Project Report

LASER COMMUNICATION SYSTEM

A PROJECT REPORTSUBMITTED TO

ELECTRONICS AND COMMUNICATION ENGINEERING DEPARTMENT

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THEAWARD OF THE DEGREE OF

BACHELOR OF ENGINEERINGIN

ELECTRONICS AND COMMUNICATIONENGINEERING

UNIVERSITY INSTITUTE OF ENGINEERING AND TECHNOLOGY,

PANJAB UNIVERSITY ,CHANDIGARH.

Under the Guidance Of : Submitted By:

Ms. Preeti Gupta Varun Raj Dhiman(UE85104)

Assistant Professor (ECE) Vijaypal(UE85105)

Vivek Negi(UE85106)

CERTIFICATE

This is to certify that the following students of BE(ECE) 8th semester have completed

the work on project entitled “LASER COMMUNICATION SYSTEM”.

1. VARUN RAJ DHIMAN(UE85104)

2. VIJAY PAL(UE85105)

3. VIVEK NEGI(UE85106)

In partial fulfillment of the degree of BE (Electronics and Communication Engineering)

by Panjab University, session 2011-12. This record of work carried under the guidance

and supervision of the undersigned.

Ms. Preeti Gupta

(Assistant Professor)

ACKNOWLEDGEMENT2

To bring something into existence is truly the work of ALMIGHTY. We thank GOD

ALMIGHTY for making this venture a success.

We express our wholehearted thanks to the Management of the college, Ms. Renu

Vig ,Director, Mr. Arvind Rajput ,Co-ordinator ECE for providing us an opportunity

to do our studies in this esteemed institution. We are extremely grateful to our project

incharge Ms. Preeti Gupta for motivating and mentoring us in our project. She has

been the guiding light and source of inspiration throughout the project. Besides

providing us with technical assistance she has also been a moral support and motivating

figure during difficult times.

At the outset we wish to place on record our sincere thanks to all the staff members of

the department of Electronics and Communication Engineering who guided us

throughout the entire course.

Varun Raj Dhiman(UE85104)

Vijaypal(UE85105)

Vivek Negi(UE85106)

ABSTRACT

3

Laser communications systems are wireless connections through the

atmosphere. They work similarly to fiber optic links, except the beam is transmitted

through free space. 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. Laser communications systems can be easily deployed since they are

inexpensive, small, low power and do not require any radio interference studies. The

carrier used for the transmission signal is typically generated by a laser diode.

This project implements a Laser Communication System, with a laser light as a

carrier signal. The project is divided into transmitting and receiving sections. At the

transmitter an audio signal is applied to the condenser microphone. The signal is

modulated with a laser as a carrier and transmitted through open space. At the receiver a

phototransistor detects the signal and demodulation of the received signal is carried out.

The demodulated signal is then fed to a loudspeaker where the input audio signal could

be heard.

The present project involves the study of wireless, open channel communication

system using laser as a carrier for audio signals. Using this circuit we can transmit

amplified audio signals wirelessly upto a few 20-50 meters. Instead of RF signals, light

from a laser torch is used as the carrier in the circuit.

The report discusses the construction and working of the project. The various

components used in the project are described in brief. The report further discusses the

advantages, limitations and applications of the Laser Communication System modelled

in this project and other potential areas where Laser Communication System could be

implemented.

TABLE OF CONTENTS

4

1. Introduction………………………………………………….. …9

2. Block Diagram…………………………………………………10

3. Block Diagram Explanation ………………………………......11

3.1. Condenser Microphone…………………………………………….11

3.2. Transmitting Section……………………………………………….11

3.3. Laser Torch………………………………………………………….12

3.4. Receiving Section…………………………………………………...12

3.5. Loud Speaker …………………………………………………….....12

4. Circuit Diagram…………………………………………………13

4.1. Transmitter…………………………………………………………..13

4.2. Receiver………………………………………………………………13

5. Component Study…………………………………………….....14

5.1. Operational Amplifier………………………………………………..15

5.2. VR (potentiometer/resistance variac/trimmer)……………………..16

5.3. Capacitor…………………………………………………………….16

5.4. Battery (9 VOLT)…………………………………………………...17

5.5. Laser Torch………………………………………………………….18

5.6. Microphone………………………………………………………….19

5.6.1. Condenser Microphone……………………………………………..19

5.7. Integrated Circuit (IC)……………………………………………....19

5.8. Phototransistors……………………………………………………...19

6. Circuit Description …………………………………………….....21

6.1. Transmitter …………………………………………………………...22

6.2. Receiver………………………………………………………………..22

6.2.1 Condenser Microphone……………………………………………….23

7. Working…………………………………………………………...24

8. List of tools and instruments used…...…………………………..25

9. Components Required………………………………………….26

9.1. Transmitter………………………………………………………….26 5

9.2. Receiver………………………………………………………..........27

10. Advantages……………………………………………….........28

11. Limitations……………………………………………………..29

12. Problems Faced ………………………………………….........30

13. Applications……………………………………...………….….31

14. Snapshots of Project……………………………………………32

15. Conclusion…………………………………………………........34

References

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LIST OF FIGURES

1. Transmitter……………………………………………… 13

2. Receiver…………………………………………………....143. Symbol of op-amp…………………………………...….... 15

4. Potentiometer…………………………………………….. 16

5. Ceramic Capacitor………………………………….…… 166. 9V Battery………………………………………...……… 17

7. Laser Torch……………………………………………….. 18

8. Phototransistor Symbol……………………….... ………… 19

LIST OF TABLES

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1. Components required for transmitter..............................262. Components required for receiver…….......................... 27

1. INTRODUCTION

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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. 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. The

present paper involves the study of wireless, open channel communication system using

laser a carrier for voice signals. Using this circuit we can communicate with your own

neighbours 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 torch. If there is any obstruction in the path of laser beam, no sounds will

be heard from the receiver.

The most important advantage of laser communication is that it allows very fast

communication service between two or more devices than other modes of

communications. It can provide speed more than 1GBps. So it is much better then LAN

or wireless LAN.

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2. BLOCK DIAGRAM

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3. BLOCK DIAGRAM EXPLANATION

3.1 CONDENSER MICROPHONE

It is also called a capacitor or electrostatic microphone. Condenser means

capacitor, which stores energy in the form of an electric field. Condenser microphones

require power from a battery or external source. Condenser also tends to be more

sensitive and responsive than dynamic, making them well suited to capturing subtle

nuances in a sound.

The diaphragm vibrates when struck by sound waves, changing the distance between

the two plates and therefore changing the capacitance. Specifically when the plates are

closer together capacitance increases and a charge current occurs and this current will

be used to trigger the transmitting section.

3.2 TRANSMITTING SECTION

The transmitter section comprises condenser microphone, transistor amplifier BC548

followed by an op-amp stage built around IC1. The gain of the op-amp can be

controlled with the help of 1-mega ohm pot meter VR1. The AF output from IC1 is

coupled to the base of transistor Bd139, which in turn, modulates the laser beam. The

transmitter uses 9V power supply. however, the 3-volt laser torch ( after the removal of

its battery) can be directly connected to the circuit--with the body of the torch connected

to the emitter of BD139 and the spring-loaded lead protruding from inside the torch to

circuit ground.

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3.3 LASER TORCH

Here we use the light rays coming from laser torch 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 communications 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 beams are used, one for

transmission and one for reception.

3.4 RECEIVING SECTION

The receiver circuit uses an NPN phototransistor as the light sensor that is followed by

a two stage transistor preamplifier and LM386-based audio power amplifier. The

receiver doesn't need any complicated alignment. We kept the phototransistor oriented

towards the remote transmitter's laser point and adjust the volume control for a clear

sound.

3.5 LOUD SPEAKER

A loudspeaker (or "speaker") is an electro acoustic transducer that converts an

electrical signal into sound. The speaker moves in accordance with the variations of an

electrical signal and causes sound waves to propagate through a medium such as air or

water.

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4. CIRCUIT DIAGRAM

4.1 TRANSMITTER

Fig 4.1. Transmitter

13

4.2 RECEIVER

Fig 4.2. Receiver

5. COMPONENT STUDY

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5.1 OPERATIONAL AMPLIFIER

An op amp is a high-gain, direct-coupled differential linear amplifier whose response

characteristics are externally controlled by negative feedback from the output to the

input. OP amps, widely used in computers, can perform mathematical operations such

as summing, integration, and differentiation. OP amps are also used as video and audio

amplifiers, oscillators, etc. in the communication electronics. Because of their versatility

op amps are widely used in all branches of electronics both in digital and linear circuits.

OP amps lend themselves readily to IC manufacturing techniques. Improved IC

manufacturing techniques, the op amp's adaptability, and extensive use in the design of

new equipment have brought the price of IC ops amps from very high to very

reasonable levels. These facts ensure a very substantial role for the IC op amp in

electronics.

Fig shows the symbol for an op amp. Note that the operational amplifier has two inputs

marked (-) and (+). The minus input is the inverting input. A signal applied to the minus

terminal will be shifted in phase 180° at the output. The plus input is the non-inverting

input. A signal applied to the plus terminal will appear in the same phase at the output

as at the input. Because of the complexity of the internal circuitry of an op amp, the op

amp symbol is used exclusively in circuit diagrams.

Fig 5.1 symbol of op-amp

5.2 VR (potentiometer/resistance variac/trimmer):

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fig 5.2 symbol

The potentiometer is a resistor of variable resistance. It has three terminals; a fixed

resistance is found between two of the terminals and the third terminal slides along the

fixed resistor. Often, it is used to control the volume in an audio amplifier.

5.3 CAPACITOR:

The capacitor plays a crucial role in electronics -- it stores electrons for when they're

needed most. Capacitors consist of two conducting plates placed near each other. Inside

the capacitor, the terminals connect to two metal plates separated by a dielectric. The

dielectric can be air, paper, plastic or anything else that does not conduct electricity and

keeps the plates from touching each other..

fig 5.3. Ceramic capacitor

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They can store electric charge for later discharge. Direct current through a capacitor

will charge the capacitor for a short time, and then stop flowing. Alternating current,

because of the changing electric fields it generates, can “flow” across a capacitor.

5.4 BATTERY (9 VOLT)

If you look at any battery, you'll notice that it has two terminals. One terminal is marked

(+), or positive, while the other is marked (-), or negative. In an normal flashlight

batteries, the ends of the battery are the terminals. In a large car battery, there are two

heavy lead posts that act as the terminals.

Electrons collect on the negative terminal of the battery. If you connect a wire between

the negative and positive terminals, the electrons will flow from the negative to the

positive terminal as fast as they can (and wear out the battery very quickly -- this also

tends to be dangerous, especially with large batteries, so it is not something you want to

be doing). Normally, you connect some type of load to the battery using the wire.

Fig 5.4: 9V Battery

Inside the battery itself, a chemical reaction produces the electrons. The speed of

electron production by this chemical reaction (the battery's internal resistance) controls

how many electrons can flow between the terminals. Electrons flow from the battery

into a wire, and must travel from the negative to the positive terminal for the chemical

reaction to take place. That is why a battery can sit on a shelf for a year and still have

17

plenty of power unless electrons are flowing from the negative to the positive terminal,

the chemical reaction does not take place. Once you connect a wire, the reaction starts.

5.5LASER TORCH

 For this project we have removed the laser assembly from a small laser pointer. The

power supply circuit is the green board attached to the brass laser head. We carry

similar laser pointers in our catalog that are easily disassembled for this project. The

power supply circuit came conveniently marked with a plus and a minus next to two

holes in the board. We solder the black negative lead from the battery clip to the hole

marked minus. We solder one of the coil leads to the hole marked plus. We solder the

red positive lead of the battery clip to the other lead from the coil.

Fig 5.5. Laser torch

5.6 MICROPHONE

Sound is an amazing thing. All of the different sounds that we hear are caused by

minute pressure differences in the air around us. What's amazing about it is that the air

transmits those pressure changes so well, and so accurately, over relatively long

distances. It was a metal diaphragm attached to a needle, and this needle scratched a

pattern onto a piece of metal foil. The pressure differences in the air that occurred when

you spoke toward the diaphragm moved the diaphragm, which moved the needle, which

was recorded on the foil. When you later ran the needle back over the foil, the vibrations

scratched on the foil would then move the diaphragm and recreate the sound. The fact

that this purely mechanical system works shows how much energy the vibrations in the

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air can have! All modern microphones are trying to accomplish the same thing as the

original, but do it electronically rather than mechanically. A microphone wants to take

varying pressure waves in the air and convert them into varying electrical signals. There

are five different technologies commonly used to accomplish this conversion. We use

condenser mic in our project.

5.6.1 CONDENSER MICROPHONES - A condenser microphone is essentially a

capacitor, with one plate of the capacitor moving in response to sound waves.

5.7 INTEGRATED CIRCUIT (IC)

An integrated circuit is a pre-made circuit shrunk down to small size and put on a

chip. IC’s save circuit makers time by serving common purposes like amplifying a

signal which would otherwise have to be done by a new circuit built from scratch every

time.

5.8 PHOTOTRANSISTORS

The standard symbol of a phototransistor, which can be regarded as a conventional

transistor housed in a case that enables its semiconductor junctions to be exposed to

external light. The device is normally used with its base open circuit, in either of the

configurations shown in fig. 5.10.2, and functions as follows.

Fig. 5.6Phototransistor symbol.

.In practice, the collector and emitter current of the transistor are virtually identical and,

since the base is open circuit, the device is not subjected to significant negative

feedback. Consequently, the alternative fig. 5.10.2(b) circuit, in which R1 is connected

to Q1 emitter, gives a virtually identical performance to that of fig. The sensitivity of a

phototransistor is typically one hundred times greater than that of a photodiode, but is

19

useful maximum operating frequency (a few hundred kilohertz) is proportionally lower

than that of a photodiode by using only its base and collector terminals and ignoring the

emitter, as shown in fig.

Phototransistors are solid-state light detectors with internal gain that are used to provide

analog or digital signals. They detect visible, ultraviolet and near-infrared light from a

variety of sources and are more sensitive than photodiodes, semiconductor devices that

require a pre-amplifier. Phototransistors feed a photocurrent output into the base of a

small signal transistor. For each illumination level, the area of the exposed collector-

base junction and the DC current gain of the transistor define the output.

The base current from the incident photons is amplified by the gain of the transistor,

resulting in current gains that range from hundreds to several thousands. Response time

is a function of the capacitance of the collector-base junction and the value of the load

resistance. Photodarlingtons, a common type of phototransistor, have two stages of gain

and can provide net gains greater than 100,000. Because of their ease of use, low cost

and compatibility with transistor-transistor logic (TTL), phototransistors are often used

in applications where more than several hundred nanowatts (nW) of optical power are

available. Selecting phototransistors requires an analysis of performance specifications.

Collector current is the total amount of current that flows into the collector terminal.

Collector dark current is the amount of collector current for which there is no optical

input. Typically, both collector current and collector dark current are measured in

milliamps (mA). Peak wavelength, the wavelength at which phototransistors are most

responsive, is measured in nanometers (nm). Rise time, the time that elapses when a

pulse waveform increases from 10% to 90% of its maximum value, is expressed in

nanoseconds (ns). Collector-emitter breakdown voltage is the voltage at which

phototransistors conduct a specified (nondestructive) current when biased in the normal

direction without optical or electrical inputs to the base. Power dissipation, a measure of

total power consumption, is measured in milliwatts (mW).

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6. CIRCUIT DESCRIPTION

There are two sections: the transmitter board and the receiver board, both powered

by a separate 9V battery or a fixed voltage power supply, depending on our needs. The

transmitter board has an electret microphone module at one end, and the laser diode at

the other end. The electronics modulates the intensity of the laser beam according to the

output of the microphone. The laser diode has an inbuilt collimating lens, and is simply

a module that connects to the transmitter board. The receiver uses a photodiode as the

receiving element, and the onboard amplifier powers a small 4-36 ohm speaker. This

board is therefore a high gain amplifier with a basic audio output stage.

This design uses a higher power (and visible) laser beam, the range is improved, and

alignment is easier and not all that critical, especially over a few 20-50 meters. The

quality of sound transmitted by the link is good. Clearly, this project is ideal for setting

up a speech channel between two areas, say adjacent houses or offices on opposite sides

of the street. For duplex (two way) communication, we'll need two laser 'channels’. An

important feature of transmission by laser beam is privacy. Because a laser beam is

intentionally narrow, it's virtually impossible for someone to tap into the link without

us knowing. If someone intercepts the beam, the link is broken, signaling the

interception. Fibre-optic cables also have high security, as it's very difficult to splice

into the cable without breaking the link.

Where the transmission distance is no more than meter of so, a LED (or two for

increased power) can be substituted for the laser diode. For instance, where the link is

being used for educational purposes, such as demonstrating fibre-optic coupling, or the

concept of communication over a light beam. The security of the transmission is much

lower as LEDs transmit light in all directions. Now to a describe how it all works. We'll

start with the transmitter.

6.1 TRANSMITTER

A laser diode needs a certain value of current, called the threshold current, before it

emits laser light. A further increase in this current produces a greater light output. The

relationship between output power and current in a laser diode is very linear, once the

21

current is above the threshold, giving a low distortion when the beam is amplitude

modulated. For example, the 65Onm 5mW laser diode used in this project has a typical

threshold current of 3OmA and produces its full output when the current is raised by

approximately 1OmA above the threshold to 4OmA.

Further increasing the current will greatly reduce the life of the laser diode, and

exceeding the absolute maximum of 8OmA will destroy it instantly. Laser diodes are

very fragile and will not survive electrostatic discharges and momentary surges!

However, if used within specifications, the typical life of one of these lasers is around

20,000 hours. In the transmitter circuit (Fig.1) the laser diode is supplied via an

adjustable constant-current source. Note that the metal housing for the laser diode and

the lens also acts as a heat sink. The laser diode should not be powered without the

metal housing in place. The increasing the voltage at VR1 reduces the laser current. The

setting of VR1 determines the quiescent brightness of the laser beam, and therefore the

overall sensitivity of the system. The electric microphone is powered through R1 and is

coupled to the non inverting input of 1C1 a via capacitor. This input is held at a fixed

DC voltage to give a DC output to bias.

6.2 RECEIVER

The transmitted signal is picked up by the photo detector diode in the receiver (shown in

Fig.2). The output voltage of this diode is amplified by the common emitter amplifier

around T4. This amplifier has a gain of 20 or so, and connects via VR2 to IC2, an

LM386 basic power amplifier IC with a gain internally set to 20.This IC can drive a

speaker with a resistance as low as four ohms, and 35OmW when the circuit is powered

from a 9V supply. Increasing the supply voltage will increase the output power

marginally. Incidentally, the photodiode used for this project has a special clear

package, so it responds to visible light, and not just infrared.

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6.3 MICROPHONE

Sound is an amazing thing. All of the different sounds that we hear are caused by

minute pressure differences in the air around us. What's amazing about it is that the air

transmits those pressure changes so well, and so accurately, over relatively long

distances. It was a metal diaphragm attached to a needle, and this needle scratched a

pattern onto a piece of metal foil. The pressure differences in the air that occurred when

we spoke toward the diaphragm moved the diaphragm, which moved the needle, which

was recorded on the foil. When we later ran the needle back over the foil, the vibrations

scratched on the foil would then move the diaphragm and recreate the sound. The fact

that this purely mechanical system works shows how much energy the vibrations in the

air can have! All modern microphones are trying to accomplish the same thing as the

original, but do it electronically rather than mechanically. A microphone wants to take

varying pressure waves in the air and convert them into varying electrical signals. There

are five different technologies commonly used to accomplish this conversion:

6.3.1 Condenser microphones - A condenser microphone is essentially a capacitor,

with one plate of the capacitor moving in response to sound waves. The movement

changes the capacitance of the capacitor, and these changes are amplified to create a

measurable signal. Condenser microphones usually need a small battery to provide a

voltage across the capacitor.

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7. WORKING

In all of the laser communicators on this page, the laser light is amplitude

modulated. This simply means that the amount of light the laser emits varies over time.

To understand what is going on, it helps to consider how a loudspeaker makes sound. A

loudspeaker is a paper cone attached to a coil of wire that sits in a magnetic field from a

strong permanent magnet. When an electric current flows in the loudspeaker coil, the

coil becomes an electromagnet, and it moves toward or away from the permanent

magnet. As it moves, the paper cone pushes on the air around it, compressing the air in

front of it, and expanding the air behind it. Waves of compressed and expanded air

travel to your ear, and cause your eardrum to move in time to the movements of the

paper cone. The laser communicator adds two components to the loudspeaker concept.

We take the electrical signal that goes to the loudspeaker, and connect it instead to the

laser, so the laser gets brighter and dimmer as the electric current varies. The second

component is the receiver, which converts the light back into an electric current. This

current varies in time with the first current, because the amount of light that it receives

is varying in time. This second electric current is used to move the paper cone of a

loudspeaker, just as before. However, now the loudspeaker can be quite a distance away

from the original electric current, without any wires connecting the two.

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8. LIST OF TOOLS AND INTRUMENTS USED

Following tools and instruments are used for preparing the project

1. Soldering iron

2. Desoldering pump

3. Multimeter

4. Screw driver

5. Two 9V Batteries

6. Flux

7. Soldering Wire

8. Various circuit components

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9. COMPONENTS REQUIRED

9.1 TRANSMITTER:

Sl.No. NAME OF THE COMPONENT QUANTITY

1. Resistance (8.2 K) 2

2 Resistance (1.8 M) 1

3. Resistance (10 K) 1

4. Resistance (15 K) 2

5. Resistance (82 ohm) 1

6. Variable Resistance (1 M) 1

7. Capacitor (1 mf) 1

8. Capacitor (0.1 mf) 1

9. Capacitor (470 mf) 1

10. Capacitor (1000 mf) 1

11. Semiconductor T1 BC548 1

12. Semiconductor T2 BD139 1

13. Condenser MIC 1

14. IC UA741 1

15. GCB 1

Table 1

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9.2 RECEIVER:

Sl.No. NAME OF THE COMPONENT QUANTITY

1. Resistor (6.8 K) 1

2 Resistor (4.7M) 1

3. Resistor (470 K) 1

4. Resistor (2.2 K) 2

5. Resistor (1 K) 1

6. Resistor (10 K) 1

7. Variable resistor (50 K) 1

8. Capacitor (0.01 mf) 1

9. Capacitor(47 pf) 1

10. Capacitor (0.1 mf) 2

11. Capacitor (1 mf) 1

12. Capacitor (100 mf) 2

13. Capacitor(10mf) 1

14. Capacitor(470 mf) 1

15. Semiconductor 2N5777 1

16. Semiconductor BC549 2

17. LM 386 1

18. GC.B 1

19. 8 ohm Speaker 1

Table 2

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10. ADVANTAGES

1. Less costly

2. Circuit can be easily constructed

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 no recurring line costs.

7. Compatibility with copper or fiber interfaces and no bridge or router

requirements.

8. Lasers 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 systems

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.

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11. LIMITATIONS

1. To avoid 50Hz hum noise in the speaker, the phototransistor should be kept

away from AC light sources such as bulbs. The reflected sunlight, however,

does not cause any problem.

2. Laser communication works only if the transmitter and receiver are in the line

of sight.

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12. PROBLEMS FACED

Although this project was successfully completed, however a few hurdles that came

during the construction of the circuit were the breaking of the thin electrical wires after

they had been soldered and some of the components became defunct after they had been

soldered .So we had to identify and replace the defunct components which took some

time.

Moreover the connections with the OP-AMP chip had to be dealt with very carefully

because one wrong connection would have damaged the whole chip. Also the supply to

the laser had to be regulated.

All these things had to be taken care of, for the efficient working of the project.

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13. APPLICATIONS

1. Using this circuit we can communicate 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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14. SNAPSHOTS OF PROJECT

Transmitter

32

Receiver

33

15. CONCLUSION

After the successful working of the project, it can be concluded that this project is

suitable for easy communication. There can be further up gradations in the project

which could lead to a much better system for communication. One of the possible way

is as follows:-

Instead of the short range laser, high range lasers can be used which range a few

hundred meters.

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REFERENCES

1. [Online] // wikipedia. - www.wikipedia.com.

2. [Online] // circuitstoday. - www.circuitstoday.com.

3. [Online] // electronics schematics. - www.electroschematic.com.

4. [Online] // electronics for you. - www.efy.com.

5. Electronics for you magazine .

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