Estimation of BER from Error Vector Magnitude for Optical Coherent Systems

Irshaad Fatadin

doi:10.3390/photonics3020021

Abstract

This paper presents the estimation of bit error ratio (BER) from error vector magnitude (EVM) for M-ary quadrature amplitude modulation (QAM) formats in optical coherent systems employing carrier phase recovery with differential decoding to compensate for laser phase noise. Simulation results show that the relationship to estimate BER from EVM analysis for data-aided reception can also be applied to nondata-aided reception with a correction factor for different combined linewidth symbol duration product at the target BER of 10 − 3 . It is demonstrated that the calibrated BER, which would otherwise be underestimated without the correction factor, can reliably monitor the performance of optical coherent systems near the target BER for quadrature phase shift keying (QPSK), 16-QAM, and 64-QAM.

Highlights

Spectrally-efficient modulation formats are currently receiving significant attention for next-generation high-capacity optical communication systems [1,2,3]
error vector magnitude (EVM) is a well known performance metric in wireless digital communication systems to evaluate the quality of vector-modulated signals [7] and is a more appropriate figure of merit at high signal-to-noise ratio (SNR) where a large number of symbols will otherwise be required for accurate error counting [8]
The estimation of bit error ratio (BER) from EVM analysis for quadrature phase shift keying (QPSK), 16-quadrature amplitude modulation (QAM), and 64-QAM with carrier phase recovery and differential decoding to compensate for laser phase noise is presented

Summary

Introduction

Spectrally-efficient modulation formats are currently receiving significant attention for next-generation high-capacity optical communication systems [1,2,3]. EVM is a well known performance metric in wireless digital communication systems to evaluate the quality of vector-modulated signals [7] and is a more appropriate figure of merit at high signal-to-noise ratio (SNR) where a large number of symbols will otherwise be required for accurate error counting [8]. For the estimated BER from EVM analysis to reflect the expected performance achievable with digital coherent receivers, the relationship between EVM and BER needs to be validated following the compensation of optical impairments using algorithms suitable for real-time implementation. The estimation of BER from EVM analysis for quadrature phase shift keying (QPSK), 16-QAM, and 64-QAM with carrier phase recovery and differential decoding to compensate for laser phase noise is presented. EVM and to accurately monitor the performance of optical coherent systems

Error Vector Magnitude

BER Estimation from EVM with Carrier Phase Recovery and Differential Decoding

BER Estimation with Correction Factor

Conclusions