Convergence of Optical and Wireless
Access Networks
Gee-Kung Chang
Byers Eminent Scholar Chair Professor
School of Electrical and Computer Engineering
Georgia Institute of Technology
Atlanta, GA 30332-0250
OFC 2008 Workshop
San Diego, California
February 25, 2008
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
2
Broadband Networking Trends
Meet the needs of future end-to-end, dynamic and
flexible Internet services
Convergence
ConvergenceofofVoice,
Voice,Data,
Data,Video
Videoand
andInteractive
InteractiveMultimedia
MultimediaServices
Services
Convergence
ConvergenceofofHigh
HighSpeed
SpeedDWDM
DWDMMetro
Metroand
andWAN
WANNetworks
Networks
Convergence
ConvergenceofofWireless
Wirelessand
andWired
WiredNetworks
Networks
3
Opportunities of using 60GHz mm-Wave
for Wireless Services
Wireless LAN
Unlicensed
I
S
M
U.S.
56
57
58
59
60
61
62
63
64
65
66
Space and fixed & mobile apps.
Unlicensed
Pt.Pt.-toto-Pt.
E.U.
Prohibited
Wireless LAN
Japan
GHz
There is a license free band near
60GHz. There is up to 8 GHz antenna
resonant bandwidth available for
wireless communications.
It can provide super broadband
wireless data links at > 1Gb/s.
4
Convergence of Broadband Access Networks
WiMAX
2.5, 3.5GHz
10, 26GHz
MVDS MBS
40GHz 60GHz
UWB
3-10GHz
MMDS
LMDS
26-29GHz
2-3GHz
Next Generation
Optical Wireless
Access Networks
Millimeter Region
Wireline
TDM-PON
GPON
2.5Gb/s
Copper
ADSL/
Cable
<10Mb/s
BPON
WDM
PON
te
Ra
ta
Da
Frequency
cit
y
WiFi
2.4GHz (802.11b/g)
5GHz (802.11a)
1Gb/s --- 10 Gb/s
Ca
pa
Wireless
10Mb/s --- 100Mb/s
Mobility
EPON
1.25Gb/s
622Mb/s
APON
155Mb/s
10G TDMTDM-PON
Fiber
Time
5
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
6
Wireless over Optical
Transport Technologies
Data/Video
Source
Center
RF
RFData/
Data/
optical
optical
interface
interface
Optical
Metro
Network
Central Office
Wireless
Network
•
Optical mm-wave
generation, modulation
and up-conversion
¾
RF wireless for roaming
connection
•
Radio air interface
Bidirectional transmission
Wired and wireless service delivery
Coverage
¾
•
Users
Users
Base Station
Optical networking,
transmission and integration
with WDM PON
>1 Gb/s for both directions
Mobility
Optical/
Optical/
RF
RFData
Data
Interface
Interface
Remote Node
Bandwidth
¾
•
Passive
Passive
Optical
Optical
network
network
Optical fiber links for long distance
Multi-channel Capacity
¾
Seamless integration with WDM PON
¾
All-optical methods for architecture
design
7
Spectrum of Optical Wireless Signals
2.5Gbit/s DC: V
π
Optical
DFB-LD
Baseband
MOD
Wireless
PD
RF at 40GHz
Dual Stage Modulation using
Optical carrier suppression
There are two components of
electrical signals after all-optical
up-conversion:
Power (dBm)
20GHz
one part occupies the baseband,
the other occupies high-frequency
band near 40 to 60GHz.
0
20
40
Frequency (GHz)
60
8
Up-Conversion Based on External Modulation
SSB
DFB LD
OCS
DFB LD
π
2.5 Gb/s
2
Shift
Dual-arm MZM
MZM1
π
Shift
0
40G H z
-1 0
-3 0
-4 0
2km
-5 0
-6 0
10
π
B-T-B
40G H z
-2 0
-7 0
1 5 5 4 .0
40GHz
DC: 0.5V
MZM1
2.5 Gb/s
Optical power (dBm)
MZM2
DC Bias: 0.5 V π
Optical power (dBm)
DFB LD
MZM1
10
40GHz
1 5 5 4 .5
1 5 5 5 .0
W a v e le n g th ( n m )
1 5 5 5 .5
40G H z
B-T-B
0
-10
-20
-30
-40
40km
-50
-60
-70
1554.0
1554.5
1555.0
1555.5
W avelength (nm )
B-T-B
10
20GHz
DC: V π
Dual –arm MZM
Optical power (dBm)
DSB
2.5 Gb/s
0
40GHz
-10
-20
-30
40km
-40
-50
-60
1554.0
1554.5
1555.0
1555.5
Wavelength (nm)
DSB: Double sideband; SSB: Single sideband; OCS: Optical carrier suppression
9
32-Channel DWDM ROF Transmission
based on OCS external modulation
1ns/div
Base Station
Core or Metro network
DFB LD 1
2.5 Gb/s
Central Office
π
Remote Node
Shift
40km SMF
10GHz
Clock
20GHz
40km SMF
MUX 1:4
TOF2
BERT
EDFA
DFB LD 32
50GHz
PIN
Dual–arm MZM
-2 0
-3 0
-4 0
-5 0
-6 0
1535
1540 1545 1550 1555
W a v e le n g t h ( n m )
100ps/div
-1 0
(i)
-1 0
Mixer
Demux
1560
Relative optical power
Relative optical power
Vπ
AWG
0
-7 0
EA
-2 0
(ii)
-3 0
-4 0
-5 0
-6 0
-7 0
1536
1544
1552
W a v e le n g t h ( n m )
1560
10
Receiver sensitivity (dBm)
Transmission of 32-Channel ROF Signals
-3 4
-3 6
B -T -B
A fte r 4 0 k m
-3 8
-4 0
-4 2
-4 4
32 DWDM ROF channels
1535 1540 1545 1550 1555 1560
W a v e le n g th ( n m )
Power penalty is less 2dB
for all channels.
J. Yu, Z. Jia and G. K. Chang, ECOC 2005, Post Deadline, 2005, Th 4.5.4.
11
Key Technologies for RoF Signal Generation
Multiple Bands RF Signal
Generation:
Microwave and Millimeter-Wave
12
Data 1
Data 2
750Mb/s 750Mb/s
18GHz
6GHz
Mixer
Coupler
-40
-60
Wavelength (nm)
-40
-60
-80
1539
1540
1541
1nm
EA
O/E
12GHz
Received power
TOF
(i)
1540
Microwave
-20
LPF
1nm
IL
-20
-80
1539
(ii)
0.3nm
LN-MOD
DC: Vpi
0
0
20km
SMF-28
1541
Relative Optical Power (dBm)
Relative Optical Power (dBm)
DFB-LD
Relative Optical Power (dBm)
Multiple RF Signal Generation
0
-20
Data 2
0.3nm EDFA
(iii)
36GHz
-40
-60
-80
1539
LPF
1540
Wavelength (nm)
1541
mm-wave
Data 1
13
Optical Wireless Access Network
Architecture Design
Full-Duplex Operation Based on
Wavelength Reuse for Upstream
14
Full-Duplex Colorless Transmission for Uplink
ƒmm-wave
CS
ƒmm-wave
BS
Downlink
Data
Antenna
Downlink
RF
CW
MZM
OC
PM
Interleaver
Uplink
Duplexer
PIN
SMF
FBG
ƒcarrier
Uplink
SOA
EA
Mixer
TD
PS
Data
Uplink
Receiver
%
%
%
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.
15
Multi-Standards Wireless Transmission
•
•
•
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.
16
What’s Next?
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
17
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 fullduplex operation when integration with WDM PON;
– Mitigating the optical mm-wave signals
transmission impairment, particularly for the
dispersion tolerance.
18
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.
mm-wave
bands
•
O/E and E/O Interfaces
– Requirement for power, noise, bandwidth and coding methods;
– Standardization issues.
19
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.
20