Repetition Rate Requirements for Time-Division Multiplexed Raman Pumping

We quantify both theoretically and experimentally the speed requirements for pump tuning or switching in a time-division multiplexed Raman pumping scheme. Our results indicate that a periodic sweep-pattern has to be repeated at a rate above 50kHz to achieve temporal Raman gain variations less than 0.25dB at an average on/off. Raman gain of 15dB in 100km of non-zero dispersion shifted fiber (NZDSF). At a repetition rate of 10kHz, the sensitivity penalty of an optically preamplified receiver following the 100km time- division multiplexed Raman span was measured to be 0.5dB. Expressed in terms of pump laser tuning requirements, this translates into a switching time of 100ns (a modulation bandwidth of ~ 10MHz). When cascading multiple time-division multiplexed Raman pumped transmission spans, we calculate that the temporal gain variations (expressed in dB) scale linearly with the number of spans. At a repetition rate of 50kHz, cascading 10 spans will require an additional 1dB of margin to be allocated in the system's power budget.