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LightPath Networking

LightPath Networking. Light Propagation. Light propagates due to total internal reflection Light > critical angle will be confined to the core Light < critical angle will be lost in the cladding. Fiber Types. Multi-Mode: supports hundreds paths for light.

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LightPath Networking

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  1. LightPath Networking

  2. Light Propagation • Light propagates due to total internal reflection • Light > critical angle will be confined to the core • Light < critical angle will be lost in the cladding

  3. Fiber Types • Multi-Mode: supports hundreds paths for light. • Single-Mode: supports a singlepath for light

  4. Multi-Mode 50/62.5um core, 125um clad Atten-MHz/km: 200 MHz/km Atten-dB/km: 3dB @ 850nm MMF has an orange jacket Single-Mode 9um core, 125um cladding Atten-dB/km: 0.4/0.3dB 1310nm/1550nm SMF has a yellow jacket Fiber Types

  5. Attenuation Vs. Wavelength

  6. Degradation In Fiber Optic Cable • Attenuation • Loss of light power as the signal travels through optical cable • Dispersion • Spreading of signal pulses as they travel through optical cable

  7. Technologies Available Transmitters (Light Sources) • LED’s - 850/1310nm • Used with MMF up to 250Mb/s • Short distances <1 Km • Semiconductor Lasers – 850/1310/1550nm • VCSEL’s, Fabry Perot and DFB • 1310/1550 can be used with MMF or SMF • Short to long distances • Low to High data rates (Mb/s to Gb/s)

  8. FP and DFB Laser Spectrum • FP laser • Emits multiple evenly spaced wavelengths • Spectral width = 4nm • DFB laser • Tuned cavity to limit output to single oscillation / wavelength • Spectral width = 0.1nm

  9. Fabry Perot Ideal for low cost pt-pt MMF or SMF Not suitable for WDM due to +/- 30nm  variation Dispersion is a serious issue at Gb/s rates Distributed Feed Back Used in wavelength division multiplexing systems Less susceptible to dispersion than FP laser Used for medium and long haul applications Which Laser Type is Better?

  10. Technologies Available Receivers (Detectors) • PIN Photodiodes • Silicon for shorter ’s (eg 850nm) • InGaAs for longer ’s (eg 1310/1550nm) • Good optical sensitivity • Avalanche Photodiodes (APD’s) • Up to 50% more sensitivity than PIN diodes • Primarily for extended distances in Gb/s rates • Much higher cost than PIN diodes

  11. Dispersion - Single-Mode • FP and DFB lasers have finite spectral widths and transmit multiple wavelengths • Different wavelengths travel at different speeds over fiber • A pulse of light spreads as it travels through an optical fiber eventually overlapping the neighboring pulse • Narrower sources (e.g DFB vs. FP) yield less dispersion • Issue at high rates (>1Ghz) for longer distances (>50Km)

  12. Dispersion - Multi-Mode Fiber • Modal Dispersion • The larger the core of the fiber, the more rays can propagate making the dispersion more noticeable • Dispersion determines the distance a signal can travel on a multi mode fiber

  13. Attenuation • It is the reduction of light power over the length of the fiber. • It’s mainly caused by scattering. • It depends on the transmission frequency. • It’s measured in dB/km ( )

  14. Chromatic Dispersion (CD) • Light from lasers consists of a range of wavelengths, each of which travels at a slightly different speed. This results to light pulse spreading over time. • It’s measured in psec/nm/km. • The chromatic dispersion effects increase for high rates. Source www.teraxion.com

  15. Transmission Bands • Optical transmission is conducted in wavelength regions, called “bands”. • Commercial DWDM systems typically transmit at the C-band • Mainly because of the Erbium-Doped Fiber Amplifiers (EDFA). • Commercial CWDM systems typically transmit at the S, C and L bands. • ITU-T has defined the wavelength grid for xWDM transmission • G.694.1 recommendation for DWDM transmission, covering S, C and L bands. • G.694.2 recommendation for CWDM transmission, covering O, E, S, C and L bands.

  16. Single Mode Fiber Standards I • ITU-T G.652 – standard Single Mode Fiber (SMF) or Non Dispersion Shifted Fiber (NDSF). • The most commonly deployed fiber (95% of worldwide deployments). • “Water Peak Region”: it is the wavelength region of approximately 80 nanometers (nm) centered on 1383 nm with high attenuation.

  17. Single Mode Fiber Standards II • ITU-T G.652c - Low Water Peak Non Dispersion Shifted Fiber.

  18. Single Mode Fiber Standards III • ITU-T G.653 – Dispersion Shifted Fiber (DSF) • It shifts the zero dispersion value within the C-band. • Channels allocated at the C-band are seriously affected by noise due to nonlinear effects (Four Wave Mixing).

  19. Single Mode Fiber Standards IV • ITU-T G.655 – Non Zero Dispersion Shifted Fiber (NZDSF) • Small amount of chromatic dispersion at C-band: minimization of nonlinear effects • Optimized for DWDM transmission (C and L bands)

  20. Single Mode Fiber Standards

  21. Multiplexing - WDM WDM Multiplexed signal Signal 1 Signal 1 • Wavelengths travel independently • Data rate and signal format on each wavelength is completely independent • Designed for SMF fiber Signal 2 Signal 2 MUX DEMUX Signal 3 Signal 3 Single-mode Fiber Signal 4 Signal 4

  22. Multiplexing - WDM WDM – Wave Division Multiplexing • Earliest technology • Mux/Demux of two optical wavelengths (1310nm/1550nm) • Wide wavelength spacing means • Low cost, uncooled lasers can be used • Low cost, filters can be used • Limited usefulness due to low mux count

  23. Multiplexing - DWDM DWDM – Dense Wave Division Multiplexing • Mux/Demux of narrowly spaced wavelengths • 400 / 200 / 100 / 50 GHz Channel spacing • 3.2 / 1.6 / 0.8 / 0.4 nm wavelength spacing • Up to 160 wavelengths per fiber • Narrow spacing = higher cost implementation • More expensive lasers and filters to separate ’s • Primarily for Telco backbone – Distance • Means to add uncompressed Video signals to existing fiber

  24. Multiplexing - CWDM CWDM – Coarse Wave Division Multiplexing • Newest technology (ITU Std G.694.2) • Based on DWDM but simpler and more robust • Wider wavelength spacing (20 nm) • Up to 18 wavelengths per fiber • Uses un-cooled lasers and simpler filters • Significant system cost savings over DWDM • DWDM can be used with CWDM to increase channel count or link budget

  25. CWDM Optical Spectrum • 20nm spaced wavelengths

  26. DWDM vs. CWDM Spectrum 1.6nm Spacing dB 1470 1490 1510 1530 1550 1570 1590 1610 Wavelength

  27. xWDM Technology Dense WDM • Fine channel spacing, 0.8 nm typical • High precision stabilization of Lasers • High component cost 0,8 nm l/nm 1550 Coarse WDM • Wide channel spacing, 20 nm typical • Lower precision of Lasers • Significantly lower component cost 20 nm l/nm 1470 1490 1510 1530 1550 1570 1590 1610

  28. DWDM Migration Capacity Expansion l/nm 1470 1490 1510 1530 1550 1570 1590 1610 • Each CWDM channel can be utilized with 8 DWDM channels • Resulting maximum system capacity: • 8 x 8 = 64 DWDM channels • CWDM and DWDM channels can be mixed • Soft migration path

  29. DWDM Migration CWDM to DWDM Channel utilization 2,5 Gbps ch1 8ch DWDM : DWDM ch2 CWDM & DWDM CWDM : ch8 ch8 • 8 channel DWDM system per CWDM channel • Soft migration path • Mixing of CWDM and DWDM channels • No interruption of CWDM channels

  30. AmplificationCWDM vs. DWDM 80 km 80 km Requires 1 amplifier per wavelength CWDM wavelengths • EDFA: Erbium-doped Fibre Amplifier • DWDM is typically used for longer distance transport, because EDFA amplifiers enable very long spans more cost-effectively than CWDM. • Amplifiers typically cost approximately US$ 20k or more { 1 EDFA amplifies all wavelengths in the C-band EDFA C-band (DWDM wavelengths) { Requires 1 amplifier per wavelength L-band

  31. How Much Capacity ?

  32. Optical Routing - Definitions • Optical Routers – Optical IN , Optical OUT • Photonic Routers – Optical IN & OUT but 100% photonic path • OOO- Optical to Optical to Optical switching • Optical switch fabric • OEO- Optical to Electrical to Optical conversion • Electrical switch fabric • Regenerative input and outputs

  33. Photonic Technologies • MEMS (Micro Electro-Mechanical System) • Liquid Crystal • MASS (Micro-Actuation and Sensing System )

  34. MEMS Technology • Steer the Mirror • Tilted mirrors shunt light in various directions • 2D MEMS • Mirrors arrayed on a single level, or plane • Off or On state: Either deployed (on), not deployed (off) • 3D MEMS • Mirrors arrayed on two or more planes, allowing light to be shaped in a broader range of ways • Fast switching speed (ns) • Photonic switch is 1:1 IN to OUT (i.e. no broadcast mode)

  35. Liquid Crystal Technology • Gate the light • No Moving Parts • Slow switch speed • Small sizes (32x32) • Operation based on polarization: • One polarization component reflects off surfaces • Second polarization component transmits through surface

  36. MASS Technology • Steer the fiber • Opto-mechanics uses piezoelectric actuators • Same technology as Hard Disk Readers and Ink Jet Printer Heads • Small-scale opt mechanics: no sliding parts • Longer switch time (<10msec)

  37. OE EO OE EO OE EO OE EO OE EO OE EO OE EO OE EO OE EO OE EO OE EO OE EO OE EO OE EO OE EO OE EO X EQ OEO Technology Fiber Inputs High BW Electrical XPNT Fiber Outputs Electrical Inputs EQ EQ EQ EQ EQ EQ EQ EQ EQ EQ EQ EQ EQ EQ EQ Electrical Outputs Local Monitoring CPU Indication Interface

  38. OEO Routing • Optical <> Electrical conversion at inputs/outputs • Provides optical gain (e.g. 23 dB) • High BW, rate agnostic electrical switching at core • SD, HD, Analog Video (digitized), RGBHV, DVI • Fast switching (<10us) • Full broadcast mode • One IN to ANY/Many outputs • Build-in EO / OE to interface with coax plant • Save converter costs

  39. Regeneration - Optical vs Photonic • Photonic is a lossy device that provide no re-amplification or regeneration • Signal coming in at –23dBm leaves at –25dBm • OEO router provides 2R or 3R (re-amplify, reclock, regenerate) • Signals come in at any level to –25dBm • Leave at –7dBm (1310nm) or 0dBm (CWDM)

  40. Applications - Design Considerations • Types of signals • Signal associations • Fiber infrastructure • Distance/Loss • Redundancy • Remote Monitoring

  41. Types of Signals FacilityLINK - Fiber Optics Platform MULTI WAVELENGTH MULTI FIBER SDI HDSDI ANALOG DVB-ASI RGB OR VIDEO AES ANALOG DOLBY E INTERCOM AUDIO OPTICAL ROUTING WDM CWDM DWDM SPLITTERS + PROTECTION SWITCHING RS232/422/485 GPI/GPO CONTROL 10/100 ETHERNET GBE FIBER CHANNEL DATACOM 70/140 MHz I/F L-BAND CATV RF SONET OC3/12 T1/E1 DS3/E3 TELECOM

  42. Design Considerations Fault Protection • Protection against fiber breaks • Important in CWDM and DWDM systems • Need 2:1 Auto-changeover function with “switching intelligence” • Measurement of optical power levels on fiber • Ability to set optical thresholds • Revert functions to control restoration

  43. Design Considerations • Remote monitoring is key due to distance issues • Monitor • Input signal presence and validity • Laser functionality and bias • Optical Link status and link errors • Pre-emptive Monitoring • Input cable equalization level • CRC errors on coax or fiber interface • Optical power monitoring • Data logging of all error’d events • Error tracking and acknowledgment

  44. Design Examples – Single Link -7dBm @ 1310nm -32dBm SDI @ 270Mb/s SDI @ 270Mb/s SD EO SD OE 40 Km’s -7dBm @ 1310nm -23dBm HDSDI @ 1.485Gb/s HDSDI @ 1.485Gb/s HD EO HD OE 40 Km’s Loss Budget Dispersion

  45. Post House Facility Link – New Location #2 Location #1 SDI @ 270Mb/s E to O O to E O to E E to O 1310 SDI @ 270Mb/s E to O O to E O to E E to O HDSDI @ 1.485Gb/s HDSDI @ 1.485Gb/s Analog Video Analog Audio Mux + EO OE+Demux Demux+OE EO + Mux Analog Video Analog Audio Mux + EO OE+Demux Demux+OE EO + Mux Analog Video Analog Audio Analog Video Analog Audio CWDM D16 CWDM M16 2 Km’s Gbe Gbe GBE GBE 10/100 Mb/s Ethernet 10/100 Mb/s Ethernet 10/100 10/100 RS422 RS422 RS422 RS422 Mux +EO Demux +OE Demux +OE Mux + EO AES AES

  46. RF Over fiber optics -Applications Satellite Receiver Typical Satellite Application With SNMP Monitoring Satellite Receiver L-Band Downlink (950Mhz – 2250Mhz) Satellite Receiver Vertical Satellite Receiver DA8-RF BPX-RF LB EO LB OE Router Horizontal Satellite Receiver BPX-RF LB EO LB OE LNB Power Satellite Receiver Remote SNMP Monitoring & Control Satellite Receiver Ethernet / SNMP Ethernet / SNMP Ethernet / SNMP HPA DA-RF Video Mod C or Ku Up Conv BPX-RF IF OE IF EO DA-RF Video Mod IF Uplink (70/140Mhz)

  47. KRCA KNBC KVEA 2.3 2.9 7.3 2.3 2.3 Extra KABC RSE Prospect 25 mi 25 mi KCBS CNN 9 Net KTLA 1.1 1.1 Australia 1.5 1.1 Ent .. 2.7 CBS Fox 2.1 Tonight VYVX 4 mi Fiber 11 mi 0 Fox Intelsat 1.5 Sports RSH 0.5 5.5 mi 8 mi RSK 0.5 8 mi 9.8 mi KSCI One Wilshire 5.5 mi 0.5 6.2 KTTV E! 0.8 NCTC Pac TV 7.25 0.7 KMEX Japan 0.75 Telecom Globesat 10.5 13.5 mi Direct TV 10.5 BT Large Video MAN – Fully protected KABC Circle seven LA Zoo 5.75 TV Gaming 7.25 Dodger Stadium 2.5 7.5

  48. Single Fiber Technology

  49. 4Gbps CWDM Link • SANET, AMREJ – cheapest solution • Gigabit Ethernet, • Low cost switches as repeaters (Cisco 3550) • CWDM

  50. 8 ch. Mux Demux CWDM ch 1 CWDM ch 2 CWDM ch 3 CWDM line .. .. CWDM ch 8 Power1 Power2 2 ch. Add Drop Mux Line West A/D West ch 1 ch 2 .. Passive Optical A/D East ch 1 Line East ch 2 Line Interf. Active Optical 4 ch. Add Drop Mux Line West A/D West ch 1 .. ch 4 .. ch 1 .. Ch 4 A/D East .. Line East Modular xWDM System Passive Optical Modules • Options: • 8 channels Mux/Demux • 2 channels Add/Drop • 4 channels Add/Drop

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