U.S. patent application number 10/903209 was filed with the patent office on 2005-01-06 for photonic switching apparatus for optical communication network.
This patent application is currently assigned to Lightbay Networks Corporation. Invention is credited to Hatam-Tabrizi, Shahab, Kiadeh, Mansur Bashardoust, Yeh, Wei-Hung.
Application Number | 20050002602 10/903209 |
Document ID | / |
Family ID | 26866930 |
Filed Date | 2005-01-06 |
United States Patent
Application |
20050002602 |
Kind Code |
A1 |
Hatam-Tabrizi, Shahab ; et
al. |
January 6, 2005 |
Photonic switching apparatus for optical communication network
Abstract
A photonic switch for an optical communication network includes
a matrix of actuator-mirror assemblies and a corresponding matrix
of optical ports. A first one of the actuator-mirror assemblies
directs a beam of light received from an input optical port to a
reference mirror, where it is reflected to a second actuator-mirror
assembly that redirects the beam to an output optical port. Each of
the actuator-mirror assemblies includes a mirror-coil assembly
mounted to a gimbal, with stationary magnets being positioned
adjacent a corresponding one of the coils such that when current
flows through the coils a force is generated that causes the
mirror-coil assembly to tilt. It is emphasized that this abstract
is provided to comply with the rules requiring an abstract that
will allow a searcher or other reader to quickly ascertain the
subject matter of the technical disclosure. It is submitted with
the understanding that it will not be used to interpret or limit
the scope or meaning of the claims. 37 CFR 1.72(b).
Inventors: |
Hatam-Tabrizi, Shahab; (San
Jose, CA) ; Kiadeh, Mansur Bashardoust; (Cupertino,
CA) ; Yeh, Wei-Hung; (Fremont, CA) |
Correspondence
Address: |
BURGESS & BEREZNAK LLP
800 WEST EL CAMINO REAL
SUITE 180
MOUNTAIN VIEW
CA
94040
US
|
Assignee: |
Lightbay Networks
Corporation
Fremont
CA
|
Family ID: |
26866930 |
Appl. No.: |
10/903209 |
Filed: |
July 29, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10903209 |
Jul 29, 2004 |
|
|
|
10171298 |
Jun 13, 2002 |
|
|
|
6813406 |
|
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|
60298488 |
Jun 14, 2001 |
|
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Current U.S.
Class: |
385/17 ;
385/18 |
Current CPC
Class: |
G02B 6/4225 20130101;
G02B 6/4227 20130101; G02B 6/3572 20130101; G02B 6/3556 20130101;
G02B 26/085 20130101; G02B 6/359 20130101; G02B 6/4226 20130101;
G02B 6/3512 20130101 |
Class at
Publication: |
385/017 ;
385/018 |
International
Class: |
G02B 006/26 |
Claims
1-22. (cancelled)
23. A photonic switch for an optical communication network,
comprising: a first matrix of actuator-mirror assemblies; a first
array of optical ports, each of which is aligned to a corresponding
one of the actuator-mirror assemblies of the first matrix; a second
matrix of actuator-mirror assemblies; a second array of optical
ports, each of which is aligned to a corresponding one of the
actuator-mirror assemblies of the second matrix; the
actuator-mirror assemblies of the first and second matrixes each
comprising: a gimbal; a mirror mounted to the gimbal; a plurality
of coils, each of the coils being fixedly attached to the mirror; a
plurality of magnets, each magnet being positioned adjacent a
corresponding one of the coils such that when current flows through
the coils a force is generated that causes the mirror to tilt; and
wherein each actuator-mirror assembly of the first matrix functions
to direct a beam of light received from an input optical port of
the first array to a target actuator-mirror assembly of the second
matrix, the target actuator-mirror assembly functioning to redirect
the beam of light to an output optical port of the second
array.
24. The photonic switch according to claim 23 wherein each of the
optical ports comprises an optical fiber coupler and a lens.
25. The photonic switch according to claim 23 further comprising an
intensity monitoring loop that includes a photodiode to detect a
portion of the beam of light, and an optical fiber coupler having a
first end connected to an optical fiber and a second end connected
to the photodiode.
26. The photonic switch according to claim 23 further comprising
control circuitry for controlling the movement of the
actuator-mirror assemblies.
27. The photonic switch according to claim 26 wherein at least a
portion of the control circuitry is located behind the
actuator-mirror assemblies.
28. (cancelled)
29. The photonic switch according to claim 26 wherein the control
circuitry comprises an open loop control system, which includes a
compensation algorithm that functions to maintain a maximum
intensity of the beam of light between the input and output optical
ports.
30. A photonic switch comprising: first and second matrixes of
actuator-mirror assemblies, the actuator-mirror assemblies each
including: a gimbal of two or more of pieces of material that
provides at least one electrically conductive path; a mirror
mounted to the gimbal; at least one coil fixedly attached to the
mirror and having wires coupled to the gimbal such that current
through the at least one coil flows through the at least one
electrically conductive path; one or more magnets positioned
adjacent the at least one coil such that when current flows through
the at least one coil a force is generated that causes the mirror
to tilt, such that each actuator-mirror assembly of the first
matrix directs an input beam of light to a target actuator-mirror
assembly of the second matrix.
31. The photonic switch according to claim 30 wherein the two or
more pieces of material comprise a metal.
32. The photonic switch according to claim 30 wherein the
conductive path is integral with the two or more pieces of
material.
33. The photonic switch according to claim 30 wherein the at least
one coil is to a back side of the mirror.
34. A photonic switch comprising: a plurality of input optical
ports; a plurality of output optical ports; a first plurality of
actuator-mirror assemblies positioned in alignment with the input
optical ports; a second plurality of actuator-mirror assemblies
positioned in alignment with the output optical ports; wherein the
actuator-mirror assemblies each include: a mirror; a gimbal of two
or more pieces of substantially planar conductive material that
support the mirror; at least one coil mounted to the mirror and
having wires coupled to the gimbal such that current through the at
least one coil flows through the conductive material of the gimbal,
current flow through the at least one coil in the presence of a
magnetic field causing the mirror to tilt; one or more magnets
positioned adjacent the at least one coil; and wherein light beams
received from the input optical ports are directed by the first
plurality of actuator-mirror assemblies to the second plurality of
actuator-mirror assemblies, the second plurality of actuator-mirror
assemblies redirecting the light beams to the output optical
ports.
35. The photonic switch according to claim 34 further comprising a
mount, and wherein the gimbal comprises first and second beams,
each having a first end attached to the mirror and a second end
attached to the mount.
36. The photonic switch according to claim 34 wherein the at least
one coil is mounted to a back side of the mirror.
Description
RELATED APPLICATIONS
[0001] This application is related to co-pending applications: Ser.
No. ______, filed ______, entitled, "GIMBAL FOR SUPPORTING A
MOVEABLE MIRROR"; and Ser. No. ______, filed ______, entitled,
"ACTUATOR ASSEMBLY FOR TILTING A MIRROR OR LIKE OBJECT", both of
which are assigned to the assignee of the present application.
FIELD OF THE INVENTION
[0002] The present invention relates generally to apparatus and
methods for movement of objects; specifically, objects such as
mirrors that direct light beams in optical systems and
networks.
BACKGROUND OF THE INVENTION
[0003] Fiberoptic technologies and systems have been widely
deployed in recent decades. However, certain key components remain
expensive and inefficient, which hinders the expansion of optical
systems and optical communication networks. One of these components
is the wavelength switch, which routes and redirects a light beam
from one fiber to another fiber so that the signal can be
provisioned and managed according to the demand. A typical
wavelength switch used today converts the input light signal into
an electronic signal to detect the routing information, switches
the electronic signal, and then eventually reconverts it back into
a light signal for further transmission. This device, commonly
referred to as an Optical-Electrical-Optical (OEO) switch, not only
depends on current semiconductor technologies and processes, but
also requires a transmitter and a receiver for each transmission
port. These factors cause OEO switches to be large in size (e.g.,
occupying two or more 7-foot tall racks), to have high power
consumption (e.g., kilowatts), to be network protocol and
transmission rate dependent, to lack scalability, and to be
costly.
[0004] Thus, there is a need for an alternative apparatus for
directing a light beam in an optical system that can be
manufactured efficiently and provide improved performance in
optical systems and fiber optic-based networks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The present invention will be understood more fully from the
detailed description that follows and from the accompanying
drawings, which however, should not be taken to limit the invention
to the specific embodiments shown, but are for explanation and
understanding only.
[0006] FIG. 1 is a top perspective view of an actuator-mirror
matrix assembly in accordance with one embodiment of the present
invention.
[0007] FIG. 2 is a perspective view of an actuator-mirror matrix
assembly in accordance with an embodiment of the present
invention.
[0008] FIG. 3 is a perspective view of an actuator-mirror bar
assembly in accordance with one embodiment of the present
invention.
[0009] FIGS. 4A & 4B are top views of a gimbal used in
accordance with one embodiment of the present invention.
[0010] FIG. 5 illustrates a platform that mounts to the gimbal of
FIGS. 4A & 4B in an actuator-mirror assembly according to one
embodiment of the present invention.
[0011] FIG. 6 is a bottom perspective view of an integrated
mirror/pedestal 210 utilized in accordance with one embodiment of
the present invention.
[0012] FIG. 7 illustrates an actuator-mirror assembly at an
intermediate point of construction according to one embodiment of
the present invention.
[0013] FIG. 8 illustrates an actuator-mirror assembly at a further
point of construction according to one embodiment of the present
invention.
[0014] FIG. 9 is a perspective view of an actuator-mirror assembly
according to another embodiment of the present invention.
[0015] FIGS. 10A & 10B are top and side views of a
magnet-housing arrangement for an actuator-mirror assembly in
accordance with one embodiment of the present invention.
[0016] FIG. 11 is a top view of a magnet-housing arrangement for an
actuator-mirror assembly in accordance with another embodiment of
the present invention
[0017] FIG. 12 is a cross-sectional side view of an actuator-mirror
assembly according to one embodiment of the present invention.
[0018] FIGS. 13A & 13B are cross-sectional side views of an
actuator-mirror assembly tilted in two different directions in
accordance with one embodiment of the present invention.
[0019] FIGS. 14A & 14B show top and side views of a bobbin coil
assembly utilized in accordance with an alternative embodiment of
the present invention.
[0020] FIG. 15 illustrates the relative position of a coil and
magnet assembly in accordance with one embodiment of the present
invention.
[0021] FIG. 16 is a top view of a gimbal utilized in accordance
with an alternative embodiment of the present invention
[0022] FIG. 17 is an exploded side view of a portion of the
exemplary actuator-mirror matrix assembly of FIG. 2.
[0023] FIG. 18 is a cross-sectional side view of an actuator-mirror
assembly in accordance with an alternative embodiment of the
present invention.
[0024] FIG. 19 illustrates a photonic switch module in accordance
with one embodiment of the present invention.
[0025] FIG. 20 is a block diagram of an open loop control system
for positioning a mirror of a photonic switch in accordance with
one embodiment of the present invention.
[0026] FIG. 21 is a block diagram of an open loop control system
for positioning a mirror of a photonic switch in accordance with
another embodiment of the present invention.
[0027] FIG. 22 is a high-level block diagram is an example of an
electronics circuit that may be used for control of a photonic
switch according to the present invention.
[0028] FIG. 23 is a block diagram of the control electronics
utilized in a photonic switch according to another embodiment of
the present invention.
[0029] FIG. 24 is a functional circuit diagram for a 256.times.256
switch fabric according to one embodiment of the present
invention.
[0030] FIG. 25 shows the hardware configuration for a
1024.times.1024 switch fabric according to one embodiment of the
present invention.
[0031] FIG. 26 illustrates an example of a folded large-matrix
photonic switch layout in accordance with one embodiment of the
present invention.
[0032] FIG. 27 is a plot that depicts the effect of pre-filter on
an input profile signal used to position a mirror in accordance
with one embodiment of the present invention.
DETAILED DESCRIPTION
[0033] A photonic switch for use in an optical communication
network is described. In the following description numerous
specific details are set forth, such as angles, material types,
configurations, etc., in order to provide a thorough understanding
of the present invention. However, persons having ordinary skill in
the opto-electronics arts will appreciate that these specific
details may not be needed to practice the present invention.
[0034] According to one embodiment of the present invention, a
photonic switch utilizing a tilting actuator-mirror assembly is
provided to control the path of a light beam for use in a fiber
optic communication network (e.g., an all-optical switch). The
present invention also has numerous other consumer, medical, and/or
industrial applications. For example, laser marking, optical
scanning devices, windshield auto projection, helmet display,
personal digital assistant ("PDA") and mobile phone projection
display, to name a few, can all benefit from the present
invention.
[0035] In another embodiment of the present invention, in an
optical switch light is guided by a fiber through a collimator,
which forms the divergent light rays into a round beam having a
specific beam width, onto a first mirror. The first mirror is part
of an actuator-mirror assembly that can be tilted to reflect the
light beam onto a second mirror. The second mirror is also part of
an actuator-mirror assembly that is used to tilt the mirror along x
and y-axes. A plurality of actuator-mirror assemblies is arranged
in a matrix in which rows or columns of actuator-mirror assemblies
are attached to one or more connector bars. The number of
actuator-mirror assemblies on a connector bar and the number of
bars per matrix depends on the particular application, for example,
the port count of a switch.
[0036] According to one embodiment, a photonic switch utilizing a
dual-axis tilting actuator is provided as a rotary moving coil
actuator suspended by a flexing, electrically conductive gimbal
component. The gimbal is comprised of a pair of beams that move
about the axis of rotation under the influence of an
electromagnetic actuator. The conductive connections in the rotary
moving coil actuator are integrated with the flexing part of the
gimbal. In various embodiments, the actuator may rotate about
either a single axis or a dual axis.
[0037] FIG. 1 is a perspective view of an actuator-mirror matrix
assembly 105 in accordance with one embodiment of the present
invention. By way of example, actuator-mirror matrix assembly 105
may be used as a photonic switch for fiber optic communication
applications. A photonic switch is typically used to provision the
path of light in a fiber optic communication network.
[0038] In the example of FIG. 1, assembly 105 includes
actuator-mirror bars (e.g., 101, 102, 103, etc.), each of which
comprises two rows of individual actuator-mirror assemblies (e.g.,
mirror assemblies 106-111, etc.). The actuator-mirror bars are
supported by a platform 104 that may also provide electrical
connection to the individual actuators. In the particular
embodiment shown, platform 104 comprises an aluminum block that
supports the bars and also facilitates connection of the bars to a
printed circuit board assembly. Matrix assembly 105 comprises six
actuator-mirror bars, with each of the bars including 2 rows of 12
mirror plates per row (2.times.12), for a total of 144 mirror
plates, which is sufficient to support a 72-port photonic switch.
Each of the individual actuator-mirror assemblies includes a mirror
plate that provides a highly reflective surface utilized to direct
a laser beam, or other light beam.
[0039] It is appreciated that the number of actuator-mirror
assemblies included on an actuator-mirror bar (i.e., the number of
rows and columns) may vary, depending, for example, upon the port
count of the photonic switch, or other system application.
[0040] FIG. 2 is a perspective view of an actuator-mirror matrix
assembly 120 in accordance with another embodiment of the present
invention. Individual actuator-mirror bars (125, 126, 127, etc.)
are shown mounted to a platform 124. Each bar supports two rows of
actuator-mirror assemblies (121, 122, 123, etc.). The reflective
surface of each mirror faces outward in the matrix assembly of FIG.
2. A printed circuit board assembly ("PCBA") 130 is coupled to the
underside of each of the bar assemblies 125, 126, 127, etc. to
drive and control the actuators. The PCBA includes current driver
integrated circuits ("IC's") and multiplexing circuitry that reduce
the number of pin connections between the actuator-mirror matrix
assembly 120 and a main PCB (not shown in this view). In the
example shown in FIG. 2, gaskets or some other seal or packing may
be included between the bars and the platform frame 124 to seal the
assembly.
[0041] FIG. 17 is an exploded side view of a portion (i.e., a
2.times.24 bar) of the exemplary actuator-mirror matrix assembly of
FIG. 2. Individual actuator-mirror assemblies (e.g., 330, 331, 332,
etc.) are shown attached to corresponding actuator flex circuits
(e.g., 333, 334, 335, etc.) The flex circuits provide electrical
connection to the coils housed in each individual actuator-mirror
assembly. The actuator-mirror assemblies and the actuator flex
circuits are shown comprising bar assembly 340. An actuator bar
connector 341 provides connection between the flex circuits of
actuator bar assembly 340 and a printed circuit board assembly
(PCBA) 345. The actuator bar flex circuit 341 includes a female pin
connector 342 and the PCBA 345 includes a male pin connector
343.
[0042] PCBA 345 contains a variety of circuits for driving and
controlling the actuator-mirror matrix assembly. Among the various
components included on PCBA 345 are current driver IC's and
multiplexing circuitry to reduce the number of pin connections
between the actuator mirror bar assembly 360 and a main controller
or main PCBA (not shown). PCBA 345 also contains a female pin
connector 344 for providing power and control signals to PCBA 345
from a main controller or main PCBA. In this example, the PCBA 350
is the same size as the bar. As is described herein, each
actuator-mirror assembly may include four coils, two of which are
connected in series. Therefore, two dedicated power drivers may be
used to drive each actuator-mirror assembly.
[0043] Referring now to FIG. 3 there is shown is a perspective view
of a single actuator-mirror bar assembly 140 (and platform portion
150) in accordance with one embodiment of the present invention.
Bar assembly 140 comprises a support bar 150 that supports two
columns (i.e., 141 & 142) by twenty-four rows of individual
actuator-mirror assemblies (143, 144, 145, etc.) for a total of
forty-eight actuator-mirror assemblies. The number of the
actuator-mirror assemblies and the number of bar assemblies per
matrix (shown in FIGS. 1 & 2) depend on the particular
application. For instance, if the actuator-mirror bar assembly 140
were to be used in an all-optical switch of a fiber communication
network, the number of actuator-mirror assemblies included on each
bar would depend on the port count of the switch.
[0044] Each of the actuator-mirror assemblies includes
subassemblies, such as a mirror-gimbal assembly. These
subassemblies may include the actuator wiring and the actuator
power drivers. In some applications, the actuator-mirror assemblies
may comprise rotary moving coil-object assemblies suspended by a
flexing gimbal component that allows the mobile coil-object
assembly to move in a desired manner.
[0045] Referring now to FIGS. 4A & 4B, there is shown a top
plan view of a gimbal 200 utilized in accordance with one
embodiment of the present invention. Gimbal 200 is made from a
single, integral sheet of thin metal. FIG. 4A shows gimbal 200
after removal of the "cutout" areas from the sheet metal. FIG. 4B
shows the gimbal after removal of the end section and perimeter
material, which step is performed during the construction of the
actuator-mirror assembly according to one embodiment of the present
invention.
[0046] The sheet metal used for gimbal 200 is preferably a fully
hardened material, such as stainless steel, having high fatigue
strength. Other materials providing similar properties may also be
used. The material selected should allow the gimbal to rotate the
attached mirror (or mirror-coil assembly) with a high rotational
angle (e.g., +/-15 degrees) over millions of movement cycles. The
material may also be heat-treated. The sheet metal material is also
preferably non-magnetic to prevent reluctance forces induced by the
magnets in the actuator. In some cases, the sheet metal may also be
coated with a corrosion-resistant material, such as titanium-nickel
or gold.
[0047] Gimbal 200 comprises four attachment pads 201-204 that are
centrally located symmetrical about the x-axis (i.e., longitudinal
axis) and y-axis (i.e., transverse axis). A mirror, or
mirror-pedestal assembly, is adhesively attached to pads 201-204.
Thus, in the completed assembly, pads 201-204 are all affixed in a
rigid plane, remaining stationary or moving in unison, depending on
the particular embodiment of the final actuator-mirror assembly.
Thin, elongated beams 191-194 support each of pads 201-204,
respectively. In operation, pairs of adjacent beams 191 & 192
and 193 & 194 each twist longitudinally about the x-axis to
permit the mirror (attached to pads 201-204) to rotate about the
x-axis.
[0048] In FIG. 4A, beams 191 & 192 are shown being integrally
connected to end section 251 through respective intermediate
sections 221 & 222. Similarly, beams 193 & 194 are
integrally connected to end section 253 through intermediate
sections 223 & 224, respectively. Intermediate sections 221-224
are also integrally connected with thin, elongated beams 195-198,
respectively, which permit rotation of the mirror about the y-axis.
During rotation of the mirror about the x-axis, pairs of adjacent
beams 195 & 196 and 197 & 198 remain substantially rigid.
Similarly, during rotation of the mirror about the y-axis, pairs of
adjacent beams 195 & 196 and 197 & 198 twist longitudinally
about the y-axis, while pairs of adjacent beams 191 & 192 and
193 & 194 remain substantially rigid.
[0049] Beams 195 & 196 are shown in FIG. 4A being connected to
end section 252 via respective L-shaped mounting sections 240 &
241. Likewise, beams 197 & 198 are both integrally connected to
end section 254 through respective L-shaped mounting sections 242
& 243. All of the end sections 251-254 are attached together
through a set of perimeter connecting sections 246-249. For
example, end section 251 attaches to end sections 252 & 254 via
connecting sections 246 & 249, respectively. End section 253
attaches to end sections 252 & 254 via connecting sections 247
& 248, respectively. In this embodiment, end sections 251-254
(beyond dashed lines 250 in FIG. 4A) are removed along with the
perimeter connecting sections during the assembly process. FIG. 4B
shows gimbal 200 after these metal sections have been removed. This
assembly process of this embodiment is described in more detail
below.
[0050] Each of the mounting sections 240-243 of gimbal 200 is
fixedly mounted (e.g., with adhesive) to a stationary point or
platform mount of the actuator-mirror assembly. FIG. 5 shows one
possible implementation of a platform 270 that may be used for this
purpose. Platform 270 comprises a base 271 that supports four rigid
posts 272-275 of equal height. Each of the posts 272-275 has a flat
end surface 282-285, respectively. The dimensions of end surfaces
282-285 and the position of posts 272-275 is such that end surfaces
282-285 align with the rectangular surface areas of mounting
sections 240-243 (see FIG. 4B) in a corresponding manner. This
permits the mounting sections 240-243 to be adhesively attached to
corresponding end surfaces 282-285.
[0051] FIG. 5 also shows a set of four thin wires 292-295, each of
which is adhesively bonded to respective posts of platform 282-285.
These wires connect with the coils that comprise the actuator of
the final assembly. Two of the wires are used to energize the coils
disposed about the x-axis, and the other two are used to energize
the coils disposed about the y-axis.
[0052] After gimbal 200 has been mounted to platform 270 each of
the wires 292-295 are soldered to corresponding tabs of the
mounting sections 240-243. For example, if surface 282 is attached
to mounting section 240, wire 292 may be soldered to tab 255.
Continuing with this example, with surfaces 283-285 respectively
attached to mounting sections 241-243, wires 293-295 may be
soldered to tabs 256-258, respectively. Note that in gimbal 200 of
FIG. 4B each of tabs 255-258 provides separate electrical
connection with respective pads 202, 203, 204, and 201. This
feature is utilized to establish electrical connection to the coils
of the actuator-mirror assembly, as discussed in more detail
shortly.
[0053] Metal may be removed from a single piece of thin sheet metal
to achieve the gimbal cutout patterns shown in FIGS. 4A & 4B
using a variety of conventional methods, such as chemical etching,
press cutting, milling, etc. Although a specific rectilinear cutout
pattern is shown in these figures, it is understood that other
embodiments may have different patterns or a different arrangement
of beams, pads, etc., yet still provide rotational movement along
the x and y axes in accordance with the present invention.
[0054] In the embodiment illustrated by FIGS. 4A & 4B, beams
191-198 are each about 0.05 mm wide, mirror-attachment pads 201-204
are each about 0.4 mm.times.0.6 mm in dimension, and the thickness
of the single piece of sheet metal is about 0.0254 mm. Wires
292-295 are also about 0.0254 mm thick. In certain embodiments,
beams 191-198 may be partially etched to make them thinner than the
rest of the sheet metal material. For example, beams 191-198 may be
chemically etched to a thickness less than 0.0254 mm to increase
flexibility and thus achieve a higher degree of rotation.
[0055] FIG. 6 is a bottom perspective view of an integrated
mirror/pedestal 210 utilized in accordance with one embodiment of
the present invention. In the drawing, the polished, reflective
surface of mirror 214 faces down and into the page. Integrated
mirror/pedestal 210 may be manufactured from a single piece of
material such as silicon, Pyrex.RTM., quartz, sapphire, aluminum,
or other types of suitable materials. Integrated mirror/pedestal
210 includes a pedestal portion 212 having a flat surface 211. The
length and width of surface 211 is such that it matches or fit
within the combined area of pads 201-204 (see FIG. 4B). During the
assembly process, surface 211 is adhesively bonded to one side of
pads 201-204.
[0056] Integrated mirror/pedestal 210 also includes a base plate
213 between pedestal portion 212 and the back of mirror 214. Base
plate is sized smaller than mirror 214 such that a step 216,
comprising a peripheral area of the back of mirror 213, is
realized. It is appreciated that other embodiments may be
constructed from discrete parts (e.g., separate mirror, base plate,
and pedestal) rather than being manufactured in integral form. In
either approach, the mirror may be about 0.25 mm thick and
2.times.2 mm in area. The mirror surface may be lapped to a highly
polished optical-flat surface. A reflective surface can also be
applied by numerous methods, including plating or sputtering gold,
silver, or aluminum on a layer of nickel.
[0057] FIG. 7 shows a bottom perspective view of an actuator-mirror
assembly after pads 201-204 have been bonded to surface 211 of
integrated mirror/pedestal 210. FIG. 7 also shows four coils
206-209 adhesively bonded to step 216 around the side back surface
of mirror 214. Thus, coils 206-209, mirror 214, and pads 201-204 of
gimbal 200 are all rigidly coupled together, and move as a single
unit, in the actuator-mirror assembly according to one embodiment
of the present invention. Note that although FIG. 7 shows the end
sections of gimbal 200 before removal at this stage of the assembly
process, this is not required. That is, the end and peripheral
connecting sections of gimbal 200 may be removed either before or
after attachment to the mirror/pedestal assembly.
[0058] FIG. 8 is another view of the assembly of FIG. 7 after
soldering of pairs of coil wires to the back of pads 201-204. (Note
that not all of the cutout portions of the gimbal are shown in this
view for clarity reasons.) For example, wires 226 & 227 of coil
208, and wires 224 & 225 of coil 206, are shown soldered to
pads 202 & 203, respectively. Similarly, wires 228 & 229 of
coil 207, and wires 230 & 231 of coil 209, are soldered to pads
204 & 201, respectively.
[0059] Upon removal of the end sections of gimbal 200, each of the
pads 201-204 is electrically connected to a separate one of the
mounting sections 240-243. In other words, removal of the end
sections of the gimbal creates four distinct conductive paths in
the remaining sheet metal material from each of the four mounting
sections to a corresponding one of the pads 201-204. According to
one embodiment of the present invention, current flows through
these four paths to control movement of the attached mirror via
coils 206-209. This embodiment therefore utilizes the metal of
gimbal 200 to conduct electrical current delivered to the moving
coil. That is, the electrical connections to the coil wires are
integrated with the flexing part of the gimbal. This arrangement
thereby eliminates movement of wires during operation of the
mirror-gimbal assembly.
[0060] Following attachment of the gimbal to platform 270 (see FIG.
5) wires 292-295 may be soldered to tabs 255-258 to establish an
electrical connection to coils 206-209. Thus, the conductive paths
provided through the flexing beams of gimbal 200 may be used to
energize the coils in order to control tilting of the mirror along
the x-axis and the y-axis. By way of example, one pair of wires
292-295 may be used to energize one pair of opposing coils (i.e.,
coils 207 & 209) to control rotation of the mirror about the
x-axis, with the remaining pair of wires 292-295 being used to
energize the other pair of opposing coils (i.e., coils 206 &
208) to control rotation of the mirror about the y-axis. In the
final assembly, permanent magnets are attached within the central
opening of each of the coils 206-209.
[0061] Torque is developed on the mirror-coil assembly upon
application of an appropriate current through the coils, in the
presence of the permanent magnetic field. The direction of the
force is made to be opposite on each side of the mirror-coil
assembly such that the resulting torque rotates or tilts the mirror
attached to the top of gimbal 200. Since the mirror-coil assembly
is fixedly attached to gimbal 200, gimbal pads 201-204 and mirror
214 rotate together as the mirror-coil assembly rotates. When the
applied current is interrupted or halted, the restoring spring
force of gimbal 200 returns the assembly to a rest position.
[0062] FIG. 9 is a perspective view of another embodiment of an
actuator-mirror assembly according to the present invention. The
actuator-mirror assembly shown in FIG. 9 rotates about a single
axis. In this embodiment, two coils 50 and 55 are adhesively
attached to step 216 on opposite sides of mirror 214 and base plate
213. The gimbal for this embodiment comprises two rectilinear, or
I-bar, shaped members 10a & 10b of thin sheet metal. Ends 12a
& 12b of respective I-bar members 10a & 10b are bonded to
surface 211 of pedestal 212. Wires 60a & 60b of coil 50 are
soldered to ends 12a & 12b, respectively. Likewise, wires 65a
& 65b of coil 55 are also soldered to ends 12a & 12b,
respectively. A stationary platform similar to that shown in FIG.
5, but having two posts, supports the assembly of FIG. 9, with the
end surfaces of the posts being bonded to ends 14a & 14b of
I-bar members 10a & 10b. A wire attached to each of the
mounting posts may be soldered to ends 14a & 14b to provide
electrical connection through the gimbal members 10a & 10b to
energize coils 50 & 55.
[0063] FIGS. 10A & 10B show top and side views of a
magnet-housing arrangement for a single actuator-mirror assembly in
accordance with one embodiment of the present invention. This
magnet-housing arrangement, for example, may be utilized in the
actuator-mirror assembly shown in FIG. 7. Magnets 81-84 are bonded
on the side surfaces of steel returns 85, attached to a base 86.
Magnets 81-84 are positioned adjacent the moving coils (e.g., coils
206-209). The polarities of the magnets are shown by conventional
nomenclature for north (N) and south (S). In one embodiment, the
magnet material is Neodymium-Iron-Boron. Of course, other types of
magnetic materials may be used as well.
[0064] FIG. 11 shows a top view of a larger magnet-housing
arrangement for use with multiple actuator-mirror assemblies.
[0065] FIG. 12 is a cross-sectional side view of an actuator-mirror
assembly utilizing gimbal 200 according to one embodiment of the
present invention. A pair of magnets 87 is shown attached to a
steel return on opposite sides of the mirror-coil-gimbal assembly.
One pair of magnets 87 are positioned adjacent coil 206, and the
other pair of magnets 87 are positioned adjacent coil 209. Each of
the coils is bonded to a notched edge surface of mirror plate 214.
A pedestal 214 is shown attached to the back of mirror plate 214
and also to pads 201 & 202 of gimbal 200. The end surfaces of
posts 74 & 75 are shown respectively bonded to mounting
sections 240 & 243, with wires 94 & 95 soldered to sections
240 and 243 in accordance with the wiring scheme described
above.
[0066] Also included in the cross-section of FIG. 12 is an optional
balancing plate 80 attached to the bottom of the coils 206-209.
Balancing plate 80 acts to counter-balance the weight of the mirror
so that the center of rotation is at the center of gravity. This
feature improves external shock and dynamic settling of the
actuator. As shown in FIG. 12, balancing plate 80 comprises a
solid, flat metal plate with several openings that allow the
stationary posts to attach to the gimbal and also permit the
gimbal-mirror-coil assembly to move. Instead of having several
openings to accommodate mounting of the mirror-coil-gimbal onto
stationary posts, balancing plate 80 may also be implemented with a
single, centrally located opening. For instance, balancing plate 80
may comprise a rectangular frame having its sides adhesively
attached to the coils, as shown in FIGS. 13A & 13B.
[0067] The embodiment of FIG. 12 further illustrates the use of an
optional damper coating 333, which covers beams 191-198 and gimbal
pads 201-204. Damper coating 333 comprises a low viscosity polymer
(e.g., an ultraviolet curing resin) that becomes a flexible gel
upon curing. Damper coating 333 acts to damp gimbal resonances and
improve the settling time of the actuator; yet, because coating 333
is flexible, it does not appreciably affect the stiffness of the
gimbal. Damper coating 333 also improves reliability by minimizing
the effect of external shock and vibration.
[0068] FIGS. 13A & 13B are cross-sectional side views of an
actuator-mirror assembly with appropriate current applied to coils
206 & 209 to tilt mirror 214 in two different directions along
a single longitudinal axis of movement. Note that in FIGS. 13A
& 13B only the rigid sections of gimbal 200 are shown for
clarity reasons. Precise movement of mirror 214 along both the
x-axis and y-axis is achieved by controlling the current applied to
the four coils 206-209 for the embodiments described above.
[0069] FIGS. 14A & 14B show top and side views of a bobbin-coil
assembly utilized in accordance with an alternative embodiment of
the present invention. In this embodiment, the coils 301, 302, 303,
and 304 are made from fine copper wire with single-built
insulation, and are each wrapped around a post member on a side of
bobbin 310. Coils 301, 302, 303, and 304 are physically located
between one or more permanent magnets (not shown in this view) in
the final assembly. FIG. 15 shows the relative position of a coil
and magnet assembly in accordance with this alternative embodiment.
The coil windings are supported by and encircle the protruding side
members of bobbin 310, shaped in accordance with the dimensions of
the permanent magnets. Bobbin pedestal 330 provides a surface for
bonding (e.g., adhesive attachment) to a gimbal that suspends
bobbin 310 between the permanent magnets.
[0070] By way of example, in the embodiment of FIGS. 14A & 14B,
each coil may include approximately 48 turns made from 6 layers,
with each layer having 8 turns. The number of turns and layers may
vary based on the type of coil used, the application, etc. Bobbin
310 may be made from a variety of machined materials (e.g.,
polymers) as is known in the art. In operation, application of
current through the coils generates a magnetic field that interacts
with the field of the permanently mounted magnets to torque to tilt
the actuator.
[0071] The bobbin coil assembly of FIGS. 14A & 14B may be
bonded to a variety of conventional gimbals. FIG. 16 shows a top
view of a conventional gimbal 320 of a type well known in the
industry, which may be used to suspend the bobbin-coil assembly
shown in FIGS. 14A & 14B. Gimbal 320 is formed of a single
sheet of material (e.g., sheet metal) that provides for dual-axis
rotation of the bobbin-coil assembly. Bobbin pedestal 330 may, for
instance, be bonded to central area 323 of gimbal 320.
[0072] FIG. 18 shows a cross-sectional side view of an
actuator-mirror assembly in accordance with an alternative
embodiment of the present invention. In this view, permanent
magnets 396 & 397 are positioned on steel returns 395 & 394
adjacent coils 381 & 382, respectively. Coils 381 & 382 are
located on opposite sides of a bobbin 310, which is bonded to the
center of a gimbal 320, such as that shown in FIG. 16. In this
example, gimbal 320 is secured to stationary steel returns 394
& 395. A mirror 391 is secured on the center-top area of gimbal
320.
[0073] Torque is developed on the bobbin-coil assembly upon
application of an appropriate current through coils 381 & 382,
in the presence of the permanent magnetic field. The direction of
the force is made to be opposite on each side of bobbin 310 such
that the resulting torque rotates or tilts mirror 391 attached to
the top of gimbal 320. The bobbin-coil assembly is attached to a
gimbal 320 and therefore the gimbal 320 and the mirror 391 will
rotate as the bobbin-coil assembly rotates. When the applied
current is interrupted or halted, the restoring spring force of
gimbal 320 returns the assembly to the rest position shown in FIG.
18.
[0074] FIG. 19 shows a photonic switch module 430 for use in an
optical communication network in accordance with one embodiment of
the present invention. The photonic switch module 430 shown in FIG.
19 includes a fiber lens matrix 425, a reference mirror 440, and an
actuator-mirror matrix assembly 435, as described above. Fiber lens
matrix 425 includes accurately drilled receptor holes. Each of the
fiber-lens receptacles functions as an optical port, which, in the
described embodiment includes an optical fiber coupler connected to
a lens. The input portions of the holes are fitted with a
collimator or lens 453 to direct light provided by a fiber optic
coupler onto the mirror of an individual actuator-mirror assembly.
Each of the lenses 453 acts to collect and collimate the light
beams passing through matrix 425. Lens 453 may comprise a gradient
index lens, a molded aspherical lens, or some other type of lens
known in the art. The embodiment of FIG. 19 may also include an
intensity monitoring feedback loop that includes a photodiode to
detect a portion of the beam of light, and an optical fiber coupler
having a first end connected to an optical fiber and a second end
connected to the photodiode.
[0075] In the example of FIG. 19, respective input and output
optical fibers 454 and 456 are each shown connected to a coupler
455 that is secured to a housing (not shown) by a fiber connector
458. The housing accommodates arrays of input/output fibers for the
switch module. Coupler 455 in this example is a 1.times.2 coupler
that passes most of the light signal (e.g., 95%-99%) to the mirror
array. A small amount of light (i.e., 1%-5%) is redirected to the
photo-detector where it can be amplified and transmitted to a
central control center in the main PCBA as part of the signal
feedback loop. Fiber lens matrix 425 and actuator-mirror matrix
assembly 435 are configured and positioned such that each
input/output fiber receptacle of matrix 425 is precisely aligned
with a corresponding mirror of assembly 435. Each lens 453,
therefore, is associated with a dedicated actuator-mirror assembly
436.
[0076] To ease the impact of beam divergence and reduce signal loss
of the light beam, the diameter of the collimator lens 453 is
chosen dependent upon the overall traveling distance of the light
beam switched from input fiber 454 to output fiber 456. A mirror of
a first actuator-mirror assembly 436 functions to direct a light
beam 460 received from fiber 454 to a reference mirror 440.
Reference mirror 440 then reflects light beam 460 to a destination
mirror 437 of a second actuator-mirror assembly. Mirror 437
functions to redirect light beam 460 to output fiber 456. Reference
mirror 440 and the mirrors of assemblies 436 may be coated with a
reflective layer in gold or aluminum to provide high reflectivity
(e.g., 98%).
[0077] The geometric layout of switch module 430 allows the light
beam to travel with minimum distance and with minimum light energy
loss. The distance between the fiber-lens matrix 425 and the
mirror-actuator assembly 435 as well as the tilting angles for the
reference mirror 440 and the mirror-actuator assembly 435 are
specified to ensure a uniform and minimized traveling distance for
the light beam. For a 1096-port photonic switch, for instance, a
typical traveling distance is 1400 mm and the corresponding Raleigh
beam diameter (which may expand by 40% over this distance) is about
1.66 mm. Collimator lenses with diameters of 1.8 mm may be chosen
in this example to suppress the divergence and reduce the light
loss due to the beam divergent issue.
[0078] The input and output mirrors of the photonic switch
described above are controlled by an intelligent, software-based
control system in one implementation. Feed forward and pre-shaping
notch filtering may be utilized to eliminate unwanted dynamics of
the mechanical structure in the mirror based photonic switch
according to one embodiment of the present invention. The input
sequence is time optimal in that it is designed to move the mirror
from one radial position to another in minimum time. The filter is
designed to shape this input sequence in order to prevent the
fundamental resonance from vibrating during move and settling
periods
[0079] Referring now to FIG. 20 there is shown a block diagram of
an open loop control system to position a mirror of a photonic
switch in accordance with one embodiment of the present invention.
Using the system shown, the individual mirrors of the
actuator-mirror matrix assembly (see FIGS. 1 and 2) are switched
between various positions. An input command profile (block 501)
produces the trajectory that the mirror has to follow to go from
point A to point B, for example. A discrete pre-filter (block 502)
is implemented as a biquad band reject filter with a transfer
function given as:
G(s)=(A.multidot.z.sup.2+B.multidot.z+C)/(D.multidot.z.sup.2+E.multidot.z+-
F)
[0080] Pre-filter 502 eliminates unwanted oscillations of the
mirrors in the actuator-mirror matrix assembly. FIG. 27 is a plot
that depicts the effect of pre-filter on the input profile signal
used to position a mirror. Waveform 490 show the command profile
without filtering, and waveform 491 is the position response
following filtering by block 502.
[0081] Continuing with the control system circuit of FIG. 20,
torque constant block 503 provides a gain that converts current
into torque. The output of block 503 is coupled to the "+" input of
summing block 504. The "-" inputs to block 504 are provided from
the feedback outputs of blocks 509 and 508, which provide the
responses due to the spring constant of the gimbal and the friction
of the gimbal, both of which act to oppose the movement of the
mirror. For example, block 508 provides a damping gain (kv) that
converts velocity into a torque term that is subtracted from the
input torque term generated by block 503. Similarly, block 509
provides a damping gain that converts position into a torque term
subtracted from the input torque.
[0082] The output of summing block 504 is coupled to inertia
conversion block 505, which converts torque into acceleration
expressed in radians/(seconds).sup.2. Inertia is converted into
velocity (radians/second) by block 511. At block 507 radians are
converted into degrees, with the output representing the signal to
achieve a desired mirror position in the switching mechanism (shown
as block 510).
[0083] Referring now to FIG. 21 there is shown a block diagram for
open loop control of mirror position for a photonic switch
mechanism in accordance with another embodiment of the present
invention. Note that in a particular embodiment, a portion (or all)
of the component control circuitry may be physically located behind
the actuator-mirror assemblies. FIG. 20 shows an open loop block
diagram with a discrete pre-filter 502 to remove unwanted
mechanical resonances. FIG. 21, on the other hand, shows a feedback
mechanism that measures the light intensity and feeds it back to
the discrete filter (block 522) using a scanning algorithm of
compensation block 521.
[0084] The algorithm functions to search and detect maximum light
intensity in an all-optical switch having one input port and one
output port, each port has two axes. The algorithm generates a
spherical scan structure for three of the four axes, and a linear
scan for the fourth, in order to find the optimum coordinates where
the light intensity transmitted through the switch is maximum
(insertion losses minimum). As commands are generated for the four
axes, a portion of the light intensity output from the switch is
read. If the current reading is larger than a previous reading, the
algorithm stores the current reading and discards the previous one.
Every time a new local maximum is found, the algorithm shifts the
center of the sphere to the new coordinates. The search starts with
a fixed radius and a fixed step.
[0085] As the program progresses, both the radius and the step
become incrementally smaller until a desired reading is reached.
For instance, the desired reading may be in terms of insertion loss
measured in dB. During operation of the switch, the calibration
values (i.e., coordinates) may be used to position the switch at
the correct coordinates. At this point, the algorithm program may
enter a tracing mode, where it attempts to maintain the maximum
light intensity by monitoring light intensity and entering into a
low-radius calibration scan should the reading fall below an
established threshold level. It is appreciated that low radius
calibration may be performed at different radii depending on the
intensity difference between the sensed or monitored light and the
maximum reading.
[0086] FIG. 22 is a high-level block diagram illustrating one
possible implementation of the electronics that may be used for
control of a photonic switch according to the present invention.
Note that the pre-filter and/or scanning algorithm functions may be
realized using a digital signal processor (DSP).
[0087] FIG. 23 is a block diagram of the control electronics
utilized in a photonic switch according to one embodiment of the
present invention. In the illustrated embodiment, DSP 601 comprises
a fixed-point 160 MHz processor with a 6.25 ns instruction cycle.
The DSP firmware reads the feedback information from the
analog-to-digital converter (ADC) 602, performs compensation, and
writes the command into the DAC 603. In addition, DSP 601 has the
capability to calibrate the positions of the input and output
mirrors in order to minimize the differential optical loss. In this
particular implementation, DSP 601 has 3 serial ports each
connected to a serial DAC 603. This allows a large number of
mirrors (e.g., 48) under control of a single DSP 601.
[0088] In operation, the control electronics of FIG. 23 operate for
a 16.times.16 port switch with 32 mirrors. An analog light
intensity signal from each of the 32 mirrors is coupled through
mutiplexor 605 to ADC 602. ADC 602 converts the analog intensity
signal into a digital 16-bit number that is received by serial port
605 of DSP 601. DSP 601 includes three serial ports 605, 606, and
607, and a memory 608. DSP 601 performs the necessary calculations
and sends the appropriate position signal to the mirrors through
the 32-channel DAC 603. Quad drivers 610, 611, 612, etc., convert
the position signal into a torque voltage to control the
actuator-mirror assemblies. To drive the individual motors, the
quad power amplifiers (i.e., the quad drivers 610, 611, 612, etc.)
are used delivering 250 mA each.
[0089] DSP 601 also combines 64k words of SRAM configured as 32k
words of data memory, 32k words of program memory, and access of up
to 16M words of external memory. DSP 601 also includes a UART 613
for personal computer communications via bus 614; general purpose
programmable flag pins; and an eight or 16-bit host port
interface.
[0090] FIG. 24 shows a 256.times.256 switch fabric in accordance
with another embodiment of the present invention. To minimize the
number of interconnect wires, the electronics may be divided in to
3 PCB's 630, 640, and 650. The main PCB 640 includes the DSPs and
ADCs. The detector PCB 630 carries the photo detector, muxes and
buffer amplifiers. The DAC/driver PCB's 650, 651, 652, etc., hold
DACs and drivers and are integrated with the mirror bars.
[0091] FIG. 25 shows the hardware configuration for a
1024.times.1024 switch fabric in accordance with one embodiment of
the present invention. The electronics for the 1024.times.1024 are
the same as the electronics illustrated in FIGS. 23 and 24, there
are simply a greater number of each component (e.g., more ADCs 660,
661, 662, etc.)
[0092] FIG. 26 shows an example of a folded, matrix switch
according to another embodiment of the present invention. An input
fiber-lens array 700 is shown directing a light beam 705 to a first
actuator-mirror matrix assembly 701, which directs beam 705 to a
second actuator-mirror matrix assembly 702. Assembly 702 redirects
light beam 702 to one of the fibers of output fiber-lens array
703.
* * * * *