High-Spatial Resolution Raman-Distributed Optical Fiber Sensing Using Differential Pulsewidth Pair Detection

The existing kilometer-level Raman-distributed optical fiber sensing mechanism encounters a physical bottleneck as its spatial resolution is limited to several meters, due to the pulsewidth of more than 10 ns in the principle of optical time-domain reflection (OTDR). In this work, we propose a differential pulsewidth pair detection scheme (DPPDS) for Raman-distributed optical fiber sensing. First, we examined the transmission and superposition effect of pulse-pair detection in the sensing fiber and developed the theoretical model. It proved that the differential pulsewidth pair sensing demodulation effectively extracted small temperature signals from the ambient temperature. Furthermore, the experimental results depict that the proposed scheme can achieve a 0.38-m spatial resolution over 6.0 km. As far as we know, this is the highest sensing spatial resolution achieved by kilometer-level Raman-distributed optical fiber sensing. This study provides a new research idea to improve the sensing spatial resolution of most distributed optical fiber sensing schemes based on the OTDR positioning principle.