University of Tripoli

Electrical and Electronic Engineering Department

Laser based wireless optical

Prepared by : Ola Adel Frewan , ID#:022161304

Supervisor by: Eng: Taissir Y.Elganimi

Mini Project

Fall 2020
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Table of Contents

1. Abstract:......................................................................................................................4

2. Introduction:..................................................................................................................

3. Block Diagram:...............................................................................................................

4. Circuit Diagram:.............................................................................................................

5. Working Circuit Diagram:..............................................................................................

6. Component List :...........................................................................................................

7. Component Description:……………………………………………………………………………………….

8. Circuit Description : …………………………………………………………………………………………….

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9. Advantage : …………………………………………………………………………………………………………

10. Application : ……………………………………………………………………………………………………..

11. Conclusion :……………………………………………………………………………………………………..

12. References:…………………………………………………………………………………………………….

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1. Abstract:
Using this circuit we can communicate with your neighbors wirelessly.
Instead of RF signals, light from a laser torch is used as the carrier in the
circuit. The laser torch can transmit light up to a distance of about 500
meters. The phototransistor of the receiver must be accurately oriented
towards the laser beam from the pointer. If there is any obstruction in the
path of laser beam, no sound will be heard from the receiver. The transmitter
circuit comprises consider microphone transistor amplifier BC548 followed
by an pomp stage built around UA741. The gain of the op-amp can be
controlled with the help of 1M oooo potmeter VR1 .The AF output from IC1 is
coupled to the base of transistor BD139 (T2), which, in turn, modulates the
laser beam.

The transmitter uses 9V power supply. However, the 3-volt laser pointer

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2. Introduction:
Laser as a communication medium can provide a good substitute for the
present day communication systems as the problem of interference faced in
case of electromagnetic waves is not there and high deal of secrecy is
available. Use of laser in communication systems is future because of the
advantages of the full channel speeds, on communication licenses required at
present, compatibility with copper or fiber interfaces and no bridge or router
requirements. Besides this there are no recurring line costs, portability,
transparency to networks or protocol, although range is limited to a few
hundred meters. Also the laser transmission is very secure because it has a
narrow beam any potential eavesdropping will result use of spectrum
analyzers and RF meters and hence can be used for diverse applications
including financial, medical and military. Laser can also transmit through
glass, however the physical properties of the glass have to be considered.
Laser transmitter and receiver units ensure easy , straightforward systems
alignment and long-term stable , service free operation , especially in
inaccessible environments , optical wireless systems offer ideal , economical
alternative to satellites for communication , as laser radar requires small
aperture as compared to microwave radar . Also there is high secrecy and no
interference like in EM waves. Further, potential bandwidth of radar using
lasers can translate to very precision range measurement. For these reasons,
the can be used as an alternative to present modes of communication. Laser
communication, which is both wide-band and high-speed.

3. Block Diagram:

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3.1. Overview:

3.2. Block Diagram Explanation:

3.2.2. Transmitting Section:

The transmitter section comprises mobile phone , transistor amplifier

The gain of the op-amp can be controlled with the help of 1MΩ pot meter
VR1. The AF output from IC1 is coupled to the base of transmitter used 9V
power supply. However ,the laser pointer (after the removal of its battery )
can be directly connected to the circuit with the body of the pointer
connected to the emitter of BD139 and the spring loaded lead protruding
from inside the pointer to circuit ground .

3.2.3. Laser Pointer:

Here we use the light rays coming from laser pointer as the medium for
transmission. Laser had potential for the transfer of data at extremely high
rates, specific advancements were needed in component performance and
systems engineering, particularly for space-qualified hardware .Free space
laser communication systems are wireless connections through the
atmosphere. They work similar to fibre optic cable systems except the beam
is transmitted through open space. The laser systems operate in the near
infrared region of the spectrum. The laser light across the link is at a
wavelength of between 780-920 nm. Two parallel beam are used, one for
transmission and one for reception.

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3.2.4. Receiving Section:

The receiver circuit used a phototransistor as the light sensor that is

3.2.5. Loud Speaker:

Speaker is an electro acoustic transducer that converts an electrical signal

4. Circuit Diagram:
4.1
6.1. List of Equipment:
1) Transmitter :
- Battery (9V).
- IC UA741.
- Laser pointer.
- Transistor: BC548, BD139.
- Breadboard.
- Capacitors: 1µF (16V), 470µF (16V), 1000µF (16V), 0.1µF.
- Resistors: 8.2kΩ, 1.8MΩ, 8.2KΩ, 10kΩ, 15kΩ, 15kΩ, 82Ω.
- Variable Resistors: 1MΩ.
2) Receiver:
- IC LM386.
- Spekra (0.5W, 8Ω).
- Transistor: BC549, BC549.
- Photo Transistor: 2N5777.

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- Capacitors:1µF(16V),100µF(16V),470µ(16V),10µF(16V),
100µF(16V),0.01µF,47pF,0.1µF,0.1µF.

6.2. Description of Equipment:

2) LM386 :

3) Laser pointer :

4) Resistors:

5) Capacitors :

6) Transistor :

7) Photo transistor:

8) Power supply :

9) Speaker :

6.3. Cost of Equipment:

7. Advantages:
1) Loss costly.
2) Circuit can be easily constructed.

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3) High data rate.
4) No communication licenses required.
5) The laser transmission is very secure because it has a narrow beam.
6) There are recurring line costs.
7) Compatibility with copper or fibre interfaces and no bridge or router
requirements.
8) Laser can also transmit through glass, however the physical properties of the
glass have to be considered.
9) Narrow beam divergence.
10) Laser transmitter and receiver units ensure easy. Straightforward
alignment and long-term stable, service free operation especially in inaccessible
environments, optical wireless systems offer ideal, economical alternative to
expensive leased lines for buildings.

8. Applications:
1) Using this circuit we can communication with our neighbours wirelessly.
2) It can be used in inaccessible areas.
3) In future it can be commissioned in satellites for communication.
4) It can be used in conference halls.

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