Cisco QSFP to four SFP+ active optical breakout cables are suitable for very short distances and offer a flexible way to connect within racks and across adjacent racks. Active optical cables are much thinner and lighter than copper cables, which makes cabling easier. Active optical cables enable efficient system airflow and have no electromagnetic interference (EMI) issues, which is critical in high-density racks. These breakout cables connect to a 40G QSFP port of a Cisco switch on one end and to four 10G SFP+ ports of a Cisco switch on the other end. Cisco currently offers active optical breakout cables in lengths of 1, 2, 3, 5, 7, and 10 meters.