Non-iterative blind linearization algorithm for DML-based multi-IF-over-fiber mobile fronthaul systems.

We propose and experimentally demonstrate a novel digital post-linearization algorithm for the mobile fronthaul system employing bandwidth-efficient multiple intermediate frequency-over-fiber technology and a low-cost directly-modulated laser (DML). The proposed linearization algorithm is distinguished for blind adaption, the absence of training signal, or prior knowledge of the transmission channel. Particularly, it provides a closed-form solution for the estimation of optimal linearizer coefficients, leading to a non-iterative mode without convergence restrictions. In our experiments, one and nine 200 MHz 64-QAM OFDM IF signals (or channels) are transmitted over a 10 km single-mode fiber link using a DML. In both cases (one and nine IF channels), the linearization performance of the proposed algorithm is experimentally validated in terms of the reduction (>8  dB) of the adjacent channel leakage ratio, decrease (>10  dB) of error vector magnitude (EVM), and an increase (>9  dB) of EVM-compliant input RF power range.