Signal loss detection method for distributed acoustic sensing systems

A method that detects locations of undesired levels of signal loss in DAS systems that use optical fibers. In the method, raw DAS signals are received from an optical fiber of a DAS system with dual photodetector positioned at the end(s) of the optical fiber. Locations on the optical fiber are named “channels” having a certain length on the optical fiber and are numbered according to distances of the channels from the photodetector. The raw DAS signals received from each channel are processed by the dual photodetector to obtain raw DAS statistical data for each channel. The obtained raw DAS statistical data are then reconstructed to produce reconstructed DAS statistical data in which noise has been removed. The reconstructed DAS statistical data form power statistics for each channel. The power statistics is expected to be linearly decreasing with a farther distance of each channel from the photodetector. A change detection algorithm is provided to detect possible undesired levels of signal loss and to find the locations of the signal loss based on the power statistics.