Mode Conditioning Patch Cord For Gigabit-Lx - HP J4111A Installation Manual

Installing the Module

Mode Conditioning Patch Cord for Gigabit-LX

The following information applies to installations in which multimode
fiber-optic cables are connected to a Gigabit-LX Module installed in the
switch.
Unlike Gigabit-SX, which connects to only multimode fiber-optic cabling,
Gigabit-LX can use either single mode or multimode cable. Multimode cable
has a design characteristic called "Differential Mode Delay", which requires
that the transmission signals be "conditioned" to compensate for the cable
design and thus prevent resulting transmission errors. Since Gigabit-SX is
designed to operate only with multimode cable, Gigabit-SX transceivers can
provide that transmission conditioning internally.
Gigabit-LX transceivers, since they are designed to operate with both single
mode and multimode cable, do not provide the transmission conditioning
internally. Thus, 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 the Gigabit-LX
ports, usually CRC or FCS errors, you may need to install one of these patch
cords between the Gigabit-LX Module installed in your switch and your
multimode fiber-optic network cabling, and between the Gigabit-LX trans-
mission device and the network cabling at the other end of the multimode
fiber-optic cable run. A patch cord must be installed at both ends.
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 multi-
mode 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 on page 22, 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.
If you are using single mode fiber-optic cabling in your network, there is no
need to use mode conditioning patch cords. Connect the single mode network
cable directly to the Gigabit-LX Module.
13