光学学报, 2005, 25 (9): 1171, 网络出版: 2006-05-22
采用光纤拉曼放大改善1550 nm外调制有线电视系统的组合二阶失真指标
Improving Composite Second Oorder Distortion Performances of Externally-Modulated CATV Systems by Optical Fiber Raman Amplifiers
光纤通信 光纤有线电视 光纤拉曼放大器 自相位调制 组合二阶失真 微扰 optical fiber communication optical fiber CATV optical fiber Raman amplifier self-phase modulation composite second order distortion perturbation
摘要
为克服长距离光纤有线电视(CATV)系统中采用高增益掺铒光纤放大器(EDFA)所带来的非线性损伤,对在残留边带调幅(AM-VSB)外调制光纤有线电视系统中采用光纤分布拉曼放大时的组合二阶失真(CSO)进行了理论研究。根据拉曼放大对信号光强的增益作用,导出了分布拉曼放大条件下的薛定谔方程,并采用微扰法解出了存在拉曼分布放大时,残留边带调幅外调制有线电视系统中,自相位调制(SPM)导致的组合二阶失真的解析表达式。相应数值计算结果表明,相对于采用掺铒光纤放大器功放,采用相同放大倍数的分布拉曼放大可使长距离系统中自相位调制导致的组合二阶失真性能改善10 dB以上。因此可以得出结论:在长距离残留边带调幅调制的有线电视系统中,采用分布式光纤拉曼放大可以较好地改善由自相位调制导致的组合二阶失真恶化。
Abstract
The composite second order distortion (CSO) induced by self-phase modulation (SPM) in a vestigial sideband amplitude modulation (AM-VSB) externally modulated CATV system employing optical fiber Raman amplifier is studied theoretically. Firstly, the SPM-induced CSO expression is obtained analytically by solving Schrdinger equation with the help of perturbation method. Subsequently the corresponding numerical results are presented and discussed. According to the calculation results, it is shown that, compared with using EDFA, the CSO performance can be improved by more than 10 dB by using distributed Raman amplification in the system.
王春华, 李力, 李风勤. 采用光纤拉曼放大改善1550 nm外调制有线电视系统的组合二阶失真指标[J]. 光学学报, 2005, 25(9): 1171. 王春华, 李力, 李风勤. Improving Composite Second Oorder Distortion Performances of Externally-Modulated CATV Systems by Optical Fiber Raman Amplifiers[J]. Acta Optica Sinica, 2005, 25(9): 1171.