Distributed sensors, based on Brillouin effect in the optical fiber, provide an excellent method for measuring temperature
and strain over long distances. There are two types of such sensors. The first type is based on spontaneous Brillouin
scattering, and is called Brillouin optical time domain reflectometer (BOTDR). It measures the Brillouin frequency shift
or Brillouin power or Brillouin gain bandwidth to get the temperature and strain information. The second type of sensor
is based on stimulated Brillouin amplification. It is called Brillouin optical time domain analyzer(BOTDA). Normally, it
uses one laser at each fiber ends, one as pump and the other as a probe light. The probe light will experience Brillouin
amplification. Through the analysis of Brillouin gain spectrum (BGS), we can get the temperature and strain information.
Both the two types of sensors are attracting attention all over the world, and temperature resolution of less than 1 degree
and strain resolution up to 5 με was reported. The fiber distances of up to 150km was presented while other papers
reported a spatial resolution of the order of 1cm with frequency domain techniques or correlation techniques. We
proposed and analyzed our design, it is an improvement of BOTDA with a single end laser, which make it easy to
implement in field. Through simulations, optimized launch power has been found for a certain design.