Non-intrusive tapping and other threats have underscored the necessity for enhanced security mechanisms in transparent optical networks (TONs). In this work, we explore the application of both intra- and inter-signal cryptography techniques to secure TON signals. The intra-signal approach utilizes spectral phase encoding, while the inter-signal technique relies on shuffling the samples among different signals, including the X - and Y polarisation components of each signal. Computer simulation results suggest that encrypted
448 Gb/s dual polarisation (DP) 16-quadrature amplitude modulation (QAM) signals may be properly recovered after
∼700 km of standard single-mode fiber propagation.
We discuss the characteristics of photon-number squeezing generated in a spectrally filtered Raman Stokes pulse obtained from a nonlinear fiber. The Raman Stokes pulse generated from a microstructure fiber with a femtosecond input laser pulse exhibits far higher photon-number squeezing. We studied the quantum correlation established among the frequency modes in the Raman Stokes pulse by using numerical calculations and experiments. To design an intra-Stokes pulse quantum correlation through the optical nonlinearities of a fiber to obtain higher photon-number squeezing, we shaped the input laser pulse by using a self-learning closed-loop control approach.