Relationship between the reference input optical power, upper threshold, and lower threshold of an OPU on the NMS

The lower threshold for reference input optical power is the reference input optical power minus 3 dBm. The upper threshold for reference input optical power is the reference input optical power plus 5 dBm. The upper and lower thresholds can be manually modified or automatically obtained after the reference input optical power is entered.
Reference input optical power refers to the optical power when the system runs properly with the best performance after deployment commissioning is complete.

After the reference input optical power, lower threshold for reference input optical power, and upper threshold for reference input optical power are set, the NMS compares the difference between the actual receive optical power and the reference input optical power of an optical port. If the difference is less than 2 dB, Normal is displayed. If the difference is greater than 2 dB and less than 4 dB, Warning Alert is displayed. If the difference is greater than 4 dB, Critical Alert is displayed.