Optical modulator

1. An optical modulator comprising:

an optical splitter comprising:

an input port for receiving light;

a multimode interference optical splitter downstream of the input port for splitting the light received at the input port; and

first to fourth output ports for outputting the split light; and

at least one Mach-Zehnder interferometer including a Mach-Zehnder combiner,

the Mach-Zehnder combiner including:

a plurality of ingress ports, each corresponding to a different one of the first to fourth output ports, and an egress port;

a multimode interference coupler between the plurality of ingress ports and the egress port; and

another non-ingress port.

2. The optical modulator of claim 1 , further comprising:

a first Mach-Zehnder interferometer and a second Mach-Zehnder interferometer,

each of the first Mach-Zehnder interferometer and the second Mach-Zehnder interferometer comprising a first Mach-Zehnder combiner and a second Mach-Zehnder combiner, respectively; and

an optical combiner comprising:

first and second inlet ports each optically coupled to the egress port of the first Mach-Zehnder combiner and the egress port of the second Mach-Zehnder combiner; and

a outlet port for outputting the light.

3. The optical modulator of claim 2 , wherein the optical combiner comprises a multimode interference coupler comprising the first and second inlet ports and the outlet port.

4. The optical modulator of claim 3 , wherein the multimode interference coupler comprises an additional outlet port for outputting residual light.

5. The optical modulator of claim 4 , further comprising:

a photodetector for detecting the residual light.

6. The optical modulator of claim 2 , wherein the optical splitter and the optical combiner are disposed on different substrates.

7. The optical modulator of claim 1 , wherein each Mach-Zehnder interferometer, of the at least one Mach-Zehnder interferometer, further includes:

first and second waveguides each optically coupled to a different one of the first to fourth output ports.

8. The optical modulator of claim 7 , wherein each Mach-Zehnder interferometer, of the at least one Mach-Zehnder interferometer, further includes:

a first phase shifter operationally coupled to the first waveguide, for modulating the split light propagating in the first waveguide; and

a second phase shifter operationally coupled to the second waveguide, for modulating the split light propagating in the second waveguide.

9. The optical modulator of claim 1 , wherein

the multimode interference optical splitter comprises first and second outlet ports, and

the optical splitter further comprises first and second Y-splitters each comprising an ingress port optically coupled to a different one of the first and second outlet ports.

10. The optical modulator of claim 9 , wherein

the first Y-splitter includes the first and second output ports of the optical splitter, and

the second Y-splitter includes the third and fourth output ports of the optical splitter.

11. The optical modulator of claim 1 , wherein

the optical splitter further comprises fifth to eighth output ports for outputting light, and

at least one Mach-Zehnder interferometer includes a first, second, third, and fourth Mach-Zehnder interferometer, each of the first, second, third, and fourth Mach-Zehnder interferometers including:

a Mach-Zehnder combiner,

first and second waveguides each optically coupled to a different one of the first to eighth output ports,

a first phase shifter operationally coupled to the first waveguide, for modulating the split light propagating in the first waveguide; and

a second phase shifter operationally coupled to the second waveguide, for modulating the split light propagating in the second waveguide.

12. An optical modulator comprising:

a multimode interference optical splitter comprising an input port for receiving light and first to M th output ports for outputting split light, wherein M is at least 2;

first and second additional splitters for receiving the split light, further splitting the split light, and outputting the further split light on first to N th output ports, wherein N is at least 4; and

first through (N/2) th Mach-Zehnder interferometers, each Mach-Zehnder interferometer, of the first through (N/2) th Mach-Zehnder interferometers, including:

a Mach-Zehnder combiner including:

a plurality of ingress ports, each corresponding to a different one of the first to N th output ports, and an egress port; and

a multimode interference coupler between the plurality of ingress ports and the egress port.

13. The optical modulator of claim 12 , wherein

each Mach-Zehnder interferometer, of the first through (N/2) th Mach-Zehnder interferometers, includes a first Mach-Zehnder combiner and a second Mach-Zehnder combiner, respectively, and

the optical modulator further includes:

an optical combiner comprising:

first and second inlet ports each optically coupled to the egress port of the first Mach-Zehnder combiner and the egress port of the second Mach-Zehnder combiner; and

a outlet port for outputting the light.

14. The optical modulator of claim 13 , wherein the optical combiner comprises a multimode interference coupler comprising the first and second inlet ports and the outlet port.

15. The optical modulator of claim 14 , wherein the multimode interference coupler comprises an additional outlet port for outputting residual light.

16. The optical modulator of claim 15 , further comprising:

a photodetector for detecting the residual light.

17. The optical modulator of claim 12 , wherein each Mach-Zehnder interferometer, of the first through (N/2) th Mach-Zehnder interferometers, includes:

first and second waveguides each optically coupled to a different one of the first to N th output ports.

18. The optical modulator of claim 17 , wherein each Mach-Zehnder interferometer, of the first through (N/2) th Mach-Zehnder interferometers, includes:

a first phase shifter operationally coupled to the first waveguide, for modulating the split light propagating in the first waveguide; and

a second phase shifter operationally coupled to the second waveguide, for modulating the split light propagating in the second waveguide.

19. The optical modulator of claim 12 , wherein the first and second additional splitters are first and second Y-splitters, respectively.

20. The optical modulator of claim 19 , wherein

the first Y-splitter includes first and second output ports, and

the second Y-splitter includes third and fourth output ports.