Optical modulators and detectors have been characterized and calibrated over the years, but less attention has been made to the optimization of converter measurement uncertainties in a practical user context. Since frequency dependencies of various error mechanisms are different, the wide bandwidths could require procedural changes for optimum results. From a subsystem simulation/modeling/analysis perspective, accuracy in microwave/mm-wave frequency domain characterizations is important but sometimes not studied in terms of how they affect final eye diagram, bit error rate, or other higher level system operational parameters. This white paper explores these characterization and calibration processes, as well as the net uncertainties and their impact on example eye diagram generation.