100G PAM-6 and PAM-8 Signal Transmission Enabled by Pre-Chirping for 10-km Intra-DCI Utilizing MZM in C-band

Abstract

In this paper, we experimentally demonstrate the transmission of 100G PAM-6 and PAM-8 signals for 10-km intra-data center interconnects (intra-DCI) in C-band, which is enabled by pre-chirping technique utilizing a commercial dual-arm Mach-Zehnder modulator (MZM). At the transmitter side, the use of pre-chirping technology can overcome frequency selective fading (FSF) caused by fiber dispersion (CD) in intensity modulation and direct detection (IM/DD) systems. The pre-chirping is realized by adjusting the bias voltage of dual-arm MZM operating at single driven state. At the receiver, Volterra Non-Linear Equalizer (VNLE) is used to eliminate nonlinear impairments caused by pre-chirping. With the joint pre-chirping and nonlinear elimination in single driven dual-arm MZM based IM/DD system, 45-Gbaud PAM-6 and 40-Gbaud PAM-8 signals are successfully transmitted over 10-km single mode fiber (SMF) with a bit-error-ratio (BER) below 3.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . While in the chirp-free IM/DD system with dual-arm MZM operating at push-pull state, BERs of 45-Gbaud PAM-6 and 40-Gbaud PAM-8 signals over 10-km SMF transmission deteriorate dramatically to nearly 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . The experimental results show that our proposed pre-chirping scheme can effectively enhance the robustness of IM/DD systems against the CD-induced FSF, and this scheme is a promising candidate for 10-km 100G intra-DCI.