Performance investigation of coded IM/DD optical OFDM for short range underwater wireless channel

The requirements for high speed, high data rate and reliable communication causes the OFDM system is an attractive technique due to its wide spectrum property. The principal matter is how effectively transfer high data rate in applications that are highly significant to the military, scientific community and the industry in optical technology. In this paper, a comparative performance evaluation is conducted for LDPC coded optical OFDM based on three classical optical OFDM schemes for the underwater optical channel in the presence of turbulence noise using Rytov variance. By the simulation, the underwater channel impulse response is performed based on Monte Carlow simulation modelling of light (MMOL). The proposed systems under investigation provide clear perception for the scientific researcher and designer to deal with factors of these environments that affect the optical wireless communication and the capability of increasing the communication distance with satisfactory reliability. Simulation results showed that a good performance could be achieved under a very complicated environment at high turbulence levels. The results also reveal that IFFT/FFT size has a significant effect on system BER. High turbulence and inappropriate clipping ratios (CRs) cause a rotation in the constellation as a result of phase noise (PN) introduced by self-phase modulation (SM). The BER curves of goodput at the receiver demonstrated that coded ACO-OFDM exhibits better performance than coded DCO-OFDM which is very sensitive due to the DC-bias. Concerning the BER results, coded Unipolar OFDM (U-OFDM) slightly outperforms the other two systems with dB coding gain ranging between 0.5 → 2.