Optical waveguides – Accessories – Attenuator
Reexamination Certificate
1999-03-16
2001-10-09
Spyrou, Cassandra (Department: 2872)
Optical waveguides
Accessories
Attenuator
C385S032000
Reexamination Certificate
active
06301426
ABSTRACT:
TECHNICAL FIELD
The present invention relates to adjustable attenuators and adjustable attenuation systems for attenuating optical energy transmitted through a fiber optic.
BACKGROUND OF THE INVENTION
There is often a requirement in fiber optic system design for precise control of the optical signal levels entering various system components. This is particularly true when a deployed fiber optic system requires tailoring for optimum performance as a final stage. An adjustable attenuator, which is set at a desired level of attenuation and remains stable with time, temperature, etc. is an important part of this tailoring stage.
The majority of fiber optic adjustable attenuator devices currently commercially available rely on controlled air gaps between polished fibers. The attenuation level is adjusted by mechanically separating the fiber ends, and reducing the fraction of light captured by the pick-up fiber. Certain steps must be taken to provide acceptable levels of back-reflected light and avoid in-line etalon affects due to reflections from the polished fiber ends. Often this requires anti-reflection coatings or angle-polishing of the fiber ends that add to the cost and fabrication complexity of the device.
Therefore, there is a need for a fiber optic adjustable attenuator device architecture that keeps the optical fiber core intact and adjusts attenuation by selectively inserting a glass preform of desired dimensions and refractive index into an evanescent field of, e.g., a side-polished fiber.
SUMMARY OF THE INVENTION
The shortcomings of the prior approaches are overcome, and additional advantages are provided, by the present invention, which in one aspect relates to an attenuator for attenuating optical energy transmitted through a portion of a fiber optic. The portion of the fiber optic has an exposed side surface through which at least some of the optical energy can be adjustably extracted. A refractive index medium preform is selectively engageable with the exposed surface for adjustably extracting the optical energy.
In another aspect of the present invention, the preform adjustably extracts optical energy in response to an adjustable force applied to the preform. For example, an actuator may be operably attached for selectively engaging the preform with the exposed surface. Desirably, the actuator is responsive to an output of the attenuator.
In another aspect of the present invention the preform may include a curve-shaped surface, e.g., cylindrical-shaped surface, tangentially engageable with the exposed surface. Desirably, the attenuator includes an actuator for selectively rocking the preform to vary the engagement between the preform and the exposed surface. Advantageously, the actuator may include an elongated flexible beam attached to the preform so that the elongated beam has a first portion which extends from the preform and a second portion which extends from the preform, and a first set screw and a second set screw for engaging the first portion and the second portion of the beam, respectively.
In another aspect of the present invention, a method for attenuating optical energy transmitted in a fiber optic includes the steps of providing a portion of the fiber optic through which the optical energy is transmitted, having an exposed side surface through which at least some of the optical energy can be controllably extracted, and selectively engaging a refractive index medium preform with the exposed surface to adjustably extract the optical energy.
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Jameson Gary O.
McCallion Kevin J.
Cherry Euncha
Heslin Rothenberg Farley & & Mesiti P.C.
Molecular OptoElectronics Corporation
Radigan, Esq. Kevin P.
Spyrou Cassandra
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