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Control of Optical Fibre Communications Networks

Control of Optical Fibre Communications Networks. Peter Farrell. Utopian Vision ALL OPTICAL NETWORK. Analogy with Internet Transmitter sends photons through the network (transparently) to Receiver Format independent Bit-rate independent Protocol independent

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Control of Optical Fibre Communications Networks

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  1. Control of Optical Fibre Communications Networks Peter Farrell

  2. Utopian VisionALL OPTICAL NETWORK • Analogy with Internet • Transmitter sends photons through the network (transparently) to Receiver • Format independent • Bit-rate independent • Protocol independent • The Network is very clever (BRIGHT?) and can figure everything out so that your information goes to its destination perfectly • A bit like • electricity too cheap to meter from the nuclear industryOR • the paper free office

  3. Interesting Problems to Solve to build Utopia • Finance • All the routing problems in the Network • BIG optical switches • Control of adjustable elements in the Network

  4. HOW BIG?

  5. Worldwide?

  6. Darwin Katherine Derby Cairns Cloncurry Tennant Creek Townsville Mt. Isa Hughenden Mackay Sth. Hedland Charters Towers Rockhampton Alice Springs Mt. Newman Bundaberg Meekatharra Toowoomba Mullewa Brisbane Geraldton Glendambo Kalgoorlie Pt. Augusta Ceduna Newcastle Parkes Perth Clare Sydney Hay Adelaide Esperance Canberra Melbourne Established by 1993 Established by 1997 Hobart Continental

  7. Metro

  8. Campus

  9. Size matters because … • Different transmission issues for • 100 m building / campus • 1 km campus • 10 km metro • 100 km metro/continental • 1000 km continental • 10000 km world • All optical network requires (?) 10000 km infrastructure for a 100 m connection

  10. Optical Network Control • Most published work is on making connections, fault location, contention avoidance and so on • Very little on control of adjustable elements in the network to optimise or at least improve the performance • Alternative is to grossly over engineer the hardware

  11. Tx Chirp Noise Finite extinction ratio Mux/Demux Filter drift Crosstalk Transmission fibre Loss Dispersion Nonlinear effects Amplifiers ASE/ Noise Crosstalk Wavelength dependent gain Rx Finite sensitivity Noise Bandwidth Everywhere PMD Tx Tx Rx Rx Point to Point Link Impairments DisCo

  12. Tx Tx Rx Rx Point to Point Link Adjustments • Tx • Power, wavelength, chirp, modulation format, extinction ratio • MUX/DEMUX • Temperature • Amplifier • Gain, gain flattening filter, tilt • Dispersion compensation • Rx • Gain (APD or preamp gain) • Decision Threshold • Decision Point DisCo

  13. Long Haul Link Configuration10 Gbit/s over >1000 km LF LF LF LF LF LF LF LF LM LM LM CCC CCC Tx Terminal Rx Terminal Rx Tx 1 C Blue C Blue Rx Tx Rx Tx 40 DCF DCF Amp n Amp1 TransmissionFibre Transmission Fibre Transmission Fibre Rx Tx 41 DCF DCF DCF DCF Rx Tx C Red C Red R R R Rx Tx 80 … Tx 81 Rx L Blue L Blue Tx Rx DCF 120 Tx DCF DCF DCF Rx DCF DCF CCC CCC Tx 121 Rx Tx Rx L Red L Red Tx Rx 160

  14. Tx Tx Rx Rx Tx Tx Rx Rx Point to Point Link with OADM DisCo OADM DisCo

  15. OADM X

  16. OADM

  17. All Optical Network Rx Tx Rx Tx

  18. Feedback & Control Lots of Feedback Loops …Amplifier • Issues • Measurement accuracy • Signal reduction • Transient response

  19. Dispersion Compensator Dispersion Measurement Lots of Feedback Loops … Dispersion Compensator • Issues • Location • Accuracy • Signal reduction

  20. Lots of Feedback Loops … Pre-emphasis • Shares OSNR, BER or received power equally among channels by adjusting transmit power with time varying disturbances • Simple linear iterative algorithm (and variations on this theme)(Chraplyvy et al 1992) • Non-linear channel!!!! • Like to know • if non-linearity is significantly affecting performance • Origin of non-linearity

  21. Feedback Loops • What do we measure and where? • BER • Channel Powers • OSNR • Dispersion • Non-linearity • Crosstalk • Local? • Central? • Tradeoffs between non linearity, dispersion and gain • How many channels? • Circuit switched or Packet switched? • Interaction with routing algorithms

  22. Control.. • THE WHOLE NETWORK – WORLD DOMINATION • Link by Link • Device by Device

  23. All Optical Network Rx Tx Rx Tx

  24. Tx Chirp Noise Finite extinction ratio Mux/Demux Filter drift Crosstalk Transmission fibre Loss Dispersion Nonlinear effects Amplifiers ASE/ Noise Crosstalk Wavelength dependent gain Rx Finite sensitivity Noise Bandwidth Everywhere PMD Tx Tx Rx Rx Point to Point Link Impairments DisCo

  25. Tx Tx Rx Rx Point to Point Link Adjustments • Tx • Power, wavelength, chirp, modulation format, extinction ratio • MUX/DEMUX • Temperature • Amplifier • Gain, gain flattening filter, tilt • Dispersion compensation • Rx • Gain (APD or preamp gain) • Decision Threshold • Decision Point DisCo

  26. Conclusion • Model network • Use standard control theory to construct a controller

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