利用多泵浦半導體光源之寬頻且增益平坦的拉曼放大器

Abstract

寬頻拉曼光纖放大器在超寬頻長途電信的應用上特別引人注意。因為與一般傳統通常放大1.55um波段的摻鉺光纖放大器相比，拉曼光纖放大器在整個從1.1到1.7um的低損耗波段皆具光放大功用。它是以原本已經舖設好的光纖作為增益介質，且拉曼放大具有分布式放大以及大大的擴展了頻寬等優點。 在此論文中，我們利用六個不同波長的泵浦半導體光源架設出一100nm頻寬之拉曼光纖放大器。我們將泵浦雷射波長以非對稱性的方式設置且無使用增益相等濾波器，達到約為1dB的增益平坦度。此外，我們也提出一雙向的泵浦架構，其同時使得拉曼增益及噪聲指數在整個放大頻寬皆有很不錯的平坦度。 最後，我們在一個六頻道的分波多工系統中比較當信號被擷取或是輸入信號功率改變時，拉曼放大器及摻鉺光纖放大器兩者增益的變化量。結果，拉曼放大器的增益變動程度是明顯的比摻鉺光纖放大器要小許多。由此我們可以得知拉曼放大器在分波多工放大器上非常具有發展潛力，因為其不只在信號擷取時提供了一個增益穩定輸出且可以有相當自由的輸入信號變化量。

Broadband silica fiber Raman amplifiers (FRAs) are particularly attractive for ultra-broadband applications in telecommunications. Raman amplifiers can operate throughout the low loss window of optical fibers from 1.1 to 1.7um compared with conventional erbium doped amplifiers, which are deployed in the 1.55um region. Raman amplification offers the advantages of greatly extended bandwidth and distributed amplification with the installed fiber as the gain medium. In this thesis, we demonstrate 100-nm bandwidth Raman amplifiers using 6-wavelength channel WDM pump laser diode unit. The gain flatness is about 1 dB, which is achieved through an asymmetric channel allocation of pump and without any gain equalization filters. Besides, we proposed an optimized bi-directional pumping scheme which realized a good flatness of Raman gain and noise figure spectra, simultaneously. Finally, in a six-channel WDM system, the gain variations of DRA and EDFA are compared under the situation of dropping the signal channel and changing the input signal power. The degree of gain fluctuation of DRA is remarkably smaller than that of EDFA. It can be concluded that the DRA is a potential candidate for WDM amplifier, which provides gain-lock output of drop channel and relatively free of input signal power variations.