Analysis of Eavesdropping on Optical 2-D OCDMA Networks

Cybersecurity and cyber resilience are becoming crucial for many industries especially in the era of digital transformation. In this work, we report on the security analysis of the physical layer of OCDMA networks based on 2-D codes such as fast frequency-hopping (FFH). We analyze eavesdropping in OCDMA networks using FFH codes spread in both, time and frequency domains that use quadrature phase-shift keying (QPSK). The analysis is based on a newly derived bit error rate (BER) formula considering the eavesdropper’s partial knowledge of the 2-D code that is needed to replicate the ONU decoder. An analytical formalism for evaluating the BER performance of the network is derived by considering 2-D codes, QPSK modulation format, avalanche photodiode shot noise, thermal noise, and multiple-access interference among optical network units (ONUs). Numerical results show that the intercepted signal is hard to decode and the information retrieved when the eavesdropper makes more than one error in guessing the used ONU code. It is shown the number of simultaneous ONUs substantially affects the eavesdropper’s capability to decode the intercepted signal. The novel 2-D FFH signal encoding is robust against the eavesdropper interception. It offers a feasible solution to increase security levels in practical optical networks.