LC loopback test assemblies from Methode Fiber Optics Products, Chicago, test transmission capability and receiver sensitivity of network equipment and give a straightforward go or no-go test result. The LC loopback features compact housing with no external fiber-optic cable loop that can snag, twist, or break. The assemblies are available in single-mode, 50/125-multimode, and 62.5/125-multimode versions.