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Radio Photonics: Radio at Optical Frequencies
Richard Schatz, Urban Westergren, Qin Wang, Marek Chacinski, Pierre-Yves Fonjallaz...Kista Photonic Research Center-Royal Institute of Technology
Kista-Stockholm, Sweden
50 GHz 200 THz50 GHz
Optical CarrierRadio Carrier
Optical Carrier
200 THz
Part1: Radio over Fiber
Optical transmitter
Optical detector
Part2: Advanced modulation formats
Use modern radio modulation techniques
directly at optical frequencies
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Why Radio over Fiber?
+larger bandwidth
+lower weight
+lower cost
+no electromagnetical interference
Transmission: Optical fibers have significantly lower loss than
coaxial cable or microwave waveguides (0.2 dB/km instead of
1000 dB/km)
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Example: Fiberoptic Transceiver
Packaged reflective electroabsorption
transceiver for Wifi 5.6 GHz developed by
UCL, KTH and Optillion withinGANDALF project presented at ECOC
2005
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SOA EAT
input
output
HRAR
Antenna
SOA EAT
input
output
HRAR
Antenna
Amplified reflective transceiver for 60 GHz RF-signals(integrated electroabsorption transceiver and semiconductor optical amplifier)
outputARHR outputARHR
DFB TW-EAMDFB TW-EAM
Optical transmitter for (up to) 100 GHz RF signals(integrated DFB laser and travelling wave modulator)
Microwave signal
Components for Radio over Fiber
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M-Z
Modulator
Subcarrier
@ GHz
Mixer
Laser
FBG
FBG
IP data
Other signal,
e.g., DVBT
Other signal,
e.g., DVBT
IP data
Residual lower
sideband is
filtered away byreceiver filter
B
-50
-40
-30
-20
-10
0
1549.5 1550 1550.5 1551
Upper sideband
filtered out anddirectly detected
with low speed
PIN detector
Signal on fiber with IP
data in baseband and
DVBT on subcarrier
Dispersion tolerant since onlyone sideband is used
400km Transmission of 12.5 Gbit/s
Baseband and DVBT on 45 GHz Subcarrier
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Radio Photonics: Radio at Optical Frequencies
50 GHz200 THz50 GHz
Optical CarrierRadio Carrier
Optical Carrier
200 THz
Part 1: Radio over Fiber
Optical transmitter
Optical detector
Part 2: Advanced modulation formats
Use modern radio modulation techniquesdirectly at optical frequencies
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Source:Great Wall Broadband Network
> 50 km, 10-40 Gbit/s
DFB with Integrated
or External Modulator
> 5 km, 1-10 Gbit/s
Directly Modulated
DFB or DBR Laser
< 5 km , 0.1-1 Gbit/s
Directly Modulated
VCSEL
Network Structure
P2P filesharing: 35% of internet traffic and increasing
Youtube: 10% of internet traffic (despite max 350 kbit/s)Next step 100 Gbit/s!
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100 Gbit Travelling Wave
Electroabsorption Modulators
80 Gb/s
100GHz bandwidth
Eye-diagram at 80Gb/sThese TWEAMs are expected to be fast
enough for 100Gb/s (e.g. 100GbE).
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Integrated DFB-TWEAM used as a
50 Gb/s transceiver
0 km
7.2 km
DFB TW-EAMDFB TW-EAM DFBTW-EAM DFB-TWEAM7.2 km Fiber
50 Gb/s 50 Gb/s
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Fiber Dispersion
Different wavelength components travel with different velocity
Dispersive fiber
Distance 1/(Bitrate)2
10 Gbit/s: 65 km40 Gbit/s: 4 km
100 Gbit/s: 650 m!
Adaptive dispersion
compensation needed butstill difficult to reach e.g. 65
km with 100 Gbit/s!
The solution?
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Radio evolution vs Photonic Evolution
1888
Spark gap
Transmitter
On-Off
keying
1906First radio
broadcast of
voice and
music
AM
modulation
1915
SSB
modul-
ation
1903First arc
transmitter
with
continuos
radio waves
On-Off
keying
1933
FM
modul-
ation.
1914First
coherent
radio
transmitter
AM
modulation.
1961
FM stereo
Broad-
casting
Subcarrier
FM
modulation.
1918
Super-
hetero-
dyne
receiver
1962
First pulsed
semiconductor
laser
1970
First CW
semiconductor
laser
1974
First DFB
singlemode
laser
1985-1989
Research on
coherent
optical
receivers
1987
First Erbium-
doped Fiber
Amplifier
Today fiber-optic systems for telecom still utilizes simple on-off
keying and direct detection (Morse code and crystal receiver)
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1998
DVBT
OFDM
with QAM
1991
GSM
GMSK
Gaussian
Minimum
Shift
Keying
1995
DVBS
QPSK
Quadrature
phase shift
keying
2001
UMTS (3G)
W-CDMA
1994
GPS
CDMA
Code
Division
Multiple
Access
1998
ADSL
DMT
Discrete
multitone
1991
WiFi
OFDM or
CCK
Orthogonal
frequency-division
multiplexing
Next generation optical transmission systems will beadvanced digital radio systems at optical frequencies
Todays radio systems is the future for photonics
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Why advanced modulation formats
Better tolerance to fiber dispersion
More wavelength channels per fiber (or higher bitrate for
same channel grid)
Lower bandwidth demands of electronics and photonics
Higher spectral efficiency!
( lower modulation bandwidth for same bitrate)
DQPSK, QPSK, QAM, OFDM, SCM, SSB...
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Optical Subcarrier System for 100GET
Compare with ADSL modem for high speed data over telephone line
High demands on linearity of modulator and detector Integrated optical components needed for low cost
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Optical QPSK system with Polarization Multiplex
Complex integratedintegrated
optical transmitters &receivers will be needed
for low cost!
(one channel in a WDM system)
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THE END
Thank you!