Alloptical gaincontrolled lumped Raman fibre amplifier

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All-optical gain-controlled lumped Raman fibre
amplifier

• Miroslav Karásek
• Jirí Kanka
• Pavel Honzátko
• Jan Radil

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All-optical gain-controlled lumped Raman fibre
amplifierOutline

• Transient effects in Raman fibre amplifiers
• Numerical simulations
• Experimental verification
• Conclusions

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All-optical gain-controlled lumped Raman fibre
amplifier Transient effects in Raman fibre
amplifiers

• 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

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All-optical gain-controlled lumped Raman fibre
amplifierNumerical simulations

• Propagation of signals, pumps and spectral
  components of amplified spontaneous emission
  (ASE) is described by the following partial
  differential equation

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All-optical gain-controlled lumped Raman fibre
amplifierNumerical simulations

• The above equation represents a set of partial
  differential equations for down-stream and
  up-stream propagating optical powers P(z,t,?),
  P-(z,t,?) contained in frequency slot ?? and
  describe their evolution in space (along the
  fibre axis), z and time t
• P(z,t,?), P-(z,t,?) represent the down-stream
  signals Ps(z,t,?s), up-stream pumps P-p (z,t,?p)
  and down-stream and up-stream ASE spectral
  components P?ASE(z,t,?)
• Vg(?), ?(?) and ?(?) is the frequency dependent
  group velocity, fiber background loss, and the
  Rayleigh back scattering coefficient
• gR(?-?) is the Raman gain coefficient between
  waves with frequency ? and ?, Keff and Aeff

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All-optical gain-controlled lumped Raman fibre
amplifierNumerical simulations
Schematic diagram for numerical simulations.
Boundary conditions for signals, pumps, and ASE
components
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All-optical gain-controlled lumped Raman fibre
amplifierNumerical simulations
Simulation data DCF - OFS EWBDK1360 L16km, D
-1260ps/nm Pp0(1445nm)800mW 8 WDM channels
starting at 1543nm 1nm spacing, Ps0
-12dBm/channel
Net gain at 1543nm as a function of input power
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All-optical gain-controlled lumped Raman fibre
amplifierNumerical simulations
Output power variation at 1543nm Unclamped
regime
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All-optical gain-controlled lumped Raman fibre
amplifierNumerical simulations
Output power variation at 1543nm clamped regime
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All-optical gain-controlled lumped Raman fibre
amplifierNumerical simulations
Time evolution of lasing power at 1551nm
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All-optical gain-controlled lumped Raman fibre
amplifierNumerical simulations
Different degree of clamping
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All-optical gain-controlled lumped Raman fibre
amplifierExperiment
Experimental set-up
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All-optical gain-controlled lumped Raman fibre
amplifierExperiment
Spectral dependence of net gain
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All-optical gain-controlled lumped Raman fibre
amplifierExperiment
Net gain at 1538nm as a function of input power
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All-optical gain-controlled lumped Raman fibre
amplifierExperiment
Output power fluctuation at 1540nm with and
without AOGC
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All-optical gain-controlled lumped Raman fibre
amplifierConclusions

• 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

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All-optical gain-controlled lumped Raman fibre
amplifier

• Thank you for your attention!