Cabling and Technology Information

 

Mode Conditioning Patch Cord

 

The following information applies to installations in which multimode fiber-

 

optic cables are connected to a Gigabit-LX port. Multimode cable has a design

 

characteristic called “Differential Mode Delay”, which requires the

 

transmission signals be “conditioned” to compensate for the cable design and

 

thus prevent resulting transmission errors.

 

Under certain circumstances, depending on the cable used and the lengths of

 

the cable runs, an external Mode Conditioning Patch Cord may need to be

 

installed between the Gigabit-LX transmitting device and the multimode

 

network cable to provide the transmission conditioning. If you experience a

 

high number of transmission errors on those ports, usually CRC or FCS errors,

 

you may need to install one of these patch cords between the fiber-optic port

 

in your switch and your multimode fiber-optic network cabling, at both ends

 

of the network link.

 

The patch cord consists of a short length of single mode fiber cable coupled

 

to graded-index multimode fiber cable on the transmit side, and only

 

multimode cable on the receive side. The section of single mode fiber is

 

connected in such a way that it minimizes the effects of the differential mode

 

delay in the multimode cable.

 

 

N o t e

Most of the time, if you are using good quality graded-index multimode fiber

 

cable that adheres to the standards listed in Appendix B, there should not be

 

a need to use mode conditioning patch cords in your network. This is

 

especially true if the fiber runs in your network are relatively short.

 

Installing the Patch Cord

 

 

As shown in the illustration below, connect the patch cord to the ProCurve

 

transceiver with the section of single mode fiber plugged in to the Tx

 

(transmit) port. Then, connect the other end of the patch cord to your network

 

cabling patch panel, or directly to the network multimode fiber.

 

If you connect the patch cord directly to the network cabling, you may need

 

to install a female-to-female adapter to allow the cables to be connected

 

together.

Information

Technology and Cabling

 

 

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