This OCTET STRING holds the lower optical-power bound below which an alarm fires, the classic 'weak signal' threshold used to catch fiber degradation, dirty connectors, or excessive splitter loss before a customer actually loses service. Admins set this specifically to get advance warning while the link is still working but degrading. For example, a lower threshold around -28 dBm triggers an alert as an ONU's receive power drifts toward that danger zone, giving a technician time to clean or repair the fiber connection before the link actually drops.