Research On The Transmission Properties Of Optical OFDM Signal

Today's research of communication technology follows two main directions:first, the continuous development of optical communication technology, including the growing speed of single channel optical signal transmission and the rapid development of reconfigurable optical network technology; second, the improvement of wireless technology, including the exploitation of new spectrum and the application of new physical layer technologies. The advance of these two directions opens the wider view for communication technology researching and makes the ultimate purpose of communication that realizing the free and unobstructed anywhere, anytime high-speed information exchange possible.(1) The conception of channel estimation commonly used in wireless OFDM systems has been introduced into OFDM-RoF system. The comparison and analysis of different channel estimation methods has been made, including estimators based on Least Square principle and Minimum Mean Square Error principle. By calculating the Mean Square Error of the deviation between received signal constellation and transmitted signal constellation, the figure of Optical Signal to Noise Ratio versus Mean Square Error of two different estimators of QPSK modulated OFDM signal along 200 Km single mode fiber transmission has been drawn.(2) The comparison between different interpolation algorithms used in channel estimation of OFDM-RoF system has been made, including linear interpolation and cubic spline interpolation. By calculating the Mean Square Error of the deviation between received signal constellation and transmitted signal constellation, the figure of Optical Signal to Noise Ratio versus Mean Square Error of two different interpolation algorithms in the of QPSK modulated OFDM signal along 200Km single mode fiber transmission has been drawn.(3) The analysis and experimental verification on the mode of chromatic dispersion influencing the optical OFDM signals has been made. Some useful results have been concluded through the experimental study on the channel amplitude response and phase response of optical OFDM signal transmitting in optical fiber.