Modified Sagnac interferometer for distributed disturbance detection

A fiber optic sensor based on Sagnac interferometer for determining the position of disturbance is presented. For this application, a disturbance simultaneously imposed on two different points of sensing fiber loop could be measured and located. The method solves the problem of isolating part of fiber loop from physical field. Experimentally, longitudinal position of a disturbance is determined with an average error of 59 m over a total length of 25 km. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1608–1610, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23436