Optical: systems and elements – Optical modulator – Light wave directional modulation
Reexamination Certificate
2001-11-20
2004-12-28
Font, Frank G. (Department: 2877)
Optical: systems and elements
Optical modulator
Light wave directional modulation
C359S281000, C385S018000, C385S024000
Reexamination Certificate
active
06836353
ABSTRACT:
BACKGROUND OF THE INVENTION
This present invention generally relates to techniques for telecommunications. More particularly, the present invention provides a method and system for switching optical signals using a redundant switch fabric system and method for long haul communications. Merely by way of example, the invention is applied to a MEMS based switching system over a wide area network for long haul communications. But it would be recognized that the invention could also be applied to other types of switching such as wave-guides, electro-optic devices, holographic switches, bubble switches, liquid crystal switches, and many others for applications including metropolitan, access, and other networks.
Over the past years, digital telephone has progressed with a desire for faster communication networks. In general, conventional analog voice telephone signals have been converted into digital signals. These signals can have transmission rates of 64,000 bits/second and greater in some applications. Other telephone circuits interleave these bit streams from 24 digitized phone lines into a single sequence of 1.5 Mbit/second, commonly called the T
1
or DS
1
rate. The T
1
rate feeds into higher rates such as T
2
and T
3
. A T
4
may also be used. Single mode fiber optics has also been used at much higher speeds of data transfer. Here, optical switching networks have also been improved. An example of such optical switching standard is called the Synchronous Optical Network (SONET), which is a switching standard designed for telecommunications to use transmission capacity more efficiently than the conventional digital telephone hierarchy, which was noted above. SONET organizes data into 810-byte “frames” that include data on signal routing and designation as well as the signal itself. The frames can be switched individually without breaking the signal up into its components, but still require conventional switching devices.
Most of the conventional switching devices often require the need to convert optical signals from a first source into electric signals for switching such optical signals over a communication network. Once the electric signals have been switched, they are converted back into optical signals for transmission over the network. As merely an example, a product called the SN 16000, BroadLeaf™ Network Operating System (NOS), made by Sycamore Networks, Inc. uses such electrical switching technique. Other systems have been developed by Lucent Technologies, Inc., Ciena Corporation, and other companies. Numerous limitations exist with such conventional electrical switching technique. For example, such electrical switching often requires a lot of complex electronic devices, which make the device difficult to scale. Additionally, such electronic devices become prone to failure, thereby influencing reliability of the network. The switch is also slow and is only as fast as the electrical devices. Accordingly, techniques for switching optical signals using a purely optical technology have been proposed. Such technology can use a wave guide approach for switching optical signals. Unfortunately, such technology has been difficult to scale and to build commercial devices.
Other companies have also been attempting to develop technologies for switching a high number of signals in other ways such as high density mirror arrays, but have been generally unsuccessful. A major obstacle for such high-density mirror arrays is that such high density switches cannot be scaled up or down for switching a greater quantity of signals or fewer signals. That is, an eight-by-eight optical switch cannot easily be scaled up to larger switch designs. Larger switch designs also cannot be scaled down in size. Accordingly, such attempts have generally been unsuccessful to provide a flexible method and system for conventional telecommunication applications.
From the above, it is seen that an improved way of switching signals is highly desirable.
SUMMARY OF THE INVENTION
According to the present invention, techniques including methods and systems for optical switching are provided. More particularly, the present invention provides a method and system for switching optical signals using a redundant switch fabric system and method for long haul communications. Merely by way of example, the invention is applied to a MEMS based switching system over a wide area network for long haul communications. But it would be recognized that the invention could also be applied to other types of switching such as wave-guides, electro-optic devices, holographic switches, bubble switches, liquid crystal switches, and many others for applications including metropolitan, access, and other networks.
In a specific embodiment, the invention provides an optical switching system. The system has a housing; and an input device coupled to the housing. An output device is also coupled to the housing. A first switch fabric is coupled between the input device and coupled between the output device. The first switch fabric comprises a plurality of MEMS based switching devices. A second switch fabric is coupled between the input device and coupled between the output device. The second switch fabric comprises a plurality of MEMS based switching devices. An input fiber bundle is coupled to the input device and an output fiber bundle is coupled to the output device. A first switching device is coupled to the first switch fabric and is coupled to the second switch fabric. The first switching device also is coupled to the input device for receiving a beam from one of the input fibers and directing the beam to the first switch fabric or the second switch fabric depending upon predetermined criterion. A second switch device is coupled to the first switch fabric and is coupled to the second switch fabric. The second switching device also is coupled to the output device for receiving the beam from either the first switch fabric or the second switch fabric depending upon the predetermined criterion. A control device is coupled to the first switch device and the second switch device. The control device provides a signal to determine if the beam is to be directed to the first switch fabric or the second switch fabric based upon the predetermined criterion.
In an alternative specific embodiment, the invention provides an optical switching method. The method includes tapping a first portion of an incoming data beam from an incoming source; and transferring the incoming data beam from the incoming source to a first path provided by a first MEMS based switching fabric. The method also transfers a monitoring source to monitor a second path of provided by second MEMS based switch fabric, while the second path of the second MEMS based switch fabric is in a stand by mode. A step of tapping a second portion of an outgoing data beam provided by the first MEMS based switching fabric is also included. The method determines if a process condition of the first path by at least the second portion of the outgoing data beam.
Many benefits are achieved by way of the present invention over conventional techniques. In a specific embodiment, the invention provides a redundant system using conventional hardware and/or software. The invention also provides a switch system, which can be maintained easily. The invention can be used to switch optical signals without conversion into electrical signals in some embodiments. In some embodiments, the invention can be used to replace a cross connect device with another, while the system is still under power without damage to software and/or hardware elements. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits will be described in more throughout the present specification and more particularly below.
Various additional objects, features and advantages of the present invention can be more fully appreciated with reference to the detailed description and accompanying drawings that follow.
REFERENCES:
patent: 4317611 (1982-03-01), Petersen
patent: 4942766 (1990-07-01), Greenwood et
Jain Raj
Ramadas Krishna Kumar
Connolly Patrick
Font Frank G.
Nayna Networks, Inc.
Townsend and Townsend and Crew
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