Gee-Kung Chang

Byers Eminent Scholar Chair ProfessorSchool of Electrical and Computer Engineering

Georgia Institute of TechnologyAtlanta, GA 30332-0250

OFC 2008 WorkshopSan Diego, California

February 25, 2008

Convergence of Optical and Wireless Convergence of Optical and Wireless Access NetworksAccess Networks

2

Outline

• Convergence of Broadband Networking • Integrated Optical Wireless Access Networks• Optical Wireless Signal Generation

– Up-conversion of optical wireless signal– Multi-band wireless signals

• Optical Wireless Network Architecture– Dual Services: Wired and Wireless – Wavelength Reuse for Full-duplex Connection

• Technology Challenges• Conclusions

3

Broadband Networking Trends

Meet the needs of future end-to-end, dynamic and flexible Internet services

Convergence of Voice, Data, Video and Interactive Multimedia ServicesConvergence of Voice, Data, Video and Interactive Multimedia Services

Convergence of Wireless and Wired NetworksConvergence of Wireless and Wired Networks

Convergence of High Speed DWDM Metro and WAN NetworksConvergence of High Speed DWDM Metro and WAN Networks

4

Opportunities of using 60GHz mm-Wave for Wireless Services

56 57 58 59 60 61 62 63 64 65 66 56 57 58 59 60 61 62 63 64 65 66 GHzGHz

ProhibitedProhibitedUnlicensedUnlicensed

Wireless LANWireless LAN

Wireless LANWireless LAN

II SS MM

UnlicensedUnlicensedPt.Pt.--toto--Pt.Pt.

Space and fixed & m

obile apps.Space and fixed &

mobile apps.

Japan

E.U.

U.S.

There is a license free band near There is a license free band near 60GHz. There is up to 8 GHz antenna 60GHz. There is up to 8 GHz antenna resonant bandwidth available for resonant bandwidth available for wireless communicationswireless communications. .

It can provide super broadband It can provide super broadband wireless data links at > 1Gb/s.wireless data links at > 1Gb/s.

5

Convergence of Broadband Access NetworksW

irelin

e

Time

Next GenerationOptical WirelessAccess Networks

Capa

city Data Rate

Mobility

ADSL/CableADSL/Cable

APONAPON

BPONBPONEPONEPON

GPONGPON

<10Mb/s

155Mb/s

622Mb/s

1.25Gb/s

2.5Gb/s

TDMTDM--PONPON WDM PONWDM WDM PONPON

CopperCopper

FiberFiber

1Gb/s --- 10 Gb/s10Mb/s --- 100Mb/s

WiFi2.4GHz (802.11b/g)

5GHz (802.11a)

WiMAX2.5, 3.5GHz10, 26GHz

MVDS40GHz

MBS60GHz

MMDS2-3GHz

LMDS26-29GHz

Frequency

Wire

less

10G TDM10G TDM--PONPON

UWB3-10GHz

Millimeter Region

6

Optical Wireless Network Applications

Emerging applications requiring super broadband optical-wireless access:

• HDTV distribution

• Interactive multimedia games

• High-speed wireless (>1Gb/s) data access

• High Mobility Communications - Base Station handoff- vehicle speed, bandwidth, and packet length

7

PassiveOpticalnetwork

PassiveOpticalnetwork

Optical networking, transmission and integration

with WDM PON

Optical mm-wave generation, modulation

and up-conversion

RF Data/optical

interface

RF Data/optical

interface

Central Office Remote Node

Data/Video Source Center

Optical Metro

Network

Wireless Network

Optical/RF Data Interface

Optical/RF Data Interface

Base Station

Radio air interfaceBidirectional transmission

Wired and wireless service delivery

UsersUsers

• Bandwidth>1 Gb/s for both directions

• MobilityRF wireless for roaming connection

• CoverageOptical fiber links for long distance

• Multi-channel CapacitySeamless integration with WDM PONAll-optical methods for architecture design

Wireless over Optical Transport Technologies

8

2.5Gbit/s

20GHz

DFB-LDMOD

PD

0 20 40 60Frequency (GHz)

Pow

er (d

Bm)

RF at 40GHzBaseband

There are two components of electrical signals after all-optical up-conversion:

one part occupies the baseband, the other occupies high-frequency band near 40 to 60GHz.

Dual Stage Modulation using Optical carrier suppression

DC: Vπ

Spectrum of Optical Wireless Signals

Optical Wireless

9

Up-Conversion Based on External Modulation

DC Bias: 0.5

2.5 Gb/s 40GHz

1 5 5 4 .0 1 5 5 4 .5 1 5 5 5 .0 1 5 5 5 .5-7 0-6 0-5 0-4 0-3 0-2 0-1 0

01 0

4 0 G H z 4 0 G H z

Opt

ical

pow

er (d

Bm

)

W a v e le n g th (n m )

B-T-B

2km

Vπ

40GHz

Dual-arm MZM

2π

Shift2.5 Gb/s

DC: 0.5Vπ1554.0 1554.5 1555.0 1555.5

-70-60-50-40-30-20-10

010 40GHz

Opt

ical

pow

er (d

Bm)

W avelength (nm)

B-T-B

40km

20GHz

DC: Dual –arm MZM

Shift

Vπ

π

1554.0 1554.5 1555.0 1555.5-60

-50

-40

-30

-20

-10

0

1040GHz

Opt

ical

pow

er (d

Bm)

Wavelength (nm)

40km

B-T-B

DSB

SSB

OCS 2.5 Gb/s

MZM1DFB LD

MZM1DFB LD

MZM2

MZM1DFB LD

DSB: Double sideband; SSB: Single sideband; OCS: Optical carrier suppression

10

32-Channel DWDM ROF Transmissionbased on OCS external modulation

Dual–arm MZM

2.5 Gb/sDFB LD 1

DFB LD 32AWG

40km SMF 20GHz40km SMF

(i) (ii)

1 5 3 5 1 5 4 0 1 5 4 5 1 5 5 0 1 5 5 5 1 5 6 0- 7 0

- 6 0

- 5 0

- 4 0

- 3 0

- 2 0

- 1 0

0

Rel

ativ

e op

tical

pow

er

W a v e le n g th ( n m ) 1 5 3 6 1 5 4 4 1 5 5 2 1 5 6 0- 7 0

- 6 0

- 5 0

- 4 0

- 3 0

- 2 0

- 1 0

Rel

ativ

e op

tical

pow

er

W a v e le n g th ( n m )

EDFA Vπ

ShiftπTOF2

EA

MUX

Mixer

1:4

10GHz Clock

50GHz PIN

BERT

Demux

1ns/div

100ps/div

Core or Metro network Central OfficeRemote Node

Base Station

11

Transmission of 32-Channel ROF Signals

1 5 3 5 1 5 4 0 1 5 4 5 1 5 5 0 1 5 5 5 1 5 6 0-4 4

-4 2

-4 0

-3 8

-3 6

-3 4 B -T -B A fte r 4 0 k m

Rec

eive

r sen

sitiv

ity (d

Bm)

W a v e le n g th (n m )Power penalty is less 2dB

for all channels.

32 DWDM ROF channels

J. Yu, Z. Jia and G. K. Chang, ECOC 2005, Post Deadline, 2005, Th 4.5.4.

12

Key Technologies for RoF Signal Generation

Multiple Bands RF Signal Multiple Bands RF Signal Generation: Generation:

Microwave and MillimeterMicrowave and Millimeter--WaveWave

13

Multiple RF Signal Generation

DC: Vpi

18GHz 6GHz

750Mb/s750Mb/s

36GHz

Data 1

LPF

IL

TOF

0.3nm

1nm

Received power

12GHz

Data 2

LPF

EA20km SMF-28

LN-MODDFB-LD

Coupler

Mixer

0.3nm

1nm

Data 1 Data 2

EDFA

O/E

1539 1540 1541-80

-60

-40

-20

0

Rel

ativ

e O

ptic

al P

ower

(dB

m)

Wavelength (nm)1539 1540 1541

-80

-60

-40

-20

0

Rel

ativ

e O

ptic

al P

ower

(dBm

)

Wavelength (nm)

1539 1540 1541-80

-60

-40

-20

0

Rel

ativ

e O

ptic

al P

ower

(dBm

)(i)

(iii)

(ii)Microwave

mm-wave

14

Optical Wireless Access Network Architecture Design

FullFull--Duplex Operation Based on Duplex Operation Based on Wavelength Reuse for UpstreamWavelength Reuse for Upstream

15

Full-Duplex Colorless Transmission for Uplink

At CS, Phase modulation and the subsequent interleaver for optical mm-wave generation.At BS, FBG is used to reflect the optical carrier while pass the downlink mm-wave signal.At BS, SOA performs the function of both amplification and modulation.

OC

ƒmm-wave

CW

Downlink

DownlinkData

PM SMF

Receiver

Uplink

ƒmm-wave

RFMZM

Uplink

DataSOA

PIN Duplexer

Antenna

Mixer

EA

Uplink

PSƒcarrier

Interleaver

FBG

TD

CS BS

16

• Various wireless services can share common fiber infrastructure.• A testbed setup consisting of four wireless standards were

simultaneously transmitted to stress the ROF distribution network.• 802.11g, WCDMA, GSM and PHS were combined electrically and

distributed via 300m of MMF ROF system.

Multi-Standards Wireless Transmission

17

Wireless over fiber systems using ROF technologies operating in the 0.8-2.5GHz band have been demonstrated

• Moving from RF and microwave to mm-wave carriers for high bandwidth services

• Moving from point-to-point links to point to multiple points network architectures

• Moving from low mobility wireless over fiber systems to high speed moving trains and planes

- Howl’s Moving Castle?

• Facilitating new system architecture and new applications

What’s Next?

18

Future Considerations and Challenges (1)

• Optical technology– Improve efficiency, simplicity and stability of signal

generation and up-conversion for the optical wireless systems;

– Increase the wavelength utilization efficiency in full-duplex operation when integration with WDM PON;

– Mitigating the optical mm-wave signals transmission impairment, particularly for the dispersion tolerance.

19

Future Considerations and Challenges (2)

• Electrical components and interfaces– Low profile, high gain, high frequency antenna and mixer design;– 40GHz, 60GHz and beyond optical millimeter carrier wave characteristics;– Improvement for wireless signals synchronization, interference and

stability.

• O/E and E/O Interfaces– Requirement for power, noise, bandwidth and coding methods;– Standardization issues.

mm-wave bands

20

Conclusions

• Optical wireless signal generation and up-conversion techniques play key roles in realizing RoF network.

• A novel architecture is developed for bidirectional wireless and optical access network integrated with WDM-PON with wavelength reuse in base stations.– Demo of uncompressed HDTV over both wireline and wireless links

• Technology challenges are ahead of us:

– low-cost optical and RF components,

– optical wireless system interface,

– optical wireless protocols, and standardization.