Scalable optical switches and switching modules

1. An optical switching device with expansion connections comprising a photonic integrated circuit, the photonic integrated circuit comprising:

N input optical ports where N≥2, M output optical ports where M≥2, and mM expansion-in ports wherein m is an integer greater than or equal to 1;

a N×M multicast switch comprising N MCS input ports connected to a unique one of the N input ports and M MCS output ports;

M (m+1)×1 optical elements, either an optical splitter or an optical switch, each optical element comprising (m+1) input ports and 1 output port, wherein each optical element has an input port connected to one of the M MCS output ports and an output port connected to a unique one of the M output optical ports;

wherein each of the remaining mM input ports of the optical elements are directly connected to a unique expansion-in port.

2. The optical switching device of claim 1 wherein the optical elements are optical switches.

3. The optical switching device of claim 1 wherein the optical elements are optical splitters.

4. The optical switch of claim 1 wherein the N×M multicast switch comprises a tree structure of optical splitters and associated plurality of optical light-paths.

5. The optical switch of claim 4 wherein each input is connected to K branches with K≥M, where if K>M, K−M optical pathways are dormant.

6. The optical switch of claim 4 wherein each input is connected to K branches with K<M and wherein the switching elements are configured to selectively direct a signal from an input to a subset of K outputs.

7. The optical switch of claim 4 wherein a switching block associated with a particular bypass switch connected with an output comprises N−1 sequentially aligned 2×1 optical switching elements.

8. The optical switch of claim 4 wherein a switching block associated with a particular bypass switch connected with an output comprises L {L=smallest integer≥log 2 (N)} sequential levels of 2×1 optical switching elements.

9. An optical switch comprising:

a first multicast switch, a second multicast switch and a third multicast switch;

the first multicast switch comprising: N input ports, M output ports and optical switches selectively connecting each of the N input ports with each of the M output ports;

the second multicast switch and the third multicast switch each comprising N input ports, M MCS output ports, M expansion in ports and M optical elements, either an optical splitter or an optical switch, wherein the optical elements have two inputs respectively connected to a unique MCS output port and expansion in port and an OE output port,

wherein the M output ports of the first multicast switch are optically connected to the M expansion in ports of the second multicast switch, and

wherein the M OE output ports of the second multicast switch are optically connected to the M expansion in ports of the third multicast switch.

10. The optical switch of claim 9 wherein the 2×1 optical elements connecting the MCS output ports and expansion in ports of the second multicast switch and 2×1 optical elements connecting the MCS output ports and expansion in ports of the third multicast switch are configured as a 3×1 optical element connecting the output port of the first multicast switch, the MCS output ports of the second multicast switch and the MCS output ports of the third multicast switch as three input lines with the OE output port being the output of the effective 3×1 optical element.

11. The optical switch of claim 9 wherein the optical elements comprise optical splitters.

12. The optical switch of claim 9 wherein the optical elements comprise optical switches.

13. The optical switch of claim 9 wherein each N×M multicast switch comprises a tree structure of optical splitters and associated plurality of optical light-paths.

14. The optical switch of claim 13 wherein a switching block associated with a particular bypass switch connected with an output comprises L {L=smallest integer≥log 2 (N)} sequential levels of 2×1 optical switching elements.