JPH07128543A - Juncture structure for optical fiber and optical waveguide - Google Patents

Abstract

PURPOSE:To enhance reliability by tightly adhering and fixing optical fibers which are tapered and are cut at one end of their clads atop optical waveguides and coupling the cores respectively adjusted in propagation constants to each other in a state of parting these cores to some extent, thereby eliminating such precise alignment like heretofore, facilitating multiple simultaneous connection, lessening the dependency on light wavelengths and lessening the deterioration of characteristics in spite of a positional fluctuation by an environmental change. CONSTITUTION:This connecting system comprises using distributed coupling to realize perfect coupling by a proper core diameter and inter-core spacings and lessening of the dependency on the wavelengths. The optical fibers 1 cut at one side end face of the coupling part are tapered to some extent are tightly adhered and fixed atop the optical waveguides 2 and the cores 1a adjusted in the respective propagation constants are coupled in the state of paring these cores from each other at a certain spacing in the coupling part. The juncture structure for the optical fibers 1 and the optical waveguides 2 which make distributed coupling by further removing the optical fiber side clads 1c to narrow the spacings between the respective optical waveguide cores is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for connecting an optical fiber and an optical waveguide in an optical waveguide type optical component used for branching and switching light in an optical communication network. is there.

[0002]

2. Description of the Related Art Heretofore, a butt joint method has been mainly used in which a part of this kind, for example, a connecting part between an input / output part of an optical waveguide device and an optical fiber is polished at both end faces and is aligned and abutted. It was This type of method could easily be jointed when the optical waveguide core diameter was around 50 μm and between large multimodes, but the optical waveguide core diameter was 1
In the case of a single mode of 0 μm or less, high precision of submicron order is required, and alignment is difficult. Therefore, especially when collectively connecting a large number of optical waveguides, the core connection is the optical waveguide spacing and V for fixing the optical fibers.
Since it depends on the accuracy of the groove and groove spacing, it is necessary to manufacture each part with extremely high accuracy on the order of submicrons, and in order to realize this kind of part, high reliability is essential. It was difficult.

In order to solve such a precision problem,
A method using distributed coupling has also been proposed, but in the case of obtaining perfect coupling, wavelength dependency (variation in coupling degree depending on wavelength) occurs, and there is a problem that power variation occurs in a branch type device.

[0004]

In order to solve the above-mentioned problems, the present invention proposes a connection method using a distributed coupling which realizes complete coupling by a proper core diameter and core spacing and reduction of wavelength dependence. The optical fiber is connected to the optical waveguide, and the optical fiber with a certain length tapered to cut one end surface of the coupling part is closely fixed to the upper surface of the optical waveguide, and each propagation constant at the coupling part. Is a connection structure of an optical fiber and an optical waveguide for coupling the cores combined with each other in a state of being separated by a certain distance, and further, by removing the optical fiber side clad, each optical waveguide core interval is made closer,
It is a connection structure of an optical fiber and an optical waveguide for distributed coupling.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are a schematic diagram and a characteristic explanatory diagram of the configuration of an embodiment of the present invention, in which the same portions are designated by the same reference numerals. 1A and 1B show an embodiment of a connecting portion structure according to the present invention. FIG. 1A is a schematic side sectional view of a connecting portion, and FIG. 1B is a schematic top view thereof. An optical fiber having a core diameter adjusted by narrowing the outer diameter is placed on the embedded optical waveguide and distributedly coupled. An adhesive agent or a low melting point glass having substantially the same refractive index as that of each clad portion is used for fixing the both. The optical fiber to be used is obtained by heating and stretching, and by expanding the heating range, a small-diameter portion having a substantially flat shape can be obtained. Further, the optical waveguide used can have a substantially circular cross section by an ion exchange method in which a part of the glass is exchanged for ions such as Na to produce a high refractive index optical waveguide.

Here, the diameter is narrowed by heating and stretching, and the propagation constant of the optical fiber is matched with that of the optical waveguide.
The coupling part of the optical waveguide is made thin so as to match the propagation constant with the fiber having a reduced diameter. The optical waveguide may be configured in that state, or only the coupling portion may be reduced in diameter. This is because the smaller the optical waveguide core diameter is, the shorter the complete coupling length is, and the variation in the coupling degree due to the difference in wavelength is small. In addition, when the core interval is narrowed, the wavelength variation is small and the coupling length is short. The cross-sectional shape in this case may be configured as shown in FIG. That is, one side of the fiber extending portion clad is removed, and the cores are brought close to each other. With this configuration, connection can be performed only in the longitudinal direction of the optical waveguide (setting of the coupling portion length).

In the present invention, the core diameter of each joint is small,
Although the propagation constants are combined, FIG. 3 shows the relationship between the core spacing and the perfect coupling length when the diameter of the distributed coupling core is changed.

[0008]

As described above, the structure and method of the present invention have the following excellent effects. In other words, (1) Since the connection is made by distributed coupling between the waveguides, the alignment is determined by the setting of the coupling length, and the conventional precision alignment is unnecessary. (2) Since simple positioning is sufficient, multiple batch connection can be easily performed. (3) The core diameter of each optical waveguide is small, the length of the coupling portion is short, and the light wavelength dependence is small. (4)
There is little characteristic deterioration even with position changes due to environmental changes,
Highly reliable.

[Brief description of drawings]

FIG. 1 is a schematic side cross-sectional view of a configuration example of a connection portion according to the present invention, and FIG.

FIG. 2 is a schematic cross-sectional view of the distributed coupling section in FIG.

FIG. 3 is a graph showing the relationship between the core spacing and the complete bond length for each core diameter used.

FIG. 4 is a schematic diagram showing a process of reducing the diameter of an optical fiber.

FIG. 5 is an example of mounting an optical waveguide device using a connecting portion according to the present invention.

[Explanation of symbols]

1 Optical Fiber 1a Optical Fiber Core 1b Elementary Wire 1c Optical Fiber Clad 2 Optical Waveguide 2a
Optical waveguide element 2b Optical waveguide substrate 2c Support 3 Buffer layer 4 Adhesive

Claims (2)

[Claims] 1. In a structure for connecting an optical fiber and an optical waveguide, an optical fiber whose one end is tapered to a tapered length is closely fixed to the upper surface of the optical waveguide, and cores whose propagation constants are adjusted at the coupling portion. A structure for connecting an optical fiber and an optical waveguide, characterized in that the optical fiber and the optical waveguide are coupled while being isolated from each other for a certain period of time. 2. The optical fiber / optical waveguide connecting portion structure according to claim 1, wherein the optical fiber side cladding is removed to bring the intervals between the optical waveguide cores closer to each other so as to achieve distributed coupling.