Simultaneous polarization demultiplexing and vibration sensing via single pilot tone in DSCM-ISAC systems

Integrating sensing capabilities into communication networks is of growing interest for developing intelligent infrastructures. Digital subcarrier multiplexing (DSCM) is a compelling technology for such integrated sensing and communication (ISAC) applications due to its spectral flexibility and compatibility with widely deployed coherent architectures. In this paper, we propose a DSCM-ISAC scheme where a single pilot tone (SPT) simultaneously enables both polarization demultiplexing for communication and vibration sensing. Our design utilizes a hardware-efficient dual-receiver architecture with a high-rate receiver for communication and a simplified low-rate receiver for sensing. This scheme has been demonstrated to achieve 240-Gb/s dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM) transmission, with vibration sensing positioning accuracy reaching 58.6 m root-mean-square error (RMSE) and 14 m standard deviation (STD) under a constrained sensing-power budget over a 42-km fiber link. The system maintains full performance under ultrafast state of polarization (SOP) transients up to 5 Mrad/s, confirming robustness for practical deployment.