Line of Sight Communication Through Laser-Physics-Lab Report, Exercises of Advanced Physics

Download Line of Sight Communication Through Laser-Physics-Lab Report and more Exercises Advanced Physics in PDF only on Docsity! Laser is known to be a well directional light source. It has plenty of applications in practical life. Here we are considering a simple application of laser in communication for two places which are in light of sight. Free Space Optics:-. Line of sight communication by laser has some practical applications. Optics which deals with such applications of laser is known as free space optics FSO. Wireless communication through radio frequency (RF) also uses free space but laser communication has some advantages over RF systems. Advantages are i) less mass, power and volume than RF systems ii) intrinsic narrow beam and high gain of laser beam and iii) no restriction in using or selecting frequency. FSO offers a high bandwidth, that is, 2.5 gigabits/second, for communication through air. In USA fiber and copper cable technologies are used for communications between companies but due demand of high bandwidths in some cities small FSO networks are used for communications. In Europe fiber-optic companies are now offering FSO to those companies which are seeking for high speed communications. Commercially FSO provides much greater data transfer rates than digital subscriber lines and coaxial cables. FSO faces some problems. These are mainly due to weather conditions. In bad foggy weather laser light is absorbed by atmosphere, which limits range of FSO. In clear-sky conditions FSO are very reliable. FSO technology started in 1960s. But due to sensitivity to bad weather conditions and also due to the invention of fiber technology, its use is not so commercialized. FSO can provide high speed communication between buildings, between building and fiber optic network or ground and satellite. It can be installed in days or even in hours while optical fiber is installed in months. Due to some limitations of optical fiber technology, interest in FSO is renewed. Principle: -. Light has an interesting property of recording information when it strikes a surface. This property of light we are able to see the world around us. When light strikes a vibrating surface it will record information about the vibration of that surface. If the vibrating surface is producing sound then the same sound is recorded by laser which can carry it to long distance. We can store sound in laser light in another way. As we know sound is converted into electrical signal by microphone. If this signal is made input to a laser typically a diode laser, then the light produced by such a laser has information of sound. Phtodetector on receiving side receive the laser light which converts it into electrical signal and that electrical signal after passing through some electronic device is converted into voice by speaker. Laser communication is safe. Radio frequency (RF) systems propagate radio frequencies in air in all direction which can be received by any receiver tuned on that frequency. In laser communication, light cannot be received by everyone. Normally laser communication is duplex. In this system sender sends data to receiver and receiver send signal as acknowledgement to sender. So if laser beam carrying data is trapped in between receiver and sender, then it is detected quickly by receiver and sender both. Some lasers have frequency in invisible range, which adds to safety of laser communication. docsity.com Some time laser signal sent by sender cannot be received by receiver but it is received with some coding. In this way laser communication is safe in comparison to RF communication. RF communication system between two parties can be jammed by some third party. It is jammed by producing strong electromagnetic waves which has same frequency as used for communication. Similarly very short distance between sender and receiver also jam the RF system. Laser communication system cannot be jammed by any such means. Laser communication experiment in lab:- Laser communication experiment can be carried out in laboratory. It is a simple experiment and need following apparatus. Apparatus:- Suitable power supply (3.5-7volt), laser light source typically He-Ne laser, a diode laser, microphone, two speakers, photodetector, a small and light strip and mirror, glue, some electronics to amplify electrical signal. This experiment has three types. Using strip:-. A small and light strip is fixed on sheath of speaker. The strip is light so that it can vibrate freely with vibrating sheath producing sound. Speaker is fixed in front of laser. Laser beam through the strip falls on detector at some distance. Detector is connected to another speaker through necessary electronics. Procedure:- Make sound in the microphone. This sound produces vibrations in speaker and also in the strip attached with speaker. Laser beam from laser touches the strip so that vibrations of strip disturb the beam of laser. Now laser beam has some fluctuations. These fluctuations have record of sound. This beam is detected by photodetctor. Photodetector records fluctuations of beam and converts into electrical signal. Second speaker attached with detector changes the electrical signal into sound. Points to be noted:- 1. First of all align laser speaker and detector such that maximum intensity of laser beam falls of photocell of detector. 2. Strip should be in such a position such that it does not destroy the whole beam and also it significantly disturbs the beam. 3. Then tune the detector and second speaker using amplifier and pre-amplifier such that coupling sound and noise is eliminated from second speaker. This will make you able to hear the transmitted sound from the second speaker. Amplifier and pre-amplifier are attached with detector and are used to tune the detector such that it can detect maximum power delivered by laser beam. Amplifier is for large scale tuning while pre-amplifier is for fine tuning in all the three types of experiment. 4. Hold the transmitter speaker in hand and adjust strip’s position attached with it such that any sound produced by this speaker is heard with maximum intensity form second speaker after transmission. 5. After adjusting strip at optimum position, make some sound in microphone and listen in the second speaker. If sound transmitted is not clearly heard then use amplifier attached with first speaker and set this amplifier at optimum position. Make sure that sound from the first position is very clear and sound from second speaker is dominated on sound of first speaker. docsity.com