In this work we propose an intrinsic fiber optic sensor for measuring surfa
ce strains, which uses two branches of multimode optical fiber in an interf
erometric configuration. A correlation operation is performed with the resu
lting intensity patterns from which the strain value is obtained for two di
fferent sensitivity ranges. A description of the method is presented and so
me experimental results are shown in order to illustrate the feasibility of
this approach. (C) 1999 Elsevier Science Ltd, All rights reserved.