彩色影像光纖傳輸系統設計

　　　　　本論文主要將彩色影像信號，利用光纖來做長距離傳輸，整個系統包括彩色CCD攝影機、光纖傳輸系統及監視器。光纖系統設計採用0.85μm波長之LED光源及PIN受光二極體的組合；0/E接收端電路採高負載阻抗，使雜訊源降低，且電路具有自動增益控制，增益大小，可隨傳輸距離的長短自動調整，維持輸出準位在1 Vp-p。 當系統的信號雜訊比（S/N）p-p維持在55db以上時，影像信號之調變指數為0.43，則O/E接收端最小平均入射光功率經估算為4.2μw，即-23.87dbm，系統之光功率損失餘裕度為8.68db，最大傳輸距離約為2.5km。整個光纖傳輸系統經測試頻寬為13MHz，圖場掃描波形之失真度為4%，差動增益及差動相位的非線性失真度分別為8%及1.2°，傳輸信號品質相當良好。
　　　　　This report is mainly discussing long distance transmission of color video signal through optical fiber. The whole system includes a color CCD camera, an optical fiber transmission system, and a monitor. The optical fiber system consists of a LED light source with 0.85μm and a PIN photo-diode. The recepting circuit adopts a high load impedance to reduce the noise source; and it can control gain automatically. The gain can be self-adjusted with the varying of transmission distance and the output level is held to 1 Vp-p. While the signal to noise ratio is held above 55 db, the modulation index of video signal at the recepting end is m-0.43 and the minimum average incident optical power at the recepting end is 4.2μW (-23.87 dbm). The allowed optical power loss is 8.68 db thus the longest transmission distance of the system is 2.5km. By testing, the actual frequency bandwidth of this optical fiber transmission system is around 13 MHz, the distortion rate of field time wave-form is 4%, and the nonlinear distortion rates of the differential gain and the differential phase are 8% and 1.2° respectively. The transmitting quality of whole color video signal will get fairly well.