De Bruijn switch

An optical circuit comprising:

• a first cyclic switch having a number (M) of input paths and the number M of output paths, the first cyclic switch being configured such that signal pulses on the input paths are cyclically shifted by a first cyclic shift (D1) onto the output paths, wherein the first cyclic shift D1 is a selectable parameter;
• and
• a plurality of waveguides, each waveguide having an input end and an output end, the input ends of at least some of the waveguides being coupled to the output paths of the first cyclic switch, wherein the plurality of waveguides includes a plurality of pairs of waveguides implementing mode swap operations having respective swap distances in a range from 0 to dmax, wherein dmax is a maximum swap distance associated with the optical circuit,
• wherein the waveguides are arranged in an order determined according to a de Bruijn sequence defined on an alphabet of dmax+1 characters representing the swap distances from 0 to dmax and a word length of L, wherein L corresponds to a number of signal pulses on different ones of the input paths of the first cyclic switch that are to be arranged onto a contiguous group of paths.

An optical circuit comprising:

• a first cyclic switch having a number (M) of input paths and the number M of output paths, the first cyclic switch being configured such that signal pulses on the input paths are cyclically shifted by a first cyclic shift (Ds) onto the output paths, wherein the first cyclic shift Ds is a selectable parameter;
• a plurality of waveguides forming a spatial de Bruijn array, each waveguide in the spatial de Bruijn array having an input end and an output end, the input ends of at least some of the waveguides being coupled to the output paths of the first cyclic switch, wherein the plurality of waveguides includes a plurality of pairs of waveguides implementing mode swap operations having respective swap distances in a range from 0 to dmax, wherein dmax is a maximum swap distance associated with the optical circuit,
• wherein the waveguides in the spatial de Bruijn array are arranged in an order determined according to a de Bruijn sequence defined on an alphabet of dmax+1 characters representing the swap distances from 0 to dmax and a word length of L, wherein L corresponds to a number of signal pulses on different ones of the input paths of the first cyclic switch that are to be arranged onto a contiguous group of paths;
• a second cyclic switch having a number (N) of input paths and the number N of output paths, the second cyclic switch being coupled to the output ends of the waveguides in the spatial de Bruijn array and configured such that signal pulses on the input paths are cyclically shifted by a second cyclic shift (Dt) onto the output paths, wherein the second cyclic shift Dt is a selectable parameter;
• and
• a number N of delay lines forming a temporal de Bruijn array, each delay line in the temporal de Bruijn array having an input end and an output end, the input end of each delay line being coupled to a different one of the output paths of the second cyclic switch, each delay line having a delay time in a range from 0 to Tmax, wherein Tmax is a maximum delay time associated with the optical circuit,
• wherein the delay lines in the temporal de Bruijn array have input ends coupled to the output paths of the first cyclic switch in an order determined according to a de Bruijn sequence defined on an alphabet of Tmax+1 characters representing the delay times from 0 to Tmax and a word length of L.