2. 2
Fiber Optic Basics and the Cell Site
Fiber Optic Lines are strands of optically pure glass as tin as a human hair
In fact the light carrying
component of an optical
fiber is in the neighborhood
of 9 to 60 microns or 9 to
60 millionths of a meter in
diameter
Ted J. Pappas
3. 3
So Why are The Service Providers
Deploying Optical Fiber Up The Tower?
Less Expensive – Optical Fiber can be manufactured cheaper than
equivalent lengths of copper
Thinner – Optical Fibers can be drawn to smaller diameters than
copper wires
Higher Carrying Capacity – More fibers can be bundled into a given
diameter and light weight
Less Signal Degradation – The loss of signal in Fiber is less than in
copper wires and can use lower power transmitters
Light Signals – Unlike electrical signals in copper light signals from one
fiber does not interfere with those other fibers in the same cable. NO
INDUCTION.
Ted J. Pappas
4. 4
What is the Basic Structure of an Optical Fiber?
plastic jacketglass or plastic
claddingfiber core
There are Three (3) Components
1. The Core
2. The Cladding
3. The Buffer / Jacket
Ted J. Pappas
5. 5
The Core is generally made of glass. The core is described as having
an index of refraction n1.
The core is surrounded by a layer of material called the Cladding.
Even though light will propagate along the fiber core without the layer
of cladding material, the cladding does perform some necessary
functions.
The cladding layer is made of a dielectric material with an index of
refraction n2. The cladding performs the following functions:
Reduces loss of light from the core into the surrounding air
Reduces scattering loss at the surface of the core
Protects the fiber from absorbing surface contaminants
Adds mechanical strength
Fiber Structure
Ted J. Pappas
6. 6
Types of Optical Fiber
Step-Index Multi-Mode fiber has a large Core (50-62.5 Microns)
composed completely of one type of glass.
Transmit infrared light at wavelengths of 850 to 1300 nm from light-emitting
diodes (LEDs)
Light travels in straight lines in the fiber reflecting off of the core/cladding
boundary. Since each mode or angle of light travels a different path, a
pulse of light is dispersed while traveling through the fiber limiting its
bandwidth.
7. 7
Types of Optical Fiber
Graded-Index Multi-Mode fiber has a large Core (50-62.5 Microns)
composed completely of one type of glass. Transmit infrared light at
wavelengths of 850 to 1300 nm from light-emitting diodes (LEDs)
Light travels faster in a lower index of refraction, the light will travel faster
as it approaches the outside of the core. Likewise---light traveling in the
center will move slower.
A properly constructed index profile will compensate for the different path
lengths of each mode, increasing bandwidth capacity by as much as 100
times over that of step index.
8. 8
Types of Optical Fiber
Single-Mode , or Monomode, fiber has small Cores (~9- Microns)
composed completely of one type of glass. Transmit infrared light at
wavelengths of 1300 to 1550 nm from Lasers.
Single Mode fiber shrinks the size of the core to a dimension of about six
times the wavelength of the fiber (microns in diameter). This causes the
light to travel in only one mode.
Modal dispersion disappears and the bandwidth of the fiber increases
tremendously over graded-index fiber. Less susceptible to signal loss.
9. 9
Fiber Optic Connectors
In the development of fiber optic technology
over the last 30 years, many companies and
individuals have invented the :better
mousetrap”---a fiber optic connector that was
lower loss, lower cost, or easier to terminate. In
all ~100 fiber optic connectors have been
introduced to the market place, but only a few
represent the majority of the market.
Most fiber optic cables are “plugs” or so-called
make connectors with a protruding ferrule that
holds the fibers in alignment.
The Ferrule may be ceramic
or polymer or plastic
*****Don’t Forget The Ferrule Cap *****
Ted J. Pappas
10. 10
The ST Connector
The ST is probably still the most popular connector for multi-mode.
The prominent feature of the ST is similar to the BNC RF Connector.
It has a bayonet mount and a long ferrule. STs are spring-loaded so
you have to make sure they are seated properly
If you have high loss, reconnect them to see if it makes a difference
Ted J. Pappas
11. 11
The SC Connector
The Ethernet Standard
The SC is a “snap-in” connector and is widely used for its
excellent performance. It is the standard connector for
Ethernet 802.3.
The connector is also available in duplex configuration
Ted J. Pappas
12. 12
The FC Connector
FC was one of the most popular single mode conductors for
many years. It screws on firmly, but you must make sure that
the “key” is aligned in the slot properly before tightening.
It has mostly been replaced by SSC and LC Connectors
Ted J. Pappas
13. 13
The LC Connector
The LC is a small form factor connector half the size of the
SC.
Come in Duplex Mode as well
Ted J. Pappas
14. 14
Fiber Bend Radius
Is there really a bend radius limit with optical cable?
YES
The minimum radius
that an optical fiber can
be bent without loss or
impairment. The radius
varies with different
cable designed but
follows a general rule
that is be no less than
15 times the cable
diameter
Ted J. Pappas
15. 15
Bending the fiber also causes attenuation. Bending loss is classified
according to the bend radius of curvature: microbend loss or macrobend
loss.
Microbends are small microscopic bends of the fiber axis that occur mainly
when a fiber is cabled. Macrobends are bends having a large radius of
curvature relative to the fiber diameter. Microbend and macrobend losses
are very important loss mechanisms. Fiber loss caused by microbending can
still occur even if the fiber is cabled correctly. During installation, if fibers are
bent too sharply, macrobend losses will occur.
Micro and Macro Bends
17. 17
Optical Cable Hoisting and Pulling
There are many derivatives of Kellums / Pulling
Grips and different lengths of the same grip to
ensure a consistent grip on the utility
Grip with “Shoulder” to protect the
leasing edge of the utility
Reinforced double and triple
weave and pulling eye
Rotating head that will move
when not under load to relieve
twist in the cable
18. 18
Kellums / Pulling Grip “ENGAGED’ Length
A “loose” grip will be as much as 50 percent shorter when fitted
onto the utility and larger diameter grips will get even shorter
than their received length.
Catalog Lengths list Engage Length when the Grip is fitted to the utility
Ted J. Pappas
19. 19
Don’t forget the LINE SWIVEL
The type of Line Swivel corresponds to pulling grip strength and
should be mounted in series to the grip to allow for rotation during
installation
Ted J. Pappas
20. 20
Fiber Optics Cable has a tensile load rating that
defines the maximum vertical rise that a cable
being hoisted can withstand without Additional
Support
The Load, The Right Tool, The Vertical Rise
1/2 x maximum long-term tensile load) / cable weight
Prevent Optical Fiber Damage
Support Network Expansion Design
Ted J. Pappas
