VFI4 | Visual Fault Identifier for more than 10 km

10 km long-distance with eye-safe-mode

A Visible Fault Identifier (VFI), also referred to as a Visual Fault Locator (VFL), is an essential tool for fiber installation and maintenance technicians.
AFL’s compact VFI4 injects high-powered red-laser light to provide exceptional brightness and range for locating defects in single-mode and multimode fibers. The light generated by these units will escape from sharp bends and breaks in jacketed or bare fibers, as well as poorly mated connectors enabling technicians to quickly spot faults. The universal connector interface mates with many connector styles without needing an adapter.
Rugged and Compact: The rugged VFI4 is designed for the rigors of real-life field testing. It has a range of up to 10 km, fits on a keychain, and features extensions that protect the red-laser port. It has both CW and pulsating modes and is powered by a single AA battery for up to 30 hours of operation.
Installation and Activation: VFI4 is used for quick continuity checks, fiber tracing, splice verification, and Pass/Fail validation for mechanical connectors. VFI4 is also an excellent complement to any OTDR because it can locate faults inside the OTDR’s dead zone.
Essential Troubleshooting Tool: The VFI4 highlights sharp bends, breaks, faulty connectors, and other defects that “leak” light. Other
applications include end-to-end continuity checks, as well as identifying connectors in patch panels and fibers during splicing operations.


  • Eye-safe Class 3R visible red laser source, 650 nm
  • Output power of 5.0 mW with 10 km range
  • 2.5 mm universal adapter (included) accepts FC, SC, ST, etc. connectors
    1.25 mm universal adapter (included) accepts LC and MU connectors


  • Identify and trace fibers during activation and installation
  • Identify poorly mated connectors
  • Verify AFL’s FASTConnect® field-installable connector installation
  • Find faults inside OTDR dead zones