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

摘要

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 $({rm P}_{1{rm dB}})$ 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.