Beyond Terabit/s/λ Nonlinearity-Free Transmission Over the Hollow-Core Fiber

In this paper, we demonstrate the beneficial ultra-low nonlinearity and ultimate-low latency of hollow-core fibers (HCFs) through transmission of 130-GBaud Terabit/s/λ wavelength-division multiplexed (WDM) signals in an optical recirculating loop. A comparative study has been performed by inserting either a ∼1.1-km length of HCF or a matched length of single-mode fiber (SMF) as the fiber under test into the loop. The transmission performance of both dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM) and DP probabilistic constellation shaping 64-ary QAM (DP-PCS-64QAM) are presented. We show that the HCF can accommodate nonlinearity-free transmission for the 130-GBaud Terabit/s/λ signals under a launch power up to 23 dBm (∼13.5 dBm/channel). As such, after 25-loop transmission with a 23-dBm launch power, more than 2-dB signal-to-noise ratio improvement and ∼17.4% higher capacity can be achieved. In the meantime, the >30% lower latency of the HCF is directly validated through the comparison of the power monitoring traces of the SMF-/HCF-based optical recirculating loop. Finally, we perform a field trial of 90.22-GBaud 16QAM transmission over a ∼1.4-km length of deployed HCF cable, confirming the practical applicability of using the HCF for high-capacity low-latency optical transmission.