SSB single carrier and multicarrier in C-band FSO transmission with KK receiver

With the increasing demand of bandwidth, a higher capacity communication system is required for optical short link and access network. Intensity modulation/direct detection (IM-DD) is considered as a reasonable method in access network, due to its low cost and power consumption. However, it reduces the spectral efficiency compared with IQ modulation. In addition, single-sideband (SSB) signal occupies less bandwidth than double-sideband signal (DSB). However, SSB systems suffer from signal-signal beat interference (SSBI) from photodiodes (PDs). Recently, Kramers-Kronig (KK) receiver is proposed to mitigate SSBI. Meanwhile, single-sideband (SSB) signal is the prerequisite for KK scheme, and this kind of signal is also tolerant to fiber chromatic dispersion and multipath-fading. On the other hand, free-space optical (FSO) communication is becoming a promising candidate for next generation optical access network. Thus we experimentally demonstrate the KK scheme in 20km SSMF and 20m FSO links with both single carrier signal and multicarrier signal. We compare the performance between them with and without pre-equalization (pre-EQ). With the help of probabilistically shaped (PS) mapping to gives an increase in the sensitivity over an additive white Gaussian noise (AWGN). We reach a 117bit/s transmission with a spectral efficiency of 5.85 bit/s/Hz of 20 Ghz bandwidth with single modulator and single photodiode (PD) in fiber-FSO system.