Optical Power Fiber Meter And 10mW Visual Fault Locator Fiber Optic Cable Tester Detector:InGaAs:Measurement Range (dBm):-70~+3 Battery supports continuous work for up to 48 hours. Portable optical power meter is an accurate and durable handheld meter designed for the installation It is a compact device with backlight swich and auto power on-off ability Besides, it provides ultra-wide measurement range, high accuracy, user self-calibration and universal port.