Impact of non-Lorentzian laser phase noise on phase-OTDR performance

We highlight the importance of the laser source phase noise in sensing applications and show that the standard Lorentzian linewidth criterion is not sufficient to characterize the performance of a sensing system. We then introduce an equivalent Lorentzian laser linewidth related to the phase noise spectral region of interest, according to the sensing setup in terms of fiber length to sense. This is illustrated in a setup based on codes interrogation and with 2 sensing dedicated laser sources