Perform Optical Link Testing of Your 40Gb QSFP+ DevicesThe N844B-LOOP-12F is an OM3-rated 50/125 fiber optic loopback cable with an MTP/MPO female connector with a 12-pin configuration (1-12, 2-11, 3-10, 4-9, 5-8, 6-7), allowing testing to be performed on a complete link. With an overall length of approximately 4 inches, the N844B-LOOP-12F is easy to take with you for testing anywhere in the network. An included dust cap protects the connector when not in use.