Photonic Integrated Circuits in Telecommunications Preview of next Nick cartoon Christopher R. Doerr Microphotonics Mtg., Nov. 2009, slide 1 Alcatel-Lucent 2009
Outline Motivation Transmitters Passives ceivers Conclusion Note: this talk focuses on Bell Labs work Microphotonics Mtg., Nov. 2009, slide 2 Alcatel-Lucent 2009
Motivation Microphotonics Mtg., Nov. 2009, slide 3 Alcatel-Lucent 2009
search is no longer keeping up with bandwidth needs Internet traffic Cisco forecast 2 db/year Minnesota Traffic Study System capacity Gb/s Tb/s 100 10 1 100 search records 2.5 db/year Single channel 0.5 db/year 10 1986 1990 1994 1998 2002 2006 WDM channels 2010 R. W. Tkach, Bell Labs Tech. J., 2009. Microphotonics Mtg., Nov. 2009, slide 4 Alcatel-Lucent 2009
Google s needs Has 36 data centers Total of 800,000 servers Average single query takes 0.25 sec, accessing 1000 machines almost all information kept in RAM Want 2-Tb/s transceiver today Want 8-Tb/s links today Microphotonics Mtg., Nov. 2009, slide 5 Alcatel-Lucent 2009
Advanced modulation formats Advanced modulation formats can increase the capacity of a single fiber and/or tolerance to filtering and dispersion OOK BPSK DB b/symbol = 1 QPSK b/symbol = 2 16 QAM TE PDM-QPSK TM Microphotonics Mtg., Nov. 2009, slide 6 Alcatel-Lucent 2009 b/symbol = 4 OOK = on-off keying BPSK = binary phase-shift keying DB = duobinary QPSK = quadrature phase-shift keying QAM = quadrature amplitude modulation PDM = polarization-division multiplexed
Typical optical coherent link 23 optical components 29 intra-component connections Data #1 Data #2 Laser PBS Data #3 Data #4 This is the golden age of photonic integration Laser Signal PBS X-pol Y-pol 90 hybrid LO 90 hybrid PD PD PD PD PD PD PD PD A/D A/D A/D A/D DSP 13 optical components 13 intra-component connections Data #1 Data #2 Data #3 Data #4 Microphotonics Mtg., Nov. 2009, slide 7 Alcatel-Lucent 2009
Popular PIC material systems Silica on silicon Pro: Low loss, precise w.g. Con: Mainly passive, large Main product:: Mux/Demux Lithium niobate (LN) Pro: High speed, linear Con: Large, expensive Main product:: Modulator Indium phosphide (InP) Pro: Laser, high speed, small Con: Expensive, lossy Main product:: Laser, receiver, modulator Silicon on insulator (SOI) Pro: High yield Con: Lossy, no laser Main product: VOA, APD, receiver, modulator Microphotonics Mtg., Nov. 2009, slide 8 Alcatel-Lucent 2009
Where are PICs well established in Glass telecommunications? Mux/demux, Vmux, 2-D ROADM LiNbO 3 MZI modulator, nested MZI modulator III-V IV EML, tunable lasers, multi-wavelength Tx and Rx Fast VOAs Microphotonics Mtg., Nov. 2009, slide 9 Alcatel-Lucent 2009
Where are PICs emerging in telecommunications? Glass PSK demodulators, 90 hybrids Tunable optical dispersion compensators LiNbO 3 Dual polarization I-Q modulators III-V IV Advanced modulation format Tx and Rx Multi-wavelength Tx and Rx Microphotonics Mtg., Nov. 2009, slide 10 Alcatel-Lucent 2009
Transmitters Microphotonics Mtg., Nov. 2009, slide 11 Alcatel-Lucent 2009
First transmitter PIC EML = electroabsorption-modulated laser DFB laser EAM M. Suzuki, et al., J. Lightwave Technol., vol. LT-5, pp. 1277-1285, 1987. Microphotonics Mtg., Nov. 2009, slide 12 Alcatel-Lucent 2009
EMLs are very successful 10-Gb/s small form-factor pluggable (XFP) transceiver Transmitter optical sub-assembly (TOSA) DWDM XFP: ~$1700 3.5 W -1 to +3 dbm 80 km ceiver optical subassembly (ROSA) But spectral efficiency is very poor Microphotonics Mtg., Nov. 2009, slide 13 Alcatel-Lucent 2009
Constellation OOK Time domain Frequency domain Typical generation Data 90 p-p Opt. power Opt. power Frequency Time Typical reception or 90 Data 90 p-p Microphotonics Mtg., Nov. 2009, slide 14 Alcatel-Lucent 2009
Advanced modulation formats OOK BPSK DB b/baud = 1 QPSK b/baud = 2 TE 16 QAM PDM-QPSK Microphotonics Mtg., Nov. 2009, slide 15 Alcatel-Lucent 2009 TM b/baud = 4 OOK = on-off keying BPSK = binary phase-shift keying DB = duobinary QPSK = quadrature phase-shift keying QAM = quadrature amplitude modulation PDM = polarization-division multiplexed
Constellation BPSK Time domain Frequency domain Typical generation Data 180 p-p Opt. power Opt. power Frequency Time Typical reception 180 Data 180 p-p Microphotonics Mtg., Nov. 2009, slide 16 Alcatel-Lucent 2009
Constellation DB Time domain Frequency domain Typical generation Opt. power Opt. power Frequency Time Typical reception Data 180 p-p 180 or Data 180 p-p 180 p-p 180 180 p-p Microphotonics Mtg., Nov. 2009, slide 17 Alcatel-Lucent 2009
Existing wavelength-selectable laser and DB modulator PIC SG-DBR Laser MZ Modulator Amplifier Front Mirror GainPhase ar Mirror PM PM π Optical duobinary transmission MQW active regions Sampled gratings Courtesy of JDSU 10 Gb/s Microphotonics Mtg., Nov. 2009, slide 18 Alcatel-Lucent 2009
lating electroabsorption and electrorefraction T V increasing V + p n ΔT λ λ QCSE Δφ λ Blue chirp d chirp Microphotonics Mtg., Nov. 2009, slide 19 Alcatel-Lucent 2009
High-speed absorption vs. phase modulators in InP 40-Gb/s absorption modulator 100 µm Data Electro-absorption modulator (EAM) B. Mason, et al., IEEE Photon. Technol. Lett., vol. 14, pp. 27-29, 2002. 40-Gb/s phase modulator 4 mm Data H. N. Klein, et al., paper TuA2.4, Integrated Photonics search M 2006. Microphotonics Mtg., Nov. 2009, slide 20 Alcatel-Lucent 2009
BPSK: can generate using phase or amplitude mod. Constellation Time domain Frequency domain Typical generation Data 180 p-p 180 Phase mod. Data 180 p-p Data on-off Opt. power Opt. power Frequency Time Typical reception Amplitude mod. 180 Data on-off Microphotonics Mtg., Nov. 2009, slide 21 Alcatel-Lucent 2009
DB: phase or amp. mod. Constellation Time domain Frequency domain Typical generation Opt. power Opt. power Frequency Time Data 180 p-p 180 Data 180 p-p Typical reception Phase mod. Data on-off 180 Data on-off Amplitude mod. Microphotonics Mtg., Nov. 2009, slide 22 Alcatel-Lucent 2009
85-Gb/s duobinary modulator PIC 1 2 MMI coupler QCSE modulator Phase shifter InP chip C. R. Doerr, IEEE Photon. Tech. Lett. Microphotonics Mtg., Nov. 2009, slide 23 Alcatel-Lucent 2009
LN sults Data 85.4 Gb/s 2 31-1 PRBS 5 ps InP Laser Mod. 1 nm Data LiNbO 3 0 km InP 0 km InP 2 km 85.4 Gb/s Microphotonics Mtg., Nov. 2009, slide 24 Alcatel-Lucent 2009
Pros and cons of novel DB modulator Uses QCSE closer to band edge so shorter and faster Low chirp despite combination of amplitude and phase modulation More lossy than pure phase modulation Microphotonics Mtg., Nov. 2009, slide 25 Alcatel-Lucent 2009
Advanced modulation formats OOK BPSK DB b/baud = 1 QPSK b/baud = 2 TE 16 QAM PDM-QPSK Microphotonics Mtg., Nov. 2009, slide 26 Alcatel-Lucent 2009 TM b/baud = 4 OOK = on-off keying BPSK = binary phase-shift keying DB = duobinary QPSK = quadrature phase-shift keying QAM = quadrature amplitude modulation PDM = polarization-division multiplexed
QPSK Constellation Time domain Frequency domain Typical generation Data #1 180 p-p 2 180 Opt. power Opt. power Frequency 90 or 180 Data #2 180 p-p 2 Time Typical reception LO 90 hybrid D S P Microphotonics Mtg., Nov. 2009, slide 27 Alcatel-Lucent 2009
InP QPSK modulator PIC using 2 EAMs 1.7 mm Star coupler Ground pad EAM pad DC bias pad 37% EAM #1 0 Au p + InGaAs 26% 225 2.2 µm p InP 37% Inlet width ratio chosen to achieve desired splitting ratio EAM #2 +90 BCB i InP 8 QWs n InP Set to 90 bias by design (using extra path length in one arm) C. R. Doerr, et al., OFC, PDP33, 2007. Microphotonics Mtg., Nov. 2009, slide 28 Alcatel-Lucent 2009
Setup 39.8-Gb/s data 79.6 Gb/s 23 ps Laser 1545.1 nm OA OA MZDI 39.8 Gb/s 39.8-Gb/s data delayed by 28 bits DQPSK receiver 4.5 V p-p, -3.3 V bias Microphotonics Mtg., Nov. 2009, slide 29 Alcatel-Lucent 2009
sults 10 ps Microphotonics Mtg., Nov. 2009, slide 30 Alcatel-Lucent 2009
Pros and cons of novel QPSK modulator ~40 times shorter than LiNbO 3 QPSK modulator Lumped-element, well suited for high speed Significantly more lossy than phasebased MZI modulator Exhibits some chirp Microphotonics Mtg., Nov. 2009, slide 31 Alcatel-Lucent 2009
Advanced modulation formats OOK BPSK DB b/baud = 1 QPSK b/baud = 2 TE 16 QAM PDM-QPSK Microphotonics Mtg., Nov. 2009, slide 32 Alcatel-Lucent 2009 TM b/baud = 4 OOK = on-off keying BPSK = binary phase-shift keying DB = duobinary QPSK = quadrature phase-shift keying QAM = quadrature amplitude modulation PDM = polarization-division multiplexed
16-QAM Constellation Time domain Frequency domain Typical generation Digital data #1 Digital data #2 180 90 180 0.25 180 90 180 Opt. power Opt. power Digital data #3 Digital data #4 Microphotonics Mtg., Nov. 2009, slide 33 Alcatel-Lucent 2009 or Frequency Multilevel 180 90 180 Multilevel Time Typical reception LO 90 hybrid D S P
Novel 16 QAM modulator PIC EAM #1 EAM #2-720-180 0 3.1 mm Stretched vertically for clarity Star coupler 0.17 0.33 90-720-90 EAM #3 EAM #4 0.33 0.17 Phase shifter/ attenuator Pulse carver EAM (not used) Use same output inlet width for all four ports. Input inlet width selected to achieve the 1:2:2:1 power splitting ratio. C. R. Doerr, et al., OFC, PDP20, 2008. Microphotonics Mtg., Nov. 2009, slide 34 Alcatel-Lucent 2009
Operation principle 0.15 0.30 0 180 0.30 0.15 90-90 Microphotonics Mtg., Nov. 2009, slide 35 Alcatel-Lucent 2009
Operation principle 0.15 0.30 0 180 0.30 0.15 90-90 Microphotonics Mtg., Nov. 2009, slide 36 Alcatel-Lucent 2009
Operation principle 0.15 0.30 0 180 0.30 0.15 90-90 Microphotonics Mtg., Nov. 2009, slide 37 Alcatel-Lucent 2009
Operation principle 0.15 0.30 0 180 0.30 0.15 90-90 Microphotonics Mtg., Nov. 2009, slide 38 Alcatel-Lucent 2009
Operation principle 0.15 0.30 0 180 0.30 0.15 90-90 Microphotonics Mtg., Nov. 2009, slide 39 Alcatel-Lucent 2009
A 4 EAMs driven with independent data streams 0.17 0.33 0 180 0.33 0.17 90-90 Microphotonics Mtg., Nov. 2009, slide 40 Alcatel-Lucent 2009
Experimental setup 10.7 Gb/s 10.7 Gb/s 43-Gb/s 16 QAM Laser PIC 90 hybrid 50 GS/s scope 10.7 Gb/s 10.7 Gb/s 4-ps sampling period 40-ns sequence Microphotonics Mtg., Nov. 2009, slide 41 Alcatel-Lucent 2009
sults sidual carrier 8 GHz 10.7 Gbaud 2 15-1 PRBS BER for Q quadrature = 9.3 x 10-4 BER for I quadrature = very high due to shifting Microphotonics Mtg., Nov. 2009, slide 42 Alcatel-Lucent 2009
Pros and cons of novel 16- QAM modulator Extremely compact Simple to operate no bias drift Potential for very high speed Higher insertion loss than if use pure phase modulators Microphotonics Mtg., Nov. 2009, slide 43 Alcatel-Lucent 2009
Advanced modulation formats OOK BPSK DB b/baud = 1 PDM-OOK TE TM QPSK b/baud = 2 TE 16 QAM PDM-QPSK Microphotonics Mtg., Nov. 2009, slide 44 Alcatel-Lucent 2009 TM b/baud = 4 OOK = on-off keying BPSK = binary phase-shift keying DB = duobinary QPSK = quadrature phase-shift keying QAM = quadrature amplitude modulation PDM = polarization-division multiplexed
Novel PDM-OOK modulator PIC Data #1 Laser PBS EAM EAM PBS Polarization oriented 45 to the PIC Data #2 PBS = polarization beam splitter EAM = electro-absorption modulator C. R. Doerr, et al., OFC, PDP19, 2008. Microphotonics Mtg., Nov. 2009, slide 45 Alcatel-Lucent 2009
Integrated PBS ΔL TE TM (at certain wavelengths) We chose ΔL = 66 µm. Other published PBS designs are broadband, but require additional/critical processing e.g., L. B. Soldano, et al., IEEE PTL, pp. 402-405, 1994. M. R. Watts, et al., OFC, PDP11, 2005. Microphotonics Mtg., Nov. 2009, slide 46 Alcatel-Lucent 2009
PDM-OOK modulator PIC layout 4.0 mm EAMs PBS PBS Microphotonics Mtg., Nov. 2009, slide 47 Alcatel-Lucent 2009 Stretched vertically for clarity Current injection phase shifters for adjusting the PBS wavelength (not used in the experiment reported here)
Laser sults 40-Gb/s data PIC 40-Gb/s data (delayed by 6 bits) Polarizer Both on, no polarizer at Rx Both on Alone Pol. #1 Microphotonics Mtg., Nov. 2009, slide 48 Alcatel-Lucent 2009 Pol. #2
Pros and cons of novel PDM modulator Simple and robust PBS Very low crosstalk PBS is wavelength dependent Difficult to monolithically integrate with laser Microphotonics Mtg., Nov. 2009, slide 49 Alcatel-Lucent 2009
Tunable optical dispersion = adjustable phase shifter compensators = adjustable coupler = adjustable lens IIR FIR All-pass filters Bragg gratings (CFBG) Coherently connected interferometers Tapped delay line (Excess loss for flat-top passband) Rings GT etalons 2-arm interferometers (Fourier/lattice filter) Gratings Series arrangement Parallel arrangement (Transversal filter) VIPA Multiple controls Single control (No phase shifters) AWG Pro: compact and simple Con: excess loss and limited compensation Microphotonics Mtg., Nov. 2009, slide 50 Alcatel-Lucent 2009
Novel EAM and TODC PIC Variable attenuator 2ΔL ΔL Phase shifter Time Waveguide layout EAM Time Device photograph Star coupler 0 ps 2.2 mm 14.3 ps 28.6 ps C. R. Doerr, et al., OFC, PDP45, 2007. Variable attenuators (negative voltage) Phase shifters (positive voltage) Microphotonics Mtg., Nov. 2009, slide 51 Alcatel-Lucent 2009
sults -106 ps/nm Dispersion range center is offset because of the EAM chirp Laser 1559 nm OA 5.6 V p-p, -2.8 V bias 39.8-Gb/s data EAM+TODC OA 0 ps/nm +174 ps/nm OA -106 ps/nm Without equalization +174 ps/nm With equalization 0 ps/nm Without equalization With equalization Total TODC power consumption < 500 µw Microphotonics Mtg., Nov. 2009, slide 52 Alcatel-Lucent 2009
Pros and cons of novel TODC Integrated into PIC Very low power consumption ~5000 times less than electronic compensation This particular design not scalable to large dispersion Microphotonics Mtg., Nov. 2009, slide 53 Alcatel-Lucent 2009
Passives Microphotonics Mtg., Nov. 2009, slide 54 Alcatel-Lucent 2009
1 9 2 10 6.2-b/s/Hz 16-QAM experiment Odd TX 1 Even TX 2 EDFAs 3-dB Coupler PC PC 14-GBaud PDM 16 QAM I L Switch 112 Gb/s per channel 16.67-GHz channel spacing PC Delay (~20 ns) PC PBS Switch ~80 km SSMF 4 Tunable filter (0.25 nm) Microphotonics Mtg., Nov. 2009, slide 55 Alcatel-Lucent 2009 2 Loops (630 km) Raman EDFA Pol-div. 90 deg Hybrid (18-pm resolution bandwidth) 150 GHz (1.2 nm) Oscilloscope LO A. H. Gnauck, OFC, PD, 2009. Slide courtesy of A. H. Gnauck I x Q x I y Q y A/D A/D A/D A/D
Novel PLC interleaver Simulated 1 2 coupler AWL AWG AWG Measured Theoretically zero chromatic dispersion over entire band Microphotonics Mtg., Nov. 2009, slide 56 Alcatel-Lucent 2009
Pros and cons of novel interleaver Very high-order Gaussian passbands Theoretically very low dispersion Path lengths are so long that need UV trimming Microphotonics Mtg., Nov. 2009, slide 57 Alcatel-Lucent 2009
ceivers Microphotonics Mtg., Nov. 2009, slide 58 Alcatel-Lucent 2009
First receiver PIC Heterodyne receiver LO laser T. L. Koch, et al., Electron. Lett., vol. 25, pp. 1621-1622, 1989. Also, H. Takeuchi, et al., IEEE Photon. Tech. Lett., vol. 1, pp. 398-400, 1989. Microphotonics Mtg., Nov. 2009, slide 59 Alcatel-Lucent 2009
Typical fiber-to-the-home system Diplexers 1.3 µm 1.5 µm 1.5 µm 1.3 µm Microphotonics Mtg., Nov. 2009, slide 60 Alcatel-Lucent 2009
Diplexer filter using a grating coupler Problem: works for only one polarization D. Vermeulen, et al., ECOC, Tu.3.C.6, 2008. Microphotonics Mtg., Nov. 2009, slide 61 Alcatel-Lucent 2009
Previously proposed polarization diversity scheme 1270 nm, Y pol. 1270 nm, X pol. 1577 nm, X pol. 1577 nm, Y pol. X+Y pol X-Y pol Problem: tilt angle is very large (~18 ), resulting in high PDL G. Roelkens, et al., Opt. Exp., pp. 10091-10096, 2007. Microphotonics Mtg., Nov. 2009, slide 62 Alcatel-Lucent 2009
Our proposed pol. diversity scheme 1270 nm, X pol. 1270 nm, Y pol. 1577 nm By using both Γ-X and Γ-M directions, the tilt is much smaller (~9 ) C. R. Doerr, et al., IEEE Photon. Tech. Lett., 2009. Microphotonics Mtg., Nov. 2009, slide 63 Alcatel-Lucent 2009
Grating coupler design 1270 nm, X pol. 1270 nm, Y pol. k in,x sinθ k out, X sinθ k out,m X Γ M X k out,x a 1577 nm al space Spatial frequency domain Microphotonics Mtg., Nov. 2009, slide 64 Alcatel-Lucent 2009
Diplexer schematic 1577 nm 1270 nm Grating coupler Ge PD MZI filter 1270 nm X pol 1270 nm Y pol 1577 nm Central office type of diplexer Microphotonics Mtg., Nov. 2009, slide 65 Alcatel-Lucent 2009
Photograph of diplexer 2.1 mm Silicon with Ge detectors Microphotonics Mtg., Nov. 2009, slide 66 Alcatel-Lucent 2009
System results Pol. DFB scr. 1.27 µm 3 Gb/s Att. Microphotonics Mtg., Nov. 2009, slide 67 Alcatel-Lucent 2009
Pros and cons of novel diplexer Compact Low polarization dependence Currently poor responsivity Difficult to have high return loss Microphotonics Mtg., Nov. 2009, slide 68 Alcatel-Lucent 2009
Novel DQPSK receiver PIC Current-injection phase shifter pad Thermo-optic phase shifter pad n-contact pads 1 2 MMI coupler 2 4 star coupler Photodetector pads 3.2 mm C. R. Doerr, et al., OFC, PDP23, 2008. Microphotonics Mtg., Nov. 2009, slide 69 Alcatel-Lucent 2009
Packaged device Fiber Microphotonics Mtg., Nov. 2009, slide 70 Alcatel-Lucent 2009 GPPO connector
Packaged device Fiber Microphotonics Mtg., Nov. 2009, slide 71 Alcatel-Lucent 2009 GPPO connector
DQPSK transmitter 1550 nm 86-Gb/s results 86-Gb/s NRZ-DQPSK 1.1-dB variation over all input polarizations 10 ps/div (single-ended detection) Microphotonics Mtg., Nov. 2009, slide 72 Alcatel-Lucent 2009
FPGA 13.375 Gb/s 4:1 Mux 4:1 Mux Data Data Data Data 107-Gb/s results 53.5 Gb/s Quadrature (Q) DFB 53.5 Gb/s In-phase (I) π/2 53.5 GHz OEQ 107-Gb/s RZ-DQPSK 1590 nm (single-ended detection) Courtesy of P. J. Winzer Pre-coded, FEC encoded SONET pattern with 2 31-1 PRBS payload Error floor at 6 10-4 BER The FEC corrected it to error free Microphotonics Mtg., Nov. 2009, slide 73 Alcatel-Lucent 2009 10 ps/div
Pros and cons of novel DQPSK receiver Extremely compact Polarization dependence not low enough for real system probably because of polarization crosstalk in the bends and couplers Microphotonics Mtg., Nov. 2009, slide 74 Alcatel-Lucent 2009
Coherent reception Signal X-pol Y-pol Local oscillator (LO) Passive optics s x +l s x -l s x +jl s x -jl s y +l s y -l s y +jl s y -jl DSP Advantages proved sensitivity over direct detection Detect magnitude and phase duce symbol rate by factor of 2 by using two polarizations DSP can correct transmission impairments Obviates some wavelength demultiplexing Microphotonics Mtg., Nov. 2009, slide 75 Alcatel-Lucent 2009
Conventional coherent receiver Signal PBS X-pol Y-pol 90 hybrid PD PD PD PD IX QX LO 90 hybrid PD PD PD PD IY QY 12 intra-component connections Skew must be kept small a b 90 hybrid (a+b)/2 (a-b)/2 (a+jb)/2 (a-jb)/2 Microphotonics Mtg., Nov. 2009, slide 76 Alcatel-Lucent 2009
Coherent receiver PICs Single pol., single quad. coherent Rx PIC T. L. Koch, et al., Electron. Lett., vol. 25, pp. 1621-1622, 1989. Also, H. Takeuchi, et al., IEEE Photon. Tech. Lett., vol. 1, pp. 398-400, 1989. Dual pol., single quad. coherent Rx PIC R. J. Deri, et al., IEEE Photon. Tech. Lett., p. 1238, 1992. III-V III-V Single pol., dual quad. coherent Rx PIC H.-G. Bach, et al., OFC, OMK5, 2009. III-V Dual pol., dual quad. coherent Rx PIC C. R. Doerr, et al., OFC, PDPB2, 2009. IV Microphotonics Mtg., Nov. 2009, slide 77 Alcatel-Lucent 2009
Novel Si/Ge dual pol. dual quad. coherent Rx PIC Germanium photodetector Thermooptic phase shifter Capacitor QY LO 127 µm QX IX Signal IY 2 2 MMI coupler 3.6 mm Microphotonics Mtg., Nov. 2009, slide 78 Alcatel-Lucent 2009
Grating coupler Y-pol Grating coupler serves as 1. fiber coupler 2. spot-size converter 3. polarization splitter λ/n eff 4. two 50/50 splitters X-pol All TE pol on chip X-pol Y-pol D. Taillert, et al., IEEE Photon. Technol. Lett., pp. 1249, 2003. Microphotonics Mtg., Nov. 2009, slide 79 Alcatel-Lucent 2009
Grating coupler details 220 nm Side view Microphotonics Mtg., Nov. 2009, slide 80 Alcatel-Lucent 2009
Principle of operation 90 90 QY QX LO Equal path lengths Signal IX IY Stretched vertically for clarity Microphotonics Mtg., Nov. 2009, slide 81 Alcatel-Lucent 2009
Principle of operation X polarization 90 90 QY QX IX IY Microphotonics Mtg., Nov. 2009, slide 82 Alcatel-Lucent 2009
Principle of operation Y polarization 90 90 QY QX IX IY Microphotonics Mtg., Nov. 2009, slide 83 Alcatel-Lucent 2009
Photograph of PIC 3.6 mm Microphotonics Mtg., Nov. 2009, slide 84 Alcatel-Lucent 2009
Photodetector Ge 8 100 µm 2 n Ge p+ p p+ Si PD bandwidth ~5 GHz with 50-Ω load, probably limited by capacitance Microphotonics Mtg., Nov. 2009, slide 85 Alcatel-Lucent 2009
Measured responsivity 53 nm From either signal fiber or LO fiber to any PD Wavelength dependence is due to the grating coupler Microphotonics Mtg., Nov. 2009, slide 86 Alcatel-Lucent 2009
Estimated loss breakdown Fiber coupling = 4 db Waveguide propagation loss = 1 db 2 2 MMI couplers = 1 db PD responsivity = 2 db Total excess loss = 8 db Microphotonics Mtg., Nov. 2009, slide 87 Alcatel-Lucent 2009
Experimental setup 10.7 or 28 Gb/s ECL 10.7 or 28 Gb/s 2 15-1 PRBS 112-Gb/s PDM-QPSK PBS Pol-mux ECL Signal LO Coh Rx PIC Storage scope Fiber array DC probe High-speed probe Row of silicon PICs Microphotonics Mtg., Nov. 2009, slide 88 Alcatel-Lucent 2009
Electrical connections TO V+ G S G G S G V- TO V+ G S G G S G V- Bias voltages = ±1.5V TO voltages = 1.6 and 3.7 V Microphotonics Mtg., Nov. 2009, slide 89 Alcatel-Lucent 2009 -V +V G S G
43-Gb/s results (0 errors in 2 10 5 symbols at 19.8 db OSNR) Microphotonics Mtg., Nov. 2009, slide 90 Alcatel-Lucent 2009
112-Gb/s results 112-Gb/s 2 15-1 PRBS BER = 1.7 10-3 Mainly limited by PD bandwidth of ~5 GHz (receiving 28 Gbaud) Microphotonics Mtg., Nov. 2009, slide 91 Alcatel-Lucent 2009
Pros and cons of novel coherent receiver Uses high-yield silicon process on 8 wafer Light is coupled from top so can do onwafer testing and need no polished facet Have only TE polarization on chip Currently photodetector bandwidth is too low Microphotonics Mtg., Nov. 2009, slide 92 Alcatel-Lucent 2009
Conclusion Microphotonics Mtg., Nov. 2009, slide 93 Alcatel-Lucent 2009
Urgent future work for telecommunications High capacity single-channel PICs 100 Gb/s and beyond High capacity multi-channel PICs 400 Gb/s and beyond Athermal PICs Very low power modulators with low loss < 1.5 V for CMOS driving L- band photodetectors integrated on silicon Microphotonics Mtg., Nov. 2009, slide 94 Alcatel-Lucent 2009
Longer term work for telecommunications Solve the coming capacity crunch what will we do after we have exhausted WDM and advanced modulation formats? Solve the coming power consumption conundrum what will we do when telecommunications consumes most of the world s electrical power? Special thank you to L. Zhang, L. Buhl, P. Winzer, P. Bernasconi, N. Sauer, J. Sinsky, A. Adamiecki, A. H. Gnauck, G. Raybon, L. Chen, N. Weimann, D. Neilson, Y.K. Chen, M. Zirngibl Microphotonics Mtg., Nov. 2009, slide 95 Alcatel-Lucent 2009