All-optical cryptography of M-QAM formats by using two-dimensional spectrally sliced keys

Abstract

There has been an increased interest in enhancing the security of optical communications systems and networks. All-optical cryptography methods have been considered as an alternative to electronic data encryption. In this paper we propose and verify the use of a novel all-optical scheme based on cryptographic keys applied on the spectral signal for encryption of the M-QAM modulated data with bit rates of up to 200 gigabits per second.

Double all-optical encryption of M-QAM signals based on spectrally sliced encoding keys

“…Herewith, we extend our previous analyses [5,6] by doubling the encoding-decoding stages applied on spectral slices obtained by optical band-pass filters (OBPFs) having identical 3-dB bandwidths. Encoding is done by independently applying a precise amount of phase-shift and delay making to each slice, which makes the signal data meaningless until the signal recovery is applied.…”

“…At the decoder (OD), which is aware of the OE key, the signal is re-sliced again (identically as in OE), where each portion i undergoes time delay, τ max -τ ι , and phase-shift ϕ max -ϕ ι (where τ max and ϕ max stand for maximum τ i and ϕ i of K e , respectively). A mathematical description for this proposal is presented in [6]. The OD reverses the delay to the correct time reference basis and to compensate for the amount of shiftedphase by knowing in advance the cryptographic key.…”

“…On the other hand, the BER for the decoded signal should be below the FEC limit. As, in [6], in this work we assume that BER FEC = 2×10 -3 and that a valid cryptographic key occurs when BER e ≥ 10 -1 . Generally speaking, the higher the number of spectral slices, the longer the cryptographic key and the more secure communication becomes.…”

“…Nevertheless, the investigated technique could also be applied to signals with other bit rates and modulation formats as in our previous work [5,6]. To investigate the sensitivity performance, we initially simulated the single-encoding Figure 3(a) shows the spectrum for the sliced signal, whereas Fig.…”

“…The SPE approach has shown effective protection on optical CDMA (OCDMA) channels, but may not be suitable for systems with high number of WDM channels. On the other side, the encoding of spectrum slices have been a technique showing a high potential for optical encryption of WDM signals with different modulation formats, [5,6].…”