Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-11-02
2003-04-29
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S018000, C359S196100, C359S224200
Reexamination Certificate
active
06556737
ABSTRACT:
FIELD OF USE
The present invention relates to fiber-optics switches, in more particularly to fiber-optics switches incorporating bulk-micromachined mirror support structures.
BACKGROUND ART
Fiber-optics is used as the transmission medium in many high-speed local-area communication networks. Typically, in these networks, all devices (including concentrators, bridges, routers, and workstations) are coupled in a ring-like fashion through specially designed bypass switches. In case of power or equipment failure or routine station removal, a selected bypass switch is actuated to de-couple a selected device from the network in order to prevent any unwanted disruption or compromise on the system performance.
FIG. 1
is a block diagram showing a fiber-optics high-speed local-area communication network
10
that includes several devices (DEVICE
1
through DEVICE
6
) and corresponding bypass switches (SW
1
through SW
6
). Each device includes a reception port R for receiving data from network
10
, and a transmission port T for transmitting data onto network
10
. Each switch is controlled by control signals to either couple its corresponding device to network
10
, or to de-couple its corresponding device from network
10
. For example, referring to switch SW
1
in
FIG. 1
, DEVICE
1
is coupled to network
10
because data is directed by switch SW
1
from a network fiber F
1
to a device receiver fiber F
2
, and data from the associated device is directed to network
10
from a device transmission fiber F
3
to a network fiber F
4
. Conversely, referring to switch SW
2
in
FIG. 1
, DEVICE
2
is de-coupled from network
10
because data is directed by switch SW
1
from network fiber F
5
to network fiber F
1
, thereby bypassing DEVICE
2
.
As suggested by the simplified diagram shown in
FIG. 1
, conventional fiber-optics bypass switches are passive devices in the sense that they do not perform any optical/electrical conversion. However, these conventional fiber-optics bypass switches are typically very bulky, and require external packaging and power supplies to perform switching operations. For example, one popular type of conventional fiber-optics bypass switch includes mirrors and motors that physically position and align the various network and device fibers so that the necessary coupling/de-coupling operation is performed. The motors and associated mechanisms require a large housing, and assembly of the various parts and motors is tedious. Accordingly, these conventional fiber-optics bypass switches are expensive to produce, and require a relatively large amount of space to incorporate into a network. Further, because of the complex mechanisms used to position the fibers, these conventional fiber-optics bypass switches are difficult to modify in order to, for example, perform multiplexing functions instead of bypass switch functions.
It would therefore be desirable to have a fiber-optic microswitch that can be fabricated at low cost and with batch manufacturing processes similar to those of microelectronics, and can be easily modified to perform multiplexing operations in addition to bypass switch operations.
SUMMARY
The present invention provides a fiber-optic microswitch that uses a monocrystalline material, such as monocrystalline silicon, to form a flexible monocrystalline structure provided with a light-reflecting mirror that is positioned using electromagnetic force to reflect light between a series of stationary optical fibers. The monocrystalline structure includes an outer fixed (stationary) frame, a movable platform upon which the mirror is formed, and two or more resilient support members (e.g., monocrystalline silicon springs or torsion beams) connecting the movable platform to the fixed frame. Monocrystalline silicon has advantageous stiffness, durability, fatigue and deformation characteristics, and can be fabricated using known techniques to produce the monocrystalline structure. Accordingly, several highly reliable monocrystalline structures can be batch produced from a single silicon substrate, thereby minimizing manufacturing and assembly costs.
In accordance with another aspect of the present invention, the fiber-optic microswitch includes an electromagnetic drive mechanism for positioning the movable platform relative to the fixed frame by electromagnetic force. Another benefit of forming the movable platform, fixed frame and resilient support members using a monocrystalline structure is that the mirror (i.e., the movable platform) can be moved relative to the fixed frame using a relatively small driving force. Accordingly, the present invention is able to utilize an electromagnetic drive mechanism that reduces both the size and the cost of the present fiber-optic microswitch relative to conventional fiber-optic switches. The electromagnetic drive mechanism includes one or more coils formed on a drive substrate mounted under the monocrystalline structure, and one or more pole pieces, formed from a magnetic material, that are mounted on the movable platform. Currents are selectively applied to the coils to generate electromagnetic forces on the pole pieces, thereby causing the movable platform to move (e.g., tilt) relative to the fixed frame. When these currents are removed, the movable platform is returned to its original (idle) position by the resilient support members.
In accordance with a first disclosed embodiment of the present invention, a fiber-optic microswitch includes a monocrystalline substrate having a substantially square movable platform connected at its corners to a fixed frame by four serpentine silicon springs. A mirror is provided on an upper surface of the movable platform, and ferromagnetic (e.g., permalloy) pads are formed on a lower surface of the movable platform. A drive substrate is provided with four coils that are located below the ferromagnetic pads. A fiber assembly, including four fibers, is fixedly mounted over the mirror such that ends of the fibers face the mirror. The coils are wired in pairs such that a first pair of coils pulls down a first side of the movable platform in response to a first control signal, and a second pair of coils pulls down a second, opposite side of the movable platform in response to a second control signal. The fibers are positioned such that when the first side of the movable platform is pulled down, light from a first (input) fiber connected to a network is reflected into a second (receiver) fiber connected to a device, and light from a third (transmission) fiber connected to the device is reflected to a fourth (output) fiber connected to the network, thereby coupling the device into the network. Conversely, when the second side of the movable platform is pulled down, light from the first (input) fiber is reflected into the fourth (output) fiber, thereby de-coupling the device from the network.
In accordance with a second disclosed embodiment of the present invention, a fiber-optic microswitch includes a monocrystalline substrate having a movable platform connected by a pair of resilient torsion beams to a fixed frame such that the movable platform is able to rotate (tilt) about an axis defined by the torsion beams. Similar to the first embodiment, a mirror is provided on an upper surface of the movable platform, and ferromagnetic (e.g., permalloy) pads are formed on a lower surface of the movable platform. The fiber-optic microswitch also includes a drive substrate and a fiber assembly that are similar to those used in the first embodiment. A first pair of the coils generate electromagnetic force that cause the movable platform to rotate (tilt) into a first position in response to a first control signal, and a second pair of the coils generate electromagnetic force that cause the movable platform to rotate (tilt) into a second position in response to a second control signal. Light from the network is reflected by the mirror to couple and de-couple a device in a manner similar to that described above with reference to the first embodiment.
In accordance with a third disclosed embodiment of the
Burns Brent E.
Miu Denny K.
Tang Weilong
Temesvary Viktoria
Bever Patrick T.
Bever Hoffman & Harms LLP
Bovernick Rodney
Integrated Micromachines, Inc.
Pak Sung
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