高頻譜效率之正交分頻多工技術應用於倍頻光載微波信號系統

Abstract

本篇論文提出一種新型的光調變技術，此種調變技術可以傳輸向量訊號並具有倍頻效果。利用單一驅動的光調變器產生載子抑制調變，驅動信號為10-GHz的正弦信號組合在5-GHz的1.25-Gb/s的開關鍵控，二相移相鍵控或四相移相鍵控信號，在光偵測器接受後，產生在15-GHz的倍頻微波信號。傳輸五十公里的單一模態光纖後，三種不同的信號靈敏度下降小於0.2dB，四相移相鍵控較開關鍵控擁有兩倍的頻譜效益而且將近提升2dB的靈敏度。並且我們展示正交分頻多工調變的下傳信號與波段再利用得到的上傳信號，系統的上傳信號為5-Gb/s的16QAM正交分頻多工調變信號與透過反射半導體光放大器傳送1.25-Gb/s的OOK下傳信號。

This investigation presents a novel modulation approach for generating optical vector signals using frequency multiplication based on double sideband with carrier suppression. A single-electrode Mach-Zehnder modulator (MZM) is biased at null point with a driving signal consists of a 10-GHz sinusoidal signal and a 5-GHz sinusoidal signal modulated with 1.25-Gb/s on-off keying (OOK), 1.25-Gb/s binary phase shift keying (BPSK) data or 625-MSym/s quadruple phase shift keying (QPSK) data. After square-law photo detection, 1.25-Gb/s RF signal at a sum frequency of 15 GHz is generated. After transmission over 50-km single mode fiber (SMF), the power penalty of all three modulation formats is under 0.2 dB. QPSK format has twice the spectral efficiency and approximately 2 dB better receiving sensitivity than OOK format. And we also demonstrate OFDM signal with wavelength reuse for uplink signal. The 5-Gb/s 16QAM OFDM signal for ROF downstream link and 1.25-Gb/s OOK signal via RSOA for upstream link are demonstrated.