Temporal Probabilistic Shaping for Mitigation of Nonlinearities in Optical Fiber Systems

Abstract

Abstract-In this paper, finite state machine sources (FSMSs) are used to shape quadrature amplitude modulation (QAM) for nonlinear transmission in optical fiber communication systems. The previous optimization algorithm for FSMSs is extended to cover an average power constraint, thus enabling temporal optimization with multi-amplitude constellations output, such as QAM. The optimized source results in increased received SNR and thereby increased achievable information rates (AIR)s under memoryless assumption. The AIR is increased even further when taking the channel and transmitter memory into account via trellis processing at the receiver. Significant gains are reported in the highly nonlinear region of transmission for an FSMS of up to second order and 16QAM and particularly for unrepeated transmission. At the optimal launch power of WDM transmission, the FSMS order needs to be increased further in order to notably outperform previous probabilistic shaping schemes.

Mitigating Fiber Nonlinearities by Short-length Probabilistic Shaping

“…It was found that temporal properties of the QAM transmit sequence that are guaranteed to occur for short CCDM outputs yet not for long blocks lead to NLI mitigation. This effect is related to previous theoretical work on shaping for the nonlinear fiber channel predicting larger gains than for a linear channel [8] and also to temporal PS over a few time slots [9,10].…”

Probabilistic Shaping for the Optical Phase Conjugation Channel

“…Variants of the BAA can be applied in such cases without guarantee of optimality or convergence. Examples include the experimental optimization of a mid-link OPC-based channel [26] and the simulation-based optimization for channels with memory [54] later applied to the optical fiber [27].…”

“…[24], [25] and references therein. Relatively recently has practical optimization using mismatched decoding principles been applied to the nonlinear optical channel [26], [22], [27], [28], [29].…”

Investigation and Suppression of Fiber Nonlinearities Using Injection-Locking in OFDM-WDM System

“…The linear impairments usually originate due to chromatic dispersion (CD), fiber loss, and polarization mode dispersion (PMD). On the other hand, the nonlinear impairments are caused by two different mechanisms: (i) inelastic scattering of photons inside the fiber (e.g., SBS and SRS nonlinearities) and (ii) changes in the refractive index of fiber core via changes in optical power intensity (e.g., FWM, SPM, and XPM nonlinearities) [11]. Out of these nonlinear effects, FWM is a third-order nonlinearity that comes into picture when two or more than two signals are propagated through the fiber.…”