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IEEE Access

Generalized Secure Superchannels: A Signal Encryption Framework

Marcelo L. F. Abbade, Marcelo Pereira Nogueira, Luiz Henrique Bonani, Eric A. M. Fagotto, Plínio S. Dester, Wilian Miranda dos Santos, Ivan Aldaya

Published Jan 1, 2026• 0 citations
Publisher

Abstract

In this work, we propose a comprehensive technique to enhance the security of superchannels (SCs). The spectral samples of the signals within a superchannel are shuffled and further encrypted in amplitude and phase, according to cryptographic keys. The strategy may be applied to SC signals with different modulation formats and bit rates. Moreover, the concept of SC is generalized, allowing for channels to be propagated through different optical routes. As a result, eavesdroppers need to tap multiple optical fibers to recover the content of a single signal. This simultaneously increases security and enhances the cost of spying. We investigate scenarios where dual polarization (DP) quadrature phase-shift keying (QPSK) and 16 quadrature amplitude modulation (16-QAM) signals are encrypted and propagated through transparent optical networks. Results reveal that no meaningful propagation penalty is introduced by signal encryption. From a security perspective, the technique is considerably more robust against brute force attacks than the Advanced Encryption Standard (AES), which is widely deployed in data encryption. A strategy to provide the properties of diffusion and confusion to the proposed encryption technique is discussed.

DOI
10.1109/access.2026.3670389

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In this work, we propose a comprehensive technique to enhance the security of superchannels (SCs). The spectral samples of the signals within a superchannel are shuffled and further encrypted in amplitude and phase, according to cryptographic keys. The strategy may be applied to SC signals with different modulation formats and bit rates. Moreover, the concept of SC is generalized, allowing for channels to be propagated through different optical routes. As a result, eavesdroppers need to tap multiple optical fibers to recover the content of a single signal. This simultaneously increases security and enhances the cost of spying. We investigate scenarios where dual polarization (DP) quadrature phase-shift keying (QPSK) and 16 quadrature amplitude modulation (16-QAM) signals are encrypted and propagated through transparent optical networks. Results reveal that no meaningful propagation penalty is introduced by signal encryption. From a security perspective, the technique is considerably more robust against brute force attacks than the Advanced Encryption Standard (AES), which is widely deployed in data encryption. A strategy to provide the properties of diffusion and confusion to the proposed encryption technique is discussed.
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/s448 \mathrm{~Gb} / \mathrm{s}448 Gb/s dual polarisation (DP) 16-quadrature amplitude modulation (QAM) signals may be properly recovered after ∼700 km\sim 700 \mathrm{~km}∼700 km of standard single-mode fiber propagation.
All-optical spectral shuffling (AOSS) is a recently proposed physical layer encryption technique. In AOSS, multiple input signals are split in several spectral slices. These slices are then shuffled to form multiple encrypted signals. In fact, it is possible to transmit each shuffled signal by a different optical route. This strategy increases security because if an eavesdropper wants to detect information from a unique signal, he needs to tap at least one fiber per route. In this work, computer simulations are used to encrypt two 112 Gbps 16-quadrature amplitude modulation (QAM) signals and to propagate the shuffled signals by distinct optical routes. Our results reveal that the shuffled signals may be propagated by optical routes as long as 600 km. Besides that, we also investigate the situations i) where the signals travel by routes with different lengths and ii) where each route imposes different physical impairments to the encrypted signals.
Optical layer attacks on optical fiber communication networks are one of the weakest reinforced areas of the network, allowing attackers to overcome security software or firewalls when proper safeguards are not put into place. Encrypting data using a random phase mask is a simple yet effective way to bolster the data security at the physical layer. Since the interactions of the random phases used for such encryption heavily depend on system properties like data rate, modulation format, distance, degree of phase randomness, laser properties, etc., it is important to determine the optimum operating conditions for different scenarios. In this work, assuming that the transmitter and the receiver have a secret pre-shared key, we present a theoretical study of security in such a system through mutual information analysis. Next, we determine operating conditions which ensure security for 4-PSK, 16-PSK, and 128-QAM formats through numerical simulation. Moreover, we provide an experimental demonstration of the system using 16-QAM modulation. We then use numerical simulation to verify the efficacy of the encryption and study two preventative measures for different modulation formats which will prevent an eavesdropper from obtaining any data. The results demonstrate that the system is secure against a tapping attack if an attacker has no information of the phase modulator and pre-shared key.
A scheme for optical parallel encryption/decryption of quadrature phase shift keying (QPSK) signals is proposed, in which three QPSK signals at 10 Gb/s are encrypted and decrypted simultaneously in the optical domain through nondegenerate four-wave mixing in a highly nonlinear fiber. The results of theoretical analysis and simulations show that the scheme can perform high-speed wiretapping against the encryption of parallel signals and receiver sensitivities of encrypted signal and the decrypted signal are −25.9 and −23.8 dBm, respectively, at the forward error correction threshold. The results are useful for designing high-speed encryption/decryption of advanced modulated signals and thus enhancing the physical layer security of optical networks.
Data encryption is gaining much attention these days from the research community and industry for transmitting secure information over access networks, i.e. `fiber-to-the-home (FTTH)' networks and data centers. It is important that the newly designed encrypted networks are fully functional, reconfigurable, compatible, flexible and scalable with the existing deployed optical fiber networks around the globe. The prime benefit of having FTTH networks is the optical end-to-end data encryption that can best be implemented by quantum-keydistribution (QKD) protocols using state-of-the-art telecommunication components, i.e. continuous-variable quantum key distribution (CV-QKD). In this paper, we numerically investigate the quadrature phase shift keying (QPSK) based CV-QKD network that is compatible with the next generation (NG) services such as point-to-point (P2P) transmission and multicast overlay (MCO) traffic for audio/video signalling. We have further investigated the performance of quantum signals on multi-user fibers by emulating 7-, 12- and 19-core multi-core fibers (MCF). 100 Mbits/s secure key rates (SKRs) can be generated for inter-core crosstalk (XT) values of <; -20 dB. These results and theoretical framework will allow the telecommunication industry to extend these scenarios not only to accommodate more complex trust constraints, but also to take into account the robustness and resiliency of a complex encrypted network.
This study investigates a multi-stage digital phase-encryption scheme designed for secure coherent optical communication. While the proposed method is implemented in DSP and can be modeled as a software-level stream cipher, it is explicitly co-designed with and tightly coupled to the physical-layer modulation structure. Unlike conventional XOR-based bitwise schemes, the encryption is applied to the symbol phase domain. It is integrated into the transmitter's modulation process, enabling symbol-level security evaluated in conjunction with transmission physics. By applying K-level phase-shift secret keys toM-ary quadrature amplitude modulation (QAM) signals, this method increases the number of secret-key bits per symbol without altering the signal constellation in its baseline configuration. This approach enhances encryption strength while maintaining signal integrity and reducing quantization overhead in phase-only operation. Experimental evaluations on nonlinear optical transmission channels confirm that baseline digital phase encryption preserves Q-factor stability under self-phase modulation, cross-phase modulation, and four-wave mixing. The proposed scheme ensures error-free transmission at forward error correction thresholds, effectively preventing eavesdroppers from reconstructing symbols under worst-case observation conditions. Additionally, simulations analyzing generalized mutual information and quantization errors demonstrate that the encryption scheme can minimize signal-to-noise ratio penalties, even when employing high-order QAM formats with limited digital-to-analog and analog-to-digital conversion resolutions. As an optional extension, we also analyze pseudo-quantum-noise-based IQ spreading and explicitly quantify the associated trade-off between additional noise masking and increased sensitivity to quantization. These findings position multi-stage digital phase encryption as a practical and power-efficient modulation-layer encryption technique whose behavior is systematically characterized under realistic nonlinear channel and hardware constraints, rather than as an entirely new cryptographic primitive.