Aiming at the problem that the concentrating efficiency and spot uniformity cannot be taken into account in underwater wireless optical communication system

a composite refractive receiving antenna is designed in this paper. The simulation results show that the concentrating efficiency of the traditional Fresnel lens is only 58.725%

while that of the newly designed composite refractive antenna is 86.557%. Moreover

the uniformity of the spot is also good

with the uniformity of 0.659 3 under the condition of ensuring high concentration efficiency. Then the change of focusing efficiency and spot position offset of parallel light source at different incident angles is analyzed. It is found that the focusing efficiency of Fresnel lens is only 3.582 2% at 2 °incident angle

while the focus efficiency of the composite refractive antenna designed in this paper can still reach more than 50% when the incident angle is 1.5 °

and the spot can still be observed when the incident angle is 4 °. The receiving antenna designed in this paper has good reception effect in underwater long-distance wireless laser communication system. Therefore

the receiving antenna designed in this paper is suitable for underwater wireless laser communication environment with high gain and small field of view.