Multiband Comb-Enabled mm-Wave Transmission

A novel architecture to generate and distribute multiband frequency-synchronized sources is studied through an experimental system for simultaneous transmission at 100 and 112.5 GHz in two of the
$W$
-band subbands. An electrooptic frequency comb, containing frequency-synchronized sources, was generated OFF-site and distributed to multiple locations using optical fibers of various lengths and total chromatic dispersion. The effect of the dispersion is studied and demonstrated experimentally. At each site, the optical comb is converted to the equivalent electrical comb (e-comb) using a photodiode (PD) without prior optical filtering. Subsequently, three different frequency-synchronized sources are extracted from the e-comb and used as oscillator and clock sources of the local mm-wave transmitters (TXs). To further provide synchronization between the mm-wave TXs and the remote mm-wave receivers (RXs) without access to the comb, the extracted clock signal at 6.25 GHz was also broadcasted over-the-air to the RXs. The optical comb was generated using the electrooptic technique whereby only one electrical oscillator, determining the phase noise characteristics, is required. The architecture thus provides the capability to generate multiple frequency-synchronized sources, with enhanced phase noise performance suitable for mm-wave transmission, across multiple sites and locations. The performance of the architecture is characterized at varying optical fiber lengths as the parameter of interest. Comparisons to electronic oscillators are also provided. Thus, this work is an experiment demonstration, with theoretical analysis, on the impact of the o-comb distribution and subsequent direct generation of the e-comb in the proposed architecture. In particular, the work demonstrates how chromatic dispersion affects the power and phase noise of the extracted sources and subsequently the mm-wave system performance as a whole.