Impact of Modem's Link-Dependent Digital Impairments on Generalized Signal to Noise Ratio Measurement

This paper discusses the importance of Modem's Link-Dependent Digital Impairments (SNRi) in measuring the Generalized Signal-to-Noise Ratio (GSNR) in Open Cables, based on the ITU-T standard. It analyzes the key factors that affect SNRi and discusses the necessity of conducting actual measuring SNRi. This paper analyzes several factors that influence SNRi using the channel pre-emphasis SNRi test method. These factors include the accuracy of channel power measurement, Optical Signal-to-Noise Ratio (OSNR) measurement, Guided Acousto-optic Wave Brillouin Scattering (GAWBS) coefficient, and Back-to-Back (BTB) curve measurements. This paper discusses the feasibility of using multiple modems to test SNRi and GNSR based on a single BTB curve in order to improve efficiency and accuracy of testing. The point is proven through a test experiment conducted on a 6000km system.