Multimode optical fiber - BSNL Durg SSA(Connecting India)

1. An optical fiber is a flexible, transparent fiber
made of very pure glass {silica}.
2.It acts as a waveguide, or "light pipe", to
transmit light between the two ends of the
3.Optical fibers are widely used in fiber-optics
communications, which permits transmission
over longer distances and at higher
bandwidths(data rates) than other forms of
Construction of Optical Fiber :A main purpose of a
fiber optic cable is to protect the fiber core
inside the cable that carries the light signal
The following Diagram
shows the construction
of a fiber optic cable.
The fiber core is made of silica glass and is the central part
of the fiber optic cable that carries the light signal.They
are hair-thin in size and the diameter of the fiber core is
typically 8 μm for single mode fiber, and 50m or 62.5 m
for multi mode fiber core
The cladding is also made of glass, and is the layer that
surrounds the fiber core. Together, they form a single
solid fiber of glass that is used for the light transmission.
The diameter of the cladding is typically 125 μm.
The buffer is third layer, buffer coatings are UV-cured
urethane acrylite composite materials applied to the
outside of the fiber during the drawing process. The
coatings protect the very delicate strands of glass
The last layer is cable jacket, which is comprised of
various materials depending on the choice of user and
application in use. They act as a mechanical protection to
the core and cladding inside
An optical fiber is a cylindrical dielectric waveguide (nonconducting waveguide) that transmits light along its axis, by
the process of total internal reflection. The fiber consists of a
core surrounded by a cladding layer, both of which are made
of dielectric materials. To confine the optical signal inthe core,
the refractive index of the core must be greater than that of
the cladding.
# It is designed to carry a single ray of light (mode).
# They have higher bandwidth than multimode.
# Equipment for single mode is expensive as
compared to multimode.
# But they themselves are cheap in bulk
# They are also called as mono-mode optical fiber,
single mode optical guide and uni-mode fibers.
Multi-mode optical fiber(MM fiber) is a type of
optical fiber mostly used for communication over
short distances, such as within a building or on a
campus. Typical multimode links have data rates
of 10 Mbit/s to 10 Gbit/s over link lengths of up
to 600 meters—more than sufficient for the
majority of premises applications.
The equipment used for communications over
multi-mode optical fiber is much less expensive
than that for single-mode optical fiber.
For the effective use of Optical Fiber, it would be
necessary to detect and localize the fiber failures
without delay , and the technique used to detect
and localize the fiber failures is known as
In general, an optical time-domain reflecto-meter
(OTDR) has been used to localize fiber failures.
Fault Localization can be demonstrated by using
instruments Such as optical a and metallic time
domain reflecto-meters (OTDR & MTDR)
The physical cable or connector damage
(Mainly for the connector and disconnect the connection
# the cable physical damage.
# Partial failure of the connector(improper construction of
connectors and cable breakage)
# line graph error(twisted pair cable)# the local cable
damage.(mostly due to poordesign or construction
# mostly due to improper construction methods or
accidental damage to network cables and other causes .
Mainly for the connector and disconnect the connection
# Mainly due to the tight binding between the short circuit
caused the cable, because cable nails embedded in gold
scrap, stripping header damaged insulation and cable multiconductor lead wire insulation faults exposed.
# Mainly as a result of the cable twisted, bending radius is
toosmthe drag force exceeds the mechanical strength of the
cable by cable damage, and many more appear in the new
wiring project.
Some specific instruments are used for localisation of
Optical Fiber Fault are as follows:-
# Optical time-domain reflecto-meter (OTDR)
#optical power meter (OPM)
#Pen-type Visual Fault Locator
Optical time-domain reflectometer (OTDR) An optical timedomain reflecto-meter(OTDR)
is an opto-electronic
instrument used to
characterize an optical fiber.
An optical power meter(OPM) is a
device used to measure the power in
an optical signal. The term usually
refers to a device for testing average
power in fiber optic systems. A typical
optical power meter consists of a
calibrated sensor, measuring amplifier
and display. The sensor primarily
consists of a photo diode selected for
the appropriate range of wavelengths
and power levels.
Locator Pen type Visual Fault Locator
FLP-8312 is simple, easy to use
instruments with stable output
designed to locate faults on fiber optic
cables. When a break or sharpend
exists in a fiber, the red light from the
visible fault locator will indicate the
trouble spot. Used with either
multimodeor single mode fiber, the
Visual Fault Locator have many useful
applications such as locating troubles
in splice trays, patch panels, cable
splice points, and tracing fiber runs
As mentioned above, Optical Fiber has
different types of fault, and techniques which
are used for recovering the damages of Optical
Fiber are known as Rectification 0f Optical
Specific instrument used for Rectification of optical Fiber
fault is fusion splicing
Fusion splicing is the act of joining
two optical fiber send-to-end
using heat. The goal is to fuse the
two fibers together in such a way
that light Passing through the
fibers is not scattered or reflected
back by the splice. The process of
fusion splicing involves using
localized heat to melt or fuse the
ends of two optical fibers
together, the fibers are placed
into the apparatus, aligned, and
they fused together.
# A University on (Mar. 2, 2011) has developed the
very first optical fiber made with a core of zinc
selnide --a light-yellow compound that can be used
as a semiconductor.
The new class of optical fiber, which allows for a
more effective and liberal manipulation of light,
promises to open the door to more versatile laserradar technology. Such technology could be applied
to the development of improved surgical and
medical lasers
# Better countermeasure lasers used by the miltary
# And superior environment-sensing lasers such as
those used to measure pollutants and to detect the
dissemination of bioterrorist chemical agents.
# They found that the new class of fiber provided
more versatility not just in the visible spectrum, but
also in the infrared --electromagnetic radiation with
wavelengths longer than those of visible light.

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