A Comparison of the LPI Performance of Optical and MM-Wave Systems

The purpose of this paper is to compare the Low Probability of Intercept (LPI) performance achievable with optical and RF systems (specifically, millimeter wave systems). The specific case of ground to space communications is considered. The LPI performance measure used in the comparison is the Circular Equivalent Vulnerability Radius (CEVR). Using the millimeter wave propagation model of Crane and Blood, a model for computing the CEVR of a millimeter wave earth to space link is described. We then show how the same model can be used to calculate the CEVR for optical systems using the optical propagation model developed by one of the authors (East). Optimal methods of intercepting frequency hopping millimeter wave systems and pulse position modulation (PPM) optical systems are also described.