Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-03-24
2001-09-18
Negash, Kinfe-Michael (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C385S018000
Reexamination Certificate
active
06292281
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to optical matrix switches, and more specifically, to protection mechanisms for micro electro-mechanical system (MEMS) cross-bar switches.
2. Discussion of the Related Art
Fiber optic technology has continued to expand across today's data communication networks. Having replaced many of the long-haul connections and other inter-office facilities, fiber optics technology has begun to replace transmission facilities and network elements used in intra-office communication. One of the primary network elements used in intra-office communication is the digital cross-connect. Generally, digital cross-connects link any of several incoming lines to any of several outgoing lines. Today's digital cross-connects switch digital signals on the electrical level. Thus, a fiber optic terminal that receives an optical signal must convert the optical signal to an electrical signal before it sends it to the digital cross-connect.
Optical cross-connects are envisioned as the replacement for the conventional digital cross-connect. Optical cross-connects switch signals at the optical level and therefore obviate the need for optical-to-electrical conversions. The elimination of unnecessary components can lower the overall cost of the network while also increasing the reliability of the network. Reliability is a paramount concern to network planners and bandwidth providers. For optical cross-connects to be considered as viable replacements for digital cross-connects, the reliability of the optical cross-connects must meet reasonable reliability expectations.
SUMMARY OF THE INVENTION
The present invention addresses reliability concerns of micro electro-mechanical system (MEMS) cross-bar switches by providing alternative protection paths for optical signals that are cross-connected by a N×N MEMS cross-bar switch. The N×N optical cross-bar switch receives, on a first side, input optical signals from an array of one or more input lines (i), and outputs, on a second side, output optical signals to an array of one or more output lines (j). Because of the physical distance the light must propagate between the input and output lines, the input lines are typically provided with lenses to convert the signal on an input fiber into a collimated beam, and the output lines are similarly provided with lenses to focus the output collimated beam onto the output fiber. The design of such collimating and focusing lenses is critically dependent on the required optical path length between the two lenses. Cross connection within the N×N switch matrix is effected through the activation of selected switch elements. For example, input line (i) can be connected to output line (j) by activating switch element (i,j) in the N×N cross-bar switch. In addition to the N×N matrix of switch elements, the MEMS cross-bar switch of the present invention includes a N×M matrix of protection switch elements, a M×N matrix of protection switch elements, and a set of at least M protection switch elements.
The N×M matrix of protection switch elements is positioned between the array of input lines (i) and the first side of the N×N optical cross-bar switch such that the N rows of the N×M matrix of protection switch elements are aligned with the N rows of the N×N optical cross-bar switch. The M×N matrix of protection switch elements is positioned between the second side of the N×N optical cross-bar switch and the array of one or more output lines (j) such that the N columns of the M×N matrix of protection switch elements are aligned with the N columns of the N×N optical cross-bar switch. Finally, each of the M protection switch elements in the set of at least M protection switch elements is aligned with one of the M columns of the N×M matrix of protection switch elements and one of the M rows of the M×N matrix of protection switch elements.
This configuration of protection switch elements in combination with the N×N optical cross-bar switch enables a portion of an original path of an optical signal from an input line (i) that is connected to an output line (j) via switch element (i,j) in the N×N optical cross-bar switch to be switched to an alternative protection path that traverses a path between a first protection switch element in row (i) of the N×M matrix of protection switch elements, a second protection switch element in column (j)of the M×N matrix of protection switch elements, and a protection switch element in the set of at least M protection switch elements that is aligned with the first and second protection switch elements. It is a feature of the present invention that the path length of the alternative protection path is the same as the original path of the optical signal.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
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Bala Krishna
Tomlinson W. John
Morgan & Lewis & Bockius, LLP
Negash Kinfe-Michael
Tellium Inc.
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