Communicating by Light

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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 [phone]
• Fax [phone]
• Url http//web.science.mq.edu.au/mams

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communication

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

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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

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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

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

• Light Amplification by Stimulated Emission of
  Radiation (LASER)

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how a LASER works

• LASER light is
• Monochromatic one specific colour
• Coherent photons move in step with each other
• Very directional

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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)

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how optical fibre works

• Total internal reflection
• n1 gt n2
• ?1 gt ?c sin-1(n2/n1)

• Light rays are governed by two laws
• Law of reflection ? ?incidence ?reflection
• Law of refraction (Snells Law) ? n1sin?1
  n2sin?2

n refractive index, ? light ray angle
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summary

• Lets summarise
• Light source LASER
• Medium optical fibre
• Light is an EM wave
• How do we use light to transmit information?

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lets call Germany
Analogue Voice Signal
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light encoding
256
Typical telephone call 64 kb/s
92
50
0
00110010
01011101 .........
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optical communication
Optical Fibre
Encoder
Transmitter
Decoder
Receiver
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bridge the world
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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

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assign a colour to each signal
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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)

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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)

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photonic chip doing my bit

• I create analogies of optical fibre devices in
  glass using a high power laser system

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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

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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