The Max Measurement Ranger:The large majority of LAN / Telco digital transmission systems have maximum power levels below +5 dBm.
Specialist systems, typically rf / analogue, without an optical amplifier, have maximum power levels below +15 dBm.
Long distance systems with an optical power amplifier have maximum power levels below +23 dBm.
On installed single mode systems with standard polished-fiber connectors (SC / LC / FC etc), total system power per fiber cannot go above +23 dBm per fiber, owing to connector power density limitations.
In fact for routine operations, +18 dBm is regarded as a maximum, above which special operational precautions are needed to avoid catastrophic connector / system failure.
Anything above +23 dBm is highly specialised, and will be either an r&d system, or will have expanded beam connectors to handle the extreme power density, or no connectors.
The Min Measurement Ranger:It’s rare to encounter system power levels below -35 dBm.
Use of a fiber amplifier pre-amp can extend recover sensitivity down to between -40 to -45 dBm.
Use of a power meter on a cabling system below about -45 dBm is problematic, due to the possibility of stray sunlight leaking into exposed cabling