What Is a Mode Conditioning Patch Cord

Transceivers modules that are used in gigabit Ethernet 1000base-LX launch only single mode 1030nm wavelength signals. This creates a problem if present network operates on multimode cables.

 

When a single mode signal is launched into multimode fiber a phenomenon called Differential Mode Delay (DMD) can create multiple signals within the multimode fibers. This effect can confuse the receiver and produce the errors. These multiple signals, caused by DMD, severely limit the cable distance lengths for operating Gigabit Ethernet. A mode conditioning patch cord eliminates these multiple signals by letting the singlemode launch to be offset away from center of the multimode fiber. This offset point creates a launch that is similar to typical multimode LED launch and the resulting multiple signals allowing the use of 1000base-LX over existing multimode cable system.

 

Mode conditioning patch cords are necessary where Gigabit 1000 Base-LX switches and routers are installed into present multimode cable plants. These specified cords help avoid Differential Mode Delay (DMD) effects that can happen when long wave transceiver modules operate at both single-mode and multimode fibers. The mode conditioning patch cord lets the single-mode transceiver to generate a launch similar to a typical multimode launch.

 

Mode conditioners are constructed in the form of a simple duplex patch cord, so they can easily be mounted in a system without the need for extra components or hardware. Their length can vary from one meter and up, to support almost any network topography.

 

 

The conditioned side of mode condoning cable comprises of a yellow (singlemode) fiber which has been spliced to an orange (multimode) fiber in an offset mode, with a specific core placement and angle. On the other hand, the non-conditioned side of cable consists of one piece of orange (multimode) cable. The yellow leg (singlemode) of the cable must be connected to the transmit side, and the orange leg (multimode) had to be connected to the receive side of the equipment.

 

Since the optical SFP transceivers used in 1000 base LX uses LC connectors, the produced mode conditioning cord will have LC connector at one side. Depending upon the production of cable the other side of the cable could be SC connector, FC connector, MTRJ connector or the other side could be same as LC connector. Not to forget that there would be also an insertion loss from 0.2dB to 0.5dB in mode conditioning cable. Mode conditioning cables are available for both 62.5/125µm and 50/125µm multimode fibers.