A filterless, polarisation-controlled 40 GHz optical millimeter-wave generation using two Mach-Zehnder modulators in parallel

Abstract

This work demonstrates polarisation-controlled millimeter-wave generation without using an optical filter. The configuration involves two lithium-niobate Mach-Zehnder modulators operating in parallel at the maximum transmission bias point (MATP). In the proposed scheme, a 5 GHz local RF signal is subjected to frequency 8-ctupling, resulting in the generation of a 40 GHz millimeter-wave signal. The system achieves sideband suppression ratios (SSRs) of 50 dB and 44 dB in the optical and RF domains, respectively, for a modulation index of 2.868. Carrier suppression is achieved using a polarisation-based control method. An analytical assessment is carried out to evaluate the variation in SSR with changes in the extinction ratio, the azimuth angle of the polarisation controller, and the amplitude of the RF drive signal.