光固子通訊系統效能提昇之研究

Abstract

本論文提出幾個改善光固子通訊系統效能的方法。其一是色散遞減光纖用做光固子通訊傳輸的研究，我們發現光固子會與放大器雜訊產生四波混合的現象，而使其能量耗損。使用拖曳型濾波器將可抑制雜訊，降低光固子能量耗損，提昇系統效能；或補償光固子能量，也可達到相同的效果。其二，調整偵測器的偵測時域窗口寬度，以改善光固子通訊系統的Q值。發現其最佳寬度與幾項因素有關，包括：雜訊誘發的時域跳動，雜訊誘發的光固子能量擾動，放大器雜訊，外擴漣波和光固子波寬。其三，在色散管理的光固子通訊系統中考濾光纖耗損與光放大器，研究光固子的穩定性。 若調整最佳化每一階放大器的增益值與光濾波器的頻?，使得其路徑平均波寬最小，將可控制色散管理光固子的穩定性，進而提高系統效益。最後，研究色散管理的光固子通訊系統中，偵測器端加後色散補償以壓縮波形，進而提高系統的Q值。數據顯示加後色散補償光纖與調整偵測時域窗口寬度有助大幅改善光固子通訊系統效能。

In this dissertation, we propose different methods to improve the performance of optical soliton communication system. First, dispersion-exponentially-decreasing fiber is used as transmission fiber between amplifier spacing. Depletion of soliton energy by the four-wave mixing between soliton and amplifier noise in the system with large amplifier spacing is studied. The improvement of the system by the use of sliding-frequency filter to reduce noise power and the depletion of soliton energy is shown. The system can further be improved by compensating for depleted soliton energy. Second, the improvements of the Q factors of 10-Gb/s soliton systems detected by adjusting detection window are studied. We have found that the optimal width of the detection window depends on the noise-induced timing jitter, noise-induced soliton energy fluctuation, amplifier noise, dispersive wave, and soliton pulsewidth. Third, the method to stabilize dispersion-managed (DM) soliton in the presence of fiber loss and optical amplifiers is presented. We optimize in-line filter bandwidth and the relating excess gain for every amplification period so that the path average pulsewidth variation is minimized and the Q factors increases. Fourth, owing to the nature of frequency chirping of a dispersion-managed (DM) soliton, one can compress its pulsewidth with a dispersion compensation fiber at receiver so that the Q value of a DM soliton system can be improved. Numerical results show that significant improvement can be achieved with the pulse compression and proper time domain gating for filtering the radiated waves resulting from the pulse compression.