VFL (Visual Fault Locator)

VFL (Visual Fault Locator)

VFL stand for Visual Fault Locator,it is also known as Visual Fault Identifier is a small device used with fiber optic Network. A Visual Fault Locator is visible light Source, Such as incandescent bulb, LED or laser diode, that transmit visible light energy. It is like the continuity tester. The visual fault locator is not one of the least expensive tools in your tool kit. It will allow us to quickly identify breaks or macrobends in the optical fiber and also identify a poor fusion splice in multi mode or single mode optical fiber.

There is so many fault occurs with fiber optic Network, such as fiber break, pressure on fiber, Wrong splicing or swapping of fiber. All of these fault is very difficult to find directly without any other devices. So to avoid such time waste or difficulty to find a problem a Device Known as VFL (Visual Fault Locator) used to find such problem or fault in fiber network.

Many problem occurs in fiber optic are related to make a proper connection. As we know that the light energy used in fiber network is infrared (IR) light, Which is beyond the human eye and no one can see it. So in such situation we need a visual fault locator which transmit easily visible light in fiber optic.

Click to Visit about Optical Fiber Splice Machine

VFL (Visual Fault Locator)
Pen type visual fault locator

Working of VFL

VFL Inject a powerful visible laser light from source such as Red diode or incandescent lamp etc into fiber, so not only fiber break can traced but also a high pressure or bad splice point make visible. The VFL are available in different shape and size in market. It may look like a pen, or other shape. There is also a port of VFL in Optical power meter.

Wave Length of VFL

The wave length use by VFL to transmit Visible laser light is of the Range of 635nm to 650nm. So the Question Aries at that point is to why to used this wave length? So the better answer is that Red color is more visible on that wave length.

Total Length

The total length of VFL Depend on its size and also on the battery within the VFL, But generally small pen type VFL range from 5 to 7KM.


  • Fiber routing.
  • Testing Lab of optical fiber.
  • Continuity of Fiber.
  • Maintenance in telecom.
  • To find fiber break, bad splice and pressure on fiber etc.

OTDR is also applicable to full fill the above application. But the difficulty is that the OTDR is too expansive and also required an most experience employ to use OTDR. On the other hand the VFL is Cheap than OTDR and also its operation is too easy. So any one can use it in easily way.

Click Here to Study about the Fiber Vs Copper Cable

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