Low-Cost Broadband Predistortion-Linearized Single-Drive x-Cut Mach–Zehnder Modulator for Radio-Over-Fiber Systems

We experimentally demonstrate a low-cost broadband predistortion circuit (PDC) for the linearization of a single-drive x-cut Mach-Zehnder modulator (sd-xMZM) in broadband analog radio-over-fiber (RoF) links over 3-5 GHz. By tuning the bias current, the nonlinear characteristic of the PDC can be adjusted to linearize different types of nonlinear components in broadband analog RoF links over 3-5 GHz. By adding the PDC in front of the sd-xMZM, input-refereed 1 dB compression point (P_1dB) is improved by 2 dB. By evaluating with the two-tone signal, the PDC allows 14 dB improvement in spurious free dynamic range at 4 GHz, and the third-order intermodulation distortion is suppressed by more than 6 dB over 3-5 GHz. Moreover, the error vector magnitude of an orthogonal frequency division multiplexing ultra-wideband signal is improved by more than 2.5 dB.