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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

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


Overview
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


Optical amplifiers in general
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


Optical fibre amplifiers
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


Erbium doped fiber amplifiers
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


Raman amplifiers
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


Semiconductor optical amplifiers
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


Spectral usability of amplifiers
Spectral usability of Amplifiers

O

C

L

S

SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 8


Amplifiers for d wdm i
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


Amplifiers for d wdm ii
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


Line spans
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


Line spans1
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


Single span
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 [email protected]/s - 68 dB 1 [email protected]/s - 63 dB (75 dB)

  • CESNET results

    • 1 [email protected]/s - 65 dB

    • 1 [email protected]/s - 71 dB

SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 13


Multiple span
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 [email protected] 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


Bibliography
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


Amplifier examples
Amplifier Examples

EDFA

Raman

SOA

SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 16


Thank you for your attention!

Questions?

SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15July 2005 17


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