Beyond 200G Direct Detection Transmission With Nyquist Asymmetric Twin-SSB Signal at C-Band

For short reach and metro applications, single sideband (SSB) is a promising scheme due to its high spectral efficiency and tolerance to chromatic dispersion. In this study, we propose a novel asymmetric twin-SSB scheme based on Nyquist pulse shaping. Without joint equalization, the two sidebands can be separately detected with a small guard band. We experimentally demonstrate 224-Gb/s 16-ary quadrature amplitude modulation (16-QAM) asymmetric twin-SSB transmission with direct detection. After 240-km standard single mode fiber (SSMF) transmission, the bit error rates (BERs) of the right-sideband (RSB) and the left-sideband (LSB) are 3.2 × 10
^-3
and 2.8 × 10
^-3
, respectively, which are below the 7% hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10
^-3
. The net bitrate is 203.7 Gb/s with consideration of both frame redundancy and HD-FEC overhead. To our best knowledge, we report the longest transmission distance for 200G single wavelength and single polarization direct detection systems. The advantages of the asymmetric twin-SSB scheme over the symmetric scheme are discussed through simulating the crosstalk resistance of both two schemes. We also demonstrate 300-Gb/s 32-QAM transmission over 80-km SSMF. The BERs of RSB and LSB are 1.50 × 10
^-2
and 1.61 × 10
^-2
, respectively, which are below the 15% soft-decision forward error correction (SD-FEC) threshold of 1.8 × 10
^-2
. The net bitrate is 254.3 Gb/s with consideration of both frame redundancy and SD-FEC overhead. To our best knowledge, it is the maximum bitrate ever reported for C-band 80-km single wavelength and single polarization direct detection transmission. The proposed scheme provides a useful and low-cost solution for high speed datacenter interconnection and metro-scale transmission.