JPH04158309A - Light wave guide path type coupler - Google Patents

Abstract

PURPOSE:To obtain a coupler with little transmission loss by providing two wave guide paths on a substrate with no intersection, and forming the light coupler with part of the wave guide paths set perpendicular to the surface of the substrate. CONSTITUTION:Multiple first wave guide paths 2 are formed on a substrate 1, and multiple second wave guide paths are formed above the first wave guide paths 2. The first wave guide paths 2 and the second wave guide paths 3 are aligned nearby in the thickness direction of the substrate 1 at the center section of the substrate 1, and this portion is formed into a branch coupler 4. End sections of the first wave guide paths 2 are arranged on one side section in package, and end sections of the second wave guide paths 3 are arranged on the other side section in package. The wave guide paths 2, 3 are connected to optical fibers 6 at end faces of the substrate 1. The occurrence of coupling of the first and second wave guide paths 2, 3 at portions other than the above light coupler is prevented. The light wave guide path type coupler has little transmission loss. The angle between the first and second wave guide paths in the plan view can be set small, and the coupler can be miniaturized.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is a communication system using optical fibers, in which signals from a large number of optical fibers installed in a station, on a line, at a terminal, etc. are branched and combined at once. Regarding optical waveguide type couplers.

[Prior Art] When branching and combining two signal lights, a 2×2 coupler is used.

FIG. 3 is a perspective view of a conventional 2×2 coupler. Note that this 2×2 coupler is an optical fiber coupler constructed from optical fibers.

In this optical fiber coupler, one pair of input optical fibers 11 and one pair of output optical fibers 11 are provided for one branching/coupling section 10 . The two signal lights respectively input from the pair of input optical fibers 11 are multiplexed and branched in the branching/coupling section 10 and outputted from the pair of output fibers 11. When branching and coupling a plurality of fibers 11, a plurality of 2.times.2 optical fiber couplers are arranged in parallel and used, as shown in FIG.

Further, as another 2×2 coupler, there is also a substrate waveguide type coupler in which two waveguides are formed in a predetermined shape on a substrate and a branching coupling portion is formed by the waveguides. In the case of this substrate waveguide type coupler, a branching coupling part in which two waveguides are formed close to each other is provided in the center of the substrate.
An end portion of a waveguide connected to this branching coupling portion is arranged on the end surface of the substrate. In this substrate waveguide coupler, an optical fiber for inputting and outputting signal light is connected to the substrate directly or via a connector.

[Problems to be Solved by the Invention] However, conventional couplers have the following problems.

In the case of an optical fiber coupler, although the signal branching ratio and wavelength uniformity are good, when attempting to branch and couple a plurality of signal lights at once, it has the disadvantage that the shape becomes large. In addition, in the case of a substrate waveguide type coupler, although the shape, size, and branching characteristics of the branching coupling part are sufficient,
When attempting to integrate these branching and coupling sections in parallel, the waveguides intersect on the same plane. Therefore, light is scattered at the intersection, causing a risk of crosstalk and increasing transmission loss. In particular, if the crossing angle of the waveguides is made small, the waveguide substrate becomes large and the coupling between the waveguides becomes strong, resulting in increased loss and crosstalk.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide an optical waveguide type coupler which is small in size, has no intersection of waveguides, and has low transmission loss.

[Means for Solving the Problems] A leading waveguide coupler according to the present invention includes a substrate, a plurality of first waveguides provided on the substrate, and a plurality of first waveguides intersecting the first waveguides on the substrate. and a plurality of second waveguides provided without any interference, and a portion of the first and second waveguides constitutes an optical coupling section in a direction substantially perpendicular to the substrate surface. It is characterized by

[Function] In the present invention, the substrate is provided with first and second waveguides, and a portion of the first and second waveguides conducts light in a direction substantially perpendicular to the surface of the substrate. It constitutes a connecting part. The first and second waveguides are formed apart from each other in a direction perpendicular to the surface of the substrate without intersecting each other. Thereby, there is no possibility that coupling will occur in the first and second waveguides at a portion other than the optical coupling portion. Therefore, the optical waveguide coupler according to the present invention has low transmission loss.

Further, the angle formed by the first and second waveguides in plan view (the sum of the branching angles of both waveguides) can be set small, and miniaturization is possible.

Note that the branching angle refers to the angle formed between the extension line of the waveguide of the branching coupling part and the waveguide from the branching coupling part to the end of the substrate in plan view.

[Embodiments] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a plan view showing an optical waveguide type coupler according to an embodiment of the present invention, and FIG. 2 is a side view thereof.

A plurality of first waveguides 2 (four in the figure) are formed on the substrate 1, and a plurality of first waveguides 2 (four in the figure) are formed above the first waveguides 2.
In the figure, four (4) second waveguides 3 are formed. Furthermore, in the center of the substrate 1, a first waveguide 2 and a second waveguide 3 are arranged close to each other in the thickness direction of the substrate 1, and this portion becomes a branching coupling portion 4. There is. In the two opposing end surfaces of the substrate 1, the ends of the first waveguides 2 are arranged together on one side, and the ends of the second waveguides 3 are arranged on the other side. They are placed together.

Further, the first waveguide 2 and the second waveguide 3 are connected to the optical fiber 6 at the end surface of this substrate.

Note that the optical fiber 6 and the substrate 1 may be directly connected, or may be connected via a connector 5 as shown in FIG. Further, a plurality of sets of branch coupling portions 4 may be formed in the longitudinal direction of the substrate 1. Furthermore, the first and second waveguides between the branch coupling section 4 and the connector 5 are so-called curved waveguides.

The waveguides 2 and 3 can be formed by a flame vapor deposition method, a vapor phase growth method such as a low pressure CVD method or a plasma CVD method, a glass ion exchange method, or the like.

When forming a waveguide by vapor phase growth, a substrate made of metal silicon, quartz, or the like is used. Then, on this substrate, Si02-GeOn/5i02, Si
O2Pz'Os/5iC)2, S 1o2-s i3N
A quartz glass such as 4/S i02 is formed. on the other hand,
When forming a waveguide by an ion exchange method, an optical glass substrate is used and a method such as exchanging Na in the substrate with Ag ions is performed to selectively improve the refractive index of the substrate.

Note that the refractive index of the glass substrate is approximately 0.3 to 0.7% in the waveguide portion. Further, the bending diameter of the waveguides 2 and 3 is set to 20 to 40 mm, although it depends on the refractive index difference.

- When optically connecting a waveguide provided on a board to an optical fiber via a connector, a mating pin is provided on either the board or the □ connector, and a hole into which the pin fits is provided on the other. to ensure that both sides are always connected in the correct position. Also in this embodiment, when connecting the waveguides 2 and 3 and the optical fiber 6 via the connector 5, it is preferable to use a fitting pin.

In this embodiment, since the first and second waveguides 2 and 3 do not intersect on the same plane, the transmission loss is small, and
Coupling between the waveguides 2 and 3 can be avoided. Furthermore, the angle formed by the first and second waveguides 2.3 (sum of branching angles) in plan view can be set small, and miniaturization is possible.

Next, a method for manufacturing the leading waveguide coupler according to this embodiment will be described.

First, a ridge-shaped first waveguide 2 is selectively formed on a substrate 1. Next, the entire surface is covered with clad glass, and the first waveguide 2 is embedded in this clad glass. Next, a ridge-shaped second waveguide 3 is formed on this clad glass.
selectively formed.

Next, the entire surface is covered with clad glass, and this second waveguide 3 is embedded in the clad glass.

This allows a fully buried waveguide to be formed.

Note that an optical waveguide type coupler can be manufactured by forming first and second waveguides in a predetermined pattern on two substrates, respectively, and coupling the substrates by optical contact, adhesive bonding, or mechanical bonding. Good too. In this case, in order to keep the branching ratio between the first and second waveguides constant, the branching angle of the first and second waveguides in plan view should be set small to reduce the effects of scattering, etc. It is preferable to do so. When the branching angle exceeds 7°, the loss increases rapidly. Therefore, the branching angle is set to 7° or less.

Next, the results of actually manufacturing an optical waveguide type coupler according to an example of the present invention and investigating its characteristics will be explained.

First, the surface of a metal silicon substrate having a thickness of 1 mm was thermally oxidized to grow a silicon oxide film to a thickness of about 5 μm on the surface of the substrate. Next, using a low pressure CVD method, a refractive index difference of 0.35% is formed on this silicon oxide film with a thickness of about 8 μm.
A 5iO3-P2O5 film was formed. The temperature condition in this reduced pressure CVD method is 400°C.

Next, this Si02-P20+s film was selectively etched and molded to form four 2% 2-branch confluence shapes in parallel, and then annealed in an argon atmosphere at a temperature of 1000°C. . This allows the ridge-type first
A waveguide was obtained. In this case, the bending diameter of the waveguide is 40 m.
It is m.

Next, using a low-pressure CVD method, a SiO2P2O5 film with a refractive index difference of 0.03% is embedded between the first waveguides, and a 5iO3-P2C) film with a thickness of 3 μm is placed on the first waveguide.
It was formed with a thickness of m. This 8102 P205 film acts as a cladding.

Next, a low-pressure CVD method is used to create a refractive index difference of 0.
A 35% S j 02 P205 film was formed to a thickness of 8 μm. In this case, the temperature condition for the CVD method is 400°C.
It is.

Next, this S i 02 P205 film was selectively etched to form four 2% bifurcated merging shapes in parallel, and then annealed in an argon atmosphere at a temperature of 000°C. was applied. As a result, a ridge-type second waveguide was obtained. The bending diameter of the waveguide in this case is 4
It is 0mm.

Next, using a low pressure CVD method, a 5tO2-P2O5 film having a refractive index difference of 0.03% was filled between the second waveguides. In this way, a leading waveguide coupler in which four 2% 2-branch coupling elements were integrated was manufactured.

The coupling loss with the optical fiber at the input/output section of this optical waveguide type coupler was about 0.3 dB. Further, the total additional loss including this coupling loss was 0.9 dB.

In this example, the size of the waveguide section is approximately
++, and the length could be reduced to 30 mm.

The optical fiber was coupled to the coupler using a quadruple molded connector. Then, the additional loss of each fiber was actually measured. As a result, the additional loss of the fiber is 0
．． It was as low as 8 to 0.9 dB.

Next, the results of manufacturing an optical waveguide coupler according to an example of the present invention using another method and investigating its characteristics will be described.

First, prepare two metal silicon substrates with a thickness of 1 mm,
Both ends of each substrate were polished down by approximately 109 m. Then, ion etching was performed so that the gap between this polished part and the central part was smooth.

Next, the surface of the metal silicon substrate was thermally oxidized to grow a silicon oxide film to a thickness of 5 μm. Next, reduced pressure CV
Using the D method, the refractive index difference on this silicon oxide film is 0.
．． 13%? 7) S102-P205 membrane 10μ
It was formed with a thickness of m. The temperature condition in this reduced pressure CVD method is 400°C. Next, this S i 02-P20
After selectively etching the 5 films into a shape in which four 2-film, 2-branch, merging shapes were formed in parallel, annealing treatment was performed in an argon atmosphere at a temperature of 1000°C. As a result, a bent waveguide with a bending diameter of 30 mm was obtained. Next, the reduced pressure C
A SiO2 film was formed as a cladding to a thickness of 4 μm by the VD method.

The coupling loss with the optical fiber at the input/output portion of this curved waveguide was approximately 0.3 dB. The total additional loss including this coupling loss was 0.9 dB.

After the two substrates having the curved waveguide thus formed were mechanically aligned, the two substrates were fixed using matching oil. In this way, a leading waveguide coupler in which four two-film two-branch coupling elements were integrated was obtained. The waveguide portion of this coupler was small, with a width of 10 mm and a length of 3011+II+.

The optical fiber was directly fixed with a fixing jig made of silicon and directly coupled to the waveguide without using a connector. When we measured the additional loss of this fiber one by one, we found that
The additional loss of each fiber is between 0.5 and 0. It was EidB.

[Effects of the Invention] As explained above, according to the present invention, the first and second waveguides are provided on the substrate without intersecting each other, and the first and second waveguides are part of the substrate. Since the optical coupling part is formed in a direction substantially perpendicular to the substrate surface,
The waveguides are not coupled at any portion other than the complete coupling portion. Therefore, the optical waveguide coupler according to the present invention has low transmission loss, and the angle formed by the first and second waveguides (sum of branching angles) in plan view can be made small, allowing miniaturization. It is. Furthermore, a coupler that branches and couples a plurality of signal lights can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an optical waveguide type coupler according to an embodiment of the present invention, FIG. 2 is a side view thereof, and FIG. 3 is a perspective view showing a conventional 2×2 coupler.

Claims (1)

[Claims] (1) It has a substrate, a plurality of first waveguides provided on the substrate, and a plurality of second waveguides provided on the substrate without intersecting the first waveguides. and the first
and an optical waveguide type coupler, wherein a portion of the second waveguide constitutes an optical coupling portion in a direction substantially perpendicular to the substrate surface.