Pulse pre-pump method for cm-order spatial resolution of BOTDA

The distributed Brillouin scattering technique, using pulse width of I ns, that is, one order of magnitude smaller than currently available in commercial applications of BOTDA, was successfully implemented and examined in laboratory environment by Bao et al(2). However, the two main problems prohibits its commercial use, namely, the measurement setting must be modified each time the measurements object is changed, and, furthermore, long-range measurements cannot be effectively carried out due to substantial increase in signal noise level with the measurement distance. This paper presents a new technique, which overcomes both of these problems, by introducing the pre-pump pulse in front of standard laser pulse. Theoretical analysis clearly demonstrates that the cm-order distributed sensing, independent of the fiber length, can be realized. Moreover, a quantitative analysis of strain measurement accuracy is also presented.