Optical interconnection structure for enlarging alignment...

Details Optical interconnection structure for enlarging alignment... Optical interconnection structure for enlarging alignment...

1999-07-09

2001-06-26

Sikder, Mohammad (Department: 2872)

Optical waveguides

With optical coupler

Input/output coupler

C385S032000, C385S033000, C385S034000, C385S036000

Reexamination Certificate

active

06253004

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical interconnection structure, and more particularly, to a structure of optical interconnection between an optoelectric device and a single mode optical fiber, for enlarging alignment tolerance.
2. Description of the Related Art
In an optoelectric device module, light transmission must be accomplished between smaller devices compared with existing electric elements. Thus, the efficiency of optical coupling between an optical source, such as a laser, and an optical fiber or optical waveguide becomes important to show the optimal performance of the optoelectric device module. The optomechanical characteristics for optimizing this optical coupling efficiency and time-consuming stabilization of thermo-mechanical characteristics are essential in determining a design, a manufacturing method, and the price of a product. Up to now, in optical connection between a single mode optical fiber and a laser diode, an edge-emitting diode laser has usually been used as the optical source. However, the edge-emitting diode laser has a laser gain medium with a thin thickness, producing an asymmetrical beam due to astigmatism, so that integration with a single mode optical fiber requires a high level of technique and a high cost. In practice, an optical fiber for single mode operation has a core diameter between 5 &mgr;m and 9 &mgr;m, and the accuracy of alignment necessary for keeping a connection loss within −3 dB is not exceeding 0.5 &mgr;m. Up to now, many attempts have been made to reduce the costs for aligning single mode optical fibers with lasers, as follows: (1) semi-automatic or automatic active alignment; (2) semi-automatic passive alignment; (3) solder reflow passive self-alignment; and (4) mechanical feature alignment. However, the above attempts are still restrictive successes. The alignment tolerance has been recently enlarged within +/−2 &mgr;m using extended beam emission from the edge-emitting diode laser, still the above alignment methods require costs at least five times higher than those for multimode module packaging.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an optical interconnection structure capable of easily connecting an optoelectric device to a single mode optical fiber in parallel while increasing an alignment tolerance.
Accordingly, to achieve the above object, there is provided an optical interconnection structure comprising: an optoelectric device for performing photoelectric conversion or optical modulation due to an electrical operation; a microlens aligned with an output aperture of the optoelectric device, for preventing the divergence of light beams output from the optoelectric device; a graded index (GRIN) multimode optical fiber of a predetermined length arranged such that light from the microlens is incident thereon; and a single mode optical fiber spliced to the GRIN multimode optical fiber.
In the present invention, a spacer for supporting the optoelectric device with a solid material that transmits light of a wavelength where the optoelectric device operates is preferably disposed between the optoelectric device and the microlens.
The optoelectric device can be an optical source selected from the group consisting of a vertical cavity surface-emitting laser, a light emitting diode, a photo diode, and a folded cavity surface-emitting laser.
The folded cavity surface emitting laser has a horizontal resonator similar to a typical edge emitting laser, but has a 45 degree deflection mirror, and is favorable to use of a long-wavelength band.
It is preferable that the spacer is a substrate, the optoelectric device is fabricated on one surface of the substrate, the microlens is fabricated on the other surface of the substrate, and the optoelectric device, the substrate and the microlens are thus incorporated into one body.
Also, in this case, an optical fiber module comprised of the GRIN multimode optical fibers and the single mode optical fibers can be a passively-aligned optical fiber array.


REFERENCES:
patent: 4875750 (1989-10-01), Spaeth et al.
patent: 5384874 (1995-01-01), Hirai et al.
patent: 5436990 (1995-07-01), Head et al.

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