Optical waveguide multi-cascaded coupling mode division multiplexer

1. An optical waveguide multi-cascaded coupling mode division multiplexer, comprising an optical waveguide layer, wherein the optical waveguide layer comprises a first optical waveguide and a second optical waveguide;

the second optical waveguide comprises a transmission optical waveguide and a plurality of coupling structures;

each coupling structure comprises a coupling optical waveguide and a connecting optical waveguide;

the coupling optical waveguide and the transmission optical waveguide are connected through the connecting optical waveguide, wherein one end of the connecting optical waveguide is connected to one end of the coupling optical waveguide and another end of connecting optical waveguide is connected to one end of the transmission optical waveguide, another end of the transmission optical waveguide is connected to a side surface of another adjacent connecting optical waveguide, and another end of the coupling optical waveguide is a free end;

the coupling optical waveguide is parallel to the transmission optical waveguide; the lengths of the coupling optical waveguides in the coupling structures are obtained so that the power of the two superimposed optical waves is equal, and the phases of the modes in the waveguides of any two superimposed coupling structures are equal at the superposition position, such that the phase difference is 0, so that the maximum power of the optical waves after coupling and superposition is ensured;

the distance between the coupling optical waveguide and the first optical waveguide is smaller than that between the transmission optical waveguide and the first optical waveguide; and

when optical waves are propagated in the first optical waveguide, the coupling structures in the second optical waveguide are used for sequentially coupling the mode power of the first optical waveguide, the sequentially coupled mode power is superposed, and the coupled and superposed power is output at the output end.

2. The optical waveguide multi-cascaded coupling mode division multiplexer according to claim 1 , wherein the connecting optical waveguide is an S-shaped bent optical waveguide.

3. The optical waveguide multi-cascaded coupling mode division multiplexer according to claim 1 , wherein the heights of the first optical waveguide and the second optical waveguide are equal, and the widths of the first optical waveguide and the second optical waveguide are adjusted to ensure that the effective refractive index of the high-order mode in the first optical waveguide is equal to that of the fundamental mode in the second optical waveguide.

4. The optical waveguide multi-cascaded coupling mode division multiplexer according to claim 3 , wherein the coupling structures comprise three coupling structures.

5. The optical waveguide multi-cascaded coupling mode division multiplexer according to claim 1 , wherein the distance between the transmission optical waveguide and the first optical waveguide is larger than the maximum effective coupling distance.

6. The optical waveguide multi-cascaded coupling mode division multiplexer according to claim 1 , wherein the distance between the coupling optical waveguide and the first optical waveguide is 4 μm.

7. The optical waveguide multi-cascaded coupling mode division multiplexer according to claim 1 , further comprising a substrate layer, wherein the substrate layer is taken as a substrate for placing and fixing the first optical waveguide and the second optical waveguide.

8. The optical waveguide multi-cascaded coupling mode division multiplexer according to claim 7 , wherein the optical waveguide layer is made of polymer photoresist, and the substrate layer is made of an FR-4 epoxy plate.

9. An optical waveguide communication system, comprising the optical waveguide multi-cascaded coupling mode division multiplexer according to claim 1 .

10. The optical waveguide communication system according to claim 9 , wherein the connecting optical waveguide is an S-shaped bent optical waveguide.

11. The optical waveguide communication system according to claim 9 , wherein the heights of the first optical waveguide and the second optical waveguide are equal, and the widths of the first optical waveguide and the second optical waveguide are adjusted to ensure that the effective refractive index of the high-order mode in the first optical waveguide is equal to that of the fundamental mode in the second optical waveguide.

12. The optical waveguide communication system according to claim 11 , wherein the coupling structures comprise three coupling structures.

13. The optical waveguide communication system according to claim 9 , wherein the distance between the transmission optical waveguide and the first optical waveguide is larger than the maximum effective coupling distance.

14. The optical waveguide communication system according to claim 9 , wherein the distance between the coupling optical waveguide and the first optical waveguide is 4 μm.

15. The optical waveguide communication system according to claim 9 , further comprising a substrate layer, wherein the substrate layer is taken as a substrate for placing and fixing the first optical waveguide and the second optical waveguide.

16. The optical waveguide communication system according to claim 15 , wherein the optical waveguide layer is made of polymer photoresist, and the substrate layer is made of an FR-4 epoxy plate.