Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2001-06-19
2004-10-19
Font, Frank G. (Department: 2877)
Optical waveguides
With optical coupler
Switch
Reexamination Certificate
active
06807332
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates generally to optical signal switching, and more particularly to a piezoelectric actuated device for switching an optical signal.
2. Description of the Prior Art
Optical data transmission offers many advantages over electrical and broadcast transmission, however, switching optical data from one channel to another has proven to be problematic. Fundamentally, a beam of light is unaffected by passage through an electric or magnetic gradient, thus the usual solid-state methods for switching electric signals are not effective to switch optical signals. Accordingly, various mechanical techniques relying typically on reflection or refraction have been developed to divert optical signals.
FIG. 1
is a schematic diagram of an optical switching array
10
of the prior art. The switching array includes input ports
12
and output ports
14
arranged in columns and rows. To switch an optical signal from the first input port
12
to the output port
14
fourth from the left in the drawing, a diverter
18
located at a point of intersection between the axes of the two ports
12
and
14
, diverts the beam from the input port
12
to the output port
14
. The diverter
18
can be a mirror, a light pipe, a refractive medium, or the like. Most diverters
18
require a form of actuation to move them into or out of the path of a light beam.
FIG. 2
shows a diverter
20
of the prior art. The diverter
20
is supported within a frame
22
by support members
24
, typically arranged in pairs on orthogonal axes as shown. The diverter
20
, frame
22
, and support members
24
are typically all fabricated from a substrate of silicon. The support members
24
are made sufficiently thin so that the diverter
20
can be rotated within the frame
22
around axes defined by the support members
24
. The top surface of diverter
20
is made highly reflective, sometimes by applying a coating, so that light can be reflected with the lowest possible loss of signal strength.
FIG. 2
illustrates that as the diverter
20
is rotated simultaneously around both axes as shown, the top surface of the diverter
20
can be made to tilt in the direction
26
indicated. Accordingly, a light beam directed at diverter
20
can be reflected to any of a plurality of output ports
14
by appropriately tilting diverter
20
.
FIG. 3
shows a cross-section of the device in
FIG. 2
taken along the line indicated. The diverter
30
includes a base
32
suspended within frame
34
. The base
32
includes a reflective coating
36
. Between the frame
34
and the bottom of the base
32
is an interdigitated electrostatic actuator
37
comprising interdigitated fingers
38
and
39
of the base
32
and frame
34
, respectively. The interdigitated electrostatic actuator
37
is actuated by applying electric charges to surfaces of fingers
38
and
39
to cause them to attract or repel. The electric charges can be applied to specific fingers
38
and
39
, or to sets of fingers
38
and
39
, to modify how much force is applied, and in what direction, to control the induced tilting of base
32
.
Diverters
30
suffer several drawbacks, however. In addition to being expensive to produce, they are also sensitive to electrostatic discharges (ESD) and microcontamination. It will be readily appreciated that ESD can destroy the interdigitated electrostatic actuator
37
by melting or fusing fingers
38
and
39
. Similarly, microcontamination in the form of fine particles or surface films, for example, can mechanically jam the interdigitated electrostatic actuator
37
and prevent it from actuating. Microcontamination can also create an electrical short between fingers
38
and
39
, thereby preventing actuation.
A piezoelectric material is one that will develop an electric potential in response to mechanical deformation, and will mechanically deform in response to an applied electric potential. This is commonly known as the piezoelectric effect. Piezoelectric materials are used in a wide variety of applications including transducers, spark generators for butane lighters, and vibration damping.
Piezoelectric materials are typically either ceramic or polymeric. Common ceramic piezoelectric materials include quartz, cadmium sulphide, and titanate compounds such as barium titanate, lead titanate, and lead zirconium titanate (PZT). Common polymeric piezoelectric materials include polyvinylidene fluoride (PVDF), copolymers of vinylidene fluoride and trifluoroethylene (VDF/TrFE), copolymers of vinylidene fluoride and tetrafluoroethylene (VDF/TeFE), and copolymers of vinylidene cyanide and vinyl acetate (VDC/NA).
Accordingly, what is desired is an optical switching device that can redirect a beam of light between multiple ports and that is less susceptible to microcontamination and ESD failures, and that is readily fabricated according to developed microfabrication technologies.
SUMMARY
An optical switching component comprises a stator, a rotor pivotally connected to the stator and including a top surface, a first piezoelectric actuator coupled to the stator and the rotor and configured to pivot the rotor relative to the stator when actuated. Embodiments also can further comprise an optically reflective coating formed on the top surface, and a seed layer between the optically reflective coating and the top surface. Other embodiments further comprise additional piezoelectric actuators, such as two actuators connecting opposite ends of the rotor to the stator and configured to cooperatively pivot the rotor relative to the stator. Four actuators can also be employed where two of the four are configured to pivot the rotor relative to the stator around a first axis and the other two are configured to pivot the rotor around a second axis.
The use of piezoelectric actuators to translate the rotor relative to the stator is advantageous in that piezoelectric actuators are less prone to ESD damage than are electrostatic actuators. Further, when a voltage is applied across a piezoelectric material to create a certain strain, a relatively high amount of stress is developed. Thus, piezoelectric actuators are able to develop substantially more force to accelerate the mass of the rotor than can electrostatic actuators acting on diverters of the prior art. Accordingly, piezoelectric actuators can easily overcome the adhesive effects of microcontamination and thereby make the optical switching components of the present invention more tolerant of less clean environments.
Further embodiments of the optical switching component additionally comprise a controller in communication with the piezoelectric actuator. The controller is capable of applying a voltage to the actuator to cause it to expand or contract along an axis in response to an instruction to switch a beam. In so doing, the controller drives the actuator to orient the top surface of the rotor such that an angle of incidence of a emitted beam from a first port is substantially equal to an angle of reflectance of a reflected beam received by a second port. Further embodiments also comprise a detector in communication with the controller and capable of determining a signal strength of the reflected beam at the second port, the controller being capable of using the output of the detector as part of a feed-back loop in order to optimize the signal strength of the reflected beam at the second port.
The present invention also includes an optical switching device comprising an optical switching component, as provided above, and further comprising an emitter port and a receiver port. The emitter port defines a first line within a plane and is fixed proximate to the optical switching component such that the first line intersects the top surface at about a center thereof to define an angle of incidence between the first line and the top surface. Likewise, the receiver port defines a second line within the plane and is fixed proximate to the optical switching component such that the second line intersects the top surface at about the same point as th
Carr & Ferrell LLP
Font Frank G.
Kianni Kevin
Western Digital (Fremont) Inc.
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