Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-05-05
2002-12-03
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S018000
Reexamination Certificate
active
06490382
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to microelectromechanical systems in general, and more particularly, to microelectromechanical optical switches.
BACKGROUND OF THE INVENTION
MicroElectroMechanical (MEM) technology has been used in a wide range of applications. For example, MEM devices have been used in optical switching systems to switch optical radiation from the switch inputs to selected switch outputs. Conventional optical switches, sometimes referred to as Optical Cross-Connect (OXC) switches can include an N×N array of reflectors to reflect optical radiation from any switch input to any switch output. Each input and output can be aligned with an associated row or column of the array. For example, in a 2×2 MEM OXC switch having 2 inputs and 2 outputs, the first and second inputs can be aligned with first and second rows of the 2×2 array and the first and second outputs can be aligned with first and second columns of the 2×2 array. In operation, a selected reflector of the 2×2 array can be used to reflect the optical radiation from any switch input to any switch output.
The selected reflector can be located in the array where the column associated with input and the row associated with the output intersect. The selected reflector can be placed in a reflecting position to reflect the optical radiation from the input to the selected output. At least some of the other reflectors can be placed in non-reflecting positions so as not to impede the propagation of the optical radiation from the input to the selected reflector and to the output.
As the number of inputs and outputs of conventional MEM OXC switches increase, so may the number of reflectors used to provide the operations thereof. The number of reflectors, R, used in a conventional N×N OXC generally can be expressed as:
R=N
2
Where N is the number of inputs and outputs of the switch. For example, a 2×2 OXC switch may include 4 reflectors, a 3×3 OXC switch may include 9 reflectors, and a 4×4 OXC switch may include 16 reflectors etc. A conventional 2×2 MEM OXC
100
is shown in FIG.
1
.
Referring to
FIG. 1
, each of the reflectors
101
-
104
includes a reflective surface
105
-
108
and can be placed in either a reflecting or non-reflecting position. Accordingly, the MEM OXC
100
can be placed in 2
N
2
possible configurations, where each configuration can be defined as a unique combination of reflector positions. Unfortunately, it may not be possible to use all of the 2
N
2
configurations. In particular, some of reflector configurations may include configurations where two or more reflectors in a row or column of the array are in the reflecting state, thereby blocking the reflection of the optical radiation from the input to the output. For example, to switch optical radiation from input I
1
to output O
1
, reflectors
102
and
103
are placed in non-reflecting positions to allow the optical radiation to propagate from input I
1
to output O
1
. Therefore, some of the possible 2
N
2
configurations may not allow the MEM OXC to operate properly.
Unfortunately, as the number of inputs and outputs increase, so may the number of reflectors. For example, a 5×5 OXC switch may use
52
reflectors, a 6×6 may use 36 and so on. It is known to reduce the number of reflectors by providing reflectors with reflective surfaces on opposite sides of the reflectors as shown, for example, in
FIGS. 2A and 2B
. According to
FIGS. 2A and 2B
, one reflector
200
can operate as a 2×2 MEM OXC switch
201
. In particular, inputs I
1
and I
2
are oriented in first and second directions
225
,
235
relative to the reflector
200
. Outputs O
1
and O
2
are oriented in the first and second directions respectively relative to the reflector
200
. When the reflector
200
is in the reflecting position, as shown in
FIG. 2A
, optical radiation can be reflected from input I
1
to output O
2
and from input I
1
to output O
1
. When the reflector
200
is in the non-reflecting position, as shown in
FIG. 2B
, optical radiation can pass from the input I
1
to the output O
1
or from the input I
1
to the output O
2
. Accordingly, the reflector
200
can operate as a 2×2 MEM OXC switch
201
. Notwithstanding the above, there continues to exist a need to provide improved OXC switches having a reduced number of reflectors therein.
SUMMARY OF THE INVENTION
Embodiments of the present invention can allow MicroElectroMechanical (MEM) Optical Cross-Connect (OXC) switches to have a reduced number of reflectors by providing N inputs to the OXC switch and N outputs from the OXC switch, where N is at least 3. The N×N OXC switch provides N! states, wherein the N! states optically couple any one of the N inputs to any one of the N outputs. The N×N OXC switch also includes a number of switching nodes that are selectively optically coupled to the N inputs and N outputs. Each of the number of switching nodes is configurable in at least one of a switching configuration and a pass-through configuration to provide selectively switched optical radiation therefrom and wherein the number of switching nodes is equal to ceiling [ln(N!)/ln(
2
)] to provide the N! states of the N×N OXC switch. The N×N OXC switch further includes at least one optical transmission apparatus coupled to at least two of the switching nodes.
Reducing the number of switches used in an N×N MEM OXC switch may allow for N×N switches that use fewer actuators than conventional N×N switches. In particular, conventional N×N switches may include N
2
switches to provide N! switch settings. Such a conventional switch may use, for example, as little as 0.04% of the 2
N
2
states for a 4×4 switch. In contrast, N×N switches according to the present invention can include ceiling [ln(N!)/ln(
2
)] reflectors. Such a 4×4 switch according to the present invention may utilize 75% of its respective possible states. For example, a conventional 4×4 switch may include 16 switches whereas an N×N switch according to the present invention may include 5 switches. Also, fewer switches and actuators may be formed on a smaller substrate area, thereby allowing a reduction in the footprint of an N×N switch according to the present invention.
In other embodiments according to the present invention a 2×2 array of reflectors is arranged in first and second rows and first and second columns. First, second and third inputs to the N×N OXC switch are selectively optically coupled to at least one of the 2×2 array of reflectors. First, second and third outputs from the N×N OXC switch are selectively optically coupled to at least one of the 2×2 array of reflectors. Related method embodiments for all of the above described OXC switches also may be provided. Accordingly, reduced numbers of reflectors and/or actuators may be used in optical cross connect switches.
In other embodiments according to the present invention, an N×N OXC switch includes a first movable reflector that is optically coupled to a first input and a second input. The first movable reflector receives first optical radiation in a first direction via the first input and receives second optical radiation in a second direction via the second input. The first moveable reflector provides the first optical radiation to a first output therefrom that propagates in the first direction when the first moveable reflector is in a non-reflecting position and provides the second optical radiation to the first output that propagates in the first direction when the first moveable reflector is in a reflecting position. A second movable reflector provides optical radiation from a third input thereto in the second direction to a second output therefrom when the second moveable reflector is in the non-reflecting position. An optical transmission apparatus optically couples the first output of the first move
Connelly Michelle R.
JDS Uniphase Corporation
Myers Bigel & Sibley & Sajovec
Ullah Akm E.
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