Numerical simulation on full-link underwater LIDAR with an optical filter using OAM modulation

Abstract

Optical filtering based on orbital angular momentum (OAM) modulation can effectively suppress background noise and multiple-scattering light in water, thereby improving the signal-to-noise ratio (SNR) of underwater lidar. Although OAM modulation has been investigated in previous studies, a full-link numerical model is still required to evaluate overall system detection performance. In this work, a full-link numerical simulation model of an underwater lidar system is developed based on the random phase screen method, incorporating the transmitter, underwater beam propagation, target characteristics, and receiver. The model can be used to investigate the effects of turbulence strength, laser energy, and telescope diameter on system performance. Under similar parameter conditions, comparison with water-pool experimental results shows good agreement in the maximum detection range, reaching approximately 15 attenuation lengths, which validates the model. Based on this model, the influences of turbulence strength, laser energy, and telescope diameter on the maximum detection range are analyzed, together with the effect of turbulence on beam divergence angle and horizontal resolution. The simulation results show that increasing turbulence strength leads to spot broadening and degradation of horizontal resolution, and this degradation becomes more pronounced when the field of view (FOV) is reduced. The proposed model provides an effective tool for evaluating the detection performance of underwater lidar systems employing OAM-based optical filtering.