Underwater Wireless Optical Communication (UWOC) offers significant research prospective with major challenges in the design and implementation. UWOC is capable of providing high rate of data transmission across large distances. This paper attempts to focus on the intricacies of practical implementations and open research issues of UWOC systems. Critical advances and progresses made in the field, modelling techniques and link design challenges are summarised. The purpose of this review is to give suggestions towards feasible and reliable UWOC design with improved performance. Finally the major points are summarized so that it will assist the future research in UWOC.

A 100 km long dense wavelength division multiplexed optical network design with a capacity of 1.28 Tbps is proposed in this paper. The novelty of this work is the use of a dispersion compensating fibre as a Raman amplifier in the S-band for a high-capacity dense wavelength division multiplexing network. The transmission is accomplished auspiciously in the wavelength range from 196 THz to 202. 35THz. The coupling of a Raman amplifier made the realisation of the S-band possible in the network, as the erbium-doped fibre amplifier is competent for amplification in C- and L-bands only. Further, a pump coupler is used for multiple pumping to enlarge the gain spectrum for a high-capacity optical network. The performance analysis of the network is carried out systematically in terms of bit error rate (BER), eye diagram, Q-factor, and optical signal to noise ratio (OSNR). The results demonstrate that the proposed set-up shows adequately low BER, sufficient Q-factor values, wide eye-opening, and commendable OSNR for all receiving channels.