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INTRODUCTION :
In today’s world where mobile based communication is become very popular and
its become very common between person to person to send messages containing
data and media to each other.This project aims at transferring data with the help
of laser from one side to another side using laser light. The data is sent in a secure
manner by making it password protected. When the data is received we enter a
password and if the password is ok data is displayed on the LCD automatically.
Data is to be transfer between two circuits, one as a transmitter and second as a
receiver. Here we show simplex communication. Data is to be transferred from
one side to another side. In the transmitter side we insert the data and on the
receiver end we only receive the data.
The simple block diagram explaining the data transfer is given below
TECHNICAL DETAILS:
Input switch: The switch is used to input the data. In this technology we
insert a minimum three digit from one switch. With the help of switch sensing for delay we insert many character from few switches.
• Transmitter: The transmitter is used to transmit the data in the form of infra red rays. The simple transmitter is shown below:
• 8051 Microcontroller : A microcontroller (often abbreviated MCU) is a single computer chip that executes a user program, normally for the purpose of controlling some device. The microcontroller receives the electrical signal from the photodiode.
• Photodiode : the photodiode receives the data in the form of infra red rays and convert it into electrical signal and then transmits it to the microcontroller.
• SBUFF register: This is an internal special register which receives the data signal and display on the LCD directly.
• Receiver : The receiver receives the the inputted data signal. At the receiver end we add a one op-amp amplifier circuit to receive the sound signal . Here in the transmitter end and on the receiver end we use one Op-amp amplifier circuit.
• LCD DISPLAY: Frequently, an 8051 program must interact with the outside world using input and output devices that communicate directly with a human being. One of the most common devices attached to an 8051 is an LCD display. Some of the most common LCDs connected to the 8051 are 16x2 and 20x2 displays. This means 16 characters per line by 2 lines and 20 characters per line by 2 lines, respectively.
Applications:
 Though this is just a small scale demonstration, It is a very promising point to point communication technology.
 As an alternative or upgrade addon to existing wireless technologies.
 As a safety addon for important fiber connections (redundancy)
 For communications between spacecraft, including elements of a satellite
constellation.
 For interstellar communication.
 The lightbeam can be very narrow, which makes it hard to intercept,
improving security.
Advantages:
It’s chief advantages over RF (radio frequency) communication and Fiber Optics are:
 Quick page link setup.
 No regulatory issues.
 High transmission security.
 High bit rates.
 Low bit error rate.
 No interference.
Compared to a microwave link, the advantages are:
 It can support higher bitrates
 It’s dispersion is lower.
 No need of expensive Optical Fibres.
Limitations:
For terrestrial applications, the principle limiting factors are:
 Beam dispersion
 Atmospheric absorption
Rain / fog /snow (attenuation)
 Background light
 Shadowing
 Pointing/alignment stability in wind
 Pollution / smog
These factors cause an attenuated receiver signal and lead to higher bit error rates