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Optical Amplifiers and Line Spans

Optical Amplifiers and Line Spans. Josef Vojtěch CESNET Czech Republic josef.vojtech(at)cesnet.cz www.ces.net. Overview . Optical Amplifiers Optical Amplifiers in General Optical Fibre Amplifiers, EDFAs Ramans SOAs Amplifiers for (D)WDM Line Spans Single Span (NIL) Multi Span.

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Optical Amplifiers and Line Spans

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  1. Optical Amplifiers and Line Spans Josef Vojtěch CESNET Czech Republic josef.vojtech(at)cesnet.cz www.ces.net The SEEFIRE project is co-funded by the European Commission under the FP6 IST contract no. 15817

  2. Overview • Optical Amplifiers • Optical Amplifiers in General • Optical Fibre Amplifiers, EDFAs • Ramans • SOAs • Amplifiers for (D)WDM • Line Spans • Single Span (NIL) • Multi Span SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 2

  3. Optical Amplifiers in General • Ideal Optical Amplifier (OA) • High gain, polarization independent • Large bandwidth • High output power • Adds no noise • Basic types of OA (according principle) • Optical fibre amplifiers • Raman OA • Semiconductor OA (SOA) SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 3

  4. OpticalFibre Amplifiers • Active environment – special fibre doped with one or more rare earth element (Er, Nd, Pr, Tm,…or combination Er/Yb, Tm/Yb,..) • PDFA • Pr doped, suitable for (1280-1340nm) • G>30dB, Pout >16 dBm, NF <7dB • TDFA • Tm doped, suitable for (1440-1520nm) • G>30dB, Pout >20 dBm, NF <7dB SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 4

  5. Erbium-Doped Fiber Amplifiers • Most widespread in telecommunications • Suitable for C band (lowest fiber attenuation) • common silica glass • Advantages • Operating range in 1520-1610nm • G>45dB, Pout >37 dBm, NF in <3.5,7>dB • Multi-channel crosstalk very low • Polarization independent • Disadvantages • Not small devices, cannot be integrated with other semiconductors • Gain spectrum not inherently flat SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 5

  6. Raman Amplifiers • Based on simulated Raman scattering, active environment – common (non- doped) fiber • Gin <10,15>dB, Pout >30 dBm, NF < 1 dB • Advantages • Usable in 1250-1650 nm regions • Bandwith can be tailored (1 pump 35nm, more pump up to 90nm) • Lower NF than EDFA • High process efficiency in DCF (loss -> gain) component • Disadvantages • Higher interchannel crosstalk than EDFA • High pump powers (safety issues) SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 6

  7. Semiconductor Optical Amplifiers • Based on conventional laser principle, active environment – waveguide region sandwiched between n and p regions • G>25dB, Pout >15 dBm, NF in <7,10>dB • Advantages • Usable in 1310 1550 nm regions • Wide band (40-80nm) • Small compact semiconductors, easy to integrate • Disadvantages • Higher NF than EDFA • Higher interchannel crosstalk than EDFA • Polarization sensitive SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 7

  8. Spectral usability of Amplifiers O C L S SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 8

  9. Amplifiers for (D)WDM I • EDFA – needs gain flattening • Glass composition (F, Te glass host) • Single stage EDFA, silica host: bandwidth 15nm • Single stage EDFA, fluoride host: bandwidth 25nm • Equalizers • Two stage, silica or fluoride host, no gain flattening: 30nm • Two stage, silica host, gain flattening: 50nm • Two stage, tellurite host, gain flattening: 80nm • Hybrid OA • Multi-arm - two band operation, silica host: 85nm SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 9

  10. Amplifiers for (D)WDM II • Hybrid EDFA/Raman • Bandwidth can be tailored ~80nm • Lower NF than EDFA separate Signal power in periodically amplified system. Comparison between original (EDFA system) and hybrid system OSNR improvement SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 10

  11. Line Spans • Main path length limitations • Losses • Optical power budget of a path (System margin) = (Tx output power) – (Rx sensitivity) – (ƩLoses) • Chromatic dispersion • Polarization-mode dispersion(>=10Gb/s) SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 11

  12. Line Spans • Other limitations • OSNR (esp. in amplifier cascades) • Crosstalk • Fiber nonlinearities • Stimulated Raman and Brillouin scattering • Four-wave mixing, Self-phase mudulation, cross-phase modulation SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 12

  13. Single span • Loss limitations especially • CD - needn´t be fully compensated • No accumulation of noise and nonlinear effect • Results - vendor 1 Results - vendor 2 • 80 channels @10Gb/s - 46 dB • 20 channels @ 10Gb/s - 57 dB 20 channels @10Gb/s - 60 dB (66 dB) • 1 channels@2.5Gb/s - 68 dB 1 channel@10Gb/s - 63 dB (75 dB) • CESNET results • 1 channel@10Gb/s - 65 dB • 1 channel@1Gb/s - 71 dB SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 13

  14. Multiple span • Noise and nonlinear effect accumulation • Typical span 20 or 25 dB • Given by non amplified OSC channel (1510nm,1625nm) • Example of system performance • 80 channels@10 Gb/s • 30*20dB or 16*25dB, 25*25dB with Raman ampliffication • However exist 35 dBspan systems • OSC is amplified (1550nm) SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 14

  15. Bibliography • Ramaswami R., Sivarijan K.N., “Optical Networks“, 2nd edition, 2002. • Agrawal G.P., “Fiber-Optic Comminications Systems”, 2002. • Islam M.N.,”Raman Amplifiers for Tellecomunication 1,2”, 2004. • Becker P.C., Olsson N.A., Simpson J.R., “Erbium-Doped Fiber Amplifiers”, 1999 SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 15

  16. Amplifier Examples EDFA Raman SOA SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 16

  17. Thank you for your attention! Questions? SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 17

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