INTRUSION DETECTION ALGORITHM WITH REDUCED TUNING REQUIREMENT

An optical fiber is monitored for an intrusion event where reflected optical signals are divided into streams each associated with a respective location on the optical fiber. Blocks of the streams are selected each containing a plurality of streams and the streams are collated, for example by averaging, to create a single stream to which an algorithm is applied to create coefficients which are compared with a threshold value to generate an output indicative of disturbance of the fiber by an intrusion event. Each block representative of a length of the fiber is thus treated as a zone and the detection algorithm is applied to each. This creates a DAS system that does not require unique tuning as each zone is independently monitored. Applying the above zone principles and algorithms to the DAS system also provides a high level of nuisance alarm and false alarm rejection