Optical transceivers typically operate reliably up to roughly 70 to 85 degrees Celsius depending on type, so an admin watching this value climb toward that range on a specific transceiver, especially in a densely packed shelf with marginal airflow, gets an early warning of an optic nearing thermal shutdown before an outright link failure occurs. For example, a reading of 78 on a transceiver rated to 85 degrees max would prompt the admin to check shelf airflow or fan health before the optic gets any hotter.