Network operations and field tech shorthand for optical power in dBm on a link, usually read from a transceiver's digital diagnostics without disconnecting anything. Comparing receive level with the far end's transmit level gives link loss, and comparing it with the optic's sensitivity and overload limits shows whether the link is near failure. It is the first question asked on any flapping fiber circuit.
What are your light levels on Te1/1? I'm sending minus 3 and the NOC says you're receiving minus 21.
Also heard as
- levels
Related terms
dBm
Optical power in decibels relative to one milliwatt, the unit of power meters and transceiver specs.
Margin
The spare optical power left after link loss is subtracted from what the transmitter and receiver can tolerate.
Roll
To swap the two fibers of a duplex pair so transmit and receive line up with the far end.
Insertion loss
The optical power lost when a component or a whole link is placed in the light path, measured in dB.