Method and system for integrated multi-port waveguide photodetectors

1. A method for communication, the method comprising:

in an optical receiver on a chip, the optical receiver comprising a multi-port waveguide photodetector having three or more input ports:

receiving optical signals in the optical receiver;

coupling one or more optical signals to different ports in a first side of the multi-port waveguide photodetector via optical waveguides in the chip;

coupling two or more optical signals to different ports in a second side opposite the first side of the multi-port waveguide photodetector via different optical waveguides in the chip; and

generating an output electrical signal based on the coupled optical signals using the multi-port waveguide photodetector.

2. The method according to claim 1 , wherein the multi-port waveguide photodetector comprises four ports coupled to two polarization splitting grating couplers (PSGCs) that receive the optical signals in the chip.

3. The method according to claim 1 , comprising coupling optical signals to the multi-port waveguide photodetector via S-bends at ends of the optical waveguides.

4. The method according to claim 1 , comprising coupling optical signals to the multi-port waveguide photodetector via tapers at ends of the optical waveguides.

5. The method according to claim 1 , wherein a width of the multi-port waveguide photodetector on the first and second sides that are coupled to the optical waveguides is wider than a width of the optical waveguides coupled to the sides.

6. The method according to claim 1 , comprising coupling the optical signals to one or more grating couplers in the chip via an optical fiber coupled to the chip.

7. The method according to claim 1 , wherein a PN junction in the multi-port waveguide photodetector is arranged laterally.

8. The method according to claim 1 , wherein a PN junction in the multi-port waveguide photodetector is arranged vertically.

9. The method according to claim 1 , wherein the multi-port waveguide photodetector comprises a germanium absorbing layer.

10. The method according to claim 1 , wherein the chip comprises a complementary metal oxide semiconductor (CMOS) photonics chip.

11. The method according to claim 1 , comprising mixing the optical signals with local oscillator signals using the multi-port waveguide photodetector.

12. The method according to claim 1 , comprising communicating an optical signal to one of the three or more input ports via a normally off optical switch in a transmitter path in the chip, thereby enabling built-in self-test of the transmitter path.

13. A system for communication, the system comprising:

an optical receiver on a chip, the optical receiver comprising a multi-port waveguide photodetector having three or more input ports, the optical receiver being operable to:

receive optical signals in the optical receiver;

couple one or more optical signals to different ports in a first side of the multi-port waveguide photodetector via optical waveguides in the chip;

couple two or more optical signals to different ports in a second side opposite the first side of the multi-port waveguide photodetector via different optical waveguides in the chip; and

generate an output electrical signal based on the coupled optical signals using the multi-port waveguide photodetector.

14. The system according to claim 13 , wherein the multi-port waveguide photodetector comprises four ports coupled to two polarization splitting grating couplers (PSGCs) that receive the optical signals in the chip.

15. The system according to claim 13 , wherein the optical receiver is operable to couple optical signals to the multi-port waveguide photodetector via S-bends at ends of the optical waveguides.

16. The system according to claim 13 , wherein the optical receiver is operable to couple optical signals to the multi-port waveguide photodetector via tapers at ends of the optical waveguides.

17. The system according to claim 13 , wherein a width of the multi-port waveguide photodetector on the first and second sides that are coupled to the optical waveguides is wider than a width of the optical waveguides coupled to the sides.

18. The system according to claim 13 , wherein the optical receiver is operable to couple the optical signals to one or more grating couplers in the chip via an optical fiber coupled to the chip.

19. The system according to claim 13 , wherein a PN junction in the multi-port waveguide photodetector is arranged laterally.

20. The system according to claim 13 , wherein a PN junction in the multi-port waveguide photodetector is arranged vertically.

21. The system according to claim 13 , wherein the multi-port waveguide photodetector comprises a germanium absorbing layer in a complementary metal oxide semiconductor (CMOS) photonics chip.

22. The system according to claim 13 , wherein the optical receiver is operable to mix the optical signals with local oscillator signals using the multi-port waveguide photodetector.

23. The system according to claim 13 , wherein the optical receiver is operable to communicate an optical signal to one of the three or more input ports via a normally off optical switch in a transmitter path in the chip, thereby enabling built-in self-test of the transmitter path.

24. A system for communication, the system comprising:

an optical receiver on a chip, the optical receiver comprising one or more grating couplers and a multi-port germanium waveguide photodetector having four input ports, the optical receiver being operable to:

receive optical signals via said one or more PSGCs;

couple one or more optical signals to different ports in a first side of the multi-port waveguide photodetector via optical waveguides in the chip;

couple two or more optical signals to different ports in a second side opposite to the first side of the multi-port waveguide photodetector via different optical waveguides in the chip; and

generate an output electrical signal based on the coupled optical signals using the multi-port waveguide photodetector.