Variable optical attenuator

Details Variable optical attenuator Variable optical attenuator

2001-12-27

2003-09-02

Kim, Robert H. (Department: 2882)

Optical waveguides

Accessories

Attenuator

Reexamination Certificate

active

06614983

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to variable optical attenuators, and particularly to a variable optical attenuator which can precisely control the amount of optical attenuation.
2. Description of Prior Art
Attenuators are widely used in optical transmission systems for reducing high power transmission signals to acceptable signals for application in a variety of optical apparatuses.
FIG. 1
shows a variable optical attenuator as disclosed in U.S. Pat. No. 4,989,938. The variable optical attenuator
100
comprises a housing
150
containing a first optical fiber connector
140
, a first optical lens
160
, a first connecting optical fiber
180
, a second optical lens
200
separated from the first optical lens
160
by an optical coupling space, a second optical fiber connector
220
, a second connecting optical fiber
240
, an optical filter
260
and a reciprocating means
280
. The optical filter
260
is a flexible film having an optical density gradient which varies along a length of the filter
260
. The filter
260
is preferably mounted substantially orthogonally to an optical axis of the optical coupling space.
When the filter
260
is moved vertically, a part of the filter
260
having a different optical density is put in a path of light passing through the optical coupling space. The filter
260
can thus control transmission and absorption of differing amounts of light. By varying the vertical position of the filter
260
, the degree of light attenuation provided by the filter
260
can be varied. Nevertheless, it is difficult and expensive to manufacture the filter
260
to attain the necessary optical density gradient.
Thus, it is desired to provide a variable optical attenuator which is inexpensive to manufacture and which can precisely control the amount of optical attenuation.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a variable optical attenuator which has low manufacturing cost.
Another object of the present invention is to provide a variable optical attenuator which can precisely control the degree of optical attenuation.
To achieve the above objects, a variable optical attenuator of the present invention comprises a base, a cover, an attenuation device and optical fibers. The attenuation device comprises a fixed collimator, a movable collimator, a holding device and an adjusting device. The two collimators are aligned end-to-end. The holding device defines a passage in which the movable collimator is retained, and a threaded hole. The adjusting device comprises a first screw rod, a second screw rod, and a rubber ring. The first screw rod comprises a thread portion, a gear, and a round head. The thread portion of the first screw rod is rotatably engaged in the threaded hole of the holding device. The second screw rod comprises a thread portion and an adjusting slot defined in a top face of the second screw rod. The thread portion of the second screw rod meshes with the gear of the first screw rod.
When the second screw rod is rotated via the adjusting slot, the thread portion of the second screw rod drives the gear to rotate the first screw rod, and the first screw rod rotatingly drives the holding device to move toward the head or away from the head. Thus an offset, if any, between the two collimators can be adjusted. Accordingly, an amount of optical attenuation of the attenuator can be precisely controlled via the two screw rods.
Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of the preferred embodiment of the present invention with attached drawings, in which:


REFERENCES:
patent: 4989938 (1991-02-01), Tamulevich
patent: 5087122 (1992-02-01), Ostrander et al.
patent: 6483982 (2002-11-01), Takahashi

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