Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2002-05-10
2004-03-16
Spector, David N. (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C398S045000, C398S048000, C385S018000
Reexamination Certificate
active
06707594
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to optical switching and, more particularly, to an optical switching system, device, and method using two-dimensional micro-electromechanical mirrors.
2. Description of Related Art
Optical communication systems are a substantial and rapidly growing part of communication networks. The expression “optical communication system,” as used herein, relates to any system that uses optical signals to convey information across an optical transmission device, such as an optical fiber. Such optical systems may include, but are not limited to telecommunication systems, cable television systems, and local area networks (LANs).
While the need to carry greater amounts of data on optical communication systems has increased, the capacity of existing transmission devices is limited. Although capacity may be expanded, e.g., by laying more fiber optic cables, the cost of such expansion is prohibitive. Consequently, there exists a need for a cost-effective way to increase the capacity of existing optical transmission devices.
Wavelength division multiplexing (WDM) has been adopted as a means to increase the capacity of existing optical communication systems. In a WDM system, plural optical signals are carried over a single transmission device, each channel being assigned a particular wavelength.
An essential part of optical communication systems is the ability to switch or route signals from one transmission device to another. For example, micro-electromechanical mirrors (MEMs) have been developed for routing signals between transmission devices. A discussion of MEM devices can be found in K. E. Peterson, “Micromechanical Light Modulator Array Fabricated on Silicon,” Applied Physics Letters, Volume 31, Page 521 (1977). This technique operates by changing the angular orientation of the mirrors, thereby reflecting signals to different locations.
Designers have also considered using bubbles that are capable of changing their internal reflection for switching optical signals. A discussion of this can be found in “Compact Optical Cross-connect Switch Based on Total Internal Reflection in a Fluid-containing Planar Lightwave Circuit,” by J. E. Fouquet, in
Trends in Optics and Photonics Series
, A. Sawchuk, ed., Vol. 37, (Optical Society of America, Washington, D.C., 2000) pp. 204-206. However, these techniques are unable to switch between multiple wavelengths. Furthermore, both of these devices have limited switching speeds, in the range of 10 kHz for the mirror devices and in the range of 100 Hz for the bubble devices.
Zigzag multiplexers are also well known in the art for transmitting signals on multiple transmission devices. For example, U.S. Pat. No. 6,008,920 discloses a multiplexer/demultiplexer device utilizing a filter that is sensitive to the angle of incidence of light. However, such multiplexers have not been used for switching or routing applications in conjunction with arrays of fibers, detectors, and emitters.
Other switching approaches, such as the approach disclosed in U.S. Pat. No. 4,769,820, issued to Holmes, can switch data at GHz rates, which is effectively switching at GHz transition rates. However, this approach requires substantial optical switching power, has potential cross talk, and cannot resolve wavelength over-utilization issues. What is needed is a means for switching wavelength division multiplexed signals that is capable of doing so at high speeds with no cross talk and requires low switching power. What is also needed is a switch device that is capable of switching large numbers of signals.
SUMMARY OF INVENTION
1. Advantages of the Invention
One or more embodiments of the present invention may achieve, but do not necessarily achieve, one or more of the following advantages:
the ability to switch signals of different wavelengths;
the ability to switch signals at high speeds;
does not require high power;
has low crosstalk;
the ability to switch between wavelengths and fibers to avoid transmission device or wavelength over-utilization;
the ability to broadcast to multiple transmission devices or couplers simultaneously; and
the ability to efficiently switch a large volume of signals.
These and other advantages of certain embodiments of the present invention may be realized by reference to the remaining portions of the specification, claims, and abstract.
2. Brief Description of One Embodiment of the Present Invention
The present invention comprises an optical switch element for use with at least one source and a plurality of targets. The source is adapted to transmit an optical signal to the optical switch device. The targets are adapted to receive the optical signal from the optical switch device.
The optical switch device comprises a beam splitter, a first wave plate, a direction altering device, and a second wave plate. The beam splitter is adapted to transmit light in a first predetermined polarization and reflect light in a second predetermined polarization. The first wave plate is positioned between the source and the beam splitter. The first wave plate is adapted to alter the polarization so that it is reflected by the beam splitter, wherein light transmitted by the source passes through the wave plate and is reflected by the beam splitter.
The direction altering device is positioned to receive light reflected by the beam splitter and to selectively reflect light to a plurality of paths, the paths corresponding to the positions of the plurality of targets. The second wave plate is positioned between the direction altering device and the beam splitter. The second wave plate is adapted to alter the polarization so that it is transmitted by the beam splitter, wherein light redirected by the direction-altering device passes through the second wave plate and is transmitted by the beam splitter.
The above description sets forth, rather broadly, a summary of one embodiment of the present invention so that the detailed description that follows may be better understood and contributions of the present invention to the art may be better appreciated. Some of the embodiments of the present invention may not include all of the features or characteristics listed in the above summary. There are, of course, additional features of the invention that will be described below and will form the subject matter of claims. In this respect, before explaining at least one preferred embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and to the arrangement of the components set forth in the following description or as illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
REFERENCES:
patent: 5317445 (1994-05-01), DeJule et al.
patent: 6097859 (2000-08-01), Solgaard et al.
patent: 6313936 (2001-11-01), Holmes
patent: 6335782 (2002-01-01), Holmes
patent: 6356679 (2002-03-01), Kapany
patent: 6532115 (2003-03-01), Holmes
patent: 6538818 (2003-03-01), Holmes
patent: 6539138 (2003-03-01), Holmes
patent: 6580845 (2003-06-01), Holmes
patent: 2002/0054418 (2002-05-01), Holmes
patent: 2003/0007234 (2003-01-01), Holmes
General Nutronics, Inc.
Heck Ryan A.
Ian F. Burns & Associates
Spector David N.
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