Real-time Distributed Fiber Optic Sensor for Security Systems: Performance, Event Classification and Nuisance Mitigation

Abstract

Abstract:The success of any perimeter intrusion detection system depends on three important performance parameters: the probability of detection (POD), the nuisance alarm rate (NAR), and the false alarm rate (FAR). The most fundamental parameter, POD, is normally related to a number of factors such as the event of interest, the sensitivity of the sensor, the installation quality of the system, and the reliability of the sensing equipment. The suppression of nuisance alarms without degrading sensitivity in fiber optic intrusion detection systems is key to maintaining acceptable performance. Signal processing algorithms that maintain the POD and eliminate nuisance alarms are crucial for achieving this. In this paper, a robust event classification system using supervised neural networks together with a level crossings (LCs) based feature extraction algorithm is presented for the detection and recognition of intrusion and non-intrusion events in a fence-based fiber-optic intrusion detection system. A level crossings algorithm is also used with a dynamic threshold to suppress torrential rain-induced nuisance alarms in a fence system. Results show that rain-induced nuisance alarms can be suppressed for rainfall rates in excess of 100 mm/hr with the simultaneous detection of intrusion events. The use of a level crossing based detection and novel classification algorithm is also presented for a buried pipeline fiber optic intrusion detection system for the suppression of nuisance events and discrimination of intrusion events. The sensor employed for both types of systems is a distributed bidirectional fiber-optic Mach-Zehnder (MZ) interferometer.

Research and Software Design of an Φ-OTDR-Based Optical Fiber Vibration Recognition Algorithm

“…But, the application of these techniques for recognition of the nuisance signals used as a security system in large infrastructures is complex and contains many practical problems in some noisy or hostile environments that must be resolved. Recently, Mahmoud et al [10] has made several attempts using the high-performance distributed optical fiber sensors in outdoor and underground infrastructures to solve the problems of recognition of a triggered alarm. Mahmoud and Katsifolis [11], and also Wu et al [12], have used features such as short-term energy and short-term zero-crossing rate in the time-domain analysis in order to improve the system performance.…”

Nuisance alarm reduction: Using a correlation based algorithm above differential signals in direct detected phase-OTDR systems

“…φ-OTDR uses phase change among Rayleigh Backscattered (RBS) signals as the only condition in measuring the disturbance along distributed fiber sensing system. Due to its low cost and relatively significant high sensitivity, it provides a range of applications including intrusion detection for security systems along a length of distance [1][2][3][4], warning systems [5], sensing for railway track systems [6], detecting damage tolerance of a system [7], and detecting ultrasonic waves [8]. It is believed that the φ-OTDR system has already attracted a great deal of study in the contemporary era.…”

“…This part of response causes a large probability of differential signals to hide within the shadow of the noise and is regarded as a source of NAR for ephemeral events. Attempts were made to alleviate the effect of NAR by improving classification accuracy, but it led to an overall increase in computational cost [4,[14][15][16]. Further Steps were taken by Q.…”

Mellin Transform-Based Correction Method for Linear Scale Inconsistency of Intrusion Events Identification in OFPS

“…Reference [8] also proposed a robust method to identify the optical fiber intrusion, which extracted the time-domain characteristics of the signals as inputs into the neural network for training and recognition. However, the adaptive threshold is almost decided by experience without definite mathematical reasoning.…”