Bandwidth-Efficient and Low-Complexity Mobile Fronthaul Transmissions Utilizing Phase Modulation and Direct Detection

Owing to its cost-effectiveness and simplicity, IMDD is preferred in the bandwidth-efficient and low-complexity MFH transmissions. However, a DC bias is still needed at the transmitter to ensure the optimal transmission performances whilst a high received optical power is required to obtain a high link gain. In this paper, by making use of MZI-based PM-to-IM conversion, PMDD is proposed to replace the traditional IMDD to not only omit the active transmitter bias, allowing for a simpler and low-power transmitter implementation, but also improve the link gain of the MFH transmission. We present a theoretical analysis to describe the important characteristics of PMDD-based MFH transmission links. To verify the feasibility of the proposed scheme, extensive numerical explorations are undertaken of the achievable MFH transmission performances for vital component features. Simulation results indicate that both the MZI FSR and laser linewidth play the significant roles in determining the transmission performances. More importantly, it is also shown that, in comparison with IMDD, PMDD gives rise to a ~3dB improvement of the receiver sensitivity for synchronously transmitting the CWs and LTE signals due to its inherent high link gain.