直接检测光正交频分复用系统噪声分析

Noise analysis in direct dection optical OFDM system

针对直接检测光正交频分复用(DDO-OFDM)系统产生的放大器自发辐射(ASE)拍频噪声。通过对系统受ASE噪声影响的数学分析得到噪声影响机理及系统信噪比表达式,根据理论推导提出载波抑制方案,通过数字仿真验证推导结果及方案可行性。理论分析和仿真结果表明,系统受ASE拍频噪声影响严重,合理选择带通滤波器带宽可有效降低噪声影响;通过加入载波抑制可有效提高系统性能,当载波抑制比为0 dB时系统性能最佳。

Optical orthogonal frequency division multiplexing（O-OFDM） has been demonstrated to combat fiber chromatic dispersion（CD） and polarization-mode dispersion（PMD）,which is being considered as a promising technology for future long-haul optical transmission.Because of computation efficiency and lower cost,the direct detection optical OFDM（DDO-OFDM） system is one of its schemes.However,the amplified-spontaneous noise induced by direct-detection seriously affects the system performance.The impact of noise introduced by amplified-spontaneous emission（ASE） is investigated and the signal-to-noise expression is got.Additionally,a carrier suppression scheme is presented.With such a scheme,the numerical simulation is done to validate the feasibility of the system.Analysis and simulation results show that the system performance is impacted by the bandwidth of band-pass filter and the optimal carrier suppression index is 0 dB for DDO-OFDM system.