Presented in Dublin at the ECOC International Symposium for Optical Interconnect in Data Centres, Annika Dochhan’s slide deck covers the latest developments in electro-photonic integrated circuits, silicon photonics and IC-TROSA.

1. Annika Dochhan
September, 2019
Photonic integrated circuits
for data center interconnects

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Motivation – data center traffic growth
Forecast 2014:
Within data
center 73.1%
Data center to user 18.2%
Data center to
data center 8.7%
Source: Cisco Global Cloud Index 2014
Forecast 2018:
Within data
center 73.4%
Data center to user 14.3%
Data center to
data center 12.4%
Source: Cisco Global Cloud
Index 2016-2021 (2018)
CAGR: 25%
CAGR: 24.7%

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Motivation – data center traffic growth
Data centers tend to be more distributed
Enabling low-cost high-speed interconnects is still an important topic!
Photonic integrated circuits fulfill these requirements!
Forecast 2018:
Within data
center 71.5%
Data center to user 14.9%
Data center to
data center 13.6%
Source: Cisco Global Cloud
Index 2016-2021 (2018)
CAGR: 24.7%

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Overview
Data center architecture
Photonic integrated circuits
Optical modules
1
2
3

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Data center architecture

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Data center architecture
Tier 0 switches service a rack
Tier 1 switches service a ”row“
(of racks)
Tier 2 switches service a “co-
location“
Tier 3 switches service a data
center
• Interface to long-haul
network
• Also interface to metro
network
Tier 0 Tier 0 Tier 0
…
Tier 1 Tier 1 Tier 1…
Tier 2 Tier 2 Tier 2…
Tier 3
Tier 3
…
Tier 1
Tier 2
Tier 3
Long-haul: 1000s of km
Metro:<80km
Copper cables
Active optical cables
≤2km optics
≤2km optics
Coherent optics
IM/DD optics

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Data center architecture
Tier 0 Tier 0 Tier 0
…
Tier 1 Tier 1 Tier 1…
Tier 2 Tier 2 Tier 2…
Tier 3
Tier 3
…
Tier 1
Tier 2
Tier 3
Long-haul: 1000s of km
Metro:<80km
Copper cables
Active optical cables
≤2km optics
≤2km optics
Coherent optics
Complexity
Volume
Standardization
Cost
IM/DD optics

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Photonic integrated circuits

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Flavors of PICs
Silicon InP SiN SiO Polymer LiNbO3
Waveguides ++ ++ +++ +++ + +
Fiber coupling - + ++ ++ +++ +
Modulators + ++ --- --- +++/--- +++
Pol. converters +++ + - - - -
Light sources --- +++ --- --- --- ---
Photo
detectors
++ +++ - - - -
Footprint +++ ++ - - -- ---
Wafer size +++ -- + + - -
Yield +++ + ++ ++ + -
Hybrid
integration
++ - + + + --
Packaging ++ - + + + -

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Silicon photonics in DCI
Tier 0 Tier 0 Tier 0
…
Tier 1 Tier 1 Tier 1…
Tier 2 Tier 2 Tier 2…
Tier 3
Tier 3
…
Tier 1
Tier 2
Tier 3
Long-haul: 1000s of km
Metro:<80km
Copper cables
Active optical cables
≤2km optics
≤2km optics
Coherent optics
Products appeared here first
Later here
Slowly coming to the market now
IM/DD optics

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Coherent silicon photonic transceiver
Polarization beam splitter
MMI coupler
Edge
coupler
Photo
diodes
Photo
diodes
Modulators Heaters
Waveguide
crossings
10mm x 5mm

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with (Bi)CMOS electronics
EPIC – electronic photonic integrated circuit
Coherent silicon photonic transceiver
Segmented driver
Segmented driver
Segmented driver
Segmented driver
TIAs
TIAs
DACs
Digital
interface (SPI)
Control logic
10mm x 5mm

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Early experiments
Single MZM, direct detect
BER vs OSNR
112 Gbit/s PAM4Bandwidth (MZM + driver)

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Early experiments
Single MZM, coherent
4
6
8
10
12
14
6 10 14 18 22 26 30 34 38 42
Q2-factor(dB)
OSNR in 0.1 nm (dB)
HD-FEC
SD-FEC
64 GBaud
DP-Bi-2ASK 128 Gbit/s
DP-Bi-4ASK 256 Gbit/s
DP-Bi-8ASK 384 Gbit/s
Promising results for use of the modulator in a nested IQ structure for DP-64QAM!
I
Q
Transmission over 120 km shown

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with (Bi)CMOS electronics and active elements
Best of both worlds: integration of III-V on silicon photonics
Coherent silicon photonic transceiver
Segmented Driver
Segmented Driver
Segmented Driver
Segmented Driver
TIAs
TIAs
DACs
Digital
interface (SPI)
Control logic
10mm x 5mm
Laser/LO
SOA
TIAs

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Optical modules

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Higher bandwidth, lower power consumption, lower footprint.
Optical interfaces

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Integrated coherent transmit receive optical sub-assembly
Coherent optical engine that enables small form-factor
pluggables
• QSFP-DD, OSFP, COBO, etc.
Brings down cost through standard assembly processes
• SMT, pick & place, …
• But active optical alignment
High RF performance through
short traces
• BGA mount
Enabling interchangable short reach IM/DD and long reach coherent modules
IC-TROSA

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MASSTART: MASS manufacturing of TrAnsceiveRs for
Terabit/s era
 Glass interface based laser/PIC and fiber/PIC coupling approaches
 Obtain spot size and pitch converters
 Increase optical I/O density, automated assembly processes
 3D packaging enabling backside connection of the high speed PIC to a Si carrier
 New flip chip bonders with enhanced placement
 Improvement in throughput
 Wafer-level evaluation of assembled circuits with novel tools
 Reduce characterization time
Cost-efficient packaging processes are essential for PICs in mass production!
Packaging of SiPh coherent transceiver

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Conclusion
Data centers tend to be more distributed
 DCI is a growing market
PICs are needed for every connection distance
Silicon photonics are a good option
 Monolithically integrated electronics (EPICs)
 Hybrid integration with active materials
Packaging is an important topic

21. Thank you
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adochhan@advaoptical.com