An achievable rate of soliton communication system is derived based on the noise model we studied. Compared to existing results, ours is derived for the system where both eigenvalues and spectral amplitudes are modulated. In addition, we also show an increment of the communication rate by modulating the spectral amplitude of a soliton.
A multistage signal estimation scheme is proposed for phase-and-amplitude modulated soliton communication systems. The estimator provides a significant mean-squared-error reduction in soliton amplitude estimation, which, in conjunction with detection of encoded phase information, results in spectral-efficiency improvements. A low-complexity version of the multistage estimation scheme is also proposed, whose performance is studied via numerical simulations under the distributed Raman amplification strategy. The achievable information rate is increased by about 1 bit/symbol for pulse bandwidth of 30 GHz, 40 GHz, and 50 GHz.
Multi-soliton pulses are studied under small perturbations. By means of mutual information, we show that the nonlinear spectrum becomes correlated when a 64-PSK modulated 2-eigenvalues soliton is perturbed by a small additive white Gaussian noise (AWGN). Transmission over two channels are considered: an AWGN channel (back-to-back scenario) and an ideal optical fiber link with distributed noise. We numerically show that the Jost coefficients b(λk) are less correlated than the discrete spectral amplitudes qd(λk) while either of them can be alternatively used for modulation. In both channels, we compare the achievable information rates (AIRs) of joint detection and separate detection if the modulation is over either qd(λk) or b(λk). We show that if the length of the link is relatively short, the separate detection of b(λk) gives almost the same total information rate as the joint detection of b(λk) or qd(λk). Moreover, the AIRs are compared with one of a first-order soliton with the same modulation.
In soliton communication systems, the continuous nonlinear spectrum, ideally zero, is conventionally ignored at the receiver. In this paper, we exploit correlation between the received continuous spectrum and perturbations of the discrete soliton eigenvalue. We propose four estimation schemes, classified into two categories, one based on the nonlinear Fourier transform (NFT) and the other based on minimum Euclidean distance. Both categories comprise two schemes, one that exploits the received continuous spectral function to achieve improved estimation and one that does not. Numerical simulations demonstrate that significant reduction in estimation error can be achieved when the continuous spectrum is exploited, translating into improved information transmission rates of up to 46% compared to the reference NFT-based scheme.
This paper introduces the concept of the Solitonic Internet, an engineering-focused alternative to quantum networking. By encoding information in phase-locked solitonic bursts transmitted through optical fiber or microwave links, the system achieves dispersion-free transport, resilience against noise, and room-temperature operation. The paper formulates an operational model based on the nonlinear Schrödinger equation, defines coherence and fidelity metrics, and presents simulated results comparing detection probability versus SNR for conventional and solitonic approaches. Security analysis highlights the robustness of soliton-based signaling against eavesdropping and jamming, while infrastructure compatibility ensures feasibility with existing telecom networks. The Solitonic Internet provides a practical pathway toward secure, long-distance communication without the complexity of quantum repeaters or cryogenic systems.
Optical solitons are pulses that propagate in optical fibers without temporal or spectral distortion, owing to balancing of the second-order dispersion of the refractive index by nonlinear self-phase modulation induced by the intensity-dependent refractive index. Classically, this stationary, distortion-free propagation requires only the proper choice of pulse width and shape for a given pulse energy. However, quantum mechanical zero-point fluctuations of the amplitude and phase of the optical pulse limit the precision with which this pulse shape can be produced. These quantum fluctuations do not undergo stationary propagation but, rather, evolve because of dispersion and self-phase modulation, As a soliton pulse propagates, this zero-point or vacuum noise associated with the pulse evolves into squeezed noise owing to self-phase modulation in the fiber.1,2