What Are Visual Locators and How Do They Help the Industry?

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The
biggest problems that arise from optical fiber networks are the troubles with
connecting them. This is why we look for efficient methods which will help us
better troubleshoot problem areas in the cables. One such product is a Visual
Fault Locator.

 

A
Visual
Fault Locator is a very important part of the installation and
maintenance kit of fiber optic cables. It can help us identify breaks, bends or
wear of the fiber glass used in single mode or multi-mode optical fiber cables.
The light used in optical fiber cables is infrared light so it’s impossible to
see where the losses in the cables are happening with the naked eye. This is
where VFLs come into the picture as they use light from a powerful laser source
which we can use to see where the high losses are taking place in an optical
fiber cable.

 

Fiber
Continuity Testers vs. VFLs

The
main difference between fiber continuity testers and visual fault locators are
the kind of light source they use. Fiber continuity testers use visible LEDs
(mainly red or green) whereas visual fault locators use a high power red laser
diode (635-670nm). The fiber continuity testers are the more basic ones as they
can only help us find out if there is a problem with the fiber by identifying
whether light will pass through the entire cable or not. If the light passes
through the cables it works well and if not, it requires a more detailed
analysis.

 

Whereas
VFLs give us a more detailed analysis by helping us pin-point the exact
location the losses are happening because of bad connections or bends, and we
don’t have to trouble ourselves with any other equipment for further diagnosis.

 

The
Principle On Which Visual Fault Locators Work

A
high power red laser diode is used to send light through the core of the
optical fiber cable which can travel for some distance and help us trace the
light as it passes through the cables and spot any high losses in them. VFLs
have a main application for short distance cables ranging up to a few
kilometers and this is why they can be used as a part of OTDRs in regions of
OTDR dead zones.

 

Types
of Visual Fault Locators

Visual
fault locators come in different shapes and sizes. There are two types based on
how they function, namely contact and non-contact. In case of a contact VFL,
the optical fiber we are testing comes in direct physical contact with the VFL
and in case of a non-contact VFL, the optical fiber we are testing does not
come in direct contact with the VFL. For commercial purposes, there are 3 main
types of Visual Fault Locators:

 

Pen-style
visual fault locator: This is pocket sized and can be carried around easily.
This is a kind of contact VFL.

 

Hand-held
visual fault locator: This is a type of contact VFL and comes in different
connector types, ranging from specific connector types to universal.

Portable
visual fiber fault locator: This is a non-contact VFL and is used to identify
faults and losses in optical fiber cables especially in short range cables like
LAN, ATM, FDDI, and telecommunication networks.

 

Important
Parameters of VFLs

 

Some
important parameters by which VFL performance can be measured which are:

 

Output
power- The output power is a very important factor for VFL performance. VFLs
can work for longer distances with higher output power.

 

Fiber
distance – This is the maximum distance in the optical fiber cables till which
we can see losses or problem areas without much problem. This is determined by
the power of the laser diode. Normal VFLs have a 5km range for industrial
single mode fibers and 10km range for multi mode fibers.

 

Wavelength
– The wavelength of the VFLs work just fine in the range of 635nm – 670nm.

Modulation
frequency – The eye is better able to pick up on a blinking light which is why
technicians prefer VFLs with a blinking light rather than a steady one as it
helps them diagnose the defects in cables better.

 

Learned
All You Need About Visual Fault Locators?

A
Visual Fault locator is an ideal instrument for installation, testing and
maintenance of fiber optic cables because it can be used to locate a lot of
defects that can occur in optical fiber cables like breaks, cracks, or bends in
regions of bad fusion splices. Since the light passing through fiber optic
cables is infrared, a visual fault locator is a great tool to help us see the
areas which need improvement through our own eyes. A VFL begins its process by
emitting light via a powerful red laser through the core of the optical fiber
cable. When light passes through the cable, it illuminates the region
surrounding the cable(buffer) in regions where there are any anomalies such as
breaks, cracks or connector bends, due to radiation of the visible red light.
This can work perfectly when used as a part of an OTDR as OTDRs have some blind
spots or dead-zones during which we don’t get readings and since VFLs can help
us see where our defects are, that solves many problems. Using VFLs can prove
to be very useful and boost productivity because it provides quick and easy
detection of the damage and helps us find the exact location where the problem
lies so technicians can diagnose, troubleshoot and fix the problem in record
time.