Abstract
It is discovered here that the chaos generated by loss modulation of EDFRL is varying with the message amplitude, frequency and phase also in addition to the modulating signal and the loop parameters so much so that the output may even become non-chaotic at some points; a phenomenon not reported earlier in literature. This makes a detailed parametric trend analysis of message signal entering in EDFRL loop for given cavity parameters mandatory which is carried out in this article. The range of parameters is identified where EDFRL seizes to generate chaos for given modulating signal and loop parameters. It is found that once message frequency is equal to integer multiples or sub-multiples of the modulating frequency the output no more remains chaotic and becomes pulsed which compromises the security of the system. A solution to this problem is proposed and verified in this work by using a dual frequency loss modulating signal with the two frequencies being not an integer multiple of each other. The Lyapunov exponent (LE) spectrum is shown for the integral sub-multiples of both frequencies separately and chaos is verified to exist at all values.