Reducing pulse narrowing in the transmitter signal that drives a limiting E/O converter for optical fiber channels

1. A method for calibrating an optical transmitter that includes a pre-converter electrical channel and a limiting E/O converter, the method comprising:

measuring a metric representative of a pulse width shrinkage of a signal produced by the optical transmitter;

increasing compensation of the pre-converter electrical channel from an initial value;

detecting a compensation level where a data-dependent jitter is minimized;

calibrating the pre-converter electrical channel to have a calibrated compensation level above the compensation level where the data-dependent jitter is minimized.

2. The method of claim 1 wherein the optical transmitter produces an OOK optical signal.

3. The method of claim 1 , further comprising:

determining a performance metric of the optical transmitter from the pulse width shrinkage.

4. The method of claim 3 , wherein determining the performance metric of the optical transmitter comprises:

failing a component in the optical transmitter if the pulse width shrinkage exceeds a pre-specified amount.

5. The method of claim 3 , wherein determining the performance metric of the optical transmitter comprises:

determining a data dependent jitter of the signal produced by the optical transmitter;

determining a combined metric representing a combination of the data dependent jitter and the pulse width shrinkage; and

failing a component in the optical transmitter if the combined metric exceeds a pre-specified amount.

6. The method of claim 5 , wherein determining the combined metric comprises:

averaging the data dependent jitter and the pulse width shrinkage.

7. The method of claim 1 , wherein measuring the metric representative of the pulse width shrinkage comprises:

determining a minimum pulse width for a plurality of pulses in the signal produced by the optical transmitter; and

determining the pulse width shrinkage based on the minimum pulse width.

8. The method of claim 7 , wherein determining the minimum pulse width comprises:

applying a repeating mixed data sequence to the pre-converter electrical channel;

measuring a crossing time for each edge of each pulse in a signal outputted from the pre-converter electrical channel; and

determining the a minimum pulse width for the plurality of pulses based on the measured crossing time differences.

9. The method of claim 1 , wherein a data rate of the optical transmitter is at least 10 G.

10. The method of claim 1 , wherein the optical transmitter complies with an SFP+ form factor.

11. The method of claim 1 , wherein the optical transmitter complies with an X2 or XFP form factor.

12. A method for calibrating an optical transmitter that includes a pre-converter electrical channel and a limiting E/O converter, the method comprising:

measuring a metric representative of a pulse width shrinkage of a signal produced by the optical transmitter;

measuring a metric representative of a data dependent jitter of the signal produced by the optical transmitter;

determining an average of the metric representative of a pulse width shrinkage and the metric representative of a data dependent jitter; and

calibrating the pre-converter electrical channel to have a calibrated compensation level based on the average of the metric representative of a pulse width shrinkage and the metric representative of a data dependent jitter.

13. The method of claim 12 , wherein calibrating the pre-converter electric channel comprises:

calibrating the pre-converter electrical channel to have a calibrated compensation level that minimizes the average of the pulse width shrinkage and the data dependent jitter.

14. The method of claim 12 , wherein the optical transmitter produces an OOK optical signal.

15. The method of claim 12 , wherein measuring the metric representative of the pulse width shrinkage comprises:

determining a minimum pulse width for a plurality of pulses in the signal produced by the optical transmitter; and

determining the metric representative of the pulse width shrinkage based on the minimum pulse width.

16. The method of claim 15 , wherein determining the minimum pulse width comprises:

applying a repeating mixed data sequence to the pre-converter electrical channel;

measuring a crossing time for each edge of each pulse in a signal outputted from the pre-converter electrical channel; and

determining the a minimum pulse width for the plurality of pulses based on the measured crossing time differences.

17. The method of claim 12 , wherein a data rate of the optical transmitter is at least 10 G.

18. A method for testing an optical transmitter that includes a pre-converter electrical channel and a limiting E/O converter, the method comprising:

measuring a metric representative of a pulse width shrinkage of a signal produced by the optical transmitter;

measuring a metric representative of a data dependent jitter of the signal produced by the optical transmitter;

determining an average of the metric representative of a pulse width shrinkage and the metric representative of a data dependent jitter; and

generating an indication that a component in the optical transmitter has failed if the average exceeds a pre-specified amount.

19. The method of claim 18 , wherein measuring the metric representative of the pulse width shrinkage comprises:

determining a minimum pulse width for a plurality of pulses in the signal produced by the optical transmitter; and

determining the metric representative of the pulse width shrinkage based on the minimum pulse width.

20. The method of claim 19 , wherein determining the minimum pulse width comprises:

applying a repeating mixed data sequence to the pre-converter electrical channel;

measuring a crossing time for each edge of each pulse in a signal outputted from the pre-converter electrical channel; and

determining the a minimum pulse width for the plurality of pulses based on the measured crossing time differences.