273.6 Tbit/s real-time S + C + L-band same-wavelength bidirectional wavelength division multiplexing transmission in anti-resonant hollow-core fiber

Based on its ultra-low backscattering characteristic, anti-resonant hollow-core fiber is a good medium for bidirectional transmission, which means that the wavelengths of the transmission channels are the same in both directions. In this Letter, we present the first, to the best of our knowledge, demonstration of S + C + L-band same-wavelength bidirectional transmission in an anti-resonant hollow-core fiber. By using a commercial real-time coherent optical transceivers and amplified spontaneous emission (ASE) source, a total net throughput of 273.6 Tbit/s is achieved over 1.4 km nested anti-resonant nodeless fiber (NANF) with 19.65 THz bandwidth and bidirectional wavelength division multiplexing (WDM) transmission. Commercial 400 G, 1 T, and 800 G optical modules are employed in the S-band, C-band, and L-band, respectively. We experimentally evaluate the same-wavelength bidirectional WDM transmission performance by verifying 2 × 102 channels of 68 Gbaud probabilistically constellation-shaped (PCS) 16 quadrature amplitude modulation (QAM) in the S-band with 75 GHz grid, 2 × 48 channels of 118 Gbaud PCS-64QAM in a C-band with 125 GHz grid and 2 × 60 channels of 91.6 Gbaud PCS-64QAM in the L-band with 100 GHz grid. All 420 test channels could satisfy the bit error ratio (BER) requirements. The result shows great potential for same-wavelength bidirectional WDM transmission in an anti-resonant hollow-core fiber.