Sensors and Actuators A 180 (2012) 15–18 Contents lists available at SciVerse ScienceDirect Sensors and Actuators A: Physical jo u rn al hom epage: www.elsevier.com/locate/sna Armored-cable-based FBG security fence for perimeter intrusion detection with higher performance Bo Dong ∗ , Jianzhong Hao, Varghese Paulose RF & Optical Department, Institute for Infocomm Research, 138632 Singapore, Singapore a r t i c l e i n f o Article history: Received 9 September 2011 Received in revised form 9 April 2012 Accepted 10 April 2012 Available online 18 April 2012 Keywords: FBG Armored cable Perimeter fence intrusion detection a b s t r a c t A novel armored-cable-based FBG security fence for perimeter intrusion detection with higher perfor- mance is proposed and demonstrated. The sensor is based on a unique armored-cable packaged FBG sensor array, which guarantees high sensitivity, crush resistance, and protection against rodents. It pro- vides fine granularity perimeter intrusion detection, with a stated pin-pointing accuracy, for the tested intrusion events that include aided or unaided climbs, tampering and cutting of the fence. It is also capa- ble of resolving nuisance events such as rain, birds sitting on the fence and seismic vibrations caused by the vehicular traffic, landing or taking off of aircrafts, etc. Moreover, it is temperature independent since the ambient temperature variation can be regarded as a direct-current (DC) signal, and has no effect on the alternating current (AC) signal of the vibration signal induced by the intruder. It is potential to be used in various scenarios where a very small physical parameter change could cause some vibration. © 2012 Elsevier B.V. All rights reserved. 1. Introduction To meet the increasing demands for perimeter fence intrusion detection (PID), various sensor products have been developed by the industries for PID [1]. Compared to the traditional PID sen- sors using ultrasonic, radar, microwave, infrared or photo-electric sensors [2], PID fiber-optic sensors have many inherent advanta- ges, including high resolution, high sensitivity, intrinsic electrical passivity, and immunity to electromagnetic interference. Seve- ral techniques, based on optical time domain reflectometry [3–5] and fiber-optic Sagnac, Michelson, and Mach-Zehnder (M-Z) inter- ferometers [6–8], have been developed for PID applications. In the case of the fiber-optic Sagnac, Michelson and M-Z sensors, the whole fiber structure acts as the sensing area. If the fiber breaks at any point, the whole sensor cannot work any more. In comparison, the FBG PID sensors have many advantages, inclu- ding wavelength encoding, excellent multiplexing capability, ease of fabrication, etc., especially, the ability of simultaneous detec- tion of multiple events and location over long perimeters up to tens or hundreds of kilometers. Moreover, when there is a break point in the fiber, only a particular zone will get affec- ted and rest of the sensors will continue working. In order to realize the PID, a high speed FBG interrogation system has to be applied, several FBG PID interrogation methods, based on the signal autocorrelation fitting [9] and matched FBG interrogation [10] were proposed for PID application. In addition, the key ele- ∗ Corresponding author. E-mail address: dbo1978@163.com (B. Dong). ment for the PID is the sensor structure. However, there were no detailed contents about the packaged FBG sensor structure for the above-mentioned PID systems. Note that the FBG array packaging method determines the sensing performance of the PID, including the repeatability, sensitivity, serviceable lifetime, etc. Besides a high speed interrogation system, a properly pac- kaged FBG array, catered for real applications for a long time, is highly desirable for the commercialization of the PID FBG sensors. In this paper, we propose a novel armored-cable-based FBG security fence for PID with higher performance. The FBG sensors are packaged in an armored cable, which provides high sensiti- vity, crush resistance, and protection against rodents. With a high speed fiber Fabry–Perot (F–P) laser scanning based interrogation system, a field test is demonstrated. To compare the performance of our sensor, the other commercial M-Z fiber interferometer based PID sensor was also installed on the same fence line. The field test shows that it has higher performance than the commercial fiber M-Z interferometer based PID sensor. The test shows the sensor provides fine granularity PID, with a stated pin-pointing accuracy, for the tested intrusion events that include aided or unaided climbs, tampering and cutting of the fence. It is also capa- ble of resolving nuisance events such as rain, birds sitting on the fence and seismic vibrations caused by the vehicular traffic, lan- ding or taking off of aircrafts etc. Moreover, the armored cable packaging structure helps in extending the serviceable lifetime of the sensor, which is important for the practical application of the PID FBG sensors. It is also expected to be used in other scenarios where a very small physical parameter change could cause some vibration. 0924-4247/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.sna.2012.04.008