We have developed Brillouin Optical Correlation Domain Analysis (BOCDA) for distributed strain measurement. BOCDA can achieve distributed strain measurement by controlling a correlation between pump and probe lightwave, with excellent spatial resolution and sampling rate compared with conventional pulse-based techniques. In this paper, we propose a scheme for polarization diversity to reduce data fluctuation by polarization state change of pump and probe lightwave in order to realize enlargement of measurement range. Stable distributed strain measurement is demonstrated along a 50m measurement range.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.