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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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