Enhanced digital diagnostics for optical PAM apparatus
A Pulse Amplitude Modulated (PAM) optical device utilizing multiple wavelengths, features a communications interface having enhanced diagnostics capability. New registers are created to house additional diagnostic information, such as error rates. The diagnostic information may be stored in raw form, or as processed on-chip utilizing local resources.
1. An optical communication module comprising:
an optical transmitter element and an optical receiver element configured to handle communication of optical data and electronic data including digital signal processing (DSP); and
a master logic control comprising a first register storing a first DSP parameter captured by a debugging memory, the master logic control configured to,
receive from the optical transmitter element or the optical receiver element, additional raw parametric information relating to the optical data or the electronic data,
cause an engine to process first DSP parameter with the additional raw parametric information to create second diagnostic information, and
store the second diagnostic information in a new register.
2. The optical communication module of claim 1 wherein processing the first DSP parameter with the additional raw parametric information comprises extracting a pulse link response highlighting a residual linear Inter Symbol Interference (ISI) component.
3. The optical communication module of claim 2 wherein the engine is further configured to break down a finite link Signal-to-Noise Ratio (SNR) into the residual linear ISI component and other components.
4. The optical communication module of claim 3 wherein one of the other components comprises noise.
5. The optical communication module of claim 4 wherein:
the DSP parameter comprises a Digital Timing Loop (DTL) parameter;
a Kf accumulator value is translated to extract lane frequency offset; and
the noise is extracted by accumulating DTL readout.
6. The optical communication module of claim 3 wherein one of the other components comprises low-frequency direct current (DC) baseline errors.
7. The optical communication module of claim 6 wherein the DSP parameter comprises analog front-end gain.
8. The optical communication module of claim 7 wherein the DC baseline errors are determined from Continuous Time Linear Equalizer (CTLE) Equalization code to assess a peak-peak value and identify DC gain and applied high-frequency analog boost.
9. The optical communication module of claim 7 wherein the DC baseline errors are determined from DC offset and timing mismatch errors.
10. The optical communication module of claim 3 wherein one of the other components comprises non-linearities.
11. The optical communication module of claim 1 wherein:
the first DSP parameter comprises a Feed Forward Equalization (FFE) output;
the additional raw parametric information comprises slicer information; and
the second diagnostic information comprises a Bit Error Rate (BER) of a Forward Error Correction (FEC) function.
12. The optical communication module of claim 1 wherein the first DSP parameter comprises an Analog-to-Digital Conversion (ADC) output.
13. The optical communication module of claim 1 wherein the engine is further configured to process tap coefficients.
14. The optical communication module of claim 13 wherein the tap coefficients comprise Feed Forward Equalization (FFE) tap coefficients.
15. The optical communication module of claim 13 wherein the tap coefficients comprise Decision Feedback Equalization (DFE) tap coefficients.
16. The optical communication module of claim 1 wherein the engine is further configured to process PAM4 levels.
17. The optical communication module of claim 1 wherein the engine is further configured to process slicer thresholds.
18. The optical communication module of claim 17 wherein:
the electronic data comprises equalizer output data; and
the second diagnostic information comprises an estimated link slicer signal-to-noise ratio (SNR) produced by,
slicing the equalizer output data using converged PAM levels and slicer thresholds internally driven by a DSP control loop,
labeling a discrepancy between the equalizer output and an expected PAM level as an error signal, and
calculating the estimated link slicer SNR as a ratio between an average level power and an error signal mean square.
19. The optical communication module of claim 1 wherein the engine is further configured to process reflection-canceller coefficients.
20. The optical communication module of claim 1 wherein the master logic control is further configured to send the second diagnostic information to a host via a communications interface.