Optical: systems and elements – Deflection using a moving element – By moving a reflective element
Reexamination Certificate
2001-03-16
2004-08-10
Lester, Evelyn A. (Department: 2873)
Optical: systems and elements
Deflection using a moving element
By moving a reflective element
C359S290000, C359S291000, C359S298000, C385S014000, C385S016000, C385S017000, C385S018000
Reexamination Certificate
active
06775043
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to optical switches and, more particularly, to reflector assemblies and cross-connect switches using such reflector assemblies for direct switching of optical signals between input and output optical fibers.
2. Description of the Background Art
Because of its advantages over conventional electrical transmission mediums, including such advantages as increased bandwidth and improved signal quality, the use of fiber optics in communications networks has become commonplace. However, as with electrical signals transmitted over wires which need to be switched between various wires in order for the signals to reach their intended destinations, optical signals similarly need to be switched between different optical fibers at appropriate junctions so that the optical signals reach their intended destinations.
One method of switching an optical signal between fibers is to convert the optical signal to an electrical signal, employ conventional electronic switching components to switch the electrical signal, and then re-convert the electrical signal to an optical signal. An alternative approach is to employ direct optical switching, wherein the optical signal is directed between fibers. The latter approach has distinct theoretical advantages, including an increase in switching speed and a reduction in signal degradation, because it does note require optical-to-electrical and electrical-to-optical conversions.
When implementing direct optical switching, it is desirable to have the capability to switch an optical signal from any one of a number of optical fibers entering a junction (input fibers) to any one of a number of optical fibers exiting a junction (output fibers). Several ways of achieving this have been previously developed. For example, the use of fixed reflectors in conjunction with bending the fiber ends is a known technique. The fiber ends are not bent to point at one another, but rather are directed at one or more reflectors so that an optical signal from the input fiber is reflected to the output fiber. Another approach is to use moveable reflectors, as described in PCT International Publications Nos. WO 99/66354 “Planar Array Optical Switch and Method” and WO 99/67666 “Mirror Based Fiber Optic Switch and Control System”, both of which are incorporated by reference herein. As can be expected, it is critical that the optical signal be directed from the input fiber such that it enters the output fiber along an optical pathway that is in substantial alignment with the output fiber. PCT International Publication No. WO 99/66354 describes various approaches to ensuring that the optical signals are properly aligned.
The problem with conventional state of the art optical switches that use moveable reflectors, however, is not the manner in which the reflectors are aligned with the input and output fibers. Techniques for controlling the position of and aligning reflectors in relation to input and output fibers in an optical switch array is well known. The most significant problem with current optical switches is that they rely heavily on microelectromechanical systems (MEMS) technology. Unfortunately, MEMS technology is not yet mature and is quite limited in its capabilities. One-axis mirrors relying on MEMS technology typically employ mechanical hinges which are susceptible to friction and wear. Therefore, such switches in general do not have an indefinite service life. Two-axis mirrors relying on MEMS technology tend to suffer from additional problems arising out of the common use of electrostatic drivers to position the MEMS mirrors. Electrostatic drivers, however, have a very limited linear response range (e.g., tens of microns) which limits the overall size of the mirror and, therefore, the beam size. The smaller the beam size, the shorter a beam can stay collimated after it passes through a collimating lens. This severely limits the path length and, therefore, the total number of fibers (and switching mirrors) that can be employed in an optical cross-connect (OXC) switch. In addition, the associated limited angular range of electrostatic drivers further limits the numbers of mirrors that can be placed in a MEMS optical cross-connect switch.
Because it is desirable to optically couple any input fiber to any output fiber in a cross-connect switch, moveable reflectors that can be positioned over a wide angular range are a necessity. There is also a need to be able to switch large numbers of signals in a limited space and, therefore, a concomitant need for an optical cross-connect switch design that is compact. Accordingly, there is a need for a reflector array design for an optical cross-connect switch which is suitable for mass production of switches, which provides for individually controllable reflectors over a wide angular range, and which does not solely rely on unreliable MEMS technology. The present invention satisfies those needs, as well as others and overcomes the deficiencies in current optical cross connect switching technologies.
BRIEF SUMMARY OF THE INVENTION
The present invention generally comprises reflector assemblies for use in optical cross-connect switches, as well as practical, area efficient, bi-directional, randomly addressable optical cross-connect switches fabricated using such reflector assemblies. More particularly, the invention comprises optical cross-connect switches that employ reflector assemblies with non-MEMS mirrors that can be fabricated using conventional materials and processes. The reflector assemblies are suitable for mass production of reflector assembly arrays (e.g., pallets) for use in optical cross-connect switches that can (i) achieve good telecom reliability and (ii) offer forward extendibility to larger numbers of switchable fibers.
By way of example, and not of limitation, a cross-connect switch fabricated according to the present invention comprises at least two reflector pallets, wherein each reflector pallet comprises a plurality of reflector assemblies configured in an array. Each reflector assembly includes a non-MEMS mirror that can be rotated in relation to a first axis as well as in relation to a second axis that is generally perpendicular to the first axis, and associated means for rotating the mirror. This two-axis system permits a beam to be steered in two-dimensional space, thus allowing any input fiber to be switched to any output fiber. Therefore, to form a cross-connect switch in accordance with the present invention, an array of input optic fibers is positioned in relation to at least a first reflector pallet, and an array of output optic fibers is positioned in relation to at least a second mirror pallet, wherein each reflector assembly is associated with a single optic fiber. As a result of this configuration, the switch is easily scalable for any number of fibers. Furthermore, the reflector assemblies provide for fabrication of a high fiber packing density, small mirror, small coil, low inductance, fast switching and reliable optical cross-connect switch system for mass production.
In an embodiment of a cross-connect switch in accordance with the present invention, reflector pallets are placed on the opposite sides of the fibers, with one pallet directly in the path of the input fibers at preferably an approximately forty-five degree angle in relation to the axis of the input fibers, and the other pallet directly in the path of the output fibers also at preferably an approximately forty-five degree angle in relation to the axis of the output fibers. The distance between the centers of the input/output fiber bundles is approximately the same as that between the centers of the two reflector pallets. In this embodiment, the reflector pallets form a generally planar switch configuration.
In an alternative embodiment of a cross-connect switch in accordance with the preset invention, a plurality of ref
Fuh Dar-Qwei (David)
Leung Chak
Leung Kent
Trang Howie
Yu Stanley
Blue Sky Research
LaRiviere Grubman & Payne, LLP
Lester Evelyn A.
LandOfFree
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