Technique for measuring the dynamic strain on an optical fiber based on Brillouin ring amplification

A new technique for measuring the dynamic strain on an optical fiber, named Brillouin ring amplification system (BRAS), is proposed. In the BRAS, Stokes light of sufficiently high intensity to detect instantaneous strain change can be obtained by the effect of Brillouin ring amplification. Experimental results demonstrate that the BRAS enables a measurement of dynamic strain with a period of about two seconds as well as its spatial distribution over an 11-km long fiber with an accuracy of /spl plusmn/0.006% strain. Theoretical studies on measurable distance indicate that the BRAS can be used in the case of a long fiber of about 40 km with a resolution of twenty meters.