OWL FO-4V VFL Fiber OWL 4 Optical Power Meter is a highly accurate, high resolution microprocessor controlled optical power meter with 75dB dynamice range and Visual Fault Locator. OWL FO4V features an integrated light source (ST connector port only) making optical length measurement a breeze. The OWL FO 4V VFL Fiber OWL 4 Optical Power Meter has a large backlit LCD display and a 2.5mm universal adapter port.