03-01-2011, 11:08 AM
Submitted By:-
Saurabh Kolhe
Vatsal Tripathi
Vipin Patel
Virendra Patel
Vivek Bhardwaj
Vivek Nandanwar
GYAN GANGA INSTITUTE OF TECHNOLOGY & SCIENCES
JABALPUR (M.P)
LASER BASED COMMUNICATION LINK
ABSTRACT
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 purpose of the project is to determine the feasibility of replacing microwave communications with laser communications to remote locations. This page link is unreliable and can be disrupted in fog or rain. The current system has a slow data rate of 1.54 Mbps, equivalent to using a dial up modem on any individual computer. When this page link goes down, all communications to and from the stationare lost, leaving the station unable to carry out its missions. The system proposed to solve this problem utilizes a long cavity laser operating at 1550 nm. The system will also use redundancies as well as spatial diversity of seven lasers to achieve reliability and high data rates averaging 2.4 Gbps. The transmitter and receiver will be set up on gimbals connected to a control system that ensures alignment based off a pulse train on the receiver plate. This pulse train also ensures that the signal is penetrating the atmosphere over the 8 mile distance. A comparison between the microwave and laser communications was completed and future work includes implementing a proposed three phase test plan.
A basic communication system is made up of three main parts being the transmitter, the medium over which the message is being sent, and the receiver. A good example of this is two people communicating from one side of a room to the other. If the person wants to communicate with the other person, he/she speaks words towards the direction of the other individual who receives the voice information and determines the message. This example is much like how any general communication system works. First, the message is determined that needs to be sent to the receiving end. The message is then sent to the transmitter. The transmitter, much like the person’s mouth, is sending the signal containing the message from one person to the other. This can be compared to using an antenna to send out a signal. The signal then must travel through some type of medium to reach the receiver. For the two people talking, this medium would be air. But, sometimes this medium is some type of cable or wire. The signal is then collected by the receiver, which is comparable to the person on the receiving end hearing the sound of the person’s voice. Sometimes the signal can be immediately understood, but other times the signal must first be decoded in order to understand the message.
