Net 30-Tb/s bidirectional IM/DD optical interconnect over 19-core fiber enabled by WDM uplink/downlink twin-SSB PAM-4 transmission

High-capacity optical interconnects with short reach are hugely demanded driven by the exponential growth of data traffic. In this work, four-channel wavelength division multiplexing (WDM) uplink/downlink twin single-sideband (twin-SSB) signals are implemented by a wavelength selective switch (WSS) at once, which simplifies the structure of multi-channel SSB transmitters and reduces the cost of high-capacity optical interconnect. Compared to a double sideband scheme, it has been experimentally proven that the performance of SSB transmission over standard single-mode fiber (SSMF) at C-band with an ultra-high baud rate has been greatly improved, which has the ability to effectively overcome the power fading induced by chromatic dispersion in an intensity modulation and direct detection (IM/DD) system. Besides, Rayleigh backscattering cross talk introduced by the same wavelengths in single-fiber bidirectional transmission is avoided by the proposed uplink/downlink twin-SSB scheme, which achieves 0.5-dB receiver sensitivity improvement compared to the conventional scheme. Finally, whtat is believed to be a record C-band 36.48-Tb/s PAM-4 4λ WDM IM/DD bidirectional optical interconnect is successfully demonstrated over 1-km 19-core fiber under a 20% soft-decision forward error correction (SD-FEC) threshold of 2.4×10^-2 for beyond net 30-Tb/s large-capacity optical interconnection application.