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Plenary: ACC Workshop

Plenary: ACC Workshop. Robust and Reconfigurable High-Capacity Optical Communication Systems. Alan E. Willner. University of Southern California Los Angeles, CA 90089-2565. Thank You !. … to Drs. Ady, Arie, and Mark.

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Plenary: ACC Workshop

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  1. Plenary: ACC Workshop Robust and Reconfigurable High-Capacity Optical Communication Systems Alan E. Willner University of Southern California Los Angeles, CA 90089-2565

  2. Thank You ! … to Drs. Ady, Arie, and Mark. The generous support and collaboration of CISCO, DARPA, HP, Intel, NSF, Packard Foundation and SPAWAR.

  3. John Tyndall

  4. The OCLAB Family OIDA : Chicago vs Hawaii

  5. Replace Function, Not Device Function Electronic Device Photonic Device Replace Integrated Photonics Nick Tabellion, CTO, Fujitsu Softek: "The commonly used number is: For every $1 to purchase storage, you spend $9 to have someone manage it." Cost:Equipment < Operation < Management Integrated Photonics Integrated Photonics Enable monitoring and automated management

  6. “Brittle Network” Bran Ferren Chief Creative Officer Applied Minds, Inc., USA OFC - Plenary Speaker ‘06 Predicted“bursting” of bubble in ‘97 • Optical systems are brittle • Optical systems are difficult to use • Need “plug-and-play” robustness

  7. Outline • Monitoring for Self-Managed Networks • Heterogeneous Systems • Reconfigurability • Modulation Formats • “Functional” Photonics • Optical Signal Processing • Delay Elements Using Slow Light • Musings

  8. Think “wireless laptop LAN” …

  9. Self-Managed Networks B A C E • “Adaptive” Resources • Diagnose and repair • BW allocation • Gain/Loss • Dispersion Compensation • -Routing • Look-up tables D Today : Measure, Make, Tweak, Pray. Automation + Intelligence + Monitoring Keep the person out of the loop

  10. Labor-intensive operation Complicated Network Planning Manual DWDM Network Life-Cycle:Present Mode of Operation Manual provisioning of optical design parameters Manual provisioning of equipment & topology into EMS/NMS Manual installation, manual power measurements and VOA tweaking at every site for every l Manual DWDM processes: labor intensive and error prone Result: high OpEx costs R. Ramaswami, L. Paraschis

  11. Window of Operability bit rate format • Window of operability is shrinking as systems become more complex • Ensuring a long-term stable and healthy network is difficult power number of channels wavelength range distance Monitor Power Wavelength Chirp Extinction ratio Chromatic dispersion Polarization mode dispersion Nonlinearities

  12. Monitoring the State of the Network Window of operability is shrinking Monitoring is required • Monitor non-catastrophic data degradation • Isolate specific impairments • Ubiquitous deployment • Graceful routing based on physical state of network? Ubiquitous Monitoring Locate Faults Detect Attacks Diagnose & Assess Repair Damage Reroute & Balance Traffic Malicious Behavior Telcos: Human Error (~1/3 of outages)

  13. Vestigial Sideband Optical Filtering Optical Carrier f VSB-U VSB-L BW fU fL Frequency f0

  14. Q. Yu, JLT, 2003

  15. Polarization Mode Dispersion (PMD) cross section side view Elliptical Fiber Core 1st-order PMD = DGD The 2 polarization modes propagate at different speeds. Probability of Exceeding a Specific DGD (%) 50 50 10 10 0.1 0.1 1 1 • PMD induces randomly changing degradations. • Critical limitation at • >10 Gbit/s data rates. Probability Distribution Maxwellian Maxwellian distribution distribution tail tail 0 0 0 10 10 10 20 20 20 30 30 30 40 40 40 50 50 50 Differential Group Delay (ps) Significant higher-order effects can exist.

  16.   t Axis 1 Axis 1 Upper t Axis 2 Lower Axis 2 In Phase Out of Phase Out of Phase RF Clock Tone Fading Two Clocks Carrier CD (Freq. Delay) t Upper Lower clock Upper clock Lower t In Phase  Power Upper Clock PMD (AxisDelay) f

  17. OSNR Monitoring Using Polarization Nulling Polarizer (Parallel) Ps + 0.5*Pase Arbitrarily Polarized signal + Unpolarized noise 0.5*Pase Polarizer (Orthogonal) Polarization controller Ps + Pase • The received signal (together with noise) is split into two orthogonal polarization components. • The polarization ratio is a measure of the OSNR (Ps/Pase). • The performance could be affected by various polarization effects (i.e., PMD, nonlinear birefringence, and partially polarized ASE noise due to polarization-dependent loss). Y. C. Chung et. al., JLT, 2006

  18. Power meter Power meter OSNR Monitoring for Multiple Modulation Formats • ¼ Bit Delay-line Interferometer is used for OSNR monitoring • One output port gives constructive (Pconst) while the other port • provides destructive interference (Pdest). • OSNR is proportional to the Ratio (=Pconst / Pdest) • This method is applicable to multiple modulation formats Y. Lize, et. al., ECOC ‘06 & OFC ‘07

  19. Concept of PMD-Based Interfermetric Filter Low DGD High DGD Fast Slow axis SOP Tunable DGD Emulator Polarization Beam Splitter Slow RF Spectrum Analyzer ∆τ Destructive 450 relative to PBS Fast axis Constructive Optical Spectrum of Destructive Port DGD-Generated Interferometric Filter RF Spectrum Optical Power RF Power ∆PRF  f f Near fcarrier 1/∆τ FSR = < 170 MHz (CD-insensitive) • The two outputs of the PBS represent the constructive and destructive filters • of a standard Mach-Zehnder delay-line interfometer (FSR = 1/∆τ). • At the destructive port, the monitored RF power will change with the DGD- • generated interferometric filter response. J.-Y. Yang et. al., ECOC, 2007

  20. -40 -40 10-Gb/s NRZ-DPSK -45 -45 RF Power (dBm) RF Power (dBm) -50 -50 -55 -55 20-Gb/s NRZ-DQPSK -60 -60 -65 -65 -70 -70 0 20 40 60 80 100 0 100 200 300 400 500 600 700 DGD (ps) Chromatic Dispersion (ps/nm) Experimental Results: PMD Monitoring • The RF power measured at 170 MHz increases by ~ 20 dB in the • presence of 0 to 100 ps of DGD. • Chromatic dispersion-insensitive measurements to be within + 1 dB. • The performance and monitoring sensitivity is very similar since • both signals have the same spectral bandwidth. J.-Y. Yang et. al., ECOC, 2007

  21. Combined Effects of PMD and PDL PSP1 Fiber with high PMD PSP1  PSP2 Differential Group Delay PSP1  PSP2 PSP1 PSP2 PSP2 Polarization Mode Dispersion  PSP 1 PDL: Frequency-dependent attenuation PMD: Enhanced time spreading Different Attenuation PSP1  PSP2 Optical Components (PDL=? dB) PSP2 Polarization Dependent Loss (PDL) B. Huttner, et al., JSTQE, 2000 L.-S. Yan, et al., PTL, 2003

  22. Outline • Monitoring for Self-Managed Networks • Heterogeneous Systems • Reconfigurability • Modulation Formats • “Functional” Photonics • Optical Signal Processing • Delay Elements Using Slow Light • Musings

  23. Heterogeneous Systems: One Network Fits All Different Modulation Formats Variable QoS Variable Bit Rate Sub-carrier Multiplexing (D+A)? Future Heterogeneous Network Circuit + Packet Switching? Multiple Wavelength Ranges • Hardware should be reconfigurable and transparent • An intelligent network could use the optimal method from • the application/user viewpoint. Economics: Early market entry of new services (CATV??)

  24. RF to Optical Transition RF/Electronic History Optical History Time Coherent Transmission Multi-level Modulation Transatlantic Transmission FEC Introduced by Shannon Equalization Coherent Optical Systems Multi-level Modulation First Transatlantic Line FEC for Transatlantic Optical Equalization Variable Bit Rate Systems Dynamic Bandwidth Allocation S/W-Defined Radio ? Coherent Systems Revisited? Device Capabilities Drive System Applications Variable Bit Rates Systems? Dynamic Bandwidth Allocation? “S/W-H/W Defined” Reconfigurable Optical Systems?

  25. Follow and Don’t Follow the Leader 2003 2006 11 QAM 37 RZ-DPSK 13 13 NRZ-OOK NRZ-DPSK Switching 23 92 RZ-OOK 7 CSRZ-DPSK 18 Amplification 46 38 5 1 APSK NRZ-DQPSK Modulation Formats 46 105 9 3 RZ-DQPSK AMI Wavelength Converters 15 21 Coherent 8 17 BPSK Special Fibers 44 61 7 5 QPSK OFDM PMD 52 60 3 8PSK Total 640 700 Don’t Follow: Be Creative “If somebody tells you it can’t be done, don’t listen to him.” - Joe Goldstein, Nobel Laureate Remember the “Inefficient” 3-Level EDFA? Follow: Don’t Be Foolish Modulation Formats, OFC’06 Number of Papers at OFC ( “Thanks, Herwig” )

  26. Differential Phase-Shift-Keying (DPSK) DPSK 1 1 0 1 0 0 t Constant optical power RZ-DPSK 1 1 0 1 0 0 t Pulse appears in every bit

  27. Concept of DPSK Phase

  28. p/2 Benefit vs. Complexity: Integration Hardware complexity Mach-Zehnder modulator Data Precoded Data LP Data Clock Delay interferometer Precoded Data Clock Precoded Data Clock Control Precoded Data • Coherent DetectionLaser LO and 90-degree hybridRF post-processing and increased sensitivity A. Gnauck, P. Winzer, R. Essiambre, 2005

  29. SlowAxis Fast Axis

  30. SlowAxis Fast Axis

  31. DQPSK Detection Overview DQPSK “typically” requires two DLI’s to detect 4 phase locations: +45° in one arm of in-phase (I) DLI -45° in one arm of quadrature (Q) DLI +45° In-Phase (I) - T -45° Quadrature (Q) - T

  32. Grooming: Dynamic BW Allocation Tunable BW filter Variable Bit-Rate Channel Yao, et al., OFC, 2006 Matched Filter 10 8 6 4 2 2 0 4 6 8 10 12 14 0 - Optimize OSNR Sensitivity Penalty Gq (dB) Optical BW (Bit-rate) - Efficient allocation Pfennigbauer, et al., PTL, 2002

  33. Outline • Monitoring for Self-Managed Networks • Heterogeneous Systems • Reconfigurability • Modulation Formats • “Functional” Photonics • Optical Signal Processing • Delay Elements Using Slow Light • Musings

  34. Delay Applications in Optically-Routed Networks Output ports Packet Switch Buffer Optical synchronization Input ports Control Optical header recognition Optical Switching Node Accurate, widely-tunable optical delays are a potentially valuablerequirement for future optically-switched networks to enable synchronization, header recognition & buffering

  35. Widely Tunable Optical Delay 10G NRZ in c in in c Tunable  Converter 2 PPLN Dispersion Module DCF Tunable Dispersion Compensator Chirped FBG Tunable  Converter 1 PPLN Signal in Signal out Fast Lane in B A B A B Wavelength Converter 1 Dispersion Module Wavelength Converter 2 + Tunable Dispersion Compensator TDC Slow Lane c A A A • Little additive noise • Phase preserving (for phase modulation signal) • Modulation format and bit rate independent • Broadband (> 80 nm) Requirements for  converter: Y. Wang, et. al., IEEE PTL, 19, 861-863 (2007)

  36. 44-ns Tunable Delay Relative Delay (ps) = Dispersion (ps/nm) x  Tuning Range (nm) Use wideband wavelength converter Use large dispersion values Use double pump configuration to achieve continuous tunability over the entire range Use dispersion compensation to restore the pulse Double pump configuration offers much wider delay tunability compared to single pump configuration Y. Wang, et. al., IEEE PTL, 19, 861-863 (2007)

  37. Bits & Delay vs. Tuning Wavelength Tuning laser (nm) 10 Gb/s Bits (500ps/div) 1548.40 Delay (ps) 1548.90 1549.42 Tuning wavelength (nm) • Delay is varied by tuning the laser  • Wide tunability is achieved by using a 2-pump PPLN configuration and 2000 ps/nm dispersion module • Continuous tunability up to 44-ns is demonstrated for a 10 Gb/s NRZ system Y. Wang, ECOC 2005 & PTL 2007

  38. Packet Processing using Widely-Tunable Delay l2 P2 P1 P2 P3 P1 l1 Delay Module P3 l1 l1 l l l c c 1 Wavelength Dispersion Wavelength Dispersion Converter Element Converter Compensator (PPLN - 1) (DCF) (PPLN - 2) (FBG) l2 lc l1 Dispersive Media P P L N P P L N l1 Intra-Channel Dispersion Compensator DCF ΔT Delay time Intra-channel dispersion Inter-channel dispersion DCF dispersion X Δlconverted Delay I. Fazal, et. al., Optics. Express, 15, (2007)

  39. Packet Synchronization and Multiplexing 276 ps Back to Back Single Channel Muxed Channel Amplitude log10(BER) Time (100ps/div) Received Power (dBm) l2 (non-delayed) Packet length = 196 bits @10G l2 MUX l1(delayed by 26.4ns) l1 Delay Module l1 and l2 and multiplexed time Reconfigurability • Two packet streams @ 10G synchronized and multiplexed • Reconfiguration time of < 300 ps demonstrated I. Fazal, et. al., Optics. Express, 15, (2007)

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