professor z. ghassemlooy associate dean for research optical communications research group, school...
TRANSCRIPT
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.
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33
Effects Options Remarks
Photon absorption
Increase transmit
optical power
Effect not significant
FSO Challenges – Rain & Snow
= 0.5 – 3 mm
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• 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
35 3rd ECAI – Romania, 3-5 July 2009
).()()()()( amam
Absorption coefficient Scattering coefficient
36
Effects Options Remarks
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
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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
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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
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Background radiation LOS requirement Laser safety Turbulence (scintillation)
FSO Challenges - Others
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Effects Options Remarks
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
3rd ECAI – Romania, 3-5 July 2009
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
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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.
45 3rd ECAI – Romania, 3-5 July 2009
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
46 3rd ECAI – Romania, 3-5 July 2009
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)
47 3rd ECAI – Romania, 3-5 July 2009
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
3rd ECAI – Romania, 3-5 July 2009
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
50 3rd ECAI – Romania, 3-5 July 2009
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
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SIM - Spatial Diversity
Single-input-multiple-output Multiple-input-multiple-output (MIMO)
52 3rd ECAI – Romania, 3-5 July 2009
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:
53 3rd ECAI – Romania, 3-5 July 2009
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.
54 3rd ECAI – Romania, 3-5 July 2009
Eric Korevaar et. alA typical reduction in intensity fluctuation with spatial diversity
One detector
Two detectors
Three detectors
Subcarrier Modulation - Spatial Diversity
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Free Space Optics Characteristics Challenges Turbulence
- Subcarrier intensity multiplexing- Diversity schemes
Results and discussions Final remarks
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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
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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
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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
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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
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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
61 3rd ECAI – Romania, 3-5 July 2009
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
64 3rd ECAI – Romania, 3-5 July 2009
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.
65 3rd ECAI – Romania, 3-5 July 2009
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
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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
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-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
3rd ECAI – Romania, 3-5 July 2009
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
3rd ECAI – Romania, 3-5 July 2009
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
3rd ECAI – Romania, 3-5 July 2009
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•
3rd ECAI – Romania, 3-5 July 2009
72
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
3rd ECAI – Romania, 3-5 July 2009
3rd ECAI – Romania, 3-5 July 2009
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
Iran 2008
74
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
Wall/Tower, Roof,Non-penetrating
Iran 2008
75
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
Mounting Options Wall/Tower, Roof,Non-penetrating
Wall/Tower, Roof,Non-penetrating
Iran 2008
76
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-penetratingWall/Tower, Roof,
Non-penetratingWall/Tower, Roof,
Non-penetrating
Iran 2008
77
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
4 x 1.54 Mbps or4 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-penetratingWall/Tower, Roof,
Non-penetratingWall/Tower, Roof,
Non-penetratingWall/Tower, Roof,
Non-penetrating
Iran 2008
78
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
Mounting Options Wall/Tower, Roof,Non-penetrating
Wall/Tower, Roof,Non-penetrating
Wall/Tower, Roof,Non-penetrating
Iran 2008
79
Model WBXT T1/E1 WBXT T4/E4
Data Rate 1 x 1.54 Mbps or1 x 2.048 Mbps
4 x 1.54 Mbps or4 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
Mounting Options Wall/Tower, Roof,Non-penetrating
Wall/Tower, Roof,Non-penetrating