Research On All Optical Orthogonal Frequency Division Multiplexing Technique

Along with the increasing demand of the information rate, the single-channel rate of optical transmission system changes from 40Gbps to 100Gbps even higher. The higher the channel rate is, the more severe the dispersion and nonlinearity is affected.Then the optical OFDM comes into being. With the same bandwidth, optical OFDM can improve the transmission rate by enhancing spectrum efficiency. Since 2005, the optical OFDM was presented, then received extensive attention of the experts of optical field. And that is actually considered as one of the important candidate solutions of realizing 100Gbps and above 100Gbps level of transmission system.In this paper, a 160Gbps four carriers all optical orthogonal frequency division technology (AO-OFDM) is studied. Firstly, this paper studies the principles of OFDM and all-optical OFDM, and the MZ interferometer according to the working theory. Secondly, on the basis of the demodulation of four carriers all-optical OFDM, this paper deduces and proposes a simplified structure to demodulate the four carriers all-optical OFDM signal based on the MZ interferometers, and further deducing the direct demodulation method of the four carrier all-optical OFDM for any center frequency, which is simulated by VPI platform to verify the correctness of it. According to the phase characteristic of the MZ interferometer in the demodulation structure, we can use different phase setting to make the output ports export different carrier signal. Thirdly this paper investigates the principle of MZ modulator and proposes three simple schemes for generating four carriers with the same frequency interval, the results show that the ratio of carrier to noise is more than 25dB. By using these schemes, it can reduce the quantity of lasers, and greatly reduce the cost.At last, the paper introduces some important influence factors in high speed optical transmission systems, and simulates the all-optical OFDM under different dispersion compensation schemes. It is concluded that in the 160Gbps four-carrier all-optical OFDM signal transmission the performance is best when using a periodic compensation mode.