Coding to increase number of channels in QAM-SCM-IM/DD lightwave system

For a fibre-optic QAM-SCM-IM/DD system, clipping noise can severely limit the channel transport capability. A theoretical analysis of the QAM-SCM-IM/DD system employing BCH codes to increase the number of channels is presented. The relations among the system parameters such as received signal power, modulation index, and carrier-to-noise ratio are investigated. A general expression of the number of channels in terms of these parameters is also presented. The example shows that by using a (255, 239) BCH code, the number of channels can be increased up to fivefold, and the influence of clipping noise can also be greatly reduced.