Perimeter protection is all about detection of threats or intrusion. As such detectors and sensors are still used in this regard. Increasingly, improvements have been made to fiber optic sensors to enhance their accuracy.
Perimeter protection is all about detection of threats or intrusion. As such detectors and sensors are still used in this regard. These can include microwave sensors, buried sensors and fiber optic sensors, each using a unique detection technology. Increasingly, improvements have been made to fiber optic sensors to enhance their accuracy and reduce false alarms.
“Ranging capabilities of our fiber optic intrusion detection sensors allow for environmental disaggregation, enabling the sensors to differentiate between randomly-distributed weather-induced disturbances and the concentrated-disturbances created by real threats, which increases probability of detection and lowers the nuisance alarm rate,” said Stewart Dewar, Product Manager at Senstar, adding that fiber optic sensors can work especially well in areas of high lightning incidence.
“Fiber optic technologies have the advantage of eliminating any concerns with nuisance alarms from lightning or lightning-induced damage. This also makes them ideal for sites such as electrical power plants and sub-stations, which may have very high electric fields at their perimeter,” Dewar said.
Bernard Lee, VP for Sensors Business Group at ST Electronics, elaborates on the company's fiber optic sensors marketed under the AgilFence brand. “An effective FIDS should be one which can determine if a long stretch of fence line is disturbed, which is likely caused by environment factors like rain and strong wind, or only a fence panel is disturbed, which is likely caused by intrusion attacking the fence. To make this determination, sensors need to be placed on fence panels at close spacing,” said Lee. “AgilFence PIDS uses Fibre Bragg Grating (FBG) technology as sensors, which are directly embedded on the fiber optic cable. We embed one FBG sensor every few meters to cover two to three fence panels, depending on the fence type. This in itself gives a detection accuracy down to the spacing interval between two FBG, because each FBG is unique and the FBG with the biggest difference from its reference wavelength is likely to be the one where the intrusion is taking place. Furthermore, these FBG in the field provide inputs to the signal processing algorithm to better adjust the noise floor according to the real-time environment. This is how our system works well even in harsh weather conditions.”
As sensors can be expensive, more and more providers are offering solutions that incur a lower total cost of ownership. “Our FBG-embedded fiber optic cable works on light and requires no power supply or electronics in the field. It also does not require any signal cable. If the FBG sensor cable is cut, an alarm is triggered immediately and the repair requires only a fusion splicing without the need to replace the sensor cable,” Lee said. “Our FBG sensor cable is implemented through a robust architecture, using multiple-ports FBG interrogator. Each port supports one channel of multiple FBG. Each channel is isolated from other channels. When one point of the cable is cut, the other channels are not affected and will remain effective. When that cable is being repaired, the other channels are again not affected. We are currently the only one in the industry which fielded PIDS using this technology on a large scale."
Product Adopted:Detectors / Sensors