OWL FO-4-SDsc Fiber OWL 4 Optical Power Meter has an integrated dual-wavelength singlemode laser source that can perform manual bi-directional tests (two identical units are required for two-way testing). Large easy to read backlit LCD display shows measurements in dBm, dB, milliwatts, and microwatts. The OWL FO 4 SDsc Fiber OWL 4 Optical Power Meter uses a InGaAs photodetector with a 2.5mm and 1.25mm universal adaptor.