Hyperparameter tuning is the main challenge of machine learning (ML) algorithms. Grid search is a popular method in hyperparameter tuning of simple ML algorithms; however, high computational complexity in complex ML algorithms such as Deep Neural Networks (DNN) is the main barrier towards its practical implementation. In this paper, two novel suboptimal grid search methods are presented, which search the grid marginally and alternating. In order to examine these methods, hyperparameter tuning is applied on two different DNN based Optical Communication (OC) systems (Fiber OC, and Free Space Optical (FSO) communication). The hyperparameter tuning of ML algorithms, despite its importance is ignored in ML for OC investigations. In addition, this is the first consideration of both FSO and Fiber OC systems in an ML for OC investigation. Results indicate that despite greatly reducing computation load, favorable performance could be achieved by the proposed methods. In addition, it is shown that the alternating search method has better performance than marginal grid search method. In sum, the proposed structures are cost-effective, and appropriate for real-time applications.