Optical Communications Technology and Modulation Formats 16 ...

Optical Impairments• Polarization ModeDispersion (PMD)• Caused by non-linearityof fiber geometry• Very disruptive at higherbit rates (> =10G)• PDMC or regen compensate• Four Wave Mixing (FWM)• Effects in multichannel systems• Effects for higher bit rates• CD, unequal channel spacing,larger spacings• Self/Cross Phase Modulation(SPM, XPM)• Effected by high channel power• Effected by neighbor channels• CD, reduce launch power,larger spacingsStrataLight proprietary and confidential information

From 10 to 40 GbpsStrataLight proprietary and confidential information

From 10 Gbps to 40Gbps• Optics• OSNR lowered by 6 dB (1/4)• CD tolerance goes down by 16• PMD tolerance goes down by 4• ROADM tolerance• Nonlinear effects• Electronics• bandwidth increases by 4• power dissipation• footprint • Economics• 40G system price expected to be x2.5-x3 the price of a 10G system CONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 10

Increasing Capacity per Channel10Gbps NRZ + 40Gbps NRZ at 100 GHz Spacing• At 10Gbps 50GHz is o.k. with minor crosstalkpenalty• At 40Gbps even 100GHz grid support is achallenge• 50GHz grid not possible with 40Gbps NRZ• Added spectrum degradation due to ROADMs• Need more spectrally efficient modulation formatI193.100 THz1552.52nm193.200 THz 193.300 THz 193.400 THz 193.500 THz1549.32nm10Gbps NRZ + 40Gbps NRZ at 50 GHz SpacingI193.100 THz1552.52nm193.200 THz 193.300 THz 193.400 THz 193.500 THz1549.32nmCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 11

Modulation SchemesStrataLight proprietary and confidential information

LASER Light properties to Modulate• Intensity• On/Off keying• Widely used for up to 10Gbps• Easy to modulate and easy to detect• Phase• Phase shift keying • Frequency shift keying• Well know technique outside optics• Polarization• Well know but not understood• Relatively new• Detection can be a little more difficultΦIPCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 13

Modulation SchemesModulation AttributesAmplitude Phase PolarizationNRZDPSKDQPSKPM-’X’CS/RZPSBTQPSK(N)RZ—(Non) Return to ZeroQPSK—Quadature Phase Shift KeyingPSBT—Phase Shaped Binary Transmission PM-’X’—Polarization MultiplexingCS-RZ—Carrier Suppressed Return to ZeroDPSK—Differential Phase Shift KeyingDQPSK—Differential Quadature Phase Shift KeyingStrataLight proprietary and confidential information

Non Return to Zero (NRZ)LASERIΦ3/2ππ1/2π01 1 0 1 043G• Intensity modulation format only• Widely used at 10Gbps• Simplest Transmitter/Receiver Configuration• Optical Spectrum has a carrier• Optical Spectrum is medium spectralefficiency• Spectral efficiency in actual systems at10Gbps and 50GHz grid => 0.2 bits/HzNRZ1/2πIm1√20πReOOK3/2πCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 15

Carrier Suppressed Return to Zero (CS-RZ)IΦ3/2ππ1/2π043Gbps Data1 -1 0 -1 021.5G Clk21.5G Clk• Intensity modulation format• Slightly more Complex Transmitter Design• Required additional clock modulation• Pulse train has RZ pulse shape with alternateπ shifts between bits slots• Optical Spectrum has suppressed carrier• Higher tolerance to non-linear effects• Higher receiver sensitivityCS-RZ1/2πIm-√2-11√20πRe3/2πCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 16

Phase Shaped Binary Transmission (PSBT)43GPre-CodeLPF• Intensity modulation formatLASER• Slightly more Complex Transmitter Design• Required data pre-coder + low pass filter43GIPre-CodeLPF• Pulse train has NRZ like pulse shape withsome residual light within “0” symbolsΦ1 1 0 -1 0• Narrow Optical Spectrum• Increased spectral efficiency3/2ππ1/2π0• Increased chromatic dispersion toleranceDuo Binary1/2πIm-√2-11√20πRePSBT3/2πCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 17

Differential Phase Shift Keying (DPSK)LASER43GIΦ3/2ππ1/2π0DPSKPre-Code1 1 0 1 01/2πImLPF• Phase Modulation only• Can be implemented via amplitude modulation only• Simpler than Duo-Binary• Slightly more Complex Transmitter Design• Required data pre-coder• Simpler than Duo-Binary• Optical Spectrum is medium• Can propagate on a 50GHz gridπ-110Re• Higher tolerance to non-linear effects• Higher receiver sensitivity by 3dB• More complex receiverDBPSK3/2πCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 18

Return to Zero Differential Phase Shift Keying (RZ-DPSK)21.5G Clk• Mainly phase modulation format• Slightly more Complex Transmitter Design• Required additional clock modulation43GIPre-Code21.5G Clk• Pulse train has RZ pulse shape in every slotwith data encode in differentially phase onlyΦ3/2ππ1/2π01 1 0 1 0• Optical Spectrum is wide• Higher tolerance to non-linear effects• Higher receiver sensitivity by 3dBRZ-DPSK1/2πIm-110πReRZ- DBPSK3/2πCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 19

Transmitted SpectraROADM50GHz ProfileNRZ10GbpsPSBTA narrow spectrum (i.e longer pulses) improves tolerance to CD, PMD, and ROADM tolerance.CONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 20

Quadrature Phase Shift Keying (QPSK)IΦ3/2ππ1/2π021.5G21.5G1/2πPre-CodePre-Code1 1 0 1 0 0 1 0• Four Level Phase Modulation• Complex Transmitter Design• Two phase modulators nested within phase shift• Decrease line rate by ½• Increased PMD tolerance• Increased chromatic dispersion tolerance• Increased spectral efficiency• Decreased receiver sensitive with respect toDSPK but increase w.r.t. NRZDuo Binary1/2πImπ-1√210RePSBT3/2πCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 21

Differential Quaternary Phase Shift Keying (DQPSK)IΦ3/2ππ1/2π021.5G21.5G1/2πPre-CodePre-Code1 1 0 1 0 0 1 0• Four Level Phase Modulation• Complex Transmitter Design• Two phase modulators nested within phase shift• Decrease line rate by ½• Increased PMD tolerance• Increased chromatic dispersion tolerance• Increased spectral efficiency• Decreased receiver sensitive with respect toDSPK but increase w.r.t. NRZDuo Binary1/2πImπ-1√210RePSBT3/2πCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 22

Dual Polarization Quadrature Phase Shift Keying (DP-QPSK)• Dual Polarization plus Four Level Phase Modulation• Reduced line rate to ¼ the transmission rate• Great spectral efficiency, increased chromatic dispersion tolerance, increasePMD tolerance by a factor of 4! (i.e. same as 10Gbps)• Very complex transmitter• 2x (phase modulators nested in phase shifter) + polarization maintaining10.75GPre-CodePBSPBS1/2πI10.75G10.75GPre-CodePre-CodeΦ x3/2ππ1/2π01 1 0 0 0 1 1 0 1 0 1 1 0 11/2π10.75GPre-CodeΦ y3/2ππ1/2π0CONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 23

Transmitted SpectraROADM50GHz ProfileNRZ10GbpsDQPSKDP-QPSKA narrow spectrum (i.e longer pulses) improves tolerance to CD, PMD, and ROADM tolerance.CONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 24

ComparisonStrataLight proprietary and confidential information

Transmitter Block DiagramsPSBTI inNRZ data DQPSKNRZ data I inNRZ data StrataLight proprietary and confidential information 26

Receiver Block DiagramsStrataLight proprietary and confidential information 27

DWDM Filter CompatibilityStrataLight proprietary and confidential information

DWDM Filter CompatibilityStrataLight proprietary and confidential information

DWDM Filter CompatibilityStrataLight proprietary and confidential information

DWDM Filter CompatibilityStrataLight proprietary and confidential information

DWDM Filter CompatibilityStrataLight proprietary and confidential information

40Gbps Modulation Scheme ComparisonStratalightPSBT NRZ-DPSK RZ-DPSK DQPSK PM-QPSKRelative cost estimate 0% +10% +30% +50% +70%Spectral efficiency 0.8bits/Hz 0.8bits/Hz 0.8bits/Hz 0.8bits/Hz 2bits/HzIntrinsic CD tolerance 320ps/nm 100ps/nm 60ps/nm 200ps/nm (1)1 st order PMD tolerance 2.1ps 2.5ps 2.8ps 5ps 30ps2 nd order PMD tolerance HIGH MEDIUM LOW HIGH HIGHOSNR sensitivity 17.5dB 13.9dB 13.9dB 15dB 11dBReach 800km 1,600km 1,600km 1,000km 2,000kmPenalty per ROADM negligible 0.2dB 0.2dB negligible negligibleNon-linear X-talk from 10G low low low high high(1)CD tolerance depends on # taps in FIR filterStrataLight proprietary and confidential information 33

Performance at 40GbpsStrataLight proprietary and confidential information

DPSK Propagation in TWCFEC cliff: 9.45.3 dB of margin2.6 dB of margin 1.7 dB of margin4dBOSNRMarginGood margin and low nonlinear penalties after 1440 km of NDSFNL x-talk from neighboring 40G channels much smaller than from 10G neighborsStrataLight proprietary and confidential information 35

DPSK WDM Penalty• 50G grid: at the optimum power (0dBm/ch), non-linear penalties are < 1 dB• 100G grid: penalties are

ROADM Tolerance in NDSFmargin• 9 spans of NDSF, 80km,17dB• ROADM: SG 3 rd order, 37.6 and 44GHzFWHM• in-line DCM, 90%comp• 0dBm/ch in NDSF; -8dBm/ch in DCM• 50GHz grid, 1 x 40G + 4 x 10G• 21.5dB OSNR at RX• Both DPSK and PSBT have good ROADM tolerance: at least 9 ROADMs can be supported on a 9x80km linkwith a 50G grid• DPSK penalty on a 37.6GHz ROADM: ~1dB/ROADM (few ROADMs); ~0.5dB/ROADM (many ROADMs)• PSBT penalty on a 37.6GHz ROADM:

Conclusions and Summary• Metro Applications• PSBT provides best cost/performance• DPSK viable where higher performance is required• LH/ULH Applications• DPSK provides best cost/performance• Optional PMDC supports high PMD requirements• DQPSK – expensive; no significant performance advantage• Improved dispersion tolerance with poorer OSNR• Modest PMD improvement still requires PMDC to be practicalStrataLight proprietary and confidential information

Conclusions and Summary• PM-QPSK• High cost, very complex, optically and electronically• Advantages in niche applications at 40Gbps• Very poor fiber and excessive cascading of narrow filters• Unnecessary cost for vast majority of applications• Performance• Limited to low launch powers, incurs penalty on long or high loss spans• Difficulty with adjacent channel 10G• Great spectral efficiency• Applications• Leading contender at 100Gbps where investment in optics and electronics can bejustified.StrataLight proprietary and confidential information

Technical LeadershipStrataLight proprietary and confidential information 40

100Gbps RequirementsStrataLight proprietary and confidential information

High level market requirements• Must retrofit into existing DWDM infrastructure• Support 50GHz channel spacing• Support up to 24 cascaded ROADMs @100GHz spacing• Support up to >10 cascaded ROADMs @50GHz spacing• Reach up to 1,500km• No change to existing line equipment (e.g. no extra amplificationrequired, use current in-line DCMs)• Same CD/PMD tolerance as current 10G (with integration of TDC/PMDC if need be)• Operate without in-line DCM • Power/footprint same as current 40G• Price 2x current 40G• First HW samples March ‘1010/16/08Client LogoCONFIDENTIAL © 2008 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 42

Transmitted Spectra – PotentialsROADM50GHz ProfileNRZ10GbpsA narrow spectrum (i.e longer pulses) improves tolerance to CD, PMD, and ROADM tolerance.DQPSK40GbpsDP-QPSK40GbpsCONFIDENTIAL © 2007 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 43

Development solution – PM-QPSKTx Block Diagram4x25Gb/s[25Gbaud]inputs GrayTEMZI Iπ/2 CW laserPBS GrayGrayMZI QMZI Iπ/2 I outTMGrayMZI QRx Block Diagram10/16/08Client LogoI inLocalOscillator90º hybrid(phase/polarizationdiversity)BalancedPhotodiodeBalancedPhotodiodeBalancedPhotodiodeBalancedPhotodiodeADC/DSPCONFIDENTIAL © 2008 STRATALIGHT COMMUNICATIONS ALL RIGHTS RESERVED. 444x25Gb/s[25Gbaud]outputs

Thank-youQuestions & CommentsPlease Contact me at: Avid@StrataLight.comStrataLight proprietary and confidential information