Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2002-03-21
2003-04-22
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S224200, C310S309000
Reexamination Certificate
active
06552839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical switch for optical communication, and more particularly to an optical switch employing microelectromechanical systems technology.
2. Description of the Prior Art
In general, MEMS (microelectromechanical systems) technology has strong advantages in developing inexpensive, high performance, sub micro devices, so studies for applying MEMS technology to inertia sensors, pressure sensors, biomedical devices, various parts for optical communication, etc. are actively carried out. An optical switch employing MEMS technology is one of these applications, and is utilized to alter the paths of optical signals transmitted via optical fibers using a precise micro mirror situated over a substrate and fabricated through a fine machining technique.
MEMS optical switches that have been developed up to now include a two-dimensional (2D) optical switch operated parallel to a substrate and a three-dimensional (3D) optical switch operated perpendicular as well as parallel to the substrate.
The 3D MEMS optical switch allows the number of micro mirrors integrated in a single chip to be easily increased, so this switch is applicable to a DWDM (Double Wavelength Division Multiplexing) system for distributing multi-channel optical signals.
The 2D MEMS optical switch is capable of not only distributing multi-channel optical signals but also minimizing free space between optical fibers in which a micro mirror is situated, when it is applied to optical switches formed in the 1×2 and 2×2 matrices. Accordingly, the 2D MEMS optical switch can allow an inexpensive system to have good optical performance. Additionally, the MEMS optical switch allows a sub micro actuator to have good mechanical characteristics, thereby providing high speed response.
In particular, of the 2D MEMS optical switches actuated parallel to the substrate, studies for a 2×2 optical switch that alters optical paths by moving its micro mirror forward or backward between four optical fibers disposed on an optical paths have been actively performed.
An example of a conventional 2×2 optical switch is disclosed in PCT publication WO 98/12589 issued to Anmelder et al. and entitled “A Fiber Optical Circuit Switch and a Process for Its Production”, in which the optical switch is fabricated in the form of a sandwich wafer having isolation films formed between a substrate and a conductive device layer.
The optical switch disclosed in the publication is characterized by the provision of a metal-deposited silicon micro mirror that is connected to a bi-directional comb drive actuator manufactured to be driven in both forward and backward directions. In accordance with this publication, optical paths are changed while the micro mirror is moved into or removed from the optical paths by the operation of the bi-directional comb drive actuator. However, the actuator is disadvantageous in that driving power is continuously consumed while the actuator is forwardly or backwardly driven in order to remain stationary state.
Another example of the conventional art is disclosed in U.S. Pat. No. 6,229,640 B1 issued to Nan Zhang et al. and entitled “Microelectromechanical Optical Switch and Method of Manufacture Thereof”, which is characterized by the provision of a single comb actuator.
In this patent, a micro mirror initially moved into optical paths can be removed from the optical paths by the operation of the actuator, and can be again moved into the optical paths in such a way that the actuator is stopped and, as a result, the micro mirror returns to its original position by the restoring force of a beam structure connecting the actuator to a substrate. Consequently, the actuator does not consume driving power in the forward movement state, but still consumes driving force in the backward movement state.
Therefore, the optical switch of this patent is disadvantageous in that power is wastefully consumed by the actuator, since the micro mirror is stopped by the application of a driving force corresponding to a restoring force in the direction opposite to the moving direction of the micro mirror while the mirror is maintained in at least one of forward and backward movement states in which the micro mirror is moved into and out of the optical paths, respectively.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an optical switch, in which its actuator is designed to move a micro mirror from a forward position to a backward position and vice versa through a single driving pulse signal, thereby minimizing the power consumption of the actuator.
In order to accomplish the above object, the present invention provides an optical switch, comprising: an electrostatic actuator, the electrostatic actuator comprising a reciprocating mass located in the center of the electrostatic actuator, first rotating axes located symmetrically at the left and right sides of the reciprocating mass, first rotating masses rotatably connected to the first rotating axes, first rotating springs for supporting the first rotating masses, linear springs connected to the first rotating masses for supporting the first rotating masses together with the rotating springs, second rotating masses connected to the linear springs to restrict their displacement in one direction, second rotating springs for supporting the second rotating masses with first ends of the second rotating masses connected thereto, second rotating axes connected to the second rotating masses, structural anchors integrated with the second rotating axes and positioned at the side ends of the actuator, drive electrodes, and a micro mirror movable by the same displacement as the reciprocating mass, wherein the electrostatic actuator having two structural stability positions for the reciprocating mass and the left and right rotating masses; and a substrate.
Preferably, the drive electrode consists of a forward drive electrode and a backward drive electrode.
Preferably, a both-sides etched silicon structure is used on the substrate, as a device layer.
Preferably, the actuator remains stopped without being driven at the two stability positions if a force is not applied.
Preferably, the silicon structure is manufactured by the steps of: machining a silicon substrate; etching one side of the silicon substrate formed at the machining step by using a first etching mask; bonding a glass plate to the side etched at the first etching step; polishing a side of the silicon substrate bonded with the glass plate at the bonding step to reduce the thickness of the silicon substrate; and etching the side of the silicon substrate reduced in thickness at the polishing step by using a second etching mask.
REFERENCES:
patent: 6229640 (2001-05-01), Zhang et al.
patent: 2002/0130586 (2002-09-01), Mao et al.
patent: WO 98/12589 (1998-03-01), None
Hong Yoon Shik
Jung Sung Cheon
Kang Joon Seok
Lee Hyun Kee
Lee Jung Hyun
Choi William
Darby & Darby
Epps Georgia
Samsung Electro-Mechanics Co. Ltd.
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