Waveguide delay based equalization with current summing in a differential transimpedance amplifier
A waveguide delay-based equalization (WDEQ) system is described. The WDEQ system provides a delay in waveguides of the system and electrical signal summing in a differential transimpedance amplifier (TIA) which increases the performance (e.g., bandwidth, etc.) of the optical receiver. The WDEQ system includes an optoelectronic circuit with a directional coupler, a first photodetector, at least two transistors connected to the first photodetector, an optical delay, and a differential transimpedance amplifier (TIA).
1. A method comprising:
receiving an input optical signal;
splitting the input optical signal into a first optical signal and a second optical signal;
delaying the first optical signal;
converting the delayed first optical signal to a first electrical signal using a first photodetector and at least two transistors connected to the first photodetector;
converting the second optical signal to a second electrical signal using a second photodetector and at least two transistors connected to the second photodetector and a differential transimpedance amplifier (TIA); and
summing the first and second electrical signals using the differential TIA.
2. The method according to claim 1 , comprising delaying the first optical signal using a waveguide delay.
3. The method according to claim 2 , wherein the waveguide delay is coupled to an output of a directional coupler.
4. The method according to claim 1 , wherein the first photodetector comprises a first photodiode, wherein the at least two transistors connected to the first photodetector comprise a first NMOS transistor and a first PMOS transistor, and wherein the second photodetector comprises a second photodiode to convert the second optical signal to the second electrical signal, wherein the at least two transistors connected to the second photodetector comprise a second NMOS transistor and a second PMOS transistor.
5. The method according to claim 4 , wherein:
an anode from the first photodiode is connected to a first stage of the differential TIA,
a cathode of the first photodiode is connected to a second stage of the differential TIA,
an anode from the second photodiode is connected to the second stage of the differential TIA, and
a cathode of the second photodiode is connected to the first stage of the differential TIA.
6. The method of claim 5 , wherein each connection between the first photodiode and the first stage and the second stage comprises a signal pad and a Metal-Insulator-Metal Capacitor, and wherein each connection between the second photodiode and the first stage and the second stage comprises a signal pad and a Metal-Insulator-Metal Capacitor.
7. The method according to claim 1 , comprising splitting the second optical signal into a third optical signal and a fourth optical signal using a second directional coupler before generating the second electrical signal.
8. The method according to claim 7 , further comprising:
delaying the fourth optical signal; and
coupling the delayed fourth optical signal and the third optical signal to the differential TIA.
9. A system for communication, the system comprising:
an optoelectronic circuit comprising a directional coupler, a first photodetector, at least two transistors connected to the first photodetector, an optical delay, and a differential transimpedance amplifier (TIA), the optoelectronic circuit being operable to:
receive an input optical signal;
split the input optical signal into a first optical signal and a second optical signal via the directional coupler;
delay the first optical signal via the optical delay;
convert the delayed first optical signal to a first electrical signal using the first photodetector;
convert the second optical signal to a second electrical signal using a second photodetector with at least two transistors connected to the second photodetector and the differential TIA; and
sum the first and second electrical signals using the differential TIA.
10. The system of claim 9 , wherein the optical delay comprises a waveguide delay.
11. The system of claim 10 , wherein the waveguide delay is coupled to an output of the directional coupler.
12. The system of claim 10 , wherein the first photodetector comprises a first photodiode, wherein the at least two transistors connected to the first photodetector comprise a first NMOS transistor and a first PMOS transistor, and wherein the second photodetector comprises a second photodiode to convert the second optical signal to the second electrical signal, wherein the at least two transistors connected to the second photodetector comprise a second NMOS transistor and a second PMOS transistor.
13. The system of claim 12 , wherein:
an anode from the first photodiode is connected to a first stage of the differential TIA,
a cathode of the first photodiode is connected to a second stage of the differential TIA,
an anode from the second photodiode is connected to the second stage of the differential TIA, and
a cathode of the second photodiode is connected to the first stage of the differential TIA.
14. The system of claim 13 , wherein each connection between the first photodiode and the first stage and the second stage comprises a signal pad and a Metal-Insulator-Metal Capacitor, and wherein each connection between the second photodiode and the first stage and the second stage comprises a signal pad and a Metal-Insulator-Metal Capacitor.
15. The system of claim 9 , the optoelectronic circuit being further operable to:
split the second optical signal into a third optical signal and a fourth optical signal using a second directional coupler before generating the second electrical signal.
16. The system of claim 15 , the optoelectronic circuit being further operable to:
delay the fourth optical signal via a second optical delay; and
wherein the delayed fourth optical signal and the third optical signal are coupled to the differential TIA.
17. A method comprising:
receiving an input optical signal;
splitting the input optical signal into a first optical signal and a second optical signal;
converting the first optical signal to a first electrical signal using a first photodetector with at least two transistors connected to the first photodetector;
converting the second optical signal to a second electrical signal using a second photodetector with at least two transistors connected to the second photodetector and a differential transimpedance amplifier (TIA); and
summing the first and second electrical signals using the differential TIA.
18. The method according to claim 17 , wherein the first photodetector is coupled to an output of a directional coupler.
19. The method according to claim 17 , wherein the first photodetector comprises a first photodiode, wherein the at least two transistors connected to the first photodetector comprise a first NMOS transistor and a first PMOS transistor, and wherein the second photodetector comprises a second photodiode to convert the second optical signal to the second electrical signal, wherein the at least two transistors connected to the second photodetector comprise a second NMOS transistor and a second PMOS transistor.
20. The method according to claim 17 , wherein an anode from the first photodetector is connected to a first stage of the differential TIA, and a cathode of the first photodetector is connected to a second stage of the differential TIA.