FIBER OPTIC DISPLACEMENT SENSOR BASED ON A DOUBLE-REFLECTING OTDR TECHNIQUE

Abstract

In this work, it is proposed a technique to implement an intensity sensor based on the generation of a double-reflecting (ghost) signal in optical time domain reflectometry (OTDR). The intensity sensor is supported by a singlemode-multimode-singlemode (SMS) fiber structure combined with a fiber loop mirror (FLM). The results of the displacement sensitivity show linear behavior for both the first-reflecting and double-reflecting signals with linear slopes of approximately -4.5 dB/mm and -6 dB/mm, respectively. The displacement resolution achieved is approximate to 0.28 mm. It is also found that the system is able to read periodic displacement variations in the millisecond time scale applied to the sensing head. (c) 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1312-1315, 2015