Main causes include dust contamination of optical ports exposed to the environment, secondary pollution to transceiver ports from pre-contaminated fiber connector end faces, scratched end faces caused by improper handling of pigtail fiber connectors, and poor port contact plus. Main causes include dust contamination of optical ports exposed to the environment, secondary pollution to transceiver ports from pre-contaminated fiber connector end faces, scratched end faces caused by improper handling of pigtail fiber connectors, and poor port contact plus. This document is a troubleshooting and selection guide for common optical switch failures, compiled based on over 500 field cases. It systematically analyzes the causes, solutions, and preventive measures for 10 typical issues of optical switches, provides a 20-item selection checklist covering. Based on typical issues encountered with optical modules in daily switch applications, this document summarizes basic troubleshooting steps for resolving common faults: 1. Check compatibility between the optical module and switch Most switch brands have specific compatibility requirements. An optical module is a critical component in modern optical communication systems, directly affecting transmission stability, network reliability, and operational efficiency. However, during installation and daily operation, various issues may arise. Therefore, understanding common optical module. In this 2025 edition of our Advanced Troubleshooting Guide, we explore common issues, diagnostic tools, and practical steps for resolving problems with optical transceivers, helping network engineers and IT teams stay ahead. Despite their robust design, these modules can experience failures due to environmental stress, contamination, or incompatibility.