1. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 1 Transient Gain Dynamics in Saturated Raman Amplifiers with Multiple Counter-propagating Pumps Alberto Bononi and Matteo Fuochi Dipartimento di Ingegneria dellInformazione, 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

2. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 2 MOTIVATION

3. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 3 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 Average inversion

4. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 4 AMPLIFIER BLOCK DIAGRAMS A. Bononi et al. OFC 02 Pump attenuation Walk-off Pump depletion %

5. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 5 Filters: depend on unsaturated pump profile Closed-form formula available RAMAN AMPLIFIER BLOCK DIAGRAM

6. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 6 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

7. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 7 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

8. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 8 EXTENSION TO MULTIPLE PUMPS Direct Signal-signal Raman xtalk

9. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 9 EXTENSION TO MULTIPLE PUMPS Filters: unsaturated pump profiles Raman coefficient Unsaturated gain Need to solve steady-state pump propagation equations to find (bias point) No closed-form filters formulae available

10. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 10 EXAMPLE: ultra-wide bandwidth system NZDSF, L=80 km 1423 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

11. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 11 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!

12. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 12 LIMITS OF MULTIPUMP MODEL less accuracy with resonant pumping 0 5 10 15 20 25 0100200300 (nm) Static Dynamic Gain (dB) Error (dB) 0 100 200 300 (nm) Static Dynamic 0 0.05 0.10 0.15 0.20 0.25

13. Università di Parma March 27, 2003 OFC2003, ThC6 - A.Bononi and M. Fuochi 13 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