February 2-4, 2004ONDM 04, Ghent, Belgium1 All-optical gain-controlled lumped Raman fibre amplifier Miroslav Karásek Jiří Kaňka Pavel Honzátko Jan Radil

February 2-4, 2004ONDM 04, Ghent, Belgium2 All-optical gain-controlled lumped Raman fibre amplifier Outline Transient effects in Raman fibre amplifiers Numerical simulations Experimental verification Conclusions

February 2-4, 2004ONDM 04, Ghent, Belgium3 Optical amplifiers saturate on the total power basis Channel addition/removal or transmission of packets in burst mode would result in output power fluctuations in other channels Some measurements must be taken to eliminate unwanted output power fluctuations Several schemes has been suggested for gain stabilization of EDFAs For lumped Raman fibre amplifiers, the all-optical gain-clamping technique can be used All-optical gain-controlled lumped Raman fibre amplifier Transient effects in Raman fibre amplifiers

February 2-4, 2004ONDM 04, Ghent, Belgium4 All-optical gain-controlled lumped Raman fibre amplifier Numerical simulations Propagation of signals, pumps and spectral components of amplified spontaneous emission (ASE) is described by the following partial differential equation

February 2-4, 2004ONDM 04, Ghent, Belgium5 The above equation represents a set of partial differential equations for down-stream and up-stream propagating optical powers P + (z,t,ν), P - (z,t,ν) contained in frequency slot Δν and describe their evolution in space (along the fibre axis), z and time t P + (z,t,ν), P - (z,t,ν) represent the down-stream signals P + s (z,t,ν s ), up-stream pumps P - p (z,t,ν p ) and down-stream and up-stream ASE spectral components P  ASE (z,t,ν) V g (ν),  (ν) and γ(ν) is the frequency dependent group velocity, fiber background loss, and the Rayleigh back scattering coefficient g R (ν-ζ) is the Raman gain coefficient between waves with frequency ν and ζ, K eff and A eff All-optical gain-controlled lumped Raman fibre amplifier Numerical simulations

February 2-4, 2004ONDM 04, Ghent, Belgium6 Boundary conditions for signals, pumps, and ASE components: Schematic diagram for numerical simulations. All-optical gain-controlled lumped Raman fibre amplifier Numerical simulations

February 2-4, 2004ONDM 04, Ghent, Belgium7 Simulation data: DCF - OFS EWBDK:1360 L=16km, D= -1260ps/nm P p0 (1445nm)=800mW 8 WDM channels starting at 1543nm 1nm spacing, P s0 = -12dBm/channel Net gain at 1543nm as a function of input power All-optical gain-controlled lumped Raman fibre amplifier Numerical simulations

February 2-4, 2004ONDM 04, Ghent, Belgium8 Output power variation at 1543nm Unclamped regime All-optical gain-controlled lumped Raman fibre amplifier Numerical simulations

February 2-4, 2004ONDM 04, Ghent, Belgium9 Output power variation at 1543nm clamped regime All-optical gain-controlled lumped Raman fibre amplifier Numerical simulations

February 2-4, 2004ONDM 04, Ghent, Belgium10 Time evolution of lasing power at 1551nm All-optical gain-controlled lumped Raman fibre amplifier Numerical simulations

February 2-4, 2004ONDM 04, Ghent, Belgium11 Different degree of clamping All-optical gain-controlled lumped Raman fibre amplifier Numerical simulations

February 2-4, 2004ONDM 04, Ghent, Belgium12 Experimental set-up All-optical gain-controlled lumped Raman fibre amplifier Experiment

February 2-4, 2004ONDM 04, Ghent, Belgium13 Spectral dependence of net gain All-optical gain-controlled lumped Raman fibre amplifier Experiment

February 2-4, 2004ONDM 04, Ghent, Belgium14 Net gain at 1538nm as a function of input power All-optical gain-controlled lumped Raman fibre amplifier Experiment

February 2-4, 2004ONDM 04, Ghent, Belgium15 Output power fluctuation at 1540nm with and without AOGC All-optical gain-controlled lumped Raman fibre amplifier Experiment

February 2-4, 2004ONDM 04, Ghent, Belgium16 Surviving channel power fluctuations in lumped RFA have been investigated both theoretically and experimentally It has been shown, that when sufficient lasing is allowed, steady-state surviving channel power fluctuations may be completely eliminated Remaining power surges are about 8 times lower than the steady-state power excursions without AOGC All-optical gain-controlled lumped Raman fibre amplifier Conclusions

February 2-4, 2004ONDM 04, Ghent, Belgium17 Thank you for your attention! All-optical gain-controlled lumped Raman fibre amplifier