Converging Broadband Access Networks: Enabling Technologies

Gee-Kung Chang

Byers Eminent Scholar Chair Professor School of Electrical and Computer Engineering Georgia Institute of Technology, Atlanta, GA 30332-0250

ICCSC, May 27, 2008 Shanghai, China Outline

‰ Convergence of Broadband Optical and Wireless Networks

‰ Integrated Optical-Wireless Access Systems

‰ Optical-Wireless Signal Generation and Transmission ‰ Based on OCS Based Intensity Modulation ‰ Based on Phase Modulation along with Optical Filtering ‰ Simultaneous Multi-band Communication ‰ Based on Frequency Quadrupling ‰ Wireless over Optical Access Network Architecture

‰ Wireless over Optical Applications

‰ Research Challenges

‰ Conclusions

2 Broadband Networking Trends

Emerging Applications • Multi-Channel HDTV Distribution Services • Interactive Multimedia Gaming and Conference • High-Speed (>1Gb/s) and High Mobility Wireless Access Users

≥100Gb/s Internet Access Internet Access

First First Metro Long Metro Last Last Meters Miles WAN Haul WAN Miles Meters

>1 Gb/s ≥10Gb/s ≥100Gb/s ≥10Gb/s >1 Gb/s Enabling Technologies System Optical Wireless WDM PON WDM PON Optical Wireless 100Gb/s Ethernet TDM PON TDM PON

PON: Passive Optical Networks such as FIOS offered by Verizon

3 Broadband Networking Research Issues Enabling Technologies

WDM PON 100-Gb/s Ethernet Optical Wireless • 10-Gb/s Colorless Transmitter &Receiver • Optical mm-wave generation • Spectral Efficiency • OFDM modulation • Protection & Restoration • Advanced DQPSK, • Multi-Cast Video Delivery • Multi-band μWave and mm- Polarization-Keying, Wave signal generation OFDM Modulation • Centralized Management • Multi-Gb/s wireless data • ROADM Nodes TDM PON • Wavelength reuse With Flexible WSS •10Gb/s Clock Recovery • Seamless integration with • Burst mode Receiver WDM PON Access • Efficient Transport • Centralized Transmitter protocol & Control • Deliver wired & wireless • MAC Protocol services in a single platform • Cascadability • Dynamic Power Mgmt

4 60-GHz mm-Wave for Wireless Services HD wireless and 60-GHz Bluetooth are coming Space and fixed & mobile apps. mobile & fixed and Space Wireless LAN Prohibited Japan

Unlicensed E.U. Pt.-to-Pt. Wireless LAN

Unlicensed U.S. I S M

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

A license free band near 60GHz has up to 8 GHz antenna resonant bandwidth available for wireless communications.

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

5 Convergence of Broadband Access Networks

1Mb/s --- 100Mb/s 274 Mb/s 1Gb/s --- 10Gb/s 10-Km 200-Km 200-Km over fiber over air 10-m over air Next Generation Integrated WiFi WiMAX DoD millimeter-waves 2.4GHz (802.11b/g) 2.5, 3.5GHz Ku-band Optical Wireless 5GHz (802.11a) 10, 26GHz 11-18 GHz MVDS MBS Systems 40GHz 60GHz 70-90GHz Wireless MMDS LMDS 2-3GHz 26-29GHz Frequency

TDM-PON WDM GPON 2.5Gb/s PON EPON Mobility BPON 1.25Gb/s Copper 622Mb/s

Wireline ADSL/ APON Optical Cable 155Mb/s <10Mb/s Time

MMDS: multichannel multipoint distribution service, LDMS: local multi-point distribution service MVDS: microwave video distribution system, MBS: mobile broadband system

6 Wireless over Fiber

CP: customer premise Mm-wave

CP1 Central Optical Fiber Base Office Networks Station CPn Data

Convergence of Optical and Wireless Access Networks

„ Bandwidth „ Coverage

9 >1 Gb/s for both directions 9 Optical fiber links for long distance „ Mobility „ Multi-channel Capacity 9 DWDM for architecture design 9 RF wireless for roaming connection

7 Key Technologies for Optical Wireless Systems

Data/Video Source Center RF Data/ DWDM Optical/ optical Optical RF Data Optical interface network Interface Users Metro Network Central Office Metro Networks Base Stations

Wireless Optical mm-wave Optical networking, Radio air interface Network generation transmission and integration Bidirectional transmission

„ Optical mm-Wave Generation „ Based on nonlinear effect in HNL-DSF fiber and EAM modulator „ Based on external intensity and phase modulation „ SCM + Interleaving „ Bidirectional Optical Connection „ Based on different modulation formats „ SCM + Interleaving

8 Optical Wireless Access Network Architecture

WDM Signals From Metro/Access Networks All-optical Up-converter Central Office λ1 ƒbaseband ƒmm-wave λN

ƒ ƒ baseband mm-wave Feeder SMF Optical-wireless Networks WDM PON Remote Node λN Antenna λ1

ƒ EA mm-wave PD

Filter Home ƒbaseband

SOHO Shopping Mall, Conference Center or Airport

9 Super Broadband Optical Wireless Applications

Emerging applications requiring super broadband optical-wireless access:

• HD wireless distribution

• Interactive multimedia events and games

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

• High mobility communications - base station handoff - vehicle speed, bandwidth, and packet length

10 Spectrum of Optical Wireless Signals

2.5Gbit/s DC: Vπ Optical Wireless

MOD Baseband DFB-LD PD RF at 40GHz 20GHz Dual Stage Modulation using Optical carrier suppression

There are two components of (dBm) Power electrical signals after all-optical up-conversion:

one part occupies the baseband, 0 20 40 60 the other occupies high-frequency Frequency (GHz) band near 40 to 60GHz.

11 Key Technologies for mm-wave Generation

External Intensity Modulation with Optical Carrier Suppression

12 Optical Wireless Signal Up-Conversion Based on External Modulation

10 2.5 Gb/s 40GHz 0 B-T-B 40GHz 40GHz DSB -10 -20

-30 -40 -50 2km MZM1 MZM2 Optical power (dBm) -60 -70 DFB LD 1554.0 1554.5 1555.0 1555.5 DC Bias: 0.5Vπ Wavelength (nm)

π Shift 2 40GHz 10 40GHz SSB 2.5 Gb/s 0 B-T-B -10 -20

-30 -40 -50

Optical power Optical(dBm) power 40km MZM1 DC: 0.5V -60 DFB LD π -70 1554.0 1554.5 1555.0 1555.5 Dual-arm MZM Wavelength (nm)

π Shift 10 B-T-B 40GHz OCS 2.5 Gb/s 20GHz 0 -10 -20 -30 -40 40km MZM1 DC: V Optical power (dBm) -50 DFB LD π -60 Dual –arm MZM 1554.0 1554.5 1555.0 1555.5 Wavelength (nm)

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

13 32-Channel DWDM ROF Transmission: based on OCS Modulation

1ns/div Base Station

Core or Metro network Central Office 10GHz Clock DFB LD 1 Remote Node 2.5 Gb/s π Shift 40km SMF MUX 1:4 40km SMF 20GHz TOF2

BERT EA Mixer EDFA Vπ 50GHz Dual–arm MZM PIN 100ps/div DFB LD 32 Demux AWG 0 -10 (i) (ii) -10 -20 -20 -30 -30 -40 -40 -50 -50

-60 -60 Relative optical power

-70 Relative optical power 1535 1540 1545 1550 1555 1560 -70 W avelength (nm) 1536 1544 1552 1560 Waveleng th ( nm) J. Yu, Z. Jia, G.K. Chang, Post deadline paper, ECOC 2005, Th4.5.4

14 Transmission of 32-ch x 2.5Gb/s Optical Wireless Signals

-34 B-T-B -36 After 40km

-38

-40

-42 32 DWDM ROF channels Receiver sensitivity (dBm) Receiver sensitivity -44 1535 1540 1545 1550 1555 1560 W avelength (nm ) 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.

15 Key Technologies for mm-wave Generation

External Phase Modulation along with Optical Filtering

16 Phase Modulation Based mm-wave Generation

10 0 -1 0 Interleaver -2 0

2.5Gbit/s Signal DFB LD 1 -3 0 -4 0 -5 0 40km SMF power Optical (dBm -6 0 20GHz 1554 1556 1558 1560 10GHz Wavelength (nm) IM (ii) SMF 60GHz MUX 1:4 EDFA PM TOF PIN DFB LD 8 Mixer AWG (i) (iii) 10 -1 0 EA 0 -2 0

-1 0 -3 0 -2 0 BERT

-4 0 -3 0 -5 0 -4 0

Optical power (dBm) power Optical -6 0 Optical power (dBm) power Optical -5 0 -6 0 -7 0 1554 1556 1558 1560 1554 1556 1558 1560 W avelength (nm ) W avelength (nm )

17 Comparison of Up-Conversion Methods

Schemes Advantages Disadvantages Cross-phase- Supporting WDM signals; Polarization sensitive; modulation THz mixing bandwidth; Need to optimize the input (XPM) in HNL- power and CSR (Carrier DSF Fiber Suppression Ratio) Direct Modulation The simplest configuration. Limited modulation bandwidth of the laser. External Intensity Easy to integrate with WDM Need a control electrical Modulation PON; High receiver sensitivity circuit to optimize the DC Low spectral occupancy bias. External Phase Supporting WDM signals; Need an optical notch filter. Modulation Simple and stable scheme; High receiver sensitivity.

External modulation scheme shows practical advantages in terms of the low cost, simplicity of system configuration, and performance over long-distance transmission.

Z. Jia, J. Yu, G. Ellinas, G.-K. Chang, J. Lightwav. Technol., Vol. 25, No. 11, 2007. 18 Key Technologies for mm-wave Generation

Multiple Bands Microwave and mm-Wave Generation

19 Multiband RF Signal Generation

Data 1 Data 2 0 (ii) 750Mb/s 750Mb/s -20 Microwave 18GHz 6GHz -40 -60

Mixer (dBm) Optical Power Relative -80 1539 1540 1541 1nm Coupler EA 20km O/E SMF-28 12GHz 0.3nm Received power DFB-LD LN-MOD TOF LPF 1nm DC: Vpi IL Data 2 0 (i) 0.3nm EDFA -20 0

-20 (iii) -40 -40 36GHz -60 -60 mm-wave

Relative Optical Power (dBm) Power Optical Relative LPF -80 1539 1540 1541 (dBm) Power Optical Relative -80 1539 1540 1541 Wavelength (nm) Wavelength (nm) Data 1

20 Optical Wireless Access Network Architecture

Full-Duplex Optical Wireless System Operation with Wavelength Reuse for Upstream Link

21 Full-Duplex Colorless Transmission for Uplink

Central Station ƒ ƒ mm-wave mm-wave Base Station (CS) Downlink (BS) Data Antenna Downlink RF data MZM

CW OC PIN Duplexer PM SMF DFB LD FBG EA PS Uplink TD ƒcarrier Mixer Interleaver RSOA Data Uplink Uplink

Receiver data

% 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, RSOA performs the function of both amplification and modulation.

22 WDM-PON Compatible with Bi-direction ROF Access

OLT in Central Office Optical link BS Downstream WDM PON Data downstream signals RN Low-speed LO Antenna PIN PIN Ch 1 Wireless DFB IM EA SMF Duplexer link Cir CU TL AWG Bi-direction High-speed PIN Ch N DFB IM Cir LPF IL Downstream Upstream SOA+EAM data data WDM PON upstream signals

23 Dual-service Signals Generation and Delivery

Simultaneous Generation of Independent Optical and Wireless Signals in the same Access Network

24 Motivation Simultaneous delivery of wired and wireless services

‰ Currently, wired and wireless services are separately provided by two independent physical networks.

‰ Next-generation access networks are driving the needs for convergence of wired and wireless services. ‰ To offer end users greater choice, convenience and high-bandwidth services in a cost-efficient way

‰ Using integrated optical wireless systems to provide dual services. ‰ Simultaneous generation of wired and wireless services ‰ Increasing the capacity and bandwidth while keeping low cost

H. Bolcskei, A. J. Paulraj, K. V. S. Hari, R. U. Nabar, W. W. Lu, IEEE Commun. Mag.,, Jan. 2001.

25 Simultaneous Generation of Wired and Wireless Signals

‰ Simultaneous generation of wired and wireless services ‰ Low-cost and simple configuration are vital to successful deployment in real networks. ‰ Current solutions ‰ Using electroabsorption modulator (EAM): Limited by EAM nonlinearity, residual chirp and crosstalk. ‰ Using multiple Mach-Zehnder modulators (MZM): Need multiple laser sources, costly AWG, integrated or cascaded MZM.

T. Kamisaka, et al, IEEE Trans. Microwave Theory Tech., vol.49, no.10, Oct. 2001. M. Bakaul, et al, PTL, VOL. 18, NO. 21, Nov. 2006

26 Simultaneous Wired and Wireless Signal Generation

Wireless -10 2.5 Gb/s

10GHz -20

20 GHz BS -30

Mixer (dBm) Power Mux 1:4 -40 EA 60GHz PIN 1548.0 1548.5 1549.0 1549.5 CO SMF-28 Mixer Wavelength (nm) EDFA Wireless EA 10 20km 0 LN-MZM 3R DFB-LD Wired -10

EA -20

Interleaver 10GHz APD (dBm) Power 10 Gb/s -30 -40

0 Without Wired Signals 1548.0 1548.5 1549.0 1549.5 W/ Wired Signals Wired -10 Wavelength (nm)

-20

Baseband -30

Interference between wired and wireless -40

Signals (dBm) Powr -50 Signals can be mitigated by electrical BPF

-60

1548.0 1548.5 1549.0 1549.5 Wavelength (nm)

1 ⎡ ⎛ ⎛ π ⎞ ⎞ ⎤ ∝ 2 2 ⎢ 2 + zJzJkEV ⎜ ⎜ + VtB ⎟ + 1))((cos2)()( ⎟ ⎥ 0 4 0 0 0 ⎜ ⎜ V bias ⎟ ⎟ Baseband ⎣⎢ ⎝ ⎝ π ⎠ ⎠ ⎦⎥

⎛ π ⎞ ⎧ ⎛ − j ⎜ ())( + VtB ⎟ ⎞ ⎫ 2 ⎪ ⎜ V bias ⎟ ⎛ ω rf ⎞ ⎛ ω rf ⎞ ⎪ + ⎜ )()( + ezJzkJE ⎝ π ⎠ ⎟ sin ⎜ − π cDL 2 ⎟ + zJzJ ⎜ − π cDL 2 ⎟ cos)(3sin)()()( t − )(' ωωβωL 0 ⎨ 1 ⎜ 0 ⎟ ⎜ ⎟ 1 2 ⎜ ⎟ ⎬ []rf rfc ⎝ ω c ⎠ ⎝ ω c ⎠ ⎩⎪ ⎝ ⎠ ⎭⎪ 1st sidebands

Z. Jia, et al, PTL, VOL. 19, NO. 20, Oct. 2007 27 Simultaneous Delivery of Wired and Wireless Services Experimental Setup

50ps/div CO 2.5 Gb/s wireless 10GHz BS 20 GHz Mixer Mux 1:4

EA 60GHz PIN Mixer

100ps/div c EDFA Wireless b EA SMF-28 a d LN-MZM DFB-LD 3R Wired EA Interleaver 10GHz APD 10 Gb/s wired

0 0 0 -15 (c) (d) (a) -15 (b) -15

-15 -30 -30 -30

-30 -45 -45 -45 -45 Optical (dBm) Power Optical Power (dBm) Power Optical Optical Power (dBm) Power Optical -60 Optical Power (dBm) -60 -60 -60 1548.0 1548.5 1549.0 1549.5 1548.0 1548.5 1549.0 1549.5 1548.0 1548.5 1549.0 1549.5 1548.0 1548.5 1549.0 1549.5 Wavelength (nm) Z. Jia, et al., PTL Nov. 2007

28 Uncompressed Wired and Wireless HDTV Services by Integrated Optical Wireless Access Systems

HD/SD DVD Player TV1 25km A/D O/E SMF Down D/A All-Optical conversion CW Modulator Up-Conversion Down TV2 O/E conversion D/A

Uncompressed SDTV Signals (SMPTE 259M): 270 Mb/s Uncompressed HDTV Signals (SMPTE 292M): 1.485 Gb/s

29 Multi-band Wireless Transmission

‰ Various wireless services can share common fiber infrastructure. ‰ A testbed setup at ASTAR-I2R 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.

30 What’s Coming 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 higher bandwidth services

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

• Moving from low mobility wireless over fiber systems to high speed moving vehicles

• Facilitating new system integration and applications

31 Optical and Wireless System Convergence

Operator Operator Operator 1 2 n Different λ plans for individual operators

Protocol Independent Wireless Over Fiber Radio over Fiber Infrastructure Control and Access Network

32 OFDM Mm-Wave ROF Systems

‰ Combination of OFDM and ROF is naturally suitable for optical- wireless systems to extend the transmission distance

‰ Fiber links: mitigate chromatic dispersion (S. L. Jansen, et al., OFC 2007, PDP15; A. Lowery, et al., OFC 2007, PDP 18; W. Sheih, et al., EL, 2007) ‰ Air links: Tolerate multi-path delay spread (IEEE 802.11a/g) ‰ Reported work only showed the results on 2.4- and 5.8-GHz

wireless LAN with low data rate (H. Sasa, et al, MWP 2003; A.Kim, et al, IEEE Trans. Consum. Electron., vol. 50, no.2, 2004

‰ We are working on mm-wave OFDM-ROF system in the following directions: ‰ Longer fiber distribution without dispersion compensation ‰ Super-broadband data rate up to 16-Gb/s by using multi-level modulation formats (OThP2 1:15pm OFC 2008)

33 OFDM mm-wave Transmission over 80-km SSMF

OFDM Source Mixer 20 GHz Adding 1/32 CP Adding 1/32 4-QAM Modulation 1Gb/s Parallel/Serial Serail/Parallel Generation LPF DAC PRBS IFFT (i) (ii)

AWG HPF b 80km MUX a c MZM TL 10 GHz EA 1:4 SSMF EDFA

Optical Receiver LPF Interleaver Optical Transmitter 4-QAM Demodulation Parallel/Serial Serial/Parallel Removing CP Removing Equalization ADC FFT Data Rx

Oscilloscope (iii) OFDM Receiver Power penalty is less than 0.5dB at 10-6 after 80-km transmission (4-QAM)

Z. Jia, et al, OFC 2008, JWA108 34 DWDM ROF Signals over ROADMs for Wide Area Networks

1551

1563

Z. Jia, et al, OFC 2008, OMO3 35 Transmission of 2.5- and 5-Gb/s Wireless Signals on 60-GHz Signals over Commercial ROADMs

Optical Eye

(B-T-B) (B-T-B)

(after 100km) (after 100km)

2.5Gb/s, 100ps/div 5Gb/s, 50ps/div 2.5Gb/s 5Gb/s

-30

-40 Electrical Eye

1 ROADM (B-T-B) (B-T-B) -50 2 ROADMs 3 ROADMs -60

-70 1557.2 1557.6 1558.0 1558.4 1558.8

(after 100km) (after 100km)

2.5Gb/s, 100ps/div 5Gb/s, 50ps/div 100km SMF-28

36 Future Research Directions

‰ MAC protocols for wireless over fiber access networks ‰ Small picocell: distributed or centralized control protocols? ‰ Protocol timing boundary: fiber propagation delay impact? ‰ Hidden terminal problem: RTS/CTS still effective? ‰ Frequency division multiplexing (FDM) in MM-Wave over fiber and FSO optical wireless links ‰ Increase capacity and distortion tolerance ‰ Without the need of complicated and expensive processing for orthogonal property ‰ High tolerance for Doppler effect in high mobility situation

‰ Low-cost, high integration CMOS chips for high fT device ‰ High loss of dielectric and conductor ‰ High gain antenna

37 Millimeter-Wave Circuits Module

Earlier 60-GHz Module

Digital CMOS can now support 60 GHz

• Bulky 60 GHz module, large antenna • GaAs HEMT, MESFET and InP processes • High power consumption

38 60-GHz IC Technologies

Current research goes to SiGe and CMOS: New designs using standard chip processes offer enormous cost reduction vs. traditional high frequency designs.

‰ 130nm and 90nm CMOS processes ‰ 180nm and 120nm SiGe BiCMOS processes ‰ Critical specifications ‰ MAG (Maximum Available Gain) and impedance of transistors ‰ Noise Figure of transistors and optimum noise impedance ‰ Transmission line performance (microstrip/ coplanar waveguide/ conductor-backed coplanar waveguide)

39 60-GHz IC Technologies

IBM's SiGe Tx & Rx ICs with antennas

Georgia Tech’s 90nm CMOS Chipsets

40 Conclusions

‰ Optical wireless signal generation, up-conversion and distribution techniques play key roles in realizing integrated optical wireless network.

‰ A novel architecture is developed for bidirectional optical wireless access network integrated with WDM-PON with wavelength reuse in base stations. ‰ Demo of uncompressed, 1.485 Gb/s HDTV services over both wireline and wireless links ‰ Demo of 2.5 Gb/s and 5 Gb/s wireless data over DWDM ROF

‰ Technology challenges are ahead of us: ‰ low-cost optical and RF components, ‰ optical wireless system interface, ‰ optical wireless protocols and standardization.

41