因為在傳統的 C-頻段及 L-頻段的單縱模輸出之摻鉺光纖迴路式雷射已經被廣泛的討論及應用，然而在 S-頻段的波長範圍內尚具較少的研究及討論。因此，在本篇文章裡，我們將先簡易地介紹 S-頻段的摻鉺光纖放大器的操作原理及設計方式，之後再並利用兩種不同的雷射架構及其他技術以獲致在 S-頻段單縱模態輸出之光纖迴路雷射，並且透過實驗結果證明該些光纖雷射可以操作在單縱模的行為上。

Conventional erbium-doped fiber ring laser with single-longitudinal-mode outputs in the C- and Lbands were discussed and applied extensively. However, the operating bandwidth in S-band has not studied and investigated enough. In this paper, we will introduce the design and operating principle in S-band erbium-doped fiber amplifier. Simultaneously, using two laser architectures will retrieve the single-frequency operation. In addition, the stability of stable output has also been demonstrated experimentally.