Analysis of Modulation Response in Erbium-Doped Fiber Amplifiers

• Main Authors: Jau-Ji Jou, 周肇基
• Other Authors: Cheng-Kuang Liu
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/33091098353307211330

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.