Superluminal and slow-light propagation in erbium-doped optical fibers are theoretically modeled. The pump and signal fields are allowed to be intensity modulated at the same frequency, and propagation effects are included in the model. The levels of advancement, delay, and distortion are determined as functions of system parameters such as modulation frequency, input pump power, modulation indexes of the pump and signal powers, input signal power, fiber length, and the relative phase of the pump and signal modulation. Two methods are analyzed for enhancing the frequency response while ensuring that distortion values remain tolerable. The first method assumes no modulation of the pump wave, although the pump power is adjusted for each signal modulation frequency. A flat frequency response for frequencies up to several kilohertz is obtained, although signal advancements are limited to low values. In the second method, the pump power is modulated with a phase that needs to be controlled with respect to that of the signal. Advancements and delays are increased by this procedure, and distortion values remain tolerable. The frequency response is not made worse for advancements and it is improved for delays. Moreover, absorption need not accompany slow light for this method.
Modulation Frequency Pump Power Signal Power Modulation Index Signal Distortion
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