Gain modulation dynamics of a Raman amplified WDM system using time-division multiplexed pumps

The gain modulation characteristics of an 80 nm wide, counter-pumped distributed Raman amplified WDM system has been studied when the pumps are time division multiplexed. When many optical amplifiers are employed in multi-repeater transoceanic systems, the pump is intensity modulated to obtain information about the health of the repeaters. Gain modulation dynamics referring to dynamics of pump modulation transferred to the signal is studied to help make a reasonable choice of pump wavelength for modulation and to provide power compensation if necessary from the resulting power penalty. In this paper, we study using numerical modeling, the effect of time division multiplexed pumping on the gain modulation dynamics in a WDM system. It is found that modulation transfer response is flatter and stronger across the WDM channels when the Raman amplifier pumps are time division multiplexed. The resulting increase in power penalty is determined.