分波多工與極化鍵控光通訊系統之偏極補償研究

Abstract

我們利用共振腔原理設計了一個非對稱性之共振腔體, 產生一極為純的單模雷射, 並利用此雷射做不同的分析。藉由調控電光交換器的偏壓電壓來改變此腔體雷射之狀態並找出最佳的工作點進行遠距離傳輸實驗。我們利用壓電材料來改變光的極化狀態進行調變並利用自製的補償器進行補償。由於傳送於光纖中的光訊號易受外界各種的環境因素而改變其偏振的方向因而影響其極化率及橢圓率。但由實驗結果可知，我們的補償器可降低光在傳輸時其極化狀態所受到外在環境的影響並有效提高極化率至87.8%；並降低其橢圓變化率至3.31°。由此可知我們的補償器可實際應用在各種傳輸的補償中，進而提高傳輸品質降低誤碼率。 此自製之極化補償器是利用程式自動偵測偏極態方向迴授給單晶片判讀，再由單晶片發出控制訊號精確的將偏極態的方向矯正至原來期望的設定值，讓偏極態不會任意的隨著環境因素而無時無刻的改變其偏態的方向，而影響到光纖的傳輸品質。在此實驗研究中我們知道在補償的過程中因傳輸的延遲現象造成此補償電路無法對訊號進行即時的補償。因此在此實驗研究中我們完成了電路的設計，製作，修改及基礎量測與分析，由量測結果可知，迴授訊號經過個個電路分別所造成的延遲現象以及電路特性﹔進而獲知設計電路板的大小(佈線路徑)以及連接電路板間的排線長度都會影顯延遲時間的長短。為此我們反覆實驗，終於將第一代的極化控制電路進行改良, 不但大幅縮小電路體積﹔並改善造成延遲因素，使迴授速度加快以提昇補償效果。 若在未來的發展中，可將整個控制電路IC化並實際應用於儀器成品中，不但可精簡體積，更可大量的應用於現今的高速光纖網路，以提高網路傳輸的品質，來符合現今高速光纖網路的需求。此一構思將為未來發展趨勢不可或缺的一環。We use the theorem of resonator to design an asymmetrical resonator, produce a very pure signal mode laser, and make different analysis using this signal mode laser. From modulating the bias voltage of electro-optic switch to changing the state of cavity laser and find the optimum work point to make the experiment of transmission compensated. We utilize PZT to modulate the polarization state of cavity laser and use homemade compensator to compensate. Because the polarization state of the light in the optical fiber is easily changed due to many factors in various environments. Therefore, the ellipticity and DOP also be influenced. But form our experimental results, we know our compensator can reduce the variation of polarization state, is influenced by the environment on the transmission system. And promote the DOP to 84.92%, reduce the variation range of ellipticity to 3.21°. Therefore, we know that our compensator can be applied on various transmission systems and improve the transmission quality, reduce bit error ratio.

Our homemade compensator is utilizing the program to scout the orientation of polarization state and feedback control by the program. Then it send out the control signal to correct the polarization station go to the set position of our expectation and let polarization state not changed arbitrarily by the factor of environment, incessantly and influence the transmission quality on the optical transmission system. From study of this experiment, we know that in the process of compensation will cause the transmission delay, so the compensator should not compensate the transmission signal, immediately. In this thesis, we finish the design, measure and analyze of this compensator circuit. From measure result, we should understand the phenomenon of delay while feedback pass through each circuit and some characters of those circuits. We obtain the size of designed circuit (wiring rout) and the length of the data bus should influence the delay time. The first generation compensator eventually ameliorated, we successful reduce the size of our compensator and improve the factors of causing the transmission delay after experimenting repeatedly. However, the feedback speed can be quickened and raise the compensation result after improving those factors.

In the future we can let all circuit became to integrated circuit (IC) and applied it on the instrument. Not only simplify the size, but also a great deal of applied it on the high-speed optic network. It can promote the transmission quality and conform to need in the nowadays network.