Impact of the laser phase noise on chirped-pulse phase-sensitive OTDR

Abstract

In this work, the impact of the laser phase noise on chirped-pulse phase-sensitive OTDR signals is theoretically and experimentally analyzed. In particular, it is shown that the noise in the readings of strain/temperature changes along the fiber scales directly with the frequency noise power spectral density of the laser. The effect of the pulse chirp on the signal to noise ratio is also investigated. Three lasers with different linewidths (5 MHz, 50 kHz and 25 kHz), i.e., with different phase noise, were used for the experimental study, confirming the validity of the theoretical model.