Introduction to the meaning of the LASER Communication and its basic principles and applications. Abdulrahman Haje Karim.

1. LASER ENGINEERING – EE420

2. • WHAT IS THE LASER COMMUNICATION?
Laser communications systems are wireless
connections through the atmosphere. They
work similarly to fiber optic links, except the
beam is transmitted through free space.

3. • While the transmitter and receiver must
require line-of-sight conditions, they have the
benefit of eliminating the need for broadcast
rights and buried cables.

4. • Laser communications systems can be easily
deployed since they are inexpensive, small,
low power and do not require any radio
interference studies.

5. • Using Laser Beams to transmit information
between two locations
• Communication over long distances, e.g
between planets
• Laser Communication
Terminals (LCT) transmit
A laser beam and are
Capable of receiving
Laser beams

6. Working principle
The Figure shows the block diagram of Laser Communication System

7. Transmitter basic circuit
Figure shows Basic Transmitter Circuit

8. receiver basic circuit
Figure shows Basic Receiver Circuit

9. Applications
• Defense Industry and Sensitive Areas
Protection.
• Airport Runways.
• Mass Communication.
• NASA and Space Discovery.
• Satellite-to-Satellite Communications.

10. Applications-Defense and Sensitive
Areas

11. Applications-Airport Runways

12. Applications-Mass Communication

13. Applications-nasa and space
discovery

14. Applications-Satellite-to-Satellite
communication

15. One-way Laser communication
system

16. Laser Transmitter
• The Transmitter involves a
signal processing circuit, and
a laser.
• A laser diode is used to
create the laser signal.
• Laser Diodes include
Photodiodes for feedback to
insure consistent output.

17. Receiver
The receiver involves:
• Telescope(‘antenna’)
• Signal processor
• Detector
 PIN diodes
 Avalanche Photo Diodes(APD)
 Single or multiple detectors

18. Modulation of One Way Laser Communication
• Amplitude Modulation ( AM )
Easy with gas lasers, hard with diodes
• PWM (Pulse Width Modulation)
Used by Ramsey in their kit
• PFM (Pulsed FM)
Potentially the highest bandwidth (>100kHz)

19. • Amplitude modulation (AM) is a modulation technique used in
electronic communication, most commonly for transmitting
information via a radio carrier wave. In amplitude modulation,
the amplitude (signal strength) of the carrier wave is varied in
proportion to the waveform being transmitted.
• Pulse-width modulation (PWM), is a modulation technique
used to encode a message into a pulsing signal. Although this
modulation technique can be used to encode information for
transmission, its main use is to allow the control of the power
supplied to electrical devices, especially to inertial[definition
needed] loads such as motors
• Pulse-Frequency Modulation (PFM) is a modulation method
for representing an analog signal using only two levels (1 and 0).
It is analogous to Pulse-Width Modulation (PWM), in which the
magnitude of an analog signal is encoded in the duty cycle of
a square wave.

20. Gain Systems In One-Way Laser Communication
• For Transmitter
Maximum output power
Minimum divergence
• For Receiver
Maximum lens area
Clarity
Tight focus on detector

21. Filters
• Sun shade over detector
• Shade in front of lens
• Detector spectral response
• Colored filters
• Absorb ~50% of available light
• Difficult to find exact frequency

22. Mounting
• Mounts and stands need only be as accurate as beam divergence
• Good laser diodes will be 1-2mR (milliRadian)
• A 32 pitch screw at the end of a 2' mount will yield 1mR per revolution. Since
quarter turns (even eighth turns) are possible, this is more than accurate enough
• Higher thread pitches allow shorter mounts which may be more stable (against
wind, vibration, wires)
• 1mR is 1.5' of divergence every 1000', 3' at 2000 ', etc.

23. Pointing
• GPS and Compass
• Scopes and Binoculars
• Strobe lights, large handheld
floods, headlights
• HTs to yell when laser light is
seen at remote location

24. Advantages of Laser Communication
Technology
• Higher data rates
– Compared to RF technology LC provides much higher data rates
– Higher data rates are essential as more and more data is moved between diff. locations
– Key Driver for investments in Laser Communication Technology
• High security regarding interception
– A focused laser beam is hard to intercept without notice
– Path to Quantum Cryptography
7/10/2017 Technical Seminar-II 24

25. Advantages of Laser Communication
Technology
• Less frequency restrictions
– RF spectrum is crowed and heavily used
• Smaller aperture dimensions and thus reduced size and mass
– Less weight and power per bit
• Autonomous alignment agility resulting in less platform manoeuvres
– Less fuel or more flexibility
7/10/2017 Technical Seminar-II 25

26. Advantages of Laser Communication
Technology
• Laser light has higher intensity, efficiency, as well as better visibility and
performance quality.
Satellite-to-submarine communication

27. Advantages of Laser Communication
Technology
• Laser light has a much lower tranmission loss per unit length.
An interplanetary TV lin

28. Advantages of Laser Communication
Technology
• Less costly then cables and much faster then RF.

29. Disadvantages
There is not really much disadvantage in laser communication. However,
environmental conditions can restrict communication with the laser.

30. • For terrestrial applications, the principal limiting factors are:
• Beam dispersion
• Atmospheric absorption
• Rain
• Fog (10..~100 dB/km attenuation)
• Snow
• Scintillation
• Interference from background light sources (including the
Sun)
• Shadowing
• Pointing stability in wind
• Pollution / smog
Disadvantages

31. Conclusion
- Laser communications offers a viable alternative to RF
communications for inter satellite links and other
applications where high-performance links are a necessity.
- High data rate, small antenna size, narrow beam divergence,
and a narrow field of view are characteristics of laser
communications that offer a number of potential advantages
for system design.

32. - With the dramatic increase in the data handling requirements for
satellite communication services, laser inter satellite links offer an
attractive alternative to RF with virtually unlimited potential and an
unregulated spectrum.
- The system and component technology necessary for successful
inter satellite link exists today.
- FSO is just starting to be applied to solve the Internet “last-mile”
interconnectivity problem. Some believe that it may be the
unlimited bandwidth solution for the metro urban core of
downtown building-to-building communication, as well as the
optimal technology for home-to-home and office-to-office
connectivity.

33. - The system level implications and variations of potential
applications including beamwidth and directivity, signal-to-noise-
ratio, spectrum constraints, signal power budget, bit-error-rate,
information bandwidth, privacy, modulation and detection
schemes, transmission channel attenuation and disturbances
(atmospheric turbulence, scintillation from index of refraction
fluctuations, absorption and scattering from thermal and
moisture variation) and beam acquisition tracking and pointing
influence on the performance metrics of optical transmission
technologies have been investigated.
- The high energy laser laboratory at Cleveland State University
was also employed to conduct experiments to investigate the
feasibility of utilizing the VMJ technology for optical
communications, including:

34. • Beam profiling (Gaussian beam waist may be detected for fine
tracking)
• Off axis performance (7% output decrease at 45° off-normal) 151
• Modulation (ability to track 1 kHz square OOK at 350 W, high
SNR)
• Dynamic range (35.6 dB, linear concurrent WPT and
communications)
• Polarization (multi-channel demonstrated with ER=10.448 dB)
• Applications (challenging atmospheric/oceanographic
environments)
• Integration (multi-use beamed energy capability)

35. REFERENCES
• http://www.academia.edu/4781330/LASER_C
OMMUNICATION_SYSTEM
• http://broadcast.net.ua
• https://www.slideshare.net/shashanksachdev
a/laser

36. References
• www.electronicsforu.co
• www.lasercommunications.weebly.com.
• http://www.space.com/missionlaunches/0601
04_laser_comm.html
• http://www.arrl.org/files/file/Technology/tis/i
nfo/pdf/9009019.pdf
• laser-communication-1222866681398711-
9.ppt

37. • ALPER ATEŞ 15050552051
• ÜMİT ESKİVAR 15050552032
• ABDULRAHMAN HAJE KARIM 13050241001
• SEZGİN DULKADİR 15050552043
• ŞÜKRÜ CAĞLUOĞLU 15050552113
• H. MURAT DURUKAN 15050552045