Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1998-10-27
2001-09-11
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S031000, C385S020000, C385S027000, C359S281000
Reexamination Certificate
active
06289152
ABSTRACT:
BACKGROUND
The present invention is directed generally to a fiber optic device, and more particularly to a device for producing parallelized output beams from a multiplicity of fibers.
Optical fibers find many uses for directing beams of light between two points. Optical fibers have been developed to have low loss, low dispersion, polarization maintaining properties and can also act as amplifiers. As a result, optical fiber systems find widespread use, for example in optical communication applications.
However, one of the important advantages of fiber optic beam transport, that of enclosing the optical beam to guide it between terminal points, is also a limitation. There are several optical components, important for use in fiber systems or in fiber system development, that are not implemented in a fiber-based form where the optical beam is guided in a waveguide. Instead, these optical components are implemented in a bulk form that light must freely propagate through. Examples of such components include, but are not limited to, isolators, circulators, polarizers, switches and shutters. Consequently, the inclusion of a bulk component in an optical fiber system necessitates that the optical fiber system have a section where the beam path propagates freely in space, rather than being guided within a fiber.
Free space propagation typically requires that the beam from each fiber be collimated and directed along the axis of the bulk component being used in the free-space propagation section. Usually, this necessitates that a collimating lens be positioned at the input fiber to collimate the incoming light and a focusing lens be positioned at the output fiber to focus the freely propagating light into the output fiber. The free-space propagation section lies between the two lenses. The introduction of a free-space propagation section requires that the collimating lens and the focusing lens are each aligned to their respective fibers and also that the focusing lens is correctly aligned relative to the collimated beam path from the collimating lens. The alignment of the collimating and focusing lens remains critical, irrespective of the number of fibers. Accordingly, the alignment process becomes more complex and time consuming when multiple fibers require the alignment of multiple collimating and focusing lenses.
In addition, each collimating and focusing lens and each fiber has to be supported transversely. The provision of transverse support increases the total cross-section required by each fiber/lens assembly, thus resulting in a large system.
Accordingly, there is a need for an improved approach to introducing a free-space propagation section into fiber optic systems that is simpler to align and is more compact.
SUMMARY OF THE INVENTION
Generally, the present invention relates to a device that produces parallel optical beams from a plurality of optical fibers, and to a system that uses two such devices to produce a free-space propagation region within a fiber optic network.
One embodiment of the invention is a device that permits two-way coupling between a free-space optical component and a plurality of fibers. The device includes an assembly couplable to the fibers receive light. The assembly includes a first focusing element positioned on a first optical axis to receive output light beams from the optical fibers, where the first focusing element has a first focusing power selected to direct the light beams to intersect the first optical axis at a first intersection position. A second focusing element is spaced apart from the first focusing element by a first separation distance along the first optical axis and positioned to receive the light beams from the first focusing element, the second focusing element having a second focusing power, the first separation distance being selected to parallelize the light beams received from the first focusing element. The assembly may be provided with pig-tailed fibers.
Another embodiment of the invention is a system for providing access to light beams propagating through a plurality of fibers. The system includes first and second sets of optical fibers and two coupling modules coupled to a respective set of optical fibers. Each coupling module includes a first focusing element positioned on a module optical axis that is coupled to receive light beams from output ends of the respective set of optical fibers. The first focusing element has a first focusing power selected to direct the light beams to intersect the module optical axis. The coupling module also has a second focusing element spaced apart from the first focusing element by an interelement separation distance along the module optical axis and positioned to receive the light beams from the first focusing element. The second focusing element has a second focusing power and the interelement separation distance is selected to parallelize the light beams received from the first focusing element. The first and second coupling modules are relatively oriented to have opposing second focusing elements so that a beam path of at least one of the parallellized beams from the first coupling module lies coincident and antiparallel to a beam path of at least one of the parallelized beams from the second coupling module.
Another embodiment of the invention is a method of producing a set of parallel light beams from outputs from a first set of optical fibers. The method includes arranging output faces of the optical fibers relative to a first focusing element and directing, with the first focusing element, output light beams from the optical fibers to intersect a first optical axis. The method also includes parallelizing, with a second focusing element, the output light beams so that the light beams intersecting the first optical axis propagate in essentially parallel directions.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description which follow more particularly exemplify these embodiments.
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Lu Liang-Ju
Zhang B. Barry
ADC Telecommunications Inc.
Altera Law Group LLC
Palmer Phan T. H.
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