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Communicating by Light

Communicating by Light. Dr Martin Ams MQ Photonics Research Centre Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS) Department of Physics & Astronomy - Faculty of Science MACQUARIE UNIVERSITY North Ryde, NSW 2109 AUSTRALIA Phone: +61 2 9850 8975 Fax: +61 2 9850 8115

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Communicating by Light

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  1. Communicating by Light Dr Martin Ams MQ Photonics Research Centre Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS) Department of Physics & Astronomy - Faculty of Science MACQUARIE UNIVERSITY North Ryde, NSW 2109 AUSTRALIA Phone: +61 2 9850 8975 Fax: +61 2 9850 8115 Url: http://web.science.mq.edu.au/~mams

  2. communication • Communication is the process of exchanging information, messages or ideas

  3. telegraphy • 18th Century – discovery and understanding of electricity led to telecommunications • Telegraphy in copper wires • Morse code, telephone • 1887 - Electromagnetic (EM) Wave Theory • Radio, TV, wireless, satellite, microwave systems

  4. can we use light? • Early 20th Century - suggested that light should be able to transmit data because it is also an EM wave • No light source and no medium to transport it • 1960s: LASER • 1970s: Optical Fibre

  5. how a LASER works Absorption of Energy Emission of Energy

  6. how a LASER works Light Amplification by Stimulated Emission of Radiation (LASER) 1 2 3 4

  7. how a LASER works • LASER light is • Monochromatic: one specific colour • Coherent: photons move in step with each other • Very directional

  8. how optical fibre works • Light travels through the core by constantly bouncing from the cladding (mirror-lined walls) via a principle called total internal reflection (TIR) Glass CLADDING Glass CORE BUFFER COATING

  9. how optical fibre works • Light rays are governed by two laws: • Law of reflection θincidence = θreflection • Law of refraction (Snell’s Law)  n1sinθ1 = n2sinθ2 Low refractive index glass CLADDING • Total internal reflection: • n1>n2 • θ1 > θc = sin-1(n2/n1) High refractive index glass CORE n = refractive index, θ = light ray angle BUFFER COATING

  10. summary • Let’s summarise: • Light source: LASER • Medium: optical fibre • Light is an EM wave • How do we use light to transmit information?

  11. let’s call Germany Analogue Voice Signal

  12. light encoding 256 Typical telephone call ~ 64 kb/s 92 50 0 00110010 01011101 .........

  13. optical communication Optical Fibre Encoder Transmitter Decoder Receiver

  14. bridge the world

  15. why use light? • Advantages of optical fibre • Speed • Bandwidth ~ 350 Tb/s • Price • Physical size and weight • Immune to EM interference • Low signal loss • Non-flammable • Flexible

  16. assign a colour to each signal

  17. unused bandwidth • The problem is not that the fibre is too slow, rather the information travels at the speed of light • However, the fibre needs to be connected to electronic detectors, routers and transmitters etc. that transfer information between different users/senders • Current detectors, routers and transmitters are not able to modulate light at these incredible speeds • Possible solution  Fibre To The Home (FTTH)

  18. $43 billion national broadband network • One of the “top three engineering challenges” in Australia • Optical fibres and light will carry data across Australia to homes and businesses • Data rates of at least 12 Mb/s to 98% of premises in Australia, and 100 Mb/s for regional towns or cities • New optical infrastructure is needed to meet these requirements  Photonic Chips (photonic integrated circuits)

  19. photonic chip & doing my bit • I create analogies of optical fibre devices in glass using a high power laser system

  20. summary • Light can be used to send data signals all over the world using lasers and optical fibres • Voice, TV, video, internet, email & gaming can all fit on one fibre as different colours • Groups around the world are working on next generation photonic chips for use in all optical networks  faster communication and optical processing systems

  21. picture sources • http://www.vislab.uq.edu.au/photonics • http://www.okcupid.com/forum • http://www.portsdown-tunnels.org.uk • http://www.thechemistrynerd.com/benfranklin • http://www.irishdentist.ie • http://science.howstuffworks.com • http://hackaday.com • http://media.photobucket.com • http://www.next-up.org/Newsoftheworld • http://www.solutions-site.org/artman/publish • http://www.alibaba.com/showroom • http://www.rp-photonics.com

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