Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
2002-09-03
2004-08-10
Healy, Brian (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S092000, C385S052000
Reexamination Certificate
active
06773169
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a method for coupling a surface-oriented opto-electronic element with an optical fiber, and an opto-electronic element for carrying out such a method.
The coupling between an opto-electronic element or chip and an optical fiber, particularly, a monomode fiber, represents a complex problem because the two components must be aligned relative to one another to achieve a high coupling performance with high efficiency in the &mgr;m or sub-&mgr;m range. Prior art methods for producing a coupling include, on one hand, a coupling technique with lenses or other beam transforming elements, and on the other hand, direct techniques, referred to as butt coupling methods.
Generally, an optical fiber is aligned relative to an opto-electronic chip for purposes of achieving a high coupling performance by an active aligning technique, i.e., an experimental determination of the favorable positioning of the optical fiber and the opto-electronic chip. Active aligning is disadvantageously time consuming and cost-intensive.
Another prior art technique is what is referred to as passive alignment, which provides for the utilization of positioning aids that are provided at one of the coupling partners or at a coupling device. The positioning aids make possible a passive alignment between an opto-electronic chip and an optical fiber that is to be coupled therewith, but the provision of the positioning aids is associated with an additional outlay and additional costs.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for coupling a surface-oriented opto-electronic element with an optical fiber and opto-electronic element for carrying out such a method that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that makes it possible to connect the two parts easily while providing a high coupling performance.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method of coupling an element with a fiber, including the steps of providing an optical fiber having a fiber rotational axis and a fiber butt, providing a surface-oriented opto-electronic element having an optically active zone, a rotational axis, and a rotationally symmetric protruding structure symmetrically disposed with respect to the optically active zone, wetting at least one of the fiber butt and the protruding structure with a transparent adhesive, moving the element and the optical fiber toward each other to spread the adhesive therebetween, disposing at least one of the element and the fiber to enable a substantially frictionless movement of the fiber perpendicular to the rotational axis of the element and perpendicular to the fiber rotational axis, waiting for the fiber and the protruding portion to self-center, and one of waiting for and bringing about a hardening of the adhesive to fix the now-centered configuration between the fiber and the protruding portion.
Accordingly, it is inventively provided that, first, the butt of an optical fiber and/or a rotationally symmetric protruding structure of an opto-electronic element are wetted with a transparent adhesive. The rotationally symmetrical structure is constructed symmetrical to the optically active zone of the opto-electronic element. Next, the two elements that are to be coupled are moved toward each other, whereby the adhesive between the front side of the fiber and the protruding structure spreads. The opto-electronic element and/or the fiber are disposed so as to allow substantially frictionless movement perpendicular to the rotational axis of the opto-electronic element, i.e., perpendicular to the rotational axis of the fiber. Such a configuration makes possible an automatic positioning of the two coupling elements relative to one another. The element automatically positions itself relative to the optical fiber and vice-versa by virtue of the surface tension and the capillary effect of the adhesive.
A rotationally symmetrical structure in the sense of the invention is any structure that is projected on itself given rotation about at least one angle not equal to 360°. In other words, if there exists a line g and at least one angle a, such that the body is projected onto itself given rotation about the line g and the angle a, then the body is rotationally symmetric. In particular, this includes not only circular and annular structures but also polygons, particularly, triangles, quadrilaterals, pentagons, etc. Rotational symmetry in the sense of the invention is, thus, identified with a structure whose center of gravity is on center.
What is meant by substantially frictionless movement perpendicular to the axis of rotation of the opto-electronic element or perpendicular to the rotational axis of the fiber is movement that is opposed by such slight friction that there is no impediment to alignment based upon the surface tension and capillary effect of the adhesive. This is the case, particularly, with a floating configuration of the element. Specifically, a symmetrical configuration of the rotationally symmetric protruding structure relative to the optically active zone means that the protruding structure and the optically active zone have a common center of gravity (i.e., one situated on a common axis of rotation). The optically active zone is, preferably, also configured rotationally symmetrical.
Due to the rotational symmetry of the protruding structure, a positioning is achieved by bringing the rotational axis of the protruding structure into congruence with the rotational axis of the (likewise rotationally symmetric) optical fiber. Because the protruding structure is disposed symmetrical to the optically active zone of the opto-electronic element, and this is, therefore, concentrically aligned relative to the protruding structure, the rotational axis of the optically active zone becomes aligned precisely on the rotational axis of the optical fiber. Such alignment produces the highest possible coupling performance.
After the successful self-centering of the protruding portion, i.e., the optically active zone, and the optical fiber, the adhesive is hardened. Hardening can occur automatically with the passage of time, or, alternatively, by a separate curing aid such as UV irradiation. The ideal positioning between the two coupling partners is fixed in time and space by the curing of the adhesive. As a result, the optically active zone or surface of the opto-electronic element is aligned concentric to the fiber core and fixed there, which makes possible an optimal coupling.
Wetting with an adhesive may occur on the butt side of the fiber only, on the protruding structure of the opto-electronic component only, or on both.
In accordance with another mode of the invention, the opto-electronic element is placed on the butt of the (perpendicularly aligned) fiber and then released, i.e., separated from outside holding components.
The element is disposed such that it floats on the butt of the fiber with the aid of the transparent adhesive and is borne by the adhesive. The element can, therefore, be displaced perpendicular to the rotational axis of the optical fiber. The relatively light element now moves relative to the butt side of the fiber under the effect of the surface tension of the adhesive and positions itself concentrically to the axis of the fiber. Under the influence of the surface tension, the surfaces of the adhesive form minimum areas, whereby the element (i.e., its rotationally symmetric protruding structure) is automatically centered.
It should be noted that, on principle, the invention can also provide that the element be borne in a floating fashion at a certain distance from the butt of the fiber by a holding device—which engages the lateral ends of the element, for example—in that the adhesive already fills the intermediate space between the protruding structure or the fiber. Here, a movement of the element perpendicular to the rotationa
Ebeling Karl-Joachim
Hanke Christian
Heinen Jochen
Greenberg Laurence A.
Healy Brian
Infineon - Technologies AG
Locher Ralph E.
Stemer Werner H.
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