Abstract
The nonlinear degradations and chromatic dispersion induced bandwidth penalty are critical obstacles for implementing the analog radio-over-fiber (A-RoF) technique in future mobile fronthaul (MFH). In this paper, we propose an analog multiple intermediate-frequency-over-fiber (multi-IFoF) MFH system with blind linearity improvement and flexible dispersion-induced bandwidth penalty mitigation. The bias adjustment of a single-electrode driven dual-drive Mach–Zehnder modulator is used to compensate the bandwidth penalty arising from the dispersion-induced power fading of fiber links in different lengths. This operation can increase the available bandwidth for the MFH system free of even-order intermodulation distortions (IMDs). At the receiver, a self-adaptive digital post-processing algorithm is introduced to blindly improve the linearity of the IFoF MFH system by suppressing the residual odd-order IMDs, with no need of training signals or prior knowledge of the transmission channel. In the proof-of-concept experiments, the transmission of 64-QAM-OFDM signals in 1 to 12 IF channels with a 500-MHz bandwidth has been demonstrated over standard single-mode fibers (SSMFs) of 20, 50, and 100 km. For the 50-km (or 100-km) SSMF, the bandwidth penalty for a broadband signal with a bandwidth of 4.5 GHz (or 2.5 GHz) is fully compensated. In addition, the proposed post-processing algorithm can significantly suppress the odd-order IMDs and thus improve the linearity by greater than 5.4 dB in terms of the input RF power range which retains an acceptable error-vector-magnitude (EVM) performance for the 64-QAM-OFDM signal.
© 2019 IEEE
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