This is typically the first alarm to trip on a degrading fiber path: dirty connectors, a bad splice, or excessive bend loss all show up as declining receive power on the local transceiver well before the link actually drops, giving the admin advance warning to clean or repair the fiber before an outage occurs. For example, RxPower slowly declining from 800 microwatts toward a 100 microwatt low threshold over several weeks would point to gradually accumulating fiber-connector contamination rather than a sudden fault.