Native and reconfigurable distributed acoustic sensing enabled by single-carrier 64QAM coherent transmission

The convergence of distributed optical fiber sensing and coherent optical communication offers a promising route toward intelligent fiber networks. However, most existing optical integrated sensing and communication schemes require additional sensing hardware, dedicated waveforms, or complex multiplexing digital signal processing (DSP). Here, we propose a native and reconfigurable distributed acoustic sensing scheme derived from a single-carrier 64-ary quadrature amplitude modulation (64QAM) transmission signal. Known and repeated symbols selected from the standard 64QAM constellation are assigned as sensing probes, while the remaining symbols carry unknown payload data. The method therefore requires neither a non-QAM sensing waveform nor a dedicated sensing subcarrier, and the sensing performance can be dynamically reconfigured by adjusting the interval between adjacent probe symbols in the transmitter-side DSP. In a 10-Gbaud 64QAM coherent transmission experiment over a 2-km fiber link, effective spatial resolutions of 1.6, 3.2, 6.4, and 8 m are achieved, with corresponding phase-noise floors of −64.5, −59.0, −53.3, and −48.9 dB rad 2 /Hz, respectively. Vibrations up to 5 kHz are successfully detected under different probe-interval configurations. The proposed scheme provides a hardware-compatible and flexible approach for integrating distributed acoustic sensing into coherent optical communication systems.