In an OA-free system, the lower threshold of the receive optical power of a line...

In OA-free systems, where no optical amplifiers are used, the lower threshold of the receive optical power of a line board or the WDM side of an OTU board is indeed the optical module’s receiver sensitivity plus 3 dB. This ensures a safety margin for stable signal reception and alarm triggering. Without optical amplifiers, signal levels are more susceptible to attenuation, so maintaining this margin helps prevent degradation due to low optical power. HCIP-Transmission highlights this threshold as a standard parameter for optical power management in non-amplified systems.