A numerical study on instantaneous-phase evolution of femtosecond pulses in an erbium-doped fiber amplifier

This paper focuses on the evolution of pulse intensity and instantaneous phase along the gain fiber. And this motivates to study the effect of pre-chirp to the pulse evolution. Femtosecond pulse amplification using erbium-doped fiber amplifiers (EDFAs) is a critical technique for fiberoptic communications, supercontinuum generation as well as optical frequency comb technology. When designing an ultrafast fiber amplifier, it is necessary to understand the evolution of pulse properties, such as temporal intensity and phase and frequency chirp, during pulse propagation in the gain fiber. Pre-chirping can help increase the obtainable peak power and total energy only when the pulses are chirped to the proper sign, i.e. negative. Also, the amplified pulses generally are positively chirped, and, therefore, require anomalous de-chirping fibers at the output of the amplifiers.