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.

[1]  Anthony Chan Carusone,et al.  Capacitively-Coupled CMOS VCSEL Driver Circuits , 2016, IEEE Journal of Solid-State Circuits.

[2]  Ronny Henker,et al.  90 Gbit/s 4-level pulse-amplitude-modulation vertical-cavity surface-emitting laser driver integrated circuit in 130 nm SiGe technology , 2016, 2016 IEEE MTT-S Latin America Microwave Conference (LAMC).

[4]  Yukito Tsunoda,et al.  8.9 A 40Gb/s VCSEL over-driving IC with group-delay-tunable pre-emphasis for optical interconnection , 2014, 2014 IEEE International Solid-State Circuits Conference Digest of Technical Papers (ISSCC).

[5]  Ling Tian,et al.  4-channel 35 Gbit/s parallel CMOS LDD , 2015 .

[6]  C. Schow,et al.  A 71-Gb/s NRZ Modulated 850-nm VCSEL-Based Optical Link , 2015, IEEE Photonics Technology Letters.

[7]  Xin Yin,et al.  40 Gb/s PAM-4 Transmitter IC for Long-Wavelength VCSEL Links , 2015, IEEE Photonics Technology Letters.

[8]  Alexander V. Rylyakov,et al.  A 50 Gb/s NRZ Modulated 850 nm VCSEL Transmitter Operating Error Free to 90 °C , 2015, Journal of Lightwave Technology.

[9]  Kunzhi Yu,et al.  A 50 Gb/s PAM-4 VCSEL Transmitter With 2.5-Tap Nonlinear Equalization in 65-nm CMOS , 2018, IEEE Photonics Technology Letters.

[10]  Ronny Henker,et al.  A 50 Gb/s 190 mW Asymmetric 3-Tap FFE VCSEL Driver , 2017, IEEE Journal of Solid-State Circuits.

[11]  Herbert Zirath,et al.  An Energy Efficient 56 Gbps PAM-4 VCSEL Transmitter Enabled by a 100 Gbps Driver in 0.25 μm InP DHBT Technology , 2016, Journal of Lightwave Technology.

[12]  Ronny Henker,et al.  A compact electro-optical VCSEL model for high-speed IC design , 2016, 2016 12th Conference on Ph.D. Research in Microelectronics and Electronics (PRIME).