| Summary: | 碩士 === 國立中山大學 === 光電工程學系研究所 === 106 === In order to achieve cost-effective transmission, intensity modulation (IM) and direct detection (DD) are preferable for short-range systems. This dissertation provides detailed descriptions of the interplay between dispersion and chirp (specifically adiabatic chirp), in an optical orthogonal frequency-division multiplexing (OFDM) transmission system based on a directly modulated DFB laser (DML). We experimentally investigated various amounts of dispersion and adiabatic chirp by, respectively, varying the length of the fiber (0–200 km) and the bias current (60-120mA) of the laser. Since adiabatic chirp was shown to mediate dispersion-induced power fading and even provide a power gain. This is an indication that a specific amount of adiabatic chirp may be beneficial to transmission performance, particularly when the nonlinear distortion is mitigated by nonlinear compensation.
The Volterra filters and neural networks are used in this dissertation to compensate for nonlinear distortion in DML-based OFDM transmission systems. By disabling the sub-carriers that suffer from significant power fading, we can effectively improve the ability of nonlinear compensation. Moreover, integrating the high/low-pass filters into neural networks can mitigate the degradation in signal-to-noise ratio at low frequency caused by neural networks. Finally, using Volterra filters and neural networks to eliminate nonlinearity can increase the data rate by up to 15 Gbps and 20 Gbps, respectively.
|
|---|
