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Fiber Optic Communication
in Practice
RAD Seminar
Stanford University
4 October 2012
Chris Cole
4 October 2012 2
Outline
Fiber Optic Communication (Optics) Inside the Internet
■ Optics Areas: Datacom & Telecom
■ Non-optical Communication: Voiceband, Wireline, Wireless
■ Mainstream Datacom & Client Optics: 1Gb/s & 10Gb/s
■ Next Gen Datacom & Client Optics: 40Gb/s & 100Gb/s
■ Future Datacom & Client Optics: 400Gb/s & 1.6Tb/s
■ Next Gen Telecom Transport Example: 100Gb/s
4 October 2012 3
Internet Ecosystem
4 October 2012 4
Internet Bandwidth Growth
100
1,000
10,000
100,000
1,000,000
1995 2000 2005 2010 2015 2020
Date
Ra
te M
b/s
Core
Networking
Doubling
≈18 mos
Server
I/O
Doubling
≈24 mos
Gigabit Ethernet
10 Gigabit Ethernet
100 Gigabit Ethernet
40 Gigabit Ethernet
4 October 2012 5
Optics Areas
Transport
300-2000km
Metro Core
80-300km
Metro
Access
2-80km
Access
1-20km
SW & LW Datacom Client & Transport Telecom
Typical
Datacenter
<100m
Intra and
Inter-Office
500m-20km
Enterprise
Datacenter
<300m
4 October 2012 6
Optics Hierarchy
Devices:
ICs, lasers,
photo-detectors
Components:
optical
sub-assemblies
Sub-systems:
pluggable transceiver
modules
Systems:
routers / switch
chassis and boxes
4 October 2012 7
Outline
■ Fiber Optic Communication (Optics) Inside the Internet
Optics Areas: Datacom & Telecom
■ Non-optical Communication: Voiceband, Wireline, Wireless
■ Mainstream Datacom & Client Optics: 1Gb/s & 10Gb/s
■ Next Gen Datacom & Client Optics: 40Gb/s & 100Gb/s
■ Future Datacom & Client Optics: 400Gb/s & 1.6Tb/s
■ Next Gen Telecom Transport Example: 100Gb/s
4 October 2012 8
SW (Short Wave) Datacom Optics
■ Multi Mode Fiber (MMF) point to point interconnect
■ 10m, 100m, 300m, intra-rack, inter-rack, data-center
interconnect applications
■ Interoperable pluggable transceiver modules
■ Ethernet (IEEE) primary standards
■ FibreChannel (storage) other standards
■ 850nm Vertical Cavity Surface Emitting Laser (VCSEL)
■ High volume (100ks to 1Ms / year)
■ Very stringent cost requirements
4 October 2012 9
LW (Long Wave) Datacom Optics
■ Single Mode Fiber (SMF) point to point interconnect
■ 2km, 10km, 40km inter-rack, data-center, central office,
campus and inter-office interconnect applications
■ Interoperable pluggable transceiver modules
■ Ethernet (IEEE) primary standards
■ FibreChannel (storage) other standards
■ 1310nm Distributed Feedback (DFB) Laser
■ Few 1550nm Electro-absorption Modulator Laser (EML)
■ High volume (100ks to 1Ms / year)
■ Stringent cost requirements
4 October 2012 10
Client Telecom Optics
■ Single Mode Fiber (SMF) point to point interconnect
between transport and switching equipment
■ 2km central office applications
■ Interoperable pluggable transceiver modules
■ ITU primary standards
■ IEEE (Ethernet) other standards
■ 1310nm Distributed Feedback (DFB) Laser
■ Few 1550nm Electro-absorption Modulator Laser (EML)
■ Moderate volume (1ks to 10ks / year)
■ Similar to and often same as LW Datacom Optics
4 October 2012 11
Transport Telecom Optics
■ Single Mode Fiber (SMF) DWDM multi-channel
■ 100km, 500km, 2000km enterprise, metro, long haul
transmission applications
■ ITU (International Tele-communications Union) standards
■ OIF (Optical Interface Forum) other standards
■ 1550nm tunable CW laser with MZ Modulator per lambda
■ Optical Amplifiers and Dispersion Compensation
■ Moderate volume (1ks to 10ks / year)
■ Stringent performance requirements
■ Only briefly discussed in this presentation
4 October 2012 12
Outline
■ Fiber Optic Communication (Optics) Inside the Internet
■ Optics Areas: Datacom & Telecom
Non-optical Communication: Voiceband, Wireline, Wireless
■ Mainstream Datacom & Client Optics: 1Gb/s & 10Gb/s
■ Next Gen Datacom & Client Optics: 40Gb/s & 100Gb/s
■ Future Datacom & Client Optics: 400Gb/s & 1.6Tb/s
■ Next Gen Telecom Transport Example: 100Gb/s
4 October 2012 13
Voiceband Datacom Examples
ITU standard V.22 (1980) V.32 (1984)
bit rate (b/s) 1200 9600
Baud (Bd) 600 2400
bits/symbol 2
(4 state QPSK)
4
(16 state QAM)
physical channels
1
(wire pair)
1
(wire pair)
frequencies 1
(unidirectional, half-band)
1
(bi-directional, full-band)
DSP none Echo cancellation, adaptive equalization and forward error correction (FEC)
4 October 2012 14
Wireline Datacom Examples
IEEE standard 100BASE-TX (1995) 1000BASE-T (1999)
bit rate (Mb/s) 100 1000
Baud (MBd) 125 125
bits/symbol 1
(3 state PAM)
~2
(5 state PAM)
physical channels
1
(2 wire pairs)
4
(4 parallel wire pairs)
frequencies 1
(unidirectional, baseband)
1
(bi-directional, baseband)
DSP 4B/5B encoding Echo cancellation and trellis coding across all channels
4 October 2012 15
Wireless Datacom Examples
IEEE standard 802.11b (WiFi) 1999 802.11a (WiFi) 1999
bit rate (Mb/s) 11 (simplex) 54 (simplex)
Baud (KBd) 1400 208
bits/symbol
8
(64 state QPSK x 4 state DQPSK CDMA)
6
(64 state QAM)
spatial channels
1 1
frequencies
1
(unidirectional, CCK, CSMA/CA full-band
48
(unidirectional, OFDM, CSMA/CA full-band)
DSP Walsh/Hadamard coding, adaptive rate selection
FFT coding, adaptive rate selection
4 October 2012 16
Outline
■ Fiber Optic Communication (Optics) Inside the Internet
■ Optics Areas: Datacom & Telecom
■ Non-optical Communication: Voiceband, Wireline, Wireless
Mainstream Datacom & Client Optics: 1Gb/s & 10Gb/s
■ Next Gen Datacom & Client Optics: 40Gb/s & 100Gb/s
■ Future Datacom & Client Optics: 400Gb/s & 1.6Tb/s
■ Next Gen Telecom Transport Example: 100Gb/s
4 October 2012 17
1G Datacom
IEEE standard 1000BASE-SX (SW) 1998 1000BASE-LX (LW) 1998
Source 850nm VCSEL 1310nm DFB laser
bit rate (Gb/s) 1 1
Baud (GBd) 1.25 1.25
bits/symbol 1
(2 state NRZ)
1
(2 state NRZ)
physical channels
1
(2 simplex MMFs)
1
(2 simplex SMFs)
wavelengths 1
(unidirectional, baseband)
1
(unidirectional, baseband)
DSP 8B/10B coding 8B/10B coding
4 October 2012 18
10G Datacom
IEEE standard 10GBASE-SR (SW) 2002 10GBASE-LR (LW) 2002
Source 850nm VCSEL 1310nm DFB laser
bit rate (Gb/s) 10 10
Baud (GBd) 10.3 10.3
bits/symbol 1
(2 state NRZ)
1
(2 state NRZ)
physical channels
1
(2 simplex MMFs)
1
(2 simplex SMFs)
wavelengths 1
(unidirectional, baseband)
1
(unidirectional, baseband)
DSP 64B/66B coding 64B/66B coding
4 October 2012 19
Electric
I/O
Optical
I/O
pin
pair
Gb
/s
fiber
pair λ
Gb
/s
1 10 1 1 10
10G SW Transceiver
4 October 2012 20
Electric
I/O
Optical
I/O
pin
pair
Gb
/s
fiber
pair λ
Gb
/s
1 10 1 1 10
10G LW Transceiver
4 October 2012 21
Why is Optical vs. Non-optical Com. so Simple?
■ Possible reasons:
● Optics engineers are lazy and/or stupid
● Fiber channel is far below Nyquist and Shannon limits
■ Voice band channel: BW = ~4kHz
■ Shielded twisted wire pair channel: BW = ~100MHz/50m
■ SMF channel:
● 1310nm window ~100nm wide → BW = ~15THz:
Nyquist limit = ~ 30TBaud
● 1550nm window ~200nm wide → BW = ~25THz:
Nyquist limit = ~ 50TBaud
● 1550nm window Mitra & Stark (Bell Labs) capacity:
Shannon limit = ~150Tbps
4 October 2012 22
Optics Architecture Design
■ Data Rate = channels * bits/symbol * baud (symbols/sec)
■ Minimum channel count is simplest and cheapest (ex. 1)
■ Minimum bits/symbol is simplest and cheapest (ex. 1, NRZ)
■ Maximum baud is simplest and cheapest if feasible
● Datacom
○ Channel bandwidth is not a limit
○ TX and RX device (IC and Laser) limits dominate
● Telecom
○ DWDM channel bandwidth (50GHz)
○ Fiber impairments over 100kms to 1000kms distance: chromatic & polarization mode dispersion (CD & PMD)
○ TX and RX device limits also important
4 October 2012 23
Baud from SiGe Limits
■ Bipolar IC process figure of merit:
fT = unity magnitude short circuit current gain
■ Reference: Paul Gray & Robert Meyer, “Analysis and Design of Analog Integrated Circuits”, ©1977
■ Based on fT of mainstream SiGe production processes:
Max Baud ≈ fT/10
■ Why fT/10?
■ All optical IC communication building blocks require gain
■ 10x gain at baud gives efficient, low power circuits
■ 3x gain is difficult; requires cascading gain stages
■ 1x gain is not usable
■ Assumes electrical signal integrity is not a limitation
4 October 2012 24
10GBaud from SiGe Limits
2002 – 2006
fT ≈ 110GHz (mainstream 250nm SiGe production processes)
■ 10GHz < fT/10
10Gbaud SiGe ICs were efficiently implemented
■ 40GHz ≈ fT/3
40Gbaud SiGE ICs were implemented but with great difficulty
4 October 2012 25
Baud from CMOS Limits
■ CMOS IC process figure of merit:
fT = unity magnitude short circuit current gain
[ fMax (unity magnitude power gain) is better but not general]
■ Reference: Thomas Lee, “The Design of CMOS Radio-Frequency Integrated Circuits”, ©1998
■ Based on fT of mainstream CMOS production processes:
Max Baud ≈ fT/10
■ Why fT/10?
■ All optical IC communication building blocks require gain
■ 10x gain at baud gives efficient, low power circuits
■ 3x gain is not usable; low CMOS gm makes cascading gain stages impractical
4 October 2012 26
10GBaud from CMOS Limits
2004 - 2006
fT ≈ 120GHz (mainstream 90nm CMOS production processes)
■ 10GHz < fT/10
10Gbaud CMOS ICs were efficiently implemented
■ 40GHz ≈ fT/3
40Gbaud CMOS ICs were not possible
4 October 2012 27
Why Pluggable Transceiver Modules?
■ the good (il buono)
● multiple applications supported
● pay as you go
● confined, replaceable failures
● common market
● specialized R&D & production
■ the bad (il cattivo)
● increased component count
● SI complicated by I/O connector
● power increased by I/O SerDes
● density limited by SFP+ size
■ & the ugly (il brutto)
● poor thermal interface
● heat localized at host front
4 October 2012 28
Outline
■ Fiber Optic Communication (Optics) Inside the Internet
■ Optics Areas: Datacom & Telecom
■ Non-optical Communication: Voiceband, Wireline, Wireless
■ Mainstream Datacom & Client Optics: 1Gb/s & 10Gb/s
Next Gen Datacom & Client Optics: 40Gb/s & 100Gb/s
■ Future Datacom & Client Optics: 400Gb/s & 1.6Tb/s
■ Next Gen Telecom Transport Example: 100Gb/s
4 October 2012 29
40G Telecom Client
Standard ITU-T G.693 40G 2000 IEEE 40GBASE-FR 2011
Source 1550nm EML 1550nm EML
bit rate (Gb/s) 40 40
Baud (GBd) 40 40
bits/symbol 1
(2 state NRZ)
1
(2 state NRZ)
physical channels
1
(2 simplex SMFs)
1
(2 simplex SMFs)
wavelengths 1
(unidirectional, baseband)
1
(unidirectional, baseband)
DSP SDH or OTN framing 64B/66B coding
4 October 2012 30
40G LW Transceiver
Electric
I/O
Optical
I/O
pin
pair
Gb
/s
fiber
pair λ
Gb
/s
10 1 1
4 40
40 40
4 October 2012 31
40G λ Typical Measurements
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
-14.00 -12.00 -10.00 -8.00 -6.00 -4.00 -2.00
BE
R
Average Power dBm
■ Test Conditions:
1550nm λ, 75oC, 39.81312Gb/s PRBS 2^31 -1 pattern
■ TX Eye Mask Margin: 23%
■ RX Average Sensitivity: -10.3dBm AOP
4 October 2012 32
40G Datacom
IEEE standard 40GBASE-SR4 (SW) 2010 40GBASE-LR4 (LW) 2010
Source 850nm VCSEL Array 1310nm DFB laser PIC
bit rate (Gb/s) 40 40
Baud (GBd) 10.3 10.3
bits/symbol 1
(2 state NRZ)
1
(2 state NRZ)
physical channels
4
(8 simplex SMFs)
1
(2 simplex SMFs)
wavelengths 1
(unidirectional, baseband)
4
(unidirectional, baseband)
DSP 64B/66B coding 64B/66B coding
4 October 2012 33
40G SW Transceiver
Electric
I/O
Optical
I/O
pin
pair
Gb
/s
fiber
pair λ
Gb
/s
10 1 10
4 4
40 40
4 October 2012 34
40G LW Transceiver
Electric
I/O
Optical
I/O
pin
pair
Gb
/s
fiber
pair λ
Gb
/s
10 1 10
4 4
40 40
4 October 2012 35
10G λ Typical Measurements
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
-18 -16 -14 -12 -10 -8
BE
R
OMA dBm
■ Test Conditions:
1310nm λ, 55oC, 10.3125Gb/s PRBS 2^31 -1 pattern
■ TX Eye Mask Margin: 37%
■ RX Average Sensitivity: -15.6dBm OMA
4 October 2012 36
100G Datacom
IEEE standard 100GBASE-SR4 2013(?) 100GBASE-LR4 2010
Source 850nm VCSEL Array 1310nm DFB laser PIC
bit rate (Gb/s) 100 100
Baud (GBd) 25.8 25.8
bits/symbol 1
(2 state NRZ)
1
(2 state NRZ)
physical channels
4
(8 simplex SMFs)
1
(2 simplex SMFs)
wavelengths 1
(unidirectional, baseband)
4
(unidirectional, baseband)
DSP 64B/66B coding 64B/66B coding
4 October 2012 37
100G SW Transceiver
Electric
I/O
Optical
I/O
pin
pair
Gb
/s
fiber
pair λ
Gb
/s
1
4 4
25 25
100 100
4 October 2012 38
100G LW Transceiver
Electric
I/O
Optical
I/O
pin
pair
Gb
/s
fiber
pair λ
Gb
/s
1
4 4
25 25
100 100
4 October 2012 39
25GBaud from SiGe Limits
2008 - 2012
fT = ~220GHz (mainstream 130nm SiGe production processes)
■ 25GHz ≈ fT/10
25Gbaud SiGe ICs were/are efficiently implemented
■ 40GHz ≈ fT/6
40Gbaud SiGe ICs are feasible
4 October 2012 40
25GBaud from CMOS Limits
2010 - 2012
fT = ~240GHz (mainstream 40nm CMOS production processes)
■ 25GHz ≈ fT/10
25Gbaud CMOS ICs were/are efficiently implemented
■ 40GHz ≈ fT/6
40Gbaud CMOS ICs are feasible with difficult
4 October 2012 41
Key GaAs Technology for 40G and 100G SW
■ Photonic Integrated Circuit (PIC*) parallel quad VCSEL array
■ Ex. monolithic GaAs quad 850nm VCSEL array, 0.25mm x 1.0mm PIC, Finisar Corp.
* The “C” in PIC is a stretch since there are no optical connections
4 October 2012 42
Key InP Technology for 40G and 100G LW
■ Photonic Integrated Circuit (PIC) WDM quad DFB array
■ Ex. monolithic InP quad 1310nm band DFB laser array with AWG, 1.1mm x 2.4mm PIC, CyOptics Inc.
4 October 2012 43
Key Si Technology for 40G and 100G LW
■ Photonic Integrated Circuit (PIC) Transceiver Chips
■ Ex. Hybrid Si Photonics quad 1550nm band PICs, Kotura
4 October 2012 44
Outline
■ Fiber Optic Communication (Optics) Inside the Internet
■ Optics Areas: Datacom & Telecom
■ Non-optical Communication: Voiceband, Wireline, Wireless
■ Mainstream Datacom & Client Optics: 1Gb/s & 10Gb/s
■ Next Gen Datacom & Client Optics: 40Gb/s & 100Gb/s
Future Datacom & Client Optics: 400Gb/s & 1.6Tb/s
■ Next Gen Telecom Transport Example: 100Gb/s
4 October 2012 45
Electric
I/O
Optical
I/O
pin
pair
Gb
/s
fiber
pair λ
Gb
/s
1
25 25
16 16
400 400
2x16 MPO
plug connector
400G SW Transceiver
4 October 2012 46
Electric
I/O
Optical
I/O
pin
pair
Gb
/s
fiber
pair λ
Gb
/s
1
8
8
50 50
400 400
400G LW Transceiver
4 October 2012 47
1.6T Transceiver Alternatives
■ 64x25Gb/s or 32x50Gb/s NRZ lasers
● Too many channels
● Not practical
■ Complex (amplitude and phase) modulation is only feasible alternative to control channel count
● PAM-N
● PSK-N
● QAM-N
● DMT-N
● Requires complex CMOS DSP and PICs
● No technology exits that can be commercialized
■ Excellent area for academic research
■ May be first used in late generation 400G Transceivers
4 October 2012 48
1.6T Transceiver Parameter Alternatives
Electrical
I/O
Optical
I/O
pin pair Gb /s Bits /
Symbol fiber pair λ Gb /s
Bits /
Symbol
1 10 1 1 1 10 1
4 12.5 2 4 4 12.5 2
8 25 3 8 8 25 3
16 50 4 16 16 50 4 = 50T
= 10G
(SFP+)
4 October 2012 49
Outline
■ Fiber Optic Communication (Optics) Inside the Internet
■ Optics Areas: Datacom & Telecom
■ Non-optical Communication: Voiceband, Wireline, Wireless
■ Mainstream Datacom & Client Optics: 1Gb/s & 10Gb/s
■ Next Gen Datacom & Client Optics: 40Gb/s & 100Gb/s
■ Future Datacom & Client Optics: 400Gb/s & 1.6Tb/s
Next Gen Telecom Transport Example: 100Gb/s
4 October 2012 50
100G Coherent Transport PM-QPSK TX
Precoding MZM
MZM
I
Q
X-pol
Y-pol
PBC Laser PM-QPSK Soft
Decision
FEC
Encoder
Re
Im
Precoding
I
Q
Re
Im
4 October 2012 51
100G Coherent Transport PM-QPSK RX
Hard
Decision
Decoding
Hard
Decision
Decoding
Soft
Decision
FEC
Decoder
SP
M C
om
p.
4 October 2012 52
100G Coherent Transport OSNR Limited BER
T. Mizuochi, “Next Generation FEC for Optical Communications,” OFC’08, Tutorial, San Diego, CA, 24-28 Feb. 2008
4 October 2012 53
Coherent Transport Trends
P. J. Winzer, “Coherent Optical Communications,” IEEE Photonics
Conference, Tutorial, San Francisco, Sep. 2012
4 October 2012 54
Fiber Optic Communication in Practice
Thank you