Fiber Optic Cable Termination and Signal Loss Detection in DAS Systems

Fiber Optic Distributed Acoustic Sensing (DAS) Systems use standard telecommunication fibers to detect acoustic vibrations up to 50 kms along the cable. In this paper we propose algorithms to detect fiber optic cable termination points and optical signal losses using DAS data. Proposed algorithms add traditional Optical Time-Domain Reflectometer (OTDR) measurement functionality to the DAS systems. Cable termination detection algorithm models the noise data in DAS signal that consists of electronic noise [e.g. Analog-to-Digital Converter (ADC) noises] and optical laser reflection noise. The cable termination detection algorithm analyzes noise statistics of the sensor data and finds the location where optic noise is no longer present. Signal loss detection algorithm first eliminates the environmental acoustic noise from the DAS signal; then, change point detection algorithm is applied to detect locations where significant signal loss occurs. Proposed algorithms are tested in various DAS installations in Turkey. Predicted cable termination and signal loss locations agree with OTDR measurements.