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SEEFIRE
Optical Amplifiers and Line Spans
www.seefire.org
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
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, 14-15 July 2005
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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, 14-15 July 2005
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Optical Fibre 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, 14-15 July 2005
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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, 14-15 July 2005
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Raman Amplifiers
Based on simulated Raman scattering, active environment – common
(non- doped) fiber
G in <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, 14-15 July 2005
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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, 14-15 July 2005
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Spectral usability of Amplifiers
O
S C L
SEEFIRE Technical Workshop – Sofia, Bulgaria, 14-15 July 2005
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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, 14-15 July 2005
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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, 14-15 July 2005
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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, 14-15 July 2005
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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, 14-15 July 2005
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Single span
Loss limitations especially
CD - needn´t be fully compensated
No accumulation of noise and nonlinear effect
Results - vendor 1
80 channels @10Gb/s - 46 dB
20 channels @ 10Gb/s - 57 dB
1 channels @2.5Gb/s - 68 dB
Results - vendor 2
20 channels @10Gb/s - 60 dB (66 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, 14-15 July 2005
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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 dB span systems
OSC is amplified (1550nm)
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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
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Amplifier Examples
EDFA
Raman
SOA
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Thank you for your attention!
Questions?
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