ROADM Technologies for Flexible - Tbitsec Optical Networks
6 likes4,757 views
This document discusses technologies for flexible, high-capacity optical networks, including ROADMs. It describes how ROADMs are used to manage traffic through optical network intersections. It then summarizes technologies like coherent Nyquist filtering, superchannels, flexible grid WSS, hybrid Raman-EDFA amplifiers, and multi-port flexgrid optical channel monitors that enable increased network capacity, reduced costs, and transparent wavelength management for 400Gb/s and 1Tb/s transmission. These improved ROADM subsystems will enable more future-proof ROADM architectures.
ROADM Technologies for Flexible - Tbitsec Optical Networks
- 1. © 2014 Finisar Corporation ROADM Technologies for Flexible, Tbit/sec Optical Networks Simon Poole Director, New Business Ventures
- 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. © 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. © 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. © 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. © 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. © 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. © 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. © 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. © 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. © 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. © 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. © 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. © 2014 Finisar Corporation 14 8 Degree ROADM Comparison
- 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. © 2014 Finisar Corporation Optical Amplifiers: Size, Power, SNR
- 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. © 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. © 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. © 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. © 2014 Finisar Corporation Optical Channel Monitors: Flexgrid, Superchannels and SDN
- 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. © 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. © 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. © 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