www.luxtera.com

400GBASE-DR4 TP2 Observations

Brian Welch

• Simulating TP2 characteristics while varying the following parameters − Transmitter BW: 22-32 GHz − Input Jitter: 2-5x (Normalized Jitter Amplitude)

• Jitter varied as a normalized input jitter amplitude − Correlated to TP2 jitter observations of a 25 GHz TX in PAM2 mode − Broadband sinusoidal input jitter o TX also has additional jitter effects (bounded and Gaussian)

• Observing eye opening and inner eye “VECP” − VECP = (High Frequency Eye Opening)/(Low Frequency Eye Opening)

• Looking at effects of reference equalizer on TP2 measurements

400GBASE-DR4 TP2 Observations

Direct TP2 Observations

No Equalization Applied

Reference TX ~ 25 GHz BW (PAM2 Mode)

2 3

4 5

0.25 UI 0.20 UI

0.15 UI 0.10 UI

Transmitter 1 ~ 32 GHz BW

0.42 UI 0.47 UI

0.51 UI 0.54 UI

2 3

4 5

Transmitter 2 ~ 29 GHz BW

0.40 UI 0.44 UI

0.48 UI 0.52 UI

2 3

4 5

Transmitter 3 ~ 25 GHz BW

0.33 UI 0.38 UI

0.42 UI 0.45 UI

2 3

4 5

Transmitter 4 ~ 22 GHz BW

0.28 UI 0.33 UI

0.37 UI 0.41 UI

2 3

4 5

Eye Width (UI) VECP (dB)

Direct TP2 Observations

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

2 3 4 5

Eye

Wid

th (U

I)

Input Jitter (Normalized)

BW = 32 GHz BW = 29 GHz BW = 25 GHz BW = 22 GHz

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

2 3 4 5

VECP

(dB)

Input Jitter (Normalized)

BW = 32 GHz BW = 29 GHz BW = 25 GHz BW = 22 GHz

• Prior results did not apply equalization to the optical TP2 observations

• As expected the lower bandwidth transmitters subsequently showed greater horizontal/vertical eye closure

• Real receivers are expected to have some equalization ability, such that an equalized TP2 observation should be more accurate

• Following slides look at the 25 GHz bandwidth case with a simple (passive) equalizer − Simulation time prohibited analyzing all cases for this meeting − Equalizer type/setting not optimized

Uncorrected TP2 Observations

Corrected TP2 Observations

Equalization Applied

Transmitter 3 ~ 25 GHz BW (Uncorrected)

0.33 UI 0.38 UI

0.42 UI 0.45 UI

2 3

4 5

Transmitter 3 ~ 25 GHz BW (Corrected)

0.40 UI 0.45 UI

0.49 UI 0.52 UI

2 3

4 5

Eye Width (UI) VECP (dB)

Corrected TP2 Observations (25 GHz Transmitter)

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

2 2.5 3 3.5 4 4.5 5

Eye

Wid

th (U

I)

Input Jitter (Normalized)

Uncorrected Corrected

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

2 2.5 3 3.5 4 4.5 5

VECP

(dB)

Input Jitter Normalized

Uncorrected Corrected

• With low bandwidth transmitters, equalization can have a significant impact on TP2 eye quality − 25 GHz transmitter saw almost 0.08 UI eye width improvement with

simple equalizer − 25 GHz transmitter saw over 2dB eye height improvement with

simple equalizer

• TP2 eye width definitions of 0.4-0.5 UI horizontal eye width should be achievable − Low bandwidth transmitters will likely need reference equalizer to

meet

• TP2 “VECP” definitions of < 2.5 dB should be achievable − Again requiring reference equalizers for low bandwidth transmitters

Corrected TP2 Observations and Summary

Thank You