JPH02285306A - Auxiliary device for coupling between plane optical waveguide and optical fiber - Google Patents

Abstract

PURPOSE:To couple the plane optical waveguide and optical fiber with each other with high efficiency by using the mount surface of a base as a reference surface, mounting a base body while bringing a plane optical waveguide formation surface into contact with the reference surface, and mounting a connector so that the optical axis of the optical fiber is on the surface where the optical axis of the plane optical waveguide is present. CONSTITUTION:The smoothly finished mount surface 1a of the base 1 is used as the reference surface and the surface of the plane optical waveguide 2 is arranged on the reference surface; and the optical axis of the optical fiber 7 is arranged on the surface where the optical axis of the plane optical waveguide 2 is present in parallel to the reference surface and the plane optical waveguide 2 and optical fiber 7 are coupled with each other. Therefore, the reference surface where the plane optical waveguide 2 is positioned becomes the reference surface for the coupling between the plane optical waveguide 2 and optical fiber 7 as it is and adjustments of the optical fiber in two different radial directions and in three axial directions are reduced to only two directions. Consequently, the plane optical waveguide 2 and optical fiber 7 can easily be coupled with each other with high efficiency without any deviation between the optical axes.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an auxiliary device for coupling a planar optical waveguide to an optical fiber. More specifically, the present invention relates to an auxiliary device that makes it possible to easily couple a planar optical waveguide and an optical fiber with low coupling loss.

Conventional planar optical waveguides are used to construct various optical control elements, optical passive elements, and the like. These optical elements are often coupled with optical fibers when actually used. When the number of optical fibers to be coupled is small, the optical fibers are directly coupled to each planar optical waveguide using resin or the like after adjusting the optical axis. In addition, when connecting multiple optical fibers to multiple planar optical waveguides formed parallel to the substrate surface, a connector that holds the optical fibers at the same spacing as the spacing between the planar optical waveguides is used, in order to only need to adjust the optical axis once. may also be used.

In Figures 5(a) and 5(a), the present applicant
This figure shows an auxiliary device for coupling a planar optical waveguide and an optical fiber, which is disclosed in Japanese Patent Application No. 63-310739 filed on May 8th. The device shown in FIG. 5 includes a base 1 having a mounting surface 1a that is finished smoothly and has a groove 10 for mounting a connector in the center and a bolt hole 9 for fixing a holder; It is composed of a holder 4 for fixing the leading waveguide base 2 mounted on the mounting surface 1a of the base 1, an upper member 8a and a lower member 8b, and the lower member 8b holds the optical fiber 7. It mainly consists of a connector 8 that fits into the groove 10 to connect the optical fiber 7 and the planar optical waveguide 3.

The optical waveguide base 2 has a planar optical waveguide 3 formed on a surface 2a, the surface opposite to the surface 2a on which the planar optical waveguide 3 is formed is fixed with resin to a holder 4, and the surface 2a is attached to the base 1. The holder 4 is mounted on the base 1 so as to be in contact with the mounting surface 1a, and is fixed to the base 1 by fixing the holder 4 with a bolt 6 passing through a bolt hole 5.

In addition, the connector 8 has a V for fixing the optical fiber 7.
An upper member 8a and a lower member 8b each having a groove 12 with a letter-shaped cross section are aligned so that the respective grooves 12 face each other. The grooves 12 are arranged at equal intervals to the planar optical waveguide 3,
Further, the optical fiber 7 is formed so that its optical axis lies on the surface in which the groove 12 of the upper member 8a is formed, and the optical fiber 7 is fixed to the groove 12 of the upper member 8a. Also,
The width of the lower member 8b matches the width of the groove 10 of the base l, the width of the upper member 8a is wider than the width of the lower member 8b, and the surface of the upper member 8a where the groove 12 is formed is lower. It protrudes from the side of the side member and is finished with high precision. Since the optical fiber 7 is fixed in the groove 12 of the upper member 8a,
The optical axis of the optical fiber 7 exists on the surface of the upper member 8a in which the groove 12 is formed, regardless of the assembly precision of the upper member 8a and the lower member 8b. In the connector 8 configured as described above, the lower member 8b fits into the groove 10 of the base 1,
The upper member 8a is mounted on the base 1 with the above surface and the mounting surface 1a of the base 1 in contact with each other.

By mounting the connector 8 in this way, the optical axis of the planar optical waveguide 3 and the optical axis of the optical fiber 7 are precisely aligned in their vertical positions.
It is only necessary to carry out the process in two directions: the radial direction parallel to the mounting surface 1a of the base l and the axial direction of the optical fiber 7.

After adjusting the optical axis, the connector 8 and the optical waveguide base 2 are fixed with resin, and the connection between the planar optical waveguide 3 and the optical fiber 7 is completed.

Problems to be Solved by the Invention The electromagnetic field distribution of light propagating in a planar optical waveguide has an intensity peak near the center of the waveguide. Planar optical waveguide formed by using a thin NbO5 crystal as a base and diffusing Ti from the surface.
This will be explained by taking a road as an example with reference to FIGS. 3(a) to 3(C). T1 extends from the surface in the depth direction, and the waveguide shape becomes as shown in FIG. 3(a). At this time, the distribution of T1 concentration in the depth direction is known to be a Gaussian distribution with the highest concentration at the surface as shown in FIG. 3 et al. The electromagnetic field distribution of light propagating through such a waveguide spreads in the air and has an intensity peak near the center of the waveguide, as shown in FIG. 3(C).

This is because the refractive index of the leading waveguide is approximately 2.22 and the refractive index of air is 1.0.

FIG. 4 shows the relationship between the distance between the substrate surface on which the planar optical waveguide is formed and the optical axis of the optical fiber and the coupling loss.

The planar optical waveguide was made of L+NbO+ as a base and Ti was thermally diffused, and the waveguide depth was approximately 2.3 μm and the waveguide width was 7 μm. The optical fiber used for coupling was a single mode fiber with a core diameter of 10 μm. Assuming that the loss when the substrate surface and the optical axis of the optical fiber are aligned is 0,
The loss is at its lowest when the distance between the substrate surface and the optical axis of the optical fiber is 2 μm.

Therefore, when coupling a planar optical waveguide and an optical fiber, it is preferable to align the intensity peak of the electromagnetic field distribution near the center of the waveguide with the optical axis of the optical fiber, as shown in FIG. However, in the conventional coupling auxiliary device, since the center of the optical axis of the optical fiber was aligned with the surface of the substrate, the coupling efficiency was low, that is, the coupling loss was large.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an auxiliary device that solves the above-mentioned problems of the prior art and can easily couple a planar optical waveguide and an optical fiber with high efficiency without causing optical axis misalignment. There is a particular thing.

Means for Solving the Problems According to the present invention, there is provided an apparatus for determining the position of an optical fiber and a substrate when optically coupling the optical fiber and a planar optical waveguide formed on the surface of the substrate. a connector for holding an optical fiber so that its optical axis is in a predetermined direction on a predetermined surface; a smooth mounting surface; and means for mounting and fixing the base so that the planar optical waveguide is in contact with the mounting surface;
and a base comprising means for mounting the connector so that the surface with the optical axis of the optical fiber is movable above the mounting surface of the base and kept parallel to the mounting surface. An auxiliary device for coupling a planar optical waveguide and an optical fiber is provided.

Function The device for auxiliary coupling between a planar optical waveguide and an optical fiber according to the present invention uses the smoothly finished mounting surface of the base as a reference surface, and arranges the surface of the planar optical waveguide on this reference surface. Further, the optical axis of the optical fiber is arranged on a plane parallel to this reference plane and on the optical axis of the planar optical waveguide, and the planar optical waveguide and the optical fiber are coupled. Therefore, coupling with less loss is possible.

Furthermore, in the apparatus of the present invention, the reference plane on which the planar optical waveguide is positioned serves as the reference plane when coupling the planar optical waveguide and the optical fiber. Therefore, the adjustment in two different radial directions of the optical fiber and the three directions in the axial direction of the optical fiber, which have been conventionally performed, can be reduced to only two directions by using the apparatus of the present invention. That is, optical axis adjustment is required only in the radial direction of the optical fiber, parallel to the reference plane, and in the axial direction of the optical fiber.

On the other hand, in the apparatus of the present invention, it is preferable that the connector for positioning and holding the optical fiber is made of a material such as Si and has a groove formed in a flat surface to accommodate the optical fiber. The groove for storing the optical fiber is, for example, V.
It is preferable that the optical fiber has a letter-shaped cross section and is formed so that the optical axis of the optical fiber lies on the above-mentioned plane. Also,
When a plurality of optical fibers are coupled to different planar optical waveguides on the substrate, the grooves are preferably formed so that the intervals between the held optical fibers are equal to the intervals between the planar optical waveguides.

In addition, if the above-mentioned connector is configured such that the optical axis of the optical fiber is on the above-mentioned plane, the above-mentioned plane is parallel to the mounting surface of the base and is separated by a predetermined distance. It is preferable that the structure is such that it can be mounted on a base.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention in any way.

Embodiment The device for auxiliary coupling between a planar optical waveguide and an optical fiber according to the present invention is an improved version of the connector 8 of the conventional device shown in FIGS. 5(a) and 5(b). Hereinafter, the differences between the devices of the present invention will be mainly explained.

Examples of the connector 8 used in the device of the present invention are shown in FIGS. 1(a) to 1(C). In this example, two optical fibers are coupled to two planar optical waveguides on the substrate.

The connector 8 is formed by bonding a rectangular parallelepiped lower member 8b to an upper member 8a having two grooves 12 with a V-shaped cross section for fixing the optical fiber 7. The grooves 12 are arranged at equal intervals to the planar optical waveguide 3 so that the optical axis of the optical fiber 7 is aligned with the surface 1 of the upper member 8a.
The optical fiber 7 is formed to be located 2 μm inside (upper side in the figure) than the optical fiber 4, and is fixed in the groove 12 of the upper member 8a with a resin 16 or the like. Further, the width of the lower member 8b is matched to the width of the groove 100 of the base 1, the width of the upper member 8a is wider than the width of the lower member 8b, and the surface 14 of the upper member 8a is on the side of the lower member 8b. It juts out towards the side and is finished with high precision. Since the optical fiber 7 is fixed in the groove 12 of the upper member 8a, the optical axis of the optical fiber 7 is 2 μm from the surface 14 of the upper member 8a, regardless of the assembly accuracy of the upper member 8a and the lower member 8b. exists inside. In the connector 8 configured as described above, the lower member 8b is connected to the groove 1 of the base 1.
and is mounted on the base 1 with the surface 14 of the upper member 8a and the mounting surface 1a of the base 1 in contact with each other.

In the connector shown in FIG. 1(a), the shape and size of the groove 12 having a V-shaped cross section formed in the upper member 8a are adjusted so that the optical axis of the optical fiber 7 is set to be higher than the above-mentioned surface 14 of the upper member 8a. 2
It is configured to be within μm.

In the connector of FIG. 1(b), a groove 12 is formed so that the optical axis of the optical fiber 7 is located on the surface 13 of the upper member 8a,
Further, by forming a metal film 15 on the surface 13, the optical axis of the optical fiber 7 is configured to be 2 μm inside the surface 14 of the upper member 8a.

The connector of FIG. 1(C) has an upper member 8a formed with a groove 12 similar to the upper member 8a of the connector of FIG. 1(b).
By using an optical fiber 7 with a small outer diameter at the portion that enters the groove 12, the optical axis of the fiber 7 is configured to be 2 μm inside the surface 14 of the upper member 8a. As a method for reducing the outer diameter of the optical fiber 7, etching using hydrofluoric acid or the like is preferable.

Using the apparatus shown in FIGS. 5(a) and 5(b) in which the connector 8 was replaced with the above connector, the optical fibers 7 were coupled to both sides of the planar optical waveguide 3, and the loss was measured. The coupling loss obtained by subtracting the waveguide loss of the optical waveguide itself and the mode mismatch between the waveguide and the optical fiber from the total loss was 0.8 dB, indicating that good coupling could be achieved.

Effects of the Invention As detailed above, by using the auxiliary device of the present invention, it becomes possible to easily couple a planar optical waveguide and an optical fiber with high efficiency. This is unique to the auxiliary device of the present invention, in which the mounting surface of the base is used as a reference surface, and the base body is mounted on the reference surface so that the surface on which the planar optical waveguide is formed is in contact with the surface of the base, and the light of the optical fiber is This is based on a configuration in which the connector is mounted so that its axis is on the plane of the optical axis of the planar optical waveguide.

[Brief explanation of drawings]

FIGS. 1(a) to (C) are front views of examples of connectors used in the device of the present invention, and FIG. 2 is a schematic diagram showing a preferable coupling state between a planar optical waveguide and an optical fiber. , FIG. 3(a) is a schematic diagram of the shape of the planar optical waveguide formed on the substrate, and FIG. 3(b) shows the distribution of T1 concentration in the planar optical waveguide of FIG. 3(a). FIG. 3(C) is a conceptual diagram showing the intensity distribution of light propagating through the planar optical waveguide of FIG. 3(a), and FIG. 5 is a graph showing the relationship between the distance between the substrate surface and the optical axis of the optical fiber and the coupling loss; FIGS. It is a diagram. [Main reference numbers] ■...Base, 1a...Base mounting surface, 2...Base, 2a...3...4...5.9 7...8a...8a...8b...10・ ・ 15. ・ Base surface, planar optical waveguide, holder, ... bolt hole, 6... bolt, optical fiber connector, connector upper member, connector lower member, connector groove, 12... V groove, metal film, 16 ...Resin patent applicant Sumitomo Electric Industries, Ltd.

Claims (1)

[Claims] (1) A device that determines the position of the optical fiber and the substrate when optically coupling the optical fiber and a planar optical waveguide formed on the surface of the substrate, the device determining the position of the optical fiber and the substrate so that the optical axis of the optical fiber is on a predetermined plane. a connector for holding an optical fiber in a predetermined direction; a smooth mounting surface; means for mounting and fixing the base so that the planar optical waveguide is in contact with the mounting surface; and a surface with an optical axis of the optical fiber. A planar optical waveguide and an optical base comprising means for mounting the connector so as to be movable above the mounting surface of the base while being kept parallel to the mounting surface. Fiber coupling aid.