高速直調雷射之傳輸性能改善及應用於WDM-PONs系統之研究

• Main Author: 林淑娟
• Format: Thesis
• Language: Chinese; English
• Published: 2007
• Subjects: 分波多工; 直接調變雷射; 頻率啁啾; 法布里-比洛 析光器; WDM-PON; directly modulated laser; frequency chirp Fabry-Perot etalon; DML
• Online Access: http://ir.lib.ntust.edu.tw/handle/987654321/7869; http://ir.lib.ntust.edu.tw/bitstream/987654321/7869/1/

國立臺灣科技大學電子工程系 學位：博士 指導教授：李三良 本論文的研究重點包括了10 Gb/s直調雷射傳輸性能的研究、針對其傳輸訊號品質提出改善方法，並將10 Gb/s直調雷射應用於分波多工被動光網路系統中。使用光頻譜與光脈波整形的設計，可以增加以直調雷射作為光發射機之光纖網路傳輸的距離。本論文中，我們提出藉由一個簡單的法布里-比洛析光器作為頻譜整形器的可行性，將其應用於分波多工光接取網路中。直調雷射產生的絕熱與暫態頻率啁啾效應可藉由使用時域解析頻譜技術量測出啁啾值，進行詳細地分析。經由頻譜整形的作用，可針對雷射設定的明滅比與絕熱啁啾值，獲得最佳的工作條件範疇，此方法可用來同時改善多個直調雷射的傳輸特性，在多個10 Gb/s直調雷射的輸出端，加入一個單共振腔式法布里-比洛析光器，可以在1550 奈米波段，將雷射傳輸距離從小於 10公里延伸到大於 50公里。因為析光器的濾波能力的限制，我們針對如何選擇雷射初始設定的明滅比與析光器的精細度，以實驗與模擬做詳細地討論。 在分波多工被動光網路系統中若用直調雷射作為中央機房的的光發射機，並以反射式半導體光放大器作為用戶端的調變器，最大的難題在於下行傳輸訊號的明滅比和上行傳輸訊號的品質之間必須作取捨。我們提出在每個用戶端下行光接收機前加入一法布里-比洛析光器增強訊號品質，析光器的功能為對下行光訊號之頻譜與光脈波波形作整形，這個方法允許下行訊號有低明滅比，有效抑制下行訊號對反射式半導體光放大器再調變上行訊號的光強度擾動現象。這個方法同時降低雷射的暫態啁啾值，因此也可以延伸傳輸距離。並且仍然可以保持無色光源的操作，並且同一法布里-比洛析光器可以用來補償多個雷射通道。實驗結果證實此方法可大幅提升一個具有10 Gb/s下行傳輸速率與1.25 Gb/s上行速率的分波多工被動光網路的傳輸品質。 This thesis includes the investigation of the chirp characteristics for 10 Gb/s directly modulated lasers (DMLs), performance improvement of the performance of a 10 Gb/s DML transmission system, and application of the technologies to a wavelength-division-multiplexing passive optical network (WDM-PON) system. The spectral and waveform reshaping schemes can enhance the transmission distance of fiber links that use DMLs as transmitters. In this thesis, we prove the feasibility of using a simple Fabry-Perot (FP) etalon as the spectral reshapers for applications in WDM access networks. The transient chirp and adiabatic chirp of a DML are analyzed in detail by using the time-resolved chirp measurement. The effects of the original extinction ratio and the adiabatic chirp on the spectral reshaping are clarified to obtain the optimal operation conditions. It is shown that by placing a single-cavity FP etalon filter after multiple 10-Gb/s directly modulated lasers can extend their transmission distances from < 10 km to >50 km at the 1.55-m wavelength window. Due to the limited filtering capability of the etalon, the choice of the original extinction ratio (ER) and finesse of the etalon is discussed in detail from the experiments and simulation. The ER for the downstream ER and the upstream transmission performance needs to be compromised for the WDM-PON systems with DMLs at the center office and reflective semiconductor optical amplifiers (RSOAs) at the user ends. We propose to enhance the performance by adding a FP etalon before the receiver of each optical network unit (ONU). The etalon performs spectral reshaping and then waveform reshaping to the downstream signals. This allows the use of low-ER downstream signals that reduce the intensity fluctuation of RSOA-remodulated upstream signals. This approach can also extend the transmission distance by reducing the transient chirp. Colorless operation can still be obtained since the same etalon can be used to enhance multiple wavelength channels. Experimental results verify considerable performance improvement on WDM-PONs with 10-Gb/s and 1.25-Gb/s data rates for the downstream and upstream transmission, respectively.