Spatial resolution enhancement of distributed strain measurement using BOTDR by partially gluing optical fiber

An effective spatial resolution enhancement method for distributed strain measurement by BOTDR is proposed. An optical fiber is glued to a structure by a length less than the spatial resolution defined by the pulse width, and the Brillouin spectrum of the light scattered from the glued optical fiber is investigated theoretically. The apparent strain x(p) observed in the fiber is found to be proportional to the accurate strain a. The ratio r = x(p)/a coincides with the ratio of the glued length to the spatial resolution. Spatial resolution as small as 0.2 m is demonstrated experimentally for small strains of less than 10(-3).