Probabilistically Shaped 4-PAM for Short-Reach IM/DD Links With a Peak Power Constraint

Thomas Wiegart, Francesco Da Ros, Metodi Plamenov Yankov, Fabian Steiner, Simone Gaiarin, Richard D. Wesel

2020Journal of Lightwave Technology34 citationsDOI Open Access PDF

Abstract

Probabilistic shaping for intensity modulation and direct detection (IM/DD) links is discussed and a peak power constraint determined by the limited modulation extinction ratio (ER) of optical modulators is introduced. The input distribution of 4-ary unipolar pulse amplitude modulation (PAM) symbols is optimized for short-reach transmission links without optical amplification nor in-line dispersion compensation. The resulting distribution is symmetric around its mean allowing to use probabilistic amplitude shaping (PAS) to generate symbols that are protected by forward error correction (FEC) and that have the optimal input distribution. The numerical analysis is confirmed experimentally for both an additive white Gaussian noise (AWGN) channel and a fiber channel, showing gains in transmission reach and transmission rate, as well as rate adaptability.

Topics & Concepts

Pulse-amplitude modulationTransmission (telecommunications)Modulation (music)Additive white Gaussian noiseProbabilistic logicAnalog transmissionQuadrature amplitude modulationExtinction ratioPulse-position modulationOpticsMathematicsDelta modulationAmplitudeGaussianGaussian noiseIntensity modulationTopology (electrical circuits)Amplitude modulationNoise (video)Signal-to-noise ratio (imaging)White noiseElectronic engineeringPower (physics)Optical communicationOptical modulation amplitudeAlgorithmOptical fiberPhysicsPhase modulationChannel spacingPulse-width modulationChannel (broadcasting)Pulse shapingDispersion (optics)Constraint (computer-aided design)Probability distributionFrequency modulationDistribution (mathematics)Bit error rateComputer scienceOptical Network TechnologiesAdvanced Photonic Communication SystemsPAPR reduction in OFDM