外部調變式光纖有線電視系統之線性化技術

Abstract

本論文提出適當地調整光調變器的偏壓點，利用由光調變器的非線性轉換特性，消除傳輸鏈路上由於非線性效應所造成訊號的二階非線性失真，得到高線性度的光纖傳輸系統。並且研製外調式高功率光纖有線電視發射機的之線性化技術，包括偏壓穩定電路以及三階非線性失真補償電路的設計與實作。使得外調式光發射機在78個AM-NTSC頻道載波的負載下，可以達到有線電視系統的要求：載波對雜訊比CNR>50dB、三次拍差失真CTB<-62dBc和二次拍差失真CSO<-65dBc。

In this thesis, we propose a novel linearization technique, which can suppress the nonlinear distortions (NLDs) generated in a transmission system. This technique is based on ffsetting the MZI bias voltage from its inflection point. In addition, we design and implement the linearization techniques, including the bias stabilization circuit and the third-order predistortion circuit, for externally modulated lightwave CATV transmitters. Under 78 unmodulated AM-NTSC carriers, the transmitter has the following overall system performances: carrier-to-noise ratio (CNR)>50dB, composite triple beat (CTB)<-62dBc, and composite second-order (CSO)<-65dBc.