Regulating a vertical-cavity surface-emitting laser (VCSEL)-based optical communication link
In one embodiment, a transmitter can bias a vertical-cavity surface-emitting laser (VCSEL) coupled to an optical medium. The biasing of the VCSEL determines at least in part an optical power output by the VCSEL to the optical medium. The transmitter can also modulate the VCSEL with data to transmit the data optically through the optical medium to a receiver; receive from the receiver through a feedback channel an error vector representing a degradation in performance of the VCSEL sensed by the receiver or an instruction vector comprising one or more coefficients for use in biasing the VCSEL; and adjust the biasing of the VCSEL based on the error vector or the instruction vector to regulate the optical power output by the VCSEL to the optical medium.
1. A method comprising:
at a transmitter, biasing a vertical-cavity surface-emitting laser (VCSEL) coupled to an optical medium, the biasing of the VCSEL determining at least in part an optical power output by the VCSEL to the optical medium;
at the transmitter, modulating the VCSEL with data to transmit the data optically through the optical medium to a receiver operable to recover the modulated data;
at the transmitter, receiving from the receiver through a feedback channel:
an error vector representing a degradation in performance of the VCSEL; or
an instruction vector comprising one or more coefficients for use in biasing the VCSEL, the coefficients having been derived from the error vector; and
at the transmitter, adjusting the biasing of the VCSEL based on the error vector or the instruction vector to regulate the optical power output by the VCSEL to the optical medium.
2. The method of claim 1 , wherein the optical medium is a short-reach optical link.
3. The method of claim 1 , wherein the optical medium comprises an optical fiber or a waveguide.
4. The method of claim 1 , further comprising deriving at the transmitter the instruction vector from the error vector.
5. The method of claim 1 , wherein the feedback channel is optical, electrical, or logical.
6. The method of claim 1 , wherein the feedback channel is physically separate from the optical medium.
7. The method of claim 1 , wherein the optical medium carries the feedback channel.
8. The method of claim 1 , wherein the error vector comprises amplitude or bias-level error information.
9. The method of claim 1 , wherein the optical power output by the VCSEL to the optical medium is regulated to have a substantially constant average.
10. The method of claim 1 , wherein the error vector represents a degradation in performance of the VCSEL sensed by a low-pass filter at the receiver.
11. The method of claim 1 , wherein the error vector represents a degradation in performance of the VCSEL sensed by an error calculator at the receiver, the error calculator comparing the power output of the VCSEL received at the receiver and the digital output of the receiver.
12. A method comprising:
at a receiver, receiving data transmitted by a vertical-cavity surface-emitting laser (VCSEL) at a transmitter optically through an optical medium;
at the receiver, recovering the received data;
at the receiver, sensing a degradation in performance of the VCSEL;
at the receiver, generating:
an error vector representing the degradation in performance of the VCSEL; or
an instruction vector comprising one or more coefficients for use in biasing the VCSEL at the transmitter, the biasing of the VCSEL at the transmitter determining at least in part an optical power output by the VCSEL to the optical medium; and
at the receiver, transmitting the error vector or the instruction vector through a feedback channel to the transmitter for adjustment of the biasing of the VCSEL based on the error vector or the instruction vector to regulate the optical power output by the VCSEL to the optical medium.
13. The method of claim 12 , wherein the optical medium is a short-reach optical link.
14. The method of claim 12 , wherein the optical medium comprises an optical fiber or waveguide.
15. The method of claim 12 , wherein the instruction vector is derived at the transmitter from the error vector.
16. The method of claim 12 , wherein the feedback channel is optical, electrical, or logical.
17. The method of claim 12 , wherein the feedback channel is physically separate from the optical medium.
18. The method of claim 12 , wherein the optical medium carries the feedback channel.
19. The method of claim 12 , wherein the error vector comprises amplitude or bias-level error information.
20. The method of claim 12 , wherein the optical power output by the VCSEL to the optical medium is regulated to have a substantially constant average.
21. The method of claim 12 , wherein the degradation in performance of the VCSEL is detected by a low-pass filter at the receiver.
22. The method of claim 12 , wherein the degradation in performance of the VCSEL is detected by an error calculator at the receiver, the error calculator comparing the power output of the VCSEL received at the receiver and the digital output of the receiver.
23. A transmitter configured to:
bias a vertical-cavity surface-emitting laser (VCSEL) coupled to an optical medium, the biasing of the VCSEL determining at least in part an optical power output by the VCSEL to the optical medium;
modulate the VCSEL with data to transmit the data optically through the optical medium to a receiver operable to recover the modulated data;
receive from the receiver through a feedback channel:
an error vector representing a degradation in performance of the VCSEL; or
an instruction vector comprising one or more coefficients for use in biasing the VCSEL, the coefficients having been derived from the error vector; and
adjust the biasing of the VCSEL based on the error vector or the instruction vector to regulate the optical power output by the VCSEL to the optical medium.
24. The transmitter of claim 23 , wherein the optical medium is a short-reach optical link.
25. The transmitter of claim 23 , wherein the optical medium comprises an optical fiber or a waveguide.
26. The transmitter of claim 23 , further configured to derive the instruction vector from the error vector.
27. The transmitter of claim 23 , wherein the feedback channel is optical, electrical, or logical.
28. The transmitter of claim 23 , wherein the feedback channel is physically separate from the optical medium.
29. The transmitter of claim 23 , wherein the optical medium carries the feedback channel.
30. The transmitter of claim 23 , wherein the error vector comprises amplitude or bias-level error information.
31. The transmitter of claim 23 , wherein the optical power output by the VCSEL to the optical medium is regulated to have a substantially constant average.
32. The transmitter of claim 23 , wherein the error vector represents a degradation in performance of the VCSEL sensed by a low-pass filter at the receiver.
33. The transmitter of claim 23 , wherein the error vector represents a degradation in performance of the VCSEL sensed by an error calculator at the receiver, the error calculator comparing the power output of the VCSEL received at the receiver and the digital output of the receiver.
34. A receiver configured to:
receive data transmitted by a vertical-cavity surface-emitting laser (VCSEL) at a transmitter optically through an optical medium;
recover the received data;
sense a degradation in performance of the VCSEL;
generate:
an error vector representing the degradation in performance of the VCSEL; or
an instruction vector comprising one or more coefficients for use in biasing the VCSEL at the transmitter, the biasing of the VCSEL at the transmitter determining at least in part an optical power output by the VCSEL to the optical medium; and
transmit the error vector or the instruction vector through a feedback channel to the transmitter for adjustment of the biasing of the VCSEL based on the error vector or the instruction vector to regulate the optical power output by the VCSEL to the optical medium.
35. The receiver of claim 34 , wherein the optical medium is a short-reach optical link.
36. The receiver of claim 34 , wherein the optical medium comprises an optical fiber or waveguide.
37. The receiver of claim 34 , wherein the instruction vector is derived at the transmitter from the error vector.
38. The receiver of claim 34 , wherein the feedback channel is optical, electrical, or logical.
39. The receiver of claim 34 , wherein the feedback channel is physically separate from the optical medium.
40. The receiver of claim 34 , wherein the optical medium carries the feedback channel.
41. The receiver of claim 34 , wherein the error vector comprises amplitude or bias-level error information.
42. The receiver of claim 34 , wherein the optical power output by the VCSEL to the optical medium is regulated to have a substantially constant average.
43. The receiver of claim 34 , wherein the degradation in performance of the VCSEL is detected by a low-pass filter at the receiver.
44. The receiver of claim 34 , wherein the degradation in performance of the VCSEL is detected by an error calculator at the receiver, the error calculator comparing the power output of the VCSEL received at the receiver and the digital output of the receiver.