Mode conditioning patch cord

[OLARU Dan]

If I use 50/125 micron multimode optical fiber cables to transport LX laser pulses (1300nm) - do I still need mode conditioning patch cords on Tx ports of the LX transceivers? Or are these patch cords nedded only on 62.5/125 micron multimode optical fibers?

[Arnaud_9]

Dan,

In theory you have to use a mode conditioning patchcord for all multimode fibers.

But you can try with standart patchcord :
-If your Gbics are in a good range of caracteristics (All optical interfaces - SX,LX,LH...- made in a same factory are ok with the minimum caracteristics garanted by the manufacturer, but they don't have the same caracteristics, some are just ok, and some have very best performances)
-If you optic link is also good (good connector, straight link, and so low end to end loss), it can work.
-So far you want to go, more luck and quality is needed.

Be sure all Optical connectors are clean, Try also your spare Gbics you can, to prevent some jokes when you change one Gbic.

Note that you have a good optical link, and good Gbics, SX interfaces could reach more than the garanted distance.

Arnaud

[SCOOTER]

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 Transceiver.
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 â Differential Mode Delayâ , which requires
that the transmission signals be â conditionedâ 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 singlemode
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 port in your switch and your multimode fiberoptic
network cabling, and between the Gigabit-LX transmission 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
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.
Note
Most of the time, if you are using good quality graded-index multimode fiber
cable that adheres to the standards listed on page 5, 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 transceiver.

Extract from Tranceiver Manual on:
ftp://ftp.hp.com/pub/networking/software/59903012.pdf

Kind Regar