With reference to the power budget, what is the meaning of receiver dynamic range?

Comprehensive and Detailed Explanation From Nokia Optical Networking Fundamentals:

In the design of a Nokia 1830 PSS optical link, thereceiver dynamic rangeis a critical parameter for ensuring error-free transmission. It defines the "window" of optical power within which a receiver (such as an SFP, XFP, or coherent line port) can accurately interpret the incoming signal. The lower bound of this range is theSensitivity, which is the minimum optical power required to achieve a specific Bit Error Ratio (BER). If the power drops below this level, the signal is "lost in the noise."

The upper bound is theOverload power(or saturation point), which is the maximum power the receiver can handle before the photo-detector becomes saturated, leading to signal distortion and errors. The dynamic range is the mathematical difference between these two points (expressed in dB). For a network to operate reliably, the calculated power at the end of a fiber span must fall comfortably within this dynamic range. If the signal is too weak, an amplifier is needed; if it is too strong (exceeding the overload point), an optical attenuator must be used to bring the power back into the dynamic range.