- 學位論文
光纖微波傳輸系統之研究與應用
Studies and Applications on Radio-on-Fiber transport systems
摘要
高密度分波多工傳輸系統可以傳輸多個光載波頻率並且傳輸不同種類的調變信號在同一條光纖上，是一個合乎成本的架構。在最近的十年間，微波光纖（ROF；radio-on-fiber）連結系統於許多應用上已經被認為是值得注意考慮的架構。一般典型的傳統網路架設上的缺點，主要的限制是使用的射頻電纜，射頻電纜具有電氣危害、電磁干擾、傳輸損耗大、頻帶窄及保密性差…等缺點；以致於從中心控制台至基地台端只能夠延展數公里的傳輸距離。而ROF於光波傳輸系統中之所以被選擇應用，是由於光纖能夠提供更大的傳輸容量與低的傳輸損失等優點，這使得傳輸距離可以大大的被延伸，光纖網路更具彈性使用及更確保光纖網路的安全及穩定性。最近一些研究中，垂直共振腔面射型雷射(VCSEL；vertical cavity surface emitting laser)的技術已經被設計出可以在1.55 μm波長的範圍下工作，並且具有單模態輸出特性，這使得VCSEL雷射可以被使用來取代傳統光纖傳輸系統中分佈式回饋雷射(DFB；distributed feedback)二極體或Fabry-Perot雷射二極體。 藉由對VCSEL雷射注入鎖模技術以改善雷射的頻率響應以提升系統的傳輸性能，所建構之外部光源注入技術，應用於微波高密度分波多工(Radio-on- DWDM)傳輸系統上，在近年來的研究中也已經被論證。本地區域網路(LAN；local area network)與智慧型傳輸系統(ITS；intelligence transport system)的應用，若能將其應用在双向式光波傳輸系統上則是非常吸引人的選擇。比較單向與雙向傳輸系統架構間的差別，可以發現雙向傳輸系統不但可以有效的減少系統中光纖的使用量，並且相較於單向傳輸系統也可以提供其兩倍傳輸容量的優點。 在本篇論文中，我們介紹數種方法來改善微波光纖系統的性能，這些方法包括外部光源注入、三階互調失真抑制技術、升頻與極化調變技術、光單旁波帶調變技術與雙重外部光注入技術。使用於本地區域網路及智慧型傳輸系統的應用，可預期的是光信號經由光纖傳送後系統可測得良好的誤碼率(BER；bit error rate)及誤差向量振幅(EVM；error vector magnitude)值，並且於三階互調失真載波比值(IMD3/C；third order intermodulation distortion to carrier ratio)上也可以得到良好的性能。
並列摘要
Dense-wavelength-division-multiplexing (DWDM) transport systems correspond to the scheme in which multiple optical carriers at different wavelengths are modulated by using independent signals and are then transmitted over the same fiber. During the last decade, radio-on-fiber (ROF) link has received considerable attention, it is the most promising candidate for lightwave transport system due to its large bandwidth and low attenuation. Typical radio network setup is limited by the employment of the RF cable, it can only extend up to a few kilometers from a central station (CS) to a base station (BS). Recently, vertical cavity surface emitting laser (VCSEL) technology is designed to operate in the 1.55μm wavelength window and with a single mode, and it can be employed to replace distributed feedback (DFB) or Fabry-Perot (FP) laser diodes in lightwave transport systems. In recent study, injection locked technique has been used in radio-on-DWDM transport systems to improve systems’ transmission performance; for local area network (LAN) and intelligence transport system (ITS) applications. Bidirectional transmission in lightwave transport system is a very attractive option. Compared with the unidirectional transmission, bidirectional transmission over the fiber span not only reduces the required number of fibers, but also offers the advantages of capacity doubling. In this thesis, we present several ways to improve the ROF systems’ performance including external light injection, third order intermodulation distortion (IMD3) suppression, up-converted and polarization modulation, optical single sideband (SSB) modulation, and double external light injection. Not only low bit error rate (BER) and error vector magnitude (EVM) were obtained, but also good performance of third order intermodulation distortion to carrier ratio (IMD3/C) was achieved for LAN and ITS applications.
參考文獻
延伸閱讀
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