Experimental Study on Chirped-Pulse DAS Coexistence With DWDM High-Speed Coherent Communication Systems in C + L Bands

The coexistence of optical fiber sensing technologies with densely deployed telecommunication infrastructures is a topic of high interest in the context of integrated sensing and communication (ISAC). In recent years, distributed acoustic sensing (DAS), based on the φ OTDR principle, has gained significant attention for its high sensitivity and localization capabilities. However, it relies on the transmission of high-peak-power optical pulses (up to ~ 23 dBm), which may interfere with coexisting communication channels. In this work, we experimentally investigate the coexistence of chirped-pulse DAS operating in the C-band with telecommunication channels across the C+L bands. By analyzing post-FEC errors, we show that Kerr-induced nonlinearities from high-peak-power pulses can distort neighboring C-band channels, with measurable impairments at 100 GHz spacing and pulse peak powers as low as 16.5 dBm. These effects can be partially mitigated by increasing channel spacing, adopting longer FEC overhead, or using lower-order modulation formats (e.g., QPSK instead of 16QAM). In contrast, L-band channels experience weaker nonlinear effects, allowing higher tolerated pulse powers (up to ~ 23 dBm for sufficiently spaced channels). Our findings highlighted Raman impairments on the L-band, reducing with increasing frequency distance, and mitigated by the chromatic dispersion walk-off. Additionally, our findings show that counter-propagation between DAS and telecom signals does not introduce measurable penalties. Finally, we did not record any worsening of the DAS sensing performances in any of the coexistence (co- and counter-propagating) scenarios tested.