JPH02257110A - Structure for connecting optical fiber and optical waveguide - Google Patents

Abstract

PURPOSE:To improve the latitude for connection of the optical waveguide and an optical fiber by forming one end part of the single mode optical waveguide to a horn shape which expands gradually in section toward one end face and connecting the end face of the single mode optical fiber to the one end face of the single mode optical waveguide. CONSTITUTION:The optical waveguide element 110 of single mode is formed of a quartz glass material and has the structure in which the optical waveguide 112 is formed on a substrate 111. The left end part of the optical waveguide 112 is formed as the tapered optical waveguide 112a. This tapered optical waveguide 112a has the horn shape which expands gradually in the width toward the left end face. On the other hand, the optical fiber 120 of the single mode has a clad 121 and a core 122 and the right end of this optical fiber 120 is connected to the left end face of the tapered optical waveguide 112a. Since there is the tapered optical waveguide 112a having the wide connecting end face, the allowance for connection in parallel with the plane of the substrate 111 is greatly improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to alignment tolerance when connecting an optical fiber and an optical waveguide element made of a dielectric or semiconductor used in optical communication systems, sensors, etc. degree (axis misalignment tolerance)
This invention relates to an optical fiber/optical waveguide connection structure that achieves a low-loss connection with a large capacity.

<Conventional technology> FIG. 4 shows a conventional optical fiber/optical waveguide connection structure.

As shown in the figure, the optical waveguide element 10 includes an optical waveguide 12 formed on a substrate 11, and the cross section of the optical waveguide 12 is the same everywhere. On the other hand, the optical fiber 20 has a cladding 21 and a core 22.
The end face of the optical waveguide 12 is connected to the end face of the optical waveguide 12 . When producing the optical waveguide 12 of glass or the like, the parameters of the optical waveguide 12 are made almost the same as the parameters of the core 22 of the optical fiber 20. This is to minimize the end face connection loss between the optical fiber 20 and the optical waveguide element 10.

<Problems to be Solved by the Invention> However, in the case of a single mode system, the connection tolerance is approximately 1 μm, which is extremely severe. For this reason, even if the axis of the connection can be accurately aligned, a misalignment occurs when fixing with adhesive, resulting in an IQIWIi that increases the connection loss by several dB after fixing.

An object of the present invention is to provide a connection structure that greatly improves the connection tolerance between an arrayed optical waveguide and an optical fiber when the optical waveguide is applied to an optical transmission system or a sensor.

Means for Solving the Problems The present invention, which achieves the above object, is characterized in that a single mode optical fiber is connected to a single mode optical waveguide whose one end is expanded into a horn shape.

<Example> Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 shows a first embodiment of the invention. As shown in the figure, the single mode optical waveguide element 110 is made of a silica glass material and has a structure in which an optical waveguide 112 is formed on a substrate 111, and its relative refractive index (△) is Δ=
It is 0.3 [%]. The left end of the optical waveguide 112 is a tapered optical waveguide 112a, and this tapered optical waveguide 112a has a horn shape whose width (cross section) gradually increases toward the left end surface, and its length (I is 1). =5
[mm], and the left end surface dimensions are 40 [μm] x 8 [μm]
]. The remaining portion of the optical waveguide 112 except for the tapered optical waveguide 112a has a constant width and a core diameter (cross-sectional dimension) of 8 [μm]×8 [μm].

On the other hand, the single mode optical fiber 120 has a cladding 112
and a core 122, the core diameter is 8 [μm], and the relative refractive index (
△) is △-0.3%. The right end surface of this optical fiber 120 is connected to the left end surface of the tapered optical waveguide 112a.

In this embodiment with such a configuration, since the tapered optical waveguide 112a is horn-shaped and has a wide connection end surface, the substrate 111
The connection tolerance parallel to the plane (axis misalignment tolerance) is significantly improved compared to the conventional technology.

FIG. 2 shows a comparison of the connection tolerance characteristics of the first embodiment and the conventional technology. It can also be seen from the characteristics shown in FIG. 2 that the connection tolerance is improved compared to the conventional technology. For example, if the wavelength of the transmitted light is 1.30 [, czml
, the connection tolerance for a loss increase of 1 [dB] was 1 [μm] in the conventional technology, whereas it was approximately 6 [μm] in the embodiment of the present invention, and the connection tolerance was significantly improved. .

FIG. 3 shows a second embodiment of the invention. This embodiment is a connection structure when arrayed. In other words, the single mode optical waveguide element 210 made of a quartz glass material is
It has an arrayed structure in which four optical waveguides #J212 are arranged side by side on one, and the distance between the center lines of the optical waveguides 212 is 1.
It is 25 [μm]. Moreover, each optical waveguide 212
As in the first embodiment, the left end portions of each are horn-shaped tapered optical waveguides 212a.

On the other hand, four grooves 231 are formed in the Sl single crystal substrate 230 by etching.

−4= Four single mode optical fibers 220 are connected one by one to groove 2
The optical fiber 220 is set and fixed with adhesive in the
The center line spacing between the cores 222 is set to <125 [μm], which is the same as the center line spacing of the optical waveguide 212. The right end surfaces of the four optical fibers 220 arranged in an array with mutual positions defined in this way are connected to the left end surface of the tapered optical waveguide 212a. Note that 221 is a cladding.

In the second embodiment configured in this way, the connection losses at the four connection points are 0.35 dB, 0.30 dB, and 0.30 dB, respectively.
They were 0.37dB and 0.34dB. By the way, in the conventional array connection, the connection loss is 0.32 dB and 0.4 dB.
0 dB, 0.55 dB, and 0.85 dB, and as the connection position shifts, cumulative errors are gradually added and the connection loss increases. From this point of view, the present invention is particularly effective when applied to an arrayed connection structure.

Note that the scope of the present invention is not limited to the above-described embodiments, but includes all aspects that utilize this technical idea.

<Effects of the Invention> As described above, according to the present invention, connection tolerance can be increased in a connection structure that introduces light from an optical fiber to an optical waveguide, and especially when optical waveguides are arrayed. The effect is extremely significant. This makes it extremely easy to implement optical waveguides in optical transmission systems and sensors, and is expected to improve reliability and lower costs.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing the first embodiment of the present invention, FIG. 2 is a characteristic diagram comparing the loss characteristics of the conventional structure and the structure of the embodiment of the present invention, and FIG. FIG. 4 is a block diagram showing an embodiment, and FIG. 4 is a block diagram showing a conventional technique. In the drawings, 10.110, 210 are optical waveguide elements, 11.111,
211 is a substrate, 2.112, 212 is a leading waveguide, 0.120, 220 is an optical fiber, 1.121, 221 is a cladding, 2.122, 222 is a core, 12a, 212a are a tapered optical waveguide, 30 is a silicon monomer. On the crystal substrate, 31 is a ■groove.

Claims (1)

[Claims] A single mode optical waveguide formed on a substrate of an optical waveguide element,
A connection structure for connecting a single mode optical fiber, wherein one end of the single mode optical waveguide has a horn shape with a cross section gradually widening toward one end surface, and the end surface of the single mode optical fiber is An optical fiber/optical waveguide connection structure characterized by being connected to one end surface of a single mode optical waveguide.