US 6,320,995 B1 · Loss equalization by means of port interconnectivity in a multistage optical switch

Abstract

A multistage optical switch includes a stage-to-stage connectivity scheme that provides equalization of losses encountered as optical signals traverse switching crosspoints. Each stage includes more than one switching unit having a first array of input ports and a second array of output ports that are selectively coupled by varying the crosspoints between transmissive states and reflective states. The input ports of a particular switching unit and the output ports of the same unit have rankings that are reflective of the number of optical crosspoints that must be traversed by optical signals propagating between input and output ports having the same ranking. High ranking output ports of the switching units of one stage are optically coupled to low ranking input ports of the subsequent stage, thereby defining stage-to-stage optical paths that ensure equalization in the sums of the crosspoints that are traversed when optical signals propagate through the two stages. Preferably, the connectivity of the second stage to a third stage is a mirror image of the connectivity of the first and second stages.

Claims19

Dependent claims

A multistage optical switch in which each stage includes a plurality of switching units having arrays of input ports and output ports, said input ports of each array and said output ports of each array having a ranking from lowest to highest, each switching unit including an arrangement of optical switching regions for selectively coupling said input ports to said output ports, said switching regions being arranged such that the number of switching regions an optical signal traverses within said each switching unit is dependent on said rankings of specific input and output ports through which said optical signal is propagated, where said number increases in correspondence with increases in said rankings of said specific input and output ports, said optical switch comprising:

a first stage of said switching units;
and
a second stage of said switching units for which high ranking input ports of said switching units of said second stage are optically coupled to low ranking output ports of said switching units of said first stage, thereby achieving at least some equalization in sums of said numbers of said switching regions through which optical signals propagate when optical signals are input at said first stage and output at said second stage.

A multistage optical switch comprising:

a plurality of first stage switches having inputs and outputs that are selectively coupled by manipulation of optical properties at optical crosspoints of waveguides, said inputs and outputs being arranged and ordered relative to said waveguides such that lower order inputs require fewer traversals of said optical crosspoints for coupling to a given output and such that lower order outputs require fewer traversals of said optical crosspoints for coupling to a given input;
a plurality of second stage switches having structural and operational similarities to said first stage switches, said second stage switches having inputs optically coupled to said outputs of said first stage switches in a reverse order such that said low order outputs of said first stage switches are coupled to high order inputs of said second stage switches and such that high order outputs of said first stage switches are coupled to low order inputs of said second stage switches;
and
a plurality of third stage switches having structural and operational similarities to said second stage switches, said second stage switches having inputs optically coupled to outputs of said second stage switches in a reverse order such that low order outputs of said second stage switches are coupled to high order inputs of said third stage switches and such that high order outputs of said second stage switches are coupled to low order inputs of said third stage switches.

1 more element

Dependencies are inferred from the claim text.

Loss equalization by means of port interconnectivity in a multistage optical switch

Life of this patent

Loss equalization by means of port interconnectivity in a multistage optical switch

Life of this patent

Abstract

Claims19