Question Paper of OPTICAL NETWORKS AND SATELLITE COMMUNICATION (22647)
In the given page below old question paper/Previous years question paper of subject OPTICAL NETWORKS AND SATELLITE COMMUNICATION is available (Summer-2022)
Model Answers of OPTICAL NETWORKS AND SATELLITE COMMUNICATION (22647)
Q 01) a) State two advantages and two disadvantages of fiber optics cable.
Ans:
Advantages of fiber optic cable:
High bandwidth: Fiber optic cable can transmit data
at a much higher bandwidth than traditional copper cables, allowing for faster
data transfer rates.
Immunity to electromagnetic interference: Unlike
copper cables, fiber optic cables are not susceptible to electromagnetic
interference (EMI), which can degrade the quality of signals.
Disadvantages of fiber optic cable:
Fragility: Fiber optic cables are more fragile than
traditional copper cables and can be easily damaged by bending or twisting.
Cost: Fiber optic cables can be more expensive than
copper cables, making them less attractive for some applications. Additionally,
specialized equipment may be required to install and maintain fiber optic
networks, which can add to the overall cost.
Q01) b) Define : (i) Critical Angle (ii) Acceptance Angle.
(i) Critical angle: The critical angle is the angle
of incidence at which a light ray traveling through a medium, such as air or
water, strikes the interface between that medium and another medium with a
higher refractive index, such as glass, at an angle where the refracted angle
becomes 90 degrees. At this angle, the refracted ray will be parallel to the
interface and will not pass through it, resulting in total internal reflection.
The critical angle is dependent on the refractive indices of the two media.
(ii) Acceptance angle: The acceptance angle is the
maximum angle at which a fiber optic cable can accept incoming light and still
maintain efficient transmission. It is determined by the refractive index of
the fiber optic core, the refractive index of the cladding surrounding the
core, and the numerical aperture of the fiber. The numerical aperture is a measure
of the fiber's ability to gather light and is related to the acceptance angle.
The acceptance angle is important in fiber optic communication because it
determines the range of angles at which the cable can receive signals and still
maintain good transmission quality.
Q01) c) List the types of optical splitters.
There are two main types of optical splitters used
in fiber optic networks:
Fused biconical taper (FBT) splitter: FBT splitters
use a pair of optical fibers that are fused together and stretched to create a
taper. The taper causes the splitting of the incoming light signal into
multiple output signals. FBT splitters are typically used in passive optical
networks (PONs) and can split a signal into two or more output ports.
Planar light wave circuit (PLC) splitter: PLC
splitters use a silica-based waveguide chip to split the incoming light signal.
The waveguide chip has multiple input and output ports, which allow the
splitter to split a signal into multiple output ports. PLC splitters are
typically used in high-density applications, such as in data centers, where
multiple fiber optic connections need to be split and distributed to different
areas. PLC splitters can split a signal into dozens or even hundreds of output
ports, depending on the configuration of the waveguide chip.
Q01) d) State the specification of 802.3j (any 4).
IEEE 802.3j is a standard for Ethernet over fiber
optic networks, specifically for Gigabit Ethernet (GbE) over fiber optic media.
Here are some of its key specifications:
Data rate: The standard supports a data rate of 1
gigabit per second (Gbps) over fiber optic media.
Fiber optic cable type: The standard specifies the
use of multimode fiber optic cable for distances up to 220 meters, and
single-mode fiber optic cable for distances up to 40 kilometers.
Optical transmitter: The standard specifies the use
of a 1300 nanometer (nm) optical transmitter for both multimode and single-mode
fiber optic cable types.
Duplex operation: The standard specifies the use of
full duplex operation, which allows for simultaneous data transmission and
reception between two devices connected over the fiber optic network.
Q01) e) State reason for difference in uplink and downlink frequency in satellite communication
The reason for the difference in uplink and downlink
frequencies in satellite communication is to avoid interference between the two
signals.
In satellite communication, the uplink signal is
transmitted from the ground station to the satellite, while the downlink signal
is transmitted from the satellite back to the ground station. To avoid
interference between the two signals, different frequencies are used for each
direction of transmission.
Specifically, the uplink frequency is typically
higher than the downlink frequency. This is because the satellite acts as a
passive reflector of the uplink signal, and as the signal is reflected back to
the ground station, it experiences a Doppler shift that reduces its frequency.
By using a higher frequency for the uplink signal, this frequency shift can be
compensated for, and the original frequency can be recovered at the ground
station.
Conversely, the downlink frequency is lower than the
uplink frequency because the satellite actively transmits the signal to the
ground station, and the signal experiences a frequency shift due to the
relative motion of the satellite and the ground station. By using a lower
frequency for the downlink signal, this frequency shift can be compensated for,
and the original frequency can be recovered at the ground station.
Q01) f) Define following terms w.r.t. satellite :
(i) footprint (ii) Elevation Angle.
(i) Footprint: In satellite communication, the term
"footprint" refers to the geographical area on the Earth's surface
that is covered by the satellite's signal. It is the region on the Earth's
surface where the satellite signal is strong enough to provide reliable
communication. The shape and size of the footprint depend on factors such as
the altitude and orbit of the satellite, the frequency of the signal, and the antenna
pattern of the satellite.
(ii) Elevation angle: In satellite communication,
the elevation angle is the angle between the horizon and the line of sight to
the satellite. It is the angle at which the satellite appears above the horizon
when viewed from a particular location on the Earth's surface. The elevation
angle is an important parameter in determining the quality of communication
between a ground station and a satellite. A higher elevation angle generally
results in a stronger signal and better communication quality. The elevation
angle is dependent on factors such as the altitude and position of the
satellite, and the latitude and longitude of the ground station.
Q01) g) Define EIRP.
EIRP stands for "Effective Isotropic Radiated
Power". It is a measure of the total power that an antenna radiates in a
specific direction, relative to the power that would be radiated by an
isotropic antenna (which radiates equally in all directions).
EIRP takes into account both the power input to the
antenna and the antenna's gain, which is a measure of how efficiently the
antenna radiates power in a particular direction compared to an isotropic
antenna. The formula for calculating EIRP is:
EIRP = power input to antenna (in watts) + antenna
gain (in dBi)
EIRP is typically used in radio and wireless
communication systems to describe the strength of the signal transmitted by an
antenna in a particular direction. It is an important parameter in determining
the coverage area and range of a wireless communication system, as well as in
complying with regulatory limits on maximum allowable transmission power.
Q01) h) List the different applications of satellite communication.
Satellite communication has a wide range of
applications in various fields. Here are some of the most common applications
of satellite communication:
Telecommunications: Satellite communication is
widely used for providing voice, data, and video communication services,
especially in remote and rural areas where terrestrial communication
infrastructure is not available.
Broadcasting: Satellites are used for broadcasting
TV and radio programs to large geographical areas, including global coverage.
Navigation: Satellite-based navigation systems such
as GPS (Global Positioning System) are widely used for location tracking,
navigation, and timing applications in various industries, including aviation,
marine, transportation, and defense.
Remote Sensing: Satellites equipped with sensors are used for remote sensing applications such as weather forecasting, climate monitoring, land use mapping, and environmental monitoring.
Scientific Research: Satellites are used for
scientific research purposes, including studying the Earth's atmosphere,
oceans, and geology, as well as for observing the universe and space
exploration.
Military and Defense: Satellites are used for
various military and defense applications, including reconnaissance,
intelligence gathering, missile warning, and communication.
Emergency Communication: Satellite communication is
often used as a backup or alternative communication system in emergency
situations, such as natural disasters, where terrestrial communication
infrastructure may be damaged or unavailable.
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