Distributed strain measurements in optical fibers using Brillouin optical-fiber time domain analysis

This paper describes a recently developed technique for the distributed strain measurements. With this technique, the strain in optical fibers can be evaluated by accessing the test fiber itself without using the above-mentioned sensors. This paper also reviews recent applications of the technique. The technique is based on time-resolved measurement of Brillouin gain spectra which depends on the strain. The technique will contribute to the improvement of technologies for fiber manufacturing, cabling, and cable installation, and also make it possible to accurately predict the lifetime of optical fibers in service. The reviewed technique accesses both ends of the test fiber. In some applications, however, single-ended measurement is required. This will be made possible by measuring backward spontaneous Brillouin scattering (SPBS) from a forward travelling pulse light, instead of stimulated Brillouin scattering (SBS) as in the reviewed technique.