The incident optical power is used to suppress nonlinear effects and ensure transmission quality. In the following figure, optical power at point C is the incident optical power. Why Do We Need Incident Optical Power? The transmission performance of a WDM system is affected by the. This AE Note explains the differences between Optical Return Loss (ORL) and Back Reflectance in fiber optic systems. Even minor deviations—whether too high, too low, or unstable—can impact signal integrity, trigger service alarms, or interrupt traffic on DWDM, OTN, or long-haul optical line systems.