Professor Z. GHASSEMLOOY Associate Dean for Research Optical Communications Research Group, School of Computing, Engineering and Information Sciences The

Professor Z. GHASSEMLOOY

Associate Dean for Research Optical Communications Research Group,

School of Computing, Engineering and Information SciencesThe University of Northumbria

Newcastle, U.K.http://soe.unn.ac.uk/ocr/

Free Space Optical Communications

Northumbria University at Newcastle, UK

2

Outline

Introduction to FSO FSO

Applications Issues

Results Simulation Experimental

Final remarks3

Free Space Optical (FSO)

Communications

800BC - Fire beacons (ancient Greeks and Romans)150BC - Smoke signals (American Indians)1791/92 - Semaphore (French)

1880 - Alexander Graham Bell demonstrated the photophone1 – 1st FSO (THE GENESIS)

(www.scienceclarified.com)

1960s - Invention of laser and optical fibre1970s - FSO mainly used in secure military applications1990s to date - Increased research & commercial use due to successful trials

When Did It All Start?

51Alexander Graham Bell, "On the production and reproduction of sound by light," American Journal of Sciences, Series 3, pp. 305 - 324, Oct. 1880.

….. BANDWIDTH when and where required.

AND THAT IS ?

Over the last 20 years deployment of optical fibre cables in the backbone

and metro networks have made huge bandwidth readily available to

within one mile of businesses/home in most places.

But, HUGE BANDWIDTH IS STILL NOT AVAILABLE TO THE END

USERS.

The Problem?

6

Quick to install; only takes few hours

No trenches

Requires no right of way

No license

fee

Huge bandwidth similar to fibre

No electromagnetic

interferenceComplements other access

network technologies

Achievable range limited by thick fog to ~500mOver 3 km in clear atmosphere

7

No multipath fading – Intensity modulation and direct detection

Securetransmission

FSO - Features

steering and tracking capabilities

Used in the following protocols: Ethernet, Fast Ethernet, Gigabit Ethernet, FDDI, ATM, Optical

Carriers (OC)-3, 12, 24, and 48.

8

(Source: NTT)

Access Network Bottleneck

8

9

Cellular Network Bottleneck

MU BS

Microwave link

Backhaul “last mile”

Mobile switchingnode

Core network

RF

PTSN

Switching centre

• Microwave radio links (installed or leased)• More than one BS is connected to MSN

10

BS A

BS C

BS B

Optical fibre

Hub BS Mobile

switchingnode

Medium capacity microwave link

High capacitymicrowave link

Cellular Network Bottleneck

Iran 2008

11

Core

“Last mile”

“Regional”

BACKHAUL

BS

MSN

Hub

12

Plaintree Systems Inc.

13

www.geodesy-fso.com

14

2009 MRV

15

xDSL Copper based (limited bandwidth)- Phone and data combine Availability, quality and data rate depend on proximity to service provider’s C.O.

Radio link Spectrum congestion (license needed to reduce interference) Security worries (Encryption?) Lower bandwidth than optical bandwidth At higher frequency where very high data rate are possible, atmospheric attenuation(rain)/absorption(Oxygen gas) limits link to ~1km

Cable Shared network resulting in quality and security issues. Low data rate during peak times

FTTx Expensive Right of way required - time consuming Might contain copper still etc

FSO

Access Network Technology

16

DR

IVE

R

CIR

CU

IT

POINT APOINT APOINT BPOINT B

SIG

NA

LP

RO

CE

SS

ING

PH

OT

OD

ET

EC

TO

R

Link Range L

FSO - Basics

Cloud Rain Smoke Gases Temperature variations Fog and aerosol

The transmission of optical radiation through the atmosphere obeys the Beer-Lamberts’s law:

Preceive = Ptransmit * exp(-αL)

α : Attenuation coefficient

This equation fundamentally ties FSO to the atmospheric weather conditions

Optical Components – Light Source

Operating Wavelength

(nm)

Laser type Remark

~850 VCSEL Cheap, very available, no active cooling, reliable up to ~10Gbps

~1300/~1550 Fabry-Perot/DFB Long life, compatible with EDFA, up to 40Gbps

~10,000

Quantum cascade laser (QCL)

Expensive, very fast and highly sensitive

For indoor applications LEDs are used.

17

Optical Components – Detectors

Material/StructureWavelength

(nm)Responsivity

(A/W)Typical

sensitivityGain

Silicon PIN 300 – 1100 0.5 -34dBm@ 155Mbps

1

InGaAs PIN 1000 – 1700 0.9 -46dBm@155Mbps

1

Silicon APD 400 – 1000 77 -52dBm@155Mbps

150

InGaAs APD 1000 – 1700 9 10

Quantum –well and Quatum-dot (QWIP&QWIP)

~10,000

Germanium only detectors are generally not used in FSO because of their high dark current.

18

Receiver Sensitivity Vs. Detector Area

PIN

APD

-20

-30

-40

-50

0.01 0.1 1 10 100

Sensitivity(dBm)

Photodiode area (mm )2

(155Mbit/s)

19

Existing System Specifications

Range: 1-10 km (depend on the data rates) Power consumption up to 60 W

15 W @ data rate up to 100 mbps and =780nm, short range 25 W @ date rate up to 150 Mbps and = 980nm 60 W @ data rate up to 622 Mbps and = 780nm 40 W @ data rate up to 1.5 Gbps and = 780nm

Transmitted power: 14 – 20 dBm Receiver: PIN (lower data rate), APD (>150 mbps) Beam width: 4-8 mRad Interface: coaxial cable, MM Fibre, SM Fibre Safety Classifications: Class 1 M (IEC) Weight: up to 10 kg

20

Safety Classifications - Point Source Emitter

880 1310 1550

0.5mW

2.5mW

8.8mW

45mW

10mW

50mW

class1

class1

class3A

class3B

class1

class3A

class3B

class1

class3A

class3B

650

1.0

5.0

500

class1

class3A

class3B

class2

0.2

visibleinfra-red

Totalpower

in a 5cmLens(mW)

Wavelength (nm)Source:BT

indoor indoor

√

√ with holography

21

Power Spectra of Ambient Light Sources

Wavelength (m)

No

rma

lise

d p

ow

er/u

nit

wa

vele

ng

th

0

0.2

0.4

0.6

0.8

1

1.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

Sun Incandescent

x 10

1st window IR

Fluorescent

Pave)amb-light >> Pave)signal (Typically 30 dB with no optical filtering)

2nd window IR

22

23Source:

Cost Comparison

24

25

26

FSO – System Requirement

Link specifications / data rate Response time Timeliness / latency Data throughput Reliability Availability

27

FSO – System Requirement

M. Löschnigg, P. Mandl, E. Leitgeb, 2009

RF wireless networks- Broadcast RF networks are not scaleable- RF cannot provide very high data rates- RF is not physically secure

- High probability of detection/intercept

- Not badly affected by fog and snow, affected by rain

A Hybrid FSO/RF Link- High availability (>99.99%)

- Much higher throughput than RF alone

- For greatest flexibility need unlicensed RF band

Hybrid FSO/RF Wireless Networks

LOS - Hybrid Systems

Video-conference for Tele-medicine CIMIC-purpose and disaster recovery29

30

In addition to bringing huge bandwidth to businesses /homes FSO also finds applications in :

Multi-campus universityHospitals

Others: Inter-satellite communication Disaster recovery Fibre communication back-up Video conferencing Links in difficult terrains Temporary links e.g. conferences

Cellular communication back-haul FSO challenges…FSO challenges…

FSO - Applications

31

Ring Topology

Star Topology

FSO - Applications

DR

IVE

R

CIR

CU

IT

POINT APOINT APOINT BPOINT B

SIG

NA

LP

RO

CE

SS

ING

PH

OT

OD

ET

EC

TO

RMajor challenges are due to the effects of:

CLOUD,

RAIN, SMOKE, GASES,

TEMPERATURE VARIATIONS FOG & AEROSOL

FSO - Challenges

To achieve optimal link performance, system design involves

tradeoffs of the different parameters.

323rd ECAI – Romania, 3-5 July 2009

33

Effects Options Remarks

Photon absorption

Increase transmit

optical power

Effect not significant

FSO Challenges – Rain & Snow

= 0.5 – 3 mm


• A heavy rainfall of 15 cm/hour causes 20 - 30 dB/km loss in optical power• Light snow about 3 dB/km power loss• Blizzard could cause over 60 dB/km power loss

Snow attenuation

FSO Challenges - Physical ObstructionsPointing Stability and Swaying Buildings

Effects Solutions Remarks Loss of signal Multipath induced Distortions Low power due to beam divergence and spreading Short term loss of

signal

Spatial diversity Mesh architectures: using diverse routes Ring topology: User’s n/w become nodes at least one hop away from the ring Fixed tracking (short buildings) Active tracking (tall buildings)

May be used for urban areas, campus etc.

Low data rate Uses feedback

34 3rd ECAI – Romania, 3-5 July 2009

FSO Challenges – Aerosols Gases & Smoke

Mie scattering Photon absorption Rayleigh scattering

These contribute to signal loss:

Increase transmit

power Diversity techniques

Effect not severe

Effects Solutions Remarks


).()()()()( amam

Absorption coefficient Scattering coefficient

36


Mie scattering Photon absorption

Increase transmit

optical power Hybrid FSO/RF

Thick fog limits link

range to ~500m Safety requirements

limit maximum optical

power

FSO Challenges - Fog

= 0.01 - 0.05 mm


Using Mie scattering to predict fog attenuations

m and r are the refractive index and radius of the fog droplets, respectively. Qext is the extinction efficiency and n(r) is the modified gamma size distribution of the fog droplets.

37Fog - Predicted specific attenuation at 10 ºC for moderate continental fog

38

Weather condition

Precipitation Amount (mm/hr)

Visibility dBLoss/km

Typical Deployment Range (Laser link ~20dB margin)

Dense fog 0 m50 m -271.65 122 m

(H.Willebrand & B.S. Ghuman, 2002.)

Very clear 23 km50 km

-0.19-0.06

12112 m13771 m

Thick fog 200 m -59.57 490 m

Moderate fog Snow 500 m -20.99 1087 m

Light fog Snow Cloudburst 100 770 m1 km

-12.65-9.26

1565 m1493 m

Thin fog Snow Heavy rain 25 1.9 km2 km

-4.22-3.96

3238 m3369 m

Haze Snow Medium rain 12.5 2.8 km4 km

-2.58-1.62

4331 m5566 m

Light haze Snow Light rain 2.5 5.9 km10 km

-0.96-0.44

7146 m9670 m

Clear Snow Drizzle 0.25 18.1 km20 km

-0.24-0.22

11468 m11743 m

FSO Challenges - Fog


39

FSO – Fog Experimental Data

City of Nice – Jan –July 2006

City of Graze – Jan - July

Ref: E Leitgeb et al 2009

40

FSO Attenuation


Background radiation LOS requirement Laser safety Turbulence (scintillation)

FSO Challenges - Others



Irradiance fluctuation (scintillation) Image dancing Phase fluctuation Beam spreading Polarisation

fluctuation

Diversity techniques Forward error control control Robust modulation techniques Adaptive optics Coherent detection not used due to Phase fluctuation

Significant for long link range (>1km)Turbulence and thick fog do not occur together In IM/DD, it results in deep irradiance fades that could last up to ~1-100 μs

FSO Challenges - Turbulence

42

Cause: Atmospheric inhomogeneity / random temperature variation along beam path. changes in refractive index of the channel

Depends on: Altitude/Pressure, Wind speed, Temperature and relative beam size.

The atmosphere behaves like prismof different sizes and refractive indices

Phase and irradiance fluctuation

• Zones of differing density act as lenses, scattering light away from its intended path. • Thus, multipath.

Result in deep signal fades that

lasts for ~1-100 μs

FSO Challenges - Turbulence


P: Channel pressure, Te: Channel temperature

Gamma-Gamma All regimes

Model Comments

Log Normal Simple; tractable

Weak regime only

I-K Weak to strong turbulence regime

K Strong regime only

Rayleigh/Negative

Exponential

Saturation regime only

Irradiance PDF by Andrews et al (2001):

0)2()()(

)(2)(

1)2

(2/)(

IIIIp

1

6/55/12

2

1

6/75/12

2

1)69.01(

51.0exp

1)11.11(

49.0exp

l

l

l

l

Ix: due to large scale effects; obeys Gamma distributionIy: due to small scale effects; obeys Gamma distributionKn(.): modified Bessel function of the 2nd kind of order n σl

2 : Log irradiance variance (turbulence strength indicator)

yx III Based on the modulation process the received

irradiance is

Irradiance PDF:

02

220

2

)2/)/(ln(exp

1

2

1)(

I

l

l

lI

II

IIp

To mitigate turbulence effect we, employ subcarrier modulation with spatial diversity

Turbulence – Channel Models


dI

II

I

iRIi

l

l

l

rr

2

220

20

2

22

2

2/)/ln(exp

.1

2

1

2

))((exp

))(/()(ˆ maxarg tdiPtd rd

Using optimal maximum a posteriori (MAP) symbol-by-symbol detection with equiprobable OOK data:

Turbulence Effect on OOK

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Log Intensity Standard Deviation

Th

resh

old

lev

el,

ith

0.5*10-2

10-2

3*10-2

5*10-2

Noise variance

OOK based FSO requires adaptive threshold to performOptimally.


The threshold depends on the noise level and turbulence strength

Photo-detector

array

Atmosphericchannel

Serial/parallelconverter

Subcarrier modulator

.

.Data in

d(t)

Summing circuit

.

.

DC bias

m(t) m(t)+bo

Optical transmitter

Spatial diversity combiner

Subcarrierdemodulator

Parallel/serialconverter .

.

Data out

d’(t) ir

SIM – System Block Diagram


Subcarrier Intensity Modulation

No need for adaptive threshold To reduce scintillation effects on SIM

Convolutional coding with hard-decision Viterbi decoding (J. P. KIm et al 1997)

Turbo code with the maximum-likelihood decoding (T. Ohtsuki, 2002)

Low density parity check (for burst-error medium): - Outperform the Turbo-product codes. - LDPC coded SIM in atmospheric turbulence is reported to achieve a

coding gain >20 dB compared with similarly coded OOK (I. B. Djordjevic, et al 2007)

SIM with space-time block code with coherent and differential detection (H. Yamamoto, et al 2003)

However, error control coding introduces huge processing delays and efficiency degradation (E. J. Lee et al, 2004)


SIM – Our Contributions

Multiple-input-multiple-output (MIMO) (an array of transmitters/ photodetectors) to mitigate scintillation effect in a IM/DD FSO link overcomes temporary link blockage by birds and misalignment when

combined with a wide laser beamwidth, therefore no need for an active tracking

provides independent aperture averaging with multiple separate aperture system, than in a single aperture where the aperture size has to be far greater than the irradiance spatial coherence distance (few centimetres)

Provides gain and bit-error performance Efficient coherent modulation techniques (BPSK etc.) - bulk of the

signal processing is done in RF that suffers less from scintillation

In dense fog, MIMO performance drops, therefore alternative configuration such as hybrid FSO/RF should be considered

Average transmit power increases with the number of subcarriers, thus may suffers from signal clipping

Inter-modulation distortion3rd ECAI – Romania, 3-5 July 2009

49

M

jjcjj twtgAtm

1

)cos()()(

Serial to Parallel

Converter

.

.

.

.

.

.

PSK modulator

at coswc1t

PSK modulator

at coswcMt

PSK modulator

at coswc2t

Σ Σ Laserdriver

)(tdInput data

g(t)

g(t)

g(t)

A1

AM

A2

m(t)

DC bias

b0

Atmopsheric channel

Subcarrier Modulation - Transmitter


Photodetector

ir

x g(-t) Sampler

PSK Demodulator

at coswc2t

PSK Demodulator

at coswcMt

Parallel to Serial

Converter

PSK Demodulator

coswc1t

)(ˆ td Output data

.

.

.

SIM - Receiver

)())(1()( tntmIRtir

Photo-current

R = Responsivity, I = Average power, = Modulation index, m(t) = Subcarrier signal

2

2

2

)(

IRASNRele


51

Performs optimally without adaptive threshold as in OOK Use of efficient coherent modulation techniques (PSK, QAM etc.)

- bulk of the signal processing is done in RF where matured devices like stable, low phase noise oscillators and selective filters are readily available.

System capacity/throughput can be increased Outperforms OOK in atmospheric turbulence Eliminates the use of equalisers in dispersive channels Similar schemes already in use on existing networks

The average transmit power increases as the number of subcarrier increases or suffers from signal clipping. Intermodulation distortion due to multiple subcarrier impairs its performance

But..

Subcarrier Modulation


SIM - Spatial Diversity

Single-input-multiple-output Multiple-input-multiple-output (MIMO)


Selection Combining (SELC). No need for phase information

))()...(),(max()( 21 titititi NT ii ia

Maximum RatioCombining (MRC)[Complex but optimum]

Naaa ...21

Equal Gain Combining (EGC)

FSO CHANNEL

PSK Subcarrier

Demodulator....

)(ˆ td

)(1 ti

)(2 ti

)(tiN

a2

a1

aN

Combiner

)(tiT

Diversity Combining Techniques

ai is the scalingfactor

)()cos()(1)( tntwtgAIN

Rti i

M

jjcjjiri

SIM - Spatial Diversity

Assuming identical PIN photodetector on each links, the photocurrent on each link is:


SIM Spatial Diversity – Assumptions Made

The spacing between detectors > the transverse correlation size ρo of the laser radiation, because ρo = a few cm in atmospheric turbulence

The beamwidth at the receiver end is sufficiently broad to cover the entire field of view of all N detectors.

Scintillation being a random phenomenon that changes with time makes the received signal intensity time variant with coherence time o of the order of milliseconds.

With the symbol duration T << o the received irradiance is time invariant over one symbol duration.


Eric Korevaar et. alA typical reduction in intensity fluctuation with spatial diversity

One detector

Two detectors

Three detectors

Subcarrier Modulation - Spatial Diversity


Free Space Optics Characteristics Challenges Turbulence

- Subcarrier intensity multiplexing- Diversity schemes

Results and discussions Final remarks


1 2 3 4 5 6 7 8 9 10-10

-5

0

5

10

15

20

Number of subcarrier

No

rmal

ised

SN

R @

BE

R =

10

-6

(dB

)

0.10.20.50.7

Log intensityvariance

Normalised SNR at BER of 10-6 against the number of subcarriers for various turbulence levels for BPSK

Increasing the number of subcarrier/users, resultsIn increased SNR

SNR gain compared with OOK

Error Performance – No Spatial Diversity


20 25 30 35 4010

-10

10-8

10-6

10-4

10-2

SNR (dB)

BE

R

DPSK

BPSK

16-PSK

8-PSK

Log intensity

variance = 0.52

0

22

)()/sin(loglog

2dIIpMMSNRQ

MBER e

BPSK based subcarrier modulation is the most power efficient

BPSK BER against SNR for M-ary-PSK for log intensity variance = 0.52

Error Performance – No Spatial Diversity


10

20

30

40

50

60

70

Turbulence Regime

Div

eris

ty G

ain

(d

B)

Weak

Saturation

Moderate

2 Photodetectors3 Photodetectors

Spatial Diversity Gain

Spatial diversity gain with EGC against Turbulence regime


Spatial Diversity Gain for EGC and SeLC

1 2 3 4 5 6 7 8 9 10-10

-5

0

5

10

15

20

25

No of Receivers

Lin

k m

arg

in (

dB

)

0.22

0.52

0.72

1

Log IntensityVariance

EGCSel.C

BER = 10-6

].)(1[2

))22exp((

1

1)(

220 llixK

n

i

NiiNSelCe exerfw

NP

ni i

x1= Zeros of the nth order Hermite polynomial

ni i

w1

= Weight factor of the nth order Hermite polynomial

NARIK 200 2

Dominated by received irradiance,reduced by factor N on each link.

Link margin for SelC is lower

than EGC by ~1 to ~6 dB


1 2 3 4 5 6 7 8 9 100

5

10

15

20

25

30

No of Receivers

Sp

atia

l D

iver

sity

Gai

n

(dB

)

MRCEGC

Log Intensity variance

1

0.52

0.22

Most diversity gain region

The optimal but complex MRC diversity is marginally superior to the practical EGC

Spatial Diversity Gain for EGC and MRC

BER = 10-6

mx

i

ZEGCe

uuieKQw

dZdZPZK

P

1

)2(1

0

2/

0

22

21

)(

)(1

)()(sin2

exp1

2/

0

0

)(

,)(1

)(/

dS

IdIPIQP

N

IMRCMRCe


62

Delay ≥ Channel coherence time

This process is reversed at the receiver side to recover the data

Retransmission on different subcarriers Other possibilities: different wavelengths different polarisations

Temporal Diversity

-32 -30 -28 -26 -24 -22 -20 -18 -16

10-10

10-8

10-6

10-4

10-2

Receiver sensitivity, Io (dBm)

BE

R

No fadingNo TDD

1-TDD

3-TDD

5-TDD2-TDD

Rb = 155MbpsLog irradiancevar =0.3

No TDD 1-TDD 2-TDD 3-TDD 5-TDDIo (dBm)

(no fading: -27.05)-17.17 -19.17 -19.85 -20.13 -20.3

Fading penalty (dB) 9.88 7.88 7.2 6.92 6.75Diversity gain (dB)

(gain / path)0 (0)

2 (2)

2.68 (1.34)

2.96 (0.99)

3.13 (0.63)

Single delay path is the optimum

BER =10-9

Temporal Diversity Gain

Multiple-Input-Multiple-Output

BPSK Modu-Lator

and

Laser driver

d(t) ...

It1

It2

ItH

FSO CHANNEL

BPSK Subcarrier

Demodulator....

)(ˆ td

)(1 ti

)(2 ti

)(tiN

a2

a1

aN

Combiner

iT

By linearly combining the photocurrents using MRC, the individual SNRe on each

link 2

122

H

jijiele I

HN

RASNR


MIMO Performance

12 14 16 18 20 22 24 26

10-9

10-8

10-7

10-6

10-5

10-4

10-3

SNR (R*E[I])2 / No (dB)

BE

R

1X5MIMO

1X8MIMO

4X4MIMO2X2MIMO

1X4MIMO

2/

0

,)(1

dSP Ne

m

juujj x

KwS

12

22 )]2(2exp[

sin2exp

1)(

HN

ARIK

2

02

2

log intensity variance= 0.52

At BER of 10-6:

2 x 2-MIMO requires additional ~0.5 dB of SNR compared with 4-photodetector single transmitter-multiple photodetector system.

4 x 4-MIMO requires ~3 dB and ~0.8 dB lower SNR compared with single transmitter with 4 and 8-photodetectors , respectively.


FSO – Turbulence Chamber

Laser Module (Direct Modulation)Power = 3mW λ = 785nm

OOK & BPSK Modulator + Demodulator

PIN Detector + Amplifier

Reflecting mirror

Heaters + Fans

Turbulence chamber

BPSK modulator •Carrier 1.5 MHz•Data rate A few kHz

Turbulence chamber •Dimension 140 x 30 x 30 cm•Temp. range 24oC – 60oC

Thermometers, T4

Reflecting mirrorOptical power meter head


0.85 0.9 0.95 1 1.05 1.1 1.150

0.5

1

1.5

2

2.5

Signal level

Bin

Siz

e

With scintillation

Lognormal fitMean =1Variance = 9e-3

Lognormal fit

2.93 V

• Total fluctuation variance = 9.10-3 (V2)• Weak scintillation obeys Lognormal distribution (variance < 1)• Simulated turbulence is very weak.

Signal DistributionReceived mean signal + Noise + Scintillation

Lognormal fit

Observations

FSO – With Scintillation Effect


-0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.040

2

4

6

8

10

12

14

16

Signal level

Bin

Siz

e

Histogram of mean signal - no scintillation

Gaussian fit

Gaussian fitMean = -0.0012Variance = 5e-5 Gaussian fit

-0.2492 -0.1992 -0.1492 -0.0992 -0.0492 0.0008 0.0508 0.1008 0.1508 0.2008 0.24920

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

Signal Level

Bin

Perc

enta

ge

-0.3488 -0.2488 -0.1487 -0.0487 0.0513 0.1513 0.2513 0.35130.39870

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

Signal Level

Bin

Perc

enta

ge Observation:The optimum symbol decision position in OOK depends on scintillation level

Transmitted

Received Signal

Received

No scintillation

With scintillationReceived Signal ≈ 400mV p-p

FSO – OOK With Scintillation Effect


Th

resh

old

po

siti

on

. ith

Th

resh

old

ra

ng

e

-0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.250

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

3.2

3.43.5

Signal Level

Bin

Per

cent

age

With scintillation

-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.20

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

3.2

3.43.5

Singal Level

BIn

Per

cent

age

No scintillation

DemodulatedNo low

Pass filtering

Before demodulation

Received Signal

Demodulated Signal ≈ 400mV p-p

Observation:Scintillation does not affect the symbol decision position in BPSK -SIM

FSO – BPSK-SIM With Scintillation Effect


Specifications:• 4x4 Du-plex communication link (The FlightStrata 155E)• VCSEL @ 650 nm wavelength• Si APD• Data rate: 155 Mbps• Maximum length: 3.5 km• Automatic Power Control and Auto Tracking

Optical Fibre @1550 nm

Agilent PhotonicResearch Lab

FSO Network – Linking Two Universities in Newcastle


Collaborators

• Graz Technical University, Austria• Houston University, USA• UCL• Hong-Kong Polytechnic University• Tarbiat Modares University, Iran• Newcastle University• Ankara University, Turkey• Agilent• Cable Free• Technological University of Malaysia• Others•


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72

Summary

Access bottleneck has been discussed

FSO introduced as a complementary technology

Atmospheric challenges of FSO highlighted

Subcarrier intensity modulated FSO (with and without spatial diversity) discussed

Wavelet ANN based receivers



73

Acknowledgements

To many colleagues (national and international) and in particular to all my MSc and PhD students (past and present) and post-doctoral research fellows

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LS Series Specifications

Model WBLS10 WBLS100 WBLS100UUltra-Wide

Data Rate 10Mbps Full Duplex 10Mbps Full Duplex 10Mbps Full Duplex

Distance (meters) up to 800m up to 500m custom

Network Protocol Ethernet Fast Ethernet Fast Ethernet

Network Interface 10Base-T (RJ45) x1 100Base-Tx (RJ45) x1 100Base-Tx (RJ45) x1

Transmitter IR - LED Class 1 IR -LED Class 1 IR - LED Class 1

Wavelength 800-900nm 800-900nm 800-900nm

Beam width 17mrad 17mrad custom

Power POE or 48V DC POE or 48V DC POE or 48V DC

Housing Weatherproof Weatherproof Weatherproof

Operating Temp. -40° C to 70° C -40° C to 70° C -40° C to 70° C

Relative Humidity 5% to 95% 5% to 95% 5% to 95%

Dimensions 9” x 6.0” x 12” 9” x 6.0” x 12” 9” x 6.0” x 12”

Weight 3.2Kg, 7.5lbs 3.2Kg, 7.5lbs 3.2Kg, 7.5lbs

Mounting Options Wall/Tower, Roof,Non-penetrating

Wall/Tower, Roof,Non-penetrating


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Model WBLS T1/E1 WBLS 4T1/4E1

Data Rate 4 x 1.54 Mbps or4 x 2.048 Mbps

1 x 1.54 Mbps or1 x 2.048 Mbps

Distance (meters) Up to 800m up to 1600m

Network Protocol ATM ATM

Network Interface 4 x RJ48C 1 x RJ48C

Transmitter IR - LED Class 1 IR - LED Class 1

Wavelength 800-900nm 800-900nm

Beam width 17mrad 17mrad

Power 48V DC 48V DC

Housing Weatherproof Weatherproof

Operating Temp. -40° C to 70° C -40° C to 70° C

Relative Humidity 5% to 95% 5% to 95%

Dimensions 9” x 6.0” x 12” 9” x 6.0” x 12”

Weight 3.2Kg, 7.5lbs 3.2Kg, 7.5lbs



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400/500 Series Specifications

Model WB410 WB4100 WB4155 WB510

Data Rate 10Mbps Full Duplex 100Mbps Full Duplex 155Mbps Full Duplex 10Mbps Full Duplex

Distance (meters) 1500m 750m 750m 2000m

Network Protocol Ethernet Fast Ethernet Clear Channel Ethernet

Network Interface 10Base-T (RJ45) x1 100Base-Tx (RJ45) x1 SPF- LC Fiber Connect 10Base-T (RJ45) x1

Transmitter IR - LED Class 1 IR -LED Class 1 IR - LED Class 1 IR - LED Class 1

Wavelength 800-900nm 800-900nm 800-900nm 800-900nmBeam width 17mrad 17mrad custom 17mrad

Power POE or 48V DC POE or 48V DC 48V DC POE or 48V DC

Housing Weatherproof Weatherproof Weatherproof Weatherproof

Operating Temp. -40° C to 70° C -40° C to 70° C -40° C to 70° C -40° C to 70° C

Relative Humidity 5% to 95% 5% to 95% 5% to 95% 5% to 95%

Dimensions 15.8" x15.3" x 19" 15.8" x15.3" x 19" 15.8" x15.3" x 19" 15.8" x15.3" x 19"

Weight 9.0Kg, 20lbs 9.0Kg, 20lbs 9.0Kg, 20lbs 9.0Kg, 20lbsMounting Options Wall/Tower, Roof,

Non-penetratingWall/Tower, Roof,



Non-penetrating

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Model WB5100 WB5155 WB5 T1/E1 WB5 T4/E4

Data Rate 100Mbps Full Duplex 155Mbps Full Duplex 1 x 1.54 Mbps or1 x 2.048 Mbps


Distance (meters) 1000m 1000m 3500m 2000m

Network Protocol Fast Ethernet Clear Channel ATM ATM

Network Interface 100Base-Tx (RJ45) x1 SPF- LC Fiber Connect 1 x RJ48C 4 x RJ48C

Transmitter IR - LED Class 1 IR - LED Class 1 IR - LED Class 1 IR - LED Class 1

Wavelength 800-900nm 800-900nm 800-900nm 800-900nmBeam width 17mrad 17mrad 17mrad 17mrad

Power POE or 48V DC 48V DC 48V DC 48V DC

Housing Weatherproof Weatherproof Weatherproof Weatherproof

Operating Temp. -40° C to 70° C -40° C to 70° C -40° C to 70° C -40° C to 70° C

Relative Humidity 5% to 95% 5% to 95% 5% to 95% 5% to 95%

Dimensions 15.8" x15.3" x 19" 15.8" x15.3" x 19" 15.8" x15.3" x 19" 15.8" x15.3" x 19"

Weight 9.0Kg, 20lbs 9.0Kg, 20lbs 9.0Kg, 20lbs 9.0Kg, 20lbsMounting Options Wall/Tower, Roof,




Non-penetrating

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XT Series Specifications

Model WBXT10 WBXT100 WBXT155

Data Rate 10Mbps Full Duplex 100Mbps Full Duplex 155Mbps Full Duplex

Distance (meters) 3000m 2000m 2000m

Network Protocol Ethernet Fast Ethernet Clear Channel

Network Interface 10Base-T (RJ45) x1 100Base-Tx (RJ45) x1 SPF- LC Fiber Connect

Transmitter IR - LED Class 1 IR -LED Class 1 IR - LED Class 1

Wavelength 800-900nm 800-900nm 800-900nm

Beam width 17mrad 17mrad custom

Power POE or 48V DC POE or 48V DC 48V DC

Housing Weatherproof Weatherproof Weatherproof

Operating Temp. -40° C to 70° C -40° C to 70° C -40° C to 70° C

Relative Humidity 5% to 95% 5% to 95% 5% to 95%

Dimensions 19" x 11" x 32" 19" x 11" x 32" 19" x 11" x 32"

Weight 15Kg, 30lbs 15Kg, 30lbs 15Kg, 30lbs




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Model WBXT T1/E1 WBXT T4/E4

Data Rate 1 x 1.54 Mbps or1 x 2.048 Mbps


Distance (meters) 4000m 3000m

Network Protocol ATM ATM

Network Interface 1 x RJ48C 4 x RJ48C

Transmitter IR - LED Class 1 IR - LED Class 1

Wavelength 800-900nm 800-900nm

Beam width 17mrad 17mrad

Power 48V DC 48V DC

Housing Weatherproof Weatherproof

Operating Temp. -40° C to 70° C -40° C to 70° C

Relative Humidity 5% to 95% 5% to 95%

Dimensions 19" x 11" x 32" 19" x 11" x 32"

Weight 15Kg, 30lbs 15Kg, 30lbs



Documents

Professor Z. GHASSEMLOOY Associate Dean for Research Optical Communications Research Group, School of Computing, Engineering and Information Sciences The