Sensing as a Service: Can In-Band Distributed Fiber Optic Sensing Coexist With Coherent Metro DWDM Communication Network?

Distributed fiber optic sensing (DFOS) holds significant promise for providing real-time monitoring and surveillance capabilities in deployed metro networks. By leveraging dense wavelength-division multiplexing (DWDM) technology, sensing channels can be integrated alongside communication channels, thereby enabling simultaneous high-capacity data transmission and fiber sensing application. However, because of the shared propagation path, fiber nonlinearities can induce significant crosstalk between the communication and sensing channels, particularly in metro pointtopoint (P2P) links longer than 80 km. In this paper, we investigate the in-band WDM coexistence case of distributed acoustic sensing (DAS) and communication channels over metro link, considering both co-propagating and counter-propagating configurations. Penalties in communication channels, due to fiber nonlinearities caused by DAS pulse, are comprehensively analyzed through numerical simulations and experimental demonstrations across the full C-band, with a 40λ × 800 Gb/s = 32 Tb/s line-rate coherent transmission over a 90 km fiber span. As less reported, the adverse effects on communication channels of stimulated Raman scattering (SRS) and nonlinear polarization rotation are investigated when the coexistence system utilizes conventional pulse-based DAS setup. In coexistence system, we observe that nonlinear polarization rotation can present a greater challenge to the receiver digital signal processing (DSP) of communication receiver than the commonly believed cross-phase modulation (XPM) induced phase noise. Furthermore, by comparing pulse-based DAS with pulse-compression DAS, our findings indicate that pulse-compression DAS imposes negligible performance penalties on legacy coherent receivers, highlighting its significant potential for adoption in future integrated sensing and communication coexistence systems.