March 27, 2003

Università di Parma

OFC2003, ThC6 - A.Bononi and M. Fuochi 1

Transient Gain Dynamics in Saturated Raman Amplifiers

with Multiple Counter-propagating PumpsAlberto Bononi and Matteo Fuochi

Dipartimento di Ingegneria dell’Informazione, Università di Parma, Parco Area delle Scienze 181A, 43100 Parma, Italy

e-mail: bononi@tlc.unipr.it

Motivation Amplifier block diagrams Model assumptions and limitations Examples Conclusions

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OFC2003, ThC6 - A.Bononi and M. Fuochi 2

MOTIVATION

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AMPLIFIER BLOCK DIAGRAMS

Y. Sun et al. JSAQE Aug 97

A. Bononi et al. JLT May 98

S. Novak et al. JLT June 02

|H

21

Average inversion

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AMPLIFIER BLOCK DIAGRAMS

A. Bononi et al. OFC 02

dp

2

Pump

attenuation

Walk-off

Pump depletion %

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OFC2003, ThC6 - A.Bononi and M. Fuochi 5

Filters:depend on unsaturated pump profile

Closed-form formula available

dp

2

RAMAN AMPLIFIER BLOCK DIAGRAM

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RAMAN AMPLIFIER BLOCK DIAGRAM

No signal-signal Raman Xtalk

in amplification region

A. Bononi et al. El. Lett. July 01

D. N. Christodoulides et al. PTL Dec. 96

Direct signal-signal

Raman xtalk can be easily

added using known model

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RAMAN AMPLIFIER BLOCK DIAGRAM

No signal-signal Raman Xtalk in amplifier

No noise (ASRS)

No Rayleigh backscattering (RBS)

Pump depletion < 30 %

Applicable only to backward pump

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EXTENSION TO MULTIPLE PUMPS

Direct

Signal-signal

Raman

xtalk

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EXTENSION TO MULTIPLE PUMPS

Filters:

dL

dLt

dzzP

dzdt

zGzP

LGdth

L

p

d

tL

jp

j

pjjpjp

2/

')'(

')'()'(

)(

/)(

0

0

unsaturated pump profilesRaman coefficient

)')'(exp()(01

z

p

M

pjpjj dzzPzzG

Unsaturated gain

Need to solve steady-state pump propagation

equations to find (bias point)

No closed-form filters formulae available

)(zPp

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EXAMPLE: ultra-wide bandwidth system

NZDSF, L=80 km1423 nm

Pumps

1443 nm

1464 nm

1465 nm

(590 mW)C. R. S. Fludger et al. OFC 02

1520 nm

1610 nm

1

80

CW Signals(1 mW/ch)

Static error < 0.3 dB

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EXAMPLE: ultra-wide bandwidth system

All 80 channels ON/OFF modulated, 1 mW ON power, slot time 200 s

Dynamic error < 0.3 dB

Computation time on a laptop:

model: 2 min; exact: 2 hours!

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LIMITS OF MULTIPUMP MODEL

less accuracy with resonant pumping

15801480

0

5

10

15

20

25

0 100 200 300

(nm)

StaticDynamic

Gai

n (

dB

)

Err

or

(dB

)

0 100 200 300

(nm)

Static

Dynamic

0

0.05

0.10

0.15

0.20

0.25

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CONCLUSIONS

Extended Raman amplifier block diagram to multiple pumps

Large computational saving for large WDM systems

Limits: moderate pumps depletion < 30 % less accurate with resonant pumping works only for backward pumps