摻鉺光纖放大器在光纖通訊上的應用

Applications of Er-Doped Fiber Amplifiers on Optical Fiber Communications

張志聿(Chih-Yu Chang)

指導教授 ： 余合興

國立臺北科技大學/電資學院/電機工程系研究所/碩士(2007年)

https://doi.org/10.6841/NTUT.2007.00421

摘要

本研究首先對傳統的摻鉺光纖放大器(EDFA)進行特性量測，以模擬的方式獲得放大器特性之後，再加以分析與討論；實驗方面，以低功率（-20 dBm）1552.5 nm波長的訊號光源及980 nm波長的激勵雷射為激勵光源，針對順向式激發的摻鉺光纖放大器，逐一詳測其系統特性，選取最佳長度的摻鉺光纖。
此外，本研究特別注重如何設計摻鉺光纖放大器以獲取最大的輸出光增益及有效地降低其雜訊數值。利用調整光隔離器位置以阻絕光纖諧振腔的最大反向放大性自發放射，並用複合式摻鉺光纖放大器來達到改善特性的目的。在激發功率為20 dBm，對摻鉺光纖長度為30 公尺的此一系統模擬時，可得最大光增益37.0 dB和低雜訊數值3.08 dB，其最佳光隔離器擺設位置在光纖總長度的前13％。對同樣系統進行實驗，其最大光增益及雜訊數值分別為26.5 dB 及4.5 dB，其最佳光隔離器位置離光源14％，與模擬的最佳位置十分相近，可獲得的光纖放大器之最佳特性比典型的傳統順向式光纖放大器改善許多。
最後，本論文也對線性及環型兩種光纖雷射進行探討。在摻鉺光纖長度為2 m時，改良式環型雷射3 dB光譜寬度約為0.05 nm，旁模抑制比約45 dB，比起一般DFB雷射，線寬0.05 nm及旁模抑制比40 dB，更為優越。

關鍵字

摻鉺光纖放大器 ； 光隔離器 ； 光增益 ； 雜訊數值

並列摘要

Simulated and experimental treatments have been carried out for conventional Er-doped fiber amplifiers (EDFAs). With appropriate signal lasers of 1552.5 nm and the pump laser of 980 nm, detailed investigation, particularly for forward-pumping EDFAs, was completed and then characterized in order to determine the optimal length of the Er-doped fiber for the further survey in this work.
It has been known that the bit-error rate is strongly relating to signal-to-noise ratio of digital communications. Successfully suppressed or filtered out the backward amplified spontaneous emission, i.e. one of the main noise sources, will certainly result in high-bit rate transmission in optical communications. We have composed composite EDFAs by using the fibers with the above-mentioned optimal length and similar configuration as conventional forward pumping EDFAs. Inserting an optical isolator in the composite amplifier and adjusting its relative position, best performance of the EDFAs can be achieved. Very low system noise figure of 4.5 dB, and high optical gain of 26.5 dB were found for the composite amplifiers by using the 30 m-long Er-doped fiber with Er density of 5.8E(24) m-3. Compared to conventional EDFAs with similar system parameters, the composite EDFAs, operated in the optimal condition, showed pronounced improvement on the system performance.
Additionally, two kinds of fiber lasers have been investigated, in which one fiber laser with the fiber length of two meters demonstrated even superior performance to conventional DFB lasers.

並列關鍵字

Er-doped Fiber Amplifiers ； Optical isolator ； Optical Gain ； Noise Figure

參考文獻

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