Study On Some Issues About Optical OFDM Technique

Two main areas of optical fiber communication including transmission and access network have been proceeding toward super large transmission capacity recently. How to realize this at limited bandwidth draws great attention of researchers. As a modulation technique, which can achieve high spectral efficiency and compensate for impairment of fiber effectively, Optical Orthogonal Frequency Division Multiplexing(OOFDM)has become a hotspot.This thesis firstly introduces research progress and significance of OOFDM and indicates that its technical core lies in the application of modulation of multiple low-speed sub-carriers instead of single high-speed carrier, thus demonstrating the characteristics of immune to optical fiber transmission impairments. And multi-carrier and high Peak-To-Average Power Ratios (PAPR) have become important factors affecting its performance.. On this basis, this thesis has studied the technology of OOFDM as the following areas:1)Radio-Over-Fiber Optical-Wireless Integration System based on OOFDM; 2) Direct detection transmission system based on OOFDM; 3)All-optical Wavelength Conversion System based on OOFDM. The innovation of this thesis is as follows:1.For OOFDM signal have good resistance to distortion caused by dispersion, a novel ROF system has been proposed with optical OFDM signal generation based on optical phase modulator. This system can immune dispersion, effectively inhibit the damage caused by the signal PAPR,offer re-use of wavelengths with a simple structure and no DC bias;2.According to the existing WDM passive optical network structural characteristics, a multi-wavelength optical OFDM operating at 60GHz band system has been proposed which is suitable for current WDM-PON configuration and be configurable for different applications flexibly. Experimental studies have shown that the system provides quadruple services in a wavelength slot, but its transmission performance has not been reduced;3.According to characteristics of Four-Wave Mixing (FMW) in semiconductor optical amplifier, a scheme of All-optical Wavelength Conversion System with low-noise and polarization-insensitivity based on OOFDM signals has been proposed. Based on this scheme, the system noise performance model is established. The experimental result agree well with experimental result;4.The studies on a scheme of ROF system based on only one phase modulator to achieve phase modulation and directly detecting at the receiver has been carried out experimentally. The result shows this scheme is low cost and stability;5.By introducing channel coding to OOFDM signals, the studies of improvement of system performance employing convolutional codes has been carried out.