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ROADM Technologies for Flexible - Tbitsec Optical Networks

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ROADM Technologies for Flexible - Tbitsec Optical Networks

  1. 1. © 2014 Finisar Corporation ROADM Technologies for Flexible, Tbit/sec Optical Networks Simon Poole Director, New Business Ventures
  2. 2. © 2014 Finisar Corporation 2 ROADM Proliferation  ROADMs are used to manage transparent traffic through the intersections of a WDM network;  3 prime functions:  Wavelength Switching  Amplification  Signal Integrity Monitoring 2 Switching Cost Relative to OSI Layer
  3. 3. © 2014 Finisar Corporation 3 Problem: How to reduce cost of transmission Increase Capacity Coherent Nyquist Filtering Superchannels Flexible Grid Amplifiers Monitoring Defragmentation etc Dual WSS Amplifiers Reduce Capex Route & Select CD/CDC Size Power Reduce Opex Cost of Transmission ($/Gb/sec/km)
  4. 4. © 2014 Finisar Corporation 4 Increasing Capacity: Nyquist & Superchannels  Third generation coherent transmitters add a filtering (digital/analog) at transmitter to minimise optical bandwidth of signal (Nyquist output)  A superchannel is a multi- carrier group of channels that is operationally managed as a single channel and which can be presented to higher networking layers as a single higher data rate channel. (May or may not be Nyquist filtered). QPSK RelativePower(dB) Normalized Freq (GHz) 16QAM RelativePower(dB) Normalized Freq (GHz)
  5. 5. © 2014 Finisar Corporation 5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 -25 -20 -15 -10 -5 0 5 10 15 20 25 Rel Freq (GHz) RelIL(dB) -3.0 -2.5 -2.0 -22 -21 -20 -19 -18 -17 Rel Freq (GHz) RelIL(dB) Flexible Grid WSS  First generation WSS allocated a single channel to a single pixel  LCoS-based WSS use a flexible matrix-based wavelength switching platform with megapixel matrices which allows programmable channel bandwidth
  6. 6. © 2014 Finisar Corporation 6 From Fixed-grid to Flexgrid  LCoS technology allows arbitrary channel bandwidth  Trade-off between flexibility and OSS requirements  12.5GHz slices as per ITU G 694.1 (Feb 2012) supports legacy fixed-grid as well as Flexgrid
  7. 7. © 2014 Finisar Corporation 7 Flexgrid & Superchannels Flexgrid™ + superchannels with Nyquist Filtering for maximum Spectral Efficiency Fixed Grid WSS require interchannel guard-bands 35 GHz Pass Bands 15 GHz “Dead Zones” Flexgrid™ WSS + superchannels allow denser channel packing by eliminating inter-channel guard-bands Up to 5 THz Pass Band, 15 GHz “Dead Zone”
  8. 8. © 2014 Finisar Corporation 8 Advanced Flexgrid Functionality  No Limit to Superchannel spectral width  37.5 GHz – 5 THz in 6.25 GHz increments  Intra-channel attenuation control  Attenuation range: 0 to 20 dB  Intra-channel attenuation control of each 6.25 GHz section of a channel  Enables equalization across super channels  Dynamic and scalable channel width  Hitlessly widen, narrow or migrate a channel with 6.25 GHz resolution  Established traffic unaffected  Simplifies defragmentation
  9. 9. © 2014 Finisar Corporation 9 Flexgrid WSS: a proven technology  Finisar has deep experience in LCoS WSS since 2004  More than half of Finisar’s shipped WSS feature flexible grid functionality  Common LCoS Platform Single WSS: 1x4 – 1x20 Dual WSS: 2x1x20, 2xMxN
  10. 10. © 2014 Finisar Corporation 10 Example ROADM Configurations  ROADM design depends on many factors  Network Design  Node Degree(s)  Electronic vs Optical switching  Expandability vs Initial Cost  etc  Traditional Broadcast and Select  Colourless, Directionless (CD)  Colourless, Directionless, Contentionless (CDC)
  11. 11. © 2014 Finisar Corporation 11 Broadcast and Select ROADM  Passive split on Drop-side  WSS on Add-side  AWG for wavelength mux/demux  Fixed Grid  Coloured Add/Drop  100% Add/Drop of 88 channels  2x100 GHz AWGs on add side for lost cost  Fixed-grid OCM Classic (B&S) ROADMOCM 44 ch AWG 88 ch AWG44 ch AWG 1x9WSS 8x8 Span Crossconnect 8x8 Span Crossconnect 1x8splitter 88 ADD 88 DROP
  12. 12. © 2014 Finisar Corporation 12 Colourless, Directionless (CD) ROADM  Typical Requirements  8 degrees with 100% Add/Drop of 96 channels  Flexgrid  NB Limited drop-side filtering – only works for coherent systems  Typical Modularity  Per degree • 2x1x16 (Dual) WSS • Flexgrid OCM • Pre-amp and booster  Per directional switch • 2x6x8 per 96 channels  Per 16 channel Add/Drop • 2x1x16 splitter/couplers • EDFA per splitter/coupler CD ROADM 16x1 coupler OCM 1x16WSS 8x8 Span Crossconnect 8x8 Span Crossconnect 1x16WSS To Directions 2-8 From Directions 2-8 Drop Port 1 16 ADD 16 DROP 6x8 WSS 8x6 WSS Drop Ports 2-8 AMP x6 x6 Add 1 Add Ports 2 - 8 1x16 splitter 8x6 WSS AMP
  13. 13. © 2014 Finisar Corporation 13 Colourless, Directionless, Contentionless, (CDC) ROADM  Typical Requirements  Scalable to 8 degrees with ~30% Add/Drop of 96 channel systems  Flexgrid  NB No drop-side filtering – only works for coherent systems  Example Modularity  Per degree • 2x1x23 (Dual) WSS • Flexgrid OCM • Pre-amp and booster  Per 16 channel Add/Drop • 2x8x16 multicast switch • Quad low-gain EDFA (2 per multicast switch) CDC ROADM OCM 1x23WSS 8x8 Optical Crossconnect 8x8 Optical Crossconnect 1x23WSS To Directions 2 - 8 From Directions 2-8 Drop Port 1 Drop Ports 2-16 16 ADD 16 DROP AMP AMP Add Port 1 Add Ports 2-16 8x16 MCS8x16 MCS
  14. 14. © 2014 Finisar Corporation 14 8 Degree ROADM Comparison
  15. 15. © 2014 Finisar Corporation 15 CDC ROADM , 100% Add Drop 100% capacity on each Add/Drop requires:  1 x 4 splitter  Higher gain amplifiers  Additional MCS on Add/Drop CDC ROADM OCM 1x23WSS 8x8 Optical Crossconnect 8x8 Optical Crossconnect 1x23WSS Drop Port 1 Drop Ports 2-16 Add Port 1 Add Ports 2-16 1x4 splitter From Directions 2-8 16 DROP 8x16 MCS From Directions 2-8 16 DROP 8x16 MCS From Directions 2-8 16 DROP 8x16 MCS AMP
  16. 16. © 2014 Finisar Corporation Optical Amplifiers: Size, Power, SNR
  17. 17. © 2014 Finisar Corporation 17 Honey, I shrunk the EDFA… XFP: 1.5W power consumption APPROXIMATE LIFETIME EXPECTATIONS* Coil diameter (mm) 10 12 14 18 125µm – 3% proof tested fiber <1 year <1 year ~3.17 years >50 years 80µm – 2% proof tested fiber <1 year 0-3.17 years >40 years >50 years 80µm – 3% proof tested fiber >40 years >50 years >50 years >50 years *Cost 218 Model, 4m of fibre
  18. 18. © 2014 Finisar Corporation 18 EDFA Arrays for ROADMs  Shared electronics – reduces cost, power, size  Uncooled pumps - lower power consumption Dual EDFA (70x90 mm) PreAmp and Booster in one box 8 EDFA (183 x 150 x 18.5 mm)
  19. 19. © 2014 Finisar Corporation 19 Hybrid Raman-EDFA  A combination of a counter-propagating Raman pump unit and a variable gain EDFA  Mesh networks  ULH inline amplification  Hut skipping (for high gain range units) Overall Gain Electronics for AGC Control and Eye Safety EDFA 980 Pump Raman 14XX pump(s) 2 or 3-Pump Hybrid Raman EDFA
  20. 20. © 2014 Finisar Corporation 20 Amplifier Trends  Availability of up to 130 channels (37.5 GHz-spaced Nyquist channels within larger superchannels) in the C-band drives higher amplifier output powers.  Mesh topology will drive lower NF (Hybrid Raman-EDFA) and superior dynamics (fast electronics) to allow flexibility in network re-configuration.  Raman and Hybrid Raman-EDFAs will proliferate in long haul systems.  To simplify ROADM control loops, gain uniformity <0.5 dB.  To reduce types of EDFAs used, either gain switched platforms will proliferate or pluggable EDFAs will take off - provided there is no cost penalty
  21. 21. © 2014 Finisar Corporation Optical Channel Monitors: Flexgrid, Superchannels and SDN
  22. 22. © 2014 Finisar Corporation 22 OCM Requirements  Spectral power information with high resolution  Intra-channel attenuation in 6.25 GHz spectral slices  Power monitoring of superchannel carriers  Location of center wavelengths of superchannel carriers  Eliminate power differential between adjacent channels  Fast scanning and response time  Superchannel Add/Drop requires OCM, not just a photodiode, to monitor traffic through Add/Drop paths  Loss of Signal (LoS) and fault detection to support protection and restoration switching  Staring mode - monitoring a fixed frequency  Applications utilizing in-band modulation signals, i.e. wavelength tracking • Possibly demodulate within the OCM  Some proprietary OSNR measurement techniques
  23. 23. © 2014 Finisar Corporation 23 Multi-port Flexgrid Optical Channel Monitor  Grating spectrally disperses light from up to four fibers.  2D MEMS mirror is used to scan the optical spectrum onto an array of photodiodes.
  24. 24. © 2014 Finisar Corporation 24 Example: Multiport Flexgrid OCM  Small size: 100x50x15 mm, Low power: <5 W  Parallel scanning of all ports in 500 ms; no need for dedicated switch  Requires deconvolution of measured signal to provide 6.25 GHz slices required for attenuation control on Flexgrid WSS 2-4 port OCM
  25. 25. © 2014 Finisar Corporation 25 To Summarise… Improved ROADM subsystems (Dual WSS, Hybrid amplifiers, Flexgrid OCM, etc) will enable future-proof ROADM Architectures to provide transparent Wavelength Management Capability for future 400 Gb/sec and 1 Tb/sec

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