a …… Blade part, 24 …… Holder 26 …… Rotary axis, 28 …… Grinding wheel 28a …… Grinding surface 30,32 …… Discharge electrode 34,36,38… … X-type branch switch

Claims (1)

(57) [Claims] 1. A substrate of an optical integrated circuit is formed with a groove having a V-shaped cross section and a bottom having a relatively gentle gradient of curvature radius, and an optical fiber is formed along the V-shaped groove bottom gradient. A substrate of an optical integrated circuit, which is flexibly positioned and fixed by directing the conical or hemispherical end of the optical fiber toward the innermost portion of the V-shaped groove in cross section. Fiber coupling method.