How to Set up Fiber Visual Fault Locator

How to Set up Fiber Visual Fault Locator

Posted on by FS.COM


Fiber visual fault locator is a kind of device which is able to locate the breakpoint, bending or cracking of the fiber glass. It can also locate the fault of OTDR dead zone and make fiber identification from one end to the other end. Designed with FC,SC,ST universal adapter, this fiber fault locator is used without any other type of additional fiber adapters, it can locate fault up to 10km in fiber cable, with compact in size, light in weight, red laser output. The Visual Fault Locator provides a visual method to verify field fiber contact with the pre-polished fiber stub when terminating.

    • Visual fault locator specifications:
    • Product: Class II Laser
    • Wavelength: 650 ± 10nm
    • Maximum Output Power: < 1mW
    • Operating Temperature: 32-104° F (0-40°C)

Installation and Care:

After connecting the Fiber Visual Fault Locator to the opti-crimp connector ferrule (with the included patch cord), turn the VFL “on”. Notice the red glow in the connector ferrule.

While carefully inserting the cleaved field fiber into the connector using constant light pressure, notice the red glow diminish as the cleaved field fiber approaches the prepolished fiber stub in the connector. The insertion mark on the fiber will also approach the end of the connector ferrule.

Why does the fiber ferrule have a red glow?

The red laser light from the VFL Fiber Visual Fault Locator will continue to radiate from the end of the pre-polished fiber stub until optimum contact is made between the cleaved field fiber and the pre-polished fiber stub in the fiber connector.

When the cleaved field fiber stops solidly against the prepolished fiber, the red glow will diminish until it is barely noticeable or disappears. The insertion mark should be even with the back edge of the connector ferrule. Continue to maintain light pressure until a slight bow forms in the fiber to maintain contact between the cleaved field fiber and the pre-polished fiber stub. Crimp the fiber connector one time. The red glow should remain diminished (barely noticeable) after crimping the fiber connector.

Why does the red glow diminish?

When optimum contact is made between the cleaved field fiber and the prepolished fiber stub, the red laser light continues through the field fiber rather than radiating from the end of the pre-polished fiber stub. If the end faces make contact and the red glow does not diminish significantly, a poor cleave may be preventing optimum face-to-face contact. This allows red laser light to radiate from the end of the pre-polished fiber stub rather than continuing through the field fiber.

  • To turn on the FVFL, press and hold the ON/OFF button for approx. 2-3 seconds. The green LED will illuminate to indicate that the unit is on. The green LED will blink.
  • if the batteries require replacing.
  • To toggle between continuous and pulsed modes, use the 2Hz button. In continuous mode the red LED will be off and in the 2Hz mode the red LED will be on.
  • Always clean the ST connector on the VFL before connecting.
  • Should be kept away from water, dust, static electricity, and environments of extreme temperature.
  • Exercise care when handling the FVFL.
  • Remove the batteries for prolonged periods of storage.
  • Never look into the path of the Laser Beam.
  • Never look into the end of a fiber that may have any fiber visual fault locator, or any other laser, coupled to it.
  • Never launch visual fault locator into active equipment or microscope. Make sure that the end opposite the Visual Fault locator is not connected to any electronics or active equipment during termination.


Maintenance: Clean both ends of the VFL after 50 matings or sooner if performance diminishes.

1. Clean ST connector ferrule end face with a lint-free wipe (FWP-C) soaked with alcohol (reagent grade isopropyl alcohol, with a minimum 90% concentration).
2. Clean the split sleeve with an alcohol soaked cleaning swab (FSWB-C). Replace the split sleeve onto fiber ferrule and screw housing into place securely.
3. Clean FVFL output by unscrewing housing and removing split sleeve. Be careful not to lose the small spacer ring around the ferrule.

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