Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
LASER COMMUNICATION SYSTEM SWATHI S BABU ROLL NO: 58 S3 EC Introduction How does it Work? One-way Laser communication system Application Advantages Disadvantages Conclusion Reference 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. Optical fiber link Laser Transmitter Receiver Direct Link 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. The receiver involves: Telescope(‘antenna’) Signal processor Detector PIN diodes Avalanche Photo Diodes(APD) Single or multiple detectors 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) Transmitter • Maximum output power • Minimum divergence Receiver • Maximum lens area • Clarity • Tight focus on detector Sun shade over detector Shade in front of lens Detector spectral response Colored filters • Absorb ~50% of available light • Difficult to find exact frequency Mounts and stands need only be as accurate as beam divergence Good laser diodes will be 1-2mR (milliRadian) A 32 pitch screw at the end of a 2' mount will yield 1mR per revolution. Since quarter turns (even eighth turns) are possible, this is more than accurate enough Higher thread pitches allow shorter mounts which may be more stable (against wind, vibration, wires) 1mR is 1.5' of divergence every 1000', 3' at 2000 ', etc. GPS and Compass Scopes and Binoculars Strobe lights, large handheld floods, headlights HTs to yell when laser light is seen at remote location 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 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 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 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. www.google.com www.wikipedia.com Thanks