Quality metrics for optical transmission

摘要: The quality of optical signals is a very important parameter in communications. Several metrics are common use, like signal-to-noise power ratio (OSNR), Qfactor, error vector magnitude (EVM) and bit (BER). While the BER final determinant for system, measured raw not necessarily useful to predict after soft-decision forward correction (FEC), if statistics noise leading errors remains unknown. In this respect EVM superior, as it allows an estimation statistics. accuracy estimate from Q-factor impaired by basic requirement that relevant must be Gaussian. Already plain on-off keying (OOK) assumption violated pre-amplifier employed, estimated becomes even worse phase modulation formats involved. We compare various analytically, simulation, through experiments. employ six quadrature amplitude (QAM) at symbol rates 20 GBd 25 GBd. were generated software-defined transmitter. conclude channels with additive Gaussian metric reliable measure. For nondata-aided QAM reception, range 10-6...10-2 can reliably EVM.