自适应调制的正交频分复用多模光纤通信系统性能分析

Performance Analysis of a Multimode Fiber Communication System Based on the Adaptive Modulation Orthogonal Frequency Division Multiplexing

随着短距离通信网的不断发展,多模光纤(MMF)已经成为实现高速大容量信息传输的理想介质,但多模光纤严重的模式色散限制了其传输能力.为了提高多模光纤的传输能力,设计了基于自适应调制(AM)的正交频分复用(OFDM)多模光纤通信系统.提出了适用于该系统的自适应比特分配算法,并通过仿真证明了该算法的有效性.在此基础上重点分析了自适应调制对系统性能的影响,对比了自适应前后不同传输速率、不同信道情况下的误码特性.结果表明,自适应调制能较好地克服深衰落点对系统性能的影响,有效降低了系统误码率(BER).

With the development of short distance communication network, multimode fiber （MMF） has become a ideal medium to realize high-speed transmission of information with large-capacity. But the severe model dispersion of the MMF restrict its transmission ability. To improve the transmission ability of the MMF, a MMF communication system based on adaptive modulation （AM） orthogonal frequency division multiplexing （OFDM） is designed. An adaptive bit loading algorithm which is fit for this communication system is proposed. Simulation is done to validate the feasibility of the algorithm. Based on the given system, the effect of adaptive modulation to the transmission performance of the system is emphatically analyzed. And the bit error rate （BER） curves of different bit rates, different transmission performance with and without adaptive modulation are compared. The result shows that adaptive modulation can improve the transmission performance of the system effectively, and overcome the effect of deep fading nulls very well.