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

The integration of fixed and mobile optical access networks can enhance resource utilization, reduce network complexity, and lower deployment costs. Here, we report the first 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 ampli- tude–phase layered modulation. In this scheme, digital bits are encoded using unipolar pulse amplitude modulation, while analog radio-frequency waveforms are imposed on the optical phase. This approach not only improves digital trans- mission for fixed optical access by rendering it phase-insensitive and eliminating the need for carrier phase recovery in digital signal processing, but also enhances analog transmission by enabling signal-to-noise ratio (SNR) adaptation and supporting ultra-high-order modulation formats for 6G applications. We exper- imentally validate the proposed scheme in a 109-km field-deployed fiber metro network in Hong Kong, providing all-optical connectivity among four nodes, including two universities and two data centers. Specifically, a 128 Gb s−1 phase- insensitive digital coherent transmission is successfully integrated with 20-GHz aggregation bandwidth wireless signals, supporting single-wavelength 1.2 Tb s−1 common public radio interface equivalent data rate and 256-ary quadrature- amplitude-modulation (QAM) format. Using this scheme, the fixed optical access achieves a power budget exceeding 38.6 dB, while analog mobile fronthaul signals reach SNRs above 47.2 dB and support modulation formats up to 16384-QAM. 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.