近年來，在通訊網路上，資料傳輸的速度及容量需求越來越大，因此為了使得傳輸速度加快，我們必須使用全光資料形式轉換，也就是說，不希望使用到任何的光電的轉換，因為ㄧ當牽扯到電的領域，資料的傳輸速度就不快(在電領域上傳輸資料最多可達幾百Mb，但是在光的領域，速度可高達幾十Gb)。在通訊網路上，資料從一個端點傳輸到另外一個端點，資料上必須隱含著位址的訊息，否則資料會不知傳送到哪兒。隱含位址訊息的稱之為標籤(label)，這個標籤訊號，會在進入通訊網路時，額外的附加上去，以期能正確傳輸，當資料送達目的地時，此標籤訊號再卸載下來。在此，不管資料或標籤，都是以光的形式傳輸，以期達到速度及容量的要求。
資料從一個端點傳送到另一個端點，標籤必須重新換過才能傳到下一個端點，也就是說，舊的標籤清除，新的標籤寫入。在本論文裡，我們將焦點集中在標籤的清除及重新寫入。在此，我們利用光放大器來實現標籤清除及重新寫入。我們提出了幾種架構來實現標籤清除及重新寫入；一種是環形架構，另一種是串聯式光放大器架構。我們就藉由量測眼圖及誤碼率來比較其效果好壞。由模擬量測得到初步的結果發現串聯式的光放大器架構效果比較好。不過，尚有可改善的空間，待以後學弟妹可加以繼續深入研究。

In the future communication network, high speed and capacity are necessary for the growing demand for data, audio and video transmission. Thus all-optical network is needed. In communication network, data from one node to another node needs a label to indicate its destination. The label carries the information of address. Therefore we need to erase old label and rewrite new one when the packet is sent from one node to another. We focus on label erasing and rewriting in this paper. A new structure is proposed to implement label erasing and rewriting. We implement this by optical amplifier. Because the optical amplifier has the characteristic of power saturation, we use this characteristic to implement it. Here, we compare some setups and their performance of label erasing and rewriting in order to construct the best setup for label erasing and rewriting.

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