Accuracy decline of the Brillouin optical time-domain analysis system induced by self-phase modulation

The Brillouin optical time-domain analysis system (BOTDA) is a distributed optical fiber sensing system based on the measurement of the effective Brillouin gain, in which high power pumping pulse is demanded to fulfill optical time domain reflectometry (OTDR) spatial orientation. As for strict rectangular pulse, BGS can maintain Lorentz line profile along the sensor fiber, while the actual rectangular pulse has power transients like the rising edge and failing edge, making BGS broadened or even distorted by the effect of self-phase modulation (SPM), which will induce the decline of the measuring accuracy. A model concerning the effects of pumping pulse power transients on the BGS by means of SPM is established based on the nonlinear Schrodinger equation (NLSE) in regular single mode fiber (SMF).