Once connected, turn on the optical power meter and let it warm up for a couple of minutes. You have to wait this warming up time, which is crucial for the meter. A power meter is a measurement instrument, not a piece of test gear you trust forever. This guide covers when to calibrate, what calibration actually involves, what a legitimate certificate. Below are general answers on how to operate, maintain, and calibrate an optical fiber ranger from the list of GAO Tek's optical power meters. These measurements are accomplished using either collimated-beam or connectorized-fiber.