Integrating fixed and mobile coherent optical access networks for unified broadband services

Abstract The integration of fixed and mobile optical access networks can enhance resource utilization, reduce network complexity, and lower deployment costs. Here, we report a field trial demonstrating the integration of hardware-efficient coherent optical transmission and high-fidelity analog waveform delivery over a single optical carrier for converged fixed-mobile networks, enabled by the proposed amplitude-phase layered modulation. This approach not only simplifies the digital coherent reception for fixed optical access, but also enhances analog transmission by enabling signal-to-noise ratio adaptation for 6G mobile front-haul. We experimentally validate the proposed scheme in a 109-km field-deployed fiber link in Hong Kong. A 128 Gb/s phase-insensitive digital coherent transmission is successfully integrated with 20-GHz aggregation bandwidth wireless signals, supporting single-wavelength 1.2 Tb/s common public radio interface equivalent data rate and 256-ary quadrature-amplitude-modulation format. Using this scheme, the fixed optical access achieves a power budget exceeding 38.6 dB, while analog mobile front-haul signals reach signal-to-noise ratios above 47.2 dB and support modulation formats up to 16384-ary quadrature-amplitude-modulation. These results highlight the potential of this solution to unlock the capacity of existing and future fiber-optic infrastructures by converging fixed access, mobile access, and metro networks within a unified framework that enhances scalability and simplifies network deployment.