Maximum length of link with mode-conditiong chords in between

[HEKnet]

Hello,

actually this question is rather generic, but I could not post it under "Networking Knowledge Base". Hence, I created it here. At least the switches are HP5412zl. Perhaps an admin could move this message.

We want to upgrade a fiber link from 100MBit/s to 1GBit/s. At present half the way is already 1000BASE-LX, the other half is still 100BASE-SX. In the middle there are two "dumb" media convertes (Allied Telesys) back-to-back with a short twisted pair cord.

We intend to have 1000BASE-LX everywhere. Because the fiber that is currently operated at 100BASE-SX is a multi-mode fiber we would like to replace the media converters by a mode conditioning cord on each side of the multi-mode fiber.

See attachment for a figure of the situation.

Is this possible? Are there any distance limits we must be aware of?

The distance limit of a multi-mode link is 500m (1640ft), the distance limit of a single-mode link is 5000m (16400ft). The former is too little for our situation, the latter is sufficient. But is this limit a trait of the transceiver or of the physical wire? Which of these both limits holds, if one uses mode conditioning cords?

Thanks, Matthias

[Chrisd131313]

Hi HEKnet,

A mode-conditioning patch lead over multimode cable will theoretically give you a distance limit of 500m @ 1Gbps. BUT based on your scenario and how you are "repeating" from OM to OS I would be hesitant to guarantee that you will be able to get that max. length - it will also depend on the quality of the multimode cable you are using.

Here's a couple of articles explaining the use of a mode-conditioning patch lead...

http://www.lanshack.com/ModeConditioning.aspx

http://www.cablestogo.com/learning/library/data-center/mode-conditioning-fiber

HTH

[HEKnet]

Thank, but I have already known both pages. But none of them goes into the details that are needed here. But if I understand you correctly, in theory the limit of 500m only applies to the multi-mode part. The single-mode part only counts as a very long patch cord that must not exceed 5000m of course ;-)

In practice I cannot expect to get 500m on the multi-mode part due to losses on the single-mode part. But as 260m is only half of 500m it might work. Correct?

Matthias

[Chrisd131313]

yes, if the OM link is only 260m then it is likely that it will work fine. Remember that your two tranceivers act somewhat as a repeater as they are doign the optical-electronic-optical conversion, so unless they do not clean the signal on conversion you should be OK.