Dynamic range improvement of broadband microwave photonic links using a linearized single-sideband modulator

Abstract

A novel linearized single-sideband modulator is proposed and demonstrated to generate optical single-sideband (OSSB) signal and improve the dynamic range of microwave photonic links. The modulator is composed of a dual-electrode Mach–Zehnder modulator (DEMZM) lying on the top branch and a phase shifter (PS) lying on the bottom branch. By optimizing the optical power split ratio of the linearized modulator and the phase shift of the PS, the third-order inter-modulation distortion (IMD3) can be efficiently suppressed while the second-order distortion components are eliminated simultaneously. It is a multi-octave linearization technique which can be applied for broadband systems. Simulation results show that, the linearized modulator can provide a spurious-free dynamic range (SFDR) of 130dB for a bandwidth of 1Hz at the received optical power of 2dBm assuming shot noise is the dominant noise contribution, which is 22dB higher than the conventional DEMZM. The effects of the finite extinction ratio of modulator, the phase deviation of PS and the dispersion of fiber on the linearization performance are also investigated.