Beyond 200 Gb/s/λ C-band PAM-4 low-latency transmission over 20-km nested antiresonant nodeless fiber

The rapid growth of modern Internet applications demands ever-increasing transmission capacity and reduced latency in optical interconnect systems utilizing intensity modulation and direct detection (IM/DD). However, the intrinsic limitations of silica-based standard single-mode fiber (SMF) will ultimately be insufficient to meet these escalating demands. The nested antiresonant nodeless fiber (NANF), a newly designed hollow-core fiber, has garnered significant attention as a potential solution to these challenges. In this paper, we simultaneously address the issues of capacity and latency in a self-developed 20 km NANF-based four-level pulse amplitude modulation (PAM-4) IM/DD system. To mitigate the chromatic dispersion-induced power fading encountered in NANF, we implement effective compensation and fast equalization based on Tomlinson-Harashima precoding (THP) and a modified feedforward equalization with parallel multi-output (MFFE). Additionally, we measure the propagation latency in NANF using high-time-resolution entangled photon pairs. Experimental results demonstrate an achievement of beyond 200 Gb/s/λ in a PAM-4 IM/DD system operating in C-band over 20 km NANF transmission. Furthermore, the fast-computational equalizer reduces the processing time by 64.6% compared to conventional FFE. In terms of latency, the NANF demonstrates a 31.72% reduction in time delay compared to SMF, offering a viable pathway for future high-capacity and low-latency fiber-optic systems.