RF via Fiber-2.pdf

7/27/2019 RF via Fiber-2.pdf

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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!

Documents

RF via Fiber-2.pdf