Laser communications ppt

far field laser communication

1. Seminar On Laser Communications Prepared By: P Saicharan Rao 14K81A0440 ECE-4A

2. Content Introduction What is Laser Communication How does it Work? One-way Laser communication system Processing of electrical signal to light Application Advantages Disadvantages Conclusion Reference

3. Introduction 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.

4. What is LASER Communication?? Laser communication systems are wireless connections through the atmosphere. They work similarly to fiber optic links, except the fact that, in lasers, beam is transmitted through free space.

5. Laser Transmitter and Receiver Laser Transmitter Receiver Optical fiber link Direct Link

6. O ne-way Laser communication system

7. Laser Transmitter The Transmitter involves a signal processing circuit, and a laser. A laser diode is used to create the laser signal. Laser Diodes include Photodiodes for feedback to insure consistent output.

8. Receiver The receiver involves: Telescope(‘antenna’) Signal processor Detector PIN diodes Avalanche Photo Diodes(APD) Single or multiple detectors

9. Modulation AM Easy with gas lasers, hard with diodes PWM (Pulse Width Modulation) Used by Ramsey in their kit PFM (Pulsed FM) Potentially the highest bandwidth (>100kHz)

10. The LASER Diode is being turned ON/OFF quickly as needed according to the OOK/PWM/PFM signal. Modulation Techniques: ON-OFF Keying(OOK) Pulse Width Modulati on ( PWM) Pulsed Frequency Modulation(PFM ) OOK P WM P FM

11. Filters Sun shade over detector Shade in front of lens Detector spectral response Colored filters Absorb ~50% of available light Difficult to find exact frequency

12. Applications Transmit voice for miles line-of-sight Use weak signal modes for ?cloud scatter? Transmit video with cheap pens Transmit high speed data without WEP Blind flies for easy extermination

13. Laser in navy

14. Military Defence

15. Advantages Ease of deployment Can be used to power devices License-free long-range operation (in contrast with radio communication) High bit rates Low bit error rates Immunity to electromagnetic interference Full duplex operation Protocol transparency Increased security when working with narrow beam(s)[citation needed] No Fresnel zone necessary

16. Disadvantages For terrestrial applications, the principal limiting factors are: Beam dispersion Atmospheric absorption Rain Fog (10..~100 dB/km attenuation) Snow Scintillation Interference from background light sources (including the Sun) Shadowing Pointing stability in wind Pollution / smog

17. Conclusion 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 forsystem design.

18. LASER COMMUNICATION Thank you