The sixth generation (6G) wireless communication has significant impact due to massive connectivity and higher data rate. 6G is enhanced with Free Space Optical (FSO) communication in which the optical data is transmitted with a free spectrum license and higher security. But atmospheric circumstances have an impact on how well FSO communication works. The novel detection approach is proposed in this paper to enhance performance by mitigating the effect of atmospheric turbulence. Initially, the input signal is modulated with an On-Off keying (OOK) based modulation technique and transmitted through FSO communication channel. On the receiver side, signal detection can be accomplished with hybrid optimization Particle Swarm Hill Climbing Algorithm based (PSHCA)-U-net. The U-net architecture is modified to enhance the U-net performance by optimizing the hyperparameters with a hybrid PSHCA algorithm. Tests are conducted using various atmospheric weather scenarios on the proposed PSHCA-U-net model.Finally, simulations are performed to determine the performance of a proposed architecture and evaluated using Bit Error rate (BER), accuracy, transmission time, latency, spectral efficiency etc. Using the proposed approach, the spectral efficiency and latency are improved with 100 Gbps/Hz and 1ms. In terms of BER and other performance measures, the proposed solution outperforms the current strategy. It shows the superiority of a proposed approach while considering 6G parameters.