Adaptive unsaturated technique for OFDM multimode fiber communication system

A novel adaptive unsaturated technique is proposed for Orthogonal Frequency Division Multiplexing (OFDM) multimode fiber communication. The core idea of this technique is that bits originally allocated to poor subcarriers are now transmitted by new extra subcarriers rather than the original good subcarriers used in adaptive modulation OFDM. It can reduce the system bit error rate (BER) which is mainly caused by some OFDM subcarriers located at the deep nulls in the high frequency region of multimode fiber. The simulation results indicate that adaptive unsaturated technique is more effective in reducing the BER of system than adaptive modulation and equal bit allocation. Moreover, adaptive unsaturated technique does not need complex bit allocation algorithm and each subcarrier has the same modulation format, so it is simple and practical.