FACULTY OF ENGINEERING
LAB SHEET
EOP4076 Laser Technology & Applications
TRIMESTER 2 (2014/2015)
Experiment II: Laser Application in Satellite Communications
* Note: On-the-spot evaluation may be carried out during or at the end of the experiment.
Students are advised to read through this lab sheet before doing experiment. Your
performance, teamwork effort, and learning attitude may count towards the marks.
Page 1 of 4
EOP4076 Laser Technology & Applications
2014/2015
LT2: Laser Application in Satellite Communications
I.
Objectives
1.
To introduce the students to the field of lasers as they are used in satellite
communication systems.
To simulate satellite transmission.
2.
II. Apparatus
1.
2.
3.
4.
5.
6.
7.
Laser and adapter
Laser video receiver and adapter
Video cables with RCA end/terminations (2)
VHS video, “Laser: The brightest Light”
Mini Satellite with mounted solar panels and adjustable mini tripod:
– The solar panels are permanently mounted to the satellite in a fixed position. Do
not attempt to rotate or change the position of the panels, as this will result in
damage to the satellite.
– The satellite is powered by the solar panels and does not require batteries or an
A/C adapter for use.
Television with video input jacks.
Video tape player.
III. Theory
Communications Satellites
A communications satellite is in orbit around earth at a location known as the “Clarke
Belt”. The “Clarke Belt” is 22,237 miles above the earth. This location allows the satellite
to remain in the same location over the earth at all times. This is known as being
“geostationary”. At this location, satellites are capable of relaying signals over the horizon
from the original broadcast point because they are in a high orbit capable of “seeing” both
the transmitting station (the uplink), and the receiving station (the downlink).
Satellite Power Systems
A communications satellite is usually powered by solar panels, which gather the sun’s
light energy and converts it into electric energy to charge the onboard batteries. The solar
panels are usually mounted off the sides of the satellite. This is due to the need for a very
large surface area of solar panel, which supplies the power needed to operate the satellite.
Page 2 of 4
EOP4076 Laser Technology & Applications
2014/2015
Lasers as Signal Carriers
Laser beams may be used as “carriers” for a signal much the same way as radiowaves are
used to “carry” the signal from the radio station to your radio. The voice signal is mixed
with the light of the modulated laser and is transmitted to the satellite. The satellite then
relays this mixed signal to the downlink station where the laser light is removed from the
mixed signal leaving the original voice signal. This small signal is amplified and sent to the
speaker.
Laser Communications and Security
A laser communication can be much more secure compared to a radio transmission due to
the tight beam of the laser. This allows the transmission to be “beamed” directly to the
downlink as opposed to a radio transmission, which can be received over a broad area. The
area where the satellite sends its signal is referred to as the “footprint” of a satellite.
IV. P recautions
1.
2.
3.
All the equipments/components are extremely sensitive to the conditions as well
orientations. So, please handle with great care.
Never put your eyes directly in front of the laser beam. It is advisable to put the rings
or wrist watches off whenever one works with lasers.
Unplug the laser any time that it is not actually being used. Never leave it unattended
while it is turned on.
V. Experiments
A.
Basics Procedure of Satellite Components
1.
Find the VIDEO OUTPUT jack on the VCR and insert one end of the video cable in
it.
2.
Connect the one unconnected end of the cable, which you connected to the VCR, to
the VIDEO INPUT jack on the laser.
3.
Connect the remaining video cable from the OUTPUT jack of the video laser receiver
to the VIDEO INPUT jack of the television.
4.
The mini tripod should be screwed into the bottom of the mini satellite.
B.
Experiment Assignments
1.
Design and construct a setup connecting the uplink (laser), mini satellite, and
downlink (video laser receiver) to broadcast a video signal in the manner of a laser
satellite system. (Cognitive – Synthesis, Level 5)
[8 marks]
Page 3 of 4
EOP4076 Laser Technology & Applications
2014/2015
2.
Draw and explain the rationale of your configuration, and explain the working
principle of every component. (Cognitive – Comprehension, Level 2)
[10 marks]
3.
Perform an experiment to evaluate the influence of path clarity on the received
signals. Describe the distortions in the received signal due to poor path clarity.
(Cognitive – Evaluation, Level 6)
[5 marks]
4.
Organize an experimental setup with another group to analyze the effect of interfering
signal. Describe the distortions in the received signal due to crosstalk. (Cognitive –
Synthesis, Level 5)
[5 marks]
VI. Questions
1.
Why is a laser a very secure way to send signals? (Cognitive – Analysis, Level 4)
[5 marks]
2.
Deduce the difficulties in a satellite communication system. (Cognitive – Analysis,
Level 4)
[5 marks]
3.
Decide what other applications that can benefit from using the similar free space laser
communication system, and justify its usage. (Cognitive – Evaluation, Level 6)
[5 marks]
VII. Lab report format, evaluation and submission
1.
2.
An individual report should be nicely handwritten and should include the following:

Date of experiment

Names and IDs of all members

Objectives [2 marks]

Procedures, results, answers and discussions, as required, for all questions and
assignments [43 marks]

Conclusions [5 marks]
The lab report has to be submitted to the lab staff of Optical Laboratory at the end of
the session.
Page 4 of 4