Optical waveguides – With optical coupler – With alignment device
Reexamination Certificate
1998-11-12
2001-06-26
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
With alignment device
C385S016000, C356S400000
Reexamination Certificate
active
06253010
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to optical systems, and relates more particularly to a system and method for efficient coupling between optical elements.
2. Description of the Background Art
Implementing techniques for efficient coupling between optical elements is a significant consideration of designers, manufacturers, and users of optical systems. Many modern optical systems use light beams, usually laser-generated, to carry various types of information. These light beams may travel through free space or through optical elements such as optical fibers. In optical systems, a light beam may alternate between travelling in free space and travelling in a fiber. This free-space-to-fiber coupling often occurs in the context of an optical switch.
Free-space-to-fiber coupling should be efficient to avoid unnecessary losses in light. Coupling efficiency is especially important in optical systems where light beams are sent through a fiber and then reflected back. If the free-space-to-fiber coupling is not efficient, then the amount of light reflected back through the fiber might be insufficient for its intended purpose.
For efficient coupling, a light beam travelling through free space must contact a fiber so that the amount of light transmitted through the fiber is maximized. The most efficient coupling between a free space beam and a fiber occurs when the light beam is centrally positioned on the core of the fiber (on the fiber center). This central positioning results in the maximum amount of light being transmitted through the fiber.
However, once positioned on the fiber center, the light beam may not remain in place. If the optical system suffers a shock or vibration, the physical components of the optical system may shift, causing the light beam to be offset from the fiber center.
Other factors may also cause the light beam to be offset from the fiber center. For example, thermal expansion of a fiber may cause it to shift, reducing the coupling efficiency between the light beam and the fiber. This type of offset poses a different problem from offset due to movements of the physical components of the optical system. A system and method for efficient coupling must be able to correct offsets due to vibration, thermal expansion, and any other cause. Therefore, an improved system and method are needed for efficient coupling between optical elements.
SUMMARY OF THE INVENTION
In accordance with the present invention, a system and method are disclosed to effectively implement efficient coupling between optical elements. The preferred embodiment of the present invention is implemented in the context of an optical switch. In the optical switch, a light beam couples with a selected optical fiber in a fiber bundle. Efficient coupling occurs when the light beam is positioned on the center of the selected fiber.
In the preferred embodiment of the present invention, a memory contains an alignment module, which is configured to align the light beam with the center of the selected fiber to maximize coupling efficiency. The preferred embodiment of the present invention also includes a processor coupled to the memory to control the alignment module, and a position sensitive device for indirectly sensing a position of the light beam on the selected fiber and sending the position to the processor.
The alignment module includes three main components. The first component, a center estimator, estimates the position of the center of a selected optical fiber in the optical switch. The estimate position for the center of the fiber is determined by using an offset in fiber position due to a temperature change in the optical system.
The second component, a center searcher, positions the light beam on the center of the selected fiber. The center searcher identifies a direction of increasing coupling efficiency and moves the light beam along that direction until the beam is positioned on the fiber center. The third component, a center maintainer, maintains the light beam on the fiber center as long as the same fiber in the fiber bundle is selected. The center maintainer continuously assesses coupling efficiency near the fiber center and repositions the light beam if an increase in coupling efficiency is found.
If a different fiber in the fiber bundle is selected, the alignment module determines an estimate position for the fiber center of the new fiber using the same offset in position used for the initially selected fiber. The alignment module then positions the beam on the center of the new fiber. Therefore, the system and method of the present invention effectively implements efficient coupling between optical elements.
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Belser Karl A.
Lee Howard S.
Szita Gabor G.
Bovernick Rodney
Flehr Hohbach Test Albritton & Herbert LLP
Iolon, Inc.
Stehl Michael J.
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