Endogenous integration of communication and interference fading free sensing using telecom pilots via joint polarization-fraction domain multiplexing

In this paper, we propose telecom pilots originally designed for polarization rotation estimation to achieve distributed acoustic sensing (DAS) for standard coherent system. Characterized by joint polarization-fraction domain multiplexing, the telecom pilots deployed in orthogonal polarizations have identical sweep bandwidths but opposite frequency modulation (FM) slopes. Through fractional Fourier transform (FrFT) processing, the telecom pilots can converge to fractional energy peaks and then be distinguished, thereby achieving state of polarization (SOP) rotation monitoring for communication. While for sensing, the Rayleigh backscattering (RBS) light-waves of different telecom pilots serving as sensing probes can not only be compressed but also extracted by FrFT. Therefore, the RBS can be used to suppress interference fading due to independent fluctuation. The feasibility of endogenous integration of sensing and communication (ISAC) is verified by an experiment of 200Gb/s DP-QPSK and 400Gb/s DP-16QAM transmission over 10.4 km fiber, co-existing with interference-fading free DAS. The fading-free DAS is demonstrated through dynamic measurements of single or sweep frequency vibrations, attaining spatial resolution of 1 m. The intensity fluctuation over 50 dB is reduced to 18 dB, with the lowest intensity of synthesized trace being 3.7 dB higher than the noise floor.