Author(s): Liao, QW (Liao, Qiwen); Zhang, YG (Zhang, Yuguang); Ma, SY (Ma, Siyuan); Wang, L (Wang, Lei); Li, LL (Li, Leliang); Li, GK (Li, Guike); Zhang, Z (Zhang, Zhao); Liu, J (Liu, Jian); Wu, NJ (Wu, Nanjian); Liu, LY (Liu, Liyuan); Chen, Y (Chen, Yong); Xiao, X (Xiao, Xi); Qi, N (Qi, Nan)

Source: IEEE JOURNAL OF SOLID-STATE CIRCUITS Volume: 57 Issue: 3 Pages: 767-780 DOI: 10.1109/JSSC.2021.3134874 Published: MAR 2022

Abstract: This article presents a 50-Gb/s optical transmitter (TX), consisting of a 40-nm distributed CMOS driver and a 180-nm silicon-photonic modulator. A lumped-segment Mach-Zehnder modulator (LS-MZM) is developed for high bandwidth (BW) four-level pulse amplitude (PAM-4) modulation. A multi-segment driver with limiting outputs is co-designed, which is distributed into each LS-MZM segment. By grouping these LS-MSM segments in a thermometer code, high-linearity modulation is realized without the need of power-hungry high-swing linear drivers. To improve the optical PAM-4 signal integrity, in-segment multiplexing along with clock phase interpolation is adopted to synchronize the electrical and optical signals across all segments. The hybrid coupling between the driver and modulator is devised to boost the BW of the high-speed data path, while a half-rate clock and data recovery (CDR) circuit is integrated to remove the accumulated jitter. Measurements show that the TX exhibits an extinction ratio (ER) of up to 9.8 dB and a 0.99 ratio of the level mismatch. A figure-of-merit (FoM) of 1.39 pJ/bit/dB corresponds to a 682-mW power, which can be further reduced by 40%, at the cost of a degraded ER of 4 dB. The PAM-4 CDR helps to achieve <10(-12) BER and >0.1-UIpp jitter tolerance (JTOL) from 10 to 100 MHz.

Accession Number: WOS:000761214100014

ISSN: 0018-9200

eISSN: 1558-173X

Full Text: https://ieeexplore.ieee.org/document/9663411