## 6 Results and Discussion
### Discussion
It might be preferable to eliminate this effect entirely by using two wavelengths of light that experience two different spectrum-dependent attenuations, whose difference in received power increases consistently with distance. This is observed in Figure 11, where the received power is modeled at the Rx for clear ocean Jerlov types I (10 m and 12 m vertical displacements)and III (1 m and 2 m vertical displacements), and coastal types 1C (5 m and 7 m vertical displacements) and 3C (1 m and 2 m vertical displacements). Here, it is observed that for all four water types, the difference in received power between each wavelength is widening consistently by a logarithmic factor with horizontal distance, irrespective of orientation. If the rate of change of this difference could be computed in real time, it could enable UUVs to determine water-condition-related attenuation while traversing through inhomogeneous environments such as in vertical channels of the euphotic zone. Using two spectral wavelengths could also help to isolate the distance attenuation factor \(e^{-c(\lambda)d}\) in Equation (16) from the orientation effect of the PD array. This feature may be advantageous for employing optical received-signal strength-indicator-based localization. Coastal types beyond Jerlov 3C showed an extremely rapid decline of the received power at very short range, implying that UOWCs in these environments may not be beneficial. However, this model cannot assess the effects of the light multipaths in these highly scattered turbid environments. For this, a Monte Carlo simulation may be more appropriate. This is due to a Monte Carlo simulation's ability to analyze outcomes from the level of a single photon. This could account for the geometric implications of array geometry towards the distribution of delay spreads in highly scattering environments. We further acknowledge that the simulation results provided here need to be verified through experimentation. It is possible to recreate the Jerlov types artificially through scattering and absorption agents, such as by using Maalox antacid [31; 32]. The 3 PD and 5 PD arrays can be designed and developed in the described F, C25, and C55 configurations. However, attaining an equal level of geometric loss requires an area as analyzed in the simulations, which is only possible in the real ocean. Instead, selecting LEDs of 450 nm, 500 nm, and 550 nm that provide a similar intensity distribution, but emit a scaled-down fraction of optical power may be ideal. Using micro-LEDs may be a good option. We propose such a test as future work. In summary, we highlight these recommendations for PD array designs:  
* Flat array designs are optimal for links where Tx-Rx alignment can be strictly maintained. This will need to be controlled dynamically as the UOWC moves to maintain orthogonality to the light ray. If not, the response may be very unpredictable and disadvantageous. There is also a significant risk of total blindness. * Curved arrays are good overall for mobile UOWCs as they have large overall FOVs. This produces more predictable outcomes and, overall, less drastic BER variation. However, the spread-out PD configurations mean that there will always be some PDs at non-optimal AOIs to light. This may cause an irregular high-and-low received-power response until a peak power is observed at a certain horizontal distance for a given height from the Tx. The horizontal location of this peak power increases with increasing distance. * The number of PDs used in the array plays a less significant role in optimal performance than the overall FOV of the array, especially as the distance from the transmitter increases. Overall, a convex shape may be better for curved arrays. * As the clarity of the water improves, the range of link coverage could be improved much more significantly by utilizing more bandwidth-efficient modulation schemes.