Nonlinearity suppression of Mach–Zehnder modulator based on optical carrier processing in radio-over-fiber links

A highly linear transmitter that consists of a dual-drive Mach Zehnder modulator (DD-MZM), an optical gain, and an optical phase shifter in radio-over-fiber links is proposed and demonstrated by simulation. The optical carrier is split equally with one part driving the DD-MZM, while the other part remaining unmodulated. By properly adjusting the magnitude and phase shift of unmodulated optical carrier, two kinds of main origins of third-order IMD (IMD3) have equal intensity and opposite phase, and cancel each other out. The comparison of the proposed technique and double-sideband modulation by MZM is presented. Simulation results shown that the spurious-free dynamic range of 125.3 dB Hz(2/3) is achieved, which is about 26 dB more than a quadrature biased MZM.