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Cedric F. Lam ( [email_address] ) and Winston I. Way ( [email_address] ) SPIE Photonics West, Jan 29, 2009, San Jose, CA A...
Outline <ul><li>Introduction </li></ul><ul><li>Information capacity and digital modulations </li></ul><ul><li>Challenges b...
Growing Broadband Applications and Technologies IPTV Nomadic Device  Tele-presence Network Gaming Wi-Max xPON Backbone net...
Broadband Access http://www.ieee802.org/3/hssg/public/nov07/HSSG_Tutorial_1107.zip Source:  IEEE 802.3 HSSG Tutorial Inter...
Information Capacity – the Shannon Limit  <ul><li>Information capacity increases linearly with bandwidth but only sub-line...
A Signal Constellation View <ul><li>An intuitive representation of  amplitude and phase of digital symbols on a complex pl...
Modulation Formats - View from Constellation Diagrams <ul><li>For the same constellation point spacing, BPSK requires the ...
Self Coherent Modulation <ul><li>A reference local oscillator (LO) required to demodulate phase encoding    coherent rece...
Complexity vs. Benefits Pre-coded Data CDR Rx Modulation Transmitter Receiver OSNR (dB)  @ 1e-3 , 42.7G  NRZ-OOK NRZ-DPSK ...
Spectral Efficiency – Where Are We Today? M. Nakazawa: ECOC 2008 paper Tu.1.E.1 C-band:  W=4THz , OSNR = 16dB (P/N=14.1dB ...
EDFA C-band (Bandwidth = 4 THz) Utilization To support 50GHz spaced 100GE, we need to achieve C/W = 2 (b/s)/Hz 4x 100GbE 1...
Metro / Regional WDM Network Architecture Metro/Regional WDM Transport Backbone PON LAN Wi-Max or LTE EDFA DCM ROADM DCM T...
Typical Optical Layer Characteristics <ul><li>Topology: Ring / Mesh </li></ul><ul><li>Reach: 300km – 1000km, irregular spa...
Challenges to Upgrade to 40Gb/s & 100Gb/s per Lambda <ul><li>OSNR    bit rate </li></ul><ul><ul><li>From 10Gb/s to 40Gb/s...
Upgrade Strategies <ul><li>Lower the power (or OSNR) requirements </li></ul><ul><ul><li>Use more power efficient phase mod...
Third-Generation Ultra-FEC
DSP Based Coherent Receiver with Polarization Multiplexing <ul><li>Best OSNR sensitivity </li></ul><ul><ul><li>12.5dB @ 46...
Non-linearity in PM-QPSK Oriol Bertran Pardo et. al:  “Investigation of design options for overlaying 40Gb/s coherent PDM-...
10-Gbaud Dense Multi-Carrier Technology <ul><li>Slice the signal into multiple 10-Gsymbol/s sub-carriers </li></ul><ul><ul...
Cost Ratio Comparison of 40G/10G Technologies Source:  H. Bosco, “Network Evolution to 40Gb/s”, ECOC 2008 Cost of 40G inte...
40Gb/s Line Side Modulation Scheme Comparison DMC – 4x10G DMC – 2x20G PSBT (ODB) NRZ-DPSK RZ-DQPSK PM-QPSK Relative Cost E...
40G Muxponder Line Card
Pay-as-you grow 100-G product Version 1 Demonstrated at NXTCOMM 2008 Version 2 Q1/2009 100G (5x20G) 40G (2x20G) 20G  Modul...
DMC 40G/100G + NRZ 10G transmission through 1000km SMF-28 100G 40G 40G 10G 10G 10G 10G 10G 10G 10G
4x10G DMC Lab/Field Trials in 2008 Lab#1 Lab#2 Lab#3 Field#1 Field#2 Field#3 Reach 975km SMF-28 1910km SMF-28 565km SMF-28...
Optical Spectrum of 39x10G NRZ + DMC 1x40G  OpVista’s 40G DMC 975km SMF-28
40G DMC through 975km SMF-28 with 39x10G Signals  #1 #2 #8 #14 Error-free transmission for 37 hours With DCF
Received spectra for a 1750 km (23 spans) customer lab test  <ul><li>The penalty from 100 GHz spacing to 50GHz is less tha...
1750 km (23 SPANS), Four-wave Mixing Test <ul><li>No FWM observed at nominal launch power conditions </li></ul><ul><li>A n...
Best-of-class Non-linearity Tolerance FEC Limit 4x 10G DMC Performance Q or OSNR (dB)
Transparent Network Backbone <ul><li>Increasing the capacity by adding more wavelengths (i.e.: BW) is easier than changing...
Scalable ROADM Principle <ul><li>All add/drops are implemented with broadband couplers and splitters </li></ul><ul><li>Fil...
Protection Switching  2 T R X T R X  1  2  1 JAD Protection Span Clients Clients Working Path Node 1 Node 2 Node 3 Nod...
Scalable ROADM Network Interface TRX: transceiver JAD: Junction add/drop (a)  System Diagram (b)  JAD Cards
Scalable ROADM Node Add/Drops <ul><li>Broadcast and select architecture </li></ul><ul><li>No initial wavelength reuse, sav...
Field Tested Technology OFC/NFOEC 2009 Paper JWA86
Conclusion <ul><li>Ubiquitous  broadband and converged networks are straining the bandwidths in backbone networks. </li></...
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A System's View of Metro and Regional Optical Networks

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Transcript of "A System's View of Metro and Regional Optical Networks"

  1. 1. Cedric F. Lam ( [email_address] ) and Winston I. Way ( [email_address] ) SPIE Photonics West, Jan 29, 2009, San Jose, CA A System’s View of Metro and Regional Optical Networks
  2. 2. Outline <ul><li>Introduction </li></ul><ul><li>Information capacity and digital modulations </li></ul><ul><li>Challenges beyond 10Gb/s transmission </li></ul><ul><li>Recent developments </li></ul><ul><li>DMC technology </li></ul><ul><li>Scalable ROADM architecture </li></ul><ul><li>Conclusion </li></ul>
  3. 3. Growing Broadband Applications and Technologies IPTV Nomadic Device Tele-presence Network Gaming Wi-Max xPON Backbone networks have to scale simultaneously!
  4. 4. Broadband Access http://www.ieee802.org/3/hssg/public/nov07/HSSG_Tutorial_1107.zip Source: IEEE 802.3 HSSG Tutorial Internet and IPTV dominate bandwidth
  5. 5. Information Capacity – the Shannon Limit <ul><li>Information capacity increases linearly with bandwidth but only sub-linearly with SNR </li></ul><ul><li>Optical fiber (old picture – SNR limited channel) </li></ul><ul><ul><li>W: “unlimited” bandwidths </li></ul></ul><ul><ul><li>P: limited by available launch power and non-linearity N: limited by cumulative ASE through cascaded EDFA </li></ul></ul><ul><li>It WAS easier and cheaper to deploy more bandwidth to obtain more capacity </li></ul>Information Capacity (bits/s) Bandwidth Signal-to-Noise Ratio Ref: C.Shannon, Bell Systems Technical J., Vol.27, p.379 (1948)
  6. 6. A Signal Constellation View <ul><li>An intuitive representation of amplitude and phase of digital symbols on a complex plane </li></ul><ul><li>Square of distance from the origin to a constellation point represent symbol energy (or instantaneous power) </li></ul><ul><li>An M-QAM modulation increases bit-rate by log 2 M </li></ul><ul><li>Noise fuzzes the constellation points and induce bit errors </li></ul><ul><li>For a certain noise level, separation between constellation points determine BER </li></ul><ul><ul><li>Signal power (amplitude squared) increases as M </li></ul></ul><ul><ul><li>Consistent with Shannon’s theory! </li></ul></ul><ul><ul><li>If we fix power, simple constellations help to space constellation points apart and give low BER </li></ul></ul>I Q noise conditional signal probability 0000 0100 a /2 I Q M-QAM signal constellation 1100 1000 0001 0101 1101 1001 1011 1111 0111 0011 0010 0110 1110 1010  d
  7. 7. Modulation Formats - View from Constellation Diagrams <ul><li>For the same constellation point spacing, BPSK requires the smallest energy </li></ul><ul><ul><li>Best OSNR performance </li></ul></ul><ul><li>Constant symbol energy for BPSK and QPSK </li></ul><ul><ul><li>Non-linear index of refraction </li></ul></ul><ul><ul><li>Minimize non-linear effects by keeping |E| constant </li></ul></ul><ul><li>Optical phase enables more robust transmission and more information to be carried </li></ul>0000 0100 a /2 I Q I Q I Q I Q (a) OOK (b) BPSK (c) QPSK (d) 16-QAM 0 1 1 0 00 10 11 01 1100 1000 0001 0101 1101 1001 1011 1111 0111 0011 0010 0110 1110 1010 Function of modulation format
  8. 8. Self Coherent Modulation <ul><li>A reference local oscillator (LO) required to demodulate phase encoding  coherent receiver </li></ul><ul><ul><li>Implemented either with traditional PLL or </li></ul></ul><ul><ul><li>With free running LO laser and high-speed DSP </li></ul></ul><ul><li>Self coherent (or differential phase ) modulation encodes information as phase difference between adjacent symbols </li></ul><ul><ul><li>Use previous symbol as reference for phase decoding </li></ul></ul><ul><ul><li>Avoid local oscillator and DSP </li></ul></ul><ul><ul><li>Quick to implement with existing optoelectronic technologies </li></ul></ul>Coherent BPSK Receiver DPSK Receiver PC Rx LO CDR CDR Rx 1-bit delay
  9. 9. Complexity vs. Benefits Pre-coded Data CDR Rx Modulation Transmitter Receiver OSNR (dB) @ 1e-3 , 42.7G NRZ-OOK NRZ-DPSK NRZ- DQPSK (no pol-mux) 16 dB 1 bit/symbol 14 dB 1 bit/symbol 15 dB 2 bits/symbol LD Data LD Pre-coded data-I LD Pre-coded Data-Q  /2 CDR Rx 1-symbol delay  CDR  I-branch data Q-branch data CDR Rx 1-bit delay
  10. 10. Spectral Efficiency – Where Are We Today? M. Nakazawa: ECOC 2008 paper Tu.1.E.1 C-band: W=4THz , OSNR = 16dB (P/N=14.1dB @40Gb/s) Total Capacity (b/s) Spectral Efficiency (b/s/Hz) Shannon Limit 18.8T 4.7 Commercial Systems 10G x 40  (100GHz spacing) 400 G 0.1 10G x 80  (50GHz spacing) 800 G 0.2 40G x 40  (100GHz spacing) 1.6 T 0.4 40G x 80  (50GHz spacing) 3.2 T 0.8
  11. 11. EDFA C-band (Bandwidth = 4 THz) Utilization To support 50GHz spaced 100GE, we need to achieve C/W = 2 (b/s)/Hz 4x 100GbE 10G,100GHz space 10G, 50GHz space 10G, 12.5GHz space 8x 100GbE 32x 100GbE (125GHz space) C-band Gain + lowest fiber loss Maximizes P/N in Shannon capacity 80 x 100GbE (50GHz space) Commercially achieved
  12. 12. Metro / Regional WDM Network Architecture Metro/Regional WDM Transport Backbone PON LAN Wi-Max or LTE EDFA DCM ROADM DCM TRX TRX TRX
  13. 13. Typical Optical Layer Characteristics <ul><li>Topology: Ring / Mesh </li></ul><ul><li>Reach: 300km – 1000km, irregular span lengths </li></ul><ul><li>Wavelength plan: </li></ul><ul><ul><li>C-band (32nm bandwidth) </li></ul></ul><ul><ul><li>40x100GHz-spaced or 80x50GHz-spaced  </li></ul></ul><ul><li>Data rate: 9.95 – 11.1Gb/s per  </li></ul><ul><li>Amplification: </li></ul><ul><ul><li>EDFA, 17dBm-21dBm, Gain controlled: G = 15dB - 25dB </li></ul></ul><ul><li>OSNR: 16dB </li></ul><ul><li>Dispersion map: </li></ul><ul><ul><li>periodically compensated with 500ps/nm residual dispersion </li></ul></ul><ul><li>PMD tolerance: </li></ul><ul><ul><li>10ps mean DGD (30ps peak DGD) </li></ul></ul>
  14. 14. Challenges to Upgrade to 40Gb/s & 100Gb/s per Lambda <ul><li>OSNR  bit rate </li></ul><ul><ul><li>From 10Gb/s to 40Gb/s, OSNR needs to increase by 6dB </li></ul></ul><ul><ul><li>Need higher launch power to obtain OSNR, non-linearity limit </li></ul></ul><ul><li>PMD tolerance  1/ (bit rate) (first order) </li></ul><ul><ul><li>20% field fiber has PMD > 0.3ps/  km, i.e. a mean DGD >9.5ps for 1000km. </li></ul></ul><ul><ul><li>Requires PMD compensation </li></ul></ul><ul><li>Chromatic dispersion tolerance  1/ (bit rate) 2 </li></ul><ul><ul><li>Dynamic CD compensation needed </li></ul></ul>For the same modulation format NRZ-OOK Bit Rate (b/s) Residual Dispersion Equivalent SMF Length 2.5G 10880 ps/nm 640 km 10G 680 ps/nm 40 km 40G 42.5 ps/nm 2.5 km 100G 6.8 ps/nm 0.4 km NRZ-OOK Bit Rate (b/s) Mean DGD @ 1dB OSNR Penalty (ps) 10G 11 40G 2.7
  15. 15. Upgrade Strategies <ul><li>Lower the power (or OSNR) requirements </li></ul><ul><ul><li>Use more power efficient phase modulation, and/or coherent receivers </li></ul></ul><ul><ul><li>Ultra-FEC </li></ul></ul><ul><li>Lower the symbol rate </li></ul><ul><ul><li>Increase dispersion tolerance with longer symbol period </li></ul></ul><ul><ul><li>Reduce the signal spectrum </li></ul></ul><ul><ul><li>Example: QPSK, DQSPK, M-QAM, OFDM, DMC (Dense Multi-Carrier) </li></ul></ul><ul><li>Spectral control </li></ul><ul><ul><li>Spectral shaping, limit dispersion BW seen by CD and PMD </li></ul></ul><ul><ul><li>Example: PSBT (i.e. duobinary) modulation, pulse shaping </li></ul></ul><ul><li>Make use of polarization dimension </li></ul><ul><ul><li>Double capacity w/o increasing symbol rate </li></ul></ul><ul><ul><li>Requires significant polarization tracking or signal processing efforts </li></ul></ul>Cost effectiveness and compatibility with legacy 10Gb/s infrastructure is very important, especially in today’s tough economy!
  16. 16. Third-Generation Ultra-FEC
  17. 17. DSP Based Coherent Receiver with Polarization Multiplexing <ul><li>Best OSNR sensitivity </li></ul><ul><ul><li>12.5dB @ 46Gb/s, BER = 10 -3 </li></ul></ul><ul><li>Dual polarization </li></ul><ul><ul><li>Lower symbol rate and high spectral efficiency </li></ul></ul><ul><li>High complexity </li></ul><ul><ul><li>Expensive DSP not readily available </li></ul></ul><ul><ul><li>23Gs/s A/D converter x 4 </li></ul></ul>0    90 - degree hybrid A/D A/D 0    90 - degree hybrid A/D A/D Rx / Tx DSP F EC X Y PBC 90 o CW X-Pol I X-Pol Q Y-Pol I Y-Pol Q DPMZ Modulators Hi-speed ASIC 90 o LO
  18. 18. Non-linearity in PM-QPSK Oriol Bertran Pardo et. al: “Investigation of design options for overlaying 40Gb/s coherent PDM-QPSK channels over a 10Gb/s system infrastructure,” OFC 2008, paper OTuM 5 Performance significantly affected by XPM induced by neighboring 10G NRZ OOK signals.
  19. 19. 10-Gbaud Dense Multi-Carrier Technology <ul><li>Slice the signal into multiple 10-Gsymbol/s sub-carriers </li></ul><ul><ul><li>Maintain the existing 10G network engineering design rules </li></ul></ul><ul><ul><li>Non-intrusive plug-and-play upgrade from 10G to 40G and 100G </li></ul></ul><ul><li>Total spectral widths of subcarriers stay within ITU grid </li></ul><ul><li>Built with 10G-grade technologies </li></ul><ul><ul><li>Take advantage of fast 10G cost erosion </li></ul></ul><ul><ul><li>A balance between cost, performance and time-to-market </li></ul></ul>10Gbaud Dense Multicarrier Technology 40G (4x10G) 100G (5x20G) 100GHz 100GHz or 50GHz-spaced 100GHz-spaced 40G (2x20G) 50GHz 50GHz-spaced 50GHz
  20. 20. Cost Ratio Comparison of 40G/10G Technologies Source: H. Bosco, “Network Evolution to 40Gb/s”, ECOC 2008 Cost of 40G interface is significantly higher than that of 4x10G! DMC 40G DMC 100G OpNext Estimate
  21. 21. 40Gb/s Line Side Modulation Scheme Comparison DMC – 4x10G DMC – 2x20G PSBT (ODB) NRZ-DPSK RZ-DQPSK PM-QPSK Relative Cost Estimate -20% -10% 0% +20% +60% +75% CD Tolerance (ps/nm) 2000 500 320 100 200 35000 PMD Tolerance (ps) 10 (17) 10 2.1 2.5 8 30 OSNR Sensitivity (dB) 16.5 13.5 17.5 14 15 11 XPM Tolerance from 10G High High High High Low Low Applications Upgrade any 10G infra-structure + Greenfield Upgrade any 10G infra-structure + Greenfield Green Field Green Field Green Field Upgrade any 2.5G/10G infrastructure without 10G NRZ neighbors
  22. 22. 40G Muxponder Line Card
  23. 23. Pay-as-you grow 100-G product Version 1 Demonstrated at NXTCOMM 2008 Version 2 Q1/2009 100G (5x20G) 40G (2x20G) 20G Module 2RU 19” CX-100G
  24. 24. DMC 40G/100G + NRZ 10G transmission through 1000km SMF-28 100G 40G 40G 10G 10G 10G 10G 10G 10G 10G
  25. 25. 4x10G DMC Lab/Field Trials in 2008 Lab#1 Lab#2 Lab#3 Field#1 Field#2 Field#3 Reach 975km SMF-28 1910km SMF-28 565km SMF-28 130km SMF-28 860km G.655 752km G.652 #spans, span distance 13x75km 80kmx25 7 spans, 50-105km 1 span 12 spans, 10-90km 50-100km span OSNR @BER=1e-3 16.5 dB 16.7 dB after 1601km 16.4 dB 17.1 dB after 752km PMD Tolerance 9 ps (1dB Q) 10 ps (1dB OSNR) CD Tolerance -135km ~ +160km SMF-28 -2500 ~ +1750 ps/nm -2500 ~ +1750 ps/nm Filtering Tolerance 100GHz DWDM Mux/demux 2x 100/50GHz inter-leavers 4 WSS 100GHz DWDM Mux/demux 25GHz OAD 0.5-dB BW 200GHz DWDM mux/demux Fiber Nonlinearity Tolerance +6 dBm/ch +0 dBm/ch +6 dBm/ch > +4 dBm/ch > +4 dBm/ch #10G OOK neighbors 39 14 2 2 3 12
  26. 26. Optical Spectrum of 39x10G NRZ + DMC 1x40G OpVista’s 40G DMC 975km SMF-28
  27. 27. 40G DMC through 975km SMF-28 with 39x10G Signals #1 #2 #8 #14 Error-free transmission for 37 hours With DCF
  28. 28. Received spectra for a 1750 km (23 spans) customer lab test <ul><li>The penalty from 100 GHz spacing to 50GHz is less than 0.3 dB </li></ul>-4dBm launch power
  29. 29. 1750 km (23 SPANS), Four-wave Mixing Test <ul><li>No FWM observed at nominal launch power conditions </li></ul><ul><li>A negligible rise of the noise floor indicated a certain amount of FWM products between sub-channels at +2dBm launch conditions. </li></ul><ul><li>Even under extreme channel power FWM penalty appeared negligible for SMF fiber systems </li></ul>Received spectrum for launch power 6 dB above the nominal (2 dBm/ch) Received spectrum for nominal launch power (-4 dBm/ch)
  30. 30. Best-of-class Non-linearity Tolerance FEC Limit 4x 10G DMC Performance Q or OSNR (dB)
  31. 31. Transparent Network Backbone <ul><li>Increasing the capacity by adding more wavelengths (i.e.: BW) is easier than changing modulation format (linear vs. logarithmic) </li></ul><ul><li>Keep the backbone free of bandwidth constraints for the most flexible wavelength plan and upgrade paths. </li></ul><ul><ul><li>Avoid OADMs with channelized filtering responses, e.g. PLC based MUX+DMUX </li></ul></ul><ul><ul><li>Avoid deploying channelized DCMs (e.g. sampled gratings) on the backbone. </li></ul></ul><ul><ul><li>Use scalable ROADMs </li></ul></ul><ul><ul><ul><li>Bandwidth narrowing is no concern </li></ul></ul></ul><ul><ul><ul><li>No channelized wavelength plan limitations </li></ul></ul></ul>
  32. 32. Scalable ROADM Principle <ul><li>All add/drops are implemented with broadband couplers and splitters </li></ul><ul><li>Filtering is done off the backbone ring </li></ul><ul><li>Open span keeps ring from lasing </li></ul> 2 T R X T R X  1  2  1 JAD Protection Span Clients Clients Working Path Node 1 Node 2 Node 3 Node 4 Node 5 Protection Path Protection Couplers
  33. 33. Protection Switching  2 T R X T R X  1  2  1 JAD Protection Span Clients Clients Working Path Node 1 Node 2 Node 3 Node 4 Node 5 Protection Path Protection Couplers
  34. 34. Scalable ROADM Network Interface TRX: transceiver JAD: Junction add/drop (a) System Diagram (b) JAD Cards
  35. 35. Scalable ROADM Node Add/Drops <ul><li>Broadcast and select architecture </li></ul><ul><li>No initial wavelength reuse, save cost by over-provisioning wavelengths </li></ul><ul><li>Add wavelength blockers as wavelengths are running out </li></ul>Line Out Line In PD Line In Line Out PD 1:n 1:n Ea st We st Tx Rx WB WB OSC T R T R
  36. 36. Field Tested Technology OFC/NFOEC 2009 Paper JWA86
  37. 37. Conclusion <ul><li>Ubiquitous broadband and converged networks are straining the bandwidths in backbone networks. </li></ul><ul><li>10G -> 40G upgrade need is imminent, 100G is being actively researched. </li></ul><ul><li>Bandwidth efficiencies are becoming more and more important as the available fiber bandwidths are being exhausted. </li></ul><ul><li>Advanced modulation schemes pave the way for future optical transport networks. </li></ul><ul><li>DMC provides a cost-effective solution for upgrading embedded 10G infrastructure with good system performance. </li></ul><ul><li>Scalable ROADM ensures a backbone path for unconstrained bandwidth upgrade. </li></ul>

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