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Information and Communications University
School of Engineering
NAME:
MWAPE MWANGO
STUDENT IDENTIFICATION NUMBER (SIN): 1406147126
PROGRAMME: B.Ed. IN INFORMATION AND
COMMUNICATIONS TECHNOLOGY
COURSE NAME: OPTIC FIBER TECHNOLOGY
ASSIGNMENT No. : 1
LECTURER: Mr N. PHIRI
Question 1.
Process and analyze information from secondary sources to compare and contrast copper cables
with fiber optic cables in relation to;
Carrying capacity
Multimode optical fiber, whether or not it is also carrying laser power, can readily transmit high
bandwidth data over moderate distances; a typical bandwidth-distance product for multimode
fiber is 500 MHz/km, so a 500 m tether can transmit 1 GHz (several Gbits/second, with
appropriate modulation). Signal losses over 500 m are negligible; the bandwidth is limited by
dispersion (time-smearing) of signals. Lightweight copper cable, by contrast, has very high
losses at high frequencies. Twisted pair optimized for high data rates (Cat 6) can transmit 500
MHz over only 100 meters (bandwidth-distance product of 50 MHz/km); lightweight unshielded
cable optimized for power transmission will have even lower bandwidth-distance product.
Cost
The raw materials for glass are plentiful, unlike copper. This means that glass can be made more
cheaply than copper. Transmission over copper or aluminum wire is, and will likely remain,
cheaper than transmission over fiber. The dominant cost of the fiber is the fiber itself, which is
not present in the electrical system. However, the cost of the laser power system is already
comparable to or less than the cost of the rest of a surveillance or communications platform, and
will decline significantly with quantity purchases.
Rate of information transfer
Fiber optic cables have a much greater bandwidth than metal cables. The amount of information
that can be transmitted per unit time over other transmission media is its most significant
advantage. An optic fiber offers low power loss. This allows for longer transmission distances. In
comparison to copper cables, in a network, the longest recommended copper distance is 100m
while with fiber it is 2000m.
Security
The fiber is nonconducting, and is therefore safe in all electromagnetic environments. On land,
this means it can safely be used around electrical transmission lines, as well as in high RF and
magnetic fields. Also, it will not attract or transmit lightning.
Copper cables tend to require very high voltages (hundreds to thousands of volts) to transmit
power efficiently over very thin conductors, which is both a safety hazard and a reliability and
maintenance issue.
Optical fiber cables are difficult to tap. As they do not radiate electromagnetic energy, emissions
cannot be intercepted. As physically tapping the fiber takes great skill to do undetected, fiber is
the most secure medium available for carrying sensitive data.
A broken or damaged, optical fiber can be detected extremely quickly by monitoring either the
actual transmission or (preferably) the transmission of a pilot signal at a shorter wavelength.
With a suitable crowbar circuit, the laser transmission can be shut off within 1-2 microseconds.
Question 2.
Fusion splicing is the act of joining two optical fibers end-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, and so that the splice and the region surrounding it are almost as
strong as the virgin fiber itself. The source of heat is usually an electric arc, but can also be a
laser, or a gas flame, or tungsten filament through which current is passed.
The process of fusion splicing normally involves using localized heat to melt or fuse the ends of
two optical fibers together. The splicing process begins by preparing both fiber ends for a fusion,
which requires that all protective coating is removed from the ends of each fiber.
Question 3.
Attenuation/ Km
(dB/Km)
Attenuation/optical
connector (dB)
Attenuation/joint
(dB)
Mini
Average
Maximum
0.17
0.22
0.4
0.2
0.35
0.7
0.01
0.05
0.1
Best Conditions
Normal
Worst situation
Estimating the Attenuation on the Optical Link
We can arrive at the total attenuation (TA) of an elementary cable section by:
TA = n x C + c x J + L x a + M
Where:

n_number of connectors

C_attenuation for one optical connector (dB)

c_number of splices in elementary cable section

J_attenuation for one splice (dB)

M_system margin (patch cords, cable bend, unpredictable optical attenuation events, and
so on, should be considered around 3dB)

a_attenuation for optical cable (dB/Km)

L_total length of the optical cable
1. Best Conditions
TA = n x C + c x J + L x a + M=2 x 0.2dB+4x0.01dB+20.5Kmx0.17/Km+3dB=6.49dB
2. Normal
TA = n x C + c x J + L x a + M = 2 x 0.35dB+ 4x 0.05dB+ 20.5Km x 0.22dB/Km+ 3dB =
8.41dB
3. Worst situation
TA = n x C + c x J + L x a + M=2 x 0.7dB+4 x 0.1dB+20.5Km x 0.4dB/Km+3dB =
11.42dB