An approach to generate high-speed and wideband frequency shift keying (FSK) signals based on carrier phase-shifted double sideband (CPS-DSB) modulation is proposed and experimentally validated. The core part of the scheme is a pair of cascaded polarization-sensitive LiNbO₃ Mach–Zehnder modulators and phase modulators, whose polarization directions of the principal axes are mutually orthogonal to each other. A proof-of-concept experiment is carried out, where a 0.5 Gb/s FSK signal with the carrier frequencies of 4 and 8 GHz and a 1 Gb/s FSK signal with the carrier frequencies of 8 and 16 GHz are generated successfully.