Experimental Optical Setup to Measure Power Loss versus Fiber Bent Radius for Tapping into Optical Fiber Communication Links

Optical fiber communication was widely believed that an optical network was a good way to prevent hacking through wiretaps which intercept network data. However, fiber optic cable is not particularly secure. Various tapping methods can be used to extract data from fiber optic networks with little or no risk of detection. One of the easiest ways of intruding into a fiber optic communication link is creating a bend on the fiber cable. Even small percentage of the transmitted light acquired with the bending method is enough for recovering the data by the attacker. Though there are some techniques and devices that can track the power and intensity inside the fiber cable, these methods cannot detect an attack exploiting small leakage. Therefore, it is critical to determine a range of radii of curvature for which tapping attacks are not detectable. Though there are some studies to quantify the power loss both theoretically and numerically, as of the authors' knowledge, there has not been any experimental validation of those studies. In this respect, an experimental optical setup and a technique relying on the ADC conversion capability of Arduino UNO to measure power loss resulting from different bending radii are proposed in this paper. A lower limit for radius of curvature for an attack to be undetected is obtained and the estimations in the literature for power loss resulting from fiber bending is validated.