Time synchronization technology based on optical fiber transmission has the advantages of high precision, high stability, and low loss. It has become the main method for high-precision time synchronization, with robust application requirements and development prospects. Bidirectional comparison technology is a widely used optical fiber time synchronization method, and relevant institutions (locally and internationally) continue to propose new methods, technologies, and applications in this field. Furthermore, by combining the research history and progress of optical fiber bidirectional alignment technologies, this paper introduces the basic principles and technical characteristics of four mainstream bidirectional comparison schemes. The uncertainties and sources of errors of the synchronization system and their impact on time synchronization results are analyzed. Accordingly, this study provides a reference to further improve the accuracy of optical fiber time synchronization and establish a high-precision, safe, and stable ground-based timing system.