Influence of the laser frequency drift in phase-sensitive optical   time-domain reflectometry
  The influence of the laser frequency drift on the operation of phase-sensitive optical time-domain reflectometry ($\Phi$-OTDR) systems is considered. Theoretical results based on a new numerical $\Phi$-OTDR model demonstrating the influence of the laser frequency instability on a signal are reported. This model is verified based on experimental data. It has been used to calculate the signal-to-noise ratio (SNR) of the system for different parameters of the laser source stability. As a result, quantitative requirements for lasers used in $\Phi$-OTDR systems are formulated. 
A.A. Zhirnov, K.V. Stepanov, A.O. Chernutsky, A.K. Fedorov, E.T.   Nesterov, C. Svelto, A.B. Pnev, and V.E. Karasik
physics.ins-det physics.data-an physics.optics