Open AccessPAM‐4 VCSEL driver with selective falling‐edge pre‐emphasis
Author(s) -
Soenen W.,
Lambrecht J.,
Yin X.,
Spiga S.,
Amann M.C.,
Van Steenberge G.,
Bakopoulos P.,
Bauwelinck J.
Publication year - 2018
Publication title -
electronics letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.375
H-Index - 146
ISSN - 1350-911X
DOI - 10.1049/el.2017.3945
Subject(s) - emphasis (telecommunications) , vertical cavity surface emitting laser , overhead (engineering) , modulation (music) , optics , laser , enhanced data rates for gsm evolution , optoelectronics , materials science , computer science , electronic engineering , electrical engineering , telecommunications , physics , engineering , acoustics
Data centre optical links are migrating to four‐level pulse amplitude modulation (PAM‐4) as a method to extend the data rate while covering longer distances. Vertical‐cavity surface‐emitting lasers (VCSELs) enable the integration of low‐power transmitters, but their non‐linear and bias‐dependent behaviour makes conventional feed‐forward equalisation less effective. This Letter presents a 0.13μ m SiGe BiCMOS PAM‐4 driver that boosts the falling‐edge to the bottom level through a selective pre‐emphasis technique. Experiments at 25 GBd (50 Gb/s) reveal that adding selective pre‐emphasis to a 4‐tap equalised current driving a 20.6 GHz 1.5μ m VCSEL, relaxes the critical PAM‐4 link budget requirements by >1 dB at the KP4 forward error correction threshold of 2.2 × 10 − 4 . The potential of PAM‐4 VCSEL transmitters can be significantly enhanced by including selective pre‐emphasis to the equalisation topology while requiring minimal overhead.