Optical: systems and elements – Light interference – Electrically or mechanically variable
Reexamination Certificate
2000-12-29
2003-07-15
Chang, Audrey (Department: 2872)
Optical: systems and elements
Light interference
Electrically or mechanically variable
C359S579000, C359S892000, C359S889000, C385S037000, C372S020000
Reexamination Certificate
active
06594081
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Co-pending U.S. patent applications, Ser. No. 09/648,525, entitled “Optical Filter Having A Shaped Filter Function”, fled Aug. 26, 2000; and co-pending U.S. patent applications, Ser. No. 09/648,524, entitled “Wide Range Tunable Optical Filter”, filed contemporaneously; contain subject matter related to that disclosed herein, and which are incorporated herein by reference in their entirety.
TECHNICAL FIELD
The present invention relates to an actuator mechanism for a tunable optical device, and more particularly to an actuator mechanism for straining an optical waveguide having at least one reflective element, such as Bragg grating, to tune the Bragg grating to a desired reflection wavelength.
BACKGROUND ART
The telecommunication industry is turning towards optical networks to provide higher capacity (bandwidth) of data transfer for new applications. Consequently, the industry is continually developing technology to increase the bandwidth of the optical networks, which includes the technology of wavelength division multiplexing (WDM). A number of optical signals can be carried simultaneously on the optical fiber by modulating each signal on a different wavelength of light. The light propagating through a single optical fiber therefore includes a plurality of wavelength bands, referred to as channels, wherein each channel or wavelength band is centered at a reflection wavelength. The wavelength bands are sufficiently separated so that they do not overlap. Typically, networks that carry about eight channels or more are referred to as dense wavelength division multiplexing (DWDM) systems; such systems can carry greater than 200 channels.
The technology of optical networks is heading toward a more dynamic, flexible, and intelligent networking architecture to improve service delivery time. A key element of the emerging optical network is a tunable optical filter for selectively filtering a channel from the DWDM light propagating through the optical network. The tunable channel filter enables a channel to be dynamically switched, routed, monitored and conditioned.
It is known in the art of optical networks that Bragg gratings written in an optical fiber may be used to act as a tunable filter, as is described in U.S. Pat. No. 5,007,705, entitled “Variable Optical Fiber Bragg Filter Arrangement; U.S. Pat. No. 5,579,143, entitled “Optical System With Tunable In-Fiber Gratings”, U.S. Pat. No. 5,815,299, entitled “Method and System for Equalizing Respective Power Levels of Channels of a Received Optical Frequency Division Multiplexed Signal”; and U.S. Pat. No. 5,995,255, entitled “Concatenated Fiber Grating Optical Monitor”.
The tunable optical filters described in the aforementioned U.S. Pat. Nos. 5,007,705 and 5,579,143 tune a Bragg grating written in an optical fiber by stretching the fiber in the region of the Bragg grating using a number of different mechanical means. It is known to use a motorized actuator and mechanical arrangement to stretch the fiber. The optical filters require accurate and repeatable tuning of the Bragg grating to set its reflection wavelength within picometers of the desired wavelength. However, inherent in these mechanical arrangements are problems or unpredictable inaccuracies in the movement of the components of the actuator, such as stiction, wear, backlash, creep, slip and general looseness between the components. Consequently, it would be advantageous to provide an actuator mechanism for tuning an optical device that compensates or reduces the effects of the inherent problems of the mechanical arrangements to tune a Bragg grating.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an actuator mechanism for tuning an optical device that reduces the effects of stiction, backlash, wear, inaccuracies and looseness of the actuator mechanism for tuning the optical device.
In accordance with an embodiment of the present invention, an actuation mechanism for tuning an optical filter comprises a slide for translating between a first and second position in a direction of translation. The slide has an engagement surface wherein the engagement surface is sloped relative to the direction of translation. A drive mechanism is coupled to the slide for translating the slide between the first and second position in response to a drive signal. A displacement arm has a first end and a second end, wherein one portion of the second end engages the engagement surface of the slide, and another portion of the second end engages the optical filter. The translation of the slide between the first and second position displaces another portion of the second end of the displacement arm in a direction of displacement to tune the optical filter.
In accordance with another embodiment of the present invention, a tunable optical filter comprises a tunable optical filter unit and an actuator mechanism. The optical filter receiving an optical input light comprising a plurality of optical channels. The optical filter includes an optical waveguide having at least one reflection element for reflecting at least one channel and passing the remaining channels. The actuator mechanism strains the optical waveguide to reflect the desired at least one channel. The actuator mechanism comprises a slide for translating between a first and second position in a direction of translation. The slide has an engagement surface wherein the engagement surface is sloped relative to the direction of translation. A drive mechanism is coupled to the slide for translating the slide between the first and second position in response to a drive signal. A displacement arm has a first end and a second end. One portion of the second end engages the engagement surface of the slide, and another portion of the second end engages the optical filter. The translation of the slide between the first and second position displaces another portion of the second end of the displacement arm in a direction of displacement to strain the optical waveguide.
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Engel Thomas W.
Sullivan James M.
Chang Audrey
CiDRA Corporation
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