Current developments in Telecommunications

Philip Allen

• Introduction

• Newer display technology for TV

• Optical Fibre Technology

• Satellite Technology

• The Future - Quantum communictions?

• Concluding Remarks

Contents

Telecommunications is pervasive and increasingly so!

Introduction

This talk focuses on a

few of the topics

covered in Information

Systems (section 9.4 of

the Senior Science

Stage 6 Syllabus)

Beyond CRTs – Colour Primer

The eye has 3 kinds of cone cells with sensitivity peaks in:

short (S, 420–440 nm),

middle (M, 530–540 nm), and

long (L, 560–580 nm) wavelengths.

The chromaticity diagram illustrates how the human eye will experience light with a given spectrum

Ref: http://en.wikipedia.org/wiki/CIE_1931_color_space

The CIE 1931 color space chromaticity diagram.

Beyond CRTs – Plasma Displays

A well known mechanism but how to make a high resolution display from it?

Ref: http://electronics.howstuffworks.com/plasma-display2.htm

& http://en.wikipedia.org/

Beyond CRTs – Plasma Displays

• xenon and neon gas is contained in 100,000s of cells

• Address electrodes used to ionise individual cells or pixels

• The phosphors give off coloured light when excited by the UV

Ref: http://electronics.howstuffworks.com/plasma-display2.htm

Beyond CRTs – LCD Displays

• LCD cell controls the light through it but how to create an array of coloured pixels?

Ref: http://electronics.howstuffworks.com/lcd2.htm

Beyond CRTs – LCD Displays

• Passive-matrix LCDs again use a simple grid to address a particular pixel

• Active-matrix LCDs additionally use thin film transistors (TFT)

Ref: http://electronics.howstuffworks.com/lcd2.htm

http://www.plasma.com/classroom/what_is_tft_lcd.htm

Optical Fibres - types

Pulse broadening decreases the Bandwidth

Ref: http://en.wikipedia.org/wiki/Optical_fiber

Typical Bandwidths

20 MHz-km

500 MHz-km at 1300nm

160 MHz-km at 850 nm

100 GHz-km

Optical Fibres

Typical fundamental intensity distribution in

single mode optical fibre (in µm).

Fundamental structure of an optical

fibre consisting of a core and cladding.

Optical fibres have been in production since the early 70s.

they can be categorised in two classes:

Multimoded fibres: Used mainly for local area networks,

they were the first type of fibre developed.

Single moded fibres (SMF): Now commonly used in all

long-haul, high speed telecom networks.

Single mode fibres have been research extensively during

the 70s, 80s and 90s. This research effort has lead to

subclasses targeting specific applications

Dispersion shifted fibres

Dispersion flattened fibres

Polarisation maintaining fibres.

Optical Fibres

High speed optical network operate in two major transparency windows due to the very low attenuation of glass fibres. These windows are centred at 1.3 and 1.55 µm respectively

Note: 0.2 dB/km ~ 95%

transmission after 1 km. Only

needing 1% of power before

regeneration means a link can be

100 km!

NB: the rayleigh scattering has a

wavelength dependence:

Optical Fibres - manufacture

Pioneered by Bell Laboratories (now Lucent Technologies), the Modified Chemical Vapour Deposition (MCVD) process is probably the most widely used fibre fabrication technique.

Optical fibres made by MCVD are produced in a preform.

SiCl4 and GeCl4 reactants reacting with oxygen to

produce SiO2 particles but P and B dopants can also be

used

Optical Fibres –at UNSW

Optical Fibres: Drawing Tower

UNSW Tower height 7.6m

Max Draw Speed: 200m/min

Preform Diameter: <50mm

Optical Fibres: Drawing Tower

Commercial towers can draw fibre at 125 km/hr using 3000 fiber-km preforms

Dimensions of single mode optical

fiber.

1.- Core 8-10 µm

2.- Cladding 125 µm

3.- Buffer 250 µm

4.- Jacket 400 µm

Optical Fibres Finished spool of optical fiber

Photo courtesy Corning

Micro-structured polymer optical fibres

(MPOF)

– also known as photonic crystal fibres (PCF) – a topical research area.

They can guide light through two mechanisms:

Effective index: The presence of (air) holes in the glass

structure results in an perceived average reduction of the

refractive index. Hence by tailoring the hole patterns, both

core and cladding regions can be defined and guidance is

very similar to standard fibres.

Bragg resonnance: In this case, guidance is achieved

through a resonance mechanism due to the radial (quasi-

)periodicity of the hole pattern. This is similar to multilayer

coating on glasses or to the periodic electronic potential in

semiconductor resulting of band gap or forbidden bands. A

photonic band gap is created and light cannot travel radially.

MPOF fabricated at the Optical Fibre Technology Centre at Sydney

University using the drilling approach. This image represent the

preform (diameter ~10 cm) before the drawing processs. Courtesy of

Martijn van Eijkelenborg and Maryanne Large

Components used in Optical Fibre Links

Injection laser diode e.g.

622 Mbit/s (OC–12)

Transmitter

Electronics drive circuit

Fibre link – single-mode

e.g. 50 km

Connector Splice

secondary channel

primary channel

Optical coupler or

beam splitter

Receiver

Photodetector

Amplifier and restorer

Optical amplifier

O/E signal

regenerator

EDFA - erbium doped fibre amplifier

Electronic Regenerator

Basic Erbium Doped Fibre Amplifier Ref: http://www.thefoa.org/

Consists of 10 to 30 meter of silica fibre lightly doped with Erbium ions:

– Its optically pumped (980nm or 1480nm);

– The amplification region is typically limited to 1530 – 1550 nm;

– Can provide gain as high as 30 dB;

– Requires no opto-electronic conversion;

– Is readily compatible with standard telecom fibres!

EDFAs – the essentials

2

1

EDFA can be configured in three ways codirectional, contradirectional and bidirectional configuration. Here are two examples.

Codirectional

Contradirectional

EDFAs – configurations

2

2

The three-level transition diagram corresponding to the Er3+ ion embedded into silica glass

1. Pump photon absorption 4. Signal photon re-absorption

2. Non-radiative decay 5. Stimulated emission

3. Spontaneous emission

EDFAs – energy-level diagram

2

3

EDFA can be used in three basic ways when building a point-to-point link.

EDFAs – applications

Fibre Link – “Hero” experiments

We demonstrate 140 7-Tbit/s, 7,326-km transmission of 7×201-

channel 25-GHz-spaced Super-Nyquist-WDM 100-Gbit/s optical

signals using seven-core fiber and full C-band seven-core

EDFAs. The record capacity-distance product of 1.03 Exabit/s×km

is achieved.

K Igarashi et. al. KDDI R&D Laboratories Inc., Japan & Furukawa

Electric Co. Ltd , Japan

1.03-Exabit/s·km Super-Nyquist-WDM Transmission over 7,326-

km Seven-Core Fiber

Ref: http://www.ecoc2013.org/

1 exabit = 1018bits = 1000000000000000000bits = 1000 petabits

Satellites permeate our lives. We depend on them in almost everything we do:

– Communications: TV broadcasting, telephony, internet…

– Navigation: GPS, Galileo, GLONASS & …

– Remote sensing and earth observation: Environmental monitoring, mapping the earth for resources…

– Meteorology: weather forecasting, natural disasters (e.g. cyclones)

– Science: astronomy, but also study of our home the Earth

Satellites

Satellite can be launched into various orbits:

– Low Earth Orbit (LEO)

– Medium Earth Orbit (MEO)

– Geostationary Orbit (GEO)

Satellite Orbits

QB50

GPS satellite

• One of the first uses for satellites was to enable

communications between vastly separated points on

Earth

• NBN Cost Per Premise – Comparison of Technologies

Satellite Communications

%

GEO satellites used for TV broadcasting, telephony, etc..

GEOs have many challenges:

– They are expensive to launch

– The signal experiences long

delays: about 0.25s

– The signal is attenuated by the

large distance

– They cannot see the poles!

GEO Satellites

Optus D1

Inmarsat operate 3 constellations of 10 satellites in

geo orbit to provide a global mobile satellite

communications system

LEOs have been proposed for communications

– Small round-trip delay

– Small relative attenuation

– Cheaper to launch

Constellation needed to cover entire earth

They move rapidly with respect to an object on earth and so must be tracked

More complicated protocols (handover…)

Satellite Communications with LEOs

Iridium

Masters in Satellite Systems Engineering

QB50 project

BLUEsat – stratospheric balloon launch

GPS receivers

Satellite research

Satellites at UNSW

The Next Communication Technology for the

21st Century – Quantum Communications?

Teleportation is

Common Place

in a Quantum Network

Quantum Communications and Quantum

Networks are anticipated to be the core

networking technologies of the 21st century.

Many major companies also think so!

Such as Toshiba, Hewlett-Packard, IBM,

Mitsubishi, NEC, & NTT, have all

commenced large-scale research projects

into quantum networks. The US, Japanese

and European Governments are spending

billions of research dollars in this area

The Next Communication Technology for the

21st Century – Quantum Communications?

The Race is on to Create a

Space-Based

Global Quantum Internet

Intense research efforts related to

these systems are being pursued by

all leading industrial nations.

A large global consortium has

commenced tests for a space-based

Global Quantum Internet

And EE&T at UNSW has PhD

studentships to carry out leading-edge

research into the development of a

large-scale global quantum internet

But what is Quantum Communications?

Quantum physics applied to communications

Creates new applications which are simply impossible to achieve using

classical communications

Examples of the ‘weird’ effects found in quantum communications are:

•teleportation of quantum qubits,

•transfer of information at twice current theoretical limits,

•instantaneous change in quantum particles located at opposite ends of

the planet, and other new effects

Quantum communications also provide ultra secure communications. No

hacker can penetrate these systems as security is based on the

fundamental laws of nature.

• The demand for higher data rates is increasing

• Different technologies are advancing to meet the growing demand

Concluding Remarks

Thank you

Additional Reference Sources

• Francois Ladouceur

• Robert Malaney

• Elias Aboutanious

(All academics from the School of Electrical Engineering and Telecommunications)