Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2002-05-06
2004-11-09
Mack, Ricky (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S199200, C359S107000, C359S254000, C359S322000
Reexamination Certificate
active
06816296
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the field of data, video, and voice communications networks, and more particularly optical switches and switching modules, and to a network or network node using an optical switching element having an electro-optic region responsive to an electric field for switching a data communications light beam between an input optical waveguide and one or more output optical waveguides.
2. Description of the Related Art
The increasing amount of data and voice communication has created a great need for improvements in the speed and capacity of the systems used to deliver communication signals. For example, the increasing number of internet users has created a demand for higher volumes of data transfers. The amount of data being communicated by each internet user has been increasing also, creating further demand for communication system capacity. As the amount of data increases, there is also a demand for quicker communication of the data. These increased demands are affecting the data communications companies, telephone companies and cable television companies.
One way to increase the speed and capacity of communication systems is to use fiber optic cables to transfer signals by light beams. A technique called dense wavelength division multiplexing (known as DWDM) has been used to allow many separate signal channels, each at a slightly different wavelength, to be sent on a single fiber optic cable. The use of DWDM allows a great increase in the quantity of data that may be sent through a single fiber optic cable.
A conventional way of routing DWDM optical signals in a network is to use nodes in the network which convert the optical signals to electronic signals using a optical receiver, process and modify the electronic signals for routing, and convert the processed and modified electronic signals back to optical signals using optical transmitters. This type of node is often referred to as o-e-o, meaning that there are conversions in the node from optical to electronic, and back to optical. A problem faced by users of such o-e-o nodes is that the processing and modification of signals in electronic form takes time, and limits the speed at which the node can operate. As the number of DWDM channels flowing through a node increases, the amount of electronic processing and modification inside such an o-e-o node also increases, and requires added electronics which is expensive, heat generating, and space consuming. A further problem faced by users of o-e-o nodes is the expense of such nodes, since many optical detectors are required in each node, and many laser light sources are required in each node, and such detectors and lasers are expensive components. An additional problem faced by users of such an o-e-o node is that optical signals sent to such a node must have a format consistent with the formats used in and supported by such a node. For example, if the particular o-e-o node uses and supports only asynchronous transfer mode (ATM) formatted signals, then an optical signal using the internet protocol (IP) format cannot be sent to and processed by such an o-e-o node. Another problem faced by users of such o-e-o nodes is that fiber optic cables are being installed into existing telephone, cable TV and communication company facilities which are cramped for space, and which do not tolerate being overheated by added electronics. A way to reduce the problem of overheating has been to add air conditioning capacity to existing facilities, but air conditioning equipment requires additional expense, additional amounts of the scarce available space, and additional amounts of electrical power.
Two important needs of modem communications networks are for bandwidth allocation and for service provisioning. Bandwidth allocation refers to the need to change the communications or data transfer capacity, such as the maximum allowable number of voice channels or maximum bit rate, between two nodes in a communications network. Service provisioning refers to the need to provide dedicated communications or data capacity, such as the use of a T3 communications line for a limited time period, to satisfy a particular need, for example a user's desire to broadcast a combined video and data transmission to a number of sites on a network simultaneously. A network of conventional o-e-o nodes requires significant time to change the configuration of signal pathway connections in all the nodes, thus limiting how fast changes may be made to bandwidth allocation in such networks, and requiring a long setup time for service provisioning in such networks.
A way to overcome some of the problems of o-e-o nodes is to use optical switch elements inside the nodes, so that the optical signals coming into the node are switched into the desired pathways inside the node, and sent out of the node, all without converting the optical signals into electronic signals. The optical switch elements have included micro-electro-mechanical systems (known as MEMS) of miniature moving mirrors that reflect the optical signals into desired pathways. Another optical switch element used in nodes is an optically transparent oil placed in the optical pathway, along with a heater used to create a vapor bubble in the oil, so that the optical signals may be reflected from the surface of the bubble to move the optical signals to the desired pathways. The MEMS optical switch elements may be expensive to manufacture, and wear and breakage of the moving mirrors can result in failure of the optical switch element. The use of oil in a switch element can lead to chemical degradation of the oil as it is heated over a long time period, or leakage of the oil, either of which can result in failure of the optical switch element. A particular problem is believed to occur in a switch which uses oil if the switch is kept in an on condition, with a bubble constantly kept heated for an extended period of time, such as for months or years; in which case the chemical breakdown of the oil is expected and failure of the switch is expected. A way to overcome some of the problems of reliability of MEMS and oil containing optical switch elements is to provide primary optical switch elements and one or more sets of backup secondary optical switch elements of the same type which operate in parallel, and to provide a backup control electronic system for selectively activating the backup secondary optical switch elements in the case of failure of the primary optical switch elements. Such use of primary and secondary optical switch elements increases the size and cost of the node, and the use of such a backup control electronic system increases the size, cost, and waste heat produced by the node. The MEMS optical switch elements require a substantial amount of time to change the optical pathway, since the miniature mirrors must physically change position. The use of oil in an optical switch element requires a substantial amount of time to change the optical pathway, since the heating of oil requires substantial time to create a bubble, and allowing the oil to cool enough to collapse a bubble also requires substantial time. Such delays in changing optical pathways inside a node are disadvantages of the MEMS optical switch element and the optical switch element which uses oil.
Optical switch elements have been suggested that use liquid crystal materials configured to create total internal reflection (known as TIR) optical switch elements. Such liquid crystal materials are known to have thermal instabilities, thus limiting their usefulness as reliable optical switch elements. Optical switches made using such liquid crystal materials are known to have undesirable cross-talk if arrays of such switches are created on a substrate, thus limiting their usefulness, and making them undesirable, since such optical switch elements. Optical switch elements have been suggested using lithium niobate (LiNbO
3
) as an electro-optic material for waveguides. Such lithium niobate switch elements are known to h
Knobbe Martens Olson & Bear LLP
Mack Ricky
Teloptics Corporation
Thomas Brandi N
LandOfFree
Optical switching network and network node and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical switching network and network node and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical switching network and network node and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3319144