Fiber Rings from AFL are often a necessity when testing with an OTDR. Fiber Rings are compact launch / receive cables designed to measure the insertion loss of the near-end and/or far-end connection of a fiber optic link using an OTDR. Both a launch and receive cable are required to measure complete link loss of a fiber with an OTDR. A launch cable, which connects the OTDR to the link under test, reveals the insertion loss and reflectance of the near-end connection. A receive cable, which connects to the far-end of the link, reveals the insertion loss and reflectance of the far-end connection. Launch and receive test cables can range from 150 m to 1 km (or longer) in length. Because very long test cables are impractical to transport and use, AFL offers coiled lengths of 50 µm multimode, 62.5 µm multimode, or single-mode fiber conveniently packaged in compact rings.