Limits of BOTDA Range Extension Techniques

Brillouin-based temperature and strain sensors have attracted great attention of both the academic and industrial sectors in the past few decades due to their ability to perform distributed measurements. In particular, Brillouin optical time-domain analysis (BOTDA) systems have been applied in many different scenarios, proving particularly useful in those requiring especially wide coverage ranging extremely long distances, such as in civil structure monitoring, energy transportation, or environmental applications. The extension of the measuring range in these sensors has, therefore, become one of the main areas of research and development around BOTDA. To do so, it is necessary to increase the signal-to-noise ratio of the retrieved signal. So far, several techniques have been applied in order to achieve this goal, such as preamplification before detection, pulse coding, or Raman amplification. Here, we analyze these techniques in terms of their performance limits and provide guidelines that can assist in finding out which is the best configuration to break current range limitations. Our analysis is based on physical arguments as well as current literature results.