Post on 11-Jul-2018
transcript
100Gbit/s, 120km, PAM 4 Based Switch to Switch, Layer 2 Silicon Photonics based Optical Interconnects for Datacenters
Radhakrishnan Nagarajan, Sudeep Bhoja and Tom Issenhuth** Microsoft Corp, Redmond, WA
2Inphi Proprarch 25, 2014 2
Increased Complexity, Speed and Volumes Driving
Application Opportunities for Silicon Photonics
Data Center Connectivity Trends
Within the Rack (Server to TOR)
― 10GbE Deployed at Scale (DAC)
― 25GbE Transition happening now (DAC/AOC)
― 50GbE forecasted to start in 18/19 (SR/AOC)
Between Racks
― 40GbE Deployed at Scale (SR4/PSM)
― 100GbE Transition in 2016 (SR4/PSM/WDM4)
― Mix of 200GbE and 400GbE in 17/28 (PSM/WDM4)
Inter Data Center
― 10GbE/40GbE/100GbE Deployed at Scale (LR/ER/DWDM)
― 100GbE/OTN Deployed at Scale for 80km+ (Coherent)
― 200GbE Starting in 2017 (80km to 600km)
― 400GbE Standardized now (DR8/FR8)
3Inphi Proprietaarch 25, 2014 3
Virtual Datacenter Architecture: Latency Limited
Data Center 1 Data Center 2
InternetInternet
TOR Switch
Edge SwitchEdge Switch
TOR Switch
ServerServer
Core Switch Core Switch
Transport Transport
4Inphi Propriarch 25, 2014 4
Virtual Datacenter Architecture: Latency Elimination
Data Center 1 Data Center 2
InternetInternet
TOR Switch
Edge SwitchEdge Switch
TOR Switch
ServerServer
4Tb/s per
FiberCore Switch Core Switch
Transport Transport
5Inphi Proprietarch 25, 2014 5
0 2 10 100 600 10,000
Distance (km)
Metro Datacenter Interconnect (DCI) Gap
Point to Point Links
IEEE 802.3ba /
CR4,SR4, LR4
Sta
nd
ard
s
100G
10G
DWDM
SFP+
ROADM Networks
OIF / Coherent
QPSK/16-QAM
100G/200G
DWDM
OIF / Coherent QPSK/8QAM
100G/200G/400G
DWDM
No Cost Effective 100Gb/s
DWDM Solutions Today
100G Switch
100G Switch
4Tb/s (40 DWDM
channels)
80km
EDFA
EDFA + DCF
Inter-datacenter links are beingupgraded to 100G.
Intra-datacenter links which enablelarge distributed architectures arethe bottleneck.
100G DWDM QSFP-28: Costeffective approach to resolve theDCI bottlenecks
6Inphi ProprA March 25, 2014 6
100G DWDM QSFP-28 Module
4x2
5G
CA
UI
Ele
ctr
ica
l In
terf
ace
λ 1
λ2
λ1
λ2
M
Z
M
D
F
B
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N
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F
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P
D
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F
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Power
Supplies
MCU
Other
ASIC’s
PAM ASIC Silicon Photonics
PAM 4 ASIC Si Photonics
Receive
Transmit
• Compatible with the QSFP28 MSA as described
in SFF-8665
• Standard CAUI4 electrical interface
• Typical power consumption < 4.5W
• Electrical Input: 4 x 25.78125Gbit/s NRZ
• Optical Output: 2 x 28.125 Gbaud PAM4
7Inphi Propriet5, 2014 7
Fat Pipes Between DC’s: DWDM QSFP 28
2λ_100Gbit/s, DWDM
D
C
M
D
C
M
OA
OA
OA
OA
100GHz Channel
Spacing Mux/DeMux
ITU 50GHz
spacing.
2λ’s in ITU 100GHz spacing,
With a 25GHz Laser offset.
Effectively a 50GHz system.
*Exact locations of OA’s and DCM’s in the link are subject to OSNR considerations.
OA: Optical Amplifier
DCM: Dispersion Compensation Module
EDFA: Erbium Doped Fiber Amplifier
9Inphi Propriet March 25, 2014 9
PAM 4 ASIC: Architecture
CML Driver with CMOS backend
Enables wide swing range and low power
½ rate TX Clocking and ¼ Rate RX Sampling
7-bit ADC-DSP based receiver with SAR core
The clock path is CMOS based with regulators providing the
required power rejection
The data path are under independent regulator domains for
proper isolation
Multi-Tap FFE / DFE and Calibration in the DSP
Reference-less, clock recovered from CAUI RX.
10Inphi Proprieta March 25, 2014 10
Silicon Photonics: Mach Zehnder Modulator
Optical Eye
PAM 4
Optical Eye
NRZ
Direct Coupled Driver
• Traveling Wave Mach Zehnder Modulator
• Optical-Electrical S21 Data
11Inphi Proprietaarch 25, 2014 11
Silicon Photonics: Receiver Path
• High Speed Ge Photodetector
• Optical-Electrical S21 Data
• Polarization Beam Splitter
• Insertion Loss and Crosstalk
PD Dark Current
12Inphi Proprich 25, 2014 12
Commercial 100GHz Multiplexer: Flat Top Gaussian
CH 34 – 193.4THz
Filter Center Frequency on 100GHz Grid
13Inphi PropriMarch 25, 2014 13
Module Dual λ Optical Output: 28.125GBaud Data
25GHz
EDFA Noise Limit
Shot Noise
Limit
14Inphi ProprietaMarch 25, 2014 14
Two Way Traffic Using a Commercial Switch
• Line system Transmit, Receive EDFAs.
• Dispersion Compensation at Mid-Stage of EDFA’s.
Commercial Switch
36 100Gbit/s ports
~3.6Tbit/s Capacity
15Inphi Proprie March 25, 2014 15
120km BER vs. OSNR Performance
• 120km SMF Fiber 26.2dB Loss
• Baud Rate = 28.125GBaud
KR4 Correction Limit
IFEC Correction Limit
• Dispersion Tolerance ±100ps/nm
• ~1dB Penalty
16Inphi Proprietch 25, 2014 16
PAM 4 Link: FEC Performance
No Errors for 30mins
ONT Module
EDFA - Gain
EDFA - Noise Loading
4 x 25Gbit/s
interface
• BER vs. OSNR for 100GbE.
• Error free overnight at OSNR = 28dB.
• KP4 and KR4 are Reed-Solomon
FEC codes.
• IFEC is a Iterative Multi-Layer code.