Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-08-31
2003-04-01
Spyrou, Cassandra (Department: 2872)
Optical waveguides
With optical coupler
Switch
C359S199200
Reexamination Certificate
active
06542655
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to optical crossconnect switches and, more particularly, to an N×N crossconnect switch implemented using wavelength routers combined with space switches.
BACKGROUND OF THE INVENTION
In high capacity optical networks, an essential device is the N×N crossconnect switch. The function of this device is to provide, at each node, full connectivity among several incoming fibers, each carrying several wavelength channels. The switch must be nonblocking, and it must be fast and efficient. If N is not too large, these properties can be realized by using a single N×N wavelength router combined with tunable transmitters capable of producing N wavelengths. However, this technique is only feasible if the size N of the router is not too large. This is because as N increased, the N×N router was difficult to realize in integrated form with satisfactory performance of low loss and low crosstalk, and each transmitter had to provide N wavelengths.
With the ever-increasing capacity of optical networks there is continuing need for even larger N×N crossconnect switches.
SUMMARY OF THE INVENTION
In accordance with the apparatus of the present invention, the problem of implementing a N×N crossconnect switch, for large N, is solved by using an arrangement of smaller wavelength routers combined with space switches. In the prior art, a large N×N switch implemented using a router was difficult to realize in integrated form, with satisfactory performance of low loss and low crosstalk, and each transmitter had to provide N wavelengths. According to the present invention, the number of router wavelengths is reduced by a factor m and the N×N crossconnect switch is constructed in three stages using space switches and smaller routers. The input and output space switches can be implemented using crossbar or Clos type construction. In the crossbar construction, the input and output switches are 1×2 and 2×1 switches respectively. In the Clos construction, the input stage uses m×(2m−1) space switches and the output stage uses (2m−1)×m space switches. In both the crossbar or Clos type construction, the reduced size of the center stage, using (N/m)×(N/m) wavelength routers, allows efficient realization in integrated form. Using input space switches with tunable transmitters, each with N/m wavelengths, provides full non-blocking connectivity of the N×N crossconnect switch. In one arrangement, the input and output space switches are implemented using 2×2, 1×2, and 2×1 switch elements. In one input space switch embodiment, a data modulator is combined with the 2×2 switch elements and integrated on a single wafer. Each input and output space switch can be realized with negligible crosstalk by using a dilated arrangement.
More particularly, my invention is directed to an N×N nonblocking optical switch for providing a connection between any of N inlets and any of N outlets, the N×N switch comprising
an input stage including a plurality of input space switches, each input of each of the input space switches connects to a different one of the N inlets;
an output stage including a plurality of output space switches, each output of each of the output space switches connects to a different one of the N outlets; and
a center stage connected between the input stage and the output stage, the center stage including a plurality of N/m×N/m wavelength routers, wherein a connecting link is provided between each N/m×N/m wavelength router and each input or output switch, so that each N/m×N/m wavelength router connects to each input space switch and each output switch.
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Bernasconi, P., Doerr, C. R., Dragone, C., Cappuzzo, M., Laskowski, E., and Paunescu, A., “Large N× Waveguide Grating Routers,” Journal of Lightwave Technology System IEEE Communications Magazine, 18(7): pp. 985-991, Jul. 2000 May 1987.
Dragone, C., “Optimum Design of a Planar Array of Tapered Waveguides,” J. Opt. Soc. Amer. A., vol. 7, No. 11, pp. 2081-2093, Nov. 1990, Applied Optics, Apr. 26, 1987.
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Amari Alessandro V.
Caccuro John A.
Lucent Technologies - Inc.
Spyrou Cassandra
LandOfFree
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