| Summary: | 碩士 === 國立臺灣科技大學 === 工程技術研究所 === 83 === The modulation response of erbium-doped fiber amplifiers
(EDFAs) is studied experimentally and theoretically in this
thesis. Experiments are performed for a 980nm pump source and
an 1560nm signal source sinusoidally modulated at frequencies
between 100Hz and 10kHz. It is found that the signal gains
decrease progressively for the modulation frequency below 1kHz.
At about 100Hz, the phase difference bteween input and output
optical signals reaches the maximum. By the rate equation
analysis and under the assumption of sinusoidal variations in
signal and population of metastable level, the theoretical
results agree well with the experimental ones. At 1kHz and
10kHz modulation frequencies, the experimental results show
that EDFAs can improve the second-order distortion, and the
distortion is reduced further as the pump power is increased.
It is found that the theoretical and experimental results have
the same trends. Moreover, the theoretical analysis shows that
the optimal length of the maximum signal gain corresponds to
the length of the minimum second-order distortion. The optical
pulses with 100Hz and 1kHz modulation frequency and 50% duty
cycle are on the experiments of the transient response of an
EDFA. The output optical pulses are similar to the electronic
pulses with low frequency distortions. It shows that the
combination of an ideal amplifier and a differentiator can be
used to describe the characteristics of an EDFA. The degree of
distortion in pulses can be reduced by increasing pump power. A
good agreement between the theoretical and experimental results
is also found.
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