Silicon photonics can make it green(er): two case-studies of mass market communication applications S. Menezo, CEA-Leti, Head of Silicon Photonics lab at Leti June 26 th 2013 Leti Annual Review Meeting Green IT
Green My understanding of green = efficiency when using resources to achieve a given goal These are: The money you are given for making a development The Materials, Hand labor of your final product The Electrical power Available room Etc Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 2
Purposes of Silicon Photonics for communications Bring, Integrate all the photonic functions onto silicon Make the technology compatible with CMOS technology laser E/O modulator l-mux Dmux Optical link l-mux Dmux O/E Photodetector Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 3
Purposes of Silicon Photonics for communications Bring, Integrate all the photonic functions onto silicon Make the technology compatible with CMOS technology laser E/O modulator Electronic Driver l-mux Dmux Optical link l-mux Dmux O/E Photodetector TIA BITS/ SYMBOLS BITS/ SYMBOLS E/O photonics CMOS Electronics 3D CMOS integration process with CMOS electronics e.g. micro pillars, shortens the electrical interconnects Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 4
Silicon Photonics Benefits and challenges Benefits: Volume fabrication and wafer level testing capabilities E/O assembly cost reduction Size reduction of photonics (/100 versus InP for passives) Tight integration with electronics = reduction of cost and power consumption, increase of density of information Challenges Devices Integration (mature the technology) Silicon waveguide spot size singlemode fibre core size Mass scale optical packaging techniques 1µm Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 5
Market segments of optical communications Optics Transmission distance Chip to Chip SiP to SiP (*) in SiP On board In rack Interack LAN Access Metro Core 1cm 10cm 1m 10m 100m 1km 10km 100km Electrical (Multi Mode fiber) Optical Optical (Single Mode fiber) Case study 2: SiP escape with 2 km reach Case study 1: Passive Optical network Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 6
Case Study 1: Passive Optical Networks Fiber users Central Office
Highly constrained market Infrastructure is set up there for decades (50 year-maintenance free and electrical power free) Make it with it Central Office (CO) Optical fibre 1x64 splitter 13-28 db power budget (CO-ONU) 20km max reach User 1 User n User 2 64 users Standards Courtesy of FSAN Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 8
G-PON - Deployed today Central Office (CO) 1l 1310nm US (1.25Gbps) 1l 1550nm 1DS (2.5Gbps) 1x64 splitter 2.5G RX 1.25G TX 13-28 db de Budget TDM/TDMA 64 users Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 9
G-PON - Deployed today 1l 1310nm US (1.25Gbps) Central Office (CO) Is made up with: 1 Tx 1310nm uncooled laser 2 Rx 1490nm & 1550nm 1 WDM filtering 1l 1550nm 1DS (2.5Gbps) 13-28 db de Budget TDM/TDMA Optical Transceiver 2.5G RX 1.25G TX 64 users Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 10
Optical solution today/ Lessons learnt Assembled optics Bulk assembled ONU triplexer or Photonic Integrated Ciruit PIC based ONU triplexer Optical integration did not represent a cost reduction compared to the discrete solution at today s deployment volumes failure of triplexer PIC Perfos need to scale x10 D. Piehler, OFC 2012 Drawings From Martin Shell, HHI, ECOC 2012 and D. Piehler, OFC2012 Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 11
XG-PON1 Next Generation deployment, 2015 1x64 splitter 10G RX 2.5G TX Central Office (CO) 1l US (2.5Gbps) 1l DS (10Gbps) 13-28 db de Budget TDM/TDMA 64 users Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 12
NG-PON2 - After next generation: deployment? 13-28 db de Budget TDM/TDMA Central Office (CO) 4l US (2.5Gbps) 4l DS (10Gbps) 10G RX Tuneable 2.5G TX Tuneable TWDM PON Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 13
Silicon Photonics Toolbox for PON Silicon Photonics can make it integrated Silicon photonics toolbox Directly modulated tunable lasers 7GHz modulation BW 12.5 Gbps direct OFDM modulation Tight integration with electronics: no need for matching resistors Wavelength Tuneability Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 14
III-V (gain) on Si (guide) Lasers InP die thinned down to 3 µm 300 µm 300 µm B. Ben Bakir et al. Opt. Express(2011) III-V gain Si waveguide Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 15
Fiber coupled power (dbm) Fiber coupled optical power (mw) Si-waveguide power (mw) 1. DBR lasers: updated (2013) results J(kA/cm²) 0,0 5,5 0,8 1,7 2,5 3,3 4,2 5,0 5,8 6,7 7,5 8,3 19,25 5,0 10 C 17,50 20 C 4,5 30 C 15,75 4,0 40 C 14,00 3,5 50 C 12,25 3,0 60 C 10,50 65 C 2,5 8,75 2,0 1,5 1,0 0,5 7,00 5,25 3,50 1,75 0,0 0,00 0 20 40 60 80 100 120 140 160 180 200 Current (ma) @ l =1.5µm, Ith <20mA, 17mW in the silicon waveguide >50dB SMSR 118mA @1546,964nm 0-10 52,7dB -20-30 A. Descos et al., to be presented at ECOC 2013 G. Beninca et al. 12.5Gbps OFDM modulation, CLEO 2013-40 -50-60 -70 1542 1544 1546 1548 1550 1552 Wavelength (nm) Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 16
1. DBR laser: updated (2013) results Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 17
A greener solution Frequency Division Multiple Access NG PON???, deployment? f Central Office (CO) f 1l US (20Gbps) 1l DS (40Gbps) B. Charbonnier, Silicon Photonics for Next Generation FDM/FDMA PON, JOCN 2012 f 64 users Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 18
Silicon Photonics and CMOS elec Toolbox e.g. : upstream link Optics: Reflective MZM at the ONU With Faraday Rotator effect allowing coherent demodulation, without the need for polarization diversity schemes S. Menezo, Reflective Silicon Mach Zehnder Modulator With Faraday Rotator Mirror effect for self-coherent transmission, OFC 2013 CMOS driver with a distributed architecture 500mW expected Copper pillar integration I LPF US data LO 400 MS/s ADC Q LPF Very simple electronics At the user side, the user data stream is generated by a 400MS/s DAC, modulated over an electrical carrier and then over an optical carrier Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 19
Fiber To The Home: conclusion FTTH shipped modules Non included = FTTx, i.e. FTTB + VDSL etc ) In 2102, 40M (mainly GPON and EPON) 60M annual volume starting in 2017 (mainly GPON + EPON, 10GEPON and XGPON1 small volumes) PON ONU market unlikely to drive Photonic integration for Next Generation PONs by itself Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 20
Case Study 2: Evaluation of optical SiP escape (0 to 2km) built up from a complete CMOS-Photonics-devices-library From Reflex Photonics
Case study 1 / outline Bottleneck and requirements Considered interconnect architecture and associated CMOS-Photonics demonstrated Devices Interconnect performances Evaluation and Discussion Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 22
I/O escape BW from SiP Mass market applis ~10 th 100 th millions Limited nb of I/Os (processor, switch, FPGA, ) I/O pitch increases as bit rate increases The ITRS projections for signal-pin count and per-pin bandwidth are nearly flat over the next decade Can use SERDES but reduces power budget, thus reach Al. Davis, et. al., 2013 Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 23
Requirements (driven by large Data Centers) A few Tb/s escape BW Below 1mW/Gbps Transmission reach Data center scale up to 2km No standard/ No optical infrastructure Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 24
Case study 2 Bottleneck and requirements Considered interconnect architecture and associated CMOS-Photonics demonstrated Device-library Interconnect performances Evaluation and Discussion Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 25
Considered link architecture o o o Transmitter: N WDM x M parallel channels Laser 1 l1 Laser 2 l2 Laser N-1 ln-1 N x M Power Splitter RRM (N-1)1 RRM-21 RRM-11 l1, l2,..., ln l1, l2,..., ln l1, l2,..., ln RRM-(N-1)M RRM-2M RRM-1M Up to 2km Single Mode Fiber -0.25dB/km Tunable RRF (N-1)M Receiver Tunable RRF -1M PD NM Signal OUT Channel 1M TIA PD 1M Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 26
Considered link architecture o o o Transmitter: N WDM x M parallel channels Laser 1 l1 Laser 2 l2 Laser N-1 ln-1 N x M Power Splitter l1, l2,..., ln l1, l2,..., ln l1, l2,..., ln RRM (N-1)1 RRM-21 RRM-11 RRM-(N-1)M PD NM RRM-2M Signal OUT Channel 1M RRM-1M Optical power budget = Almost the same for 1m or 2000 m fiber length Receiver Tunable (data RRF (N-1)M center scales) TIA Tunable RRF -1M PD 1M Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 27
Used CMOS photonics library Laser: see part 1/ DBR Laser Ring modulators Ring filters Photo detectors Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 28
Used CMOS photonics library Laser: see part 1/ DBR Laser Ring modulators Ring filters Photo detectors Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 29
Ring Modulators [D. Thomson, GFP, Avril 2012] Silicon PN depleted waveguides R=6µm 16fF capacitance, 35ohms access resistance 2.8Vpp driving voltage, 1.6 db modulation depth @30Gbps Q~1000 (high loss due to radius) 30 Gb/s Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 30
Through, db Ring Modulators (target) R=12µm (Q=8 000), N=7 WDM channels 3dB cumulated loss at ON state 6dB ER at 3Vpp 0-5 6dB ER -3dB -10-15 -20 0 1 2 3 4 5 6 7 8 Dlambda, nm Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 31
Used CMOS photonics library Laser: see part 1/ DBR Laser Ring modulators Ring filters Photo detectors Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 32
2. Ring required tuning power Puissance transmise (dbm) Power to align the Laser comb with the ring Filter combs Compensation of Dispersion of the resonant wavelength due to fabrication Temperature shifts 0.1nm/ C Flow current in a TiTiN/Si waveguide -40 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560-45 50mW power required to tune the resonance over 1 FSR -50-55 -60 I1 I2 I3 I4 I5 I6 I7 I8-65 Longueur d'onde (nm) Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 33
2. Ring- fab dispersion Fabrication/ dispersion of the resonant wavelength Si Thickness range 6.5nm Resonant wavelength range 7nm Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 34
Used CMOS photonics library Laser: see part 1/ DBR Laser Ring modulators Ring filters Photo detectors Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 35
4. Ge on Si Photo-detectors Ge on Si Photo-detectors Median dark current: <180nA @-2V <25nA @-0.5V Responsivity @1550nm 0.8 A/W -3dB BW @0V bias 40GHz L=10µm L=10µm P N [L. Virot, Photonics Europe, Avril 2012] Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 36
Outline What makes a technology suitable for interconnects with a reach of a few inches Considered interconnect architecture and associated CMOS-Photonics demonstrated Devices Interconnect performances Evaluation and Discussion Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 37
Performances evaluation @10Gbps N=8 wavelengths, 10Gbps, 25 C M=64 (-21dBm receiver sensitivity) Aggregated bit rate 5.12Tb/s Power consumption of the overall tree, fj/bit ~1500 fj/bit Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 38
Performances evaluation @10Gbps N=8 wavelengths, 10Gbps, 25 C M=64 (-21dBm receiver sensitivity) Aggregated bit rate 5.12Tb/s Power consumption of the overall tree, fj/bit ~1500 fj/bit Add : SERDES 10Gbps 1000fJ/bit Driver 200fJ/bit TIA (65nm) 500fJ/bit Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 39
Performances evaluation @10Gbps N=8 wavelengths, 10Gbps, 25 C M=16 (-21dBm receiver sensitivity) Aggregated bit rate 1,28Tb/s N=8 wavelengths, 10Gbps, 60 C M=16 (-21dBm receiver sensitivity) Aggregated bit rate 1.28 Tb/s Power consumption of the overall tree, fj/bit ~1500 fj/bit ~2700 fj/bit Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 40
Conclusion 1/2 Equal as SERDES projections for 1m, but reach 2km Bandwidth density >x 10 Optics roadmap Improve laser temperature behavior Considering uncooled laser, 1.3µm laser operation Increase the number of wavelengths Power consumption / 2 for Number of Wavelengths x 4 @25 C Increasing the data rate is not suitable (SERDES power consumption) 1500 1000 500 Power consumption (fj/bit) (optics only) vs Laser wall plug efficiency 0 0,0% 5,0% 10,0% 15,0% Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 41
Conclusion / Silicon photonics Greener My understanding of green = efficiency when using resources These are: The Materials, labor of your final product The Electrical power Available room Target the right market or markets with real synergies Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 42
Thanks to And particular thanks to B. Charbonnier for discussions case study 1 Sylvie MENEZO Leti Annual Review Meeting 2013, Grenoble 43