Abstract

Phase-sensitive optical time domain reflectometry measurements using chirped pulses and direct detection are a common option for cost-effective distributed acoustic sensing, able to reach remarkable sensitivities across long ranges in standard fibers. One of the main sources of noise of the technique originates from frequency drift and phase noise of the light source. A previous work has detailed the effects of laser phase noise in strain measurements and described a simple post-processing strategy to mitigate its first order effects. This, however, was restricted to the case where phase noise is the most dominant noise contribution to measurements. In this work, we expand the analysis for the cases of low and high phase noise lasers, and describe the considerations that should be taken in each case. We show that, when relying on the phase-noise cancellation strategy, a portion of the additive noise is converted to spatially correlated noise across the whole fiber, so whenever phase noise is not the dominant noise contribution, there is a minimum number of compensated windows that needs to be used in order to ensure an improvement.