Instantaneous Area Based Online Detection of Bend Generated Error in a Raman Optical Fiber Distributed Temperature Sensor

Abstract

Error-free temperature measurement by Raman scattering based optical fiber distributed temperature sensor (OFDTS) is possible if the sensing fiber has no sharp bend. However, in real life applications, the sensing fiber might have sharp bend that may cause discontinuity in the profiles of Raman anti-Stokes (AS) and Stokes (St) signals resulting in erroneous distributed temperature measurement by OFDTS. In such a case, it is necessary to detect the presence and location of the bend. For a human operator using OFDTS, it is difficult to detect the presence of bend and locate it by visually observing AS and St signals. In this article, an online automated technique based on measurement of a new parameter called the instantaneous area of analytic intrinsic mode functions (IMFs) of St signals is presented to serve the purpose. The proposed technique is more automation friendly than earlier reported technique where area corresponding to IMF of complete duration of St signal was considered. The instantaneous area parameter alone is able to detect both the bend induced malfunctioning of OFDTS and the location of bend.