End-to-End Multi-band Adaptive Optimization Autoencoder Framework for Bandwidth-limited Optical Wireless Fronthaul

Fronthaul solutions based on optical wireless communication (OWC) have emerged as a promising technology for 6G communications. OWC systems offer advantages such as flexible deployment and low construction costs, but face significant challenges due to severe signal-signal beat interference (SSBI), nonlinear distortions and atmospheric turbulence. Efficiently optimizing these joint impairments is particularly crucial for large-scale deployment. Additionally, various mobile network architectures typically have distinct fronthaul requirements, and different applications may necessitate a certain level of isolation. In this paper, we propose a multi-band adaptive optimization autoencoder framework (MBAE) to achieve end-to-end (E2E) optimization for OWC-based fronthaul systems supporting multi-access architecture. The impairments from the multiple transceiver systems and the propagation link can be jointly optimized to achieve performance closest to the global optimum. Studies are conducted in a simulated channel and a real optical wireless communication system respectively to verify the feasibility of the proposed channel model and MBAE. Simulation results show that MBAE can obtain an average Q factor gain of 3 dB compared with the multi-band carrier-less amplitude and phase (CAP) modulation with neural network based post-equalization (NN) and decision feedback equalization (DFE). The experimental results show that MBAE can achieve a 1.9 dB received optical power (ROP) sensitivity gain compared with CAP using NN and DFE at a transmission rate of 36 Gbps under the 7% hard decision-forward error correction (HD-FEC) threshold of 3.8×10-3 utilizing a low-cost PD with 10G-class bandwidth and support a link budget of 44.7 dB. In the performance test under turbulent conditions, MBAE also exhibits superior average performance, achieving a mean Q factor gain of 1.41 dB compared with CAP using NN and DFE. The proposed method can be a promising solution to meet the high-speed and low-cost requirements of future optical wireless fronthaul systems.