Performance evaluation of a UOWC system based on the FRS/OCDMA code for different types of Jerlov waters

Abstract

In this work, the fixed right shift (FRS) code is utilized for the optical code division multiple access (OCDMA) technique in an underwater optical wireless communication (UOWC) system. Additionally, in this system, a 532 nm laser diode (LD) source is employed to generate optical signals. The investigation encompasses an analysis of five distinct Jerlov water types, each exhibiting diverse chlorophyll concentrations. The performance of the proposed system is evaluated when each channel that is assigned a unique FRS code sequence carries different data rates (2.5, 5, and 10 Gbps). Underwater (UW) ranges, bit error rate (BER), eye diagrams, and quality factor (Q-factor) are the performance metrics used to evaluate the system performance. The proposed UOWC-FRS/OCDMA system is simulated, and the obtained results show that the eye diagram openings close, the BER increases, and the Q-factor decreases as the data rate per each channel increases from 2.5 to 10 Gbps, and the attenuation of water becomes higher. Moreover, the lower attenuation values caused by the Jerlov type I (JI) waterbody allow each channel to carry 10 Gbps of data to propagate longer UW for a range of 35 m with a log(BER) ≤−6.33 and Q-factor greater than 4.9. On the other hand, at the same values of BER and Q-factor, the shortest ranges of 12 and 5.15 m are obtained for JII and JIII waters, respectively, where their attenuation coefficient values are 0.5297 (JII) and 1.8998 m−1 (JIII). Furthermore, as our model uses three channels, the overall achieved capacity is 3×10Gbps=30Gbps.