32 Gbit/s QPSK transmission at 385 GHz using coherent fibre-optic technologies and THz double heterodyne detection

Introduction: Over the last five years, the continuously growing demand for data rates is pushing up the performance of terahertz (THz) devices and systems. Such technologies are strongly envisaged for communication applications [1]. Among the different systems already reported, the highest performances have been obtained using a combination of photonics at emission and electronic receivers [2]. As the THz bandwidth is large, the use of simple amplitude signalling can easily lead to up to >40 Gbit/s data rates [3, 4]. However, such schemes are already challenged by higher spectral efficiency (bit/s/Hz) links using quadrature phase shift keying (QPSK) or PSK-8 modulation formats and also with a required compatibility of the THz links with other services [5]. In this Letter, we present the first THz link using QPSK signalling in the sub-millimetre range with data rates of several 10 Gbit/s. Such link, associated with the development of coherent data optic fibre links in metro networks, could be used as a direct converter of a guided optical QPSK into a THz radio, for very high data rate indoor applications.