The great demand for increased bandwidth has prompted the release of the 802.3z standard (IEEE) for Gigabit Ethernet over optical fiber.
Mode conditioning patch cables for Gigabit Ethernet applications are required when Gigabit 1000 Base-LX routers and switches are installed into existing multimode cable plants, which will increase your bandwidth without having to run a whole new fiber optic network.
The need for this patch cord is due to the single-mode launch nature of the -LX or long-wave (1300 nm) transceiver modules used for Gigabit Ethernet. These modules have to operate for both single-mode and multimode fibers. Launching a single-mode laser into the center of a multimode fiber can cause multiple signals to be generated that confuse the receiver at the other end of the fiber. These multiple signals, caused by Differential Mode Delay (DMD) effects, severely limit the cable distance lengths for operating at Gigabit Ethernet. A mode conditioning patch cord eliminates these multiple signals by allowing the single-mode launch to be offset away from the center of a multimode fiber. This offset point creates a launch that is similar to typical multimode LED launches.
The launch of the light coming out of the equipment begins on a Singlemode fiber. The Singlemode fiber is precision fusion spliced to the multimode fiber to a precise core alignment. The light is launched onto the multimode fiber at a precise angle, giving the cable its mode conditioning properties. The fusion splice is protected by a black over-wrap, and on the right side there is an orange and a yellow cable. This is the side of the cable that connects to the gigabit equipment with the yellow Singlemode leg connecting to the transmit side.