JPH0328806A - Method for coupling optical wavecuide and optical fiber - Google Patents

Abstract

PURPOSE:To improve the efficiency and reliability by forming a positioning guide groove for aligning the optical fiber with optical waveguide on a quartz glass optical waveguide substrate. CONSTITUTION:When the optical waveguide 2 and optical fiber 7 are coupled with each other, the optical fiber 7 is charged in the groove 6 first and end surfaces of the core layer 4 of the opticalwaveguide 2 and the core layer 7a of the optical fiber 7 are made to about on each other on the substrate 1 and then connected to each other. This guide groove 6 has its pattern formed on the waveguide by photolithography simultaneously with the patterning of an optical circuit. Then when the optical waveguide 2 and optical fiber 7 are connected by fusion splicing, the end surface join part is heated by CO2 laser irradiation or an oxyhydrogen burner, etc. Consequently, the optical fiber is aligned only by being inserted into the guide groove 6, the time required for the connection is shortened, and the strength reliability of the connection part is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for directly connecting an optical fiber and a silica glass optical waveguide, which is necessary in optical communication. For example, when introducing waveguide optical components such as optical branching elements and optical demultiplexers into an optical communication system, the connection method between these optical components and optical fibers is efficient, reliable, and short. A method that can be used is required. Conventionally, end-face connection has been mainly performed, in which the end face of the optical fiber and the end face of the optical waveguide are simply brought into direct contact and connected. However, this method requires (i) cutting and polishing of the end face of the waveguide prior to connection, and (ii) separate and precise alignment of the optical fiber and optical waveguide, which takes time. (iii) mechanical position reliability of the connection part is lacking; (iv) the position of optical input/output is limited to the end face of the waveguide substrate, and input/output cannot be performed from any position within the substrate; (v)
Silica glass optical waveguides have the potential to be fused with optical fibers when end-connecting, but unlike fusion bonding between optical fibers, there is a large difference in heat capacity between the optical fiber and the optical waveguide. , only the optical fiber is deformed, making it difficult to align with high precision.

In order to solve these conventional problems, the present invention forms a guide groove for positioning the optical fiber and the optical waveguide on a silica glass optical waveguide substrate, and performs coupling using this groove. This is how it was done. Hereinafter, the present invention will be explained in detail based on the drawings. FIGS. 1, 2, and 3 show a method for connecting an optical fiber having an outer diameter of 125 μm and a core diameter of 50 μm to a silica-based optical waveguide as an embodiment of the present invention. In the figure, reference numeral 1 indicates a quartz glass substrate 2 that is an optical waveguide, and the structure of the optical waveguide 2 includes a bathophage layer 3, a core layer 4, and a protective layer 5. The material and thickness of each layer are as follows: buffer layer 3
, 3102 82 03 P z Os (
3 7. 5 μm) Core layer 4, Si○Z TiO
z Bz03 Pg○s (50 μm): GI layer 5, Sing BtOi P z Os
(3 μm). 6 is a guide groove. 7 is an optical fiber, and 7a is its core layer.

When joining the optical waveguide 2 and the optical fiber 7, first,
The optical fiber 7 is inserted into the guide groove 6, the end surfaces of the core layer 4 of the optical waveguide 2 and the core N7a of the optical fiber 7 are brought into contact with each other on a substrate, and then the end surfaces are connected. 2 and 3 show the positional relationship between the core N1a of the optical fiber 7 connected in this way and the core layer 4 of the optical waveguide 2. FIG. FIG. 2 is a side view, and FIG. 3 is a plan view. By setting the thickness of each layer of the optical waveguide 2 as described above, when the optical fiber 7 is inserted into the guide groove 6, the core layer 7a of the optical fiber 7 in FIG.
The height matches the height of the core layer 4 of the optical waveguide i2. The position of the guide groove 6 is set so that when the optical fiber 7 is inserted into the guide groove 6, the core IJ7a of the optical fiber 7 and the core 14 of the optical waveguide 2 are aligned. It is set to . Therefore, when connecting,
Just by inserting the optical fiber 7 into the guide groove 6, its axis can be aligned.

The guide groove 6 as described above can be shaped simultaneously with the patterning of the optical circuit, for example, as follows. In FIG. 4, 8 is a mask glass, 2a is an optical circuit pattern (
(Y branch in this example), and 6a is a guide groove pattern. This pattern is formed into a waveguide using photolithography technology.

In this example, amorphous St is used as a mask, and C. F
．． ,C. H. A pattern was formed by etching silica glass using a reactive spatter etching method using a mixed gas of The reactive sputter etching method is
This is a method with almost no undercut in the etched area, and as a result, the verticality of the waveguide end face 2C in FIG. 2 can be maintained, and θ=85' to 88'' can be achieved. 90.5 μm so that the height of the optical waveguide and the core layer of the optical fiber match.
It is sufficient to etch to a depth of . In this way, shaping the guide groove 6 at the same time as the optical circuit has the advantage that cutting out the patterned optical circuit becomes easy.

Fig. 5 shows a conventional optical branch circuit without a guide groove, which is cut out from a plurality of optical branch circuits formed on a substrate. It is a cut surface. In this example, in order to perform end-face connection, the cut surface 9a must be perpendicular to the propagation direction within the optical circuit 2b and must be smooth. For this reason, high precision is required during cutting. On the other hand, FIG. 6 shows a case in which the guide groove is shaped. In the figure, 1 is a quartz glass substrate, 2b is an optical circuit, 6b is a guide groove, and 9b is a cut surface. In this example, even if the precision of the cut surface 9b is poor or the surface is rough, it will not affect the connection with the optical fiber. Therefore, parts can be easily cut out.

Furthermore, according to this connection method, it becomes possible to input and output light from any position on the waveguide substrate, greatly increasing the degree of freedom in optical circuit design. FIG. 7 shows an optical branching circuit similar to FIGS. 5 and 6.

In FIG. 7, 1 is a quartz glass substrate, 2b is an optical circuit, 6b is a guide groove, and 9b is a cut surface. In the case of this embodiment, by using the guide groove 6b, light can be input and output at a desired position, so that an optical circuit can be formed without bending the optical waveguide after branching.

On the other hand, in the case of conventional end surface connection, as shown in FIG. 5, it is necessary that the output section be located on the end surface of the board, and... Since it is necessary to make the two waveguides parallel, bending of the optical waveguide is unavoidable.

FIG. 8 is another embodiment of the invention. In the figure, 1 is a quartz glass substrate, 2b is an optical circuit, 6b, 6c, and 6d are guide grooves, and 9b is a cut surface. In this embodiment, guide grooves 6c and 6d are provided near the center of one substrate, and an optical fiber is connected between 6c and 6d. In this way, it becomes possible to cross three-dimensionally the waveguides formed within one substrate.

In addition, in the example of FIG. 1, the optical waveguide 2 and the optical fiber 7
In the case of fusion splicing, the end surface joint may be heated by C○2 laser irradiation, an oxyhydrogen burner, or the like. In addition, as described above, since the waveguide end face has good perpendicularity, the gap between the end face of the core layer 7a of the optical fiber 7 and the end face of the core layer 2a of the optical waveguide 2 is sufficient for inserting the optical fiber 7 into the guide groove 6b. When the axis is aligned, the difference is about 1 to 3 μm. Therefore, if the optical fiber is lightly pressed during fusing, this gap will be completely eliminated, and the resulting axis deviation will hardly occur. Furthermore, in the conventional end face connection, there was a problem in that only the optical fiber with a small heat capacity was unilaterally deformed during fusion splicing, but in this embodiment, the optical fiber 7 is connected to the guide groove 6 of the quartz glass. Moreover, since it is located inside the quartz glass substrate 1, the problem of heat capacity difference can be solved. In addition to the above-mentioned fusion splicing, it is of course possible to bond the optical waveguide 2 and the optical fiber 7 together using an adhesive. Further, since the guide groove 6 also serves to protect the connection portion, the strength and reliability of the connection portion is also improved. In this example, a coupling efficiency of 90 to 95% was obtained.

As explained above, in the present invention, a guide groove for aligning the optical fiber and the silica glass optical waveguide is formed on the waveguide substrate, and the coupling is performed using the guide groove. Just by inserting the optical fiber into the guide groove, the axis can be aligned, greatly reducing the time required for connection. Furthermore, since the guide also serves to protect the connection section, the strength and reliability of the connection section can be improved. Furthermore, by using guide grooves, it is possible to input and output light from any desired position on the waveguide substrate, greatly increasing the degree of freedom in optical circuit design. Further, the heat capacity difference between the optical fiber and the optical waveguide, which is a problem during fusion splicing, is eliminated, and highly reliable fusion splicing can be achieved.

[Brief explanation of drawings]

1 to 3 show a coupling portion between an optical waveguide and an optical fiber for explaining the present invention, FIG. 1 is a perspective view, FIG. 2 is a side view, FIG. 3 is a plan view, and FIG. The figure is a plan view of the mask glass on which optical circuits and guide grooves are written simultaneously.
The figure is a partial plan view of a substrate on which only an optical circuit is formed, FIG. 6 is a partial plan view of a substrate on which a guide groove is formed together with an optical circuit, and FIG. 7 is a partial plan view of a substrate on which a guide groove is formed together with an optical circuit. The plan view, FIG. 8, is a plan view of an optical circuit having a guide groove near the center of a waveguide substrate. 1...Quartz glass substrate, 2...Quartz-based optical waveguide, 6...Guide groove, 7...
Optical fiber. Figure 5 Figure 6 Figure 4 Figure 2a Figure 7

Claims (1)

[Claims] At the same time as patterning the silica glass optical waveguide on the optical waveguide substrate, a guide groove for positioning the end of the optical fiber to be connected to the end of the optical waveguide is formed using photolithography technology, and then the guide groove is 1. A method for coupling an optical waveguide and an optical fiber, the method comprising: positioning the end of the optical fiber within the interior of the optical fiber, and coupling the end of the optical fiber to the end of the optical waveguide.