Signal loss can occur in Fiber Optic Splice Closure (FOSC) due to various reasons such as dirty connectors, broken fibers, or loose connections. To troubleshoot this issue, you can try the following: Inspect the connectors for dirt or damage. This guide is written to provide a complete and engineering-oriented understanding of fiber optic splice closures—from basic concepts and. When it comes to troubleshooting Fiber Optic Splice Closure (FOSC), there are a few common issues that may arise. In this section, we will discuss these issues and how to troubleshoot them. Some are designed for concatenation of long distance cables where two identical cables are spliced together.