A Low-Power High-BW PAM4 VCSEL Driver With Three-Tap FFE in 12-nm CMOS FinFET Process
Bibliographic record
Abstract
This work presents a low-power high-bandwidth (BW) PAM4 VCSEL transmitter. We introduce a new cascode voltage-mode (VM) driver to provide a larger output modulation current while using smaller devices and lower power consumption compared to the conventional VM driver. This improves the power efficiency and relaxes the self-loading concern in the conventional designs. The driver also includes an asymmetric three-tap feedforward equalizer (FFE) for MSB and LSB to effectively compensate for the BW and nonlinearity response of the VCSEL. Further, the driver is implemented using multiple segments to optimize the output impedance and linearity. The proposed transmitter is implemented in a 12-nm CMOS FinFET process and is packaged to facilitate both electrical and optical measurements. Based on the electrical measurement, the transmitter supports up to 50-Gb/s nonreturn to zero (NRZ) and up to 64-Gb/s PAM4 data transmission. The optical measurement is done using a commercial 850-nm anode-driven VCSEL. Based on the optical measurement, the proposed design supports up to 40-Gb/s NRZ and 50-Gb/s PAM4 data transmission with an optical modulation amplitude (OMA) of better than 1.4 dBm and power efficiency of 0.82 (excluding VCSEL power) and 0.97 pJ/b using three supplies of 1, 2, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 1.5 V providing currents of 11, 15, and 5 mA, respectively.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".