800G Low-Latency Photonic Data-Center Interconnections over 5 km Hollow-Core Fiber

Driven by the exponential growth of data-center traffic, time-sensitive applications place stringent requirements on the implementation of both high-capacity and low-latency photonic intra-data- center interconnection (Intra-DCI). Generally, both the implementation complexity of digital equalizers to deal with various transmission impairments, and the propagation delay of fiber optics, are two latency sources of photonic Intra-DCI. Even with the help of a complex Volterra decision- feedback equalizer (VDFE) to mitigate various transmission impairments arising in standard single-mode fiber (SSMF), the bit-error ratio (BER) of C-band four-lane 224 Gb/s four-level pulse amplitude modulation (PAM-4) signals can only reach the 20 percent soft-decision forward error correction (SD-FEC) threshold. Here, for the first time, we experimentally demonstrate 896 Gb/s low-latency photonic Intra-DCI over 5 km nested anti-resonant nodeless fiber (NANF) in C-band with a recirculating loop configuration, when only DFE is implemented for all four-lane signals to reach the 7 percent hard-decision FEC (HD-FEC) threshold. Additionally, the NANF-based C-band photonic Intra-DCI with a record net bit-rate of 837 Gb/s can realize 31.5 percent and 40 percent latency reduction of fiber transmission and digital signal processing (DSP), respectively, thus paving the way for next-generation photonic Intra- DCI with high data throughput and low latency.