In this paper, a performance evaluation of radio over multimode fibre system (ROMMF) using Coded orthogonal frequency division multiplexing (COFDM) is presented. The performance analyses based on bit-error ratio (BER) are extensively investigated. In addition, the effect of fibre length on BER performance is presented. Moreover, the effect of the exponent refractive index profile of the multimode fibre (MMF) on the BER of COFDM is studied considering Maximum Likelihood Ratio (MLR) and sub-optimal simplified Log Likelihood Ratio (LLR) as a soft bit metrics for soft decision Viterbi decoding. © IDOSI Publications, 2011.