Abstract

Market forecasts for intra and inter data center interconnects predict high growth rates in the upcoming years. This is associated with increasing requirements in terms of costs, power consumption, and bit rate per wavelength. Today, PAM4 systems are frequently used at up to 100 Gb/s per wavelength. The next logical step is to double the symbol rate to allow bit rates of 200 Gb/s at the same modulation format and at the same direct detection scheme. Such systems require three-digit gigasample analog-to-digital converters with bandwidths larger than 50 GHz, which are not available today as CMOS components. To extend the bandwidth of CMOS converters, we suggest the use of ADC frontends, which sample and demultiplex the analog input signals simultaneously. At the outputs of such ADC frontends, the signals can then be digitized by parallel converters with lower bandwidth and at a lower conversion rate. In this article, we present the circuit implementation of a 1-to-4 ADC frontend in IHP 130 nm SiGe HBT BiCMOS and demonstrate its integration into a 100 GBaud PAM4 transmission system with only 14 GHz of digitizer bandwidth. For optimum performance, the mitigation of intersymbol and interchannel interferences is mandatory in the transmission system. We describe and compare two different receiver DSP architectures for reduction of these interferences and evaluate their performances in electrical and optical back-to-back experiments. Furthermore, we report on transmission experiments over 500 m, 10 km, and 40 km SMF at 1550 nm wavelength. With linear equalization, we obtained a BER below the HD-FEC threshold of 3.8 × 10⁻³ and with 3rd order Volterra equalization, we even achieved a BER below the KP4 threshold of 2.3 × 10−4.

100 Gbit/s PAM4 signal transmission and reception for 2-km interconnect with adaptive notch filter for narrowband interference

Fan Li, Dongdong Zou, Li Ding, Yidan Sun, Jianping Li, Qi Sui, Liangchuan Li, Xingwen Yi, and Zhaohui Li
Opt. Express 26(18) 24066-24074 (2018)

50 GBd PAM4 transmitter with a 55nm SiGe BiCMOS driver and silicon photonic segmented MZM

Laurens Breyne, Hannes Ramon, Kasper Van Gasse, Michiel Verplaetse, Joris Lambrecht, Michael Vanhoecke, Joris Van Campenhout, Günther Roelkens, Peter Ossieur, Xin Yin, and Johan Bauwelinck
Opt. Express 28(16) 23950-23960 (2020)

100 Gb/s PAM4 transmission system for datacenter interconnects using a SiP ME-MZM based DAC-less transmitter and a VSB self-coherent receiver

Zhenping Xing, Alireza Samani, Meng Xiang, Eslam El-Fiky, Thang M. Hoang, David Patel, Rui Li, Meng Qiu, Md. Ghulam Saber, Mohamed Morsy-Osman, and David V. Plant
Opt. Express 26(18) 23969-23979 (2018)

Single channel 112Gbit/sec PAM4 at 56Gbaud with digital signal processing for data centers applications

Dan Sadot, G. Dorman, Albert Gorshtein, Eduard Sonkin, and Or Vidal
Opt. Express 23(2) 991-997 (2015)

Increasing data rate of an optical IMDD system using a cost-efficient dual-band transmission scheme based on RTZ DAC and sub-Nyquist sampling ADC

Rui Deng, Jing He, Jianjun Yu, Yiran Wei, Xin Xiao, Kai Lv, Xiangjun Xin, and Gee-Kung Chang
Opt. Express 26(9) 11599-11607 (2018)