Group Delay Compensation By Combining 3 tap FFE With CTLE for 80Gbps PAM4 Optical Transmitter
Group delay peak peak value and bandwidth bottleneck from VCSEL are challenges to achieve high speed optical interconnect at 50Gbps bits rates and above. This paper presents a PAM4 VCSEL based Optical Transmitter that employs 3 tap feedforward equalizer (FFE) and continuous time linear equalizer (CTLE) to overcome these problems. By utilizing one pre emphasis tap and CTLE, bandwidth of this system is extended to 26GHz. Moreover, peak peak value of group delay for this system is reduced to 6.7pspp by using one pre fall tap when frequency is below 26GHz. To adapt to various input signal amplitude, a variable gain amplifier (VGA) is placed in the frontend of transmitter. By using 0.18??m SiGe BiCMOS technology, the operating bits rates are up to 80Gbps with 2.8dBm optical modulation amplitude.
2019 32nd IEEE International System on Chip Conference (SOCC)