Metrology of Optical Communication Systems Using Error Vector Magnitude

Irshaad Fatadin

doi:10.4236/jamp.2021.911185

Abstract

Error vector magnitude (EVM) as a performance metric for M-ary quadrature amplitude modulation (QAM) formats in optical coherent systems is presented. It is shown that the calibrated BER, which would otherwise be under-estimated without the correction factor, can reliably monitor the performance of optical coherent systems near the target BER of 10?3 for quadrature phase shift keying (QPSK), 16-QAM, and 64-QAM employing carrier phase recovery with differential decoding to compensate for laser phase noise. The impact on the number of symbols used to estimate the BER from EVM analysis is also presented and compared to the BER obtained by error counting.

Highlights

Optical performance monitoring is an important aspect in the design of the generation of optical communication systems [1]
It is shown that the calibrated bit error ratio (BER), which would otherwise be under-estimated without the correction factor, can reliably monitor the performance of optical coherent systems near the target BER of 10−3 for quadrature phase shift keying (QPSK), 16-quadrature amplitude modulation (QAM), and 64-QAM employing carrier phase recovery with differential decoding to compensate for laser phase noise
The impact on the number of symbols used to estimate the BER from Error vector magnitude (EVM) analysis is presented and compared to the BER obtained by error counting

Summary

Introduction

Optical performance monitoring is an important aspect in the design of the generation of optical communication systems [1]. EVM is a promising alternative performance metric at a high signal-to-noise ratio (SNR) where a large number of symbols will otherwise be required for accurate error counting. EVM is a standard figure of merit to evaluate the quality of vector-modulated signals in wireless digital communication systems [6] and has been applied to assess the performance of optical channels corrupted by amplified spontaneous emission (ASE) noise and to characterize optical I-Q transmitters [3] [4]. A correction factor is necessary to reliably estimate the BER from EVM and to accurately monitor the performance of optical coherent systems. The impact on the number of symbols used to estimate the BER from EVM analysis is presented and compared to the BER obtained by error counting

Error Vector Magnitude and BER Estimation

BER Estimation with Correction Factor

Conclusion