Experimental investigation of phase noise tolerance of SSB THz signals

Wireless bridges operating at THz frequencies have drawn a lot of attention in recent years. This application requires multiple optical local oscillators (LOs) throughout the link and, hence, the accumulated phase noise may impose a major challenge for its practical implementation. Of all the techniques to mitigate phase noise, single sideband (SSB) modulation is a very promising candidate due to its simple implementation. In this paper, we show, for the first time, the transmission of a 6 GBd SSB quadrature phase shift keying (QPSK) signal at 250 GHz and investigate the impact of laser phase noise on the quality of the THz signal. The performance of the system is investigated by digitally tuning the linewidth of the optical local oscillator up to 10 MHz. The results show no observable penalty associated with increasing linewidth, confirming the validity of SSB for applications where multiple domain conversions are required.