Experimental demonstration of 10Gbaud 64QAM SDM self-homodyne coherent optical transmission in U band with low-complexity sparsity-aware volterra equalization algorithm

In this paper, we design and implement a U-band 10GBaud 64QAM space-division multiplexing (SDM) transmission system based on a multi-core fiber (MCF) with self-homodyne coherent detection (SHCD) architecture, achieving a potential aggregate gross capacity of 39.6 Tbit/s. To address the prohibitive computational overhead and asymmetric nonlinearities inherent in this high-order modulation configuration, we propose a sparsity-aware real-valued intensity-dependent volterra (SA-RIV) equalizer optimized by the zero-attracting recursive least squares (ZA-RLS) algorithm. By decoupling In-phase and Quadrature (I/Q) processing into independent real-valued paths and employing a zero-attracting mechanism to prune redundant coefficients, the proposed method achieves significant complexity reduction. The experimental results show that the proposed SA-RIV provides a significant sensitivity gain of 2.42 dB while maintaining exceptional robustness against modulator bias instability, with all channels operating reliably within the 15% soft-decision forward error correction (SD-FEC) threshold. The SA-RIV achieves a 90% reduction in computational complexity compared to traditional volterra implementations.