Abstract
We quantify both theoretically and experimentally the speed
requirements for tuning or switching the wavelength of Raman pumps in
time-division multiplexed (TDM) pumping schemes. Our results indicate that
a periodic sweep-pattern has to be repeated at a rate above 10 kHz to
achieve a temporal Raman gain variation of less than 1 dB at an average
on/off Raman gain of 15 dB in 100 km of transmission fiber. At a 10-kHz
rate, the sensitivity penalty of an optically preamplified receiver
following the 100-km TDM Raman span was measured to be 0.5 dB. Expressed
in terms of pump laser tuning requirements, this translates into a
switching time of 100 ns, requiring a modulation bandwidth of ~10 MHz.
When cascading multiple TDM Raman pumped transmission spans, we calculate
that the worst-case temporal dB-gain variation scales linearly with the
number of spans. At a repetition rate of 50 kHz and when cascading 10
spans, we predict an additional 1 dB of margin needs to be allocated in
the system's power budget.
© 2004 IEEE
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