Research On Optical Orthogonal Frequency Division Multiplexing Technology

Optical orthogonal frequency division multiplexing is currently a hot topic in optical communication research over the last couple of years. As the signal with high data-rate will be transmitted in long distance in future, conventional per-span optical dispersion compensation becomes too expensive and time-consuming. At the same time, OFDM has been widely and successfully used in wireless field by the development of digital signal processing technology. Consequently, the combination of optical communication and OFDM has emerged.In this thesis, two methods have been introduced: coherent optical and direct detection, then the analysis of DDO-OFDM has been implemented. Furthermore, with different digital modulation, we verified that O-OFDM can release chromatic dispersion and polarization mode dispersion by MATLAB. Because of the parallel transmission of OFDM subcarriers, it has a high peak-to-average power ratio, and this will increase the nonlinear distortion in system. For this reason, the high PAPR is the major disadvantage to the performance of system, and the research to decrease PAPR is important.In this thesis, three methods to decrease PAPR has been introduced: clipping,coding and scrambling. As the last two have more complexity and difficulty to be implemented, most research aim to clipping technology. This paper presents two important technologies in optical intensity modulation: asymmetrically clipped and direct current biased clipped, and compares the performance of power and frequency efficiency between them. Then, predistortion technology with phase modulation has been introduced and analyzed.