Optical: systems and elements – Light interference – Electrically or mechanically variable
Reexamination Certificate
2000-04-27
2001-09-04
Chang, Audrey (Department: 2872)
Optical: systems and elements
Light interference
Electrically or mechanically variable
C359S579000, C385S140000, C372S092000, C372S099000
Reexamination Certificate
active
06285504
ABSTRACT:
This invention relates to a variable optical filter that can be used to filter an incoming signal, attenuate an incoming signal or in one configuration switch an incoming signal from one path to another.
An optical attenuator that can serve as an optical switch is known, and is described in recently issued U.S. Pat. No. 6,031,946 in the name of Bergmann et al. assigned to Lucent Technologies. Bergmann et al. disclose a moving mirror that includes a focusing element adapted to focus an incoming beam transmitted from an input optical port, a movable mirror and an actuator. The actuator moves the mirror into two switching positions that correspond to pass-through and reflective switching states, or alternatively the actuator moves the mirror enough to achieve attenuation of the signal, thereby operating as a variable attenuator.
Another U.S. Pat. No. 5,915,063 in the name of Colbourne et al. assigned to JDS Uniphase, Inc. discloses a mirror supported by a movable flexure member that serves as a variable attenuator. The prongs of the flexure member are each connected to an actuator, which can expand or contract in response to a control signal applied thereto. The control signal may be heat, an electric field, a magnetic field or, preferably, a combination thereof. The attenuator is positioned opposite a pair of optical waveguides so that an input optical signal from an input waveguide is incident on the mirror and, upon reflection, is received by the second waveguide. Attenuation of the transmission is effected by controlled tilting of the mirror caused by appropriate control signals, single or in combination, applied to one or both of the actuators.
Although the device disclosed by Colbourne et al. achieves its intended function and is highly accurate, it is somewhat costly to produce, and through attempts to provide a low cost easy to manufacture device that could be made in a bulk fashion, the instant invention was conceived.
It is therefore an object of this invention to provide a low cost filter that in one embodiment can serve as an attenuator.
It is also an object of this invention to provide a low cost filter that will serve as a variable etalon or optical cavity having a variable or tunable output response.
It is further conceivable to use the filter as an optical switch, or multiplexor.
STATEMENT OF THE INVENTION
The present invention has found that an accurate and economical variable optical filter can be created by using an elastomeric material having a high coefficient of expansion in cooperation with a means for locally varying the temperature of the elastomeric material as an actuator for moving a reflective surface within the optical filter. The actuator can be operated in a controlled manner for example, to effect a tilt of the reflective surface for switching or attenuating an optical signal, or to vary the optical path length of a resonant cavity between partially reflective surfaces.
In accordance with the invention there is provided, a variable optical filter comprising: an input port and an output port;
a first at least partially reflective surface disposed to receive a beam of light launched from the input port;
an elastomeric material for supporting and varying the position of the at least partially reflective surface with respect to the input port;
a heater for applying variable amounts of heat to the elastomeric material to move or pivot the at least partially reflective surface relative to the input port; and,
control means for controlling the heater and for providing a signal to apply variable amounts of heat.
In accordance with the invention there is further provided, an optical filter for varying a beam of light launched therein, comprising:
a fixed input port for receiving the beam of light;
an at least partially reflective surface positioned by an elastomeric material in a first position with respect to the fixed input port to receive light therefrom, the elastomeric material having a coefficient of thermal expansion that is at least (200×10 exp-6)/K, and, means for locally controllably varying the temperature of at least a portion of the elastomeric material to relatively vary the position of the at least partially reflective surface with respect to the fixed input port.
In accordance with the invention, there is yet further provided, an optical filter for varying a beam of light launched therein, comprising:
a fixed input port for receiving a beam of light;
first and second spaced at least partially reflective surfaces disposed to form a resonant cavity having an input port and an output port and having a first set of resonant wavelengths when the surfaces are in a first position, the reflective surfaces being spaced by a spacer element comprising an elastomeric material, the elastomeric material having a coefficient of thermal expansion that is sufficient to vary the optical pathlength of the filter and,
means for locally controllably varying the temperature of at least a portion of the elastomeric material to selectively vary the optical pathlength of the of the resonant cavity by moving at least one of the first and the second surfaces to a second position having a second set of resonant wavelengths.
Advantageously, filters in accordance with the present invention can be more simply manufactured with very accurate control.
It should be understood that within this specification, the term “filter” used in accordance with this invention is meant to encompass at least, an attenuating filter, a multiplexing filter, a periodic filter and, or, a switching filter.
REFERENCES:
patent: 3546620 (1970-12-01), Erickson et al.
patent: 3666351 (1972-05-01), Pao
patent: 3740144 (1973-06-01), Walker
patent: 3802775 (1974-04-01), Hughes
patent: 5212584 (1993-05-01), Chung
patent: 5781332 (1998-07-01), Ogata
patent: 5915063 (1999-06-01), Colbourne et al.
Chang Audrey
Greene Kevin E.
JDS Uniphase Inc.
Lacasse Randy W.
Lacasse & Associates
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