Optical waveguides – Accessories – Attenuator
Reexamination Certificate
1999-11-17
2001-10-30
Bovernick, Rodney (Department: 2874)
Optical waveguides
Accessories
Attenuator
C385S060000, C385S058000, C385S055000, C385S070000, C385S072000
Reexamination Certificate
active
06311010
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to attenuators for use in fiber optic communication systems, and more particularly, fiber optic attenuators that allow the amount of fiber optic power in a fiber optic transmission to be adjusted incident to a change in amplitude of the transmission signal.
BACKGROUND OF THE INVENTION
As background, optical fiber attenuators are used for optical signal-power reduction mainly in short distance telecommunication links and in long distance trunk lines with signal repeaters having a fixed amplification. Whenever the optical signal power is higher than the range of the detectors, the optical signal needs to be lowered. Lowering the signal is accomplished by an attenuator.
While there are a variety of different attenuators, the present invention relates to a mechanical attenuator. Fiber can be attenuated mechanically in several ways. One method of attenuation is attained through bending or bundling of the fiber as illustrated in Smith U.S. Pat. No. 5,677,977 and Slaney et al. U.S. Pat. No. 5,684,912, thereby distorting the fiber and causing optical loss through the fibers. Another method of attenuation involves distorting the diameter of the fiber by heating the fiber and then compressing or pulling the cable to change its diameter, as disclosed in Takahashi et al. U.S. Pat. No. 5,321,790. Yet another method of attenuation involves axially aligning two fibers with a gap between the ends of the fibers. Air between the gap can then be used to attenuate, or the gap can be filled with a density filter or film type optical attenuator as disclosed in Serafini et al. U.S. Pat. Nos. 5,706,379 and 5,805,760.
The mechanical attenuator of the present invention is an attenuator that utilizes an air gap between the end of two fibers to attenuate the transmission signal. Typically, an attenuator having an air gap between the fiber attenuates in one of three ways. The first type of attenuation is transverse attenuation and occurs by offsetting the axes of the fiber such that the axes of the fiber remain parallel to one another. The second type of attenuation is angular attenuation, which occurs by varying the angle of the end of the fibers relative to one another. Finally, the third type of attenuation is longitudinal attenuation, which is achieved by varying the distance of the gap between the ends of two axially aligned fibers.
In the prior art, those attenuators that teach variable attenuation through angular attenuation typically angle the ends of the axially aligned cables at a fixed distance apart, as shown in
FIGS. 1 and 2
, and rotate one fiber relative to the other to vary the amount of attenuation. When one end fiber is rotated relative to the other, the opposing tangent planes of the ends of the fibers move from being generally parallel to one another to being offset by as much as 20 to 40 degrees. Thus, the attenuation can be increased and decreased by simply turning one ferrule relative to another.
The prior art attenuators that teach angular attenuation also teach the rotation between the fibers to be adjustable between 0 to 180 degrees.
FIG. 1
illustrates a prior art attenuator in its resting position, with no rotation between the fibers. In contrast,
FIG. 2
illustrates a prior art attenuator with 180 degree rotation between the fibers. Rotation between the fibers allows for an increase in attenuation as the fiber is rotated in one direction and a decrease in attenuation when the fiber is rotated in the opposing direction. By only allowing for an increase in attenuation in one direction, a field technician must, for each attenuator he encounters, determine which direction (clockwise or counterclockwise) provides an increase in attenuation and which provides a decrease.
To improve upon the prior art, the present invention provides for the 360 degree rotation of one fiber end
28
relative to the other (FIG.
3
). Unrestricted rotation of the ferrule
28
allows the optical signal to be both increased and decreased by rotating the first housing
12
in only one direction. Additionally, to achieve further variation in the amount of attenuation, in one embodiment of the present invention, the predetermined distance between the ferrules
28
can be varied by changing the interior alignment of the first housing member relative to the second housing member.
SUMMARY OF THE INVENTION
Accordingly, the principal object of the present invention is to provide a mechanical attenuator that allows for the 360 degree rotation of one fiber end relative to the other, such that the optical signal can be both increased and decreased by rotating one end of the fiber in only one direction, either clockwise or counter-clockwise. Yet another object of the present invention is to provide a variable optical attenuator that not only allows for the unrestricted rotation of one end of a fiber relative to the other, but also allows one to adjust the amount of longitudinal attenuation by varying the distance between the ends of the two aligned fibers.
To achieve these objectives, the variable optical attenuator of the present invention is comprised of a first aluminum housing and second aluminum housing. The first aluminum housing interlocks with the second aluminum housing such that the first housing is able to rotate both clockwise and counterclockwise 360 degrees relative to the second housing without any movement between the housings and along the x-axis. Additionally, in the preferred embodiment, the first housing member of the present invention has exterior rings that align with interior grooves of the second housing member. Thus, the distance between the end of the fibers can be varied by securing the exterior circular rings on the first housing with different interior grooves on the second housing.
These and other objects and advantages of the present invention will be clarified in the following description of the preferred embodiment in connection with the drawings, the disclosure and the appended claims, wherein like reference numerals represent like elements throughout.
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Bovernick Rodney
Pak Sung
Sonnenschein Nath & Rosenthal
Telephone Services, Inc. of Florida
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