Ultra-wideband optical diffractive network for mode multiplexing across the entire telecommunication range

Advancements in multi-band and space division multiplexing (SDM) technologies are rapidly progressing to support growing data traffic. Current research focuses on hybrid multiplexing in the C + L bands, pushing SDM systems to achieve capacities exceeding 10 Pb/s. Integrating ultra-wideband SDM systems with expanded spectrum leaps forward in transmission capacity. Here, we proposed a comprehensive model of an O + E + S + C + L + U ultra-wideband mode multiplexing transmission system to enhance spectrum utilization. A 4-linearly polarized mode multiplexer, designed utilizing ultra-wideband optical diffractive network with an end-to-end inverse design algorithm, achieves over 90% mode purity and mode crosstalk less than -17 dB, with below -8.87 dB in multiplexer-demultiplexer back-to-back systems, supporting a bandwidth exceeding 420 nm in experiments. Validations across O, E, S, C, L, and U bands demonstrate its efficacy in broadband wavelength-mode hybrid division multiplexing communications. The breakthrough in bandwidth and compatibility with existing application scenarios promise highly efficient ultra-high-speed communication systems for future applications.