Optical waveguides – With optical coupler – Switch
Reexamination Certificate
1999-12-21
2001-11-20
Schuberg, Darren (Department: 2872)
Optical waveguides
With optical coupler
Switch
C385S025000, C385S016000, C385S140000
Reexamination Certificate
active
06320997
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a 1×N optical switch and, more particularly, to a 1×N optical switch utilizing silicon optical technology to form a self-aligning arrangement.
BACKGROUND OF THE INVENTION
In a 1×N optical switch, a single optical fiber forms an optical path with an optical fiber selected from N optical fibers. Therefore, a signal propagating along the single fiber will be coupled into one of the selected N fibers. Similarly, a signal propagating along the selected fiber (in the opposite direction) will be coupled into the single fiber. A switching arrangement is required to assist in the selection for the one-out-of-N fibers.
In electromechanical 1×N optical switches, the switching operation is effected by the movement of an end of the single fiber relative to the ends of the N optical fibers. To form an optical path, the end of the single optical fiber is aligned with the end of the selected fiber from the N fibers. In such systems, alignment of the fiber ends is critical and much precision is required with the electromechanical drive devices, such as motors and their movements, to ensure accurate and reproducible alignment of the single fiber with each of the n optical fibers. Nonetheless, performance of such switches has remained poor with use restricted to multimode optical fibers. In present day optical networks, it is often desirable to use single mode fibers, not multimode fibers.
An exemplary prior art 1×N switch that has allowed for the use of single mode fibers is disclosed in U.S. Pat. No. 5,359,683, issued to J. Pan on Oct. 25, 1994. In this arrangement, a set of GRIN lenses, disposed between the single fiber and the N fibers, is used to ameliorate the effects of misalignment and provide better coupling between the single fiber and the selected fiber. While considered an improvement, the arrangement is difficult and expensive to manufacture, requiring individual stepper motors to align each GRIN lens with the selected fiber.
A need remains, therefore, for a 1×N optical switch, suitable for use with single mode fibers, that is relatively inexpensive to manufacture, yet provides the needed alignment between the single fiber and the selected one-out-of-N fibers.
SUMMARY OF THE INVENTION
The need remaining in the prior art is addressed by the present invention, which relates to a 1×N optical switch and, more particularly, to a 1×N optical switch utilizing silicon optical bench technology to form a self-aligning arrangement.
In accordance with the teachings of the present invention, a first “stack” of silicon substrates is formed to support a single optical fiber within a via formed through the thickness of the stack. A second “stack” of silicon substrates is formed to support an array of N optical fibers in a circular pattern. The two stacks are supported in a “face-to-face” assembly so that the endface of the single fiber will align with the endface of a selected fiber from the array of N fibers. Self-alignment between the single fiber and the selected fiber is provided in the present invention by using a set of alignment fiducials formed on the top surfaces of each substrate stack. In particular, a pair of aligning “centering” fiducials are formed on the stack surfaces, one stack including (for example) a centered pyramidal detent and the other stack including an alignment sphere. The ability to “switch” between selected fibers in the circular array is provided in accordance with the present invention by forming a circular alignment channel around the perimeter of one substrate stack, with an alignment sphere disposed on the surface of the remaining stack such that the sphere will “ride” in the channel when the stacks are mated. A set of rounded stops are disposed at proper locations around the channel so that the alignment sphere will contact a rounded stop when the selected fiber is in proper alignment with the single fiber. When it is desired to “switch” to another one of the N fibers, the piece parts can be slightly separated (either automatically or manually) to lift the alignment sphere over the rounded stop and allow the stack to rotate.
In one embodiment of the present invention, the channel is formed on the substrate stack include the circular fiber array. In an alternative embodiment, the channel is formed on the substrate stack including the single fiber. Either embodiment is acceptable and within the scope of the present invention.
It is an advantage of the present invention that silicon may be used to form the substrates (or at least a “master” set of substrates), with conventional photolithography techniques used to form the alignment channel and detents. The capability of controlling the silicon etch allows for the alignment elements to be formed with extreme accuracy, resulting in alignment between the single fiber and selected fiber on the order of 1-2 &mgr;m.
Other and further aspects of the present invention will become apparent during the course of the following discussion and by reference to the following drawings.
REFERENCES:
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patent: 4589726 (1986-05-01), Buhrer
patent: 5031986 (1991-07-01), Mori
patent: 5115481 (1992-05-01), Buhrer
patent: 5259054 (1993-11-01), Benzoni et al.
patent: 5420946 (1995-05-01), Tsai
patent: 5611009 (1997-03-01), Pan
patent: 5664034 (1997-09-01), Mock
patent: 5815614 (1998-09-01), Pan
patent: 5864643 (1999-01-01), Pan
patent: 5920667 (1999-07-01), Tiao et al.
Dautartas Mindaugas Fernand
Freund Joseph Michael
Stefanik Dennis
Agere Systems Optoelectronics Guardian Corp.
Assaf Fayez
Koba Wendy W.
Schuberg Darren
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