Power transients in time-division multiplexed discrete Raman fibre amplifier

In this paper, the effect of addition and/or dropping of wavelength-division multiplexed channels in an all-optical gain-clamped time-division multiplexed (TDM) pumped discrete Raman fibre amplifier (DRFA) has been investigated experimentally and analyzed by numerical simulation. Nineteen signals were amplified in a counter-directionally pumped DRFA consisting of 13km long dispersion compensating fibre. Light of eight DFB lasers was square-wave modulated at 2kHz to imitate channel addition/dropping and combined with signals from five 10 Gigabit Ethernet transmitters and with six continuous wave signals. Power transients of the surviving channels caused by cross-gain modulation of the DRFA were monitored at the output of the amplifier. All-optical feedback loop was implemented in the form of a ring laser. Theoretical analysis of the TDM-pumped DRFA was based on numerical solution of coupled propagation equations for backward propagating pumps, signals, and both forward and backward propagating spectral components of amplified spontaneous emission powers.