Multi-port optical circulator system
An optical circulator includes a first optical isolator including a first port and a second port and a plurality of optical isolators coupled to the second port of the first optical isolator. Each of the plurality of optical isolators comprise a first port and a second port.
1. An optical circulator comprising:
a first input/output (I/O) port;
a second input/output (I/O) port;
a first waveguide including non-reciprocal material and coupled to the first I/O port;
a second waveguide including non-reciprocal material and a reciprocal phase shift region and coupled to the second I/O port;
a first optical coupler coupled to the first I/O port, the second I/O port, the first waveguide, and the second waveguide, wherein the first optical coupler is operable to introduce a π/2 phase shift for light propagating from the first I/O port to the second waveguide;
a third input/output (I/O) port;
a reflective structure; and
a second optical coupler coupled to the third I/O port, the reflective structure, the first waveguide, and the second waveguide, wherein:
the second optical coupler is operable to introduce a π/2 phase shift for light propagating from the first waveguide to the reflective structure; and
the second optical coupler introduces no substantial phase shift for light propagating from the first waveguide to the third I/O port, and the second optical coupler introduces no substantial phase shift for light propagating from the second waveguide to the reflective structure.
2. The optical circulator of claim 1 wherein the first optical coupler is operable to introduce a π/2 phase shift for light propagating from the second I/O port to the first waveguide.
3. The optical circulator of claim 1 wherein the second optical coupler is operable to introduce a π/2 phase shift for light propagating from the third I/O port to the second waveguide.
4. The optical circulator of claim 1 wherein the non-reciprocal material in the first waveguide and the non-reciprocal material in the second waveguide comprise a magneto-optical material.
5. The optical circulator of claim 4 wherein the magneto-optical material comprises garnet.
6. The optical circulator of claim 5 wherein the non-reciprocal material in the first waveguide is operable to introduce a π/4 phase shift for light propagating in a first direction and the non-reciprocal material in the second waveguide is operable to introduce a −π/4 phase shift for light propagating in the first direction.
7. The optical circulator of claim 6 wherein the non-reciprocal material in the first waveguide is operable to introduce a −π/4 phase shift for light propagating in a second direction opposing the first direction and the non-reciprocal material in the second waveguide is operable to introduce a π/4 phase shift for light propagating in the second direction.
8. The optical circulator of claim 1 wherein the first optical coupler and the second optical coupler comprise waveguide couplers.
9. The optical circulator of claim 1 wherein the second waveguide further includes a reciprocal phase shift region operable to introduce a π/2 phase shift.
10. The optical circulator of claim 1 wherein the second optical coupler introduces no substantial phase shift for light propagating from the first waveguide to the third I/O port and the second optical coupler introduces no substantial phase shift for light propagating from the second waveguide to the reflective structure.
11. The optical circulator of claim 1 wherein the reflective structure is a distributed feedback (DFB) grating.
12. The optical circulator of claim 1 wherein the reflective structure is a Bragg grating.
13. The optical circulator of claim 1 wherein the reflective structure is a side-wall modulated waveguide.
14. The optical circulator of claim 1 wherein the reflective structure comprises a periodic reflector characterized by a stop band.
15. The optical circulator of claim 14 wherein light having a wavelength outside the stopband of the periodic reflector is transmitted through the reflective structure and out of the circulator.