Brillouin Optical Time Domain Analysis (BOTDA) is becoming a consolidated technique in applications requiring high-resolution
monitoring over extremely long distances. Extension of the measuring range has therefore become one of the
main areas of research around BOTDA technology. To increase the sensing range, it is necessary to increase the Signal
to Noise Ratio (SNR) of the retrieved signal. This has been achieved so far by applying techniques like pre-amplification
before detection, pulse coding or Raman amplification. Here, we analyze these techniques in terms of their performance
limits and provide guidelines that determine which is the best configuration to overcome current range limitations.
The predicted performance of BOTDA sensors assisted by Raman amplification provided through either cavity or laterally-pumped mirrorless random ultralong laser schemes is compared, showing that although the latter are less affected by RIN transfer for sensing lengths above 100 km, they also require much higher pump powers and suffer more from SPM-induced broadening of the pulsed Brillouin pump.