直接偵測正交分頻多工多級格式I/Q全光升頻系統

Abstract

我們提出了一個新穎的全光升頻直接偵測多級格式正交多頻分工系統。藉由外接調變器產生單邊帶載子壓制調變來產生全光升頻向量訊號，此架構不需要電的混波器及能升頻。為了產生60GHz的訊號，我們引進四倍頻的調變技術，並成功地在60GHz的免授權7GHz頻段產生28Gb/s 16-QAM OFDM訊號。在沒有任何色散補償的狀況下，經過一百公里的單模光纖傳輸，此訊號幾乎沒有損耗。 除此之外，我們還討論這個架構的不平衡效應，並針對這些問題提出補償方法來提升訊號品質。造成不平衡的因素包括:振幅不相符、角度不為直角以及兩路訊號不同步。用GSOP校正方法可以成功解決這些問題。 最後我們討論光的相位雜訊對訊號的影響。當我們的訊號傳輸量愈大時，光的相位雜訊會對訊號品質造成很大的影響。

We propose a novel all optical up-conversion direct detection OFDM multi-level system. Utilizing an external modulator, we can up-converse vector signals without electrical mixer based on single side band with carrier suppression. In order to generate 60GHz signals without expensive high-speed components, we using frequency quadrupling modulation technique. A record 28-Gb/s 16-QAM OFDM system within 7-GHz license-free band at 60 GHz employing all-optical up-conversion with frequency quintupling is experimentally demonstrated. Negligible penalty is observed following 100-km SMF transmission without any dispersion compensation. Besides, we also discuss imbalance effects and do compensation to improve signal quality. The imbalance factors include amplitude mismatch, conjugate misalignment and un-synchronization. Utilizing Gram-Schmidt Orthogonal procedure can successfully solve these problems. Finally, we also do some discussion on phase noise. It affects high data rate signals seriously.